Linear position sensor with multiple in-series windings

Abstract

The present application describes a Linear Position Sensor arrangement with multiple in-series windings and reduced edge-ef fects. It is proposed a receiver coil for inductive position sensors supporting movement along a curved axis comprised in a printed circuit board with at least two layers, a first and second layers positioned in opposite faces of a dielectric sheet, the first layer comprising a first trace section and the second layer comprising a second trace section, and the printed circuit board being characteri zed by comprising a set of loop structures in both the first trace section and second trace section of at least two electrically serially connected windings arranged in a predetermined of fset and / or distance from each other.

Description

[0001] DESCRIPTION

[0002] "Linear Position Sensor with multiple in-series windings and reduced edge -effects"

[0003] Technical Field

[0004] The present application describes a Linear Position Sensor with multiple in-series windings and reduced edge-ef fects .

[0005] Background art

[0006] According to state-of-the-art technology, an inductive linear position sensor consists of at least one excitation coil , an electrically conductive target on the rail of the position to be measured, and at least one , but usually two , receiver coils .

[0007] The excitation coil is permeated by a high- frequency current , which generates an alternating magnetic field, which induces eddy currents in the target . The inductive coupling of the excitation and receiver coils depends here on the position of the target . The induced voltage signal in the sampling coils can be used to determine the linear path . The measuring principle is known, e . g . from DE10026019B4 .

[0008] Summary

[0009] The present invention describes a receiver coil for inductive position sensors supporting movement along a curved axis comprised in a printed circuit board with at least two layers , a first and second layers positioned in opposite faces of a dielectric sheet , the first layer comprising a first trace section and the second layer comprising a second trace section, and the printed circuit board being characteri zed by comprising a set of loop structures in both the first trace section and second trace section of at least two electrically serially connected windings arranged in a predetermined of fset and / or distance from each other .

[0010] In a proposed embodiment of present invention, the first trace section is similar to a sine wave between 90 degrees and 270 degrees and the second trace section is similar to a sine wave between 270 degrees and 90 degrees .

[0011] Yet in another proposed embodiment of present invention, the first trace section is similar to a square wave between 90 degrees and 270 degrees and the second trace section is similar to a square wave between 270 degrees and 90 degrees , or the first trace section is similar to a triangular wave between 90 degrees and 270 degrees and the second trace section is similar to a triangular wave between 270 degrees and 90 degrees or the first trace section is similar to a sawtooth wave between 90 degrees and 270 degrees and the second trace section is similar to a sawtooth wave between 270 degrees and 90 degrees .

[0012] Yet in another proposed embodiment of present invention, the first trace section is connected with the second trace section by means of vias that pass through the dielectric and interconnect the first and second layers , these interconnections occurring in the 90 degrees and in the 270 degrees of the laid wave traces and which enable the formation of a loop structure of windings alternating between the first and second layer .

[0013] Yet in another proposed embodiment of present invention, the windings of the loop structure are connected at an edge of the receiver coil within a minimal clearance distance to minimi ze an edge ef fect , said connection being ensured by reversal points and / or first connection vias .

[0014] Yet in another proposed embodiment of present invention, the first connection vias enable the connection between the first layer of the printed circuit board traces and the second layer of the printed circuit board traces .

[0015] Yet in another proposed embodiment of present invention, the reversal points comprise straight line section traces perpendicular to the axis that defines the progression of the sine wave traces .

[0016] Yet in another proposed embodiment of present invention, the reversal points comprising a reversal for top layer coil and a reversal for bottom layer coil .

[0017] General Description

[0018] The present application describes a Linear Position Sensor with multiple in-series windings and reduced edge-ef fects .

[0019] From the state of the art , inductive position sensors with a single winding for each receiver coil is known . However, and to obtain multiple receiver coils in the same inductive position sensor, a multiple layer printed circuit board ( PCB ) design can be used, in particular, i f used with at least two layers . This technique can be further enabled i f the receiving coils are switched or alternated between both layers of the PCB every hal f period of sine waves , i . e . , on the 90 degrees and 270 degrees o f said wave , allowing to obtain multiple overlapped coils without intersections between them . Based on the prior, at least on the 90 degrees and on the 270 of the sine wave, traced on at least a two faced multilayer PCB, the traces will exchange from a lower layer to an upper layer of the PCB, as known from the state of the art, and from an upper layer to an lower layer. Since it is possible to have multiple receiving coils in the same two layers, some of these coils can be connected in series allowing for multiple winding designs.

[0020] Technical Problem

[0021] In this present application and currently disclosed technology considering multiple winding design, the known edge effect is minimized in the suggested inductive linear position sensors.

[0022] In inductive linear position sensors, the "edge effect" refers to a phenomenon where the output signal of the sensor varies significantly when the metal target (such as a rod or a plate) moves close to the edges of the sensor's active sensing area. This effect is particularly prominent in sensors with a narrow sensing range or when the target approaches the sensing coil's edges.

[0023] The edge effect occurs because the magnetic field generated by the sensing coil is not uniform across its entire sensing area. Near the edges of the coil, the magnetic field lines become distorted or weaker, leading to changes in the sensor's output signal when the target moves within these regions .

[0024] To mitigate the edge effect, and until present days, sensor designers would normally employ various techniques such as using shielding materials, optimizing coil geometry, or implementing signal processing algorithms to compensate for the non-uni formity of the magnetic field . This type of approach would help improve the accuracy and reliability of the sensor ' s output signal , especially in applications where precise position sensing is crucial .

[0025] However, none of the known prior art technologies used the currently disclosed approach .

[0026] Solution to Problem

[0027] In layout designs with at least two receiver coils , and with multiple windings ( two or more connected in series ) , it is not possible to close them ( reversal point of the coil ) in the same position within two layers .

[0028] For a given number "a" of coils and a given number "b" of windings it is required to have a number "a*b" of reversal points in each side of the receiver coils . With only two layers in the PCB for the coil design, it is only possible to close two of the "a*b" reversal points in each position . Considering that the receiver coils are limited to their the initial and end positions , the ideal position for the reversal points are at these two points .

[0029] By defining a minimum clearance between tracks (usually defining by the PCB layout rules ) it will enable the closing of the rest of the windings / coils at di f ferent positions from the ideal one , separated by this minimum clearance . This is repeated until all "a*b" reversals are complete . These reversals are made after the initial position and before the end position . This minimum clearance allows us to achieve the best possible edge ef fect with these designs since the edge ef fect is the direct correlation of the position we are trying to measure and the distance to the edge of the coil ( edge of the coil is the position of the reversal ) .

[0030] For the connection points between laid traces of the PCB to be performed, whenever the winding reaches their own initial or final position of the PCB according to the previously defined start and end position, a trace is laid out to unite both ends of the winding at that exact position ( reversal points ) . This will close the loop and maximi ze the area within that loop (because of the minimum clearance distance ) . When the maximum space available for the receiving (RX ) coil is reached, i f , the necessary parts of the receiver coil windings are not in contact , there is necessary a vertical trace to unite them .

[0031] Each Coil , when closed, will form several loops in which the induced current f lows . The system excitation ( TX ) coil will create a Magnetic field that will pass through those loops originating current on the receiver coils . By defining coil period lengths , multiple of the maximum receiver coil system si ze , ideally the current will cancel it out because it will have the same loop area of current going in one direction as in the other . Without any electromagnetic interference this will generate a voltage at the receiver coils that we call of fset that should be around zero . However, this offset will be influenced by the proximity to the transmitter coil to the smaller loops .

[0032] Maximi zing the winding traces to a bare maximum, it lead to a probable creation of small loops containing only a small electrical angle (360° for a full period) , However, at the same time, chasing an equilibrium between loop areas with reversed currents (achieved at a multiple of the coil period length) .

[0033] The connections in the end of the coil also mean some changes in the layer where the winding was, since, this time around, to close the loop we need the both sides of the winding to be on the same place. Therefore, it is necessary to rearrange the structure in the end to end up without any interferences and right connections of the coil windings.

[0034] In a two-receiver coil system, by having the same distance between the transmitter ( s ) and receiver (es) coils, the offset should be minimized (close to zero) with a Sin wave type coil and maximize with a Cos wave type coil. To distribute this, the coils could be designed phased + 45° from a Sin wave type coil and a Cos wave type coil, maintaining their phase shit of 90° apart from each other. Allowing a symmetric design in which both coils are symmetric to each other. Resulting in the same offset between both receiver coil system.

[0035] The proposed disclosure provides a solution for the reduction of edge effects in inductive linear position sensors based on a particular arrangement of multiple interlaced windings that switch between adjacent PCB layers. This arrangement mainly focus on the in series connection of the receiver coils .

[0036] The receiver trapping coils can comprise several loop structures and is formed by traces laid in at least two adjacent planes of the PCB. Some sections of the individual loop structures can be arranged in different planes of the circuit carrier are electrically connected to each other via vias . The loop structures can comprise opposite induced current flow directions . The loop structures of at least two electrically connected windings of the at least one receiving coil are arranged of fset by a speci fied distance from each other . The ends o f the individual loop structures o f the at least two turns of the at least one receiving reel at the end areas of the corresponding reception structure over at least one connection structure may be connected to each other in such a way as to create an electrical series connection of at least two turns and / or a reversal of a flow direction within one of the at least two turns .

[0037] The proposed inductive Linear Position Sensor with multiple in-series windings and reduced edge-ef fects can be applied in, for example , linear path sensors in which the moving body produces a translational movement to be captured along an axis of motion, or in a rotation angle sensor or rotor position sensor, in which the moving body performs a rotational movement around an axis of rotation to be detected .

[0038] Brief description of the drawings

[0039] For better understanding of the present application, figures representing preferred embodiments are herein attached which, however, are not intended to limit the technique disclosed herein .

[0040] Fig . 1 - Represents a possible embodiment of the proposed layer design of the top coil , in solid line , in a top surface composed by traces of the multilayer PCB . Fig. 2 - Represents a possible embodiment of the proposed layer design of the bottom coil, in dashed line, in a bottom surface composed by traces of the multilayer RGB.

[0041] Fig. 3 - Represents the layer design of both the top and the bottom coil, solid and dashed lines, top and bottom surfaces composed by traces of the multilayer PCB .

[0042] Fig. 4 - Represents a possible embodiment of the invention where two sets of dual adjacent coils are laid, side by side, and exchange layers simultaneously.

[0043] Fig. 5 - Represents another possible embodiment of the invention where three sets of dual adjacent coils are laid, side by side, and exchange layers simultaneously.

[0044] Description of Embodiments

[0045] With reference to the figures, some embodiments are now described in more detail, which are however not intended to limit the scope of the present application.

[0046] A particular embodiment of the herein disclosed inductive Linear Position Sensor with multiple in-series windings is intended to minimize edge-effects.

[0047] In Fig.l is illustrated a proposed embodiment of the invention for the layer design of the top layer coil layout traces (1) arrangement of the multilayer PCB. This trace layout representation on a top surface of the PCB is similar to a sine wave between the 90 degrees and the 270 degrees. The first connection via (4.1) , additionally with the reversal for bottom layer coil (4) , enables the connection of the upper section of the laid top layer sine wave type coil with the bottom layer section of the laid bottom layer sine wave type coil layout traces (2) .

[0048] In Fig.2, a bottom layer coil layout traces (2) with sections similar to a sine wave between the 270 degrees and the 90 degrees arrangement of the multilayer PCB are illustrated, where it is also possible to identify the first via (4.1) and the reversal for top layer coil (3) .

[0049] In Fig.3 it is possible to overview a proposed arrangement for the layer design of both the top and the bottom coil like trace layouts over both sides of the PCB in both solid and dashed lines, the solid representing the upper layer laid traces of the coil and the dashed representing the bottom layer laid traces, reference numbers relate to the top layer coil layout traces (1) and the bottom layer coil layout traces (2) connected by means of reversal points. The trace sections that do not have the same layout as alternated layer sine wave like, are mainly represented by straight line sections that connect the sections of the overlapping sine waves, reversal for bottom layer coil (4) and reversal for top layer coil (3) , and a fist connection via (4.1) , in order to minimize edge-effects by means of a minimum clearance (5) .

[0050] The reversal for top layer coil (3) sets the begging and end point defined for the coil design. In this position, it will be closed any two windings for two layers.

[0051] The reversal for bottom layer coil (4) sets the minimum clearance distance which is the necessary distance between traces that should not be in contact, including vias and other elements that might be in the design. The minimum clearance ( 5 ) sets the place where the second reversal for the second "pair" of windings to be closed after the initial and before the end position of the coil design . This should always follow the definition made for the reversal for bottom layer coil ( 4 ) .

[0052] As previously mentioned, sine wave type coil in both laid upper and lower traces of the multilayer PCB, are sequentially phased +45 degrees . It is wort mentioning that , through the analysis of the disclosed and proposed embodiment of the invention, the double faced / dual layer of printed circuit board comprises two electrically serially connected windings , arranged in a predetermined of fset and distance from each other . The two windings commuting between the two layers of the PCB, as previously mentioned, sequentially phased +45 degrees .

[0053] In Fig . 4 another possible embodiment of the invention is illustrated where two sets of dual adj acent coils are laid side by side on each layer and changing layer simultaneously . In a more detailed description, and in a similar approach to the one previously disclosed, two sets of dual top layer coil layout traces ( 1 ) are disposed side by side , as well as the two sets of dual bottom layer coil layout traces ( 2 ) , which are connected by means of the reversal points and the vias , in order to minimi ze edge-ef fects .

[0054] As previously mentioned, the two sets of dual sine wave type coil in both laid upper and lower traces of the multilayer PCB, are sequentially phased +45 degrees . In this illustration is disclosed two trace sections similar to a sine wave between 90 degrees and 270 degrees ( 1 ) .

[0055] It is wort mentioning that , through the analysis of the disclosed and proposed embodiment of the invention, the double faced / dual layer of printed circuit board comprises two sets of two electrically serially connected windings, arranged in a predetermined offset and distance from each other. The two sets of two windings commuting between the two layers of the PCB, as previously mentioned, sequentially phased +45 degrees.

[0056] It comprises a first set of adjacent two top layer coil layout traces (1) and two bottom layer coil layout traces

[0057] (2) , and a second set of adjacent two top layer coil layout traces (1' ) and two bottom layer coil layout traces (2' ) . It also comprises a first set of reversals for top layer coils

[0058] (3) and a second set of reversals for top layer coils (3' ) . It also comprises a first set of a first connection vias (4.1) , additionally with a first set of reversal for bottom layer coil (4) , as well as a second set of a first connection vias (4.1' ) , additionally with a second set of reversal for bottom layer coil (4' ) .

[0059] The first set of adjacent two top layer coil layout traces (1) and two bottom layer coil layout traces (2) commute between the top and bottom layers of the PCB through the bottom / top layer vias (10) , and the second set of adjacent two top layer coil layout traces (1' ) and two bottom layer coil layout traces (2' ) commute between the top and bottom layers of the PCB through further bottom / top layer vias (10' ) .

[0060] In Fig. 5 another possible embodiment of the invention is illustrated where three sets of dual adjacent coils are laid side by side and changing layer simultaneously. In a more detailed description, three sets of dual top layer coil layout traces (1) are disposed side by side, as well as the three sets of dual bottom layer coil layout traces (2) , which are connected by means of the reversal points and the vias, in order to minimize edge-effects. As previously mentioned, the three sets of dual sine wave type coil in both laid upper and lower traces of the multilayer PCB, are sequentially phased +45 degrees.

[0061] It is wort mentioning that, through the analysis of the disclosed and proposed embodiment of the invention, the double faced / dual layer of printed circuit board comprises three sets of two electrically serially connected windings, arranged in a predetermined offset and distance from each other. The three sets of two windings commuting between the two layers of the PCB, as previously mentioned, sequentially phased +45 degrees.

[0062] It comprises a first set of adjacent two top layer coil layout traces (1) and two bottom layer coil layout traces (2) , and a second set of adjacent two top layer coil layout traces (1' ) and two bottom layer coil layout traces (2' ) , and a third set of adjacent two top layer coil layout traces (1' ' ) and two bottom layer coil layout traces (2' ' ) . It also comprises a first set of reversals for top layer coils (3) and a second set of reversals for top layer coils (3' ) and a third set of reversals for top layer coils (3, f) . It also comprises a first set of a first connection vias (4.1) , additionally with a first set of reversal for bottom layer coil (4) , as well as a second set of a first connection vias (4.1' ) , additionally with a second set of reversal for bottom layer coil (4' ) , as well as a third set of a first connection vias (4.1' ' ) , additionally with a third set of reversal for bottom layer coil (4' ' ) .

[0063] The laid trace sections of the sine wave type coil commute between layers, i.e., top and bottom, or bottom and top, at each inversion point of the sine wave type coil, i.e. at 90 degrees and 270 degrees periodically, and by means of bottom / top layer vias (10) . In a proposed embodiment , the inductive position sensor supports movement along a curved axis , such as in C-shaped rotary position sensors . In a proposed embodiment , the vias can also be arranged between intermediate layers other than the top and bottom surface layers .

Claims

CLAIMS1. Receiver coil for inductive position sensors supporting movement along a curved axis comprised in a printed circuit board with at least two layers, a first and second layers positioned in opposite faces of a dielectric sheet, the first layer comprising a first trace section (1) and the second layer comprising a second trace section (2) , and the printed circuit board being characterized by comprising a set of loop structures in both the first trace section (1) and second trace section (2) of at least two electrically serially connected windings arranged in a predetermined offset and / or distance from each other.

2. Receiver coil according to the previous claim, characterized by the first trace section (1) being similar to a sine wave between 90 degrees and 270 degrees and the second trace section (2) being similar to a sine wave between 270 degrees and 90 degrees.

3. Receiver coil according to any of the previous claims, characterized by the first trace section (1) being similar to a square wave between 90 degrees and 270 degrees and the second trace section (2) being similar to a square wave between 270 degrees and 90 degrees, or the first trace section (1) being similar to a triangular wave between 90 degrees and 270 degrees and the second trace section (2) being similar to a triangular wave between 270 degrees and 90 degrees or the first trace section (1) being similar to a sawtooth wave between 90 degrees and 270 degrees and the second trace section (2) being similar to a sawtooth wave between 270 degrees and 90 degrees.

4. Receiver coil according to any of the previous claims, characterized by the first trace section (1) being connected with the second trace section (2) by means of vias (10) that pass through the dielectric and interconnect the first and second layers, these interconnections occurring in the 90 degrees and in the 270 degrees of the laid wave traces and which enable the formation of a loop structure of windings alternating between the first and second layer.

5. Receiver coil according to any of the previous claims, characterized by the windings of the loop structure being connected at an edge of the receiver coil within a minimal clearance distance (5) to minimize an edge effect, said connection being ensured by reversal points and / or first connection vias (4.1) .

6. Receiver coil according to any of the previous claims, characterized by the first connection vias (4.1) enabling the connection between the first layer of the printed circuit board traces and the second layer of the printed circuit board traces.

7. Receiver coil according to any of the previous claims, characterized by the reversal points comprising straight line section traces perpendicular to the axis that defines the progression of the sine wave traces.

8. Receiver coil according to any of the previous claims, characterized by the reversal points comprising a reversal for top layer coil (3) and a reversal for bottom layer coil (4) .

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