Improved tracking performance by H∞ control for an automatic spinach harvester

Abstract

This study was aimed at enhancing the path-following control performance of the arm length control mechanism in automatic spinach harvesters. Field experiments conducted in existing studies indicated that the root cutting blade path must be controlled to compensate for motion disturbances in the pitch direction to realize successful harvesting. Therefore, methods of path variation compensation via PID control and feedforward control have been established. Notably, using these strategies, the arm length controller cannot follow the corrected target values with an acceptable response because of uncertainties and disturbances. The insufficient performance of the controller deteriorates the harvesting performance. Consequently, the feedback control performance must be enhanced in events involving uncertainties and disturbances. To enhance the path-following performance of the arm length control mechanism, an advanced controller based on the H∞ control theory was designed in this study. The tracking performance and effectiveness of the path compensation method were experimentally evaluated.