Robot Contact Question

The section on our robot that is open for the “feeding” of the balls is obiously not protected by bumpers. 10 Inches above the ground (outside the BUMPER ZONE) we would like to have an aluminium crossbar, spanning the width of this opening (about 26 inches) and set back about 2 or 3 inches inside of the BUMPER PERIMETER. We question whether or not this would violate the rules in the fact that, if something contacted our robot inside of the “feed” opening, would this be a violation of rules, on our part or another robot’s?

Here is an attemped front profile view (B = Bumpers)

   /////////////\\\\\\\\\\\\       <----(This is the crossbar)  \

[BBBB] [BBBB] |_ 10"
|| || /

That could be a tricky question… the bumper rule:

Teams are required to use BUMPERS on their ROBOTS. BUMPERS have several advantages, such as reducing damage to ROBOTS when they contact other ROBOTS or ARENA elements, and being excluded from the calculation of ROBOT weight and volume constraints specified in Rule <R11>. The BUMPER location and design have been specified so that ROBOTS will make BUMPER-to-BUMPER contact during any collisions. If implemented as intended, a ROBOT that is driven into a vertical wall in any normal PLAYING CONFIGURATION will always have the BUMPER be the first thing to contact the wall. To achieve this, BUMPERS must be constructed as described below and illustrated in Figure 8 – 1.

That states the intent of the rule pretty clearly - bumper design is such that any contact is made bumper to bumper. Now, the sub-items underneath it don’t explicitly prohibit a design like the one you described, which is perhaps where the confusion comes in. If we do a little math, we can figure out how much the typical robot can intrude into your frame:

If you look at the attached diagram, the red triangle is the part you’re concerned about - specifically the red vertical line. Because of the two robot bumpers, you can immediately see the part of the other robot’s bumper perimeter that can intrude into your robot is pretty small. You can do some easy math to figure out exactly what that part is. With a 26 inch wide opening, the entire vertical red line is 26/2 = 13 inches long. With a maximum depth of 3.5 inches for bumpers, you immediately cut out 3.5 inches (the top 1/3 of the line). the bottom 1/3 of the line - the portion that only contains bumpers and thus not a problem for you - is the diagonal distance of a square with side 3.5 inches long - the maximum bumper depth. 3.5 * sqrt(2) = 4.95 inches. So in total, their robot (everything inside their bumper perimeter) is 13-3.5-4.95 = 4.55 inches.

So, we can tell from this that, for your stereotypical rectangular robots with full bumper coverage, you only have to worry about an incursion into your bumper perimeter of 4.55 inches, for areas above the bumpers. Of course, someone could make a robot that’s 20 inches wide with 3 inch bumpers on both sides that can drive right in the middle of your robot… How will the GDC/inspectors rule in cases like these? I can’t say. But the above math should help to illustrate the situation. With the impact energy the GDC is expecting this year (thus some of the bumper rules), it would behoove teams to take situations like these into consideration - you don’t want a fragile piece, like a roller for collecting balls, to be hit by another robot in a high speed situation.

So i guess what i’m saying is, in short, I can’t answer your question any more than quoting the bumper rules at you. but i hope i provided some additional insight into the situation :slight_smile:

bumper.bmp (85.9 KB)

bumper.bmp (85.9 KB)

<G32> would probably be a better rule to go by.

And, the rule in question is <G32-C>.

If a portion of the BUMPER PERIMETER polygon is unprotected by BUMPERS, any contact by another ROBOT within the unprotected region (including the vertical projection of the unprotected region) will be considered incidental contact and will not be penalized.
In other words, if they hit you on the bumper perimeter, it won’t be penalized. If they try to go inside, they are trying to make you violate <G32-F>, but <G18> blocks that. They may get a <G32-G>, depending on design. It is possible that <G32-D> is called into play, though highly unlikely. There is also <G33>, the entanglement rule, but I don’t expect that to be an issue.

If you do go with this design, and there is adequate protection, I don’t think it will be called on anyone in this specific case. Unless, of course, you try to take other robots in or they try to make you get a penalty.

I apparently missed <G32> when i was thinking about this rule… thanks for pointing it out :slight_smile:

Of course, the bulk of my analysis still applies, and it would behoove you to consider the likely area of impact for sections that don’t have bumper protection.