Enhanced Transparency for Physical Human-Robot Interaction Using Human Hand Impedance Compensation

In a physical human-robot interaction (pHRi) system, improving transparency that allows humans to move as if there is no robot is a challenging topic. In general pHRi, usage of the multiaxial force sensor for robot control is the norm. However, the signal measured from the force sensor contains not only the force applied to the robot by the human motion intention but also the influence of the natural force feedback between the robot and the human hand produced by the robot motion. Therefore, in order to improve the transparency, it is necessary to characterize the dynamics of the human hand as well as the dynamics of the robot. In this paper, an algorithm to improve the transparency is proposed. The proposed algorithm uses only a multiaxial force sensor and compensates the natural force feedback by using the human hand impedance. And it further improves the transparency of the pHRi system, which has a limitation adjusting admittance parameters. In order to verify the algorithm, a device that can measure the impedance of the human hand is introduced, and a system model analysis and experiments using the hydraulic upper limb exoskeleton are carried out.