| 1. |
- Albinsson, Anton, 1989, et al.
(författare)
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Identification of tyre characteristics using active force excitation
- 2016
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Ingår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015. - : CRC Press. - 9781138028852 ; , s. 501-510
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Konferensbidrag (refereegranskat)abstract
- Knowledge of the maximum tyre-road friction coefficient can improve active safety systems by defining actuator boundaries and adaptable intervention thresholds. Estimation of the coefficient of friction based on tyre response measurements requires large level of force excitation. Under normal driving conditions, manoeuvres with large tyre utilizations are rare. This study investigates a method where wheel torques with opposite signs are applied to the front and rear axle simultaneously. This procedure allows for an intervention with large tyre excitations without disturbing the motion of the vehicle. The intervention is evaluated in simulations and experiments. Further, a method is proposed which does not require measurement of the vehicle longitudinal velocity. The results show that it is possible to estimate the current friction coefficient with the proposed method, although the assumption made in the proposed method makes the friction estimate sensitive to measurement noise on the wheel speed signal.
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| 2. |
- Casanueva, Carlos, 1981-, et al.
(författare)
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Comparison of wear prediction models for different contact conditions
- 2016
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Ingår i: Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics (IAVSD 2015), Graz, Austria, 17-21 August 2015. - : CRC Press. - 9781138028852 - 9781498777025 ; , s. 871-878
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Konferensbidrag (refereegranskat)abstract
- Simulation of wheel and rail wear allows to predict long term profile evolution and thus, study the consequences of wheel damage in the dynamic behaviour of the vehicle, or study future maintenance requirements. Several models have been developed which try to solve the wear issue by relating the energy dissipated in the wheel-rail contact to the worn out material, from which two can be highlighted (Tg/A and Archard) which have significant differences on contact level. Even though, the prediction of long term wheel profile evolution has been validated with these two models, which means that for regular applications they seem to have an equivalent behaviour. In this work similarities and differences between the long term wear prediction methodologies are analysed, discussing their actual limitations. Then, these differences are exploited in specific operational cases to compare their wear prediction performance.
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| 3. |
- Daniel, Wanner, et al.
(författare)
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Experimental implementation of a fault handling strategy for electric vehicles with individual-wheel drives
- 2016
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Ingår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015. - : CRC Press. - 9781138028852 ; , s. 147-152
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Konferensbidrag (refereegranskat)abstract
- This paper presents a fault handling strategy for electric vehicles with four individual-wheel drives, which are based on wheel hub motors. The control strategy to handle the faults is based on the principle of control allocation and is implemented in an experimental vehicle. Experimental tests has been performed with the experimental vehicle and with simulation. The results show that the directional stability of such a vehicle can be improved for the analysed manoeuvre and failure mode, and the tendencies of the experimental results correspond with the simulation results. It has been found that the lateral and yaw motion could be strongly improved.
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| 4. |
- Gao, Yangyan, et al.
(författare)
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An autonomous safety system for road departure prevention based on combined path and sideslip control
- 2016
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Ingår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015. - : CRC Press. - 9781138028852 ; , s. 281-286
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Konferensbidrag (refereegranskat)abstract
- Practical limits on vehicle speed in curves depends on many factors: road friction, lateral maneuvering room, driving skill and the willingness of a driver to brakewhile cornering. This is in addition to multiple vehicle design and performance characteristics, including the classical understeer behaviour. The current paper considers an active safety control system to protect against the major effects of over-speed in curves, especially lateral drift leading to lane or road departure. The concept is to use available information about various vehicle and environmental factors-e.g. surface friction, lane and shoulder widths-and compute control interventions which will protect against lane and road departure. The proposed system is based on the optimal control of particle motions, as described previously for a Parabolic Path Reference (PPR) which provides a control reference for combined cornering and braking under computer control. The earlier work assumed very simple road geometry which is generalized in the present analysis. Further, we make use of a novel control algorithm based on nonlinear optimal control theory, capable of delivering the required integrated control of speed, path curvature and yaw stability. This paper describes the key concepts for designing and implementing such a system.
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| 5. |
- Gil Gómez, Gaspar, et al.
(författare)
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Analysing vehicle dynamics objective and subjective testing in winter conditions
- 2016
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Ingår i: The Dynamics of Vehicles on Roads and Tracks. - : Taylor & Francis Group. - 9781138028852 - 9781498777025 ; , s. 759-768
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Konferensbidrag (refereegranskat)abstract
- This paper presents a test procedure developed to gather good quality data from objective and subjective testing on winter conditions. As the final goal of this test is to analyse the correlation between objective metrics and subjective assessments on winter for steering and handling, this procedure has to ensure a minimum change of the surface properties, which has a major influence on vehicle performance, during the whole test campaign. Therefore, the method presented keeps the total test time very low and allows similar vehicle configurations to be test- ed, objectively and subjectively, very close in time. Moreover, continuous maintenance work on the ice is performed. Reference vehicles are also used to monitor the changes on vehicle per- formance caused by weather conditions, which are inevitable. The method showed to be very effective. Initial results on objective metrics and subjective assessments are also presented.
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| 6. |
- Lundahl, Kristoffer, et al.
(författare)
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Path-dependent rollover prevention for critical truck maneuvers
- 2016
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Ingår i: The Dynamics of Vehicles on Roads and Tracks. - : CRC Press. - 9781138028852 - 9781498777025 ; , s. 317-326
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Konferensbidrag (refereegranskat)abstract
- Predicting rollover is usually performed using rollover indices, where rollover is anticipated when the indices reach certain threshold values. If knowledge about the vehicle driving path is available, rollover can be detected and prevented earlier. In this work, the rollover-prediction and rollover-prevention abilities for simple vehicle models are evaluated and compared against a high-fidelity vehicle model. The analysis is performed by using the models in critical and rolloverprone maneuvers, generated with optimal control methods. The main conclusion is that a simple point-mass model would be sufficient in a velocity based rollover-prevention controller.
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| 7. |
- Pålsson, Björn, 1981
(författare)
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Robust evaluation of rail damage and track forces using representative load collectives
- 2015
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Ingår i: 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015; Graz; Austria; 17 August 2015 through 21 August 2015. - : CRC Press. - 9781138028852 ; , s. 841-850
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Konferensbidrag (refereegranskat)abstract
- This paper presents a method for robust evaluation of rail damage and lateral wheel–rail contact force spectra for rail traffic in curves. To this end the Manchester Benchmarks passenger vehicle model is used and scatter in vehicle, suspension and wheel profile properties is accounted for in the generation of load collectives that are used for rail damage assessment. Rail wear and RCF damage are evaluated at different curve radii for load collectives of different size using Archard’s wear law and the Tγ RCF damage model. Variance in damage estimates are investigated and it is shown that variance is reduced at smaller curve radii for both damage criteria. It is also found that the variance is larger for the RCF damage estimate than for the wear calculations.
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| 8. |
- Shahzamanian Sichani, Matin, et al.
(författare)
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An alternative to FASTSIM for tangential solution of the wheel-rail contact
- 2016
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Ingår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System. - : CRC Press. - 9781498777025 - 9781138028852 ; , s. 1377-1385
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Konferensbidrag (refereegranskat)abstract
- In most rail vehicle dynamics simulation packages, creep forces are estimated by means of Kalker's FASTSIM algorithm. While 5%-25% error is expected for force estimation the errors of shear stress distribution, needed for wheel/rail damage analysis, may rise above 30%. This is mainly due to the use of parabolic traction bound in FASTSIM. Thus, a novel algorithm called FaStrip is proposed as an alternative to FASTSIM. It is based on the strip theory in which elliptic traction bound is used. The comparison between the two algorithms, evaluated by CONTACT, shows that using FaStrip improves the accuracy of the estimated shear stress distribution while the creep force estimation in all studied cases is significantly improved as well. In one case, for instance, the error in force estimation reduces from 18% to less than 2%. Since FaStrip is as fast as FASTSIM, it can be an alternative for tangential solution of the wheel-rail contact in simulation packages.
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| 9. |
- Yoshimura, Kimiyasu, et al.
(författare)
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Studying Road Roughness Effect on Rolling Resistance Using Brush Tyre Model and Self-Affine Fractal Surfaces
- 2016
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Ingår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015. - : CRC Press. - 9781138028852 ; , s. 273-280
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Konferensbidrag (refereegranskat)abstract
- While there are many tyre and vehicle dependent factors that affect the rollingresistance, the road properties play also an influential role in the overall resistance on the vehicle.The aim of this study is to develop amodel that can estimate the effect of road roughness on rollingresistance of tyres where both the texture-dependent and independent factors are contributing tooverall rolling resistance. In this paper, a method based on the self-affine fractal surfaces is usedto model realistic road characteristics in order to couple it with a brush based tyre model to beable to study the influence of road roughness on tyre rolling resistance. The simulation resultssuggest that the rolling resistance increases with increased RMS-value and both the macro- andthe micro-texture have an influence on the rolling resistance while the macro-texture effect is moreinfluential. The results of this paper can be related to the estimation of fuel economy on differentroad textures, from macro-texture to micro-texture and further optimisation of road surfaces.
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