JPS6333647B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-force detector capable of detecting up to 6 components of force in a single body.

When various external forces are applied to an object, up to six types of forces and moments act on the object. Conventionally, load cells have been used to measure these component forces. However, as a force action system, a load cell assumes that only the simplest direction of force is applied, and only measures the force in that direction.If a force other than the force to be measured acts on the load cell, cannot avoid that interference. Although various technical considerations have been made to reduce the effects of other component forces, they are not perfect.

An object of the present invention is to provide a multi-force detector capable of accurately detecting up to six component forces without causing interference between component forces.

In order to achieve this object, the multi-force detector according to the present invention connects and fixes a measuring side flange and a stationary side flange which face each other at an interval by a beam, and sets the arrangement direction of the two flanges to Z. When a three-axis orthogonal coordinate system with X, Y, and Z as axes is assumed, all or part of the component forces Fx, Fy, Fz in each axis direction and the rotational moments Mx, My, Mz around each axis,
In the multi-force detector that detects the force independently from each other by a bridge circuit using strain gauges attached to the beam, the beam has an X axis around the Z axis on the measurement side flange and the fixed side flange, and Four or more beams are arranged symmetrically on each axis on the Y-axis, and the two main beams arranged on the The two main beams, which have a strain gauge attachment part and are arranged on the Y-axis, have a strain gauge attachment part with a rectangular cross section whose thickness in the Y-axis direction is smaller than the width in the X-axis direction. The bridge circuit that detects the component force Fx has a strain gauge attached to the surface in the thickness direction so as to be sensitive to shear stress at the strain gauge attached portion of the two main beams arranged on the Y axis. The bridge circuit for detecting the component force Fy is attached to the surface in the thickness direction at the strain gauge attachment part of the two main beams arranged on the X axis so as to be sensitive to shear stress. The component force is
The bridge circuit that detects Fz includes a combination of strain gauges attached to each of the four main beams so as to be sensitive to direct stress, and the bridge circuit detects the rotational moment Mx. is composed of strain gauges attached so as to be sensitive to direct stress at the strain gauge attachment portions of the two main beams arranged on the Y axis, and the bridge circuit for detecting the rotational moment My is X. The structure includes strain gauges attached so as to be sensitive to direct stress at the strain gauge attached portions of the two main beams arranged on the axis, and the rotational moment Mz is 4.
The present invention is characterized in that the strain gauge attachment portion of the main beam of the book includes a combination of strain gauges attached to the surface in the thickness direction so as to be sensitive to shear stress.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples. Figure 1a is a front view of the multi-force detector according to the present invention, and Figure 1b is the same as Figure 1a.
FIG. 3 is a cross-sectional view taken along the line _C1 - _C1 . However, beams other than the four main beams (for example, reinforcement beams, etc.) and strain gauges that are essential for component force detection are omitted.

In the figure, 1 is a flange on the measurement side, 2 is a flange on the fixed side, and these flanges 1 and 2 are separated by a distance K and are connected to four main beams (hereinafter referred to as beams in this embodiment) 3 to 6. They are connected and fixed to each other by.

In the multi-force detector having the above structure, beam 4-
The X axis is taken in the 6 direction, the Y axis is taken in the beam 3-5 direction, and the Z axis is taken in the flange 1-2 direction, and the component forces in the X, Y, and Z directions of each axis are the component forces Fx, Fy,
Suppose that Fz is the rotational moment around the axes X, Y, and Z, and Mx, My, and Mz are the rotational moments around the axes X, Y, and Z, respectively.

When a component force Fy acts on the flange 1 on the measurement side, the beers 3 and 5 are deformed as shown in FIG. 2a, and the beams 4 and 6 are deformed as shown in FIG. 2b. The force transmitted to each of the beams 3 to 6 is divided in proportion to the spring constant for the component force Fy of each beam.
Now, to simplify the explanation, it is assumed that B ₁ ≒B ₂ B ₁ ≫T ₁ and B ₂ ≫T ₂ , and the reaction forces of the beams 3 and 5 are ignored with respect to the component force Fy. The force acting on the beams 4 and 6 based on the component force Fy produces a bending stress σ and a shear stress τ due to the moment of bending the beams 4 and 6. FIGS. 3a, b, and c are diagrams showing the state of stress distribution in this case. The distribution of bending stress σ is as shown in FIG. 3b, and the distribution of shear stress τ is as shown in FIG. 3c. That is, at intermediate positions 7 and 9 on both sides of the beams 4 and 6 in the Y-axis direction, the bending stress σ becomes the maximum σ _nax , but the shear stress τ becomes zero. Also, the width of beams 4 and 6 B ₂
At an intermediate position 8, the bending stress σ is zero, but the shearing stress τ reaches a maximum of τ _nax . Therefore, by attaching a strain gauge in the direction of, for example, 45 degrees to the Z axis at the intermediate position 8, the component force Fy can be detected as the shear stress τ.

For the component force Fx, exactly the same idea holds true, only that the beams 4 and 6 in the case of the component force Fy are replaced by beams 3 and 5.

Next, as shown in Fig. 4a, when the rotation moment Mx acts on the flange 1, the beam 3~
6, a bending stress σ as shown in FIG. 4b occurs. That is, for rotational moment Mx,
The maximum bending stress σ _nax occurs at the outer end surfaces 10 and 11 of the beams 3 and 5 in the Y-axis direction. Therefore, by attaching strain gauges to the outer end surfaces 10, 11 of the beams 3, 5, the rotational moment Mx can be detected as the bending stress σ.

For the rotational moment My, exactly the same idea holds true, except that the beams 3 and 5 in the case of the rotational moment Mx are replaced by beams 4 and 6.

Further, when the rotational moment Mz is applied, shear stress is generated in each of the beams 3 to 6. To simplify the explanation, let B ₁ = B ₂ = B H ₁ = H ₂ = H L ₁ = L ₂ = L T ₁ = T ₂ = T, then the shear force F _MZ in this case is F _MZ = MZ/2L, and for each beam 3 to 6, the component force is
Similar to Fx and Fy, shearing force is generated. However, component force
For Fx, Fy, beam 3, beam 5, beam 4
The direction of the shear stress in beam 6 and beam 6 is the same, but in the case of rotational moment Mz, the direction of shear stress in beam 3 and beam 5, and beam 4 and beam 6 is opposite, so rotational moment Mz is the component force. Fx, Fy
It can be separated from and detected as shear force.

Furthermore, when the component force Fz acts, the same stress is generated in all four beams 3 to 6. Therefore, regarding component force Fz, other component forces Fx, Fy, Mx, My,
It can be detected separately from Mz.

From the above explanation of stress distribution, the 6 component forces Fx, Fy,
It was found that it was possible to detect Fz, Mx, My, and Mz. Next, a method of attaching a strain gauge to the above-mentioned stress distribution and a specific example of a bridge circuit that uses the strain gauge to eliminate mutual interference of each force component will be explained.

FIGS. 5a and 5b are views showing the direction and position of the strain gauge. Arrows I to H in FIG. 5A indicate the direction in which the strain gauge feels. First, paying attention to the beam 6, strain gauges 6-a, 6-b, 6-c and strain gauges 6-a and 6-c are located at the center of the outer surface and the center of the inner surface, where the shear stress with respect to the component forces Fx and Fy is maximum. Attach -chi, 6-li, and 6-nu, respectively. Strain gauges 6-A and 6-H are aligned in the direction perpendicular to the Z-axis (Y-axis direction), and strain gauges 6-RO and 6-RI are aligned in the Z direction.
In the same direction at 45 degrees to the axis, strain gauges 6-C and 6-H are perpendicular to strain gauges 6-B and 6-I, and intersect at a 45 degree angle to the Z-axis. Paste it on.

Furthermore, strain gauges 6 are installed at both ends of the outer and inner surfaces of the beam 6, that is, at the portions where the bending stress is maximum.
-D, 6-H and 6-L, 6-O are respectively pasted, and strain gauges 6-Heat, 6-T are pasted on both end faces of the beam 6 in the width direction, respectively.

The same number of strain gauges are attached to the other beams 3 to 5 in the same direction and in the same order considering the Z-axis. In the following description, the strain gauges for each of the beams 3 to 5 will be indicated by attaching the symbols I to O to the beams 3, 4, and 5, similarly to the case of the beam 6. In addition, strain gauges A, B, C,
The channels 1, 2, and 3 are basically constructed using a 3-axis rosette gauge, but they can also be constructed using a 4-axis rosette gauge. When a four-axis rosette gauge is used, one of the gauges can be used as a strain gauge head or a head, so there is no need to attach strain gauge heads to both ends of the beams 3 to 6 in the width direction. Furthermore, a 4-axis rosette gauge is a 4-axis rosette gauge.
This gauge is constructed by sequentially intersecting two strain gauges at a 45 degree angle on the same plane.

FIGS. 6a-f show that each beam 3 is
The detection force bridge circuits for the component forces Fx, Fy, Mx, My, Fz, and Mz each constituted by strain gauges attached to 6 are shown. First, component force Fx
The detection circuit has a circuit configuration in which a strain gauge 5-c is provided on the opposite side of the strain gauge 3-ro, and a strain gauge 5-li is provided on the opposite side of the strain gauge 3-nu. Now, a component force Fx in the direction shown in Fig. 5b is applied to the flange 1 on the measurement side.
When this occurs, a positive resistance change occurs in the strain gauges 3-B and 5-C, and a negative resistance change occurs in the strain gauges 3-N and 5-I, depending on the shear stress at that time.
As a result, the electrical balance of the bridge circuit collapses and becomes unbalanced, so that an output signal is obtained. That is, component force Fx is detected.

Next, the reason why the mutual interference of the other component forces Fy, Fz, Mx, My, and Mz is eliminated by the above-mentioned bridge circuit will be explained.

First, when component force Fy acts, strain gauge 3-
Since B, 3-N, 5-R, and 5-C are in positions that are not sensitive to the component force Fy, the bridge circuit is kept balanced and no output is generated. In addition, for the component force Fz in the direction shown in Fig. 5a, the strain gauge 3-b,
Since 3-N, 5-R, and 5-H all exhibit equal positive resistance changes, the bridge circuit is again balanced and no output is produced.

When the rotational moment Mx acts, strain gauge 3-B shows a positive resistance change, while strain gauge 5-C shows a negative resistance change with almost the same absolute value. Further, while strain gauge 3-1 shows a positive resistance change, strain gauge 5-2 shows a negative resistance change with almost the same absolute value. For this reason,
The entire bridge circuit is electrically balanced and no output is produced.

When component force My acts, strain gauge 3-ro,
Since the attachment position of 3-nu, 5-ri, and 5-c is the neutral position with respect to the component force My, strain gauges 3-ro and 3
There is no change in the resistances of -N, 5-R, and 5-C, the balance of the bridge circuit is maintained, and no output is generated.

Finally, when component force Mz acts, strain gauges 3-B and 5-I show negative resistance changes, whereas
Since the strain gauges 3-1 and 5-2 show positive resistance changes, increases and decreases in resistance cancel each other out, the bridge circuit is kept in balance, and no output is produced.

Regarding each bridge circuit shown in Fig. 6 b to f, it is possible to detect the component forces Fy, Mx, My, Fz, and Mz of each detection target separately from interference caused by other component forces.
It can be elucidated using a similar method. In addition,
The resistance r ₁ and R ₁ in Fig. 6 f are the rotational moment Mx,
This is a compensation resistor to eliminate interference caused by My.

FIGS. 7a and 7b are diagrams showing the relationship between the resistance change of the strain gauge and the output when each component force acts on the bridge circuit shown in FIGS. 6a to 6f. In the figure, an increase in the resistance of the strain gauge is indicated by (+), and a decrease is indicated by (-). Alphabets A to J attached below (+) and (-) indicate the amount of change in resistance, and the same alphabets represent almost the same amount of change. However, A>B, C>D, E>F,
The relationship is G>H and I>J.

As shown in Fig. 7a and b, by configuring the bridge circuit shown in Fig. 6 a to f, the component forces Fx, Fy, Mx, My, Fz, and Mz of each detection target can be changed between the component forces. It can be seen that detection can be performed with high accuracy without causing interference.

Also, component forces Fx, Fy and rotational moment Mz
can also be detected by a bridge circuit as shown in FIGS. 8a, b, and c. Figure 8 a, b
The resistances (r ₂ , R ₂ ) and (r ₃ , R ₃ ) are the rotational moment
This is a compensation resistor to eliminate the interference caused by Mx and My.

In the above embodiment, a 6-component force detector was shown, but the 6-component force detector was
It can also be realized as a multi-force detector that collects several force components. Also, you can freely change the combination arrangement of strain gauges, or use strain gauges attached to areas where no strain is produced as a dummy instead of strain gauges 3-A to 6-A that produce Poisson's ratio strain output. be. Further, the position where the strain gauge is attached is not necessarily limited to the example, and may be any position that can be sensitive to shear stress and bending stress.

In the above explanation, the number of strain gauges seems to be extremely large and wasteful. However, when the component force Fz is applied, the flanges 1 and 2 deform as shown in FIG. 9, and the beams 3 and 5 also deform as shown in the figure. The same applies to beams 4 and 6. Assuming that the outer gauge is A, its strain is ξ _A , the inner gauge is B, and its strain is ξ _B , the strain ξz due to component force Fz is ξz = ξ _A + ξ _B /2. Therefore, so that each bridge of component forces Fx to Mz is not affected by bending due to component force Fz, the output is averaged by combining strain gauges attached to the outside and inside of beams 3 to 6. It is necessary to incorporate it like this. This is the reason why the number of strain gauges is increased, and thereby it becomes possible to detect the component forces Fx to Mz with high accuracy even when the flanges 1 and 2 are bent largely due to the component force Fz. If the bending effect of flanges 1 and 2 due to component force Fz is small, strain gauges need only be installed on either the outside or inside of beams 3 to 6, and the number of strain gauges can be significantly reduced. . It goes without saying that the number of strain gauges can also be reduced when the number of component forces to be measured is small.

As described above, in the multi-force detector according to the present invention, the measuring side flange and the stationary side flange, which face each other at an interval, are connected and fixed by a beam, and the arrangement direction of the two flanges is aligned with the Z axis. X, Y,
When a three-axis orthogonal coordinate system of Z is assumed, all or part of the component forces Fx, Fy, Fz in each axial direction and the rotational moments Mx, My, Mz around each axis are measured using a strain gauge attached to the beam. In the multi-force detector which detects each other independently by a bridge circuit using The two main beams placed on the X-axis have a thickness of Y when viewed in the X-axis direction.
The strain gauge attachment part has a rectangular cross section that is smaller than the width seen in the axial direction, and the two main beams arranged on the Y axis have a thickness as seen in the Y axis direction and a width as seen in the X axis direction. The bridge circuit that detects the component force Fx is sensitive to shear stress at the strain gauge attachment portions of the two main beams arranged on the Y axis. It consists of a strain gauge attached to the surface in the thickness direction, and the component force is
The bridge circuit for detecting Fy includes strain gauges attached to the planes in the thickness direction so as to be sensitive to shear stress at the strain gauge attached portions of the two main beams arranged on the X-axis. , the bridge circuit for detecting the component force Fz includes a combination of strain gauges attached to each of the four main beams so as to be sensitive to direct stress at the strain gauge attachment portion,
The bridge circuit that detects the rotational moment Mx is Y
The structure includes strain gauges attached to the strain gauge attached portions of two main beams arranged on the axis so as to be sensitive to direct stress, and rotational moment
The bridge circuit for detecting My is composed of strain gauges attached to the strain gauge attachment portions of the two main beams arranged on the X-axis so as to be sensitive to direct stress, and the rotational moment Mz is The strain gauge attachment portions of the four main beams are characterized by including a combination of strain gauges attached to the surfaces in the thickness direction so as to be sensitive to shear stress, so that the strain gauges have a rectangular cross section, for example. It is possible to provide a high-performance, high-precision multi-force detector that can detect up to 6 component forces by using a beam that is easy to process and canceling the interference between component forces using a bridge circuit. .

[Brief explanation of the drawing]

Figure 1a is a front view of the multi-force detector according to the present invention. Figure 1b is a sectional view taken along line _C1 - _C1 in Figure 1a. Figures 2a and b are beam deformation in response to component force Fy. Diagrams showing the state; Figures 3a, b, and c are diagrams explaining the stress distribution of the beam with respect to the component force Fy; Figures 4a and b are diagrams explaining the stress distribution of the beam with respect to the rotational moment Mx; Figure 5 a and b are diagrams showing the strain gauge attachment position and direction, and Figure 6 a to f are component forces.
Each bridge circuit for detecting Fx, Fy, Mx, My, Fz, Mz, Figure 7 a, b shows the distortion when each component force acts on each bridge circuit shown in Figures 6 a to f. Figures 8a, b, and c are diagrams showing the relationship between gauge resistance changes and output; Figures 8a, b, and c are electrical circuit diagrams of other embodiments of the bridge circuit for detecting component forces Fx and Fy and rotational moment Mz; The figure shows beam 3 when component force Fz acts on flanges 1 and 2.
It is a figure showing the modification of ~6. 1...Flange on the measuring side, 2...Flange on the fixed side, 3-6...Beam, I-O...Strain gauge.

Claims (1)

[Claims] 1. A measuring side flange and a fixed side flange facing each other with an interval are connected and fixed by a beam, and the X, Y,
When a three-axis orthogonal coordinate system of Z is assumed, all or part of the component forces Fx, Fy, Fz in each axial direction and the rotational moments Mx, My, Mz around each axis are measured using a strain gauge attached to the beam. In the multi-force detector which detects each other independently by a bridge circuit using The two main beams placed on the X-axis have a thickness of Y when viewed in the X-axis direction.
The strain gauge attachment part has a rectangular cross section that is smaller than the width seen in the axial direction, and the two main beams arranged on the Y axis have a thickness as seen in the Y axis direction and a width as seen in the X axis direction. The bridge circuit that detects the component force Fx is sensitive to shear stress at the strain gauge attachment portions of the two main beams arranged on the Y axis. It consists of a strain gauge attached to the surface in the thickness direction, and the component force is
The bridge circuit for detecting Fy includes strain gauges attached to the planes in the thickness direction so as to be sensitive to shear stress at the strain gauge attached portions of the two main beams arranged on the X-axis. , the bridge circuit for detecting the component force Fz includes a combination of strain gauges attached to each of the four main beams so as to be sensitive to direct stress at the strain gauge attachment portion,
The bridge circuit that detects the rotational moment Mx is Y
The structure includes strain gauges attached to the strain gauge attached portions of two main beams arranged on the axis so as to be sensitive to direct stress, and rotational moment
The bridge circuit for detecting My is composed of strain gauges attached to the strain gauge attachment portions of the two main beams arranged on the X-axis so as to be sensitive to direct stress, and the rotational moment Mz is A multi-force detector comprising a combination of strain gauges attached to the planes in the thickness direction so as to be sensitive to shear stress at the strain gauge attachment portions of the four main beams.