Re: Which sensors should be used throughout the robot?
 

For a non-drifting gyro we use the NavX which only drifts 2 or 3 degrees in a match. If you wanted to track position you could doubly integrate an accelerometer and combine that with the gyro, but again you will need a good accelerometer as doubly integrating adds even more opportunity for accumulated error.

Re: Which sensors should be used throughout the robot?
 

That is a lot more positive then the last comment... I'll try the NavX... Do you think that triangulation is a possible option? Maybe with a fisheye camera on top of a bot or something like that...

Re: Which sensors should be used throughout the robot?
 

Far better than integrating an accelerometer would be a non-driven omni wheel to track position

Re: Which sensors should be used throughout the robot?
 

But if the wheel slips?

Re: Which sensors should be used throughout the robot?
 

As long as it isn't driven and is spring loaded down there should be no slip

Re: Which sensors should be used throughout the robot?
 

Anecdotally, the new NavX firmware improves upon that drift. ;)

I don't know that triangulation is the right term for this. I think you might be after something similar to Simultaneous Localization And Mapping (SLAM). SLAM is becoming more common in consumer and hobbyist robotics but it's still early days yet. I can tell you that it is something to keep digging into but I'm not sure it is the best area to invest resources into for an FRC team. It is definitely cool stuff though.

Re: Which sensors should be used throughout the robot?
 

The triangulation approach you mention has been done w/active landmarks like wireless beacons (requiring installation of multiple wifi transmitters), passive landmarks (well-known "checkerboard" patterns at well-known positions, w/identification/range calculated by a scanning camera), and by systems not dependent upon landmarks, including range-finding vision sensors (stereoscopic cameras, structured light sensors like Kinect [which are very short range, e.g. a living room], scanning LIDAR sensors, and scanning (or alternatively fisheye lens, as you say) video camers w/image recognition.

The optical approaches are non-trivial, rarely used in FIRST, and typically considered university-level. So a lot of folks tend to get a funny look on their face when these topics are discussed, and wonder why we're making things so complicated. :)

The algorthms for localization are becoming more and more available online, and there's free online courseware from MIT in probabilistic localization and related technologies.

More close to home, the Zebracorns have published as open source their 2015 vision software, which used OpenCV-based classifiers that were trained to recognize game pieces, pushing forward the State of the Art in vision processing in FIRST. If the same approach were used to recognize fixed-position field pieces, and then range to those objects was calculated and fused w/a map of the field (known ahead of time, in FIRST), you'd have what you were looking for. Again, not-trivial, but for those with interest, worth looking into in my opinion.

Looking ahead, a colleague of mine pointed out this fascinating new research from MIT that fuses object recognition with SLAM.

Re: Which sensors should be used throughout the robot?
 

I just thought of something (apologies if it has already been mentioned and I've missed it), could you not use a hall effect sensors to count wheel revolutions? It seems like a simpler solution than using a banner sensor.

Re: Which sensors should be used throughout the robot?
 

We did this in 2014 on our swerve modules. 6 neodymium magnets were mounted alternating north south on the under side of the 3.5" timming belt pulley. A Melexis US2881 Latching hall sensor was then used to give a non-contact solution. A counter was used set up for counting on the rising and falling edge. We used this to measure distance traveled. This year we used these boards.
https://www.pololu.com/product/2458
12 strips of KOP retroflective tape were mounted under the pulley. Although this is listed as an analog device, The c-rio did the chopping on a digital input set up as a counter.

Re: Which sensors should be used throughout the robot?
 

I noticed that we haven't mentioned using camera in this thread. What cameras have teams used, and how have they found them?

Re: Which sensors should be used throughout the robot?
 

Just to clarify - a "limit switch" is not a special kind of switch, it's a switch that we use to limit motion. One doesn't buy a "limit switch", you choose among microswitches, optical switches, magnetic [reed] switches, ..., for a switch that mechanically fits and triggers at that point in the motion of whatever you need to stop on your robot. They are not wired directly to a motor, but to a Digital Input on the roboRIO/cRIO/Arduino, etc. The program running on that computer will sense that the switch has opened/closed and will control that motor's Jaguar/Victor/Talon speed controller appropriately.

Re: Which sensors should be used throughout the robot?
 

Oh, geez, let's not do this - anchoring the housing/body of the encoder via securing its wires (and I've seen it). If you're using an encoder with 360 counts/rev for example, a wobble of one degree is one count. Although we're not going to use them ($$$) encoders are available with > 10K counts/rev. and imagine the error if it's poorly mounted. What you are learning (and I'm supposed to be teaching) should be applicable to an engineering job. Please mount encoders such that the threads on its body go through an appropriately-sized hole, and secure it with the lock washer and nut that come with the encoder. Have this in your CAD!

It's a good idea to mark the position of the encoder on its mount by drawing a line (sharpie, etc.) from the body of the encoder onto its bracket/panel, same thing for a pot. That way, if it comes loose (as did ours at Champs in 2010) you can put it back in about the right place, until you have time between matches to accurately remount it.

Re: Which sensors should be used throughout the robot?
 

It seemed to work well enough for 254 😜

Re: Which sensors should be used throughout the robot?
 

They have also since said that they have implemented more secure techniques to deal with the backlash.

Re: Which sensors should be used throughout the robot?
 

It's also going to work in your first engineering job if your goal is not to get a raise :)