FIRST Robotics Competition Blog

My team has run 6-motor tank drives the last two seasons. It's a relatively cheap upgrade over the stock AM14U5 chassis (roughly $400 for everything--plates, motors, controllers), and it's felt like one of the few ways for a mid-budget team to physically keep pace with teams dropping thousands more on swerve drive systems.

While I understand the need to keep the highest-end teams in check because 8-propulsion-motor swerve was about to hit like a tsunami, this phrasing feels like it's going to drive an even bigger competitive gulf between teams who have resources to swerve and teams who do not. I'm not a fan of that.

Since I was trained to not complain unless proposing an alternative, here’s mine: if you make X weight, you get another two motors.

How would this rule change affect differential swerve which uses both motors as steering and power motors?

Does this preclude something like the holonomic H drive system we've been developing? (four motors driving forward and back, two motors in the H module for lateral motion) That would be very unfortunate, as we've been developing this as a more affordable way to compete in the age of swerve

If very fast robots is the problem; how about limiting robot speeds? Or, peek drive current? This rule changes eliminates at least one class of drive currently used. Four corner (or tripod) differential swerve. And limits potential H-drive configurations. Or, limit the long open field runs available. Charged Up was designed for max speed collisions at center field. 

Will differential swerve be permitted? Once the direction is established a differential swerve could be considered 8 motors driving the robot.

limiting the number of motors doesn't seem as useful as limiting the top speed of the robots (during inspection, stick them on a treadmill and run them at their full speed, or present engineering specs that prove the top speed is less than the determined limit)

our current SDS swerve modules do 16ft/s, one of our competitors redesigned theirs to use belts rather than gears and claims they can get up to 26ft/s; we both use the same 4 motors...

This rules out the possibility of differential swerve systems, correct?

למה לא בסוף העונה יש קבוצות שכבר תכננו את העונה הבאה עם מספר המנועים

How will this ruling affect differential swerve modules Many of the modern serve modules use differentials between two motors to control direction. With 2 motors required per corner for this does this rule make 90% of current swerve modules illegal. Considering the cost of new modules will allowances be made for these existing modules.

Our current KOP tank drive has two drive motors on the left and two on the right powering just the center wheel.  So that would not be legal and we would have to remove one motor?

Hey! I just wanted a clearer definition of what 'secondary and incidental feature' would mean? Our team is confused on the difference between swerve steering motor and what was mentioned in the comment by Quinn:

 

What about a game like Deep Space where many teams used a supplemental propulsion mechanism to move their bot forward when trying to climb to higher levels of the habitat? While this could be viewed as exceeding the number of motors if four are already used for the main drive on the field, use of an additional motor in this way seems in the spirit of the new rule. Thoughts?

Would these rules apply to endgame mechanisms with powered wheels/treads such as many habitat climbs in 2019 and a few charge station side climbs in 2023? I am not completely sure if that would fall under "small amounts of thrust as a secondary or incidental feature" or if endgame climbs would not be allowed to have powered wheels which touch the field from now on. Thanks!

In the 22 season we built a working switchable gearbox - essentially a transmission where 3 motors worked towards driving and a servo flopped the gearing to use for climbing using the same motors. Can we do 2 driving and 3 climbing for example in the same gearbox - provided we can prove that only 2 are driving per side? This transmission was CAD'd by a freshman who only learned Solidworks the fall of 2021 and designed and built it with guidance only from our engineering mentor. She learned Solidworks from another student. Ultimately we went for a different climber approach but the transmission functioned great the whole season in 3D printed form with metal gears. I would hate to see that kind of innovation be stifled though this rule just means we have to be more innovative to solve problems of power vs speed.  

Every season the game is ultimately about how many different (and repetitive) tasks can be done within the window of the match. It possible the game designers did not have the time to consider the effect on the game cycles that slow robots on the field would have to contend with. Has the rules and game play taken into account the 4 max drive train rule change?

Hi I just wanted to check if these are illegal https://www.andymark.com/products/mk4-swerve-modules these are the swerves mk4

 

I find this is a good solution to help limit impact related damages that affects teams with lower budget. The price of these 3 motor swerve and replacement motor is also hard to sustain, especially for the championship. Good idea!

Hello! 
Does propulsion motors refer to the possible motors that could "touch" the ground during a match or the amount of motors that "touch" the game at any given time? To clarify, if there are smaller wheels that are in the center edges of the robot that only contact the ground when the robot is high-centered/ the front or back two wheels are not touching the ground in that instance. This assumes four motors in each corner for four wheels and two motors for the center edge wheels that only touch the ground when two of the main wheels aren't touching the ground. If this is illegal then it feels very limited in terms of drive architecture for a game with terrain field elements.

 

 

 

So does this mean that the REV Swerve is legal?

In previous years we have seen so many types of driving styles, each with its unique features and characteristics.  The abundance of chassis designs is one of the reasons why we love FRC.  So I am deeply concerned that this new rule will eliminate any possible chassis innovation and limit the drive-train solution down to one: swerve drive.
Yes, technically, the rule did not prohibit any chassis design.  But the rule has made it almost impossible for teams to think about any chassis types other than a swerve. The primary advantage of innovative drive-trains we've seen today is that they implemented some kind of mechanism, like the mecanum wheel, that allows each motor to both provide propulsion for the chassis and control the direction of movement. This saves the team from using extra motors to control the direction and allows the team to more thrust.  But now that the amount of propulsive motors is limited, it makes swerve drive literally THE INVINCIBLE CHASSIS. 

A more significant and appropriate action, in my opinion, will be to limit the total power of the robot. According to the law of physics, that is the most straightforward way to limit momentum(power = force*velocity, momentum = mass*velocity), and it encourages teams to seek for more efficient driving style. It is very easy to achieve too, just apply a power limit to the PDP in its firmware.

You commented regarding a holonomic H-drive system; however, I still have the following question because any h-drive limited by your answer would by at a significant disadvantage to teams already possessing, or with the resources to acquire, swerves drive capability. Moreovrer, it also may promote the use of holononic mecanum-drive system which may be harder on the feild carpet than other drive systems and  have an even greater power propulsion disadvantage to swerve drive systems because of shear forces and power lost due to opposing drive vectors. Therefore, my question/thought is this:

Since it would not violate the spirit of purpose of the rule because speed is always limited to four or less motors causing propulsion at any moment in time, and the other wheels roll with insignificant sheer forces on the field carpet would it be reasonable to permitted, via the rule, the use an H-drive propulsion configuration with four forward/backward propulsion omni-wheels and two right/left drive omni-wheels if proving to be limited by programming that allows only the forward/backward propulsion omni-wheels or the two right/left propulsion omni-wheels to propel the robot at any moment of movement?

 

It is realized that this would create some additional efforts on the part of inspectors during inspection of robots that would use such a transport/propulsion system, yet this overhead should not be excessive.