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In view of the current large rapeseed header losses of rape combine harvesters, the effects of the header on rapeseed header loss were studied from the perspective of vibration. First, the vibrations at various measuring points on the header during rape harvest were studied using a data acquisition and analysis system while performing collection tests of rapeseed header loss with the sample slot method. The relationships between total header vibration and total rapeseed header loss and between vertical cutter vibration and rapeseed vertical cutter loss were shown to have a positive correlation, and they all increased with the increase in engine speed. Vertical cutter loss accounted for 31.2% to 42.4% of the total rapeseed header loss. Modal analysis and optimization of the header frame were then performed by simulation and test. The natural frequencies of the first-order and second-order modes of the optimized header were increased, and the possibility of resonance with other working parts was eliminated. Finally, the improved header was tested during rape harvest. The results showed that the total vibration of the improved header was reduced by 19.9% to 43.9%, and the total rapeseed header loss was reduced by 33.2% to 46.9%. The vertical cutter vibration was reduced by 30.5% to 49.8%, and the rapeseed vertical cutter loss was reduced by 20.8% to 34.7%. In addition, the vibration and rapeseed loss of the improved header had relatively slow rates of increase with the increase in engine speed. The method of reducing rapeseed loss by reducing the header vibration achieved an obvious and positive effect. [ABSTRACT FROM AUTHOR]

This paper mainly studied the working environment modeling and coverage path planning of combine harvesters. The boundaries of the farmland to be harvested were extracted through the farmland satellite imagery and canny algorithm. The polygon approximation method was used to fit the extracted boundaries as polygons. The edge offset of the farmland and obstacles was realized based on the principle of straight skeleton. According to the structure data of the split points which were obtained through the improved scan line algorithm, the coverage path planning of the combine harvester was realized. Moreover, the circular arc transition algorithm was used to optimize the harvesting paths to achieve the smooth turning of the combine harvester at the edge of farmland and when encountering obstacles. The simulation results show that the proposed the proposed polygon approximation method can accurately depict the boundaries of the farmland to be harvested, and reduce the amount of data to be stored. Additionally, the designed path planning method can realize the coverage path planning of the combine harvester in irregular and internal obstacle farmland. [ABSTRACT FROM AUTHOR]

To improve the driving comfort of combine harvesters, driver seat low-frequency vibration and related driver ride-comfort problems were investigated on a Chinese CFFL-850 crawler-type full-feed combine harvester based on ISO2631. Driver vibration and driving seat transmission characteristics were measured under the following conditions: no-load idling, driving on the road, driving in the field, and simulated harvesting. The root mean square values composite vibration under four conditions were 3.63 m/s², 2.35 m/s², 3.34 m/s², and 2.67 m/s2 , respectively. For the same condition, the maximum root mean square scores of vibration component on driver whole-body occurred in the seat support surface (test point 1) and vertical direction (Z direction), which were 3.56 m/s², 2.05 m/s², 3.15 m/s², and 2.43 m/s², respectively. The test point 2 to test point 1 vertical-transfer function curve trends were nearly identical. Nearly all of the transfer coefficients were greater than 1 in the range of 1-50 Hz, therefore, the seat vibration attenuation performance was poor. Based on the analysis results, the driver seat structure was altered and a verification test was performed. The test results indicated that after an X-damping mechanism was installed, vibration acceleration, on the surface of the seat support under the road-driving conditions, decreased from 2.35 m/s 2 to 1.68 m/s2 . Under the simulated harvesting condition, the vibration acceleration decreased from 2.56 m/s2 to 1.46 m/s² . Nearly all of the seat vertical transfer coefficients were less than 1 within the frequency range of 1-80 Hz, therefore the dynamic comfort of the seat was ameliorated after structural improvement. [ABSTRACT FROM AUTHOR]

Though the component of threshing drum is pre-balancing on the factory, the drum after assembly still has the problem of unbalanced vibration. In this study, the unbalance mechanism produced by assembly are introduced and the centroid propagation model in the series rotation system was established. The influence of the eccentricity and assembly phase on the assembly unbalance was studied. It is shown that there was a superposition effect between the initial centroid eccentricity caused by the machining error and the centroid eccentricity caused by assembly error, the unbalance amount under the in-phase assembly was larger than that of the anti-phase assembly. Moreover, the unbalance variation was experimentally investigated using in-field balancing detection on the test rig and combine harvester. The experiment results showed the excellent vibration reduction effect of in-field balancing, which showed a reduction of 83.0% and 85.8%. In order to increase the range of in-field balance detection and reduce the calculation error, the double-speed influence coefficient method was proposed. The proposed method adopted the way of first low-speed pre-balancing, and then high-speed precision balance, taking advantage of vibration information at two speeds and avoids nonlinear vibration conditions caused by high unbalanced vibration. Finally, the doublespeed influence coefficient method was verified on the test rig. The vibration reduction effect of proposed method was better than the traditional method. [ABSTRACT FROM AUTHOR]

To reduce the inertial force of the oscillating sieve and return pan of a rice combine harvester, partial equilibrium was adopted. Firstly, based on the kinematic analysis of a slider-crank mechanism, the appropriate mass of counterweight intervals was achieved. Then, an ADAMS dynamic simulation was used to determine the optimum balance mass of the oscillating sieve and return pan individually. Considering the relative motion between the return pan and the oscillating sieve, the overall inertial force of the two parts would be reduced. The simulation results indicated that the optimum counterweight of the oscillating sieve was 15.5 kg based on an analysis of the movement tracks of the mass center and overall inertial force. The results also showed that the overall balance of inertial force not only reduced the counterweight but also decreased the overall inertial force of the oscillating sieve and return pan. Finally, a search for the most suitable crank initial angle of the return pan to reduce the overall inertial force and optimize the overall balance revealed three groups of initial angles: φ=0°, φ=45°, and φ=90°. The results indicated that arranging the initial angle of the crank of the oscillating sieve and return pan in the same position (φ=90°) was the most favorable for reducing the overall inertial force. In this situation, the optimum counterweight of the oscillating sieve was only 14.0 kg. The results can provide references for the design of the overall balance of the inertial force in the cleaning components of a combine harvester. [ABSTRACT FROM AUTHOR]

Impact damage is the main form of rice threshing and it is also a significant cause of rice injury. Based on contact mechanics, models of the compressed displacement and the largest pressure distribution were established for the case when the threshing tooth obliquely impacts against the rice kernel. A critical velocity formula for impact damage was developed. A computer-aided design model of a rice kernel comprising of three layered ellipsoids was established. HyperMesh software was used to partition mesh elements and to set material and contact parameters for each element, constructing a finite element model for the analysis. Using LS-DYNA software, the impact between the threshing tooth and the rice kernel was simulated and analysed. The simulation showed that the rice husk was subjected to tensile stresses. Tensile stress was a maximum at the front of the contact zone and shifted continuously. The entire kernel rolled during impact. The critical damage velocity for the kernel, corresponding to the critical von Mises stress was 29.5 m s−1, which was in agreement with experimental results. [Copyright &y& Elsevier]

A knowledge-based fuzzy logic model was developed on experimental data and used to predict the draft, side and vertical forces and soil disturbance area by disc tillage tool operation. The laboratory research work was conducted to evaluate the performance of the disc tool at three working speeds (1.25 m/s, 1.98 m/s and 2.47 m/s, respectively) and depths (0-5 cm, 5-10 cm and 10-15 cm, respectively) on paddy soil under soil-bin environment. Further, draft (Fx), side (Fz) and vertical (Fy) forces of disc and soil disturbance area were assessed and predicted towards working speeds and depths. A fuzzy prediction model with two input variables (speed and depth) and four output variables was developed and the Mamdani inference approach was used. Draft, side and vertical forces of disc and soil disturbance area were positively responded 0.97, 0.95 and 0.84 and 0.99, respectively. The prediction results showed a close relationship between measured and predicted data. Similarly, the measured and predicted results revealed that the draft, side, vertical forces, and soil disturbance area slightly increased, while increasing the speed and depth of the disc tool. Furthermore, disc forces and soil disturbed area were highly significant (p<0.05) for higher speed towards depth. It was concluded that the fuzzy model may be introduced for predicting the disc forces and soil disturbance area during the disc tillage tool operation with high accuracy. [ABSTRACT FROM AUTHOR]

Grain sieve losses are important parameters to judge the performance of cleaning shoes in combine harvesters. To keep grain sieve loss within acceptable limits, an impact-type piezoelectric sensor was developed for real-time monitoring. Rice grain and short straw particle models were established according to their physical properties, and discrete element method (DEM) simulations were carried out to understand their collision behaviour with the sensor. The influence of grain shape, straw length and impact angle on variations of the maximum normal contact force and force rise-time were analysed in detail. Differences in normal collision force, and force rise-time occurred which lead to corresponding differences in signal frequency and voltage amplitude. A signal processing circuit, which mainly consisted of a band-pass filter circuit and a voltage comparator circuit, was designed to discriminate for full grains. Field tests results indicated that measurement errors recorded by the sensor and checked against manually measurements were <4.48%.Highlights· Collision behaviour of rice grain and straw with the sensor was studied utilizing DEM simulations. · A signal processing circuit was designed to discriminate for rice grains. · Field tests results indicated that measurement errors of the developed sensor were <4.48%. [ABSTRACT FROM AUTHOR]

To ensure the stable driving of tracked robots in a complex farmland environment, an adaptive backstepping control method for tracked robots was proposed based on real-time slip parameter estimation. According to the kinematics analysis method, the kinematic model of the tracked robot was established, and then, its pose error differential equation was further obtained. On this basis, the trajectory tracking controller of the tracked robot was designed based on the backstepping control theory. Subsequently, according to the trajectory tracking error of the tracked robot, the back propagation neural network (BPNN) was used to adaptively adjust the control parameters in the backstepping controller, and the inputs of the BPNN are the trajectory tracking error xe, ye, θe. After that, the soft-switching sliding mode observer (SSMO) was designed to identify the slip parameters during the running of the tracked robot. And then the parameters were compensated into the adaptive backstepping controller to reduce the trajectory tracking error. The simulation results show that the proposed adaptive backstepping control method with SSMO can improve the accuracy of the trajectory tracking control of the tracked robot. Additionally, the designed SSMO can accurately estimate the slip parameters. [ABSTRACT FROM AUTHOR]

Grain separation losses is a key parameter to weigh the performance of combine harvesters, and also a dominant factor for automatically adjusting their major working parameters. The traditional separation losses monitoring method mainly rely on manual efforts, which require a high labor intensity. With recent advancements in sensor technology, electronics and computational processing power, this paper presents an indirect method for monitoring grain separation losses in tangential-axial combine harvesters in real-time. Firstly, we developed a mathematical monitoring model based on detailed comparative data analysis of different feeding quantities. Then, we developed a grain impact piezoelectric sensor utilizing a YT-5 piezoelectric ceramic as the sensing element, and a signal process circuit designed according to differences in voltage amplitude and rise time of collision signals. To improve the sensor performance, theoretical analysis was performed from a structural vibration point of view, and the optimal sensor structural has been selected. Grain collide experiments have shown that the sensor performance was greatly improved. Finally, we installed the sensor on a tangential-longitudinal axial combine harvester, and grain separation losses monitoring experiments were carried out in North China, which results have shown that the monitoring method was feasible, and the biggest measurement relative error was 4.63% when harvesting rice. [ABSTRACT FROM AUTHOR]

The performance of a vacuum-cylinder seeder for the precision sowing of rape seeds was investigated. For releasing seeds from nozzles smoothly, a positive differential pressure was applied to the seed. The forces acting on the seeds in free flight were calculated using the computational fluid dynamics (CFD) software Fluent. Using the differential equation for seed motion, seeds falling trajectories using different working parameters were numerically determined. A high-speed camera system mounted on a laboratory seeder test-rig was used to record the motion of seeds. A mean shift algorithm for tracking seeds was used. The horizontal displacement x and the fall time t f of seeds predicted by the numerical analysis and measured by the high-speed camera system were compared. The results indicated that the relative errors of x and t f were <5.5% and 6.5%, respectively, indicating good agreement. Based on the analysis of seeds falling trajectories, it was found that the variations of positive differential pressure Δp and release angle θ had significant effects on seeding uniformity. In order to analyse their effects on horizontal displacement, a coefficient of positive differential pressure variation χ p and coefficient of sowing angle variation χ θ were proposed and their values calculated. Calculations indicated that the optimum levels for Δp and θ for the precision seeding of rape seeds were in the range of 1–2kPa and from −10 to 0°, respectively. Experiments were carried out on the vacuum-cylinder precision seeder test-rig and the results showed that the average seed spacing interval error reached the minimum at Δp =1.5kPa and θ =−5° and that the error increased almost linearly with increasing of cylinder rotational speed. [Copyright &y& Elsevier]