Research On Signal Processing Circuit Based On Rotary Encoder

Various scenarios in modern control applications need to measure the angle of the rotating shaft.As the key to achieving this requirement,the rotary encoder is favored for its high reliability and high precision.The resolver is the sensing element of the rotary encoder,which is very suitable for the sensing of the shaft angle.In this context,around the inductive output of the resolver,the research on the signal processing circuit of the rotary encoder has been ongoing in various countries.With the uninterrupted improvement of the requirements for the measurement accuracy and transient response of the shaft angle,it is becoming more and more important to improve the angle tracking performance and noise suppression capability of the rotary encoder in the case that the velocity of shaft angle is not constant.Focusing on the high-precision measurement requirements of the signal processing circuit in the rotary encoder,this thesis analyzes and summarizes the basic principles of the signal processing circuit in the rotary encoder.On this basis,this thesis conducted a deep research on the shaft angle tracking circuit and the circuit for improving the accuracy of the shaft angle.The main research points and results in this thesis are as follows:1.Researched the working principle of rotary encoder.The sensing principle of the resolver and the non-ideal factors of its output signal are analyzed.Summarize the signal processing flow of the rotary encoder into the main components: modulation sensing,demodulation,angle tracking and filtering,and encoding interface output.Combined with the demodulation technology for modulated signal and shaft angle tracking technology at present,the signal processing principle of the rotary encoder is researched.2.Designed the shaft angle tracking circuit.Based on the current type II angle tracking loop,the type II loop is improved by adding the compensation module,and the type III and type IV angle tracking loop models are constructed.Based on the loop bandwidth,the dynamic performance analysis of Type III and Type IV loops are completed,and the parameter setting methods of Type IV loop is obtained.The angle tracking performance verification of the above three loops was completed by using Simulink tools.An all-digital shaft angle tracking circuit in the discrete domain is proposed,which realizes stable tracking of the shaft angle signal with uniform acceleration.3.Designed the circuit for improving the accuracy of the shaft angle.An adaptive filter circuit architecture is proposed to filter the noise of the variable shaft angle signal.The zeropass correction algorithm is used to solve the zero-pass problem of the shaft angle;the filter circuit based on the moving average accumulator is used to realize the single-stage accumulator filter circuit.Later,in terms of the realization of the overall circuit architecture,the stability detection circuit and the control module state machine are designed.Finally,an adaptive filter circuit for improving the accuracy of the shaft angle is obtained.The timing behavior of the circuit are analyzed and verified by Modelsim,and the circuit is proved to meet the design expectations.4.Designed the Shaft Angle Tracking System and realized FPGA hardware verification.Combining the all-digital shaft angle tracking circuit,the circuit for improving shaft angle accuracy and encoding interface circuit,the Shaft Angle Tracking System is constructed.The FPGA hardware verification platform was built for the system,and the shaft angle tracking system is tested and analyzed based on the completion of timing verification and hardware verification.The results show that the tracking error of the Shaft Angle Tracking System for the noisy uniform acceleration shaft angle signal is kept within 0.08 degrees,a relatively low range,which meets the design expectations.