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Reducing derailments of freight trains is of utter importance for improving railway transportation since derailments lead to large service disruption, economic losses and risk related to transported goods. The present paper studies low-speed (below 30 km/h) derailment of freight trains, performing experimental full-scale tests, using an instrumented wagon equipped with a commercial derailment detector. Specifically, the dynamics of a freight wagon during wheel-climb derailment and the motion with one axle derailed are investigated. During the tests, accelerations were measured at the bogie and at the carbody. Moreover, the intervention of the derailment detector was monitored to assess possible causes of false tripping or miss-detections. Two loading conditions were analysed: empty and loaded wagon. Main achievements may be summarised as follows: (1) the activation of the derailment detector is always triggered by impacts between the axle-box and the rail; (2) if the wagon is empty, vibrations induced by a derailed axle over the sleepers strongly depend on vehicle speed and they may not trigger the derailment detector in the range 15–25 km/h; (3) derailment detectors must be installed at both ends of each wagon. This information may be used to develop derailment detection algorithms integrated into electric control units with computing capabilities.. [ABSTRACT FROM AUTHOR]

Automobiles are becoming more and more complex as multiple control systems are integrated into the vehicle platform. This paper investigates the coordination of active rear steering (RWS) and torque vectoring (TV) – which is enabled by independent electric motors at the rear axle – in controlling vehicle lateral dynamics. The proposed controller aims at enhancing vehicle handling performance and stability while cornering. The coordination of the two actuators is achieved by weighting their contribution based on their impact on vehicle dynamics according to the working condition. The impact of each control system is assessed by means of phase portraits. These plots are a very powerful tool for analysing vehicle nonlinear dynamics as they readily display vehicle stability properties and map equilibrium point locations and movement to changing parameters and control inputs. Based on phase portrait analysis, a performance index is thus proposed, which weights more the control action (TV or RWS) capable of leading the vehicle at the nearest equilibrium point with the fastest rate. The controller performance is assessed through numerical simulations carried out using a nonlinear 14 dofs vehicle model. Results are compared with ones of the two controllers alone (RWS and TV) in different manoeuvers and adherence conditions. [ABSTRACT FROM AUTHOR]

Electric motors offer the possibility to control the braking torque in a more precise way than the hydraulic circuit. The applied torque is in fact measured and so it can be used to feedback the controller. Moreover, this information can be used to estimate the tyre–road friction coefficient, before potential friction is reached. The present paper proposes a novel ABS control strategy for electric vehicles with distributed motors. The controller is a six states machine that uses the information on applied braking torque provided by the electric motors. This information is of paramount importance to understand when the wheel reaches the peak of the braking force. Simulation results shows the benefits of the proposed strategy, comparing the results with state of the art acceleration-based controller. [ABSTRACT FROM AUTHOR]

The rollover of road heavy-duty vehicles is one of the most serious problems related to transportation safety. In this paper, an anti-rollover control system based on lateral acceleration and cross-wind force feedback is proposed. The aim of the control system is to improve the vehicle stability by reducing the carbody roll angle and consequently the vertical load transfer. The performances of the anti-rollover controller have been evaluated through simulations carried out with a MB vehicle model. In order to estimate the aerodynamic loads acting on the vehicle, an extended Kalman filter has been designed. Turbulent wind-vehicle interactions have been evaluated through a numerical algorithm based on the corrected quasi-static theory and the vehicle admittance function. [ABSTRACT FROM AUTHOR]

A set of scaling factors has been introduced by Pacejka [Pacejka, H.B., 2002, Tyre and Vehicle Dynamics (Oxford: Butterworth Heinemann Editions)] into his Magic Formula tyre model to take into account the influence of a number of external overall parameters such as road roughness, weather conditions, suspension characteristics and so on. These scaling factors are important for a correct prediction of tyre–road contact forces, but are not a function of the tyre itself. Changing the point of view, one could say that scaling factors should remain constant for different tyres on the same circuit, with the same weather conditions and with the same car. After characterizing different tyres through indoor tests (that do not consider external overall parameters) and after having identified Pacejka’s coefficients with scaling factors equal to one, several outdoor experimental tests have been carried out to assess the influence of vehicle and road surface conditions on scaling factors. These experimental data allowed us to identify, through a minimization approach, the ‘best’ set of Pacejka’s scaling factors for that vehicle and for that tyre on that track. Scaling factors for equal track and vehicle but different tyres were compared to check whether their values remained constant. To access the validity of scaling factors, a comparison between experimental data, collected on an instrumented passenger car, and MB simulations considering unity and identified scaling factors’ values, were carried out. All experimental data shown in this article come from tests carried out within the VERTEC project, a European founded research project (Task 2.a and 2.b) that puts together knowledge coming from vehicle manufacturers (Volvo, Porsche and Centro Ricerche Fiat CRF), tyre manufacturers (Pirelli and Nokian Tyres), control logic manufacturers (Lucas Varity GmbH), road maintenance experts (Centres d’Études Techniques de l’Équipement CETE), transport research organizations (Transport Research Laboratory TRL, Swedish National Road and Transport Research Institute VTI) and universities (Helsinki University of Technology HUT, Politecnico di Milano and University of Florence UNIFI). [ABSTRACT FROM AUTHOR]

This article presents a new methodology for the assessment of the limit safety conditions of road heavy vehicles subjected to cross-wind action: for a typical lorry vehicle, the critical wind curves (CWC) that represent the combination of vehicle speed and wind gust speed, which lead to the overcoming of the safety limits have been calculated. The numerical-experimental procedure allows us to evaluate the aerodynamic loads acting on a heavy vehicle for the given turbulent wind conditions and to compute the corresponding vehicle's response. Experimental data of wind-tunnel tests, together with numerical simulation results are shown. [ABSTRACT FROM AUTHOR]

A set of scaling factors has been introduced by Pacejka into his ‘magic formula’ tyre model to take into account the influence of a number of external overall parameters such as road roughness, weather conditions and suspension characteristics. These scaling factors are important for a correct prediction of tyre-road contact forces but are not a function of the tyre itself. From a different point of view, one could say that scaling factors should remain constant for different tyres on the same circuit, with the same weather conditions and with the same car. After having characterized different tyros through indoor tests (which do not consider external overall parameters) and after having identified Pacejka's coefficients with scaling factors assumed to be one, several outdoor experimental tests have been carried out to determine the influence of vehicle and road surface conditions on scaling factors. These experimental data allowed us to identify, through a minimization approach, the ‘best’ set of Pacejka's scaling factors for that vehicle and that tyre on that track. Scaling factors for the same track and vehicle but for different tyros were compared to check whether their values remained constant. All experimental data shown in this paper comes from tests carried out within the VERTEC project (vehicle, road, tyre and electronic control systems interaction: increasing active vehicle safety by means of a fully integrated model for behaviour prediction in potentially dangerous situations) (official contract G3RD-CT-2002-00805), a European funded research project that puts together knowledge from vehicle manufacturers (Volvo, Porsche and (CRF)), tyre manufacturers (Pirelli and Nokian Tyres ), control logic manufacturers (Lucas Varity GmbH), road maintenance experts (CETE), transport research organizations (TRL) and (VTI) and universities (HUT) and (UNIFI)). The results shown in this paper arc obtained by tests performed during tasks 2a (Reference tyre characterizations and tests) and 2b (Development and validation of tyre-pavement interaction model) of VERTEC project. The partners involved in these tasks are Pirelli, Nokian, Porsche, CRF, CETE, VTI, HUT and UNIFI. [ABSTRACT FROM AUTHOR]