Research On The Sliding Mode Variable Structure Control Of A Three-axis Stabilized Platform

Due to high stability,high flexibility and simple structure,three-axis stabilized platform(TSP)has been widely used in aerospace,military,civil and commercial fields.And it has very important application value.Due to that the TSP is a system with multivariable,strongly coupling and nonlinearity,the controller design of the TSP is very challenging and the traditional linear control method has certain limitations.Compared with the traditional linear control method,the nonlinear control method has better control and disturbance rejection performance.Therefore,a finite-time robust sliding mode controller designed by using the principle of terminal sliding mode control is adopted in this thesis.And that the system converges in a finite time and has good disturbance rejection performance,which effectively improves the dynamic and robust performance of the system,is guaranteed.This thesis mainly studies the stability control and tracking control problems of the TSP system.The main research work is as follows:(1)This thesis studies the frame structure of the TSP and the coupling relationship of the angular velocity as well as the moment of inertia of each axis.Considering the frictional disturbance between shafts,the Stribeck friction model is introduced.According to the Coriolis rotation theorem,the complete mathematical model of the TSP is obtained.(2)This thesis studies the stability control and tracking control problems of the TSP system in view of the linear sliding mode control method.Based on the improved approach law,a linear sliding mode controller is designed.The controller has strong disturbance rejection performance as well as robustness and simulation results demonstrate its effectiveness.(3)This thesis studies the stability control and tracking control problems of the TSP system in view of the terminal sliding mode control method.Considering the limitations of the traditional linear control methods,a finite-time robust sliding mode controller is designed in this thesis based on terminal sliding mode control method.Firstly,the controller ensures that the system state can converge in a finite time,which improves the dynamic performance and steady-state accuracy of the system.Secondly,the controller has a good inhibitory effect on the disturbance,which improves the disturbance rejection performance of the system.Finally,the controller allows system parameters to have certain uncertainties,which improves the robust performance of the system.The effectiveness of the proposed control scheme is verified by simulation results.