PnCConf axis motor/encoder max output w/pwm?

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greenbuggy
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Senior Member

01 May 2013 09:53 #33473 by greenbuggy

PnCConf axis motor/encoder max output w/pwm? was created by greenbuggy

It seems to me that a lot of the info in the users guide, hal manual and integrator manual is aimed towards people that are using a DAC on a mesa daughterboard like a 7i48 to create +/-10V signals to drive analog servo amps

Unfortunately my mill didn't have any servo amps when I got it and so I went with mesa 7i29's which are PWM servo amps

I'm curious what the "max output" in the PnCConf wizard means as it relates to setting up PWM drives output, or if it can be disregarded. As I'm doing PID tuning my servo seems sluggish I want to make sure that the default "10.00" value here doesn't somehow translate into 10%. Thanks for the help

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PCW
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01 May 2013 10:38 - 01 May 2013 10:40 #33474 by PCW

Replied by PCW on topic PnCConf axis motor/encoder max output w/pwm?

Looking at a sample pncconf created HAL file you can see that MAX_OUTPUT sets the PID output limits and OUTPUT_SCALE sets the PWM scale. As I said before you want to set OUTPUT_SCALE to the machine units per second of the machine with full motor voltage and then set MAX_OUTPUT to 95% of this value. For example if the motor speed at full on (motor voltage=DC power supply voltage) is 240 IPM (4 IPS) I would set output scale to 4 and MAX_OUTPUT to 3.8. For the 7I29 I would also make sure the PWM frequency is 20 KHz

#*******************
#  AXIS X
#*******************

setp   pid.x.Pgain     [AXIS_0]P
setp   pid.x.Igain     [AXIS_0]I
setp   pid.x.Dgain     [AXIS_0]D
setp   pid.x.bias      [AXIS_0]BIAS
setp   pid.x.FF0       [AXIS_0]FF0
setp   pid.x.FF1       [AXIS_0]FF1
setp   pid.x.FF2       [AXIS_0]FF2
setp   pid.x.deadband  [AXIS_0]DEADBAND
setp   pid.x.maxoutput [AXIS_0]MAX_OUTPUT    <<<<

net x-index-enable  <=>  pid.x.index-enable
net x-enable       => pid.x.enable
net x-output       => pid.x.output
net x-pos-cmd      => pid.x.command
net x-vel-fb       => pid.x.command-deriv
net x-pos-fb       => pid.x.feedback

# ---PWM Generator signals/setup---

setp   hm2_5i20.0.pwmgen.00.output-type 1
setp   hm2_5i20.0.pwmgen.00.scale  [AXIS_0]OUTPUT_SCALE  <<<<
net x-output  => hm2_5i20.0.pwmgen.00.value
net x-pos-cmd    axis.0.motor-pos-cmd
net x-enable     axis.0.amp-enable-out  => hm2_5i20.0.pwmgen.00.enable

Last edit: 01 May 2013 10:40 by PCW.

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LAIR82
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20 Feb 2014 03:30 #43988 by LAIR82

Replied by LAIR82 on topic PnCConf axis motor/encoder max output w/pwm?

Hello Peter,

Does this hold true for an analog amplifier signal as well?

Thanks

Rick

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PCW
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20 Feb 2014 12:02 #43996 by PCW

Replied by PCW on topic PnCConf axis motor/encoder max output w/pwm?

For velocity drives, It does make sense for the OUTPUT_SCALE and PID max output to be set to the axis velocity with 10V
applied to the drive. This makes the PID values comparable between different systems and allows guessing good starting PID and FF1 numbers

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