Actuator

Abstract

This disclosure addresses the problem of providing an actuator that can be used in a manipulator with multiple degrees of freedom, and that can at least partially solve the problem of a decrease in gear backdrivability.　Provided are an actuator and an electric motor comprising a stator and a rotor. The electric motor comprises: a first link obtained by providing a link part to the stator; and a second link that is obtained by providing a link part to the rotor.

Description

Actuator

[0001] The present invention relates to an actuator and a manipulator having the actuator.

[0002] In recent years, robots are expected to play an active role in various fields, including industry, medicine, and nursing care. Reasons for this include labor shortages due to a declining birthrate and aging population, as well as trends toward increasing work efficiency. Robots that can perform dexterous movements with multiple degrees of freedom are in demand in a wide range of fields, including industrial manipulators and human assistance devices. For example, there is a demand for multi-degree-of-freedom manipulators in industrial robot arms, prosthetic hands, and robotic hands. To address this, serial link manipulators, which achieve multiple degrees of freedom by connecting motors in series, have been developed.

[0003] Conventional manipulators have a structure in which a plurality of motors are attached in series to joints. Conventional manipulators are described in, for example, Patent Documents 1 to 9.

[0004] In link actuators used in conventional manipulators, the motor is typically attached to the outside of the link by connecting the link shaft and the motor shaft with a component called a coupling. However, this configuration, where the coupling is attached to the outside of the link, results in high inertia for the actuator, and ultimately for the manipulator equipped with it.

[0005] In some cases, the motor is placed inside the link rather than attached to the outside of the link. In such cases, a common method is to use internal gears to change the direction of rotation and increase the output torque. These conventional link actuators have problems such as increased inertia due to the link components and motor components being separate, and reduced control accuracy due to the use of gears. Furthermore, using gears (reduction gears) increases torque but slows down rotation, making them unsuitable for situations requiring high-speed operation (for example, situations where a robot is assisting a human). Another problem is that using gears reduces backdrivability. Another problem is that the gears themselves increase the weight of the manipulator.

[0006] Furthermore, in relation to the above structure, connecting motors in series to increase the degrees of freedom increases the inertia when moving the tip of the manipulator. Furthermore, because the motors and links are separate components, the number of components increases. This becomes a greater problem the more links are added, for example, in multi-degree-of-freedom manipulators or serial-link manipulators. Furthermore, when multiple links are connected in multi-degree-of-freedom manipulators, greater torque is required near the base. To address this, the conventional approach has been to increase the size of the motors for actuators near the base to accommodate the increased torque required, but this has its limitations. Furthermore, larger motors lead to increased inertia when moving the links or manipulator, creating a vicious cycle.

[0007] International Publication No. 2007 / 037131 (Patent No. 5004020), JP 2012-56082 (Patent Application No. 2011-283819), JP 2012-139770 (Patent No. 5565756), JP 2009-154261 (Patent Application No. 2007-336536), International Publication No. 2016 / 084178 (Patent No. 6443456), JP 2010-2538587 (Patent Application No. 2009-104126), Japanese Patent No. 6820633, JP 2019-42903 (Patent Application No. 2017-171609), JP 2017-047492 (Patent Application No. 2015-171595)

[0008] As described above, while there is a need to increase the number of degrees of freedom in manipulators, gears have not been a desirable solution due to issues with backdrivability and increased weight. An object of the present invention is to provide an actuator that at least partially solves the above problems, or a manipulator equipped with such an actuator.

[0009] As a result of extensive research into solving the above problems, the inventors discovered that, as an example, by providing a first link on the stator of an electric motor and a second link on the rotor, it is possible to achieve an electric motor and actuator with lower inertia than conventional links, and completed the present invention, which incorporates these as embodiments.

[0010] The present disclosure includes the following embodiments: [1] An electric motor including a first link having a stator and a second link having a rotor. [2] The electric motor according to embodiment 1, wherein the rotor is disposed within the stator, and the first link moves relative to the second link as the rotor rotates within the stator, or the stator is disposed within the rotor, and the first link moves relative to the second link as the rotor rotates within the rotor. [3] The electric motor according to embodiment 1 or 2, wherein the motor is a radial gap motor. [4] The electric motor according to embodiment 1 or 2, wherein the motor is an axial gap motor. [5] An actuator including the electric motor according to any one of embodiments 1 to 4. [6] The actuator according to embodiment 5, wherein an end of the first link opposite to the end where the stator is located is fixed to another fixed part. [7] The actuator according to embodiment 5, wherein an end of the second link opposite to the end where the rotor is located is fixed to another fixed part. [8] The actuator according to embodiment 5 or 6, characterized in that a second stator is provided at an end of the second link opposite to the end where the rotor is located. [9] The actuator according to embodiment 5 or 6, characterized in that a second rotor is provided at an end of the second link opposite to the end where the rotor is located.

[10] The actuator according to embodiment 5 or 7, characterized in that a second stator is provided at an end of the first link opposite to the end where the stator is located.

[11] The actuator according to embodiment 5 or 7, characterized in that a second rotor is provided at an end of the first link opposite to the end where the stator is located.

[12] The actuator according to embodiment 8 or 10, characterized in that a third link is provided with a link portion on the second rotor rotated by the second stator.

[13] The actuator according to embodiment 9 or 11, characterized in that a third link is provided with a link portion on the second stator rotated by the second rotor.

[14] The actuator according to any one of embodiments 5 to 13, characterized in that the actuator according to any one of embodiments 5 to 13 is connected in series to another actuator.

[15] The actuator according to any one of embodiments 5 to 13, characterized in that the actuator according to any one of embodiments 5 to 13 is connected in parallel to another actuator.

[16] The electric motor according to any one of embodiments 1 to 4, which does not have a gear, or the actuator according to any one of embodiments 5 to 15, which does not have a gear.

[17] A method of using the electric motor according to embodiment 1, 2, 3, 4 or 16, or the actuator according to any one of embodiments 5 to 16.

[18] A method of manufacturing an electric motor comprising a stator and a rotor, wherein a link portion is provided on the stator to serve as a first link, and a link portion is provided on the rotor to serve as a second link.

[19] The manufacturing method according to embodiment 18, wherein the motor is a radial gap motor.

[20] The manufacturing method according to embodiment 18, wherein the motor is an axial gap motor.

[21] The manufacturing method according to any one of embodiments 18 to 20, wherein the electric motor does not have a gear.

[0011] This specification includes the disclosure of Japanese Patent Application No. 2021-083338, from which this application claims priority.

[0012] An advantage of the present invention is that it provides an electric motor and actuator with lower inertia compared to conventional links.

[0013] 1 shows a conventional actuator having a coupling; FIG. 2 shows a conventional actuator without a coupling but with the motor located outside the link; FIG. 3 shows an in-link actuator of the present disclosure; FIG. 4 is a diagram illustrating a stator link (first link) of the present disclosure (top view); FIG. 5 is a diagram illustrating a stator link (first link) of the present disclosure (perspective view); FIG. 6 is a diagram illustrating a rotor link (second link) of the present disclosure (top view); FIG. 7 is a diagram illustrating a rotor link (second link) of the present disclosure (perspective view); FIG. 8 is a diagram illustrating how coils are wound in an in-link actuator of the present disclosure; FIG. 9 is a photograph of a stator link with a wound coil; The configuration is an example; FIG. 10 is a diagram showing an arrangement of magnets; The configuration is an example; FIG. 11 is a photograph of a rotor link of the present disclosure; The configuration is an example; FIG. 12 shows an apparatus equipped with a base for attaching link actuators to a DD motor; and FIG. 13 is a photograph of each link actuator connected to a motor and a base. Comparative Example 1 is a conventional actuator with a coupling, Comparative Example 2 is a conventional actuator without a coupling but with a motor located on the outside of the link, and the present invention is an in-link actuator of the present disclosure. The results of measuring the moment of inertia of each link are shown. The link with a conventional coupling had the largest moment of inertia (left, Comparative Example 1). The conventional actuator without a coupling but with a motor located on the outside of the link also showed a constant moment of inertia (center, Comparative Example 2). In contrast, the actuator of the present disclosure had a significantly reduced moment of inertia (right, the present invention). An example of a configuration in which a first actuator (the actuator of the present disclosure), a second actuator, and a third actuator are connected in series is shown. An example of a configuration in which a first actuator (the actuator of the present disclosure), a second actuator, and a third actuator are connected in parallel is shown. A block diagram of a servo motor when speed is controlled by a speed controller is shown. A front view of an exemplary radial gap-type in-link actuator. A rear view of an exemplary radial gap-type in-link actuator. A cross-sectional view of an exemplary radial gap-type in-link actuator. FIG. 1 is a cross-sectional view of an exemplary radial gap type in-link actuator.1 is a front view of an exemplary radial gap type in-link actuator in which the shaft is integrated with the rotor link; FIG. 2 is a rear view of an exemplary radial gap type in-link actuator in which the shaft is integrated with the rotor link; FIG. 3 is a cross-sectional view of an exemplary radial gap type in-link actuator in which the shaft is integrated with the rotor link; FIG. 4 is a cross-sectional view of an exemplary radial gap type in-link actuator in which the shaft is integrated with the rotor link; FIG. 5 is a front view of an exemplary axial gap type in-link actuator; FIG. 6 is a cross-sectional view of an exemplary axial gap type in-link actuator; FIG. 7 is a cross-sectional view of an exemplary axial gap type in-link actuator; FIG. 8 is a cross-sectional view of an exemplary axial gap type in-link actuator; FIG. 9 shows the rotation angle of an axial gap type in-link actuator. In this configuration, the rotor can rotate left and right. FIG. 10 shows the rotation angle of an axial gap type in-link actuator.

[0014] In one embodiment, the present disclosure provides an electric motor including a stator and a rotor, the electric motor including a first link having a link portion on the stator and a second link having a link portion on the rotor. In other words, in one embodiment, the present disclosure provides an electric motor including a stator having a first link and a rotor having a second link. In other words, this configuration can also be described as an electric motor including a first link having a stator and a second link having a rotor. In another embodiment, the present disclosure provides an electric motor characterized in that the rotor is disposed within the stator and rotates within the stator, thereby moving the first link relative to the second link, or the stator is disposed within the rotor and rotates within the rotor, thereby moving the first link relative to the second link. This allows the electric motor and the link to be realized in the same structure. In other words, the link and the actuator are integrated. In the actuator of the present disclosure, the electric motor is not attached to the outside of the link, but rather the link is provided on the electric motor. For convenience, such electric motors or links are sometimes referred to herein as in-link actuators, whereas conventional actuators in which the motor is located on the outside of the link are sometimes referred to herein as out-link actuators.

[0015] An electric motor has a stator and a rotor. The stator, also called a stator, refers to the fixed component of the electric motor. In other words, the stator is the fixed armature or field of the electric motor. The rotor, also called a rotor, refers to the rotating magnetic field or armature of the electric motor. Typically, the rotor rotates the shaft to transmit rotational force. Rotors include, but are not limited to, squirrel-cage, special squirrel-cage, wound, and permanent magnet types. The rotor may be an inner rotor, an outer rotor, or a flat rotor. In the electric motor disclosed herein, a first link is provided on the stator and a second link is provided on the rotor. For convenience, the second link having a link portion provided on the rotor may be referred to as a rotor link. For convenience, the first link having a link portion provided on the stator may be referred to as a stator link. However, this is a convenient expression when viewing the first link and the second link as a set, and does not prevent the rotor link from being provided with a different rotor or stator, nor does it prevent the stator link from being provided with a different stator or rotor. For example, in one embodiment, a second rotor may be provided on the side of the stator link (first link) where the stator does not exist. In this case, the electric motor formed by the stator link (first link) and the rotor link (second link) is referred to as a first electric motor (or a first actuator), and the electric motor formed by the second rotor and another second stator is referred to as a second electric motor (or a second actuator). In this case, the first link can be referred to as a stator link when viewed from the first electric motor side, and as a rotor link when viewed from the second electric motor side.

[0016] The side of the first link without a stator can be fixed to another fixed part. That is, in one embodiment, the present disclosure provides an actuator characterized in that the side of the first link without a stator is fixed to another fixed part. Also, the side of the second link without a rotor can be fixed to another fixed part. That is, in one embodiment, the present disclosure provides an actuator characterized in that the side of the second link without a rotor is fixed to another fixed part. Here, the fixed part refers to a fixed part that is fixed and does not move, or a fixed part that moves, such as a fixed part that moves or rotates. That is, it does not mean that the fixed part itself is fixed, but rather any part that fixes the link.

[0017] Furthermore, a second stator may be provided on the rotor-free side of the second link, or a second rotor may be provided. That is, in one embodiment, the present disclosure provides an actuator characterized by a second stator being provided on the rotor-free side of the second link. Also, in one embodiment, the present disclosure provides an actuator characterized by a second rotor being provided on the rotor-free side of the second link. Conversely, a second stator may be provided on the stator-free side of the first link, or a second rotor may be provided. That is, in one embodiment, the present disclosure provides an actuator characterized by a second stator being provided on the stator-free side of the first link. Also, in one embodiment, the present disclosure provides an actuator characterized by a second rotor being provided on the stator-free side of the first link. In this specification, the stator-free side of the link may be referred to as the end opposite to the end where the stator is located. Also, the rotor-free side of the link may be referred to as the end opposite to the end where the rotor is located.

[0018] When a second stator is provided, a third link having a link portion may be further connected to a second rotor rotated by the second stator. That is, in one embodiment, the present disclosure provides an actuator characterized by including a third link having a link portion on a second rotor rotated by the second stator. In another embodiment, the present disclosure provides an actuator characterized by including a third link having a link portion on a second stator rotated by the second rotor.

[0019] Any electric motor may be used in the actuator of the present disclosure. Examples of electric motors include direct current (DC) motors, alternating current (AC) motors, induction motors (IM), and synchronous motors (SM). Examples of DC motors include, but are not limited to, DC commutator motors, permanent magnet field commutator motors, electromagnet field commutator motors, and commutatorless motors. DC motors may be either inner rotor or outer rotor types. DC motors may be brushed motors, brushless motors, or stepping motors. Examples of AC motors include, but are not limited to, induction motors and synchronous motors. Examples of induction motors include, but are not limited to, single-phase induction motors and three-phase induction motors. Examples of synchronous motors include, but are not limited to, electromagnet synchronous motors, permanent magnet synchronous motors, reluctance synchronous motors, and hysteresis synchronous motors.

[0020] The actuator of the present disclosure may be used in a manipulator. That is, in one embodiment, the present disclosure provides an actuator including an electric motor having a stator and a rotor, the electric motor including a first link having a link portion on the stator and a second link having a link portion on the rotor. In another embodiment, the present disclosure provides a manipulator including the actuator. The manipulator may have one actuator or may have two or more actuators. A manipulator having two or more actuators may be referred to herein as a multi-degree-of-freedom manipulator. In one embodiment, a multi-degree-of-freedom manipulator is provided that has one or more actuators of the present disclosure (first actuators) and one or more other actuators (second actuators). The second actuator is a convenient term and may be either a conventional actuator or an actuator of the present disclosure. In one embodiment, the first actuator is connected in series with the second actuator. In another embodiment, the first actuator is connected in parallel with the second actuator. Similarly, third, fourth, fifth, ... nth actuators (n is a natural number) may be connected in series and / or parallel. An example of a series configuration is shown in Figure 12 (example n=3), and an example of a parallel configuration is shown in Figure 13 (example n=2 / 2 / 2).

[0021] In another embodiment, a method for using the electric motor, actuator, or manipulator of the present disclosure is provided. In this method, the electric motor is electrically controlled to rotate the actuator. That is, in some embodiments, the manipulator of the present disclosure may have a configuration typically found in conventional manipulators. For example, the manipulator of the present disclosure may have a control mechanism or controller, wiring, sensors, etc.

[0022] In another embodiment, the present disclosure provides a method for manufacturing an electric motor having a stator and a rotor, in which a link portion is provided on the stator to form a first link and a link portion is provided on the rotor to form a second link. In another embodiment, the present disclosure also provides a method for manufacturing an actuator having such an electric motor, and a method for manufacturing a manipulator having such an actuator. In another embodiment, the present disclosure provides a method for manufacturing a multi-degree-of-freedom manipulator having multiple actuators, including the step of connecting the manufactured actuator to another actuator.

[0023] By adopting the structure of the present disclosure, it is possible to reduce the inertia of the entire link actuator. This reduced inertia is even more effective when constructing a multi-degree-of-freedom actuator using the link actuator of the present disclosure. For example, when constructing a two-link actuator, it is possible to reduce the torque required to drive one link. Reducing the required torque also reduces the weight of the magnets and coils required, leading to a reduction in the weight of the motor section. Therefore, the inertia of the two-link actuator is also reduced. Furthermore, even when connecting 3, 4, 5, ... n links (n is a natural number) to increase the degrees of freedom, the inertia can be similarly reduced, which is even more advantageous. In addition, the number of parts required for an in-link actuator is reduced compared to conventional actuators. Conventional link actuators require links, motors, link shafts, and couplings. In the in-link actuator of the present disclosure, the motor is included in the link, and the motor shaft is common with the link shaft, eliminating the need for couplings. This reduces the number of parts used in the link actuator.

[0024] Unless otherwise specified, the electric motor of the present disclosure does not have a gear (i.e., a reducer) connected to the motor portion. Furthermore, unless otherwise specified, the actuator of the present disclosure does not have a gear. Note that this applies to one actuator of the present disclosure, not to the entire device. For example, when the actuator of the present disclosure is incorporated into a multi-degree-of-freedom manipulator, it does not mean that the entire multi-degree-of-freedom manipulator, including other actuators, must not have a single gear. Rather, it means that the actuator portion of the multi-degree-of-freedom manipulator does not have a gear, while other portions of the multi-degree-of-freedom manipulator (which may include conventional actuators) may have gears. In other words, when the actuator of the present disclosure is incorporated into a multi-degree-of-freedom manipulator, a configuration is also provided in which the actuator of the present disclosure (first actuator) does not have a gear, but the other actuator (second actuator) has a gear. Furthermore, a multi-degree-of-freedom manipulator is also provided that includes an actuator of the present disclosure (first actuator) that does not have a gear and another actuator of the present disclosure (second actuator) that does not have a gear.

[0025] In one embodiment, the present disclosure provides a radial gap in-link actuator. The radial gap in-link actuator includes a radial gap motor. In a radial gap motor, the gap between the rotor and stator is configured to be radial (i.e., parallel to) the plane in which the rotational axis rotates. The in-link actuator of FIG. 1C is an example of a radial gap in-link actuator. Further examples of radial gap in-link actuators are shown in FIGS. 15A to 15D. While the magnet section is shown as a circle in the figure, the magnet section may have any number n of magnets (e.g., n = 2, 3, 4, ..., where n is any natural number equal to or greater than 2). The magnets of the magnet section may be arranged appropriately. The coils of the coil section are merely exemplary arrangements. The coil section may have any number m of coils (e.g., m = 2, 3, 4, ..., where m is any natural number equal to or greater than 2). In such a configuration, the shaft may be integrated with the rotor link. An example of a radial gap type in-link actuator in which the shaft is integrated with the rotor link is shown in Figures 16A to 16C. The rotor link integrated with the shaft can be manufactured by, for example, but not limited to, a 3D printer.

[0026] In another embodiment, the present disclosure provides an axial gap in-link actuator. The axial gap in-link actuator includes an axial gap motor. An axial gap motor is also known as an axial flux motor or pancake motor. In an axial gap motor, the gap between the rotor and stator is configured so that it is parallel to the plane in which the rotation axis rotates (i.e., perpendicular to the rotation axis). This geometry makes it easy to make an axial gap motor thin. Furthermore, the stator or rotor can be embedded within the link. An example of an axial gap in-link actuator is shown in Figures 17A to 17D. While the magnet section is shown as a circle in the figure, the magnet section may have any number n of magnets (e.g., n = 2, 3, 4, ..., where n is any natural number equal to or greater than 2). The magnets in the magnet section may be arranged as needed. The coils in the coil section are merely exemplary. The coil section may have any number m of coils (e.g., m = 2, 3, 4, ..., where m is any natural number equal to or greater than 2). 17B illustrates a configuration in which both sides of the coil are supported by the stator. However, the coil arrangement is not limited to this. For example, two sets of coils may be arranged on both sides of the stator (i.e., on the upper and lower surfaces of the central rotating disk).

[0027] Furthermore, in certain embodiments, the arrangement of the magnets and coils may be interchanged with respect to Figures 15A-D, 16A-C, and 17A-F. For example, if the magnets and coils in Figure 15C are interchanged, the stator 1 will have the magnet portion 4 and the rotor 2 will have the coil portion 3. The same applies to Figure 16C. The same applies to Figure 17B. Such aspects are also encompassed by the present disclosure.

[0028] Figures 17E and 17F show the rotation angle of the rotor of an axial gap type in-link actuator. The configuration of Figure 17E allows the rotor to rotate left and right. As shown in Figure 17F, the rotation angle of the rotor can be increased by forming the stator link with a partially removed shape. Conversely, it is also possible to limit the rotation angle of the rotor, and by modifying the shape of the stator link and / or rotor link, the movable range of the rotor link can be set to the desired range.

[0029] In certain embodiments, for the various electric motors and actuators disclosed herein, the motor can be a radial gap motor. In other embodiments, for the various electric motors and actuators disclosed herein, the motor can be an axial gap motor.

[0030] (Example) To clarify the features of the actuator of the present disclosure, a conventional actuator will be first described.

[0031] Comparative Example 1 - Actuator with Coupling Conventional link actuators use a technique in which the motor is attached to the outside of the link joint. When attaching the motor to the outside of the link joint, the link components and the motor are connected, so the link shaft and the motor shaft are connected by a coupling. An example of such a configuration is shown in Figure 1A.

[0032] Comparative Example 2 - Actuator without Coupling but with Motor Outside the Link For precise force control, it is desirable not to use gears. Therefore, there is a conventional method of attaching a motor to the outside of the joint of a link, as a link without gears. An example of such a configuration is shown in Figure 1B.

[0033] Actuator of the Present Disclosure (In-Link Actuator) In the present disclosure, the link shaft and the motor shaft are a common shaft without using a coupling. A model of this link actuator is shown in FIG. 1C. In other words, the link of the present disclosure does not have a coupling. In the link of the present disclosure, the motor is not attached to the outside of the link, but is located inside the link.

[0034] A manufacturing example of the actuator of the present disclosure will be described. Here, as an example, a brushless DC motor is embedded in a link. Specifically, in a one-degree-of-freedom link, the tip of one link is integrated with the stator of the motor (stator link), and the tip of the other link is integrated with the rotor of the motor (rotor link). A top view of a stator link model is shown in FIG. 2, and a perspective view is shown in FIG. 3. A top view of a rotor link model is shown in FIG. 4, and a perspective view is shown in FIG. 5.

[0035] The stator at the tip of the exemplary link we fabricated had nine slots. Figure 6 shows an example of how to wind coils for nine slots. Three coils are wound for nine slots. The winding method is to wind clockwise from the point marked A into the first slot, then counterclockwise into the adjacent slot, and then clockwise into the third slot. This winding method is similarly applied to B and C. One end of each of the three coils is then connected together, allowing current to flow through the other end. Figure 7 shows the result of winding coils on a stator link using this method. The number of stator slots is not limited to this; when using three coils, it can be six, twelve, or other slots. When using two coils, it can be two, four, six, eight, ten, or twelve slots, but is not limited to these.

[0036] Meanwhile, the rotor link was designed with 10 poles. Figure 8 shows how the magnets are arranged on the rotor. As shown in Figure 8, an NS arrangement was adopted, in which the north and south poles of the magnets are arranged alternately. The arrows in the figure point from the south pole to the north pole. Figure 9 shows the result of embedding magnets in the rotor link using this magnet arrangement method. Note that the number and arrangement of magnet poles are not limited to this and can be designed appropriately to correspond to the coil.

[0037] An example of a one-link actuator formed by combining the stator link and rotor link is shown in Figure 1C. This structure allows the link joint itself to have a driving function, without treating the link and the motor as separate components. While the illustrated configuration places the rotor on the outer link portion of the link and the stator on the inner link portion of the link, the actuator of the present disclosure is not limited to this. For example, the rotor may be placed on the inner link portion of the link and the stator on the outer link portion of the link.

[0038] Next, the difference in inertia between the in-link actuator of the present disclosure and a conventional out-link actuator was measured. To evaluate the moment of inertia, three types of actuators were placed vertically and connected to a base so that the actuator rotated (yawed) when viewed from the Z-axis direction. The base was connected to a motor, and when the motor was driven, the base rotated. These configurations are shown in Figures 10A and 10B.

[0039] Next, the motor connected to the base was driven to rotate the base, and the moment of inertia of the three types of actuators was measured. First, a method for identifying the moment of inertia of a motor by controlling the motor with a speed controller will be explained. In this experiment, this method was used to conduct an identification test of the moment of inertia of a link actuator. Figure 14 shows a block diagram when the speed of a servo motor is controlled by a speed controller. ω ref is the speed reference value, ω is the speed response value, τ ref is the torque reference value, τ is the output torque, i ref is the current reference value, K p is the proportional gain, K tn is the nominal value of the motor torque constant, K t is the torque constant of the motor, J is the moment of inertia of the servo motor, and s is the Laplace operator. In this experiment, it is assumed that there is no fluctuation in the torque constant, and K t is K tn is treated as being equal to

[0040] The system in FIG. 14 is a first-order lag system, and the Laplace transform f(s) of its step response and the time constant T are shown below.

[0041] As mentioned above, the time constant T can be calculated from the steady-state value and response value data. The steady-state value and response value of the speed can be measured using an encoder attached to the motor. The measured time constant T and the set proportional gain K p By substituting into equation (2), the moment of inertia of the servo motor can be calculated.

[0042] Setup and Experimental Method The motor used in this experiment is an AC (Alternating Current) direct drive servo motor (SGMCS-02BDC41; Yaskawa) (hereafter referred to as DD motor). The DD motor is driven by a dedicated driver (SGDV2R1F; Yaskawa). This DD motor also has an encoder with 20-bit resolution. The DD motor controller is an Intel Core i7-8000 series processor. TM The program is implemented on a general-purpose computer with an i7-870 (Intel Corp.) processor. The program runs on Linux v. 26.32.2 with the Realtime Application Interface (RTAI 3.7) installed. The controller is called at a frequency of 10 kHz.

[0043] The base and each link actuator were fabricated using a 3D printer (Mark Two; Markforged Inc.). Onyx filament was used.

[0044] Next, we will describe the experimental method. First, Figure 10A shows the device in which a base for attaching a link actuator to a DD motor is attached. A speed step input (command value: 3.14 rad / s) was input to the DD motor, and the time constant was measured from the response value. Using the above method, the moment of inertia J of the DD motor and base combined around the rotation axis of the DD motor was calculated. m+bThen, a conventional link and the link actuator of the present disclosure are attached to the base. The speed command value is input in the same manner as above, and the moment of inertia J of the DD motor, the base, and the link actuator combined around the rotation axis of the DD motor is determined. all Ask for.

[0045] Moment of inertia J of the link actuator around the rotation axis of the DD motor act is calculated by equation (3). In this experiment, the proportional gain K p was set to 0.1 in the experiment.

[0046] In this experiment, we performed an experiment to identify the moment of inertia of three types of link actuators. The first one has the link shaft and motor shaft connected by a coupling.

[0047] In this experiment, to ensure consistent performance of the drive components, a motor was fabricated under the same conditions (size, magnets, coils, number of coil turns, etc.) as the motor embedded inside the link actuator of the present disclosure. In the left side of Figure 10B, the coupling is covered with a 3D printer part. This part connects the motor stator to one side of the link to transmit the motor's rotation to the link. In the center of Figure 10B, the first installed link actuator has been improved so that the link shaft and motor shaft are common. This improvement makes it possible to reduce the inertia of the entire link actuator. In the right side of Figure 10B, the in-link actuator of the present disclosure is shown.

[0048] The device equipped with these three types of link actuators is shown in Figure 10B. Measurements were taken 10 times for each link actuator, and the average was taken to determine the moment of inertia.

[0049] Experimental Results and Discussion The masses of the link actuators fabricated in this experiment were 0.194 kg for the conventional method (with coupling), 0.137 kg for the conventional method (without coupling), and 0.117 kg for the link actuator of the present disclosure.

[0050] It can be seen that the mass increases in the order of conventional method (with coupling), conventional method (without coupling), and the link actuator of the present disclosure. The reason for this is that the conventional method (with coupling) has a coupling and uses two shafts. Also, even in the case of the conventional method (without coupling), the motor parts exist separately from the link, so the mass is larger than that of the proposed method.

[0051] Ten experiments were conducted using only the DD motor and base, and each of the three types of link actuators. The results showed that the response speed was fastest in the order of DD motor and base, the link actuator of the present disclosure, the conventional link (without coupling), and the conventional link (with coupling). This shows that the moment of inertia around the rotation axis of the DD motor is smallest in this order.

[0052] The moment of inertia is also shown in Figure 11. The actuator with a conventional coupling (left side of Figure 10B) had the largest moment of inertia. A certain degree of moment of inertia was also observed in the conventional actuator without a coupling but with a motor located on the outside of the link (center of Figure 10B). In contrast, the moment of inertia of the in-link actuator of the present disclosure was significantly reduced (right side of Figure 10B). Specifically, the moment of inertia of the actuator of the present disclosure was reduced by 88% compared to the conventional actuator with a coupling, and was also reduced by 68% compared to the conventional actuator without a coupling but with a motor located on the outside of the link.

[0053] An in-link actuator with a radial gap motor was prototyped as shown in Figures 15A to 15D. This has a configuration in which the stator link 1 has a coil portion 3 and the rotor link 2 has a magnet portion 4.

[0054] Next, we prototyped a radial gap type in-link actuator, in which the shaft is integrated with the rotor link, as shown in Figures 16A to 16C. In this configuration, the stator link 1 also has a coil portion 3, and the rotor link 2 has a magnet portion 4. Furthermore, the shaft and rotor link are integrated, so the rotor link 2 functions as the shaft. A bearing 6 can be placed between the stator link 1 and the rotor link 2. By integrating the shaft with the rotor link, it is possible to reduce the number of parts and also the weight.

[0055] Next, we prototyped an in-link actuator with an axial gap motor, as shown in Figures 17A to 17F. The use of an axial gap motor allows for a thinner motor. Furthermore, with an axial gap in-link actuator, the rotor link can be positioned directly above the stator link when viewed from the side (see Figure 17B). Therefore, the axial gap in-link actuator can further reduce the moment of inertia compared to a radial gap in-link actuator.

[0056] The technique of placing the motor inside the link has the drawback of increasing the outer diameter of the link itself, and for this reason, it seems that the design of placing the motor inside the link has not been considered or has been difficult to adopt in conventional actuator designs.

[0057] In this disclosure, the stator and rotor of the motor are embedded in links, and are divided into a stator link that functions as the stator and a rotor link that functions as the rotor. By combining these two links, it has been demonstrated that the link itself functions as an actuator without the need for a separate motor. This configuration has also demonstrated that the moment of inertia of the link actuator can be reduced. In addition to lowering the inertia, it has also been possible to reduce the number of parts used in the link actuator. This not only reduces manufacturing costs, but also contributes to reducing resonance of the parts.

[0058] The actuators of the present disclosure may be used in manipulators, for example, in multi-degree-of-freedom manipulators.

[0059] Documents, including patent applications and manufacturer's manuals, are cited herein. The disclosures of these documents, while not considered relevant to the patentability of this invention, are hereby incorporated by reference in their entirety. More particularly, all referenced documents are hereby incorporated by reference to the same extent as if each individual document were specifically and individually indicated to be incorporated by reference.

[0060] The embodiments shown in this specification are merely examples for explaining the present invention. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope and spirit of the present invention. All publications, patents, and patent applications cited in this specification are incorporated herein by reference in their entirety.

[0061] 1 Stator link 2 Rotor link 3 Coil section 4 Magnet section 5 Shaft 6 Bearing

Claims

1. An electric motor having a first link having a stator and a second link having a rotor.

2. The rotor is disposed within the stator, and rotation of the rotor within the stator causes relative movement of the first link with respect to the second link; or The stator is disposed within the rotor, and the first link moves relative to the second link when the stator rotates within the rotor.

2. An electric motor according to claim 1 , characterized in that

3. 3. An electric motor according to claim 1 or 2, wherein the motor is a radial gap motor.

4. 3. An electric motor according to claim 1 or 2, wherein the motor is an axial gap motor.

5. An actuator comprising the electric motor according to claim 1.

6. 2. An actuator having an electric motor according to claim 1, wherein an end portion of the first link opposite to an end portion having a stator is fixed to another fixed portion.

7. 2. An actuator having an electric motor according to claim 1, wherein an end of the second link opposite to an end where the rotor is located is fixed to another fixed portion.

8. 7. The actuator according to claim 6, further comprising a second stator provided at an end of said second link opposite to the end at which said rotor is provided.

9. 7. The actuator according to claim 6, further comprising a second rotor provided at an end of said second link opposite to the end at which said rotor is provided.

10. 8. The actuator according to claim 7, further comprising a second stator provided at an end portion of the first link opposite to the end portion at which the stator is provided.

11. 8. The actuator according to claim 7, further comprising a second rotor provided at an end of the first link opposite to the end at which the stator is provided.

12. 9. The actuator according to claim 8, further comprising a third link having a link portion provided on a second rotor rotated by the second stator.

13. 10. The actuator according to claim 9, further comprising a third link having a link portion provided on a second stator rotated by the second rotor.

14. 6. An actuator according to claim 5, characterized in that the actuator according to claim 5 is connected in series with another actuator.

15. 6. An actuator according to claim 5, characterized in that the actuator according to claim 5 is connected in parallel to another actuator.

16. 10. The electric motor of claim 1 which is gearless.

17. 2. A method of using the electric motor of claim 1.

18. a link portion is provided on the stator to serve as a first link; A link portion is provided on the rotor to serve as a second link. A method for manufacturing an electric motor having a stator and a rotor.

19. The method of claim 18, wherein the motor is a radial gap motor.

20. The method of claim 18, wherein the motor is an axial gap motor.

21. The method of claim 18 , wherein the electric motor does not have gears.