Study Of A3D Touch Trigger Probe Based On FBGs

The probe is the key technology as to a Coordinate Measuring Machine(CMM).Theinformation of a workpiece is picked up by CMM probes during the measuring process, and thefunction, efficiency and accuracy of a CMM are all closely related to its probe. There is pre-travelvariation error for a traditional probe, and its accuracy is accordingly low. Delevoping a touchtrigger probe based on new principles, can improve the measurement accuracy and measuring speedof a CMM, and make it more functional. In recent years with the development of opticalcommunication technology, fiber Bragg grating (FBG) sensor has been researcher's favorite field forits excellent properties.FBG is taken as the sensing element in a novel touch trigger probe in this research. ThroughFBG probe, a trigger signal is generated during the measuring process while the probe touches aworkpiece, then CMM can obtain the object's shape, location and surface features, and other relatedinformation. The feasibility of FBG integrated in a touch trigger probe for CMM is verified intheory. The application of FBG in a touch trigger probe is quite different from the traditionalelectrical switch probe and the probe based on strain gauges. In the FBG based probe system, thesensor signal is modulated optically by its Bragg wavelength. The sensitivity of FBG can reach amagnitude of picometer per micro-strain. Through a wavelength interrogating system, thewavelength shift of the FBG sensor is converted into an electronic signal. The translated singnalwill be detect and process easier than optically.The main research topic and main innocations includes:1. It is the first time to adopt the FBG sensing technology in three-dimensional touch triggerprobe and in Metrology. The basic principle of touch trigger probes and methods applied on a probethrough optical channels are analyzed. FBG's basic theory and the reflection spectrum under axialstrain is studied. the composition systemof the FBG probe is built up.2. A novel probe structure is achieved. The mathematical model between themicro-displacement of the probe tip and correspondent strain on the FBG sensor is Established. Thedeformation of the stylus caused by the static and dynamic probing force are calculated. Thedeformation of the stylus and the stiffness of the suspension system are simulated.3. A cost-effective FBG demodulation system is applied. The FBG wavelength shiftinterogation methods are systematically studied. The self-demodulation based on non-tuningreference FBG is explored. The FBG signal data acquisition system based on DAQ card is carriedout. 4. The error of FBG probe is analyed and repeatability, sensitivity, and measuring force andother aspects of performance are tested.