A Contact Probe Based On Fiber Bragg Grating For A Nano-coordinate Measuring Machine

Three dimensional measurement technology for nanometer-sized objects is becoming increasingly important in many fields such as mechanical engineering,next-generation information technology,robotics and aerospace equipment,etc.The development of nano-coordinate measuring machine(Nano-CMM(is attracting more and more attention in the world.The nano probe of Nano-CMM)plays a key role because it determines the research level of CMM.Fiber Brag g grating(FBG)is a new type of sensor,which has many many good features such as high sensitivity,light weight stability,and strong anti-interference,easy for network formation and low cost.So a nano-trigger probe system using FBG as the sensor was developed in this paper.The main research work of this paper is as follows:The FBG sensing principle and the precision effect between different demodulation models were all deeply analyzed.A self-matching demodulation method based on time multiplexing system was designed to meet the demand of the miniaturization and nanometer measurement accuracy.This method also simplified the structure of the probe system and saved the cost.According to the sensing principle of the probe system,the mechanical structure model of the probe was built and a three dimensional spatial sensing vector model of the probe was established,too.Aiming at improving sensitivity,we can obtain the relationship between the structure size parameters and the output of the probe by using computer aided engineering technology.So the various size parameters of the probe suspension mechanism were determined through comprehensive optimization.A new high precision and low cost manufacturing method for elastic components was studied.This method used chemical etching techniques.It can solve the problem of difficult processing and high cost for complex structures using the traditional WEDM method.It also can reduce the shape error and dimensional error of the elastic mechanism and eliminate the effects of heat and stress on the stability of the elastic element during the cutting process.The elastic mechanism manufactured by the new method improved the service life and reliability of the probe.The experimental systems were designed to test the sensitivity,noise,resolution,stability,repeatability,pre-stroke and measurement force of the probe system in an environment where the temperature fluctuation was ±0.1?.The resolution and repeatability errors of the probe system were up to the nanometer scale in the X,Y and Z direction and the measuring force less than 3mN in Z direction.The sources of errors in the nano probe were analyzed and an effective method to reduce these errors also was given.The original probe working mode was changed and a new vibrating probe was proposed in order to solve the problem of slightly larger measuring force and the effect of surface forces on accuracy.A method of using resonance to counteract nanoscale surface interaction forces was established.The appropriate vibrating parameters including resonance amplitude,velocity and frequency were calculated through theoretical analysis and numerical simulation.The probe was designed based on the above theories and an experiment system was set up to verify its rationality.The results showed that the resonant nano probe after optimizing its parameters could effectively reduce the measuring force and improve the sensitivity compared with the original type.