tailieunhanh - Encyclopedia of Smart Materials (Vols 1 and 2) - M. Schwartz (2002) WW Part 14

Tham khảo tài liệu 'encyclopedia of smart materials (vols 1 and 2) - m. schwartz (2002) ww part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Figure 4. Radiated power ft 1I1O case using multiple smai operating in phase. reference signal for the LMS control approach was taken from the internal signal generator used to drive the disturbance termed internal reference . Figure 4 presents the radiated power with and without control when all the smart skin cells are wired together in phase as a single channel of control. The error signal is provided by a single microphone located close to the smart foam surface and at the plate-foam center. Also shown is the passive effect of the smart skin when it is located on the plate but not activated. It is apparent that the passive effect of the skin is good at high frequencies above 1000 Hz but is limited to resonant frequencies of the base plate below this value. Turning on the active control provides reasonable attenuation at low frequencies though there are some frequency ranges where the control is negligible for instance near 900Hz. In this case the smart skin transfer function is reduced in level. We now extend the controller so that the six smart skin modules can be controlled independently with a six by six LMS control arrangement. Figure 5 presents these new results for the low frequency range. For the results of Figure 5 three different reference signals control configuration are also studied one using an internal reference one using an exter signal taken from an accelerometer located representing a more realistic arrangement ternal reference signal with feedback Ĩ active component of the smart skin removed ent that much improved performance is ach SISO case of Fig. 4 particularly for the inte case due to the multicell active skin being the complex radiation impedance load near 9 ample 3 . In this case the smart skin trans also modified in a distributed manner. Using an external reference signal also pn able attenuation however it is reduced fror case implying that the system is acausal 1 lost performance is recovered when feedba employed indicating that the