I’ve been reflecting on the intricacies of kite control, particularly when contrasting control pods and rigid frames with on board control (and a single tether).
Consider the children’s toy plane with a string attached. When you spin it, the plane remains airborne, mimicking real flight. Typically, the string is fastened to a wingtip, ensuring the plane maintains a stable flight due to balanced forces. But, what if we shifted the string’s attachment from the wingtip to the plane’s center? I suspect maintaining a stable flight would become significantly more challenging, especially if the string’s tension varied.
Expanding on this thought, a single tether kite system might resemble our modified toy plane. All aerodynamic forces and control inputs would primarily channel through this singular tether. It’s somewhat like piloting an actual aircraft using a single control for both altitude and direction. As the kite’s size or speed increases, or in gusty conditions, I wonder about the challenges in maintaining stability, preventing stalling, and overall control difficulties. If we incorporate a control pod and split the lines, we actually get a bit more control. but still, any tether tension adjustments would likely impact both control surfaces. Moreover, with all the control mechanisms, power sources, and sensors aloft, the kite might be heavier, which could be counterproductive when maximizing agility and apparent wind. If you imagine spinning the plane as fast as possible, control becomes increasingly difficult from a computational standpoint.
Conversely, imagine a kite system akin to our original toy plane, but with two tethers attached to each wingtip. Even as it the spin rate increases, I assume the forces would balance out, allowing the kite to maintain its orientation. This dual-tether setup might offer the kite enhanced agility, enabling it to swiftly respond to wind shifts. As we scale this design, I believe the dual tether approach would remain consistent. The inherent direct tension control might mean the kite perceives changes instantaneously, resulting in a more intuitive control experience. Without the need for intricate algorithms, the control process might be both straightforward and precise.
Reflecting on the control dynamics I was just covering,
Paraglider/ On Board Control:
Consider a paraglider tethered to an anchor point on the ground. When the paraglider adjusts the bridles locally, his position shifts based on a combination of his movements and the resulting tether tension. Yet, this positional change isn’t instantly relative to the ground’s tether anchor point. Even with remote control direct to the bridle, the positional shift, signified by changing the tension, must travel down to the tether’s anchor point before the paraglider’s position noticeably changes in relation to that point.
Essentially, while the glider can make various adjustments, the actual response concerning the tether anchor point only materializes once the tension information reaches the tether’s base.
Explanation of “Non-Local Control”:
“Non-local control” describes a system where the immediate reaction isn’t directly influenced by the initial input point, in this case, the ground tether station. This system involves a transmission phase where the input or alteration must journey to a primary control point before the system responds. The system’s reaction is then based on this transmission phase, not the immediate input.
Drawing Parallels:
The glider example embodies the “non-local control” concept. Here, the paraglider’s local adjustments (input) don’t instantaneously dictate the system’s (glider’s) reaction. There’s an inherent delay, marked by the time required for the tension alteration to reach the ground’s tether anchor point (transmission phase). It’s only post this transmission that the glider’s position is modified concerning the anchor point. This scenario serves to demonstrate the fundamental principle of non-local control: the separation between the control or input point and the system’s immediate reaction. Understanding this distinction and the transmission phase is crucial for refining control mechanisms in tethered systems.
