No abstract

Regenerative braking can save energy consumption greatly for electric vehicles. For a series regenerative brake system, it is foundational to make the hydraulic braking torque and braking force decoupled and to provide the same pedal feeling as conventional braking system. In this paper, a high-performance and low-cost solution of series regenerative brake system is designed, which consists of a conventional anti-lock brake system and a motor-driven electromechanical booster (E-booster). Based on the series regenerative brake, a braking force decoupling control scheme without pressure sensor is proposed. First, a dynamic model of vacuum booster is established to calculate the desired brake pedal feeling in real time. Then, a sliding mode observer is used to estimate the load torque of the E-booster so that the expensive pressure sensors are eliminated. Finally, a sliding mode controller is developed to work with a robust threshold–controlled anti-lock brake system hydraulic control unit adjusting the pedal feeling and the wheel cylinder pressure simultaneously. Simulations and experiments were conducted in MATLAB/SIMULINK and on a test bench, respectively. The results show that the tracking ability of wheel cylinder pressure and quality of braking pedal feeling in different conditions are both good, providing a practical method to realize fully series regenerative brake.

Knowledge of the tire-road information is not only very crucial in many active safety applications but also significant for self-driving cars. The tire-road information mainly consists of tire-road friction coefficient and road-tire friction forces. However, precise measurement of tire-road friction coefficient and tire forces requires expensive equipment. Therefore, the monitoring of tire-road information utilizing either accurate models or improved estimation algorithms is essential. Considering easy availability and good economy, this paper proposes a novel adaptive unified monitoring system (AUMS) to simultaneously observe the tire-road friction coefficient and tire forces, i.e., vertical, longitudinal, and lateral tire forces. First, the vertical tire forces can be calculated considering vehicle body roll and load transfer. The longitudinal and lateral tire forces are estimated by an adaptive unified sliding mode observer (AUSMO). Then, the road-tire friction coefficient is observed through the designed mode-switch observer (MSO). The designed MSO contains two modes: when the vehicle is under driving or brake, a slip slope method (SSM) is used, and a recursive least-squares (RLS) identification method is utilized in the SSM; when the vehicle is under steering, a comprehensive friction estimation method is adopted. The performance of the proposed AUMS is verified by both the matlab/simulinkCarSim co-simulation and the real car experiment. The results demonstrate the effectiveness of the proposed AUMS to provide accurate monitoring of tire-road information.

Based on the guaranteed cost theory, this paper proposes a robust controller for the automotive electro-hydraulic coupling system. However, parameter perturbation caused by the model linearization is a critical challenge for the nonlinear electro-hydraulic coupling system. Generally, the electrical brake booster system (E-Booster) can be separated into three parts, a permanent magnet synchronous motor (PMSM), a hydraulic model of the master cylinder, and the transmission mechanism. In this paper, the robust guaranteed cost controller (RGCC) could adjust accurately the pushrod position of the E-Booster and has strong robustness against internal uncertainties, and the linear extended state observer (LESO) was utilized to optimize E-Booster's dynamic performance. Thus, the tracking differentiator (TD) and LESO are used to improve the dynamic precision and reduce the hysteresis effect. The overshoot is suppressed by TD, and the disturbance caused by nonlinear uncertainty is restrained by LESO. Experiment results show that RGCC sacrifices 6% phase lag in the low-frequency domain for a 10% and 40% reduction in first and second-order respectively compared with the proportion integration differentiation (PID). Results demonstrate that RGCC has higher precision and stronger robustness in dynamic behaviour.

Abstract:Unified brake service is a universal service for generating certain brake force to meet the demand deceleration and is essential for an automated driving system. However, it is rather difficult to control the pressure in the wheel cylinders to reach the target deceleration of the automated vehicle, which is the key issue of the active deceleration control system (ADC). This paper proposes a hierarchical control method to actively control vehicle deceleration with active-brake actuators. In the upper hierarchical, the target pressure of wheel cylinders is obtained by dynamic equations of a pure electric vehicle. In the lower hierarchical, the solenoid valve instructions and the pump speed of hydraulic control unit (HCU) are determined to satisfy the desired pressure with the feedback of measured wheel cylinder pressure by pressure sensors. Results of road experiments of a pure electric and automated vehicle indicate that the proposed method realizes the target deceleration accurately and efficiently.