  The restriction of feasible motions of a manipulator link constrained to move
through an entry port is a common problem in minimum invasive surgery
procedures. Additional spatial restrictions are required to ensure the safety
of sensitive regions from unintentional damage. In this work, we design a
target admittance model that is proved to enforce robot tool manipulation by a
human through a remote center of motion and to guarantee that the tool will
never enter or touch forbidden regions. The control scheme is proved passive
under the exertion of a human force ensuring manipulation stability, and smooth
natural motion in hands-on surgical procedures enhancing the user's feeling of
control over the task. Its performance is demonstrated by experiments with a
setup mimicking a hands-on surgical procedure comprising a KUKA LWR4+ and a
virtual intraoperative environment.
