Subject:
|
Re: ROM stuff: Better than PWM
|
Newsgroups:
|
lugnet.robotics
|
Date:
|
Sat, 19 Dec 1998 13:39:55 GMT
|
Original-From:
|
Markus L. Noga <MARKUS.NOGA@antispamINRIALPES.FR>
|
Viewed:
|
1307 times
|
| |
|
|
Kekoa Proudfoot wrote:
> You can avoid the O(n^2) table cost by keeping a counter. Count p cycles
> on, then count n-p cycles off. This works. But as n gets large, the
> period of n ms drops low enough that the motor becomes ineffective. For
> example, if n is 1000 and p is 500, the motor is on for 1/2 sec then off
> for 1/2 sec. That won't drive the motor the way you want it to be driven.
> Even for n = 100, things are very jittery.
>
> So here's my solution:
>
> every 1/1000th sec:
> count += p
> if (count >= n)
> turn motor on
> count -= n
> else
> turn motor off
>
> That's it.
>
> I'm sure this algorithm has been thought of before; I got the idea from
> Bresenham's line drawing algorithm and from the Floyd-Steinberg error
> diffusion dithering algorithm, but I believe this algorithm is a typical
> one used in one-bit D/A converters.
In fact, I'm using exactly this algorithm to drive the motors for my
laser scanner - though the host platform is an embedded PC, not the RCX.
I'm currently rewriting the motor drivers to:
* keep an 1ms resolution system clock
* call the task scheduler every 20 ticks, thereby making it IR
compatible
I'll integrate the Bresenham algorithm with a practical n of, say, 256,
too.
--
Markus L. Noga noga@inrialpes.fr
INRIA Rhône-Alpes http://www.inrialpes.fr/
IPR Universität Karlsruhe http://wwwipr.ira.uka.de/
|
|
Message is in Reply To:
 | | ROM stuff: Better than PWM
|
| So I was thinking about writing a motor driver that is better than what is in the ROM already. Here's the problem: You have a function called once every 1/1000th of a second. You want to allow n speeds of the motor at minimal cost in lookup tables. (...) (26 years ago, 19-Dec-98, to lugnet.robotics)
|
3 Messages in This Thread:
 
- Entire Thread on One Page:
- Nested:
All | Brief | Compact | Dots
Linear:
All | Brief | Compact
|
|
|
|
Active threads in Robotics
|
|
|
|
|
|
