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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Did some servo tuning tonight, mounted monitor
First of all, I mounted a 17" monitor on the pendant, and brought in a
wireless keyboard. That made the pendant look less like an orphan. Then I went on to deal with the annoying issue of PID tuning. First of all, I know little about tuning. Second, there is two loops, one is velocity loop in the servo drives, and also, there is a positioning loop in EMC. Third, the drives have a test/offset pot that is very hard to adjust to be anywhere close to no creep. Of the above reasons, the first is the worst, of course. So first I tuned the AMC servo drives using their standard method that Gunner mentioned: I increased gain until the motors started to vibrate, and backed out two turns. Lack of tuning evidenced itself in large following errors, such as 0.005" or so. After I increased P and slight messed with I, following error is always under 0.002" on all axes, and usually is under 0.001". I do not consider myself done, but this is a start and I can move to other things for now. i Then I went through every axis, and by manipulating P and I, reduced |
#2
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Did some servo tuning tonight, mounted monitor
Ignoramus30076 wrote:
First of all, I mounted a 17" monitor on the pendant, and brought in a wireless keyboard. That made the pendant look less like an orphan. Then I went on to deal with the annoying issue of PID tuning. First of all, I know little about tuning. Second, there is two loops, one is velocity loop in the servo drives, and also, there is a positioning loop in EMC. Third, the drives have a test/offset pot that is very hard to adjust to be anywhere close to no creep. Of the above reasons, the first is the worst, of course. So first I tuned the AMC servo drives using their standard method that Gunner mentioned: I increased gain until the motors started to vibrate, and backed out two turns. Lack of tuning evidenced itself in large following errors, such as 0.005" or so. After I increased P and slight messed with I, following error is always under 0.002" on all axes, and usually is under 0.001". I do not consider myself done, but this is a start and I can move to other things for now. i Then I went through every axis, and by manipulating P and I, reduced ability to continue typing?? G -- Steve Walker (remove wallet to reply) |
#3
Posted to rec.crafts.metalworking
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Did some servo tuning tonight, mounted monitor
Ignoramus30076 wrote:
First of all, I mounted a 17" monitor on the pendant, and brought in a wireless keyboard. That made the pendant look less like an orphan. Then I went on to deal with the annoying issue of PID tuning. First of all, I know little about tuning. Second, there is two loops, one is velocity loop in the servo drives, and also, there is a positioning loop in EMC. Third, the drives have a test/offset pot that is very hard to adjust to be anywhere close to no creep. Forget the creep, it doesn't matter, the positioning loop takes care of it. At the very final stage, you can tweak the offset pot to zero out standing-still position error. Of the above reasons, the first is the worst, of course. So first I tuned the AMC servo drives using their standard method that Gunner mentioned: I increased gain until the motors started to vibrate, and backed out two turns. Lack of tuning evidenced itself in large following errors, such as 0.005" or so. That is not really all that large. After I increased P and slight messed with I, following error is always under 0.002" on all axes, and usually is under 0.001". I do not consider myself done, but this is a start and I can move to other things for now. i Then I went through every axis, and by manipulating P and I, reduced Yes, yes??? You should be able to get the error down to well under ..001" up to 30 IPM or so, and that should cover any cutting move. At the final part of tuning, you do jog moves, they have a trapezoidal velocity profile, and you want all parts of the move, ramp up, cruise and ramp down to have low error. Adjusting FF1 and FF2 greatly help there. Jon |
#4
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Did some servo tuning tonight, mounted monitor
On 2010-08-04, Jon Elson wrote:
Ignoramus30076 wrote: First of all, I mounted a 17" monitor on the pendant, and brought in a wireless keyboard. That made the pendant look less like an orphan. Then I went on to deal with the annoying issue of PID tuning. First of all, I know little about tuning. Second, there is two loops, one is velocity loop in the servo drives, and also, there is a positioning loop in EMC. Third, the drives have a test/offset pot that is very hard to adjust to be anywhere close to no creep. Forget the creep, it doesn't matter, the positioning loop takes care of it. At the very final stage, you can tweak the offset pot to zero out standing-still position error. Of the above reasons, the first is the worst, of course. So first I tuned the AMC servo drives using their standard method that Gunner mentioned: I increased gain until the motors started to vibrate, and backed out two turns. Lack of tuning evidenced itself in large following errors, such as 0.005" or so. That is not really all that large. After I increased P and slight messed with I, following error is always under 0.002" on all axes, and usually is under 0.001". I do not consider myself done, but this is a start and I can move to other things for now. i Then I went through every axis, and by manipulating P and I, reduced Yes, yes??? You should be able to get the error down to well under .001" up to 30 IPM or so, and that should cover any cutting move. At the final part of tuning, you do jog moves, they have a trapezoidal velocity profile, and you want all parts of the move, ramp up, cruise and ramp down to have low error. Adjusting FF1 and FF2 greatly help there. OK, thanks. I will look again at following error when doing G1 F20 or something instead of G0. i |
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