Design And Analysis Of 5-DOF Parallel Driving Grinding Manipulator

The iron and steel industry is one of the process industries with a high degree of automation,and industrial robots have become the mainstream configuration of iron and steel production lines in Europe and the United States.In recent years,some iron and steel enterprises in China have also begun to apply industrial robots in key processes such as steelmaking and rolling.The special steel bar finishing operation includes unbundling,bundling,grinding,labeling,weighing and other working procedures,which has the characteristics of frequent transfer,bad environment,heavy labor and high safety risk,so there is an urgent need to promote the robotization and unmanned work posts.in order to meet the safety,high quality and efficient production needs of special steel enterprises.As a key process of special steel finishing site,grinding can eliminate product defects and improve the added value of products.Most of the existing grinding and polishing equipment adopts series mechanism,which is mainly suitable for flexible grinding and polishing tasks with small amount of metal removal,which restricts the intelligent grinding of special steel to the direction of high precision and large load.In this paper,according to the grinding mode of artificial arms in the finishing field,a five-degree-offreedom parallel driving grinding manipulator imitating human upper limb is designed,and its mechanism is studied deeply.In this thesis,the morphology characteristics of micro-cracks on the surface of special steel bar are analyzed,and the degree of freedom characteristics of grinding manipulator are determined according to the requirements of finishing process,that is,three-dimensional movement and two-dimensional rotation.By studying the topological structure and motion mode of human arms in the process of grinding,the motion characteristics of artificial arms are analyzed.Based on the principle of bionics,the actuator and driving mechanism of the grinding manipulator imitating the structure of the human upper limb are designed,and two kinds of driving mechanisms that meet the requirements of the grinding process are synthesized.The azimuth feature sets of all mechanisms are analyzed systematically,and the motion input points and corresponding motion input characteristics of the actuator are determined.The coupling characteristics of the grinding manipulator are improved by setting a coaxial rotation pair.Based on the azimuth characteristic equation,the motion matching of the driving mechanism and the actuator is studied,and the motion matching relationship between each branch of the driving mechanism and the actuator and the required topological structure conditions are determined.The configuration scheme of the 5-DOF parallel driving grinding manipulator and the principle prototype of the grinding robot are designed.The position inverse solution model of the grinding manipulator is established by using the homogeneous transformation method.The reachable workspace of the mechanism is drawn in CAD software based on variational geometry method.The complex equation of the first driving branch is established,the mapping matrix of its joint and task space is solved,the kinematic loop vector equation of the second driving branch is derived,and the Jacobian matrix of the second driving branch is obtained.By analyzing the transformation relationship between the local coordinate systems of the actuator and constructing the matrix,the full Jacobian matrix of the grinding manipulator is obtained.The forward position solution model of the mechanism is established based on Newton iterative method,and the correctness of the kinematics model is verified by simulation.By defining the global position sensitivity coefficient index of the mechanism,a set of parameterized performance graph is drawn,and the influence of the resolution of the driving system on the position resolution of the mechanism under specific working conditions is analyzed systematically.Based on the mechanical analysis of the grinding manipulator,the static analysis process between the first driving branch and the actuator is simplified by defining the miscut transformation matrix,and the mapping relationship between the driving force and the output force of the grinding manipulator in the static equilibrium state is solved.Based on the analysis of the velocity and acceleration of the centroid of each branch chain of the driving mechanism and the actuator,the dynamic model of the grinding manipulator is established.The local kinematics performance of the grinding manipulator is evaluated by using the dimensionless Jacobian matrix.Considering the coupling effect between the driving mechanism and the actuator and the characteristics of the high-dimensional parameter design space,a multi-branch collaborative optimization strategy is proposed.The optimal design models of driving mechanism and actuator are established respectively,and four design indexes are put forward according to the characteristics of special steel bar grinding task,including workspace volume index,global flexibility index,global stiffness index and matching index.The performance graph of the above indexes is drawn,the relationship between each index and different sizes is analyzed,the high-quality dimensional domain of each driving branch and actuator is obtained,and the global optimal dimensions of the grinding manipulator are calculated.The research content of this paper provides a theoretical basis for the development and application of the grinding manipulator,and has a certain significance for expanding the application range of parallel driving mechanism and promoting the intelligent development of metallurgical industry.