Position sensor

Abstract

Examples include a position sensor for determining the angular position of an electric motor rotor comprising N pole pairs, a vehicle carrying this sensor, a method for determining the angular position of an electric motor rotor, a computer program product, and a non-transient recording medium readable by a computer. Abstract figure: [Fig. 4]

Description

Title of the invention: Position sensor technical field

[0001] This disclosure relates to the field of position sensors. Previous technique

[0002] The control of an electric motor takes into account numerous parameters. The angular position of the electric motor's rotor is one of these parameters.

[0003] The angular position of the electric motor rotor can be determined by several means, including by means of an inductive position sensor. The angular position of the rotor estimated by inductive position sensors may contain an error.

[0004] The present disclosure improves this situation. Summary

[0005] In this regard, a position sensor is proposed for determining an angular position of an electric motor rotor, the sensor comprising: a target adapted to be fixed on the electric motor rotor so that it is driven in rotation with the rotor during its rotational movement; a printed circuit board comprising a primary winding, K secondary windings with K being greater than or equal to 2, and an electrical generator; and at least one signal processing unit; the primary winding surrounding the secondary windings; the secondary windings having a shape adapted to each generate a sinusoidal electrical signal, the generated electrical signals having a predetermined phase shift between them; the electric generator being adapted to deliver a current in such a way as to create an inductive coupling between the primary winding and the secondary windings, the inductive coupling being modulated by the position of the target; the signal processing unit being configured for: to obtain a cosine electrical signal and a sine electrical signal from sinusoidal electrical signals; process the cosine and sine electrical signals to obtain an electrical signal representative of an angular position of the electric motor rotor; and process the electrical signal representative of the angular position of the electric motor rotor to reduce a specific harmonic of this signal, the specific harmonic being determined from the number K of secondary windings.

[0006] Optionally, process the cosine and sine electrical signals to obtain an electrical signal representative of an angular position of the electric motor rotor corresponds to applying a mathematical function atan2 from the cosine and sine electrical signals.

[0007] Optionally, processing the electrical signal representing the angular position of the rotating element to reduce the specific harmonic of this signal includes: subtracting, from the electrical signal representing the angular position, a specific sinusoidal signal having a phase of the form: ph = 2NK + q> with ph corresponding to the phase of the specific sinusoidal signal; N corresponding to a number of pole pairs of the electric motor; K corresponds to the number of secondary windings; and q> corresponds to a determined phase shift.

[0008] Optionally, the determined phase shift is determined from an error signal obtained on a test bench for the position sensor or for a position sensor equivalent to the position sensor.

[0009] Optionally, an amplitude of the specific sinusoidal signal is determined from an amplitude of at least one of the cosine electrical signal and the sine electrical signal.

[0010] Optionally, a memory presenting a lookup table between a plurality of amplitudes associated with at least one of the cosine electrical signal and the sine electrical signal and a plurality of amplitudes associated with the specific sinusoidal signal.

[0011] The application also relates to a vehicle comprising such a position sensor.

[0012] The application further relates to a method for determining an angular position of an electric motor rotor, the process comprising: to obtain a cosine electrical signal and a sine electrical signal from a printed circuit board of a position sensor; process the cosine and sine electrical signals in order to obtain an electrical signal representative of an angular position of the electric motor rotor; process the electrical signal representing the angular position of the electric motor rotor to reduce a specific harmonic of this signal, the specific harmonic being determined from a number K of secondary windings of the position sensor.

[0013] Optionally, processing the electrical signal representing the angular position of the electric motor rotor to reduce the specific harmonic of this signal includes: subtract, from the electrical signal representing the angular position, a specific sinusoidal signal having a phase of the form: ph = 2KN + q>. with ph corresponding to the phase of the specific sinusoidal signal; N corresponding to a number of pole pairs of the electric motor; K corresponds to the number of secondary windings; and q> corresponds to a predetermined phase shift.

[0014] The application further relates to a computer program product comprising instructions for implementing any of the processes presented in this disclosure when that program is executed by a processor.

[0015] Finally, the application relates to a non-transient computer-readable recording medium on which is recorded a program for the implementation of any of the methods presented in this disclosure when this program is executed by a processor. Brief description of the drawings

[0016] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0017] [Fig. 1] schematically represents an example of a position sensor.

[0018] [Fig.2] schematically represents another example of a position sensor angular.

[0019] [Fig.3] schematically represents an example of a vehicle incorporating an angular position sensor.

[0020] [Fig.4] schematically represents an example of a method that can be implemented by a signal processing unit of an angular position sensor.

[0021] [Fig.5] schematically represents another example of a method that can be implemented by a signal processing unit of an angular position sensor.

[0022] [Fig.6] schematically represents yet another example of a process that can be implemented by a signal processing unit of an angular position sensor.

[0023] [Fig.7] schematically represents an example of the architecture of a signal processing unit of an angular position sensor.

[0024] [Fig.8] schematically represents another example of the architecture of a signal processing unit of an angular position sensor.

[0025] [Fig.9] represents an example of an electrical signal of angular position error and an example of a specific sinusoidal signal for compensating this error.

[0026] [Fig. 10] represents the example of the electrical signal of angular position error of [Fig.9] and an example of an electrical error signal corrected from the sinusoidal compensation signal of this error illustrated on [Fig.9]. Description of the implementation methods

[0027] The inventors propose estimating the angular position of a rotating element, for example an electric motor rotor, by using an inductive position sensor. This sensor uses the principle of induction to determine the position of a chosen element, in particular the angular position of the electric motor rotor.

[0028] It should be noted that the terminologies used associated with sensors such as "position sensor", "angular position sensor", "inductive sensor", and "inductive position sensor" will be used interchangeably in this disclosure to refer to a sensor enabling the determination of an angular position of a rotating element using the principle of induction.

[0029] In this case, the inductive sensor creates an inductive coupling between two windings: a primary winding, also called the transmitter winding, and a secondary winding, also called the receiver winding. An inductive target, positioned on the element whose position is to be determined, modulates, according to its position, a magnetic field created by the primary winding. In this way, the currents induced by the magnetic field in the secondary winding are representative of the target's position and, therefore, by extension, representative of the position of the selected element, which can thus be determined by signal processing. More precisely, the magnetic field created by the primary winding causes the generation of eddy currents on the surface of the inductive target, which themselves generate a magnetic field in the opposite direction to that generated by the primary winding.It is this opposing magnetic field that enables the generation of induced currents in the secondary winding, the target's position being determined from these induced currents by signal processing. The inductive position sensor can thus comprise a printed circuit board containing both the windings and the control electronics, a conductive target positioned on the element whose position is to be determined, and a processor. The control electronics generates the electrical signals in the primary winding and processes the induced signals in the secondary windings to obtain sinusoidal signals, known as sine and cosine signals, which are well understood by those skilled in the art. The processor, in turn, determines an electrical signal representing the angular position of the element whose position is to be determined (also called the electrical angle signal in this disclosure) from the sine and cosine signals.

[0030] The inventors have particularly noted that when the inductive sensor comprises a primary winding surrounding at least two secondary windings whose shape corresponds to a projection in polar coordinates into a space bounded by the primary winding of a sinusoidal shape in a Cartesian plane, the intrinsic characteristics of the sensor lead to the formation of current harmonics that introduce an error in the electrical signal of angle determined by the processor. They have also noted that the order of the harmonics that significantly impact the error in the position determined by the processor depends on the number and arrangement of the sensor's secondary windings.

[0031] The inventors have observed, for example, that a first inductive sensor topology comprising a primary winding surrounding only two secondary windings whose shape corresponds to a projection in polar coordinates into a space delimited by the primary winding of a sinusoidal shape in a Cartesian plane, results in the formation of even harmonics of rank equal to or greater than 4 in the electrical signal used to determine the target's position. Furthermore, since the amplitude of the harmonics decreases with their rank, the inventors have noted that the 4th harmonic introduces the largest proportion of the error in the target's position determined by this first sensor topology.

[0032] The inventors also noted that a second inductive sensor topology, comprising a primary winding surrounding only three secondary windings whose shape corresponds to a projection in polar coordinates into a space bounded by the primary winding of a sinusoidal shape in a Cartesian plane, results in the formation of even harmonics of rank equal to or greater than 6 on the signals used to determine the target's position. Furthermore, for this second sensor topology, the inventors identified that the 6th harmonic introduced the largest proportion of the error in the determined target position.The error generated by the second sensor topology on the angular position of the target, carried mainly by the 6th harmonic, is thus less than the error generated by the first sensor topology since its error is, for its part, mainly carried by the 4th harmonic.

[0033] In this application, the term "inductive sensor topology" refers to the shape and arrangement of the primary and secondary windings. In particular, a given sensor topology comprises the same number of secondary windings with the same predetermined phase shift between them, as well as a primary winding that surrounds the secondary windings in the same way (for example, by encircling them).

[0034] The inventors have thus identified solutions that reduce the error of the inductive position sensor by modifying the arrangement and number of primary windings. In particular, it has been described that a topology using three secondary windings introduces even harmonics of order 6 or higher into the angle signal, while the topology using two secondary windings introduces even harmonics of order 4 or higher into the angle signal. However, these solutions, although reducing the error in the target position, are complex to implement because they require defining and manufacturing suitable secondary windings and processing the signals appropriately according to the defined secondary windings. These solutions are therefore costly in terms of research and development. development, and focus on signal processing at the printed circuit board level of the inductive position sensor.

[0035] In this disclosure, the inventors propose an ingenious solution that involves processing the electrical signal representing the angular position of the electric motor rotor to reduce a specific harmonic of this signal. This specific harmonic is determined from the number K of secondary windings of the sensor. This angle signal is determined by a signal processing unit that may be an integral part of the printed circuit board of the inductive position sensor, or it may be partially separate, particularly for the digital signal processing. Thus, the solution presented in this disclosure directly addresses the processing of the electrical angle signal in order to reduce the specific harmonic of this signal that carries the largest proportion of the angle error among the signal harmonics.Therefore, the aim is not to modify the number, shape, or arrangement of the coils, nor the processing of the electrical signals generated before obtaining the angle signal, but rather to modify the initially obtained processed angle signal in order to reduce a specific harmonic of this signal identified as corresponding to the harmonic carrying the most significant angle error. The solution proposed in this disclosure thus allows for a simple reduction of the error in the position determined by the sensor, since the error is directly identified in the angle signal, so that this error can be addressed without modifying the sensor arrangement or the prior processing steps used to obtain this angle signal.

[0036] The inventors noted in particular that the angular error obtained in the electrical signal representing the angular position of the target (i.e., the angle signal) was repeatable and could therefore be characterized by a sinusoidal signal having a predetermined phase dependent on the number of secondary windings of the inductive sensor and the number of pole pairs of the motor. Specifically, this sinusoidal signal characterizing the error can be predetermined on a test bench and subtracted from the electrical angle signal so as to reduce and possibly eliminate this angular error.

[0037] Furthermore, since direct processing of the electrical angle signal to reduce a specific harmonic of this signal reduces the error of this signal, this processing can be implemented by the processor of existing position sensors, which already determines the angle signal from the sine and cosine signals provided by the integrated circuit of the position sensor, without modifying the hardware composition of the inductive position sensor. In particular, when the inductive angular position sensor is integrated into a vehicle including an electric motor, the processing of the sine and cosine signals to determine the electrical angle signal of the the rotor of the electric motor and the processing of this angle signal to reduce its error can be operated by the electronic control unit (ECU) of said vehicle.

[0038] With reference to Figures 1 and 2, an example of a position sensor 1 for determining the angular position of an electric motor rotor (not shown) is now presented. The position sensor 1 can, in particular, be mounted in a vehicle 10 comprising an electric motor (not shown), as schematically illustrated in [Fig. 3].

[0039] Angular position can be defined as a measure of the rotational position of an element with respect to a reference axis. The reference axis can, for example, correspond to the axis around which the rotor is driven in rotation.

[0040] The electric motor comprises N pair(s) of poles. N denotes an integer greater than or equal to 1. A pair of poles N of an electric motor consists of two opposite magnetic poles which generate a magnetic field.

[0041] The position sensor 1 includes a target 11 adapted to be fixed to the rotor of the electric motor so that it rotates with the rotor during its rotational movement. The target is an inductive target, that is, a target that allows the conduction of an electric current (in particular the conduction of eddy currents), and therefore the generation of a magnetic field. The target 11 is consequently made of a conductive material, for example a metal, in particular iron, copper, aluminum, or a specific metal alloy.

[0042] The target 11 can take various known forms which will not be detailed in this patent application. In particular, the shape of the target depends, in a well-known manner, on the number N of pole pairs of the electric motor.

[0043] The position sensor 1 also includes a printed circuit board 12. The printed circuit board 12 may consist of a plate or substrate, generally made of insulating material, on which conductive tracks are arranged. These tracks connect different electronic components to each other to form a functional electrical circuit.

[0044] The printed circuit board 12 includes a primary winding 121p, K secondary windings 121s and an electrical generator 122. K is a natural number greater than or equal to 2. The primary winding surrounds the secondary windings 121s.

[0045] In a known manner, when setting up the sensor, the printed circuit board 12 must be fixedly positioned opposite the target 11. More specifically, the secondary windings 121 of the printed circuit board 12 must be positioned opposite the target to receive the magnetic field generated by the target and thus generate electrical signals.

[0046] The electric generator 122 is adapted to deliver a current in such a way as to create an inductive coupling between the primary winding 121p and the secondary windings 121s.

[0047] The inductive coupling between the windings 121 is modulated by the angular position of the target 11. In particular, the electrical generator 121 can be an alternating current generator connected to the primary winding 121p, such that the current generated in the primary winding 121p produces a magnetic field that generates eddy currents in the target. The eddy currents flowing in the target also produce a magnetic field, which generates an induced current in the secondary windings 121s. The phase shift between the currents generated in the secondary windings 121s allows the angular position of the target 11 to be determined.

[0048] The secondary windings 121s have a shape adapted to each generate a sinusoidal electrical signal as a function of the angular position of the target 11. The secondary windings 121s are arranged, in particular, to exhibit a predetermined phase shift between them. This predetermined phase shift is a function of the number K of secondary windings 121s. This is a known arrangement of windings in an angular position sensor. Thus, the electrical signals generated by the secondary windings 121s, due to the geometric phase shift between these windings, exhibit a phase shift that allows the angular position of the target to be determined.

[0049] The secondary windings 121s may, for example, have a known shape corresponding to a projection in polar coordinates, within a space delimited by the primary winding, of a sinusoidal shape in a Cartesian plane. In particular, the primary winding 121p may be circular and encircle the secondary windings 121s. In these known examples, the secondary windings 121s lie in a plane radial to the circle formed by the surrounding primary winding 121p.

[0050] In early examples, there are two secondary windings 121s (K=2), and the phase shift between them corresponds to 180° or ir / 2 radians.

[0051] In second examples, there are three secondary windings 121s (K=3), and the phase shift between them corresponds to 120° or ir / 3 radians.

[0052] As explained above, the inventors astutely observed that the signal representing the angular position of the electric motor rotor included an angle error signal characterized by a specific harmonic that depends on the number of secondary windings 121s of the angular position sensor. In particular, when the sensor comprises two secondary windings 121s, the specific harmonic is a 4th harmonic of the signal. When the position sensor 1 comprises three secondary windings 121s, the specific harmonic corresponds to a 6th harmonic of the signal representing the angular position of the electric motor rotor.

[0053] The position sensor 1 also includes a signal processing unit 13. The signal processing unit 13 of the position sensor 1 is configured to implement several operations described with reference to Figures 4 to 6, which schematically illustrate examples of signal processing methods 100. These are operations that process both analog and digital signals, as detailed below.

[0054] In earlier examples, the signal processing unit 13 can be fully integrated into the printed circuit board 12 as shown in [Fig. 1]. In this case, this signal processing unit 13 can be configured to process both analog and digital signals. It can therefore comprise an analog signal processing unit 131, an analog-to-digital converter (ADC) for converting analog signals into digital signals, and a processor (PROC) associated with a memory (MEM) for processing the digital signals. An example of a signal processing unit 13 according to earlier examples is shown in [Fig. 7]. It is understood that such a fully integrated processing unit 13 could therefore implement the process examples 100 directly on the printed circuit board 12.

[0055] In some examples, the MEM memory can store the code instructions executed by the PROC processor and can optionally store the electrical signals digitized by the analog-to-digital converter (ADC). The PROC processor therefore has access to the information stored in the MEM memory.

[0056] MEM memory may, for example, include ROM (Read-Only Memory), RAM (Random Access Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or any other suitable type of storage medium. MEM memory may, for example, include optical, electronic, or magnetic storage media.

[0057] The processor PROC can for example correspond to a controller, in particular a microcontroller.

[0058] In second examples, the signal processing unit 13 may comprise two parts 13a and 13b. The first part 13a is integrated into the printed circuit board 12. The second part 13b is external to the printed circuit board 12, as shown in [Fig.2].

[0059] The first part 13a of the signal processing unit 13 can be adapted to process analog signals and then send the processed analog signals to the second part 13b of the signal processing unit. The second part 13b of the signal processing unit 13 can be adapted to convert the analog signals into digital signals and then to process the digital signals.

[0060] The first part 13a of the signal processing unit 13 can therefore include the analog signal processing unit 131 enabling the processing of analog signals and a communication unit COM enabling the communication of analog signals to the second part 13b of the signal processing unit.

[0061] The second part 13b of the signal processing unit 13 may include the analog-to-digital converter (ADC) for converting analog signals into digital signals, and the processor (PROC) associated with the memory (MEM) for processing the digital signals. An example of a signal processing unit 13 according to the second examples is shown in [Fig. 8].

[0062] In examples in which the angular position sensor is embedded in a vehicle, the PROC processor of the second part 13b of the signal processing unit 13 may correspond to the electronic control unit of the vehicle.

[0063] It is understood that in these second examples of the architecture of the signal processing unit 13, the analog signal processing operations are carried out by the first part 13a of the unit 13 at the printed circuit board level 12, while the digital signal processing operations are implemented by the second part 13b of the unit 13, in particular by a PROC processor, external to the printed circuit board 12.

[0064] Thus, the signal processing unit 13 is configured for the implementation of the operations of the example processes 100 described with reference to Figures 4 to 6.

[0065] As illustrated by block 110, the signal processing unit 13 is configured to obtain 110 a cosine electrical signal and a sine electrical signal from the sinusoidal electrical signals generated by the secondary windings 121s. In this case, as explained previously, the sinusoidal electrical signals are generated by inductive coupling, which coupling is modulated by the position of the target.

[0066] The cosine electrical signal and the sine electrical signal refer to two sinusoidal electrical signals, derived from the sinusoidal electrical signals generated by the secondary windings, and which are used to determine an electrical signal representative of the angular position of the electric motor rotor by signal processing.

[0067] Various known techniques allow the cosine and sine signals to be obtained for this type of angular position sensor.

[0068] In particular, in examples in which the position sensor includes two secondary windings 121s, the cosine and sine signals can directly correspond to the two electrical signals generated by the two secondary windings.

[0069] In other examples in which the position sensor also includes two secondary windings 121s, one of the two secondary windings can provide a so-called cosine+ signal and a so-called cosine- signal, while the other winding The secondary winding can produce a signal called sine+ and a signal called sine-. In these other examples, the cosine electrical signal is obtained by subtracting the cosine+ and cosine- signals, while the sine electrical signal is obtained by subtracting the sine+ and sine- signals. This differentiation of signals (cosine+ / cosine- and sine+ / sine-) reduces the intrinsic noise of the cosine and sine signals compared to cosine and sine signals obtained directly from the electrical signals generated by the secondary windings.

[0070] In examples in which the position sensor includes three secondary windings 121s, the cosine and sine electrical signals can be obtained by a complex calculation step (via a Park Transform for example) to project the three signals generated by the secondary windings 121s (three-phase system) into a coordinate space comprising only two signals (two-phase system).

[0071] As illustrated by block 120, the signal processing unit 13 is configured to process the cosine and sine electrical signals to obtain an electrical signal representative of the angular position of the electric motor rotor. In examples, notably illustrated by block 125 of [Fig. 5], processing the cosine and sine electrical signals to obtain an electrical signal representative of the angular position of the electric motor rotor corresponds to applying a mathematical function atan2 to the cosine and sine electrical signals. Using the mathematical function atan2 from the sine and cosine signals to obtain a signal representative of the angular position of the electric motor rotor corresponds to a known operation for this type of inductive sensor.

[0072] As illustrated by block 130, the signal processing unit 13 is configured to process the electrical signal representing the angular position of the electric motor rotor to reduce a specific harmonic of this signal. The specific harmonic is determined from the number K of secondary windings 121s. The specific harmonic can be determined to correspond to the harmonic of the signal corresponding to the angular error exhibiting the largest proportion of the error, this harmonic being dependent on the number K of secondary windings 121s used.

[0073] The signal processing unit 13 of the position sensor 1 is therefore configured to reduce the error in the angular position determined by the sensor by acting directly on the electrical angle signal so as to reduce the specific harmonic of this signal that carries the largest proportion of the angle error among the signal harmonics. Furthermore, the configuration of the processing unit according to the present disclosure makes it possible, unlike the solutions previously considered for reducing this error, to retain the existing hardware and software architecture of the inductive position sensors, by cleverly adding a post-processing step. Error reduction processing on the initially obtained angle signal. The solution is particularly advantageous as it can be implemented on inductive sensors with a different number of secondary windings (especially for inductive position sensors with 2 or 3 secondary windings).

[0074] It is further understood that, since direct processing of the electrical angle signal to reduce a specific harmonic of this signal reduces the error of this signal, this processing can be implemented by the processor of existing position sensors, which already determines the angle signal from the sine and cosine signals provided by the integrated circuit of the position sensor, without modifying the hardware architecture of the inductive position sensor. Thus, when the inductive angular position sensor is installed in a vehicle, the processing of the sine and cosine signals to determine the electrical angle signal of a rotor of an electric motor of the vehicle, and the processing of this angle signal to reduce its error, can be directly performed by the electronic control unit of said vehicle.

[0075] In examples, when the signal processing unit 13 processes 130 the electrical signal representing the angular position of the rotating element to reduce the specific harmonic of this signal, the signal processing unit 130 can be configured to implement the operation 135. These examples are shown in particular in [Fig.6].

[0076] Operation 135 consists of subtracting, from the electrical signal representing the angular position, a specific sinusoidal signal having a phase of the form: ph = 2NK + 9 with ph corresponding to the phase of the specific sinusoidal signal; N corresponds to the number of pole pairs of the electric motor; K corresponds to the number of secondary windings; and q> corresponds to a determined phase shift.

[0077] The inventors astutely noted that the angle error carried by the specific harmonic bearing the largest proportion of the error in the angle signal was repeatable insofar as this error is intrinsic to the technology on which the sensor is based. This error in the angle signal, carried predominantly by the specific harmonic, can thus be reduced, or even eliminated, by subtracting from the angle signal a sinusoidal signal, the phase of which is 2NK proportional to the phase of the signal, to which is added a determined constant phase shift q.

[0078] q> is a constant phase shift in the sense that it does not change dynamically. In other words, it is independent of time. In this case, the phase shift q> depends on the sensor topology and the manufacturer. In particular, sensors from the same manufacturer that have the same topology share the same phase shift q>. This phase shift q> can Therefore, it must be determined on a test bench for an inductive position sensor from a given manufacturer with a specific topology. Alternatively, the phase shift q can be determined during sensor operation.

[0079] In examples, the phase shift q> is determined from an error signal obtained on a test bench for the position sensor or for a position sensor equivalent to the position sensor 1. The error signal corresponds to a differential signal resulting from a difference between the signal representing the angular position of the position sensor or the equivalent position sensor obtained by processing the cosine and sine signals and a real angular position signal reconstructed from direct measurements of the angular position of the target of the sensor concerned on the test bench.

[0080] A position sensor equivalent to position sensor 1 should be understood here as an inductive position sensor from the same manufacturer having primary and secondary windings similar in shape and arrangement to those of position sensor 1, and an inductive target adapted to be fixed to an electric motor rotor having the same number N of pole pairs as the target of position sensor 1. In particular, the number K of secondary windings of the equivalent sensor must correspond to the number K of secondary windings of position sensor 1 and have a phase shift substantially equal to the phase shift of the secondary windings of position sensor 1. A position sensor equivalent to position sensor 1 may, for example, correspond to another position sensor of the same model (of the same topology and therefore from the same manufacturer), possibly manufactured on the same production line.

[0081] In early examples in which the inductive position sensor has a topology with a printed circuit comprising a primary winding surrounding only two secondary windings which have a shape corresponding to a projection in polar coordinates in a space delimited by the primary winding of a sinusoidal shape in a Cartesian plane, the sinusoidal signal to be subtracted during operation 135 may have a phase of the form: ph = 4N + q> with ph corresponding to the phase of the specific sinusoidal signal; N corresponds to the number of pole pairs of the electric motor; and q> corresponds to a determined phase shift.

[0082] In second examples in which the inductive position sensor has a topology with a printed circuit comprising a primary winding surrounding only three secondary windings which have a shape corresponding to a projection in polar coordinates in a space delimited by the primary winding of a sinusoidal form in a Cartesian plane, the sinusoidal signal to be subtracted during operation 135 can have a phase of the form: ph = 6N + q> with ph corresponding to the phase of the specific sinusoidal signal; N corresponds to the number of pole pairs of the electric motor; and q> corresponds to a determined phase shift.

[0083] In sensor examples 1 in which the signal processing unit 13 is configured to implement operation 135, an amplitude of the specific sinusoidal signal subtracted from the electrical signal representing the angular position can be determined from an amplitude of at least one of the cosine electrical signal and the sine electrical signal. In other words, the amplitude of the specific sinusoidal signal can be determined from the amplitude of the sine electrical signal, or from the amplitude of the cosine electrical signal, or from the amplitude of both of these signals.

[0084] The inventors observed that the amplitude of the sinusoidal signal used to apply a correction to the angle signal was proportional to the amplitudes of the cosine and sine signals obtained by the sensor. Therefore, rather than defining a "default" amplitude for the specific sinusoidal correction signal, which might, for example, have been previously determined on a test bench, these examples propose determining an amplitude based on the actual amplitudes of the cosine and sine signals. The amplitude of the specific sinusoidal signal can thus be adapted according to the levels of the sine and cosine signals actually obtained when using the sensor, rather than being defined a priori by measuring these amplitudes on a test bench.Furthermore, it is also understood that these examples allow the amplitude of the corrective signal to be applied to be dynamically modified according to the amplitudes of the cosine and / or sine signals obtained when using the sensor, which is not permitted when the amplitude is fixed a priori.

[0085] In examples where the amplitude of the specific sinusoidal signal is determined from the amplitude of at least one of the cosine and sine electrical signals, a sensor memory, for example the MEM memory, may have a lookup table between a plurality of amplitudes associated with at least one of the cosine and sine electrical signals and a plurality of amplitudes associated with the specific sinusoidal signal. Thus, the amplitude of the specific sinusoidal signal can be determined from an amplitude of the specific sinusoidal signal in the table associated with the amplitude of at least one of the cosine and sine electrical signals.

[0086] Figures 9 and 10 allow us to graphically represent the impact of operation 135 on the error of the angle signal determined by the angular position sensor 1. In particular, Figure 9 graphically represents an example of an electrical signal Se representing the error in the angular position of the electric motor rotor and an example of a specific sinusoidal signal Sc that at least partially compensates for this error electrical signal Se. Figure 10, on the other hand, represents the same example of an error electrical signal Se and a compensated error electrical signal Sec resulting from the difference between the error electrical signal Se and the specific sinusoidal signal Sc. In both figures, the x-axis represents the angular position of the electric motor rotor in degrees (ranging from 0 to 360°), while the y-axis represents the electrical error, also in degrees. These graphs highlight the fact that the operation 135 of subtracting the specific sinusoidal signal significantly reduces the error in the angular position determined by the position sensor.

[0087] The solution presented in this disclosure thus makes it possible to mitigate, or even eliminate, an error caused by a specific harmonic of the angle signal determined by an inductive position sensor. This solution relies on post-processing of the angle signal, which can be implemented in software, so that the electronic architectures of existing inductive sensors do not necessarily need to be modified to implement this solution. Furthermore, the solution can be applied to several different topologies of inductive sensors, including those with two or three secondary windings.

Claims

Demands

1. Position sensor (1) for determining an angular position of an electric motor rotor, the sensor comprising: a target (11) adapted to be fixed on the electric motor rotor so that it is driven in rotation with the rotor during its rotational movement; a printed circuit board (12) comprising a primary winding (121p), K secondary windings (121s) with K being greater than or equal to 2, and an electrical generator (122); and a signal processing unit (13); the primary winding (121p) surrounding the secondary windings (121s); the secondary windings (121s) having a shape adapted to each generate a sinusoidal electrical signal, the generated electrical signals having a predetermined phase shift between them;the electric generator (122) being adapted to deliver a current so as to create an inductive coupling between the primary winding (121p) and the secondary windings (121s), the inductive coupling being modulated by the position of the target (11); the signal processing unit (13) being configured to: obtain (110) a cosine electrical signal and a sine electrical signal from the sinusoidal electrical signals; process (120) the cosine and sine electrical signals in order to obtain an electrical signal representative of an angular position of the rotor of the electric motor; and process (130) the electrical signal representative of the angular position of the rotor of the electric motor to reduce a specific harmonic of this signal, the specific harmonic being determined from the number K of secondary windings (121s).

2. Sensor according to claim 1, wherein processing the cosine and sine electrical signals to obtain an electrical signal representative of an angular position of the electric motor rotor corresponds to applying (125) a mathematical function atan2 from the cosine and sine electrical signals.

3. Sensor according to any one of claims 1 or 2, wherein (130) processes the electrical signal representative of the position angular displacement of the rotating element to reduce the specific harmonic of this signal includes: subtracting (135), from the electrical signal representing the angular position, a specific sinusoidal signal having a phase of the form: ph = 2NK + <p avec ph correspondant à la phase du signal sinusoïdal spécifique; n un nombre de paires pôles moteur électrique; k au bobinages secondaires; et q>corresponding to a specific phase shift.

4. Sensor according to the preceding claim, wherein the determined phase shift (q>) is determined from an error signal obtained on a test bench for the position sensor or for a position sensor equivalent to the position sensor.

5. Sensor according to any one of claims 3 or 4, wherein an amplitude of the specific sinusoidal signal is determined from an amplitude of at least one of the cosine electrical signal and the sine electrical signal.

6. Sensor according to the preceding claim, further comprising a memory (MEM) having a lookup table between a plurality of amplitudes associated with at least one of the cosine electrical signal and the sine electrical signal and a plurality of amplitudes associated with the specific sinusoidal signal.

7. Vehicle (10) comprising a sensor (1) according to any one of the preceding claims.

8. A method (100) for determining an angular position of an electric motor rotor, the method comprising: obtaining (110) a cosine electrical signal and a sine electrical signal from a printed circuit board (12) of a position sensor (1); processing (120) the cosine and sine electrical signals to obtain an electrical signal representative of an angular position of the electric motor rotor; processing (130) the electrical signal representative of the angular position of the electric motor rotor to reduce a specific harmonic of that signal, the specific harmonic being determined from a number K of secondary windings (121s) of the position sensor.

9. A method according to the preceding claim, wherein processing (130) the electrical signal representing the angular position of the electric motor rotor to reduce the specific harmonic of this signal comprises: subtracting (135), from the electrical signal representing the angular position, a specific sinusoidal signal having a phase of the form: ph = 2KN + <p avec ph correspondant à la phase du signal sinusoïdal spécifique; n un nombre de paires pôles moteur électrique; k au bobinages secondaires (121s); et q>corresponding to a predetermined phase shift.

10. Product computer program comprising instructions for carrying out a method (100) according to any one of claims 8 or 9.

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