Hybrid force/velocity control for physical human-robot collaboration tasks

During human-robot collaboration tasks, we may physically touch the robot at a generic location and engage an intentional exchange of forces while realizing coordinated motion of the common contact point. In order to control the relative motion and the exchanged contact forces, the latter need to be estimated without using any local force sensing device. Building upon our recent works, we generalize the classical hybrid force/velocity control design to this situation, handling complementary quantities along the directions of a suitable contact task frame in a dynamically decoupled way. The contact force is estimated online using our residual method together with an external sensor to localize the contact point, and the time-varying contact task frame is obtained analytically from this estimate. Experimental results are presented for a KUKA LWR4 robot using a Kinect sensor.