esab ultrarex retro fit plasma / flame cutter

See this is what throws me every body else's parameters are like yours 40-60 on the p and such does it depend on the axis scaling ie encoder counts to axis movement as I cannot get my p above say 1 stably ATM it's around 0.9 with more d than I and I think there is still a bit much p as the scope is still quite course

Thanks for all your help john

afternoon lads just one quick question about this scope calibration method what kid of speeds do we want too be running at to tune the axis?

thanks

PID parameters do depend on scaling but this can be factored out if desired by making the PID input and output commensurate. Since the input to the PID loop is in machine units and velocities are in machine units per second, for velocity mode servos, making th e DAC scale or output scale equal to machine units per second will make the units commensurate (this has the side benefit of making the FF1 term known = ~1 for velocity mode drives)

My guess as to why you have such small P term is that you have mm machine units so the input to the PID loop is larger than a inch machine (and the PID output units are probably somthing that has not be scaled to mm/sec
like 10V)

PCW wrote:

My guess as to why you have such small P term is that you have mm machine units so the input to the PID loop is larger than a inch machine (and the PID output units are probably somthing that has not be scaled to mm/sec
like 10V)

could you give this in more detail if possible is there a way to scale the out put also the dacs and scal are limited to 8 as this is the drives max input voltage

thanks pcw i thought it was just me doing something wrong not being able to get much p or ff1

FF2 will tune out a spike during acceleration
also FF1 will tune out the constant negative following error during cruise

but something is funny here (like a lot of friction or way too low gain)

Notice that during the acceleration phase, the encoder doesn't even register any motion until
acceleration is almost done (end of the commanded velocity ramp-up).

Is this a velocity mode drive?

And like Andy says P is right when its right

Getting the input and output PID scaling right just makes the
numbers look more "normal" it will not affect the performance

thanks PCW ive got the following error down within the 0.0x range now and considering this is mm not inches that not quite good for a plasma at 8ish m/m

also the drive for my y axis came back earlier on today so ive been getting that tuned got down to 0.2 till the morning

would this suffice for a torch control / start plasma routine


o<startcut> sub
M64 P0 (turn on cap height control - D out 1)
G4 P3.1 (pause for height control)
M64 P2 (start plasma - D out 3)
M66 P5 L0 (wait for plasma arc ok - D in 1)
o<startcut> endsub
m2

also the one for end of cut

o<endcut>
M65 P0 (turn cap height off - D out 1)
M64 P1 (raise torch to clearance - D out 2)
G4 P3 (pause for torch movement)
M65 P1 (stop torch up movement)
o<endcut>
m2

also are the M2 commands needed in the o word files ? i presume there to end the o word and continue with the program