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3.3 SRF Experimental Results
In this research, the strain rate feedback control is designed to control the vibration of the fundamental
mode. The SRF controller-damping ratio q c was set at 0.10, controller frequency co c was set at 62.8
rad/sec (lOHz), which is greater than the targeted mode of 7.62Hz and the effectiveness of SRF controller
at various gains was tested. The results are shown in table 2, with maximum energy drop achieved at gain
of 0.12.
SRF
Gain
0.12
0.15
0.17
0.20
Modal dB drop
j-ij sec
52.66
52.80
50.35
49.12
Table 2 SRF Results
Contn)Ued damping ratio
0.040
0.042
0.043
0.045
% Change in damping
387.7
423.4
435.8
451.2
The excitation in the SRF experiment is the same as that in the PPF experiment. The SRF controlled
system response is depicted in Figure 5. The building vibrations disappear within 5 seconds after the
excitation signal is stopped. When compared to the PPF controller, the results are almost as dramatic as
that of PPF. The PSD plot for 5-15 seconds is shown in Figure 6. The SRF control was accompanied with
a drop of about 50 dB in the energy level of the model building in the period of active control. The
damping ratio achieved was 0.045. As compared with the undamped ratio of 0.008, this represents an
increase of 451%.
with control
CD
H,.
"55
with control
— - without control
>,.30
O)
time(s)
Frequency (Hz)
Fig. 5 SRF control response of the model
building
Fig. 6 PSD plots of uncontrolled and SRF
controlled model building for 5-15 sec
3.4 SMC Experimental Results
The sliding mode control algorithm is also applied to control the vibration of the 3-floor model building.
Since the first mode dominants the free response, the sliding mode control will suppress the first mode
vibration. Following the method discussed by Adhikari and Yamaguichi (1997)), the controller
parameters are A = 0.5, p = 1, and a = 1, and thus the sliding surface is r = £ + 0.5§ =0.
In the research, the excitation of the model building is the same as those in the PPF and SRF control. The
SMC controlled response is shown in Figure 7 and the corresponding PSD plot for 5-15 seconds is
depicted in Figure 8. An energy drop of 51dB as compared with the uncontrolled energy level is observed
during this period of active control. The vibration control of the first mode is comparable to that of the