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ricky
06-07-2013, 07:17 AM
Hello everyone ,

I am using a ultrasonic sensor for my robot. I know that my first echo of the wave gives me the distance of the robot fromthe object. I want to also know the depth of the object . So I find to segragte the first rear wall echos that I get from the object. Can some one tell me how can I distuinguish between the neighbouring noise and rear wall echo.

jwatte
06-07-2013, 11:45 AM
What sensor are you using? If you're using an off-the-shelf ultrasonic range finder, then no, you cannot make any determination like that.
If you're using your own transducer and demodulator, with analog input and digital signal processing, then you can group echos by density using something similar to k-means clustering, and find "facing edges" that way, although you won't know the side-to-side location of those.

Xevel
06-07-2013, 04:27 PM
With the Maxbotix MaxSonar AE you can get an analog image of the echo.

Depending on your application (size and shape of the detected object, distance, orientation,...) you might be able to separate the first bump corresponding to the closest refecting surface of the object from the next bump (provided your case is "good" enough for a second bump to exist, which is not necessarily true).
The fisrt thing to do would be to characterize your problem more precisely, figure out the invariants of it. For example, if the sensor is facing a wall and the object is between the wall and the sensor, with rougly always the same position and orientation => the signature due to the wall might be possible to substract from the signal somehow...
Such a problem is very non-trivial in the general case, but could be solved in some very specific cases.