I'm playing with the homing at slow speeds so I can hit the home switch
always half a turn away from the index pulse more or less.
One thing is happening is the following:
If I let the mark (keyway in this case) of the motor at 3 o'clock and then
I turn off LinuxCNC, whenever I home the axis again (with the switch and
index and home position and offset both in 0) the axis goes to this same
position after the home sequence stops. Does that make sense?
I was hoping that with both the home offset and home position in 0 the
motor would stop near the index pulse with some overshoot may be. But
always there and not in the last position when the machine turned off. By
the way I'm not using the POSITION_FILE option and I also tried to use
VOLATILE_HOME with the same results.
Sorry for all the questions but this is the first machine I'm using with a
proper homing sequence.
El vie., 10 abr. 2020 a las 19:35, Leonardo Marsaglia (<
ldmarsag...@gmail.com>) escribió:
> You can use homing with index if you use the drives encoder output
>> for feedback, but this is a bit more work and more difficult
>> to tune
>
>
> Do you think is a good practice to use them as feedback? Because I'll
> be coupling the servos to the ballscrews with a timing belt, so this might
> not be that accurate as having the encoders mounted directly on the
> ballscrews. In that case anyway I would be using the servos with analog
> voltage for velocity command because I can't use them in speed mode with
> the speed reference being pulsed.
>
> Also there's the difference in diameter of the pulleys, but that can be
> scaled so it would be no problem.
>
> By the way, I finally succeeded in using the home switch + index. I think
> it was me trying to imitate the sequence in a wrong way pushing the switch.
> I'll try a little more to be sure.
>
> El vie., 10 abr. 2020 a las 19:23, Peter C. Wallace (<p...@mesanet.com>)
> escribió:
>
>> On Fri, 10 Apr 2020, Leonardo Marsaglia wrote:
>>
>> > Date: Fri, 10 Apr 2020 19:01:51 -0300
>> > From: Leonardo Marsaglia <ldmarsag...@gmail.com>
>> > Reply-To: "Enhanced Machine Controller (EMC)"
>> > <emc-users@lists.sourceforge.net>
>> > To: "Enhanced Machine Controller (EMC)" <
>> emc-users@lists.sourceforge.net>
>> > Subject: Re: [Emc-users] Home use index problem (In step + dir mode)
>> >
>> >>> Do you have a home switch and is it working?
>> > If you want to home to index only you must set HOME_SEARCH_VELOCITY to 0
>> >
>> >
>> >The home switch is working perfectly. I'm pushing it by hand because I'm
>> >only testing in the desk but it works. If I only use home switch for
>> homing
>> >it works perfectly. The problem starts when I try to use the index pulse.
>> >
>>
>> If you have homing setup for home switch + index, motions index-enable
>> output
>> should be set high when the home switch is tripped
>>
>>
>> >If I set HOME_SEARCH_VELOCITY to 0 and try to home using index only, the
>> >joint.0.index-enable pin turns to TRUE and when the motor trips the index
>> >pulse it stops but I get the following error message and the homing
>> aborts.
>> >Always in the same position of the motor, so the index is detected.
>>
>> The following error is expected unfortunately since motion expects the
>> position
>> to have been zeroed on index detection, but the stepgen position is not
>> affected
>> by the encoder index
>>
>> >>Do the servos have a emulated encopder output (you mentioned a Z
>> signal, is
>> >> that from the drive?)
>> >
>> >
>> >Yes the drive has the encoder output pins for the A, /A, B, /B, Z and /Z
>> >signals. I'm only using the Z and /Z signals because I thought I could
>> home
>> >with index independently of the feedback I was using.
>>
>> No, index handling is intimately entangled with the position feedback.
>> This is because index detection effectively zeros the position feedback
>> at the instant of index detection so its is precise regardless of the
>> detection
>> speed. As I mentioned, there is firmware to support index detection with
>> the
>> stepgen hardware, but it is not currently supported by the hostmot2 driver
>> Also as you might expect, the stepgen index input pin is not an encoder
>> input
>> rather, its part of the stepgen.
>>
>> You can use homing with index if you use the drives encoder output
>> for feedback, but this is a bit more work and more difficult
>> to tune
>>
>>
>> Peter Wallace
>> Mesa Electronics
>>
>> (\__/)
>> (='.'=) This is Bunny. Copy and paste bunny into your
>> (")_(") signature to help him gain world domination.
>>
>>
>>
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>>
>
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