Automatic Transmission System Research Articles

Dynamics of a Ravigneaux Gear

Ravigneaux gears are planetary gears, often used in automatic power transmission systems. They represent an integration of two planetary gears, where the two planet carriers are combined, and one ring gear is omitted. They possess a complicated mesh structure and are a source of parameter-excited vibrations in the interior of an automatic transmission. In order to model the dynamics of such a gear correctly, the dynamics of the complete transmission and, additionally, at least the approximate dynamics of the complete driveline system, must be considered.

INTRODUCTION OF THE LATEST HYDRAULIC CONTROL SYSTEM FOR AUTOMATIC TRANSMISSION

From the social background of global warming issue, earth environment protection issue and the rise of oil price, the demand of the improvement of fuel economy and CO2 reduction to a vehicle is very high nowadays. Continuously variable transmission (CVT) adoption has been recently increased to respond such social demand. JATCO is now also expanding the lineup of CVT as new solution for vehicle automatic transmission. In CVT, the shift control hydraulic pressure is a little bit higher than that of conventional stepwise shifting automatic transmission. So, unstable behavior of pressure is sometimes caused, for example, pressure oscillation. Such issue should be solved in early development stage. In this paper, we would like to introduce the feature and the techniques of oil pressure control system of CVT as an example of latest hydraulic control system for automatic transmission. And we would like to introduce our recent simulation for the optimal design of hydraulic control system.

Electronic Systems for Commercial Vehicles

Within the concept of the evolution of electronic system applications in commercial vehicles, Rucker has developed solutions for clutch control in an automatic transmission system for heavy-duty trucks.

Impulsive response of an automatic transmission system with multiple clearances: Formulation, simulation and experiment

Impulsive responses in geared systems with multiple clearances are studied when the mean torque excitation and system load change abruptly, with application to a vehicle driveline with an automatic transmission. First, torsional lumped-mass models of the planetary and differential gear sets are formulated using matrix elements. The model is then reduced to address tractable nonlinear problems while successfully retaining the main modes of interest. Second, numerical simulations for the nonlinear model are performed for transient conditions and a typical driving situation that induces an impulsive behaviour simulated. However, initial conditions and excitation and load profiles have to be carefully defined before the model can be numerically solved. It is shown that the impacts within the planetary or differential gears may occur under combinations of engine, braking and vehicle load transients. Our analysis shows that the shaping of the engine transient by the torque converter before reaching the clearance locations is more critical. Third, a free vibration experiment is developed for an analogous driveline with multiple clearances and three experiments that excite different response regimes have been carried out. Good correlations validate the proposed methodology.

FEBB: Fuel Efficiency Buy-Back Program

This Efficiency Program is design to encourage the skilled truck drivers in a way to save precious fuel during their work shift. The main objectives of FEBB are: 1st The transportation and forwarding companies offer an incentive to its drivers that called FEBB program: It means all fuel savings will transformed to driver bonus monthly payment additional to its basic salary. How it is calculate? All engines have technical specification by producer state the average urban or highway fuel consumption. All below those specifications are fuel savings. You simply multiply the fuel saving in litters or gallons by the fuel price at the middle of the month (to monthly eliminate standard deviation of fuel price). How the drivers do savings? - The skilled driver would adjust the vehicle speed not only accelerating the engine but most with switching the gear while the engine is working at its optimum of rotational force (torque); 2nd It is announced as incentives to SKILLED DRIVERS, which predefined that only drivers saving fuel are skilled. That will change driver mentality to more economic and environmental safety manner. Benefits: 1. You can lower fuel consumption in average vary from 1 litter/100kms for engines below 2000cc to 5 litters/100kms for heavy engines over 12,000cc; 2. Environmental more safety; 3. Encourage the drivers not to exceed speed limits because fast driving means higher fuel consumption. Conforming with speeds limits will decrease the road incidents; 4. Engine's and suspension system physical depreciation is lower. The lower depreciation the lower costs of maintenance; 5. More cost-effective routing is chosen by the driver in order to save fuel; 6. In some countries it will reduce the fuel pilferage. Common phenomenon in south-east Europe; 7. Fuel save = Bonus Payment = Motivation. Application: Effective: In countries where the highway network is well developed; Ineffective: In urban environment where a lot of maneuvers are required during transportation. Broad application: Automotive industry: this theory leads to the term Economic Drive Gear System (EDGS). In general it is 12-18 gear automatic transmission system that is working on maximum of moment (torque) in terms of RPM. How it works? - The transmission changes the gear up when the RPM moves up with more than 10% vs. ORPM and the transmission changes the gear down when RPM drops down with more than 10% vs. ORPM. * ORPM = optimum of revolutions per minutes (see Prerequisites for the theory). Prerequisites for the theory (the following facts are well known but fundamental for FEBB theory and could be defined as Axioms): 1. Newton metre is the unit of moment (torque**) of self propelling internal combustion engines. The maximum of moment (torque) for diesel engines is achievable with the range of 1000-2000 rpm that could differ from one producer to another. The best engines are those that have wider range of revolutions per minutes (rpm) while keeping the maximum of the moment (torque). The driver can adjust the speed of the vehicle switching to higher Gear for higher speed through engine acceleration in a range of ORPM and vice versa. Herein we will call this maximum of torque in terms of rpm as ORPM Optimum of Revolutions Per Minutes. ** Torque = rotational force (Nm). 2. While keeping the maximum of moment (torque) in terms of RPM it results in lower depreciation of the engine and better combustion and lower emission of CO and (HC NOx) where NO-Nitric Oxide is toxic air pollutant.Example table of correlation between RPM (r/min), Torque (Nm) and Engine power (kW) is given below.

Design of an automatic transmission system having an arbitrary power flow using the automatic power flow generation algorithm

In this paper, the automatic power flow generation algorithm for designing an arbitrary type of automatic transmission system is proposed. The state equations of motion for the steady state and transient state of the automatic transmission system are developed, not by human hands but by the computer using this algorithm. The deliveries of the angular velocities and torques are only considered for the motion characteristics of the automatic transmission system. The effects of the vibration and noise are not considered. The automatic transmission system is defined by the basic elements, i.e. planetary gear set, clutch, brake, shaft, general gear, and inertia. The transmission system is defined by the combination of these elements. The automatic system components generation algorithm generates the automatic transmission system at each shift and during shifts. An automatic transmission system having an arbitrary power flow can be designed automatically by the software developed based on these algorithms. To prove these algorithms, the double planetary gear system is designed and the simulation results are compared with the experimental results and show good agreement.

A Control Strategy on Starting up of Vehicle with Automatic Manual Transmissions (AMT)*

Recently, starting control takes an important role in the automatic manual transmission systems; clutch engagement control is the key of it. In order to improve the starting performance of AMT vehicle, clutch dynamic response must be control during the slipping phase. Therefore, this paper puts forward a control strategy for the dry clutch engagement process, considered as a finite time optimal control problem. The main idea of this strategy is to obtain a linear quadratic state feedback controller by solving the optimal control problem. The performance obtained with the proposed controller are compared with those achievable by means of a classical open loop control strategy. Moreover, different starting operating conditions are used to test the controller performance. Numerical simulations shows the good performance obtained by the proposed controller, which guarantees fast engagement, minimize the slip losses, reduce the fuel consumption and improve in the shift quality.

소프트 컴퓨팅에 의한 지능형 자동변속 시스템

결정된 변속선도에 의한 자동변속 패턴은 운전자에게 편리한 변속을 제공한다. 하지만, 운전자의 운전 성향이 개인마다 다양함으로 고정된 변속선도를 여러 운전자에게 동일하게 제공하늘 것은 불만의 요소로 인식되고 있다. 이에, 본 논문에서는 운전자의 성향을 결정할 수 있는 입력을 이용한 학습 모듈을 설계하여 운전 성향을 판단하고자 한다. 판단된 운전 성향을 이용하여 변속선도를 조정함으로써 운전자의 의지에 부합되는 변속패턴을 제공하고자 한다. 실제 주행시 얻은 데이터를 이용하여 제안된 모듈의 성능의 우수함을 보인다. An automatic transmission pattern with the fixed standard shift map can provide comfortable shift to driver. However it may be a complain to provide shift by the same shift pattern for driver because the inclination of a driver may be various. Therefore, in this paper, we design the decision module, which can decide the driving style using input to decide the inclination of the driver and driving manner. The goal of this paper is to calibrate the shift map according to the inclination of the driver using the decided driving manner from the proposed module. As a result, the proposed intelligent automatic transmission system can provide a suitable shift point and time to the driver. To verify the performance of the proposed system, the real data that is obtained from the road test will be used.

Analysis and simulation of clutch engagement judder and stick-slip in automotive powertrain systems

Clutch engagement judder and stick—slip are investigated analytically and numerically to examine the influencing factors on these phenomena. Models are developed for a four degree-of- freedom (4DOF) torsional system with slipping clutch and for a powertrain with automatic transmission system. Stability analysis is performed to demonstrate that clutch judder is dependent on the slope of the friction coefficient and the analysis is verified with numerical simulations. An algorithm for modelling stick—slip is developed and is used in numerical simulations which show that the likelihood of stick—slip is increased by clutch pressure fluctuations, judder approaching engagement, and external torque fluctuations. Numerical simulations for second to third gear up shifts demonstrate that the likelihood of stick—slip to occur from clutch engagement is increased by clutch applied pressure fluctuations, judder approaching engagement, and external torque fluctuations and that the likelihood of stick—slip occurring is decreased dramatically by applied pressure ramps proximus to the engagement point.

Data Compression in Single Board Computer Based Data Acquisition System

This paper presents a stand alone data acquisition system for in-vehicle use. It is designed in such a manner that the torque signals of an automatic transmission system shafts can be monitored over a long period of usage. Three data compression methods are compared; two predictive methods, namely zero-order and first-order predictors and a piece-wise linear approximation method, followed by run-length and Huffman coding. Several error bands under different road condition have been investigated. A data compression method based on LOT (Lapped Orthogonal Transform) with adaptive thresholding of the transform coefficients has also been proposed. Test results show that a system with 1 GB flash card can store over 10000hrs of drive shaft load history data.

Development of a Friction Component Model for Automotive Powertrain System Analysis and Shift Controller Design based on Parallel-Modulated Neural Networks

In this study, a new hybrid-neural-network-based friction component model is developed for powertrain (PT) dynamic analysis and controller design. This new model, with significantly improved input-output scalability over conventional neural network configuration, has the capability to serve as a forward as well as an inverse system model. The structural information of the available physical and empirical correlations is utilized to construct a parallel-modulated neural network (PMNN) architecture consisting of small parallel sub-networks reflecting specific mechanisms of the friction component engagement process. The PMNN friction component model isolates the contribution of engagement pressure on engagement torque while identifying the nonlinear characteristics of the pressure-torque correlation. Furthermore, it provides a simple torque formula that is scalable with respect to engagement pressure. The network is successfully trained, tested and analyzed, first using analytical data at the component level and then using experimental data measured in a transmission system. The PMNN friction component model, together with a comprehensive powertrain model, is implemented to simulate the shifting process of an automatic transmission (AT) system under various operating conditions. Simulation results demonstrate that the PMNN model can be effectively applied as a part of powertrain system model to accurately predict transmission shift dynamics. A pressure-profiling scheme using a quadratic polynomial pressure-torque relationship of the PMNN model is developed for transmission shift controller design. The results illustrate that the proposed pressure profiling technique can be applied to a wide range of operating conditions. This study demonstrates the potential of the PMNN architecture as a new dynamic system-modeling concept: It not only outperforms the conventional network modeling techniques in accuracy and numerical efficiency, but also provides a new tool for transmission controller design to improve shift quality.

Advanced hybrid neural network automotive friction component model for powertrain system dynamic analysis. Part 2: System simulation

In this research, the advanced hybrid neural network (AHNN) friction-component model, presented in Part 1 of this two-part paper, is integrated with an automotive drivetrain model for system simulations. The AHNN model accurately predicts the dynamic behaviours of transmission friction components over a broad operating range. It also allows variable sampling time steps in a numerical integration process. In this investigation, the AHNN model is trained using experimental data obtained from a powertrain dynamometer test stand. Since typical dynamometer measurements are acquired at locations away from friction components, a backtracking algorithm is developed to evaluate friction component torque during engagement. The trained AHNN model, together with a comprehensive drivetrain model, is implemented to simulate the shifting process of an automatic transmission system under various operating conditions, including different oil-temperature and engine-throttle levels. Simulation results demonstrate that the AHNN friction component model can be effectively utilized as a part of the drivetrain model to accurately predict transmission shift dynamics.

Development of capacitor hybrid truck

Nissan Diesel Motor has developed a capacitor hybrid medium-duty truck. This vehicle involves a new power-train technology which makes for high efficiency and low emission with the basic technology being a high performance capacitor type storage device. The newly developed capacitor has an energy density that is twice as great as commercial ultracapacitors. The simple parallel hybrid system of this vehicle was composed of this capacitor, a single motor, a conventional diesel engine and a mechanical automatic transmission system. Fuel economy about 1.5 times greater than that of a conventional diesel truck is achieved. Furthermore, the TLEV level of exhaust emissions is also achieved.

Application of dynamic band brake model for enhanced drivetrain simulation

In a modern vehicle design process, analytical tools are widely employed to complement experimental approaches for design evaluation. When effectively utilized, they lead to a reduced development time with improved vehicle performance. The development process of an automatic transmission (AT) system can benefit from an analytical representation which accurately captures AT shifting behaviours. In a typical AT system, friction components such as wet clutches and band brakes are utilized to alter planetary gear configurations for automatic shifting. Thus, an accurate representation of friction component dynamics is critical in predicting AT shifting behaviour. Engagement characteristics of friction components vary widely under different operating conditions. Although the basic engagement physics was identified in the 1970s, it is relatively recently that a predictive, yet computationally efficient model became available. This paper describes the first attempt to utilize a dynamic friction component model in drivetrain simulations. Specifically, a dynamic band brake model is implemented to predict the up-shift behaviour of a four-speed AT system under various operating conditions. Simulation results are qualitatively validated with experimental data obtained from a dynamometer test stand. The dynamic band brake model enhances the shift predictability of a drivetrain model and potentially allows analytical evaluation of shift quality and control strategy.

Modelling of dynamic characteristics of an automatic transmission during shift changes

This paper describes modelling of the transient dynamics of an automatic transmission during gear changes. A brief introduction to the automatic transmission system and the dynamic characteristics of the transmission components during the gear changes are presented. Then, detailed mathematical models of a four-speed automatic transmission manufactured by BTR Automotive, Australia, are developed. A mode description method is used to describe the transient shifting process and a modular structure of the transmission system, which consists of a torque converter module, geartrain module, hydraulic system module and modules of clutches and bands, is presented. As an application, the developed simulation system is applied to investigate the transient performance of the automatic transmission during the 1–2 shift process. The output torque profiles predicted by the model simulation correlate very well with the experimental data measured from vehicle tests.

223 多目的関数最適化による歯車諸元決定方法の研究

In the design of a transmission system, there is an object to choose the optimal specifications from the design requirements which conflict each other and various conditions such as transmitted power, rotational speed, reduction ratio, etc. Conventional design usually based on the experiment of designers and round robin calculations. There was a problem of the skill of a designer, or it takes much time to complete the design. In this study, new approach for automatic transmission system design tool was proposed. The multi-objective optimizing method based on the simplex algorithm was developed to reduce design cost and to improve design quality.

Optimal Control of Automatic Transmission

An optimal control concept is proposed regarding gear shift operations of automatic transmission systems being part of a complete power train. The optimization is carried through by a dynamic programming approach with a performance measure including passenger comfort and control expenditure. The gear synchronization appears as a constraint at the end of the process. A control law is derived analytically by minimizing the performance measure over each process stage. Simulation results show a significant improvement in terms of gear shift comfort for different driving load cases. Furthermore the shift time and the frictional losses in the shift elements can be reduced by applying the proposed control.

Prediction of wet band brake dynamic engagement behaviour Part 2: Experimental model validation

A wet (oil-lubricated) band brake in a vehicle automatic transmission system exhibits widely varying engagement behaviour under different operating conditions. In recent years, analytical evaluation of the band engagement behaviour has become increasingly important to improve automatic transmission shift quality. Thus, a mathematical tool which accurately captures band engagement physics is indispensable in a transmission design process. This paper describes experimental validation of the dynamic band engagement model which includes the physics of squeeze film, asperity deformation, porous oil diffusion, heat transfer and loading pressure distribution caused by a selfenergizing mechanism. The model is implemented as a stand-alone computer program to predict the band engagement behaviour on an inertia absorption type band engagement test stand. Simulation results show good agreement with experimental torque profiles over a wide range of operating conditions. The model provides an analytical interpretation of the widely varying engagement behaviour resulting from the effects of oil temperature, friction material permeability and drum speed. The successful model validation demonstrates that the dynamic band engagement model serves as a valuable tool to assist band design and shift calibration processes of automatic transmission systems.

Prediction of wet band brake dynamic engagement behaviour Part 1: Mathematical model development

A wet (oil-lubricated) band brake is a critical component in the operation of automatic transmission systems in automotive applications. Its engagement characteristics significantly affect the quality of automatic shifting. During the automatic transmission design process, it is important to characterize band engagement behaviour accurately under a wide range of operating conditions. This paper describes a mathematical model which predicts the dynamic engagement behaviour of the wet band brake. The space-time-dependent model includes the effects of squeeze film, asperity deformation, porous oil diffusion, heat transfer and loading pressure distribution caused by a self-energizing mechanism. The model can be readily implemented and efficiently executed on a computer as a standalone program or as a subroutine for automatic transmission shift simulations. Knowledge of band engagement obtained through the model is expected to lead to improved band design and automatic transmission shift calibration processes.

A Robust Control for Engine and Transmission Systems: Enhancement of Shift Quality.

In this paper, a robust integrated control for engine and automatic transmission systems is investigated. The modeling of powertrain system is split into five subparts including an engine, a torque converter, an automatic transmission, clutch torque generation, and a drivetrain. For improving the ride quality, a two-stage control strategy, torque phase and inertia phase, is proposed. During the torque phase, the slip in first gear is maintained to near zero, while the reaction carrier speed and turbine speed during the inertia phase are controlled to track their desired speeds. The reaction carrier speed is adjusted by the second clutch torque, and the turbine speed is controlled by engine throttle angle and spark advance. Due to the uncertainty and unmodelled dynamics of the system, the uniform ultimate boundedness of the error signals is assured by applying the Lyapunov stability analysis. Simulation results are provided.