Let's Make Robots!

Sonar

Ok I've never played around with these sonar rangefinders all you guys have. This isn't so much a question of how do you use them but I'm curious to know what is the difference between them and the sonar used in boats and subs?

I mean they can just about give you Hd video of whats under your boat using sonar these days. What is in the transducer and I guess supporting hardware that allows this and is it adaptable to robotics? It seems to me that the power of sonar is underutilised if all you gonna get is, is there something 20 cm in front of me ? True or false. It's not much more than a walking stick for a sensor.

I guess if it were that easy it would have been done. Maybe the difference between water born sound waves and air is so different it makes it impractical? Or maybe I just haven't seen it yet. Can anybody offer any opinions about this?

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http://en.wikipedia.org/wiki/Speed_of_sound

http://en.wikipedia.org/wiki/Sonar

personally i would describe sonar more like a large cone than a stick, only thing close to a stick is a laser  (beam width ) this will change from model to model

in the most simplistic terms it's a speaker + tone generator for the "ping"  and a microphone + amplifier plus a tone detector

microphones and speakers are similar in the way they both can be used as a receiver and transmitter of waves thus you can use the same element to send and receive sound waves, this would include piezo        

http://en.wikipedia.org/wiki/Piezoelectric_sensor

well that's the way i see it ,get a second opinion :)

I've considered that as well. The most general explaination I got was:"The performance of an imaging sonar—from the distance at which they can detect an object, to the clarity of the image, to the number of images they can display per second—are determined by a number of specifications, most notably the operating frequency, acoustic beamwidth and processing power and time to form an image.... Generally speaking, a lower frequency increases the distance at which an image can be captured. A higher frequency and a smaller beamwidth used to map an object will deliver clearer images. The depth at which the sonar is deployed has no direct effect on how clearly an imaging sonar can capture a target."

Also found this:

http://www.imagenex.com/sonar_theory.pdf

which has a lot of interesting info on the subject. I put the idea of making an imaging sonar on the back burner after reading this lol

That looks a very useful paper. Have saved it to reread and try and understand it a bit better.