Modeling and Simulation of 6-DOF Parallel Manipulator Based on PID Control with Gravity Compensation in Simulink/ADAMS

A novel model-based controller for six degree of freedom (dof) parallel manipulator-PID controller with gravity compensation is developed, in order to improve the control precision of six-dof hydraulic driven parallel manipulator with long stroke hydraulic actuator and heavy load. In this paper, six-dof parallel manipulator is described as a thirteen rigid-body systems. The mathematical model of gravity item including upper platform and hydraulic cylinders is built using Kane method in six dimensions generalized coordinates system, based on close-form solutions and Newton-Raphson method, forward kinematics and inverse kinematics of the six-dof parallel manipulator are established. The PID controller with gravity compensation is presented with the feedback of cylinder length of platform, desired trajectories and dynamics gravity as the input. The physical systems of 6dof parallel manipulator are modeled by ADAMS, and the PID controller with gravity compensation is built with Simulink. The whole control system of 6-dof parallel manipulator is obtained by connecting ADAMS plant with PID control system with gravity compensation in Simulink. The simulation of the whole systems is executed in Simulink, the simulation results indicate the PID controller with gravity compensation can eliminate steady state error of 6-dof hydraulic driven parallel manipulator and improve the control precision.