Speed Measurement And Anti-Interference Technology Of Servo System With CPLD

Served as one of the most crucial technologies in high-precision servo control system,feedback accuracy of sensor dominates the realization of high-precision.The stability and control-precision of servo system are influenced by accuracy of speed measurement directly.Typically,the price of encoder increases with the number of lines,while the most widely employed sensor in servo system is incremental photoelectric encoder.However,the accuracy of speed measurement is directly effected by the interference signal in the encoder.This thesis focuses on the method of anti-interference and speed measurement,on the basis of the incremental encoder with low line number,so as to advance the precision of speed measurement to the same level of high-precision encoder and improve the system performance eventually.The operating principle of encoder and the typical method of speed measurement are depicted in detail at first,and the research status of domestic and overseas speed measurement methods is presented subsequently.In order to optimize the measure method on high-speed,high-precision and continuous measurement,the update rate is accelerated,and the problem of low update rate caused by the acquisition of multiple encoder pulses at low speed is solved simultaneously.Then,the optimized principle of high-speed,high precision and continuous measurement method and its implementation in CPLD are introduced in this thesis,and the compilation,synthesis and simulation of measurement method are constructed and completed in Quartus II 9.0.The simulation results illustrate that the proposed measurement method features high precision and high update rate,additionally,the measurement method on speed is simply and reliable.The interference source of speed feedback signal in servo system and the researches on the method of anti-interference currently are presented in this thesis.Then,the characteristics of interference signals are analyzed in detail respectively,meanwhile,the interference signals are summarized and classified subsequently.The anti-interference method,according to interference signal without pseudo interference pulse,edge interference signal caused by disc edge and reverse interference signal with pseudo interference pulse,is proposed.Furthermore,the principle of the anti-interference method is introduced detailedly,and the realization of which in CPLD is illustrated as well.The simulation results show that the mentioned interference signal in speed feedback can be eliminated clearly,which provides reliable feedback signal for speed measurement,additionally,the anti-interference method is simply and reliable.The experimental platform is constructed conclusively for verification.The experiment results demonstrate that the interference signal existed in encoder,composed of interference signal without pseudo interference pulse,edge interference signal caused by disc edge and reverse interference signal with pseudo interference signal,can be eliminated completely.What's more,the delay of signal is approximately equal to 0,and the precision of speed measurement can be improved as well.When the proposed speed measurement method is employed to measure the speed of the 2500-lines incremental photoelectric encoder,it features competitive accuracy to high-precision encoder in the rage of 5-2000r/min,besides,the method has no effect on the update rate in low speed range.In conclusion,the proposed speed measurement method and anti-interference method on feedback signal have significant references in servo system.