| Ultrasonic motors(USMs)are small in size and light in weight.Compared with traditional electromagnetic motors,USMs have advantages such as low speed,high torque,direct-drive,fast response,high precision,power-off self-locking,no electromagnetic interference and so on.They have enormous application potential in the aerospace field.Developed countries such as EU and USA have already successfully applied USMs as key actuators for spacecraft,especially for the single gimbal control moment gyroscopes(SGCMGs).The aerospace industry and the USMs technology of our country are developing rapidly.However,there are few successful applications of combining the two technologies.In order to promote the advancement of SGCMGs technology in China,applying USMs in SGCMGs is a win-win goal for the development of our aerospace science and technology.Based on the previous work,a traveling wave hollow ultrasonic motor for a SGCMG is proposed in this paper.The first generation prototype named TRUM-70 HA and the improved second generation prototype named TRUM-70 HB are designed and manufactured.In the development process,the dynamic model of traveling wave hollow ultrasonic motors,the optimization of low-speed and high-torque characteristics,the servo control of high-precision and high-speed stability,the construction and experiment of SGCMG platform,and the reliability test of ultrasonic motor under the simulated space environment have been carried on comprehensively and in depth.The experimental results show that the performance of TRUM-70 HB meets the requirements of the project,and it is expected to be used in aerospace engineering.The main contents and achievements of the research are as follows:1.The development status of SGCMGs technology and USMs technology at home and abroad are introduced.Taking a domestic SGCMG as the application target,this paper describes the shortcomings of the current traveling wave ultrasonic motors,such as the poor low-speed and high-torque characteristics,hard high-precision and high-speed control stability,poor reliability under special operating conditions.And the necessity of further research on the USMs is pointed out.2.According to the requirements of a SGCMG,a traveling wave hollow ultrasonic motor named TRUM-70 HA is proposed.The Lagrange dynamic equation of stator and the mechanical model of contact interface between stator and rotor are established.The dynamic model of 70 HA is calculated by MATLAB,and the effects of the pre-pressure on the stator’s normal amplitude,the critical contact angle of the stator-rotor,the position of isokinetic point and the mechanical output characteristics of the motor are simulated The test platform of stator vibration characteristics and motor mechanical characteristics is built to verify the simulation.The test results show that the weight of 70 HA is 245 g,the maximum speed is 72r/min,the maximum stall torque is 1.2N·m,and the maximum efficiency is 10%.3.A method to improve the low-speed and high-torque characteristics of traveling wave hollow ultrasonic motors is proposed.The parametric stator modeling of 70 HA is carried out by using the ANSYS Workbench Environment(AWE).The multi-objective adaptive optimization of feature size and structure of the stator is in progress.Then the second generation of optimized prototype motor named TRUM-70 HB is made.The experimental results show that the weight of70 HB is 210 g,the maximum speed is 50r/min,the maximum stall torque is 2.4N·m,and the maximum efficiency is 27%.The servo control system based on T-S-PID fuzzy controller is proposed.The pulse driving mode(speed ranges from 0.01°/s to 0.1°/s)and the continuous driving mode(speed ranges from 0.1°/s to 72°/s)are designed.The results of speed stability experiment show that the speed fluctuations of 70 HB are less than 5% and 0.01 °/s in continuous driving mode and pulse driving mode,respectively.4.The dynamic model of SGCMG system based on the traveling wave hollow ultrasonic motor is established.And the structure of SGCMG and the servo control system of gyro gimbal are designed.Then,based on SGCMG the PID-pattern reasoning controller of the servo control system of gyro gimbal is proposed.The controller model is simulated with Simulink.The simulation shows that the speed step response of gyro gimbal to the target speed is fast and stable.Finally,the SGCMG platform is built to test the speed stability of gimbal motor and the output torque of SGCMG.The experimental results show that the second generation prototype motor70 HB has good accuracy and stability on speed,which meets the demanding requirements of the SGCMG in spacecraft.5.The thermal-electric coupling effects of PZT are described,and the thermal breakdown of70HA’s PZT is observed by experiments.A method to improve the thermal reliability of motor by increasing the effective electromechanical coupling coefficient(EMCC)of stator is proposed.The influence of stator structure on the EMCC is studied by using the finite element impedance analysis.It is proved by experiments that improving the EMCC of stator is helpful to improve the efficiency,reduce the power consumption and reduce the temperature rise of the motor.Besides,the abnormal wear phenomenon of friction materials is observed through a large number of vacuum thermal cycling environmental tests.Then the friction materials formula is adjusted to improve the wear resistance by using fault tree analysis method.Finally the environmental tests show that the new friction materials improve the motor reliability in the simulated space environment. |
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