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关键词： Clutch engagement   Slip engagement   Clutch control   Powertrain control   Reference slip speed   Reference clutch torque  

摘要： Recently, as vehicles are getting more intelligent, interest in improving vehicle ride comfort has been increasing. Appropriate control of a clutch in the vehicle powertrain can play a major role in improving the vehicle ride comfort. Previously, many researches on tracking controllers of clutch slip speed and clutch transmitted torque in clutch slip engagement control have been conducted. However, little research on an optimization method of the reference clutch slip speed and clutch torque has been performed. Therefore, in this study, the optimization method of the reference clutch slip speed in clutch slip engagement in the vehicle powertrain is proposed to improve clutch lifespan and vehicle ride comfort. The proposed method is verified through clutch slip engagement simulations using AMESIM and MATLAB Simulink.

关键词： egg transport   fecundity trade-offs   male parental care -sex role reversal  

摘要： Parental care is widespread across the animal kingdom. Parental behaviours are beneficial by increasing offspring survival but induce significant costs to the parents. Because parental care is far more common in females, the associated reproductive costs have been largely studied in this sex. Although male parental care is likely to involve significant costs, it has been markedly less well investigated. We studied the costs of egg-carrying on locomotor performance in an amphibian species (Alytes obstetricans) with male parental care. We examined complementary parameters including hopping performance, righting response, hindleg muscle response to egg burden, and homing time in males carrying or not carrying eggs. We found that carrying males showed altered locomotor performance for most traits. In addition, alteration of performance was closely related to relative clutch size. Clutch desertion occurred in smaller individuals carrying larger relative clutch mass, and performance after desertion was similar to that of non-reproductive individuals. Overall, our study demonstrates that carrying eggs significantly alters male mobility and that performance-clutch size trade-offs are relevant in understanding the evolution of paternal care.

关键词： Stators  

摘要： The volumetric defocusing particle tracking velocimetry (DPTV) approach is applied to measure the flow in the sub-millimeter gap between the disks of a radially grooved open wet clutch. It is shown that DPTV is capable of determining the in-plane velocities with a spatial resolution of 12 mu m along the optical axis, which is sufficient to capture the complex and small flow structures in the miniature clutch grooves. A Couette-like velocity profile is identified at sufficient distance from the grooves. Moreover, the evaluation of the volumetric flow information in the rotor-fixed frame of reference uncovers a vortical structure inside the groove, which resembles a cavity roller. This vortex is found to extend well into the gap, such that the gap flow is displaced towards the smooth stator wall. Hence, the wall shear stress at the stator significantly increases in the groove region by up to 15% as compared to the ideal linear velocity profile. Midway between the grooves, the wall shear stress is around 4% lower than the linear reference. Furthermore, significant amounts of positive radial fluxes are identified inside the groove of the rotor;their counterpart are negative fluxes in the smooth part of the gap. The interaction of the roller in the groove and the resulting manipulation of the velocity profile has a strong impact on the wall shear stress and therefore on the drag torque production. In summary, this DPTV study demonstrates the applicability of such particle imaging approaches to achieve new insights into physical mechanisms of sub-millimeter gap flow scenarios in technical applications. These results help to bring the design- and performance-optimization processes of such devices to a new level.

关键词： internam model control   decoupling   robust   clutch engagement  

摘要： Research on the robustness of clutch engagement control is attracting considerable interest because of its wide applications in advanced powertrains. Internal model control (IMC) is advantageous because it can handle model errors and external disturbances with light computational loads. However, during clutch engagement, two control inputs (engine output torque and clutch transmitted torque) and two system outputs (driving speed and the driven part of the clutch) are coupled;moreover, the two reference inputs are considerably different. A method for directly decoupling and stabilizing multi-input multi-output systems controlled by a two-degree-of-freedom (2DOF) IMC is proposed based on the construction of V-canonical matrices. The proposed method allows simple expressions for the control algorithm to be obtained without computing an inverse matrix that is used conventionally. Two filters, considering both the reference inputs and system characteristics, are independently designed considering the decoupling operation. The simulation results show that the proposed decoupling 2DOF IMC gains a considerably less tracking error and better robustness to model error and disturbance compared to classical 2DOF IMC and model predictive control. The performance is validated via dynamometer experiments.

关键词： Sprag clutch   wedge   wear   temperature   experimental design   lubrication   abrasion test  

摘要： A formula is proposed based on Archard's wear model to calculate wedge wear depth in a positive continuous engagement (PCE)-type sprag clutch with double-disc inner cam wedge in the overrun state. Methods to solve for the equation parameters are proposed. Using a sprag clutch with an M50 steel wedge as an example, wedge wear depth variation over time under high temperatures was analyzed. An easy-to-clamp wedge was designed and a high-temperature abrasion testing machine was used to test the wedge. The worn surface profile was observed using a three-dimensional profiler and the wedge wear depth was obtained. The effects of lubrication, temperature and speed on wear were analyzed using mixed-level orthogonal experimental design. Results show that the theoretical values are consistent with test values. Therefore, the model can be used to calculate wear accurately for the overrunning sprag clutch. Lubrication affects wear depth significantly, whereas temperature has a smaller effect and speed has very little influence. Within the experimental scope, when the temperature increased by 1 degrees C, the wear depth increased by approximately 0.0145 mu m and when the speed increased by approximately 1 time/minute, the wear depth increased by 0.00854 mu m. These results provide theoretical support for optimal sprag clutch design.

关键词： Start-up judder   powertrain branched model   Stribeck effect   positive-feedback closed loop   mechanism-oriented control  

摘要： In this paper, a mechanism-oriented control strategy is proposed to cut off the introduction process of negative damping caused by the Stribeck effect for suppressing the vehicle start-up judder. From the experimental analysis, the characteristic frequency of start-up judder is mainly concentrated at about 8.25 Hz, coinciding with the first-order natural frequency of the driveline system. A 13-degree-of-freedom powertrain branched model is established, whose validity and accuracy in reflecting the characteristics of start-up judder are verified by comparing with the experimental results in time-frequency domain. The start-up judder mechanism is profoundly revealed through explaining the introduction of negative damping and the origin of characteristic frequency. The positive-feedback closed loop caused by the negative gradient characteristic of the Stribeck effect is the determining factor that promotes the aggravation of the fluctuation in the rotational speed of clutch-driven plate, which is the manifestation of the negative damping. The core idea of the mechanism-oriented control strategy is to cut off the positive-feedback closed loop, which is achieved by fine-tuning the position of release bearing. The judder-suppression performance behaves well both in simulation and in experiment.

关键词： Friction  

摘要： The torque transfer capability as well as long-term endurance are essential for wet multi-plate clutches. The quality of the torque transmission process largely depends on the tribological system consisting of friction pairing, lubricant and applied loads. The requirements on friction linings in wet multi-plate clutches increase continuously due to stricter CO2 reduction regulations and the demand of higher power densities. There is a lack of published data and information about the friction behavior of modern Carbon friction linings in wet multi-plate clutch applications, although these friction materials have successfully proven their performance capabilities over the last two decades in synchronizers. Therefore, this article presents results from experimental studies on the friction behavior of innovative Carbon friction linings carried out on a component test rig. Friction screening tests were performed with Carbon-fiber reinforced plastic (CFRP) and Carbon-fiber reinforced Carbon (C/C) linings in brake and constant slip operation. Furthermore, our research included long-term tests with different lubricants (engine/marine/tractor oil). Results show that modern Carbon friction linings can offer advantages over other materials. In the friction screening (brake and constant slip operations) and long-term tests, the torque transfer capability of both friction linings is very stable, even at high specific loads-sliding velocities near 30 m/s and axial pressures of 2.5 MPa. Influences of sliding velocity, pressure and lubricant on the friction performance are presented. Furthermore, the gradient of the Coefficient of Friction (CoF) curve usually decreases at the end of the engagement to enable good control and shift comfort.

关键词： AGE rich diet   Diabetes   Exercise   Herbal drug   Nrf2-keep pathway   Stress oxidative  

摘要： Background: SPTC is a mix of four herbal components (Salvia officinalis, Panax ginseng, Trigonella foenum-graeceum, and Cinnamomum zeylanicum) which might be prevented the development of AGE rich diet-induced diabetic complication and liver injury through activated the nuclear factor erythroid-2-related-factor-2 (Nrf2) pathway. Nrf2, as a master regulator of antioxidant response elements by activating cytoprotective genes expression, is decreased oxidative stress that associated with hyperglycemia and increases insulin sensitivity. the aim of this study was to assess whether the combination therapy of SPTC along with exercise or metformin moderate oxidative stress related liver injurie with more favorable effects in the treatment of AGE rich diet-induced type 2 diabetic mice. Methods: We induced diabetes in C57BL/6 mice by AGE using a diet supplementation and limitation of physical activity. After 16 weeks of intervention, AGE fed mice were compared to control mice. Diabetic mice were assigned into seven experimental groups (each group;n = 5): diabetic mice, diabetic mice treated with SPTC (130 mg/kg), diabetic mice treated with Salvia Officinalis (65 mg/kg), diabetic mice treated with metformin (300 mg/kg), diabetic mice with endurance exercise training, diabetic mice treated with SPTC + metformin (130/300 mg/kg), diabetic mice treated with SPTC + exercise training. Results: SPTC + exercise and SPTC + metformin reduced diabetic complications like gain weight, water and calorie intake, blood glucose, insulin, and GLUT4 content more efficiently than each treatment. These combinations improved oxidative stress hemostasis by activating the Nrf2 signaling pathway and attenuating keap1 protein more significantly. Conclusion: Eventually, combined treatment of SPTC with exercise or metformin as a novel approach had more beneficial effects to prevent the development of diabetes and oxidative stress associated with hyperglycemia.

关键词： Expression   Methylation   11 beta-hydroxysteroid dehydrogenase type 2   HSD11B2   Stress   HPA axis  

摘要： Introduction: Prenatal stress is known to influence fetal hypothalamic-pituitary-adrenal axis (HPA axis) development. Placental 11 beta-hydroxysteroid dehydrogenase type 2 (HSD11B2) is a central gene in this pathway, but little is known about what influences its functioning. We assess how maternal distress influences HSD11B2 functioning, and how HSD11B2 in turn, is associated with infant HPA axis development. Methods: Data come from 24 mother-infant dyads on the Galapagos Islands. Using adjusted linear regression models, we assess the effects of maternal psychosocial (stress and depressive symptoms, measured by the Perceived Stress Scale and the Patient Health Questionnaire-8, respectively) and physiological (HPA axis dys-regulation) distress during pregnancy on HSD11B2 methylation and expression and then test how these HSD11B2 measures influence infant HPA axis development. Results: Maternal HPA axis dysregulation during pregnancy is associated with lower placental HSD11B2 expression, which is associated with an exaggerated cortisol reactivity in infants. Sex-specific analyses revealed that maternal depressive symptoms may influence the functioning of placental HSD11B2 differently in girls (n = 11, 46%) than in boys (n = 13, 54%), though the sample size was small. Discussion: These results support a disrupted adaptive framework, in which the ability to upregulate HSD11B2 expression in response to acute stress diminishes as maternal stress becomes chronic. In this model, chronic stress may exhaust the protective mechanism of HSD11B2, leaving the infant vulnerable to high levels of maternal cortisol, which could injure the fetal HPA axis and disrupt long-term neurobehavioral and metabolic development. While larger studies will be needed to confirm these findings, this study offers exploratory results on the effects of maternal distress on both HSD11B2 methylation and expression and the effect of HSD11B2 on offspring HPA axis development.

关键词： Wet clutch   temperature field   friction disc   friction coefficient  

摘要： Wet clutches are widely used in vehicle transmission systems to start and shift. The temperature field of the wet clutch components is influenced by friction and is closely related to the vehicle performance and service life. This work improves the numerical modeling of the temperature field by taking into account groove cooling, local heat dissipation, and the time-varying friction coefficient on the contact surface. An equivalent convection heat transfer coefficient and an equivalent gain coefficient are introduced. The proposed model is more accurate than the traditional model, and its accuracy is verified by bench experiments. The influence of rotational speed difference, oil pressure, and lubrication flow on the temperature field is analyzed. Moreover, the temperature rise characteristics during deformation are measured, which also confirms the abnormal radial and circumferential change of temperature field. These results can guide the accurate simulation of interface temperature and the appropriate control operation of friction components in the wet clutch.