Re: Which sensors should be used throughout the robot?
 

^

A gryo can be a huge help in autonomous. Our team used a gryo in autonomous and it was very simple to make 90 degree or 180 degree turns, making it simple to implement turns/movements.

So to make life easier for autonomous, definitely consider using gyros. You won't have to rely on random numbers that you think will make it turn or move the way you want it to, instead you can rely on a sensor.

Re: Which sensors should be used throughout the robot?
 

We were possibly looking to use the Bosch BNO055, but we were unsure of how to connect it to the RoboRIO (via Arduino or otherwise). Can you please explain how you did it and how difficult it was to do.

Re: Which sensors should be used throughout the robot?
 

Looks like it is an I2C device so you could break out the pins to the RoboRIO. I'd probably avoid the arduino and go straight for a breakout like this one: http://www.adafruit.com/products/247...VwFxoCpIzw_wcB

If you want/need to do some formatting of the stream first then I suppose you could go the RIOduino and shield route:

http://www.andymark.com/product-p/am...tm&Click=35018
+
http://www.robotshop.com/en/arduino-...icIRoCJTXw_wcB

Re: Which sensors should be used throughout the robot?
 

From what we've done in previous years you can use limit switches to do a lot in a very simple way, so when you have boolean aplications, like an arm that only has two positions switches can do the job very well. This year we've used them to set a zero point on our elevator, this way every time it went back down the zero on our encoder would reset to avoid problems with it getting lost. Our team really likes to use this kind of limit switch http://www.amazon.com/ME-8108-Adjust...s=limit+switch they are very robust, adjustable and cheap, so we can keep it simple and still do a lot with them.

Re: Which sensors should be used throughout the robot?
 

I agree with a number of posters on this thread that limit switches are very good and extremely valuable in FRC robots.

However, I want to emphasize one item. Do NOT overlook the mechanical design of the switch actuation. I have seem too many (including our own robot in 2014) switches that were designed to be impacted by a mechanism, versus acting in a bypass fashion.

Thanks

Re: Which sensors should be used throughout the robot?
 

This is why hall effect, beam break, and inductive sensors are great! Non-contacting is the way to go.

Re: Which sensors should be used throughout the robot?
 

Just to clarify, you use a beam break by using a piece of tape to reflect its own laser back to it, and if that laser is not reflected, it returns a false value?

Re: Which sensors should be used throughout the robot?
 

It depends on the specific switch, and how it's wired.

Generally you decide based on what you want the failure mode to be. Do you want a disconnected/broken switch to read the same as seeing an object? Or do you want a broken/disconnected switch to read the same as never seeing an object.

Re: Which sensors should be used throughout the robot?
 

Yes, part of WPILib. I sent out patches in December ish, but there were too many other issues for the patches to get much attention.

With DMA, you get to read the captured data when you want. But, that capture can include both the signal that changed, all digital inputs, the timestamp of the event, all encoder values, all analog inputs, etc. If you are trying to correlate a digital input change to an encoder value, that delay is fine. If you are trying to correlate an analog input with an encoder at an edge, the delay is also fine. And by delay here, I mean up to 5 ms for our system, since we run our control loops at 200 hz and only pull out of the DMA buffer at that frequency.

Re: Which sensors should be used throughout the robot?
 

Say you planned to use a beam break to detect if a tote was in the robot or not. When the beam broke, you'd know it saw the tote. In that case, would you use the tape to reflect back to it?
Thanks!

Re: Which sensors should be used throughout the robot?
 

What would you guys use to know the position of the robot on the field at all time? And do you know any not drifting gyro?

Re: Which sensors should be used throughout the robot?
 

The gyros we've used tend to drift as well, but the drift isn't significant enough to mess up movements. (At least in autonomous) Our team only uses gyros in autonomous, and when autonomous initiates we reset the gyro in the code (so it resets the drift right when auto starts, so we don't have to worry about drift). Since auto usually is 10-15 seconds, the drift isn't significant enough to mess things up for us.

I don't know any gyros that don't drift.

Re: Which sensors should be used throughout the robot?
 

So it would be pretty hard to get a good measure during an entire match... Could we use something else to balance?

Re: Which sensors should be used throughout the robot?
 

This is something that's actually very difficult to do.

Pretty much any gyro within FRC budget is going to drift, at least a little bit. Things like the NavX, or 2 gyros stacked on top of each other upside down can help, but since a gyro is a rate sensor, getting angle requires integration, and any integral error just adds up and compounds, which is actually what creates the drift. A compass could work if the motors didn't create so much interference, but with FRC robots compass's are not reliable enough.

Position is difficult as well. Things like encoders on drive wheels can give a start to position, but since you need a gyro to detect angle, you still get error, plus if your wheel's slip everything goes bad fast. You could use a non driven wheel to measure, but those can slip too, and you still have the gyro error.

The only good options that would be within FRC price ranges would be something like a FIRST provided HD camera above the field, that teams could use to track their robots. But with current items, getting 100% accurate position and angle of the robot throughout an entire match is not easy, and I would say its not possible within the current budget and DS rule limits.

Re: Which sensors should be used throughout the robot?
 

That is a neat idea... Hard to realise but pretty cool :)

My goal is to create a semi-autonomous robot (or autonomous if possible)...