JPS61283842A - Force sensor - Google Patents

Abstract

PURPOSE:To obtain a force sensor with six degree of freedom based on a new principle suitable for a smaller size and a lighter weight with a higher sensitivity and a large load capacity, by check 2-D displacements separately with three non-contact displacement detectors to detect external force with 6 degree of freedom. CONSTITUTION:Non-contact type semiconductor 2-D position detecting elements (PSD) 13, 14 and 15 are assembled so as to continue at 90 deg. to one another and supported on a displacement detector support base 12. Now when an external force works on a hand 24 of a robot, light spots 19, 20 and 21 projected through optical fibers 16, 17 and 18 move two-dimensionally on planes PSD 13, 14 and 15. Therefore, by electrically measuring the positions of these light spots, the displacement from the initial state can be calculated and then, converted into a force working on the hand 24 from the relationship between the displacement of a spherical elastic body 10 obtained by precalibration and the force to determine the value thereof. This enables the movement of the displacement detector support base 12 with 6 degree of freedom.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application"
The present invention relates to a force sensor that detects an external force or moment acting on a hand.

"Conventional technology" Conventionally, the principle of this type of force sensor was to use a leaf spring, etc.
The displacement is measured by the strain gauge attached to the surface of the elastic body.
The most common method was to detect Therefore, in order to obtain a force sensor with 6 degrees of freedom,
171 It is necessary to simultaneously and independently detect the final axis and the moments around each axis. Figure 5 shows the Stanford Research Institute.
An example of a robot wrist force sensor invented by Hase (for Hase: "Robot's Tactile Sense", System and Control, Vo & 22. & 7. PP, 40)
9-416-1978). In Fig. 5, 1 and 1' are elastic columns that detect force in the X-axis direction, and 1 and 1' are z-axis
It is provided at a symmetrical position with respect to the axis. Similarly,
2.2' is an elastic column that detects force in the y-axis direction.

Also, 3. Elastic columns 4 and 4' detect forces in the X-axis direction. As shown in FIG. 6, strain gauges 5. A key is attached. The force sensor in Figure 5 is just one example, but almost all conventional force sensors have a modified structure of the elastic body.
The emphasis was on separating and detecting forces in six degrees of freedom.

"Problems to be Solved by the Invention" However, the conventional force detection method using the strain gauge described above has a complicated structure, and there are limits to the miniaturization and weight reduction of the force sensor. It has been difficult to manufacture a force sensor with an outer diameter of several centimeters or less, which is suitable for small robots with a payload capacity of several centimeters or less.

On the other hand, regarding the sensitivity and load capacity of a force sensor, it is difficult to realize a force sensor that is highly sensitive and can withstand high loads because it is not possible to arbitrarily change the spring constant of the elastic body using conventional technology. Met.

In addition, in the "force sensor" shown in Japanese Patent Publication No. 59-153135, one way to solve this problem is to use a potentiometer to detect the displacement in one direction received by the linear guide of the roller. A method has been proposed in which the rigidity of a force sensor is arbitrarily changed by applying a restoring force against this displacement using a drive mechanism consisting of a motor. However, in order to provide a force sensor with multiple degrees of freedom using this method, it is necessary to have the same number of feedback systems as there are degrees of freedom, which has the disadvantage that the configuration of the device becomes complicated and large-scale.

``Object of the Invention'' An object of the present invention is to provide a 6-degree-of-freedom force sensor based on a new principle that is highly sensitive, has a large load capacity, and is suitable for miniaturization and weight reduction.

In order to solve the above-mentioned problems, the present invention attaches a movable part to a support body through an elastic body, and applies a predetermined displacement of 10,000 to either the support body or the movable part. Three non-contact displacement detectors that detect two-dimensional displacement along a plane, and a target forming body that forms a target for the non-contact displacement detector, respectively. The three non-contact displacement detectors are mounted so that their bodies face each other, and the three non-contact displacement detectors are arranged so that each displacement plane is included in a plane orthogonal to each other.

"Operation" Three non-contact displacement detectors each detect two-dimensional displacement and
In addition to detecting external forces with degrees of freedom, it is also easy to reduce size and weight because it does not have a strain gauge or drive mechanism.

“Example” In describing the first example of the present invention shown in FIG.
First, the basic operating principle of the force sensor of the present invention will be explained based on FIG. 2.

FIG. 2 is for detailed explanation of the present invention,
Orthogonal X, 7. On the Z axis, 101 is the y zil plane perpendicular to the X axis, 102 is the π plane perpendicular to the y axis, 1
03 is an xy plane perpendicular to the z-axis. 104, 105, and 106 indicated by black circles in the figure are in their initial states! ,7
．． The intersections of the m-axis (solid line) and the planes 101, 102, 103 are also indicated by white circles at 107, 108, 109 in the figure.
are x' when an external force acts and is displaced, respectively.
y', # axis (two-dot chain line) and the planes 101, 102,
This is the intersection with 103. Also,! ,7. The origin of the M axis will be referred to as the target. Therefore, 110 and 111 respectively indicate the position of the target in the initial state and in the state in which an external force is applied. In addition, here, the plane 101°102.10
3 is fixed and the X, y, and axes are displaced by external force, but in the opposite case, that is, the plane 101
, 102, 103 do not change, and the same holds true even when these planes are displaced together. Furthermore,
Fx, Fy, Fg are the magnitudes of external forces applied in the X-axis, y-axis, and X-axis directions, respectively, RX z R7* Rz
are the X and y axes, respectively.

It is the magnitude of torque around two axes.

If the displacement amounts on the planes 101, 102, and 103 are defined as shown in FIG. 2, the outer force Fx, F7tFz, uKK ) (
11F 7” kg (U xy + U27)
+2) F ” = ks (u xx + uyz
) ((lRX = l t (uyz
tjzy ) (41Ry =
is (u nee U.) (5) RE = lls (ux
y uyx ) (6) Kokote, kt @
key kg, 11p 1lxy IS are constants specific to the device. If the above target is supported by an isotropic elastic body, then kg = 2 = ka = lh = lz = ls
El Also, if the above constant kl is 67 when the displacement of the isotropic elastic body is isotropically restrained from the outside and the rigidity is improved, then &)c, I>e. Therefore, in advance, various If you calibrate the restraint force under the restraint force of )t, ll, the above six displacements, U73C# ``ZZ* ``X7e''
By measuring 27m ”X1lz u7z, the external force F
F zg RXs R7tRz is calculated.

The present invention has been made based on the basic principle as explained above, and a first embodiment thereof will be described below.

FIG. 1 is a diagram illustrating a first embodiment of the present invention.
0 is a spherical elastic body made of fiber-reinforced fluorine rubber, 1
1.11' are flanges attached to the upper and lower parts of the spherical elastic body 10, 12 is a support base attached to the flange 111 and supports a displacement detector to be described later, and 13 is! ,
14 is a non-contact plate-shaped first displacement detector that detects two-dimensional displacement in the y- and z-axis directions, and a second non-contact plate-shaped displacement detector that detects two-dimensional displacement in the y- and z-axis directions. 15 is a non-contact plate-shaped third displacement detector for detecting two-dimensional displacement in the XmV axis direction, and each of these detectors 13, 14.
15 each constitute a displacement plane. The detector 13.14.
15, a semiconductor two-dimensional position detection element (PSD) was used in this embodiment. In addition, from now on, the first displacement detector 13
is the first PSD 13, and the second displacement detector 14 is the second PSD 1.
4. The third displacement detector 15 will be abbreviated as third PSD 15. Reference numeral 16 indicates an optical fiber (point forming body) facing the first PSD 13, and 17 indicates the second PSD 14.
, 18 is an optical fiber (gage point forming body) facing the fifth PSD 15, and the optical fibers 16s, 17
The tip of each t i 8 corresponds to target 110 in FIG. 19 is the first PSD via the optical fiber 16.
The light point (marker point) irradiated on Ia is shown. Similarly, 20 is a light point (gage point) on the second PSD 14 irradiated by the optical fiber 17, and 21 is a light point (gage point) on the third PSDls irradiated by the optical fiber 18. These light spots 19°20.21 correspond to 105 or 108.104 or 107.106 or 109 in FIG. 2, respectively. 22 is a sleeve that fixes the three optical fibers 16, 17, 18; 23 is a part of the arm (support body) of the robot body; the sleeve 22 is fixed to the arm 23; It is attached to the 7 langes 11. 24 is a robot hand (movable part),
Since the hand 24 is attached to the seven flange 11' and held by the spherical elastic body 10, when an external force is applied to the hand 24, the displacement detector support 12 has six degrees of freedom.
movement becomes possible. On the other hand, the PSD13.・14゜1
5 are assembled so as to be continuous at an angle of 90 degrees to each other, and are supported on the displacement detection support base 12. Therefore, when an external force acts on the optical fiber 1
The light spot 19, 20, 2 illuminated by 6.17.18
1 moves two-dimensionally on the plane of P S D 13° 14.15, so the positions of these light spots are measured electrically (the measurement method is as described in Yoshiharu Ohashi and Akinaga Yamamoto: Electronic Materials, 1
The method described in the February 980 issue is used. ), the displacement from the initial state can be calculated, and from the relationship between the displacement and force of the spherical elastic body lO obtained by pre-calibration, the value can be calculated by converting it into the force applied to the hand 24. can. In addition, when an optical method is used as the two-dimensional displacement detector as in this embodiment, various solid-state image sensors such as a CCD can also be used. The force sensor used in this example has a diameter of 3 cm, a weight of approximately 150 g, and a force sensitivity of 0.51, and commercialization is planned in 1985 (Nikkei Sangyo Shimbun, September 1959). (dated 27th) Compared to the smallest commercially available product, it was approximately 176, making it smaller and lighter. Furthermore, since the displacement measurement mechanism section of the structure is located inside the elastic body and has a sealed structure, foreign matter such as dust and oil does not enter the inside, and a highly reliable force sensor can be obtained.

Therefore, it is ideal as a force sensor for small robots for assembling small precision parts, an area in which robots are expected to play an active role in the future.

As is clear from the above explanation, in the conventional technology, strain gauges are attached to independent elastic bodies for each degree of freedom, but in this example, an isotropic elastic body is used. death,
This method uses three two-dimensional position detectors arranged facing each other on six mutually orthogonal planes to detect the displacement of a gauge point with six degrees of freedom supported by the elastic body, so the principle of the force sensor is different. ing.

Furthermore, in the prior art, the rigidity of the elastic body generally remains unchanged unless the shape and dimensions of the elastic body are changed, and the force sensitivity and load capacity are constant values unique to the device. In addition, whereas the above-mentioned Japanese Patent Publication No. 153135/1980 discloses a method in which the stiffness is adjusted by an actuator for each degree of freedom, in the present invention, the stiffness is adjusted using an actuator for each degree of freedom. Since this is a method of adjusting the rigidity by uniformly restraining the displacement of an isotropic elastic body from the outside, it has the advantage of a simple configuration.

FIG. 3 shows the light source part of the second embodiment of the present invention, and the method for measuring the displacement of the gauge point is the same as in the first embodiment.
In this embodiment, the optical 7 eyeglass 1 in the first embodiment is
K instead of 6, 17, 18.

This is an example in which only one optical fiber is used.

30 is an optical fiber (gage point forming body), 31 is an optical demultiplexing housing, 32 is an optical demultiplexing component, 33 is a through hole provided in the demultiplexing component 32 and through which light passes in the Z-axis direction, and 34 is an X-axis Similarly, 35 and 36 are rod lenses that condense light in the y-axis and x-axis directions, respectively.
7 is a light ray in the X-axis direction, and 38 and 39 are light rays in the y-axis and two-axis directions, respectively. The optical demultiplexing component 32 has a truncated quadrangular pyramid shape and is formed by molding plastic. Each surface of the optical demultiplexer 32 is AJ plated to improve reflectance, and the optical fiber 30, the optical demultiplexer 32, the rod lenses 34, 35,
36 are the housings 31! is fixed. Note that the first housing 31 also has the function of the sleeve 220 of the first embodiment, and the optical fiber 3
0 and is fixed to the arm 23 of the robot.

FIG. 4 is a sectional view illustrating a third embodiment of the present invention.

In this embodiment, the method for measuring the displacement of the gauge point is the same as in the first embodiment, but the structure of the spherical elastic body 10 in the ↑ embodiment and the pressure inside the spherical elastic body lO are the same as those in the first embodiment. It differs in that it has an additional adjustment mechanism.

In jI4@, 40 is fiber reinforced plastics (
41 is a spherical outer shell made of FRP; 42 is an elastic body made of fluorocarbon rubber filled between the inner shell 40 and the outer shell 41; 43 is the inner shell 40; A gas introduction pipe 44 connected to the inner shell 4o to adjust the internal pressure of the inner shell 4o is a gas seal valve.

The inner shell 40 is fixed to the arm 23 side of the robot, and the outer shell 41 is fixed to the hand 24 side of the robot. A certain gap d is provided between the tip of the inner shell 40 on the hand 24 side and the displacement detector support 12, and between the tip of the outer shell 41 on the arm 23 side and the arm 23. It is provided,
The relative movement between the inner shell 4o and the outer shell 41 via the elastic body 42 is not hindered. but,
When an excessive external force is applied to the hand 24, the relative movement between the inner shell 40 and the outer shell 41 is caused by the above-mentioned gap 4.
Since the optical fibers 16, 17, 18 and the two-dimensional displacement detectors 13, 14 . .

The internal pressure of the nuclear inner shell 40, which can prevent damage caused by contact with the nuclear reactor 15, was adjusted by using a small compressor installed outside to vary it from 1 to 10 υ. In this embodiment, the outer shell 41 and the inner shell 40
The diameters are 4c and m, respectively.

It is 2cm. The force sensitivity and load capacity are as follows when the internal pressure is 1.
Each is 0.5L1ki9, and in the case of internal pressure 10,
They were sg and sm, respectively.

When the internal pressure of the inner shell 40 is changed, the outer shell 4
1 and the inner shell 40 and the external force acting on the hand 24 change, so it is necessary to calibrate the relationship between the relative displacement and the external force in advance using the internal pressure as a parameter.

The internal pressure is connected to an externally installed pressure regulator, and the output of the force sensor is fed back to adjust it as needed, so that the sensitivity and load capacity of the force sensor can be arbitrarily adjusted on the spot. You can also do it.

Alternatively, a method may be adopted in which the pressure V41i device is used for one operation of force sensing and separation while maintaining a constant internal pressure using the gas sealing valve 44. Therefore, in the force sensor of this embodiment, when an excessive external force is applied to the hand U, the amount of displacement of the elastic body 42 is automatically adjusted to k and pressure by using the gap d as described above. Since it has the function of being able to be restrained by a heteronomous method by operation, damage to the force sensor can be prevented.

"Effects of the Invention" As explained above, the force sensor of the present invention has a movable part attached to the support vermilion via an elastic body, three non-contact displacement detectors for detecting two-dimensional displacement, and a gauge for the movable part. Since the forming body is attached to the movable part and the support body, the external force acting on the movable part can be calculated from the two-dimensional displacement amount of the gauge point moving on the three displacement planes. In addition, in conventional force sensors configured using strain gauges and potentiometers, in order to obtain 6 degrees of freedom, the strain gauges provided on the elastic body are arranged in double lines, so the elastic body is The force sensor of the present invention is equipped with a strain gauge on the elastic body, whereas the device configuration has become complicated and large-scale due to the large size and complexity and the need for a drive mechanism to be attached to the potentiometer. This eliminates the need for an elastic body, which simplifies the structure of the elastic body, and eliminates the need for a drive mechanism, resulting in a reduction in size and weight. Therefore, the force sensor of the present invention is most suitable for use in small robots used for assembling small precision parts.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the first embodiment of the present invention, Fig. 2 is a diagram showing the principle of the present invention, Fig. 3 is a block diagram of the light source section of the second embodiment of the present invention, The configuration diagram of the third embodiment of the invention, Figure 5 is an example configuration diagram of an elastic body adopted in a conventional force sensor using a strain gauge, and Figure 6 is a diagram of part b of Figure 5. This is an enlarged view. 10.42...Elastic body, 13. 14. 15
...Two-dimensional displacement detector, tg, 17t 18
t 30... Optical fiber (gage point forming body), 1
9.20. 21... Light point (gauge), 23...
...Robot arm (support body), 24...
・Robot hand (movable part).

Claims (3)

[Claims] (1) A movable part is attached to the support body via an elastic body,
Three non-contact displacement detectors for detecting the two-dimensional displacement of a gauge point along a predetermined displacement plane are provided on either the support body or the movable part, and the other one is provided with a gauge point on the displacement plane. A force sensor is provided in which gauge point forming bodies are respectively attached, and the three non-contact displacement detectors are provided with respective displacement planes disposed within three planes orthogonal to each other. A force sensor characterized by: (2) The force sensor according to claim 1, wherein the elastic body has a hollow portion, and the elastic body is provided with pressure control means for controlling the pressure inside the hollow portion. (3) The gauge point forming body consists of an optical fiber provided in the hollow part of the elastic body, and the gauge point is formed by a light beam projected from the optical fiber onto the displacement plane of the non-contact detector in the hollow part. Claim 1, which consists of a light spot, and the light beam is obtained by branching from three optical fibers with their tips pointing in different directions, or from one optical fiber, or The force sensor described in item 2.