Vehicle System Dynamics Research Articles

Analyzing manipulator and feel system effects in aircraft flight control

The response characteristics of modern, highly augmented aircraft have reached the point where the vehicle and control system dynamics have begun to interact adversely with the actuation dynamics of the human pilot. Actuation dynamics include the characteristics of both the pilot's neuromuscular system and those of the manipulator and feel system by which the pilot's will is imparted to the aircraft. To address this problem, a simple pilot/vehicle model is developed that can be used both to interpret pertinent flight-test and simulation results and to serve as a tractable tool for assessing proposed changes in manipulator-feel system characteristics. The model hypothesizes proprioceptive information to be a fundamental feedback quantity in the pilot's ability to adopt the compensation characteristics required by the crossover model of the human pilot. The model includes manipulator-feel system dynamics, vestibular (motion) feedback, and a rudimentary form of biodynamic feedback. Simple frequency domain control system analysis techniques are applied to the study of manipulator and force feel system effects and to an analysis of the roll ratchet phenomenon.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Transactions of the International Association for Vehicle System Dynamics (IAVSD)

Transactions of the International Association for Vehicle System Dynamics (IAVSD)

Application of Sensitivity Methods to Analysis and Synthesis of Vehicle Dynamic Systems

The development and application of sensitivity methods for determining the effects of parameter changes on the response of vehicle dynamic systems is presented. The procedures shown can be used to enhance the analysis and synthesis processes of virtually any road or rail vehicle system regardless of its complexity. The parametric sensitivity of vehicle models in time domain, steady state models and vehicle models in frequency domain can be investigated using different types of sensitivity functions, both dimensional and dimensionless including first order standard, percentage, logarithmic, second order standard, and logarithmic and percentage sensitivity measures. These sensitivity functions and measures are determined as functions of partial derivatives of system variables taken with respect to system parameters. In the case of sensitivity functions in the frequency domain the variable values are computed as either the magnitude or phase angle of a complex element of the transfer function matrix. The methods presented enable to determine the influence of all system primary (constant) and secondary (non-constant) parameters on system primary and secondary variables. The primary variables are state variables or elements of the transfer function matrix and the secondary variables may be any functions of primary variables and system parameters. Typical secondary system parameters which can be examined include initial conditions, time variant coefficients, natural frequencies, loads, and typical secondary variables are forces, weight transfers, stability factors and energy components. The analysis of sensitivity results obtained for three vehicle handling models in both linear and nonlinear regimes of vehicle performance and utilizing various types of sensitivity functions is also presented.(a)

Sensitivity Analysis of Vehicle Design Attributes in Frequency Domain

SUMMARY This paper presents a procedure for determining the sensitivity matrices of a vehicle dynamic system in the frequency domain as derivatives of the transfer function matrix with respect to system parameters. First and second order logarithmic sensitivity functions which possess normalized coefficients have been introduced to enhance analysis. The sensitivity analysis of amplitude-frequency characteristics on changes of selected parameters of a 3 degree-of-freedom vehicle handling model has been performed. It has been demonstrated that the general sensitivity measure proposed can be used to determine the combined influence of system parameters divided into groups such as design, environmental, driver, kinematic, etc., on the multi-parameter system response, prior to determining their order of influence within the groups.

Identification Methods for Vehicle System Dynamics

SUMMARY The paper presents a survey on parameter identification techniques for complex vehicle models. In order to cope with the complexity of the model, the information on the system available from the equations of motion has to be included in the identification process. Basic methods for the solution of this problem are shown. The application of the approach is demonstrated by identification of the vertical automobile dynamics. It is concluded that the presented techniques will become more important with increasing applications of theoretical modeling in vehicle system dynamics.

Comments on the Paper “The Application of Linear Optimal Control Theory to the Design of Active Automobile Suspensions” by D. A. Wilson, R. S. Sharp and S. A. Hassan Vehicle System Dynamics 15 (1986) pp. 105-118

SUMMARY

Reply to comments by Dr A. G. Thompson on the Paper “The Application of Linear Optimal Control Theory to the Design of Active Automobile Suspensions” by D. A. Wilson, R. S. Sharp and S. A. Hassan Vehicle System Dynamics 15 (1986), pp. 105-118.

Reply to comments by Dr A. G. Thompson on the Paper “The Application of Linear Optimal Control Theory to the Design of Active Automobile Suspensions” by D. A. Wilson, R. S. Sharp and S. A. Hassan Vehicle System Dynamics 15 (1986), pp. 105-118.

A Theoretical Analysis on Vehicle Cornering Behaviours in Braking and in Acceleration

(1985). A Theoretical Analysis on Vehicle Cornering Behaviours in Braking and in Acceleration. Vehicle System Dynamics: Vol. 14, No. 1-3, pp. 140-143.

On Driving Safety and Dynamic Characteristics of Rear Wheel Steered Vehicles

(1985). On Driving Safety and Dynamic Characteristics of Rear Wheel Steered Vehicles. Vehicle System Dynamics: Vol. 14, No. 1-3, pp. 74-78.

Aerodynamics of Road- and Rail Vehicles

SUMMARY The technical state-of-the-art of aerodynamics of ground transportation vehicles is reviewed. Currently available theoretical calculation methods and experimental simulation techniques as well as typical results illustrating the impact of aerodynamics on vehicle performance and running characteristics are summarized and the interactions between vehicle system dynamics and aerodynamics are adressed. Correlation of theoretical and experimental data show the present potential of vehicle aerodynamics and point to fields in which further research work is necessary.

Rail Vehicles' Riding Quality and Comfort Related to Theoretical and Experimental Optimization Application to High Speed Trains

(1985). Rail Vehicles' Riding Quality and Comfort Related to Theoretical and Experimental Optimization Application to High Speed Trains. Vehicle System Dynamics: Vol. 14, No. 1-3, pp. 107-114.

General Purpose Vehicle System Dynamics Software Based on Multibody Formalisms

SUMMARY This paper pursues two objectives: Firstly, to review the state-of-the-art of general purpose vehicle system dynamics software and secondly, to describe two representatives, the program MEDYNA and the program NEWEUL. The general modeling requirements for vehicle dynamics software, the multibody system approach and a comparative discussion of multibody software are given. The two programs NEWEUL and MEDYNA are described with respect to modeling options, computational methods, software engineering as well as their interfaces to other software. The applicability of these programs is demonstrated on two selected examples, one from road vehicle problems and the other from wheel/rail dynamics. It is concluded that general purpose software based on multibody formalisms will play the same role for mechanical systems, especially vehicle systems, as finite element methods play for elastic structures.

Properties of Non-Linear Two-Force Elements Used in Vehicle Dynamic Systems under Stationary Stochastic Excitation. Part 2 - Realistic Complex Elements

SUMMARY Realistic two-force elements used in vehicle dynamic systems have very often complex output force -inputs relations. Determination of their properties under stationary stochastic excitation must be therefore carried out experimentally for every excitational case. Evaluation of the measurements of one type of a passenger car telescopic hydraulic suspension damper and of one type of a heavy duty truck leaf spring is shown in this part of the paper. Transfers of the discussed elements, representing the frequency responses of the elements to the input deflectional process and defined in the first part of this paper, form the base for the evaluation.

Properties of Non-Linear Two-Force Elements Used in Vehicle Dynamic Systems under Stationary Stochastic Excitation. Part 1 - Ideal Elements

SUMMARY Non-linear two-force elements (springs, dampers, etc.) are commonly found in vehicle dynamic systems. Their mathematical idealization by expressing their force-excitation relation by a real function is called to be an ideal element. Excitation of these elements can be often considered as being stationary stochastic. Their general properties under such excitation are discussed and computation of the stochastic properties of the output force for known excitation are shown in this paper. Transfer functions of the elements, i.e. output force - input relations in the frequency domain, under the given excitational conditions form the base for the evaluation.

Determining the Characteristics of Helical Springs for Application in Suspensions of Railway Vehicles

ABSTRACT This study concerns the theoretical calculation of the characteristics of helical springs used, particularly, for the primary and secondary suspensions of railway vehicles: the static characteristics will be determined by an exact method where as the dynamic characteristics will be determined with the help of an approximate method whose precision is, however, sufficient to make a valid evaluation of the dynamic behavior of the vehicles themselves. The first part of the study is presented here, while a second part will appear in the next issue of “Vehicle System Dynamics”.

DISCUSSION NOTE on Karnopp's article “Active Damping in Road Vehicle Suspension Systems”

(1983). DISCUSSION NOTE on Karnopp's article “Active Damping in Road Vehicle Suspension Systems”. Vehicle System Dynamics: Vol. 12, No. 6, pp. 313-315.

A Bifurcation Analysis of Nonlinear Oscillations in Railway Vehicles

(1983). A Bifurcation Analysis of Nonlinear Oscillations in Railway Vehicles. Vehicle System Dynamics: Vol. 12, No. 1-3, pp. 5-6.

Artificial Generation of Road Surface Topography by the Inverse F.F.T. Method

(1983). Artificial Generation of Road Surface Topography by the Inverse F.F.T. Method. Vehicle System Dynamics: Vol. 12, No. 1-3, pp. 160-165.

Modeling of Complex Vehicle Systems

(1983). Modeling of Complex Vehicle Systems. Vehicle System Dynamics: Vol. 12, No. 1-3, pp. 12-14.

Dynamic Respose of the Locomotive to the Random Excitation from Track Irregularities

(1983). Dynamic Respose of the Locomotive to the Random Excitation from Track Irregularities. Vehicle System Dynamics: Vol. 12, No. 1-3, pp. 120-123.