Papers by Author: Dong Lai Zhang

Abstract: A new 5-degrees-of-freedom hybrid kinematic machine(HKM) consisting of a 4-degrees-of-freedom PTS-based parallel kinematics platform with center constraint branch and a serial X axis is developed. The will-be-machined workpiece is mounted on the platform and the spindle movement is driven by the X axis. This new HKM is very different from a conventional serial-type machine. Therefore, a special algorithm that can transfer the cutter location data (CL-data) into machine specific NC commands is essential for the applications of the PTS-X based HKM in real machining of the workpiece with the complicated surface. The workpiece’s location approach on the platform and the orientation transformation of the moving platform relative to the machine coordination system are investigated.

Abstract: In this paper a novel constraint calibration technique for Stewart platform based Parallel Kinematics Machine(PKM) is presented. A commercial trigger probe and a developed double-ball bar gauge are employed to aid the calibration. In the measuring process the characterized errors can be obtained by comparing the nominal characterized size calculated by the function using the measuring data with the real size of the double-ball gauge. An optimization approach is used to calculate the PKM structural errors, and these errors can be finally compensated into the control model. The error transferring matrix with regard to the structural error of PKM can be formulated. The calibration efficiency can be improved by the automatic calibration operation with the doubleball bar gauge. The developed calibration system has been applied in the industry where the PKM is used for machining the turbine vane, and the machining quality can meet the requirements of the specifications. The presented calibration scheme is generic to be applied for the wide range of PKMs.