Difficulty of and ideas for LWL #soccer-rules-2023

[david]

Hello everybody, @remosgro has posted some intersting experiences relating to the dynamic between LWL and OL with the changes to the ball and the robot size as well as some suggestions over in the main rules thread that I’d like to spin out into it’s own discussion thread here:

@remosgro

Hi everyone, I’m Raimondo form Italy, Team MegaHertz mentor, and Italian RR 'til 2021.
I have some point to suggest and I’ll start from Soccer Lightweight

Soccer Lightweight
This sub-league is supposed to be the entry league in the international competitions, but if we observe the international (and also national in my experience) tournament the level is quite higher than open league. I think this is due to the fact that rules in this category was substantially stable for many years. In open league, from 2016 two important rules changes was happened, and thank to this, new teams are allowed to compete with same possiblity than others. In Lightweigt is more difficult to start. In my mentor experience, in the past first with the new students I started in the Lightweight category and then they continued in the Open category. Now I start directly in the Open category, it’s easier and less frustrating because the level allows new teams to play.

Concluding I think that rule changes in the Open sub league worked well, and made international and national tournament more playable (especially for new teams), so I propose to make important rule changes in the Lightweight as well:

• reduce size to 20cm diameter
• move to “old” orange passive ball
• introduce power or torque limitation

I explain my proposal:

• reducing robot size (like Open league) corresponds to having a proportionally larger field. This should increase use of strategy in game.
• the pulsed ball is too big for a 20cm robot, so I propose to use 7cm orange passive ball. Furthermore, this make easier the first project, in fact there’s many embedded vision system, but very less pulsed ball detectors, so that in Lightweigt teams have to design their own.
• in the past rules, we can find “rules aimed to favor skills over brute force in the games” I think we have to follow this direction, and introduce power or torque limitation in this sub-league (for the moment) is the only way to avoid that the game became a money game and not a strategy game. In this moment, use powerful (and expensive) motors ensure performance. But if we want to favor game strategy is the only way, cause field is too small. Power supply limitation is not enough, cause is always possible to get powerful motors if you can spend enough.

[david]

Hello Raimondo,

thank you for spending time and though on how to improve LWL. I’ll try to respond to everything block by block and explain my views as well.

@ everyone else: Please feel free to jump in, we’d appreciate any experiences and thoughts you may have.

@remosgro

Soccer Lightweight
This sub-league is supposed to be the entry league in the international competitions, but if we observe the international (and also national in my experience) tournament the level is quite higher than open league.

A higher level of game play is to be expected for the league where the technical challenges are easier to master - IR sensors often run more than 10x the speed of cameras and have higher range and better reliability/robustness, that makes it easier to have high level game play - at least that’s my impression. Following that chain of thoughts the higher level of game play in LWL is to be expected, not a problem and the challenge of OL is to get to the same level with vision as with the “cheat” of the IR ball. In that context the weight limit doesn’t fit the picture too well anymore.

@remosgro

I think this is due to the fact that rules in this category was substantially stable for many years. In open league, from 2016 two important rules changes was happened, and thank to this, new teams are allowed to compete with same possiblity than others.

I think this difference is not mainly due to the lack of experience with the new OL rules but mostly due to the light weight robots being able to use their powerful motors because their ball sensing goes 100Hz+. I believe this to be the case because mechanically fast OL robots exist - but they don’t see quickly enough to use it.
Years of development may give some teams an edge but some stability is necessary for schools and clubs to be able to keep up and grow into the rules. There is as always a balance to be struck between teams having access to knowledge and parts at their school instead at the cost of the risk of some re-use of outgoing teams’ work versus needing to buy and learn completely new stuff on a regular basis due to ongoing extensive rule changes. Neither extreme is a great.
The balance of experience, stability and originality will continuously need adjusting. I’m not sure we have enough information to make a definitive call on that yet because it’s the first year RoboCup Junior is back and also because we’re not good at getting feedback in from all over the community, esp. questions with regards to how new teams approach it aren’t easy to evaluate as there may be large differences in different schools, regions and so on.

@remosgro

In Lightweigt is more difficult to start. In my mentor experience, in the past first with the new students I started in the Lightweight category and then they continued in the Open category. Now I start directly in the Open category, it’s easier and less frustrating because the level allows new teams to play.

That is an interesting experience that I would not have expected for the reasons explained above. Does anyone else similar experiences? Please post your experiences below everybody.

@remosgro

Concluding I think that rule changes in the Open sub league worked well, and made international and national tournament more playable (especially for new teams), so I propose to make important rule changes in the Lightweight as well:

I agree that the changes to OL worked well.

@remosgro

• reduce size to 20cm diameter

@remosgro

• reducing robot size (like Open league) corresponds to having a proportionally larger field. This should increase use of strategy in game.

We already have the enlarged playing area in the 2023 rules draft increasing the field-size-robot-size-ratio. If it is to be easy for teams to get into we should be careful about reducing how compact they have to make their robots. Such changes (requiring robots to be rebuilt) also require announcements well ahead of time so I suspect it is unlikely to impossible for this to happen for 2023.

@remosgro

• move to “old” orange passive ball

@remosgro

• the pulsed ball is too big for a 20cm robot, so I propose to use 7cm orange passive ball. Furthermore, this make easier the first project, in fact there’s many embedded vision system, but very less pulsed ball detectors, so that in Lightweigt teams have to design their own.

We moved away from this ball because it is quite difficult to get similar balls all over the world, Golf balls were how we could solve that problem. The IR ball is now down to one manufacturer of which it is not clear how long it will keep it in production though so that issue might force itself upon us at some point.

I will say about the IR sensing that while it requires to make a board (or rather to have a board made), open source designs made by teams are available and the speed and robustness of recognition lends itself to getting to decent game play much more easily than camera solutions (particularly mirror-based ones that frequently have difficulty recognizing an unobstructed ball at >1m distances.

@remosgro

• introduce power or torque limitation

@remosgro

in the past rules, we can find “rules aimed to favor skills over brute force in the games” I think we have to follow this direction, and introduce power or torque limitation in this sub-league (for the moment) is the only way to avoid that the game became a money game and not a strategy game. In this moment, use powerful (and expensive) motors ensure performance. But if we want to favor game strategy is the only way, cause field is too small. Power supply limitation is not enough, cause is always possible to get powerful motors if you can spend enough.

This has been the topic of some debate. Key points being:

• voltage limits (the now dead 9V proposal don’t work as higher current motors are available
• a power measuring device is under consideration but efficiency advantages of expensive motors are significant, esp. over very cheap ones (think 75% vs 15%) so at 20W each the difference would become bigger not smaller
• Attaching an IMU to approximate how fast robots are going is too sensitive to drift, vibrations, mounting etc.
• Tracking the robots via a camera over the field is under consideration but it is uncertain all tournament organizers could make this happen
• we are unsure on how you would implement a tourque limit without building complicated and possibly error-prone measurement devices.

Cheers and thanks again for a very thoughtful contribution,
David

[david]

The 2023 final rules, out now do not contain any concrete changes but we’d like to carry on the discussion for 2024 as LWL does have potential for some more optimization.

Best Regards
David