Despite the long-term benefit of battery electric vehicles (BEVs) to customers and environment, the initial cost and limited driving range present significant barriers for wide spread commercialization. The integration of multi-speed transmissions to BEVs' powertrain systems in place of fixed ratio reduction transmissions is considered as a feasible method to improve powertrain efficiency and extend limited driving range for a fixed battery size. The aim of this paper is to enable the researchers or BEV manufacturers, especially for transmission systems, to estimate whether their products are worthwhile for the customer in terms of the price/performance relationship of others' design solutions. To do so a generic battery electric vehicle is modelled in Matlab/Simulink® to predict motor efficiency and energy consumption for single reduction, two speeds Dual Clutch Transmission (DCT) and simplified Continuous Variable Transmission (CVT) equipped battery electric vehicles. A credible conclusion is gained, through experimental validation of single speed and two speeds DCT scenarios and reasonable assumptions to support the CVT scenario, that both two speeds DCT and simplified CVT improve the overall powertrain efficiency, save battery energy and reduce customer costs. However, each of the configurations has unique cost and energy consumption related trade-offs.

To achieve the best possible responses during shifting in dual clutch transmissions it is commonplace to integrate clutch and engine control, while the clutch is used to match speeds between the engine and wheels via reduction gears, poor engine control can lead to extended engagement times and rough/harsh shift transients. This paper proposes a method for combined speed and torque control of vehicle powertrains with dual clutch transmissions for both the engine and clutches. The vehicle powertrain is modelled as a simple four degree of freedom system with reduction gears and two clutches. Including a detailed clutch hydraulic model, comprising of the direct acting solenoids and clutch piston with the hydraulic fluid modelled as a compressible fluid. Powertrain control is realised through control of clutch solenoids and manipulation of the engine throttle input. Sensitivity study of clutch performance evaluating inaccurate torque estimation demonstrated variance in the response of the hydraulic system, with an indicative simulation of poor estimation resulting in increased powertrain vibration during and after shifting. Simulations are conducted to demonstrate the capacity for this method of engine and clutch control to further reduce shift transients developed in dual clutch transmission powertrains. The obtained results also show that the adoption of torque based control techniques for both the clutch and engine, which makes use of the estimated target clutch torque, significantly improves the powertrain response as a result of reduction in the lockup discontinuities.

The purpose of this paper is to demonstrate the application of torque based powertrain control for multi-speed power shifting capable electric vehicles. To achieve this goal it presents a detailed simulation and experimental investigation of the transient behavior of a dual clutch transmission equipped multi-speed electric vehicle powertrain during a combination of power-on and power-off up and down shifts. A system model is developed that integrates a DC equivalent motor model, hydraulic control system and multi-body powertrain model for virtual prototyping of the integral system.Control strategies for power-on and power-off up and down shifts are then presented, and detailed simulations of the transient behavior of the powertrain system model are conducted for each of the four shift cases. These results are then experimentally verified on a powertrain test rig, purpose built for the study of transmission control. Shift duration and vehicle jerk are used as metrics to demonstrate that the presented strategies are effective for shift control in electric vehicles.

The application of auxetic composites in practice often relies on a compromise between properties as auxetics are mostly too porous (not dense enough or not stiff enough) to bear structural loads. Hence, the focus of this paper is topological design optimization of new functionally graded cellular composites with auxetics using a level set method. Firstly, a new hierarchical multi-scale formulation is developed to account for both the auxetic behaviour of the microstructure and the stiffness of the macrostructure. The composite, comprising multiple layers of periodic microstructures, is tailored to have functionally graded properties for stiffness and auxetic behaviours, subject to volumetric gradient constraints. Secondly, the microstructures underpinning composite layers are topologically designed under the consideration of boundary and loading conditions of the macrostructure. Finally, a level set method is applied to evolve the shape and topology of the microstructure for each layer, with the numerical homogenization method to evaluate the effective properties of the microstructures. Several numerical examples are used to demonstrate the effectiveness of the proposed method. It can be seen that such composites systematically gear together the features of the functionally graded materials, cellular composites, and metamaterials towards a new kind of man-made composites.

Pure electric vehicles (PEVs) provide a unique problem in powertrain design through the meeting of performance specifications whilst maximising driving range. The consideration of single speed and multispeed transmissions for electric vehicles provides two strategies for achieving desired range and performance specifications. Through the implementation of system level vehicle models, design analysis, and optimisation, this paper analyses the application of both single speed and two-speed transmission applications to electric vehicles. Initially, transmission ratios are designed based on grade and top speed requirements, and impact on vehicle traction curve is evaluated. Then performance studies are conducted for different transmission ratios using both single speed and two-speed powertrain configurations to provide a comparative assessment of the vehicles. Finally, multivariable optimisation in the form of genetic algorithms is employed to determine an optimal gear ratio selection for single speed and two-speed PEVs. Results demonstrate that the two-speed transmission is capable of achieving better results for performance requirements over a single speed transmission, including vehicle acceleration and grade climbing. However, the lower powertrain efficiency reduces the simulated range results.