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Unread 14-09-2001, 00:26
Ken Leung's Avatar Unsung FIRST Hero
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Post It is extremely complicated...

Jeff, if you get to see the 4th generation swerve, you won't be able to take your hands off of that drive train... It is, as Mike said, "Four wheel drive, four wheel independant steering", and therefore more than just "allowing the robot to move sideway".

Obiviously I don't know the direction for construction of that drive train, but I can talk about the concept. Basically they use the 4 most powerful motors out of the kit: Drill motors and Fisher price motors, mounted next to the 4 wheels (or 4 belt drive in their case). So, imagine 4 small boxes with wheel/belt sticking out at the bottom contacting the carpet. A large gear sitting flat on the top face of each wheel box, so the gear reduction connected the other 4 motors can rotate wheel box independly of each other with the correct torque/speed combination...

So if you look at it, you will see drill /FP motors sticking out horizontally from the wheel box, and and globe motors sitting vertically and window motors sitting on their side (mounted on the base) with their output shaft engaged with the gear on top of each wheel box. Of course you will have to secure the wheel boxes on the base while allowing them to free-spin (when steering motors not engaged).

The tough part is using the right sensors that tell the program exactly where the wheel box are facing. Because it is hard to program a motor to turn exactly the degree desired. After changing the wheel's direction a couple of times, there are bound to be a few error and the wheel can never return to the preset direction (that is if you are only relying on only the program).

That drive train have great manuverability, because you can spin each wheel any direction you want and spin at whatever speed you want, therefore resulting 360 degree freedom, including spinning around the center of robot much smoother than normal tank drive. Really great at fine-tuning robot's position for delicate tasks such as placing the big balls exactly on top of the center of the goals.

Again, I never say this is easy to understand if you've never seen it. To tell you the truth, my first thought when I saw that CD drive train was, "uh... I am NOT making me one of these".

Well, if you think about it, the kit only come with 10 powerful motors (excluding the servo and torque motors), and just this design is using up 8 of them... (what's left are the Vandoor motors and the pneumatics) That doesn't leave too much room/weight/freedom for other device.

So, I would recommend against doing this for your robot, even if it's just an experiment. You would rather use simpler designs and get the max out of fewer of motors, and still achieve great results.

Well, I could go into much more details of that drive train, but this message is getting a little long, and so, I am going to let them remain as CD's trade secret.

I will probably talk about other simpler designs later, so remember to check back... Of course others are free to talk about designs they know, as they probably know more than I do anyway...
 


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