Research On Torque Sensing Technology Based On Fabry-Perot Interference

Rotating mechanical system mainly transmits power through a transmission shaft.Transmission shaft is a key component of rotating mechanical system,and its mechanical performance and stress state during operation are related to the safety and effectiveness of the entire transmission system.Measurement of torque is one of the important means to measure the health and running state of transmission shaft,which is directly related to whether transmission shaft can operate normally.Through the effective measurement of torque magnitude,evaluating the transmission performance of various transmission systems has been the focus of researchers’ research.However,traditional electro-mechanical and magneto-electric torque sensors are easily affected by the harsh environment,such as strong electromagnetic,high temperature and humidity,and often need to use complex protective means to measure torque,which makes the volume of the sensor larger and difficult to be used in a narrow space.Aiming at such problems,this paper proposes a torque measurement method based on extrinsic fiber-optic Fabry-Perot sensing technology,which combines high sensitivity,small size,and anti-electromagnetic interference of the fiber-optic Fabry-Perot sensor itself.Features make the sensor not affected by electromagnetic interference and have a smaller volume and wider application range.The main research contents of this paper are as follows:(1)A torque measurement method based on optical fiber Fabry-Perot interference is proposed,and its model structure is determined.Firstly,according to basic principle of Fabry-Perot interferometer,the structure of the interferometer is simulated and analyzed,and the feasibility of Fabry-Perot cavity structure is preliminarily determined.Then,this paper combines with the basic theory of torque measurement,proposes an extrinsic fiber-optic Fabry-Perot torque measurement method.Using Fabry-Perot torque measurement method,a fiber-optic Fabry-Perot torque sensing model is initially established,and its structure is theoretically analyzed to verify the feasibility of the method in this paper.(2)A torque sensor based on optical fiber Fabry-Perot interference is designed and fabricated.Considering the influence of parallelism change of optical fiber Fabry-Perot cavity on the demodulation of the sensing system,it is proposed to reduce the influence by designing the length of the sensor.Then,the dimensions of each part of the torque sensor are determined based on the torque measurement principle and experimental conditions.The installation method of the sensor is determined,and the statics simulation analysis of the sensor is carried out with Ansys finite element simulation software.The feasibility of the sensor structure and its installation method is determined,and the theoretical sensitivity of the sensor is obtained as 0.226μm/Nm.The displacement measurement system measures the cavity length of the sensor and determines the cavity length change range of the sensor.Finally,the assembly of the torque sensor is completed.(3)Design and build a torque test platform.Through the experimental research on the dynamic torque of the fiber optic Fabry-Perot torque sensor,the experimental results of the comparison between the sensor’s measurement value and the digital torque measuring instrument are obtained.The experimental results show that the measurement results of the sensor are basically consistent with the digital torque measuring instrument.At the same speed,the sensitivity of the sensor has good repeatability;at different speeds,the sensitivity of the sensor is basically consistent with the theoretical value of 0.226μm/Nm.It shows that the sensor has good stability and verifies the feasibility of the torque sensing method based on optical fiber Fabry-Perot interference proposed in this paper.