The Design Of AC Servo Unit With High Accuracy Based On Absolute Encode

Due to the processing requirements of precision and complex parts,higher and higher requirements are put forward for the position control accuracy of servo drive.In this thesis,the research and analysis of the whole digital high precision AC servo drive unit which is suitable for high grade CNC machine tools and automation field are carried out.Digital ac servo driver is mainly composed of hardware circuit and software control program of two parts.Servo drive through the current loop,speed loop and position loop of real-time control loop system,the implementation of motor smoothly(low speed/torque ripple and fast response),high precision position(high resolution)and timing.In the aspect of hardware circuit,can through to the core power device reserve high overload ratio achieve rapid response;By high precision of current detection,speed and position detection to realize low speed torque ripple,fast response,high resolution;In the aspect of software,can be realized by optimizing the control algorithm the performance index of ascension.Several main performance indexes,this paper around it for servo drive the design of hardware circuit and improve and instructions.This paper makes a simple function description about the design of software,only not as a research focus.In the hardware circuit design,first of all,in order to meet the requirements of high overload factor,the selection of core power devices is analyzed and calculated;then,in order to improve the precision of current sampling,GM's current sampling circuit is improved,choose sensor of high accuracy,high precision operational amplifier,a high precision reference source,dedicated a / D conversion chip,compared and tested before and after the improvement of current sampling precision.In addition,in order to meet the requirement of high precision of speed and position control,reduce the development cost,increase the flexibility of the system,the proposed scheme of multifunctional encoder interface based on FPGA,namely based on the same hardware platform,incremental encoder signal processing and three kinds of machine tool industry commonly used communication protocol(Heidenhain,Danaher,Tamagawa communication protocol)are integrated into the same FPGA chip,focusing on the design of several encoder's compatibility.The design results confirm the feasibility of the design of multi-functional encoder.The test results show that the application of high precision current sampling scheme and absolute encoder can reduce the speed fluctuation,improve the dynamic response and greatly improve the positioning accuracy compared with the ordinary incremental photoelectric encoder.