  In this paper, we present a hybrid position/force controller for operating
joint robots. The hybrid controller has two goals -- motion tracking and force
regulating. As long as these two goals are not mutually exclusive, they can be
decoupled in some way. In this work, we make use of the smooth and invertible
mapping from joint space to task space to decouple the two control goals and
design controllers separately. The traditional motion controller in task space
is used for motion control, while the force controller is designed through
manipulating the desired trajectory to regulate the force indirectly. Two case
studies -- contour tracking/polishing surfaces and grabbing boxes with two
robotic arms -- are presented to show the efficacy of the hybrid controller,
and simulations with physics engines are carried out to validate the efficacy
of the proposed method.
