Sliding mode control of pneumatic actuator for robotic application

A new position control algorithm, based on sliding mode control, has been developed for a pneumatic cylinder. The inherent robustness property of the sliding mode controller makes it easier to select the switching gains of the controller. Moreover, approximate dynamic modeling of the system made the controller simple. As the controller is robust and the states stick to the sliding surface, the motion of the piston is very smooth. This suggests the potential of a pneumatic actuator as a drive for robots and manipulators. In the proposed system, commercially available on-off two-way solenoid valves have been used. The controller is hybrid in nature, consisting of an error amplifier, data conversion devices and an 8088 microprocessor, along with various digital circuit accessories. Only one feedback device, in the form of a potentiometer, is used. Velocity is calculated from the sampled position signals.