CIFER®-MATLAB Interfaces: Development and ... - Cal Poly

Table 4.6: Cutoff Frequencies via RMS
Flight: Sim:
AIL 4.82 4.43
P 3.53 3.70
ELE 7.03 6.82
Q 5.62 4.87
RUD 6.21 6.03
R 2.53 3.89
WHL 6.04 5.59
R 2.53 3.83
Beta .85 none
The differences in the rudder and wheel output calculations between simulation and flight are
greater. The phase slopes are different at the mode, which suggests the simulation is more highly
damped. The outcome is surprising because the responses are very similar as shown in
Figure 4.24. The primary difference is in the spike in the flight data around 2 rad/s, which is due
to the poor coherence. When the output autospectrum is plotted, Figure 4.25, the difference
between the flight and the simulation data is more pronounced. This is the data that is integrated
in the RMS calculation. The plot of simulation data begins to roll off, losing energy, around 4
rad/s, which corresponds to the frequency from Table 4.6. The flight data begins to roll off just
above 2 rad/s, also corresponding to Table 4.6; these autospectrum plots are the source of the
discrepancy in the table.
Figure 4.24: Rudder to Yaw Rate Response
Figure 4.25: Rudder Output Autospectrum
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