Optical Mouse Navigation

[Craig Putnam]

Originally Posted by gnormhurst

Devil's Advocate here again...

Is there a findamental problem with using an optical mouse? The mouse reports a delta distance since the previous frame, as best as it can determine by performing a correlation between the current and the previous frame. But any fractional part of that measurement is not carried forward to the next measurement, and is lost.

...snip...

-Norm

It certainly is a legitimate concern, but I think in the grand scheme of things it will turn out to be a non-issue.

I am *not* using the mouse to give me lateral distances (call it the x-axis offset distance) in part for the reasons you have stated. Rather, I am using a rate gyro to tell me how much rotation the robot has experienced in the most recent time interval. I use the mouse to give me just the y-axis offset, i.e., distance traveled. A little trig and a couple of approximations later I can calculate a lateral offset which *is* accumulated.

The real question is: How much error will accumulate during autonomous mode using the <whatever> navigation system, and is it so much that the <whatever> navigation system is not reliable? Obviously all of these different systems have their individual strengths and weaknesses.

If during the (presumed) 30 seconds of autonomouse mode (good grief, I don't believe my fingers just typed that - but I like it!) - if during that time period the robot is only off by a couple inches then I will be ecstatic. [ I calculate that my refitted mouse should have a 1/4" resolution. We'll see if that holds up or not... ]

The wheel encoder system we used last year had about a 6 inch resolution. I know that much greater resolution is possible using wheel encoders, but that's what we had. So if the optical mouse works better, then great. If it doesn't work better, then maybe we all learned something.