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Subject: 
Re: Steering Drive
Newsgroups: 
lugnet.robotics
Date: 
Thu, 26 Aug 2004 02:23:33 GMT
Viewed: 
1202 times
  
Hi,

I have used this flag technique successfully.  It was easier than a
hardware solution.  I use leJOS which also provides a way to check
which direction the motor is turning.  When the touch sensor is hit,
you can do something like
if ( Motor.A.isBackward() == false )
and act accordingly.

Walt White
________________________________
"Øyvind Steinnes" <phoenix@online.no> wrote in message
news:I2zM3x.2CD@lugnet.com...

"Jon Gilchrist" <robots@DEELEETEf3p.com> wrote in message
news:cmsni0t76f5vr92g29g4d7ecg6gbu5r60i@4ax.com...
So I'm building this robot because my FLL kids told me it couldn't be
done.  It has to do a few things, line following, bumpers, nothing too
special.  I made it with a steering drive because it has to have
wheels that turn to make it look right (I'll explain after it's done,
I have to keep the design a secret for another 2 weeks).  Not a big
problem, I'm using the basic linkage that came with the racers
(8473-1) I got at the Brickfest outlet store sale.  I've got a
differential in there with a motor to drive it, and a rotation sensor
hooked up for distance measuring.  I have a light sensor for finding
the line I'm going to follow.  Here's the tricky part.  I have a touch
sensor hooked up much like this one
(http://www.marioferrari.org/brlm/f1614.jpg) so that I can tell when
the wheels are pointed straight ahead.

So my problem is, how do I tell which way I need to turn the motor to
get the wheels back to straight?

If the sensor is touched, I know that it is going straight, but if the
sensor is not touched I can't figure out any good way to tell which
side of the switch the cam is on.  At least, not without using another
sensor port, which I don't have available.  I can't double up on the
light sensor, because I can't have the sensor value go to 100 just
because I'm going straight.

I don't understand why you need to know which way to turn the wheels to go
straight?
When you initialize the robot you can test with low power first some • seconds
in one direction and then the other way until you reach center and the • tuch
sensor is pressed. You probably need to use the clutch gear to protect the
steering mechanism. Now its just all about having two flags in the
programming that tells you what direction you last turned the wheels. Eg.
set flag 1 if you turn right, and set flag 2 if left was the last • direction
and both flag reset when center. Then you can just check which flag was • set
and the tuch sensor to know if the wheels is to the right, left or • center...

Or do I miss some function in your robot? Do you want to know HOW much the
wheels are turned and in what direction?

Regards
Øyvind Steinnes
http://www.brickshelf.com/cgi-bin/gallery.cgi?m=Phoenix


Help.  Any advice appreciated.

-Jon







Message is in Reply To:
  Re: Steering Drive
 
"Jon Gilchrist" <robots@DEELEETEf3p.com> wrote in message news:cmsni0t76f5vr92...4ax.com... (...) I don't understand why you need to know which way to turn the wheels to go straight? When you initialize the robot you can test with low power first (...) (20 years ago, 25-Aug-04, to lugnet.robotics)

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