Abstract
The economy of electrified vehicles can be improved by using the motor to recover the energy released during braking. However, the vehicle’s regenerative braking system (RBS) and anti-lock braking system (ABS) are not compatible, so the energy dissipated during braking cannot be recovered under emergency braking conditions. This paper employs the method of logic threshold control combined with phase plane theory to analyze the relationship between the slip rate and the braking torque during the ABS braking process and to obtain the composition rule of the braking torque required for ABS braking. Based on this rule, a control strategy to coordinate RBS and ABS when triggering ABS is proposed to improve the efficiency of braking energy recovery. Furthermore, a comparative simulation is conducted to analyze the braking performance of electrified vehicle on roads with different adhesion coefficients by adopting the proposed control strategy and the traditional control strategy. The results show that, compared with the traditional coordinated control strategy, the braking energy recovery efficiency of the proposed coordinated control strategy is improved by 23.08%-38.54%, and can effectively shorten the braking distance and braking time, with better braking performance. Therefore, this paper offers a useful theoretical reference to the design of RBS and ABS coordinated control strategies for electrified vehicles.
Highlights
In recent years, electrified vehicles have attracted widespread attention owing to the regenerative braking system that is capable of recovering braking energy [1]–[3]
The braking energy that the motor can recover is very small or it does not participate in braking at all, so the following explanations are made before formulating the coordinated control strategy of regenerative braking system (RBS) and anti-lock braking system (ABS): (1) The SOC of the battery during braking is less than the upper limit charging threshold (i.e. 0.8 in this paper); (2) The braking vehicle speed is greater than the lower limit vehicle speed for braking energy recovery (i.e. 3 m/s in this paper)
In order to enable the vehicle to maintain stability and safety during ABS braking and improve the braking energy recovery efficiency, this paper proposes a coordinated control strategy to ensure that the motor braking torque is maintained within the ABS steady-state braking torque range and that the remaining required braking torque is supplemented by the hydraulic braking system
Summary
In recent years, electrified vehicles have attracted widespread attention owing to the regenerative braking system that is capable of recovering braking energy [1]–[3]. To improve the stability of vehicle braking and energy recovery efficiency, this paper took an electrified vehicle with front and rear dual motors as the research object, and adopted the method of logical threshold control combined with phase plane theory to obtain the composition rule of the braking torque required for ABS braking. On this basis, a coordinated control strategy of RBS and ABS is proposed to reduce the motor braking torque within the ABS steady-state braking torque range for coordinating RBS and ABS when ABS is triggered.
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