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

Abstract

The three-degree-of-freedom parallel vibration isolation platform with the quasi-zero stiffness characteristic comprises a static platform, a movable platform and a plurality of sets of branch chains, and each branch 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, and 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 below the movable platform; the lower end of the L-shaped supporting frame is fixed to the static platform, the horizontal spring is installed on the L-shaped supporting frame through the spring seat, and the spring seat, the lower connecting rod, the upper connecting rod and the movable platform form a first rotating pair, a second rotating pair and a third rotating pair which are parallel to one another. The three-degree-of-freedom vibration isolator has the flexible motion characteristic, the space three-translation-degree-of-freedom vibration isolation requirement is met, and by adjusting the pre-compression amount of the springs, the approximate zero-rigidity characteristic can be achieved in the X direction and the Y direction, and the zero-rigidity characteristic can be achieved in the Z direction.

Description

Technical Field

[0001] The invention relates to a vibration isolation platform, in particular to a three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics. Background Art

[0002] Vehicle-mounted instruments and equipment will inevitably be affected by vibrations during driving, which will affect the reliability of the vehicle-mounted instruments and equipment.

[0003] The vibration of mechanical equipment can be decomposed into linear vibration and torsional vibration. Compared with the vibration isolation problem of quasi-zero stiffness characteristics, it is more difficult to solve the problem of zero stiffness three-degree-of-freedom parallel vibration isolation using existing technology. The existing three-degree-of-freedom vibration isolators have different vibration isolation effects 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 base platform, a dynamic platform carrying the vibration-isolated equipment, a branch chain, and a quasi-zero stiffness mechanism. However, the mechanism can only achieve quasi-zero stiffness vibration isolation in the single-dimensional Z direction, and does not have zero stiffness or quasi-zero stiffness characteristics in the X and Y directions.

[0005] Existing three-DOF vibration isolators with zero stiffness or quasi-zero stiffness characteristics often combine parallel mechanisms with vibration isolation systems to achieve multi-directional vibration isolation functions. However, these directions often only have zero stiffness vibration isolation characteristics in the vertical direction, while the X and Y directions do not have zero stiffness characteristics, which in turn affects the vibration isolation effect. The limitations of these technologies make them unable to solve the problem of zero-stiffness low-frequency three-DOF vibration isolation. Summary of the invention

[0006] The first purpose of the present invention is to overcome the shortcomings of the above prior art and provide a three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics has a simple and compact structure and flexible characteristics, and can meet the requirements of quasi-zero stiffness vibration isolation of three translational degrees of freedom in space.

[0007] The objective of the present invention is achieved through the following technical solutions: the three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics comprises a static platform, a dynamic platform and multiple groups of branches, wherein the branches comprise 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 through a first adjustment mechanism; the upper end of the vertical spring is fixed under the dynamic platform; the lower end of the L-shaped support frame is fixed to the static platform, and the horizontal spring is installed on the upper part of the L-shaped support frame through a spring seat, one end of the lower connecting rod is hinged to the spring seat to form a first rotating pair, the other end of the lower connecting rod is hinged to one end of the upper connecting rod to form a second rotating pair, and the other end of the upper connecting rod is hinged to the dynamic platform through a rotating shaft mounting seat to form a third rotating pair; the central axes of the first rotating pair, the second rotating pair and the third rotating pair are parallel to each other; a second adjustment mechanism is provided on the L-shaped support frame, and this second adjustment mechanism is connected to the spring seat.

[0008] Preferably, the first adjustment mechanism comprises a vertical knob and a vertical screw rod, the lower end of the vertical screw rod and the upper end of the support column are connected by threads, and the upper end of the vertical screw rod is connected to the lower end of the vertical spring through the vertical knob.

[0009] Preferably, the second adjustment mechanism comprises a bearing seat, a horizontal screw rod and a horizontal knob, the spring seat comprises 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 through guide rails, the spring support and the sliding platform are respectively fixed to the two sliders, the two ends of the horizontal spring are respectively fixed to the spring support and the sliding platform, and the sliding platform 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 screw is installed on the bearing seat, and the other end is connected to the spring support, and the horizontal knob is installed on one end of the adjusting screw.

[0011] Preferably, the upper end of the sliding platform is provided with a boss inclined surface, and the boss inclined surface is provided with a hinge hole hinged to the lower connecting rod.

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

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

[0014] Preferably, the number of the branches is 4, and the 4 branches are evenly distributed relative to the central axis of the static platform.

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

[0016] Preferably, the support frame is provided with supporting 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 three-degree-of-freedom spatial translation vibration isolation, and by adjusting the pre-compression amount of the spring, the X and Y directions can achieve approximate zero stiffness characteristics, and the Z direction can achieve zero stiffness characteristics.

[0019] 2. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics of the present invention adds adjustable stiffness to the three-degree-of-freedom parallel mechanism design. By adjusting the stiffness of the vibration isolator, approximate zero stiffness in the X and Y directions and zero stiffness in the Z direction can be obtained, thereby more effectively isolating vibrations within a specific frequency range. This flexibility enables the platform to adapt to different working environments and vibration sources, thereby providing a better vibration isolation effect.

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

[0021] 4. Traditional vibration isolators tend to work best at specific frequencies, while adjustable stiffness vibration isolators can cover a wider frequency range, thereby providing effective vibration isolation over a wider frequency range.

[0022] 5. Compared with the existing invention application (publication number CN110778649A), the three-degree-of-freedom parallel mechanism of the invention application is a 3P-Delta mechanism, that is, the configuration of each branch is PR (4R) R, and the second kinematic pair (rotation pair) and the motion axis of the mobile pair are perpendicular to each other, and the second rotation pair axes of the three branches are arranged in the same plane. This configuration feature determines the mapping relationship between the output speed and input speed of the mechanism-the Jacobian matrix changes with the posture of the moving platform. The three-degree-of-freedom parallel mechanism of the present invention is a 3-PRRR mechanism, and the mobile pair P and the rotation pair are at a certain angle, and the rotation pair axes of the three branches are not coplanar when they intersect in space. This determines the mapping relationship between the output speed and input speed of the mechanism-the Jacobian matrix always remains constant and does not change with the change of the posture of the moving platform. At the same time, the springs in the XY plane are arranged in a cross, so that the approximate zero stiffness characteristics in the X and Y directions and the zero stiffness characteristics in the Z direction can be achieved, which is not available in the existing patents. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] Figure 2 It 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 It 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 It is a structural schematic diagram of the static platform and the spring group of the present invention.

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

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

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

[0030] The present invention will be further described below in conjunction with 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 groups of branches, wherein the branches include 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 through a first adjustment mechanism; the upper end of the vertical spring is fixed under the dynamic platform; the lower end of the L-shaped support frame is fixed to the static platform, and the horizontal spring is installed on the upper part of the L-shaped support frame through a spring seat, one end of the lower connecting rod is hinged to the spring seat to form a first rotating pair, the other end of the lower connecting rod is hinged to one end of the upper connecting rod to form a second rotating pair, and the other end of the upper connecting rod is hinged to the dynamic platform through a rotating shaft mounting seat to form a third rotating pair; the central axes of the first rotating pair, the second rotating pair and the third rotating pair are parallel to each other; a second adjustment mechanism is provided on the L-shaped support frame, and this second adjustment mechanism is connected to the spring seat.

[0032] Specifically, there are 4 branches in this embodiment, wherein the static platform and the dynamic platform are both made of square plates, the two are arranged in parallel, and the dynamic platform is located directly above the static platform. The 4 branches are evenly distributed around the central axis of the static platform, that is, the 4 branches are cross-symmetrically distributed with respect to the central axis of the static platform. In this way, the static platform, the dynamic platform and the 4 branches constitute a 4-PRRR parallel mechanism. The first adjustment mechanism and the second adjustment mechanism are respectively used to adjust the preload of the vertical spring and the horizontal spring, that is, to adjust the initial compression of the vertical spring and the horizontal spring to ensure the restoring force of the vertical spring and the horizontal spring. The vertical spring and the horizontal spring in this embodiment are perpendicular to each other, and the vertical spring, the horizontal spring, the first rotation pair, the second rotation pair and the third rotation pair constitute a quasi-zero stiffness structure. That is, the spring seat moves on the guide rail to form a moving pair; one end of the lower connecting rod is hinged to the spring seat to form a first rotation pair, the other end of the lower connecting rod is hinged to one end of the upper connecting rod to form a second rotation pair, and the other end of the upper connecting rod is hinged to the dynamic platform through the rotating shaft mounting seat to form a third rotation pair. The first rotating pair, the second rotating pair and the third rotating pair of the moving pair form a branch chain with one degree of freedom, and the 4-PRRR parallel mechanism composed of four branches has three-dimensional translational freedom.

[0033] During operation, when a three-dimensional vibration signal is applied to the moving platform, it is transmitted to the springs at the driving pair (i.e., the vertical spring and the horizontal spring) by each branch in the parallel mechanism. The Jacobian matrix of the parallel mechanism remains constant due to the composition and arrangement of the kinematic pairs of each branch. Therefore, during the operation of the vibration isolation platform of the present invention, its stiffness matrix and natural frequency will not change with the position of the moving platform, and the instantaneous natural frequency of the system at any position of the vibration isolation platform will not change. A pre-compression adjustment knob is designed at one end of the spring to achieve adjustable spring stiffness without disassembly. Therefore, the Z direction has a zero stiffness characteristic. Since the vibration isolation platform is affected by the vertical spring during movement in the X and Y directions, approximate zero stiffness characteristics can be achieved in the X and Y directions.

[0034] That is, in the initial state, the moving platform is in a certain horizontal position and forms a certain angle with the lower connecting rod and the upper connecting rod; under the action of external disturbance, the moving platform leaves the equilibrium position, and due to the limitation of the branch chain, the moving platform has only three translational degrees of freedom; by selecting appropriate stiffness values ​​of the horizontal spring and the vertical spring, the moving platform can move within a certain set stiffness range, and 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 screw rod, the lower end of the vertical screw rod and the upper end of the support column are connected by threads, and the upper end of the vertical screw rod is connected to the lower end of the vertical spring through the vertical knob. Specifically, the upper end of the support column is provided with a threaded hole for adjustment, and the vertical screw rod has an external thread matching the threaded hole. When the knob is rotated, the vertical screw rod is inserted into the threaded hole to adjust the compression amount of the vertical spring, so as to ensure that the four vertical springs achieve zero stiffness characteristics in the Z direction.

[0036] The second adjustment mechanism includes a bearing seat, a horizontal screw and a horizontal knob. The spring seat includes a spring support, a sliding platform and a pair of sliders. The slider is installed on the upper end of the L-shaped support frame through a guide rail. The spring support and the sliding platform are respectively fixed to two sliders. The two 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 screw is installed on the bearing seat, and the other end is connected to the spring support. The horizontal knob is installed on one end of the adjustment screw. The two ends of the horizontal spring are respectively fixed to the spring support and the sliding platform. When the horizontal knob is rotated, the distance between the two sliders is adjusted to achieve the initial compression adjustment of the horizontal spring, ensuring the reliability of the quasi-zero stiffness characteristic of the horizontal spring.

[0037] like Figure 6 As shown, the upper end of the sliding platform is provided with a boss slope, and the boss slope is provided with a hinge hole hinged with the lower connecting rod. The boss slope is arranged 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 revolute pair.

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

[0039] The rotating shaft mounting seat is provided with a U-shaped groove into which the upper connecting rod is embedded. The U-shaped groove ensures the stability of the connection between the upper connecting rod and the rotating shaft mounting seat, so as to ensure the working performance of the third rotating pair.

[0040] In each set of branch chains, the number of horizontal springs is 2. The number of horizontal springs is not limited to 2, and an appropriate number of horizontal springs is used to ensure horizontal stiffness.

[0041] The support frame is provided with support ribs. Specifically, the support ribs are fixed to the side of the vertical part of the support frame, and the support ribs ensure the strength of the support frame to ensure the stability of the support frame when supporting.

[0042] The above specific implementation modes are preferred embodiments of the present invention and cannot be used to limit the present invention. Any other changes or other equivalent replacement methods that do not deviate from the technical solution of the present invention are included in 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: It includes a static platform, a dynamic platform and multiple groups of branch chains, wherein the branch chains include 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 through a first adjusting mechanism; the upper end of the vertical spring is fixed under the dynamic platform; the lower end of the L-shaped support frame is fixed to the static platform, and the horizontal spring is installed on the upper part of the L-shaped support frame through a spring seat, one end of the lower connecting rod is hinged to the spring seat to form a first rotating pair, the other end of the lower connecting rod is hinged to one end of the upper connecting rod to form a second rotating pair, and the other end of the upper connecting rod is hinged to the dynamic platform through a rotating shaft mounting seat to form a third rotating pair; the central axes of the first rotating pair, the second rotating pair and the third rotating pair are parallel to each other; the L-shaped support frame is provided with a second adjusting mechanism, and this second adjusting mechanism is connected to the spring seat.

2. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 1, characterized in that: The first adjustment mechanism includes a vertical knob and a vertical screw rod. The lower end of the vertical screw rod and the upper end of the support column are connected by threads, and the upper end of the vertical screw rod is connected to the lower end of the vertical spring through the vertical knob.

3. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 1, characterized in that: The second adjustment mechanism includes a bearing seat, a horizontal screw rod and a horizontal knob, the spring seat includes a spring support, a sliding platform and a pair of sliders, the sliders are installed on the upper end of the L-shaped support frame through guide rails, the spring support and the sliding platform are respectively fixed to the two sliders, the two ends of the horizontal spring are respectively fixed to the spring support and the sliding platform, and 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 screw rod is installed on the bearing seat, and the other end is connected to the spring support, and the horizontal knob is installed on one end of the adjusting screw rod.

4. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 3, characterized in that: The upper end of the sliding platform is provided with a boss inclined surface, and the boss inclined surface is provided with a hinge hole hinged with the lower connecting rod.

5. 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 matching the vertical spring, and the upper end of the vertical spring is fixed in the mounting hole.

6. 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 seat is provided with a U-shaped groove into which the upper connecting rod is embedded.

7. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 1, characterized in that: The number of the branch chains is 4, and the 4 branch chains are evenly distributed relative to the central axis of the static platform.

8. The three-degree-of-freedom parallel vibration isolation platform with quasi-zero stiffness characteristics according to claim 1, characterized in that: In each set of branch chains, the number of horizontal springs is 2.

9. 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 provided with supporting ribs.

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