We do not have data on variances in automotive fuses. Gathering this data would involve buying and characterizing fuses from different manufacturers all around the world. That is to say to determine if tolerances are or are not large enough to be considered unfair would incur considerable expense and effort.
This could be a problem for many smaller competitions (qualification tournaments, smaller national tournaments) that already are close to the limit of what they can implement as it is. I’d like to avoid as requiring more of them than we absolutely must to keep barriers to entry low.
You are likely to be right but teams or entire schools building their first robots would have one more thing to take care of and to comply with as a prerequisite to being able to compete that is not actually about playing soccer.
And the third is that even when everyone would have the same current through motor it does not mean that everyone will have the same speed and tongue of motors because motors have different effectivity on for example some expensive Maxon motors such as Maxon RE Motor 339150 with Maxon 5.8:1 Gearhead 166157 for 310euros would have speed 1658rpm and stall tongue 1.55Nm with just 68mA of no-load current and Pololu Metal Gear Motor with 9.68:1 reduction would have speed 1030rpm with tongue 0.314Nm with no load current 300mA but would cost ‘only’ 20euros. So it would create an even bigger gap between ‘rich’ teams who can afford more effective motors and ‘poor’ teams who can afford only cheap motors.
Voltage
By reducing voltage to only 9V there would be no reduction of speed because you can buy motors for 9V with the same parameters as for 12V but with a higher current and there would be the same problem about effectiveness and price of motors as already mentioned above.
So I think that the best way to reduce a robots speed would be to measure the time that it would take to move from one goal to another on a straight line on maximum gameplay speed and set a minimum time required(1.5s or something like that). This time could be measured by a stopwatch for example on phone. Also, this measurement would be repeated for instance 5 times.
Another way is to mount a camera about the field and measure the speed of all robots during gameplay. This camera can be for example raspberry pi or even a beater smartphone with a custom app. By using this approach it will be ensured that no speed limit will be exceeded but I think that the first method is more feasible for this year because it is much simpler for implementation in real-world but the second one would be useful for next years and maybe even some data can by collected and used for some machine learning models and it might be next big step to get closer to major leagues.
To address maximum ball speed after being hit by a kicker there are multiple ways to measure it but I think that the best way is to place the robot into the bottom left corner of the playground in such a way that the ball would be on the edge of the white line and kickball next white line towards the opposite wall. The robot would pass the test when the ball would not exceed the white line boundaries after being bounced from the opposite wall(a smaller distance would be of course also allowed). Advantages of this testing method ower currently used one are that it would be possible to do this without any additional equipment and for all types of balls as well as that it would take into consideration a carpeted surface(a higher string of carpet would slow down ball more rapidly so it would travel smaller distance so the kicker strength can be increased).
@bukajlag I actually wrote a draft with your speed suggestions and we came to the conclusion that they would not be practical for this year. A stop watch would not be accurate enough given the 0.25 second average reaction time. Also this discounts any acceleration so would not be a true speed test. Finally, it is a mute point since any team could easily program their bot or change speed some other way during inspections (this could be said about the kicker test as well however the rules do state the kicker can be tested at any time and is a pretty straightforward test to run)
I agree a camera could be used, but as @Dave suggested, this would put a large burden on event holders. We also looked into apps that measure speed or rpm (e.g. strobe tachometer) and they are also not ideal solutions right now.
The voltage drop rule opens up the idea that teams that push the edge of what’s capable may begin to have to think about how much current they are using throughout a match. Cells could be placed in parallel but that also pushes against weight limits. A drop from 12V to 9V may not be too much of a change now, but it can be restricted more just as size and mass.
I know other competitions have budget restrictions on the bots but the focus of the voltage rule change is to limit speed (not only to be more “refereeable” but to also match the conditions of a human soccer player where one cannot outrun the ball - increasing kicker strenght is an option in that regard but that then balances with safety) and not address cost. Some organizations are able to invest in high end components like motors and pass them down through generations of teams.
It’s good to see many of the same suggestions we discussed being brought forth here. Thanks to those that backed up the points against fuses - maybe that issue can be put to rest for now? As for speed/current, please keep replying with ideas.
I think we underestimate the power of children too much.
If the rules specify the rated capacity of the fuse, the player will choose the product with the most favorable standard among them. If a player is unable to notice the difference in standards, it is natural that he will be at a disadvantage in the competition. I don’t see that as a problem.
It is true that teams that use expensive, high-performance motors have an advantage. But when I look at the maxon motor you gave me as an example, it’s the kind of motor that makes me think that current limiting is the optimal solution? The stall current is 23A, remember?
There is a tendency among players to think of Maxon’s RE series motors as the best, but maybe they are not. There will surely be players who will find a different answer in a few years. Aren’t we looking for players who can use their technical skills to defeat teams that use expensive components?
I oppose any regulation that limits the absolute speed of robots. It is the essence of any competition to seek speed and power under limited conditions.
It is not about underestimating the children’s capabilities, it is about doing our best to offer a level playing field in which the richest teams don’t have more of an advantage than is unavoidable.
This would greatly reduce the usefulness of the rule. We do not want to do “rule avoidance training”.
This is true but more involved than reducing battery voltages which is easy and hopefully useful. If it turns out not to be enough we can adjust for the following year.
Yes and no, we’re looking for kids to develop robotics skills, only one of which is the electromechanical engineering problem of “robot go fast”. While we cannot avoid it completely we do not want to subject them to adversity by factors out of their control such as order of magnitude differences in budgets.
That is true of racing but not quite true of this competition. It aims to further robotics education and the field of robotics itself, the overarching goal of RoboCup is to solve control and strategy problems in such a way that robots can beat humans at human(oid) soccer in 2050. This would easily be possible today if fast, powerful wheeled robots just outran humans. Advantage in this competition should come in large part from perception, coordination, strategy and other “soft(ware) skills”. And part of the shift to that direction is robots becoming slower than balls in the medium term.
In my oppinion as a person participating the RCAP, open league was quite “Referee-able” because of φ18cm making the robots motor smaller and lowpower. In opposite some teams in Lightweight league was not “Referee-able”.
And in my oppinion I truly think that we don’t need pushing because it is almost imposibble to see the ball-robot-robot contact and just take lack of progress when the ball and robot is stuck between robots near the goal.
In addition to this the refree has to “see” the robot and ball at the same time if the robots was pushed out or self out. I think that this is kind of immposible to judge too(only 2 eyes on a human).
And forcing the robots motor to move in the opposite direction(pushing back the robot) is not a good thing to the motors and motor drivers and battery.
So I think pushed out of bounds and self out of bounds should be same penalty and make it 30 seconds so that the robots can play more in the game.
I think that this will make Lightweight league “Referee-able” while maintaining the speed of the robot (using 12V rule)
Open league robots have to be φ18cm and has a omidirectional camera on top while able to see a golfball near the robot. I think that the rule for only 1 camera for a robot and handmade mirror rule is too dificult and the hardware requirement is harder than Robocup SSL robots. I think it is not nesesary and just simply making the league dificult and not exciting.
I perefer to just erace all of the camera limitation.
While I know that fuse is hard to mount on Lego robots and comercial kits, I think there must be a proper current limit fuse on Lithium based battery robots and should cut current in case of short-circit and to prevent explotion of the Lithium battery.
And addition to this there should be a rule that if you charge Lithium based battery, there should always be a student seeing the battery charging, to stop charging in emergency to prevent explotion of the battery.
Could you please attach the diagram to the PDF version of the rule book as it says “The schematic of the device can be printed from the diagram at the end of the document.” ?
Please correct the difference between the PDF version and the github version.
1）The PDF version does not have annotations 5 and 6 in the text.
*5 usually a count of three, the length of the count could be decided by the OC before a competition as long as it’s the same length within a sub-league
*6 In previous version this said “Reprogramming of robots during the gameplay can only happen when they are out of game (i.e., damaged or out of bounds), or when explicitly allowed by the referee.”
2）The numbers after Appendix A are different.
ex.) Appendix A: Technical Specification for pulsed Soccer Ball
*IR light github A.2.1. PDF 1.2.A
*Battery life github A.2.5. PDF 1.2.E
O my god, I was on holidays and missed out the probably most interesting discussion of this season…
Let me put in some more thoughts:
Current limitation (with fuses)
Well, there is a rule that allows kicker voltage pumps to produce 100+ volts for a kicker. On the other hand there are (german school) rules that do not allow voltages above 48V for students, whatever they do.
So I decided to not allow my students to use voltage pumps at all. So they decided to rewind the solenoids with 0.5mm copper wires and kick with 12V and approximately 15A to get the power to move the IR-Ball with slightly under 1m/s. Introducing a 10A or 15A fuse will kill this approach that was chosen for safety reasons. So please do not go further into this direction!
Voltage drop
as mentioned before a new voltage setup will increase the gap between “poor” and “rich” teams.
There are plenty of 12V Motors with great parameters to have a good robot at a reasonable price.
And face it, parts are recycled by lots of teams. A “good” motor / gearbox / motor-driver - combination will find its place in future robots again. Changing voltage setup will ruin this consistent workflow.
And it is not only the motor, it is the driver as well and there is no need for this at all in my opinion.
Here is my suggestion:
You want to reduce the (sometimes ridiculous high) power of the motors.
Well, just change this, if you think you have to.
There is a German subdivision called “soccer 1vs1 open” that introduced a power restriction
years ago by simply asking for the motor datasheets and have a fixed stall-current limit.
That kicked out the well known pololu HP-motors and just allowed the pololu MP-motors.
In the last few years almost all teams used these MP-motors and the “carped eating” robots vanished over night.
So what about a - lets say 25Watt - stall power motor restriction proved by the datasheet of the motor manufacturer/dealer?
That will allow this very motor pololu (2.1A stall at 12V) and lots of other motors including small brushless motors as well and there is no need to change lots of other components.
And this is much more usable than any “speed traps” ore measurement devices.
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:
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…
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.
Hey,
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,
Eddie
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…
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
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.
