Research On Cutter Wear Detection Of Tunnel Boring Machine Based On Cascaded Fiber Bragg Grating

With the rapid development of infrastructure construction in China,large-scale tunnel boring machines have been applied in tunnel field,which brings increasing demand for cutter wear detection.At present,the main detection methods based on oil pressure imbalance can't meet the needs of real-time,high efficiency and ground condition analysis.Nowadays,optical fiber sensing technology is more and more used in all aspects of structural health detection,such as bridge and tunnel,large-scale buildings,mine,oil exploration and other fields.In optical fiber sensing technology,fiber grating is widely used because of relatively mature technology.It has many advantages,such as anti electromagnetic interference,small size,high sensitivity,reuse easily and so on.In this paper,a new method based on the cascaded fiber Bragg grating(FBG)is proposed to detect the cutter wear of machine.Based on the coupled mode theory of fiber Bragg grating,the relationship between the peak power of FBG and the length of grating area is simulated to find an optimal FBG length and coupling coefficient,and then a novel sensing demodulation method of cascaded FBG sensor with ultra short grating area interval is proposed.The specific work completed is as follows:1.The theory of FBG length detection applied to the cutter of tunnel boring machine is proposed.Based on the theory of coupled mode,the amplitude response of FBG peak reflectivity under different gate length and inter mode coupling coefficient is simulated.A cascaded FBG design model with the best inter mode coupling coefficient k=0.35 mm^-1 and gate length L=3 mm is gained.2.The sensing demodulation system based on the cutter wear of tunnel boring machine is designed.The stability of photoelectric slip ring and optical switch under their limit work temperature is tested and verified.The power response of bare cascaded FBG under the conditions of light,no light,rough and smooth plane shielding is tested.3.A demodulation algorithm based on the tunnel boring machine cutter wear sensing detection is proposed.Furthermore,the packaging process of the sensor is discussed.The peak power stability of the sensor in temperature and vibration environment is tested.4.A material object system for demodulating cutter wear of tunnel boring machine is built.The 14 millimeter small range wear sensor based on four array cascaded FBGs and the improved 21 millimeter large range wear sensor based on two array cascaded FBGs are studied.The feasibility of the sensing demodulation scheme under the working condition of tunnel boring machine is simulated by the angle grinder wear test.The experimental results show that the wear demodulation accuracy of the sensor is 0.23 mm and 0.67 mm respectively.It provides a reference for the large-scale application of optical fiber sensing technology in tunnel boring machine cutter wear detection.