Pretty much all drives (the ones I've looked at) that do sinusoidal commutation internally use the encoders for the commutation, only using the Hall sensors for initializing and some checking. Since you can get encoders with the commutation tracks built in, there shouldn't be any real space limitation. (if you can fit an encoder you can have both)
----- Original Message ----- From: "andy pugh" <[email protected]> To: "Enhanced Machine Controller (EMC)" <[email protected]> Sent: Tuesday, June 4, 2013 5:03:55 AM Subject: Re: [Emc-users] Mesa 7i39 and BLDC On 4 June 2013 08:23, propcoder <[email protected]> wrote: > What reasons are for using hall sensors? As I understand, commutation > goes from software, which means there is no difference between qi or qh > modes in reaction time. With Hall sensors the motor works at full torque at switch-on. With q and qi modes it needs to perform an alignment process. q is OK for a spindle, but can't be used reliable on an axis that is under load. qi mode might be usable for an axis, if random movement during the alignment is acceptable. > I was planning to spin my 8-pole BLDC motors up to 3000rpm. This means > 5ms every electric cycle. When using 1ms servo period, this may be not > very nice.. What do you think? I think I will need to try smaller servo > periods. Hall commutation only changes state 6 times per electrical cycle, so you will end up with something similar. If you can run a 500us servo thread then that would be nicer. > I thought all this hostmot2 and bldc on 5i23 + 7i39 commutates in > hardware (I think this is possible). I am disappointed a bit. It is possible, and there are drives out there that take hall signal inputs and commutate in hardware. There are also AC servo drives that take encoder inputs, but they tend to be a _lot_ more expensive than the 7i39, and generally require a matched absolute encoder. -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. A cloud service to automate IT design, transition and operations 2. Dashboards that offer high-level views of enterprise services 3. A single system of record for all IT processes http://p.sf.net/sfu/servicenow-d2d-j _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. A cloud service to automate IT design, transition and operations 2. Dashboards that offer high-level views of enterprise services 3. A single system of record for all IT processes http://p.sf.net/sfu/servicenow-d2d-j _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
