STABILITY PROBLEM FORMULATION OF STRUCTURALLY COMPLIANT ROBOT MANIPULATORS DURING CONTACT TASK EXECUTION - A SINGULAR PERTURBATION APPROACH

Aspects of modelling, stability and control of robotic manipulators wi th structurally compliant links and joints during contact with a stiff work environment are presented in this paper. System models of n join t robotic manipulators are cast into multiple time-scale formulations. Several different models are developed, based on the relative differe nces in magnitude of the scaling parameters associated with the manipu lator link, joint and environment stiffnesses. These stiffnesses, if g reatly different, lead to a four time-scale system with virtually no i nteraction between these subsystems. In these models, as various subsy stem stiffness coefficients become approximately equal, strong interac tion among the subsystems is seen. Utilizing the theory of singularly perturbed dynamic systems, aspects of overall system stability are tou ched on, and possible use of a high speed stabilizing control is consi dered. It is seen from the analysis presented, that depending on the r elative structural stiffness of the link, joint and work environment, is is not always possible to apply a corrective control for certain st ructural compliance effects. An example serves to illustrate some of t he concepts discussed in the paper. It is noted that this paper does n ot provide general stability conclusions, but rather forms a Framework for stability investigation. Copyright (C) 1996 Elsevier Science Ltd