Optimal Design Of Backhoe Hydraulic Excavator Working Device Based On Work Efficiency

Backhoe Bucket hydraulic excavator is a kind of complex hydraulic mechatronics machine, also a symbolic product in engineering machinery. It plays important roles in a lot of areas, such as defense industries, civil construction, road and bridge construction and energy construction. Working device in backhoe bucket hydraulic excavator directly force to objects, and it influence the digging performance greatly.Recently, lots of companies and research units put many resources in design and development, the performances of products improved a lot. But, there are still some problems as inefficiency and insufficient digging force. The method of optimal design can improve performances and solve the problem more efficiently.A synchronous test platform is built to test and collect the pressures of the three hydraulic cylinders in working device of backhoe bucket hydraulic excavator and the angular displacement of mechanisms in four typical situations. The connection of pressures of three hydraulic cylinders and resultant of digging forces is analyzed by fitting of data. Based on this, the pressure data of two overseas hydraulic excavators are got by using kinematic and dynamic models of hydraulic excavators. After, the influence of the dimension of working device to the pressures of three cylinders is got comparing the pressure data of the three types. The optimization mathematical model is set up, and the optimization to the working device of hydraulic excavator is solved and the results of dimensions are got by using genetic algorithm.Through calculating the work efficiency of the types optimized before and after, the theoretical work efficiency of optimized type is improved by 3.54%. The result proves the optimal design is correct, and provides to the companies the references of design for working device.The contents and results of the study are listed below:(1) Based on the digging characteristics of hydraulic excavators, the kinematic, dynamic modal and calculating model of digging resistances are set up. And the transformations between joint space and pose space, between drive space and joint space of working device are got. This provides theoretical basis for the calculating of hydraulic cylinder pressure and optimal design of working device.(2) A synchronous test platform is built to test and collect the pressures of the three hydraulic cylinders in working device of backhoe bucket hydraulic excavator and the angular displacement of mechanisms. A domestic hydraulic excavator digs several times in four typical situations. The relation of pressure and resultant of digging resistance is obtained by conversion, fitting of collected data. Based on the kinematic, dynamic modal and calculating model of digging resistances, the pressures of two overseas hydraulic excavators are obtained and compared with that of the domestic hydraulic excavator.(3) Several commonly used optimal design methods are introduced, especially the genetic algorithm adapted in the study. The study analyses the design variables, constraint condition and object function, sets up an optimal mathematical model, and adapts Matlab language to write programs in order to obtain the optimized parameters of working device.(4) The digging process of hydraulic excavator is analyzed, and the velocities of boom cylinder, arm cylinder and bucker cylinder are calculated. Based on these, the theoretical efficiencies of optimized before and after type are calculated. The result is the theoretical efficiency of the optimized type improves by 3.54%. The result proves optimal design is feasible and correct, and provides references to the design of the same type hydraulic excavators.