Showing papers on "Vehicle dynamics published in 1981"

Application of an Optimal Preview Control for Simulation of Closed-Loop Automobile Driving

Abstract: An optimal preview control method is applied to the automobile path following problem. The technique is first used to examine the straight-line regulatory driving task and results compared with similar experimental measurements. The method is further demonstrated by closedloop simulation of an automobile driver/vehicle system during transient lane-change maneuvers. The computer simulation results are compared with equivalent vehicle test measurements.

Off-road vehicle dynamics

Abstract: SUMMARY Recent developments in off-road vehicle dynamics are reviewed. Progress on this topic and the application of new techniques to the particular problemsassociated with off-road operation tend to lag behind practices established for road vehicles. The factor which limits further progress is the lack ofappropriate off-road tyre data, in particular, on vibrational and lateral force generation characteristics. Also, a long term study should be aimed at understanding the dynamic behaviour of tyres on yielding surfaces.

Nonstationary response of vehicles on rough ground--a state space approach

Abstract: The motion of vehicles traveling over rough ground at variable speed is nonstationary. In this paper, a method for the computation of response variance is presented which uses the concept of a "spatial" shaping filter to represent the uneven ground, leading to a state space form for the combination of vehicle and excitation. The formulation is for linear systems of arbitrary order and allows any deterministic velocity history to be accommodated easily. An example is discussed in detail.

Dynamics and Hydrodynamics of Ocean Vehicles

Abstract: A state-of-the-art review of the dynamics of ocean vehicles is presented. A review of the six-degree-of-freedom nonlinear equations of motion acquaints the reader with the number, type and importance of the terms for various maneuvers. Application of these equations about the linearized equilibrium condition, U_{o} = constant, which decouples the horizontal and vertical plane equations, is discussed from both a vehicle design and control system point of view. Application of any set of equations of motion requires knowledge of the values for the hydrodynamic coefficients. The preferred method for obtaining these coefficients during the vehicle design process is to predict the coefficients from the geometry of the vehicle without resorting to tunnel testing. Present capability for the prediction of linear and nonlinear hydrodynamic coefficients is discussed, along with examples that demonstrate the current accuracy of prediction methods.

Review and summary of computer programs for railway vehicle dynamics

Abstract: OF KALKER'S EXACT THEORY The conversion of the computer program, "A Programme for Three Dimensional Steady state Rolling" developed by Professor J. J. Kalker, from the Original Algol language to FORTRAN is considered. This program determines the resultant creep forces and moment for steady state rolling of two bodies of equal or unequal linearly elastic material properties. Arelated manual for Kalker’s "Simplified Theory of Rolling Contact" is considered in the report "User's Manual for Kalker's Simplified Nonlinear Creep Theory," by James G. Goree and E. Harry Law, FRA/ORD-78/06 Contract DOTOS-40018, December, 1977. The program considered in the present report concerns the same problem except for the extension to unequal materials. It is found that, for equal materials, the "Simplified Theory" gives approximately the same results as the exact solution in most cases, and in those instances where some difference was noted, the simplified theory appears-to be in better agreement wth experimental, results. In addition, the simplified theory reduces the computation time by a factor of approximately 50 to 100. ABSTRACT OF KALKER'S SIMPLIFIED THEORYOF KALKER'S SIMPLIFIED THEORY The conversion of the computer .program, "Simplified Theory of Rolling Contact," (used for calculation of a nonlinear creep force-creepage relationship) from the origianl Algol language to FORTRAN is considered. The Algol program was written by Professor J. J. Kalker and was derived from the paper, "Simplified Theory of Rolling contact," Delft Program Rep., Series c? Mechanical and Aeronautical Engineering and shipbuilding, l (1973), pp. 110. A significant number of changes was made in the program for more convenient use; however, the fundamental equations remain unchanged. The results were checked in detail to insure agreement with the original solution. The program gives an appropriate solution for the resultant tangential creep forces and spin moment acting between two bodies of equal linearly elastic material properites. The creep forces and spin moment are due to lateral, longitudinal, and spin creepages. Assumptions corresponding to the Herts contact theory are implied and two additional simplifying assumptions are made, resulting in a significant reduction in computation time as contrasted with previous solutions. Two separate computer codes were developed, the first being the general solution with extended input and output, and the second a shortened version primarily intended for use as a subroutines. Suprisingly good agreement is found to exist between the "Simplified Theory" and published experimental results for a wide range of contact ellipse eccentricity.

Vehicle dynamics: free-flight trajectory analysis

Abstract: Vehicle crash investigators are regularly challenged to reconstruct the kinematics of collisions when there are no witnesses or there is conflicting witness testimony. Vehicle deformation, skid marks and contact points on the roadway and the roadside often permit a picture of the event to unfold. Vehicle speeds at collision are of major interest and are often estimated by studying skid marks, vehicle crush and vehicle displacement after initial collision. Some of the uncertainty in these calculations can be rectified if the vehicle in question has entered into a free-flight trajectory. Often the points of vehicle take off and landing are readily discernible and a calculation of the vehicle speed at take off can be made from the measured parameters of the trajectory. This paper presents a solution to the fundamental equations of motion in terms of the horizontal range, the vertical height change and the angle of projection of the vehicle. Data are presented which quantify the speed at take off in terms of these parameters and which will allow investigators who are unfamiliar with complex mathematical relationships to interpolate a solution for a measured set of parameters. The effects of aerodynamic drag on the vehicle are reviewed as they relate to the estimation of vehicle speed from the measured trajectory parameters. Vehicle collisions involving free flight trajectories were investigated by The University of Western Ontario Multi- disciplinary Accident Research Team and summaries of the findings are presented. These cases illustrate how this vehicle speed estimation technique can play a most valuable role in police and Coroners' investigations of such collisions.

Lateral Dynamics of a Rail Transit Vehicle: A Comparison of Experimental and Theoretical Results

Abstract: A subway rail vehicle was tested on tangent and curved track sections to provide dynamics data for validation of theoretical models. Tests were done with three combinations of primary suspension and wheel profiles which were selected using a simplified truck stability/curving trade off analysis. The test results of one configuration are compared with two lateral dynamic models. Experimental frequency and damping results are compared with the predictions of a linear Lateral Stability model for a number of vehicle speeds. The measured time histories of vehicle responses on a spiral and a 122 m (400 ft) radius curve are compared with the results obtained from a Curve Entry Dynamics model. The agreement between theory and experiment varied from good to poor depending on the parameter being compared. The discrepancies between theory and experiment can be attributed to four major sources: limitations of models, errors in vehicle parameters used in obtaining theoretical results, measurement errors and data analysis limitations.

Rail vehicle dynamics model validation

Abstract: The validation of mathematical models of rail vehicle dynamics using test data poses a number of difficult problems, which are addressed in this report. Previous attempts to validate rail vehicle models are reviewed critically, and experience gained in validating dynamic models of aircraft and marine vehicles using system identification methods is then applied to the formulation of a general procedure for validating rail vehicle dynamic models. The procedure is outlined, step by step, for application with existing test data and for use as part of a new model validation test program. An example of the application of the initial stages of the procedure is demonstrated using data from the Perturbed Track Tests (PTT) at Pueblo to validate a simple linear model of the forced vertical dynamics of a six-axle locomotive. Recommendations are offered for the conduct of future model validation efforts.

Computer simulation of the effect of cargo shifting on articulated vehicles performing braking and cornering manfuvers, volume 3. technical supplement

Abstract: The effects of sloshing liquid cargo on the limit performance of articulated trucks have been investigated. The limit performances of four vehicle configurations in cornering and braking maneuvers were simulated using an augmented version of the vehicle simulation program, TDVS (Three Dimensional Vehicle Simulation). The vehicle configurations consisted of tractor with unbaffled, baffled, and compartmentalized tank trailers and a baseline van. Simulated maneuvers were lane change, cornering, straight-line braking, and braking-in-a-turn. Both vehicle configurations and maneuvers were modeled to correspond with the full-scale experiments, "Effect of Cargo Shifting on Vehicle Handling", (DOT-FH-11-9195), conducted by Dynamic Sciences, Inc. This report covers the validation of the augmented TDVS program, and the development and implementation of a methodology for conducting limit of performance simulations. Results are discussed and summarized in the context of the simulation program and in light of experimental data. Finally, recommendations are presented for vehicle dynamics analysis methodology and for future studies. (FHWA)

Application of the parameter space method to aerospace vehicle digital control system design

Abstract: The parameter space method is a technique for determining stability, and dynamic characteristics of a control system in terms of several selected system parameters. The digital form of the technique requires that the system characteristic equation be available in the complex z -domain. The method is extended and applied to a model of a digitally controlled aerospace vehicle.

Control Technology As Applied To Space Telescope

Abstract: The pointing control system (PCS) of the Space Telescope is addressed. The sensors employed in the primary PCS mode are the rate gyro assembly and the fine guidance sensors, while four reaction wheel assemblies provide control torques. Stability considerations based on structural modes are discussed, noting the stability margin criteria used in the design. Acquisition methodology is considered with regard to the PCS component hardware simulators and vehicle dynamics simulation.

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.

Optimization of magnetic suspension and analysis of vehicle dynamics

Abstract: Optimization problems are considered for passenger-transport suspension systems employing repulsion-type permanent magnets. The characteristics for which optimization is carried out are listed. Approximate and exact numerical optimization methods are described as is the magnetic system optimized. A method is proposed for investigating the dynamics of a car on a magnetic suspension realized in the form of a "magnetic skid" coupled to the car by viscoelastic supports with the aid of mathematical modelling of distured motion and visualization of the results of means of a graph plotter and display.

Computer simulation of the effect of cargo shifting on articulated vehicles performing braking and cornering maneuvers, volume 4 user's manual for tdvs/slosh

Abstract: The effects of sloshing liquid cargo on the limit performance of articulated trucks have been investigated. The limit performances of four vehicle configurations in cornering and braking maneuvers were simulated using an augmented version of the vehicle simulation program, TDVS (Three Dimensional Vehicle Simulation). The vehicle configurations consisted of tractor with unbaffled, baffled, and compartmentalized tank trailers and a baseline van. Simulated maneuvers were lane change, cornering, straight-line braking, and braking-in-a-turn. Both vehicle configurations and maneuvers were modeled to correspond with the full-scale experiments, "Effect of Cargo Shifting on Vehicle Handling", (DOT-FH-11-9195), conducted by Dynamic Sciences, Inc. This report covers the validation of the augmented TDVS program, and the development and implementation of a methodology for conducting limit of performance simulations. Results are discussed and summarized in the context of the simulation program and in light of experimental data. Finally, recommendations are presented for vehicle dynamics analysis methodology and for future studies. (FHWA)

The response of a vehicle to a sudden movement of the steering wheel

Abstract: This mathematical study provides the response of a vehicle at a constant speed and subject to a sudden pull of the steering wheel (angle or torque step). It also enables the influence of the principal vehicle construction parameters to be studied. A particular combination of the equations will enable the vehicle response to be expressed as a combination of 3 basic movements: roll, yaw-sideslip and steering. Examining the corresponding simplified equations will lead to a physical interpretation of these movements in terms of inertia damping and stiffness. Finally, we are studying, with the complete model, the effect of combining these different movements using modes, only two of which form the main part of the response. It is therefore relatively easy to forecast, at least qualitywise, the influence of the principal parameters.(a) for the covering abstract of the conference see TRIS 378303. (TRRL)