A stable force/position controller for robot manipulators

A force/position controller for robot manipulators in contact with an elasticity compliant surface is presented. The controller consists of proportional-derivative (PD) action on the position loop and proportional-integral (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 the LaSalle invariance set theorem. A modification of the Lyapunov function leads to deriving an exponential stability result.<
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