level2.hlp

MATLAB在飞行动力学和控制中应用的工具

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Level 2 of the system BEAVER - Main level
=========================================
The actual model of the 'Beaver' dynamics, consisting of twelve
state and many output equations, is contained in level 2 of the
system BEAVER. This is therefore the main level of the system,
which clearly visualizes the modular structure of the aircraft
model. Unfortunately, Simulink does not accept vector signals to
be send through Inport and Outport blocks within the FIRST levels
of graphical systems, otherwise, the additional Mux, Demux,
Inport, and Outport blocks from the first level wouldn't have
been necessary. This is a serious limitation of Simulink, and it
is hoped that this problem will be solved in future versions of
Simulink. See also LEVEL1.HLP.

Subsystems in Level 2
=====================
Level 2 contains the following subsystems (masked subsystems
are denoted by {M}):

  Airdata Group
  Aerodynamics Group (Beaver)
  Engine Group (Beaver)
  Gravity                                  {M}
  Fwind                                    {M}
  FMsort                                   {M}
  Aircraft Equations of Motion (Beaver)
  Additional Outputs
  Hlpfcn                                   {M}

In those cases where the name of a subsystem has been enhanced
with the extension '(Beaver)', the subsystem contains aircraft-
dependent elements (currently configured for the 'Beaver' air-
craft). The masked subsystem blocks only contain a small set of
equations, whereas the other subsystem blocks contain more masked
or unmasked subsystems. In order to review the internal structure
of the masked subsystems, it is necessary to unmask these systems
first. Help-texts are available for all masked subsystem blocks.

Structure of Level 2
====================
The system should be 'read' from top to bottom and from left to
right. The upper-left subsystem is the block 'Airdata Group'.
Some of the results of this block are needed by others, for com-
puting forces and moments, which is why those blocks have been
shifted further rightwards and downwards. The different contribu-
tions to the external forces and moments are added and sorted in
the block FMsort, so this block is located on the lower right
side of the forces & moments blocks. One step further right and
downwards are the subsystems 'Aircraft Equations of Motion' and
'Additional Outputs', which use the main results from the other
blocks.

Since the subsystem 'Additional Outputs' also needs time-deriva-
tives of the state variables, a feedback loop of xdot has been
included in the blockdiagram. This does not result in an alge-
braic loop, because the Ordinary Differential Equations for the
twelve states of the aircraft are in no way involved in this loop
(the outputs are called 'additional' because they don't represent
interim results for the solution of the state equations them-
selves).

In general, all (masked) subsystems use results from other blocks
which are located on their left side, and the outputs of all sub-
systems are send to other blocks, located on their right side, if
necessary. The different subsystems also have different vertical
positions, in order to be able to connect their outputs to the
Outport blocks on the far right side in this second level of
BEAVER.
      The only exceptions to this 'rule' are the ('artificial')
feedback loops of the state vector x, its time-derivative xdot,
and the outputvector yhlp from the block Hlpfcn, which contains a
number of frequently used sines and cosines. The block Hlpfcn is
the only one which uses an input vector that enters the block on
the right side and an output vector which leaves the block on the
left side.

Inputs to Level 2
=================
   uaero = [deltae deltaa deltar deltaf]'    (aerodynamic inputs)
   uprop = [n pz]'                                (engine inputs)
   uwind = [uw vw ww uwdot vwdot wwdot]' (atmospheric disturban-
                                          ces; wind & turbulence)
Outputs from Level 2
====================
   x     = [V alpha beta p q r psi theta phi xe ye H]'   (states)
   xdot  = dx/dt                     (time-derivatives of states)
   ybvel = [u v w]'               (body-axes velocity components)
   yuvw  = [udot vdot wdot]'    (time-derivatives of u, v, and w)
   ydl   = [pb/2V qc/V rb/2V]' (dimensionless rotational veloci-
                                 ties along aircraft's body-axes)
   yfp   = [gamma fpa chi Phi]'            (flightpath variables)
   ypow  = [dpt P]'             (engine power (-related) outputs)
   yacc  = [Ax Ay Az axk ayk azk]'   (accelerations and specific
                                       forces in aircraft's c.g.)
   Caero = [CXa CYa CZa Cla Cma Cna]'   (aerodyn. force & moment
                                                    coefficients)
   Cprop = [CXp CYp CZp Clp Cmp Cnp]'     (engine force & moment
                                                    coefficients)
   FMaero= [Xa Ya Za La Ma Na]'       (aerodyn. forces & moments)
   FMprop= [Xp Yp Zp Lp Mp Np]'         (engine forces & moments)
   Fgrav = [Xgr Ygr Zgr]'                        (gravity forces)
   Fwind = [Xw Yw Zw]'          (forces due to wind & turbulence)
   yatm  = [rho ps T mu g]'                (atmosphere variables)
   yad1  = [a M qdyn]'                        (airdata variables)
   yad2  = [qc Ve Vc]'                   (more airdata variables)
   yad3  = [Tt Re Rc]'                   (more airdata variables)

See INPUTS.HLP for the exact definitions of all inputvariables,
see OUTPUTS.HLP for the definitions of the outputvariables, men-
tioned above.

For more info, consult the following helptexts in the subdirec-
tory HELP: LEVEL1.HLP, ADGRP.HLP, AEROGRP.HLP, ENGGRP.HLP,
GRAVITY.HLP, FWIND.HLP, FMSORT.HLP, EQMOTION.HLP, MOREOUTS.HLP,
and HLPFCN.HLP. See also COLORS.HLP for the color-conventions,
used in the blockdiagrams of FDC 1.2.

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The FDC toolbox, Copyright Marc Rauw 1994-1998.