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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.

The purpose of this paper is to present a concept of Hydro-Pneumatic Interconnected Suspension (HPIS) and investigate the unique property of the zero warp suspension stiffness. Due to the decoupling of warp mode from other modes, the road holding ability of the vehicle is maximized meanwhile the roll stability and ride comfort can be tuned independently and optimally without compromise. Ride comfort can be improved with reduced bounce stiffness and the progressive air spring rate can reduce the requirement of suspension deflection space. The roll stability can also be improved by increased roll stiffness. Vehicle suspension system modelling and modal analysis are carried out and compared with conventional suspension. The frequency response of tyres' dynamic load reveals that the proposed zero-warp-stiffness suspension enables the free articulation of front and rear axles at low frequency.

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.