  Physical Human-Robot Interaction (pHRI) task involves tight coupling between
safety constraints and compliance with human intentions. In this paper, a novel
switched model reference admittance controller is developed to maintain
compliance with the external force while upholding safety constraints in the
workspace for an n-link manipulator involved in pHRI. A switched reference
model is designed for the admittance controller to generate the reference
trajectory within the safe workspace. The stability analysis of the switched
reference model is carried out by an appropriate selection of the Common
Quadratic Lyapunov Function (CQLF) so that asymptotic convergence of the
trajectory tracking error is ensured. The efficacy of the proposed controller
is validated in simulation on a two-link robot manipulator.
