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The identification and positioning of a master is essential for the master-slave cooperative operation of agricultural machinery. This study aimed to develop an agricultural vehicle dynamic identification and tracking method for agricultural master-slave follow-up operation using improved YOLO v4 and binocular positioning. The regular pruning algorithm was used to trim the original YOLO v4 channel to achieve a fast and accurate identification of master vehicle. The principle of binocular vision positioning was used to calculate the position of the master. The method (IYO-BPO) proposed in this study fused target detection and binocular vision positioning together, which was used to identify and track the master vehicle in real time. To evaluate the performance of the developed method, RTK-GPS and a gyroscope were installed on the master vehicle to obtain the reference position and heading angle. Identification and tracking experiments of both the linear and S-shaped movement of the master were conducted. The RMS errors were 0.067 m, 0.203 m, and 2.602° in terms of the longitudinal, lateral, and heading angle deviation, respectively, when the master moved along a straight line. The results show that the master vehicle could be identified and tracked by the IYO-BPO correctly and effectively.

The hydro-mechanical continuously variable transmission (HMCVT) is a critical component of the power transmission system in a tractor. However, the complexity of the operating conditions imposes high requirements on the transmission characteristics. To improve the powerful performance and economy of HMCVTs and satisfy the operational demands of high-powered tractors, a new optimization design method for the characteristic parameters of an HMCVT is proposed. First, the characteristics of an HMCVT are modeled, and the influence of the structural parameters on the transmission characteristics is analyzed. Then, HMCVT performance evaluation indexes are formulated. In accordance with the speed regulation of system, power performance, and economy characteristics, a multi-objective optimization mathematical model is established, and an improved fast non-dominated sorting genetic algorithm (INSGA-II) is designed. The introduction of a normal distribution crossover operator (NDX) and an improved adaptive adjustment mutation operator not only ensures the population diversity but also improves the Pareto solution convergence properties during the process of genetic evolution. The superiority of INSGA-II is verified by comparison with a traditional multi-objective genetic algorithm. Finally, the optimization results show that the torque ratio is increased by approximately 2.81%, 14.32%, 2.31%, and 15.07% in HM1, HM2, HM3, and HM4 respectively. The transmission efficiency is increased by approximately 3.48% and 1.97% in HM1 (HM3) and HM2 (HM4). Also, INSGA-II finds the optimal solution with a faster speed and shorter optimization time than MULGA. This research can serve as a reference for the design and optimization of HMCVTs for high-powered tractors.

Seed maize Zea mays (corn in the USA) have a very high value and thus it is crucial to avoid problems of high grain damage and low removal rates that can occur during the peeling of ears to remove the bracts. A mechanical model of the dynamic process of seed maize ear peeling was established using a finite element explicit dynamics simulation of the peeling process based on the Hertz theory and a mechanical analysis of the collisions and friction between the ears and the rollers during the peeling process was carried out. The main factors that affect the magnitude of the collision force and friction force were obtained. Based on the results of the modelling, peeling rollers consisting of four rubber-cast iron mixed rollers with different patterns were designed. The rationality of the mechanical model was verified and, based on the designed peeling roller; a test rig was built to carry out high-speed video tests. The whole peeling process of seed maize ear using the rollers was observed, and the test results showed that the redesigned roller had a peeling rate of 93% and a grain damage rate of 1.87%. The performance of the peeling device designed in this study was significantly better than that of the standard peeling device. This research provides a theoretical basis for various types of seed maize peeling operations.

The performance of maize picking mechanisms directly affects harvesting quality and working efficiency. Numerous field experiments have been carried out to improving picking performance, but they have been restricted by factors such as high cost, the varieties of maize used and variable harvesting periods. Virtual simulation analysis was proposed as a replacement for field experiments to provide an accurate reference for optimising the picking mechanism. A finite element model of a maize plant and picking mechanism was established based on the experimental results and related data from the research literature. Its accuracy and reasonableness was verified by comparing the simulation results to the data obtained by an experiment using a high-speed camera. The coupling effect of the three main factors (rotational speed of the picking roller, edge angle of the picking board and feed-in speed) were investigated using simulations. The results revealed that the medium rotational speed for the picking roller reduced the damage incurred by maize during the picking process, while ensuring good harvesting efficiency and picking board edge angles in the range 13°–15° were optimal. Although reducing the feed-in speed could reduce damage to the maize, this was not the most prominent factor. Besides, the appropriate rotational speed of the picking roller to guarantee optimal working efficiency was investigated using power consumption experiments. The results of this study should be useful as a reference for the design, development, and optimisation of the maize picking mechanism.

HighlightsA knowledge-based rapid design system for combine chassis is proposed.Object-oriented knowledge representation uniformly describes the multi-source heterogeneous design knowledge.Multivariate linear regression analysis ratiocinates further unknown design principles behind existing products.Abstract. In the design of agricultural machinery, the lack of systematic and structured knowledge utilization systems results in low development efficiency and poor reusability of design knowledge. This study considers the design of a combine chassis and focuses on the application of knowledge-based rapid design to agricultural machinery. As a typical sophisticated agricultural machine, combines have a complicated design that requires the integration of multiple disciplines according to the crop types, production areas, and ability of the designers. Hence, a knowledge-based design system for a wheeled combine chassis is proposed. By integrating object-oriented technology with a mixed reasoning strategy, multi-source heterogeneous design knowledge can be applied in completing the chassis design task. To date, there are more than 2000 design ideas and 350 parameter models in the knowledge database. In addition, tacit design knowledge acquired by a knowledge discovery method can be employed to perfect the design and improve the reliability of the product. The design of a combine chassis demonstrates that the knowledge-based rapid design of agricultural machinery is completely feasible, and the design system significantly reduces the design workload, shortens the development cycle, and improves design efficiency and knowledge utilization. Keywords: Combine chassis, Knowledge-based design system, Knowledge-based engineering, Rapid design.

Background: Agricultural machinery equipment is the core element of advanced agricultural productivity. The operation system of agricultural machinery equipment involves machine-human-environment-society interactions. Limited by the production mode, operation mode, etc., the design and development, manufacturing, operation and maintenance control, recycling and other links of agricultural machinery equipment are still independent of each other. The massive information in the agricultural production process has not been fully utilized, so there are some outstanding problems such as low operating performance, low production efficiency, and poor integration of agricultural machinery and agronomy. Methods: Focusing on the agricultural production process, this paper proposes the construction method for a high-horsepower tractor digital twin, and expounds on its operation mechanism. Taking high-horsepower tractor ploughing operation as an example, by deploying tractors, central servers, and an Internet of Things (IoT) platform, we developed a digital twin service platform for the agricultural production system of intelligent agricultural machinery equipment and built a tractor digital twin to verify the effectiveness of the proposed method. Results: The accuracy rate of the tractor ploughing quality prediction service based on this platform is 96.65%. Under open-loop control, the number of excellent, good, medium and poor sets of the tractor ploughing quality are 153, 955, 1470, and 1422, respectively. After adopting closed-loop control, the number of excellent and good sets increased by 378, and 821, respectively, and the number of medium and poor groups decreases by 119 and 1080, respectively. Through this platform, the operation quality can be effectively and accurately predicted and improved, which verifies the effectiveness of the proposed construction method of high-horsepower tractor digital twin. Conclusions: This research provides a method framework for the construction of the digital twin of tractor operation and maintenance control processes, and provides strong support for the vigorous development of intelligent agriculture.

Tractor rollover is a long-term, worldwide problem that has not yet a fundamental solution. However, active steering has become a mature technology in the automobile industry, and it is widely used for anti-skidding and lane-keeping. In this study, straight-line dynamic and steering dynamic models were established to describe the dynamic behaviour of the tractor rollover process. An energy-based tractor stability indicator was derived and used to determine the steering angle to maintain stability. Random road surface classes were then generated to simulate the surfaces of actual farm roads, which are irregular and complex. The results of simulations in this study revealed that the proposed stability indicator is more accurate and effective than previous indicators. This control strategy prevents rollover within a certain range by correcting the steering angle when the indicator exceeds a threshold. Furthermore, the results of the investigation of the effectiveness of active steering under different circumstance revealed that active steering is very effective when the tractor travelling on a medium-grade road surface. What is more, a slope angle of 15° and travel speed of 6 m s−1 was the limit of tractor stability when the active steering control is engaged. For tractors operating on roads with high roughness, at speeds greater than 6 m s−1, or on a slope angle >15°, active steering is not reliable for preventing tractor rollover. The approach developed in this study provides a reference for operators and a method for solving the problem of tractor rollover.

With the rapid development of the modern vehicle industry, the automated control of new vehicles is in increasing demand. However, traditional course control has been unable to meet the actual needs of such demand. To solve this problem, more precise path-tracking control technologies have attracted increased attention. This paper presents a new algorithm based on the latitude and longitude information, as well as a dynamic trigonometric function, to improve the accuracy of position deviation. First, the algorithm takes the course deviation and adjustment time as the optimization objectives and the given path and speed as the constraints. The controller continuously adjusts the output through a cyclic “adjustment and detection” process. Second, through an integration of the steering, positioning, and speed control systems, an experimental platform of a path-tracking control system based on the National Instruments (NI) myRIO controller and LabVIEW was developed. In addition, path-tracking experiments were carried out along a linear path, while changing lanes, and on a curved path. When comparing and analyzing the experimental results, it can be seen that the average deviation in lateral displacement along the linear and curved paths was 0.32 and −0.8 cm, and the standard deviation of the lateral displacement was 2.65 and 2.39 cm, respectively. When changing lanes, the total adjustment time for the vehicle close to the target line to reach stability was about 1.5 s. Finally, the experimental results indicate that the new algorithm achieves good stability and high control accuracy, and can overcome directional and positional errors caused by road interference while driving, meeting the precision requirements of automated vehicle control. Keywords: Path-tracking control, Trigonometric function, NI myRIO controller, LabVIEW

A new rearrangement of isatin-derived N,N′-cyclic azomethine imines to afford intermediate 3-hydroxy-1H-pyrazole -substituted oxindole was found, and then Michael addition of them to a vinyl bisphosphonate ester provided 3,3-disubstituted oxindole-fused pyrazolidone derivatives containing bisphosphonates in the presence of the readily available DMAP. This transformation is particularly attractive due to features such as unexpected rearrangement, mild conditions, atom economy, the ready availability of the starting materials.

Existing agricultural tractor path tracking methods rarely consider tracking accuracy and driving stability simultaneously. To solve this problem, a novel path tracking method of tractor is proposed in this paper. The method contains two layers of controllers. The first layer is the desired front wheel steering angle controller based on path prediction, and the desired yaw rate of tractor can be obtained by reference model expression. The second layer is the front wheel steering angle compensation controller based on improved second-order sliding mode (SOSMC) to improve tractor driving stability. The innovation of SOSMC is a combination of nonlinear integral sliding mode (NISM) surface and improved Super-Twisting algorithm, which can not only improve the rate of the control system to the sliding mode surface, but also suppress chattering. To verify the performance of SOSMC, the simulations are carried out on three paths at the constant speed of 10 km/h through Matlab/Simulink and Carsim. Three working paths including arched, pear-shape and lemniscate are constructed in Carsim. The results show that the control effect under three controllers is better than no control. Compared with no control, the maximum value and root mean square (RMS) of lateral error under SOSMC are reduced by 13.09% and 25.07% on average in three paths, and that of yaw rate are decreased 53.29% and 54.64%. The tracking accuracy of SOSMC is the best of three controllers, and that of NISMC is better than SMC. Compared with NISMC, the maximum value and RMS of yaw rate under SOSMC are reduced by 37.74% and 43.62% on average. The yaw rate, front wheel steering angle compensation value and chattering amplitude of front wheel steering angle under SOSMC are significantly smaller than those of SMC and NISMC. In summary, the novel path tracking method can simultaneously satisfy the accuracy and stability of the tractor when it tracks the field working path.

In the process of field operation management, determining how to accurately realize crop row identification and path tracking control is an essential part of tractor automatic navigation. According to the linear operation in the process of cotton field management, the tractor path tracking control system was designed based on binocular vision and the pure pursuit model. A new crop row detection method based on the Census transform and the PID control algorithm with dead zone were used. First, the upper computer software was developed by C++ with the functions of parameter setting and image acquisition and processing. Second, an automatic steering controller was developed based on microprocessor MC9S12XS128 of Freescale. The control program was developed based on modular design using CodeWarrior during development of the PID-based automatic steering control strategy. Finally, a field experiment platform of tractor path tracking control was built, and field experiments under the actual cotton were conducted. The optimal visibility distance was determined by several previous experiments. When the tractor tracks the path with the optimal visibility distance in the growth environment of actual cotton crops, the mean absolute deviation of course angle was 0.95°, and the standard deviation was 1.26°; the mean absolute deviation of lateral position was 4.00 cm, and the standard deviation was 4.97 cm; the mean absolute deviation of front wheel angle was 2.99°, and the standard deviation was 3.67°. The experimental results show that (1) the crop row detection method based on Census transform can identify the crop line and plan the navigation path well, and (2) the tractor path tracking control system based on binocular vision has good stability and high control precision; thus, the control system can realize the automatic path tracking control of cotton line operation and meets the agricultural requirements of cotton field operation management. Keywords: Binocular vision, Census transform, Pure pursuit model, Path tracking, Tractor

SVM (Support Vector Machine) is a modern Data-Mining method. It is good at processing large amounts of data and has high accuracy. In this paper, an indoor 60 GHz millimeter wave channel model based on PSO (Particle Swarm Optimization) optimized SVM is established. The prediction results of GA (Genetic Algorithm) and Grid-Search optimized SVM are compared. The simulation results show the PSO optimized SVM model has high prediction accuracy

A concise, atom-economic, and highly regioselective synthetic strategy for the construction of several dinitrogen-fused heterocycles bearing bisphosphonates by 1,3-dipolar cycloaddition reaction of azomethine imines with tetraethyl vinylidene-1,1-bisphosphonate in the presence of CuI in toluene media has been developed. The targeted compounds were obtained in good yields and with excellent regioselectivity. This method for the synthesis of gem-bisphosphonates (BPs) is particularly attractive due to features such as low cost, mild conditions, atom economy, high stereoselectivity, and potential biological activity of the product.

In order to enable the automatic navigation agricultural machinery effectively avoid the local static small obstacles in the field operation process, obstacle avoidance path planning method is studied for agricultural machinery in the case of known environmental information in this paper. Firstly, the obstacle avoidance path for a single small obstacle is proposed as the path consisting of three circular arcs, which solves the problem that agricultural machine holds minimum turning radius and is difficult to achieve line turning in the driving path. Then, the different situations of many small obstacles in the same driving path are analysed and the obstacle avoidance path planning method for many small obstacles is proposed when the obstacles are on the same driving path and in the relatively far distance. Finally, simulation study is conducted and the result proves that the proposed methods can plan effective path to avoid obstacles for automatic navigation agricultural machinery in complex conditions such as multiple obstacles with relatively far distances. The research works in this paper can provide essential references for obstacle avoidance path planning in other relevant fields.

As a representative type of off-road vehicle, agricultural wheeled tractors are driven under varied and complicated road conditions such as plowed and hilly fields. Active control is the essential technique to solve tractor rollover accidents which have been identified as the most fatal incident along with agricultural mechanization. The aim of this study is to provide active correction of tractor attitude in emergency cases by combing a single-axis momentum flywheel system and active steering system. In this study, the time-varying structural nonlinear vehicle dynamic system and its subsystems are formulated during transitions among tractor states under road stimulation. By exploring the phased mutation mechanism of tractor stability, the corresponding stability criteria are proposed. The coordinated tractor safety control strategy was verified using parametric studies in a simulation and scale-model experiments. The results indicated the effective and robust control of tractor safety regarding the independent and integrated active control systems. The proposed approach is expected to provide a theoretical basis and technical support for advanced driver assistance systems applied to future intelligent agricultural vehicles.

A concise, atom-economic, and highly regio/stereoselective synthetic strategy was developed for the construction of phosphorus- and nitrogen-fused polycyclic skeleton derivatives. The one-pot, two-step, catalyst-free domino condensation/intramolecular cycloaddition reaction of various substituted 2-(vinylphosphoryloxy)benzaldehydes with pyrazolidin-3-one took place at room temperature. Three new bonds (C–C, 2 × C–N) and two new nitrogen and phosphorus heterocycles were simultaneously constructed. The reaction is particularly attractive due to features such as low cost, mild conditions, atom economy, high stereoselectivity, and potential biological activity of the product.

A one-pot, three-component condensation reaction of 8-quinolinol, 2-thiobarbituric acid and isatins or aldehydes in water to give novel barbituroquinoline derivatives for the first time, is described. The reaction is free of catalysts and toxic solvents, operating under mild conditions and allows for ease of product isolation, making it more environmentally friendly and suitable for large-scale operations.

Pyrrolizidine and coumarins both have biological activities, and their molecular skeletons are commonly found in several biomolecules and drug molecules. We have developed a catalyst-free, intramolecular 1,3-dipolar cycloaddition to synthesize phosphadihydrocoumarin-fused pyrrolizidine/pyrrolidine scaffolds with high stereoselectivity.

The viscoelastic surfactant (VES) fracturing fluid is new fracturing system, which is primarily made up of viscoelastic surfactant and some other auxiliaries. The traditional VES fracturing fluid has the obvious advantages in gel breaking, flowing back, carrying sands, etc. However, they are centered largely in the aspects of medium and low temperature system. In this paper, the work is focus on the need for the VES fracturing fluid with high temperature resistance. In the experiment, four kinds of viscoelastic surfactants with hydroxyl were firstly synthesized, which were named C14-1, C16-1, C14-2 and C16-2 respectively. Then the formulation of VES fracturing fluid was determined in accordance with the apparent viscosity of solution, and the formulation was that concentration of C16-2 and NaSal were 2.5% and 1% respectively. It was found that the VES fracturing fluid has excellent effectiveness via testing properties of temperature resistance, shear stability, sand-carrying and gel breaking. When the temperature of system was 144°C, the apparent viscosity of the VES fracturing fluid was 25 mPa s, which could demand the requirements of carrying sands as well as support agents, and it could resist high temperature well. It is also observed that the VES fracturing fluid is the pseudoplastic fluid, which contributes to getting the cracks with excellent negotiability.

In order to improve the precision of the sprayer field operation and reduce the overlapping rate as well as the missing rate during the spray process, an auxiliary navigation system based on Baidu map JavaScript API (application programming interface) was designed to prevent overlapping spray and missing spray. Technologies such as serial communication, GPS (Global Positioning System) positioning, Baidu map API, path planning and geographic information system were integrated in this system. Accordingly, the functions of vehicle positioning, path planning, job navigation, doodle in operated areas, real-time data collection and automatic processing in spray process could be achieved. In order to verify the reliability and stability of the designed navigation system, an experimental platform was developed for auxiliary navigation system based on the self-developed 3WPG-3000 high clearance self-propelled sprayer. In addition, an RTK GPS and a computer were also integrated in this system. Moreover, experiments of AB line navigation and free line navigation were carried out. The results indicated that the overlapping rate of the AB line navigation and the free line navigation as well as the missing rate of them were 2.54%, 0.26% and 4.43%, 0.88% respectively, which meet the needs of sprayer field operation.

Tractor lateral stability is an important factor in the safety of the operator. In view of the different influences of different tractor rear track on the lateral stability of the tractor, this model built a model tractor with adjustable rear track, and studied the influence of different rear track on the lateral stability of the tractor. The results show that the rear track significantly affects the lateral stability of the tractor. With the increase of the rear track, the lateral stability of the tractor increases significantly. At the same time, the rear track increase function does not show a significant correlation with the tractor lateral stability function. Since the excessive rear track increases the tractor manufacturing cost and reduces its flexibility, the choice of the rear track needs to be considered comprehensively. For all factors, choose the most suitable rear track. The research results of this study can provide reference and theoretical guidance for improving the lateral stability of the tractor and how to choose the rear track.