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I have been considering different distance sensing technologies for the following circumstance:

Range needs to be about 2.5 meters

The surface being measured is a wall that is painted black

The angle between the wall and the sensor would be at worst around 10 degrees, usually around 45 degrees (so reflective technologies will have trouble, to add to the already black wall which will absorb most light).

Preferably I would like to avoid IR because the environment is already going to have a lot of IR noise.

Essentially I want to be able to triangulate the position and angle of an object placed in a rectangular box (about 2.5m x 1.8m) with black walls, with a lot of IR noise.

All the technologies I have considered have issues:

  • From what I understand ultrasonic will fare very poorly with the angled walls

  • TOF / lidar modules will do poorly with the black (low reflection) walls.

  • Infrared sensors will be interfered with by the IR noise.

I could solve the angle issue by placing 6 or so of these sensors around the object so there are sufficient sensors with a mild angle to get accurate measurements, but the trick is eliminating the sensor readings that are inacurate due to sharp angles.

Any thoughts?

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  • $\begingroup$ Welcome to Robotics Murey Tasroc, but I'm afraid that Unbounded Design Questions are off-topic because there are many ways to solve any given design problem. We prefer practical, answerable questions based on actual problems that you face, so questions which ask for a list of approaches or a subjective recommendation on a method (for how to build something, how to accomplish something, what something is capable of, etc.) are off-topic. Please take a look at How to Ask & tour for more information on how stack exchange works. $\endgroup$
    – Chuck
    Aug 6 '18 at 13:30
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    $\begingroup$ You seem to have started out with lots of assumptions about the sensor capabilities and the operating environment. Black is the absence of energy in the visible spectrum. You cannot tell how well an object reflects or absorbs IR energy by looking at it in the visible spectrum. This could also mean that the black you choose for testing is a different black, and has different characteristics in the IR band, than the black used for competition. The real problem you'll have with lidar is that you're actually inside the minimum range for most sensors. $\endgroup$
    – Chuck
    Aug 6 '18 at 13:34
  • $\begingroup$ You said there will be "a lot of IR noise," but again, what spectrum is that noise? You could put on a filter that blocks the noise spectrum and operate on a "channel" that isn't noisy. You could have touch sensors/whiskers in contact with the walls and measure the angles the whiskers make. You could have a mast and a camera that points down. You haven't fully defined the problem - you seem to be able to instrument the target, so why not just use OpenCV and a fixed webcam? The list of possible solutions goes on and on. If you'd like to chat about your problem, please join us in Robotics Chat. $\endgroup$
    – Chuck
    Aug 6 '18 at 13:38
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If you can instrument the object that you need to detect, consider an electromagnetic tracker, such as the Aurora.

It is not susceptible to the types of challenges you've listed, but it has some of its own: a field generator produces an EM field that allows tracking of sensors that would need to be placed on objects to be tracked. I believe sensors normally require a wire, but perhaps not for all systems. And accuracy will be compromised by any conductive or ferromagnetic materials (i.e., metal) in the box.

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