Improvement of the Range Update Rate of Spread Spectrum (SS) Sound Based Range Measurements for Positioning System of Agricultural Machines

Abstract

In order to improve the range update rate of Spread Spectrum (SS) sound based range measurements, the insertion of an output time signal in the SS sound is proposed. An experiment was conducted to increase the range update rate to 1/20s, 4 times faster than the conventional method, by inserting an output time signal in the SS sound. Using this insertion method, the range of a static object could be measured out to 50m. The resulting range measurements had a bit error rate of 0%, a range error of 15mm, and a standard deviation error of 2.5mm. These results indicate that the modified SS sound based method can measure range accurately and consistently within a 50m range.