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    • 专利摘要:
    The present invention relates to a method of determining a rod force (Fbiellette) within a vehicle power steering mechanism (1), said method comprising a step (a) of determining the actuation force during of which the actuation force (Faction) resulting from the assistance effort (Fassist) exerted by the assistance motor (2) and the driver's force (Fcond) exerted by the driver of the vehicle is determined. on said steering mechanism, a step (b) of evaluation of dry friction (Fdry, Rdry), and a step (c) of calculation of the link force (Fbiellette) which comprises a substep (c1) of summation in which is calculated an expression (22) representative of the rod force, which involves the algebraic sum of the actuating force (Faction) and the dry friction force (Fdry), and a sub-step (c2) during which a low-pass filter (23) is applied, in order to to be able to smooth the result of said expression (22) when said expression is calculated at the moment of a steering reversal (15) of the steering mechanism.
    公开号:FR3023612A1
    申请号:FR1456607
    申请日:2014-07-09
    公开日:2016-01-15
    发明作者:Sebastien Bourdrez；Pascal Moulaire；Christophe Ravier
    申请人:JTEKT Europe SAS；
    IPC主号:
    专利说明:

    [0001] The present invention relates to the general field of power steering equiping vehicles, including motor vehicles, and the management processes of such power steering. In known manner, a power steering has the main function of helping the driver turn the steering wheels of the vehicle, combining an assistance effort, provided by an assistance engine, the driver effort, which is exercised manually by the driver on the steering, usually by means of a steering wheel. The combination of the driving force and the assisting force forms an actuating force which makes it possible to counteract the resisting force exerted by the vehicle environment on the steering mechanism, a resistant force which is essentially caused by the contact between the tires and the road. This resisting force, brought back to the limits of the direction, that is to say at the terminals of the system formed by the steering mechanism, constitutes the effort called "rod effort" (or "rod effort"). In practice, in a conventional directional undercarriage, said linkage force corresponds in fact to the algebraic sum of the forces exerted on the steering mechanism, and more particularly on the steering rack, on the one hand by the rod of left direction, which connects the rack to the left steering wheel, and secondly by the right steering rod, which connects the rack to the right steering wheel (one of said rods working, at a moment considered, in traction while the other works in compression). It turns out that the value of the link effort is a particularly useful, even fundamental, datum for characterizing and managing the assisted steering, since many problems directly depend on this value. By way of example, mention may in particular be made of the problem of sizing the assistance engine. However, it is difficult in practice to accurately estimate this link effort. Of course, it is possible to provide for this purpose force sensors, placed for example at the junctions between the rack and the links, but such a solution tends to increase the size, the weight and the complexity of the power steering system, as well as than its cost. According to another approach, it is possible to envisage, as a first approximation, an estimation of the link force by summing on the one hand the conductive force, which can be measured for example by means of a torque sensor. arranged between the steering wheel and the steering column, and secondly the assistance effort, which can be measured for example by means of the instruction applied to the assistance engine, and by assimilating the link force to the sum thus obtained, that is to say considering that the link force is equal to the actuating force exerted on the steering mechanism. However, the inventors have found that such an approximation is relatively crude and may have significant deviations from the true value of the link force. In particular, the inventors have discovered that these differences appear as soon as one begins to apply an actuating force, and tend to increase when said actuating force increases, so that, in practice, the aforementioned approximation is only valid in the vicinity of the straight line, when the direction is little or not solicited. Conversely, the difference between the actuating force and the actual link force is particularly pronounced, and therefore the particularly inaccurate approximation, during the steering inversions, that is to say when the driver of the vehicle (intentionally) changes the direction in which it operates the steering wheel, the change having the purpose and effect of moving from a turning situation to the left, in which the driver exerts a force that pulls the steering wheel to the left, a steering situation to the right, in which the driver exerts a force that pulls the steering wheel to the right, or vice versa. In addition, the inventors have found that the difference between the actuating force and the actual link force can be particularly sensitive to the operating conditions of the steering mechanism, in particular to the temperature conditions, as well as the wear state of said mechanism. In practice, all these limitations can therefore considerably reduce the effective availability of the link force evaluation function, or even make said evaluation of the link force relatively risky. The objects assigned to the invention therefore aim at overcoming the aforementioned drawbacks and at proposing a new method of determining the link force which makes it possible to determine reliably and accurately, at any time, in each life situation of the invention. vehicle, the linkage effort exerted on a steering mechanism. The objects assigned to the invention are achieved by means of a method of determining a force called "link force" which is representative of the effort exerted, at a given moment, the environment of a vehicle on a power steering mechanism which equips said vehicle and which is operated at least by an assistance engine, said method comprising: - a step (a) of determination of actuation force during which the engine is determined actuating force exerted at the moment considered on the steering mechanism, such that said actuating force results from the assistance force exerted by the assistance engine on the steering mechanism, and / or of the conductive force exerted by the driver of the vehicle on said steering mechanism, - a step (b) of evaluation of dry friction, during which the dry friction force exerted on the mechanism of friction is evaluated. direction at the moment considered re - a step (c) for calculating the link force which comprises a sub-step (c1) of summation during which a representative expression of the link force is calculated, which involves the algebraic sum of the actuation force and the dry friction force, and a sub-step (c2) for filtering during which a low-pass filter is applied, in order to be able to smooth the result of said expression when said expression is calculated at the time of a steering reversal of the steering mechanism.
    [0002] Advantageously, the consideration of the dry friction in the evaluation of the rod force makes it possible to determine said link force much more precisely than before. The inventors have indeed discovered that the dry friction could generally explain a significant part, if not all, of the difference found between the actuating force and the actual link force. Consequently, by correcting the evaluation of the rod force so as not to neglect the stress component related to the phenomenon of dry friction, which may be responsible for a significant difference between the actuation force and the link force improves the accuracy and reliability of said evaluation in most, if not all, vehicle life situations, especially in all maneuvering situations, whatever the nature and the intensity of the maneuver concerned, and in particular during the steering reversals. Advantageously, it will be noted that this gain in precision takes place while keeping a formula (expression) of calculation that is particularly simple and quick to implement.
    [0003] In addition, the inventors have discovered that the sensitivity of the known methods of determining the link force to the operating temperature and wear conditions was significantly attributable to the sensitivity of the dry friction to said temperature and wear conditions.
    [0004] Therefore, here again, the consideration of the dry friction allows to gain in precision. More particularly, evaluating this dry friction at the instant chosen to calculate the link force, for example by performing a friction measurement or using a model that is updated over time from empirical data. acquired within the steering mechanism, makes it possible to take into account in real time the changes in dry friction due to temperature and wear factors, and thus to estimate at any time, reliably, an estimated linkage effort which is faithfully representative of the effective linkage effort actually exerted on the steering mechanism.
    [0005] Then, the implementation of a low-pass filtering makes it possible to take into account the physical dynamics of the steering system, and more particularly of the dynamics related to the duration (even tiny) that is necessary to effect the changeover of the value. of dry friction (that is to say at the sign reversal of said friction value) at the moment of the steering reversals, when the speed of movement of the steering mechanism (and in particular of the steering wheel) s' reverse. Indeed, if the tilting of the dry friction value was perceived in a "binary" manner, that is to say as an apparent discontinuity, due in particular to the fact that the computer which manages the process according to the invention proceeds by sampling, then this changeover could punctually reveal a divergence during the instantaneous execution of the calculation of the expression representative of the link force. Such a divergence could then be translated, in the absence of a filter, by the appearance of a peak-type artifact that would totally distort the evaluation of the link force. Therefore, the use of a low-pass filter, whose time constant is of the same order of magnitude as the actual changeover time of the dry friction, advantageously makes it possible to soften the effects of the steering reversals on the calculation of the link force, by smoothing which allows to maintain in all circumstances the result of the expression, that is to say the calculated linkage effort, closer to the effective value of the effort of real link.
    [0006] Thanks to the low-pass filter which improves the stability of the calculation of the link force, the method according to the invention is therefore particularly reliable in all vehicle life situations, including during steering inversions and in the vicinity of those -this.
    [0007] Other objects, features and advantages of the invention will appear in more detail on reading the description which follows, and with the aid of the accompanying drawings, provided for purely illustrative and non-limiting purposes, among which: FIG. 1 illustrates, on a time diagram, the joint evolution, during a succession of steering inversions, on the one hand of the actuating force which corresponds to the accumulation of the assistance effort and the conductive force, secondly the dry friction force evaluated according to the invention, then the rod force calculated according to the method according to the invention, and finally the actual link force. FIG. 2 represents an enlarged detail view of a portion of FIG. 1. FIG. 3 illustrates, on a diagram which expresses the friction (on the ordinate) as a function of a variable (on the abscissa) representative of the effort of assistance, and more particularly according to the total actuation force corresponding to the accumulation of the assistance effort delivered by the engine and the manual effort exerted by the driver on the steering wheel, an example of a model empirical dry friction obtained from a cloud of characterization points measured over time, and a corresponding correlation law. Figure 4 schematically shows the implementation of a method according to the invention within a vehicle.
    [0008] The invention relates to a method for determining a force called "Fbienette rod effort" which is exerted within a power steering mechanism 1 equipping a vehicle, including a motor vehicle. As illustrated in FIG. 4, said steering mechanism 1 is operated by at least one assistance motor 2, capable of delivering for this purpose an assistance effort Fa ', st which is applied to said mechanism 1. It can indifferently consider any type of assistance engine 2, and more particularly any type of assistance engine with two directions of operation. In particular, the invention may equally well be applied to a rotary assist motor 2 intended to exert a torque assisting force Fa ', st, or to a linear assistance motor 2, intended to exert an effort of assistance Fa ', st of traction or compression type. Furthermore, said assistance motor 2 can be for example hydraulic, or preferably, electrical (the use of an electric motor 5 facilitating in particular the implementation and implementation of said motor, as well as the generation and the management of useful signals). In a particularly preferred manner, the assistance motor 2 will be a rotary electric motor, for example of the "brushless" type. Furthermore, as illustrated in FIG. 4, the power steering mechanism 1 preferably comprises, in a manner known per se, a steering wheel 3 through which the driver of the vehicle can rotate a steering column 4 which meshes, by means of a pinion 5, on a steering rack 6 slidably mounted in a steering casing secured to the chassis of the vehicle. The ends of the steering rack 6 are preferably each connected, by means of a steering rod 7, 8, to a steerable steering knuckle on which is mounted a steering wheel (and preferably a driving wheel). 9, 10 of the vehicle, such that the displacement of the rack 6 in translation in the housing causes a modification of the steering angle (ie of the yaw orientation) of said steerable wheels 9, 10. 2 can be engaged on the steering column 4, for example by means of a gearbox with a tangential wheel and worm, or else come into engagement directly on the steering rack 6, by means of a gear mechanism. drive type ball screw or via a pinion 11 distinct from the pinion 25 5 of the steering column (to form for example a steering mechanism said "double pinion", as shown schematically in Figure 4). The force reference (or, more preferably, the torque reference, denoted Fa ', st in Figure 4) which is applied to the assistance motor 2 so that said motor assists the driver in the operation of the steering mechanism 1 depends on predetermined assistance laws, stored in a non-volatile memory of a computer (here an assistance law application module 12), said assistance laws being able to adjust said effort setpoint according to various parameters such as the driving force (torque) bottom exerted by the driver on the steering wheel 3, the speed (longitudinal) VVhic of the vehicle, the angular position ° steering wheel of the steering wheel 3, etc.
    [0009] By simple convenience of description, it will be considered that the force instruction applied to the assistance engine 2 faithfully reflects the assistance effort Fassist delivered by said assistance engine, and therefore the two quantities will be assimilated to one another. to the other.
    [0010] According to the invention, the Fbienette rod force corresponds to the effort exerted, at a given instant t, the environment 20 of the vehicle (that is to say typically the road 20 on which evolves said vehicle) on the power steering mechanism 1 which equips said vehicle. In practice, with reference to the example of FIG. 4, said rod force Fb, diette indeed corresponds to the algebraic sum of the forces F716 and F816 which are exerted on the steering mechanism, here at the terminals of the rack 6, on the one hand by the left steering rod 7, which in fact transmits to the rack 6 (as schematized the effort F716) the resistant force exerted by the road 20 on the left steering wheel 9, and other on the right steering rod 8, which transmits to the same rack 6 (as shown by the effort F816) the resistant force exerted by the road 20 on the right steering wheel 10 (one of said links 7, 8 working, at one moment considered, in traction, while the other works in compression). It will be noted that the method according to the invention advantageously makes it possible to estimate substantially in real time the rod force Fb, ellette, and therefore to quantify precisely and at all times the action of the road 20 on the directional undercarriage, directional running gear which will preferably also correspond to the front axle of the vehicle. According to the invention, the method comprises a step (a) of determining the actuation force Faction during which the actuation force Faction (total) is determined which is exerted at the instant on the mechanism direction 1, such that said actuating force results from the assistance force Fass, is exerted by the assistance motor 2 on the steering mechanism 1, and / or the conductive force Fcond exerted (manually) by the driver of the vehicle on said steering mechanism 1 (here via the steering wheel 3).
    [0011] It will be noted that, in practice, the actuating force Faction may be equal to the (only) conductive force Fcond, in case of inaction of the assistance motor 2. On the contrary, the actuation force Faction may be equal the only assistance effort Fass, st if the driver Fcond force is zero, either because the driver has dropped the steering wheel 3, for example during an automatic maneuver of the direction performed by the assistance engine, such as a parking assist maneuver, or because the steering wheel 3 serves merely as a heading indicator and is not mechanically connected to the rack 6, so that the forces required for steering maneuvers are provided exclusively by the assistance engine 2. However, for convenience of description, and with regard to the example of the steering mechanism 1 illustrated in Figure 4, it will be considered in what follows that the actuating force Faction, which corresponds to the resultant of the various maneuvering forces which are applied voluntarily on the steering mechanism 1 to change the steering angle of said steering mechanism or to maintain the steering angle of said mechanism to a chosen value, is equal to the sum (algebraic) the respective contributions of the conductive force Fcond and the assistance effort Fassist. Of course, the conductive force Fcond and the assistance effort Fass can be evaluated by any appropriate means. Preferably, it will be possible to evaluate the assistance effort Fass, st by measuring (for example at the output of the application module of the assistance laws 12) the torque setpoint applied to the assistance motor 2, or even in measuring, by means of a motor torque sensor placed on the shaft 13 of the assistance motor 2, the assistance force effectively delivered by said assistance engine. The driver Fcond stress, or "flying torque", exerted by the driver on the steering wheel 3 can be measured by a suitable steering wheel torque sensor 14, such as a magnetic torque sensor measuring the elastic deformations d a torsion bar placed between the steering wheel 3 and the steering column 4. According to the invention, the method also comprises a step (b) for assessing dry friction, during which the effort is evaluated. of dry friction Fdry, Rdry exerted on the steering mechanism 1 at time t considered. By "dry friction" is meant, as opposed to the viscous friction which is dependent on (proportional to) the speed of movement of the mechanism, the friction, not dependent on the sliding speed, which is due to the surface contact (lubricated or not). ) between two solids, as described by Coulomb's law, and which can be expressed in the form: Fdry = -Rdry-sign), where Rdry is the value of said dry friction and where sign (2t) represents the sign of the speed of displacement of the steering mechanism 1. Preferably, the dry friction force Fdry, Rdry is evaluated from the fall H of the actuation force Faction, such that this fall H is observed during steering reversals 15 of the steering mechanism 1, as is illustrated in particular in FIGS. 1 and 2. Said drop height H substantially corresponds to the difference between on the one hand the extremum (maximum, called "high value") that reaches the effort 5 of actuation Faction just before turning inversion 15, steering reversal 15 which results in particular by the passage of the mechanism 1 (and therefore the steering wheel 3) by a zero speed, and secondly the value (called "low value") This action is taken by the same actuation force immediately after the turning inversion 15. More particularly, the value of the Rdry dry friction advantageously corresponds to the half-height of fall H / 2. In practice, the successive turning inversions can be detected, for example, by calculating the first time derivative of the signal representative of the actuating force Faction (or, in a substantially equivalent manner, of the signal representative of the Fass assistance effort). , st), and detecting the passage of this derivative 15 by a peak, characterized by crossing a predetermined threshold (derivative amplitude). The high value and the low value of the actuation force signal Faction which delimit (on the ordinate in FIGS. 1 and 2) and characterize the height of fall H, can be calculated at the time limits (situated on the abscissa 20 on said FIGS. 1 and 2) which are located on either side of the steering reversal, and which respectively correspond to a first reference time, which precedes, for a predetermined duration, the instant called "start time" "peak" which characterizes the passage of the derivative above the threshold, and at a second reference time which follows, of a predetermined duration, the instant called "end of peak moment" 25 which characterizes the moment when the derivative descends below said threshold. In an alternative and substantially equivalent manner, the first reference time and the second reference time may correspond to instants which respectively precede and follow, each of a predetermined duration, the mean instant at which the steering inversion takes place, i.e., the time corresponding to the center (time) of the derivative peak. Moreover, the step (b) for evaluating the dry friction Fdry, Rdry is preferably carried out on the basis of an empirical friction model 21 which is constructed and refreshed over time by measurements of dry friction force. Rmes_1, Rmes_2, --- Rmes_n which are operated successively as and when use of the steering mechanism 1, for example (and preferably) at each turning reversal 15.
    [0012] Advantageously, the model 21 which serves to evaluate the friction is thus automatically updated during the use of the steering mechanism 1, and more generally during the (current) use of the vehicle, so that said model 21 is readapted constantly changing the conditions in which the steering mechanism 1 operates, and in particular changes in temperature conditions or aging (wear). By thus using an evolutionary friction model 21 which is periodically updated, rather than a constant or an invariant chart that would be obtained by a simple factory origin calibration, the invention allows the estimation of dry friction to accurately reflect the actual state (by nature not constant) of the friction in the steering mechanism 1, at any time t considered, whatever it is. The accuracy of the process is thus increased. Preferably, the step (b) of evaluation of the dry friction comprises a sub-step (b1) of acquisition of a series of characterization points, during which one measures, for several different values taken successively by the the force of actuation Faction during the operation of the steering mechanism, the corresponding friction values, in order to obtain empirically a series of distinct characterization points P1, P2, --- Pn which each associate with a representative measured value of the actuating force Faction_i, Faction_2, Faction_n a measured value of dry friction Rmes_1, Rmes_2, Rrnes_n, then a substep (b2) of construction of an empirical friction model 21, during which a law is established correlation L between the characterization points Pi, P2,... Pn constituting the series of characterization points, from the point cloud formed by said series of said characterization points. As indicated above, the characterization points can advantageously be acquired during steering inversions 15. Advantageously, by creating a friction model 21 from a scatter plot taken in different (distinct) actuation force values. , rather than on the basis of a single calibration point, a model 21 is obtained which empirically covers a wide range of operation, and which can thus provide information faithfully on the level of dry friction Fdry which corresponds to any effort (any torque ) Faction actuation (t) considered at a given instant t, regardless of the intensity of said actuation force considered.
    [0013] In particular, it will thus be possible to take into account, in the evaluation of the dry friction, that the value of the dry friction Rdry is, in practice, an increasing function of the force (torque) of actuation Faction. Here again, the invention will thus make it possible to gain in precision in the determination of the dry friction, and therefore, consequently, in the determination of the rod force. Advantageously, the step (b1) of acquisition of characterization points and the step (b2) of model construction 21 may be iteratively refreshed during the operation of the steering mechanism 1, so that the learning allowing the construction of the model will be permanent, and will allow the model to evolve in a sliding manner over time (the newly acquired characterization points gradually replacing the oldest characterization points, and the correlation law L adapting accordingly) . As an indication, the size of the series of characterization points P1, P2,... Pn may be between at least 5 characterization points, or even at least 10 characterization points P1, P2, 2, --- Pn and on the other hand 50, even 100 points of characterization. The sample of the characterization points will thus be of sufficiently large size to create a reliable and representative model 21, including 20 in case of occasional occurrence of an erroneous measurement. As has been detailed above, the characterization points P1, P2,... Pn will preferably be acquired during steering inversions 15, the measurement of the value of the friction Rmes_1, Rmes_2, --- Rmes_n at the points characterizing P1, P2, 2, --- Pn being obtained from the drop height H (and more particularly from the half-height of fall H / 2) of the signal representative of the actuating force Faction. Preferably, the correlation law L is established in the form of an interpolation curve (for example a polynomial curve) or of a regression curve with respect to the series of characterization points P1, P2, 2, --- P In a particularly preferred manner, as illustrated in FIG. 3, the correlation law L is obtained by linear regression on the series of characterization points, P-, Pn, for example by the method of least squares. It is thus possible to obtain rapidly and by mobilizing only a modest computing power, a model 21 that is particularly well representative of the actual behavior of the dry friction. Furthermore, it will be noted that the use of a continuous correlation law L whose domain of definition and validity extends, by extrapolation, beyond the only points of characterization used in the construction of the model 21, advantageously allows to associate with any value of the actuating force Fact, one (t), measured (or calculated) at the instant t, and this including beyond the domain covered by said only points of characterization, an estimate of the Rdry dry friction value. According to the invention, the method comprises a step (c) of calculating the Fbienette rod force which comprises a sub-step (c1) of summation during which a representative expression 22 of the link force is calculated, which involves the algebraic sum of the actuation force Faction and the dry friction force Fdry: Fdry = Fcond Fa ', st + Fdry, and a sub-stage (c2) of filtering in which one applies a low-pass filter 23, in order to be able to smooth the result of said expression 22 (at least) when said expression is calculated at the moment of a steering reversal 15 of the steering mechanism. Indeed, because there exists, at the level of the contacts between real solids, a bonding stiffness which is not infinite, the real dry friction does not evolve discontinuously during the steering reversals 15, it is that is to say, does not pass instantly from a positive value to an opposite negative value (or vice versa), but on the contrary obeys a transition dynamic that is certainly rapid, but nevertheless continuous.
    [0014] Now, said dry friction Fdry is modeled here by an expression Fdry R dry - sign) which is proportional to the sign sign (2t) of the speed of displacement i of the steering mechanism 1. In practice, it may be considered as representative value of the speed of displacement i the speed of the assistance motor 2, that is to say the angular speed of rotation of the shaft 13 of said assistance motor 2, which is known very precisely. The signal sign (2t) which measures the sign of the speed of displacement of the steering mechanism (and which therefore in practice reflects the direction of rotation of the shaft 13 of the assistance motor) is, by nature, binary ( the sign of the speed being either positive or negative). As a result, if said sign signal (i ') is obtained or treated raw, in digital form, by discrete sampling, a sign change in the speed of movement of the steering mechanism 1 will be perceived as a instantaneous switching of the binary value of said sign signal (i '), tilting which will take place instantaneously at the moment of refreshing the signal which will immediately follow the moment when the speed has passed through zero.
    [0015] However, such an instantaneous tilting would have the effect of introducing a discontinuity (a peak) in the evaluation of the friction, and therefore, consequently, in the calculation of the link force. Here, advantageously, the addition of the low-pass filter 23 makes it possible to artificially introduce a dynamic limitation in the signal sign (2t) which measures the sign of the speed of displacement of the steering mechanism, a dynamic limitation which acts on (in addition to de) the binary perception of the change of sign so as to create, in said signal sign (i ') thus filtered, during a change of sign, a continuous transition which reproduces the real physical dynamics of the inversion phenomenon. In other words, the low-pass filtering 23 makes it possible to restore the progressivity of the inversion of the friction, such that this inversion is perceived by the computer which manages the method according to the invention, thus avoiding that the treatment method does not generate of itself a discontinuity which would be translated, falsely, by a peak of friction (and thus a peak of link force) without real material cause. Concretely, as is clearly visible in FIG. 2, the low-pass filtering 23, although it is not absolutely perfect in that it can leave a slight residual disturbance 24 (a damped peak) in the effort Fbeilette rod calculated, at the moment of turning inversion 15, nevertheless allows to maintain the amplitude of said residual disturbance 24 well below the difference observed between the actual link effort and the effort Faction actuation, i.e., graphically, to continuously maintain the calculated link force curve (shown in dashed lines in Figure 2) much closer to the actual link force curve (appearing in FIG. in continuous line in this same Figure 2) that is the curve representative of the actuating force Faction (shown in phantom in said Figure 2). It will be noted that, conversely, in the absence of filtering, the calculated link force curve could, at the moment of the steering inversions 15, have a peak which would distance it from the actual link force curve further. than is the curve representative of the actuating force, that is to say that, in this case, the value of calculated rod force Fbienette would be (temporarily) even less reliable than if said value d The link force was simply considered equal to the actuation force value Faction.
    [0016] It can thus be seen that the use of the low-pass filter 23 according to the invention makes it possible to determine in all circumstances the calculated rod force Fb, eilette with a precision much greater than the previously known methods, and this even at the critical moment. - Turning inversion 15. More generally, it is remarkable that the combination of, according to the invention, on the one hand a consideration of dry friction and on the other hand the use of a filter passes 23 (peak damper) makes it possible to bring the link force estimated by the calculation as close as possible to the actual link force, and to maintain this proximity (this cohesion between the curves) in all circumstances, including ( in particular) in the vicinity of the turning reversal zones 15 (in which the filter makes it possible to significantly attenuate the effects of the discontinuity of the raw signal reflecting the sign of the speed of displacement). Preferably, as illustrated in FIG. 4, the low-pass filtering will occur on the sign signal (2t) representative of the sign of the speed of displacement of the steering mechanism 1, upstream of the calculation (c 1) of the expression 22, and even upstream of the computation of the dry friction Fdry (which consists here in multiplying the sign of the sign speed (i ') by the value of dry friction Rdry), which allows in particular to restore the dynamics of continuous transition " at the source ", directly in the signal (of speed sign) concerned, in" input "of the expression 22. However, one could also consider operating this low-pass filtering 23 further downstream, for example on the dry friction signal Fdry from the product Fdry Rdry - sign), or even on the expression 22, after calculation (cl) of the latter, that is to say "output" of said expression 22. Preferably, the constant time of the low-pass filter 23 is between 0.05 s and 0.5 s, and preferably between 0.1 s (100 milliseconds) and 0.3 s (300 milliseconds), for example substantially equal to 0.15 s (150 milliseconds).
    [0017] Advantageously, these orders of magnitude correspond substantially to the characteristic duration of the actual tilting dynamic of the dry friction, that is to say of the continuous transition of said dry friction, as it is observed during the steering reversals 15. The low-pass filter 23 can thus reproduce a realistic artificial dynamic, close to the real transition dynamics. Furthermore, during the step (c) of calculating the link force, it is also preferable to also take into consideration the viscous friction force Fvisq which affects the displacement of the steering mechanism 1, and which is proportional at the speed of displacement i of said steering mechanism.
    [0018] Although the contribution of this viscous friction term Fvisq is not predominant, but on the contrary rather incidental, with regard to the contributions of the actuation force Faction and the dry friction Fdry, its consideration nevertheless makes it possible to improve even further. the precision of the calculation of the rod force Fbieliette- Concretely, this viscous friction can be expressed in the form Fvisq Rv, sq - k Where f visq is the coefficient of viscous friction and where represents the speed of movement of the steering mechanism . The viscous coefficient of friction f visq may be predetermined by a test campaign and stored in the form of an abacus in a non-volatile memory of the computer managing the process.
    [0019] The speed of displacement may for example be calculated, by a time derivative calculation, from a position sensor capable of measuring the angular position of the steering wheel 3, the linear position of the rack 6, or even the position angular of the shaft 13 of the assistance engine. Similarly, during the step (c) for calculating the link force, one can also take into account the inertial force M -: t which is exerted on the steering mechanism 1. Here again, although this is a term whose contribution is generally rather incidental with respect to the contributions of the actuation force Faction and the dry friction Fdry, its consideration will nevertheless make it possible to further improve the accuracy of the calculation. the Fbiellette rod effort. Specifically, said inertial force can be calculated by making the product of the mass (mobile) M - known - of the steering mechanism by its instantaneous acceleration which can for example be obtained by deriving the speed X.
    [0020] In practice, the inertia of the assistance motor 2 being very much greater than that of the other movable members of the steering mechanism 1 (such as rack 6), we can, as a first approximation (realistic) consider only the mass and the accelerating the shaft 13 of the assistance motor 2 to evaluate the inertial force M - X.
    [0021] Finally, the expression 22 representative of the rod force will preferably be given by: Fbiellette Fcond Fassist Fdry Fvisq -, with: - Fbiellette the rod effort, - Fcond the stress driver, - Fassist the effort of assistance, Fdry the dry friction, with Fdry Rdry - sign), where Rdry is the value of the dry friction and where sign (i ') represents the sign of the speed of displacement of the steering mechanism, Fasq the viscous friction, with Fyisq = - Rvisq -, where fiv, sq is the coefficient of viscous friction and where i represents the speed of movement of the steering mechanism, M -: t the inertial force which depends on the moving mass M of the steering mechanism and the instantaneous acceleration: t of said steering mechanism.
    [0022] As indicated above, the dry friction value Rdry is preferably obtained from a model 21, and is preferably an increasing function (which typically follows the regression line L mentioned above) of the actuation force : Rdry = fiFassist Fconcl). It will be noted that the expression representative of the link force above corresponds to the application of the fundamental principle of the dynamics at the terminals of the steering mechanism 1. It will also be noted that the predominant terms (and therefore sufficient on their own to obtain a result representative of the actual link force) of this expression 22 are, as a first approximation, the actuating force (Fa ', st + Fcond) and the dry friction force Fdry. Of course, the functions assigned to the method according to the invention may be carried out by suitable calculation modules, and more particularly by an assistance law application module 12, an acquisition module (of characterization points). a model construction module (correlation law computation module L) 17, and a friction evaluation module 18 (applying the correlation law L thus defined to estimate, at any time and for any arbitrary value the actuation force Caction (t), the friction value Rdry (t) corresponding), a module 19 for calculating rod force Fb, eilette and a filtering module (or "filter") low-pass 23.
    [0023] Each of the aforementioned modules may be formed by an electronic circuit, an electronic card, a computer (computer), a programmable controller, or any other equivalent device, preferably arranged to process the signals useful to the process in digital (discrete) form. Each of the aforementioned modules may have a physical control structure, related to the wiring of its electronic components, and / or, preferably, a virtual control structure, defined by computer programming. Of course, the invention also relates as such to any computer readable data medium containing computer program code elements for executing the method according to the invention when said medium is read by a computer. It also relates to a power steering system comprising a power steering mechanism 1 controlled by a management module including all or part of the aforementioned modules, and thus capable of implementing the method according to the invention. It also relates to a motor vehicle, in particular with steering wheels 9, 10, possibly driving, equipped with such a power steering system. Finally, it will be noted that the method according to the invention, which exploits the signals generally available within the assisted steering systems, can be easily generalized to all the assisted directions, including retrofitting on many already existing power steering, by a simple reprogramming their calculator. Of course, the invention is also in no way limited to the only embodiments described above, the person skilled in the art being able to isolate or combine freely between them one or the other characteristics mentioned above, or to substitute equivalents for them.
    权利要求:
    Claims (8)
    [0001]
    REVENDICATIONS1. A method for determining a "rod force" effort (Fbiellette) which is representative of the effort exerted, at a given moment, the environment (20) of a vehicle on a power steering mechanism (1) ) which equips said vehicle and which is operated at least by an assistance motor (2), said method comprising: a step (a) for determining the actuation force during which the actuation force is determined (Faction) which is exerted at the moment considered on the steering mechanism (1), such that said actuating force results from the assistance effort (Fass, st) exerted by the assistance motor (2). ) on the steering mechanism (1), and / or the conductive force (Fcond) exerted by the driver of the vehicle on said steering mechanism (1), a step (b) of evaluation of dry friction, during of which we evaluate the effort of dry friction (Fdry, Rdry) which is exerted on the steering mechanism to the inst considered, a step (c) for calculating the link force (Fb, diette) which comprises a summing sub-step (c1) during which an expression (22) representative of the link force is calculated , which involves the algebraic sum of the actuation force (Faction) and the dry friction force (Fdry), and a sub-stage (c2) of filtering during which a low-pass filter is applied (23), in order to be able to smooth the result of said expression (22) when said expression is calculated at the moment of a steering reversal (15) of the steering mechanism.
    [0002]
    2. Method according to claim 1 characterized in that the time constant of the low-pass filter (23) is between 0.05 s and 0.5 s, and preferably between 0.1 s and 0.3 s.
    [0003]
    3. Method according to claim 1 or 2 characterized in that the dry friction force (Fdry, Rdry) is evaluated from the fall (H) of the actuation force (Faction) observed during inversions steering (15) of the steering mechanism.
    [0004]
    4. Method according to one of the preceding claims characterized in that the step (b) for evaluating the dry friction is performed from an empirical friction model (21) which is constructed and refreshed over time by measures of dry friction force (Rmes_1, Rmes_2, --- Rmes_n) which are operatedeffuccivement as the use of the steering mechanism (1), for example at each turning reversal (15).
    [0005]
    5. Method according to one of the preceding claims characterized in that the step (b) for evaluating the dry friction comprises a substep (b1) acquisition of a series of characterization points, during which the corresponding dry friction values are measured for several different values successively taken by the actuating force (Faction) during the operation of the steering mechanism (1), in order to empirically obtain a series of characterization points ( P1, P2, Pn) each associating with a measured value representative of the actuating force (Faction_l, Faction_2, Faction_n) a measured value of dry friction (Rmes_1, Rmes_2, Rmes_n), then a substep (b2 ) of construction of an empirical friction model (21), during which a correlation law (L) is established between the characterization points (P '- 1, - P 2, - Pn) constituting the series of characterization points, from cloud of points formed by said series of said points of characterization.
    [0006]
    6. Method according to one of the preceding claims characterized in that, during the step (c) of calculation of the rod force, one also takes into consideration the viscous friction force (F ,, sq) which affects the movement of the steering mechanism, and which is proportional to the traveling speed () of said steering mechanism (1).
    [0007]
    7. Method according to one of the preceding claims characterized in that, during the step (c) of calculation of the rod force, one also takes into consideration the inertial force (M -)) s' exerts on the steering mechanism (1).
    [0008]
    8. Method according to one of the preceding claims characterized in that the expression (22) representative of the rod force is given by: Fbiellette Fcond Fassist Fdry Fvisq - with: Fbiellette the rod effort, Fcond the driver stress, Fassist the assistance effort, Fdry the dry friction, with Fdry = - Rdry - sign), where file), is the value of the dry friction, preferably obtained from a model and preferably function increasing of the actuating force: Rdry = .assist Fconcd, and where sign (i ') represents the sign of the speed of displacement of the steering mechanism (1), Fyisq the viscous friction, with Fyisq = - Rvisq -, where Rvisq is the coefficient of viscous friction and where i represents the speed of displacement of the steering mechanism (1), M -: t the inertial force which depends on the moving mass M of the steering mechanism (1) and the instantaneous acceleration: t of said steering mechanism (1).
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    同族专利:
    公开号 | 公开日
    PL3166839T3|2018-12-31|
    US20170131164A1|2017-05-11|
    CN106715244B|2019-02-15|
    EP3166839A1|2017-05-17|
    JP6615173B2|2019-12-04|
    BR112017000182A2|2018-01-16|
    US10139297B2|2018-11-27|
    CN106715244A|2017-05-24|
    FR3023612B1|2016-07-29|
    JP2017524593A|2017-08-31|
    WO2016005671A1|2016-01-14|
    EP3166839B1|2018-07-25|
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    FR3070957B1|2017-09-13|2019-09-06|Jtekt Europe|METHOD FOR ESTIMATING A FRICTION VALUE|
    FR3076530B1|2018-01-08|2020-01-10|Jtekt Europe|STEER BY WIRE POWER ASSISTED STEERING SYSTEM USING ACTUATORS MADE TRANSPARENT THROUGH THE USE OF LOCAL TORQUE AND / OR STRENGTH LOOP|
    KR102047334B1|2018-03-07|2019-11-21|재단법인대구경북과학기술원|Trasmission force measurement system and method for actuator|
    US11203377B2|2019-03-22|2021-12-21|Veoneer Us, Inc.|System and method to estimate a tie-rod force and control the steering of a vehicle|
    法律状态:
    2015-06-19| PLFP| Fee payment|Year of fee payment: 2 |
    2016-01-15| PLSC| Search report ready|Effective date: 20160115 |
    2016-06-09| PLFP| Fee payment|Year of fee payment: 3 |
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    2021-04-09| ST| Notification of lapse|Effective date: 20210305 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1456607A|FR3023612B1|2014-07-09|2014-07-09|METHOD FOR ESTIMATING REAL-TIME RELIEF TO RODS WITHIN AN ASSISTED STEERING MECHANISM|FR1456607A| FR3023612B1|2014-07-09|2014-07-09|METHOD FOR ESTIMATING REAL-TIME RELIEF TO RODS WITHIN AN ASSISTED STEERING MECHANISM|
    BR112017000182-9A| BR112017000182A2|2014-07-09|2015-06-19|method for estimating, in real time, the force on the rods within an assisted steering mechanism|
    PCT/FR2015/051630| WO2016005671A1|2014-07-09|2015-06-19|Method for estimating in real time the force on the links within a power-steering mechanism|
    PL15733851T| PL3166839T3|2014-07-09|2015-06-19|Method for estimating in real time the force on the links within a power-steering mechanism|
    EP15733851.8A| EP3166839B1|2014-07-09|2015-06-19|Method for estimating in real time the force on the links within a power-steering mechanism|
    US15/320,085| US10139297B2|2014-07-09|2015-06-19|Method for estimating in real time the force on the tie-rods within a power steering mechanism|
    JP2017501296A| JP6615173B2|2014-07-09|2015-06-19|A method to calculate the force acting on the tie rod in the power steering mechanism in real time|
    CN201580037206.4A| CN106715244B|2014-07-09|2015-06-19|The method of power on the pull rod in estimated driving force steering mechanism in real time|
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