Apparatus and method for determining the angular position of a position sensor

Abstract

A method for determining the angular position of a target relative to a substrate in a sensing angular position sensor system includes the following steps: receiving a signal, demodulating the signal, and digitizing the signal, as well as reducing the DC offset of the digital signal, and determining the angular position; wherein reducing the DC offset includes: i) initializing a DC correction value; ii) subtracting the DC correction value to obtain a DC shift signal; iii) limiting the DC shift signal to obtain a limited signal; iv) calculating a first sum by summing the values ​​of the limited signal over a period of time, and v) calculating a second sum by summing the absolute values ​​of the limited signal over the period of time; vi) adding K times the first sum to each DC correction value and dividing by the second sum, where K is a predefined constant.

Description

Technical Field

[0001] This invention relates generally to the field of angular position sensor systems, and more particularly to a method for determining the angular position of an angular position sensor system, and a sensor device configured to apply this method. Background Technology

[0002] Various sensing angle sensors are known in the art, for example, for motor control purposes. They typically comprise a printed circuit board with an excitation coil (also called a “transmitter coil”) and multiple detection coils (also called “receiver coils”). The transmitter and receiver coils are inductively coupled to each other. The amount of coupling can be affected by a coupling element (also called a “target”) movably mounted near the transmitter and receiver coils. The excitation coil can be excited, for example, with an AC signal, which induces eddy currents in the target. The receiver coil will generate a signal caused by the eddy currents in the target and the current in the transmitter coil. The signal from the receiver coil is analyzed in electronic circuitry, and the angular position can be determined in a known manner based on these signals.

[0003] Different types of sensing angle sensors exist. The shape, size, and number of coils, as well as the shape and size of the target, may vary. This invention primarily relates to a sensing sensor system that provides three-phase signals, i.e., three sinusoidal signals with a substantially 120° phase shift, but it can also be used for two-phase signals, i.e., a system that provides two sinusoidal signals with a substantially 90° phase shift.

[0004] Ideally, these two or three signals are perfect sinusoidal signals; ideally, they have exactly the same amplitude; ideally, the amplitude of the signals is constant over time; ideally, the signals have a DC value that is exactly equal to zero; and ideally, the amplitude(s) and DC(s) are insensitive to the presence of a metallic object near the sensor. However, in practice, this is not the case, and the amplitudes can vary over time and are different from each other, and the DC(s) can vary over time and are not zero.

[0005] There is a need for a sensing angle sensor that can provide accurate angle values ​​even in the presence of such anomalies. Summary of the Invention

[0006] One objective of embodiments of the present invention is to provide a method for determining the angular position of a target in a sensing angular position sensor system.

[0007] One objective of embodiments of the present invention is to provide a method that is relatively easy to implement and / or less computationally intensive.

[0008] One objective of embodiments of the present invention is to provide a method for offset compensation in a sensing angular position sensor system.

[0009] One objective of embodiments of the present invention is to provide a method for offset compensation that is less sensitive to amplitude changes.

[0010] Another object of embodiments of the present invention is to provide an angular position device configured to perform this method.

[0011] Another object of embodiments of the present invention is to provide an angular position sensor system comprising an angle sensor device configured to perform a method in addition to the mechanical movement of a target.

[0012] These and other objectives are accomplished by methods, angular position sensor systems, and angular position sensor devices according to embodiments of the present invention.

[0013] According to a first aspect, the present invention provides a method for determining the angular position of a target in a sensing angular position sensor system, wherein the sensing angular position sensor system further comprises: a substrate having at least one transmitter coil and a plurality of receiver coils; and a target movable relative to the substrate, the method comprising: a) receiving a plurality of input signals from the receiver coils; b) demodulating the plurality of input signals and optionally subtracting the plurality of input signals in pairs, and providing a plurality of sinusoidal baseband signals, each sinusoidal baseband signal having a respective amplitude and a respective DC offset; c) digitizing the plurality of sinusoidal baseband signals or digitizing the paired difference signals derived from the plurality of sinusoidal baseband signals, and A set of digital signals is provided; d) the corresponding DC offset value of each digital signal is reduced or substantially removed in an iterative manner, thereby providing a plurality of DC compensation signals; e) the angular position of the target is determined based on the DC compensation signals; wherein step d) includes: i) initializing DC correction values; ii) subtracting DC correction values ​​from the digital signals to obtain DC shift signals; iii) clipping the DC shift signals to obtain clipped signals; iv) calculating a first sum by summing the values ​​of the clipped signals over a period; v) calculating a second sum by summing the absolute values ​​of the clipped signals over the period; vi) adjusting the DC correction values ​​as a function of the ratio of the first sum to the second sum.

[0014] The advantage of this method is that DC offset correction can be performed in the digital domain, thereby reducing the component cost of analog circuits, since, for example, the high-pass filter can be omitted.

[0015] The advantage of this method is that the DC offset value is dynamically determined and corrected (unlike the DC offset value which is "determined only once during calibration," stored in non-volatile memory, and used later), because the dynamic determination and correction remain effective even when the DC offset drifts with time and temperature, or due to environmental changes (such as placing or removing a metal object near the sensor).

[0016] The advantage lies in iteratively determining the DC offset, as this allows the DC offset value to be gradually increased or decreased, which behaves like a low-pass filter.

[0017] The first and second sums are calculated primarily based on a DC-shifted, limited version of the baseband signal, rather than on the baseband signal itself. This is because the DC correction values ​​depend less on the amplitude of the sinusoidal signal. In other words, it makes the method "highly insensitive to amplitude variations." This method is particularly useful even over a relatively small number of periods when the amplitude of the sinusoidal signal can vary by approximately ±20% over time.

[0018] The advantage is that the current DC value is updated by a value proportional to the ratio of the first sum and the second sum (instead of by a constant K), as this allows for fine-tuning of the DC correction update.

[0019] In an embodiment, step d) includes: i) initializing each DC offset value to a predefined value; and repeatedly performing the following steps: ii) subtracting the DC correction value from each digital signal to obtain a DC shift signal; iii) limiting the DC shift signal to a predefined symmetrical range to obtain a limited signal; iv) calculating a first sum by summing the values ​​of the limited signal over one period of each signal; v) calculating a second sum by summing the absolute values ​​of the limited signal over the one period; vi) updating the DC correction value using the following formulas: DC0:=DC0+K*(s0 / a0); DC1:=DC1+K*(s1 / a1); DC2:=DC2+K*(s2 / a2); where “:=” is an assignment operator; s0, s1, s2 are the first sum; a0, a1, a2 are the second sum; and K is a predefined constant; and returning to step ii).

[0020] The term "symmetric range" refers to the range that extends from negative values ​​to positive values, both of which have the same absolute value, so zero is located in the middle of the symmetric range.

[0021] In an embodiment, the method further includes: providing an AC signal to excite the transmitter coil; and performing demodulation step b) synchronously with the AC signal.

[0022] In this embodiment, the multiple sinusoidal baseband signals or the multiple paired differential signals are three-phase signals.

[0023] In an embodiment, step b) includes: converting the three-phase signals into quadrature signals (e.g., using the Clarke transform); and using the arctangent function of the ratio of the quadrature signals to determine the angular position.

[0024] In one embodiment, step c) includes digitizing the signal using an analog-to-digital converter that provides at least 12 bits; and step iii) includes providing a limiting value with a maximum of 8 bits or a maximum of 5 bits.

[0025] The advantage of decreasing the number of bits by at least 4 is that the accumulator can be implemented using a fixed-point algorithm, while reducing the risk of overflow.

[0026] In an embodiment, step c) includes digitizing the signal using an analog-to-digital converter that provides at least 12 bits; and step iii) includes providing a limiting value having at least 2 bits, or at least 3 bits, or at least 4 bits.

[0027] For a 2-bit signal, the limiting signal can be one of the following values: -1, 0, +1.

[0028] For a 3-bit signal, the limiting signal can use one of the following values: -3, -2, -1, 0, +1, +2, +3, etc.

[0029] In an embodiment, the amplitude of the symmetrical range is approximately 75% to approximately 85% of the nominal or average value of the signal amplitude.

[0030] It has been found that, in embodiments of the sensing angle sensor system, the amplitude of the sinusoidal signal varies with time by approximately ±10% around the assumed or nominal amplitude. It has also been found that by limiting the signal to a symmetrical range, such that approximately 20% of the positive and upper / lower portions of the signal are reduced to a range less than (twice) the maximum amplitude of the sinusoidal signal, the top and bottom are always "cut off," and the resulting DC value is found to be less dependent on the varying amplitude.

[0031] In an embodiment, step iii) further includes: dynamically adjusting the symmetry range such that the amplitude of the symmetry range is about 75% to about 85% of the nominal or average value of the signal amplitude.

[0032] In the embodiment, the minimum and maximum values ​​of the symmetry range are dynamically adjusted so that they correspond to approximately 80% of the nominal or (short-term) average of the amplitude.

[0033] In an embodiment, the method further includes estimating or calculating the angular velocity of the target.

[0034] In an embodiment, step c) includes digitizing the signal using an analog-to-digital converter that provides at least 12 bits; and step iii) includes providing a limiting value having a bit depth in the range of 2 to 8, which is dynamically adjusted according to the estimated speed.

[0035] For example, in one embodiment, the speed is compared to a threshold, and if the actual speed is below the threshold, the number of bits is reduced from 12 to 8, and if the speed is above the threshold, the number of bits is reduced from 12 to 5.

[0036] By doing so, when the target is rotating at a lower speed, the DC correction value can be determined with a higher number of bits (resulting in more accurate DC offset correction); while when the target is rotating at a higher speed, the risk of "accumulator overflow" is reduced.

[0037] In this embodiment, the start and end times of each corresponding cycle are determined based on the moment when the DC compensation signal crosses the corresponding DC offset value.

[0038] According to a second aspect, the present invention also provides a sensing position sensor device for a sensing angular position sensor system, wherein the sensing angular position sensor system further includes a substrate having at least one transmitter coil and a plurality of receiver coils, and a target movable relative to the substrate; wherein the sensing position sensor device includes: a plurality of inputs (e.g., input ports or input nodes) for receiving a plurality of input signals (e.g., S0, S1, S2) obtained from the plurality of receiver coils; a demodulation circuit for demodulating the plurality of input signals (e.g., S0, S1, S2) and optionally subtracting the plurality of input signals (e.g., S0, S1, S2) in pairs, and providing a plurality of sinusoidal signals (e.g., In0, In1, In2); at least one analog-to-digital converter for digitizing the plurality of sinusoidal baseband signals (e.g., In0, In1, In2) or for digitizing the resulting paired difference signals (e.g., D01, D12, D20), and providing a set of digital signals (e.g., X0, X1, X2); and a digital processing circuit configured to perform steps d) and e) of the method according to the first aspect.

[0039] According to a third aspect, the present invention also provides a position sensor system comprising: a position sensor device according to a second aspect; a substrate having at least one transmitter coil and a plurality of receiver coils; and a target movable relative to the substrate.

[0040] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be suitably combined with features of the independent claims and other dependent claims, and not merely as expressly set forth in the claims.

[0041] These and other aspects of the invention will become apparent from the embodiments described herein, and are illustrated with reference to these embodiments. Attached Figure Description

[0042] Figure 1 An example of a sensing sensor arrangement, as may be used in embodiments of the invention, is shown, comprising: a substrate including a transmitter coil and a plurality of receiver coils; and a target (having five blades) that is movable relative to the substrate.

[0043] Figure 2 Examples of its use in embodiments of the invention are shown. Figure 1 The arrangement is for a variant with only three blades.

[0044] Figure 3 A schematic block diagram of an angle sensor system according to an embodiment of the present invention is shown, comprising: a substrate having at least one transmitter coil and three receiver coils; a target movable relative to the substrate; and an angle sensor device connected to the receiver coils. The method proposed in this invention can be executed by digital processing circuitry.

[0045] Figure 4A A diagram showing the three baseband signals obtained by demodulating the signal from the receiver coil under ideal conditions is presented.

[0046] Figure 4B A set of three equations representing these waveforms is shown, each with an amplitude of Arotor / √3.

[0047] Figure 4C It shows Figure 4A A graph showing the three paired differences between the baseband signals.

[0048] Figure 5A The diagram shows a result of demodulating the signal obtained from the receiver coil in a practical setting, which has three baseband signals.

[0049] Figure 5B A set of three equations representing these waveforms is shown, each with a separate amplitude and a separate DC offset value.

[0050] Figure 5C It shows Figure 5A A graph showing the three paired differences between the baseband signals.

[0051] Figure 6 A flowchart illustrating a method for determining the angular position of a target using a sensing angular position sensor is shown.

[0052] Figure 7 An implementation proposed by the present invention is shown. Figure 6 The flowchart of a feasible algorithm for step d) is shown.

[0053] Figure 8 The illustration is shown Figure 6 The diagram shown is a data flow diagram of the method proposed in this invention.

[0054] Figure 9A It shows how to use Figure 7 The algorithm shown is an example of calculating the DC offset correction value by limiting the signal to 2 bits and calculating the first and second sums of the limited signal.

[0055] Figure 9B It shows how to use Figure 7 The algorithm shown is another example of an algorithm that updates the DC value by limiting the signal to 3 bits and by calculating the first and second sums of the limited signal.

[0056] These figures are illustrative and not restrictive. In the figures, some elements may be enlarged and not drawn to scale for illustrative purposes. No reference numerals in the claims should be construed as limiting. In different figures, the same reference numerals refer to the same or similar elements. Detailed Implementation

[0057] The invention will be described with reference to specific embodiments and particular drawings, but the invention is not limited thereto but is defined only by the claims. The described drawings are illustrative only and not restrictive. In the drawings, some elements may be enlarged and not drawn to scale for illustrative purposes. Dimensions and relative dimensions do not correspond to an actual reduction in practice of the invention.

[0058] Furthermore, the terms "first," "second," etc., used in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe an order in time, space, rank, or any other way. It should be understood that the terms thus used are interchangeable where appropriate, and the embodiments of the invention described herein can be operated in other orders than those described or illustrated herein.

[0059] Furthermore, the terms "top," "bottom," etc., used in the specification and claims are for descriptive purposes and are not necessarily used to describe relative positions. It should be understood that such terms are interchangeable where appropriate, and the embodiments of the invention described herein can operate in orientations different from those described or illustrated herein.

[0060] It should be noted that the term "comprising" as used in the claims should not be construed as limiting oneself to the means listed thereafter; it does not exclude other elements or steps. Therefore, the term should be interpreted as specifying the presence of the features, integers, steps, or components stated as mentioned, but does not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the scope of the expression "device comprising means A and B" should not be limited to a device consisting solely of components A and B. It means that for the purposes of this invention, the only relevant components of the device are A and B.

[0061] Throughout this specification, the reference to "an embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrase "in an embodiment" or "in an embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, although they may. Furthermore, in one or more embodiments, particular features, structures, or characteristics that will be obvious to those skilled in the art from this disclosure can be combined in any suitable manner.

[0062] Similarly, it should be understood that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, drawing, or description for the purpose of streamlining the disclosure and aiding in the understanding of one or more inventive aspects. However, this approach to the disclosure should not be construed as reflecting an intention to claim more features than are expressly recited in each claim. Rather, as reflected in the appended claims, inventive aspects exist in fewer features than all the features of a single foregoing disclosed embodiment. Therefore, the claims appended to the Specific Embodiments are thus explicitly incorporated into this Specific Embodiments, wherein each claim itself represents a separate embodiment of the invention.

[0063] Furthermore, although some embodiments described herein include some features included in other embodiments but not in other embodiments, combinations of features from different embodiments are intended to fall within the scope of the invention and form different embodiments as will be understood by those skilled in the art. For example, any embodiment of the claimed embodiments in the appended claims may be used in any combination.

[0064] Numerous specific details are set forth in the description provided herein. However, it should be understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0065] This invention generally relates to angular position sensor systems. As described above, they typically include a substrate having one (or at least one) excitation coil (also referred to as a “transmitter coil”) and multiple detection coils (also referred to as “receiver coils”), such as two or three receiver coils, inductively coupled to the transmitter coil. The amount of coupling may be affected by a coupling element (also referred to as a “target”) mounted near the transmitter and receiver coils. The excitation coil is typically excited by an AC signal, thereby inducing eddy currents in the target. The receiver coils generate signals (e.g., voltage signals) caused by the eddy currents in the target and by the current in the transmitter coil. The signals from the receiver coils are analyzed in electronic circuitry, and the angular position is determined based on these signals.

[0066] This invention will primarily describe and explain a sensing angle sensor system with three receiver coils that provide three modulation signals from which three baseband signals electrically shifted by 120° can be derived. However, this invention is not limited to this and is also applicable to sensing angle sensor systems with only two receiver coils that provide only two modulation signals from which two baseband signals (commonly referred to as I and Q) electrically shifted by 90° can be derived.

[0067] Now refer to the attached figures,

[0068] Figure 1 A first example of a sensor arrangement is shown, including: a substrate 101 (e.g., a printed circuit board (PCB)) including a transmitter coil and a plurality of receiver coils; and a target 102 (e.g., a metallic target) rotatable relative to the substrate. The transmitter coil Tx and receiver coils Rx1, Rx2, and Rx3 are also present. Figure 2 The example shown illustrates a complete circle (also known as an O-shape), but the invention is not limited thereto and works for so-called "C-shaped" coils as well. In the example shown, the target has five leaves (or blades or leaf blades) spaced 360° / 5 = 72° apart, but the invention is not limited thereto and works for targets with different numbers of leaves (e.g., 1 to 25 leaves, or 2 to 22 leaves).

[0069] Figure 3 A schematic block diagram of a sensing angular position sensor system 300 is shown, including: a sensing sensor arrangement 310, which includes: a substrate having a coil system 311 (in... Figure 3 (Not explicitly shown in the text) The coil system 311 includes at least one transmitter coil TX and three receiver coils Rx1, Rx2, Rx3; and a target 312 rotatable relative to the coil system 311.

[0070] The sensor system 300 further includes a sensor device 320 connected at least to the receiver coils Rx1, Rx2, and Rx3 for receiving and processing signals. The sensor device 320 is preferably also connected to the transmitter coil TX, and is preferably further configured to excite the transmitter coil with an AC signal.

[0071] The sensor system 300 may have an oscillator circuit 321, and the transmitter coil TX may be part of this oscillator circuit, but this is not strictly necessary, and the excitation may also be performed by a separate circuit (e.g., by a separate chip). The transmitter coil Tx may be excited at frequencies from about 1 MHz to about 20 MHz. The excitation frequency may be higher than, lower than, or substantially equal to the resonant frequency of the oscillator circuit. These aspects are well known in the art but are not the main focus of the present invention and therefore need not be explained in more detail here.

[0072] Sensor device 320 is configured to receive signals from receiver coils Rx1, Rx2, and Rx3, and optionally to amplify these signals using amplifier 322 and demodulate them in demodulator 323 to generate three baseband signals In0, In1, and In2. Alternatively, sensor device 320 can be configured to calculate paired differential signals, for example, according to the following formulas: D01 = In0 - In1; D12 = In1 - In2; D20 = In2 - In0; and to amplify and demodulate the differential signals.

[0073] Demodulation may include synchronous rectification and low-pass filtering. Then, as will be described further (see example...) Figure 7 As shown in Figure 9), the baseband signals are “offset compensated” in an iterative manner by digitizing the signals, limiting the signal amplitude, calculating the first and second sums of the limited signals, and calculating the DC correction value individually based on the first and second sums of each of the sinusoidal signals. This is the main aspect of the invention.

[0074] Then, angles can be calculated from these offset compensation signals; for example, by using the Clarke transform to convert the three-phase signals into quadrature signals, an arctangent operation can be performed on these quadrature signals. Figure 3 In the system shown, sensor device 320 can perform a Clarke transform and provide sine and cosine signals to an external processor (e.g., an ECU (not shown)) from which the angle can be calculated. In a variant, the angle is calculated internally by sensor device 320 and can be provided to the external processor.

[0075] It is noted that Figure 3The architecture shown is merely an example of how signals obtained from the receiver coil can be processed to obtain multiple sinusoidal baseband signals, and other architectures can also be used. The primary focus of this invention is not demodulation, but rather providing techniques for reducing the offset of these baseband signals.

[0076] Static compensation methods based on calibration values ​​determined during the calibration process are known in the prior art, such as from EP patent application EP21157650.9 filed on February 17, 2021. However, this method is not ideal when the amplitude and / or DC offset may change (or “drift”) over time, for example due to temperature changes or the proximity of metallic objects.

[0077] The inventors of this invention had the task of finding a method that was less sensitive to amplitude variations (in particular, amplitude variations of about ±10% around the nominal amplitude value).

[0078] Figure 4A A diagram is shown with three baseband signals In0, In1, and In2, which can be obtained ideally (i.e., having the same amplitude and zero DC offset) by demodulating signals S0, S1, and S2 obtained from receiver coils Rx1, Rx2, and Rx3. The values ​​on the vertical axis are arbitrary. In fact, zero offset is not absolutely necessary, and if the signals have the same offset, this offset can be easily removed by calculating the paired difference signals (see [link to diagram]). Figure 4C ).

[0079] Figure 4B A set of three equations representing these ideal (or near-ideal) waveforms is shown, each with an amplitude of Arotor / √3 and zero offset, and the signals are electrically phase-shifted by 120° relative to each other. Angle θ represents the angular position of the target relative to the substrate. Figure 4A In the example shown, the DC offset value may be equal to zero due to the use of an anti-tangle receiver coil or due to the demodulation circuit, but this is not absolutely necessary for the invention to be effective. As mentioned, non-zero DC offset values ​​can be eliminated by determining the pairwise differences between the three baseband signals In0, In1, and In2, for example... Figure 4C As shown. Another advantage of using the difference signal is that the amplitude of the difference signal is greater than that of the baseband signal, thus improving the signal-to-noise ratio.

[0080] Figure 5A A diagram is shown with three baseband signals In0, In1, and In2, which can be obtained in practice by demodulating signals S0, S1, and S2 obtained from receiver coils Rx1, Rx2, and Rx3.

[0081] Figure 5BA set of three equations representing these waveforms is shown, each with its own amplitudes A0, A1, A2, and its own offsets Aasym0, Aasym1, Aasym2, and the signals are electrically phase-shifted by 120° relative to each other. Angle θ represents the angular position of the target relative to the substrate. Figure 5A In the illustrative example shown, Aasym0 is chosen to be equal to Arotor*0.1, but of course, this is just an example.

[0082] Figure 5C A graph showing paired difference signals in a real-world scenario is presented. As can be seen, the amplitudes of these signals are not the same, and the DC offset is non-zero.

[0083] Then, the above question can be rephrased as "how to base on..." Figure 5A Non-ideal signals In0, In1, In2 or based on Figure 5C The non-ideal signals D01, D12, and D20 are used to determine the angular position of the target where the sensing sensor is placed.

[0084] Figure 6 A flowchart of a method 600 for determining the angular position of a target using a sensing angular position sensor, as proposed in this invention, is shown. The method includes the following steps:

[0085] a) Receives 601 input signals S0, S1, S2 from receiver coils RX1, RX2, and RX3;

[0086] b) Demodulate the plurality of input signals S0, S1, S2 as described in 602 and optionally subtract the plurality of input signals S0, S1, S2 in pairs, and provide a set of sinusoidal baseband signals (In0, In1, In2) or (D01, D12, D20), each baseband signal having its own amplitude A0, A1, A2 and its own DC offset Aasym0, Aasym1, Aasym2;

[0087] c) Digitize the set of sinusoidal baseband signals (In0, In1, In2) or (D01, D12, D20) described in 603, and provide a set of digital signals (X0, X1, X2);

[0088] d) Reduce the corresponding DC offset (Aasym0, Aasym1, Aasym2) of each of the 604 digital signals iteratively, thereby providing multiple DC compensation signals; (e.g.) Figure 8 (shown as X0dcc, X1dcc, X2dcc);

[0089] e) For example, using the Clarke transform and arctangent function, based on DC-compensated signals (e.g. Figure 8The angular position of target 605 is determined by X0dcc, X1dcc, and X2dcc as shown.

[0090] The advantage is that the DC offset is adjusted iteratively (e.g., for each period of each corresponding signal), rather than a fixed adjustment determined during calibration. Preferably, as will be explained further, the DC offset adjustment is based on a clipped version of the DC compensation signal, and more specifically, on a first and a second sum of its samples summed over one period of the corresponding signal.

[0091] Figure 7 An implementation proposed by the present invention is shown. Figure 6 The flowchart of step d) is a feasible algorithm 700. This algorithm can be considered as a method 700 for reducing the DC offset value of a digital sine wave signal applied to each of the individual sine waves. This method uses three combiners (e.g., an adder or a subtractor block) 831a, 831b, 831c (see...). Figure 8 ) and the three DC correction values ​​DC0, DC1, and DC2 that are iteratively updated (see Figure 8 Method 700 includes the following steps:

[0092] i) Initialize the DC correction values ​​DC0, DC1, and DC2 of each sinusoidal signal X0, X1, and X2 to predefined values ​​(e.g., initialize them to zero);

[0093] ii) Subtract the DC correction value DC0, DC1, DC2 by 702 from the corresponding sinusoidal digital signals X0, X1, X2 to obtain the DC shift signal;

[0094] iii) Limit the DC shift signal 703 to a predefined symmetrical range, thereby obtaining a limited signal (e.g. Figure 8 (X0sat, X1sat, X2sat);

[0095] iv) The first sum of 704 (e.g., s0, s1, s2) is calculated by summing the values ​​of the limited signals (e.g., X0sat, X1sat, X2sat) within one period of each signal.

[0096] v) The second sum (e.g., a0, a1, a2) of 705 is calculated by summing the absolute values ​​of the clipped signals (e.g., X0sat, X1sat, X2sat) over one period of each signal.

[0097] vi) Update the corresponding DC correction values ​​(DC0, DC1, DC2) for each sine signal of 706 by adding functions of the first and second sums, for example by adding K*(s / a), where K is a predefined constant, (s) is the first sum, and (a) is the second sum.

[0098] Figure 8 The illustration is shown Figure 7 The method is a data flow diagram. This data flow is executed in the digital domain. It can be implemented in hardware circuitry or in software. Figure 3 In the sensing angle sensor circuit, the algorithm is preferably implemented in the digital processing circuit 326. An advantage is that the algorithm can be easily implemented in software using simple algebraic functions (such as summation, subtraction, and division). "Limiting" is performed by comparing the value with an upper threshold and a lower threshold; if the value is greater than the upper threshold, it is replaced with the upper threshold; if the value is less than the lower threshold, it is replaced with the lower threshold; and if the value is between the upper and lower thresholds, it is maintained. Taking the absolute value is also a simple function, implemented by checking the sign of the value and changing the sign if the sign is negative.

[0099] The signal is limited to a symmetrical range, which means that the absolute value of the upper threshold is the same as the absolute value of the lower threshold (e.g., +70 and -70, or +130 and -130, or any threshold used for limiting).

[0100] If the nominal amplitude of the sinusoidal signal is, for example, a value "B" (e.g., a digital value of 170), then the upper limit threshold of the limiting range is preferably chosen to be about 70% to 90% of B, or about 75% to 85% of B, for example, equal to about 80% of B (170 * 80% = 136 in the example). Therefore, in this example, the input value can be limited to the range of -136 to +136.

[0101] like Figure 8 The limiting signal, represented by the symbols X0sat[M:0], X1sat[M:0], and X2sat[M:0], can have fewer bits than the digital signals X0[N:0], X1[N:0], and X2[N:0]. One insight of this invention is that the DC correction value can be very accurate even when using only a small number of bits.

[0102] In the Figure 9A In the embodiment shown, the limiting signal may have only 2 bits, and assume one of the following three values: -1, 0, and +1.

[0103] In the Figure 9B In the embodiment shown, the limiting signal may have only 3 bits, and assumes one of the following seven values: -3, -2, -1, 0, +1, +2, +3.

[0104] The advantage is that only a few bits are used, because doing so reduces or eliminates the risk of overflow caused by the sum of the absolute values ​​of a sinusoidal signal over one cycle.

[0105] Figure 9A It shows how to use Figure 7 The example algorithm shown calculates the DC offset correction value. In this example, the digital sine signal has an actual DC value indicated by "actual DC," but it is assumed that this digital value is offset from zero.

[0106] In this example, the digital signal is clipped to one of three possible values: -1, 0, +1, as shown by the black circle. Assume the DC correction value is initialized to DC0_init, which in this example is zero (but another value could also be used). The first and s0 are calculated as the sum of the clipping values ​​over one period of the sine signal, producing a value of +2 in this example. And the second and a0 are calculated as the sum of the absolute values ​​of these values ​​over said period, producing a value of +10 in this example. According to the invention, the DC correction value is then updated as a function of the first and s0 and the second and a0, for example, by multiplying (a constant) K by the first and divided by the second and added. This can be written mathematically as:

[0107] DC0 (next iteration) := DC0 (current value) + K*s0 / a0, or simplified as:

[0108] DC0:=DC0+K*s0 / a0,

[0109] Where “:=" is the assignment operator (meaning the value is overwritten), DC0 is the DC correction value of the first digital signal, K is a predefined constant (equal to 0.3 in the example, but of course another value can be chosen), and s0 is the first limiting signal (e.g., Figure 8 The first sum is calculated within one period of X0sat in the first limiting signal (e.g., ...). Figure 8 The second sum is calculated within one period of X0sat. Figure 9A In the example, the DC correction value increases from 0 to 0.06 in the first iteration. A new DC correction value can be updated in each cycle.

[0110] Although not explicitly shown, the DC correction values ​​DC1 and DC2 for the other two signals can be calculated in a similar manner, and can be mathematically expressed as:

[0111] DC1:=DC1+K*s1 / a1, where s1 and a1 are the values ​​of the second limiting signal (e.g., Figure 8 The first and second sums calculated within one period of X1sat, and

[0112] DC2:=DC2+K*s2 / a2, where s2 and a2 are the third limiting signal (e.g. Figure 8 The first and second sums are calculated within one period of X2sat.

[0113] Note that the periods of the first, second, and third limiting signals are typically approximately 120° phase shift. The number of samples with this phase shift depends on the target's velocity.

[0114] It has been found that the proposed technique is highly independent of the amplitude of the sinusoidal signal, and it works even when the signal is limited to only two bits. However, it has also been found that a more stable DC value is obtained when using slightly more bits (e.g., at least three or four bits), and when the peak-to-peak value of the limiting range is approximately 80% of the peak-to-peak value of the sinusoidal signal, or in other words, when the positive threshold is approximately 80% of the nominal amplitude of the sinusoidal signal.

[0115] Figure 9B It shows how to use Figure 7 The image shows another example of the algorithm updating the DC correction value. In this example, the digital signal is clipped to 3 bits, and the peak-to-peak range of the clipping is approximately 75% of the peak-to-peak range of the sine wave. Figure 9B In the example, the value of K is set to 0.4, and the DC correction value increases from 0 to 0.09 in the first iteration.

Claims

1. A method for determining the angular position of a target (102; 312) of a sensing angular position sensor system (300), wherein the sensing angular position sensor system further comprises: A substrate and a target, the substrate having at least one transmitter coil (TX) and multiple receiver coils (RX1, RX2, RX3), the target being movable relative to the substrate, the method comprising: a) Receive multiple input signals (S0, S1, S2) from the receiver coils (RX1, RX2, RX3); b) Demodulate the plurality of input signals (S0, S1, S2) and optionally subtract the plurality of input signals (S0, S1, S2) in pairs, and provide a plurality of sinusoidal baseband signals (In0, In1, In2), each sinusoidal baseband signal having a corresponding amplitude and a corresponding DC offset; c) Digitize the plurality of sinusoidal baseband signals (In0, In1, In2) or digitize the paired difference signals (D01, D12, D20) derived from the plurality of sinusoidal baseband signals (In0, In1, In2), and provide a set of digital signals (X0, X1, X2); d) Reduce the corresponding DC offset value of each digital signal in the digital signal in an iterative manner, thereby providing multiple DC compensation signals; e) Determine the angular position of the target based on the DC compensation signal; The characteristic is that step d) includes: i) Initialize the DC correction value; ii) Subtract the DC correction value from the digital signal to obtain the DC shift signal; iii) Limit the DC shift signal to obtain a limited signal; iv) The first sum is calculated by summing the values ​​of the limiting signal over one period; v) The second sum is calculated by summing the absolute values ​​of the amplitude-limited signals within the period; vi) Adjust the DC correction value as a function of the ratio of the first sum to the second sum.

2. The method as described in claim 1, characterized in that, Step d) includes: i) Initialize each DC correction value (DC0, DC1, DC2) to a predefined value; And repeat the following steps: ii) Subtract the DC correction values ​​(DC0, DC1, DC2) from the corresponding digital signals (X0, X1, X2) to obtain the DC shift signal; iii) Limit the DC shift signal to a predefined symmetrical range to obtain a limited signal; iv) The first sum (s0, s1, s2) is calculated by summing the values ​​of the amplitude-limited signal over one period of the corresponding signal; v) The second sum (a0, a1, a2) is calculated by summing the absolute values ​​of the amplitude-limited signal within the one period; vi) Update the DC correction values ​​(DC0, DC1, DC2) using the following formula: DC0:=DC0+K*(s0 / a0); DC1:=DC1+K*(s1 / a1); DC2:=DC2+K*(s2 / a2); Where ":=" is the assignment operator; s0, s1, and s2 are the first sum; a0, a1, and a2 are the second sum; and K is a predefined constant; and return to step ii).

3. The method as described in claim 1, Further includes: An AC signal is provided to excite the transmitter coil (TX); Furthermore, the demodulation in step b) is performed synchronously with the AC signal.

4. The method as described in any one of claims 1-3, Its features are, The plurality of sinusoidal baseband signals (In0, In1, In2) or the plurality of paired difference signals (D01, D12, D20) are three-phase signals.

5. The method as described in claim 4, characterized in that, Step b) includes: Convert the three-phase signals into quadrature signals; The angular position is determined using the arctangent function of the ratio of the orthogonal signals.

6. The method as described in any one of claims 1-3, Its features are, Step c) includes: digitizing the plurality of sinusoidal baseband signals (In0, In1, In2) or digitizing the paired difference signals (D01, D12, D20) derived from the plurality of sinusoidal baseband signals (In0, In1, In2) using an analog-to-digital converter (ADC) that provides at least 12 bits; And step iii) includes: providing the limiting signal having up to 8 bits.

7. The method as described in any one of claims 1-3, Its features are, Step c) includes: digitizing the plurality of sinusoidal baseband signals (In0, In1, In2) or digitizing the paired difference signals (D01, D12, D20) derived from the plurality of sinusoidal baseband signals (In0, In1, In2) using an analog-to-digital converter (ADC) that provides at least 12 bits; And step iii) includes: providing the limiting signal having at least 2 bits.

8. The method as described in claim 2, Its features are, The amplitude of the symmetrical range is 75% to 85% of the nominal or average value of the signal amplitude.

9. The method as described in claim 2, Its features are, Step iii) further includes: dynamically adjusting the symmetry range such that the amplitude of the symmetry range is 75% to 85% of the nominal or average value of the signal amplitude.

10. The method as described in any one of claims 1-3, Its features are, The method further includes: estimating or calculating the angular velocity of the target.

11. The method as described in claim 10, Its features are, Step c) includes: digitizing the plurality of sinusoidal baseband signals (In0, In1, In2) or digitizing the paired difference signals (D01, D12, D20) derived from the plurality of sinusoidal baseband signals (In0, In1, In2) using an analog-to-digital converter (ADC) that provides at least 12 bits; And step iii) includes: providing the limiting signal having a bit depth in the range of 2 to 8, the bit depth being dynamically adjusted according to the estimated or calculated angular velocity.

12. The method as described in any one of claims 1-3, Its features are, The start and end times of each corresponding cycle are determined based on the time when the DC compensation signal crosses its corresponding DC offset value.

13. A position sensor device (320) for use in a sensing angular position sensor system (300), characterized in that, The sensing angle position sensor system further includes: a substrate having at least one transmitter coil and multiple receiver coils, and a target movable relative to the substrate; The position sensing sensor device includes: Multiple inputs, the multiple inputs being used to receive multiple input signals (S0, S1, S2) obtained from the multiple receiver coils; A demodulation circuit is used to demodulate the plurality of input signals (S0, S1, S2) and optionally subtract the plurality of input signals (S0, S1, S2) in pairs, and to provide a plurality of sinusoidal baseband signals (In0, In1, In2). At least one analog-to-digital converter (ADC) is used to digitize the plurality of sinusoidal baseband signals (In0, In1, In2) or to digitize the paired difference signals (D01, D12, D20) derived from the plurality of sinusoidal baseband signals (In0, In1, In2), and to provide a set of digital signals (X0, X1, X2). A digital processing circuit (326) configured to perform steps d) and e) of the method as described in any of the preceding claims.

14. A position sensor system (300), comprising: The sensing position sensor device (320) as described in claim 13; A substrate having at least one transmitter coil (TX) and multiple receiver coils (RX1, RX2, RX3); The target is movable relative to the substrate.

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