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Originally Posted by aldaeron
Why do teams use 4 total gear reductions instead of one central gearbox and a chain to transmit power to all 4 wheels? With a 72T or 80T 20 DP gear attaching to 4 CIMs you could make one big gearbox in the center, perhaps even add shifting for a second overall gear ratio.
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4 gearboxes allows for independent control of each wheel.
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Why do teams use 4 steering motors? This would seems to make it hard to steer straight forward (as mentioned in one paper previously linked). With 1 or 2 motors for steering and a worm gear based gearbox and a chain the wheels would be mechanically synced (minus any stretching of the chain). I realize that you would need two steering chains (i.e. 2 sets of 2 wheels chained together) to be able to rotate the bot around its center. By using less motors and therefore less controllers this would seems to save weight
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To put it bluntly, if your team can't handle putting 4 independent modules in the same direction, your team definitely can't handle the software complexity of a well tuned swerve drive.
Without being able to independently power wheels or turn modules independent of one another, a swerve base has no ability to rotate, only translate.
Assuming a four wheel swerve:
All wheels linked, all steering linked - robot can translate in any direction only, but no rotation.
Pairs of wheels linked, all steering linked - robot can translate in any direction. Robot may be able to rotate the same way a skid steer robot does, depending on which wheels are linked and if turning scrub can be overcome.
Pairs of wheels linked, opposite corner steering linked - This allows for translation in any direction, and rotation without translation, but not rotation with translation.
All wheels independent, all corners steered independent - This configuration allows for any combination of rotation and translation at the same time.
With the wide open motor rules, etc. the 4 wheel independent swerve design has gained a lot of popularity among those whom have mastered the swerve drive. I would not go to a lesser option for the sole reason that you don't think your team can handle independent swerve - if your team can't handle independent swerve, it likely can't handle ANY swerve. Not saying there aren't good reasons to make other choices, though.k