Subject:
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Re: IR collision avoidance
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 25 Feb 1997 06:37:16 GMT
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Original-From:
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Richard Vannoy <richardv@NOSPAMabac.com>
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Reply-To:
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richardv@abac/avoidspam/.com
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Viewed:
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1506 times
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Some comments and a few questions for Chris
Chris Moore wrote:
> I'm using 3 Radio Shack IR LED's in parallel and 3 Radio Shack IR receiver
> modules. One pair points straight ahead, one pair is 45 degrees to the left
> and one is 45 degrees to the right.
We have "forward" and 45 degrees right". We wall hug to the right while
you hug to the left. We ignore IR to left and use only the left contact
switch for collisions (rare).
> The LED is mounted directly to the top
> of the metal can of the detector with some double sided tape.
We had way too much power and noise with "together" mounting. We
finally mounted xmitter 2 inches above with a small copper plate to
sheild the transmitter from direct transmission to the receiver. And we
had to use sheilded cable for whatever left the circuit boards.
> Finally, to do wall following, the program uses only the front and left
> sensors.
> It first tries to 'aquire' the wall by driving straight until either
> left_ir_blocked or center_ir_blocked is true. Then it tries to follow the
> wall by keeping the left IR blocked and the center IR NOT blocked using the
> following logic:
> left_ir_blocked center_ir_blocked
> No Don't care Veer left towards the wall
> Yes Yes Veer right to avoid hitting the
> wall
> Yes No Continue straight.
Ours is similar but does not allow ahead straight. We do...
front blocked right blocked action
YES Don't care Turn left 90 degrees.
NO YES Turn wheel 10 degrees left
NO NO Turn wheel 5 degrees right
This puts the robot in a long slow right arc till a wall is detected.
Then, untill a corner comes up the shift between 10 left and 5 right
keeps the bot a nice 18 inches from the wall. People who don't know
that the wheel is almost constantly "correcting" don't even notice it.
To them it looks like a straight line.
and now my main questions....
> ir_xmit_on();
I've left the IR on ALL THE TIME because I never figured out how to turn
it on and off! Is ir_xmit_on(); part of the Handyboard pcode_hb.s19
code?? If so I missed it. If not, where is the code? Does
ir_xmit_on() send a digital or analog signal? ...to what port, or is it
programmable?
> if (left_count > 7) {
> left_ir_blocked = 1;
> } else {
> left_ir_blocked = 0;
Good algorithm!! I didn't use a loop because the response seems great
when we react to any "blocked". So far I've seen no noticable
transient/false signals, but your way seems much more elegant.
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Message has 1 Reply:
 | | Re: IR collision avoidance
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| (...) ** My only question is how do you keep the bot at a constant 18 inches ** away from the wall with a collision detection algorithm? Is it ** possible to get analog outputs from a sensor indicating the ** distance from a wall? Or is there is (...) (28 years ago, 27-Feb-97, to lugnet.robotics.handyboard)
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Message is in Reply To:
| | Re: IR collision avoidance
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| This question seems to come up a lot here so I thought I'd post to the list rather than reply individually. Here's what I'm doing for IR collision avoidance. First, the hardware: I'm using 3 Radio Shack IR LED's in parallel and 3 Radio Shack IR (...) (28 years ago, 24-Feb-97, to lugnet.robotics.handyboard)
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