Zhen Xing
email: xingz@nercita.org.cn

Wengang Zheng
email: zhengwg@nercita.org.cn

Changjun Shen
email: shencj@nercita.org.cn

Xin Zhang
email: zhangx@nercita.org.cn

Development of the Meter for Measuring Pork Quality Based on the Electrical Characteristics 1

Keywords: the electrical characteristics, pork quality, a portable meter, a lowcost

The excitation frequency on the electrical characteristics of pork had been identified by the experiments of the electrical characteristics and the theory of electrical characteristics, the relationship between the evaluation of quality of pork and the impedance characteristics was established, and a nondestructive portable meter for measuring pork quality was developed. The functions of each hardware and software design of the meter were described in detail. The result shows that the conductivity of the pork increases with the level of corruption by the experiment of the measurement selected sample of pork. The pork quality meter based on the electrical characteristics provides the measurement method and apparatus of a low-cost, rapid, qualitative assessment of pork quality.

Introduction

Food safety become the focus of attention when people's living standard have been rising, The meat is the main food in china; China is one of the biggest countries for the production of livestock and poultry meat and its products. According to The People's Republic of China Statistical Yearbook 2008, China's pork production in 2007 was 42.878 million tons, the amount of production and consumption all ranks the world. People are cautious about meat consumption when meat safety incidents, such as, the injection meat or the clenbuterol, are frequently exposed [START_REF] Goldenberg | Automation of meat pork grading process[END_REF]. In order to eliminate consumer concern for meat product, some approaches should be taken, such as, improving the moral quality of the farmers and producers, and preventing nonhealthy meat to target into the market. So the measuring meter for fast detection of meat quality is an important role in the quarantine before meat onto the market.

Zhen Xing2, Wengang Zheng3 , Changjun Shen2,3, Xin Zhang2,3

Currently, there are a lot of pork quality detection methods. For example, the fat of the pig ketene body and the lean meat were graded by using spectroscopy or ultrasonic detection in the abroad; the nutritional composition in meat and meat quality changes are studied by using the equipment of near-infrared spectroscopy or the chemo metrics in the domestic; the study group of Ding [START_REF] Ding | SPECTRAL RESEARCH ON THE EFFECT OF OPTICAL PROPA GATION IN THE FAT[END_REF] had been studied the non-destructive optical detection methods for the fatty tissue, and measured the content of the Hemoglobin and the myoglobin in different depths of muscle; the study group of Huang [START_REF] Ji | Study of Measurement Methods for Detecting the Water Content in Deep Layer of Fresh Meat[END_REF][START_REF] Ding | Development of portable bio-impedance spectroscopy system for measuring porcine meat quality[END_REF] had been studied the optical parameter properties of agricultural products, the detection of fresh pork and deep water of the fresh pork. In addition, the meat quality of detection methods, based on dielectric properties or electrochemical properties, had been developed rapidly. For example, Zhang [START_REF] Zhang | Dielectric and thermo physical properties of meat batters over a temperature range of 5-85℃[END_REF] had been studied temperature effect on the dielectric properties of the lunch pork roll; Kent [START_REF] Kent | Determination of added water in pork products using microwave dielectric spectroscopy[END_REF] soaked the meat in water at different times, attained different the water content, and studied the water content effect on the dielectric properties of chicken, scallops and pork. Zhang [START_REF] Zhang | The effect of fat, water and salt on the thermal and dielectric properties of meat batter and its temperature following microwave or radio frequency heating[END_REF] had been studied the salt effect on the permittivity and dielectric loss factor of the pork. Currently, the dielectric properties of the raw meat and meat products had been studied in abroad, especially the microwave dielectric properties, however, detecting the quality of pork by using the dielectric properties has only begun in the domestic.

A new sensor based on the transmission line impedance theory was designed by using the coaxial transmission line technology, and the meter for the meter for measuring pork quality based on this new sensor was developed in this paper; it can be more convenient, fast and efficient measurement of pork quality, and ensure the safety of the pork quality.

Sensor design

The sensor consists of a power supply unit, a high-frequency signal source, a signal processing unit, a coaxial transmission line and measuring probes. The structure is as shown in Figure 1.

Measuring principle

Coaxial transmission line measurement technique is that the electrical characteristics of biological tissue (such as conductivity, dielectric constant, etc.) was transferred into high-frequency electromagnetic wave reflection coefficient, the relationship between the electrical characteristics of biological tissue and high frequency electromagnetic wave reflection coefficient, the electrical characteristics of biological tissue can be obtained by measuring the radiation coefficient. When the power supply was at work, a fixed-and high-frequency signal, generated by the crystal oscillator, transmitted through the coaxial transmission line to the probe which was inserted into the testing material. Due to the impedance's mismatching, parts of the signals would return and superpose with the latter input ones. Consequently, it set up a doable way of associating a stabilized amplitude voltage with the coaxial transmission line and the probe, which is available to the quality detecting.

Signal Processing Circuit

According to signal detection theory, the signal processing circuit of accuracy, stability, sensitivity directly determines the overall system performance, therefore, the design of the signal processing circuit is crucial, it must eliminate noise and amplify useful signal. Aiming at catering to this need, the measurement circuit can be simplified as two-stage amplification. The signal processing circuit is shown in detail in Figure 2. Observing that the first-stage used difference amplifier to perform differential operation,and the input sinusoidal signal was changed into DC signal, the function of the current-conveyor was to ensure the working probe is held at virtual ground when it was connected at the impedance. In addition, difference amplifier has the advantage of eliminating the Zero Drift. The second-stage amplifier was simply to give rise to the former-step's output signal, which aimed at improving stability of the testing system. The parameters of every component are as follows.

System Architecture

The system architecture is shown in the figure 3. The low-power MCU MSP430F149 is used as the core of the system acquisition and control, its power consumption and input leakage current (up to 50nA) is relatively low in the industry, the MSP430F149 is an industrial grade product, stable performance, high reliability. There are many work modes of the MSP430F149; the system power consumption is reduced by selecting a low power operating mode, so the MSP430F149 is especially suitable for handheld applications. It can reduce the number of external components and the cost of the instrument because of its 12-bit A / D converter. The keyboard and LCD modules for the operator provide a friendly human-machine interface; the real-time clock module can record the system running time; the memory module can save operating parameters and measurement data; the sensor interface is using a convenient PS / 2 interface.

The Power Module

The meter is using two 1.5V batteries or a rechargeable battery, but the number of external components and the MSP430F149 must work at 3.3V, so it must increase the value of the power module. The circuit of the increasing voltage is shown in the figure 4. The chip of MAX1724, which character is a low quiescent current and high efficiency, is used in the power module.

The RTC Module

The RTC module is designed for ensuring the system time synchronization, the schematic of the RTC is shown in the figure 5. The PCF8563 is a CMOS Real-Time Clock and calendar optimized for low power consumption. A programmable clock output, interrupt output, and voltage-low detector are also provided.

3.3The Memory Module

The 24LC02B is organized as one block of 256 X 8-bit memory with a 2-wire serial interface. Low-voltage design permits operation down to 2.5V, with standby and active currents of only 1 μA and 1 mA, respectively. its feature is low power consumption, simple external circuit, and write protection. The principle circuit of the memory module is shown in the figure 6. The pins of A0, A1, and A2 connect to the ground, its address is 000, and the pin of the WP connects to the ground, so the chip can be all written. The pins of the SCL and the SDA connect respectively 10K resistor, and make the level of the SCL and the SDA high, so can conveniently read and write. The system software is modular in design, and they include a data measurement and processing module, a data storage module, a serial interface module, a keyboard and a LCD module, and act. The events are handled at the before platform and backstage.

When the system is power on, initializes kinds of parameters, and then enters into the waiting stage; when receiving the measurement command, the system begins to measure, process, and storage the data.

Experiment and discussion

Experiment analysis

The test material was obtained from swine fillet and qualified by the quarantine system. The raw meat was fed to the meat grinder by inches to chop into fillet emulsion specimen, which were uniform in composition, within five times' wring.

Using the electronic balance divided the emulsion into 10g per portion by weight.

Being intended to optimize the quality of test sample, delicately adding the demonized water into it until well-mixed was suggested. Afterwards, semi finished products were placed in the experimental beaker to prepare emulsion-aqueous solution of 10% and 20% respectively. The curvilinear was shown in Figure 7, the points of each group fluctuated around a certain value. With different water content added, the output results varied from one sample to another. Apparently, the more water it contained, the higher output voltage it may afterward lead to, and vice versa. Taking the 10%-water-addition sample for an instance, we got the average of 3.10 and standard deviation of 0.01457 by calculating. The value was 0.47%, which indicated a low dispersion degree. Similarly, that of the 20%-water-addition sample was 0.49%. So we dare to say, with the same testing sample, different sensors independently applied have obtained tolerably similar results, whose service performance and effectiveness can meet the need of measuring.

Discussions

Based on the research of the coaxial transmission line theory, the sensor and the meter for measuring pork quality were designed. The measurement results show that the stability and consistency of the sensor meet measurement requirements.

The plan of a low-power, battery-powered portable meter is designed. The characters of the MSP430F149 are low power consumption and real-time wake-up function, so the power consumption of the measuring meter of pork quality is rather lower, and this feature is ideal for portable meter. A friendly human-machine interface and standard PS/2 interface are very convenient for users.

In addition, the pork quality includes food quality, nutritional quality, technical quality, health quality and human quality, etc. At present, the quality of pork was inspected mainly through PH value, odor, color and the content of the water, the detection methods of using the PH value, odor, color were not in time in measuring the pork quality. The content of the water in the pork impacted on the pork quality

Fig. 1 .

 1 Fig. 1. The principle structure of the sensor

Fig. 2 .

 2 Fig. 2. Block diagram of signal processing circuit

Fig. 3 .

 3 Fig. 3. The system architecture

Development 5 Fig. 4 .

 54 Fig. 4. The schematic of power

Fig. 5 .

 5 Fig. 5. The schematic of the RTC

Fig. 6 .

 6 Fig. 6. The circuit of the memory module

Fig. 7 .

 7 Fig. 7. Sensor output voltages within distinguished water-addition samples

The paper was supported by the National High Technology Research and Development Program("863"Program) of China (2007AA10 Z212)

was only considered in this paper; other parameters were ignored in this paper. If the pork quality was comprehensive responded, we must considered other factors, such as the PH value, odor, color, act. So the system of the pork quality evaluation is not put forward, and requires further study.


Ergen Liu

Dan Wu

Kewen Cai

A type of Arithmetic Labels about Circulating ring

Keywords: Arithmetic graph;labeling of graph; n i C, 8 1, 8 ), 2, 1

 is given the gracefulness of m kinds 4 C with one common point.

In this paper, we researched the arithmetic labels of four kinds graph:

, and we proved they are all ) 2 , ( d d --arithmetic graph.

Introduction

The graph in this paper discussed are undirected、no multiple edges and simple graph, the unorganized state of definitions and terminology and the symbols in this graph referred to reference [START_REF] Chartrand | Graphs and Digraphs[END_REF] [START_REF] Bondy | Graph Theory with Applications[END_REF].

There are two kinds of labels of the graph: one is the reduced label, is to say that in order to get the label of one edge you should reduce the endpoints of the edge; the other is additive label, for the same you should acttive the endpoints of one edge to get the label of the edge. For example, the well-known of "Gracefulness" is reduced.

the "Compatible labels" is additive. In 1990, B.D.Achaya and S.M.Hegde import the concept of "Arithmetic lables"(referred to reference [START_REF] Chartrand | Graphs and Digraphs[END_REF]), which is a more extensive additive label, it have applied value on solution to question of the joint ventures in rights and obligations.

Definition 1.1 For ) , ( E V G  , if there is a mapping f ( called the vertices v of the label ) from   G V to the set of nonnegative integer 0 N , meet: ) ( ) ( ) 1 ( v f u f  ,which v u  ,and ) (G V v u  , ;     d q k d k k G E uv v f u f ) 1 ( ) ( ) ( ) ( ) 2 (       , , ,  . Then we call graph G is a ) ( d k, --arithmetic graph.

Main results and certification

0 ( 1 v ) 0 ( 2 v ) 0 ( 3 v ) 0 ( 4 v ) 0 ( 5 v ) 0 ( 6 v ) 0 ( 7 v ) 1 ( 1 v ) 1 ( 2 v ) 1 ( 3 v ) 1 ( 4 v ) 1 ( 5 v ) 1 ( 6 v ) 1 ( 7 v ) 2 ( 1 v ) 1 ( 1  n v ) 1 ( 2  n v ) 1 ( 3  n v ) 1 ( 4  n v ) 1 ( 5  n v ) 1 ( 6  n v ) 1 ( 7  n v ) ( 1 n v Fig.1.The Graf n C ,     n i d id v f i  , ) 1 , , 2 , 1 , 0 ( 6 8 ) ( ) ( 4     n i d id v f i  , ) 1 , , 2 , 1 , 0 ( 2 8 ) ( ) ( 5     n i d id v f i  , ) 1 , , 2 , 1 , 0 ( 5 8 ) ( ) ( 6     n i d id v f i  , ) 1 , , 2 , 1 , 0 ( 7 8 ) ( ) ( 7     n i d id v f i 
. Now we proof that the mapping

f is arithmetic labeling of n C , 1 , 8 .
We can see the mapping

f meet ) ( ) ( v f u f  which v u  and ) ( , , 1 , 8 n C V v u  . Next we prove   ) ( ) ( ) ( , 1 , 8 n C E uv v f u f   is an arithmetic progression in the way of mathematical induction. When 1  n Then 0 ) ( ) 0 ( 1  v f , d v f  ) ( ) 0 ( 2 , d v f 3 ) ( ) 0 ( 3  , d v f 6 ) ( ) 0 ( 4  , d v f 2 ) ( ) 0 ( 5  , d v f 5 ) ( ) 0 ( 6  , d v f 7 ) ( ) 0 ( 7  , d v f 8 ) ( ) 1 ( 1  . Therefore   ) ( ) ( ) ( 1 , 1 , 8 C E uv v f u f    ), ( ) ( ) 0 ( 2 ) 0 ( 1 v f v f   ), ( ) ( 0 ( 3 ) 0 ( 1 v f v f  ), ( ) ( ) 0 ( 5 ) 0 ( 3 v f v f  ), ( ) ( ) 0 ( 4 ) 0 ( 2 v f v f  ), ( ) ( ) 0 ( 7 ) 0 ( 5 v f v f  ), ( ) ( ) ( 6 ) 0 ( 4 v f v f  ), ( ) ( ) 1 ( 1 ) 0 ( 6 v f v f   ) ( ) ( ) 1 ( 1 ) 0 ( 7 v f v f    d d d d d d d d 15 13 11 9 7 5 3 , , , , , , , 
is an arithmetic progression, and the common difference is d 2 .

Suppose when

1   k n , we know   ) ( ) ( ) ( 1 , 1 , 8    k C E uv v f u f   d k d d d d d d 2 ) 9 8 ( , , 2 2 , 2 1 ,         
is an arithmetic progression, and the common difference is d 2 .

Then when

k n    ) ( ) ( ) ( , 1 , 8 k C E uv v f u f     ) ( ) ( ) ( 1 , 1 , 8     k C E uv v f u f   ), ( ) ( ) 1 ( 2 ) 1 ( 1    k k v f v f ), ( ) ( ) 1 ( 3 ) 1 ( 1    k k v f v f ), ( ) ( ) 1 ( 5 ) 1 ( 3    k k v f v f ), ( ) ( ) 1 ( 4 ) 1 ( 2    k k v f v f ), ( ) ( ) 1 ( 7 ) 1 ( 5    k k v f v f ), ( ) ( ) 1 ( 6 ) 1 ( 4    k k v f v f ), ( ) ( ) ( 1 ) 1 ( 6 k k v f v f    ) ( ) ( ) ( 1 ) 1 ( 7 k k v f v f     d k d d d d d d 2 ) 9 8 ( , , 2 2 , 2 1 ,            , 2 ) 8 8 ( d k d    , 2 ) 7 8 ( d k d    , 2 ) 6 8 ( d k d    , 2 ) 5 8 ( d k d    , 2 ) 4 8 ( d k d    , 2 ) 3 8 ( d k d    , 2 ) 2 8 ( d k d     d k d 2 ) 1 8 (      d k d d d d d d 2 ) 1 8 ( 2 2 2 1         , , , , 
is an arithmetic progression, and the common difference is d 2 .

In sum for the arbitrary

0 N n  , the mapping 0 , 1 , 8 ) ( : N C V f n  meet: (1) ) ( ) ( v f u f  when v u  and ) ( , , 1 , 8 n C V v u  ; (2)   ) ( ) ( ) ( , 1 , 8 n C E uv f u f     d n d d d d d d 2 ) 1 8 ( 2 2 2 1         , , , ,  . Therefore n C , 1 , 8 is a
0 ( 1 v ) 0 ( 2 v ) 0 ( 3 v ) 0 ( 4 v ) 0 ( 5 v ) 0 ( 6 v ) 1 ( 1 v ) 1 ( 2 v ) 1 ( 3 v ) 1 ( 4 v ) 1 ( 5 v ) 1 ( 6 v ) 2 ( 1 v ) 2 ( 2 v ) 1 ( 1  n v ) 1 ( 2  n v ) 1 ( 3  n v ) 1 ( 4  n v ) 1 ( 5  n v ) 1 ( 6  n v ) ( 1 n v ) ( 2 n v Fig.2.The Graf n C ,  , d v f 7 ) ( ) 1 ( 1  , d v f 8 ) ( ) 1 ( 2  . Therefore   ) ( ) ( ) ( 1 , 2 , 8 C E uv v f u f    ), ( ) ( ) 0 ( 2 ) 0 ( 1 v f v f   ), ( ) ( ) 0 ( 3 ) 0 ( 1 v f v f  ), ( ) ( ) 0 ( 5 ) 0 ( 3 v f v f  ), ( ) ( ) 0 ( 4 ) 0 ( 2 v f v f  ), ( ) ( ) 1 ( 1 ) 0 ( 5 v f v f  ), ( ) ( ) 0 ( 6 ) 0 ( 4 v f v f  ), ( ) ( ) 1 ( 2 ) 0 ( 6 v f v f   ) ( ) ( ) 1 ( 2 ) 1 ( 1 v f v f    d d d d d d d d 15 13 11 9 7 5 3 , , , , , , , 
is an arithmetic progression, and the common difference is d 2 .

Suppose when

1   k n , we know   ) ( ) ( ) ( 1 , 2 , 8    k C E uv v f u f   d k d d d d d d 2 ) 7 7 ( , , 2 2 , 2 1 ,
        =
is an arithmetic progression, and the common difference is d 2 .

Then when

k n    ) ( ) ( ) ( , 2 , 8 k C E uv v f u f     ) ( ) ( ) ( 1 , 2 , 8     k C E uv v f u f   ), ( ) ( ) 1 ( 3 ) 1 ( 1    k k v f v f ), ( ) ( ) 1 ( 5 ) 1 ( 3    k k v f v f ), ( ) ( ) 1 ( 4 ) 1 ( 2    k k v f v f ), ( ) ( ) ( 1 ) 1 ( 5 k k v f v f   ), ( ) ( ) 1 ( 6 ) 1 ( 4    k k v f v f ), ( ) ( ) ( 2 ) 1 ( 6 k k v f v f    ) ( ) ( ) ( 2 ) ( 1 k k v f v f    d k d d d d d d 2 ) 7 7 ( , 2 2 , 2 1 ,            , 2 ) 6 7 ( d k d    , 2 ) 5 7 ( d k d    , 2 ) 4 7 ( d k d    , 2 ) 3 7 ( d k d    , 2 ) 2 7 ( d k d    , 2 ) 1 7 ( d k d     d k d 2 7     d k d d d d d d 2 7 2 2 2 1        , , , , 
is an arithmetic progression, and the common difference is d 2 .

In sum for the arbitrary

0 N n  , the mapping 0 , 2 , 8 ) ( : N C V f n  meet: (1) ) ( ) ( v f u f  when v u  and ) ( , , 2 , 8 n C V v u  ; (2)   ) ( ) ( ) ( , 2 , 8 n C E uv v f u f     d n d d d d d d 2 7 2 2 2 1        , , , ,  . Therefore C E uv v f u f   =   d n d d d d d d 2 ) 2 5 ( 2 2 2 1         , , , ,  . By (

Labels of Some Special Graph

In order to explan the correctness of the aforementioned labels, we give the arithmetic labeling of

Proof

  As the graph shown on fig.1.

)

  graph. Proof As the graph shown on fig.2.

)

  [START_REF] Kejie | Beijing:the press of technology[END_REF],[START_REF] Chartrand | Graphs and Digraphs[END_REF] we know the mapping f is arithmetic labeling of

  Fig.5. The Graf 3 , 1 , 8 C

( 6

, 8 Label all vertices as follows:

We can see the mapping

Proof As the graph shown on fig. 3.

Label all vertices as follows:

Proof in imitation of Theorem 2.1.

For the arbitrary 0 N n  , the mapping 0 , 3 , 8

By (1), (2) we know the mapping f is arithmetic labeling of Proof As the graph shown on fig. 4.

Label all vertices as follows:


Shimin Luo

Shape Detection For Impeller Blades By Non-Contact Coordinate Measuring Machine

Keywords:

The impeller blades are very important and precise parts in turbine, but they can be worn and deformed easily. In this paper, we present a novel approach to detect the shape of the impeller blades. The proposed approach is to compare the designed 3D model of the impeller blades with the virtual 3D model of the tested part which is reconstructed by non-contact coordinate measuring machine. The non-contact coordinate measuring machine measures an object with optical triangulation, and then we can reconstruct a virtual 3D model for the part. In contrast to previous approaches which detect the parts with complex surface, the proposed shape detection approach is scatheless and reliable. Experimental results also show that our approach gets the shape of the tested part precisely and describes the deformed condition clearly.

Introduction

An impeller is a rotor inside a tube or conduit used to increase the pressure and flow of a fluid. It is the rotating component of a centrifugal pump, usually made of iron, steel, bronze, brass, aluminum or plastic, which transfers energy to the fluid. As an important part of the impeller, the impeller blade directly contacts the fluid and mixes up the fluid so that it might be worn and deformed easily. But how to detect an impeller blade with complex surface is a difficult problem to be addressed.

In reverse engineering, the noncontact coordinate measuring approaches based on laser triangulation measurement principle use multiple views of cameras to get the depth information of the object [START_REF] Snavely | Photo Tourism: Exploring image collections in 3D[END_REF][START_REF] Bradski | Learning OpenCV: Computer Vision with the OpenCV Library[END_REF][START_REF] Atcheson | Time-resolved 3d capture of non-stationary gas flows[END_REF]. The object to be tested can be measured rapidly and precisely without any damage. In recent years, this issues that how to measure object with complex surface becomes one of the hottest questions to be solved in computer vision fields and reverse engineering fields.

In this paper, we exploit one of the noncontact coordinate measuring approaches, that is binocular vision measurement, to reconstruct the virtual 3D model for the impeller blade. By comparing the designed 3D model with the virtual 3D model of the impeller blades, we can detect the shape change of the part to be tested.

The rest of the paper is organized as follows. Section 2 describes how to get the 3D points cloud of the tested object by the binocular vision measurement. Reconstructing the 3D model of the impeller blades from the point cloud data is introduced in Section 3. Section 4 presents the comparing process. Finally, Section 5 gives the conclusion.

Tested Part Digitalization

The basic principle of binocular vision measurement is to use two cameras from different views to take pictures for the tested part, extract a series of central image pixels projected by the linear laser, and pair them in the corresponding images according to stereo matching, finally acquire the 3D coordinate values by pinhole model.

Camera calibration

Camera calibration is a process that obtains the internal and external parameters of the CCD cameras, which aim at establishing a mathematical relationship between the 3D world coordinate system with the 2D image coordinate system. According to the pinhole model, we can transform from the 3D world coordinate system to the 2D image coordinate system by the following four steps [START_REF] Hirsch | BiDi Screen: A Thin, Depth-Sensing LCD for 3D Interaction using Light Fields[END_REF]:

Transform from object space coordinate system to camera coordinate system;

The pinhole perspective transformation of transforming from camera coordinate system to 2D image coordinate system;

The distortion model that considered the first order distortion; Transform from the actual image coordinate system to the image coordinate system.

Finally, we can map the spatial point P with 3D coordinate values x, y, z to the image pixel with 2D image coordinate values u, v by Formula (1):

(1) 1 where x, y, z is the coordinate values to be solved; u, v is the image values; and s, mi,j (i = 1, 2, 3; j = 1, 2, 3, 4) is the camera parameters that can be got by the two-step camera calibration approach proposed by Tsai R Y [START_REF] Tsai | A Versatile Camera Calibration Technique for High-Accuracy 3D MachineVision Metrology Using Off-the-Shelf TV Cameras and Lenses[END_REF][START_REF] Zhang | Flexible camera calibration by viewing a plane from unknown orientations[END_REF].

⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ z y x m m m m m m m m m m m m v

Laser stripe images processing

Noise reduction: The variability of the ambient light and the inside and outside noises produced by cameras lead to the laser stripe images contain a great deal of random noises, so the target features become dimness, therefore the quality of the 2D laser stripe images become worse, which affect the image segmentation, image thinning and image matching. Thus we need filtering algorithm to improve the quality of the images, Gaussian filtering algorithm and median filtering algorithm both can remove the noise points of the laser stripe images effetely, here one of them can be exploited in this situation.

Image segmentation: Image segmentation refers to the process that separate the target features from the background. In binocular vision measurement, the target parts of images are the laser stripe. Because the topology position of the laser strip is very important, and the gray information of the laser stripe is insignificant. So we can use image threshold segmentation algorithm to extract the image positions of the laser stripe. According to the intensity of the ambient light and light produced by the laser, the image threshold segmentation algorithm sets a threshold and describes the pixels that gray value is larger than the threshold with white pixel, also describes the pixels that gray value is smaller than the threshold with black pixel. After image segmentation, we can transform a gray image into a white-black image.

Laser stripe thinning: Since the projection width of the laser stripe on the images is about 1mm, the target laser stripe at each image row after noise reduction and image segmentation occupies more than one pixel, so we need thin the laser stripe. The aim of laser stripe thinning is to transform the projection of the laser stripe to single pixel at each row. The thinning algorithm must guarantee the geometry and topology property of the laser stripe remain unchanged. The gravity central algorithm is often used to get the single pixel laser stripe.

Stereo matching: In binocular vision measurement, in order to obtain the 3D coordinate values of the projection point on the laser stripe, we need to pair the pixel points on the two corresponding laser stripe in the left and right images which are taken by the two cameras at the same time, that is, match one pixel point on the laser stripe in the left image with one of the pixel points on the laser stripe in the right image. The matching algorithm must comply with the following principles: the unique constraint, the continuity constraint, the compatibility constraint, the epipolar constraint, and the order of consistency constraints. The epipolar constraint define the matching pixel points in the right image of a pixel point in left image must be on a specific lines called epipolar line. This constraint greatly reduces the number of pixel points to be verified, and the searching domains are transforming from 2D area to 1D area.

After the above digital image processing, we can extract the information of the left and right images to series of paired matching pixel points (<uL, vL>, <uR, vR>), which facilitate the subsequent calculations [START_REF] Luo Shi-Min | Research on How to Get Object's 3D Coordinate on Two CCD Camera Measure System[END_REF].

Mathematical model establishment

The Formula (2), and (3) are established after we push the coordinate values of the paired pixel points into the Formula (1) respectively and eliminate the unknown parameters.

Actually Formula (2) represents a line that is start with the left camera center to the pixel point (uL, vL) on the left image, while Formula (3) represents a line that is start with the right camera center to the pixel point (uR, vR) on the right image.

L L L L L L L L L L L L L L L L L L L L L L L L m u m z m m u y m m u x m m u m u m z m m u y m m u x m m u - = - + - + - - = - + - + - ( 2
) ) ( ) ( ) ( ) ( ) ( ) (
R R R R R R R R R R R R R R R R R R R R R R R R m u m z m m u y m m u x m m u m u m z m m u y m m u x m m u - = - + - + - - = - + - + - (3)
In order to get the coordinate values x, y, z of the 3D point, we solve the unified equation of Formula ( 2) and ( 3). If the two lines intersect, the intersection point of the two lines is exploited to calculate the 3D point. If the two lines may not intersect, we define the approximate intersection as the point which is closest to the two lines. More precisely, whether two lines intersect or not, we define the approximate intersection as the point P which minimizes the sum of the square distances to both lines [START_REF] Shapiro | Computer Vision[END_REF], as shown in Figure 1.

The precision of reconstruction

To measure the reconstruction precision of the binocular vision measurement, we design an experiment to get the center coordinates of the four tangent circles. We set the centre of the four circle centers as the world coordinate system centre, and make use of the above mathematical model to solve the coordinate values of the four circle centers. As the theoretical values of the coordinate values of the four circle centers is already known, we can get the measure precision by comparison the actual values with the theoretical values of the circle centers. The four circles are shown as Figure 2, and the measurement precision is given as Table I. From Table I, we conclude that the measurement accuracy is within 0.05mm; and this precision can satisfy with the need of industry.

The Cloud Data Post-Processing

We get a lot of point cloud after digitizing the tested part of the impeller blades with the binocular vision measurement described in the previous section, which is a dense collection of surface samples of the impeller blades. We can deal the point cloud of the impeller blades with a dot-curve-surface-based surface reconstructed approach in order to get a visual CAD model [START_REF] Radeva | 3-D Vessel Reconstruction from Biplane Angiograms Using Snakes[END_REF][START_REF] Cañero | 3-D Curve Reconstruction by Biplane Snakes[END_REF]. First, we can obtain a full outline of the tested part through eliminating point cloud noise, merging the point cloud from different views. Secondarily, by sampling the point cloud to a certain percentage and cutting the section cross the cloud point, we can get a series of 3D-spline curse. After smoothing the 3D-spline curse, we make use of them to regenerate a satisfactory watertight surface by blending the surfaces. Finally, we materialize the surface model of the impeller blades and get the visual 3D model for the tested impeller blades.

Comparisons

After the 3D visual model of the tested part are reconstructed, we compare the 3D visual model with the designed 3D model that is already exist at the stage of part designing.

The PRO/ENGINEERING commercial software can be exploited to compare the two 3D model of the part to be tested. Finally, we can get the surface deformation condition for the impeller blades, as shown in Figure 6, which describe different degrees of surface deformation with different colors.

Conclusions

In this paper, we propose a novel approach to detect the shape deformation condition for the impeller blades by comparing the designed 3D model with the virtual 3D model of the tested part that is reconstructed by non-contact coordinate measuring machine. In contrast to previous approaches which detect the parts with complex surface, the experimental results show our approach is scatheless and reliable.

Figure 1 .

 1 Figure 1. The mathematical model of calculating the 3D points

Figure 2 .

 2 Figure 2. The four circle centre is used to test the reconstructed precision

  Notice that the above steps may have to do repeatedly. If we do not satisfied with the final reconstructed model, we must return to the previous step and redo it. The point cloud, curse model, and 3D model of the impeller blades are shown as Figure3, 4, 5 respectively.

Figure 3 .Figure 4 .Figure 5 .

 345 Figure 3. The point cloud for the impeller blades to be tested

Figure 6 .

 6 Figure 6. The surface deformation condition for the impeller blades

Table 1

 1 The reconstruction precision for the four circle centre

		x	y	z	Paired image coordinate values	Distance	Distortion
	1	-30.0 -30.023	30.0 30.003	0.0 0.040	( <123.3, 132.0>, <184.4, 111.4>)	42.426 42.445	0 0.019
	2	30.0 29.966	30.0 30.009	0.0 0.067	( <121.5, 194.3>, <184.3, 179.2>)	42.426 42.409	0 -0.017
	3	-30.0 -30.017	-30.0 -30.004 -0.124 0.0	( <367.3, 131.5>, <377.3, 373.6>)	42.426 42.442	0 0.016
	4	30.0 30.001	-30.0 -30.017 0.042 0	( <366.0, 197.8>, <437.0, 117.9>)	42.426 42.439	0 0.013


Zhimin Liu
email: :liuzhimin2006@163.com

Fengqi Zhou

Hongjian Li

Bin Tang

Zhengfang Liu

Qingping Wu

Aixi Chen

Kelin Huang

An Equilateral Triangle Waveguide Beam Splitter

Keywords: Self-imaging, Equilateral triangle waveguide, beam splitter

In this paper an optical beam splitter based on an equilateral triangle waveguide (ETW) is studied theoretically and numerically. We show that an optical beam splitter bases on ETW formed only when the length of the waveguide and the location of incident light are appropriate. When the length of the ETW is one third of the selfimaging length, the incident light is divided into three identical and symmetrical beams; while the length of the ETW is one nine of the self-imaging length, the incident light is divided into twenty-seven identical and symmetrical beams, if the number is less than twenty-seven, that is because some of images overlap with each other. It is expected that the results obtained here will help to design a new splitter.

Introduction

The propagation of light along a waveguide is one of the fundamental and important questions of wave optics. In recent years the splitter and self-imaging of waveguide have been actively discussed. A theoretical and experimental investigation of the self-imaging properties of planar waveguide have been studied [START_REF] Ovchinnikov | Revivals of light in a planar metal waveguide[END_REF][START_REF] Ovchinnikov | Revivals and oscillations of the momentum of light in a planar multimode waveguide[END_REF][START_REF] Ovchinnikov | A planar waveguide beam splitter[END_REF] . Self-images in a rectangular waveguide has been reported [START_REF] He | General properties of NM self-images in a strongly confined rectangular waveguide[END_REF] . Similar studies [START_REF] Wu | Direct image transmission through a multi-mode square optical fiber[END_REF][START_REF] Wu | Optical sine transformation and image transmission by using square optical waveguide[END_REF] were performed on square fiber, and it mentioned that round fiber do not have the image transmission characteristics above, that is mainly because of the angular ambiguity and high symmetry. And optical power splitter(OPS) base on multimode interference waveguide has been studied [START_REF] Sun | Experimental demonstration of two dimensional multimodeinterference optical power splitter[END_REF][START_REF] Han | Multimode interference effect in plasmonic subwavelength waveguides and an ultra-compact power splitter[END_REF][START_REF] Zhang | Splitting-on-demand optical power splitters using multimode interference waveguide with programmed modulations[END_REF] . OPS made of photonic crystal waveguide has been studied [START_REF] Ma | Power splitter based on cascaded multimode photonic crystal waveguides with triangular lattice of air holes[END_REF][START_REF] Li | An ultra-short double-wavelength optical power splitter for two waveguides operation based on photonic crystal multimode interference[END_REF] . A few investigators have been discussed the equilateral triangle resonators [START_REF] Huang | Eigenmode confinement in semiconductor microcavity lasers with an equilateral triangle resonator[END_REF][START_REF] Guo | Resonant frequencies and quality factors for optical equilateral triangle resonators calculated by FDTD technique and the Padeapproximation[END_REF][START_REF] Huang | Analysis and numerical simulation of eigenmode characteristics forsemiconductor lasers with an equilateral triangle micro-resonator[END_REF][START_REF] Wysin | Resonant mode lifetimes due to boundary wave emission in equilateral triangular dielectric cavities[END_REF][START_REF] Huang | Analysis of semiconductor microlasers with an equilateral triangle resonator by rate equations[END_REF] and ray optics model for triangular hollow waveguides [START_REF] Isaac | Ray optics model for triangular hollow silicon waveguides[END_REF] , but few attentions are paid to investigate the properties of self-images in an ETW. So study on the behavior of light propagation through this waveguide would be of practical interest. In our previous paper [START_REF] Liu | Image transmission through a mental equilateral triangle waveguide[END_REF] , we showed that an image transmission through an ETW, in this paper, we study on the behavior of Gaussian beam propagation(GBP) through this waveguide. An optical beam splitter bases on ETW formed by the new study, the results may have convenience in beam splitter application.

Theory

As shown in our previous paper [START_REF] Liu | Image transmission through a mental equilateral triangle waveguide[END_REF] , consider an ETW with side size a and length L (see Fig. 1), and the cladding is a perfect reflector, the field vanish at the boundaries. The field inside the waveguide can be expressed by eigenfunction expansion of Helmholtz equation in the triangular section [START_REF] Doncheski | Quantum mechanical analysis of the equilateral triangle billiard: periodic orbit theory and wave packet revivals[END_REF] .

∑ ∞ = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ - - = 1 2 2 ) 0 ( ) , 2 ( ) 0 ( ) , 2 ( ) ( 3
4 1 exp ) , ( ) , , ( n n n n n a n ikz y x a z y x E λ ψ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ - + - - + + ∑ ∑ ∞ ∞ = - - + + 2 2 2 2 1 ) ( ) , ( ) ( ) , ( ) ( ) , ( ) ( ) , ( ) ( 9
) ( 4 1 exp )] , ( ) , ( [ a mn n m ikz y x a y x a n m n n m n m n m n m λ ψ ψ (1)
For integral values of , with the restriction that . For the case of , there are two degenerate states with different symmetry properties, which can be written as follows [START_REF] Lin | Quantum spectra and classical orbits in two-dimensional equilateral triangle billiards[END_REF] (the correct normalizations are included here):

n m, n m 2 > n m 2 > [
⎢ ⎢ ⎣ ⎡ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ - = - a ny a x n m a y x n m 3 2 sin 3 ) 2 ( 2 sin 3 3 16 ) , ( 2 ) ( ) , ( π π ψ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ - - a my a x m n 3 2 sin 3 ) 2 ( 2 sin π π ⎥ ⎥ ⎦ ⎤ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ - ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + a y n m a 3 ) ( 2 sin 3 n)x (m 2 sin - π π (2) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ - ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ - - ⎢ ⎢ ⎣ ⎡ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ - = + a y n m a a my a x m n a ny a x n m a y x n m 3 ) ( 2 sin 3 n)x (m 2 cos 3 2 sin 3 ) 2 ( 2 cos 3 2 sin 3 ) 2 ( 2 cos 3 3 16 ) , ( 2 ) ( ) , ( π
π π π π π ψ (3)
In the special case of there is a single nondegenerate state for each , and the wavefunction is given by

n m 2 = n ⎥ ⎥ ⎦ ⎤ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ - ⎢ ⎢ ⎣ ⎡ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = a ny a ny a nx a y x n n 3 4 sin 3 2 sin 2 cos 2 3 3 8 ) , ( 2 ) 0 ( ) , 2 ( π π π ψ (4)
The coefficients are determined by the projection of the initial distribution onto the waveguide

) ( ) , ( ) ( ) , ( ) 0 ( ) , 2 ( , , - + n m n m n n a a a ∫∫ = ) , ( ) , ( ) , ( 1 1 1 1 1 ) 0 ( ) , 2 ( 1 1 ) 0 ( ) , 2 ( y x E y x dy dx y x a n n n n ψ (5a) ∫∫ + + = ) , ( ) , ( ) , ( 1 1 1 1 1 ) ( ) , ( 1 1 )
( ) , ( y x E y x dy dx y x a n m n m ψ (5b) ∫∫ - - = ) , ( ) , ( ) , ( 1 1 1 1 1 ) ( ) , ( 1 1 )
( ) , ( y x E y x dy dx y x a n m n m ψ (5c)
In this paper, the initial light we consider a GBP

] ) 6 3 ( exp[ ) , ( 2 0 2 1 1 1 ω a y x y x E - + - = (6)
Where 0 ω is beam waist size of the GBP, The GBP is launched at

) 6 3 , 0 a ( , instead of the center ) 3 3 , 0 a (
, in order to avoid any overlap of the images. The coefficients can't be get analytic solution, which are given by oscillatory numerical integral.

λ 2 9 2 0 a L =
is the self-imaging length of the ETW, the detailed derivation as shown in [START_REF] Liu | Image transmission through a mental equilateral triangle waveguide[END_REF] , that is, at this distance (the self-imaging distance) the initial distribution repeats.

Numerical results and analysis

The output field at the back face of the waveguide was numerically calculated according to Eq.( 1) with the waveguide size ,the wavelength , n m [START_REF] Ovchinnikov | Revivals of light in a planar metal waveguide[END_REF] , in this paper 100 , = n m are used in calculation. , that is the incident wave. It is clear that the output field consists very well with the input field both in field intensity and position from Fig (2). From these we consider that the simulation procedure is correct and feasible. ,where is an integer. n

The field at the face of

The output field at the back face of other length

As shown in our previous paper [START_REF] Liu | Image transmission through a mental equilateral triangle waveguide[END_REF] , similar the results at the distance 3 0 L z = are also simulated, obviously the initial distribution is splitted into three identical and symmetrical distributions at the back face of the waveguide, and the output fields have 3 fold rotational symmetry. Moreover, the total intensity of the three beams consists with the intensity of the input field, these are displayed in Fig( 4).

Conclusion

Summarizing, from above discussed, an optical beam splitter bases on ETW formed when the length of the waveguide and the location of identical light are appropriate. When the length of the ETW is one third of the selfimaging length, the incident light is divided into three identical and symmetrical beams; while the length of the ETW is one nine of the self-imaging length, the incident light is divided into twenty-seven identical and symmetrical beams, if the number is less than twenty-seven, that is because some of images overlap with each other. It is expected that the results obtained here will help to design a new splitter.

Figure 1 .

 1 Figure 1. Schematic diagram of an equilateral triangle waveguide

λ

  But normally, the coefficients decrease rapidly with increasing , the actual number of modes which have to taken into account is much less than n m, max max

  Firstly, at the incident face of the waveguide 0 = z

Figure 2 .Figure 3 .

 23 Figure 2.The field at the distance 0 = z Figure 3. The field at the distance

Fig. 5 (

 5 a) demonstrates the similar results when the input field is launched in the other location, for example the location of ) , if the position of the input field is located in the center of the waveguide ) only one output beam is still located the center, Fig.5(b) shows the result, which is because some of images overlap with each other.

Figure 4 .

 4 Figure 4.The field at the distance 3 0 L z = Figure 5. The incident wave launched at the ) 4 3 , 0 ( a and ) 3 3 , 0 ( a

Fig 6 .

 6 Fig 6. The field at the distance 9 0 L z = : (c)the incident wave launched at the ) 6 3 , 0 ( a ; (d)launched at the ) 4 3 , 0 ( a

* This work was funded by the National Natural Science Foundation of China (Grant No. 60708014) , the Key Natural Science Foundation of Hunan Province (Grant No. 06JJ2034), the Natural Science Foundation of Jiangxi (2008GQW0017) and the Research Foundation of East China Jiaotong University (08JC04,09JC01).


Fengyun Xie

Jihui Zhou

Experimental Investigation of Influence on Non-destructive Testing by Form of Eddy Current sensor Probe

Keywords: Eddy current testing, Probe, Non-destructive testing (NDT), Sensitivity

Eddy current testing is a kind of non-destructive testing (NDT) method based on the principle of electromagnetic induction. The probe is the key of eddy current non-destructive inspection and its design or combination of form will influence detectability. A complete set of eddy current testing system is designed for standard testing copper and defect copper. Under the same liftoff distance and the same high frequency excitation signal, designed three types of probe, which are single probe single coil, single probe double coil and double probe double coil, are used to carry out NDT experiment. Experimental results show that sensitivity and resolution of detection system are obvious difference among the different form of eddy current sensor probe. Probe shape and coil winding are improved according to the experimental results. Corresponding improved probe is adopted to carry out NDT experiment at the same condition. Experimental results show that detectability is enhanced significantly.

Introduction

Eddy current testing based on the principle of electromagnetic induction is a kind of NDT method for testing metal semi-finished and metal components. It has been more and more widely used for its no need touch, high-speed of testing, easy automation, suitable for online testing and high detection sensitivity of surface defect. For example, YANG [START_REF] Yang | Identification of Corrosion Fringe in Pulsed Eddy Current Nondestructive testing[END_REF] et al, considered identification of corrosion fringe in pulsed eddy current non-destructive testing, He 2 et al, considered pulsed eddy current technique for defect detection in aircraft riveted structures. However, the form of sensor probe has a great influence on the detection performance. In recent years, it is a research focus of many scholars how to improve the sensitivity of eddy current probes. But the discussion only is in the influence of one aspect, rather than the system. For example, Ren [START_REF] Ren | Electromagnetic Detection[END_REF] et al, proposed to increase the probe diameter or adapt big pie-type probe to improve the detection sensitivity, but it will reduce detection sensitivity of small defects. Kim [START_REF] Kim | A Study of a Dual-electromagnetic Sensor System for Weld Seam Tracking of I-butt Joints[END_REF] et al, considered a dualelectromagnetic sensor system for weld seam tracking of I-butt joints. Li 5 et al, analyzed detection principle and influence factors of eddy current. Yu 6 et al, designed a novel pulsed eddy current testing probe based on 3D magnetic field measurement. Gao [START_REF] Gao | Study on Structure Optimization of Eddy Current Probe[END_REF] et al, studied on structure optimization of eddy current probe, and obtained three influence factors on eddy current sensitivity: exciting coil of eddy current is stronger than slot width ,and slot width is stronger than detection coil of eddy current.

In this paper, we summarize the previous discussion, full unscramble measurement principle of eddy current. The procedure is: to design a placed device of eddy current testing; to use different forms of probe to carry out comparative test to the standard copper and defect copper. The specific objectives are: to get the relations between probe form and sensitivity of NDT; to put forward recommendations for improvement of the probe.

Testing Principle and Methods of Eddy Current

Eddy current testing is a kind of NDT method based on the principle of electromagnetic induction, which is applied to conductive materials. Testing principle is the following: the signal generator provides high frequency alternating current to the probe in the detection coil, detection coil produces an alternating magnetic field, and the specimen produces eddy current. Eddy current is affected by the properties of the specimen, and in turn it changes impedance (voltage) of coil, then oscilloscope output impedance (voltage) of coil. Testing process includes picked up signal, signal amplification, signal processing, eliminated interference signal, and display and record test results.

There are two kinds of detection methods. One is a double-coil high frequency reflection, whose schematic diagram is shown in Fig. 1.it has a high detection sensitivity of surface defect, but it is lower defect sensitivity with deeper below the surface; The other is double-coil low frequency transmission, whose schematic diagram is shown in Fig. 2. Two methods have the same testing process. Signal generator produced alternating current flows through the coil, when the probe moves to the specimen, the eddy current will decrease. Impedance of the coil is displayed and recorded by the meter. Using auxiliary equipment to do comparative analysis of results from Standard specimens and defect specimens can obtain NDT results.

Theoretical Basis for Experimental Study

The workpiece signal of detected is from impedance of the detection coil or the induced voltage changes of secondary coil in eddy current testing. We use long straight solenoid of cylindrical conductor as the object of research, suppose the radius of cylindrical conductor as a less than the solenoid inner radius b, and suppose turns of per unit length as n. In the cylindrical conductor (0 <r <b), the magnetic field strength is

) ( . r H z
, magnetic field strength is equal to the excitation magnetic field 0 H in the gap (a <r <b).Using the concept of Foster effective permeability can obtain the magnetic flux through the coil cross-section [START_REF] Ren | Electromagnetic Detection[END_REF] .

). (

2 2 0 0 2 0 0 . a b H a H eff r - + = Φ π μ π μ μ μ (1)
Coil phasor of induced electromotive force(EMF) per unit length is written as

). ( 2 2 0 0 2 0 0 . . a b H n j a H n j n j eff r - - - = Φ - = π μ ω π μ μ μ ω ω ε (2)
Coil no-load induced EMF per unit length is .

I U Z = , normalized impedance is . 1 0 eff r Z Z μ ημ η + - = (5)
From eqs (4) and ( 5), we can obtain the same expression by normalized induced EMF of the solenoid detection coil and normalized impedance, which can instead each other in calculating sensitivity. Moreover, if the detection coil and the excitation coils have the same flux and turns N, the induced EMF of detection coil is

). 1 ( 4 2 ) 1 ( 2 0 0 . 0 . eff r eff r d H fN U U μ ημ η π μ π μ ημ η + - = + - = (6)
where the induced EMF of detection coil is relation to excitation frequency f, detection coil diameter d, detection coil turns N, excitation magnetic field for H 0 , fill factor η ,the effective permeability eff μ .

Eddy Current Testing Scheme

According the principle of eddy current testing, the scheme is shown in Fig. 3. Signal Generator issues high frequency alternating signal to the detection probe, taking into account impedance of the exciting coil and detection coil may not be equal. We use a balanced circuit to eliminate the voltage difference between the two coils in pre-test.

In the detection, the detection coil to detect defective parts will produce a slight and imbalance signal. After amplification, phase sensitive detection, filter, and removed the interference signal will turn into the DC signal which contains phase and amplitude characteristics of impedance (voltage) of coil, at last displayed and recorded by display device.

According to records of the results, we draw the normalized sensitivity curves with the lift-off change, put forward recommendations for improvement of probe the form and carry out improvement by analyzing the curves. At the same time, we draw the normalized sensitivity curves with the lift-off change, and draw final test conclusions.

NDT Experimental Study

Test Preparation

In accordance with the testing program, preparing experimental apparatus, the main instruments include a high frequency signal generator, an oscilloscope , a standard copper , a defect copper whose depth of defect size is 2mm, and length of defect size is 12mm, multiple probes which have a single probe self-inductance coil (1000 turns), a single probe mutual inductance coil (500 turns each), two double probe transmission coils (500 turns).To make the coil diameter of probe is 8mm and 10mm, thickness is 4mm and 6mm.

Test Procedure

Test procedure is to build test equipment in accordance with testing program. We regulate output frequency of high-frequency signal generator as 4KHz, adjust lift-off distance of excitation coil and detection coil respectively as 0mm, 1mm, 2mm, 3mm, 4mm, 5mm. Using different forms probe test standard copper and defect copper, output voltage peak -peak value by oscilloscope, we draw the normalized sensitivity

Influence of Detection Sensitivity by Different Probe Forms

Fig. 4 and 5 are the normalized sensitivity curves with the lift-off change to initial test standard copper and defect copper. Curve 1 is the result of oscilloscope by connecting to signal generator, curve 2 is the detective result of the single probe, curve 3 is the result of the double probe in series, curve 4 is the no-load result of the double-probe, curve 5 is the result of double probe reflection, curve 6 is the detective result of the double probe transmission.

Influence of Impedance (Voltage) by Probe Diameter

Under the 4KHz high-frequency alternating signal generator, we change the probe diameter. Fig. 6 shows the influence of probe diameter, with the probe diameter increasing, the impedance moves down along the curves, as the coil diameter increases, the detection sensitivity decreases.

Improved Probe Test

Analyzing initial test results can obtain that probe size, coil thickness and coil turns closely related test results. Improved probe is the following : arranged the copper wire of probe as far as possible orderly, enhanced the magnetic flux density of the surface, increased the probe turns by 100 turns, changed the probe diameter for 8mm and thickness for 4mm. Using the improved appropriate probe include single probe selfinductance, single probe mutual inductance , double probe transmission, double-probe reflection , double-probe in series and in parallel to carry out NDT and experimental analysis, and draw sensitivity curves of Fig. 7 and8.

Results and Discussion

We contrast sensitivity curve of before and after Probe improved. 1) Sensitivity curve 1 to 3 almost has no change under small lift-off distance. Curve 1 is the result of oscilloscope by directly connecting to signal generator, curve 2 is the detective result of the single probe, curve 1 and curve 2 almost coincide, it shows little effect on the output changes by single probe self-inductance. Curve 3 is the result of the double probe in series, curve 1 and curve 3 almost coincide, it shows the probe in series with different the number of turns, if equal of turns add, the results have no change.

2) Sensitivity curve 4 to 6 changes significantly, sensitivity of double-probe transmission no specimen is higher than the existing specimen, minimum sensitivity is double-probe reflection.

3) Detective sensitivity of standard copper is higher than defect copper. With liftoff distance increasing, sensitivity decreases rapidly, for example, Fig. 5 shows the defect signal amplitude down to the 1/ 4 of the surface when curve 6 lift-off for the 1mm,.

4) Comparing Fig. 4 and Fig. 7, Fig. 5 and Fig. 8, the sensitivity of improved probe is significantly higher than before improvement.

5) Probe diameter significant has influence on the detection sensitivity, with the coil diameter increasing, the detection sensitivity decreases. As diameter of the probe coil increases, the magnetic flux density of workpiece increases, the eddy current value increases, then the equivalent resistance decreases.

Conclusion

Eddy current NDT is high sensitivity for detecting defects of conductor surface and near surface, by comparison of the test, the following are concluding summaries:

1) The different probe forms have a significant influence on the ability of eddy current testing. Detectability of double probe transmission is greater than detectability of double probe reflection, detectability of double-probe is greater than detectability of single probe. The coil in series, detectability will be no change if equal of turns add.

2) Probe diameter has influence on the detection sensitivity, with the coil diameter increasing, the detection sensitivity decreases significantly. To increase detection sensitivity, the probe coil diameter must be equal to or less than the length of defects.

3) Probe placed has a great influence on the detection sensitivity, with lift-off distance increasing, detection sensitivity decreases rapidly.

4) Excitation coil has more influence than detection coils on detection sensitivity, increased excitation coils turns can help to improve the detection sensitivity, but increased detection coils turns will decrease the detection sensitivity.

Fig. 1 .Fig. 2 .

 12 Fig. 1. Schematic diagram of low

  .

  Thus, coil of normalized induced EMF per unit length is filling factor. Considering relationship between the impedance per unit length and the induced voltage are .

Fig. 3 .

 3 Fig. 3. Eddy current testing scheme

Fig. 4 . 5 .

 45 Fig. 4. Standard copper sensitivity Fig. 5. Defect copper sensitivity curves with the lift-off curves with the lift-off

Fig. 6 .

 6 Fig. 6. Influence of impedance by probe diameter N orm alized im pedance

Fig. 7 .

 7 Fig. 7. Standard copper sensitivity curves of Fig. 8. Defect copper sensitivity curves of improved probe with the lift-off improved probe with the lift-off

Correspondence: Email: xiefyun@163.com; Telephone: 0086-791-7046135; Fax: 0086-791-

Acknowledgment. This work is supported by the carrying tools and equipment of Ministry of education key laboratory (09JD03) .


Nannan Wen

Daoliang Li

Daokun Ma

Qisheng Ding

A Wireless Intelligent Valve Controller for Agriculture Integrated Irrigation System

Keywords: Wireless, Valve controller, Irrigation system

Abstract

Introduction

With the popularization and improvement of water-saving irrigation technology, agricultural irrigation control technology is applied gradually. However, irrigation control equipments in application at this stage are from abroad and also very expensive, which are only for demonstration and lack of significance for promotion. Current automated irrigation system with a large number of cables brings many problems such as installation, maintenance, expansion and other issues. Therefore, it is hot to develop a low-cost irrigation valve controller independently for agriculture irrigation system. For example, a low cost solar-powered feedback controller for DIC of fixed irrigation systems was developed. The controller uses soil water potential (SWP) measurements to control the amount of water applied to each specific management area of a field, and measured system hydraulic pressure to communicate with other controllers. The results indicate that the controller was effective in maintaining the SWP in the root zone close to a predetermined management allowed deficit (MAD). (F.R. [START_REF] Miranda | An autonomous controller for site-specific management of fixed irrigation systems[END_REF] A wireless broadcast irrigation control system and a low power wireless DC solenoid valve based on OOK modulation and powered by battery were design and applied throughout the greenhouse irrigation in a plantation. [START_REF] Shen Changjun | Development and Application of Low Power Wireless DC Solenoid Valve and Controlling Module[END_REF] With advanced electronic computer control and wireless transmission technology, a precision irrigation control system was designed for water-saving irrigation. (Kuang Qiuming et al, 2007) A new automatic smart controller for irrigation based on GSM network has been developed, it can receive GSM message from PC and mobile, then control the valves by wireless radio communication. (Yang Genghuang et al, 2005) Many irrigation-scheduling methods have been developed over the years, but adoption by producers has been limited by cost, installation time, maintenance, and complexity of the decisions involved. (F.R. [START_REF] Miranda | An autonomous controller for site-specific management of fixed irrigation systems[END_REF] The above-mentioned irrigation controllers which used OOK modulation, infrared, GSM and other means of communication bring with high price and high maintenance costs. Besides, most commercially available sensors and actuators assembled for irrigation system networks are too complex and/or costly to be feasible for site-specific management of integrated irrigation systems. A wireless intelligent valve controller for site-specific management and/or operation of a wireless integrated irrigation control system is easier to install and maintain as compared to cable irrigation control. As a result, a potential solution to these problems is a total wireless automation of irrigation control system. Wireless automation irrigation controllers can be implemented using spatially variable irrigation systems to optimize yields and maximize water use efficiency for fields with variation in water availability due to different soil characteristics or crop water needs. (Zhang [START_REF] Wei | Design of precision irrigation system based on wireless sensor network and fuzzy control[J][END_REF] The objectives of this research were to develop and test an autonomous, low cost, wireless intelligent irrigation valve controller for wireless integrated irrigation control system for the actual demands in agricultural irrigation.

Architecture of Wireless integrated irrigation control system

Integrated agricultural production demands and learning from foreign experience in research, the architecture of wireless integrated irrigation control system is shown in Fig. 1. The system was composed of two parts, wireless sensors monitoring network and remote control center. Wireless sensors monitoring network consists of wireless information acquisition nodes and irrigation control nodes distributed in the field, the remote control center sends the commands of data acquisition and valve control though the routing nodes. Wireless sensors monitoring network uses star topology, end nodes route by way of the routing nodes to the sink nodes, then the sink nodes transmit information to the wireless access point by GPRS and control computer receives information from the wireless access point by RS232. Information acquisition, remote control, parameter setting, intelligent alarm functions are achieved by the remote control center. The system passed soil information and meteorological parameters collected by sensors in real-time monitoring to the remote control center though wireless network.

Then the remote control center automatic analysis and makes irrigation management decision to open or close valves. With timely scientific guidance amount of irrigation, the system achieved the sustainable use of water resources and automatic and intelligent irrigation. The remote control center can also share information across users through the Internet.

Materials and methods

Irrigation valve controller description

For irrigation implementation, a field is typically divided into irrigation management units based on soil characteristics, crop water requirements, and/or economic factors prior to the installation of the control system. A wireless integrated irrigation control system is installed in each irrigation management unit to monitor soil temperature, humidity and meteorological parameters and ensure water-saving irrigation.

The valve controller developed in this study is designed to work autonomously without hard-wire connections between individual control units. Each controller is designed to operate on battery power. Soil moisture determinations and irrigation decisions occur at fixed regular intervals set by the remote control center. Real-time clocks for all controllers are synchronized for measurement and irrigation decisions. After measurements and irrigation decisions are made, remote control centre sends signal to valve controllers. Each controller installed in system is programmed to process the control commands received from remote control centre to autonomously open an irrigation solenoid valve, triggering relay boost driver unit. Finally, each controller stores the corresponding valve status feedback information from state feedback switch and transmits to remote control center.

Controller hardware

Wireless Intelligent Valve Controller shall be the core of the wireless irrigation control node, hardware modularization was adopted. UARTs, SPI port with 5 selects, 2 wire serial interface, etc. These features all make for a highly efficient, low power, single chip wireless microcontroller for battery-powered applications. This MCU was selected based on low-cost, processor speed, low power requirements, rapid software development, and ease of system integration with custom circuits.

Power unit

Two 1.5V batteries as the input source through the power unit provide a stable output voltage for other units. Power unit contains polarity protection circuit and voltage regulator circuit. Polarity protection circuit includes Schottky diode and the decoupling capacitors. Voltage regulator circuit utilizes voltage regulator chip to ensure output voltage stably. After fully considering energy in application field, controller utilizes ordinary battery as power supply to ensure that the system works over an irrigation quarter.

Wireless communication unit

ZigBee is a two-way wireless communications technology in short distance communication, with low complexity, low power consumption, low data rate. Its complete protocol stack is only 32 KB, can be embedded in a variety of devices, while support geographic targeting. It is a protocol specification developed for small device wireless network. It is a part of the family of IEEE wireless network protocol. It has a very complete hierarchy. Wireless communication unit supported by low-power radio frequency chip with the typical external circuitry, communicated with the control unit by MCU interface and completed the wireless transceiver function. It works in the global free public band (2.4GHz), reducing the traditional wireless operating cost.

Relay boost driver unit

In sleep mode, relay boost driver unit is off. Once the controller receives the valve-driven control signal, it enables relay boost driver unit. Low-power boost chips installed in the relay boost driver unit circuitry will boost the low input voltage to 5 ~ 24V working voltage suitable for solenoid valve, send the driver pulse to control valve. Finally, each controller stores the corresponding valve status feedback information from state feedback switch and transmits to remote control center. The valve controller uses 3V battery as power, based on ZigBee protocol, waiting for remote control command. It can actuate relay boost driver unit to control valve. The MCU collects the state feedback information in real-time and transmits to remote control center. The controller supports a number of pulse solenoid valves from various valve manufacturers and can be easy to installation and operation.

Controller software

There are 4 kinds of the operation states during the controller working: the initial state, the task query state, the task execution state, sleep state. Diagram of specific state transition is shown in Fig. 3. After the wireless valve controller was powered into the initial state, the microcontroller completed hardware initialization, including the port initialization, watchdog initialization, the system clock initialization, and variable initialization, etc. Then the controller starts testing a higher-level control signal which drives it into the task query state. If the wireless communication unit detected execution signal, the microcontroller will further determine the type of tasks, for instance, valve control, status detecting, parameter setting, and then enter the task execution state. If no task is detected, the controller enters sleep state. It will be wake up automatically by software timing, then checks control signal again and enters into the task query state. It contains a main loop and several subroutines such as valve control, status detecting, and parameter setting that enable the MCU to perform the following tasks:

Initialization

-initialize hardware, including the port initialization, watchdog initialization, the system clock initialization, variable initialization; -register to routing node in the same network, report device information; -request tasks from superior; -query tasks, receive remote control commands; -process the remote commands to determine the type of tasks, execute the task -store control information, time, and valve status in the controller memory; -receive control commands from remote control center to drive irrigation valve;

Irrigation valve controller testing

To measure the valve controller performance, a resistor circuit is used to series connect with the controller (Fig. 5). The circuit was powered by battery. Using a small resistor, resistance on the circuit can be neglected in the energy. Measured the voltage across the resistor by oscilloscope, circuit current value can be obtained in the series circuit to calculate the energy consumption of valve controller. The valve controller during operation including the initial state, the task query state, the task execution state and sleep state. To facilitate the analysis, the above conditions are divided into the state of active and sleep. Active Consumption w P can be calculated using the equation:

w w w P I T  (1)
Where w I is the Active Current, w T is the Active Time for the valve controller.

The Average active current wa I can be obtained by the following equation:

Results and discussion

The controller performance was evaluated at demonstrations in Beijing and Xinjiang. To verify adequate operation of the hardware and software, and the controller in the root zone on a real-time basis, some controllers were tested to simulate a site-specific irrigation system in laboratory. We chose one of them to analyze its consumption.

System hardware and software performance

The controller hardware and software performed all tasks as designed. Data downloaded from the controllers showed that the irrigation control system continually measured apparatus parameters and status information, and opened or closed the solenoid valve when needed without failure. User interactions with the controllers using a notebook computer were also successful.

4.2Consumption current in active and sleep state

Using two ordinary batteries to power the valve controller, about 1200mAh, specific test results are as follows. The performance of the irrigation controller was analyzed in terms of satisfactory operation of the controller hardware and software. The irrigation controller performance was considered satisfactory and two batteries would be sufficient to power the irrigation controller during the normal irrigation season. If the sleep time was set at 10min or more, the controller proved to be effective for the actual application in the root zone.

Tab

Conclusion

A Wireless Intelligent Valve Controller for wireless integrated irrigation control system was developed and tested. The controller proved to be reliable, affordable, and effective in practice without hard-wire connections. The wireless intelligent valve controller with control unit, combined with low-power microprocessor chip and a sound external circuit, powered by battery, received control command from remote control center, executed the tasks, such as information acquisition, remote control, parameter setting, state feedback, while the task of valve control must be driven though the relay boost driver unit. The wireless transceiver capabilities reflected in the wireless communication unit. The valve control can be widely used in different irrigation regions. Wireless intelligent valve controller fully considers the energy in application field, setting the collection/control frequency in accordance with the user demands.

Increasing solar power charge unit to controller to ensure the power supply is the next research work. Wireless intelligent valve controller is simple construction, easy maintenance, low cost and has good application prospects.

Fig. 1 .

 1 Fig. 1. Architecture of wireless integrated irrigation control system

Fig. 3 .

 3 Fig. 3. Diagram of specific state transition The irrigation controller program was written in C. The program uses the memory capacity of the microcontroller (MCU). The program flow diagram is shown in Fig. 4.It contains a main loop and several subroutines such as valve control, status detecting, and parameter setting that enable the MCU to perform the following tasks: -initialize hardware, including the port initialization, watchdog initialization, the system clock initialization, variable initialization; -register to routing node in the same network, report device information; -request tasks from superior; -query tasks, receive remote control commands; -process the remote commands to determine the type of tasks, execute the task -store control information, time, and valve status in the controller memory; -receive control commands from remote control center to drive irrigation valve;

Fig. 4 .

 4 Fig. 4. Flow diagram of controller program

Fig. 5 .

 5 Fig. 5. Resistor circuit used to calculate the valve controller energy consumption

  in one day wa P is the average current consumption for each hour multiplied by 24 hours per day, the formula can be given by valve device energy consumption in different states on one day in laboratory, we estimate the actual duration in work as follows. Days:

Battery Power supply unit Relay boost driver unit Wireless communication unit Pulse solenoid valve State feedback switch Fig. 2. Block

  It consisted of the control unit, power unit, wireless communication unit, relay boost driver unit, state feedback switch, etc. A block diagram of Wireless Intelligent Valve Controller hardware developed in this study is shown in Fig.2. Electronic devices, chips, MCU were selected to meet the low power and low cost required for the controller.

	2 11-bit DACs, 2 comparators, 2 Application timer/counters, 3 system timers, 2
	Control unit
	-Microcontroller(MCU)
	-Reset Circuit
	-Clock circuit
	-UART circuit
	-IO expansion circuit
	-AD Acquisition Circuit
	-FLASH memory circuit
	-Interface Circuit
	The microcontroller (MCU) consists of the Jennic5139, is the master device of control
	unit that is programmed to keep time and control the actuators. The device integrates
	a 32-bit RISC processor, with a fully compliant 2.4GHz IEEE802.15.4 transceiver,
	192kB of ROM, 96kB of RAM, and a rich mixture of analogue and digital peripherals.
	The JN5139 is a low power, low cost wireless microcontroller suitable for
	IEEE802.15.4 and ZigBee applications.
	It has 96kB RAM for share program and 192kB ROM for program code. It's
	peripherals include a 56-pin DIP package with 21 digital I/O pins, 4-input 12-bit ADC,

The sub-components of the control unit are a microcontroller, reset circuit, real-time clock, UART, IO expansion, analog-to-digital (A/D) acquisition, flash memory, and Interface circuit. Each irrigation controller controls four solenoid valves. diagram of Wireless Intelligent Valve Controller developed in this study

3.2.1 Control unit

  The reset circuit and clock circuit ensure equipments work reliability and stability. The JN5139 has two independent Universal Asynchronous Receiver/Transmitter (UART) serial communication interfaces. The UART connected to a level shifter connector to provide the RS232/RS485 line voltage compatible with a PC. The software developer kit uses such an interface as the debugger interface between the JN5139 and a PC. The information can be observed directly in local with RS485/RS232 communication. There are 21 Digital I/O (DIO) pins, which can be configured as either an input or an output, and each has a selectable internal pull-up resistor. Most DIO pins are multiplexed with alternate peripheral features of the device. The Serial Peripheral Interface (SPI) allows high-speed synchronous data transfer between the JN5139 and peripheral devices. The JN5139 operates as a master on the SPI bus and all other devices connected to the SPI are expected to be slave devices under the control of the JN5139 CPU.

The Intelligent Peripheral (IP) Interface is provided for systems that are more complex, where there is a processor that requires a wireless peripheral. The intelligent peripheral interface is a SPI slave interface and uses pins shared with other DIO signals. The interface is designed to allow message passing and data transfer. The controller with above DIO pins and interface circuitry can support 4-way analog inputs, 4-way control power output. A controller can support 2-way pulse solenoid valves and state switch, 2-way soil moisture sensor. Controller extends Flash memory. Data and program are stored in non-volatile memory to prevent loss if a power failure occurs. The user can download recorded data to analyze system performance.

Average energy consumption and the working duration

  .1. Valve controller power consumption current in active and sleep stateAs the sleep time is set by software, furthermore the different sleep time preprogrammed will affect the energy consumption, we test the different average current under the different circumstance. According to the different average current, we can further compute the number of days that the irrigation controller could operate without external charging at the study. was default in the program. The table lists 10s to 10 minutes of sleep time. The average energy consumption can be calculated by different time. Can be seen from Tab.2, the longer the sleep time, the longer controller can work. Moreover, the result showed that the 1200mAh battery was sufficient to maintain an irrigation quarter.

		140.000	2.0	0.280		0.300
		60.000	3.5	0.210		0.300
		140.000	1.0	0.140		0.300
		50.000	100.0	5.000		0.300
	Valve controller power consumption current in active and sleep state is shown in
	Tab.1. The range of active current w I is between 20 ~ 140mA, the operating current
	is 50mA in most of the time and the sleep current is 0.3mA. Total active time is 114.0
	ms.
	4.3 av P	D(d)	M(m)
	10000	0.586810	0.297	0.883	21.202	56.598	1.887
	20000	0.295068	0.298	0.593	14.241	84.265	2.809
	30000	0.197084	0.299	0.496	11.903	100.817	3.361
	40000	0.147953	0.299	0.447	10.730	111.832	3.728
	50000	0.118430	0.299	0.418	10.026	119.690	3.990
	60000	0.098729	0.299	0.398	9.556	125.578	4.186
	120000	0.049411	0.300	0.349	8.379	143.214	4.774
	180000	0.032951	0.300	0.333	7.986	150.258	5.009
	600000	0.009890	0.300	0.310	7.436	161.377	5.379
	w Tab.2 shows controller average energy consumption and the working duration. The I (mA) w T (ms) w p (mAs) s I (mA)
	sleep time s	10.000	2.5	0.025		0.300
		20.000	2.0	0.040		0.300
		40.000	1.5	0.060		0.300
		70.000	1.5	0.105		0.300
		40.000	2.5	0.100		0.300

Tab.2. Controller average energy consumption and the working duration

s T (ms) wa I (mA) sa I (mA) av I (mA) T

Acknowledgements. This research is supported by National Science and Technology Support Programmed (2008BAB38B03-03), Land Consolidation and Rehabilitation Center of Ministry of Land Resources and Beijing UNISM Technology Co., Ltd for their Technical Support. The authors would like to thank all the members of EU-China Center for Information and Communication Technologies for their assistance.


Leping Liu

Wen Zhao

Yuan Ma

Study on Imitating Grinding of Two-Dimensional Ultrasonic Vibration Turning System

Keywords: Two-dimensional, Ultrasonic vibration, Turning, Grinding, Finite element

According to turning instead of grinding process requirements and traditional working principle of ultrasonic vibration turning, a new idea of imitating grinding of two-dimensional ultrasonic vibration turning is brought firstly, and the mechanism of two-dimens ional ultrasonic vibration turning is elaborated. Based on the M ATLAB software, grinding trajectory simulation and honing trajectory simulation are carried out. M oreover, the design of ultrasonic transducer and ultrasonic horn is completed. Finally, the required mode shapes and resonance frequency are obtained by using the finite-element method, the results prove that the theoretical analysis is correct.

Introduction

Ultrasonic vibrat ion cutting appears in the early 20th century, because of good processing effect in difficult-to-machine materials and difficult processing procedures of common materials. It has aroused great concern to experts and s cholars at home and abroad, and actively has carried out research and development. Currently, it has infiltrated into the automotive, aerospace, defense and other areas of the various processing [START_REF] Cao | Ultrasonic M achining Technology[END_REF].

The traditional ultrasonic vibration turning can reduce cutting force and cutting temperature. It also can improve the machin ing accuracy and surface quality. But in traditional ultrasonic vib ration turning p rocess, flank will rub and strike processed workp iece surface, when tool and wo rkp iece are in the separated states, which seriously affectes the quality of the machined surface and tool life [START_REF] Ji | Press Ultrasonic Elliptical Vibration Cutting[END_REF][START_REF] Shaomoto | Study on Elliptical Vibration Cutting[END_REF]. In order to solve the problem above, a new idea of imitating grinding of two-dimensional ultrasonic vibration turning is brought. This improves the quality of ultrasonic vibration turning and realizes turning instead of grinding.

Traditional ultrasonic vibration turning mechanis m

The traditional u ltrasonic vibration turning is to apply a certain frequency and amp litude of v ibration to the tool, which imp roves the effect of turning [START_REF] Lu | Analysis and Simulation of M echanism in Ultrasonic-Vibration Cutting Based on Dynamic Fracture M echanics[END_REF].

Tool's displacement in the cutting direction:

sin( )

x a t   (1) Tool's vibration speed: cos( ) at      (2)
Tool's vibration accelerat ion:

In formu la (1) and formula (2), a is vibration amp litude for the tool,  is vibration angular frequency. Workpiece cutting speed is  . The tool separates fro m workp iece, when a   . The tool and the workpiece touch, when a   , so repeated cycles. For this reason, tip bears alternate pu lling stress and compressive stress with the high-frequency ultrasonic vibration.

3

Two-dime nsional ultrasonic vibration turning structure and working principle Ultrasonic processing system consists of ultrasonic generator, ultrasonic transducer, horn, tools, technology devices and so on. Ult rasonic transducer is the core of the system components. Piezoelectric ceramic stack is co mposed of 4 piezoelectric ceramic disks, which is divided into group A and group B. Each group is composed of 2 axial polarized ring piezoelectric ceramic disks. In group B, each of p iezoelectric ceramic disks is splited into a half circle, and the two semi-circu lar is polarized in the opposite direction. Two piezoelectric ceramic disks are stacked in reverse polarity, and the arrangement is shown in Fig. 2.

In formu la (4) and formu la (5), a is amp litude for the X-axis, b is amp litude for the Z-axis, and  is phase difference between the two directions. According to formula (4) and fo rmula [START_REF] Wu | Analysis of Kinematic Geometry on Face Grinding Process on Lapping M achines[END_REF], equation of motion can be written as follows:

2 2 2 2 2 2 2 2 2 2cos 1 sin sin sin z b x xz b a b ab        (6)
Required u ltrasonic turning track can be obtained by adjusting the phase differernce of the AC electric field which is added to Piezoelectric ceramic d isks.

Two-dimensional ultrasonic turning simulates grinding, honing track

Grinding technology has extensive application in precision machin ing and ultra precision machining [START_REF] Wu | Analysis of Kinematic Geometry on Face Grinding Process on Lapping M achines[END_REF][START_REF] Chang | Computer Simulation Technology for Precision Lapping Process of Workpiece[END_REF][START_REF] Tian | Elimination of Surface Scratch/Texture on The Surface of Single Crystal Si Substrate in Chemo-mechanical Grinding (cmg) Process[END_REF]. The movement of disseminated abrasive is at random. This paper mainly simu lates the motion trace of sedentary abrasive. The trajectory of a single abrasive grit is shown by Fig. 3.

Fig. 3. grinding, honing motion trace

Tool vibration displacement on the X-axis is shown in formula [START_REF] Lu | Analysis and Simulation of M echanism in Ultrasonic-Vibration Cutting Based on Dynamic Fracture M echanics[END_REF]. With the velocity  , tool along the Z-axis does uniform linear motion, wh ich is also called the feed motion. Then simu lative t rajectory is gotten, as shown in Fig. 4. This track is similar to swing straight grinding mot ion trace which is shown by Fig. 3

Two-dimensional ultrasonic vibration turning system design

In this paper, ultrasonic transducer uses sandwich piezoelectric ceramic transducer, which is proposed by the French physicist Langevin. Th is transducer can reduce the problems which are caused by firing and polarization, while reducing the frequency of the piezoelectric ceramic transducer [START_REF] Lin | Ultrasonic Transducer Principle and Design[END_REF]. Transducer is symmetrical structure, the resonant frequency is 20KHz, and back shroud's material is 45# steel, outside diameter is Ф55mm, inside diameter is Ф17mm, ( 1  =7.8g/cm 3 ,C 1 =5.2×10 5 cm/s, E 1 =200GPa); The total of piezoelectric ceramics is 5 and its materials use PZT-8, outside diameter is Ф55mm, inside diameter is Ф17mm and thickness is 5mm, ( 2  =7.5g/cm 3 , C 2 =3.1×10 5 cm/s, E 2 =113GPa). Front shroud's material is alu minu m, outer d iameter is Ф55mm and inside diameter is Ф17mm, ( 3  =2.7g/cm 3 , C 3 =5.1×10 5 cm/s, E 3 =75GPa).  is materials density, C is sound velocity, E is elastic modulus. The total of copper electrode is 5 and its thickness is 0.4mm. The length of back shroud is 1 l and the length of front shroud is 3 l .

27.3mm ll 

Co mposite conical horn is shown in Fig. 13, wh ich is made of alu minu m, outside diameter is D 4 =55mm, inside diameter is D 5 =17mm, ( 45

  =2.7g/cm 3 , C 4 =C 5 =5.1×10 5 cm/s, E 4 =E 5 =75GPa).
N kl kl k D N Nk k N l D C              , , ; (7)
Displacement node 0

2

kl kx kl kl kl                         (8)
Amp lification factor

M : 44 5 1 = cos cos M N kl kl k kl  ( -sin ) (9 )
N is area factor and k is wave nu mber. According to formula [START_REF] Tian | Elimination of Surface Scratch/Texture on The Surface of Single Crystal Si Substrate in Chemo-mechanical Grinding (cmg) Process[END_REF] and formula (9), the simulat ive curve is shown in Fig. 14.

Two-dime nsional ultrasonic vibration system dynamics simulation

Piezoelectric ceramic uses Solid5 in ANSYS element library to establish solid model [START_REF] Ju | Linear Ultrasonic M otor with Two Degree of Freedom Using Longitudinal and Bending Vibration M odes[END_REF]. Solid5 is used in thermal, magnetic, acoustic, piezoelectric and analysis of three-dimensional coupled field. Th is unit has eight nodes, and each node has six degrees of freedom. As for the piezoelectric coupling analysis, Solid5 has large deformability.

For others used Solid95. Its unit has 20 nodes and each unit also has X,Y,Z freedom. Solid95 is higher than Solid45, and it doesn't reduce the accuracy of the case.

Piezoelectric ceramic d isks are made of PZT-8, and they are thickness polarization. The polarized piezoelectric ceramic is anisotropic, so it is different fro m isotropic materials. The dielectric constant matrix, the piezoelectric constant matrix and elasticity matrix are g iven as follo ws.

C                     (12)
The horn is a axial symmet ry revolving body, and uses bottom-up model. The points generate lines, and lines generate a axial plane. The model o f the twodimensional ultrasonic vib ration system is obtained by the axial plane rotated 360°a round the axis. Free mesh is used to generate finite element mesh, which is shown in Fig. 15.

Conclusion

Traditional u ltrasonic vibration turning mechanism and the pros and cons of the processing are analysed in this paper. On this basis, the imitating grinding of twodimensional ultrasonic vibrat ion turning is proposed. The structure of twodimensional ultrasonic v ibration transducer is different fro m the structure of traditional longitudinal ultrasonic transducer. Necessary grinding track and honing track can be obtained by changing the voltages that apply to piezoelectric ceramic. Meanwhile, the design methods of transducer and horn are given, and which realize the transducer and horn modal analysis by using finite element software . The research improves the machining precision, and makes the application of this technology possibly in ultraprecision machining.

Fig. 1 Fig. 1 .

 11 Fig.1is a diagram of t wo-dimensional ultrasonic transducer.' A shows front shroud

Fig. 2 .

 2 Fig. 2. The arrangement of piezoelectric ceramics

Fig. 4 .Fig. 5 .

 45 Fig. 4. Simulation trajectory

Fig. 6 .Fig. 7 .Fig. 8 .

 678 Fig. 6. Synthesis of complex movement

Fig. 9 .

 9 Fig. 9. Synthesis of complex movement(φ = 0)

  Fig.12 is d iagram of two-dimensional sandwich transducer, wh ich consists of front shroud, back shroud, and piezoelectric ceramic. A stress bolt connects these three parts closely.

Fig

  Fig. 12. diagram of two-dimensional sandwich transducer

  Fig. 13. Diagram of composite conical horn Frequency equation:

Fig. 14 .

 14 Fig. 14. The curve about 4

Fig. 15 .

 15 Fig. 15. Finite element mesh Mode extraction method is subspace iteration method, and the modal number is 10. In modal analysis, side surface o f all nodes between piezoelectric ceramic and front shroud constrain Y displacement, as shown in Fig.16. The electrode voltage (V = 0) is coupled on upper and lower surface, which is shown in Fig.17.

  .

Fig. 16 .

 16 Fig. 16. Constrained Y displacement

Fig. 18 .

 18 Fig. 18. Relative displacement nephogram

Acknowledgement. The authors gratefully acknowledge the financial support provided by the University-Industry Cooperation Project of Jiang xi Education Depart ment (Grant No. GJJ09005). Corresponding author: Leping Liu; Tel: 13970086701; E-mail: jxllp@163.co m