Multi-Objective Optimization of Gear Ratios of a Seamless Three-Speed Automated Manual Transmission for Electric Vehicles Considering Shift Performance

Abstract

Multi-speed transmission can greatly improve the power and economic performance of electric vehicles (EVs) compared with single-speed transmission. Gear ratio is the key design parameter of multi-speed transmission. Optimizing gear ratios can further improve vehicle performance. Most of the existing optimization methods of gear ratios take the power and economy of vehicles in gear as the optimization objectives, but rarely consider the shift performance of the transmission, such as shift time, friction, and shift jerk. Considering the shift performance in the process of gear ratio optimization can not only optimize the vehicle performance in gear, but also improve the shift performance of the transmission. Therefore, this paper proposes a multi-objective optimization method of gear ratios considering the shift performance. Firstly, a seamless three-speed automated manual transmission (AMT) of EVs is selected as the research object, the structure and the shift process without power interruption of the three-speed AMT are introduced, and the detailed EV simulation model is established. Then, the multi-objective optimization method of gear ratios considering shifting performance is described. Specifically, the acceleration time, energy consumption, and jerk of the vehicle in gear are taken as the objective functions, and the shift time, clutch friction, and the shift jerk are added to the corresponding objective functions, respectively. Finally, the multi-objective optimization algorithm is used to solve the gear ratio optimization problem. The simulation results show optimization of the gear ratios significantly improves the power, economy, and comfort of the vehicle compared with the original. More importantly, compared with the optimization method without shift performance, gear ratios optimized by the proposed optimization method has better shift performance, and the feasibility of the proposed method is verified by simulations.

Electric Motor and Transmission Integration for Light-Duty Electric Vehicles: A 2023 Benchmarking Perspective and Component Sizing for a Fleet Approach

“…Omitted from Figure 2 are the selectable elements used to kinematically determine a fixed or variable ratio state, such as wet or dry clutches, one-way clutches or selectable dog clutches to minimize the scope of the paper. Additional engineering details for selectable shifting elements in TRMs can be found in [56][57][58][59], while those that are specific and innovative to EV TRMs can be found in [39,44,46,47,49]. In Figures 2 and A1 of Appendix A, the variables n and d represent the number of teeth on a gear or sprocket while representing the active diameter of the variator sheave.…”

Working mode division and shift schedule extraction of a parallel hybrid power system

“…Common methods for the design or optimization of shift schedules commonly focused on the vehicle's dynamic and economic performance [5][6]. Typical further studies used the multi-objective optimization, taking shift time, friction and shift jerk into account aiming to improve the shift performance of the transmission [7][8][9]. These algorithms can reach higher accuracy and robustness, but greatly add complexity, occupying more computing resources.…”

Development of a Real-Time Tractor Model for Gear Shift Performance Verification

“…Although many studies have been conducted to produce and validate a real-time simulation model according to the specific purpose of the vehicle, no studies have been conducted on models driven in real time while finely simulating the mechanical systems involved in gear shift performance. Improving gear shift performance is directly related to the ride comfort of the vehicle, making it one of the key factors in vehicle development [20][21][22]. The gear shift performance varies depending on the synchronization time of speed and torque generated through the clutch and synchronizer during the gear shift process [23][24][25].…”