1,721,053 research outputs found
Preface to "Vehicle Dynamics. Fundamentals and Ultimate Trends"
No full textThis book examines the fundamentals of vehicle dynamics, as well as the recent trends in the field, such as torque vectoring control, vehicle state estimation, and autonomous vehicles. It investigates the most pressing problems that vehicle dynamics engineers have been facing nowadays, and the challenges of autonomous vehicles in terms of perception, path planning, and analysis of the road environment. The book will serve as a useful tool for graduate students and researchers in vehicle dynamics and contro
Gravity balancing of a spatial serial 4-dof arm without auxiliary links using minimum number of springs
No full textThe principle of gravity balancing has been studied for a long time. It allows a system to be in
indifferent equilibrium regardless of the configuration. In the literature, gravity balancing
has often been achieved using appropriate combinations of springs and auxiliary links. Some
paper address potential layouts without auxiliary links, but limited to planar mechanisms.
This paper proposes a method to passively balance an anthropomorphic arm, with spatial
kinematics, avoiding the use of auxiliary links.
The approach used in this paper includes the analysis of all the contributions to the potential
energy of the arm. It is shown that they are proportional (according to geometrical and inertial
parameters) to scalar products between configuration-dependent unit vectors and/or configuration-
independent unit vectors.
Analysing the potential energy contributions for each combination of unit vectors, it is shown
how to minimize the number of springs required to balance the mechanism without additional
links. As a result, four possible layouts are developed, all of them using only two springs.
Features and design issues of the four layouts are discussed. Finally, one of them is chosen
for actual implementation
Analytical Derivation and Analysis of Vertical and Lateral Installation Ratios for Swing Axle, McPherson and Double Wishbone Suspension Architectures
No full textIn the context of suspension design, the installation ratio (or motion ratio) is a parameter that relates wheel movement with spring deflection, quite an important kinematic property of a suspension. Yet, no study in the literature provides a clear relationship between the installation ratio and the geometrical features of a suspension. This paper employs rigid body kinematics and appropriate geometrical schematics to fill such a gap. Analytical expressions of the installation ratio are derived for three suspension layouts: swing axle, McPherson, double wishbone. Key concepts such as instant center, roll center and camber gain are harnessed to provide insightful analyses for relevant case studies of suspension passenger cars. Among the key results, the typical assumption of a McPherson installation ratio close to 1 is supported by a formal demonstration, and the new concept of “lateral” installation ratio is introduced which, alongside the classical “vertical” installation ratio, further characterizes suspension motion. Numerical results obtained through a multibody software support the findings of this paper. In conclusion, this study provides valuable insights for suspension design engineers
Torque Vectoring Control for Enhancing Vehicle Safety and Energy Efficiency
Full text linkTorque vectoring control is one of the most interesting techniques applicable to electric vehicles with multiple motors. Essentially it is the possibility to allocate desired amounts of torque to each motor. With an uneven allocation of torque between left and right sides of the vehicle, a direct yaw moment can be generated and exploited to enhance the vehicle handling behaviour. This allows to enhance vehicle safety, stability and cornering performance. Significant energy efficiency benefits are also achievable, either as a main priority or as a secondary objective when the main target is the vehicle handling behaviour. This Chapter explains the underlying principles of each element of a torque vectoring control framework: reference generator, high level controller, and low level controller. Notable applications are also presented and discussed in detail
Estimating vehicle sideslip angle through kinematic and dynamic contributions: Theory and experimental results
No full textVehicle lateral stability plays an important role within vehicle passenger safety. The study of lateral stability is typically related to investigating the dynamics of relevant vehicle states: among these, the vehicle sideslip angle ((Formula presented.)) emerges as a prominent candidate. Sideslip angle measurement is expensive and impractical, hence estimation techniques are often used, typically based on Kalman filters or neural networks, both with their issues. This work presents an alternative estimation method based on the idea of splitting sideslip angle into kinematic and dynamic contributions, and by observing that the kinematic contribution is straightforward to estimate. Therefore, efforts are devoted into estimating dynamic sideslip angle, which is herein obtained through a parametric interpolation harnessing lateral acceleration. Only data available from traditional vehicle onboard sensors are used in the process. Experimental results are presented along several manoeuvres on a full-scale vehicle, with the estimator running online within a dSPACE unit, ultimately supporting the efficacy and real-time feasibility of the proposed approach
Analytical solution of vehicle phase-plane equilibria through the Root-Rational tyre model
No full textPassenger vehicle steady-state behaviour has been investigated for a long time. Among the existing methods, the phase portrait is rather popular and useful. However, the computation of vehicle equilibria may only be done numerically. Furthermore, the numerical procedure must be repeated in case of changes in the inputs (e.g. steering angle). This paper proposes a new methodology to obtain an analytical solution of vehicle equilibria. The key is the definition of a new tyre model, denoted as Root-Rational (RR) tyre model, which allows inverting the vehicle dynamics equations in closed form. Using the proposed tyre model reduces the equilibria location problem to finding the roots of a third-order polynomial. After describing the procedure in detail, comparisons are made between the analytical solution and a classical numerical approach, either using the same RR tyre model or a more classical one. Results show great accuracy when locating the equilibria coordinates and a significantly re..
Maps of Achievable Performance: A New General Tool for Vehicle Handling Analysis
No full textMAPs are two-dimensional representations of potentially any pair of vehicle-related variables. MAPs provide the reader with an at-a-glance grasp of any possible steady-state condition achievable by a vehicle, identified by a region in the chosen two-dimensional plane. Level curves depicted inside the achievable region allow to include information on a third variable of interest. After presenting how to build a generic MAP, this paper analyzes several MAPs for three case-study vehicles, providing new insights to be grasped and harnessed by vehicle dynamicists
Optimal torque management strategies for all-wheel-drive electric motorcycles
No full textThe need for more sustainable mobility is fostering the electrification of all types of road vehicles. Electrification has also led to increased interest in multi-motor solutions for all-wheel-drive powertrains, to the benefit of handling and stability, and offering the possibility of reducing energy usage thanks to the optimisation of multi-motor torque management. This paper investigates whether the energy efficiency of a dual-motor, all-wheel-drive electric motorcycle is greater than the efficiency of a standard single-motor, rear-wheel-drive one. A mathematical model for the estimation of the driving losses is presented first. The model is then used to develop an optimal torque management strategy that minimises powertrain losses under propulsion as well as a strategy that maximises energy recovery under braking. A case study is used to quantitatively assess the proposed strategies, which are also compared to the performance of standard rear-wheel-drive motorcycles both in terms of energy efficiency and riding safety. Simulation results highlight that the all-wheel-drive electric motorcycle outperforms the rear-wheel-drive both in terms of energy efficiency and tyre-road friction usage. Overall, the maximisation of energy efficiency or safety–depending on specific driving conditions–is achievable with a feed-forward torque management system
Loading system mechanism for dielectric elastomer generators with equi-biaxial state of deformation
Full text link...
Proceedings of SPIE - The International Society for Optical Engineering
Volume 9056, 2014, Article number 90561F
Electroactive Polymer Actuators and Devices, EAPAD 2014; San Diego, CA; United States; 10 March 2014 through 13 March 2014; Code 106848
Loading system mechanism for dielectric elastomer generators with equi-biaxial state of deformation (Conference Paper)
Fontana, M. , Moretti, G., Lenzo, B., Vertechy, R.
PERCRO SEES, TeCIP Institute, Scuola Superiore sant'Anna, Piazza Martiri della Libertà 33, Pisa, 5612, Italy
View references (18)
Abstract
Dielectric Elastomer Generators (DEGs) are devices that employ a cyclically variable membrane capacitor to produce electricity from oscillating sources of mechanical energy. Capacitance variation is obtained thanks to the use of dielectric and conductive layers that can undergo different states of deformation including: uniform or non-uniform and uni- or multi-axial stretching. Among them, uniform equi-biaxial stretching is reputed as being the most effective state of deformation that maximizes the amount of energy that can be extracted in a cycle by a unit volume of Dielectric Elastomer (DE) material. This paper presents a DEG concept, with linear input motion and tunable impedance, that is based on a mechanical loading system for inducing uniform equi-biaxial states of deformation. The presented system employs two circular DE membrane capacitors that are arranged in an agonist-antagonist configuration. An analytical model of the overall system is developed and used to find the optimal design parameters that make it possible to tune the elastic response of the generator over the range of motion of interest. An apparatus is developed for the equi-biaxial testing of DE membranes and used for the experimental verification of the employed numerical models
Revisiting the mechanical limited-slip differential for high-performance and race car applications
Full text linkThis 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
- …
