Discrete first and second order sliding mode controllers for a pneumatic artificial muscles robot manipulator

Pneumatic artificial muscles are widely used in the field of robotics in the development of robot manipulators to help or assist human beings. This can be attributed to their inherent compliance and low cost. However, their highly nonlinear dynamics and their time varying properties, make it challenging for classical controllers to accurately control such systems. Sliding mode control is a powerful tool to overcome control problems related to highly nonlinear systems that features robustness against modeling uncertainties, parameter variations and external disturbances. This paper investigates the use of discrete time sliding mode control for position control and trajectory tracking of a robot manipulator actuated by pneumatic artificial muscles. First and second order discrete sliding mode controllers are designed to make the joint angle track a desired angular position or trajectory within a guaranteed accuracy. A comparative study is presented along with simulations results.