Papers by Author: L.J. Zhang

Abstract: An ultra-precision machine is developed by Precision Engineering Research Institute of Harbin Institute of Technology to machine components made of KDP crystal with single point diamond fly cutting technique . A stable ultra-low speed feed of worktable is necessary in the machining process inasmuch as the KDP crystal components to be machined must be high form accuracy, low surface roughness and low surface waveness . This paper analyses the effect on speed stability and positioning accuracy under the control of semi-closed loop and full-closed loop based on the experimental data, and also present a compensating control algorithm of error disturbance feed-forward which enhances the stability of ultra-low speed motion of the semi-closed loop feed control servo system of the machine. The simulation results indicate that the values of the steadystate tracking error decreased to 1/10 after using compensating control algorithm. The P-V value of the aluminum specimen machined by the ultra-precision machine tool was 0.27 wavelengths.

Abstract: The method of single point diamond turning is used to machine KDP crystal. A regression analysis is adopted to construct a prediction model for surface roughness and cutting force, which realizes the purposes of pre-machining design, prediction and control of surface roughness and cutting force. The prediction model is utilized to analyze the influences of feed, cutting speed and depth of cut on the surface roughness and cutting force. And the optimal cutting parameters of KDP crystal on such condition are acquired by optimum design. The optimum estimated values of surface roughness and cutting force are 7.369nm and 0.15N, respectively .Using the optimal cutting parameters, the surface roughness Ra, 7.927nm, and cutting force, 0.19N, are obatained.

Abstract: An ultra-precision machine is developed to machine components made of KDP crystal with single point diamond fly cutting technique. This paper presents a compensating control algorithm of error disturbance feed-forward which enhances the stability of ultra-low speed motion of the semi-closed loop feed control servo system of the machine. The simulation results indicate that the values of the steady-state tracking error decreases to 1/10 after using the compensating control algorithm. The fluctuation ratio is less than 4% when machining KDP crystal with the feed rate of 60μm/s.