Question about ultrasonic receiver orientation

[nikosb]

I would like to use an ultrasonic transmitter and three receivers to be able to determine the position of the transmitter relative to the receivers. The distances to be measured are around 3-4 ft. I want to understand how the receivers orientation relative to the transmitter can affect the distance measurement. I attach some simple pictures for illustration, in the first one the receiver is placed directly in front of the transmitter and opposite which is the ideal situation. In the second picture the receiver is placed in front of the transmitter but it is facing away from it. In the third picture the receiver is within the beam angle but is facing almost tangent to the beam. Basically as long as the receiver is within the beam range does its orientation matter?

 

[berkeman]

I would like to use an ultrasonic transmitter and three receivers to be able to determine the position of the transmitter relative to the receivers. The distances to be measured are around 3-4 ft. I want to understand how the receivers orientation relative to the transmitter can affect the distance measurement. I attach some simple pictures for illustration, in the first one the receiver is placed directly in front of the transmitter and opposite which is the ideal situation. In the second picture the receiver is placed in front of the transmitter but it is facing away from it. In the third picture the receiver is within the beam angle but is facing almost tangent to the beam. Basically as long as the receiver is within the beam range does its orientation matter?

It sounds like you are wanting to use an omnidirectional ultrasound transmitter and 3 triangulating receivers to do this. First problem is that there aren't any omnidirectional US transmitters that I know of, at least not simple ones. Second problem is if there can be reflections from any nearby walls or structures, that will confuse any amplitude-centric triangulation algorithms.

Can you say more about what your overall project is? Is it something like robotic location or something? Can you use other techniques for the location function? One variation would be time-of-flight measurements to triangulate with US...

 

[Baluncore]

If this is a 2D positioning system then phase and orientation of the Rx and Tx will be important. To resolve the problem, mount all transducer elements on the same plane with their axis vertical. Place a conical reflector on axis to give phase independent 360° azimuth radiation patterns. The cone profile can be adjusted to a hyperboloid which will give a better horizontal radiation pattern.

To measure position you need to measure the arrival time of pulses from the transmitter. To measure more accurately you might transmit a pseudo random sequence, then correlate the received channels to get the relative delay times. I would also consider transmitting a chirp, then multiplying the RX channels by each other to get the beat frequencies and hence period = differential time.

Depending on the number and position of RXs there may be a position error due to wind speed. It may also be a Doppler anemometer.

 

[Danger]

The reason that I didn't respond to this before is that I think he's still referring to the 3D feet and wrist motion tracking system that he introduced a couple of thread back.

 

[alphy]

I would approach this question by first understanding the principles behind ultrasonic technology and how it works. Ultrasonic technology uses high-frequency sound waves to measure distances and detect objects. The transmitter emits sound waves, and the receiver detects the waves that bounce back from objects in its path.

In this case, the orientation of the receiver relative to the transmitter can affect the distance measurement in a few ways. First, the angle at which the receiver is facing can affect the strength and accuracy of the ultrasonic waves it receives. If the receiver is facing directly towards the transmitter, it will receive the strongest and most accurate signal. However, if it is facing away or at an angle, the signal may be weaker and less accurate, leading to potential errors in the distance measurement.

Additionally, the distance between the receiver and the transmitter can also impact the accuracy of the measurement. If the receiver is too close to the transmitter, it may receive a distorted or incomplete signal. On the other hand, if it is too far away, the signal may weaken and also result in inaccuracies.

Furthermore, the beam angle of the ultrasonic waves also plays a role in the accuracy of the measurement. In the third picture provided, the receiver is within the beam range, but its orientation is almost tangent to the beam. This means that the receiver may not be directly in the path of the strongest signal, and the measurement may be less accurate.

In conclusion, while it is important for the receiver to be within the beam range of the transmitter, its orientation can still affect the accuracy of the distance measurement. I would recommend experimenting with different receiver orientations and distances to determine the most accurate setup for your specific needs. Additionally, using multiple receivers at different angles can also improve the accuracy of the measurement.