Hi,
I'm a complete newbie to this forum - can someone answer a question I have regarding altitude control?
If I understand the situation correctly, altitude control on the APM is achieved with GPS. Is this correct? I'm wondering if it would be possible, given the hardware available, whether it would be possible to integrate a second altitude sensor, e.g. sonar or laser, to help with landings or accurate low-altitude flight.
I think this will be particularly relevant as and when conventional helis start landing autonomously.
Cheers,
Nigel
Replies
I think the barometric variation and barometric issues in general have been well discussed previously - a search will reveal a wealth of interesting information and methods. I have commented previously on the danger of assuming that the variation in barometric pressure at ground level will vary little over the short period of a flight - probably less than an hour. However, here in Luanda, Angola the airport records show variations of greater than 10m over a one hour period on an almost daily basis - I was confused as I could not get a stable reading from my baro and after doing some research found out why!
Other issues:
- correction from a ground station helps a lot and I have used this system to make topographic surveys for new reservoir sites in Africa.
- sonar, at least the modules I have tried, will not work under a traditional helicpoter - simply too much noise. There is a model for outdoor, noisy environments and maybe that may work but the cost is prohibitive.
- in spite of what many many people and experts say I have had excellent results from a BMP085 under a traditional heli.
Cheers,
Mike
A short search will find that ACM and ArduPirates both have Sonar altitude control for low level flight.
Others are working on more ranged methods as sonar requires a fairly stable platform (no speedy movements), optical flow being one.