ABSTRACT
This chapter describes the system components and operation including very simple mathematical models of the system. The seven-parameter friction model captures the four detailed friction phenomena, as well as coulomb, viscous, and static friction. The model has the advantage that the friction phenomena are explicitly represented with physically motivated model parameters. In general, mechanisms in which the normal force in sliding contacts varies during motion show position-dependent friction. The position-dependent friction can be measured by observing the breakaway friction, the level of force required to initiate motion, throughout the range of motion of the mechanism. Friction compensation techniques are broken down into three categories: problem avoidance, nonmodel-based compensation techniques, and model-based compensation techniques. The division of control-based compensation techniques into model-based and nonmodel-based reflects the challenge associated with developing an accurate friction model. The most common hardware modifications to reduce frictional disturbances relate to increasing stiffness or reducing mass.
