Epycyclic Differential Swerve

Hello, I have made a differential swerve drive module.

Features a 4*1 billet wheel with a planetary differential to drive it.

Estimated cost of about $360 per module

Onshape link:

some of the assemblies are set up for the gears to be properly mated if you want to see how the powertrain works.

if you have any questions or feedback, feel free to comment.


If you’re using one of the planets to drive the wheel, is there a torque imbalance that needs one of the motors to hold the ring still more than the other? If not, this looks like a great design.


the gear ratio for driving the planet is the same from both motors so there would be minimal to no torque imbalance

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Wow, this design is really cool. My one concern would be the rounded corner of the module, which would require curved bumpers to be legal. Shouldn’t be too hard of a fix to make it square if you wanted to.

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I might just be missing something, but I do not see any sort of absolute encoder on this design. Although it seems like a small thing, a zero backlash (preferably on-axis) absolute encoder is a necessity for any good swerve module.


If you draw the torque diagram for the caster box, you might find that the torque used to drive the main wheel does not balance out.

thats correct theres no encoder on the module which is something i would definitely add if we are to ever build this, theres a bolt coming up from the bottom that could be extended for an encoder to go onto.

ive never drawn a torque diagram before, are there any resources you can recommend that would help with making one for the swerve module?

Lemme get back to you this evening. The basic idea is that you should track starting at the wheel the torques operating on each shaft. Any imbalance will make the module spin, which will load the motors. I think you’re ok here because you said the gear ratios are the same.

Is there a reason why there is no turn encoder on the swerve? or maybe there is and i just don’t see it

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