Method for determining the positioning of a rotating element of a vehicle based on a positioning sensor

Abstract

A method for determining the position of a rotating element of a motor vehicle on the basis of a position sensor configured to measure the position of the rotating element to simultaneously generate a sinusoidal output signal and a cosinusoidal output signal reflecting the angular position of the rotating element as it rotates, and to deliver these output signals to a control module of the vehicle, the method implemented by the control module comprising the steps of rotating the rotating element, receiving (E3) the output signals generated by the position sensor as the rotating element rotates, determining (E7) an average period of the output signals received over a predetermined time range, correcting (E8) the two received output signals so that the period of each of the signals is equal to the determined average period, determining the angular position of the rotating element on the basis of the corrected output signals.

Description

TECHNICAL FIELD

[0001] The present invention relates to the automotive field, and more specifically, to a method for processing signals generated by a positioning sensor for the positioning of a rotating element of a vehicle, and to a control module implementing said method. BACKGROUND

[0002] In electric or hybrid vehicles, in particular vehicles with synchronous electric machines, it is known practice to use sensors to determine the positioning of the rotor of the electric machine, in order to allow an electronic control unit to control the electric machine via a power converter.

[0003] Sensors of this type are preferably placed in line with the end of the rotor shaft, and send information on the angular positioning to the electronic control unit, so that the electronic control unit controls the power converter, and thus the electric machine.

[0004] Sensors of this type, known as "resolvers", comprise in a known manner an integrated circuit comprising one or more sensitive elements associated with a bipolar magnet positioned at the end of the shaft facing the sensor, for axial reading. The one or more sensitive elements of the sensor allow the rotation angle of the magnetic vector of the magnet to be detected. The measured angle is transcribed into two sine and cosine output signals. The electronic control unit receives these two output signals simultaneously, and determines the absolute angle of the rotor via an arctangent trigonometric calculation.

[0005] The influence of the environment or of the technology used (sensors, magnets, etc.) tends to distort these output signals, in particular in terms of amplitude and phase, which leads to residual errors in the angle estimation. This error can be significant, and leads to electric machine control faults. More particularly, if the positioning of the rotor exceeds predefined limits in the vehicle safety control system, the electric machine stops and the vehicle cannot move, which is one of the most serious faults for a motor vehicle.

[0006] In the prior art, the solution adopted to reduce signal distortion and thus residual errors in these sensors consists in using correctors for the amplitude, offset and quadrature associated with a time-domain filtering with a cut-off frequency set. Time-domain filtering is used for simplicity. The filtering is low frequency, since the wanted signal is low frequency: a rotor rotation speed conventionally between for example 0 and 20000 RPM corresponds to a frequency band between 0 and 333 Hz.

[0007] The correctors for the amplitude, offset and quadrature make it possible to at least partially compensate for the distortion of the amplitude and timing of the signal, respectively. The quadrature corrector makes it possible to correct the phase shift in the signal, in order to keep it at a value of the order of 90°.

[0008] The performance of this method is first limited by the effectiveness of the corrector which does not allow the residual errors to be sufficiently reduced. In particular, when the slope of the signal is maximum, the signal is significantly distorted, shifted and therefore the shift of the orthogonality is common and difficult to correct with the existing correctors.

[0009] Moreover, the performance of this method depends on the rotational speed of the rotor since the filtering depends on the frequency of the signal, i.e. on the rotation of the shaft. In particular, at low rotational speeds or during the acceleration phase, the estimation error is greater, which presents a major drawback. More specifically, the yield of the electric machine is not optimized for the entire operating range but depends on the filtering which in turn depends on the speed.

[0010] There is therefore a need for a solution which makes it possible to at least partially overcome these drawbacks. SUMMARY

[0011] To this end, the first subject of the invention is a method for determining the positioning of a rotating element of a motor vehicle based on a positioning sensor configured to measure the positioning of the rotating element to simultaneously generate a sinusoidal output signal and a cosinusoidal output signal reflecting the angular positioning of the rotating element as it rotates, and to deliver these output signals to a control module of the vehicle, the method implemented by the control module comprising the following steps:

[0012] - rotating the rotating element,

[0013] - receiving the output signals generated by the positioning sensor as the rotating element rotates,

[0014] - determining the average period of the output signals received over a predetermined time range,

[0015] - correcting the two received output signals so that the period of each of the signals is equal to the determined average period,

[0016] - determining the angular positioning of the rotating element based on the corrected output signals.

[0017] The "average period of the signal" means the average of the average period of the sinusoidal signal and the average period of the cosinusoidal signal.

[0018] This method makes it possible to achieve the establishment of a steady state in order to determine the period of the signal over a small time range, then this period is stabilized, which allows the signal to be corrected with a stable and precise period value in order to eliminate the distortions which cause errors in the estimation of the angular positioning. Thus, the use of the average period makes it possible to eliminate the temporal shift generated by the distortion of the signal over the predetermined time range. Moreover, by using the average of the estimates of the period to smooth the estimate of the period, it is possible to filter the speed information in order to obtain a more precise speed estimate.

[0019] According to one feature of the application, the positioning of the rotating element is determined at a given time by computing the arctangent of the sine and cosine signal values at said given time.

[0020] Preferably, the method determines the rotational acceleration of the rotating element before determining the average period of the output signal received over a predetermined time range, the steps of determining the average period of the received output signal and correcting the received output signal being implemented only if the acceleration value is lower than a predetermined threshold value characterizing a steady state, and the step of determining the angular positioning of the rotating element based on the corrected output signal.

[0021] According to one aspect of the application, the method comprises the steps of computing the average of the periods of the sine signal generated over a predetermined time range and the average of the periods of the cosine signal generated over a predetermined time range.

[0022] Advantageously, the operation of determining the average period of the received output signal is performed by computing the average of the periods of each output signal over a predetermined time range, each period being measured between two successive zero amplitudes of said signal for each of the two output signals.

[0023] Preferably, the duration of the predetermined time range can be chosen so as to meet the needs in terms of dynamics and angular accuracy expected for controlling the rotating element, for example for controlling a rotor in the case of an electric machine.

[0024] Advantageously, the method comprises, before correcting the output signal in terms of period, a step of checking that the average period is lower than a predefined period threshold or higher than a predefined speed threshold so as to ensure that the speed is high enough to reach a steady state. This threshold can be determined as a function of the expected system dynamics.

[0025] Advantageously, the acceleration can be defined by computing the difference in rotational speed of the rotating element between two successive rotations.

[0026] Preferably, the predetermined acceleration threshold is determined as a function of the expected system dynamics.

[0027] Advantageously, the method comprises, before determining the average period or when the acceleration value is higher than the predetermined acceleration threshold, a step of correcting the output signal in terms of amplitude and / or offset.

[0028] Advantageously, the method comprises, before correcting the output signal in terms of period, a step of time domain filtering of the received signal at a set cut-off frequency.

[0029] The application also relates to a computer program product comprising a set of program code instructions which, when they are executed by one or more processors, configure the one or more processors to implement the method as described above.

[0030] The application also relates to a control module for a vehicle, configured to implement the method as described above.

[0031] The control module can be an electronic control unit (ECU) installed in the vehicle at a distance from the sensor and connected to said sensor by a communication link in order to receive the output signal generated by said sensor.

[0032] As a variant, the control module can be integrated into the same housing as the sensor, for example by taking the form of a preprogrammed digital signal processor (DSP).

[0033] The application also relates to a motor vehicle comprising a rotating element, a sensor for the angular positioning of said rotating element and a control module as presented above.

[0034] In one embodiment, the rotating element is an electric machine rotor. BRIEF DESCRIPTION OF DRAWINGS

[0035] Other features and advantages of the application will become more apparent on reading the following description. This description is purely illustrative and should be read in conjunction with the appended drawings in which:

[0036] Figure 1 One embodiment of a vehicle according to the application is schematically illustrated;

[0037] Figure 2 One embodiment of a method according to the application is schematically illustrated;

[0038] Figure 3 Examples of the distorted sine and cosine signals received from the sensor are illustrated with respect to an ideal sine signal (i.e. a signal without distortion) and an ideal cosine signal;

[0039] Figure 4 Examples of the corrected sine and cosine signals are illustrated, in which the average period is determined by the control module and the rotor is rotating in steady state;

[0040] Figure 5 Examples of the error in estimating the rotor angle as a function of time in the rotor acceleration are illustrated. DETAILED DESCRIPTION

[0041] Figure 1 One example of a vehicle 1 according to the application is illustrated. Preferably, the vehicle 1 is a motor vehicle 1, in particular an electric or hybrid motor vehicle.

[0042] The vehicle 1 comprises an electric machine 5, a sensor 10 and a control module 20.

[0043] The electric machine 5

[0044] The electric machine 5 comprises a stator 6 in which a rotor 7 is mounted, which allows to provide a torque suitable for driving the wheels of the vehicle 1.

[0045] The rotor 7 comprises a central rotation shaft 8 having a free end 8A on which a bipolar magnet 9 is mounted.

[0046] The sensor 10

[0047] The sensor 10 is a positioning sensor which allows to determine the angular positioning of the rotor by measuring the angular positioning of the central shaft 8.

[0048] To this end, the sensor 10 comprises an integrated circuit and one or more sensitive elements (not shown for the sake of clarity) which allow to detect the angle of rotation of the magnetic vector of the bipolar magnet 9 as it rotates.

[0049] The integrated circuit is designed to generate, on the basis of the magnetic vector detected by the one or more sensitive elements, a sinusoidal output signal and a cosinusoidal output signal reflecting the angular positioning of the rotor 7 as it rotates, and to deliver these two output signals to the control module 20.

[0050] Since this type of sensor 10 is known per se, it will not be described in detail here.

[0051] The control module 20

[0052] The control module 20 uses the information sent by the sensor 10 to determine the angular positioning of the rotor 7. To this end, the control module 20 is configured to receive the two measured output signals generated by the sensor 10 as the rotor 7 rotates, in order to determine the angular positioning of the rotor 7 and to control the power converter, allowing the electric machine 5 to be controlled as a function of the angular positioning determined.

[0053] The control module 20 is configured to determine the acceleration of rotation of the rotor 7 on the basis of the output signals received. For example, the acceleration can be determined by calculating the difference in rotation speed between two successive rotations of the rotor 7.

[0054] The control module 20 is configured to compare the acceleration value determined with a predetermined acceleration threshold S characterizing a steady state, for example a difference in speed X m / s between two successive rotations of the rotor 7. Figure 2

[0055] The control module 20 is configured to calculate the average period of the output signal in sinusoidal form and the average period of the output signal in cosinusoidal form, and then to calculate the average of the two average periods thus calculated.

[0056] ​The control module 20 is configured to correct the two output signals received from the sensor 10 so that the period of each of said signals becomes equal to the determined average period.

[0057] The control module 20 is configured to determine the angular positioning of the rotor 7 based on the corrected output signals using the arctangent calculation known per se.

[0058] The predetermined time range can advantageously be chosen as a function of the range of rotational speeds of the rotor 7 so as to ensure that the speed remains substantially constant over said time range.

[0059] Advantageously, the control module 20 can also be configured to correct the sine and cosine signals before the calculation so as to reduce the estimation error. For example, knowing the last angular positioning calculated for the rotor 7 and the duration elapsed since the last angular positioning calculated (the sampling period), the ideal sine and cosine signals can be determined before calculating a new value of the angular positioning of the rotor 7.

[0060] The control module 20 comprises a processor capable of implementing an instruction set allowing these functions to be performed.

[0061] Preferably, the control module 20 is an electronic control unit (ECU) which is installed in the vehicle 1 at a distance from the sensor 10 and is connected to said sensor 10 by a communication link LI so as to receive the output signals generated by the sensor 10.

[0062] As a variant, the control module 20 can be integrated into the same housing as the sensor 10, for example by taking the form of a preprogrammed digital signal processor (DSP).

[0063] Exemplary implementation

[0064] First, reference is made to Figure 2 In step E1, the rotor 7 is rotated.

[0065] Then, in step E2, the integrated circuit of the sensor 10, supplied with electrical power by the battery of the vehicle 1, detects, via one or more sensitive elements, the magnetic field variations generated by the bipolar magnet 9 as it rotates concentrically at the end of the central shaft 8 of the rotor 7 and simultaneously generates a sine signal and a cosine signal.

[0066] In step E3, these signals are received by the control module 20 via the communication link LI.

[0067] In step E4, the control module 20 then determines, on the basis of the signals received from the sensor 10, the instantaneous acceleration value A of the rotor 7.

[0068] In step E5, when the acceleration value A is lower than a predetermined threshold S characteristic of a steady state, the control module 20 does not make any correction or optionally makes a standard correction CS of the amplitude and / or of the offset and / or of the orthogonality. The offset correction is to recenter the signal on a 0 V amplitude, since the sensor signal is off-center, for example between 1 V and 4 V, i.e. an offset with respect to an average amplitude of + 2.5 V. Furthermore, since the amplitude can fluctuate due to environmental constraints, the amplitude correction is to correct the signal so that the signal maximums exhibit the same amplitude and the signal minimums exhibit the same amplitude. These compensations are made in a known manner by detecting the minimum and maximum and correcting the signal in the manner described above.

[0069] In step E6, the control module 20 next calculates the angle giving the angular positioning PA of the rotor 7 by calculating the arctangent of the received signal, by triangulation.

[0070] When the acceleration value A is lower than a predetermined threshold S characteristic of a steady state, the control module 20 optionally makes a standard correction CS of the amplitude and / or of the offset and / or of the orthogonality in step E5, determines the average period PM of the output signals received over a predetermined time range, i.e. the average of the average periods of the two received sinusoidal and cosinusoidal signals, in step E7, modifies, i.e. transforms, the two received output signals so that the period of each of said signals is equal to the determined average period PM, in step E8, and calculates the optimized angular positioning PAO of the rotor 7 using the arctangent of the values of the corrected signals, in step E9.

[0071] At any time, the control module 20 can filter the received or processed signals with a set cut-off frequency, for example using an anti-aliasing filter or an impulse response filter of an analog-to-digital converter implemented by the control module 20.

[0072] Exemplary results

[0073] Figure 3 An example is shown of the deformed sinusoidal signal SD and the deformed cosinusoidal signal CD received from the sensor 10 with respect to the ideal sinusoidal signal SP, i.e. the signal without deformation, and the ideal cosinusoidal signal CP, in order to show the signal deviations that cause errors in estimating the angular positioning of the rotor 7.

[0074] Figure 4 An example is shown of the corrected sinusoidal SC and cosinusoidal CC signals, in which the average period PM is determined by the control module 20 and the rotation of the rotor 7 is in a steady state.

[0075] Figure 5An example of the error in estimating the rotor 7 angle as a function of time in the rotor 7 acceleration (phase PI, in which the method according to the application is not implemented) is shown. The error is still very large in the transient state (high acceleration), but it becomes close to zero once the rotor 7 reaches the steady state (phase P2, in which the method according to the application is implemented) after about 200 seconds.

[0076] The application has been described in its application on the motor 5 rotor 7, but it is more generally applicable to any rotating element of the vehicle 1 for which it is necessary to determine the angular positioning PA / PAO based on a sensor 10 that simultaneously generates a sinusoidal signal and a cosinusoidal signal to characterize the angle of the rotating magnetic vector associated with said rotating element.

Claims

1. A method for determining the positioning of a rotating element (7) of a motor vehicle (1) based on a positioning sensor (10) configured to measure the positioning of the rotating element (7) to simultaneously generate a sinusoidal output signal and a cosinusoidal output signal reflecting the angular positioning of the rotating element (7) as it rotates, and to deliver these output signals to a control module (20) of the vehicle (1), the method implemented by the control module (20) comprising the following steps: - rotating (El) the rotating element (7), - receiving (E3) the output signals generated by the positioning sensor (10) as the rotating element (7) rotates, - determining (E7) the average period of the output signals received over a predetermined time range, - correcting (E8) the two received output signals so that the period of each of the signals is equal to the determined average period, - determining the angular positioning of the rotating element (7) based on the corrected output signals, the method being characterized in that, before determining the average period of the received output signals, the rotational acceleration of the rotating element (7) is determined, the steps of determining the average period of the received output signals and correcting the received output signals and the step of determining the angular positioning of the rotating element (7) being implemented only when the acceleration value (A) is lower than a predetermined acceleration threshold (S) characterizing a steady state.

2. The method according to the preceding claim, wherein the operation of determining the average period of the received output signals is performed by calculating the average of the periods of each output signal in the predetermined time range, each period being measured between two successive zero amplitudes of each of the two output signals for each of the two output signals.

3. The method according to any one of the preceding claims, comprising the step of checking that the average period is lower than a predefined period threshold before correcting the output signals in terms of period.

4. The method according to claim 1 or 2, wherein the acceleration (A) is defined by calculating the difference in rotational speed of the rotating element (7) between two successive rotations.

5. The method according to claim 1 or 2, comprising the step of correcting the output signals in terms of amplitude and offset before determining the average period or when the acceleration value (A) is higher than the predetermined acceleration threshold (S).

6. The method according to claim 1 or 2, comprising a filtering step for the received output signals before correcting the output signals in terms of period.

7. A computer program product, characterised in that, It comprises a set of program code instructions which, when executed by one or more processors, configure the one or more processors to implement the method as claimed in any one of the preceding claims.

8. A control module (20) for a vehicle (1) configured to implement the method as claimed in any one of the preceding claims.

9. A motor vehicle (1) comprising a rotating element (7), a sensor (10) for the angular positioning of the rotating element (7) and a control module (10) as claimed in claim 8.

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