📄 uvw.htm
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FDC help: uvw
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<h2>
The subsystem <i>uvw</i>
</h2>
<p>The block <i>uvw</i> computes the body-axes velocities <i>u</i>, <i>v</i>, and <i>w</i>. The body-axes velocity components must be known to solve the state-equations for the coordinates <i>x<sub>e</sub></i>, <i>y<sub>e</sub></i>, and the altitude <i>H</i>, so even though <i>u</i>, <i>v</i>, and <i>w</i> have been replaced by the true airspeed <i>V</i>, angle of attack <i>alpha</i>, and sideslip angle <i>beta</i> as state variables, it is not allowed to delete this block from the aircraft model!</p>
<p>The outputs from <i>uvw</i> are used by the block <i><a href=
"xyhdot.htm">xyHdot</a></i> in the subsystem <i><a href="12odes.htm">12 ODEs</a></i>. <i>uvw</i> is included in the subsystem <i><a href=
"eqmotion.htm">Aircraft Equations of Motion</a></i> of the <i><a href="beaver.htm">Beaver</a></i> model.</p>
<p>Since <i>u</i>, <i>v</i>, and <i>w</i> are not state variables, their
time-derivatives do not have to be known to solve the equations of motion.
However, for some purposes, knowledge of these time-derivatives still may
be useful; therefore, a separate block <i><a href=
"uvwdot.htm">uvwdot</a></i> has been included in the subsystem <i><a href=
"moreouts.htm">Additional Outputs</a></i> within the <i>Beaver</i> model.</p>
<h3>
Inputvectors: <i>x</i> and <i>yhlp</i>
</h3>
<pre>
x = [V alpha beta p q r psi theta phi xe ye H]' (states)
yhlp = [cos(alpha) sin(alpha) cos(beta) sin(beta) ...
... tan(beta) sin(psi) cos(psi) sin(theta) ...
... cos(theta) sin(phi) cos(phi)]'
(frequently used sines and cosines, coming from <a href=
"hlpfcn.htm">Hlpfcn</a>)
V : airspeed [m/s]
{alpha: angle of attack [rad] }
{beta : sideslip angle [rad] }
{p : roll rate [rad/s] }
{q : pitch rate [rad/s] }
{r : yaw rate [rad/s] }
{psi : yaw angle [rad] }
{theta: pitch angle [rad] }
{phi : roll angle [rad] }
{xe : x-coordinate in Earth-fixed reference frame [m] }
{ye : y-coordinate '' '' '' '' [m] }
{H : altitude above sea-level [m] }
</pre>
<p>The inputvariables which are not actually used by the block <i>uvw</i> have
been displayed between curly braces. From <i>yhlp</i> the signals
<i>cos(alpha)</i>, <i>cos(beta)</i>, <i>sin(alpha)</i> and <i>sin(beta)</i>
are used.</p>
<h3>
Outputvector: <i>ybvel</i> (bvel = 'body-axes velocities')
</h3>
<pre>
ybvel = [u v w]',
u : component of the true airspeed V along XB-axis [m/s]
v : component of the true airspeed V along YB-axis [m/s]
w : component of the true airspeed V along ZB-axis [m/s]
</pre>
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