Terrestrial Vehicles Research Articles

Minimal structural response under random excitation using the vibration absorber

AbstractThe equations of motion are derived for the first mode response of a linear multistorey structure having a linear vibration absorber attached to the roof. Furthermore, the variance of the first mode response to a gaussian white noise lateral base acceleration (as a model of earthquake excitation) is determined. Smallest possible values of the variance of the response along with corresponding absorber parameters are established using an optimization program. It is demonstrated that the absorber is quite effective in reducing first mode response for 5‐ and 10‐storey structures even with relatively small values of the absorber mass. Moreover, minimal responses for the randomly excited single‐degree‐of‐freedom system have been determined, and a design example is presented. The absorber system has potential application not only in earthquake engineering but also in aerospace and terrestrial vehicle design.

The cosmic-ray spectral modulation above 2 GV during the descending phase of solar cycle number 19

This is the first of a series of three papers meant to study the short- and long-term spectral modulation of primary cosmic rays above 2 GrV during the time from the IGY to the IQSY, for a large part of solar cycle No. 19, which showed the highest activity recorded so far, and a complex superposition of different kinds of conspicuous solarinduced interplanetary perturbations. In Part I we discuss the information on the modulation as gained by means of neutron monitor data, provided sufficient accuracy is reached; in fact this information covers a fair primary rigidity range and offers a time and rigidity resolution which is not reached by other experimental data. We also present and apply to the 1957–65 data an indirect calibration procedure for practically the whole network of the near-sea-level neutron monitors by means of seven latitude surveys performed by ship or by terrestrial vehicle. This procedure provides a set of daily latitude curves suitable for directly deriving the isotropic variation of the primary differential spectrum.

Doppler steering system for terrestrial vehicles

A Doppler radar unit has been added to a remotely controlled automobile for automatic control of steering. This Doppler-type unit causes the vehicle to turn toward areas of minimum reflectivity, areas usually smooth with low vegetation. The vehicle with this steering system is shown to avoid all obstacles such as trees, automobiles, and people.

Closed-loop control of stochastic non-linear systems

A new approach for optimum control of stochastic non-linear systems is developed from practical engineering assumptions. Systems amenable to this new approach include optimum guidance and navigation systems for space and terrestrial vehicles, optimum closed-loop process controllers and optimum controllers for systems with unknown parameters. The classical quadratic synthesis approach—optimization of a deterministic cost and perturbation estimation and control about that solution—is shown to give 24 per cent more cost and 97 per cent more mean-squared terminal error than the combined optimization approach presented for a sample problem involving control of a first-order system with an unknown time constant. A similar improvement in terminal error is shown for an atmospheric entry problem. Furthermore, the optimum controller automatically designs the best controller to minimize the effects of the unknown parameter without artificial augmentation of the cost function as is done in the sensitivity theory approach. The solution is obtained by expansion of the cost function in a power series around a deterministic trajectory with the assumption of linear perturbation estimation and control about that trajectory. Optimization of the expanded cost function gives necessary conditions dependent on the covariance matrices and the deterministic portion of the cost. When the necessary conditions are solved, a set of open-loop controls, perturbation controller gains, and perturbation estimator gains are obtained that can be precomputed and implemented into the system.

The Practical Cycloconverter

A high power capacity frequency conversion system that employs a unique combination of new semiconductor devices has recently been developed and placed in full scale operation. The classical cycloconverter in this embodiment has been reconfigured with thyristors (or silicon controlled rectifiers) in the power circuit with monolithic integrated circuitry for controls. The previous short-comings of the cycloconverter have been overcome by new circuit concepts resulting in dramatic reductions in size, weight, and complexity. The fully practical new frequency converter is expected to become a significant factor in many types of power conversion and control systems. Particular emphasis is currently being placed on the application to high-performance terrestrial and rail vehicles.

The correlative advantages of lunar and terrestrial vehicle and power train research: D. Friedman.S.A.E. Paper, Automot. Engng. Congress, January, 1966.

The correlative advantages of lunar and terrestrial vehicle and power train research: D. Friedman.S.A.E. Paper, Automot. Engng. Congress, January, 1966.

Propagation and scattering in plasmas

The discussion begins with a review of some of the physical assumptions that underlie the mathematical model of a temperate plasma as a continuous medium. On the basis of these assumptions, the tensor permittivity of a locally homogeneous electron plasma in a uniform magnetic field is derived and incorporated in the usual Helmholtz integral for the scattering of an electro-magnetic plane wave by a dielectric region. By extending this integral to a plasma with random space-time fluctuations, formulas are derived for the coherent and incoherent components of the power scattered per unit solid angle in any direction. On the basis of these formulas, a summary account is given of the various attempts that have been made to explain the observed scattering from laboratory plasmas, from the ionosphere, and from the turbulent wakes associated with hypersonic re-entry of large terrestrial vehicles into the earth's atmosphere.