| Ultra-precision turntable is an important part of micro-nano CT system and its motion performance has a decisive influence on the quality of CT images.The turntable servo control system is the key technology to realize its function.The development of servo control strategies and control algorithms for turntables is essential to the precise positioning of ultra precision turntables and stable operation at low speeds.This project takes the ultra-precise turntable for micro-nano CT developed by Chongqing University ICT Research Center as the research object,and starts the research on its servo control system.At present,the turntable uses a high-priced drive controller from abroad and its software and hardware is highly integrated while its source code is closed,which increases the complexity and redundancy of the drive system,and limits the turntable servo system improvement of control performance in the future.In the environment of the Sino-US trade war,once a foreign company stops its product supply,the development of China’s industrial CT non-destructive testing technology will be affected.Therefore,it is urgent to develope the ultra-precision turntable servo control system independently.In response to the above-mentioned problems,this subject studies the ultra-precision turntable servo control system with the characteristics of openness,high reliability and autonomy.The main contents are as follows:(1)This paper Analyzes the research status of precision turntable technology and brushless torque motor servo control technology at home and abroad,the technical indicators and structural characteristics of the ultra-precision turntable for micro-nano are introduced,and the overall scheme design for the turntable servo control system is carried out.(2)The principles of square wave drive control strategy and vector control strategy are analyzed.Based on the low friction structure of the turntable,a new excitation current control strategy was proposed: make the torque current approximately zero,make full use of the excitation current for control,and design The speed observer is used to perform impedance torque current compensation.This strategy does not have a current closedloop circuit,and improves the stability of the turntable motion at the expense of motor efficiency without high-precision current feedback.(3)The limitations of the classic PID algorithm in the turntable servo system are analyzed,and the fuzzy control algorithm is introduced to modify the parameters online,the particle swarm algorithm to optimize the quantization and scaling factors in the fuzzy PID algorithm is further introduced for the low-speed motion characteristics of the turntable.The MATLAB/Simulink simulation analysis was carried out under the environment,the results show that the particle swarm optimization fuzzy PID algorithm can significantly improve the dynamic response of the turntable servo system and enhance anti-disturbance capability.(4)The design of the lower computer control software and the upper computer monitoring software of the turntable servo control system are completed,an ultraprecision air-floating turntable experimental platform are set up,and experimental verification on the studied turntable servo system are carried out.The results show that the system can realize the turntable High-precision positioning and ultra-low-speed stable operation.The speed adjustment range is down to 3 hours per revolution,and the positioning accuracy reaches 2.87",which meets the technical specifications of ultraprecision turntables for micro-nano CT. |
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