Research On Sliding Mode Variable Structure Control Method Of Stewart Platform

The Stewart platform has the advantages of multiple degrees of freedom,high stiffness,and so on.As a complement to the serial mechanism,it is widely used in aerospace,robotics and other fields.In this project,the Stewart platform is used to simulate the elastic vibration of the missile,and six linear motion simulations with three linear displacements and three angular displacements can be realized.The elastic vibrations of missiles are generally high-frequency small-amplitude vibrations,so the control system of the platform needs to have strong command tracking capabilities.In order to improve the control performance of the Stewart platform,this paper conducts research work on the kinematics and decentralized control of the Stewart platform.First,separate the six connecting rod branches of the Stewart platform into separate control channels,analyze the kinematic characteristics of the Stewart platform,and establish the nominal model of the single-channel control system according to the working principle of the voice coil motor.The dynamic characteristic nonlinear curve of the voice coil motor is added to the nominal model to improve the mathematical model of the controlled object.Secondly,for the dynamic nonlinear characteristics of the voice coil motor and the perturbation of the controlled object model under high-frequency conditions,a sliding mode control method based on adaptive approach law was carried out,and the effectiveness of the control method was verified by simulation examples Sex.Thirdly,under the influence of external interference,the control signal chattering phenomenon is obvious,which leads to the poor tracking effect of the command signal.For the chattering problem,a sliding mode control method based on fuzzy control switching gain adjustment is proposed,that is,the switching term coefficient It can be changed according to the amplitude of the disturbance,and the effectiveness of the control method is verified by simulation examples.Finally,according to the parameters of the voice coil motor,MATLAB / SIMULINK is used to build a dual-loop control model of the actual controlled object,and the design of the current loop and position loop controllers is carried out.Among them,the design of the position loop controller adopts the traditional series correction method and the sliding mode variable structure method successively,and the advantages of the sliding mode variable structure method are verified through simulation comparison analysis.