Adaptive real-time optimal energy management strategy based on equivalent factors optimization for plug-in hybrid electric vehicle

Regenerative braking is an important technology in improving fuel economy of an electric vehicle (EV). However, additional motor braking will change the dynamic characteristics of the vehicle, leading to braking instability, especially when the anti-lock braking system (ABS) is triggered. In this paper, a novel semi-brake-by-wire system, without the use of a pedal simulator and fail-safe device, is proposed. In order to compensate for the hysteretic characteristics of the designed brake system while ensure braking reliability and fuel economy when the ABS is triggered, a novel switching compensation control strategy using sliding mode control is brought forward. The proposed strategy converts the complex coupling braking process into independent control of hydraulic braking and regenerative braking, through which a balance between braking performance, braking reliability, braking safety and fuel economy is achieved. Simulation results show that the proposed strategy is effective and adaptable in d...

Transient switching control strategy from regenerative braking to anti-lock braking with a semi-brake-by-wire system

This paper introduces a novel approach for dynamically detecting the lowest speed threshold at which regenerative braking is effective in electric vehicles (EVs). The control approach is based on real-time sensing of the motor controller dc link current and disabling regenerative braking when current changes direction while the motor is operating as a generator. Various factors influencing the regenerative braking capability of EVs at low speed are discussed, and the simulation studies are carried out to illustrate the effect of each factor on the displacement of the low-speed threshold. Based on the results obtained from the simulation studies, a dynamic low-speed cutoff point (LSCP) detection method is proposed. This method requires no hardware modification to the vehicle braking architecture and can be implemented solely by modifying the brake controller. The proposed method is tested on an experimental EV test platform for a predetermined drive cycle. It is shown that in comparison to considering a constant low-speed threshold during braking, the amount of energy recaptured through the regenerative braking process can be improved by taking advantage of the proposed method.

Maximizing Regenerative Braking Energy Recovery of Electric Vehicles Through Dynamic Low-Speed Cutoff Point Detection

AMT downshifting strategy design of HEV during regenerative braking process for energy conservation

The development of a novel electrohydraulic brake system named REHB is presented in this paper. Neither high-pressure accumulator nor linear valves are adopted to reduce the system cost, the difficulty of manufacturing, assembling, and the risk of leakage. Stroke simulators are implemented to elevate the quality of pedal feel. The braking force blending control strategy is well designed to coordinate regenerative and friction brake force, which has ensured maximized regenerative brake force. In the aspect of underlying control, current amplitude modulation control is adopted to improve the accuracy of hydraulic pressure modulation and eliminate vibration noise. High fidelity models of vehicle and brake system are built based on MATLAB-AMESim co-simulation platform. Three demand levels of one-step-brake scenarios are simulated. Simulation results show the reasonability of proposed hydraulic structure and designed control strategy. A regenerative brake test bench is set up based on a prototype of the developed system. Three identical one-step-brake experiments are conducted on the test bench. According to the bench test results, the blending of regenerative and friction brake force tracks driver brake demand adequately well. Regenerative efficiencies are calculated as 46.32%, 43.93%, and 31.88%, respectively, in three bench tests. Compared with the previous generation, no obvious valve buzzing noise is observed, and jerks are whittled significantly. REHB has provided a brake-by-wire solution of safety, high energy recuperation efficiency with low cost, and uncompromising performance.

A Novel Regenerative Electrohydraulic Brake System: Development and Hardware-in-Loop Tests

In this paper, a rear-wheel-driven series hybrid electric vehicle which has a mechanically operated friction brake system is studied. A new cooperative control of regenerative braking and friction braking called ‘combined braking’ is proposed for this vehicle configuration. A mechanism to adjust the proportions of regenerative braking and friction braking was proposed in this paper. Further, the braking force distribution between the front wheels and the rear wheels was analysed to ensure stable braking. The brake system characteristics were considered to ensure that the driver’s feel remains the same in the new proposed combined braking strategy. The simulation results under urban driving and across the Modified Indian Driving Cycle and vehicle road testing results show that the proposed combined braking can regenerate more than twice the braking energy of conventional parallel braking. Also, with combined braking, the braking force distribution between the front wheels and the rear wheels is closer to t...

Cooperative control of regenerative braking and friction braking for a hybrid electric vehicle

Analysis of Handling Performance of Hybrid Electric Vehicles

In electric and hybrid vehicles, regenerative braking is applied only at the driven wheels by the electric drive, whereas the non-driven wheels are not subjected to brake force during the pure rege...

Brake force sharing to improve lateral stability while regenerative braking in a turn

Hybrid Electric Vehicles (HEVs) are emerging as alternatives to the traditional Internal Combustion Engine (ICE) driven vehicles to meet stringent emission norms, environmental and energy concerns. A commonly seen HEV configuration is the Parallel Hybrid Electric Vehicle (PHEV), in which both the ICE and electric motor are mechanically coupled to drive the wheels. Depending on the level of hybridization, which is defined as the ratio of motor power to the total power of the drive train, the PHEV is further classified into Mild, Full, and Plug-in hybrid. Regenerative braking is a key feature in HEVs that improves the fuel economy. The amount of energy regenerated depends on the motor, battery specifications and the control strategy. The design and analysis of the drive system and the control strategy for a typical Indian vehicle is the key focus of this paper. This involves the determination of engine power, motor power, gear ratios of transmission and battery specification to meet the drive requirements such as acceleration, maximum speed and gradeability. Also, the control strategies for both traction and braking have been discussed in this paper. Further, by considering the Modified Indian Drive Cycle and a real time speed plot, numerical simulation has been performed to evaluate the benefits in terms of fuel economy, compared to the conventional ICE driven vehicle. The simulation results shows that, in a full hybrid configuration with regenerative braking, the vehicle fuel economy can be improved by up to 32% in Indian driving conditions compared to the conventional ICE drive. The fuel economy can be improved further in hybrid powertrain with the engine turned off while braking instead of operating at idle speed.

C. S. Nanda Kumar

Papers

Cooperative control of regenerative braking and friction braking for a hybrid electric vehicle

Analysis of Handling Performance of Hybrid Electric Vehicles

Brake force sharing to improve lateral stability while regenerative braking in a turn

Design and analysis of a parallel hybrid electric vehicle for Indian conditions

Analysis of Vehicle Lateral Response During Regenerative Braking in a Turn