Team Update #18

[EricH]

http://usfirst.org/uploadedFiles/Rob...pdate%2018.pdf

It's a real game-changer...

Spoiler for :

Minibot scoring will be automated from here on out, and watch out for the bolts on the bottom target.

[Tyler Hicks]

Can you imagine how this will effect the Finals on Einstein? You know there are going to be minibots that are almost equal speed...

[bearbot]

no!!! thanks FIRST that you make it clear i like updates and seeing this from what you learned in previous week but cant this wait till championship

[Cory]

Not a fan. Witnessed MANY minibot climbs this weekend at San Diego that most certainly imparted 3-4 N of force yet were not auto triggered. It's going to suck when the field fails to work correctly and teams lose points they should have earned.

[Vikesrock]

I saw far too many missed triggers (at least they appeared to be) on webcast this past weekend to be comfortable with this update going into our event this week.

[JB987]

Originally Posted by Cory

Not a fan. Witnessed MANY minibot climbs this weekend at San Diego that most certainly imparted 3-4 N of force yet were not auto triggered. It's going to suck when the field fails to work correctly and teams lose points they should have earned.

I agree, Cory. More than once a 1 second minibot with significant momentum failed to trigger. Is it possible that the triggers still need too much contact time to register? BTW, we had a great time partnering with you guys and 3704!

[Eagleeyedan]

Originally Posted by Cory

Not a fan. Witnessed MANY minibot climbs this weekend at San Diego that most certainly imparted 3-4 N of force yet were not auto triggered. It's going to suck when the field fails to work correctly and teams lose points they should have earned.

When that happened at the WI regional, the refs manually triggered it.

[AdamHeard]

Originally Posted by JB987

I agree, Cory. More than once a 1 second minibot with significant momentum failed to trigger. Is it possible that the triggers still need too much contact time to register? BTW, we had a great time partnering with you guys and 3704!

Not a fan as well, we ran our minibot at around 2 seconds at san diego and it impacted with well over 2 newtons of force. It would certainly hurt to get hit by it.

We've since increased the speed a lot, more along the lines of 254, and the impact is pretty violent.

[alectronic]

Originally Posted by JB987

Is it possible that the triggers still need too much contact time to register? BTW, we had a great time partnering with you guys and 3704!

The triggers are designed with multiple sensors, and the FMS only looks for 1 of those to be triggered for any amount of time. Thus making the minimal amount of force still trip the tower. The towers have been tested and proved to be much more accurate since week 1, so I think this should be a non-issue now at week 3.

[Cory]

Originally Posted by techalex

The triggers are designed with multiple sensors, and the FMS only looks for 1 of those to be triggered for any amount of time. Thus making the minimal amount of force still trip the tower. The towers have been tested and proved to be much more accurate since week 1, so I think this should be a non-issue now at week 3.

Someone in another thread on Chief commented that the towers are now looking for a triggered sensor for a certain amount of time to be sure it wasn't just a jostle from a robot.

Whatever the circuitry I am 100% confident that there were multiple (greater than 10) instances at San Diego where minibots compressed the platform upwards into the sensors without the tower actually triggering.

[JB987]

Originally Posted by Cory

Someone in another thread on Chief commented that the towers are now looking for a triggered sensor for a certain amount of time to be sure it wasn't just a jostle from a robot.

Whatever the circuitry I am 100% confident that there were multiple (greater than 10) instances at San Diego where minibots compressed the platform upwards into the sensors without the tower actually triggering.

Seconded!

[Daniel_LaFleur]

Originally Posted by Cory

Someone in another thread on Chief commented that the towers are now looking for a triggered sensor for a certain amount of time to be sure it wasn't just a jostle from a robot.

Whatever the circuitry I am 100% confident that there were multiple (greater than 10) instances at San Diego where minibots compressed the platform upwards into the sensors without the tower actually triggering.

Do you have proof that enough force was exerted? or is this just your 'gut feeling'?

[Karibou]

Originally Posted by Cory

Someone in another thread on Chief commented that the towers are now looking for a triggered sensor for a certain amount of time to be sure it wasn't just a jostle from a robot.

Whatever the circuitry I am 100% confident that there were multiple (greater than 10) instances at San Diego where minibots compressed the platform upwards into the sensors without the tower actually triggering.

Do you know what thread that was? I'm curious about how that would work without limit switches.

The sensitivity of the towers now is highly dependent on how the field crew that implemented the fix did it. Really, what the minibots are doing now are pushing the bottom plate up about a quarter of an inch. However, that distance may vary depending on how meticulously the field crew assembled the plates. I was told to get up on the ladder on Saturday morning and adjust the distance a little bit more and make sure that the distances were equal, but it was only by an eighth of an inch by so. FIRST's solution works, as long as the instructions are followed to the T.

[Cory]

Originally Posted by Daniel_LaFleur

Do you have proof that enough force was exerted? or is this just your 'gut feeling'?

I could do the math for a 2.5 lb object moving 10 ft/s hitting that plate and you'd see it's more than 3-4 N, but if the plate is being violently slammed into the top plate such that you can hear it from the stands, I'd say it's a pretty safe bet they were triggered. Additionally we have 4 official towers and I can confirm that every single time ours goes up the pole it depresses the limit switches, but twice this weekend it did not show the tower as triggered at San Diego.

It seems pretty clear there are still problems with the field and I don't just say this because the tower failed to trigger with our minibot. It was a very common occurrence.

[pfreivald]

Assuming a .5 kg minibot can climb 10 feet (about 3 m) in 2 seconds, and that the plate depresses at most 2 cm (0.02 m), this means that its average (not top) speed is about 1.5 m/s and:

Using the work-energy theorem,

W = KE
F*d = .5(m)v^2
F = .5 (m)(v^2)/d
F = [.5 (.5 kg) (1.5 m/s)^2]/.02 m
F = 28 N

...is (actually less than) the average force needed to stop said minibot (because 1.5 m/s is the average speed, and not the top speed). If the compression distance is less, the average force will be higher. If the minibot is faster than 2 s, then the average force will be higher. If the minibot is more massive than 0.5 kg, then the average force will be higher...

...which means that, if the towers are doing their jobs properly, no one with what I would consider a "competitive" minibot has anything to worry about -- and if they DO NOT trigger the towers, then we have direct evidence that the specifications given (2-4 N of force to trigger) are simply wrong.

I'm quite tired, and didn't put much thought into this. Anyone want to poke holes in my analysis?