Sensorless and modeless estimation of external force using time delay estimation: application to impedance control

This paper proposes an external force estimation algorithm that requires neither dynamical models nor force-torque (FIT) sensors. Considering cost reduction, 'indirect estimation' of external force can be preferable to 'direct sensing' of the force. However, the explicit use of robot dynamical models, required by most previous studies on 'indirect estimation' of external force, can be practically unfavorable due to inevitable modeling errors as well as arduous identification of system parameters. As a remedy for this problem, the Time-Delay Estimation (TDE) scheme has been incorporated in this research. TDE efficiently provides an accurate estimate of nonlinear robot dynamics including external force. Using TDE, the external force has been effectively and efficiently estimated without F/T sensors or robot dynamical models. Through application to impedance control of a robot, the practical advantages of the proposed estimation algorithm are demonstrated.