System Design and Control Considerations of Automotive Continuously Variable Transmissions

Chan, Calvin M. L.; Yang, Dan; Volz, Thorsten; Breitweiser, D.; Jamzadeh, Fereidoon S.; Frank, Andrew A.; Omitsu, T.

doi:10.4271/840048

Cited by 24 publications

(19 citation statements)

References 2 publications

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“…They are used in very demanding applications, which require high torque transmission. Power-split transmissions are appealing since they provide a good compromise between traditional mechanical transmissions (highly efficient but discontinuous) and standard CVTs without torque-split widely used for automotive applications ( [2], [4], [6], [12], [13], [14]), which are very smooth but characterized by modest efficiency and unsuited to deliver high torque. The final goal of a CVT in an agricultural tractor is to track the required transmission-ratio -defined as the ratio between output and input rotational speeds, namely τ = ω out /ω in -in a very smooth and regular way.…”

Section: Introductionmentioning

confidence: 99%

On Transmission-Ratio Computation for the Control of a Continously Variable Transmission in Agricultural Tractors

Tanelli

Codecà

Savaresi

et al. 2007

2007 American Control Conference

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This paper discusses the design of the transmission-ratio control for a power-split continuously variable transmission (CVT) used in agricultural tractors. In particular, we focus on transmission ratio control, highlighting the issues related to the computation of the controlled variable in presence of significant sensor quantization errors, which are particularly significant in the Power-Zero condition, where the tractor has to be kept still independently of the input engine speed . The validity of the design procedure is assessed on an experimental system.

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Section: Introductionmentioning

confidence: 99%

On Transmission-Ratio Computation for the Control of a Continously Variable Transmission in Agricultural Tractors

Tanelli

Codecà

Savaresi

et al. 2007

2007 American Control Conference

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“…In this integrated powertrain control [4], [24], [33], [46], [49], the stationary operating points lie on the optimal operating line (OOL), being the set of operating points in which a required power at the wheels is delivered with minimal fuel consumption. 1 The OOL will not completely coincide with the E-line. This is trivial for powertrains with a stepped transmission [17], [40], but is true also for powertrains with a continuously variable transmission (CVT) because the ratio coverage of current CVTs is fairly limited [24], [35].…”

mentioning

confidence: 99%

“…The CVT and throttle controllers [1], [7], [11], [21], [35], [45], [49], aim to operate the engine in stationary situations in points on or close to the OOL. In general, the engine speed in these points is low (large CVT ratio) and the engine torque is high (large throttle opening), meaning that the power reserve (the difference between the power in the chosen operating point and the power at the same engine speed with a wide open throttle) is small.…”

mentioning

confidence: 99%

“…However, a further, fast increase is possible only if the engine is speeded up quickly by a fast downshift of the CVT [41]. If is too small to realize the enforced large engine acceleration, power will be withdrawn from the vehicle to accelerate the engine [11], [24], [26], [27], [35], [41] and the vehicle will decelerate, whereas the driver clearly wants an acceleration [1], [7], [11], [24]. This inverse behavior can be avoided by a (much) slower downshift of the CVT.…”

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confidence: 99%

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Analysis and Control of a Flywheel Hybrid Vehicular Powertrain

Shen

Veldpaus

2004

IEEE Trans. Contr. Syst. Technol.

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Abstract-Vehicular powertrains with an internal combustion engine, an electronic throttle valve, and a continuously variable transmission (CVT) offer much freedom in controlling the engine speed and torque. This can be used to improve fuel economy by operating the engine in fuel-optimal operating points. The main drawbacks of this approach are the low driveability and, possibly, an inverse response of the vehicle acceleration after a kick-down of the drive pedal. This paper analyzes a concept for a novel powertrain with an additional flywheel. The flywheel plays a part only in transient situations by (partly) compensating the engine inertia, making it possible to optimize fuel economy in stationary situations without loosing driveability in transients. Two control strategies are discussed. The first one focuses on the engine and combines feedback linearization with proportional control of the CVT ratio. The CVT controller has to be combined with an engine torque controller. Three possibilities for this controller are discussed. In the second strategy, focusing on control of the vehicle speed, a bifurcation occurs whenever a downshift of the CVT to the minimum ratio is demanded. Some methods to overcome this problem are introduced. All controllers are designed, using a simple model of the powertrain.

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“…The study of CVT control technology is mainly focused on the speed ratio control to increase the engine's output torque and decrease it's fuel consumption, through controlling engine speed according to the engine power or economy operation line, and how to achieve the target operating condition instantaneously. [1][2] [3] From the research available, the main study focuses are on the analysis of control strategy, and different control strategies adopted for different working conditions. Because of the complex working conditions encountered in vehicle operation, the control strategies research on CVT speed ratio when cornering is very rare.…”

mentioning

confidence: 99%

The CVT's Speed Ratio Control Research When the Vehicle Bending at High Speed

Yang¹

2018

Proceedings of the 2017 2nd International Conference on Electrical, Control and Automation Engineering (ECAE 2017)

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Abstract-When the speed ratio of the vehicle equipped with CVT changes rapidly, the acceleration of the vehicle will change synchronously, that means to exert an extra force on the driving tires. Using this feature, the desired results can be obtained in certain specific conditions, such as vehicle cornering at high speed. The models of multi DOF vehicle and CVT transmission were established to study the rapid changes in the turning process of the vehicle through the CVT ratio control. This paper introduces a method based on safety factor of CVT speed ratio control strategy. The simulation results show that if the driver fails to effectively reduce vehicle speed during high-speed cornering. As the speed ratio of CVT increasing rapidly, and the backward force can be acquired on the driving wheel, so that the vehicle can keep straight in a short time while reducing vehicle speed. The results of this paper can achieve better control results if the engine fuel injection control is combined.

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System Design and Control Considerations of Automotive Continuously Variable Transmissions

Cited by 24 publications

References 2 publications

On Transmission-Ratio Computation for the Control of a Continously Variable Transmission in Agricultural Tractors

On Transmission-Ratio Computation for the Control of a Continously Variable Transmission in Agricultural Tractors

Analysis and Control of a Flywheel Hybrid Vehicular Powertrain

The CVT's Speed Ratio Control Research When the Vehicle Bending at High Speed

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