JPH075054A - Power detection method and apparatus - Google Patents

Abstract

PURPOSE:To achieve a highly accurate detection by a method wherein light from a light source is introduced to an optical fiber on the projection side and emitted light of which optical path is curved through a prism, is condensed to detect a quantity of light and a quantity of light value varying with a holding force, is compared with a reference value. CONSTITUTION:Light from a light source 7 is condensed by a lens 6 and introduced through an optical fiber 1a to reach the tip part thereof. The light enters a prism 3a from the end of the optical fiber 1a at the tip thereof, and projected into the air after being curved by 90 deg.. A part of the light projected becomes the incident light 10 into an optical fiber 1b on the photodetecting side and curved by 90 deg. by a prism 3b to enter the tip part of the optical fiber 1b. When work 5 is gripped and a certain magnitude of force F works between finger parts 4a and 4b, a deviation is caused in a direction between the prisms 3a and 3b fastened on the finger parts 4a and 4b. Only a part alone of the emitted light 9 becomes incident light 10 corresponding to the deviation and enters the optical fiber 1b on the photodetecting side to be detected with a photodetecting sensor 8 as a small quantity of light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a force detecting method and apparatus for gripping a component when the component is mounted and fixed at a predetermined position on an assembly part, and more particularly to a device for detecting the force. ,
The present invention relates to a force detection method and apparatus suitable for highly accurately detecting and controlling a gripping force with respect to a minute component whose one side is about 0.5 mm to 5 mm.

[0002]

2. Description of the Related Art Conventionally, a strain gauge has been generally used to detect a force such as a gripping reaction force in a gripping mechanism portion. On the other hand, as described in Japanese Patent Publication No. 4-20240 "Optical fiber type sensor" for performing highly accurate force detection without being affected by electromagnetic noise, light on the side to which force is applied is detected. An interferometer is composed of two optical fibers, which are a fiber and an optical fiber that generates a reference signal. The method of detecting the amount of movement of the interference fringes according to the magnitude of the force to be detected and processing it is a method. Proposed.

[0003]

The above-mentioned conventional force detection technique using a strain gauge is to electrically detect a change in resistance value in accordance with a change in length of the resistance wire, and the resistance wire has a certain degree of sensitivity. Since it requires a long length, there is a drawback that a small-sized detection element cannot be constructed.

Further, in the conventional force detection technique based on the interference action of light, in order to take out the light propagated in the fiber whose transmission state is changed by the action of force to the position where the interference action is generated, It is necessary to pull back the optical fiber laid on the affected portion and return it, but at this time, the radius of curvature for making the optical fiber into a loop cannot be reduced so much in terms of transmission efficiency. Has the problem of. Therefore, similar to the above method, there is a problem in that it cannot be formed into a small-sized detection element that can be mounted on a fine portion.

The present invention has been made in view of the above problems of the prior art.
In particular, it is a first object of the present invention to provide a force detection method and device capable of accurately detecting and controlling the gripping force when gripping a minute component.

A second object of the present invention is to be able to directly detect the stress occurring in the gripped minute component,
An object of the present invention is to provide a force detection device including an ultra-small force detection element that can be mounted on a minute portion.

A third object of the present invention is to provide a force detecting method capable of detecting with high sensitivity the stress generated in a minute gripping component even when the force detecting device is made extremely small as described above. Especially.

[0008]

In order to achieve the above object, the force detecting method of the present invention comprises a pair of finger portions for holding a work, an optical fiber on the light emitting side, an optical fiber on the light receiving side, and the respective optical fibers. A pair of prisms adhered to the end of the optical fiber are made to face each other and fixedly mounted, and the light emitted from the light source is collected and guided to the optical fiber on the projecting side, and reaches the tip of the optical fiber. The light is bent by 90 degrees and emitted through the prism bonded to the tip portion, and the emitted light is further bent by 90 degrees through the prism facing the prism and is emitted to the light receiving side. The light that enters the optical fiber and is emitted from the other end of the optical fiber is collected, and the amount of light is guided to a light receiving sensor to be detected, and changes with the opening and closing amount between the finger parts according to the gripping force for gripping the workpiece. The light intensity value to be , In which comparison processing through the light quantity value and the control circuit of the pre-stored reference, it detects a gripping force for gripping the workpiece, and was capable of controlling.

Then, the amount of light detected by the light receiving sensor may be set to be the amount of incident light which decreases with the shift of the optical axis between the optical fibers facing each other.

On the other hand, the force detecting device of the present invention has a pair of finger portions which can open and close so as to grasp the work at the tip portion, and the light emitting side and the light receiving side which are fixedly mounted on both sides of the finger portions. Each optical fiber, an optical system that collects the light emitted from the light source and guides the light to the optical fiber on the light projecting side, and an optical path of the light that reaches the end of the optical fiber on the light projecting side is adhered to the optical fiber. A prism that bends 90 degrees and emits light, a pair of prisms and a prism that makes the light path of the prism further bend the optical path by 90 degrees and enters the optical fiber on the light receiving side, and the other end of the optical fiber on the light receiving side. Through an optical system that collects the emitted light, a force detection element including a light receiving sensor that detects the amount of light that changes with the opening / closing amount between the finger portions according to the gripping force that grips the work,
An actuator that opens and closes the finger portions so as to be controllable to a predetermined opening and closing amount, and a control circuit that compares the detected light amount of the light receiving sensor and a reference light amount corresponding to the opening and closing amount between the finger portions by the actuator, It is configured to include.

Further, the finger portion is constituted by a pair of arm portions at a tip portion and a bifurcated base integrally connected to the arm portions, and a bifurcated root portion of the base. In addition, it is preferable to provide a notch that facilitates opening and closing of the arm portion together with the base.

The prism may be a mirror, and the optical fibers provided with the mirror may be arranged relative to each other with their optical axes aligned.

Further, it is desirable that the actuator is a piezo element.

Further, the force detecting element and the actuator may be mounted on a hand base to form a gripping force control type micro hand.

[0015]

With the above structure, the light propagating in the optical fiber always maintains a constant amount of light, and is emitted from the optical fiber and the prism adhered thereto,
For example, the light propagated in the air goes to the prism and the optical fiber which face each other according to the law of straight traveling. The incidence coupling efficiency to the opposing optical fiber at this time changes according to the minute deformation amount between the opposing light transmitting and receiving parts. Therefore, the amount of incident light when a work is gripped is detected by the light receiving sensor as the amount of light, and if there is no deformation detected in advance that the work is not gripped, the work is gripped and the predetermined deformation is performed. By performing comparison processing with the reference light amount up to when the amount is generated, the minute deformation amount of the light transmitting / receiving unit can be accurately detected, and at the same time, the deformation amount can be controlled. Since there is a correlation (usually a positive correlation) between the minute deformation amount between the light transmitting and receiving parts and the stress value of the part, it is possible to obtain this relationship from the stress value at any detected light amount by obtaining this relationship in advance. It is possible to accurately detect and control the gripping force of the work.

Further, since the gripping force detecting device can be formed by each structure having a minute size including the optical fiber, the entire device can be formed in a minute size. The detection of the stress corresponding to the amount of deformation acting on the finger portion uses the detection principle based on the light transmission efficiency, so that it is possible to prevent the S / N ratio from being lowered due to electromagnetic noise and to achieve high precision and high sensitivity. Enables the stress detection of.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an explanatory view of the principle of the force detecting method of the present invention, FIG. 2 is an enlarged perspective view of an A portion of FIG. 1, FIG. 3 is a diagram schematically showing a change in the amount of received light, and FIG. 4 is a force detecting device of the present invention. As a specific example, a perspective view of a gripping force control type micro hand, and FIG. 5 is a block diagram showing the configuration of the control circuit of FIG.

In FIG. 1, 1a is an optical fiber on the light-projecting side, 1b is an optical fiber on the light-receiving side which is arranged relative to the optical fiber 1a, and 2a and 2b are members for protecting and holding the optical fibers 1a and 1b. In the (window), a Teflon tube or a stainless steel pipe is used. Reference numerals 3a and 3b are a pair of prisms facing each other, and are arranged on one end (tip) side of the optical fibers 1a and 1b. Reference numerals 4a and 4b denote a pair of finger portions for gripping the components, and the finger portions 4a and 4b.
The optical fibers 1a and 1b and the window 2 along both sides thereof.
As shown in FIG. 2, a and 2b and prisms 3a and 3b are fixedly mounted via an adhesive (or solder) 11 respectively. Reference numeral 5 is a target component (hereinafter, referred to as a work) to be gripped by the tips of the finger portions 4a and 4b, 6 is a lens arranged on the other end side of the optical fibers 1a and 1b, 7 is a light source, 8 is a light receiving sensor, and a dotted line. Indicated by 9 is outgoing light, and 10 is a hatched portion between the prisms 3a and 3b, which is a combined portion of the outgoing light 9, and is referred to as incident light here. A force detection element is formed by each of the above configurations.

FIG. 1 (a) is a diagram showing a state immediately before gripping the work 5, that is, a state where the gripping force F = 0, FIG. 1 (b).
[Fig. 4] is a diagram showing a state of gripping with a gripping force F (> 0).

Next, the operation principle will be described with reference to FIG. The light emitted from the light source 7 is condensed by the lens 6 and guided into the optical fiber 1a. This light reaches the tip portion while totally reflecting inside the core wire according to the well-known principle of an optical fiber. The arriving light is incident on the prism 3a from the end of the optical fiber 1a at the tip, the optical path is bent 90 ° by the prism 3a, and then the light is projected into the air. A part of the projected light becomes incident light 10 on the optical fiber 1b on the light receiving side, and the prism 3b bends the optical path by 90 ° and enters the tip end of the optical fiber 1b on the light receiving side. The incident light reaches the other end while totally reflecting the inside of the core wire in the optical fiber 1b in the same manner as described above, is emitted from the end of the optical fiber 1b, is condensed by the lens 6, and is detected as a light quantity by the light receiving sensor 8. To be done.

Here, as shown in FIG. 1A, the gripping force F
Is not acting, the finger portions 4a and 4b are not deformed, so that the optical coupling between the optical fiber 1a on the light projecting side and the optical fiber 1b on the light receiving side is the strongest, and the outgoing light 9
Almost all of the light amount becomes incident light 10 and is incident on the optical fiber 1b on the light receiving side. On the other hand, as shown in FIG. 1B, when the work 5 is gripped and a gripping force F having a certain amount between the finger portions 4a and 4b is applied, the gripping force F is applied according to the applied gripping force F. The finger portions 4a and 4b are deformed, and a displacement occurs in the direction between the prisms 3a and 3b fixed to the finger portions 4a and 4b according to the deformation amount. Therefore, the optical coupling becomes weaker according to the deviation,
Only part of the emitted light 9 becomes incident light 10 and enters the light receiving side optical fiber 1b, and is detected as a small amount of light by the light receiving sensor 8 via the lens 6. The emitted light 9
The incident light 10 and the incident light 10 are preferably parallel light fluxes, and therefore, it is desirable to use a collimating lens that converges each light.

The change in the amount of light detected by the light receiving sensor 8 will be described with reference to FIG. Here, the horizontal axis of the figure represents a spatial distance taken in a direction perpendicular to the optical axis in an arbitrary plane including the optical axis of the optical fiber 1b on the light projecting side, and the vertical axis represents each of the spatial distances. The light intensity of the emitted light 9 at the position is shown. Figure 3
(A) shows immediately before gripping the work 5, that is, the gripping force F = 0.
FIG. 3B is a diagram showing a state of gripping with a gripping force F (> 0). Although the spatial intensity distribution of the light emitted from the optical fiber 1b is assumed to be a Gaussian distribution here, the distribution form is not particularly limited to this. As shown in FIG. 3 (a), the finger portions 4a, 4b are not deformed and the optical fibers 1a, 1b are not deformed.
In the state where there is no deviation of the optical axis between them, for example, the light in the range shown by the diagonal lines in the drawing becomes the incident light 10 and a high detected light amount is obtained. On the other hand, as shown in FIG. 3 (b), when the finger portions 4a and 4b are deformed and the optical axes are displaced from each other, the portion of the emitted light 9 which becomes the incident light 10 is centered as shown in the figure. Deviation, and as a result, only a small amount of detected light can be obtained. Since the ratio of the decrease in the light amount has a unique correspondence with the deformation amount of the finger portions 4a and 4b, the relationship and the finger portions 4a and 4b are previously set.
Deformation amount of the fingers and the finger portions 4a, 4b corresponding to the deformation amount
It is possible to obtain the stress value at an arbitrary amount of detected light by obtaining the relationship with the stress value generated in the above and calibrating it.

Each of the force detecting elements shown in FIG. 1 is formed by each structure having a minute size. Therefore, it becomes possible to form the force detection element as a whole in a minute dimension. The detection of the stress corresponding to the amount of deformation acting on the finger portion uses the detection principle based on the light transmission efficiency, so that it is possible to prevent the S / N ratio from being lowered due to electromagnetic noise and to achieve high precision and high sensitivity. This has the effect of enabling the stress detection of.

Next, in FIG. 4, 12 is an optical fiber 1.
a, 1b is an optical coupler for optically coupling the light source 7 or the light receiving sensor 8 via the lens 6, and 13 is a bifurcated base integrally formed with the finger portions 4a, 4b.
A notch 13a is provided at the bifurcated root of the base 13 so as to easily open and close (deform) a pair of arms provided at the tips of the fingers 4a and 4b together with the base 13. ing. Reference numeral 14 is a piezo element which is an actuator for opening and closing the base 13, and 15 is a hand base. In the figure, those having the same reference numerals as those in FIG. 1 indicate the same things, and the gripping force control type micro hand is formed by the above respective configurations. Here, the optical fibers 1a and 1b
Has a diameter of about 1 mm, and the prisms 3a and 3b have a size of about 1
As small as mm square, and as shown in the figure, the optical fiber 1
Since a and 1b are mounted on the base 13 and the finger portions 4a and 4b without forming a loop, the optical fibers 1a and 1b and the prisms 3a and 3b, etc., have a side of 1 m.
Even a finger portion having a minute angular cross section of about m can be mounted.

Next, the operation of the minute hand shown in FIG. 4 will be described. In the state before the work 5 is gripped between the finger portions 4a and 4b, the piezo element 14 is in the most extended state, and the action of the notch 13a causes the finger portion 4 to move.
The opening / closing amount between a and 4b is controlled to the maximum amount. The minute hand is moved to a position where the work 5 can be gripped by a known means (not shown), and the gripping operation is started. Simultaneously with the start of the gripping operation, the applied voltage to the piezo element 14 is changed, and the length of the piezo element 14 is shortened at a preprogrammed speed. And at the same time, notch 1
Due to the action of 3a, the opening / closing amount between the finger portions 4a and 4b also decreases. In accordance with the decrease in the opening / closing amount, the distance between the optical fibers 1a and 1b on the light projecting side and the light receiving side is shortened, so that the light coupling efficiency between the two is increased and the light receiving sensor 8
The amount of light detected by is gradually increasing.

When the work 5 is gripped from the above state and the finger portions 4a and 4b start to be deformed, the angle between the prisms 3a and 3b facing each other changes according to the principle explained in FIG. 1, and the prisms 3a and 3b change. There is a deviation of the optical axis between the optical fibers 1a and 1b on the light emitting side and the light receiving side which are connected to each other. Therefore, the light coupling efficiency decreases, and the light amount detected by the light receiving sensor 8 becomes a lower value than the light amount value expected from the control signal of the piezo element 14. By comparing the expected value and the actual value via the control circuit, the deformation amount of the finger portions 4a, 4b can be detected, and the stress value received by the finger portions 4a, 4b can be detected based on the deformation amount. Can be detected.

The above processing can be automatically performed by the control circuit shown in FIG. Here, 10 is incident light which is a detection signal, 16 is a light quantity comparison circuit, 17 is a piezo voltage-opening / closing quantity conversion circuit, and 18 is an opening / closing quantity-light quantity conversion circuit.
Further, Vpz is a voltage output to the piezo element by a control device (not shown), W is the opening / closing amount of the finger portion, Ir is the detected light amount signal, and Ir ₀ (Ir ′) is expected from the opening / closing amount of the finger portion. The light amount signal is a no-load light amount in the sense of the light amount when the gripping force F is absent, and F ′ is a stress value obtained by the control circuit and is output as a gripping force detection signal. The piezo voltage-open / closed amount conversion circuit 17 obtains the open / closed amount of the finger portion from the piezo voltage Vpz. In the opening / closing amount-light amount conversion circuit 18, the light amount determined by the opening / closing amount is calculated as the no-load light amount I.
Output as r ₀ . On the other hand, from the light receiving sensor 8, a light amount signal Ir containing information on the actual gripping force is obtained. The no-load light quantity Ir ₀ and the light quantity signal Ir are input to the light quantity comparison circuit 16, and the stress value F ′ is calculated from the inputted light quantity ratio Ir ₀ / Ir according to the light quantity ratio-stress conversion table previously obtained. It is requested and output.

Based on the value of the stress value F'determined by the above method and the desired stress value Fref, the voltage applied to the piezo element is constantly corrected by the controller (not shown), and the workpiece is moved by the hand. The gripping force is controlled to a desired value. A known control law, for example, a proportional control operation Vpz = Kp. (Fref-F ') can be applied as an algorithm for this correction operation, but various other methods may be used.

As described above, according to the present embodiment, it is possible to control the gripping force exerted on the work at the finger portion, so that the object to be gripped is a delicate gripping force such as a flexible or fragile object. It is possible to realize the handling even in the case of being required, and it is possible to freely perform the assembling operation.

FIG. 6 shows an example of a product to be assembled according to the present invention, showing a magnetic head which is a signal reading portion of a magnetic disk. Here, 21 is a core slider, 22 is a gimbal having a spring function for automatically correcting the posture of the core slider 21, 2
3 is a load arm, 24 is a wiring pattern, 25 is a lift angle attached to the load arm 23, 26 is a bent portion,
Reference numeral 27 is a mounting portion to the base material, and 28 is a terminal. These parts are becoming smaller and smaller. Among them, when assembling the core slider 21, it is easy to scratch the surface of the core slider 21 when it is gripped, and the spring-shaped gimbal 22 is used.
Since it is difficult to determine the upward posture, it has been one of the difficult and time-consuming operations in the past. However, the micro hand shown in FIG. 4 can be used for easy assembly. That is, while detecting the gripping force by the above-described method, the core slider 21 is sandwiched and lifted from both sides by the finger portions, and the gimbal 2 is moved by the moving mechanism (not shown).
After moving to the upper position, it is bonded and fixed onto the gimbal 22 whose posture is difficult to determine because it has a spring shape. For this reason,
It is possible to assemble with high accuracy by stable gripping without scratching the surface.

FIG. 7 is a diagram showing an example of an automatic assembling machine for mounting the minute hand shown in FIG. 4 and assembling the magnetic head shown in FIG. In the figure, the core slider 21 is gripped from the core slider supply unit 35, and the X stage 29,
The Y stage 30 and the Z stage 31 are operated to apply the adhesive on the lower surface of the core slider 21 by the adhesive application section 39, and then the core slider 21 is carried to the position on the load arm 23 positioned on the stage 36. , Visual device 4
After calculating the position correction amount from 0, the θ stage 32,
The position is corrected by the XY fine movement stage 33 and it is bonded onto the gimbal 22. During this time, the minute hand moves the core slider 21 by the force detection principle and the force control method according to the present invention.
Since it operates so as to keep the force applied to the core constant, an unreasonable force is not applied to the core slider 21 throughout the assembly work,
It is easy to keep the product quality high. In this way, even with this automatic assembly machine, 1 m
Even a fine and fragile part of about m can be assembled with high quality without damage.

[0032]

As described above, according to the present invention, it is possible to realize an ultra-small force detecting element and a minute hand using the element, which acts on the finger portion of the minute hand when holding a minute component. It becomes possible to detect and control the gripping force. Since this detection uses the detection principle based on the transmission efficiency of light, S / N due to electromagnetic noise is detected.
It is possible to prevent a decrease in the ratio and achieve an effect of being performed with high accuracy and high sensitivity.

Further, according to the present invention, since the gripping force exerted on the work can be controlled, it is possible to realize the handling of a flexible object or a fragile object, and it is possible to freely perform an assembling operation.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of a force detection method of the present invention.

FIG. 2 is an enlarged perspective view of a portion A of FIG.

FIG. 3 is a diagram schematically showing changes in the amount of received light.

FIG. 4 is a perspective view of a gripping force control type micro hand, which is a specific example of the force detection device of the present invention.

5 is a block diagram showing a configuration of a control circuit of the minute hand shown in FIG.

FIG. 6 is a diagram showing an example of an assembly target product of the present invention.

7 is a diagram showing an example in which the micro hand shown in FIG. 4 is mounted on an automatic assembly machine.

[Explanation of symbols]

1a ... Optical fiber on projecting side, 1b ... Optical fiber on receiving side, 2a, 2b ... Member (window), 3a, 3b ... Prism,
4a, 4b ... finger parts, 5 ... work (target part),
6 ... Lens, 7 ... Light source, 8 ... Light receiving sensor, 9 ... Emitted light,
10 ... Incident light, 11 ... Adhesive (or solder), 12
... Optical coupler, 13 ... Base, 14 ... Piezo element, 15 ...
Hand base, 16 ... Light quantity comparison circuit, 21 ... Core slider.

Claims (7)

[Claims] 1. An optical fiber on the light emitting side, an optical fiber on the light receiving side, and a pair of prisms adhered to the ends of the respective optical fibers are made to face each other and fixedly mounted on a pair of finger portions for holding a work. Then, the light emitted from the light source is condensed and guided to the optical fiber on the light projecting side, and the light reaching the tip of the optical fiber is bent 90 degrees through the prism bonded to the tip. The light is emitted and the optical path is further moved through the prism facing the prism.
The light emitted from the other end of the optical fiber is condensed and guided to the light receiving sensor to detect the amount of light, which is determined by the gripping force for gripping the workpiece. The light amount value that changes with the opening / closing amount between the finger portions is compared with a reference light amount value stored in advance through a control circuit, and the gripping force for gripping the work is detected and made controllable. A force detection method characterized by the above. 2. The amount of light detected by the light receiving sensor is
The force detecting method according to claim 1, wherein the amount of incident light decreases with a shift in optical axis between the optical fibers facing each other. 3. A pair of finger portions which can open and close a work so as to be able to hold a work at the tip portion, optical fibers on the light emitting side and the light receiving side, which are fixedly mounted on both side portions of the finger portions, and emitted from a light source. An optical system that collects the reflected light and guides it to the optical fiber on the projecting side; and a prism that is adhered to the tip of the optical fiber on the projecting side and bends the optical path of the light reaching the tip by 90 degrees and emits it. , The light emitted from the prism is converged by the prism and a pair of prisms which enter the optical fiber on the light receiving side by bending the optical path further by 90 degrees and the other end of the optical fiber on the light receiving side. Through the optical system, a force detection element composed of a light receiving sensor that detects the amount of light that changes with the opening / closing amount between the finger portions according to the gripping force for holding the work, and the predetermined opening / closing amount between the finger portions. Controllable to A force detection device comprising: an actuator that opens and closes; and a control circuit that performs a comparison process of the amount of light detected by the light receiving sensor and a reference amount of light that corresponds to the amount of opening and closing between the finger portions by the actuator. 4. The finger portion includes a pair of arm portions at a tip portion and a bifurcated base integrally connected to the arm portions, and a bifurcated root portion of the base, The force detection device according to claim 3, wherein a notch that facilitates opening and closing of the arm portion is provided together with the base. 5. The force detection device according to claim 3, wherein the prism is a mirror, and the optical fibers provided with the mirror are arranged relative to each other with their optical axes aligned with each other. 6. The force detection device according to claim 3, wherein the actuator comprises a piezo element. 7. The force detection device according to claim 3, wherein the force detection element and the actuator are mounted on a hand base to form a gripping force control type micro hand.