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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.

Product development in automotive industry is still deeply based on experimentation: test benches and road test facilities are used both for components testing and models validation. Nevertheless a growing role is played by numerical simulation and nowdays by virtual experimentation. The latter is required by the increasing complexity of the systems and cost saving. Moreover new products involve a higher level of integration between mechanics, electronics and computer science, which makes difficult a rapid and low cost prototyping. The design of the vehicle is currently applied to the overall system instead of assembling subsystems separately developed and tested. This approach requires that the same level of integration is achieved on numerical codes and simulators, to be able to operate hardware and software for virtual experimentation in mechatronic systems. This paper briefly describes the experience done since few years, by Fiat Auto and Politecnico di Torino (Dept.

The paper shortly describes an ABS/ESP Hardware-In-the-Loop (HIL) test bench built by the Vehicle Dynamics Team of the Department of Mechanics of Politecnico di Torino. It consists of a whole brake system, integrated through specific interface (e.g. wheel pressures signals) with a vehicle model running in real time on a dSPACE® board. Different commercial ABS strategies are compared, in a large spectrum of manoeuvres: slow brake apply manoeuvres, panic brake manoeuvres, μ-split brake manoeuvres, brake manoeuvres with a sudden variation of the friction coefficient between tyres and ground. The paper deals with the generation of all the signals required for activating a commercial ESP: steering wheel angle, body yaw rate, body lateral acceleration, engine control, etc… Some of them are transmitted by CAN. Typical handling manoeuvres are used to test the ESP: step steer, double step steer, ramp steer, etc… Several brake manoeuvres are simulated while turning.

H-ergo, a concept of light electric vehicle devoted to personal mobility, will here be presented. H-ergo is a low-noise, user-friendly, zero-emission vehicle, with a pleasant style. Its main features include high payload/vehicle mass ratio, electric energy supplied either by batteries or by fuel cell, ergonomic style in order to transport a driver or a person whit mobility problems, chassis design to minimize cost of production, variable wheelbase (through electric actuator). The paper presents the main ideas on which the vehicle design was based and summarizes the most important results obtained.

The paper presents a 4-wheel-steering (4WS) control strategy devoted to reduce the turn diameter for small longitudinal speed values and to obtain a yaw rate damping effect in dynamic manoeuvres. Moreover, the 4WS active system conceived produces compensation both for lateral wind and road irregularities. The main results obtained through a functional vehicle model are presented. 4WS was integrated with a Vehicle Dynamics Control (VDC), which was improved for turn while braking manoeuvres. The results due to integration were very good, with a reduction of both systems interventions. Finally, a VDC-4WS-Active Roll Control (ARC) integration was tried, based on only one reference body yaw rate for all the active systems. The main results obtained are presented and discussed.

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.

The paper focuses on the advantages of the diesel electric traction applied to military vehicles. In recent years electric cars developed mainly to reduce the dependence on fossil fuels and cut down the emissions. The reduction of fuel consumption, important for civil vehicles above all to reduce emissions and to lower costs, is important also for the military in order to increase vehicle autonomy. In addition, the interest for hybrid electric military vehicles is linked with vehicle packaging flexibility, on board power generation and stealth potential related to their abilities of silent movement. Among many possible layouts the optimum is considered to be hub mounted drive motors in each wheel [ 1 ]. This study shows the development of a demonstrator of an hybrid electric 4×4 military vehicle. It was carried out for a future extension of the technology to a 8×8 armoured vehicle.

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.

Vehicles equipped with Automated Manual Transmissions (AMT) for gear shift control show many advantages in terms of reduction of fuel consumption and improvement of driving comfort and shifting quality. In order to increase both performance and efficiency, an important target is focused on the minimization of the typical torque interruption during the gear shift, especially in front of the conventional automatic transmission. Recently, AMT are proposed to be connected with planetary gears and friction brakes, in order to reduce the torque gap during the gear change process. This paper is focused on a block-oriented simulation methodology developed in Matlab/Simulink/Stateflow® environment, able to simulate the performance of a complete FWD powertrain and in particular to predict dynamic performance and overall efficiency of the AMT with innovative Torque Gap Filler devices (TGF).

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.

This paper presents the methodology adopted by Politecnico di Torino Vehicle Dynamics Research Team to obtain objective indices for the evaluation of the comfort during the gear change process. Some test drivers and different passengers traveled on a test vehicle and assigned marks on the basis of their subjective feeling of comfort during the gearshifts. The comparison between the most significant subjective evaluations and the experimental values obtained by the instruments located on the vehicle is presented. As a consequence, some indices (based on physical parameters) to evaluate the efficiency and the comfort of the gearshift process are obtained. They are in good agreement with the subjective evaluations of the drivers and the passengers. The second part of the paper presents a driveline and vehicle model which was conceived to reproduce the phenomena experimented on the vehicle. The experimental validation of the model is presented.

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.

The paper deals with the elaboration of an Active Roll Control (ARC) oriented both on comfort and handling improvement. The ARC determines hydraulically the variation of the equivalent stiffness of the anti-roll bars. The control strategies conceived were extensively validated through road tests managed on an Alfa Romeo sedan. The first part of the paper deals with comfort improvement, mainly consisting in an absence of bar effect during straight-ahead travel and in a modification of the roll characteristic of the car. To increase driver's handling feeling, it was necessary to optimise the ratio between front and rear roll stiffness. This purpose can be reached through control strategies based exclusively on lateral acceleration. Some control strategy corrections were necessary to optimise roll damping and front/rear roll stiffness balancing.

This paper investigates the effect of the powertrain mounting system on the linear and nonlinear torsional dynamical behaviour of a transmission system. To this aim, two dynamic models, one with rigid mounts and the other with flexible mounts, are presented and compared: the first model considers only the torsional dynamics of transmission and driveline, while the second model includes also a 3 degrees-of-freedom powertrain block. The mechanical coupling and interaction between the powertrain block and transmission system is discussed and formulated. These models are then analyzed in terms of vibrational mode shapes, natural frequencies and Frequency Response Functions (FRFs); a sensitivity analysis of the main transmission parameters, e.g. the gear ratio, is also presented.

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.

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.

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.

The paper presents a failsafe strategy conceived for a Vehicle Dynamics Control (VDC) system developed by the Vehicle Dynamics Research Team of Politecnico di Torino. The main equations used by the failsafe algorithm are presented, especially those devoted to estimate steering wheel angle, body yaw rate and lateral acceleration, each of them fundamental to correctly actuate the VDC. The estimation is based on redundancy; each formula is considered according to a weight depending on the kind of maneuver. A new recovery algorithm is presented, which does not deactivate VDC after a sensor fault, but substitutes the sensor signal with the virtually estimated value. The results obtained through simulation are satisfactory. First experimental tests carried out on a ABS/VDC test bench of the Vehicle Dynamics Research Team of Politecnico di Torino confirmed the simulation results.