Mechanisms And Control Strategies Research On Threshing And Separating Quality Of Combine Harvester

A combine harvester is a compound agricultural machine used for cutting,conveying,threshing,separation of grain and straw,cleaning and transporting the clean grain.Threshing chamber is like the heart of combine harvester and it takes charge of breaking away the corn from crop and separating the grain from the straw,that is called threshing and separating.The grain loss and percentage broken grains are two quality indicators of threshing and separating,which are the important indexes farmers focused on and the core competency of combine harvest.In order to increase the threshing and separating quality and the operation efficiency of combine harvester,the operation information measuring method,the feed rate detection method and the influence mechanism and control strategies of threshing and separating quality were studied and an operation information measuring system of combine harvest was also build in this paper.The operation information measuring system of combine harvest mainly includes feed rate detection and wheat plants water content measurement.In feed rate detection part,the rotational speed and torque sensors for feeding auger,inclined conveyor,and threshing cylinder were developed;in wheat plants water content measurement part,a rapid detection device for wheat plant water content measurement was developed based on near infrared photoelectric technology.The wireless data transmission terminal was built to collect,analyze,store and transmit operation information.And,the integrated operation information remote measuring system realized the field working data collection and provided a method to carry out field experiment.In order to accurately measure the feed rate of combine harvester,based on large experimental data,identified the association relationship of feed rate and its related factors by gray relative analysis method,and established model the the impact intensity of each factor on feed rate.The correlation analysis of feed rate related parameters was made and the correlation degree of related single parameter on the feed rate was obtained in this paper.Grains passed from the header to threshing chamber takes some time,as a consequence,time lag existed in the established single models of feeding auger,inclined conveyor,and threshing cylinder.Aim at this situation,a feed rate error measurement model was established based on grey correlation.Then,the correlation degree of feed rate related factors on feed rate was calculated by assign to correlation weight and time delay compensation and the feed rate model was established.At last,revised feed rate on the basis of grey system prediction error,and the accuracy of feed rate measurement has been raised.Field tests results of feed rate value showed that maximum absolute error was 0.43kg/s,the average absolute error was 0.17kg/s,the mean relative error was 5.67%.For the sake of research on influence mechanism of threshing and separating,grain loss and percentage broken grains trends of different crop properties,different feed rate in various working conditions was studied based on large field tests data.Then summarized the influence of crop properties,feed rate and working conditions on threshing and separating quality,revealed the mechanism of threshing and separating.It provides a good foundation for building the control strategy model of threshing and separating quality.The control strategy of threshing and separating quality is a fundamental technique of high-quality automatic control.Aiming at the characteristics of feed rate influenced by many factors,complex operating system and uncertainty influence relationships of some relate factors,a control strategy of threshing and separating quality based on fuzzy control was proposed based on the mechanism of threshing and separating.This control strategy could provide a real-time optimal cylinder concave clearance and drum rotational speed,improving threshing and separating efficiency,reducing grain loss and percentage broken grains.Field experiments were conducted to validate the efficacy of this control strategy.