I got the parts for the Smoking Ace this weekend from Bill at "Unique Cutting and Metal Works". Bill is great to work with and help us on this project.
The parts are coming together well. They were bracketed this weekend and got a coat of enamel. The issue that I see at the moment, is that small variations in a straight line make a big difference now that the spars are weight reduced. Lots more small radii to worry about. I do not think it is a big deal, but I lost a bunch of holes because they were too close to other penetrations.
The best thing, that has come out so far, is that the battery carriers really look like they fit as designed. That is cool, I hope that I can get the heat pipe design to work too. One of my coups of engineering will be to steer some of the motor, esc and battery heat to the same spot across a Peltier device and out to the free stream. I am not sure it will be worth more than a few volts, but something is better than nothing. Peltier recovery is one of several technologies that we hope will get our electronics power-management efficiency up.
I will get some pictures up as soon as the fuselage gets a bit further along. One of the most interesting things about this design, is that it is based on triangles. Any third year structures student will remind you that triangles are the only self supporting shape. Self-supporting makes the air-frame easier to construct because it tends to stiffen up as you assemble it. This means that you can break the assembly up a bit more than normal and things self-support and then support when assembled. Anything that makes this easier to do is good.
More to come.
Buzz Labs' unmanned vehicle blog and cool DIY remote controlled stuff blog. For techies by techies, maybe also some interesting tidbits about small business and international business.
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Sunday, January 23, 2011
Wednesday, November 17, 2010
UGV Autopilot Revisited
We have been working on lots of projects lately, mostly about the UAVs again. Only two hands and all, the last parking lot test that we ran were successful in clear areas. If you just wanted a clear circuit, our simple guidance system was good about being repeatable around 20mph. However, we want to get more in the low end in this, so that we can handle cornering better. The avoidance model is where we are looking for some help.
We are trying to get a working optical flow system to work at these speeds. You can get a working system at low frame rates, but we will need to increase our computing capacity to get it to work successfully at these speeds. Our issue we think, is in the matrix inversions. The determinant terms are making too many things blow up by divisions of small numbers.
We are looking for anyone with experience getting an effective Kalman filter to work on Android. We have a few older phones, bhat we think would be a good platform for doing 2d control. Yes, I am mixing discussions a bit. If we can better estimate the net acceleration, it would help debug our optical flow system. We are having to bracket our responses so that the AI does not jerk the wheel. This seems to be an issue. If optical flow can be used to manage the jerk, I think that we can even have moving obstacles in the scene and still reacquire the path with no issue.
We are trying to get a working optical flow system to work at these speeds. You can get a working system at low frame rates, but we will need to increase our computing capacity to get it to work successfully at these speeds. Our issue we think, is in the matrix inversions. The determinant terms are making too many things blow up by divisions of small numbers.
We are looking for anyone with experience getting an effective Kalman filter to work on Android. We have a few older phones, bhat we think would be a good platform for doing 2d control. Yes, I am mixing discussions a bit. If we can better estimate the net acceleration, it would help debug our optical flow system. We are having to bracket our responses so that the AI does not jerk the wheel. This seems to be an issue. If optical flow can be used to manage the jerk, I think that we can even have moving obstacles in the scene and still reacquire the path with no issue.
It seems to be that the vectors estimated with Kalman divides by zero and runs a huge acceleration and that ruins the math for several iterations. Then the ringing dies out and the system cam go on, by that time we are either running for the hills because a dog liked the truck or because something blew across the scene. I have to find the math error.
Contour 1080p HD helmet cam
So far so good with the helmet cam. We have been playing with its high frequency stabilization technology. This is pretty effective at taking the jelly and jam out of the motor shakes. Which is a good sign, it is effective at taking out suspension bob when riding a bike, but low frequency motion it can only do so much with. If you move the camera 3" it can't take the shake out of that. You would not really expect it to.
At night, or in low-light conditions it gives a pretty good picture until it is hard to see. Once you break that threshold it is too dim as well. It does have a pretty good sensor, it can pick up even small changes in brightness well and does well with edges.
At the moment, I have yet to get virtual dub to open a quicktime movie. None of the plugins that have been found work. Although I am loathe to say it, it may be better to just go the Quicktime Pro route. Legendary fail of customer support is always a reason why Mr. Jobs' overpriced fanboi kit rarely graces my workspace. It may be a necessary evil this time. Especially, if it can automatically export all of the movie's frames in one drop.
I am not done testing the camera, but so far I recommend it. For the money, it is very usable, rugged and has a functional output that is good for tv viewing. Reliving past exploits are always a great way to kill time while you lie to yourself about how good you were.
At night, or in low-light conditions it gives a pretty good picture until it is hard to see. Once you break that threshold it is too dim as well. It does have a pretty good sensor, it can pick up even small changes in brightness well and does well with edges.
At the moment, I have yet to get virtual dub to open a quicktime movie. None of the plugins that have been found work. Although I am loathe to say it, it may be better to just go the Quicktime Pro route. Legendary fail of customer support is always a reason why Mr. Jobs' overpriced fanboi kit rarely graces my workspace. It may be a necessary evil this time. Especially, if it can automatically export all of the movie's frames in one drop.
I am not done testing the camera, but so far I recommend it. For the money, it is very usable, rugged and has a functional output that is good for tv viewing. Reliving past exploits are always a great way to kill time while you lie to yourself about how good you were.
Wednesday, October 27, 2010
Countour HD Helmet Cam
We are looking into using the Contour HD helmet cam as the data source for some GIS experiments. After a detailed review of available products, we found the Contour. It is a well-received and rugged helmet cam aimed at mountain biking and snowboarding. Out of the box, it is a well built camera with an interesting rubberized back cover that gives access to the battery and the memory card in one flip of the thumb.
I will see about posting the movies that were shot with the camera. The output is a QuickTime movie, that we will feed to virtual dub. Virtualdub will strip the frames out of the movie so that we can analyze frames to look for patterns in the vegetation. The goal is to make a semi-automated habitat estimator and/or plant specie histogram.
As my batteries run low at dinner, I promise more interesting things to come.
I will see about posting the movies that were shot with the camera. The output is a QuickTime movie, that we will feed to virtual dub. Virtualdub will strip the frames out of the movie so that we can analyze frames to look for patterns in the vegetation. The goal is to make a semi-automated habitat estimator and/or plant specie histogram.
As my batteries run low at dinner, I promise more interesting things to come.
Sunday, August 1, 2010
Can't Get It Up?
Hey it happens to everyone...
No little blue pills, but a rainy afternoon is keeping us from seeing how the wings sit in the mount. There is a bit of concern that the lovely tolerance that made the spars so easy to insert, is making life hard for other reasons. It will not be an issue. As long as the system is stiff once it is bolted together. There is some concern that the foam may crush under side-load. That could be fixed but I do not see a good solution that will work.
The fix if necessary is a wing root cap. That is probably a good idea under most circumstances. However, what could it hold to? The thing that was great about the design was that it had little in the way of internal structure, it is foam after all. That may be limiting the usable weight in the end because you cannot make strong mounts between primary parts.
We will see. At the moment I cam going to see if 0.060" piece of Aluminum sheet will tip the system in the right direction. It may need more like 0.090" to correct the wing tip height. I can't see that until it stops raining enough to take it outside and measure it. Ten foot wingspan makes it problematic to measure in the house. Oh yeah, it is being built in a 900ft^2 apartment that I live in at the same time. It is a good drill for the initial facilities that I will have in CZ. I will dream of the day of such a large place.
More to come...
No little blue pills, but a rainy afternoon is keeping us from seeing how the wings sit in the mount. There is a bit of concern that the lovely tolerance that made the spars so easy to insert, is making life hard for other reasons. It will not be an issue. As long as the system is stiff once it is bolted together. There is some concern that the foam may crush under side-load. That could be fixed but I do not see a good solution that will work.
The fix if necessary is a wing root cap. That is probably a good idea under most circumstances. However, what could it hold to? The thing that was great about the design was that it had little in the way of internal structure, it is foam after all. That may be limiting the usable weight in the end because you cannot make strong mounts between primary parts.
We will see. At the moment I cam going to see if 0.060" piece of Aluminum sheet will tip the system in the right direction. It may need more like 0.090" to correct the wing tip height. I can't see that until it stops raining enough to take it outside and measure it. Ten foot wingspan makes it problematic to measure in the house. Oh yeah, it is being built in a 900ft^2 apartment that I live in at the same time. It is a good drill for the initial facilities that I will have in CZ. I will dream of the day of such a large place.
More to come...
Sunday, July 25, 2010
Lifting Bodies Are More Than Just Another Pretty Shape - Opinions on Aircraft Design
Lifting Bodies Are More Than Just Another Pretty Shape - Opinions on Aircraft Design
There are many ways to look at aircraft design. Most of which are field dependent, why design for supersonic flight if your device will never climb above 500'? It would be cool thought, right? I digress, if you are designing for normal flight regimes you will be operating at an altitude with an engine power curve which will vary by altitude and temperature. Now, if you are designing in other regimes, you need to know where you can get small performance boosts where they are available.
Managing wing thicknesses is and use the concept of "wing tip thrust". By making tip vortices more manageable there is a significant reduction in overall wing drag. This "free" reduction in drag is called "wing tip thrust". Like this, there is another simple idea to take into account. If you can design a fuselage that is not pressurized with an essentially flat belly, you can play some shape games. These shape games can effectively make a Clark-Y airfoil. Now it is more complicated than this, but if you begin your mental experiments from this perspective, you can eek out some under-represented performance.
But how do he do it? It is all in the magic. If lift is generated by circulation of a lift envelope, that is created by the difference in pressure created by fluid moving around a shape. Why not generate lift around your fuselage? It will not get you 25% of your lift... but if your fuselage planform area is 15% of your wing area and you can get 40% efficient lift out of minding your p's and q's you could be looking at 6% more total lift. Yeah, you are right, this is all pie in the sky stuff. However, if you could generate 2-3% more lift for the length of your flight, you could reduce the angle of attack on your wings and trim out your drag. Reducing your drag means that you use less energy in the case of electric or less fuel in the engine.
Less fuel means that you can carry more, or fly farther. Nice. 1-2% may not be a lot if you weigh 4oz. . However, if you are looking at varying wind conditions or being able to react to changing conditions and you can play some games about fuselage profiles. Why not, it is not really so hard to get as much as 5-6% out of playing your profiles against each other. That makes for a good amount more flight time in rc. Not the 7min guys, but as you go for 20min... you get 21min. Yeah, it does not sound like much, but if it makes your fun go for 22min... It will be worth it.
Why do I pick Clark-Y? They have flat bottoms, reasonable thickness and a fast taper to the trailing edge. Construction-wise they are easy to construct, because you can lay them on a table. Their CL/alpha is pretty steep, so 1-2deg can get you something and if you can play with what level is, you can get a fuselage angle of attack to a point where you can make some dividends. Most importantly is that they do not separate their boundary layer fast. Most designs will never get to a critical angle of attack, drag will eat you alive if you fly your fuselage at such a high angle of attack.
We make lots of 60" fuselages these days with a mean 12" beam. That gets us an additional 4-5lbs of lift at take off and 1-2 lbs at cruise. Nothing to write home about, NASA will never give me a Ph.D. for it, but it does get me lots of "clever"s and "I would not have thought of that"s. Pretty high praise in engineering circles.
There are many ways to look at aircraft design. Most of which are field dependent, why design for supersonic flight if your device will never climb above 500'? It would be cool thought, right? I digress, if you are designing for normal flight regimes you will be operating at an altitude with an engine power curve which will vary by altitude and temperature. Now, if you are designing in other regimes, you need to know where you can get small performance boosts where they are available.
Managing wing thicknesses is and use the concept of "wing tip thrust". By making tip vortices more manageable there is a significant reduction in overall wing drag. This "free" reduction in drag is called "wing tip thrust". Like this, there is another simple idea to take into account. If you can design a fuselage that is not pressurized with an essentially flat belly, you can play some shape games. These shape games can effectively make a Clark-Y airfoil. Now it is more complicated than this, but if you begin your mental experiments from this perspective, you can eek out some under-represented performance.
But how do he do it? It is all in the magic. If lift is generated by circulation of a lift envelope, that is created by the difference in pressure created by fluid moving around a shape. Why not generate lift around your fuselage? It will not get you 25% of your lift... but if your fuselage planform area is 15% of your wing area and you can get 40% efficient lift out of minding your p's and q's you could be looking at 6% more total lift. Yeah, you are right, this is all pie in the sky stuff. However, if you could generate 2-3% more lift for the length of your flight, you could reduce the angle of attack on your wings and trim out your drag. Reducing your drag means that you use less energy in the case of electric or less fuel in the engine.
Less fuel means that you can carry more, or fly farther. Nice. 1-2% may not be a lot if you weigh 4oz. . However, if you are looking at varying wind conditions or being able to react to changing conditions and you can play some games about fuselage profiles. Why not, it is not really so hard to get as much as 5-6% out of playing your profiles against each other. That makes for a good amount more flight time in rc. Not the 7min guys, but as you go for 20min... you get 21min. Yeah, it does not sound like much, but if it makes your fun go for 22min... It will be worth it.
Why do I pick Clark-Y? They have flat bottoms, reasonable thickness and a fast taper to the trailing edge. Construction-wise they are easy to construct, because you can lay them on a table. Their CL/alpha is pretty steep, so 1-2deg can get you something and if you can play with what level is, you can get a fuselage angle of attack to a point where you can make some dividends. Most importantly is that they do not separate their boundary layer fast. Most designs will never get to a critical angle of attack, drag will eat you alive if you fly your fuselage at such a high angle of attack.
We make lots of 60" fuselages these days with a mean 12" beam. That gets us an additional 4-5lbs of lift at take off and 1-2 lbs at cruise. Nothing to write home about, NASA will never give me a Ph.D. for it, but it does get me lots of "clever"s and "I would not have thought of that"s. Pretty high praise in engineering circles.
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