Gearshift Performance Research Articles

Experimental Investigation and Control of Driveline Torsional Vibrations during Clutch-to-Clutch Shifts of Electrified Vehicles

An electrified vehicle equipped with a stepped-ratio transmission and clutch(es) requires precise control of the clutch actuator(s) and power sources to achieve optimal gear shift performance, which is characterized by smooth and swift gear shifts. Owing to the absence of the smoothing effect of torque converters, dual-clutch transmission (DCT) powertrains are prone to inducing abrupt shift shocks—particularly during rapid clutch-to-clutch shifts. Balancing the smoothness and speed of shifts is a significant challenge and was the key focus of this study. Multiple experiments and model-based analyses were conducted to investigate the tradeoff between smoothness and shift time during the clutch-to-clutch shifts of a parallel-type hybrid electric vehicle with a dry DCT. Additionally, the adverse effects of inaccurate power-source control on shift quality were experimentally investigated. The results revealed the primary physical factors in terms of control causing torsional driveline oscillations in clutch-to-clutch shifts. According to these observations, a detailed quantitative guide including how to generate reference trajectories for shift control is proposed, with the aim of reducing the driveline torsional vibrations without compromising the shift time. The effectiveness of the proposed control strategy was demonstrated through real-time experiments on an electrified powertrain with a DCT using a dedicated test bench. This study provides valuable insights for optimizing the shift performance of electrified vehicles—particularly for managing torsional vibrations during clutch-to-clutch shifts.

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

Verification of the system is essential during the development of a tractor; however, there are cost and time limitations when verification is performed on an actual tractor. To solve this problem, we developed a tractor model for real-time simulation to verify the gear shift performance of the tractor and evaluate the control algorithm. This study examined and modeled a dual-clutch transmission (DCT)-type 105 kW class tractor. The proportional control valve, synchronizer, and clutch were modeled to accurately implement the shift behavior, and the developed individual model was verified based on actual individual product test data. The 45 s driving simulation was conducted to confirm whether real-time simulation of the entire developed tractor model was possible and whether it simulated the behavior of the target tractor well. The driving simulation results confirmed that the driving speed of the tractor model matched the engine speed, transmission gear ratio, and tractor specifications, and the gear shift performance of the tractor model according to the number of gears was confirmed. The simulated model thus satisfies the characteristics of the target tractor and can be used to verify the gear shift performance, indicating that the model can verify the performance of the control algorithm in real time.

Design of an Improved Active Disturbance Rejection Control Method for a Direct-Drive Gearshift System Equipped with Electromagnetic Linear Actuators in a Motor-Transmission Coupled Drive System

In this study, a type of direct-drive gearshift system integrated into a motor-transmission coupled drive system is introduced. It used two electromagnetic linear actuators (ELAs) to perform gearshift events. The adoption of ELAs simplifies the architecture of the gearshift system and has the potential to further optimize gearshift performance. However, a number of nonlinearities in the gearshift system should be investigated in order to enhance the performance of the direct-drive gearshift system. An active disturbance rejection control (ADRC) method was selected as the principal shifting control method due to the simple methodology and strong reliability. The nonlinear characteristics of the electromagnetic force produced by the ELA were subsequently reduced using the inverse system method (ISM) technique. The ADRC approach also incorporated an acceleration feedforward module to enhance the precision of displacement control. The extended state observer (ESO) module used a nonlinear function in place of the original function to improve the ability to reject disturbances. Comparative simulations and experiments were carried out between the ADRC method and improved ADRC (IADRC) method. The outcomes demonstrate the effectiveness of the designed control method. The shift force fluctuates less, and the shift jerk decreases noticeably during the synchronization procedure. In conclusion, combined with the optimized IADRC method, the direct-drive gearshift system equipped with ELAs shows remarkable gearshift performance, and it has the potential to be widely used in motor−transmission coupled drive systems for EVs.

Evaluation and Improvement of Shifting Quality of the Vehicle Gearbox from the Perspective of Sustainable Development in China’s Vehicle Industry

Energy saving and environmental protection are still two important themes in the vehicle industry. The recent rapid transition in energy markets and the technological advances in the demand-side interventions have renewed attention on the driving behavior of the vehicle consumers. The inappropriate gearshift performance of vehicle gearbox would not only increase the fuel consumption, but also interfere with the driver’s driving emotional state, so that the driver is easy to feel uncomfortable and boring, thus further affecting the fuel consumption. Hence, based on the necessity of improving the gearshift performance of vehicle gearbox, this study adopts GSA test technology to study the problems existing in the shifting quality of the commercial vehicle, so as to achieve high shifting efficiency and low fuel consumption. It could establish the subjective and objective evaluation criteria of the gearshift performance of commercial vehicles determined by the test, which provides a reliable theoretical basis for the optimal design of products and the evaluation of gearshift performance. Then, the technicians could formulate the corresponding shift manipulating schemes and optimal matching steps accordingly, to reach the required technical indexes of power, stability and transmission of the whole vehicle system, thus providing a direction for reducing fuel consumption and emissions, and improving the gearshift performance and quality of the whole vehicle.

Study on the improvement of gearshift performance in commercial vehicle based on ergonomics

Due to the more demanding quality requirements for the vehicle manipulating comfort imposed by the market in recent years, the driver's feeling during gear shifting has become very important in the design stage of the shifting systems. This paper combines the ergonomics theory with the vehicle shifting device, and expounds the application and practice of the ergonomics in the innovative design of the vehicle shifting device. Firstly, GSA analysis system is used to pre-evaluate the static and dynamic shifting performance of the whole vehicle, and analyzes the shifting device of the vehicle transmission according to ergonomics theory. And then the corresponding improvement measures are put forward for the existing defects in the shifting device. Finally, the post-test analysis is carried out to verify the effectiveness in improving the driving experience of the whole vehicle, and ultimately enhance the competitiveness of the studied shifting device in the vehicle industry.

Gear Shifting Based on MIMO Model Predictive Control for Convenient Adjustment of Shifting Performance

When shifting gears, it is necessary to properly adjust the gear shift time and the Maximum Variation of Output shaft Torque (MVOT) which are related to gear shift performance. At this time, the gear shift time and MVOT are related to the clutch slip speed and the output shaft torque, which can be controlled by the engine torque and clutch torque. Therefore, in order to adjust the gear shift performance, it is necessary to perform Multi-Input-Multi-Output (MIMO) control. In MIMO control, the system output is the clutch slip speed and output shaft torque, and the system input is the engine torque and clutch torque. In the past, several trajectories of the engine torque and clutch torque have been generated heuristically to adjust the gear shift performance. Therefore, a MIMO control method that is capable of adjusting the gear shift performance conveniently with a few tuning parameters during gear shifting is needed. In this study, a gear shift controller for generating target driveline torque (engine and clutch torque) based on MIMO model predictive control that can adjust the gear shift performance with only one tuning parameter is proposed. The gear shift controller proposed in this study is verified experimentally on a test bench equipped with a production dual-clutch transmission.

Improving gearshift controllers for electric vehicles with reinforcement learning

During a multi-speed transmission development process, the final calibration of the gearshift controller parameters is usually performed on a physical test bench. Engineers typically treat the mapping from the controller parameters to the gearshift quality as a black-box, and use methods rooted in experimental design – a purely statistical approach – to infer the parameter combination that will maximize a chosen gearshift performance indicator. This approach unfortunately requires thousands of gearshift trials, ultimately discouraging the exploration of different control strategies. In this work, we calibrate the feedforward and feedback parameters of a gearshift controller using a model-based reinforcement learning algorithm adapted from pilco. Experimental results show that the method optimizes the controller parameters with few gearshift trials. This approach can accelerate the exploration of gearshift control strategies, which is especially important for the emerging technology of multi-speed transmissions for electric vehicles.

Offline model predictive control approach to micro-slip control in gearshifts of dual clutch transmission

Dual clutch transmission can avoid some noise vibration and harshness issues caused by other transmissions with single clutch. And applying micro-slip control on clutches can further improve the gearshift performance of transmission compared to the lock-up control. Considering the real-time characteristic of vehicle control, an offline model predictive controller designed by multi-parameter quadratic programming was creatively applied in dual clutch transmission to obtain both clutch torque at the same time with optimal control algorithm. In this way, while realizing the micro-slip state of the clutches, the fast response speed can be realized through the off-line controller, which makes it more feasible and practical for transmission control. A six degrees of freedom vehicle powertrain system model was built in MATLAB/Simulink to simulate the proposed control algorithm. The simulation results show that the micro-slip control avoid the negative torque compared to the lock-up control, which leads to a smoother shift process. In addition, compared with the proportional–integral–derivative micro-slip controller, the offline model predictive controller can achieve more stable control effects with less output torque fluctuation and shorter gearshift time.

Identification of drivers’ driving habits and shift schedule correction for vehicles with automatic transmission

Resource conservation has become a hot topic, and driving habits also have a significant impact on a car’s fuel consumption. In view of the different needs of drivers with different driving habits for automatic transmission and shift characteristics, a vehicle automatic transmission, and shift correction control strategy based on driving habit recognition is proposed. Based on the analysis of drivers’ driving behavior, the phase space reconstruction method is first used to reconstruct the time series of driving control signals, and the driving habit identification and gear shift correction control are conducted based on the correlation dimension and Kolmogorov entropy evaluation index. Simulation and real car test show that the identification method based on phase space reconstruction method and driving habits evaluation index can accurately identify drivers’ driving habits. The gear shift correction control strategy based on driving habit recognition fully meets the different requirements of different drivers for the gearshift performance of vehicles and improves the intelligence degree of automatic transmission of vehicles.

Adaptive gearshift control of wet dual clutch transmission based on extended state observer and H∞ robust control

The clutch characteristics of dual clutch transmission (DCT) will change as the service time increases, which will lead to the deterioration of gearshift performance. To reduce the influence of the change in clutch characteristics on the gearshift performance, an adaptive gearshift control method based on the extended state observer and H∞ robust control is proposed. First, the gearshift problem of the DCT is transformed into the reference trajectory tracking problem, and the gearshift reference trajectory is designed using the minimum principle. The uncertain term related to the change in clutch characteristics in the DCT gearshift dynamic model is defined, and an extended state observer is designed to estimate the uncertain term. On this basis, the gearshift controller is designed using the backstepping method, and H∞ robust control is introduced to further improve the adaptation effect of the controller, then the adaptive control laws of the clutch pressure and engine torque are obtained. Finally, the adaptation effect of the proposed method was verified by both simulation and experiment. The results show that the proposed adaptive gearshift control method can effectively avoid the gearshift delay caused by the change in clutch characteristics, and the gearshift jerk in the simulation and experiment is reduced by 55.01% and 34.8%, respectively.

Testing and analysis of automotive gearshift performance based on gear shift analysis

AbstractWith the increasing demand for vehicle handling comfort in the market, the development of gear shifting performance test systems for automobile transmission has become one of the keys to improving the competitiveness of automobile products. In order to continuously improve the shifting quality of the automobile gearshift control, this research focuses on the study of shifting quality, uses GSA (gear shift analysis) test technology to test and verify the shifting performance of a domestic automobile gearbox, establishes the subjective and objective evaluation criteria for the shifting performance of automobile gearbox, provides a reliable theoretical basis for product optimization design and shifting performance evaluation, and formulates shifting control pertinently. Strategies and optimization measures to ensure that the power, ride, and transmission of the whole vehicle system meet the technical requirements and can shift quickly and smoothly. Not only does this allows to reduce the driver's fatigue strength, but also increases the comfort of the whole shifting process, so as to provide direction to improve the quality of the vehicle's shifting performance and effectively reduce the impact on the driver's health.

Modelling, Analysis and Simulation of a Novel Automated Manual Transmission with Gearshift Assistant Mechanism

To eliminate or reduce torque interruption and driveline jerk for traditional automated manual transmission (AMT), AMT with a gearshift assistant mechanism (GAM) is originally proposed in this paper. The GAM consists of a torque complementary motor and an epicyclic mechanism with a synchronizing clutch. During gear upshift, the electrical motor provides complementary torque to primary (output) shaft after synchronizer discharges, then the synchronizing clutch will work to synchronize primary shaft with anticipated gear. The lockup of the synchronizing clutch will ensure the synchronization of primary shaft and anticipated gear. After finishing synchronizing, synchronizer will lock up the anticipated gear and engine recovers torque supply to finish gearshift. Based on the mathematical model of the proposed transmission, its detailed structure, kinematic character and dynamic behavior are discussed. Controllers are designed to achieve presumed gearshift performance, and simulation results show its effectiveness. Problems may be encountered in engineering application and possible application on electrical vehicle (EV) of the proposed transmission are also discussed. Finally, this paper summarized the merits and further research targets of the proposed transmission, which is a promising structure to achieve swift and smooth gearshift.

Shift Force Optimization and Trajectory Tracking Control for a Novel Gearshift System Equipped With Electromagnetic Linear Actuators

Electromagnetic linear actuators (ELAs) are used to engage gears in an electric automated manual transmission. The structure is simplified due to the elimination of intermediate mechanisms. An ELA can provide 1500 N of electromagnetic force to drive the synchronizer mechanisms. Additionally, the dynamic characteristics of the actuator are remarkable, improving the performance of shifting gears. To achieve balanceable and comprehensive gearshift performance including shift time, friction work, and degrees of jerk, Pontryagin's minimum principle is employed to optimize the friction torque, and current feed-forward active disturbance rejection control is proposed to track the optimized shift force. Moreover, a double closed-loop controller based on active disturbance rejection control is used to achieve fast and stable displacement control. Comparative simulations and experiments are carried out, and the results indicate that the proposed tracking method can implement the optimal shift force well and can integrate the optimal shift indices, including shift time, degrees of jerk, and friction work. Combined with the proposed control method, the superiority and feasibility of the novel direct-drive electromagnetic gearshift system are validated.

Gearshift performance improvement for an electromagnetic gearshift system based on optimized active disturbance rejection control method

Electric automated manual transmission usually adopts direct current motors and intermediate gearings to accomplish gear change. The structure can be simplified further to achieve better dynamic response and mechanical efficiency. A new type of gearshift system which adopts two electromagnetic linear actuators is presented. The intermediate gearings including motion converters are canceled, and the electromagnetic linear actuators drive the shift fork directly to move the synchronizer to engage different gears. The novel gearshift system is described in detail, including the connection, working principle, and performance. Specific working phases of the synchronization are introduced and mathematical equations of each phase are provided. After the specific feature analysis of each phase, the performance effect factors are deduced and the corresponding control requirements are proposed. Considering the stability of the performance, the robust control method, namely, active disturbance rejection control, is adopted. The time optimal method is introduced to optimize the dynamic response of the active disturbance rejection control method to achieve a shorter gearshift time. Comparative simulations among the active disturbance rejection control, time optimal–active disturbance rejection control, and proportional–integral–derivative methods show the distinct improvements of the novel gearshift system combined with the time optimal–active disturbance rejection control method. Finally, gearshift experiments are implemented. The results demonstrated the availability of the novel gearshift system and the designed control strategy.

Innovative design and gearshift control for direct-drive electromagnetic gearshift system equipped with servo synchronizer

Automated mechanical transmission has many advantages such as simple structure, high mechanical efficiency, and low cost. But the poor gearshift performance restricts the massive application of the automated mechanical transmission, and it can be improved through innovation of structure and control. To reduce the requirement of shift force and improve the shift performance, a new direct-drive electromagnetic gearshift system which consists of servo synchronizer and 2-degree-of-freedom electromagnetic actuator is adopted. The specific structure and working principle of the gearshift system including servo synchronizer are described, and the equation of force-amplifying ratio is deduced. Due to the complexity of the gearshift system and uncertainties of the gearshift process, active disturbance rejection control method is designed. The active disturbance rejection controller can eliminate the nonlinearity of the 2-degree-of-freedom actuator. The extended state observer can estimate and compensate the uncertainties, parameter variations, and external disturbances. Simulations are carried out, and the result comparison with proportional–integral–derivative controller indicates the superiority of the active disturbance rejection control method. Test bench and control system are developed to verify the performance of the newly designed system and control method. The experimental results show that, when the gearshift system is equipped with servo synchronizer, the driving force and the maximum volatility of driving force can be reduced by 35% and 5%, respectively, and the impact generated by active disturbance rejection control method is reduced by 36% compared with proportional–integral–derivative method. The new gearshift system achieves a better gearshift performance. Combined with the newly designed control strategy, the direct-drive electromagnetic gearshift system provides a new solution for automated mechanical transmission applications.

Shift Quality Amelioration of EV with AMT by Speed Regulation

Due to torque interruption and clutch friction of Automated Manual Transmissions (AMT) during gear shift, the shift quality is not as positive as other kinds of transmissions, several ways to improve shift quality such as reduce shift time have been researched. During the gear shift process in AMT, new gear speed needs to be regulated as gear ratio changes. In this paper, the research topic is concerning gear shift process of an AMT of electric vehicles, the influence of the speed difference between new gear and synchronizer on gear shift time is studied. Powertrain model of the electric vehicles with AMT is built in ADAMS and several simulations are conducted. Simulation results demonstrate that by controlling the speed difference between new gear and synchronizer in a positive small range from 0rpm to +10rpm with the shift force at 200N, shifting synchronizer can be engaged in a short time. In addition, results also demonstrate that within small speed difference range, the existence of synchronizer ring has little effect on gear shift performance, which illustrates that the structure of AMT on electric vehicles can be simplified.

A Parallel Hybrid Electric Drivetrain Layout with Torque-Fill Capability

Copyright © 2015 SAE International.This paper discusses the torque-fill capability of a novel hybrid electric drivetrain for a high-performance passenger car, originally equipped with a dual-clutch transmission system, driven by an internal combustion engine. The paper presents the simulation models of the two drivetrains, including examples of experimental validation during upshifts. An important functionality of the electric motor drive within the novel drivetrain is to provide torque-fill during gearshifts when the vehicle is engine-driven. A gearshift performance indicator is introduced in the paper, and the two drivetrain layouts are assessed in terms of gearshift quality performance for a range of maneuvers.

Gearshift control system development for direct-drive automated manual transmission based on a novel electromagnetic actuator

A novel gearshift system which comprises a 2 degree-of-freedom electromagnetic actuator is introduced to simplify the structure of gearshift system of automated manual transmission (AMT), increase transmission efficiency and improve shift quality. The working principle and characteristics of the actuator are analyzed. The gearshift process is divided into the non-synchronization and the synchronization phase. Extended state observer (ESO) based inverse system method (ISM) and active disturbance rejection controller (ADRC) are designed for the two processes respectively. ISM can eliminate the nonlinearity of the actuator and ESO can estimate and compensate the uncertainties, parameter variations and external disturbances. ADRC is adopted to improve the tracking accuracy of the synchronization process. Comparative simulations and experimental results demonstrate the effectiveness of the proposed control method, and good gearshift performance has been achieved. Combined with the new designed control strategy, the novel gearshift system provides a new solution for AMT applications.

Modelling the cushion spring characteristic to enhance the automated dry-clutch performance: The temperature effect

The cushion spring plays an important role in an automotive dry-clutch system. It strongly influences the clutch torque transmission from the engine to the driveline through its non-linear load–deflection curve. Therefore, knowledge of the cushion spring compression behaviour is crucial to improve the gearshift performance in an automated manual transmission. Furthermore, the cushion spring compression behaviour is influenced by the temperature because of the frictional heat generation of the clutch facings with the flywheel and the pressure plate surfaces during the engagement phase. In this paper an analysis of the load–deflection curve, taking into account the thermal load to which it is subjected, of a typical passenger car cushion spring is proposed. Six temperatures, in addition to room temperature, were analysed to investigate how the cushion spring load–deflection curve depends on the temperature.

The new 5-speed manual gearbox for Mini One and Mini Cooper

In the model year 2005 Mini One and Mini Cooper have been equipped with a new 5-speed manual gearbox. The gearbox has been specially developed for Mini and the transmission ratios adapted to the performance characteristics of the Mini range. Furthermore, the gearbox is characterised by a substantial reduction in weight, as well as a noticeably improved gearshift performance.