Collision avoidance of a multiple-redundant-joint manipulator operating through a window

An efficient gradient projection optimization scheme is presented for the kinematic control of manipulators with multiple degrees of redundancy. This scheme, which does not require the evaluation of the generalized inverse of the Jacobian, is an extension of the gradient projection scheme presented by Dubey et al. [1] for manipulators with one degree of redundancy. Feasibility and effectiveness of this scheme are verified through simulations of the seven-degree-of-freedom NASA Laboratory Telerobotic Manipulator (LTM). Only the position of the LTM end-effector is controlled, which requires three degrees of freedom. Remaining joints, except for the wrist roll joint which does not contribute to the end-effector linear velocity, provide three degrees of redundancy. This scheme was implemented for avoiding collision of the manipulator links with the inner edges of the window as the manipulator works through the window. The window is modeled by a polygon with the sides representing the edges of the window. A performance criterion for collision avoidance is defined to maximize the shortest distances between the arm link axes and the edges of the window. The software for the control scheme was written in C and implemented on the IRIS-4D GT SiliconGraphics workstation. The program has a user interface capable of creating a trajectory, setting up parameters related to performance criteria, switching between performance criteria, setting up the 3-D solid model of LTM, and simulating real-time motion of the LTM as it demonstrates collision avoidance while working through a window.