Automatic spindle gear detection

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19 Aug 2014 02:08 #50020 by mariusl
mariusl replied the topic: Automatic spindle gear detection
It seems that the spindle is hunting before it starts to cut. Could be because the distance of the tool is changing during the approach.

Then I have something weird on my lathe with CSS.
Does spindle at speed have an influence.

Mine is tied high at the moment as I have not sorted the feedback to the requested speed out just yet.
I was hoping that your work will help me do that. I mean scale the feedback to match the request no matter what gear in order for me to get the spindle at speed signal working.
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19 Aug 2014 04:39 #50024 by andypugh
andypugh replied the topic: Automatic spindle gear detection

It seems that the spindle is hunting before it starts to cut. Could be because the distance of the tool is changing during the approach.


What is the source of the motor speed input? Ideally it should be some sort of feedback from the VFD. If you only use the commanded speed then as the spindle accelerates it apparently moves through the gears.

Mine is tied high at the moment as I have not sorted the feedback to the requested speed out just yet.
I was hoping that your work will help me do that. I mean scale the feedback to match the request no matter what gear in order for me to get the spindle at speed signal working.


There shouldn't be any need to scale that. you take the velocity from the encoder, and compare that to the commanded speed.
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19 Aug 2014 13:12 #50034 by mariusl
mariusl replied the topic: Automatic spindle gear detection

What is the source of the motor speed input? Ideally it should be some sort of feedback from the VFD. If you only use the commanded speed then as the spindle accelerates it apparently moves through the gears.


I am using a 2048 spr quadrature encoder.
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19 Aug 2014 14:57 #50039 by andypugh
andypugh replied the topic: Automatic spindle gear detection

mariusl wrote:

What is the source of the motor speed input? Ideally it should be some sort of feedback from the VFD. If you only use the commanded speed then as the spindle accelerates it apparently moves through the gears.

I am using a 2048 spr quadrature encoder.


If you have an encoder on the spindle and a separate encoder on the motor then I can't see any reason at all for it to hunt, unless you don't have the X-axis set up quite right. How did you get the base data?

I did it by setting up the system with the link to the pwm disconnected, then comanded a fixed 50% pwm by hand and looked at the speed ratios. I then used those numbers as the centre-points for "stair steps" on the X axis.
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19 Aug 2014 15:07 #50040 by mariusl
mariusl replied the topic: Automatic spindle gear detection

If you have an encoder on the spindle and a separate encoder on the motor then I can't see any reason at all for it to hunt, unless you don't have the X-axis set up quite right. How did you get the base data?


The hunting was maybe just an illusion as the tool was some distance away from the job. (air cutting) So it would seem to hunt.
I dont have an encoder on the spindle, I just read the rpm from the VFD display. So the loop is not really closed properly.

I am starting the spindle stuff from scratch as I Have to much spaghetti in the hal file now. I was thinking of putting a little gladevcp panel on the screen to show spindle speed and then manually select with a button, the gear position. I use that info to lookup the speed range that can be used for every gear. Remember it is belts not gears so I have to manually change things. I might as well have a manual selection on screen then with a indicator to show that I need to go up or down on pulleys. I will stick a component behind it to do the calculations and show me to go up or down.
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19 Aug 2014 16:20 #50041 by andypugh
andypugh replied the topic: Automatic spindle gear detection

mariusl wrote: I dont have an encoder on the spindle, I just read the rpm from the VFD display.


If you don't have an encoder on the spindle then this whole idea won't work.
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19 Aug 2014 17:00 #50046 by mariusl
mariusl replied the topic: Automatic spindle gear detection
Sorry, I did not explain myself well. I meant that I dont have another encoder on the motor just one directly on the spindle. After the gearing in other words. The motor speed I read on the VFD.
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19 Aug 2014 17:01 #50047 by andypugh
andypugh replied the topic: Automatic spindle gear detection

mariusl wrote: Sorry, I did not explain myself well. I meant that I dont have another encoder on the motor just one directly on the spindle. After the gearing in other words. The motor speed I read on the VFD.


How do you get the motor speed from the VFD into HAL?
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19 Aug 2014 17:07 #50048 by mariusl
mariusl replied the topic: Automatic spindle gear detection
I dont per say. It matches the requested speed. So it is not measured at the motor at all. Just at the spindle.

Are you suggesting that I get a motor speed encoder as well? I dont have input for that any more.
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19 Aug 2014 17:29 #50050 by andypugh
andypugh replied the topic: Automatic spindle gear detection

mariusl wrote: Are you suggesting that I get a motor speed encoder as well? I dont have input for that any more.

Well, it would help.
But, depending on the VFD, there may be ways to get the motor speed from the VFD. I think that flux-vector VFDs actually know the motor speed and will communicate that on an analogue output or on Modbus.
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