JPH0658829A - Optical tactile sensor - Google Patents

Abstract

PURPOSE:To enable the computing and detecting of a force working on the tactile sensor sections accurately by varying the attenuation factors of light rays with optical fibers with respect to the tactile pressure of the sensor sections. CONSTITUTION:Light rays from light sources 1a and 1b are admitted through one end of optical fibers 2. The light rays admitted into the fibers 2 are transmitted through a tactile sensor section 5 and received with photosensors 3a and 3b provided at other ends of the fibers 2. Optical fiber pressing jigs 6 and 6 (6 for upper one and 6' for lower one) have areas enough to press the optical fibers and for all varying pressing thereof. Therefore, when the same force works, possible deformation of the fibers 2 is varies. The attenuation ratio of light has a value varying at tactile sensor sections 5 of the respective fibers 2. Even when the clad thickness of the fibers is changed at the sensor sections 5, the attenuation factor of the light for the force is varied in value for the fibers 2 and enables the detection of a force distribution faithfully likewise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tactile sensor,
In particular, the present invention relates to a distributed optical tactile sensor that is applied to a hand of an industrial robot and simultaneously measures the contact position and contact pressure of an object when the object is grasped.

[0002]

2. Description of the Related Art Conventionally, as a tactile sensor, optical fibers are arranged in a grid pattern, light is incident from one end of the optical fiber, an intersection of the optical fibers is used as a tactile sensor portion, and light is generated by deformation of the optical fiber due to a force applied thereto. A method has been proposed in which the amount of attenuation of the object is monitored by a photodetector provided for each optical fiber, and the position where the target object contacts and the contact pressure are measured from each amount of attenuation (for example, Japanese Patent Application No. 3440274). FIG. 5 shows a configuration of such a conventional tactile sensor. 1a and 1b are light sources such as LEDs, lasers, and discharge tubes. Reference numeral 2 is an optical fiber, which is arranged in a lattice pattern of an upper layer and a lower layer. The intersection serves as the tactile sensor unit 5. 3a
3b is an optical sensor that detects the intensity of light. 4 is an arithmetic processing unit. Light from each of the light sources 1a and 1b enters from one end of each optical fiber 2. The light that has entered each of the optical fibers passes through the tactile sensor unit 5 and is received by the optical sensors 3a and 3b arranged at the other end of each of the optical fibers 2. When the object applies a contact pressure to the tactile sensor unit 5, each optical fiber forming the intersection is deformed. As a result, the condition of total reflection of light transmitted through the optical fiber is broken, and the tactile sensor unit 5
Leakage of light occurs according to the force applied to. As a result, the amount of light in the optical fiber of the tactile sensor unit touching the target object decreases. It is possible to obtain the tactile position and the contact pressure with the target object by calculating the light attenuation in each tactile sensor unit 5 in the arithmetic processing unit 4 from the light intensity signals from the respective optical sensors 3a and 3b.

[0003]

However, in the prior art, since the two optical fibers forming the tactile sensor section have the same attenuation, the force applied is only in two states in which the total sum of the applied forces is equal, that is, the diagonal components of the lattice. Added state (Fig. 6)
It is impossible to distinguish between (a)) and a state in which a force is applied to each point of a quadrangle having the diagonal line (FIG. 6 (b)). That is, the amount of light attenuation due to the force applied to each tactile sensor unit is distinguished only by measuring the amount of light attenuation p1 · p2 in the x direction and the amount of light attenuation q1 · q2 in the y direction as shown in FIG. I can't do it. The present invention solves this problem and proposes an optical tactile sensor capable of distinguishing two states and accurately calculating and detecting the force applied to each measurement point.

[0004]

In order to solve the above-mentioned problems, the present invention arranges optical fibers in a grid pattern and forms intersections thereof with a tactile sensor portion, and allows light to enter from one end of each optical fiber and the other end. In the optical tactile sensor for detecting and detecting the light amount in the optical fiber, and calculating and detecting the force applied to each tactile sensor unit from the attenuation amount of the light amount of each optical fiber, the light attenuation rate with respect to the tactile pressure of the tactile sensor unit is calculated as follows. By varying each fiber, the force applied to each tactile sensor unit is calculated and detected. The first method of changing the attenuation rate is
This is to change the area of the tactile sensor unit that presses the optical fiber. The second method of changing the attenuation factor is to change the characteristics of the optical fiber in the tactile sensor unit.

[0005]

By the above means, even if the same total force is applied,
Since the fiber pressing area of each tactile sensor is different, the deformation amount of the optical fiber for the same force will be different.
An attenuation factor distribution of light with respect to force occurs. Further, if the characteristics (attenuation rate) of the optical fiber in the tactile sensor section are different, the attenuation of light when the same force is applied is also different, and an attenuation rate distribution of light with respect to the force is generated. When a light attenuation rate distribution with respect to force occurs in each tactile sensor unit, even if the same total force is applied, if the distribution of the applied force changes, the observed attenuation of the optical fiber light will be different.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of the present invention. In the figure, 6 and 6 ′ are optical fiber pressing jigs (6
Is up and 6'is down). The pressing jigs for pressing each optical fiber have different areas. Therefore, when the same force is applied, the deformations of the optical fibers are different, and the light attenuation rate has different values in the tactile sensor units of the optical fibers. The relationship between the force acting on each tactile sensor unit and the light attenuation rate will be described with reference to FIG. (A) shows the distribution of the force acting on each tactile sensor unit, (b) shows the optical attenuation factor distribution of the upper layer fiber, and (c) shows the optical attenuation factor distribution of the lower layer fiber. Here, a22>a21>a12>a11>b11>b12> b
21> b22 and a11 + b11 = a12 + b12 = a21 + b21 = a
It is assumed that the light attenuation rate is given so that 22 + b22 = 2. Consider the case where the force takes an integer value as a model. The light attenuation for the upper layer is a11 * f11 + a12 * f12 = p1 a21 * f21 + a22 * f22 = p2 for the lower layer b11 * f11 + b21 * f21 = q1 b12 * f12 + b22 * f22 = q2 Observed light attenuation p1, p2 , Q1, q2 are applied to the following algorithm to calculate and detect the distribution of the applied force.

Algorithm (Step 1) ... Gives initial values of each tactile sensor unit. fij (0) = INT {((p1 + p2 + q1 + q2) * pi * qj) / (2 * (p1 + p2) * (q1 + q2))} (i, j = 1, 2) Formula (1) Here, INT is a decimal point or less. Represents the operation of rounding off. (Step 2) ri (n) = ai1 * fi1 (n) + ai2 * fi2
(N), (i = 1, 2) sj (n) = b1j * f1j (n) + b2j * f2j
Calculate (n) and (j = 1, 2), respectively. Here, if the following mathematical expression 1 is used, movement is performed between columns.

[0008]

[Equation 1]

That is, if q1-s1 (n)> 0, then f11 (n + 1) = f11 (n) -1 f21 (n + 1) = f21 (n) +1 If q1-s1 (n) <0 then f11 (n + 1) = F11 (n) +1 f21 (n + 1) = f21 (n) -1 q2-s2 (n)> 0, then f12 (n + 1) = f12 (n) -1 f22 (n + 1) = f22 (n) +1 q2- If s2 (n) <0, f12 (n + 1) = f12 (n) +1 f22 (n + 1) = f22 (n) -1

[0010]

[Equation 2]

According to the equation (2), similar movement is performed between rows.

[Equation 3] Fij when Equation 2 is repeated and Equation 3 becomes the minimum
(N) is the solution to be obtained. FIG. 3B shows a11 and a1.
2, a21, a22, (c) are b11, b12, b2
An example in which specific values are entered in 1 and b22 is shown. In such a tactile sensor, (f11, f12, f21, f2
2) = (4,0,0,4) In the case of (2), (f11, f12, f21, f2
Consider the case where the force of 2) = (2,2,2,2) acts (Fig. 4). In these two cases, the conventional optical fiber tactile sensor cannot observe the same light attenuation value and distinguish between the two. When the present invention is applied, the observed light attenuation is (p1, p2, q1, q2) = (4.4, in the case of (1).
5.6, 3.6, 2.4) In the case of (2), (p1, p2, q1, q2) = (4.6,
It gives observation values different from 5.4, 3.2, 2.8). This is detected according to the algorithm described above. In the case of (1) (Step 1) ... Initial values of each tactile sensor unit are given.

[0012]

[Equation 4]

(Step 2) n = 1 r1 (0) = 3.4, r2 (0) = 6.7 s1 (0) = 3.9, s2 (0) = 2.0 | p1-r1 (0 ) | + | P2-r2 (0) | = 2.1 | q1-s1 (0) | + | q2-s2 (0) | = 0.7 Therefore, movement is performed between columns.

[0014]

[Equation 5]

N = 2 r1 (1) = 3.3, r2 (1) = 6.8 s1 (1) = 4.1, s2 (1) = 1.8 | p1-r1 (1) | + | p2-r2 (1) | = 2.3 | q1-s1 (1) | + | q2-s2 (1) | = 1.1 Therefore, movement is performed between columns.

[0016]

[Equation 6]

N = 3 r1 (2) = 4.4, r2 (2) = 5.5 s1 (2) = 4.3, s2 (2) = 1.8 │p1-r1 (2) │ + │ p2-r2 (2) | = 0 | q1-s1 (2) | + | q2-s2 (2) | = 0.1 Therefore, movement is performed between rows.

[0018]

[Equation 7]

## EQU6 ## The applied force is detected. In the case of (2) (step 1) ... Initial values of each tactile sensor unit are given.

[0020]

[Equation 8]

Equation 8 is obtained, and both cases are detected. FIG. 4 shows a second embodiment of the present invention. Also in the case of having NxN tactile sensor units, the optical attenuation factor with respect to the force of each optical fiber is changed by changing the area of the pressing jig as in the case of 2x2, and the same algorithm as in the first embodiment is used. Thus, the force applied to each tactile sensor unit can be detected. As a third embodiment of the present invention, when the thickness of the clad of the optical fiber in each tactile sensor unit is changed, the light attenuation rate with respect to the force has a different value in each optical fiber, which is the same as in the first embodiment. The force applied to each tactile sensor unit can be detected by the algorithm.

[0022]

As described above, according to the present invention, since the attenuation rate of light with respect to the force of the optical fiber of each tactile sensor unit is changed, the same tactile sensor cannot distinguish the same. There is an effect that states having different force distributions can be distinguished from each other even by the total sum, and an optical tactile sensor that can faithfully detect the force distribution can be formed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a detection method according to the first embodiment of the present invention.

FIG. 3 is a diagram of specific values of the attenuation rate of FIG.

FIG. 4 is a configuration diagram showing a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a conventional tactile sensor.

FIG. 6 is a diagram of specific values of the attenuation rate of FIG.

[Explanation of symbols]

 1a, 1b Light source 2 Optical fiber 3a, 3b Optical sensor 4 Arithmetic processing device 5 Tactile sensor part 6, 6'Pressing jig

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masao Matono 2-1, Kurosaki Shiroishi, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Yasukawa Electric Co., Ltd.

Claims (3)

[Claims] 1. An optical fiber is arranged in a grid pattern, and the intersection is used as a tactile sensor part. Light is incident from one end of each optical fiber and the light amount is detected at the other end, and the attenuation amount of the light amount of each optical fiber is detected. In an optical tactile sensor that calculates and detects the force applied to each tactile sensor unit from each of the tactile sensor units, by varying the optical attenuation rate for the tactile pressure of the tactile sensor unit with each fiber of each tactile sensor unit An optical tactile sensor that calculates and detects force. 2. The optical tactile sensor according to claim 1, wherein the optical attenuation factor with respect to the tactile pressure of each fiber is changed by changing the area of the fiber pressing jig of the tactile sensor unit. 3. The optical tactile sensor according to claim 1, wherein the optical attenuation factor with respect to the tactile pressure of each fiber is changed by changing the clad thickness of the optical fiber of the tactile sensor section.