Robust tracking control of servo systems with backlash: Nonsmooth ℋ∞ control vs. linear ℋ∞ control

Backlash and Coulomb friction occurring in systems with mechanical transmissions produce undesired inaccuracies, oscillations, and instability thereby degrading the system performance. In this paper, we made a comparative analysis of a nonsmooth ℋ_∞ controller [1] vs. a linear ℋ_∞ controller applied to a two-mass drive system with flexible shaft including backlash and Coulomb friction using measurements of the motor. The numerical results show the effectiveness of the nonsmooth ℋ_∞ synthesis, whereas the linear ℋ_∞-controller does not attenuate the undesirable oscillations in the control signals and the plant outputs.