Joint center of rotation alignment device

Abstract

The utility model provides a joint rotary center alignment device, its alignment device includes seat, dynamometer, support and measurement component, support sliding configuration is in the mechanical arm of dynamometer, is used for connecting the user's limbs on seat, and according to its position adjustment effective arm length of mechanical arm on the mechanical arm, measurement component is configured to dynamometer, is used for measuring the rotary angle of dynamometer mechanical arm and corresponding dynamometer mechanical arm's side swing angle and the distance of support relative mechanical arm rotary center. The utility model calculates joint actual rotary center through the space geometric model of establishment, automatically compares the theoretical rotary center position, generates the calibration parameter and feeds back to the control system of alignment device, real -time monitoring mechanical arm and the pose difference of limb movement, realizes the dynamic compensation of mechanical rotary center relative joint rotary center in the testing process, promotes the training effect and the comfort, to solve the measurement error problem of traditional equipment because the man -machine rotary center does not coincide.

Description

Technical Field

[0001] This utility model relates to the field of rehabilitation medical technology, and in particular to a joint rotation center alignment device. Background Technology

[0002] Isokinetic strength testing is a professional device used to accurately assess muscle strength, endurance, and muscle function, and is widely used in medicine, rehabilitation, sports science, and other fields. Unlike traditional muscle strength assessment methods, isokinetic strength testing measures muscle force output by maintaining a constant movement speed, ensuring that the muscle contraction speed does not change during the test. This eliminates the interference of movement speed on muscle strength measurement results and provides more accurate and consistent test data.

[0003] The core principle of isokinetic muscle strength testing is isokinetic motion, meaning that during the test, the instrument uses mechanical devices to maintain the subject's muscle contraction at a specified speed. In this way, muscle force output is independent of speed, accurately reflecting muscle performance at a specific speed. This principle is particularly suitable for sports injury rehabilitation, muscle strength assessment, and performance monitoring during sports training. Unlike traditional "maximum strength" testing methods, isokinetic testing eliminates biases caused by differences in operation or testing speed between test subjects, thus obtaining more standardized results.

[0004] Isokinetic muscle strength testing instruments have a wide range of applications. They are mainly used in the clinical rehabilitation field to assess the muscle strength recovery of patients (such as those with stroke or spinal cord injury) and guide personalized rehabilitation plans; in the field of sports medicine to analyze athletes' muscle strength, endurance, imbalance, and fatigue levels to optimize training and prevent injury; in the field of elderly health management to monitor signs of muscle decline and develop anti-aging exercise and rehabilitation programs; and in the scientific research field to accurately quantify muscle physiological mechanisms, training effects, and neuromuscular synergy, promoting the development of sports science and biomechanics research.

[0005] While isokinetic muscle strength testing devices offer significant advantages in muscle function assessment, they also face several challenges and limitations. The most significant is that, because isokinetic muscle strength testing devices operate on the principle of equivalent human movement, they need to maintain consistency with the limb's movement path. This means the center of rotation of the testing device must coincide with the center of rotation of the limb. However, existing isokinetic muscle strength testing devices lack the function to calibrate the actual center of rotation of the user's limb. They typically rely on touch and observation to roughly determine the position of the joint's center of rotation. This method introduces errors in the position of the limb's center of rotation, leading to discrepancies between the measured torque and the actual torque.

[0006] Other devices used to assist in training human joints often require alignment between the human joint and the center of the device.

[0007] It should be noted that the information disclosed in the above background section is only used to enhance the understanding of the background of this utility model and does not constitute any limitation on this utility model. Utility Model Content

[0008] In view of the shortcomings of the prior art described above, this utility model provides a joint rotation center alignment device, which reduces measurement errors and improves training effect and comfort by determining the position of the equivalent joint rotation center of the alignment device rotation center, thereby solving the measurement error problem caused by the misalignment of human and machine rotation centers in traditional equipment.

[0009] This utility model provides a joint rotation center alignment device, comprising: Seats are used to support users; A force gauge is used to measure a user's limb strength. It is supported and slidably mounted on the robotic arm of the force measuring instrument to connect to the user's limbs and adjust the effective lever arm length of the robotic arm according to the user's position on the robotic arm. The measuring component, configured on the force gauge, is used to measure the rotation angle of the force gauge robotic arm, the corresponding lateral swing angle of the force gauge robotic arm, and the distance of the support relative to the rotation center of the robotic arm.

[0010] In one embodiment of this utility model, the measuring component includes: The lateral swing section is located at the hinge between the robotic arm and the robotic arm's rotation axis, and is used to allow the robotic arm to swing laterally relative to its rotation axis. A displacement sensor, configured on the support, is used to measure the displacement parameters of the support; An angle sensor, located on the lateral swing shaft at the pivot and hinge, is used to measure the rotation angle of the pivot and the lateral swing angle of the robotic arm.

[0011] In one embodiment of the present invention, a displacement sensor is used to obtain the distance between the support and the rotation axis and the displacement distance of the support on the robotic arm, and an angle sensor is used to obtain the rotation angle of the robotic arm as it rotates with the rotation axis and the lateral swing angle of the robotic arm around the lateral swing axis.

[0012] This utility model also provides a method for aligning the rotation center of a joint, including: Step 1: Initially align the rotation center of the joint to be tested on the human body with the rotation center of the robotic arm of the force measuring instrument; Step 2: Fix the limb of the joint to be tested on the support of the force measuring machine's robotic arm; Step 3: Keep the joint to be tested stationary on the support of the force measuring instrument's robotic arm, and rotate the limb; Step 4: Record at least three different rotation angles of the force measuring robot arm during the movement process, the corresponding lateral swing angle of the force measuring robot arm, and the distance of the support relative to the rotation center of the robot arm; Step 5: Based on at least three rotation angles, side swing angles, and the distance of the support relative to the rotation center of the robotic arm, obtain the position parameters of the joint under test relative to the rotation center, or the position parameters relative to the rotation center and the angle between the plane containing the support motion trajectory and the plane perpendicular to the rotation axis of the force measuring instrument robotic arm. Step 6: Align the rotation center of the joint to be tested on the human body with the rotation center of the force measuring robot arm.

[0013] In one embodiment of this utility model, the step of recording at least three different rotation angles of the force measuring robot arm and the corresponding lateral swing angle of the force measuring robot arm, as well as the distance of the support relative to the rotation center of the robot arm, during the motion includes: Obtain the rotation angle α of the force measuring robot arm as it rotates around the robot arm's rotation axis; Obtain the lateral swing angle β of the force measuring robot arm rotating about a lateral swing axis that is perpendicular to the rotation axis of the robot arm; Obtain the distance L between the support on the force measuring robot arm and the center of rotation of the robot arm during motion; Using the rotation center of the robotic arm as the origin of the spatial coordinate system, the Y-axis of the spatial coordinate system is set to correspond to the axis of the robotic arm's rotation axis, and the X-axis of the spatial coordinate system is located in the rotation plane and corresponds to the initial position of the robotic arm's rotation angle α. The coordinate expression of the position parameters corresponding to the spatial coordinate system is calculated.

[0014] In one embodiment of this utility model, the step of obtaining the position parameters of the joint to be tested relative to the center of rotation further includes: Select the coordinate expressions of the support position parameters corresponding to at least three sets of different rotation angles during the limb movement driven by the force measuring instrument in a spatial rectangular coordinate system; The position parameters of the rotation center of the joint under test are calculated based on the cocircular geometric relationship of the corresponding support positions.

[0015] In one embodiment of this utility model, the step of determining at least three rotation angles, lateral swing angles, and the distance of the support relative to the rotation center of the robotic arm includes: Taking the selection of three positional parameters as an example, we define... The coordinates of the limb rotation center are: The coordinates of the support on the force measuring robot arm at three different positions during the operation of the force measuring instrument; based on Robotic arm rotation angle corresponding to position parameters Substituting it into the coordinate expression yields The coordinate parameters.

[0016] In one embodiment of this utility model, the step of selecting the coordinate expressions of the position parameters of at least three sets of supports with different rotation angles during the movement of the limb driven by the force measuring instrument in a spatial rectangular coordinate system includes: Calculate the plane normal vector and plane equation based on the coordinate parameters in the spatial rectangular coordinate system corresponding to at least three sets of position parameters; Establish constraint equations based on at least three sets of coordinate parameters and the equidistant condition of the rotation center of the joint to be tested; Calculate the coordinates of the center of rotation of the joint to be tested, or the coordinates and included angle of the center of rotation of the joint to be tested.

[0017] In one embodiment of this utility model, the step of calculating the plane normal vector based on the coordinate parameters in a spatial rectangular coordinate system corresponding to at least three sets of position parameters includes: Select any point from the support coordinates of at least three force gauge robotic arms as a reference point, and calculate the spatial vector from the reference point to the other points respectively; The normal vector of the plane containing the coordinate parameters is obtained by the cross product operation.

[0018] In one embodiment of this utility model, the step of establishing constraint equations based on at least three sets of coordinate parameters and the equidistant condition of the limb rotation center includes: Establish constraint equations based on at least three sets of coordinate parameters and the equidistant condition of the limb rotation center; A set of constraint equations is formed based on the constraint equations and the plane equations determined by at least three sets of coordinate parameters.

[0019] The beneficial effects of this invention are as follows: The actual rotation center of the joint is calculated through an established spatial geometric model. It automatically compares the theoretical rotation center position with the actual position, generates calibration parameters, and feeds them back to the alignment device's control system. Utilizing the characteristic of the support on the force measuring robotic arm moving in a circular motion around the joint center, the center position is determined through inverse geometric calculation. The measuring component monitors the pose difference between the robotic arm and the limb movement in real time, achieving dynamic compensation of the mechanical rotation center relative to the joint rotation center during testing. Furthermore, it can be reused to achieve higher alignment accuracy.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the present invention. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments conforming to the present invention and, together with the description, serve to explain the principles of the present invention. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 A schematic diagram of the spatial coordinate system established for the joint rotation center alignment device of this utility model.

[0022] Figure 2 This is a schematic diagram showing three position points selected in the spatial coordinate system of the joint rotation center alignment device of this utility model.

[0023] In the diagram: 10, seat; 20, force gauge; 21, robotic arm; 22, support; 23, side swing section; 24, rotary axis. Detailed Implementation

[0024] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. It should also be understood that the terminology used in the embodiments of this utility model is for describing specific implementation schemes and not for limiting the scope of protection of this utility model.

[0025] Please see Figures 1 to 2 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of this invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness or purpose of this invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms used in this specification regarding position, quantity, etc., are merely for clarity and not intended to limit the scope of this invention. Changes or adjustments to these relative relationships, without substantially altering the technical content, should also be considered within the scope of this invention's implementation.

[0026] Please see Figure 1 This utility model also provides a joint rotation center alignment device, comprising: Seat 10 is used to support the user; Force gauge 20 is used to measure the user's limb strength; A measuring component, configured in force gauge 20, is used to measure positional parameters of the positional relationship between the actual rotation center of the limb joint and the theoretical rotation center of the robotic arm 21 of force gauge 20.

[0027] Specifically, in this embodiment of the invention, the user sits on the seat 10 to complete various force measurement experiments. The force measuring instrument 20 is an isokinetic muscle strength tester, which is used to perform force measurement experiments on the user's limbs. The power mechanism of the force measuring instrument 20 provides power to make its robotic arm 21 move synchronously with the limbs, and the force measurement results are analyzed based on the torque fed back to the robotic arm 21. The measurement component is an instrument component set up to collect the parameters required to calculate the position of the limb's rotation center.

[0028] Thus, motion calibration is achieved through an integrated joint rotation center alignment device. The main structure of the alignment device includes an ergonomically adjustable seat 10, which can be equipped with a multi-directional locking mechanism and a body position fixation device to ensure the stability of the user's body position during testing. The force meter 20, i.e., the isokinetic muscle strength tester, serves as the core measurement unit and can integrate a high-precision servo drive system and a six-dimensional force sensor, enabling real-time acquisition of mechanical parameters during limb movement. The measurement components employ multiple sensors, including angle encoders, displacement sensors, and inertial measurement units, forming a comprehensive motion parameter acquisition network.

[0029] Thus, based on a dynamic motion compensation mechanism, the alignment device monitors the pose difference between the robotic arm 21 and the limb movement in real time during the test, and calculates the actual rotation center of the joint through an established spatial geometric model. It automatically compares the theoretical rotation center position, generates calibration parameters, and feeds them back to the alignment device's control system, achieving dynamic compensation during the test. This solves the measurement error problem caused by the misalignment of the human-machine rotation centers in traditional equipment.

[0030] Please see Figure 2 In one embodiment, the measurement component includes: Support 22 is mounted on the robotic arm 21 of the force measuring instrument 20 to connect to the user's limb and adjust the effective lever arm length of the robotic arm 21 according to the user's position on the robotic arm 21. The lateral swing section 23 is disposed at the hinge between the robotic arm 21 and the rotation axis 24 of the robotic arm 21, and is used to allow the robotic arm 21 to swing laterally relative to its rotation axis 24. A displacement sensor, configured on support 22, is used to measure the displacement parameters of support 22; An angle sensor, configured on the lateral swing shaft at the hinge of the rotary shaft 24, is used to measure the rotation angle of the rotary shaft 24 and the lateral swing angle of the robotic arm 21.

[0031] Specifically, in this embodiment of the utility model, with Figure 2 The isokinetic muscle strength testing device shown is a testing mechanism aimed at measuring the force of knee flexion and extension in humans. During the preparation phase, it calibrates to address the issue of misalignment of the joint centers. Its support 22 is mounted on the aforementioned robotic arm 21, and the support 22 can slide along the arm length of the robotic arm 21 within a groove. The support 22 is fixed to the user's limb by clamps or straps, and the lever arm length of the robotic arm 21's rotational movement can be changed by sliding it on the robotic arm 21. A lateral swing section 23 is mounted at the hinge connection between the robotic arm 21 and the rotation axis 24, allowing the robotic arm 21 to swing laterally around the hinge point in a plane perpendicular to the rotation plane of the rotation axis 24. A displacement sensor is mounted on the support 22 to measure the support displacement caused by the misalignment of the limb joint rotation center with the rotation center of the force measuring device 20 during movement. Angle sensors are mounted on the rotation axis 24 and the lateral swing axis of the lateral swing section 23 to measure the angle of synchronous rotation of the limb with the rotation axis 24 and the angle of lateral swing of the robotic arm 21 relative to the rotation axis 24. In this way, the coordinated work of the two sets of sensors completely records the motion trajectory and posture changes of the robotic arm 21 in three-dimensional space, providing displacement and angle parameter data for joint center calculation.

[0032] Please see Figure 2 In one embodiment, a displacement sensor is used to obtain the distance between the support 22 and the rotation axis 24 and the displacement distance of the support 22 on the robotic arm 21, and an angle sensor is used to obtain the rotation angle of the robotic arm 21 as it rotates with the rotation axis 24 and the lateral swing angle of the robotic arm 21 about the lateral swing axis.

[0033] Specifically, in this embodiment of the invention, joint kinematic parameters are acquired through collaborative measurement. The displacement measurement module monitors the radial distance change between the support 22 and the rotation axis 24 in real time using a high-precision displacement sensor, reflecting the dynamic adjustment of the effective lever arm length of the robotic arm 21; and the displacement of the support 22 along the axial direction of the robotic arm 21, capturing the compensating motion caused by the joint center offset. Angle sensors collect and record the circular motion trajectory of the robotic arm 21 around the rotation axis 24, and measure the attitude deviation of the robotic arm 21 relative to the ideal rotation plane, i.e., the lateral swing angle. Thus, the measured displacement parameters provide a linear motion reference for joint center calculation. The measured angle parameters reflect the complex motion state of the robotic arm 21 in three-dimensional space, providing an angular reference for subsequent joint center calculation.

[0034] This embodiment also provides a method for aligning the center of rotation of a joint, including: Step 1: Initially align the rotation center of the joint to be tested on the human body with the rotation center of the robotic arm of the force measuring instrument; Step 2: Fix the limb of the joint to be tested on the support of the force measuring machine's robotic arm; Step 3: Keep the joint to be tested stationary on the support of the force measuring instrument's robotic arm, and rotate the limb; Step 4: Record at least three different rotation angles of the force measuring robot arm during the movement process, the corresponding lateral swing angle of the force measuring robot arm, and the distance of the support relative to the rotation center of the robot arm; Step 5: Based on at least three rotation angles, side swing angles, and the distance of the support relative to the rotation center of the robotic arm, obtain the position parameters of the joint under test relative to the rotation center, or the position parameters relative to the rotation center and the angle between the plane containing the support motion trajectory and the plane perpendicular to the rotation axis of the force measuring instrument robotic arm. Step 6: Align the rotation center of the joint to be tested on the human body with the rotation center of the force measuring robot arm.

[0035] Specifically, in this embodiment of the invention, the force measuring instrument is an isokinetic muscle strength tester. Taking the selection of three support position parameters as an example, the position of the support on the force measuring instrument's robotic arm relative to the rotation center of the robotic arm is measured during the operation of the force measuring instrument. Then, three different support position parameters are selected and substituted into the formula to determine the coordinates in the spatial coordinate system. Finally, the actual position of the rotation center can be determined by the fixed geometric relationship between the three coordinate points and the limb rotation center in space.

[0036] More specifically, the alignment of the human limb joint center with the mechanical rotation center of the force measuring instrument is achieved through measurement and calculation, or the angle between the position of the joint under test relative to the rotation center and the plane containing the support trajectory and the vertical plane of the rotation axis of the force measuring instrument's robotic arm is calculated. This achieves alignment between the human limb joint center and the mechanical rotation center of the force measuring instrument, as well as between the rotation axis of the human limb joint center and the rotation axis of the force measuring instrument's robotic arm. During the test, the dynamic motion parameters of the support on the force measuring instrument's robotic arm relative to the rotation center are collected in real time. These parameters may include the rotation angle of the robotic arm around the rotation axis, the lateral swing angle of the robotic arm relative to the rotation axis, the distance between the support on the force measuring instrument's robotic arm and the rotation center of the force measuring instrument's robotic arm, and the compensated displacement of the support along the robotic arm. Measurements are performed using corresponding sensors mounted on the robotic arm to ensure the accuracy and timeliness of data acquisition.

[0037] Furthermore, by selecting three distinct feature points along the limb's motion trajectory, the motion parameters corresponding to each point are substituted into the spatial coordinate transformation formula. The measured rotation angle, lateral swing angle, and displacement are converted into coordinate values ​​in a three-dimensional Cartesian coordinate system, yielding the coordinates of three non-collinear spatial points. Then, a system of equations for these three spatial coordinate points is established based on spatial geometry principles. Utilizing the geometric relationship that the three feature points are coplanar and equidistant from the center of rotation, a system of equations for equidistant conditions and planar constraints is constructed. Solving this system of equations through matrix operations allows for the accurate calculation of the spatial coordinates of the actual center of rotation of the limb. Finally, the calculated coordinates of the actual center of rotation are compared with the theoretical center of rotation of the robotic arm. Automatic calibration is achieved by adjusting the robotic arm's motion trajectory or test parameters, effectively eliminating measurement errors caused by center misalignment and making the test results more accurate and reliable. This method is applicable to various isokinetic muscle strength testing devices and joint movement devices, significantly improving the accuracy of rehabilitation assessment and user experience.

[0038] In one embodiment, the step of recording at least three different rotation angles of the force-measuring robotic arm and the corresponding lateral swing angles of the force-measuring robotic arm, as well as the distance of the support relative to the rotation center of the robotic arm, during the motion includes: Obtain the rotation angle α of the force measuring robot arm as it rotates around the robot arm's rotation axis; Obtain the lateral swing angle β of the force measuring robot arm rotating about a lateral swing axis that is perpendicular to the rotation axis of the robot arm; Obtain the distance L between the support on the force measuring robot arm and the center of rotation of the robot arm during motion; Using the rotation center of the robotic arm as the origin of the spatial coordinate system, the Y-axis of the spatial coordinate system is set to correspond to the axis of the robotic arm's rotation axis, and the X-axis of the spatial coordinate system is located in the rotation plane and corresponds to the initial position of the robotic arm's rotation angle α. The coordinate expression of the position parameters corresponding to the spatial coordinate system is calculated.

[0039] Specifically, in this embodiment of the invention, the position parameters of the joint to be tested relative to the rotation center of the force measuring robot arm during operation are obtained by fixing the limb to be tested on the support of the force measuring robot arm. This position parameter is then used to determine the position parameters of the support of the robot arm relative to the rotation center of the force measuring robot arm during operation. A precise spatial motion model is established through multi-sensor collaborative measurement. First, a spatial rectangular coordinate system is established; please refer to the appendix. Figure 1 and Figure 2Using the physical connection point between the robotic arm and the rotation axis as the origin, the Y-axis is determined to coincide with the rotation axis, the X-axis corresponds to the initial horizontal position of the robotic arm, and the Z-axis is established vertically upward according to the right-hand rule. This coordinate system provides a unified reference for all motion parameters. Through real-time measurements by displacement and angle sensors, the rotation angle α of the robotic arm in the rotation plane is obtained, reflecting the basic motion state of the robotic arm. The rotation direction of the robotic arm rotation angle α is from the positive X-axis direction to the positive Z-axis direction. The lateral swing angle β of the robotic arm relative to the rotation plane is obtained to capture the spatial attitude changes during motion. The rotation direction of the lateral swing angle β is from the XOZ coordinate plane to the positive Y-axis direction. Simultaneously, the effective lever arm length L is recorded to fully describe the changes in the positional parameters of the support on the force measuring robotic arm.

[0040] Furthermore, a mapping relationship between position parameters and spatial coordinates is established. The collected rotation angle α, lateral tilt angle β, and effective lever arm L parameters are mapped to a pre-established spatial rectangular coordinate system according to a defined transformation rule, providing an accurate coordinate data foundation for subsequent joint center calculations.

[0041] In one embodiment, the step of obtaining the position parameters of the joint to be tested relative to the center of rotation further includes: Select the coordinate expressions of the support position parameters corresponding to at least three sets of different rotation angles during the limb movement driven by the force measuring instrument in a spatial rectangular coordinate system; The position parameters of the rotation center of the joint under test are calculated based on the cocircular geometric relationship of the corresponding support positions.

[0042] Specifically, in this embodiment of the invention, high-precision positioning of the supports on the force-measuring robotic arm at three different positions is achieved by using the spatial characteristics of the limb movement trajectory for reverse engineering. By clarifying the geometric relationship between the supports on the force-measuring robotic arm and the joint center, it is known that during the movement, the supports on the force-measuring robotic arm always perform circular motion around the joint rotation center. By selecting three different position points on the limb movement trajectory, it can be determined that these points must be located on the same spatial circle, and the center of this circle is the position of the joint rotation center that needs to be determined.

[0043] Furthermore, geometric constraints are established to ensure that the three points are concyclic. The support positions on the three force-measuring robotic arms must satisfy the coplanarity condition in a spatial rectangular coordinate system and maintain an equal radial distance from the joint rotation center. The selection of the three feature points needs to consider the representativeness of the motion range, and they are usually spaced at least 30 degrees apart to form a good spatial distribution.

[0044] Thus, the center of rotation is determined through circular center positioning. Based on the characteristics of circular motion, the center position of the spatial circumference corresponding to the support on the three force-measuring robotic arms is the actual center of rotation of the limb joint. This avoids the difficulty of directly measuring the joint center and achieves indirect positioning through motion trajectory analysis, resulting in non-contact, high-precision measurement.

[0045] In one embodiment, the step of determining at least three rotation angles, lateral swing angles, and the distance of the support relative to the rotation center of the robotic arm includes: Taking the selection of three positional parameters as an example, we define... The coordinates of the limb rotation center are: The coordinates of the support on the force measuring robot arm at three different positions during the operation of the force measuring instrument; based on correspond Substituting it into the coordinate expression yields The coordinate parameters.

[0046] Specifically, in this embodiment of the invention, the rotation center is defined using three location points as an example. and the position coordinates of three different locations By establishing a mathematical model, motion parameters are standardized to convert the collected raw motion parameters into unified spatial coordinates. A spatial coordinate reference system is established, with the robotic arm's rotation center as the origin. The X, Y, and Z axes are determined according to the right-hand rule, constructing a complete spatial rectangular coordinate system. This coordinate system provides a unified mathematical foundation for all motion parameters, ensuring the accuracy and consistency of subsequent calculations. The distance from any position point to the center point is L.

[0047] Furthermore, the motion parameters (including rotation angle, lateral swing angle, and displacement) collected at three different positions are substituted into a preset coordinate transformation model to generate three sets of corresponding spatial coordinate values. Then, the correlation between the coordinate parameters and the joint center is established. The three sets of transformed spatial coordinates not only reflect the specific position of the support on the force gauge robotic arm but also its spatial geometric relationship with the joint's rotation center. These coordinate parameters provide standardized parameters for subsequent geometric analysis, serving as the data basis for solving the joint center position.

[0048] In one embodiment, such as Figure 1 and Figure 2 As shown, let The coordinates of the limb rotation center. Calculate the coordinates of the support at three different positions during the operation of the force measuring instrument. The required parameters include: the robot arm rotation angle α and the robot arm lateral swing angle β, measured by the aforementioned angle sensors; the initial lever arm L, the distance from the connection point of the upper rotary shaft of the robot arm to the support in the initial stationary state; and the support displacement ΔL, measured by the displacement sensor. Taking any point in the spatial rectangular coordinate system as an example, given the robot arm rotation angle α, the robot arm lateral swing angle β, and the effective lever arm L, its coordinate expression can be calculated as follows: .and Each has a corresponding Substituting the above parameters into the coordinate expression will yield the corresponding coordinates.

[0049] In one embodiment, the step of selecting the coordinate expressions of the position parameters of at least three sets of supports with different rotation angles during the movement of the limb driven by the force measuring instrument in a spatial rectangular coordinate system includes: Calculate the plane normal vector and plane equation based on the coordinate parameters in the spatial rectangular coordinate system corresponding to at least three sets of position parameters; Establish constraint equations based on at least three sets of coordinate parameters and the equidistant condition of the rotation center of the joint to be tested; Calculate the coordinates of the center of rotation of the joint to be tested, or the coordinates and included angle of the center of rotation of the joint to be tested.

[0050] Specifically, in this embodiment of the invention, the geometric constraint equations of the system are established by using the principles of spatial analytical geometry to achieve the positioning of the joint center through inverse solving. The normal vector of the motion plane is calculated and determined using vector analysis methods based on the spatial coordinates of the supports on the three force-measuring robotic arms, thereby capturing the spatial orientation characteristics of the limb's motion trajectory and providing planar constraint conditions for subsequent calculations, ensuring that the solution process conforms to the actual kinematic laws of the limb.

[0051] Furthermore, based on the fundamental characteristics of circular motion, equidistant constraints were established between the supports and the joint rotation centers of the three force-measuring robotic arms. These constraints were transformed into equations, forming a complete system of equations together with the planar equations, providing sufficient mathematical constraints for solving the problem. Thus, the established constraint equation system was solved using matrix operations to obtain the spatial coordinates of the joint rotation centers. Through systematic geometric modeling and constraint solving, the joint centers were located, thereby enabling the calibration of the rotation centers of the force-measuring robotic arms.

[0052] In one embodiment, the step of calculating the plane normal vector of a plane determined by coordinate parameters in a spatial rectangular coordinate system corresponding to at least three sets of position parameters includes: Select any point from the support coordinates of at least three force gauge robotic arms as a reference point, and calculate the spatial vector from the reference point to the other points respectively; The normal vector of the plane containing the coordinate parameters is obtained by the cross product operation.

[0053] Specifically, in this embodiment of the invention, by constructing a feature vector space relationship, for example... and The relative positions of three points are expressed using two vectors. Then, the cross product operation is used. By calculating the cross product of two eigenvectors, the normal vector of the plane is directly obtained. The cross product operation ensures the perpendicular relationship between the normal vector and the motion plane, providing planar orientation parameters for the subsequent establishment of constraint equations. Thus, by analyzing the calculation results, it is ensured that they accurately represent the spatial characteristics of the plane containing the limb movement trajectory.

[0054] In one embodiment, the step of establishing constraint equations based on at least three sets of coordinate parameters and the equidistant condition of the limb rotation center includes: Establish constraint equations based on at least three sets of coordinate parameters and the equidistant condition of the limb rotation center; A set of constraint equations is formed based on the constraint equations and the plane equations determined by at least three sets of coordinate parameters.

[0055] Specifically, in this embodiment of the invention, calculations are performed by constructing effective mathematical constraints using spatial geometric relationships based on established geometric constraints. First, a mathematical expression for the equidistant condition is established. According to the basic characteristics of circular motion, the distances from the joint rotation center to the supports on the three force-measuring robotic arms must be equal. Based on its geometric characteristics, this is transformed into two independent equations, providing crucial distance constraints for solving the problem.

[0056] Furthermore, the calculated plane normal vector is combined with the support coordinates on any of the force gauge robotic arms to establish a plane equation. This equation serves as the third key constraint condition, forming a complete set of constraint equations together with the two equidistant equations. By analyzing the mathematical properties of this set of equations, the condition for a unique solution is confirmed, ensuring the accurate determination of the spatial coordinates of the joint's rotation center. This ultimately yields the required coordinate parameters for the joint center position.

[0057] In one embodiment, such as Figure 2 As shown, Since the fixed point is on the user's lower leg, it is coplanar with the four points of the knee joint rotation center in the spatial rectangular coordinate system, and lies in the plane. With the knee joint rotation center as the center, Since these four points lie on the same circle, this is a fixed geometric relationship in a spatial rectangular coordinate system. The steps for calculation using this geometric relationship are as follows: Calculate the normal vector n of the plane determined by the three points, using vectors and The cross product yields:

[0058] vector

[0059] ,

[0060]

[0061] vector

[0062]

[0063]

[0064]

[0065] Cross product n: n=

[0066] Expanded to:

[0067] = , = , = , The equation of a plane can be expressed as:

[0068] Equidistant condition from the center of the circle to the three points set up

[0069] From the center to the point The distance is:

[0070] The condition for P1 and P2 to be equidistant can be written as:

[0071] Right now:

[0072]

[0073] After expansion, we get an equation:

[0074]

[0075] Similarly, the condition for the centers of the circles to be equidistant from P1 and P3 is:

[0076]

[0077] These two equations represent two constraints for finding the center of the circle.

[0078] Combining the above three constraints, the following system of equations can be established:

[0079] It can be simplified to:

[0080]

[0081] The matrix is ​​denoted as:

[0082]

[0083] The coordinates of the center of the circle are: .

[0084] If we calculate the pose of the plane containing the support trajectory relative to the vertical plane of the force measuring robot arm's rotation axis, then: The angle between the plane containing the support trajectory and the XOZ plane: The normal vector of the XOZ plane is

[0085] Angle between two planes , Similarly, we can conclude that: Angle with the YOZ plane , In summary, this utility model provides a joint rotation center alignment device, which includes a force gauge and a measuring component. The measuring component integrates a support, a lateral swing section, and a displacement / angle sensor. It collects position parameters such as the rotation angle α, lateral swing angle β, initial lever arm L, and displacement ΔL of the force gauge's robotic arm. A spatial coordinate system is then established to convert the motion parameters at three different positions into coordinate points. The normal vector of the motion plane is calculated using the cross product of vectors. An equidistant constraint equation is established based on the principle of three points being concyclic. The coordinates of the joint rotation center are obtained by solving the equation system. Utilizing the characteristic that the support on the force gauge's robotic arm performs circular motion around the joint center, the center position is determined through inverse geometric calculation. The measuring component monitors the pose difference between the robotic arm and the limb movement in real time and calculates the actual rotation center of the joint using the established spatial geometric model. The theoretical rotation center position is automatically compared, calibration parameters are generated, and fed back to the alignment device's control system, achieving dynamic compensation of the mechanical rotation center relative to the joint rotation center during testing. This method can also be reused to continuously improve alignment accuracy.

[0086] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A joint rotation center alignment device, characterized in that, include: Seats are used to support users; A force gauge is used to measure a user's limb strength. The support is slidably mounted on the robotic arm of the force measuring instrument to connect to the user's limb, and the effective lever arm length of the robotic arm is adjusted according to the user's position on the robotic arm. A measuring component, configured on the force gauge, is used to measure the rotation angle of the force gauge robotic arm, the corresponding lateral swing angle of the force gauge robotic arm, and the distance of the support relative to the rotation center of the robotic arm.

2. The alignment device according to claim 1, characterized in that, The measurement component includes: A lateral swing section is disposed at the hinge between the robotic arm and the robotic arm's rotation axis, for allowing the robotic arm to swing laterally relative to its rotation axis; A displacement sensor, configured on the support, is used to measure the displacement parameters of the support; An angle sensor, configured on the lateral swing shaft at the hinge, is used to measure the rotation angle of the rotation shaft and the lateral swing angle of the robotic arm.

3. The alignment device according to claim 2, characterized in that, The displacement sensor is used to obtain the distance between the support and the rotation axis and the displacement distance of the support on the robotic arm. The angle sensor is used to obtain the rotation angle of the robotic arm as it rotates with the rotation axis and the lateral swing angle of the robotic arm about the lateral swing axis.

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