Research On Parameter Optimization Of Key Components And Header Profiling System Of Corn Combine

With the rapid development of agriculture,liberating labor force is urgent and it is imperative to quicken the process of mechanization of our agriculture.In this paper,aiming at corn grain combine,in the aspects of ear picking,threshing and header height control,due to the pull of stem roller on stem,the impact of threshing element on ear are too large,and the height of harvesters’header is not controlled properly,problems such as early stem break,grain damage and harvesters’header collision are caused.The solutions such as vibration picking,conical threshing and header profiling were proposed.It provides a theoretical reference for the development of low-loss,high-efficiency and intelligent corn grain combine in the future.and it is very important to enhance Chinese corn mechanization harvest level.The specific research contents are as follows:（1）Based on the analysis of the principle and structural characteristics of corn mechanical picking,guided by the vibration theory.A vibration picking plate corn picking device is designed.Through the kinematic analysis,the feasibility of the corn picking device to realize the vibration picking is verified.The corn picking device was optimized and imported into ADAMS software to complete the simulation test.Through response surface analysis,a nonlinear fitting equation that describes data changes is obtained.The results show that the stem tension required by the new type of vibration picking plate device is significantly reduced by 230 N compared with the traditional picking device.When the effective radius of the vibration crank is 3.1cm,the rotation speed of the vibration crank is894r·min^-1,and the rotation speed of the stem pulling roller is 781r·min^-1,the effect of vibration picking is the best.（2）Based on the study of corn mechanical threshing damage mechanism.A corn conical threshing separation device is designed.By establishing the contact model between the ear and the concave plate,the optimal structural parameter combination of the threshing separation device is determined.The three-dimensional model of threshing and separating device was completed and imported into EDEM software for simulation test.The results show that the threshing effect is the best when the cone angle of the threshing drum is 8°,the threshing concave plate is selected as the left circular tube type,and the rotation speed of the threshing drum is 400 r·min^-1.Compared with the traditional threshing cylinder,the collision force of the threshing element on the ear was reduced from 284 N to 234 N,and the collision reaction force was reduced from 202.54 N to 171.52 N.It is verified that the conical threshing cylinder has the characteristics of reducing the impact strength of the ear.The kinematics analysis and dynamic balance simulation analysis are completed,and the structure design of threshing drum is reasonable.（3）Aiming at the problem that the height of corn harvesters’header is not controlled properly,a header profiling system is designed.Through discussing the measuring method of harvesters’header height,a measurement scheme based on ultrasonic sensor measurement and supplemented by mechanical profiling mechanism is proposed.According to the system control requirements,the sensors were analyzed,the electronic devices with better compatible performance were selected to form the header profiling system,and the software was designed under Keil MDK5 software,and the system test was completed.The results show that the deviation between the measured value and the set value of the ultrasonic sensor is controlled within 0cm～1cm at different heights.The overall performance of the measurement and control system is superior and meets the design requirements.（4）In order to accurately control the motion of the header,the kinematic analysis and force analysis of the harvester’s header are carried out,and the transfer function of controlling the motion of the header is obtained.The PID control algorithm based on Kalman filter is adopted to effectively suppress the noise signal that may exist in the working process of the system.The parameter optimization experiment of the algorithm was carried out in MATLAB software,and finally the field experiment was completed.The results showed that the control errors of the system were all within 2cm when the operating speed of the whole machine was less than 6km·h^-1,and the actual stubble height controlled by the system was better than that of manual control,which met the requirements of corn harvesting.