The Study Of Position Control For Pneumatic Experiment Platform

With the advantages of simple structure, non-pollution, high performance-price ratio and reliability in operation, pneumatic systems have wide applications in industry, agriculture, defence and health care fields. However, the compressibility of air and nonlinearity of pneumatic components make it difficult to achieve precise positioning control. High positioning control for pneumatic systems has become one of the hot spots in the contemporary research. Since the valve controlled cylinder system is one of typical pneumatic systems, it has been widely studied. However, the high position of a pneumatic cylinder needs improvement. Then, a pneumatic platform is built and an active disturbance rejection control approach is proposed to study the high position of a rodless pneumatic cylinder in this paper.Firstly, the movement rule of blocks is needed to finish the effect of pneumatic platform. Camera is installed to capture blocks’ images, and the color of every block is obtained by target extraction and color recognition methods. Then, movement algorithm is designed based on image processing techniques..Then, since there exists the strong nonlinearity for rodless pneumatic cylinder system, a simplified system model is built and an active disturbance rejection control approach is proposed to study the high position of a rodless pneumatic cylinder. And, the effectiveness of this approach is proved by self-stable theory and Lyapunov stability method. Moreover, an extended state observer is designed to estimate the total nonlinear term in real time. Further, the estimated state is fed back to a nonlinear controller to compensate influence of the total nonlinear term. Finally, experimental results show that the steady-state error within 0.05 mm is achieved for a 200 m step signal.Finally, an active disturbance rejection control approach is applied to achieve the high position for a rodless pneumatic system. There is some room for improvement in response time. Therefore, the backstepping-based controller with pressure feedback is proposed to increase response rate. Meanwhile, the original nonlinear error feedback controller is used to keep accurate positioning. Both controllers switch according to given rule to achieve good performance. Finally, for the given 200 mm step signal, experimental results with response time 0.5s and accuracy 0.05 mm indicate the capabilities of the proposed method.