This (mux2 and  short-circuited feedback loop) is a good idea, i will try it.

BTW, I thought the index and home is the same thing. In my case the index 
switch signals the absolute position on the axis, so there is no need for 
additional homing afterwards. This is why I thought it would be better to use 
the home button instead of e-stop + homing.

Regards, Klemen



________________________________
 From: andy pugh <[email protected]>
To: Klemen Dovrtel <[email protected]>; Enhanced Machine Controller 
(EMC) <[email protected]> 
Sent: Thursday, February 28, 2013 2:16 PM
Subject: Re: [Emc-users] bldc/axis homing
 
On 28 February 2013 10:42, Klemen Dovrtel <[email protected]> wrote:

> Is there any other option how to home the axis and bldc?

This quite an interesting puzzle..

One possibility might be to use a mux2 in the HAL to feed the value of
axis.N.motor-pos-fb.
Inputs would be axis.N.motor-pos-cmd and encoder.N.position.

So, in one state the feedback loop is completely short-circuited, and
in the other it works normally.

The Axis "Home" button explicitly starts the homing sequence. I
suspect that this could be deleted (or altered) in the .axisrc file
(but I am not expert enough in Python to say how).

What would be needed would be a GUI button that starts the bldc homing
sequence. Then the init-done signal would start the standard homing
sequence _and_ re-enable f-error checking via the mux2.

This still might not work. When the mux2 switches it may well be that
the f-error is big. I don't know at what point f-error checking is
enabled.

I thought you had the motors homing when coming out of e-stop? Much as
I dislike this approach it ought to avoid the problem:
e-stop off, f-error checking not yet enabled, motors initialise.
machine-on, f-error enabled, command position set to actual position,
so no f-error
home-pressed, motors search for home index.

is it possible that the real problem is the three-way debate between
bldc.index-enable, encoder.index-enable and axis.index-enable?

-- 
atp
If you can't fix it, you don't own it.
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