Low profile heavy load 2R1T parallel platform

Abstract

The application discloses a low-profile heavy-load 2R1T parallel platform and belongs to the technical field of parallel robots. The low-profile heavy-load 2R1T parallel platform comprises a static platform, a dynamic platform, three driving branch chains and three constraint branch chains connecting the static platform and the dynamic platform; the lower ends of the three driving branch chains are connected to three connecting points of the static platform through Hooke joints, and the three connecting points form an equilateral triangle; in an initial state, the axes of the three driving branch chains are parallel to each other and are perpendicular to the static platform and the dynamic platform respectively; the three constraint branch chains are distributed in space and are perpendicular to each other and are parallel to three coordinate axes of a Cartesian coordinate system respectively. The three driving branch chains are all in the UPS structure, and the three constraint branch chains are in the SS structure, the variable PUU structure and the SS structure respectively. The low-profile heavy-load 2R1T parallel platform is a parallel mechanism, has the advantages of large bearing capacity, low profile, low gravity center, difficulty in toppling and structural stability, and the mechanism can obtain an analytical solution through establishment of a kinematic equation.

Description

Technical Field

[0001] This invention belongs to the technical field of parallel stable platforms, and specifically refers to a low-profile heavy-duty 2R1T parallel platform. Background Technology

[0002] Industrial robots are developing rapidly. Although they appeared after serial robots, parallel robots are widely used in many military and civilian fields due to their characteristics such as high stiffness, strong stability, high control precision, strong load-bearing capacity and easy motion inversion. They are an important branch of the science of mechanisms.

[0003] Parallel mechanisms typically consist of a static platform and a moving platform connected by multiple branches. Compared to serial mechanisms, parallel mechanisms are characterized by their compactness, high stiffness, strong load-bearing capacity, and small cumulative error, making them widely used in motion simulation, motion compensation, and posture adjustment. However, parallel mechanisms with few degrees of freedom often lack the characteristics of low profile, high load-bearing capacity, and driving branches subjected only to tension and compression, which limits their application and widespread adoption to some extent.

[0004] Two-rotor-one-transfer parallel mechanisms are low-degree-of-freedom mechanisms. They generally have a high cross-section, and the drive chain bears bending moments in addition to tensile and compressive forces, making them unsuitable for heavy loads. For example, the 3RSR parallel mechanism uses a rotating joint as the drive joint, which severely limits its load-bearing capacity. While the 3RPS parallel mechanism offers improved load-bearing capacity, its high cross-section and the fact that the drive chain also bears bending moments further restrict its load. Summary of the Invention

[0005] To solve the above-mentioned technical problems, this invention proposes a low-profile heavy-duty 2R1T parallel stabilizing platform. This parallel mechanism has the characteristics of large load-bearing capacity and low profile, and can realize a two-rotation-one-transfer motion mode.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a low-profile heavy-duty 2R1T parallel platform, comprising a static platform and a dynamic platform, wherein the static platform and the dynamic platform are connected by three driving branches and three constraint branches, wherein the three driving branches are a first driving branch, a second driving branch and a third driving branch capable of linearly extensible motion, and the three constraint branches are a first constraint branch, a second constraint branch and a third constraint branch.

[0007] The lower ends of the three drive chains are connected to three connection points on the stationary platform via Hooke hinges, and the three connection points form an equilateral triangle; the upper ends of the three drive chains are connected to three endpoints on the moving platform via ball joints, and the three endpoints also form an equilateral triangle.

[0008] One end of the first constraint branch and the third constraint branch are connected to the endpoint of the moving platform through a ball joint, and the other end is connected to the support column of the stationary platform through a ball joint. One end of the second constraint branch is connected to the midpoint of the moving platform through a Hooke joint, and the other end is a follow-up telescopic rod connected to the midpoint of the stationary platform.

[0009] In the initial state, the first drive branch, the second drive branch, and the third drive branch are placed vertically and perpendicular to the static platform and the moving platform; the first constraint branch and the third constraint branch are placed horizontally and perpendicular to each other, and the second constraint branch is placed vertically and perpendicular to the first constraint branch and the third constraint branch, respectively.

[0010] Furthermore, the static platform includes a main static platform base and a first static platform base, a second static platform base, and a third static platform base disposed on the main static platform base; a first static platform support column is also fixedly installed on the first static platform base, and a third static platform support column is fixedly installed on the third static platform base.

[0011] Furthermore, the first drive branch, the second drive branch, and the third drive branch each include a Hooke hinge assembly disposed at one end, a telescopic rod assembly connected to the Hooke hinge assembly, and a ball joint assembly connected to the other end of the telescopic rod assembly.

[0012] Furthermore, the telescopic rod assembly is a hydraulic cylinder, a pneumatic cylinder, or an electric linear actuator.

[0013] Furthermore, the telescopic rod assembly is also provided with a controller assembly for controlling the movement of the telescopic rod assembly.

[0014] Furthermore, both the first constraint branch and the third constraint branch include a fixed-length rod and ball joints disposed at both ends of the fixed-length rod, and the center distance between the ball joints at both ends of the first constraint branch and the third constraint branch is equal.

[0015] Furthermore, the ball joint is a spherical bearing.

[0016] Furthermore, the second constraint branch is a modified PUU structure, including a follower telescopic rod assembly, a single-axis hinged to the follower telescopic rod assembly, two equal-length connecting rods hinged to the single-axis hinge, and a Hooke hinge assembly hinged to the two connecting rods.

[0017] Furthermore, the moving platform includes a lower shelf and an upper shelf, which are fixedly connected at three ends by shelf connecting plates.

[0018] Furthermore, the upper shelf of the moving platform is detachable.

[0019] Beneficial technical effects of the present invention:

[0020] 1. The parallel mechanism of this invention employs a 3UPS structure driving chain plus a 2SS + variant PUU structure constraint chain between the static and dynamic platforms. This results in a parallel platform with high load-bearing capacity, low profile, structural stability, and uniform and stable stress distribution on each chain. Furthermore, all three driving chains and three constraint chains are two-force members, ensuring uniform and stable stress distribution on each chain. This invention achieves a low profile and good chain stress distribution while retaining the high load-bearing capacity, compact structure, and good stability of parallel mechanisms.

[0021] 2. The second constraint branch of this invention adopts a modified PUU connection form. The design of the second constraint branch uses a parallelogram mechanism to restrict the rotation of the moving end about its own axis. That is, the structure of this branch restricts the rotation of the moving platform about the z-axis, effectively eliminating a useless accompanying motion, and its analytical expression and analytical solution can be obtained. The parallel platform in this invention can solve for the obtained inverse kinematic analytical expression and construct the Jacobian matrix.

[0022] 3. In this invention, the nonlinear system is transformed into a linear system through the Jacobian transformation to obtain a state-space expression. The first-order differential equation is optimally linearly approximated to the given points, and the joint velocity during the motion of the stable platform is controlled using the Jacobian matrix inversion method. Therefore, when the structure of this invention is used in engineering applications, it can shorten the computation time, reduce the computational complexity of the controller in engineering applications, and save on controller costs.

[0023] 4. This invention employs a double-layer shelving design. The lower shelf has a low cross-section and a low center of gravity, allowing for the placement of smaller, heavier items with better stability; the upper shelf has a large area and good flatness, enabling the placement of larger items. Furthermore, the upper shelf is detachable. When goods are tall, the detachable portion of the upper shelf can be removed, allowing for the placement or stacking of even more and taller goods. Attached Figure Description

[0024] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0025] Figure 1 This is a schematic diagram of the overall structure of a low-profile heavy-duty 2R1T parallel platform as described in an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the static platform according to an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of three drive branches in an embodiment of the present invention;

[0028] Figure 4This is a schematic diagram of the first constraint branch and the third constraint branch structure according to an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the structure of the second constraint branch in an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the structure of the moving platform according to an embodiment of the present invention;

[0031] Figure 7 This is a schematic diagram of the detachable shelf on the upper level of the platform according to an embodiment of the present invention;

[0032] Figure 8 This is a simplified schematic diagram of the mechanism model for an embodiment of the present invention.

[0033] Among them, 1-static platform, 11-main static platform base, 12-first static platform base, 13-first static platform support column, 14-first static platform support column pin, 15-second static platform base, 16-third static platform base, 17-third static platform support column, 18-third static platform support column pin, 2-first drive branch, 3-second drive branch, 4-third drive branch, 5-first constraint branch, 6-second constraint branch, 7-third constraint branch, 21-first Hooke hinge, 31-second Hooke hinge, 41-third Hooke hinge, 22-first drive telescopic rod assembly, 32-second drive telescopic rod assembly, 42-third drive telescopic rod assembly, 23- First ball joint, 33-Second ball joint, 43-Third ball joint, 24-First drive controller, 34-Second drive controller, 44-Third drive controller, 51 / 53 / 71 / 73-Ball joint, 52 / 72-Fixed length rod, 61-Second constraint Hooke joint, 62-Second constraint cross shaft, 63-Second constraint cross shaft rotating cap, 64-Parallel rod, 65-Second constraint straight shaft, 66-Second constraint telescopic cylinder rod, 67-Second constraint telescopic cylinder, 8-Moving platform, 81-Lower shelf of moving platform, 82-Upper shelf of moving platform, 83 / 84 / 85-Shelf connecting plate, 86 / 87-Fisheye joint connecting block, 9-Detachable shelf of moving platform. Detailed Implementation

[0034] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar mechanisms or mechanisms having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. In particular, the driving method is not limited to hydraulic drive, but can also be electric or pneumatic drive, and the controller can also be a servo control valve or other types of controller. In addition, in kinematics, C represents a cylindrical joint, R represents a revolute joint, P represents a prismatic joint, S represents a ball joint, U represents a Hooke's joint; SS refers to a fixed-length connecting rod with ball joints at both ends, which will not be described further hereafter.

[0035] The following is in conjunction with the accompanying drawings. Figures 1-8 The present invention provides a further description of a low-profile heavy-duty 2R1T parallel platform.

[0036] See Figure 1 This is a schematic diagram of a specific embodiment of the present invention, including a static platform 1, a moving platform 8, three driving branches connecting the static platform 1 and the moving platform 8, and three constraint branches connecting the static platform 1 and the moving platform 8. The three driving branches include a first driving branch 2, a second driving branch 3, and a third driving branch 4, with one end of each branch distributed at one of the three vertices of an equilateral triangle on the static platform 1. The three constraint branches include a first constraint branch 5, a second constraint branch 6, and a third constraint branch 7. Initially, the first driving branch 2, the second driving branch 3, and the third driving branch 4 are all placed vertically.

[0037] The first constraint branch 5, the second constraint branch 6, and the third constraint branch 7 are arranged perpendicularly to each other, wherein the first constraint branch 5 and the third constraint branch 7 are placed horizontally, and the second constraint branch 6 is placed vertically.

[0038] The first drive chain 2, the second drive chain 3, and the third drive chain 4 use the same drive telescopic rod assembly. The first constraint chain 5 and the third constraint chain 7 are two horizontal constraint chains that are fixed-length rigid rods of equal length. All three drive chains and three constraint chains are connected at one end to the static platform 1 and at the other end to the moving platform 8. The upper ends of the three drive chains are connected to the inner sides of the three endpoints of the moving platform 8 via ball joints, and the lower ends of the three drive chains are connected to the static platform 1 via Hooke's joints. The first constraint chain 5 and the third constraint chain 7 are both connected at one end to the endpoint of the moving platform 8 via ball joints, and at the other end to the support column of the static platform 1 via ball joints. The vertical second constraint chain 6 is connected at one end to the midpoint of the moving platform 8 via a Hooke's joint, and the other end is a follower telescopic rod assembly connected to the midpoint of the static platform 1. In the initial state, the axes of the three drive chains are parallel to each other and perpendicular to the static platform 1 and the moving platform 8, respectively.

[0039] In the initial state, the three constraint branches are distributed in space and are perpendicular to each other, parallel to the three coordinate axes of the Cartesian coordinate system. In this invention, all three driving branches are configured as UPS structures, with the P-joint being the driving joint, and the three constraint branches are configured as SS, a modified PUU, and an SS structure, respectively. This invention has a high load-bearing capacity, low profile, structural stability, and uniform and stable stress distribution across all branches.

[0040] like Figure 2 The diagram shows one embodiment of a static platform 1, comprising a main static platform base 11, a first static platform base 12, a first static platform support column 13, a first static platform support column pin 14, a second static platform base 15, a third static platform base 16, a third static platform support column 17, and a third static platform support column pin 18. The first static platform base 12, the second static platform base 15, and the third static platform base 16 are respectively placed on the main static platform base 11. The first static platform support column 13 is located on the first static platform base 12, the third static platform support column 17 is located on the third static platform base 16, the first static platform support column pin 14 is located on the first static platform support column 13, and the third static platform support column pin 18 is located on the third static platform support column 17.

[0041] like Figure 3 The diagram shows a specific embodiment of the drive chain. Since the first drive chain 2, the second drive chain 3, and the third drive chain 4 have the same structure, they are shown in the same diagram to avoid complexity. Taking the first drive chain 2 as an example, it includes a first Hooke hinge 21, a first drive telescopic rod assembly 22, a first ball joint 23, and a first drive controller 24 that controls the extension and retraction of the first drive telescopic rod assembly 22. Similarly, the second drive chain 3 includes a second Hooke hinge 31, a second drive telescopic rod assembly 32, a second ball joint 33, and a drive controller 34 that controls the extension and retraction of the second drive telescopic rod assembly 32. The third drive chain 4 includes a third Hooke hinge 41, a third drive telescopic rod assembly 42, a third ball joint 43, and a drive controller 44 that controls the extension and retraction of the third drive telescopic rod assembly 42. The first Hooke hinge 21, the second Hooke hinge 31, and the third Hooke hinge 41 are connected to the stationary platform 1. The first ball joint 23, the second ball joint 33, and the third ball joint 43 are connected to the moving platform 8. The three drive branches of this invention are all UPS structures, where P is a drive branch, that is, the three drive telescopic rod assemblies 23 / 33 / 43 are controlled to extend and retract by three drive controllers 24 / 34 / 44, thereby controlling the moving platform 8 to move.

[0042] like Figure 4The diagram shows the structural schematics of the first constraint branch 5 and the third constraint branch 7. Since the structures of the first constraint branch 5 and the third constraint branch 7 are identical, they are shown in the same figure. The first constraint branch 5 has ball joints 51 and 53 at both ends, and a fixed-length rod 52 in the middle. Similarly, the third constraint branch 7 has ball joints 71 and 73 at both ends, and a fixed-length rod 72 in the middle. The ball joints 51 / 53 / 71 / 73 on both constraint branches are implemented using spherical plain bearings. These bearings are standard parts, meeting usage requirements and offering good interchangeability.

[0043] like Figure 5 The diagram shows the structure of the second constraint branch 6. The second constraint branch 6 includes: a second constraint Hooke's hinge 61, a second constraint cross shaft 62, and a second constraint cross shaft rotating cap 63, which together form a Hooke's hinge. Additionally, a parallel rod 64, a second constraint straight shaft 65, and a second constraint telescopic cylinder rod 66 form another Hooke's hinge mechanism. The second constraint telescopic cylinder rod 66 and the second constraint telescopic cylinder 67 form a sliding pair. The second constraint branch 6 uses a parallelogram mechanism to restrict the rotation of the moving end of the mechanism around its own axis. The second constraint telescopic cylinder 67 is connected to the center of the stationary platform 1, and the second constraint branch Hooke's hinge 63 is connected to the center of the moving platform 8. The follower telescopic rod assembly here only moves between the stationary platform 1 and the moving platform 8, and is not actively driven to extend or retract by an external force.

[0044] The first constraint branch 5 and the third constraint branch 7 are configured as SS structures, and the second constraint branch 6 is configured as a modified PUU structure. In the initial state, the axes of the first drive branch 2, the second drive branch 3, and the third drive branch 4 are parallel to each other and perpendicular to the static platform 1 and the moving platform 8, respectively.

[0045] In addition, all three driving branches and three constraint branches are two-force members, and each branch is subjected to uniform and stable forces. The first constraint branch 5 and the third constraint branch 7 have the same length, and the center distance between the ball joints at both ends of each branch is equal.

[0046] As an embodiment of the present invention, see Figure 6 As shown, the moving platform 8 includes a lower shelf 81 and an upper shelf 82. The lower shelf 81 and the upper shelf 82 are connected by shelf connecting plates 83 / 84 / 85. The moving platform is also provided with fisheye connector connecting blocks 86 / 87 to connect with the first constraint chain 5 and the third constraint chain 7.

[0047] like Figure 7The diagram shows the structure of the movable platform detachable shelf 9. The movable platform detachable shelf 9 and the upper shelf 82 can be easily installed and disassembled. The lower shelf 81 of the movable platform has a low cross-section and a low center of gravity, allowing for the placement of smaller, heavier items with better stability. The upper shelf 82 of the movable platform has a large area and good flatness, allowing for the placement of larger items. With the detachable design of the upper shelf, when goods are tall, the detachable part of the upper shelf can be removed, allowing for the placement or stacking of more and taller goods.

[0048] like Figure 8 The diagram shows a simplified mathematical model of the structure according to the present invention. In this model, A1A2A3 represents the static platform, D2 is the center of the static platform, B1B2B3 represents the moving platform, and C2 is the center of the moving platform. A1B1, A2B2, and A3B3 represent the first driving branch 2, the second driving branch 3, and the third driving branch 4, respectively. C1D1, C2D2, and C3D3 represent the first constraint branch 5, the second constraint branch 6, and the third constraint branch 7, respectively.

[0049] The three drive branches A1B1, A2B2, and A3B3 are connected to the static platform via U-joints A1, A2, and A3, respectively, and to the moving platform via S-joints B1, B2, and B3, respectively. All three drive branches A1B1, A2B2, and A3B3 are UPS structures. Hinge points C1 and C3 are S-joints located at the 1st and 3rd vertices of the equilateral triangular moving platform, respectively. Hinge points D1 and D3 are also S-joints located at the connection points of the corresponding static platforms. The two fixed-length constraint rigid rod branches C1D1 and C3D3 are both SS structures, coplanar and perpendicular to each other. The third constraint branch C2D2, connecting the centers of the two platforms, is a modified PUU structure with a telescopic rod, used to restrict the rotation of the upper platform around the z-axis. The first constraint branch C1D1 and the third constraint branch C3D3 move with rotation centers at D1 and D3, respectively, and rotation radii at C1D1 and C3D3.

[0050] Based on the kinematic analysis of this mechanism, the following spiral system was obtained:

[0051]

[0052] Based on this motion helical system, a 2R1T three-degree-of-freedom asymmetric parallel mechanism is obtained, whose motion modes are rotation (turning and pitching) about the X and Y axes and vertical movement along the Z axis. Since the variant PUU branch restricts the rotation of the moving platform about the z axis, the design of this mechanism eliminates a useless accompanying motion, making the motion more efficient and the theoretical calculation more convenient.

[0053] The constraint equations can be established based on the position of the constraint bars:

[0054]

[0055] Analytical solutions for the displacements of the three actuators are obtained based on the constraint equations:

[0056]

[0057] For parallel mechanisms, it is difficult to obtain an analytical solution. A numerical solution, which is usually obtained through a progressive numerical approach, is typically found to be as close as possible. Obtaining an analytical solution allows for the calculation of accurate numerical results, is computationally efficient, and has significant advantages in engineering applications.

[0058] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0059] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A low-profile heavy-duty 2R1T parallel platform, comprising a static platform and a dynamic platform, characterized in that: The static platform and the dynamic platform are connected by three driving branches and three constraint branches. The three driving branches are a first driving branch, a second driving branch, and a third driving branch that can linearly extend and retract. The three constraint branches are a first constraint branch, a second constraint branch, and a third constraint branch. The lower ends of the three drive chains are connected to three connection points on the static platform via Hooke hinges, and the three connection points form an equilateral triangle; the upper ends of the three drive chains are connected to three endpoints on the moving platform via ball joints, and the three endpoints also form an equilateral triangle. One end of the first constraint branch and the third constraint branch are connected to the endpoint of the moving platform through a ball joint, and the other end is connected to the support column of the stationary platform through a ball joint. One end of the second constraint branch is connected to the midpoint of the moving platform through a Hooke joint, and the other end is a follow-up telescopic rod connected to the midpoint of the stationary platform. In the initial state, the first drive branch, the second drive branch, and the third drive branch are placed vertically and perpendicular to the static platform and the moving platform; the first constraint branch and the third constraint branch are placed horizontally and perpendicular to each other, and the second constraint branch is placed vertically and perpendicular to the first constraint branch and the third constraint branch, respectively. The moving platform includes a lower shelf and an upper shelf, which are fixedly connected at three ends by shelf connecting plates. The second constraint branch includes: a second constraint Hooke's hinge, a second constraint cross shaft, and a second constraint cross shaft rotating cap, which together constitute a Hooke's hinge; the second constraint branch also includes: a parallel rod, a second constraint straight shaft, and a second constraint telescopic cylinder rod, which together constitute another Hooke's hinge mechanism; the second constraint telescopic cylinder rod and the second constraint telescopic cylinder barrel constitute a sliding pair; the second constraint telescopic cylinder barrel is connected to the center of the stationary platform, and the second constraint branch Hooke's hinge is connected to the center of the moving platform. The static platform includes a main static platform base and a first static platform base, a second static platform base, and a third static platform base disposed on the main static platform base; a first static platform support column is also fixedly installed on the first static platform base, and a third static platform support column is fixedly installed on the third static platform base.

2. The low-profile heavy-duty 2R1T parallel platform according to claim 1, characterized in that: The first drive branch, the second drive branch, and the third drive branch each include a Hooke hinge assembly at one end, a telescopic rod assembly connected to the Hooke hinge assembly, and a ball joint assembly connected to the other end of the telescopic rod assembly.

3. The low-profile heavy-duty 2R1T parallel platform according to claim 2, characterized in that: The telescopic rod assembly is a hydraulic cylinder, a pneumatic cylinder, or an electric linear actuator.

4. The low-profile heavy-duty 2R1T parallel platform according to claim 2, characterized in that: The telescopic pole assembly is also equipped with a controller assembly for controlling the movement of the telescopic pole assembly.

5. The low-profile heavy-duty 2R1T parallel platform according to claim 1, characterized in that: Both the first constraint branch and the third constraint branch include a fixed-length rod and ball joints at both ends of the fixed-length rod. The center distance between the ball joints at both ends of the first constraint branch and the third constraint branch is equal.

6. The low-profile heavy-duty 2R1T parallel platform according to claim 5, characterized in that: The ball joint is a spherical bearing.

7. The low-profile heavy-duty 2R1T parallel platform according to claim 6, characterized in that: The upper shelf of the moving platform is also equipped with a detachable shelf.

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