Showing papers on "Vehicle dynamics published in 1982"

Lateral dynamics of commercial vehicle combinations. a literature survey

Abstract: SUMMARY This paper presents a review of theoretical and experimental works relative to the handling performance of commercial vehicle combinations. A commercial vehicle combination (road train) is defined as a tractor unit and an arbitrary number of trailers. The review contains literature corresponding the most widely used types of trains: tractor-semitrailer, truck-trailer and tractor-semitrailer-semitrailer (doubles). The vehicle dynamic performance has been investigated taking into consideration the following features: directional performance, roll dynamics, braking performance and combined braking and directional performance. With the aim of evaluating the present state of research activities in the field of lateral dynamics of articulated commercial vehicles, the author has compiled some 250 references.

Introduction to Vehicle Dynamics

Abstract: Today’s and tomorrow’s vehicles are based on various principles and travel with very different speeds. For a first classification of all kinds of vehicles the support and propulsion principles are used. The support mechanism has to balance the gravity acting on vehicles and the propulsion generates the forward speed, Fig. 1.

Directional Dynamics of a Tractor-Loader-Backhoe

Abstract: SUMMARY This paper presents a study of the directional dynamics of large industrial tractors. These vehicles have special properties which make their dynamics interesting, including soft rear tires, large yaw moments of inertia and low or negative understeer gradients. A linear yaw plane model was used for the analysis. The lateral compliance of the tires was included via a simplified version of the stretched-string model. Measurements were performed in support of the modeling effort, including inertial parameters, understeer gradient and transient response. A comparison between calculations and test results indicated that lateral compliance was an important influence on the transient response of these vehicles.

Modal Analysis of Gyroscopic Flexible Spacecraft: A Continuum Approach

Abstract: In the past, modal analyses of gyroscopic spacecraft have been performed after constructing a discrete model of the dynamics. This, however, obscures any momentum interaction between different parts of the spacecraft. This paper uses a continuum approach and gives a clear formulation of the complex gyroscopic vehicle modes. It is shown that unlike discrete modal analysis, special care is required while composing the phase space representation of the vehicle dynamics for a continuum modal analysis. The motion of the vehicle is shown to consist of two phases. In the first phase the vehicle executes a rigid body rotation with respect to an inertial frame. This rotation depends on the instantaneous angular momentum of the vehicle and determines the location of the associated Tisserand's frame. The second phase accounts for deformation measured from the Tisserand's frame and is expressed as a superposition of infinite gyroscopic modes. This phase contributes zero overall angular momentum. Throughout the analysis, a complex inner product in Hilbert space is found to be an essential tool for analysis.

Dynamic Simulation through Analytic Extrapolation

Abstract: In spite of the rapid progress of computational fluid dynamics (CFD) the existing capability to predict fullscale missile dynamics is very limited. The main reason for this is the existing strong coupling between boundarylayer transition and vehicle motion, which cannot be simulated by present CFD methods and can be obtained experimentally only in tests at the full-scale Reynolds number. The present paper describes the interactive use of theoretical and experimental techniques to provide the means to "extrapolate analytically" to full-scale flight conditions. This capability is especially needed in regard to elastic vehicle dynamics because of the difficulties inherent in performing dynamic simulation of an elastic vehicle in the high Reynolds number ground testing facilities presently becoming available.

Simulation of the Ford Vehicle Speed Control System

Abstract: This paper describes a mathematical model of the Ford Vehicle Speed Control System (Cruise Control). The model consists of component models of the engine, fluid coupling, speed sensor, actuator (pneumatic or electric), and vehicle dynamics. A computer implementation of the model is used to calculate the dynamic response of system variables to a sequence of driver commands, and to a sinusoidal road profile. Example computer solutions are given. The model is useful in evaluating system performance of proposed design innovations, determining performance sensitivity to component parameter values, and serves as a learning tool.

Digital simulation of the dynamic response of a vehicle carrying liquid cargo on a random uneven surface

Abstract: The dynamic response of a railway wagon carrying liquid cargo on a railway track is investigated. The dynamic behaviour of the sloshing liquid-mass is considered through its mechanical model. Two vehicle-liquid system models are considered to determine the dynamic response of the system moving with constant acceleration. The first model (S1) is assumed to respond under the heave mode and is subjected to single base point excitation. The second model (S2) responds under both the heave and the pitch degrees of freedom and is subjected to two-point base excitation. Two vehicle models, N1 and N2, with an equivalent solidified mass of the liquid and corresponding to models S1 and S2 are also considered to compare the vehicle response with and without the effect of the liquid sloshing. The equations of motion for the vehicle-liquid cargo system models (S1 and S2) are nonlinear and coupled. The equations of motion for the vehicle carrying equivalent solid cargo (models N1 and N2) are linear. The track unevenness is assumed to be a homogeneous random process. The vehicle is assumed to move over the track with constant acceleration and is therefore subjected to nonstationary base exitation. The equations of motion are solved numerically using the simulated track unevenness. It is found that the sloshing of liquid reduces the vehicle response whenever the natural frequencies of the vehicle and the sloshing liquid are far apart. The opposite is found to be true whenever the two natural frequencies are close to each other. Further it is found that the model S1 overestimates the heave response and underestimates the free surface response as compared to the model S2. It is concluded that the model S1 is inadequate to take into account the effect of the sloshing of liquid on the vehicle dynamics.

An electric vehicle dynamic simulation

Abstract: A complete electric vehicle dynamic simulation has been developed for evaluating the performance of drive train components and control strategies. The simulation includes models for the drive motor and its field controller and armature chopper, the battery, a transmission, and a transmission actuator and associated transmission control to accomplish automatic gear changes. These component models along with a vehicle dynamics model provide simulated vehicle performance in response to driver commands. The simulation provides a tool for developing control algorithms, and serves as a basis for examining other electric vehicle problems. The modular structure readily allows adding or substituting component models so that other hardware configurations can be studied. (A) For the covering abstract see IRRD 860793.

Instrumented car and driving simulation : measurements of vehicle dynamics

Abstract: The motion characteristics of an automobile in the longitudinal and lateral direction are described in terms of a mathematical model. The coefficients of this model were determined for an instrumented car by a series of field tests. The results were implemented in the mathematical models which are used in driving simulation research. Analog and digital computer programs, which describe the mathematical vehicle models, are also described.

Mathematical Methods in Vehicle Dynamics

Abstract: The dynamic analysis of deterministic and random vehicle vibrations and the consequences especially to passenger comfort requires an integrated study of three subproblems: (i) modeling and characterization of guideway roughness (ii) prediction of vehicle motion for traversal of a given guideway (iii) prediction or characterization of passenger response to vibration exposure.

Evaluation of automobile handling test procedures using a variable characteristic car

Abstract: Although it is agreed that production automobiles vary widely in their lateral handling quality, the identification and objective specification of "optimum" handling characteristics has proved a difficult problem. Evaluation of handling quality requires the selection of (a) vehicle characterisations that can be objectively determined and are relevant to the driver's control needs, (b) steering tasks which are representative of critical real-life manoeuvres and which "exercise" the vehicle dynamics, and (c) performance measures which are relevant to handling quality and reliably discriminate between different vehicles. These aspects of test procedure design have been investigated experimentally using the Melbourne University variable characteristic car (VCC). Both "free control" and "fixed control" vehicle parameters have been varied in steering tasks which involved highway curve negotiation, a double lane change, a slalom course and disturbance regulation, including both discrete pulse and continuous random steering disturbances. A large number of subjective and objective performance measures have been investigated. Experiences gained in the design of test procedures are described. The various handling parameters, tasks and measures are compared and evaluated. Interactions between handling parameters are demonstrated and recommendations are made for "acceptable" and "optimum" ranges of vehicle handling characteristics. (Author/TRRL)

Effect of wheel slip on the stability and stopping ability of a road vehicle

Abstract: The effects of a road vehicle's front and rear wheel slips on its stability and stopping ability under different conditions are studied. A simple in–plane model of a road vehicle is employed. The vehicle parameters used for simulation are those of a commercial vehicle. Two road conditions have been considered. During a given braking manoeuvre front and rear wheel slips are kept constant. From the results of digital simulation it is observed that even when both front and rear wheels are locked the vehicle will become unstable when there is a yaw angle disturbance at the beginning of a braking manoeuvre. Optimum slip ranges are determined for various road and speed conditions.

Dynamic stability of a buoyant quad-rotor aircraft

Abstract: Stability characteristics of a buoyant quad-rotor aircraft (BQRA) in hover and forward flight are examined by considering linear, state-variable, and nonlinear flight simulation models of such a configuration. The effects of carrying a sling load on the vehicle dynamics is predicted by considering a coupled model of the two bodies. Inherent stability characteristics of the vehicle are analyzed and compared with those of a helicopter and an airship in free flight. Typical operational conditions that could lead to vehicle instability are described in the flight envelope of interest.

Research in vehicle dynamics and tyre mechanics

Abstract: The study of vehicle dynamics, more specifically the horizontal plane motion of rubber tyred vehicles requires an exceptionally good knowledge of the force and moment generating properties of pneumatic tyres. These forces and moments are the result of the motion and orientation of the wheel with respect to the road. These position and velocity variables depend on the motion of the vehicle body and on the deflection of the wheel suspension and the steering system which in turn are governed by the forces acting from the road onto the vehicle, that is via the tyres. A number of problem areas exist roughly divided into low frequency motions, controlled by the driver and influenced by road geometry (transverse and forward slope variations) and side wind pressure variations, and relatively high frequency motions of say more than 4 hz which are caused by road-unevenness, imbalance and non-uniformities of the wheel and through instability of the system giving rise to self-excited vibrations. Development of theoretical vehicle models and of analysis and evaluation methods helped considerably in understanding peculiar features of vehicle behaviour and of its limitations regarding manoeuvring. Models are of increasing importance in the creation process of new vehicle designs and for the optimization of existing constructions. Testing equipment available in the laboratory, outlined in the first article contributed a great deal to the establishment and quantification of tyre models. The next sections successively deal with the laboratory's efforts in automobile handling and stability, front wheel vibrations and motorcycle dynamics. (Author/TRRL)

Modeling Rotational Dynamics of a Flexible Space Platform for Application of Multilevel Attitude Control

Abstract: Augmented body and multilevel modeling techniques are applied to the three axis ten body approximation of a typical flexible space platform

Complex Nonlinear Vehicles under Stochastic Excitation

Abstract: The modeling of guideways and vehicles and the corresponding mathematical methods of solution including linear and nonlinear techniques, random response and ride quality evaluation have been presented in detail. In this paper firstly the equations of motion of a complex automobile vehicle are derived and secondly numerical results for stochastic excitation of this vehicle by guideway irregularities are presented. It will be shown in particular that the dynamical analysis of random vehicle vibrations requires an integrated investigation of guideway roughness, nonlinear vehicle dynamics and human response to vibration exposure.