Miniature force sensor for flexible ureteroscope and decoupling method

Abstract

The invention relates to the technical field of medical instruments, in particular to a miniature force sensor for a flexible ureteroscope and a decoupling method.The miniature force sensor comprises a base, a top cover and a hollow tubular elastic body, the two ends of the elastic body are connected with the base and the top cover respectively, and a first optical fiber and a second optical fiber are arranged in the elastic body; a first fiber bragg grating is engraved on the first fiber, and two ends of the first fiber are respectively connected with the base and the top cover; the two ends of the second optical fiber are a first end arranged in a suspended mode and a second end connected with the base respectively, a second fiber bragg grating is carved on the first end, and a plurality of hollow structures arranged in a staggered mode are arranged on the surface of the elastic body in the circumferential direction of the elastic body. Through the above arrangement, the influence of the transverse force on the miniature force sensor can be effectively reduced, the interference caused by temperature change can be overcome, and the measurement precision of the miniature force sensor is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical devices, and in particular to a micro force sensor for a flexible ureteroscope and a decoupling method. BACKGROUND

[0002] Flexible ureteroscopy (FURS) is a minimally invasive technique widely used in urology. FURS specifically refers to a procedure in which a flexible ureteroscope is inserted through the natural urethra, bladder, and ureter into the upper urinary tract to diagnose and treat upper urinary tract diseases such as kidney stones or urothelial tumors. During FURS, urologists often need to stand for long periods of time and manually manipulate the flexible ureteroscope, which not only increases the complexity of the procedure but also increases the risk of musculoskeletal disorders for the surgeon. In addition, due to the frequent use of X-ray imaging during the procedure, surgeons also face the risk of radiation exposure.

[0003] To address the above challenges, robot-assisted FURS systems have emerged. Robot-assisted FURS systems refer to systems that combine robotic technology to assist urologists in performing flexible ureteroscopy. These systems not only allow remote operation of the flexible ureteroscope, thereby reducing the surgeon's radiation exposure, but also improve the accuracy of the procedure through more stable operation.

[0004] However, existing robot-assisted FURS systems lack force feedback on the tip of the flexible ureteroscope during operation, which prevents the surgeon from obtaining real-time tactile information during the procedure, which can lead to instrument damage or surgical complications. SUMMARY

[0005] To address the above challenges, the present application proposes a micro force sensor for a flexible ureteroscope and a decoupling method.

[0006] The technical solution adopted by the present application is a micro force sensor for a flexible ureteroscope, comprising a base, a top cover and a hollow tubular elastic body, both ends of the elastic body are connected with the base and the top cover respectively, and the elastic body is provided with: a first optical fiber with a first fiber Bragg grating engraved thereon, both ends of the first optical fiber are connected with the base and the top cover respectively; a second optical fiber with a first end suspended and a second end connected with the base, a second fiber Bragg grating is engraved on the first end.

[0007] Preferably, the first optical fiber is arranged along the central axis of the elastic body.

[0008] Preferably, the second optical fiber is parallel to and not collinear with the first optical fiber.

[0009] Preferably, the surface of the elastic body is provided with a plurality of hollow structures arranged in a staggered manner in the circumferential direction.

[0010] Preferably, the cross-sectional shape of the hollow structure is an inclined parallelogram, and the inclined directions of the plurality of hollow structures are not completely the same.

[0011] Preferably, the inclined directions of the hollow structures at different positions along the axial direction of the elastic body are different.

[0012] Preferably, the material of the elastic body is stainless steel or epoxy resin.

[0013] Preferably, the base and the top cover are respectively bonded and fixed with the first optical fiber.

[0014] The application also discloses a sensor decoupling method based on the micro force sensor, and the method comprises the following steps: acquiring the Bragg center wavelength offset of the first fiber Bragg grating and the second fiber Bragg grating respectively; constructing a first relationship between the Bragg center wavelength offset of the first fiber Bragg grating and the second fiber Bragg grating and the contact force; and bringing the Bragg center wavelength offset of the first fiber Bragg grating and the second fiber Bragg grating into the first relationship to obtain the contact force.

[0015] Preferably, the first relationship between the Bragg center wavelength offset of the first fiber Bragg grating and the second fiber Bragg grating and the contact force also comprises the following steps: calibrating the force sensitivity coefficient and the temperature sensitivity coefficient of the first fiber Bragg grating and the temperature sensitivity coefficient of the second fiber Bragg grating, and constructing the first relationship between the Bragg center wavelength offset of the first fiber Bragg grating and the second fiber Bragg grating and the contact force by using the force sensitivity coefficient and the temperature sensitivity coefficient of the first fiber Bragg grating and the temperature sensitivity coefficient of the second fiber Bragg grating.

[0016] Compared with the prior art, the application has the following beneficial effects:

[0017] 1. The micro force sensor in the embodiment decouples the external force value through the first fiber Bragg grating on the first optical fiber, and performs temperature compensation through the second fiber Bragg grating on the second optical fiber, thereby reducing the influence of temperature change on the measurement result, improving the measurement accuracy, and reducing the measurement error. The first fiber Bragg grating and the second fiber Bragg grating are respectively engraved on a unique corresponding optical fiber, and the wavelength drift of the two does not interfere with each other, and the stability and robustness are greatly improved. The second optical fiber provided with the second fiber Bragg grating is directly connected in the elastic body for fixing the first optical fiber, and is fixed on the base together with the first optical fiber, without the need to additionally increase the length of the sensor, and without the need for other complex parts and structures, thereby facilitating production and assembly, being low in cost, small in size, and convenient for popularization and application.

[0018] 2、First fiber is arranged along the axis of the elastomer, the surface of the elastomer is provided with a plurality of hollow structures arranged alternately along the circumference thereof, the plurality of hollow structures arranged alternately reduces the conduction effect of the transverse force, the transverse force applied by the outside can be dispersed on each groove on the surface of the elastomer, the dispersion makes the transverse force not excessively concentrated on a small part of the elastomer, but uniformly distributed on the entire surface, improves the resistance of the micro force sensor to the transverse force, effectively reduces the influence of the transverse force on the micro force sensor, overcomes the requirement that palpation must be perpendicular to the tissue surface, and improves the application feasibility of the micro force sensor. BRIEF DESCRIPTION OF DRAWINGS

[0019] The application will be described in detail below with reference to embodiments and drawings, in which:

[0020] Figure 1 is a schematic view of a micro force sensor;

[0021] Figure 2 is an internal structure diagram of a micro force sensor;

[0022] Figure 3 is a schematic view of a hollow structure on an elastomer.

[0023] 1, top cover; 2, elastomer; 3, base; 4, first fiber; 5, second fiber;

[0024] 3.1, first fiber Bragg grating; 3.2, second fiber Bragg grating. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings. The examples of the embodiments are shown in the drawings, in which the same or similar reference numerals represent the same or similar parts or parts having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are only used to explain the present application, and cannot be explained as a limitation on the present application.

[0026] In one embodiment, as shown in Figure 1 A micro force sensor for a flexible ureteroscope includes a top cover 1, an elastomer 2 and a base 3, the elastomer 2 is a hollow tubular, the two ends of the elastomer 2 are connected with the base 3 and the top cover 1 respectively, and the first fiber 4 and the second fiber 5 are arranged in the elastomer 2.

[0027] The two ends of the first optical fiber 4 are connected with the base 3 and the top cover 1 respectively, and the first optical fiber 4 is fixed in the elastic body 2 by the base 3 and the top cover 1, so as to realize the stable support of the first optical fiber 4 in the micro force sensor, and ensure that the first optical fiber 4 can accurately measure the small force changes from all directions when the elastic body 2 is deformed under force. The first fiber Bragg grating 3.1 is engraved on the first optical fiber 4, and the first fiber Bragg grating 3.1 on the first optical fiber 4 is suspended in the interior of the elastic body 2, so that the first fiber Bragg grating 3.1 can freely respond to deformation when the elastic body 2 is stressed, reducing mechanical interference from the connecting parts or other structures, improving the accuracy and sensitivity of the measurement, and ensuring that the force sensor can provide reliable tactile feedback in a complex surgical environment.

[0028] The two ends of the second optical fiber 5 are a first end and a second end, and the second end is connected to the base 3, and the first end is suspended in the elastic body 2, and the second fiber Bragg grating 3.2 is arranged on the first end. Since the first end of the second optical fiber 5 is suspended, that is, there is no direct tensile or compressive force acting on the second optical fiber 5, the second fiber Bragg grating 3.2 will not produce a strain response due to the deformation of the elastic body 2. Temperature changes will uniformly act on the entire second optical fiber 5, including the suspended second fiber Bragg grating 3.2, so the wavelength drift of the second fiber Bragg grating 3.2 is mainly caused by temperature changes, which enables the second fiber Bragg grating 3.2 to accurately detect temperature changes and provide a signal for temperature compensation without being disturbed by force. And the micro force sensor detects external force through one end of its top cover 1, that is, one end of its top cover 1 is more affected by external force, so the second optical fiber 5 is fixed to the base 3 of the micro force sensor through its second end, which can further reduce the influence of external force on the wavelength drift of the second fiber Bragg grating 3.2 compared to being fixed on the top cover 1.

[0029] The micro force sensor in this embodiment decouples the external force value through the first fiber Bragg grating 3.1 on the first optical fiber 4, and performs temperature compensation through the second fiber Bragg grating 3.2 on the second optical fiber 5, which reduces the influence of temperature changes on the measurement results, improves the measurement accuracy, and reduces the measurement error. The first fiber Bragg grating 3.1 and the second fiber Bragg grating 3.2 are engraved on their respective corresponding optical fibers, and their wavelength drifts do not interfere with each other, and the stability and robustness are greatly improved. The second optical fiber 5 provided with the second fiber Bragg grating 3.2 is directly connected in the elastic body 2 that fixes the first optical fiber 4, and is fixed together with the first optical fiber 4 on the base 3, without the need to increase the length of the sensor or other complex parts and structures, which is convenient for production and assembly, low in cost, small in size, and convenient for popularization and application.

[0030] In other embodiments, the second end of the second optical fiber 5 can be connected to the top cover 1, which also allows the first end of the second optical fiber 5 to be suspended in the elastic body 2, and the second fiber Bragg grating 3.2 can also detect temperature changes more accurately.

[0031] In one embodiment, the first optical fiber 4 is arranged along the central axis of the elastic body 2. When the elastic body 2 is subjected to an external force, the first optical fiber 4, arranged along the central axis, can uniformly bear and sense the deformation of the elastic body 2 in all directions. The first optical fiber 4 maintains symmetry under force, reducing nonlinear errors that may be caused by eccentric arrangement. This allows the first fiber Bragg grating 3.1 on the first optical fiber 4 to accurately capture the strain changes of the elastic body 2 in any direction, thereby improving the sensitivity and accuracy of force sensing.

[0032] In one embodiment, the first optical fiber 4 and the second optical fiber 5 are arranged in parallel and not collinear. The second optical fiber 5 can sense temperature changes in the same environment as the first optical fiber 4, while remaining relatively insensitive to force, and can avoid interference between the first optical fiber 4 and the second optical fiber 5, simplifying the calculation of external force values. In addition, the parallel optical fiber structure simplifies the assembly process of the miniature force sensor, facilitates its integration in a flexible ureteroscope, and maintains the miniaturization and flexibility of the miniature force sensor.

[0033] The FBG sensor is a single-dimensional force sensor, which requires palpation perpendicular to the tissue surface. This is difficult to control in practical applications, resulting in low measurement accuracy.

[0034] In one embodiment, the first optical fiber 4 is arranged along the axis of the elastic body 2, and the surface of the elastic body 2 is provided with a plurality of staggered perforated structures along its circumference. The staggered perforated structures reduce the transmission effect of lateral force. The lateral force applied from the outside will be dispersed to each groove on the surface of the elastic body 2. This dispersion effect prevents the lateral force from being excessively concentrated in a small part of the elastic body 2, but is evenly distributed to the entire surface, thereby improving the resistance of the micro force sensor to lateral force and effectively reducing the influence of lateral force on the micro force sensor.

[0035] Specifically, the cross-sectional shape of the hollow structure is an inclined parallelogram, and the inclination directions of multiple hollow structures are not exactly the same. This allows the applied lateral force to be evenly distributed across the four sides, rather than being excessively concentrated in a small area, thus improving the stability and reliability of the miniature force sensor. Furthermore, the different inclination directions of the hollow structures at different positions along the axial direction of the elastic body 2 significantly reduce the impact of lateral forces on the miniature force sensor, resulting in strong robustness and anti-interference capabilities.

[0036] like Figures 2-3 As shown, the hollow elastic body has a length of L and a diameter of d. The staggered structure used to resist lateral forces is as follows...Figure 3 As shown, the length, width, and angle of the inclined parallelogram are a, b, and c, respectively. The values of the above-mentioned dimensions L, d, a, b, and c can be designed according to the size of the instrument to which the micro force sensor is connected and the accuracy and sensitivity of the force to be measured. Meanwhile, the material of the elastic body can also be selected according to the actual application scenario.

[0037] In an embodiment, the material of the elastic body can be stainless steel, such as 304 stainless steel, which has good biocompatibility. The material of the elastic body can also be epoxy resin, such as medical epoxy resin glue (EP42HT-2Med) for 3D printing, which can reduce production costs.

[0038] In an embodiment, the connection between the base, the top cover, the elastic body, and the first optical fiber, and the connection between the base and the second optical fiber can be fixed by medical-grade glue, which can be medical instant adhesive, medical epoxy resin glue, or medical UV glue. In other embodiments, welding or mechanical clamping can also be used for fixation.

[0039] In an embodiment, a sensor decoupling method based on the micro force sensor in the above embodiment, the method comprising:

[0040] obtaining the Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating, respectively;

[0041] constructing a first relationship between the Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating and the contact force;

[0042] bringing the Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating into the first relationship to obtain the contact force.

[0043] The first relationship between the Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating and the contact force further comprises:

[0044] calibrating the force sensitivity coefficient and the temperature sensitivity coefficient of the first fiber Bragg grating and the temperature sensitivity coefficient of the second fiber Bragg grating, and constructing the first relationship between the Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating and the contact force using the force sensitivity coefficient and the temperature sensitivity coefficient of the first fiber Bragg grating and the temperature sensitivity coefficient of the second fiber Bragg grating.

[0045] Specifically, according to the sensing principle of the fiber Bragg grating, under the simultaneous action of temperature and force, the first optical fiber 4 will generate strain and temperature change accordingly. At this time, the center wavelength of the first fiber Bragg grating 3.1 will drift as follows:

[0046]

[0047] wherein Δλ is the Bragg center wavelength shift of the first fiber Bragg grating 3.1, λ is the Bragg center wavelength, ρ e is the effective photoelastic coefficient of the first fiber 4, Δε is the strain of the first fiber Bragg grating 3.1 under the axial force, α f is the thermal expansion coefficient of the first fiber 4, ξ f is the thermo-optic coefficient of the first fiber 4, ΔT is the environmental temperature change of the measured object.

[0048] Equation (1) can be simplified as:

[0049] Δλ=K F F+K T ΔT (2)

[0050] wherein K F and K T are the force sensitivity coefficient and the temperature sensitivity coefficient of the first fiber Bragg grating 3.1, which can be obtained in the calibration process.

[0051] The second fiber Bragg grating 3.2 on the second fiber 5 is only sensitive to temperature and is not affected by the strain caused by force. When the temperature changes, the second fiber Bragg grating 3.2 will have a center wavelength shift, as follows:

[0052] Δλ1=K T1 ΔT

[0053] wherein Δλ1 is the Bragg center wavelength shift of the second fiber Bragg grating 3.2, KT1 is the temperature sensitivity coefficient of the second fiber Bragg grating 3.2, which can be obtained in the calibration process.

[0054] Therefore, the first relationship, that is, the contact force value after temperature compensation, can be calculated as:

[0055]

[0056] The contact force value under temperature disturbance can be accurately obtained.

[0057] The sensor decoupling method measures the temperature change through the second fiber Bragg grating 3.2 as temperature compensation, and calculates the decoupled contact force and temperature change information. The sensor decoupling method accurately separates the mutual influence of force and temperature, thereby improving the accuracy of contact force measurement and improving the measurement accuracy of the contact force at the middle and distal ends of the flexible ureter.

[0058] The force sensitivity coefficient of the first fiber Bragg grating is obtained through calibration. Specifically, the first fiber 4 is fixed to a controllable tensioning device, which gradually applies a known axial force. A fiber optic sensing instrument is used to record the center wavelength drift of the first fiber Bragg grating 3.1. Under constant ambient temperature, the known axial force is gradually increased, and the corresponding change in the center wavelength of the Bragg grating 3.1 is recorded. This experiment is repeated multiple times to obtain multiple sets of data. The wavelength change is plotted against the applied force value, and the force sensitivity coefficient is obtained through linear regression fitting.

[0059] The temperature sensitivity coefficient of the first fiber Bragg grating is calibrated and obtained. Specifically, the first fiber 4 can be placed in a temperature-controlled environment, such as a constant temperature chamber, where the temperature can be gradually changed. A fiber optic sensing instrument is used to record the center wavelength drift of the first fiber Bragg grating 3.1. Without external force, the ambient temperature is gradually changed, and the change in the center wavelength of the first fiber Bragg grating 3.1 is recorded. This experiment is repeated multiple times to obtain multiple sets of data. The wavelength change is plotted against the temperature change, and the temperature sensitivity coefficient is obtained through linear regression fitting.

[0060] The temperature sensitivity coefficient of the second fiber Bragg grating is obtained by calibration, and the process is the same as that for obtaining the temperature sensitivity coefficient of the first fiber Bragg grating.

[0061] In other embodiments, the force sensitivity coefficient and temperature sensitivity coefficient of the first fiber Bragg grating, as well as the temperature sensitivity coefficient of the second fiber Bragg grating, can be obtained through theoretical calculations, numerical simulations, experimental database searches, and other methods.

[0062] The miniature force sensor and decoupling method in this invention can be used not only for force sensing during minimally invasive surgical palpation, but also for force sensing in interventional catheter surgery and other scenarios.

[0063] In the description of this specification, the use of terms such as "Embodiment 1," "this embodiment," or "in one embodiment" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in one or more embodiments or examples.

[0064] In the description of this specification, the terms "connection," "installation," "fixing," "setting," and "having" are interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0065] In the description of this specification, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0066] The above description of the embodiments is intended to enable those skilled in the art to understand and apply the technology of this invention. Those skilled in the art can easily make various modifications to these examples and apply the general principles described herein to other embodiments without creative effort. Therefore, this invention is not limited to the above embodiments. Modifications in the following situations should be within the scope of protection of this invention: ① New technical solutions implemented based on the technical solution of this invention and combined with existing common knowledge, where the technical effects of the new technical solution do not exceed the technical effects of this invention; ② Equivalent substitutions of some features of the technical solution of this invention using known technology, resulting in the same technical effects as those of this invention; ③ Extendable technical solutions based on the technical solution of this invention, where the substantive content of the extended technical solution does not exceed the technical solution of this invention; ④ Equivalent transformations made using the content of this specification and drawings, directly or indirectly applied to other related technical fields.

Claims

1. A micro force sensor for a flexible ureteroscope, characterized by, The base, the top cover and the hollow tubular elastomer are connected with each other, and the hollow tubular elastomer is provided with: A first optical fiber with a first fiber Bragg grating is arranged in the hollow tubular elastomer. A second optical fiber with a second fiber Bragg grating is arranged in the hollow tubular elastomer.

2. The micro force sensor of claim 1, wherein, The first optical fiber is arranged along the central axis of the hollow tubular elastomer.

3. The micro force sensor of claim 2, wherein, The second optical fiber is parallel to the first optical fiber but not collinear with the first optical fiber.

4. The micro force sensor of claim 3, wherein, The surface of the hollow tubular elastomer is provided with a plurality of hollow structures arranged in a staggered manner along the circumference of the hollow tubular elastomer.

5. The micro force sensor of claim 4, wherein, The cross-sectional shape of the hollow structure is an inclined parallelogram, and the inclined directions of the plurality of hollow structures are not completely the same.

6. The micro force sensor of claim 5, wherein, The inclined directions of the hollow structures at different positions along the axial direction of the hollow tubular elastomer are different.

7. The micro force sensor according to any one of claims 1-6, wherein, The material of the hollow tubular elastomer is stainless steel or epoxy resin.

8. The micro force sensor according to any one of claims 1-6, wherein, The base and the top cover are respectively bonded and fixed with the first optical fiber.

9. A sensor decoupling method based on the micro force sensor according to any one of claims 1-8, characterized in that, The method comprises: The Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating is obtained respectively. A first relationship between the Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating and the contact force is constructed. The Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating is brought into the first relationship, and the contact force is obtained.

10. The sensor decoupling method of claim 9, wherein, The first relationship between the Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating and the contact force further comprises: The force sensitivity coefficient and the temperature sensitivity coefficient of the first fiber Bragg grating and the temperature sensitivity coefficient of the second fiber Bragg grating are calibrated, and the force sensitivity coefficient and the temperature sensitivity coefficient of the first fiber Bragg grating and the temperature sensitivity coefficient of the second fiber Bragg grating are used to construct the first relationship between the Bragg center wavelength shift of the first fiber Bragg grating and the second fiber Bragg grating and the contact force.

Images