Newsgroups: comp.robotics
Path: brunix!sgiblab!swrinde!gatech!howland.reston.ans.net!pipex!sunic!uts!imada!zaphod
From: zaphod@imada.ou.dk (Anders S. Soerensen)
Subject: PWM DC motor control
Message-ID: <1994Mar23.122134.20592@imada.ou.dk>
Sender: news@imada.ou.dk (USENET News System)
Nntp-Posting-Host: idun
Organization: Dept. of Math. & Computer Science, Odense University, Denmark
Date: Wed, 23 Mar 1994 12:21:34 GMT
Lines: 44

National semicunductors have made a single IC that does the modulation
and REGULATION of PWM signal to at DC motor.

I quote from their databook:

* 32 bits position, velocity, and acceleration registers
* Programmable PID filter with 16-bit coefficients
* Programmable derivative sampling intrtval
* 8- or 12- bit DAC output data (LM628)
* 8-bit sign-magnitude PWM output data (LM629)
* Internal Trapezioidal velocoty profile generator
* Velocoty, target position an filer charecteristics may be changed
  during motion
* Position and velocity modes of operation
* Real-time programmable host interrupts
* 8-bit paralel asyncronous host interface
* Quadrature incremental encoder interface with index-pulse input


The LM 628/629 can be uses whenever you have a DC-motor connected
to an (optical) incremental encoder. It can be used to contol the motors
position, velocity, and acceleration. You might say that the LM628/629 converts
a DC motor with encoder to a position/velocity servo.

The IC is rather expensive (eqv. of 60$ in Denmark), but I expect it to solve
a great deal of problems connected with motor-control.

The LM628/629 can be connected directly to an 8-bit microcomputer CPU-BUS, or 
it can be connected with an I/O port.

The LM628 generates an 8/12 bit output, which can drive the motor via a Digital
to analog converter.

The LM629 generates a PWM coded signal, and a direction (sign) signal; which
can easily be interfaced to drive a H-bridge.


I hope this info can be used by some of you!

Anders Stengaard Soerensen  (zaphod@imada.ou.dk)




