Modeling of Static Friction in Closed-Loop Kinematic Chains with Multiple Degrees of Freedom - A Study of Uniqueness and Parametric Sensitivity Problems

摘要

Problems with uniqueness and high parametric sensitivity of solution of equations of motion, encountered in the static friction regime, are addressed. Friction in joints of a multiple degree of freedom closed-loop kinematic chains is discussed. Two different models of friction are studied: the discontinuous Coulomb model with stiction regime represented in terms of additional constraints and the approximate Coulomb model, smoothed in the vicinity of zero relative velocity. Origins of non-uniqueness and high sensitivity are investigated; the questionable credibility of the stiction regime simulation results is pointed out. Two examples are provided to illustrate the discussed issues.