1、附录 A Research on Linear Motor Driving System Based on Wavelet Transform Abstract end-effect is a main reason of influence on the characteristic of linear motor driving system, its direct impact is nonstableand undulate edges magnetic field. the wavelet transform is applied to analyze the linear moto
2、r driving system performance in this paper. The improving thrust response system has been presented based on choice wavelet function and wavelet transform. Simulation results indicate that the proposed control strategy can abate the thrust ripple problem caused by end effect in linear motor control
3、system, and make the system have good performances. Keywordswavelet transform； Linear motor； End effect； Direct thrust control system Introduction France physicist Morlet first applied the wavelet to analyzing the partial characteristic of earthquake wave in 1984. Because wavelet transform is a kind
4、 of analysis method for time-scale (frequency) signal, in time-domain and frequency-domain, which has the ability of exploring signal features with partial characteristic. Therefore, in the last years, the special analysis method has made itself theories rapid development and extensive application,
5、especially in the aspects of signal analyzing and image processing areas. Linear motor has longitudinal edge and transverse edge, for this reason the linear motor exist special end-effect. Longitudinal end-effect is caused by finite length primary iron-core. Transverse end-effect is caused by finite
6、 width of primary and secondary, secondary current and secondary plates affecting the air-gap magnetic field. This is the main difference between the linear motor and the rotating machine. Longitudinal end-effect not only causes motor losses, lower electric efficiency and thrust, but also leads to m
7、otor work characteristic aggravation. Therefore, key factor is to analyze the longitudinal end effect in this paper. Traditional analysis method, Fourier transform, has localization contradiction of time-domain and frequency-domain, some messages while analyzing nonstable signal will be usually lost
8、. Therefore, it is necessary to researcha new method that can solve this problem reasonably and effectively so as to improve linear motor driving system performance. Single dimension continuous wavelet transform has higher sensitivity, stronger ability of denoising and lower demand of the input sign
9、al, and doesnt need objects mathematic model. The single dimension continuous wavelet transform is used for analysis the performance of linear motor driving system. single dimension continuous wavelet transform The continuous wavelet sequence can be described as, )(1)(, atata 0；R, aa (1) where a is
10、scale parameter， is shift parameter. The square-integrable function )(t is called Mother Wavelet. A wavelet sequence can be obtained by dilation and shift transformation of the mother wavelet )(t . The continuous wavelet transform of arbitrary function )()( 2 RLtx is expressed by (2). ttxataaWT x d)
11、(1),( (2) the mother wavelet )(t formed wavelet sequence has an observable window function, so )(t should satisfy following constraint condition: tt d)( (3) )( is a continuous function which must be zero at the initial point for satisfying (2), then, 0d)()0( tt (4) And its Fourier transform is )( ,
12、when )( fulfills the admissible condition: d)( 2RC (5) It is shown that single dimension continuous wavelet transform uses )(t both scale a dilations and time shifts to analyze the signal. The signal is expanded in window area , * , , where and represent the time-span and the frequent-span of window
13、 respectively. The time-frequency analysis is multi-resolution if varying the window area. The high frequency signal is suitably analyzed by the gradually exquisite time step, and the low frequent signal is finely analyzed by the exquisite frequency step. The windows of the time and frequency are ad
14、justed through changing the signal frequency. Time-frequency localization analysis of signal can be achieved. Conclusions Comparing with the Fourier transform analysis method, the wavelet transform technique has the characteristics that it analyzes the signal combining time domain with frequency dom
15、ain together, for this reason it can effectively solve the problem of time-domain and frequency-domain limitation. It is important to search a new method that can solve the problem in linear motor driving system so as to improve linear motor servo characteristic. Through correct choice wavelet funct
16、ion, it is possible to consider both the frequency spectrum of mother wavelet and the characteristics of original signal. The result of signal analyzed is beneficial for abating the end effect influence on linear motor driving system. Simulation results indicate that the proposed control strategy ca
17、n reasonably and effectively abate the thrust ripple problem of linear motor control system, and make the control system have good performance. References 1 Liu Lili, Xia Jiakuan and Jiang Ping. Study on the end effect and compensation technique of permanent magnetic linear synchronous motor. Journa
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19、he Wavelet Transform Technique”, IEEE Transactions on magnetics, 35(5), pp.3739-3741, 1999. 4 Li. haodong, “Research on the End-effect and Control of the PM Linear Motor Used in the Electric Discharge Machining”, Shenyanguniversity of technology, 2003. 5 Guo. Qingding and Wang. Chengyuan and Zhou. M
20、eiwen and Sun. Yanyu, “precision control of linear AC serve system”, China Machine Press, pp.30-37, 2000. 6 Hu. Changhua, Li. Guohua, and Liu.Tao, “The system analysis and design based on MATLAB6.X- wavelet transform”, Xianuniversity of electron science & technology press, pp.15-17, 2004. 7 Liu Lifeng. Research of Direct Thrust Force Control System of Linear Motor Based on DSP. ShenyangUniversity of Technology. 2005.
