Author Topic: fire fighter sensor scheme  (Read 2244 times)

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Offline frank26080115Topic starter

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fire fighter sensor scheme
« on: October 13, 2007, 08:45:27 PM »
i want to enter a firefighting robot competition

the "maze" is made with 12" high walls with a semi-gloss white paint, there are 4 rooms the fire is randomly placed in, the floor is black with 3/4" white lines on doorways, the starting circle is also white but solid.

my avrcam can spot a fire and ignore the wall, so that's no problem, the camera is mounted on a pan-tilt servo setup along with a single standard sharp IR range sensor, but the sensor face is at the very front of the robot, so some clever programming is needed to use the IR ranger when a wall is close up

the drive system is 2 hs475hb servos with 3" wheels, battery is 7.2v, and the MCU is an arduino

i want to find the room with the fire, while watching out for walls, while recording the steps the robot took so it can find the home circle, all under 5 minutes

I was thinking of doing this, if i have a floor line sensor arrangement with 4 reflective sensors spaced 1" apart, the only thing that can activate all 4 is the circle as it is physically impossible for the doorway lines to set off all 4 at once, and when 1-3 are active, the robot will know it is in a doorway, look around for the fire, and extinguish it.

the problem is that the robot can't tell if there is a door, so i was thinking of this, on the top servo, have 2 IR sensors, and if their readings increase significantly, there is a door and the robot will checkout the walls surrounding it, if the IR ranger reports a hole, it will turn, go in, and check for a line, if no line, then it's another hallway, it keeps going

does that sound good, or should i just have it go a few inches, check both sides, and repeat? (very slow)

also, is it practical to store absolutely every step the robot takes, store it in eeprom, and after the fire is out, and reverse the speed values for each servo to find home circle? i can't use encoders

the head servo can be mounted backwards to see towards the rear of the robot if needed

also would a dollar store fan work well enough to put out a fire? i'm watching youtube videos and i'm not sure how powerful it needs to be
« Last Edit: October 13, 2007, 09:02:10 PM by frank26080115 »

Offline Ro-Bot-X

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Re: fire fighter sensor scheme
« Reply #1 on: October 14, 2007, 01:46:07 AM »
Check this message I have posted a while ago: http://www.societyofrobots.com/robotforum/index.php?topic=2001.msg13497#msg13497, you will find the shortest way to the exit easier. Have 2 IR sensors looking sideways for gaps in the wall, any gap found it will be a node. If door line found, look for the fire and estinguish. That means you are done, go back using the nodes in the array to turn. You may need to turn the oposite way since you are going backwards...
One important thing: modified servos can be used to record traveled distance... and turn angle... you just have to measure the distance traveled with one servo pulse...

Edit: I was thinking about the layout of the model house... Sometimes you may go the long route to the fire, sometimes you may go the shortest route. Have a counter or timer that will decide if you are past the halfway through the layout and for returning to the entrance just keep going since this will be the shortest path to the exit/entrance.
« Last Edit: October 14, 2007, 03:11:46 AM by Ro-Bot-X »
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Offline Admin

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Re: fire fighter sensor scheme
« Reply #2 on: October 19, 2007, 08:26:25 PM »
Quote
One important thing: modified servos can be used to record traveled distance... and turn angle... you just have to measure the distance traveled with one servo pulse...
ehhhh the error will be too high for this method. There are encoder kits you can buy to attach directly to a servo.

Quote
also, is it practical to store absolutely every step the robot takes, store it in eeprom, and after the fire is out, and reverse the speed values for each servo to find home circle? i can't use encoders
ive seen this done with encoders, but even then the robots had a high error rate - crashing into walls after awhile . . . i can only imagine way worse without encoders . . .

scroll down halfway where it says 'Range Finder Basic 2D Mapping' on this page:
http://www.societyofrobots.com/sensors_sharpirrange.shtml
It might help you a bit with ideas . . .

Offline frank26080115Topic starter

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Re: fire fighter sensor scheme
« Reply #3 on: October 19, 2007, 09:08:36 PM »
yea i gave up on that idea, now i think i should just remember the last decision point and which choices has already been taken, range sensors will help it navigate

 


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