Tactile feedback electromagnetic actuator based on ferrofluid

Abstract

The invention discloses a tactile feedback electromagnetic actuator based on ferrofluid. The performance of the electromagnetic actuator is enhanced by using the ferrofluid. The high thermal conductivity of the ferrofluid is beneficial to heat dissipation, and the parametric magnetic performance of the ferrofluid reduces the magnetic resistance of an electromagnetic circuit, so that the generated force is increased. Due to the fact that the heat dissipation problem is solved, the tactile feedback electromagnetic actuator based on the ferrofluid can be compact in layout, the size of the tactile feedback electromagnetic actuator can be designed to be equal to the size of a small handheld object or the fingertip of an adult, and the tactile feedback electromagnetic actuator can be easily integrated into various devices. In addition, two axially aligned permanent magnets and a copper electromagnetic coil are wound around the high-permeability electromagnetic iron core. According to the design, larger force is generated under the condition that the size is not increased, and compared with a traditional electromagnetic actuator, the electromagnetic actuator can be operated in a wider frequency range and can generate continuous force, instantaneous force or oscillating force, and the wide sensing capacity of human touch sense is simulated.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic actuators, and in particular relates to a tactile feedback electromagnetic actuator based on ferromagnetic fluid. Background Art

[0002] The development of high-fidelity tactile feedback technology is challenged by the tactile sensing properties of human skin. Existing tactile feedback actuators can produce oscillatory motion when driven, but cannot provide continuous or low-frequency force and displacement, which are common sensations during continuous or transient contact with familiar surfaces.

[0003] When the tactile feedback actuators in the prior art need to be integrated into various devices, such as mobile computing devices, game controllers, wearable electronic devices, and virtual reality interfaces, they are limited by the heat transfer effect and cannot be compact enough in structure, resulting in large size and mass. In addition, the tactile feedback actuators in the prior art also generally have the problem of insufficient frequency response range. Summary of the invention

[0004] The purpose of the present invention is to provide a tactile feedback electromagnetic actuator based on ferromagnetic fluid to solve the problems in the prior art that the tactile feedback actuator has an insufficiently compact structure and an insufficiently wide frequency response range.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0006] A tactile feedback electromagnetic actuator based on ferromagnetic fluid, comprising an actuator housing with an open upper portion; an actuator and a magnetic circuit are arranged inside the actuator housing;

[0007] The magnetic circuit comprises a first permanent magnet coaxially fixedly arranged at the bottom of the actuator housing, an annular electromagnet core is coaxially fixedly arranged on the first permanent magnet; a coil is sleeved on the outer ring of the electromagnet core;

[0008] The upper end of the actuator housing is covered with an elastic membrane, and the lower surface of the elastic membrane is coaxially connected to an elastic cavity with a through hole at the lower part; when the elastic cavity is in a natural state, the lower end surface is in contact with the upper end surface of the electromagnet core;

[0009] The actuator comprises a linear bearing and a high magnetic index guide plate, a second permanent magnet and a connecting plate arranged in sequence from top to bottom inside the elastic cavity; the upper portion of the linear bearing passes through the through hole of the elastic cavity and is fixedly connected to the connecting plate, and the remaining portion of the linear bearing slides into the inner ring of the electromagnet core;

[0010] The first permanent magnet and the second permanent magnet are arranged opposite to each other with the same magnetic pole;

[0011] The actuator housing is provided with a power interface, and an external power source can apply current to the coil through the power interface;

[0012] The actuator housing is encapsulated with ferromagnetic fluid.

[0013] The present invention also has the following features:

[0014] Furthermore, the elastic membrane and the elastic cavity are made of Ecoflex00-30 platinum-cured silicone.

[0015] Furthermore, the thickness of the elastic membrane and the wall thickness of the elastic cavity are both 0.5 mm.

[0016] Furthermore, the actuator housing, the electromagnet core and the high magnetic rate guide plate are all made of Permalloy 80 alloy.

[0017] Furthermore, a replacement hole is provided on the actuator housing, and a matching seal is detachably installed in the replacement hole.

[0018] Furthermore, the first permanent magnet and the second permanent magnet are permanent neodymium iron boron magnets.

[0019] Furthermore, the linear bearing is a hollow structure.

[0020] Furthermore, the actuator housing and the elastic cavity are both cylindrical;

[0021] The upper end surface of the actuator housing is provided with a circle of fixed ring groove, and the outer ring of the elastic membrane is fixedly clamped into the interior of the fixed ring groove.

[0022] Compared with the prior art, the present invention has the following technical effects:

[0023] (I) The ferrofluid-based tactile feedback electromagnetic actuator of the present invention uses ferrofluid to enhance the performance of the electromagnetic actuator. The high thermal conductivity of the ferrofluid helps to dissipate heat, and its parametric magnetic properties reduce the magnetic resistance of the electromagnetic circuit, thereby increasing the force generated. In addition, the rheological properties of the ferrofluid help to improve dynamic performance and reduce mechanical resonance by lubricating motion and providing viscous damping. The use of ferrofluid not only improves the force output, but also helps to disperse the heat generated by resistive and inductive heating. Since the heat dissipation problem has been solved, the ferrofluid-based tactile feedback electromagnetic actuator of the present invention can be compactly arranged, and its size can be designed to be comparable to that of a small handheld object or an adult fingertip, so that it can be easily integrated into various devices.

[0024] In addition, the ferrofluid-based tactile feedback electromagnetic actuator of the present invention adopts an electromagnetic device, including two axially aligned permanent magnets and a copper electromagnetic coil wound around a high magnetic permeability electromagnetic core. This design generates greater force without increasing the size, and can operate over a wider frequency range (from 0 to 1000 Hz) than traditional electromagnetic actuators, enabling it to generate continuous force, instantaneous force or oscillating force, simulating the wide range of human tactile perception.

[0025] (II) The ferrofluid-based tactile feedback electromagnetic actuator of the present invention employs a fiber-reinforced elastic membrane to provide the necessary restoring force, and a special hollow linear bearing is designed to limit radial displacement and out-of-plane rotation, thereby improving the accuracy and reliability of the actuator.

[0026] In addition, the present invention optimizes the selection of materials to ensure overall performance and durability. Ecoflex 00-30 platinum-cured silicone is used as the material of the fiber-reinforced elastic film, and Permalloy 80 alloy is used as the material required for the high magnetic permeability plate, high magnetic permeability shell, and high magnetic permeability electromagnet core components.

[0027] In general, the ferrofluid-based tactile feedback electromagnetic actuator constructed by the present invention improves the heat dissipation efficiency and output force while reducing the magnetic resistance of the electromagnetic circuit, can simulate human touch within a wide frequency range, and the optimization of material selection further ensures the performance and durability of the actuator. Its small size is suitable for integration into a variety of portable devices, and is suitable for large-scale use and promotion in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a cross-sectional view of a ferrofluid-based tactile feedback electromagnetic actuator of the present invention;

[0029] Figure 2 This is a structural breakdown diagram of the ferrofluid-based tactile feedback electromagnetic actuator of the present invention;

[0030] Figure 3 It is a schematic diagram of the structure of the actuator housing in the present invention;

[0031] Figure 4 It is a schematic diagram of the working principle of the ferrofluid-based tactile feedback electromagnetic actuator of the present invention.

[0032] The meanings of the numbers in the figure are: 1. actuator housing; 2. first permanent magnet; 3. electromagnet core; 4. coil; 5. elastic membrane; 6. elastic cavity; 7. linear bearing; 8. high magnetic guide plate; 9. second permanent magnet; 10. connecting plate; 11. power interface; 12. replacement hole; 13. seal; 14. fixed ring groove. DETAILED DESCRIPTION

[0033] It should be noted that, unless otherwise specified, all components in the present invention are components known in the prior art. For example, the linear bearings are known and commonly used linear bearings.

[0034] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0035] like Figure 1 As shown, a tactile feedback electromagnetic actuator based on ferromagnetic fluid includes an actuator housing 1 with an open upper portion; an actuator and a magnetic circuit are arranged inside the actuator housing 1;

[0036] The magnetic circuit includes a first permanent magnet 2 coaxially fixedly arranged at the bottom of the actuator housing 1, and a ring-shaped electromagnet core 3 coaxially fixedly arranged on the first permanent magnet 2; a coil 4 is arranged on the outer ring of the electromagnet core 3;

[0037] The upper end of the actuator housing 1 is covered with an elastic membrane 5, and the lower part of the elastic membrane 5 is connected to an elastic cavity 6 with a through hole at the lower part; when the elastic cavity 6 is in a natural state, the lower end surface is in contact with the upper end surface of the electromagnet core 3;

[0038] The actuator includes a linear bearing 7 and a high magnetic index guide plate 8, a second permanent magnet 9 and a connecting plate 10 which are arranged in order from top to bottom inside the elastic cavity 6; the upper portion of the linear bearing 7 passes through the through hole of the elastic cavity 6 and is fixedly connected to the connecting plate 10, and the remaining portion of the linear bearing 7 slides into the inner ring of the electromagnet core 3;

[0039] The first permanent magnet 2 and the second permanent magnet 9 are arranged opposite to each other at the same level;

[0040] The actuator housing 1 is provided with a power interface 11, and an external power source can apply current to the coil 4 through the power interface 11;

[0041] The actuator housing 1 is encapsulated with ferromagnetic fluid, which is encapsulated between the magnetic circuit, the elastic membrane 5 and the elastic cavity 6 to provide damping and heat transfer. The ferromagnetic fluid has high thermal conductivity and can improve the overall thermal performance.

[0042] When the ferromagnetic fluid-based tactile feedback electromagnetic actuator of this embodiment is in use, the first permanent magnet 2 and the second permanent magnet 9 have the same polarity facing each other, generating a static repulsive force. The first permanent magnet 2 is embedded in the actuator housing 1, and the second permanent magnet 93 is suspended at the far end and located inside the elastic cavity 6.

[0043] The coil 4 is wound around the electromagnet core 3 and placed between the first permanent magnet 2 and the second permanent magnet 9, so that it contacts the first permanent magnet 2 and maintains a certain gap with the suspended and floating second permanent magnet 9. When the coil 4 passes current, it will generate additional magnetic flux, which interacts with the suspended second permanent magnet 9 and exerts additional electromagnetic force on it, so that when different currents are passed, the degree of repulsion between the opposite magnetic poles is controlled to achieve the effect of changing the degree of up and down vibration, so that the generated vibration completes the signal transmission of tactile feedback on the surface of the fiber-reinforced elastic membrane. The elastic membrane 5 acts like a spring in the annular area between the second permanent magnet 9 and the actuator housing 1, providing a restoring force.

[0044] The ferrofluid-based tactile feedback electromagnetic actuator of this embodiment uses ferrofluid to enhance the performance of the electromagnetic actuator. The high thermal conductivity of the ferrofluid helps to dissipate heat, and its parametric magnetic properties reduce the magnetic resistance of the electromagnetic circuit, thereby increasing the generated force.

[0045] In addition, the rheological properties of the ferrofluid improve the dynamic performance of the overall device, reducing mechanical resonance by lubricating the motion and providing viscous damping. The use of ferrofluid not only improves the force output, but also helps disperse the heat generated by resistive and inductive heating. Since the heat dissipation problem is solved, the ferrofluid-based tactile feedback electromagnetic actuator of this embodiment can be compactly arranged, and its size can be designed to be comparable to that of a small handheld object or an adult's fingertip, so that it can be easily integrated into various devices.

[0046] In addition, the ferrofluid-based tactile feedback electromagnetic actuator of this embodiment adopts an electromagnetic device, including two axially aligned first permanent magnets 2 and second permanent magnets 9, and a coil 4 wound around the electromagnetic core 3. This design generates greater force without increasing the size, and can operate in a wider frequency range (from 0 to 1000 Hz) than traditional electromagnetic actuators, generating continuous force, instantaneous force or oscillating force, simulating the wide range of perception of human touch.

[0047] The elastic membrane 5 and the elastic cavity 6 provide the necessary restoring force, and the hollow linear bearing 7 is designed to limit radial displacement and out-of-plane rotation, thereby improving the overall accuracy and reliability.

[0048] In general, the ferrofluid-based tactile feedback electromagnetic actuator constructed in this embodiment improves the heat dissipation efficiency and output force while reducing the magnetic resistance of the electromagnetic circuit. It can simulate human touch within a wide frequency range. The optimization of material selection further ensures the performance and durability of the actuator. Its compact size is suitable for integration into a variety of portable devices.

[0049] Here is a specific size selection:

[0050] The diameter of the actuator housing 1 is set to 18.5 mm, which is about the width of an adult's index finger, and the overall mass is about 20 g.

[0051] The thickness of the elastic membrane 5 and the elastic cavity 6 is 0.5 mm. Due to manufacturing limitations, the thickness of the elastic membrane 5 can only be changed in increments of 0.5 mm. Therefore, in order to maximize the displacement, the minimum thickness of 0.5 mm is used. In the static state, the distance between the first permanent magnet 2 and the second permanent magnet 9 is 7 mm, and the height of the coil 4 is set to 4.5 mm.

[0052] The coil 4 is wound with a 30AWG wire with a conductor diameter of 0.255 mm.

[0053] Specifically, the elastic membrane 5 and the elastic cavity 6 are made of Ecoflex 00-30 platinum-cured silicone to provide high-fidelity tactile feedback.

[0054] The actuator housing 1, the electromagnet core 3 and the high magnetic index guide plate 8 are all made of Permalloy 80 alloy, which is used to reduce the magnetic resistance of the magnetic circuit and enhance the output of force.

[0055] The first permanent magnet 2 and the second permanent magnet 9 are made of permanent neodymium iron boron magnets.

[0056] As a preferred solution, the linear bearing 7 is a hollow structure to further achieve lightweight.

[0057] According to the simulation analysis carried out based on the structure of this embodiment, the tactile feedback electromagnetic actuator based on ferromagnetic fluid in this embodiment can achieve a maximum elastic change displacement of 1.6 mm.

[0058] In the linear working mode, the effective stroke length is 1.25mm, and the total harmonic distortion remains below -30dB in the working range frequency, which shows that the dynamic response of the actuator is very linear and the harmonic distortion is very low.

[0059] The measured stroke lengths as well as the very short rise and fall times of the ferrofluid-based haptic feedback electromagnetic actuators make it possible to use the present device to transmit vibrations not only in continuous contact but also to generate transient contact sensations by configuring a small gap with the skin.

[0060] The optimized heat transfer characteristics of this device enhance power handling. When a DC current is passed and the input power is 2.7W, it can generate a static force of 0.45N (static force refers to the force generated under static conditions, that is, the force that does not change with time. This force is usually used to simulate the continuous contact or pressure when touching an object).

[0061] Practical applications of tactile devices rarely involve such long force or vibration durations. Setting the current to 6A allows for at least 3 seconds of use without damaging the structure, generating a quasi-static force of nearly 3N. In addition, a 10-millisecond current pulse of 38A can generate a transient force of 12N. Simulations show that at all frequencies below 1000Hz, the heat generated inside the bearings and manufactured ferromagnetic components is less than 100mw, which ensures a wide range of usable operating ranges for this device.

[0062] The response range of traditional structures is concentrated within the range of 1000Hz, such as 200-300Hz, 0-500Hz, or within 1000Hz for specific numerical frequencies, and does not have the wide frequency response of the designed structure within the range of 0-1000Hz. Therefore, the tactile feedback electromagnetic actuator structure based on ferromagnetic fluid in this embodiment increases the effective force by about 35% compared with the traditional structure.

[0063] As a preferred solution, a replacement hole 12 is provided on the actuator housing 1, and a matching seal 13 is detachably installed in the replacement hole 12. This arrangement facilitates the replacement of the ferromagnetic fluid, and the seal 13 can be disassembled for injection when replacement is required.

[0064] As a preferred solution, the actuator housing 1 and the elastic cavity 6 are both cylindrical;

[0065] A circle of fixing groove 14 is formed on the upper end surface of the actuator housing 1 , and the outer circle of the elastic membrane 5 is fixedly inserted into the fixing groove 14 , thereby enhancing the stability of the elastic membrane 5 installed on the actuator housing 1 .

Claims

1. A tactile feedback electromagnetic actuator based on ferromagnetic fluid, characterized in that: It comprises an actuator housing (1) with an open top; an actuator and a magnetic circuit are arranged inside the actuator housing (1); The magnetic circuit comprises a first permanent magnet (2) coaxially fixedly arranged on the inner bottom of the actuator housing (1), an annular electromagnet core (3) coaxially fixedly arranged on the first permanent magnet (2); a coil (4) is sleeved on the outer ring of the electromagnet core (3); The upper end of the actuator housing (1) is covered with an elastic membrane (5), and the lower surface of the elastic membrane (5) is coaxially connected to an elastic cavity (6) with a through hole at the bottom; when the elastic cavity (6) is in a natural state, the lower end surface is in contact with the upper end surface of the electromagnet core (3); The actuator comprises a linear bearing (7) and a high magnetic conductivity guide plate (8), a second permanent magnet (9) and a connecting plate (10) which are arranged in order from top to bottom inside the elastic cavity (6); the upper part of the linear bearing (7) passes through the through hole of the elastic cavity (6) and is fixedly connected to the connecting plate (10), and the remaining part of the linear bearing (7) slides into the inner ring of the electromagnetic core (3); The first permanent magnet (2) and the second permanent magnet (9) are arranged opposite to each other with the same magnetic pole; The actuator housing (1) is provided with a power interface (11), and an external power source can apply current to the coil (4) through the power interface (11); The actuator housing (1) contains ferromagnetic fluid encapsulated inside.

2. The ferrofluid-based tactile feedback electromagnetic actuator according to claim 1, characterized in that: The elastic membrane (5) and the elastic cavity (6) are made of Ecoflex 00-30 platinum-cured silicone.

3. The ferrofluid-based tactile feedback electromagnetic actuator according to claim 1, characterized in that: The thickness of the elastic membrane (5) and the wall thickness of the elastic cavity (6) are both 0.5 mm.

4. The ferrofluid-based tactile feedback electromagnetic actuator according to claim 1, characterized in that: The actuator housing (1), the electromagnet core (3) and the high magnetic rate guide plate (8) are all made of Permalloy 80 alloy.

5. The ferrofluid-based tactile feedback electromagnetic actuator according to any one of claims 1 to 4, characterized in that: The actuator housing (1) is provided with a replacement hole (12), and a matching sealing member (13) is detachably installed in the replacement hole (12).

6. The ferrofluid-based tactile feedback electromagnetic actuator according to any one of claims 1 to 4, characterized in that: The first permanent magnet (2) and the second permanent magnet (9) are permanent neodymium iron boron magnets.

7. The ferrofluid-based tactile feedback electromagnetic actuator according to any one of claims 1 to 4, characterized in that: The linear bearing (7) is a hollow structure.

8. The ferrofluid-based tactile feedback electromagnetic actuator according to any one of claims 1 to 4, characterized in that: The actuator housing (1) and the elastic cavity (6) are both cylindrical; The upper end surface of the actuator housing (1) is provided with a circle of fixed annular groove (14), and the outer ring of the elastic membrane (5) is fixedly clamped into the interior of the fixed annular groove (14).

Images