Difference between revisions of "Tuning position controller"

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(Created page with "Position controller tuning means finding the correct drive settings and feedback gain values to achieve a proper Servo stiffness and response to a position Setpoint sign...")
 
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==Position control tuning method==
 
==Position control tuning method==
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TODO Manual tuning of torque controller is some times done in order to optimize the torque controller response or to find the correct motor resistance [[MR]] and inductance [[ML]] parameters if unknown. Manual tuning also usually yields better torque response than the direct method which may help tuning of velocity or position tuning.
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This article describes a practical approach for finding proper drive parameters to achieve a stable and stiff position control.
  
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In order to change torque tuning, one needs to change motor resistance [[MR]] and inductance [[ML]] parameters until the torque response looks satisfactory.
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{{tip|If motor has been tuned without the real load (i.e. motor shaft not attached), tuning parameters should be re-adjusted with the real load as the dynamic properties of the load has a significant effect on them. Large change of load properties may even cause servo instability.}}
 
===Preparations===
 
===Preparations===
 
[[File:postestingtab.png|thumb|An example of Testing tab settings for position controller tuning. Different settings should be experimented during the process to observe the stability and behavior of the settings.]]
 
[[File:postestingtab.png|thumb|An example of Testing tab settings for position controller tuning. Different settings should be experimented during the process to observe the stability and behavior of the settings.]]
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**Set delay1 [[STD2]] to 0.25 s
 
**Set delay1 [[STD2]] to 0.25 s
 
**Choose sample rate [[TSR]] of 500 to 2500 Hz
 
**Choose sample rate [[TSR]] of 500 to 2500 Hz
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**Choose ''Capture setpoint change ind positive direction'' from the dropdown
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**Choose ''Capture setpoint change in positive direction'' from the dropdown
 
**''Tick Continuously repeating capture''
 
**''Tick Continuously repeating capture''
 
**Tick ''Position setpoint'' and ''Position achieved'' from signals
 
**Tick ''Position setpoint'' and ''Position achieved'' from signals

Revision as of 20:20, 28 August 2013

Position controller tuning means finding the correct drive settings and feedback gain values to achieve a proper Servo stiffness and response to a position setpoint change.

Position control tuning method

This article describes a practical approach for finding proper drive parameters to achieve a stable and stiff position control.

If motor has been tuned without the real load (i.e. motor shaft not attached), tuning parameters should be re-adjusted with the real load as the dynamic properties of the load has a significant effect on them. Large change of load properties may even cause servo instability.

Preparations

An example of Testing tab settings for position controller tuning. Different settings should be experimented during the process to observe the stability and behavior of the settings.

Steps to do to begin position tuning:

  • Ensure that motor is parameterized correctly and working and torque control tuning has been properly done.
  • Attach motor to the target machine in a position where it can rotate in both directions
  • Make following parameter changes to Granity and click apply afterwards:
    • Set drive in position control mode CM
    • Choose Serial only setpoint input CM
    • Make other necessary adjustments to have drive powered and enabled
  • Optional but recommended:
    • Untick Setpoint smoothing CIS
    • Set Goals tab DIV and MUL to 50
  • Set-up the test stimulus and capture settings from Testing tab (an example, may be varied):
    • Set target setpoint 1 TSP1 to 100
    • Set delay 1 TSD1 to 0.25 seconds
    • Set target setpoint 2 TSP2 to -100
    • Set delay1 STD2 to 0.25 s
    • Choose sample rate TSR of 500 to 2500 Hz
    • Choose Capture setpoint change in positive direction from the dropdown
    • Tick Continuously repeating capture
    • Tick Position setpoint and Position achieved from signals
    • Tick Start capture to begin continous capture.
    • Tick Enable test stimulus TSE to begin a continuous position back and forth motion generation

Once the steps above are done, motor should be generating short distance back and forth motion motion and position response graphs should appear on the right side of Granity about once in 3-5 seconds.

Adjusting MR and ML to for optimum torque control

The task here is to adjust the MR and ML parameters to achieve near optimum step response for the torque controller. Observe the images below for guidance.
If the drive faults during this testing due to overcurrent, try reducing TSP1 value or increase fault current tolerance FOC parameter. Or try radically different MR and ML values.

Posgains1.png Posgains2.png Posgains3.png Posgains4.png Posgains5.png Posgains6.png Posgains7.png Posgains8.png Posgains9.png


Steps to do after manual tuning finished

UPDATE

  • Stop test stimulus by unticking TSE
  • Stop scope catpure by unticking Continuously repeating capture
  • Undo all temporary changes made to settings (such as TBW, CM, DIV, MUL) but leave the optimized MR and ML values active
  • Save settings to drive memory by clicking Save settings on drive non-volatile memory button
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