Actuator, and robot, orthostic device, and haptic device equipped with the actuator

Abstract

The invention provides an actuator, and a robot, an orthosis, and a haptic device provided with the actuator. This actuator is provided with: a plurality of wires, one end of each of which engages with a load; a support member to which the other end of each of the plurality of wires is fixed; and a drive source that twists the plurality of wires by rotating the support member, and an actuator that changes the distance between the support member and the load in accordance with the rotation of the support member. Each of the plurality of wires is fixed to the support member in a state of being twisted in the same twisting rotation direction in advance, and when the distance between the support member and the load is reduced, the plurality of wires are twisted while being rotated in the same rotation direction as the twisting rotation direction.

Description

Technical Field

[0001] The present disclosure relates to an actuator, a robot, an orthosis, and a tactile device including the actuator. Background Art

[0002] There is known a twisted string actuator (TSA: Twisted String Actuator) that converts rotational motion into linear motion by twisting multiple wires. In Patent Document 1, such an actuator is used as a drive source for driving the joints of a robotic hand.

[0003] Patent Document 1: U.S. Patent No. 4,843,921 Specification Summary of the Invention

[0004] Regarding the actuator disclosed in Patent Document 1, the inventors have found the following problems.

[0005] In such an actuator, when the number of revolutions of the twist of the wires is increased to increase the stroke, a state called over-twist occurs in which the twisted wires are twisted into a coil shape. If over-twist occurs, the variation in stroke or torque with respect to rotation becomes unstable, and thus the actuator cannot be controlled. Therefore, an actuator that can obtain a larger stroke within a range where over-twist does not occur is desired.

[0006] The present disclosure is an invention completed in view of such circumstances, and provides an actuator that can obtain a larger stroke within a range where over-twist does not occur.

[0007] The actuator according to one aspect of the present disclosure includes:

[0008] Multiple wires, each end of the multiple wires being engaged with a load;

[0009] A support member on which the other ends of the multiple wires are fixed;

[0010] A drive source that rotates the support member to twist the multiple wires,

[0011] The actuator changes the distance between the support member and the load according to the rotation of the support member,

[0012] In the actuator,

[0013] The multiple wires are respectively fixed to the support member in a state where they are pre-twisted in the same twisting rotation direction,

[0014] When reducing the distance between the support member and the load, the multiple wires are rotated and twisted in the same rotation direction as the twisting rotation direction.

[0015] In the actuator according to one aspect of the present disclosure, a plurality of wire rods are fixed to a support member in a state where they are respectively pre-twisted in the same twisting rotation direction. And when the distance between the support member and the load is reduced, the plurality of wire rods are rotated and twisted in the same rotation direction as the twisting rotation direction. With such a structure, a larger stroke can be obtained within the range where over-twisting does not occur in the plurality of wire rods.

[0016] It is also possible to adopt the following method, that is, a position where the distance between the support member and the load becomes maximum by rotating and twisting the plurality of wire rods in a rotation direction opposite to the twisting rotation direction starting from a state where the plurality of wire rods are not twisted is set as an operation start point. With such a structure, a larger stroke can be further obtained.

[0017] It is also possible to adopt the following method, that is, the plurality of wire rods are each made of ultra-high molecular weight polyethylene. With such a structure, the wire rods can be made to have high strength.

[0018] It is also possible to adopt the following method, that is, the plurality of wire rods are each a stranded wire in which a plurality of single wires are stranded together. With such a structure, the wire rods can be made to have high strength.

[0019] It can also be a robot that drives a joint by the actuator according to the present disclosure.

[0020] It can also be an orthosis that is worn by a person and assists the movement of the joints of the person, wherein the orthosis is driven by the actuator according to the present disclosure.

[0021] It can also be a tactile device that is worn by a person and gives virtual tactile sensation to the person, wherein the tactile device is driven by the actuator according to the present disclosure.

[0022] Through the present disclosure, an actuator that can obtain a larger stroke within the range where over-twisting does not occur can be provided.

[0023] The above and other objects, features, and advantages of the present disclosure will be more fully understood from the detailed description and the drawings given below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a side view schematically showing the structure of the actuator according to the first embodiment.

[0025] Figure 2 It is a graph showing changes in the stroke and torque of the wire rods W1 and W2 in Example 1 with respect to the number of turns of twisting.

[0026] Figure 3 A graph showing the changes in the stroke and torque of wire rods W1 and W2 in Comparative Example 1 with respect to the number of revolutions of twisting.

[0027] Figure 4 A graph showing the change in the effective stroke with respect to the amount of pre - twisting.

[0028] Figure 5 A graph showing the change in the effective number of revolutions with respect to the amount of pre - twisting.

[0029] Figure 6 To represent Figure 2 in Example 1 and Comparative Example 2 shown, and Figure 3 a graph showing the change in mechanical efficiency with respect to the effective stroke in Comparative Example 1 shown. Detailed Description of the Embodiment

[0030] Hereinafter, the specific embodiments to which the present disclosure is applied will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. In addition, for clarity of explanation, the following description and drawings are appropriately simplified.

[0031] (First Embodiment)

[0032] <Structure of the Actuator>

[0033] First, with reference to Figure 1 , the actuator according to the first embodiment will be described.

[0034] Figure 1 is a side view schematically showing the structure of the actuator according to the first embodiment. As Figure 1 shown, the actuator according to the present embodiment includes a pair of wire rods W1, W2, a support member SP, and a motor MT.

[0035] As Figure 1 shown, in the actuator, the support member SP is rotationally driven by the motor MT, and by twisting the wire rods W1, W2, the distance between the support member SP and the load LD is changed. That is, the actuator according to the present embodiment is a type of string - torsion actuator.

[0036] The actuator according to the present embodiment drives, for example, the joints of a robot. This actuator can also drive an orthosis worn by a person to assist the movement of the person's joints. Alternatively, this actuator can also drive a tactile device worn by a person to give a virtual sense of touch to the person.

[0037] As Figure 1As shown, one end of each of a pair of wire rods W1 and W2 is engaged with a load LD. Here, the engagement includes fixation. In Figure 1 In the example shown, a pair of wire rods W1 and W2 that are twisted with each other is one wire rod inserted through a through-hole provided at an end portion of the load LD. On the other hand, the other end of each of the pair of wire rods W1 and W2 is fixed to a support member SP.

[0038] The pair of wire rods W1 and W2 is, for example, a resin wire rod. More specifically, the wire rods W1 and W2 are made of ultra-high molecular weight polyethylene, for example, which has excellent strength. With such a structure, the wire rods W1 and W2 can be made to have high strength.

[0039] In addition, of course, the pair of wire rods W1 and W2 can also be different wire rods. Further, the number of wire rods twisted with each other is not limited to two, and may be three or more. Further, each of the wire rods W1 and W2 may also be a stranded wire in which a plurality of single wires are twisted together. With such a structure, the wire rods W1 and W2 can be made to have high strength.

[0040] As described above, the support member SP supports the other end of each of the pair of wire rods W1 and W2. The support member SP is connected to the rotating shaft of the motor MT and is rotationally driven by the motor MT. In Figure 1 In the state shown on the upper side, when the support member SP is rotated in the direction of the arrow shown on the Figure 1 lower side, the wire rods W1 and W2 are twisted, and the distance between the support member SP and the load LD becomes smaller. That is, the load LD is pulled toward the support member SP side and approaches the support member SP.

[0041] On the other hand, in Figure 1 the state shown on the lower side, when the support member SP is rotated in the direction opposite to the arrow, as Figure 1 shown on the upper side, the twisted wire rods W1 and W2 are untwisted, and the distance between the support member SP and the load LD becomes larger. That is, the load LD moves away from the support member SP.

[0042] The motor MT is a drive source that rotates the support member SP to twist the wire rods W1 and W2. The motor MT is driven based on a control signal output from a motor control unit (not shown). The motor control unit includes, for example, an arithmetic unit such as a CPU (Central Processing Unit), a storage unit such as a RAM (Random Access Memory) that stores various control programs and data, and a ROM (Read Only Memory). The control signal is, for example, a PWM (Pulse Width Modulation) signal.

[0043] In addition, the drive source for rotationally driving the support member SP is not limited to the motor MT, and may be, for example, an engine.

[0044] In the actuator according to the present embodiment, the wire rods W1 and W2 are fixed to the support member SP in a state where they are respectively twisted in advance in the same twisting rotation direction. Then, when the distance between the support member SP and the load LD is reduced, the wire rods W1 and W2 are rotated and twisted in the same rotation direction as the twisting rotation direction. As will be described in detail later, with such a structure, a larger stroke is obtained within the range where over-twisting does not occur in the wire rods W1 and W2.

[0045] Hereinafter, the case where the wire rods W1 and W2 are pre-twisted in order to be fixed to the support member SP will be referred to as pre-twisting.

[0046] In addition, in the actuator according to the present embodiment, when the wire rods W1 and W2 are rotated a certain degree in the rotation direction opposite to the pre-twisting of the wire rods W1 and W2 from the state where the wire rods W1 and W2 are not twisted, the distance between the support member SP and the load LD becomes maximum. Therefore, by setting this position as the operation start point, the effective stroke (hereinafter referred to as the effective stroke) can be further increased.

[0047] Furthermore, as will be described in detail later, in the actuator according to the present embodiment, by changing the pre-twisting amount of the wire rods W1 and W2, the reduction ratio of the actuator can be easily changed.

[0048] [Embodiment]

[0049] Hereinafter, an embodiment and a comparative example of the actuator according to the first embodiment will be described. However, the actuator according to the first embodiment is not limited to the following embodiments.

[0050] <Example 1>

[0051] As the wire materials W1 and W2, stranded wires formed by twisting two single wires together were used. As each single wire, fishing lines made of ultra-high molecular weight polyethylene with a total length of 100 mm and a diameter of 0.47 mm were used. The amount of twist of the single wires in the wire materials W1 and W2 was set to 34 turns, and the twist pitch was set to 2.9 mm. The amount of twist of the stranding of the single wires is the pre-twist amount of the wire materials W1 and W2. Here, for convenience, the pre-twist amount in Example 1 was set to 100%.

[0052] Starting from the unstranded state of the wire materials W1 and W2, the wire materials W1 and W2 were rotated and stranded in the same rotational direction as the pre-twist of the wire materials W1 and W2 to obtain the stroke (positive direction stroke) within the range where over-twist does not occur. On the other hand, starting from the unstranded state of the wire materials W1 and W2, the wire materials W1 and W2 were rotated and stranded in the rotational direction opposite to the pre-twist of the wire materials W1 and W2 to obtain the stroke (negative direction stroke) within the range where over-twist does not occur.

[0053] Here, Figure 2 is a graph showing the changes in the stroke and torque of the wire materials W1 and W2 in Example 1 with respect to the number of turns of stranding. Figure 2 The horizontal axis represents the number of turns of stranding (turns). Here, the number of turns of rotation in the same rotational direction as the pre-twist of the wire materials W1 and W2 (positive direction rotation) is represented by a positive value, and the number of turns of rotation in the rotational direction opposite to the pre-twist of the wire materials W1 and W2 (negative direction rotation) is represented by a negative value.

[0054] Figure 2 The upper vertical axis of Figure 2 represents the stroke (mm),

[0055] As Figure 2 shown, the positive direction stroke within the range where over-twist does not occur is 46.6 mm at 20 turns. On the other hand, the negative direction stroke within the range where over-twist does not occur is 6.4 mm at -34 turns.

[0056] Here, as Figure 2 shown, at -15 turns, a peak of -6.5 mm of stroke occurred.

[0057] Therefore, in Example 1, by setting -15 turns as the action start point, an effective stroke of 53.1 mm can be obtained.

[0058] In addition, as Figure 2 shown, if over-twist occurs, hysteresis will occur in the stroke, and the variation of torque will also become unstable.

[0059] Furthermore, as Figure 2As shown, -15 turns is taken as the starting point of the action indicated by a single-dashed line, so that the rotation in the positive direction compared thereto is Example 1 ( Figure 2 E1 in it), and the rotation in the negative direction compared thereto becomes the comparative example. This comparative example is set as Comparative Example 2 ( Figure 2 C2 in it).

[0060] <Example 2>

[0061] Except that the amount of twist of the single wire in the wire rods W1 and W2 is set to 24.5 turns and the twist pitch is set to 4.1 mm, the rest are the same as in Example 1. The pre-twist amount in Example 2 is 72%.

[0062] In Example 2, the positive direction stroke within the range where over-twisting does not occur is 37.5 mm at 21 turns. On the other hand, the negative direction stroke within the range where over-twisting does not occur is 17.5 mm at -33.5 turns.

[0063] Here, at -10 turns, a peak of -3.5 mm of stroke occurred.

[0064] Therefore, in Example 2, by setting -10 turns as the starting point of the action, an effective stroke of 41.0 mm can be obtained.

[0065] <Example 3>

[0066] Except that the amount of twist of the single wire in the wire rods W1 and W2 is set to 19.5 turns and the twist pitch is set to 5.1 mm, the rest are the same as in Example 1. The pre-twist amount in Example 3 is 57%.

[0067] In Example 3, the positive direction stroke within the range where over-twisting does not occur is 37.0 mm at 22 turns. On the other hand, the negative direction stroke within the range where over-twisting does not occur is 21.0 mm at -33 turns.

[0068] Here, at -7.5 turns, a peak of -2.5 mm of stroke occurred.

[0069] Therefore, in Example 3, by setting -7.5 turns as the starting point of the action, an effective stroke of 39.5 mm can be obtained.

[0070] <Example 4>

[0071] Except that the amount of twist of the single wire in the wire rods W1 and W2 is set to 7 turns and the twist pitch is set to 14.3 mm, the rest are the same as in Example 1. The pre-twist amount in Example 4 is 21%.

[0072] In Example 4, the positive stroke within the range where over-twisting does not occur is 35.0 mm at 26 revolutions. On the other hand, the negative stroke within the range where over-twisting does not occur is 34.0 mm at -32.5 revolutions.

[0073] Here, at -4 revolutions, a peak stroke of -0.5 mm occurred.

[0074] Therefore, in Example 4, by setting -4 revolutions as the starting point of the operation, an effective stroke of 35.5 mm can be obtained.

[0075] <Comparative Example 1>

[0076] Except that two single wires in the wire rods W1 and W2 were used without being stranded, the rest were the same as in Example 1. The pre-twisting amount in Comparative Example 1 was 0%.

[0077] Here, Figure 3 is a graph showing the changes in the stroke and torque of the wire rods W1 and W2 in Comparative Example 1 with respect to the number of revolutions of stranding. Figure 3 The horizontal axis of represents the number of revolutions (turns) of stranding. Figure 3 The upper vertical axis of represents the stroke (mm), Figure 3 and the lower vertical axis of represents the torque (Nm).

[0078] As Figure 3 shown, the positive stroke within the range where over-twisting does not occur is 30.4 mm at 28 revolutions. On the other hand, the negative stroke within the range where over-twisting does not occur is 32.1 mm at -28 revolutions.

[0079] Here, as Figure 3 shown, in Comparative Example 1, the stroke at 0 revolutions is the smallest, being 0 mm, and no negative stroke peak occurs.

[0080] Therefore, in Comparative Example 1, taking 0 revolutions as the starting point of the operation, an effective stroke of 30.4 mm (or 32.1) can be obtained.

[0081] In Figure 3 the shown Comparative Example 1, the rotational dependence of the stroke and torque is symmetric about the 0-revolution, i.e., the y-axis. In contrast, in Figure 2 the shown Example 1 and Comparative Example 2, the rotational dependence of the stroke and torque is not symmetric about the -15 revolutions indicated by the single-dot dash line. Specifically, as Figure 2 shown, in Example 1, which is a rotation in the positive direction compared to -15 revolutions, the effective stroke is greater than that in Comparative Example 1, and in Comparative Example 2, which is a rotation in the negative direction compared to -15 revolutions, the effective stroke is less than that in Comparative Example 1.

[0082] Here, inFigure 4 In this, the forward stroke, negative stroke peak value, and effective stroke of Examples 1 to 4 and Comparative Example 1 are summarized and presented. Figure 4 It is a graph showing the change of the effective stroke with respect to the amount of pre-twist. Figure 4 The horizontal axis represents the amount of pre-twist (%), and the vertical axis represents the stroke (mm). In Figure 4 , Examples 1 to 4 are represented as E1 to E4, and Comparative Example 1 is represented as C1.

[0083] As Figure 4 shown, compared with Comparative Example 1, the effective strokes within the range where over-twisting does not occur are all larger for Examples 1 to 4. In addition, the larger the amount of pre-twist, the larger the forward stroke and the negative stroke peak value. As a result, the effective stroke is also larger.

[0084] Next, in Figure 5 , the number of revolutions corresponding to the forward stroke and the negative stroke peak value shown in Figure 4 for Examples 1 to 4 and Comparative Example 1 are summarized and presented. Figure 5 It is a graph showing the change of the effective number of revolutions with respect to the amount of pre-twist. Figure 5 The horizontal axis of it represents the amount of pre-twist (%), and the vertical axis represents the number of revolutions (turns). The effective number of revolutions is the number of revolutions corresponding to the effective stroke.

[0085] As Figure 5 shown, the larger the amount of pre-twist, the smaller the number of revolutions corresponding to the forward stroke. On the other hand, the larger the amount of pre-twist, the more the number of revolutions corresponding to the negative stroke peak value moves in the negative direction. Here, since the amount of movement in the negative direction of the number of revolutions corresponding to the negative stroke peak value is larger than the decrease amount of the number of revolutions corresponding to the forward stroke, the larger the amount of pre-twist, the larger the effective number of revolutions.

[0086] Next, Figure 6 it is a graph showing the change of the mechanical efficiency with respect to the effective stroke for Example 1 and Comparative Example 2 shown in Figure 2 , and Comparative Example 1 shown in Figure 3 . Figure 6 The horizontal axis of it represents the effective stroke (mm), and the vertical axis represents the mechanical efficiency (%). In addition, Example 1 is E1 in Figure 2 , and it is the case of rotating more in the positive direction than -15 turns indicated by the single-dot chain line in Figure 2 . Comparative Example 2 is C2 in Figure 2 , representing the case of rotating more in the negative direction than -15 turns indicated by the single-dot chain line in Figure 2 .

[0087] As Figure 6As shown, in Comparative Example 2, the maximum value of the effective stroke is 12.9 mm, which is 12.9% (=12.9 mm / 100 mm × 100). It is not only small, but also the mechanical efficiency is low.

[0088] The mechanical efficiency of Comparative Example 1 shows a peak at an effective stroke of about 10 mm, which is 10%, and then gradually decreases. Also, when the effective stroke is 20 mm or more, the mechanical efficiency of Comparative Example 1 is lower than that of Example 1. The maximum value of the effective stroke of Example 1 is 30.4 mm, which is 30.4%.

[0089] In contrast, as Figure 6 shown, in Example 1, the maximum value of the effective stroke is 53.1 mm, which is 53.1%. It is not only large, but also the mechanical efficiency stably maintains a high value when the effective stroke is 20 mm or more. In this way, it can be seen that Example 1 is not only excellent in that the maximum value of the effective stroke is large, but also excellent in mechanical efficiency.

[0090] From the present disclosure thus described, it is obvious that the embodiments of the present disclosure can be varied in many ways. Such variations should not be regarded as departing from the spirit and scope of the present disclosure, and all such modifications that are obvious to those skilled in the art are intended to be included within the scope of the appended claims.

Claims

1. An actuator comprising: A plurality of wires, each of which has one end engaged with a load; a supporting member on which the other ends of the plurality of wires are fixed; a driving source that rotates the support member to twist the plurality of wires, The actuator changes the distance between the support member and the load according to the rotation of the support member. In the actuator, The plurality of wires are fixed to the support member in a state where they are twisted in the same twisting rotation direction in advance. When the distance between the support member and the load is reduced, the plurality of wires are rotated in the same rotation direction as the twisting rotation direction and twisted.

2. The actuator according to claim 1, wherein: The position where the distance between the support member and the load becomes maximum by rotating and twisting the plurality of wires in a rotation direction opposite to the twisting rotation direction from a state where the plurality of wires are not twisted is set as an operation start point.

3. The actuator according to claim 1 or 2, wherein: The plurality of wires are respectively made of ultra-high molecular weight polyethylene.

4. The actuator according to claim 1 or 2, wherein: The plurality of wires are respectively twisted wires formed by twisting a plurality of single wires together.

5. A robot, wherein a joint is driven by the actuator according to claim 1 or 2.

6. An orthosis which is worn by a person and assists the movement of the person's joints, wherein: The orthosis is driven by an actuator according to claim 1 or 2.

7. A haptic device that is worn by a person and provides a virtual sense of touch to the person, wherein: The haptic device is driven by the actuator according to claim 1 or 2.

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