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

[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.

[Tristan Lall]

Originally Posted by Alan Anderson

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).

I agree with respect to ring laser gyros—in fact, those are specifically permitted per the 2011 rules.

The definition question depends on the conditions under which the laser is "exposed". Couldn't you argue that because the robot is designed to point the laser at the floor from within a shielded enclosure, that the combination of floor and robot serve to completely enclose the laser? Does the presence of an obvious failure mode (overturning the robot) negate this argument? (And what if the robot compensates for this by shuttering the laser as this failure is detected?) And given that <R02> is a safety rule, is exposure defined in terms of exposure to the surroundings in general, to humans, or to the laser-sensitive parts of humans (eyes, for ordinary lasers)? Furthermore, given that lasers are (almost completely) collimated, if the start and end points of a laser are not directly in any plausible line of sight (e.g. a laser beam across an opening in the robot), is that considered exposed? And what about reflected (i.e. substantially less collimated) light from a laser? Does that figure into exposure? Finally, there's the pedantic question of whether the rule is referring to a laser (the device), the aperture of a laser device, a beam of laser light, or some combination of those, when it talks about exposure.

It's not that your interpretation is unreasonable—quite the opposite. It's just that there are a number of other interpretations that might plausibly have been intended.

[Alan Anderson]

Originally Posted by Tristan Lall

Couldn't you argue that because the robot is designed to point the laser at the floor from within a shielded enclosure, that the combination of floor and robot serve to completely enclose the laser?

I reject that argument. The laser in that application is designed to shine on something outside the robot (e.g. the floor). Only an exposed laser could do that. As you point out, if the floor isn't where it's supposed to be, the light escapes.

And given that <R02> is a safety rule, is exposure defined in terms of exposure to the surroundings in general, to humans, or to the laser-sensitive parts of humans (eyes, for ordinary lasers)?

Without further detail in the rule, it has to be interpreted as the most general possibility. While one could reasonably assume that eyes won't be underneath or inside a robot during a match, a reflective surface could be anywhere.

Finally, there's the pedantic question of whether the rule is referring to a laser (the device), the aperture of a laser device, a beam of laser light, or some combination of those, when it talks about exposure.

I think the only reasonable answer to that question is the thing which makes a laser distinct from any other component: the laser light itself.

An easy relaxation to the "no lasers" rule would be to permit the equivalent of a cheap laser pointer by limiting the power of any emitted beam to a safe level (i.e. Class 1).

[Garrett.d.w]

I am pretty sure that this was mentioned before, but because it is continuously mentioned in this thread I would like to restate it. What most people refer to as a "Laser" mouse, is really just a camera pointed down at a flat surface that tracks the movement of the unit. The red light that you see coming out of the mouse ("laser") is an LED that illuminates the surface for easier tracking. There are a few true laser mice out there that replace the LED with a laser and use a slightly different type of camera, however, these are few and far between (I can only think of 3 or 4 models).

Because most "laser" mice don't actually contain a laser, just a camera and a red LED, I am pretty sure that they are legal as long as they abide by the rules governing custom circuits.

[EricVanWyk]

Originally Posted by Alan Anderson

Which rule would rule them out?

Originally Posted by Garrett.d.w

The red light that you see coming out of the mouse ("laser") is an LED that illuminates the surface for easier tracking. There are a few true laser mice out there that replace the LED with a laser and use a slightly different type of camera, however, these are few and far between (I can only think of 3 or 4 models).

My apologies - the models I have worked with had actual lasers.

[Ether]

Originally Posted by Ether

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

I forgot to post the computation for Vn:

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