RoboSavvy Forum

First step towards cheapo IMU.

2008-09-12T22:05:48+01:00

I couldn't resist.. I ordered a lot of 20 "gyromouse pro" off of ebay. So if anyone is looking to get there hands on a MG100 2-axis gyro sensor let me know and we can work something out.

Here's the spec..

http://bobodyne.com/web-docs/robots/Tri ... 100s~1.pdf

Here's what it looks like inside..

http://www.worldwideflood.com/ark/model ... _model.htm

I'll post progress with the sensor as I make it.

Statistics: Posted by billyzelsnack — Fri Sep 12, 2008 10:05 pm

First step towards cheapo IMU.

2008-09-12T21:40:12+01:00

The sensor is the one mounted on that little standoff? It's an accelerometer/magnetometer on a single chip. Cool.

What happens if you have the compass just next to the robot while it is running? Not that that is real world or anything, but it would show how the sensor is effected by the robot's magnetic fields.

Statistics: Posted by billyzelsnack — Fri Sep 12, 2008 9:40 pm

First step towards cheapo IMU.

2008-09-12T18:07:13+01:00

I did now...

Here's a graph showing heading over time, as MicroRaptor went from a squat to a stand, and then back again, with pauses in between. The compass was mounted about an inch from one of the AX-12 servos that was moving during these two sequences. I'm sampling the compass heading at 4 Hz in this example.

Almost certainly some of this variance is due to the accelerometer inside the compass module getting jolted as the robot moved. Without having a 2-axis non-tilt compass to compare to, I can't say how much is magnetic interference and how much is strictly motion.

Here's a pic showing where the compass is mounted:

- Jon

Statistics: Posted by JonHylands — Fri Sep 12, 2008 6:07 pm

First step towards cheapo IMU.

2008-09-12T06:12:51+01:00

JonHylands wrote:
I'll try and do a test with it mounted on MicroRaptor soon...

- Jon

Did you do the test yet? I'm really interested in how much interference a bioloid based robot will create. I'm thinking of ordering one of these..

http://www.pnicorp.com/products/all/sen-xy

and want to know if I should even bother if the interfence is going to make the data useless.

Statistics: Posted by billyzelsnack — Fri Sep 12, 2008 6:12 am

First step towards cheapo IMU.

2008-08-31T06:50:59+01:00

Ok this is funny..

http://www.murata.com/catalog/s42e.pdf

Apparently that's the gyro in the SIXAXIS. Which I think is the same gyro inside the RC heli gyro I've been messing with. Which also is the same gyro that's in lower end heli 4-in-1 controllers. So I have literally 8 of these things laying around in my workshop. haha.

So after looking at that spec and then looking at the actual gyro on the RC gyro board.. 4 pins!!! How did I not notice this before. I can easily just unsolder it and not mess around with reading the PWM! I guess it is nice to be able to read it because that makes it plug and play with my high-end heli gyros when I end up daring to test them.

One other thing.. I also saw in my readings ( and mentioned in that pdf above ) that you can't put multiple gyros in the same circuit. I guess they mess with each other. Hopefully that's just power and they can share the same ground.

Statistics: Posted by billyzelsnack — Sun Aug 31, 2008 6:50 am

First step towards cheapo IMU.

2008-08-31T06:29:22+01:00

PS3 gamepads have a 3 axis accelerometer ( I knew that ) AND a gyro! Combined with bluetooth this might be a pretty easy ( almost ) solution.

IF YOU CAN GET IT TO WORK. haha.

I tried for a couple of hours and could not get any of the various Windows drivers found via google searching to work.

The SIXAXIS controller is being discontinued so pretty soon it should be possible to find these suckers for cheap.

http://www.kako.com/neta/2006-018/2006-018.html
Could the gyro be the one with the connector!!!! Man. If so I am going to start buying broken controllers on ebay.

Statistics: Posted by billyzelsnack — Sun Aug 31, 2008 6:29 am

First step towards cheapo IMU.

2008-08-27T19:06:59+01:00

Yeah I know. I just thought it was funny that I go searching for some random thing to post in a thread that another Hylands would most likely read.

Statistics: Posted by billyzelsnack — Wed Aug 27, 2008 7:06 pm

First step towards cheapo IMU.

2008-08-27T12:36:30+01:00

billyzelsnack wrote:
haha..

Look at the author..

http://www.nabble.com/Re%3A-How-to-read ... 61252.html

Dave is my brother, in case you were wondering...

- Jon

Statistics: Posted by JonHylands — Wed Aug 27, 2008 12:36 pm

First step towards cheapo IMU.

2008-08-27T07:18:21+01:00

More much infos and a much more elaborate method..

http://homepages.which.net/~paul.hills/ ... coder.html

Statistics: Posted by billyzelsnack — Wed Aug 27, 2008 7:18 am

First step towards cheapo IMU.

2008-08-27T07:04:28+01:00

More infos on converting PWM to analog.

http://www.ontrak.net/pwm.htm

Statistics: Posted by billyzelsnack — Wed Aug 27, 2008 7:04 am

First step towards cheapo IMU.

2008-08-27T07:00:16+01:00

haha..

Look at the author..

http://www.nabble.com/Re%3A-How-to-read ... 61252.html

Statistics: Posted by billyzelsnack — Wed Aug 27, 2008 7:00 am

First step towards cheapo IMU.

2008-08-27T06:52:09+01:00

I was messing around with getting data out of heli gyros again tonight. I came across this post..

http://www.arduino.cc/cgi-bin/yabb2/YaB ... 926139/1#1

Grabbing data this way would be nice because the load on the uc is not much so it scales better for sampling multiple gyros.

I gave it a go and it didn't work out so well. I would get many different values and they may or may not of been changing in response to mucking the gyros. My electronics skill is zero so this probably is way off, but would I need to be sampling this at a specific rate? I guess I don't understand how it magically turns the digital PWM into a single analog value.

Statistics: Posted by billyzelsnack — Wed Aug 27, 2008 6:52 am

First step towards cheapo IMU.

2008-08-26T22:02:40+01:00

This is an example data set, with the compass board held down in one place:

Code:: Heading: 286.9 Pitch: 2.1 Roll: 0.3 Heading: 287.6 Pitch: 2.2 Roll: 0.2 Heading: 287.4 Pitch: 2.2 Roll: 0.5 Heading: 286.8 Pitch: 2.1 Roll: 0.3 Heading: 285.9 Pitch: 1.8 Roll: 0.4 Heading: 287.0 Pitch: 2.1 Roll: 0.3 Heading: 287.6 Pitch: 2.3 Roll: 0.3 Heading: 286.7 Pitch: 2.1 Roll: 0.4 Heading: 287.1 Pitch: 2.1 Roll: 0.4 Heading: 287.3 Pitch: 2.2 Roll: 0.4 Heading: 287.3 Pitch: 2.2 Roll: 0.2 Heading: 286.0 Pitch: 1.8 Roll: 0.3 Heading: 286.6 Pitch: 1.9 Roll: 0.3 Heading: 286.9 Pitch: 2.0 Roll: 0.3 Heading: 287.3 Pitch: 2.2 Roll: 0.2 Heading: 286.4 Pitch: 1.8 Roll: 0.5 Heading: 287.4 Pitch: 2.3 Roll: 0.3 Heading: 286.1 Pitch: 2.0 Roll: 0.3 Heading: 286.0 Pitch: 2.0 Roll: 0.0 Heading: 286.6 Pitch: 2.0 Roll: 0.2 Heading: 286.4 Pitch: 2.0 Roll: 0.3 Heading: 286.1 Pitch: 1.9 Roll: 0.3 Heading: 287.0 Pitch: 2.0 Roll: 0.3

The only point of having the accelerometer is to allow the actual level orientation to be extracted from the 3-axis magnetometer. Of course, if the compass is being bumped around a lot, you won't get a stable heading.

I'll try and do a test with it mounted on MicroRaptor soon...

- Jon

Statistics: Posted by JonHylands — Tue Aug 26, 2008 10:02 pm

First step towards cheapo IMU.

2008-08-26T19:34:48+01:00

So I went and did a little more research.

Looks like you don't get an 3 axis absolute orientation. It gives you basically the same data as an accelerometer except its data is not going to be corrupted by translations. However its data can be corrupted by nearby metal objects.

Statistics: Posted by billyzelsnack — Tue Aug 26, 2008 7:34 pm

First step towards cheapo IMU.

2008-08-26T19:16:36+01:00

Is the data consistently nice and clean? What about when near metal objects? What about near an operating Bioloid?

Looks like it gives you a heading/pitch/roll. So that's an actual absolute 3-axis orientation ( minus gimble lock? )? I don't fully understand the implication of adding in the magnetometer. What's your understanding of how it pairs with an accelerometer?

Statistics: Posted by billyzelsnack — Tue Aug 26, 2008 7:16 pm