-------------------------------------------------------------------------------
   Simulates two DC motors.
-------------------------------------------------------------------------------
   Form:
   xDot = DualDCMotors( x, t, d )
-------------------------------------------------------------------------------

   ------
   Inputs
   ------
   x              (4,1)  State vector [theta;omega;theta;omega]
   t              (1,1)  Time
   d              (1,1)  Motor structure

   -------
   Outputs
   -------
   xDot           (4,1)  State vector derivative [theta;omega;theta;omega]

-------------------------------------------------------------------------------