文摘
GPS has become a common technology for a positioning system of vehicles outdoor. In agriculture, the RTK-GPS has been used for autonomous tractors and harvesters in researches, and their measurement accuracy was sufficient. In room, however, the GPS measurement errors were larger because of delayed or covered electric waves. Rail or electromagnetic induction type position sensing methods have been used for autonomous mobile robots under greenhouses or other facilities. There are problems that installation costs are expensive and route modification is not easy, when those systems are used in agricultural facilities. In this research, a positioning system using spread spectrum sound is described and noise tolerance and signal identification could be improved by using a spread spectrum technique. So far, a system for measuring distance was developed and estimation of measurement accuracy was conducted. As a result of measurement distance 10m between microphone and speaker under non wind and non temperature gradient, RMSE 3.4mm was obtained. It is also known, however, the measurement error increases under windy and changeable temperature conditions. In this research, a correction method of the measurement error by wind and temperature is developed and estimated.
