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.
Keywords
- Static friction
- Solution uniqueness
- Parametric sensitivity
- Redundant constraints