Compound optimal control for shift processes of a two-speed automatic mechanical transmission in electric vehicles

Abstract

Public interest in pure electric vehicles equipped with two-speed automatic mechanical transmission is increasing because of not only widened high-efficiency operation zone but also reduced speed range and cost of electric drive system. In this paper, transient dynamic behaviors of an e-drive passenger car including clutch-free two-speed automatic mechanical transmission are analyzed during up and down shifts. Bench tests for the proposed electric driveline are conducted, by which the dynamic model and the shift control strategy are validated. In experiments, severe jerking phenomena are observed when the drive motor torque sharply decreases before the separation with current gear meanwhile fast increases after the engagement with target one. For alleviation of the torsional shocks, feed-forward control in combination with optimal torque feedback control is developed for the drive motor according to torque estimation of the half shaft using extended Kalman filtering method. Meanwhile, a sliding mode control is employed for precise positioning of the shift fork for the transmission. By comparisons of the simulation and test results, it is demonstrated that the proposed control strategy reduces the jerking intensity of driveline as well as the shift period effectively in shift process.

Gear Ratio Optimization along with a Novel Gearshift Scheduling Strategy for a Two-Speed Transmission System in Electric Vehicle

“…Each type of transmission system has its own benefits or limitations. Chai et al [36] and Kim et al [37] made enough reasonings in favor of using AMT in EVs. Some of those are features of ATs with higher-energy economy, higher controllability, converting existing manual transmission (MT) into AMT causing lower development cost, etc.…”

“…A minimum waiting period or shift interval is maintained between every consecutive gearshift to avoid frequent gear shifting as well as to ensure riding comfort. The shift interval must be greater than the maximum gearshift time, because the gearshift time is not necessarily the same for every gear change in a transmission system with more than two gears for both upshift and downshift [36,49]. Based on the study conducted by Zhang et al [46], a minimum shift interval of 4 s is assumed to be sufficient for an acceptable level of riding comfort.…”

Coordinated speed and position control of integrated motor-transmission system

“…A force and position switching scheme of AMT system was further developed by Wang et al (2018), in which sliding mode control was utilized of sleeve position tracking while sliding model based disturbance observer are designed to reduce chattering and increase robustness. Considering parameter uncertainty and external load disturbance, Chai et al (2018) presented a sliding mode control for precise position tracking of the shift fork in clutchless AMT system. It can be seen that the speed synchronization control and position control of shifting actuator are usually conducted separately.…”

Torsional Oscillations Control of Integrated Motor-Transmission System Over Controller Area Network

“…Integrated motor-transmission (IMT) system is emerging as one promising solution for electrified powertrain systems [6], [7]. Compared with electric driving system with single ratio reducer, the IMT system can better balance the powertrain efficiency and vehicle dynamical performance by using gear shifting [8], [9]. Meanwhile, compact structure design of IMT can further help reduce the powertrain efficiency loss that caused by gear The associate editor coordinating the review of this manuscript and approving it for publication was Ricardo De Castro.…”