Force/position regulation of compliant robot manipulators

Stable force/position regulation of robot manipulators in contact with an elastically compliant surface is discussed in this work. The controller consists of a PD action on the position loop, a PI action on the force loop, together with gravity compensation and desired contact force feedforward. Asymptotic stability of the system in the neighborhood of the equilibrium state is proven via the classical Lyapunov method with LaSalle invariant set theorem. A modification of the Lyapunov function leads to deriving an exponential stability result. Numerical case studies are developed for an industrial manipulator.