FBG-based four-dimensional puncture force / torque sensor

Abstract

The invention provides an FBG-based four-dimensional puncture force / torque sensor, and relates to the field of puncture force measurement sensors, the FBG-based four-dimensional puncture force / torque sensor is composed of a 16G puncture needle, a radial force / torque measurement unit, an axial force measurement unit and a base, the puncture needle is connected to the radial force / torque measurement unit, and the axial force measurement unit is connected to the base. The radial force / torque measuring unit and the axial force measuring unit are arranged in series, the base is connected to the rear end of the axial force measuring unit, and decoupling measurement of axial force and radial force / torque is achieved structurally. The invention develops an axial force sensitive structure by carrying out deformation design on a traditional parallelogram linear guide mechanism. The original parallelogram guide mechanisms are sequentially connected in series, symmetrically and annularly arranged, so that an axial force measurement sensitive structure which is high in anti-interference capability, large in motion range and excellent in force-deformation linearity is designed, and the sensitivity and the precision of axial force measurement of the sensor are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of puncture force measurement sensors, and in particular to a Bragg grating optical fiber sensor that can achieve low crosstalk, high precision, and high sensitivity measurement of four-dimensional interactive forces and torques between a puncture needle and human tissue in minimally invasive percutaneous puncture surgery. Background Art

[0002] With the continuous increase in the incidence of cancer, percutaneous puncture is increasingly used in modern clinical cancer diagnosis and treatment methods such as biopsy sampling, radiofrequency ablation, and radioactive particle implantation. Compared with traditional open surgery, percutaneous puncture has the advantages of less trauma, less pain, lower risk of infection, fewer complications, and shorter postoperative recovery time, while robot-assisted puncture has obvious advantages in operational accuracy, stability, and safety. However, the master-slave operation mode of the puncture robot makes it impossible for doctors to perceive the terminal interaction force information through tactile feedback, which may cause surgeons to apply excessive force during surgery and introduce unsafe factors. Accurate puncture force feedback helps assist surgeons in evaluating tissue characteristics and adjusting operations in a timely manner, which is crucial to improving surgical results and reducing surgical risks.

[0003] Researchers have developed a large number of sensors to measure the puncture force during percutaneous puncture surgery, which can be divided into distal measurement methods and proximal measurement methods according to the sensor integration position. The distal measurement method is to integrate the sensor element on the surface of the puncture needle or at the axis of the puncture needle. However, due to the small diameter of the puncture needle, it is difficult to optimize the design of the force-sensitive structure, resulting in the distal measurement scheme usually having obvious problems of low axial force sensitivity and serious multi-dimensional force coupling. The proximal measurement method of integrating the sensor at the needle seat reduces the requirements for the size of the integrated space, and the design and packaging of the sensor are significantly less difficult, making it easier to achieve low coupling and high-precision measurement of multi-dimensional forces. FBG-based optical fiber sensors have been more popular in the field of medical sensors in recent years due to their small size, no electromagnetic interference, good flexibility, good biocompatibility, and high measurement accuracy.

[0004] Ambastha et al. developed an axial force sensor for lumbar spinal puncture needles. They pasted FBG on a cylindrical thin rod located on the axis of the sensor. The sensor achieved a measurement resolution of 21mN in the range of [0,20N]. However, due to the full pasting arrangement of the sensor, the measurement accuracy of the sensor is easily affected by the chirp effect caused by the uneven strain of the optical fiber, and the anti-interference ability of the force-sensitive structure is poor, resulting in a large radial crosstalk of the sensor. Shi et al. used a double-layer planar spring to develop a puncture axial force sensor with good linearity, high sensitivity and strong anti-interference ability. It adopts a suspended optical fiber arrangement to avoid the influence of the chirp effect and effectively improve the measurement resolution, accuracy and robustness of the sensor. The sensor achieves a high resolution of 1.5mN in the range of [0,6N]. However, these two sensors only support axial force measurement, which is difficult to meet the needs of providing doctors with real force feedback in clinical practice.

[0005] Aiming at the demand for more dimensional interactive force measurement during percutaneous puncture, Xiong et al. proposed an FBG sensor that can measure axial force and torque. The axial force is measured by designing a groove on the surface of the puncture needle and pasting the FBG optical fiber. The spoke-shaped flexible beam structure is designed near the needle tip to measure the torque. The temperature compensation optical fiber is designed to improve the measurement accuracy. The sensor achieves an axial force resolution of 30mN and a torque resolution of 0.8N·mm, and has low repeatability error and hysteresis error. However, the large size of the sensor limits its application in actual clinical operations. Liu et al. developed a three-dimensional puncture force sensor for prostate puncture biopsy surgery based on the S-shaped folded beam. A force measurement optical fiber and a temperature compensation optical fiber are configured in each of the three folded beam modules. The simulation results show that the axial force and radial force resolutions of the sensor are 32.5mN and 7.2mN, respectively.

[0006] In summary, although many researchers have developed puncture force measurement sensors, there is still a lack of mature force sensing equipment for commercial puncture robots. The main technical difficulties are: ① The puncture needle has a large aspect ratio, and its axial stiffness is much greater than the radial stiffness, which makes it difficult to achieve high-sensitivity axial force measurement. In addition, the radial force applied to the end of the puncture needle is easily amplified by the lever effect, resulting in excessive axial / radial sensitivity differences and reduced sensor measurement accuracy. ② The design and integration of the sensor are subject to strict size restrictions, making it difficult to achieve multi-dimensional force / torque decoupling measurement through force-sensitive structure design. Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] In view of the shortcomings of the prior art, the present invention provides a four-dimensional puncture force / torque sensor based on FBG, which solves the problems of few measurement dimensions, low sensitivity and severe inter-dimensional coupling in traditional percutaneous puncture force sensors.

[0009] (II) Technical solution

[0010] To achieve the above objectives, the present invention is implemented through the following technical solutions: a four-dimensional puncture force / torque sensor based on FBG: composed of a 16G puncture needle, a radial force / torque measuring unit, an axial force measuring unit and a base, the puncture needle is connected to the radial force / torque measuring unit, the radial force / torque measuring unit and the axial force measuring unit are configured in series, and the base is connected to the rear end of the axial force measuring unit, which structurally realizes the decoupled measurement of axial force and radial force / torque.

[0011] Preferably, the axial force measuring unit includes an annular axial guide structure, an FBG optical fiber, a connecting flange and a connecting cylinder, the annular axial guide structure is connected to the base through the connecting cylinder, the connecting flange is arranged inside the annular axial guide structure, the upper end of the connecting flange is connected to the radial force / torque measuring unit, and the FBG optical fiber is arranged in the middle of the axial force measuring unit.

[0012] Preferably, the annular axial guide structure is designed by a composite of a parallelogram linear motion flexible structure, and is composed of three symmetrical composite modules configured in parallel in an annular manner. The symmetrical composite module is composed of two parallelogram guide mechanisms configured in reverse series and then arranged symmetrically.

[0013] Preferably, the radial force / torque measurement unit consists of a spoke-type sensitive structure, four radially arranged optical fibers, and a needle seat. The needle seat is arranged in the center of the spoke-type sensitive structure, and four adhesive columns are located on the outer ring of the spoke-type sensitive structure and are distributed at equal angles. The two ends of the four radially arranged optical fibers are respectively connected to the needle seat and the adhesive columns with glue.

[0014] Preferably, the spoke-type sensitive structure is a sensitive structure configured with three spokes, the spokes are arranged at equal angles around the circumference, and each of the spokes is designed as a rectangular cantilever beam with a cross-sectional dimension of height greater than width.

[0015] Preferably, the four optical fibers are suspended and arranged at equal intervals of 90° along the radial direction of the structure in the central needle seat of the puncture needle and the outer ring of the spoke-type sensitive structure, thereby realizing low-coupling measurement of radial forces Fx, Fy and torque Mz.

[0016] Preferably, the optical fibers are fixed on both sides of the force-sensitive structure in a two-point suspension configuration to improve sensitivity and avoid chirp.

[0017] (III) Beneficial effects

[0018] The present invention provides a four-dimensional puncture force / torque sensor based on FBG. It has the following beneficial effects:

[0019] The present invention develops an axial force sensitive structure by deforming the traditional parallelogram linear guide mechanism. By successively connecting the original parallelogram guide mechanism in series, symmetrically and in an annular arrangement, an axial force measurement sensitive structure with strong anti-interference ability, large motion range and excellent force-deformation linearity is designed, thereby improving the sensitivity and accuracy of the sensor's axial force measurement.

[0020] In addition, the traditional spoke-type force-sensitive structure is improved and designed for radial force and torque measurement. The cross-sectional dimension design in which the beam height is greater than the beam width is adopted to improve the torque measurement sensitivity of the sensor. At the same time, the structure's ability to resist axial force is enhanced, the radial force and torque measurement accuracy is improved, and it helps to balance the sensitivity of each measurement direction.

[0021] In addition, four optical fibers were suspended at 90° intervals along the radial direction of the structure in the center of the puncture needle seat and the outer ring of the structure, realizing low-coupling measurement of radial forces Fx, Fy and torque Mz. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of a four-dimensional puncture force / torque sensor based on FBG of the present invention;

[0023] Figure 2 This is a schematic structural diagram of an axial force measurement unit of a four-dimensional puncture force / torque sensor based on FBG according to the present invention;

[0024] Figure 3 Schematic diagram of the radial force / torque measurement unit structure of a four-dimensional puncture force / torque sensor based on FBG in the present invention Figure 1 ;

[0025] Figure 4 Schematic diagram of the radial force / torque measurement unit structure of a four-dimensional puncture force / torque sensor based on FBG in the present invention Figure 2 ;

[0026] Figure 5 The present invention provides a design process of an annular axial guide structure of a four-dimensional puncture force / torque sensor based on FBG;

[0027] Figure 6 It is a schematic diagram of the performance simulation results of a four-dimensional puncture force / torque sensor based on FBG of the present invention;

[0028] Figure 7 It is a schematic diagram of a specific implementation of a four-dimensional puncture force / torque sensor based on FBG of the present invention.

[0029] In the figure: 1. 16G puncture needle; 2. radial force / torque measuring unit; 21. spoke-type sensitive structure; 211. spoke; 212. adhesive column; 22. needle seat; 23. optical fiber two; 24. optical fiber three; 25. optical fiber four; 26. optical fiber five; 3. axial force measuring unit; 31. annular axial guide structure; 311. symmetrical composite module; 312. parallelogram guide mechanism; 32. connecting flange; 33. connecting cylinder; 34. optical fiber one; 4. base. DETAILED DESCRIPTION

[0030] The embodiment of the present invention provides a Bragg grating optical fiber sensor that can realize low crosstalk, high precision, and high sensitivity measurement of four-dimensional puncture force and torque in percutaneous puncture surgery, such as Figure 1 As shown, it is composed of a 16G puncture needle 1, a radial force / torque measuring unit 2, an axial force measuring unit 3 and a base 4. Figure 1 As shown. The radial force / torque measurement unit 2 and the axial force measurement unit 3 are configured in series, and the decoupled measurement of the axial force and the radial force / torque is realized in the structure. The axial force measurement unit 3 includes an annular axial guide structure 31, an FBG optical fiber 34, a connecting flange 32 and a connecting cylinder 33; the radial force / torque measurement unit 2 consists of a spoke-type sensitive structure 21, 4 radially configured optical fibers (23 to 26) and a needle seat 22. The optical fibers are fixed on both sides of the force-sensitive structure in a two-point suspension configuration to improve sensitivity and avoid chirping.

[0031] The annular axial guide structure 31 is designed by a parallelogram linear motion flexible structure. Figure 5 As shown. The classic parallelogram guide module has horizontal movement along the x-axis and parasitic movement around the z-axis during its movement along the y vertical direction. The present invention first configures two parallelogram guide modules in reverse series, and the horizontal movement parasitic motions of the two modules cancel each other out; then the obtained composite parallelogram guide module is symmetrically designed to eliminate the rotational parasitic motion; finally, the three symmetrical composite guide modules are configured in parallel in a ring to obtain the proposed annular axial guide structure 31, which provides high-precision axial guide capability, improves the sensor's anti-interference capability and axial force measurement accuracy. In addition, the series design of the multi-layer planar beam increases the deformation of the structure when subjected to axial force, thereby improving the sensitivity of the sensor.

[0032] The radial force / torque measuring unit 2 adopts a sensitive structure with three spokes, such as Figure 3 and Figure 4As shown, it also includes four radially configured optical fibers and a needle seat 22. The needle seat 22 is arranged in the center of the spoke-type sensitive structure 21, and four adhesive columns 212 are arranged around the needle seat 22. The four radially configured optical fibers (23 to 26) are respectively connected to the needle seat 22 and the adhesive columns 212 by glue. Compared with the traditional four-spoke cross-beam design, this design has greater torque flexibility and improves the torque measurement sensitivity; each spoke 211 adopts a rectangular cantilever beam design with a cross-sectional dimension whose height is greater than its width, which improves the axial deformation stiffness and bending-torque stiffness ratio of the sensor, limits the deformation of the force-sensitive structure under axial force, reduces the inter-dimensional coupling of the axial force on the radial force / torque measurement, balances the sensitivity of each measurement direction, and improves the measurement accuracy.

[0033] The key size parameters of the FBG penetration force sensor are optimized based on a multi-objective genetic algorithm. The sensor model after structural parameter optimization is added to the ANSYS Workbench for simulation analysis, and the relationship between the sensor force and the optical fiber center wavelength offset can be calculated, such as Figure 6 shown.

[0034] When the sensor is subjected to radial force, the maximum radial force Fx is 1.5N. The center wavelength offsets of optical fiber 23 and optical fiber 4 25 are 1198pm and 1264pm respectively. The sensitivity of the sensor radial force Fx can be calculated to be 1984pm / N, and the corresponding resolution is 0.5mN. Similarly, the sensitivity and resolution of Fy can be calculated to be 2512pm / N and 0.40mN respectively. Under radial force loading conditions, the center wavelength offset of optical fiber 1 34 is small, so the radial loading of the sensor has little effect on the axial force measurement.

[0035] When the sensor is subjected to the axial force Fz, within the measurement range of 0-6N, only the optical fiber 34 has an obvious central wavelength shift. It can be calculated that the sensitivity and resolution of Fz are 559pm / N and 1.79mN respectively, and the influence of the axial force loading on the radial force and torque measurement is relatively small.

[0036] When the sensor is subjected to torque Mz, within the measurement range of 0-60 N·mm, optical fibers 23 to 26 show obvious and basically consistent wavelength shifts, while the wavelength shift of optical fiber 1 34 is extremely small. It can be calculated that the sensitivity and resolution of torque measurement are 148 pm / (N·mm) and 6.7 mN·mm, respectively, and the sensor has a good ability to decouple axial force and torque measurement.

[0037] In addition, under all full-scale loading conditions, the safety factor of the sensor is always greater than 2, ensuring that the sensor has sufficient structural strength.

[0038] Based on the characteristics of high sensitivity and strong anti-interference ability of the sensor, the four-dimensional puncture force sensor can provide high-precision real-time interactive force / torque feedback when doctors perform percutaneous puncture operations, overcoming the problem of doctors losing terminal tactile interaction in the master-slave operation mode of robot-assisted surgery. Doctors can adjust the puncture operation and insertion path in time according to the terminal force feedback to improve puncture accuracy and surgical safety, and reduce the incidence of surgical complications.

[0039] The specific implementation of the designed puncture force sensor is as follows Figure 7 As shown, all Bragg grating optical fibers of the sensor are connected to a fiber demodulator to detect the physical properties of the grating reflected light, and the fiber demodulator is connected to a computer system to read the optical fiber center wavelength offset data, and perform relevant data processing, so that the center wavelength offsets of the five optical fibers can be converted into the magnitude of the force and torque applied to the end of the puncture needle 1.

[0040] Working principle: When the sensor is subjected to axial force, the axial force is transmitted to the annular axial guide structure 31 through the radial force / torque measuring unit 2, causing the structure to deform, and then the optical fiber 34 and the FBG grating area suspended at both ends generate compressive strain, causing the central wavelength of the FBG optical fiber reflection to shift. The wavelength offset is measured by the optical fiber demodulator, and the axial force applied to the sensor can be measured based on the conversion formula between the grating area strain and the wavelength offset. The spoke-type sensitive structure 21 has a large axial stiffness, so the strain generated on the optical fiber 2-5 is small, realizing the decoupling of the axial force and radial force / torque measurement.

[0041] When the sensor is subjected to radial force, taking Fx as an example, the external force Fx causes the spoke-type force-sensitive structure to deflect around the y-axis, causing the optical fiber 23 and the optical fiber 4 25 to be subjected to pressure and tension respectively, resulting in a central wavelength shift of the same magnitude and opposite direction, while the optical fiber 3 24 and the optical fiber 5 26 produce the same small shift along the radial direction of the optical fiber, and the strain is much smaller than that of the optical fiber 23 and the optical fiber 4 25. The wavelength shift of the optical fiber 23 and the optical fiber 4 25, the optical fiber 3 24 and the optical fiber 5 26 are differentially calculated, respectively, to improve the measurement sensitivity and reduce the crosstalk error. Similarly, when the sensor is subjected to Fy, the optical fiber 3 24 and the optical fiber 5 26 are compressed and stretched respectively, and the strain on the optical fiber 23 and the optical fiber 4 25 is small. The sensitivity of the sensor to Fy can be obtained through differential calculation. In addition, since the optical fiber 1 34 is arranged along the axis of the sensor and is on the neutral axis of the sensor bending under radial force, the strain of the optical fiber 1 34 under radial force is small, realizing the decoupling of radial force and axial force measurement.

[0042] When the sensor is subjected to torque, the four optical fibers of the radial force / torque measurement unit 2 are simultaneously pulled or compressed, resulting in a central wavelength shift of the same magnitude and direction. The torque sensitivity of the sensor can be obtained by summing up the wavelength shifts of the optical fibers 23 to 5 26. In addition, since the designed annular axial guide mechanism has a large torsional stiffness, the strain of the optical fiber 1 34 under the action of torque is extremely small, thus achieving the decoupling of torque and axial force measurement.

[0043] In summary, the present invention has developed an axial force-sensitive structure by deforming the traditional parallelogram linear guide mechanism. By successively connecting the original parallelogram guide mechanism 312 in series, symmetrically and in an annular arrangement, an axial force measurement sensitive structure with strong anti-interference ability, large range of motion, and excellent force-deformation linearity is designed, thereby improving the sensitivity and accuracy of the sensor's axial force measurement. In addition, by optimizing the number and size of spokes of the spoke structure and using it as a radial force / torque sensitive structure, the torque measurement sensitivity is improved, the sensitivity of each measurement direction of the sensor is balanced, and the decoupled measurement of axial force and radial force / torque is achieved.

[0044] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A four-dimensional puncture force / torque sensor based on FBG, characterized in that: The invention comprises a 16G puncture needle (1), a radial force / torque measuring unit (2), an axial force measuring unit (3) and a base (4); the puncture needle (1) is connected to the radial force / torque measuring unit (2); the radial force / torque measuring unit (2) and the axial force measuring unit (3) are arranged in series; the base (4) is connected to the rear end of the axial force measuring unit (3); and the decoupled measurement of the axial force and the radial force / torque is realized in terms of structure.

2. The FBG-based four-dimensional puncture force / torque sensor according to claim 1, characterized in that: The axial force measurement unit (3) comprises an annular axial guide structure (31), an FBG optical fiber, a connecting flange (32) and a connecting cylinder (33); the annular axial guide structure (31) is connected to the base (4) via the connecting cylinder (33); the connecting flange (32) is arranged inside the annular axial guide structure (31); the upper end of the connecting flange (32) is connected to the radial force / torque measurement unit (2); and the FBG optical fiber is passed through the axial position of the axial force measurement unit (3).

3. The FBG-based four-dimensional puncture force / torque sensor according to claim 2, characterized in that: The annular axial guide structure (31) is designed by combining a parallelogram linear motion flexible structure, and is composed of three symmetrical composite modules (311) arranged in parallel in an annular manner. The symmetrical composite module (311) is composed of two parallelogram guide mechanisms (312) arranged in reverse series and then arranged symmetrically.

4. The FBG-based four-dimensional puncture force / torque sensor according to claim 1, characterized in that: The radial force / torque measurement unit (2) is composed of a spoke-type sensitive structure (21), four radially arranged optical fibers, and a needle seat (22); the needle seat (22) is arranged at the center of the spoke-type sensitive structure (21); four adhesive columns (212) are arranged around the needle seat (22); and the four radially arranged optical fibers are respectively connected to the needle seat (22) and the adhesive columns (212) by glue.

5. The FBG-based four-dimensional puncture force / torque sensor according to claim 4, characterized in that: The spoke-type sensitive structure (21) is a sensitive structure configured with three spokes (211), the spokes (211) are arranged at equal angles around the circumference, and each spoke (211) is designed as a rectangular cantilever beam with a cross-sectional height greater than a width.

6. The FBG-based four-dimensional puncture force / torque sensor according to claim 4, characterized in that: The four optical fibers are suspended and arranged at equal intervals of 90 degrees along the radial direction of the structure on the central needle seat (22) of the puncture needle and the outer ring of the spoke-type sensitive structure (21), thereby realizing low-coupling measurement of radial forces Fx, Fy and torque Mz.

7. A four-dimensional puncture force / torque sensor based on FBG according to any one of claims 2 to 6, characterized in that: The optical fibers are fixed on both sides of the force-sensitive structure in a two-point suspension configuration to improve sensitivity and avoid chirping.

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