OpenServo.com

eric_lmi · Joined: 08 Mar 2007 Posts: 41

planning make a brushless DC motor servo, speed, torque , position control

maxon EC brushless motor, 80W, 18V, hall sensor, 3 phase

FPGA generate PWM, any control circuit suggestion for Motor Driver part, separated power supply

Eric

Toortanga · Joined: 16 Mar 2008 Posts: 14

I'm a bit curious as to why I keep hearing the use of FPGAs pop up so often rather than an MCU. THey're great and all, but need a lot of support, difficult to develop, and are expensive, etc. Their parallelism isn't really needed for something like a motor drive I don't think.

ginge · Posted: Sun Mar 16, 2008 2:03 pm Post subject:

Agreed,

FPGAs have their uses, but I can't see them in a servo driver application. Where I do use them, and they work well, is to use them as multiple i2c bus drivers. You can drop a few i2c master blocks in and control a whole load of i2c slave devices without running into bus sharing issues inherent with serial protocols.
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bren · Joined: 01 Jul 2007 Posts: 79

Hi all

Slightly of topic, ginge I'm in the middle of writing some VHDL code for i2c. So that I can control my openservos using my FPGA. Just wondering if I'm reinventing the wheel if you have already got some code knocking around. I'm using the opencore i2c at the moment, got it working in simulation but it doesn't work in the real thing. Just my little bit about FPGA I use this with a gumstix the FPGA for I/O and the Gumstix for the brains.

Bren

wurpfel · Joined: 20 Dec 2006 Posts: 25 Location: swiss

Hi folkz

I use a IGLOO-FPGA to read out a VGAcam and compress the videostream..
only a 8051softcore is also working in the IGLOO, a lot of power is left blank, maybe it would be usefull to controll all servos too Very Happy

to drive a 3ph-motor a ATm48 is much as enough. look for the atmel-app-note 441 ff for sensor or sensorless opperations.

in the past a 3ph was controlled with a logic-array (diodes!), timerelais and a handfull hall-sensors.

I`m not sure, but proably it`s possible to add the needed number of AVRsoftcores and run on them the OPENSERVO-soft Embarassed

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eric_lmi · Joined: 08 Mar 2007 Posts: 41