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Unread 23-01-2004, 00:04
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Re: pic: Swerve^2 Prototype

Quote:
Originally Posted by Paul H
How much does that prototype weigh?
It's about 100 pounds, but about half of that is the wood base which will be aluminum for the competition guy. But it is heavy. Lot of hardware in each wheel. We're a tad concerned about it...

Bill
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Unread 23-01-2004, 02:12
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Re: pic: Swerve^2 Prototype

Do you think you might be able to post a CAD or two of the wheel modules? I am very interested in how you implemented the coaxial swerve system.
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Unread 23-01-2004, 11:42
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Re: pic: Swerve^2 Prototype

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Originally Posted by FotoPlasma
Do you think you might be able to post a CAD or two of the wheel modules? I am very interested in how you implemented the coaxial swerve system.
Here's a photo of a pre-season prototype wheel, #0 as it were. Though the new ones have minor improvements (e.g. better spacers), they are essentially like this one.

http://crush1011.wookus.net/pix/2003...lPrototype.jpg

The motive drive comes down the center shaft, through the miter gear pair, then by chain to the wheel. The ratio is 1-1 all the way from the S-B motor up to the last sprocket, where it gets geared down by 1-2.8 (10 to 28 tooth sprocket). The vertical shaft is spinning in and supported by a half inch bore in the large teflon bushing.

The steering drive comes in the big sprocket on top. That sprocket is bolted through the large teflon bushing to the top plate of the yoke. Steering is accomplished by turning the teflon bushing in the top plate. The top plate mounts to the robot frame. The steering drive is also a 1-2.8 geardown, using the globe motor.

For size reference, the top plate is 6"x6". The large teflon bushing is 3" OD with a 3/8" groove where it rides in the top plate. The teflon splits in two pieces within this groove in order to make assembly possible.

We have some CAD drawings, but a few changes were made to the design post-CAD. Hopefully this picture makes it all reasonably clear. If not, please ask.

This system is not without its challenges, but we're working through them. First, it's a lot of gears and chain, and resulting end-to-end losses. Second, there is some coupling from the motive drive to the steering drive, which makes good steering tracking code more important.

It's very fun working on it though [;-)

Bill
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Unread 23-01-2004, 11:59
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Re: pic: Swerve^2 Prototype

hey, i was just wondering how exactly the driver will control all of this. would it mbe one person, or would both drivers have to work together to achieve topmost maneuveurability
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Unread 23-01-2004, 12:11
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Re: pic: Swerve^2 Prototype

Quote:
Originally Posted by bjammin64
hey, i was just wondering how exactly the driver will control all of this. would it mbe one person, or would both drivers have to work together to achieve topmost maneuveurability
We have a few different driver control options in the works, but all are single driver, at least for the "driving" part. Another operator will probably manage other gadgets on the 'bot.

We think the "preferred" driving mode will be a single joystick, where the joystick displacement from center is speed, and joystick angle is the drive direction. All four wheels steer in tandem to the same angle and always roll the same direction (never have to run the drill motor backwards).

We'll also be able to lock the back wheels and steer just the front, which makes it drive like a car more or less. This is one way we could rotate the body of the 'bot. Notice that in the "preferred" mode above there's no way for the driver to rotate the body. In "car" mode we'll enable the motors to go backwards for more maneuverability.

Another variation will be to steer the wheels in opposite directions and do a turn-in-place (a tank turn), then return to swerve for moving around the field. This gives a quick way to turn the body to a needed orientation.

Bill
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