--- Tan Chun Chiek wrote: > Hi, > This idea of an autopilot landing system just popped up in my > mind, and other details came almost immediately. You're aiming for the big league here! I know manufacturers are working to create safe landing capabilities for airliners, (don't know the details), but I doubt they have a system that can 100% replace the human factor in all conditions... > before? The runway is something like 10m X 50m. GPS is used for > longitudinal/latitudinal positioning and preferably velocity > measurement, I don't want to discourage you, but there are loads of problems... First of all, I am not sure GPS, (unless military weapons grade, which I doubt anyone can get their hands on) would be of any real use, other then to have navigation and get the model in the vicinity of the airport. With model aircraft, aside from scale reduction, aerodynamic rules work the same, but many parameters change dramatically due to the small size. Absolute speed measurement, the one that GPS can provide is practically irrelevant for a model, espacially at landing. It may be usefull for general navigation, remember, you need to have mapping and stuff for this. What you need is airspeed measurement, which GPS cannot provide. This is the key. Let's say your model flies well at 30kph and begins to stall below 18kph. If you come in for a landing, with 22kph, with headwind of 10 kph, GPS will say you have 12kph, and by this, will assume that you are way below stall speed and will accelerate, landing you with excess speed, and then you wander why the autopilot shoved your plane into the ground... Such a small scale air speed sensor is a challenge itself (I think). Another thing, an autopilot can be built and used ONLY, I repeat, ONLY when you know very well all the handling characteristics of the plane in all conditions. Research and flight testing of real airplanes takes years to gather most of the data for the flight manual and for the autopilot. Without this, an autopilot is next to useless. The autopilot needs to know exactly in the given conditions, and the given orders how to control the plane. Changing the propeller, adding 200grams of weight somewhere, another type of engine, etc, would throw off completely the autopilot and the planes characteristics will have to be retested and the autopilot refitted. A human pilot learns very easily and adapts very quickly to a situation, but a computer-driven pilot who has a limited knowledge of the plane and no learning capability (you're not putting an array of multiprocessor systems with complex neural nets in your model aircraft...), it won't be able to cope. Also take into account that for such a small scale, even small, apparently insignificant changes can dramatically affect the plane's handling. As a human pilot, one can adapt quickly, sometimes instinctively, maybe barely noticing it... Example: your plane, fully equiped, at 20kph stalls at 14deg. Let's say that you put a new battery pack with more capacity, but it also weighs 100 grams more. This will shift the center of gravity of the plane and now it will stall at 12 deg at 20kph. The difference may seems small, but it is actually huge! The autopilot WILL stall this plane, because it assumes that at 20kph, it is safe to fly at 13deg inclination! Unless ofcourse, you go through the whole process of getting the new flight characteristics. Don't even think of putting an autopilot in another type of plane!!! Well, it can be built, to work in a very limited range of situations and flight conditions, with less research, but will have to be at least supervised and override options should be available at all times. Actually, making such an autopilot would be much easier for model helicopter then for a plane. Due to the nature of the helicopter, and the way it flies, (excluding acrobatics, ofcourse), many things are simpler to handle. The advantage of model helicopters is the fact that they can reach a dynamic equilibrium in which they appear static and can hold this. Then it's a simple matter of slightly lowering the collective... (simplified) The plane, although by it's nature tends to fly, while the helicopter does the opposite, dynamicly balancing the parameters on a plane could be more challenging then for a helicopter. I hope this will help. P.S. keep us posted ===== ing. Andrei Boros Centrul pt. Tehnologia Informatiei Societatea Romana de Radiodifuziune __________________________________________________ Do You Yahoo!? Yahoo! - Official partner of 2002 FIFA World Cup http://fifaworldcup.yahoo.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body