Angle measurement for balancing robot.

[HenrikOlsson]

Thank you for the link, Darrel. I'll read the code and the .pdf Tom says he based it on and see if may work. I'm not sure in what way it resembles the Kalman filter. Since I don't really understand how the Kalman filter works that may or may not make any difference.... ;-)

Arnie, thanks for the sugestion. However, reading the datasheet for the Accustar I came to the conclusion (from the description of how it works and please do correct me if I'm wrong here) that it will suffer from the same problem as the acceleromter. It would work when it's stationary and rotated around its own axis but as soon as it is exposed to a "another" acceleration (except gravity) (robot starts to move) the reading will no longer reflect the true angle of the platform.

The only one I've found that would work is the FAS-G from Microstrain (which contains an acceleromter, gyro and uC) but it's WAY to expensive.

Please keep the suggestions coming. I have some more reading to do.

Thanks!

/Henrik Olsson.

[HenrikOlsson]

Hi again,
I read Tom's code and the pdf he based it on. Turns out that his code is not based on the Kalman filter but a "simpler" weighted average filter which is actually what I'm using. The pdf shows the code for the Kalman filter but it is again in C which doesn't make it very easy for me.....

What's that saying, it's the last 10% of the project that takes 90% of the time - the devil certanly IS in the details.

/Henrik Olsson.

[Luciano]

Hi,

See the PDF file below.

Adjustable weight position, shock resistant.

Swiss Made! (This is a special note for Alain).

PDF doc:
http://leiwww.epfl.ch/publications/g...fer_mic_01.pdf

See the movies:
http://leiwww.epfl.ch/joe/

Best regards,

Luciano

[HenrikOlsson]

Hi Luciano,
Yep, seen that one before too, very cool and seems to work extremely well. The problem again is that the math described in that pdf is so over my head that I can't even begin to understand it. I was hoping that someone (with enough math skills) already had wrote a routine or ported one of the available routines to PBP.

Thanks!
/Henrik Olsson.

[Ioannis]

Just out of curiosity...
How will the robot rise if it is in a initial horizontal position? Alone I think, will not!

Anyway, JOE is very impressive!

The PBP in my opinion is a little slow for the required math.

Ioannis

[sayzer]

Just out of curiosity...
How will the robot rise if it is in a initial horizontal position? Alone I think, will not!
....

A second one will help it to stand up of course!
Like a for loop.

IF the second one is also at initial position THEN NEXT.

---------------------

[Ioannis]

Aha! Good idea Sayzer!

Ioannis

[HenrikOlsson]

Ioannis,
I don't think Joe can stand from a horisontal position on it's own. If I ever get mine to work it will hopefully be something like this one:

http://www-robotics.cs.umass.edu/Res...uBot/uBot.html

In one of the videos they show how it recovers from its "resting" position. Very cool and stable two wheeler.

The math seems to range from rather complicated to extremly complicated. Since my mathskills are rather (very, in this case) limited I'm aming for complicated at the most. I'm confident it CAN be done with PBP i just have to understand HOW it works.

I have quadrature encoders mounted on the wheels and I'm thinking I can calculate the robots acceleration by comparing current speed with previous speed and subtract that from the acceleromter reading ending up with 'pure' tilt. My concern now is that the resolution of the encoders are to low. But hopefully I'll be able to understand this Kalman thing any year now..... ;-/

Atleast it's a fun project :-)

/Henrik Olsson.