| 摘要 |
The present invention provides a method of position sensing between a wireless mobile component carrying a mobile ultrasonic transducer and a fixed component carrying a plurality of fixed ultrasonic transducers in a predetermined spaced-apart relationship, the method comprising turning off all the transducers to establish a period of silence, activating one or more of the fixed transducers to transmit an ultrasonic signal, starting a plurality of timers corresponding to the respective plurality of fixed transducers generally simultaneously with transmitting the signal, receiving the signal at the mobile transducer, transmitting a signal from the mobile transducer responsive to the received signal, receiving the signal transmitted by the mobile transducer at each fixed transducer and stopping the respective timer generally at the time of reception of an edge of the received signal found within the first twenty received edges and preferably within the first ten received edges and more preferably at the first received rising edge, calculating the distance between the mobile transducer and each fixed transducer based on a predetermined constant representative of the speed of sound and the time taken for transit of the signal to each fixed transducer as measured by the respective timers, and performing trigonometric calculations using the calculated distances in order to determine the 3-dimensional position of the mobile component relative to the fixed component. |
