7I90HD with Raspberry pi and getting weird joint 0 following errors

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23 Feb 2021 16:29 #199847 by creisey
Hi i have a question i have a XXYZ config

the attached one is working without the error, but the homing takes forever
[AXIS_X]
MAX_VELOCITY =       	200
MAX_ACCELERATION =   	300
MIN_LIMIT =             -9999.0
MAX_LIMIT =             9999.0

[JOINT_0]
TYPE =              LINEAR
# Set Stepgen max 20% higher than the axis
STEPGEN_MAXVEL =    	250
STEPGEN_MAXACCEL =    	375

as long as i have MAX_VELOCITY & MAX_ACCELERATION in the Joint section the homing is quick as usual but after some movements i run in a joint error. > check example below
[AXIS_X]
MAX_VELOCITY =       	200
MAX_ACCELERATION =   	300
MIN_LIMIT =             -9999.0
MAX_LIMIT =             9999.0

 [attachment=35102]iosi.hal[/attachment] [attachment=35103]iosi.ini[/attachment]

[JOINT_0]
TYPE =              LINEAR
MAX_VELOCITY =       	200
MAX_ACCELERATION =   	300
# Set Stepgen max 20% higher than the axis
STEPGEN_MAXVEL =    	250
STEPGEN_MAXACCEL =    	375
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23 Feb 2021 16:34 #199848 by Aciera
Note that your STEPGEN_MAXVEL is actually more than "20%" higher than the axis.
So maybe try reducing that bit.

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23 Feb 2021 16:41 - 23 Feb 2021 16:42 #199850 by creisey
i tried that with 20% as well. same effect...
funny thing is there are examples with 20% and 25%

# The values below should be 25% larger than MAX_VELOCITY and 
MAX_ACCELERATION
Last edit: 23 Feb 2021 16:42 by creisey.

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23 Feb 2021 16:44 #199852 by Clive S
Re this:-

HOME = 0.000
HOME_OFFSET = 0.0
HOME_SEARCH_VEL = -10 This is the speed it will search for the home switch
HOME_LATCH_VEL = 2.5
HOME_USE_INDEX = NO
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 2 if you want gantry squaring this has to be a -ve number

# these are in nanoseconds
DIRSETUP = 2500
DIRHOLD = 2500
STEPLEN = 2500 might have to increase these
STEPSPACE = 2500

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23 Feb 2021 16:53 #199856 by creisey

Clive S wrote: Re this:-

HOME = 0.000
HOME_OFFSET = 0.0
HOME_SEARCH_VEL = -10 This is the speed it will search for the home switch
HOME_LATCH_VEL = 2.5
HOME_USE_INDEX = NO
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 2 if you want gantry squaring this has to be a -ve number

# these are in nanoseconds
DIRSETUP = 2500
DIRHOLD = 2500
STEPLEN = 2500 might have to increase these
STEPSPACE = 2500


right those values are getting read while i set MAX_VELOCITY & MAX_ACCELERATION in the [JOINT_0] section, but if they are missing the search velocity is set to very slow value. after the slow homing process, jogging is working without the sudden following errors.

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23 Feb 2021 17:01 #199857 by Aciera
Have you tried reducing velocity and acceleration by say 50% ?

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23 Feb 2021 17:15 #199861 by Clive S
I only see one set of stepgens etc for the X motors in the hal file.

Are sending the output to 2 drives.

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23 Feb 2021 17:23 - 23 Feb 2021 17:26 #199863 by creisey
the hal-file is not properly commented.

stepgen.00 and stepgen.01 are my X-axis

i have tried also slower rates and they might work better, but i dont understand why the setup is working when "STEPGEN_MAXVEL & STEPGEN_MAXACCEL" is missing in the Joint section with the side-effect is a slow homing
Last edit: 23 Feb 2021 17:26 by creisey.

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23 Feb 2021 17:32 - 23 Feb 2021 17:33 #199864 by PCW
A couple of things:

With a 0.050 mm maximum following error, 250 usec of servo thread jitter will cause a
following error with your current setup . What is you servo thread jitter?

There are a couple of things that can be done to improve stepgen performance with regard to host jitter:

1. Use the stepgen in velocity mode and a PID loop to control the position (use a pncconf created hal/ini file set as a model)

2. Use the DPLL to reduce host servo thread jitter impact on position sampling errors
Last edit: 23 Feb 2021 17:33 by PCW.
The following user(s) said Thank You: Clive S, Aciera, creisey

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23 Feb 2021 19:02 - 25 Feb 2021 08:02 #199878 by creisey
i set to FERROR = 0.08 and it works. thx a lot

and set MIN_FERROR = 0.02
Last edit: 25 Feb 2021 08:02 by creisey.

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