Semi-active controller dynamics in a magneto-rheological tuned vibration absorber

The primary objective of this study is to experimentally implement semi-active control to a Magneto-Rheological Tuned Vibration Absorber (MRTVA) and evaluate the dynamic performance of the MRTVA. The MRTVA is a semi-active TVA that employs an MR damper as its damping element. A test apparatus was built to represent a two-degree-of freedom system - a primary structure coupled with an MRTVA. Using this test setup, a series of tests were performed to assess the dynamics of the MRTVA and to compare them with those of a passive TVA. The TVA used displacement-based, on-off groundhook (on-off DBG) control to regulate the MR damper. Unlike a passive TVA, the MRTVA was able to effectively control the resonant vibrations without sacrificing the isolation valley at high damping. To interpret the dynamics of the passive and semi-active system, the damper lock-up dynamics were investigated. The lock-up analysis further explains the actual implementation of the on-off DBG control policy in the system. The results of the lock-up analysis indicated that the dynamics of the control logic prevented lock-up in the MRTVA. This paper demonstrates that the MRTVA with the on-off DBG semi-active control can offer the benefits of high damping at the resonant peaks while still maintaining good isolation at the natural frequency of the structure. In other words, the semi-active TVA that employed an MR damper was more effective than an equivalent passive system in reducing vibrations of the primary structure.