Study Of High Precision Two-Dimensional Turntable Control Based On Ultrasonic Motor

Turntable is a kind of high precision measurement and simulation equipment,which is widely applied in military industry measurement and spacecraft flight simulation.It is suitable for high-speed measurement and simulation in complex environment can make up for the shortcomings of traditional measurement methods.It can be used in spacecraft flight simulation,which can greatly improve work efficiency and reduce the probability of safety accidents.At present,the domestic research on high precision turntable is still in the exploratory stage,so the research and development of turntable is of great significance to national defense and economic construction.This article presents a novel high precision turntable system based on ultrasonic motor,and proposes a driving circuit scheme of ultrasonic motor,achieve stable and controllable speed of ultrasonic motor,angle measurement and scanning control function.With high precision phased ranging module,it can realize 3D surface shape measurement of large-scale non-cooperative targets.The background of this paper is research and development of high precision phase 3D surface measuring instrument,a high precision 2D turntable system which takes ultrasonic motor and absolute rotary encoder as the core is designed.It utilizes a ultrasonic motor as power driver,to realize vertical scanning and add a precision horizontal rotating platform to provide horizontal deflection for the turntable,and uses encoder to measure angle of turntable to control scanning model in real time,respectively.The challenges of this system design can be summarized as follows:1)It is difficult to control stability while the ultrasonic motor is moving;2)How to utilize encoder to measure angle in high speed and high accuracy;3)It is necessary to realize motion mode control of turntable.Specifically,the main research contents of this paper are as follows: 1?Designing the architecture of the 2D turntable system,giving the motion mode of the turntable,explaining the working principle and working process of the turntable.2?According to the driving principle of the ultrasonic motor,a new driving circuit of the ultrasonic motor is proposed in this paper.The encoder is used to measure the speed of the ultrasonic motor in real time,and the driving frequency of the ultrasonic motor is adjusted by feedback,so as to realize the frequency tracking and achieve the goal of the speed stabilization and controllability of the ultrasonic motor.In this paper,the design scheme of driving circuit is given,and the specific circuit modules are simulated and analyzed.The schematic design,PCB production of hardware circuit and debugging of board are completed.The board level test shows that the driving circuit has good driving ability and the motor speed is stable and controllable.3?In this paper,the communication circuit design and software code implementation of angle measurement module based on absolute rotary encoder are completed.Firstly,the realization scheme of the encoder angle measurement module is given and the communication interface circuits of encoder are designed.Secondly,software program structure of the module is analyzed.Based on communication protocol EnDat2.1 of encoder,communication link between encoder and FPGA is established.Finally,the real-time angle measurement is achieved.4?Based on the structure of 2D turntable system and FPGA used as the main control chip,the laser carried by turntable which is actuated by ultrasonic motor is used to scan objects,and the encoder is used to complete angle measurement in real time,respectively.Accordingly,scanning function is achieved.The final test results show that the field of view on the vertical and horizontal is 180°,360°,respectively,the speed of measurement is 13333pts/s.The dynamic resolution of vertical and horizontal is 5.7as(arc-seconds),5.4as,respectively,and the turntable static angle accuracy of vertical and horizontal is 0.1043 as,0.0910 as,respectively.