Posted by Tj Bordelon on December 31, 2009 at 12:44pm
Here in Boston, we have snow and wind. Not good for testing landing code. I hope to have some time in a few weeks to test and post the results of my new landing code. The old landing code can be seen in this video. Unfortunately coming in for a single approach like this has the EZ-STAR touching down at 28mph, and taking about 800 feet to land. The new landing code which I flew a few weeks ago does it in 300 feet.The new idea is to circle in a radius of 125 feet, exit the loiter once the plane has descended to roughly 40 feet altitude, deploy flaps, and use throttle to control altitude while holding a fixed angle of attack. This worked 4/5 times for perfect touchdowns at 15 mph!! The 5th time crashed because the battery died unexpectedly. (I ignored the low battery alert so that's my fault.)I know some of you out there argue auto land is a waste of time, but I like the idea of my plane having a failsafe that will take it to the nearest waypoint and land. Imagine what happens if a dog pees on your ground station! Things like this do happen, and autoland will save you.
I just did the maiden flight (and some others, including glider tow) of a new FunCub. Pushing it at the limits I had a lot of fun, doing landings with flaps at 90° :
plane over head, throttle off, flaps full down, vertical dive (I mean 90° vertical, at constant speed !), pull up elevator at about 10m from ground and plane gently landing at foot at walking speed.
From vertical dive to plane fully stopped there are about 50m (?) horizontally. From pull up about 20m (?).
I had a though at you and what you were searching for landing in small spots with trees all around.
With a good programming and a reliable altitude feedback, this could be a plane capable to do that.
I think I understand your AOA "backoff algorithm" based on airspeed threshold.
I assume what you are going to do in the next version is to make a PID loop that controls the airspeed with the AOA. I guess you then will have certain max and min limits for the AOA that you will not exceed.
Would you be interested in sharing the Pitot tube design? I guess the pitot tube needs to be corrected with both air temperature (density) as well as static barometric pressure offset (high pressure vs. low pressure days) ?
You may want to take a look at the pressure altimeter discussion going on on my blog page as well. We discuss using Kalman filters for an implementation.
I know electronics but can't program a light bulb, but I have a pic programmer, would the the UAVDeBoard be a good start???? I've played a little with picaxe, and pic in basic on simple robots. It seems that programming is the key to success.
@william - I don't know what I'm going to do with my stuff. There are plenty of others that seem to want to sell into this market. I would love to sell UAVs ready-to-go but my understanding is that you can't do this legally right now :(. The market for DIY is too small for my tastes right now. Maybe one day?
@Moril: Thanks! It's good, but it's still landing too fast with the old way. There's usually minor dings from the landings, which isn't good. This code has landed in 20 mph winds, and the high speed helps in those situations. The new landing code hasn't been tested in high winds... I'm eager to see what happens!
@UFO-MAN- I have a pitot and it "backs off" of the commanded pitch angle as the airspeed slows below a threshold. That is soon to be replaced with an airspeed command to elevator feedback loop. It's very cold in boston and I just added much needed calibration to that sensor. So-called calibrated pressure sensors from digi-key were off by as much as 10 mph when in cold weather! I use GPS for height, and I know the error at all times (DOP) so I add a fudge to the flare altitude.
This is the new code that loiters then lands. I think the ultrasonic sensor idea (@Morli) would let me be more agressive on the approach since I know exactly where the ground is. I could hold a negative AOA until I detected the ground, then go to a positive AOA for flare. But right now I just hold a positive AOA with flaps (which gives me a constant airspeed) until I finally land. But this makes the landing take a few hundred feet more space.
My stuff is custom (http://bordelon.net/) so there isn't really a channel on my setup... just a jack for alierons which I offset downward for flaps.
Also, a word on flaps-- Some prefer spoilerons (which are flaps that go up) because it avoids stalls and is more effective. I agree, but the downside is that the plane comes in at a very high AOA and the tail hits the ground. On the easystar this tends to cause damage!
Hi William , welcome
If I may say so , most if not all info here is free and effort is DIY :) , kits and parts ofcourse are for sale from number of kit makers :)
Comments
Ciao Robert,
the FunCub is still in pure RC configuration (no AP on board), so no particularly interesting and a little OT here.
I still don't know if this will be devoted to that or if I leave it to have some pure simple fun.
If I will find a cameramen I will probably do a video to show its amazing landing (and aerobatics) abilities.
Will post the link.
Best regards,
Ric
ciao riccardo,
it might be interesting to see some picts of your funcup.
installing the electronics is always interesting.
the funcup was sold during the last few weeks ... was thinking about getting one.
regards
robert
Hi TJ,
I just did the maiden flight (and some others, including glider tow) of a new FunCub. Pushing it at the limits I had a lot of fun, doing landings with flaps at 90° :
plane over head, throttle off, flaps full down, vertical dive (I mean 90° vertical, at constant speed !), pull up elevator at about 10m from ground and plane gently landing at foot at walking speed.
From vertical dive to plane fully stopped there are about 50m (?) horizontally. From pull up about 20m (?).
I had a though at you and what you were searching for landing in small spots with trees all around.
With a good programming and a reliable altitude feedback, this could be a plane capable to do that.
Best regards,
Ric
I think I understand your AOA "backoff algorithm" based on airspeed threshold.
I assume what you are going to do in the next version is to make a PID loop that controls the airspeed with the AOA. I guess you then will have certain max and min limits for the AOA that you will not exceed.
Would you be interested in sharing the Pitot tube design? I guess the pitot tube needs to be corrected with both air temperature (density) as well as static barometric pressure offset (high pressure vs. low pressure days) ?
You may want to take a look at the pressure altimeter discussion going on on my blog page as well. We discuss using Kalman filters for an implementation.
UFO_MAN
@UFO-MAN- I have a pitot and it "backs off" of the commanded pitch angle as the airspeed slows below a threshold. That is soon to be replaced with an airspeed command to elevator feedback loop. It's very cold in boston and I just added much needed calibration to that sensor. So-called calibrated pressure sensors from digi-key were off by as much as 10 mph when in cold weather! I use GPS for height, and I know the error at all times (DOP) so I add a fudge to the flare altitude.
This is the new code that loiters then lands. I think the ultrasonic sensor idea (@Morli) would let me be more agressive on the approach since I know exactly where the ground is. I could hold a negative AOA until I detected the ground, then go to a positive AOA for flare. But right now I just hold a positive AOA with flaps (which gives me a constant airspeed) until I finally land. But this makes the landing take a few hundred feet more space.
My stuff is custom (http://bordelon.net/) so there isn't really a channel on my setup... just a jack for alierons which I offset downward for flaps.
Also, a word on flaps-- Some prefer spoilerons (which are flaps that go up) because it avoids stalls and is more effective. I agree, but the downside is that the plane comes in at a very high AOA and the tail hits the ground. On the easystar this tends to cause damage!
If I may say so , most if not all info here is free and effort is DIY :) , kits and parts ofcourse are for sale from number of kit makers :)
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