WO2017182040A1 - Measuring assembly for the contactless measurement of a relative movement or a relative position and method - Google Patents

Abstract

The invention relates to a measuring assembly for the contactless measurement of a relative movement or a relative position of a first object in relation to a second object. The measuring assembly comprises at least one transmitter coil arranged on the first object and at least two receiver coils (A, B) arranged on the second object, wherein the transmitter coil is excited by an excitation alternating signal, wherein the receiver coils detect a measurement variable that is proportional to a first relative movement or relative position, and wherein at least one further receiver coil (C) is arranged on the second object, which detects a second measurement variable that is proportional to a second relative movement or relative position. The invention also relates to a method which uses the device according to the invention.

Description

 MEASURING ARRANGEMENT FOR THE CONTACTLESS MEASUREMENT OF A RELATIVE MOVEMENT OR A RELATIVE POSITION AND

METHOD The present invention relates to a measuring arrangement for the contactless measurement of a relative movement or a relative position of a first object with respect to a second object. Furthermore, the invention relates to a method which uses the device according to the invention. There are numerous measurement tasks in research, development and industry, where the relative position of two objects is measured to each other. Distance or position sensors are usually used for this purpose. In the semiconductor industry, positions of mirrors, masks, holders or other machine parts relative to one another are detected very precisely, for example in production plants for semiconductors, so that a correct exposure takes place due to the ever smaller feature sizes. In many other industrial applications, it is increasingly important to precisely determine the relative position of machine or plant components in order to be able to intervene regulatively. Another application concerns the modern large telescope for astronomy. The main mirrors of large telescopes consist of a large number of mirror segments, usually in a hexagonal arrangement. These segments must be aligned exactly with each other to achieve the desired contour of the overall mirror surface (GRoC = General Radius of Curvature). To accurately position the segments, displacement sensors are required to detect the relative position of two segments to each other. If the segments are hexagonal, there will be an edge for every two adjacent segments whose position is to be detected relative to one another. Per measuring point up to six measured quantities are required, whereby the three different types of tilting (Dihedral, Twist and Clock) usually play only a minor role. Frequently, the mutual distance (Gap), the lateral displacement in the mirror plane (Shear) and the lateral displacement (Piston) from the mirror plane are to be determined. The biggest influence on the deviation from the ideal mirror shape provides the Piston, whose measurement therefore the highest demands for accuracy are made.

A large number of sensor solutions already exist for use with large telescopes. In addition to capacitive sensors inductive sensors are mostly used, since they have the lowest susceptibility to interference, for example, for moisture.

 US 4,825,062 A describes inductive sensors. Two transmission coils in half-bridge arrangement are supplied with high-frequency AC voltage. In receiving coils, which are tuned by means of a capacitor near the resonance frequency, currents are induced, which lead to a damping of the transmitting coil. The damping changes with the relative position, which can thus be measured. The receiver coils are not connected to any evaluation electronics and act like an active target.

A further development of this principle is disclosed in EP 1 904 806 B1. It is a transformatory principle. For precise detection of the distance (Gap) or the displacement (Piston) of two mirror segments to each other, a transformer sensor (inductive principle) is used. For this purpose, a first, in constant frequency and voltage supplied coil (transmitting coil) is mounted on a segment. A second coil (receiving coil) is attached to the transmitting coil on the second, opposite segment. Due to the inductive coupling, an alternating voltage v _{a is} induced in the receiving coil, which is proportional to the distance or to the displacement to the transmitting coil. This signal is evaluated with a suitable circuit.

So that the distance and the displacement can be evaluated simultaneously, two separate coils are placed on the receiving side. Two alternating voltages v _a and Vb are then induced in the coils, which are independent of each other and are combined for the evaluation of the measured quantities distance and displacement. By evaluating the sum of the signals (A + B), the distance can be evaluated independently of the shift. The difference (AB) of both coils represents the displacement distance-dependent. If one forms the quotient of difference by sum ((AB) / (A + B)), the displacement can be determined independently of the distance.

However, the arrangement according to which two independent measuring magnitudes can be detected with only two receiving coils is disadvantageous if the measured variables differ greatly. Normally, measurement signals are digitized in modern measurement technology, in order to then be further processed by microcontrollers or computers. The AD converters used for digitizing have a limited, defined input range, for example 0.5 ... 4, 5 V. Analog signals must therefore be adapted to the input range by suitable amplifier circuits so that the full digitizing range is used in the best possible way. However, each amplifier generates noise, so that the lowest possible gain is desirable, or that even the primary signal covers the input area as possible.

As mirror-telescope applications make the out-of-plane displacement (Piston) the highest resolution measure, the A-B signal should be in an ideal voltage range for AD conversion. The coil arrangement will therefore have to be designed so that even the primary signal largely exhaust the input range of the AD converter. However, at the same time the signal A + B for the distance (Gap) is detected. A simultaneous optimal adjustment is not possible, which is why a compromise must be found. This conflict of objectives means that an optimal measurement of both parameters is not possible.

In the light of the above, the invention has for its object to provide a measuring arrangement and a method for using the measuring arrangement, in which / the disadvantages identified above are at least largely eliminated. A precise measurement of at least two measured variables should be possible independently of one another, preferably with the simplest construction of the arrangement.

The above object is achieved with respect to the measuring arrangement by the features of claim 1, wherein the measuring arrangement with at least one of the the transmitting coil is excited by an excitation change signal, wherein the receiving coil detect a measured variable which is proportional to a first relative movement or relative position, and wherein at the second object at least one further receiving coil is arranged, which detects a second measured variable, which is proportional to a second relative movement or relative position.

With respect to the method according to the invention, the underlying object is achieved by the features of the independent claim 15, wherein the method uses the measuring arrangement according to the invention.

So that no compromise in the design of the receiving coil pair in terms of distance measurement or displacement measurement is necessary, the receiving coil pair can be extended by at least one additional coil 6. This allows two receiver coils (A and B) to be designed and positioned so that they are optimally suited for measuring the displacement (piston). The additional third coil C is used for distance measurement. Since the lateral displacement measurement can also have a distance dependence, the signal for the displacement is corrected with a function f of the distance, generally P = (AB) ^* f (C). In the simplest form the function is the inverse function f (C) = 1 / C. The function f can also be a function of higher order, for example a polynomial. In the simplest version for two measured variables (distance and displacement), three receiving coils are thus fed by one transmitting coil. The receiver coils are arranged so that the optimum signal level is achieved for each measured variable.

By adding a further receiving coil D, a symmetrization is achieved with a further improvement in accuracy. The further coil pair (C and D) is then optimized with respect to the distance measurement. Thus, for the distance-independent measurement of the displacement, the relationship arises: P = (AB) ^* f (C, D). For a given coil arrangement, the function depends only on the sum of the two signals of the receiver coils, ie P = (AB) ^* f (C + D). The receiver coils may be arranged in parallel relative to the transmitter coil. Parallel means that the coil axes are aligned in parallel. Thus, the highest inductive coupling between the coils and thus the largest signal swing is achieved. Depending on the requirements, the coils can be designed as planar coils or wound coils. The area of the coils or the number of turns can be adapted to the respective measuring arrangement.

It can be provided a further transmitting coil, so that the first transmitting coil feeds the two receiving coils A, B and the second transmitting coil feeds the receiving coil C or C and D. This gives you additional degrees of freedom in the arrangement of the coils. The second transmitter coil can also be fed with a different frequency and / or voltage. Thus, the two signal paths for the distance and the displacement are separated from each other, so that no mutual influence takes place.

The receiving coils can also be aligned in a rectangular arrangement to the transmitting coil. Rectangular means that the coil axes are at right angles to each other, or the projection of the coil axes is perpendicular to each other.

It is also a mixed arrangement of the receiving coils relative to the transmitting coil conceivable: For example, two receiving coils A and B can be arranged perpendicular to the transmitting coil, while at least one further receiving coil C is aligned in parallel, or the two receiving coils A and B are parallel to the transmitting coil, at least one further receiver coil C perpendicular thereto, arranged.

If the first two receiving coils A and B are arranged perpendicular to the transmitting coil and parallel to each other, the third or fourth receiving coil C and D could be arranged concentrically around the two first receiving coils. This makes a very compact design on the receiving side possible. The coils can be wound in conventional form as wound coils, for example with copper wire or silver wire, be it as air coils, wound on a wound body, or provided with a coil core of ferritic material. Particular degrees of freedom in the coil geometry can be achieved if the coils are arranged in the form of planar coils on or in a multilayer substrate. A separate substrate can be used for each coil. As a result, the production can be simplified because identical parts can be used for a large number of coils. However, it is also possible for a plurality of coils to be integrated in a substrate. This applies to both transmit and receive coils.

By the layout of the tracks, from which the coils are formed, as well as with the help of suitable vias, any coil arrangements can be achieved, for example, intertwined coils. In the case of a multilayer arrangement of the coils in one printed circuit board, one layer for one coil, then one layer for another coil, can be used alternately for each layer. It is also conceivable to intertwine the coils within one layer by arranging the interconnects for both coils next to one another, that is, they extend substantially parallel. These arrangements ensure that two different coils are flowed through by the same magnetic flux.

Particularly advantageous is the arrangement of the coils in a ceramic substrate, for example in LTCC technology (Low Temperature Co-fired Ceramic). The coils together with the ceramic form a solid, stable unit. Due to the low coefficient of thermal expansion of the ceramics, the coils are very temperature-stable and therefore predestined for high-resolution, long-term stable measurements. Another advantage of the ceramic is its mechanical robustness and insensitivity to moisture. It is particularly advantageous if two or more coils are arranged in a common substrate. Thus, the relative position of the coils is fixed to each other. Due to the low expansion coefficient of the ceramic, the relative position remains stable even with temperature changes. The previous embodiments describe coil arrangements for the measurement of two variables, for example Gap and Piston. If a further measured variable is required, the arrangement can be easily extended by additional coils. If, for example, the shear should also be measured, another pair of coils A "and B" are added, analogous to the piston, but rotated by 90 degrees. The excitation can be achieved simply by an extended transmitting coil, or by a second transmitting coil. Here, too, the gap Gap can additionally be measured by adding at least one additional receiver coil. By additionally measuring the gap at another position, a tilt can also be determined, or an averaging over both values is performed, or a plausibility check.

The combination of different receiver coils offers many possibilities for solving even complex measuring tasks.

The signals A-B and C + D can be digitized by means of an AD converter. Ideally, the coil parameters (diameter or dimension, number of layers, thickness of the conductor track, etc.) and the control parameters (frequency, amplitude of the AC voltage) are already coordinated so that the input range of the AD converter is used in the best possible way. For example, given a given amplitude of the alternating voltage with which the transmitting coil is fed, the dimensions and number of layers determine the range of the alternating voltage induced in the receiving coils such that only a simple rectification is required before the signal in the AD converter is converted. Alternatively, even without rectification, a phase-synchronous sampling can take place. If the optimum adaptation is not possible due to the boundary conditions, each signal path can be adapted to the input range of the AD converter by means of suitable amplifier circuits. Further processing of the digitized signals takes place in a computer, for example in a microcontroller, which calculates the function f and determines the result, e.g. for P supplies.

There are now various possibilities for designing and developing the teaching of the present invention in an advantageous manner. On the one hand to the claims subordinate to claim 1 and on the other hand on the to refer to the following explanation of preferred embodiments of the invention with reference to the drawing. In conjunction with the explanation of the preferred embodiments of the invention with reference to the drawings, also generally preferred embodiments and developments of the teaching are explained. In the drawing show

Fig. 1 in a schematic representation of a measuring arrangement according to

 State of the art,

2 shows a schematic representation of an exemplary embodiment of a measuring arrangement according to the invention with wound coils

3 is a schematic representation of another embodiment of a measuring arrangement according to the invention with wound coils,

4 is a schematic representation of a further embodiment of a measuring arrangement according to the invention with wound coils,

5 is a schematic representation of another embodiment of a measuring arrangement according to the invention with wound coils,

6 is a schematic representation of another embodiment of a measuring arrangement according to the invention with planar coils,

7 is a schematic representation of another embodiment of a measuring arrangement according to the invention with planar coils,

8 is a schematic representation of another embodiment of a measuring arrangement according to the invention with planar coils,

9 is a schematic representation of another embodiment of a measuring arrangement according to the invention with planar coils, in a schematic representation of another embodiment of a measuring arrangement according to the invention with planar coils, in a schematic representation of another embodiment of a measuring arrangement according to the invention with planar coils, in a schematic representation of another embodiment of a measuring arrangement according to the invention with planar coils, wherein the measuring arrangement for determining at least three Measured variables serves, and in a schematic representation, cut, the arrangement of two receiving coils in a planar configuration, integrated in a common substrate.

FIG. 1 shows the state of the art. The measuring arrangement 1 is used to determine the position of a first object 2 relative to a second object 3 by means of a transmitting coil S (4) and two receiving coils A and B (5 ', 5 ") The transmitting coil 4 is fed with alternating voltage and induced in the receiving coils 5 ', 5 "in each case an AC voltage v _a and Vb. With this arrangement, the mutual distance x and the relative displacement y of the two objects 2, 3 can be measured. The coils are shown only schematically as an equivalent circuit diagram. The representation should not be understood as a concrete representation of coil windings. It is crucial that the mutual arrangement is guaranteed by the actual arrangement.

Figure 2 shows a first exemplary arrangement of the invention. In addition to the two receiving coils 5 ', 5 ", a further receiving coil C (6) is arranged on the second object 3. The alternating voltage v _{c is} induced in the receiving coil 6. The third receiving coil C can be used to measure the distance x of the two objects 2, 3. The displacement y will be with the first two Receiving coils 5 ', 5 "measured. Again, the design and arrangement of the coils is to be understood only schematically.

3 shows an arrangement with receiving coils 5 ', 5 ", 6 which are aligned differently relative to one another. While the third receiving coil 6 is aligned parallel to the transmitting coil 4, the two first receiving coils 5', 5" are aligned perpendicular thereto.

4 shows an arrangement with a further transmitting coil 4 ". The first transmitting coil 4 'induces the signals for the displacement y in the receiving coils 5', 5". The second transmitting coil 4 "induces the signal for the distance x in the receiving coil 6.

5 shows an arrangement with two transmitting coils 4 ', 4 "and a total of four receiving coils 5', 5", 6 ', 6 ". The first transmitting coil 4' induces the signals for the displacement y in the receiving coils 5 ', 5". The second transmitting coil 4 "induces the signal for the distance x in the receiving coil 6 ', 6".

6 shows a perspective arrangement of coils in planar form, each of which is integrated in a substrate 7, 8 ', 8 ", 9. The three receiving coils 5', 5", 6 are arranged parallel to the transmitting coil 4. The displacement in the y direction is measured with the two receiving coils 5 ', 5 ", the distance x with the receiving coil 6. FIG. 7 shows an arrangement with successive receiving coils.

8 shows an arrangement according to which the first two receiver coils 5 ', 5 "are arranged perpendicular to the transmitter coil 4. The third receiver coil 6 is arranged parallel to the transmitter coil 4 and is adjacent to the first two receiver coils.

9 shows an arrangement where the first two receiver coils 5 ', 5 "are arranged perpendicular to the transmitter coil 4. The third receiver coil 6 is arranged parallel and concentrically around the first two receiving coils. This results in a particularly compact design.

10 shows an arrangement with two transmitting coils 4 ', 4 ". The first transmitting coil 4' feeds the first two receiving coils 5 ', 5", the second transmitting coil 4 "feeds the third receiving coil 6. In this arrangement, the two signal paths for the Decouple shift y and the distance x.

1 1 shows an arrangement with two transmitting coils 4 ', 4 "and four receiving coils 5', 5", 6 ', 6 ". The first transmitting coil 4' feeds the first two receiving coils 5 ', 5", the second transmitting coil 4 ", the third and fourth receiving coil 6 ', 6". In this arrangement, the two signal paths for the displacement y and the distance x can be decoupled. FIG. 12 shows a measuring arrangement for at least three measured variables (Gap, Piston, Shear). First, two transmitter coils 4 ', 4 "are integrated in a common substrate 7. The first transmitter coil excites the four receiver coils Α', B ', C and D' Two of which are for the measured variable Piston (displacement in the y direction), two for the measured variable Gap (distance x) Similarly, the second transmitting coil 4 "excites the four receiving coils A", B ", C" and D ". Two of them are for the measurand shear (displacement in z-direction), two for Gap (distance x). From the two measured values for Gap, an average value can be formed, or in addition a further tilt (rotation about the y-axis) can be determined. FIG. 13 shows in a sectional view an arrangement of two receiving coils A 'and C in planar form, which are integrated in a common substrate 7. The two receiving coils ¹ A ', C are aligned in parallel and intertwined in such a way that alternately one layer contains three turns of the coil A' (solid lines) and the respective overlying layer three turns of the coil C (dashed lines). With regard to further advantageous embodiments of the teaching of the invention reference is made to avoid repetition to the general part of the specification and to the appended claims. Finally, it should be expressly understood that the above-described embodiments of the teaching of the invention are only for the purpose of discussion of the claimed teaching, but do not limit these to the embodiments.

LIST OF REFERENCE NUMBERS

A receiver coil

 B receiving coil

 A "receiver coil

 B "receiver coil

 C Reception coil

 D Reception coil

 S transmitting coil

 1 eating arrangement

 2 first object

 3 second object

 4 transmitting coil S

 5 'receiving coil A

 5 "and B

 6 receiver coil C

 7 substrate

Claims

Claims 1. Measuring arrangement for the contactless measurement of a relative movement or a relative position of a first object relative to a second object, with at least one transmitting coil arranged on the first object and at least two receiving coils (A, B) arranged on the second object, wherein the transmitting coil is excited by an excitation change signal wherein the receiving coils detect a measured variable which is proportional to a first relative movement or relative position, and wherein at least one further receiving coil (C) is arranged on the second object, which detects a second measured variable which is proportional to a second relative movement or relative position , 2. Measuring arrangement according to claim 1, characterized in that the measured variables are used to determine a distance and a displacement, wherein in the concrete, the two receiving coils (A, B) are configured and arranged such that they measure a displacement between the two objects and that the third receiver coil (C) is used to measure the distance between the objects. 3. Measuring arrangement according to claim 1 or 2, characterized in that for the purpose of balancing a further receiving coil (D) is provided, wherein the coil pair (C, D) can be optimized for distance measurement. 4. Measuring arrangement according to one of claims 1 to 3, characterized in that to obtain a further measured variable, for example for determining a lateral displacement of the objects, a further pair of receiving coils (A ", B") is provided, which to the first pair of receiving coils (A, B) is rotated by 90 °. 5. Measuring arrangement according to one of claims 1 to 4, characterized in that the receiving coils are aligned parallel to the transmitting coil with their coil axes. 6. Measuring arrangement according to one of claims 1 to 4, characterized in that the receiving coils are perpendicular to each other to the transmitting coil with their coil axes. 7. Measuring arrangement according to one of claims 1 to 4, characterized in that two of the receiving coils are arranged with their coil axes orthogonal to the transmitting coil and that a further receiving coil (C) is aligned with its coil axis parallel to the transmitting coil or vice versa. 8. Measuring arrangement according to one of claims 1 to 7, characterized in that the two receiving coils (A, B) are arranged parallel to each other and with their coil axes orthogonal to the transmitting coil and that the third and fourth receiving coil (C, D) concentrically around the two receiving coils (A, B) is arranged. 9. Measuring arrangement according to one of claims 1 to 8, characterized in that a further transmitting coil is provided, wherein the first transmitting coil, the two receiving coils (A, B and / or A ", B") excites and the second transmitting coil, the receiving coil (C ) or the receiver coils (C, D). 10. Measuring arrangement according to claim 9, characterized in that the two transmitting coils work with identical frequency and / or voltage or with different frequency and / or voltage. 1 1. Measuring arrangement according to one of claims 1 to 10, characterized in that the coils are designed planar or wound or combined. 12. Measuring arrangement according to one of claims 1 to 1 1, characterized in that the coils (transmitting and / or receiving coils) are formed in a substrate, each coil being formed in a separate substrate or a plurality of coils in a common substrate. 13. Measuring arrangement according to claim 12, characterized in that in multilayer arrangement of the coils in a circuit board alternately one layer per coil is used or that each layer at least two coils are intertwined, the interconnects of the coils side by side, preferably parallel to each other. 14. Measuring arrangement according to claim 12 or 13, characterized in that it is the substrate is a ceramic substrate, for example in LTCC technology (Low Temperature Cofired Ceramics), wherein the layers together form a solid unit. 15. A method for the contactless measurement of a relative movement or a relative position of a first object relative to a second object, comprising at least one transmitting coil arranged on the first object and at least two receiving coils (A, B) arranged on the second object, wherein the transmitting coil is excited by an excitation change signal wherein the receiving coils detect a measured variable which is proportional to a first relative movement or relative position, and wherein at least one further receiving coil (C) is arranged on the second object, which detects a second measured variable which is proportional to a second relative movement or relative position , in particular with features according to one of claims 1 to 14.