Homing with 2 inputs/sensors?

More
1 year 2 months ago #333817 by hitchhiker
Replied by hitchhiker on topic Homing with 2 inputs/sensors?
But its open loop... i was thinking velocity mode is for closed loop.

Please Log in to join the conversation.

More
1 year 2 months ago #333818 by PCW
Replied by PCW on topic Homing with 2 inputs/sensors?
Actually all LinuxCNC stepgens run in velocity mode. The velocity is typically
calculated with dp/dt (rate change of position). When index is detected, this causes
a step in the position (position is zeroed on index detection). The step will cause a large
bogus velocity calculation in position mode stepgens. This is bounded by the stepgen
acceleration bound so not huge but definitely will generate a detectable motion glitch.

In velocity mode, this is worked around by the fact that the PID component has an index-enable
input, so can work around this issue (by skipping the velocity calculation for the position step).

It would be possible to fix this issue in the position mode, but since in general, velocity mode works better
it has not been addressed.

Overall these issues show that LinuxCNCs index handling needs reworking, The encoder position should really
not be cleared (unless the hardware has no other option) , as it creates the need for all these ugly work-arounds
and in fact the index position offset should be applied at a higher level and not at the low (hal control loop) level

Please Log in to join the conversation.

More
1 year 2 months ago #333819 by hitchhiker
Replied by hitchhiker on topic Homing with 2 inputs/sensors?
... i have no pid for x y z... but for s.. spindle in my hal.

Could this be a reason?
But then.. what a good values for the pid when its open loop?

P i d ff and the rest?

Thanks

Please Log in to join the conversation.

More
1 year 2 months ago #333820 by PCW
Replied by PCW on topic Homing with 2 inputs/sensors?
But its open loop... i was thinking velocity mode is for closed loop.

Even with open loop stepgens there is a local closed loop that
takes the commanded position, the stepgen feedback position,
and current velocity and generates a new velocity command
every servo thread invocation.

In position mode, this loop is still there but embedded in the driver.
 

Please Log in to join the conversation.

More
1 year 2 months ago #333822 by hitchhiker
Replied by hitchhiker on topic Homing with 2 inputs/sensors?
if its so.. then i got it...

on the table it works...

here my ini for the axis
Code:
#******************** # Axis Z #******************** [AXIS_Z] MIN_LIMIT = -2000.0 MAX_LIMIT = 2000.0 MAX_VELOCITY = 83 MAX_ACCELERATION = 500 [JOINT_2] TYPE = LINEAR MAX_VELOCITY = 83 MAX_ACCELERATION = 500 STEPGEN_MAXVEL = 150 STEPGEN_MAXACCEL = 1500 STEPSPACE  = 5000 STEP_SCALE = 400 STEPLEN    = 5000 MIN_LIMIT = -2000.0 MAX_LIMIT = 2000.0 HOME = 0.0 HOME_OFFSET = 0.0 FERROR = 1 MIN_FERROR = 0.25 HOME_SEQUENCE = 0 DIRSETUP   = 5000 DIRHOLD    = 5000 P = 1000 I = 0 D = 0 BIAS = 0 FF0 = 0 FF1 = 1 FF2 = 0 DEADBAND = 0.001 MAX_OUTPUT = 0 MAX_ERROR = 0.0001 HOME_SEARCH_VEL = -30.000000 HOME_LATCH_VEL = -0.100000 HOME_FINAL_VEL = -0.10000 HOME_USE_INDEX = YES HOME_SEQUENCE = 0

and here my hal for the axis
Code:
####Z-Axis Setup#### setp   pid.z.Pgain     [JOINT_2]P setp   pid.z.Igain     [JOINT_2]I setp   pid.z.Dgain     [JOINT_2]D setp   pid.z.bias      [JOINT_2]BIAS setp   pid.z.FF0       [JOINT_2]FF0 setp   pid.z.FF1       [JOINT_2]FF1 setp   pid.z.FF2       [JOINT_2]FF2 setp   pid.z.deadband  [JOINT_2]DEADBAND setp   pid.z.maxoutput [JOINT_2]MAX_OUTPUT setp   pid.z.error-previous-target true setp   pid.z.maxerror [JOINT_2]MAX_ERROR net z-index-enable  <=> pid.z.index-enable net z-enable        =>  pid.z.enable net z-pos-cmd       =>  pid.z.command net z-pos-fb        =>  pid.z.feedback net z-output        <=  pid.z.output net z-pos-cmd    <= joint.2.motor-pos-cmd net z-vel-cmd    <= joint.2.vel-cmd net z-output     <= [HMOT](CARD0).stepgen.02.velocity-cmd net z-pos-fb     <= [HMOT](CARD0).stepgen.02.position-fb net z-pos-fb     => joint.2.motor-pos-fb net z-enable     <= joint.2.amp-enable-out net z-enable     => [HMOT](CARD0).stepgen.02.enable setp   [HMOT](CARD0).stepgen.02.dirsetup        [JOINT_2]DIRSETUP setp   [HMOT](CARD0).stepgen.02.dirhold         [JOINT_2]DIRHOLD setp   [HMOT](CARD0).stepgen.02.steplen         [JOINT_2]STEPLEN setp   [HMOT](CARD0).stepgen.02.stepspace       [JOINT_2]STEPSPACE setp   [HMOT](CARD0).stepgen.02.position-scale  [JOINT_2]STEP_SCALE setp   [HMOT](CARD0).stepgen.02.step_type        0 setp   [HMOT](CARD0).stepgen.02.control-type     1 setp   [HMOT](CARD0).stepgen.02.maxaccel         [JOINT_2]STEPGEN_MAXACCEL setp   [HMOT](CARD0).stepgen.02.maxvel          [JOINT_2]STEPGEN_MAXVEL net z-pos-fb => joint.2.motor-pos-fb net z-index-enable    joint.2.index-enable  <=>  [HMOT](CARD0).stepgen.02.index-enable


i write it by hand... do i forget something? or does it looks ok?

on the table i only work with 2 button switches .. and it do what it should do.
if this was the solution it was not the big deal to do the changes...

Please Log in to join the conversation.

More
1 year 2 months ago #333961 by hitchhiker
Replied by hitchhiker on topic Homing with 2 inputs/sensors?
works now perfect

Please Log in to join the conversation.

Time to create page: 0.048 seconds
Powered by Kunena Forum