Contact force estimation for robotic assembly using motor torques

For tasks in robotic assembly, a basic requirement is the capability of the robotic system to detect contacts with the environment. While this information can readily be obtained from dedicated force-torque sensors, it might either be technically difficult to mount such sensors or too expensive to do so. In this paper, an alternative approach is presented which reconstructs the external forces and torques based on signals that can be obtained without a force sensor, namely motor currents/torques and joint angles. After an automatic offline calibration of the algorithm, the method allows for a lean online implementation. Apart from the theoretical development of the method, its applicability to contact force estimation is demonstrated by measurement results obtained from an ABB Dual-Arm Concept Robot.