Sliding Mode Control Of The Optoelectronic Stabilized Platform With Input Saturation And Disturbance

The optoelectronic stabilized platform is mainly used to achieve real-time precise positioning and precise tracking of moving targets,which requires it to have good characteristics of isolating disturbances and maintaining boresight stability.However,the optoelectronic stabilized platform will be affected by various non-linear disturbances in the actual operation process,which will make the tracking accuracy of the system decreased.The traditional PID control technology is generally approximated when modeling.The controller designed in this way has limited stability and tracking performance.Therefore,this paper mainly improves the sliding mode control strategy according to the application requirements of the optoelectronic stabilized platform to improve the disturbance suppression ability and tracking ability of the optoelectronic stabilized platform.Taking the photoelectric pod as the research background,the mathematical model of the optoelectronic stabilized platform was established by analyzing the mechanism of the pod and adopting the system identification method.Based on this,this paper first adopts the classic PID control method and the parameter tuning criteria under the constraint conditions to obtain the basic design results of the multi-closed-loop control system for acceleration,velocity and position.Then,in view of the lack of antiinterference ability of the PID control method under the actual nonlinear disturbance of the pod,a sliding mode variable structure control was introduced in the position loop of the pod platform to suppress the nonlinear disturbance.Simulation results show that in the frequency range of 0~40Hz,the disturbance rejection of sliding mode control is improved by about 10 dB compared with PID control,which fully shows that the disturbance suppression capability of sliding mode control is better than PID control.In the aspect of tracking and disturbance suppression,the idea of feedforward is introduced,and the disturbance is estimated using the internal model principle and the disturbance feedforward compensation is realized by the internal model controller,which reduces sliding mode chatter and improves the tracking and anti-disturbance ability.Aiming at the problem that conventional internal model control cannot be applied in actual systems,an improved internal model control method is proposed.The simulation results show that the tracking and disturbance suppression capabilities of the composite control strategy are better than the sliding mode control.Under the sinusoidal input signal with a frequency of 0.5 Hz,the maximum tracking error value of the composite control strategy is about 0.09,while the maximum tracking error value of the sliding mode control is about 0.34,in addition,no matter how the disturbance signal changes,the steady-state error of the composite control strategy is always smaller than the sliding mode control.In the aspect of stability,in order to solve the problem of input saturation when sliding mode control is applied to the optoelectronic stabilized platform,a time optimal theory is introduced,and a new transition process algorithm is designed,which changes a rapidly changing step signal into a slow rise input signal,the system maintains a small error in the entire process of tracking the input signal,thereby eliminating the input saturation phenomenon and improving the stability of the system.A series of simulations and experiments verify the effectiveness of the above method.