A centimeter-level composite positioning method for electronic capsules

Abstract

The present invention provides a centimeter-level composite positioning method for an electronic capsule. The electronic capsule has a built-in Bluetooth receiving module and a MEMS inertial navigation module, and a Bluetooth transceiver module is provided outside the human body. The Bluetooth receiving module and the MEMS inertial navigation module are used to obtain the electronic capsule's initial position information, initial attitude information, displacement change information, and heading angle information. The MEMS inertial navigation module then performs high-precision position information calculation, and uses Bluetooth to obtain real-time position information for auxiliary correction. The present invention uses Bluetooth's AOA measurement technology to assist the MEMS inertial navigation module in calculating the electronic capsule's motion trajectory. Auxiliary positioning is then performed using Bluetooth output real-time position and attitude information calculation technology. A fusion algorithm for MEMS and Bluetooth position signals is employed, and combined positioning complements the shortcomings of the two positioning methods, thereby improving the overall positioning accuracy of the electronic capsule to the centimeter level.

Description

Technical Field

[0001] The present invention relates to the field of medical instruments, and in particular to a centimeter-level composite positioning method for electronic capsules. Background Art

[0002] The medical smart electronic capsule is an invasive detection / imaging microsystem used for gastrointestinal examinations. After entering the human body, it can capture images or videos of the digestive tract and obtain data such as temperature and pH of the digestive tract and transmit it to equipment outside the body for further diagnosis. It has the characteristics of painless, convenient and fast detection, and can complete the detection of the entire digestive tract.

[0003] Precise positioning of medical electronic capsules is a prerequisite for identifying lesions and subsequent targeted treatment. Currently, magnetic field positioning and radio frequency positioning are the most widely used positioning methods. Magnetic field positioning technology is characterized by its small size and high accuracy, but magnetic field sensors are typically large, expensive, and have strict requirements for the working environment. Radio frequency positioning technology is the most widely used capsule positioning method due to its small size and low cost. However, wireless radio frequency signals are subject to multipath effects and significant attenuation, resulting in low positioning accuracy (sub-meter level) and poor stability.

[0004] In recent years, with the development of millimeter-wave, terahertz, and ultra-wideband (UWB) wireless positioning technologies, researchers at China Electronics 43rd Research Institute and others have proposed UWB-based capsule positioning methods, which can further improve positioning accuracy (sub-meter to centimeter levels). However, UWB positioning methods consume high power and require external equipment, resulting in high system construction costs. Besides magnetic field and wireless positioning technologies, commonly used inertial navigation positioning technologies are not yet widely adopted in electronic capsules due to inherent flaws such as long-term position accumulation errors, which lead to reduced positioning accuracy (meter to sub-meter levels), limiting their practical application. However, inertial positioning allows for autonomous positioning, is less susceptible to interference, and offers high short-term positioning accuracy. It also offers advantages such as small size and low cost.

[0005] It can be seen that under the existing technology, there is a lack of a method for positioning medical electronic capsules that can take into account both volume and cost and precision and stability. Summary of the Invention

[0006] The purpose of the present invention is to provide a centimeter-level composite positioning method for electronic capsules, which adopts a composite positioning method, that is, a combination of wireless signals and inertial navigation positioning, to achieve low-cost, high-precision combined positioning of electronic capsules, so as to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A centimeter-level composite positioning method for an electronic capsule. The electronic capsule has a built-in Bluetooth receiving module and a MEMS inertial navigation module, and a Bluetooth transceiver module is provided outside the human body. After the electronic capsule is started, composite positioning is achieved through the following steps:

[0009] S1. Obtain the initial position information of the electronic capsule through the Bluetooth receiving module;

[0010] S2, obtaining the initial posture information and displacement change information of the electronic capsule through the MEMS inertial navigation module;

[0011] S3, combining the MEMS inertial navigation module and Bluetooth real-time attitude information to obtain the heading angle information of the electronic capsule;

[0012] S4, use the MEMS inertial navigation module to calculate high-precision position information, and obtain real-time position information through Bluetooth function for auxiliary correction;

[0013] S5. Transmitting the position information and image or video information of the electronic capsule to the terminal device via a Bluetooth signal, and comparing them with the image of the human digestive tract model to eliminate erroneous information.

[0014] Furthermore, the Bluetooth receiving module and the MEMS inertial navigation module are integrated into a single chip. The Bluetooth receiving module includes an antenna array, a radio frequency switch, and an I / Q sample capture receiver. The antenna array is provided with at least two antennas connected in sequence at a fixed interval of no more than 6 cm; the MEMS inertial navigation module includes a three-axis accelerometer, a three-axis gyroscope, and a three-axis magnetometer.

[0015] Furthermore, the Bluetooth transceiver module is fixed to the human body feature identification point by pasting, is provided with a single transmitting line, and the frequency of the Bluetooth signal is 2.4 GHz.

[0016] Furthermore, obtaining the initial position information of the electronic capsule through the Bluetooth receiving module in step S1 is achieved based on the Bluetooth AOA measurement technology, and specifically includes the following steps:

[0017] S11, collecting I / Q information of each antenna in the Bluetooth receiving module, and calculating the phase difference between the same RF signal reaching each antenna;

[0018] S12. Convert the phase difference between two adjacent antennas into an arrival angle. The calculation formula is:

[0019]

[0020] Where: θ is the angle between the incident RF signal wave and the antenna array, λ is the incident wavelength, and d is the spacing between the antennas;

[0021] S13. Obtain the distance or angle information between the tag and each base station in a given network and establish the equation:

[0022]

[0023] S14. After solving the above equation to obtain the initial position information of the electronic capsule, the Bluetooth receiving module is turned off.

[0024] Furthermore, step S2 is specifically implemented by the following steps:

[0025] S21, obtaining acceleration and angular velocity information in three directions of capsule movement through the three-axis accelerometer and three-axis gyroscope in the MEMS inertial navigation module and outputting the information;

[0026] S22, fusing the output speed information to calculate the initial posture information of the electronic capsule;

[0027] S23 , integrating the output acceleration information over time to calculate the movement speed of the electronic capsule, and then integrating the movement speed to calculate the displacement change information of the electronic capsule.

[0028] Furthermore, in step S3, the Bluetooth real-time attitude information solution is implemented by using the AOA arrival angle solution technology. Bluetooth is turned on at fixed time intervals to perform attitude information solution, and the heading angle information and attitude solution information output by the MEMS inertial navigation module are processed by Kalman filtering.

[0029] Furthermore, in step S4, high-precision position information solution is performed by the MEMS inertial navigation module, which takes the initial position information and initial attitude information as input, and solves the displacement change information and high-precision heading angle information to obtain the position information of the capsule navigation; the real-time position information is obtained by repeating step S1 through the Bluetooth receiving module according to the switching interval of 1μs.

[0030] From the above technical solution, it can be seen that the present invention has a built-in Bluetooth receiving module and a MEMS inertial navigation module in the electronic capsule. First, the Bluetooth-based AOA measurement technology is used to assist the MEMS inertial navigation module in calculating the motion trajectory of the electronic capsule, and then auxiliary positioning is performed through the real-time position and attitude information solution technology output by Bluetooth. The fusion algorithm of MEMS and Bluetooth position signals is adopted, and the combined positioning complements the shortcomings of the two types of positioning methods, so that the overall positioning accuracy of the electronic capsule is improved to the centimeter level. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic block diagram of the overall structure of the present invention;

[0032] Figure 2 Schematic diagram of the principle of AOA arrival angle and position calculation of the present invention. DETAILED DESCRIPTION

[0033] A preferred embodiment of the present invention is described in detail below with reference to the accompanying drawings.

[0034] The electronic capsule described in this preferred embodiment has a built-in Bluetooth receiving module and a MEMS inertial navigation module, and a Bluetooth transceiver module is arranged outside the human body; specifically, the Bluetooth receiving module and MEMS inertial navigation module described in this preferred embodiment are integrated into a single chip, which is easy to SIP package and mass production, and the Bluetooth receiving module includes an antenna array, a radio frequency switch and an I / Q sample capture receiver, and the MEMS inertial navigation module includes a three-axis accelerometer, a three-axis gyroscope and a three-axis magnetometer; the Bluetooth transceiver module is provided with at least one transmitting module and is fixed to the human body feature identification point by pasting, greatly reducing the distance between the transmitter and the capsule to improve the guidance accuracy of the AOA (angle of arrival) measurement, and the frequency of the Bluetooth signal is 2.4Ghz, which is relatively low and can reduce damage to the human body; in specific use, Bluetooth-assisted positioning can be combined with human CT or X-ray abdominal images to further improve the overall positioning effect.

[0035] It is known that when two or more antennas are placed at a fixed distance apart, the radio frequency signals they receive will have a phase difference proportional to the difference between their respective distances from the transmitter; therefore, the antenna array described in this preferred embodiment is provided with two antennas connected in sequence at a fixed interval of no more than 6 cm, thereby ensuring direction-finding accuracy.

[0036] like Figure 1 As shown, after the electronic capsule starts working, the composite positioning method described in this preferred embodiment specifically includes the following steps:

[0037] S1. Obtain the initial position information of the electronic capsule through the Bluetooth receiving module. This step is implemented based on the Bluetooth AOA measurement technology and includes the following specific steps:

[0038] S11, collecting I / Q information of each antenna in the Bluetooth receiving module, and calculating the phase difference between the same RF signal reaching each antenna;

[0039] S12. Convert the phase difference between two adjacent antennas into an arrival angle. The calculation formula is:

[0040]

[0041] Where: θ is the angle between the incident RF signal wave and the antenna array, λ is the incident wavelength, and d is the spacing between the antennas;

[0042] S13. Obtain the distance or angle information between the tag and each base station in a given network and establish the equation:

[0043]

[0044] S14. After solving the above equation to obtain the initial position information of the electronic capsule, the Bluetooth receiving module is turned off.

[0045] S2. Obtaining the initial attitude information and displacement change information of the electronic capsule through the MEMS inertial navigation module; specifically comprising the following steps:

[0046] S21, obtaining acceleration and angular velocity information in three directions of capsule movement through the three-axis accelerometer and three-axis gyroscope in the MEMS inertial navigation module and outputting the information;

[0047] S22, fusing the output speed information to calculate the initial posture information of the electronic capsule;

[0048] S23 , integrating the output acceleration information over time to calculate the movement speed of the electronic capsule, and then integrating the movement speed to calculate the displacement change information of the electronic capsule.

[0049] S3, combining the MEMS inertial navigation module and Bluetooth real-time attitude information to obtain the heading angle information of the electronic capsule;

[0050] In specific use, since the electronic capsule moves slowly in the human body and is affected by the earth's gravity and its own acceleration, and when the attitude information is calculated through the gyroscope, the accuracy after integration gradually decreases. Therefore, it is difficult to obtain high-precision heading angle information using only MEMS accelerometers and gyroscopes. This preferred embodiment combines Bluetooth real-time attitude information calculation for real-time correction to reduce the amount of data processing during attitude information calculation, so as to improve the accuracy of obtaining the electronic capsule heading angle information in a gravity environment, and achieve centimeter-level positioning accuracy.

[0051] Specifically, the Bluetooth real-time attitude information solution is realized through the AOA arrival angle solution technology, such as Figure 2 As shown, Bluetooth beacons are set at the head and tail of the electronic capsule, denoted as A and B, respectively. The external device is equipped with an antenna array P required to meet Bluetooth AOA. At this time, A, B, and P are in the same plane.

[0052] Bluetooth sends information to the outside of the body at a fixed interval. At time t1, A and B respectively send radio frequency information to the antenna array P. The external receiving device obtains the relative position of A and B through I / Q calculation, and reversely calculates the angle ∠α t1 , ∠β t1 , where ∠α t1 is the angle between ray PA and line AB, ∠β t1 is the angle between ray PB and line AB. At time t2, A and B send information to the antenna array respectively and calculate the angle ∠α in reverse.t2 , ∠β t2 By determining the change in the angle between time t1 and time t2, the capsule's translation or rotation can be determined, and the movement curve and target position can be fitted using an in vitro device, thereby further improving the accuracy of obtaining positioning and capsule status information.

[0053] It is known that the short-term drift and cumulative error of inertial navigation will eventually cause it to lose its function. In this preferred embodiment, at time t1, A and B respectively send information containing the inertial information at the current moment. After the information is sent, the integrated error is cleared. The integration time is the fixed Bluetooth interval time. At time t2, A and B respectively send information containing the inertial information within the interval time.

[0054] Turning on Bluetooth to calculate attitude information at intervals of Δt=t2-t1, and performing Kalman filtering on the heading angle information output by the MEMS inertial navigation module and the Bluetooth attitude solution information can further improve the accuracy of the capsule's heading angle calculation.

[0055] S4. Calculate high-precision position information through the MEMS inertial navigation module, and obtain real-time position information through the Bluetooth function for auxiliary correction; specifically: the high-precision position information is calculated through the MEMS inertial navigation module with the initial position information and initial attitude information as input, and the displacement change information and high-precision heading angle information are calculated to obtain the position information of the capsule navigation; the real-time position information is obtained by repeating step S1 with a switching interval of 1μs through the Bluetooth receiving module; at the same time, the real-time position information output by the Bluetooth signal is used to correct the output information of the MEMS inertial module. The short-term error of the inertial system is very small, but since the inertial drift still exists, this error correction can reduce the cumulative error.

[0056] S5, transmitting the position information and image or video information of the electronic capsule to the terminal device via a Bluetooth signal, comparing the information with the image of the human digestive tract model, and eliminating erroneous information;

[0057] The present invention uses Bluetooth signals, which can simultaneously meet the functions of AOA direction-finding positioning and detection graphic or video signal transmission, and can transmit the detection graphic or video signal in real time to a smart phone or other terminal including a Bluetooth receiving device. It is convenient, fast and low-cost, and can better meet daily inspection needs. At the same time, the Bluetooth module has low power consumption, which can further reduce the overall power consumption of the capsule and increase the working time of the capsule.

[0058] In specific use, the AOA (angle of arrival) measurement technology described in this preferred embodiment can be replaced by the AOD (angle of departure) measurement technology. The technical principles are similar, but the difference is that the Bluetooth receiving module in the electronic capsule only needs to be set up with a single antenna, and the Bluetooth transceiver module outside the human body uses an antenna array. Therefore, the use of AOD measurement technology can reduce the number of antennas of the Bluetooth module in the electronic capsule, which is conducive to further reducing the volume of the electronic capsule.

[0059] The above-described embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A centimeter-level composite positioning method for an electronic capsule, wherein the electronic capsule has a first Bluetooth transceiver module and a MEMS inertial navigation module built in, and a second Bluetooth transceiver module is provided outside the human body, characterized in that: Bluetooth beacons, denoted as A and B, are set at the head and tail of the electronic capsule respectively. The external device is equipped with an antenna array P required for Bluetooth AOA, with A, B, and P located in the same plane. After the electronic capsule is started, composite positioning is achieved through the following steps: S1. Obtaining initial position information of the electronic capsule through the first Bluetooth transceiver module; S2, obtaining the initial posture information and displacement change information of the electronic capsule through the MEMS inertial navigation module; S3, combining the MEMS inertial navigation module and Bluetooth real-time attitude information to obtain the heading angle information of the electronic capsule; S4. Calculate the position information through the MEMS inertial navigation module and obtain real-time position information through the first Bluetooth transceiver module for auxiliary correction; S5, transmitting the position information and image or video information of the electronic capsule to the terminal device via a Bluetooth signal, comparing the information with the image of the human digestive tract model, and eliminating erroneous information; In step S3, the Bluetooth real-time attitude information solution is implemented by AOA arrival angle solution technology. Bluetooth is turned on at fixed time intervals to perform attitude information solution. At time t1, A and B respectively send radio frequency information to the antenna array P. The external device obtains the relative position of A and B through I / Q solution and reversely solves the angle ∠ 、∠ At time t2, A and B send information to the antenna array P respectively, and reversely calculate the angle ∠ 、∠ ; By judging the change of the angle information between time t1 and time t2, the translation or rotation of the capsule is judged, where ∠ is the angle between ray PA and line AB at time t1, ∠ is the angle between ray PB and line AB at time t1, ∠ is the angle between ray PA and line AB at time t2, ∠ It is the angle between ray PB and line AB at time t2.

2. The centimeter-level composite positioning method for an electronic capsule according to claim 1, characterized in that: The first Bluetooth transceiver module and the MEMS inertial navigation module are integrated into a single chip. The first Bluetooth transceiver module includes an antenna array, a radio frequency switch, and an I / Q sample capture receiver. The antenna array is provided with at least two antennas connected in sequence at a fixed interval of no more than 6 cm; the MEMS inertial navigation module includes a three-axis accelerometer, a three-axis gyroscope, and a three-axis magnetometer.

3. The centimeter-level composite positioning method for an electronic capsule according to claim 1, characterized in that: The second Bluetooth transceiver module is fixed to the human body feature identification point by pasting, and is provided with a single transmitting module. The frequency of the Bluetooth signal is 2.4Ghz.

4. The centimeter-level composite positioning method for an electronic capsule according to claim 1, characterized in that: Acquiring the initial position information of the electronic capsule by the first Bluetooth transceiver module in step S1 is achieved based on Bluetooth AOA measurement technology, and specifically includes the following steps: S11, collecting I / Q information of each antenna in the first Bluetooth transceiver module, and calculating the phase difference between the same radio frequency signal reaching each antenna; S12. Convert the phase difference between two adjacent antennas into an arrival angle. The calculation formula is: in: is the angle between the incident RF signal wave and the antenna array, is the incident wavelength, d is the antenna spacing; S13. Obtain the distance or angle information between the tag and each base station in a given network and establish the equation: ； S14. After solving the above equation to obtain the initial position information of the electronic capsule, the first Bluetooth transceiver module is turned off.

5. The centimeter-level composite positioning method for electronic capsule according to claim 2, characterized in that: Step S2 is specifically implemented by the following steps: S21, obtaining acceleration and angular velocity information in three directions of capsule movement through the three-axis accelerometer and three-axis gyroscope in the MEMS inertial navigation module and outputting the information; S22, fusing the output acceleration and angular velocity information to calculate the initial posture information of the electronic capsule; S23 , integrating the output acceleration information over time to calculate the movement speed of the electronic capsule, and then integrating the movement speed to calculate the displacement change information of the electronic capsule.

6. The centimeter-level composite positioning method for an electronic capsule according to claim 1, characterized in that: In step S3, the heading angle information output by the MEMS inertial navigation module and the Bluetooth real-time attitude solution information are processed through Kalman filtering.

7. The centimeter-level composite positioning method for an electronic capsule according to claim 1, characterized in that: In step S4, the position information is calculated by the MEMS inertial navigation module, which uses the initial position information and initial attitude information as input, and calculates the displacement change information and heading angle information to obtain the position information of the capsule navigation; the real-time position information is obtained by repeating step S1 through the first Bluetooth transceiver module according to the switching interval of 1μs.

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