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What is a reversible flight control?

Most general aviation airplanes have "reversibleflight controls, which means you have a direct physical connection (push-pull tubes, cables, torque tubes, etc.) between the cockpit controls and the control surfaces. Therefore, the pilot feels the air load on a deflected control surface.

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Characteristics of Mechanical Flight Control Systems:

 

+ small forces required to control control surfaces

- no physical feedback from the CS to the pilot (if no Artificial feel system installed)

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Three main components of a Flight Control System:

  • Inceptors
    • Control function: to control aerodynamic surface position -> control flightpath
    • Feel function: to return position and force feedback to the pilot
  • Linkages
    • Function: position the actuator at the desired location
  • Actuator
    • Function: transfer pilot commands to the actuation system
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Purpose of automatic controls:

  • Improve Flight Performance
    • Systems’ response can be faster than human, more precise than human and not subject to human fatigue, for example:
    • Hover
    • Speed hold
    • Altitude hold
    • Terrain Following (coupled to radar)
  • Aircraft Command and Stabilization functions
    • Load Factor Demand System
    • Pitch damper
    • Yaw Damper
    • Speed stability
  • Flight Path Control functions
    • Speed hold
    • Altitude hold
    • Attitude hold
  • Navigation functions
    • VOR tracking
    • Route following
    • 3D and 4D navigation
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What does GNC stand for?

  • Navigation:
    • determining where you are relative to where youwant to be
  • Guidance:
    • determination of desired path of travel
  • Control:
    • control of the vehicle to track guidance command

size (N>G>C)

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Controller Goals:

  • To control means, to influence the output variables in such a way that a prescribed reference is reached, independent of outside noise.
  • The output variable shall, in case of a change of the noise or a new reference, reach the desired value
    • as fast, as accurateand as damped(stable) as possible

 

  • Noise Rejection (störsignale)
  • Tracking of Reference (Tracking)

 

  • Transient response
    • Fast
    • Not excessive overshoot
  • Robust
    • Against system parameter changes
  • Stability
    • Must be stable
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Controll System Terminology:

types of signals in a control system:

  • Reference             r(t)
  • Control variable    u(t)
  • Error                     e(t)
  • Disturbance          d(t)
  • System output      y(t)
  • Measured output  ȳ(t)

     
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Controll System Terminology:

Components of a control system:

  • Controller
  • Actuating element
  • Sensor
  • Measuring device