A suspension control system for a suspension support ing a mass body on a support base via a parallel combi nation of a shock absorber having a variable damping coefficient and a spring. The control system cyclically measures absolute velocity (Z) of the mass body along a moving path of expansion and contraction of the shock absorber, relative velocity (Y) of the mass body in refer ence to the support base along the moving path, and acceleration (Z) of the mass body along the moving path. A control unit of the control system controls the damping coefficient according to a ratio (Z/Y) of the absolute velocity to the relative velocity with cyclic readjustment thereof so that at least either the damping coefficient is greater relative to the ratio when the ac celeration is rich in low frequency components or a frequency of the cyclic readjustment of the damping coefficient is lower when the acceleration is rich in high frequency components.

A classic tuned vibration absorber (TVA) is a device that, when attached to a structure, will greatly reduce the motion of the attachment at a specific excitation frequency. When a fixed frequency input is present, a TVA can be manufactured for the specific frequency input. When the input frequency changes during the course of operation, then an active adaptive TVA can be used where sensors, signal conditioning, and power are provided so that the tuned frequency can be varied over some range. A self-tuning vibration absorber (STVA) is a device that uses energy from the vibrating structure to produce some physical motion that changes the tuned frequency of the device. Through proper design, the tuned frequency will change in the appropriate direction and then stop changing when the tuned frequency matches the input frequency. This paper addresses the physics of one realization of a STVA and shows both analytical and experimental results.

This paper will discuss how controllable material technology, such as the use of active magneto-rheological (MR) dampers, improves vehicle primary and secondary suspensions. Although relatively new to the marketplace, semi-active suspensions in commercial automobiles and off-highway vehicles have been proven through the use of active MR dampers since 1998. In fact, MR suspension dampers are found today on the commercial vehicles of an increasing number of automotive OEMs and leading off-highway OEMs. MR fluid dampers are simple in design and have the advantage of no moving parts. The resistive force from an MR damper is generated as iron particles, suspended in the magneto-rheological fluid (MR fluid); pass through a magnetic field controlled by the electrical current passing through an electric coil contained within a moving piston surrounded by fluid. By adjusting the current to the damper coil in response to feedback from vehicle sensors and a controller, the damping response of the suspension can be optimized and controlled in real time to provide optimal operator comfort. The MR Damper System has a full-scale step response of less than 10 milliseconds. Sophisticated control algorithms adapt to large changes in payload, enabling the vehicle to meet ride metrics without pneumatic load leveling. Other benefits of the MR damping system include higher speed in NATO double-lane change tests, reduced risk of roll-over, improved accuracy of mounted weapons, and improved vehicle durability and readiness.

The enhancement of Herschel–Quincke (HQ) waveguides to incorporate adaptive capabilities is investigated. Passive HQ waveguides are known to provide noise attenuation in pipes and ducts at selective narrow frequency bands associated with their resonances. The approach to achieve adaptation is to produce a frequency shift in these resonances to allow targeting incoming tonal noise of variable frequency. The frequency shift is obtained by placing a variable cross-section constriction along the interior of the waveguide. Two adaptive devices are considered. The first consists of a ball with fixed diameter that can be axially displaced inside the waveguide. Then, the frequency tuning is obtained as a function of the ball position. The second device consists of a diaphragm at fixed axial location which can be deformed to obtain a variable cross section. In this case, the frequency shift is obtained as a function of the diaphragm deflection. The internal acoustic dynamics of the two devices are investigated both analytically and experimentally. The created constriction inside the HQ waveguide is modeled as a series of constant cross-section tube elements with small finite area jump between adjacent pieces. The model is validated by comparing the predicted dynamics with experimental data from an extended impedance tube setup based on the two-microphone technique. Finally, attenuation predictions on a one-dimensional pipe are presented in order to illustrate the performance of the proposed adaptive HQ waveguides.

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