Design Of The Centroid Adjustment And Attitude Tracking Control Systems For Air Bearing Platform

The air bearing platform is a frictionless device for simulating microgravity in space by gas lubrication.The simulator can simulate the motion of the spacecraft in outer space.This thesis focuses on the attitude stability control and centroid adjustment of the simulator.Firstly,two coordinate systems are established for the simulator to describe the attitude motion of the simulator.Several common attitude description methods are listed,and finally the four element method is chosen for attitude description.The kinematics and dynamics equations of the simulator are established by means of the four-element method and the momentum moment theorem,which provides the basis for the implementation of the following control algorithms.For the nonlinear and strong coupling simulator model,the sliding mode variable structure algorithm is adopted to control the attitude stability.And to study the chattering problem in sliding mode,the improvement and simulation analysis is carried out.Aiming at the two problems existing in sliding mode control,which contain the assumption of upper bound of interference and inertia matrix.Adaptive rate is used to improve it.Adaptive sliding mode controller is designed to realize attitude stability control.The simulation of sliding mode controller is compared with that of sliding mode controller.Then,the attitude stability control is used as the inner loop,and the inner and outer loop control method is designed to realize the adjustment of the center of mass of the attitude platform.A mathematical description of the relationship between the moving mass of the slider and the centroid,the moment of inertia,and the moment of inertia is established for the non-orthogonal structure slider.The PID controller is used to control the center of mass.The nonlinear mapping ability of BP neural network is used to improve it,and the BP neural network PID controller is designed to achieve the optimal control of the centroid.Simulation analysis and comparison of the two algorithms.Finally,the hardware framework and software design of the actual experiment system are completed.Physical connection test is carried out,multi thread control software is written and human-computer interaction is realized.The software and hardware are debugged together,and finally,the feasibility and validity of the control algorithm are completed on the whole physics experiment platform.