Physical Human-Robot Interaction Coupled with a Moving Environment or Target: Contact and Track

There is an increasing number of applications in physical human-robot interaction (pHRI) where the end-effector of the robot is compliant in response to the force exerted by the human. The force sensor is normally mounted with an instrument on the end-effector to measure the human operational force. However, when the robot is in contact with the human and an environment simultaneously, the force sensor reading includes both the human and the environmental force resulting in ineffective contacting interaction within these three objects (robot, human and environment). In addition, if the environment is moving, it is more challenging for the operator to track the target with the robot. Therefore, in this paper, we address the issue of pHRI coupled with a moving environment. More specifically, we use a collaborative robot with an ultrasound probe as an illustration due to its sophisticated condition: the operator needs to contact the environment using a sufficient force to get clearer images and track the moving target. The proposed control scheme is employed using only one force sensor to guarantee a stable physical interaction within three objects and provide the compliant and intuitive operation for human. Experiments with a collaborative robot are conducted to evaluate the effectiveness of the proposed controller.