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   Create an object of class acstate
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   Form:
   x = acstate( r, q, w, v, wR, mass, inertia, cG, engine, 
                actuator, sensor, flex, disturb )
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   Inputs
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   r       (3,1) ECI position vector
   q       (4,1) Quaternion from ECI to body
   w       (3,1) Inertial body rate in body frame
   v       (3,1) Velocity of cm wrt air
   wR      (:,1) Angular velocity of rotors
   mass    (1,1) Mass
   inertia (6,1) Inertia
   cG      (3,1) Center of mass
   engine  (:,1) Engine states
   actuator(:,1) Actuator states
   sensor  (:,1) Sensor states
   flex    (:,1) Flex model states organized [x;v] by appendage
   disturb (:,1) Disturbance model states

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   Outputs
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   x           (1,1) State vector

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