Roger M. Glaese, Eric H. Anderson
CSA Engineering, Inc.
Mountain View, CA
To be presented at SPIE Smart Structures Conference, March 2005.
ABSTRACT
One general class of devices for vibration suppression makes use of a mechanical resonance in the device to cause it to be particularly effective in a narrow frequency range. Passive devices including tuned vibration absorbers (TVAs) and tuned mass dampers (TMDs) have been in use for a century or more and employed in quantities of millions each year. Active devices that combine actuation with electrical inputs and outputs including sensing and control systems offer higher performance, with the required addition of external power.
This paper will treat passive and active resonant vibration control devices in a general framework, and will highlight the benefits and costs of each approach. In the simplest models, passive devices can be represented as a mass-spring-damper combination, and active devices typically add a force actuator and some type of control. The passive TVA, designed to greatly increase mechanical impedance at a specific frequency, has an analog in active devices that employ particular control algorithms for force cancellation. The passive TMD has an analog in active dampers. Each of these approaches will be considered with reference to low-order models of structural systems, including well-defined disturbance inputs and performance metrics.
Non-dimensional quantities extending the well-known tuning ratios for passive devices (Timoshenko, et al) will be developed. One of the emphases of the paper will be careful tracking of the differences in the behavior of the passive and active devices and an explicit tracking of where the vibrational energy goes in ach case.
Limitations of the idealized models will be addressed and specific hardware examples will be cited for each of the passive and active vibration suppression approaches.