Improvements in the assessment of the absolute angular position of the steering wheel by taking into account the condition of the steering wheel when the vehicle is switched off

Abstract

The invention relates to a method for estimating the absolute angular position (P_absolute_SW) of a steering wheel (2) equipped with a power steering device (1), during which the position of the shaft (13) of the power steering motor (11) is evaluated, referred to as the "relative steering wheel position" (P_relative_SW), a first estimate of the absolute angular position of the steering wheel (2) is evaluated by at least one first model using the speed difference between the left rear wheel (14) and the right rear wheel (15), a first dynamic offset (OffsetDYN_RS) equal to the difference between the first estimate of the absolute angular position of the steering wheel (2) (Angle1) and the relative steering wheel position (P_relative_SW) is estimated, and the absolute angular position of the steering wheel is calculated by adding the relative steering wheel position (P_relative_SW) to a total compensation offset (Offset_final) determined by the first dynamic offset (OffsetDYN_RS) and also taking into account a shutdown offset (Offset_save) corresponding to the value of the total compensation offset (Offset_final) at the time when the vehicle was previously turned off when the vehicle (6) is restarted.

Description

Technical Field

[0001] The present invention relates to a power steering system that includes a function known as “Angle Find” (ANF) which allows for the evaluation of the absolute angular position of the steering wheel relative to a center position (which corresponds to the straight trajectory of the vehicle). Background Technology

[0002] Patent application FR-2992937 filed by the applicant describes a method for implementing such an angle-finding function.

[0003] The general principle of this method involves measuring a value called "steering wheel relative position," P_relative_SW, which corresponds to a measured value of the absolute angular position of the auxiliary motor shaft in a first reference frame (relative) attached to the auxiliary motor; and then correcting the steering wheel relative position value by applying a compensation value ("offset") Offset_final, which corresponds to a time-varying angular offset between the first reference frame attached to the auxiliary motor and the second reference frame attached to the steering wheel (and more specifically, attached to a fixed support fixed to the vehicle, relative to which the steering wheel rotates).

[0004] Therefore, the absolute angular position of the steering wheel (represented by the center position of the line in the reference frame attached to the steering wheel) P_absolute_SW is:

[0005] P_absolute_SW = P_relative_SW + Offset_final

[0006] The compensation numerical (offset) offset is ultimately determined essentially in real time from the model, or preferably from a plurality of models known as “dynamic models”, which allow for the evaluation of the power steering angle based on the vehicle’s dynamic parameters (such as, but not limited to, the vehicle’s yaw rate or even the speed deviation between the two wheels on the rear axle) and typically based on the so-called “Jeantaud / Ackermann” geometric representation.

[0007] More specifically, at each iteration n, a dynamic offset offset DYN can be defined for each dynamic model, which for the relevant iteration is equal to the difference between the steering angle evaluated from the dynamic model under consideration on the one hand and the steering wheel relative position P_relative_SW represented in the reference frame attached to the auxiliary motor on the other hand.

[0008] We can then calculate the compensated numerical offset_final as a weighted sum of the dynamic offset numerical offsets DYN (OffsetDYN), which are determined over a series of iterations, or even over all iterations performed since the vehicle was started. Each dynamic offset value is weighted by a weighting factor called a “score,” which represents an index of the confidence level that an estimate can have in the estimate generated by the dynamic model, taking into account the vehicle’s lifespan.

[0009] Through this form of evolutionary learning, one can obtain, for example, the following type of compensated numerical offset: _Offset_final.

[0010]

[0011] in

[0012]

[0013] and

[0014]

[0015] and

[0016] ∑ rating RS (n)=∑Score RS (n-1)+score RS (n)

[0017] ∑ rating YR (n)=∑Score YR (n-1)+score YR (n)

[0018] in

[0019] OffsetDYN_RS(n)(OffsetDYN_RS(n)) is the first dynamic offset obtained from the first dynamic model for the considered iteration n, using the rear velocity deviation (“rear velocity”);

[0020] Score_RS(n) is the weighting factor that can be applied to the first dynamic offset at the considered iteration;

[0021] OffsetDYN_YR(n)(OffsetDYN_YR(n)) is the second dynamic offset obtained from the second dynamic model for the considered iteration n, using the vehicle's ("yaw rate");

[0022] Score_YR(n) is the weighting factor that can be applied to the second dynamic offset at the considered iteration;

[0023] ∑...(N) is the summation operation of n related continuous values ​​(the sum of i = 1 to n).

[0024] However, the inventors have noted that although the angle discovery method described in the aforementioned patent application is accurate and reliable, there may sometimes be some difficulties during the implementation of the method, particularly those related to the sensor technology used to measure the I value known as the "steering wheel relative position" P_relative_SW.

[0025] In fact, after the vehicle's ignition is turned off ("power off"), it is necessary to collect a sufficient amount of reliable dynamic data during the next start-up, that is, during the ignition start-up ("power on"), and therefore collect a sufficient amount of reliable offset DYN (OffsetDYN) dynamic offset values ​​to achieve a sufficiently high global score (the sum of scores obtained in successive iterations) so that we can be confident in the estimate of the steering wheel's angular position.

[0026] Therefore, it is sometimes difficult to make an accurate estimate of the absolute angular position of the steering wheel immediately after starting the vehicle. However, the time required to obtain and reliably estimate the angular position of the steering wheel may temporarily render functions that rely on that estimate of the absolute angular position of the steering wheel unavailable. Summary of the Invention

[0027] Therefore, the purpose assigned to this invention is to overcome the above-mentioned shortcomings and to propose a new and improved method for estimating the absolute angular position of the steering wheel, which allows for a rapid and reliable estimation of the absolute angular position of the steering wheel, especially immediately after the vehicle has started.

[0028] The object assigned to this invention is achieved by means of a method for estimating the absolute angular position of a steering wheel equipped with a power steering system, in which:

[0029] Measure the position of movable components of the steering system other than the steering wheel (referred to as "direction relative position"), for example, the position of the shaft of the auxiliary motor of the power steering system.

[0030] Based on the analysis of first rolling parameters representing the vehicle's dynamics, such as the speed difference between the left and right wheels on the same rear axle, at least a first estimate of the absolute angular position of the steering wheel is evaluated according to at least a first model.

[0031] The first dynamic offset is evaluated based on the difference between a first estimate representing the absolute angular position of the steering wheel and the relative position of the steering wheel.

[0032] The absolute angular position of the steering wheel is calculated by adding a total compensation offset to the relative position of the steering wheel, and the total compensation offset is determined based on the first dynamic offset.

[0033] The method is characterized by recording a value called "closing offset" during the period when the vehicle is shut down, which is obtained from the total compensation offset at the time of shutdown, and calculating the total compensation offset taking into account the closing offset during the next restart of the vehicle.

[0034] Advantageously, by storing the closing offset, the method can maintain information about the offset between closing and the next vehicle start-up regarding the offset between the reference frame associated with the movable member used to measure the relative position of the steering wheel at the time of closing and the reference frame attached to the steering wheel (in which one wants to know the absolute position of the steering wheel).

[0035] By recalling the closing offset value upon restarting, and by using this closing offset value as the basis for evaluating the new total compensation offset that can be applied once the vehicle restarts, rather than arbitrarily and artificially assuming that the total compensation offset is reset to zero during the closing period, the advantages of the learning performed before closing are advantageously preserved, and the total compensation offset can therefore be determined immediately and directly applied to the calculation of the absolute angular position of the steering wheel.

[0036] Therefore, the method according to the invention makes it impossible to start the vehicle again when the total compensation offset is uncertain or at least inaccurate.

[0037] Because the reliable value of the total compensation offset is available from startup, once the measurement of the position of the movable component (usually the measurement of the angular position of the auxiliary motor shaft) is refreshed, that is, once the relative position of the steering wheel is refreshed, a reliable estimate of the absolute angular position of the steering wheel can be generated without delay through the total compensation offset.

[0038] Of course, the power steering system implementing the method includes a structure that can record a reliable value of the off offset in a non-volatile memory, so that the value is available from startup.

[0039] Furthermore, as will be seen in the description below, the stored closing offset can be weighted as a function of the latter's reliability, and thus the closing offset can be corrected by means of an appropriately weighted score when necessary. In this way, the reliability of the process for calculating the absolute angular position of the steering wheel is optimized by avoiding the introduction of a closing offset into the calculation, which would otherwise be distorted and therefore inaccurate due to an unknown offset occurring between the auxiliary motor reference system and the reference system attached to the steering wheel. Attached Figure Description

[0040] Other objects, features, and advantages of the invention will become more apparent from the following description and accompanying drawings, which are for illustrative purposes only and not for limiting purposes, wherein:

[0041] Figure 1 A vehicle equipped with a power steering system that applies the method according to the invention is shown schematically.

[0042] Figure 2 The principle of offset compensation is shown, which obtains the numerical value of the absolute angular position of the steering wheel through the relative position of the steering wheel. Detailed Implementation

[0043] The present invention relates to a method for estimating the absolute angular position P_absolute_SW of a steering wheel 2 equipped with a power steering system 1.

[0044] In a manner known in itself, and as Figure 1 As shown, the power steering system 1 includes a steering wheel 2 that allows the driver to limit the direction of the vehicle, and a steering mechanism that can orient one or more steering wheels 3, 4.

[0045] The steering mechanism may preferably include a rack 5, which is translatably mounted in a steering housing intended to be fixed to the frame of the vehicle 6.

[0046] The end of the rack 5 is connected to the steering tie rods 7 and 8, and the steering tie rods themselves are connected to the short shaft, which can be oriented in yaw and carry the steering wheels 3 and 4.

[0047] Preferably, the steering wheel 2 is mechanically connected to the rack 5 via a steering column 9, the steering column carrying a drive pinion 10 that meshes with the rack 5.

[0048] However, the present invention can be perfectly applied to power steering systems of the "steer by wire" type, which do not have a mechanical connection for direct motion transmission between the steering wheel 2 and the rack 5.

[0049] The device 1 also includes an auxiliary motor 11, preferably an electric motor, such as a brushless motor.

[0050] Preferably, the auxiliary motor 11 is a rotary motor.

[0051] The auxiliary motor 11, preferably connected to the reduction gear, can be engaged with the rack 5 via the steering column 9 or directly by means of a connecting member 12 different from the drive pinion 10 (such as, for example, a secondary pinion or a ball screw).

[0052] The absolute angular position P_absolute_SW of the steering wheel 2 corresponds to the angular position occupied by the steering wheel 2 relative to the center position P0 under the consideration, which corresponds to the straight trajectory of the vehicle 6.

[0053] Preferably, the useful travel of the steering wheel is one revolution greater than the center position P0 in each direction (left or right), such that the possible total travel of the steering wheel 2 is, for example, three revolutions, so that the absolute angular position corresponds to a multi-revolution position, which can therefore be greater than 360 degrees (equivalent to one revolution).

[0054] The absolute angular position P_absolute_SW of the steering wheel is represented in the first reference frame R_abs attached to the fixed support of the steering wheel 2. This first reference frame R_abs can actually be equated to the reference frame attached to the vehicle frame.

[0055] In the method according to the invention, the position of the movable member 13 of the steering device 1 other than the steering wheel 2, P_relative_SW, is measured, and this position is referred to as the "steering wheel relative position".

[0056] The movable member 13 is selected such that its position is associated with the absolute angular position of the steering wheel 2.

[0057] For example, the (rotational) shaft of the auxiliary motor 11 of the power steering device 1 can be selected as a movable component.

[0058] The relative position of the steering wheel P_relative_SW corresponds to the absolute angular position of the shaft 13 of the auxiliary motor 11.

[0059] The relative position of the steering wheel, P_relative_SW, will be represented in the second reference frame, R_rel, and the movable member 13 moves relative to the second reference frame.

[0060] Preferably, the second reference frame is attached to the auxiliary motor 11, and more specifically, to the stator of the auxiliary motor 11.

[0061] Therefore, preferably, the steering wheel relative position P_relative_SW will correspond to the absolute angular position of the shaft 13 of the auxiliary motor 11 as represented in the second reference frame R_rel attached to the stator of the auxiliary motor.

[0062] The position can be measured by means of a suitable position sensor, such as a resolver-type position sensor, which is preferably integrated into the auxiliary motor 11.

[0063] Ideally, the first reference frame R_abs attached to the fixed support of the steering wheel 2 and the second reference frame R_rel attached to the auxiliary motor 11 should overlap. However, in practice, angular offsets and fluctuations between the reference frames can be observed, which must be characterized by calculating the total compensated offset offset_final (Offset_final) and are therefore taken into account, as will be described in detail below.

[0064] In the method according to the invention, at least a first estimated angle 1 (AngIe1) of the absolute angular position of the steering wheel 2 is also evaluated by at least a first model, the first model being based on an analysis of a first rolling parameter representing vehicle dynamics.

[0065] The first rolling parameter could be, for example, the difference in speed (rotation speed) between the left wheel 14 and the right wheel 15 on the same rear axle, V14-V15.

[0066] These speeds can be measured, for example, by an anti-lock braking system (ABS).

[0067] Based on this information about the speed difference between the rear wheels 14 and 15, the radius of curvature of the trajectory of vehicle 6 at the considered moment can be determined by referring to the Jeantaud-Ackermann geometry, and thus the lateral acceleration of the vehicle can be determined. From this, the steering angles of the steering wheels 3 and 4 can be derived, and thus the first estimate of the absolute angular position of the steering wheel 2, angle 1 (AngIe1), can be derived.

[0068] Such a first model is specifically described in the applicant’s patent application FR-2992937, and therefore, for all useful purposes, that patent application may be considered to be incorporated herein by reference.

[0069] Alternatively, the first model can of course use any other rolling parameter that can characterize the lateral dynamics of the vehicle 6 and thus provide an assessment of the steering wheel's angular position.

[0070] For example, the yaw speed of vehicle 6 can therefore be used as a rolling parameter, as described in the aforementioned application.

[0071] In the following text, for ease of description, reference will be made to the parameters and estimates of the extension_RS, which are derived from or associated with a first model using the difference in speed of the rear wheels. It should be understood that they may be replaced with parameters or estimates associated with any other suitable model (particularly with a model based on the yaw speed identified by the extension_YR) without departing from the scope of the invention.

[0072] In the method according to the invention, a first dynamic offset DYN_RS (OffsetDYN_RS) is evaluated, the first dynamic offset representing and more preferably equal to the difference between a first evaluated angle 1 (obtained by means of a first model) of the absolute angular position of the steering wheel 2 and the relative position P_relative_SW of the steering wheel (preferably obtained by measuring the position of the shaft 13 of the auxiliary motor 11):

[0073] Offset DYN_RS = Angle1 - P_relative_SW

[0074] Since the first estimate AngIe1 provided by the dynamic model and the steering wheel relative position P_relative_SW provided by the measurement of the position of the movable member 13 (here, the shaft 13 of the auxiliary motor 11) represent the same physical quantity in principle, namely the absolute angular position of the steering wheel 2, the first dynamic offset OffsetDYN_RS thus gives a first evaluation of the difference (offset) between the first reference frame R_abs (in the case considered) attached to the fixed support of the steering wheel 2 and the second reference frame R_rel attached to the auxiliary motor 11.

[0075] This difference may be due, for example, to measurement errors or drift of a resolver-type sensor responsible for measuring the relative position P_relative_SW of the steering wheel, that is, more specifically, the sensor responsible for measuring the angular position of the shaft 13 of the auxiliary motor 11.

[0076] This process repeats continuously over time.

[0077] Therefore, in each iteration n, the measured value of the steering wheel relative position P_relative_SW(n), the first estimated value of the absolute angular position of the steering wheel 2 provided by the first model, the angle 1(n), and the calculated value of the first corresponding dynamic offset DYN_RS(n)(OffsetDYN_RS(n)) are refreshed.

[0078] According to the method of the present invention, the total compensated offset offset_final can then be determined based on the first dynamic offset offset DYN_RS, and the absolute angular position P_absolute_SW of the steering wheel can be calculated by adding the relative position P_relative_SW of the steering wheel to the total compensated offset offset_final.

[0079] P_absolute_SW=P_relative_SW+offset_final

[0080] Preferably, the calculation of the total compensated offset offset_final(n) applicable to the considered iteration n involves a weighted average of multiple consecutive first dynamic offsets offset DYN_RS(n), each of the first dynamic offsets being weighted by a score_RS(n) (Score_RS(n)) that weights the first dynamic offset.

[0081] The weighted average can be expressed in the form of a quotient, the numerator of which includes (at least) the sum of the product offset DYN_RS(n)*score_RS(n) (preferably summed over n relevant iterations), and the denominator of which includes (at least) the sum of the weighted scores_RS(n) over these same iterations.

[0082] According to the present invention, during the vehicle's shutdown ("power off"), values ​​are recorded, and more specifically, the last value is recorded, referred to as the "offset offset" (Offset_save), which is obtained from the total compensated offset offset_finally obtained during the shutdown:

[0083] Offset_Save = Offset_Final (Power Off)

[0084] In practice, this "offset_save" will more specifically correspond to the final value of the total compensation offset that is refreshed before closing, immediately before the closing time (when the key is turned off), or during the iteration immediately before the closing time.

[0085] During the next restart of the vehicle (“power-on”), that is, when ignition is started, and then during the iteration after the restart, the total compensated offset offset can then be advantageously calculated by taking into account the off offset offset_save.

[0086] Therefore, we can formalize the calculation of the total compensation offset into a function of the following type:

[0087] Offset_final = f(offsetDYN_RS, offset_saved)

[0088] As described above, the fact that the closing offset offset_save is stored and saved before the next start, and the fact that the calculation of the total compensation offset_final is completed by including the closing offset parameter offset_save obtained at the previous closing in the calculation during the recovery period after the start of the calculation, makes it possible to set the information element when the vehicle 6 restarts, which helps to quickly provide a reliable total compensation offset Offset_final, and thus quickly provide the calculated absolute angular position P_absolute_SW of the steering wheel 2.

[0089] Therefore, in general, the present invention includes: when the vehicle is restarted, increasing the calculation of the absolute angular position of the steering wheel, which takes into account historical information of the parameters used to perform the calculation, here taking into account the shutdown offset Offset_save stored during shutdown, preferably the shutdown offset stored at the last shutdown (preferably exactly before this).

[0090] Therefore, despite one or more consecutive shut-off and restart cycles, the present invention can still ensure the continuity of the total compensated offset offset - the final learning process, and thus ensure the continuity (or quasi-continuity) of the availability of the steering wheel's absolute angular position P - absolute - SW.

[0091] According to a particularly preferred feature (which itself can constitute an invention), during the final calculation of the total compensated offset offset, the off offset offset is weighted by the off offset weighted score score (whose value is adjusted according to the conditions under which it is off).

[0092] By reviewing the forms used above, we can write it like this:

[0093] Offset_final = f(offsetDYN_RS, offset_saved * rating_saved)

[0094] In fact, the weighted score_save corresponds to a confidence index that characterizes the reliability of the total compensation offset obtained when off, that is, it characterizes the reliability of the off offset_save, and therefore it quantifies the capacity of the off offset_save to accurately represent the situation where the power steering 1 finds itself when the ignition is off and then on the next restart.

[0095] Because of the lifespan of vehicle 6, a reliable total compensation offset can be determined just before the shutdown occurs, so the weighted score of the shutdown offset is saved higher.

[0096] This is especially true in situations where, in the minutes before the ignition is turned off, the vehicle is driven under conditions favorable to the first model, such as by traveling at a sufficiently high longitudinal speed (typically exceeding 5 km / h) on a road that is not slippery and the route is essentially straight, without any specific action by the driver on the steering wheel 2.

[0097] Conversely, if it is determined that the closed offset_save is incorrect or does not demonstrate sufficient reliability, we can reduce (absolute value) or even cancel (set to zero) the weighted score_save of the closed offset, so as to reduce the impact of the closed offset_save in the new total compensation offset_final calculation after restarting, or even so as to disregard the closed offset_save in the new total compensation offset_final calculation after restarting.

[0098] This could be assuming, for example, that if the vehicle 6 rarely turns around before ignition is turned off, the data obtained is not reliable enough or quantitatively sufficient to effectively calculate the total compensation offset offset_final, or even under conditions that contribute to uncontrolled offset between the first reference frame R_abs attached to the fixed support of the steering wheel 2 and the second reference frame R_rel attached to the auxiliary motor 11, and therefore under appropriate conditions that produce poor quantification errors in the evaluation of the total compensation offset offset_final.

[0099] For example, this uncontrolled drift may occur if the measurement of the absolute angular position of the steering system fails between ignition shutdown and the next vehicle start-up.

[0100] In all cases, in the final calculation of the total compensated offset offset, and therefore in the final calculation of the absolute angular position P_absolute_SW of the steering wheel, the introduction of the weighted score of the off offset score save is advantageous in correcting the effect of the off offset offset save on a case-by-case basis, and more specifically, this effect is more favorable when the off offset offset save is reliable.

[0101] If the calculation of the total compensation offset Offset_final preferably includes a weighted average of multiple consecutive first dynamic offsets DYN_RS(n) (each weighted by a weighted score score_RS(n) of the first dynamic offset, as described above), then the value of the weighted score score_save setting for the off offset can preferably depend on the value reached at the time of shutdown by the first global reference score score_RS_ref (Score_RS_ref) (which corresponds to the cumulative sum of the weighted scores of the first dynamic offsets (when power-off is turned off and the off offset is recorded)).

[0102] For convenience, we can therefore represent the weighted score of the off offset in the form of a law denoted by "g" of the following type:

[0103] Score_save = g(Score_RS_ref(Score_RS_ref)),

[0104] Among them

[0105] Scoring_RS_ref = ∑ Scoring_RS(n = power-off)

[0106] The first global reference score Scoring_RS_ref (Score_RS_ref) advantageously represents the overall reliability degree of the calculation of the total compensation offset Offset_Final derived from the estimated value provided by the first model.

[0107] When the first global reference score Scoring_RS_ref is high, and more specifically, when it exceeds the predetermined thresholds S1, S2, this means that the error risk of the value of the total compensation offset Offset_Final is reduced because the estimated value made by the first model is carried out under favorable conditions and thus receives a high weighted score Scoring_RS(n), ensuring reliability, and / or because the weighted average contains a large number of terms and thus the continuous evaluation values based on a large number of weighted scores Scoring_RS(n) and a large number of dynamic offsets DYN_RS(n) statistically reduce the probability of high errors even if some of the values of the series of these terms are individually uncertain or defective.

[0108] Preferably, the first global reference score Scoring_RS_ref can be compared with increasing score thresholds S1, S2, which define N reliability levels, preferably exactly three reliability levels L1, L2, L3, which are classified by increasing reliability level, and the closed offset weighted score Scoring_Save can then receive predefined numerical scores Scoring_Save_L1, Scoring_Save_L2, Scoring_Save_L3 associated with the achieved reliability levels L1, L2, L3 (the value is higher when the achieved reliability level is high).

[0109] Therefore, formally, we can have the following content in the form of, for example, a corresponding table (corresponding to the above law "g"):

[0110] If Scoring_RS_ref < S1, at the level L1 with low or no reliability, then Scoring_Save = Scoring_Save_L1;

[0111] If S1 < Scoring_RS_ref < S2, at the level L2 with average reliability, then Scoring_Save = Scoring_Save_L2;

[0112] If S2 < Scoring_RS_ref, at the level L3 with high reliability, then Scoring_Save = Scoring_Save_L3;

[0113] Among them, Scoring_Save_L1 < Scoring_Save_L2 < Scoring_Save_L3.

[0114] It is worth noting that a limited number of reliability levels L1, L2, L3 (e.g., three levels), and therefore a limited number of possible values ​​for the weighted score of the off offset (e.g., three possible values), can limit the computational complexity while providing sufficient accuracy and reliability in practice.

[0115] In a preferred embodiment of the invention, at least a second estimated angle 2 (Angle2) of the absolute angular position of the steering wheel 2 is evaluated by at least one second model based on an analysis of a second rolling parameter (different from the first rolling parameter) representing vehicle dynamics.

[0116] The second rolling parameter could be, for example, the vehicle's yaw rate, or even a measurement of the vehicle's lateral acceleration.

[0117] Measurements of yaw rate and / or lateral acceleration can be provided, for example, by an electronic trajectory stability control system (ESP).

[0118] Based on this information about yaw speed (or lateral acceleration), the radius of curvature of the trajectory of vehicle 6 at the moment under consideration can be determined by referring to mechanical laws, and the steering angles of steering wheels 3 and 4 can then be derived from it, thus providing a (second) estimate of the absolute angular position of steering wheel 2, angle 2.

[0119] Such a second model is specifically described in the applicant's patent application FR-2992937, and therefore, for this purpose, the patent application may be considered to be incorporated herein by reference.

[0120] By employing a method similar to that described above with reference to the first model, we can then evaluate the second dynamic offset offset DYN_YR (OffsetDYN_YR), which represents the difference between the second estimated angle 2 of the absolute angular position of the steering wheel and the relative position P_relative_SW of the steering wheel (the latter here more specifically corresponds to the absolute angular position of the shaft 13 of the auxiliary motor 11 (considered in the reference frame R_rel attached to the stator of said auxiliary motor 11)):

[0121] Offset DYN_YR = Angle 2 - P_relative_SW

[0122] Ultimately, we can calculate the total compensated offset by performing the following weighted average:

[0123] (i) The first dynamic offset is offset DYN_RS(n)(OffsetDYN_RS(n)), which is continuously evaluated over multiple consecutive iterations n (according to the first model) and the weighted score of each assigned first dynamic offset is score _RS(n).

[0124] (i) A second dynamic offset, offset DYN_YR(n)(OffsetDYN_YR(n)), is continuously evaluated (according to the second model) over the plurality of consecutive iterations n, and a weighted score of _YR(n) is assigned to each second dynamic offset.

[0125] (iii) and disable Offset_save, which is weighted by disabling Offset_Weighted_Save.

[0126] This can be expressed formally as follows:

[0127]

[0128] in

[0129]

[0130] and,

[0131]

[0132] and,

[0133] ∑ rating RS (n)=∑Score RS (n-1)+score RS (n)

[0134] ∑ rating YR (n)=∑Score YR (n-1)+score YR (n)

[0135] in

[0136] Offset DYN_RS(n) is the first dynamic offset obtained by the first dynamic model for the considered iteration n, which preferably uses the speed deviation of the rear wheels as the rolling parameter ("rear speed").

[0137] The score _RS(n) is the weighting factor that can be applied to the first dynamic offset at the considered iteration;

[0138] The offset DYN_YR(n) is the second dynamic offset obtained through the second dynamic model for the considered iteration n, which preferably uses the vehicle's yaw rate as the roll parameter.

[0139] The score _YR(n) is the weighting factor that can be applied to the second dynamic offset at the considered iteration;

[0140] ∑...(N) is the summation operation of n related continuous values ​​(the sum of i = 1 to n).

[0141] In the weighted average above, the presence of Offset_save*Score_save advantageously allows for a simple consideration of the off offset, and the effect of the off offset on the calculation of the total compensated offset, Offset_final, can be measured by weighted score_save.

[0142] Of course, as a variation, the present invention and therefore the above formula can be applied, in particular, to a method using only one of the two models described above by adding or deleting corresponding items in the weighted average, or to a method using a third model based on a third rolling parameter to estimate a third dynamic offset, which will participate in the calculation of the total compensation offset Offset_final.

[0143] Preferably, when the method uses several models (preferably the first and second models in this case) to determine the corresponding dynamic offsets of multiple series (here, a series of first dynamic offsets DYN_RS(n) and a series of second dynamic offsets DYN_YR(n)), the weighted score of the off offset can be determined based on the maximum value between the first global reference score_RS_ref on one hand and the second global reference score_YR_rel on the other hand.

[0144] The first global reference score, RS_ref, is equal to the cumulative sum of the weighted scores of the first dynamic offset (when power is off and the power-off offset is recorded):

[0145] Rating_RS_ref = ∑Rating_RS (n = Power Outage)

[0146] The second global reference score, score_YR_ref, is equal to the cumulative sum of the weighted scores of the second dynamic offset (when power is off and the power-off offset is recorded):

[0147] Rating_YR_ref = ∑Rating_YR (n = power outage)

[0148] This can be formalized as follows:

[0149] Score_save = g(X),

[0150] in

[0151] X = MAX(Score_RS_ref(Score_RS_ref); Score_YR_ref(Score_YR_ref))

[0152] Right now

[0153] X = MAX[∑ Score_RS(n = power-off); ∑ Score_YR(n = power-off)]

[0154] Of course, here too, the above function g can be a function of the number of models used and the number of different dynamic offset series thus established, in order to calculate the global reference score for each said series and in order to study to determine the applicable shutdown offset weighted score Score_save, and thus the maximum global reference score X in the set of global reference scores considered.

[0155] Advantageously, the use of the maximum value X makes it possible to simply test before shutdown whether at least one of the models used has provided sufficiently reliable data so that the recorded shutdown offset can be relied upon.

[0156] In fact, if at least one of the global reference scores Score_RS_ref, Score_YR_ref, and in particular if at least the highest score among said global reference scores reaches or exceeds the predetermined thresholds S1, S2, then this means that before shutdown, at least the corresponding model has aggregated sufficiently reliable data so that the total compensation offset calculated from these data, and thus the recorded shutdown offset Offset_save, represents the actual situation with a reasonable degree of certainty.

[0157] Preferably, similar to what was described above with reference to the first global reference score Score_RS_ref, the maximum value X between the first global reference score and the second global reference score can be compared with increasing score thresholds S1, S2, said score thresholds defining N reliability levels L1, L2, L3, preferably exactly three reliability levels, which are classified by increasing reliability level, and the shutdown offset weighted score Score_save can then receive a predetermined numerical value Score_save_L1, Score_save_L2, Score_save_L3 associated with the reached reliability level (this value is higher when the reached reliability level L1, L2, L3 is high).

[0158] For example, we can apply the following correspondence table:

[0159] If X < S1, in the level L1 with low reliability or even zero reliability, then Score_save = Score_save_L1;

[0160] If S1 < X < S2, in the level L2 with average reliability, then Score_save = Score_save_L2;

[0161] If S2 < X, in the level L3 with high reliability, then Score_save = Score_save_L3;

[0162] Among them, Rating_Save_L1 < Rating_Save_L2 < Rating_Save_L3.

[0163] Advantageously, the offset-weighted numerical score is saved within the same range (e.g., between 0 and 1) as the weighted score score_RS and score_YR that may be assigned to the dynamic offset.

[0164] Of course, the present invention also relates to a power steering system 1 equipped with a computer configured or programmed to perform a method according to any variant of the present invention, and a vehicle 6 equipped with such a power steering system 1.

[0165] Furthermore, the present invention is by no means limited to the aforementioned variations, and those skilled in the art are particularly able to separate or freely combine all or some of the above features.

Claims

1. A method for estimating the absolute angular position of a steering wheel (2) equipped with a power steering system (1) of a vehicle, wherein: The measurement is referred to as the relative position of the steering wheel, which corresponds to the measurement of the angular position of the movable component (13) of the steering device other than the steering wheel (2) as represented in a first reference frame. Based on the analysis of the first rolling parameter representing vehicle dynamics, at least a first estimate of the absolute angular position of the steering wheel (2) is evaluated using at least a first model. The first dynamic offset is evaluated, which represents the difference between a first estimate of the absolute angular position of the steering wheel (2) and the relative position of the steering wheel. The absolute angular position of the steering wheel is calculated by adding the total compensation offset to the relative position of the steering wheel, and the total compensation offset is determined by the first dynamic offset. in, When the vehicle is turned off, a value called the shutdown offset is recorded. This value is obtained from the total compensation offset at the time of ignition shutdown. Upon the next restart of the vehicle, the shutdown offset is taken into account to calculate the total compensation offset. During the calculation of the total compensation offset, the shutdown offset is weighted by a shutdown offset weighted score, the value of which is adjusted according to the conditions under which the ignition was turned off. The calculation of the total compensation offset involves a weighted average of a plurality of consecutive first dynamic offsets, each of which is weighted by a first dynamic offset weighted score. The set of values ​​for the shutdown offset weighted scores depends on the value achieved at the time of ignition shutdown via a first global reference score, which corresponds to the cumulative sum of the weighted scores of the first dynamic offsets.

2. The method according to claim 1, characterized in that, Based on the analysis of a second rolling parameter that represents vehicle dynamics and differs from the first rolling parameter, at least a second estimate of the absolute angular position of the steering wheel (2) is evaluated using at least a second model. The second dynamic offset is evaluated, representing the difference between a second estimate of the absolute angular position of the steering wheel and the relative position of the steering wheel. The total compensation offset is calculated by performing the following weighted average: (i) A first dynamic offset, which is evaluated consecutively over multiple successive iterations, and each first dynamic offset is assigned a weighted score of the first dynamic offset. (ii) A second dynamic offset, which is evaluated continuously over the plurality of successive iterations and a weighted score is assigned to each second dynamic offset. (iii) and, the closing offset, which is weighted by a closing offset weighted score.

3. The method according to claim 2, characterized in that, The weighted score of the closing offset is determined based on the maximum value between a first global reference score and a second global reference score, wherein the first global reference score is equal to the cumulative sum of the weighted scores of the first dynamic offset, and the second global reference score is equal to the cumulative sum of the weighted scores of the second dynamic offset.

4. The method according to claim 1, characterized in that, The first global reference score is compared with an increased score threshold, which defines N reliability levels, which are classified by increasing the degree of reliability. The offset-weighted score receives a predefined value, which is related to the achieved reliability level. When the achieved reliability level is high, all the predefined values ​​are high.

5. The method according to claim 3, characterized in that, The maximum value between the first global reference score and the second global reference score is compared with an increased score threshold, which defines N reliability levels, which are classified by increasing the degree of reliability. The off-off offset weighted score receives a predefined value that is related to the achieved reliability level. When the achieved reliability level is high, all the predefined values ​​are high.

6. The method according to claim 4 or 5, characterized in that, The N reliability levels refer to three reliability levels.

7. The method according to claim 1, characterized in that, The position referred to as the relative position of the steering wheel is the position of the shaft of the auxiliary motor (11) of the power steering device.

8. The method according to claim 1, characterized in that, The first rolling parameter is the speed difference between the left wheel (14) and the right wheel (15) on the same rear axle.

9. The method according to claim 2, characterized in that, The second rolling parameter is the vehicle's yaw speed.

10. A power steering device (1) equipped with a computer, said computer being configured or programmed to perform the method according to any one of the preceding claims.

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