A Multi-Task Energy-Aware Impedance Controller for Enhanced Safety in Physical Human-Robot Interaction

In physical human-robot interaction (pHRI), ensuring human safety in all tasks conducted by the robot is crucial. Traditional compliance control strategies, such as admittance and impedance control, often lead to unpredictable robot behavior due to incidents like contact loss or unexpected external forces, which can cause significant harm to humans. To overcome these limitations, this study introduces a multi-task energy-aware impedance controller for kinematically redundant robots. This controller extends the energy-aware impedance control strategy, which ensures the passivity and safety of a single task using a virtual global energy tank, to kinematically redundant robots performing multiple tasks. The proposed controller effectively regulates the power flow of all tasks performed by the robot through a single global energy tank, ensuring the safety and passivity of the tasks. Experimental results in a shared environment, where external forces are simultaneously applied to the end-effector and the third joint of the Franka Emika Panda, showed that the robot's energy and power, as well as the power of all tasks, consistently remained within predefined thresholds. Additionally, when comparing the proposed controllers with controller that do not consider null space projection in the power regulation stage and controller that do not regulate the robot's power, our approach effectively managed the robot's energy and power and the power of all tasks, ensuring passivity and enhanced safety.