改良到達時差法三維超音波定位系統及誤差分析

Abstract

在無線感測網路的領域內，室內定位系統是一個重要的研究課題，本論文建立一個三維超音波定位系統，由五個超音波接收換能器配合訊號處理所構成，其硬體架構簡單且造價便宜。並以到達時間差計算法為基礎，根據本研究所建立的系統加以改進，提出創新的定位計算公式，此計算公式是根據四個訊號接收的時間差進一步推算出未知目標的位置，比起原本的計算方程式更加的簡單，讓定位系統更加穩健。在決定訊號時間的過程，不同於傳統的最大值時間法，本研究提出新的50%~90%振幅時間法來決定訊號的時間點，比最大值時間法所得到的時間更加精確。建立的系統透過不同的接收陣列大小以及不同的訊號時間法來做性能測試，從結果可以得知上面提出的新方程式和決定訊號方法能成功的運作使用，最後分析本系統對不同方位聲源的誤差以及標準差，觀察定位系統運作的可靠區域範圍。

This work established a 3-D ultrasonic position measurement system which is composed of five ultrasonic transducers. The signal processing method is based on acoustic time-difference-of-arrival (TDOA) and improved according to our positioning system. A new algorithm of four differences of arrival time to locate the unknown acoustic source was used. Compare to the original algorithm, our method is simpler and of higher reliability. Our method of time signal processing is different from the traditional one which fetch the time signal correspond to maximum signal amplitude. We presented a new method with higher accuracy of fetching the average time correspond to 50%~90% amplitude of signal. The experimental positioning system was established with different receiver array size and different time acquisition method. The experiment results, confirm that our system using new algorithm and new time acquisition method is well operated. Finally we analyzed the system performance by examining the error percentages and standard deviation of arbitrary source locations. The highly reliable spatial region in which the location performance is well was then identified.