Tactile sensor and tactile sensing system

Abstract

To slim down a part attached to a robot and easily adjust the measurement range and measurement sensitivity of an external force without replacing a sensor itself.SOLUTION: A tactile sensing system 10 comprises a tactile sensor 12 that detects the state of external force when an object comes into contact and generates an electrical signal corresponding to that state, an air supply / exhaust mechanism 13 that supplies and exhausts a predetermined gas to the tactile sensor 12, and a processing unit 13 that calculates the magnitude of the external force applied to the tactile sensor 12 based on the detection results of the tactile sensor 12. The tactile sensor 12 is provided elastically deformable as the site on which the external force acts, and comprises an external force application unit 16 that generates a magnetic field in a predetermined range of magnetic field space 20, and a magnetic sensor 18 that detects changes in the magnetic field in the magnetic field space 20 based on the displacement of the external force application unit 16 due to the external force. The air supply / exhaust mechanism 13 is configured to be able to supply and exhaust gas to and from the magnetic field space 20, and the measurement sensitivity and measurement range of the external force are adjusted by the supply and exhaust of the gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tactile sensor and a tactile sensing system, and more particularly to a tactile sensor and a tactile sensing system that are capable of adjusting the measurement range and measurement sensitivity of an external force. [Background technology]

[0002] A robotic hand that grasps an object is equipped with a tactile sensor that detects external forces, such as pressing and shearing forces, acting on the contact point of the object. Based on the sensor's detection results, the robotic hand adjusts its gripping force according to the object's weight, flexibility, and other properties. A known example of this type of tactile sensor is a magnetic tactile sensor that utilizes changes in a magnetic field due to the action of an external force, as disclosed in Patent Document 1. In this magnetic tactile sensor, a magnetic layer that generates a magnetic field displaces in response to the magnitude of the external force, and the external force is detected from the changes in the surrounding magnetic field that accompany this displacement. Patent Document 2 also discloses a sensor device using a magnetorheological elastomer whose elastic modulus is variable by changing the strength of an external magnetic field. This sensor device calculates the load applied to the magnetorheological elastomer based on the electrical resistance between a pair of electrode plates arranged above and below the magnetorheological elastomer. In this sensor device, the elastic modulus of the magnetorheological elastomer is adjusted by applying current to an electromagnet arranged around the magnetorheological elastomer, thereby changing the sensitivity and measurement range of the external force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-97453 [Patent Document 2] Patent No. 6019227 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the tactile sensor of Patent Document 1 cannot adjust its measurement range or sensitivity appropriately depending on the properties of the object being grasped by the robot hand, making it difficult to adopt in general-purpose robots that perform a variety of tasks using various objects. For example, the measurement range and sensitivity required for a tactile sensor differ when grasping a heavy object with a robot hand versus when grasping a lightweight, fragile object. In the former case, a wide measurement range is required, but low sensitivity is not required. In the latter case, a narrow measurement range is acceptable, but high sensitivity is required for more precise force control. In this regard, the tactile sensor of Patent Document 1 is not versatile because it must be replaced with a different type of tactile sensor with a different configuration or structure, such as a magnetic layer, when the required specifications for measurement range and sensitivity differ. Furthermore, the sensor device of Patent Document 2 requires a pair of electromagnets (each consisting of a coil and an iron core) and electrode plates to be arranged above and below the magnetorheological elastomer, which increases the thickness of the sensor body located on the surface of the robot hand and limits the flexibility of sensor placement.

[0005] The present invention was devised with an eye to these problems in mind, and its purpose is to provide a tactile sensor and tactile sensing system that allows the part attached to the robot to be slimmed down while easily adjusting the measurement range and measurement sensitivity of external forces without having to replace the sensor itself. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention is primarily a tactile sensor comprising an external force application part that is elastically deformable as an external force application part and generates a magnetic field in a magnetic field space of a predetermined range, and a magnetic sensor that detects the state of the magnetic field in the magnetic field space, and the magnetic sensor generates an electric signal based on the magnetic field change in the magnetic field space due to the displacement of the external force application part when the external force is applied, and the measurement sensitivity and measurement range of the external force are adjustable by supplying and discharging a predetermined gas to and from the magnetic field space. [Effects of the Invention]

[0007] In the present invention, when no external force is applied and no load is applied, the supply and exhaust of gas into the magnetic space causes pressure changes within the magnetic space and deformation of the external force application unit, which changes the distance between the external force application unit and the magnetic sensor and the elasticity of the external force application unit. Therefore, according to the present invention, when no load is applied, adjusting the supply and exhaust of gas into the magnetic space makes it possible to easily adjust the external force measurement sensitivity and measurement range with a slim structure for the entire part attached to the robot, without replacing the sensor itself. This makes the tactile sensor of the present invention applicable to general-purpose robots that perform a variety of tasks. Furthermore, by using a permanent magnet elastomer as the external force application unit, electrical components such as electrical circuits and insulating structures to ensure safety at the contact point with the object are unnecessary, allowing for a more compact attachment part to the robot. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a tactile sensing system according to an embodiment of the present invention. [Figure 2] FIG. 1A is a schematic cross-sectional view illustrating the expanded state of the tactile sensor, and FIG. 1B is a schematic cross-sectional view illustrating the contracted state of the tactile sensor. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] A schematic diagram of the tactile sensing system according to this embodiment is shown in Figure 1. In this figure, the tactile sensing system 10 comprises a tactile sensor 12 that detects the state of an external force acting upon contact with a predetermined object or the like and generates an electrical signal corresponding to that state, an air supply / exhaust mechanism 13 that supplies and exhausts a predetermined gas to and from the tactile sensor 12, and a processing unit 14 that calculates the magnitude of the external force applied to the tactile sensor 12 based on the detection results of the tactile sensor 12.

[0011] The tactile sensor 12 comprises an external force acting portion 16 that serves as the site of action of an external force and generates a magnetic field within a predetermined range, a base 17 that supports the external force acting portion 16, and a magnetic sensor 18 that detects the state of the magnetic field generated by the external force acting portion 16.

[0012] The external force application portion 16 is a flexible elastic body made of a material that can be elastically deformed by the action of an external force, and is made of a permanent magnetic elastomer that also functions as a permanent magnet. Note that the external force application portion 16 in the present invention may be any material that can be elastically deformed as a portion where an external force is applied, and that also functions as a magnet that generates a magnetic field in a predetermined range.

[0013] The base 17 is made of silicon, but is not particularly limited thereto, and has a cylindrical shape with a bottom and an internal space that is open at the top end in FIG. 1 . A disk-shaped external force application unit 16 is fixed to the periphery of the upper end of the base 17, and the external force application unit 16 closes the open portion at the center of the upper end of the base 17. Therefore, the internal space of the base 17, surrounded by the external force application unit 16 and the inner peripheral wall of the base 17, becomes a magnetic field space 20 in which a magnetic field generated by the external force application unit 16 exists. In addition, a gas inlet / outlet port 21 connected to the air supply / exhaust mechanism 13 is formed in the peripheral wall of the base 17, and gas can flow between the air supply / exhaust mechanism 13 and the magnetic field space 20 through the gas inlet / outlet port 21. The base 17, except for the gas inlet / outlet port 21, has a sealed structure that prevents gas from flowing between the magnetic field space 20 and the outside, and is designed so that the base 17 itself does not deform due to pressure changes caused by air supply / exhaust to / from the magnetic field space 20 by the air supply / exhaust mechanism 13.

[0014] In the base 17 having the above configuration, the upper surface of the external force application portion 16 in FIG. 1 becomes the contact surface with the object, and the portion of the external force application portion 16 spanning the open portion of the base 17 becomes elastically deformable within the magnetic field space 20 due to the action of an external force associated with the contact of the object.

[0015] The magnetic sensor 18 has a known structure including a magnetic detection element such as a Hall element or a magnetoresistance element, a circuit board, and the like, and is fixedly disposed on the bottom side of the base 17 within the magnetic field space 20 so as to face the external force application unit 16. When an external force is applied to the external force application unit 16, the magnetic sensor 18 detects changes in the magnetic field in three orthogonal axial directions corresponding to the displacement of the external force application unit 16 within the magnetic field space 20, and generates electrical signals corresponding to the changes in the magnetic field in each of the three orthogonal axial directions. In other words, the magnetic sensor 18 detects the difference in magnetic field strength when an external force is applied compared to when no external force is applied. Note that the three axial directions here are the x- and y-axis directions, which are shear directions along a horizontal plane facing the magnetic sensor 18, and the z-axis direction, which is a pressing direction perpendicular to the horizontal plane, as shown in FIG. 1 .

[0016] Although not shown, the air supply and exhaust mechanism 13 employs a known configuration consisting of a fluid machine including a pump and its control equipment, and a fluid circuit including a relief valve, a check valve, etc. connected to the fluid machine, and a detailed description of its structure and configuration will be omitted. The air supply and exhaust mechanism 13 supplies and exhausts air as a fluid to the magnetic space 20 in response to a predetermined command from the outside. The air supply and exhaust mechanism 13 also monitors the internal pressure of the magnetic space 20, and as described below, an external force is calculated by the arithmetic processing unit 14 in accordance with the internal pressure. The gas supplied to the magnetic space 20 is not limited to air, and any gas that exhibits the effects described below and does not directly affect the magnetic field of the magnetic space 20 may be used.

[0017] The arithmetic processing device 14 is configured by a computer including an arithmetic processing device such as a CPU and storage devices such as a memory and a hard disk. The arithmetic processing device 14 stores a relational expression between the magnetic field and the external force, and calculates the magnitude of the external force in the three axial directions from the magnetic field strength detected by the magnetic sensor 18. This relational expression is as follows, and is specified for each pressure in the magnetic field space 20, which is determined according to the state of air intake and exhaust from the air intake and exhaust mechanism 13 to the magnetic field space 20.

number

[0018] Next, the operation of the tactile sensing system 10 will be described.

[0019] When air is supplied into the magnetic field space 20 by the air supply / exhaust mechanism 13 from the standard state shown in FIG. 1 in which the external force application portion 16 is horizontally flat, the pressure inside the magnetic field space 20 increases, and as shown in FIG. 2(A), the external force application portion 16 deforms by expanding outward from the magnetic field space 20 like a balloon, increasing the volume of the magnetic field space 20. In this expanded state, the internal pressure of the magnetic field space 20 is higher than in the standard state, and when an external force is applied to the external force application portion 16 toward the inside of the magnetic field space 20, the external force application portion 16 becomes harder and less susceptible to elastic deformation than in the standard state. Therefore, in the expanded state, a larger external force is required to displace the external force application portion 16 by a certain amount compared to the standard state, resulting in lower measurement sensitivity. In addition, in the expanded state, the external force acting portion 16 expands outward on the opposite side of the magnetic sensor 18 when no load is applied, compared to the standard state, so the maximum distance between the external force acting portion 16 and the magnetic sensor 18 when no load is applied increases, and the range of motion of the external force acting portion 16 is expanded compared to the standard state, resulting in a wider measurement range.

[0020] On the other hand, when air is exhausted from the magnetic field space 20 by the air supply / exhaust mechanism 13 from the standard state during the no-load period, the pressure within the magnetic field space 20 decreases, and as shown in FIG. 2(B), the external force application unit 16 deforms so as to be recessed inward into the magnetic field space 20, resulting in a contracted state in which the volume of the magnetic field space 20 decreases. In this contracted state, the internal pressure of the magnetic field space 20 is lower than in the standard state, and when an external force is applied to the external force application unit 16 toward the inside of the magnetic field space 20, the external force application unit 16 becomes more flexible and more susceptible to elastic deformation than in the standard state. Therefore, in the contracted state, a smaller external force is required to displace the external force application unit 16 by a certain amount compared to the standard state, resulting in a state of high measurement sensitivity. Furthermore, in the contracted state, the external force acting portion 16 is recessed inward toward the magnetic sensor 18 when no load is applied, compared to the standard state. This reduces the maximum distance between the external force acting portion 16 and the magnetic sensor 18 when no load is applied, reducing the range of motion of the external force acting portion 16 compared to the standard state, and narrowing the measurement range compared to the standard state.

[0021] In the above-described tactile sensing system 10, prior to external force detection, the pressure and volume inside the magnetic field space 20 are changed by adjusting the air intake and exhaust with the air intake and exhaust mechanism 13 according to the properties of the target object, thereby adjusting the external force measurement range corresponding to the maximum distance between the external force application unit 16 and the magnetic sensor 18 when no load is applied, and the external force measurement sensitivity corresponding to the internal pressure of the magnetic field space 20. Then, with air intake and exhaust to the magnetic field space 20 stopped, the external force is measured when an object comes into contact with the tactile sensor 12. In other words, the magnetic field change in the magnetic field space 20 due to the displacement of the external force application unit 16 relative to when no load is applied is detected by the magnetic sensor 18, and the external force for each axis is calculated from the magnetic field change by the arithmetic processing device 14.

[0022] The configuration of each part of the device in the present invention is not limited to the illustrated configuration example, and various modifications are possible as long as they provide substantially the same effect. [Explanation of symbols]

[0023] 10 Tactile Sensing System 12 Tactile Sensor 13 Air intake and exhaust mechanism 14 Processing unit 16 External force acting part 17 Base 18 Magnetic Sensor 20 Magnetic field space

Claims

1. A tactile sensor comprising: an external force application unit that is elastically deformable as an external force application site and generates a magnetic field in a magnetic field space of a predetermined range; and a magnetic sensor that detects the state of the magnetic field in the magnetic field space, wherein the magnetic sensor generates an electric signal based on a change in the magnetic field in the magnetic field space caused by displacement of the external force application unit when the external force is applied; A tactile sensor characterized in that the sensitivity and measurement range of the external force can be adjusted by supplying and discharging a predetermined gas into the magnetic field space.

2. A tactile sensor comprising: an external force application part that is elastically deformable as an external force application part and that generates a magnetic field in a magnetic field space of a predetermined range; a base that supports the external force application part; and a magnetic sensor that detects the state of the magnetic field in the magnetic field space, wherein the magnetic sensor generates an electric signal based on a change in the magnetic field in the magnetic field space caused by the displacement of the external force application part when the external force is applied; The magnetic field space is formed in a space surrounded by the external force application part and the base, the magnetic sensor is disposed therein, and the magnetic sensor is configured to be able to supply and exhaust a predetermined gas, and the supply and exhaust of the gas makes it possible to adjust the distance between the external force application part and the magnetic sensor when no load is applied and no external force is acting.

3. 3. The tactile sensor according to claim 2, wherein the elasticity of the external force acting portion can be adjusted by changing the pressure in the magnetic field space when no load is applied by supplying or discharging the gas.

4. 4. The tactile sensor according to claim 1, wherein the external force application portion is made of a permanent magnet elastomer.

5. A tactile sensing system that detects the magnitude of an external force based on a change in the surrounding magnetic field caused by the action of the external force when an object is touched, a tactile sensor that detects the state of the external force and generates an electrical signal corresponding to the state; an air supply / exhaust mechanism that supplies and exhausts a predetermined gas to and from the tactile sensor; and a processing unit that calculates the magnitude of the external force applied to the tactile sensor based on the detection result of the tactile sensor, the tactile sensor is provided elastically deformable as an acting portion of the external force, and includes an external force acting portion that generates a magnetic field in a magnetic field space of a predetermined range, and a magnetic sensor that detects a change in the magnetic field in the magnetic field space based on a displacement of the external force acting portion due to the external force; The tactile sensing system is characterized in that the air supply and exhaust mechanism is configured to be able to supply and exhaust the gas to and from the magnetic field space, and the measurement sensitivity and measurement range of the external force are adjusted by the supply and exhaust of the gas.

6. The tactile sensing system described in claim 5, characterized in that the arithmetic processing device calculates the magnitude of the external force from the detection results of the magnetic sensor using a relational equation between the magnetic field and the external force, and the relational equation is specified for each pressure in the magnetic field space.

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