Motion control of robot manipulators by a joint acceleration controller

A simple and high performance motion control method for robot manipulators in task-oriented coordinates is proposed. In this method, it is necessary that a controller for each joint generates a specified acceleration. To extend the result to robot manipulators with multiple degrees of freedom (DOF), the acceleration tracing orientation method (ATOM) is used. The ATOM is a controller design method in task-oriented space. A high performance position controller and hybrid position/force controller are easily realized by the ATOM. From the analyses of the controllers, it is known that a precise acceleration controller is the key to improving the performance of the ATOM. Realization of a strict acceleration controller, however, is almost impossible using conventional disturbance compensation methods. For example, inverse dynamics involves complicated calculations and is susceptible to parameter variations. Recent research on a disturbance observer has enabled the realization of an acceleration controller. Contrary to inverse dynamics, the observer is simple and robust against parameter variations. A high performance acceleration controller is realized by the disturbance observer. The effectiveness of the ATOM is shown by some experiments performed with a 3-DOF robot.