Integrating a BCL-AMP capacitive sensor to LinuxCNC

PCW wrote:

A cleaner, linear response signal could be the ticket, as I have fiddled with the PID parameters quite a bit as well as my Z axis velocities and accelerations and it is still not really where I'd like it to be.

Have you considered linearizing the output (with lincurve) before feeding the linearized distance to the
PID loop?

This has already been done.

Have you seen linear graphs?

This has its drawbacks though.

Non-linear characteristics are very good because they have higher resolution/accuracy for useful focus ranges and lower for a larger distance which is not very important but you are right, it is more difficult to handle for a standard PID.

The sensor can be switched between linear and non-linear characteristics as needed and desired.

PCW wrote:

A cleaner, linear response signal could be the ticket, as I have fiddled with the PID parameters quite a bit as well as my Z axis velocities and accelerations and it is still not really where I'd like it to be.

Have you considered linearizing the output (with lincurve) before feeding the linearized distance to the
PID loop?
 

 

PCW: That is not something that I had thought to try. I'll have to give that some thought and see how it performs. Thanks for the tip


prokopcio, I'd recommend starting a new thread in this subforum so we can discuss your design. Looks promising!

forum.linuxcnc.org/plasma-laser/55477-la...a-beta-tester#322786

Hi All

Thanks for the help with this. But I am truly stuck up in calculation of the below.: 22900 and 23900 & 930000.0
 If the head is away I am getting a safe value of about 24000 for capacitive-sense-velocity in the halshow
My hm2_7c81.0.encoder.00.velocity-rpm is about 1440000 in the halshow.

When i run my program, the IHS happens perfectly but when the the THC takes control the torch just gets the down signal and never goes up. Kindly help with any formulas with these three parameters. Thanks!

# Configure a limit component for the capacitive sensor output since it is scaled
loadrt limit1
addf limit1.0 servo-thread
net capacitive-sense-velocity limit1.0.in
setp limit1.0.min 22900
setp limit1.0.max 23900
# hook up the limited signal to the plasmac arc voltage
net plasmac:arc-voltage-in <= limit1.0.out

and 

# Make a fake Ohmic probe based on the capacitive sensor
# Use the .velocity-rpm so the .velocity can be left unused for arc_ok
loadrt comp count=1
addf comp.0 servo-thread
net fake-ohmic-probe-in hm2_7c81.0.encoder.00.velocity-rpm comp.0.in0
setp comp.0.in1 930000.0
net plasmac:ohmic-probe comp.0.out
# ohmic output is comp.0.out



 

Please share min and max values calculation formulas for capacitive sense velocity for the optimum up and low signals for the fiber laser cutter. Eg to set up 100 volts 100/(fmax-fmin) for arc volt scale. Please correct if i am interpreting it wrong.

Those values need a massive offset (-22900), has that been applied?

Does this value always needs to be equal to the min value? Please help, thanks.

If you do not, you will have a huge offset that would have to be compensated
by using a similar setpoint. If you use the 22900 offset, you will now have
a 0 to 1000 active range ( if scale = 1)

Thanks for the reply.
For the 930000, fake ohmic sensing are we expecting the voltage value to around 15500.

Please let me know