Team 1658 prototype flying inverse differential(gyro-encabulator) bi-swerve

A unique, one of a kind, never before seen drive system. We have two flying inverse differentials(gyro-encabulators) that each power two swerve wheels for a complete robot. Stay posted for video!

Besides the coolness factor (which, btw, is off the charts) what is the point of designing a drivetrain like this? It looks more complicated and more motors than a normal swerve drive (which is an accomplishment in and of itself).

Actually it uses the same allotment of motors as a regular swerve so we don’t lose anything there. as far as the point of doing it, it’s multi faceted. with normal drive systems and the systems that are used for FRC, when you want a motor to go slowely or just a little bit, it often lacks the power to move at those lower values, so you have to give it a higher value than desired to get it to even move. with this design. you can move at 10% speed but have as much power as possible and make micro movements for very precise aiming without overshoot. if we run the reference motors at 100% all out, and the other one at 90% in the reverse direction. the total output will be 10%… at 90% of the motors power. At worst it will perform like a normal swerve when they spin the same direction, but when they spin opposite directions you get that major benefit at having lots of power at low speed so it offers a lot more versatility.

That’s really cool! I love the engineering and fabrication that went into this. The only thing I would suggest is to consider a way to lock your differentials if necessary (either with a limited-slip design, or a pneumatic clutch). Right now, if your robot loses traction on any corner (going over a field obstacle, or being lifted in defense), the unloaded wheel will spin freely, sapping all power from that side of the bot. (unless I’m misunderstanding the design)

Oh, I am misunderstanding. I thought the differential split the power between wheels, but it splits the power between two motors to make an infinitely variable transmission. Neat!

indeed you are. this is an inverse differential not a normal differential. the wheels are locked together in speed so it doesn’t matter if any of them lose traction. you can see the chain routing, it’s impossible for any of the paired wheels to move at a different speed than the wheel it’s paired to.

Here is a bonus pic, almost like a kit.

yup exactly. all without any additional motors or actuators than what would be required for a normal swerve. More complex? yes. Although it’s less complex than a shifting one would be. Worth it? We shall see.

I know I’m focusing on the “wrong part” but those Jags that appear to be nearly floating amuse me.

Looking forward to the video.

ye we were short 2 SRXs. We have 1 coming as part of first choice whenever that comes in and we’ll order 1 more. but won’t let that stop us from advancing the project xD I have come to have a major dislike of jags. the SRXs are a beut though.

Anyone who saw 1658’s robot from last year knows they are an up and coming powerhouse of the St. Louis area. This off-season prototype is crazy awesome, can’t wait to see some video of it running!

I had a similar idea over the summer, but I never had time to design it. Looks awesome!

Are there any apparent problems? Does the differential work as planned?

This is amazing. That is about as close to the definition of inspiring as I know of. Fantastic. Wow.

I’m sure it’s not optimized for weight yet, but what does it weigh?

This is the coolest swerve drive (or drive, really) I have ever seen!
As far as this versus a shifting swerve goes, an IVT only gets a maximum torque equal to the maximum torque at the lowest gear ratio, so lowering the speed does not increase your torque unless the motors are drawing more current (not sure on that last part). I really want to see efficiency/ acceleration specs on this beast.
You also won’t be able to do turn + drive maneuvers without scrubbing, it looks like, but you hardly need those anyway.

What algorithm are you using to choose the motor speeds? Lets say you want to speed up the right side. You could speed up the top motor, slow down (or reverse) the bottom motor, or some combination of the two. How do you avoid running either motor at an inefficient part of its range (such as stalling one while the other runs flat out)? Just curious.

This is pretty wild. Really cool idea and thanks for sharing!
What was your inspiration?

we already did a test with half a robots worth of parts and it looked very promising so we decided to continue and make the whole bot. we already know it WILL work, it’s just a matter of how well as an overall design

in that configuration around 48 lbs however we can easily shave off over 5 lbs since a lot of the stuff on here was just thrown on because we had it and would work rather than trying to make it as low weight as possible. we will be well under 45 lbs on an actual game implementation.

actually you can turn+drive without much issue. it just wont necessarily rotate around it’s center depending on the driver/rotation relationship

still working on it but with the previous test we did my approach was as such:

the top cims are the reference motors, they always run just about full out but still PID speed controlled(so lets say 1k rpms) but that’s completely up to us and arbitrary depending how much total power we want available. i will try to remove this though and just have them be full forward or full reverse without needing the extra control here. As you said there are a variety of ways to control this and we are still researching. Not sure how well that will work but will see. then the opposite side is variable speed to give us the speed we want from the output. with some simple math(just the average of the two inputs) we can get any output speed we want. so currently each cim is being speed(or position) PID controlled. We made half a bot work and currently in the process of making the whole bot work. Whole point of doing it is to see just how well and effective this design can be, it may or may not be favorable and that’s why we’re doing it, to find out!