JPH0551440B2 - - Google Patents

Description

[Detailed Description of the Invention] [Table of Contents] Industrial Application Fields Prior Art Problems to be Solved by the Invention Means for Solving the Problems Effects of the Invention [Industrial Application Fields] The present invention The present invention relates to an improvement in the structure of a support device having a first member that supports a plate-shaped elastic body and a displacement regulating means that regulates displacement of the plate-shaped elastic body.

In recent years, industrial robots have been frequently introduced into production lines. However, since position-controlled robots operate regardless of restraining forces from the environment, it is extremely difficult to introduce them into assembly line automation, which requires delicate force adjustment.

This is because many assembly operations require absolute positional accuracy of parts, such as fitting and attaching parts.

If the fitting of parts is to be carried out by a position-controlled robot, the locus of movement determined from the assembly object must be accurately described with respect to the robot coordinates, and the tip must be precisely controlled to follow a predetermined locus.

However, in actual position-controlled robots,
It is extremely difficult to increase absolute positional accuracy due to mechanical errors and control errors inherent in the robot itself.

For this reason, in assembly robots, a compliance mechanism is provided at the wrist between the robot and the hand to correct or absorb the relative position error between the robot and the object.

Furthermore, the amount of error correction or absorption that can be corrected or absorbed by the compliance mechanism provided on the wrist is extremely small, and therefore cannot correct or absorb the relative position error between the robot and the object.

For this reason, the above-mentioned relative position error is detected as a reaction force generated at the wrist, and the reaction force that detects the reaction force is fed back to the robot to correct the position of the robot so that the reaction force becomes zero. The development of force detection devices (sensors) is progressing.

FIG. 11 is a diagram for explaining such a compliance mechanism and force detection device.

In the figure, 9 is a parallel spring in the X direction, and 10
are parallel springs in the Y direction, and the force detection device 6 is constituted by two sets of parallel plate springs 9 and 10 that can be displaced in the X direction and the Y direction, which are orthogonal to each other.

Therefore, the upper part of the force detection device 6 can be displaced in the X direction by the parallel plate spring 9 in the X direction, and the lower part can be displaced in the Y direction by the parallel plate spring 10 in the Y direction.

11 is a cross spring, and parallel leaf spring groups 9,
The connecting rod 12, which consists of a cross-shaped leaf spring provided on the top of the cross-shaped spring 1, is connected to the hand.
1, the vertical axis (Z
It can be tilted laterally with respect to the Z-axis (axis), and can also be displaced in the Z-axis direction (vertical direction).

A leaf spring assembly (compliance mechanism) that can be displaced in the X, Y, and Z directions is provided at the wrist between the arm and hand of the robot to absorb positioning errors of the robot.

In addition, by detecting the amount of displacement of each leaf spring body using a force detection device configured by attaching a strain gauge to each leaf spring body that makes up the compliance mechanism, we can detect the reaction force caused by positioning errors of the robot. The magnitude and direction of the reaction force are detected, and the robot is driven to cancel this reaction force based on the detected output.

Below, an example of attaching a strain gauge for detecting a reaction force and an example of calculating the reaction force applied to the hand from the output of the strain gauge will be described.

In FIG. 11, 13a, 13b, 13c,
13d is a strain gauge (detector), which is provided on each piece of the cross spring 11 and measures the moment of each piece.
The strain gauge 13a detects the moment Ma, and the strain gauge 13a detects the moment Ma.
The strain gauge 13b detects the moment Mb, the strain gauge 13c detects the moment Mc, and the strain gauge 13d detects the moment Md.

The strain gauges 14a and 14b are strain gauges, and are provided on the walls of the parallel leaf spring 9 in the X direction and the parallel leaf spring 10 in the Y direction, respectively, and are used to detect moments Me and Mf applied to the parallel leaf springs. be.

As is well known, each strain gauge is constructed by connecting four resistor groups to form a bridge circuit, and detects a moment based on a change in output voltage with respect to input voltage.

In addition, each of these strain gauges 13a to 13d, 14a
The forces Fx, Fy, Fz in the directions of the respective axes X, Y, Z and the moments Mx, My in the X, Y directions which are applied to the tip of the hand 4 from the outputs Ma to Mf of ~14b are determined as follows.

Ma=a・Fz+My …(1) Mb=a・Fz+Mx …(2) Mc=a・Fz−My …(3) Md=a・Fz−Mx …(4) Me=n・Fx … ...(5) Mf=m・Fy ...(6) However, a is the center of the cross spring 11 and each strain gauge 1
Distance from 3a to 13d (see Figure 11), m, n
are the center of each parallel leaf spring 9, 10 and the strain gauge 14
a, 14b (see FIG. 11).

In FIG. 11, Fx to My represent the force and moment at the upper end of the connecting rod 12, but the equations (1) to (6) above are applied to the lower end of the connecting rod, that is, the cross spring 11. This is the formula for calculating the force and moment above.

Therefore, from equations (1) to (6) above, each component Fx to Fz, Mx, My of each force vector is: Fx=Me/n...(7) Fy=Mf/m...(8) Fz = (Ma + Mb + Mc + Md) / 4a ... (9) Mx = (Mb - Md) / 2 ... (10) My = (Ma - Mc) / 2 ... (11).

As is clear from Fig. 11, in the conventional compliance mechanism and force detection device as described above, each leaf spring body is extremely thin, so if the robot goes out of control, or the positioning error of the robot is excessive. In such cases, if a large external force is applied, plastic deformation occurs, resulting in the detection device being destroyed.

[Prior art]

For this reason, the present applicant has proposed a device in which a limit mechanism is provided to restrict the displacement of the leaf spring body, as disclosed in, for example, Japanese Patent Laid-Open No. 59-59388.

FIG. 12 is a diagram for explaining a compliance mechanism having a limit mechanism.

In the figure, the force detection device 6 includes parallel plate springs 9a and 9b that are displaceable in the X direction and Y
It is composed of parallel plate springs 10a and 10b that can be displaced in the direction. Each parallel plate spring 9a, 9b, 10
The upper ends of a and 10b are removably fixed to each side of a square common mounting base 16 with screws 15. X
The lower ends of the direction parallel leaf springs 9a and 9b are fixed to the mounting base 16a with screws 15, and the Y direction parallel leaf springs 1
The lower ends of 0a and 10b are fixed to another mounting base 16b with screws 15. A connecting rod 18 connected to an arm (not shown) located above the force detection device 6 is fixed to a lower end mounting base 16b of the parallel plate springs 10a, 10b in the Y direction.
b, 10a, 10b are connected to the arm through the through hole 16c of the common mounting base 16 at the upper end. 18a
is a screw hole for connection with the arm. The X-direction leaf springs 9a, 9b and the Y-direction leaf springs 10a, 10b are fastened to the mounting bases 16, 16a, 16b with screws 15 so that arbitrary spring constants can be obtained by replacing them. When a force F is applied to the connecting rod 18 between the wrist and the arm, the parallel leaf springs 9a and 9b in the X direction and the parallel leaf springs 10a and 10b in the Y direction are deformed in accordance with the component forces Px and Py, and this force F is absorb. In this case, since the movable range of the connecting rod 18 is determined by the diameter of the through hole 16c, the displacement of the parallel plate spring is regulated by the through hole 16c.

FIG. 13 is a perspective view of another example. In this example, each parallel plate spring 9a, 9b, 10a, 10
As shown in FIG.
6b'. The mounts 16a and 16b are arranged so that their recesses face each other and are orthogonal to each other so that each mount fits into the recess of the other mount. The width _{of each} mounting base is
The movable range in the Y direction is determined, and the displacement of the parallel leaf spring is regulated. In this example, each parallel plate spring 9a,
The lengths Lx and Ly of 9b, 10a, and 10b are equal. Therefore, the same spring constant can be obtained in the X and Y directions using one type of spring shape.

In addition, each force component is measured by attaching a strain gauge to each leaf spring.
The output can be calculated by using the above-mentioned formulas.

[Problem that the invention seeks to solve]

However, in the conventional compliance mechanism and force detection device as described above, the structure of the limit mechanism is complicated, and calculations such as the above formula must be performed in order to calculate the force component.
It is necessary to improve the force detection device for real-time control of robots.

[Means for solving problems]

FIG. 1 is a basic block diagram of the support device of the present invention.

In FIG. 1, a first member 1 (or a second member 5) has a slit-like groove 1a formed therein to form a thin part 2a and a thick part 3a.

The thin portion 2a constitutes the plate-like elastic body 2, and the thick portion 3a constitutes a displacement regulating member that restricts excessive displacement of the plate-like elastic body 2.

The first member 1 (or the second member 5) flexibly supports the second member 5 (or the first member 1) via the plate-like elastic body 2.

That is, the second member 5 (or the first member 1)
It is supported by the plate-shaped elastic body 2 so that it can be displaced relative to the first member 1 (or the second member 5) when it receives an external force.

Further, the width of the slit-like groove portion 1a is a width corresponding to the amount of displacement within the elastic deformation range of the thin-walled portion 2a constituting the plate-like elastic body 2.

[Effect]

That is, in the present invention, the strip-like elastic body 2 and the strip-like elastic body 2 are formed only by forming the slit-like groove portion 1a in the first member 1 (or the second member 5) and forming the thin-walled portion 2a and the thick-walled portion 3a. It becomes possible to form the displacement regulating member 3 at the same time.

〔Example〕

2 and 3 are explanatory diagrams of an embodiment of the support device of the present invention, in which FIG. 2 is a perspective view and FIG.
FIG.

4 is a plan view of the XYZ module, FIG. 5 is a side view of the XYZ module, and FIG. 6 is a plan view of the γ module.

In the figure, 30 is a force detection module that detects forces in the X, Y, and Z axis directions, and is a cross-shaped structure composed of square rods 21 and 22 that deform in the three directions of X, Y, and Z. be.

This XYZ module 20 has a slit-like gap a,
By forming a', b, b', c, and c' (corresponding to the slit-shaped grooves in the principle block diagram shown in Fig. 1) by wire electric discharge machining, parallel to each of the square bars 21 and 22, Leaf spring bodies 23, 24, 25, 26, 2
7 and 28 (corresponding to the plate-like elastic body and thin wall portion in the principle block diagram shown in FIG. 1) are formed.
In addition, in Figures 4 and 5, 50, 51, 5
Reference numerals 2, 53, 54, and 55 are through holes formed in advance by a drill or the like to pass wires for wire electrical discharge machining, and are not shown in FIGS. 2 and 3.

Therefore, the slit-like gaps a, a', b, b', c, and c' are formed in this XYZ module 20 to form the parallel leaf spring bodies 23 to 28, and at the same time, the displacement of the parallel leaf spring bodies is restricted. Displacement regulating member 5 for
6, 57, 58, 59, 60, and 61 (corresponding to the displacement regulating member and thick wall portion in the principle block diagram shown in FIG. 1) are formed.

That is, even if each parallel leaf spring body 23-28 is displaced by an external force, it will not be displaced any further because the displacement regulating members 56-61 are arranged with a minute gap (approximately 3 mm for the thickness of the wire). Therefore, even if the plate spring portion is made thin, it will not buckle when an excessive external force is applied.

As is clear from FIGS. 3, 4, and 5, the force detection module 30 includes parallel leaf spring bodies 23, 2.
4, 25, 26, 27, and 28 are provided so that their displacement directions are orthogonal to each other, and parallel plate spring bodies 2
3 and 24 share the displacement (deflection) in the X-axis direction, parallel plate spring bodies 25 and 26 share the deflection in the Y-axis direction, and parallel plate spring bodies 27 and 28 share the deflection in the Z-axis direction, respectively.
It has a degree of freedom.

31 and 32 are supports that support the force detection module 30, respectively. The support 31 is connected to the square bar 22 by a screw 33, and the support 32 is connected to the square bar 21 by a screw 34. The end of the square rod 21, which is the part connected to the support body 32, is connected to the first
This corresponds to the first member of the principle block diagram shown in the figure. Note that only one of the screws 33 and 34 is shown, and the screw hole 33a into which each screw 33 is screwed and the other hole are set at the same distance from the center position of the hole 37, and the screw 34 is similarly screwed into the hole 33a. Screw hole 34a
and 34b are at equal distances (L
9=L10).

Reference numeral 35 is an output rod connected to the support body 31 by a screw 36, and is configured to pass through a hole 37 provided in the force detection module 30. The output rod 35 and the portion extending to the connecting portion between the output rod 35 and the square rods 21 and 22 correspond to the second member in the principle block diagram shown in FIG.

In this case, the support 32 is fixed on a base such as a robot. In addition, the support body 32 for the robot
For fixing, screws (not shown) that are screwed into the screw holes 32a and 32b are used.

40a, 40b, 40c, 40d, 40e, 4
0f is a strain gauge, and each parallel plate spring body 2
Detect displacements of 3, 25, and 28.

In addition, since each strain gauge detects the force in the axial direction without being affected by torque, each parallel plate spring body 24, 2
6 and 27, and each strain gauge is provided to constitute a known bridge circuit, and is configured to detect the displacement of each parallel leaf spring body.

Here, a method will be explained in which the force in each axial direction is detected without the influence of torque by attaching strain gauges to each of the parallel plate spring bodies 23 to 28 so as to be symmetrical about the hole 37. .

FIG. 7 is an explanatory diagram of a method for detecting axial force without the influence of torque.

Figure 7a shows the XYZ module 2 shown in Figure 3.
7b is a diagram showing a state in which a force F in the Y-axis direction is applied to the square bar 21 of 0. Similarly, FIG.
FIG. 4 is a diagram showing a state in which a force F in a direction of rotation about the center D of the hole 37 is applied to the hole 37.

In the figure, 23 to 26 indicate parallel leaf spring bodies, and 23a, 23b, 24a, . . . 26b are leaf springs. 14g, 14h, 14i, and 14j are strain gauges, which are attached so as to be aligned with the center line passing through the center D of the hole 37, respectively. That is, the strain gauges 14g and 14i and the strain gauges 14h and 14j are connected to the leaf spring 2 at the center point symmetrical position with the center point D as the center.
6a and 25b. Note that the resistance value of each strain gauge 14g to 14j is R.

Further, the strain gauges 14g to 14j are connected to their respective output lines (not shown) so as to form a bridge circuit shown in FIG.

Therefore, as shown in FIG. 7a, the axial force F
When , the strain gauges 14g and 14h are in a contracted state, so the resistance value becomes (R - ΔR),
Since the strain gauges 14i and 14j are in a stretched state,
Since the resistance value is (R+ΔR), the voltage between terminals a and b of the bridge circuit shown in FIG. 8 is (R−ΔR)i−(R+ΔR)i=−2ΔRi (12).

In addition, as shown in Fig. 7b, the force in the rotational direction, F
When , strain gauges 14g, 14h and strain gauges 14i, 14j are all in a contracted state, so the voltage between terminals a and b is (R-ΔR)i-(R-ΔR)i=0... (13) becomes.

Therefore, by attaching the strain gauges 14g to 14j as shown in Fig. 7 and configuring a bridge circuit as shown in Fig. 8, it is possible to detect only the force in the axial direction without being affected by torque. can.

Although the above description is only for the case of one axis (Y axis), it can be attached to the leaf springs 23b and 24b in the same way, or the leaf spring body 2
8, 27 (Figure 3),
Forces in the XYZ axes can be detected without the influence of torque.

That is, in FIG. 3, strain gauges 40a to 40
Although only f is shown in the figure, the strain gauge is actually attached so that the hole 37 is the center point and is at the target position.

Further, in FIG. 3, reference numeral 41 denotes a γ module for detecting torque around the Z-axis, which is attached to the output rod 35 of the force detection module 30 via a central member 42 with a screw 39.

As shown in FIG. 6, the γ module 41 is made of leaf springs 41a, 41b, 41c, and 41d by forming slit-shaped gaps a, b, c, and d in a disc-shaped member 43 by wire electric discharge machining. is formed.

Also, like the XYZ module, through holes 62 and 63 are formed for passing wires for electrical discharge machining. (Figure 3 not shown) Therefore, at the same time as the leaf springs 41a to 41d are formed, displacement regulating members 64, 65, 66, and 67 for regulating the displacement of the leaf springs 41a to 41d are formed.

Note that 68 and 69 are escape holes that are formed during wire electrical discharge machining, and are
This is to make it easier to attach the marks a, 44b, 44c, and 44d.

As is clear from FIG. 3, the strain gauge 44a
44d are attached to the same side of the leaf springs 41a and 41b with the center point of the central member 42 as the target position.

By attaching the strain gauge in this manner, the torque around the shaft can be detected independently without the influence of axial force.

This will be explained using FIG. 9.

FIG. 9 is an explanatory diagram of a method for detecting torque around an axis without being affected by axial force.

Note that this example will be explained using the XYZ module 20.

In FIG. 9, parts that are the same as those in FIG. 7 are given the same numbers and their explanations will be omitted. The difference from FIG. 7 is that the strain gauges 14i, 14j are plate springs 25.
The point attached to a, that is, the strain gauge 14
Points g to 14j are the points where the same side of the leaf spring is attached. In addition, each strain gauge 14g to 14j
are attached at the same distance from the center point D.

Furthermore, the strain gauges 14g to 14j constitute a bridge circuit as shown in FIG.

Therefore, when an axial force F is applied as shown in FIG. 9a, all strain gauges 14g to 14j are in a contracted state, so the voltage between terminals a and b is (R-ΔR)i- (R-ΔR)i=0...(14).

Similarly, as shown in FIG. 9b, when a force F around the axis is applied, the strain gauges 14g and 14h are contracted, and the strain gauges 14i and 14j are stretched, so that the voltage between terminals a and b is is (R-ΔR)i-(R+ΔR)i=-2ΔRi...(15).

Therefore, without being affected by axial force,
It becomes possible to independently detect the force around the axis, that is, the torque.

In the above description, the reason why the strain gauges are placed at equal distances from the center point is to ensure that the same voltage value is obtained for the same force. In other words, if the distance is different, the amount of displacement of the leaf spring will be different, and therefore the output voltage will be different.

Note that the γ module 41 is attached to the output rod 35 using only the screw 39 at the center of the output rod 35, but with this configuration, when torque is applied to the outer ring 43, the screw 39 may loosen. Actually, the pin protruding from the central member 42 is connected to the output shaft 35.
It is necessary to prevent rotation by engaging with the center position, and to fix it with a screw 39 at a position deviated from the center position.

Further, this also applies to the connection between the output shaft 35 and the support body 32. Also, 43a, 4
The screw holes indicated by 3b, 43c, and 43d are for attaching the hand.

With this configuration, when the center member 42 is fixed and torque around the center axis (Z axis) is applied to the disk-shaped member 43, the leaf springs 41a, 41b, 41c,
41d is deflected. This deflection is measured by the strain gauge 44a,
By detecting at 44b, 44c, and 44d and taking out the output via the bridge circuit, the Z-axis (γ)
It is possible to detect only the torque related to

As described above, according to the present embodiment, it is possible to obtain a force detection device in which force components can be obtained independently and the structure of the limit mechanism is simple.

According to the embodiment described above, it is possible to obtain a limit mechanism with a simple configuration, but in the case of the XYZ module, as is clear from FIGS. 4 and 5, the displacement of each leaf spring is Regulation members 56-6
1 and the hole 37 side portion of each leaf spring come into contact with each other.

Therefore, symbols B, B', D, in FIGS. 4 and 5,
Since the external force concentrates on the arrow parts D', H, H', I, I', J, J', K, and K', there is a drawback that if the thickness of the leaf spring is made thinner, it will easily buckle.

An example of a support device that can overcome these drawbacks will be described below.

FIG. 10 is a diagram for explaining another embodiment of the present invention.

In the figure, 24a and 24b are leaf springs, and 56 is a displacement regulating member. A is a slit-like gap, which is formed by wire electrical discharge machining.

Here, when forming the slit-like gap a by wire electrical discharge machining, an L-shaped part is formed as shown by arrows L and M in the figure, and the respective parts of the leaf springs 24a and 24b where external force is concentrated are formed. Increase the plate thickness of D and D'.

As is clear from FIG. 10, when the leaf springs 24a and 24b are displaced by an external force, the leaf springs 24
Since the thickened portions D and D' of plates a and 24b abut against the displacement regulating member 56, the plate springs 24a and 24b
24b is less likely to buckle.

In this embodiment, the slit-like gap a is formed into L-shaped portions L and M, but it is not necessarily limited to this, and may be formed obliquely.

Further, although this embodiment describes only the leaf springs 24a and 24b, it goes without saying that the present invention can also be applied to other leaf springs of the XYZ module shown in FIGS. 4 and 5.

〔Effect of the invention〕

As explained above, according to the present invention, a limit mechanism can be realized with a simple configuration.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a perspective view of an embodiment, Fig. 3 is an exploded perspective view, and Fig. 4 is a
A plan view of the XYZ module, Fig. 5 is a side view of the XYZ module, Fig. 6 is a plan view of the γ module,
Fig. 7 is an explanatory diagram of the method of detecting force in the axial direction, Fig. 8 is an explanatory diagram of the bridge circuit, Fig. 9 is an explanatory diagram of the method of detecting force around the axis, and Fig. 10 is an explanation of another embodiment. 11, 12, 13, and 14 are explanatory diagrams of conventional examples. In the figure, 1 is a first member, 2 is a plate-like elastic body, 3 is a displacement regulating means, and 4 is a member.

Claims (1)

[Claims] 1. A plate-shaped elastic body 2, a first member 1, a second member 5, and a displacement regulating member 3 that regulates excessive displacement of the plate-shaped elastic body 2, The first and second members 1 and 5 are mutually supported via the plate-like elastic body 2 so as to be relatively displaceable when receiving an external force, the support device comprising: The first member 1 or the second member 5 includes a thin wall portion 2a and a thick wall portion 3a formed by opening a slit-like groove portion 1a having a width within the elastic deformation range of the plate-like elastic body 2. A support device characterized in that: the thin wall portion 2a is a plate-like elastic body 2; and the thick wall portion 3a is a displacement regulating member 3.