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Author Topic: srf04 ultrsonic sensor for obstacle avoidance  (Read 1460 times)
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Hi i have been working on my final year project which is to avoid obstacles for that purpose am using srf04 sensor to detect objects.

problem:
*it works fine when object is in front of it but if i place the obstacle at some angle its not detecting it and my robot is hitting with that obstacle.

things i tried
* to cover the maximum angle i place my sonar over a servo and am nw continoulsy scanning 120 degree field twice in a second and sitll am having the same problem its not detect the object or walls when its moving at some angle.
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i have remove the other post i created , cuz i found this sensor category more relevant to my problem
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Brunsbüttel, SH, F.Rep.GERM
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is it this one:
http://www.robotstorehk.com/srf04tech.pdf
?

it seems like it has a quite thin beam width...

furthermore at certain angles and certain materials the reflected ultrasonic noise, that reaches the sensor, is too weak...
e. g. pyramids out of a special rubber foam can be used to trap audible noise, so that nobody can listen, if he/she is behind those pyramids...

can u use obstacles with a certain coating?
maybe metal (foil) works better than paper?
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-Arne

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yes it is this one its beam angle is 40 degree , which i tested it cover the 40 degree at a distance of two feet or 70 cm.

in my project there is pre defined arena which is made up of wood now how can i cover the boundaries with metal foil

yes i can replace my obstacles with the metals ones rather than paper.
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Brunsbüttel, SH, F.Rep.GERM
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can u use multiple sensors?
one that sits over the left front wheel and looks at -15° and
one that sits over the right front wheel and looks at +15° (looking to the front would be 0°)...
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-Arne

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yes it is this one its beam angle is 40 degree , which i tested it cover the 40 degree at a distance of two feet or 70 cm.

in my project there is pre defined arena which is made up of wood now how can i cover the boundaries with metal foil

yes i can replace my obstacles with the metals ones rather than paper.

Multiple sensors at different angles would probably work best.  The problem is that the object needs to be a certain width and basically facing the sensor for sound to bounch off it.  If the object is pointed, sound won't bounce off to get an echo.  However, if you have two angles, it raises the odds that you will find the object.

Most ping libraries don't work well when using multiple sensors due to their 1 second delay at times.  However, my NewPing is specifically designed to be fast enough to use multple sensors.

NewPing Library

I also have a two sensor example sketch that you can use as a basis for your code.  With the NewPing library, you could ping both sensors easily around 10 times per second (20 pings) while still doing other things like controlling your bot.

Tim
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Arduino - Teensy - Raspberry Pi
My libraries: NewPing - LCDBitmap - toneAC - NewTone - TimerFreeTone

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