Abstract

Recent developments of pure electric vehicles have shown that pure electric vehicles equipped with two-speed or multi-speed gearbox possess higher energy efficiency by ensuring the drive motor operates at its peak performance range. This article presents the design, analysis, and control of a two-speed automatic mechanical transmission for pure electric vehicles. The shift actuator is based on a motor-controlled camshaft where a special geometric groove is machined, and the camshaft realizes the axial positions of the synchronizer sleeve for gear engaging, disengaging, and speed control of the drive motor. Based on the force analysis of shift process, the parameters of shift actuator and shift motor are designed. The drive motor’s torque control strategy before shifting, speed governing control strategy before engaging, shift actuator’s control strategy during gear engaging, and drive motor’s torque recovery strategy after shift process are proposed and implemented with a prototype. To validate the performance of the two-speed gearbox, a test bed was developed based on dSPACE that emulates various operation conditions. The experimental results indicate that the shift process with the proposed shift actuator and control strategy could be accomplished within 1 s under various operation conditions, with shift smoothness up to passenger car standard.

Highlights

  • Pure electric vehicles have many advantages, such as low level of noise, zero-emission, and easiness to operate and maintain

  • The following highlights the results of the study: 1. A brand-new shift actuator was designed to meet the requirements of gear shift based on the analysis of the characteristics of the two-speed transmission

  • The parameters of the power source and reduction mechanism for the shift actuator were designed based on the force analysis in the shift process

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Summary

Introduction

Pure electric vehicles have many advantages, such as low level of noise, zero-emission, and easiness to operate and maintain. Keywords Pure electric vehicle, automatic mechanical transmission, shift actuator, parameter design, shift control strategy

Results
Conclusion
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