The paper aims to show the possibility of the actuation and the measurement of mechanical step displacements of 10 picometers or less than using a designed piezoelectric (PZT) driving stage and heterodyne interferometry. In our experiment, we use a designed parallel spring stage made by LEX-ZERO (low thermal expansion material) with a high-voltage PZT actuator (0 to -1000 V) to generate mechanical displacements with a step of 10 pm or less than. For a measurement system to achieve these picometer-order displacement measurements, the proposed single phase-locked loop  developed on a field-programmable gate array (FPGA) platform aiming to high-resolution phase measurement is used, and a modified heterodyne interferometer with two spatially separated beams is established. Both the actuation and measurement systems are located inside a vacuum chamber for suppressing environmental fluctuations that impact the measurement results. In this paper, the design, instrumentation, and experimental results are discussed. Reference  T-D Nguyen, et al., Direct phase determination using phase lock loop for heterodyne displacement-measuring interferometers, Proceedings of Photonic Asia Conference, 2018.
The five-axis machine tools have been increasingly used among all fields of manufacturing, and the research related to geometric errors is the most non-negligible subject of five-axis machining accuracy. According to the shape generation theory, the geometric error model is established through the D-H matrix of each geometric error to achieve the coordinate transformation. In this study, the authors propose a modification of the previous geometric error model, through the additional workpiece coordinate transformation. The simulation results of cubic-machining test show that it is necessary to consider the workpiece coordinate system to make the proper error reflection onto the simulated machining surface.
This paper investigates the mechanical and electrical power losses in the feed drive systems driven by an AC servo motor and a ball-screw. The electric power consumption of the servo motor has been measured for several velocities and loads and the efficiency map has been drawn. The velocity dependent power consumption of each component; bearings, ball-screw nut, and linear guides has also been identified. Four ball-screws differing for the lead and the preload have been tested. Finally it is clarified that the total power consumption of the system is determined as a balance of the mechanical and electrical power losses.