| With the rapid development of economic construction in our country,there is an increasing demand on major engineering technical equipment.As a kind of major equipment in the engineering machinery,the face-shovel hydraulic excavators have outstanding advantages in the face of complex geology and bad working conditions.Especially,they can play an important role in the large open-pit mining,water conservancy construction,national defense construction and other projects.However,due to the monopoly of foreign intellectual property rights and the immature domestic research,the face-shovel excavators on the domestic market are single.The working device is the most important part for the face-shovel hydraulic excavator to complete various tasks.Its innovative design plays an indelible role in improving the performance of the whole machine.Therefore,the configuration synthesis of the face-shovel hydraulic excavators’ working device is studied in this paper,and then a new configuration is selected to carry out the performance analysis and optimization design.The main research contents are as follows:Based on the superposition method,the partial selection principles of the working device configuration of the face-shovel hydraulic excavators are taken as the constraint condition,and on the basis of the degree of freedom formula of the plane mechanisms,the configuration synthesis of the working device of the 12-bar face-shovel hydraulic excavators is carried out by adding the II-level basic bar group.According to the characteristics that the two components of the basic bar group have two,three or four joints,a series of 12-bar working device configurations satisfying the freedom requirements are obtained by integrating them in five situations.The improved superposition method simplifies the process of configuration synthesis and greatly reduces the workload of excellent configuration selection after the completion of configuration synthesis.Finally,a new configuration is selected from the obtained configurations,and its degree of freedom is verified according to its multi-loop coupling structure characteristics.According to the movement property of face-shovel hydraulic excavator working device,its structure is divided into two parts: the serial part composed of the frame,the arm,the bucket rod,the bucket and the part of three hydraulic cylinders.The analytical expression between the three joints’ angles and the position and orientation of bucket of the serial part is established by using the D-H method,and according to the geometric relationships between the three hydraulic cylinders and the serial part,the relationship between the lengths of the three hydraulic cylinders and the three joints’ angles of the serial part is deduced,and then of the positive kinematics analysis of the new configuration is completed.In addition,the main operation parameters of face-shovel hydraulic excavator and the kinematic performances of the new configuration in main working conditions are analyzed.The analytical expressions of the theoretical excavating force of the hydraulic cylinders and the whole machine are derived by the torque balance method,and the main forces of the new configuration are analyzed under the main working conditions.On the basis of kinematics analysis and digging force,the dimensional parameters among the main articulated points on the working device and the lengths of the three hydraulic cylinders as the decision variables,set up five optimization objective functions are built by considering the kinematics performance and digging force of the new configuration.According to the structure characteristics of the working device and the experience formula about the joints’ angles,the constraint conditions are determined,and the reference value ranges of the dimension parameters of face-shovel hydraulic excavators weighing more than 100 tons are given through the analogy method and empirical formula method.And then the multi-objective optimization design of the working device is carried out by using RW algorithm,and the optimized dimensional parameters are obtained.Finally,according to the optimization results,a three-dimensional model of the new configuration of the working device is established,and the kinematics simulation analysis is carried out based on Adams software,and the comparison with the working device before optimization was made.The results show that the kinematic performances of the working device after optimization have been improved under the working conditions of boom lifting,bucket rod digging and horizontal pushing and pressing. |
