enggrp.hlp

MATLAB在飞行动力学和控制中应用的工具

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System BEAVER - subsystem 'Engine Group (Beaver)'.
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The subsystem 'Engine Group' is used to compute the forces and
moments which arise due to the operation of the engine. These in-
clude slipstream effects, induced by the propeller. In the case
of the 'Beaver', this is done by first computing the engine power
and the closely related increase of pressure across the propeller,
then using this result for determining the magnitude of dimension-
less force and moment coefficients, and finally computing the forces
and moments in N and Nm, respectively. A similar sequence will
usually be followed for other piston-engined aircraft.

The subsystem 'Engine Group (Beaver)' consists of three masked
subsystems: Power, Engmod, and FMdims. Power computes the engine
power and pressure increase across the propeller, Engmod contains
the actual engine model according to ref.[1] which determines the
dimensionless force and moment coefficients, and FMdims is used to
compute the forces and moments in N and Nm. The block Power uses the
state vector x, the vector with external inputs to the engine, uprop,
and the outputvector yatm from the block Atmosph in the subsystem
'Airdata Group' as inputs. Engmod uses x and the outputvector ypow
from the block Power, hence, Engmod has been placed on the lower
right side of Power. Finally, FMdims uses the outputvector of the
block Engmod, Cprop, and the outputvector of the block Airdata1 in
the subsystem 'Airdata Group', yad1. Hence, FMdims is located on
the right side of the block Engmod. Power, Engmod, and FMdims
have also been shifted vertically with respect to eachother, to
make it possible to connect their outputs to the Outport blocks
on the right side of the subsystem 'Engine Group (Beaver)'.

Inputs:
=======
  x    = [V alpha beta p q r psi theta phi xe ye H]'    (states)
  uprop= [n pz]'           (external engine inputs (propulsive))
  yatm = [rho ps T mu g]'    (atmosphere variables, computed in
                                   the masked subsystem ATMOSPH)
  yad1 = [a M qdyn]'        (airdata variables, computed in the
                                      masked subsystem AIRDATA1)

where:

  V    : true 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, relative to Earth-axes [m]               }
 {ye   : Y-coordinate, relative to Earth-axes [m]               }
 {H    : altitude above sea level [m]                           }

  n    : engine speed [RPM]
  pz   : manifold pressure ["Hg]

  rho  : air density [kg/m^3]
 {ps   : static pressure [N/m^2]                                }
 {T    : air temperature [K]                                    }
 {mu   : dynamic viscosity [kg/(m*s)]                           }
 {g    : acceleration of gravity [m/s^2]                        }

 {a    : speed of sound [m/s]                                   }
 {M    : Mach number [-]                                        }
  qdyn : dynamic pressure [N/m^2]

The accolades denote variables which are not used by any of the
blocks from the subsystem 'Engine Group (Beaver)'.

Outputs (prop = 'propulsive'):
==============================
  ypow  = [dpt P]'
  Cprop = [CXp CYp CZp Clp Cmp Cnp]'
  FMprop= [Xp Yp Zp Lp Mp Np]'

where:

  dpt  : dimensionless pressure increase across the propeller [-]
  P    : engine power [Nm/s]

  CXp, CYp, CZp: propulsive force coefficients along body-axes [-]
  Clp, Cmp, Cnp: propulsive moment coefficients along body-axes [-]

  Xp, Yp, Zp: propulsive force components along body-axes [N]
  Lp, Mp, Np: propulsive moment components along body-axes [Nm]

References:
===========
[1]  R.T.H. Tjee and J.A. Mulder. Stability and Control Deriva-
     tives of the De Havilland DHC-2 "Beaver" aircraft. Report
     LR-556, Delft University of Technology, 1988.

More info:
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See POWER.HLP, ENGMOD.HLP, and FMDIMS.HLP for more info about the
masked subsystem blocks from the subsystem 'Engine Group (Bea-
ver)'. See ATMOSPH.HLP and AIRDATA1.HLP for more info about the
determination of yatm and yad1.

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The FDC toolbox, Copyright Marc Rauw 1994-1998.