Sensorless Nonsmooth H_∞-Tracking Synthesis of Servosystems with Backlash and Coulomb Friction

The nonsmooth phenomena such as backlash and Coulomb friction, often occurring in mechanical systems, typically produce undesired inaccuracies, oscillations and instability thereby degrading the system performance. In this paper, the H_∞ synthesis is developed for a class of nonsmooth systems and it is then applied to an industrial emulator where the described phenomena are present, and an elastic band is included in the transmission motor-load, and only motor position measurements are feasible. The effectiveness of the proposed method is supported by experimental results.