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A methodology for an efficient failure prediction of automotive steel wheels during fatigue experimental tests is proposed. The strategy joins the CDTire simulative package effectiveness to a specific wheel finite element model in order to deeply monitor the stress distribution among the component to predict damage. The numerical model acts as a Software-in-the-loop and it is calibrated with experimental data. The developed tool, called VirtualWheel, can be applied for the optimisation of design reducing prototyping and experimental test costs in the development phase. In the first section, the failure criterion is selected. In the second one, the conversion of hardware test-rig into virtual model is described in detail by focusing on critical aspects of finite element modelling. In conclusion, failure prediction is compared with experimental test results.

Brake systems represent important components for passenger cars since they are strictly related to vehicle safety: Anti-lock Braking Systems (ABS) and Electronic Stability Control (ESC) are the most well-known examples. The paper is focused on the characterization of the braking hydraulic plant and on the design of a pressure following control strategy. This strategy is aimed at pursuing performances and/or comfort objectives beyond the typical safety task. The low-level logic (focus of the paper) consists of a Feedforward and Proportional Integral controller. A Hardware In the Loop (HIL) braking test bench is adopted for pressure controller validation by providing some realistic reference pressure histories evaluated by a high-level controller. Results prove that innovative control strategies can be applied to conventional braking systems for achieving targets not limited to braking issues, i.e., comfort or NVH tasks.

This paper presents a study related to an Articulated Amphibious All-Terrain Tracked Vehicle (ATV) characterized by a modular architecture. The ATV is composed by two modules: the first one hosts mainly the vehicle engine and powertrain components, meanwhile the second one can be used for goods transportation, personnel carrier, crane and so on. The engine torque is transmitted to the front axle sprocket wheel of each module and finally distributed on the ground through a track mechanism. The two modules are connected through a multiaxial joint designed to guarantee four relative degrees of freedom. To steer the ATV, an Electro Hydraulic Power System (EHPS) is adopted, thus letting the vehicle steerable on any kind of terrain without a differential tracks speed. The paper aims to analyze the steady-state lateral behavior of the ATV on a flat road, through a non-linear mathematical vehicle model built in Matlab/Simulink environment.

In automotive market, today more than in the past, it is very important to reduce time to market and, mostly, developing costs before the final production start. Ideally, bench and on-road tests can be replaced by multi-body studies because virtual approach guarantees test conditions very close to reality and it is able to exactly replicate the standard procedures. Therefore, today, it is essential to create very reliable models, able to forecast the vehicle behavior on every road condition (including uneven surfaces). The aim of this study is to build an accurate multi-body model of a heavy-duty truck, check its handling performance, and correlate experimental and numerical data related to comfort tests for model tuning and validation purposes. Experimental results are recorded during tests carried out at different speeds and loading conditions on a Belgian blocks track. Simulation data are obtained reproducing the on-road test conditions in multi-body environment.

Steer by wire (SbW) system is examined, considering the positive effects of the lack of direct mechanical connection between steering wheel and rack. SbW system's steering wheel has to generate a resistant torque which adds to the friction one. Such torque must be felt as natural by the average driver and carry information about vehicle dynamic condition. System prototype is obtained from a classical steering system. Steering wheel is linked to a brushless 12V DC current electric motor designed to develop resistance torque, after steering column is removed, triple stadium planetary gear is necessary to increase the torque output. A hardware in the loop test bench is realized in order to test feedback torque generation and steering wheel efficiency influence on vehicle behaviour. Steering wheel is fixed to the bench and its rotation acquired by an optic encoder. Steering wheel angle is used as input for a ten degrees of freedom vehicle model through an acquisition data board.

The superior mobility of a military vehicle provides the combat crew with a tactical advantage through increased cross country speed. The suspension system plays a fundamental role in evaluating a vehicle mobility. A mathematical model that allows realistic simulations of vehicles operating in a wide spectrum of environmental conditions may help to lower costs and time required during their development. The paper concerns with vehicle-terrain interaction modeling, for a military tracked tank, through multi-body and block-oriented approaches. It is focused on the consequences that the suspension system has got on the comfort and on the performance. Thus through a multi-body software a realistic three dimensional model of a tracked fighting vehicle is developed. This virtual model confirms some experimental data available on its longitudinal dynamics. In order to simplify the multi-body simulations, a block-oriented approach is adopted to develop a model of the same vehicle.

The paper discusses a gearbox design method based on an optimization algorithm coupled to a fully integrated tool to draw 3D virtual models, in order to verify both functionality and design. The aim of this activity is to explain how the state of the art of the gear design may be implemented through an optimization software for the geometrical parameters selection of helical gears of a manual transmission, starting from torque and speed time histories, the required set of gear ratios and the material properties. This approach can be useful in order to use either the experimental acquisitions or the simulation results to verify or design all of the single gear pairs that compose a gearbox. Genetic algorithm methods are applied to solve the optimization problems of gears design, due to their capabilities of managing objective functions discontinuous, non-differentiable, stochastic, or highly non-linear.

The paper deals with a method implemented to study braking systems design, modelling components' characteristics through commercial software. It summarizes the potential improvement possible by using modelling techniques in chassis systems design. The first part consisted in producing a passive braking system model. A first validation was carried out on a test bench by using components of different braking systems. Particular attention was devoted to booster modelization both in semi-stationary and dynamic conditions. The second part was callipers, roll-back and thermal phenomena modelization. Finally, it were modelled Anti-lock Braking System (ABS) and Vehicle Dynamics Control (VDC) Hydraulic Units and their integration with control strategies and with vehicle dynamics model.

The first step toward a braking system ‘by wire’ is Electro-Hydraulic Braking System (EHB). The paper describes a method to evaluate through virtual experimentation the actual improvement in vehicle behaviour, from the point of view of both handling and comfort, including also pedal feeling, due to EHB. The first step consisted in modelling the hydraulic unit, comprehensive of sensors. Then it was conceived a control logic devoted to medium-low intensity braking manoeuvres, without ABS intervention, to determine an optimal braking force distribution and pedal feeling depending on the manoeuvre. A failsafe strategy, complete of on board diagnosis, to prevent dangerous system behaviour in the eventuality of a component failure was carried out and tested. Finally, EHB wheel pressure sensors were used to improve both ABS performance, increasing the adherence estimation, and Vehicle Dynamics Control (VDC) performance, through a more precise actuation.

This paper explores the potentiality of reducing noise and vibration of a vehicle transmission thanks to powertrain control integration with active braking. Due to external disturbances, coming from the driver, e.g. during tip-in / tip-out maneuvers, or from the road, e.g. crossing a speed bump or driving on a rough road, the torsional backlashes between transmission rotating components (gears, synchronizers, splines, CV joints), may lead to NVH issues known as clonk. This study initially focuses on the positive effect on transmission NVH performance of a concurrent application of a braking torque at the driving wheels and of an engine torque increase during these maneuvers; then a powertrain/brake integrated control strategy is proposed. The braking system is activated in advance with respect to the perturbation and it is deactivated immediately after to minimize losses.

A prototype vehicle (PV) is equipped to test powertrain and active chassis systems with innovative control strategies for safety and energy saving. Additional sensors installed on-board allow the measurement and estimation of new information useful to the vehicle dynamic control. The PV was based on a serial production passenger car with Electronic Stability Control (ESC). Testing activities on Controller Area Network (CAN) and ESC Electronic Control Unit (ECU) are carried out to compare the vehicle dynamic performance obtainable using serial production rather than customized control strategies, while maintaining the same hardware. The PV is also utilized to provide reverse engineering analysis about the implemented control strategy for the ESC working in serial production mode.

The paper deals with the Hardware-In-the-Loop based methodology which was adopted to evaluate the dynamic characteristics of Electronic Stability Program (ESP) and Electro-Hydraulic Brake (EHB) components. Firstly, it permits the identification of the time delays due to the hardware of the actuation system. Secondly, the link between the hardware of the hydraulic unit and a vehicle model running in real time permits the objective evaluation of the performance induced by the single components of different hydraulic units in terms of vehicle dynamics. The paper suggests the main parameters and tests which can help the car manufacturer in evaluating ESP hydraulic units, without expensive road tests.

A four wheel steer control logic is described. A first control logic release, obtained during previous research activity, is based only on feed forward (F.F.) but is here upgraded merging closed loop control (C.L.). Integration between F.F. and C.L. is described. Rear steering electromechanical actuator frequency response is analyzed, in order to consider its not ideal behaviour during control logic design. Several simulation are performed to qualitatively evaluate the error committed considering an ideal actuator during the control logic design. Specific manoeuvres are chosen to investigate about active system influence on vehicle handling; a 14 degrees of freedom vehicle model is validated in order to compare simulation results with experimental data.

Through a single track model, correspondence between typical frequency analysis coefficients and test driver's opinion developed after experimental tests has been stated. Benchmark analysis of several vehicles, considered significant, has been carried out as well as a sensitivity analysis of vehicle behavior depending on passive design parameters, such as vehicle sideslip stiffness and tyre relaxation length. It led to the definition of the different transfer function capable of describing passive vehicle linear behavior; vehicle performance limits, due to unbridgeable physical phenomenon, has been also considered. 4WS vehicle chance to overcome these limits has been investigated, depending on rear steering control logic complexity. Vehicle frequency response has been then analyzed for different longitudinal velocity, introducing thus the concept of “natural vehicle”. The design of a four wheel steer system control logic, based only on feed forward, is described.

Chassis Control Systems development methodology is nowadays strongly based on analyzing performance by using PC vehicle dynamics simulation. Generally, the overall design, test bench and road validation process is continuously accompanied by simulation. The Base Model Simulator was developed by the Vehicle Dynamics Group at the Department of Mechanics of Politecnico di Torino both to satisfy this requirement and for educational purposes. It considers a complete vehicle dynamics mathematical model, including driver, powertrain, driveline, vehicle body, suspensions, steering system, brakes, tires. The Base Model Simulator takes in account the suspensions system elastokinematics, including, for example, automatic computation of camber variation during the vehicle roll motions. Tire model considered are either Pacejka's models or experimental data.

In the last few years, the number of Advanced Driver Assistance Systems (ADAS) on road vehicles has been increased with the aim of dramatically reducing road accidents. Therefore, the OEMs need to integrate and test these systems, to comply with the safety regulations. To lower the development cost, instead of experimental testing, many virtual simulation scenarios need to be tested for ADAS validation. The classic multibody vehicle approach, normally used to design and optimize vehicle dynamics performance, is not always suitable to cope with these new tasks; therefore, real-time lumped-parameter vehicle models implementation becomes more and more necessary. This paper aims at providing a methodology to convert experimentally validated light commercial vehicles (LCV) multibody models (MBM) into real-time lumped-parameter models (RTM).

In vehicle dynamics, simple and fast vehicle models are required, especially in the framework of real-time simulations and autonomous driving software. Therefore, a trade-off between accuracy and simulation speed must be pursued by selecting the appropriate level of detail and the corresponding simplifying assumptions based on the specific purpose of the simulation. The aim of this study is to develop a methodology for map and parameter estimation from multibody simulation results, to be used for simplified vehicle modelling focused on handling performance. In this paper, maneuvers, algorithms and results of the parameter estimation are reported, together with their integration in single track models with increasing complexity and fidelity. The agreement between the multibody model, used as reference, and four single track models is analyzed and discussed through the evaluation of the correlation index.

This paper investigates the torsional dynamic behaviour of a Dual Mass Flywheel (DMF) both numerically and experimentally. First, the experimental setup is described, followed by a mathematical description in the frequency domain of the mechanical system under test, using a lumped parameter model. An analytical expression for the frequency response function describing the rotational dynamics is derived and compared with experimental data. Sine sweep tests are used to characterise the system, imposing constant amplitude excitation, i.e. the torque applied to the engine side of the DMF. Moreover a method for enhancing the dynamic performance of the electric motor torque control is suggested in order to use it as a torsional shaker.

Over the next decade, CO2 legislation will be more demanding and the automotive industry has seen in vehicle electrification a possible solution. This has led to an increasing need for advanced powertrain systems and systematic model-based control approaches, along with additional complexity. This represents a serious challenge for all the OEMs. This paper describes a novel reverse engineering methodology developed to estimate relevant powertrain data required for fuel consumption-oriented hybrid electric vehicle (HEV) modelling. The estimated quantities include high-voltage battery internal resistance, electric motor and transmission efficiency, gearshift thresholds, torque converter performance diagrams, engine fuel consumption map and front/rear hydraulic brake torque distribution. This activity provides a list of dedicated experimental tests, to be carried out on road or on a chassis dynamometer, aiming at powertrain characterization thanks to a suitable post-processing algorithm.