PHRI Safety Control using a Virtual Flexible Joint Approach

J. Diab, A. Fonte, G. Poisson, C. Novales

Abstract

Physical Human-Robot Interaction (PHRI) emphasize on human safety. In literature, two techniques were presented to improving this critical factor concerning moving devices; the first solution is purely mechanical, while the second one is based on the control. In this paper, we describe a new approach combining the two previous solutions. Our proposed paper explores a control scheme involving the use of a virtual component with an adjustable stiffness supposed to be placed between the motor shaft and the robot link. This scheme proposes a Variable Impedance Actuator (VIA) robot control methodology based on the integration of a virtual component, reflecting the behaviour of a real intrinsic Series Elastic Actuator (SEA). This novel method is potentially beneficial in reducing injuries in human/robot interaction by combining a mechanical operating principle and a control approach in order to reduce the collision forces in collaborative applications. This proposed approach was simulated and validated using a UR3 robot model, showing great capacities in reducing collision’s peak forces. This paper begins with particular attention to the robot dynamics, then the articulation flexibility and force estimation have been tackled and finally ending the control architecture.

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