ABSTRACT
Now, in a sequel to what we have been considering so far, we will deal with compensation of kinetic friction in the controlled motion systems. If we do so, we should be aware that this application relevant topic has attracted attention in the broad academic and practical engineering communities for already more than three decades. Still, kinetic friction, as one of the most cumbersome and less straightforward dynamic disturbance effects, requires continuous investigation and refinement of the appropriate compensation methods. We will start with classical linear feedback controllers which include an integral control action and can, this way, guarantee for a complete cancelation of the Coulomb and viscous friction during the steady-state motion only. Then, we will switch from a problem of tracking the motion trajectory to a more challenging, with respect to the friction compensation, task of the set-point position control. In such control problem, the nonlinear friction with stiction must be overcome, while one needs to ensure the controlled system converges sufficiently fast to the set reference value. Two rather principally simple compensation strategies will be discussed here, one based on the output relay feedback, and another based on the observation of dynamic friction state and its matched feed-forwarding.
