## Autopilot subsystem Reference Signals

The autopilot subsystem Reference Signals supplies the reference values of the pitch angle, roll angle, altitude, rate of climb/descent, and heading for the different autopilot modes.

Before starting a new simulation, double-click the block 'Select Mode and Reference Signals', or type `apstart` at the Matlab command line in order to define the autopilot modes (and hence, the initial switch-settings). The reference signals will be stored by the initialization routine APMODE in the vectors yrefS and yrefA in the Matlab workspace. These vectors are defined as follows:

- yrefS: symmetrical reference signals (pitch angle, altitude, rate of climb/descent)
- yrefA: asymmetrical reference signals (roll angle, heading)

### Symmetrical reference signals:

     yrefS = [Dtheta_ref, DH_ref, DHdot_ref]

where:

              Dtheta_ref = reference pitch-angle [rad]
              DH_ref     = reference altitude [m]
              DHdot_ref  = reference rate of climb/descent [m/s]

### Asymmetrical reference signals:

     yrefA = [Dphi_ref, Dpsi_ref]

where:

              Dphi_ref   = reference roll-angle [rad]
              Dpsi_ref   = reference heading [rad]

### More information

See the source-code of APMODE.M for more details on the mode-initialization of the autopilot simulation models.

### References

A detailed description of the 'Beaver' autopilot can be found in the FDC user-manual, and the following references:

1. M.O. Rauw: A Simulink environment for Flight Dynamics and Control analysis - Application to the DHC-2 'Beaver' (PART II). MSc-thesis, Delft University of Technology, Faculty of Aerospace Engineering, Delft, The Netherlands, 1993.
2. P.N.H. Wever: Ontwerp en implementatie van de regelwetten van de De Havilland DHC-2 'Beaver' (in Dutch). MSc-thesis, Delft University of Technology, Faculty of Aerospace Engineering, Delft, The Netherlands, 1993.