Team Update #18

[boomergeek]

Originally Posted by Ether

It could if implemented well.

If the minibot on the host is higher than the deployment line on the tower pole then in theory the difference in height is potential energy that gets converted into kinetic.

It all depends on whether the friction loss traveling the curve pipe is greater than the KE gain due to the added PE.

I think, in the context of the rule, it's irrelevant whether the the ramp on the hostbot starts above or below the deployment line. If the minbot loses gravitational potential on its run up to crossing into the cylinder of deployment, and the minibot design converts horizontal into vertical motion, then my read is it is in violation of <G19>.

I would imagine that most design have the ramp start BEHIND the deployment cylinder in order to get everything lined up prior to the 10 second mark: I think such designs would need to be completely horizontal or uphill prior to crossing into the cylinder in order to stay within the confines of <G19>

Are there any pictures or videos available of the various ramp bots?

[Ether]

Originally Posted by boomergeek

I think, in the context of the rule, it's irrelevant whether the the ramp on the hostbot starts above or below the deployment line.

You misunderstood the point I was making, which was simply that if the minibot starts at a point on the hostbot above the height of the deployment line on the tower pole, then the conversion of this stored potential energy into kinetic during the downward movement on the hostbot track could in theory add to the upward motion of the minibot on the pole. I wasn't suggesting this was legal or suggesting it as a design strategy.

[Al Skierkiewicz]

OK Ether, you run the numbers and give us a report on how high that pipe inside the robot has to be before there is a payback for the added weight, length of travel and increase in speed that makes a difference in the time it takes to get to the top. Make sure you include data on how long it takes for the minibot to cross the plane of the tower base as it begins it's downward travel and how long it takes from that point to actually hitting the top.

[boomergeek]

Originally Posted by Ether

You misunderstood the point I was making, which was simply that if the minibot starts at a point on the hostbot above the height of the deployment line on the tower pole, then the conversion of this stored potential energy into kinetic during the downward movement on the hostbot track could in theory add to the upward motion of the minibot on the pole. I wasn't suggesting this was legal or suggesting it as a design strategy.

My mistake, my apologies: I was assuming you wanted to focus on physics within the confines of the rules as opposed to broadening the scope of the discussion outside the game.

A legal ramp can work a bit like the blocks in a runners race, allowing the motors to get to the range of most work within the power curve, faster.
Does that speed to the best part of the motor curve exceed the extra work needed to cover a longer path? Probably too complicated to be discoverable by mathematical analysis of easily measured parameters.
Testing it directly would be the only realistic way to know.

Assuming a single speed transmission, I would guess that one can compute a drop angle and distance that optimized the time to the best part of the motor curve- at that point, I don't think there is an advantage of continued downward trajectory. In a sub 2 second race, getting to optimum portions of the motor curve faster (let's guess 1/10th of a second) might have measurable advantages at the finish line.

In such cases, front wheel drive can have a significant advantage!

[Ether]

OK guys, I'll give it one more shot. Al made the statement "I cannot see that a downward movement on a pipe adds anything to the upward motion of the minibot". I was simply stating that it can*. I don't know whether or not it's legal, and I don't think it's the best strategy to pursue (for a number of reasons).



* It's not about the robot. It's about science, technology, engineering, and mathematics.

[boomergeek]

For what it's worth, the slowed down version of our non-ramp minibot climbing a slightly shortened pole in about 1.5 seconds shows it accelerating significantly through at least the first second. I'd extrapolate that it is not reaching the "most work" portion of the motor curve within the first half second. (I.e., a significant portion of the race time).
Probably time to lessen the diameter of the wheels.

http://www.youtube.com/watch?v=KLZCNbcNopU

Sure wish we still had license access to Dartfish video analysis software...
(It's a physics rockstar)

[jspatz1]

Originally Posted by Ether

OK guys, I'll give it one more shot. Al made the statement "I cannot see that a downward movement on a pipe adds anything to the upward motion of the minibot". I was simply stating that it can*. I don't know whether or not it's legal, and I don't think it's the best strategy to pursue (for a number of reasons).



* It's not about the robot. It's about science, technology, engineering, and mathematics.

Of course it can. Imagine a car with no motor gaining speed coasting down a steep hill. As it reaches the bottom, it begins a race with a car with a motor that was standing still, and they race up the next smaller hill. The car with no motor can win with initial velocity and energy gained from the first hill.

[Ether]

For physics and/or math students who may be interested, I just posted a short write-up showing how to setup and solve the differential equation for the MINIBOT accelerating from a dead stop up the pole. An analytical solution is given so you can just plug numbers in using a calculator (if you have the patience), or better yet a spreadsheet.

The model ignores friction, which may be a significant factor, but the physics (and math) is nonetheless interesting and useful for gaining insight and rough approximation.

http://www.chiefdelphi.com/media/papers/2470

[nikeairmancurry]

First instances of this came up... At West Michigan District, 67 clearly made it up the tower probably second of the four and didnt set of the light, and where not given any points... Didnt effect match results...

[Francis-134]

As a member of team 190, and having built the robot, the ramp does not go downward, but slopes upward. The motors turn on only after the 10 second mark. The entire system is below the deployment line.

[Matt Krass]

So, it seems like my hunch may have been wrong, it seems like the system is working much better now. I'm excited about this, but I'd still like more information. At the very least, it would be nice to know if all the discussion in this thread is valid, and I think it could be a great learning experience to show students how to design to a full specification. Plus, I personally think it's pretty impressive how two groups can collaborate with just specifications and at the end of the day their two separate solutions, developed in complete isolation, work together because they followed the agreed upon design specification.

Good luck teams, lets hope things continue to work well,
Matt

[Vikesrock]

I didn't get to watch a ton of matches at Peachtree this weekend, but every minibot I saw that looked like it should have triggered the pole did so.

[Navid Shafa]

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.

We just had a match yesterday where we launched our slower mini-bot (1.7 seconds). It clearly hit the top, but it apparently didn't trigger...

It was frustrating for that match to swing that way, it makes me empathetic for all of the teams who have these kinds of rulings which are out of their hands.

[bduddy]

At St. Louis, one tower was hit twice with no response; they determined it was defective, switched it out, and fixed the previous scores. There were one or two other incidences of towers not registering hits, but they were borderline in terms of the amount of force applied. Overall the system seems to work OK.

[Lil' Lavery]

I didn't really watch many webcasting this weekend, but from the bit of Bayou I saw, the referees were still using their judgement to call the minibot races. There were many false positives, though I only recall one instance of a minibot not triggering at the top.