Research And Implementation Of Digital Interface For High Precision Encoder

The Sinusoidal encoder is a precision sensor that measures angular and angular velocities.As the resolution and accuracy requirements are getting higher and higher in CNC and modern industrial control system,relying solely on the original resolution or fourfold frequency count has been unable to meet the real-time feedback requirement in industrial control system,so higher resolution and precision encoder signals are needed.The methods of improving the encoder resolution mainly include hardware method and software method.This dissertation used the electronic subdivision method to subdivide the encoder signal.In order to obtain more accurate position and speed information of motor,a high resolution encoder signal processing system based on the improved coordinate rotation digital compute(CORDIC)algorithm was designed.Firstly,signal of encoder was processed by differential amplifying,shaping,filtering and so on through the signal conditioning circuit.Secondly,coarse code was obtained by fourfold frequency,and precise code information was obtained by electronics subdivision method based on improved CORDIC algorithm.Finally,high resolution and precision angular position of the motor information was obtained by integrating coarse code and precise code.In speed measurement,this dissertation used the improved M and the full differential velocity measurement method.In data commutation,the CANopen protocol was used on data commutation between the interface module and the host computer.The dissertation used a 16-bit AD converter and 2048 line sine and cosine encoder,and the resolution of encoder angle value reaches 27-bit.The encoder interface module was tested,and experimental results show that the position resolution based on four frequency measurement is at 100 arc-seconds,while the position accuracy based on electronic subdivision is about 60 arc-seconds.the relative error of the differential speed measurement is smaller than the M variable speed method,furthermore,the precision is higher.The module meets the design requirements.