Fiber grating multi-dimensional force composite sensing device

Abstract

The application provides a blade type fiber grating multi-dimensional force composite sensing device, and belongs to the technical field of fiber grating sensing; the device utilizes the characteristics that the fiber Bragg grating (FBG) is sensitive to strain and that the grating period changes when the FBG is subjected to force to influence the central wavelength of reflected light, is arranged on a strain arm to measure the strain of a sensitive area of the strain arm when a torque is applied to the strain arm; and the interference fringe changes generated when the Fabry-Perot interference cavity (FP cavity) cavity length changes, which is combined with a spring, when subjected to an axial force, the spring is compressed, the spring compression amount is converted into the FP cavity length change amount, the cavity length change is obtained by demodulating the interference fringe, and thus the axial force is calculated. The FBG and the FP cavity are combined on the same sensing optical fiber to fully use the optical fiber, reduce the number of optical fibers required for different detection quantities, and reduce the system complexity.

Description

Technical Field

[0001] This application relates to the field of fiber optic grating sensing technology, and in particular to a blade-type fiber optic grating multidimensional force composite sensing device. Background Technology

[0002] In orthopedic surgery, the trephine is an indispensable core instrument, widely used in various orthopedic procedures such as bone fenestration, bone graft preparation, core decompression, and endoscopic spinal decompression. Its operational precision directly determines the surgical outcome and postoperative recovery. The core requirement of trephine surgery is precise cutting of bone tissue, and the torque and axial pressure applied during the cutting process are key mechanical parameters affecting the cutting effect—torque directly determines the rotational speed and depth of cut, while axial pressure affects cutting efficiency and the degree of bone damage. However, currently used traditional trephines lack effective real-time mechanical parameter measurement devices. Surgeons rely entirely on long-accumulated clinical experience and tactile sensation to judge the cutting force, failing to achieve quantitative feedback of torque and axial pressure during trephine cutting. This situation has become a core bottleneck restricting the development of orthopedic trephine surgery towards precision and intelligence.

[0003] Due to the lack of real-time quantitative feedback on torque and pressure, traditional trephine surgery is prone to operational deviations: excessive torque or axial pressure can lead to over-cutting of bone tissue, damaging surrounding nerves, blood vessels, and other soft tissues, and even causing serious surgical complications such as fractures and bone perforation, endangering the patient's life; insufficient torque or axial pressure results in low cutting efficiency, prolonged operation time, increased risk of intraoperative infection and surgical trauma, and affects the smoothness of surgical operation and clinical treatment outcomes. With the rapid development of minimally invasive orthopedic techniques such as spinal endoscopy and the increasingly widespread application of new instruments such as visual trephine saws, higher demands are placed on the precision of surgical operations. A technical solution is needed that can measure torque and axial pressure during trephine surgery in real time and accurately, enabling the quantification, display, feedback, and recording of mechanical parameters. This would provide surgeons with a scientific basis for operation, improve the precision and safety of the surgery, and promote the upgrading of orthopedic trephine surgery towards minimally invasive and precise procedures.

[0004] Precise measurement of torque and pressure is a core prerequisite for quantifying trephine surgery. Currently, mainstream torque measurement methods primarily rely on electrical sensors such as strain gauges, magnetoelectric sensors, piezoelectric sensors, and phase difference sensors, while pressure measurement often employs traditional electrical sensing solutions like resistance strain gauges and piezoelectric ceramics. However, these electrical sensors have significant technical limitations. They have poor environmental adaptability and are easily affected by factors such as temperature and humidity changes in the surgical environment, dust generated during bone cutting, intraoperative disinfectants and body fluids, and electromagnetic interference from surgical equipment. This leads to decreased measurement accuracy, response delays, and the devices are prone to aging and have short lifespans, making them unsuitable for the complex working conditions required in orthopedic surgery. Furthermore, orthopedic trephines are mostly miniaturized instruments, while traditional electrical sensors are bulky and heavy, making integration into the trephine instrument difficult. They also require additional power supply lines, posing safety hazards such as leakage, and failing to meet the sterile, miniaturized, and intrinsically safe requirements of orthopedic surgery.

[0005] With the rapid development of fiber optic sensing technology, fiber optic grating (FBG) sensors, with their unique advantages such as small size, light weight, resistance to electromagnetic interference, corrosion resistance, intrinsic safety, and distributed measurement capabilities, have become a core development direction in the field of high-end torque sensing, and have also provided a new technical path for the mechanical measurement of orthopedic surgical instruments. FBG sensors achieve torque measurement based on the linear relationship between the wavelength drift and strain of a Bragg grating. By combining the FBG sensor with the torsional transmission structure of a ring saw, the torsional torque generated during ring saw cutting can be converted into grating strain. Furthermore, by detecting the wavelength drift, the magnitude of the torque can be inverted. This effectively solves the problems of poor anti-interference capability and large size of traditional electrical sensors, making them suitable for the complex environment of orthopedic surgery and the need for miniaturized instrument integration.

[0006] In the measurement of axial pressure on a ring saw, Fabry-Perot (FP) cavity fiber optic sensors are increasingly being used in the field of micro-pressure measurement due to their compact structure, high sensitivity, and strong anti-interference capabilities. FP cavity sensors detect pressure by inducing an interference spectrum shift through changes in cavity length. Combining the FP cavity with an elastic sensitive structure can effectively improve the sensitivity and stability of pressure measurement. Among these, the spring structure, as a classic elastic sensitive element, has advantages such as simple structure, stable elastic response, and a good linear relationship between deformation and pressure. Combining the FP cavity with the spring structure allows the elastic deformation of the spring under axial pressure to drive changes in the FP cavity length, thereby achieving accurate measurement of the axial pressure on the ring saw. Furthermore, this structure is compact and easily integrated into the front end or handle of the ring saw instrument, adapting to the design requirements of miniaturized surgical instruments.

[0007] Furthermore, current technologies lack a comprehensive mechanical measurement scheme for trephine surgery that combines FBG torque measurement with FP cavity-spring pressure measurement. Most studies only measure a single mechanical parameter, failing to fully reflect the mechanical characteristics during trephine cutting and thus hindering surgeons' ability to comprehensively assess cutting force. Additionally, existing sensing solutions often suffer from integration difficulties, insufficient measurement accuracy, and weak anti-interference capabilities, making them unsuitable for the complex conditions and precision requirements of orthopedic trephine surgery.

[0008] In summary, as orthopedic surgery advances towards precision, intelligence, and minimally invasive techniques, the lack of real-time quantitative feedback of torque and pressure in traditional trephine surgery is becoming increasingly prominent. Existing torque and pressure measurement technologies all face insurmountable technical bottlenecks and cannot meet the clinical application needs of trephine surgery. Therefore, developing a measurement device that integrates FBG torque measurement and FP cavity-spring pressure measurement functions, is adapted to trephine surgery conditions, and possesses anti-interference, miniaturization, high precision, and real-time response characteristics, enabling the synchronous quantification, feedback, and recording of torque and axial pressure during trephine surgery, has significant clinical significance, academic value, and industrialization prospects for improving the precision and safety of orthopedic trephine surgery and promoting the upgrading and development of orthopedic surgical techniques. Summary of the Invention

[0009] To address the problems of insufficient measurement accuracy, high integration difficulty, and weak anti-interference capability in current ring saw applications, this application proposes a blade-type fiber optic grating multidimensional force composite sensing device.

[0010] The technical solution adopted in this application is as follows: a blade-type fiber grating multidimensional force composite sensing device, including a fiber grating torque sensing system based on Bragg reflection, a FP cavity axial force sensing system based on multi-beam equal-inclination interference, and a mechanical structure. The mechanical structure includes a central stage and an FP sensing head fixed on the central stage. Strain arms are equally spaced around the central stage, and each strain arm is provided with at least two strain-sensitive areas. The fiber grating torque sensing system includes a sensing fiber, a sensing light generation module, and a demodulation device. The FP cavity axial force sensing system includes an FP cavity. The fiber grating torque sensing system and the FP cavity axial force sensing system share the sensing light generation module and the demodulation device. Torque sensing fiber gratings are spaced apart on the sensing fiber and fixed on the strain-sensitive area of ​​the strain arm to detect the torque force applied to the strain arm and the position of the force application point. The sensing fiber passes through all strain arms in sequence and then enters the FP sensing head through the circular hole in the center of the central stage. The FP sensing head has a hollow structure with an internal fiber optic channel. The end face of the sensing fiber is parallel to the end of the FP sensing head. A mirror parallel to the end face of the sensing fiber is placed outside the FP sensing head. The parallel end faces of the sensing fiber and the mirror form the FP cavity. A spring is fitted outside the FP sensing head. When the FP sensing head moves downward, it compresses the spring. At the same time, the sensing fiber moves downward, reducing the distance between the end face of the sensing fiber and the mirror, thereby changing the length of the FP cavity and causing the interference fringes to shift. By analyzing and calculating the shift of the interference fringes, the reduction in the FP cavity length is obtained. The spring compression is obtained from the reduction in cavity length, and then the axial force is calculated.

[0011] Furthermore, the sensing light generation module includes a tunable laser with a center wavelength of 1528~1568nm, an optical attenuator, a light intensity monitor, and a circulator. The demodulation device includes a PD detector, a data acquisition card, and a host computer. The output of the tunable laser is connected to the input of the optical attenuator; the output of the optical attenuator is connected to the input of the light intensity monitor to monitor the light intensity; the output of the light intensity monitor is connected to input a of the circulator, the output b of the circulator is connected to the sensing optical fiber, and the output c of the circulator is connected to the input of the PD detector; the output of the PD detector is connected to the input of the data acquisition card, and transmits the electrical signal data converted from the light intensity into the data acquisition card; the output of the data acquisition card is connected to the host computer, and packages the light intensity data from the PD detector and sends it to the host computer's demodulation program for demodulation.

[0012] Furthermore, a temperature-sensing fiber optic grating is also installed on the sensing fiber, and the temperature-sensing fiber optic grating is fixed on the central platform.

[0013] Furthermore, the FP sensor head is also equipped with a limiting stage to prevent the spring from being over-compressed.

[0014] Furthermore, the tunable laser emits 1528~1568nm laser light in a scanning manner by adjusting the internal parameters of the laser.

[0015] Furthermore, three strain arms are arranged at equal intervals around the perimeter of the central stage. Each strain arm has two strain-sensitive areas. The torque-sensing fiber grating on the sensing fiber is aligned with the middle part of the strain-sensitive area to obtain the maximum strain on the strain arm.

[0016] Furthermore, as the sensing fiber passes through the circular hole at the top of the FP sensing head and enters the central stage, the two ends of the temperature sensing fiber grating on the sensing fiber are glued to the central stage to prevent it from being affected by torque and axial forces. After being led out, it enters the strain arm through the fiber slot, and the two torque sensing fiber gratings are aligned with the center positions of the two strain-sensitive areas, and the two ends of the torque sensing fiber gratings are glued to them, so that the torque sensing fiber gratings can sense the strain generated in the sensitive areas. Then, it is led back to the central stage through the fiber hole on the strain arm and through the rear side of the strain arm. The same process is performed on the other two strain arms. After the three strain arms are glued, the sensing fiber is glued and fixed through the central stage and led out of the mechanical structure, connected to the output end b of the circulator, and the reflected light enters the subsequent demodulation device.

[0017] Furthermore, the center wavelengths of the six torque-sensing fiber Bragg gratings on the three strain arms are all different. The tunable laser emits laser light sequentially from 1528nm to 1568nm according to the set step size. The torque-sensing fiber Bragg gratings reflect the light of their center wavelengths. When the PD detector receives a strong light intensity signal, it records the wavelength value emitted by the tunable laser. After completing one cycle of scanning, a peak-finding algorithm is performed to locate the point with the largest light intensity, i.e., the point with the largest peak value, among several wavelength values ​​with larger light intensity. This point is taken as the center wavelength of the reflected light in this scan. The torque-sensing fiber Bragg grating corresponding to the reflected light is determined by the wavelength value of the demodulated reflected light. After matching the reflected light of different torque-sensing fiber Bragg gratings with the grating positions represented by their corresponding wavelength variation ranges, the position where the torque force is applied is calculated using the position data of the torque-sensing fiber Bragg gratings and the strain data.

[0018] Furthermore, the reflected light in the FP cavity forms interference fringes, which exhibit alternating bright and dark light intensity variations. The intensity of the reflected light is detected by the PD detector, and the light intensity is compared by the demodulation program to obtain the distance between the light intensity peaks, i.e., the wavelength difference between two adjacent interference peaks. Based on the linear relationship between the wavelength difference and the FP cavity length, the cavity length of the FP cavity in this scanning cycle is calculated. The change in the FP cavity length is consistent with the spring compression. Based on the known parameters of the spring, the axial force is calculated.

[0019] The advantages of this application over the prior art are as follows: I. This application uses a single optical fiber to achieve multi-parameter sensing, which is different from the traditional multi-fiber parallel sensing method. It can significantly reduce the number of optical fibers used, effectively avoid problems such as tangling and pulling interference of multiple optical fibers during operation, and improve system stability and ease of operation.

[0020] Second, this application can simultaneously measure multiple forces, comprehensively acquiring force information in two key directions during the trephine cutting process. One is the axial force along the axis, and the other is the torque force perpendicular to the axis plane. Simultaneous measurement and analysis of multiple forces allows for more accurate determination of the trephine cutting depth and whether it penetrates the bone, overcoming the limitations of measuring a single mechanical parameter and improving surgical safety and assessment reliability.

[0021] Third, this application integrates two sensing functions into the same optical fiber, which can share the same light source and the same signal demodulation system. While realizing multi-parameter detection, it simplifies the overall sensing system structure, reduces system complexity and size, and is more suitable for the simple and reliable use requirements in medical surgical environments. Attached Figure Description

[0022] The following description, in conjunction with the accompanying drawings, further illustrates this application: Figure 1 This is a schematic diagram of the device system connection structure provided in the embodiments of this application; Figure 2 This is a schematic diagram of the mechanical structure of the device provided in the embodiments of this application; Figure 3 for Figure 2 A plan view of the cut-open limit platform; In the diagram: 1. Tunable laser; 2. Optical attenuator; 3. Optical intensity monitor; 4. Circulator; 5. PD detector; 6. Data acquisition card; 7. Host computer; 101. FP sensor head; 102. Spring bearing surface; 103. Spring; 104. Mirror; 105. Limiting stage; 106. Central stage; 107. Strain arm; 108. First strain sensitive area; 109. Second strain sensitive area; 201. Sensing fiber; 202. First fiber grating; 203. Second fiber grating; 208. FP cavity. Detailed Implementation

[0023] like Figures 1 to 3As shown, this application provides a blade-type fiber optic grating multidimensional force composite sensing device, including a fiber optic grating torque sensing system based on Bragg reflection, an FP cavity axial force sensing system based on multi-beam equal-inclination interference (Fabry-Perot interference), and a mechanical structure. The fiber optic grating torque sensing system includes a tunable laser 1 with a center wavelength of 1528~1568nm, an optical attenuator 2, an optical intensity monitor 3, a circulator 4, a PD detector 5, a data acquisition card 6, a host computer 7, and a sensing fiber 201. Fiber optic gratings are spaced on the sensing fiber 201. The FP cavity axial force sensing system includes an FP cavity 208. 208 includes a first reflective surface and a second reflective surface. The end face of the sensing fiber 201 is used as the first reflective surface, and the reflector 104, which is parallel to the end face of the sensing fiber 201, is used as the second reflective surface. The cavity formed between the end face of the sensing fiber 201 and the reflector 104 is used as the reflective cavity. The distance between the end face of the sensing fiber 201 and the reflector 104 is used as the cavity length. The FP cavity axial force sensing system and the fiber optic grating sensing system share the output sensing light from the tunable laser 1, the optical attenuator 2, the light intensity monitor 3, and the circulator 4, and share the demodulation from the PD detector 5, the data acquisition card 6, and the host computer 7.

[0024] The output of the tunable laser 1 is connected to the input of the optical attenuator 2; the output of the optical attenuator 2 is connected to the input of the light intensity monitor 3 to monitor the light intensity. When the light intensity is too high or too low, the light intensity is adjusted by rotating the knob of the optical attenuator 2 to adjust the light intensity to a safe working range, so as to avoid the light intensity being too high and burning the subsequent optical components, or the light intensity being too low and the light intensity being too weak after passing through multiple optical components, resulting in insufficient sensing or no response from the PD detector 5; the output of the light intensity monitor 3 is connected to the input a of the circulator 4. The circulator 4 outputs light to the output b of the circulator 4 through the internal optical path, and then receives the reflected light from the sensing fiber 201 connected to the output b, and outputs the reflected light to the output c of the circulator 4 through the internal optical path; the output c of the circulator 4 is connected to the PD detector 5. Light undergoes a first reflection at the end face of sensing fiber 201, then a second reflection after passing through FP cavity 208 and external parallel mirror 104. The two reflected beams form interference fringes. Axial force causes the mechanical structure to move downward relative to mirror 104, thus changing the cavity length of FP cavity 208. After the cavity length changes, the interference fringes formed by the two reflected beams change, and the light then passes through circulator 4 and enters PD detector 5 for subsequent demodulation. PD detector 5 detects the intensity of the received light and converts it into an electrical signal. The output of PD detector 5 is connected to the input of data acquisition card 6, and the converted electrical signal data is transmitted into data acquisition card 6. The output of data acquisition card 6 is connected to host computer 7, which packages the intensity data from PD detector 5 and sends it to the demodulation program for demodulation.

[0025] The mechanical structure includes a central stage 106, strain arms 107 equally spaced around the central stage 106, an FP sensor head 101, and a reflective cavity. The multiple strain arms 107 are connected by the central stage 106 to ensure the balance and uniform distribution of the strain arms 107. Each strain arm 107 has a weakened strain-sensitive area. The sensing fiber 201 is laid on the strain arm 107, and the fiber grating on the sensing fiber 201 is aligned with the middle part of the strain-sensitive area to obtain the maximum strain on the strain arm 107, thereby obtaining a more obvious wavelength change, which helps to make the subsequent demodulation steps clearer.

[0026] The fiber grating on the sensing fiber 201 includes a temperature sensing fiber grating and multiple torque sensing fiber gratings. The temperature sensing fiber is fixed on the central stage 106 for temperature compensation. The torque sensing fiber grating is fixed on the strain-sensitive area of ​​the strain arm 107 to obtain the specific location and torque magnitude of the hand application point. Each strain arm 107 is provided with at least two strain-sensitive areas, and a torque sensing fiber grating is fixed on each strain-sensitive area. The location and torque magnitude of the hand application point are obtained through at least two torque sensing fiber gratings on the same strain arm 107.

[0027] like Figure 2 and Figure 3 As shown in the embodiment of this application, the central platform 106 adopts an equilateral triangle shape. This shape is formed by fixing a strain arm 107 at the midpoint of each of the three sides to form three equally spaced strain arms 107. In other embodiments, the central platform 106 can also be circular, with three strain arms 107 equally spaced around the perimeter of the circle.

[0028] Each strain arm 107 is provided with two strain-sensitive areas, namely a first strain-sensitive area 108 and a second strain-sensitive area 109. A first fiber optic grating 202 is fixed on the first strain-sensitive area 108, and a second fiber optic grating 203 is fixed on the second strain-sensitive area 109. Both the first fiber optic grating 202 and the second fiber optic grating 203 are torque-sensing fiber optic gratings.

[0029] The sensing fiber 201 passes through three strain arms 107 and enters the FP sensing head 101 through the central hole of the central stage 106. The FP sensing head 101 has a hollow structure with an internal fiber optic channel. The end face of the sensing fiber 201, which is parallel to the end of the FP sensing head 101, is arranged in the middle. A spring 103 is fitted around the FP sensing head 101 to align with the reflective cavity. A reflector 104 is set at the bottom of the reflective cavity. A limiting stage 105 is set outside the reflective cavity. The limiting stage 105 can prevent the spring 103 from being over-compressed, causing the FP sensing head 101 to collide with the reflector 104 at the bottom of the reflective cavity and damage the reflector 104.

[0030] Two torque-sensing fiber gratings on the sensing fiber 201 are arranged in pairs within two stress-sensitive areas of a strain arm 107. When a torque force is applied to the strain arm 107 by hand, the bending moment of the force on the two stress-sensitive areas is different, depending on the distance from the point of application of the force. The greater the distance, the greater the bending moment. Since the position of the sensitive area is fixed and its distance from the central stage 106 is known, the strain of the two sensitive areas can be obtained through the two torque-sensing fiber gratings. Then, the distance from the point of application of the force to the central stage 106 can be calculated, thereby realizing the positioning of the point of application of the force. The FP sensor head 101 is fitted with a spring 103. When the mechanical mechanism is subjected to axial force, the FP sensor head 101 moves downward to compress the spring 103. At the same time, the sensing fiber 201 moves downward, reducing the distance between the end face of the sensing fiber 201 and the reflector 104, thereby changing the cavity length of the FP cavity 208 and causing the interference fringes to move. The parameters of the spring 103 can be found in the manual. The compression of the spring 103 is linearly related to the axial force. By analyzing and calculating the movement of the interference fringes, the reduction in the cavity length of the FP cavity 208 can be obtained. The axial force can be calculated from the compression of the spring 103 obtained from the reduction in cavity length.

[0031] The sensing fiber 201 is attached to the fiber optic channel of the hollow structure of the FP sensing head 101, ensuring precise alignment between the end face of the sensing fiber 201 and the end face of the FP sensing head 101. This maximizes the coupling of reflected light from the reflector 104 into the sensing fiber 201, resulting in higher contrast and clearer interference fringes. When the sensing fiber 201 passes through the circular hole at the top of the FP sensing head 101 and through the central stage 106, the two ends of the temperature-sensing fiber grating on the sensing fiber 201 are attached to the central stage 106 to prevent it from being affected by torque and axial forces. The temperature-sensing fiber grating detects the wavelength shift caused by temperature, and temperature compensation is applied to the torque-sensing fiber grating and the axial force sensing FP cavity 208 during demodulation. After exiting the stage, the fiber optic cable passes through the fiber slot on the strain arm 107, where the two torque points are... The sensing fiber optic grating is aligned with the center of two strain-sensitive areas and its ends are attached, enabling the fiber optic grating to sense the strain generated in the sensitive areas. The fiber optic cable is led back to the central stage 106 through the fiber optic hole on the strain arm 107. The same process is performed on the other two strain arms 107. After the three strain arms 107 are attached, the sensing fiber optic cable 201 is attached and fixed through the central stage 106 and led out of the mechanical structure, connected to the output end b of the circulator 4, and the reflected light enters the subsequent demodulation device.

[0032] This application combines fiber optic grating torque measurement and FP axial force measurement on a single sensing fiber 201, achieving simultaneous detection and output of torque and axial force measurements. The implementation method based on fiber optic grating torque measurement and FP axial force measurement is described below: Tunable laser 1 emits 1528~1568nm laser light in a scanning manner by adjusting the internal parameters of the laser. The laser intensity is adjusted by optical attenuator 2 and monitored by optical intensity monitor 3. The optical intensity is adjusted to a safe operating range in conjunction with optical attenuator 2. The laser light with adjusted intensity enters the input end a of circulator 4, passes through the output end b of circulator 4 to multiple fiber gratings on sensing fiber 201 in the sensing optical path, exits through the end face of sensing fiber 201, and is reflected back to sensing fiber 201 by reflector 104 to form FP cavity 208. The generated interference fringes carry the cavity length information of FP cavity 208 and are input to the output end b of circulator 4 in the basic optical path. From the output end c of circulator 4, the signal is input to the input end of PD detector 5. PD detector 5 converts the received light intensity signal into a level signal and inputs it to the input end of data acquisition card 6. Data acquisition card 6 sends the data to the demodulation program of host computer 7 for demodulation.

[0033] Tunable laser 1 emits laser light sequentially from 1528nm to 1568nm in a set step size. Torque-sensing fiber optic gratings reflect the light at their center wavelength. When PD detector 5 receives a strong light intensity signal, it records the wavelength value emitted by tunable laser 1. After completing one cycle of scanning, a peak-finding algorithm is performed to locate the point with the largest light intensity (i.e., the point with the largest peak value) among several wavelength values ​​with relatively high light intensity as the reflection center wavelength of this scan. Different torque-sensing fiber optic gratings have different center wavelengths when not under stress, and the change in center wavelength under stress is within ±3nm. When selecting, six torque-sensing fiber optic gratings with different center wavelengths are chosen, and the ranges of their center wavelength changes do not overlap. This enables the determination that the reflected light belongs to a torque-sensing fiber optic grating when the center wavelength of the reflected light is within the center wavelength range of a certain torque-sensing fiber optic grating. After correlating the reflected light from the six torque-sensing fiber Bragg gratings with the positions of the gratings represented by their corresponding wavelength variation ranges, the position where the torque force is applied is calculated using the position data and strain data of the torque-sensing fiber Bragg gratings. The reflected light in the FP cavity 208 forms interference fringes, which exhibit alternating bright and dark light intensity variations. The light intensity can be detected by the PD detector 5, and the distance between the light intensity peaks is obtained by comparing the light intensity magnitudes through the demodulation program. That is, the wavelength difference (FSR) between two adjacent interference peaks. Since the FSR is linearly related to the cavity length of the FP cavity 208, the cavity length of the FP cavity 208 in this scanning cycle can be calculated. The change in the cavity length of the FP cavity 208 is consistent with the compression of the spring 103. Since the parameters of the spring 103 are known, the axial force can be calculated.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A blade-type fiber optic grating multidimensional force composite sensing device, characterized in that: The system includes a fiber optic grating torque sensing system based on Bragg reflection, an FP cavity axial force sensing system based on multi-beam equal-inclination interference, and a mechanical structure. The mechanical structure includes a central stage (106) and an FP sensing head (101) fixed on the central stage. Strain arms (107) are equally spaced around the central stage (106). Each strain arm (107) has at least two strain-sensitive areas. The fiber optic grating torque sensing system includes a sensing fiber (201), a sensing light generation module, and a demodulation device. The FP cavity axial force sensing system includes an FP cavity (208). The fiber optic grating torque sensing system and the FP cavity axial force sensing system share the sensing light generation module and the demodulation device. Torque sensing fiber gratings are spaced on the sensing fiber (201). The torque sensing fiber gratings are fixed on the strain-sensitive area of ​​the strain arm (107) to detect the torque force applied to the strain arm (107) and the position of the force application point. The sensing fiber (201) passes through all strain arms (107) in sequence and then enters the FP sensing head (101) through the circular hole in the center of the central stage (106). The FP sensing head (101) is a hollow structure with an internal fiber optic channel. The end face of the sensing fiber (201) is parallel to the end of the FP sensing head (101). A reflector (104) parallel to the end face of the sensing fiber (201) is provided on the outside of the FP sensing head (101). The end faces of the parallel sensing fibers (201) and the reflector (104) form an FP cavity (2). 08), the FP sensor head (101) is fitted with a spring (103). The FP sensor head (101) moves downward to compress the spring (103). At the same time, the sensing fiber (201) moves downward to reduce the distance between the end face of the sensing fiber (201) and the reflector (104), thereby changing the cavity length of the FP cavity (208) and causing the interference fringes to move. The reduction in the cavity length of the FP cavity (208) is obtained by analyzing and calculating the movement of the interference fringes. The compression of the spring (103) is obtained by the reduction in the cavity length, and then the axial force is calculated.

2. The blade-type fiber optic grating multidimensional force composite sensing device according to claim 1, characterized in that: The sensing light generation module includes a tunable laser (1) with a center wavelength of 1528~1568nm, an optical attenuator (2), a light intensity monitor (3), and a circulator (4). The demodulation device includes a PD detector (5), a data acquisition card (6), and a host computer (7). The output end of the tunable laser (1) is connected to the input end of the optical attenuator (2); the output end of the optical attenuator (2) is connected to the input end of the light intensity monitor (3) to monitor the light intensity; the output end of the light intensity monitor (3) is connected to the input end a of the circulator (4), the output end b of the circulator (4) is connected to the sensing fiber (201), and the output end c of the circulator (4) is connected to the input end of the PD detector (5); the output of the PD detector (5) is connected to the input end of the data acquisition card (6), and the electrical signal data converted from the light intensity is transmitted into the data acquisition card (6); the output end of the data acquisition card (6) is connected to the host computer (7), and the light intensity data of the PD detector (5) is packaged and sent to the demodulation program of the host computer (7) for demodulation.

3. The blade-type fiber optic grating multidimensional force composite sensing device according to claim 2, characterized in that: A temperature sensing fiber grating is also provided on the sensing fiber (201), and the temperature sensing fiber grating is fixed on the central platform (106).

4. The blade-type fiber optic grating multidimensional force composite sensing device according to claim 1, characterized in that: The FP sensor head (101) is also provided with a limiting stage (105) to prevent the spring (103) from being over-compressed.

5. The blade-type fiber optic grating multidimensional force composite sensing device according to claim 3, characterized in that: The tunable laser (1) emits 1528~1568nm laser light in a scanning manner by adjusting the internal parameters of the laser.

6. The blade-type fiber optic grating multidimensional force composite sensing device according to claim 5, characterized in that: Three strain arms (107) are arranged at equal intervals around the center stage (106). Each strain arm (107) has two strain-sensitive areas. The torque-sensing fiber grating on the sensing fiber (201) is aligned with the middle part of the strain-sensitive area to obtain the maximum strain on the strain arm (107).

7. The blade-type fiber optic grating multidimensional force composite sensing device according to claim 6, characterized in that: When the sensing fiber (201) is led out through the circular hole at the top of the FP sensing head (101) and passes through the central stage (106), the two ends of the temperature sensing fiber grating on the sensing fiber (201) are pasted on the central stage (106) so that it is not affected by torque and axial force. After being led out, it enters the strain arm (107) through the fiber groove on the strain arm (107). The two torque sensing fiber gratings are aligned with the center positions of the two strain sensitive areas respectively, and the two ends of the torque sensing fiber gratings are pasted so that the torque sensing fiber gratings can sense the strain generated in the sensitive area. Then, it is led back to the central stage (106) through the fiber hole on the strain arm (107) and the same treatment is performed on the other two strain arms (107). After the three strain arms (107) are pasted, the sensing fiber (201) is pasted and fixed through the central stage (106) and led out of the mechanical structure, connected to the output end b of the circulator (4), and the reflected light enters the subsequent demodulation device.

8. The blade-type fiber optic grating multidimensional force composite sensing device according to claim 6, characterized in that: The center wavelengths of the six torque-sensing fiber gratings on the three strain arms (107) are all different. The tunable laser (1) emits laser light sequentially from 1528nm to 1568nm according to the set step size. The torque-sensing fiber grating reflects the light of its center wavelength. When the PD detector (5) receives a strong light intensity signal, it records the wavelength value emitted by the tunable laser (1). After completing one cycle of scanning, a peak-finding algorithm is performed to locate the point with the largest light intensity, i.e. the point with the largest peak value, among several wavelength values ​​with larger light intensity as the center wavelength of the reflected light in this scan. The torque-sensing fiber grating corresponding to the reflected light is determined by the wavelength value of the demodulated reflected light. After the reflected light of different torque-sensing fiber gratings is matched with the position of the grating represented by its corresponding wavelength variation range, the position of the applied torque force is calculated by the position data of the torque-sensing fiber grating and the strain data.

9. The blade-type fiber optic grating multidimensional force composite sensing device according to claim 1, characterized in that: The reflected light in the FP cavity (208) will form interference fringes. The interference fringes show alternating bright and dark light intensity changes. The light intensity of the reflected light is detected by the PD detector (5). The light intensity is compared by the demodulation program to obtain the distance between the light intensity peaks, that is, the wavelength difference between two adjacent interference peaks. According to the linear relationship between the wavelength difference and the cavity length of the FP cavity (208), the cavity length of the FP cavity (208) in this scanning cycle is calculated. The change in the cavity length of the FP cavity (208) is consistent with the compression of the spring (103). According to the known parameters of the spring (103), the axial force is calculated.

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