The Development Of The Two-axis Precision Non-magnetic Electric Turntable Based On The Linear Standing Wave Ultrasonic Motor

The coordinator is a key component of the missile seeker and is closely related to the missile’s strike accuracy,so it’s very important to keep the coordinator with a high precision.The test and calibration accuracy of the coordinator is determined by the accuracy of the turntable,and improving the accuracy of the test turntable is the most effective way to improve the calibration accuracy.Therefore,it is of great practical significance and value to research a test calibration turntable for a certain type of coordinator.This article uses the method combining the theoretical analysis and prototype experiment,mainly around the key technology about two-axis precision non-magnetic turntable based on ultrasonic motor,the overall scheme design,the analysis and calculation of driving performance of linear standing wave ultrasonic motor,analysis and calculation of the turntable pointing accuracy,stability and control accuracy of servo control system and the experimental verification,etc,to carry out the research work.Firstly,according to the requirements of the two-axis turntable design indicators,such as the size of load,the requirements of precision performance,no magnetic field interference and other requirements,proposed the overall scheme of the two-axis turntable based on ultrasonic motor,including the design of the driving mode,guide rail type and position detection system.According to the load size and motion parameters of the two-axis turntable,to calculate the number of ultrasonic motors of azimuth and pitch axis.Then designed the control system and the control process of the two-axis turntable.Secondly,study the driving performance of the turntable motor and turntable start-stop characteristics.Based on the working principle of ultrasonic motor,the mathematical model of friction coupling interface is established,and the steady-state output force of the ultrasonic motor driven by the ultrasonic motor is calculated and the maximum angular velocity of the rotor is calculated by the mathematical model.The influence of the type of friction material,the size of the pre-tightening force and the angular velocity of the rotor on the maximum output force of the ultrasonic motor is analyzed,and the maximum output force of the ultrasonic motor is obtained when the aluminum oxide is selected as the friction material and the pre-tension force is 45 N,and the maximum output force of the ultrasonic motor is 3.2N.By analysis,the maximum velocity of the turntable is inversely proportional to the pre-tightening,but the increased pretension can reduce the time of the transfer.Finally,the relationship between the pretension force size and the output force of the ultrasonic motor and the maximum angular velocity of the rotor is verified through the simulation analysis,and it is verified that the driving form of the ultrasonic motor is very nonlinear.Again,around two-axis turntable mechanical noumenon and control system in two aspects,the pointing accuracy and precision are analyzed.By establishing an error model of the mechanism,analyzing the effects of each error source to the overall point of error,finding the most sensitive source of error,and then avoiding or compensating for error in processing assembly.Then analyzes the precision of control system,through the PID parameter setting experimental analysis,the second shaft precision can achieve 0.001 ’position resolution,and have a very small response time and repeat positioning accuracy.Finally,combining with the analysis of the previous section,the prototype made a series of experiments.To test the non-magnetic energy of the second axis,the ultrasonic motor has not introduced the magnetic field,and has not caused the existing magnetic field to be distorted;By testing the relationship of the pre-tension force and the output of the ultrasonic motor and the velocity of the rotor,it confirms that the ultrasonic motor drive has a strong nonlinear problem;The experimental results show that the motion platform based on ultrasonic motor has a high position resolution and repeat positioning accuracy.