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Feedback Control of Synchronizers for Reducing Impacts during Sleeve to Gear Engagement

CEVT China Euro Vehicle Technology-Johan Hellsing
Chalmers University of Technology-Muddassar Zahid Piracha, Anders Grauers
  • Technical Paper
  • 2020-01-0960
To be published on 2020-04-14 by SAE International in United States
This paper presents a feedback control strategy aimed to reduce noise and wear during gearshifts in conventional and hybrid Dual Clutch Transmissions (DCT and DCTH) and Automated Manual Transmissions (AMT). The control strategy is based on a new dog teeth position sensor developed by China Euro Vehicle Technology AB and existing speed sensors in the transmission. During gear shifting, noise is generated by impacts between the sleeve teeth and the idler gear dog teeth after speed synchronization. Besides noise, these impacts are also responsible for delaying the completion of shift and contribute to wear in the dog teeth, hence reducing the lifespan of the transmission. The presented control strategy controls speed synchronization such that the impact between sleeve and idler gear dog teeth, before the start of torque ramp up, is avoided. Since drag torque is an important factor in speed synchronization, this paper also contains an algorithm to identify friction torque coefficient in the transmission. The identification method ensures that the controller adapts to varying conditions without the need for offline calibration. The control…
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Validation of Road-Preview-Based Predictive Gear Selection on Heavy-Duty Vehicle Transmission Control Unit

AVL-Zhen Zhang, Bernhard Knauder, Martin Ackerl, Johannes Pell
  • Technical Paper
  • 2020-01-0962
To be published on 2020-04-14 by SAE International in United States
The eHorizon unit enables the possibility, to get information of the road ahead in a defined prediction horizon. This data, like road gradient, curve radius, velocity limitation and road class, can be used by the on-board transmission control unit (TCU) via Controller Area Network (CAN) bus. This obtained predictive road information combined with the actual driving conditions are used to optimize the shifting strategy by a nonlinear model predictive control (NMPC) algorithm which intends to reduce the fuel consumption. The optimization problem in the PGS strategy is solved by a nonlinear optimization based dynamic programming. In this paper, the predictive gear selection (PGS) strategy will be compared to a conventional automatic gear shifting strategy in a simulation environment and validated on road by implementing it a heavy-duty truck with a 16-speed automated manual transmission (AMT). At last, this strategy consumes in total around 20kb RAM which can be handled by modern SOP TCU.
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A Gear Shifting Indication Strategy of Eco-driving Vehicle

Jiangsu University-Nannan Hu
Jiangsu University-Ren He
  • Technical Paper
  • 2020-01-0966
To be published on 2020-04-14 by SAE International in United States
The current indication strategy of gear shifting indication system for manual transmission vehicles is developed based on the gear shifting strategy of the automatic transmission. In this paper, the driving data of several automatic transmission and manual transmission vehicles are collected. It is found that the shifting frequency of automatic transmission vehicles is significantly higher than that of manual transmission vehicles, which increases the fatigue of drivers. Aiming at this problem, an interval algorithm of gear shifting indication strategy is proposed based on the fuel consumption rate of engine in this paper. The strategy uses genetic algorithm to process the data of fuel consumption rate, finding the maximum and minimum values in the interval of torque and engine speed, and then the interval algorithm is adopted to transform the search of least fuel consumption value into the seeking of optimal interval to avoid the shifting busyness caused by the sudden change of the data of fuel consumption rate. The model of gear shifting indication strategy is established in Matlab/Simulink. Gear shifting tolerance is defined and…
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A Study on the Development of the CPA (Centrifugal Pendulum Absorber)Reducing the Rattle & Booming Noise in the Manual Transmission Vehicle

Ukjin Kim
  • Technical Paper
  • 2020-01-0397
To be published on 2020-04-14 by SAE International in United States
In recent years, the automotive engine strategies are forced on downsizing and down speeding to enhance fuel economy and reduce the emission. These make torque increase significantly in order to improve the vehicle performance, especially in diesel engines. At this time, the torsional damper performs the most important role in the driveline NVH of the manual transmission system. The clutch disk with torsional dampers is not easy to be applicable to the high torque of low speed RPM range. And DMF with sufficient isolation of vibrations of driving system includes disadvantages of the expensive cost, delayed response, and engine NVH aspect deteriorated due to increase of angular acceleration of engine. This paper presents that the Centrifugal Pendulum Absorber (CPA) is applied to maximize the isolation and to compensate for the disadvantages of DMF and SMF system. Furthermore, CPA was developed for the first time in the world on SMF clutch discs in manual transmission.
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A unique approach to optimize the gear-shift map of a compact SUV to improve fuel economy and performance

Mahindra & Mahindra, Ltd.-Sangeetha RT, Vignesh Shankar, Anshuman Bose, Bharatraj Jayaraman
  • Technical Paper
  • 2020-01-0969
To be published on 2020-04-14 by SAE International in United States
Automated manual transmission (AMT) is often preferred by the car manufacturers as an entry-level automation technology. The AMT technology can provide the comfort of an automatic gearbox at a reasonable cost impact over the manual transmission (MT). This paper explains the unique approach to define the gear-shift map of a compact sports utility vehicle (SUV) considering the unique requirements of the Indian market. The real-world measurements revealed that an aggressive shift pattern with delayed upshift and quick downshift can deliver a good low-end drivability and performance while compromising on fuel economy. Moreover, the chassis dyno measurements in the modified Indian drive cycle (MIDC) indicated lower fuel economy values. On the other hand, a shift pattern with early upshifts and delayed downshifts could help in achieving a better fuel economy while compromising on drivability and performance. Hence, a unique approach is used to derive the most optimal gear shift map for each operating gear. Gear-shift points of actual vehicle were measured in real-world operating conditions in a reference vehicle under different operating conditions (traffic, user, road)…
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Statistical Model for the Prediction of Shift Points for Manual Motorcycles

U.S. Environmental Protection Agency-Peter James Caffrey
  • Technical Paper
  • 2020-01-1046
To be published on 2020-04-14 by SAE International in United States
Emissions from manual transmission motorcycles have been shown to be dependent upon transmission shift patterns. Presently, when undergoing an emission test for EPA certification a manufacturer can designate their own shift points during the cycle or utilize an Environmental Protection Agency (EPA) prescribed shift pattern which uses basic up or down shifts at specific speeds regardless of the type of motorcycle. In order to predict the real-life emissions from motorcycles, a comparative real-life shift pattern has been developed which can then be used to evaluate the suitability of the manufacturer’s shift schedule. To that end, a model that predicts shift points for motorcycles has been created. This model is based on the actual operation of different motorcycles by real life operators in a combined city and highway operational setting. Recognizing that no model is sufficient to adequately predict user operation in all situations, this model maintains a degree of flexibility in allowing the user to designate various limits to the shift probability, thus representing various rider scenarios. This would include a broad range of probability…
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Design and Implementation of a Sequential Manual Gearbox in a Baja SAE Vehicle

Kettering University-Eric Stuckey, Arnaldo Mazzei, Jennifer Bastiaan, Gregory Davis
  • Technical Paper
  • 2020-01-0428
To be published on 2020-04-14 by SAE International in United States
Baja SAE is one of the SAE International Collegiate Design Series (CDS) competitions focused on the design of off-road vehicles by teams of engineering students from participating educational institutions. It is a well-established series that is currently in need of a new transmission with greater mechanical efficiency, to take full advantage of the low power of the Briggs & Stratton spec engine that is mandated by the rules. Powertrain designs utilizing a Continuously Variable Transmission (CVT) have become the standard, primarily because of their ease of use in the vehicle assembly process and their simplicity of operation. With no need for manual shifting of the transmission, any student can navigate the vehicle through a competition course. Conversely, the tuning of a CVT is complex, and durability is poor, especially under the often wet and dirty conditions of the Baja SAE series. While there are a few teams using manual transmissions, these designs are typically heavier, less efficient, and prone to failure due to poor implementation. In this work, a Sequential Manual Gearbox (SMG) is investigated…
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Two-Speed Transmission Gear Shift Process Analysis and Optimization Using Genetic Algorithm

SAE International Journal of Alternative Powertrains

China Automotive Technology and Research Center Co., Ltd., China-Zhan Cao, Jiansen Yang, Xinyu Wang
  • Journal Article
  • 08-09-01-0001
Published 2020-01-16 by SAE International in United States
Electric Vehicle (EV) equipped with two-speed transmission has benefit in improving dynamic performance and saving battery consumption. However, during gear shift process, torque interruption and shift impact may lead to a bad shift quality. This work investigates gear shift process in an Automated Manual Transmission (AMT) configuration-based two-speed transmission. First of all, a typical gear shift process is analyzed. Parameters like motor speed, shift force, motor torque change rate, and speed difference between synchronizer and target engage gear are all included to find the relationships with shift duration. Then vehicle jerk is introduced as a criterion to evaluate shift impact. Besides, a comprehensive shift control strategy is developed. While keeping the output torque at wheels unchanged, the shift strategy also improved motor working efficiency after gear shift. Therefore, to determine an optimum shift strategy and achieve a balance among different parameters, Genetic Algorithm (GA) multi-objective optimization method is implemented. Through GA optimization, several solutions are presented and discussed. The final results can well satisfy the requirements of different objectives. This work provides a novel and…
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Dynamic modeling and simulation of a powertrain system with a six-speed automatic transmission

Schaeffler Brasil Ltda.-Marcel T. da S. de Araujo, Murilo F. Falleiros, Gustavo dos S. Gioria
  • Technical Paper
  • 2019-36-0100
Published 2020-01-13 by SAE International in United States
The constant growth of the automotive market demands for comfort to the user and energy efficiency have caused the intensification of the industry researches and development of the automatic transmissions (AT). However, vehicles equipped with these gearboxes entails in higher fuel consumption levels than the one required by vehicles equipped with manual transmission. In the automotive industry due to the advantages offered using computer simulations, such as fast evaluation an optimization, many researchers are using virtual models for optimization of dynamic behavior of systems and fuel consumption. Aiming to study the dynamic behavior of an AT and the influence of its components on that behavior, this paper presents an AT dynamic model developed in MATLAB® / Simulink®. The AT model has three main subsystems: a torque converter model, which includes the dynamic of both the forward flow mode and the reverse flow mode; a Lepelletier gearbox model, composed by a set of three planetary gearsets in parallel, resulting in a six forward speeds gearbox; and a gear-shift schedule, which has the vehicle speed and accelerator…
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Inside Tremec's SUPERCAR DCT

Automotive Engineering: January/February 2020

Don Sherman
  • Magazine Article
  • 20AUTP02_04
Published 2020-01-01 by SAE International in United States

To polish the 2020 mid-engine Corvette's driving prowess, GM and Tremec engineers joined forces to create a new and better automated transaxle.

Explaining Corvette's move to one transmission for all buyers, global chief engineer Tadge Juechter notes, “Our customers began requesting a dual-clutch automatic transmission [DCT] several years ago. Following the introduction of the C7 Corvette in 2014, our take-rate for sticks [manual gearboxes] fell from 50 percent to less than 20 percent this year.” Searching the globe - read Europe - for a suitable DCT, Juechter's team found none with sufficient torque capacity to survive behind the lively LT2 6.2-L V8 planned for the all-new 2020 mid-engine edition of GM's reimagined sports car.

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