Pioneer 3DX strange sonar behavior

Question

Hi,

I'm doing experiments with the frontal sonar ring present in the Pioneer 3DX using ROSARIA with ROS Fuerte. However, the output from the array wasn't what I expected. The sonar readings often return the maximum range of the sonar, even though the wall is clearly not so far away. I made a video where is possible to compare the sonar readings with an LFR in my campus corridors. Also, I have uploaded a photo of the corridor to give a general overview of the scenario.

Video

Campus

Yellow dots are the sonar readings (pointcloud published by ROSARIA), red dots are LFR scans and the green dots can be ignored.

I've tried both ROSARIA and the p2os drivers. Both gave me the same output. I also tried it with two more pioneers available in my lab, but they gave me the same results. Is there an hardware issue with the p3dx sonars? Does anyone know if changing the frequency of the sonar readings solves this issue?

Best regards,

João Santos

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Originally posted by JSantos on ROS Answers with karma: 55 on 2013-05-31

Post score: 1

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Original comments

Comment by gustavo.velascoh on 2013-05-31:
I have worked with ARIA libraries, and have no problems with sonars... so I dont think this could be a hardware issue.

Comment by ayush_dewan on 2013-06-01:
Check the max range of sonar in the code. Just to confirm whether sonar is working fine try getting some obstacle very close to sonar and see whether it detects it and slowly move it away from robot to get some rough estimate of range of sonar.

Answer 1

That looks pretty much like what I would expect from sonar sensors. There's a reason why they are cheap and why LIDARs are generally used when one wants to have (more) accurate data.

It clearly looks like the sensors don't like it when their emitted sound hits walls at oblique angles (as this means it is reflected away from the sensor, thus giving no return). Observe that the two sensors to the sides work reliably in your video and that these are the only ones that consistently emit at a right angle against the walls, thus retrieving strong returns. The material the environment is made of of course also plays a significant role in overall performance.

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Originally posted by Stefan Kohlbrecher with karma: 24361 on 2013-06-01

This answer was ACCEPTED on the original site

Post score: 2