Showing papers on "Vehicle dynamics published in 1978"

A Two-Level Model of Driver Steering Behavior

Abstract: In evaluating the performance of the driver-vehicle system and in establishing design criteria for favorable vehicle dynamics, a quantitative description of driver steering behavior such as a mathe...

Correlation and Evaluation of Driver/Vehicle Directional Handling Data

Abstract: This paper summarizes the results of a study whose purpose was to analyze and correlate recent data on the directional response and performance of driver/vehicle systems. The driving situations considered included open and closed loop limit maneuvers, avoidance maneuvers, and nominal closed loop regulation and maneuver tasks. For automobiles, the two parameters (gain and time constant) used in most of the correlation plots effectively describe the key handling properties. The available data suggest composite boundaries for steady state steering gain and effective time constant, based on a combination of system performance and workload-related driver subjective opinion measures. The resulting criteria plot, defined at 50 mph shows that there is a range of steering gains which are satisfactory - the unsatisfactory regions involving values which are either too low or too high. There is also an upper limit on the effective time constant beyond which the vehicle's directional response is not rapid enough. This upper limit varies with steering gain.

Lateral-Directional Motorcycle Dynamics and Rider Control

Abstract: A theoretical and empirical view is taken of motorcycle lateral-directional dynamics, handling, and rider control behavior. The analytical development includes equations of motion for the vehicle and a multiple loop feedback model for the control response rider/cycle system. Connections with manual control and vehicle response data are shown. The effects of changing fork geometry, operating conditions, and tire lag properties are discussed. Implications are drawn for handling requirements, vehicle design, and rider control techniques.

Effectiveness of Basic Display Augmentation in Vehicular Control by Visual Field Cues

Abstract: The effectiveness of different basic display augmentation concepts (fixed reticle, velocity vector, and predicted future vehicle path) for remotely piloted vehicles (RPV) controlled by a vehicle mounted television camera is investigated. The task is lateral manual control of a low flying RPV along a straight reference line in the presence of random side gusts. The man-machine system and the visual interface are modeled as a linear time-invariant system. Minimization of a quadratic performance criterion is assumed to underly the control strategy of a well-trained human operator. The solution for the optimal feedback matrix enables the explicit computation of the variances of lateral deviation and directional error of the vehicle and of the control force that are used as performance measures. These variances are initially calculated with assumed values of human operator parameters such as weighting coefficients and noise levels. In particular, it is investigated whether and to what extent the human operator actually utilizes the display of information representing higher order state components such as lateral velocity and acceleration. The results show that the effectiveness of the display aids strongly depends on the vehicle dynamics and the spectrum of the disturbance. A velocity vector reticle is very effective for fast vehicle dynamics and rather ineffective for slow vehicle dynamics. On the other hand, a future vehicle path reticle is very effective for slow vehicle dynamics but less effective for fast vehicle dynamics and fast disturbances. The analytical results obtained are then validated by means of a specially developed flight simulator.

Tune to Win - The Art and Science of Race Car Development and Tuning

Abstract: Covers the development and tuning of race car by clearly explaining the basic principles of vehicle dynamics and relating these principles to the input and control functions of the racing driver. An exceptional book written by a true professional.

Viscous Interaction or Support Interference-The Dynamicst's Dilemma

Abstract: In hypersonic low-density flows, slender vehicle dynamics are affected by various viscous flow phenomena. The true viscid-inviscid interaction is often difficult to extract from the background of support interference in wind tunnel tests and nonlinear six-degree-of-freedom motion effects in ballistic range tests, as was demonstrated by Welsh, Winchenbach, and Madagan several years ago. The range data and wind tunnel results for a 10-deg cone were shown to give completely different M^ trends for the pitch damping derivative. The aim of the present paper is to resolve this ambiguity and to help the vehicle designer decide how to obtain the best possible information about the full-scale vehicle dynamics using subscale dynamic test data.

Display Augmentation in Manual Control of Remotely Piloted Vehicles

Abstract: The effectiveness of display aids for the manual control,of remotely piloted vehicles by television during landing approach is investigated. The task is lateral and vertical control along a required glide-slope trajectory in the presence of lateral and vertical random disturbances. By superimposing suitable glide-slope reference lines on the TV monitor, the glide-slope error can be derived directly from the visual field. It is theoretically investigated whether and under what conditions the display of higher-order state components, such as the vertical velocity and/or acceleration, is required. It is shown that, for a body-mounted camera, essential angular rate information can be detected from the vertical relative motion of the visual field due to vehicle pitching. This information is required, in particular, for relatively slow vehicle dynamics. On the other hand, rapid pitching, which occurs with fast vehicle dynamics, may be detrimental to its effective control. These disturbing motions can be easily eliminated by a gyro-stabilized camera, but then the essential angular and pitch information is also eliminated and control becomes difficult. A display configuration is, therefore, proposed in which position, rate, and acceleration cues are derived from a single error displayed by special reference bars. It is theoretically and experimentally shown that the effectiveness of the display configuration and the type of camera mounting (body-mounted or inertially stabilized) is highly dependent on vehicle dynamics and disturbance bandwidth.

Analysis of the Rollover Dynamics of Double-Bottom Tankers

Abstract: A roll dynamic analysis was undertaken to determine the rollover threshold for typical double-bottom tanker vehicles and to compare that threshold with the corresponding values for other common tractor-trailer combinations. A secondary objective was to provide the methodology for predicting the effect of changes to vehicles and operational procedures in order to improve the rollover stability of such vehicles. A dynamic model of the vehicle in the roll plane was formulated for study of roll motions under arbitrary lateral force input time histories. The roll response and limit maneuver capabilities predicted by the model showed good agreement with those of actual vehicles. The model was used to predict the relative rollover thresholds of the double-bottom tanker (associated with a high incidence of rollover accidents in Michigan) and other tanker configurations for comparison with those of other commercial vehicles in a selected double lane-change maneuver. The model confirmed that double-bottom tankers of the current design exhibit a low rollover threshold compared to other commercial vehicles. The major sensitivity to rollover derives not so much from the lateral acceleration limit of the pup trailer as from the rearward amplification of the tractor lateral accelerations. The model demonstrated that a modification of the vehicle via a composite rigidified hitch/rubber mount enhances pup trailer stability through reduction of suspension backlash, and allows roll moment sharing among all the vehicles in the train. The result is a vehicle with manuever levels comparable with other commercial vehicles.

The application of quasi-linearization techniques to rail vehicle dynamic analyses

Abstract: The objective of the work reported here was to define methods for applying the describing function technique to realistic models of nonlinear rail cars. The describing function method offers a compromise between the accuracy of nonlinear digital simulation and the computational efficiency of linear methods. This work entailed the development of realistic describing function representations for nonlinearities such as the wheel/rail contact interaction and the development of algorithms for using these describing functions to predict the occurrence and stability of hunting and the forced response of rail vehicles to sinusoidal and statistical track irregularities. This report explains the describing function technique, demonstrates how it can be applied to nonlinear rail vehicle dynamics problems, describes algorithms that can be used for such problems, and presents results for typical nonlinear problems, including wheel profile and suspension nonlinearities.

Programmable digital vehicle control system

Abstract: The Programmable Digital Vehicle Control System or PDVCS is based upon the Intel 8080A microprocessor, and is designed to replace the hardwired, discrete components traditionally used in the on-board control of automated rapid transit vehicles. Although designed specifically for the Advanced Group Rapid Transit (AGRT) system under development by The Boeing Company, with funding by the Department of Transportation, the PDVCS can easily be adapted for use in any automated transit system. A breadboard PDVCS has been programmed to perform the basic AGRT longitudinal control system functions, including closed-loop emergency braking, and has been subjected to closed-loop laboratory testing. Prototype tachometers and a 7th order nonlinear analog computer simulation of motor, brake and vehicle dynamics were used to close the control loop for test purposes; command scenarios were input manually. The test results demonstrate the feasibility of microcomputers in on-board vehicle control and show their capability to meet the performance requirements associated with a short headway (3 second) system.

Users' manual for kalker's 'exact' nonlinear creep theory

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Nondeterministic analysis of a four-wheeled model vehicle traversing a simulated random terrain

Abstract: In order to increase confidence in the reliability and accuracy of the linear random vibration theory in predicting vehicular behavior, an experiment was performed with a four-wheeled model vehicle having an independent suspension system The vehicle has three degrees of freedom (vertical translation, pitch, and roll) and was made to operate at different speeds on a simulated road bed with randomly distributed surface roughness Using linear random vibration theory, equations giving the power spectral density of each degree of freedom about the vehicle's center of gravity were derived as a function of the power spectral density of the four wheels' vertical displacement Numerical and experimental techniques enabled a direct comparison to be made between theoretical predictions and experimental results The linear random vibration theory gave reliable predictions at higher speeds and on rougher terrain Deliberate, asymmetrical loading of the model vehicle had little effect on the reliability of linear random vibration theory predictions A comparison between results of linear random vibration theory and a numerical-nonlinear technique showed the superiority of the former in predicting experimental results, with a relatively small computing time requirement

Computer models for railway vehicle operation

Abstract: The paper summarizes the computer programs developed under the Track-Train Dynamics project, designed to study the dynamic interaction of rolling stock and/or train-consist with track The models describe the vehicle response on tangent and curved track and also discuss the phenomenon of lateral dynamic stability Results obtained from lateral, vertical and longitudinal train action models, are presented Analytical results are compared with field data Possible application, of the computer program for train-handling and train-make up are also discussed

General purpose program for the simulation of vehicle-guideway interaction dynamics

Abstract: The models which can be treated are: multibody rigid or elastic vehicles, any degrees of freedom, kinematic constraints; a variety of linear and nonlinear suspension laws including active control systems; elastic guideways (or bridges) including irregularities; the nominal track can be straight and level but also curves, grades as well as variable velocity can be simulated. Special features of the resulting simulation program are: automatic generation of the linearized system equations, generation of subroutines by the program to reduce the numerical effort, modular construction of the whole program. The time-response of the overall time-varying and possibly nonlinear state-equations is obtained via numerical integration. The program is supplemented by evaluation and interpretation routines which allow one to compute vehicle stability, controllability and observability as well as the transfer function matrix. Also, the time-responses can be Fourier-transformed and vehicle ride-quality can be calculated. As a typical application, the simulation of a design of an electrodynamic repulsion system is presented for both the magnetically suspended- as well as the emergency-mode.

Interactive Vehicle Dynamics and Ride Evaluation Package

Abstract: : This report describes an integrated package for evaluating the dynamic effects of driving a vehicle across any described section of terrain. The model incorporated includes only the pitch and roll motions of the chasis (or hull). The package is composed of a four digital computer programs. Each program is designed to be run interactively and does not require that the user have any programming experience. The programs provide the capability to create vehicle data files, perform simulations, and specify the form and types of the output desired. A general description of the model structure, its capabilities and its limitations is included along with user instructions for running each program in the package.

Dynamic response of tractor-semitrailer vehicle to random input

Abstract: This paper is concerned with the dynamic analysis of vehicle-road using the theory of stochastic processes. The tractor-semitrailer vehicle is treated as a discrete, linear, time-invariant dynamic system subjected to a stationary random input from the road surface. The vehicle model, including primary and secondary suspension systems, and subject to both heave and pitch motions, has six degrees of freedom. A representation of random roughness of the road is given, frequency domain analysis is applied, and a parametric study is presented. The theoretical investigation described in this paper represents an attempt to obtain a better understanding of the significant parameters of vehicle construction and road characteristics involved in (a) the vibrations transmitted from the roadbed to the tractor-semitrailer vehicle, (b) the dynamic forces at the tyre-road interface. The results of the computer analysis of vehicle and road are presented in two forms; the amplitude spectra and the root mean square amplitudes which are used to predict vehicle ride quality and evaluate the design concepts. (Author/TRRL)

Theoretical and experimental research on freight car lateral dynamics

Abstract: A five year study of rail freight car dynamics is summarized. The paper emphasizes the effort to validate theoretical analyses of rail vehicle dynamics with results from field testing. The theoretical analysis, solution techniques, field testing, data processing and validation results are given.

Improved hybrid computer vehicle handling program (ihvhp)

Abstract: The Improved Hybrid Computer Vehicle Handling Program (IHVHP) is an extension of the Hybrid Computer Handling Program (HVHP) described in DOT-HS-802-059, Jul 1976. The computing tasks have been redistributed between the analog and digital computers. Many of the simplifications that existed in the HVHP have been removed. The equations of motion for the sprung and unsprung masses of a vehicle have been expanded to include higher order terms and large pitch and roll angles. Numerous geometric and kinematic calculations have been modified to include large pitch and roll angles. The hybrid computer simulation for vehicle handling studies has been in use for 6 years and can simulate (a) independent front and rear axles, (b) independent front with solid rear axle, (c) independent front and solid rear axle with dual rear tires, (d) solid front and rear axles, and (e) solid front and rear axles with dual rear tires. For validation purposes, braking, steering, and combinations of braking and steering were put into the simulated mathematical model; the simulation time histories were then compared to fullscale test data. The hybrid vehicle handling program can be used for general studies of vehicle dynamics. Performance of the National Highway Traffic Safety Administration (NHTSA) standard passenger car Vehicle Handling Test Procedures (VHTP's) and calculation of the associated performance comparison variables (PCV's) are simulation options. A special interactive user's interface allows program use by vehicle engineers as well as by computer specialists.

Sensitivity Considerations in Trajectory Optimization

Abstract: A technique by which the trajectory optimization problem can be formulated to include the trajectory sensitivity functions in the performance index is presented. It is shown that an explicit steering law, which can be derived for the upper atmospheric flight of a vehicle, is a function of the sensitivity state, adjoint vectors, and the parameters of the chosen trajectory dynamics. The new steering law is compared with the one without sensitivity considerations. A computational method is presented to implement the new steering law.

Minimum Number of Vehicles to Meet Dynamic Transportation Demand

Abstract: The fundamental resources of a transportation network are channels, terminals, and vehicles. In practical situations, however, all of them do not always restrict flow volume, usually one of them constrains it. Channels restrict the flow in conventional network flow models. An example where terminal constraints are realized is a multistage inventory model. A new flow model is proposed where flow is limited by the number of vehicles. It is noted that the problem can be reduced to a minimum cost circulation problem when transportation demand is assumed to be time-independent. However, the minimum number of vehicles required to satisfy time-varying transportation demands is obtained. This problem is formulated as a transportation problem in linear programming. In the case where the number of terminals n = 2, however, the problem is not only solved analytically, but its solution also yields an interesting interpretation. Furthermore, the case of "compound operation" is investigated and discussed where vehicles are separated into two groups and operated among m terminals on a single path. The first group of vehicles shuttles between terminal 1 and terminal m. The second group shuttles between terminal p and terminal q, where 1 ? p < q ? m. Consequently, the minimum number of vehicles required for a compound operation is obtained.