Road Surface Irregularities Research Articles

Assessing dynamic tyre forces occurring after traversing local roadway irregularities by the pothole dynamic amplification factor method

A technique to assess the dynamic tyre forces arising after passing road surface irregularities by a vehicle modelled as a general linear multiple-degrees-of-freedom system is presented. The equations governing vibration of a vehicle moving along an uneven profile are, first, transformed to the state-space form and, then, to a system of uncoupled first-order complex differential equations. For a local roadway irregularity described functionally, solutions of all equations are found analytically and expressed in terms of a unique function of one complex variable, the so-called pothole dynamic amplification factor (DAF). The problem is shown to be decomposed into separate calculating vehicle- specific data, which are easily constructed in terms of physical and modal vehicle characteristics, and the DAF function, which does not depend on the vehicle model. The dynamic tyre forces are obtained then by simple arithmetic manipulation of the complex numbers obtained. The technique discussed is not specific to a particular vehicle model or an irregularity shape. The discussion is amply illustrated by examples of the application of the technique to the calculation of the tyre forces for three simple vehicle models.

Assessing tire forces due to roadway unevenness by the pothole dynamic amplification factor method

A technique is developed to assess the dynamic contact forces arising after passing road surface irregularities by a vehicle modelled as a general linear MDOF system. The equations governing vibration of a vehicle moving along an uneven profile are, first, transformed to the state-space form and, then, to a system of uncoupled first order complex differential equations. For a local roadway irregularity described functionally, solutions of all equations are found analytically and expressed in terms of a unique function of one complex variable, the so-called pothole dynamic amplification factor, which is specific to the irregularity shape. The solutions obtained are combined to give dependencies of the harmonic components of the contact forces arising after the passage of the irregularity on the vehicle speed and irregularity dimensions. The problem is shown to be decomposed into separate calculation of vehicle and pothole-specific data. The technique developed is not specific to a particular vehicle model or an irregularity shape: the vehicle model is represented by its mass, stiffness, and damping matrices, and the replacement of one irregularity by another simply requires replacement of one dynamic amplification factor function by another. The latter are derived in Appendix A for several pothole configurations. The discussion is amply illustrated by examples of the application of the technique to the calculation of the tire forces for two simple vehicle models and several potholes of different shape.

Application of the pothole DAF method to vehicles traversing periodic roadway irregularities

This paper is a sequel to the work discussed in Pesterev et al. (Journal of Sound and Vibration, in press). In that paper, it was suggested that the technique to determine the effect of a local road surface irregularity on the dynamics of a vehicle modelled as a linear multi-degree-of-freedom system relies on the so-called pothole dynamic amplification factor (DAF), which is a complex-valued function specific to the irregularity shape. This paper discusses the companion problem of how to determine the DAF function for an irregularity represented as a superposition of simpler ones. Another purpose of this paper is to demonstrate the application of the pothole DAF functions technique to finding a priori estimates of the effect of irregularities with a repeated structure. Specifically, we solve the problem of finding the conditions under which the dynamic effect of two identical potholes located one after another is greater than that due to the single pothole. We also find the estimate for the number of periods of a periodic irregularity that are sufficient in order to consider the oscillator response as steady state. The discussions are illustrated by numerical examples.

A generally applicable 3D truck ride simulation with coupled rigid bodies and finite element models

The aim of this paper is to present a three dimensional ride simulation for a medium weight truck equipped with two axles. The dynamics of both a rigid body and a flexible frame structure are considered in the vehicle model. The road surface irregularities are modelled as stationary Gaussian random excitations taking into account the cross correlation between the vehicle axles and tracks. The free-free modal properties of the frame structure have been calculated using the FEM (finite-element method) considering two different configurations for the vehicle frame. The results from the FE models are incorporated with the general vehicle model to study their effect on the vehicle ride behaviour. The equations of motion of the general vehicle model have been formulated applying the Lagrangian approach and the modal superposition theory. Random responses, including power spectral densities and root mean square values, are calculated and analysed. The results covered 23 response variables including driver, cab and body accelerations and the induced dynamic forces in the cab and main suspension systems and tyres. The results showed that the structure dynamics of the frame strongly affects several response variables. Moreover, it has been found that the present simulation technique is practical, powerful, and economic, and can be commercially used for the assessment of truck dynamics. Conclusions and recommendations for further work are given.

Design aspects of reducing the generated dynamic tyre loads of the articulated tanker vehicles

The investigation of the dynamic tyre loads generated due to the liquid slosh in a tanker vehicle is an important research topic because of their harmful effect on both vehicle and road surfaces. In this paper, a comprehensive study concerning the ride behaviour of an articulated tanker vehicle, equipped with a cylindrical container, has been made. The road surface irregularities and a step deceleration in the longitudinal direction have been used to excite the vehicle system. A 7-DOF mathematical model has been constructed to represent an articulated tanker vehicle and simulate its dynamic behaviour. A computer program using the PC MATLAB software has been designed to solve the differential equations of motion of the vehicle system. The nonlinearity generated by the dynamic interaction between the vehicle structure and the moving liquid cargo is included in the vehicle model considering different filling ratios. An experimental investigation has been carried out to validate the modelling and numerical techniques that are used to simulate the dynamic motions of the tanker vehicle. For this purpose, an experimental model has been designed, constructed and utilised. The trends of the theoretical model results are compared with the experimental results, and good agreement between them has been found. The possibility of reducing the dynamic tyre loads is examined by tuning the following design parameters: (a) distance between the centres of gravity of both the empty tank/semi-trailer unit and the liquid cargo, (b) damping coefficient of the semi-trailer suspension, (c) use of anti surge (kinetic energy) safety baffles. Specific values for these parameters are recommended considering a 3-axle articulated tanker vehicle as a case study. Results analysis, conclusions and suggestions for further work are given.

不整路でも使える歩行支援機の動力学的研究(J05-1 ライフサポート(1),J05 ライフサポート)

不整路でも使える歩行支援機の動力学的研究(J05-1 ライフサポート(1),J05 ライフサポート)

A novel approach to the calculation of pothole-induced contact forces in MDOF vehicle models

A technique is developed to predict the dynamic contact forces arising after passing road surface irregularities by a vehicle modelled as an undamped multiple-degrees-of-freedom (MDOF) system. An MDOF system moving along an uneven profile is decomposed into an aggregate of independent oscillators in the modal space, such that the response of each oscillator can be calculated independently. An equation relating the contact forces in the physical space to the modal forces is established. The technique developed is applied to the calculation of the coefficients of the harmonic components of the contact forces arising after the passage of a “cosine” pothole. The application of the technique to various problems, such as evaluation of the effect of parameter modifications on the vehicle dynamics and reduction of vehicle models in bridge-related problems, as well as its extension to the damped case, are also discussed. One interesting phenomenon reported in the DIVINE project [1], regarding the replacement of a steel suspension by an air suspension, resulting in an increase of the maximum response of short-span bridges, is explained by applying the technique suggested. The discussion is amply illustrated by examples of the application of the technique to the calculation of the tire forces due to a pothole for two simple—quarter-car and half-car—vehicle models.

A study on tire modeling for camber thrust and camber torque

This study deals with a tire model for camber thrust and camber torque on an irregular road surface such as road with ruts. At first, tire characteristics with camber angle are measured, for example dimensions of contact area, width, radius of tire and so on. In this research, it is shown to be necessary to those for tire model. The design parameters of brush model are decided. In this tire model, it is considered that the dimensions of contact area is related to the tire camber angle and load, and also the contact pressure is changed according to the contact length, and also the rigidity is changed according to the contact pressure. Finally, it is shown that the calculation result of the tire model has a good expression for the characteristics of camber thrust and camber torque.

Simulation of Road Surface Profiles

This paper presents a novel technique for the simulation of shock and vibrations related to road surface irregularities. The technique is based on a recently developed universal road profile classification scheme, which is one of the main outcomes of a project aimed at better understanding the statistical nature of road surfaces and their interactions with road vehicles. The method, which focuses on the nonstationary and non- Gaussian nature of road profiles, is described along with an analysis procedure developed and implemented to automatically detect and extract transient events from the road spatial acceleration data as well as identify stationary segments of similar roughness (RMS). The paper shows how the concept of treating road surface irregularities as two fundamental components, namely, steady-state road surface irregularities and transient events, can be employed for classification and simulation purposes. The simulation technique is based on a universal statistical model of road surface profiles that characterizes the power spectral density of the underlying irregularities, the probability distribution function of the RMS level using the offset Rayleigh distribution function, and the transient density. The transient events are generated with random amplitudes according to the Gaussian distribution, the mean and standard deviation of which are functions of the underlying RMS level. This paper shows how these two components can be combined to numerically synthesize a process that faithfully represents the nonstationary, transient-laden nature of road surface profiles. The synthesized process can be physically realized on a vibration shaker to simulate road profiles.

DYNAMICS OF MULTI-SPAN CONTINUOUS STRAIGHT BRIDGES SUBJECT TO MULTI-DEGREES OF FREEDOM MOVING VEHICLE EXCITATION

The paper presents an analytical approach to the problem of vehicle–bridge dynamic interaction. Starting from early studies based on a simply supported beam interacting with a lumped mass moving at constant speed, in recent years researchers have improved the models of both the bridge and the vehicle. On this basis, the bridge is modelled here as a multi-span continuous isotropic plate; its response to external loads is defined by applying the mode superposition principle and takes into account both flexural and torsional mode shapes, the latter being usually neglected in the literature. The plate is considered proportionally damped and its modes are computed by means of the Rayleigh–Ritz method. The scheme adopted for the vehicle consists of a seven degrees-of-freedom system moving at constant speed over the isotropic rough bridge surface. The numerical investigation, based on these analytical models, refers to a three-span bridge and includes the importance of torsional mode shapes, of road surface irregularities and of vehicle speed.

Effect of frame flexibility on the ride vibration of trucks

The aim of the paper is to study the ride vibration behaviour of trucks and in particular the effect of including a flexible frame. The work is a theoretical investigation and concentrates on the ride comfort, cargo protection, structural integrity and vehicle safety. The road surface irregularities are represented as stationary Gaussian random excitations. To analyse the vehicle dynamic responses, the spectral analysis technique has been used and the driver acceleration reponses have been weighted according to the ISO ride comfort techniques. To study the effects of the frame flexibility, the truck frame has been modelled using the FEM (finite element method) and its modal properties have been calculated. An explanation of the modal superposition theory is given and the possibility of incorporating this theory with Lagrange's equations for modelling a truck containing flexible subsystems is discussed and applied. Numerical results are presented for the truck, including power spectral densities and root mean square values of the vehicle dynamic response variables. The results show that there is good agreement with the previous experimental published work and that the modelling technique established is very powerful and economical for the analysis of complex vehicle structures. From comparison of the responses of the rigid and flexible body models it has been found that the frame flexibility strongly affects the accelerations of both the driver and the truck body. Therefore, it is critical that frame flexibility effects are taken into account in the design of primary, cab and engine suspension systems.

AN ANALYSIS OF VEHICLE BEHAVIOUR DURING LANE-CHANGE MANOEUVRE ON AN UNEVEN ROAD SURFACE

SUMMARY The paper presents results of simulation investigations of biaxial vehicle motion on an even and uneven road during lane-change-type manoeuvre. Test conditions, method, data processing, analysis and presentation are according to ISO/TR 8725 [l]. The road surface irregularities adopted for the investigations correspond to two roads of different class according to ISO/TC 108/253 [2] and one ideal, even surface. Obtained results indicate that there is a considerable influence of road irregularities on vehicle behaviour during lane-change-type manoeuvre.

An analytical investigation of isolation systems for cab ride

The dynamic performance capabilities of heavy duty trucks with suspended cabs are identified using a linearized model of heave-fore-aft-pitch dynamics. Cab acceleration levels and dynamic deflections are determined for vehicle performance on a randomly irregular road surface. The important trade-offs that limit the overall design are illustrated.

Finite element and analytical modelling of a tractor-semitrailer vehicle

A tractor-semitrailer vehicle travelling over a random road surface is modelled using finite element and analytical methods. The vehicle's linear models are constructed in such a way as to describe the bounce and pitch modes of both the tractor and semitrailer, the bounce of each wheel-axle assembly, and also to account for the semitrailer beaming effect. The road surface irregularities are represented as stationary Gaussian random excitations. Spectral analysis technique is employed to analyze the dynamic response of the vehicle. In this paper, the problem of the interaction of the vehicle with the road is discussed, the proposed mathematical models are presented, and the numerical results showing system eigenvalues, eigenvectors and power spectral densities of the vehicle stochastic response are given and analyzed. The finite element provides a powerful means for the prediction and assessment of the ride motion for this complex structure. The technique of spectral analysis is an effective tool for the analysis of road irregularities and the stochastic response of the road vehicles.

VEHICULAR ENERGY LOSSES ASSOCIATED WITH THE TRAVERSAL OF AN UNEVEN ROAD

SUMMARY The energy losses which derive from the vibratory phenomenon experienced by a motor vehicle when It traverses an Irregular road surface have been examined. The study has revealed that there are, at least, four “dynamic” energy-loss mechanisms contributing to vehicular rolling resistance. Specifically, it was determined that the energy losses associated with the dynamic deflection of the tire and the stroking of the suspension damper are predicted reasonably well by a linear mass-spring-damper model of a motor vehicle traversing an uneven road surface at constant speed. The energy losses attributable to impacts between tire and road become significant only when the speed is very high or the road is very rough. Finally, measurements have shown that the angular accelerations associated with time-varying radial deflections of the tire will cause an energy loss when the shear forces required to accelerate or decelerate the wheel become larger than can be sustained by the frictional coupling prevailing ...

Road surface irregularity and vehicle ride: D.R.C. Cooper and J.C. Young, pp. 105–111 (7 pages, 3 figures, 1 tables)

Road surface irregularity and vehicle ride: D.R.C. Cooper and J.C. Young, pp. 105–111 (7 pages, 3 figures, 1 tables)

Road surface irregularity and vehicle ride part 3—riding comfort in coaches and heavy goods vehicles : D. R. C. Cooper and J. C. Young 1980 Transport and Road Research Laboratory Supplementary Report 560. (27 pages, 12 figures, 5 tables, 9 references)

Road surface irregularity and vehicle ride part 3—riding comfort in coaches and heavy goods vehicles : D. R. C. Cooper and J. C. Young 1980 Transport and Road Research Laboratory Supplementary Report 560. (27 pages, 12 figures, 5 tables, 9 references)

Road surface irregularity and vehicle ride part 2—Riding comfort in cars driven by the public : D. R. C. Cooper and J. C. Young 1978 Transport and Road Research Laboratory Supplementary Report 400. (26 pages, 6 figures, 10 tables, 1 reference)

Road surface irregularity and vehicle ride part 2—Riding comfort in cars driven by the public : D. R. C. Cooper and J. C. Young 1978 Transport and Road Research Laboratory Supplementary Report 400. (26 pages, 6 figures, 10 tables, 1 reference)

Bridge dynamic loading due to road surface irregularities and braking of vehicle

AbstractSingle span highway bridges of composite construction are idealized as beams as well as orthotropic plates. A standard HS–20–44 highway vehicle is represented by a planar, two‐axle, sprung mass system with frictional device. The response equations are derived in terms of the natural modal co‐ordinates of the bridge and of displacement co‐ordinates of the vehicle. The road surface irregularities, generally found at the junctions of the approach road and bridge ends, are idealized as a 45° ramp. The maximum impact factors for bending moment and deflection are obtained due to the ramp and in combination with the braking of vehicle for symmetric as well as essentric loading of the vehicle.

An Investigation of the Origins of Vibration of an Automobile Rear Axle

SUMMARY An investigation was carried out to determine the origins of vibration of an automobile rear axle with the object of establishing the significance of road-surface-induced vibratory inputs. This was achieved by measuring the vibratory acceleration of the rear axle of an automobile as it traverses straight sections of typically paved roads, at uniform speeds, then comparing the results with those obtained by laboratory simulation. The investigation revealed significant levels of vertical, longitudinal and, to a much lesser extent, lateral vibrations. The main source of vertical vibrations is shown to be induced mainly by vertical displacements imposed by the road-surface irregularities on the vehicle tyres. The longitudinal and lateral components are shown to be induced mainly by the engine and the drive-line (including tyre/wheel assemblies) as well as due to coupling between the vertical, longitudinal and lateral motions of the rear axle imposed by the geometry of the rear axle suspension.