  In laparoscopic robot-assisted minimally invasive surgery, the kinematic
control of the robot is subject to the remote center of motion (RCM) constraint
at the port of entry (e.g., trocar) into the patient's body. During surgery,
after the instrument is inserted through the trocar, intrinsic physiological
movements such as the patient's heartbeat, breathing process, and/or other
purposeful body repositioning may deviate the position of the port of entry.
This can cause a conflict between the registered RCM and the moved port of
entry.
  To mitigate this conflict, we seek to utilize the interaction forces at the
RCM. We develop a novel framework that integrates admittance control into a
redundancy resolution method for the RCM kinematic constraint. Using the
force/torque sensory feedback at the base of the instrument driving mechanism
(IDM), the proposed framework estimates the forces at RCM, rejects forces
applied on other locations along the instrument, and uses them in the
admittance controller. In this paper, we report analysis from kinematic
simulations to validate the proposed framework. In addition, a hardware
platform has been completed, and future work is planned for experimental
validation.
