Design And Experimental Research Of Servo System Based On Characteristic Model

With the development of science and technology, Permanent Magnet Synchronous Motor (PMSM) is being used in weapon servo systems more and more widely. Because the maneuvering target motion trajectory is unpredictable and changing quickly, and it is hard to obtain useful feedforward control signals from command signals deriving from fire control computer, the dynamic response performance and steady precision of the weapon servo systems should be very high even without feedforward control signals. What’s more, the weapon servo system which is driven by PMSM is a high-order, strong-coupling and complex nonlinear system. In conclusion, further research about how to build a simple and precision model of the PMSM servo system and how to improve the dynamic response performance and steady precision of the PMSM servo system are still needed.Based on the characteristic model theory which is proposed by Academician Hongxin Wu, building model of a kind of PMSM positional servo system, compensation control for the backlash and friction in the PMSM servo system and designing high performance control strategy without feedforward control signals for the PMSM servo system are explored and researched in this paper. The main contents of this paper are as follows:(1) The dynamical model of the PMSM positional servo system is built. Due to the dead-zone model and Stribeck friction model that are used generally to model the backlash and friction in servo systems respectively are all non-differentiable, designing controller for servo system containing backlash and friction is not convenient. In order to solve this problem, the dead-zone model and Stribeck model are smoothed in this paper. Simulations using MATLAB verify that the modeling errors of smooth backlash model and smooth frition model are within permission bounds.(2) The elements that influence the precision of the characteristic model of the PMSM servo system are researched. The influences of sampling time, control signals and identification algorithms to the precision of characteristic modeling are analysised respectively. And the conclusions are verified by simulations. In order to verify the feasibility of building characteristic model for the PMSM positional servo system, the characteristic model of servo system containing smooth backlash model and smooth friction model and the characteristic model of servo system with practical backlash model and friction model are verified respectively by simulations. Based on these conclusions, the characteristic model of the positional PMSM servo system is built, and it is verified by simulations. (3) Because the command sgnals are complex in weapon servo systems, and obtaining feedforward control signals from them is hard, in the context of using Golden-section adaptive controller to maintain the stability of the system during the characteristic model being identified, a kind of intelligent integration control strategy which can improve the steady precision and decrease the bad influence of the integration to the dynamic response of the servo system in the mean time is proposed in this paper.(4) The backlash in a gear transmission servo system which is driven by single motor can not be removed entirely, which influences the performance of the servo system seriously. In order to solve this problem, the backlash compensation controller is propsed. Because the characteristic model do not include all the information about backlash, the backlash compensation information can be extracted from the difference between the output of practical servo system and the output of characteristic model, which can be used as the backlash compensation dosage of the servo system.(5) The hardware structure and software designing of the PMSM positional servo system experiment platform are introduced. According to the general test method of servo system, the precision of the characteristic model of the servo system and the performance of the "Golden-section adaptive+Intelligent integration+Backlash compensation" compund controller are verified by practical experiments that are conducted through the servo system experiment platform.