Adaptive passive velocity field control

Passive velocity field control (PVFC) was previously developed for mechanical systems which have strong coordination and must interact with the physical environment. Applications include teleoperated manipulators, contouring in machining and smart exercise machines. The methodology encodes tasks using time invariant desired velocity fields instead of the more traditional method of timed trajectories and guarantees that the closed loop system behave passively with environment power as the supply rate. By maintaining the passivity property of the closed loop system, stability and robustness will be enhanced, especially when interacting with uncertain environments. The present paper extends PVFC to situations where the inertia parameters of the mechanical system are unknown. A direct adaptive control scheme is proposed which preserves the passivity of the closed loop system and ensures that the asymptotic convergence of the velocity to the direction of desired velocity field.