Showing papers by "N.H. McClamroch published in 1989"

A singular perturbation approach to modeling and control of manipulators constrained by a stiff environment

Abstract: Mathematical models for robot manipulator dynamics which incorporate the effects of interaction forces between the manipulator end effector and a stiff environment are presented. With appropriate assumptions, the model is transformed into a standard singularly perturbed form expressed in terms of a small parameter which is inversely proportional to the stiffness and the damping of the environment. The model for the slow time scale dynamics, corresponding to the case where the environment is rigid, is shown to be equivalent to the differential-algebraic equations which have been developed previously for mechanical systems with holonomic constraints. the model for the fast time scale dynamics is also derived. A feedback structure based on control of the slow time scale dynamics is proposed and justified. A simple example is presented to illustrate the concepts. >

Position/force control design for constrained mechanical systems: Lyapunov's direct method

Abstract: A design procedure for simultaneous position/force control is developed, using Lyapunov's direct method for mechanical systems with holonomic constraints. Many mechanical systems which interact with their environment require the effects of these constraints to be taken into account in the control design. The force applied by the constraint plays a critical role in constrained motion and is, along with displacements and velocities, to be regulated at specified values. Lyapunov's direct method is used to develop a class of decentralized position/force controllers. The approach avoids coordinate transformation and does not require force feedback. The conditions for gain selection demonstrate the importance of the constraints. An example is used to demonstrate this control design method; closed-loop characteristics are indicated by computer simulations. >