Study On A Horizontal CNN Machine Tool Based On Tripod Parallel Universal Joint

The parallel mechanism has a series of advantages, such as, high stiffness, high carrying capacity, excellent dynamic character, quick moving, simple frame etc, which has attracted the comprehensive attention of the international academic and engineering communities. Although the parallel mechanism’s appearance can cover the shortages of the traditional series mechanism, the parallel mechanism itself has lots of drawbacks, like incapacious workplace, movement coupling, low contact stiffness, complex mathematic model, difficult to control and so on, which make the application of parallel mechanism fall into confinement. To improve the foregoing disadvantage efficiently, it’s better to adopt series-parallel structure when designing the structure of mechanisim. In this paper, a novel hybrid mechanism based on the tripod parallel universal wrist machine is proposed and its spatial mechanism theory is detailedly studied.In the kinematic analysis, the inverse kinematics solution is established by means of coordinate conversion. The Jacobian matrix of the tripod parallel universal joint mechanisms is deduced by means of differential and kinematic influence coefficient separately and velocity and acceleration are analyzed. Based on the above, the kinematic simulation is conducted and the relationships of velocity and acceration between the input and output are established. Meanwhile, the velocity and acceleration of parallel bars are analyzed in detail. Then the kinematic model of the hybrid mechanism is deduced.In the dynamic analysis, based on the kinematic analysis, the dynamic state static analytic equation is eatablished. By using the Lagrange equation, the dynamic model is created and the corresponding dynamic simulation is conducted to analyze its dynamic characteristic.In the performance analysis, the workspace is deduced by the method of boundary search. The singularity of the mechanism is analyzed by discriminating the characteristic of the Jacobian matrix. According to introducing Jacobian condition number as evaluating indicator of the performance, the dexterity is studied. The simulation on the performance is conducted to make the analysis procedure visualized.In the drilling experiment of the machine tool, in the Institute of Advanced Manufacturing Technology, Northeastern University, an existing parallel machine grinding machine prototype for an appropriate transformation, the functions carried out drilling to achieve theoretical and experimental research, analysis of performance characteristics of existing machines and to suggest improvements.