A design method and system of a reconfigurable electromagnetic navigation system

Abstract

The application discloses a design method and system of a reconfigurable electromagnetic navigation system, and relates to the technical field of magnetic robot electromagnetic navigation; the method comprises the following steps: determining the curved surface configuration parameters of a curved surface coil according to lesion point cloud data and human body surface point cloud data, and determining the coil turn number and three-dimensional size parameters of the curved surface coil in combination with target magnetic field intensity; for a rectangular coil, determining the coil turn number according to the target magnetic field intensity, and determining the three-dimensional size parameters according to the size of a target lesion area; adjusting the spatial pose of each coil relative to the target lesion area to form a plurality of candidate coil spatial configurations; for each candidate coil spatial configuration, solving the driving current of each coil under the condition of meeting a preset current amplitude constraint and a preset target magnetic field requirement, and calculating the corresponding magnetic field error; and determining a coil configuration scheme according to the magnetic field error. The application can simultaneously realize efficient driving, accurate control and good spatial adaptability in a large-scale space.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic navigation technology for magnetic robots, and in particular to a design method and system for a reconfigurable electromagnetic navigation system. Background Technology

[0002] Magnetic micro / nano robotic navigation systems typically generate controllable magnetic fields using external electromagnetic coils or permanent magnet arrays to drive and position microscale robots within the body, showing significant application potential in areas such as vascular intervention, targeted therapy, and minimally invasive surgery. Currently, common magnetic control systems mainly include multi-coil electromagnetic drive systems, rotating magnetic field drive systems, enhanced magnetic field systems, and robotic arm movement coil or permanent magnet solutions.

[0003] However, these existing technologies all have limitations to varying degrees. The workspace of multi-coil fixed systems is constrained, making them unable to flexibly cope with large spaces or complex human environments; rotating magnetic field systems may exhibit anisotropy in magnetic field amplitude and direction within a large workspace, leading to undesirable gradient forces that cause micro-nano robots to deviate from their trajectory or become unstable; enhanced magnetic field systems improve long-distance driving force through high current or soft magnetic cores, but high current increases thermal load, and soft magnetic cores introduce nonlinear magnetic effects, affecting magnetic field accuracy; while robotic arm-moving coil solutions expand the system's operable space, the robotic arm's movement speed and accuracy directly affect the magnetic field response, increasing control complexity, and the overall system size remains large, limiting clinical applicability; robotic arm-driven permanent magnet solutions suffer from the problem of the magnetic field not being able to switch on or off quickly or adjust its amplitude, with magnetic field strength and direction depending on the robotic arm's posture, limiting control response speed and making real-time control difficult in continuous complex path navigation.

[0004] In summary, the main drawback of existing technologies is that magnetic control systems cannot simultaneously guarantee sufficient magnetic field strength and high-precision control in large workspaces. This makes it difficult to achieve effective actuation and high-precision control in large spaces and deep environments, leading to instability or uncontrollability risks in deep or complex path navigation. Furthermore, existing systems suffer from spatial interference, hindering practical deployment. Fixed coil systems are large, and their enclosed layout occupies significant space, easily causing spatial conflicts with imaging equipment, surgical instruments, and operating spaces, limiting system flexibility and clinical adaptability. In addition, multi-coil fixed systems are prone to local gradient inhomogeneity due to magnetic field superposition in large spaces. Undesirable gradient forces generated by rotating magnetic field systems and insufficient gradient accuracy due to the inability of permanent magnet systems to quickly adjust amplitude both contribute to uneven magnetic field distribution within the target area, making precise control of the micro / nano robot's trajectory and attitude difficult and reducing navigation accuracy.

[0005] Therefore, in complex environments constrained by human anatomy and the space of medical equipment, how to achieve a synergistic improvement in magnetic field strength and accuracy over a greater operating distance, thereby constructing a magnetic navigation system with both high-efficiency driving capability and high-precision control capability, has become a pressing technical problem to be solved in this field. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a design method and system for a reconfigurable electromagnetic navigation system, which can solve the problem that existing magnetic control systems are unable to simultaneously achieve efficient drive, precise control, and good spatial adaptability in large-scale spaces.

[0007] To achieve the above objectives, the present invention provides a design method for a reconfigurable electromagnetic navigation system, wherein the electromagnetic navigation system includes multiple coils, and each coil is a rectangular coil or a curved surface coil; the design method includes: Based on the lesion point cloud data corresponding to the target lesion area in the human body and the human body surface point cloud data, the surface configuration parameters of the curved coil are determined. Based on the surface configuration parameters and the target magnetic field strength, determine the number of turns and three-dimensional dimensional parameters of the surface coil; The number of turns of the rectangular coil is determined based on the target magnetic field strength, and the three-dimensional dimensional parameters of the rectangular coil are determined based on the size of the target lesion area. Adjust the spatial pose of each coil relative to the target lesion region to form multiple candidate coil spatial configurations; For each candidate coil spatial configuration, the driving current of each coil is solved under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement, and the corresponding magnetic field error is calculated. The candidate coil spatial configuration with the smallest magnetic field error and the corresponding driving current of each coil are determined as the final coil configuration scheme.

[0008] Optionally, based on the surface configuration parameters and the target magnetic field strength, the number of turns and three-dimensional dimensional parameters of the curved surface coil are determined, including: Based on the minimum coverage area and surface type, a parametric geometric model of the surface coil is constructed; the curvature parameter and three-dimensional dimension parameter of the parametric geometric model are variables to be adjusted. Under the condition of satisfying the preset safety gap between the curved coil and the human body surface, determine the range of penetration distance from the surface of the parameterized geometric model to the target lesion area; Based on the penetration distance range and the target magnetic field strength, and combined with the magnetic field attenuation law, the required number of coil turns is determined under a preset current constraint. The curvature parameters and three-dimensional dimension parameters of the parametric geometric model are iteratively adjusted, the penetration distance range is recalculated and the required number of coil turns is updated until the required number of coil turns converges. The number of coil turns and three-dimensional dimension parameters at the convergence point are determined as the final number of coil turns and three-dimensional dimension parameters.

[0009] Optionally, adjusting the spatial pose of each coil relative to the target lesion region includes: Establish a spatial mapping relationship between the spatial pose of each coil and its mechanical structure parameters; Based on the spatial mapping relationship, the spatial pose of each coil relative to the target lesion area is adjusted by changing the corresponding mechanical structure parameters.

[0010] Optionally, the driving current of each coil is calculated under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement, including: Establish the electromagnetic mapping relationship between the unit current of each coil and the magnetic field at the target point; Based on the electromagnetic mapping relationship, an optimization problem is constructed with the driving current of each coil as the variable, the objective being to minimize the deviation between the actual generated magnetic field and the preset target magnetic field, and the preset current amplitude constraint as the boundary condition. Solve the optimization problem to obtain the driving current of each coil.

[0011] Optionally, calculate the corresponding magnetic field error, including: An evaluation area is selected within the target lesion region, and spatial discrete sampling is performed on the evaluation area to obtain multiple sampling points; Based on the driving current of each coil obtained by the solution, the actual generated magnetic field at each sampling point is calculated; The actual generated magnetic field at each sampling point is compared with the preset target magnetic field requirement to calculate the magnetic field error.

[0012] Optionally, the plurality of coils specifically includes: Two rectangular coils are symmetrically arranged on both sides of the target lesion area of ​​the human body and have the same normal direction, which are used to generate the main direction magnetic field component. Two curved coils, arranged in conjunction with two rectangular coils and with adjustable spatial orientation, are used to form a three-dimensional controllable magnetic field in the target lesion area in cooperation with the two rectangular coils.

[0013] Optionally, when the driving current of each coil obtained by the solution does not meet the preset current amplitude constraint, it can be corrected by scaling the target magnetic field amplitude in the preset target magnetic field requirement and / or by redistributing the driving current of each coil. If the preset current amplitude constraint still cannot be met after correction, the corresponding candidate coil spatial configuration is discarded.

[0014] This invention also provides a design system for a reconfigurable electromagnetic navigation system, the electromagnetic navigation system comprising multiple coils, wherein each coil is a rectangular coil or a curved surface coil; the design system includes: Curved coil design unit, used for: Based on the lesion point cloud data corresponding to the target lesion area in the human body and the human body surface point cloud data, the surface configuration parameters of the curved coil are determined; Based on the surface configuration parameters and the target magnetic field strength, determine the number of turns and three-dimensional dimensional parameters of the surface coil; A rectangular coil design unit is used to determine the number of turns of the rectangular coil based on the target magnetic field strength, and to determine the three-dimensional dimensional parameters of the rectangular coil based on the size of the target lesion area. Coil configuration design unit, used for: Adjust the spatial pose of each coil relative to the target lesion region to form multiple candidate coil spatial configurations; For each candidate coil spatial configuration, the driving current of each coil is solved under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement, and the corresponding magnetic field error is calculated. The candidate coil spatial configuration with the smallest magnetic field error and the corresponding driving current of each coil are determined as the final coil configuration scheme.

[0015] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: The design method for a reconfigurable electromagnetic navigation system provided by this invention determines the surface configuration parameters of a curved coil based on lesion point cloud data corresponding to the target lesion area on the human body and point cloud data of the human body surface. This enables the curved coil to conformally fit with the human body surface, thereby reducing the ineffective space occupation between the coil and the human body. This conformal design effectively alleviates the spatial interference problem caused by the large size and enclosed layout of existing fixed coil systems, improving the clinical adaptability and deployment flexibility of the electromagnetic navigation system.

[0016] By determining the number of turns and three-dimensional dimensions of the curved coil based on the curved surface configuration parameters and the target magnetic field strength, and by determining the number of turns and three-dimensional dimensions of the rectangular coil based on the target magnetic field strength and the size of the target lesion region, the parameter design of each coil is closely aligned with the actual needs of the target lesion region. The determination of the number of turns for the curved coil fully considers the distance from the coil surface to the lesion region, and uses reverse calculations based on the physical law of magnetic field attenuation with distance. Under the same driving current, similar wire usage, and the same target region, the magnetic field response per unit current at the target region is improved by reducing the distance between some effective current paths and the target region. The dimensions of the rectangular coil are designed according to the size of the target lesion region, ensuring that the magnetic field can effectively cover the entire target lesion region. This targeted parameter design method solves the problem of insufficient deep navigation capability caused by the rapid attenuation of the magnetic field with distance in existing technologies.

[0017] Furthermore, by adjusting the spatial pose of each coil relative to the target lesion area, multiple candidate coil spatial configurations with different spatial coverage ranges can be formed. This allows the electromagnetic navigation system to flexibly adjust the coil arrangement according to the individualized anatomical structure of different patients and the spatial constraints of different lesion locations. This reconfigurable design gives the electromagnetic navigation system good spatial adaptability, overcoming the limitation of limited working space in existing fixed coil systems.

[0018] Based on this, for each candidate coil spatial configuration, the driving current that meets the preset target magnetic field requirements is solved under the preset current amplitude constraint, and the magnetic field error is calculated. Finally, the candidate coil spatial configuration with the smallest magnetic field error and the corresponding driving current are determined as the final coil configuration scheme. This process takes magnetic field strength and magnetic field accuracy as the objectives of synergistic optimization. Through multi-configuration comparison and selection, it ensures that the selected coil configuration scheme can generate a sufficiently strong magnetic field in the target lesion area while ensuring the accuracy of the magnetic field distribution, under the condition of meeting the current hardware constraints. This solves the problem of not being able to balance magnetic field strength and accuracy in the existing technology, and provides technical support for the stable navigation of micro-nano robots in complex human environments. Attached Figure Description

[0019] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same parts.

[0020] Figure 1 This is a schematic flowchart illustrating the design method of a reconfigurable electromagnetic navigation system according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a coil system for the knee joint shown in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating different coil spatial configurations for the knee joint according to embodiments of the present invention; wherein, Figure (a) is an example of a coil spatial configuration. Figure 1 Figure (b) shows an example of a coil spatial configuration. Figure 2 Figure (c) shows an example of a coil spatial configuration. Figure 3 ; Figure 4 This is a schematic diagram of the modular structure of a design system for a reconfigurable electromagnetic navigation system, as shown in an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1 , Figure 1 This is a flowchart illustrating the design methodology for a reconfigurable electromagnetic navigation system.

[0023] The reconfigurable electromagnetic navigation system comprises multiple coreless electromagnetic coils, including rectangular coils and curved coils; that is, each coil is either rectangular or curved. The curved coils are conformally adapted based on the point cloud data of the lesion corresponding to the target lesion area on the human body and the point cloud data of the human body surface, ensuring that the overall contour of the curved coil matches the spatial morphology of the corresponding external human body surface. The rectangular coils are used to generate the main directional magnetic field component. The two types of coils work together to form a three-dimensional controllable magnetic field in the target lesion area.

[0024] The design methodology for reconfigurable electromagnetic navigation systems includes: S101: Determine the surface configuration parameters of the curved coil based on the lesion point cloud data corresponding to the target lesion area of ​​the human body and the human body surface point cloud data.

[0025] Among them, the surface configuration parameters include the minimum coverage area and the surface type.

[0026] In practical applications of magnetic navigation systems, the human body surface is not an ideal plane, but a three-dimensional curved surface with complex curvature changes, while the target lesion area is located at a certain depth inside the human body. To ensure that the electromagnetic coil conformally adapts to the human body surface and that the magnetic field generated by the coil effectively covers the target lesion area, it is necessary to simultaneously acquire the three-dimensional spatial occupancy information of the target lesion area and its corresponding external surface morphology information. Specifically, the target lesion area is the internal human body region (the micro-nano robot's workspace) where the micro-nano robot needs to perform magnetic navigation operations; the lesion point cloud data represents the three-dimensional spatial occupancy range of the target lesion area within the human body; and the human body surface point cloud data represents the corresponding external contour of the human body.

[0027] It should be noted that the so-called conformal fitting does not require the curved coil to form a perfect mechanical shape fit with the human body surface. Rather, it refers to designing the type and coverage of the coil's surface according to the spatial geometric characteristics of the external curved surface of the target area of ​​the human body, so that the overall outline of the curved coil has a high degree of consistency with the external curved surface of the target area of ​​the human body in terms of spatial morphology.

[0028] Specifically, three-dimensional model data corresponding to target areas of the human body can be obtained through medical imaging equipment. This equipment can be CT or MRI, or other imaging devices capable of acquiring information about the internal structure of the human body. The acquired three-dimensional model data is then converted into a computer-readable three-dimensional data format, and a simulation platform is built to import the data. This three-dimensional model data simultaneously contains structural information about both the external surface contours of the human body and the internal lesion areas. From the same three-dimensional model data, lesion point cloud data and human surface point cloud data can be extracted separately.

[0029] After obtaining point cloud data of the lesion area and the human body surface, it is necessary to determine the surface configuration parameters of the curved coil. The surface configuration parameters include the minimum coverage area and the surface type. These two parameters are the preliminary constraints for the geometric design of the curved coil, providing a geometric basis for the subsequent accurate determination of the number of coil turns and three-dimensional dimensional parameters.

[0030] The minimum coverage area is determined based on the point cloud data of the lesion region. The target lesion region has a certain volume and shape in three-dimensional space. To ensure that the magnetic field generated by the curved coil can completely cover the entire target lesion region, the opening span of the coil should at least accommodate the spatial range of the target lesion region. Specifically, the minimum circumscribed sphere of the point cloud of the target lesion region can be calculated. The diameter of this circumscribed sphere reflects the maximum span of the target lesion region in each direction. The opening size of the curved coil in the transverse and longitudinal (X, Y directions) directions should not be less than the projected size of the circumscribed sphere diameter in the corresponding directions, thereby determining the minimum coverage area of ​​the coil. This minimum coverage area is the lower limit constraint for the coil's geometric design, ensuring that the coil can completely cover the target lesion region under any working posture.

[0031] The surface type is determined based on point cloud data of the human body surface. Considering that in practical applications, the surface coil needs to work in different spatial poses, and the area of ​​the human body surface it faces will also change accordingly, the curvature of the human body surface corresponding to the surface coil may differ under different spatial poses. Therefore, the determination of the surface type is not only based on a local human body surface, but also needs to achieve a comprehensive judgment of the human body surface area corresponding to multiple working poses in an overall sense.

[0032] To achieve this goal, firstly, based on the clinical application scenario, multiple representative working positions of the curved coil around the target lesion area are determined. For each representative working position, the point cloud of the corresponding sub-region of the human body surface within the coil's coverage area at that position is extracted. The point clouds of the human body surface sub-regions corresponding to each representative working position are then uniformly transformed to a global coordinate system with the center of the lesion area as the origin, according to the spatial orientation parameters of each position, through rigid body coordinate transformation. After the transformation, the point clouds of the human body surface at all working positions form a composite point set in the same space. This composite point set fully represents the set of human body surface spaces that the coil needs to adapt to at all expected working positions.

[0033] Principal curvature analysis is performed on the aforementioned composite point set to determine the overall curvature characteristics of the human body surface around the target lesion area. If the composite point set mainly exhibits curvature in a single direction globally, i.e., the principal curvature in one direction is significantly greater than the principal curvature in its orthogonal direction, then the surface type of the surface coil is determined to be an arc surface; if the composite point set exhibits significant curvature in both orthogonal directions, and the curvature directions are opposite, then the surface type of the surface coil is determined to be a saddle-shaped surface.

[0034] S102: Determine the number of turns and three-dimensional dimensions of the curved coil based on the surface configuration parameters and the target magnetic field strength.

[0035] Specifically, S102 includes: Based on the minimum coverage area and surface type, a parametric geometric model of the surface coil is constructed; the curvature parameter and three-dimensional dimension parameter of the parametric geometric model are variables to be adjusted. Under the condition of satisfying the preset safety gap between the curved coil and the human body surface, determine the range of penetration distance from the surface of the parametric geometric model to the target lesion area; Based on the penetration distance range and the target magnetic field strength, and combined with the magnetic field attenuation law, the required number of coil turns is determined under the preset current constraint. Iteratively adjust the curvature parameters and three-dimensional dimension parameters of the parametric geometric model, recalculate the penetration distance range and update the required number of coil turns until the required number of coil turns converges. The number of coil turns and three-dimensional dimension parameters at the convergence point are determined as the final number of coil turns and three-dimensional dimension parameters.

[0036] In applications, after determining the surface configuration parameters of the curved coil, it is necessary to further determine the number of turns and three-dimensional dimensional parameters. The minimum coverage area in the surface configuration parameters determines the basic dimensional boundary of the coil in space, and the surface type determines whether the coil uses an arc-shaped or saddle-shaped surface. Since there is a coupling relationship between the curvature parameters, three-dimensional dimensional parameters, and the number of turns of the curved coil—curvature parameters affect the spatial shape of the coil and the distance distribution to the lesion, three-dimensional dimensional parameters determine the overall size of the coil, and the number of turns directly affects the magnetic field strength—these three factors need to be treated as co-variables. Under the premise of satisfying various constraints, the final parameters are determined through iterative optimization.

[0037] First, the rigid constraints of the coil design need to be clearly defined. As mentioned earlier, the minimum circumscribed sphere of the target lesion area is calculated based on the lesion point cloud data. To ensure that the magnetic field generated by the coil can completely cover the entire lesion area, the opening span of the coil should not be less than the diameter of the minimum circumscribed sphere in both the horizontal and vertical directions. The upper limit of the height is determined by the travel of the mechanical adjustment mechanism; the highest point of the coil's outer surface in the direction perpendicular to the human body surface must not exceed the safe range of movement of the robotic arm or adjustment mechanism.

[0038] The upper limit of curvature is constrained by two factors. First, there is the upper limit of geometric curvature. Under the combined constraints of the upper limit of height and the minimum coverage size, the curvature of the coil has a geometrically permissible maximum value. If the curvature is too large and the bending too severe, the coil's bow height will inevitably increase while still meeting the opening span requirement. Once the bow height exceeds the upper limit of height, the outer surface of the coil will exceed the height limit of the mechanical adjustment mechanism. This upper limit of geometric curvature can be determined by the upper limit of height and the minimum coverage size. Second, there is the upper limit of manufacturable curvature. The coil conductor has a minimum bending radius during physical winding. If the coil's curvature radius is less than this value, the conductor cannot be wound smoothly or will be damaged. This manufacturability constraint gives the upper limit of curvature as the reciprocal of the minimum bending radius. Ultimately, the upper limit of curvature allowed by the coil design is the smaller of the two. For any feasible coil design, the principal curvature at all points must not exceed this upper limit. The current amplitude constraint is jointly determined by the power output capability, coil thermal load, and system safety requirements. The coil drive current must not exceed the preset upper limit of current.

[0039] After clarifying the aforementioned constraint framework, a parametric geometric model of the surface coil is constructed based on the surface type determined in S101. This parametric geometric model uses curvature parameters and three-dimensional dimension parameters as variables to be adjusted, and can describe the geometric shape of the coil in three-dimensional space. For coils with arc-shaped surfaces, the curvature parameter is the radius of curvature of the cylindrical surface; for coils with saddle-shaped surfaces, the curvature parameter includes the principal radii of curvature in two orthogonal directions. The three-dimensional dimension parameters include the arc length, unfolded width, and wire diameter of the coil in the unfolded direction of the surface, and their initial values ​​are limited to the minimum coverage area. The initial value of the curvature parameter, provided it does not exceed the upper limit of curvature, can be preferentially set by referring to the statistical average curvature obtained from the above analysis of the composite point set of the human body surface, so that the initial shape of the coil is as close as possible to the natural curvature of the human body surface, which helps to accelerate iterative convergence.

[0040] After constructing the parametric geometric model, the penetration distance range from the coil surface to the target lesion area is determined, provided that a preset safety gap between the coil and the human body surface is met. This safety gap is used to accommodate the surgical operating space, medical imaging channel, and patient movement allowance; its value can be determined empirically or flexibly based on actual clinical circumstances.

[0041] During subsequent use, the curved coil's spatial orientation is altered via a mechanical adjustment mechanism. The range of motion of this mechanism limits the spatial reach of the coil, thus determining the upper and lower limits of the penetration distance. The distance from the coil surface to the lesion area varies depending on the coil's orientation; therefore, the penetration distance is not a fixed value but varies within a certain range. The minimum penetration distance corresponds to the distance when the coil is in its closest possible orientation to the human body surface, at which point a preset safety gap is maintained. The maximum penetration distance corresponds to the distance when the coil is in its furthest possible orientation allowed by the mechanical adjustment mechanism, representing the scenario with the most severe magnetic field attenuation. The coil turns are designed based on the maximum penetration distance to ensure that the target magnetic field strength remains sufficient even under the most unfavorable conditions.

[0042] In specific calculations, the parametric geometric model of the curved coil can be discretized into several nodes, and the target lesion region can be represented as a three-dimensional set of voxels or a point cloud. For each coil node, the Euclidean distance from it to all points in the lesion region is calculated, and the minimum value is taken as the local penetration distance from that node to the lesion. By traversing all nodes, the distribution range of the penetration distance is obtained.

[0043] After obtaining the penetration distance range, the required number of coil turns is calculated under a preset current constraint, based on the target magnetic field strength and the penetration distance range, combined with the physical law of magnetic field attenuation with distance. According to the basic principle that a current-carrying coil generates a magnetic field in space, the magnetic field strength is proportional to the number of coil turns and the current, and decreases with increasing distance between the coil and the target area. This relationship can be obtained through analytical calculation using the Biot-Savart law or finite element simulation of the electromagnetic field. Using the maximum penetration distance within the penetration range as the calculation benchmark, and given the target magnetic field strength, maximum penetration distance, and preset current upper limit, the number of coil turns required to meet the magnetic field requirements under the most unfavorable operating conditions is calculated in reverse. During the solution process, within the current limit, increasing the number of turns is prioritized to increase the magnetic field strength, rather than simply relying on increasing the current. Although increasing the number of turns increases the coil volume and resistance, it effectively reduces the system's thermal load and power supply burden, making it more conducive to engineering implementation overall.

[0044] Since changes in curvature and three-dimensional dimensional parameters alter the spatial shape of the coil, thus affecting the distribution of the penetration distance, and changes in the penetration distance in turn change the required number of coil turns, an iterative optimization approach is needed for a coordinated solution. The iterative process aims to reduce the required number of coil turns, and the specific procedure is as follows.

[0045] First, given the current curvature and 3D dimension parameters, calculate the penetration distance range and determine the required number of coil turns based on the maximum penetration distance, denoted as the current number of turns. Then, under the premise of satisfying all constraints, adjust the curvature and / or 3D dimension parameters by a preset step size, guided by reducing the maximum penetration distance. The curvature and 3D dimension parameters can be adjusted independently or simultaneously. For example, the arc length and width can be fixed first, and the curvature can be appropriately increased to increase the degree of coil bending, thereby reducing the distance from the coil surface to the lesion; or the curvature parameter can be fixed, and the arc length or width can be appropriately adjusted to optimize the spatial coverage effect of the coil.

[0046] After adjustment, the geometric model is updated based on the new parameters, the penetration distance range is recalculated, and the required number of coil turns is recalculated using the updated maximum penetration distance as input. This updated number of turns is then recorded. The updated number of turns is compared with the current number of turns. If the updated number of turns decreases, it indicates that the adjustment direction is correct, and the next round of adjustment continues in that direction with the same step size. If the updated number of turns increases, it indicates that the adjustment direction is incorrect, and the adjustment is performed in the opposite direction, or the step size is halved and the attempt is repeated. If the absolute value of the difference between the two is less than the preset convergence threshold, convergence is determined, the iteration stops, and the current three-dimensional dimension parameters and the number of coil turns are output as the final result.

[0047] If the number of turns fluctuates repeatedly after adjustment or fails to converge after multiple iterations during the iteration process, check whether the initial values ​​of the curvature and 3D dimension parameters deviate too far from the feasible region, or whether the constraints are too strict, resulting in the absence of a feasible solution. If confirmed, adjust the initial values ​​and restart the iteration, or appropriately adjust the step size and the aforementioned adjustment strategies. For example, halve the step size for a more refined search, or switch the priority of the adjustment variables, first fixing the curvature parameters and then optimizing the 3D dimension parameters, and then fine-tuning the curvature parameters after the number of turns stabilizes.

[0048] Once the iteration converges, the three-dimensional dimensional parameters and the number of coil turns are the final optimized design values ​​that satisfy all constraints. These parameters define the geometry and electromagnetic characteristics of the curved coil and can serve as the design basis for subsequent coil manufacturing, assembly, and spatial orientation adjustment.

[0049] S103: Determine the number of turns of the rectangular coil based on the target magnetic field strength, and determine the three-dimensional dimensional parameters of the rectangular coil based on the size of the target lesion area.

[0050] While designing the parameters of the curved coil, it is also necessary to determine the parameters of the rectangular coil. The rectangular coil is mainly used to generate the main direction magnetic field component, and its three-dimensional dimensional parameters and number of turns are determined by the size of the target lesion region and the target magnetic field strength, respectively.

[0051] Specifically, the number of turns in a rectangular coil is determined based on the target magnetic field strength. Consistent with the design approach of curved coils, the number of turns in a rectangular coil is also calculated in reverse based on the required magnetic field strength in the target area. Given the target magnetic field strength, and considering the physical law that the magnetic field weakens with distance after current is applied to the coil, the magnetic field contribution that a rectangular coil can provide at the target point per unit number of turns can be determined. This allows for the reverse calculation of the number of turns required to meet the magnetic field requirements. In determining the number of turns, the allowable current range of the system is also considered, and the matching relationship between the number of turns and the current is optimized while meeting the magnetic field strength requirements to reduce system power consumption and thermal load.

[0052] The three-dimensional dimensions of the rectangular coil are determined based on the size of the target lesion area. The size of the target lesion area defines the spatial range that the magnetic field needs to cover, and the opening size of the rectangular coil must match this range to ensure that the magnetic field generated by the coil can effectively cover the entire lesion area. In the actual design process, the spatial bounding box dimensions of the target lesion area can be extracted, and key geometric parameters such as the length and width of the rectangular coil can be determined accordingly. The three-dimensional dimensions of the rectangular coil also include the wire diameter of the coil conductor, etc. These parameters, together with the number of turns, determine the electrical characteristics of the rectangular coil, such as resistance and inductance, as well as its magnetic field generation capability.

[0053] S104: Adjust the spatial pose of each coil relative to the target lesion area to form multiple candidate coil spatial configurations.

[0054] Adjusting the spatial pose of each coil relative to the target lesion region includes: Establish the spatial mapping relationship between the spatial pose of each coil and the mechanical structure parameters; Based on the spatial mapping relationship, the spatial pose of each coil relative to the target lesion area is adjusted by changing the corresponding mechanical structure parameters.

[0055] After determining the number of turns and three-dimensional dimensional parameters of each coil in the electromagnetic navigation system, the spatial arrangement of these coils relative to the target lesion area needs to be adjusted to form multiple candidate coil spatial configurations, providing a set of alternatives for subsequent selection of the optimal configuration. This step is crucial for realizing the reconfigurable characteristics of the electromagnetic navigation system.

[0056] To achieve precise adjustment of the coil's spatial pose, it is first necessary to establish a spatial mapping relationship between the spatial pose of each coil and the mechanical structure parameters. In applications, each coil can be installed and positioned using mechanical structures such as supports, guide rails, or robotic arms. Its spatial position and orientation are not directly measured but determined by the parameters of the corresponding mechanical structure. For coils with degrees of freedom of motion, their position and orientation can be described by the control parameters of the corresponding joints, such as rotation angles or translational displacements. Based on the geometric relationships of the mechanical structure, a mapping model between the coil's pose and structural parameters can be established. Therefore, by reading or setting the structural parameters, the actual position and orientation of each coil in space can be calculated. This method of determining coil pose through structural constraints does not rely on a complex external positioning system; it only requires obtaining the mechanical structure parameters to complete the calculation and updating of the coil's spatial position.

[0057] Based on the established spatial mapping relationship, the spatial pose of each coil relative to the target lesion area can be adjusted by changing the corresponding mechanical structural parameters. Changing different mechanical structural parameters will result in different combinations of spatial positions and postures for the coils, thus forming multiple candidate coil spatial configurations with different spatial coverage characteristics. For example, for curved coils, different configuration modes such as large-angle coverage, medium coverage, or small-angle concentration can be formed by changing their spatial posture adjustment angle or spatial position relative to the target lesion area. The candidate spatial configurations differ in terms of spatial coverage, magnetic field generation efficiency, and degree of adhesion to the human body surface, providing a diverse selection space for subsequent configuration screening based on magnetic field performance indicators.

[0058] During spatial configuration adjustment, the inherent geometry of the surface coils remains unchanged; only the relative spatial attitude between the two surface coils is altered via a mechanical adjustment mechanism. The two surface coils are mounted on corresponding pose adjustment mechanisms. The spatial attitude adjustment angle between the two surface coils is changed (see [reference]). Figure 3 (corresponding to θ), which can change the degree of spatial coverage of the target area by the two curved coils.

[0059] The spatial attitude adjustment angle θ is the relative opening and closing angle between the two curved coils. Taking the target region reference center as the vertex, and the directions pointing from the target region reference center to the geometric centers of the two curved coils as the sides, the angle formed by these two directions within the attitude adjustment plane is defined as θ. The attitude adjustment plane is either a plane perpendicular to the opening and closing axis of the curved coils, or a plane jointly determined by the geometric centers of the two curved coils and the target region reference center. By adjusting the value of θ, the two curved coils can form different relative spatial positions and attitude combinations, thereby creating candidate coil spatial configurations with different degrees of human body surface coverage, magnetic field generation efficiency, and clinical operation open space.

[0060] Through the above mapping and parameter adjustment process, the spatial layout of each coil can be flexibly adjusted, enabling the electromagnetic navigation system to be reconfigurable to adapt to the individualized anatomical structures of different patients and the spatial constraints of the clinical operating environment.

[0061] S105: For each candidate coil spatial configuration, solve for the driving current of each coil under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement, and calculate the corresponding magnetic field error.

[0062] The calculation of the driving current of each coil under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement includes: Establish the electromagnetic mapping relationship between the unit current of each coil and the magnetic field at the target point; Based on the electromagnetic mapping relationship, an optimization problem is constructed with the driving current of each coil as the variable, the objective being to minimize the deviation between the actual generated magnetic field and the preset target magnetic field, and the preset current amplitude constraint as the boundary condition. Solve the optimization problem to obtain the driving current of each coil.

[0063] After forming multiple candidate coil spatial configurations, it is necessary to solve the driving current of each coil for each candidate configuration and evaluate the deviation between the actual magnetic field generated and the preset target magnetic field requirement, so as to serve as the basis for subsequent configuration selection.

[0064] For a given spatial configuration of candidate coils, the electromagnetic mapping relationship between the unit current of each coil and the magnetic field at the target point is first established. This mapping relationship can be established based on the principle of superposition of coil magnetic fields, that is, the magnetic field at any point in space is the vector sum of the magnetic fields generated by each coil at that point. Specifically, for each coil in the system, under the condition of a unit current, the magnetic field vector generated by the coil at the target point is pre-calculated based on the Biot-Savart law or its equivalent numerical calculation method. This magnetic field vector contains magnetic field components in three orthogonal directions. By combining the magnetic field responses of each coil under a unit current, a coil constant matrix can be constructed. Each column of this matrix corresponds to the magnetic field contribution of a coil under a unit current, and each row corresponds to the magnetic field component in a certain coordinate direction at the target point. The coil constant matrix represents the linear mapping relationship between energizing the coil and generating a magnetic field at the target point.

[0065] Specifically, the magnetic field of the coil is modeled: Combine the unit current magnetic field responses of all coils to construct the coil constant matrix:

[0066] in, This refers to the number of coils; .

[0067] Based on the actual movement requirements of micro-nano robots, the required magnetic field at the target point is set as follows:

[0068] in, These represent the components of the magnetic field in the target region in three orthogonal directions.

[0069] Based on the principle of magnetic field superposition, we have:

[0070] in, Let be the vector of the coil current to be determined.

[0071] After establishing the electromagnetic mapping relationship, an optimization problem is constructed based on this relationship, with the driving current of each coil as the variable, minimizing the deviation between the actual generated magnetic field and the preset target magnetic field as the objective, and a preset current amplitude constraint as the boundary condition. According to the motion requirements of the micro-nano robot, the target magnetic field vector required at the target point is defined. This target magnetic field vector can be a uniform magnetic field or a three-dimensional dynamic magnetic field, and its components in the three orthogonal directions constitute the preset target magnetic field requirement. A system of linear equations is established between the target magnetic field vector, the coil constant matrix, and the coil current vector to be determined, where the coil constant matrix multiplied by the current vector equals the actual generated magnetic field. Based on this, an optimization objective function is constructed, which minimizes the error between the actual generated magnetic field and the target magnetic field. A regularization term is added to the optimization objective to suppress the system burden caused by excessive current amplitude. The preset current amplitude constraint is determined by the power supply capacity, coil thermal load, and safety requirements, serving as the boundary condition of the optimization problem, limiting the current of each coil to not exceed the maximum allowable value.

[0072] The functional expression for the target magnetic field vector can be adaptively set according to different control requirements. When the magnetic field is uniform, the functional expression is: ; For example, when the target magnetic field is a magnetic field rotating about a specified axis, the target magnetic field function can be set according to the orientation and frequency of the axis of rotation. The following expression is only an example and does not constitute a limitation on the form of the target magnetic field; the function expression is: .

[0073] For example, the above-mentioned constrained optimization problem can be solved using a least-squares optimization algorithm with regularization terms. Compared to the traditional direct inversion method, introducing regularization terms can effectively avoid ill-conditioned problems that may occur in the matrix in a multi-coil system, improving the numerical stability of the current solution. By solving this optimization problem, the driving currents of each coil that minimize the target magnetic field error and satisfy the current amplitude constraints under the current candidate configuration can be obtained.

[0074] Specifically, an amplitude limit is set for the current of each coil:

[0075] in, For the first Current in each coil; The determination is based on power supply capacity, coil thermal load, and safety requirements.

[0076] In the process of solving for the current, a current amplitude constraint is introduced, transforming the original least squares problem into a constrained optimization problem:

[0077] When the analytical solution does not meet the constraints, the current is adjusted through optimization methods to make it as close as possible to the target magnetic field while meeting the constraints.

[0078] Since matrix A in a multi-coil system may exhibit ill-conditioned or underdetermined behavior, a least-squares method with regularization is used to solve it. The optimization objective is: minimize

[0079] in, This is a regularization coefficient used to suppress excessive current amplitude and improve solution stability; The corresponding analytical solution is: .

[0080] It should be noted that when the driving current of each coil obtained by the solution does not meet the preset current amplitude constraint, it is corrected by scaling the target magnetic field amplitude in the preset target magnetic field requirement and / or redistributing the driving current of each coil. If the preset current amplitude constraint still cannot be met after correction, the corresponding candidate coil spatial configuration is discarded.

[0081] In the process of calculating the driving current of each coil, the actual current output capability of the electromagnetic system is limited by factors such as power supply, coil thermal load, and safety requirements. Therefore, the calculation results may show that the driving current of one or more coils exceeds the preset current amplitude constraint. In this case, the calculation results need to be corrected to approximate the preset target magnetic field requirement as closely as possible while meeting hardware constraints. Specifically, when the calculated driving current of each coil does not meet the preset current amplitude constraint, the following correction strategy can be adopted.

[0082] On the one hand, the target magnetic field amplitude in the preset target magnetic field requirement can be scaled down, that is, the amplitude of the target magnetic field components in each direction is reduced proportionally, so that the calculated driving current decreases proportionally until the current of all coils returns to within the allowable range. In this process, priority is given to ensuring the accuracy of the magnetic field direction, and the amplitude is adjusted appropriately. On the other hand, the driving current of each coil can be redistributed. That is, in a multi-coil system, the redundancy contributed by the magnetic fields between the coils is utilized, and the current distribution scheme of each coil is readjusted through optimization algorithms, transferring the current burden of some overloaded coils to other coils with current margin, thereby reducing local overload as a whole. These two correction methods can be used alone or in combination, depending on the degree of current overrun in the actual solution results and the coupling relationship between the coils in the system.

[0083] After implementing the above corrections, if the correction result meets the preset current amplitude constraint, the corrected drive current scheme is considered a valid scheme under the current candidate configuration, and the corresponding magnetic field error is calculated accordingly for subsequent configuration selection. If, after correction methods such as scaling the target magnetic field amplitude or redistributing the current, the drive current still fails to meet the preset current amplitude constraint, it indicates that under the current candidate coil spatial configuration, limited by the coil's geometric arrangement and magnetic field generation efficiency, the system cannot generate a drive scheme that effectively approximates the target magnetic field within the hardware's capabilities. In this case, the candidate configuration is determined to be invalid and discarded, without generating a corresponding magnetic field error value, and is no longer included in the configuration comparison based on magnetic field error in subsequent steps.

[0084] Through the above-mentioned correction and screening mechanism, when traversing multiple candidate coil spatial configurations, schemes that are not feasible in hardware can be eliminated, ensuring that the final output coil configuration scheme is not only optimal in terms of magnetic field accuracy, but also practically feasible in engineering, thereby improving the practicality and reliability of the overall design of the electromagnetic navigation system.

[0085] After obtaining the driving current, the corresponding magnetic field error is further calculated. The calculated magnetic field error specifically includes: An evaluation area was selected within the target lesion region, and spatial discrete sampling was performed on the evaluation area to obtain multiple sampling points; Based on the driving current of each coil obtained from the solution, the actual generated magnetic field at each sampling point is calculated. The actual generated magnetic field at each sampling point is compared with the preset target magnetic field requirement, and the magnetic field error is calculated.

[0086] After obtaining the driving current of each coil, it is necessary to further evaluate whether the generated magnetic field meets the motion requirements of the micro / nano robot. This requires calculating the corresponding magnetic field error. First, an evaluation area with a certain spatial range is selected within the target lesion region. This evaluation area should cover the critical path or workspace that the micro / nano robot may traverse. Then, spatial discrete sampling is performed on this evaluation area to obtain multiple spatial sampling points. The sampling density can be adjusted according to the accuracy requirements; generally, the more sampling points, the more accurate the magnetic field evaluation.

[0087] Next, based on the calculated driving currents of each coil, the actual generated magnetic field at each sampling point is calculated using the principle of coil magnetic field superposition. Specifically, for any sampling point, its actual magnetic field is equal to the vector sum of the magnetic fields generated by all coils at that point, where the contribution of each coil can be obtained by multiplying the driving current of that coil by a pre-established coil constant matrix. The calculated actual generated magnetic field is compared point by point with the preset target magnetic field requirement. The magnetic field error at each sampling point is defined as the vector difference between the actual magnetic field vector and the target magnetic field vector, and its magnitude or the absolute difference of each component can be used as the error metric. Furthermore, an overall error index can be calculated for the entire evaluation area, such as the average error of all sampling point errors, or the maximum error of all sampling point errors. The average error reflects the overall deviation of the magnetic field within the entire target area, while the maximum error reflects the magnetic field accuracy in the worst-case scenario.

[0088] The formula for calculating magnetic field error is:

[0089] in, Indicates the first The location of each sampling point express The actual magnetic field at that location. This represents the target magnetic field vector.

[0090] The formula for calculating the average error mentioned above is:

[0091] The formula for calculating the maximum error mentioned above is:

[0092] A magnetic field is considered effective when the following conditions are met:

[0093] in, The first preset error threshold is... This is the second preset error threshold.

[0094] The above method allows for a quantitative evaluation of the accuracy of the magnetic field generated under the current coil spatial configuration, providing a basis for subsequent selection of the optimal coil spatial configuration. When the overall error index meets the preset error threshold, the magnetic field generated under this coil spatial configuration can be considered to meet the motion requirements of micro / nano robots; otherwise, it will be replaced by a coil spatial configuration with smaller error in subsequent selection.

[0095] S106: The candidate coil spatial configuration with the smallest magnetic field error and the corresponding driving current of each coil are determined as the final coil configuration scheme.

[0096] After traversing all candidate coil spatial configurations and calculating the magnetic field error corresponding to each configuration, the candidate coil spatial configuration with the smallest magnetic field error is determined as the final coil spatial configuration by comparing the magnetic field errors of each candidate configuration. The corresponding driving current of each coil under this configuration is then used as the final driving current scheme. The two together constitute the final coil configuration scheme.

[0097] The basis of this selection process is that the magnetic field error directly reflects the degree of deviation between the actual generated magnetic field and the preset target magnetic field requirement under this configuration. The smaller the magnetic field error, the closer the magnetic field generated by the electromagnetic navigation system under this configuration is to the ideal magnetic field distribution required for the motion control of micro-nano robots, and the higher the navigation accuracy. Among all candidate coil spatial configurations, the configuration with the smallest magnetic field error represents the coil spatial layout scheme with the optimal magnetic field accuracy under the current system hardware conditions and human space constraints.

[0098] Understandably, during the selection process, if a candidate coil spatial configuration is discarded because it fails to meet the preset current amplitude constraint during the drive current solution stage, then that configuration will not generate effective magnetic field error and naturally will not need to participate in subsequent comparisons based on magnetic field error. Therefore, the candidate coil spatial configuration ultimately determined as the coil configuration scheme is the one that satisfies both the current amplitude constraint and performs optimally in terms of magnetic field accuracy.

[0099] Furthermore, it should be noted that the finalized coil configuration scheme includes a complete set of parameters for the electromagnetic navigation system design, covering the number of turns and three-dimensional dimensions of each coil, the spatial orientation of each coil relative to the target lesion area, and the driving current of each coil. This coil configuration scheme can directly serve as the basis for the subsequent manufacturing, assembly, and control of the electromagnetic navigation system, enabling the electromagnetic navigation system to generate a high-precision, high-intensity controllable magnetic field within the target lesion area in a real human body environment with optimal spatial layout and driving strategy. This solves the technical challenge of existing magnetic control systems being unable to simultaneously achieve both magnetic field strength and accuracy under large working space conditions.

[0100] For example, the multiple coils in an electromagnetic navigation system may specifically include: Two rectangular coils are symmetrically arranged on both sides of the target lesion area of ​​the human body and have the same normal direction, which are used to generate the main direction magnetic field component. Two curved coils, arranged in conjunction with two rectangular coils and with adjustable spatial orientation, are used to form a three-dimensional controllable magnetic field in the target lesion area in collaboration with the two rectangular coils.

[0101] In one possible implementation, the multiple coils in the electromagnetic navigation system specifically include two rectangular coils and two curved coils. These four coils, through spatial coordination and functional division of labor, jointly constitute a minimized configuration of a three-dimensional magnetic field generation system, which effectively reduces system complexity and space occupation while ensuring magnetic field strength and control accuracy.

[0102] Two rectangular coils are symmetrically arranged on either side of the target lesion area on the human body, with their coil normal directions aligned. Alignment means that the axial directions of the magnetic fields generated by the two rectangular coils are parallel, thus creating a dominant magnetic field component within the target lesion area. In practical applications, this dominant direction can be set according to the movement requirements of the micro / nano robot, such as along the longitudinal direction of the human body, to provide the robot with driving force or attitude control torque in that direction. The dimensions of the rectangular coils are determined based on the dimensions of the target lesion area, and their openings cover the entire lesion area, ensuring that the dominant magnetic field acts uniformly throughout the target space. See also... Figure 2 , Figure 2 The image shows a spatial arrangement of the coil system when the target lesion area is the knee joint.

[0103] Two curved surface coils are used in conjunction with two rectangular coils. The curved surface coils are conformal structures, and their geometric curvature is determined based on the surface curvature fitting results of the target lesion area on the human body. This allows the curved surface coils to conformally fit the surface and be arranged, reducing spatial interference. The two curved surface coils are arranged around the target lesion area, and their spatial position and orientation are adjustable. By changing the spatial orientation of the two curved surface coils relative to the target area, two magnetic field components in other directions independent of the principal direction of the rectangular coils can be provided, thereby adjusting the magnetic field in the other two orthogonal directions. See also... Figure 3 , Figure 3 Examples of various coil spatial configurations adapted to treatment needs when the target lesion area is specifically the knee joint are shown in (a), (b) and (c).

[0104] Figure 3 In this context, θ represents the spatial attitude adjustment angle of the surface coil relative to the target region's reference coordinate system, used to characterize the attitude change of the surface coil relative to the target region during spatial reconstruction. By adjusting the value of θ, the spatial positional relationship between the surface coil and the target region, as well as the direction of the magnetic field, can be changed, thereby forming different spatial configurations of candidate coils.

[0105] Here, Θ1, Θ2, and Θ3 represent the sets of attitude adjustment angles corresponding to three different candidate coil spatial configurations. These represent the allowable attitude adjustment range determined by mechanical structural constraints, human space limitations, and coil installation methods under each candidate configuration. Different candidate spatial configurations may have different sets of attitude adjustment angles. By traversing the combinations of attitude parameters within each set, the magnetic field performance under different spatial layouts can be obtained and further used for optimizing the selection of coil spatial configurations. Simply put, each configuration has a corresponding set of attitude adjustment angles; exceeding this set requires switching to another configuration.

[0106] The set of attitude adjustment angle values ​​is not arbitrarily set in advance, but is determined based on the mechanical structure, human body space, and coil installation constraints. Specifically, firstly, based on the rotation axis position, linkage size, guide rail stroke, driver stroke, and mechanical limits of the curved coil mounting mechanism, a mapping relationship between the mechanical structure parameters and the spatial poses of the two curved coils is established, and the initial mechanical allowable range of the relative attitude adjustment angle is determined.

[0107] Within the initial mechanical allowable range, the relative attitude adjustment angle is continuously or discretely measured, and the spatial position and attitude of the two curved coils at each attitude adjustment angle are calculated based on the spatial mapping relationship. For each attitude adjustment angle, it is determined whether the curved coils meet the mechanical motion constraints, human space constraints, and coil installation constraints. The mechanical motion constraints include at least one of the following: mechanical rotation range, actuator stroke, linkage limit position, mechanism singular position, and anti-collision requirements between different coils or mechanical components; the human space constraints include at least one of the following: minimum safe clearance between the curved coil and the external surface of the human body, human motion margin, and anti-collision requirements of the human body safety envelope; the coil installation constraints include at least one of the following: anti-collision requirements between the curved coil and the mounting base, between the rectangular coil and the supporting structure, and the length and minimum bending radius requirements of the power supply cable.

[0108] Optionally, it is also determined whether the curved coil intrudes into a preset surgical operating space, medical imaging channel, or other equipment working space. Relative attitude adjustment angles that simultaneously satisfy the above constraints are retained, forming a set of attitude adjustment angle values ​​corresponding to the current candidate coil spatial configuration. When the attitude adjustment angles satisfying the constraints form multiple discontinuous continuous intervals, each continuous interval is determined as a set of attitude adjustment angle values ​​corresponding to different candidate coil spatial configurations. Among them, the first The set of values ​​for the attitude adjustment angle can be represented as:

[0109] in, and The first The minimum and maximum attitude adjustment angles of the candidate coil spatial configurations under all constraints.

[0110] The four coils work together to achieve a combined output of three orthogonal magnetic field components within the target lesion area. The magnetic field component generated by the rectangular coil and the magnetic field component generated by the curved coil are superimposed in space. By adjusting the driving current of each coil, when the coil magnetic field mapping matrix satisfies the full-rank condition (i.e., the magnetic field directions generated by the four coils in the target area are linearly independent), a three-dimensional controllable magnetic field of arbitrary direction and amplitude can be generated within the target area. This four-coil configuration achieves omnidirectional controllability of the three-dimensional magnetic field with a minimum number of coils. While meeting the multi-degree-of-freedom motion control requirements of micro-nano robots, it reduces the overall size and complexity of the electromagnetic navigation system. Therefore, it is easier to deploy in conjunction with medical imaging equipment and surgical instruments in limited clinical space, reducing spatial conflicts between them.

[0111] Corresponding to the aforementioned application function implementation method embodiments, the present invention also provides a design system for a reconfigurable electromagnetic navigation system and corresponding embodiments.

[0112] Please see Figure 4 , Figure 4 This is a schematic diagram of the modular structure of a reconfigurable electromagnetic navigation system.

[0113] The reconfigurable electromagnetic navigation system comprises multiple coils, each of which is either a rectangular coil or a curved coil; its design system includes: Curved coil design unit 41, used for: Based on the lesion point cloud data corresponding to the target lesion area in the human body and the human body surface point cloud data, the surface configuration parameters of the curved coil are determined. Based on the surface configuration parameters and the target magnetic field strength, determine the number of turns and three-dimensional dimensional parameters of the surface coil; The rectangular coil design unit 42 is used to determine the number of coil turns of the rectangular coil according to the target magnetic field strength, and to determine the three-dimensional dimensional parameters of the rectangular coil according to the size of the target lesion area. Coil configuration design unit 43, used for: Adjust the spatial pose of each coil relative to the target lesion area to form multiple candidate coil spatial configurations; For each candidate coil spatial configuration, the driving current of each coil is solved under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement, and the corresponding magnetic field error is calculated. The candidate coil spatial configuration with the smallest magnetic field error and the corresponding driving current of each coil are determined as the final coil configuration scheme.

[0114] In one embodiment, the curved coil design unit 41 is specifically used to determine the number of turns and three-dimensional dimensional parameters of the curved coil based on the curved surface configuration parameters and the target magnetic field strength: Based on the minimum coverage area and surface type, a parametric geometric model of the surface coil is constructed; the curvature parameter and three-dimensional dimension parameter of the parametric geometric model are variables to be adjusted. Under the condition of satisfying the preset safety gap between the curved coil and the human body surface, determine the range of penetration distance from the surface of the parametric geometric model to the target lesion area; Based on the penetration distance range and the target magnetic field strength, and combined with the magnetic field attenuation law, the required number of coil turns is determined under the preset current constraint. Iteratively adjust the curvature parameters and three-dimensional dimension parameters of the parametric geometric model, recalculate the penetration distance range and update the required number of coil turns until the required number of coil turns converges. The number of coil turns and three-dimensional dimension parameters at the convergence point are determined as the final number of coil turns and three-dimensional dimension parameters.

[0115] In one embodiment, the coil configuration design unit 43 is specifically used for adjusting the spatial pose of each coil relative to the target lesion region: Establish the spatial mapping relationship between the spatial pose of each coil and the mechanical structure parameters; Based on the spatial mapping relationship, the spatial pose of each coil relative to the target lesion area is adjusted by changing the corresponding mechanical structure parameters.

[0116] In one embodiment, the coil configuration design unit 43 is specifically used to: solve for the driving current of each coil under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement; Establish the electromagnetic mapping relationship between the unit current of each coil and the magnetic field at the target point; Based on the electromagnetic mapping relationship, an optimization problem is constructed with the driving current of each coil as the variable, the objective being to minimize the deviation between the actual generated magnetic field and the preset target magnetic field, and the preset current amplitude constraint as the boundary condition. Solve the optimization problem to obtain the driving current of each coil.

[0117] In one embodiment, the coil configuration design unit 43 is specifically used for calculating the corresponding magnetic field error: An evaluation area was selected within the target lesion region, and spatial discrete sampling was performed on the evaluation area to obtain multiple sampling points; Based on the driving current of each coil obtained from the solution, the actual generated magnetic field at each sampling point is calculated. The actual generated magnetic field at each sampling point is compared with the preset target magnetic field requirement, and the magnetic field error is calculated.

[0118] In one embodiment, the coil configuration design unit 43 is further configured to: When the driving current of each coil obtained by the solution does not meet the preset current amplitude constraint, it is corrected by scaling the target magnetic field amplitude in the preset target magnetic field requirement and / or redistributing the driving current of each coil. If the preset current amplitude constraint still cannot be met after correction, the corresponding candidate coil spatial configuration is discarded.

[0119] Regarding the system in the above embodiments, the specific manner in which each unit module performs operations has been described in detail in the embodiments related to the method, and will not be elaborated further here.

[0120] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A design method for a reconfigurable electromagnetic navigation system, characterized in that, The electromagnetic navigation system includes multiple coils, and each coil is a rectangular coil or a curved coil; the design method includes: Based on the lesion point cloud data corresponding to the target lesion area in the human body and the human body surface point cloud data, the surface configuration parameters of the curved coil are determined. Based on the surface configuration parameters and the target magnetic field strength, determine the number of turns and three-dimensional dimensional parameters of the surface coil; The number of turns of the rectangular coil is determined based on the target magnetic field strength, and the three-dimensional dimensional parameters of the rectangular coil are determined based on the size of the target lesion area. Adjust the spatial pose of each coil relative to the target lesion region to form multiple candidate coil spatial configurations; For each candidate coil spatial configuration, the driving current of each coil is solved under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement, and the corresponding magnetic field error is calculated. The candidate coil spatial configuration with the smallest magnetic field error and the corresponding driving current of each coil are determined as the final coil configuration scheme.

2. The design method for the reconfigurable electromagnetic navigation system according to claim 1, characterized in that, Based on the surface configuration parameters and the target magnetic field strength, the number of turns and three-dimensional dimensional parameters of the surface coil are determined, including: Based on the minimum coverage area and surface type, a parametric geometric model of the surface coil is constructed; the curvature parameter and three-dimensional dimension parameter of the parametric geometric model are variables to be adjusted. Under the condition of satisfying the preset safety gap between the curved coil and the human body surface, determine the range of penetration distance from the surface of the parameterized geometric model to the target lesion area; Based on the penetration distance range and the target magnetic field strength, and combined with the magnetic field attenuation law, the required number of coil turns is determined under a preset current constraint. The curvature parameters and three-dimensional dimension parameters of the parametric geometric model are iteratively adjusted, the penetration distance range is recalculated and the required number of coil turns is updated until the required number of coil turns converges. The number of coil turns and three-dimensional dimension parameters at the convergence point are determined as the final number of coil turns and three-dimensional dimension parameters.

3. The design method for a reconfigurable electromagnetic navigation system according to claim 1, characterized in that, Adjusting the spatial pose of each coil relative to the target lesion region includes: Establish a spatial mapping relationship between the spatial pose of each coil and its mechanical structure parameters; Based on the spatial mapping relationship, the spatial pose of each coil relative to the target lesion area is adjusted by changing the corresponding mechanical structure parameters.

4. The design method for a reconfigurable electromagnetic navigation system according to claim 1, characterized in that, Solving for the driving current of each coil under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement includes: Establish the electromagnetic mapping relationship between the unit current of each coil and the magnetic field at the target point; Based on the electromagnetic mapping relationship, an optimization problem is constructed with the driving current of each coil as the variable, the objective being to minimize the deviation between the actual generated magnetic field and the preset target magnetic field, and the preset current amplitude constraint as the boundary condition. Solve the optimization problem to obtain the driving current of each coil.

5. The design method for a reconfigurable electromagnetic navigation system according to claim 1, characterized in that, Calculate the corresponding magnetic field error, including: An evaluation area is selected within the target lesion region, and spatial discrete sampling is performed on the evaluation area to obtain multiple sampling points; Based on the driving current of each coil obtained by the solution, the actual generated magnetic field at each sampling point is calculated; The actual generated magnetic field at each sampling point is compared with the preset target magnetic field requirement, and the magnetic field error is calculated.

6. The design method for a reconfigurable electromagnetic navigation system according to claim 1, characterized in that, The plurality of coils specifically includes: Two rectangular coils are symmetrically arranged on both sides of the target lesion area of ​​the human body and have the same normal direction, which are used to generate the main direction magnetic field component. Two curved coils, arranged in conjunction with two rectangular coils and with adjustable spatial orientation, are used to form a three-dimensional controllable magnetic field in the target lesion area in cooperation with the two rectangular coils.

7. The design method for a reconfigurable electromagnetic navigation system according to claim 4, characterized in that, When the driving current of each coil obtained by the solution does not meet the preset current amplitude constraint, it is corrected by scaling the target magnetic field amplitude in the preset target magnetic field requirement and / or by redistributing the driving current of each coil. If the preset current amplitude constraint still cannot be met after correction, the corresponding candidate coil spatial configuration is discarded.

8. A design system for a reconfigurable electromagnetic navigation system, characterized in that, The electromagnetic navigation system includes multiple coils, and each coil is a rectangular coil or a curved coil; the design system includes: Curved coil design unit, used for: Based on the lesion point cloud data corresponding to the target lesion area in the human body and the human body surface point cloud data, the surface configuration parameters of the curved coil are determined. Based on the surface configuration parameters and the target magnetic field strength, determine the number of turns and three-dimensional dimensional parameters of the surface coil; A rectangular coil design unit is used to determine the number of turns of the rectangular coil based on the target magnetic field strength, and to determine the three-dimensional dimensional parameters of the rectangular coil based on the size of the target lesion area. Coil configuration design unit, used for: Adjust the spatial pose of each coil relative to the target lesion region to form multiple candidate coil spatial configurations; For each candidate coil spatial configuration, the driving current of each coil is solved under the conditions of satisfying the preset current amplitude constraint and the preset target magnetic field requirement, and the corresponding magnetic field error is calculated. The candidate coil spatial configuration with the smallest magnetic field error and the corresponding driving current of each coil are determined as the final coil configuration scheme.

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