Stable and Compliant Motion of Physical Human-Robot Interaction Coupled With a Moving Environment Using Variable Admittance and Adaptive Control

There are an increasing number of applications that require the end-effector of a robotic manipulator to be compliant in response to the intended force exerted by a human operator. In physical human-robot interaction, the stability and compliance are often affected in the presence of both human and an environment, especially during the transition from noncontact to contact. Unlike previous works, the physical human-robot interaction in this letter takes into consideration of the interaction of the human, robot, and a moving environment. To achieve this, this letter proposes a variable admittance control strategy with an adaptive controller to produce a time-varying stiffness interacting with the human and a moving environment simultaneously. The passivity of the system is guaranteed for time-varying admittance with human interaction coupled with a moving environment. Experiments are conducted to demonstrate the capability of the controller.