Showing papers in "Vehicle System Dynamics in 1975"
TL;DR: In this paper, a radial-spring tire model was developed to envelop irregular features of a rigid terrain and redefine the terrain as an equivalent ground plane reflecting both the elevation and slope characteristic of the original terrain contacting the tire.
Abstract: SUMMARY A radial-spring tire model was developed to envelop irregular features of a rigid terrain and redefine the terrain as an “equivalent ground plane” reflecting both the elevation and slope characteristic of the original terrain contacting the tire. Three different methods were proposed for defining the maximum deflection of the tire, thereby locating the “equivalent ground plane” and defining the radial tire force. Errors in the maximum tire deflections resulting from approximations in the solution procedure could be maintained below 3 per cent of the actual tire deflections when the tire model was tested on a rigid planar surface.
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TL;DR: In this article, the adequacy of Sharp's analysis to predict the dynamic behavior of single-track vehicles is reviewed, and it is concluded that the pneumatic tire with respect to lateral force and overturning moment produced by fixed and time-varying inclination should be accurately described, statically and dynamically.
Abstract: The adequacy of Sharp's analysis to predict the dynamic behavior of single-track vehicles is reviewed. A noteworthy feature of Sharp's analysis is his inclusion of the lag between lateral force and lateral slip which is exhibited by a tire undergoing a time rate of change in lateral slip. In another study, Eaton has pointed out that every analysis of single-track vehicles published prior to 1960 failed to include external forces created by a sideslipping tire. The question is raised as to whether the nonstationary response to inclination is comparable to the nonstationary response to lateral slip or slip angle. The review of Sharp's analysis and Eaton's findings indicates that the attainment of better agreement between theory and experimentation will require that the motorcycle tire be described in greater detail, from both static and dynamic points of view. Transient measurements of lateral force resulting from inclination show that a small component of this force is in phase with inclination, whereas the remaining component lags the inclination angle. The component of force lagging the inclination angle appears to involve greater lag, i.e. larger relaxation length, than the force produced by lateral slip. The overturning moment caused by inclination also contains lagging and nonlagging components, although the lagging component is very small relative to the nonlagging component. It is concluded that lateral force and overturning moment due to inclination should be accurately described, statically and dynamically, to predict the dynamics of single-track vehicles. There is also a need to analyze the pneumatic tire with respect to lateral force and overturning moment produced by fixed and time-varying inclination.
17 citations
TL;DR: In this article, the complete vehicle-guideway system is considered, where the suspension control and the guideway dynamics are coupled, resulting in a multivariable system for personal rapid transit in highly populated areas and high speed transport over large distances.
Abstract: Magnetically levitated vehicles have been discussed in recent years for application on personal rapid transit in highly populated areas and high speed transport over large distances. The magnetic suspension control of the vehicle has been usually designed assuming rigid guideways. On the other hand, the dynamics of the guideways has been investigated only for vehicles, with spring-dashpot suspension. However, the suspension control and the guideway dynamics are coupled resulting in a multivariable system. In this paper the complete vehicle-guideway system is considered.
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TL;DR: In this article, the equations of motion for a single wheel steerable pneumatic tire system were derived and the results showed that the built-in wheel wobble caused a steady shimmy which is large when the wheel rotation frequency is close to the natural shimming frequency.
Abstract: SUMMARY The equations of motion are derived for a single wheel steerable pneumatic tire system. Included in this system are a built-in wheel wobble and wheel-tire irregularities which produce oscillation of the normal load. Special emphasis is placed on the dynamic characterization of the tire cornering force and aligning torque. The results show that the built-in wheel wobble causes a steady shimmy which is large when the wheel rotation frequency is close to the natural shimmy frequency. The results also show that a normal load oscillation which has a frequency approximately twice the natural shimmy frequency causes a decrease in shimmy stability.
9 citations
TL;DR: In this paper, the authors examined the rolling motions of vehicles with pneumatic tires and identified two sources of instability related to center of gravity position and the other to tire and suspension characteristics.
Abstract: SUMMARY This paper examines the rolling motions of vehicles with pneumatic tires. From a simplified analysis two sources of instability are identified–one related to center of gravity position and the other to tire and suspension characteristics. When a specimen vehicle is considered, it is shown that current semi-trailer design can display instability from either source.
TL;DR: In this article, a control system has been designed, constructed and tested which provides a suspension for a low-speed transport vehicle over a track with irregularities characterised by a secondary railway line, and the ride in the vehicle is equivalent to that obtained in conventional, modern urban transport vehicles.
Abstract: A control system has been designed, constructed and tested which provides a suspension for a low-speed transport vehicle. The technical concepts have been investigated in great depth. It has been shown that the effects of the non-linearities inherent in the hardware can be minimised. Over a track with irregularities characterised by a secondary railway line the ride in the vehicle is equivalent to that obtained in conventional, modern urban transport vehicles. The physical constraints on the control system specification of the track has been shown to be suitable. of the track has been shown to be suitable.
TL;DR: In this article, Liapunov analysis with the Hamiltonian and with a modified Hamiltonian proposed by Walker, and analysis of characteristic equations using theorems due to Routh, Hurwitz, Cronin, and Lienard and Chipart were examined and compared in the context of a simple idealization of a transit vehicle moving at constant speed on a straight, horizontal, fixed guideway, supported by idealized rubber tires, air cushion pads, or semiconical steel wheels on steel rails.
Abstract: SUMMARY Several methods of motion stability analysis are examined and compared in the context of the problem posed by a simple idealization of a transit vehicle moving at constant speed on a straight, horizontal, fixed guideway, supported by idealized rubber tires, air cushion pads, or semiconical steel wheels on steel rails. Stability analysis methods examined include Liapunov analysis with the Hamiltonian and with a modified Hamiltonian proposed by Walker, and analysis of characteristic equations using theorems due to Routh, Hurwitz, Cronin, and Lienard and Chipart It is concluded that for rubber-tired and aircushioned vehicles a Liapunov analysis employing the Hamiltonian is most efficient, and for the tracked vehicle the criteria of Lienard and Chipart are most useful.
TL;DR: In this article, a simulation of the lateral motion of a 2-Axle railway vehicle in running is presented, and the simulation is extended to a 3-axis locomotive.
Abstract: (1975). Simulation of Lateral Motion of 2-Axle Railway Vehicle in Running. Vehicle System Dynamics: Vol. 4, No. 2-3, pp. 165-169.
TL;DR: In this article, the roll motions of the sprung mass are assumed to take place about a roll axis, which is a significant complication in the case of digital computer simulations of multi-unit vehicles.
Abstract: SUMMARY Vehicle dynamicists have frequently assumed that the roll motions of the sprung mass take place about a roll axis. Equations of motion based on this assumption must be expected to exhibit dynamic coupling, a significant complication in the case of digital computer simulations of multi-unit vehicles. Digital simulations have been developed which, while preserving the physical character of the roll axis formulation, use further approximations to avoid the dynamic coupling. Validation exercises have been performed which demonstrate the accuracy of this methodology.
TL;DR: In this paper, the authors show that freight vehicles already succesfully use a high-conicity approach with good linear curving, and they also expect to see improvements in the design of commuter vehicles to increase the linear curve regime and reduce flange and rail wear problems.
Abstract: World-wide the consensus is generally towards the use of rather low conicities for high speed vehicles. Whether the improvement of understanding and prediction techniques will alter this trend remains to be seen. For lower speed vehicles the consensus is less general. Some freight vehicles already succesfully use a high-conicity approach with good linear curving, and the authors expect to see this trend continued. They also expect to see improvements in the design of commuter vehicles to increase the linear curving regime and therby reduce flange and rail wear problems.
TL;DR: In this paper, a 14 degrees of freedom mathematical model was used to predict car handling behavior on smooth and bumpy roads, and the model was applied to predict vehicle handling behavior in the real world.
Abstract: (1975). A 14 Degrees of Freedom Mathematical Model to Predict Car Handling Behaviour on Smooth and Bumpy Roads. Vehicle System Dynamics: Vol. 4, No. 2-3, pp. 95-99.
TL;DR: Several mechanical models have been developed to simulate the dynamic action of railway vehicles moving along railway bridges as discussed by the authors, where the behavior of the vehicle is described by a system of ordinary differential equations of second order with variable parameters.
Abstract: Several mechanical models have been developed to simulate the dynamic action of railway vehicles moving along railway bridges. Vehicles are very complex mechanical systems with a number of degrees of freedom, linear and non-linear springs and damping. Modern vehicles possess also clearly differentiated unsprung and sprung masses. Therefore, with respect to the purpose of the analysis, several mechanical models have been set up to idealize the basic properties of the dynamic movement of the vehicle. The behavior of the vehicle is described by a system of ordinary differential equations of second order with variable parameters.
TL;DR: In this paper, the longitudinal vibrations of long trains composed of identical cars caused by braking forces are investigated. But the authors focus on the braking forces and do not consider the other components of the train.
Abstract: (1975). The longitudinal vibrations of long trains composed of identical cars, caused by braking forces. Vehicle System Dynamics: Vol. 4, No. 2-3, pp. 75-76.
TL;DR: In this article, the models used for the analyses of the vehicle dynamics (on rigid track) and for the coupled vehicle/track dynamics are described and compared with those obtained for the case of an infinitely rigid track.
Abstract: Dynamic coupling occurs between a railway vehicle and the track due to the reaction forces acting between the wheels and the track, and the elasticity of the track and the foundation. It has become apparent that track elasticity can influence the dynamic behaviour of the railway vehicle, yet in most of the research work in the area of railway vehicle dynamics reported so far, the track is regarded simply as a rigid structure, providing the reactions to the loads of passing vehicles. In this paper the models used for the analyses of the vehicle dynamics (on rigid track) and for the coupled vehicle/track dynamics are described. The equations of motion are derived, and the results obtained for the coupled vehicle/track model are presented and compared with those obtained for the case of an infinitely rigid track. Particular empahsis is on the lateral stability and the response to vertical track irregularities.
TL;DR: In this paper, the stability of control systems consisting of a guideway fixed on the road and a controller built in the motor-vehicle can substitute the vehicle driver is discussed for the case of low speed vehicles.
Abstract: SUMMARY Control systems consisting of a guideway fixed on the road and a controller built in the motor-vehicle can substitute the vehicle driver. In this paper stability of such systems is discussed for the case of low speed vehicles. In this case it is possible to simplify the model by neglecting some dynamic vehicle properties. Der Fahrer im Kraftfahrzeug kann durch eine Leitlinie in der Fahrbahn und durch einen Regler im Kraftfahrzeug ersetzt werden. Fur solch ein System werden die Stabilitatsbedingungen diskutiert, und zwar fur Kraftfahrzeuge, die langsam fahren. Dabei konnen die dynamischen Eigenschaften vernachlassigt werden.