Adaptive passivity-based control of a flexible-joint robot manipulator subject to collision

In this paper, passivity-based methods are used to perform tracking control of flexible robot manipulators subject to impact collision. The model taken for colliding system is an n-degree of freedom body moving in the manipulator’s workspace. Impulsive forces generated in the course of impact cause sudden changes in velocity/acceleration of the links of robot and the colliding system. On the other hand, under-actuated systems subject to impact are likely to have instabilities, or poor transient responses, due to excitation of some un-actuated states. The proposed adaptive passivity-based controller not only improves the post-impact transient response of the under-actuated system (e.g. flexible-joint robot), but also needs no force sensor to measure impulse force during the impact phase of robot motion. The main advantage of the proposed controller relative to model-based inverse-dynamic algorithms is its highly robust characteristics in dampening effects of oscillation right after impact collision for an under-actuated system. This can be done through the introduction of an energy-storage function which incorporates the effects of both actuated and un-actuated states of the system.