Re: Low cost Servo Controller

In a message dated 09/10/1999 9:25:14 AM Hawaiian Standard Time,
dhowland@... writes:

<< Subj: [CAD_CAM_EDM_DRO] Low cost Servo Controller
Date: 09/10/1999 9:25:14 AM Hawaiian Standard Time
From: dhowland@... (David Howland)
Reply-to: CAD_CAM_EDM_DRO@onelist.com
To: CAD_CAM_EDM_DRO@onelist.com ('CAD_CAM_EDM_DRO@onelist.com')

From: David Howland <dhowland@...>

I am working on specifications for a Servo driver board which will allow any
low or medimum cost DC motor to be converted to a Servo motor and connected
to a parallel I/O board. I hope this electronic assembly will allow high
performance motion control for a reasonable cost. Steppers + Stepper
controllers seem to be less expensive and easier to use than Servos + Servo
controllers. Many of us use steppers and put up with speed - torque
limitations. I know that many low cost DC motors will not perform as well as
a low inertia high quality servo motor, however the board development I am
considering will out perform most steppers for less or equal system cost.
<snip>

Has anyone seen high performance Servos with Servo controllers which
competed in price to the steppers

<snip>

Will someone make a list of stepper controller costs vs. Servo controller
costs plus motor costs, with a little performance data one might get at each
cost? Aside from the main stream sources such as Minarik or the likes. What
does it look like as you travel up the performance - cost curve for
"underground" motion controller components and difficulty with CAM software
interfacing? Even more important, What kind of CNC performance might one end
up with along the way? Frankly, I hate dissapointment, even when it's my own
fault for not spending enough money.


David Howland

Dave,
I was surfing around the Oriental Motor site yesterday. They came out with
a new stepper motor driver combination (called Alpha Step) that has an
encoder feed back circuit. The driver's onboard brain corrects any missed
steps on it's own and raises a flag to signal a following error if it tries
unsuccesfully to correct the difference. Perhaps a servo can be set up in
that way where the driver hardware takes care of all house keeping? It seems
then that a stepper based control program can run servo's. I believe Dan
Mauch and Bill W's Servo Lite is such a system. I have the information on
order from him. Perhaps Dan could shed more light on this before any more
re-inventing is done. I believe also that between Tom Kulaga and Dan Mauch
and/or others, there is another effort to build a servo controller in the
works. WAnliker, Am I mistaken?

Peter
PT Engineering Co.