Comment by Michael Pursifull on October 10, 2011 at 2:10am

It is for the plane and the quads. For my problem and also for the future, I want to promote "sense and avoid" technologies because in the US and other places, UAVs will soon fall into two categories... those with sense and avoid, and those without. And I want hobbyists to have options (including transceivers, too) not just the commercial and government UAVs... 

 

I agree... about lasers and IR, but I also think sonar has many problems, too. I have many of them, and they cannot detect small objects (tree branches) until you get very close. They also take too long, for fast moving vehicles, it is sound, out and back, and if you are flying at 30-90 Kt/h, a typical range many planes here, and the object is maybe a tree w/o leaves - maybe 2-8cm wide at the top, how far away can it detect? Not far enough to turn, I think.... but I haven't tested yet. But here is my bigger worry, and I have not tested them, but I suspect since the sonar is sound, that flying into air at 30+ Kt/h, that the sonar might just not work at all. I was going to test in my car, but I do not want to drive towards something at 30mph to see if the sonar detects... I only have max 70m to test, or about 30m before I have to turn or stop. So I was just going to build it and use my quad to start testing. And in any case, I know that there is a plan to try sonar for landing flare, so that is more argument to at least try with a sonar for now.

 

I think, maybe, optical flow sensors will be a good plan, during the day time. But with my plan to use a separate processor board, I can, in theory, use all four for different purposes. I can use a laser for long distances in front and maybe pointing down (on the bottom of the camera, for accurate survey data collection)  I can make a lidar for the forward motion, and collect mapping data of obstacles at that elevation. I can use IR and sonar for landing altitude control for minimums, and laser for higher elevations, with the baro, and also to help calibrate the baro maybe?) and I can use optical flow sensors for collision avoidance (and fall back to ultrasound and lasers for night flights

 

But of course these are just ideas, and I will never get to all of them, and hopefully I will have better ideas. But I can have ideas all day long.... I have to keep building too... which is why I said that my specific problem is not solved with this sonar idea, to add to your Low Altitude limit (and also because there will be many challenges, even if I can make it work.... I know this from other robot projects years ago... if you add simple algorithms for input and behavior, sometimes very strange things appear to happen for conditions you did not think of. 

 

And that is the most interesting thing about robotics for me. When it begins to sense its environment, and you try to give it a general set of rules, and see how it behaves in the real world with real sensors and messy places.

Comment by Michael Pursifull on October 10, 2011 at 2:30am

Most IR sensors just do not have the range. They should work great for the last part of the landing, and also for very low terrain following (they will not, however work well for collision avoidance... you can easily fly into a pole or a tree ... too short distance, even if it was not a narrow beam.)

 

But once you have a laser, since it is not sound, and it is not optical processing, because it is light, you can move it very fast side to side, and record the angle and distance. Now you have LIDAR. And LIDAR is outstanding for trees, hills, buildings, glass, people, birds, other airplanes, terrain following (if you dedicate it and point it the right direction, but I would not because I can only carry one, and it is more valuable for other things) and for environment mapping. But the problem is, LIDAR is expensive, and not just in terms of money. You have to drive a powerful laser, and also drive a servo or motor all the time, and pretty fast, if you are not a quad and if you want good enough data to fly fast. So you cannot expect to have 360 degree LIDAR; but you can mix these sensors, and even control all of them from one board ... and just give a packet of data to the APM with i2c, and record the mapping data in more detail to a chip on the controller board or something. 

 

If you have just a little more processing power, you can also build a confidence table with the mapping data, and let the collision board "predict" obstacles based on previous readings. Then you can fly faster than your sensors can detect, if you have reason to believe that environment has not changed much. If you think about it, it is what humans do ... imagine you are training for a race, you walk the course, also in parker, winter olympic sports - learning the turns... same thing. But what is important for us is imagine the what it could do for videographers like TBS, for fast movie filming (rather than program the path, you tell it to map the environment, then you give it a basic path, and tell it to stay away from obstacles, and it can go faster and faster, until it can race with the stuntman as he falls....

 

Well, anyway, lots of ideas. But I have basic problems to solve, so those ideas are only good to plan the next tiny step.

Comment by Michael Pursifull on October 10, 2011 at 2:33am

sorry if I sound like I am teaching... I know you understand all the technology, I only share my thinking because I get excited to share the idea that goes with it, and so have to share my understanding of how it might work so we both are talking about the same thing.

 

I have learned good things from listening to you about this. And thank you for working on the low altitude limit!

Comment by YureZzZ on October 10, 2011 at 6:44am

Have you thought about using Bee Vision stuff? It is small and could be pretty accurate.

Comment by Mike on October 25, 2011 at 8:58am

Excellent work getting your code into APM YureZzZ, I'm looking forward to the next release so I can test it out.

 

Do you have any plans for your next project? ;)

 

 

Comment by YureZzZ on December 30, 2011 at 5:58am

I've added wiki page about this feature. Can be found here.

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