What is A robot as opposed to TWO robots?

I have a question regarding a bizarre concept.
When does a robot cross the line from being one robot to two?

And this is irrelevant but do the IFI guys ever design a game with some strange design in mind and hope to see it at competitions?

While this might seem a bizarre question, it did generate some controversy in FRC just over a year ago. This was due to the fact that the wording of the rules left ambiguity as to what, exactly constituted a robot, versus what constituted removable parts.

In VEX the situation is somewhat different… we expect robots to change and evolve over the course of a season… or even over the course of a competition. If a team attends a multi-day competition, uses a robot on Friday, then takes it back to their hotel/home and rebuilds it overnight to improve performance… I’ll take that as a good thing. (It has to go through tech inspection again, however.)

I think the best way to define a VEX robot would be “that which passes tech inspection”. In other words… it all has to fit in the sizing box at one time. Spare and replacement parts that you bring with you to a competition should be just that… unassembled parts, substantially the same as you could order direct online. Not bolted together, not cut to a predefined length nor bent to a predefined shape.

So… if it has passed tech, it’s a robot. If it hasn’t then it isn’t. If its a spare part… no big deal, but if its bolted together, leave it at home, or put it in the sizing box.

Thats how I’d call it.


What you are saying here is that modular robots are highly discouraged as far as their physical components are concerned.

That is a very interesting position to take since modular software is highly encouraged. It’s an accepted practice to have software routines that can be turned on and off by the team and it’s very easy to swap pre-written software modules between matches.

This is also interesting from a historic robotic competition perspective. One of the best combat robots of it’s time, The Master*, built and run by Team Sinister (or was it just Mark Setrakian back then?), was an extremely modular robot, competing and winning in multiple weight classes.

Here is what Peter Abrahamson had to say about the Master:

I believe encouraging people to build modular robots is much more in line with the goals of Vex and these competitions than discouraging them is. It’s this very modularity that makes Vex so useful to hobbyists and even professionals in the field. (Has anyone actually counted how many projects M5 industries have used some vex components on without being exclusively vex?)

I agree that swapping modules would justify a re-inspection but I must disagree that teams shouldn’t bring pre-fabricated modules with them to allow for easier changes to their robot.

The rules simply state that a robot can only have 1 microcontroller. And beyond that, we’re limited, of course we can only use 2 batteries.

So if you were to take a PMW cable…and make it as long as the field and have “technically” 2 robots there, LEGALLY, I think it’d be ok, but don’t forget, that if you have those two parts separate, one of the parts can be considered to be “detatched” from the original bot, so then, it’s illegal. If you’re considering thing, I would recommend you hit the FAQ.

But I mean I don’t see any reason to do this, but I’m sure you have a devious strategy that will cause frustration for referees, judges, inspectors, and most of all, your oponents.

i agree with Sunny
but since you are only allowed one microcontroller, it would impossable for you do separate them
you would need LONG wires that cuold streach out the entire field
and they would easily get tangles up too…
so the ref might call it as a tangling issue

is the question concerning having one robot formation in one round and then a different in another (like in the link about the FRC team) or is it like having one robot that has a second body be connected only by the motor cables and such that works along with the motherbot.

isn’t **robot **talked about in the rules?
Robot – Anything (which has passed inspection) a team places on the field prior to the start of a match.

i think the real issue is the skills challeng cause we are allowed one robot. but what does that mean. assuming you have anough time you cold reconfigure the bot you used for normal play to just about anything. but if you say one of the normal play configs must be used teams have optons for many configusrations.
very tricky very trcky.

As we can see… counting robots is not as simple as it might, at first, appear.

I agree that modular robots have a noble tradition in robotics competition, but it does present a challenge in determining what, exactly, is one robot with multiple configurations, and what is two seperate robots.

This is an issue as teams are only allowed to use one robot at a competition. This presents a challenge when, as in the FRC case I linked to above, the two configurations appear to be two seperate robots.

What if teams brought three complete “configurations” each of which, when a microcontroller is added, could serve as an independent robot? For competition matches they use robot (or configuration) one, then move the microcontroller to robot (configuration) two for the programming challenge, and finally move the microcontroller to robot (configuration) three for the driver challenge.

This is clearly a violation of the spirit of the “bring one robot” rule, but in the absence of a clear definition of what is a robot and what is a configuration this is not clearly a violation of the wording of the rule.

So what I would suggest… and keep in mind, that just because I’m suggesting this doesn’t mean that it IS the rule… is that a spare part is one that is not attached to any other part and that has not been cut, bent, or otherwise configured to a specific shape beneficial to this robot. (ie, the stuff you cut and bent last year still counts as spare parts). If parts are attached to each other when you arrive at the competition… or if you want to have different configurations, they must ALL fit inside the sizing box at one time and must meet ALL the rules describing one robot. Once you have done that, you may remove parts before heading to the playing field, and exchange parts that have already passed tech and been removed from the robot, but would have to go back to tech if you added any parts that had not already been in the sizing box.

This would be difficult (impossible?) to police perfectly, but would provide guidelines for teams to follow to differentiate between one robot with multiple configurations (which all fit in the box and pass tech at once) and multiple robots.

It would also give tournament organizers and tech inspectors a standard guideline for addressing the multiple configuration/multiple robot issue.


the way i look at it we can all figure out what the spirit is behind the rule and although it may be very easy for teams to go against the spirit of the rule i would feel way better about myself if i were to compete well following the idea behind this rule while others may not.

Here are the “bring one robot” rules as far as I can see.

and from the inspection checklist:

In addition there is this interesting rule from the inspection zip file:

This rule tells me that the spirit of the rules allow for multiple starting configurations, which can be interpreted in different ways.

I would appreciate it if people would quote the rules that show me how modularity is a clear violation of the spirit of the rules because I’m not seeing it. I see allowances for different starting configurations, significant changes during a match, and re-inspections.

I don’t think anyone is disagreeing with the notion that modular designs are allowed, or that robots might change during a tournament… but at what point does a “configuration” actually constitute a seperate robot?

At present there is nothing in the rules, and hence nothing to quote, on how to differentiate between a robot and a configuration. I have suggested one technique that would be clear and unambiguous, however it is a technique that some might find overly restrictive. I would be interested in hearing other attempts to answer the original poster’s question.

What is A robot (with two configurations) as opposed to TWO robots? Where do you draw the line?


Reminder: a “robot” must fit in the 18x18x18 box - that would include ALL configurations and modules …

If you’re saying that all configurations have to fit in the box at the same time during the first inspection then I really want to see where you’re getting that belief from. The rules clearly state that “If significant changes are made to a robot, it must be re-inspected before it will be allowed to compete.”, therefore it’s clear that it’s expected that some robots will undergo significant changes and re-inspection.

On the other hand, if the robot and ALL modules that could be put on the robot would have to fit in the 18x18x18 box on first inspection, then that also means all the spare parts would need to be in there too, which clearly hasn’t been done in the past. It might also imply that since the robot has a limit on the number of batteries that can be used, that swapping batteries would become an issue. I don’t think many teams want those artificial restrictions imposed on them.

The only obstruction I see to a modular robot entering is a big enough obstacle as it is. The team has to be capable of designing and building and running a modular robot.

Honestly when I asked the question I meant the kind of robot with a 12 foot extension cable.


The extension cable concept has been pretty well covered in the “string” discussions. Basically, as long as you avoid the entanglement rules, it looks like you’re good to go.


The robot only has to fit in the box at the beginning of the match… so wouldn’t that mean that you could configure it however you want before and after matches as long as you have it fit by the beginning…

if you bolt together TWO robots (configurations)
at the tech inspection and it fits in the 18x18x18
THEN you can probrably use the microcontroller for whichever robot you wish
since the other robot can be a “part that you dont need right now”
thats just my basic concept
because then you would need to fit them ALL in the sizing box

If you design a modular robot, then your robot is everything that is part of the design, including all modules.

Therefore, your modular robot (including all modules since that IS the definition of your ‘robot’) must fit in the 18x18x18 box.

Spare parts, on the other hand, are replacements of identical parts - they don’t change the design, form, fit & function of the robot. You can swap out screws, batteries, crystals, metals all day long - if it doesn’t change the design of the robot, it is a spare part and is not an additional robot module.

(Side note: the FRC rules CLEARLY spell this out… I know this isn’t FRC, but it is a point of reference)

Using your definition, we could build two entirely different robots and simply swap the controller. We would call the second (and third and fourth …) robot a module. That is clearly not the intent.

So yes, the robot and ALL modules must fit inside the 18x18x18 box.

Post a Q&A to be sure, but that is my read on it.

By that logic, if you design a robot that can be repaired then your robot is everything that is part of the design, including all repair equipment. I’m sorry, but I can’t find a single rule that supports your claim here. Please, find me that rule or set of rules.

From the rules I’m quoting where a robot can have “significant changes” and a re-inspection, it certainly seems like the intent to me. As long as you can build two configurations that will work with the same controller and the swapping of the controller happens between matches, I don’t see anything in the rules that indicates that’s not acceptable as long as the robot is re-inspected. I can’t find **any **rules that say all modules need to be in the box at the first inspection, including in the inspector’s guidelines and checklists.

Show me where, as an inspector, I would have any just grounds for blocking a team that has one configuration inspected for their first match and then comes to me for a re-inspection with a new configuration before a later match or an autonomous or driver challenge.

Good question on the official “Q&A” thread. I’m looking forward to seeing the official definition (or at least some guidelines) to help provide some standard discrimination between a “robot” and a very-well developed “configuration”.


In the clean sweep manual, it states:

<R2> Every robot will be required to pass a full inspection before being cleared to compete. This inspection
will ensure that all robot rules and regulations are met. Initial inspections will take place during team
registration/practice time.
a. If significant changes are made to a robot, it must be re-inspected before it will be allowed to
b. All robot configurations must be inspected before being used in competition.
c. Teams may be requested to submit to random spot-inspections by event personnel. Refusal to
submit will result in disqualification.
d. Referees or inspectors may decide that a robot is in violation of the rules. In this event, the
team in violation will be disqualified and the robot will be barred from the playing field until it
passes re-inspection.

Doesn’t this imply that if you make a significant change (aka putting on a modular part) you can get re-inspected (aka you wouldn’t have had to put that into the sizing box innitially)

also, the only place in the Robot Rules where the 18"cube is mentioned (that i saw) is where it states:

<R4> At the beginning of any match, the maximum allowed size of a robot is 18” x 18” x 18”.
a. During inspections, robots will be placed into a “sizing box” which has interior dimensions
matching the above size constraints. To pass inspection, a robot must fit within the box without
touching the box walls or ceiling.
b. Robots may expand beyond their starting size constraints after the start of a match.
c. Any restraints used to maintain starting size (i.e. zip ties, rubber bands, etc) MUST remain
attached to the robot for the duration of the match.

Though point <r4>a mentions the robot in the inspection, <r2>a seems to say that a modular component isn’t part of the robot unless it is attached (or at least that’s how i read it)