Active disturbance rejection control in Stribeck friction dynamic compensation for high-accuracy servo systems

The servo systems are always difficult to design with high-accuracy due to nonlinear stick-slip at the low velocities and the uncertainties of friction dynamic model. A linear active disturbance rejection control (ADRC) dynamic compensation solution is presented independent of the friction model. To deal with the problem of observing or tracking for unknown discontinuous signals of friction with Stribeck effect, a kind of linear extended state observer (LESO) algorithm is designed. Then a linear control law is proposed to compensate the friction disturbance dynamically. In comparison with proportional-integral-derivative (PID) controller, the simulation results show that the proposed method not only has better accuracy of the discontinuous friction signal tracking, but also ensures better dynamic friction compensation at the low velocities.