Study On The Method Of Friction And Torque Ripple Identification And Compensation In Low Speed Control Of Space Load

Spacecraft Payload, such as optical remote sensor, are carried in the satellite completing the tracking scan imaging, staring imaging and other tasks based on mission requirements. In tracking scan imag, space load is required to track the target while in orbit. In the actual tracking process, the space load servo control system usually state in the low speed operation, because of the task needs. At this time, the speed of the input signal of servo system is small, and the disturbance of servo system is serious, Load Los oscillating, affecting the imaging quality of space load even missing the target. The stability control under the low speed operation of the space load is the necessary condition for the high quality imaging.In this paper, the permanent magnet synchronous motor(PMSM) direct drive system of the stabilize image space load system is studied. The control strategy of permanent magnet synchronous motor is introduced. The high precision control technology of servo system is analyzed, and the main reasons of the low speed performance of the servo system are analyzed. The cause and the phenomenon of affecting the accuracy of servo system are analyzed and discussed. The control algorithm and the control strategy are also analyzed and discussed.First, this paper introduces the structure and composition of the control system of the Permanent magnet synchronous motor, the structure and the corresponding FOC control strategy of the permanent magnet synchronous motor, and analyzed the reason why the permanet magnet synchronous motor is used in the spatial load servo system. Introduced the correlation between the vector control strategy of stator phase current, voltage and motor torque output. The mathematical model of permanent magnet synchronous motor is established from the point of view of mathematics.Then, the reasons for the low speed stable of the servo system of the space load and the corresponding compensation strategies are analyzed. the friction and torque ripple of the servo system are studied and analyzed in depth. Several typical friction models are given. Based on LuGre friction model, the effect of friction on the speed of the motor at low speed is analyzed. The cause and the existing form of the torque ripple are given. The effect of torque fluctuation on the system speed is analyzed.Third, using the spectrum generator to measure the transfer function of closed loop system of the motor current loop, we obtain the closed-loop transfer function of the current loop. The zero speed of the motor is analyzed, proposed the method of using genetic algorithm to identify the parameters of LuGre friction model. The principle of friction compensation method based on the model is presented, and the current loop compensation method based on LuGre friction model is studied. The principle of the disturbance observer is given, and the compensation method of the speed loop of the disturbance observer is analyzed.Finally, the speed loop of space load servo system is established by using Matlab/simulnk module. The LuGre friction model is analyzed from the mathematical point of view. According to the low speed operating condition of the servo system, the simple method of LuGre friction model is proposed, and the method of current loop compensation based on the simplified LuGre friction model is presented. In view of the existence of the error term of the friction compensation and the torque ripple of the motor, the compensation method of the disturbance observer based on the speed loop is proposed.