Dynamics coordination in a manipulator with 7 joints

Abstract

A control system for a 7-joint manipulator with three intersecting shoulder axes is presented. A singularity avoidance scheme is developed, where the redundancy is resolved through a position transformation. The internal and external motions are decoupled using nonlinear feedback linearization in an augmented task space. It is then possible to use linear controllers both for the internal nullspace and for the end-effector coordinates. It is shown how optimal control theory can be applied to coordinate the motion in the arm, and how to do this so that the input generalized forces are minimized. This gives a coordination of internal and external motion which resembles the motion of the human arm; this is demonstrated by simulating a throwing motion with the manipulator.<>