Adaptive control of manipulator interaction with environment: theory and experiments

The role of adaptive controllers for controlling the force as well as the contact behavior of manipulators is examined. It is shown how the standard model-reference adaptive control (MRAC) scheme can be employed to explicitly control the force of contact for a linear system despite unknown stiffness. This is extended to the impedance control of the end-effector in contact with a similar environment. Also analyzed is an interesting case where the system achieves explicit force control as well as the desired impedance through adaptive control within the MRAC framework. It is shown that similar results hold for an end-effector with nonlinear dynamics, provided a specially-designed robust adaptive controller is used. Both simulations and experiments are performed to validate theoretical conclusions