Method for designing and manufacturing an invertible soft robot

Description

[0001] The present invention concerns a process for designing and manufacturing of a soft robot with the ability to grow or a soft robot capable of everting according to a predefined path. An apparatus for its realization is also described.

[0002] The everting soft robots, as will be called in the following, are known also as growing soft robots, and are of the kind described in WO 2021 / 072295 A1. The pneumatically everting soft robots imitate plant-like growth by extending new material from their tip to navigate their environment.

[0003] As for US 10954789, this results in several advantages. First, there is no sliding friction between the growing body and its surroundings. Second, the body's power source can be stationary, and be located far from the robot body. Finally, a growing body does not need to apply forces to its immediate environment to move but can exploit contacts more proximal on the body. These characteristics mean a growing robot is less sensitive to the mechanical properties of its surroundings and make growth an appealing strategy for navigating a constrained, cluttered, or inhomogeneous environment.

[0004] WO 2022 / 043670 A1 describes a robotic device and a method of operating the same. Further, it discloses a process for designing and manufacturing an everting soft robot as described in the preamble of the enclosed claim 1.

[0005] US 2019 / 143539 A1 concerns a soft robotic linkage comprising first and second strip assemblies with first and second strip sections and different types of fibres that help distribute forces under pressure.

[0006] US 6171424 B1 describes a method of manufacturing fabric Venetian blinds. The equipment includes two different parts, a first part that creates strips of fabric in three portions and a second part that creates tubular bodies.

[0007] US 6045890 describes a cellular window panel, and a method and apparatus for making it. The equipment includes tension reels and rollers.

[0008] The present invention advances the art of robotics by providing mobility through growth.

[0009] An object of the present invention is to provide a tubular element configured to become a soft robot capable of growing by following pre-programmed straight or curved trajectories.

[0010] The subject is achieved by the invention that discloses a process for designing and manufacturing an everting soft robot, having a tubular structure formed by sections, the everting soft robot being capable of growing along a pre-programmed path, comprising the following steps: generation or reconstruction of the three-dimensional CAD model representing the environment in which the everting soft robot must navigate, identification of a starting point, an end point and obstacles to be overcome, avoided or exploited by the everting soft robot, generation of a path to reach the arrival point from the starting point avoiding the obstacles, the path including at least one of path straight segments, curvilinear segments and axial rotation segments, design of tubular structure straight sections, tubular structure curvilinear sections and tubular structure axial rotation sections corresponding to the straight segments, curvilinear segments and axial rotation segments, respectively, and according to the invention: choice between a plurality of first fabric patches, second fabric patches, third fabric patches, and fourth fabric patches for each section of tubular structure, subjecting each fabric patch to its own state of traction deriving from its weaving, positioning or orienting each fabric patch in the tubular structure of the robot, and union of the plurality of fabric patches on the basis of said design of the sections, capable of providing a determined tubular structure rectilinear section, curvilinear section and axial rotation section, so that the everting soft robot is adequate to follow this path during its growth.

[0011] Further features and advantages of the invention will emerge more clearly from the description of an apparatus for the creation of a tubular structure for an everting soft robot, illustrated by way of an indicative and non-limiting example in the attached drawings in which: Figure 1 is a plan view of the path required for an everting soft robot according to the present invention; Figure 2 is a plan view of the everting soft robot according to the present invention in the path required to it in figure 1; Figure 3 represents a curved section of tubular structure of the everting soft robot in figure 2. Figure 4 is a perspective view of an example of a tubular structure for the everting soft robot in figure 2; Figure 5 is a schematic representation of four possible fabric patches with different weaving and pretension factor that can be used to create the tubular structure for an everting soft robot according to the present invention; Figure 6 is a schematic plan representation of an example of combination of three possible fabric patches in figure 5 that can be used to create the tubular structure for an everting soft robot according to the present invention; Figure 7 is an axonometric representation of the example of combination in figure 6 with joined lateral edges; Figure 8 is a schematic plan view showing an apparatus for the creation of a tubular structure for an everting soft robot according to the present invention; and Figure 9 is a side view, partially sectioned, of the apparatus in figure 1.

[0012] Reference can be made to figures 1 and 2, which are a plan view of the path required to an everting soft robot and, respectively, a plan view of the everting soft robot according to the present invention in the path required to it in figure 1.

[0013] Take the case that an everting soft robot must complete a path p, which is supposed between a starting point, or entry point I in a closed space SC, and a final or arrival point F. The path p extends between obstacles indicated with O. Black circles N indicate nodes where the path changes direction. The path p includes straight segments sd, curvilinear segments sc and axial rotation segments sr. It is understood that the rectilinear segments sd and the curvilinear segments sc develop in the plane, while the axial rotation segments sr instead serve to ensure that the robot rotates while it everts along its axis due to the applied pressure.

[0014] The straight path segments sd are defined by the length of the segment, the curvilinear path segments sc are defined by the length of the segment, the radius of curvature, and the normal to the plane in which the curve lies indicating the direction of curvature and the sense of the curve, and said axial rotation segments along the axial direction sr of path are defined by the length of the segment and the angle of rotation in space.

[0015] The object of the present invention is achieved if the everting soft robot R shown in figure 2 can be made to complete the path p in its growth. In figure 2 the same parts of figure 1 are indicated with the same numeral references, with the difference that the nodes N substantially correspond to the separation lines s between one section and the next one of the everting soft robot R in its use. In accordance with figure 1, the sections of the robot R include straight sections TD, curvilinear TC sections, and axial rotation TR sections, intended to cover the straight segments sd, the curvilinear segments sc and the axial rotation segments sr of the path p in figure 1.

[0016] The ability to pre-program the growth trajectory of the everting soft robot is based on the principle whereby by distributing, along the circumference of the everting soft robot, fabric patches having different elastic characteristics or being differently pretensioned, the trajectory followed by the robot during its growth is forced to compose straight segments, curved segments or sections with rotation about the axis of the cylinder that makes up the robot. The patches are flexible and airtight.

[0017] Reference can be made to figure 3 which represents a curved section TC having tubular structure R of the everting soft robot in figure 2. It is useful for showing the relationship of the radius of curvature of the tubular structure R which will give rise to the everting soft robot by pre-tensioning the fabric patches.

[0018] Let us consider, for simplicity, the planar case of the curved section TC: Given L s the length of the patch at rest to which traction was applied so that, after gluing, its length, due to the elastic force, is less than the length L of the patch to which traction was not applied; given α the angle of curvature; given r and r s and d respectively the internal and external radii of the two fabric patches and the diameter of the tubular structure for the everting soft robot L = α 360 2 πr L s = α 360 2 πr s r = r s + d r s = 360 L s 2 απ α = 360 L − L s 2 πd L = rα

[0019] Therefore L = L s + 2 παd 360 r = L α

[0020] Then, the curvature defined as the ratio of α to L is: δ = α L = 360 2 πdL L − L s L

[0021] Therefore, the curvature of the tubular structure R of the everting soft robot is proportional to the difference between L and L s , i.e. to the pre-tension of the patch with length L compared to that with length L s . This pre-tension value can be easily linked to the pre-tension force applied to the section with length L (F) being known the elastic constant of the material used in the range of linear behaviour: L − L s = F ∗ k

[0022] Therefore, from the previous relations it is possible to link the radius of curvature to the pre-tension force, as the properties of the material used are known.

[0023] In the three-dimensional case, i.e. three patches at 120 degrees, the previous relations can be made explicit by defining the plane of curvature of the robot and calculating the combination of the three pre-tension forces applied to the three patches equivalent to the two forces of an equivalent planar robot lying on the plane of curvature, in a hypothetical case where the weight force is neglected.

[0024] Reference is made to figure 4 which is a perspective view of an example of a tubular structure for a part of the everting soft robot in figure 2. Imagine that, in the growth of the soft robot, the straight section TD covers the straight segment sd near the input I, the curvilinear section TC covers the subsequent curvilinear segment sc, the rectilinear section TD covers the subsequent rectilinear segment td, the axial rotation section TR covers the axial rotation segment in the space sr, and the section TD, final in figure 4, covers the straight segment sd in the path p in figure 1.

[0025] Each section TC, TD, TR is made up of elastic, airtight, silicone-coated and nylon-reinforced patches sewn longitudinally. The fabric patches, generically indicated with M, have different textures. Refer to figure 5, which is a schematic representation of four possible fabric patches that can be used to create the tubular structure for an everting soft robot according to the present invention. With M1 a fabric patch with a 45° reticular weave is shown, while with M4 a fabric patch with a 90° reticular weave between warp and weft is shown. No traction is applied to the patches M1 and M4. With M2 the patch with a 45° weave is shown, like M1, subjected to longitudinal traction, while with M3 the patch with a 45° weave, like M1, subjected to transversal traction is shown. It is important to avoid deformation of the patch in the direction orthogonal to the traction force, preferably by means of a system that keeps the patch blocked while under tension, or any mechanism that avoids sticking to a slightly curved patch.

[0026] Figure 6 is a schematic plan representation of an example of combination of three possible fabric patches in figure 5 that can be used to create the tubular structure for an everting soft robot according to the present invention. The three fabric patches, formed by M1, M2 and M3, are combined flat and joined laterally in the longitudinal direction and transversely, i.e. at the end. The result is a right ribbon, a central ribbon and a left ribbon. Subsequently, as shown in figure 7, which is an axonometric representation of the combination example of figure 6, with the final stitching of the end lateral edges, the tubular structure is obtained.

[0027] In figure 4 the fabric patches of the different sections are represented with different shades of grey: the sections TD are made up of fabric patches M1 and M4 not subjected to traction; the section TC is made up of a fabric patch M1 not subjected to traction and two patches M2 subjected to low longitudinal traction; and the section TR is formed by two patches M1 not subjected to traction and by a patch M3 subjected to transverse traction.

[0028] In the following, reference is made to figures 8 and 9, which are a schematic plan view and, respectively, a partially sectioned, side view of the apparatus for the creation of a tubular structure for an everting soft robot according to the present invention.

[0029] In figures 8 and 9, a roller on which the right fabric patch is wound is indicated as 1, a roller on which the central fabric patch is wound is indicated as 2, and a roller on which the left fabric patch is wound is indicated as 3. The rollers 1, 2 and 3 are able to be moved in the same plane to traction the fabric patches, indicated generically with 5. The fabric patches 5 rest on a flat base 4 adjacent to the rollers 1, 2, and 3.

[0030] Above the flat base 4 a guillotine 6 is used to block the three patches 5 before they are subjected to traction. Devices for gluing or welding the fabric of the patches 5 are indicated schematically as 7.

[0031] Guide rollers are marked with 8. The lines 9 indicate gluing or welding lines of the fabric. A first row 10, a second row 11, a third row 12 and, a fourth row 13 of guide rollers, respectively are shown. The guide rollers in the various rows are vertical and variously inclined to convey the fabric ribbons in order to obtain the tubular structure R.

[0032] To allow this, a cylindrical guide element 14 is used to create the tube shape of the everting soft robot.

[0033] Indicated as 15 is a gluing or welding device to complete the tubular shape for the everting soft robot, which through a guide roller 16 of the tubular shape reaches an exit coil 17 on which the tubular structure for the everting soft robot 18 is wound.

[0034] In figures 8 and 9, F1, F2, F3 indicate the forces applied to the three rollers 1, 2 and 3 in order to subject the fabric to traction for each section of the future everting soft robot, generating the different configurations.

[0035] The arrows S1 and S2 indicate the movement of the guillotine 6 and, respectively, of the gluing device 7.

[0036] It should be clear that what has been obtained is a tubular structure of fabric that must be turned inwards in order to be put into operation as an everting soft robot.

[0037] The procedure for creating the tubular structure for everting soft robots includes: the generation or reconstruction of the three-dimensional CAD model of the environment in which the everting soft robot must advance; the identification of the starting point, the objective point and the related obstacles; the generation of the optimal path of the robot to reach the objective point from the starting point while avoiding obstacles.

[0038] For this purpose, a planner must be provided which will generate a route consisting of: straight segments sd defined by the length of the path segment; curvilinear segments sc defined by the length of the path segment, the radius of curvature, and the normal to the plane in which the curve lies, indicating the direction of curvature and the sense of the curve; sr axial rotation segments capable of rotating in space around the axial direction characterized by the length of the path segment and the torsion angle in space.

[0039] For each sd, sc, sr segment to be covered, the traction to be applied to the different fabric patches making up the tubular structure for the everting soft robot is calculated, the specification of the weft and the distribution of patch types, M1, M2, M3, M4, along the outer surface of the soft robot tubular structure.

[0040] The parameters or characteristics are downloaded to the machine which performs the following assembly steps for each segment, to establish: the descent of the guillotine 6 to fix the fabric of all three patches on the terminal line s of the segment; subjecting the three patches to traction or tensioning by applying the forces F1, F2 and F3 as generated by the planner; the gluing or welding of the three patches together along the lines 9 with the devices 7 for the length of the segment; waiting for gluing; the advancement of the fabric along the length of the next segment by simultaneously rotating the exit roller 18 and the three entry rollers 1, 2, 3; closing the robot to obtain the tube shape and gluing by using the device 15.

Claims

1. A process for designing and manufacturing an everting soft robot, having a tubular structure formed by sections, the everting soft robot being capable of growing along a pre-programmed path, comprising the following steps: - generation or reconstruction of the three-dimensional CAD (Computer-Aided Design) model representing the environment in which the everting soft robot must navigate, - identification of a starting point, an end point and obstacles to be overcome, avoided or exploited by the everting soft robot, - generation of a path to reach the arrival point from the starting point avoiding the obstacles, the path including at least one of path straight segments (sd), curvilinear segments (sc) and axial rotation segments (sr), - design of tubular structure straight sections (TD), tubular structure curvilinear sections (TC) and tubular structure axial rotation sections (TR) corresponding to the straight segments (sd), curvilinear segments (sc) and axial rotation segments (sr), respectively, further characterised by the following steps: - choice between a plurality of first fabric patches (M1), second fabric patches (M2), third fabric patches (M3), and fourth fabric patches (M4) for each section of tubular structure, - subjecting each fabric patch to its own state of traction deriving from its weaving, - positioning or orienting each fabric patch in the tubular structure of the robot, - union of the plurality of fabric patches (M1, M2, M3, M4) on the basis of said design of the sections, capable of providing a determined tubular structure rectilinear section (TD), curvilinear section (TC) and axial rotation section (TR), so that the everting soft robot is adequate to follow this path during its growth.

2. The process according to claim 1, wherein said path straight segments (sd) are defined by the length of the segment, said path curvilinear segments (sc) are defined by segment length, radius of curvature, and the normal line to the plane in which lies the curve indicating the direction of curvature and the sense of the curve, and said path segments of axial rotation along the axial direction (sr) are defined by the length of the segment and the torsion angle in space.

3. The process according to claim 1, wherein said first fabric patches (M1) have a 45° weft weave without any state of traction, said second fabric patches (M2) have a 45° weft weave with a longitudinal traction state, said third fabric patches (M3) have a 45° weft weave with a vertical traction state, and said fourth fabric patches (M4) have a 90° weft weave without any traction state.

4. The process according to claim 1, wherein said plurality of first fabric patches (M1), second fabric patches (M2), third fabric patches (M3), and fourth fabric patches (M4) for each tubular structure section is three in number.

5. The process according to claim 1, characterized in that the process uses an apparatus configured for the realization of an everting soft robot having a tubular structure formed by rectilinear sections (TD), curvilinear sections (TC) and axial rotation sections (TR), so that the everting soft robot is adequate to complete a predetermined path during its growth, the apparatus comprising: - a multiplicity of adjacent fabric reels (1, 2, 3) for feeding a corresponding plurality of fabric patches (5) (M1, M2, M3, M4) for each section of tubular structure, each patch (5) having its own state of traction deriving from its weaving and a position or orientation in the tubular structure of the robot, each reel of said multiplicity of fabric reels (1, 2, 3) being able to be subjected to longitudinal traction to impart the desired state of traction to the relative fabric patch (5); - a flat base (4); - an elongated pressing device (6), able to cooperate with said flat base (4) to block the plurality of fabric patches (5) before each reel of said multiplicity of reels (1, 2, 3) is subjected to longitudinal traction; - a first joining device (7) for joining said fabric selected from the group comprising a gluing device and a device for sealing the fabric adapted to join a fabric patch (5) with the adjacent one; - a multiplicity of successive pairs of guide rollers (10, 11, 12, 13) suitable for conveying the plurality of longitudinally joined fabric patches so that it assumes a tubular shape; - a cylindrical guide element (14) adapted to improve the tubular shape of the plurality of longitudinally joined fabric patches; - a second longitudinal joining device (15) for said fabric selected from the group comprising a gluing device and a fabric sealing device adapted to join the plurality of fabric patches joined longitudinally in a tubular shape along the opposite lateral ends; - a pair of guide rollers (16) for the tubular structure for the everting soft robot; and - a coil (17) for winding the everting soft robot.

6. The process according to claim 5, wherein said plurality of fabric patches (M1, M2, M3, M4) for each tubular structure section is three in number.