In this paper a new task-space regulation scheme for a system of two cooper
ative manipulators tightly grasping a rigid object is proposed. The control
architecture is based on individual task-space regulators for the two mani
pulators. in order to overcome problems arising from representation singula
rities, the unit quaternion is used to describe the orientation of relevant
frames. To avoid steady-state internal stresses at the held object, kineto
static filtering of the control action is introduced together with internal
force feedback. Also, the performance of the control scheme is analyzed in
the presence of a class of modeling uncertainties. The equilibria of the c
losed-loop system are then explicitly computed and asymptotic stability is
proven via Lyapunov-like analysis. (C) 2000 Elsevier Science Ltd. All right
s reserved.