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In this paper, a two-degree-of-freedom model of a semi-actively suspended vehicle is used as a starting point in the design of an optimal suspension. The optimization is performed with respect to a quadratic performance index reflecting suspension design constraints and ride quality requirements. Two closely related mathematical descriptions of the model are given, one leading to a linear and the other to a bilinear system of differential equations, with an additional inequality constraint reflecting the passivity of the semi-active device. Since the resulting stochastic optimization problem does not allow for a closed-form analytical solution, a numerical method is proposed as an approximate solution. The justification for the method is based on a recent existence theorem from stochastic optimal control theory. Illustrative simulation results of the optimization are presented.

Regenerative Systems for Vibration ControlThe potential for energy regeneration in vibration control systems is investigated. Such control systems hold the possibility of self-sustainability by alternately extracting and releasing energy originating from the vibrating system in a controlled nonpassive manner. To be self-sustaining, more energy must on average flow into the control system than flows out. Generally speaking, the performance of such a system will approach that of an active system while theoretically requiring no externally supplied power. As research progresses in this area, an increasing number of viable applications for regenerative vibration control systems are being uncovered. This paper examines two broad applications: base-excited suspensions and periodically excited compound mounts. Some experimental results of the former are presented to support our claims. / VOL 119, APRIL 1997Transactions of the ASME Copyright © 1997 by ASME Downloaded From: http://vibrationacoustics.asmedigitalcollection.asme.org/ on 05/24/2015 Terms of Use: http://asme.org/terms (^ start) Fig. 3 A pulse-width modulation algorithm for a regenerative force actuator

The results of semiempirical analytical and experimental studies of the acoustic frequency response of circular tubes with a mean turbulent flow are given. For the frequency range tested, it is seen that the hypothesis of a time-invariant eddy viscosity profile across the tube predicts the behavior well. For lower frequencies a simple lag in the turbulence profile from its equilibrium values is hypothesized which should be of moderate importance in acoustic behavior and of great importance in large-amplitude behavior. The lag is estimated using the steady-flow results of Goldberg.

A method is presented for incorporating planar mechanisms into dynamic system models using bond graphs. Through the use of stiff coupling springs at the mechanism joints, the nonlinear geometrical relationships are uniformly and simply described by displacement modulated transformers and the system state equations can be written with no algebraic complications. In contrast to the more elegant kinematic techniques for describing mechanism dynamics, the present method results in higher order systems of equations but the equations themselves are simpler and not densely coupled. In addition, coupling forces are available at the joints. An example demonstrates that the extra eigenvalues associated with the coupling springs can readily be found for any configuration so that the spring constants can be chosen to minimize computation time.