Silvio Cocuzza
email: silvio.cocuzza@unipd.it

Rosanna Fornasiero
email: rosanna.fornasiero@itia.cnr.it

Stefano Debei
email: stefano.debei@unipd.it

Novel Automated Production System for the Footwear Industry

Keywords: Footwear automation, production systems, robotics, CAD-CAM integration, production performance

The production process of most of the footwear companies working in the market segment of classic, casual, and fashion shoes is still handicraft. Moreover, the actual design and production processes are largely independent, and both of them need the physical prototypes of the semi-finished shoes in order to be accomplished. In this context, the IDEA-FOOT project introduces a new method for the shoe integrated design and production in which most of the production parameters are derived from the shoe 3D CAD model and an innovative automated production plant in which manipulators and automated machines are fully integrated. The aim of this paper is to present the main features of the automated plant, the advantages in using a new integrated design and production process, which is totally new for this market segment, and to analyze the impact of this new production model on the production performance and on the company organization.

Introduction

Footwear companies working in the market segment of classic, casual, and fashion shoes, due to the global competition, need to reduce time to market and increase product diversification with small batches production, while keeping a high fashion and quality content of the product. The actual design and production processes are not suitable for this small batches and variegated production. Indeed, the production process has still a handicraft connotation; most of the production operations are performed manually by workers, and even when automatic machines are used, the operators have to program them manually for each batch of shoes, and the semi-finished shoes and components handling is done by means of conventional conveyors that are manually loaded/unloaded. Shoe manufacturing of classic, casual, and fashion shoes has a low degree of automation [START_REF] Ronthaler | Automation in the Footwear Industry -Innovative Robotics to Support Complex Artisan Production[END_REF], mainly due to the complexity of the product and of the production process. On the other hand, the manufacturing of technical and sportwear shoes is highly automated.

Several works can be found in the literature on the use of automation in different production stations of the shoe manufacturing, such as the automation of the lasting operation [START_REF] Nemec | Automation in shoe assembly[END_REF], of the grinding operation [START_REF] Nemec | Shoe grinding cell using virtual mechanism approach[END_REF], of the roughing and cementing operations [START_REF] Nemec | Automation in shoe assembly[END_REF][START_REF] Hu | Automatic surface roughing with 3D machine vision and cooperative robot control[END_REF][START_REF] Rooks | Robots bring automation to shoe production[END_REF][START_REF] Kochan | Actis and the shoe industry[END_REF], of the bonding of the sole [START_REF] Tae-Jung | A study on development of 3D outsole profile scanner for footwear bonding automation[END_REF], of the finishing operations [START_REF] Nemec | Automation in shoe assembly[END_REF][START_REF] Choi | Development of a new buffing robot manipulator for shoes[END_REF], and of the quality control [START_REF] Alcantud | Inspection and quality control based on artificial vision techniques for the automation of manufacturing process in the footwear industry[END_REF]. In the EUROShoE project an automated production plant has been developed for the production of mass-customized shoes [START_REF] Dulio | Integrated production plant (IPP): an innovative laboratory for research projects in the footwear field[END_REF][START_REF] Boër | Mass Customization and Footwear -Myth, Salvation or Reality?[END_REF].

The need of the physical prototypes of the semi-finished shoes to have the geometrical information necessary for the design and production phases is the main technological problem of the footwear companies of the considered market segment. Indeed, the actual design and production processes are largely independent, and both of them need the physical prototypes of the semi-finished shoes in order to be accomplished. In the design phase, the semi-finished shoe is necessary for the sequential development of the other shoe components to be assembled, whereas in the production process, the semi-finished product is necessary to program the semi-automatic machines for each batch of shoes.

In this context, the main objectives of the IDEA-FOOT project are:

• the introduction of a new method for the integrated design and production of the shoe, in which the key elements are the 3D CAD design of the shoe components and the transfer of the required geometrical information, tool paths, and production parameters from the design to the production process in a digital standard data format using a CAM S/W; • the design, construction, test, and validation of the automated production plant in which the aforementioned method is implemented.

The proposed automated production plant is based on a production process that has been redesigned in order to reduce the complexity of the production and to increase flexibility, such as in the lean manufacturing approach [START_REF] Womack | The Machine That Changed the World: The Story of Lean Production[END_REF].

In particular, the automated plant has been designed in order to have a flexible production both in terms of batch size (the minimum batch size is one shoe pair) and in terms of product style diversification. This is in line with the agile and adaptive manufacturing approaches arisen at the beginning of the last decade as approaches to improve the competitiveness of the companies. Agile production is characterized by the integration of suppliers and customers in the value chain from the design to the production, to the marketing, and to the support services. There are many works applying different dimensions of the adaptive and agile paradigms (such as, for example in [START_REF] Ashall | Leaning towards Agile[END_REF][START_REF] Gunasekaran | Agile Manufacturing: A Framework for Research and Development[END_REF][START_REF] Sharifi | Agile Manufacturing: A Management and Operational Framework[END_REF][START_REF] Dashchenko | Manufacturing Technologies for Machines of the Future -21st Century Technologies[END_REF]), both from the point of view of technology improvement (implementation of flexible production systems, information and communication technology (ICT) tools, system integration) and people enhancement (competency management and training at all levels).

The aim of this paper is to present the main features of the automated plant, the advantages in using a new integrated design and production process, which is totally new for this market segment, and to analyze the impact of this new production model on the production performance and on the company organization.

New automated production system

The automated production plant has been realized by means of integrating existing technologies and existing dedicated machines, which have been modified in order to work in an integrated way. All the production operations from the shoe lasting to the shoe bottom processing operations (up to the cementing of the shoe bottom) have been successfully automated.

In the automated plant, manipulators are used both for pick and place and for shoe bottom processing operations. A centralized control S/W, which has been customized for this project (DESMA), is used for the monitoring of the production and for the integration and synchronization of the dedicated production machines, the manipulators, the shoe last identification system (based on radio-frequency identification (RFID) technology), the oven, and the pallet conveyor.

The core of the automated plant is subdivided in two robotic cells: the robotic cell A, in which research and development activities are involved, has been developed by CISAS, and the robotic cell B, in which state of the art technologies are involved, has been subcontracted to DESMA.

In particular, in the robotic cell A the two lasting machines (Brustia) receive the information on the article code for their automatic setup from an RFID chip inserted in the last, and moreover the heel seat and side lasting machine is loaded/unloaded by a manipulator (this was not possible for the toe lasting machine because a skilled operator is needed to assist that operation). On the other hand, in the robotic cell B some technologies already available in the market for the shoe bottom processing of technical and sportwear shoes have been modified for the scopes of this project.

The layout of the automated production plant, which have been defined comparing different solutions in terms of production time, work in progress (WIP), number of human operators, and required space, is presented in Fig. 1.

Before the robotic cell A, a human operator picks the last, the insole, and the upper from the related trolleys, assembles them together and puts the semi-assembled shoe in a trolley (station nr. 7 in Fig. 1). In the robotic cell A, first some manual operations are performed: a human operator picks the semi-assembled shoe from its trolley and puts it in a conditioning unit (nr. 8); after that operation, the operator places the last in front of an RFID station for the automatic setup of the toe lasting machine (nr. 9), performs the toe lasting operation, and then places the last in the man-robot exchange station (nr. 11), which is also a conditioning unit. Then, a manipulator is used to pick the last from the man-robot exchange station, place the chip of the last in front of a second RFID station for the automatic setup of the heel seat and side lasting machine (nr. 13), load and unload that machine, and finally place the last in the pallet conveyor.

In the robotic cell B, a second manipulator is used to pick the last from the pallet conveyor (after that the last has been processed in the oven and that some optional manual operations have been performed, such as hot air application, cream application, and ironing), perform the shoe bottom processing operations (grinding, hammering, roughing, cleaning with compressed air, and cementing (nr. 18-22)), and then place it in the aspirator (nr. 23-24) to dry the water-based adhesive. The grinding, hammering, roughing, and cementing operations are performed by the robot, which presses the shoe bottom against the related ground-fixed rotating tool.

Two overall views of the robotic cell A and of the robotic cell B of the automated plant, which is installed at the BZ Moda premises, are presented in Fig. 2.

The main features of the new automated production plant are:

• use of manipulators to perform both pick and place and shoe bottom processing operations, thus reducing the processing time and the number of required human operators, and increasing the product quality; • use of dedicated production machines (for the operations that cannot be performed by robots) that have been modified in order to reduce their setup time and to be loaded/unloaded by means of manipulators;

• implementation of a centralized control S/W for the monitoring of the production and the integration and synchronization of manipulators and automated machines.

The above presented approach represents a solution that can be rapidly adopted by the footwear companies of the considered market segment, in a smooth and gradual change toward automation.

Existing dedicated production machines have been modified in their mechanical and communication interfaces in order to be integrated with the rest of the automated plant and served by manipulators, to receive the setup parameters and tool paths generated automatically by the CAM S/W, and for their automatic setup during the production by using RFID systems.

An RFID tag is used to store in each last the batch information that is called up, when required, to guide the manipulators or the automated machines. The identification code of each shoe model is used in order to recall the production parameters and tool paths from the local databases of the machines and manipulators for their automatic setup in function of the shoe model.

The daily productivity of the automated pilot plant is approximately 320 [pairs/shift] (1 shift = 8 hours), and only 5 human operators are required (considering all the production operations from assembling the last with the insole and the upper up to delasting, excluding the aforementioned optional manual operations).

In the traditional plant with classic conveyor line taken as a reference, 13 human operators are needed, and the daily productivity is 554 [pairs/shift]. In the proposed automated plant, if 2 manipulators are used in the shoe bottom processing robotic cell, the daily productivity can be increased up to 600 [pairs/shift] and the number of human operators can be reduced to 7. Productivity can be additionally increased by adding more manipulators and/or duplicating production stations at the bottlenecks.

Once that the automated plant has been realized, it has been interfaced with the rest of the traditional production plant (including sole application, heel application, finishing, and delasting stations) and small batches of shoes have been produced for validation purposes. The analysis of the produced shoes evidenced that increased quality production operations have been performed, which turned out in high quality finished shoes.

Impact on production performance and on company organization

The implementation of the proposed integrated design and production model will contribute to enhance the competitive strength of the footwear companies through leveraging and optimizing the value of knowledge within and across companies by supporting the creation of a sustainable industrial production process. In particular, the solution proposed in this project goes both in the direction of economic sustainability, allowing companies to reduce production costs, and towards environmental and social sustainability, going beyond the lean paradigm. Time to market will be significantly reduced and footwear companies will have the possibility to be more flexible and responsive in the development of new shoe models. The new production system is extremely flexible both in terms of production of small batches (up to one shoe pair) and in terms of product diversification, with very limited setup time to manage product variants.

Moreover, the relationship between the shoe producer and its suppliers is totally revised: the design of new shoe models will be mainly carried out by the shoe producer with limited intervention of subcontractors, and the production of the shoe components will be made concurrently by the suppliers, saving up to 50% of the design and development time with respect to the actual sequential development of the shoe components based on physical prototypes.

The impact will be on three major dimensions of sustainability: economic, social, and environmental.

Concerning the economic sustainability, an important reduction of the production costs and time to market is envisioned. Moreover, the implementation of these new technologies allows to maintain the production (or, at least, part of it) in the origin country reducing delocalization and assuring workplaces.

Concerning the social sustainability, the introduction of the new integrated design and production method requires the development of new skills and competences both in the area of design, where people have to learn to use new CAD modules, and in the area of production, where workers are asked to do added-value operations in the automated plant. Moreover, the introduction of the new automated production plant improves working conditions: operations that require physical efforts and repetitive manipulations are performed by manipulators, workers are no more involved in risky operations, and the direct contact with harmful substances is eliminated (toxic adhesives have been substituted by water-based adhesives and the operations where leather powder can be breathed causing health problems are carried out in a protected area).

The environmental sustainability of the production processes is nowadays a relevant issue requiring that companies manage the negative externalities caused by their production. In the framework of this project, thanks to the innovative production system, scraps and material waste during the production phase can be significantly reduced (the integration of the design and production phases allows a better organization of the shoe development) and toxic adhesives and solvents are eliminated (waterbased adhesives are used).

Based on qualitative information gathered from company managers and technology providers, the analysis of the impact of the implemented technologies on the production performance has been carried out, which can be summarized as follows:

• Impact on flexibility. The production is highly flexible both in terms of batch size (the minimum batch size is one shoe pair) and in terms of product style diversification.

• Impact on productivity. The automated plant productivity is about 320 [pairs/shift]. Nevertheless, productivity can be increased by adding more manipulators and/or duplicating production stations at the bottlenecks.

• Impact on quality. Defects are reduced thanks to the increased accuracy of the automated operations. The product quality is also improved thanks to the upstream improvement in the more precise product design.

• Impact on balancing of production flow. Bottlenecks are eliminated and WIP is minimized thanks to an accurate design of the automated plant and of the centralized control S/W.

• Impact on waiting periods. Waiting periods due to inadequate manufacturing schedules and long production stops for the machines setup are eliminated. The production system is based on an initial plant setup for all the planned production models, which allows to have a seamless flow of production.

• Impact on motion waste. The automated plant design has been optimized so that any operation of workers or machines identified as non-value-adding action is eliminated.

• Impact on capability to find errors. The centralized control S/W generates an alert any time there is a problem in the production so that the worker knows where the problem is located and what caused it.

Conclusions

The IDEA-FOOT project introduces a new method for the integrated design and production of shoes and an innovative automated production plant in which manipulators and automated machines are fully integrated. Most of the production parameters and tool paths are derived from the shoe 3D CAD model and then transferred to the production using a dedicated CAM S/W. The production data is then recalled in the manipulators and in the production machines by means of RFID systems, thus reducing their setup time. In the automated plant, all the production operations from the shoe lasting to the shoe bottom processing operations (up to the cementing of the shoe bottom) have been successfully automated. A centralized control S/W is used for the monitoring of the production and for the integration and synchronization of manipulators and automated machines. The plant productivity is about 320 [pairs/shift] (1 shift = 8 hours), which can be increased up to 600 [pairs/shift] by adding one manipulator. Productivity can be additionally increased by adding more manipulators and/or duplicating production stations at the bottlenecks. Once that the automated plant has been realized, it has been interfaced with the rest of the traditional production plant and it has been validated by producing small batches of high quality shoes, which demonstrated the accuracy of the production operations. The presented approach, which is totally new for this market segment, allows the reduction of production costs and time to market, with a highly flexible production both in terms of batch size (the minimum batch size is one shoe pair) and in terms of product style diversification. The introduction of automation implies a reduction of the number of human operators required, thus reducing production costs. On the other hand, more qualified workers are needed and their working conditions are improved. Thanks to the new integrated design and production process based on the shoe 3D CAD model, the relationship between the shoe producer and its suppliers is totally revised: the design of new shoe models will be mainly carried out by the shoe producer, and the production of the shoe components will be made concurrently by the suppliers, saving up to 50% of the design and development time. Finally, the improved quality of the production operations implies a significant reduction of scraps and material waste during the production.

Fig. 1 .Fig. 2 .

 12 Fig. 1. Automated plant layout (Source: S. Cocuzza, Manipulation system for the toe lasting machine, EU FP7 IDEA-FOOT Project, Deliverable D 430.1, p. 5, 2012)

Acknowledgement. The results presented in this paper have been obtained in the framework of the IDEA-FOOT project (Innovative DEsign and mAnufacturing systems for small series production for European FOOTwear companies) -7th Frame-work Programme -Research for the benefit of SMEs -FP7-SME-2008-I -Project n. 232585.


Spyridon G Mouroutsos

Eleftheria Mitka

Safety-guided design concerning standardization's requirements of mowing robots

Keywords: safety-guided design, systemic method, mowing robot, safety requirements, standards

Considering the rapidly expanding market for mowing robots to homeowners the noticeable question that arises is what are the safety-guided design requirements that could be applied to production management via safety standards? Standardization attempts to protect human during the interaction with this device. It makes an effort to confine residents by implementing more legible guidelines. There is no correct or incorrect list of hazards, only a list that customers and designers agree that is necessary to be handled. However, the requirements may differ in the design stage. All the design requirements shall be included in the physical system design of the robotic mower. In this paper, the authors believe that it is essential to put forward a comprehensive and systematic list of corrective or preventive measures in order to provide a safety checklist throughout the design stages of robot use. These safety criteria intend to minimize the chance of an accident and offer the adequate protection to users.

Introduction

Recently, everyday people are dreaming about having a device that could be a kind of useful robot. Such robots for residential use, consider capable of taking over chores successfully in the domestic environment. Mowing robot is designed to automatically mow lawn in gardens at any day and time. It is small, compact, silent and easy to transport. The robot can be programmed to mow several areas. During operation, the robot mows the area delimited by the perimeter wire. Its performance depends mostly on the weather conditions (sunlight and temperature), the shape of the garden, the state of blades, the growth of grass and the humidity. It is indented for mowing large areas, preferably at daytime depends on the battery life. Whenever it comes in contact with an obstacle such as branches, small stones, wall or fence, it reverses and follows a different direction. This system uses an irregular movement pattern that is never repeated according to its sensing of growing of lawn.

Since particular safety guidelines for mowing robots do not exist, the authors suggest that their safety-guided design should be based on standards that developed in areas of agriculture and garden equipment. In addition, the methodologies for safety for agricultural equipment [1], safety signs [6], the standard for Robots and Robot Systems [START_REF]Robots and Robot Systems[END_REF] providing safety requirements for robot systems, as well as the "Safety certification requirements for domestic robots", proposed by the authors [START_REF] Mitka | Safety certification requirements for domestic robots[END_REF] should be made applicable to robotic lawn-mowers. Every manufacturer should follow the basic instructions summarized in the basic safety standards such as Definitions of Powered Lawn and Garden Equipment [START_REF]ANSI/ASAE S323[END_REF], Safety Specifications for Commercial Turf Care Equipment [START_REF]Safety Specifications for Commercial Turf Care Equipment[END_REF] and safe features according to Safety Specifications for Turf Care Equipment -Power Lawn Mowers, Lawn and Garden Tractors [START_REF][END_REF].

With aim to expand and grow the acceptance of robots by the society, the authors propose a new list of safety design constraints. The authors use a systemic method that covers the safety design of the production, managing product (mowing robot) and information (standards) [START_REF] Mouroutsos | Applying System Safety Engineering to Safety Standards of Domestic Robots[END_REF].

2

Safety-guided design

Possible accidents

The first step in any safety analysis is to define which types of accidents needs to be considered. The definition of an accident derives from the user's experience and from government efforts for systems that are certified by technical committees and corresponding regulations. Accidents are a consequence from ineffective implementation of safety requirements on the design level of the system [START_REF] Leveson | Safeware, System Safety and Computers[END_REF]. In addition, potential accidents of a mowing robot are the following:

A1.

Electromagnetic or radio frequency interference may cause person injury.

A2.

Severe injury could occur if hair, fingers or clothing of resident are caught in the exposed mechanism of the robot due to indented opening of the cover.

A3.

Battery may explode if user does not follow the appropriate procedure and the nearby resident could suffer from electrical shock.

A4.

Stones, tools, toys and other loose objects may be thrown by the mower blades leading to harmful injuries.

A5.

A resident could be pinned under the robot due to overturning of the robot that is caused by operating in slopes.

A6.

A resident could be injured by contact with the blades.

A7.

A resident that uses the robot via remote control hits a person or a pet by pulling the mower backward without looking.

A8.

The released electrolyte of an intended open of the power pack may cause damages to skin or eyes. A9. Contact of human with hot parts may cause burns. A10. The cord/ perimeter wire may lead to tripping hazard. A11. Electrical component damage due to inadequate cleaning of the device. A12. A child may fall off and be seriously injured if he rides on an operating robot.

A13.

Coexistence everyday problems occur if the robot is moving at high speed.

Adjusting a level of severity

A risk management is arranged at early design stages with a risk matrix (counting severity and probability) to agree on which types of hazards shall be mitigated during design stage or to categorize them. Statistically analyzed data estimating the probability of accidents, however, at this specific type of robots, does not exist so far. The safety policy for prioritizing the severity of an accident is that all accidents result in a loss of human life or human injury should be eliminated at the design level.

Level 1: A1-1: Rotating blades catches part of resident's body. A1-2: Coming in contact with any exposed mechanism part of the robot. A1-3: A child rides on an operating robot. A1-4: A resident is pulling the mower backward without paying attention. A1-5: A resident could be pinned under the robot due to overturning. Level 2: A2-1: Hot parts cause burns. A2-2: A battery could explode. A2-3: The cord/ perimeter wire causes tripping hazard. A2-4: Electromagnetic or radio frequency interference. Level 3: A3-1: Problems with the coexistence in everyday living. A3-2: Loose objects may be propelled. A3-3: Electrical or electronic component damage. A3-4: Released corrosive electrolyte affects human skin and eyes.

High level system hazards

A restricted set of high level system hazards need to be identified combining potentially hazardous conditions with accidents identified at section 2.

Define design constraints

The next step is to define the safety constraints that are considered critical to protect from incidents (Table 1). The greatest challenge is to design such robot that enforces the requirements as much as achievable. Furthermore, we accompanied these protective measures by one real lawnmower in order to prove that implementation of these guidelines are crucial and ought to be applied. The chosen product is Friendly robotics RL850 (Fig. 1). Table 1. Safety-Guided Design constraints concerning mowing robot's hazards.

HAZARD SAFETY DESIGN CONSTRAINTS FRIENDLY ROBOTICS RL 850 Electromagnetic or radio frequency interference

• The device shall not be subject to interferences such as high ambient noise, radio transmissions, unshielded computers, infrared remote controllers and magnetic fields. • If the robot is operating in close proximity to another one (by the same or a different manufacturer), then you should make adjustments so that the frequencies of the two robotic devices do not interfere with each other. • Make sure that mower is placed away from light, microwaves, magnetic fields, heat or sound.

• The device shall not be subject to interference cause by nearby metal objects, underground wires, and another wire in a nearby grass, neighbor's lawnmower or another electric device using similar frequency. • The interference shall not lead to calibration failure, ignoring of wire and mowing outside the designated area, changing of direction with no progress.

Exposed mechanism • The mechanism of the robot shall be protected. The respective covers shall be kept in good condition.

• The mowing covering hood shall not collect grass residuals after mowing damp or wet lawn.

It shall be inspected and maintained regularly for foreign material using a damp cloth or another similar tool. • The mechanism of Robomow is protected with plastic cover to prevent from bumping or changing it.

Explosion of the battery

• Safety features such as battery pack or sealed batteries shall continue to be active in order to protect residents under all emergency circumstances. • User shall be informed by the manufacturer that in case of mowing robot performing on batteries, there exist electrical hazards such as fire, electrical shock or chemical burn hazard in case that battery is mistreated and explosion hazard, if the battery is incorrectly placed [START_REF] Mitka | Safety certification requirements for domestic robots[END_REF].

• The 24V sealed lead acid battery, that is used to drive the three 150W motors on the RL850 and all electronic components ought to be charged at the recommended charging station. Improper charging may causes shock or overheating hazard.

• The charging station ought to be designed according to the following: • It shall be placed on compact, flat and stable surface with good drainage, on level ground, preferably in a wide span area of the house. • Make sure that water or other liquids is not directed inside the charging station. • The entrance of the charging station shall be positioned so that the robot can enter away from leaves, sticks or twigs. • The charging-station shall be well fastened to the ground. • Deal with any insect with a proper insecticide.

Loose objects

• The operational area shall be well defined • Safety features, in case of Robomow [START_REF]Robomow operating and safety manual of Friendly Robotics Acquisition Ltd[END_REF], such and operational contingencies detected shall be eliminated by the designer. Such operational contingencies include: inability to determine location in the house; obstacles within its path; not accessible charging station; inability to follow the tasking path. • Guards and shields are designed to protect user.

as lift sensor, sensor equipped bumpers, perimeter switch, automatic departure warning alert shall continue to be active in order to protect residents under all emergency circumstances.

Overturning of the robot

• Designer should simulate some test manoeuvres on first use to identify the commands and main functions. • Robomow is already equipped with an emergency stop switch on the manual controller in order to block its mowing path. • The emergency stop switch shall be applied with a push button switch in series among the battery and the robot. When pushed, the switch shuts-off power to the robot, pausing the turning of motors and blades until the button is released. When power is returned to the robot, the controller will execute the command of the robot.

Contact with the sharp rotating blades

• Manual should advice the user to present dramatic description on the hazardous behaviors of mistreating the robot and warn correctly concerning the appropriate safety features. • The replacement of not well-maintained or worn out blades shall not require routine or extraordinary maintenance more than once a year. • User's manual indicates that every maintenance, service, replacement or inspection of worn or damaged parts should be carried out by service experts.

• Blades shall be sharp and offer a safe and effective cut. • Not well-maintained blades will shred the lawn, which can provide an entry point for disease organisms and weaken the grass plant. • It is recommended to replace all three Robomow blades once a year [START_REF]Robomow operating and safety manual of Friendly Robotics Acquisition Ltd[END_REF].

Pulling the mower backwards without looking

• Online tutorials and help menus shall contain the appropriate instructions, so that users shall have direct access to information on how to operate the robot. • A built-in electronic hardware control system and/or safety operational software shall be selected to force the robot to shut itself down in an emergency. • Mowing robot shall be equipped with an emergency stop switch on the manual controller that ceases the rotation of blades and wheels within seconds.

• The remote emergency stop shall be applied to Robomow with a radio frequency receiver and relay positioned in series among the battery and the robot. When the receiver receives a signal from the remote RF transmitter, the relay ceases the power to the robot blocking any hazardous movement. When power is returned to the robot, the controller will execute the command of the robot.

Released electrolyte • The power pack shall not be able to be opened or spoiled. • The robot ought to be designed so that no additional clothing against hazardous materials and solvents requires to be worn by the user during the charging of the device. the robot, the designer should ensure that any increase of temperature will not cause burn injury.

• Hot parts of Robomow shall not cause burns, the engine and exhaust system shall be kept as cool as possible.

The power cord/ perimeter wire causes tripping hazard

• The use of adequate insulation, cable crosssections, panel covers shall prevent an electrical shock.

• Robomow cables must be embedded inside the body of the robot. • Robomow shall use cable cross-sections and

Assign responsibility to the user for implementing safety requirements

The responsibility for enforcing each behavioural requirement ought to be assigned to the users of the product as in any production management system. The high-level system requirements for eliminating the hazard was recognized and then enhanced into more distinctive requirements. However, there is no possibility to develop an ultimate list of requirements that controls every robotic product apart from a restricted list of requirements quite essential with aim to be helpful in a safety analysis. Each production manager has to decide what its specific safety features are possible to certify a particular product. Design takes account of the whole spectrum of the product eliminating human errors by redesigning the equipment.

HIGH LEVEL SYSTEM HAZARD (1): Electromagnetic interference.

Protective measures taken by user

• Do not use solvents or benzene for cleaning purpose.

• Do not wash the internal parts of the robot and do not use jets of pressurised water.

• To clean from deposits and residuals from the blade, use an indented brush.

• Use a dry cloth to clean the battery charger and the contact plates.

• Non waterproof robots shall be prevented from washing with liquids and shall be prevented from being turned over in water completely. panel covers. A child rides on an operating robot

• Warning signs shall be established to protect residents who may consider that they can ceaselessly be reckless with the operating robot. • Specific responsibilities concerning safety shall be assigned to an adult user. • The robot shall be equipped with a specific audio or visual signal, easily recognizable by everyone, to let people know whether it is on or off. Use a frequency that is not within the range of noise frequencies, in case of an audio signal. • The designer should take into account the fact that objects will be dropped and liquids will be spilled upon the robot, eventually. • Adequate electrical protection shall be provided such as regulators, filters, proper ground circuit.

• The robot electrical equipment should follow the appropriate instructions of the relevant requirements. • An appropriate danger sign for electrical shock shall be generated if needed.

Robot is moving at high speed

• Post-manufacture check of the full scale system, about its maximum, minimum, optimal speed and settings, start / end points, path, process. • Speed mode should meet the performance criteria.

• Switch "deadman" shall be applied to Robomow in order to cease the power supply or blocks only the blade or only the rotation of the wheels in case that speed exceeds the manufacturer's specification tolerance. • The emergency stop switch, ought to perform the same function as the switch "deadman" blocking all abnormal high speed movements.

HIGH LEVEL SYSTEM HAZARD (2): Exposed mechanism.

• To prevent human health, residents shall not open the mower's covering hood with aim to avoid damaging internal electrical components.

HIGH LEVEL SYSTEM HAZARD (3): Explosion of the battery.

• Charge the battery in a dry, well-ventilated area where the temperature is moderate.

• Follow the correct procedure for charging.

• Keep all sparks, open flames, and smoking materials away from the battery.

• Keep the battery away from explosive and/or flammable environments.

• Station for battery charging shall not be placed in sites subject to vibration and away from concrete, incline or hard surfaces.

HIGH LEVEL SYSTEM HAZARD (4): Loose objects.

• User shall be informed that mowing over objects may cause malfunction to the blade and lead to an injury due to thrown objects from the mower's chute.

HIGH LEVEL SYSTEM HAZARD (5):

Overturning of the robot.

• Check the slope of the ground and make sure the maximum values allowed.

• User is not supposed to operate the machine on slops or hills. Mow the slope as recommended by the manual.

HIGH LEVEL SYSTEM HAZARD (6):

Contact with the sharp rotating blades.

• Wear heavy work gloves when working with and around the blades.

• User shall be informed from the manual about maintenance information.

HIGH LEVEL SYSTEM HAZARD (7):

Pulling the mower backward.

• Look down and behind before and while operating backwards.

• Never try to mow in reverse using the manual controller.

HIGH LEVEL SYSTEM HAZARD (8):

A child rides on an operating robot.

• The operating area should be clear of people (in particular children, the elderly or disabled people) and domestic animals. Operate the robot at suitable times of the day. • Do not let a child to ride on a mower or walk along side. Children ought to stay inside the house and supervised so they don't suddenly come into the garden while robot is operating. • Shut off the product in case of a child coming in the lawn.

HIGH LEVEL SYSTEM HAZARD (9):

The perimeter wire causes tripping hazard.

• Ensure the robot does not run into obstacles, corners or harmful objects.

• Wear gloves when installing the perimeter wire and driving the wire pegs.

• The power cord shall be fixed firmly to the ground.

HIGH LEVEL SYSTEM HAZARD (10):

Robot is moving at high speed.

• Never turn on the device in a garage even if the outdoors and openings are opened.

Conclusion

Safety in a domestic environment is much more complicated, due to the presence of much more untrained people as well as due to many unpredicted situations that might arise. This gave the main thrust to this paper, which attempt to approach the problem of robots safety, from a systemic point of view. This method could be applied as a preventive means at the stages of planning, organizing, directing and controlling the safety design of production in order to reduce the defective procedures that could lead to an incident. Moreover, it could be applied to other types of robot such as biped, toy-robots, personal care, service and automated guided vehicle robots. A robot is considered safe when fulfill the safety standards, which draws from research on the national, and when all requirements that had been pointed out by the authors, are fully satisfied. This Systems-Theoretic framework supports robot's business firm to achieve objectives, increasing firms reputation and facing the competition in the market, while supporting in decision-making related to rapid changes according to specification of the robotic system.

Fig. 1 .

 1 Fig. 1. A commercially available robotic mower (Source: http://www.robomow.com).

  • User command execution precisely without putting the resident's life in danger. • The robot shall have easily accessible safety commands and functions, so that the user shall be able to stop the robot in case of overturning. • Emergency stop shall execute the proper stop function in case of overturning. In particular, wiring, communication devices, sensors, electrical and utility connections should meet the performance criteria.


Hyun Woo

Vittaldas V Prabhu
email: prabhu@engr.psu.edu

Modeling Green Fabs -A Queuing Theory Approach for Evaluating Energy Performance

Keywords: Sustainability, Queueing Network, Re-entrant Networks, Semiconductor Manufacturing, Energy-aware Model

More than 30% of the total energy consumed in the U.S. is attributed to industrial sector which motivated improvements in energy efficiency of manufacturing processes and entire factories. Semiconductor fabrication (fab) represents an interesting challenge for energy efficiency because of their relatively high energy consumption to process a unit mass of material. The focus of this paper is to develop an energy-aware analytical model based on queuing theory that has re-entrant network structure commonly found in fabs to analyze the impact of reducing idle power consumption in individual equipment. The proposed analytical model based on BCMP network for re-entrant lines has the same mathematical form as serial lines and is tested for using detailed simulation of a generic CMOS fab with three processing steps. Results show that the energy consumption predicted by the analytical model differs from simulation typically within 10% and worst case of 14%, in the tested cases.

Introduction

Faced with a growing trend of increasing energy consumption worldwide, various organizations are trying to be more energy efficient [START_REF] Prabhu | Energy Information Administration: International Energy Outlook 2011[END_REF]. Especially there is a particular need for the U.S., as one of the largest energy consumers among nations, to increase energy efficiency across all segments of the economy as the American industrial segment accounts for 31% of its total energy consumption [START_REF]Annual Energy Review 2010[END_REF]. Two benefits that can be expected from improved energy efficiency in the industry segment are direct cost savings and indirect environmental benefit, both stemming from reduced energy consumption. Consequently there has been increasing research on understanding energy consumption of various manufacturing processes and associated equipment [START_REF] Gutowski | Thermodynamic analysis of resources used in manufacturing processes[END_REF]. This prior research has found that semiconductor manufacturing processes is among the highest energy consumption per unit mass in the manufacturing industry. For example, the oxidation process in fabs typically consumes 1.E+13 -14 J/kg compared to milling steel which consumes about 1.E+05 J/kg. Moreover, idling manufacturing machines typically consume as much as 40 to 60% of the power when they are busy for processing parts [START_REF] Diaz | Energy Consumption Characterization and Reduction Strategies for Milling Machine Tool Use[END_REF]. A logical progression of research effort is to build on the energy consumption models of unit processes to higher levels such as the factory level and the supply chain level. For analyzing busy/idle states of a system consisting of many machines, simulation and queuing modeling are attractive approaches. Good insights can be acquired when both approaches are used, including testing and validation of each other judiciously [START_REF] Connors | A Queueing Network Model for Semiconductor Manufacturing[END_REF].

Our recent efforts in this direction include developing hybrid simulation models consisting of continuous and discrete process for predicting energy consumption in discrete manufacturing [START_REF] Prabhu | Simulation Modeling of Energy Dynamics in Discrete Manufacturing Systems[END_REF]. We have also proposed queuing models to predict energy savings in serial production lines when idling machines are switched to a lower power state in serial production lines consisting of machines with Poisson arrival and exponential service time [START_REF] Prabhu | Modeling Green Factory Physics -An Analytical Approach[END_REF].

This paper builds on our previous work [START_REF] Prabhu | Modeling Green Factory Physics -An Analytical Approach[END_REF] to extend and generalize the energy-aware queuing model to a re-entrant structure which is applied to model semiconductor fabs. Section 2 reviews the prior analytical model along with its parameters and limitations.

In Section 3 a model for re-entrant lines is introduced and energy performance characteristics are derived. In Section 4 a generic semiconductor production system is used for comparing results predicted by the analytical model with those by detailed simulation. Section 5 summarizes this paper with possible future research directions.

Energy-aware Queuing Model

Our recently proposed approach for improving energy efficiency in manufacturing system is to use energy control policies that switch machines to a lower power consumption state when a machine is anticipated to be idle for longer than some threshold, [START_REF] Prabhu | Simulation Modeling of Energy Dynamics in Discrete Manufacturing Systems[END_REF][START_REF] Prabhu | Modeling Green Factory Physics -An Analytical Approach[END_REF]. In order to predict the efficiency gained by using such energy control policies, the state transitions between the various energy consumption states and production states of the machines need to be modeled. Without any energy control policy ( ) the machine power consumption in its idle state will be , the nominal power for idling. When energy control policy is used ( ), energy state will be switched to the low power idling of if the idle time duration is anticipated to be longer than ; otherwise it will be . In the busy state the power consumption will be regardless of whether or used.

For an M/M/1 queue with an arrival rate of and a service rate , the probability that a new arrival arrives after the time threshold is given by

( ) ∫ (1)
Based on this, the total energy consumption with and over time can be modeled as follows

{ ( )} (2)
{ ( )( ) ( ) } (3)
In Equations 2 and 3 is the machine utilization. Therefore the total energy saving can be expressed as

( )( ) (4)
It should be noted from Equation 4that energy saving can be increased by decreasing and for a given . The above model for a single queue can be extended to serial production lines [START_REF] Prabhu | Modeling Green Factory Physics -An Analytical Approach[END_REF].

3

Re-entrant System Modeling

Queueing Model for Re-entrant System

Semiconductor fabs are markedly different from serial production lines or job shops [START_REF] Graves | A review of production scheduling[END_REF][START_REF] Kumar | Re-entrant lines[END_REF]. A typical semiconductor fab has a re-entrant structure in which the products flow through a fixed route visiting a machine multiple times [START_REF] Jaeger | Introduction to Microelectronic Fabrication[END_REF][START_REF] Kumar | Queueing Network Models in the Design and Analysis of Semiconductor Wafer Fabs[END_REF]. Semiconductor fabs can be modeled as an open queuing network in which parts visit a machine multiple times. It should be pointed out that because the route in semiconductor fab is deterministic such systems cannot be modeled as Jackson networks [START_REF] Jackson | Networks of waiting lines[END_REF]. Therefore in this paper we will model semiconductor fabs as a BCMP network, which is also the approach taken by several other researchers [START_REF] Kumar | Re-entrant lines[END_REF][START_REF] Kumar | Queueing Network Models in the Design and Analysis of Semiconductor Wafer Fabs[END_REF][START_REF] Baskett | Open, Closed, and Mixed Networks of Queues with Different Classes of Customers[END_REF]. The main parameters and assumptions in modeling a semiconductor fab as a BCMP queuing network are as follows  Arrival rate from outside is and is the number of visits to machine m before a part exits the system.  Arrival process is Poisson and mean service time follows exponential distribution with rates of and , respectively.  Queueing discipline is FCFS (first come first serve) and parts are served regardless of buffer in which the part is located.  Service rate is same for all parts in any buffer of the machine.  Route of each part is fixed and deterministic.  Idle time threshold for is for machine m.

Based on the above model, the arrival rate at machine m can be expressed as [START_REF] Connors | A Queueing Network Model for Semiconductor Manufacturing[END_REF] The utilization of machine m can be also defined as [START_REF] Prabhu | Simulation Modeling of Energy Dynamics in Discrete Manufacturing Systems[END_REF] The long run probability that there are n parts at a machine m is therefore given by

( ) ( ) (7)
From ( 6), [START_REF] Prabhu | Modeling Green Factory Physics -An Analytical Approach[END_REF] the probability of machine m is busy, ( ) can be expressed as

( ) (8)
The re-entrant structure of the model gives rise to multiple arrival streams at a machine that may not be independent of each other. Furthermore, summing these arrivals may not be an exact model for a composite Poisson process an exponentially distributed inter-arrival time [START_REF] Wolff | Stochastic Modeling and the Theory of Queues[END_REF]. However treating the composite arrivals as a Poisson process can be a reasonable approximation [START_REF] Kuehn | Approximate Analysis of General Queueing Networks by Decomposition[END_REF], which we adopt for modeling the probability of a machine being in nominal power idling ( ) and low-power idling ( ) states when is used. These probabilities for machine m are

( ) ( )( ) (9)
( ) ( ) (10)
From ( 8)-( 10), the energy consumption for machine m of a re-entrant system for time period can be modeled as

( ) { ( ) ( )( )} (11)
( ) { ( ) ( )( )( ) ( )( ) } (12)
where ( ), ( ), and ( ) are power consumption levels of machine m for busy, nominal power idling, and low power idling states respectively. It should be emphasized that this energy model for a re-entrant line has the same mathematical structure as the M/M/1 model reviewed in the previous section. Therefore the total spent energy in the entire re-entrant system can be modeled as

( ) ∑ ( ) (13)
( ) ∑ ( ) (14)
In the next section the energy consumption predicted by this analytical model is compared with a detailed simulation model to the efficacy of the model.

Simulation Experiments

Figure 1 illustrates a generic CMOS (Complementary Metal Oxide Semiconductor) fab with Deposition (D), Lithography (L), and Etching (E) processes and a re-entrant structure that follows an overall processing sequence indicated by the numerical values on the arrowed lines. The power consumption levels in these processes are hy-pothesized based on published data [START_REF] Hu | Power consumption of semiconductor fabs in Taiwan[END_REF] and shown in Table 1 along with other parameters used to simulate three different scenarios with varying arrival rates into the system.

Fig. 1. Example re-entrant system for CMOS

The simulation model was implemented by using the SIMIO simulation software package. For each scenario, , , and are estimated by fraction of the time a machine is in the corresponding state during a simulation run of 10,000 time units and averaged over 30 replications which is then used to compute the results in Tables 2 and3. The Figure 2 illustrates energy consumed with and of each of the deposition process in scenario 1. As expected, energy savings in all three processes increases with time. Figure 3 shows the power consumption for the deposition processing step with and in scenario 1. 2 and 3, it can be observed that analytical and simulation estimate of total energy consumed typically differ within 10% with the worst case being 14.3%. Figures 4 and5 graphically illustrate the difference between analytical and simulation models (delta) presented in Tables 2 and3. The difference is much less with compared to and delta decreases as utilization increases. We conjecture that the exponential distribution assumption for the composite inter-arrival times used in the analytical model underestimates the probability of being in low-power idling states, therefore overestimating the energy consumption. From energy efficiency perspective, consumes less energy than as expected. Energy savings ( ) decrease as increases because there is lesser opportunity for as machines get busier. Moreover, for a given , smaller will make more energy efficient. In practice, the choice of will be constrained by the physics and economics of the process.

Conclusions

An energy-aware analytical model based on BCMP network is proposed in this paper for semiconductor fabs with re-entrant structure commonly. Focus of the analysis is to assess the energy efficiency gained by reducing idle power consumption by switching machines to a lower power state when idling. Simulation tests indicate that the energy consumption predicted by the analytical models are typically differ within 10% from detailed simulations with worst case being about 14%, which makes the approach promising for rapid evaluation of candidate energy control strategies. Future work could focus on analyzing the factors that can influence the accuracy of the analytical model including the composite inter-arrival distribution model. Another potential future direction is to generalize the queuing networks to include G/G/1 and GI/G/1 systems [START_REF] Whitt | The Queueing Network Analyzer[END_REF][START_REF] Daley | Queueing Output Processes[END_REF].

Fig. 2 .Fig. 3 . 1 Fig. 4 .Fig. 5 .

 23145 Fig. 2. Energy consumed in the deposition process in scenario 1

Table 1 . Simulation parameters Parameters for each Simulation Scenario

 1

	Scenario		1			2			3
	Process	D	L	E	D	L	E	D	L	E
		0.050	0.050	0.025	0.040	0.040	0.020	0.030	0.030	0.015
		0.100	0.067	0.029	0.100	0.067	0.029	0.100	0.067	0.029
		0.500	0.750	0.875	0.400	0.600	0.700	0.300	0.450	0.525
		8.00	10.00	24.00	10.00	12.50	30.00	13.33	16.67	40.00
		0.40	0.50	0.60	0.40	0.50	0.60	0.40	0.50	0.60
		24857	9140	12238	24857	9140	12238	24857	9140	12238
		8286	3047	4079	8286	3047	4079	8286	3047	4079
		1657	609.3	815.9	1657	609.3	815.9	1657	609.3	815.9
	Replication		30			30			30

Table 2 .

 2 Comparison of Simulation and Analytical Models with

Table 3 .

 3 Comparison of Simulation and Analytical Models withFrom Table


David Jentsch
email: david.jentsch@mb.tu-chemnitz.de

Ralph Riedel
email: ralph.riedel@mb.tu-chemnitz.de

Egon Mueller
email: egon.mueller@mb.tu-chemnitz.de

Flow and Physical Objects in Experiential Learning for Industrial Engineering Education

Keywords: Experiential learning, flow, serious play, case study

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

According to Riedel et al. [START_REF] Riedel | Integrating experimental learning into Industrial Engineering curriculaa case study[END_REF] learning is in the curricula of operations management and industrial engineering primarily based on a one-way transfer of concepts and methods. Especially early stages of education in this field are prone to these "transmission" models of learning, where rather fixed ideas are floated into to the learner [START_REF] Kolb | Learning Styles and Learning Spaces: Enhancing Experiential Learning in Higher Education[END_REF] and personal interaction as well as experimentation is limited.

Research on experiential learning yielded four (respectively nine) learning style types that help to develop curricula allowing for a greater variety of learning processes [START_REF] Kolb | Learning Styles and Learning Spaces: Enhancing Experiential Learning in Higher Education[END_REF]. The consequent goal is to expose students to a variety of learning opportunities related to different learning styles in order to foster the individual realization of preferred learning processes in different course formats. Adequate learning processes may yield in turn that students immerse themselves into the activity being fully concentrated, absent-minded and even losing all sense of time. These characteristics pertain to what Csikszentmihalyi called flow [START_REF] Csikszentmihalyi | Beyond boredom and anxiety[END_REF] and seem desirable for effective and positive learning processes in institutions [START_REF] Summers | On undergraduate education[END_REF][START_REF] Clinton | The Studio experience at the University of Georgia: an example of constructionist learning for adults[END_REF].

A second starting point of this article is the notion of the hand-brain-connection rooted in the work of Penfield and Rasmussen [START_REF] Penfield | The cerebral cortex of man; a clinical study of localization of function[END_REF] and its implication for learning highlighted by Papert's theory of constructionism [START_REF] Papert | Situating Constructionism. Constructionism[END_REF]. This theory may be summarized as learning-by-making and emphasizes that the material used during the learning process is decisive for deep engagement in the task [START_REF] Gauntlett | Creative explorations: new approaches to identities and audiences[END_REF], hence for entering the state of flow. The outlined conceptual building blocks are merged into three subsequent research questions.

1. Do different course formats, implying different learning styles, impact students' experience of flow? 2. How does course material impact flow? 3. How is flow linked to the learning outcome? Figure 1 summarizes these questions and the given context. The research questions are intended to be explorative.

Fig. 1. Conceptual framework

The rest of the paper is structured as follows. We will give a brief review on experiential learning and flow theory first. A subsequent section provides an overview on the method and three case studies. Finally, preliminary findings and conclusions are discussed.

2

Theoretical Background

Experiential Learning

Experiential learning accentuates the learning process including the total person, e.g. their behavior, emotions and perceptions [START_REF] Kolb | Learning Styles and Learning Spaces: Enhancing Experiential Learning in Higher Education[END_REF]. Knowledge is therefore created due to two distinct learning processes: The grasping and the transforming of experience [START_REF] Kolb | Experiential learning: experience as the source of learning and development[END_REF]. Grasping may be conceptualized as a continuum between concrete experience and abstract conceptualization. Transforming spans from active experimentation to reflective observation.

Combining both process dimensions yields the classical four learning styles (diverging, assimilating, converging, and accommodating) [START_REF] Kolb | Learning Styles and Learning Spaces: Enhancing Experiential Learning in Higher Education[END_REF] that can be expanded by the work of Abbey et al. [START_REF] Abbey | Variations on a Theme by Kolb: A New Perspective for Understanding Counseling and Supervision[END_REF] into nine styles [START_REF] Kolb | Learning Styles and Learning Spaces: Enhancing Experiential Learning in Higher Education[END_REF]. We will reconsider these learning styles in order to classify the case studies in section 3.

Flow Theory

The state of flow is strongly linked to positive emotions and can be attained when task requirements and the abilities of the person match, the task is clearly structured, there is immediate feedback, and concentration is undisturbed [START_REF] Csikszentmihalyi | Beyond boredom and anxiety[END_REF][START_REF] Drenger | Does Flow Influence the Brand Image in Event Marketing[END_REF]. Experiencing flow during learning processes is supposed to be linked to improved learning outcomes [START_REF] Shernoff | Student engagement in high school classrooms from the perspective of flow theory[END_REF]. Three major dimensions of flow are the control of the activity (control), the absence of mind during the activity indicated e.g. by losing the sense of time (absentmindedness) and being focused on the activity (concentration) [START_REF] Drenger | Does Flow Influence the Brand Image in Event Marketing[END_REF]. However, most studies of flow in education seem biased towards computer based games and neglect other types of "material" like physical objects [START_REF] Procci | An Examination of Flow and Immersion in Games[END_REF].

Method and Case Description

We selected a case study approach due to the explorative nature of the study and multiple cases in order to explore contrasting differences concerning the learning types and material [START_REF] Voss | Case Research in Operations Management[END_REF]. The underlying conceptual framework, in accordance to Miles and Huberman [START_REF] Miles | Qualitative Data Analysis: An Expanded Sourcebook[END_REF], is displayed in Figure 1. Data was collected by questionnaires, observations, and interviews with students. Table 1 illustrates the sampling logic and summarizes all three cases.

Results

Preliminary findings indicate that students experience a high level of flow when experimenting with physical objects especially when combining it with technical problem solving (case 1). However, even more abstract and reflective settings like in case 2 evoke flow-like experiences. The descriptive statistics in Table 2 give evidence for this observation. The measurement is based on questionnaires with four point scales (1 -strong agreement … 4strong disagreement). It is furthermore observable from Table 2 that the utilization of physical material tends to yield positive emotions ("fun") among students. An independent sample t-test showed a significant difference between the means of PS and PPC, t(101) = 2.775, p = .01 for the item "the exercise was fun". The eta square index (η² = .07) indicated a medium effect size. Furthermore, most participants agree that physical 3D material helps them to express thoughts and explore complex technical systems. Participants for the LSP case were convinced that 3D models evoke richer communication (M = 1.63). One participant stated: "I can use this serious play in creative discussion, where flip charts are too abstract." Someone added that the models help when … "defending your own ideas".

Table 2. Descriptive Statistics

Item

However, an estimated participants share of 10 to 15% tend to feel unconvertible using physical objects based on Lego bricks. One participant, who was certainly not in the state of flow according to his answers in the questionnaire, stated that he… "[felt] like a child" and suggested "to use serious play for school and not for graduate students".

The learning outcomes are more difficult to grasp. Despite good overall evaluations, some participants indicate that formats with a high degree of concrete experience and active experimentation are fun (case 1 and 2) but the value of the learning remains unclear or too time consuming to be achieved. An example may explain this line of reasoning: A group of students were trying to build a particular production system (case 1). They had spent more than 25 extra hours additional to their class experimenting in a mind-absent flow and were driven by unnecessarily ambitious plans for a fully automated system, but failed to implement their plan with the available material. They decided to quit the exercise and asked for a final consultation with their supervising tutors in early January 2012. Throughout the consultation the students explored their tendency to over-engineer the system and made up their mind for a much simpler solution in order to complete the course. This was apparently a painful experience for the students since they invested long hours into their first concept. However, the most remarkable quotation during the final presentation was the following.

"The most important learning of this course took place when we failedto recognize that we were too ambitious and how much it had cost us. That is certainly something useful for the future."

Further evidence for these unintended learning outcomes can be found in an earlier edition of case 1 in 2011. A participant stated: These insights are certainly some of the basic issues explained in every standard course on project management. However, the self-exposure to a project that is not successful since it lacks these fundamentals seems to provide a suitable alley for students towards really understanding what the course is actually about.

"I did

Discussion and Conclusion

Finally, we may return to the research questions. The first question asked if different course formats impact students' experience of flow. We conclude a tentative yes: Active experimentation is a supportive condition to enter the state of flow but it is not a sufficient feature. We found flow also in more abstract and reflective situations. As to the second question, we conclude that material has an impact on entering the state of flow. Especially the modular structure of physical objects allows for an easy entry into the learning process and provides enough complexity to cope with higher levels of skill and abstraction. However, we observed a notable level of cynicism among some participants, which is at least partly due to utilized material. Other researchers [e.g. 19] observed the same issue and argued that cynicism is due to the blurring of the border between private and professional life. We may add that not every course format suits every student due to different learning styles and it is therefore rather simple to derive from the obvious and have objections against using plastic bricks.

Furthermore, our results suggest that flow is linked to the learning outcome (research question 3). The link is established in a rather unexpected manner since high levels of flow yield learning with a scope different to the intended (case 1). From a learning perspective we see a strong need to further enable participants taking responsibility of their own learning when finding themselves in an environment fostering active experimentation and reflecting. We were lucky to find a striking example were high flow and experience based learning was successfully transferred into a new task. However, such success stories need to be further studied in order to give this opportunity to more students. Despite all limitations of this study, we see a strong argument for physical objects in industrial engineering education and support for the theory of constructionism. Nonetheless, there is a strong need to further elaborate our findings and to study also combinations of physical and digital "cyber" objects in the future.

Figure 2

 2 gives an impression of students building and programming their model. Data is sampled from five runs of the course involving approximately 90 students since 2009. Case 2 belongs to an advanced course on leadership skills. Participants work in heterogeneous teams to model a shared understanding of leadership including the various facets of the topics, their personal experience and perceptions. Modeling is realized by means of abstract physical metaphors. The process utilizes a method based on Lego Serious Play (LSP)[START_REF] Gauntlett | Creative explorations: new approaches to identities and audiences[END_REF][START_REF] Tröger | Serious Games as a Transfer Method in Industrial Management and Engineering[END_REF][START_REF] Rasmussen | When You Build in the World, You Build in Your Mind[END_REF]. Figure3gives a workshop-impression. The analysis makes use of data from two courses with 25 students since autumn 2011. Case 3 is the exercise of an intermediate course on production planning and control (PPC). Students learn e.g. how to calculate economic lot sizes, use a standard ERPsystem and interpret characteristic curves of logistics and production systems. The course is established for almost ten years and mainly held by the second author of this paper. Our in-depth analysis includes 15 participants from the summer term 2012.

Fig. 2 .Fig. 3 .

 23 Fig. 2. Students working on their production system (case I)

Table 1 .

 1 Case Overview

		Case I: PS	Case 2: LSP	Case 3: PPC
	Material	3D	3D	2D
		(Lego bricks, sen-	(Lego bricks)	(paper and pencil,
		sors and actuators,		computer)
		computer)
	Experience	concrete experience	between ce and ac	abstract conceptual-
	grasping	(ce)		ization (ac)
	Experience	active experimenta-	between ae and ro	reflective observa-
	transforming	tion (ae)		tion (ro)
	All cases have in common that they represent the exercise module of courses that
	contain classical "transmission" modules with oral lectures as well.
	Case 1 is part of a course that teaches the fundamentals of facility planning and sys-
	tems engineering, including requirements engineering and project management. Stu-
	dents are required to build in teams a production system (PS) based on Lego
	Mindstorms [1, 16, 17].

  not learn too much from the game itself. What I learned was the importance of good and organized communicationto do intermediate presentations and define a project plan. I found it interesting to see how different roles evolved during the project. There were leaders, thinkers, implementers etc. […] not everybody is able to lead a project." Hence, does this learning prove any value? Fortunately we were able to do a follow up interview in July 2012 with a member of the previously mentioned "overengineering-group". After participating in the Lego-exercise until February 2012 he had to complete a complex case study concerning facility planning in teamwork from April until July 2012. He suggested the following among several other insights transferred from case 1 to the new task. "The tendency of getting obsessed with details was resolved; problems were tackled in a more pragmatic manner. Due to strict milestones and central project controlling (and the related pressure) results were always delivered […]."


Nikos Papathanasiou

Christos Emmanouilidis

Petros Pistofidis
email: pistofid@ceti.gr

Dimitris Karampatzakis

Context Aware E-Support in E-Maintenance

Keywords: E-support, e-maintenance, mobile learning, e-training, context awareness

Mobile learning is a powerful addition to the toolset offered by e-Learning solutions. It can extend current e-Learning benefits to provide support and training everywhere, anytime and to anyone registered to have access and with affordable costs. Mobile devices with substantial computational, networking and storage capabilities are ubiquitous today. However, attempts to employ them in training are mostly addressing educational needs of end users with existing competencies in computing, such as students. We propose the development of a specially built mobile learning solution with the aim to provide e-Support to technicians within an e-Maintenance framework. This system will be backed and collaborate with a Learning Management System platform in order to provide on the spot aid and adequate supporting content to maintenance personnel.

Introduction

The reported research work aims to combine an integrated e-Maintenance framework with e-Training based on web and supporting mobile devices. The e-Maintenance framework realizes platform-independent Condition-Based Maintenance by integrating an intelligent sensor network deployment, a Computerised Maintenance Management System (CMMS), a knowledge management system and an intelligent maintenance advisor, in the context of the WelCOM project [START_REF] Pistofidis | A Layered E-Maintenance Architecture Powered by Smart Wireless Monitoring Components[END_REF]. It can provide an advanced, proactive type of Maintenance support that processes maintenance information throughout the plant, transparently providing it to anyone with authorized access. In this setting, our main aim is to study to what extend the e-Training system can be coupled with the other e-Maintenance components so as to provide context-aware support to shop-floor maintenance personnel and basic training on the system use to stakeholders.

E-Learning can be an effective way to train industrial employees, irrespective of their exact work placement due to some key attributes:  First, it can offer time and location independent training, which has significant merit in workforce training. Industrial staff is hardly in position to attend formal classes and any probable pressure to become familiar with a new e-maintenance system could easily lead to overkill and negative attitude against the whole system.

 Second, e-learning can provide a stimulating, intuitive and straight to the point way of delivering technical knowledge that can adapt and readily fit in the everyday schedule of a modern industrial plant.  Third, e-learning content can be formatted and delivered directly to mobile devices as context-dependent technical support. This has the potential to accelerate the familiarity and facilitate the acceptance of the new training system by maintenance staff.

Modern mobile devices support connectivity, autonomy and offer computing and graphics capabilities that can be exploited to create appealing training environments at affordable cost. In the present work, supporting technical material is provided by a web server running a LMS (learning management system). The aim is to make it easy to locate directly the knowledge part that is requested on the mobile device and to update content regularly to reflect changes in maintenance practice. Our aim is to seek to adhere to elearning standards, so as to increase the reusability of the content. Lately, our experimentation is focused on methods to seamlessly interconnect a customized mobile interface with the server side e-learning infrastructure. Based on this interconnection and on context-dependent data available from other WelCOM components, we will be able to provide contextualised support to the shop floor staff. Context may refer to different categories, such as user, environment, system, social and service [START_REF] Emmanouilidis | Mobile Guides: Taxonomy of Architectures, Context Awareness, Technologies and Applications[END_REF]. In an industrial maintenance setting, the context can be quite wide. It may comprise information about specific machine, sensor readings, type of machinery operation, operation and maintenance history, type of maintenance action, possible failure, staff profile and role, relevant actions. This information should be communicated between e-Support and the rest of WelCOM e-Maintenance framework tools in a transparent and unobtrusive way, in order to simplify the delivered e-Support interface. Thus, e-Support is adequately offered via web services. Furthermore we seek to employ multiple modalities in human-computer interfaces, including speech interfaces.

e-Learning and mobile Learning

In the last decade e-Learning has gained popularity and ubiquity, with relevant research carried out towards a wide spectrum of applications. Interconnectivity offered by ICT pushed the way for the implementation of solutions based on learner-centric Learning Theories, as well as to learning by direct interaction with others, typical in collaborative constructivism and groupware learning. Application of Constructivism and Activity Theory to mobile learning (m-Learning) in relation to acceptance by learners has been studied through questionnaires, highlighting significant advantages, such as learner initiative, improved interactivity and autonomy [START_REF] Liaw | Exploring Learners' Acceptance Toward Mobile Learning / Technology Acceptance in Education[END_REF]. Attempts have also been reported to implement known learning theories to develop 3D multimedia courseware [START_REF] Noordin | Implementation of design and learning theories in multimedia courseware development: Lines & Planes in 3-Dimensions[END_REF]. In research focused on engaging learning environments, Augmented Reality (AR) has been employed to deliver new platforms for easy creation of Virtual Scenes without previous programming knowledge [START_REF] Jee | An augmented reality-based authoring tool for E-learning applications[END_REF]. Serious games are shown to bring significant benefits and personalisation options in order to create highly motivating and engaging learning experiences [START_REF] Oliveira | The Use of Integrative Framework to Support the Development of Competences / Serious Games Development and Applications[END_REF]. Employment of social networks in the Learning process has also been studied. Specifically, Web 2.0 elements, such as participant collaboration and virtual communities were evaluated, noting the connection between social learning networks and the "social constructivism" theory [START_REF] Jones | Social Networks for Learning: Breaking Through the Walled Garden of the VLE. Computational Social Networks[END_REF]. Work with elementary school pupils has shown how critical it is to deal with e-learning not as simply an extension of printed material but as medium with a multitude of advantages to exploit, like interactivity, multimedia and personalisation [START_REF] Huang | Empowering personalized learning with an interactive e-book learning system for elementary school students[END_REF].

E-Learning Standards

The development costs for quality training material can be brought down by the adoption of Learning Standards that will promote content reusability, interoperability and discoverability. However, these standards still seem inefficient to support modern and engaging learnersystem interactions such as multimedia and educational games. An important step to overturn this situation is a project named "Next Generation Learning Environment", carried out by ADL (Advanced Distributed Learning), founders of the SCORM model, one of the most widespread e-learning standards. The primary goal is to provide a standard that will support modern learning experiences, such as games, mobile learning, social networks, learner collaboration and mixed modalities. A straightforward model of integration in Learning Management Systems through improvements in the sequencing procedures has been presented [START_REF]Sharable Content Object Reference Model (SCORM®) 2004 4th Edition Testing Requirements (TR) Version 1.1 2009, Advanced Distributed Learning (ADL) Initiative[END_REF].

Industrial Training

Currently demands for improved system productivity, availability, quality, safety and customer satisfaction, highlight the critical role of maintenance as an indispensable activity in industrial production. A significant number of complex factors must be taken into account in modern maintenance and fuel a demand for advanced ICT solutions [START_REF] Arnaiz | Information and Communication Technologies Within E-maintenance[END_REF]. The potential impact of an e-Maintenance framework on the implementation of a Condition Based Monitoring strategy is significant [START_REF] Jantunen | e-Maintenance: a means to high overall efficiency[END_REF]. Mobile and collaborative technologies are enabling information and services to become available to the shop floor technical personnel, anywhere and anytime [START_REF] Emmanouilidis | Mobile solutions for engineering asset and maintenance management[END_REF]. Furthermore, the concept of a Virtual Factory as an integrated virtual environment that facilitates knowledge and information sharing throughout all industrial production phases is offered as an open alternative to costly proprietary solutions for platform independent monitoring of production assets [START_REF] Sacco | Virtual Factory Manager / Virtual and Mixed Reality -Systems and Applications[END_REF]. A learning engine capable of delivering learning material in the form of 3D knowledge objects to pilots and maintenance technicians in an aviation setting, emphasising access of maintenance technicians to "Learning on Demand (LoD)" instructions and trouble shooting references is an effective training enabler [START_REF] Christian | Virtual and Mixed Reality Interfaces for e-Training: Examples of Applications in Light Aircraft Maintenance[END_REF].

Industrial Maintenance can benefit from a common accreditation framework that will enhance workers mobility, support enterprise recruitment and enhance staff development.

In Europe, such a framework has been set by EFNMS with the definition of competence requirements for maintenance managers and technicians [START_REF] Franlund | Some European Initiatives in Requirements of Competence in Maintenance[END_REF], as well as by the PAS55 specification for optimising Asset Management practice, put forward by the Institute of Asset Management in the UK.

Problem Statement

Developing e-Learning based e-Support for industrial maintenance technicians presents certain challenges:  Mobile devices pose different restrictions due to monitor sizes, lack of keyboards and mice, limited battery life, unstable network connections and sometimes harsh working conditions. Despite the fact that there are devices with high-end characteristics and industrial design, restrictions have to be addressed to create a usable support application.  Learners in a typical e-Learning setting would benefit by presenting the learning material gradually, in small sections, with intertwining comprehension questions so as to evaluate their performance and understanding as they proceed through the courses.

Technicians on the shop floor would find all these as annoying distractions in their effort to access the exact information they need to perform their job as they need precise, on the spot information.  Procedures such as registration, login, course enrolment, searches through a breadth of learning content, are typical in every e-Learning setting. However, they would hinder the work of a technician, even more when he has to interact with other applications, as needed to complete the work orders.

Delivering technical support through mobile devices directly to the technicians on the shop floor, presents some unique benefits that we are planning to exploit:

 Real-time interactions with the supporting material could constitute an invaluable set of information regarding efficiency and appropriateness of the followed procedures and the relevant material. The underlying LMS would record all this information and technicians, engineers or technical managers would have access to it.  Based on the above, a technician could select to attend a section of the e-learning that is relevant to a difficult part of his task. An engineer, supervisor or technical manager could pinpoint support elements that gather the most inquiries and initiate procedures to update and enrich them. As an example, the e-support system can notify the LMS that there are requests for maintenance actions on a specific machine. Based on this, the LMS can inform supervisors or managers and deliver a short web-based support relevant to the machine, so as to reach a better understanding of the problem at hand and possibly improve performance.  Context definition in industrial e-support has not received sufficient attention and is usually restricted to localisation and specific user-context. Having a more thorough definition of context in this domain is among our research goals.  Technically a major challenge we have to face up to is related to the fast and accurate delivery of e-support content to the mobile device. It is clear that under no circumstances this delivery should rely solely on wireless connections, due to number of obstacles, such as metal wall surfaces and roofs that are present in a factory. One solution that was examined initially was to transfer permanently all the supporting material inside the mobile devices. This idea is not satisfactory, first because the volume of this information could easily overload a mobile device and more importantly, it would negate the whole idea of intelligent interaction and collection of feedback by the LMS. Apart from breaking down the content into small entities, the Learning Objects, a potential solution to this problem is for the technician to be provided only with relevant for his job content. Avoiding redundancies on content delivery, all these objects will undergo custom compression procedures before their transfer to the mobile devices so as to minimize latency. Furthermore, a dynamic caching mechanism can be used to temporarily store large content entities, such as videos, to enhance the user experience.  Intuitive environment and simplicity are two prerequisite qualities of the proposed solution, in order to minimize the case of rejection from low ICT-skilled users.

Although the role of the supervisor is crucial and it is enhanced through the whole emaintenance system, the e-support platform is expected to be gradually enriched at such level that it will allow for simple tasks to be performed without further human intervention and authorization. Thus, shop floor supervisors can focus on higher level activities.  Another aspect of simplicity deals with the creation of new content. It is impractical to design a system that will need an ICT expert each time a new element, such as an image, video or technical document has to be added in the supporting database. Therefore, we opt for procedures that will be easily accessible to different staff categories inside an enterprise. The learning support software that will help the creation of new learning objects from raw support data is currently being developed.

A simple sequence diagram, showing the involved processes, invoked by technical staff, is shown in Fig. 1. The above sequence diagram illustrates that the main e-support interaction commences when the technician on the shop floor requests support through the corresponding interface on the mobile device. The native application that is executed on the device proceeds to authorizationcontext definition procedures by requesting the relevant information from the other e-maintenance components (IMA) through web-services. Consequently, the mobile application contacts the corresponding Moodle module that gathers the requested support material from the learning database by searching based on meta-tags of Learning Objects. This material is processed, i.e. compressed by the module and is been transferred to the mobile device to be presented to the technician. Essential in the procedure of delivering the appropriate content to each user is the formation of an extended learner profile that will contain constantly updated information about his knowledge, interactions and performance in theoretic learning and industrial work. This profile defines an important part of the context awareness and should be accessible at any time, so that it becomes possible to use the e-Learning system in order to enrich knowledge in the areas that he deems appropriate. It has to be also available to unit or line managers and maintenance supervisors, so they would have the necessary information to suggest improvements on the supporting material and possibly also on the maintenance policy implementation, with the aim to improve the technicians' performance.

Apart from the learner profile, all the learning and supporting content has to be broken down into fine-grained learning objects. These learning objects must be appropriately described and characterized by tags that will enable their search and their instant identification to be delivered to the field worker. The components of this e-Support system, within the WelCOM e-Maintenance architecture is shown in Fig 2. E-support data will be constantly updated and enhanced through the contribution of both managers and technicians. This purely practical knowledge content is expected to formulate a comprehensive library of information about machines and industrial procedures, organised through meta-tags and learning object interrelations in a way that is suitable to the end users, the technicians. As a step further, this library can be redeployed to other parts or subsidiaries of the industry or even to be traded as an asset with industries that use the same machinery. e-Learning has been integrated in m-learning scenarios in various works. The combination of e-learning with m-learning has been tested in a school setting, in order to provide personalised learning [START_REF] Nedungadi | A new approach to personalization: integrating elearning and m-learning[END_REF]. Our work is differentiated in that (a) it addresses industrial training needs (b) knowledge is treated as Learning Objects that are dynamic so as to be updated with user-contributed content, e.g. by the technicians. Furthermore, the nature of the industrial processes themselves makes the provision of all assistive functions, including e-support, fundamentally important. Although a minor latency delay may be tolerated, the delivery of fast and contextually relevant support through mobile devices is one of the requirements in the WelCOM project. The placement of the e-support as a single module inside an integrated e-maintenance framework and the interconnectivity between the autonomous modules though web-services is also considered to be a key contribution.

Further work

Currently, our focus is the examination in close collaboration with experts from the industry, of the latest SCORM and IMS standards and composition of a prototype model for our learning objects that will serve the requirements of our project. The development of the Moodle e-Support module has started based on the latest style and security guidelines.

Conclusion

Placing an e-Learning system as part of a working procedure in a demanding and dynamic setting, such as supporting industrial maintenance technicians, is a considerable challenge and the evaluation of its educational value is among our objectives. E-Support integration should be transparent, intuitive and offer streamlined access to contextually relevant content. It is considered that the integrated e-Training system, comprising both e-Learning and e-Support, would facilitate the adoption of a modern e-Maintenance system. Maintenance staff will be in position to employ more efficiently the offered technological solutions with the provision of context-dependent support and closely coupled e-Learning.

Fig. 1 .

 1 Fig. 1. E-Support Sequence Diagram

Fig. 2 .

 2 Fig. 2. WelCOM Training Portal Support Components

Acknowledgements

The author wish to acknowledge the enthusiasm and contribution by the WelCOM (GSRT grant 09SYN-71-856) project partner's staff, namely KLEEMANN Lifts, National Research Foundation, Prisma Electronics, GDT SA and ATLANTIS Engineering (welcomproject.ceti.gr).