Three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics

Abstract

The application discloses a three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics, which comprises a static platform, a dynamic platform and multiple groups of support chains, wherein each support chain comprises a supporting column, a vertical spring, an L-shaped supporting frame, an upper connecting rod, a lower connecting rod and a horizontal spring; the lower end of the supporting column is fixed to the static platform, the upper end of the supporting column is connected with the lower end of the vertical spring through a first adjusting mechanism; the upper end of the vertical spring is fixed to the lower surface of the dynamic platform; the lower end of the L-shaped supporting frame is fixed to the static platform, and the horizontal spring is installed on the upper surface of the L-shaped supporting frame through a spring seat; the spring seat, the lower connecting rod, the upper connecting rod and the dynamic platform constitute a first rotating pair, a second rotating pair and a third rotating pair which are parallel to each other. The application has flexible motion characteristics, meets the space three-translational-degree-of-freedom vibration isolation requirement, and through adjusting the pre-compression amount of the spring, the X direction and the Y direction can realize the quasi-zero stiffness characteristics, and the Z direction realizes the zero stiffness characteristics.

Description

Technical Field

[0001] This invention relates to vibration isolation platforms, and more specifically to a three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics. Background Technology

[0002] Vehicle-mounted instruments and equipment are inevitably subject to vibration during vehicle operation. This vibration can affect the reliability of the instruments and equipment.

[0003] The vibrations experienced by mechanical equipment can be decomposed into linear vibrations and torsional vibrations. Compared to the vibration isolation problem with quasi-zero stiffness characteristics, solving the problem of zero-stiffness three-degree-of-freedom parallel vibration isolation using existing technology is more challenging. Existing three-degree-of-freedom vibration isolators exhibit significant differences in vibration isolation effectiveness in different directions, resulting in poor vibration isolation efficiency.

[0004] The invention application (publication number CN110778649A) discloses a three-degree-of-freedom vibration isolation device with quasi-zero stiffness characteristics. The vibration isolation device consists of a static platform connected to an external foundation platform, a dynamic platform supporting the equipment to be isolated, a support chain, and a quasi-zero stiffness mechanism. However, this mechanism can only achieve quasi-zero stiffness vibration isolation in the single-dimensional Z-direction, while it does not have zero stiffness or quasi-zero stiffness characteristics in the X and Y directions.

[0005] Existing three-degree-of-freedom vibration isolators with zero or near-zero stiffness characteristics often combine parallel mechanisms with the vibration isolation system to achieve multi-directional vibration isolation. However, these directions often only possess zero-stiffness vibration isolation characteristics in the vertical direction, while the X and Y directions lack zero-stiffness characteristics, thus affecting the vibration isolation effect. These technological limitations prevent them from being used to solve the problem of low-frequency three-degree-of-freedom vibration isolation with zero stiffness. Summary of the Invention

[0006] The primary objective of this invention is to overcome the shortcomings of the existing technology and provide a three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics. This three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics has a simple and compact structure, flexible characteristics, and can meet the requirements for quasi-zero stiffness vibration isolation of three translational degrees of freedom in space.

[0007] The objective of this invention is achieved through the following technical solution: This three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics includes a static platform, a dynamic platform, and multiple sets of branches. Each branch includes a support column, a vertical spring, an L-shaped support frame, an upper connecting rod, a lower connecting rod, and a horizontal spring. The lower end of the support column is fixed to the static platform, and the upper end of the support column is connected to the lower end of the vertical spring via a first adjusting mechanism. The upper end of the vertical spring is fixed below the dynamic platform. The lower end of the L-shaped support frame is fixed to the static platform. The horizontal spring is mounted on the L-shaped support frame via a spring seat. One end of the lower connecting rod is hinged to the spring seat to form a first revolute joint, and the other end of the lower connecting rod is hinged to one end of the upper connecting rod to form a second revolute joint. The other end of the upper connecting rod is hinged to the dynamic platform via a rotating shaft mounting seat to form a third revolute joint. The central axes of the first, second, and third revolute joints are parallel to each other. The L-shaped support frame is provided with a second adjusting mechanism, which is connected to the spring seat.

[0008] Preferably, the first adjusting mechanism includes a vertical knob and a vertical lead screw, the lower end of the vertical lead screw and the upper end of the support column are connected by a thread, and the upper end of the vertical lead screw is connected to the lower end of the vertical spring through the vertical knob.

[0009] Preferably, the second adjustment mechanism includes a bearing seat, a horizontal lead screw and a horizontal knob, the spring seat includes a spring support, a sliding table and a pair of sliders, the sliders are mounted on the upper end of the L-shaped support frame via a guide rail, the spring support and the sliding table are respectively fixed to the two sliders, the two ends of the horizontal spring are respectively fixed to the spring support and the sliding table, and the sliding table is hinged to one end of the lower connecting rod;

[0010] Preferably, the bearing seat is fixed to the outer end of the L-shaped support frame, one end of the horizontal lead screw is installed in the bearing seat, the other end is connected to the spring support, and the horizontal knob is installed at one end of the adjusting lead screw.

[0011] Preferably, the upper end of the sliding table is provided with a boss inclined surface, and this boss inclined surface is provided with a hinge hole for hinge connection with the lower connecting rod.

[0012] Preferably, the lower end of the moving platform is provided with a mounting hole that matches the vertical spring, and the upper end of the vertical spring is fixed in the mounting hole.

[0013] Preferably, the rotating shaft mounting base is provided with a U-shaped groove into which the upper connecting rod is embedded.

[0014] Preferably, the number of branches is four, and these four branches are evenly distributed relative to the central axis of the static platform.

[0015] Preferably, in each branch chain, the number of horizontal springs is 2.

[0016] Preferably, the support frame is provided with support ribs.

[0017] The present invention has the following advantages over the prior art:

[0018] 1. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics of the present invention has a simple and compact structure, flexible motion characteristics, meets the requirements of spatial three-degree-of-freedom translational vibration isolation, and can achieve near-zero stiffness characteristics in the X and Y directions and zero stiffness characteristics in the Z direction by adjusting the pre-compression of the spring.

[0019] 2. The three-degree-of-freedom parallel vibration isolation platform of the present invention incorporates adjustable stiffness into the design of the three-degree-of-freedom parallel mechanism. By adjusting the stiffness of the vibration isolator, near-zero stiffness in the X and Y directions and zero stiffness in the Z direction can be achieved, thereby more effectively isolating vibrations within a specific frequency range. This flexibility allows the platform to adapt to different working environments and vibration sources, thus providing superior vibration isolation performance.

[0020] 3. The adjustable stiffness vibration isolator of the three-degree-of-freedom parallel vibration isolation platform of the present invention, with quasi-zero stiffness characteristics, can adjust its performance according to changes in load, ensuring a stable vibration isolation effect under different load conditions. This is especially important for applications that need to support precision instruments or equipment, as these devices are highly sensitive to vibration.

[0021] 4. Traditional vibration isolators often perform best at specific frequencies, while adjustable stiffness vibration isolators can cover a wider frequency range, thus providing effective vibration isolation over a broader frequency range.

[0022] 5. Compared with the existing invention application (publication number CN110778649A), the three-degree-of-freedom parallel mechanism of that invention application is a 3P-Delta mechanism, that is, the configuration of each branch is PR(4R)R, and the axes of motion of the second kinematic joint (revolute joint) and the prismatic joint are perpendicular to each other, and the axes of motion of the second revolute joints of the three branches are arranged in a coplanar manner. This configuration feature determines the mapping relationship between the output speed and the input speed of the mechanism—the Jacobian matrix changes with the pose of the moving platform. In contrast, the three-degree-of-freedom parallel mechanism of this invention is a 3-PRRR mechanism, and the prismatic joint P and the revolute joint are at a certain angle, and the axes of motion of the revolute joints of the three branches spatially intersect but are not coplanar. This determines the mapping relationship between the output speed and the input speed of the mechanism—the Jacobian matrix remains constant and does not change with the pose of the moving platform. At the same time, the springs in the XY plane are arranged in a cross shape, thereby achieving near-zero stiffness characteristics in the X and Y directions, and zero stiffness characteristics in the Z direction, which is not present in the existing patent. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics of the present invention.

[0024] Figure 2 This is a front view of the three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics of the present invention.

[0025] Figure 3 This is a top view of the three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics of the present invention.

[0026] Figure 4 This is a schematic diagram of the static platform and spring assembly of the present invention.

[0027] Figure 5 This is a schematic diagram of the structure of the moving platform of the present invention.

[0028] Figure 6 This is a schematic diagram of the slider and spring on the guide rail of the present invention.

[0029] Among them, 1 is the static platform, 2 is the moving platform, 3 is the support chain, 4 is the support column, 5 is the vertical spring, 6 is the L-shaped support frame, 7 is the upper connecting rod, 8 is the lower connecting rod, 9 is the horizontal spring, 10 is the first adjustment mechanism, 11 is the spring seat, 12 is the second adjustment mechanism, 13 is the first rotating pair, 14 is the second rotating pair, 15 is the third rotating pair, 16 is the vertical knob, 17 is the vertical lead screw, 18 is the bearing seat, 19 is the horizontal lead screw, 20 is the horizontal knob, 21 is the spring support, 22 is the sliding table, 23 is the slider, 24 is the boss inclined surface, 25 is the hinge hole, 26 is the mounting hole, 27 is the U-shaped groove, 28 is the support rib, 29 is the guide rail, and 30 is the rotating shaft mounting seat. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] like Figures 1 to 4 As shown, a three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics includes a static platform, a dynamic platform, and multiple sets of branches. Each branch includes a support column, a vertical spring, an L-shaped support frame, an upper connecting rod, a lower connecting rod, and a horizontal spring. The lower end of the support column is fixed to the static platform, and the upper end of the support column is connected to the lower end of the vertical spring via a first adjusting mechanism. The upper end of the vertical spring is fixed below the dynamic platform. The lower end of the L-shaped support frame is fixed to the static platform. The horizontal spring is mounted on the L-shaped support frame via a spring seat. One end of the lower connecting rod is hinged to the spring seat to form a first revolute joint, and the other end of the lower connecting rod is hinged to one end of the upper connecting rod to form a second revolute joint. The other end of the upper connecting rod is hinged to the dynamic platform via a rotating shaft mounting seat to form a third revolute joint. The central axes of the first, second, and third revolute joints are parallel to each other. A second adjusting mechanism is provided on the L-shaped support frame, and this second adjusting mechanism is connected to the spring seat.

[0032] Specifically, in this embodiment, there are four branches. Both the stationary and moving platforms are made of square plates and are arranged in parallel, with the moving platform directly above the stationary platform. The four branches are evenly distributed around the central axis of the stationary platform, forming a cross-shaped symmetrical distribution. Thus, the stationary platform, moving platform, and four branches constitute a 4-PRRR parallel mechanism. The first and second adjustment mechanisms are used to adjust the preload of the vertical and horizontal springs, respectively, i.e., to adjust the initial compression of the vertical and horizontal springs to ensure their restoring force. In this embodiment, the vertical and horizontal springs are perpendicular to each other. The vertical spring, horizontal spring, first revolute joint, second revolute joint, and third revolute joint constitute a quasi-zero stiffness structure. Specifically, the spring seat moves on the guide rail to form a sliding joint; one end of the lower connecting rod is hinged to the spring seat to form the first revolute joint, the other end of the lower connecting rod is hinged to one end of the upper connecting rod to form the second revolute joint, and the other end of the upper connecting rod is hinged to the moving platform via a pivot mounting seat to form the third revolute joint. The first, second, and third revolute joints of this prismatic joint form a chain with one degree of freedom, and the 4-PRRR parallel mechanism composed of the four chains has three-dimensional translational degrees of freedom.

[0033] During operation, when a three-dimensional spatial vibration signal is applied to the moving platform, it is transmitted to the springs (i.e., vertical and horizontal springs) at the drive joints via the various branches of the parallel mechanism. The composition and arrangement of the kinematic pairs of each branch determine that the Jacobian matrix of the parallel mechanism remains constant. Therefore, during the operation of the vibration isolation platform of this invention, its stiffness matrix and natural frequency do not change with the position of the moving platform; the instantaneous natural frequency of the system at any position on the vibration isolation platform remains unchanged. A pre-compression adjustment knob is designed at one end of the spring, enabling adjustable spring stiffness without disassembly. Therefore, the Z-direction exhibits zero stiffness characteristics. Because the vibration isolation platform is affected by the vertical springs during movement along the X and Y directions, near-zero stiffness characteristics can be achieved in the X and Y directions.

[0034] In the initial state, the moving platform is in a certain horizontal position and forms a certain angle with the lower and upper connecting rods. Under the action of external disturbance, the moving platform leaves the equilibrium position. Due to the restriction of the branches, the moving platform only has three translational degrees of freedom. By selecting appropriate stiffness values ​​for the horizontal and vertical springs, the moving platform can move within a certain stiffness range. Under the action of this quasi-zero stiffness mechanism, the entire system produces a vibration isolation effect.

[0035] The first adjustment mechanism includes a vertical knob and a vertical lead screw. The lower end of the vertical lead screw and the upper end of the support column are connected by a thread, and the upper end of the vertical lead screw is connected to the lower end of the vertical spring via the vertical knob. Specifically, the upper end of the support column has a threaded hole for adjustment, and the vertical lead screw has an external thread that matches the threaded hole. When the knob is rotated, the vertical lead screw is inserted into the threaded hole to adjust the compression of the vertical spring, thereby ensuring that the four vertical springs achieve zero stiffness in the Z direction.

[0036] The second adjusting mechanism includes a bearing seat, a horizontal lead screw, and a horizontal knob. The spring seat includes a spring support, a sliding platform, and a pair of sliders. The sliders are mounted on the upper end of the L-shaped support frame via guide rails. The spring support and the sliding platform are respectively fixed to the two sliders. Both ends of the horizontal spring are respectively fixed to the spring support and the sliding platform. The sliding platform is hinged to one end of the lower connecting rod. The bearing seat is fixed to the outer end of the L-shaped support frame. One end of the horizontal lead screw is mounted on the bearing seat, and the other end is connected to the spring support. The horizontal knob is mounted on one end of the adjusting lead screw. Since both ends of the horizontal spring are fixed to the spring support and the sliding platform, rotating the horizontal knob adjusts the distance between the two sliders, thereby adjusting the initial compression of the horizontal spring and ensuring the reliability of the quasi-zero stiffness characteristics of the horizontal spring.

[0037] like Figure 6 As shown, the upper end of the sliding platform is provided with a boss-shaped inclined surface, which has a hinge hole for hinged connection with the lower connecting rod. The boss-shaped inclined surface is provided to ensure the stability of the lower connecting rod and the sliding platform, so as to ensure that the lower connecting rod and the sliding platform form a stable rotating pair.

[0038] like Figure 5 As shown, the lower end of the moving platform is provided with a mounting hole that matches the vertical spring, and the upper end of the vertical spring is fixed in the mounting hole. The mounting hole ensures the firm connection between the vertical spring and the moving platform, further improving the working performance of the vertical spring.

[0039] The rotating shaft mounting base is provided with a U-shaped groove into which the upper connecting rod is embedded. This U-shaped groove ensures the stability of the connection between the upper connecting rod and the rotating shaft mounting base, thereby ensuring the working performance of the third rotating pair.

[0040] In each branch, there are two horizontal springs. The number of horizontal springs is not limited to two; an appropriate number should be used to ensure horizontal stiffness.

[0041] The support frame is equipped with support ribs. Specifically, the support ribs are fixed to the side of the vertical part of the support frame. These support ribs ensure the strength of the support frame and thus ensure its stability when supported.

[0042] The above-described specific embodiments are preferred embodiments of the present invention and are not intended to limit the present invention. Any other changes or equivalent substitutions made without departing from the technical solution of the present invention are included within the protection scope of the present invention.

Claims

1. A three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics, characterized in that, The system includes a static platform, a dynamic platform, and multiple sets of branches. Each branch includes a support column, a vertical spring, an L-shaped support frame, an upper connecting rod, a lower connecting rod, and a horizontal spring. The lower end of the support column is fixed to the static platform, and the upper end of the support column is connected to the lower end of the vertical spring via a first adjusting mechanism. The upper end of the vertical spring is fixed below the dynamic platform. The lower end of the L-shaped support frame is fixed to the static platform. The horizontal spring is mounted on the L-shaped support frame via a spring seat. One end of the lower connecting rod is hinged to the spring seat to form a first revolute joint, and the other end of the lower connecting rod is hinged to one end of the upper connecting rod to form a second revolute joint. The other end of the upper connecting rod is hinged to the dynamic platform via a pivot mounting seat to form a third revolute joint. The central axes of the first, second, and third revolute joints are parallel to each other. The L-shaped support frame is equipped with a second adjusting mechanism connected to the spring seat. The central axes of the first, second, and third revolute joints are all located in a vertical plane and form a certain angle with the horizontal plane. The first adjustment mechanism includes a vertical knob and a vertical lead screw. The lower end of the vertical lead screw and the upper end of the support column are connected by a thread. The upper end of the vertical lead screw is connected to the lower end of the vertical spring through the vertical knob. The second adjustment mechanism includes a bearing seat, a horizontal lead screw and a horizontal knob. The spring seat includes a spring support, a sliding table and a pair of sliders. The sliders are mounted on the upper end of the L-shaped support frame via a guide rail. The spring support and the sliding table are respectively fixed to the two sliders. The two ends of the horizontal spring are respectively fixed to the spring support and the sliding table. The sliding table is hinged to one end of the lower connecting rod. The bearing housing is fixed to the outer end of the L-shaped support frame, one end of the horizontal lead screw is installed in the bearing housing, and the other end is connected to the spring support. The horizontal knob is installed at one end of the adjusting lead screw. The number of branches is 4, and these 4 branches are evenly distributed relative to the central axis of the static platform.

2. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 1, characterized in that: The upper end of the sliding table is provided with a boss inclined surface, and this boss inclined surface is provided with a hinge hole for hinge connection with the lower connecting rod.

3. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 1, characterized in that: The lower end of the moving platform is provided with a mounting hole that matches the vertical spring, and the upper end of the vertical spring is fixed in the mounting hole.

4. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 1, characterized in that: The rotating shaft mounting base is provided with a U-shaped groove into which the upper connecting rod is embedded.

5. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 1, characterized in that: In each branch chain, there are 2 horizontal springs.

6. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 1, characterized in that: The support frame is equipped with support ribs.

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