Motions With Minimal Joint Torques for Redundant Manipulators

The article presents a method for obtaining motions with minimal joint torques for redundant mechanical manipulators. The existing methods based on the local resolution of redundancy do not guarantee that singular configurations, which lead to large joint torques and joint accelerations, will also be avoided while optimizing joint torques. For the present method, the degrees of redundancy are resolved at the global level. It is observed that motions with optimal joint torques are usually associated with large joint speeds and joint accelerations, compared with the joint speeds and joint accelerations for motions with minimal joint speeds or joint accelerations. To overcome this problem, the optimization criterion for minimal joint torques is modified by combining it separately with the optimization criteria for both minimal joint speeds and minimal joint accelerations. The resulting optimal motions, with smaller joint speeds and joint accelerations, are achieved at the expense of having larger joint torques.