Abstract: Non-linear friction force is one ofthe most important factors which affects the position tracking accuracy of the electric brake booster(EBB) system. Aiming at the discontinuity of the standard Pol-Ind model in the friction state, asimilar Pol-Ind model(SPol-Ind) with continuous and smooth transition of the friction state is proposed. The nonlinear friction characteristics of the EBB system based on the SPol-Ind model are studied. In order to eliminate the influence of disturbance on control precision, a feedforward compensation control strategy including speed compensation, inertia compensation and SPol-Ind model friction compensation is put forward. Separately, take thesine signal and the triangle wave signal as the inputsof the EBB system, the position tracking and the speed tracking control are realized. Compared with conventional PID control, the position tracking errors of both sinusoidal and triangular waveform signals are significantly reduced and the rise time of speed tracking is also significantly shortened, demonstrating that the feedforward compensated control system has higher position tracking accuracy and faster response than conventional PID control. The “brake-pressure hold-un-brake” process, the position tracking accuracy, and the responsiveness of the EBB system based on feedforward compensation control are analyzed on a Hardware-in-the-loop(HiL) test rig. The experiment results are shown that the maximum values of position tracking error and speed rise time are about 0.18 mm and 0.028 s, which are consistent with the simulation results and verify the accuracy of the control strategy of the EBB system under feedforward compensation controlmethod.

Key words: electric brake assist system, SPol-Ind friction model, feedforward compensation control, position tracking, speed tracking