ULTRASONIC HEAD HEIGHT CONTROL FOR A TOMATO HARVESTER
Abstract
Advanced mechanization of farm equipment requires more sophisticated controls to relieve the operator and to improve energy efficiency and yield. An air sonar device was designed and constructed for use on a tomato harvester to control header height. The controller was to be capable of utilizing the signal from the air sonar to ignore the presence of foliage and tomatoes while sensing the soil surface and maintaining the header to within (+OR-) .3 cm of the correct position. The air sonar was capable of ignoring the tomato plants and weeds but was not able to distinguish between tomatoes and bare soil areas between tomatoes. The tomatoes were more responsive targets to the sonar than was the soil. Higher frequency sonars are needed to provide smaller measurement error if proper control is to be achieved. Acoustic scatter and absorption patterns of irregular surfaces make the measurement error large because echo detection is amplitude sensitive.
Degree
Ph.D.
Subject Area
Agricultural engineering
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