Four-axis parallel mechanism and four-axis parallel robot

Abstract

The invention discloses a four-axis parallel mechanism and a robot. The four-axis parallel mechanism comprises a static platform, a movable platform and four driving structures evenly distributed between the static platform and the movable platform. Each driving structure is a kinematic chain composed of two driving arms, the top end and the bottom end of each driving structure are hinged to the static platform and the movable platform respectively, a closed-loop mechanism driven in a parallel mode is formed, and the mechanism has three degrees of freedom, is more flexible in movement and high in bearing capacity, and is suitable for large-scale popularization and application. The four-axis parallel mechanism has the advantages of being free of accumulative errors, high in precision, good in dynamic response and the like in structural design, and a robot formed by the four-axis parallel mechanism can adapt to the fields of rapid and accurate grabbing and carrying, feeding and discharging, sorting and the like of workpieces in an automatic production line.

Description

Technical Field

[0001] The present invention relates to the technical field of automated operation equipment, and in particular to a four-axis parallel mechanism and a four-axis parallel robot. Background Art

[0002] At present, in factory automation production lines, robot structures with serial and parallel mechanisms are widely used in fields such as handling, sorting, 3D printing, and assembly of electronic products.

[0003] At present, the parallel mechanisms commonly used in robots include 3-RPRU, 3-RRC, and 3-RRRT; among them, the three-axis parallel mechanism has the characteristics of high stiffness, high precision, flexible control, and multiple motion chains operating the terminal output parts at the same time, which offsets the cumulative effect of joint errors and has the characteristics of low motion inertia. Therefore, it has been widely used in many fields, including: in the field of industrial manufacturing, it is used for automobile body welding, precise cutting and processing of metal materials, etc., in the field of automated logistics, it is used for cargo handling, sorting and packaging, etc. In aerospace testing, parallel robots can withstand high impact forces and achieve precise positioning to ensure the smooth progress of aerospace missions; however, the three-axis parallel mechanism has a small working space and has certain limitations in function realization.

[0004] Based on this, it is necessary to improve the above-mentioned technical problems of the three-axis parallel mechanism in order to increase the working space to meet the needs of a wider range of industrial applications and improve the load capacity, motion accuracy and stability of the mechanism. Summary of the invention

[0005] The purpose of the present invention is to provide a four-axis parallel mechanism that solves the above-mentioned technical problems.

[0006] Another object of the present invention is to provide a four-axis parallel robot based on the above four-axis parallel mechanism.

[0007] To this end, the technical solution of the present invention is as follows:

[0008] A four-axis parallel mechanism comprises a static platform, a dynamic platform and four driving structures evenly arranged between the static platform and the dynamic platform; wherein:

[0009] The static platform includes a horizontally arranged platform, and four upper drive structure connecting frames are evenly arranged along the circumferential direction at the edge of the bottom surface of the platform; the dynamic platform includes a horizontally arranged platform, which is arranged in parallel below the static platform, and four lower drive structure connecting bodies are evenly arranged along the circumferential direction at the edge of the top surface of the platform, and the four lower drive structure connecting bodies are respectively arranged directly below the four upper drive structure connecting frames, so that the two ends of the four drive structures are respectively connected to each two upper and lower corresponding upper drive structure connecting frames and lower drive structure connecting pieces in a one-to-one correspondence;

[0010] The driving structure includes a driving motor, a first driving arm and a second driving arm; the driving motor is fixed on the upper driving structure connecting frame in a horizontally arranged output shaft thereof, and the top end of the first driving arm is fixed on the output shaft so as to drive the first driving arm to swing back and forth through the driving motor; the bottom end of the first driving arm is movably connected to the top end of the second driving arm through a universal joint, and the bottom end of the first driving arm and the top end of the second driving arm are rotatably connected to both ends of the universal joint respectively; the bottom end of the second driving arm is hingedly connected to the moving platform through a lower driving structure connecting member; in the four driving structures, the two driving motors in the first group of two driving structures located on opposite sides are arranged in a manner that the output shafts are parallel, and the two lower driving structure connecting members of the two can enable the second driving arm to swing in the axial direction of the output shaft of the upper driving motor; the two driving motors in the second group of two driving structures located on opposite sides are arranged in a manner that the output shafts are parallel and perpendicular to the output shafts of the driving motors in the first group, and the two lower driving structure connecting members of the two can enable the second driving arm to swing in the axial direction of the output shaft of the upper driving motor.

[0011] Furthermore, the upper drive structure connecting frame is composed of a motor mounting plate, a first connecting plate and a second connecting plate which are arranged in parallel and spaced apart in a line and vertically fixed on the bottom surface of the rectangular platform, and the three plates are provided with intersecting through holes in the horizontal direction; the driving motor is fixed on the motor mounting plate, and its output shaft is horizontally inserted into the through holes of the motor mounting plate, the first connecting plate and the second connecting plate in sequence with a gap, and is rotatably connected to the through hole of the second connecting plate through a rotating bearing arranged at the end of the shaft; a connecting sleeve is sleeved and fixed on the outer side of the output shaft between the first connecting plate and the second connecting plate, so that the top end of the first driving arm is fixed on the sleeve.

[0012] Furthermore, the bottom end of the first driving arm is rotatably connected to the top end of the universal joint through a turntable bearing, and the top end of the second driving arm is rotatably connected to the bottom end of the universal joint.

[0013] Furthermore, the universal joint is a cross-axis universal joint or a ball-joint universal joint, so that the second driving arm can rotate in any direction relative to the first driving arm.

[0014] Furthermore, the lower driving structure connecting member is a hinge, a ball joint or a Hooke's joint, so that the second driving arm can swing back and forth relative to the moving platform.

[0015] Furthermore, a first mounting hole for connecting with the frame is opened at the center of the static platform, and a second mounting hole for connecting with the tool is opened at the center of the dynamic platform.

[0016] A robot comprises a frame, a four-axis parallel mechanism and an execution tool; the four-axis parallel mechanism adopts the above-mentioned four-axis parallel mechanism, which is connected to the frame through the static platform of the four-axis parallel mechanism and is connected to the execution tool through the dynamic platform of the four-axis parallel mechanism.

[0017] Compared with the prior art, the four-axis parallel mechanism includes four parallel driving structures, each driving structure is a motion chain composed of two driving arms, and the top and bottom ends are respectively hinged on the static platform and the dynamic platform, forming a closed-loop mechanism driven in parallel. The mechanism has three degrees of freedom, more flexible movement, and strong carrying capacity. The structural design has the characteristics of no cumulative error, maintaining high precision, and good dynamic response. The robot formed by the four-axis parallel mechanism can adapt to the fields of fast and accurate grasping and handling, loading and unloading, and sorting of workpieces in automated production lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the four-axis parallel mechanism of the present invention;

[0019] Figure 2 It is a partial side view of the static platform of the four-axis parallel mechanism of the present invention;

[0020] Figure 3 for Figure 1 A schematic diagram of a local enlarged structure;

[0021] Figure 4 It is a front view of the four-axis parallel mechanism of the present invention;

[0022] Figure 5 for Figure 4 A schematic diagram of a local enlarged structure;

[0023] Figure 6 A top view of the four-axis parallel mechanism of the present invention;

[0024] Figure 7 It is a height displacement variation curve diagram of the hinge points between the four driving mechanisms and the moving platform during the process of the four-axis parallel mechanism performing the action design I in the embodiment of the present invention;

[0025] Figure 8 It is a curve diagram of the height displacement changes of the hinge points between the four driving mechanisms and the moving platform during the process of the four-axis parallel mechanism executing the action design II in the embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention in any way.

[0027] Example 1

[0028] See also Figure 1 The four-axis parallel mechanism includes a static platform 1, a dynamic platform 2, and four driving structures evenly distributed between the static platform 1 and the dynamic platform 2.

[0029] See also Figure 2 The static platform 1 includes a horizontally arranged rectangular platform, the center of which is provided with a first mounting hole 7 for mounting the four-axis parallel mechanism on a designated frame through the static platform 1. In some embodiments, the four-axis parallel mechanism is mounted on the frame through the static platform 1, so that the four-axis parallel mechanism can be applied to the production line and applied to the fast and accurate grasping and handling, loading and unloading, sorting and other operations of workpieces in the automated production line.

[0030] See also Figure 5 At the edge of the bottom surface of the rectangular platform located on the static platform 1, four upper drive structure connecting frames are evenly distributed along the circumferential direction; each upper drive structure connecting frame is composed of a motor mounting plate 101, a first connecting plate 102 and a second connecting plate 103 which are arranged in parallel and spaced in a line and vertically fixed on the bottom surface of the rectangular platform, and the three plates are provided with interconnected through holes in the horizontal direction.

[0031] The moving platform 2 is also a horizontally arranged rectangular platform, which is arranged parallel and spaced directly below the static platform 1. It is used to install different tools such as fixtures and cutters according to different uses, so as to drive the tools to move along the specified motion trajectory through the surrounding parallel mechanisms; a second mounting hole is opened at the center of the rectangular platform of the moving platform 2 for conveniently installing the processing tools on the movable disk.

[0032] See also Figure 1 At the edge of the top surface of the rectangular platform located on the moving platform 2, four lower driving structure connecting parts are evenly fixed along the circumferential direction, and the four lower driving structure connecting parts correspond to the four upper driving structure connecting frames on the static platform 1 one by one, so that the two ends of the four driving structures are movably connected to each corresponding upper driving structure connecting frame and the lower driving structure connecting part, so that they are initially arranged vertically in parallel with each other.

[0033] The driving structure includes a driving motor 3, a first driving arm 4 and a second driving arm 5; wherein,

[0034] The driving motor 3 is fixed on the motor mounting plate 101 in such a manner that its output shaft is parallel to the adjacent edge of the static platform 1, and its output shaft is horizontally inserted into the through holes of the motor mounting plate 101, the first connecting plate 102, and the second connecting plate 103 in sequence with a gap, and is rotatably connected to the through hole of the second connecting plate 103 through a rotating bearing arranged at the end of the shaft; a connecting shaft sleeve is sleeved and fixed on the outer side of the output shaft between the first connecting plate 101 and the second connecting plate 102;

[0035] The first driving arm 4 and the second driving arm 5 are both cylindrical rod bodies; wherein, the top end of the first driving arm 4 is fixed on the outer wall of the connecting sleeve, so that when the driving motor 3 drives the connecting sleeve to rotate, the first driving arm 4 performs reciprocating swinging motion inside and outside the middle formed by the connecting sleeve between the static platform 1 and the moving platform 2; the bottom end of the first driving arm 4 is connected to the top end of the second driving arm 5 through a universal joint 6, so that the second driving arm 5 can rotate in any direction relative to the first driving arm 4; the bottom end of the second driving arm 5 is hingedly connected to the moving platform 2 through the lower driving structure connecting member.

[0036] See also Figure 3 In some embodiments, the universal joint 6 adopts a cross-axis universal joint, and the bottom end of the first driving arm 4 and the top end of the second driving arm 5 are rotatably connected to the two ends of the universal joint 6 respectively; specifically, the cross-axis universal joint is composed of an active fork 61, a cross shaft 62 and a driven fork 63, a group of symmetric axes of the cross shaft 62 is hingedly connected to the bottom end of the active fork 61, and another group of symmetric axes is hingedly connected to the top end of the driven fork 63; an upper turntable bearing is provided between the first driving arm 4 and the active fork 61, and the outer ring of the upper turntable bearing is fixed on the top surface of the active fork 61, and the inner ring is fixed on the upper surface of the first driving arm 4. On the bottom end surface of the arm 4, the first driving arm 4 can rotate freely relative to the universal joint 6; a lower turntable bearing is provided between the driven fork 63 and the second driving arm 5, and the outer ring of the lower turntable bearing is fixed on the bottom surface of the driven fork 63, and the inner ring is fixed on the top end surface of the second driving arm 5, so that the second driving arm 5 can rotate freely relative to the universal joint 6; furthermore, the first driving arm 4 can rotate relative to the second driving arm 5 at any angle, and can be set at any angle, and at the same time, the first driving arm 4 can perform variable-angle power transmission to the second driving arm 5 through the universal joint 6.

[0037] See also Figure 5 In some embodiments, the lower driving structure connecting member includes a cylinder vertically fixed on the rectangular platform of the moving platform 2, and a U-shaped member fixed at the bottom end of the second driving arm 5. The U-shaped member is opened downward and is sleeved on the outside of the cylinder. The two are hingedly connected by a horizontally-articulated shaft, so that the second driving arm 5 can swing relative to the moving platform 2.

[0038] In the four driving structures, the two driving motors 3 in the two driving structures on the opposite sides of the first group are arranged with their output shafts in parallel, and the two lower driving structure connecting parts of the two can enable the second driving arm 5 to swing in the axial direction of the output shaft of the upper driving motor 3; the two driving motors 3 in the two driving structures on the opposite sides of the second group are arranged with their output shafts in parallel and perpendicular to the output shafts of the driving motors 3 in the first group, and the two lower driving structure connecting parts of the two can enable the second driving arm 5 to swing in the axial direction of the output shaft of the upper driving motor 3.

[0039] In actual applications, the two driving mechanisms located on the opposite sides can swing in the same direction or in different directions around the output shaft of the driving motor 3 under the drive of the driving motor 3. Specifically, the swing range of the first driving arm 4 of the driving mechanism is 45° inward to 45° outward, wherein the inner side is defined as the central area surrounded by four driving structures, and the outer side is defined as the outer side of the four-axis parallel mechanism; furthermore, the two groups of driving structures located on the opposite sides can increase the movement radius and the up and down stroke of the moving platform 2, so that the movement range of the moving platform 2 is larger, meeting the needs of different operations and being more flexible; at the same time, in terms of structural design, since the four-axis parallel mechanism includes four driving mechanisms, it has three degrees of freedom; since the four driving structures are arranged between the static platform 1 and the moving platform 2 in a mutually coordinated manner, the movement accuracy of the moving platform 2 is higher, the flexibility of movement is increased, and the carrying capacity is enhanced, so that it can adapt to fields with high precision requirements and complex operations, such as fast and accurate grasping and handling of workpieces in automated production lines, loading and unloading, and sorting.

[0040] The four-axis parallel mechanism of this embodiment is a closed-loop mechanism, and its advantages are analyzed as follows:

[0041] 1) The stiffness-to-mass ratio is large. Specifically, because the mechanism adopts a parallel closed-loop rod system, the rod system theoretically only bears tension and compression loads. It is a typical two-force rod, and multiple rods are stressed, which makes the transmission mechanism have a very high load-bearing strength;

[0042] 2) Excellent dynamic performance. Specifically, since the mechanism is constructed in parallel, the operation requirements can be achieved by using a combination of lightweight rod joints, and it has the advantage of low inertia, which effectively improves the dynamic performance of the servo controller, so that the moving platform 2 can obtain a very high feed speed and acceleration, which is suitable for high-speed CNC operations; and, since the mechanism is constructed by connecting four drive mechanisms in parallel, even if one drive mechanism is damaged during use and cannot be used, it will not cause too much impact on the normal operation of the mechanism;

[0043] 3) High motion accuracy. Specifically, compared with the traditional serial mechanism, the machining error of the traditional serial mechanism is the accumulation of errors of each joint, while the errors of each joint of the parallel mechanism can offset and compensate each other. Therefore, the parallel mechanism is the development direction of future machine tools;

[0044] 4) Multifunctional and highly flexible. Specifically, the mechanism can form various layouts and combinations of degrees of freedom. Tools can be installed on the moving platform 2 for multi-axis milling, grinding, drilling, special surface processing, etc. Fixtures can also be installed for complex spatial assembly. It has strong adaptability and is an ideal flexible mechanism.

[0045] 5) Long service life. Specifically, due to the reasonable force structure, the moving parts have little wear and tear, and there is no guide rail. There is no possibility of iron filings or coolant entering the guide rail to cause scratches, wear or rust.

[0046] In summary, the four-axis parallel mechanism has the advantages of small motion space, light weight, high rigidity and high precision.

[0047] Example 2

[0048] A robot comprises a frame, a four-axis parallel mechanism and an execution tool; wherein the four-axis parallel mechanism is the four-axis parallel mechanism of Example 1, wherein a static platform 1 is connected to the frame, and a dynamic platform 2 is connected to the execution tool.

[0049] In some embodiments, the robot is centered on an industrial control computer and uses a PLC controller as the main control unit to perform servo control and switch quantity control, including servo control of the robot body, pneumatic system control, and transmission system control, thereby realizing complex operations of the robot.

[0050] In order to verify that the four-axis parallel mechanism has stable translational performance, the four-axis parallel mechanism of Example 1 is used, and its four driving structures are driven to swing in different ways. The longitudinal displacement of the four drives and the moving platform 2 is measured respectively to determine the movement form of the moving platform 2.

[0051] Specifically, see Figure 1 First, a coordinate system is constructed to monitor the height displacement of the moving platform 2 during the execution of the action of the four-axis parallel mechanism; specifically, with the center point of the static platform 1 as the center of the circle, the x-axis and the y-axis are respectively located in the horizontal direction, and the two are perpendicular to each other, and the z-axis is set vertically upward.

[0052] In order to facilitate the description of the action execution status of the four drive structures, Figure 1 Based on the mechanism orientation shown, the driving mechanisms located on the front and rear sides are defined as driving mechanism A and driving mechanism B respectively, and the driving mechanisms located on the left and right sides are defined as driving mechanism C and driving mechanism D respectively; and the driving motors of each driving motor rotate at a constant speed at the same speed from beginning to end.

[0053] (1) The four-axis parallel mechanism executes action design I, which is specifically as follows: first, through the driving motors of driving mechanism C and driving mechanism D, the first robotic arms of the two are driven to swing 30° to the left and maintain; then, through the driving motors of driving mechanism A and driving mechanism B, the first robotic arms of the two are driven to swing 30° forward; then, through the driving motors of driving mechanism A and driving mechanism B, the first robotic arms of the two are driven to swing 30° backward, so that driving mechanism A and driving mechanism B return to the initial vertical setting state; finally, through the driving motors of driving mechanism C and driving mechanism D, the first robotic arms of the two are driven to swing 30° to the right, so that driving mechanism C and driving mechanism D return to the initial vertical setting state.

[0054] like Figure 7 FIG. 1 is a graph showing the height displacement variation curves of the hinge points between the four drive mechanisms and the moving platform during the four-axis parallel mechanism performs the above-mentioned action design I; FIG. Figure 7 It can be seen that the corresponding heights of the curves at different time points remain the same, which means that in the process of executing action design I, the four hinge points remain at the same height position from beginning to end, that is, the moving platform always maintains a translational state under drive.

[0055] (2) Four-axis parallel mechanism execution action design II, which is specifically as follows: first, through the driving motors of driving mechanism C and driving mechanism D, the first robotic arms of the two are driven to swing 30° to the left. At the same time, through the driving motors of driving mechanism A and driving mechanism B, the first robotic arms of the two are driven to swing 30° forward; then, through the driving motors of driving mechanism C and driving mechanism D, the first robotic arms of the two are driven to swing 30° to the right. At the same time, through the driving motors of driving mechanism A and driving mechanism B, the first robotic arms of the two are driven to swing 30° backward; at this time, driving mechanism A, driving mechanism B, driving mechanism C and driving mechanism D all return to their initial vertical setting state.

[0056] like Figure 8 FIG. 1 is a graph showing the height displacement variation curves of the hinge points between the four drive mechanisms and the moving platform during the four-axis parallel mechanism performs the above-mentioned action design I; FIG. Figure 8 It can be seen that the corresponding heights of the curves at different time points remain the same, which means that during the execution of Action Design II, the four hinge points remain at the same height position from beginning to end, that is, the moving platform always maintains a translational state under drive.

[0057] (3) The execution action design III of the four-axis parallel mechanism is as follows: first, through the driving motors of driving mechanism A, driving mechanism B, driving mechanism C and driving mechanism D, the first robot arm of driving mechanism A is driven to swing forward 30°, the first robot arm of driving mechanism B is driven to swing backward 30°, the first robot arm of driving mechanism C is driven to swing left 30°, and the first robot arm of driving mechanism D is driven to swing right 30°; then, the first robot arm of driving mechanism A is driven to swing backward 30°, the first robot arm of driving mechanism B is driven to swing forward 30°, the first robot arm of driving mechanism C is driven to swing right 30°, and the first robot arm of driving mechanism D is driven to swing left 30°, so that the four driving mechanisms return to their initial states.

[0058] During the execution of the above-mentioned action design III by the four-axis parallel mechanism, the moving platform exhibits a straight up and down movement process; at the same time, the same as the above-mentioned two execution processes, the heights of the hinge points between the four driving mechanisms and the moving platform remain the same at different time points, that is, the moving platform always maintains a translational state under drive.

[0059] According to the above-mentioned action execution status test structure, the four-axis parallel mechanism can keep its moving platform driving the execution tool to perform stable translational movement from beginning to end, and can move at different height positions according to the work requirements; in addition, the four-axis parallel mechanism can also further expand the operating range of the mechanism by adjusting the length of the first robotic arm 4 and the second robotic arm 5.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A four-axis parallel mechanism, It is characterized in that The invention comprises a static platform (1), a dynamic platform (2) and four drive structures evenly arranged between the static platform (1) and the dynamic platform (2); wherein the static platform (1) comprises a horizontally arranged platform, and four upper drive structure connecting frames are evenly arranged along the circumferential direction at the edge of the bottom surface of the static platform (1); the dynamic platform (2) comprises a horizontally arranged platform, which is arranged in parallel below the static platform (1), and four lower drive structure connecting bodies are evenly arranged along the circumferential direction at the edge of the top surface of the platform, and the four lower drive structure connecting bodies are respectively arranged directly below the four upper drive structure connecting frames, so that the two ends of the four drive structures are respectively connected to each two upper and lower corresponding upper drive structure connecting frames and lower drive structure connecting pieces in a one-to-one correspondence; the drive structure comprises a drive motor (3), a first drive arm (4) and a second drive arm (5); the drive motor (3) is fixed to the upper drive structure connecting frame in a horizontally arranged manner with its output shaft, and the top end of the first drive arm (4) is fixed to the output shaft so as to pass through the drive motor (3) The first driving arm (4) is driven to swing back and forth; the bottom end of the first driving arm (4) is movably connected to the top end of the second driving arm (5) through a universal joint (6), and the bottom end of the first driving arm (4) and the top end of the second driving arm (5) are respectively rotatably connected to the two ends of the universal joint (6); the bottom end of the second driving arm (5) is hingedly connected to the moving platform (2) through a lower driving structure connecting piece; in the four driving structures, the two driving motors (3) in the first group of two driving structures located on the opposite sides are arranged in a manner that the output shafts are parallel, and the two lower driving structure connecting pieces of the two can enable the second driving arm (5) to swing in the direction of the output shaft axis of the upper driving motor (3); the two driving motors (3) in the second group of two driving structures located on the opposite sides are arranged in a manner that the output shafts are parallel and perpendicular to the output shafts of the driving motors (3) in the first group, and the two lower driving structure connecting pieces of the two can enable the second driving arm (5) to swing in the direction of the output shaft axis of the upper driving motor (3).

2. The four-axis parallel mechanism according to claim 1, It is characterized in that The upper drive structure connecting frame is composed of a motor mounting plate (101), a first connecting plate (102) and a second connecting plate (103) which are arranged in parallel and spaced apart in a straight line and fixed vertically on the bottom surface of a rectangular platform, and through holes which intersect each other are opened in the horizontal direction on the plates of the three. The drive motor (3) is fixed on the motor mounting plate (101), and its output shaft is horizontally inserted into the through holes of the motor mounting plate (101), the first connecting plate (102) and the second connecting plate (103) in sequence with a gap, and is rotatably connected to the through hole of the second connecting plate (103) through a rotating bearing arranged at the end of the shaft. A connecting shaft sleeve is sleeved and fixed on the outer side of the output shaft between the first connecting plate (101) and the second connecting plate (102), so that the top end of the first drive arm (4) is fixed on the shaft sleeve.

3. The four-axis parallel mechanism according to claim 1, It is characterized in that The bottom end of the first driving arm (4) is rotatably connected to the top end of the universal joint (6) through a turntable bearing, and the top end of the second driving arm (5) is rotatably connected to the bottom end of the universal joint (6).

4. The four-axis parallel mechanism according to claim 1, It is characterized in that The universal joint (6) is a cross-axis universal joint or a ball-jointed universal joint, which enables the second driving arm (5) to rotate in any direction relative to the first driving arm (4).

5. The four-axis parallel mechanism according to claim 1, It is characterized in that The lower drive structure connecting member is a hinge, a ball joint or a Hooke's joint, so that the second drive arm (5) can swing back and forth relative to the moving platform (2).

6. The four-axis parallel mechanism according to claim 1, It is characterized in that A first mounting hole (7) for connecting to a frame is provided at the center of the static platform (1), and a second mounting hole (8) for connecting to a tool is provided at the center of the dynamic platform (2).

7. A robot, It is characterized in that It comprises a frame, a four-axis parallel mechanism and an execution tool; the four-axis parallel mechanism adopts the four-axis parallel mechanism as described in any one of claims 1 to 6, which is connected to the frame through a static platform (1) of the four-axis parallel mechanism, and is connected to the execution tool through a dynamic platform (2) of the four-axis parallel mechanism.

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