JP3168027B2 - Tactile sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tactile sensor for detecting the spatial frequency of a surface of an object to be measured by sliding the surface of the object.

[0002]

2. Description of the Related Art A sensor has a function of detecting, detecting, discriminating, recognizing, and measuring various kinds of physical quantities such as displacement, temperature, pressure, magnetism, gas, light, quantum rays, and the like. With the development of systems and robots, sensor development,
Research has been conducted from various angles. The sensors include those that recognize the position, shape, size, and the like, those that recognize it by physical contact or by sound or light, and those that capture an image and recognize it by image processing.

The initial sensors applied to the automatic control system include a cam switch and a proximity switch, which are used for detecting the position of an object driven by a motor or the like and controlling the position. It is used. Also,
An infrared camera, a television camera, or the like is used as a sensor for controlling the robot arm, and control information is obtained by processing image signals.

[0004]

A sensor corresponding to human hearing is a microphone, and a sensor corresponding to vision is a camera, while a sensor corresponding to touch is equivalent to a microphone or a television camera. Has not yet been realized.

In order to realize a sensor corresponding to the tactile sensation of a human, information on the surface of the object must be extracted only by sliding the surface of the object lightly like a human finger. For example, one of the important functions of the tactile sense is the perception of surface texture information obtained by rubbing an object. To realize this perception, a sensor that perceives fine irregularities on the surface is necessary, but for this purpose, a conventional two-dimensional array sensor or a tactile sensor using an optical method is not necessarily suitable. .

That is, in a structure in which a flexible sheet is covered on a relatively rigid substrate such as a conventional two-dimensional array sensor or a tactile sensor using an optical method, sufficient contact between an object and the sensor is maintained. Therefore, it is difficult to simultaneously solve the requirement that the sheet must be made thicker and the requirement that the sheet must be made thinner in order to obtain high resolution. Further, if it is intended to obtain high resolution only from two-dimensional data, it is necessary to increase the density of the sensor, and the subsequent processing must be complicated.

An object of the present invention is to provide a tactile sensor capable of extracting information on the surface of an object by lightly sliding the surface of the object. .

For this purpose, the tactile sensor of the present invention comprises: an elastic body which comes into contact with an object to be measured; and a plurality of detecting means which are provided at different depths from the surface of the elastic body and detect distortion inside the elastic body due to surface deformation. Processing the detection signals of the plurality of detection means to detect surface deformation when the measurement object is slid inside the elastic body having different attenuation to obtain uneven tactile information based on the spatial frequency of the measurement object surface. Signal detecting means, and the detecting means is a probe provided in an elongated shape parallel to the contact surface.

[0009]

According to the tactile sensor of the present invention, by providing a plurality of detecting means for detecting the strain inside the elastic body at different depths from the surface of the elastic body which comes into contact with the object to be measured, the surface deformation can be made differently inside the elastic body. Can be detected by depth,
By calculating them, it is possible to obtain surface deformation and obtain tactile information on the object.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing one embodiment of the tactile sensor of the present invention, in which (a) is an external view, (b) is a view taken along the line AA 'shown in (a), and (c) is shown in (b). FIG. 2 is a diagram showing an example of a circuit configuration of a signal processing system. In the figure, 1 is an elastic body, 2-1 and 2-2 are hard pipes, 3-1 and 3-2
Is a probe, 4-1 and 4-2 and 11 are microphones,
5 is a lead wire, 6 is a signal processing device, 12 is an amplifier, 13
Denotes an FFT and 14 denotes a data processing unit.

In FIG. 1, an elastic body 1 is made of a material such as silicon rubber provided with two probes 3-1 and 3-2 inside, as shown in FIG. It slides in contact with the surface. Probe 3-1
3-2 is a cylindrical cavity having a diameter of φ and a length of l as shown in (b), which is provided at different depths ε ₁ and ε ₂ from the surface to reduce distortion of the elastic body 1. It is to detect. The hard pipes 2-1 and 2-2 are made of, for example, an elastic body 1 detected by a probe 3-1 or 3-2 using a stainless steel pipe.
The microphones 4-1 and 4-2 convert the detection signal into an electric signal. At low frequencies where the sound wavelength in air is much smaller than the scale of the probes 3-1, 3-2, the output of the microphones 4-1 and 4-2 is proportional to the change in the volume of the hole. The signal processing device 6 inputs and processes the output signals of the microphones 4-1 and 4-2 through the lead wire 5, and can measure the spatial frequency of the surface irregularities of the measurement object here. This is because, when the sensor is slid on the object to be measured, the output ratio between the upper probe 3-1 and the lower probe 2-2 is k, the wave number (spatial frequency) of the surface unevenness in the sliding direction is k, and the distance between the probes is k. When the difference in depth is ε (ε ₂ −ε ₁ ), exp (−kε) is utilized. FIG. 2 shows a configuration example of the signal processing device 6.

In FIG. 2, microphones 11 are microphones 4-1 and 4-2 shown in FIG.
The amplifier 12 amplifies the output signal of the microphone 11 to a predetermined level. And FFT13 is
The output of the amplifier 12 is Fourier-transformed to extract each frequency component, and the data processing unit 14 performs arithmetic processing on each of the Fourier-transformed signals to extract surface information of the measurement object. The data processing unit 14 measures the ratio P '(ω ₀ ) / P (ω ₀ ) between the most main frequency components P (ω ₀ ) and P ′ (ω ₀ ) of the output p obtained through the microphone 11. This makes it possible to detect the spatial frequency of the surface irregularities of the measurement object.

Next, the operation principle of the tactile sensor of the present invention will be described. FIG. 3 is a diagram for explaining the relationship between the output ratio and the wave number of the upper and lower probes at different depths, FIG. 4 is a diagram for explaining the relationship between the probe depth and the output, and FIG. Diagram for explaining the relationship with the output of
FIG. 6 is a diagram showing an example of observation data of surface irregularities.

When the tactile sensor of the present invention is slid in the direction perpendicular to the longitudinal direction of the probe, the displacement inside the elastic body when the strain u ₀ (x, y) is applied to the elastic body surface (xy plane) u
The relationship with (x, y, z) is as follows: | ∂u / ∂x |, | ∂u / ∂x |, | ∂u / ∂x | ≪1Δu + ｛1 / (1-2σ)｝ grad div u = 0 where σ: Poisson's ratio. In this equation, the solution U (k) for a surface deformation with wave numbers k = (κ _x , κ _y ) and κ = | k | _{) Ψ a + b (k)} Ψ b + c (k) Ψ 3 single vector components [psi _a as _c, Ψ _b, can be expressed as a composite of [psi _c. Each vector Ψ
_a, the Ψ _b, Ψ _c, is as shown in the following Equation 1.

[0015]

(Equation 1)

[0016] Thus, z dependence of div U (k) _{is, div Ψ a = (2-4σ)} κexp (iκ x x + iκ
proportional to _{z) | y y) exp (} κz) div Ψ b = 0 div Ψ c = 0 becomes, exp (| k.

[0017] Thus, p = ∫Ldiv udv, however, ∫ is integral _{sign, L = (Ln x, Ln} y, Ln z),
n _x, n _y, n _z, respectively x, y, when a unit vector in the z-axis direction, p = ∫a (k, t ) M (k) dk p '= ∫a (k, t) M' ( k) dk where M (k) = ∫Lexp (iκ _x x + iκ _y y)
exp (κz) dv M ′ (k) = M (k) exp (−κε) That is, div u is exp (| κ for a displacement u generated inside by the periodic deformation of the wave number κ applied to the surface.
| Z) Decreases in proportion. Therefore, even if the probe has a finite width (size), if the same structure is at a different depth by ε, the output ratio of the upper and lower probes becomes exp exp
(−κε), which can be used as a ruler.

Therefore, when u ₀ is moved at a constant speed v in the x direction by a probe made longer in the y direction, the outputs p (t) and p ′ (t) of the upper and lower probes are as follows. become.

P (t) = ∫a (κ _x , 0,0) m
(Κ _x ) exp (iκ _x vt) dκ _x p ′ (t) = ∫a (κ _x , 0,0) m ′ (κ _x ) exp
(Iκ _x vt) dκ _x provided that _{M (κ x, κ y)} = m (κ x) δ (κ y) m '(κ x) = m (κ x) exp (-κ x ε).

From the above, the output p (t) of the upper and lower probes,
P (ω), P ′ obtained by Fourier transform of p ′ (t)
The ratio of (ω) is given by P ′ (ω) / P (ω) = exp (−κ _× ε), and FIG. 4 shows the time change of the probe output. A spatial frequency corresponding to each frequency component of the probe output is obtained from this ratio, and a spectrum U (κ _x , 0,0) · m (κ _y ) in one direction of the surface unevenness is obtained from this and P.

In FIG. 1, w = 5 mm, φ = 0.5 m
FIGS. 5 and 6 show measurement examples of the tactile sensor of the present invention with m, ε ₁ = 0.2 mm and ε ₂ = 0.2 mm.
It is. FIG. 5 shows a signal obtained by using a pin array as shown in (c) as a measurement target and sliding along the pin array. The case where the interval d = 1.3 mm is shown in FIG.
= 2.6 mm is shown in (b). As described above, among the outputs p (t) and p '(t) of the upper and lower probes, the output p' (t) of the lower probe has a larger attenuation as the distance d becomes smaller. In FIG. 6, data of a different pitch d for the bolt and pin array as shown in (b) is plotted on the abscissa with the reciprocal of the pitch d, 1 /.
d, the vertical axis is shown on a logarithmic scale of | P ′ (ω) / P (ω) |.

According to the present invention, a plurality of probes are provided for detecting strains inside the elastic body at different depths from the surface of the elastic body, and surface deformation is detected and calculated inside the elastic bodies having different attenuations. This is for obtaining tactile information on the surface, and is not limited to the above embodiment, and various modifications are possible. For example, in the above-described embodiment, the change in volume is detected by a combination of a probe having a cavity and a microphone. However, any probe that detects internal stress of an elastic body can detect internal stress. Alternatively, another detection material such as a piezoelectric rubber may be used. In addition, although the long probe is provided only in a direction perpendicular to the direction in which the surface of the measurement object is slid, two sets of probes orthogonal to the xy direction are provided so as to detect the respective spatial frequencies in the xy direction. You may.
Further, the spatial frequency of the surface irregularities is determined, but of course, for example, the existence of a specific spatial frequency or other frequencies can be identified, or the distribution or change of the spatial frequency can be output, for example. It goes without saying that various processing and processing can be performed from the information, and it can be applied to control and the like.

[0023]

As described above, according to the present invention, when measuring the spatial frequency of the irregularities on the surface of the object, the distance between the sensor probes is not so close as compared with arranging the probes in the horizontal direction. It is also possible to measure the period of irregularities having a much finer period. Further, at this time, there is no problem of aliasing that occurs when the pixels are arranged in the horizontal direction (the unevenness having a cycle smaller than the probe interval is measured as if the unevenness has a large cycle). Moreover, the surface roughness can be quantitatively measured just by rubbing, so if you can not handle the material that should not be exposed to light or work in a dense gas, etc.
In a case where the actual irregularities are difficult to see by the eyes due to the pattern of the surface, the present invention can be particularly effectively used as a measuring instrument for the surface roughness (statistical evaluation of the size of the particles of the surface irregularities). Further, the present invention can be used as a slip sensor for slip detection and speed detection, and can provide a sensor that is resistant to contamination of the sensor itself, which is a problem in an optical method.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a tactile sensor of the present invention.

FIG. 2 is a diagram illustrating a circuit configuration example of a signal processing system.

FIG. 3 is a diagram for explaining a relationship between an output ratio of upper and lower probes at different depths and a wave number.

FIG. 4 is a diagram for explaining the relationship between probe depth and output.

FIG. 5 is a diagram for explaining a relationship between a spatial frequency and an output of a probe.

FIG. 6 is a diagram showing an example of observation data of surface irregularities.

[Explanation of symbols]

1. Elastic body, 2-1, 2-2 ... Hard pipe, 3-1, 3
1-2 probe, 4-1 4-2, 11 microphone, 5 lead wire, 6 signal processor, 12 amplifier,
13: FFT, 14: Data processing unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01L 1/10 G01L 5/10 B25J 13/08

Claims (2)

(57) [Claims] 1. An elastic body which comes into contact with an object to be measured, a plurality of detecting means provided at different depths from a surface of the elastic body to detect distortion inside the elastic body due to surface deformation, and Signal processing means for detecting surface deformation when the measurement object is slid by processing the detection signal inside the elastic body having different attenuation to obtain uneven tactile information based on the spatial frequency of the surface of the measurement object. A tactile sensor characterized in that: 2. The tactile sensor according to claim 1, wherein said detection means is a probe provided in an elongated shape parallel to a contact surface.