PTC self-limiting temperature knee pad and multi-source sensing combined control method

Abstract

The application provides a PTC self-limiting temperature knee pad and a multi-source sensing combined control method, which comprises the following steps: collecting real-time pressure values of each pressure sensor in a pressure sensor array and a real-time inclination angle value of an inclination sensor; calculating a pressure difference value and judging whether the resistance measurement value is in a low resistance state defined by a positive temperature coefficient effect; limiting the heating temperature below the resistance mutation temperature by using the positive temperature coefficient effect; continuously monitoring the change of the real-time inclination angle value; when the real-time inclination angle value changes continuously below a preset activity angle threshold value for a time and exceeds a preset static time threshold value, outputting a stiffening prevention reminding instruction by a controller, and issuing a vibration reminder based on the stiffening prevention reminding instruction. The application realizes reliable judgment of heating start through a double-condition combined verification mechanism of a pressure difference value threshold and a low resistance state of PTC material.

Description

Technical Field

[0001] This invention relates to the field of intelligent physiotherapy and wearable device technology, and in particular to a PTC self-limiting temperature knee brace and a multi-source sensor combined control method. Background Technology

[0002] The knee joint is a crucial link in the human body for weight-bearing and movement, and is prone to discomfort due to sports injuries, degenerative arthritis, and cold stimulation. Heat therapy is a commonly used and effective method to promote local blood circulation and relieve pain. Currently, commercially available electric heated knee braces mainly fall into the following two categories.

[0003] The first type is the ordinary electrothermal knee brace based on resistance wires (such as nickel-chromium alloy wires or carbon fiber wires). Its temperature control relies on a closed-loop electronic temperature control system composed of a microcontroller, thermistor, and power switch. This type of solution has the following drawbacks: In terms of safety hazards, if the electronic temperature control system experiences sensor failure or program malfunction, the resistance wire will continue to heat, which can easily cause low-temperature burns; in terms of temperature control quality, electronic switch-type or PID temperature control is a passive feedback regulation, and the temperature fluctuates greatly around the target value, resulting in poor comfort during heat application; in terms of system complexity, in order to achieve closed-loop temperature control, additional sensors, control circuits, and complex leads must be integrated for feedback heating temperature, increasing the product's size, weight, and potential failure points, which is not conducive to the development of knee braces towards thinner and more flexible designs.

[0004] The second type is self-regulating electric heating knee braces based on polymer PTC materials. Existing patents disclose technical solutions that simply embed the PTC heating element within the knee brace (such as Chinese patent CN2199893Y titled "Motor Vehicle Steering Wheel and Seat Heater" and Chinese utility model patent CN205267056U titled "Self-Regulating Temperature Health Knee Brace"). These knee braces, when powered on, automatically limit the temperature near the Curie point (temperature of sudden change in resistance) due to the material's positive temperature coefficient effect, thus eliminating the risk of overheating at the material level. However, these knee braces lack sensor monitoring functions and intelligent control logic. They cannot actively start and stop heating based on the user's real-time physiological state (such as local pressure distribution, skin temperature, and joint range of motion), nor can they provide health management functions such as reminders to prevent stiffness from prolonged sitting. Essentially, they remain passive heating tools.

[0005] In recent years, smart knee brace solutions integrating multiple sensors have emerged. Existing research has disclosed technical approaches for constructing multimodal fusion sensing systems using inertial measurement units, surface electromyography sensors, and flexible pressure sensors to achieve real-time monitoring of knee joint movement posture and muscle activation status (such as the research on "smart rehabilitation knee braces").

[0006] However, existing technologies either lack heating therapy functions, failing to meet the core need for heat therapy and pain relief; or they employ closed-loop electronic temperature control, whose temperature control still relies on sensor feedback and controller power adjustment. If the sensor fails, the temperature control system collapses, posing a safety risk. Furthermore, while existing research has disclosed knee braces based on flexible pressure sensors and inertial sensors for knee joint motion monitoring, these also lack a deep integration of heating therapy and intelligent control. Summary of the Invention

[0007] In view of the above situation, the main objective of this invention is to propose a PTC self-limiting temperature knee brace and a multi-source sensing joint control method to solve the above-mentioned technical problems.

[0008] This invention proposes a PTC self-limiting temperature knee brace and a multi-source sensor joint control method, the method comprising the following steps: Step 1: Use the controller to establish the individual baseline pressure value of each pressure sensor and the individual baseline temperature value of each temperature sensor in the pressure sensor array. Step 2: Collect the real-time pressure values ​​of each pressure sensor in the pressure sensor array and the real-time tilt angle values ​​of the tilt sensor. Step 3: Calculate the pressure difference between the real-time pressure value of each pressure sensor and the corresponding individual baseline pressure value. When the pressure difference of any pressure sensor exceeds the preset pressure threshold, the controller reads the resistance measurement value from the electrode circuit layer of the flexible PTC composite heating layer and determines whether the resistance measurement value exhibits a low resistance state as defined by the positive temperature coefficient effect. Step 4: When the pressure difference exceeds the preset pressure threshold and the resistance measurement shows a low resistance state, the controller outputs a heating start command to the flexible PTC composite heating layer. Step 5: The flexible PTC composite heating layer responds to the heating start command by being energized and heated, and the heating temperature is limited to below the resistance change temperature by utilizing the positive temperature coefficient effect. Step 6: Repeat steps 3 to 5 and continuously monitor the change in the real-time tilt angle value. When the change in the real-time tilt angle value is continuously lower than the preset active angle threshold for a continuous period of time and exceeds the preset static duration threshold, the controller outputs an anti-rigidity reminder command and issues a vibration reminder based on the anti-rigidity reminder command.

[0009] The present invention also proposes a PTC self-regulating knee brace, which includes: a knee brace body, a multi-source sensing unit and a controller; the knee brace body includes: a skin-friendly layer, a thermally conductive and temperature-equalizing layer, a flexible PTC composite heating layer, an electrode circuit layer, an insulating protective layer and an outer layer; The multi-source sensing unit is integrated into the knee brace body and includes: a pressure sensor array, a temperature sensor, and a tilt sensor. The flexible PTC composite heating layer is made of a conductive polymer composite material with a positive temperature coefficient effect; The controller includes a vibration alert unit; the controller is electrically connected to the electrode circuit layer and the multi-source sensing unit, and performs data analysis on the signals collected by the multi-source sensing unit to obtain analysis results, and outputs a heating start command or heating stop command to the flexible PTC composite heating layer according to the analysis results.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves reliable judgment of heating initiation through a dual-condition joint verification mechanism of pressure difference threshold and low resistance state of PTC material. The controller only outputs a heating initiation command when it detects abnormal pressure in the user's knee joint (reflecting the need for thermotherapy) and the flexible PTC composite heating layer is in a low resistance state capable of normal heating. This mechanism effectively avoids heating initiation due to false triggering by a single sensor (such as a sudden increase in pressure caused by a change in posture) or when the PTC material is in a high resistance state due to insufficient cooling, significantly improving the accuracy and safety of heating initiation.

[0011] 2. This invention utilizes the positive temperature coefficient effect of the flexible PTC composite heating layer to autonomously achieve heating temperature limiting, realizing an open-loop control architecture that ensures temperature safety without the need for temperature sensor feedback. Unlike traditional closed-loop electronic temperature-controlled knee braces that rely on thermistors to collect temperature data in real time and adjust power, the controller of this invention does not participate in any temperature regulation after outputting the heating start command. The temperature is entirely limited within a safe range by the physical properties of the PTC material itself (resistance increases exponentially when the temperature rises to the point of sudden change in resistance, and heating power automatically decreases). This not only eliminates the risk of temperature control failure due to temperature sensor malfunction but also greatly simplifies the control algorithm and reduces system power consumption.

[0012] 3. This invention achieves system-level safety redundancy by completely decoupling the safety temperature control function from the health monitoring function at the architectural level. The self-limiting temperature capability of the flexible PTC composite heating layer does not depend on any signal from the multi-source sensing unit. Even if the pressure sensor, temperature sensor, or tilt sensor completely fails, the PTC material can still autonomously limit its temperature after being powered on, eliminating the risk of overheating. At the same time, the health monitoring function of the multi-source sensing unit operates independently. The sensor signals are only used to decide whether to start heating or issue an alert. Sensor failure does not affect the safety of basic hyperthermia. This design of "monitoring and temperature control being independent of each other" fundamentally overcomes the structural defect of existing smart knee braces where "sensor failure equals temperature control failure".

[0013] 4. This invention achieves coordinated management of on-demand thermotherapy and anti-stiffness reminders by parallel integration of multi-source data from pressure sensing, resistance detection, and tilt angle sensing. The controller uses pressure difference to determine local load anomalies, uses PTC resistance status to verify heating conditions, and uses tilt angle changes to identify prolonged sitting stillness. These three mechanisms operate in parallel based on their independent time scales and triggering logics. When thermotherapy conditions are met, the controller activates the PTC material to autonomously complete safe heating; when prolonged stillness is detected, the controller outputs a vibration reminder. This multi-source sensing combined control method upgrades the knee brace from a passive warmth-keeping tool to an intelligent terminal capable of actively identifying the health status of the knee joint and providing targeted interventions, representing a significant technological advancement.

[0014] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by means of embodiments of the invention. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the steps of the multi-source sensing joint control method for the PTC self-limiting knee brace proposed in this invention.

[0016] Figure 2 This is a structural diagram of the PTC self-limiting temperature knee brace proposed in this invention.

[0017] The names and serial numbers of the components in the picture are: knee brace body 1, controller 2, and Velcro 201. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0019] These and other aspects of the embodiments of the present invention will become clear from the following description and accompanying drawings. In these descriptions and drawings, some specific embodiments of the present invention are specifically disclosed to provide some ways of implementing the principles of the embodiments of the present invention; however, it should be understood that the scope of the embodiments of the present invention is not limited thereto. Example

[0020] Please see Figure 1 This invention proposes a PTC self-limiting temperature knee brace and a multi-source sensor joint control method, which includes the following steps: Step 1: Use controller 2 to establish the individual baseline pressure value of each pressure sensor and the individual baseline temperature value of each temperature sensor in the pressure sensor array.

[0021] In step 1, the controller 2 is used to establish the individual baseline pressure value of each pressure sensor and the individual baseline temperature value of each temperature sensor in the pressure sensor array. This specifically includes the following steps: During the initial wear phase, the controller 2 continuously collects the pressure readings of each pressure sensor in the pressure sensor array to obtain the first set of pressure readings for each pressure sensor. The first set of pressure readings of each pressure sensor is statistically processed to obtain the individual baseline pressure value of each pressure sensor, and the individual baseline pressure value of each pressure sensor is stored in the internal memory of the controller 2. During the initial wear phase, the controller 2 continuously collects temperature readings from the temperature sensor. The temperature readings of the temperature sensor are statistically processed to obtain individual baseline temperature values, which are then stored in the internal memory of the controller 2.

[0022] In this embodiment of the invention, through continuous data acquisition and statistical processing during the initial wear phase, individual baseline pressure values ​​for each pressure sensor and individual baseline temperature values ​​for each temperature sensor are established, achieving personalized adaptation to the user's physiological characteristics. Since there are significant differences in the baseline knee joint pressure and baseline body temperature among different users, a fixed threshold can lead to numerous false alarms or missed alarms. This invention introduces an individual baseline establishment mechanism, enabling the knee brace to adapt to the physiological characteristics of different users, providing an accurate reference benchmark for subsequent pressure difference calculations, and avoiding the false triggering problem caused by a "one-size-fits-all" threshold. Simultaneously, the individual baseline values ​​are stored in the internal memory of the controller 2, ensuring rapid retrieval upon each startup without the need for repeated calibration.

[0023] Step 2: Collect the real-time pressure values ​​of each pressure sensor in the pressure sensor array and the real-time tilt angle values ​​of the tilt sensor.

[0024] In step 2, the real-time pressure values ​​of each pressure sensor in the pressure sensor array and the real-time tilt angle values ​​of the tilt sensor are collected, specifically including the following steps: The real-time pressure values ​​of each pressure sensor in the pressure sensor array are acquired using a continuous acquisition method. The real-time tilt angle value of the tilt sensor is acquired through continuous acquisition.

[0025] In this embodiment of the invention, real-time pressure values ​​from each pressure sensor in the pressure sensor array and real-time tilt angle values ​​from the tilt sensor are acquired through continuous acquisition, providing a real-time data foundation for subsequent pressure difference calculation and anti-stiffness judgment. Continuous acquisition ensures the real-time nature and integrity of the data, enabling the capture of transient changes in knee joint pressure distribution and the continuous trajectory of joint movement. The multiple sensors in the pressure sensor array correspond to different areas around the patella, while the tilt sensor is installed laterally to the axis of knee flexion and extension. The data acquired by both are synchronized in time and complementary in space, providing data support for multi-source sensor joint control.

[0026] Step 3: Calculate the pressure difference between the real-time pressure value of each pressure sensor and the corresponding individual baseline pressure value. When the pressure difference of any pressure sensor exceeds the preset pressure threshold, the controller reads the resistance measurement value from the electrode circuit layer of the flexible PTC composite heating layer and determines whether the resistance measurement value exhibits a low resistance state as defined by the positive temperature coefficient effect.

[0027] In step 3, the pressure difference between the real-time pressure value of each pressure sensor and the corresponding individual baseline pressure value is calculated. When the pressure difference of any pressure sensor exceeds a preset pressure threshold, the controller reads the resistance measurement value from the electrode circuit layer of the flexible PTC composite heating layer and determines whether the resistance measurement value exhibits a low resistance state as defined by the positive temperature coefficient effect. Specifically, this includes the following steps: The controller 2 reads the individual baseline pressure value of each pressure sensor from the memory and calculates the difference between the real-time pressure value of each pressure sensor and the corresponding individual baseline pressure value to obtain the pressure difference of each pressure sensor. Determine whether the pressure difference value of the pressure sensor exceeds a preset pressure threshold to obtain a first determination result; When the first judgment result is yes, the controller 2 applies a detection voltage to the flexible PTC composite heating layer through the electrode circuit layer, measures the feedback current, and calculates the resistance measurement value. The second judgment result is obtained by determining whether the measured resistance value is lower than the preset low resistance threshold; wherein, the low resistance threshold corresponds to the upper limit of the resistance when the flexible PTC composite heating layer is in the low resistance state defined by the positive temperature coefficient effect.

[0028] In this embodiment of the invention, by calculating the pressure difference and comparing it with a preset pressure threshold, it is first determined whether there is an abnormal pressure in the user's knee joint that requires heat therapy (such as excessive local load, inflammatory reaction, etc.). When an abnormal pressure is detected, the controller 2 does not immediately start heating, but further reads the resistance measurement value of the flexible PTC composite heating layer from the electrode circuit layer to determine whether it is in a low resistance state. A low resistance state means that the temperature of the PTC material is lower than the resistance jump temperature (i.e., the Curie point temperature), the conductive network is unobstructed, and it can heat up normally after being powered on; conversely, if the PTC material is in a high resistance state (the temperature is close to or exceeds the Curie point), heating will not be effective and may even damage the material due to re-energizing. This dual-condition joint verification mechanism effectively avoids starting heating due to false triggering by a single sensor (such as a sudden increase in pressure caused by a change in posture) or when the PTC material is in a high resistance state due to insufficient cooling, significantly improving the accuracy and safety of heating start-up. At the same time, the detection voltage applied during the resistance detection process is much smaller than the normal operating voltage, which will not cause a significant temperature rise in the material, and is a non-destructive test.

[0029] Step 4: When the pressure difference exceeds the preset pressure threshold and the resistance measurement shows a low resistance state, the controller 2 outputs a heating start command to the flexible PTC composite heating layer.

[0030] In step 4, when the pressure difference exceeds the preset pressure threshold and the resistance measurement shows a low resistance state, controller 2 outputs a heating start command to the flexible PTC composite heating layer, specifically including the following steps: The first and second judgment results are obtained using controller 2. When the first judgment result indicates that the pressure difference exceeds the preset pressure threshold and the second judgment result indicates that the resistance measurement value is in a low resistance state, the controller 2 generates a heating start permission flag. Controller 2 receives the heating start permission flag and outputs a heating start command to the flexible PTC composite heating layer through the electrode circuit layer.

[0031] In this embodiment of the invention, controller 2 generates a heating start permission flag and outputs a heating start command only when both conditions are met simultaneously. This command is a binary level signal (high level to start, low level to stop) and does not carry any parameters for adjusting the heating power. Unlike the complex power adjustment signals (such as PWM signals) output by existing closed-loop electronic temperature-controlled knee braces, the heating start command of this invention only indicates "start heating" without specifying "to what temperature" or "at what power." This design completely entrusts the responsibility of temperature control to the physical properties of the PTC material, achieving separation of controller 2's decision-making from material execution. After outputting the heating start command, controller 2 no longer intervenes in the power adjustment during the heating process; the sensor feedback signal is only used for health monitoring and does not participate in the temperature closed loop.

[0032] Step 5: The flexible PTC composite heating layer responds to the heating start command by being energized and heated, and the heating temperature is limited to below the resistance change temperature by utilizing the positive temperature coefficient effect.

[0033] In step 5, the flexible PTC composite heating layer is energized and heated in response to the heating start command. The heating temperature is limited to below the resistance change temperature by utilizing the positive temperature coefficient effect. Specifically, this includes the following steps: The flexible PTC composite heating layer receives a heating start command and begins to heat up. The conductive polymer composite material inside the flexible PTC composite heating layer maintains a low resistance state when the temperature is below the resistance change temperature, thus generating high heating power. When the temperature of the flexible PTC composite heating layer rises to the resistance change temperature, the volume expansion of the conductive polymer composite material inside the flexible PTC composite heating layer causes the conductive network to break, the resistance to increase, and the heating power to decrease. When the temperature of the flexible PTC composite heating layer drops below the resistance mutation temperature, the conductive network reconnects, the resistance returns to a low resistance state, and the heating power is restored.

[0034] In this embodiment of the invention, the flexible PTC composite heating layer begins heating upon receiving a heating start command. When the temperature is below the resistance jump temperature (40℃~45℃), the conductive polymer composite material (PDMS / graphite / carbon nanotube system) inside maintains a complete conductive network with low resistance, generating high heating power when current flows through, causing the temperature to rise rapidly. When the temperature rises to near the resistance jump temperature, the polydimethylsiloxane (PDMS) matrix expands due to heat, causing the conductive network (the conductive pathways formed by graphite and carbon nanotubes) to be stretched or even broken, resulting in an exponential increase in resistance and an automatic reduction in heating power to near zero, thus preventing further temperature increases. When the temperature naturally drops below the resistance jump temperature, the PDMS matrix contracts, the conductive network reconnects, the resistance returns to a low resistance state, the heating power recovers, and the temperature rises again. This process requires no external sensor feedback or controller 2 adjustment; it is entirely autonomously completed by the material's own physical properties, forming a dynamic thermal equilibrium cycle. Because the resistance change temperature is designed to be between 40℃ and 45℃, which is exactly within the safe temperature range for human body heat therapy, this knee brace ensures the heat therapy effect while fundamentally eliminating the risk of low-temperature burns.

[0035] Step 6: Repeat steps 3 to 5 and continuously monitor the change in the real-time tilt angle value. When the change in the real-time tilt angle value is continuously lower than the preset active angle threshold for a continuous period of time and exceeds the preset static duration threshold, the controller outputs an anti-rigidity reminder command and issues a vibration reminder based on the anti-rigidity reminder command.

[0036] It should be noted that in step 6, when the controller performs the aforementioned cycle of pressure detection, resistance verification, and heating start / stop, the specific operation is as follows: Steps 3 to 5 are repeatedly executed according to the preset sampling frequency, including repeatedly determining whether the pressure difference exceeds the preset pressure threshold and whether the resistance measurement value shows a low resistance state at the beginning of each sampling cycle; if the conditions are met, a heating start command is output; the controller repeatedly executes the autonomous temperature limiting cycle after heating start for the PTC material in each sampling cycle; the above cycle is continuously repeated until the joint determination condition in step 4 is not met, at which point heating is stopped.

[0037] In this embodiment of the invention, step 6 is executed in parallel with steps 3 to 5: On one hand, controller 2 continuously repeats the cycle of pressure detection, resistance verification, and heating start / stop to achieve intermittent heat therapy on demand; on the other hand, controller 2 continuously monitors the real-time tilt angle value change of the tilt sensor and calculates the angle change per unit time. When the angle change is continuously lower than the preset activity angle threshold (e.g., 2 degrees / minute) for a period exceeding the static duration threshold (e.g., 30 minutes), it is determined that the user is in a prolonged static state (such as prolonged sitting or standing). At this time, controller 2 outputs an anti-stiffness reminder command, driving the vibration reminder unit to emit intermittent tactile vibrations to prompt the user to change posture and move joints to prevent joint stiffness. This anti-stiffness reminder function and the heating therapy function are based on completely different sensor data, different time scales, and different intervention methods, and are executed independently in parallel in time without interfering with each other. This "dual-channel independent parallel" control architecture enables the knee brace to simultaneously possess the capabilities of active heat therapy and active health management, upgrading the passive warming tool into an intelligent terminal that can actively identify the health status of the knee joint and provide targeted intervention.

[0038] It should be noted that in the anti-stiffness reminder trigger judgment, the controller also calculates the absolute posture angle of the knee brace relative to the horizontal plane based on the reading of the tilt sensor; when the posture angle indicates that the user is in a lying position (the angle between the knee brace and the horizontal plane is less than 30 degrees), the controller automatically disables the anti-stiffness reminder function to avoid generating invalid reminders when the user is lying down to rest; when the posture angle returns to a sitting or standing position, the static duration timer of the anti-stiffness reminder function restarts. Example

[0039] Please see Figure 2 This invention proposes a PTC self-regulating knee brace, which includes: a knee brace body 1, a multi-source sensing unit and a controller 2; the knee brace body 1 includes: a skin-friendly layer, a thermally conductive and temperature-equalizing layer, a flexible PTC composite heating layer, an electrode circuit layer, an insulating protective layer and an outer layer; The multi-source sensing unit is integrated into the knee brace body 1. The multi-source sensing unit includes: a pressure sensor array, a temperature sensor, and a tilt sensor. The flexible PTC composite heating layer is made of a conductive polymer composite material with a positive temperature coefficient effect; The controller 2 is electrically connected to the electrode circuit layer and the multi-source sensing unit. It analyzes the signals collected by the multi-source sensing unit to obtain analysis results, and outputs a heating start command or heating stop command to the flexible PTC composite heating layer according to the analysis results.

[0040] Preferably, the skin-friendly layer is disposed on the innermost side for contact with the skin; the thermally conductive and temperature-equalizing layer is attached to the outer side of the skin-friendly layer; the flexible PTC composite heating layer is attached to the outer side of the thermally conductive and temperature-equalizing layer; the electrode circuit layer is attached to the outer side of the flexible PTC composite heating layer and has flexible silver electrodes printed on it; the insulating protective layer is wrapped around the outer side of the electrode circuit layer; and the outer layer is disposed on the outermost side and is sewn with adjustable Velcro 201. The pressure sensor array, temperature sensor, and tilt sensor are respectively attached and fixed to preset positions on the inner side of the skin-friendly layer; A vibration reminder unit is provided on the inner side of the skin-friendly layer corresponding to the two sides of the femur. The vibration reminder unit is electrically connected to the controller and is a vibration motor array.

[0041] Preferably, the conductive polymer composite material is made by melt blending and hot pressing of polydimethylsiloxane, paraffin, graphite, carbon nanotubes, with added curing agent and catalyst; The curing agent is hydrogen-containing silicone oil, and the catalyst is a platinum catalyst. Based on 100 parts by weight of polydimethylsiloxane, the composition includes 20 parts by weight of paraffin, 30 parts by weight of graphite, and 0.5 parts by weight of carbon nanotubes. After the polydimethylsiloxane, paraffin, graphite, and carbon nanotubes are melt-blended, 2% by weight of hydrogen-containing silicone oil and 0.5% by weight of platinum catalyst are added. The flexible PTC composite heating layer is arranged in a serpentine pattern within the knee brace body 1, avoiding the central axis of the knee joint, and the resistance change temperature of the flexible PTC composite heating layer is 40℃.

[0042] Preferably, the pressure sensor array consists of four thin-film pressure sensors, symmetrically distributed in a cross shape on the inner side of the skin-friendly layer corresponding to the area around the patella; the temperature sensor is located on the inner side of the skin-friendly layer corresponding to the central area of ​​the patella; the tilt sensor is located on the inner side of the skin-friendly layer corresponding to the lateral position of the knee joint flexion and extension axis, and the bottom of the tilt sensor is provided with a rigid base to isolate fabric deformation interference; the vibration motor array consists of two miniature eccentric wheel motors, symmetrically distributed on the inner side of the skin-friendly layer corresponding to the area of ​​the medial and lateral femoral condyles. Example

[0043] This invention proposes a PTC self-regulating knee brace. The difference between Example 3 and Example 2 is that, based on 100 parts by weight of polydimethylsiloxane, 22 parts by weight of paraffin wax, 35 parts by weight of graphite, and 0.75 parts by weight of carbon nanotubes, after the polydimethylsiloxane, paraffin wax, graphite, and carbon nanotubes are melt-blended, 3% by weight of hydrogen-containing silicone oil and 0.75% by weight of platinum catalyst are added. Furthermore, the resistance change temperature of the flexible PTC composite heating layer is 42°C. Example

[0044] This invention proposes a PTC self-regulating knee brace. The difference between Example 4 and Example 2 is that, based on 100 parts by weight of polydimethylsiloxane, 25 parts by weight of paraffin wax, 40 parts by weight of graphite, and 1 part by weight of carbon nanotubes, after the polydimethylsiloxane, paraffin wax, graphite, and carbon nanotubes are melt-blended, 5% by weight of hydrogen-containing silicone oil and 1% by weight of platinum catalyst are added to the polydimethylsiloxane. Furthermore, the resistance change temperature of the flexible PTC composite heating layer is 45°C.

[0045] In summary, this invention completely decouples the self-limiting physical properties of the flexible PTC composite heating layer from the intelligent monitoring function of the multi-source sensing unit at the architectural level. This eliminates the fundamental flaw of existing closed-loop electronic temperature-controlled knee braces, which rely on temperature sensor feedback to adjust heating power and face the risk of overheating if the sensors fail. It also overcomes the limitation of existing PTC self-limiting knee braces, which can only passively heat up and cannot be turned on and off as needed. The invention creatively employs a dual-condition joint verification mechanism of pressure difference threshold and the low resistance state of the PTC material. This ensures that the controller 2 only outputs a binary heating start command when the user's knee joint has a genuine need for heat therapy and the heating layer is in a low-resistance state suitable for normal operation. After heating starts, the controller completely withdraws its intervention, relying entirely on the PTC material's autonomous dynamic thermal balance cycle of "low resistance heating → high resistance temperature limiting → cooling recovery" around the resistance mutation temperature range of 40℃ to 45℃ to achieve precise temperature control. This realizes an open-loop control architecture of "decision-execution separation," ensuring that even if all sensors fail, the PTC material can still automatically limit the temperature after being powered on, completely eliminating the risk of low-temperature burns.

[0046] Meanwhile, a multi-source sensing parallel system consisting of a cross-shaped symmetrical pressure sensor array, a tilt sensor with a rigid base, and a PTC resistance detection module independently monitors local load anomalies, prolonged sitting stillness, and the availability of the heating layer at different time scales. When the heat therapy conditions are met, autonomous and safe heating is initiated, and a vibration reminder is issued when the stillness time exceeds the limit. This upgrades the knee brace from a passive warming tool to an intelligent terminal that can actively identify the health status of the knee joint and provide targeted intervention. In addition, the composite material formula optimized for the knee brace, using PDMS as a flexible matrix, graphite and carbon nanotubes as dual conductive fillers, and paraffin as a phase change modifier, as well as the six-layer stacked structure of skin-friendly layer, thermally conductive and temperature-equalizing layer, heating layer, electrode layer, insulating layer, and outer layer, further ensures uniform heat distribution, accurate sensor signal acquisition, and mechanical durability for long-term wear. The innovations in the three dimensions of materials, structure, and control reinforce each other and emerge as a whole, jointly solving the technical contradiction of "safety and intelligence being mutually exclusive" in existing technologies, and achieving a high degree of unity between inherent safety and intelligent physiotherapy.

[0047] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A multi-source sensing joint control method for a PTC self-limiting temperature knee brace, characterized in that, The method includes the following steps: Step 1: Use the controller to establish the individual baseline pressure value of each pressure sensor and the individual baseline temperature value of each temperature sensor in the pressure sensor array. Step 2: Collect the real-time pressure values ​​of each pressure sensor in the pressure sensor array and the real-time tilt angle values ​​of the tilt sensor. Step 3: Calculate the pressure difference between the real-time pressure value of each pressure sensor and the corresponding individual baseline pressure value. When the pressure difference of any pressure sensor exceeds the preset pressure threshold, the controller reads the resistance measurement value from the electrode circuit layer of the flexible PTC composite heating layer and determines whether the resistance measurement value exhibits a low resistance state as defined by the positive temperature coefficient effect. Step 4: When the pressure difference exceeds the preset pressure threshold and the resistance measurement shows a low resistance state, the controller outputs a heating start command to the flexible PTC composite heating layer. Step 5: The flexible PTC composite heating layer responds to the heating start command by being energized and heated, and the heating temperature is limited to below the resistance change temperature by utilizing the positive temperature coefficient effect. Step 6: Repeat steps 3 to 5 and continuously monitor the change in the real-time tilt angle value. When the change in the real-time tilt angle value is continuously lower than the preset active angle threshold for a continuous period of time and exceeds the preset static duration threshold, the controller outputs an anti-rigidity reminder command and issues a vibration reminder based on the anti-rigidity reminder command.

2. The multi-source sensing joint control method for PTC self-limiting knee brace according to claim 1, characterized in that, The controller is used to establish the individual baseline pressure value for each pressure sensor in the pressure sensor array and the individual baseline temperature value for each temperature sensor. This process includes the following steps: During the initial wear phase, the controller continuously collects the pressure readings of each pressure sensor in the pressure sensor array to obtain the first set of pressure readings for each pressure sensor. The first set of pressure readings for each pressure sensor is statistically processed to obtain the individual baseline pressure value for each pressure sensor, and the individual baseline pressure value for each pressure sensor is stored in the controller's internal memory. During the initial wear phase, the controller continuously collects temperature readings from the temperature sensor. The temperature readings of the temperature sensor are statistically processed to obtain individual baseline temperature values, which are then stored in the controller's internal memory.

3. The multi-source sensing joint control method for PTC self-limiting knee brace according to claim 2, characterized in that, The controller calculates the pressure difference between the real-time pressure value of each pressure sensor and the corresponding individual baseline pressure value. When the pressure difference of any pressure sensor exceeds a preset pressure threshold, the controller reads the resistance measurement value from the electrode circuit layer of the flexible PTC composite heating layer and determines whether the resistance measurement value exhibits a low resistance state as defined by the positive temperature coefficient effect. Specifically, this includes the following steps: The controller reads the individual baseline pressure value of each pressure sensor from the memory and calculates the difference between the real-time pressure value of each pressure sensor and the corresponding individual baseline pressure value to obtain the pressure difference of each pressure sensor. Determine whether the pressure difference value of the pressure sensor exceeds a preset pressure threshold to obtain a first determination result; When the first judgment result is yes, the controller applies a detection voltage to the flexible PTC composite heating layer through the electrode circuit layer, measures the feedback current, and calculates the resistance measurement value. The second judgment result is obtained by determining whether the measured resistance value is lower than the preset low resistance threshold; wherein, the low resistance threshold corresponds to the upper limit of the resistance when the flexible PTC composite heating layer is in the low resistance state defined by the positive temperature coefficient effect.

4. The multi-source sensing joint control method for PTC self-limiting knee brace according to claim 3, characterized in that, When the pressure difference exceeds the preset pressure threshold and the resistance measurement shows a low resistance state, the controller outputs a heating start command to the flexible PTC composite heating layer, which includes the following steps: The controller is used to obtain the first and second judgment results. When the first judgment result indicates that there is a pressure difference exceeding the preset pressure threshold, and the second judgment result indicates that the resistance measurement value shows a low resistance state, the controller generates a heating start permission flag. The controller receives the heating start permission flag and outputs a heating start command to the flexible PTC composite heating layer through the electrode circuit layer.

5. The multi-source sensing joint control method for PTC self-limiting temperature knee brace according to claim 4, characterized in that, The flexible PTC composite heating layer responds to a heating start command by being energized and heating up. Utilizing the positive temperature coefficient effect, the heating temperature is limited to below the resistance change temperature. Specifically, the process includes the following steps: The flexible PTC composite heating layer receives a heating start command and begins to heat up. The conductive polymer composite material inside the flexible PTC composite heating layer maintains a low resistance state when the temperature is below the resistance change temperature, thus generating high heating power. When the temperature of the flexible PTC composite heating layer rises to the resistance change temperature, the volume expansion of the conductive polymer composite material inside the flexible PTC composite heating layer causes the conductive network to break, the resistance to increase, and the heating power to decrease. When the temperature of the flexible PTC composite heating layer drops below the resistance mutation temperature, the conductive network reconnects, the resistance returns to a low resistance state, and the heating power is restored.

6. A PTC self-regulating temperature knee brace, characterized in that, The PTC self-limiting temperature knee brace adopts the multi-source sensor joint control method for the PTC self-limiting temperature knee brace as described in any one of claims 1-5; The PTC self-limiting temperature knee brace includes: a knee brace body, a multi-source sensing unit, and a controller; the knee brace body includes: a skin-friendly layer, a thermally conductive and temperature-equalizing layer, a flexible PTC composite heating layer, an electrode circuit layer, an insulating and protective layer, and an outer layer. The multi-source sensing unit is integrated into the knee brace body and includes: a pressure sensor array, a temperature sensor, and a tilt sensor. The flexible PTC composite heating layer is made of a conductive polymer composite material with a positive temperature coefficient effect; The controller is electrically connected to the electrode circuit layer and the multi-source sensing unit. It performs data analysis on the signals collected by the multi-source sensing unit to obtain analysis results, and outputs a heating start command or heating stop command to the flexible PTC composite heating layer according to the analysis results.

7. The PTC self-regulating knee brace according to claim 6, characterized in that, The skin-friendly layer is located on the innermost side and is used for contact with the skin; the thermally conductive and temperature-equalizing layer is attached to the outer side of the skin-friendly layer; the flexible PTC composite heating layer is attached to the outer side of the thermally conductive and temperature-equalizing layer; the electrode circuit layer is attached to the outer side of the flexible PTC composite heating layer and has flexible silver electrodes printed on it; the insulating protective layer is wrapped around the outer side of the electrode circuit layer; the outer layer is located on the outermost side and is sewn with adjustable Velcro. The pressure sensor array, temperature sensor, and tilt sensor are respectively attached and fixed to preset positions on the inner side of the skin-friendly layer; A vibration reminder unit is provided on the inner side of the skin-friendly layer corresponding to the two sides of the femur. The vibration reminder unit is electrically connected to the controller and is a vibration motor array.

8. The PTC self-regulating knee brace according to claim 7, characterized in that, The conductive polymer composite material is made by melt blending and hot pressing of polydimethylsiloxane, paraffin wax, graphite, carbon nanotubes, with added curing agent and catalyst; The curing agent is hydrogen-containing silicone oil, and the catalyst is a platinum catalyst. Based on 100 parts by weight of polydimethylsiloxane, paraffin wax is 20-25 parts by weight, graphite is 30-40 parts by weight, and carbon nanotubes are 0.5-1 parts by weight. After the polydimethylsiloxane, paraffin wax, graphite, and carbon nanotubes are melt-blended, 2%-5% by weight of hydrogen-containing silicone oil and 0.5%-1% by weight of platinum catalyst are added. The flexible PTC composite heating layer is arranged in a serpentine pattern within the knee brace body, avoiding the central axis of the knee joint, and the resistance change temperature of the flexible PTC composite heating layer is 40℃~45℃.

9. The PTC self-regulating temperature knee brace according to claim 8, characterized in that, The pressure sensor array consists of four thin-film pressure sensors, symmetrically distributed in a cross shape on the inner side of the skin-friendly layer corresponding to the area around the patella; the temperature sensor is located on the inner side of the skin-friendly layer corresponding to the central area of ​​the patella; the tilt sensor is located on the inner side of the skin-friendly layer corresponding to the lateral position of the knee joint flexion and extension axis, and the bottom of the tilt sensor is provided with a rigid base to isolate fabric deformation interference; the vibration motor array consists of two miniature eccentric wheel motors, symmetrically distributed on the inner side of the skin-friendly layer corresponding to the area of ​​the medial and lateral femoral condyles.

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