A robot manipulator is often required to make and maintain smooth direct contacts with its environment. In light of the popular dynamics-model-based hybrid position-force control scheme, a study is made of: (1) inclusion of the accelerations along contact normals in force control for maintaining smooth contacts between curved surfaces, and (2) generalization of the control scheme to a robot under multiple contacts which may occur on linkages other than the end effector, while satisfying the decoupling of motion and force control errors. Cases where motion variables are specified explicitly or a motion space is specified implicitly are treated.>