Jan 17, 2013 - In a wide range of scenarios, we found that animals are crucial for maintenance in the. We use a mathematical model of gambiense HAT transmission to. Welburn SC, Picozzi K, Fvre EM, Coleman PG, Odiit M, et al. Infect Genet Evol 10: 115–121. (2009) GNU Scientific Library Reference Manual.
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Abstract Dry dual clutches are widely used in automated manual transmissions. In such systems the clutch engagement maneuvers require a precise knowledge of the characteristics that relate the frictional torque transmitted by the clutches with the corresponding actuators variables. In this paper a temperature and slip speed dependent model of the torque characteristic for dry dual clutches is proposed. Dynamic models of the temperature evolution are determined and linked to the characteristics of the mechanical components influencing the torque. The models, whose parameters are tuned with dedicated experiments and realistic data coming from an industrial automotive environment, show the temperature influence on the torque transmitted by the clutch.
Real time simulation results, obtained through a detailed software in the loop driveline model, show that, if not compensated, the temperature variation can determine critical degradations of the clutch engagement performances. It is shown how the use of the clutch temperature estimation in the torque transmissibility model allows to compensate for such negative effects. The torque model is also exploited for the realization of a decoupling clutch engagement controller. The corresponding closed loop results show the effectiveness of the proposed compensations for the dependencies of the clutch torque on temperature and slip speed. Automated manual transmissions with dry dual clutches are wide spreading thanks to their capability to combine high efficiency and comfort. In order to obtain smooth and fast gearshifts it is fundamental to have an accurate knowledge of the torque transmitted by the clutch during the engagements. Unfortunately, it is quite difficult to provide an on-board measurement of this torque and then the use of torque estimators is the typical solution adopted in practice, for both dry and wet clutches ,.
Several phenomena and components influence the torque in a dry dual clutch transmission (DDCT), such as friction, transmission kinematics , friction facing wear and diaphragm spring fatigue , pressure and, overall, temperature and slip speed between the clutch disk and the flywheel. Some models proposed in the literature are based on the inversion of the driveline dynamic model , , but the robustness of this solution depends on the availability of the system parameters and on clutch disk acceleration and engine torque measurements. In any case, the engagement controllers are typically equipped with a characteristic that describes the friction phenomena by providing the torque transmitted by the clutch as a function of the throwout bearing force or the throwout bearing position ,. The influence of the temperature on the clutch torque characteristic has been considered in the literature. In it is shown how the temperature affects the torque through the variations of the so called Incipient Sliding Point (ISP), also called kiss point. In the authors investigated the temperature distributions in automotive dry clutch during single and repeated engagements under two different hypotheses: uniform pressure and uniform wear. In , under the assumptions that the friction coefficient is uniform along the whole contact surface, the clutch torque is assumed to be a function of the product between the friction coefficient and the clamping (or contact) force.
In these papers, the temperature influence on the two functions is separately considered: the temperature influence on the friction is modeled by using experimental data from while, in order to model the temperature influence on the contact force, a finite element analysis is used. Indeed, finite element analysis is considered by several authors in order to study the temperature distributions in transmissions which include dry clutches. In it is investigated how the flywheel and friction facings temperature distributions change during the engagement. The friction facings temperature distribution is also dependent on the grooves shape , and in it is shown that the thermal proprieties are also affected by some manufacturing process parameters.
The temperature distributions are usually assumed to be uniform and average temperatures are considered in order to determine the torque characteristic ,. Since the clutch torque is only controllable through the proper position of the actuator driven throwout bearing, it is fundamental to have an accurate model of the clutch torque characteristic in order to design effective clutch shift and vehicle launch controllers.
This point is highlighted in the literature from different perspectives and strategies dedicated to dry clutches: to improve the actuator technology , , for torque limitations during the engagements , for gearshift and sliding mode controllers , for the use of multivariable control strategies , for real-time estimation and simulation. The clutch torque characteristic, which relates the actuator position to the transmitted torque, is widely used in the clutch engagement controllers because it can be considered as an add-on solution with respect to the classical engagement controllers currently used for automated manual transmissions and also, as a feedforward component, to solutions which adopts clutch torque observers based on the driveline model. In this paper a new dry clutch torque model which includes the temperature and slip speed influences is presented.
The typical dry clutch system and its configuration will be recalled. The proposed model of the clutch torque as a function of the actuator position is presented in Sect. And its influence on the slip speed and temperature is explicitly analyzed.
Two dynamic thermal models of the DDCT are determined and linked to the torque characteristic. The thermal models are forced by the power dissipated due to friction. The parameters of the torque and thermal models are tuned by using experimental data. A decoupling engagement controller which exploits the proposed torque model is presented. The engagement performances are tested by using a software in the loop real time platform. All results are obtained by considering a realistic DDCT powertrain model by Fiat Chrysler Automobiles (FCA); the quantitative values of the variables reported throughout the paper are not indicated because of confidentiality reasons. The results reported in Sect.
Demonstrate the effectiveness of the proposed dual clutch torque model to compensate the effects of current temperature and slip speed. Finally, Sect. Concludes the paper.
Clutch Engagement System. (17c) where ( ) and ( ) are obtained from direct substitution in ( ) and ( ), respectively, and ( ) is obtained by adding ( ), ( ) and ( ) and by introducing a new notation for the model constants with respect to ( ) because of the simplifying assumption introduced. Parameters Tuning The data used for the identification and the validation of ( ) and ( ) have been achieved by means of a temperature acquiring system in the framework of the experiments described in Sect. For the simplified model ( ), the body temperature is considered equal to the average of the two pressure plates and the central disk temperatures. The parameters corresponding to the convective terms of the two models have been obtained by formulating corresponding least squares problems.
These problems use a data-set obtained by bringing the clutch at high operating temperatures and then by leaving the temperature to decrease with a free evolution and by analyzing the transmission thermal behavior with both clutches open. Because of the symmetry of the dry dual clutch system, the data used for the convective heat transfer parameters identifications, which correspond to the even gearbox ratios, are used also for the odd ratios. The other model parameters are obtained by using a genetic algorithm applied to a second data-set, which is the same set used for the parameterization of the torque models. A third data-set is used to validate the parameters. The validation results are shown in Figs.
In particular the body temperature reported in Fig. Is obtained by averaging the measured temperatures of the pressure plates and central disk. These figures show a good capability of the two models to reproduce the real system behavior. The model ( ) has a slight different behavior compared to the real system, in the open clutch state (the second part of the acquisition shown in the figures). This can be explained with an unsymmetrical thermal behavior of the real system or it could be due to the larger number of model parameters of ( ) compared to those of ( ) that it seems unaffected by the problem. A third cause could be the influence of the conductive flux between the clutches and their support. A further result is that for both models the variation of the clutch temperature increases at higher temperatures, which is justified by the corresponding larger torques predicted by the proposed clutch torque model.