On Fri, 15 Nov 2013, Marius Alksnys wrote: > Date: Fri, 15 Nov 2013 12:04:50 +0200 > From: Marius Alksnys <[email protected]> > Reply-To: EMC developers <[email protected]> > To: [email protected] > Subject: Re: [Emc-developers] BLDC component homing to encoder index - is it > correct? > > On 11/15/2013 02:05 AM, andy pugh wrote: > > However, if the motor can move a significant proportion of a > > "commutation period' in one servo thread, from rest, then software > > commutation is not likely to be successful anyway. > > You are right, but I don't agree to all 100%. I did run motors with BLDC > component successfully. But success was much higher when testing motor > with some load than free motor itself. And this could be explained by > the bldc.init nuances. As I wrote, when bldc.init starts (I worked with > qi mode), it starts blindly, so at the first moment the rotor adapts to > magnetic field, causing big vibrations. Yes, they do decay later, but > what happens when an index is nearby? Init ends right at the peak of > vibrations - quite high velocity and accelerations at this moment. > > Running free motors is convenient for testing and tuning, finding right > encoder-offset. > > And the servo thread of my test-setup was running much faster than 1 > kHz. I tested it successfully up to 5 kHz. > > Another reason to get true measurement of encoder-offset is that even > several counts of encoder makes significant influence in results. It may > mean tripping over-current protection on the drive or not, which can > result in servo following error. Or it may let the system (pid-output) > run smoothly or not.
What type of index do you have? its possible to home to index at full motor speed to within 1 encoder count, as the actual capture of the encoder count at index is done in hardware, so Motor speed is immaterial. I have noticed the BLDC thump on startup but I think this is due to a position step or ungraceful transition to PID control > > That's why I would like for bldc.init to work correctly or at least > better. Thus, I am asking for you if you know what and how could be > corrected in the code? > > > ------------------------------------------------------------------------------ > DreamFactory - Open Source REST & JSON Services for HTML5 & Native Apps > OAuth, Users, Roles, SQL, NoSQL, BLOB Storage and External API Access > Free app hosting. Or install the open source package on any LAMP server. > Sign up and see examples for AngularJS, jQuery, Sencha Touch and Native! > http://pubads.g.doubleclick.net/gampad/clk?id=63469471&iu=/4140/ostg.clktrk > _______________________________________________ > Emc-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-developers > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ DreamFactory - Open Source REST & JSON Services for HTML5 & Native Apps OAuth, Users, Roles, SQL, NoSQL, BLOB Storage and External API Access Free app hosting. Or install the open source package on any LAMP server. Sign up and see examples for AngularJS, jQuery, Sencha Touch and Native! http://pubads.g.doubleclick.net/gampad/clk?id=63469471&iu=/4140/ostg.clktrk _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
