Three-DOF parallel mechanism with reconfigurable DOF

Abstract

A three-degree-of-freedom parallel mechanism with a reconfigurable degree-of-freedom form includes a fixed platform, a moving platform, and three branches evenly distributed around the axis of the fixed platform, each branch chain includes a linear slide, a slider, a torsion mechanism, a rotating block, a connecting rod, and two Hooke's hinges, the upper end of the linear slide is vertically connected to the fixed platform, the slider is slidably connected to the linear slide and connected to the rotating block through the torsion mechanism, so that the rotating block can move up and down and rotate around the horizontal axis with the slider, one end of the connecting rod is connected to the rotating block through the first Hooke's hinge, and the other end is connected to the moving platform through the second Hooke's hinge, the posture of the Hooke's hinge is changed through the torsion mechanism, and the reconstruction of the degree-of-freedom form is achieved by changing the posture of the Hooke's hinge. The three-degree-of-freedom parallel mechanism of the present invention can work in both a three-degree-of-freedom mobile mode and a three-degree-of-freedom rotation mode, so that the moving platform can complete different spatial movements without changing the mechanism, thereby effectively reducing equipment investment and improving work efficiency.

Description

Technical Field

[0001] The invention relates to a three-degree-of-freedom parallel mechanism in a reconfigurable degree-of-freedom form, belonging to the technical field of parallel robots. Background Art

[0002] Compared with serial mechanisms, parallel mechanisms have the advantages of easy inverse solution, good controllability, high precision, and stable operation. Three-degree-of-freedom parallel mechanisms are widely used in the industrial field. They can complete tasks such as fast grasping, special matching, and sorting. The mechanisms currently used in industry mainly include Delta mechanisms and Cross-IV. However, these mechanisms can only complete movements with specific degrees of freedom, such as three-degree-of-freedom movement or two turns and one shift. When the movement of a specific degree of freedom cannot meet the use requirements, the task can only be completed by replacing the mechanism, which not only increases equipment investment, but also affects work efficiency. Therefore, it is very necessary to find a parallel mechanism that can quickly convert the degree of freedom. Summary of the invention

[0003] The purpose of the present invention is to provide a three-DOF parallel mechanism with a reconfigurable degree of freedom to address the shortcomings of the prior art, so as to reduce equipment investment and improve work efficiency.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A three-degree-of-freedom parallel mechanism in a reconfigurable degree-of-freedom form comprises a fixed platform, a moving platform and three branches evenly distributed around the axis of the fixed platform, each branch comprising a linear slide, a slider, a torsion mechanism, a rotating block, a connecting rod and two Hooke's hinges, the upper end of the linear slide is vertically connected to the fixed platform, the slider is slidably connected to the linear slide and connected to the rotating block through the torsion mechanism, so that the rotating block can move up and down with the slider and rotate around the horizontal axis, one end of the connecting rod is connected to the rotating block through a first Hooke's hinge, and the other end is connected to the moving platform through a second Hooke's hinge.

[0006] The three-degree-of-freedom parallel mechanism in the above-mentioned reconfigurable degree-of-freedom form, the torsion mechanism includes a torsion motor, a motor seat, a coupling, a bearing and a rotating shaft, the rotating shaft is rotatably connected to the slider through a bearing, the vertical bisector of the rotating shaft passes through the axis of the fixed platform, the rotating block is fixed to the middle of the rotating shaft, the torsion motor is fixed to the slider through the motor seat, and the output shaft of the torsion motor is connected to the rotating shaft through a coupling.

[0007] In the above-mentioned three-degree-of-freedom parallel mechanism in the form of reconfigurable degrees of freedom, each Hooke's joint includes a cross axis and two semicircular rings, the cross axis includes an A axis and a B axis which are perpendicular to each other, and the two ends are rotatably connected to the two ends of the two semicircular rings respectively; the A axis of the first Hooke's joint is connected to the rotating block through a semicircular ring, so that it can rotate with the rotating block to be parallel to the linear slide rail or parallel to the fixed platform and point to the axis of the fixed platform, and the B axis of the first Hooke's joint is connected to the connecting rod through a semicircular ring; the A axis of the second Hooke's joint is connected to the connecting rod through a semicircular ring, and the B axis is connected to the moving platform through a semicircular ring; the A axis of the second Hooke's joint is parallel to the B axis of the first Hooke's joint and perpendicular to the connecting rod, and the B axis of the second Hooke's joint is parallel to the moving platform.

[0008] In the above-mentioned three-DOF parallel mechanism in the form of reconfigurable DOF, the slider is provided with a driving device for sliding along the linear slide rail, and the driving device is a motor driving device, a hydraulic driving device or a pneumatic driving device.

[0009] In the above-mentioned three-DOF parallel mechanism with reconfigurable DOF, the torsion motor is a stepping motor.

[0010] The present invention utilizes a torsion mechanism to change the posture of the Hooke's joint, and realizes reconstruction of the degree of freedom by changing the posture of the Hooke's joint, so that the parallel mechanism can work in both a three-degree-of-freedom mobile mode and a three-degree-of-freedom rotation mode, and the moving platform can complete different spatial movements without changing the mechanism, thereby effectively reducing equipment investment and improving work efficiency.

[0011] In addition, the present invention has the advantages of large working space, flexible movement, simple control and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0013] Figure 1 It is a schematic diagram of the three-degree-of-freedom moving state of the present invention;

[0014] Figure 2 It is a schematic diagram of the three-degree-of-freedom rotation state of the present invention;

[0015] Figure 3 Schematic diagram of the three-degree-of-freedom movement state of the branch chain;

[0016] Figure 4 It is a schematic diagram of the three-degree-of-freedom rotation state of the branch chain;

[0017] Figure 5 It is the structural diagram of Hooke's hinge;

[0018] Figure 6 It is a structural diagram of the conversion mechanism.

[0019] The numbers in the figure are: 1, fixed platform, 2, linear slide rail, 3, branch chain, 4, moving platform, 5, slider, 6, first Hooke's hinge, 7, connecting rod, 8, second Hooke's hinge, 9, torsion motor, 10, motor seat, 11, coupling, 12, bearing, 13, rotating block, 14, rotating shaft, 15, semicircular ring, 16, cross shaft. DETAILED DESCRIPTION

[0020] The present invention provides a three-degree-of-freedom parallel mechanism with a reconfigurable degree of freedom, which can be switched to a three-degree-of-freedom mobile form or a three-degree-of-freedom rotation form according to different requirements of users. At the same time, the mechanism is a mechanism with fewer degrees of freedom and avoids redundancy of degrees of freedom. The introduction of the mechanism increases the choice of parallel mechanisms in industry.

[0021] like Figure 1 and 2 As shown, the present invention mainly consists of three parts, namely, a fixed platform 1, a moving platform 4 and three branch chains 3 connecting the fixed platform 1 and the moving platform 4. Among them, the three branch chains are installed between the moving platform 4 and the fixed platform 1 at 120 degrees, and each branch chain is exactly the same, including a linear slide 2, a slider 5 installed on the linear slide 2, a torsion motor 9, a motor seat 10, a coupling 11, a bearing 12, a rotating shaft 14, a rotating block 13, a first Hooke's hinge 6, a connecting rod 7, and a second Hooke's hinge 8 installed on the moving platform 4. The same branch chains can reduce processing costs.

[0022] During installation, three linear guide rails 2 parallel to each other are evenly distributed around the vertical axis of the fixed platform 1 (i.e., the three linear guide rails are 120 degrees apart), and their upper ends are vertically fixed to the lower surface of the fixed platform 1. The slider 5 (i.e., the moving pair) on each branch chain is installed on the linear guide rail 2, and the slider 5 can only slide up and down along the linear guide rail 2, limiting the freedom of the slider 5 on other axes. The rotating block 13 is fixed on the rotating shaft 14, and the rotating shaft 14 is rotatably connected to the slider 5 through the bearing 12. The torsion motor 9 is fixed to the slider 5 through the motor seat 10, and the output shaft of the torsion motor 9 is connected to the rotating shaft 14 through the coupling 11. One end of the connecting rod 7 is connected to the rotating block 13 through the first Hooke's hinge 6, and the other end is connected to the moving platform 4 through the second Hooke's hinge 8.

[0023] The first Hooke's hinge 6 and the second Hooke's hinge 8 have the same structure, both comprising a cross shaft 16 and two semicircular rings 15. The two ends of the two semicircular rings 15 are rotatably connected to the two ends of the A axis and the B axis of the cross shaft respectively. The two semicircular rings 15 are used to connect with other components.

[0024] The specific connection method of the first Hooke's joint 6 and the second Hooke's joint 8 is: the A axis of the first Hooke's joint 6 is connected to the rotating block 13 through a semicircular ring 15, and the B axis is connected to the connecting rod 7 through a semicircular ring 15; the A axis of the second Hooke's joint 8 is connected to the connecting rod 7 through a semicircular ring 15, and the B axis is connected to the moving platform 4 through a semicircular ring 15; the A axis of the second Hooke's joint 8 is parallel to the B axis of the first Hooke's joint 6, and the B axis of the second Hooke's joint 8 is parallel to the moving platform 4.

[0025] The rotating block 13 rotates around the rotating shaft 14 under the drive of the torsion motor 9, and drives the A axis of the first Hooke's joint 6 to rotate synchronously, thereby realizing the reconstruction of the degree of freedom.

[0026] like Figure 1 As shown, a branch chain coordinate system A-xyz is established, and the origin of the coordinate system is at the rotation center of the first Hooke's joint 6 (i.e., the center point of its cross axis), and the z-axis is parallel to the linear slide 2 and points upward, and the x-axis is parallel to the fixed platform and points to the vertical axis of the fixed platform. When the A-axis of the first Hooke's joint 6 is parallel to the specified x-axis, the mechanism is a three-degree-of-freedom mobile form; when the sliders on the linear slide are placed at the same height, and the A-axis of the first Hooke's joint is rotated to make it parallel to the linear slide 2, the mechanism is a three-degree-of-freedom rotation form (the moving platform 4 rotates around the x-axis and y-axis and moves along the z-axis).

[0027] The driving device of the parallel mechanism is installed on the slider 5, and can be driven by a motor or by hydraulic or pneumatic pressure. The up and down movement of the slider drives the Hooke's joint to move, and at the same time, the Hooke's joint is rotated, thereby changing the posture of the connecting rod, so that the posture of the Hooke's joint connected to the moving platform changes, and finally drives the moving platform of the parallel mechanism to complete the required action.

[0028] During initial installation, the mechanism is in a three-degree-of-freedom mobile form, the A axis of the first Hooke's joint 6 of each branch chain is parallel to the specified x axis of the branch chain, that is, parallel to the fixed platform 1 and pointing to the vertical axis of the fixed platform, the A axis of the second Hooke's joint 8 is parallel to the B axis of the first Hooke's joint 6, and the B axis of the second Hooke's joint 8 is parallel to the A axis of the first Hooke's joint 6 and parallel to the moving platform 4. When the mechanism is transformed into a three-degree-of-freedom rotation form, the three sliders need to be placed at the same height, and the A axis of the first Hooke's joint 6 of each branch chain is rotated to be parallel to the z axis. At this time, the moving platform 4 of the mechanism has the freedom to rotate around the x-axis and y-axis and move along the z axis.

[0029] The following uses the spiral method to clarify two different degrees of freedom. When the mechanism is a three-degree-of-freedom mobile form, analyze a single branched spiral system, the formula is as follows:

[0030] $ 1 =(0 0 0; 0 0 1)

[0031] $ 2 =(1 0 0; 0 0 0)

[0032] $ 3 =(0 1 0; 0 0 0)

[0033] $ 4 =(0 0 0; d 4 0 f 4 ) (1)

[0034] $ 5 =(1 0 0; 0 e 5 f 5 )

[0035] $ 6 =(0 1 0; d 6 0 f 6 )

[0036] From the spiral, we can infer the anti-spiral:

[0037] $ 1 r =(0 0 0; 0 0 1) (2)

[0038] Formula (2) shows that when the A axis of the first Hooke's hinge 6 of each branch chain is parallel to the B axis of the second Hooke's hinge 8 (such as Figure 3 ), each branch chain exerts a constraint couple on the moving platform. The three couples exerted by the three branches are not parallel to each other and are linearly independent of each other. The three couples restrict the three rotations of the moving platform, so the moving platform only has three degrees of freedom to move.

[0039] $ 1 =(0 0 0;0 0 1)

[0040] $ 2 =(0 0 1;0 0 0)

[0041] $ 3 =(0 1 0; 0 0 0 )

[0042] $ 4 =(0 0 0; d 4 0 f4 ) (3)

[0043] $ 5 =(0 1 0;0 0 0)

[0044] $ 6 =(1 0 0;0 e 6 0)

[0045] From the spiral, we can infer the anti-spiral:

[0046] $ 1 r =(0 1 0;0 0 0) (4)

[0047] Formula (4) shows that when the A axis of the first Hooke's hinge 6 of each branch chain is parallel to the linear guide rail 2 (such as Figure 4 ), the constraint forces exerted by the three branches on the moving platform are intertwined, and the three forces are in the same plane, thus limiting the movement of two degrees of freedom and the rotation of one degree of freedom, so the moving platform only has three degrees of freedom rotation.

[0048] The invention realizes the rapid switching of the freedom degree of the mechanism by changing the axis direction of the Hooke's joint. At the same time, the mechanism has the advantages of a parallel mechanism, namely, simple inverse solution, good controllability, high precision, stable operation and the like.

[0049] The parallel mechanism is described in detail above with reference to the accompanying drawings, which aims to provide a three-DOF parallel mechanism with a variable DOF form in actual production. However, the present invention is not limited to the above-mentioned scheme, and various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A three-degree-of-freedom parallel mechanism in a reconfigurable degree-of-freedom form, characterized in that: The invention comprises a fixed platform (1), a movable platform (4) and three branch chains (3) uniformly distributed around the axis of the fixed platform (1), each branch chain (3) comprising a linear slide rail (2), a slider (5), a torsion mechanism, a rotating block (13), a connecting rod (7) and two Hooke's hinges, the upper end of the linear slide rail (2) being vertically connected to the fixed platform (1), the slider (5) being slidably connected to the linear slide rail (2) and connected to the rotating block (13) through the torsion mechanism, so that the rotating block (13) can move up and down and rotate around a horizontal axis with the slider (5), one end of the connecting rod (7) being connected to the rotating block (13) through a first Hooke's hinge (6), and the other end being connected to the movable platform (4) through a second Hooke's hinge (8); the posture of the Hooke's hinge is changed through the torsion mechanism, and the reconstruction of the degree of freedom form is achieved by changing the posture of the Hooke's hinge; Each Hooke's joint comprises a cross shaft (16) and two semicircular rings (15), wherein the cross shaft (16) comprises an A shaft and a B shaft which are perpendicular to each other, and the two ends of the cross shaft (16) are rotatably connected to the two ends of the two semicircular rings (15) respectively; the A shaft of the first Hooke's joint (6) is connected to the rotating block (13) through a semicircular ring (15), so that it can rotate with the rotating block (13) to be parallel to the linear slide rail (2) or parallel to the fixed platform (1) and point to the axis of the fixed platform (1); the B shaft of the first Hooke's joint (6) is connected to the connecting rod (7) through a semicircular ring (15); the A shaft of the second Hooke's joint (8) is connected to the connecting rod (7) through a semicircular ring (15), and the B shaft is connected to the moving platform (4) through a semicircular ring (15); the A shaft of the second Hooke's joint (8) is parallel to the B shaft of the first Hooke's joint (6) and perpendicular to the connecting rod (7), and the B shaft of the second Hooke's joint (8) is parallel to the moving platform (4).

2. A three-DOF parallel mechanism with a reconfigurable DOF form according to claim 1, characterized in that: The slide block (5) is provided with a driving device for sliding along the linear slide rail (2); the driving device is a motor driving device, a hydraulic driving device or a pneumatic driving device.

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