Research Of Controllable Damper For PKM Joint

PKM is a kind of new generation machine tools which is combined with modern robot technology and modern CNC technology.This new tool completely broken the traditional concept of machine tool structure,abandoned the fixed guide way of the tool-oriented style.It is drived by multi-bar parallel closed-loop mechanism,It should have good dynamic characteristics, high accuracy and stiffness advantages in theory. But most PKM developed in China have the problems of low dynamic stiffness and low precision.The reason is the joints’ contact stiffness and accuracy has an important influence on the machine performance.Ball joints and hooke joint has the problem of low contact stiffness,low damping and exist gap between joint surface.The error broght by them will directly affect the precision machine tools as they are important connectors in parallel mechanism.Therefore, increasing joint stiffness and damping of PKM is one of the approaches to improve the dynamic stiffness and precision of such machine tools. Change the damping of joints can improve the anti-vibration capabilities of PKM.So the controllable Magnetorheological dampers used in PMT joint for control the damping of machines joint can improve its precision.Based on the above ideas,some research is done on the model of3-TPS PKM virtual prototype which is developed by Northeastern University, The main work including the following aspects:(1) Introduced the related content of parallel machine tools and Magnetorheological Technology.(2) Dynamic analysis of3-TPS Parallel Machine rigid-flexible coupling model based on ADAMS,identified the key joint position which affect its dynamic performance.(3) Get the damper design parameters through research in the vibration conditions of installed controllable damper in machine tool joints during machining process.(4) Structural design and magnetic circuit analysis for MR damper used in rotational joints of PKM.The above study suggests that, it can improve the dynamic performance through install damper in the joints of PKM.It can also restrain vibration phenomenon during machining process.It gives the design process of MR damper and establishes the foundation for further optimization of the machine.