Study On Adaptive And Low Breaking Threshing Method Of Soybean

In this paper,the breaking rate of soybean in mechanized harvesting is high as the starting point.Through investigation and analysis,the reason of high breaking rate of soybean in mechanical harvesting is found.The soybean threshing system of combine harvester is optimized from two aspects of mechanical structure and operating parameters of threshing device.It improves the adaptability of combine threshing device to soybean and the automatic control level of threshing system.The main research work of this paper is as follows:(1)Summarize and analyze the existing literature research.According to the working principle of the combine harvester,a soybean low-crushing threshing device with strong brushing effect and small impact is designed.The device uses longitudinal closed bowtooth drum plus circular hole concave screen as the main threshing element.According to the design manual,the structure parameters of the threshing drum are calculated,and the diameter of the longitudinal closed bow-tooth drum is 460 mm,and the working height of the threshing element is 65 mm.At the same time,in order to make the longitudinal feeding of crops smoothly,theoretical analysis and design are carried out on the screw feeding of threshing drum.The double-head screw feeding head is used with a screw angle of 20 degrees.In order to keep a high threshing rate of Soybean under rated feeding amount when threshing with closed bow-tooth drum and circular-hole concave screen,the arrangement rule of the threshing elements on the threshing drum is designed.The threshing bow teeth are arranged with three-head helix,with the distance between the teeth being 33 mm and the distance between the teeth being 100 mm.The round-hole concave sieve was designed with the sieve porosity of 25 mm and the designed pelletizing concave sieve porosity of not less than 50%.(2)Design the working parameter adjustment device of the threshing system.The adjustable parameters are the speed and clearance of the threshing drum.Determine the driving scheme of the speed control of the threshing drum.With the hydraulic pump as the power source,the hydraulic pump drives the hydraulic motor and the hydraulic motor power output shaft drives the drive pulley,which drives the threshing drum to rotate through the toothed rod drive.The control device for threshing clearance is to make one end of the concave plate articulate with the frame and the other end articulate with the drive mechanism,which is moved by the extension of the electric push rod,thus changing the size of the threshing clearance.The hydraulic pump and electric push rod are both electric control units,which provide conditions for the establishment of control system.(3)The soybean threshing system control system is designed,the control system hardware is selected,and the SPC-SFMC-X2214 A motion controller is used as the master controller to build the control system.The principle of speed control of threshing drum is that the motion controller sends out analog current signal to control the displacement of hydraulic pump,and then changes the speed of hydraulic motor,finally the speed of drum reaches the control.Threshing clearance control controls the action of forward and reverse relays through the output pins of motion controller,thus realizing the forward and reverse rotation of electric push rod motor,extending or retracting the push rod,driving the movement of the threshing concave plate and achieving the purpose of adjusting the threshing clearance.Incremental rotary encoder is used as speed sensor in speed monitoring of threshing drum.When the threshing drum rotates,the encoder sends a pulse digital signal to the controller,which calculates the number of pulses per unit time,thus calculating the speed of the threshing drum.The monitoring of threshing clearance outputs the analog voltage signal to the controller through the potentiometer provided by the electric push rod.The controller compares the analog voltage signal and calculates the corresponding threshing clearance.With feedback value of working parameters of threshing system,precise closed-loop control can be realized by PID control algorithm.In this paper,the PID control program is designed and the reliability of working parameters of subsequent field test system is also guaranteed.Selecting touch screen as HMI equipment,HMI interface and its program are designed.HMI interface can display the current working parameters of the threshing system.The operating parameters of the threshing system can be directly modified by HMI equipment.The on-line monitoring value of the breakage rate is displayed in the HMI interface.When the breakage rate rises,corresponding adjustments can be made in time.(4)The designed soybean low-crushing threshing device was simulated and compared with field test.Through the simulation test results,it was found that the impact of this threshing device on soybean during the threshing process was less than that of common rod-tooth grille-type concave screen.Field test was also carried out to verify that under different forward speeds,the crushing and non-degrading rates of this threshing device were lower than those of the comparative threshing device.Soybean threshing works better.Then,through single-factor test and multi-factor response surface optimization test,with breakage and non-detergency as indexes,the influence of advance speed,speed of threshing drum and threshing clearance on the performance of soybean low-breaking and threshing device was analyzed,and a breakage rate model was established.Through the model pre-side,the optimum operating parameters of soybean threshing device designed are: forward speed 4.38km/h,speed of threshing drum 536r/min,and threshing clearance 31.4mm.Three field tests were carried out at harvester forward speed of 4.5km/h,speed of threshing drum of 550 r/min and threshing clearance of 32 mm.The results showed that the average values of breakage and un-threshing rate were 0.9% and0.46% respectively,with errors less than 5% compared with the predicted values.It proves that the preliminary results are credible and the designed threshing device can improve the quality of soybean machine harvesting and threshing operation.