Brother TC-225 / TC-229 adventure!
- ihavenofish
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- ihavenofish
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pcw, remember that these drives in their current tuning state are running 100% perfectly under the stock control, at the same speed and acceleration.
I also did try tweaking the gain on one axis and it had minimal effect. the only time my machine behaves smooth is in a g64 corner, which is effectively jerk control on each axis as it rounds the corner - even if the rounding is 0.005" at 787ipm 2.5G. so I would not be shocked if jerk control is a major factor here - though I cant believe linuxcnc simply cant handle it correctly.
that said - could someone with a velocity controlled drive with high performance (500+ipm, 0.25G) show me their results? both the scope and the machine moving. cause, to be completely honest I have never actually seen a properly tuned velocity drive at high speed and acceleration. ive seen some low speed ones. and low acceleration, and some torque controlled ones at what seem to be moderate performance, but not one single example similar to my machine.
the only high performance linuxcnc machines I have ever seen are step and direction..
if we have to just say linuxcnc cant handle velocity drives well enough, that's at least a resolution. this wild goose chase for some hardware issue that seems to not actually exist is wearing me down.
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I was a little imprecise with my description: I am seeing ripples and overshoot. It's not unstable. It's just, that the velocity ramp has some pronounced frequency. My guess is, that this frequency component is weaker in the jerk limited control and hence more tolerable.
I will do some screenshots next time I'm in the workshop. I think it's possible to solve this problem with tuning the servo.
Which brings me to the next problem: I don't have a manual for the Toshiba RA Drive.
There are 6 potentiometers on the front. I, SZ, P, SPD and WZ, UZ
I and P are clear,
SPD = speed?
SZ = ?
WZ = ?
UZ = ?
@ihavenofish
Do you know the stock values of the acceleration? Were does this information of jerk limit in the brother control come from? Could the jerk control be an analog low pass filter?.
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ihavenofish wrote: that said - could someone with a velocity controlled drive with high performance (500+ipm, 0.25G) show me their results? both the scope and the machine moving. cause, to be completely honest I have never actually seen a properly tuned velocity drive at high speed and acceleration. ive seen some low speed ones. and low acceleration, and some torque controlled ones at what seem to be moderate performance, but not one single example similar to my machine.
the only high performance linuxcnc machines I have ever seen are step and direction..
if we have to just say linuxcnc cant handle velocity drives well enough, that's at least a resolution. this wild goose chase for some hardware issue that seems to not actually exist is wearing me down.
velocity mode
ferror 0.05mm, no ripple nor overshoot
g0 = 72m/min = 2800ipm
MAX_VELOCITY = 1200
MAX_ACCELERATION = 3200.0
P = 51
I = 0
D = 0
FF0 = 0
FF1 = 0.97
FF2 = 0.0013
BIAS = 0
DEADBAND = 0
MAX_OUTPUT = 1200
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- ihavenofish
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thanks!
you don't happen to have a hal scope pic while its doing that?
your f error is high - is that error during acceleration, or through the whole move? mine is about 0.025mm +- spike during acceleration, then only about 0.005mm or so during the steady motion.
only other thing I notice is you have deadband at 0. I cant remember what happened when I tried 0, or if I tried 0 at all.
also what drives and motors and encoder counts are on that machine?
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Are these set to reasonable values?
Also its easy to differentiate between tuning and jerk limiting issues with LinuxCNC by doing a motion that is inherently jerk limited (like a G2/G3 helical move) Once up to speed, commanded motion will be jerk limited
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