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Integrated Regenerative Braking System and Anti-lock Braking System for Hybrid Electric Vehicles & Battery Electric Vehicles
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
Regenerative braking in hybrid electric vehicles is a critical feature to achieve the maximum fuel economy benefit of hybridization. In order to maximize energy recuperation, it is desired to enable regenerative braking during an Anti-lock Braking System (ABS) event. For certain driveline configurations with a single electric motor connected to the axle shaft through an open differential, it has been observed that the regenerative braking torque can increase the wheel slip during the ABS operation, and significantly impact vehicle dynamics. This negative effect introduced by regen braking during ABS control may also lead to hardware failures, such as breaking a drive shaft. This paper describes development of an integrated regenerative braking and ABS control for hybrid and electric drive vehicles, referred to as RBS-ABS Event Control. This control is intended for drivelines containing a single electric motor connected to the axle shaft through an open differential. The design objectives are to recuperate the maximum amount of kinetic energy during an ABS event, and to provide no degraded anti-lock control behavior as seen in vehicles with regen braking disabled. This paper first presents a detailed analysis that shows regenerative braking torque can increase the wheel slip during ABS operation with existing regenerative braking control methods. Then, the RBS-ABS Event Control design is described that delivers the following characteristics: (1) ABS has control over the regenerative braking torque; (2) maintaining the same vehicle stopping distance in comparison with ABS with friction braking control only; (3) maintaining the required wheel slip for system stability, and (4) providing optimal and robust control performance during vehicle braking. Finally, simulation tests are provided to illustrate RBS-ABS Event Control as an effective solution to satisfy desired wheel slip with the same level of stop distance in comparison with that of ABS control only while performing energy recuperation.