| Abstract |
In this paper we discuss the theoretical design of a N axes robot arm dynamic controller, called computed voltage controller, which includes the current dynamics of a synchronous driver (brushless DC motor). The method is implemented on an experimental one axe robot joint. Generally, the advanced control laws of robot manipulators, such as computed torque control, consider the joint drive chain as a constant gain, that is to say the controllers are designed at the 'torque input' level [1][2]. But in the case of high speed motion/force control of robot manipulators the dynamics associated with the actuators can't be neglected [3]. Including the robot actuator dynamics into the robot equations typically makes the latter a system of third order non linear differential equations. A few authors have discussed this problem, but with complicated control law such as Freud’s nonlinear control theory or with the Riccati equation applied to a robot driven with a DC motor [4][5]. Based on the dynamic control technique [6], we propose to include the current dynamics of brushless motor to yield to a global stability of a robot arm. Compared with the computed torque control law which needs the desired joint position, velocity and acceleration, the global computed voltage control law requires the desired joint position, velocity, acceleration and jerk to track. To realize this type of control law, the parameters identification has to be done carefully. A closed loop identification of an inverse model which is linear in relation to the parameters has been performed using least squares techniques and exciting trajectories [7]. These method has been use to get the electrical parameter of the synchronous machine [8] and the mechanical parameter of the robot [9]. |
