PitchLoop:

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   Design the Pitch Loop including a tach loop for the wheel. 
   If no output arguments are entered, or torqueStep is entered, the function 
   will plot the step response of the system.

   The pitch controller input is pitch and the output is wheel speed demand.
   The tach controller has two inputs: [wheel speed;wheel speed demand + nominal  wheel speed]
   Its output is torque. The wheel speed demand must include the nominal wheel
   speed!

   Each controller has one state.

   Since version 1.
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   Form:
   [aM, bM, cM, dM, aP, bP, cP, dP, clEv] = PtchLoop( inrPitch, inrWheel, beta, zetaM, zetaP,
                                                      wM, wP, dT, dTransform, torqueStep )
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   ------
   Inputs
   ------
   inrWheel         (1,1) Wheel inertia
   inrPitch         (1,1) Pitch inertia
   beta             (1,1) Wheel rate damping constant
   zetaM            (1,1) Tach loop damping ratio
   zetaP            (1,1) Pitch loop damping ratio
   wM               (1,1) Tach loop undamped natural frequency
   wP               (1,1) Pitch loop undamped natural frequency
   dT               (1,1) Sampling period
   dTransform       (1,1) 'Delta', or 'Z' default is 'Z'
   torqueStep       (2,1) External disturbance and friction torque

   -------
   Outputs
   -------
   aM               (1,1) Tach loop plant matrix
   bM               (1,2) Tach loop input matrix
   cM               (1,1) Tach loop measurement matrix
   dM               (1,2) Tach loop feedthrough matrix
   aP               (1,1) Pitch loop plant matrix
   bP               (1,1) Pitch loop input matrix
   cP               (1,1) Pitch loop measurement matrix
   dP               (1,1) Pitch loop feedthrough matrix
   cLEv             (5,1) Closed loop eigenvalues

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Children:

Common: Control/C2DZOH
Common: Control/C2DelZOH
Common: Graphics/NewFig
Common: Graphics/TitleS
Common: Graphics/XLabelS
Common: Graphics/YLabelS