Abstract
This paper deals with an ultrasonic orientation sensing system. The system measure the orientation of an objective surface, using the phase information of the reflected echos.
In order to identify the three-dimensional orientation, the system needs two phase difference of three receivers at least. However, the phase difference can not be distinguished over one period of the reflected echo. Then the measurable range is restricted in a relatively small orientation.
This paper propose a method to overcome the difficulty by increasing the number of the receivers. The closely arranged receivers encircling a transmitter can provide the smaller difference between two adjacent echo trajectories. They hold the individual phase difference in a sufficientry small value and allow the orientation measurement over a wide range.
The paper shows the principle of measuring two directional angles of a surface normal based on the least squares method. The redundant phase information obtained by the many receivers also contribute to the improvement of the accuracy.
Two prototype sensing system using the 6 or 8 receivers are constructed and the experiments demonstrate the basic performance of the system. It is shown that the high resolution measurement is possible over a wide range of orientation.
