Mandibular movement track acquisition mechanism based on inertial sensor

Abstract

The invention belongs to the technical field of mandibular movement track acquisition, and discloses an inertial sensor-based mandibular movement track acquisition mechanism, which comprises a sensor module and a wearable bracket, and is characterized in that the sensor module adopts two inertial sensors, and calculates relative movement data between the two inertial sensors according to real-time data; the wearable stent comprises an intraoral stent and an extraoral stent, the intraoral stent is made of a dental impression material, is rigidly connected with a mandibular dentition through impression plaster and adapts to an individual oral cavity structure, and the extraoral stent is of a 3D printing structure and is used for fixing an inertial sensor and realizing light weight through topological optimization. The IMU inertial sensor is introduced into the acquisition platform, so that compared with a stereoscopic vision measurement technology, the precision is higher, and the cost is lower; the lower jaw is connected with the measuring bracket by using an impression material, so that the structure is simpler, and the use is more convenient; the method comprises a corresponding trajectory resolving algorithm, so that a user can obtain a real mandibular trajectory of a patient at a lower cost for subsequent diagnosis.

Description

Technical Field

[0001] The present invention belongs to the technical field of mandibular motion trajectory acquisition, and in particular relates to a mandibular motion trajectory acquisition mechanism based on an inertial sensor. Background Art

[0002] Motion trajectory acquisition refers to the use of various sensing devices and imaging technologies to accurately record and measure the motion trajectory data of the target object during movement, including capturing the displacement, velocity, acceleration and other dynamic parameters of the target object in various motion modes. A denture is a removable prosthesis used to replace missing teeth. It is made by processing artificial teeth and bases, and can restore chewing function, pronunciation ability, and improve facial contours. Collecting and analyzing the mandibular motion trajectory is crucial for making a precisely suitable restoration. By analyzing and modeling this data, not only can a more precisely fitting denture or restoration be made and its adaptability be improved, but it can also be used to diagnose and treat certain mandibular movement disorders.

[0003] At present, judging from the current research status at home and abroad, the current denture trajectory acquisition devices have the following main shortcomings:

[0004] (1) Foreign commercial mandibular trajectory acquisition device:

[0005] 1. High equipment cost: At present, the price of a complete set of equipment abroad is around 100,000 yuan, and the production is extremely unstable and the delivery cycle is long.

[0006] 2. The interface is closed and difficult to adapt to domestic standards: Since the source code cannot be obtained after purchase, subsequent secondary development is difficult, and it is difficult to adapt to domestic standards, resulting in low cost performance.

[0007] (2) Current status of domestic research:

[0008] 1. Insufficient research investment: Currently, there is a serious lack of relevant research in China, which has led to researchers only being able to use hypothetical universal trajectories when they need mandibular motion trajectories as input.

[0009] 2. Insufficient accuracy: At present, domestic related research uses stereo vision measurement technology for trajectory determination. This method has strict requirements on the lighting of the measurement environment, and its accuracy is much lower than that of inertial sensors. Summary of the Invention

[0010] In view of the problems existing in the prior art, the present invention provides a mandibular motion trajectory acquisition mechanism based on an inertial sensor.

[0011] The present invention is implemented as follows: a mandibular motion trajectory acquisition mechanism based on an inertial sensor, characterized in that it includes a sensor module and a wearable bracket: the sensor module uses two inertial sensors to calculate the relative motion data between them based on real-time data; the wearable bracket includes an intraoral bracket and an extraoral bracket. The intraoral bracket uses dental impression material and is rigidly connected to the mandibular dentition through impression plaster to adapt to the individual oral structure. The extraoral bracket adopts a 3D printed structure to fix the inertial sensor and is lightweight through topological optimization.

[0012] Furthermore, in the sensor module, two sensors are respectively fixed to the forehead (reference rigid body) and the mandibular support (moving rigid body).

[0013] Furthermore, the mandibular motion trajectory acquisition mechanism obtains relative motion data through the data of the two sensors, and calculates the relative motion trajectory through data preprocessing and conversion. The specific measurement steps are as follows:

[0014] S1: Sensor calibration, connect the sensor, perform magnetic calibration and attitude check;

[0015] S2: Bracket assembly, screw-nut assembly, sensor assembly, and connection to the mandibular dentition;

[0016] S3: Collect records, confirm the recording environment, and record the trajectory;

[0017] S4: Data export, perform data check and export data.

[0018] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0019] First, the present invention introduces IMU inertial sensors into the acquisition platform, which can achieve higher accuracy and lower cost compared to stereo vision measurement technology.

[0020] The present invention uses the impression material to complete the connection between the mandible and the measuring bracket, which can reduce the number of overall parts, make the structure simpler, and make it more convenient to use.

[0021] The present invention includes a corresponding trajectory calculation algorithm, and the user can obtain the patient's true mandibular trajectory at a relatively low cost for subsequent diagnosis.

[0022] Secondly, by combining the 3D printing service of personalized stents with the value-added analysis of motion data, the present invention not only achieves an economic benefit of a gross profit margin of more than 60% on disposable consumables, but also controls the hardware cost within 20,000 yuan, greatly improving the penetration rate of grassroots hospitals; at the same time, the oral motion database based on inertial sensing and rigid coupling can cover an average of 1 million cases per year. By developing non-quantitative evaluation tools and outputting accurate kinematic parameter reports, it is estimated that the annual consumption of each patient can be increased by 3,000-5,000 yuan, thus forming a sustainable data value-added service, which significantly enhances the commercial appeal of this technical solution.

[0023] Compared with existing international optical marker systems that are easily occluded (such as Zebris / NDI) and domestic CFDA-certified products that only support single-parameter measurement and have not solved the dynamic drift problem, the present invention pioneered the use of inertial sensing and mandibular rigid coupling to achieve 0.3mm accuracy and 50Hz real-time sampling, breaking the limitations of the measurement environment and allowing continuous monitoring under all-day conditions; more importantly, the present invention successfully overcomes the problem of complex head and neck motion interference through the composite solution of the dual-sensor posture matrix, and improves the signal-to-noise ratio to 28dB (compared to the single-sensor solution SNR <10dB), truly solving the dynamic tracking problem that has long been unsolved in the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an assembly diagram of a mandibular motion trajectory acquisition mechanism based on an inertial sensor provided in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the installation of the sensor module provided by an embodiment of the present invention;

[0026] Figure 3 This is a flow chart of trajectory collection provided by an embodiment of the present invention;

[0027] Figure 4 is a flow chart of a motion trajectory algorithm provided by an embodiment of the present invention;

[0028] Figure 5 is a schematic diagram of a coordinate system provided by an embodiment of the present invention;

[0029] Figure 6 is a diagram of data processing results provided by an embodiment of the present invention;

[0030] Figure 7 This is a data visualization diagram provided by an embodiment of the present invention.

[0031] In the figure: 1. Sensor; 2. Sensor; 3. M10 flange nut; 4. External bracket; 5. Sensor bracket; 6. Measuring bracket; 7. M10 handle screw; 8. M10 anti-loosening washer; 9. Intraoral bracket. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] Current methods for capturing mandibular motion primarily rely on optical tracking or mechanical linkage devices. The former requires complex calibration and spatial arrangement, while the latter suffers from mechanical interference, bulk, and unsuitability for routine clinical practice. This is particularly problematic for achieving authentic, unobstructed motion reconstruction during dynamic chewing or natural opening and closing. The proposed dual-inertial sensor-based trajectory capture method, structurally designed to avoid the interference of traditional mechanisms with facial muscle activity while retaining sensitivity and responsiveness to true mandibular motion patterns, makes it particularly suitable for capturing and reconstructing a variety of functional movements, including natural closing, opening, and deflection.

[0034] Inertial measurement units (IMUs) offer a compact structure and fast data response, enabling free-form tracking without markers or spatial placement. This method employs a rigid connection structure separated from the reference datum by placing one IMU on the forehead as a head reference and another IMU on the mandible in conjunction with an oral impression. This structure then models the relative posture of the two rigid bodies. This structure forms a highly coupled connection with the dentition via the impression plaster, ensuring that sensor movement reflects the true trajectory of the mandible, unaffected by skin slip and tension.

[0035] In terms of data processing, this method abandons absolute position coordinate reconstruction and instead relies on relative attitude information for trajectory calculation. The system first uses a Kalman filter to fuse and reduce noise on the data output by each sensor, then calculates the attitude information represented by the quaternions of the two sensors. The difference between the quaternions is converted into Euler angles, and then the relative rotation matrix is ​​calculated. This processing method preserves the integrity of spatial attitude changes while avoiding positional drift caused by magnetic drift or time-accumulated errors.

[0036] During posture modeling, the present invention constructs three coordinate systems: the head coordinate system O1, the mandibular coordinate system O2, and the world coordinate system O. With O1 as the reference rigid body and O2 as the moving rigid body, the mandibular trajectory with six degrees of freedom in the world coordinate system is reconstructed by real-time updating of O2's rotation and position relative to O1. Specifically, the relative rotation matrix is ​​combined with the initial displacement offset to further construct a sequence of temporal transformation matrices. This outputs a trajectory point set, velocity vector, and acceleration trajectory, enabling reproducible modeling of continuous motion states.

[0037] This invention achieves excellent repeatability and inter-user consistency in its implementation. The bracket structure, based on 3D printing topology optimization, is lightweight, strong, quick to install, and adaptable to varying mandibular structural characteristics. Its structural versatility and sensor detachability significantly reduce the systematic errors and structural perturbations associated with multiple clinical sampling, making data comparable across space and time, facilitating subsequent occlusal diagnosis, comparative evaluation, and therapeutic feedback.

[0038] The collected data is imported into a visualization system via an export interface, where a spatial trajectory model of mandibular motion is constructed on a three-dimensional graphics platform. The trajectory point set can be integrated with a digital denture design platform, enabling functional denture modeling or appliance customization driven by real-world motion data. Furthermore, the system outputs multidimensional parameters such as velocity change and trajectory offset, providing precise quantitative indicators for conditions such as occlusal disorders and temporomandibular joint dysfunction, filling a technical gap in the ability of existing static occlusal design methods to identify dynamic features.

[0039] like Figure 1-Figure 2 As shown, an embodiment of the present invention provides a mandibular motion trajectory acquisition mechanism based on an inertial sensor, including an inertial sensor 1, an inertial sensor 2, an M10 flange nut 3, an extraoral bracket 4, a sensor bracket 5, a measurement bracket 6, an M10 handle screw 7, an M10 anti-loosening washer 8, and an intraoral bracket 9.

[0040] Intraoral bracket 9: This connects the impression material to the teeth or oral tissue, securing the device and measuring relevant data. Combined with the extraoral bracket 4 via an adjustable connection, the intraoral bracket 9 is used for fixation and data collection inside the mouth, while the extraoral bracket 4 provides support and connection to other measurement components outside the mouth.

[0041] Extraoral bracket 4: Located on the outside of the head, it is connected to the inertial sensor 2 through a certain connection structure to provide external support for the entire measuring device.

[0042] Sensor bracket 5: It is installed on the forehead together with the inertial sensor 1 to measure inertial data related to the head, such as motion acceleration, angular velocity, etc.

[0043] Measuring bracket 6: connected to the extraoral bracket 4, used to adjust the position or angle of the sensor to ensure accurate measurement.

[0044] Inertial sensor 1: associated with the sensor bracket 5, used to collect physical quantity data at a specific position, such as angle, angular velocity, displacement, etc., as a reference point for the relative movement of the mandible.

[0045] Extraoral bracket 4: It has an arc-shaped structure that fits the outer contour of the head and provides a mounting base for other components.

[0046] Inertial sensor 2: fixed at one end of the extraoral bracket 4, positioned and supported by the measuring bracket 6, which can adjust the position and angle of the inertial sensor 2.

[0047] Measuring bracket 6: one end is connected to the extraoral bracket 4, and the other end is connected to the inertial sensor 2, playing the role of bridge and adjustment.

[0048] M10 flange nut 3: has a flange structure, can increase the connection area, provide a stable connection, and is used to connect the extraoral bracket 4 and other related components.

[0049] M10 handle screw 7: with a handle for easy manual tightening or loosening, used to fix the connection between the extraoral bracket 4 and other components.

[0050] M10 anti-loosening washer 8: installed between the M10 handle screw 7 and the connecting component to prevent the screw from loosening and ensure the reliability of the connection.

[0051] The device installs components such as the inertial sensor 2 and the measurement bracket 6 in appropriate positions through the cooperation of the intraoral bracket 9 and the extraoral bracket 4, and uses connectors such as the M10 flange nut 3, M10 handle screw 7 and M10 anti-loosening washer 8 to ensure the stable connection of each component, so as to realize the measurement of head-related motion and mechanical data.

[0052] Sensor module and wearable bracket: The sensor module uses two inertial sensors to calculate the relative motion data between them based on real-time data; the wearable bracket includes an intraoral bracket and an extraoral bracket. The intraoral bracket uses dental impression material and is rigidly connected to the mandibular dentition through impression plaster to adapt to the individual oral structure. The extraoral bracket uses a 3D printed structure to fix the inertial sensor and is lightweight through topological optimization.

[0053] The sensor module is installed in the following way:

[0054] Sensor 1 is fixed on the forehead (reference rigid body);

[0055] The sensor 2 is fixed to the mandibular support (moving rigid body).

[0056] The inertial sensor-based mandibular motion trajectory acquisition mechanism is shown in the figure. The overall structure consists of a wearable bracket and a sensor module, offering high integration and ergonomic compatibility. Sensor 1 is fixed to the forehead via adhesive or straps and serves as a reference rigid body, providing a reference coordinate system for both stationary and moving head conditions. Sensor 2 is mounted on the extraoral bracket via a fixed structure and moves with the mandible, acting as a moving rigid body. The spatial relationship between the two sensors changes over time. Combined with the inertial measurement data, the mandibular six-degree-of-freedom motion trajectory can be calculated.

[0057] The wearable bracket consists of two parts: an intraoral bracket and an extraoral bracket, characterized by precise fit and rigid connection. The intraoral bracket is made of dental impression material and securely connected to the wearer's mandibular dentition via impression plaster, ensuring that mandibular movement is fully transmitted to the entire system. This structure effectively secures the inertial sensor, preventing measurement errors caused by device slippage or loose bite. Furthermore, the personalized nature of the impression makes the mechanism adaptable to different individual anatomy.

[0058] The extraoral bracket is constructed from lightweight, high-strength materials using 3D printing technology. Its shape is topologically optimized to minimize wearer burden. It is integrally connected to the intraoral bracket and features a structural slot for mounting sensor ②, secured by bolts or fasteners. The bracket design provides the necessary adjustment space, allowing the sensor to be fine-tuned to accommodate varying head shapes, thereby enhancing the system's adaptability and repeatability for diverse users.

[0059] The entire system operates based on the relative motion between two inertial sensors. The forehead sensor records the reference head posture and position, while the mandibular sensor tracks the mandibular motion trajectory. Using a built-in algorithm, the system fuses the acceleration, angular velocity, and posture data from these two sensors to calculate the mandibular trajectory, velocity, and acceleration in three-dimensional space in real time. This enables unconstrained, non-contact, and high-precision mandibular motion analysis, providing precise data support for fields such as oral healthcare, occlusal reconstruction, and sleep apnea monitoring.

[0060] The relative motion data is obtained through the data of the two sensors, and is converted into a relative motion trajectory through data preprocessing and conversion. The specific measurement steps are as follows: Figure 3 As shown:

[0061] S1: Sensor calibration, connect the sensor, perform magnetic calibration and attitude check;

[0062] S2: Bracket assembly, screw-nut assembly, sensor assembly, and connection to the mandibular dentition;

[0063] S3: Collect records, confirm the recording environment, and record the trajectory;

[0064] S4: Data export, perform data check and export data.

[0065] The embodiment of the present invention proposes a corresponding trajectory calculation algorithm, which allows users to obtain the patient's true mandibular trajectory at a relatively low cost for subsequent diagnosis. Figure 4 shown.

[0066] According to the above sensor installation positions, the embodiment of the present invention adopts the following Figure 5 Coordinate system shown.

[0067] After the measurement step, the data is processed and the data is obtained as follows Figure 6 As shown, the data is visualized and we get Figure 7 ,On this basis, the trajectory can be used for subsequent analysis, for example: ,the feasibility of the motion trajectory for dynamic analysis, and based on the ,analysis results, reversely guide the previous denture design.

[0068] The present invention proposes a method for acquiring mandibular motion trajectories based on inertial sensors. Its working principle includes five key stages: sensor calibration, bracket assembly, data acquisition and recording, trajectory solution, and data visualization. The system structure and algorithm process are highly integrated, enabling high-precision dynamic capture of mandibular motion trajectories. It has good adaptability and repeatability, and is suitable for clinical needs such as occlusal diagnosis, functional restoration, and denture design.

[0069] First, the system initialization phase includes the calibration process of the inertial sensor. Figure 4 As shown, the head reference sensor and jaw sensor are connected separately to complete signal confirmation, magnetic calibration, and attitude check. This ensures that the two sensors achieve initial state consistency in an interference-free environment, providing a stable baseline for subsequent relative motion calculations. Magnetic calibration primarily compensates for errors in attitude calculations caused by the geomagnetic environment, while the attitude check confirms that there has been no misinstallation or signal drift during installation.

[0070] The next step is bracket assembly. The sensor module is securely attached to the 3D-printed extraoral bracket using a screw-nut mechanism. The extraoral bracket is integrally connected to the intraoral impression bracket and rigidly coupled to the mandibular dentition via the impression plaster, ensuring that the sensor's movement accurately represents actual mandibular motion. This step ensures structural stability and positioning accuracy, preventing systematic errors caused by loosening or drift during recording.

[0071] During the data collection phase ( Figure 3 In S3, the system confirms that the current environment is stable (e.g., no significant head movement and minimal background magnetic interference), and then activates the trajectory recording module. Two sensors collect three-axis acceleration, angular velocity, and magnetic force data and transmit them to the processing unit in real time. This data records the trajectory of the mandible from rest to opening, closing, and chewing. The sampling frequency can be adjusted as needed, enabling high-resolution tracking of rapid movements.

[0072] like Figure 4As shown in the figure, the trajectory calculation algorithm uses Kalman filtering to reduce noise in the inertial data. It then obtains the initial quaternions (q1 and q2) of the head reference sensor and the mandibular sensor, respectively. The quaternions are converted to Euler angles to calculate their attitude angles. The relative Euler angles and relative rotation matrix are then derived. Combining the initial offset vector with the position coordinates, a relative motion transformation matrix is ​​established from the reference rigid body to the moving rigid body, enabling reconstruction of the mandibular position in six degrees of freedom in three-dimensional space.

[0073] In order to express the spatial structural relationship of the motion process, such as Figure 5 As shown, the present invention uses dual sensors to establish three coordinate systems: the head reference coordinate system O1 (X1Y1Z1), the mandibular coordinate system O2 (X2Y2Z2), and the overall analysis coordinate system O(XYZ). Sensor calculations are used to track and transform the dynamic changes of the O2 coordinate system relative to the O1 coordinate system in real time, accurately reflecting the entire process of mandibular rotation and translation. The final solution includes a trajectory point set, an angular velocity sequence, and a posture transformation matrix.

[0074] After data analysis, the trajectory data is exported to visualization software or diagnostic platform, such as Figure 6 and Figure 7 As shown, this system achieves three-dimensional reconstruction and visualization of mandibular motion trajectories. Combined with biomechanical or dynamic analysis tools, it can further analyze indicators such as opening and closing rate, deflection angle, and the symmetry and stability of the chewing path. These results not only assist physicians in assessing the patient's mandibular function but also provide guidance for personalized optimization of denture design, orthodontic appliance customization, and postoperative functional recovery plans, possessing high clinical application value and potential for widespread adoption.

[0075] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for collecting mandibular movement trajectory, characterized in that: The following steps are involved: S1: Connect the first inertial sensor and the second inertial sensor, perform magnetic calibration and attitude initialization on them; S2: Connect the second inertial sensor to the mandibular dentition through the bracket; S3: Collecting posture and motion data of the first inertial sensor and the second inertial sensor; S4: Calculating the relative Euler angle and relative rotation matrix of the second inertial sensor relative to the first inertial sensor; S5: Based on the relationship between the initial offset vector and the posture, the motion trajectory of the mandible in three-dimensional space is solved.

2. An inertial sensor device for collecting mandibular motion trajectory, characterized in that: include: A wearable bracket, a first inertial sensor, a second inertial sensor, and a data processing module; The first inertial sensor is fixed to the wearer's forehead and serves as a reference rigid body; The second inertial sensor is mounted on the bracket on the mandibular side and serves as a moving rigid body; The data processing module receives the three-axis acceleration, angular velocity and magnetometer data from the two sensors, and calculates the mandibular movement trajectory based on the relative posture relationship.

3. The inertial sensor device according to claim 2, wherein: The wearable bracket includes an intraoral bracket and an extraoral bracket, The intraoral bracket is made of impression plaster material and is rigidly connected to the mandibular dentition; The extraoral bracket is a topologically optimized 3D-printed structure used to fix the second inertial sensor and is integrally formed with the intraoral bracket.

4. The inertial sensor device according to claim 2, wherein The second inertial sensor is fixed in an embedding groove provided on the extraoral bracket through a threaded structure. The embedding groove is provided with multiple positioning surfaces for adjusting the installation angle of the second sensor.

5. A method for calculating the relative motion trajectory of the mandible, characterized in that: include: Perform Kalman filtering on the data of the two inertial sensors respectively; Convert the filtering result into quaternion form; Solve the relative Euler angle and rotation matrix based on the initial quaternion; Combining the initial position offset with the coordinate transformation relationship, the pose transformation matrix is ​​constructed; Output the motion trajectory information of the mandible in three-dimensional space.

6. The method according to claim 5, wherein Construct three coordinate systems for attitude calculation: The O1 coordinate system is the reference coordinate system of the first inertial sensor; The O2 coordinate system is the second inertial sensor moving coordinate system; The O coordinate system is the general analysis coordinate system; The solving step includes converting the O2 coordinate system relative to the O1 coordinate system at each sampling time point and mapping the O2 coordinate system to the O coordinate system.

7. A mandibular trajectory visualization method, characterized in that: The following steps are included: Obtain the three-dimensional trajectory point set obtained through coordinate transformation; Importing trajectory data into a 3D modeling tool to generate a curve image; Dynamically mark trajectory key points, speed changes and rotation postures in the interface; A trajectory export interface is provided for subsequent dynamic analysis or denture design feedback.

8. An inertial analysis module for assisting mandibular function diagnosis, characterized in that: include: Sensor initialization submodule, used for attitude reference calibration; A data acquisition submodule, for synchronously acquiring data from the first and second sensors; Data fusion submodule, used to perform filtering, rotation transformation and coordinate mapping; The trajectory output submodule is used to generate three-dimensional trajectory files and related analysis indicators.

9. The inertial sensor device according to claim 2, wherein: The system is suitable for occlusal reconstruction, oral function diagnosis, mandibular corrector design and postoperative follow-up evaluation. Through real-time trajectory capture and precision feedback, it assists medical personnel in formulating personalized treatment plans.

10. The inertial sensor device according to claim 2, wherein The extraoral support structure is provided with an adjustable connection portion according to the user's face shape, and can realize rapid adaptation and repeated installation of the mandibular structures of different groups of people through slide groove cooperation or replaceable interface components.

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