Research On Active Disturbance Rejection Control Of A Pneumatic Hybrid Motion Simulator

A 3-D freedom pneumatic hybrid motion simulation platform is studied mainly in this paper,which is used to simulate the uniform speed,turning,drifting,up and down and other motion states for automobiles,airplanes,steamships and so on.There exist some uncertain factors in the motion process of platform,such as the compressibility of air,the flexibility of pneumatic artificial muscle,internal friction resistance of cylinder,viscous resistance and varing loads and so on.Therefore,it is difficult and chanllenge for controlling of the motion simulation platform.The technology of active disturbance rejection control is investigated to overcome the problem of model uncertainty and respond slowly which is caused by itself of the platform and the external disturbances.Meanwhile,the problem of actuator saturation is considered to ensure precise position and orientation control in the safe range.Firstly,the composition structure of the motion simulation platform is introduced.Through the studying of the principle for the joint actuated by pneumatic artificial muscles and the valve controlled cylinder,the complicated nonlinearsystems are modeld with the characteristics of sufferance force.Secondly,the tracking control of deflection angle is studied for pneumatic artificial muscle joint in the case of constant load.A tracking differentiator is designed to arrange an adaptive transition process for avoiding the phenomenon of overshoot coused by tracking error in the initial.Moreover,a nonlinear extended state observer is introduced to estimate the uncertain terms.The estimation is compensated to a linear error feedback controller in real-time.Some experiment results are given to illustrate the effectiveness of the control strategy.Additionally,consider the joint of pneumatic artificial muscles subjected to varing load.The variable loads and the uncertain factors as total disturbances are estimated by a linear extended state observer.Moreover,to overcome the adverse effect of the total disturbances and enhance the robustness of the system,a nonlinear error feedback controller is designed.The effectiveness of strategy is proved by experiment results.Finally,the problem of actuator saturation is considered for the two systems of the pneumatic artificial muscle joint and the valve controlled cylinder.Based on the tracking error system,the active disturbance rejection control is used to overcome the total disturbances.And the controller with saturation is replaced with convex hull.Moreover,the problem of convex optimization is solved by the technique of linear matrix inequality.The domain of attraction is gotten which is a stability region for the system with actuator saturation.Therefore,the 3-D freedom motion is ensured in the safe range for the pneumatic hybrid motion simulation platform.