Trajectory tracking control of a pneumatically actuated 6-DOF Gough-Stewart parallel robot using Backstepping-Sliding Mode controller and geometry-based quasi forward kinematic method

In this paper, the trajectory tracking control of a 6-DoF pneumatically actuated Gough-Stewart parallel robot is investigated. The dynamic model of each link, comprising of a pneumatic actuator and a proportional electrical valve is extracted with the aim of obtaining the corresponding state space representation of the pneumatic system. Unknown parameters of the dynamic model consisting friction force of the cylinder and parameters of the proportional valve are identified by employing genetic algorithm. Position control of the pneumatic actuator is performed based on Back-Stepping Sliding Mode controller according to the dynamic model of the system. As such trajectory tracking control is performed for different trajectories by employing a rotation sensor and calculated position based on joint space and task space simultaneously. Desired sinusoidal trajectories with pure motions are tracked with root mean square error of the pure translations and rotations lower than 0.85 (cm) and 1.9 (deg), respectively. The results reveal that the trajectory is tracked by the Back-Stepping Sliding Mode controller properly. This shows the efficiency of the control strategy and the proposed method for calculating the position of the end-effector.