Study on Proximity Sensor for Robots and its Application

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Analysis and application of ultrasonic proximity sensor for robots is the main theme of this research.Last year, a new method to discern flat surface and edges of an object using an ultrasonic sensor array. This array has seven identical condenser transducers. Diameter of each transducer is 10 [mm]. The basic idea of recognition is that the mirror images of the transmitters differs according to the shape of the reflecting surface. However, in the course of this development, a further analysis on mechanism of ultrasound reflection became necessary.This year, analysis on ultrasound reflection has been carried out based on Fourier analysis. The results are as follows : 1) When the same transducer is used both as transmitter and receiver, its directional characteristics can be approximated by exponential function. 2) Acoustic impulse response of the reflecting surface can be obtained by measuring the frequency response relative to a reflection from a flat surface. Edges of an workpiece show a distinct difference in both amplitude and phase compared to smooth surface. This difference is used in recognition process. 3) Directional characteristics of a transducer is frequency dependent. This frequency dependence should be taken into account when measuring the frequency response of the reflecting surface.These results of the analysis indicates some ideas for further development of the ultrasonic sensor array developed last year.The performance of the robot controller which has been modified last year was not sufficient for real-time sensor feedback control of a robot. This year, a further modification has been carried out. The sampling interval has been shortened to 2[msec] which is short enough for the purpose. However, this modification took much more time than originally planned. Due to this delay, verification of the sensor performance using the robot was not sufficient. This is to be done in the near future.