Development of Complex Hybrid 3d Robot with Parallel Links via Nonlinear Pneumatic Servo System for Path Tracking Control

This study aims to develop a complex hybrid 3D robot with parallel links driven by the nonlinear pneumatic servo system for path tracking control. The mechanical system and the control system are the primary parts for developing a complex hybrid 3D robot. In the mechanical system, a complex hybrid 3D robot contains serial manipulators, parallel links, base plates, a movable platform and a pneumatic servo system. Based on the structure design theory of the robot mechanism, the structure is analyzed and the end-effector of the robot can move a 3D motion in the X-Y-Z coordinate system. According to the characteristics of the mechanism, the inverse kinematics and the forward kinematics of the robot are proposed by the coordinate transformation theory. The pneumatic actuators for the three axes are modeled by including the dynamics of the pneumatic servo valve and the cylinder. In the control system, the control scheme is applied to follow the computed trajectory for real-time control. In order to improve path tracking accuracy for a complex hybrid 3D robot, a Fourier series-based adaptive sliding mode controller with H ∞ tracking performance (FSB-ASMC+ H∞) is proposed for controlling the pneumatic flows acting on the pistons of the actuators. The proposed controller first employs a Fourier series-based functional approximation technique to estimate the dynamic models and time-varying uncertainties of the system. Next, further efforts are made to improve the dynamic tracking performance by combining the H∞ tracking strategy with an adaptive sliding -mode control method to make the derived controller robust against approximation errors, un-modeled dynamics and disturbances. To verify the usefulness, simulations and experiments are carried out on a complex hybrid 3D robot based on the proposed methods. The results show that the complex hybrid 3D robot is successfully implemented with different path tracking profiles.