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Sorniotti A.,University of Surrey | Boscolo M.,University of Surrey | Turner A.,Vocis Driveline Controls | Cavallino C.,Oerlikon Graziano Automotive
2010 IEEE Vehicle Power and Propulsion Conference, VPPC 2010 | Year: 2010

This paper deals with the advantages of a multi-speed transmission system for an electric axle, in comparison with a single-speed layout. The selection of the gear ratios for the multispeed application is described in detail for a case study vehicle, for two different electric motor units. © Copyright 2011 IEEE - All Rights Reserved. Source


Sorniotti A.,University of Surrey | Pilone G.,University of Surrey | Viotto F.,Oerlikon Graziano Drive Systems | Bertolotto S.,Oerlikon Graziano Drive Systems | And 3 more authors.
SAE International Journal of Engines | Year: 2011

This article deals with a novel 2-speed transmission system specifically designed for electric axle applications. The design of this transmission permits seamless gearshifts and is characterized by a simple mechanical layout. The equations governing the overall system dynamics are presented in the paper. The principles of the control system for the seamless gearshifts achievable by the novel transmission prototype - currently under experimental testing at the University of Surrey and on a prototype vehicle - are analytically demonstrated and detailed through advanced simulation tools. The simulation results and sensitivity analyses for the main parameters affecting the overall system dynamics are presented and discussed. © 2011 SAE International. Source


Sorniotti A.,University of Surrey | Subramanyan S.,University of Surrey | Turner A.,Vocis Driveline Controls
SAE International Journal of Engines | Year: 2011

The paper describes the advantages due to the adoption of multi-speed transmission systems within fully electric vehicles. In particular, the article compares a conventional single-speed transmission layout, a 2-speed layout based on a novel gearbox architecture capable of seamless gearshifts, and a Continuously Variable Transmission layout. The selection of the optimal gear ratios for the 2-speed system has been based on an optimization procedure, taking into account the efficiency characteristics of the components of the whole vehicle powertrain. The control system for the Continuously Variable Transmission system has been designed with the aim of maximizing the efficiency of the operating points of the electric motor. The results show that there is a significant advantage in adopting a 2-speed transmission system over the single-speed layout, and, despite a reduction in motor losses, the typically lower efficiency characteristics of Continuously Variable Transmissions do not result in lower energy consumption for the four case study vehicles. © 2011 SAE International. Source


Holdstock T.,University of Surrey | Sorniotti A.,University of Surrey | Everitt M.,Vocis Driveline Controls | Fracchia M.,Vocis Driveline Controls | And 2 more authors.
2012 IEEE Vehicle Power and Propulsion Conference, VPPC 2012 | Year: 2012

The electric vehicle is becoming increasingly prevalent as a viable option to replace hydrocarbon fuelled vehicles, and as such the development of high efficiency fully electric drivetrains is a particularly relevant research topic. The drivetrain topology is one of the main focuses of research on fully electric drivetrains, because of the variety of available options. For example, the adoption of multiple-speed mechanical transmissions can improve both the performance and energy consumption when compared to a single-speed transmission. A four-speed, dual motor drivetrain design is presented in this article which works on the principle of two double-speed transmissions, each driven by a separate motor linked through a sole secondary shaft. This drivetrain architecture provides increased flexibility of the electric motor operating points, theoretically being beneficial to the overall efficiency of the system for any driving condition. This paper presents the design of the transmission, its governing equations and the method adopted to optimize the state selection map and electric motor torque distribution. A backward-facing energy consumption model is used to compare the results of the four-speed transmission with those of single- and double-speed transmissions for four case study vehicles. © 2012 IEEE. Source


Sorniotti A.,University of Surrey | Holdstock T.,University of Surrey | Pilone G.L.,University of Surrey | Viotto F.,Oerlikon Graziano SpA | And 5 more authors.
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering | Year: 2012

Electric vehicle powertrains traditionally consist of a central electric motor drive, a single-speed transmission and a differential. This electric powertrain layout, for use in either fully electric vehicles or through-the-road parallel hybrid electric vehicles, will be extensively adopted in the next few years, despite the ongoing research in electric vehicles with individually controlled motors. However, current research suggests that electric powertrains with a central electric motor drive can still be widely improved. For example, the installation of a seamless multiple-speed transmission instead of a single-speed transmission can cause an increase in the vehicle performance, together with an enhancement in the overall efficiency of the electric powertrain. These novel transmission systems for electric powertrains require a specific design, in order to be efficient, compact, easy and robust to control and cheap to manufacture. This article presents the mechanical layout and the control system of a novel two-speed transmission system designed by the present authors, with particular focus on the achievement of optimal gearshift dynamics. The torque characteristics of typical electric motor drives require a different actuation of the seamless gearshifts, in comparison with the equivalent operation for a dual-clutch transmission within a powertrain driven by an internal combustion engine. © 2012 IMechE. Source

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