Showing papers in "Vehicle System Dynamics in 1976"
TL;DR: In this article, modern optimal control theory is applied to the design of an active suspension system for a motor vehicle, where the road profile is assumed to be continuous and random with a power spectral density (P.S.D) which varies inversely with the square of the frequency.
Abstract: SUMMARY In this paper modern optimal control theory is applied to the design of an active suspension system for a motor vehicle. The road profile is assumed to be continuous and random with a power spectral density (P.S.D.) which varies inversely with the square of the frequency. The quadratic integral type performance index employed is a weighted sum of the integral squares of body acceleration, dynamic tyre deflection and relative body-to-axle displacement. A solution is obtained for the infinite time case which is both computationally and physically realizable as an active suspension in which the only continuous measurements required are the body absolute velocity and the body displacement relative to the road. The performance is compared with that of a conventional type passive suspension and found to be significantly better in practically all respects.
217 citations
TL;DR: In this article, the stiffness and kinematic properties of all possible interwheelset connections are characterised by two properties describing the distortional characteristics of the vehicle in plan, and various possibilities for steered wheelsets are considered, and several past and current proposals are reviewed.
Abstract: SUMMARY For railway vehicles having coned wheels mounted on solid axles there is a conflict between dynamic stability and steering ability It is shown that the stiffness and kinematic properties of all possible interwheelset connections are characterised by two properties describing the distortional characteristics of the vehicle in plan. Within this framework, the various possibilities for steered wheelsets are considered, and several past and current proposals are reviewed. Using the linear approach to dynamic stabibty and curve negotation the performance of existing and newly proposed configurations is discussed For any symmetric, two-axle vehicle it is shown that for perfect steering on a curve there should be zero bending stiffness between the wheelsets. It is further shown that if the bending stiffness is zero, the vehicle lacks dynamic stability as the critical speed of instability, is zero. In this case, the vehicle undergoes a steering oscillation which occurs at the kinematic frequency of a sing...
54 citations
TL;DR: In this article, a review of the state-of-the-art work relevant to the state of the art as regards passenger cars towing trailers is presented. But the focus is on the role of the driver.
Abstract: SUMMARY Work relevant to the state of the art as regards passenger cars towing trailers is referenced and reviewed. Not only included is the very limited amount of work specifically dealing with passenger cars towing trailers, but also reviewed is the much larger body of work having a bearing on car-trailer systems. Topics included are aerodynamic forces, tire forces, the compliance concept, relevant work on vehicles without trailers, vehicles with trailers, and the role of the driver. The types of stability problems exhibited by car-trailer systems are discussed. The state of the art as regards ability to predict vehicle response to specific steering inputs is shown to be fairly advanced. Recent significant advances include the appearance of experimental data useful for validating theoretical models. However, the state of the art as regards definition of what constitute desirable handling characteristics is still at a primitive stage, largely because of a lack of understanding of the roles played by driv...
41 citations
TL;DR: This work has established that a stationary gaussian stochastic process does provide a satisfactory basic model for a road surface, and it has now reached a state of considerable sop...
Abstract: SUMMARY During the 1950's increasing awareness of the available theory of stochastic processes, together with the wider availability of digital computers, brought to automobile engineers a new and powerful technique for treating the response of vehicles to the irregular undulations of roads. But while a road profile may reasonably be regarded as a realisation of a stochastic process, the theory of stochastic processes brings practical advantages only where the processes concerned satisfy certain stringent criteria The paper explains the basis of the standard spectral techniques which are available for the description and analysis of stochastic processes, and emphasises the restrictions implied by their acceptance. Progress towards the present state of the art is indicated by reference to work published over the last 25 years; this work has established that a stationary gaussian stochastic process does provide a satisfactory basic model for a road surface, and it has now reached a state of considerable sop...
38 citations
TL;DR: The present state of knowledge of human control of road vehicles concerns lateral control and most is of an ad hoc nature, andequate mathematical models for longitudinal motion of the vehicle are yet to be developed.
Abstract: SUMMARY This paper reviews the present state of knowledge of human control of road vehicles. Lateral and longitudinal control of motorcycles and automobiles are discussed, whenever information is available. Although knowledge has increased greatly in the last decade, the major part of this concerns lateral control and most is of an ad hoc nature. Adequate mathematical models for longitudinal motion of the vehicle are yet to be developed. Their development is a necessary step in the attainment of a complete understanding of longitudinal control.
33 citations
30 citations
TL;DR: A review of the more subjective aspects of the steering behavior of single track vehicles can be found in this paper, along with an assessment of the current state of understanding and likely ways in which further progress can be made.
Abstract: SUMMARY The paper contains a brief review of the more subjective aspects of the steering behaviour of single track vehicles, a review of the more significant published work in the field, and an assessment of the current state of understanding and likely ways in which further progress can be made Attention is drawn to the many areas of agreement between theory and practice and to some areas of disagreement. The greatest need now seems to be for the incorporation of more complex tyre models into vehicle handling models.
29 citations
TL;DR: In this article, the authors reviewed the studies that have attempted to find a relationship between closed-loop task performance, and driver subjective opinion, and various steady-state and transient characteristics revealed in open-loop tests of the vehicle.
Abstract: SUMMARY The advantages of being able to objectively specify desirable vehicle handling characteristics, which can be determined without recourse to closed-loop tests on a prototype vehicle, are widely recognised. This paper reviews the studies that have attempted to find a relationship between closed-loop task performance, and driver subjective opinion, and various steady-state and transient characteristics revealed in open-loop tests of the vehicle. It is found that the level of definition of these relationships is not sufficient to justify mandatory regulations for vehicle design. However, the basic requirements for steering control sensitivity, and the rapidity and stability of the fixed-control dynamic response of vehicles in normal manoeuvres, are beginning to emerge. Data are particularly lacking for the closed-loop effects of vehicle sideslipping characteristics, free-control responses and vehicle behaviour in limit manoeuvres.
20 citations
TL;DR: In this article, the vertical motions of a large motorcycle on its tyres and suspension system are analyzed, and the possibility of one of the natural frequencies being close to that of the lateral oscillation, the weave mode, is demonstrated.
Abstract: SUMMARY The vertical motions of a large motorcycle on its tyres and suspension system are analysed, and the possibility of one of the natural frequencies being close to that of the lateral oscillation, the weave mode, is demonstrated. Interactions between the vertical and lateral modes, and the implications for motorcycle design and development are discussed.
19 citations
TL;DR: In this article, the role of multi-axle bogies in vehicle handling and how the lateral tyre forces vary between the axles is analyzed. And the analysis may also be applied to the general case of vehicle handling.
Abstract: SUMMARY Legislation limits the load that may be transferred to the roadway by the axies of a commercial vehicle and this has resulted in the development of multi axle bogies for both the tractor and trailer units of articulated vehicles and at the rear of rigid vehicles, some of these bogies contain self steering or articulation steered axles Experience shows that the tyre wear characteristics of multi axle bogies may be unsatisfactory. The paper analyses the role of such bogies in the context of vehicle handling and shows how the lateral tyre forces vary between the axles. An hypotheses relating the forces in a steady state turn to wear is given. The analysis may also be applied to the general case of vehicle handling.
11 citations
TL;DR: In this article, the authors present a review of the literature for both steady state and transient response behaviour of road vehicles to steering inputs and conclude that satisfactory methods of measurement and description are available but that desirable levels cannot yet be firmly specified.
Abstract: SUMMARY This paper is concerned with the description of the open loop response of road vehicles to steering inputs. The important literature is reviewed for both steady state and transient response behaviour. The measures available for steady state response covering the whole range of lateral acceleration are discussed in detail, and sample measured data are presented. It is shown that the important quantities are the effective cornering stiffnesses of the front and rear tyres, how they are related, and how they vary with lateral acceleration. Transient response is only considered for the region of linear behaviour, where it is seen that a control theory approach is appropriate. A sample set of frequency response curves and step input responses are presented. It is concluded that satisfactory methods of measurement and description are available but that ‘desirable’ levels cannot yet be firmly specified.
TL;DR: The formalism of Robertson/Wittenburg is generalized to systems whose configuration includes closed loops, thereby adapting it to the dynamic simulation of terrestrial vehicles.
Abstract: SUMMARY The development of general Eulerian dynamic formalisms for the digital simulation of multi-body systems is reviewed. The formalism of Robertson/Wittenburg is generalized to systems whose configuration includes closed loops, thereby adapting it to the dynamic simulation of terrestrial vehicles.
TL;DR: In this paper, the steering performance in a simple circular lane-keeping task, as dependent on the directional response characteristics of the vehicle, was measured and response surface methodology models of steering performance were presented.
Abstract: Driver steering performance in a simple circular lane-keeping task, as dependent on the directional response characteristics of the vehicle, was measured. Response surface methodology models of steering performance are presented. Several canonical variables describe the drivers' responses to vehicle changes. Clear-cut optimum vehicle characteristics cannot be determined, but certain combinations of vehicle characteristics are seen to be undesirable for various reasons related to theoretical mechanisms of driver steering control. /Author/TRRL/
TL;DR: In this article, a simulation of the directional behavior of road vehicles is presented, and the simulation is extended to the case of vehicles with a fixed steering wheel and a four-wheel drive.
Abstract: (1976). Simulation of Directional Behaviour of Road Vehicles. Vehicle System Dynamics: Vol. 5, No. 1-2, pp. 47-66.
TL;DR: In this paper, a simulation of the steering behaviour of a double bottom articulated vehicle is presented, in particular the effects that arise when certain axles are locked, and the authors describe the development, operation and some of the results obtained from a simulation.
Abstract: SUMMARY The paper describes the development, operation and some of the results obtained from a simulation of the steering behaviour of the double bottom articulated vehicle, in particular the effects that arise when certain axles are locked.
TL;DR: In this article, the effects of steering compliance and aerodynamic life on high speed automobile's steering response was investigated on two vehicles, a Ford Falcon XW (1969) station-wagon and a GM-Holden Kingswood HQ (1974) sedan.
Abstract: SUMMARY The significance of the effects of steering compliance and aerodynamic life on high speed automobile's steering response was investigated on two vehicles, a Ford Falcon XW (1969) station-wagon and a GM-Holden Kingswood HQ (1974) sedan. An aerofoil was mounted above the front bumper bar of the Ford Falcon to enable the simulation of vehicles with very degraded aerodynamic characteristics. Mathematical analysis showed the importance of the inclusion of steering compliance effects in determining stability factor, and hence the vehicle's high speed yaw rate sensitivity. Both experiments and theory showed that the actual high speed yaw rate response is not significantly less than that predicted from a low speed skid pad test, however, slight errors were found which are likely to be due to steering system nonlinearity and the effects of aerodynamic lift.
TL;DR: In this paper, the authors prove in a theoretical way that a controlled seat movement relative to the passenger compartment will result in an improvement of passenger deceleration during vehicle frontal impacts.
Abstract: SUMMARY The present study is meant to prove in a theoretical way that a controlled seat movement relative to the passenger compartment will result into an improvement of passenger deceleration during vehicle frontal impacts. This effect could be of advantage in some respects: as possible alternative for the most favourable design of the energy absorbing zones of a vehicle, as an additional safety device for the occupants of heavy vehicles with relatively soft impact absorbing zones in case of crashes against rigid obstacles, and in small vehicles where only little space exists for passenger protection. With regard to the complexity of this subject, the study at hand must be regarded as a first step towards the final solution of the problem.