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How To Tune Ksff and SffCycles
#1
In Ver 2.6.1 firmware , it have two parameters for static friction compensation, is there a notes about how to tune Motor[x].Servo.Ksff and Motor[x].Servo.SffCycles ?
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#2
This is described in the latest version of the Power PMAC SRM and Users Manual.

You can get them from your local Omron technical support or download it from the US website available here.
https://assets.omron.com/m/76e3f5e50c46e...Manual.pdf
https://assets.omron.com/m/2c1a63d391d6b...Manual.pdf

Basically we add Motor[x].Servo.Ksff to the servo loop output for Motor[x].Servo.SffCycles servo cycles to break free from static friction.
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#3
Hi Eric
How can I kown how big this value should be, is there a recommend move to test it ?
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#4
I haven't used them, but I would try parabolic or point to point tune moves.
Does your system have stiction?
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#5
yes , if push the motor by hand,it's clearly the static friction will be larger than Coulomb friction
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#6
You might try using the open loop test with a single iteration to look for the smallest value that makes the motor moves. This can be taken as the sum of Motor[1].Servo.Kfff and Motor[1].Servo.Ksff . If PMAC is sending an analog signal to the amplifier, you would want to make sure the DAC bias is calibrated first.

Another option would be to try Parabolic or point to point tuning moves and look for low initial following error. Point to point tuning moves in the newer IDE versions are jog like moves. In older IDE versions they may be replaced with trapezoidal and S-Curve tuning moves.
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#7
open loop percent times max dac
Just to be clear, the size of the dac output is the percent from the open loop test times Motor[x].MaxDac, so if you want to go the route of finding a value that barely moves the motor.
Code:
Motor[1].Servo.Ksff = (Open Loop Percent) * Motor[x].MaxDac - Motor[1].Servo.Kfff
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