transponder of intensity modulated diffuse light for low cost navigation systems

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This study was conducted for the purpose of producing a low cost navigation system, which is necessary for the autonomous vehicles and precision farming. In this study, high precision ultrasonic speed sensors, range finding systems and movement vector estimation methods using optical flows have been developed.The authors developed an ultrasonic Doppler speed sensor in the previous study. In this project, the accuracy of the speed sensor was improved to conduct stable measurement even in the case of smooth ground. The sensor showed the good results also in farm teats and indoor tests on the model plants. Farther more, the possibility of vector measurement including the sideslip was confirmed.The one directional diffuse light range finder could measure the distance with the standard error of about 3%. However, the omni directional range finder had the phase difference between the directions, which should be compensated. The standard error was 5 % in cloudy condition, but the accuracy was decreased and measurable range was also decreased under the sunshine. The signal processing units including the amplifiers should be improved. The vehicle position measurement was possible using two fixed stations and one on-vehicle unit, but the problem of the temperature drift still remained.Concerning to the movement determination by optical flow, two programs were developed using the Hough transform to decrease the computation time. The computation time for one measurement was considerably improved into about 0.3s, and the average ratio of the positional error to the movement distance was about 5%. The measurable range of the movement distance was about 30 mm in each of the X and Y-directions, which should be improved for the real time measurement.