Research On Error Analysis And Optimization Design Of Coplanar Guide Profilometer

Coordinate scanning measurement is one of the common methods for measuring complex surface profile.Coordinate Measuring Machine(CMM)and Taylor Hobson PGI 1240 are the most representative measuring equipments.For optical fabrication,because of its high precision,the general accuracy of Three-coordinate Measurement is between 5 and 10μm,which can not meet the requirement of measurement before polishing.Although Taylor Hobson PGI 1240 is a profile measuring instrument specially developed for high-precision optical fabrication,it can only scan the lines and can not meet the requirements of optical fabrication measurement.In this paper,the error factors of the three-dimensional profilometer of coplanar guideway designed independently by the laboratory are analyzed.By optimizing the transmission system design,adjusting the stiffness of the motion system and optimizing the sampling strategy,the measurement accuracy is improved to meet the sub-micron precision measurement requirements of Cartesian coordinate scanning.The main contents of the thesis are as follows:The structure composition and precision generation principle of profilometer are analyzed.It is pointed out that the transmission of coplanar open air-floated guide wire rope with double-frame system is the key to improve the measurement accuracy.Based on the theory of multi-body system,the geometric error model of the coplanar rail scanning profilometer is established.The influence of the system error on the measuring accuracy is determined by theoretical calculation and experimental analysis,which lays a good foundation for further optimizing the design and improving the measuring accuracy.Based on the theoretical calculation,the static stiffness characteristics of the thrust bearing with single orifice are measured experimentally.According to the measured stiffness curve,the loading scheme of the profiler is optimized to ensure that the system works in the optimal stiffness state.The drive scheme of wire rope with well-shaped structure is designed.The pretension force is tested and adjusted to improve the transmission stiffness of the wire rope in the direction of motion and to reduce the stiffness of the wire rope in the direction of vertical motion to the greatest extent,so as to ensure the high transmission accuracy and reduce the influence of disturbance on the measurement accuracy.Analyzing the motion model of the driving state of the open coplanar guide wire rope,optimizing the driving and sampling strategy of the measurement process,improving the stability of the movement,reducing the overshoot time,realizing the measurement and sampling under the stable state of the air-floated guide,effectively improving the measurement accuracy and system stability.The error of the measuring system is calibrated with a standard gauge.The planarity plain crystal of 0.03μm is used as the standard plane.The error of the optimized profilometer in the whole stroke is evaluated,PV < 0.4μm.The planar experimental piece with rotational symmetrical surface shape of PV 0.7μm was measured.Compared with the interferometer measurement results,the surface residual error was 0.5μm,indicating that the measurement system error was within 0.5μm.