1,721,057 research outputs found
The Control of the Handling of a Front Wheel Drive Vehicle by Means of a Magnetorheological Differential
No full textThis paper presents a semi-active differential, called MRF LSD (MagnetoRheological Fluid Limited Slip Differential) that allows to bias torque between the driving wheels. It is based on the magnetorheological (MR) fluid employment, that allows to change, in a controlled manner, the differential locking torque and, consequently, the torque bias ratio. The device is an adaptive one and allows to obtain an asymmetric torque distribution in order to improve vehicle handling. The device modelling and the control algorithm, realized for this activity, are described. The illustrated results highlight the advantages that are attainable regarding directional behaviour, stability and traction for a front wheel drive (FWD) vehicle. A comparison with a traditional passive limited slip differential has been conducted
A Test Rig for Tyre Envelope Model Characterization
No full textThis paper deals with tyre enveloping behaviour on uneven road surface. To build realistic and reliable vehicle dynamics models it is of fundamental importance to study the influence of road obstacles and irregularities on forces and displacements involving a rolling tyre. After a brief review about early studies concerning this phenomenon, the tandem model with elliptical cams is introduced and described, highlighting its hypothesis and the parameters on which it is based, the most important of which are the cams profiles and the distance between them. The main aim of this paper is the executive project of a test rig aimed to carry out an experimental campaign for the identification of the parameters of the tandem cam model and for its validation.
The idea is to experimentally acquire the path of the patch centre of a tyre rolling over an obstacle, to define the parameters of the curves employed for the cam profiles and the distance between them in the tandem model. It is important to highlight that these parameters are strictly connected to tyre properties and need tests to be investigated and identified.
The design started from a test bench for motorcycles already available at DII’s Tyre Lab, introducing proper changes without compromising original test bench destination
A Physical Analytical Model to Study the Elasto-Kinematic Behaviour of a MacPherson Suspension
No full textThis paper describes a physical analytical model able to characterize the elasto-kinematic behaviour of a MacPherson suspension for automotive applications. The presented model allows to determine the position and the orientation of the wheel upright as a function of the generalized three-dimensional loads applied to the center of the tire-road contact patch, and consequently to determine the variation of the characteristic suspension parameters of main interest: wheel base, track, camber and toe. All the steps carried out to build the model are described, starting from the kinematic analysis, ongoing with the static and finally with the elasto-kinematic ones, describing how compliance has been taken into account in equilibrium conditions. The kinematic and static analyses have been validated by comparing the results with the ones of a multibody model. In order to obtain the desired elasto-kinematic curves it is possible to act both on the geometry of the suspension, and on the stiffness of the bushings and of the arms, which cause compliance, modifying the positions of the various elements of the suspension and ultimately of the hub. By means of the proposed model it is possible to rapidly evaluate the effects of these variations. Numerical examples relative to a suspension for the front axle of a vehicle are presented
Tension in a Flat Belt Transmission: Experimental Investigation
No full textIn this paper we report the results of an experimental investigation aimed at determining the tension variation in a flat belt transmission. The belt tension was obtained by measuring its deformation with electrical resistance strain gauges. The investigation results are preceded by a reference to the belt transmission theory, in particular to Grashof's and Firbank's models. With regards to the Firbank model, in order to better interpret the experimental results, some original calculations were carried out starting from Firbank's paper.
The test results showed the efficiency of the Grashof model, as regards the presence of both an adhesion arc and a sliding one, which respectively decrease and increase with the growth of the force transmitted into the device and, at the same time, showed the Firbank model's validity in relation to the presence both of a shear strain and different sliding angles on the driving and driven pulleys
Dynamic Behavior and Motion Planning of a Robot Arm with Non-Rigid Transmission
No full textIn this paper some aspects of the dynamical behavior of manipulators with non-rigid transmissions between servomotors and links are reported.
The dynamical effects related with transmission elasticity are analysed by means of a mathematical model and some dedicated software.
The simulation results show how different laws of motion can induce end-effector vibrations, sometimes quite wide caused by occurrence of resonance.
These vibrations can be reduced by means of an appropriate computing of the servomotors laws of motion; in this paper an algorithm is described to determine the above-mentioned laws of motions.
The authors propose a method to compute servomotors laws of motion that permit to the end-effector to describe a planned trajectory with a robot arm having non rigid transmission between motors and links; this technique just needs the knowledge of a simple manipulator mathematical model and is apart from the control system.
This method has been validated using a virtual prototype realized by co-simulations between ADAMS code, for the mechanical model, and SIMULINK code, for the control and actuator systems
Virtual Testing of Advanced Driving Assistance Systems
No full textThis paper presents some results on the development and testing of new solutions in the field of driving automation. The introduction of increasing levels of vehicle automation aimed at enhancing road safety requires a renewed approach to the research and development process and needs a multi-actor environment where the innovation can be tested. Indeed, vehicle automation spans several scientific disciplines and it is becoming exceedingly difficult and too costly for a single research innovation team to go in depth into all technologies and solutions. This is shifting the innovation process toward a multidisciplinary approach in which the only way to ensure an easy, rapid, efficient and scalable introduction of the required innovation is to adopt integrated and complex testing platforms for the simulation of automation solutions, based on a modular architecture, where independent components can be developed and then integrated and tested in a multi-actor environment. A platform for virtual testing is presented herein and employed to assess the performance of an integrated driving assistance solution based on computing appropriate surrogate measures of safety that allow for the transition between different automation logics in free-flow, car-following and emergency braking conditions
A Flexible Ring Tyre Model for Normal Interaction
No full textA physical – numerical tyre model has been developed. The whole model allows to obtain the tyre – road interactions which can be used in vehicle dynamics simulations. In this paper its capabilities in terms of normal interaction analysis are presented. The tyre normal interaction, i.e. the relationship between the normal load and the normal deflection, influences the tangential (longitudinal plus lateral) one, which determines the vehicle’s handling behaviour. The parameters used in the model depend on the structure of the tyre and they can be measured on the real tyre. The tyre has been schematized as composed by a flexible belt, by the sidewalls and by a rigid ring (rim). The flexible belt is composed by a number of lumped masses linked by extensional and bending stiffnesses and dampers. The tyre model has been developed using the finite segment method. Using this method it is possible to include in the tyre simulations various non-linear structural effects due to large displacements and rotations. The model allows to simulate both steady state and transient conditions
Software in the Loop Development and Validation of a Cornering Brake Control Logic
No full textIn this article, a logic for vehicle dynamics control during partial braking while turning a corner is presented, which only requires knowledge of the instantaneous speed of the four wheels. For this reason, the proposed control algorithm can be adopted on all ABS equipped cars. A scheme of the simulation program for logic validation is described, which is constituted by a loop of software models of the principal vehicle subsystems which are singly illustrated. The proposed logic has been tested both in closed and open-loop maneuvers. The results are provided in the form of time histories of the principal analyzed quantities. The analysis of the results confirms the goodness of the proposed control strategy
Physical Modelling of Tire Wear for the Analysis of the Influence of Thermal and Frictional Effects on Vehicle Performance
No full textThe tire and vehicle setup definition, able to optimise grip performance and thermal working conditions, can make the real difference as for motorsport racing teams, used to deal with relevant wear and degradation phenomena, as for tire makers, requesting for design solutions aimed to obtain enduring and stable tread characteristics, as finally for the development of safety systems, conceived in order to maximise road friction, both for worn and unworn tires. The activity discussed in the paper deals with the analysis of the effects that tire wear induces in vehicle performance, in particular as concerns the consequences that tread removal has on thermal and frictional tire behaviour. The physical modelling of complex tire–road interaction phenomena and the employment of specific simulation tools developed by the Vehicle Dynamics UniNa research group allow to predict the tire temperature local distribution by means of TRT model and the adhesive and hysteretic components of friction, thanks to GrETA model. The cooperation between the cited instruments enables the user to study the modifications that a reduced tread thickness, and consequently a decreased SEL (Strain Energy Loss) and dissipative tread volume, cause on the overall vehicle dynamic performance
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