Ultra-Low Normal Coupling Deflection Mechanism with Redundant Design and Its Control Method

Abstract

The present invention discloses an extremely low normal coupling deflection mechanism with redundant design and its control method. The deflection mechanism includes a mirror flexure adjustment frame, a mirror, a transmission rod, a differential lever, a diamond ring, and a piezoelectric stack. The mirror is arranged inside the mirror flexure adjustment frame. The mirror contacts the front end face of the transmission rod. The side of the transmission rod is fixedly connected to a biaxial decoupling hinge in the middle of the differential lever. Both ends of the differential lever are flexible hinges. Each end face of the two flexible hinges is fixedly connected to the short axis end face of a diamond ring. A piezoelectric stack is embedded in the long axis direction of the diamond ring. The present invention converts the linear drive of the piezoelectric stack into a pure torque drive to control the deflection of the mirror surface. The normal force is reduced through decoupling by multiple flexible hinges, and the normal stiffness is increased and the torsional stiffness is reduced through cross hinges, thereby reducing the normal displacement and realizing extremely low normal coupling of the mirror surface. The redundant piezoelectric drive design using two piezoelectric stacks realizes three piezoelectric drive displacement transmission modes, meets the requirements of various working conditions, and improves the overall output stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical precision pointing mechanisms, and particularly relates to a deflection mechanism with redundant actuation design, capable of realizing pure torque-driven mirror deflection, and having extremely low normal coupling, and a control method therefor. Background Art

[0002] Space gravitational wave detection is of extremely high value for humans to understand and observe the universe. Currently, the mainstream international method for space gravitational wave detection is satellite-based laser interferometric measurement capture. The inter-satellite laser interference mutual alignment accuracy reaches the nanoarcsecond level. An ultra-high-precision beam pointing mechanism has become an important part of gravitational wave detection. Size changes caused by assembly, thermal deformation, mechanical stress, etc. will all affect the path length of the output of the laser interferometer. During the mirror deflection process, mirror normal coupling will inevitably occur, resulting in the translation of the outgoing light path, introducing an additional optical path difference, affecting the pointing accuracy of the mechanism, and causing errors in space laser measurement. Therefore, a beam pointing mechanism with low mirror normal coupling and capable of pure deflection motion is of great significance in gravitational wave scientific detection. Summary of the Invention

[0003] In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide a deflection mechanism with extremely low normal coupling and a control method therefor with redundant design. By decoupling multiple flexible hinges and designing the size and structure of the force transmission mechanism to control the generation of normal forces, pure torque drive is realized. By using a cross hinge to increase the normal stiffness and reduce the torsional stiffness, the normal displacement is further reduced, realizing extremely low normal coupling of the mirror; the redundant piezoelectric drive design using two piezoelectric stacks can achieve outputs under three working conditions, having the advantages of redundancy and meeting the requirements of multiple working conditions, and improving the overall output stability.

[0004] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0005] A very low normal coupling deflection mechanism with redundant design, including a mirror flexure adjustment bracket 1, a mirror 2, a transmission rod 3, a differential lever 4, a rhombic ring 5 and a piezoelectric stack 6; the mirror flexure adjustment bracket 1 is a boss structure with a hollow middle part, and cross hinges 1-1 are embedded in the central holes on the upper and lower side surfaces. The main body of the cross hinge 1-1 is a regular even-sided polygon boss. A constraint stator 1-2 is arranged in the hollow structure in the middle of the mirror flexure adjustment bracket 1. The constraint stator 1-2 is a square boss with a hollow middle part, and its end face is parallel to the corresponding end faces of the mirror flexure adjustment bracket 1. The upper and lower end faces of the constraint stator 1-2 are connected to the centers of the regular even-sided polygon bosses of the cross hinge 1-1. The mirror 2 is embedded in the hollow part of the constraint stator 1-2. The bottom surface of the constraint stator 1-2 is fixedly connected to the mirror support 3-1 by threads. At the same time, the mirror 2 also contacts the end face of the mirror support 3-1. The mirror support 3-1 is a square boss on the front end face of the transmission rod 3, and threaded holes are machined at the four corners. Behind the mirror support 3-1 is a trapezoidal constant stiffness beam 3-2 part, and behind the constant stiffness beam 3-2 is a flat straight beam 3-3 part. The integrated constant stiffness beam 3-2 and flat straight beam 3-3 form the transmission rod 3; the side surface of the flat straight beam 3-3 is fixedly connected to the end face of the biaxial decoupling hinge 4-1 by bolts. The biaxial decoupling hinge 4-1 is located in the middle of the differential lever 4. The two ends of the differential lever 4 are respectively a uniaxial decoupling hinge 4-2 and an X-shaped hinge 4-3. The end faces of the flexible uniaxial decoupling hinge 4-2 and X-shaped hinge 4-3 are fixedly connected to the short-axis end faces of the rhombic ring 5. A piezoelectric stack 6 is embedded in the long-axis direction of the rhombic ring 5.

[0006] The rhombic ring 5 has a displacement amplification function. The larger the length ratio of the long axis to the short axis, the greater the amplification multiple of the displacement output by the short axis; the rhombic ring 5 provides constraints for the piezoelectric stack 6. A pre-compressive stress is applied to the rhombic ring 5 in advance before installing the piezoelectric stack 6 to avoid damage to the piezoelectric stack 6 caused by tensile stress; the rhombic ring 5 has a power-off locking function and can still maintain the deformed state of the piezoelectric stack 6 under the condition of stopping voltage input, thereby keeping the swing angle of the mirror 2 unchanged and reducing energy loss.

[0007] The edge of the beam end is subjected to the greatest stress. The constant stiffness beam 3-2 of the force transmission part of the transmission rod 3 is designed as a trapezoid, and the middle part of the constant stiffness beam adopts a hollow design to reduce the weight while meeting the edge stiffness requirements.

[0008] The distance from the rotation center of the X-shaped hinge 4-3 to the differential lever 4 is half of the distance from the rotation center of the uniaxial decoupling hinge 4-2 to the differential lever 4. The forces on both ends of the differential lever 4 are the same. The rhombic ring 5 includes a main actuating rhombic ring 5-1 and an auxiliary actuating rhombic ring 5-2. The rhombic ring 5 adopts a redundant actuating design. The main actuating rhombic ring 5-1 and the auxiliary actuating rhombic ring 5-2 push and pull symmetrically left and right to reduce coupling; the one fixedly connected to the uniaxial decoupling hinge 4-2 is the main actuating rhombic ring 5-1, and the one fixedly connected to the X-shaped hinge 4-3 is the auxiliary actuating rhombic ring 5-2.

[0009] The generation of the normal force is controlled by decoupling through multiple flexible hinges and the dimensional structure design of the force transmission mechanism to achieve pure torque drive. Specifically: The piezoelectric linear force in the short-axis direction output by the main actuating diamond ring 5-1 and the auxiliary actuating diamond ring 5-2 is transmitted to the differential lever 4 through the single-axis decoupling hinge 4-2 and the X-shaped hinge 4-3 respectively. The flexible hinge has the function of reducing the action of the force in the non-short-axis direction; The force perpendicular to the side surface of the flat straight beam 3-3 is transmitted through the biaxial decoupling hinge 4-1. The biaxial decoupling hinge 4-1 has the function of reducing the force and torsional action in the non-perpendicular end face direction; The receiving end face of the transmission rod 3 is designed so that the normal line of the mirror 2 falls on the extended plane of the force-receiving end face of the flat straight beam 3-3. The transmission rod 3 only generates a torque action on the mirror 2, further reducing the generation of the normal force.

[0010] By cooperating the cross hinge 1-1 with the constraint stator 1-2, the normal displacement of the mirror surface of the mirror 2 is reduced. Specifically: The mirror 2 is embedded in the constraint stator 1-2 to limit the translational movement of the mirror 2; The constraint stator 1-2 is connected to the regular even-sided polygon body of the cross hinge 1-1. The cross hinge 1-1 includes four branch hinges, two of which are along the normal direction of the mirror surface, and the other two are along the force-receiving direction of the transmission rod 3. When the mirror 2 is subjected to a normal force, the cross hinge 1-1 can provide a large normal stiffness, further reducing the normal displacement; The rotation center of the cross hinge 1-1 falls on the extended plane of the mirror surface of the mirror 2, and the normal height of the rotation center of the cross hinge 1-1 is consistent with the center of the mirror 2.

[0011] The actuating method of this deflection mechanism is as follows: A voltage is applied to the piezoelectric stack 6. The piezoelectric stack 6 deforms along the long axis direction of the diamond ring 5 and outputs a displacement in the long axis direction. The long axis direction of the diamond ring 5 is subjected to a tensile or compressive action, and the corresponding short axis direction is subjected to a compressive or tensile action, and the end face outputs a displacement in the short axis direction; The diamond ring 5 drives one end of the differential lever 4 to generate the same displacement through the connected flexible hinge, drives the middle part of the differential lever 4 to generate a displacement in the same direction, and is transmitted through the biaxial decoupling hinge 4-1 to apply a perpendicular force to the end face fixed to the flat straight beam 3-3. The transmission rod 3 is stressed to generate a single-axis planar deflection motion, and the deflection axis is perpendicular to the force direction, driving the constraint stator 1-2 and the mirror 2 to generate a single-axis planar deflection motion with the same deflection magnitude and direction, converting the piezoelectric linear drive into a single-axis deflection motion to achieve the deflection adjustment of the mirror 2.

[0012] The control method of the extremely low normal coupling deflection mechanism with redundant design has three piezoelectric drive displacement transmission modes. By controlling the voltage of different piezoelectric stacks 6, the displacement requirements under three working conditions can be met. The first displacement transmission mode is: applying the same voltage to the piezoelectric stacks 6 inside the main actuating diamond ring 5-1 and the auxiliary actuating diamond ring 5-2 simultaneously. Both ends of the differential lever 4 will perform the same linear motion, driving the double-axis decoupling hinge 4-1 in the middle to generate the same displacement. In this displacement transmission mode, the output displacement is large, and the corresponding deflection amplitude of the mirror surface of the mirror 2 is large, meeting the requirements of the large stroke working condition.

[0013] The second displacement transmission mode is: applying voltage to the piezoelectric stack 6 inside the main actuating diamond ring 5-1 and not applying voltage to the auxiliary actuating diamond ring 5-2. The main actuating diamond ring 5-1 outputs displacement in the short axis direction. According to the lever principle, the displacement output at the midpoint of the differential lever 4 is half of that of the main actuating diamond ring 5-1. The other end of the differential lever 4 is fixed and constrained by the auxiliary actuating diamond ring 5-2 and does not generate displacement as the lever fulcrum. In this displacement transmission mode, only voltage needs to be applied to the piezoelectric stack 6 of the main actuating diamond ring 5-1 to meet the requirements of the normal working condition.

[0014] The third displacement transmission mode is: in the case of a failure of the main actuating diamond ring 5-1 or when high-precision deflection is required, applying voltage to the piezoelectric stack 6 inside the auxiliary actuating diamond ring 5-2. The auxiliary actuating diamond ring 5-2 outputs displacement in the short axis direction. The displacement output at the midpoint of the differential lever 4 is half of that of the auxiliary actuating diamond ring 5-2. The other end of the differential lever 4 is fixed and constrained by the main actuating diamond ring 5-1 and does not generate displacement as the lever fulcrum, ensuring that the entire mechanism works normally when the displacement output of the main actuating diamond ring 5-1 is blocked. The distance from the rotation center of the X-shaped hinge 4-3 to the auxiliary actuating diamond ring 5-2 is half of the distance from the single-axis decoupling hinge 4-2 to the main actuating diamond ring 5-1, making the motion range of the third displacement transmission mode half of that of the second displacement transmission mode to meet the requirements of the high deflection precision working condition.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. By decoupling multiple flexible hinges and designing the size and structure of the force transmission mechanism to control the generation of normal force, pure torque drive is achieved.

[0017] 2. By providing normal stiffness with hinges and designing the co-rotation center of the hinge and the mirror, the normal displacement of the mirror is reduced.

[0018] 3. It has three piezoelectric drive displacement transmission modes. By controlling the voltage of different piezoelectric stacks, the displacement requirements under three working conditions can be met.

[0019] 4. The structure of the present invention is compact. Through the displacement amplification mechanism and transmission conversion, linear drive is converted into a large-amplitude single-axis deflection motion. Description of the Drawings

[0020] Figure 1a With Figure 1b are side views of the present invention in different directions.

[0021] Figure 2a With Figure 2b is a sectional view of the present invention.

[0022] Figure 3a 、 Figure 3b And Figure 3c are respectively schematic diagrams of three piezoelectric drive modes of the present invention. Specific Embodiments

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] As Figure 1a 、 Figure 1b 、 Figure 2a And Figure 2b shown, the present invention is a very low normal coupling deflection mechanism with redundant design, including a mirror flexure adjustment bracket 1, a mirror 2, a transmission rod 3, a differential lever 4, a diamond ring 5, and a piezoelectric stack 6; the mirror flexure adjustment bracket 1 is a convex platform structure with a hollow middle, and a cross hinge 1-1 is embedded in the central holes on the upper and lower side surfaces. The main body of the cross hinge 1-1 is a regular even-sided polygon convex platform. The advantage of using a regular even-sided polygon convex platform is that the overall mirror flexure adjustment bracket 1 is a symmetric structure, and the rotation center coincides with the geometric center. In this embodiment, it is a regular octagon convex platform. A constraint stator 1-2 is arranged in the hollow structure in the middle of the mirror flexure adjustment bracket (1). The constraint stator 1-2 is a square convex platform with a hollow middle, and its end surface is parallel to the corresponding end surfaces of the mirror flexure adjustment bracket 1. The upper and lower end surfaces of the constraint stator 1-2 are connected to the center of the regular octagon convex platform of the cross hinge 1-1. The mirror 2 is embedded in the hollow of the constraint stator 1-2. The bottom surface of the constraint stator 1-2 is fixedly connected to the mirror support 3-1 by threads. At the same time, the mirror 2 also contacts the end surface of the mirror support 3-1. The mirror support 3-1 is a square convex platform on the front end surface of the transmission rod 3, and threaded holes are processed at the four corners. Behind the mirror support 3-1 is a trapezoidal equal stiffness beam 3-2 part, and behind the equal stiffness beam 3-2 is a flat straight beam (3-3) part. The integrally designed equal stiffness beam 3-2 and flat straight beam 3-3 form the transmission rod 3; the side surface of the flat straight beam 3-3 is fixedly connected to the end surface of the biaxial decoupling hinge 4-1 by bolts. The biaxial decoupling hinge 4-1 is located in the middle of the differential lever 4. The two ends of the differential lever 4 are respectively a flexible uniaxial decoupling hinge 4-2 and an X-shaped hinge 4-3. The end surfaces of the two flexible hinges are fixedly connected to the short axis end surface of a diamond ring 5. A piezoelectric stack 6 is embedded in the long axis direction of the diamond ring 5.

[0025] As a preferred embodiment of the present invention, for the extremely low normal coupling deflection mechanism with redundant design, the rhombic ring 5 has a displacement amplification function. The larger the ratio of the major axis length to the minor axis length, the greater the amplification multiple of the displacement output by the minor axis. The rhombic ring 5 provides constraints for the piezoelectric stack 6, and prestresses are applied to the rhombic ring 5 in advance before installing the piezoelectric stack 6 to avoid damage to the piezoelectric stack 6 caused by tensile stress. The rhombic ring 5 has a power-off locking function and can still maintain the deformed state of the piezoelectric stack 6 under the condition of stopping voltage input, thereby keeping the swing angle of the mirror 2 unchanged and reducing energy loss.

[0026] As a preferred embodiment of the present invention, for the extremely low normal coupling deflection mechanism with redundant design, the edge of the beam end is subjected to the maximum stress. The force-transmitting part of the transmission rod 3 is designed as a trapezoidal equal-stiffness beam 3-2, and the middle part of the equal-stiffness beam adopts a hollow design, which can reduce the weight while meeting the edge stiffness requirements.

[0027] As a preferred embodiment of the present invention, for the extremely low normal coupling deflection mechanism with redundant design, the distance from the rotation center of the X-shaped hinge 4-3 to the differential lever 4 is half of the distance from the rotation center of the single-axis decoupling hinge 4-2 to the differential lever 4. The forces on both ends of the differential lever 4 are the same. The rhombic ring 5 includes a main actuating rhombic ring 5-1 and an auxiliary actuating rhombic ring 5-2. The rhombic ring 5 adopts a redundant actuating design, and the main actuating rhombic ring 5-1 and the auxiliary actuating rhombic ring 5-2 push and pull symmetrically left and right to reduce coupling. The main actuating rhombic ring 5-1 is fixedly connected to the single-axis decoupling hinge 4-2, and the auxiliary actuating rhombic ring 5-2 is fixedly connected to the X-shaped hinge 4-3.

[0028] As a preferred embodiment of the present invention, for the extremely low normal coupling deflection mechanism with redundant design, the generation of normal force is controlled by decoupling through multiple flexible hinges and the design of the size and structure of the force-transmitting mechanism to achieve pure torque drive: the piezoelectric linear forces in the minor axis direction output by the main actuating rhombic ring 5-1 and the auxiliary actuating rhombic ring 5-2 are respectively transmitted to the differential lever 4 through the single-axis decoupling hinge 4-2 and the X-shaped hinge 4-3. The flexible hinge has the function of reducing the acting force in the non-minor axis direction; the acting force perpendicular to the side surface of the flat straight beam 3-3 is transmitted through the biaxial decoupling hinge 4-1, and the biaxial decoupling hinge 4-1 has the functions of reducing the acting force in the non-perpendicular end face direction and the torsional effect; the force-receiving end face of the transmission rod 3 is designed such that the normal line of the mirror 2 falls on the extended plane of the force-receiving end face of the flat straight beam 3-3, and the transmission rod 3 only generates a torque effect on the mirror 2, further reducing the generation of normal force.

[0029] As a preferred embodiment of the present invention, the extremely low normal coupling deflection mechanism with redundant design cooperates with the constraint stator 1-2 through the cross hinge 1-1 to reduce the normal displacement of the mirror surface: the mirror 2 is embedded in the constraint stator 1-2 to limit the translational movement of the mirror 2; the constraint stator 1-2 is connected to the regular octagon body of the cross hinge 1-1. The cross hinge 1-1 includes four branch hinges, two of which are along the normal direction of the mirror surface, and the other two are along the force direction of the transmission rod 3. When the mirror 2 is subjected to a normal force, the cross hinge 1-1 can provide a large normal stiffness to further reduce the normal displacement; the rotation center of the cross hinge 1-1 falls on the extended plane of the mirror surface of the mirror 2, and the rotation center of the cross hinge 1-1 is consistent with the normal height of the center of the mirror 2. In this way, the translation of the outgoing light path is avoided from introducing an optical path difference, ensuring the high pointing accuracy of the mechanism.

[0030] The actuation method of the extremely low normal coupling deflection mechanism with redundant design is as follows: a voltage is applied to the piezoelectric stack 6, and the piezoelectric stack 6 deforms along the long axis direction of the diamond ring 5, outputting a displacement in the long axis direction. The long axis direction of the diamond ring 5 is subjected to tensile and compressive forces, and the corresponding short axis direction is subjected to compressive (tensile) forces, and the end face outputs a displacement along the short axis direction; the diamond ring 5 drives one end of the differential lever 4 to generate the same displacement through the connected flexible hinge, drives the middle part of the differential lever 4 to generate a displacement in the same direction, and transmits it through the biaxial decoupling hinge 4-1, applies a vertical force to the end face fixed to the flat straight beam 3-3, and the transmission rod 3 is stressed to generate a uniaxial planar deflection motion. The deflection axis is perpendicular to the force direction, driving the constraint stator 1-2 and the mirror 2 to generate a uniaxial planar deflection motion with the same deflection magnitude and direction, converting the piezoelectric linear drive into a uniaxial deflection motion, and realizing the deflection adjustment of the mirror 2.

[0031] As Figure 3a 、 Figure 3b and Figure 3c shown, the control method of the extremely low normal coupling deflection mechanism with redundant design has three piezoelectric drive displacement transmission modes, and the displacement requirements under three working conditions can be met by controlling the voltages of different piezoelectric stacks 6.

[0032] The first displacement transmission mode is to apply the same voltage to the piezoelectric stacks 6 in the main actuation diamond ring 5-1 and the auxiliary actuation diamond ring 5-2 at the same time. Both ends of the differential lever 4 will perform the same linear motion, driving the biaxial decoupling hinge 4-1 in the middle to generate the same displacement. In this displacement transmission mode, the output displacement is large, and the corresponding deflection amplitude of the mirror surface is large, which can meet the requirements of the large stroke working condition.

[0033] For the extremely low normal coupling deflection mechanism with redundant design and its control method described above, the second displacement transmission mode is as follows: A voltage is applied to the piezoelectric stack 6 inside the main actuating rhombic ring 5-1, while no voltage is applied to the auxiliary actuating rhombic ring 5-2. The main actuating rhombic ring 5-1 outputs displacement in the short-axis direction. According to the lever principle, the displacement output at the midpoint of the differential lever 4 is half of that of the main actuating rhombic ring 5-1. The other end of the differential lever 4 is fixedly constrained by the auxiliary actuating rhombic ring 5-2 and does not generate displacement as the lever fulcrum. In this displacement transmission mode, only a voltage needs to be applied to the piezoelectric stack 6 of the main actuating rhombic ring 5-1 to meet the requirements of normal working conditions.

[0034] For the extremely low normal coupling deflection mechanism with redundant design and its control method described above, the third displacement transmission mode is as follows: In the case of a failure of the main actuating rhombic ring 5-1 or when high-precision deflection is required, a voltage is applied to the piezoelectric stack 6 inside the auxiliary actuating rhombic ring 5-2. The auxiliary actuating rhombic ring 5-2 outputs displacement in the short-axis direction. The displacement output at the midpoint of the differential lever 4 is half of that of the auxiliary actuating rhombic ring 5-2. The other end of the differential lever 4 is fixedly constrained by the main actuating rhombic ring 5-1 and does not generate displacement as the lever fulcrum, ensuring that the entire mechanism works normally when the displacement output of the main actuating rhombic ring 5-1 is blocked. The distance from the rotation center of the X-shaped hinge 4-3 to the auxiliary actuating rhombic ring 5-2 is half of the distance from the single-axis decoupling hinge 4-2 to the main actuating rhombic ring 5-1, making the motion range of the third displacement transmission mode half of that of the second displacement transmission mode, which can meet the requirements of high-deflection-precision working conditions.

[0035] The present invention converts the linear drive of the piezoelectric stack into a pure torque drive to control the deflection of the mirror surface. It reduces the generation of normal force through decoupling by multiple flexible hinges, increases the normal stiffness and reduces the torsional stiffness through the cross hinge, thereby reducing the normal displacement and achieving extremely low normal coupling of the mirror surface; it uses a redundant piezoelectric drive design with two piezoelectric stacks to achieve three piezoelectric drive displacement transmission modes, which has redundancy and the advantages of meeting the requirements of various working conditions, and improves the overall output stability.

Claims

1. A very low normal coupling deflection mechanism with redundant design, characterized in that: It includes a mirror flexure adjustment bracket (1), a mirror (2), a transmission rod (3), a differential lever (4), a rhombic ring (5) and a piezoelectric stack (6); the mirror flexure adjustment bracket (1) is a boss structure with a hollow middle part. Cross hinges (1-1) are embedded in the central holes on the upper and lower side surfaces. The main body of the cross hinge (1-1) is a regular even-sided polygon boss. A constraint stator (1-2) is arranged in the hollow structure in the middle of the mirror flexure adjustment bracket (1). The constraint stator (1-2) is a square boss with a hollow middle part, and its end face is parallel to the corresponding end faces of the mirror flexure adjustment bracket (1). The upper and lower end faces of the constraint stator (1-2) are connected to the centers of the regular even-sided polygon bosses of the cross hinge (1-1). The mirror (2) is embedded in the hollow part of the constraint stator (1-2). The bottom face of the constraint stator (1-2) is fixedly connected to the mirror support (3-1) by threads. At the same time, the mirror (2) also contacts the end face of the mirror support (3-1). The mirror support (3-1) is a square boss on the front end face of the transmission rod (3), and threaded holes are machined at the four corners. Behind the mirror support (3-1) is a trapezoidal constant stiffness beam (3-2) part, and behind the constant stiffness beam (3-2) is a flat straight beam (3-3) part. The integrally designed constant stiffness beam (3-2) and flat straight beam (3-3) form the transmission rod (3); the side face of the flat straight beam (3-3) is fixedly connected to the end face of the biaxial decoupling hinge (4-1) by bolts. The biaxial decoupling hinge (4-1) is located in the middle of the differential lever (4). The two ends of the differential lever (4) are respectively a uniaxial decoupling hinge (4-2) and an X-shaped hinge (4-3). The end faces of the flexible uniaxial decoupling hinge (4-2) and X-shaped hinge (4-3) are fixedly connected to the short-axis end faces of the rhombic ring (5). A piezoelectric stack (6) is embedded in the long-axis direction of the rhombic ring (5); Through the cooperation of the cross hinge (1-1) and the constraint stator (1-2), the normal displacement of the mirror surface of the mirror (2) is reduced. Specifically: the mirror (2) is embedded in the constraint stator (1-2) to limit the translational movement of the mirror (2); the constraint stator (1-2) is connected to the regular even-sided polygon main body of the cross hinge (1-1). The cross hinge (1-1) contains four branch hinges, two of which are along the normal direction of the mirror surface, and the other two are along the force direction of the transmission rod (3). When the mirror (2) is subjected to a normal force, the cross hinge (1-1) can provide a large normal stiffness to further reduce the normal displacement; the rotation center of the cross hinge (1-1) falls on the extended plane of the mirror surface of the mirror (2), and the rotation center of the cross hinge (1-1) is consistent with the normal height of the center of the mirror (2).

2. The very low normal coupling deflection mechanism with redundant design according to claim 1, characterized in that: The rhombic ring (5) has a displacement amplification function. The larger the ratio of the long axis to the short axis length, the greater the amplification multiple of the short-axis output displacement; the rhombic ring (5) provides constraints for the piezoelectric stack (6). Before installing the piezoelectric stack (6), a pre-compressive stress is applied to the rhombic ring (5) to prevent the piezoelectric stack (6) from being damaged by tensile stress; the rhombic ring (5) has a power-off locking function. It can still maintain the deformed state of the piezoelectric stack (6) under the condition of stopping voltage input, thereby keeping the swing angle of the mirror (2) unchanged and reducing energy loss.

3. The very low normal coupling deflection mechanism with redundant design according to claim 1, characterized in that: The stress is the greatest at the edge of the beam end. The equal-stiffness beam (3-2) of the force transmission part of the transmission rod (3) is designed as a trapezoid, and the middle part of the equal-stiffness beam adopts a hollow design to reduce the weight while meeting the edge stiffness requirements.

4. The very low normal coupling deflection mechanism with redundant design according to claim 1, characterized in that: The distance from the rotation center of the X-shaped hinge (4-3) to the differential lever (4) is half of the distance from the rotation center of the single-axis decoupling hinge (4-2) to the differential lever (4). The forces on both ends of the differential lever (4) are the same. The diamond ring (5) includes a main actuating diamond ring (5-1) and an auxiliary actuating diamond ring (5-2). The diamond ring (5) adopts a redundant actuation design. The main actuating diamond ring (5-1) and the auxiliary actuating diamond ring (5-2) push and pull symmetrically left and right to reduce coupling; the one fixedly connected to the single-axis decoupling hinge (4-2) is the main actuating diamond ring (5-1), and the one fixedly connected to the X-shaped hinge (4-3) is the auxiliary actuating diamond ring (5-2).

5. The very low normal coupling deflection mechanism with redundant design according to claim 1, characterized in that: The generation of the normal force is controlled by the decoupling of multiple flexible hinges and the dimension structure design of the force transmission mechanism to achieve pure torque drive. Specifically: the short-axis direction piezoelectric linear acting forces output by the main actuating diamond ring (5-1) and the auxiliary actuating diamond ring (5-2) are respectively transmitted to the differential lever (4) through the single-axis decoupling hinge (4-2) and the X-shaped hinge (4-3). The flexible hinge has the function of reducing the acting force in the non-short-axis direction; the acting force perpendicular to the side surface of the flat straight beam (3-3) is transmitted through the double-axis decoupling hinge (4-1). The double-axis decoupling hinge (4-1) has the functions of reducing the acting force in the non-perpendicular end face direction and the torsional action; the receiving end face of the transmission rod (3) is designed so that the normal line of the mirror (2) falls on the extended plane of the force-receiving end face of the flat straight beam (3-3). The transmission rod (3) only generates a torque action on the mirror (2), further reducing the generation of the normal force.

6. The very low normal coupling deflection mechanism with redundant design according to claim 1, characterized in that: The actuation method of this deflection mechanism is as follows: Apply a voltage to the piezoelectric stack (6). The piezoelectric stack (6) deforms along the long axis direction of the diamond ring (5) and outputs a displacement in the long axis direction. The long axis direction of the diamond ring (5) is subjected to a tensile or compressive action, and the corresponding short axis direction is subjected to a compressive or tensile action, and the end face outputs a displacement in the short axis direction; the diamond ring (5) drives one end of the differential lever (4) to generate the same displacement through the connected flexible hinge, drives the middle part of the differential lever (4) to generate a displacement in the same direction, and is transmitted through the double-axis decoupling hinge (4-1), and a perpendicular acting force is applied to the end face fixedly connected to the flat straight beam (3-3). The transmission rod (3) is stressed to generate a single-axis plane deflection motion, and the deflection axis is perpendicular to the acting force direction, driving the constraint stator (1-2) and the mirror (2) to generate a single-axis plane deflection motion with the same deflection magnitude and direction, converting the piezoelectric linear drive into a single-axis deflection motion to achieve the deflection adjustment of the mirror (2).

7. A control method for the very low normal coupling deflection mechanism with redundant design according to any one of claims 1 to 6, characterized in that: There are three piezoelectric drive displacement transmission modes. By controlling the voltage of different piezoelectric stacks (6), the displacement requirements under three working conditions can be met. The first displacement transmission mode is: applying the same voltage to the piezoelectric stacks (6) inside the main actuating diamond ring (5-1) and the auxiliary actuating diamond ring (5-2) simultaneously. Both ends of the differential lever (4) will perform the same linear motion, driving the double-axis decoupling hinge (4-1) in the middle to generate the same displacement. In this displacement transmission mode, the output displacement is large, and the corresponding deflection amplitude of the mirror surface of the mirror (2) is large, meeting the requirements of the large stroke working condition; The second displacement transmission mode is: applying voltage to the piezoelectric stack (6) inside the main actuating diamond ring (5-1) and not applying voltage to the auxiliary actuating diamond ring (5-2). The main actuating diamond ring (5-1) outputs displacement in the short axis direction. According to the lever principle, the displacement output at the midpoint of the differential lever (4) is half of that of the main actuating diamond ring (5-1). The other end of the differential lever (4) is fixed and constrained by the auxiliary actuating diamond ring (5-2) and does not displace as a lever fulcrum. In this displacement transmission mode, only voltage needs to be applied to the piezoelectric stack (6) of the main actuating diamond ring (5-1) to meet the requirements of the normal working condition; The third displacement transmission mode is: in the case of a failure of the main actuating diamond ring (5-1) or when high-precision deflection is required, applying voltage to the piezoelectric stack (6) inside the auxiliary actuating diamond ring (5-2). The auxiliary actuating diamond ring (5-2) outputs displacement in the short axis direction. The displacement output at the midpoint of the differential lever (4) is half of that of the auxiliary actuating diamond ring (5-2). The other end of the differential lever (4) is fixed and constrained by the main actuating diamond ring (5-1) and does not displace as a lever fulcrum, ensuring that the entire mechanism works normally when the displacement output of the main actuating diamond ring (5-1) is blocked. The distance from the rotation center of the X-shaped hinge (4-3) to the auxiliary actuating diamond ring (5-2) is half of the distance from the single-axis decoupling hinge (4-2) to the main actuating diamond ring (5-1), making the motion range of the third displacement transmission mode half of that of the second displacement transmission mode to meet the requirements of the high deflection precision working condition.

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