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<== Date ==> <== Thread ==>

Subject: RE: Motor home status
From: "Mark Rivers" <[email protected]>
To: <[email protected]>, <[email protected]>
Date: Thu, 21 Aug 2008 08:17:43 -0500
> This assumes that the current position information is somehow still
valid, 
> at least approximately. However, tehre is no guarantee taht this is so

> before the motor gets homed. Thus, I agree that soft limits make no
sense 
> during home operation.

I disagree.  There are other ways besides home to know that a motor is
in approximately the correct position.  For example, there may be
indicators on the motor slides, or one may use a limit switch as a
fiducial.  

Save/restore motor positions are another example. If the IOC and
controller have been rebooted, so the motor has not been "homed" in the
memory of the controller or IOC, but the positions are almost certainly
still correct.

Mark


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Benjamin Franksen
Sent: Thursday, August 21, 2008 6:51 AM
To: [email protected]
Subject: Re: Motor home status

On Thursday 14 August 2008 18:10, Kurt Goetze wrote:
> It would be dangerous to automatically override soft limits for a
homing
> operation, in my opinion.  If soft limits had been set within the home
> position,
> and a decision was made to home the positioner, then some human
> intervention
> would be needed to decide whether the situation that the soft limits
> were set
> to protect against is still valid.  If a positioner is to be expected
to
> *always* be ready for a homing operation, then the soft limits should
> be set and left outside of the home position.

This assumes that the current position information is somehow still
valid, 
at least approximately. However, tehre is no guarantee taht this is so 
before the motor gets homed. Thus, I agree that soft limits make no
sense 
during home operation.

> Also, if a positioner is homed accidentally, before any obstructions
were
> cleared out of the way, it would be good to know that the soft limits
> will do
> their job.

Again, in general they can't. Thus all you get is a false sense of
security.

Cheers
Ben
-- 
"Programming = Mathematics + Murphy's Law" (E.W.Dijkstra)


Replies:
Re: Motor home status Benjamin Franksen
Re: Motor home status Maren Purves
References:
Re: Motor home status Benjamin Franksen

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