阅读说明：本技术 一种多材料柔性仿生义指系统及其设计方法 (Multi-material flexible bionic artificial finger system and design method thereof ) 是由 龚子丹 雷屹松 王子文 张�杰 刘建勋 黄少通 陈煜� 麦智鑫 于 2021-07-22 设计创作，主要内容包括：本发明公开了一种多材料柔性仿生义指系统及其设计方法,属于仿生人体假肢技术领域,其包括柔性气动义指、空气差压传感器、光纤拉力传感器、气泵、控制器辅助单元和微控制器；本发明相较于传统刚性结构材料仿生义指系统,提出采用不同刚度材料的气动波纹管进行义指仿生,并基于简化数学模型进行分析构建,以解决柔性气动义指弯曲角度和夹持力难以测量的问题,使得该系统能够进行实时的精准的反馈,能够有效刺激患肢的肌肉运动,使患者在社会生活中,能适应简单环境,做一些力所能及的生活自理活动。(The invention discloses a multi-material flexible bionic artificial finger system and a design method thereof, belonging to the technical field of bionic human artificial limbs and comprising a flexible pneumatic artificial finger, an air differential pressure sensor, an optical fiber tension sensor, an air pump, a controller auxiliary unit and a microcontroller; compared with the traditional bionic artificial finger system made of rigid structural materials, the invention provides the method for carrying out artificial finger bionic by adopting the pneumatic corrugated pipes made of different rigid materials, and carries out analysis and construction based on a simplified mathematical model so as to solve the problem that the bending angle and the clamping force of the flexible pneumatic artificial finger are difficult to measure, so that the system can carry out real-time accurate feedback, can effectively stimulate the muscle movement of the affected limb, and can adapt to simple environments and do certain physical self-care activities in social life.)

1. A multi-material flexible bionic artificial finger system is characterized by comprising a flexible pneumatic artificial finger, an air differential pressure sensor, an optical fiber tension sensor, an air pump, a controller auxiliary unit and a microcontroller;

the flexible pneumatic artificial finger is designed based on a flexible pneumatic corrugated pipe and is used for assisting the upper limb disabled person to perform object movement;

the air differential pressure sensor is used for acquiring pressure required by the flexible pneumatic artificial finger during activity and measuring pressure, and performing difference calculation on the pressure required by the flexible pneumatic artificial finger to obtain a pressure difference result;

the optical fiber tension sensor is used for acquiring tension generated by the flexible pneumatic sensor during movement;

the air pump is used for providing the required air pressure for bending the prosthetic finger;

the controller auxiliary unit is used for outputting a PWM (pulse-width modulation) to adjust the opening and closing of the electromagnetic valve according to the pressure difference result so as to realize real-time accurate control operation on the flexible pneumatic artificial finger;

the microcontroller is used for performing powerful and accurate gripping control according to the pulling force generated by the flexible pneumatic artificial finger during activity.

2. A design method of a multi-material flexible bionic artificial finger system is characterized by comprising the following steps:

the method comprises the following steps: the flexible pneumatic artificial finger design is carried out by adopting a rubber corrugated pipe, and the flexible pneumatic artificial finger is composed of three parts, namely a pneumatic corrugated pipe, a rigid section and a semi-rigid section, wherein the pneumatic corrugated pipe is made of materials with different rigidity;

step two: the method comprises the following steps of designing a micro-strain flexible high-sensitivity optical fiber sensor, and integrating a Fiber Bragg Grating (FBG) sensor with PDMS to form the micro-strain flexible high-sensitivity optical fiber sensor;

step three: constructing a flexible bionic artificial finger system, analyzing the motion of a multi-material pneumatic actuator and a robot finger by using a simplified mathematical model, and predicting design and manufacturing parameters so as to construct the flexible bionic artificial finger system;

step four: and (4) optimizing the system, namely realizing the optimized design of the flexible bionic artificial finger system through an infrared optical 3D motion capture system.

3. The method for designing the multi-material flexible bionic artificial finger system according to claim 2, wherein the step one of the flexible pneumatic artificial finger design comprises the following specific steps:

s1: firstly, reinforcing and forming the adopted pneumatic corrugated pipe;

s2: then, the pneumatic bellows is fixed and covered with fluid polydimethylsiloxane;

s3: then, connecting the air pipe to the opening side of the corrugated pipe, and assembling the air pipe into a single multi-material pneumatic actuator, namely forming a flexible pneumatic prosthetic finger;

s4: preparing a bionic super-hydrophobic PDMS surface on the surface of the sense finger by femtosecond laser ablation so as to keep the sense finger dry and clean;

the fluid polydimethylsiloxane is prepared from a prepolymer and a cross-linking agent in proportion.

4. The method for designing the multi-material flexible bionic finger system according to claim 2, wherein the micro-strain flexible high-sensitivity optical fiber sensor is obtained by using PDMS as a substrate of the flexible optical fiber sensor and FBG as a sensing unit and by designing the embedding posture of the FBG sensor in the PDMS, the PDMS is firstly prepared by mixing a liquid polymer and a curing agent in a mass ratio of 10:1, then the FBG is fixed at the center of a mold, and after heating in a conventional oven at 60 ℃ for 12 hours, the mold is taken out and the FBG is embedded in a PDMS gasket.

5. The method for designing the multi-material flexible bionic finger system according to claim 2, wherein the simplified mathematical model is analyzed as follows:

SS 1: first, the angular deflection θ of the top of the bellows is calculated from the bellows and beam theory₁The formula is as follows:

in the formula: m is the moment acting on the free end; EI (El)_xaIs the area moment of inertia of the cross section of the bellows and the substrate; e is Young's modulus, and L is the length of the corrugated pipe;

SS 2: f for decomposing pressure of multi-material artificial finger into upper and lower corrugated pipes respectively_bAnd F_pAnd calculating the total force, the formula of which is as follows:

F＝F_b+F_p＝K_bKw_b+K_pKw_p (2)

in the formula: w is a_bAnd w_pRespectively deflection; k_bAnd K_pAxial stiffness corresponding to the upper bellows side and the lower flat side respectively;

SS 3: calculating wavinessAngular deflection theta of the interior of a tube₂The formula is as follows:

SS 4: calculating the total deflection angle phi of the multi-material pneumatic actuator in the bending process, wherein the formula is as follows:

φ＝θ₁-θ₂ (4)

SS 5: determining the moment generated by expansion of the bellows, wherein the formula is as follows:

M_mexp＝∫dFr_msinα (5)

SS 6: determining the total moment of the multi-material pneumatic actuator generated by pressure, wherein the formula is as follows:

M＝F*e*M_exp (6)。

6. the method for designing a multi-material flexible bionic artificial finger system according to claim 5, wherein the axial stiffness K corresponding to the lower flat side of the upper corrugated pipe_pThe calculation formula of (a) is as follows:

K_p＝(E₂*A_s)/L (7)

in the formula: a. the_sIs the cross-sectional area of the substrate; e₂Is the Young's modulus of PDMS.

Technical Field

The invention relates to the technical field of bionic human body artificial limbs, in particular to a multi-material flexible bionic artificial finger system and a design method thereof.

Background

The traditional artificial hand has heavy weight, low functionality and limited degree of freedom, so that the traditional artificial hand cannot adapt to the shape of an object; the various prosthetic hands or prosthetic fingers available are basically based on linkage or hydraulic and electromechanical mechanism elements, such as wires, cables and chain bands, artificial muscles, etc.; the prosthetic hands currently in use are complex in design and control structure and are also expensive to implement for robotic or prosthetic applications; although the structure is simple, the problems of inflexible operation, unnatural use and the like exist; for prosthetic or prosthetic applications, it is most desirable to have a strong adaptable hand with similar flexibility, dexterity and load-bearing capacity as the human hand, so flexible robotic finger systems have been studied from many aspects; a multiplicity of materials including soft pneumatic actuators composed of soft linear or non-linear materials for creating a wide range of pre-designed actions, control modules and applications; soft actuators are lightweight, flexible, and compatible with human-computer interaction, and have found application in everyday life; soft actuators with pneumatic chambers can provide smooth and flexible bending movements, which makes them ideal components for using soft robotic fingers; the bending angle and the gripping force of the robot fingers are usually measured experimentally or analyzed using mathematical and finite element models; however, finite element models are difficult to construct due to the highly nonlinear nature of the materials used and the complex coupling between the human finger and the actuator; therefore, it becomes important to invent a multi-material flexible bionic artificial finger system and a design method thereof;

most of the traditional bionic artificial finger systems are constructed by analyzing finite element models based on traditional rigid structural materials, and although the traditional bionic finger systems are simple in structure, the traditional bionic finger systems have the problems of inflexible operation, unnatural use and the like; therefore, the development of a bionic artificial finger system based on a flexible material becomes the next important research direction, but a finite element model of the bionic artificial finger system based on the flexible material is difficult to construct, and the bending angle and the clamping force of the flexible pneumatic artificial finger are difficult to measure or evaluate; therefore, a multi-material flexible bionic artificial finger system and a design method thereof are provided.

Disclosure of Invention

The invention aims to solve the defects in the prior art and provides a multi-material flexible bionic finger system and a design method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a multi-material flexible bionic artificial finger system comprises a flexible pneumatic artificial finger, an air differential pressure sensor, an optical fiber tension sensor, an air pump, a controller auxiliary unit and a microcontroller;

the flexible pneumatic artificial finger is designed based on a flexible pneumatic corrugated pipe and is used for assisting the upper limb disabled person to perform object movement;

the air differential pressure sensor is used for acquiring pressure required by the flexible pneumatic artificial finger during activity and measuring pressure, and performing difference calculation on the pressure required by the flexible pneumatic artificial finger to obtain a pressure difference result;

the optical fiber tension sensor is used for acquiring tension generated by the flexible pneumatic sensor during movement;

the air pump is used for providing the required air pressure for bending the prosthetic finger;

the controller auxiliary unit is used for outputting a PWM (pulse-width modulation) to adjust the opening and closing of the electromagnetic valve according to the pressure difference result so as to realize real-time accurate control operation on the flexible pneumatic artificial finger;

the microcontroller is used for performing powerful and accurate gripping control according to the pulling force generated by the flexible pneumatic artificial finger during activity.

A design method of a multi-material flexible bionic artificial finger system comprises the following steps:

the method comprises the following steps: the flexible pneumatic artificial finger design is carried out by adopting a rubber corrugated pipe, and the flexible pneumatic artificial finger is composed of three parts, namely a pneumatic corrugated pipe, a rigid section and a semi-rigid section, wherein the pneumatic corrugated pipe is made of materials with different rigidity;

step two: the method comprises the following steps of designing a micro-strain flexible high-sensitivity optical fiber sensor, and integrating a Fiber Bragg Grating (FBG) sensor with PDMS to form the micro-strain flexible high-sensitivity optical fiber sensor;

step three: constructing a flexible bionic artificial finger system, analyzing the motion of a multi-material pneumatic actuator and a robot finger by using a simplified mathematical model, and predicting design and manufacturing parameters so as to construct the flexible bionic artificial finger system;

step four: and (4) optimizing the system, namely realizing the optimized design of the flexible bionic artificial finger system through an infrared optical 3D motion capture system.

Further, the flexible pneumatic artificial finger design in the step one comprises the following specific steps:

s1: firstly, reinforcing and forming the adopted pneumatic corrugated pipe;

s2: then, the pneumatic bellows is fixed and covered with fluid polydimethylsiloxane;

s3: then, connecting the air pipe to the opening side of the corrugated pipe, and assembling the air pipe into a single multi-material pneumatic actuator, namely forming a flexible pneumatic prosthetic finger;

s4: preparing a bionic super-hydrophobic PDMS surface on the surface of the sense finger by femtosecond laser ablation so as to keep the sense finger dry and clean;

the fluid polydimethylsiloxane is prepared from a prepolymer and a cross-linking agent in proportion.

Furthermore, the microstrain flexible high-sensitivity optical fiber sensor is characterized in that PDMS is used as a substrate of the flexible optical fiber sensor, FBG is used as a sensing unit, and the embedding posture of the FBG sensor in the PDMS is designed to obtain the microstrain flexible high-sensitivity optical fiber sensor, the PDMS is firstly prepared according to the mixing ratio of the liquid polymer to the curing agent of 10:1 in mass ratio, then the FBG is fixed at the center of a mould, the mould is taken out after the FBG is heated in a conventional oven at 60 ℃ for 12 hours, and the FBG is embedded into a PDMS liner.

Further, the analysis process of the simplified mathematical model is as follows:

SS 1: first, the angular deflection θ of the top of the bellows is calculated from the bellows and beam theory₁The formula is as follows:

in the formula: m is the moment acting on the free end; EI (El)_xaIs the area moment of inertia of the cross section of the bellows and the substrate; e is Young's modulus, and L is the length of the corrugated pipe;

SS 2: f for decomposing pressure of multi-material artificial finger into upper and lower corrugated pipes respectively_bAnd F_pAnd calculating the total force, the formula of which is as follows:

F＝F_b+F_p＝K_bKw_b+K_pKw_p (2)

in the formula: w is a_bAnd w_pRespectively deflection; k_bAnd K_pAxial stiffness corresponding to the upper bellows side and the lower flat side respectively;

SS 3: calculating the angular deflection theta inside a corrugated pipe₂The formula is as follows:

SS 4: calculating the total deflection angle phi of the multi-material pneumatic actuator in the bending process, wherein the formula is as follows:

φ＝θ₁-θ₂ (4)

SS 5: determining the moment generated by expansion of the bellows, wherein the formula is as follows:

M_mexp＝∫dFr_msinα (5)

SS 6: determining the total moment of the multi-material pneumatic actuator generated by pressure, wherein the formula is as follows:

M＝F*e*M_exp (6)。

further, the axial rigidity K corresponding to the lower flat side of the upper corrugated pipe_pThe calculation formula of (a) is as follows:

K_p＝(E₂*A_s)/L (7)

in the formula: a. the_sIs the cross-sectional area of the substrate; e₂Is the Young's modulus of PDMS.

Compared with the prior art, the invention has the beneficial effects that:

1. the multi-material flexible bionic artificial finger system and the design method thereof provide a non-invasive family help mode through a flexible pneumatic artificial finger, and the obvious characteristics of the flexible pneumatic artificial finger, which are different from the traditional rigid structure, are flexibility, compliance, adaptability and safety inherent in human interaction; analyzing the illness requirements of specific crowds, and implementing a help scheme by combining factors such as human engineering, biomechanics and the like;

2. the multi-material flexible bionic artificial finger system and the design method thereof provide a flexible and comfortable optical fiber linear sensor, the flexible sensor and the artificial finger are combined through a PDMS (polydimethylsiloxane) pouring process, the influence of each material parameter on the kinematic parameter of the artificial finger is explored, and the accuracy and the comfort of the artificial finger are improved;

3. the multi-material flexible bionic artificial finger system and the design method thereof develop an artificial finger auxiliary system with accurate real-time feedback and self-adaptive adjustment functions based on a flexible optical fiber sensor, a differential pressure sensor and a layout control strategy.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

FIG. 1 is a schematic view of an overall structure of a multi-material flexible bionic artificial finger system according to the present invention;

FIG. 2 is an overall flowchart of a design method of a multi-material flexible bionic finger system according to the present invention;

FIG. 3 is a schematic structural diagram of the components of the flexible pneumatic artificial finger of the present invention;

FIG. 4 is a schematic diagram of the structure of the human finger skeleton according to the present invention;

fig. 5 is a schematic structural diagram of a microstrain flexible high-sensitivity optical fiber sensor in the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention.

Referring to fig. 1, the embodiment discloses a multi-material flexible bionic artificial finger system, which comprises a flexible pneumatic artificial finger, an air differential pressure sensor, an optical fiber tension sensor, an air pump, a controller auxiliary unit and a microcontroller;

the flexible pneumatic artificial finger is designed based on a flexible pneumatic corrugated pipe and is used for assisting the disabled with upper limbs to perform object movement;

the air differential pressure sensor is used for acquiring pressure required by the flexible pneumatic artificial finger during activity and measuring pressure, and performing difference calculation on the pressure required by the flexible pneumatic artificial finger to obtain a pressure difference result;

the optical fiber tension sensor is used for acquiring tension generated by the flexible pneumatic sensor during movement;

the air pump is used for providing the required air pressure for bending the prosthetic finger;

the controller auxiliary unit is used for outputting a PWM (pulse-width modulation) to adjust the opening and closing of the electromagnetic valve according to the pressure difference result so as to realize real-time accurate control operation on the flexible pneumatic artificial finger;

the microcontroller is used for performing powerful and accurate gripping control according to the pulling force generated by the flexible pneumatic finger during activity.

Referring to fig. 2 to 5, the embodiment discloses a design method of a multi-material flexible bionic artificial finger system, which specifically comprises the following steps:

the method comprises the following steps: the flexible pneumatic artificial finger design is carried out by adopting a rubber corrugated pipe, and the flexible pneumatic artificial finger is composed of three parts, namely a pneumatic corrugated pipe, a rigid section and a semi-rigid section, wherein the pneumatic corrugated pipe is made of materials with different rigidity;

specifically, the flexible pneumatic artificial finger design comprises the following specific steps: firstly, reinforcing and forming the adopted pneumatic corrugated pipe, wherein the pneumatic corrugated pipe is made of a silicon rubber material; then, the pneumatic bellows is fixed and covered with fluid Polydimethylsiloxane (PDMS), which has the typical low surface free energy and elastic characteristics, as well as chemical inertness and durability compared with other materials, so that the pneumatic bellows can be easily manufactured by mould pressing, and particularly, the fluid polydimethylsiloxane is prepared by mixing a prepolymer and a cross-linking agent; then, connecting the air pipe to the opening side of the corrugated pipe, and assembling the air pipe into a single multi-material pneumatic actuator, namely forming a flexible pneumatic prosthetic finger; and then, preparing a bionic super-hydrophobic PDMS surface on the surface of the sense finger by femtosecond laser ablation so as to keep the sense finger dry and clean.

Step two: the method comprises the following steps of designing a micro-strain flexible high-sensitivity optical fiber sensor, and integrating a Fiber Bragg Grating (FBG) sensor with PDMS to form the micro-strain flexible high-sensitivity optical fiber sensor;

specifically, the microstrain flexible high-sensitivity optical fiber sensor is characterized in that PDMS is used as a substrate of the flexible optical fiber sensor, FBG is used as a sensing unit, the embedding posture (trigonometric function type) of the FBG sensor in the PDMS is designed, the microstrain flexible high-sensitivity optical fiber sensor is obtained, PDMS is firstly prepared according to the mixing ratio of a liquid polymer to a curing agent in a mass ratio of 10:1, the FBG is then fixed in the center of a mold, the mold is taken out after the FBG is heated in a conventional oven at 60 ℃ for 12 hours, and the FBG is embedded in a PDMS gasket.

Step three: constructing a flexible bionic artificial finger system, analyzing the motion of a multi-material pneumatic actuator and a robot finger by using a simplified mathematical model, and predicting design and manufacturing parameters so as to construct the flexible bionic artificial finger system;

specifically, the analysis process of the simplified mathematical model is as follows:

first, the angular deflection θ of the top of the bellows is calculated from the bellows and beam theory₁The formula is as follows:in the formula: m is the moment acting on the free end; EI (El)_xaIs the area moment of inertia of the cross section of the bellows and the substrate; e is Young's modulus, and L is the length of the corrugated pipe;

then, the pressure of the multi-material artificial finger is decomposed into F of upper and lower corrugated pipes respectively_bAnd F_pAnd calculating the total force, the formula of which is as follows: f ═ F_b+F_p＝K_bKw_b+K_pKw_pIn the formula: w is a_bAnd w_pRespectively deflection; k_bAnd K_pAxial stiffness corresponding to the upper bellows side and the lower flat side respectively; in particular, the axial rigidity K corresponding to the lower flat side of the upper corrugated pipe_pIs calculated as follows K_p＝(E₂*A_s) L, wherein: a. the_sIs the cross-sectional area of the substrate; e₂Is the Young's modulus of PDMS.

Next, the angular deflection θ inside the bellows is calculated₂The formula is as follows:

then, calculating the total deflection angle phi of the multi-material pneumatic actuator in the bending process, wherein the formula is as follows: phi is equal to theta₁-θ₂；

The moment generated by expansion of the bellows is then determined, which is formulated as follows: m_mexp＝∫dFr_msinα；

Finally, the total moment of the multi-material pneumatic actuator caused by the pressure is determined, and the formula is as follows: m ═ F ═ e ═ M_exp。

Step four: optimizing a system, namely realizing the optimized design of a flexible bionic artificial finger system through an infrared optical 3D motion capture system;

specifically, the infrared optical 3D motion capture system is a reflective-based optical motion capture system with accurate data, and is composed of 12 infrared capture cameras, a switch, control software, and the like; specifically, the system optimization is that the light-reflecting ball of the motion capture system is used as a marker and is respectively attached to the palm finger (MP) joint, the near finger (PIP) joint, the far finger (DIP) joint, the back of the hand and the tip of the finger (human finger skeleton), the bending angle, the speed and the acceleration of each joint are directly obtained by recording the coordinates of three joint points of the finger and the change of the fingertip coordinates, and the motion of the artificial finger is further optimized through the motion condition of the normal human finger.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.