Variable Gain Robust Pressure Tracking Control for Integrated Brake-by-Wire System Under Time-Varying Hydraulic Time Delay

Brake-by-wire (BBW) technology is pivotal in chassis-by-wire systems, as it governs the safety and stability of autonomous vehicles. Currently, the most advanced BBW technology is the one-box electro-hydraulic breaking (EHB) system. However, the inherent time delay associated with hydraulic systems poses significant challenges, leading to inaccurate or unstable pressure control in one-box EHB systems, which hinders their implementation. To address this issue, we propose a novel integrated BBW system (IBS) capable of achieving pedal decoupling and independent pressure control for four-wheel cylinders. Our approach mitigates the time-varying hydraulic time-delay problems by employing a time-dependent variable gain robust pressure tracking control strategy. We utilize innovative clustering methods to determine hydraulic time-delay boundaries and implement a robust classifier for real-time identification of these boundaries. The results of this identification are then utilized to optimize the gain of the robust pressure tracking controller, accommodating different time delays to reduce the conservatism associated with minor delays while ensuring control performance during significant delays. Ultimately, simulations and experiments validate that this strategy enhances the pressure control performance of the IBS under hydraulic time delays, thereby improving the chassis safety and stability of autonomous vehicles.