Circuit and method for determining angular position

Abstract

The present application discloses a circuit and method for determining an angular position. A sensor circuit for determining the angular position of a rotating object, the object being configured to generate or modulate a magnetic field, the sensor circuit comprising: a) a first sensor for providing a first sensor signal; b) a second sensor for providing a second sensor signal; c) a signal correction block for receiving the first / second sensor signal or a signal derived therefrom as a first / second input signal, and receiving a plurality of feedback signals; and configured to provide a first corrected signal and a second corrected signal; d) an angle calculation block, the angle calculation block being configured to receive the first corrected signal and the second corrected signal, and determining the angular position signal as a function of the ratio of the first corrected signal and the second corrected signal; e) a feedback block, the feedback block being configured to receive the angular position signal, and to generate the plurality of feedback signals with improved linearity based on the angular position signal.

Description

Technical Field

[0001] The present invention relates generally to the field of magnetic sensor devices and methods, and more particularly to angular position sensor systems and methods. Background Art

[0002] Angular position sensor systems are known in the art. They offer the advantage of being able to measure angular position without physical contact, thereby avoiding problems with mechanical wear, scratching, friction, etc.

[0003] There are basically two types of magnetic angular position sensor systems: (1) inductive angular position sensor systems, and (2) angular position sensor systems using permanent magnets.

[0004] An inductive angular position sensor system typically includes an excitation coil (also called a "transmitter coil") and a plurality of detection coils (also called "receiver coils").

[0005] In an angular position sensor system using a permanent magnet, the magnet usually generates a magnetic field that is sensed by a number of magnetosensitive elements arranged in a specific manner at a certain distance from the magnet. The signals from these magnetosensitive elements are processed in an electronic circuit and the angular position is determined from these signals.

[0006] The present invention generally relates to an electronic circuit and a method for determining an angular position based on a sensor signal.

[0007] There is always room for improvement or substitution. Summary of the invention

[0008] It is an object of embodiments of the present invention to provide a sensor circuit and method for determining the actual angular position of a rotating object.

[0009] An object of embodiments of the present invention is to provide a sensor circuit and method for determining the actual angular position of an object rotating at a certain angular velocity, which is in the range of from about 4 to about 3200 revolutions per second (mechanical) or from about 20 to about 16000 revolutions per second (electrical).

[0010] It is an object of embodiments of the present invention to provide a sensor circuit and method that provides an accurate (or more accurate) angular position, or provides an angular position with a small error (or reduced error) between the output signal and the actual mechanical position.

[0011] It is an object of embodiments of the present invention to provide a sensor circuit and method having improved linearity between output signal and actual mechanical position.

[0012] It is an object of certain embodiments of the present invention to provide an inductive angle sensor system having a reduced sensitivity to the presence of unwanted metal parts in the vicinity of the sensor device.

[0013] It is an object of certain embodiments of the present invention to provide an angle sensor system and method having improved robustness to one or more of: temperature variations, mounting requirements (axial offset, radial offset, tilt angle, wobble).

[0014] It is an object of embodiments of the present invention to provide an inductive or magnetic sensor system or circuit or method suitable for use in an industrial, robotic or automotive environment.

[0015] These objects are achieved by embodiments of the present invention.

[0016] According to a first aspect, the present invention provides a sensor circuit for determining an angular position of an object when it is rotated relative to the sensor circuit, wherein the object is configured to generate or modulate a magnetic field, the sensor circuit comprising: a) a first sensor, the first sensor being configured to measure a first characteristic of the magnetic field and to provide a first sensor signal (e.g. ss1); b) a second sensor, the second sensor being configured to measure a second characteristic of the magnetic field and to provide a second sensor signal (e.g. ss2); c) a signal correction block, the signal correction block being configured to receive a first sensor signal (e.g., ss1) or a signal derived therefrom as a first input signal (e.g., Isig), and a second sensor signal (e.g., ss2) or a signal derived therefrom as a second input signal (e.g., Qsig), and a plurality of feedback signals (e.g., Idc_c, Qdc_c, Gmm_c); and being configured to provide a first corrected signal (e.g., Iadj) having a first amplitude and an optional first DC value, and a second corrected signal (e.g., Qadj) having a second amplitude substantially equal to the first amplitude and an optional second DC value and optionally also having reduced crosstalk; d) an angle calculation block, the angle calculation block being configured to receive the first corrected signal and the second corrected signal (e.g., Iadj, Qadj), and determine an angular position signal (e.g., an angular position signal) as a function (e.g., an inverse tangent function) of the ratio of the first corrected signal and the second corrected signal (e.g., Iadj, Qadj) ); e) a feedback frame configured to receive an angular position signal (eg ), and based on the angular position signal (e.g. ) generates multiple feedback signals (e.g., Idc_c, Qdc_c, Gmm_c) so that the angular position has improved linearity.

[0017] Advantageously, the angular position is calculated based on a ratio of signals having substantially the same amplitude, since the ratio is independent of the magnetic field strength (e.g. independent of the magnet strength, e.g. independent of the distance between the sensor device and the magnet, e.g. independent of the amplitude of the modulated signal).

[0018] It is an advantage that all feedback signals are derived from a single signal (ie the angular position signal) rather than being calculated separately for the first and second signals, as this improves overall signal consistency and may improve the stability of the feedback loop.

[0019] This is an advantage of a closed loop system, since it is able to dynamically adjust itself depending on the introduced error. This provides an angle signal value that is more robust to aging, long term drift etc. Another advantage is that a calibration test, which is usually implemented in an open loop system, can be omitted, in which the error value is determined and the calibration value is stored (e.g. in the form of a table) in a non-volatile memory. Another advantage is that an accurate reference angle measurement system is also not required to perform such a test.

[0020] The first input signal may be a sinusoidal signal having a first amplitude and a first phase.

[0021] The second input signal may be a second sinusoidal signal having a second amplitude that may be less than or greater than the first amplitude (e.g., in the range of 80% to 120% of the first amplitude), and having a second phase that may be offset from the first phase by a value in the range of 80° to 100°.

[0022] Preferably, the sensor circuit comprises a semiconductor substrate, the semiconductor substrate comprising at least a signal correction frame, an angle determination frame and the feedback frame. The semiconductor substrate is preferably packaged in a ceramic or plastic package (also referred to as a "chip"). Depending on the implementation, the first sensor and the second sensor may also be integrated on the semiconductor substrate, or on a second substrate (e.g. a printed circuit board (PCB)).

[0023] In an embodiment, the first sensor and the second sensor are or include one or more magnetic sensitive elements, such as one or more magnetic sensitive elements selected from the group consisting of: horizontal Hall element, vertical Hall element, magnetoresistive element (MR element). These elements are preferably also integrated on the above-mentioned semiconductor substrate.

[0024] In an embodiment, the first sensor and the second sensor are a first receiver coil and a second receiver coil implemented on a printed circuit board (PCB). The packaged semiconductor substrate including the above electronic circuit can be mounted, for example, soldered, on the PCB.

[0025] The first input signal may be a sinusoidal signal having a first amplitude and a first phase.

[0026] The second input signal may be a second sinusoidal signal having a second amplitude that may be less than or greater than the first amplitude (e.g., in the range of 80% to 120% of the first amplitude), and having a second phase that may be offset from the first phase by a value in the range of 80° to 100°.

[0027] In an embodiment, the electronic circuit comprises a programmable processor (eg a digital signal processor, DSP) comprising or connected to a non-volatile memory comprising executable instructions for executing at least the signal correction block, the angle determination block and the feedback block in software.

[0028] In an embodiment, the plurality of feedback signals include: a first error signal (e.g., Idc_c), a second error signal (e.g., Qdc_c), and a first scaled signal (e.g., Gmm_c); and the signal correction block includes: i) a first combiner arranged to receive and combine (e.g., sum or subtraction) the first input signal (e.g., Isig) and the first error signal (e.g., Idc_c), thereby providing a first combined signal (e.g., s1); and ii) a second combiner arranged to receive and combine (e.g., sum or subtraction) the second input signal (e.g., Qsig) and the second error signal (e.g., Qdc_c), thereby providing a second combined signal (e.g., s2); and iii) a first scaler arranged to scale the second combined signal (e.g. s2) using the first scaling signal (e.g. Gmm_c) (e.g. by multiplying the signals) to provide a third signal (e.g. s3); wherein the first corrected signal (e.g. Iadj) is the first combined signal (e.g. s1), or is derived from the first combined signal (e.g. s1) and the third signal (e.g. s3); (e.g., as a linear combination thereof); and wherein the second corrected signal (e.g. Qadj) is the third signal (e.g. s3), or is derived from the first combined signal (e.g. s1) and the third signal (e.g. s3) (e.g., as a linear combination thereof).

[0029] Figure 1 and Figure 2 An example of this embodiment is shown in FIG.

[0030] In an embodiment, the multiple feedback signals further include: a second scaled signal (e.g., Gmm2_c); and the signal correction box further includes: iv) a second sealer, arranged to scale a third signal (e.g., s3) using the second scaled signal (e.g., Gmm2_c) (e.g., by multiplying these signals); v) a third combiner, arranged to combine (e.g., by summing or subtracting) the output of the second sealer and the first combined signal (e.g., s1) to provide a first corrected signal (e.g., Iadj); iv) a third sealer, arranged to scale the first combined signal (e.g., s1) using the second scaled signal (e.g., Gmm2_c) (e.g., by multiplying these signals); v) a fourth combiner, arranged to combine (e.g., by summing or subtracting) the output of the third sealer and the third signal (e.g., s3) to provide a second corrected signal (e.g., Qadj).

[0031] Figure 2 An example of this embodiment is shown in FIG.

[0032] The advantage of this embodiment is that crosstalk between signals can be reduced or substantially eliminated.

[0033] In an embodiment, the plurality of feedback signals include: a first error signal (e.g., Idc_c), a second error signal (e.g., Qdc_c), and a first scaled signal (e.g., Gmm_c); and wherein the feedback circuit includes: an α) guidance frame configured to receive an angular position signal (e.g., ) and determining the time derivative signal of the angular position signal to generate a fourth signal (e.g., s4); β) a DC removal box, the DC removal box is configured to receive the fourth signal (e.g., s4) and remove the DC level of the fourth signal (e.g., s4) (e.g., high-pass filtering the time derivative signal) to generate a fifth signal (e.g., s5); γ) multiple correlators, configured to receive the fifth signal (e.g., s5) and correlate the fifth signal (e.g., s5) with each of three (optionally clipped) sine and cosine waveforms or patterns to generate three correlated signals (e.g., c1, c2, c3); δ) multiple scalers and integrators, configured to generate a first error signal (e.g., Idc_c), a second error signal (e.g., Qdc_c) and a first scaled signal (e.g., Gmm_c) by scaling and integrating each of the three correlated signals (e.g., c1, c2, c3), respectively.

[0034] Selectable clipped sine and cosine waveforms or patterns are synchronized with the angular position signal. Scaling can be applied before or after integration.

[0035] In an embodiment, the plurality of feedback signals further include: a second scaled signal (e.g., Gmm2_c); and the feedback circuit is further configured to: ε) correlate a fifth signal (e.g., s5) with a fourth optional clipped sinusoidal waveform or pattern to generate a fourth correlated signal (e.g., c4); ζ) generate a second scaled signal (e.g., Gmm2_c) based on an integral of the fourth correlated signal (e.g., c4).

[0036] In an embodiment, the angle calculation block is configured to determine (eg, calculate) the angular position (eg, ).

[0037] For example, using the classic inverse tangent function, called arctan(), or using the two-argument inverse tangent function, called arctan2() or atan2(). This can be implemented using a lookup table (optionally with interpolation).

[0038] According to a second aspect, the invention also provides an angular position sensor system comprising: a sensor circuit according to the first aspect; a rotatable object (eg a shaft), and a permanent magnet connected to the object.

[0039] According to a third aspect, the present invention also provides an angular position sensor system, comprising: a sensor circuit according to the first aspect; a printed circuit board, the printed circuit board comprising a transmitter coil and at least two receiver coils; a rotatable object, the rotatable object is in the form of a conductive target (e.g. a metal target).

[0040] This system is an "Inductive Angle Sensor System".

[0041] The target can be C-shaped or O-shaped.

[0042] In an embodiment, the sensor circuit further comprises: a demodulator for demodulating signals acquired from the three receiver coils; and a Clarke transform block arranged to convert the demodulated signals into said first input signal and a second signal.

[0043] This system is an "Inductive Angle Sensor System".

[0044] The inductive sensor may be of a C-type or an O-type.

[0045] Converting the three-phase signal to a two-phase signal before calculating the angle is an advantage because this requires less processing power and less memory.

[0046] According to a fourth aspect, the invention also relates to an electric machine comprising an angular position sensor system according to the second or third aspect.

[0047] According to a fifth aspect, the present invention also provides a method for determining an angular position of an object rotating relative to a sensor circuit (e.g. ) method, the object is configured to generate or modulate a magnetic field, the method comprising the following steps: a) measuring a first characteristic of the magnetic field and providing a first sensor signal (e.g. ss1) or a signal derived therefrom as a first input signal (e.g. Isig); b) measuring a second characteristic of the magnetic field and providing a second sensor signal (e.g. ss2) or a signal derived therefrom as a second input signal (e.g. Qsig); c) using a plurality of feedback signals (e.g. Idc_c, Qdc_c, Gmm_c) to correct the first and second input signals (e.g. Isig, Qsig) and provide a first corrected signal (e.g. Iadj) having a first amplitude and a second corrected signal (e.g. Qadj) having a second amplitude substantially equal to the first amplitude (and optionally also having reduced crosstalk); d) determining (e.g. calculating) the angular position signal (e.g. ) (e.g., the inverse tangent function of the ratio of these signals); e) based on the angular position signal (e.g. ) to generate the multiple feedback signals (eg, Idc_c, Qdc_c, Gmm_c).

[0048] In an embodiment, the plurality of feedback signals include: a first error signal (e.g., Idc_c), a second error signal (e.g., Qdc_c), and a first scaled signal (e.g., Gmm_c); and step c) includes: i) combining the first input signal (e.g., Isig) and the first feedback signal (e.g., Idc_c) (e.g., summing or subtracting) to generate a first combined signal (e.g., s1); and ii) combining the second input signal (e.g., Qsig) and the second feedback signal (e.g., Qdc_c) (e.g., summing or subtracting) to generate a second combined signal (e.g., s2); and iii) scaling the second combined signal (e.g., s2) using the first scaled signal (e.g., Gmm_c) to generate a third signal (e.g., s3); iv) providing the first corrected signal (e.g., Iadj) as the first combined signal (e.g., s1), or as a signal derived from the first combined signal (e.g., s1) and the third signal (e.g., s3); (e.g., as a linear combination thereof); v) providing a second corrected signal (e.g., Qadj) as the third signal (e.g., s3), or as a signal derived from the first combined signal (e.g., s1) and the third signal (e.g., s3) (e.g., as a linear combination thereof).

[0049] Figure 1 and Figure 2 An example of this embodiment is shown in FIG.

[0050] In an embodiment, the plurality of feedback signals further include: a second scaled signal (e.g., Gmm2_c), and step c) further includes: iv) providing a first corrected signal (e.g., Iadj) as a signal obtained by scaling a third signal (e.g., s3) using the second scaled signal (e.g., Gmm2_c) and v) combining the resulting signal with the first combination signal (e.g., s1); vi) providing a second corrected signal (e.g., Qadj) as a signal obtained by scaling the first combination signal (e.g., s1) using the second scaled signal (e.g., Gmm2_c) and vii) combining the resulting signal with the third signal (e.g., s1).

[0051] In an embodiment, the plurality of feedback signals include: a first error signal (eg, Idc_c), a second error signal (eg, Qdc_c), and a first scaling signal (eg, Gmm_c); and step e) includes: α) determining an angular position signal (eg, ) to generate a fourth signal (e.g., s4); β) removing the DC level from the time derivative signal (e.g., s4) (e.g., by high-pass filtering the time derivative signal) to generate a fifth signal (e.g., s5); γ) correlating the fifth signal (e.g., s5) with each of three optional clipped sine and cosine waveforms or patterns to generate three correlated signals (e.g., c1, c2, c3); δ) generating a first error signal (e.g., Idc_c), a second error signal (e.g., Qdc_c), and a first scaled signal (e.g., Gmm_c) by scaling and integrating the correlated signals (e.g., c1, c2, c3).

[0052] In an embodiment, the multiple feedback signals further include: a second scaled signal (e.g., Gmm2_c); and step e) further includes: ε) correlating the fifth signal (e.g., s5) with a fourth optional clipped sinusoidal waveform or pattern to generate a fourth correlated signal (e.g., c4); ζ) generating a second scaled signal (e.g., Gmm2_c) based on the integration of the fourth correlated signal (e.g., c4).

[0053] In an embodiment, the angle calculation block is configured to determine (eg calculate) the angular position (eg, ).

[0054] According to another aspect, the invention also relates to a computer program product comprising executable instructions for performing the method according to the fifth aspect when executed on the above-mentioned sensor circuit.

[0055] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not just as explicitly set out in the claims.

[0056] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A high-level block diagram of a circuit that can be used in embodiments of the present invention is shown. The circuit receives two sinusoidal signals of approximately the same amplitude (with a tolerance of ±20%) and phase shifted by approximately 90° (with a tolerance of ±20°) and provides an angular position signal. The circuit includes three main blocks: a signal correction block, an angle calculation block, and a feedback block. The feedback signal is derived from the angular position signal and is injected into the signal correction block located upstream of the angle calculation block. The circuit is capable of reducing the effects of signal offsets of the input signals and amplitude variations between the input signals.

[0058] Figure 2 is a high-level block diagram of another circuit that may be used in embodiments of the present invention, which may be viewed as Figure 1 A variation of the circuit. The circuit is further capable of reducing the effects of crosstalk between signals.

[0059] Figure 3 Shows Figure 1 Specific example of a circuit of , which shows that the feedback block may include a derivation block, a DC removal block and multiple correlators, scalers and integrators.

[0060] Figure 4 (a) to Figure 4 (d) shows illustrative waveforms to illustrate some of the principles used in the feedback box.

[0061] Figure 5 Shows Figure 2 Specific example of a circuit, which shows that the signal correction block may further include a circuit for reducing crosstalk between input signals, and shows that the feedback block provides an additional feedback signal. Optionally, the circuit may also include a triple amplifier and a Clarke transform block.

[0062] Figure 6 Shows Figure 5 A variation of the circuit of is configured to allow the correlation to start with a delay to allow the high pass filter to stabilize.

[0063] Figure 7 A flow chart showing a method for determining the angular position of a rotating object based on two sinusoidal signals having substantially the same (±20%) amplitude and a phase shift of approximately 90° (±20°) is shown. Figures 1 to 3 and Figures 5 and 6 Any one of the circuits in the may be executed.

[0064] Figure 8 A block diagram of an angle sensor system comprising a permanent magnet and a sensor circuit as described above is shown.

[0065] Fig. 9 A block diagram of an angle sensor system including a sensor circuit as shown above, a printed circuit board having a plurality of coils, and a conductive target mountable to a motor shaft is shown.

[0066] The drawings are schematic and non-limiting. In the drawings, for illustrative purposes, the size of some of the elements may be exaggerated and not drawn to scale. Any reference numerals in the claims should not be interpreted as limiting the scope. In different drawings, the same or similar reference numerals (e.g., the same module 100) generally refer to the same or similar elements. DETAILED DESCRIPTION

[0067] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims.

[0068] The terms first, second, etc. in the specification and in the claims are used to distinguish between similar elements and not necessarily to describe a sequence in time, space, level, or in any other manner. It should be understood that the terms so used are interchangeable where appropriate, and that the embodiments of the invention described herein are capable of operating in a different sequence than described or illustrated herein.

[0069] The terms top, bottom, etc. in the specification and claims are used for descriptive purposes and not necessarily for describing relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the invention described herein are capable of operation in orientations other than those described or illustrated herein.

[0070] It is to be noted that the term "comprising" used in the claims should not be interpreted as being limited to the means listed thereafter; it does not exclude other elements or steps. Thus, the term should be interpreted as specifying the presence of the stated features, integers, steps or components 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 stating a device comprising means "A and means B" should not be limited to devices consisting only of components A and B. This means that the only relevant components of the device in terms of the present invention are A and B.

[0071] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, but may refer to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner as will be apparent to one of ordinary skill in the art from this disclosure.

[0072] Similarly, it should be understood that in the description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the present disclosure and assisting in understanding one or more of the various inventive aspects. However, this disclosure method should not be interpreted as reflecting an intention that the claimed invention requires more features than those expressly recited in each claim. On the contrary, as reflected in the appended claims, inventive aspects reside in fewer features than all of the features of a single preceding disclosed embodiment. Therefore, the claims appended to the detailed description are hereby expressly incorporated into the detailed description, with each claim itself representing a separate embodiment of the present invention.

[0073] In addition, although some embodiments described herein include some features included in other embodiments but do not include other features included in other embodiments, as will be understood by those skilled in the art, the combination of features of different embodiments is intended to fall within the scope of the present invention and form different embodiments. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

[0074] In the description provided herein, numerous specific details are set forth. However, it is to be understood that embodiments of the present invention may be implemented without these specific details. In other instances, well-known methods, structures, and techniques are not shown in detail to avoid obscuring an understanding of this description.

[0075] In the context of the present invention, the formulas arctan(x / y), atan2(x,y), arccot(y / x) are considered equivalent.

[0076] In this document, the terms "integrator" and "accumulator" actually refer to the same function, but the term "integrator" is generally used when describing the implementation in analog hardware and / or the continuous-time domain, while the word "accumulator" is generally used when describing the implementation of this function in the discrete-time domain (for example, in digital hardware or software).

[0077] Likewise, the terms "scaler" and "multiplier" actually refer to the same function.

[0078] The present invention relates to angular position sensor systems and methods, and more particularly to systems and methods for calculating the angular position of a rotating object that generates or modulates a magnetic field. The principles of the present invention are applicable to systems including a sensor device and a permanent magnet that can rotate relative to the sensor device, and to an inductive angular position sensor system.

[0079] Reference is now made to the drawings.

[0080] Figure 1 A high-level block diagram of a circuit 100 that may be used in an angular position sensor device or system is shown.The circuit 100 receives two sinusoidal signals Isig, Qsig having approximately the same amplitude and being phase-shifted by approximately 90° relative to each other.

[0081] As we all know, if the input signals Isig, Qsig have exactly the same amplitude and will be exactly 90° phase shifted, they will be called "quadrature signals" and the angular position can be easily determined using the inverse tangent function or atan2 function However, if the amplitudes of the two input signals are not exactly the same, or if the two signals are not exactly 90° phase shifted, or if one or both of the two signals are offset from zero, or any combination of the above, the inverse tangent function will not provide the correct angular position.

[0082] However, in many systems, the two input signals Isig, Qsig may not have exactly the same amplitude, but the ratio of the signal amplitudes may be a value in the range from 80% to 120% or from 90% to 110%; and / or the two signals may not be phase-shifted by exactly 90°, but by an angle in the range from 80° to 100° or by an angle in the range from 85° to 95°; and / or the respective DC values ​​of the two input signals may not be 0.0, but may be offset by a value in the range of -10% to +10% of their respective amplitudes, and simply applying the inverse tangent function will provide an incorrect angular position. Various reasons may cause such anomalies. For example, in the case of an inductive angular position sensor, the layout of the coil may not be perfect, or the rotating target may be tilted relative to the PCB containing the coil, or there may be an unwanted metal object at the location of the PCB, etc. One of the objects of the present invention is to improve the accuracy of angular position of such systems, particularly when the object is rotating at a substantially constant angular velocity (in which case the angular output should vary linearly with time), and / or when the object is accelerating at a substantially constant angular acceleration.

[0083] The present invention provides a method for determining the angular position of an object (e.g., a permanent magnet 885 or a conductive target 981) when it is rotated relative to a sensor circuit. Sensor circuits (see e.g. Figure 8 800 or Fig. 9 900 in the figure). The object may be configured to generate or modulate a magnetic field. The sensor circuit 800, 900 includes:

[0084] a) A first sensor 871, 971 (eg, a first Hall element, a first MR element, a first receiver coil), configured to measure a first characteristic of the magnetic field and provide a first sensor signal (eg, Figure 8 or Fig. 9 ss1 in );

[0085] a) A second sensor 872, 972 (eg, a second Hall element, a second MR element, a second receiver coil) configured to measure a second characteristic of the magnetic field and provide a second sensor signal (eg, Figure 8 or Fig. 9 ss2 in );

[0086] and the processing circuits 860, 960 or 100, 200, 300, 500, 600 showing the processing circuits in more detail.

[0087] The processing circuit 100 comprises:

[0088] c) A signal correction block 110 configured to receive the first and second sensor signals (e.g., ss1, ss2) or signals (e.g., Isig, Qsig) derived therefrom (e.g., after sensitivity correction or after demodulation and / or Clarke transformation). The signal correction block 100 is further configured to receive a plurality of feedback signals (e.g., Idc_c, Qdc_c, Gmm_c), and to provide a first corrected signal Iadj and a second corrected signal Qadj based on the input signal and the feedback signal. The first corrected signal has a first amplitude, and the second corrected signal has a second amplitude substantially equal to the first amplitude. Depending on the implementation, the first and second corrected signals may also have reduced crosstalk. The processing circuit 100 further includes:

[0089] d) Angle calculation block 120 configured to receive the first and second corrected signals Iadj, Qadj and to determine the angular position signal as a function of the first and second corrected signals Iadj, Qadj (e.g. as an arctangent function of the ratio of the first and second corrected signals) The processing circuit 100 further comprises:

[0090] e) A feedback block 130 configured to receive the angular position signal And based on the angular position signal Generate or extract angular position signals from The plurality of feedback signals (eg, Idc_c, Qdc_c, Gmm_c) are derived.

[0091] from Figure 1 As can be seen, the processing circuit 100 comprises a closed loop, wherein a plurality of feedback signals are derived from a single signal (i.e. from the angle value) and fed back to a signal correction block 110 located upstream of the angle calculator block 120. This is in stark contrast to a solution in which the angle value is calculated in an open loop, which value is then corrected in a post-processing circuit.

[0092] Figure 1 The diagrams show block diagrams that may be implemented in hardware (eg, using analog and / or digital circuits), or in software, or partly in hardware and partly in software.

[0093] In some embodiments, the "processing circuit" 860, 960 may include a programmable processor, such as a digital signal processor (DSP), and the functions of the signal correction block 110, the angle calculator block 120 and the feedback block 130 are performed by software instructions executed by the programmable processor. Figure 1 Can also be thought of as a "signal flow graph" rather than a hardware block diagram.

[0094] exist Figure 1 In the example shown, the plurality of feedback signals include: a first error signal Idc_c, a second error signal Qdc_c, and a first scaling signal Gmm_c, which are respectively used to correct the signal value (e.g., DC level) and to reshape the waveform of the first input signal Isig, to correct the DC value and to reshape the waveform of the second input signal Qsig, and to correct the amplitude of the second input signal Qsig. It will be further explained how these signals can be generated (e.g., see Figure 3 and Figure 4 ).

[0095] exist Figure 1 In the specific implementation shown, the signal correction block includes: a first combiner "∑1", arranged to receive and combine the first input signal Isig and the first error signal Idc_c (e.g., summing or subtracting), thereby providing a first combined signal s1; and a second combiner "∑2", arranged to receive and combine the second input signal Qsig and the second error signal Qdc_c (e.g., summing or subtracting), thereby providing a second combined signal s2; and a first scaler "A1", arranged to scale the second combined signal s2 using the first scaling signal Gmm_c (e.g., by multiplying these signals), thereby providing a third signal s3. It can be seen that in Figure 1 In the example of , the first signal s1 and the third signal s3 are input to the angle calculator block 120 .

[0096] In the processing circuit 100, the angle calculator block 120 is configured to determine the angular position as a function of the signals s1, s3. This may be achieved or illustrated by calculating the inverse tangent function of the ratio of the signals, or by using a look-up table (optionally with interpolation) or any other suitable means.

[0097] In a practical implementation, the combiners Σ1, Σ2 may be implemented as sum or subtraction blocks, or sum or subtraction instructions; and the scaler A1 may be implemented by a multiplier block (eg, a 16-bit floating point multiplier or a fixed point multiplier).

[0098] Figure 2 2 shows a high-level block diagram of another processing circuit 200 that may be used in embodiments of the present invention. The processing circuit 200 is Figure 1 A variation of the processing circuit 100 of FIG. 1 and mutatis mutandis Figure 1 Everything mentioned applies here as well. Figure 2 The processing circuit 200 and Figure 1The main difference between the processing circuit 100 and the circuit 200 is that the circuit 200 is also capable of reducing the crosstalk (if any) between the input signals Isig, Qsig.

[0099] exist Figure 2 In a specific implementation of the invention, the plurality of feedback signals further include: a second scaling signal Gmm2_c, the second scaling signal Gmm2_c may be obtained as follows: Figure 5 The feedback block 230 described in more detail in ; and the signal correction block 210 also includes: a second scaler "A2", arranged to scale the third signal s3 using the second scaling signal Gmm2_c (e.g., by multiplying these signals); a third combiner "∑3", arranged to combine the output of the second scaler "A2" and the first combined signal s1 (e.g., by summing or subtracting), thereby providing a first corrected signal "Iadj"; a third scaler "A3", arranged to scale the first combined signal s1 using the second scaling signal Gmm2_c (e.g., by multiplying these signals); and a fourth combiner "∑4", arranged to combine the output of the third scaler "A3" and the third signal s3 (e.g., by summing or subtracting), thereby providing a second corrected signal Qadj. It can be said that the signals Iadj and Qadj are linear combinations of the signals s1 and s3.

[0100] An advantage of this embodiment is that crosstalk between signals can be reduced or substantially eliminated. It has been found that this may be particularly interesting in the case where the input signals Isig and Qsig are derived from a three-phase signal using a transformation (e.g. Clarke transformation), such as Figure 5 and Figure 6 Will be further described in .

[0101] Figure 3 Shows Figure 1 The signal correction block 310 may be the same as block 110 , and the angle determination block 320 may be the same as block 120 .

[0102] Figure 3 The main purpose of is to show more details about the feedback box 330 .

[0103] It can be seen that the feedback block 330 includes a derivation block 331 which is arranged to receive the angle signal and is configured to determine the phase , and provides the time derivative as a fourth signal s4.

[0104] The feedback block 330 further includes a DC removal block 332, which can be implemented as, for example, a high-pass filter, but the present invention is not limited thereto and other techniques can also be used. The DC removal block 332 is configured to receive the fourth signal s4, to remove its DC component, for example, by high-pass filtering the signal, and to provide the filtered signal as the fifth signal s5.

[0105] The feedback block 330 further comprises a plurality of correlators 333a, 333b, 333c configured to receive the fifth signal (s5) and correlate the fifth signal (s5) with each of three optionally clipped sine and cosine waveforms or patterns to generate three correlated signals (c1, c2, c3).

[0106] The feedback box 330 further includes: a plurality of scalers 334a, 334b, 334c and integrators or accumulators 335a, 335b, 335c, configured to generate a first error signal Idc_c, a second error signal Qdc_c and a first scaled signal Gmm_c by respectively scaling and integrating or accumulating each of the three related signals c1, c2, c3.

[0107] exist Figure 3 The bottom of the figure shows the waveforms of sine and cosine waveforms or patterns with optional peak clipping. The values ​​of these signals are +1 or 0 or -1, depending on the angle These waveforms or patterns can be stored in a lookup table, or can be configured to test whether the angle value is less than or greater than Figure 3 The boundaries of the various regions of the waveform shown are generated "dynamically" by a small number of comparators.

[0108] For the sake of completeness, it should be noted that Figure 3 The signal used in block 330 is: Peak Shaving Peak Shaving For example, peak shaving for:

[0109] if is +1 for values ​​in the range 0° to 45°, or +1 for values ​​in the range 315° to 360°,

[0110] if is 0 if it is a value in the range of 45° to 135° or 225° to 315°,

[0111] if is a value in the range of 135° to 225°, then it is -1, as shown in the figure.

[0112] In other words, for peak shaving And for peak shaving The angular range is divided into 90° wide areas; The angular range is divided into 45° wide areas as shown in the figure.

[0113] The use of clipped sine and cosine signals is a major advantage because by doing so, the correlators 333a to 333c do not actually need to be multipliers, it is sufficient that the accumulators can selectively add and subtract signals. This means that the correlators can be implemented by addition or subtraction rather than multiplication, which is generally faster and uses less energy. However, the invention will also work when the sine and cosine signals are not clipped.

[0114] It is also found that the scalers 334a to 334c need not be multipliers, but can and are preferably implemented using shift registers, again saving silicon area and / or processing time and / or processor power. It can be seen that the signals c1 and c2 are preferably "multiplied" by a predefined value Kdc, and the signal c3 is preferably "multiplied" by a predefined value Kmm.

[0115] The loop gain and the duration of the stabilization process depend on the factors Kdc and Kmm. When the values ​​of Kdc and Kmm are chosen as 1 / 2 N and 1 / 2 M When representing a value of , where N and M are integer values, the multiplication can be avoided and replaced with a bit shift operation.

[0116] Figure 4 (a) to Figure 4 (d) shows an illustrative waveform to illustrate the Figure 3 Note that these waveforms are shown as time-continuous waveforms (continuous time), but as already mentioned above, the present invention is not limited thereto and the processing circuits described in this application can also be implemented in the digital domain (discrete time).

[0117] Figure 4 (a) In particular, curve 401 shows the angle signal as a function of time Assume that the object rotates at a constant speed and assume that the input signals Isig and Qsig are not perfectly orthogonal signals, but have one or more of the following disadvantages: slightly different amplitudes, different DC values ​​from zero, and slightly different phase shifts from 90°. Curve 401 shows the calculated angular signal in the case of an open loop system or in the case where the feedback loop has not yet stabilized. What it might look like. It can be seen that curve 401 is not perfectly straight, but (in the example) looks like a sinusoidal signal superimposed on a straight line.

[0118] Figure 4(b) shows what the time derivative of the angular signal (referred to above as fourth signal s4) might look like. In the example, signal s4 looks like a cosine signal with a constant (ie a DC value) superimposed.

[0119] Figure 4 (c) shows what the fifth signal may look like as the fourth signal s4 after removing the DC value (eg by high pass filtering). As described above, this fifth signal s5 is related to the optionally clipped sine and cosine signals, which have the following characteristics: Figure 3 or Figure 5 or Figure 6 The waveform is shown at the bottom.

[0120] The techniques proposed by the present invention are based at least in part on the recognition that offsets in the input signal result in fundamental harmonics in the angle error.

[0121] Assuming the object (e.g., a magnet or conductive target) is rotating at a constant speed, the loop will be stable and the angular signal will be "linearized," meaning that the waveform looks more like line segment 402. Thus, the system with a closed loop system has improved accuracy compared to an open loop system.

[0122] Figure 5 Shows Figure 2 A more detailed version of the circuit can also be viewed as Figure 3 variants. Figure 5 The processing circuit 500 and Figure 3 The main differences between the processing blocks 300 of FIG. 5 and FIG. 3 are as follows: the processing block 530 is configured to generate a fourth feedback signal (i.e., the second scaled signal Gmm2_c), which is fed back to the signal correction block 510, where the signal is used to reduce crosstalk, as described above (see Figure 2 ). The feedback signal Gmm2_c is obtained by combining the fifth signal s5 with a signal having Figure 5 The bottom waveform is shown with optional clipping The fourth correlation signal c4 is generated by signal correlation, thereby forming a fourth correlation signal c4, which is scaled by the scaler 534d using the scaling factor Kmm and integrated (or accumulated) using the integrator or accumulator 535d.

[0123] In the case of an inductive angle sensor (e.g. Fig. 9 In the case of a 3D image sensor (as shown in Figure 1), the sensor signals can be three modulated AC signals, which after demodulation produce three sinusoidal signals. Ideally, these signals have exactly the same amplitude, are 120° phase-shifted relative to each other, and have a 0DC value. However, in practice, this is only approximately correct.

[0124] Assuming the demodulated three-phase signals are: In0, In1 and In2, then the differential amplifier block 545 may generate the following signals:

[0125] D01=In0–In1[1]

[0126] D12=In1–In2[2]

[0127] D21=In2–In0[3]

[0128] Where In0, In1, In2 are demodulated signals, and D01, D12 and D21 are differential signals,

[0129] And the Clarke transform block 540 can convert these signals into two signals Isig, Qsig according to the following formula:

[0130] Isig=D01-0.5*(D12+D20)[4]

[0131] Qsig=(D12+D20)*1 / 2√3[5]

[0132] Blocks 545 and 540 are well known in the art and may be added upstream of signal correction block 510 if they are not already present in the system, e.g., as Fig. 9 A portion of the "Receiver and Demodulation Circuit" 976 is shown.

[0133] Figure 6 Shows Figure 5 A variation of the circuit in which the correlation start is delayed to allow the high-pass filter to stabilize. Without this delay, the correlation with the high-pass setting curve would generate a deviation of the correction values ​​Idc_c, Qdc_c, thus increasing the error. This error would disappear later, but would extend the total settling time.

[0134] To overcome the ripple on the correction value, the amount of filtering of the correlator output can be increased by averaging the correlation signal over one electrical rotation cycle. In this way, the ripple generated by multiplying the waveform or pattern with a constant dphi value can be completely suppressed. For simplicity, accumulation can be performed only over one cycle, without having to divide by the number of samples. For example, this can be achieved by adding multiple accumulators and by a "start detection box" 631 configured to detect a new cycle and generate a "start-detection" signal for resetting the first set of accumulators. These accumulators are timed by the system clock (e.g., once every Tstep=1.3μs). At the "start of a new cycle", the second set of accumulators (also called "loop filter accumulators") will take over the values ​​of the first set of accumulators so that their values ​​are updated at the time indicated by the "start detection" signal at the beginning of each new rotation. In this way, error accumulation is avoided.

[0135] In other words, the first stage of accumulators (or integrators) averages the correlation results for one electrical rotation. At the end of a rotation, these accumulator values ​​are passed via the gain block to the second stage of accumulators (or integrators). Afterwards, the accumulators (or integrators) of the first stage are reset and accumulation (or integration) starts in the next rotation. The first set of accumulators (or integrators) therefore works at the rate of the phase-advanced samples. The second stage of accumulators (or integrators) acts as a loop filter for the regulation loop. They are updated at the rate at which detections are started, and therefore only once per (electrical) rotation. This is in contrast to Figure 5 This is in contrast to the block diagram shown in , where the loop (and correction value) is updated with the rate of incoming phase samples.

[0136] Figure 7 A flow chart of a method 700 is shown for determining the angular position of a rotating object based on two sinusoidal signals having substantially the same amplitude (deviating by at most 20%, or at most 10%, or at most 5%) and phase-shifted by 90°±20°, 90°±10°, or 90°±5° The method may be directed to a system including at least two magnetic sensors (eg, Hall elements, MR elements, receiver coils), and including: Figures 1 to 3 or Figures 5 and 6 The sensor circuit of any of the processing circuits shown in the accompanying drawings is implemented. Examples of such sensor circuits are shown in Figures 8 to 9 Shown in.

[0137] The method 700 comprises the following steps:

[0138] a) measuring 701 a first characteristic of the magnetic field (eg a first magnetic field component or a first magnetic field gradient) and providing a first sensor signal ss1 or a signal derived therefrom as a first input signal Isig;

[0139] b) measuring 702 a second characteristic of the magnetic field (e.g. a second magnetic field component or a second magnetic field gradient) and providing a second sensor signal ss2 or a signal derived therefrom as a second input signal Qsig;

[0140] c) correcting 703 the first input signal Isig and the second input signal Qsig using the plurality of feedback signals Idc_c, Qdc_c, Gmm_c and providing a first corrected signal Iadj having a first amplitude and a second corrected signal Qadj having a second amplitude substantially equal to the first amplitude and optionally also having reduced crosstalk;

[0141] d) determining 704, for example, calculating the angular position signal as a function of the first corrected signal Iadj and the second corrected signal Qadj (for example, using an inverse tangent function of the ratio of the first corrected signal Iadj and the second corrected signal Qadj)

[0142] e) Based on the angular position signal To generate 705 the multiple feedback signals Idc_c, Qdc_c, Gmm_c.

[0143] Figure 8 and Fig. 9 It is provided for completeness only.Since all blocks except processing circuits 860 and 960 are known in the art, a brief description thereof will suffice.

[0144] Figure 8An angle sensor system is shown that includes a sensor circuit 800 and a permanent magnet 885 that is rotatable relative to the sensor circuit 800. The sensor circuit 800 is preferably implemented as an integrated semiconductor device (also referred to as a "chip"). The permanent magnet 885 can be a bipolar magnet, a quadrupole magnet, or a magnet that includes more than four poles. The magnet 885 can be rotated around an axis of rotation, and the sensor circuit 800 is configured to determine its angular position. Many arrangements of magnetic sensors for measuring a first magnetic signal that is a sine function of a mechanical position and a second magnetic signal that is a cosine function of the mechanical position are known in the art. The first sensor may, for example, include a first sensor element 871, and the second sensor may, for example, include a second sensor element 872, such as a horizontal Hall element, a vertical Hall element, a magnetoresistive element (MR element), etc. The biasing and readout circuits of such magnetic sensor elements are well known in the art and are not the focus of the present invention, and therefore do not need to be explained in more detail here. It can be said that the Hall element is usually biased by a current source or a voltage source, while the MR element is incorporated in a Wheatstone bridge. Relevant to the present invention, the first sensor provides a first sensor signal ss1 and the second sensor provides a second sensor signal ss2, which behave more or less like sine and cosine signals, but need not be perfectly orthogonal signals as described above. These signals may also be digitized using an analog-to-digital converter ADC and provided to a processing circuit 860 where they are further processed as described above. Figure 8 In the system, the sensors provide two-phase signals, which are not AM modulated and do not require Clarke transformation.

[0145] Fig. 9 An angle sensor system is shown that includes a sensor circuit 900 that includes three sensors implemented in the form of receiver coils (not explicitly shown) on a printed circuit board 983 together with a transmitter coil. The transmitter coil and the receiver coil are inductively coupled to each other. The amount of coupling can be affected by a conductive object 981 (also called a "target") that is rotatably mounted near the transmitter coil and the receiver, whose angular position is to be determined. The target 981 can be connected to the shaft of a motor 980.

[0146] In this embodiment, the sensor circuit 900 typically includes an excitation circuit 975 for injecting AC current into the transmitter coil to induce eddy currents in the target 981. The sensor circuit 900 also includes three magnetic sensors 971, 972, 973 in the form of three receiver coils. The receiving coils will generate AC signals caused by the eddy currents in the target and the currents in the transmitting coils. These signals are demodulated in a known manner to obtain three sinusoidal signals, which ideally have exactly the same amplitude, a DC value of exactly zero, and a phase shift of exactly 120°. As mentioned above, in practice this is only approximately correct.

[0147] exist Fig. 9 In the block diagram of , the receiver and demodulator circuit 976 also includes one or more analog-to-digital converters (ADCs) and circuits for performing Clarke transforms, thereby generating two signals v1, v2 that are provided to the processing circuit. Figure 5 and Figure 6 As implied, Clarke transform blocks 540, 640 may be part of processing circuit 960. In either case, in sensor circuit 900, the three-phase signal is converted to a two-phase signal and then processed in the manner described above (e.g., as Figure 2 or Figure 5 or Figure 6 as described) for further processing.

[0148] The simulations were performed using a time step of 13 μs corresponding to a sampling frequency of about 77 MHz, but of course the invention is not limited thereto and other time steps larger or smaller than 13 μs may also be used, for example, time steps ranging from 5 μs to 100 μs or from 25 μs to 100 μs.

[0149] Simulations were performed on a three-phase signal with a DC offset and a gain mismatch of 10%, with a mechanical speed of 20 to 500 revolutions per second and a number of poles equal to 5, not only for an object rotating at a constant speed, but also for an object with a linear increase in speed (i.e., constant acceleration). It was found that the offset correction value Kdc=0.0039 and the gain mismatch correction value Kmm=0.0039 (combined with a time step Tstep=13 μs and a delay of about 52 ms) provide a relatively fast stabilization of the closed-loop system after about 100 to 150 ms. When the loop is stabilized, the angular error is reduced from about ±10° to a value less than ±1° if the object speed is constant.

[0150] The values ​​of Tstep, Kdc, and Kmm are not critical, but the values ​​of Kdc and Kmm preferably scale approximately proportionally with Tstep, so if Tstep is doubled, then Kdc and Kmm preferably also approximately double.

[0151] The high pass filter may be implemented, for example, as an IIR filter (Infinite Impulse Response). Such filters are well known in the art and therefore require no further explanation here.

[0152] Simulations show that for speeds up to about 1000 rev / s 2 acceleration, or even up to about 2500rev / s 2 acceleration, or even up to about 5000rev / s 2 Or even up to about 7500rev / s 2 The loop remains stable for accelerations of 100°. Small angular errors of less than about ±2° or about ±0.5° are found during acceleration, depending on the values ​​of Kdc and Kmm.

[0153] Typical values ​​of Kdc and Kmm are: Kdc = Kmm = 1 / 256 (about 0.0039), or Kdc = Kmm = 1 / 512 (about 0.002), or Kdc = Kmm = 1 / 1024 (about 0.001). These values ​​apply to angular velocities ranging from about 4 rev / s to 3200 rev / s (mechanical), with a settling time corresponding to 10 electrical revolutions of less than about 0.5 s, and with accelerations up to 8000 rev / s in 2 s. 2 Note, however, that the values ​​of Kdc and Kmm do not need to be the same value, but may be different.

Claims

1. A sensor circuit (800; 900) for determining an angular position of an object (885; 983) when it is rotated relative to the sensor circuit, wherein the object is configured to generate or modulate a magnetic field, the sensor circuit (800; 900) comprising: a) a first sensor (871; 971) configured to measure a first characteristic of the magnetic field and to provide a first sensor signal (ss1); b) a second sensor (872; 972) configured to measure a second characteristic of the magnetic field and to provide a second sensor signal (ss2); c) a signal correction block (110; 210; 310; 510; 610) configured to receive the first sensor signal (ss1) or a signal derived therefrom as a first input signal (Isig), and the second sensor signal (ss2) or a signal derived therefrom as a second input signal (Qsig), and a plurality of feedback signals (Idc_c, Qdc_c, Gmm_c); and configured to provide a first corrected signal (Iadj) having a first amplitude and a second corrected signal (Qadj) having a second amplitude substantially equal to the first amplitude; d) an angle calculation block (120; 220) configured to receive the first corrected signal (Iadj) and the second corrected signal (Qadj), and to determine the angular position signal (φ) based on a ratio of the first corrected signal (Iadj) and the second corrected signal (Qadj); e) a feedback block (130; 230; 330; 530; 630) configured to receive the angular position signal (φ) and to generate the plurality of feedback signals (Idc_c, Qdc_c, Gmm_c) based on the angular position signal (φ) so that the angular position has improved linearity; It is characterized in that - the plurality of feedback signals include: a first error signal (Idc_c), a second error signal (Qdc_c) and a first scaling signal (Gmm_c); and -The signal correction frame includes: i) a first combiner (Σ1) arranged to receive and linearly combine said first input signal (Isig) and a first error signal (Idc_c) thereby providing a first combined signal (s1); and ii) a second combiner (Σ2) arranged to receive and linearly combine said second input signal (Qsig) and a second error signal (Qdc_c) to provide a second combined signal (s2); and iii) a first sealer (A1) arranged to scale the second combined signal (s2) using the first scaled signal (Gmm_c) thereby providing a third signal (s3); wherein the first corrected signal (Iadj) is a first combined signal (s1) or is derived from the first combined signal (s1) and the third signal (s3); and Wherein the second corrected signal (Qadj) is the third signal (s3), or is derived from the first combined signal (s1) and the third signal (s3).

2. The sensor circuit (800; 900) according to claim 1, The plurality of feedback signals further include: A second scaled signal (Gmm2_c); And wherein, the signal correction frame (210; 510; 610) further comprises: iv) a second sealer (A2) arranged to scale the third signal (s3) using the second scaled signal (Gmm2_c); v) a third combiner (Σ3) arranged to linearly combine the output of the second scaler (A2) and the first combined signal (s1) to provide the first corrected signal (Iadj); vi) a third sealer (A3) arranged to scale the first combined signal (s1) using the second scaled signal (Gmm2_c); vii) a fourth combiner (Σ4) arranged to linearly combine the output of the third sealer (A3) and the third signal (s3) to provide the second corrected signal (Qadj).

3. The sensor circuit (800; 900) according to claim 1 or 2, The plurality of feedback signals include: A first error signal (Idc_c), a second error signal (Qdc_c), and a first scaling signal (Gmm_c); and The feedback box (330; 530; 630) includes: a) a derivation block (331), the derivation block (331) being configured to receive the angular position signal (φ) and to determine a time derivative signal of the angular position signal (φ), thereby generating a fourth signal (s4); β) a DC removal block (332) configured to receive the fourth signal (s4) and remove a DC level of the fourth signal (s4) to generate a fifth signal (s5); γ) a plurality of correlators (333a, 333b, 333c) configured to receive the fifth signal (s5) and correlate the fifth signal (s5) with each of three sine and cosine waveforms or patterns to generate three correlated signals (c1, c2, c3); δ) a plurality of scalers (334a, 334b, 334c) and integrators (335a, 335b, 335c), configured to generate the first error signal (Idc_c), the second error signal (Qdc_c) and the first scaled signal (Gmm_c) by respectively scaling and integrating each of the three correlation signals (c1, c2, c3).

4. The sensor circuit (800; 900) of claim 3, wherein the three sine and cosine waveforms or patterns are three clipped sine and cosine waveforms or patterns.

5. The sensor circuit (800; 900) according to claim 3, The plurality of feedback signals further include: A second scaled signal (Gmm2_c); and wherein the feedback box (530; 630) is further configured to: ε) correlating the fifth signal (s5) with a fourth sinusoidal waveform or pattern to generate a fourth correlated signal (c4); z) generating the second scaling signal (Gmm2_c) based on the integration of the fourth correlation signal (c4).

6. The sensor circuit (800; 900) of claim 5, wherein the fourth sinusoidal waveform or pattern is a fourth clipped sinusoidal waveform or pattern.

7. The sensor circuit (800; 900) according to claim 1 or 2, Wherein the angle calculation block (120; 220) is configured to determine the angular position (φ) using an inverse tangent function of the ratio of the first corrected signal and the second corrected signal (Iadj, Qadj).

8. An angular position sensor system comprising: - A sensor circuit (800) according to any one of claims 1 to 7; - A rotatable object, and a permanent magnet (885) connected to said object.

9. An angular position sensor system, comprising: - A sensor circuit (900) according to any one of claims 1 to 7; - a printed circuit board (983) comprising a transmitter coil and at least two receiver coils; - A rotatable object in the form of a conductive target (981).

10. The angular position sensor system according to claim 9, The sensor circuit (900) further comprises: - a demodulator for demodulating the signals acquired from the three receiver coils; - a Clarke Transform block arranged to convert the demodulated signal into said first input signal and said second input signal.

11. A method (700) of determining an angular position (φ) of an object rotating relative to a sensor circuit, the object being configured to generate or modulate a magnetic field, the method comprising the steps of: a) measuring (701) a first characteristic of the magnetic field and providing a first sensor signal (ss1) or a signal derived therefrom as a first input signal (Isig); b) measuring (702) a second characteristic of the magnetic field and providing a second sensor signal (ss2) or a signal derived therefrom as a second input signal (Qsig); c) correcting (703) the first input signal (Isig) and the second input signal (Qsig) using a plurality of feedback signals (Idc_c, Qdc_c, Gmm_c) and providing a first corrected signal (Iadj) having a first amplitude and a second corrected signal (Qadj) having a second amplitude substantially equal to the first amplitude; d) determining said angular position signal (φ) based on a ratio of said first corrected signal (Iadj) and said second corrected signal (Qadj); e) generating (705) the plurality of feedback signals (Idc_c, Qdc_c, Gmm_c) based on the angular position signal (φ); It is characterized in that - the plurality of feedback signals include: a first error signal (Idc_c), a second error signal (Qdc_c) and a first scaling signal (Gmm_c); And wherein step c) comprises: i) linearly combining the first input signal (Isig) and the first error signal (Idc_c) to generate a first combined signal (s1); and ii) linearly combining the second input signal (Qsig) and the second error signal (Qdc_c) to generate a second combined signal (s2); and iii) scaling the second combined signal (s2) using the first scaling signal (Gmm_c) to generate a third signal (s3); iv) providing said first corrected signal (Iadj) as said first combined signal (s1), or as a signal derived from said first combined signal (s1) and said third signal (s3); v) providing said second corrected signal (Qadj) as said third signal (s3), or as a signal derived from said first combined signal (s1) and said third signal (s3).

12. The method (700) according to claim 11, The plurality of feedback signals further include: The second scaled signal (Gmm2_c), And wherein step c) further comprises: iv) providing the first corrected signal (Iadj) as a signal obtained by scaling the third signal (s3) with the second scaling signal (Gmm2_c) and by v) linearly combining the resulting signal with the first combined signal (s1); vi) providing the second corrected signal (Qadj) as a signal obtained by scaling the first combined signal (s1) with the second scaled signal (Gmm2_c) and by vii) linearly combining the resulting signal with the third signal (s3).

13. The method (700) according to claim 11 or 12, The plurality of feedback signals include: A first error signal (Idc_c), a second error signal (Qdc_c), and a first scaling signal (Gmm_c); And wherein step e) comprises: α) determining a time derivative signal of the angular position signal (φ) to generate a fourth signal (s4); β) removing a DC level from the time derivative signal (s4) thereby generating a fifth signal (s5); γ) correlating the fifth signal (s5) with each of three sine and cosine waveforms or patterns, thereby generating three correlated signals (c1, c2, c3); δ) generating the first error signal (Idc_c), the second error signal (Qdc_c) and the first scaled signal (Gmm_c) by scaling and integrating the correlation signals (c1, c2, c3).

14. The method (700) of claim 13, wherein the three sine and cosine waveforms or patterns are three clipped sine and cosine waveforms or patterns.

15. The method (700) according to claim 13, The plurality of feedback signals further include: A second scaled signal (Gmm2_c); And wherein step e) further comprises: ε) correlating the fifth signal (s5) with a fourth sinusoidal waveform or pattern to generate a fourth correlated signal (c4); z) generating the second scaling signal (Gmm2_c) based on the integration of the fourth correlation signal (c4).

16. The method (700) of claim 15, wherein the fourth sinusoidal waveform or pattern is a fourth clipped sinusoidal waveform or pattern.

17. The method (700) according to claim 11 or 12, Wherein step d) comprises: The angular position (φ) is determined using an inverse tangent function of the ratio of the first and second corrected signals (Iadj, Qadj).

Images