Hi Roger,
My understanding is that this feature is available for both Mach3 and Mach4 now. However, for me it removes most any reasons for switching from Mach3 to Mach4, as Mach3 now does everything I want.
Mach3 enacts proportional only feedback whereas Mach4 offers genuine PID.
While PID control sounds good, and it is a marked improvement over what was, it is still a long way short of servo control.
Firstly there is the means that the ESS derives its speed updates...by timing between pulses. Thus you have a resolution/
refresh rate compromise to make. A regular servo gets its speed information not differentiating its input pulse stream,
aka timing between pulses, but by monitoring the feedback term of a high gain integrator loop. This achieves the same
result, namely providing an estimate of the differentiated input stream but with an order of magnitude better noise
performance, especially at low speeds.
Secondly because Mach uses only one channel of the encoder it has no sense of direction. The PID feedback loop controls
velocity only and has to wait for a speed update for the duration of the interval between pulses associated with the speed
measuring procedure. Therefore the resolution/refresh rate compromise is doubly fraught because is the same compromise
that determines the delay between a speed change and the estimate of that speed change being available to the feedback
controller.
Any delay between physical event and an estimate of that event to a control system counts
VERY heavily against
its stability and bandwidth.
For this reason the spindle PID offered by the ESS is good, certainly much better than we've ever had before it still
pales into insignificance to the bandwidth and accuracy of a servo loop....and before you say but this is a spindle.....
remember Mach4 has out-of-band axes that can be driven independently of the coordinated axes but with exactly the
same tight control of a coordinated axis.
Craig