At present, Chinese corn grain harvesters lack cleaning loss monitoring. Cleaning parameters cannot be automatically adjusted, and the loss rate is high. In view of the above problems, a cleaning loss monitoring sensor is designed, composed of a metal impact plate, piezoelectric ceramic and signal processing circuit. The factors affecting the characteristics of vibration signals are analyzed from the material, size and other aspects. The sensitive plate is composed of a 304 stainless steel impact plate and piezoelectric ceramic. The sensitive plate can convert the vibration signal of the impact plate into a voltage signal, and the output voltage range can reach ±3 V or more. The signal generated by the collision of corn kernel and damaged corn cob with the sensitive plate was analyzed.It was found that the frequency domain range of corn grains was wider, with signals above 6 kHz, but broken corncobs did not have such signals. Based on the frequency distribution, a signal processing circuit is designed, which consists of high-pass filter circuit, an envelope detection circuit, and a voltage comparison circuit. The circuit can convert analog signals into pulse signals, which facilitates the counting process by the microprocessor. In order to obtain the monitoring accuracy and installation parameters of the integrated corn cleaning loss monitoring sensor, a Central Composite Design was carried out with the installation height and angle of the sensitive plate as the test factors and monitoring accuracy as the test index. Based on the test results and field test conditions, a regression model was established to determine the optimal installation parameters: the installation angle of the sensitive plate is 30°, and the installation height is 30 cm. At this stage, the accuracy of the sensor monitoring corn grains was 92.82%, and the accuracy of monitoring the mixture of corn grains and broken corncobs was 90.07%. The verification test shows that the monitoring accuracy can reach more than 94% after the sensor is debugged. This research can provide a reference for the design of corn cleaning loss monitoring devices.

A variable speed anti-tangling reel mechanism was designed to address the problems of tangling, hanging and rewinding of the tassel wheel and the high paddling loss in the current Chinese rape combine harvester cutting table. The kinematic equations of the reel mechanism were developed, and the analysis showed that the speed in the entry stage is low and the speed in the exit stage is high, and the attitude of the reel teeth change with the rape plant movement during the whole paddling process. A single-factor test and a multi-factor regression orthogonal combination test were carried out using the cutting table loss rate of rape harvesting as the evaluation index. The main and secondary factors affecting the cutting table loss of the variable speed reel were obtained as the reel input speed, the machine travel speed and the ground angle of the frame. The optimal range of the input speed of the reel is from 25 r·min⁻¹ to 31 r·min⁻¹, the optimal range of the forward speed of the implement is 0.8 m·s⁻¹~1 m·s⁻¹, and the optimal range of the rack level angle is from −10°to 10°. A mathematical model of regression of cutter loss and the main influencing factors was established, with the coefficient of determination R² = 0.9918, the relative error between the test value and the optimised value of the regression equation was 5.36%. The optimal combination of parameters for the variable speed reel was obtained with the lowest cutting table loss rate in rape harvesting as the optimization target: reel input speed 25 r·min⁻¹, frame parallel to the ground and implement travel speed 0.7 m·s⁻¹. Field validation tests and comparative tests of cutting table loss of the two reels were carried out. The test results show that the regression mathematical model of the cutting table loss is more accurate, and the cutting table loss is reduced by 13.9% with the variable speed reel compared to the cam-action reel, and there are no problems with the paddle teeth hanging and tangling during the paddling process.

A variable speed anti-tangling reel mechanism was designed to address the problems of tangling, hanging and rewinding of the tassel wheel and the high paddling loss in the current Chinese rape combine harvester cutting table. The kinematic equations of the reel mechanism were developed, and the analysis showed that the speed in the entry stage is low and the speed in the exit stage is high, and the attitude of the reel teeth change with the rape plant movement during the whole paddling process. A single-factor test and a multi-factor regression orthogonal combination test were carried out using the cutting table loss rate of rape harvesting as the evaluation index. The main and secondary factors affecting the cutting table loss of the variable speed reel were obtained as the reel speed, the machine travel speed and the ground angle of the frame. A mathematical model of regression of cutter loss and the main influencing factors was established, with the coefficient of determination R2 = 0.9918. The optimal combination of parameters for the variable speed reel was obtained with the lowest cutting table loss rate in rape harvesting as the optimization target: reel speed 25r/min, frame parallel to the ground and implement travel speed 0.7m/s. Field validation tests and comparative tests of cutting table loss of the two reels were carried out. The test results show that the regression mathematical model of the cutting table loss is more accurate, and the cutting table loss is reduced by 13.9% with the variable speed reel compared to the cam-action reel, and there are no problems with the paddle teeth hanging and tangling during the paddling process.

In order to reduce the silique shattering loss of the rapeseed mechanical harvesting process, based on the state of force on the silique during the rapeseed harvesting reel branch stage, Ningza 1810, Zhenyou 8, and Fengyou 306 were used as research objects, and the experimental research on the factors affecting rapeseed silique shattering was carried out using the swing impact method. The experimental analysis showed that rapeseed varieties, silique moisture content, silique growth position, collision material, impact speed, force position, and other factors had significant effects on silique shattering. The impact velocity was less than 1.5 m·s⁻¹, the difference in the effect of each factor on pod shattering was not significant, and it was not easy to shatter when the moisture content of the rapeseed silique was higher. The impact resistance of the front side of rapeseed was two to four times that of the bonding surface of rapeseed petals, the shattering rate of the top rapeseed silique was twice that of the bottom siliques, and when siliques were supported, they were more likely to shatter under external forces than when they were unsupported. The experimental study of the mechanical properties of rapeseed siliques was carried out using the impending fracture method; the experimental analyses showed that the support position and force position of the silique, the loading speed, and the growth position of the silique had a significant effect on the mechanical properties of the silique. The maximum cracking force was higher and the bending strength was stronger when the body of the silique was supported; the range of the maximum cracking force was 3.05 N to 4.16 N, and the bending strength range was 8.48 MPa to 11.57 MPa. The maximum cracking force and bending strength of the silique were stronger when the front side of the silique petal was pressurized than when the bonding surface of the petal was pressurized. Based on Pearson’s correlation and grey correlation analysis, the morphological characteristics of rapeseed siliques were ranked in order of their influence on the performance of siliques in terms of the angle between the silique and stalk, stalk diameter, petal thickness, beak length, silique thickness, silique width, and silique length. This study can be used as a reference for the design and optimization of the rapeseed harvesting reel branch mechanism and the selection of machine-harvestable rapeseed varieties.