Method for detecting inclination of a mild hypothermia treatment device based on a three-dimensional acceleration sensor

Abstract

This invention discloses a tilt detection method for a hypothermia treatment device based on a three-dimensional accelerometer sensor, comprising a human vascular temperature control device, a main controller, and an accelerometer sensor. The main controller periodically detects the tilt state of the human vascular temperature control device. This invention uses a low-pass filter to reduce data noise, resulting in low computational load and memory usage. The acceleration measured by the accelerometer sensor is based on the sensor itself as the coordinate system; by changing the coordinate system, the acceleration in the global coordinate system is obtained. This allows the measured acceleration to be compared with gravitational acceleration. Compared to traditional device tilt indicators, this invention adds three additional indicators: vector difference, amplitude difference, and included angle. These three indicators can more accurately and quickly detect the state of the human vascular temperature control device, improving the device's temperature control response speed and accuracy.

Description

Technical Field

[0001] This invention relates to the field of hypothermia therapy equipment technology, specifically to a tilt detection method for hypothermia therapy equipment based on a three-dimensional accelerometer. Background Technology

[0002] In the field of hypothermia therapy, human vascular temperature control devices are frequently used. The main function of these devices is to facilitate energy exchange between the human blood vessels and the device's coolant, thereby controlling the temperature of the blood vessels. During use, if the device is violently moved, tilted, or overturned, it can cause coolant to splash or leak out, or reduce the amount of coolant, thus affecting the energy exchange efficiency between the human blood vessels and the coolant. These failure modes can affect the response speed and accuracy of patient temperature control, thereby seriously impacting the therapeutic effect. Therefore, the tilt detection device of the human vascular temperature control device is an important component of the device's safety system. To address this issue, we propose a tilt detection method for hypothermia therapy devices based on a three-dimensional accelerometer to solve the aforementioned problems. Summary of the Invention

[0003] The purpose of this invention is to provide a tilt detection method for hypothermia treatment devices based on a three-dimensional accelerometer, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a tilt detection method for a hypothermia treatment device based on a three-dimensional accelerometer, comprising a human blood vessel temperature control device, a main controller, and an accelerometer. The main controller performs periodic tilt state detection on the human blood vessel temperature control device, and each period of tilt state detection includes the following steps:

[0005] Step S1: Acquire accelerometer data;

[0006] Step S2: The collected acceleration data is denoised using a filter;

[0007] Step S3: Transform the acceleration of the accelerometer after noise reduction in different coordinate systems to obtain the acceleration of the human blood vessel temperature control device;

[0008] Step S4: The acceleration of the human blood vessel temperature control device is compared with the gravitational acceleration to obtain different tilt states of the human blood vessel temperature control device.

[0009] Preferably, the main controller is fixedly installed inside the human blood vessel temperature control device, and the accelerometer is installed in the main controller. In step S1, the main controller collects data from the accelerometer every a millisecond via SPI.

[0010] Preferably, in step S2, the acquired acceleration is denoised using an average filter / median filter / low-pass filter to obtain the denoised acceleration.

[0011] Preferably, step S3 specifically includes establishing a first coordinate system with the center of the human blood vessel temperature control device as the origin, a second coordinate system with the center of the main control board as the origin, and a third coordinate system with the center of the acceleration sensor as the origin. The acceleration collected in step S1 belongs to the third coordinate system, and the acceleration of the human blood vessel temperature control device obtained in step S3 belongs to the first coordinate system.

[0012] Preferably, the rotation matrix of the second coordinate system relative to the first coordinate system is denoted as the first matrix;

[0013] The rotation matrix of the third coordinate system relative to the second coordinate system is denoted as the second matrix;

[0014] The rotation matrix of the third coordinate system relative to the first coordinate system is denoted as the third matrix;

[0015] The first, second, and third matrices are constant matrices.

[0016] Preferably, in step S4, the relative deviation δ, the included angle θ, and the relative deviation Δ of the amplitudes of the two accelerations are used as specific evaluation indicators;

[0017]

[0018]

[0019]

[0020] This represents the acceleration vector within the first coordinate system. Represents the gravitational acceleration vector. Representing vectors with vector The length of the difference, Representing vectors Length, Representing vectors length, Representing vectors with vector The dot product.

[0021] Preferably, the specific method for determining the normal working state is to use δ≤20% as the main evaluation indicator, and calculate the other two evaluation indicators under this state;

[0022] θ=Arctanδ≤11.3°

[0023]

[0024] If δ≤20%, the equipment is considered to be in normal working condition.

[0025] Preferably, the specific method for determining the overturning state satisfies 80°≤θ≤100°. This means the equipment is considered to be in a tilted state;

[0026] Preferably, the specific method for determining the tilt state satisfies 11.3°≤θ≤30°. This means that the equipment is considered to be in a tilted state.

[0027] Preferably, the specific method for judging a state of strenuous exercise is to assess whether a state of strenuous exercise is defined as one of the following conditions:

[0028] Condition 1: δ≥20%, Δ≥2%;

[0029] Condition 2: δ≥20%, Δ≤2%, θ∈(30°, 80°)∪(100°, 180°).

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention uses a low-pass filter to reduce noise in the data, which requires less computation and memory. The acceleration measured by the accelerometer is based on the sensor itself as the coordinate system. The acceleration in the global coordinate system is obtained by changing the coordinate system. This allows the measured acceleration to be compared with the acceleration due to gravity. Compared with the tilt index of traditional equipment, this invention adds three additional indicators: vector difference, amplitude difference, and included angle. These three indicators can more accurately and quickly detect the status of the human blood vessel temperature control device, improving the response speed and accuracy of the device's temperature control. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating the principle and flow of the present invention;

[0033] Figure 2 The distribution of the three coordinate systems established for this invention;

[0034] Figure 3 This is a schematic diagram of the equipment evaluation indicators of the present invention;

[0035] Figure 4 This is a schematic diagram of the evaluation indicators under the ideal working conditions of the present invention;

[0036] Figure 5 This is a schematic diagram of the evaluation indicators under normal working conditions of the present invention;

[0037] Figure 6 This is a schematic diagram of the evaluation indicators under overturned conditions according to the present invention;

[0038] Figure 7This is a schematic diagram of the evaluation index under tilted conditions according to the present invention;

[0039] Figure 8 This is a diagram illustrating the derivation of the principle of acceleration coordinate transformation. Detailed Implementation

[0040] 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.

[0041] In order to detect device tilt, human blood vessel temperature control equipment needs to add a fixed three-dimensional acceleration sensor to the device. The tilt state of the device is converted into the tilt state of the three-dimensional acceleration sensor. When the device moves or tilts, the data of the three-dimensional acceleration sensor is different from the data of gravitational acceleration. Fault analysis is performed based on these differences.

[0042] Example 1

[0043] refer to Figure 1 A tilt detection method for a hypothermia treatment device based on a three-dimensional accelerometer sensor includes a human blood vessel temperature control device, a main controller, and an accelerometer sensor. The main controller is fixedly installed inside the human blood vessel temperature control device, and the accelerometer sensor is installed in the main controller. The main controller performs periodic tilt state detection on the human blood vessel temperature control device every 20 milliseconds. Each tilt state detection cycle includes the following steps:

[0044] Step S1: Acquire accelerometer data;

[0045] Step S2: The collected acceleration data is denoised using a filter;

[0046] Step S3: Transform the acceleration of the accelerometer after noise reduction in different coordinate systems to obtain the acceleration of the human blood vessel temperature control device;

[0047] Step S4: The acceleration of the human blood vessel temperature control device is compared with the gravitational acceleration to obtain different tilt states of the human blood vessel temperature control device.

[0048] Specifically, the accelerometer uses a three-dimensional accelerometer, and the main controller collects the accelerometer data {x}, {y}, {z} via SPI. The collected data forms a data time series.

[0049] Example 2

[0050] The acceleration data acquired by the accelerometer is denoised using an average filter, a median filter, and a low-pass filter, and the denoised acceleration is obtained.

[0051] Specifically, the raw three-dimensional acceleration data {x}, {y}, {z} are acquired by the sensor. Due to sensor errors, linearity characteristics, and the influence of ambient temperature and humidity, the raw data generally contains white noise. Therefore, the raw data needs to be processed. White noise can generally be processed using moving average filters, median filters, low-pass filters, etc.

[0052] Using a low-pass filter in system implementation minimizes code and computation. In practice, a first-order low-pass filter is generally chosen. The principle of a first-order low-pass filter is as shown in the following equation:

[0053]

[0054]

[0055]

[0056] The first-order filter coefficient k = 0.85–0.99. The specific value is generally determined by considering the noise level of the original data and the timeliness of fault handling. The low-pass filter filters the original three-dimensional acceleration data a = {xn, yn, zn}, and the filtered data is...

[0057] Example 3

[0058] refer to Figure 8 The derivation process of acceleration changes in different coordinate systems is shown in the figure. Point P moves in space, and its trajectory in coordinate system m is represented as follows: Assuming the rotation matrix of coordinate system m relative to coordinate system n is R, and the origin of coordinate system m is represented as P in coordinate system n, the locus of point P in coordinate system n is calculated as follows according to the coordinate transformation formula:

[0059]

[0060] Coordinate systems n and m are predefined coordinate systems, and P and R are fixed values. The first and second derivatives are calculated by finding the trajectory of P in coordinate system n.

[0061]

[0062]

[0063] According to the above formula, when performing coordinate transformations based on acceleration, only a rotation matrix is ​​needed for the transformation, regardless of the position of the origin.

[0064] Example 4

[0065] refer to Figure 2 A first coordinate system O1 with the center of the human blood vessel temperature control device as the origin, a second coordinate system O2 with the center of the main control board as the origin, and a third coordinate system O3 with the center of the accelerometer as the origin are established. The rotation matrix of the second coordinate system O2 relative to the first coordinate system O1 is denoted as the first matrix R1, the rotation matrix of the third coordinate system O3 relative to the second coordinate system O2 is denoted as the second matrix R2, and the rotation matrix of the third coordinate system O3 relative to the first coordinate system O1 is denoted as the third matrix R3. The three-dimensional acceleration raw data {x}, {y}, {z} collected by the accelerometer belong to the third coordinate system O3. The acceleration transformation of the third coordinate system O3 needs to be transferred to the first coordinate system O1. The first coordinate system O1 is consistent with the world coordinate system.

[0066] Specifically, the three-dimensional acceleration value returned by the accelerometer is relative to its own coordinate system, while the gravitational acceleration to be compared is in the world coordinate system. Therefore, the three-dimensional acceleration value returned by the accelerometer cannot be directly compared with the gravitational acceleration; a coordinate system transformation is required before comparison.

[0067] For the established coordinate system, the rotation matrix is ​​a constant matrix, and its value is fixed. The x, y, z unit vectors of the third coordinate system O3 are represented in the second coordinate system O2 as follows: Then the rotation matrix

[0068]

[0069] Since the first coordinate system O1, the second coordinate system O2, and the third coordinate system O3 are pre-defined, the following is obtained based on the specific positional relationships during the practical process:

[0070]

[0071]

[0072]

[0073]

[0074] Similarly, the x, y, z unit vectors of the second coordinate system O2 are represented in the first coordinate system O1 as follows: Then the rotation matrix

[0075]

[0076]

[0077]

[0078]

[0079]

[0080] Based on the rules of spatial coordinate system transformation, the rotation matrix of the accelerometer relative to the human body temperature control device can be derived:

[0081]

[0082] The acceleration vector collected by the accelerometer The first coordinate system O1 of the human blood vessel temperature control device is obtained by transformation using the third matrix R3:

[0083]

[0084] Example 3

[0085] refer to Figure 3 and Figure 4 The ideal operating condition for a human blood vessel temperature control device is when the device is placed statically on a horizontal surface. In this state, the gravity acceleration sensor... In the first coordinate system O1, it is represented as

[0086]

[0087] Under ideal operating conditions, the accelerometer data from the human blood vessel temperature control device is represented in the first coordinate system O1. It should be related to gravitational acceleration. Same, that is However, due to equipment movement or tilting, or other malfunctions, the acceleration sensor may collect data that could otherwise be affected. and gravitational acceleration Unlike other methods, both are vectors, and the analysis primarily focuses on their differences in direction and amplitude. These two aspects are used as fault analysis indicators. The vector relative deviation δ, the included angle θ, and the amplitude relative deviation Δ are defined as specific evaluation indicators, as follows:

[0088]

[0089]

[0090]

[0091] in, Representing vectors with vector The length of the difference, Representing vectors Length, Representing vectors length, Representing vectors with vector The dot product.

[0092] Ideally, In this state, δ = 0, θ = 0, and Δ = 0.

[0093] Specifically, due to factors such as the data acquisition error of the accelerometer, the installation accuracy of the equipment, and the levelness of the working ground, the ideal working state is generally not met. The state that does not meet the ideal state but does not affect the normal operation of the equipment can be called the normal working state.

[0094] Human vascular temperature control equipment requires the coolant level to be measured using a communicating vessel method. If the equipment is tilted at too large an angle, it will affect the coolant level measurement, thus affecting the smooth execution of the level detection. Furthermore, human vascular temperature control equipment is generally used in hospital wards and is placed statically on a level surface. However, minor, slight movements are inevitable during the use of the equipment.

[0095] Based on the safety system of human blood vessel temperature control equipment, it can be determined that under normal working conditions, δ≤20% is the main evaluation index. Under this condition, the other two evaluation indices can be easily calculated.

[0096] θ=tan -1 δ≤11.3°

[0097]

[0098] In actual implementation, the equipment can be considered to be in normal working condition as long as δ≤20%.

[0099] Specifically, during the use of human blood vessel temperature control equipment, vibration, impact, or other reasons may cause the equipment to tip over. Given the equipment's rectangular shape, when it tilts... direction and Vertical and equal in size, that is Under this condition, the evaluation indicators are: |θ-90°|≤10°, Δ≤2%. The above two evaluation indicators are the main indicators of this condition, and the vector relative deviation δ can be calculated using the above two evaluation indicators.

[0100] 80°≤θ≤100°

[0101] cos100°≤cosθ≤cos80°

[0102]

[0103]

[0104] Combining the above formulas, we can calculate the result as follows: 127.28% ≤ δ ≤ 154.74%.

[0105] In practical application, the following indicators must be met:

[0106] 80°≤θ≤100°

[0107]

[0108] This means the equipment is considered to be overturned.

[0109] Specifically, the human blood vessel temperature control device was on a horizontal surface, but the device itself did not tip over. The unevenness of the ground caused the accelerometer to collect data... and gravitational acceleration There is a certain included angle, which is between the normal working state and the overturning state. In addition, the stability of the equipment also needs to be considered. Under this state, the evaluation index is: 11.3°≤θ≤30°, Δ≤2%. The above two evaluation indexes are the main indicators for this state. With the above two evaluation indexes, the vector relative deviation δ can be calculated.

[0110] 11.3°≤θ≤30°

[0111] cos30°≤cosθ≤cos11.3°

[0112]

[0113]

[0114] Combining the above formula, we can calculate the result as follows: 19.59% ≤ δ ≤ 52.32%.

[0115] In practical application, the following indicators must be met:

[0116] 11.3°≤θ≤30°

[0117]

[0118] This means the equipment is considered to be tilted.

[0119] Specifically, any state other than those mentioned above constitutes a state of vigorous exercise, which may be caused by the following reasons:

[0120] a. The equipment was pushed rapidly.

[0121] b. The equipment moves rapidly up and down in the elevator.

[0122] c. The equipment is in a fast-moving vehicle.

[0123] Based on the above analysis, the evaluation index is in a state of vigorous activity under one of the following conditions:

[0124] Condition 1: δ≥20%, Δ≥2%

[0125] Condition 2: δ≥20%, Δ≤2%, θ∈(30°, 80°)∪(100°, 180°)

[0126] The flowchart of the entire process is shown below. The entire process is executed once every 20ms. If the device is in normal working condition after the test is completed, it waits for the next cycle to perform the cyclic test. If the device is in a fault state, it needs to perform an alarm. The alarm indicator light of the device will flash, and the operation interface will display the corresponding fault and corresponding handling method. The detection cycle remains unchanged at 20ms throughout the entire process.

[0127] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A tilt detection method for a hypothermia treatment device based on a three-dimensional accelerometer, comprising a human blood vessel temperature control device, a main controller, and an accelerometer, characterized in that: The main controller performs periodic tilt state detection on the human blood vessel temperature control device. Each tilt state detection cycle includes the following steps: Step S1: Acquire accelerometer data; Step S2: The collected acceleration data is denoised using a filter; Step S3: Transform the acceleration of the accelerometer after noise reduction in different coordinate systems to obtain the acceleration of the human blood vessel temperature control device; Step S4: The acceleration of the human blood vessel temperature control device is compared with the gravitational acceleration to obtain different tilt states of the human blood vessel temperature control device. In step S4, the relative deviation of the two accelerations is... Angle Amplitude relative deviation As specific evaluation indicators; This represents the acceleration vector within the first coordinate system. Represents the gravitational acceleration vector. Representing vectors and The length of the difference, Representing vectors Length, Representing vectors length, Representing vectors and The dot product; The specific methods for determining normal working status Using this as the primary evaluation indicator, two other evaluation indicators are calculated under this condition. This means that the equipment is considered to be in normal working condition. The specific method for determining the tilt state satisfies... , This means that the equipment is considered to be tilted. The specific method for determining the overturning state, satisfying... , This means that the equipment is considered to be in a tilted state. The specific methods for determining a state of strenuous exercise include assessing whether a person is in a state of strenuous exercise under any of the following conditions: Condition 1: , ; Condition 2: , , .

2. The tilt detection method for a hypothermia treatment device based on a three-dimensional accelerometer according to claim 1, characterized in that: The main controller is fixedly installed inside the human blood vessel temperature control device, and the accelerometer is installed in the main controller. In step S1, the main controller collects data from the accelerometer every a millisecond via SPI.

3. The tilt detection method for a hypothermia treatment device based on a three-dimensional accelerometer according to claim 1, characterized in that: Step S2 involves denoising the acquired acceleration using an average filter / median filter / low-pass filter to obtain the denoised acceleration.

4. The tilt detection method for a hypothermia treatment device based on a three-dimensional accelerometer according to claim 1, characterized in that: Step S3 specifically includes establishing a first coordinate system with the center of the human blood vessel temperature control device as the origin, a second coordinate system with the center of the main control board as the origin, and a third coordinate system with the center of the acceleration sensor as the origin. The acceleration collected in step S1 belongs to the third coordinate system, and the acceleration of the human blood vessel temperature control device obtained in step S3 belongs to the first coordinate system.

5. The tilt detection method for a hypothermia treatment device based on a three-dimensional accelerometer according to claim 4, characterized in that: The rotation matrix of the second coordinate system relative to the first coordinate system is denoted as the first matrix; The rotation matrix of the third coordinate system relative to the second coordinate system is denoted as the second matrix; The rotation matrix of the third coordinate system relative to the first coordinate system is denoted as the third matrix; The first, second, and third matrices are constant matrices.

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