PitchServoRHS:

--------------------------------------------------------------------------
   Pitch servo model.
--------------------------------------------------------------------------
   Form:
   betaDot = PitchServo( beta, t, d )
--------------------------------------------------------------------------

   ------
   Inputs
   ------
   beta          (1,1)       Pitch angle
   t             (1,1)       Time (not used)
   d             (1,1)       Data structure
                             .k             (1,1) Forward gain
                             .betaLimit     (1,1) Maximum beta
                             .betaRateLimit (1,1) Maximum beta rate

   -------
   Outputs
   -------
   betaDot       (2,1)       Beta rate

--------------------------------------------------------------------------
   Reference: Gill Estevez, P. ,"Model Dinamico de Una Turbina 
              de velocidad variable con Generador de Imanes Permanentes y 
              control de angulo de calaje ? Analisis de Control de 
              Velocidad. Figure 6.
--------------------------------------------------------------------------