CN112229553B - A flexible tactile sensor based on light attenuation, array and preparation method thereof - Google Patents

Abstract

The invention discloses a flexible touch sensor based on light attenuation, an array and a preparation method thereof, belonging to the technical field of sensing, wherein the flexible touch sensor comprises: the device comprises a laser light source, a first optical fiber, a flexible dome, a second optical fiber, a photoelectric sensor and a flexible optical fiber coupler, wherein the flexible dome is adhered to the surface of a soft object through the flexible optical fiber coupler, one ends of the first optical fiber and the second optical fiber are aligned with the flexible dome, the other ends of the first optical fiber and the second optical fiber are respectively connected with the laser light source and the photoelectric sensor, laser generated by the laser light source sequentially passes through the first optical fiber for transmission, the flexible dome for reflection and the second optical fiber for transmission, then reaches the photoelectric sensor, the photoelectric sensor is used for calculating the light intensity of the received laser, and the light intensity is determined by the force born on the surface of the soft object. The compliance of the soft robot can be maintained, the environment stimulus can be responded quickly, the contact force of the surrounding environment can be perceived quickly, and the problem that the soft robot lacks touch sense is solved.

Description

A flexible tactile sensor based on light attenuation, array and preparation method thereof

Technical Field

The present invention belongs to the field of sensor technology, and more specifically, relates to a flexible tactile sensor based on light attenuation, an array and a preparation method thereof.

Background technique

Tactile receptors are essential for biological perception of external environmental stimuli. However, integrating tactile sensors into soft robots is challenging. This is because traditional rigid tactile sensors have a negative impact on the softness and compliance of soft robots, and existing soft sensors are either difficult to manufacture or slow to respond.

The inherent flexibility and compliance of soft robots allow their shapes to bend and stretch to adapt to complex environments and achieve motion in a continuous manner to manipulate objects. However, compliance is a disadvantage for modeling soft manipulators because their kinematics and dynamics are different from those of rigid manipulators. In addition, the sense of touch of soft robots helps to estimate the environment, such as surface unevenness and the location of edges and corners, and can also transmit and utilize external stimuli (such as contact forces) for accurate modeling and control. However, traditional tactile sensors (such as metal strain gauges, array-based force sensors, optical tactile sensors, and hydroacoustic pressure sensors) generally have rigid materials, which will affect the stiffness of the soft robot if they are integrated into the body of the soft robot. Therefore, it is still challenging to design and manufacture flexible tactile sensor arrays embedded in soft robots.

Summary of the invention

In view of the defects of the prior art and the need for improvement, the present invention provides a flexible tactile sensor, array and preparation method based on light attenuation, which aims to maintain the compliance of the soft robot, quickly respond to environmental stimuli, quickly perceive the contact force of the surrounding environment, solve the problem of the lack of tactile sensing of the soft robot, and thus achieve accurate modeling and control.

To achieve the above-mentioned purpose, according to one aspect of the present invention, a flexible tactile sensor based on light attenuation is provided, comprising: a laser light source, a first optical fiber, a flexible dome, a second optical fiber, a photoelectric sensor and a flexible optical fiber coupler; the flexible dome is arranged on the flexible optical fiber coupler, the flexible optical fiber coupler is adhered to the surface of the soft object, and a through hole aligned with the top of the flexible dome is arranged in the flexible optical fiber coupler; one end of the first optical fiber is connected to the laser light source, one end of the second optical fiber is connected to the photoelectric sensor, and the other ends of the first optical fiber and the second optical fiber pass through the through hole in parallel; the laser light generated by the laser light source is transmitted through the first optical fiber to reach the flexible dome, and enters the second optical fiber after being reflected by the flexible dome, and is then transmitted to the photoelectric sensor through the second optical fiber; the photoelectric sensor is used to calculate the light intensity of the received laser light, and the light intensity is determined by the force borne on the surface of the soft object.

Furthermore, the first optical fiber and the second optical fiber each include a portion that passes through the interior of the soft object and reaches the through hole and a portion that is arranged outside the soft object.

Furthermore, it also includes: an elastic rubber tube, which is arranged inside the soft object and sleeved on the outside of the first optical fiber and the second optical fiber.

Furthermore, it also includes: two elastomeric sheaths, which are respectively sleeved on the outside of the parts of the first optical fiber and the second optical fiber located outside the soft object.

Furthermore, the material of the first optical fiber and the second optical fiber is PMMA plastic optical fiber.

Furthermore, the material of the flexible dome is silicone elastomer.

Furthermore, the light intensity is a photocurrent intensity, and the photocurrent intensity is:

Wherein, I is the photocurrent intensity, M is the radiation flux of the first optical fiber, _P0 is the effective output power of the first optical fiber, T is the penetration rate of the laser through the cross section of the second optical fiber, λ is the wavelength of the laser, α is the reflectivity of the flexible dome to the laser, d is the distance between the flexible dome and the cross section of the other end of the first optical fiber, θ is the scattering angle of the first optical fiber, A is the cross-sectional area of the second optical fiber, and R(λ) is the responsiveness of the photoelectric sensor to the laser with a wavelength of λ.

According to another aspect of the present invention, a flexible tactile sensor array based on light attenuation is provided, comprising N*M flexible tactile sensors based on light attenuation as described above, where N and M are positive integers, and N*M>1.

According to another aspect of the present invention, a method for preparing a flexible tactile sensor based on light attenuation as described above is provided, comprising: S1, preparing a flexible dome and a flexible fiber optic coupler respectively by a layered casting process, and connecting the flexible dome to the flexible fiber optic coupler; S2, placing a first optical fiber and a second optical fiber into the through hole of the flexible fiber optic coupler, and leading them out after passing through the interior of a soft object; S3, adhering the flexible fiber optic coupler to the surface of the soft object; S4, connecting the lead-out end of the first optical fiber to a laser light source, and connecting the lead-out end of the second optical fiber to a photoelectric sensor.

Furthermore, in the operation S1, the flexible dome is prepared by using silicone with a hardness of Shore D00-20, and the flexible optical fiber coupler is prepared by using silicone with a hardness of Shore D00-50.

In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) The flexible dome is set on the surface of the soft object. When the soft object is subjected to force, the distance between the two changes. Based on this, the optical path is set to calculate the force exerted on the soft object, which can maintain the compliance of the soft robot, quickly respond to environmental stimuli, and quickly perceive the contact force of the surrounding environment, thus solving the problem of the soft robot's lack of tactile sensing;

(2) The sensor is made of soft materials and integrated into the body of the soft robot, which will not affect the stiffness of the soft robot;

(3) Elastic protective bodies are embedded in the optical fibers inside and outside the soft robot to protect the optical fibers, thereby extending the service life of the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a flexible tactile sensor based on light attenuation provided by an embodiment of the present invention;

FIG2 is a schematic diagram showing the principle of pressure sensing by a flexible tactile sensor based on light attenuation provided by an embodiment of the present invention;

FIG3 is a schematic diagram of the structure of a flexible tactile sensor array based on light attenuation provided by an embodiment of the present invention;

FIG4 is a schematic structural diagram of a casting mold for a flexible dome provided in an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a casting mold for a flexible optical fiber coupler provided in an embodiment of the present invention.

Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

1 is a laser light source, 2 is a first optical fiber, 3 is a flexible dome, 4 is a second optical fiber, 5 is a photoelectric sensor, 6 is a flexible optical fiber coupler, 61 is a through hole, 7 is an elastomeric rubber tube, 8 is an elastomeric sheath, 9 is a soft object surface, 401 is a first lower mold, 402 is a first upper mold, 501 is a second lower mold, 502 is a second upper mold, and 503 is a metal column.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

In the present invention, the terms "first", "second", etc. (if any) in the present invention and the drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

Fig. 1 is a schematic diagram of the structure of a flexible tactile sensor based on light attenuation provided by an embodiment of the present invention. Referring to Fig. 1 and in combination with Fig. 2, the flexible tactile sensor based on light attenuation in this embodiment is described in detail.

The flexible tactile sensor based on light attenuation includes a laser light source 1, a first optical fiber 2, a flexible dome 3, a second optical fiber 4, a photoelectric sensor 5 and a flexible optical fiber coupler 6. The flexible dome 3 is arranged on the flexible optical fiber coupler 6, and the flexible optical fiber coupler 6 is adhered to the surface of a soft object. A through hole 61 aligned with the top of the flexible dome 3 is arranged in the flexible optical fiber coupler 6. The soft object is, for example, a manipulator of a soft robot. One end of the first optical fiber 2 is connected to the laser light source 1, one end of the second optical fiber 4 is connected to the photoelectric sensor 5, and the other ends of the first optical fiber 2 and the second optical fiber 4 pass through the through hole 61 in parallel, so that the first optical fiber 2 and the second optical fiber 4 are aligned with the top of the flexible dome 3. The flexible optical fiber coupler 6 can fix the first optical fiber 2 and the second optical fiber 4 so that the ends of the two optical fibers remain parallel. The laser light source 1 is used to generate laser, for example, for generating red laser.

The laser light generated by the laser light source 1 is transmitted through the first optical fiber 2, then passes through the surface of the soft object, and is further transmitted to the flexible dome 3. The flexible dome 3 reflects the received laser light, and the reflected laser light enters the second optical fiber 4. The second optical fiber 4 transmits the received laser light to the photoelectric sensor 5. The photoelectric sensor 5 is used to calculate the light intensity of the received laser light, which is determined by the force exerted on the surface of the soft object. Specifically, the photoelectric sensor 5 sends the sensed light intensity to a computer, which calculates the distance between the top of the flexible dome 3 and the surface of the soft object based on the light intensity of the received laser light, and calculates the force exerted on the surface of the soft object based on the obtained distance.

In the embodiment of the present invention, the flexible dome 3 is made of a silicone elastomer, which has high deformability and flexibility. The elastomer refers to a material that can return to its original shape after the external force is removed. It can be understood that the shape of the flexible dome 3 can be a hemispherical dome, or a semi-ellipsoidal or cubic top structure. The bottom opening edge of the flexible dome 3 is, for example, adhered to the flexible fiber optic coupler 6, and the flexible fiber optic coupler 6 is adhered to the surface of the soft object, so that the flexible dome 3 is at a certain distance from the surface of the soft object.

In the embodiment of the present invention, the first optical fiber 2 and the second optical fiber 4 both include a portion that passes through the inside of the soft object and reaches the through hole 61 and a portion that is arranged outside the soft object.

Furthermore, the flexible tactile sensor based on light attenuation also includes an elastomeric rubber tube 7 and two elastomeric sheaths 8. The elastomeric rubber tube 7 is arranged inside the soft object, and is sleeved on the outside of the first optical fiber 2 and the second optical fiber 4 to protect the pair of optical fibers inside the soft object. Specifically, the elastomeric rubber tube 7 can be buried in the manufacturing process of the soft object (such as flexible skin), and the first optical fiber 2 and the second optical fiber 4 can pass through the elastomeric rubber tube 7 to be buried inside the soft object, and be led out from the side of the soft object to connect the laser light source 1 and the photoelectric sensor 5 respectively. The two elastomeric sheaths 8 are respectively sleeved on the outside of the parts of the first optical fiber 2 and the second optical fiber 4 located outside the soft object to protect each optical fiber outside the soft object respectively.

In the embodiment of the present invention, the materials of the first optical fiber 2 and the second optical fiber 4 are polymethyl methacrylate (PMMA) plastic optical fibers, thereby completely manufacturing a flexible tactile sensor without any hard parts.

Referring to FIG. 2 , the laser light source 1 emits a red laser with a wavelength of λ. The laser is transmitted to the top of the flexible optical fiber coupler 6 via the first optical fiber 2. The radiation flux of the first optical fiber 2 is M, the effective output power is P ₀ , and the scattering angle is θ. The laser output from the first optical fiber 2 will irradiate the top surface of the flexible dome 3. The distance between the flexible dome 3 and the cross section of the first optical fiber 2 is d, and the distance d is the first distance. The laser reaches the end of the second optical fiber 4 after being reflected by the flexible dome 3. The reflectivity of the flexible dome 3 to the laser with a wavelength of λ is α. The penetration rate of the laser through the cross section of the second optical fiber 4 is T. The cross-sectional area of the second optical fiber 4 is A. The second optical fiber 4 transmits the received laser to the photoelectric sensor 5. The responsivity of the photoelectric sensor 5 to the laser with a wavelength of λ is R(λ). Therefore, the photocurrent intensity I obtained after processing by the photoelectric sensor 5 is:

The flexible dome 3 is adhered to the surface of the soft object through the flexible optical fiber coupler 6. When an external force is applied to the flexible tactile sensor, the flexible dome 3 is deformed, and the distance d between the top of the flexible dome 3 and the surface of the soft object changes. For example, the distance d changes from _d1 to _d2 . The intensity of light entering the second optical fiber 4 changes, that is, the photoelectric sensor 5 will detect the change in light intensity, so that the external computer calculates the distance d according to the change in light intensity, and calculates the change in contact force on the surface of the soft object according to the distance d.

FIG3 is a schematic diagram of the structure of a flexible tactile sensor array based on light attenuation provided in an embodiment of the present invention. Referring to FIG3 , the flexible tactile sensor array based on light attenuation includes N*M flexible tactile sensors based on light attenuation in the embodiments shown in FIG1-FIG2 , N*M＞1, and N and M are positive integers. The N*M flexible tactile sensors are independent of each other and can sense the contact force borne by each part of the flexible robot respectively. The size and shape information of environmental objects can be obtained through the sensor array, realizing the function of environmental perception.

The embodiment of the present invention further provides a method for preparing a flexible tactile sensor based on light attenuation in the embodiment shown in FIG. 1-FIG . 2 , and the method includes operations S1-S3.

In operation S1 , the flexible dome 3 and the flexible optical fiber coupler 6 are separately prepared by a layered casting process, and the flexible dome 3 is connected to the flexible optical fiber coupler 6 .

The first lower mold 401 and the first upper mold 402 are used in the preparation process of the flexible dome 3. As shown in FIG4 , the first lower mold 401 and the first upper mold 402 are made by 3D printing. The second lower mold 501, the second upper mold 502 and the metal column 503 are used in the preparation process of the flexible optical fiber coupler 6. As shown in FIG5 , the second lower mold 501 and the second upper mold 502 are made by 3D printing.

The flexible skin is made of silicone with a hardness of Shore D00-00. In order to make the flexible tactile sensor match the stiffness of the flexible skin, in operation S1, the flexible dome 3 is prepared using silicone with a hardness of Shore D00-20, and the flexible optical fiber coupler 6 is prepared using silicone with a hardness of Shore D00-50.

Specifically, when preparing the flexible dome 3, uncured silicone is injected into the first lower mold 401, and then the first upper mold 402 is placed on the uncured silicone. The silicone is left for a while to cure, and the fully cured silicone dome between the two molds is the required flexible dome 3. The cured flexible dome 3 can be taken out.

When preparing the flexible optical fiber coupler 6, insert the metal column 503 into the hole of the second lower mold 501, then inject the uncured organic silicon into the second lower mold 501, and finally place the second upper mold 502 on the uncured organic silicon, wait for a period of time for the organic silicon to cure, and the fully cured organic silicon material between the two molds is the required flexible optical fiber coupler 6, and the cured flexible optical fiber coupler 6 can be taken out. After the preparation is completed, the flexible dome 3 and the flexible optical fiber coupler 6 are connected together, for example, using special silicone glue.

In operation S2, the first optical fiber 2 and the second optical fiber 4 are placed into the through hole 61 of the flexible optical fiber coupler 6, and are led out after passing through the inside of the soft object.

Specifically, an elastomeric rubber tube 7 is embedded in the flexible skin during manufacturing, and the first optical fiber 2 and the second optical fiber 4 are sequentially passed through the through hole 61 and the elastomeric rubber tube 7 and then embedded in the soft object, and are led out from the side of the soft object to respectively connect to the laser light source 1 and the photoelectric sensor 5, and the outer sides of the led-out first optical fiber 2 and the second optical fiber 4 can also be covered with elastomeric sheaths 8 respectively.

In operation S3, the flexible optical fiber coupler 6 is adhered to the surface of the soft object. Furthermore, the preparation method can be used to adhere N*M flexible optical fiber couplers 6 to the surface of the soft object, thereby forming a flexible tactile sensor array to realize the function of sensing the environment.

In operation S4 , the lead end of the first optical fiber 2 is connected to the laser light source 1 , and the lead end of the second optical fiber 4 is connected to the photoelectric sensor 5 .

In this embodiment, the structure of the flexible tactile sensor based on light attenuation prepared by the preparation method is the same as the structure of the flexible tactile sensor based on light attenuation in the embodiments shown in FIG. 1-FIG . 2 , and will not be described in detail here.

It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. A light attenuation-based flexible tactile sensor comprising: the device comprises a laser light source (1), a first optical fiber (2), a flexible dome (3), a second optical fiber (4), a photoelectric sensor (5) and a flexible optical fiber coupler (6);

The flexible dome (3) is arranged on the flexible optical fiber coupler (6), the flexible optical fiber coupler (6) is adhered to the surface of a soft object, and a through hole (61) aligned with the top of the flexible dome (3) is arranged in the flexible optical fiber coupler (6); one end of the first optical fiber (2) is connected with the laser light source (1), one end of the second optical fiber (4) is connected with the photoelectric sensor (5), and the other ends of the first optical fiber (2) and the second optical fiber (4) parallelly penetrate through the through hole (61);

The laser generated by the laser light source (1) reaches the flexible dome (3) after being transmitted by the first optical fiber (2), enters the second optical fiber (4) after being reflected by the flexible dome (3), and is transmitted to the photoelectric sensor (5) through the second optical fiber (4), and the photoelectric sensor (5) is used for calculating the light intensity of the received laser, wherein the light intensity is determined by the force born on the surface of the soft object;

The first optical fiber (2) and the second optical fiber (4) each comprise a portion passing through the inside of the soft object and reaching the through hole (61) and a portion disposed outside of the soft object;

The flexible dome (3) is made of a silica gel elastomer.

2. The light attenuation-based flexible tactile sensor according to claim 1, further comprising:

and the elastomer rubber tube (7) is arranged inside the soft object and sleeved outside the first optical fiber (2) and the second optical fiber (4).

3. The light attenuation-based flexible tactile sensor according to claim 1, further comprising:

And the number of the elastomer jackets (8) is two, and the elastomer jackets are respectively sleeved outside the parts of the first optical fiber (2) and the second optical fiber (4) which are positioned outside the soft object.

4. The flexible tactile sensor based on light attenuation according to claim 1, characterized in that the material of the first optical fiber (2) and the second optical fiber (4) is PMMA plastic optical fiber.

5. The light attenuation based flexible tactile sensor according to any one of claims 1-4, wherein said light intensity is a photocurrent intensity, said photocurrent intensity being:

Wherein, For the photocurrent intensity,/>For the radiant flux of the first optical fiber (2)/>For the effective output power of the first optical fiber (2)/>For the transmissivity of the laser light through the cross section of the second optical fiber (4)/>For the wavelength of the laser,/>For the reflectivity of the flexible dome (3) to the laser light,/>For the distance between the flexible dome (3) and the cross section of the other end of the first optical fiber (2)/>For the scattering angle,/>, of the first optical fiber (2)For the cross-sectional area of the second optical fiber (4),For the photosensor (5) the wavelength is/>Is a laser response of the laser.

6. A light attenuation based flexible tactile sensor array comprising N x M light attenuation based flexible tactile sensors according to any one of claims 1-5, N and M being positive integers and N x M > 1.

7. A method of making a light attenuation based flexible tactile sensor according to any one of claims 1-5, comprising:

S1, preparing a flexible dome (3) and a flexible optical fiber coupler (6) respectively by using a layered casting process, and connecting the flexible dome (3) to the flexible optical fiber coupler (6);

s2, placing the first optical fiber (2) and the second optical fiber (4) into a through hole (61) of the flexible optical fiber coupler (6) and leading out after passing through the interior of the soft object;

S3, adhering the flexible optical fiber coupler (6) to the surface of a soft object;

s4, connecting the leading-out end of the first optical fiber (2) to the laser light source (1), and connecting the leading-out end of the second optical fiber (4) to the photoelectric sensor (5).

8. The method of manufacturing as claimed in claim 7, wherein the flexible dome (3) is manufactured in operation S1 using a silicone having a hardness of shore D00-20 and the flexible optical fiber coupler (6) is manufactured using a silicone having a hardness of shore D00-50.