Comprehensive System Identification of Ducted Fan UAVs - Cal Poly

Figure 3.35 – Rise Time for Linear Model of DS8417 at 5VDetermining the rise time from the nonlinear, rate-limited model wasaccomplished by analyzing the square wave time responses and found to betR= 0.192NLsec. Comparing this rise time to the linear rise time reveals a ratio of t ˆR= 0.38. Althoughnot exactly the predicted 0.17, the only nonlinearity that was included in this model wasthe rate limiting.As mentioned previously from Figure 3.34, the predicted maximum difference inphase lag would be expected at a normalized frequency of ˆnω = 0.6. The bandwidth of theDS8417 is approximately ωn= 20 rad/sec (Table 8). The error function in Figure 3.33shows the maximum additional lag to occur at 14 rad/sec. This corresponds to anormalized frequency of ˆnω = 0.7. This is very close to the predicted frequency where theadditional lag is most apparent and is consistent with the STI trend.- 86 -