Voice coil motor, execution device and control method

Abstract

This invention discloses a voice coil motor, relating to the field of voice coil motor technology. It includes a stator assembly employing a superconducting coil, a mover assembly, and a flexible guide mechanism connected between the stator and mover assemblies. The flexible guide mechanism comprises at least two helical thin-plate flexible elements, with the inner ring of each element connected to the stator assembly and the outer ring connected to the mover assembly. This constraint restricts the mover assembly to only having a single degree of freedom of motion along a single axis. This invention achieves low resistance characteristics in low-temperature environments through the superconducting coil, significantly reducing heat loss during current conduction and increasing the motor's output force density. Simultaneously, the flexible guide mechanism replaces traditional bearings, ensuring the motor operates under frictionless, contactless, and lubrication-free conditions, thereby improving high-frequency response and precise positioning capabilities. This design is not only suitable for extreme environments such as low temperatures and vacuum, but also possesses high precision, long lifespan, and high stability.

Description

Technical Field

[0001] This invention relates to the field of precision automation equipment technology, specifically to a voice coil motor, an actuator, and a control method. Background Technology

[0002] Voice coil motors (VCMs) are widely used in precision positioning due to their simple structure, high thrust density, and fast dynamic response. However, traditional VCMs face three bottlenecks when dealing with extreme environments and high-frequency, high-thrust demands, which limit further performance improvements.

[0003] First, there is the issue of resistive heat loss in copper coils. Traditional copper winding coils have a significant DC resistance. Under high-frequency, high-current conditions, Joule heating increases with the square of the current, causing severe heat accumulation. In environments with limited heat dissipation, such as vacuum or low-temperature environments, overheating is particularly prominent. This can lead to thermal drift affecting positioning accuracy, or even insulation failure or demagnetization of permanent magnets, severely limiting the motor's continuous output force and upper limit of operating frequency.

[0004] Second, there is the contradiction between the environmental adaptability and performance of the guiding mechanism. High-frequency motion requires lightweight movers and a guiding mechanism with high rigidity, frictionless operation, and low wear. Traditional ball bearings or sliding bearings have inherent defects such as clearance, friction, and lubrication dependence. In ultra-high vacuum environments, they can contaminate the cavity due to degassing, and in extremely low temperature environments, they face the risk of failure such as lubricant solidification and cold shrinkage jamming, making them unsuitable for the above extreme working conditions. Although existing flexible hinges (such as parallel leaf springs and bridge hinges) can eliminate friction, their anisotropic stiffness characteristics are limited, making it difficult to simultaneously meet the dual requirements of low axial stiffness (ensuring large stroke and high-frequency motion) and high radial stiffness (resisting the lateral magnetic attraction caused by magnetic field asymmetry), which is particularly prominent in strong magnetic field motors.

[0005] Third, there is an inherent contradiction between thrust enhancement and high-frequency targets. Increasing output thrust usually requires increasing the drive current or enhancing the air gap magnetic field density. The former leads to increased heat generation, while the latter often requires a larger and heavier magnetic circuit structure. Both will increase the mass of the mover or increase the heat dissipation requirements, thereby lowering the first-order natural frequency of the system, which contradicts the goal of achieving high-frequency response and creates a vicious cycle of performance trade-offs.

[0006] While there are existing explorations of applying high-temperature superconducting (HTS) materials to motor coils, there is still no complete solution that systematically integrates superconducting coil technology with mechanical structures that adapt to extreme environments and meet the requirements of high-frequency and high-rigidity guidance. In particular, there is still a lack of specialized guidance designs for the huge radial magnetic force generated under superconducting high-current conditions. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-frequency, high-thrust voice coil motor and actuator based on a high-temperature superconducting coil and a spiral thin-film flexible guiding mechanism. This invention combines the zero-resistance characteristics of superconductivity with an innovative spiral flexible guiding structure to achieve ultra-high thrust output under extremely low heat dissipation conditions. Furthermore, by utilizing a high-rigidity, frictionless guiding mechanism and a lightweight mover design, it significantly improves the motor's operating frequency and dynamic response capability, while ensuring long-term reliable operation in extreme environments such as low temperatures and vacuum.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a voice coil motor, comprising: The stator assembly includes a back iron frame, a permanent magnet array fixed within the back iron frame, and a fixedly mounted superconducting coil. The permanent magnet array generates a static magnetic field in the region where the superconducting coil is located. The mover assembly includes a mover frame and a drive magnet fixed thereon, the drive magnet interacting with the permanent magnet array of the stator assembly. A flexible guide mechanism connects the stator assembly and the mover assembly. The flexible guide mechanism includes at least two helical thin-plate flexible elements. The inner ring of each helical thin-plate flexible element is connected to the mover assembly, and the outer ring is connected to the stator assembly, constraining the mover assembly to have only one degree of freedom of motion along a single axis. By combining the superconducting coil and the helical flexible guide mechanism, the motor can maintain efficient and frictionless operation in extreme environments such as low temperature and vacuum, while providing high torque and high-frequency response. The flexible guide mechanism provides a single degree of freedom of motion, ensuring precise axial movement of the mover and preventing radial offset or contact, maintaining precise control.

[0009] Preferably, the superconducting coil is wound with high-temperature superconducting tape, and the coil has a solenoid configuration. Preferably, the superconducting coil is wound with rare-earth barium copper oxide (ReBCO) tape. Superconducting coils wound with rare-earth barium copper oxide (ReBCO) material have extremely low resistance, can carry extremely large currents at low temperatures, and generate almost no heat. The solenoid configuration design avoids the problem of current passing through the contact points, reduces energy loss and quench risk, thereby improving motor efficiency.

[0010] Preferably, the width of the superconducting strip is no greater than 3 mm. Limiting the width of the superconducting strip helps reduce strain during winding, thereby improving coil stability and preventing material deformation and quench loss. Furthermore, the use of narrow strips helps improve the overall performance of the coil, reduces its volume and weight, and thus increases the thrust density of the motor.

[0011] Preferably, the spiral sheet flexible component is machined from a single flexible metal sheet. The design of the spiral sheet flexible component provides strong radial rigidity and axial flexibility, allowing the mover to move freely in the axial direction, while effectively resisting radial magnetic attraction and motion deviations caused by assembly errors. This design greatly improves the accuracy and stability of the motor.

[0012] Preferably, the helical thin-sheet flexible component has a stiffness of less than 5 N / mm in the axial direction of motion and a radial stiffness greater than 100 N / mm perpendicular to the axial direction of motion. By setting different stiffnesses in the axial and radial directions, the helical flexible guide mechanism can provide very low resistance in the axial direction, allowing the mover to move easily, while providing extremely high support stiffness in the radial direction to prevent the mover from shifting due to radial magnetic attraction or other factors. This difference in stiffness optimizes the frequency response of the motor and ensures stability under high-frequency operation.

[0013] Preferably, the driving magnet on the mover assembly is a permanent magnet, and the permanent magnet array on the stator assembly, together with the back iron frame, constitutes a magnetic circuit for providing a static air gap magnetic field. By using permanent magnets as the driving magnets, combined with the optimized design of the back iron frame, a stable and powerful static magnetic field can be generated, thereby improving the motor's output force and performance. The optimized design of the magnetic circuit enhances the uniformity and density of the magnetic field, ensuring efficient motor operation.

[0014] On the other hand, the present invention also provides a high-frequency precision actuator, including the aforementioned voice coil motor and a tool head connected to the mover assembly, the tool head being an execution terminal for precision machining, positioning, or measurement. This actuator utilizes the voice coil motor to drive the tool head for high-precision machining, positioning, or measurement. Combining the high-frequency response and high-thrust output of the voice coil motor, precision control tasks can be accomplished.

[0015] Preferably, the entire device is encapsulated in a cryogenic environment that maintains the superconducting coil below the critical temperature.

[0016] The present invention also provides a control method for a voice coil motor, comprising the steps of: placing the entire voice coil motor in a low-temperature environment to cool the superconducting coil to a superconducting state; applying a driving current to the superconducting coil and using the axial flexibility of the helical thin sheet flexible member to guide the mover assembly to perform high-frequency reciprocating linear motion, while relying on the high radial stiffness of the helical thin sheet flexible member to maintain motion accuracy.

[0017] Compared with the prior art, the present invention has the following significant technical effects: 1. High thrust and low heat dissipation. The ReBCO high-temperature superconducting coil has a DC resistance close to zero in the superconducting state, and can carry a drive current of tens of amperes while generating only milliwatts of heat. Combined with a high-strength permanent magnet circuit design, it can generate a continuous thrust of hundreds of Newtons in a compact volume, with a thrust density far exceeding that of traditional copper-wound motors, fundamentally solving the thermal management problem in extreme environments.

[0018] 2. High frequency and high response. The lightweight mover design, combined with the extremely low axial stiffness of the helical flexible guide mechanism, significantly improves the first-order axial natural frequency of the system; the near-zero inductance of the superconducting coil shortens the drive current settling time, further enhancing the electrical response speed, and comprehensively realizing the high-frequency reciprocating motion capability of the system.

[0019] 3. High precision and high reliability. The spiral flexible guide mechanism is a fully solid-state, non-contact design, with no friction, no gaps, and no need for lubrication. The repeatability and positioning accuracy can reach the sub-micron level. Its inherent low-temperature mechanical stability makes it perfectly compatible with extreme environments such as liquid helium temperature range (4.2K), liquid nitrogen temperature range (77K), ultra-high vacuum, and strong radiation. Its theoretical lifespan is not limited by mechanical wear.

[0020] 4. High radial stiffness and anti-interference. The high radial and torsional stiffness of the helical flexible component enables the actuator to effectively resist external vibration interference and strong internal lateral magnetic force, ensuring the purity of motion under high thrust conditions, which is crucial for precision positioning applications.

[0021] 5. Compact structure and high integration. The flexible guiding mechanism is highly integrated with the motor body, and the helical flexible component also serves as a structural support component, eliminating the need for an independent guide rail and achieving miniaturization and weight reduction of the entire actuator.

[0022] The technical solution of the present invention will be further described in detail below through embodiments. Attached Figure Description

[0023] Figure 1 This is an overall schematic diagram of the voice coil motor provided by the present invention; Figure 2 Modal simulation results of the voice coil motor provided by this invention; Figure 3 Modal simulation results of the voice coil motor provided for this invention (II); Figure 4 The third modal simulation result of the voice coil motor provided for this invention; Figure 5 The fourth modal simulation result of the voice coil motor provided for this invention; Figure 6 It is the current-voltage curve of the ReBCO coil inside the motor; Figure 7 It is the current-output force curve of the motor.

[0024] Figure Labels 1. Stator assembly; 2. Mover assembly; 3. Flexible guide mechanism. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present application, the technical solutions in specific embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by those skilled in the art.

[0026] The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0027] The XYZ axis coordinates and the terms "up," "down," "left," and "right" used are used to represent changes in the relative positions between movable parts, not their absolute positions in space. When the device itself changes direction, the absolute position of the object being described changes accordingly, and its direction of movement in space may or may not change. However, the direction of the relative position change between two movable parts (such as the vertical direction) remains unchanged.

[0028] Example 1 like Figure 1 As shown, the voice coil motor of the present invention has a coaxial cylindrical structure and is composed of three main parts: stator assembly 1, flexible guide mechanism 3, and mover assembly 2. The three parts are assembled in sequence from the inside to the outside in the radial direction. The stator assembly 1 and the mover assembly 2 are elastically connected through the flexible guide mechanism, and together they form a highly integrated direct drive linear actuator.

[0029] Stator assembly 1 is the fixed part of the motor, serving the dual function of establishing a static working magnetic field and fixing the superconducting coil. It includes a back iron frame, a permanent magnet array, and the superconducting coil. The back iron frame, made of a high-permeability soft magnetic material, is cylindrical and forms the main structural component of the stator assembly. Both ends of the back iron frame are closed by lateral frames, which are axially secured together by several back iron connecting rods, forming a rigid cage structure that provides a complete magnetic circuit and serves as the internal load-bearing skeleton of the entire motor. The permanent magnet array is fixedly mounted on the back iron frame, evenly distributed along the circumference, establishing a high-intensity static magnetic field dominated by the radial component in the axial air gap region. The permanent magnet array can be arranged using a Halbach array or a symmetrical distribution of multiple pairs of magnetic poles to improve the amplitude and uniformity of the air gap magnetic flux density, thereby increasing the thrust coefficient. The superconducting coil is fixedly mounted on the outer wall of the back iron frame, located axially in the central region of the air gap magnetic field established by the permanent magnet array. The superconducting coil is wound into a solenoid configuration using high-temperature superconducting tape. There are no electrical joints inside the coil, and both ends are led out to an external driving power source through low-temperature compatible current leads.

[0030] The mover assembly 2 is the moving part of the motor, serving as both the thrust-bearing and output end. It includes the mover frame and the drive magnet. The mover frame is made of a non-magnetic, lightweight material and serves as the mounting carrier for the various mover components and the thrust output connector. One axial end of the frame has an interface for connecting to an external load or tool head. The selection of the mover frame material must strike a balance between structural strength and minimizing the mover mass to maximize the system's first-order axial natural frequency. The drive magnet is mounted on the mover frame and, together with the stator-side back iron frame and permanent magnet array, forms a closed magnetic circuit. Preferably, the drive magnet uses two permanent magnets clamping the magnetic core with their N and S poles facing each other, concentrating and enhancing the magnetic flux density in the air gap. All mover components are axially fastened together by a central threaded rod.

[0031] The flexible guide mechanism 3 functions to constrain the motion degrees of freedom of the mover assembly through frictionless and gapless pure elastic deformation. The flexible guide mechanism 3 is composed of a spiral thin-sheet flexible component, connecting the mover assembly 2 and the stator assembly 1 to form an elastic suspension structure. The spiral thin-sheet flexible component is made from a single elastic metal sheet through integrated precision machining. Its shape is a planar spiral structure with multiple spiral arms. The inner ring is fixed to the stator assembly 1 by fasteners, and the outer ring is fixed to the mover assembly 2 by fasteners. In this embodiment, it is fixed axially at both ends of the stator assembly 2.

[0032] The mechanical properties of the helical sheet flexible component are determined by its anisotropic stiffness. Along the motor axis, the helical arm exhibits low stiffness in bending deformation mode, allowing the mover to move freely axially under driving force, while providing guiding constraint through elastic restoring force. In the radial plane perpendicular to the axial direction, the helical arm exhibits extremely high stiffness in tensile and in-plane shear modes, effectively resisting the lateral magnetic attraction force on the mover caused by magnetic field asymmetry or assembly errors, maintaining the coaxial accuracy of the mover and stator, and preventing mechanical interference. These anisotropic stiffness characteristics can be quantitatively designed by adjusting parameters such as the number of helical arms, sheet thickness, number of helical rotations, and effective arm length. Figures 2 to 5 As shown, simulations can reveal the deformation of the two spiral sheets under different directional forces.

[0033] When an external driving power supply applies current to the superconducting coil, the current-carrying conductor in the superconducting coil experiences an axial Lorentz force in the radial air gap magnetic field generated by the moving permanent magnet, following the relationship... Since the superconducting coil is fixed to the stator, the reaction force of the Lorentz force acts on the mover driving magnet through magnetic field coupling, causing the mover assembly to displace axially. The helical thin-sheet flexible component allows for axial displacement of the mover while maintaining the coaxial accuracy of the mover with high radial stiffness. By controlling the magnitude and direction of the driving current, the output thrust and direction of motion of the mover can be precisely adjusted, achieving closed-loop control of the mover's displacement or force.

[0034] Example 2 In this embodiment, the back iron frame is made of pure iron. The two ends of the frame are closed by two annular lateral frames, and the lateral frames are axially fastened by several evenly distributed back iron connecting rods. The permanent magnet array consists of two pairs of neodymium iron boron (NdFeB) permanent magnets (grade N45), which are symmetrically installed on the inner wall of the back iron frame along the circumference. The N and S poles are arranged radially, establishing a radial working magnetic field with an average magnetic flux density of about 0.8T in an air gap with an inner diameter of 52mm.

[0035] The superconducting coil is wound into a solenoid shape using ReBCO high-temperature superconducting tape with a width of 2 mm and a thickness of 0.1 mm. The inner radius of the coil is 44 mm, the outer radius is 50.5 mm, and it is wound in 21 layers with a total of 198 turns. The coil is mounted on a back iron after being vacuum impregnated and cured with epoxy resin. The two ends of the coil are led out through copper-superconducting transition cryogenic current leads, with intermediate thermal anchor points on the leads to reduce heat leakage.

[0036] The mover frame is made of 7075 high-strength aluminum alloy. The drive magnet consists of two neodymium iron boron permanent magnets clamping a low-carbon steel magnetic core with their N and S poles facing each other. It is axially pressed and fixed to the mover frame by an M10 central threaded rod. The total mass of the mover assembly is 0.675 kg.

[0037] The flexible guide mechanism consists of two identical helical thin-plate flexible components symmetrically mounted at both ends of the mover assembly. Each helical thin-plate flexible component is made of beryllium bronze sheet by wire cutting, with an outer diameter of 100mm. The specific geometric parameters are as follows: number of helical arms 4, evenly distributed at 90° angles; sheet thickness 0.8mm; number of helical rotations 0.85 turns; effective arm length (Leff) 72mm; offset arm width (Woff) 7.4mm.

[0038] The inner ring connection area of ​​each spiral thin flexible component is fixed to the end flange of the mover assembly 2 by four M4 bolts, and the outer ring connection area is fixed to the lateral frame of the stator assembly 1 by eight M3 bolts. The above assembly method allows the mover assembly to retain only a single translational degree of freedom along the motor axis (X direction), while the other five degrees of freedom are elastically constrained.

[0039] To address the varying stiffness ratio requirements across different application scenarios, this invention also provides parameters for 3-arm and 5-arm solutions. A detailed comparison is shown in the table below.

[0040] Table 1: Optimized dimensions of the spiral flexible component

[0041] As shown in the figure, finite element modal simulation was performed on the above embodiment. The results show that the first-order mode (Mode 1) is the overall translational mode of the mover along the axial direction, with a natural frequency of 17.1 Hz. The second to fourth-order modes are the radial oscillation and torsional modes of the mover, respectively, with natural frequencies of 120 Hz, 128 Hz, and 255 Hz, which are all much higher than the first-order axial mode. The frequency ratio of the axial mode to the lowest radial mode is approximately 1:7, which fully verifies the anisotropic design goal of the helical flexible guide mechanism of "axial flexibility and radial stiffness," indicating that the mover motion has good purity and stability in the axial driving frequency range below 17.1 Hz.

[0042] like Figure 6-7 As shown, a static thrust test was conducted on the motor under a liquid nitrogen cooling environment of 77K. The experimental results show that the output thrust has a good linear relationship with the drive current, and the thrust coefficient is approximately 13.5 N / A. When the drive current is 26A, the continuous output thrust of the motor is approximately 350 N, which is in good agreement with the theoretical design value.

[0043] Under the same test conditions, the experimentally measured terminal voltage of the superconducting coil at a working current of 26A was lower than the lower limit of measurement resolution, corresponding to a resistance heat dissipation of less than 1mW. Compared with the tens of watts of Joule heat generated by a copper coil with the same winding parameters at the same current, the heat dissipation is reduced by more than four orders of magnitude, fully demonstrating the fundamental advantage of the zero-resistance characteristic of superconductivity in environments with extreme thermal management constraints.

[0044] Finally, it should be noted that the described embodiments are merely some, not all, of the embodiments of the present invention. Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents; that is, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A voice coil motor, characterized in that, include: The stator assembly includes a back iron frame, a permanent magnet array fixed within the back iron frame, and a fixedly mounted superconducting coil, wherein the permanent magnet array is used to generate a static magnetic field in the region where the superconducting coil is located. A mover assembly includes a mover frame and a drive magnet fixed thereon, the drive magnet interacting with the permanent magnet array of the stator assembly; A flexible guiding mechanism is connected between the stator assembly and the mover assembly. The flexible guiding mechanism includes at least two helical thin-plate flexible elements. The outer ring of the helical thin-plate flexible element is connected to the mover assembly, and the inner ring is connected to the stator assembly. The flexible guiding mechanism is used to constrain the mover assembly to have only one degree of freedom of motion along a single axis.

2. The voice coil motor according to claim 1, characterized in that, The superconducting coil is made of high-temperature superconducting tape and has a solenoid configuration.

3. The voice coil motor according to claim 2, characterized in that, The superconducting coil is made of rare earth barium copper oxide tape.

4. The voice coil motor according to claim 2 or 3, characterized in that, The width of the strip is no more than 3mm.

5. The voice coil motor according to claim 1, characterized in that, The spiral thin-sheet flexible component is made from a single flexible metal sheet.

6. The voice coil motor according to claim 1 or 5, characterized in that, The helical sheet flexible component has a stiffness of less than 5 N / mm in the axial direction of motion and a radial stiffness greater than 100 N / mm perpendicular to the axial direction of motion.

7. The voice coil motor according to claim 1, characterized in that, The driving magnet on the mover assembly is a permanent magnet, and the permanent magnet array on the stator assembly, together with the back iron frame, constitutes a magnetic circuit for providing a static air gap magnetic field.

8. A high-frequency precision actuator, characterized in that, Includes a voice coil motor as described in any one of claims 1-7, and a tool head connected to the mover assembly, the tool head being an execution terminal for precision machining, positioning, or measurement.

9. The high-frequency precision execution device according to claim 8, characterized in that, The entire device is encapsulated in a cryogenic environment that keeps the superconducting coil below the critical temperature.

10. A control method based on the voice coil motor of claim 1, characterized in that, The steps include: placing the voice coil motor as a whole in a low-temperature environment to cool the superconducting coil to a superconducting state; applying a driving current to the superconducting coil and using the axial flexibility of the spiral thin sheet flexible member to guide the mover assembly to perform high-frequency reciprocating linear motion, while relying on the high radial stiffness of the spiral thin sheet flexible member to maintain motion accuracy.

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