Gear Shift Quality Research Articles

Gear Shift Quality Enhancement Parameters in Light Commercial Vehicles

In the present scenario enhancements of human ergonomics in Light commercial vehicles are imperative to implement customer comfort in vehicle level. Thus the gear shift mechanism plays an important role in the interface between the driver and vehicle. An exact and smooth running gear shift feel typically depends on the combination of both internal and external shifting elements of the gearbox and Change shift operation(CSO) system. The objective of this paper is to explain the parameters that impacts the gear shift quality and how it is improved by taking multiple design iterations in Light commercial vehicle platform through both objective and subjective evaluations. These iterations are given better results on gear shift feel in dynamic as well as static condition. This lead us to facilitate better shift comfort to end users. The content of the paper is limited to the scope of gear shift quality improvements at manual transmission and change shift operation components.

Objective evaluation of gearshift process of agricultural tractors

In the last 20 years, manufacturers have invested in continuously variable transmissions (CVTs) for agricultural tractors, since farmers have demanded more easy-to-use transmissions to increase comfort and driveability. Recently, stepped transmissions have been of interest due to their greater efficiency compared to continuously variable transmissions. To fully compete with CVTs, stepped transmissions must be fully automated and properly handle the operator's comfort during gearshifts. This paper aims to define a test procedure and data analysis method for evaluating the gearshift quality of transmissions for agricultural tractors. The procedure is composed of two tests and aims to reproduce the typical manoeuvres that occur during farming, such as accelerating and shuttling. This method was applied to 14 tractors with different transmissions and engine peak power. On each tractor, an inertial measuring unit and a CAN-Logger were installed to record vehicle and powertrain operating conditions. From the recorded data, a set of metrics was calculated to objectively quantify the impact of gearshift. These metrics were combined to obtain an overall score, which allows for the ranking of tractors in terms of gearshift quality and its dependence on design parameters. Based on our metrics, CVTs outperform stepped transmissions due to their ability to combine high performance with comfort measures. The approach outlined in this study enables manufacturers to quickly spot the weak points of the gearshift behaviour of a tractor so that they can address specific issues and increase operator satisfaction and the overall quality of their tractors. • A simple methodology to evaluate the gearshift quality was developed. • A set of metrics able to describe gearshift behaviour was defined. • The metrics permitted to rank tractors in function of their shifting behaviour. • CVT tractors outperform stepped transmissions in terms of comfort and performance.

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.

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.

Engine Speed Regulation During Gear Shift Process of Torque Decoupled HEV Using Triple-Step Nonlinear Method

For the torque decoupled hybrid electric vehicles (HEVs) equipped with automated manual transmission (AMT), the motor torque can be used to compensate for traction loss during gear shift. Thus, engine speed regulation can be used to achieve speed synchronization, and the clutch can be removed, which simplifies the overall structure of AMT. A triple-step nonlinear method is proposed in this paper to improve the engine speed tracking accuracy, which utilizes the steady-state, reference trajectory dynamics, and the tracking error information comprehensively. By the expense of the intake manifold pressure tracking performance, the developed controller can guarantee the asymptotic convergence of the engine speed tracking error. After the triple-step controller is deduced, it is verified through co-simulation between AMT HEV plant model in AMESim and controller model in Simulink. The simulation results demonstrate that the proposed controller can exert the advantages of the two control inputs: throttle opening α and spark advance deviation Δθ, and certificate the overall gear shift quality, including shift time and vehicle jerk.

Dry Clutch Control of Two-Speed Electric Vehicles by Using an Optimal Control Scheme With Persistent Time-Varying Disturbance Rejection

A novel two-speed inverse automatic mechanical transmission (I-AMT) is proposed to eliminate the torque interruption in conventional AMT and improve the working performance of electric vehicles (EVs). However, due to the intrinsic structural characteristics of I-AMT, the requirements for clutch slip control are different from current AMT. Besides, clutch slip control is sensitive to internal uncertainties and external persistent time-varying disturbances during gear shifting. This study proposes a unified framework to build a clutch slip model for gear upshift and downshift. A high-order disturbance observer-based optimal controller is developed to reject persistent time-varying disturbances in a dry clutch system. During controller deduction, a novel multiplier function λ is introduced, and the optimal control law is presented as a feedback form of system states, the disturbance, and the derivatives of the disturbance. The controller is then applied to the clutch slip processes during gear shifting of an EV equipped with I-AMT. Simulation and experimental results under gear upshift and downshift demonstrate that the controller guarantees consistent performance under various working scenarios with different kinds of disturbances. The rapidity and smoothness of the clutch slip process are ensured without large speed or torque fluctuation, thus improving the overall gear shift quality.

Integrated Prognostics Observer for Condition Monitoring of an Automated Manual Transmission Dry Clutch System

The closed loop feedback control system of an Automated Manual Transmission (AMT) electro-pneumatic clutch actuator is used for intelligent real time condition monitoring, enhanced diagnostics and prognostic health management of the dry clutch system, by integrating with the existing gearbox prognostics observer. The real-time sensor data of the clutch actuator piston position is analyzed for monitoring the condition of the clutch system. Original parameters of the new clutch are stored in the Electrically Erasable Programmable Read-only Memory (EEPROM) of the AMT controller and the real-time data is used by the observer for assessing the degradation/wear of the frictional clutch parts. Also, clutch slip during torque transmission is monitored, using the engine speed and the gearbox input shaft speed from Controller Area Network (CAN). Condition monitoring of clutch system provides enhanced prognostic functionality for AMT system which ensures consistent clutch performance, gear shift quality and timely warning for recalibration, repair and/or replacement of the critical wear and tear parts. Also, systematic analysis of the monitored data provides an accurate diagnosis of a developing fault. Thus, with the advanced control systems in place for AMT, a closed loop feedback based condition monitoring system is modelled for improved diagnostics and prognostics of AMT clutch system.

Comparative results of evaluating the smoothness of automatic transmission gear shifting during car operation

The authors have studied the process of gear shifting, smoothness of it and peculiarities of automatic gearbox functioning of during car operation. The article describes the urgency of the problem of jerks and vibrations when changing gears. When assessing the smoothness of gear shifting, the method of technical state vibroacoustic diagnostics is applied. The method is based on the recorded parameters of vibration velocity, vibration acceleration, vibration movement with their further conversion (fast Fourier transform) into a spectralsignal. The procedure of longitudinal vibration acceleration measurements on cars in operation is described. A comparative analysis of the smoothness of gear shifting in an automatic transmission was carried out using the example of modern passenger cars. Keywords car; car operation; automatic gearbox; technical condition; gearbox malfunction; smoothness; jerks; jolts; gear shift quality criteria; vibration acceleration

Thermal Compensation Control Strategy in Automated Dry Clutch Engagement Dynamics and Launch Manoeuvre

Repeated engagements in dry clutch systems could yield remarkable increase of clutch disk temperature. In dry clutch based transmissions like Automated Manual Transmissions and Dual Clutch Transmissions the overheating leads to poor control of gearshift quality due to unpredictable and fast change of frictional characteristic. Even permanent damage of clutch facings may occur. Under this light, this paper focusing on thermal effects to improve control performances and prevent uncomfortable engagements. To this aim, detailed analyses of dry clutch architecture have been carried out to understand the main phenomena which affect the clutch torque transmissibility. Moreover, a lumped thermal model has been developed to predict both the disk surface and cushion spring temperature in real-time environment. To validate the proposed thermal model, a non-linear least squares method has been used by comparing simulations with finite element results. A control strategy based on model predictive control and thermal compensation effects has been proposed to simulate vehicle launch manoeuvres in flat and up-hill road conditions with low and high initial clutch temperature as well. Finally, the proposed control approach has been compared with classic PI control strategy to prove its effectiveness.

Gearshift Quality Sensitivity Analysis

<div class="section abstract"><div class="htmlview paragraph">Gearshift quality is a perceived quality parameter. Hence, is getting much importance because of the increased awareness about comfortable and refined driving experience, especially in the case of passenger cars. When the topic of gearshift feeling is broached in manual transmission vehicles, synchronizer pack (shifter sleeve, engaging gear, strut, synchronizer and gear synchro ring assembly) have been the focus point for optimization. Synchronizer type (single, double or triple cone), lining material, datch chamfer angle of shifter sleeve/synchro ring of gear/synchronizer, all of these have been extensively studied in the past to improve the gearshift quality. With stringent timelines for vehicle development, OEMs prefer to use off-the-shelf powertrain systems developed by powertrain manufacturers. Due to this, avenues to refine gearshift feel gets reduced to a large extent and hence refinement becomes difficult. The scope of this paper is to discuss gearshift quality parameters used to assess the gearshift feel of a vehicle. It primarily examines ways to refine the gearshift quality by optimizing the external gearshift mechanism and other powertrain aggregates. It also extends to a sensitivity analysis of gearshift cables, gear shifter, dead weights and driveshaft on gearshift quality. Objective parameters were evaluated on vehicle level to understand the aspects of the gearshift, which when tweaked, resulted in an improved shift feel. Different proposals with regard to possible avenues were worked out for possible fine-tuning of the selected parameters. These were then validated on the vehicle. During the evaluation and optimization of gearshift quality, GSQA kit from M/s Ricardo was used to evaluate the gearshift quality.</div></div>

Model-based gear-shift optimization for an automated manual transmission

Gear shift quality is traditionally optimized in a vehicle on the road, through the evaluation of the driver’s perception. This classical human-feedback-based method faces different challenges, such as low reproducibility and high cost. In order to overcome these drawbacks, an innovative automatic virtual calibration framework is proposed in the Model-in-the-Loop environment. The devised framework is composed of a dynamic model of the transmission system, an adaptive gear shift controller, an objective assessment of the gear shift quality, and a multi-objective optimization algorithm. The Pareto-optimal front with multi-conflicting criteria, such as shift time and shift comfort, can be obtained within this framework. In particular, an improved hybrid multi-objective evolutionary algorithm is developed to enhance the optimization performance. The optimization of the shift trajectory for an automated manual transmission synchronization system is implemented as a case study. The obtained optimal shift trajectories are also validated on a transmission test bench.

Gear Shift Quality Parameters Optimization for Critical to Quality Dimensions

Gear Shift Quality Parameters Optimization for Critical to Quality Dimensions

Modelling and control of a novel two-speed transmission for electric vehicles

Multiple speed transmissions adopted by electric vehicles (EVs) provide the probability of further improving the global efficiency of the drivetrain, as well as extending limited driving range for the fixed power storage. This paper proposes a novel two-speed transmission for an electric vehicle (EV), which is capable of realizing power-on gear shifting by operating the band brake to lock or unlock the one-way-clutch. The band brake controlled by the actuator provides a smooth and efficient gear shifting. To achieve power-on gear shifting, three alternative control strategies are proposed and applied in this novel two-speed transmission system. To verify the transient behaviour during the gear shifting, the EV powertrain equipped with the proposed two-speed transmission is undertaken. Firstly, a mathematical model is developed, including the electric motor, the proposed two-speed transmission, the vehicle, etc. Then, model-based alternative power-on gearshift strategies are developed, and a torque-based gearshift closed-loop controller with the desired speed trajectory is proposed. The vehicle jerk and the friction work are taken as the foremost metrics to evaluate the gearshift quality. The simulation results demonstrate that all strategies can achieve power-on gearshifts. The disadvantages and advantages of these strategies are exhibited clearly, which provides beneficial knowledge and reference to the researchers engaged in the development of the transmission controller.

Architecture Optimization of Hybrid Electric Vehicles with Future High-Efficiency Engine

The great development of engine technologies can help to improve the engine characteristics and performance: a better thermal efficiency and an extending fuel economy area, which will subsequently decrease the fuel consumption and thus influence the overall architecture of the vehicle. In this paper, an investigation is carried out to assess the influence of the high-efficiency engine on the transmission gear numbers. First, according to the relevant studies and the integration of the advanced engine technology, a future engine fuel consumption map is obtained, based on which, the preliminary simulations are applied to explore the best match between the transmission and the proposed future engine from the perspective of fuel consumption. The simulation results indicate that the transmission with four gears is the best option to match the future engine while maintaining good fuel economy and meeting the driving demands. Then, based on this conclusion, a new hybrid powertrain architecture, which includes four gears for the engine, is introduced and analyzed in detail, with the advantage of seamless gear shift due to the compensation torque of the motor. Finally, to further examine the fuel economy and gear shift quality of the proposed powertrain, the dynamic model is established and the simulation results demonstrate that the new powertrain architecture shows a good fuel consumption performance and the gear shift process can be achieved without power interruption.

A heuristic synthesis of multistage planetary gearbox layout for automotive transmission

The automatic transmission system is very crucial for the high-speed vehicles, where the planetary or epicyclic gearbox is a standard feature. With the increase in design intricacies of planetary gearbox, mathematical modelling has become complex in nature and therefore there is a need for modelling of multistage planetary gearbox including the shifting scheme. A random search-based synthesis of three degrees of freedom (DOF) high-speed planetary gearbox has been presented in this paper, which derives an efficient gear shifting mechanism through designing the transmission schematic of eight speed gearboxes compounded with four planetary gear sets. Furthermore, with the help of lever analogy, the transmission power flow and relative power efficiency have been determined to analyse the gearbox design. A simulation-based testing and validation have been performed which show the proposed model is efficient and produces satisfactory shift quality through better torque characteristics while shifting the gears. A new heuristic method to determine suitable compounding arrangement, based on mechanism enumeration, for designing a gearbox layout is proposed here. An important finding on automotive gear shift quality due to closer gear ratio is also reported in this work.

Position and Force Switching Control for Gear Engagement of Automated Manual Transmission Gear-Shift Process

Gear-shift control is essential in automated manual transmission (AMT) systems, because it has a significant influence on comfort of vehicle and lifespan of AMT. Gear engagement process is the most important part of gear-shift process, and it has multistage and nonlinear characteristics, which make it difficult to realize smooth and fast control. This paper proposes a position and force switching control scheme for gear engagement. At the beginning and the end of gear engagement process, the combination sleeve is supposed to reach the desired position quickly with a small resistance for which a position controller is designed by using sliding mode control (SMC) method. A force controller is designed for the midsynchronizing stage, because the combination sleeve is blocked at this stage until the synchronization is finished. Simulations and experiments are carried out to show that gear-shift quality is improved and gear-shift shock is reduced greatly by the proposed method.

Unified modelling and control for the power-on gear shift of a planetary transmission

Estimation of the oil hydraulic pressure for the gear-shift elements can be useful for the development of closed-loop control of the automatic transmission fitted to a heavy off-highway vehicle for a good gear-shift quality, to reduce the dissipated energy and the vehicular shift jerk in complex working conditions. The unified dynamic model for a three-degree-of-freedom planetary automatic transmission is presented, and the power-on upshift from first gear to second gear is considered as an example. The unified model is more efficient than the conventional model for the dynamic analysis; furthermore, it provides a computational method for the inertia of the transmission when in gear. From a phased characteristic analysis, real-time estimation of the oil pressure for the gear-shift elements in the sliding process, i.e. the torque phase and the inertia phase, is addressed; then the improved control scheme for the power-on upshift from first gear to second gear is developed and validated using a heavy off-highway vehicle equipped with a high-power full-range speed-regulating diesel engine. The experimental results show that the model-based oil pressure estimation is able to reflect the dynamic characteristics of the system in changing conditions, and the corresponding control strategy can improve the gear-shift quality and the vehicular performance effectively.

Cloud-based shaft torque estimation for electric vehicle equipped with integrated motor-transmission system

In order to improve oscillation damping control performance as well as gear shift quality of electric vehicle equipped with integrated motor-transmission system, a cloud-based shaft torque estimation scheme is proposed in this paper by using measurable motor and wheel speed signals transmitted by wireless network. It can help reduce computational burden of onboard controllers and also relief network bandwidth requirement of individual vehicle. Considering possible delays during signal wireless transmission, delay-dependent full-order observer design is proposed to estimate the shaft torque in cloud server. With these random delays modeled by using homogenous Markov chain, robust H∞ performance is adopted to minimize the effect of wireless network-induced delays, signal measurement noise as well as system modeling uncertainties on shaft torque estimation error. Observer parameters are derived by solving linear matrix inequalities, and simulation results using acceleration test and tip-in, tip-out test demonstrate the effectiveness of proposed shaft torque observer design.

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.

Robust driveshaft torque observer design for stepped ratio transmission in electric vehicles

Knowledge of driveshaft torque is very important to powertrain oscillation damping control as well as gear shift quality improvement. However, the driveshaft torque cannot be easily measured by using affordable sensors. This paper provides a robust driveshaft torque observer design for electric vehicle equipped with stepped ratio transmission. The proposed observer is constructed using the measurable angular velocity signals and designed to be robust against modeling error, system uncertainties as well as external load disturbance. Torsion angle of the driveshaft is selected to be estimated instead of direct torque observation, which can be further used to calculate the driveshaft torsion based on driveshaft׳s spring–damper model. The H∞ performance is adopted in the observer design to minimize the effect of the disturbance on the estimation error. Furthermore, the decay rate of the estimation error and transient response of the observer are also considered by using an eigenvalue placement technique. The observer gain is derived by solving the linear matrix inequality while simulation results are adopted to show the effectiveness of the proposed observer design.