Research On The Digital Design Of The Mounted Plough And Its Key Technology

Ploughing is an essential production course in modern agricultural production. And the mounted plough plays an important role in the cultivation of soil. At present, it is still a long way for the design approach of the mounted plough in China to go before catching up with the advanced world levels. With the fast development of computer technology and with the constant improvement in CAD and CAE software, the digitization in design process has become a basic feature in modern product design. Therefore, the research on the digitization of the mounted plough will become a new research task faced by the researchers of agricultural machines. The adoption of the digitized design technique in designing the mounted plough can raise the level of design and avoid the construction of physical prototype. Moreover, the adoption of the digitized design technique in designing the mounted plough is in favour of shortening design cycle, lowering the design cost, and team work processing.The design model of the mounted plough constructed in this thesis makes digitized product definition of the whole process of the mounted plough design become possible. According to the phases that the mounted plough normally goes through, this model can be divided into conceptual design submodel, structural design submodel and part design submodel, which can cover the whole design process of the mounted plough. The adoption of object orientated modeling method and unified modeling language constructs the grading model of basic object type of the design model of the mounted plough, which displays clearly and effectively all the objects in the design process of the mounted plough. This model is applied in the development of software of the digitized design system of the mounted plough, which proves the validity of the model.This thesis constructs the three-dimensional wholly digitized model to determine the ploughing position of the mounted plough relative to the tractor, the relative positions of other working parts, and to reasonably choose suspension parameters, which can achieve the required operational performance. This model mainly includes population calculating parameter submodel, loading calculating parameter submodel, rising-falling calculating parameter submodel, and performance analysis submodel, which provide the accurate calculating means and the sound theoretical base for the design of the mounted plough. Population calculating parameter submodel can calculate the basic parameters of the mounted plough and define the coordinate array of space vector corresponding to some key points in both the tractor and the mounted plough, which makes the three-dimensional digitization of the mounted plough become possible. According to the condition of rigid body equilibrium in spatial force systems, cultivating loading calculating submodel can calculate the spatial stress of the mounted plough, when the mounted plough is ploughing in the state of static balancing. Based on the multi-rigid-body Cartesian spatial kinematics and the principle of dynamics, rising-falling calculating submodel can establish kinematical equation and dynamics equation in the process of three-dimensional rising-falling of the mounted plough, which can be calculated by the means of ADAMS. On the basis of the calculation results of cultivating loading and rising-falling movement, performance analysis submodel realizes the corresponding performance calculation, which can make all-aspect performance evaluation of the mounted plough. The check calculation is carried out on the new type series plough 1L435 (matching with dongfanghong 802 tractor) and 1L235(matching with tieniu 55 tractor), certified by Jilin provincial science and technology committee. All the technical specifications are within the specified scope, which prove the validity of the model.The roll-over mechanism is an important part for the mounted turn-about plough to complete the left working-station and right working-station reversing at the same time, which is a unity of the combination of mechanical system and hydraulic system. As a result, on account of different types of attachment between headstock and plow stock (pivot turn or rotating turn), and different configuration forms of oil cylinder (horizontal type or vertical type, on the right side of trip shaft or on the left side of trip shaft), this thesis constructs the three-dimensional digitized design model which couples the mechanical system and hydraulic system unfriendly. This model includes the kinematical equation of the mounted turn-about plough, the dynamical equation of the mounted turn-about plough and the hydraulic system equation of the mounted turn-about plough. And dynamic simulation calculation is made by the means of ADAMS. Through the thorough theoretical research and massive simulating calculation, on the basis of this model, the four-step simulation theory of the roll-over mechanism of the mounted turn-about plough is proposed. This theory can solve the following problems: (1) To calculate the initial angle of oil cylinder and the angular velocity of oil cylinder passing over the middle-ground position while oil cylinder is suspending. (2) To calculate the end angle of oil cylinder while oil cylinder is suspending. (3) To calculate the angle of throttle when it begins to work. (4) To determine the whole moving process of the mounted turn-about plough. (5) To analyze the influence of design parameters and different configuration forms on the mounted turn-about plough's passing over the middle-ground position, which provides the reliable theoretical guidance and principle to produce the mounted turn-about plough with excellent performance. By means of four-step simulation theory, this thesis discusses the influence of different amount of flow rate on the angular velocity of oil cylinder passing over the middle-ground position, and calculates the initial angle range of oil cylinder in different configuration forms, while oil cylinder is suspending. Through comparing the simulating results, we jump to the following conclusion: The vertical overturn is better than the horizontal overturn, when the mounted turn-about plough adopts the pivot-turn configuration or the rotating-turn configuration. For the same amount of flow rate, with the same roll-over mechanism and the same centre-of-gravity position, the rotating- turn configuration is better than the pivot-turn configuration. When given the following two kinds of configurations, the simulation curve of the angular velocity of the mounted turn-about plough and the angular acceleration of the mounted turn-about plough, together with the speed of oil cylinder and roll-over temporal change, is presented: vertical roll-over mechanism, rotating turn and center of gravity and oil cylinder to be deployed on the same side of trip shaft; horizontal roll-over mechanism, pivot turn and center of gravity and oil cylinder to be deployed on the different side of trip shaft.A new type of roll-over transposition mechanism designed for the depth wheel of the mounted turn-about plough makes good use of disk cam mechanism and the depth wheel's self weight, which makes the depth wheel realize auto-overturn and orientation in the roll-over process of the mounted turn-about plough. On the basis of the kinematics analysis and based on Newton-Euler equations, the kinematical equation and dynamical equation of the roll-over of the depth wheel are made. The dynamical simulation of the movement of the depth wheel and the stress of the depth wheel in the roll-over process are made by the means of the equations.The roll-over experiment by the means of three-dimensional dynamic behavior determinator for the rotation components proves that the simulation curves based on the four-step simulation theory of the roll-over mechanism agree with the experimenting datum very well. Thus this simulation theory is validated. Based on this determinator, it is proved that the roll-over theory of reversible transposition mechanism designed for the depth wheel is right and the working orientation mechanism is reliable.On the basis of the digitized designing model of the mounted plough and the theoretical research, the digitized designing system software of the mounted plough is developed, which has the intelligent character and integrated character. On the basis of expounding the development strategy, this thesis analyzes the choice of basic software platform, developing language, access methods to the database, and the integration of basic software platform. In this thesis, the"four-level"system and structure is constructed, the functional modules are divided, and the system flow is programmed. This thesis gives a sketch of the use of the software by the example of integrated design. This software adopts the visualized development technology based on Windows operating system, with VB serving as the development tool, and with Microsoft Access 2000 serving as the database support software. This software integrates the instrument software such as AutoCAD 2000, ADAMS 2003 and MATLAB 6.1. This software can simulate experts'decision-making thinking process of"design-evaluation-redesign", in the integrated design process and in the component design process, until the design meets the requirements. This software uses the case based reasoning and rule based reasoning, which can make quick response to the new design and make the performance prediction and quantitative assessment of the output design program, supporting the both top-down and bottom-up bidirectional design process. This software can guide the designers to complete the type selection of the complete machine of the mounted plough and the type selection of the functional unit of the mounted plough, and to complete designing parameters and inspection of the complete machine. Using this software can help the designers design the mounted plough of different configurations and the mounted plough of high performance in a very short period of time, which can both improve the design efficiency to a great extent and lighten designers'labour intensity.