The Perfect swerve

[Tyler2517]

I am looking in to design and manufacture the perfect swerve drive. What would be the best features if you had unlimited resources. Would you use field centric control robot centric or some type of hybrid? 2 speed shifters or a static gearing? What speeds? 4 wheel's or 3 wheel's? Do you care about the weight more then shifting? What wheel size? Any cool layouts that save weight or make it stronger?

Opinions are welcome.

[magnets]

hmm... an interesting question. Personally, I think that this is my favorite. It's really small, really light, and really cool. It's also nice because you don't have the drive axle after the supports on the module. Having the drive axle higher up than the module rotation bearing will really decrease the loads that part will see.

If you want two speed, I've seen a team 111/team 16 style swerve that has both the motor and the shifting mechanism in the rotating part. another cool idea would be to use a vex pro ball shifter, but then have the output shaft go directly into the module, so you're "direct driving" the swerve.

[EricH]

973's Emperor Swerve is the closest to a "Unicorn"-class swerve out there.

The "Unicorn" class, as I recall, is 2-speed, unlimited turning, non-coaxial (AKA, the motor is in the module), and each side (or is it each wheel) can be rotated independently of the other (minimum of 2 steering motors). It's not easy to do, but the benefits can be worth it.

OTOH, then there's 118's V6 designs...

[s_forbes]

Each module needs a CVT to transmit power to the drive wheel, and must not be limited by module rotation (similar to a coaxial module or a module with slip rings to power the motor).

Must be controlled by a plug directly into the driver's brain.

1717 has the best I've seen so far, and it improves every year. They do not have the restriction of unlimited resources, but do a good job of hiding it!

[DampRobot]

Originally Posted by s_forbes

1717 has the best I've seen so far, and it improves every year. They do not have the restriction of unlimited resources, but do a good job of hiding it!

Quoted for truth. I hear they actually cut all their own gears, because it's cheaper and faster for them to make it out of round stock, in house than it is for them to buy and wait a few days for shipping.

I'd also check out 368's swerve, especially their driver setup. They played really well at SVR, and were the first swerve I've ever seen where the swerving actually improved their gameplay, rather than just being a cool way to move around the field.

[Gdeaver]

The perfect swerve for each team is the design that a team can implement in the build season constraints and with their resources.

[Zaque]

Originally Posted by Gdeaver

The perfect swerve for each team is the design that a team can implement in the build season constraints and with their resources.

Originally Posted by JamesCH95

The perfect swerve drive is the one that your team can design, build, and implement with the greatest degree of success.

Personally, I think you are missing the point of the thread. The hypothetical is with no limits on resources of any kind, so some designs are certainly going to be better than others.

[Conor Ryan]

Mechanically, a good swerve design is a good design. Teams that have gone through numerous iterations probably have it figured out better than most. Personally, I would love to see a 3 wheel swerve design with two cims driving each wheel, I'm not convinced the swerves we have seen so far are as fast as some of the tank bots. Additionally, I doubt a shifter gives much of an advantage to a swerve unless you are playing overdrive. 67 did an awesome 3 wheel swerve in 05, and I think that was the most dominant robot they have built to date.

I believe, the best swerve probably take their advantages from the controls that are engineered into the design. It goes above just having the right sensors, but having the correct algorithms to make driving intuitive and easy. Field oriented drive, with the ability to make the robot do what you want when you want is the hallmark of a well controlled swerve. Anyone have suggestions of teams that did this well? I know 16 and 111 did a lot of controls development to allow their drive teams to get the results they wanted, but I can't really comment on specifics.

I think we are just touching the tip of the iceberg with what can be done with the controls, the revised CAN system will really open up possibilities with finer control, and even make an auto shifting 2 speed shifter simple to implement.

[Tyler2517]

I think using a high end gaming mouse in the future to track the robot on the field will be something to watch out for in the future. I know i have been looking in to when it was mentioned in another thread.

[Dunngeon]

Originally Posted by Tyler2517

I think using a high end gaming mouse in the future to track the robot on the field will be something to watch out for in the future. I know i have been looking in to when it was mentioned in another thread.

If we attempt a swerve this offseason, this is going to be something we will try. It will be much more accurate for a field centric control scheme than what is currently being used (to my knowledge)

[Ether]

Originally Posted by Dunngeon

If we attempt a swerve this offseason, this is going to be something we will try. It will be much more accurate for a field centric control scheme than what is currently being used (to my knowledge)

Field-centric is about robot angular orientation. How are you planning to measure robot angular orientation with a single mouse? Won't you need two?

[Gdeaver]

In 2013 looked at high end gaming mice. With swerve and the chassis orientation decoupled, there are 2 solutions of the x and y counts coming from the mouse. On competition carpet and no changes to the optics we found the accuracy to be less than needed. The optic flow algorithm is not tuned for this use. With a usb port on the roborio in 2015, A usb camera highly filtered and a more robust optic flow algorithm may yield better results. A gyro at minimum would need to be fused with the optic flow. This is all for field centric control. There are 2 paths 2 look at. Sensing from the robot reference frame (gyro accelerometer fusion). Adding a world reference frame with a magnetometer or some other sensor to reference out side the robot frame of reference. GPS is out. Constellation navigation has grabbed my curiosity. It's hard. In 2013 we could have reset the gyro every time we went up against the feeder station wall to correct for drift. This year we considered IMU field centric control not doable because of the constant impacts and never having time for a reset. The last thing our drivers need this year is for the field centric control to suddenly shift several degrees while being smash defended and trying to roll out. With our low designs the last several years a magnetometer location and calibration issues ruled out that solution. Fortunately for the future of swerve field centric a couple of companies have released affordable IMUs based on gyro, accelerometer and magnetometer sensors coupled with highly tuned extended state kalman filters that should handle the rough First environment. The key is constant hard and soft iron calibrations on the magnetometer sensor. I'm hoping to make this an off season project if I can get some programming students on board. I think soon a plug and play Field centric IMU solution will be available for FIRST.

[JamesCH95]

Originally Posted by Zaque

Personally, I think you are missing the point of the thread. The hypothetical is with no limits on resources of any kind, so some designs are certainly going to be better than others.

No, you're missing my point. All else being equal, a given design will work better with some teams and some games than others.

OP asks questions like 'are 3in wheels better than 4in wheels?' That depends a lot on what exactly the robot needs to do. Does it have to traverse any obstacles? Does it need the extra ground clearance of a 4in wheel? Or does it need the extra wheelbase size afforded by the 3in wheels? One isn't inherently better than the other, just different. OP also asked 'are 2spd transmissions worth the weight and hassle?' Well, that depends a lot on the game and style of play of the team driving the robot. Small field with relatively short sprints to get from one place to another? Single spd is probably fine. Wide open field, demands for strong pushing forces AND high speeds? Might want to go with a 2spd setup. Again, one isn't simply better than the other, just better suited to different games and play styles.

Is field-centric control better than robot-centric control? Ask your drivers. Whatever they want or prefer is the right answer, one isn't automatically better than the other. The effectiveness of a given control style depends heavily upon the person behind the glass.

Then there is construction style. Is it 'better' to have a swerve module made out of CNC milled plates that are bolted together than to have a swerve module made out of bent and riveted sheet metal? Well.. a team with 6 CNC mills would have a different answer than a team with a waterjet and press brake. One design isn't necessarily better than the other, but a given design will be better suited to a particular team. I know, I know, you want to insert 'unlimited resources' caveat here, but that really doesn't matter. The fabrication style is very secondary to a well thought-out design. And looking at what's been posted in this thread so far it is obvious that there are a wide variety of designs that have been used very successfully.

[ekapalka]

Originally Posted by s_forbes

1717 has the best I've seen so far, and it improves every year. They do not have the restriction of unlimited resources, but do a good job of hiding it!

Not to change the subject, but is there any info about this swerve aside from the gallery on the Google+? Like maybe a disassembled version? Or a discussion here about it?

[buchanan]

Originally Posted by ekapalka

Not to change the subject, but is there any info about this swerve aside from the gallery on the Google+? Like maybe a disassembled version? Or a discussion here about it?

Presumably all the designs that are being reused over multiple years are publicly available somewhere per R13, right?

It would be a great thing if someone assembled links or other references to all of them in one place. Has anyone attempted such a thing?