Ping Senor Range estimation/characterization
divzr0
Posts: 7
Hey guys, I'm not very familiar with sonar technologies so I'm hoping someone out there might be able to help me out.· I am no stranger to complex math though.
How can I estimate how wide the sonar beam is at a particular height?· I mean to say, not just the beam, but the approximate detection radius for an object.· I have done some basic testing and at about 5 feet, I found that a log can be detected once it enters in a 9.5" circular radius, directly below the sensor.
However, now that I know this, I'd like to know how to mathematically characterize it.· Any suggestions?
How can I estimate how wide the sonar beam is at a particular height?· I mean to say, not just the beam, but the approximate detection radius for an object.· I have done some basic testing and at about 5 feet, I found that a log can be detected once it enters in a 9.5" circular radius, directly below the sensor.
However, now that I know this, I'd like to know how to mathematically characterize it.· Any suggestions?
Comments
Because the devices are not perfectly invariant, nor are their beams·perfectly circular, nor do they detect all surfaces equally effectively/accurately/repeatably/etc,·..., etc., there will be·significant variability in the device's behavior which you will·need to understand and characterize in order to shape how the math fits into the solution.
So, the answer to "how can I..." is "Many ways". To narrow the problem down to a solveable one, the next·question then is "Why (in sufficient detail)·do you want to know?"
PAR
PAR
The reason I want to characterize the beam diameter at a specified distance is to know how wide the detection diameter/radius/shape will be at a particular height. For example, if I am at 5', my tests show that obstacle detection can occur within approximately a 9.5" (diameter) circle. Well if I have to detect an area of 4 foot by 4 foot, I need to know how many sensors I will need to cover this area. Also, what if my height changes.... the detection radius may also change, thereby leaving holes in my 4 by 4 grid. I need these characteristics in order to determine how much I can change the height before gaps appear, or how much I need to overlap their detection area in order to provide optimal coverage over a certain range of heights.
AIman -
I looked at parallax's website for the ping))) sensor. All I found was the following http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
The math in this datasheet is all about the calculation of the distance, not how wide a detection radius it will/may provide.
And if I'm interpreting this correctly, the test that they provide only show object detection in the -x to +x range, they do not describe elevation.
Thanks for any replies
For example, you refer to "height"; presumably you mean 'distance' from the target of interest? Or, are you concerned about aiming the sensor parallel to the floor at some 'height' from the floor and need to know how the shape of the sensor's field will be truncated by intersection with the floor at a given distance?
You refer to a 4x4 area target. But, do you simply want to know if any portion of the target is within the field of the sensor, or because you later refer to 'grid', 'holes' and 'gaps', are you attempting to discover how large your target is, or perhaps where your entire target is located within the field of view of the sensor?
You originally posted information about a detecting a 'log', and later you refer to a 4x4 grid (plane?). As I mentioned earlier, the shape of the target and the way its surface is oriented relative to the sensor will affect the nature of the readings.
You mention "optimal coverage", in the context of overlapping detection fields of view. But, you don't really indicate what you mean by "optimal". Are you trying to determine whether the echos are coming from a single plane as compared to echos coming from multiple planes set close but not touching each other? (E.g., how large a 'hole' or 'gap' are you willing to allow the sensor to miss detecting? That would suggest how many sensors you would need to install.)
If you want to simply know what the shape/size of the echo field·is at various distances of radius, you would start perhaps with a small flat target positioned perpendicular to the sensor at a specific radius, and then record several echo distances (times) for that position, and for a number of other positions at the same radial distance, to discover when the target is in the field of view of the sensor and when it is not.
You might then do the same procedure at another somewhat different radial distance, and then use your math to see whether there is a simply linear relationship between the two 'cones' (if that's what the shape of the signal's field turns out to be) to see if the cones are congruent. If they are, then you might want to assume that as fact, and interpolate size of field for other distances in between.
But, those tests would be for a "small planar surface"; now, you would want to do similar testing for targets of other shapes (e.g., cylinders, spheres, or whatever your particular shape(s) your·targets will assume) and of differing angles of orientation to the sensor.
Any 'formulas' for the sensor's ability to detect a target will be very specific to the conditions of the situation the sensor is operating in (and to the goals of the operator of the sensor).
PAR