Adaptive control for frictional robot contact tasks on uncertain surface slopes

In robot constrained motion problems with frictional contacts, uncertainties on the contacted surface slope distort control targets and affect the control system performance. The surface normal direction cosines are in this case uncertain parameters that are involved in both the control law and the control targets. This work proposes an adaptive controller that achieves the desired goal given a persistently excited tip velocity magnitude on the surface by achieving the convergence of the estimated direction parameters to their actual values. The controller requires measurements of total force and joint variables. A simulation example for a 6 d.o.f. robot is used to illustrate the theoretical results.