A near-constant force magnetic spring device based on edge magnetic field compensation and a force value regulation method thereof

Abstract

The application discloses a near-constant force magnetic spring device based on edge magnetic field compensation and a force value regulation method thereof, and belongs to the technical field of electromechanical elements and precision machinery. The device comprises a magnetic circuit pair composed of a mover and a stator coaxially sleeved, the mover is a cylindrical permanent magnet with radial magnetization, the stator is a sleeve of soft magnetic material, the axial length of the sleeve is less than the axial length of the permanent magnet; and an adjusting and connecting mechanism for adjusting the initial insertion depth of the permanent magnet. The application actively shapes the force-displacement curve by regulating the permanent magnet parameters, the radial single-sided air gap, the sleeve length and other magnetic circuit parameters, and combines with the initial insertion depth fine adjustment, so that the approximately constant axial magnetic elastic force can be generated within a wide working stroke. The device is non-contact and non-friction, the force value characteristics can be designed, and is suitable for occasions such as gravity compensation, vibration isolation and constant force suspension.

Description

Technical Field

[0001] This invention belongs to the field of electromechanical components and precision machinery technology, specifically relating to a passive magnetic spring device based on an edge magnetic field compensation mechanism, and its force characteristic design and control method. This device can be used in applications requiring stable elastic force, such as gravity compensation, vibration isolation, and constant force suspension. Background Technology

[0002] As a fundamental component providing elastic restoring force, the performance of springs directly affects the accuracy, reliability, and lifespan of equipment. Traditional mechanical springs rely on material deformation, which leads to problems such as fatigue, friction, fixed stiffness, and poor environmental adaptability.

[0003] Existing magnetic spring technologies, such as multi-pole repulsive types or Halbach array types, while enabling contactless operation, have force-displacement characteristics (such as constant force or linear stiffness) that cannot be changed once manufactured. Furthermore, they are structurally complex, costly to manufacture, and difficult to flexibly adjust output force for different applications. In addition, the force-displacement curves of existing magnetic springs typically exhibit significant nonlinear characteristics, making it difficult to maintain a stable, nearly constant elastic force output over a wide working stroke.

[0004] Therefore, there is a need in the field for a novel magnetic spring device with a relatively simple structure, force characteristics that can be flexibly controlled by design, and the ability to provide a stable and approximately constant elastic force over a wide working stroke. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a near-constant force magnetic spring device based on edge magnetic field compensation and its force value control method. This device can generate a nearly constant axial magnetoelastic force, and its force value and effective working stroke can be precisely controlled through systematic magnetic circuit parameter design, thus flexibly adapting to diverse application needs.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a near-constant force magnetic spring device based on edge magnetic field compensation, comprising:

[0007] The magnetic circuit pair consists of a mover and a stator coaxially fitted together. The mover is a radially magnetized cylindrical permanent magnet with an axial length of Lm; the stator is a sleeve made of a soft magnetic material with high permeability, with an axial length of Ls, where Ls is less than Lm. A radial single-sided air gap g is formed between the permanent magnet and the sleeve. The inner diameter of the sleeve is equal to the sum of the outer diameter of the permanent magnet and twice the radial single-sided air gap g. Since the sleeve length Ls is less than the permanent magnet length Lm, when the permanent magnet is in the middle position of the sleeve, the magnetic fields (edge ​​fields) exposed at both ends outside the sleeve generate axial forces in opposite directions. Under ideal symmetry conditions, the axial forces generated by the edge fields at both ends cancel each other out. When the permanent magnet deviates from the center position, the asymmetry of the edge fields at both ends generates a restoring force, but within a certain range, the rate of change of this restoring force is extremely small, thus forming a near-constant force plateau.

[0008] An adjustment and connection mechanism is used to set and lock the initial axial insertion depth c0 of the permanent magnet in the sleeve and to achieve connection with an external load.

[0009] During axial movement, the permanent magnet is always exposed outside the sleeve at both ends. The mutual compensation effect of the magnetic fields at both ends suppresses the fluctuation of the force value. Furthermore, the size parameters of the magnetic circuit pair are matched with the initial axial insertion depth c0, so that the device generates an approximately constant axial magnetoelastic force within the working stroke.

[0010] Preferably, the permanent magnet is made of neodymium iron boron permanent magnet material.

[0011] Preferably, the ratio of the sleeve length Ls to the permanent magnet length Lm satisfies: 0.5 ≤ Ls / Lm<1.0, so that both ends of the permanent magnet are always exposed outside the sleeve during axial movement, forming a near-constant force platform with mutually compensating edge magnetic fields.

[0012] Preferably, the radial single-sided air gap g is in the range of 0.5mm to 2.0mm, so as to control the slope of the Fz-c curve and control the fluctuation range of the axial magnetoelastic force within the working stroke to within ±15%.

[0013] Preferably, the adjustment and connection mechanism adopts thread adjustment, shim adjustment or slide rail with locking screw to adjust and lock the initial axial insertion depth c0.

[0014] Preferably, when the device is in operation, there is no physical contact between the mover and the stator.

[0015] The present invention also provides a method for controlling the force value of the above-mentioned near-constant force magnetic spring device, comprising the following steps:

[0016] S1: Determine the required working stroke ΔZ, target force value Ftarget, and its allowable fluctuation range based on the target application.

[0017] S2: Establish a parameterized finite element model of the device, perform simulation calculations based on Maxwell's stress tensor integral formula, and use finite element software to perform simulation calculations to obtain the curve of axial magnetoelastic force Fz changing with displacement.

[0018] The Maxwell stress tensor integral formula is as follows:

[0019] Where Br and Bz are the radial and axial components of the magnetic flux density, μ0 is the free permeability, and nr,

[0020] nz is the surface normal component.

[0021] S3: Systematically scan and optimize key parameters such as permanent magnet size and material, radial single-sided air gap g, and sleeve length Ls.

[0022] Specifically, this includes: increasing the volume of the permanent magnet or upgrading its material grade to enhance the magnetic field source strength, thereby shifting the overall force value of the force-displacement curve horizontally upward; adjusting the radial single-sided air gap g to control the force gradient and sensitivity: reducing the air gap to enhance magnetic field coupling to increase the peak force and make the curve steeper, and increasing the air gap to smooth the force-displacement relationship in exchange for a wider near-constant force platform; and setting the sleeve length Ls to be less than the permanent magnet length Lm so that both ends of the permanent magnet are always exposed during movement, utilizing the mutual compensation of the edge magnetic field within the middle stroke to form a near-constant force platform.

[0023] S4: Select a set of parameter combinations that meet the following conditions in the simulation results: on its Fz-c curve, there is a continuous interval with a length greater than the working stroke ΔZ, and within this interval, the value of the axial magnetoelastic force Fz is near the target force value Ftarget and fluctuates the least.

[0024] S5: Manufacture the device according to the optimized parameters, and align the actual working range of the load with the optimal force value platform determined by simulation by adjusting the initial insertion depth c0.

[0025] Preferably, the adjustment process of the initial insertion depth c0 in step S5 is as follows: after the structural parameters of the device are fixed, the permanent magnet is moved axially by rotating the adjusting nut, and the reading of the tension gauge is monitored simultaneously. When the reading reaches the target value Ftarget, the locking fastener completes the position locking, thereby achieving fine adjustment of the output force reference of the device.

[0026] The present invention also provides a design method for a near-constant force magnetic spring device. By using the above-mentioned force control method, the magnetic circuit parameters of the device are systematically designed so that the device provides a stable and nearly constant elastic force over a wide working stroke, which can be used for gravity compensation, vibration isolation or constant force suspension applications.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. Designable near-constant force characteristics: Through the above-mentioned systematic parameter design, a near-constant force-displacement curve that meets specific requirements can be actively "shaped", breaking the limitation of fixed characteristics of traditional springs.

[0029] 2. Non-contact and highly reliable: The moving and stators have no physical contact, no friction or wear, theoretically unlimited lifespan, and require no maintenance.

[0030] 3. Flexible control and strong adaptability: Combining "coarse adjustment of parameter design" and "fine adjustment of initial position", it can flexibly adapt to different force values ​​and stroke requirements, and has high versatility.

[0031] 4. Good environmental robustness: Resistant to high and low temperatures and corrosion, suitable for harsh or special environments. Attached Figure Description

[0032] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0033] Figure 1 This is an exploded three-dimensional structural diagram of the device of the present invention;

[0034] Figure 2 This is a cross-sectional view of the magnetic field generating unit, showing the magnetic field distribution;

[0035] Figure 3 A schematic diagram showing the magnetization direction of a permanent magnet;

[0036] Figure 4 This is a schematic diagram of the adjustment and connection mechanism of the present invention;

[0037] Figure 5 These are the key data of the Fz-c curve obtained from simulation in the embodiments;

[0038] Figure 6 The image shows the force distribution of Fz within a 100mm stroke obtained from the simulation in the example.

[0039] In the diagram: 1. Permanent magnet; 2. Sleeve; 3. Permanent magnet mounting base. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] I. Specific Implementation Methods of the Device Structure

[0042] like Figures 1 to 3 As shown, the near-constant force magnetic spring device provided by the present invention mainly includes two parts: a magnetic circuit pair and an adjustment and connection mechanism.

[0043] (a) Specific structure of magnetic circuit pairs

[0044] The magnetic circuit consists of a mover and a stator coaxially mounted. The mover is a radially magnetized cylindrical permanent magnet 1 (e.g., Figure 3 The magnetization direction is shown, and its axial length is Lm; the stator is a sleeve 2 made of a soft magnetic material with high permeability, and its axial length is Ls, satisfying Ls < Lm. A radial single-sided air gap g is formed between the permanent magnet 1 and the sleeve 2, and the inner diameter of the sleeve 2 is equal to the sum of the outer diameter of the permanent magnet 1 and twice the radial single-sided air gap g.

[0045] Preferably, the permanent magnet 1 is made of neodymium iron boron permanent magnet material with a material grade of N48M or N52. The sleeve 2 is made of a soft magnetic material with high magnetic permeability (such as electrical pure iron, permalloy, or silicon steel sheet) to form a magnetic circuit channel with low magnetic resistance.

[0046] The radial single-sided air gap g between the permanent magnet 1 and the sleeve 2 is preferably in the range of 0.5mm to 2.0mm. By selecting an appropriate air gap value within this range, the slope of the Fz-c curve can be controlled, so that the fluctuation range of the axial magnetoelastic force within the working stroke is controlled within ±15%.

[0047] The ratio of the length Ls of sleeve 2 to the length Lm of permanent magnet 1 preferably satisfies: 0.5 ≤ Ls / Lm < 1.0. This ratio range ensures that both ends of permanent magnet 1 are always exposed outside sleeve 2 during axial movement, utilizing the mutual compensation effect of the edge magnetic fields in the middle stroke to form a stable near-constant force platform. Specifically, when permanent magnet 1 is centered relative to sleeve 2, the axial forces generated by leakage magnetic fields (edge ​​fields) at both ends are equal in magnitude and opposite in direction, theoretically resulting in zero net force. As permanent magnet 1 moves axially, the edge field at one end strengthens and the edge field at the other end weakens, but due to the specific geometric relationship of the magnetic field distribution, the difference between the two changes very little within a certain stroke, thus exhibiting near-constant force characteristics.

[0048] (II) Specific Implementation Methods of Adjustment and Connection Mechanism

[0049] like Figure 4 As shown, the adjustment and connection mechanism is used to set and lock the initial axial insertion depth c0 of the permanent magnet 1 in the sleeve 2, and to achieve connection with the external load. As an optional implementation, the adjustment and connection mechanism can adopt a threaded adjustment method: one end of the permanent magnet 1 is connected to an adjustment screw, which engages with the threaded hole on the fixed bracket. By rotating the adjustment nut or the screw, the permanent magnet 1 is driven to move axially, thereby achieving stepless adjustment of c0; after adjustment, the position is locked by tightening the lock nut.

[0050] As another optional implementation, the adjustment and connection mechanism can adopt a shim adjustment method: by adding or removing shims of different thicknesses set between the end of the permanent magnet 1 and the permanent magnet fixing seat 3, the discrete adjustment of c0 can be achieved; after adjustment, it can be locked by fasteners.

[0051] As another alternative implementation, the adjustment and connection mechanism can be implemented by using a slide rail and locking screws: the end of the permanent magnet 1 is mounted on a linear slide rail, and after sliding axially to the target position, the slider is fixed on the slide rail by locking screws.

[0052] All of the above-described embodiments can achieve the adjustment and locking of c0. Those skilled in the art can select the appropriate adjustment mechanism form according to the actual application scenario.

[0053] (III) Operating characteristics of the device

[0054] When the device is working, there is no physical contact between the permanent magnet 1 (mover) and the sleeve 2 (stator), and the axial magnetoelastic force is generated by the interaction of magnetic fields. Since the two ends of the permanent magnet 1 are always exposed outside the sleeve 2 during the axial movement, a mutual compensation effect of the edge magnetic field is formed, which enables the device to generate an approximately constant axial magnetoelastic force within the working stroke.

[0055] II. Specific Implementation Methods of Force Value Control

[0056] The force control method of the near-constant force magnetic spring device provided by this invention achieves precise control of force-displacement characteristics through systematic magnetic circuit parameter design. Specifically, it includes the following steps:

[0057] S1: Define design objectives

[0058] Determine the required working stroke ΔZ, target force Ftarget, and its allowable fluctuation range based on the target application. For example, for gravity compensation applications, the target force should be slightly greater than the load weight to ensure sufficient compensation force is provided.

[0059] S2: Establishing a parametric finite element model

[0060] Based on Maxwell's stress tensor integral formula, a parametric finite element model of the device is established. The formula is:

[0061]

[0062] Where Bᵣ and Bz are the radial and axial components of the magnetic induction intensity, μ0 is the free permeability, and nᵣ and nz are the surface normal components. The axial magnetoelastic force Fz generated by this device is microscopically described by the Maxwell stress tensor. The resultant force acting on the permanent magnet can be calculated by integrating over its outer surface S. This formula shows that the final output force Fz is the integral result of the magnetic field stress at all points on the surface of permanent magnet 1. Therefore, by changing the physical parameters of the magnetic circuit to "shape" the magnetic field distribution (Bᵣ, Bz) on the surface of permanent magnet 1, precise control of Fz and its relationship with displacement c (Fz = f(c)) can be achieved. In particular, by controlling the ratio of Ls to Lm, the distribution shape of the edge field at both ends can be actively designed, which is the mathematical and physical basis for realizing edge magnetic field compensation. The curve of the axial magnetoelastic force Fz changing with displacement c is obtained by simulation calculation using finite element software (such as ANSYS Maxwell, COMSOL Multiphysics, etc.). During modeling, a two-dimensional axisymmetric model can be used to reduce computational costs based on the axisymmetric characteristics of the device; the magnetization direction of permanent magnet 1 is set to radial, and the material properties of sleeve 2 are set to high permeability soft magnetic material.

[0063] S3: Parameter Scanning and Multi-Objective Optimization

[0064] A systematic scan and multi-objective optimization were performed on key parameters such as the size and material of permanent magnet 1, the radial single-sided air gap g, and the length Ls of sleeve 2. Specifically:

[0065] Permanent Magnet 1 Parameters – Control Force Value Baseline: By increasing the volume (diameter or length) of permanent magnet 1 or upgrading the material grade (e.g., from N48M to N52), the magnetic field source strength can be enhanced, causing the overall force value level of the Fz-c curve to shift upward. This is the main means of controlling the absolute magnitude of the force value.

[0066] Air gap size – controlling force gradient and sensitivity: The force gradient and sensitivity are controlled by adjusting the radial unilateral air gap g. Reducing the air gap enhances magnetic field coupling and significantly increases the peak force, but it makes the force extremely sensitive to changes in displacement, causing the Fz-c curve to steepen. Increasing the air gap weakens the peak force, but it makes the force-displacement relationship smoother, sacrificing some peak force for a wider near-constant force plateau.

[0067] Sleeve 2 dimensions – controlling the formation of the near-constant force platform: By setting the length Ls of sleeve 2 to be less than the length Lm of permanent magnet 1, both ends of permanent magnet 1 are always exposed outside sleeve 2 during movement, and a near-constant force platform is formed by the mutual compensation of the edge magnetic fields in the middle stroke. The length of Ls and the ratio of Ls / Lm directly determine the width and flatness of the near-constant force platform.

[0068] S4: Select the optimal parameter combination

[0069] A set of parameter combinations that meet the following conditions is selected from the simulation results: on its Fz-c curve, there exists a continuous interval with a length greater than the working stroke ΔZ. Within this interval, the value of the axial magnetoelastic force Fz is near the target force value Ftarget and exhibits minimal fluctuation. The physical cause of this interval is that the edge magnetic field formed by the exposed portions at both ends of the permanent magnet generates mutually canceling axial force components during axial movement, thus smoothing the overall output force curve.

[0070] S5: Manufacturing and Fine-tuning

[0071] The device is manufactured based on the optimized parameters. After the device's structural parameters are fixed, the actual working range of the load is aligned with the optimal force value platform determined by simulation by adjusting the initial insertion depth c0. The adjustment process of c0 is as follows: the permanent magnet 1 is moved axially by rotating the adjusting nut, and the reading of the tension gauge or force sensor is monitored simultaneously. When the reading reaches the target value Ftarget, the locking fastener is tightened to complete the position locking, thereby achieving fine adjustment of the device's output force reference.

[0072] III. Preferred Embodiments

[0073] The following describes the implementation of the present invention in detail through a preferred embodiment.

[0074] like Figure 6 As shown in the example: a near-constant force compensation device for a 2.6kg load and a 100mm stroke.

[0075] 1. Design Goals

[0076] Load weight G = 2.6 kg × 9.8 m / s 2 ≈25.5 N. A magnetic spring needs to be designed to provide a compensation force slightly greater than G and as stable as possible within its 100mm working stroke, with a target force value Ftarget≈28 N and a fluctuation requirement of ±15%.

[0077] 2. Parametric Design and Optimization

[0078] Finite element modeling and parameter scanning are performed based on the principle of Maxwell's stress tensor integral formula. The control parameters are selected as follows:

[0079] Permanent magnet 1: To provide sufficient magnetic flux, neodymium iron boron N48M material is selected, with a diameter of 16mm and an axial length Lm = 150mm.

[0080] Air gap g: To obtain a smooth force curve, after simulation and consideration, the single-sided air gap is set to 0.8 mm.

[0081] Sleeve 2: To form a wide platform, the length Ls of sleeve 2 needs to be significantly less than Lm, and is set to 120 mm, with an inner diameter of 17.6 mm (= 16 mm + 2 × 0.8 mm). At this time, Ls / Lm = 0.8, which satisfies the preferred range of 0.5 ≤ Ls / Lm < 1.0.

[0082] 3. Simulation Verification and Result Analysis

[0083] Simulations were performed on the optimized parameters to obtain key data for the Fz-c curve, as follows: Figure 5 As shown, within a 100mm stroke of c = 5mm to 105mm, the magnetic force Fz varies between -26.5N and -32.6N, with a minimum value of 26.5N > 25.5N and an average value of approximately 29.9N, exhibiting a fluctuation range of approximately ±6%. This result fully meets the design target (fluctuation within ±15%), demonstrating that by controlling parameters such as the size of permanent magnet 1, the air gap (0.8mm), and the length of sleeve 2 (120mm), a near-constant force platform with a wide range and high stability was successfully designed, verifying the effectiveness of the edge magnetic field compensation mechanism.

[0084] Compared with mechanical springs of the same specifications, the force fluctuation of the device of the present invention is only ±6% within a stroke of 100mm, while the force of mechanical springs changes linearly with displacement, and the force deviation at the end of the same stroke can reach more than ±50%. Compared with Halbach array type magnetic springs, the device of the present invention only requires a single permanent magnet and a single sleeve. By utilizing the principle of edge magnetic field compensation, the number of parts is reduced by more than 60%.

[0085] 4. Device installation and operating point setting

[0086] After installing the device, the initial insertion depth c0 = 55mm is set by adjusting and connecting the mechanism, so that the 100mm stroke of the load corresponds exactly to the platform area of ​​the simulation verification mentioned above. This device can provide a stable and safe overcompensation force for the load and achieve self-locking protection in the event of a power failure.

[0087] IV. Comparative Experiment

[0088] To verify the effect of sleeve length Ls on the near-constant force platform, simulations were conducted with Ls = 75mm (Ls / Lm = 0.5), Ls = 120mm (Ls / Lm = 0.8), and Ls = 135mm (Ls / Lm = 0.9) while keeping other parameters constant. The results show that when Ls / Lm = 0.5, the width of the near-constant force platform is approximately 60mm, with a force fluctuation of ±8%; when Ls / Lm = 0.8, the platform width is approximately 100mm, with a force fluctuation of ±6%; and when Ls / Lm = 0.9, the platform width is approximately 40mm, with a force fluctuation of ±12%. Therefore, Ls / Lm = 0.8 is the optimal ratio, verifying the rationality of the range 0.5 ≤ Ls / Lm < 1.0, and confirming that the edge magnetic field compensation effect is best within this range.

[0089] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A near-constant force magnetic spring device, characterized in that, include: The magnetic circuit pair consists of a mover and a stator coaxially sleeved together; wherein the mover is a radially magnetized cylindrical permanent magnet with an axial length of Lm; the stator is a sleeve made of a soft magnetic material with high permeability with an axial length of Ls, and Ls < Lm. A radial single-sided air gap g is formed between the permanent magnet and the sleeve, and the inner diameter of the sleeve is equal to the sum of the outer diameter of the permanent magnet and twice the radial single-sided air gap g; An adjustment and connection mechanism is used to set and lock the initial axial insertion depth c0 of the permanent magnet in the sleeve, and to achieve connection with an external load; During axial movement, the permanent magnet is always exposed outside the sleeve at both ends, forming mutually compensating edge magnetic fields. The size parameters of the magnetic circuit pair are matched with the initial axial insertion depth c0, so that the device generates an approximately constant axial magnetoelastic force within the working stroke.

2. The near-constant force magnetic spring device according to claim 1, characterized in that, The permanent magnet is made of neodymium iron boron permanent magnet material.

3. The near-constant force magnetic spring device according to claim 1, characterized in that, The ratio of the sleeve length Ls to the permanent magnet length Lm satisfies: 0.5 ≤ Ls / Lm < 1.0, so that both ends of the permanent magnet are always exposed outside the sleeve during axial movement, forming a near-constant force platform with mutually compensating edge magnetic fields.

4. The near-constant force magnetic spring device according to claim 1, characterized in that, The radial single-sided air gap g is in the range of 0.5mm to 2.0mm to control the slope of the Fz-c curve, so that the fluctuation range of the axial magnetoelastic force within the working stroke is controlled within ±15%.

5. The near-constant force magnetic spring device according to claim 1, characterized in that, The adjustment and connection mechanism uses threaded adjustment, shim adjustment, or slide rail with locking screw to adjust and lock the initial axial insertion depth c0.

6. The near-constant force magnetic spring device according to claim 1, characterized in that, When the device is in operation, there is no physical contact between the mover and the stator.

7. A method for force value control of a near-constant force magnetic spring device based on edge magnetic field compensation, characterized in that, Includes the following steps: S1: Determine the required working stroke ΔZ, target force value Ftarget, and its allowable fluctuation range based on the target application; S2: Establish a parameterized finite element model of the device, perform simulation calculations based on Maxwell's stress tensor integral formula, use finite element software for simulation calculations, and obtain the curve of axial magnetoelastic force Fz changing with displacement. S3: Systematically scan and optimize key parameters such as permanent magnet size and material, radial single-sided air gap g, and sleeve length Ls; S4: Select parameter combination based on edge magnetic field compensation principle: Select a set of parameter combinations that meet the following conditions in the simulation results: On its Fz-c curve, there is a continuous interval with a length greater than the working stroke ΔZ, and within this interval, the value of the axial magnetoelastic force Fz is near the target force value Ftarget and the fluctuation is minimal; S5: Manufacture the device according to the optimized parameters, and align the actual working range of the load with the optimal force value platform determined by simulation by adjusting the initial insertion depth c0.

8. The force control method according to claim 7, characterized in that, The parameter scanning and optimization described in step S3 specifically includes: By increasing the volume of the permanent magnet or upgrading the material grade to enhance the magnetic field source strength, the overall force value of the force-displacement curve is horizontally shifted upward. The force gradient and sensitivity are controlled by adjusting the radial single-sided air gap g: reducing the air gap enhances magnetic field coupling to increase the peak force and make the curve steeper, while increasing the air gap makes the force-displacement relationship smoother in exchange for a wider near-constant force platform. By setting the sleeve length Ls to be less than the permanent magnet length Lm, the two ends of the permanent magnet are always exposed during movement, and a near-constant force platform is formed by the mutual compensation of the edge magnetic fields in the middle stroke.

9. The force control method according to claim 7, characterized in that, The adjustment process of the initial insertion depth c0 in step S5 is as follows: After the structural parameters of the device are fixed, the permanent magnet is moved axially by rotating the adjusting nut, and the reading of the tension gauge is monitored simultaneously. When the reading reaches the target value Ftarget, the locking fastener is locked to complete the position locking, thereby achieving fine adjustment of the output force reference of the device.

10. A design method for a near-constant force magnetic spring device, characterized in that, The force control method described in any one of claims 7 to 9 is used to systematically design the magnetic circuit parameters of the device using an edge magnetic field compensation mechanism, so that the device provides a stable and approximately constant elastic force over a wide working stroke, for use in gravity compensation, vibration isolation or constant force suspension applications.

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