Inductive position sensor and obtaining process thereof

Abstract

An inductive position sensor, and obtaining process thereof, comprising a printed circuit board, PCB, an excitation coil, a first receiver coil, and a second receiver coil, wherein said coils are printed circuits on said PCB, wherein each of the receiver coils is configured as a wave arranged along the PCB defining a direction for the reception coil and the wave having a spatial oscillation transversal to this direction, wherein at least one of said waves comprises two or more sinusoidal components.

Description

I N DUCTIVE POSITI ON SENSOR AN D OBTAINING PROCESS THEREOFTECHNICAL FIELD

[0001] The present disclosure relates to an inductive position sensor and a process for obtaining said inductive position sensor.BACKGROUND

[0002] Inductive position sensors are used to measure their relative position to a target. Generally, those sensors are based on the coupled coils principle, typically constituted by one excitation coil, one or more receiver's coils and one electrically conductive target. The coils are usually printed directly on a printed circuit board, where an electronic circuit sources the excitation coil and demodulates the induced signals in the receiver coils. The induced signals are amplitude modulated, and the target's position is correlated with their amplitude.

[0003] Full-scale inductive position sensors typically present high non-linearity and low signal levels. The present application is a solution for these limitations. The described methodology designs inductive position sensors with a minimal non-linearity output signal and maximal output levels by its distinctive coils' design geometry (receiver and target) composed of multiple harmonics components.

[0004] Document W02007000653A1 discloses an apparatus for providing a signal related to a position of a part comprises an exciter coil, and a receiver coil disposed proximate to the exciter coil. The exciter coil generates magnetic flux when the exciter coil is energized by a source of electrical energy, such as an alternating current source. The receiver coil generates a receiver signal when the exciter coil is energized, due to an inductive coupling between the receiver coil and the exciter coil. The receiver coil has a plurality of sections, the inductive coupling tending to induce opposed voltages in at least two of the sections.

[0005] Document US6304076B1 discloses a non-contact angular position sensor which has juxtaposed transmit and receive disks with a coupler disk, carrying a conductive attenuating pattern interposed therebetween. A pattern of inductive coils, which completely encircle both the transmit and receive disks have their inductive coupling individually attenuated in accordance with the angular position of the symmetrical conductive pattern on the intermediate coupling disk. The transmit disk is driven by a signal source which when received and demodulated by the receive coils and summed together provides a unique sinusoidal signal whose phase is indicative of the angular position of the intermediate coupler. The conductive pattern on the coupler is designed to provide a linear output.

[0006] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.GENERAL DESCRIPTION

[0007] The present application describes an inductive position sensor whose coils' design is based on multiple harmonics that allow a minimal non-linearity sensor output signal, when compared to receiver coils that only have a quadrature sinusoidal geometry (sine and cosine).

[0008] The present application describes a methodology for the optimal design of inductive position sensors for measuring linear, rotational, and angular displacements. A few sensors designed with this methodology - optimal sensors - are also presented.

[0009] They are arranged in a multi-layer printed circuit board comprising an excitation coil and two receiver coils. The position is measured relative to a conductive target which can be another printed circuit board or not. The inductive position sensors obtained by this application present an output signal with minimal non-linearity through its receiver's coil design that is optimized in the Fourier space - adding to the coils' geometry the appropriate harmonics with both appropriate amplitude and phase. Any search algorithm (which may be also described as an optimization algorithm) can be used to search the solution space for the appropriate harmonics. Furthermore, thedisclosure can also optimize the exciter coil and target geometries to achieve maximum induced currents on the sensor's receiver coils. Many restrictions can be taken into consideration on the solution space such as the sensor's dimension, number of layers, the gap between the layers in the sensor's printed circuit board as well as the gap between the coils and the target.

[0010] The present application describes a methodology for the optimal design of inductive position sensor to achieve high induced current on the sensor's receiver coils and minimal non-linearity on the sensor output signal. The sensor comprises one or more excitation coils, two or more receiver coils and one conductive target - the receiver's coils have a distinctive shape not necessarily based on a single sinusoidal geometry but preferably based on multiple harmonics that, added together, minimize the non-linearity of the sensor. Finding the best coils' geometry configuration is important to accomplish higher induced current on the sensor's receiver coils and low non-linearity on the sensor output signal. A search algorithm, for example a global search algorithm (e.g. Genetic Algorithm, Simulated Annealing, Particle Swarm Optimization, or others), can be used. In an embodiment, the search algorithm can be used in two independent iterations to achieve both goals with the proposed inductive position sensor design. In the first iteration, the algorithm searches for one possible design that maximizes the induced current in the receiver's coils and fulfils the inductive position sensor constraints. Typically, those constraints are related to the selected printed circuit board (e.g., stack size and the number of layers), the sensor's maximum allowed dimensions, and the working frequency. Those constraints could be imposed (e.g., the working frequency), or an allowed range could be given (e.g., the sensor's coils' minimum and maximum permitted dimensions, including the target coil). In the second iteration, the geometry generator tool harmonically deforms one or both receiver coils to minimize the sensor's non-linearity. This is done by searching the amplitudes and phases of harmonics components that are added to the receiver's coils' geometry.

[0011] Along with the global search algorithm, a numerical method is disclosed to solve the field equations in order to ascertain sensor performance, for example in terms of non-linearity or induced current output. It is used within the search algorithm to scoreor classify the generated geometries and, in this way, guide the optimization process. The higher the score or classification, the closer the geometry is to the optimization goal. Due to the large number of geometries generated during the optimization process (depending on the search algorithm employed, it can easily exceed ten thousand simulations), the finite element method (FEM) is usually not feasible, requiring a fast field simulator. The method of moments (MoM) is, for example, a good option. This numerical method is then used to provide information for the fitness function of the search algorithm.

[0012] The present disclosure relates to an inductive position sensor whose coils' design is based on multiple harmonics that, by its unique combination, allow a minimal nonlinearity sensor output signal, when compared to receiver coils which only have the quadrature sinusoidal geometry (sine and cosine).

[0013] The present disclosure relates to an inductive position sensor comprising a printed circuit board, PCB, an excitation coil, a first receiver coil, and a second receiver coil, wherein said coils are printed circuits on said PCB, wherein each of the receiver coils is configured as a wave arranged along the PCB defining a direction for the receiver coil and the wave having a spatial oscillation transversal to this direction, wherein at least one of said waves comprises two or more sinusoidal components.

[0014] In an embodiment, each of said waves comprises two or more sinusoidal components.

[0015] In an embodiment, said sinusoidal components are harmonic sinusoidal components.

[0016] Harmonic sinusoidal component can be defined as a sinusoidal component which occurs at a first frequency that is a whole number multiple of a second frequency of another sinusoidal component; this second frequency can also be termed a fundamental frequency; in the present disclosure a coil wave frequency is a spatial frequency, i.e. measurable in terms of oscillations per length, for example oscillations per metre or per millimetre.

[0017] In an embodiment, said sinusoidal components are harmonic sinusoidal components of one or more fundamental frequencies.

[0018] In an embodiment, each said sinusoidal component has a predetermined amplitude and phase.

[0019] In an embodiment, the PCB is a multi-layer PCB, in particular comprising a plurality of layers where each layer comprises one or parts of said coils.

[0020] In an embodiment, the sensor includes a conductive target displaceable relative to the PCB for altering induced currents in the receiver coils from the excitation coils, depending on the position of the conductive target displaceable relative to the PCB.

[0021] A linear position sensor can be provided, for example, by arranging the coils in a linear arrangement that is, where the direction for the receiver coils is linear. A rotational or angular position sensor can be provided, for example, by arranging the coils in a circular arrangement, that is, where the direction for the receiver coils is circular.

[0022] It is also disclosed a process for obtaining an inductive position sensor comprising a printed circuit board, PCB, an excitation coil, a first receiver coil, and a second receiver coil, wherein said coils are printed circuits on said PCB, wherein each of the receiver coils is configured as a wave arranged along the PCB defining a direction for the reception coil and the wave having a spatial oscillation transversal to this direction, wherein at least one of said waves comprises two or more sinusoidal components, the process comprising: perform a computer-implemented method to iteratively adjust said sinusoidal components in number, amplitude, or phase, or combinations thereof, to minimize non-linearity of the inductive position sensor; print the PCB with excitation coil and receiver coils, with the iteratively adjusted sinusoidal components.

[0023] Non-linearity of the inductive position sensor can be measured in terms of deviation of the relationship of the sensor output versus sensor input from a linear relationship, i.e. deviation from a proportional sensor transduction function.

[0024] In an embodiment, the process comprises a preliminary step of performing the computer-implemented method to iteratively adjust PCB parameters to maximize induced current in the receiver coils.

[0025] In an embodiment, the PCB parameters comprise PCB stack size, number of PCB layers, PCB dimensions, gap between coil PCB layers, gap between coil and target, or sensor working frequency, or combinations thereof.

[0026] In an embodiment, the computer-implemented method comprises simulating performance of the inductive position sensor for providing a fitness function, in particular simulating performance of the inductive position sensor by a numerical method comprising a fast field simulator, further in particular a numerical method based on Method of Moments.BRI EF DESCRIPTION OF TH E DRAWINGS

[0027] The following figures provide preferred embodiments for illustrating the disclosure and should not be seen as limiting the scope of invention.

[0028] Figure 1 represents the automatic geometry generator for the inductive position sensors' global search algorithm, particularly a real-coded genetic algorithm.

[0029] Figure 2 represents the fitness function algorithm, particularly a modified version of the method of moments.

[0030] Figure 3 represents a top view of an angular position sensor geometry commonly found in the literature, where its receiver's coils have a sinusoidal shape curved along a circumference centred at the rotational axis of the target. This sensor is capable of measuring a full range (360°).

[0031] Figure 4 illustrates the error between the true position and the one measured by the sensor in Fig. 3.

[0032] Figure 5 represents a top view of the angular position sensor generated by the automatic geometry generator. Its receiver's coils have multiple harmonics (DC,fundamental, 3rd and 5th) curved along a circumference centred at the rotational axis of the target. This sensor is capable of measuring a full range (360°).

[0033] Figure 6 illustrates the error between the true position and the one measured by the optimized sensor in Fig. 5.

[0034] Figure 7 represents a perspective view of the angular position sensor in Fig. 5 generated by the automatic geometry generator for the inductive position sensors described.

[0035] Figure 8 represents a top view of the angular position of a first sensor receiver coil (sensor receiver coil 1).

[0036] Figure 9 represents a top view of the angular position of a second sensor receiver coil (sensor receiver coil 2).

[0037] Figure 10 represents a top view of a linear position sensor commonly found in the literature, where its receiver's coils have a sinusoidal shape. This sensor is capable of measuring a full range.

[0038] Figure 11 illustrates the error between the true position and the one measured by the sensor in Fig. 10.

[0039] Figure 12 represents a top view of the linear position sensor generated by the automatic geometry generator, whose receiver's coils have multiple harmonics (DC, fundamental and 2nd to 5th). This sensor is capable of measuring a full range.

[0040] Figure 13 illustrates the error between the true position and the one measured by the optimized sensor in Fig. 12.

[0041] Figure 14 represents a perspective of the linear position sensor in Fig. 12 generated by the automatic geometry generator for the inductive position sensors described.

[0042] Figure 15 represents a top view of the linear position of a first sensor receiver coil.

[0043] Figure 16 represents a top view of the linear position of a second sensor receiver coil.DETAILED DESCRIPTION

[0044] In the present disclosure, the coils' geometry of the inductive position sensor are composed of multiple harmonics added together that, by its combination, allow a minimal non-linearity sensor output signal, when compared to single harmonic coils' geometries.

[0045] In the present disclosure, a global search algorithm can be used to find in the Fourier space of the coils' geometry the proper amplitudes and phases of each harmonic component to be added to the sensor receiver's coils' geometry and to the target coils that allows to achieve the lowest non-linearity inductive position sensor output. Usually, the non-linearity criteria can be combined with a search for maximizing the induced current in the receivers' coils in a multi-criteria search. This results in an optimized geometry as well as the identification of the number of turns and PCB layers of the excitation coil(s) and the dimensions of the excitation's and receiver's coils as well as the target's geometry that minimize non-linearities and maximize the induced current on the receiver's coils.

[0046] Figure 1 represents the automatic geometry generator for the inductive position sensors' global search algorithm (for an embodiment using a real-coded genetic algorithm). Reference numbers represent:100 - Automatic geometry generator for the inductive position sensors' global search algorithm (real-coded genetic algorithm);101 - Fixed settings;102 - Optimizable settings;103 - Number of individuals setting;104 - Number of generations setting;105 - Mutation probability setting;106 - Mutation standard deviation setting;107 - Elitism ratio setting;108 - Population initialization;109 - Fitness function;110 - Selection (tournament selection);111 - Crossover;112 - Mutation (gaussian mutation);113 - Elitism;114 - End condition;115 - Best geometry selection.

[0047] Figure 2 represents the fitness function algorithm according to an embodiment, particularly an embodiment of a modified version of the method of moments. Reference numbers represent:200 - Fitness function algorithm (modified version of the method of moments);201 - Geometry generator;202 - Geometry discretization;203 - System of linear equations generation;204 - Frequency domain conversion;205 - System of linear equations solver;206 - Inverse conversion;207 - End condition;208 - Target displacement;209 - Fitness value calculation.

[0048] Figure 3 represents a top view of an angular position sensor geometry commonly found in the literature, where its receiver's coils have a sinusoidal shape curved along a circumference centred at the rotational axis of the target. This sensor is capable of measuring a full range (360°). Reference numbers represent:300 - Angular position sensor;301 - Excitation coil;302 - First Receiver coil;303 - Second Receiver coil;304 - Target coil.

[0049] Figure 4 illustrates the error between the true position and the one measured by the sensor in Fig. 3.

[0050] Figure 5 represents a top view of the angular position sensor generated by the automatic geometry generator. Its receiver's coils have multiple harmonics (DC, fundamental, 3rd and 5th) curved along a circumference centred at the rotational axis of the target. This sensor is capable of measuring a full range (360°). Reference numbers represent:400 - Angular position sensor;401 - Excitation coil;402 - First Receiver coil;403 - Second Receiver coil;404 - Target coil.

[0051] Figure 6 illustrates the error between the true position and the one measured by the optimized sensor in Fig. 5.

[0052] Figure 7 represents a perspective view of the angular position sensor in Fig. 5 generated by the automatic geometry generator for the inductive position sensors described. Reference numbers represent:400 - Angular position sensor;401 - Excitation coil;402 - First Receiver coil;403 - Second Receiver coil;404 - Target coil.

[0053] Figure 8 represents a top view of the angular position sensor (400) receiver coil1. Reference numbers represent: 402 - Receiver coil 1.

[0054] Figure 9 represents a top view of the angular position sensor (400) receiver coil2. Reference numbers represent: 403 - Receiver coil 2.

[0055] Figure 10 represents a top view of a linear position sensor commonly found in the literature, where its receiver's coils have a sinusoidal shape. This sensor is capable of measuring a full range. Reference numbers represent:500 - Linear position sensor;501 - Excitation coil;502 - First Receiver coil;503 - Second Receiver coil;504 - Target coil.

[0056] Figure 11 illustrates the error between the true position and the one measured by the sensor in Fig. 10.

[0057] Figure 12 represents a top view of the linear position sensor generated by the automatic geometry generator, whose receiver's coils have multiple harmonics (DC, fundamental and 2nd to 5th). This sensor is capable of measuring a full range. Reference numbers represent:600 - Linear position sensor;601 - Excitation coil;602 - First Receiver coil;603 - Second Receiver coil;604 - Target coil.

[0058] Figure 13 illustrates the error between the true position and the one measured by the optimized sensor in Fig. 12.

[0059] Figure 14 represents a perspective of the linear position sensor in Fig. 12 generated by the automatic geometry generator for the inductive position sensors described. Reference numbers represent:600 - Linear position sensor;601 - Excitation coil;602 - First Receiver coil;603 - Second Receiver coil;604 - Target coil.

[0060] Figure 15 represents a top view of the linear position sensor (600) receiver coil1. Reference numbers represent: 602 - First Receiver coil.

[0061] Figure 16 represents a top view of the linear position sensor (600) receiver coil2. Reference numbers represent: 603 - Second Receiver coil.

[0062] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above-described embodiments are combinable. The following claims further set out particular embodiments of the disclosure.

Claims

C L A I M S1. An inductive position sensor comprising a printed circuit board, PCB, an excitation coil, a first receiver coil, and a second receiver coil, wherein said coils are printed circuits on said PCB, wherein each of the receiver coils is configured as a wave arranged along the PCB defining a direction of forthe reception coil and the wave having a spatial oscillation transversal to this direction, wherein at least one of said waves comprises two or more sinusoidal components.

2. The inductive position sensor according to the previous claim wherein each of said waves comprises two or more sinusoidal components.

3. The inductive position sensor according to any of the previous claims wherein said sinusoidal components are harmonic sinusoidal components.

4. The inductive position sensor according to the previous claim wherein said sinusoidal components are harmonic sinusoidal components of one or more fundamental frequencies.

5. The inductive position sensor according to any of the previous claims wherein each said sinusoidal component has a predetermined amplitude and phase.

6. The inductive position sensor according to any of the previous claims wherein the PCB is a multi-layer PCB, in particular comprising a plurality of layers where each layer comprises parts of said coils.

7. The inductive position sensor according to any of the previous claims comprising a conductive target displaceable relative to the PCB for altering induced currents in the receiver coils from the excitation coils, depending on the position of the conductive target displaceable relative to the PCB.

8. The inductive position sensor according to any of the previous claims wherein the receiver coils are arranged in a linear arrangement as a linear position sensor, or the receiver coils are arranged in a circular arrangement as a rotational or angular position sensor.

9. A process for obtaining an inductive position sensor comprising a printed circuit board, PCB, an excitation coil, a first receiver coil, and a second receiver coil, wherein said coils are printed circuits on said PCB, wherein each of the receiver coils is configured as a wave arranged along the PCB defining a direction for the receiver coils and the wave having a spatial oscillation transversal to this direction, wherein at least one of said waves comprises two or more sinusoidal components, the process comprising: perform a computer-implemented method to iteratively adjust said sinusoidal components in number, amplitude, or phase, or combinations thereof, to minimize non-linearity of the inductive position sensor; print the PCB with the excitation coil and the receiver coils with the iteratively adjusted sinusoidal components.

10. The process according to the previous claim wherein the process comprises a preliminary step of performing the computer-implemented method to iteratively adjust PCB parameters to maximize induced current in the receiver coils.

11. The process according to the previous claim wherein the PCB parameters comprise PCB stack size, number of PCB layers, PCB dimensions, gap between coil PCB layers, gap between coil and target, or sensor working frequency, or combinations thereof.

12. The process according to any of the claims 9-11 wherein each of said waves comprises two or more sinusoidal components.

13. The process according to any of the claims 9-12 wherein said sinusoidal components are harmonic sinusoidal components.

14. The process according to the previous claim wherein said sinusoidal components are harmonic sinusoidal components of one or more fundamental frequencies.

15. The process according to any of the claims 9-14 wherein each said sinusoidal component has a predetermined amplitude and phase.

16. The process according to any of the claims 9-15 wherein the computer- implemented method comprises simulating performance of the inductive position sensor for providing a fitness function, in particular simulating performance of the inductive position sensor by a numerical method comprising a fast field simulator, further in particular a numerical method based on Method of Moments.

17. Computer-readable medium comprising computer program instructions that when executed by a computer cause it to carry out the process according to any of the claims 9-16.

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