Quote:
Originally Posted by John Gutmann
Ok, so I have spent a few hours playing with this. calculating the bias is working well. I added a tolerance constant. This works very well. One thing I noticed is because of my awkward neutral value the linearity of this is well....not linear any more so I had to add in scaling values because it will be mostly consistent in either direction, but the mV/deg/sec isn't the same for above and below the neutral value. It is more or less decent for getting in the ballpark. But I am beginning to think just by the behavior of the device that it is broken in some way. I know it is a VERY old gyro that i got from my team at least 2 years ago. So I am going to see what it is going to take to get a new working gyro from somewhere. This way I won't be programming in circles.
-John
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Hey John,
I wouldn't jump to the conclusion that your Gyro is bad yet. Let me explain why. I have been playing with my Gyro and Arduino set up most of the day. I seem to be stuck on virtually the same situation that you seem to be seeing. Simply put, when I rotate my Gyro 180° in a positive direction, I will get approximately 180° read out from the software. When I rotate it in a negative direction I do not get the same -180°. So when I rotate it forward 180 and then backward 180° I always end up with a total somewhere near five to 10°. If I continue to rotate the Gyro back-and-forth 180° I continue to increase my total about 10° positive every repetition.
What I seem to be seeing it a nonlinearity of the output when rotating clockwise and counterclockwise. I have observed this behavior in the past with Analog Device gyros, both the 150 and 300° percent conversion. Although, I have never seen it to this extent. I do know when this particular chip that I have had this problem in the past, but because I was using it for prototyping I wasn't too concerned about it. It may just be a characteristic of this particular chip.
When building the navigation system for our robot this year, we used an Analog Devices' 300° per second gyro. It did exhibit this behavior but too much lesser extent. Because the only plan on using the Gyro for returning the robot in one direction, we did not feel that it was worth worrying about. Besides the air we would get with less than 1°.
So what I'm looking for now is a way to compensate for what appears to be the nonlinearity of this Gyro.