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In this paper, hydraulic driving system parameters of a parallel hydraulic hybrid vehicle are designed based on the regenerative braking requirement. Torque, speed and power demands during typical driving cycles are analyzed. The braking control strategy is designed considering both the braking safety and braking energy recovery efficiency. The hydraulic braking torque is determined by the braking control strategy. The proportional relationship of hydraulic pump/ motor output torque and its working pressure is considered. Through simulation with typical city driving cycles, most braking energy can be recovered by the proposed hydraulic driving system and braking control strategy.

Driven by stricter mandatory regulations on fuel economy improvement and emissions reduction, market penetration of electrified vehicles will increase in the next ten years. Within this growth, mild hybrid vehicles will become a leading sector. The high cost of hybrid electric vehicles (HEV) has somewhat limited their widespread adoption, especially in developing countries. Conversely, it is these countries that would benefit most from the environmental benefits of HEV technology. Compared to a full hybrid, plug-in hybrid, or electric vehicle, a mild hybrid system stands out due to its maximum benefit/cost ratio. As part of our ongoing project to develop a mild hybrid system for developing markets, we have previously investigated improvements in drive performance and efficiency using optimal gearshift strategies, as well as the incorporation of high power density supercapacitors.

Regenerative braking has been widely accepted as a feasible option to extend the mileage of electric vehicles (EVs) by recapturing the vehicle’s kinetic energy instead of dissipating it as heat during braking. The regenerative braking force provided by a generator is applied to the wheels in an entirely different manner compared to the traditional hydraulic-friction brake system. Drag torque and efficiency loss may be generated by transmitting the braking force from the motor, axles, differential and, specifically in this paper, a two-speed dual clutch transmission (DCT) to wheels. Additionally, motors in most battery EVs (BEVs) and hybrid electric vehicle (HEVs) are only connected to front or rear axle. Consequently, conventional hydraulic brake system is still necessary, but dynamic and supplement to motor brake, to meet particular brake requirement and keep vehicle stable and steerable during braking.

Electric vehicles (EV) are considered a practical alternative to conventional and hybrid electric passenger vehicles, with higher overall powertrain efficiencies by omitting the internal combustion engine. As a consequence of lower energy density in the battery energy storage as compared to fossil fuels powered vehicles, EVs have limited driving range, leading to a range phobia and limited consumer acceptance. Particularly for larger luxury EVs, electric motors with a single reduction gear typically do not achieve the diverse range of function needs that are present in multi-speed conventional vehicles, most notably acceleration performance and top speed requirements. Subsequently, multi-speed EV powertrains have been suggested for these applications. Through the utilization of multiple gear ratios a more diverse range of functional needs can be realized without increasing the practical size of the electric motor.

Regenerative braking energy recovery bears significance in extending the driving mileage of electric vehicles (EVs) while fulfilling real-time braking demands. Braking energy strategy plays a significant role in improving the regenerative braking performance and ensuring braking safety. This paper presents a regenerative braking energy recovery strategy for an example EV with a two-speed Dual Clutch Transmission (DCT). The two-speed DCT, with simple structure, can effectively extend the active vehicle speed-range for regenerative braking. Meanwhile, a shifting strategy is proposed for the DCT, working with the presented braking energy recovery strategy, to optimize the brake force distribution between front and rear wheels, motor and friction brake force. The EVs' model with the proposed regenerative braking strategy and the optimal shifting schedule was established and implemented in Matlab/Simulink.

This paper mainly studies the power losses in a refined two-speed dual clutch transmission which is equipped in a electric vehicle test rig. Both numerical and experimental investigations are carried out. After theoretical analysis of the power losses original sources, the developed model is implemented into simulation code to predict the power losses. In order to validate the effectiveness of the proposed model, results from experimental test are used to compare the difference the simulation and test. The simulation and test result agree well with each other. Results show that the power losses in the two-speed are mainly generated by multi-plate wet clutch drag torque and gear churning loss.

This paper proposes an approach to optimize the economy performance of a two-speed electric vehicle (EV) by combining gear shifting schedule design and gear ratios selection. Mathematic models for the two-speed EV subsystems are developed, including those of the battery module, electric machine, the driver, transmission and vehicle. Then a procedure for obtaining the optimal gear ratio pairs and corresponding shift schedule for the two-speed EV is presented in detail. The optimized EV powertrain parameters can not only ensure that basic requirements in dynamic performance are achieved, but realize the optimal economic performance of the EV as well. In order to investigate the effectiveness of the proposed method for EV design, simulations based on the developed powertrain model is conducted using different test driving cycles, including NEDC and constant speed. Results of these simulations validate the effectiveness of the proposed optimization method.

Method to improve the efficiency and the design of more efficient pure electric vehicle (PEV) system is a research hotspot for the automobile industry worldwide. Traditionally, PEV powertrains are dominated almost exclusively by single reducer structures in both concept and commercially available PEVs. This paper presents a novel two motor two speed pure electric power-train structure to study alternate methods for improving the operating efficiency of a typical PEV. This idea is derived from conventional power splitting transmissions to achieve motor efficiency optimization and ultimately lead to running range improvement. Through parameter matching and simulation, results demonstrated that the proposed two motor two speed PEV can realize better vehicle performance than single reducer PEV system; furthermore it can behave even better than a similar single motor two speed system.