Gearchange help controlling a BLDC motor

I am having some trouble with my spindle speed control in LinuxCNC. I am using the current stable release of LinuxCNC with gmoccapy as my GUI.

Currently my setup allows me to control speed and direction of my spindle from LinuxCNC and it has a good deal of accuracy. I have a single pulse encoder on my spindle which drives a display so I can see current speed but in no way does this feed back into LinuxCNC.

My spindle is a BLDC motor and I'm using velocity mode to control my spindle by regulating the variable voltage to my BLDC motor controller. I have that velocity set up as basically a 4th axis and it's working great. My spindle has a high and a low speed and I spend 90% of my time cutting in the high range. In the odd days when I need to switch, I simply trick my control and input a much higher RPM than what I want and vary that until my display on the mill gives me my intended output (i.e. I know if I want 750rpm in low gear, I tell my control to go 1750rpm). Unfortunately this is not linear for my spindle and is very difficult to work around when programming with a cam package.

I am looking for a way to offset my variable resistance that the control issues as well as some sort of button and display of what gear I am I'm as well as switching between the two. (this would all be manual and I have no plan to auto change gears or use limit switches for it to auto detect).

I believe the gearchange comp is correct for me, however, my Hal understanding is very limited and the only examples I see are those using gearchange to control a PWM signal to a VFD and similar applications. Any help would be greatly appreciated.

you can also use a gear component to setup a 2 stage Spindle
anothere way woudt be just use a Pin to change the gear and use 2 different spindles in the setup
and just change to the second spinle[1] from a Extra button

Thank you very much for the fast reply. Reading the description, it sounds like that will do exactly what I want. I will just have to make sure I know the value for RPM where I have decided to switch gears because there will be no way for the control to know using this method. For example, if I switch to low gear below 1200RPM, I can use the linear multiplier to scale the output, but nothing would prompt me to switch to low gear below 1200RPM or pause the program to do so correct?

I have gotten pretty good at taking an existing Hal file and editing it to suite my needs, unfortunately I don't think I have enough experience to use the description to generate my own from scratch. I will have to look around for someone who has used this for a similar application and try to tweak it to do what I need

I really like the idea of setting it up as 2 spindlss. That would allow me to use the full range if speeds in both high and low gear with no issue. Sounds like it would be the best option for me.

When you say to use a pin to change gears, do you mean a physical pin on the BOB and use a physical button to send a signal that they have switched or a button inside the control software?

I apologise for my lack of knowledge here, I was able to get this far in my own and have basically been ignoring the two speeds for a year now because I had such a hard time understanding it when I setup my machine go begin with.

I tried to find a few similar applications for what I am doing but keep getting results who try to use lincurve for PWM. I think I am like 60% there, but I am having issues with the correct terms to put in the outputs of lincurve and inputs of my spindle speed out commands. Below is the majority of my hal file, if you have a second to look at what I am doing wrong.

I basically just put my spindle in low gear and started at S250 (which actually yielded 85RPM) and moved up from there writing down the actual speed that came back at each requested value. I made 16 total data points which looked like the max for lincurve. I put 2 points right next to each other at 1300 and 1301 so it wouldnt try to interpolate at the transition between low and high gear.

#This adds a velocity controlled 4th axis
loadrt stepgen step_type=0,0,0,0 ctrl_type=p,p,p,v
loadrt scale count=1

#setup for scaling
setp scale.0.in 0
#must be tuned
setp scale.0.gain 0.885
#no current offset
setp scale.0.offset 0

#connect scale to servo clock thread
addf scale.0 servo-thread

#setup for stepgen to drive spindle
setp stepgen.3.position-scale 1.83
#max RPM of Spindle
setp stepgen.3.maxvel 2950

setp stepgen.3.steplen 1
setp stepgen.3.stepspace 0
setp stepgen.3.dirhold 28000
setp stepgen.3.dirsetup 23000
#max accel for spindle
setp stepgen.3.maxaccel 800

net spindle-enable <= motion.spindle-on => stepgen.3.enable

#sends the speed request from EMC to scale module
net spindle-cmd motion.spindle-speed-out => scale.0.in

#sends scaled spindle speed to EMC and spindle stepgen for requested speed
net spindle-freq <= scale.0.out => stepgen.3.velocity-cmd

#sends frequency out to par port 16 and to EMC
net spindle-out <= stepgen.3.step => parport.0.pin-16-out

loadrt lincurve personality=16
addf lincurve.0 servo-thread
setp lincurve.0.x-val-00 0
setp lincurve.0.y-val-00 0
setp lincurve.0.x-val-01 85
setp lincurve.0.y-val-01 250
setp lincurve.0.x-val-02 182
setp lincurve.0.y-val-02 550
setp lincurve.0.x-val-03 290
setp lincurve.0.y-val-03 700
setp lincurve.0.x-val-04 340
setp lincurve.0.y-val-04 850
setp lincurve.0.x-val-05 395
setp lincurve.0.y-val-05 1000
setp lincurve.0.x-val-06 500
setp lincurve.0.y-val-06 1150
setp lincurve.0.x-val-07 550
setp lincurve.0.y-val-07 1300
setp lincurve.0.x-val-08 1237
setp lincurve.0.y-val-08 1301
setp lincurve.0.x-val-09 1360
setp lincurve.0.y-val-09 1450
setp lincurve.0.x-val-10 1575
setp lincurve.0.y-val-10 1600
setp lincurve.0.x-val-11 1709
setp lincurve.0.y-val-11 1750
setp lincurve.0.x-val-12 1930
setp lincurve.0.y-val-12 2000
setp lincurve.0.x-val-13 2271
setp lincurve.0.y-val-13 2300
setp lincurve.0.x-val-14 2611
setp lincurve.0.y-val-14 2600
setp lincurve.0.x-val-15 2950
setp lincurve.0.y-val-15 2950
net spindle-raw motion.spindle-out => lincurve.0.in
net spindle-corrected lincurve.0.out => pwmgen.0.in

addf parport.0.read base-thread
addf stepgen.make-pulses base-thread
addf parport.0.write base-thread
addf parport.0.reset base-thread

addf stepgen.capture-position servo-thread
addf motion-command-handler servo-thread
addf motion-controller servo-thread
addf stepgen.update-freq servo-thread
#net spindle-cmd-rpm <= motion.spindle-speed-out
#net spindle-cmd-rpm-abs <= motion.spindle-speed-out-abs
#net spindle-cmd-rps <= motion.spindle-speed-out-rps
#net spindle-cmd-rps-abs <= motion.spindle-speed-out-rps-abs
net spindle-cmd <= motion.spindle-speed-out
net spindle-cw <= motion.spindle-forward
net spindle-ccw <= motion.spindle-reverse
net coolant-mist <= iocontrol.0.coolant-mist

Thank you very much for getting back to me. I have been having a bear of a time wrapping my head around this but I am finally making a little progress. I know you replied to both of my threads but I am going to keep the replies on here from now on because I think I am back in the boat of needing to use Gearchange and have (mostly) figured out the lincurve aspect of tuning the spindle. Hopefully the moderators will just delete the other thread because this one should contain all of the information once I figure out the issue for future people to reference if they find themselves as confused as I am.

To answer your question, there really isnt a reason that PWM isn't suitable for my application. I am using a C6 variable speed control board from CNC4PC to output my 0-10V signal to my BLDC motor controller. Right now I have it configured to output from LinuxCNC using stepgen set up in velocity mode for my spindle and that has been working great with the minor issue of my low speed belt not corresponding. Since my last post I have figured out enough syntax to be able to get lincurve to work for my application but it is not 100%.

I will paste my hal file below and maybe you can help me. I realize now that I should probably be putting all of this in the customhal file but I don't ever rerun stepconfig so I am not super worried about losing the data.

The way I have it set up now, lincurve has corrected the issue with spindle speed not matching the requested S value from LinuxCNC while in low range and it is quite accurate from 0-550RPM. The issue I have now is that the accuracy entirely falls off after 550RPM and from 550-1300 RPM there is essentially no change in actual speed when I raise commanded speed. The actual speed actually tops at 550 rpm no matter what I command from 550-1300 RPM. After 550RPM, I have to continue doing what I used to do to get the actual speed any faster (i.e. to get it to actually rotate at 1300RPM I have to command max spindle speed of 2950 or command around 2200RPM to get 1000 RPM actual speed).

I think my issue is that the lincurve function is attempting to make linear the numbers between 550-1450 or so due to the fact that I have a 1300RPM value in low range and a 1301 value in high. It sees that there is a step jump there and I assume it is trying to make a line of best fit which essentially results in no change in the output for any value in that range. In high range, the spindle speed control is now better than ever before and like I said, between 0-550RPM in low range it is now extremely accurate.

I think now I either need to find a better way to input the lincurve values or use a combination of the gearchange comp and 2 separate scaling features with lincurve so I can tune the 2 ranges in the end. I unfortunately have no idea how I would accomplish this and that is where I need help. I would like the gearchange comp to be 0-1300RPM in first gear and 1301-2950 in second with a separate lincurve for both low and high so I can fine tune the values after the gearchange comp does it's magic if that makes any sense. Sorry for the super long reply, but my lack of knowledge means I have to try to explain all of this like a 4th grader. Thanks so much if you can lend a hand.

#This adds a velocity controlled 4th axis
loadrt stepgen step_type=0,0,0,0 ctrl_type=p,p,p,v
loadrt scale count=1

#setup for scaling
setp scale.0.in 0
#must be tuned
setp scale.0.gain 0.885
#no current offset
setp scale.0.offset 0

#connect scale to servo clock thread
addf scale.0 servo-thread

#setup for stepgen to drive spindle
setp stepgen.3.position-scale 1.83
#max RPM of Spindle
setp stepgen.3.maxvel 2950

setp stepgen.3.steplen 1
setp stepgen.3.stepspace 0
setp stepgen.3.dirhold 28000
setp stepgen.3.dirsetup 23000
#max accel for spindle
setp stepgen.3.maxaccel 800

net spindle-enable <= motion.spindle-on => stepgen.3.enable

loadrt lincurve personality=16
addf lincurve.0 servo-thread
setp lincurve.0.x-val-00 0
setp lincurve.0.y-val-00 0
setp lincurve.0.x-val-01 85
setp lincurve.0.y-val-01 250
setp lincurve.0.x-val-02 182
setp lincurve.0.y-val-02 550
setp lincurve.0.x-val-03 290
setp lincurve.0.y-val-03 700
setp lincurve.0.x-val-04 340
setp lincurve.0.y-val-04 850
setp lincurve.0.x-val-05 395
setp lincurve.0.y-val-05 1000
setp lincurve.0.x-val-06 500
setp lincurve.0.y-val-06 1150
setp lincurve.0.x-val-07 550
setp lincurve.0.y-val-07 1300
setp lincurve.0.x-val-08 1237
# high speed
setp lincurve.0.y-val-08 1301
setp lincurve.0.x-val-09 1360
setp lincurve.0.y-val-09 1450
setp lincurve.0.x-val-10 1575
setp lincurve.0.y-val-10 1600
setp lincurve.0.x-val-11 1709
setp lincurve.0.y-val-11 1750
setp lincurve.0.x-val-12 1930
setp lincurve.0.y-val-12 2000
setp lincurve.0.x-val-13 2271
setp lincurve.0.y-val-13 2300
setp lincurve.0.x-val-14 2611
setp lincurve.0.y-val-14 2600
setp lincurve.0.x-val-15 2950
setp lincurve.0.y-val-15 2950

#sends the speed request from EMC to scale module
net spindle-cmd motion.spindle-speed-out => lincurve.0.in

#sends scaled spindle speed to EMC and spindle stepgen for requested speed
net spindle-corrected lincurve.0.out => scale.0.in
net spindle-freq <= scale.0.out => stepgen.3.velocity-cmd

#sends frequency out to par port 16 and to EMC
net spindle-out <= stepgen.3.step => parport.0.pin-16-out