The performance analysis and enhancement on a parallel kinematic machine

A Parallel Kinematic Machine (PKM) is studied in this research. The prototype of the machine is located at Sandia National Laboratory, New Mexico. The advantages of the PKM prototype over the traditional machine tool include high force/torque capacity, high mechanical structural rigidity, low moving mass and especially high manufacturing flexibility, but the PKM's accuracy may be reduced by its structural and thermal errors. The motivation of this research is to analyze and enhance the performance of this new concept machine.; The PKM in this research is also called hexapod machine. Firstly, hexapod machine's inverse and forward kinematics are introduced to construct the relation between the hexapod platform position, orientation and its six strut lengths. Then the hexapod structural errors, which consist of hexapod strut length errors and joint position errors, are simulated and modeled. The structural error detection model is developed to determine hexapod structural errors via measured platform position and orientation information.; Secondly, hexapod structural sensitivity analysis is implemented to resolve the significance rankings among all structural error terms. A Design of Experiment (DOE) test is employed to examine the joint position errors and strut length error respectively in the real laboratory condition.; Thirdly, some studies on hexapod thermal errors are performed. The thermal error regression model, the thermal error expansion model, and the thermal error finite-element model are built respectively to study the thermal effect on hexapod performance. The derived thermal errors are combined with the structural errors to fabricate a complete error model.; Finally, a near optimal part setup model (NOPSM) is built to search the near optimal position and orientation for mounting a part on the machine working table. The studies on hexapod workspace, stiffness and the complete hexapod error model are incorporated into the NOPSM. Simulation on NOPSM is also executed to validate the model. This model provides an effective and efficient solution for improving PKM's manufacturing quality.