Originally Posted by JiriK Most of the parts in my mill, including servos (Dunkermotoren BG63S55) I have found from local junk yard.. So no complete drivers here.
I found these custom made high current drivers along with the servos that seem to work using PWM and direction signals.. But current limit is a bit of a problem. Also, these donīt spin as smooth on low rev as Iīs like them to spin. |
That's a very nice machine. Are you sure that you can't use the drivers you found? Maybe modify them? Better is the enemy of good enough.
Originally Posted by JiriK But that high current drive of the brushless motors..
They seem to be two phase motors, two coils like on a bipolar stepping motor + 2 hall- sensors for position feedback. Those two Hall- sensors donīt give enough precision, so Iīm wondering wether there might be a chip somewhere that could count the steps from the rotary encoders (Optical, 1000steps/rev) of my motors and use them as reference.
Have you seen such chips?
Or do I have to add another uC to the driver board for the commutation... |
These are 4 phase motors, not 2. Two phase would have two independent coils, these are not independent. I have a BG83S. I believe you only need 2 halls to handle the 4 states of the motor.
There are chips from LSI computer systems that will handle the quad encoder. The ls7266 counters will handle 2 encoders. THey also make chips that will output to a counter, which would be nicer if you have enough counters on your processor.
http://www.usdigital.com/products/lsi/
Seems like motorola/On semi/Freescale semi made commutation chips that would handle 4 phase, but probably only using the halls. To get better commutation, you may need to go to one of the dsps that are made for this. TI, Microchip, Analog Devices, and Freescale all make devices that will suffice. All 4 companies make devices that have quadrature counters built in. Siemens does too, I believe.
Freescale has some very nice app notes. Wish I could cite them for you.