Method for limiting a steering intervention of a driver assistance system

Abstract

The invention relates to a method for limiting a steering intervention of a driver assistance system of a vehicle. According to the invention, in order to limit the steering intervention, an adjustment variable (u) of the driver assistance system generated for the steering intervention is multiplied by a weighting factor (f (a, b, c)), the weighting factor (f (a, b, c)) being determined on the basis of a detected manual steering intervention of a driver and on the basis of a predefined permitted steering intervention of the driver.

Description

[0001] Method for limiting a steering intervention of a driver assistance system

[0002] The invention relates to a method for limiting a steering intervention of a driver assistance system of a vehicle according to the preamble of patent claim 1.

[0003] Such a method is known from DE 102008 033688 A1. This document discloses a method for operating a steering control unit to control a lateral movement of a vehicle according to two setpoint variables generated outside the steering control unit. A first setpoint variable represents a steering angle or yaw rate setpoint and is limited as a function of speed. A second setpoint variable represents a steering torque setpoint. A difference between the speed-dependently limited first setpoint variable and an actual variable assigned to the first setpoint variable is determined as a control deviation, wherein the control deviation is converted into a control variable according to a predetermined control function. The control variable is limited as a function of externally generated limiting parameters by means of a weighting, a gradient limit, and a value limit.The limited manipulated variable is added to the second setpoint variable to form a control signal for controlling a steering actuator acting on a steering system of the vehicle.

[0004] Furthermore, DE 102018200 388 A1 discloses a method for operating a vehicle with a driver assistance system that intervenes in the vehicle's lateral dynamics. The method comprises the following steps:

[0005] - Detection of a driver intervention on the driving behavior of the vehicle due to an intervention of an actuator triggered by the driver assistance system;

[0006] - interpreting the driver intervention as an override of the actuator intervention; and - reducing the actuator intervention in a defined manner depending on the interpretation of the driver intervention such that a driving task is returned to the driver in a defined and controlled manner.

[0007] DE 10 2018200 327 A1 describes a method for adjusting the level of assistance of a driver assistance system in a vehicle that can autonomously intervene in a vehicle unit influencing driving dynamics. A driver intervention leads to an override of an autonomous intervention performed by the driver assistance system if the intensity of the driver intervention exceeds an adjustable threshold. The threshold is set as a function of the relationship between the driver state and the quality of the information underlying the driver assistance system intervention.

[0008] From DE 102014 226 781 A1 a method for controlling a steering device of a vehicle is known, in which setpoint values ​​for an automated steering operation and for a manual steering operation are determined and are summed in a weighted manner to realize a cross-fade between the automated and manual steering operation.

[0009] The invention is based on the object of specifying a novel method for limiting a steering intervention of a driver assistance system of a vehicle.

[0010] The object is achieved according to the invention by a method which has the features specified in claim 1.

[0011] Advantageous embodiments of the invention are the subject of the subclaims.

[0012] In a method for limiting a steering intervention of a driver assistance system of a vehicle, according to the invention, a control variable of the driver assistance system generated for the steering intervention is multiplied by a weighting factor in order to limit the steering intervention, wherein the weighting factor is determined as a function of a detected manual steering intervention of a driver and as a function of a predetermined permitted steering intervention of the driver.

[0013] Lateral vehicle control is primarily comprised of the superimposed planning and control of vehicle movement using steering angle control in a steering system. It is necessary to monitor the steering movement and limit it in the event of a fault to ensure the safety of the overall system. This means that, in particular, partially automated driver assistance functions that intervene in a vehicle's steering operation must be monitored by the driver at all times, and steering interventions must be limited so that the driver can control them. This limitation can be implemented in a steering actuator or in a command control unit.

[0014] This method enables reliable and safe limitation of steering intervention. This allows for a particularly smooth transition during driver intervention, thus optimizing steering feel during driver intervention. Furthermore, a particularly high permissible steering performance can be achieved while maintaining driver control of the vehicle.

[0015] According to one possible embodiment of the method, the permissible steering intervention is specified depending on the vehicle's driving speed. This further increases the reliability and safety of limiting the steering intervention.

[0016] According to a further possible embodiment of the method, the manual steering intervention is carried out based on

[0017] - a steering angle speed and / or

[0018] - a steering angle and / or

[0019] - a manual torque applied to a steering handle of the vehicle. This enables, on the one hand, a very reliable and easy-to-implement detection of the manual steering intervention, and, on the other hand, very robust monitoring can be ensured through time-dependent monitoring of at least one of these variables.

[0020] According to a further possible embodiment of the method, the specified permitted steering intervention

[0021] - when detecting manual steering intervention based on the steering angle speed as the permitted steering angle speed and / or

[0022] - when detecting manual steering intervention based on the steering angle as the permitted steering angle and / or

[0023] - when manual steering intervention is detected, it is specified as the permissible manual torque based on the manual torque. According to another possible embodiment of the method, the weighting factor is formed from several individual weighting factors, with each individual weighting factor being a steering angle velocity weighting factor, which is determined depending on the permissible steering angle velocity specified based on the detected steering angle velocity and the driving speed. This enables a simple and reliable calculation of the weighting factor.

[0024] According to a further possible embodiment of the method, the steering angle velocity weighting factor is determined

[0025] - a deviation of an amount of the recorded steering angle speed from the permitted steering angle speed is determined and standardised to the permitted steering angle speed to form a standardised deviation of the recorded steering angle speed,

[0026] - a robust steering angle speed deviation is determined from the standardized deviation of the detected steering angle speed in such a way that the standardized deviation of the detected steering angle speed only leads to a limitation of the steering intervention if the driver assistance system carrying out the steering intervention is active and a determined driver intervention falls below a specified limit,

[0027] - an error integral is formed as an integral of the robust steering angle velocity deviation and

[0028] - the steering angle velocity weighting factor is determined from a characteristic map as a function of a value of the error integral.

[0029] This design enables a robust determination of the steering angle velocity weighting factor in a simple and reliable manner.

[0030] According to another possible embodiment of the method, the weighting factor is formed from several individual weighting factors, with each individual weighting factor being a steering angle weighting factor, which is determined depending on the permissible steering angle specified based on the detected steering angle and the driving speed. This also enables a simple and reliable formation of the weighting factor.

[0031] According to a further possible embodiment of the method, to determine the steering angle weighting factor - a deviation of an amount of the detected steering angle from the permitted steering angle is determined and standardized to form a standardized deviation of the detected steering angle to the permitted steering angle,

[0032] - a robust steering angle deviation is determined from the standardised deviation of the detected steering angle in such a way that the standardised deviation of the detected steering angle only leads to a limitation of the steering intervention if the driver assistance system carrying out the steering intervention is active and a determined driver intervention falls below a specified limit,

[0033] - an error integral is formed as an integral of the robust steering angle deviation and

[0034] - the steering angle weighting factor is determined from a characteristic map as a function of a value of the error integral.

[0035] This design enables a robust determination of the steering angle weighting factor in a simple and reliable manner.

[0036] According to another possible embodiment of the method, the weighting factor is formed from several individual weighting factors, with each individual weighting factor being a manual torque weighting factor, which is determined depending on the permissible manual torque specified based on the detected manual torque and the driving speed. This also enables a simple and reliable formation of the weighting factor.

[0037] According to a further possible embodiment of the method, the manual torque weighting factor is determined

[0038] - a reduced hand torque is formed by subtracting a defined constant value from the permitted hand torque,

[0039] - the measured hand torque is compared with the reduced hand torque,

[0040] - if an amount of the detected hand torque is less than or equal to the reduced hand torque, the hand torque weighting factor is assigned the value 1,

[0041] - if the amount of the detected hand torque is greater than the reduced hand torque, the hand torque weighting factor is assigned the value 0, and

[0042] - if the amount of the recorded hand torque lies between the permitted hand torque and the reduced hand torque, the hand torque weighting factor is assigned a value between 0 and 1 determined in a linear scale.

[0043] This design enables a simple and reliable determination of the manual torque weighting factor. Exemplary embodiments of the invention are explained in more detail below with reference to the drawings.

[0044] Showing:

[0045] Fig. 1 schematically shows a sequence of a method for limiting a steering intervention of a driver assistance system,

[0046] Fig. 2 shows a schematic block diagram of a limiter for limiting a steering intervention of a driver assistance system,

[0047] Fig. 3 schematically shows a possible process for generating an individual weighting factor for weighting a steering angle speed,

[0048] Fig. 4 schematically shows a possible process for generating an individual weighting factor for weighting a steering angle and

[0049] Fig. 5 schematically shows a possible process for generating an individual weighting factor for weighting a hand torque.

[0050] Corresponding parts are provided with the same reference numerals in all figures.

[0051] Figure 1 shows a sequence of a possible embodiment of a method for limiting a steering intervention of a driver assistance system of a vehicle.

[0052] Lateral vehicle control is primarily comprised of the superimposed planning and control of vehicle movement using steering angle control in a steering system. It is necessary to monitor the steering movement and limit it in the event of a fault to ensure the safety of the entire system. This limitation can be implemented in a steering actuator or in a command control unit.

[0053] For this limitation, a manual steering intervention is first detected in a method step VS1 based on a detection of a steering angle speed v and / or a steering angle a and / or a manual torque M applied to a steering handle of the vehicle.

[0054] In a second process step VS2, the robustness of the detection is increased by time-dependent monitoring.

[0055] In a third method step VS3, the steering intervention of the driver assistance system is limited in particular by limiting a manipulated variable u shown in more detail in Figure 2.

[0056] Figure 2 shows a block diagram of a possible embodiment of a limiter 1 for limiting a steering intervention of a driver assistance system.

[0057] The limiter 1 comprises four modules 1.1 to 1.4, wherein a first module 1.1 is a steering angle speed limiter, a second module 1.2 is a steering angle limiter, a third module 1.3 is a hand torque limiter and a fourth module 1.4 is a total limiter.

[0058] The first module 1.1 monitors the steering angle velocity v and generates a steering angle velocity weighting factor a as an individual weighting factor.

[0059] The second module 1.2 monitors the steering angle a and generates a steering angle weighting factor b as an individual weighting factor.

[0060] The third module 1.3 monitors the hand torque M and generates a hand torque weighting factor c as an individual weighting factor.

[0061] In the fourth module 1.4, all individual weighting factors are weighted and a weighting factor f (a, b, c) is generated as a function of the individual weighting factors.

[0062] The weighting factor f (a, b, c) can be determined as a minimum function according to f (a, b, c) = minimum (a, b, c), as a multiplication function according to f (a, b, c) = multiplication (a, b, c) and / or as a mean value function according to f (a, b, c) = mean value (a, b, c).

[0063] The steering intervention is then limited by multiplying the manipulated variable u, which is, for example, a required rack force, with the weighting factor f (a, b, c) according to uiim = f (a, b, c) * u, so that a limited manipulated variable uij m for the driver assistance system.

[0064] This means that to limit the steering intervention, the control variable u generated by the driver assistance system for the steering intervention is multiplied by the weighting factor f (a, b, c). By forming the weighting factor f (a, b, c) as a function of the aforementioned individual weighting factors, the weighting factor f (a, b, c) is determined as a function of a detected manual steering intervention by a vehicle driver and as a function of a predefined permitted steering intervention by the driver.

[0065] Figure 3 shows a possible process for generating the individual weighting factor for weighting the steering angular velocity v, i.e., for generating the steering angular velocity weighting factor a. This process occurs, for example, in the first module 1.1 according to Figure 2.

[0066] In a block B1, depending on input variables in the form of a driving speed v Fzg of the vehicle and the steering angle speed v a permissible steering angle speed ev from a map as a function of the driving speed v Fzg calculated.

[0067] This calculation of the permissible steering angle speed ev as a function of the driving speed v Fzg is carried out using a table with support points, where the driving speed v Fzgin this table, for example, is shown on a horizontal axis (x-axis) and the steering angular velocity v on a vertical axis (y-axis). Values ​​between the reference points are determined using any desired interpolation method, for example linear interpolation. Reference points for values ​​of the driving speed vpzg are, for example, fixed in km / h, for example vpzg = [0, 10, 20, 30, 50, 80, 100, 130, 180, 250], reference points for the permissible steering angular velocity ev are determined, for example, through driving tests and / or with the help of a simulation. The aim is to ensure controllability requirements for the steering angular velocity v for functional safety for the driver.

[0068] In a second block B2, a deviation of the magnitude of the detected steering angular velocity v from the permissible steering angular velocity ev is determined and normalized to the permissible steering angular velocity ev. The result of the normalization is a normalized deviation Av of the detected steering angular velocity v, hereinafter also referred to as the normalized steering angular velocity deviation Av.

[0069] In a third block B3, the standardized steering angle speed deviation Av is filtered and the filtering produces a robust steering angle speed deviation Av r The filtering or the formation of the robust steering angle velocity deviation Av ris carried out in such a way that the standardized steering angle speed deviation Av only leads to a limitation of the steering intervention if the driver assistance system carrying out the steering intervention is active and the driver does not intervene too strongly, in particular does not countersteer too strongly, for example only countersteers to a predetermined extent against the steering intervention of the driver assistance system.

[0070] The robust steering angle velocity deviation Av r can be calculated, for example, as follows:

[0071] Av r = Av * S * c where Av r for the robust steering angle velocity deviation Av rstands for the standardized steering angular velocity deviation Av filtered, S stands for a signal that represents the activation state of the driver assistance system carrying out the steering intervention and has the value 1 if the driver assistance system is active and otherwise has the value 0, and c is a driver intervention limiting factor that can assume values ​​between 0 and 1 and has the value 0 if the driver intervenes too strongly, in particular countersteers too strongly, i.e. countersteers against the steering intervention of the driver assistance system by more than the specified amount. The driver intervention limiting factor c is in particular the manual torque weighting factor c generated with the third module 1.3.

[0072] In a fourth block B4, an error integral f Av r as an integral of the robust steering angle velocity deviation Av r formed, with a lower limit of the error integral f Av r, also called lower bound, in particular 0.

[0073] In a fifth block B5, depending on a value of the error integral f Av r The steering angle velocity weighting factor a is determined from a characteristic map. The steering angle velocity weighting factor a is calculated, for example, using a table with support points, where the value of the error integral f Av r on a horizontal axis (x-axis) and the steering angle velocity weighting factor a on a vertical axis (y-axis). Values ​​between the interpolation points are determined using any interpolation method, for example, linear interpolation methods. Interpolation points for values ​​of the error integral f Av r are fixed, for example f Av r= [0, 1 , 2, 5, 10, 50], Support points for the steering angle velocity weighting factor a are determined via driving tests and / or with the help of a simulation, so that, for example, a = [1 , 1 , 1 , 1 , 0, 0],

[0074] Figure 4 shows a possible process for generating the individual weighting factor for weighting the steering angle a, i.e., for generating the steering angle weighting factor b. This process occurs, for example, in the second module 1.2 according to Figure 2.

[0075] In a block B6, depending on input variables in the form of the driving speed v Fzg and the steering angle a, a permissible steering angle ea from a map as a function of the driving speed v Fzg calculated.

[0076] This calculation of the permitted steering angle ea as a function of the

[0077] Driving speed v Fzg is carried out using a table with support points, where the driving speed vFzg In this table, for example, the speed is shown on a horizontal axis (x-axis) and the permitted steering angle ea is shown on a vertical axis (y-axis). Values ​​between the interpolation points are determined using any interpolation method, for example, linear interpolation methods. Interpolation points for values ​​of the driving speed v Fzg are specified in km / h, for example v Fzg = [0, 10, 20, 30, 50, 80, 100, 130, 180, 250], Reference points for the permissible steering angle ea are determined, for example, through driving tests and / or simulation. The goal is to ensure controllability requirements for the steering angle a for functional safety for the driver.

[0078] In a second block B7, a deviation of the detected steering angle a from the permitted steering angle ea is determined and normalized to the permitted steering angle ea. The result of the normalization is a normalized deviation Aa of the detected steering angle a, hereinafter also referred to as the normalized steering angle deviation Aa.

[0079] In a third block B8, the standardized steering angle deviation Aa is filtered and a robust steering angle deviation Aa is calculated by the filtering. r The filtering or the formation of the robust steering angle deviation Aa ris carried out in such a way that the standardized steering angle deviation Aa only leads to a limitation of the steering intervention if the driver assistance system carrying out the steering intervention is active, given by the signal S, and the driver does not intervene too strongly, in particular does not countersteer too strongly, for example countersteers against the steering intervention of the driver assistance system to a maximum of a predetermined extent.

[0080] The robust steering angle deviation Aa r can be calculated, for example, as follows:

[0081] Aa r = Aa * S * c where Aa r for the robust steering angle deviation Aa r stands for the standardized steering angle deviation Aa, S stands for the above-mentioned signal representing the activation state of the driver assistance system, and c stands for the above-mentioned driver intervention limiting factor, in particular for the manual torque weighting factor c generated with the third module 1.3.

[0082] In a fourth block B9, an error integral f Aa r as an integral of the robust steering angle deviation Aa r formed, with a lower limit of the error integral f Aa r , also called lower bound, in particular 0.

[0083] In a fifth block B10, depending on a value of the error integral f Aa r The steering angle weighting factor b is determined from a characteristic map. The steering angle weighting factor b is calculated, for example, using a table with support points, where the value of the error integral f Aa r on a horizontal axis (x-axis) and the steering angle weighting factor b on a vertical axis (y-axis). Values ​​between the interpolation points are determined using any interpolation method, for example, linear interpolation methods. Interpolation points for values ​​of the

[0084] Error integral f Aa rare fixed, for example f Aa r = [0, 1 , 2, 5, 10, 50], Support points for the steering angle weighting factor b are determined via driving tests and / or with the help of a simulation, so that, for example, b = [1 , 1 , 1 , 1 , 0, 0],

[0085] Figure 5 shows a possible process for generating the individual weighting factor for weighting the manual torque M, i.e., for generating the manual torque weighting factor c. This process occurs, for example, in the third module 1.3 according to Figure 2.

[0086] To determine the manual torque weighting factor c, it is first determined in a first block B11 whether a detected manual torque M steers in the same direction + or opposite direction - to the manipulated variable u of the driver assistance system.

[0087] If the detected manual torque M is in the same direction +, then the manual torque weighting factor c is set to the value 1 in a second block B12.

[0088] If the measured manual torque M is in the opposite direction, a third block B13 is used depending on the input variable driving speed v Fzg a permissible manual torque eM from a characteristic map as a function of the driving speed v Fzg calculated.

[0089] This calculation of the permissible manual torque eM as a function of the driving speed v Fzg is carried out using a table with support points, where the driving speed v Fzgin this table, for example, is shown on a horizontal axis (x-axis) and the permitted manual torque eM on a vertical axis (y-axis). Values ​​between the reference points are determined using any desired, for example linear, interpolation method. Reference points for values ​​of the driving speed vpzg are, for example, fixed in km / h, for example vpzg = [0, 10, 20, 30, 50, 80, 100, 130, 180, 250], reference points for the permitted manual torque eM are determined, for example, through driving tests and / or with the aid of a simulation. The aim here is to ensure controllability requirements for the manual torque M of functional safety for the driver. In a fourth block B14, a reduced manual torque rM is formed by subtracting a defined constant value, for example 0.5, from the permitted manual torque eM.

[0090] Subsequently, the detected hand torque M is compared with the reduced hand torque rM, whereby if an amount of the detected hand torque M is less than or equal to the reduced hand torque rM (shown in section A1), the hand torque weighting factor c is assigned the value 1.

[0091] However, if the magnitude of the detected hand torque M is greater than or equal to the permitted hand torque eM (shown in section A2), the hand torque weighting factor c is assigned the value 0.

[0092] If the magnitude of the detected hand torque M lies between the permitted hand torque eM and the reduced hand torque rM (shown in section A3), the hand torque weighting factor c is assigned a value between 0 and 1 determined in a linear scale.

Claims

Claims: A method for limiting the steering intervention of a driver assistance system of a vehicle, wherein, to limit the steering intervention, a control variable (u) generated for the steering intervention by the driver assistance system is multiplied by a weighting factor (f (a, b, c)), characterized in that the weighting factor (f (a, b, c)) is determined as a function of a detected manual steering intervention by a driver and as a function of a predetermined permissible steering intervention by the driver. A method according to claim 1, characterized in that the permissible steering intervention is determined as a function of a driving speed (v). Fzg ) of the vehicle. Method according to claim 1 or 2, characterized in that the manual steering intervention is based on - a steering angle velocity (v) and / or - of a steering angle (a) and / or - a hand torque (M) applied to a steering handle of the vehicle is detected. Method according to claim 3, characterized in that the predetermined permissible steering intervention - when detecting manual steering intervention based on the Steering angle speed (v) as permissible steering angle speed (ev) and / or - when detecting manual steering intervention based on the steering angle (a) as the allowed steering angle (ea) and / or - when manual steering intervention is detected based on the hand torque (M), a permissible hand torque (eM) is specified. Method according to claim 4, characterized in that the weighting factor (f (a, b, c)) is formed from several individual weighting factors, wherein an individual weighting factor is a steering angle velocity weighting factor (a), which depends on the detected steering angle velocity (v) and the vehicle speed (v). Fzg) specified permissible steering angle speed (ev) is determined. Method according to claim 5, characterized in that the steering angle speed weighting factor (a) is determined. - a deviation of an amount of the detected steering angle velocity (v) from the permitted steering angle velocity (ev) is determined and normalized to form a normalized deviation (Av) of the detected steering angle velocity (v) to the permitted steering angle velocity (ev), - a robust steering angle velocity deviation (Av) r ) is determined from the normalized deviation (Av) of the detected steering angle velocity (v) in such a way that the normalized deviation (Av) of the detected steering angle velocity (v) only leads to a limitation of the steering intervention if the driver assistance system performing the steering intervention is active and a determined driver intervention falls below a predetermined limit value, - an error integral (f Av r ) as the integral of the robust steering angle velocity deviation (Av) r ) is formed and - depending on a value of the error integral (f Av r ) the steering angle velocity weighting factor (a) is determined from a characteristic map. Method according to one of claims 4 to 6, characterized in that the weighting factor (f (a, b, c)) is formed from several individual weighting factors, wherein an individual weighting factor is a steering angle weighting factor (b) which is determined as a function of a characteristic map based on the detected steering angle (a) and driving speed (v) Fzg ) specified permissible steering angle (ea) is determined. Method according to claim 7, characterized in that the steering angle weighting factor (b) is determined. - a deviation of an amount of the detected steering angle (a) from the permissible steering angle (ea) is determined and is normalized to form a normalized deviation (Aa) of the detected steering angle (a) to the permissible steering angle (ea), - a robust steering angle deviation (Aa r ) from the normalized deviation (Aa) of the detected steering angle (a) is determined in such a way that the normalized deviation (Aa) of the detected steering angle (a) only leads to a limitation of the steering intervention if the driver assistance system performing the steering intervention is active and a determined driver intervention falls below a predetermined limit value, - an error integral (f Aa r ) as the integral of the robust steering angle deviation (Aa r ) is formed and - depending on a value of the error integral (f Aa r) the steering angle weighting factor (b) is determined from a characteristic map. Method according to one of claims 4 to 8, characterized in that the weighting factor is formed from several individual weighting factors, wherein an individual weighting factor is a hand torque weighting factor (c), which depends on the detected hand torque (M) and the vehicle speed (vp). zg ) specified permissible hand torque (eM) is determined. Method according to claim 9, characterized in that the hand torque weighting factor (c) is determined by - a reduced hand torque (rM) is formed by subtracting a defined constant value from the allowed hand torque (eM), - the measured hand torque (M) is compared with the reduced hand torque (rM), - then, if an amount of the recorded hand torque (M) is less than or equal to the reduced hand torque (rM), the hand torque weighting factor (c) is assigned the value 1, - then, if the amount of the recorded hand torque (M) is greater than or equal to the allowed hand torque (eM), the hand torque weighting factor (c) is assigned the value 0, and - then, if the amount of the recorded hand torque (M) lies between the allowed hand torque (eM) and the reduced hand torque (rM), the hand torque weighting factor (c) is assigned a value between 0 and 1 determined in a linear scale.

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