Magnetic control capsule endoscope steering control device and method based on rotation strategy

Abstract

The invention provides a magnetic control capsule endoscope steering control device and method based on a rotation strategy, belongs to the technical field of medical image diagnosis, and utilizes an external permanent magnet to form a rotating magnetic field in an intestinal tract to accurately control the movement of a magnetic control capsule endoscope. The magnetic force and the torque between the permanent magnet and the capsule endoscope are accurately modeled, the complex structure of the intestinal tract and the rotating motion of the endoscope are considered, and a more flexible and safer driving scheme is provided. By optimizing the key driving angles (such as alpha and beta), the capsule endoscope can accurately advance in the intestinal tract, the influence of friction force and static friction force is effectively overcome, it is ensured that the endoscope can smoothly pass through bent and folded areas of the intestinal tract, high safety is achieved, and the potential intestinal injury risk is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical imaging diagnosis, and in particular relates to a magnetically controlled capsule endoscope steering control device and method based on a rotation strategy. Background Art

[0002] Digestive tract diseases seriously endanger people's health and safety. According to GLOBOCAN 2018 data, colon cancer and rectal cancer are the fourth and eighth most common types of cancer in the world. Colorectal cancer ranks third in global cancer diagnosis, accounting for 11% of all cancer diagnoses. Due to the rapid spread of cancer, patients are often in the late stage of cancer when diagnosed. Therefore, shifting the response strategy from simple treatment to early detection and early intervention has become an important means to reduce the harm of the disease. Therefore, the development of effective early digestive tract screening tools is of great significance to digestive tract health.

[0003] Permanent magnets have become a hot topic in the research of magnetic field drive devices due to their low cost. The permanent magnet drive methods mainly include magnetic dragging and rotating magnetic field driving capsule endoscopes with threaded structures. The magnetic dragging method has a simple structure, but due to the nonlinear distribution of the magnetic lines of force of the external permanent magnet and the high elasticity of the intestine, when the permanent magnet is close to the magnetically controlled capsule endoscope, it may cause the magnetically controlled capsule endoscope to be quickly attracted to the surface of the external permanent magnet, thereby increasing the risk of potential damage to the intestine. In contrast, the rotating magnetic field converts the rotational motion into linear motion by applying magnetic force and magnetic torque to the magnetically controlled capsule endoscope with a threaded structure, which has a better ability to reduce potential risks.

[0004] Although rotary drive can improve the safety of drive to a certain extent. However, the human intestinal system has a complex structure, including a variety of bends, folds and collapsed areas, making the flexible drive of the magnetically controlled capsule endoscope in the intestine a key technical challenge. The ideal driving state is that the external permanent magnet should be located directly above the capsule endoscope to achieve the best driving effect. In actual clinical operations, the position of the external permanent magnet is limited by factors such as the accessible space of the robotic arm and the position of the bed, making it difficult to intuitively observe the spatial alignment between it and the magnetically controlled capsule endoscope. Therefore, in order to improve the driving performance of the magnetically controlled capsule endoscope in a tortuous intestinal environment, it is necessary to find a suitable driving range in the intestine to ensure that the capsule endoscope can start and move forward from a stationary state. Summary of the invention

[0005] As described in the background art, although the rotating magnetic field driving method can reduce the direct contact between the endoscope and the intestinal wall, due to the complex structure of the human intestine, the application of the rotating magnetic field in the intestine still faces flexibility problems. Especially in the curved and folded areas of the intestine, the movement of the endoscope may not be able to maintain the optimal trajectory. In addition, the position control of the external permanent magnet is also limited by the actual conditions of clinical operations, resulting in unstable driving effects of the magnetically controlled capsule endoscope. To solve the above problems, the present invention proposes a steering control device and method for a magnetically controlled capsule endoscope based on a rotation strategy.

[0006] The technical solution of the present invention is described as follows:

[0007] A steering control device for a magnetically controlled capsule endoscope based on a rotation strategy, comprising:

[0008] An external permanent magnet system for generating a rotating magnetic field in the intestine;

[0009] A drive control module for controlling the direction of the rotation axis of the magnetically controlled capsule endoscope by adjusting the spatial position and rotation angle of the permanent magnet;

[0010] A magnetic field modeling module for calculating the magnetic force and torque between the permanent magnet and the capsule endoscope in real time based on the dipole model;

[0011] A rotation drive mechanism for adjusting the circular motion trajectory of the permanent magnet by optimizing the drive angles α and β, so that the capsule endoscope can achieve stable linear motion in the curved intestine.

[0012] In the above technical solution, in the magnetic field modeling module:

[0013] The magnetic force calculation formula is:

[0014] ,

[0015] The torque calculation formula is:

[0016] ,

[0017] Wherein, is the magnetic permeability, is the magnetic moment of the capsule endoscope, is the magnetic moment change rate, is the magnetic field strength of the external permanent magnet;

[0018] In the above technical solution, the drive control module includes:

[0019] A dynamic balance unit for establishing a dynamic equation by decomposing the magnetic force into x-axis, y-axis, and z-axis component forces and combining centrifugal force, fluid resistance, and friction;

[0020] The annular trajectory planning unit adjusts the annular motion radius of the permanent magnet according to the intestinal bending radius to ensure that the angular velocity of the capsule endoscope is synchronized with that of the permanent magnet.

[0021] In the above technical solution, the external permanent magnet system includes:

[0022] An adjustable robotic arm that controls the movement of the permanent magnet inside or outside the annular intestine to form a magnetic force component radially inward or outward;

[0023] An angle sensor that real-time monitors the deflection errors of the driving angles α, β and the rotation axis of the capsule endoscope.

[0024] In the above technical solution, the rotary drive mechanism converts the rotary motion of the capsule endoscope into a linear motion through a threaded structure, and the torque received by the magnetically controlled capsule endoscope is:

[0025] ,

[0026] Wherein, is the moment of inertia, is the angular acceleration during rotation, is the frictional torque between the magnetically controlled capsule endoscope and the intestine.

[0027] A method for controlling the steering of a magnetically controlled capsule endoscope based on a rotation strategy includes the following steps:

[0028] (a) Construct a reference coordinate system centered on the capsule endoscope and define the initial position and magnetic moment direction of the external permanent magnet;

[0029] (b) Calculate the magnetic force and torque based on the dipole model, and establish a dynamic equilibrium equation by combining the centrifugal force, fluid resistance and friction force;

[0030] (c) Adjust the annular motion trajectory of the permanent magnet according to the intestinal bending radius, and optimize the driving angles α, β to maximize the horizontal magnetic force component;

[0031] (d) Dynamically adjust the position of the permanent magnet through the robotic arm to keep the capsule endoscope at a stable angular velocity and linear motion in the curved intestine.

[0032] In the above technical solution, and and , , , The spatial geometric relationship of is:

[0033] ,

[0034] .

[0035] In the above technical solution, the component forces of the magnetically controlled capsule endoscope in the three-axis directions are as follows:

[0036] ,

[0037] .

[0038] In the above technical solution, the speeds of the magnetically controlled capsule endoscope and the external permanent magnet in the circular orbit are as follows:

[0039] ,

[0040] .

[0041] In the above technical solution, the method further includes reducing the fluid resistance in the intestine by dimethyl silicone oil, and its viscosity coefficient is used to correct the fluid resistance term in the kinetic equation.

[0042] Beneficial effects:

[0043] By accurately modeling the relative position, magnetic force, torque, etc. between the external permanent magnet and the endoscope, the present invention proposes an optimized rotation drive angle (α, β) and drive model, which can achieve more flexible and stable control in a complex intestinal structure. This solution accurately regulates the movement of the magnetically controlled capsule endoscope by dynamically calculating the magnetic field force and torque and considering factors such as friction force and centrifugal force, overcoming the problems of inaccurate control and potential damage in the prior art. Description of the drawings

[0044] Figure 1 : Force relationship diagram under the three-dimensional space rotation drive strategy, where (a) is the force relationship of the magnetically controlled capsule endoscope from a three-dimensional perspective; (b) is the force relationship when the external permanent magnet deflects at an angle in the y-z plane inside the circular intestine angle, and (c) is the force relationship when the external permanent magnet deflects at an angle in the y-z plane outside the circular intestine angle.

[0045] Figure 2 : Schematic diagram of the driving angles of the external permanent magnet in the inner and outer rings respectively, where (a) is the external permanent magnet inside the ring; (b) is the external permanent magnet outside the ring. Detailed implementation manners

[0046] The present invention will be described in detail below with reference to the drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the protection scope of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0047] Embodiment

[0048] This embodiment discloses a steering control device for a magnetically controlled capsule endoscope based on a rotation strategy. The device includes an external permanent magnet system for generating a rotating magnetic field in the intestine; a drive control module for controlling the direction of the rotation axis of the magnetically controlled capsule endoscope by adjusting the spatial position and rotation angle of the permanent magnet; a magnetic field modeling module for calculating the magnetic force and torque between the permanent magnet and the capsule endoscope in real time based on the dipole model; and a rotation drive mechanism for adjusting the circular motion trajectory of the permanent magnet by optimizing the driving angles α and β to enable the capsule endoscope to achieve stable linear motion in a curved intestine.

[0049] This embodiment also discloses a steering control method for a magnetically controlled capsule endoscope based on a rotation strategy, including the following steps: (a) constructing a reference coordinate system centered on the capsule endoscope and defining the initial position and magnetic moment direction of the external permanent magnet; (b) calculating the magnetic force and torque based on the dipole model and establishing a dynamic equilibrium equation by combining the centrifugal force, fluid resistance, and friction; (c) adjusting the circular motion trajectory of the permanent magnet according to the bending radius of the intestine and optimizing the driving angles α and β to maximize the horizontal component of the magnetic force; and (d) dynamically adjusting the position of the permanent magnet by a robotic arm to enable the capsule endoscope to maintain a stable angular velocity and linear motion in a curved intestine.

[0050] In the following, this embodiment will describe the above content in detail from five parts: magnetic force and torque, rotation drive model, dynamic model, key driving angles, and driving force analysis of the magnetically controlled endoscope.

[0051] I. Magnetic Force and Torque

[0052] The external permanent magnet generates a magnetic field in space, which acts on the permanent magnet inside the magnetically controlled capsule endoscope to generate a magnetic force and torque .

[0053] ,

[0054] ,

[0055] Among them, is the magnetic permeability of space, is the dipole moment of the permanent magnet inside the magnetically controlled capsule endoscope, is the magnetic moment change rate, is the magnetic field generated by the external permanent magnet.

[0056] II. Rotation Drive Model

[0057] In the intestinal environment, a reference coordinate system centered on the magnetically controlled capsule endoscope with the origin at is defined , as shown in Figure 1 . The external permanent magnet is located at 。Assume that the ideal rotation axis of the magnetically controlled capsule endoscope and the external permanent magnet , is aligned with the +x axis at the initialization, where is available , is represented.

[0058] ,

[0059] In order to generate a rotating magnetic field at around , the rotation axis of the external permanent magnet can be calculated by the following formula .

[0060] ,

[0061] where is the identity matrix, is the unit direction vector between the permanent magnet and the magnetically controlled capsule endoscope. Let the unit vector of the magnetic moment of the external permanent magnet be parallel to the +z axis at the initialization. Let be the rotation axis around which the magnetic moment rotates, then can be calculated as:

[0062] ,

[0063] In (a) of Figure 1 , let the plane perpendicular to the normal vector of the external permanent magnet and be . is the relative position between the external permanent magnet and the magnetically controlled capsule endoscope. and the normal vector The included angle is defined as the driving angle , The included angle between the plane and is . The actual distance between the external permanent magnet and the magnetically controlled capsule endoscope is , so , assuming The initialization unit vector of is , and it rotates with , , , to obtain the actual unit vector:

[0064] ,

[0065] represents the magnitude of the magnetic moment of the external permanent magnet. Therefore, according to the dipole model, the magnetic field applied to the magnetically controlled capsule endoscope is:

[0066] ,

[0067] Since the actual movement direction of the magnetically controlled capsule endoscope may not be consistent with its rotation axis . Therefore, the direction of its rotation axis is:

[0068] ,

[0069] Therefore, the magnetic force and torque received by the magnetically controlled capsule endoscope are:

[0070] ,

[0071] .

[0072] III. Dynamic Model

[0073] When the magnetically controlled capsule endoscope is driven by the rotation of the external permanent magnet, its force in the intestine is as Figure 1 shown and expressed as:

[0074] ,

[0075] where is the magnetic force received, is the frictional force, is the gravitational force, is the centrifugal force of circular motion, is the intestinal deformation pressure generated by the capsule on the intestinal wall, is the fluid resistance (there will be dimethyl silicone oil in the intestine during the experiment). The centrifugal force is directly related to the mass of the magnetically controlled capsule endoscope, the speed of circular movement, and the radius

[0076] of the circle.

[0077] ,

[0078] is the viscosity coefficient of the fluid,

[0079] To accurately describe the movement of the magnetically controlled capsule endoscope, each position in its circular movement is represented as a temporary coordinate system , where: the z-axis is the vertical direction, the x-axis is the direction of the circular motion section plane, and the y-axis is the radial direction of the circular motion. The radial direction is perpendicular to the section plane direction. Therefore, the force received by the magnetically controlled capsule endoscope can be decomposed into the force in the z-axis direction , the force in the x-axis direction and the force in the y-axis direction . Its force balance formula is:

[0080] ,

[0081] ,

[0082] where the symbol indicates that when the external permanent magnet is at different positions on the circular orbit, has different directions (inward or outward).

[0083] ,

[0084] ,

[0085] where, is the frictional force that the magnetically controlled capsule endoscope receives in the intestine, is the friction coefficient, and are the magnetic forces that the magnetically controlled capsule endoscope receives in the z-axis direction and the x-axis direction in the coordinate system formed at the current position respectively. Because there are two different positions in the drive of the external permanent magnet that can generate the same magnetic force effect, as shown in Fig. 1(b) and Figure 1 (c). In addition, when the external permanent magnet is inside the circular orbit, the magnetic force in the y-axis direction is radially inward; when the external permanent magnet is located outside the circular intestine, is radially outward. Therefore, the resultant force in the -axis direction is different at different positions, which in turn leads to a difference in the magnitude of the frictional force .

[0086] The torque received by the magnetically controlled capsule endoscope is:

[0087] ,

[0088] where, is the moment of inertia, is the angular acceleration during rotation, is the frictional torque between the magnetically controlled capsule endoscope and the intestine. The external permanent magnet drives the magnetically controlled capsule endoscope to rotate synchronously by applying torque. Through the frictional action between the threaded housing and the intestine, the rotational motion is converted into a linear motion, thereby realizing the advancement of the magnetically controlled capsule endoscope.

[0089] IV. Key driving angles

[0090] The external permanent magnet is inside the ring ( Figure 2 (a) of), and the height of the external permanent magnet is with respect to the xy plane. At this time, the position of the external permanent magnet and the projection axis of the magnetically controlled capsule endoscope form a local coordinate system, where is the x-axis, and is the y-axis. Based on this, the angular relationships and are constructed, and the projection of the external permanent magnet on the xy plane is defined as . is the radius of the actual circular motion of the external permanent magnet (satisfying < ). and form an included angle of . Similarly, when the external permanent magnet is outside the circular intestine ( Figure 2 (b) of), the actual circular motion radius of the external permanent magnet can also be defined (satisfying < ), and the included angle is defined. Therefore, and and , , , The spatial geometric relationship can be expressed as follows:

[0091] ,

[0092] .

[0093] V. Analysis of the driving force of the magnetically controlled endoscope

[0094] When the external permanent magnet is in , the magnetically controlled capsule endoscope is subjected to the magnetic force . In this state, the two key driving angles and satisfy the following conditions, enabling the horizontal magnetic force of the magnetically controlled capsule endoscope to overcome the maximum static friction force, thereby enabling stable driving.

[0095] ,

[0096] Furthermore, decompose the magnetic force in the horizontal and vertical directions according to Figure 1. The center point of the external permanent magnet The projection on the axis is , and the projection on the plane is, and the distance to the point satisfies . Therefore, can be expressed as:

[0097] ,

[0098] Therefore, in the , geometric relationship, the component forces of the magnetically controlled capsule endoscope in the three-axis directions can be calculated:

[0099] ,

[0100] ,

[0101] The velocities of the magnetically controlled capsule endoscope and the external permanent magnet in the circular orbit can be described as:

[0102] ,

[0103] ,

[0104] where is related to and is related to, so the velocity solution is based on a quartic equation in one variable. Among them, , are the magnetic moments of the magnetically controlled capsule endoscope, represents the linear velocity of the magnetically controlled capsule endoscope at the position , represents the actual distance between the capsule endoscope at the position and the center point of the circular intestine. is related to and satisfies the same angular velocity. Since the external permanent magnet and the magnetically controlled capsule endoscope have the same angular velocity, the driving velocity of the external permanent magnet can be calculated through their respective circular motion radii.

[0105] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A magnetically controlled capsule endoscope steering control device based on a rotation strategy, characterized in that: include: an external permanent magnet system to generate a rotating magnetic field in the intestine; A drive control module controls the rotation axis direction of the magnetically controlled capsule endoscope by adjusting the spatial position and rotation angle of the permanent magnet; Magnetic field modeling module, which calculates the magnetic force and torque between the permanent magnet and the capsule endoscope in real time based on the dipole model; The rotary drive mechanism adjusts the circular motion trajectory of the permanent magnet by optimizing the drive angles α and β, so that the capsule endoscope can achieve stable linear motion in the curved intestine.

2. According to the rotation strategy-based magnetically controlled capsule endoscope steering control device of claim 1, it is characterized in that: In the magnetic field modeling module: The magnetic force calculation formula is: ， The torque calculation formula is: ， in, is the magnetic permeability, is the magnetic moment of the capsule endoscope, is the rate of change of magnetic moment, is the magnetic field strength of the external permanent magnet.

3. The magnetically controlled capsule endoscope steering control device based on a rotation strategy according to claim 1, characterized in that: The drive control module comprises: The dynamic balance unit decomposes the magnetic force into x-axis, y-axis, and z-axis forces, and combines the centrifugal force, fluid resistance, and friction to establish a dynamic equation; The circular trajectory planning unit adjusts the circular motion radius of the permanent magnet according to the intestinal curvature radius to ensure that the angular velocity of the capsule endoscope is synchronized with the permanent magnet.

4. The magnetically controlled capsule endoscope steering control device based on a rotation strategy according to claim 1, characterized in that: The external permanent magnet system comprises: An adjustable mechanical arm controls the permanent magnet to move inside or outside the annular intestine to form a radially inward or outward magnetic force component; The angle sensor monitors the driving angles α, β and the deflection error of the capsule endoscope's rotation axis in real time.

5. The magnetically controlled capsule endoscope steering control device based on a rotation strategy according to claim 1, characterized in that: The rotary drive mechanism converts the rotary motion of the capsule endoscope into linear motion through a threaded structure, and the torque on the magnetically controlled capsule endoscope is: ， in, is the moment of inertia, is the angular acceleration during rotation, is the friction torque between the magnetically controlled capsule endoscope and the intestine.

6. A magnetically controlled capsule endoscope steering control method based on a rotation strategy, characterized in that: The following steps are involved: (a) Construct a reference coordinate system centered on the capsule endoscope and define the initial position and magnetic moment direction of the external permanent magnet; (b) Calculate magnetic force and torque based on the dipole model, and establish the dynamic equilibrium equation by combining centrifugal force, fluid resistance and friction; (c) adjusting the circular motion trajectory of the permanent magnet according to the intestinal curvature radius and optimizing the driving angles α and β to maximize the horizontal magnetic force component; (d) The position of the permanent magnet is dynamically adjusted by the robotic arm, so that the capsule endoscope maintains a stable angular velocity and linear motion in the curved intestine.

7. The method for steering control of a magnetically controlled capsule endoscope based on a rotation strategy according to claim 6, characterized in that: as well as and , , , The spatial geometric relationship is: ， 。 8. The method for steering control of a magnetically controlled capsule endoscope based on a rotation strategy according to claim 6, characterized in that: The force components of the magnetically controlled capsule endoscope in three axes: ， 。 9. The method for steering control of a magnetically controlled capsule endoscope based on a rotation strategy according to claim 6, characterized in that: The speed of the magnetically controlled capsule endoscope and the external permanent magnet in the circular orbit is: ， 。 10. The method for steering control of a magnetically controlled capsule endoscope based on a rotation strategy according to claim 6, characterized in that: It also includes reducing the fluid resistance in the intestine by using dimethicone, and its viscosity coefficient is used to correct the fluid resistance term in the kinetic equation.

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