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Help please !!! Servo configuration with stepconf.
03 May 2012 15:40 #19764
by andypugh
Replied by andypugh on topic Re:Help please !!! Servo configuration with stepconf.
ishman wrote:
The maximum speed will probably depend on the encoder counts and the base thread rate.
If you have a 1024 count encoder then that is 4098 pulses per rev (probably). If you have a 40,000nS base thread (on the slow side, what number do you actually have?) then you can pulse at 25kHz, which gives you 25,000 / 4098 = 6rps = 366rpm.
A faster base-thread will help, but you probably can't go much below 20,000 (what was your latency test result?) and I think I saw that you can change the "electronic gearing" of the drive so that one input pulse = more than one encoder count.
I tried to move an empty motor with stepconf jog and it runs smooth from there as well. But it lacks speed.
The maximum speed will probably depend on the encoder counts and the base thread rate.
If you have a 1024 count encoder then that is 4098 pulses per rev (probably). If you have a 40,000nS base thread (on the slow side, what number do you actually have?) then you can pulse at 25kHz, which gives you 25,000 / 4098 = 6rps = 366rpm.
A faster base-thread will help, but you probably can't go much below 20,000 (what was your latency test result?) and I think I saw that you can change the "electronic gearing" of the drive so that one input pulse = more than one encoder count.
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03 May 2012 15:46 #19765
by ishman
Replied by ishman on topic Re:Help please !!! Servo configuration with stepconf.
with
"gzip -c /dev/urandom > /dev/null"
I am getting
Servo Max jitter = 16350
Base max jitter = 19001
Encoder is 2500 C/T
I am running it with electronic gearing disabled.
"gzip -c /dev/urandom > /dev/null"
I am getting
Servo Max jitter = 16350
Base max jitter = 19001
Encoder is 2500 C/T
I am running it with electronic gearing disabled.
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03 May 2012 15:55 #19766
by andypugh
Replied by andypugh on topic Re:Help please !!! Servo configuration with stepconf.
ishman wrote:
I think that turning it on is the only practical way to get more speed.
Work out what physical distance one encoder count is, and compare that to your desired machine accuracy, and adjust the electronic gearing to suit.
On a very simple level, your 2500PPR encoder servo is acting like a 2500 step/rev stepper motor, and 200 steps/rev is usual. 4:1 electronic gearing would give you a lot more speed and probably still adequate resolution.
I am running it with electronic gearing disabled.
I think that turning it on is the only practical way to get more speed.
Work out what physical distance one encoder count is, and compare that to your desired machine accuracy, and adjust the electronic gearing to suit.
On a very simple level, your 2500PPR encoder servo is acting like a 2500 step/rev stepper motor, and 200 steps/rev is usual. 4:1 electronic gearing would give you a lot more speed and probably still adequate resolution.
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03 May 2012 16:22 #19769
by ishman
Replied by ishman on topic Re:Help please !!! Servo configuration with stepconf.
Thanks ! it's basic and useful knowledge.
So then I should put 10000 in motor step per revolution at axis configuration window.
But should I put the driver micro-stepping ratio in wizard when I use drives electronic gear ?
Most annoying queries for me is at "Basic Machine Configuration" page where it's asking "step time" , " step space" , "direction hold" and " direction setup". I don't know how to calculate these numbers.
So then I should put 10000 in motor step per revolution at axis configuration window.
But should I put the driver micro-stepping ratio in wizard when I use drives electronic gear ?
Most annoying queries for me is at "Basic Machine Configuration" page where it's asking "step time" , " step space" , "direction hold" and " direction setup". I don't know how to calculate these numbers.
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03 May 2012 16:28 #19770
by BigJohnT
Replied by BigJohnT on topic Re:Help please !!! Servo configuration with stepconf.
According to your manual the Maximum Input Pulse Frequency is 500KHz. I'm not good with KHz and I assume that is minimum of both the on and off time of a step.
John
John
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03 May 2012 17:47 #19779
by ishman
Replied by ishman on topic Re:Help please !!! Servo configuration with stepconf.
BigJohnT wrote:
It means a billion divide by 500k = 2000 is it a correct number for step time ? I hope so.
According to your manual the Maximum Input Pulse Frequency is 500KHz. I'm not good with KHz and I assume that is minimum of both the on and off time of a step.
It means a billion divide by 500k = 2000 is it a correct number for step time ? I hope so.
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03 May 2012 18:08 #19780
by ishman
Replied by ishman on topic Re:Help please !!! Servo configuration with stepconf.
Yes ! I have confirmed. It's total 2 microseconds (2000ns) for an entire pulse frequency. We just have to divide in two for step time and step space. It means 1000 for "step time" and 1000 for "step space" THANKS JOHN !
Can anyone explain about what is actually "Direction Hold" and "Direction Setup" ?
Can anyone explain about what is actually "Direction Hold" and "Direction Setup" ?
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03 May 2012 18:42 #19781
by andypugh
Replied by andypugh on topic Re:Help please !!! Servo configuration with stepconf.
ishman wrote:
Probably not all that relevant with that drive. But a you always stop before changing direction, it doesn't matter too much. 20,000 ought to be safe.Can anyone explain about what is actually "Direction Hold" and "Direction Setup" ?
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03 May 2012 19:07 #19783
by ishman
Now I think I have all the numbers needed to run my machine with servo and step/dir with stepconf.
Step Time = 1000
Step Space = 1000
Direction hold = 20000
Direction setup = 20000
Step/Revolution = 10000
Drive Microstepping = ??? (oops! one thing still to understand.)
Pully teeth = 1:1
Lead-screw pitch = 5mm
Maximum Velocity = 1
Maximum Acceleration = 25000/10000*5 = 12.5mm per sec * electronic gear ratio.
Replied by ishman on topic Re:Help please !!! Servo configuration with stepconf.
Thanks !Probably not all that relevant with that drive. But a you always stop before changing direction, it doesn't matter too much. 20,000 ought to be safe.
Now I think I have all the numbers needed to run my machine with servo and step/dir with stepconf.
Step Time = 1000
Step Space = 1000
Direction hold = 20000
Direction setup = 20000
Step/Revolution = 10000
Drive Microstepping = ??? (oops! one thing still to understand.)
Pully teeth = 1:1
Lead-screw pitch = 5mm
Maximum Velocity = 1
Maximum Acceleration = 25000/10000*5 = 12.5mm per sec * electronic gear ratio.
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12 May 2012 14:48 - 12 May 2012 15:05 #20032
by ishman
Replied by ishman on topic Re:Help please !!! Servo configuration with stepconf.
One good news is that I can run my servo's with stepconf wizard as an open loop system. Every axis is tuned and responding accordingly, smoothly and fast as well. One thing is cleared in which I was confused that Drive Microstepping means Linuxcnc's internal microstepping and it doesn't care about drives electronic gearing system. I don't know how to tell linuxcnc about drives gearing. so it can calculate position accordingly and we can ramp up the speed with the help of drive's processor as well.
I found an indirect solution is to divide screw pitch according to drives gearing ratio. But I think there should be any direct solution.
Right now I have just jogged and tuned the servo with stepconf because I have only two servo drives expansion board in my hand.
I found an indirect solution is to divide screw pitch according to drives gearing ratio. But I think there should be any direct solution.
Right now I have just jogged and tuned the servo with stepconf because I have only two servo drives expansion board in my hand.
Last edit: 12 May 2012 15:05 by ishman.
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