Abstract: The increasing emissions of greenhouse gases (GHG) and pollutants like particulate matter and nitrogen oxides (NOx) have led to environmental concerns. Hybrid and electric powertrains are being introduced as means to reduce pollutant emissions, especially at the local level. Additionally, the finite availability of fossil fuel sources, which are used to produce gasoline and diesel, highlights the need for alternative technical solutions. One approach to partly address these issues is lightweighting, which involves reducing the weight of vehicles to minimize their impact during the use phase. Mathematical models are employed to simulate the longitudinal dynamics of vehicles and estimate the energy required to accomplish driving missions. Appropriate metrics have been developed to quantify energy-saving effects that, in addition, can support the decision making, design, and development phase of future vehicles. To facilitate this process, it would be useful to build a database of ERV (Energy Reduction Value) and FRV (Fuel Reduction Value) figures derived through a unified procedure. Such a database would be useful in evaluating the effectiveness of vehicle lightweighting and its impact on energy consumption and pollutant emissions. The last phase of the analysis is the assessment of the overall reduction in the environmental impact of the vehicle throughout its life cycle by using the LCA (Life Cycle Assessment) approach. From this study, it was possible to conclude that lightweighting can be an appropriate solution to improve the energy efficiency of vehicles and that appropriate metrics, can support the development of new car models. The potential to integrate enhanced energy efficiency, lower emissions, and higher safety features into our everyday vehicles would represent a significant advancement in the automotive industry. There is a gap in the scientific literature on the effects of lightweighting on vehicle dynamics and energy usage which deserves to be investigated.

Abstract: Nowadays, the topic of reducing vehicles’ energy consumption is very important. In particular, for electric vehicles, the reduction of energy consumption is necessary to remedy the most critical problems associated with this type of vehicle: the problem of the limited range of the electric traction, also associated with the long recharging times of the battery packs. To reduce use-phase impacts and energy consumptions of vehicles, it is useful to reduce the vehicle mass (lightweighting). The aim of this work is to analyze the parameters of a vehicle which influence the results of lightweighting, in order to provide guidelines for the creation of a vehicle model suitable for studying the effects of lightweighting. This study was carried out through two borderline case models, a compact car and an N1 vehicle, and simulating these through a consolidated vehicle simulation tool useful for consumption estimations. This study shows that the parameters that most influence the outcome of lightweighting are the rolling resistance, the battery pack characteristics, the aerodynamic coefficients, and the transmission efficiency, while the inertia contributions can be considered negligible. An analysis was also carried out with the variation of the driving cycle considered.

Keywords: automotive | consumption analysis | energy consumption | Energy Reduction Value (ERV) | Fuel Reduction Value (FRV) | vehicle lightweighting

Abstract: To promote the development of new technologies that allow an intensive use of renewable green energies and to overcome the problem of the lack of range of full electric vehicles, an interesting energy source is biomethane. The Fuel Cells (FCs) systems benefit from high efficiency and zero emissions, and they are generally powered by hydrogen. One of the main problems related to hydrogen FCs is the current weak network of infrastructure’s need to supply the hydrogen itself. An alternative may be the development of FC vehicles powered by methane, or biomethane, to exploit a renewable energy source. The type of Fuel Cells that lends itself to a methane (or biomethane) power supply is the Solid Oxide Fuel Cell (SOFC). Considering the limitations of the SOFCs, a vehicle model powered by Fuel Cells fueled by methane (or biomethane) is created. This work concerns the creation of a vehicle model, and the sizing of the SOFC system (generator delivering a constant 3 kW) and battery pack (30 Ah), for a door-to-door waste collection vehicle, whose mission is known. The latter is a fundamental requirement due to the limitations found for Solid Oxide Fuel Cells: slow transient and long ignition times.

Keywords: alternative propulsion | energy consumption | Fuel Cells powered by methane | mathematical modeling | Solid Oxide Fuel Cell (SOFC) | vehicle model

Abstract: Solid oxide fuel cells (SOFCs) are well suited to be used with different fuels, including methane and biomethane. Therefore, it may be useful to study their possible application on board hybrid electric vehicles and exploit the fuel cell system, which is characterized by high efficiency, and allow the use of biomethane as a renewable green energy source. Furthermore, there is not yet a consolidated hydrogen distribution network for automotive use, while biomethane would make it possible to take advantage of the existing distribution network and infrastructures of methane. SOFC technology is well suited to be used on vehicles operating in fleets, with a consistent and known mission through the working days, which helps to mitigate SOFCs known limitations such as slow transients and long ignition times. In this work, a model of a fuel cell hybrid vehicle equipped with a SOFC is presented and then used for the sizing of a door-to-door waste collection vehicle. After that, a case study has been carried out considering such a vehicle working on a real-world, door-to-door waste collection mission profile (maximum around 10h/days shift for 7days/week), showing the entire potential of this architecture in terms of environmental impact.

Keywords: alternative propulsion | energy consumption | mathematical modelling | solid oxide fuel cell | vehicle model

Abstract: This paper presents a regenerative braking logic to be adopted on full electric vehicles with front, rear-drive or all-wheel drive with one motor for each axle, which aims at maximizing energy recovery under braking, avoiding wheel locking thus preventing vehicle instability. The logic implies the adoption of a brake-by-wire system i.e., the hydraulic braking system can be activated independently from the brake pedal. As a matter of fact, with the pedal pressed, the logic gives priority to the braking action of the electric motor(s) which acts as a generator, thus maximizing energy recovery, however taking into account various limitations, including the wheel locking limit, ensuring the stability of the vehicle. When the electric motor cannot satisfy the regenerative torque request, braking is integrated with the help of the hydraulic brakes, whose contribution aims to bring the braking towards a condition of optimal braking distribution. The front and rear hydraulic systems must therefore be independent of each other and controllable separately. This logic was tested via simulation, and it emerged that, on the WLTC driving cycle, the logic saved about 30% in consumption compared to the same vehicle without regenerative recovery, and about 23% compared to a logic commonly adopted on the market. On cycle US06, it saves about 24% and 19%, respectively.

Keywords: electric vehicle | energy optimization | energy recovery | regenerative braking logic | vehicle stability

Abstract: This work aims to develop a mathematical model for the simulation of a fuel cell (FC) hybrid powertrain. The work starts from modeling a single cell to obtain information on the entire FC stack. The model obtained was integrated into a simulation tool presented in the literature that simulates the longitudinal dynamics of auxiliary power unit hybrid electric vehicles and fully electric vehicles. Therefore, the integrated model allows the simulation of hybrid vehicles equipped with FC and a battery pack that acts as a peak power source. The tool simulates the mechanical and electrical behavior of the vehicle, introducing an investigation of the power flows relating to the FC and batteries. An appropriate power split logic has been implemented, allowing the correct management of the power distribution between the FC and the batteries. The importance of analyzing FC vehicles’ behavior arises from the recent necessity to find alternative propulsion systems, overcoming the range problems associated with fully electric vehicles. The innovation lies in the versatility and modularity of the model, which is open to modifications and features a low computational burden, making it suitable for testing new solutions by performing first design and sizing calculations.

Keywords: alternative propulsion | control strategy | energy consumption | mathematical modelling | performance prediction

Abstract: This paper presents a regenerative braking logic that aims to maximize the recovery of energy during braking without compromising the stability of the vehicle. This model of regenerative braking ensures that the regenerative torque of the electric motor (for front- and rear-wheel drive vehicles) or electric motors (for all-wheel drive vehicles equipped with one motor for each axle) is exploited to the maximum, avoiding the locking of the driving wheels and, subsequently, if necessary, integrating the braking with the traditional braking system. The priority of the logic is that of maximizing energy recovery under braking, followed by the pursuit of optimal braking distribution. This last aspect in particular occurs when there is an integration of braking and, for vehicles with all-wheel drive, also when choosing the distribution of regenerative torque between the two electric motors. The logic was tested via simulation on a front-, rear-, and all-wheel drive compact car, and from the simulations, it emerged that, on the WLTC driving cycle, the logic saved between 29.5 and 30.3% in consumption compared to the same vehicle without regenerative recovery, and 22.6–23.5% compared to a logic commonly adopted on the market. On cycle US06, it saves 23.9–24.4% and 19.0–19.5%, respectively.

Keywords: electric vehicle | energy optimization | energy recovery | EV | regenerative braking logic | vehicle stability

Abstract: The so-called porpoising is a well-known problem similar to bouncing that is affecting the dynamic behavior of basically all the field of 2022 Formula 1 racing cars. It is due to the extreme sensitivity of aerodynamic loads to ride height variations along a lap. Mid-way through the season race engineers are still struggling to cope with this phenomenon and its consequences, with regard to either physiological stress experienced by the drivers or to overall vehicle performance and stability. The paper introduces two kinds of models based on real-world chassis and aerodynamic data, where the above-mentioned downforce sensitivity has been arbitrarily recreated through the application of a decay function to aero maps. The first one is a quasi-static model, usually adopted as a trackside tool for controlling ride heights and aero balance, while the second, a fully dynamic model, recreates the interaction between oscillating aerodynamic loads and suspension dynamics resulting in a visible porpoising phenomenon. Basic setup changes have been tested, including significant static ride height variations. The paper should be seen as a proposal of guidelines in the search of a trade-off between aerodynamic stability and overall performance, without pretention of quantitative accuracy due to the highly confidential topic, which makes numerical validation impossible.

Keywords: aerodynamic efficiency | aerodynamic stability | high-downforce race cars | vehicle dynamics simulations

Abstract: This paper provides a comprehensive revision of the working principles and limitations of the mechanical limited-slip differential (LSD), a passive device used to improve traction capabilities and to extend the performance envelope of high-performance road cars, racing and rally cars. The LSD has been in use for decades. However, according to the authors’ experience, its impact on vehicle dynamics appears to be somewhat neglected in the literature and often misunderstood, especially in the semi-pro racing community. Current research on the subject is usually focused on side aspects and/or on modern control applications such as active differentials and torque-vectoring systems. These state-of-the-art technologies still rely on the same principles of the LSD, which should therefore be fully explained. The authors intend to fill this gap by starting with a comprehensive literature review. Then, an intuitive explanation of the impact of limited slip systems on vehicle behaviour is proposed with simple mathematical models and examples to integrate what seems to be missing. The peculiar shape of the torque-sensitive LSD working zone on the torque bias diagram is explained to an unprecedented level of detail. Real-world application examples are provided, including data recorded on a single-seater racecar integrated with examples based on a virtual model.

Keywords: Limited slip differential | Torque bias diagram | Vehicle dynamics | Vehicle stability | Yaw moment control

Abstract: Understanding the amount of energy a tire is subjected to is one of the key elements to perform in motorsport competitions, especially in Formula 1 feeder categories, where the number of tires is limited over the race weekend to contain costs. This forces teams to use worn tires towards the end of the event. Therefore, tires are usually chosen only relying on their external shape or based on the kilometers traveled. Moreover, being aware of how a setup change impacts tires can be a breakthrough in tire management, especially in tracks where tire wear is limiting the overall performance. This paper provides a scientific method aimed at helping race engineers in tire management to maintain a high performance level through the entire race weekend.

Keywords: Racing tires | Tire management | Tire sensitivity | Tire sliding power

Abstract: Vehicle sideslip angle estimation is still one of the most challenging research topics in the automotive industry. Many papers can be found on this topic, where authors propose varied methods to reach the goal. Which is the most effective? After an extensive literature review, two very different methods have been identified as the most used: Extended Kalman Filter with dynamic model and Artificial Neural Network. In this work a comparison among these methods is presented. A fully instrumented car has been used to gather typical vehicle dynamics data and feed the models required for a model-based design approach. Results showed that each method has either positive aspects or drawbacks.

Abstract: Due to problems related to environmental pollution and fossil fuels consumption that have not infinite availability, the automotive sector is increasingly moving towards electric powertrains. The most limiting aspect of this category of vehicles is certainly the battery pack, regarding the difficulty in obtaining high range with good performance and low weights. The aim of this work is to provide a simulation tool, which allows for the analysis of the performance of different types of electric and hybrid powertrains, concerning both mechanical and electrical aspects. Through this model it is possible to test different vehicle configurations before prototype realization or to investigate the impact that subsystems’ modifications may have on a vehicle under development. This will allow to speed-up the model-based design process typical for fully electric and hybrid vehicles. The model aims to be at the same time complete but simple enough to lower the simulation time and computational burden so that it can be used in real-time applications, such as driving simulators. All this reduces the time and costs of vehicle design. Validation is also provided, based on a real vehicle and comparison with another consolidated simulation tool. Maximum error on mechanical quantities is proved to be within 5% while on electrical quantities it is always lower than 10%.

Keywords: Alternative propulsion | Balance of forces | Electric powertrain | Energy consumption | Energy consumption prediction | Hybrid powertrain | Mathematical modelling | Performance prediction

Abstract: The aim of this review article is the analysis of the results obtained from the scientific literature concerning all the phases that make up the life cycle of traction batteries for electric vehicles, in order to evaluate the associated environmental impact. In this regard, some scientific articles dealing with LCA studies concerning electric vehicles, with particular reference to batteries, will be examined. The revision of these articles will provide a general framework for the production, use and recycling phases of traction batteries. In particular, different parameters that influence the outcome of the LCA studies will be shown, parameters on which we can then act to improve the environmental impacts of the transition from internal combustion vehicles to electric mobility. These parameters are represented by the chemistry of the battery considered, aspect at the centre of the discussion, by the specific energy and efficiency of the battery pack, by the durability of the latter, but also by other aspects, such as the energy mix considered (both for the production phase, for the use phase and for recharging) and the functional unit chosen for the study, which determines a different approach, related to the analysis of a specific problem or aspect rather than another. Finally, the usefulness of the recycling practice and the related problems will be shown. In fact, the recycling must be perfected according to the battery chemistry in question to obtain benefits and better reduce environmental loads.

Keywords: Automotive | electric mobility | electric vehicles | global warming | green mobility | LCA (Life Cycle Assessment) | lithium batteries | resource depletion | sustainability

Abstract: Feedback through the steering wheel is known as the most important source of information to the driver. The so-called steering feeling, composed of self-aligning actions coming from tyres and suspension geometry all the way through mechanical linkages to the driver's hands, provides vital communication for intuitive driving, and it is therefore utterly important for safety and for a pleasant driving experience as well. Subtle forces and vibrations, due to the interaction between the tyre contact patch and the road surface texture, also play a role, provided they are not heavily filtered or cancelled by the power steering system. Human perception is guided by experience in order to establish correlations between steering feedback and vehicle motion in terms of straight-line stability, cornering speed, tyre adhesion and available friction, vehicle balance, and so on. A front-wheel drive car is potentially a critical vehicle from this point of view, especially when the powertrain can deliver large torque figures, and even more so if a limited-slip differential (LSD) or a similar active device is present in order to improve traction capabilities. Any difference between the two wheels in terms of tractive force can result into the so-called torque steer issue, that is to say, a "pulling" sensation on the steering wheel or a shifting of the vehicle from the desired trajectory. This paper analyses the torque steer phenomenon on an all-wheel-drive, full electric sportscar where a significant portion of the torque is transferred to the front axle. The effects of suspension kinematics and the load variation at tyre contact patch level are taken into account. For evaluating the impact of steering feedback, the VI-grade® simulation software is adopted and a test campaign on the professional driving simulator available at the University of Brescia has been carried out in order to understand the impact of steering feedback on driver perception and performance.

Keywords: Electric cars | Steering feeling | Torque steer

Abstract: Beyond the well-known benefits of electric and hybrid powertrains in terms of environmental impact, the peculiar torque curve of electric motors for automotive applications offers extensive opportunities for improved vehicle dynamics control, such as yaw moment control through the application of different tractive forces across the axle: the so-called Torque Vectoring [1]. This is made possible for instance by fitting an independent motor on each wheel of a drive axle. On the other side, whenever Torque Vectoring is achieved on the front axle it can give birth to the so called torque steer effect: an undesirable influence of tractive or braking torque on the steering [2]. This is perceived by the driver as a “tugging or pulling sensation in the steering wheel, or a veering of the vehicle from the intended path” [3]. The steering feedback and self-aligning properties, often considered a vital portion of the feedback required for safe and intuitive driving control [4, 5], are thus jeopardized, especially under heavy acceleration. This is very similar to what can be experienced on front-wheel-drive cars featuring a high torque-to-weight ratio, often requiring the adoption of a LSD or active differential device in order to optimize traction capabilities [6]. The paper presents an approach to the torque steer problem on high-performance electric and hybrid vehicles, where the effects of suspension and steering geometry as well as tyre contact patch load variation are taken into account and various design solutions are proposed as an improvement. The VI-grade® software tools for vehicle dynamics analysis are adopted, also in co-simulation with MATLAB-Simulink® whenever an active control strategy is used. The impact on steering feedback quality is assessed through a testing campaign carried out on a state-of-the-art driving simulator.

Keywords: Torque steer

Abstract: The paper provides a quick overview on system integration methodologies for advanced vehicle chassis and powertrains through an extension of the model-based design concept. Physics modeling and Driver-In-the-Loop (DIL) simulation techniques are described with an eye on the related hardware and software tools. In greater detail, the design workflow pivots around a state-of-the-art device: the Driver-In-the-Loop simulator, where subjective, “human” factors can be taken into account together with objective, engineering factors. A framework of complementary tools with integrated functionalities supports the designer in order to merge traditional chassis engineering with advanced vehicle dynamics skills and modern control system design. An interactive design framework is proposed in order to report the authors’ experience. A self-developed utility for suspension and steering design, specifically conceived for intuitive integration in the design process, is also presented.

Keywords: Automotive chassis | Driver-In-the-Loop simulator | Interactive design | Steering | Suspension | Vehicle dynamics

Abstract: mHealth technology, by using habitual devices, i.e., smartphones, improves prevention, diagnosis, treatment, monitoring, and management of health. Monitoring heart profile during intense sports activities allows to diagnose pathologies, not identifiable with the traditional Holter approach and, therefore, it can help preventing possible injuries. On the other hand, denoising and extracting features from electrocardiographic (ECG) signal acquired during physical activity is a challenging task due to motion artifacts and measurement noise. In this paper, we propose a solution enabling a complete analysis of ECG signal through the implementation of a robust denoising algorithm, which has been characterized on synthetic signals and then has been tested on real traces acquired with a low-cost smartphone-based device during motorbike and car races.

Keywords: Compressive sensing (CS) | denoising | electrocardiographic (ECG) | mHealth | motion artifacts | races | wearable

Abstract: The paper presents a feasibility study for a prototype motorbike (bike in short) with an alternative front suspension. Novel features include the adjustability of steering axis inclination, front trail, and anti-dive effect i.e. the main parameters affecting rider feedback and perception as well as motorcycle behaviour. Although being based on the well-known double-wishbone layout, the system can be adjusted to replicate the geometry of a conventional fork as a baseline for experimental testing. Unlike similar concepts that can be found in literature the kinematics can be modified by means of straightforward adjustments that do not require complex disassembly. Independent adjustability is provided for each parameter. These innovative features enable a back-to-back comparison between significantly different settings, in order to explore a wide range of characteristics in terms of dynamic response, handling properties and rider's perception with a single vehicle. The project is aimed at fostering knowledge on motorcycle dynamics within the research group and especially on rider feedback and subjective perception, somehow a neglected topic in current literature. It was undertaken under the form of a student educational project in mechanical engineering and named "F.A.B." (Fully Adjustable Bike). The paper is mainly focused on front suspension kinematics; chassis design and related structural aspects are outlined as well.

Abstract: This work builds on some of the current industry techniques used in racing to evaluate vertical dynamics performance and propose a new methodology to evaluate vehicle performance. The proposed method creates a quantitative numerical index from the classic tyre vertical load variation frequency response function with some novelties that cover all peculiarities of high downforce race cars. In this method the aerodynamic forces are included as non-linear functions vs ride height and it is shown that they affect system stiffness and damping. As a result, the system response changes as a function of vehicle longitudinal speed. The importance of non-linear suspension rates in this kind of vehicle is also highlighted. The proposed index can also be customized for a certain vehicle speed range. A Formula 3 racecar model has been used as an application example.

Abstract: Student competitions can play an important role in education: they promote interest and engagement of the students, as well as of the teachers. In the case of engineering, one of the most challenging contests in Europe is the Motostudent event, joined by the University of Brescia (UniBS) in 2016 for the first time. It is a typical implementation of Kolb’s theory of experiential learning, where engineering theory and application meet in an intensive, ‘hands-on’ team work experience, resulting in a very effective learning process that involves the so-called soft skills as well. The paper aims at briefly reviewing the scope of competitions like the Formula SAE and sharing the authors’ experience in a similar event, the Motostudent contest.

Keywords: engineering education | Experiential learning | Formula SAE | motorbike design | Motostudent | student design competitions

Abstract: The paper presents an integrated approach to suspension design with educational purposes. A dedicated design tool was created to instruct automotive engineering students in the whole process of suspension design across the various CAE tools involved, from early kinematics studies to CAD, vehicle dynamics simulations and FEM modelling. The tool has given birth to a proven design procedure that the authors would like to share in this paper with focus on the educational side, although suspension kinematics design is not certainly a novel subject in itself. The tool includes geometries like the widely used McPherson strut, complex five-link schemes for high-end road cars, and typical racing car geometries like the so-called push/pull rod systems used on Formula 1 and Le Mans racecars. It has been applied successfully to various projects developed by professionals as well as by students, including the latest three Formula SAE (FSAE) single-seaters of the University of Brescia (Brescia, Italy) team. The paper is structured as follows. The introduction describes the role student design competitions play in higher engineering education, and within the frame of the Automotive Engineering course at UniBS in particular. A selection of relevant bibliography on the topic is listed. The Educational scenario section deals with the specific case of the Automotive Engineering course at UniBS and the requirements posed by student competitions, also in the frame of the Dublin Descriptors, and shows how suspension design can play a pivot role in a FSAE project. The A tool for suspension kinematics: requirements, description, solution section presents the software tool in itself. The math underlying the user interface is outlined. Finally, the integration features towards other CAE tools are presented with the related advantages.

Keywords: Dublin Descriptors | engineering education | Software integration | suspension kinematics | vehicle design

Abstract: A servo-hydraulic road simulator test rig (aka four-poster) can play a key role in testing and development of road vehicles. Its use for durability testing, NVH analysis, suspension setup optimization etc. is widespread. Engineers often make use of four-poster testing to validate their dynamic simulation models as well. The use of a so-called four poster is normally restricted to four-wheeled vehicles, typically passenger cars and light commercial vehicles. Motorbikes might also require similar R&D activities, even more so now that the market appears to be interested in electronically adjustable and semi-active suspension systems, especially for adventure/touring bikes; however, there are not many specific rigs around. This work proposes a method to retrofit a four-poster into a two-poster dedicated to motorbikes by means of a simple auxiliary structure: the so-called BikeShake. A case study has been reported at the end of the paper to validate the project.

Keywords: Four-poster | Indoor testing | Motorcycle testing | Motorcycle vertical dynamics | Road reproduction | Two-poster

Abstract: Purpose: Currently, the reduction of weight in automotive is a very important topic in order to lower the air pollution. In this context, the purpose of the present paper was to analyze a real case study through a comparison of the environmental sustainability between a conventional steel crossbeam for light commercial vehicles and an innovative lightweight aluminum one. Methods: For both scenarios, a cradle-to-grave life cycle assessment methodology and a sensitivity analysis has been used through the study of the following phases: mineral extraction, component manufacturing, use on vehicle, and end of life. In particular, many primary data and a complete vehicle model simulation with three different European driving cycles have been used in order to reach the highest possible level of accuracy during the analysis. Results and discussion: Regarding the manufacturing phase, the aluminum component’s production gave the highest impact because of the high energy required in the mineral reduction. Anyway, this stage of the analysis had a low effect on the entire LCA, because the benefit of weight reduction during vehicle use showed a strongly higher contribution. The urban driving cycle had the most relevant impact, as a consequence of the frequent start and stop operations and the longest time with engine at idle speed, while the extra-urban cycle is the less demanding due to its higher average speed and no start and stop. Conclusions: In conclusion, the present research demonstrated the environmental importance of the lightweight for an actual case study in the commercial vehicles field.

Keywords: Aluminum | Automotive | Commercial vehicles | Life cycle assessment (LCA) | Lightweighting | Steel

Abstract: Race car performance is strongly affected by aerodynamics. Due to downforce generated by the vehicle floor (i.e. diffuser), vehicle ride heights are key parameters to improve performance, and the coupling of aerodynamics and suspension is one of the key points of race car setting. This work focuses on the suspension and aerodynamic coupling from the vertical dynamics point of view. Besides road holding performance, for race cars, aerodynamic performance and stability are major factors. Downforce decreases laptime (the main performance target) but pitch instability is a non-desired effect that can happen in high downforce race cars. A new vertical dynamic performance index is proposed through the use of simulation to improve aerodynamic performance and understand the pitch instability phenomenon. This new index uses all relevant vehicle nonlinearities related to vertical dynamics and can handle a specific track profile and vehicle speed range, allowing the analysis be conducted according to a circuit specification. A previously validated Formula 3 car model was used as an example.

Keywords: Aerodynamics | stability analysis | suspension systems

Abstract: In this work, optimal control theory is applied to minimum lap time simulation of a GP2 car, using a multibody car model with enhanced load transfer dynamics. The mathematical multibody model is formulated with use of the symbolic algebra software MBSymba and it comprises 14 degrees of freedom, including full chassis motion, suspension travels and wheel spins. The kinematics of the suspension is exhaustively analysed and the impact of tyre longitudinal and lateral forces in determining vehicle trim is demonstrated. An indirect optimal control method is then used to solve the minimum lap time problem. Simulation outcomes are compared with experimental data acquired during a qualifying lap at Montmeló circuit (Barcelona) in the 2012 GP2 season. Results demonstrate the reliability of the model, suggesting it can be used to optimise car settings (such as gearing and aerodynamic setup) before executing track tests.

Keywords: Car | control | GP2 | lap | minimum | optimal | race | simulation | time

Abstract: In this work, a reliable and effective method to predict the vehicle side-slip angle is given by means of an artificial neural network. It is well known that artificial neural networks are a very powerful modelling tool. They are largely used in many engineering fields to model complex and strongly non-linear systems. For this application, the network has to be as simple as possible in order to work in real-time within built-in applications such as active safety systems. The network has been trained with the data coming from a custom manoeuvre designed in order to keep the method simple and light from the computational point of view. Therefore, a 5-10-1 (input-hidden-output layer) network layout has been used. These aspects allow the network to give a proper estimation despite its simplicity. The proposed methodology has been tested by means of the CarSim® simulation package, which is considered one of the reference tools in the field of vehicle dynamics simulation. To prove the effectiveness of the method, tests have been carried out under different adherence conditions.

Abstract: Typical active safety systems that control the dynamics of passenger cars rely on the real-time monitoring of the vehicle sideslip angle (VSA), together with other signals such as the wheel angular velocities, steering angle, lateral acceleration, and the rate of rotation about the vertical axis, which is known as the yaw rate. The VSA (also known as the attitude or "drifting" angle) is defined as the angle between the vehicle's longitudinal axis and the direction of travel, taking the centre of gravity as a reference. It is basically a measure of the misalignment between vehicle orientation and trajectory; therefore, it is a vital piece of information enabling directional stability assessment, such as in transience following emergency manoeuvres, for instance. As explained in the introduction, the VSA is not measured directly for impracticality, and it is estimated on the basis of available measurements such as wheel velocities, linear and angular accelerations, etc. This work is intended to provide a comprehensive literature review on the VSA estimation problem. Two main estimation methods have been categorised, i.e., observer-based and neural network-based, focussing on the most effective and innovative approaches. As the first method normally relies on a vehicle model, a review of the vehicle models has been included. The advantages and limitations of each technique have been highlighted and discussed.

Keywords: Extended Kalman Filter | GPS-aided estimation | Neural networks | Unscented Kalman Filter | Vehicle dynamics | Vehicle state estimation

Abstract: This study presents a modelling system to evaluate the impact of weight reduction in light commercial vehicles with diesel engines on air quality and greenhouse gas emissions. The PROPS model assesses the emissions of one vehicle in the aforementioned category and its corresponding reduced-weight version. The results serve as an input to the RIAT + tool, an air quality integrated assessment modelling system. This paper applies the tools in a case study in the Lombardy region (Italy) and discusses the input data pre-processing, the PROPS-RIAT + modelling system runs, and the results.

Keywords: Air quality | Greenhouse gases | Lightweighting | Multi-objective optimization | Road transport | Scenario analysis

Abstract: The paper presents a comparison between the emission levels produced along the most used standard driving cycles (NEDC, WLTC, CADC) by a Light Commercial Vehicle (LCV). A proven simulation tool based on real-world emission data (RDE, Real Driving Emissions) has been used instead of a demanding test campaign. Emission levels have been computed for each cycle in three conditions (urban, combined, extra-urban/highway). Then the results have been compared with Euro 5 limits and real-world emission levels to highlight each driving cycle objectivity and representativeness. Among others, the WLTC driving cycle seems to be the most plausible one yet, as expected, it is not very representative of the real world.

Keywords: Diesel Emissions | Driving Cycle | Emissions Simulation | European Driving Cycles

Abstract: Four-wheeled vehicles are often tested on indoor, four-poster road simulator rigs. Road loads are simulated with the use of servo-hydraulic systems for suspension set-up optimisation, NVH analysis, and fatigue life cycles. The use of a road simulator is not such a common practice for two-wheeled vehicles despite problems to be faced being extremely similar. The paper presents a device for testing motorcycles on a Servotest® four-poster. A dedicated restraint system had to be devised in order to support the motorcycle without altering its inertial characteristics. Additional pneumatic actuators with a purposely developed instrumentation have been designed to reproduce braking and power thrusts.

Keywords: Indoor testing | Motorcycles | Ride testing | Road simulator

Abstract: Indoor testing should reproduce the real-world environment in order to be effective. In this article, an efficient methodology to reproduce road profiles on a four-poster rig is presented: such a method includes a complex rig control strategy based on an iterative process. Road profiles come from a purposely designed set of sensors fitted on the car which remains the same regardless of the vehicle or surface type. Particular stresses such as speed humps, potholes and manholes can be reproduced as well. Since there are no previous similar studies, a validation is provided by comparing road and rig data streams and using the maximum absolute error and root mean square error as performance indexes. Results show that the rig is able to reproduce road profiles and the related inputs to the vehicle successfully; hence, the method is reliable and effective.

Keywords: chassis and suspensions testing | durability tests | four-poster test rig | indoor testing | Road reproduction | vehicle ride testing

Abstract: This work analyses the effect of friction in suspension components on a race car vertical dynamics. It is a matter of fact that race cars aim at maximising their performance, focusing the attention mostly on aerodynamics and suspension tuning: suspension vertical and rolling stiffness and damping are parameters to be taken into account for an optimal setup. Furthermore, friction in suspension components must not be ignored. After a test session carried out with a F4 on a Four Poster rig, friction was detected on the front suspension. The real data gathered allow the validation of an analytical model with friction, confirming that its influence is relevant for low frequency values closed to the car pitch natural frequency. Finally, some setup proposals are presented to describe what should be done on actual race cars in order to correct vehicle behaviour when friction occurs.

Keywords: friction | Passive suspension | suspension system | validation

Abstract: The automotive steering system inevitably presents internal friction that affects its response. This is why internal friction phenomena are carefully monitored either by OEMs and by vehicle manufacturers. An algorithm to predict the mechanical efficiency and the internal friction of a steering gear system has been developed by the ZF-TRW Technical Centre of Gardone Val Trompia and the University of Brescia, Italy. It is focused on mechanical steering gear of the rack and pinion type. The main contributions to the overall friction have been identified and modelled. The work is based on theoretical calculation as well as on experimental measurements carried out on a purpose-built test rig. The model takes into account the materials used and the gear mesh characteristics and enables the prediction of the steering gear friction performance before the very first prototypes are built.

Keywords: Friction | Rack and pinion | Steering | Steering feel | Vehicle dynamics

Abstract: This work analyzes a double wishbone type front suspension using a pushrod/rocker system to connect the chassis directly to the upright, linking the steering to the spring movement, and the related impact on racecar handling dynamics. The system has been used in the last 15 years in open wheel racing but yet no scientific analysis was done. Up to now its behaviour was analyzed using extensive testing. In this work this particular suspension design is analyzed using an analytical steady-state vehicle model, which includes previously calculated suspension derivatives and a full vehicle Multibody System (MBS) model to validate the theoretical approach. The final results are the suspension design guidelines.

Abstract: The monitoring of vital parameters for athletes of all disciplines is becoming more and more essential, to improve performances and to ensure a constant control of athletes' physical conditions, thus preventing health risks and injuries. However, especially in amatorial competitions, the low available budget limits leads to the use of inexpensive and thus ineffective instrumentation. In this paper, a low-cost system, based on a commercial smartdevice, for monitoring purposes in the context of amatorial car races is proposed. A single-lead electrocardiographic trace, body temperature, and driver acceleration profile are simultaneously acquired, locally stored and preprocessed, and periodically sent to a cloud service, allowing data sharing and remote processing. Experimental tests operated by means of a Formula SAE car in a test track have demonstrated the effectiveness of the proposed approach for the acquisition of important data to evaluate the degree of stress of a driver during the race.

Keywords: amatorial car race | smartphone-based system | Vital parameters monitoring

Abstract: This paper deals with the design and implementation of a double wishbone front suspension for a vineyard-orchard tractor, developed in conjunction with a major tractor brand. To date, independent front suspensions are only found on commercial tractors over 150 kW. A front suspended axle is recognized as a popular option in improving tractor ride performance on larger vehicles. Despite their narrow track, vineyard-orchard tractors are required to have good lateral stability and stability on slopes (i.e. at least 28° rollover angle) and an extremely tight turning diameter for a 4WD vehicle (less than 7 m). The discussion is concered with retrofitting an existing vehicle with a double wishbone front suspension. This paper focuses on the layout and kinematic analysis phases of the design process. These were conducted in collaboration with the vehicle manufacturer to demonstrate suspension feasibility in terms of available space and correct kinematic layout. The final kinematic turning diameter obtained is about 6.4 m, with a ±65 mm suspension travel available. The roll centre height value is not very sensitive to steering (about -95 mm excursion in the Z axis from no-steer position to full steer).

Keywords: Double wishbone suspension | Front axle independent suspension | Narrow-track tractor | Suspension design

Abstract: Hybrid and electric vehicles are taking an increasingly important slice of the market, gaining much interest from major car manufacturers which have decided to invest in this sector, taking as example the pioneers like Toyota. The key factor to hybrid and electric vehicle success is a good overall mileage achieved from the battery back or powertrain. The purpose of this work is to provide a support to design, testing, and development of such vehicles through the implementation of a mathematical model in order to simulate the operation and predict the performance of a generic ground vehicle equipped with either a purely electric or a hybrid-electric type powertrain. The model should enable the user to estimate the impact of various control strategies on mileage range, efficiency, energy consumption, etc. The model should also allow for a significant time to market reduction with all the related benefits in terms of cost etc. A validation is also provided, based on the application of this tool on a so-called micro-car (0.5t GVW class). Thanks to a joint research project with the manufacturer it has been possible to compare model results with real-world data directly obtained during road testing with the help of a data acquisition system. © 2014 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.

Keywords: Electric vehicle | Hybrid electric vehicle | Mathematical modelling | Performance prediction

Abstract: It is well known that vehicle slip angle is one of the most difficult parameters to measure on a vehicle during testing or racing activities. Moreover, the appropriate sensor is very expensive and it is often difficult to fit to a car, especially on race cars. We propose here a strategy to eliminate the need for this sensor by using a mathematical tool which gives a good estimation of the vehicle slip angle. A single-track car model, coupled with an extended Kalman filter, was used in order to achieve the result. Moreover, a tuning procedure is proposed that takes into consideration both nonlinear and saturation characteristics typical of vehicle lateral dynamics. The effectiveness of the proposed algorithm has been proven by both simulation results and real-world data. © 2014 Taylor & Francis.

Keywords: analytic model | extended Kalman filter | real-word validation | tyre modelling | vehicle dynamics | vehicle slip angle

Abstract: This paper focuses on the design of the power management strategy as the key factor in improving the performance in terms of the efficiency, the range and the fuel consumption for a small-scale series hybrid electric vehicle. A complex hybrid vehicle system is considered, and a practically realisable and traceable neurofuzzy strategy for improving the vehicle efficiency is introduced. The method results in extending the vehicle's range while deciding when to switch the internal-combustion engine on or off as a function of the state of charge of the battery and the electrical power produced from the generator. Consequently, the speed of the internal-combustion engine (i.e. the current produced) is determined as a function of the driving conditions. Suitable tests were performed in order to verify the effectiveness of the proposed strategy; the verification tests were carried out using a consolidated model which also includes real-world experimental vehicle data. The results show that, by using the proposed power management strategy, a good compromise between the efficiency, the range and the fuel consumption can be obtained in many practically useful driving conditions. © 2014 IMechE.

Keywords: Electric vehicles | hybrid vehicles | intelligent vehicles | vehicle control systems | vehicle electronics

Abstract: This paper deals with an "atypical" bike design. It can be considered atypical due to the materials used and the peculiar engine - chassis combination. The project was born as a consequence of the manufacturing company desire to access a niche motorcycle market. The project is about a new bike with an adequate family feeling with the factory style, totally customizable; it will be a large capacity, naked sporty two-seater, with innovative design and a very good handling. In the paper the entire design process leading to the presentation will be briefly explained.

Keywords: Chassis | Design | Handling | Motorcycle

Abstract: In the racecar design process the definition of suspension type and geometry is an important stage. A good design of the main parameters, in terms of static and dynamic angles in bump and steer, is the basis of a successful racecar quite often. This paper aims at introducing the development of a new software tool, called MLKrace, that can analyse the suspensions kinematics for a wide range of different layouts. There are today a lot of commercial tools that analyse or simulate suspension behaviour. In general their application is restricted to the classic double wishbone suspension and in this case the calculation of the kinematics is not so difficult. This layout is used on both ends of the majority of formula and sports race cars but it isn't the only possible one. The MLKrace software is instead more suitable to analyse innovative suspension geometries, the mathematics being based on the resolution of the so-called Stewart platform, a method originally devised for parallel robot kinematics. Therefore full multilink or hybrid systems can be designed as easily as a double wishbone. In addition push rod, pull rod or outboard spring systems can be added and the driveshaft required float is computed. Multilink-McPherson hybrid suspensions can be designed as well. The flexibility is the great advantage of this new software. Apart from the mathematic model, a massive effort was devoted to the design of the Windows interface with the aim of making the designer's job particularly easy and effective compared to outdated MS-Dos interfaces of most of the existing software. The output is shown in the form of 2D and 3D animations, a large number of predefined diagrams, numeric tables and regression functions. Copyright © 2002 SAE International.

Abstract: Despite massive research efforts carried out by racing car manufacturers aerodynamics is probably the most unexplored field in the design of high performance vehicles. Scale wind tunnel testing is still the most effective way for the development of a new car, CFD codes being at the experimental stage. Wind tunnel engineers produce what is called an "aero map": a simple graph expressing aerodynamic forces versus ride height. That means, drag, downforce, and relative distribution are measured on an array of front and rear different ride heights. The same concept can be applied to track testing with the use of proper sensors on the real vehicle, such as ground height laser sensors and suspension force transducers. Reading such a map and relating it to static and dynamic suspension characteristics is a vital task for performance optimisation. In the perfect world the centre of pressure would always be in the ideal position anywhere on the track, thus enabling the driver to make the most out of the car. As a matter of fact any unwanted, back and forth movement of the centre of pressure due to pitch and/or heave (e.g. under power, in braking, or on road bumps) affects cornering behaviour: the car can be perceived as difficult and tricky for the driver thus jeopardising performance. A module dedicated to non-linear aerodynamics (called "Aerolap") has been added to the RCS software for lap time simulation, working in close co-operation with the Minardi Formula 1 and BMS Scuderia Italia teams. The vehicle model can now take into account the effects of ride height variations on aerodynamic forces, as well as non-linear suspension and tire ground stiffness. The user can therefore simulate the impact of set-up modifications on aerodynamic balance along the track as well as on overall performance. The RCS project (presented at the 2000 SAE Motorsports Engineering Conference in Detroit) was conceived as a pit lane support tool for the race engineer, who usually works under pressure in a noisy, stressing environment were things happen -and decisions are taken- all very quickly. Therefore a particular effort was devoted to interface and graphics. Regarding the Aerolap an innovative method was devised for map visualisation as an alternative to the usual contour plot. This seems to enable a far more intuitive correlation with performance results. On the math side two different methods were used to approximate the aero map surface: a Gaussian array and the so-called Akima's triangles, the former giving more reliable results where extrapolation is required. Copyright © 2002 SAE International.

Abstract: The paper aims at introducing the developments of a performance simulation method for predicting the potential lap time of a given racing car on a given circuit. It is based on a previous work published in [1]. This first attempt produced fairly reliable results but it was not totally satisfactory since computation was very slow. It was then decided to restart from scratch with the following approach. Reference is made to the renowned «Milliken» [2]. The vehicle maximum G-G envelope is estimated. Then the model follows the «real» raceline -acquired with on-board instrumentation- performing within the G-G envelope. Accurate comparison with real-world data is used to identify and calibrate some of the model parameters. After calibration the model can be used to study the effect of different set-ups, aerodynamic balance, gear ratios etc. Where the circuit is new to the team a trajectory can be designed on a circuit map by using a built-in, parametric CAD-like interface. G-G envelope estimation prior to actual simulation has largely improved the computational speed. Also, the graphic interface aims at pit-lane use by the race engineer. The software is the product of a joint research between the University of Brescia and the team BMS Scuderia Italia therefore it is not available on the market. Copyright © 2000 Society of Automotive Engineers, Inc.

Abstract: One of the hidden aspects of the past Formula One season was the use of indoor road simulators as a mean of speeding up the springing and damping set-up over the race weekend. According to the rumours some teams can perform an indoor set-up optimization overnight by reproducing freshly acquired road profile data. The optimized set-up is then communicated back to the team and tested on-track the day after. The optimization is carried out on a so-called hydraulic four-post rig (or seven-post rig), where a car is shaken at such frequencies and amplitudes to reproduce the same inputs and forces encountered during a typical circuit lap. The Vehicle Dynamics Group of the University of Brescia has recently acquired a four-post rig by Servotest England. The paper aims to describe this facility while future papers will describe the first results obtained in research. Copyright © 1998 Society of Automotive Engineers, Inc.

Abstract: The use of aluminium cast components as the uprights is as old as racing; nevertheless this traditional technology is still a standard on budget racing cars, where the advantages of a steel sheet, welded upright are simply not affordable. It is very well known that cast uprights allow for savings in the case of large production numbers (where "large" should be intended relatively to the racing world). The upright is the component which links the wheel and brake to the rest of the suspension. Being subjected to all the road loads and part of the unsprung mass, it is a fairly critical component. Any failure can lead to an accident; also, it must be as stiff and light as possible for better suspension performance hence roadholding. The paper describes the design of a small single-seater cast upright from the drafting phase to FEM computation to experimental testing. It is a case study rather than an innovative project, but it could be a reference for those involved in a similar design. Copyright © 1998 Society of Automotive Engineers, Inc.

Abstract: Quite a lot has been written on active suspension, the topic being suitable for theoretical studies. Unfortunately only a few applications has seen the road and even less went into production; by now very few road cars equipped with a real active suspension system are available on the market, and the interest to this kind of application seems to be reduced, perhaps because of high costs and restrictive regulations applied to the race car world. For this reason this paper presents the results of a study conducted on the vertical dynamics of a two wheel car model with a semi active suspension system, a possible alternative way to a fully active system to considerably improve suspension performance. Here the damping force of each suspension is obtained by modulating its damping factor according to opportune functions of the system state variables. This allows to reach several of the objectives achievable with a fully active suspension, without the need of a big amount of energy. © Copyright 1996 Society of Automotive Engineers, Inc.

Abstract: The top Formula 1 and Indycar teams make large use of computer simulation to improve the performance of their cars and make the set-up process quicker on the circuit. The paper aims to present a lap time simulation software dedicated to racing cars. It is based on the background of vehicle dynamics research developed at the University of Brescia, Italy (see [1]). It should be stated that racecar dynamics is strongly non-linear due to the fact that tyres are always very near the limit of adhesion. Moreover this makes the effect of lateral load transfer fundamental for the general balance of the car. Therefore Pacejka's Magic Formula has been used for lateral force/slip while longitudinal force computation is based on the assumption of a maximum longitudinal coefficient of friction μ. This is not only for simplicity but it is also due to lack of available data. The combined case is then based on the so-called "traction circle". Lateral and longitudinal load transfer and downforce as well as their effects on tyre load are taken into account. The vehicle model is capable of following a trajectory acquired with the on-board instrumentation. Also, the use of genetic algorithms enables the program to find the optimum cornering line for any given track. Some results are shown and compared with real world data. © Copyright 1996 Society of Automotive Engineers, Inc.

Abstract: The time of the "magic touch" approach to race car design is nearly over, and modern engineering techniques are more and more employed in high-level racing. Finite Element Analysis, Computational Fluid Dynamics, Vehicle Dynamics are some of the computer-aided methods which are being successfully applied to improve engine performance, aerodynamics, structural effectiveness and driveability. People at the Department of Mechanical Engineering of the University of Brescia have been working on chassis and suspension modeling in co-operation with racing and sports car makers and leading-edge teams since 1989. Current research partners are the FIAT Research Centre (CRF), Dallara Racing Cars, the Scuderia Italia Touring Car Team, and others.