This paper developed a position and force control scheme for a class of fle
xible joint robots with model uncertainties based on the singular perturbat
ion theory. The controller is composed of two parts: a fast controller and
a slow controller to regulate the joint elastic force, the position and con
tact force respectively. In the fast controller, an additional control sign
al was designed to compensate for the deviation of the joint elastic force
from the integral manifold due to the effect of model uncertainties. The st
ability of the closed-loop system was analyzed based on Lyapunov stability
theory. The proposed controller is experimentally evaluated on a flexible j
oint manipulator. In comparison with fixed parameter controller, the experi
mental results show that the proposed controller improves the position and
force tracking accuracy for a class of flexible joint robots with uncertain
knowledge of the dynamic model. (C) 2001 Elsevier Science Ltd. All rights
reserved.