CN110301919B

CN110301919B - Cramp detection alarm method and device using magnetic positioning technology

Info

Publication number: CN110301919B
Application number: CN201910178627.9A
Authority: CN
Inventors: 吴小玲; 刘佳敏; 朱铱楠
Original assignee: Nanjing Medical University
Current assignee: Nanjing Medical University
Priority date: 2018-12-07
Filing date: 2019-03-11
Publication date: 2024-02-23
Anticipated expiration: 2039-03-11
Also published as: CN110301919A

Abstract

The invention relates to the technical field of safety alarm, in particular to a swimming cramp detection method and a swimming cramp detection device based on a magnetic positioning technology. According to the swimming cramp detection method and device based on the magnetic positioning technology, the triaxial magnetic sensor can be positioned on one side of a knee joint through the leg fixing device, the small magnet is positioned on one side of calf gastrocnemius muscle, leg movements are detected conveniently, meanwhile, the whole leg fixing device is made of elastic materials, the whole size is adjustable, the swimming cramp detection method and device are suitable for different people to use, the swimming effect cannot be affected, whether the cramp occurs or not is judged through real-time monitoring of the contraction acceleration of muscles such as the calf gastrocnemius muscle and the like which are prone to the cramp in the movement or the knee joint angle corresponding to the calf linear velocity mutation, and once the cramp occurs, an alarm is sent to a life-saving person immediately.

Description

Cramp detection alarm method and device using magnetic positioning technology

Technical Field

The invention relates to the technical field of safety alarm, in particular to a cramp detection alarm method and a cramp detection alarm device using a magnetic positioning technology.

Background

Cramps, i.e. muscle cramps. Muscle spasms are movement disorders caused by high excitability of stretch reflex, characterized by velocity dependent, enhanced stretch reflex with tendon reflex surprise. When the muscle is spastic, the hardness of the muscle is obviously enhanced and deformed, and the muscle is often accompanied by strong pain. The calf gastrocnemius muscle cramp is usually caused by abrupt movement or work fatigue or intense twisting of the tibia, when the cramp occurs, the gastrocnemius muscle deformation is obvious, and the muscle is obviously bulged when the muscle is more normal. Swimming is a sport with very high popularity, and has no great health benefit, but at the same time, once leg cramps occur in the swimming process, the swimming is not timely rescued, and the life safety of the swimmer is easily threatened. Compared with professional swimming athletes, the probability of the cramp of beginners and children during swimming is larger, the water is weaker, and the swimming pool is a high-risk group easy to lose life due to the cramp. At present, swimming places are regulated to be provided with life-saving safety personnel, but accidents occur when a swimming person can not obtain timely rescue and dies due to drowning of the swimming person due to carelessness and unauthorized duty of the life-saving personnel. Therefore, the alarm reminding to the life saving staff and other staff at the first time of the cramp is an important measure for greatly reducing the swimming drowning caused by the sudden cramp. In view of this, we propose a cramp detection method and apparatus based on magnetic positioning technology.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a method for alarming leg cramps and a device for realizing the method, which can judge whether cramps occur by monitoring the contraction acceleration of muscles such as gastrocnemius which are liable to occur cramps during exercise or the knee joint angle corresponding to the abrupt change of the calf line speed in real time, and immediately give an alarm to a lifeguard once cramps occur. The system is suitable for detecting and alarming the cramp of a swimmer during swimming.

In order to achieve the above object, in one aspect, the present invention provides a cramp detection apparatus based on a magnetic positioning technology, which comprises a leg fixing device, wherein the leg fixing device comprises a knee joint bandage and a shank bandage, a first waterproof bag is installed on the inner surface of the knee joint bandage, a triaxial magnetic sensor is placed in the first waterproof bag, a second waterproof bag is installed on the inner surface of the shank bandage, a small magnet is placed in the second waterproof bag, a plurality of connecting belts are arranged between the knee joint bandage and the shank bandage, one side of the knee joint bandage is fixedly connected with the connecting belts through knee joint bandage connecting cloth, and one side of the shank bandage is fixedly connected with the connecting belts through shank bandage connecting cloth.

Preferably, the knee joint band and the shank band are both annular.

Preferably, the size of the knee strap is larger than the size of the calf strap.

Preferably, the size of the triaxial magnetic sensor is adapted to the size of the first waterproof bag.

As a preferred aspect of the present invention, the size of the small magnet is adapted to the size of the second waterproof bag.

Preferably, the size of the connecting band is adapted to the size of the knee joint band connecting cloth, and the size of the connecting band is adapted to the size of the calf band connecting cloth.

As the optimization of the invention, a permanent magnet positioning module and an alarm module are also arranged in the triaxial magnetic sensor, and the permanent magnet positioning module realizes data transmission through a wireless transmission module and the alarm module.

As a preferable mode of the invention, the permanent magnet positioning module comprises a coordinate positioning module, a magnetic field positioning module, a continuous positioning module and a data processing module;

the coordinate positioning module is used for positioning coordinates and directions of the knee joint and the lower leg;

the magnetic field positioning module is used for determining the space position and the magnetic moment vector of the permanent magnet;

the continuous positioning module is used for continuously positioning the knee joint and the lower leg in the leg movement process;

the data processing module is used for integrating and outputting the coordinate and direction data of the knee joint and the lower leg.

As the optimization of the invention, the alarm module comprises a signal interception module, an integral algorithm module, a normal value range algorithm module, an alarm value judging module and a voice alarm module;

the signal interception module is used for intercepting the signals measured by the permanent magnet positioning module according to time;

the integral algorithm module is used for carrying out integral processing on the intercepted signals;

the normal value range algorithm module is used for determining a normal value range;

the alarm value judging module is used for determining the range of alarm values;

the voice alarm module is used for giving out a voice alarm when the alarm value is exceeded.

On the other hand, the invention also provides a cramp detection method based on the magnetic positioning technology, which comprises the cramp detection device based on the magnetic positioning technology, and the specific using steps are as follows:

s1, wearing a leg fixing device: the user penetrates the leg from one side of the knee joint bandage and enables the foot of the user to penetrate out from the calf bandage, the knee joint bandage is fastened on one side of the knee joint of the user, the triaxial magnetic sensor inside the first waterproof bag is attached to one side of the knee joint, the calf bandage is fastened on one side of the calf gastrocnemius of the user, the small magnet inside the second waterproof bag is attached to one side of the calf gastrocnemius, the triaxial magnetic sensor can be positioned on one side of the knee joint through the leg fixing device, and the small magnet can be positioned on one side of the calf gastrocnemius;

s2, leg movement detection: the method comprises the steps of positioning coordinates and directions of a knee joint and a shank through a coordinate positioning module, determining the space position and magnetic moment vectors of a permanent magnet through a magnetic field positioning module, continuously positioning the knee joint and the shank through a continuous positioning module in the leg movement process, and integrating and outputting data of the coordinates and directions of the knee joint and the shank through a data processing module;

s3, working of an alarm module: the leg movement signals detected by the permanent magnet positioning module are transmitted into the alarm module through the wireless transmission module, signals measured by the permanent magnet positioning module are intercepted according to time through the signal interception module, the intercepted signals are subjected to integral processing through the integral algorithm module, the normal value range is determined through the normal value range algorithm module, the alarm value range is determined through the alarm value judgment module, and the voice alarm module is used for giving out voice alarms when the alarm value is exceeded.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the cramp detection method and the cramp detection device based on the magnetic positioning technology, the triaxial magnetic sensor can be positioned on one side of a knee joint through the leg fixing device, the small magnet is positioned on one side of calf gastrocnemius, leg movements are conveniently detected, meanwhile, the leg fixing device is integrally made of elastic materials, the whole size is adjustable, and the cramp detection device is suitable for different crowds and does not influence swimming effects.

2. According to the cramp detection method and device based on the magnetic positioning technology, whether cramp occurs or not is judged by monitoring the contraction acceleration of muscles such as gastrocnemius which are prone to cramp during movement or the knee joint angle corresponding to the calf line speed mutation in real time, and once the cramp occurs, an alarm is immediately sent to a life-saving person.

Drawings

FIG. 1 is a schematic view of a leg fixing device according to the present invention;

FIG. 2 is an overall block diagram of the present invention;

fig. 3 is a circuit diagram of a wireless transmission module according to the present invention;

FIG. 4 is a schematic diagram of a permanent magnet positioning module according to the present invention;

FIG. 5 is a magnetic field positioning model diagram of the present invention;

FIG. 6 is a flow chart of the LM algorithm of the present invention;

FIG. 7 is a schematic diagram of an alarm module according to the present invention.

In the figure: 1. leg fixing means; 11. a knee joint strap; 12. shank straps; 13. a first waterproof bag; 14. a three-axis magnetic sensor; 15. a second waterproof bag; 16. a small magnet; 17. knee joint bandage connection cloth; 18. the shank strap is connected with cloth; 19. and (5) connecting the belts.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

Example 1

In one aspect, as shown in fig. 1, the invention provides a cramp detection device based on a magnetic positioning technology, which comprises a leg fixing device 1, wherein the leg fixing device 1 comprises a knee joint bandage 11 and a shank bandage 12, a first waterproof bag 13 is arranged on the inner surface of the knee joint bandage 11, a triaxial magnetic sensor 14 is arranged in the first waterproof bag 13, a second waterproof bag 15 is arranged on the inner surface of the shank bandage 12, a small magnet 16 is arranged in the second waterproof bag 15, a plurality of connecting belts 19 are arranged between the knee joint bandage 11 and the shank bandage 12, one side of the knee joint bandage 11 is fixedly connected with the connecting belts 19 through a knee joint bandage connecting cloth 17, one side of the shank bandage 12 is fixedly connected with the connecting belts 19 through a shank bandage connecting cloth 18, the knee joint bandage 11 and the shank bandage 12 are circular, the size of the knee joint bandage 11 is larger than the size of the shank bandage 12, the size of the triaxial magnetic sensor 14 is matched with the size of the first waterproof bag 13, the size of the small magnet 16 is matched with the size of the second waterproof bag 15, the size of the connecting belts 19 is matched with the size of the knee joint bandage connecting cloth 17, and the size of the connecting belts 19 is matched with the size of the connecting belts 19.

In this embodiment, the knee joint strap 11 and the shank strap 12 are made of elastic cloth, and the materials have good elasticity and good ventilation effect, and are tightly tied on the knee joint of the user through the knee joint strap 11, and are tightly tied on the shank of the user through the shank strap 12, so that the leg fixing device 1 is fixed on the leg of the user.

Further, the first waterproof bag 13 and the second waterproof bag 15 are made of PVC plastic films, and the PVC plastic films have waterproof characteristics, are light in weight and good in abrasion resistance.

Specifically, the first waterproof bag 13 and the knee joint bandage 11 are adhered and fixed, so that the first waterproof bag 13 is conveniently mounted on one side of the knee joint bandage 11, and the second waterproof bag 15 and the shank bandage 12 are adhered and fixed, so that the second waterproof bag 15 is conveniently mounted on one side of the shank bandage 12.

In addition, the connecting band 19 is made of elastic cloth, so that the connecting band 19 has good elasticity, the length of the connecting band 19 can be conveniently adjusted, and the distance between the knee joint binding band 11 and the calf binding band 12 can be further adjusted.

In addition, the fixing manner of the knee joint strap connecting cloth 17 and the connecting strap 19 may be any fixing manner in the prior art, and in this embodiment, it is preferable to use a needle thread sewing for fixing, and the other side of the knee joint strap connecting cloth 17 is fixed on the knee joint strap 11 by the needle thread sewing, so that the connecting strap 19 is fixed on one side of the knee joint strap 11.

It should be noted that, any fixing manner of the connecting cloth 18 and the connecting band 19 of the calf strap may be adopted, and in this embodiment, it is preferable to fix the connecting band by sewing with needle and thread, and the other side of the connecting cloth 18 of the calf strap is fixed on the calf strap 12 by sewing with needle and thread, so as to fix the connecting band 19 on one side of the calf strap 12.

When the cramp detection device based on the magnetic positioning technology in this embodiment wears the leg fixing device 1, the user penetrates the leg from the knee joint bandage 11 side, and makes the user's foot wear out from the calf bandage 12, tightens the knee joint bandage 11 on the knee joint side of the user, makes the triaxial magnetic sensor 14 inside the first waterproof bag 13 paste on the knee joint side, tightens the calf bandage 12 on the calf gastrocnemius of the user, makes the small magnet 16 inside the second waterproof bag 15 paste on the calf gastrocnemius side, can position the triaxial magnetic sensor 14 on the knee joint side through the leg fixing device 1 that sets up, and fixes the small magnet 16 on the calf gastrocnemius side, is convenient for detect the leg motion, and the leg fixing device 1 is made of elastic material as a whole, and is adjustable in overall size, is suitable for different crowds to use, and can not influence swimming effect.

Example 2

As a second embodiment of the present invention, in order to facilitate data transmission between the permanent magnet positioning module and the alarm module, the present inventor sets a wireless transmission module, and as a preferred embodiment, as shown in fig. 2, the three-axis magnetic sensor 14 is further provided with a permanent magnet positioning module and an alarm module, and the permanent magnet positioning module realizes data transmission through the wireless transmission module and the alarm module.

In this embodiment, the wireless transmission module is composed of a transmitting end and a receiving end, where the transmitting end is composed of an STC12C5a60S2 single-chip microcomputer and an nRF24L01 wireless transceiver chip, and the circuit is shown in fig. 3, where the transmitting end performs a/D conversion and wireless transmission through the single-chip microcomputer, the receiving end receives data through nRF24L01 and sends the data to the STC12C5a60S2 single-chip microcomputer for display and analysis, all configuration work of the wireless module nRF24L01 is completed through SPI, and a 30B configuration word is shared, and an enhanced shockburst (tm) transceiver mode is generally adopted.

Example 3

As a third embodiment of the present invention, in order to facilitate positioning of coordinates and directions of the knee joint and the calf, the present inventor sets a permanent magnet positioning module, which includes, as a preferred embodiment, a coordinate positioning module for positioning coordinates and directions of the knee joint and the calf, a magnetic field positioning module for determining spatial positions and magnetic moment vectors of the permanent magnet, a continuous positioning module for continuously positioning the knee joint and the calf during leg movements, and a data processing module for integrating and outputting data of coordinates and directions of the knee joint and the calf.

In this embodiment, the coordinate positioning module uses the three-axis magnetic sensor 14 as the origin of coordinates, positions the corresponding small magnet 16, the positioning result includes coordinates and directions, the three-axis magnetic sensor 14 is placed at the knee joint to spatially position the small magnet 16, the distance between the small magnet 16 and the three-axis magnetic sensor 14 is known as h0, and the three-axis magnetic sensor 14 is used as the origin of coordinates to solve the spatial position (x ₀ ，y ₀ ，z ₀ ) The coordinates of the magnet a are (a 0, b0, c 0) and the directions are (α0, β0, γ0).

Further, as shown in fig. 5, the magnetic field positioning module is shown in fig. 5, M is the position of the permanent magnet, R is the magnetic moment of the permanent magnet, and according to the magnetic dipole model, the magnetic induction intensity at the observation point a (x, y, z) in space is:

in the method, in the process of the invention,

specifically, the continuous positioning module adopts an LM algorithm, and the code is set as follows:

cal_func(x，t，y，func)；//f＝y-f(x，t)

cal_jacob(x，t，jacob)；//j＝f'(x，t)

cal_hessian(jacob，hessian)；//A＝j(T)*j

cal_grad(jacob，func，grad)；//g＝j(T)*f

bFound= (cal_max (grad) <=e1); the initial value of the/(end flag is typically 0 unless the initial solution is an optimal solution

miu =cal_max2 (hessian) 1e-6; initial value of/(drop length)

for(n＝0；n<500&&！bFound；n++)

{

cal_hess_miu(hessian，miu，hess_miu)；//A'＝A+miu*I

gauss_jordan(hess_miu，grad，h_lm)；//h_lm＝h^-1*grad

if(cal_norm(h_lm)<＝e2*(e2+cal_norm(x)))

bFound＝true；

else

{

for(i＝0；i<N；i++)

x_new[i]＝x[i]+h_lm[i]；//x_new＝x+h_lm

objFi＝cal_objFi(func)；//φ＝∑f^2

cal_func(x_new，t，y，fun_new)；//f_new＝y-f(x_new，t)

objFi_new＝cal_objFi(fun_new)；//φ_new＝∑f_new^2

rou＝(objFi-objFi_new)/cal_l(h_lm，grad，miu)；

if(rou>0)

{

for(i＝0；i<N；i++)

x[i]＝x_new[i]；

cal_func(x，t，y，func)；//f＝y-f(x，t)

cal_jacob(x，t，jacob)；//j＝f'(x，t)

cal_hessian(jacob，hessian)；//A＝j(T)*j

cal_grad(jacob，func，grad)；//g＝j(T)*f

bFound＝cal_max(grad)<＝e1；

miu*＝(1.0f/3.0f)>(1-pow(2*rou-1，3))？(1.0f/3.0f):(1-pow(2*rou-1，3))；

v＝2；

cout<<n<<"\t"<<miu<<"\t"<<cal_max(grad)<<"\t"<<objFi<<endl；

}

else

{

miu*＝v；

v*＝2；

cout<<n<<"\t"<<miu<<"\t"<<cal_max(grad)<<"\t"<<objFi<<endl；

}

It should be noted that, the LM algorithm flow is shown in fig. 6, and the steps are as follows:

(1) Defining a functionGiven an initial value x ⁽⁰⁾ Setting an error limit epsilon, an iteration parameter mu, a scaling factor beta and a maximum iteration number k _max The current iteration number k=1.

(2) Calculating step length h, calculating x ^(k+1) ＝x ^(k) +h, calculate

(3) Updating mu. If F (x) ^(k+1) )＞F(x ^(k) ) The method shows that the most recent optimal solution is far away, and at the moment, the mu value is increased, and mu=mu beta, so that the algorithm is closer to the fastest descent method, and the global convergence is ensured; if F (x) ^(k+1) )＜F(x ^(k) ) Then it is shown that the nearest solution is closer to the optimal solution, at which point the mu value is reduced,the algorithm is closer to the Gauss-Newton method, and the convergence speed is increased.

(4) When k=k _max Or (b)When the algorithm is terminated; otherwise, k=k+1, and return to step 2.

When the cramp detection device based on the magnetic positioning technology detects leg movement, the coordinates and directions of the knee joint and the lower leg are positioned through the coordinate positioning module, the spatial position and the magnetic moment vector of the permanent magnet are determined through the magnetic field positioning module, the knee joint and the lower leg are continuously positioned through the continuous positioning module in the leg movement process, and the data of the coordinates and the directions of the knee joint and the lower leg are integrated and output through the data processing module.

Example 4

As a fourth embodiment of the present invention, in order to facilitate the timely alarm reminding when the cramp occurs, the present inventor sets an alarm module, as a preferred embodiment, as shown in fig. 7, the alarm module includes a signal interception module, an integration algorithm module, a normal value range algorithm module, an alarm value judgment module and a voice alarm module, the signal interception module is used for intercepting the signal measured by the permanent magnet positioning module according to time, the integration algorithm module is used for performing the integration processing on the intercepted signal, the normal value range algorithm module is used for determining the normal value range, the alarm value judgment module is used for determining the range of the alarm value, and the voice alarm module is used for sending the voice alarm when the alarm value is exceeded.

In this embodiment, the signal capturing module is configured to collect a spatial displacement data signal of the gastrocnemius muscle on a plane perpendicular to the calf bone, and specifically includes the following steps:

(1) A space rectangular coordinate system is established by taking the position of the triaxial magnetic sensor 14 as the origin of coordinates, and the space position of the small magnet 16 is obtained as (a) ₀ ，b ₀ ，c ₀ )；

(2) When the muscle is cramped, the muscle spasm contracts towards the center to generate obvious deformation, the muscle spasm bulges outwards, the displacement of the small magnet 16 in the Z direction is obviously increased, the deformation in the X and Y directions is very tiny, the deformation can be ignored approximately, and the space position of the small magnet 16 is (a) ₁ ，b ₁ ，c ₁ )；

(3) Calculating s=x+y+z at intervals of 0.5S, when S _n+1 -S _n |≥5％S _n At this point, the signal starts to be intercepted at t=3s.

Further, the integral algorithm module formula is as follows:

specifically, the normal value range algorithm module can obtain delta through analysis of multiple groups of experimental data ₁ 、δ ₂ 、δ ₃ Is set to be delta epsilon (delta) _L ，δ _H )。

It should be noted that, the alarm value determination module is expressed as: when the cramp occurs, the muscle contracts rapidly and severely, the displacement becomes obviously large, and the obtained delta' is obviously beyond the normal range of delta. Let |delta' -delta _H |=μ, calculated μ ₁ 、μ ₂ 、μ ₃ Three sets of data, for μ ₁ 、μ ₂ 、μ ₃ And carrying out weighted summation to obtain a parameter lambda, and judging that cramp occurs when lambda meets lambda not less than epsilon, namely the alarm value.

When the alarm module of the cramp detection device based on the magnetic positioning technology works, leg movement signals detected by the permanent magnet positioning module are transmitted into the alarm module through the wireless transmission module, signals measured by the permanent magnet positioning module are intercepted according to time through the signal interception module, the intercepted signals are subjected to integral processing through the integral algorithm module, a normal value range is determined through the normal value range algorithm module, the range of an alarm value is determined through the alarm value judging module, and the voice alarm module is used for giving out voice alarms when the alarm value is exceeded.

On the other hand, the invention also provides a cramp detection method based on the magnetic positioning technology, which comprises any cramp detection device based on the magnetic positioning technology, and the specific using steps are as follows:

s1, wearing the leg fixing device 1: the user penetrates the leg from the knee joint strap 11 side and wears out the foot of the user from the calf strap 12 side, tightens the knee joint strap 11 on the knee joint side of the user, tightens the three-axis magnetic sensor 14 inside the first waterproof bag 13 on the knee joint side and tightens the calf strap 12 on the calf gastrocnemius of the user, tightens the small magnet 16 inside the second waterproof bag 15 on the calf gastrocnemius side, and enables the three-axis magnetic sensor 14 to be positioned on the knee joint side and the small magnet 16 to be positioned on the calf gastrocnemius side by the leg fixing device 1 provided;

The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, and that the above-described embodiments and descriptions are only preferred embodiments of the present invention, and are not intended to limit the invention, and that various changes and modifications may be made therein without departing from the spirit and scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. Swimming cramp detection device based on magnetism location technique, including shank fixing device (1), its characterized in that: the leg fixing device (1) comprises a knee joint binding band (11) and a shank binding band (12), wherein a first waterproof bag (13) is arranged on the inner surface of the knee joint binding band (11), a triaxial magnetic sensor (14) is arranged in the first waterproof bag (13), a second waterproof bag (15) is arranged on the inner surface of the shank binding band (12), a small magnet (16) is arranged in the second waterproof bag (15), a plurality of connecting belts (19) are arranged between the knee joint binding band (11) and the shank binding band (12), one side of the knee joint binding band (11) is fixedly connected with the connecting belts (19) through a knee joint binding band connecting cloth (17), and one side of the shank binding band (12) is fixedly connected with the connecting belts (19) through a shank binding band connecting cloth (18); the knee joint binding band (11) and the shank binding band (12) are both in a ring shape; the size of the knee joint strap (11) is larger than the size of the calf strap (12); the size of the triaxial magnetic sensor (14) is matched with the size of the first waterproof bag (13); the size of the small magnet (16) is matched with the size of the second waterproof bag (15); the size of the connecting band (19) is matched with the size of the knee joint binding band connecting cloth (17), and the size of the connecting band (19) is matched with the size of the calf binding band connecting cloth (18); a permanent magnet positioning module and an alarm module are further arranged in the triaxial magnetic sensor (14), and the permanent magnet positioning module realizes data transmission through a wireless transmission module and the alarm module; the permanent magnet positioning module comprises a coordinate positioning module, a magnetic field positioning module, a continuous positioning module and a data processing module;

the data processing module is used for integrating and outputting the coordinate and direction data of the knee joint and the lower leg;

the alarm module comprises a signal interception module, an integral algorithm module, a normal value range algorithm module, an alarm value judging module and a voice alarm module;

2. A method for detecting swimming cramps based on the swimming cramp detection apparatus based on the magnetic positioning technology as claimed in claim 1, comprising the following specific steps:

s1, wearing a leg fixing device (1): the user penetrates the leg from the knee joint bandage (11) side, and enables the foot of the user to penetrate out of the calf bandage (12), the knee joint bandage (11) is tightly tied on the knee joint side of the user, the triaxial magnetic sensor (14) inside the first waterproof bag (13) is stuck on the knee joint side, the calf bandage (12) is tightly tied on the calf gastrocnemius of the user, the small magnet (16) inside the second waterproof bag (15) is stuck on the calf gastrocnemius side, the triaxial magnetic sensor (14) can be positioned on the knee joint side through the leg fixing device (1), and the small magnet (16) can be positioned on the calf gastrocnemius side;