On Thursday 28 October 2021 11:45:49 Sam Sokolik wrote:

> All my machines - steppers and servos are running pid.    I think
> Peter forgot to mention - The reason PID is recommended is because it
> handles latency spikes way better.  We have seen situations where a
> latency spike confuses the hell out of position mode stepgens.  
> (ymmv)

But thats why we run preempt-rt kernels Sam. Even on the pi, the maximum 
spike is 200 microseconds while FF is initializing. W/O FF, 4 to 50 
u-secs. And the big lathe has never noticed that. The little mill, 
before it commited suicide by spitting out all the balls of the y nut, 
was running sw steppers, and they did notice occasionally. It also 
severely limited that machines rapids, to around 8 or 9" a minute. 
Putting a 5i25 in it and it ran about 50 ipm w/o any stutters.


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