## 5 Experimental Verification  
In the Section 4, the active vibration control for the MIMO system has been simulated and analyzed. On this basis, a vibration isolation platform is built to further verify the control effect. The equipment mainly included an NI PXIe-8880 controller, a PXI-4498 input board, a PXI-6733 output board, a vibration exciter, a power amplifier, an acceleration sensor, and electromagnetic rubber active and passive hybrid integrated vibration isolator/actuators, etc. The platform installation is shown in Figure 14.  
On the bottom of the platform, four BE85 rubber isolators are installed at each foot position; its lateral stiffness is much higher than the vertical stiffness, and its vertical stiffness, natural frequency, and damping ratio are 342 N/mm, 8.5 Hz, and 0.095, respectively. The actuators 1#-4# and the error sensors are installed in four foot positions of the platform. Among them, the actuator is a permanent magnet electromagnetic actuator, which can output the control force as the active component of the secondary path, and the BE85 rubber acted as the passive isolating component. The actuator is connected between the upper and middle platform by screws, and it only provided the vertical force to control the middle vibration. Therefore, in order to decrease the influence of the actuator output force on the control system, the response curves between the output force, the current amplitude, and the current frequency are obtained by 20-200 Hz and 2-9A current excitation, as shown in Figure 15. It could be seen that the actuator displacement is basically linear with the current amplitude where, in the same amplitude condition, the higher the frequency, and the smaller the output force. In the experimental system, the excitation is 37 Hz, 60 Hz, and 110 Hz composite signals consistent with the simulation, and the identification values for sixteen offline secondary paths in Figure 9 are also introduced into the control algorithm. The sampling frequency is 1 kHz, and the sym20 wavelet base is used for the wavelet packet transfor  
Figure 14: Test rack and some equipment. mation with five layers. Then, the experiments are carried out by the M-FxLMS and the WPTDDM-FxLMS algorithm, respectively. During the test, the NI PXI-6733 D/A board card first sends an initial excitation to drive the vibration exciter by a power amplifier. At the same time, the upper and the middle acceleration sensors acquire the reference signal and four error signals; all of them will be converted by the PXI-4498 A/D board card to the PXIe-8880 controller. Then, the output signals are produced with the controller real-time decoding, and they are passed through the NI PXI-6733 D/A board card to drive the actuator and generate the  
It could be seen from Figures 16-19 that acceleration is intensified for the M-FxLMS algorithm in point 1#; the other points are only slightly attenuated, and the time-domain control effect is not obvious enough. In addition, the 110 Hz line spectrum control fails in measuring point 1# in Table 2; its vibration is also intensified. In particular, the control induces a 73 Hz line spectrum. Whereas, in measuring point 2#, the 37 Hz and 60 Hz line spectrum had a certain effect, and the attenuation of the 110 Hz line spectrum reached 15.06 dB. Furthermore, the attenuation of 37 Hz line spectrum reached 10 dB in measuring point 3#; the 60 Hz and 110 Hz line spectra are both attenuated to some degree. Moreover, the 37 Hz line spectrum is obviously attenuated in measuring point 4#; the 60 Hz line spectrum is basically unchanged, while the 110 Hz line spectrum is intensified. In contrast,