Airship_KLon:

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   The longitudinal control laws for an airship.
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   Form:
   d = Airship_KLon( action, data )
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   ------
   Inputs
   ------
   action        (:)   String name of action to take. Choices are:
                          * 'init'        ...  Supply statespace controllers and 
                                                             initialize matrices
                          * 'update'      ...  Supply the error inputs and compute 
                                                                      the controls
                          * 'reset'       ...  Reset controller states to zero
   data          (.)   Data structure required for action
                          if action == 'init'
                             - data.k_tu  ...  statespace controller, 
                                                     u -to- throttle
                             - data.k_mu  ...  statespace controller, 
                                                     u -to- mu (prop pitch angle)
                             - data.k_dw  ...  statespace controller, 
                                                     w -to- elevator deflection
                             - data.k_dq  ...  statespace controller, 
                                                     q -to- elevator deflection
                             - data.rate  ...  update rate [Hz]
                          if action == 'update'
                             - data.q     ...  pitch rate error       [rad/s]  
                             - data.u     ...  axial velocity error   [m/s] 
                             - data.w     ...  normal velocity error  [m/s] 

   -------
   Outputs
   -------
   d             (.)   Data structure of control outputs
                             - d.throttle ... Throttle command
                             - d.mu       ... Propeller pitch command      [rad]
                             - d.dELV_sym ... Symmetric elevator command   [rad]

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Children:

Common: Control/C2DZOH