Abstract
The high redundant brake-by-wire system reveals vehicular safety handling ability and rarely emerges in the automotive area at the present time. This paper presents a novel brake-by-wire system, DREHB (Double Redundant Electro-Hydraulic Brake), with extensible fail-safe operations for high-automation autonomous driving vehicles. The DREHB is designed as a decoupled-architecture system containing three-layer cascaded modules, including a hydraulic power provider, a hydraulic flow switcher, and a hydraulic pressure modulator, and each of the modules can share dual redundancy. The operating principles of the DREHB in normal and degraded initiative braking modes are introduced, especially for the consideration of fail-safe and fail-operational functions. The matching and optimization of selected key parameters of the electric boost master cylinder and the linear solenoid valve were conducted using computer-aided batched simulations with a DREHB system modeled in MATLAB/Simulink and AMESim. The prototype of the DREHB was tested in hardware-in-the-loop experiments. The test results of typical braking scenarios verify the feasibility and effectiveness of the DREHB system, and the hydraulic pressure response as 28.0 MPa/s and tracking error within 0.15 MPa and the desirable fail-safe braking ability fully meets the requirements of higher braking safety and efficiency.
Highlights
In the past few decades, the energy crisis and air pollution have forced the automotive industry to turn to the development pathway of electrification [1]
On the basis of the introduction on the development of the brake-by-wire systems, this paper proposes a novel decoupled electro-hydraulic brake system, featured with a double redundant backup with dual hydraulic power sources and hydraulic pressure-regulating units
Likewise, when the DREHB system is in the working mode, as shown in Figure 2b, the EHPA provides the hydraulic supply of the four-wheel cylinder solely, and the linear solenoid valves are responsible for the hydraulic pressure regulation of four-wheel cylinders
Summary
In the past few decades, the energy crisis and air pollution have forced the automotive industry to turn to the development pathway of electrification [1]. The hydraulic boost braking function is executed through the coordinated control of the high-pressure accumulator and the solenoid valves, and the fail-safe backup is guaranteed by the driver as well. The existing brake-by-wire systems mostly suffer from an insufficient braking redundancy design, and high-reliability braking capability for autonomous driving cannot be guaranteed For this reason, termed as a ‘redundancy brake-by-wire system’, the system has to be designed to activate the vehicle’s emergency and consistency brake, even if the brakes are not activated due to electrical or mechanical failures or external shocks. On the basis of the introduction on the development of the brake-by-wire systems, this paper proposes a novel decoupled electro-hydraulic brake system, featured with a double redundant backup with dual hydraulic power sources and hydraulic pressure-regulating units. With multiple complementarities in terms of designed structure, the proposed DREHB can handle the fail-backup of brake functions in multiple failures, thereby ensuring the driving safety of high-level autonomous vehicles.
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