Method for detecting vehicle slip

Abstract

Method (100) for detecting loss of grip in a vehicle equipped with a power steering system, the method (100) comprising: - at least one first measurement (101) by a first sensor configured to measure a first physical quantity representative of a direction of travel defined by a driver of the vehicle; - at least one second measurement (102) by a second sensor configured to measure a second physical quantity representative of a response of the vehicle to the direction of travel; - determining (103) that the vehicle is oversteering (SURV) or understeering (SOUV) based on a criterion that is a function of the at least one first measurement and the at least one second measurement.

Description

Technical Field

[0001] This application discloses a method for detecting vehicle skidding.

[0002] This invention relates to the field of power steering systems, and more particularly to the detection of loss of grip in vehicles equipped with power steering systems. Background Technology

[0003] Importantly, by improving the quality of the information provided when vehicle slippage occurs, drivers can be warned of loss of traction in vehicles equipped with electric power steering, enabling suggestions and activation of specific functions, such as reducing steering wheel torque when the vehicle is understeerable or increasing counter-steering when the vehicle is oversteerable. Summary of the Invention

[0004] The present invention is therefore intended to provide solutions to all or part of these problems.

[0005] Therefore, the present invention relates to a method for detecting loss of grip in a vehicle including a power steering system, the method comprising:

[0006] - At least one first measurement is performed by a first sensor, which is configured to measure a first physical quantity representing the direction of travel defined by the driver of the vehicle;

[0007] - At least one second measurement performed by a second sensor configured to measure a second physical quantity representing the vehicle's response to the direction of travel;

[0008] - Determine the oversteer or understeer condition of the vehicle based on criteria that are functions of at least one first measurement and at least one second measurement.

[0009] Based on these arrangements, vehicle slippage can be detected and information can be provided to the driver to activate or automatically activate supplementary functions, such as, for example, reducing steering wheel torque when the vehicle is understeerable, or increasing counter-steering of the front axle when the vehicle is oversteerable.

[0010] According to one embodiment, the present invention includes one or more of the following features, individually or in a technically acceptable combination.

[0011] According to one implementation model, the first physical quantity is the vehicle's steering wheel rotation angle θ. 方向盘 .

[0012] According to one implementation mode, the second physical quantity is the vehicle's lateral acceleration or yaw rate. .

[0013] According to one implementation mode, the equivalent steering wheel rotation θ of the vehicle is determined based on at least one second measurement.eq .

[0014] According to one implementation mode, the equivalent steering wheel rotation θ eq Depend on Defined as follows, where V is the vehicle speed and K is a constant value, which is the vehicle wheelbase E and the steering wheel rotation angle θ. 方向盘 A function of the ratio of the steering wheel rotation angle α of the vehicle.

[0015] According to one implementation model, the criteria include the following conditions (1) and (2):

[0016] ;

[0017] ;

[0018] If either criterion is met, the vehicle is determined to be oversteer; if neither criterion is met, the vehicle is determined to be understeer.

[0019] According to one implementation, the oversteer rate is defined as the product of the maximum oversteer and the oversteer coefficient, which is the equivalent steering wheel rotation θ. eq and steering wheel rotation angle θ 方向盘 The function.

[0020] According to one implementation, the understeer rate is defined as the product of the maximum understeer and the understeer coefficient, which is the equivalent steering wheel rotation θ. eq and steering wheel rotation angle θ 方向盘 The function.

[0021] According to one implementation mode, the oversteering coefficient is the smaller of a first value and a second value, where the first value is the equivalent steering wheel rotation θ. eq The first value is the absolute value of the function, and the second value is the steering wheel rotation angle θ. 方向盘 And equivalent steering wheel rotation θ eq The second function of the absolute value of the difference.

[0022] According to one implementation mode, when the equivalent steering wheel rotates θ... eq When the absolute value of is between 0 and the first lower threshold, the first function is constant and equal to 0, and where, when the equivalent steering wheel rotates θ eq When the absolute value of is greater than the first upper threshold, the first function is constant and equal to 1, and wherein, within the interval between the first lower threshold and the first upper threshold, the first function increases linearly between 0 and 1, for example.

[0023] According to one implementation, when the steering wheel rotation angle θ 方向盘 And equivalent steering wheel rotation θ eqWhen the absolute value of the difference is between 0 and the second lower threshold, the second function is constant and equal to 0, and where, when the steering wheel rotation angle θ 方向盘 And equivalent steering wheel rotation θ eq When the absolute value of the difference is greater than the second upper threshold, the second function is constant and equal to 1, and wherein the second function increases linearly between 0 and 1, for example, within the interval between the second lower threshold and the second upper threshold.

[0024] According to one implementation model, the understeer coefficient is the smaller of a third and a fourth value, where the third value is the equivalent steering wheel rotation θ. eq The third function of the absolute value, and the fourth value is the steering wheel rotation angle θ. 方向盘 And equivalent steering wheel rotation θ eq The fourth function of the absolute value of the difference.

[0025] According to one implementation, when the equivalent steering wheel rotates θ eq When the absolute value of is between 0 and the third lower threshold, the third function is constant and equal to 0, and where, when the equivalent steering wheel rotates θ eq When the absolute value of is greater than the third upper threshold, the third function is constant and equal to 1, and the third function is linear between 0 and 1 in the interval between the third lower threshold and the third upper threshold.

[0026] According to one implementation mode, when the steering wheel rotation angle θ 方向盘 And equivalent steering wheel rotation θ eq When the absolute value of the difference is between 0 and the fourth lower threshold, the fourth function is constant and equal to 0, and where, when the steering wheel rotation angle θ 方向盘 And equivalent steering wheel rotation θ eq When the absolute value of the difference is greater than the fourth upper threshold, the fourth function is constant and equal to 1, and the fourth function is linear between 0 and 1 in the interval between the fourth lower threshold and the fourth upper threshold.

[0027] According to one implementation, at least one first measurement includes a plurality of first measurements filtered by a first frequency filter, and wherein at least one second measurement includes a plurality of second measurements filtered by a second frequency filter.

[0028] According to one embodiment, the first frequency filter and the second frequency filter are configured to allow frequencies contained between 0.5 Hz and 10 Hz to pass through, preferably between 1 Hz and 5 Hz.

[0029] Based on these arrangements, the first and second measurements will be synchronized.

[0030] According to one aspect, the present invention relates to a vehicle including a power steering or steer-by-wire system and an electronic steering system control unit, the electronic steering system control unit being configured to:

[0031] - Collect at least one first measurement from a first sensor, the first sensor being configured to measure a first physical quantity representing the direction of travel defined by the driver of the vehicle;

[0032] - Collect at least one second measurement from a second sensor, which is configured to measure a second physical quantity representing the vehicle's response to the direction of travel;

[0033] The electronic control unit is further configured to implement method 100 of one of the embodiments described above. Attached Figure Description

[0034] For proper understanding, embodiments and / or implementation modes of the invention are described with reference to the accompanying drawings, which illustrate embodiments or implementation modes of the devices and / or methods according to the invention by way of non-limiting example. The same reference numerals in the drawings denote similar elements or elements having similar functions.

[0035] [ Figure 1 [ ] is a graphical representation of the points corresponding to the oversteer and understeer zones, respectively, which are determined by the steering wheel rotation angle θ along the first horizontal axis. 方向盘 The first value and the value along the second vertical axis are equal to the equivalent steering wheel rotation θ. eq The second value is determined, which is the equivalent steering wheel rotation θ. eq It is based on the vehicle's lateral acceleration or yaw rate. It's confirmed.

[0036] [ Figure 2 [] is another graphical representation of the points corresponding to the oversteering and understeering regions, respectively, where the oversteering and understeering regions are truncated near the boundary between these regions, and the truncation is symmetrical on both sides of the boundary.

[0037] [ Figure 3 ] is another graphical representation of the points corresponding to the oversteering and understeering zones, respectively, where the oversteering and understeering zones are truncated near the boundary between these zones, and the truncation is asymmetrical on both sides of the boundary.

[0038] [ Figure 4 [Illustrated diagram] is a schematic representation of the sequence of method steps according to an embodiment of the present invention. Detailed Implementation

[0039] As known to those skilled in the art, vehicles equipped with electric steering systems may in particular include a subsystem comprising a power steering motor and its control unit, which is coupled via an associated reduction gear to a subassembly comprising a rack and pinion. A torque sensor is typically positioned on the driveshaft of the steering member to estimate the driver torque. The auxiliary motor control unit is configured to calculate the auxiliary torque as a function of the driver torque estimated by the torque sensor and based on information derived from the internal vehicle network, such as vehicle speed or lateral acceleration. This invention can also be used in vehicles equipped with electric steering systems of the "steer-by-wire" type.

[0040] The perception of loss of grip is affected by internal friction within the electric steering system, damping effects, the quality of auxiliary controls, and all adjustments designed to provide comfort for the driver and passengers.

[0041] To improve the quality of information provided to the driver when the vehicle slips, and to enable suggestions to the driver and / or activation of certain supplemental functions, such as reducing steering wheel torque when the vehicle is understeer or increasing counter-steering when the vehicle is oversteer, it is important to be able to detect oversteer or understeer conditions and to be able to independently determine the vehicle's oversteer rate and understeer rate.

[0042] The present invention therefore relates to a method 100 for detecting loss of traction in a vehicle equipped with a power steering system, the method 100 comprising the steps of, in Figure 4 The diagram illustrates:

[0043] - At least one first measurement 101 performed by a first sensor, the first sensor being configured to measure a first physical quantity representing the direction of travel defined by the driver of the vehicle;

[0044] - At least one second measurement 102 performed by a second sensor, the second sensor being configured to measure a second physical quantity representing the vehicle’s response to the direction of travel;

[0045] - Determine whether a vehicle is oversteer (SURV) or understeer (SOUV) based on a criterion that is a function of at least one first measurement and at least one second measurement.

[0046] The first physical quantity is, for example, the steering wheel rotation angle θ of a vehicle. 方向盘 .

[0047] The second physical quantity is, for example, the vehicle's lateral acceleration or yaw rate. .

[0048] Specifically, the vehicle's equivalent steering wheel rotation θ eqIt can be determined based on at least one second measurement of lateral acceleration or yaw rate, using relationships known to those skilled in the art, which allows the yaw rate of the vehicle to be determined on the one hand. The vehicle's speed V and the radius of curvature R of its trajectory are related to the steering wheel's orientation. On the other hand, the front wheel's angular orientation is expressed as a function of the vehicle's wheelbase E and the radius of curvature R. Finally, the steering wheel's angular orientation θ is determined. 方向盘 A constant ratio between the angle orientation α of the vehicle's steering wheels and the angle orientation α.

[0049] For example, the following relation is obtained Where K is a constant, which is the steering wheel angle orientation θ of the vehicle. 方向盘 The constant ratio between the steering wheel angle α and the vehicle wheelbase E is a function of the yaw rate. A similar relationship can be obtained by using the vehicle's lateral acceleration instead of the yaw rate.

[0050] Based on these arrangements, their coordinates θ can be obtained. eq and θ 方向盘 The defined points are graphically represented as either the vehicle's oversteer condition (SURV) or understeer condition (SOUV), as shown below. Figure 1 As shown. Therefore, these points are determined by a distance along the first horizontal axis equal to the steering wheel rotation angle θ. 方向盘 The first value and the value along the second vertical axis are equal to the equivalent steering wheel rotation θ. eq The second value defines the equivalent steering wheel rotation θ. eq It is based on the vehicle's lateral acceleration or yaw rate. It's confirmed.

[0051] Criteria that allow determination of whether a vehicle is in an oversteer condition (SUR) or an understeer condition (SOUV) include, for example, the following two conditions (1) and (2):

[0052] ;

[0053] ;

[0054] Thus, according to one embodiment of the method, if one of the criteria is met, the vehicle is determined to be in an oversteer condition (SURV), and if neither of the criteria is met, the vehicle is determined to be in an understeer condition (SOUV).

[0055] Based on these arrangements, vehicle slippage can be detected and information can be sent to the driver to activate or directly and automatically activate supplementary functions, such as, for example, reducing steering wheel torque when the vehicle is understeerable, or increasing counter-steering of the front axle when the vehicle is oversteerable.

[0056] To account for approximations related to sensor accuracy, simplified calculations, and certain delays, it would be advantageous to partially truncate the oversteer SURV and understeer SOUV zones near the boundary FR between these two zones, such as... Figure 2 As shown. For this purpose, if, for example, a symmetric truncation is sought on either side of the boundary FR, then, for example, a first truncation function K1 and a second truncation function K2 can be defined.

[0057] Therefore, the oversteer rate is defined as the product of the maximum oversteer and the oversteer coefficient, where the maximum oversteer is, for example, equal to 1, and the oversteer coefficient is the equivalent steering wheel rotation θ. eq and steering wheel rotation angle θ 方向盘 Functions: For example, the oversteer coefficient is the equivalent steering wheel rotation θ eq The absolute value of the first function K1 is related to the steering wheel rotation angle θ 方向盘 And equivalent steering wheel rotation θ eq The smaller value between the absolute values ​​of the difference and the second function K2. Specifically, when the equivalent steering wheel rotates θ. eq When the absolute value of K1 is between 0 and the first lower threshold SI1, the first function K1 is constant and equal to 0, and when the equivalent steering wheel rotates θ... eq When the absolute value of the first function K1 is greater than the first upper threshold SS1, the first function K1 is constant and equal to 1, and within the interval between the first lower threshold SI1 and the first upper threshold SS1, the first function K1 varies linearly between 0 and 1. Similarly, when the steering wheel rotation angle θ 方向盘 And equivalent steering wheel rotation θ eq When the absolute value of the difference is between 0 and the second lower threshold SI2, the second function K2 is constant and equal to 0, and when the steering wheel rotation angle θ 方向盘 And equivalent steering wheel rotation θ eq When the absolute value of the difference is greater than the second upper threshold SS2, the second function K2 is constant and equal to 1, and the second function K2 varies linearly between 0 and 1 within the interval between the second lower threshold SI2 and the second upper threshold SS2.

[0058] If a symmetrical cutoff is sought on either side of the boundary FR, the understeer rate can be similarly determined based on the maximum understeer and the understeer coefficient, which is, for example, equal to 1, and the understeer coefficient is equal to, for example, the oversteer coefficient mentioned above.

[0059] According to another example of the implementation, an asymmetric truncation can be sought on either side of the boundary FR; thus, an understeer coefficient different from the oversteer coefficient described above can be defined; in this case, for example, as Figure 3As explained, the understeer coefficient can be the smaller of the third function K3 and the fourth function K4, where the third function is the equivalent steering wheel rotation θ. eq The fourth function is a function of the absolute value of the steering wheel rotation angle θ. 方向盘 And equivalent steering wheel rotation θ eq A function of the absolute value of the difference. For example, when the equivalent steering wheel rotates by θ... eq When the absolute value is between 0 and the third lower threshold, the third function K3 is constant and equal to 0, and when the equivalent steering wheel rotates θ... eq When the absolute value of the third function K3 is greater than the third upper threshold, the third function K3 is constant and equal to 1, and within the interval between the third lower threshold and the third upper threshold, the third function K3 varies linearly between 0 and 1. Similarly, for example, when the steering wheel rotation angle θ... 方向盘 And equivalent steering wheel rotation θ eq When the absolute value of the difference is between 0 and the fourth lower threshold, the fourth function K4 is constant and equal to 0, and when the absolute value of the difference is greater than the fourth upper threshold, the fourth function K4 is constant and equal to 1, and the fourth function K4 varies linearly between 0 and 1 within the interval between the fourth lower threshold and the fourth upper threshold.

[0060] According to these arrangements, an asymmetric cutoff of oversteering and understeering zones is obtained on either side of the boundary between these zones. Figure 3 The star-shaped ET shown is positioned at a point in the plane when the equivalent steering wheel rotates by θ. eq When the value is low and positive, this point corresponds to very high understeer, and when the equivalent steering wheel rotation θ... eq When the value is low and negative, the point corresponds to very low oversteer. In this case, to ensure a sufficient understeer detection rate while accepting that no very low oversteer is detected, an asymmetric truncation is required. More generally, depending on the vicinity of the boundary FR where it is applied, the asymmetric truncation allows for preferential detection of understeer or oversteer near said boundary FR.

[0061] According to one example of the implementation, the first, second, third, and fourth lower thresholds and upper thresholds are determined empirically.

[0062] According to these arrangements, in cases such as understeer, the method 100 according to the invention determines a rate between 0 and 1, where 0 corresponds to "no understeer" and 1 corresponds to "full steering wheel steering with no vehicle response". In this case, according to the supplementary method described in document WO2011010058A1, the method may include a correction step by automatically modifying the "target steering wheel torque", for example by multiplying it by (1 - rate).

[0063] For example, in the case of oversteering, according to another supplementary method described in document FR3086920B1, the method may include a correction step involving automatically adding the contribution of the yaw rate term to the calculation of the return function.

[0064] According to one example of the implementation, the first and second measurements are filtered by a frequency filter, for example, through a filter with frequencies between 0.5 Hz and 10 Hz, preferably through a filter with frequencies between 1 Hz and 5 Hz. In fact, this corresponds to an equivalent rotation θ. eq The signal is related to vehicle dynamics, and it is relatively slow due to the vehicle's mass and inertia, as well as suspension compliance, while corresponding to steering wheel rotation θ. 方向盘 The signals are related to faster dynamics because they correspond to driver commands. Therefore, filtering these signals allows the primary and secondary signals to be phased or synchronized before comparison in the same plane between the primary signal originating from the driver and the secondary signal corresponding to the vehicle's response to the primary signal, such as... Figure 1 As shown.

[0065] According to one aspect, the present invention relates to a vehicle comprising a power steering system or "steer-by-wire" system and an electronic control unit for the steering system, the electronic control unit being configured to:

[0066] - Collect at least one first measurement from a first sensor, the first sensor being configured to measure a first physical quantity representing the direction of travel defined by the driver of the vehicle;

[0067] - Collect at least one second measurement from a second sensor, which is configured to measure a second physical quantity representing the vehicle's response to the direction of travel;

[0068] The electronic control unit is further configured to implement method 100, one of the implementation modes described above.

Claims

1. A method (100) for detecting loss of grip in a vehicle including a power steering system, the method (100) comprising: - At least one first measurement (101) performed by a first sensor, the first sensor being configured to measure a first physical quantity representing a direction of travel defined by the driver of the vehicle; - At least one second measurement (102) performed by a second sensor, the second sensor being configured to measure a second physical quantity representing the vehicle's response to the direction of travel; - Determine (103) vehicle oversteer (SURV) or vehicle understeer (SOUV) based on criteria that are functions of the at least one first measurement and the at least one second measurement. The first physical quantity is the steering wheel rotation angle θ of the vehicle. 方向盘 ; The second physical quantity is the vehicle's lateral acceleration or yaw rate. ; The equivalent steering wheel rotation θ of the vehicle is determined based on the at least one second measurement. eq ; The criteria include the following conditions (1) and (2): ； ； If one of the conditions of the stated criteria is met, the vehicle is determined to be oversteer (SURV); if none of the conditions of the stated criteria are met, the vehicle is determined to be understeer (SOUV). The oversteer rate is defined as the product of the maximum oversteer and the oversteer coefficient, where the oversteer coefficient is the equivalent steering wheel rotation θ. eq and steering wheel rotation angle θ 方向盘 The function; The oversteering coefficient is the smaller of a first value and a second value, where the first value is the value with an equivalent steering wheel rotation θ. eq The first function K1 is the absolute value of the second value, which is the steering wheel rotation angle θ. 方向盘 and equivalent steering wheel rotation θ eq The second function K2 is the absolute value of the difference.

2. The method according to claim 1, wherein, When the equivalent steering wheel rotates by θ eq When the absolute value of is between 0 and the first lower threshold, the first function K1 is constant and equal to 0, and where, when the equivalent steering wheel rotates θ eq When the absolute value of K1 is greater than the first upper threshold, the first function K1 is constant and equal to 1, and wherein, within the interval between the first lower threshold and the first upper threshold, the first function K1 increases linearly between 0 and 1, for example.

3. The method according to claim 1 or 2, wherein, When the steering wheel rotation angle θ 方向盘 and equivalent steering wheel rotation θ eq When the absolute value of the difference is between 0 and the second lower threshold, the second function K2 is constant and equal to 0, and where, when the steering wheel rotation angle θ 方向盘 and equivalent steering wheel rotation θ eq When the absolute value of the difference is greater than the second upper threshold, the second function K2 is constant and equal to 1, and wherein, within the interval between the second lower threshold and the second upper threshold, the second function K2 increases linearly between 0 and 1, for example.

4. A method (100) for detecting loss of grip in a vehicle including a power steering system, the method (100) comprising: - At least one first measurement (101) performed by a first sensor, the first sensor being configured to measure a first physical quantity representing a direction of travel defined by the driver of the vehicle; - At least one second measurement (102) performed by a second sensor, the second sensor being configured to measure a second physical quantity representing the vehicle's response to the direction of travel; - Determine (103) vehicle oversteer (SURV) or vehicle understeer (SOUV) based on criteria that are functions of the at least one first measurement and the at least one second measurement. The first physical quantity is the steering wheel rotation angle θ of the vehicle. 方向盘 ; The second physical quantity is the vehicle's lateral acceleration or yaw rate. ; The equivalent steering wheel rotation θ of the vehicle is determined based on the at least one second measurement. eq ; The criteria include the following conditions (1) and (2): ； ； If one of the conditions of the stated criteria is met, the vehicle is determined to be oversteer (SURV); if none of the conditions of the stated criteria are met, the vehicle is determined to be understeer (SOUV). The understeer rate is defined as the product of the maximum understeer and the understeer coefficient, where the understeer coefficient is the equivalent steering wheel rotation θ. eq and steering wheel rotation angle θ 方向盘 The function; The understeer coefficient is the smaller of the third and fourth values, where the third value is the value with an equivalent steering wheel rotation θ. eq The third function K3 is the absolute value of the fourth value, which is the steering wheel rotation angle θ. 方向盘 and equivalent steering wheel rotation θ eq The fourth function K4 is the absolute value of the difference.

5. The method according to claim 4, wherein, When the equivalent steering wheel rotates by θ eq When the absolute value of is between 0 and the third lower threshold, the third function K3 is constant and equal to 0, and where, when the equivalent steering wheel rotates θ eq When the absolute value of K3 is greater than the third upper threshold, the third function K3 is constant and equal to 1, and wherein the third function K3 is linear between 0 and 1 in the interval between the third lower threshold and the third upper threshold.

6. The method according to any one of claims 4 and 5, wherein, When the steering wheel rotation angle θ 方向盘 and equivalent steering wheel rotation θ eq When the absolute value of the difference is between 0 and the fourth lower threshold, the fourth function K4 is constant and equal to 0, and wherein, when the steering wheel rotation angle θ 方向盘 and equivalent steering wheel rotation θ eq When the absolute value of the difference is greater than the fourth upper threshold, the fourth function K4 is constant and equal to 1, and wherein the fourth function K4 is linear between 0 and 1 in the interval between the fourth lower threshold and the fourth upper threshold.

7. The method according to any one of claims 1 to 6, wherein, The at least one first measurement includes a plurality of first measurements filtered by a first frequency filter, and wherein the at least one second measurement includes a plurality of second measurements filtered by a second frequency filter.

8. A vehicle including a power steering or steer-by-wire system and an electronic steering system control unit, the electronic steering system control unit being configured to: - Collect at least one first measurement from a first sensor, the first sensor being configured to measure a first physical quantity representing the direction of travel defined by the driver of the vehicle; - Collect at least one second measurement from a second sensor, the second sensor being configured to measure a second physical quantity representing the vehicle's response to the direction of travel; The electronic control unit is further configured to implement the method (100) according to any one of claims 1 to 7.

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