Measuring device and measuring method for knee joint movement

Abstract

The invention relates to a knee joint movement measuring device and method.The device is installed at a knee joint and comprises an upper connecting rod, a lower connecting rod, an angle encoder, a display unit and a control box, the upper connecting rod is connected with the lower connecting rod, and the angle encoder is installed at the joint of the upper connecting rod and the lower connecting rod; the control box is installed on the upper connecting rod and is in communication connection with the display unit and the angle encoder. The method is applied to the measuring device. The current angle variable quantity is collected through the angle encoder, the display unit carries out processing according to real-time data, the processing result is visually displayed, the change trend of the current angle is displayed, angle measurement is accurate, and the result is visually displayed.

Description

Technical Field

[0001] The present invention relates to the technical field of knee joint angle measurement, and in particular to a device and method for measuring knee joint motion. Background Art

[0002] While existing technologies related to measuring knee joint angular velocity or acceleration have made some progress, they still face significant limitations. Some existing methods based on accelerometers are widely used to detect gait information and indirectly calculate knee joint angular velocity through complex calculations. For example, lower-body posture recognition systems utilize small accelerometers to measure joint motion angles. Triaxial accelerometer-based inclinometers utilize the output of a third accelerometer to determine the relevant angles. However, these methods are affected by factors such as accelerometer noise, model errors, angle calculation methods, ambient temperature, and magnetic field perturbation errors, resulting in measurement accuracy that cannot reach arcseconds. Other measurement schemes employing triaxial geomagnetic decoupling and triaxial accelerometers can output roll and pitch attitude angles under ideal conditions without external acceleration interference. However, in real-world motion or vibration environments, these methods are significantly affected by external acceleration, resulting in significant angular errors in the output. Furthermore, accelerometers cannot accurately distinguish between gravitational acceleration and external acceleration, resulting in inaccurate data during variable-speed motion. Other methods use gyroscopes to measure angles, but these often suffer from cumulative errors and only provide relatively accurate results over short timescales. More critically, these devices typically focus solely on data collection and preliminary calculations, lacking the ability to deeply process and effectively present the acquired data. This makes it difficult for users to intuitively and clearly grasp the changing trends, characteristics, and inherent patterns of knee joint motion data.

[0003] The invention patent with publication number CN111904426A discloses a method for measuring the angle of the knee joint and its application method, which solves the problems of the current knee joint angle measurement device requiring the use of multiple components, being inconvenient to wear, and being inconvenient to use due to the different leg lengths of people of different heights. The invention patent includes an angle measurement component, which includes a fixed arm, one end of which is rotatably connected to a rotating arm, and the lower part of the rotating arm is rotatably connected to a footrest through a connecting plate. When in use, the patent can adjust the first movable plate and the second movable plate according to the leg length of the person being measured, so that the device can be suitable for people of different heights and is easy to use and wear; the patent has the problem of inaccurate measurement and inability to achieve data visualization.

[0004] Therefore, providing a measuring device that can measure accurately and realize data visualization is an issue that needs to be solved urgently. Summary of the Invention

[0005] The purpose of the present invention is to provide a device and method for measuring knee joint motion in order to overcome the defects of the above-mentioned prior art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] According to one aspect of the present invention, a device for measuring knee joint movement is provided, which is installed at the knee joint. The device includes an upper connecting rod, a lower connecting rod, an angle encoder, a display unit and a control box. The upper connecting rod and the lower connecting rod are connected, the angle encoder is installed at the connection between the upper connecting rod and the lower connecting rod, and the control box is installed on the upper connecting rod. The control box is communicatively connected to the display unit and the angle encoder respectively.

[0008] As a preferred technical solution, the device further includes a third screw, and the angle encoder is fixed by the third screw and the upper connecting rod.

[0009] As a preferred technical solution, the device further includes an intermediate shaft and a transmission shaft, wherein the intermediate shaft is mounted on the lower connecting rod, the transmission shaft is mounted on the intermediate shaft, and the transmission shaft is connected to an angle encoder.

[0010] As a preferred technical solution, the intermediate shaft, transmission shaft and angle encoder are coaxial; the angle encoder and knee joint are coaxial.

[0011] As a preferred technical solution, the device further includes a retaining spring and a fourth screw, the intermediate shaft is connected and fixed to the upper connecting rod via the retaining spring, and the transmission shaft is connected and fixed to the angle encoder via the fourth screw.

[0012] As a preferred technical solution, the device also includes a hinge, the upper connecting rod includes a first upper connecting rod and a second upper connecting rod, the lower connecting rod includes a first lower connecting rod and a second lower connecting rod, the first upper connecting rod is connected to the second upper connecting rod by a hinge, the first lower connecting rod is connected to the second lower connecting rod by a hinge, and the second upper connecting rod is connected to the first lower connecting rod.

[0013] As a preferred technical solution, the device further includes a fixing unit, which is installed on the upper connecting rod and the lower connecting rod.

[0014] As a preferred technical solution, the fixing unit includes a fixing sleeve and a binding strap, the fixing sleeve is mounted on the upper connecting rod and the lower connecting rod, and the binding strap is mounted on the fixing sleeve.

[0015] As an optimal technical solution, the control box includes a control unit, a battery function board and a Bluetooth unit. The battery function board is electrically connected to the control unit, the Bluetooth unit and the angle encoder respectively. The control unit is communicatively connected to the Bluetooth unit and the angle encoder respectively. The Bluetooth unit is communicatively connected to the display unit.

[0016] According to another aspect of the present invention, a measurement method for a knee joint motion measurement device as described above is provided, the measurement method comprising the following steps:

[0017] S1. Install the device correctly;

[0018] S2, start the device and record the initial angle and initial time of the angle encoder;

[0019] S3. Obtaining an angle change from the angle encoder at preset intervals to obtain a set of time and angle change;

[0020] S4. Fitting an expression of angle change over time based on the data in the set, drawing a curve based on the expression and displaying it on a display unit;

[0021] S5. Perform real-time derivative calculation on the expression to calculate the angular velocity and angular acceleration at the corresponding time.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention collects the current angle change through the angle encoder, and the display unit processes the real-time data and visualizes the processing results to show the change trend of the current angle. The angle measurement is accurate and the result display is intuitive.

[0024] 2. The angle encoder of the present invention is installed at the knee joint, and the knee joint and the angle encoder are coaxial, ensuring that the rotation directions of the two are consistent, which can better detect angle changes.

[0025] 3. The present invention is also provided with a hinge, so that both the upper connecting rod and the lower connecting rod can be locally fine-tuned according to different body shapes, so that they can better fit the legs and provide measurement accuracy.

[0026] 4. The present invention uses a Bluetooth unit as a wireless communication module, which facilitates the transmission of real-time collected data to the display module for real-time display.

[0027] 5. In the measurement method of the present invention, a collection of multiple sets of data is collected and fitted into corresponding equation expressions. The first-order and second-order derivatives of the expressions are respectively taken, so that the corresponding angular velocity and angular acceleration can be calculated. The appropriate step size can be selected according to the accuracy requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a front view of the present invention;

[0029] Figure 2 is a side view of the present invention;

[0030] Figure 3A top view of the present invention;

[0031] Figure 4 This is a schematic diagram of the installation of the angle encoder of the present invention;

[0032] Figure 5 This is a schematic diagram of the installation of the present invention;

[0033] Figure 6 It is a schematic diagram of the measurement process of the present invention;

[0034] 1. Lower connecting rod; 2. Hinge; 3. Control box; 4. Upper connecting rod; 5. First screw; 6. Fixing block; 7. Strap; 8. Angle encoder; 9. Second screw; 10. Third screw; 11. Circlip; 12. Fourth screw. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figure 1-Figure 5 As shown, a device for measuring knee joint movement is installed at the knee joint. The device includes an upper connecting rod 4, a lower connecting rod 1, an angle encoder 8, a display unit and a control box 3. The upper connecting rod 4 is connected to the lower connecting rod 1, and the angle encoder 8 is installed at the connection between the upper connecting rod 4 and the lower connecting rod 1. The control box 3 is installed on the upper connecting rod 4, and the control box 3 is communicated with the display unit and the angle encoder 8 respectively.

[0038] The device further includes a third screw 10 , and the angle encoder 8 is fixed via the third screw 10 and the upper connecting rod 4 .

[0039] The device further comprises an intermediate shaft and a transmission shaft. The intermediate shaft is mounted on the lower connecting rod 1 , and the transmission shaft is mounted on the intermediate shaft. The transmission shaft is connected to an angle encoder 8 .

[0040] The intermediate shaft, the transmission shaft and the angle encoder 8 are coaxial; the angle encoder 8 and the knee joint are coaxial.

[0041] The device further comprises a retaining spring 11 and a fourth screw 12 . The intermediate shaft is connected and fixed to the upper connecting rod 4 via the retaining spring 11 , and the transmission shaft is connected and fixed to the angle encoder 8 via the fourth screw 12 .

[0042] The device also includes a hinge 2, the upper link 4 includes a first upper link and a second upper link, the lower link 1 includes a first lower link and a second lower link, the first upper link is connected to the second upper link through the hinge 2, the first lower link is connected to the second lower link through the hinge 2, and the second upper link is connected to the first lower link.

[0043] The device further comprises a fixing unit, which is mounted on the upper connecting rod 4 and the lower connecting rod 1 .

[0044] The fixing unit includes a fixing sleeve 6 and a binding belt 7 . The fixing sleeve 6 is mounted on the upper connecting rod 4 and the lower connecting rod 1 , and the binding belt 7 is mounted on the fixing sleeve 6 .

[0045] The control box 3 includes a control unit, a battery function board and a Bluetooth unit. The battery function board is electrically connected to the control unit, the Bluetooth unit and the angle encoder 8 respectively. The control unit is communicatively connected to the Bluetooth unit and the angle encoder 8 respectively. The Bluetooth unit is communicatively connected to the display unit.

[0046] In this embodiment, the measuring device is composed of an upper connecting rod 4, a lower connecting rod 1, a hinge 2, an angle encoder 8, a control box 3, a fixing block 6 and a strap 7. The lower connecting rod 1 is connected to the upper connecting rod 4 and the angle encoder 8 respectively through the intermediate shaft and the transmission shaft thereon. Electronic components such as the battery power supply board, the Bluetooth unit and the control unit are installed in the electric control box 3, and the control box 3 is fixed to the upper connecting rod 4 by a first screw 5. A hinge 2 is installed in the middle of the upper connecting rod 4 and the lower connecting rod 1, so that the upper connecting rod 4 and the lower connecting rod 1 can rotate a certain angle around the hinge 2, so that the device has a better fit when worn on the human body. Two groups of fixing units are installed on each of the upper connecting rod 4 and the lower connecting rod 1, and each group of fixing units includes a fixing sleeve 6 and a strap 7. The fixing sleeve 6 is fixedly connected to the upper connecting rod 4 and the lower connecting rod 1 respectively by a second screw 9.

[0047] The angle encoder 8 is fixed to the upper connecting rod 4 by a third screw 10, and the lower connecting rod 1 is connected to the upper connecting rod 4 and axially fixed through the intermediate shaft and the retaining ring 11 thereon. The rotating shaft on the lower connecting rod 1 is connected to the hole of the angle encoder 8, and the transmission shaft and the angle encoder 8 are fixed together by screws 12, so that the transmission shaft and the angle encoder 8 can rotate synchronously.

[0048] The measuring device is placed on the outside of the human leg. The rotation axis of the angle encoder is aligned with the human knee joint by adjusting the installation position. The device is fixed to the human thigh and calf through four sets of fixing sleeves 6 and straps 7 installed on the upper connecting rod 4 and the lower connecting rod 1 of the device. The hinge 2 installed on the upper connecting rod 4 and the lower connecting rod 1 can rotate at a small angle, which can change the fit between the device and the curve of the human leg, thereby improving the comfort of the subject wearing the device and the accuracy of the measurement.

[0049] like Figure 6 As shown, the workflow of the device for collecting, processing, and analyzing knee joint angle data is as follows: the test subject performs movements, interacting with the angle encoder 8, which transmits the collected angle data to the single-chip microcomputer (MCU) in the control box 3. The display unit includes a display screen and a data processing terminal. After the MCU processes the angle data, it wirelessly transmits the data to the data processing terminal via a Bluetooth unit also located in the control box 3. The data processing terminal simultaneously performs data analysis and image generation, and ultimately outputs the processed results to the display unit (specifically, a monitor) for presentation, thus fully implementing the entire process from knee joint angle data collection, transmission, processing, to visual display. The data processing terminal can be omitted, and all processing by the control unit (MCU) is then transmitted to the display unit for display.

[0050] Example 2

[0051] A measurement method for a measurement device for knee joint motion, the measurement method comprising the following steps:

[0052] S1. Install the device correctly;

[0053] S2, start the device and record the initial angle and initial time of the angle encoder 8;

[0054] S3, obtaining the angle variation from the angle encoder 8 at preset intervals to obtain a set of time and angle variation;

[0055] S4. Fitting an expression of angle change over time based on the data in the set, drawing a curve based on the expression and displaying it on a display unit;

[0056] S5. Perform real-time derivative calculation on the expression to calculate the angular velocity and angular acceleration at the corresponding time.

[0057] In this embodiment, the measurement method includes two specific situations, namely swing measurement and walking measurement.

[0058] Swing measurement

[0059] This embodiment provides a method for using a device for measuring changes in the angle of a human knee joint. The device comprises an angle encoder 8, an upper connecting rod 4, a lower connecting rod 1, a hinge 2, a fixing sleeve 6, and a control box 3. The angle sensor 8 is centrally located and cylindrical. The upper and lower connecting rods are connected to the angle encoder 8. The angle encoder used is MK386C, with an accuracy of ±0.2°. The specific measurement process is as follows:

[0060] Place the person being measured in a quiet, undisturbed environment with ample space. Stand naturally with both knees straight. Use fixing sleeves to firmly fix the upper and lower connecting rods to the thigh and calf of the person being measured, respectively. Ensure that the angle encoder is located directly in front of the knee joint and that the upper and lower hinges can rotate flexibly to ensure that the movement of the device and the knee joint are synchronized and stable during the measurement process.

[0061] Set the initial knee joint angle to 0°, start the measurement program in the control box, and record the starting time t0 = 0s. Instruct the subject to perform knee swinging movements at a moderate speed. The measurement device automatically begins timing, recording the knee joint angle A and the corresponding time t in real time at 0.1s intervals. The recorded data are shown in Tables 1 and 2:

[0062] Table 1

[0063]

[0064] Table 2

[0065] Time t(s) 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 Angle A° 34.1 32.5 29.6 25.5 20.6 14.5 9.4 5.3 2.2 0.6

[0066] While the measuring device is recording data, the wireless communication module in the control box synchronously transmits the real-time collected angle data A and the corresponding time data t to the paired terminal device. After receiving the data, the terminal device performs a fitting analysis on the data, which can be performed using polynomial fitting or other fitting methods. The function of angle with respect to time is obtained as:

[0067] A(t)=-0.34t 6 +2.85t 5 -9.32t 4 +14.43t 3 -8.08t 2 +2.46t

[0068] Compute the derivative of this function:

[0069] (1) First-order derivative (angular velocity ω):

[0070] Taking the first-order derivative of A(t) yields:

[0071] ω(t)=A′(t)=-2.04t 5 +14.25t 4 -37.28t 3 +43.29t 2 -16.16t+2.46

[0072] Substitute different time points into the angular velocity function:

[0073] When t = 0.5s, ω(0.5) = -2.04×(0.5) 5 +14.25×(0.5) 4 -37.28×(0.5) 3 +43.29×(0.5) 2 -16.16×0.5+2.46=1.47° / s

[0074] When t = 1s, ω(1) = -2.04×15 + 14.25×14 - 37.28×13 + 43.29×12 - 16.16×1 + 2.46 = 4.52° / s (2) Second-order derivative (angular acceleration α):

[0075] Taking the second-order derivative of A′(t) yields:

[0076] α(t)=A″(t)=-10.2t 4 +57t 3 -111.84t 2 +86.58t-16.16

[0077] Substitute different time points into the angular acceleration function:

[0078] When t=0.5s, α(0.5)=-10.2×(0.5) 4 +57×(0.5) 3 -111.84×(0.5) 2 +86.58×0.5-16.16=5.65° / s 2

[0079] When t = 1s, α(1) = -10.2×14+57×13-111.84×12+86.58×1-16.16 = 5.38° / s 2

[0080] After the terminal completes data processing, it visualizes the results, including curves showing angle, angular velocity, and angular acceleration over time. It also generates detailed data reports, recording the angle, angular velocity, and angular acceleration values at each time point. In this knee joint motion measurement, the maximum angular velocity and maximum angular acceleration can be further compared with all calculated data.

[0081] Example 3

[0082] Walking measurement

[0083] This embodiment provides a method for using a device for measuring changes in the angle of a human knee joint. The device consists of an angle encoder, an upper connecting rod, a lower connecting rod, a hinge, a fixing sleeve, and a control box. The angle sensor is centered and cylindrical. The upper and lower connecting rods are connected to the angle encoder. The angle encoder used is MK386C, with an accuracy of ±0.2°. The specific measurement process is as follows:

[0084] Choose a quiet, spacious, and flat area for the subject to be measured. Have them stand in a natural and comfortable position with their knees naturally straight. Secure the upper and lower connecting rods to their thighs and calves using mounting sleeves, ensuring the angle encoder is precisely positioned lateral to the knee joint. Also, adjust the upper and lower hinges for flexible rotation, ensuring the device and knee joint movement remain synchronized and stable throughout the measurement process.

[0085] Set the initial knee joint angle to 0°. Activate the measurement function in the control box and accurately record the starting time t0 = 0s. Instruct the subject to begin walking at a normal walking speed and cadence. The measurement device automatically activates the timing function and records the knee joint angle A and the corresponding time t in real time at 0.1s intervals. The specific recorded data are shown in Tables 3 and 4:

[0086] Table 3

[0087]

[0088] Table 4

[0089] Time t(s) 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 Angle A° 18.1 14.6 10.1 6.5 3.4 1.1 0.1 1.1 3.5 6.4

[0090] While the measuring device is recording data, the wireless communication module in the control box synchronously transmits the real-time collected angle data A and the corresponding time data t to the paired terminal device. After receiving the data, the terminal device performs a fitting analysis on the data and obtains the function of angle with respect to time as:

[0091] A(t)=-0.35t 5 +2.24t 4 -4.69t 3 +3.83t 2 +3.05 t .

[0092] Derivative calculation:

[0093] (1) First-order derivative (angular velocity ω):

[0094] Taking the first-order derivative of A(t) yields:

[0095] ω(t)=A′(t)=-1.75t 4 +8.96t3 -14.07t 2 +7.66t+3.05

[0096] Substitute different time points into the angular velocity function:

[0097] When t = 0.5s, ω(0.5) = -1.75×(0.5) 4 +8.96×(0.5) 3 -14.07×(0.5) 2 +7.66×0.5+3.05

[0098] =4.37° / s

[0099] When t = 1s, ω(1) = -1.75×14 + 8.96×13 - 14.07×12 + 7.66×1 + 3.05 = 3.85° / s

[0100] (2) Second-order derivative (angular acceleration α):

[0101] Taking the second-order derivative of A′(t) yields:

[0102] α(t)=A″(t)=-7t 3 +26.88t 2 -28.14t+7.66

[0103] Substitute different time points into the angular acceleration function:

[0104] When t = 0.5s, α(0.5) = -7×(0.5) 3 +26.88×(0.5) 2 -28.14×0.5+7.66=-0.56° / s 2

[0105] When t = 1s, α(1) = -7×13+26.88×12-28.14×1+7.66=-0.6° / s 2

[0106] After the terminal completes data processing, it visualizes the results, including curves showing angle, angular velocity, and angular acceleration over time. It also generates detailed data reports, recording the angle, angular velocity, and angular acceleration values at each time point. In this knee joint motion measurement, the maximum angular velocity and maximum angular acceleration were determined by comparing all calculated data.

[0107] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A device for measuring knee joint motion, the device being installed at the knee joint, characterized in that: The device comprises an upper connecting rod (4), a lower connecting rod (1), an angle encoder (8), a display unit and a control box (3); the upper connecting rod (4) and the lower connecting rod (1) are connected; the angle encoder (8) is installed at the connection between the upper connecting rod (4) and the lower connecting rod (1); the control box (3) is installed on the upper connecting rod (4); and the control box (3) is respectively connected to the display unit and the angle encoder (8) for communication.

2. A knee joint motion measuring device according to claim 1, characterized in that: The device further comprises a third screw (10), and the angle encoder (8) is fixed via the third screw (10) and the upper connecting rod (4).

3. A knee joint motion measuring device according to claim 2, characterized in that: The device further comprises an intermediate shaft and a transmission shaft, wherein the intermediate shaft is mounted on the lower connecting rod (1), the transmission shaft is mounted on the intermediate shaft, and the transmission shaft is connected to an angle encoder (8).

4. The knee joint motion measuring device according to claim 3, characterized in that: The intermediate shaft, the transmission shaft and the angle encoder (8) are coaxial; the angle encoder (8) and the knee joint are coaxial.

5. The knee joint motion measuring device according to claim 3, characterized in that: The device further comprises a retaining spring (11) and a fourth screw (12); the intermediate shaft is connected and fixed to the upper connecting rod (4) via the retaining spring (11); and the transmission shaft is connected and fixed to the angle encoder (8) via the fourth screw (12).

6. The knee joint motion measuring device according to claim 1, characterized in that: The device also includes a hinge (2), the upper link (4) includes a first upper link and a second upper link, the lower link (1) includes a first lower link and a second lower link, the first upper link is connected to the second upper link via the hinge (2), the first lower link is connected to the second lower link via the hinge (2), and the second upper link is connected to the first lower link.

7. The knee joint motion measuring device according to claim 1, characterized in that: The device further comprises a fixing unit, which is mounted on the upper connecting rod (4) and the lower connecting rod (1).

8. The knee joint motion measuring device according to claim 7, characterized in that: The fixing unit comprises a fixing sleeve (6) and a binding belt (7); the fixing sleeve (6) is mounted on the upper connecting rod (4) and the lower connecting rod (1); and the binding belt (7) is mounted on the fixing sleeve (6).

9. The knee joint motion measuring device according to claim 1, characterized in that: The control box (3) comprises a control unit, a battery function board and a Bluetooth unit, wherein the battery function board is electrically connected to the control unit, the Bluetooth unit and the angle encoder (8) respectively, the control unit is communicatively connected to the Bluetooth unit and the angle encoder (8) respectively, and the Bluetooth unit is communicatively connected to the display unit.

10. A measurement method for the knee joint motion measurement device according to any one of claims 1 to 9, characterized in that: The measurement method The following processes are included: S1. Install the device correctly; S2, starting the device and recording the initial angle and initial time of the angle encoder (8); S3, obtaining an angle variation from the angle encoder (8) at predetermined intervals to obtain a set of time and angle variation; S4. Fitting an expression of angle change over time based on the data in the set, drawing a curve based on the expression and displaying it on a display unit; S5. Perform real-time derivative calculation on the expression to calculate the angular velocity and angular acceleration at the corresponding time.

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