A quasi-zero stiffness fast steering mirror

Abstract

The application discloses a kind of quasi-zero stiffness fast mirrors, including pedestal, upper plate, mirror, flexible hinge, negative stiffness mechanism, voice coil motor and eddy current sensor.The lower end of the flexible hinge is fixedly connected with the pedestal, and the upper end is fixedly connected with the upper plate, and the upper end of the upper plate is fixedly connected with the mirror, and the mirror can change the corner of rotation by the rotation of flexible hinge.The negative stiffness mechanism includes upper spring block, knurled nut, spring, screw, lower spring block, and the spring is in pre-compressed state.The voice coil motor includes voice coil motor stator and mover, and the voice coil motor stator is fixedly connected with the pedestal, and the mover is fixedly connected with the upper plate.The eddy current sensor includes eddy current sensor probe and sensor patch, and the eddy current sensor probe is fixedly connected with the pedestal, and the sensor patch is fixedly connected with the upper plate.Because negative stiffness mechanism and positive stiffness flexible hinge are connected in parallel to form quasi-zero stiffness system, the initial vibration isolation frequency of the system is reduced, and the vibration isolation capacity for low-frequency vibration can be improved.

Description

Technical Field

[0001] This invention relates to the field of optical-mechanical structure design technology, and specifically to a quasi-zero stiffness fast reflector. Background Technology

[0002] In composite-axis photoelectric tracking systems within the field of precision optics, fast reflectors are a crucial component. By altering the rotation angle of the reflector surface, the direction of the probe beam can be precisely controlled. If the fast reflector is mounted on an airborne platform, the vibration of the base inevitably affects the control accuracy of the reflector through the support structure. Designing the support structure of the fast reflector as a near-zero stiffness mechanism improves its vibration isolation capability for low-frequency vibrations and increases the system's vibration isolation bandwidth.

[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. According to vibration isolation principles, the minimum isolation frequency of a vibration isolation system is twice the system's natural frequency. Quasi-zero stiffness systems are composed of parallel positive and negative stiffness mechanisms, resulting in near-zero dynamic stiffness and near-zero natural frequency. This reduces the minimum effective isolation frequency, thereby improving the system's low-frequency vibration isolation capability.

[0004] Traditional fast reflector mirror support structures are flexible hinge structures. In order to ensure the load-bearing capacity of the flexible hinge for the upper platform of the fast reflector, the stiffness of the flexible hinge cannot be too low. Existing flexible hinge materials cannot achieve both load-bearing capacity and low torsional stiffness. Therefore, the flexible hinge support structure cannot effectively isolate low-frequency vibrations. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, the present invention aims to provide a quasi-zero stiffness fast reflector that, while ensuring sufficient load-bearing capacity, achieves ultra-low torsional stiffness, thereby improving the vibration isolation capability against low-frequency vibrations and reducing the impact of vibrations on the mirror surface of the fast reflector.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a quasi-zero stiffness fast reflector, comprising a base 2, an upper plate 1, a reflector 4, a flexible hinge 3, a negative stiffness mechanism, a voice coil motor, and an eddy current sensor. The lower end of the flexible hinge 3 is fixedly connected to the base 2, and the upper end of the flexible hinge 3 is fixedly connected to the upper plate 1. The upper end of the upper plate 1 is fixedly connected to the reflector 4. The negative stiffness mechanism includes a first screw 5, an upper spring stop 6, a second screw 7, a knurled nut 1 8, a spring 9, a knurled nut 2 10, a third screw 11, a lower spring stop 12, and a fourth screw 13. The four negative stiffness mechanisms are arranged with two screws on each side of the flexible hinge 3 as the center of symmetry. Each voice coil motor includes a voice coil motor stator 16 and a voice coil motor mover 15. The voice coil motor stator 16 is fixedly connected to the base 2, and the voice coil motor mover 15 is fixedly connected to the upper plate 1 by a fifth screw 14. One voice coil motor is arranged on each side with the flexible hinge 3 as the center of symmetry. The eddy current sensor includes an eddy current sensor probe 17 and a sensor patch 18. The eddy current sensor probe 17 is fixedly connected to the base 2, and the sensor patch 18 is fixedly connected to the upper plate 1. The sensor patch 18 is located directly above the eddy current sensor probe 17 and has a gap with the eddy current sensor probe 17. One eddy current sensor is arranged on each side with the flexible hinge 3 as the center of symmetry.

[0007] Furthermore, the upper spring stop 6 is fixed to the upper plate 1 by the first screw 5, and the lower spring stop 12 is fixed to the base 2 by the third screw 11. The upper spring stop 6 is connected to the second screw 7 by a thread, and the other end of the second screw 7 is connected to a knurled nut 8 by a thread. The lower spring stop 12 is connected to the fourth screw 13 by a thread, and the other end of the fourth screw 13 is connected to a knurled nut 10 by a thread. The two ends of the spring 9 are fixed to the knurled nut 8 and the knurled nut 10 respectively. The central axes of the second screw 7, the knurled nut 8, the spring 9, the knurled nut 10 and the fourth screw 13 are located on the same axis. By turning the knurled nut 8, its relative position with the upper spring stop 6 can be changed. By turning the knurled nut 10, its relative position with the lower spring stop 12 can be changed. By turning the knurled nut 8 and the knurled nut 10, the compression length of the spring 9 can be changed.

[0008] The principle of this invention lies in a quasi-zero stiffness fast reflector, comprising a base, an upper plate, a reflector, a flexible hinge, a negative stiffness mechanism, a voice coil motor, and an eddy current sensor. The lower end of the flexible hinge is fixed to the base, and its upper end is fixed to the upper plate. The upper end of the upper plate is fixed to the reflector. The negative stiffness mechanism includes an upper spring stop, a screw, a knurled nut, a spring, and a lower spring stop. Four negative stiffness mechanisms are arranged with two on each side, symmetrically positioned around the flexible hinge. The voice coil motor includes a stator and a mover. The stator is fixed to the base, and the mover is fixed to the upper plate via screws. One voice coil motor is arranged with one on each side, symmetrically positioned around the flexible hinge. The eddy current sensor includes an eddy current sensor probe and a sensor patch. The eddy current sensor probe is fixed to the base, and the sensor patch is fixed to the upper plate. The sensor patch is located directly above the eddy current sensor probe and has a gap with the eddy current sensor probe. An eddy current sensor is set on each side with the flexible hinge as the center of symmetry.

[0009] Furthermore, the upper spring stop of the negative stiffness mechanism is fixed to the upper plate by a first screw, and the lower spring stop is fixed to the base by a third screw. The upper spring stop is threaded to the second screw, and the other end of the second screw is threaded to a knurled nut. The lower spring stop is threaded to the fourth screw, and the other end of the fourth screw is threaded to a knurled nut. A knurled nut is fixed to each end of the spring, and the central axes of the knurled nuts, the spring, and the screws are located on the same axis. The compression length of the spring can be changed by tightening the two knurled nuts at both ends of the spring, and the spring is always in a pre-compressed state.

[0010] Furthermore, the pre-compression of the spring and its position relative to the flexible hinge can be changed by tightening the knurled nuts at both ends of the spring, thereby adjusting the initial torque and negative stiffness generated by the negative stiffness mechanism. The initial torque generated by the negative stiffness mechanism is used to counteract the initial torque generated by the gravity of the upper part of the flexible hinge when the fast reflector is not placed horizontally, keeping the upper plate of the fast reflector in a balanced position parallel to the base. The negative stiffness mechanism, in conjunction with the flexible hinge with positive stiffness characteristics, achieves near-zero torsional stiffness of the reflector surface within a certain angle range at the equilibrium position, realizing quasi-zero stiffness, thereby improving the low-frequency vibration isolation capability of the fast reflector.

[0011] Compared with existing technologies, the present invention has the following advantages:

[0012] 1. A quasi-zero stiffness fast reflector 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 fast reflector is difficult to isolate low-frequency vibration, reduces the disturbance of the base vibration on the reflector surface, and improves the control accuracy of the fast reflector on the mirror surface.

[0013] 2. A negative stiffness mechanism for a quasi-zero stiffness fast reflector is a mechanism in which the initial torque and negative stiffness are adjustable. The knurled nuts at both ends of the adjustable spring can change the position and compression of the spring, thereby changing the initial torque to adapt to installation at different tilt angles, and adjusting 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 and the spring stiffness error after design. Attached Figure Description

[0014] Figure 1 : A schematic diagram of a quasi-zero stiffness fast reflector.

[0015] Figure 2 A front view of a fast-reflecting mirror with quasi-zero stiffness.

[0016] Figure 3 : A schematic diagram of a flexible hinge for a quasi-zero stiffness fast reflector.

[0017] Figure 4 A comparison of the stiffness of a quasi-zero stiffness fast reflector calculated in parallel using Matlab theory and Adams simulation results.

[0018] Figure 5 Bode plot of vibration transmission characteristics of a fast-reflecting mirror platform under the same damping but different stiffness.

[0019] Figure 6 Bode plots of vibration transmission characteristics of fast reflecting mirror platforms with quasi-zero stiffness and non-quasi-zero stiffness.

[0020] In the diagram: 1 is the upper plate, 2 is the base, 3 is the flexible hinge, 4 is the reflector, 5 is the first screw, 6 is the upper spring stop, 7 is the second screw, 8 is the first knurled nut, 9 is the spring, 10 is the second knurled nut, 11 is the third screw, 12 is the lower spring stop, 13 is the fourth screw, 14 is the fifth screw, 15 is the voice coil motor mover, 16 is the voice coil motor stator, 17 is the eddy current sensor probe, and 18 is the sensor patch. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples.

[0022] Reference Figure 1 , Figure 2 and Figure 3A quasi-zero stiffness fast reflector includes a base 2, an upper plate 1, a reflector 4, a flexible hinge 3, a negative stiffness mechanism, a voice coil motor, and an eddy current sensor. The lower end of the flexible hinge 3 is fixed to the base 2, and the upper end of the flexible hinge 3 is fixed to the upper plate 1. The upper end of the upper plate 1 is fixed to the reflector 4. The negative stiffness mechanism includes a first screw 5, an upper spring stop 6, a second screw 7, a knurled nut 1 8, a spring 9, a second knurled nut 10, a third screw 11, a lower spring stop 12, and a fourth screw 13. Two negative stiffness mechanisms are arranged on each side of the flexible hinge 3 as a center of symmetry. The voice coil motor includes a voice coil motor stator 16 and a voice coil motor mover 15. The voice coil motor stator 16 is fixed to the base 2, and the voice coil motor mover 15 is fixed to the upper plate 1 via a fifth screw 14. One voice coil motor is arranged on each side of the flexible hinge 3 as a center of symmetry. The eddy current sensor includes an eddy current sensor probe 17 and a sensor patch 18. The eddy current sensor probe 17 is fixedly connected to the base 2, and the sensor patch 18 is fixedly connected to the upper plate 1. The sensor patch 18 is located directly above the eddy current sensor probe 17 and has a gap with the eddy current sensor probe 17. An eddy current sensor is set on each side with the flexible hinge 3 as the center of symmetry.

[0023] Reference Figure 1 , Figure 2 and Figure 3 The voice coil motor serves as the driving element for the mirror's rotation. The central axes of the voice coil motor stator 16 and the voice coil motor mover 15 are located on the same axis. The mover 15 can move axially relative to the stator 16. During operation, the two voice coil motors at both ends of the flexible hinge 3 drive their respective movers to produce minute displacements in opposite directions, causing a slight deformation at the thinnest point of the flexible hinge 3, thereby changing the rotation angle of the reflector 4. Two eddy current sensors, symmetrically positioned around the flexible hinge, can detect the distance between the eddy current sensor probe 17 and the sensor patch 18.

[0024] Reference Figure 1 and Figure 2 The upper spring stop 6 is fixed to the upper plate 1 by the first screw 5, and the lower spring stop 12 is fixed to the base 2 by the third screw 11. The upper spring stop 6 is connected to the second screw 7 by a thread, and the other end of the second screw 7 is connected to a knurled nut 8 by a thread. The lower spring stop 12 is connected to the fourth screw 13 by a thread, and the other end of the fourth screw 13 is connected to a knurled nut 10 by a thread. The two ends of the spring 9 are fixed to the knurled nut 8 and the knurled nut 10 respectively. The central axes of the second screw 7, the knurled nut 8, the spring 9, the knurled nut 10 and the fourth screw 13 are located on the same axis. By turning the knurled nut 8, its relative position with the upper spring stop 6 can be changed. By turning the knurled nut 10, its relative position with the lower spring stop 12 can be changed. By turning the knurled nuts 8 and 10, the compression length of the spring 9 can be changed.

[0025] Reference Figure 1 , Figure 2 and Figure 3 The pre-compression of spring 9 and its position relative to flexible hinge 3 can be changed by twisting the knurled nuts 8 and 10 at both ends of spring 9. This allows adjustment of the initial torque and negative stiffness generated by the negative stiffness mechanism. The initial torque generated by the negative stiffness mechanism is used to counteract the initial torque generated by the gravity of the upper part of flexible hinge 3 when the fast reflector is installed in a non-horizontal position, keeping the upper plate 1 of the fast reflector in a balanced position parallel to the base 2. The negative stiffness mechanism, in conjunction with the flexible hinge 3 which has positive stiffness characteristics, achieves near-zero torsional stiffness of the reflector 4 within a certain angle range at the balance position, thus achieving quasi-zero stiffness and improving the low-frequency vibration isolation capability of the fast reflector.

[0026] Reference Figure 4 A comparison of the stiffness results from Matlab theoretical calculations and Adams simulations of a quasi-zero stiffness fast reflector with parallel positive and negative stiffness values ​​is presented. Matlab was used to perform theoretical calculations on the structure with parallel positive and negative stiffness values, generating a curve showing 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 stiffness values, simulating the relationship between torque and deformation angle. The curve's slope 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. The high degree of consistency between the Matlab theoretical analysis results and the Adams analysis results demonstrates that a quasi-zero stiffness fast reflector structure can achieve quasi-zero stiffness within a certain angular range.

[0027] Reference Figure 5 The Bode plots of vibration transmission characteristics obtained from simulations of a fast-reflecting mirror platform under the same damping but different stiffnesses show that, for 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 reduced to a certain level, the resonance peak disappears. The plots also show that the smaller the stiffness, the more significant the suppression effect on low-frequency vibrations of the structure. Therefore, a quasi-zero stiffness structure can effectively suppress the vibration transmission of the fast-reflecting mirror base to the mirror surface.

[0028] Reference Figure 6 The vibration transmission characteristics Bode plots obtained from simulations of quasi-zero stiffness and non-quasi-zero stiffness fast reflector platforms show that traditional fast reflectors do not have quasi-zero stiffness characteristics, making it difficult to suppress low-frequency vibrations of the base and the influence of resonance on the mirror surface. The quasi-zero stiffness fast reflector has a significant effect on suppressing low-frequency vibrations and resonances.

[0029] Working principle: When the upper plate 1 and reflector 4 of the fast reflector undergo positive angular displacement about the thinnest part of the flexible hinge 3, a reverse restoring torque is generated due to the bending deformation of the flexible hinge 3. Therefore, the flexible hinge 3 acts as a positive stiffness element in the quasi-zero stiffness system. At this time, the torque generated by the negative stiffness mechanism is exactly opposite. Due to the pre-compression force of the spring 9 in the negative stiffness mechanism, the direction of the pre-compression force of the spring 9 also changes when the upper plate 1 deflects. The pre-compression force of the spring 9 generates a positive torque relative to the rotation center of the upper plate 1. When the reverse restoring torque generated by the flexible hinge 3 is almost equal in magnitude to the positive torque generated by the negative stiffness mechanism, the system composed of the flexible hinge 3 and the negative stiffness mechanism is a quasi-zero stiffness system. The fast reflector is driven by two voice coil motors, which drive the reflector 4 to deflect. The deflection angle of the reflector 4 is detected by two eddy current sensors, thus providing feedback on the deflection angle of the reflector 4.

Claims

1. A quasi-zero stiffness fast-reflecting mirror, characterized in that: The system includes a base (2), an upper plate (1), a reflector (4), a flexible hinge (3), a negative stiffness mechanism, a voice coil motor, and an eddy current sensor. The lower end of the flexible hinge (3) is fixed to the base (2), and the upper end of the flexible hinge (3) is fixed to the upper plate (1). The upper end of the upper plate (1) is fixed to the reflector (4). The negative stiffness mechanism includes a first screw (5), an upper spring stop (6), a second screw (7), a knurled nut one (8), a spring (9), a knurled nut two (10), a third screw (11), a lower spring stop (12), and a fourth screw (13). There are two negative stiffness mechanisms on each side of the flexible hinge (3) as the center of symmetry. The voice coil motor includes a voice coil motor stator. (16) and voice coil motor mover (15), voice coil motor stator (16) is fixedly connected to base (2), voice coil motor mover (15) is fixedly connected to upper plate (1) by fifth screw (14), and a voice coil motor is set on each side with flexible hinge (3) as the center of symmetry. The eddy current sensor includes eddy current sensor probe (17) and sensor patch (18). Eddy current sensor probe (17) is fixedly connected to base (2), and sensor patch (18) is fixedly connected to upper plate (1). The sensor patch (18) is located directly above eddy current sensor probe (17) and has a gap with eddy current sensor probe (17). An eddy current sensor is set on each side with flexible hinge (3) as the center of symmetry. The upper spring stop (6) is fixed to the upper plate (1) by the first screw (5), and the lower spring stop (12) is fixed to the base (2) by the third screw (11). The upper spring stop (6) is connected to the second screw (7) by a thread, and the other end of the second screw (7) is connected to a knurled nut (8) by a thread. The lower spring stop (12) is connected to the fourth screw (13) by a thread, and the other end of the fourth screw (13) is connected to a knurled nut (10) by a thread. The two ends of the spring (9) are respectively connected to the knurled nuts. Knurled nut 1 (8) and knurled nut 2 (10) are fixed together. The central axes of the second screw (7), knurled nut 1 (8), spring (9), knurled nut 2 (10) and fourth screw (13) are located on the same axis. By turning knurled nut 1 (8), its relative position with the upper spring stop (6) can be changed. By turning knurled nut 2 (10), its relative position with the lower spring stop (12) can be changed. By turning knurled nut 1 (8) and knurled nut 2 (10), the compression length of spring (9) can be changed.

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