CN115839792A - Three-dimensional force sensor for abdominal cavity minimally invasive surgery instrument and use method thereof - Google Patents

Abstract

The invention discloses a three-dimensional force sensor for an abdominal cavity minimally invasive surgery instrument and a using method thereof, wherein the three-dimensional force sensor comprises a strain elastomer and a fiber bragg grating sensor; the strain elastic body is of an integrated structure and is made of elastic materials, the strain elastic body comprises an upper disc, a lower disc and three spiral beams, the top ends of the spiral beams are connected with the bottom end of the upper disc, the bottom ends of the spiral beams are connected with the top end of the lower disc, and the three spiral beams are distributed on the circumferences of the upper disc and the lower disc at intervals of 120 degrees respectively; the fiber grating sensor comprises a first fiber grating, a second fiber grating, a third fiber grating and a fourth fiber grating which are connected in sequence; the first fiber grating, the second fiber grating and the third fiber grating are respectively arranged on the inclined plane of the spiral beam, and the fourth fiber grating is arranged on the surface of the lower disc. The sensor can accurately detect the contact force between tissues and instruments in real time in the process of operating the minimally invasive surgery robot by a doctor, reduce the damage to a patient caused by misoperation and improve the safety of the surgery.

Description

A three-dimensional force sensor for abdominal minimally invasive surgical instruments and its application method

technical field

The invention relates to the field of abdominal minimally invasive surgery, in particular to a three-dimensional force sensor used for abdominal minimally invasive surgical instruments and a method for using the same.

Background technique

During the laparoscopic minimally invasive surgery, the doctor operates the main hand manipulator according to the visual feedback of the endoscope, the control system obtains the position information of the main hand, and controls the slave hand manipulator to follow the movement through calculation, and the doctor perceives and estimates based on visual feedback and experience From the contact force between the instrument end of the hand manipulator and the tissue, the existing clinical surgical robots generally lack force feedback. At present, force feedback control has attracted much attention in the research of minimally invasive surgical robots. The ability to sense the contact force during surgery in real time is of great significance to the safety and completion time of surgery.

The role of force feedback control in minimally invasive surgical robots: the judgment of abnormal tissues, such as tumors, arterial calcification and other abnormal tissues will show different force sensations from normal tissues, and force feedback can help doctors further confirm the condition; Doctors feel the sense of presence to prevent excessive operating force during the operation, causing secondary injury to the patient, and even threatening the life of the patient in severe cases.

The process of force feedback control of a minimally invasive surgical robot is as follows: firstly, the force information is obtained from the multi-dimensional force sensor of the surgical instrument at the end of the hand; the control system controls the torque of the main hand motor after calculation, so that the doctor can obtain a sense of force presence.

The premise of force feedback control is to accurately obtain the tissue interaction force through the multi-dimensional force sensor, and the surgical environment has the following restrictions on the sensor: ① meet the restrictions of disinfection and temperature changes in the surgical environment; safety; ③sufficient sensitivity to ensure measurement accuracy.

Contents of the invention

The technical problem to be solved by the present invention is to provide a three-dimensional force sensor for minimally invasive surgical instruments in the abdominal cavity and its use method in view of the above-mentioned deficiencies in the prior art. It is an important part of the force feedback control of minimally invasive surgical robots to detect the contact force between tissues and instruments, reduce the harm caused by misoperation to patients, and improve the safety of surgery.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A three-dimensional force sensor for minimally invasive surgical instruments in the abdominal cavity, including a strained elastic body and a fiber grating sensor; the strained elastic body is an integral structure and made of elastic materials, and the strained elastic body includes an upper disc and a lower disc And three spiral beams, the top of the spiral beam is connected to the bottom of the upper disc, the bottom of the spiral beam is connected to the top of the lower disc, and the three spiral beams are distributed at intervals of 120 degrees on the circumference of the upper disc and the lower disc The fiber grating sensor includes the first fiber grating, the second fiber grating, the third fiber grating and the fourth fiber grating connected in sequence; the first fiber grating, the second fiber grating and the third fiber grating are respectively arranged on the slope of the spiral beam , the fourth fiber grating is arranged on the surface of the lower disk.

As a further preference of the present invention, the first fiber grating, the second fiber grating and the third fiber grating are respectively arranged along the centerline of the upper surface of the slope of the spiral beam.

As a further preference of the present invention, a fiber grating demodulator is also included, and the head end of the first fiber grating and the tail end of the fourth fiber grating are both connected to the fiber grating demodulator.

As a further preferred embodiment of the present invention, the connection between the first fiber grating, the second fiber grating and the third fiber grating and the helical beam is a fixed connection, and the connection method is glue packaging.

As a further preference of the present invention, the first fiber grating, the second fiber grating, the third fiber grating and the fourth fiber grating are all Bragg grating fibers.

As a further preference of the present invention, the outer diameter of the three-dimensional force sensor is 8mm.

A method of using a three-dimensional force sensor for abdominal minimally invasive surgical instruments,

Step 1. Obtain the wavelength variation of the first fiber Bragg grating, the second fiber Bragg grating, and the third fiber Bragg grating due to temperature changes through the center wavelength and detection wavelength of the fourth fiber Bragg grating;

Step 2, obtaining the detection wavelengths of the first fiber Bragg grating, the second fiber Bragg grating, and the third fiber Bragg grating respectively, and obtaining the wavelength variation of the first fiber Bragg grating, the second fiber Bragg grating, and the third fiber Bragg grating according to the central wavelength and the detection wavelength;

Step 3, according to the wavelength variation of the first fiber Bragg grating, the second fiber Bragg grating, the third fiber Bragg grating and the wavelength variation of the fourth fiber Bragg grating, obtain the first fiber Bragg grating, the second fiber Bragg grating caused only by the external force strain after eliminating the temperature strain The wavelength variation of the second fiber grating and the third fiber grating;

Step 4, the amount of wavelength change based on the external force strain obtained in step 3, through the relationship formula between the strain of the fiber Bragg grating sensor and the wavelength, to obtain the strain amount of the elastic structure where the fiber Bragg grating sensor is located;

Step 5. According to the decoupling obtained by the least square method and the strain generated by external force, the magnitude of the detection force in each dimension is finally obtained.

As a further preference of the present invention, the reflected wavelength variation of the fiber grating sensor is affected by axial strain and temperature changes, and the relational expression is:

where λ is the initial center wavelength of the FBG, Δλ is the wavelength offset, _Pe is the effective elasto-optic coefficient of the fiber, α is the thermal expansion coefficient of the material used in the FBG, η is the thermo-optic coefficient of the fiber, and ΔT is the temperature change ε is the axial strain.

As a further optimization of the present invention, the relationship between the three elastic strains on the spiral beam and the three-dimensional force of the remote load is expressed as:

F=Mε

Among them, ε=[ε ₁ ε ₂ ε ₃ ] ^T is the strain at the position where the first FBG, the second FBG and the third FBG are finally obtained, and F=[F _x F _y F _z ] ^T is the detected three-dimensional Force, M∈R ^3×3 is the calibration matrix to be solved;

The M matrix is solved by the least square method, and by measuring n sets of strain ε and applied force F, it can be obtained:

Among them, i=1,2,...,n;

Solved:

M = Fε ^T (εε ^T ) ⁻¹ .

The present invention has following beneficial effects:

Restricted by the requirements in the background technology, at the same time commercialized multi-dimensional sensors have fixed dimensions and structures, so the design of the present invention is based on the fiber grating force sensor, when the external force or moment load is applied, the deformation information such as strain and displacement generated by the elastic body , the fiber grating is arranged on the elastic body, and deformation information such as strain and displacement act on the fiber grating, causing the center wavelength of the fiber grating to drift, and the external force or moment load information received is obtained by detecting the drift information of the wavelength. Compared with traditional sensors such as resistors and capacitors, fiber grating sensors have the advantages of small size, anti-electromagnetic interference, corrosion resistance, high temperature resistance, and can work in complex environments.

Specifically, compared with the traditional three-dimensional force sensor, the beneficial effects of the three-dimensional force sensor based on the fiber grating design of the present invention are:

First: The present invention uses a fiber grating sensor, which uses the wavelength change as the sensor output. Compared with the traditional resistance strain type three-dimensional force sensor, it has good electromagnetic compatibility and corrosion resistance, and can work in the surgical environment of disinfection and temperature changes. middle;

Second: The helical elastic body structure adopted by the three-dimensional force sensor has good sensitivity under the constraints of small volume and sufficient and safe stiffness.

Third: the present invention only uses 3 fiber grating force sensors, saving costs;

Fourth: small size, the outer diameter of the three-dimensional force sensor is only 8mm, which is better suitable for minimally invasive surgical instruments.

Fifth: temperature compensation is performed by replacing the temperature sensor with the fourth fiber grating.

Description of drawings

Fig. 1 is a system schematic diagram of a three-dimensional force sensor used in abdominal minimally invasive surgery according to the present invention.

Fig. 2 is a schematic diagram of the elastic body structure of a three-dimensional force sensor used in abdominal minimally invasive surgery according to the present invention.

Fig. 3 is a schematic diagram of a fiber grating arrangement of a three-dimensional force sensor used in abdominal minimally invasive surgery according to the present invention.

Among them: 1. Three-dimensional force sensor; 2. Optical fiber grating demodulator; 3. Computer; 101. Upper disc; 102. Spiral beam, 103. Lower disc; 104. Optical fiber grating for force detection; 105. Fiber Bragg gratings for temperature compensation.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

In the description of the present invention, it should be understood that the orientations or positional relationships indicated by the terms "left side", "right side", "upper", "lower" are based on the orientations or positional relationships shown in the accompanying drawings, and are only For the purpose of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, "first", "second" and the like do not represent components importance, and therefore should not be construed as limiting the invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the protection scope of the present invention.

The purpose of the present invention is to provide a three-dimensional force sensor for minimally invasive surgical instruments in the abdominal cavity. The sensor can accurately detect the contact force between the tissue and the instrument in real time during the operation of the minimally invasive surgical robot by the doctor, and reduce the impact of misuse on the patient. It is an important part of the force feedback control of minimally invasive surgical robots to improve the safety of surgery.

As shown in FIG. 1 , it is a schematic diagram of a three-dimensional force sensor system for minimally invasive abdominal surgery, which includes a three-dimensional force sensor 1 , a fiber grating demodulator 2 , and a computer 3 . The grating optical fiber of the three-dimensional force sensor 1 and the fiber grating demodulator 2 perform optical signal transmission, and the fiber grating demodulator 2 and the computer 3 perform digital signal transmission.

The three-dimensional force sensor 1 includes a strain elastic body and a fiber grating sensor.

As shown in accompanying drawing 2, the elastic body structure of the three-dimensional force sensor used for minimally invasive surgery in the abdominal cavity shows the force sensor of the present invention, and the elastic strain body consists of an upper disc 101, a lower disc 103 and three helical beams 102, which are One-piece structure and made of elastic material 304 steel, its elastic modulus E=2.04*10 ¹¹ N/m ² , Poisson's ratio μ=0.285. The material has good corrosion resistance, biocompatibility, impact resistance, fatigue resistance, high strength, low Young's modulus, low hysteresis, and is easy to process. The upper disc 101 and the lower disc 103 are rigidly connected to the wall of the surgical instrument, and the three helical beams 102 are distributed at intervals of 120 degrees on the circumference of the disc, connecting upward to the upper disc 101 and downward to the lower disc 103. The helical beams 102 Helix angle, thickness, and width are determined after structure optimization.

As shown in FIG. 3 , it is a schematic diagram of the fiber grating arrangement of the three-dimensional force sensor used in abdominal minimally invasive surgery.

The optical fibers used in the present invention are all Bragg grating optical fibers. It includes a fiber grating 104 for force detection and a fiber grating 105 for temperature compensation. The first fiber Bragg grating, the second fiber Bragg grating and the third fiber Bragg grating are fiber Bragg gratings 104 for force detection, and the fourth fiber Bragg gratings are fiber Bragg gratings 105 for temperature compensation. The first fiber grating, the second fiber grating, and the third fiber grating are respectively arranged at the centerlines of the inclined surfaces of the three helical beams 102 to detect the far-end three-dimensional force. Due to the coupling effect between them, this is also a multi-dimensional The problems existing in force sensors are solved through subsequent calibration and decoupling.

The fourth fiber grating is arranged on the surface of the lower disk 103, and is not affected by the applied load to generate strain, and its center wavelength offset is not affected by the load force, but only by the temperature change, and is used to control the first fiber grating, the second The fiber grating and the third fiber grating perform temperature compensation.

The first fiber Bragg grating, the second fiber Bragg grating, the third fiber Bragg grating and the fourth fiber Bragg grating are sequentially connected through optical fibers. The head end of the first fiber Bragg grating and the tail end of the fourth fiber Bragg grating are connected to an external demodulation device, the tail end of the first fiber Bragg grating is connected to the head end of the second fiber Bragg grating, and the tail end of the second fiber Bragg grating is connected to the third fiber Bragg grating The head end is connected, and the tail end of the third fiber grating is connected with the head end of the fourth fiber grating.

The volume of the present invention is small, and the outer diameter of the three-dimensional force sensor 1 is only 8 mm, which is better suitable for minimally invasive surgical instruments.

The principle of fiber grating is to use the photosensitivity of the fiber material to write a periodic refractive index modulation grating on the fiber core, and use laser light as the detection and transmission signal. Multiple gratings with different central wavelengths are written on a single fiber to form distributed measurement.

The fiber grating demodulator 2 is connected with the fiber grating sensor, and is used to emit laser light to the fiber grating sensor, receive the laser light of a specific wavelength returned by the fiber grating sensor, convert the laser signal into a digital electrical signal, and demodulate the corresponding signal of each grating point. wavelength.

Three-dimensional force sensor 1 detection process of the present invention is:

The first optical fiber, the second optical fiber, and the third optical fiber on the spiral beam 102 are fixedly connected to the three spiral beams 102 respectively, and are preferably packaged with glue. Compared with the rigidity of the spiral beam 102, the stiffness of the optical fiber can be ignored. When strained, the optical fiber can be subjected to the same strain, and the strain of the grating in the fiber is the same as the strain of the helical beam 102 where the grating sits.

The three-dimensional force sensor 1 is fixed near the driving end of the surgical instrument, and the end of the instrument contacts the tissue to generate an interactive force. Since the upper disc 101 of the three-dimensional force sensor 1 is rigidly connected with the instrument tube wall, it is transmitted to the helical beam 102, within a certain ratio limit range The linear proportional relationship between the internal stress and the strain generates elastic strain, which makes the wavelengths of the first fiber grating, the second fiber grating, and the third fiber grating on the helical beam 102 shift.

When broadband light propagates in a fiber grating, wavelengths that meet certain conditions will be reflected back, and the reflected light satisfies the Bragg reflection condition:

λ _B = 2n _ef Λ

The change of reflection wavelength of fiber grating sensor is affected by axial strain and temperature change, and the relationship is as follows:

where λ is the initial center wavelength of the FBG, Δλ is the wavelength offset, _Pe is the effective elasto-optic coefficient of the fiber, α is the thermal expansion coefficient of the material used in the FBG, η is the thermo-optic coefficient of the fiber, and ΔT is the temperature change ε is the axial strain.

The fourth fiber Bragg grating is only affected by temperature changes, and the first fiber Bragg grating, the second fiber Bragg grating, and the third fiber Bragg grating are affected by the strain generated by temperature and load at the same time.

Therefore, through the wavelength offset of the four gratings of the optical fiber, the strain caused by the load at the position of the first fiber grating, the second fiber grating and the third fiber grating on the helical beam 102 can be obtained.

The relationship between the three elastic strains on the spiral beam 102 and the three-dimensional force of the remote load is expressed as:

F=Mε

Among them, ε=[ε ₁ ε ₂ ε ₃ ] ^T is the strain at the position where the first FBG, the second FBG and the third FBG are finally obtained, and F=[F _x F _y F _z ] ^T is the detected three-dimensional Force, M∈R ^3×3 is the calibration matrix to be solved.

The M matrix is solved by the least square method, and by measuring n sets of strain ε and applied force F, it can be obtained:

Wherein, i=1, 2, . . . , n.

Solved:

M＝ ^FεT ( ^εεT ) ^-1

The three-dimensional force can be detected based on the strain and the calibration matrix of the fiber grating, and the average error can be obtained from the calculation of the applied load to test the feasibility of the method and the accuracy of the calibration matrix.

The three-dimensional force sensor 1 uses the wavelength drift of the fiber grating as the output signal of the sensor, and realizes temperature compensation through the fourth fiber grating, thereby solving the problem of temperature changes during the operation; It has the advantages of small size, anti-electromagnetic interference, corrosion resistance, high temperature resistance, and can work in complex environments. It can meet the special requirements of small surgical instruments and repeated disinfection.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be carried out to the technical solutions of the present invention. These equivalent transformations All belong to the protection scope of the present invention.

Claims (9)

1. A three-dimensional force sensor for a minimally invasive laparoscopic surgical instrument, comprising: the sensor comprises a strain elastic body and a fiber bragg grating sensor;

the strain elastomer is of an integrated structure and is made of an elastic material, the strain elastomer comprises an upper disc (101), a lower disc (103) and three spiral beams (102), the top end of each spiral beam (102) is connected with the bottom end of the upper disc (101), the bottom end of each spiral beam (102) is connected with the top end of the lower disc (103), and the three spiral beams (102) are distributed on the circumferences of the upper disc (101) and the lower disc (103) at intervals of 120 degrees;

the fiber grating sensor comprises a first fiber grating, a second fiber grating, a third fiber grating and a fourth fiber grating which are connected in sequence; the first fiber grating, the second fiber grating and the third fiber grating are respectively arranged on the inclined plane of the spiral beam (102), and the fourth fiber grating is arranged on the surface of the lower disc (103).

2. The three-dimensional force sensor for the laparoscopic minimally invasive surgical instrument of claim 1, wherein: the first fiber grating, the second fiber grating and the third fiber grating are respectively arranged along the central line of the upper surface of the inclined plane of the spiral beam (102).

3. The three-dimensional force sensor for the laparoscopic minimally invasive surgical instrument of claim 1, wherein: the fiber bragg grating demodulator is characterized by further comprising a fiber bragg grating demodulator (2), wherein the head end of the first fiber bragg grating and the tail end of the fourth fiber bragg grating are connected with the fiber bragg grating demodulator (2).

4. The three-dimensional force sensor for the laparoscopic minimally invasive surgical instrument of claim 2, wherein: the first fiber bragg grating, the second fiber bragg grating and the third fiber bragg grating are fixedly connected with the spiral beam (102) in a glue packaging mode.

5. The three-dimensional force sensor for the laparoscopic minimally invasive surgical instrument of claim 1, wherein: the first fiber grating, the second fiber grating, the third fiber grating and the fourth fiber grating are all Bragg grating fibers.

6. The three-dimensional force sensor for the laparoscopic minimally invasive surgical instrument of claim 1, wherein: the outer diameter of the three-dimensional force sensor (1) is 8mm.

7. A use method of the three-dimensional force sensor for the celiac minimally invasive surgery instrument based on any one of claims 1 to 6, is characterized in that: step one, obtaining wavelength variation of a first fiber grating, a second fiber grating and a third fiber grating caused by temperature variation through the central wavelength and the detection wavelength of a fourth fiber grating;

step two, respectively obtaining the detection wavelengths of the first fiber bragg grating, the second fiber bragg grating and the third fiber bragg grating, and obtaining the wavelength variation of the first fiber bragg grating, the second fiber bragg grating and the third fiber bragg grating according to the central wavelength and the detection wavelength;

obtaining the wavelength variation of the first fiber grating, the second fiber grating and the third fiber grating caused only by external force strain after temperature strain is eliminated according to the wavelength variation of the first fiber grating, the second fiber grating and the third fiber grating and the wavelength variation of the fourth fiber grating;

step four, obtaining the strain quantity of the elastic structure where the fiber grating sensor is located through a relation formula of strain and wavelength of the fiber grating sensor according to the wavelength variable quantity generated based on the external force strain obtained in the step three;

and step five, obtaining decoupling and dependent variable generated by external force according to a least square method, and finally obtaining the magnitude of each dimension detection force.

8. The method of claim 7, wherein the three-dimensional force sensor is used in a minimally invasive laparoscopic surgical instrument, and comprises: the reflection wavelength variation of the fiber grating sensor is influenced by axial strain and temperature variation, and the relation is as follows:

wherein λ is the initial center wavelength of the fiber grating, Δ λ is the wavelength offset, P _e The effective elasto-optic coefficient of the optical fiber, alpha is the thermal expansion coefficient of the material used for the fiber grating, eta is the thermo-optic coefficient of the optical fiber, delta T is the temperature change, and epsilon is the axial strain.

9. The method of claim 7, wherein the three-dimensional force sensor is used in a minimally invasive laparoscopic surgical instrument, and comprises: the relationship between the three-dimensional forces of the remote load and the three-dimensional elastic strains on the spiral beam (102) is expressed as follows:

F＝Mε

wherein epsilon = [ epsilon ] ₁ ε ₂ ε ₃ ] ^T F = [ F ] for finally obtaining the strain of the positions of the first fiber grating, the second fiber grating and the third fiber grating _x F _y F _z ] ^T For three-dimensional forces to be detected, M ∈ R ^3×3 A calibration matrix to be solved;

solving the M matrix by a least square method, and measuring n groups of strain epsilon and applied force F to obtain:

wherein i =1,2, \8230, n;

solving to obtain:

M＝Fε ^T (εε ^T ) ^-1 。

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