Controlling floor vibration with active and passive devices

This paper reviews research, conducted by the authors over the last decade, pertaining to the control of excessive floor vibration using active and passive devices. The active device studied uses a proof-mass actuator to deliver the control force to the floor system. Effectiveness and stability characteristics for a single-input/single-output (SISO) control scheme, using velocity feedback, are explored. The SISO system is shown to increase damping to 40% of critical on an experimental floor when amplitudes remain in the linear range. When implemented on two in-place floors, at least a 70% reduction in vibration amplitudes due to walking was observed. Next, the benefits of expanding to a practical single-input/multi-output (SIMO) control system are identified. Additionally, techniques to optimize the SIMO scheme are presented. Because of the stability characteristics of the controlled system, the improvement noted for the SIMO scheme is most dramatic for floors with fundamental frequencies near the natural frequency of the actuator. In a 2 Hz floor example, a SIMO control scheme provided seven times more reduction than that of the SISO system. The passive device research focuses on the experimental implementation of tuned mass dampers (TMDs) to control floor vibration. Two different configurations are explored. The uniqueness of the first device is that liquid filled bladders are used to provide an economical damping mechanism. When implemented on an office floor, a significant improvement of walking vibration levels was observed. Satisfaction with the repair was noted from the occupants. The second device utilizes a configuration that has great flexibility in the field, thus allowing for more economical mass production. Using two TMDs, a significant reduction of response was noted for the 5 and 6 Hz modes. Research to improve these active and passive strategies continues and will be reported as significant results are achieved.