Has anyone ever used a Computer Mouse to locate themselves on the field

[staplemonx]

I have worked on an inertia navigation system for aircraft (http://en.wikipedia.org/wiki/Inertial_navigation_system) and was thinking of how to do something similar on the cheap. Last year I was able to see how different teams located themselves on the field for autonomous systems. Some worked well and others, eh...

So I am curious if anyone has ever tried using one or more laser computer mice to replicate an INS system. As long as my tolerance is over 12 inches in the x and y it should work great. In fact if I put two or three on their and was really picky about my starting position I bet it could hold a tolerance of less than a few inches. It’s cheap, the drivers exist and it does not rely on any external references.

Any thoughts?

[rahilm]

I know team 972 tried this before they merged with our team in 2008. IIRC, they used just a mechanical mouse, where they had the ball running against the ground. I don't think they had all too much success, but it looked fairly promising. I think with laser mice, you will run into a similar problem of having to have it very close to the ground. This could have been a problem for the last two years (bumps + lip by goal for Breakaway, and lip by poles for Logomotion).

[staplemonx]

Originally Posted by rahilm

This could have been a problem for the last two years (bumps + lip by goal for Breakaway, and lip by poles for Logomotion).

That makes sense.

Good to know though.

Thanks

[EricH]

A few teams used a follower-wheel system in 2009, using unpowered omni wheels attached to encoders or something similar.

[Colin P]

Originally Posted by EricH

A few teams used a follower-wheel system in 2009, using unpowered omni wheels attached to encoders or something similar.

I know some of these were used for traction control. They would compare the rotation on their powered wheel encoders to the rotation in the unpowered wheel to see if they were actually moving as fast as they thought they were (if at all).
I know team 51 had some kind of location on their drivers station in 2010. I'm not sure why they used it, but it worked pretty well.

[lemiant]

This has been my pet project for a while. As long as your robot pivots around a single point and doesnt strafe, then a follower wheel and a high accuracy gyro should be able to integrate for position. Alternatively if you can find a high speed trackball (over 15fps, which I have so far been unable to do), you could use that and strafing wouldn't be an issue.

If you are really interested in using a laser mouse, i would suggest looking up the razor gaming mouse (as it is the only one that i know is fast enough), then milling it a plastic mount with rounded edges to get over bumps, and spiring tensioning the mount against the ground.

[DonRotolo]

(Laser mice don't actually use lasers. And in 2011 "lasers" were not allowed. FWIW.)

Anyway, if this were combined with some distance sensors (I'm thinking ultrasonic) you should be able to recalibrate your position from time to time, when conditions are 'right'. Add odometry and a 2-axis accelerometer and you might be onto something...

[lemiant]

Originally Posted by DonRotolo

(Laser mice don't actually use lasers. And in 2011 "lasers" were not allowed. FWIW.)

Anyway, if this were combined with some distance sensors (I'm thinking ultrasonic) you should be able to recalibrate your position from time to time, when conditions are 'right'. Add odometry and a 2-axis accelerometer and you might be onto something...

Why so many sensors? Im especially interested in the accelerometers, how would you use them? An accelerometer is pretty much useless for tracking given our restrictions (as I'm sure the asker knows), since you needs an impressively accurate attitude value in order to filter out gravity.

EDIT: would laser mice be allowed in the 2011 rules?

[EricH]

Originally Posted by lemiant

Why so many sensors? Im especially interested in the accelerometers, how would you use them? An accelerometer is pretty much useless for tracking given our restrictions (as I'm sure the asker knows), since you needs an impressively accurate attitude value in order to filter out gravity.

EDIT: would laser mice be allowed in the 2011 rules?

<R02-D> prohibits any device with an exposed laser. I highly doubt that you could argue that the mouse's optics are not exposed.

BTW, a number of teams use accelerometers without any problems. Gravity is either accounted for or ignored, but the accelerometers are reasonable in cost and complexity.

[rahilm]

Originally Posted by EricH

<R02-D> prohibits any device with an exposed laser. I highly doubt that you could argue that the mouse's optics are not exposed.

BTW, a number of teams use accelerometers without any problems. Gravity is either accounted for or ignored, but the accelerometers are reasonable in cost and complexity.

Using accelerometers to yield position though would be fairly inaccurate. Integrating once to get velocity shouldn't be too bad, but the second integration won't be too accurate, especially considering that you're going to be 1 processor cycle behind (time wise) on position.

Edit: This is what I mean by being 1 processor cycle behind. To integrate, you basically have to use Reimann sums in this case. For best accuracy, you'd want trapezoidal sums, so for 1 position value, you need 2 velocity values, so 3 acceleration values. This means you'd have to integrate acceleration for 2 cycles to get the two velocity values required for a single position value, putting you 1 cycle behind realtime.

[Ether]

Originally Posted by rahilm

...you're going to be 1 processor cycle behind (time wise) on position.

Edit: This is what I mean by being 1 processor cycle behind. To integrate, you basically have to use Reimann sums in this case. For best accuracy, you'd want trapezoidal sums, so for 1 position value, you need 2 velocity values, so 3 acceleration values. This means you'd have to integrate acceleration for 2 cycles to get the two velocity values required for a single position value, putting you 1 cycle behind realtime.

Assuming that X₀ and V₀ are given, and assuming that the update period dt is short enough that the acceleration is accurately approximated as a linear function of time, then the position is given by:

X₁ = X₀ + dt*V₀ + dt²*(a₁ + 2*a₀)/6

X₂ = X₁ + dt*V₁ + dt²*(a₂ + 2*a₁)/6

.
.
.

X_n = X_n-1 + dt*V_n-1 + dt²*(a_n + 2*a_n-1)/6

[ratdude747]

my former team (1747) once considered trying the optical mouse routine in 2009. however, getting a mouse to track on the regolith while not touching the floor was next to impossible... and the need for it wasn't there in 2010. I was on a different team in 2011 and the idea was never mentioned

If one can get the robot and the mouse to communicate effectively, the rest is code, calibration, and some vectors. good luck on the project!

[Alan Anderson]

Originally Posted by Tristan Lall

The laser rules have been a bit of a mess in the past, but the general trend has been to prohibit them if exposed. ("Exposed" is ambiguous—exposed to what, when, and on purpose?)

It's clear to me that "exposed laser" means that the laser light itself can escape the assembly in which it is generated. A "laser ring gyro" which uses a sealed optical path would be permitted (as long as it satisfied all other rules, of course).

Originally Posted by EricVanWyk

Optical Mice would not be legal by last years rules.

Which rule would rule them out?

Originally Posted by EricVanWyk

We did some visual odometry using a pair of optical mice (chips) and different lenses a while back. We were only able to get it to work at fixed focal lengths - each length requiring a different lens. We were unable to get it to work with variable lengths, but I have to admit that optics isn't my strong suit.

The TechnoKats experiments with a "telephoto mouse" system showed early promise. We eventually found that the distance from sensor to carpet was a critical parameter, and a few millimeters of variation in height ruined the calibration between measured mouse motion and actual distance traveled. An FRC robot bounces enough while driving to make accurate odometry impractical.

[lemiant]

I think that if you placed a high speed mouse in a plastic mount with rounded sides to ride over obstacles and then pressed it against the floor with compression springs you might be able to make this work.

I have posted a CAD illustrating this (http://www.chiefdelphi.com/media/papers/2576?), and I tried to post some pictures, but for some reason they aren't showing up.

[FRC4ME]

In 2009 (Lunacy), 339 contacted a company that manufactured the optical sensors used in mice. They said they do not recommend their products for absolute motion tracking applications.

That doesn't mean a dedicated team couldn't get it to work, though.