Draft rules for RoboCupJunior Soccer 2022 released

@stiebel thank you for your insights!

Asking teams for their motor specifications arguably employing the honor system which is not necessarily a bad thing. There are two criteria for rules that your suggestion may not meet well however:

  1. rules need to be approachable especially for light weight - finding motor specs from some suppliers and even for well known kit bots (e.g. Lego) could be a challenge for teams - the forums could help here but a point was bought up that some teams with hand-me-down motors may not have any spec sheets. That’s also implying that teams understand what stall current is and why we’re making a point to ask for it. One could argue that this isn’t really a big deal but…

  2. rules need to be enforceable - this rule would trust that teams aren’t supplying faulty datasheets and have easily identifiable motors w/o disassembly. Testing stall current on a brushed motor isn’t too bad but what about brushless? In the end, how can we verify that motors are indeed in spec if a team is suspected of being in violation? This also isn’t drilling a few holes to make the bot lighter or shaving down an axle to meet the diameter - a team not meeting this spec would have a major advantage over the others and wouldn’t be easy for a team to remedy at competition. Imagine a team not being able to play or at least compete fully if an honest mishap occurred.

I’m about to compile a summary of all of the discussion had here and in our meetings on the potential of limiting/capping the speed within the next week or so. If anyone has any other suggestions/comments, please feel free to add to this thread; we’re taking everything posted in the forums into consideration even if we haven’t directly responded. Thanks.

Hi Mike,
thanks for your response.
I see your points and you are right.
We need hard facts to check.
So let me rethink my thoughts:
I still think, we should stick to our voltage. Most good and inexpensive brushless controllers start at 10V, so we would make all these well approved driver-motor combinations to e-waste, if we drop the voltage level. I do not see the benefit of this kind of rule-changes.
And let’s face it: even if we drop the voltage to 5V, a well designed robot will surpass any lego-robots anyway. So please leave the voltage as it is.
Current limitations can be a way to reduce the power, but again, a kicking device that does not use pumped voltage but uses high current would burn a fuse and this is not intended by this rule change.
However, if the fuse is slow we could place a capacitor behind the fuse, so there would be a workaround.
But then we need a new rule as well, only allowing one battery for the whole robot, otherwise you will find teams sourcing out all “not-motor-components” the the unfused circuit.

Or, we just want this very idea. We have the fuse not for the whole robot, but only for the motors.
Then we actually could remove the fuse to see if all motors stop moving without killing raspberry pi or similar systems when switching off without a proper shutdown.
This in fact would also give the chance to use more powerful motors when designing a 3-mot-bot in comparison to a 4-mot-bot.

We could set international standards with car fuses and we could specify the exact fuse and even provide fuses for the competitions to make sure everyone uses the same fuse.

One last thought about speed measurement:
If you do not trust teams to provide correct datasheets than be sure they will cheat as well when driving a speed test. You cannot securely check the speed during gameplay and every robot can drive slower when in measurement mode, especially if a well designed robot has to fit to new rules by just beeing slower then before.

Thanks for allowing this kind of open discussion!
We all want to see fair and fascinating games and it is great to understand the thoughts behind rule changes.


The goal is not so much to slow everybody to lego-levels but to prevent teams from having so much speed that strategy becomes pointless.

Seems reasonable.

What worries me about fuses (particularly automotive ones) is variance: Automotive spec is fairly loose, as long as they blow in case of a short circuit it doesn’t matter if it is tens or hundreds of milliseconds, if they survive 9.5A or 10.5A continuously and so on and these differences are bound to exist between factories.

Then there is variance in manufacturing: If one team gets +5% and the other gets -5% (which may well be within standard deviation for automotive) they wind up at a significant (dis)advantage. Therefore fuses to tight manufacturing specs would have to be supplied by tournament organizers who already have a lot of details to take care of and it still wouldn’t enable teams to properly calibrate on exactly those fuses.

That is the same problem that the kicker measurement device already has to an extent, we can of course grab a bot from a running game and do a sanity-chek, but scientifically precise it is not. Unfortunately actual movement data is hard to get without lots of effort (both financially and in setup, calibration, requirements for lighting of the rooms that the game is being played in etc. even if money for motion capture systems was available everywhere).

We have even entertained electronic current measurement, robot-mounted accelerometers (small board, coin cell battery, accelerometer, red LED flashes and beeps if robot is accelerating too fast; but that has development, manufacturing and distribution issues, not to mention false-positives if filtering crashes doesn’t work as intended and so on).

What we are looking for is a way to dial down the speed of robots for two reasons:

  • Fast robots being dominant leads to very little reward for people doing good perception and/or clever strategy if all robots are close to the ball at all times through sheer speed.
  • Robot speed being a dominant factor makes it hard for teams without expensive hardware to compete on their merits as opposed to their motors’.

Any ideas to make progress on these issues would greatly appreciated.


David and I are on the same page here. To reinforce his points, I did a little digging on fuse specifications. Reading from this guide sheet from Littlefuse, a system should be designed to not exceed 75% of the fuse’s nominal current rating in part because fuses will heat up and become easier to open at currents closer to their ratings. There doesn’t seem to be a practice of listing tolerances like resistors, but rather average time v current charts like the one shown in this doc. This shows that it is unlikely we’d be able to ensure fuses are within a certain tolerance at all.

I’ll add a third point to critical criteria for rules: participants and spectators need to trust that the rules give a fair chance to everyone. It is heartbreaking when teams speculate whether or not poor performances or losses were because they may have been cheated. For example, a team says they’ve done extensive testing on their drive system and then blow a fuse the day of competition - can we say without a doubt they didn’t get an out of spec fuse? Conversely, what about the team that overperforms and their competitors speculate that perhaps the winning team is swapping out their fuse or bypassing it?

I would not recommend any rules that allow for speculation like this especially in this case when teams will be surely designing circuits outside of the guidelines.

First of all, where can i find the draft Rules for 22/23?
Secondly, what’s about limiting the max rpm of the Motors or of the wheelshaft with no load on it?
Often these can be found in the Datasheet and If not it can be mesured
Best wishes,

Hello everybody,

we’d like your feedback on a change to camera rules. We have started a thread with a couple ideas for where camera rules could be going, come have a look and give us some feedback: Feedback on possible changes to camera rules


Hi david,
I very much appreciate the idea to drop of general camera restrictions.
And my first thought was to drop it at all, but I really love the idea to have two rules.
One robot with no restrictions and the other with a fov of 140° and absolutely no increasing allowed whatsoever would bring an absolutely new task to the game: communication. having one robot “seeing it all” and the other one “seeing in only one direction” would force the teams to build two different robots and to think about communication to pass the information from one robot to the other.
Great idea!
(We could think about dropping the restrictions to bluetooth as well as espnow or other peer2peer wifi as well as UWB could offer some more and interesting features with this now need of transferring data…

Hi @stiebel ,

This is something we’ve been indeed thinking about for a few years. The standard problem with allowing WiFi was the potential inference with Major leagues, as well as venue infrastructure. Perhaps this could indeed be revisited again :slight_smile:

Thank you for your suggestion!

With regard to WiFi I think concerns are relaxing somewhat seeing as the 2019 venue even got guest WiFi. Maybe channel allocations and tx power restrictions could alleviate further concerns - although it would have to be narrow channels on 5GHz because 2.4GHz only has 3 non-overlapping channels.

Pushing full semi-compressed video streams probably won’t be on the cards in proximity this close for a couple more years, esp. with UWB which I would have concerns with because the spectrum isn’t very internationally harmonized afaik. There is some 60GHz±stuff that is but that is usually both expensive and very directional.

RF is unfortunately always a bit of a rabbit hole as soon as you go international and/or simultaneous operation.

Dear forum and dear chair members,
I do not know where to post this message if not here.
I just read the final rules for soccer 2022 which are no surprise.

But then I read the line: “For the 2023 rules, the Soccer Committee intends to limit the voltage to 9.0 V
nominal for both leagues.”

I know there where discussing about this right here and I definitely want to protest to this decision!
Every single soccer team I know uses LiPo or Li-IO batteries which have 7.4V, 11.1V or 14.8V per definition.
So If you want to reduce power from 15V (where I still do not understand the reason), than you have to consider these voltage steps.
If you set a voltage limit to 9V, you push us to using 6 non-recharchable 1.5V batteries or to reduce to 7.4V with a 2S Lipo setting.
This will have only one effect: all the motors and motor drivers the teams kept buying over the last years will be pushed beside to buy some other motors with higher currents to provide the torque needed to run the robot. This will have no effect to reduce speed.
Please rethink this decision!
If - at all - reduce to 12V for all classes. This could possibly bring teams to user their existing stuff, but if you half the voltage of the open2vs2 robots, you will generate plenty of e-waste without any need and without any benefit.


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Hi @stiebel ,

This is not yet set in stone, but it is a consideration, could have been phrased “is considering”…

The idea is to have more passing, kicking and strategy by slowing robots down (i.e. more preception and planning, less faster motors winning games).

I’ll cross-post your assertion to the battery voltage thread and respond in technical detail. Please do post dissenting views there: Resolve: lowering voltage limits to 9V will significantly reduce robot speed. Show me the data! - #4 by david

You make a valid point about not making equipment obsolete - that should only be done if it’s worth it for the improvement in gameplay, please also argue this in the battery thread linked above.


Dear chair and forum members,
the proposed Rule to lower the “nominal” Voltage to 9.0 V with the supposed Goal of reducing the speed, is in my mind quite problematic.
As other members here have pointed out, this will not result in a speed reduction, it will only force higher cost and difficulty in designing a drive chain. Also, will it not improve controlled movement on the field. I probably will elaborate, in the more technical thread, about this topic.
If you want to have more controlled and precise game play on the field, a proper rule would be to limit the velocity of the drive. This rule can easily be checked even during a game or after it, if for example suspicious activity or accusation have been found.
This will create more equal ground without forcing to compete with ever more expensive motors and drives. Also, 9V does not make sense in terms of Battery Technology. In addition, it will complicate electromagnetic kickers which do not use voltage pumps, also something I would never allow any of my students to use in such a robot, in my opinion this is irresponsible at best.


Taking into consideration that there is very little space to accelerate and a very short distance available on soccer fields combined with the inaccuracy of the human-with-stopwatch-measurements means you won’t get good data there. I do agree with most your other points though.

I don’t think it is too hard, just need one robot length to measure in a video, and you have the speed to a satisfactory accuracy. It will also be quite obvious if someone is driving too fast on the field. I think any other measure to reduce speed besides defining a specific drive train, which I think is also not a good idea, will be more difficult to define/check. With little space, the speed limit will probably not be reached, or it would have to be very low. But yes, we have to think about that more closely, voltage is definitely not the solution we are looking for.

You still don’t get good resolution from handheld cameras held at the side of the table but even if you could it is unrealistic to pixel-analyze video footage without severely disrutping tournament schedules.

I think we are all in agreement that reducing voltage isn’t going to have the effect we’re trying to achieve.

Hi @david!

Given the aforementioned, will the committee still be intending to go ahead with its 9.0V voltage limit drop in the year 2023 as previously mentioned? Thanks!

Hi @neohaojun

The actual quote from the rules would be

For the 2023 rules, the Soccer Committee intends to limit the voltage to 9.0 V nominal for both leagues.

so this really was not set in stone in any way :slight_smile: Though I am not able to speak for the whole committee, I can assure you that this sort of feedback will be taken into the account when the final decision gets made. This is also why the intention got announced this way – so that the community could provide its feedback and so that if it did happen, the change would not be a complete surprise, but it never meant that it would have to happen.

I hope that makes the situation a bit more clear. To me this shows that it might make sense to provide a bit more clarity in the rules themselves. I will try to convey that to the committee as well.

Please do let me know if this helps :slight_smile:


Even if there would be way to measure the speed of a robot, do we have to buy motors with the speed in the rules, or can we control the speed by software?

Because it would be impossible to find motors, with an exact speed limit and good power.

@Elias you bring up one of the points that makes limiting the speed so challenging! As of right now, there is no intent to limit what motors you can/cannot have on your robots regrading the idea behind restricting speed. The only announced intention was to lower the voltage in hopes that it would restrict the speed. As already pointed out in several places, lowering the voltage doesn’t seem to be the best solution :slight_smile: .

Thanks for you answer @Mike . I already read about the new voltage and that it will hopefully not come.

To make my point clear, I don´t see any sense in regulation in speed or power.
I see the Problem of teams with a low budget Robot, but regulation in speed or power is not the way. (At this point, I don´t know a better solution, if I get one, I will probably post it here).
And even if there will be a regulation in Speed or Power, how will you stop the Ball, if it comes fast because of a good kicker?