Tight space and fast placement may make some traditionally tank teams consider other drive train options for this year’s game.
In 2019 our team was thinking the same thing. We did not feel ready to take on swerve and opted to build a mecanum drivetrain that year. It was our most successful year up to that point, we ranked first at two competitions and went on to worlds to be an alliance captain on our field. So it is most definitely playable in FRC.
Having said all of that, I would not recommend building a mecanum drivetrain unless there is zero defense in a game or where your robot will be. It is difficult for an alliance to select that robot due to the risk under defense being the most obvious reason, speed being second. Secondly, as we found out in the 2019 post season when we switched our comp bot to tank we also did really well. The robot was not as maneuverable but what we lost in agility we made up in speed. With some effort on vision assisted placement the robot can perform very well with tank.
Our team ran swerve in 2021, 2022, and most likely 2023 and if your team is ready to try it this could be a great year for you to make the change. This will be a great swerve game.
But if your are at a comp with mecanum bot possibly on the selection list I would strongly consider picking them if you have right strategy that they could fit into. It could be the formula for an upset.
Heavy agree. If your team (obviously not referring to OP) hasn’t gotten a swerve system figured out in the next week or so, I wouldn’t try it now unless you have excessive time and programming resources (took me almost 2 weeks to get the software working well during the off-season). There’s a lot of learning involved. Mecanum is probably the next best choice for holonomic drivetrains which seem like they’re going to be very handy (though not mandatory) this year. And WPILib has excellent support for it nowadays.
The biggest complaint I’ve seen about mecanum drives is that they’re easy to push around. Which is true… relatively. As anyone who’s ever pushed a powered-off mecanum bot can tell you, there’s still plenty of resistance, just not as much as trying to slide a normal rubber wheel on carpet. A mecanum bot will get pushed around, but they can still fight back, and the drivetrain is still holonomic. When it comes to picking allies, pay attention to how they play, not what they’re made of.
As an anecdote, my team has been using mecanum drive since at least 2011, and we’ve generally had a very competitive robot, almost always landing in the finals, and even making it to internationals a few times (and when we did poorly, it was usually due to unfortunate design choices that weren’t the drive). Even with the rise of swerve, our team has still done well, so mecanum is absolutely viable, especially on a budget (specifically one that can’t afford 4 swerve modules, 8 nice motors, and 4 absolute encoders, in addition to the rest of the robot).
My biggest concern for mecanum or omni-wheel based drivetrains this year is the charge station. Until you try it out you won’t know just how easy it is for these drivetrains to slide or slip around. But, clever methods of putting down a braking pad may alleviate this.
Last year that we did mecanum was 2017. We were finalists at one event, ranked 2nd at our next, and placed 16th in our division at champs… where NO ONE selected us.
The stigma is real.
I suspect some clever programming and either a decent accelerometer and math or encoders on the drivetrain should help with this as well. Accelerometer would be best if sliding is more of a problem than rolling.
Ideally, some method would detect the fact the robot was rolling or slipping, and the robot could drive very slightly in the opposite direction to compensate automatically.
Here is a video of a mecanum drivetrain maneuvering on a charging station surface. ( It is tilted at 19 degrees instead of 15 because that’s what boxes I had).
I noticed it was hard to strafe while straight but towards the end of the video you can strafe as long as you tilt in the direction you want to go. Plenty of traction and easy to hold position on the polycarbonate.
They are the VEX 6" Mecanums. They have a firm rubber on the rollers for traction. So any mecanum wheels with rubber on the rollers should preform about the same.
If you dont have swerve in your shop at this very moment by the time you get the parts and it all together you will be significantly behind let alone the hours it will take to figure out and get comfortable. Like another thread said you can order swerve now but dont expect to use it until next season.
As for mecanum… My team (3205) ran mecanum for last years game and played defense (1st and 2nd place district event along with regional). The biggest complaint about mecanum is being pushed around, however we were the one doing the pushing. Our programers had made PID loops for the motors so that if they experienced increased resistance or the robot wasnt moving how it should it would dump more power into the motors (It was a lot more complex than that but thats just a brief explanation) with the PIDs we were able to push tank drive robots (from front and side) along with swerve robots along with resiting being pushed. It wasnt “easy” to push other robots but it was still relativly effortless. we were even able to use the strafing ability to get around robots and into their way.
Long story short we can prove true all the benifits of mecanum but with the right programming most of the negatives can be (almost) completely overcome.
Robot as tested was 149 lbs and 12oz.
Depends on the height of the bumpers and what the surface of your test ramp is that you are testing on. The other thing to remember is that it is articulated It will move under weight and will push down and make it easier to climb as you push down the ramp.
I would be interested to hear more about how you did this if one of your mentors or students would be willing. We ran mecanum last year and did quite well. But we did get shoved around the field some. Our driver tried to shove back one match, and we believe it burned out some of the motors as they had to be replaced later that day. So we told him not to get in a shoving match going forward and just let them push. I did look up your code on GitHub, but I wasn’t able to follow it given the custom coding structure you used.
G201 is not a sure defense here. It requires that referees see the opposing robot’s strategy as clearly intended to draw penalties. There’s a very busy crossroads between the loading zones; a robot getting pushed into a zone because it was in the way of a robot going to get a game piece would be penalized under G207.
In practice, G201 has typically only prevented the most obviously penalty-grabbing strategies like trapping in a protected zone.
The blue box specifically states that pushing a robot completely outside of the opponent loading zone into the loading zone applies under G201. I would also think that it isn’t consistent with standard game play to attempt to put a robot between yourself and your objective.
Blue box is also not part of the rule. It’s intended to clarify and provide examples.
And it also very clearly states that strategies consistent with standard gameplay are not against the rule. That may include trying to score through defense, and as a byproduct shoving the defender into the protected zone!
