PERFORMANCE, STABILITY, DYNAMICS, AND CONTROL2(145)

曝光台 注意防骗 网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者

in ground-based test faciMes is the so-called free fiight or semifree fiight test
technique.ll  Here, the test model is allowed to fly either free or semifree [loosely
constrained in some degree(s) of freedom] in the viewing area of the test facility.
The model motion is recorded in the form ofvarious accelerometer outputs or higX-
speed motion picture records. The dynamic stability derivatives are then obtained
implicitly by matching the predicted time history of the model with the observed
 time history. Because the time and effort involved in fabricating and testing aircraft
models in the ground-based facilities are considerable, these approaches are also
usually used in the final stages of the vehicle design.
      On the other hand, the semiempirical or engineering methods provide quick and
cost-effective estimates of the static and dynamic stability derivatives, which can
be readily used for assessing the vehicle fiyability, stability, and control. Also, the
 predictions based on these engineering methods can be used in the design of fiight
control and guidance systems. The only disadvantage is that such predictions are
 less accurate compared to the CFD or the wind-tunnel test data. However, this type
 ofinformation is very useful in the early stages of the design to quickly evaluate
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582          PERFORMANCE, STABILI-f'Y, DYNAMICS, AND CONTROL
_ Dutch RollApproximation
---  Complete Fifl.h-Ordcr System
t18
Fig. 6 23   Urut-step response (lateral-direchonal) of the general aviation airplane:
angle of yaw.
where
ASm = (mi'- btC:.B) (Ixllzl _"I2zl)                   (6.242)
B8ut = (-C}.p) (Ixllzl - Ix2zl) _ (Trll - biC).B)(lx  Cnrbi + IziCipbi
        + Ixz] Ctrbt + Ixzi Cnpbi) - bi C).p(CiBb} Izl + Cn/Jbi Ixzl)
            + (mi  - bi Cyr)(CIBbllxzl  +  IxICnBbl)                                                    (6.243)
C8   = bjz(mi - bi C),B)(Cip Cnr - qr C,,p) + bi Cyp(lxi Cnr + Izl Clp
        + Ixzl Clr + Ixzl Cnp) - Cy*bi(Cip Izl + Cnp I,zl)
         +bi C).p (C,BC"rb~- - Cip Izl  - Ixzl C"p - Cu C"Bb~)
         + (mi - bi Cyr) (Cip Ixzl + CiBCnpb<- - qp C~b2i + Ixl Cnp)
          (6.244)
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T
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-2.5
AIRPLANE RESPONSE AND CLOSED-LOOP CONTROL          583
          Roil Subsidence Approximation
-  Complete Fifth-Order System
      .I.I.I.                    
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┃      -- -:  - - - --- -- - - ┃
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┃'~'};l{j                      ┃
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┃                              ┃
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┃                              ┃
┣━━━━━━━━━━━━━━━┫
┃ -...I.II..\-                 ┃
┗━━━━━━━━━━━━━━━┛
o      0.5
2     2.5     3     3.5     4
　
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