The simplest kite state-machine is a binary pair- Flying or Not-Flying. A workable sensor is a contact switch lever at the anchor-point that trips when the kiteline lays down on the surface. One nice experiment is to let a Morse Sled land & self re-launch for extended sessions while recording state against a time-base. The next logical elaboration of the state-machine is to measure the wind-speed dimension while tracking kite-state. This allows failures & latencies to be sorted from the data stream. The Beaufort Scale is a fine default minimal granularity assumption.

From there the state machine becomes more application or operation driven. One might care most about certain dimensions like wind direction, altitude, kiteline state, generation, etc., but the essential task is to minimize the number & precision of dimensions lest the state machine grow intractable. Intractability takes many forms, but complex processing in real-time is a common hurdle. High dimensional combinatorics burdens processing. Sensor fusion challenges the designer. Uncertainty of every kind limits reliable performance.

The natural wind-field is a major uncertainty. Active control is only as good as one's wind sensing & modeling, but both engineering functions are weak at present. A basic wind state model is around seven dimensions. More complex versions soon become intractable.

Much work is ahead to digitize kites. A practical hint is to use videogrammetry to gather experimental data in mass-parallel. Video provides an inherent discrete time-base, enables space measurement with color-coded reference markings, and the visual frame easily includes real-time instrument read-outs in the foreground. Post-processing of the image stream automates digitization. Eventually one may migrate to simpler sensing and process fast enough to automate acceptable actuation in real-time.

A most useful single-actuation dimension (or degree-of-freedom (DOF)) to automate is yaw output as this is useful to resist wind-veering upset and lock-out looping. Angle of attack (AoA) is a primary control input for power modulation and even killing, but an elastic aft-bridle can embody the logic to reduce AoA in gusts. Yaw, roll, and pitch mixing are desirable for kiteplane aerobatics.

NEXT: Critical Reliability of Autonomous AWECS 

FairIP/CoopIP        ~~Dave Santos         May 23, 2010 Happy Birthday Otto Lilienthal   M1555    

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