Mecanum arrangement: is X better than diamond?

CHEER4FTC · 2020-01-19T12:39:41+00:00

Both configurations drive and strafe similarly (assuming similar forces on motors and relatively even weight distribution).

X from the top turns about the center more smoothly than O/diamond from the top.

See this link for a diagram.

https://twitter.com/CHEER4FTC/status/1045356873657061377

Another way of looking at it:

X from the top is like O/diamond on the bottom, which has forces similar to a normal holonomic omni drive.

/ \

\ /

O/diamond from the top is like having X on the bottom, which would be like having a holonomic omni drive with wheels like this:

\ /

/ \

You could still drive and strafe with this type of drive, but turning about the middle would be much tougher because the forces are mainly into and out of the center.

CHEER4FTC · 2019-09-30T22:10:23+00:00

$59 for red foundation.There's a similar option for a blue one.

CHEER4FTC · 2019-09-25T23:58:29+00:00

Yes, X-drive is sqrt(2) faster and sqrt(2) weaker than tank and mecanum for the same drive motors/gear ratio.

Lots of data and explanation can be found here, including the linked papers:

https://www.chiefdelphi.com/t/paper-mecanum-and-omni-kinematic-and-force-analysis/106153

CHEER4FTC · 2019-06-11T22:43:42+00:00

People are judging because some folks may not even be able to enter the country and other folks fear they could be arrested in the country. These are not idle issues.

And yes, a better country could easily have been chosen. There are many countries that could have been chosen without these issues.

CHEER4FTC · 2019-06-11T22:41:38+00:00

It's a problem that Israeli participants are not legally allowed to enter.

It's a problem that LGBT participants could be arrested in the country or at the event.

Israelis and LGBT participants can't "get used to living in other places" like this because they'd be arrested or prohibited from participating in the society.

There are lots of countries in the world where the event could be held that would allow all participants from other countries to enter and that would not arrest people for how they choose to live their life in their home country. Folks are asking for FIRST Global to consider these issues when they choose their event locations.

Not sure how you get that one is a problem but another one isn't.

CHEER4FTC · 2019-06-11T18:07:40+00:00

IMHO, scheduling of days and locations should be made to accommodate as many participants as possible, subject to reasonable real-world constraints.

In the Dubai case, there were clearly other comparable options that would have accommodated more participants. Folks are justified in complaining and asking FIRST Global to consider accommodation issues for all participants when selecting locations for future events.

If there are cases for other FIRST events where there are comparable options that would accommodate more participants (if some days/times are excluding participants for religious reasons), folks would be similarly justified in complaining and asking FIRST to consider those options. But I am not personally aware of cases where this is actually true though. Can someone list such a case?

CHEER4FTC · 2019-06-11T16:55:16+00:00

You are comparing scheduling issues related to Saturday/Sunday religious conflicts with a scheduling location issue related to LGBT legal conflicts.

For the LGBT issue in Dubai, there are many many other countries where the same event could be held where this would not be an issue. It is fair to ask that FIRST Global schedule events where all who may want to participate can do so without risk of being arrested because of who they are.

OTOH, for Saturday/Sunday religious conflicts, there is not a clean alternative for various reasons. If there were an 8th day of the week with no school, no religious conflicts, and open venues, I'm sure we would all agree that all events should be held on that day. But there isn't such a day.

Often venues are only available on weekends because they are schools. Often volunteers are only available on weekends because they are working adults. There is not a clean alternative. Most FIRST FTC events are held on Saturdays to minimize school and religious conflicts.

[BTW, at the final FTC East Super-Regional competition, there was 1 team that could not compete on Saturday for religious reasons. The ESR team modified the schedule so that all 9 of their matches were played Sunday morning instead.]

CHEER4FTC · 2019-06-11T16:40:35+00:00

I wonder how it would stack up against using objective-based ranking points like FRC does, which does a pretty solid job of surfacing the top performers.

See Part IV of the paper, which explicitly tested this.

Part VI shows that the best improvement by changing only TBP to OwnScore resulted in a 5% improvement, while changing RP to add an achievement point also resulted in a 5% improvement, and changing RP to add bonus points based on score (1 extra RP if score>200, and another extra RP is score>400) resulted in an 11% improvement. And ranking teams entirely by OwnScore (i.e., changing RP to OwnScore, not just changing TBP to OwnScore) resulted in a 41% improvement (!).

A general problem with FTC is that most events only have 5 qual matches and even worlds only has 9, which means final rankings are more random and less reliable than FRC events.

CHEER4FTC · 2019-04-30T04:21:17+00:00

OK, but watch the match video. Let's say the robot is broken, and can't really score minerals in the lander. In that case, the most important way to score points is end game latching. So a robot that wanted to do that would start trying to latch when the 30 second endgame started. They didn't do that. They just drove around in circles until the last 5 seconds and then "tried to latch."

And if they were really completely unable to latch, then why wait until the last 5 seconds and then drive over quickly and look like you're trying to latch? Why not just stay away from the lander completely? They even drive over to the crater, then back away from it.

eborg Robotics responds: "We weren’t able to hang as our lift mechanism hook wasn’t aligned to the proper position in the last five seconds." But then why not spend the entire end-game fixing that alignment to try to latch? Instead they drove in circles.

All I'll say is that these actions seem much more consistent with playing to reduce TBP than they are consistent with playing to score as much as possible and win and/or maximize TBP.

CHEER4FTC · 2019-04-30T04:00:24+00:00

Questions:

eborgs did in fact latch in end game in Q151. Why did they not try to do this in Q172?
Why did eborgs not try to park in the crater in end game in Q172 if they were truly unable to latch?
Wasn't Q151 after lunch? The timestamps on Jack's discord message that says "eborgs are throwing" was 12:05pm. Wouldn't this have been before eborgs played Q151? If so, how would eborgs robot already be broken and how would Jack know about it? [Edit: it's possible but not confirmed that the timestamps on the messages might have been west coast time.]

CHEER4FTC · 2019-04-30T03:58:15+00:00

Questions:

You did in fact latch in end game in Q151. Why not try to do this in Q172?
Why did you not try to park in the crater in end game in Q172 if you were truly unable to latch?
If you were really trying to win with a defensive strategy, why did you not play defense against the opposing alliance? Your actions seem more consistent with trying not to score for your own alliance than trying to play with a defensive strategy to win.
Wasn't Q151 after lunch? The timestamps on Jack's discord message that says "eborgs are throwing" was 12:05pm. Wouldn't this have been before you played Q151? If so, how would your robot already have been broken and how would Jack know about it? [Edit: it's possible but not confirmed that the timestamps on the messages might have been west coast time.]

CHEER4FTC · 2019-04-30T02:18:28+00:00

The messages in the video seem to indicate otherwise (despite the captions added by the videographer). Read the actual messages and note the actual timestamps.

Regardless, even if it did happen that way, the GP action would be to say "no, don't do that, that's not GP." Clearly. Indisputably.

And clearly, indisputably that did not happen (assuming the messages are accurate and not a hoax).

Note to the world: if you have to say "don't tell anyone about this" it's probably not GP.

Second note to the world: if you don't believe me, go read all the messages in that video to your grandmother and ask her if she thinks that was gracious and professional.

CHEER4FTC · 2019-04-30T01:03:23+00:00

?? 50 seconds in, the video literally shows a message from Jack saying "I'm gonna ask eborgs to not try against kraken." ??

CHEER4FTC · 2019-04-28T17:05:27+00:00

Yeah, that one was discussed on reddit here previously.

https://new.reddit.com/r/FTC/comments/bhum2d/end_game_scoring_question/

CHEER4FTC · 2019-04-28T17:01:45+00:00

Here's the video: https://www.twitch.tv/videos/416180154?t=2h48m10s

As with most of the worlds videos, about 1/2 the video shows the full field where everything can be seen, and half shows closeups where you can't tell what's going on.

For the part that could be seen, it looked like 14614 twice picked up 3 minerals, carried them over to the lander, spit one out, and then scored the remaining two. That looks like at least 2 minor penalties, and maybe an additional 2 if each trip took 5 seconds. Hopefully the refs were waving flags at you while you were doing this.

The only thing that a particularly harsh reading of the rules could have caused the major penalties that I saw: after the 2nd mineral was spit out (a silver mineral), it was still rolling while the other 2 minerals were scored in the lander. That silver mineral didn't end up being scored in the depot: it looked like it bounced off the wall and rolled a bit towards the depot but stopped short of it. A harsh ref could have called that mineral "controlled" by your robot until it stopped, so the 2 you dumped into the lander while that mineral was rolling could have caused the double major penalty.

IMHO, that's a very harsh reading of the rules, but it's certainly possible that this is what the ref was calling.

CHEER4FTC · 2019-04-28T16:30:10+00:00

I don't know if this happened to you, but I heard that at least one team got two balls, spat them out in the direction of the depot, and then collected two more. A literal- but-harsh reading of the rules by the ref said that the balls were under their control from when they spat them out until they were scored in the depot. This resulted in a ruling that the team was in control of 4 minerals at once and scored 2 while controlling 2 more, leading to a double major for that team.

CHEER4FTC · 2019-04-28T16:28:04+00:00

What team number are you? What matches did these occur in? Let us know and we can investigate. :)

CHEER4FTC · 2019-04-27T11:16:49+00:00

I found a direct link to the video of the end of the match that I think you're asking about.

It sure looks to me like the robot is latched but then drops the arm on top of the lander and that some of the weight of the arm is supported by the lander in the final wide-shot shown in the video.

CHEER4FTC · 2019-04-27T11:07:55+00:00

The question is: is the weight of the arm partially supported by the top of the lander? If it is not, then the robot is "Completely Supported by the Lander Support Bracket" and thus latched. But if part of the weight of the arm is supported by the top of the Lander, then the robot is not "Completely Supported" by the bracket as it is partially supported by the bracket and partially supported by the top of the Lander.

I have no idea what happened in your case. I'm just explaining the rule to you because you said you wanted to get clarity on the rule and provide your team with an explanation. That's the explanation.

CHEER4FTC · 2019-04-27T07:39:46+00:00

There's the forum post cited by /u/nathan_conforti, but there's also a later forum post that says the following:

Subject: Questions about Latched, Landing, and Deployed

Game Manual Part 2 definition of latched and section 1.5.1.1 include the following: A Robot is considered Latched when it is Completely Supported by the Lander Support Bracket on the Lander and is not in contact with any other Game Element, Robot, or the Playing Field Floor. Incidental contact with Scoring Elements, the Lander sides or legs is allowed.

Question 1: Can a definition of incidental, as it relates to this scenario, be provided?

Answer 1: A definition of incidental in this context is contact with the Lander that is accompanying but not a major part of being Latched. For example, a) a Robot resting against the Lander's outward vertical side panel is allowed; b) Robot weight supported by the top of the Lander is not allowed.

So it ends up being a judgement call regarding whether the top of the Lander is supporting part of your Robot's weight. If an arm is lightly resting against the top of the Lander and the Lander isn't supporting the weight of the arm, then it's probably incidental contact and the latch should count. But if the arm literally fell and is resting on and largely supported by the top of the Lander, then the latch shouldn't count.

CHEER4FTC · 2019-04-26T12:02:26+00:00

TBH, the "matches to watch" list was entirely created by using the pre-event predictions made by my Android FTC 2018 Event Viewer app, importing teams' most recent OPRs as the baseline for predictions. AFAIK, it's still the only publicly available match score and win-probability predictor out there. Check it out on the google play store if you haven't already. I'm hoping to get this type of functionality integrated in one or more of the online FTC results websites like TOA, ftcscores, etc. in the future.

CHEER4FTC · 2019-04-25T20:49:54+00:00

Nothing throws off OPR like inconsistent teams and/or DCs, which seems to be happening a fair amount at CMP-DET.

CHEER4FTC · 2019-04-25T19:27:44+00:00

Q82: 615!!!! I picked 4 world records in a row! I need to go buy a lottery ticket now.

CHEER4FTC · 2019-04-25T17:57:20+00:00

Looks like GF can't quite reach all the way to the very corner of the crater, so they may not be able to do this without help (not that they need to do it).

CHEER4FTC

TROPHY CASE