Modeling and tracking control of a pneumatic servo positioning system

Pneumatic actuators are low-cost, safe, clean and exhibit a high power to weight ratio. In this paper a novel control strategy for solving the tracking problem of pneumatic servo positioning systems copes with the nonlinearities of air flow through the 5/3-way proportional directional control valves and the nonlinear friction by considering position, velocity and pressure difference in the chambers of the pneumatic cylinder, as feedback states. The experimental and simulated results from the proposed tracking control strategy, probe that the time delay in the system that depends on the valve's flow rate and the size of the pneumatic cylinder, is low but cannot be eliminated and it is the main source of the obtained tracking error.