Real-Time Estimation of Sensorless Planar Robot Contact Information

The real-time estimation of sensorless planar robot contact information is a very important but also difficult subject in human-robot interaction. This paper proposes a method for the real-time estimation of contact location and contact force along a planar joint robot manipulator without using external sensory systems. A momentum-based method is used to estimate external joint torques due to the contact force and to determine a minimum contact range firstly. A nonlinear constrained optimization algorithmis presented to search the contact point. The contact force is calculated by dynamics. The searching space determined by the momentum-based approach is limited within the length range of the contact arm, so the solution speed of the optimization algorithm is high. The proposed method of combining observation algorithm and optimization algorithm transforms a complex detection problem of the any contact point on the robot body into a simple one-dimensional optimization solution with simple bound. The effectiveness of the proposed approach is validated through simulations and experimental results for the planar robot manipulator.