Showing papers in "Vehicle System Dynamics in 1988"
TL;DR: In this paper, a static roll plane model of an articulated vehicle employing partially filled cylindrical tank is developed to evaluate the roll moments arising from vertical and lateral translation of the liquid cargo.
Abstract: SUMMARY The rollover immunity levels of articulated tank vehicles with partial loads are investigated. A static roll plane model of the articulated vehicle employing partially filled cylindrical tank is developed. The vertical and lateral translation of the liquid cargo due to vehicle roll angle and lateral acceleration, encountered during steady turning, are evaluated. The roll moments arising from vertical and lateral translation of the liquid cargo are determined and incorporated in the roll plane model of the vehicle. The adverse influence of the unique interactions of the liquid within the tank vehicle, on the rollover limit of the articulated vehicle is demonstrated. The influence of compartmenting of the tank on the steady turning roll response of the vehicle is analyzed, and an optimal order of unloading the compartmented tank is discussed.
80 citations
TL;DR: In this paper, an optimal control law for a vehicle suspension is developed using a discrete linear quadratic regulator framework, and the time delay between the disturbance due to the road at the front and rear wheels is incorporated into the model.
Abstract: SUMMARY An optimal control law for a vehicle suspension is developed using a discrete linear quadratic regulator framework. The time delay between the disturbance due to the road at the front and rear wheels is incorporated into the model, and it is shown that the optimal control law requires information gathered at the front wheels. A comparison is made between the optimal control law and a suboptimal one which does not incorporate front wheel road information.
59 citations
TL;DR: In this paper, a first-order theory for the motion of a railway vehicle wheelset on a tangent track is described and the geometrical aspect of this theory is further evaluated and a method for solving the constraint equations between the coordinates of the wheelset is indicated.
Abstract: SUMMARY In previous publications the author has described a so-called first-order theory for the motion of a railway vehicle wheelset on a tangent track. In the present report the geometrical aspect of this theory is further evaluated and a method for solving the constraint equations between the coordinates of the wheelset is indicated.
59 citations
TL;DR: In this paper, the authors studied the control behavior of a single lane change maneuver by means of a simulation model for the ridermotorcycle system, which stresses the control actions of the riders.
Abstract: SUMMARY The control behaviour of motorcycle riders is studied by means of a simulation model for the ridermotorcycle system, which stresses the control actions of the riders. The rider model describes the major steering torque control as well as the rider's own body control actions. This simulation model is applied to a single lane change maneuver and the results of this simulation are compared with the experiments in order to examine its validity.
49 citations
TL;DR: In this article, the authors considered the application of linear optimal control to the design of an active automobile suspension system and achieved zero steady state axle to body response to both static body forces and ramp road inputs.
Abstract: SUMMARY This paper considers the application of linear optimal control to the design of an active automobile suspension system. By inclusion of an integral constraint in the performance index it is possible to achieve zero steady state axle to body response to both static body forces and ramp road inputs. Full state feedback is achieved by reconstructing the state variables from easily measured quantities.
40 citations
TL;DR: In this article, the authors proposed a system with infinite stiffness towards static loading, but which is soft with respect to road inputs, which is also able to eliminate the steady state deflections due to step and ramp type inputs at the wheel.
Abstract: SUMMARY In optimally controlled active suspensions with either full or incomplete state feedback there is tradeoff between system performance and overall stiffness. It is sought to remove this limitation by incorporating integral action which results in a system with infinite stiffness towards static loading, but which is soft with respect to road inputs. The system is also able to eliminate the steady state deflections due to step and (potentially) ramp type inputs at the wheel. Optimality is retained at the cost only of a derivative constraint and the system can be physically realised using output feedback control.
40 citations
TL;DR: In this article, the optimal performance comparison of variable component suspensions, including active damping and full-state feedback, for "quartercar" heave models was examined using performance indicators to find the component parameters (control gains) that provide optimal performance for statistically described roadway inputs.
Abstract: SUMMARY Most vehicle suspension systems use fixed passive components that offer a compromise in performance between sprung mass isolation, suspension travel, and tireroad contact force. Recently, systems with discretely adjustable dampers and air springs been added to production vehicles. Active and semi-active damping concepts for vehicle suspensions have also been studied theoretically and with physical prototypes. This paper examines the optimal performance comparisons of variable component suspensions, including active damping and full-state feedback, for “quartercar” heave models. Two and three dimensional optimizations are computed using performance indicators to find the component parameters (control gains) that provide “optimal” performance for statistically described roadway inputs. The effects of performance weighting and feedback configuration are examined. Active damping is shown to be mainly important for vehicle isolation. A passive vehicle suspension can control suspension travel and tire c...
26 citations
TL;DR: In this article, an active suspension system for a cab ride in a tractor-semitrailer vehicle is proposed, where a discrete-continuous vehicle model with eleven degrees of freedom is augmented by a stochastic road excitation model and human perception of vibration shape filter.
Abstract: SUMMARY Stochastic optimal control and estimation theories are used to design an active suspension system for a cab ride in a tractor-semitrailer vehicle. A discrete-continuous vehicle model with eleven degrees of freedom is augmented by a stochastic road excitation model and a human perception of vibration shape filter. Both perfect measurement and estimated state cases are considered. The impact of the measurement noise on the design of the optimal controller is demonstrated. The performance of the optimally controlled system is compared with an optimal passive system. It is shown that significant improvements in ride comfort can be achieved through the use of actively controlled cab suspensions.
24 citations
TL;DR: In this paper, the effects of structural bending modes on model results have been explored in an effort to provide an accurate and dependable simulation, using the wheel profiles as geomtry inputs to the model.
Abstract: SUMMARY Railroad wheel tread radial profile (runout) errors produce high dynamic loads at the wheel/rail interface that can often exceed 400 kN in peak amplitude. These impact loads are propagated Into the bogie com ponents (bearings, suspension) and into the track structure, where fatigue and fracture damage can occur. Studies have been conducted to measure the loads at the rail, to measure the wheel profiles, and to validate a mathematical vehtcle/track interaction model, using the wheel profiles as geomtry inputs to the model. The effects of structural bending modes on model results have been explored in an effort to provide an accurate and dependable simulation.
21 citations
TL;DR: In this paper, a linear wear model was developed which takes into account all contact physical effects and which can be used in combination with different wheelset-track models to estimate the wear of railway tracks.
Abstract: SUMMARY Based on the assumption that high frequency vibrations of the wheelset-track system may be the reason for corrugations on railway track a linear wear model was developed which takes into account all contact physical effects and which can be used in combination with different wheelset-track models
18 citations
TL;DR: The Australian Road Research Board (ARRB) developed a highway speed, road profile measuring system to collect profile data on Australian roads as mentioned in this paper, which can be used for vehicle dynamic analysis.
Abstract: A large proportion of road roughness measuring equipment used throughout the world today is based on transducers which sense the relative movement between the vehicle body and its rear axle. Although these systems are reliable, simple to use, and have the capacity for the measurements to be performed over a range of travel speeds, the resulting roughness statistic is influenced by the ride characteristics of the host vehicle. In most cases the data are of limited use in the detailed study of vehicle dynamics. Other problems are calibration of the roughness vehicle, comparison between similar and dissimilar systems, and stability of the measures over time. To circumvent these problems, road profile based reference systems are gaining popularity with a resulting increase in useful data for vehicle dynamicists. To meet this need, the Australian Road Research Board (ARRB) has developed a highway speed, road profile measuring system to collect profile data on Australian roads. This device and the signal processing are described in this paper and some results are presented.
TL;DR: In this article, a simple pragmatic tire model which is especially suitable to be used in vehicle simulation studies has been developed and compared with the adapted bare string tyre model, which shows good agreement with experimental results in the range of wavelengths not less than about two meters (i.e. about ten times the tyre contact length).
Abstract: SUMMARY The cornering behaviour of the tyre and the vehicle on uneven roads has been studied both experimentally and theoretically. A simple pragmatic tyre model which is especially suitable to be used in vehicle simulation studies has been developed and compared with the adapted bare string tyre model. Both models show good agreement and also the models agree well with experimental results in the range of wavelengths not less than about two meters (i.e. about ten times the tyre contact length). Moreover, full vehicle simulations have been conducted in which the simple tyre model has been used and also road experiments with Volvo's experimental computer controlled suspension car where each suspension is excited to simulate road uneveness. It is concluded that a change may occur in understeer/oversteer nature on roads having short wavelength undulations through the decrease of average tyre side force. In case of undulations of rather long wavelength, the periodic variation of yaw rate appears to become rat...
TL;DR: In this article, a simplified approach for creating road surface elevation information for simulation of vehicle vertical response to roadway unevenness is presented, where roadways for single and parallel track simulations and averaged roads for variable velocity simulation are developed.
Abstract: SUMMARY With a simplified approach for creating road surface elevation information for simulation of vehicle vertical response to roadway unevenness, roadways for single and parallel track simulations and averaged roads for variable velocity simulation are developed. Sets of correctly chosen random roadway slopes are averaged appropriately for the variable velocity simulation. The procedure generates approximately “white” slope spectral density roadways in the frequency ranges of interest, and the elevation profiles are representative of average road profiles. The method is simple in practice yet suffices for many parameter studies of suspensions and vehicle dynamics.
TL;DR: In this article, the accuracy of the isotropic road roughness assumption by a comparison of model predictions with spectral analyses of multi track road surface measurements, covering a wide range of pavement types and quality, was considered.
Abstract: This paper considers the accuracy of the isotropic road roughness assumption by a comparison of model predictions with spectral analyses of multi track road surface measurements, covering a wide range of pavement types and quality. A new procedure for the calculation of cross spectra is employed which overcomes the problems of the previous method.
TL;DR: In this paper, the dynamic characteristics of guided-steering railway trucks are described both in a general sense and in terms of a specific design, and stability margins and curving performance have been predicted and compared for both conventional and steered vehicles.
Abstract: SUMMARY The dynamic characteristics of guided-steering railway trucks are described both in a general sense and in terms of a specific design. Stability margins and curving performance have been predicted and are compared for both conventional and steered vehicles. It is shown that guided-steering trucks exhibit modes of instability which, although surmountable by proper design, are not found in conventional trucks. In particular, a low conicity, divergent, leading truck instability is described together with a companion high conicity, divergent trailing truck instability. Curving and dynamic performance for steered vehicles is shown to have the potential of being far superior to that of comparable conventional vehicles. Factors influencing the design of steered rail vehicles are presented and discussed.
TL;DR: In this article, an approximate method is proposed which allows the determination of the actual contact zones as Hertz's ellipses but without disregarding the elastic cross-influence of the two zones.
Abstract: SUMMARY In this paper a type of contact between two bodies is considered, which leads to the formation of two separate contact zones. The contact zones considered are Hertzian ellipses if the distance between them is large. When the distance between the zones is finite it is necessary to take into account the elastic cross-influence of the two zones. In this paper an approximate method is proposed which allows the determination of the actual contact zones as Hertz's ellipses but without disregarding the cross-influence. Numerical results are presented for two, two-humped bodies pressed against each other and for steady state rolling of a flanged wheel along a steel rail. It is shown that neglecting the cross influence for a flanged wheel leads to a negligible error in the contact forces but the forces are transmitted between wheel and rail through contact patches which are generally more slender than with the cross-influence neglected.
TL;DR: In this article, a stability analysis of a vehicle flexible in the plane of yawing and being controlled by a human pilot is presented, where the vehicle is represented by a two degrees-of-freedom model and the pilot is assumed to respond to lateral displacement and to the lateral velocity with a time delay.
Abstract: SUMMARY This paper presents a stability analysis of a vehicle flexible in the plane of yawing and being controlled by a human pilot. The vehicle is represented by a two degrees-of-freedom model and the pilot is assumed to respond to the lateral displacement and to the lateral velocity with a time delay. It is shown that in order for the pilot model to exhibit a realistic human operator behavior, driver's gain must be linearly proportional to vehicle velocity and also inversely related to frontal visibility. Moreover, application of the Hurwitz criterion indicated that flexibility of the vehicle frame has a destabilising effect on the lateral stability and reduces the stable domain of operation.
TL;DR: In this article, a velocity dependent steering gear has been developed to enable neutral steering characteristics independent of the position of the vehicle's center of gravity, however, this system may produce stability problems due to increased steering sensitivity.
Abstract: SUMMARY Four different four-wheel steering systems have been investigated using analytical methods as well as computer simulations. Combining a simple model of a vehicle and an analytical driver model, increased stability behaviour of the overall driver-vehicle system has been found for three steering systems described in literature. These steering systems, however, result in vehicles with extreme understeer behaviour. Therefore a velocity dependent steering gear has been developed. This modification enables neutral steering characteristics Independent of the position of the vehicle's center of gravity. However, this system may produce stability problems due to Increased steering sensitivity. The influence on the driving behaviour is additionally investigated using a complex vehicle model for a standard driving manoeuvre. In this case, the general purpose multibody program MEDYNA has been used to generate the equations of motion and perform computer simulations.
TL;DR: In this article, the authors present a procedure for determining the sensitivity matrices of a vehicle dynamic system in the frequency domain as derivatives of the transfer function matrix with respect to system parameters.
Abstract: SUMMARY This paper presents a procedure for determining the sensitivity matrices of a vehicle dynamic system in the frequency domain as derivatives of the transfer function matrix with respect to system parameters. First and second order logarithmic sensitivity functions which possess normalized coefficients have been introduced to enhance analysis. The sensitivity analysis of amplitude-frequency characteristics on changes of selected parameters of a 3 degree-of-freedom vehicle handling model has been performed. It has been demonstrated that the general sensitivity measure proposed can be used to determine the combined influence of system parameters divided into groups such as design, environmental, driver, kinematic, etc., on the multi-parameter system response, prior to determining their order of influence within the groups.
TL;DR: In this paper, the authors show that passive response of the vehicle on wind impact can be measured and simulated accurately enough, but these results do not fully correlate with drivers impression of sidewind sensitivity.
Abstract: SUMMARY This paper shows that passive response of the vehicle on wind impact can be measured and simulated accurately enough, but these results do not fully correlate with drivers impression of sidewind sensitivity. Measurements have been made on several cars on motorway under natural wind conditions and records of the complete car-driver system have been taken and compared to driver's subjective ratings. A method is beeing presented which shows the correlation of any combination of motion parameters with driver's assessment on sidewind sensitivity.
TL;DR: In this paper, the authors present two methods for physical simulation of rail contact loading in curves of moderate radii using a contact fatigue machine, and compare the forces generated by a rail vehicle on curved track and the loading on the machine for one and two-point contact between wheel and rail on curve.
Abstract: SUMMARY According to present knowledge, the contact fatigue failures of rails, referred to as shelling, most frequently appear on the inner side of high rail in curves of moderate radii. In order to improve the understanding of the failure mechanism the studies on the several related research subjects are necessary, among them the laboratory fatigue tests. This paper presents two methods for physical simulation of rail contact loading in curves of moderate radii using a contact fatigue machine. The description of methods is followed by the estimation of the available range of parameters influencing contact forces on the machine, a theory of contact forces occurring on the machine and by comparison between forces generated by a rail vehicle on curved track and the loading on the machine for one and two-point contact between wheel and rail on curve.
TL;DR: In this article, the wheel forces generated by three popular articulated commercial vehicles are simulated and an examination is made of the effects of vehicle configuration, vehicle speed and road surface roughness on simulated road damage.
Abstract: SUMMARY A number of criteria and associated statistical analysis procedures are presented for relating the dynamic wheel forces generated by heavy vehicles to road surface damage. Apart from one case, the criteria must be evaluated in the time domain from time histories of the dynamic forces generated by all axles of a vehicle. Calculation of the transient stresses and strains in the road structure during the passage of a vehicle is also required for some of the criteria. The criteria may be used for evaluating the road damaging effects of measured or simulated wheel forces. In this paper, the wheel forces generated by three popular articulated commercial vehicles are simulated and an examination is made of the effects of vehicle configuration, vehicle speed and road surface roughness on simulated road damage. Conclusions are drawn about the likely increase in road damage caused by the dynamic component of wheel forces and the ways that various modes of vehicle vibration contribute to road damage.
TL;DR: In this article, the dynamic stability of forced-steering rail vehicles is considered through the use of three models having three, eight, and seventeen degrees of freedom respectively, and it is shown that, at low values of conicity, these trucks may experience instabilities which are not found in conventional rail vehicles.
Abstract: SUMMARY The dynamic stability of forced-steering rail vehicles is considered through the use of three models having three, eight, and seventeen degrees-of-freedom respectively. It is shown that, at low values of conicity, these trucks may experience instabilities which are not found in conventional rail vehicles. The simpler of these models of varying complexity is used to establish an understanding of the basic phenomenon. The more detailed models are included to give realistic results which show the potential magnitude of the problem.
TL;DR: In this article, the authors evaluated the steady-state curving behavior of a freight car system with Damper Coupled Wheelset (DCW), where the wheels of conventional shape within an axle are coupled through a damper element.
Abstract: SUMMARY The focus of this paper is on the steady-state curving behaviour of a freight car system with Damper Coupled Wheelset (DCW), where the wheels of conventional shape within an axle are coupled through a damper element. A freight truck model with two DCW and pseudo-car body on curved track is developed to study the influence of wheelset coupler parameter on the curving response and performance. The response is primarily evaluated in terms of wheelset tracking error and yaw misalignment in response to track curvature and cant deficiency. The curving performance is evaluated in terms of slip and flange boundaries. The results in general, indicate that when the value of coupler parameter is reduced, the wheelset response to track curvature increases, and results in flanging and wheel slip on a less tighter curve than those corresponding to conventional rigid axled wheelsets.
TL;DR: In this paper, a quasi-steady-state method is applied to four-wheel-drive (4WD) vehicles to study on the effects of traction force distribution controls on the vehicle turning behavior during acceleration and power off braking.
Abstract: SUMMARY In this paper, a quasi-steady-state method is applied to four-wheel-drive (4WD) vehicles to study on the effects of traction force distribution controls on the vehicle turning behavior during acceleration and power off braking. Solving the quasi-steady-state equilibrium equations, the steering wheel angle to turn with a certain turning radius of curvature with respect to lateral acceleration is obtained for various longitudinal acceleration to describe understeer/oversteer(u.s./o.s.) characteristics in acceleration and power off braking in a turn having the same implication as in a steady state turning. The optimum traction force distribution control having relation to tire vertical loads with additional rear wheel steer to attain vehicle turning behavior which are insensitive to acceleration and power off braking as well as to get high acceleration capabilities is investigated.
TL;DR: In this paper, the authors describe the stabilization of articulated vehicles at high speeds by a steering system set up on the trailer, and the steering angle of the trailer in the presence of disturbances is studied by solving these equations through the application of modern control theory.
Abstract: SUMMARY This paper describes the stabilization of articulated vehicles at high speeds by a steering system set up on the trailer. First, the equations of motion of the articulated vehicles with a steering system on the trailer were obtained. Furthermore, the steering angle of the trailer in the presence of disturbances was studied by solving these equations through the application of modern control theory. From such analysis, the magnitude of the optimal feedback coefficients of each state variable was obtained. It was found that the stability of articulated vehicles at high speeds was significantly improved by the active control method for the trailer steering system. However, the active control system needs a power supply, and it is difficult to apply it to articulated vehicles at present, especially for passenger car-trailer combinations. Thus, a new trailer steering system with viscous coupling arms to be set between the tractor and trailer was proposed. Furthermore, the semi-active control method whi...
TL;DR: In this article, a two-dimensional model of pneumatic tire interacting with even and uneven road surface is presented, where the model describes jointly radial and tangential tire properties, assuming variation of the friction coefficient at the contact points.
Abstract: SUMMARY The paper presents a two-dimensional model of pneumatic tire interacting with even and uneven road surface. The model describes jointly radial and tangential tire properties, assuming variation of the friction coefficient at the contact points. Such a model can be useful in describing the interaction between the pneumatic tire and road, that is characterized by a relatively big value of the ratio of the road unevenness height to its length.
TL;DR: In this paper, a multibody dynamics program MEDYNA is extended by tire and driver modules to simulate relevant driving manoeuvres, and the numerical simulation of vehicle handling dynamics and the evaluation of primary vehicle safety opens the way to provide criteria for an avoidability study of road traffic accidents.
Abstract: SUMMARY Accident relevant driving manoeuvres are simulated by the multibody dynamics programme MEDYNA, which is now extended by tire and driver modules. The numerical simulation of vehicle handling dynamics and the evaluation of primary vehicle safety opens the way to provide criteria for an avoidability study of road traffic accidents.
TL;DR: In this paper, a nonlinear stability analysis of the steady state horizontal and downhill straight line motion of a controlled truck-trailer system is given, where two different types of controllers including the effect of the reaction time of the driver are used.
Abstract: SUMMARY A nonlinear stability analysis of the steady state horizontal and downhill straight line motion of a controlled truck-trailer system is given. Special emphasis is given to the modelling of the controller simulating the steering actions of the driver. Two different types of controllers both including the effect of the reaction time of the driver are used. The basic question to be answered is whether the truck-trailer system after loss of stability of the steady state still is controlable by the driver or not. I.e. whether after loss of stability nearby stable states exist or not. A question which can only be answered by a nonlinear analysis. The answer is given for the variation of a number of parameters.