Jump to content
Sign in to follow this  
gjestico

Helicopter altitude hold

Recommended Posts

I think your main problem will be deriving the attitude of the helicopter. Basically the same mechanism that controls your vertical thrust (that is your throttle and pitch) are directly coupled to your pitch and roll (that is the attitude). Furthermore, in order to control altitude, you will need to know your heli's attitude, so as to be able to know the thrust vector. In a sense you can think of your heli as a thrust unit with variable vector. So determining your vector relative to ground will be crucial.

The accelerometer should, in theory, provide you with the attitude information. Unfortunately it is also affected by lateral accelerations and cannot be relied upon to provide attitude information on it's own under all circumstances. So, your primary challenge, is not in getting the altitude at a sufficient precision since even a 1 feet resolution will be pretty good. It will be working out the attitude, and basically keeping the heli level.

Daniel

Share this post


Link to post
Share on other sites

Nice work :)

I don't see why using an accelerometer for sudden gust type changes and a pressure sensor to show the height should not work well together. As Daniel said though you must make sure the data is not corrupted by any other movements.

Terry

Share this post


Link to post
Share on other sites

The intention is to use this only in a stationary hover. I was hoping this would simplify things. Currently the device when engaged has control over the collective pitch channel, thus directly affecting the vertical lift force. This is on an electric heli so the motor speed control has a governor that keeps the rotor RPM steady state. Not looking to control the helis angular attitude whith this device.

Edited by gjestico

Share this post


Link to post
Share on other sites

gjestico,

Daniel's advice is right - you need to control the attitude. Instead of doing it manually (the cyclic... ;) ) why don't you use this:

http://www.helicommand.com/

and free up both your thumbs?

There are a bunch of demo videos on youtube and long threads both at rcgroups and runryder.com and the verdict is that it works surprizing well day and night/ cold or hot/ cloudy or not!

The basic version 3A is pretty affordable too and many are using it for professional aerial photography.

Dimitris

Share this post


Link to post
Share on other sites

Also to save you some trouble - I've attempted the same thing with an accelerometer in a supposedly stable hover. The way the accelerometer behaves with lateral acceleration makes it very difficult to use. It will hover for a second or two and the slightest lateral movement will avalanche into serious false data and cause the heli to flip over. So this is not just theory - it's actual test results, backed up by theory.

Daniel

Share this post


Link to post
Share on other sites
Also to save you some trouble - I've attempted the same thing with an accelerometer in a supposedly stable hover. The way the accelerometer behaves with lateral acceleration makes it very difficult to use. It will hover for a second or two and the slightest lateral movement will avalanche into serious false data and cause the heli to flip over. So this is not just theory - it's actual test results, backed up by theory.

Daniel

This baro based altitude hold seems to work well:

http://www.rcmovie.de/view_video.php?viewk...1cca159e48eceb2

Mike

Share this post


Link to post
Share on other sites

Yeah but it worksalong with the whole control system of the quadro - not usable on a heli without quite a few mods. Using the hardware for a heli could be a neat idea though.

Share this post


Link to post
Share on other sites
Yeah but it worksalong with the whole control system of the quadro - not usable on a heli without quite a few mods. Using the hardware for a heli could be a neat idea though.

Looks like another advantage for the quads.... B)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×