On the global optimum path planning for redundant space manipulators

Robotic manipulators will play a significant role in the maintenance and repair of space stations and satellites, and other future space missions. Robot path planning and control for the above applications should be optimum, since any inefficiency in the planning may considerably risk the success of the space mission. This paper presents a global optimum path planning scheme for redundant space robotic manipulators to be used in such missions. In this formulation, a variational approach 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 (reaction wheels or thrust jets) is off. Linear and angular momentum conditions for this system lead to a set of mixed holonomic and nonholonomic constraints. These equations are adjoined to the objective functional using a Lagrange multiplier technique. The formulation leads to a system of differential and algebraic equations (DAEs). A numerical scheme for forward integration of this system is presented. A planar redundant space manipulator consisting of three arms and a base is considered to demonstrate the feasibility of the formulation. The approach to optimum path planning of redundant space robots is significant since most robots that have been developed for space applications so far are redundant. The kinematic redundancy of space robots offers efficient control and provides the necessary dexterity for extra-vehicular activity that exceeds human capacity