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

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25 Feb 2021 08:06 #200070 by creisey

PCW wrote: 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


can i make a pid loop in an openloop configuratuion? i thought i need an encoder for that.

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25 Feb 2021 14:05 #200097 by PCW
Yes, take a look at a pncconf created step/dir hal file.

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01 Mar 2021 19:37 - 02 Mar 2021 08:03 #200719 by creisey
i made a config with the pncconf that works

there are two things

1. im not sure if the shared home switch for x & x2 are correct set
2. ferror seems to be a bit high

what do you think?

File Attachment:

File Name: test-pnc.hal
File Size:13 KB

File Attachment:

File Name: test-pnc.ini
File Size:5 KB
Attachments:
Last edit: 02 Mar 2021 08:03 by creisey.

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01 Mar 2021 19:53 #200723 by PCW
You should be able to set the ferror and min ferror much smaller
also all lines like: setp pid.?.maxerror .0005 should be commented out

You can further improve the following error by using the DPLL:
# latch stepgen position feedback 100 usec before nominal read time:
setp hm2_[HOSTMOT2](BOARD).0.dpll.01.timer-us -100
setp hm2_[HOSTMOT2](BOARD).0.stepgen.timer-number 1
The following user(s) said Thank You: creisey

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