A two-dimensional quasi-zero stiffness swing mechanism

Abstract

This invention discloses a two-dimensional quasi-zero stiffness swing mechanism, belonging to the field of optical-mechanical structure design. It includes a base, an upper plate, a reflector, a flexible hinge, a magnetic negative stiffness mechanism, a linear motor, and a displacement sensor. The lower end of the flexible hinge is fixed to the base, and its upper end is fixed to the upper plate. A reflector is fixed to the upper end of the upper plate, and the reflector's rotation angle can be changed by rotating the flexible hinge. The magnetic negative stiffness mechanism includes an upper permanent magnet holder, a permanent magnet sleeve, a permanent magnet, a screw, and a lower permanent magnet holder; the two permanent magnets have the same magnetic poles on their opposing surfaces. The linear motor includes a stator and a mover; the stator is fixed to the base, and the mover is fixed to the upper plate. The displacement sensor includes a displacement sensor probe and a sensor holder, both of which are fixed to the upper plate. The magnetic negative stiffness mechanism and the positive stiffness flexible hinge are connected in parallel to form a quasi-zero stiffness system, reducing the minimum vibration isolation frequency and improving the system's low-frequency vibration isolation capability.

Description

Technical Field

[0001] This invention relates to the field of optical mechanical structure design technology, specifically to a two-dimensional quasi-zero stiffness oscillating mechanism. Background Technology

[0002] In composite-axis photoelectric tracking systems within the field of precision optics, the oscillating mechanism is a crucial component. It precisely controls the direction of the probe beam by altering the rotation angle of the reflecting mirror. If the oscillating mechanism is installed on an airborne motion platform, the vibration of the base inevitably affects the mirror's control accuracy through the flexible hinge support structure. Therefore, designing the support structure of the oscillating mechanism as a near-zero stiffness mechanism improves its vibration isolation capability, particularly its ability to isolate low-frequency vibrations.

[0003] Quasi-zero stiffness systems possess the characteristics of high static stiffness and low dynamic stiffness, enabling them to bear significant weight while maintaining very low dynamic stiffness near the equilibrium position. Based on vibration isolation principles, the minimum isolation frequency of the vibration isolation system is... The quasi-zero stiffness system, composed of parallel positive and negative stiffness mechanisms, achieves near-zero dynamic stiffness and a near-zero natural frequency, thus reducing the system's minimum effective vibration isolation frequency and improving its low-frequency vibration isolation capability. In the invention application (application number 202211530955.9) entitled "A Quasi-Zero Stiffness Fast Reflector," the spring-type negative stiffness mechanism achieves negative stiffness through the elastic force generated by a pre-compressed spring element. Traditional swing mechanism mirror support structures are flexible hinge structures. To ensure the load-bearing capacity of the flexible hinge for the upper platform of the swing mechanism, the stiffness of the flexible hinge cannot be too low. Existing flexible hinge materials cannot simultaneously guarantee load-bearing capacity and achieve low torsional stiffness. Therefore, traditional flexible hinge support structures cannot effectively isolate low-frequency vibrations. Summary of the Invention

[0004] To address the technical problems existing in the prior art, the present invention provides a two-dimensional quasi-zero stiffness swing mechanism. While ensuring sufficient load-bearing capacity, the swing mechanism can achieve ultra-low torsional stiffness through the setting of a magnetic negative stiffness mechanism, thereby improving the vibration isolation capability for low-frequency vibrations and reducing the impact of vibrations on the mirror surface of the swing mechanism.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a two-dimensional quasi-zero stiffness swing mechanism, comprising a base, an upper plate, a reflector, a flexible hinge, a magnetic negative stiffness mechanism, a linear motor, and a displacement sensor; wherein,

[0006] The lower end of the flexible hinge is fixed to the base, and the upper end of the flexible hinge is fixed to the upper plate. A reflector is fixed to the upper end of the upper plate. The magnetic negative stiffness mechanism includes a first screw, an upper permanent magnet fixing frame, a second screw, a first permanent magnet sleeve, a first permanent magnet, a second permanent magnet sleeve, a third screw, a lower permanent magnet fixing frame, a fourth screw, and a second permanent magnet. The four magnetic negative stiffness mechanisms are placed equidistantly on all four sides with the flexible hinge as the center of symmetry. The linear motor includes a linear motor stator and a linear motor mover. The linear motor stator is fixed to the base, and the linear motor mover is fixed to the upper plate through a fifth screw. One linear motor is placed equidistantly on all four sides with the flexible hinge as the center of symmetry. The displacement sensor includes a displacement sensor probe and a sensor fixing frame. Both the displacement sensor probe and the sensor fixing frame are fixed to the base. There is a certain gap between the displacement sensor probe and the upper plate. Four displacement sensors are set equidistantly at 45° angles to the magnetic negative stiffness mechanism with the flexible hinge as the center of symmetry.

[0007] Compared with existing technologies, the present invention has the following advantages:

[0008] 1. The two-dimensional quasi-zero stiffness swing mechanism of the present invention has high static and low dynamic torsional stiffness. While ensuring that the flexible hinge has sufficient load-bearing capacity for the upper platform, it achieves low-frequency vibration isolation, solves the problem that the flexible hinge of the traditional swing mechanism is difficult to isolate low-frequency vibration, reduces the disturbance of the base vibration to the reflective mirror, and improves the control accuracy of the swing mechanism on the mirror.

[0009] 2. The magnetic negative stiffness mechanism of the two-dimensional quasi-zero stiffness swing mechanism of the present invention is a mechanism in which the initial torque and negative stiffness are adjustable. The positions of the first permanent magnet and the second permanent magnet can be adjusted to change their relative positions with the flexible hinge and the magnitude of the magnetic force between the two permanent magnets, thereby changing the initial torque to adapt to installation at different tilt angles, and adjusting the magnitude of the negative stiffness to cooperate with the positive stiffness flexible hinge to form a quasi-zero stiffness system. The adjustable negative stiffness structure can also eliminate the influence caused by the processing error of the flexible hinge after design and the magnetic error of the permanent magnet.

[0010] 3. The present invention provides a magnetic negative stiffness mechanism for a two-dimensional quasi-zero stiffness swing mechanism. Its negative stiffness is achieved through the mutual repulsion of the magnetic forces of two permanent magnets. It has the characteristics of no friction and no excessive mechanical deformation, and is suitable for achieving negative stiffness in precision machinery with small displacement. Compared with the prior art, it has one more degree of freedom of rotation axis. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a two-dimensional quasi-zero stiffness swing mechanism according to the present invention.

[0012] Figure 2 This is a schematic diagram of the flexible hinge of a two-dimensional quasi-zero stiffness swing mechanism according to the present invention.

[0013] Figure 3 This is a schematic diagram of a two-dimensional quasi-zero stiffness swing mechanism of the present invention, excluding the portion above the flexible hinge.

[0014] Figure 4 This is a comparison chart of the stiffness calculated by Matlab theory and the stiffness simulation results of Adams after the positive and negative stiffnesses of the swing mechanism are connected in parallel.

[0015] Figure 5 Bode plots of vibration transmission characteristics of the swing mechanism platform under the same damping but different stiffness.

[0016] Figure 6 Bode plots of vibration transmission characteristics for quasi-zero stiffness and non-quasi-zero stiffness swing mechanism platforms.

[0017] In the diagram: 1 is the base, 2 is the flexible hinge, 3 is the linear motor stator, 4 is the linear motor mover, 5 is the sensor mounting bracket, 6 is the displacement sensor probe, 7 is the upper plate, 8 is the third screw, 9 is the lower permanent magnet mounting bracket, 10 is the fourth screw, 11 is the second permanent magnet sleeve, 12 is the second permanent magnet, 13 is the first permanent magnet sleeve, 14 is the fifth screw, 15 is the first screw, 16 is the reflector, 17 is the upper permanent magnet mounting bracket, 18 is the first permanent magnet, and 19 is the second screw. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples.

[0019] Reference Figure 1 The present invention discloses a two-dimensional quasi-zero stiffness swing mechanism, comprising a base 1, an upper plate 7, a reflector 16, a flexible hinge 2, a magnetic negative stiffness mechanism, a linear motor, and a displacement sensor. The lower end of the flexible hinge 2 is fixedly connected to the base 1, and the upper end of the flexible hinge 2 is fixedly connected to the upper plate 7. The upper end of the upper plate 7 is fixedly connected to the reflector 16. The magnetic negative stiffness mechanism includes a first screw 15, an upper permanent magnet fixing frame 17, a second screw 19, a first permanent magnet sleeve 13, a first permanent magnet 18, a second permanent magnet sleeve 11, a third screw 8, a lower permanent magnet fixing frame 9, a fourth screw 10, and a second permanent magnet... Magnet 12, four magnetic negative stiffness mechanisms are placed equidistantly on all four sides with flexible hinge 2 as the center of symmetry. The linear motor includes linear motor stator 3 and linear motor mover 4. The linear motor stator 3 is fixed to the base 1. The linear motor mover 4 is fixed to the upper plate 7 by the fifth screw 14. One linear motor is placed equidistantly on all four sides with flexible hinge 2 as the center of symmetry. Displacement sensor probe 6 and sensor mounting bracket 5 are both fixed to the base 1. There is a gap between displacement sensor probe 6 and upper plate 7. Four displacement sensors are set equidistantly at 45° with flexible hinge 2 as the center of symmetry and with respect to the magnetic negative stiffness mechanism.

[0020] Reference Figure 1 The linear motor serves as the driving element for the rotation of the mirror. The central axes of the linear motor stator 3 and the linear motor mover 4 are located on the same axis. The linear motor mover 4 can move axially relative to the linear motor stator 3. During operation, two opposing linear motors, with the flexible hinge 2 as the center of symmetry, drive their respective movers to produce two small displacements in opposite directions. This causes a small rotational deformation of the flexible hinge 2 at its thinnest point, thereby changing the rotation angle of the reflector 16 on one axis of the flexible hinge 2. The other two opposing linear motors drive the reflector 16 on the other axis of the flexible hinge 2 using the same principle. Four displacement sensors, with the flexible hinge 2 as the center of symmetry, can detect the distance between the displacement sensor probe 6 and the upper plate 7, and thus calculate the rotation angle of the reflector 16 on the two axes of the flexible hinge 2.

[0021] Reference Figure 1 The upper permanent magnet fixing bracket 17 is fixed to the upper plate 7 by the first screw 15, and the lower permanent magnet fixing bracket 9 is fixed to the base 1 by the third screw 8. The upper permanent magnet fixing bracket 17 is threaded to the second screw 19, and the other end of the second screw 19 is threaded to the first permanent magnet sleeve 13. The first permanent magnet 18 is fixed inside the first permanent magnet sleeve 13. The lower permanent magnet fixing bracket 9 is threaded to the fourth screw 10, and the other end of the fourth screw 10 is threaded to the second permanent magnet sleeve 11. A second permanent magnet 12 is internally fixed. The two opposing magnetic poles of the first permanent magnet 18 and the second permanent magnet 12 are identical. The central axes of the second screw 19, the first permanent magnet sleeve 13, the first permanent magnet 18, the second permanent magnet 12, the second permanent magnet sleeve 11, and the fourth screw 10 are located on the same axis. Tightening the second screw 19 can change the position of the first permanent magnet 18, and tightening the fourth screw 10 can change the position of the second permanent magnet 12. The first permanent magnet 18 and the second permanent magnet 12 repel each other under the action of magnetic force. The two rotation axes of the flexible hinge 2 are perpendicular to each other and horizontal, and the two rotation axis directions are parallel to the directions of the two opposing displacement sensors.

[0022] Reference Figure 1The positions of the first permanent magnet 18 and the second permanent magnet 12 relative to the flexible hinge 2 can be changed by tightening the second screw 19 and the fourth screw 10. Tightening the second screw 19 and the fourth screw 10 can also change the distance between the first permanent magnet 18 and the second permanent magnet 12, thus changing the magnitude of the magnetic force. This allows adjustment of the initial torque and negative stiffness generated by the magnetic negative stiffness mechanism. The initial torque generated by the magnetic negative stiffness mechanism is used to counteract the initial torque generated by the gravity of the upper part of the flexible hinge when the swing mechanism is not placed horizontally, keeping the upper plate of the swing mechanism in a balanced position parallel to the base. The magnetic negative stiffness mechanism, in conjunction with the flexible hinge 2 which has positive stiffness characteristics, achieves near-zero torsional stiffness of the mirror surface 16 within a certain angle range at the balanced position, thus improving the low-frequency vibration isolation capability of the swing mechanism.

[0023] like Figure 2 As shown, the flexible hinge 2 is an arc-shaped flexible hinge. Two arc-shaped holes on the same side are symmetrical and the same size. The center of rotation is located at the midpoint of the thinnest part of the two arc-shaped holes. The front and back surfaces of the flexible hinge 2 have the same shape, and the left and right surfaces have the same shape. The front and back surfaces, along with the left and right surfaces, each form a mutually perpendicular intersecting axis of rotation. The flexible hinge 2 is made of spring steel and is a single-piece frame structure. When machining the four axes of the flexible hinge 2, the machining tool should be perpendicular to the machining surface. The machined arc surface should be perpendicular to the surface, and the machined surface should be flat and free of scratches or damage.

[0024] Reference Figure 3 This is a schematic diagram of the present invention with the above part of the flexible hinge removed, which more intuitively and clearly shows the positional relationship of the flexible hinge 2 and other components. The flexible hinge 2 is located at the center of the base 1, and the centers of symmetry of all symmetrically arranged components coincide at this center position.

[0025] Reference Figure 4 A comparison of the stiffness results from Matlab theoretical calculations and Adams simulations of a swing mechanism with parallel positive and negative stiffnesses is presented. Matlab was used to perform theoretical calculations on the structure with parallel positive and negative stiffnesses, plotting the relationship between torque and deformation angle. Adams, a classic dynamic analysis software, was then used to perform dynamic analysis on the structural model with parallel positive and negative stiffnesses, simulating the relationship between torque and deformation angle. The graph shows that the slope of the curve represents the torsional stiffness of the structure, and within a certain range from the equilibrium position of 0°, the slope approaches zero, achieving quasi-zero stiffness of the system. The high degree of consistency between the Matlab theoretical analysis results and the Adams analysis results demonstrates that a two-dimensional quasi-zero stiffness swing mechanism structure can achieve quasi-zero stiffness within a certain angle range.

[0026] Reference Figure 5Bode plots of vibration transmission characteristics of a swing mechanism platform under the same damping but different stiffnesses show that, in structures with the same damping but different stiffnesses, the smaller the stiffness, the smaller the resonance peak of the vibration transmission. When the stiffness is small enough, the resonance peak disappears. From... Figure 5 It can also be seen that the smaller the stiffness, the more obvious the effect of suppressing low-frequency vibration of the structure. Therefore, the quasi-zero stiffness structure can effectively suppress the vibration of the swing mechanism base from being transmitted to the mirror surface.

[0027] Reference Figure 6 Bode plots of vibration transmission characteristics of quasi-zero stiffness and non-quasi-zero stiffness swing mechanism platforms. Traditional swing mechanisms do not have the characteristic of quasi-zero stiffness, so they are difficult to suppress low-frequency vibration of the base and also difficult to suppress the influence of resonance on the mirror. Quasi-zero stiffness swing mechanisms are significantly effective in suppressing low-frequency vibration and resonance.

[0028] In this invention, when the upper plate 7 and the reflector 16 of the swing mechanism undergo a positive angular displacement with the thinnest part of the flexible hinge 2 as the axis of rotation, a reverse restoring torque is generated due to the bending deformation of the flexible hinge 2. Therefore, the flexible hinge 2 serves as a positive stiffness element in the quasi-zero stiffness system. Since there are magnetic negative stiffness mechanisms positioned opposite each other on the flexible hinge, the magnetic repulsion between the permanent magnets causes the flexible hinge 2 to bend and deviate from its equilibrium position. The torque generated by the magnetic force further increases the deformation of the flexible hinge 2. Therefore, the magnetic negative stiffness mechanism exhibits negative stiffness characteristics. By adjusting the positions of the first permanent magnet 18 and the second permanent magnet 12, when the generated negative stiffness is approximately equal to the positive torsional stiffness of the flexible hinge, it constitutes a quasi-zero stiffness system. The swing mechanism is driven by four linear motors to rotate the two shafts of the flexible hinge 2, which in turn drives the reflector 16 to deflect. Two displacement sensors detect the deflection angle of the reflector 16 and provide feedback on the deflection angle of the reflector 16.

Claims

1. A two-dimensional quasi-zero stiffness oscillating mechanism, characterized by: The application relates to a novel type of parallel kinematics mechanism, which comprises a base (1), an upper plate (7), a reflecting mirror (16), a flexible hinge (2), a magnetic negative stiffness mechanism, a linear motor and a displacement sensor. The lower end of the flexible hinge (2) is fixedly connected with the base (1), the upper end of the flexible hinge (2) is fixedly connected with the upper plate (7), the upper end of the upper plate (7) is fixedly connected with the reflecting mirror (16), the magnetic negative stiffness mechanism comprises a first screw (15), an upper permanent magnet fixing frame (17), a second screw (19), a first permanent magnet sleeve (13), a first permanent magnet (18), a second permanent magnet sleeve (11), a third screw (8), a lower permanent magnet fixing frame (9), a fourth screw (10) and a second permanent magnet (12), four magnetic negative stiffness mechanisms are symmetrically arranged at equal intervals on four sides of the flexible hinge (2), the linear motor comprises a linear motor stator (3) and a linear motor mover (4), the linear motor stator (3) is fixedly connected with the base (1), the linear motor mover (4) is fixedly connected with the upper plate (7) through a fifth screw (14), one linear motor is arranged at equal intervals on each of the four sides of the flexible hinge (2) as the center of symmetry, the displacement sensor comprises a displacement sensor probe (6) and a sensor fixing frame (5), the displacement sensor probe (6) and the sensor fixing frame (5) are both fixedly connected with the base (1), the displacement sensor probe (6) has a certain gap with the upper plate (7), four displacement sensors are arranged at equal intervals and at an angle of 45 degrees with the magnetic negative stiffness mechanism as the center of symmetry of the flexible hinge (2). The upper permanent magnet fixing frame (17) is fixedly connected with the upper plate (7) through the first screw (15), the lower permanent magnet fixing frame (9) is fixedly connected with the base (1) through the third screw (8), the upper permanent magnet fixing frame (17) is threadedly connected with the second screw (19), the other end of the second screw (19) is threadedly connected with the first permanent magnet sleeve (13), the first permanent magnet sleeve (13) is fixedly connected with the first permanent magnet (18) in the first permanent magnet sleeve (13), the lower permanent magnet fixing frame (9) is threadedly connected with the fourth screw (10), the other end of the fourth screw (10) is threadedly connected with the second permanent magnet sleeve (11), the second permanent magnet sleeve (11) is fixedly connected with the second permanent magnet (12) in the second permanent magnet sleeve (11), the opposite two faces of the first permanent magnet (18) and the second permanent magnet (12) have the same magnetic pole, the central axes of the second screw (19), the first permanent magnet sleeve (13), the first permanent magnet (18), the second permanent magnet (12), the second permanent magnet sleeve (11) and the fourth screw (10) are located on the same axis, the position of the first permanent magnet (18) is changed by screwing the second screw (19), the position of the second permanent magnet (12) is changed by screwing the fourth screw (10), the first permanent magnet (18) and the second permanent magnet (12) repel each other under the action of magnetic force, the two rotation shaft directions of the flexible hinge (2) are perpendicular to each other, intersect horizontally and are parallel to the directions of the opposite two displacement sensors.

2. A two-dimensional quasi-zero stiffness oscillating mechanism according to claim 1, characterized in that: The position of the first permanent magnet (18) and the second permanent magnet (12) relative to the flexible hinge (2) is changed by screwing the second screw (19) and the fourth screw (10), and the size of the magnetic force is changed by screwing the second screw (19) and the fourth screw (10) to change the distance between the first permanent magnet (18) and the second permanent magnet (12).

3. A two-dimensional quasi-zero stiffness oscillating mechanism according to claim 1, characterized in that: When the upper plate (7) and the mirror (16) produce a positive angular displacement with the thinnest part of the flexible hinge (2) as the rotation axis, a reverse restoring torque is generated due to the bending deformation of the flexible hinge (2), so the flexible hinge (2) acts as a positive stiffness element in the quasi-zero stiffness system, and the opposite sides of the flexible hinge (2) are provided with a magnetic force type negative stiffness mechanism, the magnetic force type negative stiffness mechanism is under the action of the repulsive magnetic force between the permanent magnets, when the flexible hinge (2) produces bending deformation and deviates from the equilibrium position of the flexible hinge (2), the torque generated by the magnetic force makes the deformation of the flexible hinge (2) further increase, so the magnetic force type negative stiffness mechanism has negative stiffness characteristics, the position of the first permanent magnet (18) and the second permanent magnet (12) is adjusted, when the generated negative stiffness is approximately equal to the positive torsional stiffness of the flexible hinge (2), it is a quasi-zero stiffness system, the swing mechanism drives the two rotation axes of the flexible hinge (2) to rotate by four linear motors, drives the mirror (16) to deflect, and the deflection angle of the mirror (16) is detected by two displacement sensors, thereby feeding back the deflection angle of the mirror (16).

4. A two-dimensional quasi-zero stiffness oscillating mechanism according to claim 1, characterized in that: The flexible hinge (2) is a circular arc flexible hinge, the two circular arc holes on the same side are left-right symmetrical and the same size, the rotation center point is located at the middle position of the thinnest part of the two circular arc holes, the front and back surfaces of the flexible hinge (2) are the same shape, the left and right surfaces are the same shape, and the front and back surfaces and the left and right surfaces each form a rotation axis perpendicular to each other.

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