Closing the servo loop with HAL mesa 7i76

PCW wrote:

Yes
You should also be able to check the scale by commanding one turn worth of motion (say 5mm for 5mm pitch ballscrew) and verifying that the motor makes 1 turn. If this works, command 10 or 100 turns worth of motion and verify the the motor shaft ends up in the same place...

Ok I can verify that 1 turn on the shaft is 5mm on the DRO and encoder position also shows 5 with both going +ve

I have noticed that when using a feed rate of 1000mm/min then encoder velocity pin shows about 16.8 and half that with a feed rate of 500mm/min.

I am still getting following errors if I used above about 1000mm/min in open loop with P = 1000

MIN_FERROR = 1.0
MAX_VELOCITY = 35
MAX_ACCELERATION = 500
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Note the comment

STEPGEN_MAXVEL = 31.25
STEPGEN_MAXACCEL = 600

PCW wrote:

MIN_FERROR = 1.0
MAX_VELOCITY = 35
MAX_ACCELERATION = 500
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Note the comment

STEPGEN_MAXVEL = 31.25
STEPGEN_MAXACCEL = 600

Thank you I could not see the wood for the trees.
I have changed them to 43.75 and 625

Now I can get the the feed rate up to 2500mm/min it errors at about 2800mm/min
this is with closed loop and P10

Is this relevant "I have noticed that when using a feed rate of 1000mm/min then encoder velocity pin shows about 16.8 and half that with a feed rate of 500mm/min."

16.8 is about correct (1000 mm/m = 16.666 mm/s)

43.75 mm/s = 2625 mm/m so 2800 mm/m is not reachable with that stepgen velocity limit

Ok Thanks

I have upped the stepgen to 100. I have a bit of oscillation of the third digit which of the P terms do I need to adjust ?

[AXIS_0]
TYPE = LINEAR
HOME = 0.0
FERROR = 10
MIN_FERROR = 1.0
MAX_VELOCITY = 100
MAX_ACCELERATION = 500
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.
STEPGEN_MAXVEL = 125
STEPGEN_MAXACCEL = 625
P = 10.0
I = 0.01
D = 0.0
FF0 = 0.0
FF1 = 1.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 0.0
ENCODER_SCALE = -2000

if the error is in the 1-2 encoder count range it may be normal dithering
You can reduce this with a small amount of deadband (say .001 mm)

I am still struggling with this. This is my first time with a servo and not sure what to set the follow to
DIRSETUP = 1000
DIRHOLD = 1000
STEPLEN = 1000
STEPSPACE = 1000
STEP_SCALE = 2000 ENCODER_SCALE = -2000

I am getting an error " hm2/hms_5i25.0: stepgen.00.maxvel is too big for current step timings & position-scale, clipping to max possible
what do I need to adjust for this.

I would like to get 20mtr/min The servo rotates 1 rev when commanded 5mm the encoder position pin shows the same

The servo is new 1.8kw I believe 10000 count connected to 7i76 with differential step/dir when the servo is stationary and I try to move it. It returns back to position. So I assume that is correct.

from the X axis section of your ini file:
MAX_VELOCITY = 250
STEPLEN = 1000
STEPSPACE = 1000
STEP_SCALE = 2000

With a max velocity of 250 mm/s and a step scale of 2000 steps/mm you are right at the
limit of the stepgens maximum rate at the current steplen and stepspace settings:

Maximum step rate = 1/(steplen+stepspace) so 500 Khz at your current settings
500 KHz is also stepscale * maxvel = 2000*250 = 500 KHz.

If you need higher velocities you will need to shorten the steplen and stepspace.

Thanks Tom have you checked your email or changed it?