JPH01138431A - Optical force sensor - Google Patents

Abstract

PURPOSE:To detect a load in three axial direction by a single sensor by combining a light source and a division type photosensor together opposite each other across elastic bodies. CONSTITUTION:A mobile body 40 whose tip outer peripheral surface is pointed has a support rod 41 in the center of the base end surface and a fixed body 50 is formed by coupling a small-diameter storage part 51 with a large-diameter equipment mount part 52 across a partition wall 53. Further, the elastic body 60 has a center small cylinder part 61 and thin elastic plates 62 and 63. Further, the moving body 40 and fixed body 50 are coupled with adjacent parts relatively movably in respective axial directions X, Y, and Z across the elastic body 60, and the support rod 41 of the moving body 40 penetrates the small cylinder part 51 of the elastic body 60 and projects into the storage part 51 of the fixed body 50. Further, a light source 20 is fixed atop of the support rod 41 in the storage part 51 of the fixed body 50, and the photosensor 10 is mounted on the partition wall 53 of the fixed body 50. Thus, the photosensor 10 and light source 20 face each other and their axes are aligned with each other. Consequently, the single sensor can detect at least the load in the three axial directions.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical force sensor suitable for use in measuring force acting on an object.

rPrior Art j Generally, when a robot is made to perform various complicated tasks, the force control of the robot must be advanced, and therefore it is necessary to detect the force applied to the robot.

Incidentally, in industrial robots it is necessary to detect wrist force, and in mobile robots it is necessary to detect supporting force.

As a force sensor to detect such force.

In addition to those using strain gauges, piezoelectric effects of semiconductors,
Various force sensors using capacitance and pressurized conductive rubber are also used, but each of these sensors has the following problems.

For example, in the case of a force sensor using a strain gauge, the detected signal is a minute change in resistance value of a few percent or less, so not only a dedicated Ma@meter with high sensitivity and noise resistance is required, but also temperature disturbance If a sufficiently stable and highly accurate 7111 system were constructed to avoid this, the entire system would be extremely expensive.

Moreover, the resistance wire of strain gauges is thin and has the disadvantage of breaking due to repeated fatigue.

Methods using semiconductor elements can obtain a larger signal than the strain gauge method, but such a signal level is not sufficient, and as mentioned above, requires a high-performance amplifier and is susceptible to temperature disturbances. .

Force sensors that use capacitance have a simple structure, but the measurement circuit that measures minute changes in capacitance is expensive, and the effects of stray capacitance must be excluded. Therefore, noise countermeasures for the entire sensor system are required, and handling is complicated.

Furthermore, in the case of a force sensor using pressurized conductive rubber, it is easy to handle, but since the conductive rubber has hysteresis, it is not suitable for measurements that aim to always accurately measure force.

In contrast to the existing force sensors mentioned above, several force sensors that use light have been considered, and these can measure the minute displacement of an object caused by the action of the force to be measured by using changes in the amount of reflected light or light sensitivity. Detection is performed based on a change in the transmittance of a type semiconductor or a change in the amount of light passing through a slit.

Such optical force sensors can receive relatively high level signals and also have the advantage of not having hysteresis characteristics.

“Problem to be Solved by the Invention 1” However, even in the case of the above-mentioned optical force sensor, there remain technical issues to be solved.

One of these is that a single sensor can detect many load components and multiple load components, the other is that it is small and lightweight, and the other is that the measurement system can be installed at a low cost. It is configurable.

In view of the above-mentioned problems, the present invention provides an optical force sensor that can detect loads in at least three axial directions with a single unit, and that also satisfies the requirements of high performance, small size and light weight, and low cost. This is what I am trying to do.

Means for Solving Problems J In order to achieve the intended purpose, the optical force sensor according to the present invention has a light source and a split photosensor combined with each other facing each other via an elastic body. It is characterized by

1 Implementation Example” Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a specific example of the optical force sensor according to the present invention, and FIG. 2 is an explanatory diagram for explaining the basic principle of the optical force sensor.

In FIGS. 1 and 2, the photosensor IO consisting of a four-division type consists of four cells 11, 12, 13 that are assembled together.
．． 14, and each of these cells 11, 12, 13, and 14 is arranged at a first coordinate, a second coordinate, a third coordinate, and a fourth coordinate, respectively, with the central axis of the photosensor 10 as the origin.

In FIGS. 1 and 2, the light source 20 is, for example, a high-intensity LED without a lens and with an open chip.
(0.8 mmφ), with a pinhole added at its center.

In FIGS. 1 and 2, a casing 30 made of synthetic resin, metal, etc. includes a movable body 40, a fixed body 50, and an elastic body 80.
It is equipped with

In such a casing 30, the movable body 40 having a pointed outer circumferential surface has a support rod 41 at the center of its proximal end surface, and the fixed body 50 has a small-diameter storage section 51 and a large-diameter device mounting section 52. are connected to each other via a partition wall 53, and the elastic body 60 has a small cylindrical portion 61 at the center and both ends of the small cylindrical portion 61.
It has thin elastic plates 62 and 63 connected to.

Further, in the relative quantity form of the movable body 40, the fixed body 50, and the elastic body 60, the movable body 40 and the fixed body 50 are arranged in the x, y, and z axis directions via the elastic body 60 between these adjacent parts. The movable body 40 is coupled to be movable relative to each other.
The support rod 31 passes through the small cylindrical portion 51 of the elastic body 80 and protrudes into the storage portion 41 of the fixed body 50.

Of the photosensor 10 and light source 20 described above, the light source 20
is attached to the tip of the support rod 41 in the housing 51 of the fixed body 50, and the photosensor 10 is attached to the partition wall 53 of the fixed body 50, so that the photosensor lO and the light source 20 face each other, and their axes Their hearts are in agreement with each other.

Note that an amplifier 70 is installed in the device mounting section 52 of the fixed body 50.
The amplifier 70 is connected to an electrical or electronic output calculation circuit (not shown).

Hereinafter, force measurement in three axial directions using an uninvented optical force sensor will be explained.

The optical force sensor of the present invention calculates the displacement of the light source (LED) 20 in the x-, y-, and z-axis directions in FIG. 2 from the outputs of four photodiodes.

In this case, the origin of the x, y, and z directions is set on the central axis of the photosensor 10 as described above, and each cell 11, 12, 13, 14 of the photosensor 10 outputs these outputs from Sl, S2, . S3, S4, O at the origin
Add an offset so that

First, the independent displacement of the light source 20 in the x, y, and X axis directions and the output of the photosensor 10 will be described.

When y=z=0 and the light source 20 is displaced only in the X-axis direction, the sensor output S× in the )become that way.

5X=SI -92-S3+S4... (1) If we approximate this with the straight line of equation (2) and magnify only the deviation from equation (2), we get as shown in Figure 3 (2). Become.

5X=A*X (2) In this case, A = 187 (mV/am), and the standard deviation σ was σ-0.15%.

When X=Z=O and the light source 20 is displaced only in the y-axis direction, the sensor output SV in the y-axis direction is expressed by equations (3) and (4), as in the case of the X-axis direction.

5V=Sl +52-33-9++””(3) $=A@
y... (4) When x=y=o and the light source 20 is displaced only in the X-axis direction, the sensor output Sl in the X-axis direction is as shown in equation (5), and in that case, The change in is shown in Figure 4 (1).

5y=S1+S2+S3+Sa...(5) Approximating this with equation (6), which is a quadratic equation of 2, and magnifying only the deviation from equation (6), we get as shown in Figure 4 (2). Become.

5z=B*z2+C*z...-(8) In this case, B=48 (mV/mm2), C=104.
9 (mV/am), and the standard deviation σ is σ=0.22
It became.

Next, a case where there is interference in the displacement of each axis of the light source 20 will be described.

FIG. 5 shows the sensor outputs Sx and Sy when the light source 20 is displaced in the x and y axis directions and moved along a square (-side Q, 4+sm) centered on the origin, with 2=0.

In Figure 5, for example, the straight part is X = 0.2m
Although y was changed from −0.2 mm to +0.2 layer weight in m, almost no change was observed in Sx during that time.

As is clear from these results, the independence of the X-axis direction and the y-axis direction is good.

At y=Q, z=0, ±0.1+am, ±0.2
Fix each to +IIm and divide X from -0,2mtm
〇、2!Sensor output SZ when changed up to 1m,
It is shown in FIG. 6 (1).

In the case of FIG. 6(1), 2 is constant, but X increases as it approaches O.

This is thought to be because even if the distance is the same, the closer the light source (LED) 20 is to the center of the photosensor 10, the larger the sum of light irradiated via the sensor lO becomes. Therefore, Sz is only 2. It can be said that it is also a function of X and y.

For such a functional form, due to its symmetry, add the minimum even-order quadratic term and use equation (7) as Sz = equation (
8) -D -x2 fist D * y2
-----(7) In this case, S is the formula (2) (4
) can be corrected as shown in equation 1 (8).

Sz' =Sz+D/A(SX2+5V2) ””
”(8) As a more specific example, D/A=8.5
When l0-4, as shown in Figure 6 (2), Sz
+ became almost constant.

When y=Q and x=O1±0.1mm,±0.2mm, 2 is set from -0.2mm to +0.2mm at 5 points.
The sensor output Sz when changed up to 2 mm is shown in FIG. 7 (1).

In the case of FIG. 7(1), by increasing 2 at any point, the absolute value of Sx becomes slightly smaller.

This is thought to be because the farther the distance from the light source 20 is, the weaker the light irradiated onto the photosensor 10, and the smaller A in Equation 1 (1) becomes.

To deal with this, correction is made as shown in equation (9).

SX' = Sx・E/(SZ'+E) (9
) Thus, even if 2 is changed as shown in Figure 7 (2), Sx
' does not change much.

At this time, E = 270 (V).

SV can also be corrected in the same way as above, that is, as shown in equation (10).

SV' = Sv・E/(Sz'+E) "" (10) The optical force sensor according to the present invention is characterized in that the photo sensor lO and the light source 20 are independently displaced relative to each other in the x, y, and z axis directions. Of course, even if these photosensor 10 and light source 20 are simultaneously relatively displaced in the x, y, and z axis directions,
In order to perform the above correction, SX', SV', S? By calculating ', a predetermined output can be detected.

In other words, calculate Sx, SV, and SZ from the sensor output based on equations (1), (3), and (5), and calculate these using equation (8).
(9) Corrected by (10), the S,',SV',
SZ' is expressed as Sx, Sv,
By substituting in place of Sl, the outputs of X, y, and z can be obtained.

Therefore, in the optical force sensor of FIG. 1, a force acts on the movable body 40 of the casing 30, and together with this, the elastic body 60 is elastically deformed including one or more components in the x, y, and z axis directions, and the movable body 40 When the light source 20 on the side and the photosensor lO on the fixed body 50 side are relatively displaced in a predetermined direction, the output from the photosensor 10 is amplified via the amplifier 70, and an output calculation circuit connected to the amplifier 70 , x,
Find the output in the y and z axis directions.

In addition, in the case of the first illustrated example, the casing 30 is a moving body 40,
The fixed body 50 and the elastic body 80 are integrally formed, but the movable body 40, the fixed body 50, and the elastic body 60 may be formed separately and combined by means such as adhesion, fixation, or coupling. You can.

Regarding the photosensor IO1 light rA20, the photosensor 10 may be attached to the moving body 40, and the light source 20 may be attached to the fixed body 50.

As for the moving body 40, since this is a component that receives the force to be detected, the abutting part (for example, the shape of the tip) of the moving body 40 that comes into contact with the detected object should correspond to the detected object. It is formed.

In addition, for the elastic body 60, a shape that is easily elastically deformable is appropriately adopted, and as an exception to the illustrated example, a bellows shape, a diaphragm shape, etc. can be adopted.

"Effects of the Invention J As explained above, the optical force sensor according to the present invention has a light source and a split-type photosensor that are combined to face each other via an elastic body, so that the optical force sensor can be used alone in three axial directions. In addition to being able to detect loads, force sensors with three or more axes can also be configured with a small number of components, mainly consisting of a photosensor and a light source, thus achieving high performance, size, and weight reduction. A force sensor can be provided at low cost.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the optical force sensor according to the present invention, Fig. 2 is a perspective view for explaining the basic principle of the force sensor, and Figs. 3 (1) and (2) are An explanatory diagram of the original form and a corrected explanatory diagram showing the relationship between the sensor output and the amount of movement in the X-axis direction. Figure 4 (1) (2) is an explanatory diagram of the original form that shows the relationship between the sensor output and the amount of movement in the X-axis direction. Figures and correction explanatory diagrams. Figure 5 is an explanatory diagram showing the relationship between the sensor output in the X-axis direction and the z-axis direction. Figure 6 (1) and (2) is the relationship between the sensor output and the amount of movement in the X-axis direction. FIGS. 7(1) and 7(2) are an original explanatory diagram and a corrected explanatory diagram showing the relationship between the sensor output in the X-axis direction and the amount of movement in the X-axis direction. 10...Photo sensors 11-14...
...-Cell 20...Light source (LED) 30...
...Casing 40...Moving body 50...Fixed body 60...Elastic body Agent Patent attorney Yoshio Saito

Claims (2)

[Claims] (1) An optical force sensor characterized in that a light source and a split-type photosensor are combined so as to face each other via an elastic body. (2) The optical force sensor according to claim 1, wherein the photosensor is of a four-segment type.