Motion control

Abstract

In Chap. 4, trajectory planning techniques have been presented which allow the generation of the reference inputs to the motion control system. The problem of controlling a manipulator can be formulated as that to determine the time history of the generalized forces (forces or torques) to be developed by the joint actuators, so as to guarantee execution of the commanded task while satisfying given transient and steady-state requirements. The task may regard either the execution of specified motions for a manipulator operating in free space, or the execution of specified motions and contact forces for a manipulator whose end-effector is constrained by the environment. In view of problem complexity, the two aspects will be treated separately; first, motion control in free space, and then control of the interaction with the environment. The problem of motion control of a manipulator is the topic of this chapter. A number of joint space control techniques are presented. These can be distinguished between decentralized control schemes, i.e., when the single manipulator joint is controlled independently of the others, and centralized control schemes, i.e., when the dynamic interaction effects between the joints are taken into account. Finally, as a premise to the interaction control problem, the basic features of operational space control schemes are illustrated.