An experimental and theoretical analysis of a vibration isolation system that uses magnetorheological (MR) fluid-based semi-active isolators is presented. In doing so, a vibration isolator that uses MR fluids is designed, manufactured, and experimentally evaluated. Typically, a Bingham-plastic model, with its accompanying zero speed force step discontinuity, would be used to model an MR isolator. A new nonlinear model, with simple low-speed hysteresis characteristics, is proposed to describe the hysteresis force characteristics of the MR isolator. The damping forces of the MR isolator with different excitation frequency and current input are measured and compared with that resulting from the hysteresis model for the verification of the theoretical analysis. A vibration isolation system with the MR isolator is constructed, and its dynamic equation of motion is derived. A simple skyhook controller is formulated to attenuate the vibration of the system. Controlled performances of the vibration isolation system are experimentally and theoretically evaluated in the frequency and time domains. A key conclusion is that a simple model of the low-speed force vs low-speed velocity hysteresis characteristics is necessary for successful prediction of open- and closed-loop performance in both the time and frequency domains.

Semi-Active Vibration Isolation Using Magnetorheological Isolators

Dynamic modelling of a shape memory alloy adaptive tuned vibration absorber

This paper presents a review of active techniques for aerospace vibro-acoustic control. First, the mechanisms of airborne or structure-borne sound generation and transmission in aerospace vehicles are briefly reviewed. The main approaches of passive and active noise/vibration control are then summarised, and three examples of active systems that have already been developed into practical aerospace applications are briefly described. Finally the actuator, sensor, and control system requirements for aerospace applications are discussed.

Review of Active Techniques for Aerospace Vibro-Acoustic Control

Automotive Vehicle Engine Mounting Systems: A Survey

Application of an active controller for reducing small-amplitude vertical vibration in a vehicle seat

The performance of an active vibration isolator consisting of a fluid mount and an electromagnetic actuator is discussed. The electromagnetic actuator augments the inertia effects of the fluid mount to reduce the dynamic stiffness of the mount at the vibrational disturbance frequencies of the engine. The active isolator is modeled using bond graphs. Dynamic stiffness, blocked force, and free displacement transfer functions are developed from the bond graph model to gain insight into the active mount’s performance. A mount effectiveness analysis shows that reducing the mount’s dynamic stiffness results in better dynamic isolation. Numerical simulations along with laboratory testing of the active isolator are used to evaluate the performance of the mount. A simple laboratory experiment shows that an active mount can be controlled to have a dynamic stiffness that is 100 times (40 dB) lower than a passive mount, without sacrificing static stiffness.

C. M. Nobles

Papers

Modelling and Performance of an Experimental Active Vibration Isolator