Analysis Of Mechanisms And Development Of Control System For A Novel 5-DOF Parallel Machine Tool

Parallel Machine Tool (PMT), a new-style machine tool, complements the traditional NC machine tool perfectly. With the development of the PMT technology, the potential of the lower-mobility PMT will be revealed. The 5-UPS/PRPU 5-DOF PMT is based on the novel lower-mobility parallel mechanism of 5-UPS-X series (Patent No. 1371786) invented by the project team. This paper focuses on the research of basic theory and key techniques of the PMT. The main contributions are as follows: A novel 5-UPS/PRPU 5-DOF parallel mechanism is put forward, which can perform three translational DOF and two rotational DOF. By using kinematic screw theory and D-H parameter method, the rotational constraint along the vertical axis of the moving platform is confirmed by the PRPU limb. The computational relationship between the joint variables of the PRPU limb and the parameters of the pose of the moving platform is both concise and analytical. The scheme of measuring the pose of the moving platform in real time by means of the PRPU limb is brought forward. The inverse solution of the position and the forward and inverse solution of the velocity are analyzed. The kinematic inverse solution equation and the velocity equation are deduced. The 5× 5 Jacobian matrix of the PMT is established to prove that the velocity mapping between the joint space and the workspace of the PMT is one-to-one. The kinematic performances of the PMT, such as workspace, dexterity and singularity, etc, are described in brief. The static force acted on the moving platform is analyzed. The static equilibrium equation is established and the force transfer matrix is obtained. The mapping relationship among the 6-dimension external load acted on the moving platform, five driving force and the constraining couple of the middle limb. The kinematics of the main parts is analyzed and the velocity mapping relationships between the parts and the driving axis are established. The exterior force load and the equivalent driving force are educed. Finally the dynamics analytic equation about the relation between the driving force and the motional parameters of the PMT is obtained by using virtual work theory. The "embedded NC" control system with parallel double-CPU is developed for the PMT. Open architecture composed of PC and PMAC is adopted for the system hardware. The control software, based on Windows Operating System, is designed with the functional modularization. The basic control functions of PMT are realized. The algorithms for motion control are discussed in detail, such as coarse interpolation of the cutter location, the mapping between transforming the cutter location data to the length of driving axis, velocity control of the driving axis and pose measuring method of the cutter. The prototype of the novel 5 DOF PMT is developed. The debugging and machining experiments are performed. The better moving stability, better maneuverability, less noise, lower vibration, etc, are shown in the operation of the PMT. The curved surface can be processed in the PMT. Theoretical analysis is proved to be correct and the expectant goal is attained by and large.