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Valen
Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
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We use the mesa toolchain with our mill.
http://www.mesanet.com/
I suggest getting their FPGA card, if you use linuxcnc its plug and play.
They have some pretty cheap ones (5i25 I think).
Then if you want to build your own motor drivers you are going to be getting direction and PWM input, you just need to add your own deadtime and fets and an interface for your encoders.
We use 500w scooter motors 1:1 direct mounted to the ballscrews, I had to defeat the current limiting on the mesa motor drivers, (7i40) so we are pulling more than 10A (I'm guessing 20A peaks perhaps a bit more)
But our setup is very intolerant of backlash because we are using glass scales for the position feedback, no encoders on the motors.
The biggest problem we had with the motors was they have tiny tiny shafts on them so the couplers don't have a lot to grab on to.
Go a smaller motor (250w would be fine), belt drives and encoders on the motors and it'd probably run nicer. You can combine motor encoders as well as linear scales in linuxcnc ,it uses the motor encoders for velocity feedback and the scales for position feedback. You wind up with great accuracy and nice smooth control.
We cant fit motor encoders on ours because the shaft is too darn small. As a result we have some control loop issues due to the spring in everything (20mm ballscrew, preloaded everything) _________________ Mechanical engineers build weapons, civil engineers build targets
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Mon Mar 02, 2015 10:07 am |
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