JPS639938B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a minute displacement device for precisely positioning a moving object to a target position.

Conventionally, as a device for precisely positioning a moving object, there is a device that uses a spring and an electromagnet, controls the electromagnetic force of the electromagnet, and positions the moving object at a position where this and the restoring force due to the deformation of the spring are balanced. It is being

FIG. 1 is a schematic plan view showing the basic configuration of such a conventional device.
A table 3 is supported by a structure in which four L-shaped leaf springs 2, one end of which is fixed to a book support 1, and the other ends of which are connected to the four corners of a table 3 on which a moving object is placed. Adsorption members 4 and 5 made of magnetic material are fixed to the side surface of the table 3, and there is a gap between the adsorption members 4 and the air gap.
An electromagnet 6 consisting of a _U -shaped iron core 61 and an excitation coil 62 wound around the iron core 61 is fixedly installed on the base 10, and is separated from the adsorption member 5 by a gap l _2. Lever-shaped iron core 71 and this iron core 7
An electromagnet 7 consisting of an excitation coil 72 wound around 1 is fixedly installed on a base 10.

According to such a positioning device, when an excitation current is applied to the excitation coil of the electromagnet 6, an electromagnetic force corresponding to the excitation current acts between the electromagnet 6 and the attraction member 4, and the table 3 is moved by this electromagnetic force. It can be displaced in the X direction to a position where the spring forces of the four L-shaped leaf springs 2 are balanced. Similarly, when an excitation current is applied to the excitation coil 72 of the electromagnet 7, the table 3 can be displaced in the y direction. Therefore, by appropriately controlling the excitation currents to be applied to the excitation coils 62 and 72 of the electromagnets 6 and 7, the position of the table 3 on the xy plane can be controlled.

When positioning is performed using this device, the excitation current applied to the excitation coils 62 and 72 is applied by increasing or decreasing a displacement current corresponding to a predetermined amount of displacement around a certain constant DC current. A minute displacement corresponding to the displacement current is applied to the table 3, centered on the position where the electromagnetic force due to the DC current and the restoring force of the spring are balanced.

However, when the electromagnetic core is used in a non-saturation region, there is a nonlinear relationship between the deflection current and the table displacement, so in the conventional device as shown in Figure 1, the displacement current and table displacement are approximately equal to each other. Not only does the range that can be considered linear be narrow, but it also has the disadvantage that it is difficult to construct a position control system with stable operability using such a device.

The object of the present invention is to eliminate the above-mentioned drawbacks and to provide a micro-displacement device having a wide linear range and stable dynamic characteristics.

In this invention, at least one pair of electromagnets that generate opposing electromagnetic forces are installed in each displacement direction across a table supported by a spring provided on a base, and an appropriate gap is left between the table and the electromagnets. Of the pair of electromagnets, an adsorption member is provided, and the electromagnet that generates an electromagnetic force in the displacement direction generates a constant electromagnetic force and a displacement electromagnetic force corresponding to a predetermined displacement amount, and the other electromagnet generates the above-mentioned constant electromagnetic force. By subtractively generating a displacement electromagnetic force corresponding to the force and a predetermined amount of displacement, the constant electromagnetic force is canceled out, and the table is brought to an equilibrium position between the force twice the displacement electromagnetic force and the restoring force of the spring. This is a micro-displacement device that moves and positions.

Next, the principle and embodiments of the invention will be explained with reference to the drawings. FIG. 2 is a schematic plan view showing the first embodiment of the invention, in which each of the four pillars 1 fixed on the base 10A has an L-shaped leaf spring 2.
One end of the L-shaped leaf spring 2 is fixed, and the other end of the L-shaped leaf spring 2 is attached to the four corners of the table 3 on which the object to be moved is placed.
The table 3 is elastically supported by these four leaf springs 2, and adsorption members 4, 4' made of magnetic material are attached to each side of the table 3 in the x direction of the figure.
The adsorption members 5 and 5' made of magnetic material are provided at corresponding positions across the table 3, and the adsorption members 5 and 5'
are provided at positions corresponding to the directions. An electromagnet 6 consisting of a U-shaped iron core 61 and an excitation coil 62 wound around the iron core 61 is installed on the base 10A with a suitable gap l ₃ to the above-mentioned attracting member 4. Similarly to the suction member 4, the U-shaped iron core 61' and the excitation coil 62' wound around the iron core 61' are connected to each other with an appropriate gap _l3 '. An electromagnet 6' consisting of an electromagnet 6' is provided on the base 10A. In addition, appropriate gaps l ₄ and l ₄ ' are provided for the adsorption members 5 and 5', and the iron cores 71 and 71'
and an electromagnet 7 consisting of excitation coils 72, 72',
7' are respectively provided on the base 10A. The sizes of the gaps l ₃ , l' ₃ , l ₄ , l' ₄ between the adsorption member and the electromagnet are determined based on the spring constant of the leaf spring, the strength of the electromagnetic force generated by the electromagnet, etc.

The principle of movement and displacement of the table 3 in the x direction by exciting the electromagnets 6 and 6' will be explained below, but the same applies to the displacement of the table 3 in the y direction.

If a current I is applied to the excitation coil 62 of the electromagnet 6 and a current I' is applied to the excitation coil 62' of the electromagnet 6', the iron cores 61, 61' of the electromagnet and the attraction members 4, 4' are in a non-saturated state. When in
Assuming that the gaps l ₃ and l' ₃ between the adsorption members 4 and 4' and the iron cores 61 and 61' of the electromagnets are sufficiently long compared to the range of movement displacement of the table 3, the electromagnetic force generated by each electromagnet is Regarding the forces F and F′, F≒kI ² (1) F′≒kI′ ² (2) holds. However, k is a proportionality constant determined by the magnetic path length of the iron core, the air gap length, the magnetic permeability of the iron core and the air gap, the number of turns of the excitation coil, and the cross-sectional area of the magnetic path.
Since F and F' are electromagnetic forces in opposite directions,
The force △F=F−F′ acts on the table in the x direction, and △F≒k(I ² −I′ ² )=k(I+I′)(I−I′)(3
) becomes. If the current applied to the excitation coil 62 is now I = Io + △I/2 (4) and the current applied to the excitation coil 62' is I' = Io - △I/2 (5), then from equation (3), △F≒k・Io・△I (6) Therefore, if Io is constant, the electromagnetic force in the x direction △
F is approximately proportional to △I. FIG. 3 is a diagram showing changes in electromagnetic force with respect to changes in current due to the moving displacement principle of the present invention, in correspondence with the case of a conventional device. It can be seen that the linear range is much wider than that of the method.

Since the restoring force of spring 2 that is in equilibrium with electromagnet △F is ^proportional to the displacement x of spring 2, the following relationship holds: (proportionality constant K ^-1 kIo) displacement can be given to the table. However, K is the composite spring constant of the four leaf springs in FIG.

FIG. 4 shows an example of the drive circuit for the electromagnets of the device in FIG. Here, A ₁ , A ₂ , and A ₃ are operational amplifiers, Q ₁ and Q ₂ are power transistors, and L ₁ and L ₂ are coils wound around electromagnets. V ₀ and V ₁ indicate + voltage sources, and VR is a variable resistor (for bias current setting).

Now for simplicity the resistance Ro ₁ = Ro ₂ , the resistance R ₁₁ = R ₁₂
= R ₂₁ = R ₂₂ ≫R, resistance R ₁₀ = R ₂₀ = R, then
The circuit formed by resistors Ro ₁ and Ro ₂ and operational amplifier A ₃ becomes an inverting amplifier circuit, and for input voltage l,
Operational amplifier _A3 outputs an output voltage -l.

Operational amplifier A ₁ , A ₂ set by variable resistor VR
If the positive phase input terminal voltage of is V (Io), then the resistance R ₁₀
The voltages E ₁ and E ₂ between the terminals of the resistor R ₂₀ are expressed by the following equations.

E ₁ = 2V (Io) - l E ₂ = 2V (Io) + l Therefore, the currents flowing through the coils L ₁ and L ₂ are respectively I ₁ = 2V (Io) / R - 1 / R = Io - △I I ₂ =2V(Io)/R+1/R=Io−△I. For example, when Io = 2A, the conversion coefficient is G
In order to obtain the desired displacement x by driving a pair of electromagnets with =x/△I=100μm/A with the above circuit when R=1Ω and V(Io)=1V, l=R. It is sufficient to input the voltage ΔI=R/Gx. For example x=-10μ
When m, l=1/100・(-10)=-0.1, so it is sufficient to input -0.1V.

By using the drive circuit as described above for the electromagnets provided in the pair of devices shown in FIG.
The linearity of displacement and current is better over a wider range than in the case of a device using a single electromagnet, and the table can be displaced with high precision.

FIG. 5 shows another embodiment of a drive circuit for a pair of electromagnets, in which a reference current circuit and a control current supply circuit are provided separately to increase or decrease the generated electromagnetic force. 6C and 6D are a pair of electromagnets provided with the table 3 in between, and each has an iron core 61C and an iron core 61D, and these iron cores are equipped with reference current circuits 62C, 62D and 62D for generating a constant magnetic flux. Control current circuits 621C and 621D are provided for adding and subtracting magnetic flux.

The pair of reference current circuits 62C and 62D have the same number of coil turns, wire diameter, pitch, etc., so that the generated magnetic flux is equal to each other, and the control current circuits 621C and 621D also have the same number of coil turns and wire diameter. Make the diameter, pitch, etc. the same so that the generated magnetic flux is the same, and the magnetic flux acts additively on one electromagnet for a certain magnetic flux, and the magnetic flux acts subtractively on the other electromagnet. Determine the direction of the current.

In the electromagnets 6C and 6D described above, when a current is supplied to the reference current circuits 62C and 62D, a certain magnetic flux is generated through the iron cores 61C and 61D, respectively, and the control current circuits 621C and 621D are supplied with a constant magnetic flux depending on the displacement of the table 3. By supplying the required current, the magnetic flux acts additively on the one hand and subtractively on the other hand with respect to the above-mentioned constant magnetic flux, respectively, so that the attraction members 5C made of magnetic material provided on the table 3, 5D to displace the table 3 by a predetermined amount.

FIG. 6 is a schematic plan view showing a second embodiment of the invention, in which the device is capable of not only linear displacement but also rotational displacement. Four magnetic supports 1A, 1′A′, 1B, fixed on the base 10B,
Both ends of magnetic plate springs 2A and 2A' are respectively fixed to 1B', and there are a member 40 made of a magnetic substance fixed to the plate spring 2A, and a member 40 made of a magnetic substance fixed to the plate spring 2A'. ′, each end of a plate spring 2B made of a magnetic material is fixed between the table 3 and an attraction member 5 made of a magnetic material, and a magnetic plate spring 2B is fixed between the table 3 and an attraction member 5 made of a magnetic material. Each end of the leaf spring 2B' of the body is fixed. Magnetic poles 64A', 64A' fixed to pillars 1A, 1A',
Magnetic poles 64B, 64 fixed to columns 1B, 1B'
B', electromagnetic core 61 consisting of magnetic poles 65, 65',
Excitation coil 62 is attached to the magnetic poles 64A and 64A' of 61'.
Excitation coils 62B, 62B' are wound around the magnetic poles 64B, 64B', and excitation coils 63, 63' are wound around the magnetic poles 65, 65', respectively.

The magnetic poles 64A, 64A' have a plane perpendicular to the x direction, and face the side surfaces 51, 51' perpendicular to the x direction of the adsorption members 5, 5' made of magnetic material with an appropriate gap, and the magnetic poles 64B, 64B The end faces of the magnetic poles 65, 65' are also perpendicular to the x direction, and face the side faces 52, 52' of the adsorption members 5, 5', which are perpendicular to the x direction, with a suitable gap therebetween. A side surface 5 perpendicular to the y direction and perpendicular to the y direction of the suction members 5, 5'
3 and 53', facing each other with a suitable gap.

In the above device, when an excitation current is applied to the excitation coil 63 and the excitation coil 63' in accordance with the movement displacement principle of the present invention, the magnetic pole 65 and the magnetic pole 65' paired therewith generate a differential electromagnetic force in the y direction. occurs,
Excitation coils 62A, 62A' and excitation coil 6
When an excitation current is applied to 2B and 62B' in the same manner as above, a differential electromagnetic force in the x direction is generated between the magnetic poles 64A and 64A' and their paired magnetic poles 64B and 64B', but By controlling the electromagnetic force at the magnetic pole 64B and the electromagnetic forces at the magnetic poles 64A' and 64B' differently, rotational displacement can be given to the table 3. displacement can be given. In the device shown in Figure 6, there is a concern about mutual interference between the magnetic fluxes that are the source of the electromagnetic forces in the x and y directions, but since both the leaf spring and the support are magnetic, for example, the dotted lines in Figure 6 As shown, the magnetic path 1L related to the electromagnetic force in the x direction and the magnetic path 2L related to the electromagnetic force in the y direction are independent, and the above-mentioned mutual interference is slight.

In the device shown in FIG. 6, the magnetic path 1L and the magnetic path 2L are formed by a magnetic leaf spring 2B and a leaf spring 2.
However, as the magnetic flux density of the magnetic path increases, magnetic saturation occurs due to the small effective cross-sectional area of the leaf spring, and even if the moving displacement principle of the present invention is used ( 7) The linear relationship shown in formula no longer holds true.

FIG. 7 is a plan view of a device showing a third embodiment of the present invention, which is a displacement device in which magnetic saturation as described above is unlikely to occur. This device has the same main parts as the device of the second embodiment, and is characterized in that a flexible magnetic material is installed between the iron cores 61, 61' and the adsorption members 5, 5'. 8A, 8B, 8A', and 8B' are the flexible magnetic materials, for example, soft magnetic powder or particles mixed with a flexible material such as rubber at an appropriate density. Therefore, it easily deforms in response to stress. Flexible magnetic material 8
The side surfaces of A and 8B are tightly fixed to at least the electromagnet iron core 61 and the adsorption member 5, and the flexible magnetic body 8
Similarly, A' and 8B' are tightly fixed to the iron core 61' and the adsorption member 5', and due to the presence of the flexible magnetic bodies 8A, 8B, 8A', and 8B' with large effective cross-sectional areas, these are magnetically Since it forms part of a path, the problem of magnetic saturation mentioned above is solved. As shown in FIG. 7, the flexible magnetic bodies 8A, 8B, 8A', 8B' are shaped like the shaded areas, and their sides are shaped like the iron cores 61, 6.
1', magnetic bodies 5, 5' as well as leaf springs 2A, 2
By bringing A, 2B, and 2B' into close contact with each other, the flexible magnetic bodies 8A, 8B, 8A', and 8B' function as dampers in each direction of deformation of the leaf spring due to their flexibility. There are also additional effects.

In the device of the present invention, the relationship between the magnitude of the control current supplied and the displacement of the table via the spring is linear over a wide range, and the object to be moved can be displaced as desired. In addition, the gap between the electromagnet and the adsorption member, which must be set to obtain a predetermined linear range, can be made smaller than in conventional devices, and therefore less bias current is required, so the amount of heat generated is small, and the device itself has small thermal displacement. This allows the table to be displaced with high precision.

Furthermore, in this device, since the control current and electromagnetic force have a point-symmetrical relationship as shown in Figure 3, the control current and displacement also have a point-symmetrical relationship, and the positive direction displacement response and the negative direction response centering on the reference position. Since the displacement response has the same shape, this combined with good linearity is suitable for dynamic minute displacement.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of a conventional device, FIGS. 2 to 7 are related to the device of the present invention, FIG. 2 is a schematic plan view showing a first embodiment of the present invention, and FIG. The figure is a diagram showing the change in electromagnetic force with respect to the change in current due to the moving displacement principle of the present invention, in correspondence with the case of a conventional device. Figure 4 is a circuit showing an example of the electromagnet drive circuit of the device of the present invention. Figure, 5th
The figures are explanatory diagrams showing another example of the electromagnet drive circuit, FIG. 6 is a schematic plan view showing a second embodiment of the invention, and FIG. 7 is a schematic plan view showing a third embodiment of the invention. FIG. Explanation of the symbols: 1 is the column, 2 is the leaf spring, 3 is the table, 4, 4' are the suction members, 5, 5' are the suction members,
6, 6' are electromagnets, 7 is an electromagnet, 5C, 5D are adsorption members, 61, 61', 61C, 61D are iron cores,
62C, 62D are reference current circuits, 71, 71' are iron cores, 72, 72' are exciting coils, 8A, 8B,
8A', 8B' are flexible magnetic materials, 621C, 621
D is a control current circuit.

Claims (1)

[Claims] 1. A base, one or more pairs of springs provided on the base, a table supported by the springs, and an adsorption member made of a magnetic material fixed to the side surface of the table in the direction of movement. , an electromagnet installed on the base so as to face the adsorption member with a predetermined gap therebetween, and an electric circuit that supplies current to the electromagnet, and the electric circuit has a reference voltage for each of the pair of electromagnets. It has a reference current setting circuit that supplies current, and a control current supply circuit that additively supplies current to one of the electromagnets and subtractively supplies an equal amount of current to the other electromagnet, and A micro-displacement device characterized in that the relationship between the displacement of the table and the change in is linear.