Electromagnetic-driven Adjustable Stiffness Nanopositioning Platform

Abstract

The present invention provides an electromagnetically driven adjustable stiffness nanopositioning platform relating to the field of nanopositioning platforms. The platform comprises a compliance mechanism, a normal stress electromagnetic actuator, an electromagnetic spring and a base. The normal stress electromagnetic actuator comprises an actuator stator and an actuator mover, and air gaps are provided on both sides of the actuator stator and the actuator mover. The electromagnetic spring comprises an electromagnetic spring stator and an electromagnetic spring mover, and air gaps are provided on both sides of the electromagnetic spring stator and the electromagnetic spring mover. The actuator stator and the electromagnetic spring stator are respectively connected to the base, the actuator mover and the electromagnetic spring mover are respectively connected to the moving end of the compliance mechanism, and the fixed end of the compliance mechanism is connected to the base. The overall rigidity of the electromagnetically driven adjustable stiffness nanopositioning platform is adjustable through the adjustable negative stiffness of the electromagnetic spring. The present invention adjusts the stiffness of the nanopositioning platform by adjusting the current of the electromagnetic spring coil, and can realize online switching between a high-stiffness state, a low-stiffness state, and any intermediate state therebetween. It can break through the bottleneck of the traditional nanopositioning platform's fixed stiffness and the irreconcilable contradiction between the natural frequency and the stroke, and can adapt to a wider range of application scenarios.

Description

Technical Field

[0001] The present invention relates to the field of nanopositioning platforms, and in particular to an electromagnetically driven nanopositioning platform with adjustable stiffness. Background Art

[0002] The core technologies of nanopositioning platforms (techniques that nanopositioning platform designers must master) are precision drive and transmission technologies. Commonly used precision drive technologies include intelligent material drives (piezoelectric materials, dielectric elastomers, magnetostrictive materials, etc.) and electromagnetic drives (voice coil motor drives, normal stress electromagnetic drives, etc.). Precision transmission technologies primarily utilize compliant mechanisms (flexure hinges, elastic beams, and combinations of the two). Other technologies (techniques that nanopositioning platform users will already have access to) include drive circuits (such as pre-voltage and current amplifiers), sensing technologies (laser displacement sensors, capacitive displacement sensors, stress and strain sensors, etc.), and control technologies (feedforward control, feedback control, and intelligent control).

[0003] Traditional nanopositioning platforms are designed based on precision actuators and compliant mechanisms. Their maximum active driving force, stiffness, and dynamic mass are fixed, resulting in fixed natural frequency and maximum travel. All other conditions being equal, higher stiffness results in a higher natural frequency for the nanopositioning platform, making it more suitable for high-frequency operation. However, its travel is lower, making it less suitable for wide-range operation. Lower stiffness results in a greater travel, making it suitable for wide-range operation. However, its natural frequency is lower, making it less suitable for high-frequency operation. Therefore, there is an irreconcilable conflict between the natural frequency and travel of traditional nanopositioning platforms, necessitating the design or purchase of different nanopositioning platforms to meet different requirements.

[0004] If the stiffness of the nanopositioning platform is adjustable, the natural frequency and stroke of the nanopositioning platform can be adjusted.

[0005] In his master's thesis, "Design and Analysis of a Piezoelectric Ceramic-Driven Long-Stroke Fast Tool Servo System," Li Jinyin of Shandong University proposed an adjustable-stiffness nanopositioning platform. This platform utilizes a compliant mechanism with adjustable stiffness as its transmission mechanism. When two holes in the mechanism are bolted to the base, the platform exhibits high stiffness; when the holes are not bolted, the platform exhibits low stiffness. However, its disadvantages are: 1. The stiffness can only be adjusted in two settings: "high stiffness" and "low stiffness," with no intermediate setting available. 2. This stiffness adjustment method requires manual adjustment, which is difficult to perform and must be performed after the nanopositioning platform is stopped. Online adjustment is not possible, and servo control of the stiffness is impossible. 3. Manual mechanical adjustment necessitates the provision of adjustment holes and reserved operating space, making integration with other equipment difficult, especially in confined spaces. Summary of the Invention

[0006] In view of the defects in the prior art, the purpose of the present invention is to provide an electromagnetically driven nanopositioning platform with adjustable stiffness.

[0007] According to the present invention, an electromagnetically driven nanopositioning platform with adjustable stiffness includes a compliance mechanism, a normal stress electromagnetic actuator, an electromagnetic spring, and a base. The normal stress electromagnetic actuator includes an actuator stator and an actuator mover, and air gaps are provided on both sides of the actuator stator and the actuator mover. The electromagnetic spring includes an electromagnetic spring stator and an electromagnetic spring mover, and air gaps are provided on both sides of the electromagnetic spring stator and the electromagnetic spring mover. The actuator stator and the electromagnetic spring stator are respectively connected to the base, the actuator mover and the electromagnetic spring mover are respectively connected to the moving end of the compliance mechanism, and the fixed end of the compliance mechanism is connected to the base.

[0008] When not in operation, the air gaps on both sides of the actuator mover and the electromagnetic spring mover are equal; when in operation, under the guidance of the compliance mechanism, the actuator mover and the moving end of the compliance mechanism are displaced, driving the electromagnetic spring mover to also displace, making the air gaps on both sides of the actuator mover and the electromagnetic spring mover unequal, and the actuator mover, the electromagnetic spring mover and the moving end of the compliance mechanism further displace toward the side with the smaller air gap until reaching the equilibrium position;

[0009] The compliant mechanism provides positive stiffness, the normal stress electromagnetic actuator provides a part of fixed negative stiffness, and the electromagnetic spring provides a part of adjustable negative stiffness, thereby realizing the overall rigidity adjustment of the electromagnetically driven adjustable stiffness nanopositioning platform.

[0010] In some embodiments, the electromagnetic spring includes an electromagnetic spring armature, an electromagnetic spring yoke, and an electromagnetic spring coil, wherein the electromagnetic spring armature and the electromagnetic spring yoke are connected end to end, the electromagnetic spring armature is connected to the moving end of the compliance mechanism, the electromagnetic spring coil is wound around the electromagnetic spring yoke, and the electromagnetic spring yoke is fixed to the base;

[0011] The electromagnetic spring armature is the mover of the electromagnetic spring, and the electromagnetic spring yoke and the electromagnetic spring coil are the stator of the electromagnetic spring.

[0012] In some embodiments, air gaps are respectively provided between the two ends of the electromagnetic spring yoke and the electromagnetic spring armature. In a non-operating state, the air gaps on both sides of the electromagnetic spring armature are equal.

[0013] In some embodiments, the normal stress electromagnetic actuator includes an actuator yoke, an actuator coil, a permanent magnet, and an actuator armature, wherein the actuator yoke and the actuator armature are connected end to end, one end of the permanent magnet is attracted to the middle of the actuator yoke, an air gap is provided between the other end of the permanent magnet and the actuator armature, the actuator armature is connected to the moving end of the compliant mechanism, the actuator coil is wound around the actuator yoke, and the actuator yoke is connected to the base;

[0014] The actuator armature is a mover of the normal stress electromagnetic actuator, and the actuator yoke, the actuator coil and the permanent magnet are a stator of the normal stress electromagnetic actuator.

[0015] In some embodiments, air gaps are provided between the actuator yoke and both sides of the actuator armature. In a non-operating state, the air gaps on both sides of the actuator armature are equal.

[0016] In some embodiments, the active driving force of the normal stress electromagnetic actuator acts on the actuator armature, which transmits the active driving force to the moving end of the compliant mechanism. Under the guidance of the compliant mechanism, the actuator armature and the moving end of the compliant mechanism are displaced, causing the air gaps on both sides of the actuator armature to be unequal. At this time, the DC magnetic flux generated by the permanent magnet will be distributed at different densities between the air gaps on both sides of the actuator armature, with a higher density on the side with a smaller air gap, and the normal stress electromagnetic actuator will generate a passive driving force.

[0017] When the actuator armature and the moving end of the compliant mechanism are displaced, the electromagnetic spring armature is displaced at the same time, making the air gaps on both sides of the electromagnetic spring armature unequal. The DC magnetic flux generated by the electromagnetic spring coil being energized has different densities distributed between the air gaps on the left and right sides of the electromagnetic spring armature, with the side with the smaller air gap having a higher density. The electromagnetic spring generates a passive driving force.

[0018] The actuator armature, the electromagnetic spring armature and the moving end of the compliance mechanism are further displaced toward the side with a smaller air gap until reaching an equilibrium position.

[0019] In some embodiments, the current intensity and the number of coil turns of the actuator coil are proportional to the active driving force of the normal stress electromagnetic actuator;

[0020] The passive driving force of the normal stress electromagnetic actuator is proportional to the displacement of the actuator armature and has the same direction.

[0021] In some embodiments, the passive driving force of the electromagnetic spring is proportional to and in the same direction as the displacement of the electromagnetic spring armature;

[0022] The strength of the passive driving force of the electromagnetic spring is proportional to the square of the current intensity passed through the electromagnetic spring coil.

[0023] In some embodiments, the electromagnetic spring yoke includes an arcuate segment and a straight segment, the arcuate segment is connected end to end to the electromagnetic spring armature, the electromagnetic spring coil is wound around the straight segment, one end of the straight segment is connected to the middle of the arcuate segment, and the other end of the straight segment is connected to the electromagnetic spring armature;

[0024] An air gap is provided between the arc section and both sides of the electromagnetic spring armature, and an air gap is provided between the straight section and the electromagnetic spring armature.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention adjusts the stiffness of the nanopositioning platform by adjusting the current of the electromagnetic spring coil, and can achieve online switching between a high stiffness state, a low stiffness state, and any intermediate state therebetween. This can break through the bottleneck of the traditional nanopositioning platform's fixed stiffness and the irreconcilable contradiction between the natural frequency and the stroke, and can adapt to a wider range of application scenarios;

[0027] (2) In the present invention, no mechanical adjustment is required during the stiffness adjustment process, which makes the industrial integration of the electromagnetically driven adjustable stiffness nanopositioning platform very simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0029] Figure 1 is an axonometric drawing of the present invention;

[0030] Figure 2 It is a top view of the present invention.

[0031] Numbers in the figure:

[0032] Compliant mechanism 1 , actuator yoke 2 , actuator coil 3 , permanent magnet 4 , actuator armature 5 , electromagnetic spring armature 6 , electromagnetic spring yoke 7 , arc segment 71 , straight segment 72 , electromagnetic spring coil 8 , base 9 . DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0034] Example 1

[0035] According to the present invention, an electromagnetically driven nanopositioning platform with adjustable stiffness includes a compliance mechanism 1, a normal stress electromagnetic actuator, an electromagnetic spring, and a base 9. The normal stress electromagnetic actuator includes an actuator stator and an actuator mover, with air gaps provided on both sides of the actuator stator and the actuator mover. The electromagnetic spring includes an electromagnetic spring stator and an electromagnetic spring mover, with air gaps provided on both sides of the electromagnetic spring stator and the electromagnetic spring mover. The actuator stator and the electromagnetic spring stator are respectively connected to the base 9. The actuator mover and the electromagnetic spring mover are respectively connected to the moving end of the compliance mechanism 1, and the fixed end of the compliance mechanism 1 is connected to the base 9. Preferably, when not in operation, the air gaps on both sides of the actuator mover and the electromagnetic spring mover are equal.

[0036] How it works During operation, under the guidance of the compliance mechanism 1, the actuator mover and the moving end of the compliance mechanism 1 are displaced, driving the electromagnetic spring mover to also displace, making the air gaps on both sides of the actuator mover and the electromagnetic spring mover unequal. The actuator mover, the electromagnetic spring mover, and the moving end of the compliance mechanism 1 further displace toward the side with the smaller air gap until they reach the equilibrium position.

[0037] The compliant mechanism 1 provides positive stiffness, the normal stress electromagnetic actuator provides a portion of fixed negative stiffness, and the electromagnetic spring provides a portion of adjustable negative stiffness, thereby achieving overall rigidity adjustment of the electromagnetically driven adjustable stiffness nanopositioning platform.

[0038] More specifically, based on the operating principle of the normal stress electromagnetic actuator, it provides two driving forces: an active driving force and a passive driving force. The active driving force of the normal stress electromagnetic actuator is proportional to the current intensity and number of turns of the actuator coil 3. The normal stress electromagnetic actuator has a negative stiffness characteristic, thus generating a passive driving force. The passive driving force of the normal stress electromagnetic actuator is proportional to the displacement of the actuator armature 5 and is in the same direction as the normal stress electromagnetic actuator. This is the negative stiffness characteristic of the normal stress electromagnetic actuator.

[0039] Example 2

[0040] This embodiment 2 is completed on the basis of embodiment 1. By adjusting the current of the electromagnetic spring coil, the adjustment of the electromagnetically driven adjustable stiffness nanopositioning platform is achieved. Specifically:

[0041] The electromagnetic spring comprises an electromagnetic spring armature 6, an electromagnetic spring yoke 7, and an electromagnetic spring coil 8. The electromagnetic spring armature 6 and the electromagnetic spring yoke 7 are connected end to end, with air gaps between the two ends of the electromagnetic spring yoke 7 and the electromagnetic spring armature 6. When not in operation, the air gaps on both sides of the electromagnetic spring armature 6 are equal. The electromagnetic spring armature 6 is connected to the moving end of the compliant mechanism 1 via strong glue or bolts. The electromagnetic spring coil 8 is wound around the electromagnetic spring yoke 7, which is fixed to the base 9 via bolts. The electromagnetic spring armature 6 is the mover of the electromagnetic spring, while the electromagnetic spring yoke 7 and the electromagnetic spring coil 8 are the stator of the electromagnetic spring. The passive driving force of the electromagnetic spring is proportional to the displacement of the electromagnetic spring armature 6 and is in the same direction. The strength of the passive driving force of the electromagnetic spring is proportional to the square of the current intensity flowing through the electromagnetic spring coil 8. Preferably, the electromagnetic spring armature 6 and the electromagnetic spring yoke 7 are made of soft magnetic material for magnetic conductivity.

[0042] Preferably, the electromagnetic spring yoke 7 includes an arcuate segment 71 and a straight segment 72. The arcuate segment 71 is connected end to end to the electromagnetic spring armature 6. The electromagnetic spring coil 8 is wound around the straight segment 72. One end of the straight segment 72 is connected to the middle of the arcuate segment 71, and the other end of the straight segment 72 is connected to the electromagnetic spring armature 6. An air gap is provided between the arcuate segment 71 and the two sides of the electromagnetic spring armature 6, and an air gap is provided between the straight segment 72 and the electromagnetic spring armature 6.

[0043] The normal stress electromagnetic actuator comprises an actuator yoke 2, an actuator coil 3, a permanent magnet 4, and an actuator armature 5. The actuator yoke 2 and the actuator armature 5 are connected end to end, with air gaps between the actuator armature 5 and the actuator yoke 2 on either side. When not in operation, the air gaps on both sides of the actuator armature 5 are equal. One end of the permanent magnet 4 is attracted to the center of the actuator yoke 2, with an air gap between the other end of the permanent magnet 4 and the actuator armature 5. The actuator armature 5 is connected to the moving end of the compliance mechanism 1. The actuator coil 3 is wound around the actuator yoke 2, which is connected to the base 9. The actuator armature 5 is the mover of the normal stress electromagnetic actuator, while the actuator yoke 2, actuator coil 3, and permanent magnet 4 are the stator of the normal stress electromagnetic actuator. The current intensity and number of turns of the actuator coil 3 are proportional to the active driving force of the normal stress electromagnetic actuator; the passive driving force of the normal stress electromagnetic actuator is proportional to and in the same direction as the displacement of the actuator armature 5. Preferably, the actuator yoke 2 and the actuator armature 5 are made of soft magnetic material for magnetic conductivity.

[0044] The active driving force of the normal stress electromagnetic actuator acts on the actuator armature 5, which transmits the active driving force to the moving end of the compliant mechanism 1. Under the guidance of the compliant mechanism 1, the actuator armature 5 and the moving end of the compliant mechanism 1 are displaced, making the air gaps on both sides of the actuator armature 5 unequal. At this time, the DC magnetic flux generated by the permanent magnet 4 has different densities distributed between the air gaps on both sides of the actuator armature 5, with a higher density on the side with a smaller air gap. The normal stress electromagnetic actuator generates a passive driving force.

[0045] When the actuator armature 5 and the moving end of the compliant mechanism 1 are displaced, the electromagnetic spring armature 6 is displaced at the same time, causing the air gaps on both sides of the electromagnetic spring armature 6 to be unequal in size. The DC magnetic flux generated by the electromagnetic spring coil 8 being energized has different densities distributed between the air gaps on the left and right sides of the electromagnetic spring armature 6, with the side with the smaller air gap having a higher density. The electromagnetic spring generates a passive driving force.

[0046] The actuator armature 5, the electromagnetic spring armature 6 and the moving end of the compliance mechanism 1 are further displaced toward the side with a smaller air gap until reaching an equilibrium position.

[0047] More specifically, the compliant mechanism 1 provides positive stiffness, the electromagnetic spring provides a portion of adjustable negative stiffness, and the permanent magnet 4 of the normal stress electromagnetic actuator provides a portion of fixed negative stiffness. The three stiffnesses are superimposed to form the overall stiffness of the electromagnetically driven adjustable stiffness nanopositioning platform. Since the negative stiffness strength provided by the electromagnetic spring can be adjusted by adjusting the current passed through the electromagnetic spring coil 8, the overall stiffness of the electromagnetically driven adjustable stiffness nanopositioning platform is adjustable.

[0048] Theoretically, the overall stiffness of the electromagnetically driven adjustable stiffness nanopositioning platform can be adjusted downward arbitrarily from the sum of the positive stiffness of the compliant mechanism 1 and the negative stiffness provided by the permanent magnet 4. However, it should be noted that its overall stiffness should not be less than zero and a certain margin should be ensured, otherwise it will cause system instability.

[0049] The maximum absolute active driving force that the stress electromagnetic actuator can provide is F max，act =K act NI max，act , where N is the number of turns of the actuator coil 3, I max，act is the maximum absolute current intensity flowing into the actuator coil 3, K act It is related to the geometric design parameters and material performance parameters of the normal stress electromagnetic actuator, and is the maximum absolute active driving force and NI max The proportional coefficient between them. Assume that the stiffness of the compliant mechanism 1 is k comp , which is related to the geometric design parameters and material performance parameters of the compliant mechanism 1. The negative stiffness strength provided by the permanent magnet 4 of the stress-stressed electromagnetic actuator is k FM, which is related to the geometric design parameters and material performance parameters of the normal stress electromagnetic actuator. Assume that the negative stiffness provided by the adjustable stiffness electromagnetic negative stiffness spring is Among them I sp is the current intensity of the electromagnetic spring coil 8, K sp It is related to the geometric design parameters and material properties of the adjustable stiffness electromagnetic negative stiffness spring. It is the negative stiffness provided by the adjustable stiffness electromagnetic negative stiffness spring. The proportional coefficient between .

[0050] Based on this, the overall stiffness of the electromagnetically driven adjustable stiffness nanopositioning platform is k = k comp -k FM -k sp .

[0051] Furthermore, the maximum absolute travel of the adjustable stiffness nanopositioning stage can be calculated as Calculate the natural frequency of a nanopositioning stage with adjustable stiffness where m is the dynamic mass of the mover of the electromagnetically driven adjustable stiffness nanopositioning stage.

[0052] Based on this, since the overall stiffness k of the electromagnetically driven adjustable stiffness nanopositioning platform is adjustable, its maximum absolute stroke S max The natural frequency f is adjustable. The process of adjusting the stiffness does not require any mechanical adjustment, only the current flowing into the electromagnetic spring coil 8 needs to be adjusted, which also makes it possible to servo-control the stiffness.

[0053] Because the passive actuating force in the normal stress electromagnetic actuator is provided by the permanent magnet 4, the negative stiffness of the normal stress electromagnetic actuator is fixed and cannot be adjusted. However, the passive driving force strength caused by the negative stiffness of the electromagnetic spring is related to the current intensity flowing through the electromagnetic spring coil 8 and is adjustable. Therefore, compared to traditional non-adjustable nanopositioning platforms, the electromagnetically driven adjustable stiffness nanopositioning platform offers flexible performance specifications and can adapt to different application scenarios. A single electromagnetically driven adjustable stiffness nanopositioning platform can meet the performance requirements of high frequency and long travel.

[0054] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0055] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. An electromagnetically driven nanopositioning platform with adjustable stiffness, characterized in that: The invention comprises a compliance mechanism (1), a normal stress electromagnetic actuator, an electromagnetic spring and a base (9), wherein the normal stress electromagnetic actuator comprises an actuator stator and an actuator mover, air gaps are provided on both sides of the actuator stator and the actuator mover, the electromagnetic spring comprises an electromagnetic spring stator and an electromagnetic spring mover, air gaps are provided on both sides of the electromagnetic spring stator and the electromagnetic spring mover, the actuator stator and the electromagnetic spring stator are respectively connected to the base (9), the actuator mover and the electromagnetic spring mover are respectively connected to the moving end of the compliance mechanism (1), and the fixed end of the compliance mechanism (1) is connected to the base (9); When not in operation, the air gaps on both sides of the actuator mover and the electromagnetic spring mover are equal; when in operation, under the guidance of the compliance mechanism (1), the actuator mover and the moving end of the compliance mechanism (1) are displaced, driving the electromagnetic spring mover to be displaced, so that the air gaps on both sides of the actuator mover and the electromagnetic spring mover are unequal, and the actuator mover, the electromagnetic spring mover and the moving end of the compliance mechanism (1) are further displaced toward the side with the smaller air gap until reaching an equilibrium position; The compliant mechanism (1) provides positive stiffness, the normal stress electromagnetic actuator provides a portion of fixed negative stiffness, and the electromagnetic spring provides a portion of adjustable negative stiffness, thereby achieving overall rigidity adjustment of the electromagnetically driven adjustable stiffness nanopositioning platform; The electromagnetic spring comprises an electromagnetic spring armature (6), an electromagnetic spring yoke (7), and an electromagnetic spring coil (8); the electromagnetic spring armature (6) and the electromagnetic spring yoke (7) are connected end to end; the electromagnetic spring armature (6) is connected to the moving end of the compliant mechanism (1); the electromagnetic spring coil (8) is wound on the electromagnetic spring yoke (7); and the electromagnetic spring yoke (7) is fixed on the base (9); The electromagnetic spring armature (6) is the electromagnetic spring mover, and the electromagnetic spring yoke (7) and the electromagnetic spring coil (8) are the electromagnetic spring stator.

2. The electromagnetically driven adjustable stiffness nanopositioning platform according to claim 1, characterized in that: Air gaps are respectively provided between the two ends of the electromagnetic spring yoke (7) and the electromagnetic spring armature (6); in a non-operating state, the air gaps on both sides of the electromagnetic spring armature (6) are equal.

3. The electromagnetically driven adjustable stiffness nanopositioning platform according to claim 2, characterized in that: The normal stress electromagnetic actuator comprises an actuator yoke (2), an actuator coil (3), a permanent magnet (4) and an actuator armature (5); the actuator yoke (2) and the actuator armature (5) are connected end to end; one end of the permanent magnet (4) is adsorbed in the middle of the actuator yoke (2); an air gap is provided between the other end of the permanent magnet (4) and the actuator armature (5); the actuator armature (5) is connected to the moving end of the compliant mechanism (1); the actuator coil (3) is wound on the actuator yoke (2); and the actuator yoke (2) is connected to the base (9); The actuator armature (5) is the actuator mover, and the actuator yoke (2), the actuator coil (3) and the permanent magnet (4) are the actuator stator.

4. The electromagnetically driven adjustable stiffness nanopositioning platform according to claim 3, characterized in that: Air gaps are provided between the actuator yoke (2) and the two sides of the actuator armature (5). In a non-operating state, the air gaps on the two sides of the actuator armature (5) are equal.

5. The electromagnetically driven adjustable stiffness nanopositioning platform according to claim 4, characterized in that: The active driving force of the normal stress electromagnetic actuator acts on the actuator armature (5), and the actuator armature (5) transmits the active driving force to the moving end of the compliant mechanism (1). Under the guidance of the compliant mechanism (1), the actuator armature (5) and the moving end of the compliant mechanism (1) are displaced, so that the air gaps on both sides of the actuator armature (5) are unequal. At this time, the DC magnetic flux generated by the permanent magnet (4) has different densities distributed between the air gaps on both sides of the actuator armature (5), and the density is denser on the side with a smaller air gap. The normal stress electromagnetic actuator generates a passive driving force. When the actuator armature (5) and the moving end of the compliant mechanism (1) are displaced, the electromagnetic spring armature (6) is displaced simultaneously, so that the air gaps on both sides of the electromagnetic spring armature (6) are unequal in size, and the DC magnetic flux generated by energizing the electromagnetic spring coil (8) has different densities distributed between the air gaps on the left and right sides of the electromagnetic spring armature (6), with the side with the smaller air gap having a higher density, and the electromagnetic spring generates a passive driving force; The actuator armature (5), the electromagnetic spring armature (6) and the moving end of the compliant mechanism (1) are further displaced toward the side with a smaller air gap until reaching an equilibrium position.

6. The electromagnetically driven adjustable stiffness nanopositioning platform according to claim 3, characterized in that: The current intensity and the number of coil turns of the actuator coil (3) are proportional to the active driving force of the normal stress electromagnetic actuator; The passive driving force of the normal stress electromagnetic actuator is proportional to the displacement of the actuator armature (5) and has the same direction.

7. The electromagnetically driven adjustable stiffness nanopositioning platform according to claim 1, characterized in that: The passive driving force of the electromagnetic spring is proportional to the displacement of the electromagnetic spring armature (6) and is in the same direction; The intensity of the passive driving force of the electromagnetic spring is proportional to the square of the intensity of the current passed through the electromagnetic spring coil (8).

8. The electromagnetically driven adjustable stiffness nanopositioning platform according to claim 1, characterized in that: The electromagnetic spring yoke (7) comprises an arc segment (71) and a straight segment (72), the arc segment (71) is connected end to end with the electromagnetic spring armature (6), the electromagnetic spring coil (8) is wound on the straight segment (72), one end of the straight segment (72) is connected to the middle of the arc segment (71), and the other end of the straight segment (72) is connected to the electromagnetic spring armature (6); An air gap is provided between the arc section (71) and both sides of the electromagnetic spring armature (6), and an air gap is provided between the straight section (72) and the electromagnetic spring armature (6).

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