130,403 research outputs found
Experiential learning in engineering education: The role of student design competitions and a case study
No full textStudent 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
Revisiting the mechanical limited-slip differential for high-performance and race car applications
No full textThis 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
BikeShake: the design of an indoor simulator dedicated to motorcycle ride testing as an interactive project
No full textA 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
On the vehicle sideslip angle estimation: a literature review of methods, models and innovations
No full textTypical active safety systems controlling the dynamics of passenger cars rely on real-time monitoring of the vehicle sideslip angle (VSA), together with other signals like wheel angular velocities, steering angle, lateral acceleration, and the rate of rotation about the vertical axis, known as the yaw rate.
The VSA (aka attitude or “drifting” angle) is defined as the angle between the vehicle 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, in transients 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 like 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, focusing 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. Advantages and limitations of each technique have been highlighted and discussed
On the Passive Limited Slip Differential for High Performance Vehicle Applications
No full textThe paper is aimed at a comprehensive revision of the working principles and limitations of the mechanical limited slip differential, the traditional, passive device used to improve traction capabilities and to extend the performance envelope of high performance road cars, racing and rally cars. Its impact on vehicle handling through a yaw moment generated with passive torque distribution across the drive axle is investigated by means of vehicle dynamics simulations
A road-holding index based on ride dynamics for high-downforce racing cars.
No full textThis work builds on some of the current industry techniques used in racing to evaluate vertical dynamics performance and propose a new methodology. It creates an 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
The design of a motorcycle featuring fully independent adjustability for front suspension and steering geometry
No full textThe 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
Integrated design tools for model-based development of innovative vehicle chassis and powertrain systems
No full textThe 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
ON THE TORQUE STEER PROBLEM FOR FRONT-WHEEL-DRIVE ELECTRIC CARS
No full textBeyond 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 intui-tive 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 op-timize 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 con-tact 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
Efficient Regenerative Braking Strategy Aimed at Preserving Vehicle Stability by Preventing Wheel Locking
No full textThis 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
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