Research On The Control System Of The Threshing Unit Of A Maize Seed Harvester

After years of development,the machine harvesting ratio in China has increased significantly,but there are still problems of low kernel harvesting ratio and high moisture content maize harvesting losses.In response to these problems,this study is based on the YF8166 maize seed combine harvester and the multi-functional threshing and cleaning test stand,and carries out the design of the control system of the threshing device and maize harvesting tests,improving and optimising the drum speed and concave plate gap control system of the original machine,and controlling both with PLC as the core.The main research elements and conclusions of this paper include the following:(1)Taking the YF8166 maize seed combine harvester as a reference,the principle of the drum speed infinitely adjustable device was analysed and the hydraulic control system of the valve-controlled cylinder was improved,the hydraulic circuit was constructed,the calculation of hydraulic cylinder parameters,the selection and parameter analysis of the three-position four-way solenoid-operated proportional directional valves and the selection of other hydraulic components are carried out.The concave plate gap adjustment device was electrically modified and its working process was verified in the field.Simulation tests of the hydraulic system were carried out using Amesim software to verify the optimisation performance of the PID controller for the system.(2)On the basis of the improved drum speed and concave plate gap adjustment device,the type of speed sensor,frequency converter,PLC and analogue expansion module were selected to build an electronic control system with PLC as the core.The control process of drum speed and concave plate gap was analysed and software programs for parameter adjustment were written.(3)In this paper,three single-factor trials were conducted using Zhengdan 958 peeled maize cobs with 32% to 34% moisture content as test material,drum speed,concave plate clearance and feed rate as test factors,and crushing rate,un-threshing rate,loss rate and impurity rate as test indicators.Three levels of each factor were selected as more advantageous,and an orthogonal regression combination test was carried out on this basis.The orthogonal test data were subjected to ANOVAand response surface analysis to arrive at the best combination of working parameters for the harvester with the crushing rate as the main evaluation index: the drum speed level was346.5r/min,the concave plate clearance level was 45 mm and the feeding rate level was 9.7kg/s.The average crushing rate of 6.311% was obtained from three replicate tests,which was similar to the 6.241% obtained from the response surface analysis,and at this time the un-threshing rate was 0.187%,the loss rate was 0.912% and the impurity rate was 4.251%.Summarising the findings of previous researchers,optimal parameter combinations are given for maize harvesting at 24% to 34% moisture content of maize kernels.