Six degree of freedom active electromagnetic positioning system and method

Abstract

The application discloses a kind of six degrees of freedom active electromagnetic positioning systems and methods, wherein the system includes: induction module, fixed on the object to be measured, induction module includes magnetic sensor and inertial measurement unit, magnetic sensor is used to collect magnetic field intensity information, and inertial measurement unit is used to collect attitude information;Variable magnetic moment electromagnetic device is used to generate magnetic source, and the position of variable magnetic moment electromagnetic device is fixed;Host computer is used to obtain the first pose of magnetic sensor according to the collected magnetic field intensity information and attitude information, adjusts the magnetic field information of variable magnetic moment electromagnetic device according to the first pose;According to the updated magnetic field information of variable magnetic moment electromagnetic device, and the second pose of sensor is estimated as the pose of object to be measured according to preset model.The application adopts the method of active control electromagnet magnetic moment, improves the magnetic positioning space sensitivity of electromagnetic positioning system, so as to improve the positioning accuracy, expand its measurement range, and can be widely applied in electromagnetic positioning technical field.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electromagnetic positioning technology, and in particular to a six-degree-of-freedom active electromagnetic positioning system and method. BACKGROUND

[0002] Currently, mobile object positioning systems for positioning in a small or medium range are mainly optical tracking systems, which can achieve high accuracy. However, optical sensing-based methods require line-of-sight accessibility and cannot be applied to the positioning of objects that are obstructed, such as medical instruments moving in the body. Ultrasonic-based positioning systems are another commonly used positioning system, but the measurement accuracy of ultrasonic positioning is affected in non-uniform media. Some positioning systems use radio frequency wave-based methods, but radio frequency waves are difficult to accurately establish the relationship between the measured signal strength or propagation time and the position of the measured object in non-uniform or attenuating media such as the human body, and the positioning accuracy is limited.

[0003] Magnetic fields can penetrate most non-ferromagnetic objects (such as the human body), so magnetic field-based positioning methods are not affected by line-of-sight obstruction and have good application prospects for positioning in small or medium range spaces where the line of sight is blocked, such as in the positioning of flexible medical robots through natural cavities of the human body.

[0004] Magnetic positioning systems have an inherent defect: the magnetic field strength of the magnetic source and the gradient of the magnetic field with respect to the position are extremely unevenly distributed in space, and change with the distance and relative attitude of the sensor and the magnetic source. The positioning accuracy of the measured object is relatively low when it is far away from the magnetic source or in some specific positions relative to the magnetic source, and the effective measurement range of the positioning system is limited. SUMMARY

[0005] To at least partially solve one of the technical problems existing in the prior art, the purpose of the present application is to provide a six-degree-of-freedom active electromagnetic positioning system and method.

[0006] The technical solution adopted by the present application is:

[0007] A six-degree-of-freedom active electromagnetic positioning system, comprising:

[0008] An induction module fixed on a measured object, the induction module comprising a magnetic sensor and an inertial measurement unit, the magnetic sensor being used to collect magnetic field strength information, and the inertial measurement unit being used to collect attitude information;

[0009] A variable magnetic moment electromagnetic device for generating a magnetic source, the position of the variable magnetic moment electromagnetic device being fixed;

[0010] The host computer is used for obtaining a first pose of the magnetic sensor according to the collected magnetic field intensity information and the attitude information, adjusting the magnetic field information of the variable magnetic moment electromagnetic device according to the first pose, so that the magnetic moment direction is aligned with the sensor, and the magnetic moment size is ensured, and estimating a second pose of the sensor as the pose of the object to be measured according to the updated magnetic field information of the variable magnetic moment electromagnetic device and a preset model.

[0011] Further, the variable magnetic moment electromagnetic device is a mechanical control type variable magnetic moment electromagnetic device, comprising:

[0012] A single-axis electromagnet is used for generating a magnetic field.

[0013] A two-axis holder composed of two motors is used for controlling the position and angle of the single-axis electromagnet.

[0014] A direct current driving board is used for controlling the current on the single-axis electromagnet.

[0015] Further, the two-axis holder comprises:

[0016] A first support frame is used for fixing the single-axis electromagnet.

[0017] A first motor is connected with the first support frame and used for driving the single-axis electromagnet to rotate in a vertical plane.

[0018] A second support frame is connected with the first motor at one end and connected with a second motor at the other end.

[0019] The second motor is used for driving the single-axis electromagnet to rotate in a horizontal plane.

[0020] Further, the second support frame is an L-shaped support frame.

[0021] Further, the variable magnetic moment electromagnetic device is a current control type variable magnetic moment electromagnetic device, comprising:

[0022] A three-axis orthogonal electromagnetic coil comprises three electromagnetic coils and is used for generating a magnetic moment in any direction.

[0023] Three direct current driving boards are used for controlling the current on the three electromagnetic coils respectively.

[0024] Further, the variable magnetic moment electromagnetic device further comprises an iron core for enhancing the magnetic field.

[0025] Another technical solution adopted by the present application is:

[0026] A six-degree-of-freedom active electromagnetic positioning method comprises the following steps:

[0027] The magnetic source and the magnetic sensor are modeled as a magnetic dipole model.

[0028] determining the relationship between the magnetic field and the pose of the magnetic sensor, and establishing a mathematical model;

[0029] collecting magnetic field intensity information by a magnetic sensor and collecting attitude information by an inertial measurement unit; wherein the magnetic sensor and the inertial measurement unit are installed on the object to be measured;

[0030] obtaining a first pose of the magnetic sensor according to the collected magnetic field intensity information and attitude information;

[0031] adjusting the magnetic field information of the variable magnetic moment electromagnetic device according to the first pose, so that the magnetic moment direction is aligned with the sensor and the magnetic moment size is ensured;

[0032] estimating a second pose of the sensor according to the updated magnetic field information of the variable magnetic moment electromagnetic device and the mathematical model, as the pose of the object to be measured.

[0033] Further, the variable magnetic moment electromagnetic device is a mechanically controlled variable magnetic moment electromagnetic device, including a single-axis electromagnet, a two-axis gimbal and a direct current driving board;

[0034] The adjusting of the magnetic field information of the variable magnetic moment electromagnetic device according to the first pose includes:

[0035] According to the first pose, the relative pose between the magnetic sensor and the single-axis electromagnet is obtained, the magnetic moment direction of the single-axis electromagnet is controlled by the two-axis gimbal, so that the magnetic moment direction is aligned with the sensor to obtain the maximum magnetic positioning sensitivity;

[0036] According to the first pose, the distance between the magnetic sensor and the single-axis electromagnet is obtained, the current on the single-axis electromagnet is controlled by the direct current driving board, so that the magnetic moment size of the electromagnet is controlled in real time to ensure sufficient magnetic positioning sensitivity.

[0037] Further, the variable magnetic moment electromagnetic device is a current controlled variable magnetic moment electromagnetic device, including three pairs of orthogonal electromagnetic coils and three direct current driving boards, and the three direct current driving boards are matched with the three electromagnetic coils respectively;

[0038] The adjusting of the magnetic field information of the variable magnetic moment electromagnetic device according to the first pose includes:

[0039] According to the first pose, the three direct current drivers are controlled respectively, so that the generated magnetic field is changed, and the vector sum of the magnetic moments generated by the three electromagnetic coils is aligned with the magnetic sensor to obtain the maximum magnetic positioning sensitivity;

[0040] According to the first pose, the distance between the magnetic sensor and the electromagnetic coil is obtained, the current on the electromagnetic coil is controlled by the direct current driving board to control the size of the magnetic moment vector sum, so as to ensure sufficient magnetic positioning sensitivity.

[0041] Further, the expression of the mathematical model is:

[0042]

[0043] Wherein, The magnetic field strength value measured by the magnetic sensor is represented by B, The vacuum permeability is represented by mu0, The sensor posture rotation matrix is represented by R, The electromagnet magnetic moment vector is represented by M, The absolute value of the distance between the magnetic sensor and the electromagnet center is represented by r, A matrix about the position of the magnetic sensor is represented by Rr, The position of the magnetic sensor in the world coordinate system is represented by r, The axis, The axis, The axis)

[0044]

[0045] The beneficial effects of the present application are: the present application adopts the method of actively controlling the electromagnet magnetic moment, improves the magnetic positioning space sensitivity of the electromagnetic positioning system, thereby improving the positioning accuracy and expanding the measurement range. The system is especially suitable for the positioning of moving objects in line-of-sight occluded environment, such as the positioning of medical instruments moving in the body. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following introduces the drawings of the related technical solutions in the embodiments of the present application or the prior art. It should be understood that the drawings in the following introduction are only for the convenience of clearly describing part of the embodiments in the technical solutions of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0047] Figure 1 is a step flow chart of a six-degree-of-freedom active electromagnetic positioning method in the embodiments of the present application;

[0048] Figure 2 is a schematic diagram of a mechanical control type active electromagnetic positioning device in the embodiments of the present application;

[0049] Figure 3 is a schematic diagram of a current control type active electromagnetic positioning device in the embodiments of the present application;

[0050] Figure 4is a device schematic diagram of the universal magnetic source in the embodiment of the present application;

[0051] Figure 5 is an estimated value and a reference value of the position of the sensor in the embodiment of the present application.

[0052] Figure 2 Reference signs: 2.1 - electromagnet; 2.2 - first support frame; 2.3 - first motor; 2.4 - second support frame; 2.5 - second motor; 2.6 - induction module; 2.7 - upper computer; 2.8 - DC drive board.

[0053] Figure 3 Reference signs: 3.1 - induction module; 3.2 - three-axis orthogonal electromagnetic coil; 3.3 - first DC drive board; 3.4 - second DC drive board; 3.5 - third DC drive board; 3.6 - upper computer.

[0054] Figure 4 Reference signs: 4.1 - coil frame; 4.2 - core; 4.3 - inner electromagnetic coil; 4.4 - middle electromagnetic coil; 4.5 - outer electromagnetic coil. DETAILED DESCRIPTION

[0055] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only, for the purpose of explaining the present application, and should not be understood as a limitation of the present application. For the step numbers in the following embodiments, they are only set for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0056] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as a limitation of the present application, which does not indicate or imply that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation.

[0057] In the description of the present application, the meaning of several is one or more, and the meaning of multiple is more than two, greater than, less than, more than, etc. are understood as not including the number, above, below, etc. are understood as including the number. If it is described as first, second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of indicated technical features.

[0058] In the description of the present application, the words such as arrangement, installation, connection and the like should be understood in a broad sense unless otherwise explicitly limited, and the skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0059] In view of the low magnetic positioning accuracy of the prior art, the present application adopts a method of actively controlling the magnetic moment of an electromagnet to improve the magnetic positioning spatial sensitivity of the electromagnetic positioning system, thereby improving the positioning accuracy and expanding the measurement range. The system is particularly suitable for positioning moving objects in line-of-sight blocked environments (such as positioning of medical instruments moving in the body).

[0060] Referring to Figure 2 The embodiment provides a six-degree-of-freedom active electromagnetic positioning system, comprising:

[0061] An induction module fixed on the object to be measured, the induction module comprising a magnetic sensor and an inertial measurement unit, the magnetic sensor being used to collect magnetic field strength information, and the inertial measurement unit being used to collect attitude information;

[0062] A variable magnetic moment electromagnetic device for generating a magnetic source, the position of the variable magnetic moment electromagnetic device being fixed;

[0063] An upper computer for acquiring a first pose of the magnetic sensor according to the collected magnetic field strength information and attitude information, adjusting the magnetic field information of the variable magnetic moment electromagnetic device according to the first pose to align the magnetic moment direction with the sensor and ensure the magnetic moment size, and estimating a second pose of the sensor as the pose of the object to be measured according to the updated magnetic field information of the variable magnetic moment electromagnetic device and a preset model.

[0064] As an optional implementation, the variable magnetic moment electromagnetic device is a mechanically controlled variable magnetic moment electromagnetic device, comprising:

[0065] A single-axis electromagnet for generating a magnetic field;

[0066] A two-axis holder composed of two motors for controlling the position and angle of the single-axis electromagnet;

[0067] A direct current driving board for controlling the current on the single-axis electromagnet.

[0068] Further as a preferred implementation, the two-axis holder comprises:

[0069] A first support frame for fixing the single-axis electromagnet;

[0070] A first motor connected with the first support frame for driving the single-axis electromagnet to rotate in a vertical plane;

[0071] A second support frame, one end of which is connected with the first motor, and the other end of which is connected with a second motor;

[0072] A second motor is used to drive the single-axis electromagnet to rotate in a horizontal plane.

[0073] As another alternative embodiment, the variable-magnetic-moment electromagnetic device is a current-controlled variable-magnetic-moment electromagnetic device, which comprises:

[0074] A three-axis orthogonal electromagnetic coil, which comprises three electromagnetic coils, is used to generate a magnetic moment in any direction.

[0075] Three direct-current driving boards are used to control the currents in the three electromagnetic coils, respectively.

[0076] Further as a preferred embodiment, the variable-magnetic-moment electromagnetic device further comprises an iron core for enhancing the magnetic field.

[0077] The above system is explained in detail below in combination with the accompanying drawings and specific embodiments.

[0078] As shown in the drawings, Figure 2 The present embodiment provides a six-degree-of-freedom active electromagnetic positioning system, which comprises an induction module 2.6, a variable-magnetic-moment electromagnetic device, and an upper computer 2.7.

[0079] In the present embodiment, the induction module 2.6 adopts an MPU9250 module, which integrates a magnetic sensor and an inertial measurement unit. The sensor 2.6 is installed in an object to be measured.

[0080] The variable-magnetic-moment electromagnetic device is a mechanically controlled variable-magnetic-moment electromagnetic device, which comprises a single-axis electromagnet (hereinafter referred to as electromagnet), a two-axis gimbal composed of two motors, and a direct-current driving board. The electromagnet 2.1 is selected to have a maximum voltage of 24V, a diameter of 100mm, and a thickness of 40mm. A constant-voltage direct-current power supply is used to provide power for the direct-current driving board 2.8, which adopts an AQMD3620NS-B direct-current motor driver produced by Aishikong Company.

[0081] As an alternative embodiment, the two-axis gimbal comprises a first support frame 2.2, a first motor 2.3, a second support frame 2.4, and a second motor 2.5. Specifically, one end of the first support frame 2.2 is tightly fitted with the electromagnet 2.1 and is fixed with a screw. The other end of the first support frame 2.2 is locked with the first motor 2.3 with a screw. The second support frame 2.4 is L-shaped, and its two ends are connected with the first motor 2.3 and the second motor 2.5, respectively. Both the first support frame 2.2 and the second support frame 2.4 are made of aluminum.

[0082] The induction module 2.6 moves in the magnetic field and transmits the acquired magnetic field information and attitude information to the host computer 2.7 in real time through serial communication by cable. The host computer 2.7 receives information from the induction module 2.6, estimates the pose of the magnetic sensor according to the magnetic field measurement value, the mathematical model of the electromagnet 2.1, the attitude information of the inertial measurement unit, and the motion model of the object to be measured.

[0083] The host computer 2.7 controls the first motor 2.3 and the second motor 2.5 according to the estimated magnetic sensor pose, drives the electromagnet 2.1 to rotate, and aligns the magnetic moment of the electromagnet 2.1 with the magnetic sensor. The host computer 2.7 controls the current size in the electromagnet, so that the size of the magnetic moment of the electromagnet 2.1 changes with the distance between the sensor and the electromagnet. At the same time, the host computer 2.7 updates the mathematical model between the magnetic field measurement value and the relative pose of the sensor and the electromagnet 2.1 according to the updated magnetic field information, and obtains the final pose of the magnetic sensor as the pose of the object to be measured.

[0084] As shown in Figure 3 The embodiment provides a six-degree-of-freedom active electromagnetic positioning system, which comprises an induction module 3.1, a variable magnetic moment electromagnetic device, and a host computer 3.6.

[0085] The induction module 3.1 is installed in an object to be measured and comprises a magnetic sensor and an inertial measurement unit. Specifically, the induction module 3.1 is implemented by using an MPU9250 module, and the module is integrated with a magnetic sensor and an inertial measurement unit.

[0086] The variable magnetic moment electromagnetic device is a current-controlled variable magnetic moment electromagnetic device, which comprises three-axis orthogonal electromagnetic coils 3.2, a first direct current driving plate 3.3, a second direct current driving plate 3.4, and a third direct current driving plate 3.5. The three direct current driving plates are implemented by using direct current driving plates with the model AQMD3620NS-B.

[0087] Figure 3In the middle, the induction module 1 moves in the magnetic field, and the acquired magnetic field information and attitude information are transmitted to the host computer 3.6 through serial communication. The host computer 3.6 receives information from the induction module 3.1, estimates the position and attitude of the magnetic sensor according to the magnetic field measurement value, the mathematical model of the three-axis orthogonal electromagnetic coil, the attitude information of the inertial measurement unit, and the motion model of the object to be measured. The host computer 3.6 controls the first DC driver 3.3, the second DC driver 3.4, and the third DC driver 3.5 according to the estimated position and attitude of the magnetic sensor, so that the magnetic fields generated by the inner coil, the middle coil, and the outer coil of the three-axis orthogonal electromagnetic coil 3.2 change, and the vector sum of the magnetic moments generated by the three coils is aligned with the magnetic sensor; the size of the vector sum of the magnetic moments is controlled according to the distance between the magnetic sensor and the three-axis orthogonal electromagnetic coil 3.2, so as to ensure high magnetic field spatial sensitivity; at the same time, the host computer 3.6 updates the relationship model between the magnetic field measurement value and the relative position and attitude of the magnetic sensor and the three-axis orthogonal electromagnetic coil 3.2, and obtains the final position and attitude of the magnetic sensor as the position and attitude of the object to be measured.

[0088] Referring to Figure 4 , Figure 4 is a schematic diagram of a three-axis orthogonal electromagnetic coil device. The three-axis orthogonal electromagnetic coil includes a coil frame 4.1, a core 4.2, an inner electromagnetic coil 4.3, a middle electromagnetic coil 4.4, and an outer electromagnetic coil 4.5. Among them, Figure 4 (a) is a schematic diagram of the inner core of the three-axis orthogonal electromagnetic coil, Figure 4 (b) is a schematic diagram of the inner electromagnetic coil of the three-axis orthogonal electromagnetic coil, Figure 4 (c) is a schematic diagram of the middle electromagnetic coil of the three-axis orthogonal electromagnetic coil, Figure 4 (d) is a schematic diagram of the outer electromagnetic coil of the three-axis orthogonal electromagnetic coil.

[0089] Based on the above six-degree-of-freedom active electromagnetic positioning system, as shown in Figure 1 , the embodiment also provides a six-degree-of-freedom active electromagnetic positioning method, which comprises the following steps:

[0090] S1, model the magnetic source and the magnetic sensor as a magnetic dipole model.

[0091] S2, determine the relationship between the magnetic field and the position and attitude of the magnetic sensor, and establish a mathematical model.

[0092] Establish the relationship between the magnetic field of the active electromagnetic device in the initial state and the position and attitude of the magnetic sensor, establish a mathematical model, and calibrate and calibrate the model.

[0093] It is assumed that the magnetic source and the magnetized soft magnetic body can be approximated by a magnetic dipole model:

[0094]

[0095] represents a magnetic field strength value measured by a magnetic sensor, represents a vacuum permeability, represents a sensor attitude rotation matrix, represents an electromagnet magnetic moment vector, represents an absolute value of a distance between a magnetic sensor and a center of an electromagnet, represents a matrix (1) about a position of a magnetic sensor represents a position of a magnetic sensor in a world coordinate system axis, axis, axis

[0096]

[0097] S3, collecting magnetic field strength information by a magnetic sensor and collecting attitude information by an inertial measurement unit; wherein the magnetic sensor and the inertial measurement unit are installed on the object to be measured.

[0098] The position of the electromagnet is fixed, and the sensor is fixed on the measured moving object, so as to represent the pose of the measured moving object by the pose of the magnetic sensor. Specifically, the inertial measurement unit can be implemented by a gyroscope.

[0099] S4, obtaining a first pose of the magnetic sensor according to the collected magnetic field strength information and attitude information.

[0100] Based on the pose measurement model, the magnetic field information measured by the magnetic sensor and the information of the gyroscope are fused to estimate the position and attitude of the sensor.

[0101] S5, adjusting the magnetic field information of the variable magnetic moment electromagnet device according to the first pose, so as to align the magnetic moment direction with the sensor and ensure the magnetic moment size.

[0102] According to the relative attitude between the magnetic sensor and the magnetic source, the magnetic moment direction of the electromagnet is controlled in real time, so that the magnetic moment direction of the electromagnet is aligned with the sensor to obtain the maximum magnetic positioning sensitivity; according to the distance between the magnetic sensor and the magnetic source, the magnetic moment size of the electromagnet is controlled in real time by controlling the current of the electromagnet, so as to ensure sufficient magnetic positioning sensitivity.

[0103] S6, estimating a second pose of the sensor according to the updated magnetic field information of the variable magnetic moment electromagnet device and the mathematical model, as the pose of the object to be measured.

[0104] The new pose of the magnetic sensor is estimated by using the updated magnetic field, as the final pose of the object to be measured. The mathematical model is updated, and the step S3 is returned to continue to estimate the pose at the next time.

[0105] In the embodiment, the position of the magnetic sensor is estimated according to the information collected by the sensor, and the magnetic field has a relatively strong range. Then, the electromagnet is turned towards the sensor to the magnetic sensor to obtain the maximum magnetic positioning sensitivity. The final pose is calculated according to the mathematical model, so as to greatly improve the measurement accuracy.

[0106] As an optional implementation, the extended Kalman filter algorithm (EKF) and a method of designing a nonlinear observer can be used as the pose estimation algorithm, but are not limited thereto. In the embodiment, the EKF algorithm is used as the pose estimation algorithm.

[0107] Referring to Figure 5 , Figure 5 are the estimated value and the reference value of the position of the sensor in the embodiment. In the figure, the dashed line is the reference motion trajectory of the sensor, the thin solid line is the motion trajectory estimated by using the fixed magnetic moment positioning method, and the cross line is the motion trajectory estimated by using the active sensor positioning method. The figure is the test result obtained by using the mechanical control type variable magnetic moment electromagnet device.

[0108] In summary, the six-degree-of-freedom active electromagnetic positioning method and device based on real-time control of the magnetic moment are used in the embodiment, the measurement sensitivity of the electromagnetic positioning system is improved, and thus the positioning accuracy is improved or the measurement range is expanded.

[0109] In the above description of the present specification, the description of the terms "one embodiment", "another embodiment", "certain embodiments", or the like means that the specific features, structures, materials or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0110] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

[0111] The above is a specific description of the preferred embodiment of the present application, but the present application is not limited to the above embodiment, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A six degree of freedom active electromagnetic positioning system, characterized by, The application relates to a magnetic field sensor system, which comprises the following parts: a sensing module fixed on a measured object, the sensing module comprising a magnetic sensor and an inertial measurement unit, the magnetic sensor being used for collecting magnetic field intensity information, and the inertial measurement unit being used for collecting attitude information; a variable magnetic moment electromagnetic device used for generating a magnetic source, the position of the variable magnetic moment electromagnetic device being fixed; a host computer used for obtaining a first attitude of the magnetic sensor according to the collected magnetic field intensity information and attitude information, adjusting the magnetic field of the variable magnetic moment electromagnetic device according to the first attitude, so that the magnetic moment direction is aligned with the sensor, and the magnetic moment size is ensured; a second attitude of the sensor is estimated according to the updated magnetic field information of the variable magnetic moment electromagnetic device and a preset mathematical model, and the second attitude is taken as the attitude of the measured object; the mathematical model is as follows: wherein denotes a magnetic field strength value measured by the magnetic sensor, denotes the vacuum permeability, denotes a sensor attitude rotation matrix, denotes an electromagnet magnetic moment vector, denotes an absolute value of the distance of the magnetic sensor from the electromagnet center, denotes a matrix related to the magnetic sensor position.

2. A six degree of freedom active electromagnetic positioning system according to claim 1, characterized in that, the variable magnetic moment electromagnetic device is a mechanical control type variable magnetic moment electromagnetic device, which comprises the following parts: a single-axis electromagnet used for generating a magnetic field; a two-axis holder composed of two motors, which is used for controlling the position and angle of the single-axis electromagnet; a direct current driving board used for controlling the current on the single-axis electromagnet.

3. A six degree of freedom active electromagnetic positioning system according to claim 2, characterized in that, the two-axis holder comprises the following parts: a first support frame used for fixing the single-axis electromagnet; a first motor connected with the first support frame, which is used for driving the single-axis electromagnet to rotate in a vertical plane; a second support frame, one end of the second support frame being connected with the first motor, and the other end of the second support frame being connected with a second motor; the second motor is used for driving the single-axis electromagnet to rotate in a horizontal plane.

4. A six degree of freedom active electromagnetic positioning system according to claim 3, wherein, the second support frame is an L-shaped support frame.

5. A six degree of freedom active electromagnetic positioning system according to claim 1, wherein, the variable magnetic moment electromagnetic device is a current control type variable magnetic moment electromagnetic device, which comprises the following parts: a three-axis orthogonal electromagnetic coil comprising three electromagnetic coils, which is used for generating a magnetic moment in any direction; three direct current driving boards used for controlling the current on the three electromagnetic coils respectively.

6. A six degree of freedom active electromagnetic positioning system according to claim 5, wherein, the variable magnetic moment electromagnetic device further comprises an iron core used for enhancing the magnetic field.

7. A six degree of freedom active electromagnetic positioning method, characterized by, The application further discloses a method for measuring the attitude of a measured object, which comprises the following steps: modeling the magnetic source and the magnetic sensor as a magnetic dipole model; determining the relationship between the magnetic field and the attitude of the magnetic sensor, and establishing a mathematical model; collecting the magnetic field intensity information through the magnetic sensor and collecting the attitude information through the inertial measurement unit, wherein the magnetic sensor and the inertial measurement unit are installed on the measured object; obtaining the first attitude of the magnetic sensor according to the collected magnetic field intensity information and attitude information; adjusting the magnetic field information of the variable magnetic moment electromagnetic device according to the first attitude, so that the magnetic moment direction is aligned with the sensor, and the magnetic moment size is ensured; estimating the second attitude of the sensor according to the updated magnetic field information of the variable magnetic moment electromagnetic device and the mathematical model, and taking the second attitude as the attitude of the measured object; the expression of the mathematical model is as follows: wherein denotes a magnetic field strength value measured by the magnetic sensor, denotes the vacuum permeability, denotes a sensor attitude rotation matrix, denotes the electromagnet magnetic moment vector, denotes the absolute value of the distance of the magnetic sensor from the electromagnet center, denotes a matrix relating to the magnetic sensor position.

8. The six degree of freedom active electromagnetic positioning method according to claim 7, characterized in that, the variable magnetic moment electromagnetic device is a mechanical control type variable magnetic moment electromagnetic device, which comprises a single-axis electromagnet, a two-axis holder and a direct current driving board; the adjustment of the magnetic field information of the variable magnetic moment electromagnetic device according to the first attitude comprises the following steps: according to the first attitude, the relative attitude between the magnetic sensor and the single-axis electromagnet is obtained, the magnetic moment direction of the single-axis electromagnet is controlled through the two-axis holder, and the magnetic moment direction is aligned with the sensor. According to the first pose, the distance between the magnetic sensor and the single-axis electromagnet is obtained, and the current on the single-axis electromagnet is controlled through the direct current driving plate to control the magnetic moment size of the electromagnet in real time.

9. The six degree of freedom active electromagnetic positioning method according to claim 7, wherein, The variable magnetic moment electromagnetic device is a current control type variable magnetic moment electromagnetic device, which comprises three mutually orthogonal electromagnetic coils and three direct current driving plates, and the three direct current driving plates are matched with the three electromagnetic coils respectively. The magnetic field information of the variable magnetic moment electromagnetic device is adjusted according to the first pose, which comprises: According to the first pose, the three direct current driving plates are controlled respectively, so that the generated magnetic field changes, and the vector sum of the magnetic moments generated by the three electromagnetic coils is aligned with the magnetic sensor; According to the first pose, the distance between the magnetic sensor and the single-axis electromagnet is obtained, and the current on the single-axis electromagnet is controlled through the direct current driving plate to control the magnetic moment size of the electromagnet in real time.

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