1,720,992 research outputs found
A state-of-the-art review on torque distribution strategies aimed at enhancing energy efficiency for fully electric vehicles with independently actuated drivetrains
No full textElectric vehicles are the future of private passenger transportation. However, there are still several technological barriers that hinder the large scale adoption of electric vehicles. In particular, their limited autonomy motivates studies on methods for improving the energy efficiency of electric vehicles so as to make them more attractive to the market. This paper provides a concise review on the current state-of-the-art of torque distribution strategies aimed at enhancing energy efficiency for fully electric vehicles with independently actuated drivetrains (FEVIADs). Starting from the operating principles, which include the "control allocation" problem, the peculiarities of each proposed solution are illustrated. All the existing techniques are categorized based on a selection of parameters deemed relevant to provide a comprehensive overview and understanding of the topic. Finally, future concerns and research perspectives for FEVIAD are discussed
A real-time thermal model for the analysis of tire/road interaction in motorcycle applications
No full textWhile in the automotive field the relationship between road adherence and tire temperature is mainly investigated with the aim to enhance the vehicle performance in motorsport, the motorcycle sector is highly sensitive to such theme also from less extreme applications. The small extension of the footprint, along with the need to guarantee driver stability and safety in the widest possible range of riding conditions, requires that tires work as most as possible at a temperature able to let the viscoelastic compounds-constituting the tread and the composite materials of the whole carcass structure-provide the highest interaction force with road. Moreover, both for tire manufacturing companies and for single track vehicles designers and racing teams, a deep knowledge of the thermodynamic phenomena involved at the ground level is a key factor for the development of optimal solutions and setup. This paper proposes a physical model based on the application of the Fourier thermodynamic equations to a three-dimensional domain, accounting for all the sources of heating like friction power at the road interface and the cyclic generation of heat because of rolling and to asphalt indentation, and for the cooling effects because of the air forced convection, to road conduction and to turbulences in the inflation chamber. The complex heat exchanges in the system are fully described and modeled, with particular reference to the management of contact patch position, correlated to camber angle and requiring the adoption of an innovative multi-ribbed and multi-layered tire structure. The completely physical approach induces the need of a proper parameterization of the model, whose main stages are described, both from the experimental and identification points of view, with particular reference to non-destructive procedures for thermal parameters definition. One of the most peculiar and challenging features of the model is linked with its topological and analytical structure, allowing to run in real-time, usefully for the application in co-simulation vehicle dynamics platforms, for performance prediction and setup optimization applications
Vehicle Sideslip Angle Estimation for a Heavy-Duty Vehicle via Extended Kalman Filter Using a Rational Tyre Model
No full textVehicle sideslip angle is a key state for lateral vehicle dynamics, but measuring it is expensive and unpractical. Still, knowledge of this state would be really valuable for vehicle control systems aimed at enhancing vehicle safety, to help to reduce worldwide fatal car accidents. This has motivated the research community to investigate techniques to estimate vehicle sideslip angle, which is still a challenging problem. One of the major issues is the need for accurate tyre model parameters, which are difficult to characterise and subject to change during vehicle operation. This paper proposes a new method for estimating vehicle sideslip angle using an Extended Kalman Filter. The main novelties are: i) the tyre behaviour is described using a Rational tyre model whose parameters are estimated and updated online to account for their variation due to e.g. tyre wear and environmental conditions affecting the tyre behaviour; ii) the proposed technique is compared with two other methods available in the literature by means of experimental tests on a heavy-duty vehicle. Results show that: i) the proposed method effectively estimates vehicle sideslip angle with an error limited to 0.5 deg in standard driving conditions, and less than 1 deg for a high-speed run; ii) the tyre parameters are successfully updated online, contributing to outclassing estimation methods based on tyre models that are either excessively simple or with non-varying parameters
Tyre Mechanics and Thermal Effects on Tyre Behaviour
No full textThis chapter deals with tyre mechanics and it has a particular focus on thermal effects on its dynamical behaviour. In the first part the typical tyre structure is introduced together with the tyre mechanical/dynamical behaviour according to a classical approach, so recalling the main kinematic and dynamic quantities involved in tyre pure and combined interactions. The core of this chapter is the description of a physical-analytical tyre thermal model able to determine the thermal status in each part of the tyre useful for vehicle dynamics modelling and driving simulations in order to take into account thermal effects on tyre interactions and consequently on vehicle dynamical behaviour. Successively also the tyre wear modelling is faced, after a brief introduction to the different models available in literature some considerations are reported concerning the thermal effects on wear
RANS 3D CFD simulations to enhance the thermal prediction of tyre thermodynamic model: A hierarchical approach
No full textIn this work, a combined numerical/experimental analysis is performed for an automotive tyre. A preliminary experimental activity is realized on examined tyre to measure the temperatures of its layers under various operating conditions. In a second stage, a 3D CFD model of tyre is developed in a commercial code and steady RANS simulations are performed in the full range of angular velocity with the aim to refine the prediction of convective thermal power and heat transfer coefficient. CFD simulation results are passed to a user-defined 3D thermodynamic model to furnish a detailed and reliable tyre thermal output with the advantage of a low computational time. Tyre thermodynamic model, enhanced by CFD-related thermal characteristics, demonstrates the capability to properly forecast the measured temperature of tyre layers in a wide range of investigated operating conditions. The proposed numerical approach represents a valuable tool supporting the optimization of tyre behavior and the development of advanced control rules for optimal tyre management
An effective tyre to road friction estimation applied to heavy vehicles
No full textKnowledge about the tyre to road friction is central to many vehicle functions as well as the overall performance of the vehicle. In this paper, a new real-time algorithm is presented for estimating the coefficient of friction using available on-board sensor information. A computationally efficient algorithm is presented, that reduces resources usage compared to previously published approaches. Issues connected to heavy vehicles and friction estimation is addressed, such as wind up of hub assembly and vehicle speed sensing. The performance of the algorithm is illustrated on data sets acquired from the test track recordings in winter conditions
Extension of the multiphysical magic formula tire model for ride comfort applications
No full textIn the development of physical tire models, the complexity of the composite structure and the multiphysical variables require strongly nonlinear mathematical formulations to guarantee a desired degree of accuracy. The aim of the current work is to extend the applicability of the multiphysical magic formula-based tire model, already developed and presented by the authors, within a wider frequency range, interposing a rigid ring body between the contact patch and the wheel hub. The contact patch, varying in terms of size, shape, and relative position, is evaluated using instantaneous cams to define the effective plane. Here the advanced slip model, taking into account thermodynamic and wear effects, is then integrated. The adopted formulations have been mathematically and physically justified. They have been analytically compared to formulations related to the rigid-ring implementation available in the literature. Specific experimental activities concerning both the tire’s vertical kinematics and dynamics have been conducted to demonstrate the model’s improved physical consistency on small wavelength unevennesses
Necessity of the Tire Temperature-Dependant Parameters in Vehicle Virtual Sensing
No full textVehicle state estimation plays a crucial role in the design and development of advanced systems for vehicle control and autonomous driving applications. In this context, the knowledge of vehicle side slip angle is required to optimize lateral dynamics control, improving the overall handling performance. On one hand, the direct measurement of lateral velocity can only be provided by employing sophisticated and expensive onboard sensors. On the other hand, the vehicle system and, in particular, the tires can significantly modify their behaviour through time due to temperature, pressure and wear influences, thus modifying both the vehicle handling behaviour and the parameters of the installable control logic. For this reason, the authors propose an innovative estimation method, combining the vehicle mathematical implementation with a double-track model enriched with virtual observations obtained through a kinematic observer. To validate its applicability in contexts covering a wide range of tire thermodynamic conditions, the proposed estimation approach has been integrated with a multiphysical tire formulation, proposed by the authors in the previous studies, able to take into account of temperature and pressure effect on the tire dynamic response. The results have been analysed in terms of the vehicle sideslip angle acquired in a dedicated experimental campaign comparing the accuracy of the proposed approach to the commonly adopted one, not accounting for temperature and pressure influences
Rolling, tilting and spinning spherical wheels: Analytical results using the brush theory
No full textThis paper investigates the rolling dynamics of spherical wheels using the theoretical framework provided by the brush models. The analysis is mainly conducted under the assumption of vanishing sliding inside the contact patch. Different types of kinematics are considered: simply rolling wheels, rolling and tilting, and purely spinning. For the first two cases, a complete solution is derived concerning both the steady-state and transient behaviours. Some qualitative trends for the forces and moments generated inside the contact patch are then provided when accounting for limited friction. For the case of a purely spinning spherical wheel, it is shown that steady-state conditions are never possible owing to the assumption of vanishing sliding. Moreover, it is demonstrated that the shear stresses acting inside the contact patch grow unbounded if the additional contribution relating to the deflection of the bristle is not taken into account when calculating the total sliding velocity. In this case, a stationary solution may be eventually recovered as an asymptotic distribution only by assuming limited friction inside the contact patch
An Enhanced Greenwood-Williamson Contact Model for the Evaluation of Local Tire/Road Contact Area
No full textContact modeling plays a crucial role in tire road interaction, impacting several fields, including vehicle dynamics, road safety, and transportation efficiency. As the tire is in contact with the road, the real contact area is smaller than the nominal area due to the indentation of the rubber over the road profile, influenced by the distribution of road texture. This paper introduces a novel approach to contact modeling, focusing on the evaluation of the ratio between the real contact area and the nominal one (AcA0), considering the Greenwood-Williamson formulation. This ratio is fundamental for characterizing the tire-road contact behavior, as it depends on tire viscoelastic properties, road roughness characterization and tire operating conditions. The paper presents some simulations conducted in MATLAB to assess the AcA0 ratio for various road specimens. These simulations were conducted considering a specific compound, while varying parameters such as contact pressure and compound temperature, with a fixed sliding velocity. This research, thus, enhances the understanding of how the road texture, combined with the tire properties and operating conditions, affects tire indentation over the road profile which is strictly related to the perceived friction values
- …
