Disturbance-rejection pressure control for integrated brake system based on improved non-singular fast terminal sliding mode

Abstract

Integrated brake system (IBS) is a critical component of intelligent electric vehicle electronics. However, the pressure control of IBS is usually affected by lumped disturbance such as friction uncertainties, time-varying hydraulic characteristics and unmodeled dynamics, which present significant challenges to the pressure tracking. In order to achieve high-precision, fast-response, and robust pressure tracking performance, this article proposes a disturbance-rejection pressure control strategy. First, to improve the response rate, a non-singular fast terminal sliding mode control (NFTSMC) with finite-time convergence is applied in the basic pressure regulator. Subsequently, a super-twisting algorithm is used to reduce the control chattering in NFTSMC and enhance pressure tracking accuracy. On this basis, we design a finite-time extended state observer to estimate the lumped disturbance, which is then integrated into the NFTSMC to maintain the robustness with small control gains. This integration also reconciles the contradiction between control chattering and robustness in the NFTSMC. The finite-time convergence of the proposed strategy is rigorously validated during both the reaching and sliding phases of sliding mode control. Finally, hardware-in-the-loop experiments are performed. The experimental results demonstrate that compared to the baseline, the proposed strategy achieves at least a 28% improvement in pressure-tracking root mean square error and maximum error.