Computed Torque Control Simulation For 6dof Industrial Robot

Dynamics play a fundamental role in control algorithms synthesis, mechanical structure design, and motion simulation of robots. The challenge in robot control arises from the nonstationarity and the nonlinear coupling effects in the dynamic model, and many advanced control strategies have emerged within the robot control problem [1]. Besides the modelling complexity in the case of multiple DoFs, taking the dynamic model into account within the design of robot control systems in practice has drawbacks due to potential difficulties in implementation and errors that stem from structured/unstructured uncertainties. From the perspective of the appropriate selection of control strategy for a particular robot, control system performance simulation based on the robot dynamic model is a useful tool [2]. In this paper, a numerical simulation of the computed torque control (CTC) for the 6DoF industrial robot RL15 is presented. CTC is a feedforward control method used for tracking of robot’s time-varying trajectories in the presence of varying loads [3]. The method implemented in this study considers the speed PI controller in the joint space of the robot, with feedforward compensation of the load torque due to the movement of interconnected robot links. Herein, the following is taken into account for realistic simulation of control system performance: 1) resonant properties of the mechanical structure; 2) the effective inertia of the actuator calculated from the inverse dynamic model; 3) motor torque limits. CTC-based control system performance is compared with the traditional speed PI controller using the realistic simulation model.