An electromagnetic actuator with stiffness compensation function

Abstract

This invention discloses an electromagnetic actuator with stiffness compensation function. The inner end face of the C-shaped stator core has a trapezoidal inclined notch, and the working surface of the mover is an inclined surface matching the stator core notch. The N and S poles of the permanent magnet are attracted to the upper end arm of the stator core, and the coil winding is wound on the yoke of the stator core. A flexible guiding mechanism is connected to the mover and the base respectively. The lower end arm of the stator core is connected to the base via fasteners, and the relative distance between the stator core end face and the mover working surface is adjusted by tightening the fasteners. This invention uses an inclined air gap formed by the mover and stator core. The linear displacement of the mover is no longer equal to the normal thickness of the air gap, but is geometrically amplified. This overcomes the fundamental contradiction of strong coupling between stroke and thickness in traditional planar air gaps, achieving a macroscopic motion stroke several times the thickness while maintaining a small initial normal air gap. From a structural principle perspective, this solves the problem of the difficulty in simultaneously achieving "large stroke" and "high linearity."

Description

Technical Field

[0001] This invention relates to the field of precision drive technology, and more specifically to an electromagnetic actuator with stiffness compensation function. Background Technology

[0002] Precision actuators, as one of the fundamental core components of micro-actuation, micro-measurement, and micro-manufacturing, are widely used in precision machining, space communication, optical engineering, robotics, and aerospace. However, traditional voice coil motor actuators suffer from low power density, failing to meet the design requirements of minimizing size, weight, and power consumption; piezoelectric ceramic actuators have small actuation strokes, making them unsuitable for millimeter-level large-stroke precision actuation applications. Electromagnetic actuation technology, utilizing Maxwell's electromagnetic force principle, is considered an effective solution that simultaneously achieves high power density and large actuation stroke, and is increasingly being applied to high-end electromechanical systems such as high-speed mirror systems, imaging optical scanning systems, high-speed tool servos, and robots.

[0003] Maxwell electromagnetic actuators generate driving force by changing the magnetic flux / magnetic flux density in the air gap of a magnetic circuit. Their basic principle can be summarized as follows: In a magnetic circuit composed of a magnetically conductive material (such as silicon steel sheets), when a working air gap exists, if a magnetic flux is established in the circuit through coil excitation or a permanent magnet, according to Maxwell's stress tensor theory, a mutual attractive force will be generated on the ferromagnetic material surfaces at both ends of the air gap; this is the Maxwell force. To achieve linear control, a permanent magnet bias is usually introduced, making the force approximately proportional to the current and displacement (i.e., the change in air gap) within a certain range (manifested as negative stiffness). However, its linearity heavily depends on the small air gap assumption.

[0004] As is known, the basic structure of such actuators typically includes: a magnetically conductive stator core (usually C-type or E-type), a permanent magnet, a coil wound on the stator, a movable ferromagnetic component (mover), and a mechanism that guides the mover (such as a flexible hinge or bearing). The magnetomotive force generated by energizing the control coil modulates the total magnetic flux in the air gap, thereby changing the Maxwell force and driving the mover to move.

[0005] In existing technologies, typical Maxwell electromagnetic actuators mainly include the following two types: one is a toothed meshing linear enhanced Maxwell electromagnetic actuator. For example, Chinese patent application CN119315792A discloses a biaxial linear enhanced Maxwell electromagnetic actuator, which mainly consists of a pair of stator cores, a mover core, permanent magnets, and excitation coils. The stator cores are usually two "C"-shaped or specifically shaped cores, and their working end faces facing the mover are machined into symmetrical triangular teeth. The two sides of the mover are machined with triangular tooth grooves that match the stator teeth. In the assembled state, the mover tooth grooves mesh with the stator teeth, and a uniform air gap is maintained between each relative tooth surface. The permanent magnet is located on the side of the stator core, providing a constant bias magnetic flux. The coil is wound on the yoke of the stator core to generate a control magnetomotive force. The mover is supported by linear bearings or a flexible guide mechanism and is located between the two stator cores.

[0006] The core idea of ​​this scheme is to use a toothed structure to reduce the effective length of the local air gap path through which the magnetic flux passes, even though the macroscopic displacement is large. The design intent is to make the rate of change of magnetic reluctance with displacement of the entire magnetic circuit tend to be gradual, thereby "linearizing" the relationship between electromagnetic force and displacement, and hoping to enhance the magnetic field utilization and suppress leakage flux under large gaps by reducing the local air gap. This scheme attempts to improve linearity from the source by changing the geometry of the magnetic circuit interface (toothing), but introduces a problem that is extremely sensitive to the machining and assembly alignment accuracy of the tooth grooves.

[0007] Another typical approach is to use a Maxwell actuator with passive compensation employing a nonlinear stiffness-flexibility mechanism, such as the one described in "A Large-Stroke Reluctance-Actuated Nanopositioner: Compliant Compensator for Enhanced Linearity and Precision Motion Control" published in IEEE / ASME Transactions on Mechatronics. This approach can be viewed as a hybrid system, consisting of a standard electromagnetic drive unit and a specially designed mechanical compensation unit connected in series. The electromagnetic drive unit is a Maxwell force generator composed of a traditional C-type stator (containing permanent magnets and coils) and a flat mover. This unit itself generates electromagnetic negative stiffness that varies nonlinearly with displacement. The mechanical compensation unit is a single-piece or multi-piece flexible guiding mechanism with complex topology optimization. It no longer possesses simple linear spring characteristics but is designed so that its stiffness increases nonlinearly with deformation (displacement) (e.g., gradually hardening characteristics). The mover is fixedly connected to this nonlinear flexible mechanism. The overall stiffness of the entire system is the sum of the electromagnetic negative stiffness and the mechanical positive stiffness.

[0008] This scheme employs a passive compensation strategy of "using mechanical nonlinearity to offset electromagnetic nonlinearity." Through precise calculation and design, the nonlinear positive stiffness curve of the flexible mechanism and the nonlinear negative stiffness curve of the electromagnetic actuator are complementary in shape and cancel each other out in magnitude within the working stroke. Ideally, the sum of the two is close to a constant throughout the entire stroke, thereby achieving linear force-displacement characteristics of the system as a whole and improving control accuracy. This scheme accepts the inherent nonlinearity of the magnetic circuit and instead introduces a complex flexible mechanism with matching nonlinear stiffness for end-effector compensation, but this leads to increased complexity of the mechanical system and increased design difficulty.

[0009] In summary, existing Maxwell electromagnetic actuators have the following main drawbacks:

[0010] (1) The inherent contradiction between stroke and linearity: In the traditional Maxwell actuator with a planar air gap, the stroke of the mover is equal to the physical thickness of the working air gap. Increasing the air gap thickness to obtain a large stroke will directly lead to a significant increase in magnetic leakage flux and cause the electromagnetic force characteristics (especially the displacement negative stiffness) to exhibit severe nonlinearity, which makes it impossible for the actuator to maintain high-precision positioning under large stroke, and the control algorithm becomes more complex and the system robustness is reduced.

[0011] (2) Tooth meshing scheme is too sensitive to assembly accuracy: The scheme that uses tooth meshing between the mover and stator to reduce the effective air gap is highly dependent on the precise geometric alignment between the tooth grooves. Even a small assembly error can cause harmful lateral parasitic forces and actually reduce the effective stroke, thus reducing the practicality and reliability of the project.

[0012] (3) Passive stiffness compensation scheme leads to structural complexity: The scheme of using specially designed nonlinear flexible mechanism to compensate for electromagnetic negative stiffness nonlinearity introduces flexible components with complex topology and large spatial volume, which greatly increases the difficulty of design, processing and assembly of mechanical parts, which is contrary to the development trend of miniaturization and compactness of precision actuators.

[0013] (4) Fixed actuator stroke, lack of adjustability: The maximum stroke of most existing actuators is determined in the mechanical design stage and fixed by rigid connection. It is impossible to make flexible and convenient adjustment of the stroke range according to the specific needs of different applications, resulting in insufficient versatility.

[0014] The reason why existing technologies cannot overcome the above-mentioned shortcomings stems from the inherent limitations in their basic structural principles and design concepts, as analyzed in detail below:

[0015] The fundamental reason for the "contradiction between stroke and linearity" lies in the strong geometric coupling of traditional planar air gap structures. In this structure, the working air gap interface is perpendicular to the direction of motion of the mover, causing the physical thickness of the air gap (a key parameter determining magnetic reluctance and Maxwell force) to be completely equivalent to the linear displacement of the mover. Therefore, any design aimed at increasing stroke will directly and linearly increase the air gap thickness. Under large gaps, the leakage flux ratio increases nonlinearly, leading to a significant deviation of the Maxwell force-displacement characteristics from linearity. This structural coupling causes the two objectives of "large stroke" and "small air gap (good linearity)" to conflict at the physical level.

[0016] The "precision sensitivity of the toothed meshing scheme" stems from the fact that while the toothed air gap scheme "segments" and "shortens" the effective air gap path through local triangular teeth / grooves, its meshing mechanism introduces stringent requirements for assembly precision. Its performance depends on the precise lateral and axial relative positions of the moving and stator teeth throughout the entire stroke. Since minor errors in machining tolerances, assembly clearances, and guiding mechanisms are unavoidable, this ideal alignment cannot be consistently maintained in engineering practice, leading to performance degradation. Therefore, while this scheme improves nonlinear characteristics, it does not provide a robust solution insensitive to assembly errors.

[0017] The reason why "passive compensation schemes lead to structural complexity" lies in the fact that this scheme, in terms of its technical approach, belongs to end-point compensation. It acknowledges that the electromagnetic subsystem itself is nonlinear and attempts to "reverse-shape" a complex, nonlinear stiffness curve in the mechanical subsystem (guiding mechanism) to compensate for this. This approach necessitates the introduction of spatially flexible structures with specific nonlinear deformation characteristics (such as beams with variable cross-sections, complex lever combinations, etc.), which inevitably increases the topological complexity, design dimensions, and manufacturing difficulty of the mechanism. Achieving precise matching between two nonlinear curves is itself a highly challenging and low-tolerance design task, often at the expense of structural simplicity, compactness, and economy.

[0018] The reason for the "fixed actuator stroke" is that existing designs generally use rigid, non-adjustable assembly interfaces. The stator core is usually rigidly fixed to the base directly through simple positioning holes and screws, and the installation position cannot be changed once locked. This design focuses on the certainty of a single assembly and structural rigidity, but completely abandons adjustability. To change the stroke, key components with different dimensions (such as movers or pads of different thicknesses) must be replaced, which is essentially a new product design, rather than a flexible configuration of the same product function. Summary of the Invention

[0019] The technical problem to be solved by the present invention is to address the inherent technical defects exposed by existing electromagnetic actuators based on Maxwell force in the pursuit of large stroke and high linearity, and to provide an electromagnetic actuator with stiffness compensation function that is compact in structure, easy to operate and has a preset or adjustable stroke.

[0020] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0021] An electromagnetic actuator with stiffness compensation function includes: a mover, a permanent magnet, a stator core, a coil winding, a flexible guide mechanism, and a base; the mover has a trapezoidal structure, the permanent magnet includes a first permanent magnet and a second permanent magnet, and the stator core includes a first stator core and a second stator core; both the first and second stator cores have a C-shaped structure, and the inner end faces of the first and second stator cores are provided with trapezoidal inclined notches; the working surfaces on both sides of the mover are inclined surfaces matching the notches of the stator cores, and multiple uniform inclined working air gaps are formed between the mover and the stator cores; the first permanent magnet and The second permanent magnet is attracted to the upper arms of the first and second stator cores with its N and S poles respectively; the coil winding is wound on the yoke of the stator core; the inner top of the flexible guide mechanism is rigidly connected to the top center of the mover, and the bottom of the flexible guide mechanism is fixed to the base to ensure that the mover has only a single translational degree of freedom along the X-axis; the lower arms of the first and second stator cores are connected to the base by fasteners, and the fasteners are tightened to adjust the relative distance between the inner end faces of the first and second stator cores and the working surface of the mover, thereby changing the initial normal thickness Δ of the inclined working air gap.

[0022] As a further improvement of the present invention, a first air gap and a second air gap are formed between the working inclined surfaces on both sides of the mover and the inner end faces of the first stator core, respectively; a third air gap and a fourth air gap are formed between the working inclined surfaces on both sides of the mover and the inner end faces of the second stator core, respectively; the bottom angle α of the working inclined surface of the mover is between 15° and 75°.

[0023] As a further improvement of the present invention, the maximum theoretical stroke L0 of the mover satisfies the following relationship with the initial normal air gap thickness Δ and the bottom angle α of the mover's working inclined plane: L0∝Δ / sin(α).

[0024] As a further improvement of the present invention, each of the lower end arms of the first stator core and the second stator core is provided with a semi-open waist-shaped groove, and the fixing screw passes through the waist-shaped groove and connects to the threaded hole on the base.

[0025] As a further improvement of the present invention, the flexible guiding mechanism includes a motion platform, a first flexible side beam, a second flexible side beam, and a flexible bottom beam. The top inner side of the motion platform is rigidly connected to the mover, and the flexible bottom beam is rigidly connected to the base. The first flexible side beam and the second flexible side beam are parallel to each other to form a parallelogram flexible hinge.

[0026] As a further improvement of the present invention, the motion platform is rigidly connected to the top center of the mover by connecting screws and connecting pins; the flexible bottom beam is rigidly connected to the base by mounting screws.

[0027] As a further improvement of the present invention, both the first permanent magnet and the second permanent magnet are made of neodymium iron boron material.

[0028] As a further improvement of the present invention, both the first stator core and the second stator core are made of laminated silicon steel sheets.

[0029] As a further improvement of the present invention, when the electromagnetic actuator is in a static state, the permanent magnet circuit starts from the N pole of the first permanent magnet and the second permanent magnet, passes through the second stator core, and then enters the mover through the third air gap and the fourth air gap, respectively. After passing through the mover, it flows out from the first air gap and the second air gap, passes through the first stator core, and returns to the S pole of the first permanent magnet and the second permanent magnet, respectively, forming a closed loop.

[0030] As a further improvement of the present invention, when the electromagnetic actuator drives the mover to move in the X-axis direction, a positive control current is applied to the first coil winding on the first stator core. The resulting first control magnetic flux enhances the magnetic field of the second air gap and weakens the magnetic field of the first air gap, causing a difference in the Maxwell normal attraction force on the working inclined surfaces on both sides of the mover. The component of the resultant force of the Maxwell normal attraction force in the X-axis direction drives the mover to move towards the side of the second air gap. When a reverse control current is applied to the first coil winding on the first stator core, the movement direction of the mover is reversed.

[0031] Compared with the prior art, the electromagnetic actuator with stiffness compensation function of the present invention has the following significant advantages:

[0032] (1) A novel Maxwell force electromagnetic actuator structure is provided. By decoupling the linear relationship between the mover displacement and the working air gap physical thickness, a linear motion stroke several times that thickness can be obtained without significantly increasing the air gap physical thickness. This fundamentally suppresses the problem of magnetic circuit nonlinear deterioration caused by the surge in air gap thickness.

[0033] (2) A magnetic circuit interface design with inherent robustness to assembly errors is provided. This design adopts continuous inclined surface mating to replace the triangular tooth meshing which is extremely sensitive to precision, eliminates parasitic forces caused by small misalignments, and ensures that the theoretical motion stroke is fully realized in actual assembly.

[0034] (3) A simple and compact nonlinear compensation mechanism is provided. By cleverly utilizing the natural component of the driving force and the physical characteristics of the guiding mechanism (such as stiffness hardening effect), the structure achieves endogenous and adaptive stiffness compensation, thereby avoiding the use of additional complex and customized nonlinear flexible mechanisms. While improving performance, the overall structure of the system remains simple and compact.

[0035] (4) An actuator with adjustable stroke is provided. By designing a simple adjustable installation interface, the user can conveniently adjust the initial working point during the assembly stage, thereby flexibly changing the maximum stroke of the actuator and enhancing its adaptability and versatility in different application scenarios. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the overall structure of an electromagnetic actuator with stiffness compensation function in a specific embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram of the exploded structure principle of an electromagnetic actuator with stiffness compensation function in a specific embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the permanent magnet circuit in a specific embodiment of the present invention;

[0039] Figure 4 This is a front cross-sectional view of the control magnetic circuit in a specific embodiment of the present invention;

[0040] Figure 5 This is a rear cross-sectional view of the control magnetic circuit in a specific embodiment of the present invention;

[0041] Figure 6 This is a schematic diagram of a partial analysis of the inclined working air gap in a specific embodiment of the present invention;

[0042] Figure 7 This is a schematic diagram of the force distribution on the mechanism in a specific embodiment of the present invention.

[0043] Legend: 1. Moving element; 2. Permanent magnet; 21. First permanent magnet; 22. Second permanent magnet; 3. Stator core; 31. First stator core; 32. Second stator core; 4. Coil winding; 41. First coil winding; 42. Second coil winding; 5. Flexible guide mechanism; 51. Motion platform; 52. First flexible side beam; 53. Second flexible side beam; 54. Flexible bottom beam; 6. Base; 61. Threaded hole; 7. Fixing screw; 8. Inclined working air gap; 81. First air gap; 82. Second air gap; 83. Third air gap; 84. Fourth air gap; 9. Waist-shaped groove; 10. Connecting screw; 11. Connecting pin; 12. Mounting screw; 13. Positioning pin; 141. First bias flux; 142. Second bias flux; 151. First control flux; 152. Second control flux. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0045] In the description of this invention, it should be understood that the terms "side", "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more unless otherwise explicitly specified.

[0047] Example

[0048] like Figure 1 and Figure 2As shown, the electromagnetic actuator with stiffness compensation function of the present invention includes: a mover 1, a permanent magnet 2, a stator core 3, a coil winding 4, a flexible guiding mechanism 5, and a base 6. The mover 1 has a trapezoidal cross-section and is made of a high permeability material. The permanent magnet 2 includes a first permanent magnet 21 and a second permanent magnet 22, both of which are made of high-performance neodymium iron boron material. The stator core 3 includes a first stator core 31 and a second stator core 32 made of low-loss silicon steel sheets; both the first stator core 31 and the second stator core 32 have a C-shaped structure, and the inner end faces of the first stator core 31 and the second stator core 32 are provided with trapezoidal inclined notches. The working surfaces on both sides of the mover 1 are inclined surfaces that match the notches of the stator core 3, and multiple uniform inclined working air gaps 8 are formed between the mover 1 and the stator core 3. The first permanent magnet 21 and the second permanent magnet 22 are respectively attracted to the upper arms of the first stator core 31 and the second stator core 32 with their N and S poles to provide a strong bias magnetic field. The coil winding 4 is wound on the yoke of the stator core 3, and an insulating layer is provided between the coil winding 4 and the stator core 3. The inner top of the flexible guide mechanism 5 is rigidly connected to the top center of the mover 1, and the bottom of the flexible guide mechanism 5 is fixed to the base 6 to ensure that the mover 1 has only a single translational degree of freedom along the X-axis. A semi-open waist-shaped groove 9 is provided on both sides of the lower arm of the first stator core 31 and the second stator core 32, and the fixing screw 7 passes through the waist-shaped groove 9 and connects to the threaded hole 61 on the base 6. Tightening the fixing screw 7 adjusts the relative distance between the inner end faces of the first stator core 31 and the second stator core 32 and the working surface of the mover 1, thereby changing the initial normal thickness Δ of the inclined working air gap 8.

[0049] In this embodiment, the mover 1, the first stator core 31, and the second stator core 32 have high requirements for surface roughness precision. The inclined working surface needs to maintain a low roughness, which can be achieved by slow wire EDM to ensure morphological accuracy and consistency. The flexible guide mechanism 5 can be made of materials with good elasticity and fatigue strength, such as spring steel, beryllium bronze, or titanium alloy, and is integrally formed by wire EDM.

[0050] The electromagnetic actuator with stiffness compensation function of the present invention is built around three core functional units: a magnetic circuit and drive unit, a motion conversion and guidance unit, and a mechanical adjustment unit. The three functional units are highly integrated on a common base 6, forming a compact and fully functional actuator.

[0051] The magnetic circuit and drive unit are the core of generating controllable electromagnetic force, and their key lies in constructing a special magnetic circuit geometry. The magnetic circuit and drive unit includes a mover 1 with a trapezoidal cross-section, a pair of permanent magnets 2 providing a bias magnetic field, two symmetrically arranged C-shaped stator cores 3, and coil windings 4 wound on the stator cores 3. The first stator core 31 and the second stator core 32 are arranged facing each other at both ends of the mover 1. The inner end faces of the first stator core 31 and the second stator core 32 are machined with inclined surface structures that match the shape of the inclined surfaces on both sides of the mover 1, thereby forming four symmetrically distributed inclined working air gaps with the same inclination angle between the mover 1 and the first stator core 31 and the second stator core 32. Figure 3 , Figure 4 and Figure 5 As shown, a first air gap 81 and a second air gap 82 are formed between the working inclined surfaces on both sides of the mover 1 and the inner end faces of the first stator core 31, respectively. A third air gap 83 and a fourth air gap 84 are formed between the working inclined surfaces on both sides of the mover 1 and the inner end faces of the second stator core 32, respectively.

[0052] The motion conversion and guidance unit converts electromagnetic force into precise linear motion of the mover 1 along a single degree of freedom, and plays a crucial role in achieving nonlinear stiffness compensation. At the core of the motion conversion and guidance unit is a parallelogram-shaped flexible guidance mechanism 5 rigidly connected to the mover 1. The flexible guidance mechanism 5 consists of a first flexible side beam 52 and a second flexible side beam 53 arranged in parallel. The flexible bottom beam 54 of the flexible guidance mechanism 5 is fixed to the base 6 by mounting screws 12. The motion platform 51 of the flexible guidance mechanism 5 is rigidly connected to the top center of the mover 1 by connecting screws 10 and connecting pins 11. This design provides the mover 1 with precise X-axis unidirectional translational guidance and the necessary linear restoring force. Furthermore, the specific mechanical characteristics of this flexible mechanism serve as the physical carrier for achieving passive stiffness compensation.

[0053] The mechanical adjustment unit enables the preset function of key operating parameters (maximum stroke) of the actuator. This is specifically reflected in the adjustable mounting design of the stator core 3. At the lower end arm mounting portion of each stator core 3, an elongated hole, such as a slot 9, extending along the adjustment direction (usually perpendicular to the mover's direction of movement) is provided. Through the cooperation of this elongated hole and fasteners (such as fixing screws 7), the spatial position of the stator core 3 relative to the fixed mover 1 can be continuously adjusted during the assembly stage.

[0054] In this implementation, the assembly and adjustment process of the electromagnetic actuator is as follows:

[0055] Installation of the mover and guide mechanism: First, fix the motion platform 51 of the flexible guide mechanism 5 to the mover 1. Using the positioning pin holes pre-set on the mover 1 and the base 6, insert the positioning pin 13 to initially and accurately position the assembly at the center of the base 6. Then, lock the bottom of the flexible guide mechanism 5.

[0056] Magnetic circuit unit installation and air gap setting: Insert a set of standard spacers, each with a thickness of Δ (e.g., 0.5 mm), at the four inclined positions between the mover 1 and the first stator core 31 and the second stator core 32. Place the first stator core 31 and the second stator core 32 on the base 6, allowing the fixing screws 7 to pass through the slots 9. Slide the first stator core 31 and the second stator core 32 up and down until their inclined surfaces are completely in contact with the spacers and the inclined surface of the mover 1. At this point, the initial normal air gap thickness is set to Δ. Finally, tighten all screws to fix the first stator core 31 and the second stator core 32, and carefully remove the spacers.

[0057] In this implementation, the working principle and core mechanism of the electromagnetic actuator are as follows:

[0058] In terms of magnetic circuit and drive, the static bias magnetic flux established by the permanent magnet 2 constitutes the main magnetic circuit. Taking either side of the mover 1 as an example, the magnetic flux starts from the N pole of the permanent magnet 2, flows through the stator core 3, passes through the inclined working air gap 8 and enters the mover 1. After converging in the mover 1, it passes through the other inclined working air gap 8 and enters the stator core 3 on the opposite side, finally returning to the S pole of the permanent magnet 2, forming a closed loop. When a control current is applied to the coil winding 4, the control magnetomotive force generated in each stator core 3 will superimpose or weaken the bias magnetic flux in each air gap, thereby changing the magnetic flux density at the air gap. Since the four inclined working air gaps 8 are symmetrically arranged, the change in the direction of the control current will cause an asymmetrical change in the superimposed magnetic flux density of the air gaps on both sides, which in turn causes the Maxwell normal attraction force acting on the inclined working surfaces on both sides of the mover 1 to lose balance. The resultant force component of this unbalanced force along the inclined surface direction (i.e., the direction of mover motion, X direction) is the net driving force driving the mover.

[0059] The core mechanism of this invention lies in creating and utilizing a built-in passive stiffness compensation mechanism. This mechanism originates from the mechanical decomposition effect of the inclined plane working air gap and its physical coupling with the guiding mechanism. For example... Figure 7 As shown, the normal Maxwell force Fe acting on the working air gap of the inclined plane can be decomposed into two components according to the geometry of the inclined plane: the driving force Fx parallel to the direction of motion of the mover (X direction), and the component perpendicular to the direction of the inclined plane (in the direction of motion of the mover). Figure 7 In this direction, there is an additional component force Fz (which includes the Z-direction component along the axis of the flexible beam), and the two satisfy the relationship: Fz = Fx / tan(α), where α is the bottom angle of the working inclined plane of the mover 1.

[0060] Crucially, this additional force Fz is transmitted through the mover 1 to the two parallel flexible side beams of the flexible guide mechanism 5, causing it to undergo bending deformation to allow the mover 1 to translate while also bearing axial tensile loads. For common flexible beams with uniform cross-sections, the presence of axial tension induces a "stiffness hardening" effect, meaning its lateral bending stiffness increases with increasing axial tension. Therefore, the equivalent mechanical restoring stiffness of the flexible guide mechanism 5 to the mover 1 is no longer constant, but a function of the axial force Fz (and consequently, the driving state and displacement x).

[0061] Through systematic parameter design, such as optimizing the inclined plane angle α and the dimensions of the flexible beam, the equivalent positive stiffness of the flexible mechanism, which increases nonlinearly due to Fz, can exhibit opposite trends to the electromagnetic negative stiffness of the magnetic circuit system, which deteriorates nonlinearly due to changes in the air gap, within the working stroke. The superposition of these two factors causes the overall system stiffness to stabilize over a wider displacement range, thus achieving self-compensation for the system's nonlinearity within the structure, eliminating the need for external active control algorithms or additional complex compensation mechanisms.

[0062] Furthermore, the inclined working air gap 8 structure increases the effective working area of ​​the air gap without increasing the cross-sectional area of ​​the stator core 3, such as... Figure 6 As shown, the effective area S of the magnetic flux in the inclined working air gap 8 satisfies the cross-sectional area A of the stator core 3: S = A / sin(α). This is beneficial for improving the magnetic field utilization rate and relatively reducing the leakage flux ratio, thereby further optimizing the linearity of the magnetic line. Simultaneously, by changing the installation position of the stator core 3 through the mechanical adjustment unit, the initial normal thickness Δ of the inclined working air gap 8 can be directly set. According to geometric relationships, the maximum theoretical stroke L0 of the mover 1 satisfies Δ and α: L0 ∝ Δ / sin(α). Therefore, by adjusting Δ, the maximum stroke of the actuator can be linearly and accurately preset, greatly enhancing the application flexibility of the equipment.

[0063] In this implementation, the working process of the electromagnetic actuator is as follows:

[0064] like Figure 3 As shown, in the static state, taking the first bias flux 141 as an example, it starts from the N pole of the first permanent magnet 21, passes through the second stator core 32 and the third air gap 83, enters the mover 1, crosses the mover 1, flows out from the first air gap 81, and returns to the S pole of the first permanent magnet 21 through the first stator core 31. The second bias flux 142 is similar.

[0065] like Figure 4 and Figure 5As shown, taking the first control flux 151 as an example, when a positive control current is applied to the first coil winding 41, the generated first control flux 151 enhances the magnetic field of the second air gap 82 while weakening the magnetic field of the first air gap 81, causing a difference in the Maxwell normal attraction force on both sides of the moving part 1. The component of the resultant force of the Maxwell normal attraction force in the X-axis direction drives the moving part 1 to move towards the side of the second air gap 82. When a reverse control current is applied to the first coil winding 41 on the first stator core 31, the moving part 1 moves in the opposite direction. The second control flux 152 works similarly.

[0066] In this implementation, the stroke adjustment and nonlinear compensation of the electromagnetic actuator are achieved as follows:

[0067] like Figure 6 As shown, based on geometric relationships, in this embodiment, the maximum theoretical stroke L0 of the mover 1 satisfies the following relationship with the initial normal air gap thickness Δ and the inclined plane angle α: L0 = Δ / sin(α). Therefore, by replacing the gap plates with different thicknesses Δ for assembly settings, or by directly fine-tuning the position of the stator core 3 within the waist-shaped slot 9 to change Δ, different strokes can be obtained on the same mechanical structure. For example, when α = 45°, Δ is adjusted from 0.3 mm to 0.6 mm, and L0 correspondingly increases from approximately 0.42 mm to approximately 0.85 mm.

[0068] like Figure 7 As shown, the Z-axis component force Fz (Fz=Fx / tan(α)) generated during the driving process acts on the first flexible side beam 52 and the second flexible side beam 53 through the motion platform 51, causing them to generate axial tension. For the uniform cross-section rectangular flexible beam in this embodiment, its transverse bending stiffness increases with the increase of axial tension, i.e., a "strain hardening" effect occurs. This makes the mechanical recovery stiffness of the system no longer a constant, but a function of displacement x (i.e., with Fx and Fz). Through finite element analysis, the angle α and the length of the flexible beam can be optimized so that the increasing trend of mechanical recovery stiffness can partially offset the deteriorating trend of electromagnetic negative stiffness caused by magnetic circuit nonlinearity, thereby keeping the total stiffness of the system relatively stable over a wider displacement range. This compensation process is automatically completed by the physical coupling inside the structure.

[0069] The electromagnetic actuator of this invention employs an inclined air gap formed by a trapezoidal mover 1 and a stator core 3 with a notched slope. This causes the linear displacement of the mover 1 to be no longer equal to the normal thickness of the air gap, but rather to be amplified geometrically. This directly overcomes the fundamental contradiction of strong coupling between stroke and thickness in traditional planar air gaps. Thus, while maintaining a small initial normal air gap, it is beneficial to maintain magnetic linearity and high efficiency, achieving a macroscopic motion stroke several times that of the thickness. From a structural principle perspective, this solves the problem of the difficulty in simultaneously achieving "large stroke" and "high linearity".

[0070] Furthermore, the inclined air gap structure itself has a continuous and smooth mating surface, reducing sensitivity to assembly precision and avoiding parasitic forces and stroke losses caused by minor misalignments in toothed meshing schemes. Simultaneously, the additional force generated by the inclined air gap naturally couples with the inherent stiffness hardening effect of conventional parallel beam flexible mechanisms, forming a built-in, passive nonlinear compensation mechanism. Without the need for additional design and fabrication of complex spatial nonlinear flexible mechanisms, the overall nonlinearity of the system can be effectively suppressed, improving performance while ensuring the simplicity, reliability, and compactness of the structure.

[0071] Furthermore, thanks to the clear proportional relationship between the stroke and the initial normal thickness determined by the inclined air gap geometry, the maximum stroke of the actuator can be linearly, accurately, and conveniently preset by changing this initial thickness through a simple waist-shaped slot adjustment mechanism on the stator core 3. This allows the same actuator to flexibly adapt to different application requirements, fundamentally solving the problems of fixed stroke and poor versatility of traditional actuators.

[0072] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An electromagnetic actuator with stiffness compensation function, characterized in that, include: The moving part (1), permanent magnet (2), stator core (3), coil winding (4), flexible guide mechanism (5), and base (6) are arranged in a trapezoidal structure. The permanent magnet (2) includes a first permanent magnet (21) and a second permanent magnet (22). The stator core (3) includes a first stator core (31) and a second stator core (32). The first stator core (31) and the second stator core (32) are both C-shaped structures. The inner end faces of the first stator core (31) and the second stator core (32) are provided with trapezoidal inclined notches. The working surfaces on both sides of the moving part (1) are inclined surfaces that match the notches of the stator core (3). Multiple uniform inclined working air gaps (8) are formed between the moving part (1) and the stator core (3). The first permanent magnet (21) and the first stator core (3) are arranged in a trapezoidal structure. The first permanent magnet (21) and the second ... The second permanent magnet (22) is attracted to the upper arm of the first stator core (31) and the second stator core (32) with its N pole and S pole respectively; the coil winding (4) is wound on the yoke of the stator core (3); the inner top of the flexible guide mechanism (5) is rigidly connected to the top center of the mover (1), and the bottom of the flexible guide mechanism (5) is fixed on the base (6) to ensure that the mover (1) has only a single translational degree of freedom along the X-axis; the lower arm of the first stator core (31) and the second stator core (32) are connected to the base (6) by fasteners, and the fasteners are tightened to adjust the relative distance between the inner end face of the first stator core (31) and the second stator core (32) and the working surface of the mover (1), thereby changing the initial normal thickness Δ of the inclined working air gap (8).

2. The electromagnetic actuator with stiffness compensation function according to claim 1, characterized in that, The working inclined surfaces on both sides of the mover (1) form a first air gap (81) and a second air gap (82) between the working inclined surfaces on both sides of the mover (1) and the inner end faces of the first stator core (31), respectively. The working inclined surfaces on both sides of the mover (1) form a third air gap (83) and a fourth air gap (84) between the working inclined surfaces of the second stator core (32), respectively. The bottom angle α of the working inclined surface of the mover (1) is between 15° and 75°.

3. The electromagnetic actuator with stiffness compensation function according to claim 2, characterized in that, The maximum theoretical stroke L0 of the mover (1) satisfies the following conditions: L0∝Δ / sin(α) as well as the initial normal air gap thickness Δ and the bottom angle α of the working slope of the mover (1).

4. The electromagnetic actuator with stiffness compensation function according to claim 2, characterized in that, The first stator core (31) and the second stator core (32) each have a semi-open waist-shaped groove (9) on both sides of the lower end arm, and the fixing screw (7) passes through the waist-shaped groove (9) and connects to the threaded hole (61) on the base (6).

5. The electromagnetic actuator with stiffness compensation function according to any one of claims 1 to 4, characterized in that, The flexible guiding mechanism (5) includes a motion platform (51), a first flexible side beam (52), a second flexible side beam (53), and a flexible bottom beam (54). The top inner side of the motion platform (51) is rigidly connected to the mover (1), and the flexible bottom beam (54) is rigidly connected to the base (6). The first flexible side beam (52) and the second flexible side beam (53) are parallel to each other to form a parallelogram flexible hinge.

6. The electromagnetic actuator with stiffness compensation function according to claim 5, characterized in that, The motion platform (51) is rigidly connected to the top center of the mover (1) by connecting screws (10) and connecting pins (11); the flexible bottom beam (54) is rigidly connected to the base (6) by mounting screws (12).

7. The electromagnetic actuator with stiffness compensation function according to any one of claims 1 to 4, characterized in that, Both the first permanent magnet (21) and the second permanent magnet (22) are made of neodymium iron boron material.

8. The electromagnetic actuator with stiffness compensation function according to any one of claims 1 to 4, characterized in that, The first stator core (31) and the second stator core (32) are both made of stacked silicon steel sheets.

9. The electromagnetic actuator with stiffness compensation function according to any one of claims 2 to 4, characterized in that, When the electromagnetic actuator is in a static state, the permanent magnet circuit starts from the N pole of the first permanent magnet (21) and the second permanent magnet (22), passes through the second stator core (32), and then enters the mover (1) through the third air gap (83) and the fourth air gap (84). After passing through the mover (1), it flows out from the first air gap (81) and the second air gap (82), passes through the first stator core (31), and returns to the S pole of the first permanent magnet (21) and the second permanent magnet (22) to form a closed loop.

10. The electromagnetic actuator with stiffness compensation function according to claim 9, characterized in that, When the electromagnetic actuator drives the mover (1) to move in the X-axis direction, a positive control current is applied to the first coil winding (41) on the first stator core (31). The resulting first control flux (151) enhances the magnetic field of the second air gap (82) and weakens the magnetic field of the first air gap (81), causing a difference in the Maxwell normal attraction on the working inclined surfaces on both sides of the mover (1). The component of the resultant force of the Maxwell normal attraction in the X-axis direction drives the mover (1) to move towards the side of the second air gap (82). A reverse control current is applied to the first coil winding (41) on the first stator core (31), and the movement direction of the mover (1) is reversed.

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