Research On New FBG-based Measurement System For Dynamic Nano-CMM Probe

Aiming at requirement of the high precision measurements of small size elements,and the demand for coordinate measuring machine(CMM)probe applied to the micro-/nanometer scale,an Fiber Bragg grating(FBG)-based measurement system for dynamic touch nano-CMM probe is proposed in this research.FBG is used as sensing element,a PZT is packaged in the probe to realize dynamic measurement,and true three-dimensional coordinate measurement can be realized.The probe system mainly consists of a displacement transfer mechanism and an FBG-based sensing system.The displacement transfer mechanism consists of stylus,cantilever,support,vibration plate and a shell,used to convert displacements of the probe in any direction into the axial strain of the FBG sensors.The FBG-based sensing system consists of three FBGs,a matching FBG,broad band source,optical switch,and couplers,used to achieve three-dimensional measurement.The main works of this research are as below:(1)The measuring mechanism of the probe is proposed based on the basic sensing,demodulation and multiplexing principles of FBG.The sensing mechanism and the mechanical structure of the probe are introduced,and the FBG demodulation schemes suitable for the probe are studied.The application of FBG demodulation based on the unbalanced Mach-Zehnder(M-Z)interferometer scheme and the matched filter interrogation scheme is compared with each other in the probe environment,and finally the match filter interrogation method based on the space division multiplexing method is used to establish the sensing system.(2)A prototype of the probe system is established based on the study of the measuring mechanism of the probe.And the test system is established to test the sensitivity,resolution and repeatability of the probe.The test results show that the resolution of the probe reaches 13.18 nm,the sensitivity of the probe is greater than 100.47 mV / um,the repeatability standard deviations are less than 48 nm,the nonlinearity errors are less than 1.58%,the homing and triggering repeatability standard deviations are less than 25 nm.(3)The theoretical space coordinate decoupling model is deduced according to the mechanical structure of the probe,the coupling model of the probe based on multiple-linear regression scheme is given,and the coordinate decoupling method of the probe is proposed.The feasibility of the decoupling model is analyzed and the experimental results show that the model estimation errors are less than 56 nm.The main error sources and the error transmission relation of the probe system are given.