Two-speed Dual Clutch Transmission Research Articles

Optimal Gear Shift Control of Two-Speed Dual-Clutch Transmission in Electric Vehicle for Smoothness and Friction Loss Reduction

Optimal Gear Shift Control of Two-Speed Dual-Clutch Transmission in Electric Vehicle for Smoothness and Friction Loss Reduction

Design and Optimization of Low Impact Shift Control Strategy for Aviation Transmission Power System Based on Response Surface Methodology

The utilization of a variable-speed power system significantly improves the forward flight speed and cruising range of the helicopter. Nevertheless, the shock of speed and torque during the shift process brings stability and safety problems that cannot be ignored. Thus, swift and stable shift control is a key issue in the research on aviation power systems. This study focuses on the design and optimization of low-impact shift control strategies for a variable-speed power system, which involves multiple control variables, long adjustment times, and uncontrollable risks due to the nonsteady state. A comprehensive power system model that integrates the engine, a two-speed dual-clutch transmission system, and the main rotor was proposed. By selecting the engine fuel flow, friction clutch hydraulic pressure, and rotor pitch angle as input signals, regression fitting models between the input signals’ starting time points and speed or torque shock were obtained using Response Surface Methodology (RMS). The interaction effect of multiple time series was analyzed, and four kinds of low-impact nonlinear programming multi-objective optimized models for speed or torque are proposed. The results indicate that the P values of the RMS fitting models at upshift and downshift are less than 0.0001 and 0.05, respectively, which are highly significant and can effectively predict the shift dynamic response; under the optimized upshift and downshift control strategy, the speed and torque shock are reduced by 5–10%.

Performance Comparison of Pure Electric Vehicles with Two-Speed Transmission and Adaptive Gear Shifting Strategy Design

The two-speed automatic transmission can adjust the drive motor speed of electric vehicles and expand their output torque range. This study proposes a rule-based partitioned gear-shifting strategy for pure electric vehicles equipped with a two-speed dual-clutch transmission, combining economic and dynamic shifting strategies to ensure low energy consumption and strong power. Specifically, fuzzy logic is applied to adaptively modify the partition shifting strategy online, to reduce invalid gearshifts, increase the service life of the transmission, and improve driving comfort. Finally, we compare the economic performance and dynamic performance of pure electric vehicles equipped with a two-speed dual-clutch transmission and a single-speed final drive. The results show that the vehicle equipped with the two-speed dual-clutch transmission has better economic and dynamic performance. In addition, its maximum climbing ability was verified by rig testing. These results prove that the two-speed dual-clutch automatic transmission and the gear-shifting strategy proposed in this study can comprehensively improve the performance of pure electric vehicles.

Development of two-speed dual-clutch transmission for seamless gear shifting in EVs

In recent years, there has been a shift from gasoline-powered vehicles to electric vehicles (EVs) owing to the tightening of fuel consumption and emission regulations in many countries. One of the challenges of using EVs is their short driving range, and transmissions are being designed especially for EVs to solve this problem. The installation of these transmissions should increase the driving power, efficiency, and maximum vehicle speed, resulting in improved driving performance. However, one of the problems of EV transmissions is the generation of shocks owing to the large gear ratio for the second speed. The magnitude of the shifting shock can be controlled by adjusting the amount of force applied to the clutch friction member, and seamless shifting can be achieved by controlling the motor torque based on the clutch-passing torque. However, the clutch-passing torque is not easy to estimate, as it depends on several factors, such as the difference in the rotational speed, temperature, and time-related deterioration. Therefore, in this study, a new system was developed to directly monitor clutch torque using a dual clutch transmission (DCT). Specifically, to achieve seamless shifting of a two-speed DCT for EVs, a system was devised to monitor the clutch transmission torque using a torque sensor, and seamless shifting by controlling the motor torque and the two clutches was investigated. First, a theoretical equation was constructed to elucidate the input–output relationship for the transmission. Next, it was confirmed that seamless gear shift control is possible based on this theoretical equation. Finally, a delay was added to the motor torque to verify if seamless gear shifting was possible.

Application of Driving Style Recognition in the Shift Control of a Two-speed DCT for Pure Electric Vehicles

The driving style recognition algorithm can be used to obtain the driver’s current driving style in real time. Thus, the algorithm is combined with the transmission control logic to make the shifting operation of the transmission adaptive to drivers of different driving styles. Firstly, by introducing the dynamic coefficient, the comprehensive shift schedule that match different driving styles is calculated. Next, the two transmission shift evaluation indexes, i.e., shift time and degree of jerk are determined, with the corresponding objective function established. Using this function as the constraint function of the NSGA-II multi-objective genetic optimization algorithm, the Pareto optimal solution set of the engagement speed control parameters of the two clutches under different motor output torques is obtained. The transmission shift control strategy proposed herewith is validated by the co-simulation of MATLAB/Simulink and MSC Carsim software. The co-simulation results show that the transmission can automatically adjust the shift parameters according to different types of driving styles, so that the shift schedule and shift quality of the two-speed dual-clutch transmission are in accordance with the needs of drivers with different driving styles.

Seamless shifting of a two-speed dual clutch transmission for electric vehicles using machine learning

Seamless shifting of a two-speed dual clutch transmission for electric vehicles using machine learning

The LQG/LTR control method for turboshaft engine with variable rotor speed based on torsional vibration suppression

In order to realize the rapid response control for turboshaft engine during the process of variable rotor speed, the linear quadratic Gaussian with loop transfer recovery (LQG/LTR) control method for turboshaft engine based on torsional vibration suppression is proposed. Firstly, the two-speed dual clutch transmission model is applied to realize the variable rotor speed of helicopter. Then, based on the state variable model of turboshaft engine, the proper LQG/LTR controller is available. In order to eliminate the limitation of low-order torsional vibration on the bandwidth of LQG/LTR controller, a frequency-domain analysis method for the effect of torsional vibration suppression on LQG/LTR controller performance is developed. Finally, the numerical simulation is conducted to verify the LQG/LTR control for turboshaft engine with variable rotor speed based on torsional vibration suppression. The results show that the bandwidth of the LQG/LTR control loop can increase by 2–3 times under torsional vibration suppression. Meanwhile, when the rotor speed varies continuously by 40%, the overshoot and sag of the power turbine speed can decrease to less than 2% through LQG/LTR controller based on torsional vibration suppression, which achieves the rapid response control of the turboshaft engine.

Theoretical and experimental investigation of the thermal behaviour of a two-speed dual clutch transmission

Understanding the heating behaviour of automotive transmissions in an important step in prototype development, it plays a significant role in achieving appropriate tolerances at the design phase and strongly influences the system's durability in the long term. Furthermore, lubricant viscosity is strongly dependent on operating temperature, understanding this behaviour will provide insight into how transmission efficiency is affected during vehicle warm-up. In this paper, an experimental and simulation based study has been conducted to investigate the thermal behaviour of a two-speed dual clutch transmission (DCT) that has been developed for electric vehicle applications. This is achieved through the modelling of the power losses in the system that is then integrated with a compact thermal model of the transmission. Transient heating simulations for the transmission are conducted at constant speeds and compared with experimental studies, showing a strong correlation between results. Simulations are then utilised to investigate the load and speed dependencies of the transmission's thermal behaviour.

Theoretical and experimental investigation of the thermal behaviour of a two-speed dual clutch transmission

Understanding the heating behaviour of automotive transmissions in an important step in prototype development, it plays a significant role in achieving appropriate tolerances at the design phase and strongly influences the system's durability in the long term. Furthermore, lubricant viscosity is strongly dependent on operating temperature, understanding this behaviour will provide insight into how transmission efficiency is affected during vehicle warm-up. In this paper, an experimental and simulation based study has been conducted to investigate the thermal behaviour of a two-speed dual clutch transmission (DCT) that has been developed for electric vehicle applications. This is achieved through the modelling of the power losses in the system that is then integrated with a compact thermal model of the transmission. Transient heating simulations for the transmission are conducted at constant speeds and compared with experimental studies, showing a strong correlation between results. Simulations are then utilised to investigate the load and speed dependencies of the transmission's thermal behaviour.

Comprehensive design and optimization of an electric vehicle powertrain equipped with a two-speed dual-clutch transmission

This article develops a systematic model to study electric vehicle powertrain system efficiency by combining a detailed model of two-speed dual-clutch transmission system efficiency losses with an electric vehicle powertrain system model. In this model, the design factors including selection of the electric machine, gear ratios’ change, multi-plate wet clutch design, and gear shift schedule design are considered. Meanwhile, the application of detailed model for drag torque losses in the gearbox is discussed. Furthermore, the proposed model, developed with the MATLAB/Simulink platform, is applied to optimize/maximize the efficiency of the electric vehicle powertrain system using genetic algorithms. The optimization results demonstrate that the optimal results are different between simulations via New Europe Drive Cycle and Urban Dynamometer Driving Schedule, and comprehensive design and optimization of the powertrain system are necessary.

Shift control of a dry-type two-speed dual-clutch transmission for an electric vehicle

In this paper, a shift control algorithm to improve the shift quality was proposed for an electric vehicle with a dry-type two-speed dual-clutch transmission. To analyse the shift characteristics of the target electric vehicle, dynamic models for the two-speed dual-clutch transmission and the drivetrain were developed. Based on the dynamic models, dynamic equations for the transient shift states were derived, and a shift performance simulator was constructed. From analysis of the transient shift state, it was found that the fluctuations in the driveshaft torque, which cause the shift quality to deteriorate, occurred as a result of the inertia torque. Based on the analytical results, a control algorithm was proposed using traction motor torque control as well as shift actuator stroke control. For traction motor control, a compensation torque was applied during the inertia phase. In that phase, actuator stroke control was performed by considering the torque margin and the kissing point during the torque phase instead of the existing map-based control. To evaluate the performance of the proposed control algorithm, a test bench for the target electric vehicle was developed. From the experimental results, it was found that the variations in the driveshaft torque and in the jerk were reduced by the proposed control algorithm, which thereby provides an improved shift quality.

Numerical and experimental investigation of drag torque in a two-speed dual clutch transmission

The theoretical analysis of drag torques within a two-speed dual clutch transmission is presented in this article. The numerical models are developed to study the different sources of drag torques in dual clutch transmission. Simulations are performed in Matlab/Simulink platform to investigate the variation of drag torques under different operating conditions. Then an experimental investigation is conducted to evaluate the proposed model using an electric vehicle powertrain test rig. Outcomes of experimentation confirm that simulation results agree well with test data. Therefore the proposed model performs well in the prediction of drag torque for the transmission, and can be applied to assess the efficiency of the transmission. Results demonstrate that the entire drag torque is dominated by the viscous shear in the wet clutch pack and gear churning losses. This lays a theoretical foundation to future research on reducing drag torque and applications of drag torque in powertrain system efficiency optimization.