Legality of Downwards-Sloping Ramps

There’s been lots of discussion of various ramps, and it appears that most, if not all, ramps were accepted by inspectors from regional events to the Championship.

But that doesn’t really satisfy me. At any event, possibly questionable or even outright illegal robots are passed and allowed into competition. There’s hasn’t been a thorough, rules-based discussion of downwards-sloping ramps (including, but not limited to, those of a U shape or those beginning at higher than 30’').

So that’s why I’ve started this thread. The first real question I have about the legality of a downwards-sloping ramp comes from the following rule:

<G19> MINIBOTS must remain completely autonomous and move up the POST solely through electric energy provided after the start of DEPLOYMENT by the permitted, unaltered battery and converted to mechanical energy by the permitted unaltered motors (and associated, appropriate circuitry). <G19> means that HOSTBOTS are not allowed to launch the MINIBOT up the pole at the TARGET, or otherwise contribute to the vertical movement of the MINIBOT. Energy for vertical movement may not be stored in the MINIBOT before DEPLOYMENT (except that which is contained within the battery and excluding incidental kinetic energy stored in the motors or wheels, but NOT, for example, in a flywheel).

Emphasis mine. It is possible that gravitational potential energy, if utilised before or during deployment, is not legal. Some argue that this usage requires the minibot goes down, and that this is actually a disadvantage. I don’t think so.

The minibot is required to go up the pole from the deployment line to the sensor to score. During that period, there’s no plausible way to gain an advantage by going down. That’s why this is (or should be) legal.

However, going downwards before or during deployment can be an advantage. It provides a kinetic energy that, though directed downwards, can be and was converted into kinetic energy propelling the minibot upwards. Because it is an advantageous use of energy not stemming from the minibot battery, a downwards-sloping ramp should not be legal.

Thoughts?

i had this idea as well, say you were to direct drive a wheel with a diameter of something like 1.5 inches, and your mini-bot started 4 feet above the pole, races down a ramp until it reaches the pole, even though it would de-decelerate on the pole, the change in potential energy would be the equivalent of 6 feet of height gain, instead of 10 feet of height gain. the question is, will this be faster than a pure ramp bot.

If you look at it that way, then any minibot raised above the surface of the arena has “stored energy” and is therefore illegal, and I think that we can all agree that this is ridiculous and not the way the rules were intended to be read. I don’t think there’s much of an issue here.

Have you even seen a downward sloping ramp pass inspection and compete?

I haven’t, I would assume because essentially everyone agrees they are not legal.

Specifically, no. However, this entire discussion came out of comments on a facebook video from a team working on a ramp sloping downwards. When the suggestion was given that is may be illegal, they stated “multiple lead inspectors passed it. one here in [state] before we left. and the one in St Louis did too.” I’m still not sure if it was an offseason project or for that team’s competition robot, but if inspectors WOULD pass them, it’s believable that there could be a few.

That method is without a doubt illegal. <G19> states "MINIBOTS must remain completely autonomous and move up the POST solely through electric energy provided after the start of DEPLOYMENT by the permitted, unaltered battery and converted to mechanical energy by the permitted unaltered motors. This is quite simple. MINIBOTS must move up the post SOLELY through electric energy provided after the start of DEPLOYMENT. The gravitional energy from the downwards ramp is not electrical energy, is not provided by the motors, and is not an allowed form of gaining energy to move up the post.

Guys,
The downward sloping ramp is still manipulated by a minibot using energy stored in it’s battery and converted to mechanical energy in the motors. While some will argue that there is an advantage here, I disagree. While it may be true that gravity will accelerate the minibot while traveling down the ramp, the motors will still have to overcome gravity on the way back up a slope and still travel a longer distance to do so. Add to this any increased friction as the minibot transitions from the down side to upside of the ramp and you will see that there is likely a net loss in energy during this time.
As to inspector involvement in this design, we simply inspect on the rules in the robot section not the game rules unless specifically directed by the GDC. The ramp needed to be constructed of allowed materials, exist entirely inside the bumper zone at the start of the match, be safe with no sharp edges, etc. It is the refs on the field who make the determination as to the legal use of such device that passed inspection. I think it is easy to realize that if the minibot deployment occurred within the correct time frame, these ramped designs would add feet to the travel distance encountered by the minibot.

There was one at the Championship on the Newton Field. The slope wasn’t as crazy as people are talking about in this thread, but it was noticeably sloped.

Yes - ours.

There was a discussion in a different thread around week 2 or 3 of regionals on this topic. The consensus seemed to be as long as the minibot stays below the deployment line the entire time it contacts the ramp AND the end of the ramp is higher than the beginning, then there is no net potential energy converted to kinetic energy.

Our ramp starts out downward, but the minibot does not gain any energy from the downward slope since the end of the ramp is higher than the start of the ramp (i.e. there’s a net loss of potential energy by the time the minibot leaves the ramp). Furthermore, the minibot stays below the deployment line the entire time it is touching the ramp.

Why do we do it? Becuase the Tetrix motors inhale audibly and we’re trying to unload them as much as possible during acceleration.

I have seen 2. Teams 51 and 340.

I actually walked over to my good friends on 340 on Wednesday afternoon, and questioned it’s legality. They had a level one ready in case it didn’t pass.

-Nick

What if the motor is pushing the minibot down a slope? One could argue that the minibot is being solely driven by the motor, and that gravity is only providing a force to pull it down, like it normally does. If all else fails, just ask the judges to turn off the gravity! :smiley:

I agree with what Al says, but I have a few questions.

To those of us who are still scratching our heads about this, perhaps the questions should focus on what has been Deployed, and when Deploying ends.

If the Host bot is not supposed to impart any pole-climbing help to the mini-bot after the mini-bot is deployed (and if starting the mini-bot motors is one way to know that deployment is ended?), then a ramp that is part of the host-bot deployment mechanism(s) would seem to violate that rule; regardless of whether the mini-bot pays the universe back on the upward climb after reaching the bottom of the ramp.

If the mini-bots include both the parts that climb to the tops of the poles and the ramps that are left at the bottom of the pole, that might make a difference; but my instinct is that the ramps are parts of the host-bots, not part of the mini-bots

If the device that gets deployed (the mini-bot) is supposed to only use battery power and not begin with any other stored energy, then a ramp that is not part of the host-bot would seem to be a violation of the rules governing mini-bot construction and behavior (but maybe not).

If you can’t spin up a flywheel during deployment and carry that angular momentum into the race, I don’t see why you should be allowed to drive down a hill and carry that angular and linear momentum into the race.

On the other hand, if when the race begins you want to start off of the pole and then drive along a track to reach the pole, and if the time spent driving on that track is part of your total race time, and if you are allowed to race along things that are not the pole (such as a track you bring and keep below the line), then I can understand that a ramp would be legal.

I admit that I have not (re)studied every deployment, etc. rule before writing this; but I do hope that a careful examination of what it means to be deployed, and of when the state of “being deployed” ends for a mini-bot, will help clear this up. There are plenty of gurus who can cite the precise rules that apply. I’m just trying to think through how many of those rules need to be examined.

Blake

Blake - what your looking for is the official definition of DEPLOYMENT, found in Section 1.6:

DEPLOYMENT – the act of positioning a MINIBOT on a TOWER. DEPLOYMENT starts when the MINIBOT breaks the vertical projection of the TOWER BASE circumference. DEPLOYMENT ends when the HOSTBOT is no longer in contact with the MINIBOT. (Related form, DEPLOY, verb)

The act of deployment starts when the minibot breaks the plane of the tower. Pretty straight forward - it hasn’t started when the minibot is still within your robot, or when it’s fallen off and is sitting in the middle of the arena. It’s only when it’s actually over the tower.

The act of deployment ends when the hostbot is no longer in contact with the minibot. Again, pretty straight forward - if you’re still pushing the minibot towards the pole, you haven’t finished deploying yet. It’s only when the minibot is on the pole and moving (hopefully) away from your robot that it’s deployed.

Who said you can’t use a fly wheel. Provided that the energy stored was generated by A) tetrix motors on the minibot or B) a change in position of a mass that is part of the minibot, or the entire minibot, as a result of gravity only (it is ridiculous to say that you can’t use gravity on your minibot to gain an advantage, then making your minibot lighter would be declared illegal as well) then a flywheel would be perfectly legal from what I can tell.

The rulebook

<G19> MINIBOTS must remain completely autonomous and move up the POST solely through electric energy provided after the start of DEPLOYMENT by the permitted, unaltered battery and converted to mechanical energy by the permitted unaltered motors (and associated, appropriate circuitry). <G19> means that HOSTBOTS are not allowed to launch the MINIBOT up the pole at the TARGET, or otherwise contribute to the vertical movement of the MINIBOT. Energy for vertical movement may not be stored in the MINIBOT before DEPLOYMENT (except that which is contained within the battery and excluding incidental kinetic energy stored in the motors or wheels, but NOT, for example, in a flywheel).

I meant after the start of deployment, sorry for not clarifying that.

Oh boy look what we started. It was on my Facebook that the video of our downwards sloping ramp was posted.

Our minibot never “rolls” down the ramp. Any movement on the ramp is purely from the battery and minibot motors.

Chris said it best, the minibot stays below the deploy line the entire time and our “exit” point off the ramp is higher then the starting point so any energy gained by the ramp is lost.

I mean if we’re going to lawyer this then the refs should have used a bubble level to make sure all deployment mechanisms fired out level or downwards. Any increase in degrees would mean the deployment mechanism is “pushing” the minibot up when it contacts the pole and arguably providing vertical movement to the minibot.

Our team was also slightly confused by the wording, and noticed several teams on our field (Arch) at St. Louis with downward-sloping ramps. We asked the lead inspector of the field and he very specifically told us that they ARE legal as long as all the other language is met (below the deployment line while in the tower cylinder, etc).

I’ll throw in against downward sloping ramps. Actually most ramps if you’re strict about the rules. I’ll admit up front that this is all going to be based off an extreme examples that have never and would never make it to the floor. The first example being a ramp that starts several feet above the top of the pole, and a deployment mechanism that’s smart enough to trigger far enough in advance that the falling minibot crosses the cylinder just after the endgame starts.

That said, I think it’s patently obvious that said minibot gains an advantage from dropping from such a height. That can be pretty readily demonstrated by the fact that you could use this ramp to create a (highly dangerous) ball bearing minibot that wouldn’t be fundamentally different from a spring catapulted minibot. So I’m failing to appreciate how slapping two motors and a battery on to would appreciably change the situation. You’re storing potential/kinetic energy in the minibot that it pretty directly transfers into vertical motion. It seems patently obvious to me that said minibot has gained a significant advantage over minibots that run a straight track out to the pole.

If you admit that the extreme example creates an advantage, then you’re down to deciding how much of an advantage is too much. Which I’m fine with, but we should be honest that that’s what we’re discussing.

Similarly, I think the argument could be made that nearly ALL ramp systems are illegal by a (very) strict reading of the rules. G19 etc. state that the minibot must move up the pole with electric energy provided by the battery AFTER deployment. Deployment starts when the minibot crosses the cylinder. Ergo, any ramp system where the minibot starts a significant distance away from the cylinder is putting significant energy into the minibot system before deployment starts. It’s kinetic energy stored in the inertia of the battery and frame, but it’s stored energy all the same, and it would still provide an advantage.

You’re again down to the question of what degree of advantage is acceptable. Which again is fine, but we should admit that.

Don’t believe me? Grab your current interpretation of the deployment rules and reason along with me. Let’s assume that the no-load speed of a legal minibot is 30 fps, versus a climbing speed of 15 fps. The following systems all have deployment timing such that the minibot crosses the cylinder after the endgame starts. Which, then, is illegal? Which is going to be the fastest?

  1. A ramp system where the minibot starts just outside the cylinder at a dead stop.
  2. The above sloped ramp system, where a minibot is dropped from a height sufficient to achieve 30 fps as it crosses the cylinder.
  3. A novel flat ramp that is long enough that the minibot reaches 30 fps before crossing the cylinder.
  4. An even more novel spring-loaded system that shoves the minibot up to a speed of 30 fps, releasing it just before it crosses the cylinder.

Timing and construction issues aside, I think system 1 loses to systems 2-4. But the interesting question is which of 2-4 seems illegal to you by your current reading of the rules. A really strict reading should deem all three illegal. If you think any of 2-4 are legal, ask yourself what real difference there is between them, as regards energy stored before deployment. On the plus side, it’d make rulings a lot easier, since you’d just be judge the speed of the minibot before deployment started.

Like I said, for me it all comes down to just how picky you want to be and want what degree of advantage you’re willing to tolerate with the minibot rules. My level is set somewhere around all net energy coming from the battery, and the equivalent energy of a 3 foot long ramp. Mostly for practical reasons, since this would pass most ramp systems out there.

This is clearly illegal since after deployment not all of the energy came from the batteries - some of the energy came from the potential energy of having the minibot well above the deployment line.

If the minibot starts below the exit point of the ramp, then ZERO potential energy is used in the speed of the minibot at the end of deployment - even if the minibot travels all the way down to the floor before starting upward. Thus ALL energy comes from the batteries, which is 100% legal.

Similarly, I think the argument could be made that nearly ALL ramp systems are illegal by a (very) strict reading of the rules. G19 etc. state that the minibot must move up the pole with electric energy provided by the battery AFTER deployment. Deployment starts when the minibot crosses the cylinder. Ergo, any ramp system where the minibot starts a significant distance away from the cylinder is putting significant energy into the minibot system before deployment starts. It’s kinetic energy stored in the inertia of the battery and frame, but it’s stored energy all the same, and it would still provide an advantage.

I agree with you here. Our ramp was constructed so our minibot starts on the edge of the cylinder (at least as close as can be repeatable). Starting the minibot a long distance from the the cylinder does provide an advantage as kinetic energy is stored before deployment begins.