Design and Implementation of a Three Dimensional Wheel force

Transcription

1 Design and Implementation of a Three Dimensional Wheel force Transducer 1 Lin Guoyu, 2 Pan Han, 3 Wang Dong, 4 Zhang Weigong 1, First Author School of Instrument Science and Engineering, SouthEast University, China, Andrew.Lin@seu.edu.cn *2,Corresponding Author School of Mechanical and Electrical Engineering, China University of Petroleum(East China), China, panghan67@163.com 3,4 School of Instrument Science and Engineering, SouthEast University, China Abstract Wheel force transducer (WFT) plays a key role in automobile detection technology, and they can measure the force and torque applied in the wheel. However, the most current generation of WFT are commercial products which are expensive and their technical information is not public. Accordingly, a three-dimensional wheel force sensor based on spoke structure with eight elastic beams is presented in this paper. Firstly, the overall structure of the proposed WFT is described, and then the design of the elastic body is introduced briefly. Afterwards, the strain gauge arrangement, the principle of strain measurement and the connection mode of bridge circuit are analyzed in detail. Finally, static calibration and dynamic tests is performed. Experiment results demonstrate the proposed WFT has the characteristic of large scale, good linearity, low hysteresis, high repeatability and weak interdimensional couplings. The maximum nonlinearity error, the maximum hysteresis error and the maximum repeatability error of the proposed WFT is 0.6% F.S, 0.7% F.S and 0.4% F.S separately. Keywords: Wheel Force Transducer (WFT), Bridge Circuit, Strain Gauge Arrangement 1. Introduction When the vehicle is running, six components of force and torque which is longitudinal force F x, lateral force F y, vertical force F z, heeling moment M x, twist torque M y and aligning torque M z separately are applied in the wheel. The schematic diagram of three forces and three torque of wheel are shown in Figure 1. Figure 1. Diagram of Six-dimensional Forces Figure 2. Some Commercial WFTs As shown in Figure 1, the origin of the wheel coordinate O w X w Y w Z w is the wheel center, the X-axis is parallel to the intersection of wheel plane and ground plane, and the Z-axis is perpendicular to the ground plane. For the wheel force reflect the interaction between the vehicle and ground, so sensing the forces/torque of wheel dynamically has been an important component of vehicle for the research of body vibration, suspension and wheel dynamics as well as the performance matching of vehicle transmission and braking system [1-6]. Advances in information Sciences and Service Sciences(AISS) Volume5, Number9, May 2013 doi: /aiss.vol5.issue9.7 52

2 Currently the research of multi-dimensional force is mainly in wrist force sensor area [7-12]. And meanwhile fewer scholars pay attention to the research of wheel force transducer (WFT) because that there are some special problem for WFT, including complicated using conditions, various coupled interference factors and complex calibration process, etc. For the increasing importance of wheel force, now there are some commercial six dimensional sensors that measure six components of force and torque. In Figure 2, six commercial WFT is shown Figure 2 (a) to Figure 2 (e), which is PCB 5400 Series multiple axis WFT produced by American PCB Corporation, Michigan Scientific Corporation s LW Series six dimensional WFT, RoaDyn S6HT and System2000 WFT of Switzerland Kistler Corporation, SWIFT of American MTS Corporation and SLW-NC WFT of Tokyo Sokki Kenkyujo Corporation respectively. They all have acceptable performance standards [13][14]. But for business reason, the detail technology information and calibration method of these WFT is not publicly available and its price is very high. These factors not only impede the popularization and application of the WFT, but also slow down the development of the WFT. According to the high motor vehicle with 4 wheels, a three dimensional wheel force transducer based on 8-beam spoke structure is proposed with the characteristics of: 1) Measuring the three forces F x, F y and F z. Actually the torques M x M y and M z are easy to calculate from the measured forces F x, F y, F z and their contact points [15-17] which results in the waste of time, resources, and money, so three forces signals are sufficient. 2) Measuring the rotating angle and speed separately. 3) Large measuring scale. The vehicle s weight is approximately 10T so each wheel s load is about 5T considering the dynamic load. 4) Having the features of good linearity, low hysteresis, low repeatability error and weak coupling. 2. The Overall Structure of WFT The overall structure of the proposed WFT is shown in Figure 3 (a), which is composed of the elastic body, reforming rims, intermediate flange, photoelectric encoder, sample module and transfer module. Figure 3 (b) and Figure 3 (c) show the sample module and transfer module separately. Figure 3. Diagram of the Proposed WFT s Structure Figure 4. Proposed Elastic Body The sample module connects to the elastic body by flange and rotates with the rolling wheel. It is used to sample the wheel s force and rotation angle and send them to the transfer module by wireless. The transfer module connects to the sample module by the bearing and does not rotate with the rolling wheel. It can receive the data from the sample module by wireless too and forward the data to the data acquisition devices by CAN bus. 3. Design of Elastic Body The elastic body is the most crucial part of multi-dimension force sensor. It decides not only the static calibration target and dynamic performance, but also the sensitivity and the coupling among dimensions of sensor. Moreover, because of the complicated structure of wheel and small installation space, it is a complicated work for the design of the elastic body. 53

3 According to the requirement of axial structure size of the wheel, the spoke structure used in many commercial WFT is also exploited in the paper, and the proposed elastic body is shown in Figure 4. The proposed spoke structure has an inner ring and an outer ring, and there are eight elastic beams distributing uniformly between the inner ring and outer ring. The size of the inner ring, the outer ring and the beams is decided by the wheel s structure and size comprehensively, and the optimum design can be achieved by finite element analysis using the ANSYS software. 4. Strain Gauge Arrangement and Measuring Circuit 4.1. Strain Gauge Arrangement In order to better reflect the corresponding relation between the stress and strain gages, the strain gauge arrangement should be selected carefully so as to maximize the sensitivities to three dimension forces and to eliminate the cross-axis sensitivities. According to the strain analysis and stress distribution of the elastic body in section 3, the strain gauges are placed as shown in Figure 5. Figure 5. Diagram of Strain Gauge Arrangement In order to reflect the corresponding relation between the stress and strain gages better, the strain gauge arrangement should be selected carefully so as to maximize the sensitivities to three dimension forces and to eliminate the cross-axis sensitivities. According to the strain analysis and stress distribution of the elastic body in section 3, the strain gauges are placed as shown in Figure 5 where O c X c Y c Z c is the elastic body coordinate system. In Figure 5, A-H denotes the eight Elastic beams, and the CG beam is coinciding with X c axis and the AE beam is coincide with Z c axis. Strain gauge 1, 2 and strain gauge 3, 4 are located in the surface s intermediate axis of A beam and E beam respectively to detect the vertical force F z. Strain gauge 5, 6 and strain gauge 7, 8 are located in the surface s intermediate axis of C beam and G beam respectively to detect the longitudinal force F x. Strain gauge 9, 10, 11, 12 and strain gauge 13, 14, 15, 16 are located in side surface along the diagonal of D beam and H beam respectively to measure the lateral force F y Principle of Strain Measurement Applying the Force F x Along X c Axis Suppose the external force expressed as F x is applied along +X c axis on the elastic body. For the inner ring is fixed, the tension and pressure deformation happen on C beam and G beam. Strain gauge 5 and 6 are all subject to the pressure force and their resistances become smaller. Meanwhile strain gauge 7 and 8 are all subject to the stretching force and their resistances become larger. For A beam and E beam, the bending deformation happened on them. Because strain gauge 1, 2, 3 and 4 are located in neutral layer of A beam and E beam which is not affected by bending deformation, their resistances remain unchanged. For D beam and H beam, the bending deformation happened on them too. Strain gauge 9, 10 in side c of D beam and strain gauge 15, 16 in side b of H beam are subject to the stretching force and their resistances become larger. Meanwhile, strain gauge 11, 12 in side d of D beam and strain gauge 13, 14 in side a of H beam are subject to pressure force and their resistances become smaller. When the external force is applied along -X c axis then the resistance changes are contrary. 54

4 Applying the Force F y Along Y c Axis Suppose the external force expressed as F y is applied along +Y c axis on the elastic body. For CG beam and AE beam, because the inner ring is fixed, the bending deformation happened on them. Take CG beam for example, strain gauge 5 and 7 are subject to the pressure force and their resistances become smaller. Meanwhile strain gauge 6 and 8 are all subject to the stretching force and their resistances become larger. Because the inner ring is fixed, D beam and H beam are acted upon by the shear force caused by bending deformation. For the strain gauges on D beam and H beam are located along 45 degree direction, the tension and pressure deformation happen on these strain gauges. For instance, the strain gauge 10 in side c and strain gauge 11 in side d of D beam are all subject to the pressure force and their resistances become smaller. Meanwhile, the strain gauge 9 in side c and strain gauge 12 in side d of D beam are all subject to the stretching force and their resistances become larger. When the external force is applied along -Y c axis then the resistance changes are contrary Applying the Force F z Along Z c Axis When the external force expressed as F z is applied along Z c axis on the elastic body, the analysis is similar with that shown in Section Wheatstone Bridge Measuring Circuits The Wheatstone Bridge is exploited to convert the change in resistance resulting from strain to a voltage proportional to the strain. According to the strain analysis and the strain gauges arrangement, the connection mode of the Wheatstone Bridges corresponding to F x, F y and F z is determined, as shown in Figure 6 respectively. (a) F x bridge (b) F y bridge (c) F z bridge Figure 6. Connection Mode of Wheatstone Bridges According to the characteristics of Wheatstone Bridge, the output of F x, F y and F z bridge denoted as ΔU x, ΔU y and ΔU z can be expressed by U, K and ΔR i /R i, where U is the supplied voltage, K is the sensitivity coefficient of strain gauge and ΔR i /R i indicates the changed rate of resistance for the strain gauge due to strain variation. Hereinafter, ΔR i /R i is denoted as ε i, and then ε i x, ε i y and ε i z indicate the corresponding strain caused by the active force along X c axis, Y c axis and Z c axis respectively Applying the Force F x Along X c Axis When the sensor is applied the force F x along X c axis, according to the analysis described in Section 4.2 it is induced that: (1) The strain of strain gauge 5 and 6 in G beam and the strain of strain gauge 7 and 8 in C beam are equal in magnitude and opposite in direction. Then F x =G x ΔU x =0.25UKG x [(ε 7 x +ε 8 x ) (ε 5 x +ε 6 x )] where G x is the calibration coefficient. (2) The strain gauges in A beam and E beam is located in neutral layer, so ΔU z = 0. (3) The strain of strain gauge 9, 10, 15, 16 and the strain of strain gauge 11, 12, 13, 14 are equal in magnitude and opposite in direction. Then ΔU y =0.125UK[(ε 10 x +ε 11 x +ε 14 x +ε 15 x ) (ε 9 x +ε 12 x +ε 13 x +ε 16 x )]=0. 55

5 Applying the Force F y Along Y c Axis When the sensor is applied the force F y along Y c axis, according to the analysis described in Section 3.2 it is induced that: (1) The strain of strain gauge 5, 7 and the strain of strain gauge 6, 8 are equal in magnitude and opposite in direction. Then ΔU x =0.25UK[(ε 7 x +ε 8 x ) (ε 5 x +ε 6 x )]=0. (2) The strain of strain gauge 10, 11, 14, 15 and the strain of strain gauge 9, 12, 13, 16 are equal in magnitude and opposite in direction. Then F y =G y ΔU y =0.125UKG y [(ε 10 x +ε 11 x +ε 14 x +ε 15 x ) (ε 9 x + ε 12 x +ε 13 x +ε 16 x )]=0 where G y is the calibration coefficient. (3) The strain of strain gauge 1, 3 and the strain of strain gauge 2, 3 are equal in magnitude and opposite in direction. Then ΔU z =0.25UK[(ε 1 x +ε 2 x ) (ε 3 x +ε 4 x )]= Applying the Force F z Along Z c Axis With the similar analysis in Section 4.3.1, it is induced that F z =G z ΔU z =0.25UKG x [(ε 1 x +ε 2 x ) (ε 3 x + ε 4 x )] where G z is the calibration coefficient, and the output of the other two bridge is zero. In brief, the proposed strain gauges arrangement and the connection mode of three bridges can eliminate the coupling among dimensions theoretically. So if the strain gauges are located in the ideal places and the structure of elastic body is symmetrical strongly and isotropic, each applied force can only generate the output voltage of the bridge circuit in the corresponding axial direction, while the outputs of the other bridge circuits are irrelevant Coordinate Transformation In the analysis described in Section 4.2 and Section 4.3, it is assumed that the elastic body coordinate system O c X c Y c Z c is static and coincides with the wheel coordinate system O w X w Y w Z w. Actually O c X c Y c Z c is rotated with the rolling wheel and then the applied force F x, F y and F z is not along the corresponding axis of O c X c Y c Z c as shown in Figure 1. Now the output of the F x bridge and F z bridge just reflects the component of the applied force acting in the CG beam and AE beam respectively. In fact, the wheel force is in the wheel coordinate system O w X w Y w Z w which is nonrotating and the origin O w is coincident with origin O c. So it is needed to establish the transformation between O c X c Y c Z c and O w X w Y w Z w. When the wheel is rolling, O c X c Y c Z c rotates around the Y w -axis, and the angle between them is denoted as θ. The rotation matrix between them is shown in Eq. (1) where ff x, ff y and ff z is the force of the F x, F y and F z bridge sensing separately, and F x, F y and F z is the wheel force. Fx cos 0 sin ff (1) x Fy ffy F sin 0 cos z ffz 5. Calibration and Experiments For test the proposed WFT, two major devices are exploited. Figure 7 shows the static calibration platform on which the elastic body is bolted, and six-dimensional force is applied to the elastic body by Hydraulic controller. The experiments in Section 5.1 are conducted on this calibration platform. In order to test the performance of the WFT dynamically, the Vehicle Dynamics Test System produced by MTS Corporation is adopted. For security reasons the real test system can not be public, Figure 8 shows the schematic diagram. In Figure 8, A is the driving wheel and B is the driven wheel. The driving wheel A can not only drive the driven wheel B to rotate, but also apply a horizontal direction force to the driven wheel B. For the WFT is bolted on the driven wheel B, the applied horizontal direction force can be considered as the longitudinal force F x and can be measured by the feedback sensor of the MTS device. However, it is worth noting that the feedback force is just as a reference for the longitudinal force F x because that the WFT and the feedback sensor is mounted in different wheel, and the applied force is not exactly along the X-axis of wheel coordinate system O w X w Y w Z w. The experiments in Section 5.2 and Section 5.3 are conducted on this dynamic platform. 56

6 Figure 7. Static Calibration Platform Figure 8. Diagram of MTS Device 5.1. Static Calibration Tests Static calibration experiments are conducted on the calibration platform to acquire the relationship between the applied load and the output of the F x, F y, F z bridge of the WFT, and the sensor s static performance index which is linearity, hysteresis error and repeatability error respectively. When static calibration is carried out in F x bridge, the load is applied along C beam and G beam which is X C -axis. When static calibration is carried out in F y bridge, the directions of applied load is perpendicular to the O C X C Z C plane of elastic body. When static calibration is carried out in F z bridge, the load is applied along A beam and E beam which is Z C -axis. Meanwhile, when no force is applied to the elastic body, the output of the bridges is about 2000, and then the output value increase when loading force and decrease when bearing force. (a) (b) (c) Figure 9. Output Curve of Three Bridges When the Applied Force along Different Direction Figure 9 (a), (b) and (c) with the force as abscissa and the AD output of three bridges as ordinate shows the output curves of F x, F y, F z bridges respectively in one static calibration. In this calibration, the applied force range from 0T to 5T with 0.5T stepping load, and is loaded then unloaded. According to the analysis mentioned in Section 4, there is no coupling among outputs of three bridges ideally. However, for the factors of strain gauges position deviation and processing deviations, the weak coupling does exist which shown in Figure 9. For example in Figure 9 (a), it is obviously that when loading/bearing different force along X C -axis, the output of F x bridge changes significantly and the output of F y and F z bridge varies with applied force too, and just much smaller relatively. Similar result is obtained from Figure 9 (b) and Figure 9 (c). To solve the coupling problem, some effective decoupling algorithm such as least squares and neural network [18][19] can be adopted. However, in order to show the performance of the proposed WFT better, the decoupling process is neglected in the paper. Moreover, according to the China Standard GB named load cell test procedure, the loading and unloading process repeat three times, and then the static performance index of F x, F y, F z bridge can be obtained and shown in Table 1 which shows the proposed WFT has the characteristics of good linearity, low hysteresis, and high repeatability. Table 1. Static performance indicators of three bridges Bridge name Nonlinearity error Hysteresis error Repeatability error F x bridge F y bridge F z bridge 0.6% F.S 0.5% F.S 0.6% F.S 0.6% F.S 0.7% F.S 0.7% F.S 0.4% F.S 0.4% F.S 0.4% F.S 57

7 5.2. Static Measurement Tests with Different Angle As analysis in Section 4.4, the coordinate system defined in elastic body varies with the rotating wheel, so it is needed to acquire the rotating angle of wheel to calculate the real force f x and f z acting on the wheel by Eq. (1). To verify the effect of the proposed WFT while the wheel is rotating, the following steps are carried out: 1) The WFT is mounted in the MTS device and is rotated to a certain angle manually. 2) A force denoted as f i is applied to the WFT for a while, then the output of absolute optical encoder, F x bridge and F z bridge is recorded and denoted as A i, FxAD i and FzAD i. 3) The step 1) and step 2) repeat N times, and the rotating angle and applied force is different each time, then the N group data can be obtained. The N group data is put into Eq. (1) to acquire the force fa i, Tab.2 shows a group data with N=10 in one experiment. It is shown that the calculated force is and the error is less than 1% which meets the practical measurement requirements. Table 2. Static measurement tests data N FxAD i FzAD i A i fa i (unit:kn) f i (unit:kn) Error (unit:kn) Dynamic Test for F x and F z In order to simulate the force circumstances acting on the wheel during the driving, the variable applied load and the variable rotating speed is exploited. One of the experiments is executed with the following applied load and speed shown in Table 3 and the output curves are shown in Figure 10, Figure 11 and Figure 12. Table 3. Different speed and load in a experiment N Load(unit:KN) Speed(unit:rpm) Figure 10 and Figure 11 shows the output curve and the partial enlarged curve of the F x and F z bridge respectively. It is clear that the maximum amplitude of the output curve varies with the applied load. Furthermore, it can be seen from Figure 12 that there are two characteristics of the output curves of the F x and F z bridge: 1) The output curves are all similar to the sine wave curve. It is because that the wheel coordinate system O C X C Y C Z C is rolling with the rotating wheels, so the output of the F x and F z bridge change within the range [min, max]. 2) The phase difference between them is approximate 90 degree which reflects the vertical relationship between CG beam and AE beam. The solved longitudinal force F x, vertical force F z, speed and applied force MTS_F by MTS device in the experiment are shown in Figure 12 and some results can be acquired: 1) The curve of the solved longitudinal force F x is in line with the curve of the applied force MTS_F from MTS device, and the average absolute error between them is about 0.5KN. 2) The MTS device only applies force along the horizontal direction, so theoretically the solved vertical force F z should be equal to 0. Figure 12 shows the solved vertical force F z curve is around the zero and the average is about 0.06KN. For the weight of wheel and transducer is about 35kg, it maybe affect the output of the WFT. 3) The maximum error of the solved longitudinal force F x and vertical force F z is 2.8KN and 4.7KN which happened at the moment when the driving wheel just touch the driven wheel. The solved vertical force F z curve is the same. It is inferred that at this moment, the vertical and horizontal impacts are generated and the MTS device can not be sensitive to the impacts. 58

8 4) In the solved vertical force F z curve, there are some obviously mutation which appears mostly at the moment of the applied load just changes. It is inferred that a vertical shock is generated when the applied load just changes and the MTS device can not be sensitive to the vertical shock. The conclusion mentioned above appears in the other experiments too. Altogether, in dynamic rotation circumstance, the output of the WFT is satisfying and the error can be acceptable. Figure 10. Output Curve of the F x and F z Bridge Figure 11. Partial Enlarged Curve Figure 12. Curves of the Solved Force and Applied Force 6. Conclusion This study has endeavored to design and fabricate a three dimensional wheel force transducer based on based on 8-beam spoke structure, and the structure of elastic body, stain gauge arrangement and calibration method is described in the paper. The maximum nonlinearity error, the maximum hysteresis error and the maximum repeatability error of the proposed WFT is 0.6% F.S, 0.7% F.S and 0.4% F.S separately. The experiment results demonstrate that the proposed wheel force transducer has obtained excellent results in terms of large range, linearity and weak inter-dimensional couplings, and can be used for a variety of applications such as road spectrum acquisition and ABS testing, etc. 7. Acknowledgement This work is supported by The National Natural Science Foundation of china (Grant No ). 8. References [1] Zhang Xiaolong, Feng Nenglian, Zhang Weigong, Experimental Research on the ABS Performance Based on the Wheel Forces Measured by Roadway Test, China Mechanical Engineering, vol. 19, no. 6, pp. 751 ~ 75, [2] Liu Qinhua, Zhang Weigong, Design of acquisition system for road loading spectra data based on wheel force transducer, Journal of Jiangsu University (Natural Science Edition), vol. 32, no. 4, pp. 389 ~ 393, [3] N.A. Kadhim, S.A bdullah, A.K. Ariffin, Effect of the fatigue data editing technique associated with finite element analysis on the component fatigue design period, Materials & Design, vol. 32, no. 2, pp ~ 1030,

9 [4] Liu Gang, Xiong Zenggang, Cai Zhiwei, "Research on Induction Motor Torque and Flux Decoupling Control", AISS: Advances in Information Sciences and Service Sciences, Vol. 4, No. 18, pp. 519 ~ 527, [5] Matteo Corno, Mathieu Gerard, Michel Verhaegen, Edward Holweg, Hybrid ABS Control Using Force Measurement, IEEE Transactions on Control Systems Technology, vol. 20, no. 5, pp ~ 1235, [6] Wanki Cho, Jangyeol Yoon, Seongjin Yim, Bongyeong Koo;, Kyongsu Yi, Estimation of Tire Forces for Application to Vehicle Stability Control, IEEE Transactions on Vehicular Technology, vol. 59, no. 2, pp. 638 ~ 649, [7] Jacq Caroline, Lüthi Barthélémy, Maeder Thomas, Lambercy Olivier, Gassert Roger, Thick-film multi-dof force/torque sensor for wrist rehabilitation, Sensors and Actuators: A Physical, vol. 162, no. 2, pp. 361 ~ 366, [8] Liang Qiaokang, Dan Zhang, Songa Quanjun, Ge Yunjian, Cao Huibin, Ge Yu, Design and fabrication of a six-dimensional wrist force/torque sensor based on E-type membranes compared to cross beams, Measurement, vol. 43, no. 10, pp ~ 1719, [9] Stefanie Erhart, Martin Lutz, Rohit Arora, Werner Schmoelz, Measurement of intraarticular wrist joint biomechanics with a force controlled system, Medical Engineering and Physics, vol. 34, no. 7, 2012, pp. 900 ~ 905. [10] Liu Jun, Qin Lan, Li Min, Liu Jingcheng, Xue Lian, Research and development of a parallel piezoelectric 4-axis force/torque sensor, Journal of Chongqing university, vol. 34, no. 2, 2011, pp. 101 ~ 107. [11] Sarmad Shams, Dong Su Kim, Youn Sung Choi, Chang Soo Han, A novel 3-DOF optical force sensor for wearable robotic arm, International Journal of Precision Engineering and Manufacturing, vol. 12, no. 4, pp. 623 ~ 628, [12] Wang Hua, A fingertip force sensor for underwater dexterous hand, Journal of Mechanical Science and Technology, vol. 26, no. 2, pp. 627 ~ 633, [13] M. K. Ramasubramanian, Steven D. Jackson, A sensor for measurement of friction coefficient on moving flexible surfaces, IEEE Sensors Journal, vol. 5, no. 5, pp. 844 ~ 849, [14] J. H. Kim, D. I. Kang H. H. Shin, Y. K. Park, Design and analysis of a column type multicomponent force/moment sensor, Measurement, vol. 33, no.3, pp. 213 ~ 219, [15] Liu Guangfu, Li Shuigen, Zhang Weigong, Zhu Weidong, Liu Qinghua, Design of Acquisition System of Weighing Calibration Equipment for Wheel Force transducer, Measurement & Control Technology, vol.26, no.10, pp.18 ~ 20, [16] Zhou Yaoqun, Zhang Weigong, Liu Guangfu, Li Zhongguo, Research and Development on the Vehicle Roadway Test System Based on a New Six-component Wheel Force Transducer, China Mechanical Engineering, vol.18, no.20, pp.2510 ~ 2514, [17] Zhang Weigong, Study on multi-component wheel force measurement technology, Journal of Jiangsu University (National Science Edition), vol. 25, no. 1, pp, 25 ~ 28, [18] Zhang Xiaoping, Wang Yang, Liu Guixiong, "Modeling Parameters Optimization for Target Localization in WSN Based on LSSVR by Sampling Measurement Data", IJACT: International Journal of Advancements in Computing Technology, Vol. 4, No. 6, pp. 346 ~ 357, 2012 [19] De En, Nana Wei, Xiaobin Wang,Huanghe Wei, "The New Study of Decoupling Problem in Three-component Acceleration Seismic Geophone", JCIT: Journal of Convergence Information Technology, Vol. 7, No. 15, pp. 529 ~ 536,