-50 -40 -30 -20 -10 0 10 20 30 40 dB (m/s2)/N HBcc - Reference HBcc - Mobility HBcc - Impedance 0 128 256 384 512 640 768 896 1024 -180 -90 0 90 180 Phase o Hz Figure 8. System AB-TT Estimation of Beam B Translational FRF at Node 6 using Synthesized Perturbed FRF with Internal Translational DOF at Node 1. -30 -20 -10 0 10 20 30 40 dB (m/s2)/N HBcc - Reference HBcc - Mobility HBcc - Impedance 0 128 256 384 512 640 768 896 1024 -180 -90 0 90 180 Phase o Hz Figure 9. System AB-TT Estimation of Beam B Translational FRF at Node 6 using Synthesized Perturbed FRF with Internal Translational DOF at Node 16. While multiple internal DOF can be used in a single computation, averaging of results using a single internal DOF was also considered. Figure 10 displays the results when both internal DOF at node 1 and node 16 are used in a single computation with the Mobility approach, as well as results when each of the FRF are averaged together from the previous case. Figure 11 presents the same results using the Impedance approach. For this case, averaging degrades the results when using Mobility approach. As previously shown, a spurious peak is produced in the resulting FRF when the translational DOF at node 16 is included. While this peak is reduced when averaged, using both internal DOF with the Mobility approach produces more accurate results. However, for the Impedance approach, averaging the results significantly improves the results and minimizes the error produced at lower frequencies. -30 -20 -10 0 10 20 30 40 dB (m/s2)/N HBcc - Reference HBcc - Single Mobility HBcc - Averaged Mobility 0 128 256 384 512 640 768 896 1024 -180 -90 0 90 180 Phase o Hz Figure 10. System AB-TT Estimation of Beam B Translational FRF at Node 6 using Mobility Approach with Internal Translational DOF at Nodes 1 and 16. -50 -40 -30 -20 -10 0 10 20 30 40 dB (m/s2)/N HBcc - Reference HBcc - Single Mobility HBcc - Averaged Mobility 0 128 256 384 512 640 768 896 1024 -180 -90 0 90 180 Phase o Hz HBcc - Reference HBcc - Single Impedance HBcc - Averaged Impedance Figure 11. System AB-TT Estimation of Beam B Translational FRF at Node 6 using Impedance Approach with Internal Translational DOF at Nodes 1 and 16. System Description – Experimental Models The experimental structure of the two-beam system is shown in Figure 12. The structure consists of two hollow aluminum beams with approximate cross section and physical properties as presented in Figure 1 and Table 1, respectively. The beams were bolted together using threaded rod and nuts were used to secure each beam in place. Enough space between the beams 180
RkJQdWJsaXNoZXIy MTMzNzEzMQ==