Calculating the Supplied Energy for Physical Human-Robot Interaction

As the safety of robotics is highly demanded, injury criteria are widely investigated and employed in control strategies because of their guiding roles, in which the energy (density) tolerances are of priority owing to unification of other physical variables for injury criteria. However, the calculation method for the supplied energy of the physical Human-Robot Interaction (pHRI) is not addressed by considering the viscoelasticity of the human soft tissue. This paper presents four collision modes for classifying the pHRI and proposes a generic method for calculating the supplied energy of each collision mode. Consequently, specific calculation instances are given by treating the human soft tissue as a three-element Maxwell model with maximum/allowable compressive displacement. The feasibility and precision of the proposed calculation method are verified by comparing the computational and simulation results. This calculation method is intended to provide a way of directly determining or indirectly converting the allowable velocity or mass of an approaching robot.