Servo Wiring and Tuning detailed How To example Mesa 7i77.

PCW
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14 Jan 2025 22:34 #318985 by PCW

Replied by PCW on topic Servo Wiring and Tuning detailed How To example Mesa 7i77.

If the machine uses mm units, 200m = 0.2 mm/division
and a velocity of 1 means 1mm/s

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tommy
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25 Mar 2025 19:37 #324907 by tommy

Replied by tommy on topic Servo Wiring and Tuning detailed How To example Mesa 7i77.

I would need a bit of hint on my tuning of AC servos + 7i95t, as I cannot decrease those spikes on acceleration and deceleration, doesn't matter if I go higher or lower with FF2. On linear move there is f-error 0.001mm or less. Should I start adjusting parameters on diver?
Also if I "go crazy" with short presses on arrow keys for jog, especially with changing direction, f-error is all the way up to 1mm or more.

Captures below are taken during running some test g-code:

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PCW
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25 Mar 2025 19:58 - 25 Mar 2025 20:01 #324908 by PCW

Replied by PCW on topic Servo Wiring and Tuning detailed How To example Mesa 7i77.

Are these step/dir servos with encoder feedback to LinuxCNC?

If so it seems there is significant delay from command to motion.
This may well be a drive tuning/setup issue. Maybe drive acceleration
set lower than LinuxCNCs setting or some other filtering or constraints
in the drive.

Last edit: 25 Mar 2025 20:01 by PCW.

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tommylight
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25 Mar 2025 20:08 #324910 by tommylight

Replied by tommylight on topic Servo Wiring and Tuning detailed How To example Mesa 7i77.

If those are step/dir drives, you should be looking here:
forum.linuxcnc.org/10-advanced-configura...glass-scale-feedback
Also
dirsetup and dirhold to 20000
and stepspace and steplen to 5000
Untill you get things working properly, then you can lower the steplen and stepspace while testing to make sure there are no missed steps.
As you have them, chances are some steps are being missed by the drive so LinuxCNC keep upping the number of steps till it catches up.
-
Yes, i am aware the drive manual might say 200ns, but that is almost always not correct, except on very good quality drives.

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tommy
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25 Mar 2025 20:19 #324913 by tommy

Replied by tommy on topic Servo Wiring and Tuning detailed How To example Mesa 7i77.

Yes, it is step/dir driver.

If it helps, here are .ini and .hal sections, related to this axis:

[AXIS_X]
MIN_LIMIT          = -1
MAX_LIMIT          = 1100
MAX_VELOCITY       = 170
MAX_ACCELERATION   = 200

[JOINT_0]
CARD               = 0
TAB                = 0
AXIS               = X
TYPE               = LINEAR
HOME               = 0.000
MAX_VELOCITY       = 170
MAX_ACCELERATION   = 200
#PID_MAX_VEL        = 10
BACKLASH           = 0.000
STEP_INVERT        = False
DIR_INVERT         = False
STEPGEN_MAX_VEL    = 220
STEPGEN_MAX_ACC    = 250
DIRSETUP           = 200
DIRHOLD            = 200
STEPLEN            = 800
STEPSPACE          = 800
SCALE              = -1998.6
ENCODER_SCALE      = -1998.6
MIN_LIMIT          = -1.0
MAX_LIMIT          = 1100
FERROR             = 10
MIN_FERROR         = 7
HOME_OFFSET        = -4.0
HOME_SEARCH_VEL    = -10
HOME_LATCH_VEL     = 2
HOME_USE_INDEX     = NO
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE      = 1
DEADBAND           = 0.001
P                  = 100
I                  = 0
D                  = 15
BIAS               = 0
FF0                = 0
FF1                = 1
FF2                = 0.01
MAX_OUTPUT         = 0

# PID Setup

setp    pid.x.Pgain        [JOINT_0](P)
setp    pid.x.Igain        [JOINT_0](I)
setp    pid.x.Dgain        [JOINT_0](D)
setp    pid.x.bias        [JOINT_0](BIAS)
setp    pid.x.FF0        [JOINT_0](FF0)
setp    pid.x.FF1        [JOINT_0](FF1)
setp    pid.x.FF2        [JOINT_0](FF2)
setp    pid.x.deadband    [JOINT_0](DEADBAND)
setp    pid.x.maxoutput [JOINT_0](MAX_OUTPUT)
#setp    pid.x.error-previous-target True
# limit stepgen velocity corrections caused by position feedback jitter
#setp    pid.x.maxerror    [JOINT_0](MAX_ERROR)

# joint-0 enable chain

net x-index-enable  <=>  pid.x.index-enable
net x-enable       => pid.x.enable
net x-output       => pid.x.output
net x-pos-cmd      => pid.x.command
net x-vel-fb       => pid.x.feedback-deriv
net x-pos-fb       => pid.x.feedback



# Joint 0 Step Gen signals/setup

setp hm2_[MESA](BOARD).0.stepgen.00.dirsetup        [JOINT_0](DIRSETUP)
setp hm2_[MESA](BOARD).0.stepgen.00.dirhold            [JOINT_0](DIRHOLD)
setp hm2_[MESA](BOARD).0.stepgen.00.steplen            [JOINT_0](STEPLEN)
setp hm2_[MESA](BOARD).0.stepgen.00.stepspace        [JOINT_0](STEPSPACE)
setp hm2_[MESA](BOARD).0.stepgen.00.position-scale     [JOINT_0](SCALE)
setp hm2_[MESA](BOARD).0.stepgen.00.maxvel            [JOINT_0](STEPGEN_MAX_VEL)
setp hm2_[MESA](BOARD).0.stepgen.00.maxaccel        [JOINT_0](STEPGEN_MAX_ACC)
setp hm2_[MESA](BOARD).0.stepgen.00.step_type 0
setp hm2_[MESA](BOARD).0.stepgen.00.control-type 1

# ---closedloop stepper signals---

net x-pos-cmd    joint.0.motor-pos-cmd
net x-output                             => hm2_[MESA](BOARD).0.stepgen.00.velocity-cmd
net x-enable     joint.0.amp-enable-out  => hm2_[MESA](BOARD).0.stepgen.00.enable

# ---Encoder feedback signals/setup---

setp    hm2_[MESA](BOARD).0.encoder.00.counter-mode 0
setp    hm2_[MESA](BOARD).0.encoder.00.filter 1
setp    hm2_[MESA](BOARD).0.encoder.00.index-invert 0
setp    hm2_[MESA](BOARD).0.encoder.00.index-mask 0
setp    hm2_[MESA](BOARD).0.encoder.00.index-mask-invert 0
setp    hm2_[MESA](BOARD).0.encoder.00.scale  [JOINT_0]ENCODER_SCALE

net x-pos-fb               <=  hm2_[MESA](BOARD).0.encoder.00.position
net x-vel-fb               <=  hm2_[MESA](BOARD).0.encoder.00.velocity
net x-pos-fb               =>  joint.0.motor-pos-fb
net x-index-enable    joint.0.index-enable  <=>  hm2_[MESA](BOARD).0.encoder.00.index-enable

net joint-0-pos-rawcounts        <=  hm2_[MESA](BOARD).0.encoder.00.rawcounts

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tommy
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26 Mar 2025 17:57 #324992 by tommy

Replied by tommy on topic Servo Wiring and Tuning detailed How To example Mesa 7i77.

Rising up STEPGEN_MAX_ACC significantly, gave me much much better response, now I'm well below 0.01mm f-error during g-code run!

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