vdryd2.hlp

MATLAB在飞行动力学和控制中应用的工具

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VDRYD2 = Lateral Dryden filter #2. This masked subsystem block,
which is contained in the library WINDLIB from the subdirectory
WIND, implements a lateral Dryden filter with coefficients that
vary with the true airspeed V. The user must specify the scale
lenght Lvg and the standard deviation sigma_vg. The airspeed V is
used as inputsignal to the block VDRYD2. Often, the changes in V
due to atmospheric turbulence are not very large. In such cases,
you may wish to use a Dryden filter with constant coefficients,
computed under the assumption that V is constant and equal to a
user-specified value, in stead. The block VDRYD1 contains such a
filter for lateral turbulence (see VDRYD1.HLP for more info).

The lateral gust velocity vg is obtained by passing white noise
through a Dryden filter, which is defined by the following transfer
function:

            b0 + b1*s        a0 = (V/Lvg)^2
  Hvg = -----------------    a1 = 2*(V/Lvg)
         s^2 + a1*s + a0     b0 = sigma_vg*sqrt(Lvg/V)*(V/Lvg)^2
                             b1 = sigma_vg*sqrt(3*Lvg/V)*(V/Lvg)

where:

  V       : true airspeed [m/s]
  sigma_vg: standard deviation of lateral gust velocity [m/s]
  Lvg     : scale length for lateral gust [m]

Here, V is the INPUTSIGNAL to the masked subsystem block. V it-
self has to be obtained from the aircraft model considered, e.g.,
V may be an outputsignal from the system BEAVER, which uses the
turbulence velocity ug and its time-derivative as inputsignals!

Input to the block VDRYD2:
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  V       : true airspeed [m/s]

Outputs from the block VDRYD2:
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  vg      : lateral gust velocity [m/s]
  d(vg)/dt: time derivative of vg [m/s^2]

The gust velocity and its time derivative have to be added to the
total wind velocity component vw and its time derivative vwdot in
the vector uwind.

More info.
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See UDRYD2.HLP, WDRYD2.HLP, and TURB2.HLP for more info about
other Dryden filters with coefficients that vary with the air-
speed V. See UDRYD1.HLP, VDRYD1.HLP, WDRYD1.HLP, and TURB1.HLP
for more info about Dryden filters with constant coefficients,
assuming V = constant.

See CWIND.HLP and BLWIND.HLP for more information about blocks
to compute the components of wind along the aircraft's body-axes
(constant wind and a wind profile in the Earth's boundary layer,
respectively). The use of the vector uwind within the aircraft
model is outlined in the helpfiles LEVEL1.HLP, FWIND.HLP, and
XYHDOT.HLP, which refer to blocks within the system BEAVER.

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The FDC toolbox, Copyright Marc Rauw 1994-1998.