During the design of harvesting machinery chassis, a lot of factors should be considered, such as the standard data, expert experience, design formulas and the components' 3D models.It is very difficult to use and manage so many kinds of design data reasonably.Accordingly, the knowledge base system for design of combine harvester chassis is developed based on KBE in this paper.Based on the comprehensive analysis of structural characteristics and design requirements about harvesting machinery chassis, the design knowledge is divided into two parts as follows: one is case knowledge including machine parts, standard parts and hydraulic components; the other is rule knowledge composed of formulas, parameters and type selection.In consideration of the obvious structure of case knowledge and clear causal relationship of rule knowledge, an objectoriented hybrid knowledge representation method combining production knowledge representation with frame knowledge representation is proposed.According to the knowledge representation method, the attribute labels of structural parameters, performance parameters and concept description are determined, and the storage structures of assembly relationships and 3D models of instance knowledge are designed.Meanwhile, the knowledge tree approach is used to design the storage structure to save the rule knowledge such as formula sheets, parameter tables, rule tables, etc.Then the storage of knowledge is realized with the application of relational database SQL Server 2008.Finally, by using Visual Studio 2008 and ADO, a knowledge base system for rapid design of harvesting machinery chassis is built up.The function modules of user management, casebase management and rule-base management are designed and the user operation functions including the addition, modification, inquiry and deletion of knowledge are developed in this system.Most important of all, the system, which is not only convenient to use and manage the knowledge, but also comprehensive to support the rapid design of harvesting machinery chassis, will shorten the developing time of new products and improve design efficiency.
The hydro-mechanical continuously variable transmission (HMCVT) is the critical component in the transmission system of the high-horsepower tractor. However, different structural layouts have a significant influence on transmission efficiency, especially for the HMCVT with multiple planetary rows. Therefore, the double planetary HMCVT, which, based on efficiency characteristics, was designed in this study, as well as the efficiency distribution area under different loads, were analysed. First, the method of the single planetary row in structure layout is constructed and redefined, revealing the transformation law of transmission in different layouts. Moreover, the different layout efficiencies and output transmission ratios were derived as the theoretical basis for selection. Then, the obtained transmission and efficiency characteristics were selected as the best combination to design the double planetary HMCVT. The theoretical efficiency and hydraulic power shunt characteristics were analysed with the circulating power, and the influence of circulating power on operational efficiency was determined. Finally, the hardware-in-the-loop system of HMCVT was designed. Herein, a new type of variable load efficiency characteristic analysis method is proposed, which treats the engine and transmission as an efficient whole. The variational performance of the efficiency field in hydro-mechanical stages are discussed under full load and variable load. This research provides theoretical support for efficiency improvements in design and analysis of the multi-planetary HMCVT tractor.
According to the requirements of tractor automatic steering hydraulic system, a proportional integrated control valve was designed. Based on the non-linearity of the hydraulic system, the state equation of the integrated proportional control valve that works in the open-center hydraulic steering systems was established. With the establishment of the MATLAB/Simulink models, the static and dynamic performance of the integrated proportional control valve were simulated. Furthermore, the indoor test platform was built on the basis of the proposed test scheme, on which the properties of steady flow, load flow and pressure loss of the integrated proportional control valve were analyzed. The simulation and experimental results show that the valve flow can be better to follow the drive voltage; when the spool opening unchanged, load step change, the simulation and test results of the flow is about 10L/min. The differential pressure relief valve pressure compensation performance is better. Finally, the actual test of the proportional integrated control valve is carried out. The experimental results show that the average deviation of the target tracking is less than 2.192° and the maximum deviation is less than 2.44°. The valve proposed in this study performed well referring to the tracing and quick response characteristics, which meets the requirements of tractor navigation control.
A mathematical model for tractor dynamics was expanded by considering the rotatable tractor front end.The fundamental shortcoming of the simplified model was revealed by the loss of contact of the tire with a rigid horizontal surface in an obstacle-passing case.Further shortcom-ings of the simplified model arise from aspects of the motion and vibration characteristics.The improved model provides a better and more realistic representation of the tire-ground contact condition and is applicable to tractors on lateral slopes.The independent roll motions of the two main tractor parts (the front end and main body) significantly reduce the motions of the tractor and thus increase its stability.Furthermore, the effects of the forward tractor speed and obstacle height were studied for a tractor on a 10° lateral slope.By analyzing the motion amplitude and tire-ground contact condition, the tractor speed and obstacle height parameters associated with danger and risk were evaluated.The results suggest the greater capability of the improved model to predict tractor dynamic response in Phase I overturn.
For now, the research and implementation of dynamic terrain are all based on OpenGL. In order to realize virtual field experiments of agro-machinery in the Vega Prime virtual reality platform, a real-time visualization method of wheel ruts based on class vrGeometry in Vega Prime was proposed. Firstly, the small three-dimensional terrain is established in Multi gen Creator, the 3d terrain models of variable points are redrawn and generated and the terrain models are generated and loaded quickly by using multi threading technology. Then the collision points between wheels and the ground are obtained by collision detection, and Multi-Thread technology is used to search the vertices on the terrain near collision points synchronously and quickly, then the real-time dynamic wheel ruts are produced by modifying coordinates of the vertices and updating the terrain data real-time.
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.
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