Pentapod configuration

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17 Jan 2022 17:08 - 17 Jan 2022 17:14 #232136 by Tawhiri
I'm having problems with a pentapod configuration.

I prepared the basic configuration settings with the config selector/pentapod. In the HAL I configured the threads, ports, and connected the signals from the functions to the right pins in the ports. I used the same stepper and port settings as in my trivial config, which is working ok.

The problem is that the actual steppers are barely moving, they are just making weird noises. I checked the pulse signals, they are looking very odd (I see only single pulses with very large gaps in between, on all 5 steppers).

I would appreciate some expert advice how to correct my HAL settings.

Many thanks, AndrĂ¡s
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Last edit: 17 Jan 2022 17:14 by Tawhiri. Reason: Photo added

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18 Jan 2022 22:59 #232352 by andypugh
Replied by andypugh on topic Pentapod configuration
Steplen and stepspace seem very short. Did your previous config use the "reset" function?

Section 7: linuxcnc.org/docs/2.8/html/hal/parallel-...ml#_using_doublestep

The units of steplen and stepspace are nanoseconds, 1 is very short.
linuxcnc.org/docs/2.8/html/man/man9/stepgen.9.html

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20 Jan 2022 14:46 #232532 by Tawhiri
Replied by Tawhiri on topic Pentapod configuration
The prevoius config was set up with stepconfig, and it didn't add the reset.
I added it now as the link suggests, but it doesn't seem to help.
I also tried to use longer step and space lengths, but unfortunately there is no improvement.

It appears that at each motor rotation direction change the steppers move a single step, then they stop. Maybe there is a problem with the way the pins and signals are connected, but I can't find it.

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25 Jan 2022 14:51 #233073 by andypugh
Replied by andypugh on topic Pentapod configuration
That sounds very much like step and dir are reversed somewhere.

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26 Jan 2022 15:57 #233186 by Tawhiri
Replied by Tawhiri on topic Pentapod configuration
I inverted the steps at the parallel ports. I also changed the scales in the ini. These make the signals look much healthier, but from the motors I still get weird noises and tiny movements only.
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26 Jan 2022 16:25 #233192 by andypugh
Replied by andypugh on topic Pentapod configuration
What I meant was that the step and dir pins might be swapped. So every time you change direction you get one step, and every time you try to make a step you change direction.

Your HAL file seems to contain a lot of unused cruft. Here is a simplified one, which might, or might not, work. Be aware that it was done without reference to a LinuxCNC installation and from memory....
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27 Jan 2022 18:53 #233298 by Tawhiri
Replied by Tawhiri on topic Pentapod configuration
Thank you for taking time to look at this.

With this hal I get joint following error on all joints immediately after clicking "home all".

I see you removed all the PID related stuff. I thought they are necessary for the forward kinematics iterations. But at the same time they are missing from the hexakins config, and the kinematics should be related. I am super confused now.

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27 Jan 2022 21:50 #233321 by andypugh
Replied by andypugh on topic Pentapod configuration
PID on the stepgens is useful with the Mesa cards. It might also help in some circumstances with the parallel port, but I was trying to make the simplest possible config.

You probably need to set the stepgen velocity and accel limits to be 20% higher than the joint limits. Typically the INI of a stepper system defines
MAX_VELOCITY
MAX_ACCELERATION
STEPGEN_MAX_VELOCITY
STEPGEN_MAX_ACCELERATION

in the [JOINT_N] section, then the HAL section that sets the stepgen limits uses the [JOINT_N]STEPGEN* numbers. This is to make sure that the stepgens can kep up with the motion commands.

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