JPH0565808B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a small and inexpensive multi-force detector.

[Prior art]

In complex structures such as industrial robots, multi-force detectors that simultaneously and accurately detect the complex force and moment exerted on each joint have conventionally used strain gauges and piezoelectric elements. However, they are both expensive and large in size, so they cannot be used in small robots such as tabletop robots.

[Summary of the invention]

In order to solve these drawbacks, this invention combines a plurality of permanent magnets and Hall elements, and detects the forces acting in each direction by changes in their relative positions.The purpose of this invention is to The objective is to realize an inexpensive multi-force detector. The present invention will be explained below with reference to the drawings.

[Embodiments of the invention]

FIG. 1 is an embodiment of the present invention, and shows the external appearance of a multi-force detector. In this figure, 1 is the housing, which has a cylindrical shape, and has an axis 2 coaxial with the axis of the cylinder.
is provided. In addition, in this specification, the first
The axial center direction of axis 2 in the figure is defined as the z-axis, and the orthogonal directions on a plane perpendicular to this are defined as the x-axis and the y-axis. The shaft 2 is movable in the radial and circumferential directions with respect to the housing 1, and when the axial center of the shaft 2 is the z-axis, the moment M _z around the z-axis and the force F _x in the x-axis direction, y
When an axial force F _y acts on the shaft 2, a corresponding output is output from the signal line 3.

FIG. 2 shows an exploded view of the multi-force detector shown in FIG. 1. A disk 4 is fixed to the shaft 2, and four permanent magnets 5a, 5 are arranged at equal intervals on the circumference of the disk 4.
b, 5c, 5d (hereinafter collectively referred to as 5. The same applies to other symbols) and plate springs 6a, 6b, 6c, 6d are provided with their inner sides fixed. Further, on the upper surface of the disk 4, there is a plate made of a material with a small coefficient of friction, such as a fluororesin plate 7, which makes it easy to slide between it and the upper plate 8. A ring 9 having approximately the same thickness as the disk 4 is located outside the disk 4, and the ring 9 is located outside the leaf springs 6a to 6d.
The ring 9 and the disk 4 have a concentric structure. Furthermore, four Hall elements 10a, 10b, 10c, 10d are provided at equal intervals inside the ring 9, and permanent magnets 5a, 5b, 5
c and 5d, each forming a pair. There is a lower plate 11 below the ring 9.
A material having a small coefficient of friction, for example, a fluororesin plate 12 is disposed on the upper surface of the disc 4, so that the disc 4 can easily slide against the lower plate 11.

As mentioned above, the disk 4 is restrained by the upper plate 8 and the lower plate 11 via the fluororesin plates 7 and 12,
It is movable only around the z-axis and in the x- and y-axis directions. In addition, due to the action of the leaf springs 6a to 6d,
It is configured to be displaced in proportion to the force around the z-axis and in the x- and y-axis directions.

FIG. 3 is a cross-sectional view taken in a plane perpendicular to the z-axis. Permanent magnets 5a to 5d, Hall elements 10a to 10d,
The positional relationship of leaf springs 6a to 6d is more clearly shown. The leaf springs 6a to 6d have the role of producing a displacement proportional to the force as described above, and are not limited to leaf springs, but may be made of a polymeric material that fills the space between the disk 4 and the ring 9 as shown in FIG. elastic material 13
It may be.

Next, the principle by which force can be detected with such a configuration will be explained.

FIG. 5 shows a pair of permanent magnets 5 and Hall elements 10 facing each other. When the centers of the opposing surfaces are A and B, the distance between points A and B in the x-axis direction is p, and the distance in the y direction is q.
When the permanent magnet 5 is magnetized so as to have N pole and S pole in the x-axis direction, and the Hall element 10 is opposed in an appropriate posture, the distance p is changed while keeping the distance q in the y-axis direction constant. The Hall voltage V changes as shown by the solid line 14 in Fig. 6a, and if the distance q is changed while keeping the distance p constant, it changes as shown by the solid line 15 in Fig. 6b. well known. As shown in the figure, the solid lines 14 and 15 are approximated by dotted lines 16 and 17, respectively. Dotted line 16 is a tangent to solid line 14 at the origin, dotted line 17 is tangent to solid line 15
is the tangent at q=q ₀ . q=q ₀ means the distance between the permanent magnet 5 and the Hall element 10 which serve as a reference.

Now, by approximating the Hall voltage as shown by dotted lines 16 and 17, the Hall voltage V can be expressed as follows: V={d(q ₀ +q)+β}p. Here, α and β are constants.

FIG. 7 shows a state in which the reference position shown in FIG. 3 or 4 has been moved by δ in the θ direction.

The centers of the opposing surfaces of the permanent magnet 5 and the Hall element 10 are A ₁ , A ₂ , A ₃ , A ₄ and B ₁ , B ₂ , B ₃ , B ₄
Then, at the reference position shown in Figure 4, from the relationship between ₁ point A and ₁ point B, p ₁ = 0, q ₁ = q ₀ From the relationship between ₂ points A and ₂ points B, p ₂ = 0, q ₂ = From the relationship between q ₀ A ₃ points and B ₃ points, p ₃ = 0, and q ₃ = q ₀ From the relationship between A ₄ points and B ₄ points, p ₄ = 0 and q ₄ = q ₀ . p ₁ to _{p 4} are p and q ₁ to _{q 4} shown in FIG.
is equivalent to q.

Similarly, when moving as shown in Figure 7, from the relationship between A ₁ and B ₁ , p ₁ = -δcosθ, q ₁ = q ₀ -δsinθ From the relationship between A ₂ and B ₂ , p ₂ = -δsinθ, q ₂ = q ₀ + δcosθ From the relationship between A ₃ and B ₃ , p ₃ = δcosδ, q ₂ = q ₀ + δsinθ From the relationship between A ₄ and B ₄ , p ₄ = δsinθ, q ₂ = q ₀ −δcosθ Also, as shown in Figure 8, , θ', and if r is the radius of the disk 4, then from the relationship between A ₁ and B ₁ , p ₁ = rsin θ', q ₁ = q ₀ + r (1 - cos θ') of A ₂ and B ₂ . From the relationship p ₂ = rsin θ', q ₂ = q ₀ + r (1-cos θ') From the relationship between A ₃ and B ₃ , p ₃ = rsin θ', q ₃ = q ₀ + r (1- cos θ') A ₄ and B ₄ , p ₄ = rsin θ', q ₄ = q ₀ + r (1-cos θ'). Therefore, when each Hall voltage changes as shown in Figure 7, V ₁ = - (β + α δ sin θ) δ cos θ V ₂ = - (β - α δ cos θ) δ sin θ V ₃ = (β - α δ sin θ) δ cos θ V ₄ = (β + α δ cos θ ) δsinθ, and when it changes as shown in Figure 8, V ₁ ′={β−αr(1−cosθ′)}rsinθ′ ×rβθ′ V ₂ ′={β−αr(1−cosθ′)}rsinθ ′ ×rβθ′ V ₃ ′={β−αr(1−cosθ′)}rsinθ′×rβθ′ V ₄ ′={β−αr(1−cosθ′)}rsinθ′×rβθ′.

If both are mixed, the sum is the sum, and the respective Hall voltages are expressed as E ₁ = V ₁ + V ₁ ′ E ₂ = V ₂ + V ₂ ′ E ₃ = V ₃ + V ₃ ′ E ₄ = V ₄ + V ₄ ′ Ru.

Now, by using these outputs and performing the following calculations using appropriate well-known calculation means, displacement in each direction can be detected.

Rotation _direction E _r =E ₁ + _{E 2} +E ₃ +E ₄ =4rβθ′ Y-axis direction E _y =E _{4 −E 2 = 2βδsinθ} Each displacement can be detected by 4rβ δ=1/2β√ ² + ² θ=tan ^-1 E _x /E _y . Furthermore, since the displacement is proportional to the force acting in that direction, the magnitude and direction of the force can be detected.

FIG. 9 shows still another embodiment of the present invention, in which the permanent magnet 5 and the Hall element 10 are offset and face each other. In this embodiment as well, the permanent magnet 5 and the Hall element 10 are disposed facing each other between the outer periphery of the disk 4 and the inner periphery of the ring 9.

In addition, in the above explanation, the permanent magnet 5 is attached to the ring 9.
Although the case where the Hall element 10 is arranged on the disk 4 has been described, it is clear from the principle that the opposite arrangement is also possible. In addition, in the above embodiment, the disk 4
Although the ring 9 is used, it is not limited to the disk 4, but other shapes may be used, and in general, a disk body is sufficient.
Similarly, the ring 9 may also have other shapes.
Any cyclic body is sufficient. Furthermore, the pairs of permanent magnets 5 and Hall elements 10 do not necessarily have to be spaced at equal intervals, and may be corrected even if they are spaced at unequal intervals.

〔Effect of the invention〕

As explained above, the present invention supports a disc body concentrically within an annular body with an elastic body that generates a displacement proportional to force, and has a hole between the outer periphery of the disc body and the inner periphery of the annular body. By installing multiple sets of elements and permanent magnets, it is possible to simultaneously detect forces acting in multiple directions based on changes in the relative positions of the two, which has the advantage of creating an inexpensive and compact multi-force detector. be.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of an embodiment of the present invention, and FIG. 2 is an exploded perspective view showing the internal configuration.
FIG. 3 is a sectional view of FIG. 1, FIG. 4 is a sectional view showing another embodiment of the invention, FIG. 5 is a diagram showing the positional relationship between the Hall element and the permanent magnet, and FIGS. 6 a and b are FIGS. 7 and 8 are diagrams showing the output characteristics of the Hall voltage, respectively. FIGS. 7 and 8 are diagrams showing the ring state and the relative displacement of the disk, and FIG. 9 is a sectional view showing still another embodiment of the present invention. In the figure, 1 is a housing, 2 is a shaft, 3 is a signal line, 4 is a disk, 5 is a permanent magnet, 6 is a leaf spring, 7 is a fluororesin plate, 8 is an upper plate, 9 is a ring, and 10 is a Hall element , 11 is a lower plate, 12 is a fluororesin plate, 13 is an elastic body, 14 and 15 are solid lines showing the characteristics of the Hall voltage, and 16 and 17 are dotted lines approximating the characteristics of the Hall voltage.

Claims (1)

[Claims] 1 An elastic body that produces a displacement proportional to the force so that the disc is concentric with the annular body.
The magnet is supported so as to be displaceable in the axial and y-axis directions, and a plurality of sets of permanent magnets and Hall elements are arranged between the outer periphery of the disk body and the inner periphery of the annular body so as to face each other. force detector.