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From: email@example.com (Tomas Modeer)
Subject: Re: Constant Frequency at LOW temperature
Date: 8 Nov 2002 06:27:08 -0800
References: <3DC53B22.firstname.lastname@example.org> <3DC543F3.8C692E48@webaccess.net> <3DC54ABE.email@example.com> <3DC553C3.D48D866E@webaccess.net> <3DCB4E2A.D3198E12@webaccess.net>
NNTP-Posting-Date: 8 Nov 2002 14:27:08 GMT
Chuck Simmons wrote in message news:<3DCB4E2A.D3198E12@webaccess.net>...
> SNIP <
> Thus the stepper drive motor will
> experience varying torque and its rotational angle from the ideal
> unloaded angle will vary during tracking. This turns out to be a
> nonrepeatable error of significant magnitude with practical gear ratios.
> Thus a conventional DC torque motor with sufficiently fine encoder will
> give about an order of magnitude better tracking accuracy than a
> stepper. This has been tested in retrofitting microstep drives with high
> quality DC servo drives. For the same gears, the improvement is
Thanks! Learning each day. I can see the use of a position feedback if
load varies a lot, especially if the rest of the tracking system is
In my mind this does not necessarily rule out any motor type. The
advantage as I see it (open loop positioning) is gone. A high
resolution synchronous motor (i.e. a stepper) should not do any worse
than a (brushed) DC motor.
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