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Hi all, 

Looking for some help with my closed loop spindle. It's a no-name "AT4" chinesium VFD driving a 3kW motor and a 2.2:1 belt drive to a BT30 spindle. Control is 0-5V from a 7i76e, encoder feedback from the motor shaft. The encoder is a 2500ppr unit I had left over so I'm only using the index pulse and have the encoder in counter mode because the A/B pulses were too fast. Encoder feedback into a 7i89.

Anyway, with P only control, I see the motor hunting a lot, a slow oscillation a few hundred rpm triangular wave, but I don't think it's as a result of too high P : there still a significant offset error so the oscillation is maintained even though the error is always a negative value (spindle slower than target). Lowering the P more increases the offset but doesn't change the amplitude or frequency of the oscillation, increasing P moves the speed closer to the setpoint but again no change in the oscillations. No screenshot but I can get one later on. Because it "hunts" even though the error is large and always one side of the setpoint makes me think it's not true hunting like a system with overly high P gain? The oscillation doesn't decay over time.. same behaviour with P anywhere from 0.8 to 10. 

I reduced P way down (to 0.5) and tried to get it working by using D to stop the oscillation and I to actually hit the setpoint, but it's still a bit shit so I think it could be much improved. I added a ramp constraint to the speed command to stop the vfd erroring out. There's an accel limit on the VFD side too so maybe that's affecting the control loop?  

It's getting to it's setpoint now but there's an over-acceleration initially, then a ramp that doesn't quite keep up, and then a weird over/undershoot/dip when the ramp ends and the I term seems to take over to slowly creep the speed to the setpoint. 

Can anyone who knows controls better than me suggest a methodology to follow to improve this?

First Question.

For a 1mm jog, I originally set my MUX40.in1 to 1.0. This was resulting in an exact 4mm jog each count. To fix this I need to set the scale below to 0.25. While I can do this and get the result I want, it bothers me that I have to use a ratio instead of direct number and will be harder to decode at latter dates. It seem arbritary that each count would be 4mm exact.

setp mux4.0.in1 1 (jogs 4 mm per count)

setp mux4.0.in1 0.25 (Jogs 1 mm per count)

net encoder-counts  <= encoder.0.counts
net encoder-counts => axis.x.jog-counts

Question is, where is the actual jog value recorded in LinuxCNC.? I cold find nothing in the .ini or .hal files that seems to indicated it would jog exactly 4mm each jog count.



Second question,

Per the below, I am currently using mux4 to determine the jog scale. But my MPG switch does is not using an encoder switch but instead has 3 simple outputs of which I placed into input 26 (1x), 27(10x), 28(100x)

I got everything to work but can not find any details in .hal how to use something other than mux4 logic to place the correct scale into the axis jog. This seems like it should be simple. More or less just want if one of those pins are true, the correct scale is selected. Below is partial code referancing the scale portion. Note. Only using pins 26 and 27 at the moment due to the mux4 requirements. Other than this, everything is working fine.

# This sets the scale that will be used based on the input to the mux4
setp mux4.0.in0 0.025
setp mux4.0.in1 0.25
setp mux4.0.in2 2.5

# The inputs to the mux4 component
net scale1 mux4.0.sel0 <= hm2_7i76e.0.7i76.0.0.input-26
net scale2 mux4.0.sel1 <= hm2_7i76e.0.7i76.0.0.input-27

# The output from the mux4 is sent to each axis jog scale
net mpg-scale <= mux4.0.out
net mpg-scale => axis.x.jog-scale

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Basically want:

if Pin 26 true then axis.x.jog-scale == 0.025
if pin 27 true then axis.x.jog-scale == 0.25
if pin 28 true then axis.x.jog-scale == 2.5

Hallo Michael,

Danke für deine Antwort.Ich habe damals(ca.8 Jahren) mit LinuxCNC schon angefangen.Da hatte ich ein TB6560 Board von Modellbau Letmathe.Ich begann mit einen (China)Kreuztisch.Dann baute ich mir eine Portalfräse.Irgendwie bin ich auf den Planetcnc Controller gestossen.Denn habe ich genommen.
Zum Schluß wollte ich wieder umsteigen auf LinuxCNC.Habe mir dann eine MESA 7i76E gekauf und einen VFD mit Spindel.
Dann wurde ich krank und das Geld wurde knapp.Da verkaufte ich die Karte und Spindel wieder.

Jetzt habe ich nur das USB Board,die Motortreiber(Endstufen) und meinen Schaltschrank denn ich damals gebaut habe.
Ich habe sogar einen Pendant gebaut.Als USB HID Device,mit einen Teensy 3.2 und Joystick/Keypad.

Jetzt wollte ich das WHB04-4 Handrad in Planetcnc integrieren.Geht aber irgenwie nicht.Habe die .rules geändert usw. ......

Ich habe mir gedacht,man könnte die 26pin Schnittstelle verwenden.Ohne viel umzuverdrahten.

Hab gleich einen Termin.Melde mich wieder.

Grüße-Martin

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Hello Michael,

Thanks for your answer.I started with LinuxCNC back then (about 8 years ago).I had a TB6560 board from Modellbau Letmathe.I started with a (China) cross table.then I built myself a portal milling machine.somehow I came across the Planetcnc controller.because I took it.
Finally I wanted to switch back to LinuxCNC and bought a MESA 7i76E and a VFD with spindle.
Then I got sick and ran out of money, so I sold the board and spindle again.

Now I only have the USB board, the motor drivers (power amplifiers) and my control cabinet that I built back then.
I even built a counterpart as a USB HID device with a Teensy 3.2 and joystick/keypad.

Now I wanted to integrate the WHB04-4 handwheel into Planetcnc, but somehow I couldn't. I changed the .rules etc. ......

I thought you could use the 26pin interface without having to rewire much.

I have an appointment in a few minutes.

Greetings-Martin