Control And Friction Compensation Of Simulator For Motion Objects

Motion objects generator of space TDICCD (Time Delay and Integration Charge Coupled Device) camera is an important integral part in test system for camera. Motion objects generator is used to generate the motion objects of uniform velocity considering the effect of drift motion, in order to simulate the ground image motion related to the space aerocraft and to validate the capability of image speed matching. To ensure on-orbit high resolution imaging capability, it is extremely significant to develop this device. High precision turntable is the core drive unit of motion objects generator. The precision of turntable servo control system is directly related to the reliability and precision of the entire device. Therefore, it is significant and valuable to design high precision turntable servo control system.This paper first introduces the structure of turntable servo system, and then carries out the system modeling according to the turntable structure and performance index. On this basis, turntable steady speed servo control system based on hardware PLL is designed and implemented owing to turntable system needs high speed stable precision. On account of the shortage of hardware PLL system, a software PLL control strategy based on strong processing capacity of DSP is presented. Moreover, control system based on software PLL system is designed and implemented.Speed stability performance is the most important index of steady speed turntable servo system. Thus the evaluation method for speed stability performance is an important content of high precision speed control to turntable servo system. In this paper, a new implementation way of position difference method is designed in the basis of the analysis of common evaluation method for speed stability performance. On account of the shortage of common evaluation method for speed stability performance, two evaluation methods using maximum instantaneous velocity error are presented. According to the evaluation methods above, the control systems designed in this paper are tested.On account of the problem that servo system appears creeping phenomenon in low-speed, it is necessary to analyze the low-speed characteristics of high precision turntable servo system. Since nonlinear friction torque is the main factor affecting low-speed characteristics, this paper carries out theoretical research and simulation analysis to the low-speed effect of nonlinear friction towards turntable system. First the friction torque of turntable is measured. To simplify analysis, a friction model based on piecewise linear function is proposed and the actual friction model is obtained via the experimental data fitting. Then theoretical analysis to the low-speed effect of nonlinear friction towards turntable system by mathematical deduction is processed. Finally in the foundation of the friction model established above, simulation research to nonlinear friction influence is processed. The simulation results show that system would appear“stick-slip”phenomenon due to nonlinear friction influence when velocity falls to a certain value.In order to further improve system performance, it is necessary to reduce nonlinear friction influence. However, the decrease of the friction torque is restricted by level of technology. Therefore, it is a proper and feasible method that research on the control strategy to reduce nonlinear friction influence and improve system control precision. In the basis of the above realized turntable control system, two nonlinear friction compensation methods not based on model are presented considering friction model is hard to obtain accurately.One, the friction compensation method based on multi-loop control is presented. First, the noise immunity performance is analyzed in detail combined with turntable servo control system and the principle of two friction compensation methods based on speed inner-loop control and based on acceleration feedback control are expounded. On this basis, the friction compensation methods based on speed inner-loop control and acceleration feedback control are designed concretely and analyzed by simulation and experimentation. Simulation and experimental results show that this method can effectively restrain nonlinear disturbance torque influence.The other, the friction compensation method based on CMAC network is presented. Considering CMAC network is easy to realize and has high efficient algorithm, it is proposed to apply to nonlinear friction compensation of turntable system. In this paper, the learning algorithm of this compensation method is analyzed in detail and the system stability is proved by Liapunov theory. Finally, the simulation research is carried out. Simulation results show that the friction compensation method based on CMAC network can better compensate nonlinear friction influence and effectively improve low-speed performance of servo system.