Dynomotion

Group: DynoMotion Message: 1983 From: kyrylus Date: 10/17/2011
Subject: Encoders without Index
Hi,

I'm new here. Trying to figure out if KFLOP is going to work with my linear motors that have Renishaw RGH22 encoders which don't have index pulse output. Some intelligent servo drives manage to establish the initial commutation iformation at startup by slowly moving the motor. Question is, can KFLOP do it without an index pulse?

Thanks in advance!
Group: DynoMotion Message: 1984 From: Tom Kerekes Date: 10/17/2011
Subject: Re: Encoders without Index
Hi Kyrylo,
 
Are you planning to use our SnapAmp as the amplifier?  If so, an alternate method of establishing the commutation is to energize one coil phase.  In this case the motor will snap to the pole location much like a stepping motor.  This is the position where this coil will have zero torque.  Max torque for this coil will be generated when the position is 1/4 pole cycle away.  For this method to work well the motor must be free to move with little friction after power-up. 
 
Regards
TK

Group: DynoMotion Message: 1988 From: kyrylus Date: 10/18/2011
Subject: Re: Encoders without Index
Hi Tom,

Thanks for the quick reply. I think there is a possibility to use the SnapAmp as the amlifier. Max voltage is a little low, but may work for low speeds. As I understand it, I will have to program the commutation detection procedure myself. I'm not sure I am ready to do it unless there are some code examples available.

Thanks,
Kyryl
--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> Hi Kyrylo,
>  
> Are you planning to use our SnapAmp as the amplifier?  If so, an alternate method of establishing the commutation is to energize one coil phase.  In this case the motor will snap to the pole location much like a stepping motor.  This is the position where this coil will have zero torque.  Max torque for this coil will be generated when the position is 1/4 pole cycle away.  For this method to work well the motor must be free to move with little friction after power-up. 
>  
> Regards
> TK
>
> From: kyrylus <kyrylo@...>
> To: DynoMotion@yahoogroups.com
> Sent: Monday, October 17, 2011 2:04 PM
> Subject: [DynoMotion] Encoders without Index
>
>
>  
> Hi,
>
> I'm new here. Trying to figure out if KFLOP is going to work with my linear motors that have Renishaw RGH22 encoders which don't have index pulse output. Some intelligent servo drives manage to establish the initial commutation iformation at startup by slowly moving the motor. Question is, can KFLOP do it without an index pulse?
>
> Thanks in advance!
>
Group: DynoMotion Message: 1989 From: Tom Kerekes Date: 10/18/2011
Subject: Re: Encoders without Index
Hi Kyryl,
 
Yes you will need to program the commutation detection.  See the example: HomeBrushless.c.  That example is energizing a coil (which would snap the rotor to a known location like you need to do), but then moves the motor slowly (much like a stepper motor moves) until it detects an index pulse.  If you just remove the part that moves it should suit your purpose.  We can help if you get stuck.  To find the necessary commutation offset it is often easiest to just use trial and error.  If you are unlucky it may take a dozen trys before you find the angle that starts working properly.  If you are lucky (or a bit logical) less.
 
Regards
TK