Kinematics and methods for combined quasi-static stance/reach planning in multi-limbed robots

This paper provides kinematic analysis and local motion planning methods for multi-limbed robots. In particular, we consider combined stance and reach tasks for robotic mechanisms whose limbs can be used either as legs or manipulator arms. An example of such a system is the RoboSimian robot participating in the DARPA Robotics Challenge (Figure 1). We develop relationships which model the key quasi-statics and kinematics of these mechanisms: the stance map, the stance Jacobian, and the reach Jacobian, as well as the stance constrained center-of-mass Jacobian. We also introduce characterizations of multi-limbed mechanism configurations in terms of the properties of these maps: local dexterity and limberness. This paper also introduces local planning methods which seek to balance the motion of legs, body, and arms of such mechanisms so as to realize manipulation goals while also maintaining awareness of stance stability issues. Examples with a simple planar model illustrate the methods.