Design of robust nonlinear force and stiffness controller for pneumatic actuators

This paper introduces a new backstepping-sliding mode controller designed specifically for pneumatic actuators. Based on a detailed mathematical model of the pneumatic system that included the dynamics of the valves, the algorithm was proven able to track the desired force and stiffness independently without chattering. The global Lyapunov asymptotic stability of the pressure tracking for each chamber was analyzed. Numerical simulations and validating experiments using a real-time platform were performed for a pneumatic actuator suitable for wearable robotics applications.