Reconfigurable software driver for variable stiffness skeleton

Abstract

The application discloses a reconfigurable soft driver of a variable stiffness skeleton, which comprises a soft continuum, a pneumatic driving part and a deformation constraint part arranged in the soft continuum; the pneumatic driving part comprises a gas cavity arranged in the soft continuum, the gas cavity is arranged along the axial direction of the soft continuum, and one end of the soft continuum is provided with a gas inlet communicated with the gas cavity; the soft continuum is provided with a fiber winding body surrounding the gas cavity, and the limiting winding body is used for limiting or constraining the soft continuum to expand and deform in the radial direction; the deformation constraint part comprises deformation constraint bodies arranged at intervals along the axial direction of the soft continuum, and the deformation constraint bodies are made of shape memory polymers; the soft continuum is further provided with a heating wire, and the heating wire is used for temperature control of the deformation constraint bodies so that the deformation constraint bodies are transformed between the glass state and the rubber state; when the soft continuum is in a free state, the deformation constraint bodies are in a strip shape, and the included angle between the axis of the deformation constraint bodies and the axis of the soft continuum is an acute angle.

Description

TECHNICAL FIELD

[0001] The present application relates to a soft actuator, in particular to a reconfigurable soft actuator with variable stiffness skeleton. BACKGROUND

[0002] At present, common soft actuators include multi-chamber actuators, fiber-reinforced actuators, pneumatic artificial muscles, and hydraulic amplification self-repairing electrostatic actuators. Although there are various types of actuators, due to the pre-programmed structural design, the constraints of most actuators cannot be adjusted during the deformation process, and only single bending, stretching, twisting, and spiral deformation can be achieved, which makes it difficult to fully exert the flexibility and motion diversity of soft actuators, and severely limits the application range of soft actuators. SUMMARY

[0003] Therefore, the present application aims to provide a reconfigurable soft actuator with variable stiffness skeleton, which can realize bending and spiral deformation.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] A reconfigurable soft actuator with variable stiffness skeleton comprises a soft continuum, wherein a pneumatic driving part and a deformation constraint part are arranged in the soft continuum.

[0006] The pneumatic driving part comprises a gas cavity arranged in the soft continuum, wherein the gas cavity is arranged along the axial direction of the soft continuum, and one end of the soft continuum is provided with a gas inlet connected with the gas cavity; a fiber winding body is arranged around the gas cavity in the soft continuum, and the fiber winding body is used to limit or constrain the radial expansion deformation of the soft continuum.

[0007] The deformation constraint part comprises deformation constraint bodies arranged along the axial direction of the soft continuum at intervals, and the deformation constraint bodies are made of shape memory polymers; a heating wire is further arranged in the soft continuum, and the heating wire is used to control the temperature of the deformation constraint bodies to make the deformation constraint bodies change between glass state and rubber state.

[0008] When the soft continuum is in a free state, the deformation constraint body is in a strip shape, and the acute angle between the axis of the deformation constraint body and the axis of the soft continuum satisfies:

[0009] 0° < acute angle < 90°.

[0010] Wherein, acute angle represents the acute angle between the axis of the deformation constraint body and the axis of the soft continuum.

[0011] ​Further, the soft continuum is made of silica gel; and the heating wire is made of nickel-chromium wire.

[0012] Further, the deformation constraint bodies are arranged at equal intervals along the axial direction of the soft continuum.

[0013] Further, when the soft continuum is in a free state, the projection length of two adjacent deformation constraint bodies in the axial direction of the soft continuum is greater than the interval of the two adjacent deformation constraint bodies in the axial direction of the soft continuum.

[0014] Further, the outer wall of the soft continuum comprises an outer curved surface and an outer flat surface, the inner wall of the air cavity comprises an inner curved surface and an inner flat surface, the outer curved surface and the inner curved surface are arranged correspondingly, and the outer flat surface and the inner flat surface are parallel to each other.

[0015] Further, the outer curved surface and the inner curved surface are coaxial circular arc surfaces or coaxial elliptical curved surfaces.

[0016] Further, when the soft continuum is in a free state, the outer curved surface, the inner curved surface, the outer flat surface and the inner flat surface are symmetrically arranged relative to the same symmetry plane.

[0017] Further, the deformation constraint bodies and the heating wire are arranged between the outer flat surface and the inner flat surface.

[0018] Further, the fiber winding body comprises flat segments arranged at intervals and located between the outer flat surface and the inner flat surface; adjacent two flat segments are the i-th flat segment and the i+1-th flat segment, and a curved segment located between the outer curved surface and the inner curved surface is arranged between the first end of the i-th flat segment and the second end of the i+1-th flat segment and between the second end of the i-th flat segment and the first end of the i+1-th flat segment.

[0019] Further, the two curved segments arranged between the adjacent two flat segments intersect, and the two curved segments are fixedly connected or integrally arranged at the intersection position.

[0020] The present application has the following beneficial effects:

[0021] This invention relates to a reconfigurable soft actuator with a variable stiffness skeleton. It comprises a pneumatic drive unit and a deformation constraint unit within a soft continuum. Within the deformation constraint unit, deformation constraint bodies are spaced apart and inclined relative to the axis of the soft continuum. These deformation constraint bodies are made of a shape memory polymer (SMP). SMP is a two-phase material with shape memory properties and a glass transition temperature (Tg). In its unheated state at room temperature (below Tg), it exists in a high-stiffness glassy state, while in its heated state at high temperature (above Tg), it exists in a low-stiffness rubbery state. Thus, the temperature of the deformation constraint body can be controlled by a heating wire disposed within the soft continuum, allowing the deformation constraint body to transition between the glassy and rubbery states. When the deformation constraint is in a glassy state, it possesses high rigidity relative to the soft continuum, thus constraining its deformation. When high-pressure gas is introduced into the air chamber through the inlet, the soft continuum, under the constraint of the fiber winding, does not expand or deform very little in the radial direction, but deforms in the axial direction, exhibiting helical deformation under the constraint of the high-rigidity deformation constraint. When the deformation constraint is in a rubbery state, its rigidity is the same as or close to that of the soft continuum. When high-pressure gas is introduced into the air chamber through the inlet, the soft continuum, under the constraint of the fiber winding, does not expand or deform very little in the radial direction, but bends in the axial direction. Therefore, the reconfigurable soft actuator with variable stiffness frame of this invention can dynamically adjust the rigidity of the deformation constraint through a heating wire, thereby achieving both bending and helical deformation forms. This makes the actuator reconfigurable, improving the diversity, flexibility, and adaptability of the soft actuator's motion. In addition, the helical deformation soft actuator has a larger contact area with the object and greater friction, thus it has a stronger load-bearing capacity and is more suitable for grasping slender rod-shaped objects compared to the bending deformation actuator. Attached Figure Description

[0022] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0023] Figure 1 This is a schematic diagram of the reconfigurable software driver embodiment of the variable stiffness skeleton of the present invention;

[0024] Figure 2 for Figure 1 AA section view;

[0025] Figure 3 for Figure 2 BB cross-sectional view;

[0026] Figure 4 for Figure 3 CC section view;

[0027] Figure 5 The first axonometric view of the soft continuum hidden from the soft actuator;

[0028] Figure 6 The second axonometric view of the soft continuum hidden from the soft actuator;

[0029] Figure 7 The model view of the reconfigurable soft actuator of the variable stiffness skeleton of the embodiment;

[0030] Figure 8 The schematic view of the spiral deformation of the deformation constraint;

[0031] Figure 9 The state view of the spiral deformation of the reconfigurable soft actuator of the variable stiffness skeleton of the embodiment;

[0032] Figure 10 The state view of the bending deformation of the reconfigurable soft actuator of the variable stiffness skeleton of the embodiment;

[0033] Figure 11 The curve view of the elastic modulus of the shape memory polymer changing with temperature.

[0034] Explanation of reference signs:

[0035] 10-soft continuum; 101-outer curved surface; 102-outer flat surface; 11-air cavity; 111-inner curved surface; 112-inner flat surface; 12-air inlet; 13-fiber winding body; 131-straight section; 132-curved section; 14-deformation constraint body; 15-heating wire. DETAILED DESCRIPTION

[0036] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it.

[0037] As Figures 1-6As shown, the reconfigurable soft driver of the variable stiffness framework in the embodiment includes a soft continuum 10, and a pneumatic driving part and a deformation constraint part arranged in the soft continuum. Specifically, the pneumatic driving part in the embodiment includes a gas cavity 11 arranged in the soft continuum 10, the gas cavity 11 is arranged along the axial direction of the soft continuum 10, and one end of the soft continuum 10 is provided with a gas inlet 12 in communication with the gas cavity. The soft continuum 10 is provided with a fiber winding body 13 arranged around the gas cavity, and the fiber winding body 13 is used to limit or constrain the radial expansion deformation of the soft continuum 10. The deformation constraint part in the embodiment includes deformation constraint bodies 14 arranged along the axial direction of the soft continuum 10 at intervals, and the deformation constraint bodies 14 are made of shape memory polymers. The soft continuum 10 in the embodiment is also provided with a heating wire 15, and the heating wire 15 is used to control the temperature of the deformation constraint bodies 14 to make the deformation constraint bodies 14 change between the glass state and the rubber state. In the embodiment, the soft continuum 10 is made of silica gel, the heating wire 15 is made of nichrome wire, and the fiber winding body 13 is made of a material that can bend but cannot be elongated. Specifically, when the soft continuum 10 is in a free state, the axis of the soft continuum 10 at this time is a straight line, the deformation constraint bodies 14 are long strips, and the acute angle between the axis of the deformation constraint bodies 14 and the axis of the soft continuum 10 satisfies:

[0038] 0°< <90°

[0039] wherein, represents the acute angle between the axis of the deformation constraint body and the axis of the soft continuum.

[0040] That is, when the soft continuum 10 is in a free state, the deformation constraint bodies 14 are arranged obliquely relative to the axis of the soft continuum 10. In the preferred embodiment of the embodiment, the deformation constraint bodies 14 are arranged at equal intervals along the axial direction of the soft continuum 10, so that the bending deformation of the soft continuum 10 in the length direction can be kept consistent. Specifically, when the soft continuum 10 is in a free state, the projection length of the adjacent two deformation constraint bodies 14 in the axial direction of the soft continuum 10 is greater than the interval of the adjacent two deformation constraint bodies 14 in the axial direction of the soft continuum 10, so that when the deformation constraint bodies 14 are in the glass state, the bending deformation direction of the soft continuum 10 can be better constrained, and the axis of the soft continuum 10 after the deformation constraint bodies 14 is in the glass state is helical, as Figure 8 shown.

[0041] As Figure 2As shown, in the embodiment, the outer wall of the soft continuum 10 includes an outer curved surface 101 and an outer flat surface 102, the inner wall of the air cavity 11 includes an inner curved surface 111 and an inner flat surface 112, the outer curved surface 101 and the inner curved surface 111 are correspondingly arranged, and the outer flat surface 102 and the inner flat surface 112 are parallel to each other. Specifically, the outer curved surface 101 and the inner curved surface 111 are coaxial circular arc surfaces or coaxial elliptical curved surfaces. In the embodiment, the outer curved surface 101 and the inner curved surface 111 are coaxial circular arc surfaces. When the soft continuum 10 is in a free state, i.e., the axis of the soft continuum 10 is a straight line, the outer curved surface 101, the inner curved surface 111, the outer flat surface 102, and the inner flat surface 112 are symmetrically arranged relative to the same symmetry plane. The deformation constraint body 14 and the heating wire 15 in the embodiment are arranged between the outer flat surface 102 and the inner flat surface 112.

[0042] As shown in the figure, Figures 5-6 The fiber winding body 13 in the embodiment includes flat sections 131 arranged at intervals and located between the outer flat surface 102 and the inner flat surface 112. Let the adjacent two flat sections be the ith flat section and the (i+1)th flat section. The first end of the ith flat section and the second end of the (i+1)th flat section, and the second end of the ith flat section and the first end of the (i+1)th flat section are respectively provided with curved sections 132 located between the outer curved surface 101 and the inner curved surface 111, i.e., two curved sections 132 are respectively arranged between the two ends of the adjacent two flat sections 131. In the embodiment, the curved sections 132 are spiral curves, so that the fiber winding body 13 forms a double helix-like structure. In the embodiment, the two curved sections 132 arranged between the adjacent two flat sections 131 intersect, and the two curved sections 132 are fixedly connected or integrally arranged at the intersection position.

[0043] Specifically, the following assumptions are made for the soft actuator when designing the embodiment:

[0044] 1) The deformation constraint body 14 and the soft continuum 10 do not separate during the deformation process;

[0045] 2) The actuator always maintains constant curvature deformation during the deformation process;

[0046] 3) The influence of the heating wire on the deformation of the actuator is ignored;

[0047] 4) The elastic potential energy stored in the fiber winding body 13 is ignored;

[0048] 5) The silicone is an isotropic material.

[0049] Based on the principle of minimum potential energy, under the above assumptions, combined with the knowledge of material mechanics, theoretical mechanics, elasticity, tensors, etc., the expression of the final deformation output quantity of the actuator, the pitch and the spiral radius, is obtained:

[0050]

[0051]

[0052] wherein: represents the pitch; represents the spiral radius; , is the curvature of the main strain plane along the axis and axis; is the acute angle between the axis of the deformation constraint body and the axis of the soft continuum. During the process of driving the soft continuum 10 to deform, there is always a plane on which the shear deformation does not exist, and this plane is the plane.

[0053] The reconfigurable soft driver of the variable stiffness framework in this embodiment is configured by arranging a pneumatic driving part and a deformation constraint part in the soft continuum 10, arranging deformation constraint bodies 14 in the deformation constraint part at intervals and at an angle relative to the axis of the soft continuum, and making the deformation constraint bodies 14 of shape memory polymer. Shape memory polymer (SMP) is a two-phase material with shape memory performance, and its glass transition temperature is Tg. In the normal temperature and unheated state (below Tg), it is in a glass state with high rigidity, and in the high temperature and heated state (above Tg), it is in a rubber state with low rigidity, as shown in Figure 11 . In this way, the temperature of the deformation constraint body 14 can be controlled by using the heating wire 15 arranged in the soft continuum 10, so that the deformation constraint body 14 is converted between the glass state and the rubber state. When the deformation constraint body 14 is in the glass state, the deformation constraint body 14 at this time has high rigidity relative to the soft continuum 10, so that the deformation of the soft continuum 10 can be constrained. When high-pressure gas is introduced into the air cavity 11 through the air inlet 12, the soft continuum 10 will not expand and deform or will have little expansion and deformation in the radial direction under the constraint of the fiber winding body 13, and will produce deformation in the axial direction. Under the constraint of the deformation constraint body 14 with high rigidity, the soft continuum 10 produces spiral deformation, as shown in Figure 9 . When the deformation constraint body 14 is in the rubber state, the rigidity of the deformation constraint body 14 at this time is the same as or close to that of the soft continuum 10. When high-pressure gas is introduced into the air cavity 11 through the air inlet 12, the soft continuum 10 will not expand and deform or will have little expansion and deformation in the radial direction under the constraint of the fiber winding body 13, and will produce bending deformation in the axial direction, as shown in Figure 10The reconfigurable soft driver of the stiffness-changing framework can dynamically adjust the rigidity of the deformation constraint body by heating the wire 15, so as to realize both bending and spiral deformation forms, so that the driver has reconfigurability, and the diversity, flexibility and adaptability of the movement of the soft driver are improved. In addition, the spiral deformation soft driver has a larger contact area with the object and a larger friction force, so that compared with the bending deformation driver, the carrying capacity is stronger, and the spiral deformation soft driver is more suitable for grabbing slender rod-like objects.

[0054] The above-described embodiments are only preferred embodiments for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent replacement or transformation made by those skilled in the art on the basis of the present application is within the protection scope of the present application. The protection scope of the present application is subject to the claims.

Claims

1. A reconfigurable software actuator for a variable stiffness skeleton, characterized in that: It includes a soft continuum, which is provided with a pneumatic drive unit and a deformation constraint unit; The pneumatic drive unit includes an air cavity disposed within the soft continuous body, the air cavity being disposed along the axial direction of the soft continuous body, and an air inlet communicating with the air cavity being provided at one end of the soft continuous body; a fiber winding body is disposed within the soft continuous body surrounding the air cavity, the fiber winding body being used to restrict or constrain the expansion and deformation of the soft continuous body in the radial direction. The deformation constraint part includes deformation constraint bodies spaced apart along the axial direction of the soft continuum, and the deformation constraint bodies are made of shape memory polymer; the soft continuum is also provided with a heating wire, which is used to control the temperature of the deformation constraint body so that the deformation constraint body can transform between a glassy state and a rubbery state; The outer wall of the soft continuum includes an outer curved surface and an outer flat surface. The deformation constraint bodies are spaced apart along the axial direction of the soft continuum on one side of the outer flat surface of the soft continuum, thereby realizing two deformation forms: bending and spiral. When the soft continuum is in a free state, the deformation constraint body is elongated, and the acute angle between the axis of the deformation constraint body and the axis of the soft continuum satisfies: 0°＜ ＜90° in, This represents the acute angle between the axis of the deformation constraint and the axis of the soft continuum.

2. The reconfigurable software actuator for the variable stiffness skeleton according to claim 1, characterized in that: The soft continuum is made of silicone; the heating wire is made of nickel-chromium wire.

3. The reconfigurable software actuator for the variable stiffness skeleton according to claim 1, characterized in that: The deformation constraint bodies are arranged at equal intervals along the axial direction of the soft continuum.

4. The reconfigurable software actuator for the variable stiffness skeleton according to claim 3, characterized in that: When the soft continuum is in a free state, the projected length of two adjacent deformation constraint bodies in the axial direction of the soft continuum is greater than the distance between the two adjacent deformation constraint bodies in the axial direction of the soft continuum.

5. The reconfigurable software actuator for the variable stiffness skeleton according to any one of claims 1-4, characterized in that: The inner wall of the air cavity includes an inner curved surface and an inner flat surface, the outer curved surface and the inner curved surface are respectively arranged, and the outer flat surface and the inner flat surface are parallel to each other.

6. The reconfigurable software actuator for the variable stiffness skeleton according to claim 5, characterized in that: Both the outer and inner curved surfaces are coaxial circular arc surfaces or coaxial elliptical surfaces.

7. The reconfigurable software actuator for the variable stiffness skeleton according to claim 5, characterized in that: When the soft continuum is in a free state, the outer surface, inner surface, outer plane, and inner plane are all symmetrically arranged with respect to the same symmetry plane.

8. The reconfigurable software actuator for the variable stiffness skeleton according to claim 5, characterized in that: The deformation constraint body and the heating wire are disposed between the outer plane and the inner plane.

9. The reconfigurable software actuator for the variable stiffness skeleton according to claim 5, characterized in that: The fiber winding body includes straight segments spaced apart and located between the outer plane and the inner plane; let two adjacent straight segments be the i-th straight segment and the (i+1)-th straight segment, and respectively, between the first end of the i-th straight segment and the second end of the (i+1)-th straight segment, and between the second end of the i-th straight segment and the first end of the (i+1)-th straight segment, there are curved segments located between the outer surface and the inner surface.

10. The reconfigurable software actuator for the variable stiffness skeleton according to claim 9, characterized in that: Two curved segments are provided between two adjacent straight segments and intersect, and the two curved segments are fixedly connected or integrally provided at the intersection position.

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