Development of cleaning systems for combine harvesters: A review
Zhenwei Liang, M. Wada
Abstract
Combine harvesters are important for modern agriculture since they can significantly increase the efficiency of grain harvesting process. The cleaning unit is one of the core components of the combine harvester and it can be considered as the ‘digestive system’ of a machine. In recent years, new cleaning devices and intelligent technology have emerged to increase the harvesting adaptability for different crops, field conditions and to improve harvesting efficiency . This review provides an overview of cleaning unit structures and the optimisation methods that have been used to improve the cleaning performance. It introduces the structures of cleaning unit and examines the arrangements of the grain pan, fan, and sieve structures. It examines the effects of fan geometries on airflow velocity distribution ; numerical simulation and experimental methods for airflow velocity measurement; material movement analysis and determination of pressure drop due to the material layer and chaffer sieve; sensors to acquire the working status and control methods for adjusting the parameter settings. From the literatures, it can be realised that to obtain good cleaning performance, proper cleaning structures and combinations should be selected carefully. In addition, the development of sensors and controllers for cleaning units should focus on their adaptability for different crops and field conditions. Further studies are needed to determine the thresholds for these indicators, the introduction of deep learning and artificial intelligence algorithms could overcome the uncertainty and non-linearity and improve the cleaning performance.