Variable Admittance Control in pHRI using EMG-based Arm Muscles Co-Activation

In this paper, the co-activation level of the arm muscles is used as an indication of the end-point stiffness for improving human-robot cooperation. A variable admittance controller is proposed to adjust the virtual damping in real time by measuring the operator's muscle activation by means of surface EMG. An experimental user study is conducted that simulates both high accuracy and fast transition movements, involving human-robot interaction with a 7-DOF LWR serial manipulator. The proposed method is compared to constant admittance and is evaluated in terms of movement accuracy, execution time, and the operator's energy consumption. The results demonstrate that there is a significant reduction of the operator's effort and an improvement of the cooperative motion accuracy.