Asymmetrically resonantly driven multi-legged micro magnetic robot

Abstract

This invention proposes an asymmetric resonant driven multi-legged magnetically controlled microrobot, belonging to the field of magnetically controlled microrobot technology. The microrobot consists of a flexible body frame and a magnetic actuator. The flexible body frame comprises a central hub and three cantilever legs. The three cantilever legs are radially connected to the central hub at 120-degree intervals. Each cantilever leg consists of a leg connected to the central hub and a widened and thickened foot portion away from the central hub. Each cantilever leg has micropores inside its foot portion. The length, thickness, and foot length of each cantilever leg are asymmetric. The magnetic actuator is a micro-permanent magnet, which is tightly embedded in the aforementioned foot micropores through an interference fit. The microrobot proposed in this invention features perfectly decoupled independent control performance, a simple structure, a highly durable hingeless design, and convenient manufacturing process, significantly reducing the manufacturing threshold and cost of microrobots.

Description

Technical Field

[0001] This invention belongs to the field of magnetically controlled microrobot technology, and particularly relates to an asymmetric resonant driven multi-legged magnetically controlled microrobot. Background Technology

[0002] In recent years, magnetic microrobots have shown great application potential in minimally invasive medicine, targeted drug delivery, and microfluidic manipulation due to their untethered nature, high penetration depth, and high biocompatibility. Among them, multi-legged biomimetic microrobots have superior terrain adaptability and motion stability compared to traditional rolling or helical robots.

[0003] Currently, existing technical solutions for achieving independent control of each leg of a multi-legged robot in a globally uniform magnetic field suffer from the following main drawbacks:

[0004] 1. The drive system is extremely complex: It usually relies on a complex multi-coil system (such as a three-dimensional Helmholtz coil or electromagnetic array) to generate a high gradient or complex rotating magnetic field in three-dimensional space, resulting in large and expensive external control equipment.

[0005] 2. Fragile structure and difficult fabrication: Existing multi-legged microrobots often employ traditional micro-nano fabrication processes to manufacture complex micro-hinges or multi-joint structures. These micro-hinges are prone to mechanical wear during continuous movement, and the yield rate and cost of multi-material micro-assembly are low.

[0006] 3. Difficulty in local independent control: Under a single global magnetic field, all magnetic parts of the robot usually produce synchronous responses, making it difficult to break the symmetry to achieve independent drive of a single leg or a local area, which limits its multimodal mobility (such as precise steering, in-situ spin, etc.). Summary of the Invention

[0007] The purpose of this invention is to provide an asymmetric resonant driven multi-legged magnetically controlled microrobot to solve the technical problems of existing multi-legged robots, such as extremely complex drive systems, fragile structures, difficult fabrication, and difficulty in local independent control of each leg.

[0008] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0009] A multi-legged magnetically controlled microrobot driven by asymmetric resonance, the microrobot consisting of a flexible body skeleton and a magnetic actuator;

[0010] The flexible body skeleton consists of a central hub and three cantilever legs. The three cantilever legs are 120 degrees apart and are radially connected to the central hub. Each cantilever leg consists of a leg connected to the central hub and a widened and thickened foot away from the central hub. Each cantilever leg has foot micropores inside its foot.

[0011] The length, thickness, and foot length of each cantilever leg are asymmetrical;

[0012] The magnetic actuator is a miniature permanent magnet, which is tightly embedded in the micro-hole of the foot through an interference fit; the magnetization direction of the miniature permanent magnet is parallel to the plane where the cantilever leg is located.

[0013] Furthermore, the first cantilever leg has a leg length of 1mm, a leg width of 1.5mm, and a leg thickness of 0.2mm; the foot of the first cantilever leg has a length of 3mm, a foot width of 2.7mm, and a foot thickness of 1.5mm. The second cantilever leg has a leg length of 2mm, a leg width of 1.5mm, and a leg thickness of 0.3mm; the foot of the second cantilever leg has a length of 2mm, a foot width of 2.7mm, and a foot thickness of 1.5mm. The third cantilever leg has a leg length of 3mm, a leg width of 1.5mm, and a leg thickness of 0.4mm; the foot of the third cantilever leg has a length of 1mm, a foot width of 2.7mm, and a foot thickness of 1.5mm.

[0014] Furthermore, the flexible body skeleton is integrally molded from a highly elastic thermoplastic polyurethane elastomer.

[0015] Furthermore, the miniature permanent magnet is a nickel permanent magnet cylinder.

[0016] Furthermore, the three cantilever legs have three completely different first-order natural resonant frequencies.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] 1. Extremely simple drive system and reduced control complexity: It abandons complex three-dimensional magnetic field control, requiring only the application of a simple single-axis (Z-axis) alternating magnetic field to achieve drive. By inputting a one-dimensional frequency signal, multi-modal two-dimensional spatial motion control can be achieved, greatly reducing the cost and operational complexity of the drive equipment.

[0019] 2. Perfectly Decoupled Independent Control Performance: An innovative asymmetric structural design (by varying the thickness of the legs and the length ratio of the legs to the feet) gives each leg completely different bending stiffness, thus endowing each leg with a unique and decoupled inherent resonant frequency. Under specific frequency excitation, only a specific target leg produces high-frequency, large-amplitude oscillations, achieving perfect local independent control.

[0020] 3. Simple structure, high durability, and hinge-free design: The robot body is made of a flexible elastomer in one piece, with a magnet embedded at the far end, completely eliminating the traditional micro-hinge structure. This "continuous" structure avoids mechanical wear and significantly improves the robot's service life and robustness.

[0021] 4. Convenient manufacturing process and low cost: The flexible skeleton can be rapidly formed using high-precision FDM 3D printing technology. Combined with simple interference fit assembly of micro magnets, the manufacturing threshold and cost of micro robots are greatly reduced. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the asymmetric resonant driven multi-legged magnetically controlled microrobot structure of the present invention.

[0024] Figure 2 This is a top view schematic diagram of the asymmetric resonant driven multi-legged magnetically controlled microrobot of the present invention.

[0025] Figure 3 This is a simplified model of the present invention, showing a simulation diagram of the forced vibration displacement field at different excitation frequencies.

[0026] Figure 4 This is a schematic diagram of the test platform for the magnetic drive and kinematic acquisition system used in this invention.

[0027] The markings in the diagram are as follows: 1-Central hub; 2-Cantilever leg; 3-Foot micro-hole; 4-Miniature permanent magnet. Detailed Implementation

[0028] 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.

[0029] This invention proposes an asymmetric resonant driven multi-legged magnetically controlled microrobot, such as... Figure 1 As shown, the microrobot consists of two parts: a flexible body skeleton and a magnetic actuator.

[0030] The flexible body frame consists of a central hub 1 and three cantilever legs 2. The three cantilever legs 2 are 120 degrees apart and radially connected to the central hub 1. Each cantilever leg consists of a leg connected to the central hub and a widened and thickened foot away from the central hub. Each cantilever leg has foot micropores 3 inside the foot.

[0031] Specifically, the first cantilever leg has a leg length of 1mm, a leg width of 1.5mm, and a leg thickness of 0.2mm; the foot of the first cantilever leg has a length of 3mm, a foot width of 2.7mm, and a foot thickness of 1.5mm. The second cantilever leg has a leg length of 2mm, a leg width of 1.5mm, and a leg thickness of 0.3mm; the foot of the second cantilever leg has a length of 2mm, a foot width of 2.7mm, and a foot thickness of 1.5mm. The third cantilever leg has a leg length of 3mm, a leg width of 1.5mm, and a leg thickness of 0.4mm; the foot of the third cantilever leg has a length of 1mm, a foot width of 2.7mm, and a foot thickness of 1.5mm.

[0032] The length, thickness, and foot length of each cantilever leg are asymmetrical, breaking the geometric symmetry of the three cantilever legs and giving them differentiated cross-sectional geometric parameters while maintaining their overall length.

[0033] The flexible body skeleton is integrally molded from a highly elastic thermoplastic polyurethane elastomer (such as TPU 85A).

[0034] The magnetic actuator is a miniature permanent magnet 4, which is a nickel-Ni permanent magnet cylinder. The miniature permanent magnet 4 is tightly embedded in the aforementioned foot micro-hole 3 through an interference fit. The magnetization direction of the miniature permanent magnet 4 is parallel to the plane where the cantilever leg 2 is located.

[0035] Since the bending stiffness of a cantilever leg is proportional to the cube of the leg thickness, changes in thickness will cause significant differences in the stiffness of each leg.

[0036] Combined with magnetic actuators of equal mass embedded in the distal foot, this difference in stiffness results in the first, second, and third cantilever legs having three completely different first-order natural resonant frequencies, namely the first resonant frequency... Second resonant frequency and the third resonant frequency Furthermore, the frequency bands are staggered to achieve frequency decoupling.

[0037] The working principle and dynamic process of the microrobot are described below:

[0038] Equivalent Resonance Driving Mechanism: The microrobot is placed in a global single-axis (Z-axis) alternating magnetic field. Due to the dynamic damping effect (motion hysteresis response) of the microrobot's flexible material and the friction introduced when the feet strike the base, the actual equivalent resonant frequency of each cantilever leg reaching its maximum swing amplitude under actual working conditions will shift from the theoretical natural frequency of the cantilever leg under ideal conditions. When the alternating frequency of the externally applied magnetic field matches the equivalent resonant frequency of a certain cantilever leg, that cantilever leg will resonate, converting the magnetic field torque into a large-amplitude forced vibration of that cantilever leg in the vertical direction; at the same time, the other two cantilever legs, due to frequency mismatch, have their oscillation amplitude greatly suppressed and remain basically stationary, thus achieving independent activation of the local structure.

[0039] Asymmetric friction propulsion (stick-slip mechanism): During the continuous impact of the resonant cantilever legs on the ground, the geometric asymmetry of the cantilever legs and the asymmetry of their motion trajectory disrupt the frictional symmetry of the microscopic contact surface. The active cantilever leg generates differentiated interfacial frictional forces during the contact phase with the substrate (viscous state, generating thrust) and the lifting and return phase (sliding state, with less resistance), thereby rectifying the periodic vertical oscillations into a continuous net thrust along the direction of the cantilever leg.

[0040] Multi-parameter coordinated multimodal control strategy: This invention is not limited to finding the main resonance point of a single cantilever leg, but establishes a global control scheme through coordinated modulation of multiple parameters (frequency, magnetic field amplitude, duty cycle) to achieve rich maneuvering modes:

[0041] Directional straight-line movement: No complex frequency alternation is required; only a single frequency identical to the equivalent resonant frequency of one of the three cantilever legs needs to be input into the system. At this single frequency, one cantilever leg provides the dominant thrust, while the other two cantilever legs generate only minor vibrations. By exciting the microrobot to generate coupled vibration modes with asymmetrical forces (e.g., obtaining the dominant thrust in a direction where the leg-to-foot length ratio is 2:2), the microrobot can automatically counteract the yaw torque, achieving stable linear gliding forward.

[0042] Controllable steering and in-situ spin: When the input magnetic field frequency deviates from the equivalent resonant frequency of the three cantilever legs, the system enters a non-single cantilever leg-dominated drive state. Based on this, by further finely adjusting the amplitude of the applied magnetic field (controlling the magnitude of the magnetic field torque to change the grounding positive pressure) and the duty cycle of the drive signal (controlling the injection time ratio of effective energy within a single cycle), the existing thrust balance of the system can be broken, generating a controllable yaw torque. Through the coordinated modulation of these multi-dimensional parameters, the robot can stably achieve left turns, right turns, and even in-situ clockwise (CW) or counterclockwise (CCW) rotations.

[0043] The asymmetric resonant driven multi-legged magnetically controlled microrobot proposed in this invention is fabricated as follows: Using an FDM 3D printer equipped with a 0.2 mm nozzle, with a layer height of 0.1 mm, the flexible skeleton of the microrobot is printed using TPU 85A filament. To achieve frequency decoupling, the Z-axis thicknesses of the three first cantilever legs are designed to be 0.2 mm, 0.3 mm, and 0.4 mm, respectively. After printing, cylindrical nickel magnets with dimensions φ = 0.5 × 0.5 mm are pressed into the micropores of the legs to complete assembly, thus obtaining the microrobot. The maximum span of the entire structure is approximately 1 cm. Figure 2 As shown.

[0044] The experimental results of the resonance of the cantilever beam model show that, as Figure 3 As shown in Figure a, at 20 Hz, the first cantilever leg exhibits significant resonance with an amplitude of 1.5 mm, while the amplitudes of the other cantilever legs are less than 0.3 mm; Figure 3 As shown in b, at 45 Hz, the second cantilever leg exhibits significant resonance with an amplitude of 2 mm, while the amplitudes of the other cantilever legs are less than 0.3 mm; Figure 3 As shown in c, at 85Hz, the third cantilever leg resonates significantly with an amplitude of 1.8 mm, while the amplitudes of the other cantilever legs are less than 0.3 mm.

[0045] This application verifies the resonant frequency decoupling of the microrobot prepared above: the prepared microrobot is placed in a custom Z-axis Helmholtz coil, such as... Figure 4 As shown, a vertical alternating magnetic field with an amplitude of approximately 12 mT was applied. A frequency scan was performed within the range of 1–150 Hz. At 15 Hz, the robot moved linearly along the direction of the first cantilever leg; at 35 Hz, the robot moved linearly along the direction of the second cantilever leg; and at 65 Hz, the robot moved linearly along the direction of the third cantilever leg. This verified that when the robot was placed in contact with a plane, the actual equivalent resonant frequency of each cantilever leg deviated from the first-order natural resonant frequency. Simultaneously, clockwise and counterclockwise rotation of the robot were functionally verified at 20 Hz and 80 Hz, respectively, ultimately achieving full-angle multi-path movement of the robot on a two-dimensional plane.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An asymmetric resonant driven multi-legged magnetically controlled microrobot, characterized in that, The microrobot consists of two parts: a flexible body skeleton and a magnetic actuator. The flexible body skeleton consists of a central hub and three cantilever legs. The three cantilever legs are 120 degrees apart and are radially connected to the central hub. Each cantilever leg consists of a leg connected to the central hub and a widened and thickened foot away from the central hub. Each cantilever leg has foot micropores inside its foot. The length, thickness, and foot length of each cantilever leg are asymmetrical; The magnetic actuator is a miniature permanent magnet, which is tightly embedded in the micro-hole of the foot through an interference fit; the magnetization direction of the miniature permanent magnet is parallel to the plane of the cantilever leg.

2. The asymmetric resonant driven multi-legged magnetically controlled microrobot according to claim 1, characterized in that, The first cantilever leg has a leg length of 1mm, a leg width of 1.5mm, and a leg thickness of 0.2mm; the foot of the first cantilever leg has a length of 3mm, a foot width of 2.7mm, and a foot thickness of 1.5mm; the second cantilever leg has a leg length of 2mm, a leg width of 1.5mm, and a leg thickness of 0.3mm; the foot of the second cantilever leg has a length of 2mm, a foot width of 2.7mm, and a foot thickness of 1.5mm; the third cantilever leg has a leg length of 3mm, a leg width of 1.5mm, and a leg thickness of 0.4mm; the foot of the third cantilever leg has a length of 1mm, a foot width of 2.7mm, and a foot thickness of 1.5mm.

3. The asymmetric resonant driven multi-legged magnetically controlled microrobot according to claim 1, characterized in that, The flexible body skeleton is integrally molded from highly elastic thermoplastic polyurethane elastomer.

4. The asymmetric resonant driven multi-legged magnetically controlled microrobot according to claim 1, characterized in that, The miniature permanent magnet is a nickel permanent magnet cylinder.

5. The asymmetric resonant driven multi-legged magnetically controlled microrobot according to claim 1, characterized in that, The three cantilever legs have three completely different first-order natural resonant frequencies.

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