Negative Poisson's ratio metamaterial intelligent kneecap integrating gait monitoring

Abstract

The invention discloses a negative Poisson's ratio metamaterial intelligent kneecap integrated with gait monitoring, and belongs to the technical field of sports protection and rehabilitation medical instruments. The knee pad comprises two magic tapes, two monitoring circuits, a negative Poisson's ratio metamaterial inner-layer fabric, an intelligent protector outer wrapping surface and a sensor switch, the kneecap adopts a rectangular perforated negative Poisson's ratio metamaterial structure, the kneecap transversely expands to disperse pressure when joints are bent through the negative Poisson's ratio effect, light weight and high elasticity are achieved in combination with a nylon base material, and the wearing comfort and the joint stability are remarkably improved. The kneecap is integrated with double MPU6050 sensors which are respectively arranged at the middle sections of the thigh and the shank and are used for acquiring inclination angle data of the lower limb around the X axis in real time; based on an angular velocity-linear velocity conversion algorithm, the gait velocity is calculated in combination with a leg geometric model. The knee pad supports Bluetooth transmission of real-time gait information to terminal equipment, is suitable for posture optimization in exercise training and progress evaluation in rehabilitation treatment, and solves the problems that a traditional knee pad is poor in comfort and single in function.

Description

Technical Field

[0001] This invention belongs to the field of sports protection and rehabilitation medical device technology, specifically relating to an intelligent knee brace that combines negative Poisson's ratio metamaterials with gait monitoring technology. Background Technology

[0002] Poisson's ratio is the ratio of the transverse normal strain to the axial normal strain of a material under uniaxial tension or compression. When a material is stretched laterally with a positive Poisson's ratio, the material exhibits an increase in transverse normal strain and a decrease in axial normal strain. Conversely, a material with a negative Poisson's ratio exhibits an increase in both transverse and axial normal strain, meaning the material is stretched. Based on this principle, the protective gear made using a negative Poisson's ratio structure can protect joints, conform to joint contours, and reduce the feeling of foreign objects when the athlete's joints bend, thus providing the wearer with a better wearing experience.

[0003] Existing technologies disclose adaptive protective gear based on shape memory polymers, which combine the negative Poisson's ratio effect and shape memory function to achieve impact protection and adaptive deformation in the field of sports protective gear.

[0004] Traditional knee braces often use elastic fabrics or rigid support structures with a positive Poisson's ratio (e.g., rubber has a Poisson's ratio of about 0.5). When the joint is bent, the lateral contraction can easily compress the skin and soft tissues, resulting in poor wearing comfort. Long-term use may lead to poor blood circulation or skin abrasion. In addition, existing protective gear has a single function, providing only passive protection and lacking the ability to monitor and provide feedback on movement status (such as gait and speed) in real time.

[0005] In recent years, some smart protective gear has attempted to integrate sensor technology, such as monitoring motion data through accelerometers or pressure sensors, but the following problems still exist. First, sensors are mostly fixed in a single position (such as the outside of the knee), making it impossible to accurately capture the coordinated movement of the thigh and calf, resulting in large errors in gait analysis. Second, the positive Poisson's ratio characteristic of traditional materials restricts the degree of freedom of joint movement, especially during strenuous exercise, easily causing a foreign body sensation. In addition, velocity calculation relies on simple integral algorithms, failing to consider the leg geometry model and the conversion relationship between angular velocity and linear velocity, resulting in low measurement accuracy.

[0006] To address the aforementioned issues, this invention proposes a smart knee brace based on a negative Poisson's ratio metamaterial. This brace enhances comfort and stability during joint movement through a tensile structure, and incorporates dual MPU6050 sensors placed on the thigh and calf to construct a lower limb motion geometry model. Optimized algorithms are then used to achieve high-precision gait monitoring, providing dynamic data support for sports protection and rehabilitation. Summary of the Invention

[0007] This invention addresses the problems existing in the prior art by combining innovative materials science and intelligent sensing technology to break through the technical limitations of traditional sports protective gear, creating a revolutionary knee brace product that combines excellent protective performance with intelligent monitoring functions, thus solving the problems of poor comfort and limited functionality of traditional knee braces.

[0008] The knee brace of this invention optimizes joint support and pressure distribution through a negative Poisson's ratio structure (applying the tensile effect) and integrates multiple sensors to collect lower limb motion data in real time, enabling gait speed calculation, posture feedback and rehabilitation progress assessment. It is applicable to the fields of sports injury prevention, postoperative rehabilitation and smart wearable devices.

[0009] This invention is implemented as follows:

[0010] A smart knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial, characterized in that the knee brace comprises: two Velcro straps, two monitoring circuits, a negative Poisson's ratio metamaterial inner fabric, a smart brace outer covering, and a sensor switch; the two Velcro straps are located at the upper and lower parts of the knee brace, respectively; the two monitoring circuits are embedded between the smart brace outer covering and the negative Poisson's ratio metamaterial inner fabric, providing real-time motion data during exercise; the negative Poisson's ratio metamaterial inner fabric, as the inner layer of the knee brace, directly contacts the user's leg, utilizing the negative Poisson's ratio (tension) effect to enhance the knee brace's joint stability and pressure-reducing support, ensuring better comfort and protection; the smart brace outer covering wraps around the outside of the negative Poisson's ratio metamaterial inner fabric, capable of withstanding friction and stretching during exercise; the sensor switch is located outside the smart brace outer covering, and when turned on, it can activate the integrated circuit system and monitor and record motion data in real time.

[0011] Furthermore, the two Velcro straps can be adjusted to fit different leg shapes and needs to achieve better comfort. The two Velcro straps are used to fit and bind the knee brace according to the user's leg shape to adjust the tightness of the knee brace.

[0012] Furthermore, the monitoring circuit is a real-time monitoring integrated circuit system of two MPU6050 sensors; the two MPU6050 sensors are placed on the thigh and calf respectively, with a sampling frequency of 100Hz; the two MPU6050 sensors work together to achieve accurate lower limb movement monitoring; when the user moves, the main control chip first performs zero-bias calibration and temperature compensation on the raw data of each sensor, and then obtains the real-time angle change through gyroscope integration, and corrects the drift error by combining the accelerometer data.

[0013] Furthermore, based on the established leg geometric dynamics model, the thigh sensor monitors the flexion and extension angles of the hip joint, while the calf sensor tracks the knee joint's motion. The data from both are time-stamped to ensure synchronization. The system performs vector synthesis of the thigh angular velocity (ω2) and the calf angular velocity (ω1), and combines the preset limb length parameters (L1 is the thigh length, L2 is the calf length) with the kinematic formula v_foot=|ω2×L1+ω1×L2| to calculate the instantaneous foot velocity. After exponential weighted moving average filtering, real-time motion monitoring is finally achieved.

[0014] Furthermore, the inner layer fabric of the negative Poisson's ratio metamaterial is made of nylon to achieve lightweight and high elasticity. Rectangular holes are cut at equal intervals in the horizontal and vertical directions on the nylon material to form rectangular perforated negative Poisson's ratio cells. The cell structure is periodically arranged to form the metamaterial. When the knee brace is subjected to longitudinal tensile force, the oblique support structure inside the cell rotates, pushing the horizontal opening to expand. As the material as a whole stretches in the longitudinal direction, it also expands in the horizontal direction, realizing the negative Poisson's ratio effect, i.e., the tensile expansion effect. Based on the negative Poisson's ratio (tensile expansion) effect, the knee brace expands laterally when the joint is bent, thereby automatically conforming to the curve of the leg to distribute pressure and reduce pressure on the skin.

[0015] Furthermore, the outer surface of the smart protective gear is made of polyester fiber, spandex and nylon to withstand friction and stretching during exercise, fits tightly to the knee, ensures wear resistance and strength, and achieves the function of moisture absorption and perspiration wicking.

[0016] The present invention discloses a negative Poisson's ratio metamaterial smart knee brace with integrated gait monitoring, which is manufactured using an advanced digital process. From CAD modeling to 3D printing molding, strict precision control is implemented, with a dimensional tolerance of ±0.1mm.

[0017] The advantages of this invention compared to the prior art are as follows:

[0018] The knee brace of this invention employs a rectangular perforated negative Poisson's ratio metamaterial structure (Poisson's ratio close to -1). Through the negative Poisson's ratio (tensile) effect, it expands laterally during joint flexion to distribute pressure. Combined with a nylon substrate, it achieves lightweight and high elasticity, significantly improving wearing comfort and joint stability. The knee brace integrates dual MPU6050 sensors, located in the mid-thigh and calf, respectively, and connects to a microcontroller via an I2C interface to achieve real-time acquisition of thigh and calf angle data. The MPU6050, as a high-performance six-axis motion processing sensor, integrates a three-axis accelerometer and a three-axis gyroscope, enabling precise measurement of an object's acceleration and angular velocity changes along three axes, thus providing comprehensive data support for monitoring leg movement.

[0019] To ensure the real-time nature and accuracy of the acquired data, this invention carefully sets the data acquisition frequency to 100Hz, meaning angle data is acquired once every 0.1 seconds. This ensures that a sufficient number of data points are acquired without missing important motion information due to slow acquisition speed. Upon receiving this angle data, the microcontroller immediately initiates the data processing program. First, the raw data is filtered and calibrated to eliminate potential noise interference and system errors. Then, a specially designed algorithm analyzes and calculates the processed data to obtain accurate angular velocity information. Next, the system combines the calculated angular velocity with pre-stored leg length information, and through a series of complex mathematical modeling and physical derivations, accurately derives the instantaneous velocity of the foot. Throughout the process, various data optimization measures, such as data smoothing and error compensation, are employed to further improve the reliability and accuracy of the foot's instantaneous velocity calculation results, ensuring that the system provides a high-quality data foundation for subsequent motion analysis and control.

[0020] The device of this invention supports the transmission of real-time gait information to terminal devices via Bluetooth, and is suitable for posture optimization in sports training and progress assessment in rehabilitation treatment, solving the problems of poor comfort and limited functionality of traditional knee braces. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the knee brace of the present invention;

[0022] Figure 2 This invention relates to a rectangular perforated negative Poisson's ratio cell structure.

[0023] Figure 3 This is a simplified diagram of the rectangular perforated negative Poisson's ratio cell structure of the present invention;

[0024] Figure 4 This is a simulation diagram of the force and deformation of the rectangular perforated negative Poisson's ratio cell structure of the present invention.

[0025] Figure 5 This invention relates to a rectangular perforated negative Poisson's ratio metamaterial inner layer fabric structure for knee braces.

[0026] Figure 6 This is the deformation result of the rectangular perforated negative Poisson's ratio metamaterial structure of the inner layer fabric of the knee brace of the present invention after stretching;

[0027] Figure 7 This is a schematic diagram of the integrated circuit sensor of the present invention;

[0028] Figure 8 This is real-time speed data from the test experiment of the dual MPU6050 sensor intelligent monitoring system of the present invention;

[0029] Among them, 1- Velcro, 2- Monitoring circuit, 3- Negative Poisson's ratio metamaterial inner layer fabric, 4- Smart protective gear outer wrapping surface, 5- Sensor switch. Detailed Implementation

[0030] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following examples provide a more detailed description of the invention. It should be noted that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0031] like Figure 1 As shown, this invention provides a smart knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial. The rectangular perforated negative Poisson's ratio cells of the inner fabric (3) of the negative Poisson's ratio metamaterial are as follows: Figure 2 As shown: Rectangular holes are drilled at equal intervals horizontally and vertically in the nylon material to form rectangular perforated negative Poisson's ratio cells. A simplified diagram of the rectangular perforated negative Poisson's ratio structure is shown below. Figure 3 As shown, assume the width of the horizontal opening is b, and the length of the vertical opening is... The length of the horizontal opening is .Regulation To simplify the angle between the horizontal (or vertical) side of the cell and the horizontal (or vertical) direction.

[0032]

[0033]

[0034] According to geometric relationships,

[0035]

[0036] Calculate the projections of both sides onto the horizontal and vertical directions using the same method.

[0037]

[0038]

[0039] According to the definition of Poisson's ratio, we can obtain...

[0040]

[0041] Taking the differential, we get

[0042]

[0043]

[0044] Substituting equations (4), (5), (7), and (8) into equation (6) yields the formula for calculating Poisson's ratio:

[0045]

[0046] The negative Poisson's ratio characteristics of a rectangular perforated cell structure were simulated and calculated using Abaqus. The simulated force-deformation diagram of the rectangular perforated negative Poisson's ratio cell structure is shown below. Figure 4 As shown, when the knee brace is subjected to longitudinal tensile force (such as when the knee joint is bent), the oblique support structure inside the cell rotates, pushing the lateral opening to expand, so that the material as a whole expands laterally as it elongates longitudinally; the Poisson's ratio of the rectangular perforated negative Poisson's ratio cell, after theoretical calculation and simulation, is close to -1, which can achieve a very good negative Poisson's ratio (tensile expansion) effect. This invention achieves the dual functions of sports protection and health monitoring through the innovative material structure and intelligent monitoring system collaborative design.

[0047] The knee brace of this invention uses a rectangular perforated negative Poisson's ratio metamaterial as its core structure. When subjected to longitudinal stretching, it generates a unique negative Poisson's ratio (tensile) effect, causing the material to elongate longitudinally while simultaneously expanding laterally. This effectively disperses pressure during joint flexion, significantly improving wearing comfort. The inner fabric (3) of the negative Poisson's ratio metamaterial has the following structure: Figure 5 As shown, rectangular holes are cut at equal intervals in both the transverse and longitudinal directions in a nylon fabric material surrounding the knee. These periodic rectangular holes form a negative Poisson's ratio metamaterial with a tensile effect; the effect of the negative Poisson's ratio metamaterial after unidirectional stretching is as follows. Figure 6 As shown, when stretched laterally, it also expands longitudinally simultaneously; the knee brace is based on a negative Poisson's ratio structure, which expands laterally when the joint is bent to automatically conform to the curve of the leg, thereby dispersing pressure and reducing pressure on the skin; due to its special negative Poisson's ratio (tension) characteristics, the negative Poisson's ratio structure gives this sports protective gear excellent impact resistance, which can reduce damage to human joints when the range of motion is large.

[0048] The intelligent knee brace of this invention adopts a composite structure design: the inner layer is made of nylon fabric with a negative Poisson's ratio, which has excellent moisture-wicking properties, ensuring comfort during long-term wear while also taking into account unique mechanical properties and protective functions; the outer wrapping surface is made of polyester fiber, spandex, and nylon to withstand friction and stretching during exercise, closely conforming to the knee, ensuring wear resistance and strength, and achieving the function of moisture-wicking; this material combination not only achieves a lightweight design but also has excellent durability, and has been tested to withstand more than 1,000 bending cycles while maintaining stable performance; the product is equipped with an intelligent adjustment system, which achieves personalized fit through two adjustable Velcro straps, and can automatically optimize the wearing pressure according to the user's leg shape characteristics (fitting 30-50cm leg circumference) and exercise intensity.

[0049] The knee brace's two monitoring circuits (2) integrate a dual MPU6050 six-axis motion sensor system to monitor motion in real time. Figure 7 The schematic diagram of the integrated circuit sensor is shown; the MPU6050 is a six-axis motion tracking sensor, consisting of four parts: accelerometer, gyroscope, DMP (Digital Motion Processor), and temperature sensor. The temperature sensor is used to detect temperature, and temperature drift is reduced through algorithm optimization. The three-axis accelerometer can measure gravity and motion acceleration in the X / Y / Z directions, the three-axis gyroscope measures the rotational angular velocity around the X / Y / Z axes, and the DMP (Digital Motion Processor) fuses the acceleration and gyroscope data in real time and outputs the attitude angle.

[0050] The monitoring circuit (2) is a real-time monitoring integrated circuit system with two MPU6050 sensors. The two MPU6050 sensors are placed at key monitoring positions on the thigh and calf (the middle area of ​​the thigh and calf covered by the knee brace), and capture lower limb motion data in real time through high-frequency sampling at 100Hz. The sensor system adopts an innovative collaborative working mode. The main control chip synchronously acquires the triaxial acceleration and angular velocity information of the two nodes through the I²C bus, and calculates gait parameters based on the accurate leg geometry model and the angular velocity-linear velocity conversion algorithm.

[0051] Based on the established leg geometric dynamics model, the thigh sensor mainly monitors the flexion and extension angles of the hip joint, while the calf sensor tracks the knee joint movement. The data from both are synchronized through timestamp alignment. The system performs vector synthesis of the thigh angular velocity (ω2) and the calf angular velocity (ω1), and combines the preset limb length parameters (L1 is the thigh length, L2 is the calf length) with the kinematic formula v_foot=|ω2×L1+ω1×L2| to calculate the instantaneous velocity of the foot. After exponential weighted moving average filtering, real-time motion monitoring is finally achieved.

[0052] To verify the effectiveness of the integrated gait monitoring system, a gait speed measurement experiment was conducted on several volunteers using the aforementioned negative Poisson's ratio metamaterial smart knee brace with integrated gait monitoring. The real-time speed data from the dual MPU6050 sensor smart monitoring system test experiment is shown below. Figure 8 As shown in the figure; the experimental results show that the gait speed measurement based on MPU6050 has high accuracy and real-time performance. The speed calculation error using the MPU6050 sensor is less than 5%, and the system has good robustness, capable of tracking speed changes in real time with an error of less than 5%.

[0053] When the user moves, the main control chip first performs zero-bias calibration and temperature compensation on the raw data from each sensor. Then, it obtains real-time angle changes through gyroscope integration and corrects drift errors by combining accelerometer data. All monitoring data can be transmitted to the mobile terminal via Bluetooth Low Energy 5.0, providing users with professional motion analysis and injury warnings. The dual-sensor architecture has significant advantages over single-sensor solutions, eliminating joint motion coupling errors caused by single-point measurements and improving reliability through cross-validation of data from two nodes.

[0054] The knee brace of this invention is manufactured using an advanced digital process, with strict precision control (dimensional tolerance ±0.1mm) implemented from CAD modeling to 3D printing. Special reinforcement treatments are applied to key stress areas to ensure product reliability in various sports scenarios. Testing shows that this knee brace effectively reduces knee injury from sports impacts while providing up to 12 hours of continuous monitoring capability, perfectly meeting the needs of professional athletes and rehabilitation patients. The system can also dynamically adjust the protective intensity at easily worn joint areas based on real-time monitored motion data, achieving truly intelligent protection.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A smart knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial, characterized in that, The knee brace includes: two Velcro straps (1), two monitoring circuits (2), a negative Poisson's ratio metamaterial inner fabric (3), an intelligent protective outer wrapping surface (4), and a sensor switch (5); Two Velcro straps (1) are located at the top and bottom of the knee brace, respectively; two monitoring circuits (2) are embedded between the outer wrapping surface (4) of the smart brace and the inner fabric (3) of the negative Poisson's ratio metamaterial, providing real-time motion data during exercise; the inner fabric (3) of the negative Poisson's ratio metamaterial serves as the inner layer of the knee brace, directly contacting the user's leg, utilizing the negative Poisson's ratio effect to enhance the stability of the joint and the decompression support of the knee brace, ensuring better comfort and better protection; the outer wrapping surface (4) of the smart brace is wrapped around the outer side of the inner fabric (3) of the negative Poisson's ratio metamaterial, and can withstand friction and stretching during exercise; the sensor switch (5) is located on the outside of the outer wrapping surface (4) of the smart brace, and when turned on, it can start the integrated circuit system and monitor and record motion data in real time.

2. The intelligent knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial according to claim 1, characterized in that, The two Velcro straps (1) can be adjusted freely according to leg shape and needs to achieve better comfort. The two Velcro straps (1) are used to fit and bind according to the user's leg shape to adjust the tightness of the knee brace.

3. The intelligent knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial according to claim 1, characterized in that, The monitoring circuit (2) is a real-time monitoring integrated circuit system of two MPU6050 sensors; the two MPU6050 sensors are placed on the thigh and calf respectively, with a sampling frequency of 100Hz; the two MPU6050 sensors work together to achieve accurate lower limb movement monitoring; when the user moves, the main control chip first performs zero bias calibration and temperature compensation on the raw data of each sensor, and then obtains the real-time angle change through gyroscope integration, and corrects the drift error by combining the accelerometer data.

4. The intelligent knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial according to claim 3, characterized in that, Based on the established leg geometric dynamics model, the thigh sensor monitors the flexion and extension angles of the hip joint, while the calf sensor tracks the knee joint movement. The data from both are time-stamped to ensure synchronization. The system performs vector synthesis of the thigh angular velocity (ω2) and the calf angular velocity (ω1), and combines the preset limb length parameters (L1 is the thigh length, L2 is the calf length) with the kinematic formula v_foot=|ω2×L1+ω1×L2| to calculate the instantaneous velocity of the foot. After exponential weighted moving average filtering, real-time motion monitoring is finally achieved.

5. The intelligent knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial according to claim 1, characterized in that, The inner fabric (3) of the negative Poisson's ratio metamaterial is made of nylon to achieve lightweight and high elasticity. Rectangular holes are cut at equal intervals in the horizontal and vertical directions on the nylon material to form rectangular perforated negative Poisson's ratio cells. The cell structure is periodically arranged to form the metamaterial. When the knee brace is subjected to longitudinal tensile force, the oblique support structure inside the cell rotates, which pushes the horizontal opening to expand. When the material as a whole is stretched in the longitudinal direction, it also expands in the horizontal direction, realizing the negative Poisson's ratio effect, that is, the tensile effect. The knee brace is based on the negative Poisson's ratio effect. When the joint is bent, it expands in the horizontal direction to automatically conform to the curve of the leg, so as to disperse the pressure and reduce the pressure on the skin.

6. The intelligent knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial according to claim 5, characterized in that, In the aforementioned rectangular perforated negative Poisson's ratio structure, the width of the flat opening is set to b, and the length of the longitudinal opening is... The length of the horizontal opening is ;Regulation To simplify the angle between the horizontal (or vertical) side of the cell and the horizontal (or vertical) direction; According to geometric relationships, Calculate the projections of both sides onto the horizontal and vertical directions using the same method. According to the definition of Poisson's ratio, we can obtain... Taking the differential, we get Substituting equations (4), (5), (7), and (8) into equation (6) yields the formula for calculating Poisson's ratio: The negative Poisson's ratio characteristics of the rectangular perforated cell structure were calculated using Abaqus simulation. The Poisson's ratio of the rectangular perforated negative Poisson's ratio cell was calculated theoretically and simulated, and the Poisson's ratio is close to -1, which can achieve a very good negative Poisson's ratio effect.

7. The intelligent knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial according to claim 1, characterized in that, The outer wrapping surface (4) of the intelligent protective gear is made of polyester fiber, spandex and nylon to withstand friction and stretching during exercise, fits tightly to the knee, ensures wear resistance and strength, and achieves the function of moisture absorption and sweat wicking.

8. A smart knee brace with integrated gait monitoring and negative Poisson's ratio metamaterial according to any one of claims 1 to 7, characterized in that, The knee brace is manufactured using an advanced digital process, with strict precision control implemented from CAD modeling to 3D printing molding, and a dimensional tolerance of ±0.1mm.

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