| Backhoe loader consist of the excavating attachment—Backhoe and the loading attachment—loader, it can work as the excavator and the loader. Backhoe loader is used widely in the field of farm irrigation works, industry and civilian structure, urban construction, gardens, highway maintenance, ports, oil field, electric power construction, etc. When installed various work appurtenances using the swift-replacing attachments, it will have a wider use. Along with the advancing economy, the change of engineering techniques and engineering objects, the market prospect of backhoe loader at home is very broadness. Therefore, many construction manufacturers have advanced their backhoe loader. Due to the limitation of energy, experience and research put to the backhoe loader fields, research on the system characteristic is superficial, the theory and experience to be consulted is lacking, complete machine technical level has much difference with the international advanced level, especially in the research of dynamic characteristic of the backhoe loaders' hydraulic slewing system.The characteristic of hydraulic slewing system in the excavating work attachment is the key factor to machine using stationarity and hydraulic impact. And the hydraulic system cushioning attachment has a great effect on kinematics characteristic and dynamics characteristic of the slewing system. Study on characteristic effects that cushioning attachment have on hydraulic slewing system is far from the international advanced technical levels, relational articles about that have not appeared in home. In practice, if the design for slewing hydraulic system of backhoe loader is unreasonable, the arm of slewing work attachment will be broken, and the hydraulic components will be damaged. In this paper, simulation analysis for static characteristic and dynamic characteristic of slewing hydraulic system is executed, and the analysis lays theory foundation for designing of slewing hydraulic system in backhoe loader's excavating attachment.According to geometrical relation and kinematics knowledge, the slewing kinematics mathematical model is built, and then program and calculation is executed by the software MATLAB. The right oil cylinder and left oil cylinder's kinematic relation in the slewing mechanisms is analyzed, and the relation of angular displacement and cylinder stroke is also analyzed. Because of the existence of discontinuity point, the stretching direction of one cylinder will be changed when moving to the point. At the point, piston rod has the max stroke. Then the stroke begin to decrease restricted by the mechanism. Because the flow direction of hydraulic oil is unchanged, all hydraulic oil enters into the small chamber, which may cause the slewing speed of working attachment growing fast. At the same time, large angular acceleration will cause impact in the hydraulic system. Through the simulation analysis of kinematics of slewing mechanism, the basis for dynamitic characteristics analysis of slewing hydraulic system is made.In this paper, dynamic model of slewing hydraulic system of excavating working attachment is established by means of power bond graph. According to the actual working condition of slewing hydraulic system, power bond graphs of two states are obtained as follows: 1. cylinder dynamic model with buffering attachment; 2. cylinder dynamic model with relief buffering. The equation deduced by power bond graph has simple structure, and can be checked and computed by computer easier. Certainly, power bond graph may be used to deduce the tradition transfer function or state variable equation too, which is not recommended because of having no precedence. The equation deduced in the paper can be used to simulate and compute the system directly. Considering model structured design, the whole system is divided into several submodel for simplification and call convenience. According to the simulation model graph of Simulink, the actual parameters of model machine are substituted into the block to simulate and compute. A...
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