Design of remotely located and multi-loop vibration controllers using a sequential loop closing approach

In some applications, vibration control objectives may require reduction of levels at locations where control system components cannot be sited due to space or environmental considerations. Control actuators and error sensors for such a scenario will need to be placed at appropriate locations which are potentially remote from the points where ultimate attenuation is desired. The performance of the closed loop system, therefore, cannot be assessed simply by the measurement obtained at this local error sensor. The control design objective has to take into account the vibration levels at the remote locations as well. A design methodology was recently proposed that tackles such problems using a single-loop feedback control architecture. The work in this paper describes an extension of this control design procedure to enable the systematic design of multiple decentralised control loops. The approach is based upon sequential loop closing and conditions are provided that ensure that closed loop stability is maintained even in the event of failure in some control loops. The design procedure is illustrated through its application to a laboratory scale slab floor that replicates the problems associated with human induced vibration in large open-plan office buildings. The experimental results demonstrate the efficacy of the approach and significant suppression of the dominant low frequency modes in the floor is achieved using two independent acceleration feedback control loops.