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.

For the prompt planting of subsequent crops, most of China’s corn harvest must occur before full maturity, with a grain moisture content above 25%. Harvesting moist corn presents challenges due to significant grain damage during threshing. We conducted a high-speed photography observation test of moist corn threshing. It demonstrated that corn ears, when passing through the threshing cylinder, often break into pieces. Grains on divided corncobs can be threshed more easily and earlier than those on undivided ones, suggesting that pre-dividing corn ears reduces grain damage. An experiment using the Lianchuang 825 variety examined the effect of moisture content and the divided rate of corncobs (DRC) on grain damage. The results showed that as moisture content increased from 25% to 37%, grain damage to undivided ears increased from 3.75% to 37.71%. Dividing corn ears before threshing significantly reduced damage, with an eight-piece division reducing damage by approximately 70% across all moisture levels. Verification with the Jinyu 1233 variety confirmed that a higher DRC consistently reduced damage. This study provides a new approach to reducing damage in moist corn threshing and aids in the development of low-damage threshing devices.

Aiming to address the problem of low recognition accuracy in the current cleaning loss detection system of rapeseed harvesters, a rapeseed cleaning loss detection system was developed using the energy distinction method based on the principle of impact piezoelectricity. A signal processing circuit, centered around a hardware integral circuit and a triple voltage comparison circuit, was designed. The energy of the impact signals generated by rapeseed kernels and impurities was calculated through hardware integration. The distinction threshold for the energy of the impact signals generated by kernels and impurities under the operating wind speed of the cleaning system was found through experiments, and a fitting model relating the fan speed to the distinction threshold was constructed. A loss detection and counting system for rapeseed kernels was designed to realize the statistics and real-time display of rapeseed kernels regarding cleaning loss. Performance verification tests were conducted on mixtures of rapeseed kernels and impurities with different mixing ratios, and a field test was carried out on the platform of a 4LZY-5.0Z rapeseed combine harvester. The test results showed that the accuracy of the designed loss detection system for kernel identification was more than 91.6%. Under operating conditions of 700, 900 and 1200 r/min fan speeds in the combine harvester cleaning system, the relative errors of the loss detection system compared to manual detection were 5%, 4.7% and 3.8%, respectively. The developed loss detection system for rapeseed kernels has high detection accuracy and good overall performance, which means it can provide feedback information for the control of the harvester.

Uneven straw conveying and unstable throwing can reduce the operational performance of rice combine harvesters. To address these problems, an integrated straw conveying and throwing device combining guided conveying with pneumatic throwing was developed. The brachistochrone principle was introduced into the curved-surface design of the diversion plate as a geometry-guided approach to provide a continuous transition between the straw-falling region and the conveying inlet. Based on the motion characteristics of straw in the diversion and throwing regions, a coordinated feeding–acceleration–throwing process was established. The effects of diversion plate angle, blade rotational speed, and blade installation angle on throwing distance and distribution stability were investigated. A computational fluid dynamics model based on the mixture multiphase approach was used to characterize the macroscopic gas–solid flow field and compare airflow organization under different blade installation angles. A Box–Behnken response surface design was subsequently employed to establish regression models for throwing distance and the coefficient of variation in straw distribution, followed by multi-response numerical optimization. The optimal parameter combination consisted of a blade rotational speed of 2500 r/min, a diversion plate angle of 1.25 rad, and a backward blade installation angle of 15°. Under these conditions, the predicted throwing distance and coefficient of variation were 7.89 m and 14.6%, respectively. Validation tests produced throwing distances of 6.94–8.21 m and coefficients of variation of approximately 13%, showing good agreement with the predicted performance. The developed device and optimization results provide a basis for improving the conveying continuity and throwing uniformity of straw-handling systems in combine harvesters.

High-moisture rice straw processed by whole-feed combine harvesters often exhibits high cutting resistance and uneven particle size distribution after comminution. To address these issues, a straw comminution device integrated with the straw outlet of the threshing and cleaning system was developed, and the shear fracture mechanism and operating parameters were investigated. The geometric characteristics, density, contact properties, and bending properties of rice straw cultivars Yongyou 7301 and Kenuigeng 1 were measured. A hollow flexible straw discrete element model was established using the Hertz–Mindlin with Bonding contact model, and its parameters were calibrated and validated through quasi-static shear cutting tests. The effects of shear cutting angle on maximum cutting force, bond failure evolution, and load transfer behavior were analyzed at shear angles of 30°, 45°, and 60°. Device-scale DEM simulations combined with field experiments were further conducted to optimize the guide plate angle and rotor speed. The results showed that the maximum cutting force under quasi-static single-stalk cutting conditions initially decreased and then increased with increasing shear angle. At a shear angle of 45°, the maximum cutting force was 78 N, representing a 44.8% reduction compared with that at 30°. Meanwhile, the fracture zone expanded along the blade sliding direction and stress concentration was alleviated. The DEM model effectively characterized the fracture behavior of rice straw, with an average relative error of 11.07% between simulated and experimental cutting forces. The optimized operating parameters under the tested conditions were a shear angle of 45°, guide plate angle of 55°, and rotor speed of 2500 r/min, resulting in average chopped lengths of 17.3 mm in simulation and 20.5 mm in field experiments, with a comminution qualification rate of 95.26%. These findings provide theoretical support for improving the fracture characteristics and chopping performance of straw comminution systems.

To address the high kernel breakage rate and incomplete threshing of high-moisture maize ears, a low-damage core-splitting–threshing method was proposed, and a maize-ear core-splitting device based on the internal expansion action of a splitting cone was developed. During operation, the splitting cone was screwed axially into the cob, and a radial splitting load was applied to the cob interior through thread-induced self-feeding and conical wedging, dividing the intact ear into several block-like segments and thereby weakening the kernel–cob connection and the supporting constraints among adjacent kernels. The main structural parameters of the splitting cone and clamping and conveying mechanism were determined through theoretical analysis. The discrete element method was used to investigate the core-splitting process at different splitting-cone rotational speeds, and core-splitting and subsequent threshing tests were conducted at kernel moisture contents of 25–30%. As the splitting-cone rotational speed increased from 150 to 650 r/min, the simulated and measured cob fragmentation degrees increased from 5 to 11 and from 6 to 11, respectively, while the measured kernel damage rate remained below 1.0% under all core-splitting conditions. In the subsequent threshing tests, the mean kernel breakage rate and unthreshed kernel rate of the core-split treatment group were 4.75% and 1.55%, respectively, representing reductions of 44.0% and 15.8% compared with 8.49% and 1.84% for the unsplit control group. Analysis of variance showed that threshing-element type had highly significant effects on both the kernel breakage rate and unthreshed kernel rate, while drum rotational speed and cob fragmentation degree had significant effects on both responses. Type C movable spike teeth exhibited good compatibility with core-splitting pretreatment, with mean kernel breakage and unthreshed kernel rates of 3.52% and 1.30%, respectively, corresponding to reductions of 48.6% and 18.9% relative to the corresponding unsplit controls. Increasing the cob fragmentation degree reduced both response indices, whereas increasing drum rotational speed reduced the unthreshed kernel rate but increased kernel breakage. Multi-objective optimization identified the optimal parameter combination as the Type C threshing element, a drum rotational speed of 1000 r/min, and a cob fragmentation degree of 11. Under these conditions, the predicted kernel breakage rate and unthreshed kernel rate were 3.30% and 1.18%, respectively, with an overall desirability of 0.939. These results provide a reference for pre-threshing core-splitting pretreatment of high-moisture maize ears and for the design and parameter matching of low-damage threshing devices.