Stepped Automatic Transmission Research Articles

High nonlinearity of BEV's stepped automatic transmission design objectives and its optimal solution by a novel ISA-RSA

The battery electric vehicle's (BEV's) stepped automatic transmission (SAT) has a significant influence on the power and economic performance of the new-energy vehicle system dynamics. The SAT entails a complex design process, where the transmission ratio parameter and the control strategy are interactively coupled, causing a difficulty in achieving a globally optimal solution. The actual design process involves multiple design objectives and incurs high design costs. The purpose of this study is to explore the variation characteristics of the design objectives of BEV's SAT and propose a transmission parameter optimization design method with reduced design costs. The paper investigates the interactive coupling property of the transmission ratio parameter and the control strategy, analyzing the high nonlinearity of SAT design objectives using the example of two-gear transmission. It proposes a design method that combines a heuristic optimization algorithm and an estimation model (Method Ⅲ), and a design method that utilizes an improved simulated annealing algorithm and a region search algorithm (ISA-RSA, Method Ⅳ). These methods are compared with a design method based on combination tests using the traversing method (Method Ⅰ) and a design method based on the heuristic optimization algorithm (Method Ⅱ). The results indicate that Method I incurs high design costs with limited effectiveness, while Method II exhibits unstable economic performance and integrated design objectives with fluctuations. Method III is highly dependent on the accuracy of the estimated model and performs poorly in optimizing acceleration time. However, Method Ⅳ, with low design costs, demonstrates remarkable optimization ability to solve high nonlinearity problems and exhibits a high probability of converging to the area near the globally optimal solution. This paper also aims to provide a direct solution to high design cost and highly nonlinear design objective problems in other engineering fields.

Data Mining Approach for the Identification of the Intelligent Gear Decision Strategy for the Stepped Automatic Transmission

The primary goal of automatic transmission vehicle design and optimization is to ensure that drivers can operate automatic transmission vehicles with the same driving experience as skilled drivers driving manual transmission vehicles. However, the existing gear decision strategies of stepped automatic transmission vehicles have poor adaptability to different driving intentions and complex driving environments. When operating manual transmission vehicles, skilled drivers can make intelligent gear decision to satisfy their driving intentions and adapt to different driving environments. Therefore, this study's objective is to establish the design and formulation process for the identification of the intelligent gear decision strategy for the stepped automatic transmission that adapts to different driving intentions and complex driving environments. This is achieved using the data mining method to identify skilled drivers' gear decision strategy from their driving data. To this end, the driving data of skilled drivers operating manual transmission vehicles are collected. The shift boundary points of each gear under the target driving condition are obtained through data preprocessing, data cleaning, outlier processing, and boundary points extraction. Thereafter, the gear decision strategy of skilled drivers is established by fitting the shift boundary points. Taking the flat-straight road condition as an example, the gear decision strategy is established and experimental comparisons are made to verify the effectiveness of proposed gear decision design method.

Fuel Consumption Comparison between Hydraulic Mechanical Continuously Variable Transmission and Stepped Automatic Transmission Based on the Economic Control Strategy

Hydraulic mechanical continuously variable transmission (HMCVT) is a transmission system combining mechanical and hydraulic power flow. The matching and design of the power source and transmission system contribute to the energy-saving and emission reduction of vehicles, and meet the requirements of modern society for environmental protection and energy-saving. This paper takes the transmission system of the pickup truck as a research object to research the transmission ratio control strategy of a self-designed new HMCVT with the goal of minimizing fuel consumption. The research compares it with the standard stepped automatic transmission (SAT). The vehicle model was based on CarSim and MATLAB/Simulink. The simulation was carried out under the EPA cycle, NEDC, and the six-mode cycle. The fuel consumption of SAT and that of HMCVT were compared. The results show that the average fuel savings of the pickup truck with HMCVT are 4.52% in the EPA cycle, 7.01% in the NEDC, and 4.84% in the six-mode cycle compared to the eight-speed SAT. In conclusion, HMCVT is more economically efficient than SAT.

Research on the novel discretized ratio control strategies and hardware-in-the-loop test for continuous variable transmission system

Based on traditional continuous control strategy for Continuously Variable Transmission (CVT) ratio, according to the principles of shift control strategy for stepped automatic transmission, the influences of throttle opening and external resistance or vehicle speed on CVT ratio control are analyzed on bumpy road. Under the same variation of external resistance condition, the differences between optimal economic control strategy and optimal dynamic control strategy are discussed. Then, the traditional continuous optimal dynamic and economic control lines are divided into multi-step upshift points. Meanwhile, the corresponding downshift points are set to avoid the interference near shift points. After that, the novel discretized ratio control methods for CVT system are proposed. By respectively discretizing throttle opening and vehicle speed, the discretized ratio control strategy for throttle opening, and the integrated discretized ratio control strategy for throttle opening and vehicle speed are further proposed and simulated. Furthermore, the hardware-in-the-loop (HIL) test system is built to further verify the feasibility and accuracy of discretized ratio control strategies. Both simulation and HIL test results show that the sensitivity of throttle opening and vehicle speed to ratio control is reduced dramatically, the fluctuation of ratio is decreased considerably, the transmission efficiency is increased significantly, and the jerk is declined moderately.

Development of High Efficiency Dog Clutch with One-Way Mechanism for Stepped Automatic Transmissions

Development of High Efficiency Dog Clutch with One-Way Mechanism for Stepped Automatic Transmissions

Hybrid Electric Vehicle Downshifting Strategy Based on Stochastic Dynamic Programming During Regenerative Braking Process

Regenerative braking is the most important way to save energy for hybrid electric vehicles (HEVs) and electric vehicles (EVs). Wherein, for HEVs/EVs equipped with stepped automatic transmissions, downshifting is an effective method to improve recovery energy by adjusting motor work points. However, it is difficult to design a proper downshifting strategy due to complicated traffic conditions and unknown drivers’ intention. Therefore, this paper proposes a downshifting strategy using cluster-based stochastic dynamic programing (SDP). First, driving conditions are clustered using K-means algorithm based on a large quantity of urban traffic historical data. Then, static Markov chains are built to describe the transition of the future braking torque demand for each cluster. Next, a four-dimensional SDP optimization problem for downshifting is formulated and solved through Bellman iteration. Finally, support vector machine is adopted to identify the driving conditions online, based on which SDP results are used to give the downshifting command. Simulations and controller-in-loop tests are carried out, and the results show that regenerative braking could recover more energy by SDP-based strategy than no downshifting and rule-based strategy.

Modeling of a Hybrid Powertrain with a Stepped Automatic Transmission

In this paper a physics-based overall model of a hybrid powertrain equipped with a stepped automatic gearbox is derived. On the one side, the model approach serves as plant model for the development of new control strategies for clutch-to-clutch gear shifts. On the other side, it provides important insight into the dominant dynamic effects. This study focuses on wet clutches and their hydraulic actuation as well as a compact mathematical representation of the planetary gear train. The use of a modified elasto-plastic friction model allows for a physical representation of the friction torque occurring during gear shifts without the need of structural model changes.

Optimal shifting control strategy in inertia phase of an automatic transmission for automotive applications

Shifting quality is a crucial factor in all parts of the automobile industry. To ensure an optimal gear shifting strategy with best fuel economy for a stepped automatic transmission, the controller should be designed to meet the challenge of lacking of a feedback sensor to measure the relevant variables. This paper focuses on a new kind of automatic transmission using proportional solenoid valve to control the clutch pressure, a speed difference of the clutch based control strategy is designed for the shift control during the inertia phase. First, the mechanical system is shown and the system dynamic model is built. Second, the control strategy is designed based on the characterization analysis of models which are derived from dynamics of the drive line and electro-hydraulic actuator. Then, the controller uses conventional Proportional-Integral-Derivative control theory, and a robust two-degree-of-freedom controller is also carried out to determine the optimal control parameters to further improve the system performance. Finally, the designed control strategy with different controller is implemented on a simulation model. The compared results show that the speed difference of clutch can track the desired trajectory well and improve the shift quality effectively.