Fig. 2(a), (b), and (c) show how the reflected waves from an
object vary according to the shape of the side of the object. Figure
2(a) presents the output distribution of the reflected waves
when the side of a rectangular prism and the ultrasonic transmitter
are placed in parallel. Figure 2(b) and (c) present the
case of a triangular prism and a cylinder as the measured object,
respectively. The edge of the triangular prism is faced to
the transmitter. In these figures, because the receivers array is
the size of 8 x 5, the output distributions are plotted by five
kinds of marks, respectively.
As seen in the figures, In the case of a rectangular prism,
the peak value of the output distribution is larger than that of
others. The number of peaks in the output distribution of a triangular
prism is two because of the edge of the object. The
area of the output distribution of a cylinder is wide comparatively.
Therefore, the peak values and the area of the amplitude
output distribution of the reflected signals received by the ultrasonic
sensor array are different, corresponding to the edge
forms of the sides of the objects. Here, we extract the amplitude
output from each receiver, and identify the shape of the
measured objects based on the extracted features.