Rigid tapping and PID control
17 May 2022 12:14 #243141
by Masa
Replied by Masa on topic Rigid tapping and PID control
Thank you for the information, andypugh.
The index-enable matter is currently enabled.
It's a suggestion about PID gain, but when I gain was set to 0, it didn't run out of control.
However, it is rotating with a decrease of about 20% of the command rotation speed.
It is unthinkable in normal use. Normally
Pgain = 0.4
Igain = 0.5
Dgain = 0
Even if I gain is set to 0 and P gain is increased, overshoot may occur during rotation and the desired adjustment cannot be made.
If the servo amplifier is used for speed control, the orientation operation will be unstable, and it will take a long time to settle and time out. Therefore, the servo amplifier is used for torque control.
The encoder output from lcec will be count and Position when using the Beckhoff EM7004. The speed must be calculated using ddt. I don't know if I used another encoder module.
thank you for everything. I would like to try various things that can be considered.
The index-enable matter is currently enabled.
It's a suggestion about PID gain, but when I gain was set to 0, it didn't run out of control.
However, it is rotating with a decrease of about 20% of the command rotation speed.
It is unthinkable in normal use. Normally
Pgain = 0.4
Igain = 0.5
Dgain = 0
Even if I gain is set to 0 and P gain is increased, overshoot may occur during rotation and the desired adjustment cannot be made.
If the servo amplifier is used for speed control, the orientation operation will be unstable, and it will take a long time to settle and time out. Therefore, the servo amplifier is used for torque control.
The encoder output from lcec will be count and Position when using the Beckhoff EM7004. The speed must be calculated using ddt. I don't know if I used another encoder module.
thank you for everything. I would like to try various things that can be considered.
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17 May 2022 12:26 #243144
by andypugh
Replied by andypugh on topic Rigid tapping and PID control
Setting I gain to zero was intended as a test only. The fact that it worked seems to suggest that my theory about what is happening is correct.
If index-enable is configured in the pid_sp then I think that the problem now is that the ddt, pid and encoder read are running in the wrong order.
Currently you have (keeping only the relevant items)
Which, actually, looks correct.
It might be possible to mask (but not fix) the issue by using:
add
To the HAL file and see if that helps.
500 is a guess. It might need to be higher to get spindle speed control, or lower to have the required result.
If index-enable is configured in the pid_sp then I think that the problem now is that the ddt, pid and encoder read are running in the wrong order.
Currently you have (keeping only the relevant items)
addf lcec.read-all servo-thread
addf ddt_spPos servo-thread
addf pid_sp.do-pid-calcs servo-thread
addf lcec.write-all servo-threadWhich, actually, looks correct.
It might be possible to mask (but not fix) the issue by using:
pid.N.maxerrorI float in
Limit on error integrator. The error integrator used by the Igain term will be limited to this value, unless it is zero. Can be used to prevent integrator windup and the resulting overshoot during/after sustained errors. Not normally needed.
add
setp pid_sp.maxerrorI 500To the HAL file and see if that helps.
500 is a guess. It might need to be higher to get spindle speed control, or lower to have the required result.
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17 May 2022 23:51 #243223
by Masa
Replied by Masa on topic Rigid tapping and PID control
Thank you, andypugh.
setp pid_sp.maxerrorI 0.8
This value seems to solve the problem. If this value is small, it approaches I gain = 0, and if it is large, the acceleration will be large at the start and it will be a runaway.
Thank you for your proper advice.
setp pid_sp.maxerrorI 0.8
This value seems to solve the problem. If this value is small, it approaches I gain = 0, and if it is large, the acceleration will be large at the start and it will be a runaway.
Thank you for your proper advice.
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18 May 2022 00:03 #243227
by andypugh
Replied by andypugh on topic Rigid tapping and PID control
I have raised a request that this be addressed in the lcec driver:
github.com/sittner/linuxcnc-ethercat/issues/113
github.com/sittner/linuxcnc-ethercat/issues/113
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