Title: Power-on downshift analysis of a seamless two-speed transmission in electric vehicles

Authors: Yang Tian; Boyu Tong; Shilei Zhou; Xiaoyu Ji; Xiaorun Tian; Yahui Zhang; Xun Shen; Guilin Wen

Addresses: School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066004, China; Hebei Innovation Center for Equipment Lightweight Design and Manufacturing Qinhuangdao, Hebei 066004, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao, 066004, China; Hebei Innovation Center for Equipment Lightweight Design and Manufacturing Qinhuangdao, Hebei 066004, China ' Faculty of Engineering and Information Technology, University of Technology Sydney, Sydney, NSW 2007, Australia ' School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China; Hebei Innovation Center for Equipment Lightweight Design and Manufacturing, Qinhuangdao, Hebei 066004, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China; Hebei Innovation Center for Equipment Lightweight Design and Manufacturing, Qinhuangdao, Hebei 066004, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China; Hebei Innovation Center for Equipment Lightweight Design and Manufacturing, Qinhuangdao, Hebei 066004, China ' Department of Systems and Control Engineering, Tokyo Institute of Technology, Yanshan University, Qinhuangdao, Hebei 066004, China ' School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China; Hebei Innovation Center for Equipment Lightweight Design and Manufacturing, Qinhuangdao, Hebei 066004, China

Abstract: Electric vehicles (EVs) have many advantages over internal combustion engine vehicles (ICEs) and have caught the interest of academics and industry together. The two-speed transmission of electric vehicles improves the overall power and expands the mileage of EVs. In this paper, the power-on downshifting tactics of a seamless two-speed transmission are studied. The seamless two-speed transmission is controlled by a one-way clutch and two brakes for shifting gears. Three control strategies are proposed to achieve a smooth downshifting process. Firstly, the mathematical model of the two-speed transmission for electric vehicles is constructed. Then, three downshift strategies are analysed based on a simplified mathematical model. In this study, the difference between vehicle jerk and friction work in different downshifting strategies is explored by keeping the gearshift time unchanged. After analysing the simulation results, the advantages and disadvantages of different gear downshift strategies are summarised.

Keywords: electric vehicles; two-speed transmission; seamless transmission; power-on gearshift; three downshift strategies; downshift simulations; vehicle jerk; friction work; gearshift quality; advantages of different strategies.

DOI: 10.1504/IJVD.2023.134733

International Journal of Vehicle Design, 2023 Vol.92 No.2/3/4, pp.236 - 260

Received: 26 Apr 2022
Received in revised form: 14 Jul 2022
Accepted: 01 Sep 2022
Published online: 09 Nov 2023 *

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