Flexible artificial muscle and control system thereof

Abstract

The invention discloses a flexible artificial muscle and a control system thereof, and the flexible artificial muscle comprises a flexible housing which is internally provided with a sealed cavity and is filled with liquid as a force transmission medium; the flexible limiting framework comprises a plurality of hollow triangular prism units; the adjacent hollow triangular prism units are connected through flexible connecting parts; and the liquid pump is communicated with the closed cavity through a pipeline. Through bionic structure design and mechanical modeling, the output performance and reliability of the artificial muscle are improved, upgrading of rehabilitation medical equipment is promoted, and the life quality of old people and disabled people is improved.

Description

Technical Field

[0001] This invention relates to the field of medical rehabilitation technology, and in particular to a flexible artificial muscle and its control system. Background Technology

[0002] For stroke patients with hemiplegia or upper limb motor dysfunction, rehabilitation is a long and challenging process. Upper limb rehabilitation training is primarily performed manually by rehabilitation physicians, with therapists repeatedly guiding limb movements according to the patient's intentions. This model heavily relies on the physician's clinical experience and physical exertion, resulting in significant limitations such as low training efficiency and difficulty in quantifying and assessing motor parameters. With the continuous increase in the number of patients with upper limb dysfunction, the supply of professional rehabilitation therapists is severely insufficient to meet clinical needs; furthermore, prolonged, high-intensity manual manipulation can easily lead to therapist fatigue, thus affecting training consistency and rehabilitation outcomes.

[0003] In the field of medical rehabilitation, flexible artificial muscles have broad application prospects due to their excellent compliance, inherent safety, and actuation mechanism similar to biological muscles. However, challenges remain: on the one hand, the performance of actuation materials needs significant improvement, with further advancements in self-healing ability, mechanical strength, and actuation efficiency; on the other hand, breakthroughs are urgently needed in multimodal sensor fusion technology, accuracy of motion intention recognition, and human-machine compliant interactive control methods; finally, the current clinical translation of rehabilitation robots still has significant limitations, especially in effectively translating functional improvements gained during training into enhanced daily living abilities. Therefore, the development of high-strength, flexible artificial muscle actuation systems and the design of corresponding control systems are of great significance for improving patient rehabilitation outcomes. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the existing technology, it is desirable to provide a flexible artificial muscle and its control system, which improves the output performance and reliability of the artificial muscle through biomimetic structural design and mechanical modeling, promotes the upgrading of rehabilitation medical equipment, and improves the quality of life of the elderly and disabled.

[0005] The present invention provides a flexible artificial muscle, comprising:

[0006] A flexible outer shell forms a sealed cavity inside, which is filled with liquid as a force transmission medium;

[0007] The flexible limiting frame includes several hollow triangular prism units arranged side by side, with the apex of each hollow triangular prism unit facing upwards and the bottom surface being arc-shaped; the bottom corners of adjacent hollow triangular prism units are connected by a flexible connecting part.

[0008] A liquid pump is connected to the sealed cavity via a pipeline.

[0009] Furthermore, the flexible shell is formed by hot-pressing a polyethylene film with excellent biocompatibility.

[0010] Furthermore, the flexible limiting skeleton is integrally molded using soft silicone casting.

[0011] Furthermore, when the liquid pump draws the force transmission medium to create a negative pressure within the sealed cavity, the flexible outer shell elastically bends along with the flexible limiting skeleton; at this time, the total output force F of the flexible artificial muscle... out for:

[0012] ;

[0013] Among them, T x This represents the horizontal tension component generated by the flexible shell along the horizontal direction, expressed in N.

[0014] F p The axial thrust applied to the cross-section of the flexible restraint frame by the pressure of the force transmission medium, expressed in N;

[0015] α is the angle between the sidewall of the hollow triangular prism element and the vertical direction, in degrees.

[0016] Furthermore, the axial thrust F p for:

[0017] ;

[0018] Where ΔP is the vacuum pressure difference inside the sealed cavity, and the unit is MPa;

[0019] A represents the cross-sectional area of ​​the flexible restraint frame, in meters (m²). 2 W represents the width of the flexible restraint frame, in meters (m); H represents the height of the flexible restraint frame, in meters (m).

[0020] Furthermore, the horizontal tension component T x for:

[0021] ;

[0022] Where T is the tension of the flexible shell, in N;

[0023] β is the angle between T and the horizontal direction, in degrees;

[0024] ;

[0025] ;

[0026] Where R is the skin curvature radius at the contact point O between the flexible artificial muscle and the user, in meters;

[0027] ;

[0028] Where c is the chord length of the parabola between the tops of adjacent hollow triangular prism units, in meters, c = 2L;

[0029] h is the vertical height from the vertex of the parabola to the upper surface of the flexible limiting frame, in meters (m).

[0030] Furthermore, the present invention also provides a control system for the flexible artificial muscle as described above, comprising:

[0031] Control module;

[0032] An electromyography module, including a surface electromyography sensor electrically connected to the control module;

[0033] The pose module includes a MEMS inertial measurement unit electrically connected to the control module;

[0034] The drive module is electrically connected to both the control module and the liquid pump, and is used to receive instructions sent by the control module and control the liquid pump to execute the instructions.

[0035] Furthermore, the control module uses an STM32G431RBT6 as its core main controller.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] This invention addresses the needs of patients with upper limb motor dysfunction by designing a fluid-driven flexible artificial muscle and its control system. Combining multi-sensor fusion and intention recognition, it achieves precise control of the flexible artificial muscle. Through biomimetic structural design and mechanical modeling, the output performance and reliability of the artificial muscle are improved. By utilizing electromyography signal processing and pose sensor technology, patient-led adaptive control strategies are explored to promote neural function remodeling and motor function recovery. This provides further theoretical basis and technical support for the development of flexible rehabilitation robot systems, promotes the intelligent upgrading of rehabilitation medical equipment, ultimately reduces the social medical burden, and improves the quality of life for the elderly and disabled. The proposed flexible artificial muscle's high compliance, high-precision bimodal intention recognition, and embedded real-time control capabilities are suitable for rehabilitation training scenarios for patients with upper limb motor dysfunction, such as those suffering from stroke.

[0038] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0039] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0040] Figure 1 This is a schematic diagram of the structure of a flexible artificial muscle;

[0041] Figure 2 A schematic diagram of a mathematical model of a flexible artificial muscle;

[0042] Figure 3 A schematic diagram of the main view mathematical model of a flexible artificial muscle;

[0043] Figure 4 This is a block diagram of the control system.

[0044] The diagram shows: 1. Flexible outer shell; 2. Flexible limiting frame;

[0045] 11. Sealed cavity;

[0046] 21. Hollow triangular prism unit; 22. Flexible connection part. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0048] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0049] Please refer to Figures 1-3 An embodiment of the present invention provides a flexible artificial muscle, comprising:

[0050] The flexible shell 1 forms a sealed cavity 11 inside, which is filled with liquid as a force transmission medium; the flexible shell 1 is formed by hot pressing a polyethylene film with excellent biocompatibility.

[0051] The flexible limiting frame 2 includes several hollow triangular prism units 21 arranged side by side. The apex of the hollow triangular prism unit 21 faces upward and the bottom surface is arc-shaped. The bottom corners of adjacent hollow triangular prism units 21 are connected by flexible connecting parts 22. The flexible limiting frame 2 is integrally molded by casting with soft silicone.

[0052] A liquid pump is connected to the sealed cavity 11 via a pipeline;

[0053] When the liquid pump's extraction force transmission medium creates a negative pressure within the sealed cavity 11, the flexible outer shell 1 elastically bends along with the flexible limiting frame 2; at this time, the total output force F of the flexible artificial muscle... out for:

[0054] ;

[0055] Among them, T x The horizontal tension component generated by the flexible outer shell 1 along the horizontal direction is expressed in N.

[0056] F p The axial thrust applied to the cross section of the flexible limiting frame 2 by the pressure of the force transmission medium is expressed in N.

[0057] α is the angle between the sidewall of the hollow triangular prism element 21 and the vertical direction, in degrees;

[0058] ;

[0059] Wherein, ΔP is the vacuum pressure difference inside the sealed cavity 11, in MPa;

[0060] A represents the cross-sectional area of ​​the flexible restraint frame 2, in meters (m²). 2 W represents the width of the flexible limiting frame 2, in meters; H represents the height of the flexible limiting frame 2, in meters.

[0061] ;

[0062] Where T is the tension of the flexible shell 1, in N;

[0063] β is the angle between T and the horizontal direction, in degrees;

[0064] ;

[0065] ;

[0066] Where R is the skin curvature radius at the contact point O between the flexible artificial muscle and the user, in meters;

[0067] ;

[0068] Where c is the chord length of the parabola between the tops of adjacent hollow triangular prism units 21, in meters, c=2L;

[0069] h is the vertical height from the vertex of the parabola to the upper surface of the flexible limiting skeleton 2, in meters.

[0070] In this embodiment, traditional artificial muscles mostly use rigid materials and motor-driven structures. Although the output force and positioning accuracy are high, their inherent rigidity significantly limits the compliance and safety of human-computer interaction, and can easily cause secondary damage or patient discomfort in medical rehabilitation scenarios where there is direct contact with the human body.

[0071] Against this backdrop, inspired by the mechanisms of biological muscle contraction and the biomechanics of human upper limb movement, this application proposes a flexible artificial muscle structure driven by negative pressure liquid. This structure employs a multi-layered composite film and a biomimetic paper-cut design. It achieves orderly contraction and relaxation of biological muscles by drawing liquid from a sealed cavity 11, exhibiting high flexibility, lightweight design, and excellent force-displacement output characteristics. Targeted optimizations were made in material selection, sealing technology, and integration methods to meet the specific requirements of medical rehabilitation scenarios for hygiene, intrinsic safety, and long-term wearing comfort.

[0072] The working principle is as follows: By rapidly extracting liquid from the sealed cavity 11 to reduce the internal pressure, the flexible limiting skeleton 2, composed of triangular prism units 21, plays a crucial guiding and constraining role. Its geometric configuration ensures that controllable elastic bending occurs preferentially in specific areas, thereby transforming the disordered contraction of the flexible shell 1 into an ordered and coordinated bending motion of the entire unit along a preset axis. This causes the flexible shell 1 to undergo ordered collapse and bending deformation under the constraint of the flexible limiting skeleton 2. Since both the inner and outer structures are made of flexible materials, the entire deformation process is highly biomimetic, similar to the contraction of biological muscles, avoiding local stress concentration. After restoring normal pressure, the flexible artificial muscle resets under the elastic action of the material, thereby realizing a drive-reset cycle, which in turn drives the coordinated movement of the upper arm and forearm.

[0073] In the unactivated state, the flexible artificial muscle maintains the initial serrated geometric configuration of the flexible restraint skeleton 2. To establish an accurate mathematical model, reasonable kinematic assumptions are first made for the complex nonlinear deformation, and a parabolic model is used to approximate the bending profile of the flexible shell 1 on the cross section. While ensuring computational efficiency, the key features of fluid volume change are effectively captured, enabling the flexible artificial muscle to be applied in medical rehabilitation.

[0074] Also, please refer to Figure 4 Embodiments of the present invention provide a control system for a flexible artificial muscle as described above, comprising:

[0075] The control module uses STM32G431RBT6 as the core main controller;

[0076] An electromyography module, including a surface electromyography sensor electrically connected to a control module;

[0077] The pose module includes a MEMS inertial measurement unit electrically connected to the control module;

[0078] The drive module is electrically connected to both the control module and the liquid pump. It is used to receive commands from the control module and control the liquid pump to execute the commands.

[0079] In this embodiment, the controller module is the core hub of the flexible artificial muscle control system. Its core objective is to achieve the integration of dual-modal signal processing, intent recognition algorithm deployment, and drive control. It must simultaneously meet the stringent requirements of rehabilitation scenarios for real-time performance, low power consumption, and resource compactness. It must be compatible with the high-frequency signal acquisition of surface electromyography sensors and MEMS inertial measurement units, support efficient inference of the model, and be compatible with the negative pressure drive control logic of the flexible artificial muscle.

[0080] In summary, STM32Cube.AI offers significant advantages on the STM32 platform. It fully leverages the instruction set and peripheral resources of the Cortex-M4 core to achieve deep model optimization, significantly reducing inference latency and resource consumption. This tool supports direct import of models from TensorFlow, PyTorch, or ONNX and automatically generates highly optimized C code libraries, eliminating the need for manual refactoring and drastically shortening the development cycle. Furthermore, in low-power medical rehabilitation scenarios, STM32Cube.AI's targeted optimizations effectively reduce energy consumption, ensuring comfort and safety during extended wear.

[0081] In the intention recognition system of rehabilitation robots, surface electromyography (sEMG) signals capture the potential changes during muscle contraction through electrodes attached to the skin surface. This method offers significant advantages, including being completely non-invasive, easy to operate, having a moderate signal-to-noise ratio, and directly reflecting the degree of muscle activation and movement intention. Since sEMG signals are generated 30-150 ms ahead of actual limb movement, this electrophysiological lead time provides the physical basis for real-time predictive control of rehabilitation robots.

[0082] In upper limb rehabilitation training, real-time and accurate acquisition of the spatial posture of the affected limb is a prerequisite for achieving closed-loop control and motion assessment. MEMS inertial measurement units have the advantages of small size, light weight, low power consumption, and no need for external reference base stations. By wearing them on the surface of the limb, posture information can be calculated, which greatly improves the portability and wearing comfort of rehabilitation equipment.

[0083] Among the many IMU (Inertial Measurement Unit) solutions, this application selects the MPU6050 six-axis motion processing unit from InvenSense, which has the following advantages:

[0084] (1) High integration: A single chip integrates a 3-axis microelectromechanical gyroscope and a 3-axis accelerometer, eliminating the inter-axis difference between discrete components and meeting the requirements for multi-degree-of-freedom detection of upper limb movements;

[0085] (2) DMP hardware acceleration: It integrates a Digital Motion Processor (DMP). Unlike ordinary sensors that only output raw data, the DMP can perform complex attitude fusion calculations directly inside the chip and output quaternions directly through the I2C interface, which significantly reduces the computational burden of the STM32 main control chip, allowing it to focus more on running the complex DMS-Net intention recognition algorithm and ensuring the overall real-time performance of the system.

[0086] This application presents a negative pressure liquid-driven flexible artificial muscle. Through structural design and mechanical modeling, a compliant actuation scheme based on a silicone skeleton and flexible skin was established. Simultaneously, an embedded hardware control system with an STM32 microcontroller as its core was constructed, completing the integrated design of sEMG electromyography acquisition and IMU posture monitoring. This meets the specific requirements of medical rehabilitation scenarios for hygiene, intrinsic safety, and long-term wearing comfort, and has broad market prospects.

[0087] In the description of this specification, the terms "connection," "installation," and "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0088] In the description of this specification, the terms "one embodiment," "some embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0089] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A flexible artificial muscle, characterized in that, include: A flexible shell (1) forms a closed cavity (11) inside, which is filled with liquid as a force transmission medium; The flexible limiting frame (2) includes several hollow triangular prism units (21) arranged side by side. The apex of each hollow triangular prism unit (21) faces upward and the bottom surface is arc-shaped. The bottom corners of adjacent hollow triangular prism units (21) are connected by a flexible connecting part (22). A liquid pump is connected to the sealed cavity (11) via a pipeline.

2. The flexible artificial muscle according to claim 1, characterized in that, The flexible shell (1) is formed by hot-pressing a polyethylene film with excellent biocompatibility.

3. The flexible artificial muscle according to claim 1, characterized in that, The flexible limiting skeleton (2) is integrally molded by casting with soft silicone.

4. The flexible artificial muscle according to claim 1, characterized in that, When the liquid pump draws the force transmission medium to create a negative pressure inside the sealed cavity (11), the flexible outer shell (1) elastically bends along with the flexible limiting skeleton (2); at this time, the total output force F of the flexible artificial muscle... out for: ； Among them, T x The horizontal tension component generated by the flexible shell (1) along the horizontal direction is expressed in N. F p The axial thrust applied to the cross section of the flexible limiting skeleton (2) by the pressure of the force transmission medium is expressed in N. α is the angle between the sidewall of the hollow triangular prism element (21) and the vertical direction, in degrees.

5. The flexible artificial muscle according to claim 4, characterized in that, The axial thrust F p for: ； Wherein, ΔP is the vacuum pressure difference inside the sealed cavity (11), in MPa; A represents the cross-sectional area of ​​the flexible limiting frame (2), in meters. 2 W represents the width of the flexible limiting skeleton (2), in meters; H represents the height of the flexible limiting skeleton (2), in meters.

6. The flexible artificial muscle according to claim 5, characterized in that, The horizontal tension component T x for: ； Where T is the tension of the flexible shell (1), in N; β is the angle between T and the horizontal direction, in degrees; ； ； Where R is the skin curvature radius at the contact point O between the flexible artificial muscle and the user, in meters; ； Where c is the chord length of the parabola between the tops of adjacent hollow triangular prism units (21), in meters, c = 2L; h is the vertical height from the vertex of the parabola to the upper surface of the flexible limiting skeleton (2), in meters.

7. A control system for a flexible artificial muscle as described in any one of claims 1-6, characterized in that, include: Control module; An electromyography module, including a surface electromyography sensor electrically connected to the control module; The pose module includes a MEMS inertial measurement unit electrically connected to the control module; The drive module is electrically connected to both the control module and the liquid pump, and is used to receive instructions sent by the control module and control the liquid pump to execute the instructions.

8. The flexible artificial muscle according to claim 7, characterized in that, The control module uses STM32G431RBT6 as the core main controller.

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