ON THE GLOBAL OPTIMUM PATH PLANNING FOR REDUNDANT SPACE MANIPULATORS

Robotic manipulators will play a significant role in the maintenance a nd repair of space stations and satellites, and other future space mis sions. Robot path planning and control for the above applications shou ld be optimum, since any inefficiency in the planning may considerably risk the success of the space mission. This paper presents a global o ptimum path planning scheme for redundant space robotic manipulators t o be used in such missions. In this formulation, a variational approac h is used to minimize the objective functional. It is assumed that the gravity is zero in space, and the robotic manipulator is mounted on a completely free-flying base (spacecraft) and the attitude control (re action wheels or thrust jets) is off. Linear and angular momentum cond itions for this system lead to a set of mixed holonomic and nonholonom ic constraints. These equations are adjoined to the objective function al using a Lagrange multiplier technique. The formulation leads to a s ystem of Differential and Algebraic Equations (DAEs). A numerical sche me for forward integration of this system is presented. A planar redun dant space manipulator consisting of three arms and a base is consider ed to demonstrate the feasibility of the formulation. The approach to optimum path planning of redundant space robots is significant since m ost robots that have been developed for space applications so far are redundant. The kinematic redundancy of space robots offers efficient c ontrol and provides the necessary dexterity for extra-vehicular activi ty that exceeds human capacity.