CN108593161A - A kind of minimally invasive surgical operation robot three-dimensional force sensor based on fiber grating - Google Patents

Abstract

The invention proposes a three-dimensional force sensor for a minimally invasive surgical robot based on optical fiber gratings, which is mainly composed of four pairs of optical fiber Bragg gratings, which are respectively fixed in circumferential grooves along the outer wall of a hollow glass fiber rod; In the processing module, the digital signal of stress is drawn out from the connection end of the manipulator. The optical path of the three-dimensional force sensor is: the light emitted by the broadband light source enters the sensing fiber grating through the optical frequency isolator and the fiber beam splitter in sequence, and the reflected light of the grating passes through the fiber beam splitter and the transmission of the matching grating to the signal processing circuit in turn. After the optical signal is processed, it is transmitted to the control circuit, and the central wavelength of the sensing fiber grating is deduced inversely through the driving signal of the measurement circuit, and then the digital signal of the stress is obtained. In addition, aiming at the phenomenon of three-dimensional force information coupling, the static decoupling of three-dimensional force information is realized through corresponding algorithms. The invention has the advantages of simple structure, high precision, no influence of electromagnetic interference, easy processing and low cost.

Description

A 3D force sensor for minimally invasive surgery robot based on fiber grating

technical field

The invention belongs to the technical field of minimally invasive surgical robots, and in particular relates to a three-dimensional force sensor for a minimally invasive surgical robot based on an optical fiber Bragg grating.

Background technique

In recent years, robots have been widely used in assisting surgical operations, but the existing robotic systems for minimally invasive surgery generally lack force sensory information feedback. The force detection and force feedback technology of robot-assisted minimally invasive surgery enables the system to have on-the-spot force perception capabilities, enabling the operator to feel the interaction between the surgical instrument and the patient's tissue in real time, improving the surgeon's surgical skills and improving the surgical performance. quality.

The basic process of realizing the force feedback function in a minimally invasive surgical robot is: first, the sensor array installed at the end of the manipulator obtains the force signal, and the signal is sent to the main hand controller after processing; after a series of calculations, the controller controls the motor output Corresponding torque, reproduce the changing presence force information during the operation to the doctor.

The extraction of force information is an important part of the robot force feedback system. The multi-dimensional force sensor designed for the structure of the manipulator should meet the following requirements: ① Accuracy. The sensor has suitable sensitivity and good stability, and can truly and stably reflect the force information in the corresponding direction; ②Safety. Change the shape and stiffness of the operator as little as possible to ensure its structural stability; ③ Adaptability. Meet the special requirements of the medical environment (preoperative disinfection treatment, large temperature and humidity changes in the working environment, etc.) and the limitation of the force measurement range; ④ economy. Keep the cost of force sensors as low as possible.

Based on the limitations of the above requirements, the current commercialized miniature multi-dimensional force sensors are not suitable for minimally invasive surgical robotic systems. Therefore, it is necessary to study and improve multi-dimensional force sensors suitable for minimally invasive surgical robotic systems in combination with the structure of the manipulator. Previously, the multi-dimensional force sensor involved in the Chinese patent No. 201110123095.2 patent/application document entitled "Three-dimensional Force Sensor for Minimally Invasive Surgical Robots" used eight strain gauges to form a force sensor array to detect force information. It is made of stainless steel and is easily affected by electromagnetic interference; in the present invention, the force sensor is designed based on fiber grating. The fiber force sensor is small in size, light in weight, has excellent insulation and anti-interference performance, and can be used in precision measurement environments. The material of the operator is changed to glass fiber, which is lighter than metal materials.

Fiber Bragg Grating is a new type of optical passive device. Its basic measured physical quantities are temperature and strain. In order to realize the detection of force/torque information, generally multiple gratings are formed into an array and laid on a specially designed elastic structure. Similar to the detection method based on traditional strain gauges, in particular, the optical fiber itself with gratings can be directly used as the sensing elastic body. As shown in Figure 3, when there is an external force or moment load, the deformation information such as strain and displacement generated by the elastic body or optical fiber acts on the fiber grating, causing the grating pitch of the fiber grating to change, thereby bringing about a change in the center wavelength of the fiber grating Drift, the external force or moment load information received can be characterized by detecting the drift information of this wavelength.

In addition to the inherent advantages of being free from electromagnetic interference, low loss, easy to bend, small size, light weight, low cost, corrosion resistance, waterproof, and fire prevention, the fiber grating force sensor has extremely high accuracy for important measurement parameters such as temperature and stress. Measurement accuracy and linearity, as well as ample measurement range, low hysteresis, and strong NMR compatibility.

The optical fiber slip ring is a precision device that can transmit optical signals without interruption between the rotating part and the stationary part. It meets the 270° rotation range required by the degree of freedom of the rotation of the manipulator and the base, and avoids the impact caused by the rotation of the movable joint. fiber optic damage.

Theoretically, the force applied in one direction of the force sensor alone will not affect other directions, but due to the nature of the hollow glass fiber rod itself, the fixing accuracy of the grating and other factors, almost every force component acting on the sensor will have an impact on the sensor. Each output signal of the sensor has an influence, which is coupling. The coupling of force information will affect the signal accuracy and cause distortion in the output of three-dimensional force information. Static decoupling can be carried out from two aspects: ①In terms of hardware, the accuracy of grooving hollow glass fiber rods and the pasting accuracy of gratings can be increased, and the coupling between dimensions can be reduced or even eliminated from the root. It increases the cost and is not easy to implement repeatedly; ②The software decouples the three-dimensional force information and processes the sampling data through the algorithm. The decoupling is more accurate and has advantages in terms of processing cost.

Chinese patent CN106248269A "Temperature-insensitive two-dimensional stress sensor based on fiber grating" provides a method for measuring stress using a fiber grating force sensor, but the force sensor in this patent is limited to the measurement of two-dimensional directional force and cannot be obtained. The force in the axial direction is known, and the decoupling of the force information is lacking. Although for the hollow glass fiber rod, the radial force has a greater influence on the deformation of the rod than the axial force, but the lack of axial force Measurements would render the system unusable for actual surgical control.

Chinese patent CN103822738A "Stress Sensor Based on Fiber Bragg Grating" provides a method of pasting the grating pair on the elastic body to measure the external stress. In this patent, the fiber grating is pasted at both ends, which can effectively curb the chirp effect , but the fiber grating demodulation method it provides is not universal, and the measurement of stress by this method is limited to the measurement of one-dimensional radial force, and the patent also lacks the decoupling of force information.

Chinese patent CN106644253A "Three-dimensional force sensor decoupling calibration and filtering method and device for constant force grinding" proposes a method of solving the calibration matrix by using the matrix direct inversion method, and then decoupling the three-dimensional force information, However, in practice, in order to ensure the decoupling accuracy, a force greater than the number of output shafts is often required for decoupling, so it is more accurate to use the least squares method to solve the calibration matrix. The force sensor decoupling method proposed in this patent has the advantage of simple calculation, but due to random errors, it has the defect of low decoupling accuracy.

At present, the main methods of decoupling are commonly used: ① Static decoupling algorithm based on linear calibration; ② Static decoupling algorithm based on least square linear fitting. Regarding the decoupling of multi-dimensional force sensors, someone proposed a decoupling method based on neural network. This method relies on multiple learning of neural network to gradually approach the optimal decoupling matrix. Training to get an optimal decoupling matrix. However, this method requires a large number of samples for network training and learning, the workload of data processing is too large, the requirements for software and hardware are high, and the time-consuming is too long, so it is difficult to use in the actual calibration process.

Contents of the invention

The technical problem to be solved by the present invention is to provide a high-precision and high-sensitivity optical fiber grating force sensor suitable for minimally invasive surgical robots, which can make surgeons feel real-time force changes during operation.

The three-dimensional force sensor for the minimally invasive surgical robot provided by the present invention is mainly composed of four pairs of fiber Bragg gratings, and each pair of grating fibers is a group including a transmitting optical fiber and a receiving optical fiber, which are responsible for adjusting the hollow glass fiber rod The radial force and axial force are measured. Wherein, the radial force measurement is the measurement of the forces Fx and Fy in the X and Y directions, and the axial force measurement is the measurement of the force Fz in the Z direction. First, four grooves with rectangular cutting surfaces are cut on the outer wall of the hollow glass fiber rod at intervals of 90° in the circumferential direction. Four pairs of optical fibers engraved with Bragg gratings are respectively fixed in the grooves, and each group of optical fiber pairs is ensured to be in contact with the hollow glass fiber. The central axis of the round rod has the same radial distance, and the optical fiber pair extends to the optical fiber slip ring from the base of the operator; wherein, the gap between the optical fiber and the groove is filled with epoxy resin. Cutting the rod has two meanings: one is to make the rod an elastic body of the fiber grating, which is convenient for the detection of the contact force, and the other is to facilitate the fixing of the fiber grating. The optical fiber pair refers to that each matching fiber grating is locked together with the corresponding sensing fiber grating to form a sensing/receiving fiber grating pair; at the same time, all matching fiber gratings are connected in series.

The strain decomposition generated by the two-dimensional radial force and one-dimensional axial force applied to the hollow glass fiber rod acts on the four sensing fiber gratings, and the force in three directions is reversed according to the wavelength change of the fiber grating, and then Static decoupling of 3D force information from force sensors. Among them, in the two dimensions of the X-direction and the Y-direction, two opposite pairs of sensing/receiving fiber gratings with similar structures are used to measure the stress. A pair of gratings is stretched, the length of the grating becomes longer, and the reflection wavelength When the fiber grating becomes longer, the other pair of gratings is compressed, the grating length becomes shorter, and the reflection wavelength becomes shorter; in the case of small deflection, the reflection wavelength difference of the fiber grating in the same dimension has a linear relationship with the external force, so the arrangement can play a role in temperature The function of compensation; the force in the Z direction is measured by four pairs of fiber gratings at the same time, and the digital signal of the stress is obtained through the fiber grating force sensor array and subsequent static decoupling.

Further, the fiber grating-based force sensor system also includes: a broadband light source, an optical frequency isolator, a fiber beam splitter, a sensing grating array, a matching grating array, a signal processing module, and a control circuit. The direction of the optical signal of the fiber optic force sensor is: The light emitted by the broadband light source enters the sensing fiber grating array through the optical frequency isolator and the fiber beam splitter in sequence, and the reflected light of the grating passes through the fiber beam splitter in turn and is transmitted to the signal processing module through the matching grating array, and then the processed light The signal reaches the control circuit, and the control circuit drives the matching grating array to follow the wavelength change of the sensing grating array. The signal processing module includes: a photoelectric detector, micro-analog signal amplification and filtering, and digital signal sampling and filtering.

Four pairs of optical fibers extend all the way to the optical fiber slip ring from the operator's base, which can avoid damage to the optical fiber due to the rotation of the movable joint; the optical fiber slip ring is installed at the rotation center of the operator's base after special design, and is hollow The fiberglass round rod passes through the central axis of the slip ring and consists of two parts, the rotating part and the stationary part.

Further, the optical fiber slip ring is composed of a slip ring stator and a slip ring rotor, the inner ring is the slip ring rotor, the outer ring is the slip ring stator, and the hollow glass fiber rod drives the slip ring rotor to rotate. There are two screws used to fix the rotor on the side of the screw-in end of the hollow glass fiber rod, and a slip ring anti-rotation plate is installed on the side of the slip ring close to the base to stop the rotation of the slip ring rotor and anti-rotation pins to prevent rotation of the slip ring stator.

When the actually designed fiber grating force sensor is subjected to a single force in a certain direction, it not only has a signal output in this direction, but also has a non-zero output in the other directions. Static coupling is a major factor affecting the measurement accuracy of multidimensional force sensors, so static decoupling of multidimensional force sensors is very important. The present invention intends to use software decoupling to deal with the linear coupling problem between three-dimensional force information.

A typical four-degree-of-freedom minimally invasive surgical manipulator is shown in Figure 1. The manipulator is installed at the end of the robotic arm of the surgical robot through a quick conversion interface. The manipulator includes four degrees of freedom: three rotational degrees of freedom and one end tool opening and closing degrees of freedom. The part of the manipulator is a hollow glass fiber material round rod with an outer diameter of 9.5mm, an inner diameter of 8mm, and a length of about 500mm. There are six thin steel wires that play a transmission role in the rod. The manipulator is installed on the manipulator arm of the minimally invasive surgical robot, and the translation of three degrees of freedom in space can be completed under the drive of the manipulator arm.

The scope of the invention is defined by the claims, which are incorporated into this section by reference. Those skilled in the art will be able to more fully understand the embodiments of the present invention, and to recognize other advantages related thereto, by considering the following detailed description of the embodiments.

Advantage and positive effect of the present invention:

The invention has simple structure, is not affected by electromagnetic interference, has high sensitivity, is easy to process and has low cost.

Description of drawings

Fig. 1 is a schematic diagram of a manipulator of a minimally invasive surgical robot;

Figure 2 is a system structure diagram of a force sensor for a minimally invasive surgical robot based on an optical fiber grating;

Figure 3 is a schematic diagram of the hollow glass fiber rod after cutting grooves and fixing four pairs of fiber gratings;

Fig. 4 is a transverse sectional view of the hollow glass fiber rod in Fig. 3;

Fig. 5 is a schematic diagram of the installation method of the optical fiber slip ring and the hollow glass fiber rod.

In the figure: 1. Base; 2. Hollow glass fiber rod; 3. Sensing grating array; 4. Optical fiber beam splitter; 5. Optical frequency isolator; 6. Broadband light source; 7. Matching grating array; 8. Signal processing module; 9. Control circuit; 10. Transmission steel wire; 11. Slip ring stator; 12. Slip ring rotor; 13. Screw; 14. Slip ring anti-rotation plate; 15. Anti-rotation pin.

31. The first sensing fiber Bragg grating; 32. The second sensing fiber Bragg grating; 33. The third sensing fiber Bragg grating; 34. The fourth sensing fiber Bragg grating.

71. First matched fiber Bragg grating; 72. Second matched fiber Bragg grating; 73. Third matched fiber Bragg grating; 74. Fourth matched fiber Bragg grating.

81. Photoelectric detector; 82. Micro-analog signal amplification and filtering; 83. Digital signal sampling and filtering.

Detailed ways

Example 1:

Below in conjunction with accompanying drawing and embodiment this patent is described further.

The invention intends to measure the force on the end tool of the manipulator in the directions of three translation degrees of freedom. During the operation, the manipulator is first inserted into the abdominal cavity through the sheath fixed on the abdominal wall of the patient; the fiber grating force sensor is arranged on the groove on the outer periphery of the hollow glass fiber rod 2 to measure the contact between the end tool of the manipulator and the patient's tissues and organs Installed at this position can effectively avoid the influence of the friction between the manipulator and the sheath on the force measurement. Considering that there are 6 transmission steel wires 10 arranged inside the hollow glass fiber rod 2, the internal space is crowded, so the fiber grating needs to be arranged on the outer wall of the hollow glass fiber rod 2, so the hollow glass fiber The round rod 2 is grooved, and four pairs of optical fibers are placed in the grooves, and it is ensured that each pair of optical fibers has the same radial distance from the central axis of the hollow glass fiber round rod 2 .

The three-dimensional force sensor for a minimally invasive surgical robot provided by the present invention is mainly composed of four pairs of fiber gratings, each pair of fiber gratings includes a transmitting (sensing)/receiving (matching) fiber grating, and the layout of the four pairs of fiber gratings is shown in Figure 3 and As shown in Figure 4, each pair of optical fibers is arranged in the groove of the hollow glass fiber round rod 2 periphery of the manipulator shown in Figure 1; the manipulator of the minimally invasive surgical robot shown in Figure 1 consists of a base 1, a hollow glass fiber The round rod 2 and the end tool are composed of four degrees of freedom including three rotations and one end tool opening and closing. The force sensor array composed of four pairs of fiber gratings measures the forces Fx, Fy and Fz of the hollow glass fiber rod in the X, Y and Z directions respectively; among them, the three coordinate axes of the XYZ coordinate system are perpendicular to each other and intersect at one point.

In the present invention, the optical fiber grating matched with the sensing optical fiber grating is used as a reference element, so that the matching optical fiber grating can track the wavelength change of the sensing optical fiber grating under the action of the control circuit, and by measuring the driving signal of the control circuit, it can be deduced inversely The central wavelength of the optical fiber grating is sensed, and then the external force on the hollow glass fiber rod 2 is obtained. As shown in Figure 2, it is a system structure block diagram of the embodiment of the force sensor based on the fiber grating that the present invention provides, and it comprises: Sensing grating array 3 (comprising the first sensing fiber grating 31, the second sensing fiber grating 32 , the third sensing fiber grating 33, the fourth sensing fiber grating 34), fiber beam splitter 4, optical frequency isolator 5, broadband light source 6, matching grating array 7 (including the first matching fiber grating 71, the second matching Fiber Bragg Grating 72, a third matching Fiber Bragg Grating 73, a fourth matching Fiber Bragg Grating 74), a signal processing module 8 and a control circuit 9. Each matching fiber grating is locked with the corresponding sensing fiber grating to form a sensing/receiving fiber grating pair; all matching fiber gratings are connected in series, and the Bragg wavelength is controlled by the control circuit 9 through the driving element to track the sensing Variation of grating center wavelength.

The signal transmission direction of the force sensor system is as follows: the light emitted by the broadband light source 6 passes through the optical frequency isolator 5 and the fiber beam splitter 4 to reach the sensing grating array 3 in turn, and the narrow-band light wave formed after being reflected from the sensing grating array 3 again After passing through the fiber beam splitter 4 and reaching the matching grating array 7 , after being transmitted through the matching grating array 7 , it reaches the signal processing module 8 and is converted into an electrical signal, which is then sent to the control circuit 9 . The signal processing module 8 includes: a photodetector 81 , a micro-analog signal amplification filter 82 , and a digital signal sampling and filter 83 .

For the specific structure of the manipulator used in the present invention, please refer to the patent/application document No. 200910306053.5 titled "A Minimally Invasive Surgical Wire Drive, Four Degrees of Freedom Surgical Tool".

To measure the radial force and axial force on the hollow glass fiber rod 2, first cut out four grooves with rectangular cutting surfaces on the outer wall of the hollow glass fiber rod 2 at intervals of 90° in the circumferential direction, four pairs engraved with optical fiber The optical fibers of the gratings are respectively fixed in the grooves, ensuring that each pair of optical fiber gratings has the same radial distance from the central axis of the hollow glass fiber rod 2, and the gap between the optical fibers and the grooves is filled with epoxy resin; wherein, each The structure of the sensing/receiving fiber grating pair is the same or similar, where the similarity means that the error of the two fiber gratings is within the acceptable range of those skilled in the art; and the two pairs of fiber gratings for measuring X-direction or Y-direction stress also satisfy the same structure or similar.

A modified optical fiber slip ring is fixed from the rotation center of the operator base, and its installation method is a through-hole slip ring installation, which is used to nest the hollow glass fiber rod 2. As shown in Figure 5, the optical fiber slip ring consists of The slip ring stator 11 and the slip ring rotor 12 are composed of the inner ring as the rotor and the outer ring as the stator. The hollow glass fiber rod 2 drives the slip ring rotor 12 to rotate; wherein, on the side of the screw-in end of the hollow glass fiber rod 2 there is Two screws 13 are used to fix the rotor. At the same time, a slip ring anti-rotation piece 14 that can stop the rotor from rotating and a anti-rotation pin 15 that prevents the stator from rotating are installed on the side of the slip ring close to the base 1 . Four pairs of optical fibers extend to the optical fiber slip ring through grooves on the outer wall of the manipulator; among them, four pairs of optical fibers are fixed in the through hole of the optical fiber slip ring rotor 12, and the broadband light source 6 is fixed in the through hole of the optical fiber slip ring stator 11; the hollow glass fiber When the round rod 2 (mechanical arm) rotates, the four pairs of sensing/receiving fiber gratings located on the slip ring rotor 12 rotate accordingly, while the broadband light source 6 fixed on the slip ring stator 11 remains stationary relative to the base 1 . The optical fiber slip ring here is used to transmit four-way optical fibers, and each matching fiber grating is locked with the corresponding sensing fiber grating to form a sensing/receiving fiber grating pair. These four-way optical fibers need to meet the requirements of 0-270 ° rotation range, while requiring no loss of optical fiber; optical fiber slip ring provides the best technical solution for data transmission between rotating connected system components, especially suitable for transmission of large-capacity data and signals from a fixed position to a rotating position It can improve the mechanical performance, simplify the operation of the system, and avoid damage to the optical fiber due to the rotation of the movable joint. The accuracy and alignment should be maintained during design.

The broadband light source 6 and the optical frequency isolator 5 are placed on the slip ring stator 11, four pairs of optical fibers and optical fiber beam splitter 4 are arranged on the slip ring rotor 12, and the signal processing module 8 and the control circuit 9 are arranged on the base 1 of the manipulator , the matching grating transmits the transmitted light to the base 1 of the manipulator through the guide fiber, and finally the processed digital signal of the stress is drawn out from the connection end of the manipulator through the leads.

Among them, the effective way to fix the four pairs of fiber gratings used for three-dimensional force measurement to the hollow glass fiber rod 2 is as follows: firstly, the fiber gratings are pre-tightened to generate internal stress, and then epoxy resin glue (adhesive) is used to fix the gratings It is fixed in the groove of the hollow glass fiber rod 2, and the gap between the optical fiber and the groove is also filled with epoxy resin glue.

The reflected light wavelength of the fiber Bragg grating satisfies the Bragg scattering condition, namely:

λ=2nΛ (1)

(1) where n and Λ are the effective refractive index and grating period of the fiber grating, respectively.

The relationship between the drift value of the fiber Bragg grating center wavelength and its ambient temperature and axial strain is:

In formula (2), λ is the initial center wavelength of the fiber Bragg grating, Δλ is the wavelength shift, Pe is the effective _elasto -optic coefficient of the fiber, α is the thermal expansion coefficient, and η is the thermo-optic coefficient of the fiber material.

When statically decoupling the three-dimensional force information of the force sensor, it is first necessary to collect coupling data, and attention should be paid to the acquisition accuracy during the process. The data collection method that the present invention adopts is: select X-axis, Y-axis, Z-axis unidirectional force and four units of XYZ axis simultaneous force to carry out data collection; Wherein, X-axis, Y-axis, Z-axis unidirectional force The force is used as decoupling data for analysis, and when the XYZ axes are applied simultaneously, it is used as the coupled force information to detect the decoupling effect. The data acquisition process is summarized as follows: use pulleys to hang weights of different masses in the X, Y, and Z directions of the end of the hand, respectively, measure the data before and after loading the weights, and calculate the difference for decoupling analysis. The data is collected by modulus quantization. In order to reduce the interference of random errors, the selection of each difference must be measured multiple times to obtain the average value.

Among them, since the force on the Z axis is not obvious, the mass of the hanging weight is at least an order of magnitude larger than that of the X axis and Y axis. The data collection of simultaneous force addition on the XYZ axis is: Weights of different masses are hung in the direction of °, and weights of the same certain mass are loaded on the Z axis each time. The four measurement units are tested according to the load (the mass of the added weight) from small to large and then from large to small, completing multiple measurement cycles, and calculating the average value of the difference before and after loading the weight to reduce the error.

For the static linear decoupling of the three-dimensional force information of the force sensor, assuming that the sensor is a linear system, its main task is to find the calibration matrix, and process the sampled data through the matrix, so as to accurately reflect the input value of the sensor.

When the number of force vectors is equal to the number of sensor output channels, the calibration matrix can be obtained by direct matrix inversion.

F=C U (3)

In the formula (3), F＝[f ₁ , f ₂ , f ₃ ] ^T is the equivalent component of the external force acting on the three coordinate axes of the force sensor; U＝[u ₁ , u ₂ , u ₃ ] ^T is the sensor The output column vector of , C is the calibration matrix of the required sensor, which converts the output vector of the sensor into a force vector.

When the output of the sensor is linear, there are:

When the number of force vectors is equal to the number of sensor output channels, when the matrix composed of calibration force vectors is an orthogonal matrix, its condition number reaches the minimum (equal to 1), and the sensor calibration accuracy is optimal at this time. When the collected data is small, this method is simple to calculate, but the random error will lead to low decoupling accuracy. Therefore, in order to ensure the accuracy, a force greater than the number of output shafts is used for decoupling, and the calibration matrix is calculated based on the least square theory. Can be described as:

The system of equations is expressed as:

i=1,2,...,n

At this point, the calibration matrix based on least squares is:

C＝FU ^T (UU ^T ) ^-1 (7)

In the formula (7), F is the equivalent component of the external force acting on the three coordinate axes of the force sensor; U is the output column vector of the sensor, and C is the calibration matrix of the sensor to be obtained.

On the basis of multiple sets of data measured in the experiment, the three coordinate axes of X, Y, and Z are used as the main channels to construct the input matrix and output matrix, and the calibration matrix in the sense of least squares is calculated and obtained. Finally, the three-dimensional force of the XYZ axis is used Coupling input and output matrices are used to test the decoupling effect, and the data obtained after decoupling is the magnitude of the force on the hollow glass fiber rod.

Claims (9)

1. A three-dimensional force sensor for a minimally invasive surgical robot based on fiber gratings, characterized in that: the three-dimensional force sensor is mainly composed of four pairs of fiber Bragg gratings, each pair of fiber gratings is a group that includes sensing fiber gratings and matching Fiber Bragg grating, responsible for the measurement of the radial force and axial force on the hollow glass fiber rod (2), wherein the measurement of the radial force is the measurement of the forces Fx and Fy in the X and Y directions, and the measurement of the axial force is Z The measurement of the force Fz in the direction; four pairs of optical fibers engraved with Bragg gratings are respectively fixed in the grooves on the outer circumference of the hollow glass fiber rod (2), and it is ensured that each group of optical fiber pairs has the same center axis as the hollow glass fiber rod. Radial distance, the optical fiber pair extends to the optical fiber slip ring at the base of the operator, and the above-mentioned groove is cut along the outer wall of the hollow glass fiber rod (2) at intervals of 90° to cut four cutting planes into a rectangle groove. 2. The three-dimensional force sensor of minimally invasive surgical robot based on fiber grating according to claim 1, is characterized in that: comprise force sensor system, this system comprises broadband light source (6), optical frequency isolator (5), optical fiber splitter Beamer (4), sensing grating array (3), matching grating array (7), signal processing module (8) and control circuit (9), the direction of the optical signal is: the light emitted by the broadband light source (6) passes through The optical frequency isolator (5) and the fiber beam splitter (4) enter the sensing grating array (3), and the reflected light of the grating passes through the fiber beam splitter (4) in turn and transmits to the signal through the transmission of the matching grating array (7). In the processing module (8), the optical signal is transmitted to the control circuit (9) after being processed. 3. The three-dimensional force sensor for minimally invasive surgical robot based on fiber gratings according to claim 2, characterized in that: the sensing grating array (3) comprises four sensing fiber gratings, and the matching grating array (7) including four matching optical fiber gratings, the driving signal applied by the control circuit (9) makes the matching optical fiber grating track the wavelength change of the sensing optical fiber grating, and the central wavelength of the sensing optical fiber grating can be deduced by measuring the driving signal, Thus, the change amount of the central wavelength of the sensing fiber grating can be obtained. 4. The three-dimensional force sensor for a minimally invasive surgical robot based on fiber gratings according to claim 1 or 3, wherein each matching fiber grating is locked with a corresponding sensing fiber grating to form a sensing/receiving optical fiber Grating pair; all matched fiber gratings connected in series. 5. the three-dimensional force sensor of minimally invasive surgical robot based on fiber grating according to claim 2, is characterized in that: signal processing module (8) comprises photodetector (81), micro-analog signal amplification filter (82) and digital Signal sampling and filtering (83). 6. The three-dimensional force sensor for a minimally invasive surgical robot based on fiber gratings according to claim 1, wherein the optical fiber slip ring adopts a through-hole installation method to avoid damage to the optical fiber due to the rotation of the movable joint. 7. according to claim 1 or 6 described based on the minimally invasive surgical robot three-dimensional force sensor of fiber grating, it is characterized in that: optical fiber slip ring is made up of slip ring stator (11) and slip ring rotor (12), and inner ring is The slip ring rotor (12), the outer ring is a slip ring stator (11), and the hollow glass fiber rod (2) drives the slip ring rotor (12) to rotate. 8. The three-dimensional force sensor for a minimally invasive surgical robot based on fiber gratings according to claim 7, characterized in that: there are two screws for fixing the rotor on one side of the screw-in end of the hollow glass fiber rod (2) (13), and at the same time, a slip ring anti-rotation piece (14) that can stop the rotation of the slip ring rotor (12) and a stop that prevents the rotation of the slip ring stator (11) are installed on the side of the slip ring close to the base (1). Resell (15). 9. The fiber grating-based three-dimensional force sensor for minimally invasive surgery robot according to claim 1, characterized in that: for the phenomenon of three-dimensional force information coupling, the static decoupling of three-dimensional force information is realized through corresponding algorithms.