Magnetic Jamming Mechanism

Abstract

A magnetic field jamming mechanism of one embodiment comprises a pouch containing a magnetic material, at least two types of soft magnetic particles of different sizes stored in the pouch, an electromagnet disposed at the opening side of the pouch and magnetically aligning the soft magnetic particles, a sensor part disposed between the soft magnetic particles and the electromagnet, and a frame that binds the electromagnet to the opening side of the pouch, and can be used in potential applications such as the palm of a gripper, the palm of a robot hand, a variable stiffness rotary joint, a variable stiffness 3D haptic display, a high-speed modular continuous robot, and a terrain-adaptive sole of a walking robot.

Description

Technology Field

[0001] The present invention relates to a magnetic field-based jamming mechanism having variable stiffness and shape adaptation capabilities that can adapt to various characteristics (shape, flexibility, etc.) of the external environment. Background Technology

[0002] Robot technology applicable to everyday life has been developed in various forms, such as grippers and manipulators, to perform specific movements repetitively, quickly, and accurately. In particular, for robots to perform high-repetition, high-precision, and high-load tasks, the robot manipulator is the most critical drive system for actual work execution.

[0003] Manipulators have been developed in various forms, such as SCARA robots, Stewart platforms, and multi-degree-of-freedom robotic arms, depending on the type of task and the size of the work environment; they are primarily driven by rigid actuators, such as electric motors and hydraulic cylinders. Constructed from rigid materials and utilizing high output from electric motors and hydraulics, they are suitable for performing high-repetition, high-precision, and high-load tasks, and are utilized in various industrial settings. However, there were limitations to their application in daily life involving frequent human interaction, as collisions or malfunctions could pose a significant risk and the working environment was restricted.

[0004] For robust movement, manipulators with high precision, high repetition, and high load capabilities, despite their low mechanical flexibility, have been developed; however, they have faced issues such as safety risks and limited working radius. To address these problems, robot arms that mimic the human body and manipulators based on redundant actuation have been developed to increase mechanical flexibility. In addition, various adaptive control theories have been developed to address the lack of mechanical structural flexibility and ensure safe interaction.

[0005] To address the limitations of existing rigid material-based manipulators, robotics researchers have conducted various studies, including research on the manipulator's own drive mechanisms and control algorithms for safe operation. Conventional rigid manipulators suffered from high inertia due to the presence of motors at each joint; research has been conducted to reduce the manipulator's moment of inertia by relocating drive motors outside the robotic arm using cable structures and spring-based gravity compensation mechanisms. Additionally, studies have been developed applying time-delay control-based impedance control algorithms to manage contact forces between the robot and the human, along with various AI-based control technologies for safety detection.

[0006] However, as an effort to solve the fundamental problems of these rigid material-based manipulators, soft actuators based on soft materials have been developed in various forms and applied as manipulators. Notably, as research on soft robots has become more active, this can be explained as an evolution from conventional non-redundant and redundant manipulators to manipulators that possess high adaptability and complex movements by utilizing the high multi-degrees-of-freedom characteristics of soft materials.

[0007] With efforts to apply soft actuator-based manipulators to daily human life, there have been attempts to mimic the actuation mechanisms of various animals and plants found in nature, leading to the development of various soft manipulators.

[0008] Many robot researchers have drawn inspiration from the shapes of creatures with high adaptability in their natural environments, such as octopuses and elephant trunks, and applied this to the development of soft manipulators; in particular, the highly adaptable octopus has been a major subject of interest for robot researchers studying soft manipulators.

[0009] General soft manipulators have been developed in the form of continuous robots with soft actuators made of soft flexible materials arranged in a circularly symmetrical manner. Soft actuators have been implemented by various drive mechanisms, such as electroactive polymers (EAPs), shape memory alloys (SMAs), pneumatic actuators, and actuators using cables and motors; however, drive mechanisms based on SMAs and EAPs have struggled to generate sufficient force to perform actual robot tasks, and general soft grippers have primarily utilized drive methods using cables and motors or pneumatic drive methods.

[0010] Continuum robots, which have been studied since the 1960s, are driven primarily by cables and motors. They are configured in a continuous form with a rigid structure (backbone) capable of transmitting force and implementing movement via cable routers, allowing them to adapt to the external environment and perform various movements and robotic tasks.

[0011] To mimic the movements of living organisms such as elephant trunks and octopus tentacles, and to adapt to external environments in irregular environments and achieve desired movements and successful robot operations, they have been developed in various shapes with diameters ranging from a few millimeters to tens of centimeters. While a rigid material-based backbone is essential for implementing bending movements by cables, there is a problem that unwanted collisions can occur when performing tasks in irregular environments, potentially causing safety issues with the interacting external environment.

[0012] Soft manipulators using pneumatics have begun to be developed to replace conventional rigid-structure-based continuous robots, inspired by natural organisms such as elephant trunks and octopus tentacles, and utilizing the high adaptability of soft materials. In particular, they have been developed in the form of continuous robots consisting of three or four soft pneumatic actuators per manipulator module, utilizing compartmentalized deformation.

[0013] By applying different pressures to each drive module, omnidirectional bending and linear movement are implemented. Generally, manipulators have been developed as compartmentalized manipulator modules, such as STIFF-FLOP structures, but manipulators using honeycomb structures and air-bladder structures have also been developed.

[0014] However, due to the characteristics of soft materials, soft manipulators face challenges such as difficult efficient force transmission, sagging caused by gravity, and low payloads for practical robot operations; consequently, there has been a growing need for research on additional variable stiffness structures to address these issues.

[0015] For safe interaction using soft manipulators, robot technology capable of high payload capacity without losing the high adaptability of soft, flexible materials is the most important factor to be addressed for the popularization of soft robots, and can also be a groundbreaking solution to resolve the safety issues of existing rigid robots.

[0016] Variable stiffness structures have primarily been developed for operation embedded in robots, and representative driving methods for variable stiffness can be divided into stiffness changes utilizing structural interactions and stiffness changes utilizing the electrochemical properties of the material itself or physical phenomena.

[0017] The method utilizing the interaction of mechanical structures employs a mechanism that maintains the stiffness of the entire robot structure in a stable state by utilizing the interaction of mechanical elements, with jamming being a representative application.

[0018] It is being applied to many soft robots because it enables the realization of a continuous stiffness state and allows for relatively fast operation through the control of a variable stiffness mechanism to maintain a stable state. The jamming mechanism generally implements a change in stiffness by causing materials within a pneumatic chamber to interlock due to negative pressure generated by a pneumatic pump.

[0019] This method allows for the stable gripping of objects with various characteristics (shape, flexibility, etc.) by embedding fine granules inside a balloon-shaped pouch and turning the air pressure on and off.

[0020] However, since this jamming method uses a pneumatic pump to grip objects, modularization is difficult due to the space and weight occupied by the system because it utilizes bulky devices such as pumps and regulators. Additionally, due to the characteristics of the pneumatic drive system, there is a problem in that high-speed and high-precision rigidity control is difficult. Prior art literature

[0021] PCT Application No. PCT / US2015 / 014970 (Application Date: 2015.02.09) The problem to be solved

[0022] The technical problem that the present invention aims to solve is to develop a magnetic field-driven jamming technology that possesses high-speed, high-precision variable stiffness and shape adaptability, has a simple structure, and enables modularization of the entire system.

[0023] In addition, the present invention aims to develop a magnetic field-driven jamming technology that can be used in various applications, such as robot grippers or hand grippers, variable stiffness robot joints, terrain-adaptive soles of walking robots, and shape or stiffness variable 3D tangible displays. means of solving the problem

[0024] To solve the above technical problem, a magnetic field jamming mechanism of one embodiment includes a pouch containing a magnetic material, at least two types of soft magnetic particles of different sizes stored in the pouch, an electromagnet disposed at the opening side of the pouch and magnetically aligning the soft magnetic particles, a sensor part disposed between the soft magnetic particles and the electromagnet, and a frame that binds the electromagnet to the opening side of the pouch.

[0025] The magnetic material contained in the above pouch is iron powder with a purity of 99% or higher, and the above pouch further contains silicon, and the mixing ratio of the iron powder and the silicon is 3:2 based on weight%.

[0026] The thickness of the above pouch is 1 (mm) or more and 2 (mm) or less.

[0027] The above soft magnetic particles include iron powder with a purity of 99% or higher and iron granules with a purity of 99% or higher, and the mixing ratio of the iron powder and the iron granules is 3:2 weight% (wt%).

[0028] The size of the above iron granules is 1-2 (mm).

[0029] The electromagnet has a hollow interior, and in this case, the jamming mechanism of the present invention is located between the electromagnet and the sensor part and further includes a mesh filter attached to a part corresponding to the hollow of the electromagnet.

[0030] The sensor unit includes a first sensor that detects stiffness based on the magnetic force between the soft magnetic particle and the electromagnet, and a second sensor that detects an external force applied perpendicularly to the surface of the pouch. Effects of the invention

[0031] According to a magnetic field jamming mechanism of one embodiment of the present invention, by utilizing the change in stiffness of soft magnetic particles to grip an object, objects having various shapes can be easily gripped. Furthermore, even for objects having flexibility, the stiffness of the soft magnetic particles can be adjusted to be weak during the initial gripping to allow for easy gripping, and after gripping the object, the stiffness of the soft magnetic particles can be maintained at a high level to stably maintain a state adapted to the external shape with which it interacts.

[0032] The magnetic field jamming mechanism of this embodiment has the advantage of being able to be arranged in multiple units or used in conjunction with a robot hand to serve as a gripping assistance means.

[0033] In addition, the magnetic field jamming mechanism according to one embodiment of the present invention can be used in potential applications such as the ground of a gripper, the palm of a robot hand, a variable stiffness rotary joint, a variable stiffness 3D haptic display, a high-speed modular continuous robot, and a terrain-adaptive sole of a walking robot. Brief explanation of the drawing

[0034] FIG. 1 is a drawing showing a magnetic field jamming mechanism of one embodiment. Figure 2 is a disassembled view of the magnetic field jamming mechanism illustrated in Figure 1. Figure 3 is a drawing showing a cross-sectional view along the line A-A' of Figure 1. Figure 4 is a diagram showing the magnetic arrangement of soft magnetic particles. FIG. 5 is a diagram illustrating the operation of a magnetic field jamming mechanism of one embodiment. FIG. 6 shows photographs of a magnetic field jamming mechanism implemented according to one embodiment gripping objects of various shapes. Figure 7 is a graph showing the results of measuring the change in stiffness of soft magnetic particles as a function of voltage. Figure 8 is a graph showing the results of measuring the response speed of soft magnetic particles due to magnetic field jamming. Specific details for implementing the invention

[0035] Embodiments of the present invention will be described in detail below with reference to the drawings. However, detailed descriptions of known functions or configurations that may obscure the essence of the present invention in the following description and the attached drawings are omitted. Additionally, throughout the specification, the term 'comprising' a component means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0036] Additionally, terms such as first, second, etc. may be used to describe various components, but said components should not be limited by said terms. said terms may be used for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0037] The terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "comprising" are intended to specify the existence of the described features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0038] Unless specifically defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0039] Hereinafter, a magnetic field jamming mechanism (100) of one embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a drawing showing a magnetic field jamming mechanism of one embodiment, FIG. 2 is a drawing showing the magnetic field jamming mechanism shown in FIG. 1 in disassembly, and FIG. 3 is a drawing showing a cross-sectional view along the line A-A' of FIG. 1.

[0040] Referring to this drawing, a magnetic field jamming mechanism (100) of one embodiment comprises a pouch (110) having an opening and containing a magnetic material and silicon, at least two types of soft magnetic particles (120) of different sizes stored in the pouch, an electromagnet (140) disposed on the opening side of the pouch and magnetically aligning the soft magnetic particles, a sensor part (130) disposed between the soft magnetic particles and the electromagnet, and a frame (150, 160) that binds the electromagnet to the opening side of the pouch.

[0041] The soft magnetic particles dispersed in the silicone of the pouch (110) may be iron powder with a purity of 99% or higher, and in this case, the mixing ratio of the iron powder and the silicone is 3:2 based on weight%.

[0042] The above soft magnetic particles include iron powder with a purity of 99% or higher and iron granules with a purity of 99% or higher, the mixing ratio of the iron powder and the iron granules is 3:2 weight% (wt%), and the size of the iron granules is 1-2 (mm).

[0043] The sensor unit includes a first sensor that detects stiffness based on the magnetic force between the soft magnetic particle and the electromagnet, and a second sensor that detects an external force applied perpendicularly to the surface of the pouch.

[0044] The above-described configuration will be explained in more detail below.

[0045] The pouch (110) is configured to be deformable by responding to the magnetic field of the electromagnet (140) and adapting to the three-dimensional shape of the internal soft magnetic particles (120). In the present invention, the pouch (110) is composed of a magnetorheological elastomer. If the thickness of the pouch (110) is too thick, the gripping performance of the object is reduced, and if the thickness is thin, the gripping performance of the object is improved, but there is a disadvantage that it tears easily. In addition, since the soft magnetic particles stored in the pouch (110) of the magnetic field jamming mechanism of the present invention respond to the magnetic field and adapt well to the external shape, the thickness of the pouch must be set so that the soft magnetic particles respond well to the magnetic field and adapt well to the external shape.

[0046] As confirmed by the inventors through various experiments, if the thickness of the pouch is thinner than 1 mm, its durability decreases or it tears easily, and if it is thicker than 2 mm, its ability to adapt to the external shape it interacts with decreases. Therefore, it is desirable for the pouch to have a thickness greater than 1 mm and less than 2 mm.

[0047] In one example, the magnetic reactive pouch (110) can be made by mixing soft magnetic granules, e.g. -20 mesh, 99.9% purity iron powder, with curable silicone, e.g. Ecoflex00-20.

[0048] When soft magnetic granules are included in the pouch (110) in this way, the magnetic reactivity with the soft magnetic particles (120) stored in the pouch (110) is improved, so that the ability to transmit force to the external environment, such as the gripping force of the jamming mechanism gripping an object, can be improved, and the response performance measured when a signal is applied to the jamming mechanism (100) can also be improved.

[0049] The above-described pouch (110) can be made through various known methods, for example, by mixing silicone and soft magnetic granules, pouring them into a mold, and curing them.

[0050] The pouch (110) has a hollow, ladder-shaped cross-section and is configured to include a protrusion (111) on the opening side where a frame (150, 160) is located. The frame (150, 160) is connected with the protrusion (111) in between to secure the parts constituting the jamming mechanism (100).

[0051] Below, soft magnetic particles (120) will be described.

[0052] The soft magnetic particles (120) use a soft magnetic material to achieve variable stiffness characteristics, and in one example, the soft magnetic particles (120) use pure iron (purity 99% or higher) with excellent magnetic properties (permeability).

[0053] Due to the material properties of soft magnetic metals, they are not magnetically aligned in the initial state (Fig. 4 (A)), but when a magnetic field is applied (jamming state), the magnetic domains within the particles align in the direction of the magnetic field (Fig. 4 (B)). Therefore, the strength of the magnetic force applied to the soft magnetic particles (120) can be adjusted to control the ability to interact with the external environment (grip force) during jamming.

[0054] In one example, the soft magnetic particles (120) include particles of at least two different sizes to increase effective permeability by minimizing the air layer between the particles. In a preferred embodiment, the soft magnetic particles (120) include iron powder with a purity of 99% or higher and iron granules with a purity of 99% or higher, and the mixing ratio of the powder to the granules is preferably 2:3. In this case, the size of the iron granules is 1-2 (mm). If the iron granule size is smaller than 1 (mm), the proportion of large particles with high effective permeability is reduced, so effective permeability cannot be effectively increased, and if it is larger than 2 (mm), the adaptability to flexibly conform to the external shape during unjamming is reduced.

[0055] The sensor unit (130) is described below.

[0056] The sensor unit (130) is configured to include a first sensor that detects stiffness based on the magnetic force between the soft magnetic particle (110) and the electromagnet (140), and a second sensor that detects an external force applied perpendicularly to the surface of the pouch (110).

[0057] Since the jamming mechanism of the present invention operates based on a magnetic field, it is preferable that such a sensor part (130) be made of a chemical resin and a conductive film that do not react to a magnetic field for more accurate measurement.

[0058] In addition, the sensor unit (130) is configured with a thin thickness, for example, 1 mm or less, and the specifications and number of sensing cells can be adjusted as needed.

[0059] The first sensor measures the change in stiffness of the soft magnetic particle (120) by measuring the magnetic attraction between the particle and the electromagnet (140), and the second sensor detects the external force applied to the surface of the pouch (110) to detect whether the object being held is in contact, the contact strength, and the position.

[0060] Such first and second sensors may be composed of various known types of sensors, for example, sensors that measure changes in electromagnetic force or pressure generated upon contact with an object, and various known types of sensors may be used unless there are special limitations.

[0061] The following describes the electromagnet (140).

[0062] In one preferred form, the electromagnet (140) may be a pot core type positive electromagnet. The core is made of pure iron material and may be annealed to recover magnetic properties after machining. The coil is composed of a heat-resistant coil capable of operating at high temperatures (120°C).

[0063] The electromagnet (140) is cylindrical as illustrated, but its shape is not particularly limited and a polygonal column can also be used. However, it is preferable that the electromagnet (140) be configured to have a hollow shape to prevent the pouch (110) from lifting up. The hollow (141) provided in the electromagnet (140) not only prevents the pouch from lifting up but also functions as an air passage for hybrid jamming.

[0064] When the electromagnet (140) is configured to include a hollow (141), the jamming mechanism of the present invention is configured to further include a mesh filter (131). This mesh filter (131) is attached to the surface of the electromagnet (140), preferably around the hollow (141) of the electromagnet (140), and is positioned between the electromagnet (140) and the sensor part (130). With this configuration, air inside the pouch (110) generated during the jamming process can be easily discharged to the outside through the hollow (131, 141), and soft magnetic particles can be prevented from leaking to the outside through the hollow.

[0065] The above description is based on the mechanical aspects of the magnetic field jamming mechanism (100). In addition to this configuration, electronic components such as a microcontroller and a driver are also required to operate the magnetic field jamming mechanism (100).

[0066] The electronic circuit used to operate the above-described magnetic field jamming mechanism (100) is composed of miniaturizable components such as a microcontroller and a MOSFET. Depending on the purpose of use, it may be used in an array in which multiple jamming mechanisms are connected, but it is configured so that integrated control is possible with a single controller and a single voltage input even if the number of magnetic field jamming mechanisms increases.

[0067] The microcontroller has a switching function to instantaneously activate the magnetic field of the electromagnet (140) and a voltage control function to control the voltage input in a PWM manner to control the magnetic field strength of the electromagnet (140).

[0068] Hereinafter, with reference to FIG. 5, the operation of the jamming mechanism (100) described above will be explained. In FIG. 5, the dotted line represents the airflow, and the solid line represents the path of the magnetic circuit.

[0069] Referring to FIG. 5, when current flows through the coil of the electromagnet (140), a magnetic field flowing along the electromagnet core and the soft magnetic particles is generated as shown by the solid line in FIG. 5, and then the soft magnetic particles (120) placed on the upper part of the electromagnet (140) form a magnetic circuit together with the electromagnet.

[0070] At this time, magnetic attraction is generated between the soft magnetic particles (120) due to the magnetic field (solid line), and as they attract each other, the rigidity (or gripping force) of the soft magnetic particles (120) is generated, and the rigidity is generated in proportion to the strength of the applied current.

[0071] Additionally, since the pouch (110) contains soft magnetic granules, an attractive force (dotted line) is generated between the soft magnetic granules of the pouch and the soft magnetic particles (120), so the pouch (110) adheres to the shape of the internal soft magnetic particles (120), thereby allowing the entire structure to be rigidified to match the shape of the external environment, and the intensity of the change in rigidity can be adjusted by the intensity of the current applied to the electromagnet.

[0072] FIG. 6 shows photographs of a magnetic field jamming mechanism implemented according to one embodiment gripping objects of various shapes. This experiment is intended to evaluate the shape adaptability of the magnetic field jamming mechanism (100) according to one embodiment for objects of various shapes.

[0073] In FIG. 6, (a) shows the magnetic field jamming mechanism of one embodiment gripping an object (a), and (b) shows the object removed from the state of (a) (b).

[0074] As a result of experiments, it was confirmed that the magnetic field jamming mechanism of one embodiment is capable of gripping even flexible objects (objects whose shape changes easily) with weak rigidity during the initial gripping. Furthermore, it was possible to stably grip the object even after increasing the magnetic field strength (adjusting the grip force strongly) following the initial gripping.

[0075] Figure 7 is a graph showing the results of measuring the change in stiffness of soft magnetic particles according to voltage. In Figure 7, (A) is the result of the experiment with iron powder, and (B) is the result of the experiment with iron granules.

[0076] The experiment measured the intensity while changing the input voltage to 0(V), 12.5(V), and 25(V), respectively, and measured the relative intensity of 12.5(V) and 25(V) relative to 0V. As a result, it was found that the relative intensity increased as the input voltage increased, and this result shows that the stiffness (grip force) of jamming can be controlled according to the input voltage.

[0077] Figure 8 is a graph showing the results of measuring the response speed of soft magnetic particles according to magnetic field jamming. In Figure 8, (A) shows the response speed during jamming, and (B) shows the response speed during non-jamming.

[0078] According to the experimental results, during jamming (or gripping), the soft magnetic particles reacted in 0.05 seconds and stabilized in 0.12 seconds. During unjamming (or ungripping), the soft magnetic particles reacted in 0.03 seconds and stabilized after 0.13 seconds.

[0079] As a result of the experiment, it was confirmed that soft magnetic particles responded at a very high speed to jam or unjamm.

[0080] The present invention has been described above with reference to various embodiments. Those skilled in the art will understand that the present invention may be implemented in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the invention is defined by the claims, not by the foregoing description, and all variations within the scope of the claims should be interpreted as being included in the invention.

Claims

Claim 1 A magnetic field jamming mechanism comprising: a pouch made of silicone in which a magnetic material is dispersed; at least two types of soft magnetic particles of different sizes stored in the pouch; an electromagnet disposed at the opening side of the pouch and magnetically aligning the soft magnetic particles; a sensor portion disposed between the soft magnetic particles and the electromagnet; and a frame that secures the electromagnet to the opening side of the pouch; wherein the electromagnet has a hollow that acts as an air passage for discharging air inside the pouch to the outside during the jamming process. Claim 2 A magnetic field jamming device according to claim 1, wherein the magnetic material is iron powder with a purity of 99% or higher. Claim 3 A magnetic field jamming mechanism according to paragraph 2, wherein the mixing ratio of the iron powder and the silicon is 3:2 based on weight %. Claim 4 A magnetic field jamming mechanism according to claim 1, wherein the thickness of the pouch is 1 (mm) or more and 2 (mm) or less. Claim 5 In claim 1, the soft magnetic particles comprise iron powder with a purity of 99% or higher and iron granules with a purity of 99% or higher, forming a magnetic field jamming mechanism. Claim 6 A magnetic field jamming device according to claim 5, wherein the mixing ratio of the iron powder and the iron granules is 3:2 weight% (wt%). Claim 7 In claim 5, a magnetic field jamming mechanism in which the size of the iron granules is 1-2 (mm). Claim 8 delete Claim 9 A magnetic field jamming mechanism according to claim 1, further comprising a mesh filter located between the electromagnet and the sensor part and attached to a portion corresponding to the hollow of the electromagnet, wherein the mesh filter discharges air inside the pouch to the outside and blocks the soft magnetic particles inside the pouch from leaking out to the outside. Claim 10 In claim 1, the sensor unit comprises a first sensor that detects stiffness based on the magnetic force between the soft magnetic particle and the electromagnet, and a second sensor that detects an external force applied perpendicularly to the surface of the pouch, forming a magnetic field jamming mechanism.

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