Brice Trouillet
email: brice.trouillet@univ-nantes.fr

Stephen Jay

The complex relationships between Marine Protected Areas and Marine Spatial Planning: towards an analytical framework

Keywords: Marine protected area, Marine spatial planning, Ocean management, Ocean policy, Zoning, Multiple-use, Conservation, England, Germany

Systems of marine spatial planning (MSP) are now being introduced in many countries, with the intention of more rational arrangement of maritime uses and interests. It would be expected that marine conservation, especially the designation of marine protected areas (MPAs), would be incorporated into MSP. In practice, however, MSP and MPA designation are often taking place in parallel to each other, with relatively little integration between them, partly because of marine conservation's longer history and established institutional frameworks which cannot be simply subsumed into MSP processes. There are, nonetheless, a series of options available by which the two sets of process could be more closely linked. These options can be conceptualised temporally, by, for example, MSP improving the status of preexisting MPAs, or spatially, by, for example, facilitating the creation of multiple-use MPAs. These difficulties and possibilities are illustrated through two national European experiences.

Introduction

Marine spatial planning (MSP) is becoming increasingly recognised as a means of managing the marine environment and maritime activities more coherently than in the past [START_REF] Ehler | Maritime/Marine Spatial Planning at the Interface of Research and Practice[END_REF]. It introduces a more explicit spatial dimension to the regulation and management of activities, with the aim of allocating space more clearly to sea uses, so that they do not conflict with each other, make the best use of resources and minimise their environmental impact [START_REF] Douvere | The importance of marine spatial planning in advancing ecosystembased, sea use management[END_REF][START_REF] Gilliland | Key elements and steps in the process of developing ecosystem-based marine spatial planning[END_REF]. Marine conservation is generally reckoned to be one of the interests that should be included in MSP exercises, as economic activities should not compromise valuable habitats and species. Designating marine protected areas (MPAs) through systematic conservation planning [START_REF] Margules | Systematic conservation planning[END_REF][START_REF] Sarkar | Biodiversity Conservation Planning Tools: Present Status and Challenges for the Future[END_REF]) is a strong spatial mechanism for protection. This corresponds closely to the area-based rationale of MSP, and it is reasonable to assume that in a marine spatial plan, MPAs would sit alongside spatial allocations for economic uses, such as mineral extraction, shipping, fishing and energy supply [START_REF] Agardy | Mind the gap: Addressing the short comings of marine protected areas through large scale marine spatial planning[END_REF]. Moreover, it would be expected that MPAs would enjoy protection from these other uses, by creating no-take zones with regard to fishing, for example.

A logical and scientific approach, therefore, would be to integrate the planning of MPAs and other uses within a MSP process, so that their various demands can be considered alongside each other and an optimum, balanced arrangement of uses can be achieved, with attention given to the most important ecological sites through MPAs designation. In this model, MPAs are both incorporated into and prioritised through an all-encompassing system of MSP [START_REF] Craig | Marine Protected Areas, Marine Spatial Planning, and the Resilience of Marine Ecosystems[END_REF][START_REF] Harris | Systematic Conservation Planning as a Tool to Advance Ecologically or Biologically Significant Area and Marine Spatial Planning Processes[END_REF]. However, it would appear that other logics are at work, notably when a real world-MSP is dominated by a neoliberal blue growth [START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF]; this calls into question the extent to which the above ideal is being seen in practice and, possibly, its desirability. In addition, marine conservation efforts and MPAs have longerstanding conceptual roots and institutional processes of their own that may not be easily subsumed into MSP processes and that may suggest alternative relationships with MSP.

It may even be that MSP and MPA designation are diverging processes. Nonetheless, it appears that they also have a potential for co-evolution [START_REF] Jones | Governing Marine Protected Areas: Resilience through diversity[END_REF][START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF]. For example, [START_REF] Vaughan | Marine protected areas and marine spatial planning -allocation of resource use and environmental protection[END_REF] set out how MSP can assist MPAs, as well as vice-versa: "Recognising that MPAs might be best treated as one part of a unified conservation strategy means that MSP needs to be harnessed to create better, more durable MPAs. Conversely, incorporating MPA planning into MSP can reduce conflict for marine space through optimization of that space." [START_REF] Jones | Governing Marine Protected Areas: Resilience through diversity[END_REF] also argues "Whilst it is widely agreed that an important objective of MPAs is to contribute to MSP, it is important to bear in mind that there are many different views on what MSP means and how MPAs should be designed to contribute to it." In addition, [START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF] have looked at other aspects of the relationships between MSP and MPAs, such as potential convergences in terms of governance, conflicts, integration, participation, justice and uncertainty. This paper explores further the ways in which MPAs and MSP have developed alongside and in relation to each other, with reference, firstly, to their scientific and policy-based backgrounds (part 2), leading to a discussion of their interacting dynamics (part 3). Building upon previous studies, this contribution aims to reconsider the perspective on these relationships by developing a framework of their spatial and temporal relations. Secondly, this paper applies this analytical framework to two national cases of MSP and MPA processes, throwing further light on the uneasy relationship between them (part 4). Finally, the implications of the complex relationships between these processes are discussed (part 5).

A "chicken-or-egg" problem

The need to manage and protect the seas has recently led to various approaches supported by tools and policies that are not necessarily in keeping with each other and that raise the question of which should come first.

Marine Spatial Planning

Rooted in initiatives dating from the late 1970s, MSP is a relatively new process that has been widely disseminated over the two last decades to the point that by 2017 approximately 40 countries were carrying out MSP activities that produced over 60 plans completed at various scales [START_REF] Ehler | World-Wide Status and Trends of Maritime/Marine Spatial Planning[END_REF]; these figures have since considerably increased. One of the most significant developments was the adoption of a European Union Directive requiring coastal Member States to implement MSP (EPC, 2014). However, MSP is best understood as a 'soft process' which is open to various interpretations and means of implementation [START_REF] Collie | Marine spatial planning in practice[END_REF][START_REF] Domínguez-Tejo | Marine Spatial Planning advancing the Ecosystem-Based Approach to coastal zone management: A review[END_REF][START_REF] Ehler | Maritime/Marine Spatial Planning at the Interface of Research and Practice[END_REF][START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF][START_REF] Trouillet | Reinventing marine spatial planning: a critical review of initiatives worldwide[END_REF]. Hence only a general definition can encompass all understandings, focusing on a few key principles that constitute the core of MSP. The most common definition of MSP is: "a public process of analyzing and allocating the spatial and temporal distribution of human activities in marine areas to achieve ecological, economic, and social objectives that usually have been specified through a political process1 ." [START_REF] Ehler | Marine spatial planning: A step-by-step approach toward ecosystem-based management[END_REF]. Originally conceived as a means of supporting marine conservation [START_REF] Agardy | Ocean Zoning: Making Marine Management More Effective[END_REF], MSP has been more recently oriented towards multi-use planning of marine space [START_REF] Degnbol | Spatial planning on the North Sea: A case of cross-scale linkages[END_REF][START_REF] Douvere | The importance of marine spatial planning in advancing ecosystembased, sea use management[END_REF]Douvere and Ehler, 2009a), or on the need to support "blue growth" [START_REF] Frazão Santos | How sustainable is sustainable marine spatial planning? Part I-Linking the concepts[END_REF][START_REF] Qiu | The emerging policy landscape for marine spatial planning in Europe[END_REF][START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF]. However, its initial environmental imperative still characterises MSP and distinguishes it partly from terrestrial planning [START_REF] Kidd | From the Land to Sea and Back Again? Using Terrestrial Planning to Understand the Process of Marine Spatial Planning[END_REF][START_REF] Kidd | Taking Account of Land-Sea Interactions in Marine Spatial Planning[END_REF][START_REF] Smith | The integration of land and marine spatial planning[END_REF]. Consequently, MSP is often presented as an essential means and tool to achieve "ecosystem-based sea use management", with reference to wider notion of ecosystem-based management [START_REF] Ansong | An approach to ecosystem-based management in maritime spatial planning process[END_REF][START_REF] Domínguez-Tejo | Marine Spatial Planning advancing the Ecosystem-Based Approach to coastal zone management: A review[END_REF][START_REF] Long | Key principles of marine ecosystem-based management[END_REF][START_REF] O'higgins | Challenges and Opportunities for Ecosystem-Based Management and Marine Spatial Planning in the Irish Sea[END_REF]. Nonetheless, in this regard, it should be recognised that an ecosystem-based approach can be understood either as a fundamental goal (hard sustainability) or as one element amongst others (soft sustainability) [START_REF] Frazão Santos | How sustainable is sustainable marine spatial planning? Part I-Linking the concepts[END_REF][START_REF] Qiu | The emerging policy landscape for marine spatial planning in Europe[END_REF][START_REF] Jones | Governing Marine Protected Areas: Resilience through diversity[END_REF]Jones et al., 2016).

Marine Protected Areas

The concept of MPAs similarly has universal ambitions and can be considered to belong to the same family of general measures as MSP. The Convention on Biological Diversity (1992) promoted the concept of "protected area" at the international scale, defined as "a geographically defined area which is designated or regulated and managed to achieve specific conservation objectives"2 . This understanding was complemented by [START_REF] Dudley | Guidelines for Applying Protected Area Management Categories[END_REF]: "A clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values". An important stage in the creation of MPAs was the World Summit on Sustainable Development (2002), at which a quantified objective was set, that 10% of the sea surface should be designated as MPAs by 2010. This deadline was extended to 2020 by the 2010 Nagoya Conference (target n°11 of the Aichi Biodiversity Targets). MPAs are nowadays considered to be a mainstream tool for achieving marine conservation [START_REF] Agardy | Dangerous targets? Unresolved issues and ideological clashes around marine protected areas[END_REF] and quantitative facts are presented as testimony to their success: for example, 16,924 MPAs had been established around the world by 2020, covering 26.9 million km², corresponding to approximately 7.4% of the global ocean and just over 17% of areas within national jurisdiction (UNEP-WCMC and IUCN, 2020). In 1994, the International Union for Conservation of Nature (IUCN) defined six categories of protected areas with a wide range of objectives from strict protection to the sustainable use of natural resources [START_REF] Dudley | Guidelines for Applying Protected Area Management Categories[END_REF] (Table 1). According to an evaluation of the compatibility of maritime activities with each category of MPAs [START_REF] Day | Guidelines for applying the IUCN Protected Area Management Categories to Marine Protected Areas[END_REF] (Table 1), between two and five of the categories might be considered as "Multiple-use MPAs". It is necessary to distinguish these categories from the names given to MPAs (national park, sanctuary, etc.) [START_REF] Dudley | Guidelines for Applying Protected Area Management Categories[END_REF]. Practically speaking, and without a clear definition, it would seem that a Multiple-use MPA should be considered as a "large-scale MPA" where activities are allowed with some restrictions with regard to access and certain uses in all or part of the area (possibly with zoning, including nested no-take zones) [START_REF] Garcia | Les aires marines protégées dans la gestion des pêches[END_REF][START_REF] Gascuel | Etude sur l'état de l'art du rôle des[END_REF][START_REF] Kelleher | Guidelines for Marine Protected Areas[END_REF]. This would be close to the 6 th IUCN category, or possibly the 5 th , though this is more difficult to apply in the marine context at present [START_REF] Day | Guidelines for applying the IUCN Protected Area Management Categories to Marine Protected Areas[END_REF]. Also, one should keep in mind that some countries (France for instance; see MEDDTL, 2012), may have developed further the IUCN categories by promoting MPAs that are focused on sustainable activities, scientific or educational purposes, etc. Moreover, account should be taken of the different situations that may complicate the role of MPAs: (i) the presence of several IUCN categories within a single MPA, (ii) the combination of terrestrial and marine protected areas, (iii) the nesting of (marine) protected areas, (iv) the potential for vertical zoning of MPAs [START_REF] Day | Guidelines for applying the IUCN Protected Area Management Categories to Marine Protected Areas[END_REF].

Can MSP and MPAs produce the same results?

MSP and MPAs are not necessarily aiming for the same results. But potentially, there is coevolution [START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF] or convergence between the two systems [START_REF] Vaughan | Marine protected areas and marine spatial planning -allocation of resource use and environmental protection[END_REF], that may produce the same results. In a first scenario, if well-defined, a large Multipleuse MPA may be able to play practically the same role as an area covered by an "ecosystembased marine spatial plan". MPAs could thus be viewed as a substitute for MSP or indeed as the basis for maritime planning and strategy. Conversely, in a second scenario, a network of MPAs may arise from a MSP process, especially through the application of zoning. In this situation, MPAs could be perceived as simple areas for marine conservation that are zoned within a marine plan, just as other ocean uses might be3 . Thus MSP would constitute a framework for the creation of a MPA network and the role of MPAs may be reduced to reserves or "no-take zones" in the wider marine area. Hence these tools may follow different paths that raise a "chicken-or-egg" problem. Alternatively, MSP and MPAs may appear to be different sides of the same coin. Accordingly, one may ask: which is part of which?

Along with [START_REF] Gubbay | Marine Protected Areas in the context of Marine Spatial Planning -discussing the links[END_REF] and [START_REF] Blaesbjerg | Marine Spatial Planning in the Nordic region -Principles, Perspectives and Opportunities[END_REF], it is generally considered that MSP has a broader remit and:

-provides "an overall framework for managing activities, whereas MPAs are one of the management tools (…)" [START_REF] Gubbay | Marine Protected Areas in the context of Marine Spatial Planning -discussing the links[END_REF]; -is "likely to include an element of zoning, with MPAs incorporated into such schemes as areas where the conservation of biodiversity has priority. Some of these may be "no-take zones", whereas others may allow a variety of extractive activities to take place, but only under certain conditions." [START_REF] Blaesbjerg | Marine Spatial Planning in the Nordic region -Principles, Perspectives and Opportunities[END_REF].

Thus MSP forms a framework in which MPAs should be developed, both from a strategic point of view (planning as a policy tool) and from a spatial point of view (planning as a technical tool). This may be summarised as follows: "Multiple use areas with Sustainable Development objectives are probably more correctly described as areas subject to Marine Spatial Planning whereas multiple use areas with biodiversity conservation objectives are probably more correctly described as MPAs" [START_REF] Gubbay | Marine Protected Areas and Zoning in a System of Marine Spatial Planning[END_REF]. Despite these points, there may be no simple answer to the "chicken-or-egg" question for two main reasons. This is firstly because MPAs are diverse and MSP is a soft and flexible process which does not systematically produce zoning, depending on the underlying approach to planning. Secondly, this is because the answer involves the political issue of priority between marine conservation and economic growth [START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF][START_REF] Kidd | From the Land to Sea and Back Again? Using Terrestrial Planning to Understand the Process of Marine Spatial Planning[END_REF]). The answer is even less obvious given that, according to [START_REF] Caveen | MPA policy: What lies behind the science?[END_REF] discussing MPAs, the assumptions and ideological postures are often hidden behind "scientific" arguments. This seems to be particularly relevant when, in the EU for instance, Integrated Maritime Policy (IMP) encompasses several policies with specific legal obligations (Natura 2000 network, Marine Strategy, Marine Spatial Planning, Blue Growth, Common Fisheries Policy, Renewable energy…) and has also to play with different priorities and national interests.

Finally, looking beyond the "chicken-or-egg" problem to consider the complex relationship between MSP and MPAs systems is crucial. Indeed, the combined or separate use of these two processes is a pressing question in everyday practice. For instance, [START_REF] Trouillet | Reinventing marine spatial planning: a critical review of initiatives worldwide[END_REF] showed that in hard sustainability MSP systems, MSP tends to be envisaged as a 'zoom-out' tool to take into account pressures outside an existing MPAs network, while in soft sustainability MSP systems, MPAs are rather considered as a single-sector use at the same level than other single-sector uses. So that in the first case, the two processes of MPAs and MSP are used jointly, whereas in the second case they are by essence envisaged separately. This also points to the question of effectiveness of the two systems. Again, this could be seen as being achieved jointly or separately. In some cases, MSP may provide leverage to make conservation more effective in "paper parks". In other cases, MSP may result in a weak document or a document that is not applied or is poorly applied [START_REF] Stelzenmüller | Evaluation of marine spatial planning requires fit for purpose monitoring strategies[END_REF][START_REF] Varjopuro | Evaluation of Marine Spatial Planning: Valuing the Process, Knowing the Impacts[END_REF].

Parallel or converging?

Accordingly, links between MPAs and MSP are diverse and complex, due to their different purposes, ideological backgrounds and varying territorial circumstances. For instance, [START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF] established that MSP and MPAs can take different roles depending on the type of MSP, whether it is on the side of ecosystem-based approach or supporting maritime economic development. From a theoretical point of view, these relationships can be explored from an alternative perspective offering a complementary outlook: temporal and spatial. So, here again, we do not claim to capture all the possible relationships between MSP and MPAs, but rather to propose a framework -still partial-that helps to think about these relationships from the only two perspectives of space and time. Figure 1 presents some of the relations between MSP and MPAs schematically along temporal and spatial axes, reflecting the two main kinds of MPAs, (whilst ignoring the diversity of MSP). Using this figure, we propose a tool for systematic analysis of the relationships between MSP and MPAs from a twinned temporal and spatial point of view. This should be regarded as a draft that provides food for thought.

From a temporal point of view

Although MSP and MPA processes are relatively recent and still in progress, marine environmental awareness has been established for some time. As far as the development of MSP is concerned, in the EU for instance, IMP emerged in the form of a "green book" in 2006 then, after public consultation, with a "blue book" in 2007 and formally in 2012 with the Limassol Declaration. This policy led to a reorganisation of the Commission services, with the enlargement of DG Mare's responsibilities and the establishment of a steering structure, the "Common Implementation Strategy" [START_REF] Chaigneau | Mer et gestion intégrée: analyse du cas français dans son contexte européen[END_REF]. One of the three tools of this policy is MSP, with different drivers that are difficult to reconcile (Qui and [START_REF] Qiu | The emerging policy landscape for marine spatial planning in Europe[END_REF][START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF]. However, MSP has lagged behind notably when compared to the development of MPA networks which has been in progress since the beginning of the 2000s and has gathered greater momentum following the Malahide Conference (European Commission, 2007). Furthermore, the EU's Marine Strategy Framework Directive (presented as the "environmental pillar" of the IMP) dates from 2008, while that on MSP was only adopted in 2014. In other words, MSP has been slower than the advance of MPAs in the European context, except where Member States have taken their own initiatives ahead of the European timetable. In all likelihood, the fact that the designation of MPAs has mostly preceded MSP compromises the scope of MSP and creates some practical difficulties (Figure 1a):

-Reserves and No-take zones could represent a constraint for the MSP process because the network of MPAs, effectively zoned, has to be "taken as it is". Conversely, it could be an opportunity for MPAs insofar as "the development of a system of MSP will be an opportunity to expand the role and design of individual and networks of MPAs [if MPAs are to be a type of "use zone" within MSP] and clarify this role to other user groups." [START_REF] Gubbay | Marine Protected Areas in the context of Marine Spatial Planning -discussing the links[END_REF]). -As suggested for instance by [START_REF] Ban | Recasting shortfalls of marine protected areas as opportunities through adaptive management[END_REF], multiple-use MPAs could present an opportunity for MSP insofar as the experience gained from the MPA process improves MSP or if synergies are encouraged (if MSP substitutes or complements MPAs), depending on the characteristics of the MPAs (size, efficiency, partnership quality, etc.). It could also increase the risk of biasing the MSP process, if that MSP is intended to balance different interests.

This temporal shift is familiar in spatial planning in general, because planning rarely begins with a clean sheet. This suggests at least a need to re-examine the MPAs strategy, if appropriate, by replacing it with the wider perspective of strategic planning of the oceans. This could also be the case for pre-existing sectoral planning and other forms of planning at a lower level than MSP. But, in the case of a temporal shift, the main problem would be if the policy context did not provide a clear direction, possibly due to political inability to decide or a lack of political will in the context of subsidiarity.

Furthermore, the basic difference of timescales between MSP and MPA processes (adapted to the short/mid-term for the former and the long term for the latter) inevitably introduces problems. For instance, if MPAs are fixed in maritime plans due to long-term conservation objectives, they risk hindering further discussion during plan-making.

From a spatial point of view

There are several possible ways of interpreting technically the spatial aspects of links between MSP and MPAs, with reference to: types of MPA in relation to the categories mentioned above, land-sea integration, geographical scale, considerations beyond national jurisdiction, transboundary issues, state-of-play of sectoral planning, etc. Indeed, there is a wide range of possible connections between MSP and MPAs that will be influenced by these factors and their combinations. Without attempting to cover all of them, Figure 1b presents an initial characterisation of five cases exploring the roles that MPAs (summarized in two types: (i) No-Take zones / Reserves, (ii) Multiple-use areas) could play:

-If MSP is comprehensive, MPAs may considered to be a "sectoral use" (type i) on the one hand, or would allow good integration of management objectives (type ii) on the other hand, especially if its scale approaches that of the MSP perimeter; -If MSP is partial, MPAs could provide an effective extension of MSP outside MSP areas (types i and ii), possibly with more environmental requirements than MSP (type ii); -In the context of land-sea integration, Protected Areas straddling the land and the sea could provide a continuum that may help to strengthen the links between land and sea for certain conservation planning matters (type i) or for some broader concerns (type ii); -In the context of areas beyond national jurisdictions (ABNJ), MPAs could provide an extension (types i and ii). This could be seen as contributing to a creeping jurisdiction process, which also raises the question of applicability beyond national jurisdictions; their status may be unclear whatever the type of MPAs [START_REF] Ardron | Marine spatial planning in the high seas[END_REF][START_REF] Freestone | Can existing institutions protect biodiversity in areas beyond national jurisdiction? Experiences from two on-going processes[END_REF][START_REF] Gjerde | Regulatory and Governance Gaps in the International Regime for the Conservation and Sustainable Use of Marine Biodiversity in Areas beyond National Jurisdiction[END_REF][START_REF] Gjerde | Marine Protected Areas beyond National Jurisdiction: Some Practical Perspectives for Moving Ahead[END_REF][START_REF] Matz-Lück | The impact of OSPAR on protected area management beyond national jurisdiction: Effective regional cooperation or a network of paper parks?[END_REF][START_REF] Molenaar | Marine protected areas in areas beyond national jurisdiction.The pioneering efforts under the OSPAR Convention[END_REF][START_REF] Rochette | The regional approach to the conservation and sustainable use of marine biodiversity in areas beyond national jurisdiction[END_REF]; UNEP-MAP-RAC/SPA, 2011); [START_REF] Wright | Marine spatial planning in areas beyond national jurisdiction[END_REF], and certainly incomplete; -In the context of transboundary issues, MPAs could provide a continuum facilitating coordination between states. This could be especially in the European Union, for instance, in relation to shared concerns such as conservation matters.

Obviously, these theoretical models of spatial relationships between MPAs and MSP are mixed, and will fluctuate with the contents, issues, expected outputs and stakeholder engagement in the two processes.

As a first attempt, this analysis is incomplete because, for instance, it underestimates the role of the scale/size of MPAs, notably with "large-scale MPAs" currently encouraged by public authorities with certain political targets [START_REF] Leenhardt | The rise of large-scale marine protected areas: conservation or geopolitics?[END_REF] who consider that the size and age of marine reserves matter [START_REF] Claudet | Marine reserves: size and age do matter[END_REF]. It also neglects the way that MPAs are designed and managed, including participation issues (even if social considerations are as important in marine conservation as in MSP (Ban et al., 2013)). In practice, things are also more nuanced with, for instance the inclusion of one or several No-Take zones in a Multiple-use MPAs, the possible mixing of situations presented here, the question of the size of MPAs which may influence the relations with MSP or even the need for MSP. In addition to these temporal and spatial considerations, one should consider that processes could be interlinked and progressive: no process is done in a vacuum (for example, stakeholders who are involved in one process, producing knowledge and contributing to decision-making, could influence other processes). Governance processes also play an important role. Moreover, as well as the particular case of MSP and MPAs, there are interactions with other management tools (including sectoral ones), especially when they focus, possibly partly, on the same space even (in the case of overlapping, interlocking scales...). In addition, the different possible levels of decision-making (local, national, regional) -referring themselves to the different kinds of distribution of competencies in national contexts (federal model, centralised model, etc.)-play an important role in the relationship between MSP and MPAs systems. In this respect, it seems that no approach has proved more successful than another in its ability to integrate the systems of MSPs and MPAs. With this in mind, this analytical framework highlights many issues that are often unexplored in the literature discussing the links between MSP and MPAs. Some of them will be further analysed by using this analytical framework in two case studies.

Box 1-Few illustrations about the French case

The French context helps to illustrate potential relations between MSP and MPAs for three main reasons. Firstly, within the European Union which is at the forefront of MSP, France has already (quantitatively speaking) an extended MPAs network 4 , whilst MSP is not yet fully implemented but still in progress (though due to meet the deadline of March 2021 according to Article 15 of the European Union Directive on MSP). Secondly, France has a very large maritime domain with overseas territories, and MSP is only anticipated for some of them 5 . Thirdly, most French MPAs have a broader purpose of sustainable multiple-use of the sea rather than conservation-only MPAs and, thus has similarities to some other spatial planning tools.

Based on this experience, some examples of models shown in Figure 1 are as follows:

-MPAs prior to MSP: What could be considered as No-Take zones represent about 30% of French MPAs (mainly due to the 670.000 km² of the national reserve of the French Southern Lands). On one hand, these have to be incorporated as they stand into maritime plans. On the other hand, MSP is now an opportunity to introduce connectivity and networks, especially in the case of spatially-fragmented and size-reduced reserves. Regarding Multiple-use MPAs, many existing MPAs (mostly at a lower scale than those of the forthcoming maritime plans) may benefit from ongoing MSP processes. But, at the same time, there could be a risk of bias in the MSP process, especially in the case of large-scale MPAs such as, for instance, the Marine Natural Park of Mayotte (68,381 km²) which covers an entire EEZ and has already a management plan until 2028. -Comprehensive MSP: For mainland France, where MSP will be implemented throughout the whole of the marine area, the remarks above also apply -Partial MSP: To date, no maritime plan is anticipated in New Caledonia and a very large MPA (the Natural Park of the Coral Sea; 1,290,000 km² covering its entire EEZ) has been in place since 2014. In such cases, MPAs could constitute a framework for MSP and provide an extension for broader concerns in the case of Multiple-use MPAs (regarded as planning tools). -Land / sea: Because MSP is indirectly connected to coastal matters, protected areas that are straddling the land and the sea may facilitate a degree of land/sea integration which can complement MSP processes. For instance, this would be (type i) the case for National Reserves with a marine part (Seine estuary, Scandola, French Southern Lands…), and (type ii) for the three National Parks with a marine part (Port-Cros, Calanques, Guadeloupe). -Beyond national jurisdictions: France has been involved for some years in actions of the Oslo-Paris Convention (OSPAR) and the Convention on the Conservation of Antarctic Marine Living resources (CCAMLR) concerning MPAs in the Atlantic and in the Antarctic beyond national jurisdictions. To date, no MSP exists in the high seas, but it is an objective which was confirmed at a recent EU-UNESCO conference on MSP (Paris, March 2017).

First lessons from two European case studies

In the European context where the devices for MSP and MPA have been designed, two cases are particularly interesting because the processes have been initiated over several years: England and Germany. As far as possible, the different perspectives above will be used as an analytical framework.

England: Two separate processes

A statutory system for MSP was introduced to the United Kingdom through a series of policy documents which culminated in primary legislation in 2009[START_REF] Agardy | Ocean Zoning: Making Marine Management More Effective[END_REF](Defra, 2007;;HM Government et al., 2011). This paved the way for MSP implementation, which was devolved to the four constituent parts of the UK (England, Scotland, Wales and Northern Ireland). In England, the newly-formed Marine Management Organisation (MMO) became responsible for preparing maritime plans and began a rolling programme of plan-making for English waters, of which the first ones, for parts of the North Sea and the English Channel, were completed in 2014 and 2018 (Defra, 2011;HM Government, 2014[START_REF]East Inshore and East Offshore Marine Plans[END_REF]. Plans for the remaining areas are currently being prepared.

In parallel to this, a process got underway for designating a suite of new MPAs, referred to as Marine Conservation Zones (MCZs). This was described in some of the same policy documents that introduced MSP, and for England, the statutory basis for MCZs is set out in the same legislation (Marine and Coastal Access Act 2009). However, MCZs are dealt with in a without to mention upcoming referendums about self-determination in the first case and independence for the second one).

separate part of the Act, and statutory responsibility for the MCZ process lies not with the MMO but with government bodies that have a nature conservation remit (Natural England within the 12 nm limit and the Joint Nature Conservation Committee beyond 12 nm).This led to a lengthy consultation process that aimed to decide on the most appropriate locations for MCZs. English waters were divided into four areas for this purpose, and a separate exercise was carried out with conservation experts and stakeholders for each area. The intention was to incorporate rare, threatened and representative marine flora and fauna and features of geological and geomorphological interest, though also taking into account social and economic impacts.

This led to proposals for 127 MCZs spread throughout English waters, covering 15% of the marine area, varying greatly in size and in terms of the features to be protected. 65 of the areas were recommended for high level protection. These stakeholder-led proposals were broadly supported by a further scientific study (though with some questioning about the degree of confidence with which the MCZs could capture the intended features) (JNCC and Natural England, 2012). This exercise was hailed as a great success by marine conservationists6 . However, this soon turned to disappointment when government did not accept the recommendations in full, but, in 2013, only gave official designation to 27 of the proposed MCZs. This was seen as a shift away from an integrated network approach towards preservation of sitespecific features [START_REF] Lieberknecht | From stormy seas to the doldrums: The challenges of navigating towards an ecologically coherent MPA network through England's Marine Conservation Zone process[END_REF]. Moreover, the designations did not introduce any restrictions on activities within them, leading to accusations of these being MCZs on paper only (Appleby and Jones, 2012)7 . A designation order simply includes the definition of boundary coordinates, conservation objectives and key natural features for the MCZ in question. Nonetheless, two further rounds ('tranches') of MCZ designation followed in 2016 and 2019, leading to a total of 91 MCZs8 .

MCZs are intended to supplement a range of existing marine conservation designations. These have been established under various national, European and international conservation frameworks, and in England include Sites of Special Scientific Interest, Special Areas of Conservation, Special Protected Areas and Ramsar Sites. These are generally terrestrial designations, but in many cases they are coastal in nature and extend into coastal waters, especially estuarine and inter-tidal waters. The marine components of these designations are considered to be MPAs, and along with the newly-formed MCZs (and their equivalent in Scotland) form a national MPA Network9 . Figure 2 shows the potential network in England's first maritime plan areas. The designation of MPAs in England does not of itself generally impose any restriction on activities within them. It is intended that protection will be achieved through advice and management measures, tailored to individual MPAs. In the case of MCZs, for example, authorities are expected to contribute to conservation objectives when licensing activities; they should also work with stakeholders in developing suitable measures, which may be voluntary in nature (Defra, 2013).

The procedure of MPA designation in England is therefore divorced from the preparation of maritime plans. The MMO was not involved in the MCZ exercise, and it was not the primary purpose of identifying possible MCZs to integrate marine conservation with other interests. The MMO is, however, clearly one of the authorities that should work towards achieving MPA objectives, both in plan-making and licencing decisions.

So as far as MSP is concerned, the preparation of maritime plans is taking place against a backdrop of existing MPA designations in coastal areas and an ongoing process of establishing new MPAs (MCZs) throughout UK waters 10 . This approximates to multiple-use MPAs es-tablished prior to MSP in Figure 1. It should also be noted that some other protected areas, shown in Figure 2, straddle the land-sea divide, providing a continuum as shown in Figure 1.

However, in England, MSP is expected to contribute towards achieving the objectives of MPAs. This is evident both at strategic and plan-making levels. To begin with, the national guidance for MSP reiterates government commitment to the MPA Network and to protecting biodiversity throughout UK waters (HM Government et al., 2011). Following on from this, the first maritime plans give policy support to MCZs and the wider MPA network (HM Government, 2014). This implies that MPA objectives will be an important consideration in any licensing decisions that may affect MPAs and may weigh against permitting certain activities.

Although this falls short of guaranteeing that MPAs will be fully protected, it does allow for the needs of individual MPAs to be addressed in future planning decisions. This is, arguably, in keeping with the wider UK tradition of spatial planning, which is to establish policy priorities through plans and judge development proposals in the context of these priorities and other relevant considerations. Moreover, the MMO may collaborate with other agencies and stakeholders in developing management measures for individual MCZs, as envisaged by the designation process.

So MPA designation is not being incorporated fully into the MSP process in England; it is the subject of a separate exercise rather than being part of an integrative process of planning all maritime activities. Also, it has not met initial expectations, leading in the eyes of some to no more than 'paper parks'. But MSP does offer the opportunity for MPAs to be given greater prominence and protection through ongoing incorporation into planning and management processes, within the context of a flexible approach to marine nature conservation.

Germany: a missed opportunity?

Germany was the first European nation to implement a statutory system of MSP for its waters. This was done at two levels of governance, reflecting Germany's federal structure: the federal government took on responsibility for MSP in the nation's exclusive economic zone (EEZ) and the coastal states extended their planning competencies into the coastal waters as far as the EEZ. This system was established on the basis of existing planning legislation [START_REF] Douvere | New perspectives on sea use management: Initial findings from European experience with marine spatial planning[END_REF]. MSP in the EEZ has been the most striking initiative. This was delegated to the federal maritime agency (Bundesamt für Seeschifffahrt und Hydrographie (BSH)), which began the process in 2005, leading to two plans for Germany's EEZ, one for the North Sea part in 2008 and the other for the Baltic Sea part in 2009 (BSH, 2009). These plans are currently being revised11 .

The plans for the EEZ focused on a few key maritime interests, by setting out extensive priority areas and other measures for them. The sectors covered were shipping, offshore wind energy, pipelines and cables and scientific research. Notably, the plans did not establish any new areas or significant measures for nature conservation. BSH worked on the assumption that nature conservation areas had already been designated through Natura 2000 legislation, implementing the European Union's bird and habitat directives. These sites cover about 30% of the EEZ and most of the coastal waters (and are the only form of MPA in Germany). BSH held that the purpose of MSP was to cater for other, under-represented, interests.

This approach was contested by environmental organisations, research institutions and the federal environment agencies. They argued that the plan provided an opportunity for additional measures that would help protect the Natura 2000 areas in the EEZ, by being made into na-ture conservation priority areas on a par with those for shipping, etc. In response, BSH simply showed the Natura 2000 areas on the EEZ maps by way of information (they had not been shown at all on the first drafts), maintaining that these areas had a separate legal basis and that the plan, as a legal ordinance, was concerned with other matters. Environmental stakeholders continued to criticise this as an overly-legalistic approach to MSP and a missed opportunity as far as the Natura 2000 sites were concerned; they contended that these sites were not getting the protection they needed under the narrow provisions of the Natura 2000 legislation and that there would be additional value in giving them greater recognition in the plans. BSH resisted these arguments, claiming that management plans under Natura 2000 would be sufficient. The agency also pointed to the plans' broader provisions for nature conservation, that other uses must respect ecological concerns throughout the whole of the EEZ, not just in Natura 2000 areas. Indeed, biodiversity and environmental protection concerns do recur throughout the plans; for example, offshore wind farms are not allowed in Natura 2000 areas, and the need to ensure best environmental practice is repeatedly stated [START_REF] Jay | Early European experience in marine spatial planning: planning the German exclusive economic zone[END_REF]. Also, nature conservation was given a prominent role through a lengthy environmental report accompanying the plans, which had major input from the federal agency for nature conservation (Bundesamt für Naturschutz).

But environmental organisations remained unconvinced, continuing to feel that the plan did not succeed in balancing conflicting interests and was biased towards certain sectors, especially those for which BSH has other statutory responsibilities. Indeed, the plans might be thought to compromise further the integrity of the Natura 2000 sites, as maritime activities such as shipping are given priority areas through the sites [START_REF] Jay | Consensus and variance in the ecosystem approach to marine spatial planning: German perspectives and multi-actor implications[END_REF] (Figure 3).

For the coastal waters, the states have made much less definitive proposals. There has been little more than a broad indication of key interests, with some integration with the EEZ plans, such as a continuation of shipping areas and routes for cables and pipelines. Natura 2000 areas have, however, been treated on an equal, if not very strong, footing. This reflects the different nature of these plans, as they offer strategic level guidance for the state territories (mostly covering land), rather than legally-binding instruments, as in the case of the EEZ. They have also been prepared by the states' established agencies of planning, who have simply added the coastal waters to their remit. Arguably, they have adopted a more integrative approach to marine interests, including nature conservation, than BSH has in federal waters (which represents not only a new geographical domain for planning, but also a new federal role in spatial planning).

So in Germany, MSP is not acting as a mechanism for designating MPAs or for improving their management, but is being used primarily for the benefit of more economically-focused activities. MPAs rely on other legal provisions, namely European conservation frameworks. However, they are being accommodated to some extent into emerging patterns of sea-use, as expressed in marine spatial plans, and are a constraint on some potentially harmful activities.

As is generally the case in England, therefore, MPAs also approximate to multiple-use MPAs established prior to MSP (Figure 1), but MSP is not specifically expected to contribute to MPA objectives.

Discussion & Conclusion

There are multiple ways to consider the links between MPAs and MSP; approaches are both parallel and converging depending on the different forms they take in practice. The two examples presented above, from England and Germany, illustrate different paths where there are difficulties of integration, perhaps more for political than technical or practical reasons. Real world-MSP is often driven by Blue Growth logics [START_REF] Jones | Marine spatial planning in reality: Introduction to case studies and discussion of findings[END_REF] which challenges the convergence between the two processes. The relationships between MPAs and MSP are complex, multiple, changing, and must be viewed from various angles. MSP and MPAs sometimes share tools (namely decision-support tools), sometimes not depending of the type of planning in play.

The framework proposed in this paper emphasizes relationships in space and time. This is not intended as the final tool with which to conceptualize the relationships between MSP and MPAs, but it does provide a complementary point of view for discussion. Furthermore, this reflection draws attention to four points in order to improve the integration of MPAs and MSP. Firstly, inter-relations must be considered from a policy point of view, as technical discussions alone remain purely theoretical. It would appear that in the European context, either policy choices have not been made or they are not yet clearly expressed. Whatever the situation, the development of planning initiatives (MSP, sectoral planning, conservation zoning…) is not neutral and may raise in some cases questions of "ocean grabbing" [START_REF] Bennett | Ocean grabbing[END_REF] and "sea sparing" (protecting areas from uses while intensifying uses in other areas) [START_REF] Wolff | From sea sharing to sea sparing -Is there a paradigm shift in ocean management?[END_REF]. Secondly, taking into account the relative weakening of public power and the rise of non-state actors (companies, NGOs, associations...), the choices available to ocean management underline the need of a democratic and open debate. Both MSP and MPAs have the potential of 'hijacking' if political considerations are in the backseat when, in the same time, an evidence-based-rationalist planning is driving the system. Thirdly, the issue of financial resources should not be overlooked as it has a bearing on technical and, indirectly, political choices. There is therefore a question about the tools promoted by different communities of scientists and practitioners (coastal and marine planners, conservationists...). Finally, there is an important issue around data, information and knowledge (including non-scientific knowledge), because whatever the links between MPAs and MSP, much will depend on the availability, quality and uses of all kinds of data and knowledge to inform these processes and ensure a real and effective participation.

Fig. 1 :

 1 Fig. 1: Models of links between MSP and MPAs

Figure 2 :

 2 Figure 2: Potential MPA network in England's East Inshore and Offshore marine plan areas

Figure 3 :

 3 Figure 3: Part of the North Sea plan for the German EEZ

Table 1 : Matrix of maritime activities that may be appropriate for each IUCN category

 1

Characteristics of effective marine spatial planning include: ecosystem-based, integrated, area-based, adaptive, strategic and anticipatory and participatory (ibid.).

https://www.cbd.int/doc/legal/cbd-en.pdf

For instance, the European Union Directive on MSP considers "nature and species conservation sites and protected areas" as "possible activities and uses and interests" (Article 8).

According to their French definitions, MPAs cover 2,419,325 km² in the early 2019, that is to say 23.57% of waters under jurisdiction (http://indicateurs-biodiversite.naturefrance.fr/fr/indicateurs/surfaces-en-aires-marinesprotegees). This is the result of the national strategy for MPAs in France, defined in 2007 and revised in 2012, whilst that constituting a frame for MSP has been adopted ten years later (2017).

 5 Even if overseas territories are not concerned by the European Union Directive on MSP, the French government still decided to set up marine spatial plans in four "maritime basins" (West Indies, South of Indian ocean, Guyana and St.Pierre-et-Miquelon). On the other side, French Polynesia and New Caledonia have their own competencies for maritime affairs and no marine spatial plan could be expected by the French government (and

The Wildlife Trusts Marine Conservation Zones (England): http://www.wildlifetrusts.org/mcz

C. Roberts, England's marine conservation network is worse than useless. The Guardian, 17 June, 2014: http://www.theguardian.com/environment/2014/jun/17/england-marine-conservation-zones

Department for Environment, Food and Rural Affairs (Defra) : https://www.gov.uk/government/collections/marine-conservation-zone-designations-in-england#2019-mczdesignations-and-factsheets

 9 Joint Nature Conservation Committee (JNCC): http://jncc.defra.gov.uk/

This is, in fact, in keeping with terrestrial planning practice, which works within ever-changing contexts of natural conditions and built development, only some of which it has direct control over.

Bundesamt für Seeschifffahrt und Hydrographie (BSH): https://www.bsh.de/EN/TOPICS/Offshore/Maritime_spatial_planning/maritime_spatial_planning_node.html

Acknowledgements

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.


est destinée au dépôt

Modeling the heat treatment of a starch suspension inside a tubular exchanger

  Artemio Plana-Fattori, Etienne E. Chantoiseau, Christophe Doursat, Denis Flick To cite this version: Artemio Plana-Fattori, Etienne E. Chantoiseau, Christophe Doursat, Denis Flick. Modeling the heat treatment of a starch suspension inside a tubular exchanger. 4th European COMSOL Conference, Nov 2010, Versailles, France. hal-03144706 A. Plana-Fattori 1,2,* , E. Chantoiseau 1,2 , C. Doursat 1,2 and D. Flick 1,2 1: AgroParisTech, UMR1145 Ingénierie Procédés Aliments, F-91300 Massy, France 2: INRA, UMR1145 Ingénierie Procédés Aliments, F-91300 Massy, France * Artemio Plana-Fattori, AgroParisTech, Départ. MMIP, 16 rue Claude Bernard, 75231 Paris, France, artemio.planafattori@agroparistech.fr


Jing Geng
email: jing.geng@insa-rennes.fr

Vigen Arakelian

Damien Chablat

Philippe Lemoine

Balancing of the Orthoglide taking into account its varying payload ‡

Keywords: balancing, shaking force, center of mass, optimal control, "bang-bang" motion profile

For the fast-moving robot systems, the fluctuating dynamic loads transmitted to the supporting frame can excite the base and cause noise, wear, and fatigue of mechanical components. By reducing the shaking force, fully or partially, the dynamic characteristics of the robot system can be improved. However, the complete inertial force and inertial moment balancing can only be achieved by adding extra counterweight and counter-rotation systems, which largely increases the total mass, overall size, and complexity of robots. In order to avoid these inconveniences, an approach based on the optimal motion control of the center of mass is applied for the shaking force balancing of the robot Orthoglide. The application of the "Bang-bang" motion profile on the common center of mass allows a considerable reduction of the acceleration of the total mass center, which results in the reduction of the shaking force. With the proposed method, the shaking force balancing of the Orthoglide is carried out taking into account the varying payload. Note that such a solution by purely mechanical methods is complex and practically inapplicable for industrial robots. The simulations in ADAMS software validate the efficiency of the suggested approach.

Introduction

It is known that a mechanical system with unbalanced shaking force/moment transmits substantial vibration to the frame. Thus, a primary objective of the balancing is to cancel or reduce the variable dynamic loads transmitted to the frame and surrounding structures.

The methods of shaking force balancing can be arranged as follows:  By adding counterweight in order to keep the total mass center of moving links stationary [START_REF] Filaretov | Static balancing and dynamic decoupling of the motion of manipulation robots[END_REF]. It is obvious that the adding of the counterweights is not desirable because it leads to the increase of the total mass, of the overall size and of the efforts in joints. To avoid these drawbacks, the masses of the motors can be used as counterweights [START_REF] Bayer | Industrial robot with a weight balancing system[END_REF] (Figure 1(a)). Taking into account the complexity of the parallel manipulators, adding counterweights became not interesting especially in spatial ones [START_REF] Gosselin | Gravity compensation, static balancing and dynamic balancing of parallel mechanisms[END_REF] (Figure 1(b));  By adding auxiliary structures. In [START_REF] Agrawal | Reactionless space and ground robots: novel design and concept studies[END_REF][START_REF] Fattah | Design and modeling of classes of spatial reactionless manipulators[END_REF][START_REF] Fattah | Design arm simulation of a class of spatial reactionless manipulators[END_REF], the parallelograms were used as auxiliary structures in order to create the balanced manipulators. In [START_REF] Wijk | Dynamic Balancing of Clavel's Delta Robot[END_REF], the pantograph (Figure 1(c)) has been added in order to balance the shaking force of Delta robot. Such a solution leads to a decrease in the added masses of counterweights but practical application remains a challenge;  By installing elastic components [START_REF] Alici | Optimum force balancing with mass distribution and a single elastic element for a five-bar parallel manipulator[END_REF][START_REF] Alici | Optimum force balancing of a planar parallel manipulator[END_REF] (Figure 1(d)). The addition of elastic elements can successfully reduce the input torque and dynamic loads in the robot joints. However, it is less effective in reducing vibrations of the robot's base;

 By adjustment of kinematic parameters [START_REF] Ouyang | A Novel Force Balancing Method for Real-Time Controllable Mechanisms[END_REF] (Figure 1(e)). The result shows that the such a method is consistently better than the counterweight balancing in terms of the reduction of the joint forces and the torques in the servomotors, but less efficient for reduction of the shaking forces;  Via center of mass acceleration control [START_REF] Briot | Shaking Force Minimization of High-Speed Robots via Center of Mass Acceleration Control[END_REF][START_REF] Briot | Shaking Forces Minimization of High-Speed Robots via an Optimal Motion Planning[END_REF][START_REF] Arakelian | Design of Partially Balanced 5R Planar Manipulators with Reduced Center of Mass Acceleration (RCMA)[END_REF][START_REF] Arakelian | Minimization of Shaking Loads in Planar Parallel Structure Manipulators by Means of Optimal Control[END_REF][START_REF] Geng | Design of Partially Balanced Planar 5R Symmetrical Parallel Manipulators via an Optimal Motion Planning[END_REF][START_REF] Geng | Partial Shaking Force Balancing of 3-RRR Parallel Manipulators by Optimal Acceleration Control of the Total Center of Mass[END_REF][START_REF] Geng | Balancing of Planar 5R Symmetrical Parallel Manipulators Taking into Account the Varying Payload[END_REF]. This approach is based on the optimal control of the acceleration of the manipulator center of masses. For this purpose, the "bang-bang" profile has been used. The aim of the suggested method consists in the fact that the manipulator is controlled not by applying end-effector trajectories but by planning the displacements of the total mass center of moving links. Such a solution does not allow for complete balancing, but it leads to a significant decrease in shaking forces. In [START_REF] Geng | Balancing of Planar 5R Symmetrical Parallel Manipulators Taking into Account the Varying Payload[END_REF], a substituted point mass (Figure 1(f)) was found to replace the common center of mass of the 5R parallel manipulators as a virtual point. In this case, the motion planning of the substituted point mass can ensure a reduction of the shaking force. (a) Motors used as counterweights [START_REF] Bayer | Industrial robot with a weight balancing system[END_REF]; (b) Spatial parallel manipulator balanced by adding counterweights [START_REF] Gosselin | Gravity compensation, static balancing and dynamic balancing of parallel mechanisms[END_REF]; (c) Shaking force balancing by adding a pantograph [START_REF] Wijk | Dynamic Balancing of Clavel's Delta Robot[END_REF]; (d) A combination of a proper distribution of link masses and two springs [START_REF] Alici | Optimum force balancing of a planar parallel manipulator[END_REF]; (e) Two-step kinematic parameter adjustment in the adjusting kinematic parameters method [START_REF] Ouyang | A Novel Force Balancing Method for Real-Time Controllable Mechanisms[END_REF]; (f) The optimal acceleration control of the substituted center of mass * S of 5R parallel manipulator [17].

This paper deals with the shaking force balancing problem of the Orthoglide [START_REF] Wenger | Kinematic Analysis of a New Parallel Machine Tool: The Orthoglide[END_REF][START_REF] Chablat | Architecture Optimization of a 3-DOF Translational Parallel Mechanism for Machining Applications, the Orthoglide[END_REF] via the last-mentioned approach taking into consideration the robot structure. The robot Orthoglide is a three-degrees-of-freedom parallel manipulator with regular workspace and good compactness. Its three actuators are arranged according to the Cartesian coordinate space. The prototype and architecture of the robot are shown in Figures 2 and3. Here we point out that this paper is an extended version of a work first published at the 29th International Conference on Robotics in Alpe-Adria-Danube Region (RAAD 2020) [START_REF] Geng | Shaking Force Balancing of the Orthoglide[END_REF]. With regard to [START_REF] Geng | Shaking Force Balancing of the Orthoglide[END_REF], additional simulation results are presented here, i.e., the balancing of shaking force taking into account the varying payload and its sensitivity analysis. The rest of the paper is organized as follows: Section 2 describes the balancing approach based on optimal motion planning of the common center of mass; In Section 3, the numerical simulations in ADAMS software are conducted to validate the efficiency of the proposed balancing approach and the sensitivity to the design variables.

Now, let us consider the shaking force balancing of the Orthoglide.

Shaking force Balancing of the Orthoglide

Problem formulation

Let us first consider the kinematic architecture of the Orthoglide (Figure 3(a)). It consists of three identical kinematic chains that are formally described as a PRP R , where P , R and a P denote the actuated prismatic, revolute, and parallelogram joints respectively. The mechanism input is made up by three actuated orthogonal prismatic joints. The output body is connected to the prismatic joint through a set of three kinematic chains. Inside each chain, one parallelogram is used and oriented in a manner that the output body is restricted to translational movements only. The three parallelograms have the same lengths ii L B C  . The arrangement of the joints in the a PRP R chains has been defined to eliminate any constraint singularity in the Cartesian workspace. Each frame point i A is fixed on the i th  linear axis so that 1 2

1 3 2 3
A A A A A A . The points i B and i C are located on the i th  parallelogram, as is shown in Fig. 1. The reference frame is located at the intersection of the prismatic joint axes and aligns the coordinate axis with them. The details of the design of the Orthoglide and its optimization can be found in [START_REF] Wenger | Kinematic Analysis of a New Parallel Machine Tool: The Orthoglide[END_REF][START_REF] Chablat | Architecture Optimization of a 3-DOF Translational Parallel Mechanism for Machining Applications, the Orthoglide[END_REF]. . Note that for the Orthoglide robot, a single inverse kinematic solution is reachable.

                      (1)
The shaking forces sh F of mechanisms can be written in the form:

()

sh payload mm  Fs && (2)
where

1 n i i mm   
is the total mass of the moving links of the manipulator, payload m

is the mass of the payload and s && is the acceleration of the total mass center. In the proceeding of 29 th International Conference on Robotics in Alpe-Adria-Danube Region, the balancing problem of the Orthoglide has been addressed without counting the varying payload payload m . As mentioned above (in section 1), the shaking force balancing via mass redistribution consists in adding counterweights in order to keep the total mass center of moving links stationary [START_REF] Arakelian | Balancing of Linkages and Robot Manipulators: Advanced Methods with Illustrative Examples[END_REF]. In this case, 0  s && for any configuration of the manipulator and, as a result, the shaking force is cancelled. It is obvious that the adding of supplementary masses as counterweights is not desirable because it leads to the increase of the total mass, of the overall size of the manipulator, the efforts in joints, the shaking moment and the input torques. Therefore, in the present study, it is proposed to minimize the shaking force via reduction of the total mass center acceleration:

() max min st  s && (3)
i.e. to apply an optimal control of the total mass center of moving links that allows one to reduce the maximal value of its acceleration.

For this purpose, let's consider the control of the spatial parallel manipulator Orthoglide through the motion planning of its center of mass. To ensure it, let us assume that the center of mass moves along a straight line between its initial and final positions. Thus, the motion profile used on this path will define the values of shaking forces. For the same displacement of the total center of mass S and the displacement time f t , the maximal value of the acceleration changes following the motion profile [START_REF] Khalil | Modeling, Identification and Control of Robots[END_REF]: For quantic polynomial profile, the . It means the application of bang-bang law theoretically brings about a reduction of 30.7% of the maximal value of the acceleration. Hence, to minimize the maximum value of the acceleration of the total mass center and, as a result, shaking forces, the "bang-bang" profile should be used. Thus, by reducing the acceleration of the center of mass of the Orthoglide, a decrease in its shaking forces is achieved. Therefore, to achieve the shaking force balancing through the approach described above, it is necessary to consider the relationship between the input parameters ( , , )

x y z     ρ
and the center of mass positions ( , , )

x y z p p p P of the Orthoglide.

The relationship between the total center of mass and the input parameters of the robot

In order to control the manipulator according to the method described above, it is necessary to establish the relationship between the displacement of the total center of mass and the input parameters ( , , )

x y z     ρ , i.e.,

S -S D

. Subsequently, a straight line connecting the initial and final positions of the comment center mass of the manipulator can be established and its motion planning by "bang-bang" profile with the time interval f t can be ensured:

  t  COM SS , i.e. 2 2 2( ) , (0 ) 2 () 1 4( ) 2( ) , ( ) 2 f f f f ff t t t t t t tt tt tt                      COM_i COM_i SD S SD (4)
Let us now consider the relationship between   ( ), ( ), ( ) x t y t z t  COM S and the input displacement ( , , )

x y z     ρ .
The common COM of the manipulator can be expressed as:

1 n i payload i mm M     iP COM rr S ( 5
)
where i is the number of the moving link  

1, , in  ,

COM

S

is the coordinate vector of the total mass center of the manipulator, i r is the the coordinate vector of the linkage i , i m is the mass of the linkage i ; P r is the the coordinate vector of the payload, payload m is the mass of the payload;

1 n i payload i M m m   
is the total mass of the Orthoglide including the payload.

In the developed prototype, the slider of prismatic joint is designed as body AB , where A is not on the three axes but has an offset named l . At the same time, 1 2 3

C C C P    . Thus, the coordinates of the joints along X, Y and Z axes are the followings: X-axis : 1 ( , , )

x y z C p p p  ; 1 ( ,0,0) x B   ; 1 ( ,0, ) x A l l   .
Y-axis : 2 ( , , )

x y z C p p p  ; 2 (0, ,0) y B   ; 2 ( , ,0) y A l l   .
Z-axis : 3 ( , , )

x y z C p p p  ; 3 (0,0, ) z B   ; 3 (0, , ) z A l l   .
The mass centers of the parallelograms can be written as:

      0.5 , 0.5 , 0.5 i i i i i i C B C B C B x x y y z z     
, and their masses are 1 m . The masses center of the three actuated links are:

      0.5 , 0.5 , 0.5 i i i i i i A B A B A B x x y y z z     
, the masses of input links are denoted as 2 m . The coordinates of the mass center of the joint of end-effector P are ( , , )

x y z p p p and its mass is 3 m . With the masses of the corresponding links, the expressions of the total center of mass of the moving links of the Orthoglide can be expressed as:

      1 2 3 1 2 3 1 2 3 0.5 3 ( ) ( ) 0.5 3 ( ) ( ) 0.5 3 ( ) ( ) x x x x payload x y y y y payload y z z z z payload z S m p m l m m p M S m p m l m m p M S m p m l m m p M                                     (6)
where,

1 2 3 3( ) payload M m m m m    
is the total mass of the moving components.

According to the proposed method, the displacement of the total center of mass should follow Bang-bang motion profile () t S , i.e.

                                                  2 ) , ( ) 2 f zf f t d t t                                  (7)
Note that the output parameters ( , , )

x y z p p p of the manipulator Orthoglide can be expressed with the functions including the input parameters ( , , )

x y z    via direct kinematics [START_REF] Pashkevich | Kinematics and Workspace Analysis of a Three-Axis Parallel Manipulator: The Orthoglide[END_REF]. Thus, Equation (6) becomes a group of three equations expressed with three unknowns ( , , )

x y z

   and it has a unique solution. Finally, the time-varying input displacements of the actuated prismatic joints can be obtained in order to ensuring the displacement of the COM.

Illustrative example via CAD model

To validate the proposed method, numerical simulations are conducted in ADAMS software. We created a CAD model and carry out the simulations by applying the following parameters of the Orthoglide [START_REF] Guegan | Identification of the dynamic parameters of the Orthoglide[END_REF] which correspond to the geometrical parameters of the prototype developed in LS2N (Figure 1). The detailed geometric parameters are: the length of the longer side of the three parallelograms is

1 1 2 2 3 3 0.31 L B C B C B C m     ,

Balancing of the Orthoglide without taking into account the payload

The traditional control strategy based on the trajectory and motion planning of the end-effector. In the application of the pick-and-place robot, the displacement of the end-effector is defined as a straight line and parameterized with a motion profile such as a quantic polynomial profile. With the proposed approach in this paper, the trajectory of the end-effector is not defined but the trajectory of the COM. Then, the "bang-bang" motion profile is applied to the trajectory of the COM. Thus, in this section, three studied cases are designed in order to see the efficiency of the proposed method:  Case 1: Defining the displacement of the end-effector of the unbalanced manipulator as a straight line and parameterized with "fifth-order polynomial" profile;  Case 2: Defining the displacement of the end-effector of the unbalanced manipulator as a straight line and parameterized with "bang-bang" profile;  Case 3: The generation of the motion via defining the displacement of the manipulator center of mass as a straight line and parameterized with "bang-bang" profile. By comparing Cases 1 and 2, we can see the necessity of using "bang-bang" law; by comparing Cases 2 and 3, the advantage of COM motion planning become obvious; in comparison of Cases 1 and 3, the difference between the traditional control method and proposed one becomes evident. The simulation results (Figure 4(a)) show that, compared to the traditional control technique (Case 1), the shaking force has been reduced up to 33.2% by applying "Bang-bang" law to the COM (Case 3) without carrying a payload. Employing the "Bang-bang" motion on the end-effector (Case 2) reduces the shaking force by 24.9%. Obviously, the motion control of the COM of the Orthoglide is more efficient.

Compared to the increase of the shaking moment of the balancing method based on adding counterweights, the shaking moment (see in Figure 4(b)) has a reduction of 33.6% with the approach based on the motion planning of the COM (Case 3). The method that defines the motion of the end-effector with "bang-bang" (Case 2) motion profile reduces the shaking moment by 23.8%.

Another advantage of this method is its simplicity and versatility. In the case of changing trajectory, it is just necessary to provide the initial and final coordinates of the end-effector, calculate the input parameters according to the proposed method and implemented in the manipulator control system.

Balancing of the Orthoglide while taking into account the payload

With the balancing method by adding counterweights, once the payload changed, the mass redistribution needs to be redone, which brings about the complexity of the balancing process.

However, the proposed approach by optimal motion planning of the COM is still efficient taking into account the varying payload because the motion planning can be conducted without modifying the robot components and configuration. In view of the payload capacity of the Orthoglide (5kg), Table 1 and Table 2 demonstrate the shaking force and shaking moment for three cases when the Orthoglide is carrying a payload. The variations and reduction ratio of the shaking force and the shaking moment taking into account the payloads are respectively presented in Table 1 and Table 2. As is shown in Table 1, the shaking force of the Orthoglide has been reduced up to 33.2%. Following the increase of the payload, the reduction ration is approaching the theoretical value 30.7%. Thus, we have the conclusion that, with the proposed balancing approach, a minimum reduction (30.7%) of the shaking force can be achieved. Compared to Case 3, Case 2 has a minimum reduction of the shaking force of 24.9%.

It should be noted that the purpose of these simulations was not an illustration of the decrease in the shaking moment. However, it was considered useful to give the simulation results, which show that a decrease in shaking force is accompanied by a decrease in shaking moment. It can be considered a further advantage of the suggested balancing solution.

Sensitivity analysis of the shaking force and shaking moment

In the current industry, manufacturing errors are unavoidable and should be considered during the design process in order to ensure high accuracy of achieved results. With the proposed balancing strategy, the mass of the payload is one of the design variables, which can largely influence the final values of shaking forces and shaking moments acting on the frame. During the balancing process, if a mass error exists, the balancing condition can be different. Thus, we assume that the error presents. Then, two cases are designed in order to evaluate its sensitivity:  Case 3: balancing by optimal motion planning with "bang-bang" law taking into account the mass error;  Case 4: balancing by optimal motion planning with "bang-bang" law without taking into account the mass error. By comparing Case 3 and 4, the errors of shaking force and shaking moment to the payload can be obtained. is the difference of the shaking moment between the Case 4 and Case 3.

The simulation results given in Table 3 and Table 4 show the variations of shaking force and shaking moment. As we can see, both shaking force and shaking moment are not very sensitive to the payload's variations, which means the proposed balancing solution has good stability even under manufacturing errors. Following the increase of the payload, the difference between Cases 3 and 4 is reducing, which indicates that the mass error of the payload carried by the Orthoglide can be ignored.

Conclusion

It is known that the shaking force balancing by counterweights mounted on the moving links is more appropriate for serial and planar parallel manipulators. It is much more difficult for spatial parallel manipulators. Therefore, in this paper, an alternative method based on optimal acceleration control of the common COM is applied for shaking forces minimization of the Orthoglide robot. The suggested balancing technique consists in the fact that the Orthoglide is controlled not by applying platform trajectories but by motion planning of the total mass center of moving links. The trajectories of the total mass center of the manipulator are defined as straight lines and are parameterized with "bang-bang" profile. Such a control approach allows the reduction of the maximum value of the center of mass and consequently the shaking force. The numerical simulations show the efficiency of the proposed solution.

Future works concern now the experimental validation of the suggested balancing technique via tests that will be carried out on the prototype of the Orthoglide developed in LS2N (Figure 2).

Figure 1 .

 1 Figure 1. (a) Motors used as counterweights[START_REF] Bayer | Industrial robot with a weight balancing system[END_REF]; (b) Spatial parallel manipulator balanced by adding counterweights[START_REF] Gosselin | Gravity compensation, static balancing and dynamic balancing of parallel mechanisms[END_REF]; (c) Shaking force balancing by adding a pantograph[START_REF] Wijk | Dynamic Balancing of Clavel's Delta Robot[END_REF]; (d) A combination of a proper distribution of link masses and two springs[START_REF] Alici | Optimum force balancing of a planar parallel manipulator[END_REF]; (e) Two-step kinematic parameter adjustment in the adjusting kinematic parameters method[START_REF] Ouyang | A Novel Force Balancing Method for Real-Time Controllable Mechanisms[END_REF]; (f) The optimal acceleration control of the

Figure 2 .

 2 Figure 2. The prototype of the Orthoglide (LS2N).

Figure 3 .

 3 Figure 3. (a) The structure of the Orthoglide; (b) The geometrical model of the Orthoglide

  configuration indices that are equal to 1  ; The input vector of the three prismatic joints variables as ρ ( , , )

Figure 4 .

 4 Figure 4. (a) Variations of shaking forces for three studied cases; (b) Variations of shaking moments for three studied cases.

  for the given position and the law of motion of the Common Center of Mass (COM) of the manipulator determine its input displacements. Then, by means of the obtained input parameters via forward kinematics determine the position of the output axis ( , , )

	P	p p p
		x	y	z
																P	x p p p y	z	of the platform
	i P	( , , ) i i i x y z	and	f ( , , ) f f x y z
						ρ	i	xi    yi	zi	and	ρ	f	( , , ) xf yf zf   	. The corresponding values of the
	common COM of the manipulator can also be found:	S	COM_i		(	Si x	, , ) S i i S z y	and	S	COM_f		Sf ( , x	y	Sf	Sf ,) z
	d d d  . The displacement of the total center of mass is ( , , ) x y z	COM_f	COM_i

. For this purpose, it is necessary to establish the relationship between the common center of mass of the manipulator and its input parameters.

Let us start this issue with the initial and final positions ( , , ) f P . So, by invers kinematics

[START_REF] Pashkevich | Kinematics and Workspace Analysis of a Three-Axis Parallel Manipulator: The Orthoglide[END_REF]

, the input angles corresponding to these positions will be determined: ( , , )

  the configuration indices of the current mechanism

	are	1    . The masses of sliders are: 1 0.396 y z s s s x m kg 	, the masses of the parallelograms are
	2 m		0.248 kg	and the mass of the revolute joint P is 3 0.1 m kg 	. The trajectory of the output axis P of
	the platform is given by its initial position	i P with the coordinates:	0 x  , i	0 y  , i	0 z  and the i
	final position	f P with the coordinates:	0.1 xm  f	,	0.07 ym  f	,	0.11 zm  f	. The corresponding
	input displacements are determined via inverse kinematics:	0.31 m ,   xi xf	0.1 8 m	,	yi  	0.31 m	,
	yf  	0.34 m	,	zi  	0.31 m	,	zf  	0.17	m	. The coordinates of the common COM of the manipulator for
	two positions have been found:	0.04 xm  Si	,	0.04 ym  Si	,	0.04 zm  Si	,	0.04 xm  Sf 	,	0.09 ym  Sf	,
	0.05 zm  Sf 	. The traveling time of this trajectory is	0.1 ts  f	, the designed acceleration of the center
	of mass is	com a		38.7 / m s	2	.

Table 1 .

 1 The shaking force and its reduction of the Orthoglide while carrying a payload

	Mass of	Shaking force 1 / Newton	Reduction 2 / %
	payload / kg	Case 1	Case 2	Case 3	Case2	Case3
	0	117.99	88.56	78.86	24.9	33.2
	1	212.08	152.82	144.57	27.9	31.8
	2	306.73	218.08	210.55	28.9	31.3
	3	401.55	283.65	276.31	29.3	31.2
	4	496.43	349.36	342.22	29.6	31.1
	5	591.35	415.14	408.14	29.8	30.9
	1 The maximum value of the shaking force during the movement
	2 The reduction ratio of shaking force is calculated by	2 Case Case 1 11 3 Case Case 1 and Case Case 	.

Table 2 .

 2 The shaking moment and its reduction of the Orthoglide while carrying a payload

	Mass of	Shaking moment 1 /	Reduction 2 / %
	payload / kg		Newton*m
		Case 1	Case 2	Case 3	Case2	Case3
	0	38.19	29.11	25.35	23.8	33.6
	1	64.11	47.18	43.66	26.4	31.9
	2	90.08	65.25	61.82	27.6	31.4
	3	116.06	83.33	79.93	28.2	31.1
	4	142.03	101.40	98.02	28.6	31.0
	5	168.01	119.47	116.09	28.9	30.9

Table 3 .

 3 Maximal value of the total shaking force of the robot taking into account the mass error of the payload  is the difference of the shaking force between the Case 4 and Case 3.

	Mass of payload/kg	Case 3/Newton	Case 4/Newton	sh F  /Newton
	1+	m 	157.73	158.36	0.63
	2+	m 	223.60	223.95	0.35
	3+	m 	289.49	289.70	0.20
	4+	m 	355.40	355.51	0.11
	5+	m 	421.32	421.36	0.04

sh F

Table 4 .

 4 Maximal value of the total shaking moment of the robot taking into account mass error of the payload

	Mass of payload/kg	Case 3/Newton*m	Case 4/Newton*m	M 	sh	/Newton*m
	1+	m 	47.30	47.74			0.43
	2+	m 	65.44	65.75			0.30
	3+	m 	83.55	83.78			0.23
	4+	m 	101.63	101.82			0.19
	5+	m 	119.70	119.86			0.16

sh M 

The maximum value of the shaking moment during the movement

Funding: This research was supported by a scholarship funded by the China Scholarship Council.

Conflicts of Interest:

The authors declare no conflict of interest.

Author Contributions: Conceptualization, methodology and investigation, software, validation, data curation, writing-original draft preparation, writing-review and editing, G.J., A.V., C.D. and L.P. All authors have read and agreed to the published version of the manuscript.