Actuator angle estimation device and actuator angle estimation method

Abstract

An actuator angle estimation device 10 is an actuator bend angle estimation device 10 comprising a tube member 24 that has a first chamber 25A and a second chamber 25B which are spaced apart from each other, disposed along the axial direction, and arranged parallel to each other. The actuator bend angle estimation device 10 estimates the bend angle of an elongated actuator body section 22 that is bent as a result of one side of a tube wall being shortened in the axial direction in response to a rise in the internal pressure of the first chamber 25A. The actuator bend angle estimation device 10 additionally comprises: a fluid supply unit that supplies a fluid to the first chamber 25A; a pressure sensor 62 that acquires the internal pressure of the second chamber 25B; and an angle estimation unit that estimates the bend angle of the actuator body 22 on the basis of the internal pressure of the second chamber 25B, which is in a sealed state, as acquired by the pressure sensor 62.

Description

Actuator angle estimation device and actuator angle estimation method

[0001] The present invention relates to an actuator angle estimation device and an actuator angle estimation method for a fluid pressure actuator.

[0002] A McKibben type fluid pressure actuator has been known in the past, which has a rubber tube and a sleeve (made of woven high-tensile fiber) covering the outer surface of the rubber tube. This McKibben type fluid pressure actuator can change the axial length of the rubber tube and the sleeve. Furthermore, a technology has been proposed in which a restraining member is provided on a portion of the circumference of the rubber tube from one end to the other in the axial direction, thereby shortening and bending the side of the fluid pressure actuator where the restraining member is not provided (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2021-88999

[0004] Various uses for such fluid pressure actuators have been proposed. For example, it has been proposed to combine multiple actuators to use them as fingers that grasp objects by bending and deforming. Such uses would be easier if the bending angle of the fluid pressure actuator could be determined. Generally, angle sensors are used to measure the bending angle, but because angle sensors are attached directly to the actuator, wiring is required, and the sensor must be waterproof when washed, resulting in a complex configuration.

[0005] In view of the above, an object of the present disclosure is to provide an actuator angle estimation device and an actuator angle estimation method that are capable of determining the angle of a bending fluid pressure actuator with a simple configuration.

[0006] In order to achieve the above object, a first aspect of the actuator angle estimation device is an actuator bending angle estimation device that comprises a tube member having a first chamber and a second chamber that are separated from each other, arranged axially, and aligned parallel to each other, and that estimates the bending angle of a long actuator main body portion in which one side of the tube wall shortens in the axial direction and bends due to an increase in internal pressure in the first chamber, and that comprises: a fluid supply unit that supplies fluid to the first chamber; a pressure sensor that acquires the internal pressure of the second chamber; and an angle estimation unit that estimates the bending angle of the actuator main body based on the internal pressure of the second chamber in a sealed state acquired by the pressure sensor.

[0007] The actuator angle estimation device of the first aspect includes a tube member having a first chamber and a second chamber that are separated from each other, arranged axially, and parallel to each other. When the second chamber is sealed and fluid is supplied from the fluid supply unit to the first chamber, the internal pressure of the first chamber increases, causing the actuator main body to bend. The second chamber, which is sealed, bends and deforms in response to this bending. The inventors focused on the relationship between the internal pressure of the second chamber and the bending angle of the actuator main body at this time and found that the internal pressure of the second chamber changes depending on the bending angle of the actuator main body. Therefore, the internal pressure of the second chamber is acquired by a pressure sensor, and the bending angle of the actuator main body is estimated by an angle estimation unit based on the internal pressure of the second chamber.

[0008] According to the actuator angle estimation device of the first aspect, the bending angle of the fluid pressure actuator can be determined with a simple configuration, without using a conventional angle sensor.

[0009] In the actuator angle estimation device of the second aspect, the second chamber is pre-pressurized higher than atmospheric pressure when sealed.

[0010] In this way, by applying a pre-pressure higher than atmospheric pressure to the second chamber, it is possible to suppress the influence of noise on angle estimation.

[0011] The actuator angle estimation method of the third aspect is an actuator angle estimation method that estimates the bending angle of a long actuator main body that includes a tube member having a first chamber and a second chamber that are isolated from each other and aligned parallel to each other along the axial direction, and in which one side of the tube wall shortens and bends in the axial direction due to an increase in internal pressure in the first chamber, by supplying a fluid to the first chamber with the second chamber in a sealed state, and estimating the bending angle of the actuator main body based on the internal pressure of the second chamber in the sealed state.

[0012] In the actuator angle estimation method of the third aspect, when the second chamber is sealed and fluid is supplied to the first chamber, the internal pressure of the first chamber increases, causing the actuator body to bend. The second chamber, which is sealed, bends and deforms in response to this bending. The inventors focused on the relationship between the internal pressure of the second chamber and the bending angle of the actuator body at this time, and found that the internal pressure of the second chamber changes depending on the bending angle of the actuator body. Therefore, the bending angle of the actuator body is estimated based on the internal pressure of the second chamber.

[0013] According to the actuator angle estimation method of the second aspect, the bending angle of the fluid pressure actuator can be determined with a simple configuration, without using a conventional angle sensor.

[0014] In the actuator angle estimation method of the fourth aspect, the second chamber is pre-pressurized higher than atmospheric pressure in a sealed state.

[0015] In this way, by applying a pre-pressure higher than atmospheric pressure to the second chamber, it is possible to suppress the influence of noise on angle estimation.

[0016] According to the present disclosure, the bending angle of the actuator can be easily determined.

[0017] Fig. 1 is a diagram showing a schematic configuration of an actuator angle estimation device according to the present embodiment. Fig. 2 is a side view of a fluid pressure actuator as a measurement target of the actuator angle estimation device according to the present embodiment. Fig. 3 is a partially exploded perspective view of the fluid pressure actuator. Fig. 4 is a cross-sectional view of the fluid pressure actuator. Fig. 5 is a schematic block diagram of a control system of the actuator angle estimation device according to the present embodiment. Fig. 6 is a diagram showing a schematic configuration of an actuator angle estimation device according to a modified example of the present embodiment. Fig. 7 is a graph showing an example of the relationship between bending angle and internal pressure.

[0018] Hereinafter, embodiments for realizing the technology of the present disclosure will be described in detail with reference to the drawings.

[0019] In addition, components and processes that perform the same actions and functions are given the same reference numerals throughout the drawings, and duplicated explanations may be omitted as appropriate. Furthermore, the present disclosure is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present disclosure.

[0020] 1, the actuator curvature angle estimation device 10 of the present disclosure includes an air supply unit 60 as a fluid supply unit, a pressure sensor 62, and a control unit 64. The air supply unit 60 is connected to a first chamber 25A of the fluid pressure actuator 20 (described later) via a pipe 54, and supplies compressed air to the first chamber 25A. The pressure sensor 62 is connected to the second chamber 25B via a pipe 56, and is capable of measuring the internal pressure of the second chamber 25B of the fluid pressure actuator 20 in a sealed state. The air supply unit 60 and the pressure sensor 62 are connected to the control unit 64, which will be described later.

[0021] 2 shows a fluid pressure actuator 20 as a measurement target of the actuator bending angle estimation device 10 of the present disclosure. The fluid pressure actuator 20 includes an actuator main body 22 and sealing members 30A and 30B.

[0022] As also shown in FIG. 3, the actuator body 22 includes a tube member 24 , a sleeve 26 , a restraining member 28 , a locking ring 34 , and a crimping member 36 .

[0023] The tube member 24 is composed of two tubes (a first tube 24A and a second tube 24B), with a first chamber 25A formed within the first tube 24A and a second chamber 25B formed within the second tube 24B. The first tube 24A and the second tube 24B are cylindrical members that can expand and contract due to elastic deformation, and expand and contract due to pressure changes of the fluid inside. Note that, when the fluid pressure actuator 20 is assembled, the longitudinal directions of the first tube 24A and the second tube 24B coincide with the axial direction X. As shown in FIG. 4 , the first chamber 25A and the second chamber 25B are aligned parallel to each other when the fluid pressure actuator 20 is assembled.

[0024] The tube member 24 can be made of an elastic material such as butyl rubber. Air can be used as the fluid supplied to the tube member 24, in which case the fluid pressure actuator 20 becomes a pneumatic actuator. If the fluid pressure actuator 20 is hydraulically driven, it is preferable to use at least one type of rubber selected from the group consisting of highly oil-resistant NBR (nitrile rubber), hydrogenated NBR, chloroprene rubber, and epichlorohydrin rubber.

[0025] The sleeve 26 is a cylindrical member that covers the outer periphery of the tube member 24. The sleeve 26 is an elastic structure in which fiber cords oriented in a predetermined direction are woven, and the oriented cords intersect at a predetermined angle θ with respect to the axial direction X. By having such a shape, the sleeve 26 undergoes pantograph deformation that changes the angle θ, and follows the contraction and expansion of the tube member 24 while regulating this contraction and expansion.

[0026] It is preferable to use fiber cords made of aromatic polyamide (aramid fiber) or polyethylene terephthalate (PET) as the cords constituting the sleeve 26. However, the cords are not limited to these types of fiber cords, and other high-strength fiber cords such as PBO fiber (polyparaphenylene benzobisoxazole) may also be used.

[0027] The restraining member 28 is provided in the opposing portion between the first tube 24A and the second tube 24B. The restraining member 28 is in the form of a long plate, and is arranged so that its longitudinal direction is along the axial direction X of the tube member 24. The restraining member 28 is arranged from one end to the other end of the tube member 24 while contacting part of the outer periphery of the first tube 24A and the second tube 24B.

[0028] The restraining member 28 is formed of a material that does not expand or contract when pressurized, and is capable of flexural deformation in the direction in which its ends approach each other. A so-called leaf spring can be used as the restraining member 28. The dimensions of the leaf spring are determined according to the size of the fluid pressure actuator 20, the required gripping force, and other factors. The material of the leaf spring is not particularly limited, but typically, any material that is easily flexurally deformed and resistant to compression, such as a metal such as stainless steel, may be used. Alternatively, the leaf spring may be formed of a thin plate of carbon fiber reinforced plastic (CFRP).

[0029] The locking ring 34 is a ring-shaped member that is disposed on the outside of the sleeve 26 so as to sandwich the sleeve 26 between itself and a locking portion 58 (described later), and locks the sleeve 26 to the semi-proximal end portion 40. As a result, the sleeve 26 is folded back to the outer periphery via the locking ring 34. The locking ring 34 may be made of a material such as metal, hard plastic, fiber, or rubber.

[0030] The crimping member 36 is disposed so as to cover the outer periphery of the actuator body 22 where the insertion portion 50 is inserted, and presses the actuator body 22 against the insertion portion 50, which will be described later. This fixes the actuator body 22 to the insertion portion 50 of the sealing member 30, which will be described later. The crimping member 36 can be made of a metal such as aluminum alloy, brass, or iron.

[0031] The sealing member 30 is divided into a first sealing member 30A and a second sealing member 30B at the middle in the arrangement direction Z. The first sealing member 30A and the second sealing member 30B have the same shape.

[0032] The first sealing member 30A has a semi-proximal end portion 40 and an insertion portion 50. The semi-proximal end portion 40 has a larger diameter than the insertion portion 50, and the insertion portion 50 is formed to protrude inward in the axial direction X of the semi-proximal end portion 40 (toward the center of the actuator body 22). A flow path is formed in the semi-proximal end portion 40, forming part of a flow path R1 that runs from a connection hole H through a radial center of the insertion portion 50 in the axial direction X. A tube 54 is connected to the connection hole H, and compressed air is supplied to the flow path R1 from an air supply unit 60 serving as a fluid supply unit.

[0033] An insertion groove 42 is formed in the dividing surface 33 of the half base end portion 40. The end of the restraining member 28 is inserted into the insertion groove 42.

[0034] An attachment portion (not shown) is formed on the base half portion 40, and the fluid pressure actuator 20 is fixed to a shaft member (not shown) via the attachment portion.

[0035] 3 and 4, the insertion portion 50 has a bamboo shoot shape in which a plurality of tapered portions that taper inward in the axial direction X are connected in the axial direction X. A through hole is formed in the insertion portion 50 along the axial direction X, and this through hole forms a part of the flow path R1 described above. One end of the first tube 24A is fitted onto the insertion portion 50.

[0036] The first sealing member 30A is preferably made of a metal such as stainless steel, but is not limited to such a metal and may be made of a hard plastic material or the like.

[0037] The second sealing member 30B has the same shape as the first sealing member 30A across the dividing surface 33. A flow path is formed in the proximal half portion 40 of the second sealing member 30B, forming part of the flow path R2 that extends from the connecting hole H through the radial center of the insertion portion 50 in the axial direction X. One end of the second tube 24B is fitted onto the insertion portion 50 of the second sealing member 30B. A pipe 56 is connected to the connecting hole H, and a pressure sensor 62 is connected to the second chamber 25B via the pipe 56. The second chamber 25B is sealed and is pre-pressurized higher than atmospheric pressure. For example, the pre-pressure can be set to approximately 80 kPa to 120 kPa. The pressure sensor 62 is capable of measuring the internal pressure of the second chamber 25B.

[0038] The sealing member 31 provided at the other end side (the right side in FIG. 2 ) in the axial direction X of the fluid pressure actuator 20 has a lid portion 38 and a pair of insertion portions 50. The lid portion 38 of the sealing member 31 is similar to the half base end portion 40 of the sealing member 30 except that the connection hole H and the flow paths R, R2 are not formed in the lid portion 38 and the tip is rounded.

[0039] As shown in FIG. 5 , the control unit 64 includes a CPU (Central Processing Unit) 71, a ROM (Read Only Memory) 72, a RAM (Random Access Memory) 73, an input / output interface (I / O) 74, and a storage unit 75.

[0040] The CPU 71, ROM 72, RAM 73, storage unit 75, and I / O 74 are connected to each other via a bus 76. The air supply unit 60, pressure sensor 62, display unit 66, input unit 68, and other functional units are connected to the I / O 74. These functional units can communicate with the CPU 71 via the I / O 74.

[0041] For example, a hard disk drive (HDD), a solid state drive (SSD), a flash memory, or the like is used as the storage unit 75. The storage unit 75 stores a control program for controlling the fluid pressure actuator 20 and various data. Note that the control program and various data may be stored in the ROM 72.

[0042] Next, angle estimation by the actuator bending angle estimation device 10 of the present disclosure will be described.

[0043] The fluid pressure actuator 20 is used with the sealing member 30 on one end side fixed and the sealing member 30B on the other end side being a free end.

[0044] When an operation command for the fluid pressure actuator 20 is input from the input unit 68, the control unit 64 instructs the air supply unit 60 to supply compressed air. In response, the air supply unit 60 outputs compressed air, which is supplied to the first chamber 25A through the tube 54 and the flow path R1. When compressed air flows into the first chamber 25A through the connection hole H, the pressure within the first chamber 25A increases. Due to the increase in internal pressure, the first tube 24A elastically deforms and expands, and the sleeve 26 deforms so that the angle θ increases, exerting a force in a direction that shortens the length of the actuator main body 22. At this time, because the outer peripheral side wall of the first tube 24A where the restraining member 28 is disposed is restricted from shortening, the outer peripheral wall on the side where the restraining member 28 is not disposed, as viewed in the axial direction of the first tube 24A, shortens. This causes the restraining member 28 to bend, and the entire actuator main body 22 bends as shown by the two-dot chain line in FIG. 4 . The second tube 24B is curved and deformed in response to this bending, and the internal pressure of the second chamber 25B increases.

[0045] The angle between the axial direction of the tip end (sealing member 31 portion) of the actuator body 22 and the axial direction of the base end (sealing member 30 portion) of the actuator body 22 during this bending is defined as a bending angle α.

[0046] At this time, the pressure sensor 62 measures the internal pressure of the sealed second chamber 25B and outputs the internal pressure data to the control unit 64. The control unit 64 performs a process to estimate the bending angle α based on the internal pressure data. The bending angle α is correlated with the internal pressure P of the second chamber 25B, and the relationship between the bending angle α and the internal pressure P is determined in advance for the fluid pressure actuator 20 to be used. As an example, the relationship shown in FIG. 7 is obtained, and the bending angle α is estimated from this relationship based on the internal pressure data. The bending angle α obtained by the estimation process is output to the display unit 66.

[0047] In the actuator bending angle estimation device 10 of this embodiment, the bending angle α is estimated based on the internal pressure of the second chamber 25B, so it is possible to determine the bending angle α of the fluid pressure actuator 20 without using a conventional angle sensor. The pressure sensor 62 does not need to be closely attached to the fluid pressure actuator 20 and can be installed at a distance, allowing the fluid pressure actuator 20 itself to have a simple configuration. Furthermore, compared to conventional angle sensors, electrical wiring to the fluid pressure actuator 20 is not required, allowing for a simpler configuration.

[0048] Furthermore, by applying a pre-pressure higher than atmospheric pressure to the second chamber 25B when the fluid pressure actuator 20 is driven, it is possible to suppress the influence of noise on angle estimation.

[0049] <Modification>

[0050] In the above-described embodiment, both the first chamber 25A and the second chamber 25B may be connected to the air supply unit 60 and also to the pressure sensor 62. In this case, as shown in Fig. 6, the pipe 54 is branched into pipes 54A and 54B, and the pipe 56 is branched into pipes 56A and 56B, and three-way valves V1 and V2 are provided at each branch point.

[0051] The fluid pressure actuator 20-2 in Fig. 6 can be bent in two directions, toward the Z+ side and the Z- side in Fig. 6. When bending it toward the Z+ side, the pipe 54A side of the three-way valve V1 is opened, and the pipe 56B side of the three-way valve V2 is opened. This allows the fluid pressure actuator 20 to bend toward the Z+ side, and the bending angle can be estimated based on the internal pressure of the second chamber 25B.

[0052] When bending the fluid pressure actuator 20 toward the Z- side, the tube 54B side of the three-way valve V1 is opened, and the tube 56A side of the three-way valve V2 is opened. This allows the fluid pressure actuator 20 to bend toward the Z- side, and the bending angle to be estimated based on the internal pressure of the first chamber 25A.

[0053] The disclosure of Japanese Patent Application No. 2023-213374, filed on December 18, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. An actuator angle estimation device that estimates the bending angle of a long actuator main body comprising a tube member having a first chamber and a second chamber that are separated from each other, arranged along the axial direction, and aligned parallel to each other, and in which one side of the tube wall shortens in the axial direction and bends due to an increase in internal pressure in the first chamber, the actuator angle estimation device comprising: a fluid supply unit that supplies fluid to the first chamber; a pressure sensor that acquires the internal pressure of the second chamber; and an angle estimation unit that estimates the bending angle of the actuator main body based on the internal pressure of the second chamber in a sealed state acquired by the pressure sensor.

2. The actuator angle estimation device according to claim 1, wherein the second chamber is pre-pressurized higher than atmospheric pressure in a sealed state.

3. A method for estimating the bending angle of a long actuator body, comprising a tube member having a first chamber and a second chamber that are isolated from each other and aligned parallel along the axial direction, and in which an increase in internal pressure in the first chamber shortens one side of the tube wall in the axial direction and bends, the method comprising: supplying a fluid to the first chamber with the second chamber in a sealed state; and estimating the bending angle of the actuator body based on the internal pressure of the second chamber in the sealed state.

4. The actuator angle estimation method according to claim 3, wherein the second chamber is pre-pressurized higher than atmospheric pressure in a sealed state.

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