Showing papers in "Journal of Dynamic Systems Measurement and Control-transactions of The Asme in 1974"

A Survey of Railway Vehicle Dynamics Research

Abstract: Presents a survey of the research concerned with the dynamics of single, conventional railway vehicles. Attention is concentrated on analytical research and only that experimental research that has been performed in conjunction with analytical efforts. The often conflicting objectives for railway vehicle suspension design and the research done to understand the design implications of these objectives are discussed.

Performance of magnetic suspensions for high-speed vehicles operating over flexible guideways

Abstract: This paper examines the performance of attraction (ferromagnetic) and repulsion (superconducting) MAG-LEV Suspensions suitable for use on high-speed ground vehicles. The effects of guideway roughness, guideway flexibility and of force nonlinearities are examined. It is concluded that for the particular cases examined here, MAG-LEV suspension systems for 300-mph vehicles which provide reliable tracking while meeting ride quality criteria can be designed. It is also apparent that a considerable effort is required to achieve MAG-LEV system optimization and refinement.

Transportation Vehicle/Beam-Elevated Guideway Dynamic Interactions: A State-of-the-Art Review

Abstract: The importance of elevated guideway/vehicle dynamics to the design of advanced ground transportation systems is discussed and the general vehicle-suspension-guideway interaction problem is outlined. Simplifying assumptions valid for many practical beam-type elevated guideway systems are described including the Bernoulli-Euler beam assumptions, support conditions, and simplified vehicle models. The theoretical and experimental literature on beam-guideway/vehicle dynamics is reviewed and recent computer-based analytical techniques (lumped mass, finite difference and modal analysis) are discussed. Available simulation programs are described and published results for wheeled, air cushion and magnetically levitated vehicles operating over beam-elevated guideways are reviewed. The influences of critical system parameters on guideway deflection and vehicle vibrational acceleration (ride comfort) are illustrated through simple limiting case analyses. Low ratios of vehicle-suspension to guideway natural frequency and distribution of vehicle weight over finite pressure pads as in air or magnetic suspensions reduce guideway structural requirements for specified ride comfort. Continuous guideway beams on simple supports provide lower static deflection and greater dynamic range than simply supported single or multiple span beams. Severe resonance problems which may occur in synchronous vehicle systems are illustrated using a point-force vehicle model.

Analysis, Design, and Optimization of High Speed Vehicle Suspensions Using State Variable Techniques

Abstract: This article applies state variable techniques to high speed vehicle suspension design When a reasonably complex suspension model is treated, the greater adaptability of state variable techniques to digital computer application makes it more attractive than the commonly used integral transform method A vehicle suspension model is developed, state variable techniques are applied, numerical methods are presented, and, finally, an optimization algorithm is chosen to select suspension parameters A fairly complete bibliography is included in each of these areas The state variable technique is illustrated in the solution of two suspension optimization problems First, the vertical plane suspension of a high speed vehicle subject to guideway and aerodynamic inputs will be analyzed The vehicle model, including primary and secondary suspension systems, and subject to both heave and pitch motions, has thirteen state variables Second, the horizontal plane suspension of a high speed vehicle subject to guideway and lateral aerodynamic inputs is analyzed This model also has thirteen state variables The suspension parameters of both these models are optimized Numerical results are presented for a representative vehicle, showing time response, mean square values, optimized suspension parameters, system eigenvalues, and acceleration spectral densities

On a Piezoelectric Flapper Type Servovalve Operated by a Pulse-Width-Modulated-Signal

Abstract: As a first step to developing a servovalve with minimum moving parts, a new servovalve is devised in which a piezoelectric flapper (a quartz strip) is used instead of a conventional flapper actuated through a torque motor. A servovalve of this type is desirable from the viewpoint of fast response, however it has not been in common use because of the strong hysteresis of piezoelectric material. In order to linearize the nonlinear characteristics of the flapper, a pulse width modulated wave is used as the input signal to the flapper. The frequency characteristics of the pulse width modulator is theoretically analyzed in detail to establish the theoretical basis of the pulse width modulation control system. As well-known, this basis has been ambiguous so far. The experimental frequency responses show that the bandwidth of the servovalve using this new technique is comparable to that of conventional valves having the same power output in spite of its simple construction in comparison with conventional ones.

The Lateral Dynamics of the Linear Induction Motor Test Vehicle

Abstract: The dynamic behavior of the LIM Test vehicle has been the subject of theoretical and experimental studies conducted for the U.S. Department of Transportation by British Rail's Research and Development Division. Key aspects of the studies of lateral stability, curving and response to irregular track are described showing that an adequate stability margin exists for a conicity of 0.025. Satisfactory response characteristics are available for the anticipated roughness spectrum, but the linear curving regime does not encompass the higher range of operating speeds on the test track curve of 2.5 miles radius. To date (October 1973) measured performance compares well with theory but change of conicity with tire wear is an unexpected difficulty due in part to the very high track quality. This tire wear is of peculiar form and not typical of the normal high speed railway.

Longitudinal Track-Train Dynamics: A New Approach

Abstract: Using a measured functional relationship for draft gear characteristics a nonlinear model is developed to predict the coupler forces between cars of a railroad train. The model is then simplified, using modal expansion, to effect an economy of digital computation time.

Dynamic Interaction Aspects of Cable-Stayed Guideways for High Speed Ground Transportation

Abstract: This paper describes the dynamic considerations in the design of a long span (200 to 600 ft) cable-stayed guideway for future tracked levitated vehicles (TLV's) which will be used for high speed ground transportation. A design approach is described in which a cable-stayed guideway structure can be synthesized to simulate the behavior of a beam on elastic foundation. This result is achieved by the "cable-tuning" approach, in which the cable stays are selected to achieve an equivalent uniform elastic foundation. The design approach insures that the live load deflection of the trackway beam is manifested as a traveling wave which moves horizontally at the same velocity as the vehicle, thereby minimizing dynamic interaction problems. Parametic results are presented for the dynamic response of a beam on elastic foundation. Optimum cable and tower configurations are developed for this guideway concept and a typical conceptual design is described. /Author/

Automatic Parameter Identification Applied to a Railroad Car Dynamic Draft Gear Model

Abstract: One of the most important components in simulating track-train dynamics is the mathematical model of the connection between two cars, the draft gear-coupler combination. In this paper an automatic parameter identification technique is presented which can be used to generate a nonlinear functional relationship of dynamic draft gear characteristics using experimental data.

Dynamic Whip of Elastically Restrained Plate Strips to Rapid Transit Loads

Abstract: A plate strip of infinite length and constant width is cantilevered on a uniform elastic support along one edge and free along its opposite edge. A normal line load of constant intensity applied across its width travels along the strip at constant speed. Using plate theory, steady state solutions for the flexural waves are derived in terms of the generalized Fourier integral. Superposition is used to simulate responses to distributed transit loads. Results are applicable to the design of cantilevered guidance panels for air cushion vehicles and also in the design of the metal plates for the linear induction motors sometimes used to power these vehicles. /Author/

Stabilization of nonlinear systems using linear observers

Abstract: It is shown that a linear observer can always be employed to stabilize a nonlinear system which contains a true Popov type nonlinearity in the closed interval from 0 to k, where k is finite, provided the nonlinear function and a completely observable output of the linear portion are available as inputs to the observer. Taking into consideration the case in which a completely observable output is not available from the linear portion, stabilization is shown to be possible if the original linear approximation of the system is asymptotically stable.