Flexible exoskeleton system and working method

Abstract

The invention relates to a flexible exoskeleton system and a working method thereof, the flexible exoskeleton system comprises an exoskeleton device and a controller unit, the exoskeleton device comprises a shoulder fixing band, a waist fixing band, an artificial muscle fiber bundle, a driver fixer and a knee joint fixing band; the shoulder fixing belt is connected with the waist fixing belt, the waist fixing belt is connected with the artificial muscle fiber bundle, the artificial muscle fiber bundle is connected with the driver fixator, the driver fixator is connected with the knee joint fixing belt, and the controller unit is arranged in the center of the exoskeleton device. A micro force sensor is further arranged at the connecting position of the waist fixing band and the artificial muscle fiber bundle and is connected with the controller unit through a signal line. The artificial muscle fiber based on the dielectric elastomer is used for the flexible exoskeleton to replace a motor and a speed reducer so as to achieve driving of intrinsic flexibility, resistance brought by the elastomer during energy storage is relieved or eliminated through voltage stimulation, voltage is turned off when elastic force is released, and the power assisting effect is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical devices, and in particular relates to a flexible exoskeleton system and a working method. Background Art

[0002] Flexible lower limb exoskeletons play an important role in fields such as medical treatment and rehabilitation, industry and manufacturing. Compared with traditional rigid exoskeleton systems, benefiting from their flexible structures, they show a large number of advantages in many aspects such as comfort, flexibility, and environmental adaptability.

[0003] Existing active flexible exoskeleton systems mainly rely on pneumatic or cable drives. The pneumatic flexible exoskeleton completes the energy conversion of the flexible driving member through components such as air pumps and air tanks. The cable-driven flexible exoskeleton completes the corresponding assisting effect through the cooperation of motors and reducers. However, whether it is an air pump or an air tank, a motor or a reducer, it will cause the exoskeleton system to be large in volume, heavy in weight, and difficult to integrate.

[0004] In addition, passive flexible exoskeletons with elastic elements as driving units have also attracted much attention. Benefiting from their elastic energy storage characteristics, they can provide a certain assisting effect during walking, but they need to overcome the resistance generated by the elastic elements during the walking cycle.

[0005] Currently, the following problems exist in flexible exoskeleton systems:

[0006] Although the driver is replaced by a flexible element, rigid components still need to be introduced, resulting in the equipment being too heavy and not conducive to use, and the essential flexible drive has not been achieved.

[0007] For passive flexible exoskeletons without rigid components, they need to overcome relevant resistances by themselves, that is, the assisting effect is not obvious and active modulation cannot be achieved. Summary of the Invention

[0008] In view of this, the present invention aims to overcome the above deficiencies in the prior art and proposes a flexible exoskeleton system and a working method.

[0009] To achieve the above object, the technical solution of the present invention is realized as follows:

[0010] In the first aspect of the present invention, a flexible exoskeleton system is provided, which includes an exoskeleton device and a controller unit. The overall structure of the exoskeleton device is longitudinally arranged and includes a shoulder fixing strap, a waist fixing strap, an artificial muscle fiber bundle, a driver holder, and a knee joint fixing strap. The shoulder fixing strap is arranged at the upper part of the exoskeleton device, the waist fixing strap is arranged at the middle part of the exoskeleton device, and the knee joint fixing strap is arranged at the lower part of the exoskeleton device. The shoulder fixing strap is connected to the waist fixing strap, the waist fixing strap is connected to the artificial muscle fiber bundle, the artificial muscle fiber bundle is connected to the driver holder, and the driver holder is connected to the knee joint fixing strap. The controller unit is arranged at the central position of the exoskeleton device. A micro force sensor is also provided at the connection position between the waist fixing strap and the artificial muscle fiber bundle, and the micro force sensor is connected to the controller unit through a signal line.

[0011] Further, the shoulder fixing strap, the waist fixing strap, and the knee joint fixing strap are all made of flexible woven materials.

[0012] Further, the controller unit includes a signal acquisition unit, a voltage modulation unit, and a power amplification unit.

[0013] Further, both the controller unit and the driver holder are printed by a 3D printer using PLA material.

[0014] Further, the artificial muscle fiber bundle is composed of multiple artificial muscle fibers. The preparation process includes dielectric elastomer artificial muscle film stacking, rolling, fibrosis, and integration. The diameter of a single fiber does not exceed 2 mm.

[0015] Further, the shoulder fixing strap, the waist fixing strap, and the knee joint fixing strap are all adjustable.

[0016] Further, the shoulder fixing strap, the controller unit, the waist fixing strap, the micro force sensor, the driver holder, and the knee joint fixing strap are fixed in a binding buckle manner.

[0017] Further, the artificial muscle fiber bundle and the driver holder are fixed in a bolt tightening manner.

[0018] Further, the signal line is fixed to the micro force sensor, the driver holder, and the controller unit in a plug-in tightening manner.

[0019] In the second aspect of the present invention, a working method of the flexible exoskeleton system is provided, including the following steps:

[0020] (1) Elastic energy storage stage:

[0021] The hip joint angle decreases, and the artificial muscle fibers begin to be stretched to store elastic energy.

[0022] (2) Resistance generation stage:

[0023] The micro force sensor detects the force change effect of the artificial muscle fiber, collects signals through the control unit, and at the same time outputs a voltage signal to the power amplifier unit to supply power to the artificial muscle fiber. After the artificial muscle fiber is powered on, Maxwell stress is generated inside, which offsets the stress generated by strain and slows down the resistance effect generated during this process;

[0024] (3) Starting assistance stage:

[0025] When the artificial muscle fiber is stretched to the longest, the Maxwell stress is the largest, the hip joint angle changes direction, and the pulling force effect generated by the artificial muscle fiber is the same as the movement direction of the human leg. The voltage is removed, and the artificial muscle fiber is restored to the elastic state caused by strain;

[0026] (4) Energy release stage:

[0027] As the hip joint angle gradually increases, the assistance magnitude gradually decreases, and the assistance behavior is completed.

[0028] Compared with the prior art, the flexible exoskeleton system and working method described in the present invention have the following advantages:

[0029] The flexible exoskeleton system involved in the present invention has a simple structure, and all materials are non-metallic materials. The system has a friendly interaction and high safety;

[0030] The exoskeleton device of the present invention is adjustable and suitable for wearers with different heights and weights, with strong applicability;

[0031] The driver of the flexible exoskeleton system involved in the present invention is a fiber bundle driver integrated with artificial muscle fibers. This is the first application of this type of artificial muscle in an exoskeleton device. This driver has high-level performance parameters such as fast response speed, large deformation ability, and high energy output. At the same time, the material for preparing the dielectric elastomer has certain cost advantages;

[0032] The driver of the flexible exoskeleton system involved in the present invention is different from the pneumatic or cable-driven active flexible exoskeleton system. It does not need to carry driving devices such as gas cylinders, air pumps, and motors, and truly realizes the essential flexibility of driving.

[0033] The present invention first proposes a combined active and passive flexible exoskeleton driving scheme. The driver of the flexible exoskeleton system involved realizes the function of active regulation compared with the existing passive flexible exoskeleton system based on a single elastic element, slows down the resistance consumption generated by the passive structure during the assistance process, and improves the overall assistance effect of the device. Description of the Drawings

[0034] The accompanying drawings, which form a part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0035] Figure 1 is the parts assembly drawing of the flexible exoskeleton system of the present invention;

[0036] Figure 2 is the rear view of the flexible exoskeleton system of the present invention;

[0037] Figure 3 is the structure diagram of the artificial muscle fiber bundle in the flexible exoskeleton system of the present invention;

[0038] Figure 4 is the preparation flow chart of the artificial muscle fiber bundle of the present invention;

[0039] Figure 5 is the physical diagram of the artificial muscle fiber of the present invention;

[0040] Figure 6 is the physical diagram of the artificial muscle driver of the flexible exoskeleton system of the present invention

[0041] Figure 7 is the schematic diagram of the driving method of the flexible exoskeleton system of the present invention;

[0042] Figure 8 is the flow chart of the control method of the flexible exoskeleton system of the present invention;

[0043] Figure 9 is the experimental result diagram of the surface electromyogram signal detection of 6 subjects in the performance test of the flexible exoskeleton system of the present invention.

[0044] Figure 10 is the experimental result diagram of the respiratory oxygen consumption metabolism detection of 6 subjects in the performance test of the flexible exoskeleton system of the present invention.

[0045] Description of reference numerals

[0046] 1 - Shoulder fixing strap; 2 - Controller unit; 3 - Waist fixing strap; 4 - Signal line; 5 - Micro force sensor; 6 - Artificial muscle fiber bundle; 7 - Driver holder; 8 - Knee joint fixing strap. Detailed implementation manners

[0047] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0048] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0049] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0050] The present invention will be described in detail below with reference to the drawings and in conjunction with embodiments.

[0051] As Figure 1 shown, the present invention provides a flexible exoskeleton system based on dielectric elastomer artificial muscle fibers. The overall structure of the system is longitudinally arranged, where the controller unit 2 is located at the central position of the device, on the "center" line directly behind the human waist; the shoulder fixing strap 1 is arranged on the upper "upper side" of the exoskeleton device, the waist fixing strap 3 is located in the middle, and the knee fixing strap 8 is installed on the lower "lower side" of the device. Each fixing strap can achieve precise position adjustment in the left and right "inner" and "outer" directions through an adjustment mechanism, ensuring that the front, rear, left, and right directions of the fixing strap are closely fitted to the corresponding parts of the human body.

[0052] Specifically, the shoulder fixing strap 1 and the knee fixing strap 8 are provided with adjustable buckles in the "transverse" direction, and the buckles are distributed along the "transverse" direction for symmetric adjustment; the waist fixing strap 3 is made of flexible woven fabric material, and its "longitudinal" extension part can be adapted along the front and rear directions of the human torso.

[0053] As Figure 2As shown, the controller unit 2 is installed on the "outer side" of the center of the device. Its housing is formed of PLA material, with a rectangular shape. There are reserved interfaces on both its "left side" and "right side" for connecting the micro force sensor 5 and the signal line 4. The outer layer of the signal line 4 is coated with a flexible electrical insulating material, and its layout follows a uniform layout in the "longitudinal" and "transverse" directions to ensure stable electrical connection and no external force interference during the movement of the device.

[0054] As Figure 3 shown, the artificial muscle fiber bundles 6 are arranged on the "lower side" or "upper side" of the actuator holder 7, close to the leg muscle groups of the human body. The production diameter of each individual artificial muscle fiber can reach a minimum of 0.85 mm, while fibers with a diameter of 1.95 mm are selected in this exoskeleton device to ensure sufficient driving force; the "longitudinal" length of each fiber bundle is 140 mm, and it is integrated by arranging 18 single fibers evenly in the "longitudinal" direction. The center position of the fiber bundle is aligned with the center line of the actuator holder, and its "left and right" distribution ensures balanced assistance on both sides.

[0055] The dielectric elastomer material used has the following key physical parameters: the dielectric constant is 17 (measured at a frequency of 10 Hz); the elastic modulus is 3 MPa; the breakdown strength is 70 V / μm. In addition, the response time of a single fiber is less than 0.1 s, and it can quickly generate a deformation of about 15% after the driving voltage is applied, meeting the requirements of large deformation and high energy output, so as to achieve a rapid response and precise assistance to human movement.

[0056] As Figure 4 shown, the preparation process of the artificial muscle fiber bundle of the present invention includes the following steps, which are described through operations in specific directions:

[0057] Dielectric elastomer film stacking (combination of transverse and longitudinal): First, the dielectric elastomer films with the above physical parameters are arranged in parallel in the "longitudinal" direction and stacked in multiple layers in the "transverse" direction to form a multi-layer structure with a predetermined thickness;

[0058] Rolling (along the longitudinal direction): After stacking, the film is rolled in the "longitudinal" direction to form a preliminary strip structure. During the rolling process, it is required that the layers fit tightly "inside and outside";

[0059] Fibrillation treatment: The rolled body is processed through a specific fibrillation process to uniformly control the diameter of a single fiber within 2.0 mm;

[0060] Integrated assembly: Finally, the 18 processed fibers are arranged evenly in the "transverse" direction and integrated into a fiber bundle. The "center" of the fiber bundle is aligned with the installation center of the actuator holder to ensure uniform stress distribution during the movement of the device.

[0061] Figure 5and Figure 6 In the physical diagram shown, three artificial muscle fibers with different diameters and lengths indicate that artificial muscle fibers of different sizes can be prepared according to different requirements, and through electron microscope images, it is shown that on the "cross-section", the contacts between each layer are complete, and the layers are stacked on top of each other to form a stable integrated structure.

[0062] In the present invention, a dielectric elastomer artificial muscle fiber is used as the driving element. The driving voltage required during its operation is within 2000V (which can be adjusted according to the magnitude of the assistance), and the voltage is output through a power amplification module by a controller unit. The signal output by the voltage modulation unit in the controller is a square wave, and its frequency is less than 1.5Hz (the same as the human gait cycle, and the output frequency is judged according to the signal returned by the force sensor). The square wave signal is transmitted along the center of the device in the "longitudinal" direction to ensure coordination with the human gait cycle.

[0063] Figure 7 Schematically shows the specific process of the driving method. This method adopts a combination of active and passive methods. Among them, active assistance refers to using voltage to regulate the assistance effect of the driver, and passive assistance refers to passive driving, that is, using an elastic element as the driving unit without subjective regulation behavior. Its process can be divided into the following four stages, and the relative position changes of "front and back", "up and down", and "left and right" are clearly indicated in each stage:

[0064] Elastic energy storage stage:

[0065] When the hip joint angle of the human body decreases (when the "front side" starts to stretch), the artificial muscle fiber is stretched along the "longitudinal" direction and is in an energy storage state. The fiber generates uniform energy storage on the "upper side" and "lower side" due to its inherent elasticity.

[0066] Resistance generation stage:

[0067] When the fiber is stretched to a certain extent in both the "transverse" and "longitudinal" directions, due to forced stretching, it generates a resistance in the "inner side" in the opposite direction to the "rear side" of the human leg movement. At this time, a micro force sensor installed near the "center" of the fiber (its installation position is on the "inner side" of the driver holder) real-time detects the force value generated by the fiber stretching and feeds the signal back to the controller unit located at the "center" of the device. The controller unit then outputs an appropriate voltage, which is applied to the artificial muscle fiber through the power amplification module, so that it generates a Maxwell stress on the "outer side" to partially offset the resistance effect caused by the tensile strain.

[0068] Starting assistance stage:

[0069] When the artificial muscle fiber is stretched to the maximum extent, the hip joint angle of the human body reaches the minimum (i.e., the "front side" angle is the smallest, and the "rear side" of the fiber reaches the maximum stretching state). At this time, the controller unit adjusts to the maximum voltage output to make the fiber generate the maximum Maxwell stress. Subsequently, when the hip joint angle is reversed and the human movement is converted from the "rear side" to the "front side", the pulling force direction generated by the fiber changes to be consistent with the movement of the human leg. The voltage is turned off to make the fiber restore the force effect generated by the strain, so as to achieve active assistance on the "inner side".

[0070] Energy release stage:

[0071] In the human gait cycle, as the hip joint angle gradually recovers (gradually changing from the "front side" to the "rear side"), the artificial muscle fiber releases the stored elastic energy. During this process, the assistance effects of the "upper side" and the "lower side" gradually decrease until the fiber returns to the initial energy storage state, completing a complete driving cycle.

[0072] As Figure 8 shown, the present invention adopts a closed-loop control system. The system structure includes a signal acquisition module, a voltage modulation module, and a power amplification module located inside the controller unit. The system collects real-time feedback signals from sensors in all directions of the "left and right" of the device at the "center" position. After data processing, the voltage signal is regulated to ensure that the voltage applied to the artificial muscle fiber reaches the optimal match in the "inner and outer" directions.

[0073] As Figure 9 shown, in the actual application of the present invention, surface electromyography signals of 6 subjects are tested. In the case of no assistance as a reference: for the VLO muscle group, the activation level decreased by 42.1% during active assistance and 28.9% during passive assistance; for the VMO muscle group, the activation level decreased by 34.5% during active assistance and 27.6% during passive assistance; for the BF muscle group, the activation level decreased by 47.7% during active assistance and 42.7% during passive assistance. The above data indicate that during a gait cycle, the active assistance mode significantly reduces the activation levels of the main muscle groups, thus achieving a more efficient movement assistance effect.

[0074] These data are all the maximum activation values measured for each muscle group in the "inner and outer" directions during the "front and rear" movement conversion process within a gait cycle, indicating that the present invention has obvious advantages in reducing the human muscle load and improving the movement assistance effect.

[0075] As Figure 10 shown, through the respiratory oxygen consumption metabolism test of 6 subjects, the results show that compared with the non-assistance state, the respiratory metabolism level in the active assistance mode decreased by 15.3%, and the passive assistance mode decreased by 7.2%, further verifying the superior performance of the present invention in reducing human metabolic consumption.

[0076] Each fixing strap (shoulder, waist, knee joint) is made of high-strength flexible woven fabric material, and the specific parameters are as follows:

[0077] The width of the shoulder fixing strap is generally 80 mm, and the thickness is about 3 - 5 mm;

[0078] The width of the waist fixing strap is 150 mm, and the thickness is about 4 - 6 mm;

[0079] The height of the knee joint fixing strap is 200 mm, and the thickness is about 3 mm;

[0080] Each fixing strap is provided with adjustable devices that are symmetric in "left" and "right", allowing for fine-tuning in the "front-back" and "inside-outside" directions to ensure the comfort and stability of the wearer during use.

[0081] The controller unit and the driver holder are both made of PLA material. The specific model and 3D printing parameters are: layer thickness 0.2 mm, filling rate 20%, and printing temperature 210 °C. This manufacturing process not only ensures the stability of the "center" structure of the device, but also maintains lightweight and high mechanical strength on the "outside".

[0082] From the above detailed embodiments, it can be seen that the present invention uses dielectric elastomer artificial muscle fibers as the driving element, giving full play to the advantages of the material's fast response, large deformation, and high energy output. In the entire device, precise energy transfer and dynamic regulation are achieved in both the "upper side", "lower side", "front side", and "rear side", achieving the following technical effects:

[0083] Essential flexible drive: By using dielectric elastomer materials, the limitations of metal rigid components in traditional exoskeleton systems are avoided, realizing the flexible and lightweight design of the entire system.

[0084] Combined active and passive assistance: Through the closed-loop control system and the segmented drive method, seamless conversion between active regulation and passive energy storage is achieved in the "inside-outside" and "longitudinal" directions, thereby providing a high-efficiency assistance effect in each gait cycle.

[0085] Ergonomic adaptation: The reasonable layout of each fixing strap, sensor, and driving element in the "center", "left-right", and "front-back" directions effectively reduces muscle load and improves movement comfort and energy utilization efficiency.

[0086] Experimental data verification: The surface electromyography and respiratory oxygen consumption test data fully prove that the present invention has a significant effect of reducing physiological metabolism and muscle activation compared with the non-assisted state in the active assistance mode, meeting the basic requirements of human motion assistance.

[0087] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A flexible exoskeleton system, characterized in that: The invention comprises an exoskeleton device and a controller unit (2). The overall structure of the exoskeleton device is arranged longitudinally, and comprises a shoulder fixing belt (1), a waist fixing belt (3), an artificial muscle fiber bundle (6), a driver fixer (7), and a knee joint fixing belt (8). The shoulder fixing belt (1) is arranged at the upper part of the exoskeleton device, the waist fixing belt (3) is arranged at the middle part of the exoskeleton device, and the knee joint fixing belt (8) is arranged at the lower part of the exoskeleton device. The shoulder fixing belt (1) is connected to the waist fixing belt (3), the waist fixing belt (3) is connected to the artificial muscle fiber bundle (6), the artificial muscle fiber bundle (6) is connected to the driver fixer (7), and the driver fixer (7) is connected to the knee joint fixing belt (8). The controller unit (2) is arranged at the center position of the exoskeleton device. A micro force sensor (5) is also arranged at the connection position between the waist fixing belt (3) and the artificial muscle fiber bundle (6), and the micro force sensor (5) is connected to the controller unit (2) via a signal line (4).

2. A flexible exoskeleton system according to claim 1, characterized in that: The shoulder fixing belt (1), the waist fixing belt (3) and the knee joint fixing belt (8) are all made of flexible woven fabric materials.

3. A flexible exoskeleton system according to claim 1, characterized in that: The controller unit (2) comprises a signal acquisition unit, a voltage modulation unit, and a power amplification unit.

4. A flexible exoskeleton system according to claim 1, characterized in that: the controller unit (2) and the driver holder (7) are both printed using PLA material through a 3D printer.

5. A flexible exoskeleton system according to claim 1, characterized in that: The artificial muscle fiber bundle (6) is composed of a plurality of artificial muscle fibers, and the preparation process includes dielectric elastomer artificial muscle film stacking, rolling, fiberization, and integration, and the diameter of a single fiber does not exceed 2 mm.

6. A flexible exoskeleton system according to claim 1, characterized in that: The shoulder fixing belt (1), the waist fixing belt (3) and the knee joint fixing belt (8) are all adjustable.

7. A flexible exoskeleton system according to claim 1, characterized in that: The shoulder fixing belt (1), the controller unit (2), the waist fixing belt (3), the micro force sensor (5), the driver fixator (7), and the knee joint fixing belt (8) are fixed together by means of binding buckles.

8. A flexible exoskeleton system according to claim 1, characterized in that: The artificial muscle fiber bundle (6) and the driver fixer (7) are fixed in a bolt-fastening manner.

9. A flexible exoskeleton system according to claim 1, characterized in that: The signal line (4) is fixed to the micro force sensor (5), the driver fixture (7) and the controller unit (2) by means of plug-in fastening.

10. A working method of a flexible exoskeleton system, characterized in that: The steps include: (1) Elastic energy storage stage: The hip joint angle decreases, and the artificial muscle fibers begin to lengthen, storing elastic energy; (2) Resistance generation stage: The micro force sensor detects the force change effect of the artificial muscle fiber, collects the signal through the control unit, and outputs the voltage signal to the power amplifier unit to supply power to the artificial muscle fiber. After the artificial muscle fiber is powered on, Maxwell stress is generated inside to offset the stress generated by the strain and reduce the resistance generated in this process. (3) Start the support phase: When the artificial muscle fiber is stretched to its longest length, the Maxwell stress is the largest, the hip joint angle changes direction, and the pulling effect generated by the artificial muscle fiber is in the same direction as the movement of the human leg. The voltage is removed and the elastic state of the artificial muscle fiber caused by the strain is restored. (4) Energy release stage: As the hip joint angle gradually increases, the magnitude of the assist gradually decreases, completing the assisting action.

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