Comprehensive System Identification of Ducted Fan UAVs - Cal Poly

The fact that the rate saturated during the sweep was readily noticeable in the factthat all the natural frequencies and damping ratios were higher for the 50% sweeps thanthe 100% ones. Plotting this trend as in Figure 3.36 shows that as expected, the naturalfrequency drops with increased sweep amplitude. This trend is also evident in Figure 16where the addition of the rate limit effectively causes the response to break sooner andillustrates how much an effect the rate limit has on the response.1.210.80.60.40.200% 20% 40% 60% 80% 100%Amplitude of Sweep (% of max deflection)Figure 3.36 – Sweep Amplitude and Natural Frequency with Rate LimitingThe result of the comparison to the STI data is that the general trends of the dataare correct. The addition of the rate limit in the model effectively corrects the magnitudeof the response. According to the error function in Figure 3.33, the model should losefidelity in the phase of the response around 14 rad/sec where the error is at a maximum.- 87 -