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Unread 22-04-2009, 23:02
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daltore daltore is offline
Electronics/programming/design
AKA: Aaron Osmer
FRC #3529 (ausTIN CANs)
Team Role: Mentor
 
Join Date: Dec 2007
Rookie Year: 2007
Location: San Antonio, TX
Posts: 272
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Re: AM' swerve modules

Any team that says they simply don't have the resources to be able to make a swerve drive is deceiving themselves. This year the ausTIN CANs, team 2158, made a 3-wheel swerve drive completely out of 3/8" lexan, using a band saw, drill, and a jigsaw. It was plenty sturdy for this year's competition, and the modules never gave us any problems, it was the motors that we were using (i.e. back to the control part). We decided to use the two FP's and one BB motor for the drive, and the Banebots caught fire 4 times throughout the competition. Over the summer, we're redesigning the system to use CIM's with continuous rotation (this year's modules only rotated 270 degrees), also primarily out of lexan and made completely by hand, that can stand up to forces of a 120-pound robot reversing direction at full speed with high-traction wheels on carpet. We already have a design, and all of the parts look to be checking out. It CAN be done no matter what team you're on, and with what resources.

I will reemphasize the issue of control, also. We steered the modules independently with the two Nippon-Denso window motors and one globe motor. The window motors jammed many times before we could get them aligned correctly, and we had to replace the globe motor when the mounting screws sheered off and jammed themselves into the holes of the gearbox. To measure the angle, we had a 10-turn potentiometer on each wheel that meshed to the module with band saw-made 3/8" lexan gears (a small one for the pot shaft and a large one as the entire top part of the module). By not declaring the location of the pot inputs correctly, we ripped wires off the robot several times when the modules started rotating out of control. Not to mention, when centering the modules (take the gear off the pot and turn it slightly until the module rotates to center, then center the pot again and put the gear back on), my hand has been sucked into the robot. There was much blood, and I still have a scar. That gives you an indication of how precarious having a ton of moving parts on your robot can be. Controlling swerve drive is not all about trigonometry.

The point of FIRST is not to have a level playing field. There are always teams out there with way more money and resources than your team ever will. The point of FIRST is to learn something and utilize the skills that your team DOES have to beat those teams. Selling a complete swerve module would probably detract many teams from their skills and make them think they would win if they just used swerve drive. If it's not in your repertoire, your team should either focus on getting it in your repertoire (i.e. LEARNING how to MAKE swerve drive), or focus on something you're already good at (like driving regularly).