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Crawler combine harvesters are mostly used in paddy field operation in South China. The field operation load is complex and variable, which leads to fatigue fracture and other accidents of gearboxes under the impact of variable loads and seriously affects the trouble-free working time of the whole machine. In order to solve the problem of high fault rate of gearboxes of crawler combine harvesters, the single HST hydro-mechanical differential steering gearbox developed by the team is taken as the test object, this study designs and builds the gearbox assembly fatigue test bench, and then carries out the fatigue test of differential steering gearboxes. The test results show that the test bench can well test the comprehensive working performance and durability of differential steering gearboxes, and has advantages of simple structure, convenient installation, etc. This is of great significance to study the fatigue damage rule of differential steering gearboxes, optimize and improve the mechanical structure of gearboxes and reduce the fault rate of its internal parts in the future.

Cleaning is one of the most important steps in the harvesting process, and the prolonged and high-load operation of the vibrating sieve can decrease its reliability. To uncover the structural flaws of the cleaning sieve in the crawler combine harvester and establish a foundation for quality inspection, this paper proposes a method for durability testing and analysis using vibration and strain signals. Via the modal analysis of the cleaning sieve, the most susceptible areas for fault signals are identified. Subsequently, a specialized test rig exclusively designed for the examination of the durability of the cleaning sieve is constructed. After following 96 h of uninterrupted operation, the vibration plate of the cleaning sieve sustains damage, resulting in atypical noise. A signal analysis reveals that the primary vibration signal of the cleaning sieve primarily consists of a fundamental frequency of 5 Hz, corresponding to the driving speed, as well as a frequency doubling signal of 50 Hz. After the occurrence of damage, the peak amplitude of the received vibration signal increases by over 86.3%. Furthermore, the strain gauge sensor situated on the support plate of the rear sieve detects anomalous signals with frequencies exceeding 300 Hz, which are accompanied by a considerable rise in the power spectral density. This research has significant importance for enhancing the service life of the cleaning sieve and optimizing the overall machine efficiency. [ABSTRACT FROM AUTHOR]

The single HST (Hydro Static Transmission) mechanical differential transmission gearbox of crawler combine harvester is subjected to the impact of alternating loads in the field operation, resulting in its fatigue failure. The traditional durability fatigue test can improve the fault-free working time of machinery, but it is not suitable for agricultural machinery with time-varying load frequency bandwidth and stress amplitude. Therefore, in this paper, a fault diagnosis method based on order analysis was proposed considering the comprehensive influence of load amplitude and frequency on the fatigue life of gearbox. The location and the corresponding type of fault were found by comparing the spectral line peak changed before and after. Then, the test verification was carried out on the gearbox assembly fatigue test bench according to the compiled load spectrum. The results show that the analysis results of the fault diagnosis method based on order analysis were consistent with the unpacking inspection, which had reference significance for the research on the fault diagnosis method of the crawler combined harvester gearbox. [ABSTRACT FROM AUTHOR]

The threshing gap of the thresher device for rice combine harvester has to be adjusted in real time based on different feed rates to ensure the operation efficiency in the harvesting process. However, adjusting the threshing gap by changing the position of concave grid may result in unevenness of threshing gap of the thresher device and further impact on the fluidity of material in the thresher device; in addition, it is also unavailable to adjust the threshing gap by changing the drum diameter when the rice combine harvester is in operation. In view of the above and based on axial flow threshing drum, the design of a variable-diameter threshing drum available for overall and rapid drum diameter adjustment and the research on diameter adjustment device as well as electronic control self-locking device were introduced in this study. Besides, stress analysis was implemented to the diameter adjustment device to ensure the stability of the variable-diameter threshing drum. Field experiment was implemented to identify the difference between the impacts brought to the threshing performance (grain-entrainment loss rate, damage rate, threshing efficiency, and threshing power consumption) by both methods for threshing gap adjustment. The experiment result shows that the drum adjustment method with variable-diameter drum features higher grain-entrainment loss rate, threshing efficiency, and threshing power consumption, yet stable in terms of consumption fluctuation, but a lower damage rate than their counterparts with concave adjustment method. [ABSTRACT FROM AUTHOR]

Rice is one of the most important grain crops in China and most of these fields are harvested by combine harvesters. With increasing rice grain yields and feed rates, the cleaning systems rice combine harvesters have to deal with larger volumes of threshed output. Field experiments have shown that the standard single-duct cleaning systems used in most rice combine harvesters has become a limiting factor, resulting in high grain losses and producing high grain impurity ratios. To investigate the reasons for poor cleaning performance, the terminal velocity of the different categories of threshed outputs were quantified and turbine flow meter measurements were performed to obtain insights into the airflow distribution inside the cleaning shoe. Based on these insights, a multi-duct cleaning device with return pan was proposed for tangential-longitudinal-flow rice combine harvesters. The new cleaning system was benchmarked against a commercial system during parallel field tests and it was concluded that the design adaptations improved the sieve losses by 85% and the grain impurity ration by 73%. • Terminal velocity of different components of threshing outputs were quantified. • Distribution of the threshing outputs in the cleaning shoe were studied. • The proposed multi-duct cleaning device improved cleaning performance greatly. [ABSTRACT FROM AUTHOR]

The main working parts of the cleaning device of a rice combine harvester can be controlled by an established control strategy in real time based on the monitored grain sieve loss. This is an efficient way to improve their cleaning adaptability, since as a consequence, the main working parameters of combine harvesters can automatically adapt to crop and environment changes, and the corresponding cleaning performance can be improved. To achieve the target of cleaning control based on the monitored grain sieve loss, a fuzzy control system was developed, which selected S7-1200 PLC as the main control unit to build the lower computer hardware system, utilized ladder language to complete the system compilation, and used LabVIEW 14.0 software to design the host–computer interface. The effects of fan speed, guide plate angle, and sieve opening on the grain sieve loss and grain impurity ratio have been investigated through a large number of bench tests. The relevance level of the operating parameters on the performance parameters has been determined also, and finally, a fuzzy control model was developed for the cleaning system. The experiment results indicated that the designed fuzzy control model can control the cleaning section settings, such as fan speed and guide plate angle automatically, and reduce the grain sieve loss to some extent. [ABSTRACT FROM AUTHOR]

Operating parameters such as threshing cylinder speed, concave clearance and bar spacing are the most important factors that influence the power consumption of threshing apparatus and grain loss ratio during the threshing process. In order to obtain rice threshing optimal operating parameters, investigations were conducted on the longitudinal axial threshing apparatus test bench of combine harvester. The threshing power consumption and grain loss ratio of longitudinal axial threshing apparatus were measured at the different combination of cylinder speed, concave clearance and bar spacing. Rice threshing experiment results were analyzed by carrying out regression analysis and the significance of regression effects assessing. The confidence interval of the optimal operating parameters was used to control the performance of threshing and separation process, and the optimal variables of the longitudinal axial threshing apparatus were predicted in advance and tested soon afterwards. When the total grain loss ratio was controlled within less than 0.33% and the threshing power consumption was less than 46.36 kW with a confidence of 0.95, the confidence interval of the best cylinder speed was 772.61-905.74 r/min, the best confidence interval of concave clearance was 22.18-37.93 mm, and the best confidence interval of bar spacing was 104.96-170.17 mm. The results showed that the best threshing cylinder speed was 839 r/min, the best concave clearance was 30 mm and the best bar spacing was 138 mm. These operating parameters can reduce the energy requirements of threshing process and also can lead to low grain loss. [ABSTRACT FROM AUTHOR]

Cleaning and screening of agricultural materials is an important process in agricultural production. Many researchers have carried out important works in this area based on mechanism, parameter optimization, and particles’ motion. In this paper, both advantages and disadvantages of the traditional reciprocating screen widely used in combine harvester were analyzed. Furthermore, a variable-amplitude screening mechanism developed from classical swing bar type reciprocating screens in Adams software was studied, and the trajectories of 11 marker points on the screen under different conditions were obtained. After transforming the motion of a variable-amplitude screen to 3 DOF (degree-of-freedom) motions (two translations and one rotation, 2T–1R), DEM (discrete-element method) simulations of agricultural particles (grain and stalk) in a variable-amplitude screen box were performed based on the Hertz–Mindlin contact model in an EDEM software environment. The results show that the variable-amplitude screen could make the agricultural particles at the front of the screen be quickly thrown up and moved back but could not favor their segregation and separation at the screen front. This variable-amplitude screening method can provide reference for solving the retention problem of agricultural materials at the screen front. [ABSTRACT FROM AUTHOR]

Because rape stalk has a high water content, rape materials easily adhere to the cleaning screens of combine harvesters leading to a high screen loss. Inspired by friction-reducing research on bionic non-smooth metal surfaces, a special rape cleaning screen with non-smooth surface was developed and compared with a standard screen in field experiment. It showed good anti-adhesion performance to rape components. To understand the mechanism, a reciprocating friction test between a rape stalk and non-smooth metal surface was carried out. The result was consistent with the findings of a field experiment. In the test, a vertical micro-vibration was discovered between rape stalk and the non-smooth metal surface. This did not exist in the case of a common smooth metal surface and was considered as an important factor in the mechanism. In this paper, a theoretical analysis was proposed to explain how the vertical micro-vibrations occurred during a horizontal reciprocating translation of non-smooth units. Firstly, according to the case of friction test, a geometry contact model and a dynamic equation were established. Then computing methods of vertical impact force and its action time were respectively deduced. Finally, a simulation was produced with a time-scale factor of two. The result from the simulation was consistent with basic trend of test data. Although the theoretical analysis requires improvement for further investigation, it could still provide the basis of a theoretical model and the foundation for further friction-reducing research for non-smooth surfaces. [ABSTRACT FROM AUTHOR]

In order to optimize the length of longitudinal-flow threshing cylinder of combine harvester, in this paper the length-adjustable longitudinal-flow threshing cylinder was designed and used to conduct rice threshing and separating performance experiments. The grain distribution rules and distribution equation under the grid concave were developed. The length of longitudinal-flow threshing cylinder was optimized by calculating the optimal deflector helical angle of cylinder cover. The optimal length of the longitudinal-flow threshing cylinder was used to conduct rice threshing and separation performance confirmatory test. The result showed that when the feeding rate was 7 kg/s, adapted deflector helical angle of 7.64°, the optimal length of the longitudinal-flow threshing cylinder was 3 159.77 mm, and then the un-separated grain loss ratio could be controlled at the range from 0.2 % to 0.3%. The verification test result was about 0.29%. This study may provide a basis and method for design the length of longitudinal- flow threshing cylinder of combine harvester. [ABSTRACT FROM AUTHOR]

The cleaning performance of the cleaning shoe of a multi-rotor combine harvester has proven to be poor owing to the threshed output entering the cleaning section in an uneven manner. Experimental results indicated that the arrangement of the guide blades on the return plate surface has a significant effect on the threshed output distribution. In this paper, DEM (discrete element method) simulations were carried out in the EDEM software to examine the effect of the height of the guide blade, the installation angle, and the number of guide blades on threshed output distribution before entering the cleaning shoe. Based on the simulated results under different guide blades arrangements, the optimum arrangement location was obtained. The simulation's results were verified by a field experiment and were consistent with the experimental results. The field experiment results indicate that the cleaning performance significantly improved with the proper guide blade arrangement. The corresponding grain impurity ratio declined significantly from 1.26% to 0.67%, and the grain sieve loss ratio, with a decrease of 53.2%, was reduced from 1.11% to 0.52%. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a numerical study of the gas–solid flow in an air-and-screen cleaning shoe is carried out by use of the combined Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) model where the motion of discrete particles phase is obtained by DEM which applies EDEM software and the flow of continuum fluid by the traditional CFD which solves the Navier–Stokes equations at a computational cell scale. The effect of inlet airflow velocity is studied and analyzed in terms of grains and short straws’ longitudinal velocity and vertical height, and cleaning loss. Simulation results showed that, in a certain range, different inlet airflow velocity only affects the magnitude of airflow velocity in the cleaning shoe, but does not affect the distribution regularity of flow field in the cleaning shoe. With the inlet airflow velocity increase, vibrating screen processing power improves, while grain losses increase. Grains mainly concentrate on 4–12 sections under the screen surface. Comparison of numerical simulation results with experiments has demonstrated adequate agreement. It showed that numerical simulation of material motion on vibrating screen of air-and-screen cleaning device based on CFD–DEM is feasible. The results provide a basis for improving the design on air-and-screen cleaning device of combine harvester. [Copyright &y& Elsevier]

Abstract: Based on laboratory experimental results obtained with an axial threshing test-rig with tangential feeding, cumulative distribution functions of separated grain in axial and radial directions of threshing rotor were built. Based on the analysis of the relationship between grain separation loss and grain separation flux in an area under the concave, an indirect grain separation loss monitoring method is presented in this paper. Piezo-electric polyvinylidene fluoride (PVDF) film was selected as sensitive material to design a grain flux sensor. While grain and material-other-than-grain (MOG) separated in the monitoring area impact on piezo-electric PVDF films, different electric charges are generated. After signal progressing with a charge amplifier, frequency discrimination and wave shaping, the number of grain can be counted by a microcontroller (MCU) and the grain separation loss of combine harvester can be measured in real-time. Field test results indicated that the measurement errors of grain separation loss recorded by the monitoring system relative to the loss checked manually were less than 12%. [Copyright &y& Elsevier]

One of the most important means of improving the mechanization of rapeseed harvests and increasing farmers' income is to reduce the cleaning loss of rapeseed. In this study, a fuzzy grey control system was developed using an assembled cleaning loss sensor. Based on experimental data, the relationship between the cleaning loss and the opening of the louver sieve in the cleaning device was obtained. The fuzzy control scheme was established by combining grey prediction and the fuzzy control principle. Secondly, a microcontroller unit (MCU) was used as the controller, and the opening of the louver sieve was automatically regulated by detecting the signal of the cleaning loss. Finally, the performance and robustness of the control system was evaluated in field tests. Different experiments were conducted under different speed conditions to reflect the variable throughput. Results showed that using the grey prediction control system can realize the adjustment of the louver sieve opening in real time. The cleaning loss could be maintained within the ideal setpoint interval, compared with the operation with the control system switched off. These findings indicate that the application of the grey fuzzy control system reduces cleaning loss, and the nonlinear, time-variable and time delay problems in cleaning devices can be solved effectively. [ABSTRACT FROM AUTHOR]

• Field test of combine harvester under different load conditions. • The multi-point vibration signals on the outer surface of the threshing and separation device were studied. • The short-time feature set can combine the original vibration signal with the actual operating conditions. • The vibration signals at different positions have great differences in intensity and sensitivity. • Multi-sensor signals integration is important for the comprehensiveness and correctness of threshing load state diagnosis. In order to identify the load conditions of threshing and separating device of combine harvester quickly and accurately, this experiment was conducted to collect vibration acceleration signals of the outer surface of threshing and separating device under different load conditions by field test in 2020 with the new rice variety Nanjing Jinggu as the research object. Firstly, based on the statistical analysis and signal analysis method, time domain, frequency domain, and time–frequency domain characteristics were extracted and fused into total domain characteristics to characterize the overall signal attributes of load conditions of the threshing and separation device so as to reduce the difficulty of data decision. Secondly, Principal Component Analysis (PCA) and Kernel Principal Component Analysis (KPCA) were used to remove the correlation and nonlinearity among the extracted characteristics, reduce the dimensionality of the characteristic vector and improve the accuracy of the diagnostic model. Finally, Support Vector Machine (SVM), Extreme Learning Machine (ELM) and Random Forest (RF) were used to diagnose the load conditions of the dimension reduction collection of total domains, and the accuracy rate and recognition time were used as evaluation indexes for the comparative analysis of model recognition. The results showed that the KPCA clustering separation effect is significant. RF has the highest recognition accuracy, which the accuracy of training set and prediction set are 100% and 98% respectively. The accuracy of ELM-KPCA model training set and prediction set is 100% and 90% respectively, and the analysis time is 6.206 s. This model accuracy is high, and the analysis time is the shortest, then ELM-KPCA model can be the best model for load conditions recognition of combine harvester. [ABSTRACT FROM AUTHOR]

• A rice grain impurity sensor in grain-bin of combine harvester was designed. • Structure parameters of grain sampling box and reciprocating motion of choke plate were analyzed. • Image sensing was improved through light source illumination and installation. • The decision tree algorithm was applicated to recognize rice grains and stalks. The cleaning of rice on a combine harvester is a complex process, which leads to differences in impurity ratio of harvested grain, and the impurity ratio is one of the key criteria for the assessment of performance of a combine harvester. Combine operators usually optimize parameter settings only once for harvesting each crop because of time pressure, and therefore differences in site- and temporal-specific conditions are neglected. In this paper, to offer combine operators the opportunity to make better management decision, a machine vision method for grain impurity monitoring of a rice combine harvester in real time was proposed, and the classification of kernel and impurity particles using decision tree algorithm was presented. To obtain images of high quality during harvesting, the structure of the sampling device depending on the working properties in grain bin was designed, the illumination and installation of the light source were optimized, and finally lateral lighting system was constructed. To monitor and recognize grains and impurities, the morphological features of the particles extracted from the images were acquired. The selected 6 features (A1-A6), including area, perimeter, maximal feret diameter, elongation factor, compactness factor and Heywood circularity factor, were fed to the decision tree algorithm for classification. Output of the algorithm, a visualized tree, was used to classify the particles labeled in the binary image. The decision tree provided a classification accuracy of about 76% for the given training data set extracted from the captured images. From the experimental results, it is suggested that the method of monitoring the impurity ratio of harvested grains based on decision tree algorithm using image processing can be recommended as the basis of parameter optimization of combine harvesters. [ABSTRACT FROM AUTHOR]

To reduce the variability of cleaning performance caused by uneven airflow distribution, the theory of fan design and the characteristic parameters of threshed rice outputs were used to develop a prototype of cleaning fan. Computational Fluid Dynamics (CFD) was employed to simulate the air distribution inside the fan and the airflow speed distribution at the fan outlet. Response surface methodology (RSM) with three factors and three levels was employed to optimise fan impeller geometry parameters, this included blade inlet mounting angle, blade curvature and blade inlet curvature. According to the least squares analysis of RSM, the influence of each factor on the airflow distribution at each sub-outlet was estimated. The optimal values of blade inlet mounting angle, blade curvature and blade inlet curvature were 107°, 190 mm and 135 mm, respectively. The uniformity of the outlet airflow distribution of the optimised fan was clearly improved. The number of eddy currents in the flow passage were reduced, and the transporting performance of optimised fan was improved. The maximum pressure at 5% blade height away from the central plate was reduced by 37.78%, which indicates that the service life of the cleaning fan could be increased. • A prototype cleaning fan with a central plate developed and optimised. • Optimised fan improves the uniformity of the outlet airflow distribution. • Optimised fan could enhance the cleaning performance of the combine harvester. [ABSTRACT FROM AUTHOR]

• This article compares the results of the simulation and that of the experiment carried out on the unloading of the grain tank from the combine harvester. • The rice grains motion, the mass flow rate, and the velocity of the moving particles were determined. • The stress on the different walls of the tank has been determined. this could help to improve the future design of the grain tank of the combine harvester or other equipment for handling or storing the rice grain. Problems associated with the discharge of rice from the grain tank of a combine harvester can be avoided if the tank is designed based on the rice's flow properties. The precise prediction of the rice movement during discharge from the grain tank is important for the design, manufacture, and improvement of the grain tank. In this research, a discrete element method (DEM) was used to simulate the rice movement during unloading of the grain tank, and the flow type, the pressure exerted on the walls, the particle velocity, the discharge time, and the mass flow rate were analyzed and compared to the experimental results. The results of this research reveal a similarity between the numerical simulation and the experimental test bench. The results show that 1 s after the grain tank starts to unload, a funnel flow was created at the back of the tank and spreads to the rest of the tank. The grain tank is asymmetrical; thus, the pressure exerted on the different walls is not the same. When the tank is filled with rice grain, the four vertical walls receive a little stress compared to the two inclined walls at the bottom of the tank. The walls at the bottom of the tank receive the highest pressure. the two velocity sensors attached to the screw feeder in different parts of the tank to measure the axial speed of the rice grains show that the velocity of the rice velocity is the same between the threads of the screw at the tank exit and inside the tank. the average value of the mass flow rate was 3.5 kg/s for the simulation and 3.35 kg/s for the experiment. The mass flow rate remains constant at zero acceleration of the screw. [ABSTRACT FROM AUTHOR]