Faizan and Adan’s Impact of Object’s Angular Orientation on Ultrasonic Distance Measurement

(Faizan Muhammad and Adan Leos)

We tested the ability of ultrasonic sensor to detect the distance from an object when the object is oriented at different angles. The fact that it detects reflected sound means that it should be unable to detect objects oriented at certain angles because the sound waves do not reflect back to the sensor but are deflected away. We tested the sensor both horizontally and vertically. For the sake of clarification, we define horizontal to be as given in the picture below:

And vertical to be as shown below:

Data Collection and Results:
We used the apparatus shown below. We used port view in the brick to note down the distance values. The cardboard was moved at 5 degree increments until the sensor started giving 255 which meant that it was no longer able to calculate the distance.
We noted the results down in an Excel sheet shown below.

Our results indicate that vertical position has about the same tolerance to angular orientation as horizontal position despite the fact that vertical orientation does not produce as accurate values of distance. We believe the floor might be the reason for that.
What is interesting in both the cases is that the angle at which the sensor is unable to detect the cardboard decreases as distance increases, which makes sense as when the distance increases a small angle can create a bigger deflection of the sound wave relative to the sensor which makes it more difficult for the sensor to detect it.

Finally, here is a graph of angles against distance which shows the angles at which the sensor starts being unable to detect the distance values (assuming linear relationship):


Link to Autonomous Navigation:
This investigation is relevant to autonomous navigation because measuring distance is one of the most critical functions that an autonomous vehichle needs to be able to perform. Judging by the results, this sensor can not be used effectively in such a system because it is not reliable enough. In the real world, the sensor should be able to detect objects regardless of their orientation and distance away from it. The fact that this sensor is unable to do so would call into the question the reliability of the entire vehicle if this is used.


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