Stiffness-variable planar parallel positioning platform with switchable contact state flexible hinges

Abstract

The present application discloses a variable stiffness planar parallel positioning platform with switchable contact state flexible hinge, and belongs to the field of parallel robots. The positioning platform comprises a moving platform, four static platforms are arranged circumferentially on the moving platform, and a branch chain is arranged between the static platform and the moving platform. The branch chain comprises two groups of flexible hinges, and the two groups of flexible hinges are respectively fixed opposite to the static platform and the moving platform. The number of flexible hinges in each group is two, and the two flexible hinges in each group are distributed above and below. The two flexible hinges in each group are fixed through a connecting piece. The two connecting pieces are connected through a linear actuator, and the distance between the static platform and the moving platform can be adjusted. The flexible hinge deforms in the circumferential direction when subjected to force, and the relative torsion of the static platform and the moving platform can be realized. The joint stiffness is adjusted by changing the pre-tightening force, gap and other parameters of the hinge, so as to improve the stability and motion accuracy of the mechanism, help to optimize the dynamic response of the mechanism, and improve the response speed and stability of the mechanism under rapidly changing load.

Description

Technical Field

[0001] This invention belongs to the field of parallel robots, specifically relating to a variable stiffness planar parallel positioning platform with a flexible hinge that can switch contact states. Background Technology

[0002] With the development of modern technology, especially in fields such as microelectronics manufacturing, aerospace equipment, micromanipulators, ultra-precision machining, semiconductor assembly, and laser communication, increasingly higher demands are being placed on the precision, stability, and reliability of mechanical drive and transmission systems. Traditional mechanical drive and transmission systems face numerous challenges in these applications, such as insufficient precision, poor stability, limited load-bearing capacity, and slow dynamic response. Therefore, developing a high-precision, high-stability mechanical drive and transmission system with a large working space and high load-bearing capacity is of great significance.

[0003] Among them, the patent application with publication number CN115592653A proposes a planar three-degree-of-freedom redundant parallel mechanism, which uses a traditional hinge block as a traditional hinge structure to connect the moving platform and the telescopic rod and the rotating rod to realize the rotational degree of freedom. However, since the T-shaped rod structure may require more space to accommodate its structure, this is a limitation in space-constrained applications.

[0004] Patent application CN105936045A proposes a partially decoupled six-degree-of-freedom parallel mechanism. Although it uses a composite ball joint to replace the traditional T-shaped rod structure, reducing the complexity and space requirements of the mechanism, the mechanism still exhibits singular phenomena when the telescopic rods are symmetrically distributed and coplanar with the normal of the moving platform. This limits the range of motion of the mechanism. At the same time, the support stiffness will decrease significantly when the rotation angle increases. When the mechanism approaches the motion limit, the stiffness change will be more obvious due to the accumulation of internal stress.

[0005] To address this, a variable stiffness planar parallel positioning platform with a flexible hinge that can switch contact states is proposed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a variable stiffness planar parallel positioning platform with a flexible hinge that can switch contact states, thereby solving the problems in existing technologies.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A variable stiffness planar parallel positioning platform with switchable contact state flexible hinges includes a moving platform, four stationary platforms arranged circumferentially around the moving platform, and a support chain between the stationary platforms and the moving platform. The support chain includes two sets of flexible hinges, which are fixed relative to the stationary platforms and the moving platform, respectively. Each set contains two flexible hinges, which are distributed vertically, and the two flexible hinges in each set are fixed together by a connector. The two connectors are connected by a linear actuator, which can adjust the distance between the stationary platforms and the moving platform.

[0009] Flexible hinges deform when subjected to external forces and torques, enabling relative torsion between the static and dynamic platforms.

[0010] Furthermore, the flexible hinge includes two fan-shaped connecting areas and two fan-shaped hollow areas symmetrically distributed in the circumferential direction, with the fan-shaped connecting areas and fan-shaped hollow areas spaced apart; each of the two ends of the fan-shaped hollow area is provided with a fixed end, which is fixed relative to the corresponding static platform and moving platform; the fan-shaped connecting areas are fixed to the connector.

[0011] Furthermore, the two edges of the fan-shaped hollow area are respectively provided with segment one and segment four; the hollow area in the middle of the fan-shaped hollow area is provided with T-shaped segment three, and the edge of the hollow area in the middle is provided with segment two.

[0012] Furthermore, when the flexible hinge is subjected to tangential force transmitted from the connector, the fan-shaped connecting area deforms towards the fan-shaped hollow area, while segments one and four also deform, and segment three rotates at the middle hollow. As the flexible hinge continues to deform, segment three can contact segment two and generate friction to improve the stiffness of the flexible hinge.

[0013] Furthermore, the linear actuator is fixed to one of the connecting members, and the push rod of the linear actuator is fixed to the other connecting member.

[0014] Furthermore, the linear actuator is fixed to one of the connectors by bolts, and the linear actuator's push rod is fixed to the other connector by bolts and nuts.

[0015] Furthermore, a cover plate is fixed to the upper end of the static platform by bolts, and the cover plate is fixed to the flexible hinge by bolts.

[0016] Furthermore, cover plates are fixed to the eight corners at the upper and lower ends of the moving platform by bolts, and flexible hinges are fixed to the cover plates by bolt connection.

[0017] Furthermore, the flexible hinge is made of spring steel.

[0018] A parallel robot includes the aforementioned variable stiffness planar parallel positioning platform with a flexible hinge that can switch contact states.

[0019] The beneficial effects of this invention are:

[0020] 1. In this invention, redundant drive provides additional degrees of freedom, thereby reducing or avoiding singular configurations, effectively expanding the working space of the mechanism and significantly improving system stability.

[0021] 2. The switchable contact state flexible hinge structure adopted in this invention has a simple design. Compared with the traditional T-shaped rod structure and multi-degree-of-freedom parallel mechanism, it greatly reduces the number of components and connection nodes, which not only reduces the complexity of the mechanical structure, but also simplifies the algorithm design of the control system.

[0022] 3. The switchable contact state flexible hinge in this invention achieves dynamic control of joint stiffness by adjusting key geometric parameters such as hinge preload and clearance, providing an efficient stiffness adjustment scheme. This scheme enables precise control of joint stiffness, thereby significantly improving the motion accuracy and stability of the mechanism. Furthermore, this adjustable stiffness characteristic can optimize the dynamic performance of the mechanism, enabling it to maintain excellent response speed and operational stability under rapidly changing load conditions. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a perspective view of the variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to the present invention.

[0025] Figure 2 This is a right view of the variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to the present invention.

[0026] Figure 3 This is a top view of the variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to the present invention.

[0027] Figure 4 This is a perspective view of a single branch of the present invention;

[0028] Figure 5 This is a dimensional analysis diagram of the variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to the present invention.

[0029] Figure 6This is a three-dimensional configuration diagram of the flexible hinge of the present invention;

[0030] Figure 7 This is a dimensional design drawing of the flexible hinge of the present invention;

[0031] Figure 8 This is the coordinate positioning and force diagram of the flexible hinge of the present invention;

[0032] Figure 9 This is a flowchart illustrating the deformation and switching process of the flexible hinge of the present invention;

[0033] Figure 10 This is a flow chart of the displacement and stiffness of the variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to the present invention.

[0034] In the diagram: 1-First stationary platform, 2-First branch, 3-First cover plate, 4-Second cover plate, 5-Third cover plate, 6-Second stationary platform, 7-Second branch, 8-Fourth cover plate, 9-Fifth cover plate, 10-Sixth cover plate, 11-Third stationary platform, 12-Third branch, 13-Seventh cover plate, 14-Eighth cover plate, 15-Ninth cover plate, 16-Moving platform, 17-Fourth stationary platform, 18-Fourth branch, 19-Tenth cover plate, 20-Eleventh cover plate, 21-Twelfth cover plate, 22-First flexible hinge, 23-First connector, 24-Second flexible hinge, 25-Linear actuator, 26-Third flexible hinge, 27-Second connector, 28-Fourth flexible hinge; 29-Fixed end, 30-Segment 1, 31-Segment 2, 32-Segment 3, 33-Segment 4, 34-Fan-shaped connection area, 35-Fan-shaped hollow area. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figures 1 to 4As shown, a variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge includes a moving platform 16. A first static platform 1, a second static platform 6, a third static platform 11, and a fourth static platform 17 are arranged around the moving platform 16 and are fixed to each other to form a square frame. The first static platform 1, the second static platform 6, the third static platform 11, and the fourth static platform 17 are respectively connected to the moving platform 16 through a first branch 2, a second branch 7, a third branch 12, and a fourth branch 18, and the first branch 2, the second branch 7, the third branch 12, and the fourth branch 18 are evenly distributed around the moving platform 16.

[0038] The internal structure and installation method of the first branch 2, the second branch 7, the third branch 12, and the fourth branch 18 are the same. The following description uses the first branch 2 as an example to introduce the structure and installation method of the branch:

[0039] like Figure 4 As shown, the first branch 2 includes: a first flexible hinge 22, a second flexible hinge 24, a third flexible hinge 26, and a fourth flexible hinge 28; the first flexible hinge 22 and the second flexible hinge 24 are arranged vertically and are both fixed relative to the first static platform 1, and are fixedly connected to each other by a first connector 23; the third flexible hinge 26 and the fourth flexible hinge 28 are arranged vertically and are both fixed relative to the moving platform 16, and are fixedly connected to each other by a second connector 27; a linear actuator 25 is fixed to the first connector 23 by bolts, and the push rod of the linear actuator 25 is fixedly connected to the second connector 27 by bolts and nuts;

[0040] When the flexible hinge is subjected to force, it deforms in the circumferential direction, which enables relative torsion between the static platform and the moving platform 16; and by controlling the linear actuator 25, the distance between the static platform and the moving platform 16 can be adjusted; the same applies to other branches.

[0041] In this embodiment, the upper ends of the first static platform 1, the second static platform 6, the third static platform 11 and the fourth static platform 17 are respectively fixed with the first cover plate 3, the fourth cover plate 8, the seventh cover plate 13 and the tenth cover plate 19 by bolts; the flexible hinge is fixed to the cover plate by bolt connection to realize the relative fixation between the flexible hinge and the static platform, so as to facilitate the processing and manufacturing of the structure.

[0042] Similarly, at the four corners of the upper end of the moving platform 16, the following are fixed with bolts: the third cover plate 5, the fifth cover plate 9, the eighth cover plate 14, and the eleventh cover plate 20; at the four corners of the lower end of the moving platform 16, the following are fixed with bolts: the second cover plate 4, the sixth cover plate 10, the ninth cover plate 15, and the twelfth cover plate 21; the flexible hinge is fixed to the cover plate by bolt connection to achieve relative fixation between the flexible hinge and the moving platform 16, so as to facilitate the processing and manufacturing of the structure.

[0043] Example 2

[0044] In this embodiment, a mechanical analysis is performed on the variable stiffness planar parallel positioning platform in Example 1;

[0045] In this embodiment, the variable stiffness planar parallel positioning platform is driven by four linear actuators, and the end effector has three degrees of freedom. Therefore, the redundancy of its mechanism is re = 4 - 3 = 1. Figure 5 As shown, A i and C i These represent the torsional axes of the flexible hinge on the static platform and the flexible hinge on the moving platform, respectively. O and O' represent the global and local coordinate systems of the end-effector moving platform, respectively. i A represents i The position vector relative to the global coordinate system O, c i C represents i The position vector relative to the global coordinate system O. r represents the Cartesian coordinate system of the end-point platform, and R represents the rotation matrix of coordinate system O' relative to coordinate system O.

[0046] The length vector of a single-branch link is:

[0047] l i =a i -rR×c i (1)

[0048] In the formula, l i Let be a branch vector, and its unit vector be:

[0049]

[0050] According to the Newton-Euler model, the static model of the end-effector dynamic platform can be expressed as:

[0051] W×T=F (3)

[0052] In the formula, W∈R 3×4 Let T be a Jacobian matrix, and T∈R 4×1 Let F be the thrust matrix, and F ∈ R. 3×1 This is the external force matrix (including the forces and moments acting on the end-effector moving platform);

[0053]

[0054] When the structure matrix W is full rank, the thrust can be expressed as:

[0055] T = W + F + Nλ = t p + Nλ (5)

[0056] where W + = W T (WW T ) -1 ∈R 4×3 is the Jacobian matrix; N is the null space matrix of the Jacobian matrix, expressed as N = null(W) = [N1, N2, N3, N4] T ∈R n×re ; t p = W + F represents the particular solution of Equation (3); λ ∈ R re×1 represents an arbitrary column vector, and the thrust is adjusted by the null space vector λ to adapt to different external forces and torques.

[0057] The feasible set of the thrust for the random column vector λ can be expressed as:

[0058] Ω = {λ丨T min ≤ Nλ + t p ≤ T max} (6)

[0059] All columns (re) of N in Equation (6) form a set of bases of the vector space. λ is the re-dimensional coordinate in the local coordinate system O,. Through linear analysis, T min is the minimum value of the tension of the link connecting rod, T max is the maximum value of the tension of the link connecting rod. If the coordinate transformation matrix P -1 ∈R re×re , the change between another coordinate V and λ in the local coordinate system O, can be achieved through λ = V·P -1 to describe the same feasible set of thrust with another set of coordinates in a similar vector space.

[0060] Since re = 1, any i-th linear actuator is taken for force control (1 ≤ i ≤ 4), and there is the following relationship:

[0061] N i λ + t pi = T i (7)

[0062]

[0063] where λ = N C1 × T i , t pi Let be the particular solution value of the thrust of the linear actuator i. Substituting equation (8) into equation (5) yields the expression for the thrust:

[0064]

[0065] In the formula, N o =N·N C1 .

[0066] The feasible set of thrust forces satisfying the condition that all links are within the linear force boundary conditions is:

[0067]

[0068] Assuming the end effector is not in a geometrically singular pose, and the i-th linear actuator is selected for force control (1≤i≤4), then the thrust of the k-th linear actuator (1≤k≤4, k≠i) can be determined by T. i Indicate:

[0069] T k =t pk +N k1 ·N C1 (T i -t pi (11)

[0070] Using the Euler-Lagrange equations as the kinematic model, the following are the stiffness balance formulas:

[0071] W T (q)·τ=Q(q) (12)

[0072] Among them W T (q) is the transpose of the Jacobian matrix, representing the transformation of joint torque into end effector torque. q consists of three independent coordinates, typically chosen as the Cartesian coordinate system of the end effector. ee y ee and its rotation θ ee Let τ be the torque vector of the linear actuator, and Q(q) be the nonlinear stiffness contribution of the flexible hinge. From this equation, we can find an efficient solution for τ; all other solutions can be found by adding any vector to the null space of the Jacobian matrix W.

[0073] Example 3

[0074] In this embodiment, a flexible hinge is described;

[0075] Based on the interaction between the cross-section flexible hinge and the contact, this embodiment adds an internal force redundancy adjustable stiffness design to the flexible hinge; according to the function of each flexible segment, it is divided into contact segment and non-contact segment;

[0076] like Figure 6 As shown, the flexible hinge includes two fan-shaped connecting areas 34 and two fan-shaped hollow areas 35 symmetrically distributed in the circumferential direction. The fan-shaped connecting areas 34 and the fan-shaped hollow areas 35 are spaced apart and have gaps between them. Each end of the fan-shaped hollow area 35 is provided with a fixed end 29, which is fixed relative to the corresponding static platform and the moving platform 16 (i.e., fixed with bolts between it and the corresponding cover plate to achieve relative fixation). The fan-shaped connecting areas 34 are used to fix the connecting parts (first connecting part 23 and second connecting part 27).

[0077] The two edges of the fan-shaped hollow area 35 are respectively provided with segment 1 30 and segment 4 33 as non-contact segments; the hollow area in the middle of the fan-shaped hollow area 35 is provided with T-shaped segment 32, and the edge of the hollow area in the middle is provided with segment 2 31. Segment 32 and segment 2 31 serve as contact segments.

[0078] The two-dimensional and three-dimensional diagrams of the flexible hinge under no stress and deformation are shown below. Figure 8 (a) and Figure 9 As shown in (a) in the figure; as Figure 9 As shown in (b), when the flexible hinge is subjected to a tangential force F transmitted from the connector... Z At that time, the fan-shaped connecting area 34 deforms towards the fan-shaped hollow area 35, while segment one 30 and segment four 33 also deform, and segment three 32 rotates at the middle hollow area; as Figure 8 (b) and Figure 9 As shown in (c), as the flexible hinge continues to deform, segment 32 will come into contact with segment 2 31, thereby increasing the stiffness of the entire flexible hinge and achieving the purpose of changing the stiffness of the positioning platform.

[0079] In this embodiment, for the sake of simplicity, the fixing hole of a single flexible hinge is omitted in the figure, and the material of the flexible hinge is spring steel.

[0080] Specifically: the overall model of a branch with flexible hinges is represented by a set of parameters, see... Figure 7 To limit the computation time, the parameter values ​​are restricted to a reasonable range, and some parameters are designed to be fixed. See Table 1, the flexible hinge dimension analysis table, which lists the different parameters with lower and upper limits.

[0081] Table 1: Dimensional Analysis of Flexible Hinges

[0082]

[0083] The flexible hinge fixed to the stationary platform is the inner ring s flexible hinge, and the flexible hinge fixed to the moving platform is the inner ring e flexible hinge. At the hinge level, the characteristic of a flexible hinge is its diameter A. se Diameter D of the hollowed-out area se The height h and thickness t, the first two are obtained from finite element analysis of the flexible hinge as spring steel, based on the elastic stiffness of the flexible hinge. se and the diameter D of the hollowed-out area se The optimal values ​​are found for the latter two dimensions, which are fixed for all flexible hinges. The minimum thickness *t* reduces stress accumulation without significantly affecting the support rigidity, while the height *h* is... Figure 7 The out-of-plane dimensions of the flexible hinge are set to fixed values. To achieve optimal performance of the outer ring s and inner ring e flexible hinges (specifically, s is the flexible hinge fixed to the fixed platform, and e is the flexible hinge fixed to the moving platform), optimization is required. Figure 7 The gap angle ε shown s and ε e Therefore, these angles are fixed as the minimum estimated gap angles required for the expected range of motion.

[0084] The coordinate system for a single flexible hinge is defined below as follows: Figure 9 As shown in (a), the stiffness matrix of a single flexible hinge can be expressed as:

[0085]

[0086] Where E is the elastic modulus of the flexible hinge, and A se Where is the diameter of the flexible hinge, h is the height of the flexible hinge, and k is the diameter of the flexible hinge. 11 k represents the stiffness of the flexible hinge in the z-axis direction. 22 k represents the stiffness of the flexible hinge in the x-axis direction. 33 k represents the stiffness of the flexible hinge in the y-axis direction. 44 k represents the torsional stiffness of the flexible hinge about the x-axis. 55 k represents the torsional stiffness of the flexible hinge in the y-axis direction. 66 This represents the torsional stiffness of the flexible hinge about the z-axis.

[0087] Then, a torque M is added to the flexible hinge around the z-axis. Z And the thrust (tangential force) F at a distance S = 4 mm from the z-axis Z like Figure 9 As shown in (b) above. Its deformation is as follows. Figure 9 As shown, based on the contact condition of the flexible segment, the hinge motion is divided into three stages: (a) The flexible hinge is not under force, L is a fixed non-zero positive value, θ=0°, and stiffness k 11 k 22 k 33 k44 k 55 k 66 (a) The flexible hinge deforms, at which point the deformation of segments 1 (30) and 4 (33) contributes to the motion, but the segments do not come into contact, 0 < L1 < L, 0 < θ1 < θ2, and the stiffness k remains unchanged; 11 k 22 k 33 k 44 k 55 k 66 (c) As deformation increases, segment 32 will contact and frictionally lock with segment 2 31, L2 = 0, and θ2 is a fixed non-zero positive value. During this stage, the effective length shortens, and the hinge stiffness increases to k. 11 '、k 22 '、k 33 '、k 44 '、k 55 '、k 66 '.

[0088] like Figure 10 As shown, the moving platform 16, initially positioned, moves 5mm along the y-axis and then 5mm along the x-axis. At these three different positions, while maintaining the current position of the moving platform, the loading state of each branch can be adjusted by redistributing torque within the zero-space. This adjustment allows the flexible hinge to... Figure 9 In (b), the deformation is not switched, and additional force and torque deformation are added through the linear actuator. Figure 9 The switching state of (c) in the middle, at this time due to k ii '>k ii The stiffness of the flexible hinges is improved, significantly enhancing the local stiffness of the mechanism and thus increasing the overall output stiffness. Furthermore, the synergistic effect between the branches allows for mutual compensation of deformation states in different branches, maintaining the positional stability of the moving platform. By optimizing the internal force distribution of each branch, both local and overall stiffness can be adjusted.

[0089] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," 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, 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.

[0090] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge, comprising a moving platform, characterized in that, The moving platform has four stationary platforms arranged circumferentially, and the stationary platforms are connected to the moving platform by a chain. The chain includes two sets of flexible hinges. One set of flexible hinges is fixed relative to the stationary platform, and the other set of flexible hinges is fixed relative to the moving platform. Each set has two flexible hinges, and the two flexible hinges in each set are distributed vertically. The two flexible hinges in each set are fixed together by a connector. The two connectors are connected by a linear actuator, which can adjust the distance between the stationary platform and the moving platform. Flexible hinges deform under external forces and torques, enabling relative torsion between the static and dynamic platforms; The flexible hinge includes two fan-shaped connecting areas and two fan-shaped hollow areas symmetrically distributed in the circumferential direction, with the fan-shaped connecting areas and the fan-shaped hollow areas spaced apart; each of the two ends of the fan-shaped hollow area is provided with a fixed end, which is fixed relative to the corresponding static platform and moving platform; the fan-shaped connecting areas are fixed to the connectors; The two edges of the fan-shaped hollow area are respectively provided with segment one and segment four; the hollow area in the middle of the fan-shaped hollow area is provided with T-shaped segment three, and the edge of the hollow area in the middle is provided with segment two.

2. The variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to claim 1, characterized in that, When the flexible hinge is subjected to tangential force transmitted from the connector, the fan-shaped connecting area deforms towards the fan-shaped hollow area, while segments one and four also deform, and segment three rotates at the middle hollow. As the flexible hinge continues to deform, segment three can contact segment two and generate friction to improve the stiffness of the flexible hinge.

3. The variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to claim 1, characterized in that, The linear actuator is fixed to one of the connecting parts, and the push rod of the linear actuator is fixed to the other connecting part.

4. The variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to claim 3, characterized in that, The linear actuator is fixed to one of the connectors by bolts, and the linear actuator's push rod is fixed to the other connector by bolts and nuts.

5. The variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to claim 1, characterized in that, The upper end of the static platform is fixed with a cover plate by bolts, and the cover plate is fixed to the flexible hinge by bolts.

6. The variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to claim 1, characterized in that, The eight corners at the upper and lower ends of the moving platform are respectively fixed with cover plates by bolts, and the flexible hinges are fixed to the cover plates by bolt connection.

7. The variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge according to claim 1, characterized in that, The flexible hinge is made of spring steel.

8. A parallel robot, characterized in that, Includes the variable stiffness planar parallel positioning platform with a switchable contact state flexible hinge as described in any one of claims 1-6.

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