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Simultaneous Sampling Algorithm for Sensors Spread Over a Wide Area

Outline

One of the problems with our existing ultrasonic three-dimensional measuring system was that sampling frequency decreased as the number of tagged objects increased. This problem was caused by the time division method used to control ultrasound transmission. In this research we developed a method of sustaining a high sampling frequency when transmitters and receivers are positioned over a wide area (36m × 10m), then tested our algorithm by conducting a simulation. The results of the simulation showed that when sensors are fixed to the ceiling at 1m intervals, sampling is possible at an average of 40Hz per tagged object even with twenty transmitters spread around the room at a height of 1.5m above the floor.

Ultrasound Simultaneous Sampling Algorithm

  1. Check ultrasound transmission priority level. If priority level is high, transmit ultrasound. If priority level is low, raise the priority level by 1 and do not transmit
  2. Check for interference with transmitters at higher priority levels. If there is no interference, proceed to step 3. If there is interference, raise the priority level by 1 and do not transmit.
  3. Check whether the transmitter's are able to receive ultrasound. If the location can be calculated, transmit ultrasound. If calculation is not possible, raise the priority level by 1.

Results of Simulations

The following figure shows the results of two simulations that were performed. In the first, ultrasound was simultaneously transmitted from 10 transmitters spread over a wide area (36m × 10m), and in the second, 20 transmitters were used. 360 receivers were positioned at 1 m intervals. With 10 transmitters, measurement was possible at approximately 50Hz per transmitter, and with 20 transmitters, calculation was possible at approximately 35Hz.

The following graph compares the results from simulations for ultrasound transmission conducted using the time division method (conventional method), and the simultaneous sampling algorithm method. When using the time division method, sampling frequency decreases rapidly as the number of transmitters rises, making increasing the number of transmitters problematic. With the simultaneous sampling algorithm, sampling is possible at approximately 10Hz per transmitter even when using 100 transmitters. Compared to the conventional method, it is possible to maintain a higher sampling frequency as the number of transmitters is increased.

References

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