subsection{Experiment description}
In order to validate this data procedure and estimation method, we carried out experiment on the ROMAC stability test rig as depicted in Fig. ef{fig2:subfig:a}. The fluid and magnetic bearing configurations were in cite{cloud2007stability}, and during the excitation process, the temperature of inlet oil was 37 ${}^{circ}mathrm{C}$. The shaft rotates at 3500 rpm, and the actuator #2 that is located at the node 47 in the FE model excited this test rig at six frequencies (55 Hz to 80 Hz by step of 5 Hz). The excitation force is expressed in Eq.( ef{eq32}). egin{equation}label{eq32}
m{F}{
m{ = }}left( {egin{array}{*{20}{c}}
{{F_{ex}}}\
{{F_{ey}}} end{array}} ight) = {F_e}left( {egin{array}{*{20}{c}}
{Xcosleft( …show more content…
egin{table}[htbp] …show more content…
ef{fig15}. The first forward log decrement remain nearly invariant in the excitation frequency range, while the first backward frequency drops a little.
egin{figure}[htbp] centering includegraphics[width=8cm]{Fig15.pdf} caption{Mode paramenters} label{fig15} end{figure} Using the sine-swept excitation method, we did both backward and forward excitaions for the test rig, and Fig. ef{fig16:subfig} shows the full spectrum waterfall for the left bearing (Node 10). Using the idenitification method [Li], the first mode parameters are estimated (1B: f=85.3Hz, LogDec=0.726; 1F: 86.3Hz, LogDec=0.442). By comparing the prdicted and measured first forward mode parameters, we can drow conclusion that the force coeffients of bearings are reasonably
In order to validate this data procedure and estimation method, we carried out experiment on the ROMAC stability test rig as depicted in Fig. ef{fig2:subfig:a}. The fluid and magnetic bearing configurations were in cite{cloud2007stability}, and during the excitation process, the temperature of inlet oil was 37 ${}^{circ}mathrm{C}$. The shaft rotates at 3500 rpm, and the actuator #2 that is located at the node 47 in the FE model excited this test rig at six frequencies (55 Hz to 80 Hz by step of 5 Hz). The excitation force is expressed in Eq.( ef{eq32}). egin{equation}label{eq32}
m{F}{
m{ = }}left( {egin{array}{*{20}{c}}
{{F_{ex}}}\
{{F_{ey}}} end{array}} ight) = {F_e}left( {egin{array}{*{20}{c}}
{Xcosleft( …show more content…
egin{table}[htbp] …show more content…
ef{fig15}. The first forward log decrement remain nearly invariant in the excitation frequency range, while the first backward frequency drops a little.
egin{figure}[htbp] centering includegraphics[width=8cm]{Fig15.pdf} caption{Mode paramenters} label{fig15} end{figure} Using the sine-swept excitation method, we did both backward and forward excitaions for the test rig, and Fig. ef{fig16:subfig} shows the full spectrum waterfall for the left bearing (Node 10). Using the idenitification method [Li], the first mode parameters are estimated (1B: f=85.3Hz, LogDec=0.726; 1F: 86.3Hz, LogDec=0.442). By comparing the prdicted and measured first forward mode parameters, we can drow conclusion that the force coeffients of bearings are reasonably