On Fri, 9 Jan 2009, Jon Elson wrote: > Date: Fri, 09 Jan 2009 21:04:17 -0600 > From: Jon Elson <[email protected]> > Reply-To: "Enhanced Machine Controller (EMC)" > <[email protected]> > To: "Enhanced Machine Controller (EMC)" <[email protected]> > Subject: Re: [Emc-users] Simple 3 phase drive > > Peter C. Wallace wrote: >> >> >> Permanent magnet servo motor. Its possible to get very good performance >> without a current loop at least for small motors, you may need to add a phase >> lead feed forward term for very high drive speeds. Of course it is closed >> loop >> in the sense that drive voltage is controlled by the normal position PID >> loop. >> Not really much different than straight PWM control of a DC brush motor >> >> Some (mod) math is required to generate the reference angle from the >> encoder count of course. >> >> > OK, so you want to run it without commutation signals. The problem is > getting the motor to the index position. All sorts of sensorless > schemes were worked out 20 years ago to get motors from an unknown > position to index without causing runaways or other jerky behavior. I > would think you'd need to disable the regular servo loop and have the > controller try different commutation angles until the motor starts to > move, and then keep it moving until you get the index pulse.
Runaways cant happen because we just slowly ramp up VD (simple voltage type bridge like our 7I39) or ID (current controlled bridge like our 8I20) so the motor moves gently into position like a step motor. Weve also tried some fancier startup routines but if you dont mind a small, ( max +- 90 degrees for a 2 phase motor +- 45 degrees if you do it a little smarter) slow but uncontrolled motion at startup, thats the easiest way. We can also use hall effect signals (or index) but we only use them for initial encoder sync > > Jon > > ------------------------------------------------------------------------------ > Check out the new SourceForge.net Marketplace. > It is the best place to buy or sell services for > just about anything Open Source. > http://p.sf.net/sfu/Xq1LFB > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ Check out the new SourceForge.net Marketplace. It is the best place to buy or sell services for just about anything Open Source. http://p.sf.net/sfu/Xq1LFB _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
