Re: Low cost Servo Controller

>Message: 2
> Date: Sat, 18 Sep 1999 23:09:04 -0700
> From: "Dean Franks" <dean@...>
>Subject: Re: Low cost Servo Controller
>Snip
> The system
>would then generate target velocities for the current cycle goal, and

send

>them to the 629's. This is would not be the most accurate way to do

things,

>I suspect that the positioning error inside a single cycle will be
>unacceptable for moderate to high precision applications.
>
>I am not advocating this approach, I believe that it would be much

easier to

>develop an integrated system using the TI motion DSP's (TMS320 series).

The

>chips are cheaper, the hardware simpler, and the development exercise
>becomes almost totally a software one. It's much easier to do basic
>research (incremental design) in software than hardware (particularly

when

>you have DSP's with flash memory).

I have been looking at the all digital approach too. Has anybody else
looked at the Analog Devices ADMC401. Apparently it is being used for
next generation Baldor drives. The ADMC401 is a DSP derivative with all
the bits needed to produce a PWM control output. Although it is aimed at
single channel AC drives, I think we could get 3 Axes out of the one
chip if they were constrained to brush DC motors. Anyway if this can't
be done the chip has the all important sync pin for multi axis
operation. One thing about DSPs is that it is relatively easy to
implement feed-forward compensation without producing oscillation.
The Analog Devices web site has some good information on it including
assembly code for digital PI; assemblers and motion debugging tools all
for download.
See http://products.analog.com/products/info.asp?product=ADMC401
Also
http://www.analog.com/industry/motor_control/tools/index.html#ADMC401
plus many more.

John C.