Angle measurement for balancing robot.

[Archangel]

Because you are moving the part with the lower mass

[Ioannis]

That's right. It is easier to adjust something with lower mass than the Lead-Acid Batteries!

Also putting the accelerator sensors down, produces less spastic movements of the motors. Inertia of the highest parts takes care of the rest.

It is a very impresive project and needs good close loop control design. Although I don't know if it worths it since the energy to accomplish that is way to high.

But, on the other hand, for the wow's that the designer is going to accept, may be it is worth it!

Ioannis

[uffi]

Hi Henrik,

thanks for the file and the link. I downloaded all the stuff from the nuts 'n volts FTP server. Obviously these guys creating B-Bot have adapted some code originally developed for the helicopter autopilot on sourceforge. Thank you again.

Regarding my implementation: no, I am working on a C-code implementation for the ATMEGA16 to be compiled with win-avr or gcc, resp.

When you adapt my formulas for the tilt angle from accelerometer data, please care for the fact, that the accelerometers have different sign for dynamic and static acceleration. This fact is not yet considered in my formulas. So the sign of "a" must be inverted for the real measurements.

Have you done any work on implementing my formulas?

Kind regards, uffi.

[HenrikOlsson]

Hi Uffi,

Regarding my implementation: no, I am working on a C-code implementation for the ATMEGA16 to be compiled with win-avr or gcc, resp.

Oh crap, yet another C implementation....and not even for PIC... ;-) I've started to look at C for PIC's but that's not a topic for this forum.

Yes, the Kalman code comes from the UAV project. I have not had time to work on implementing your formulas yet but thanks for the pointer on the sign of the acceleromter readings. I'm not sure the accelerometer formulas will work with the sensor I got now. It is a two axis accelerometer, X and Y but I'm not sure how it will respond if mounted so it "becomes" X & Z. I will have to experiment with that too.

I got the SHARP sensors yesterday and managed to get the robot balancing fairly well. It's still a little "nervous" but I think I'll get it better by filtering the readings and/or experimenting with the sensors mounting. The goal, however, is the acceleromter/gyro aproach since the SHARP sensors introduce too many drawbacks IMO. But hey, atleast it works!

Thanks!
/Henrik Olsson.

[InitialDriveGTR]

If you need gyros, try the analod devices ADIS16250 or ADIS16255

[sayzer]

Henrik,

Do you need 180º or 360º for your angle measurement?

I "think" it should be 180º.

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[HenrikOlsson]

Hi,
I'd say +/-45 degrees from "down" will be more than enough. The problem, again, is that it needs (I'd like it) to be an absolute value in reference to gravity.

/Henrik Olsson.