Method for limiting steering intervention of driver assistance systems

Abstract

The present invention relates to a method for limiting steering interventions of a driving assistance system of a vehicle. According to the present invention, in order to limit the steering interventions, an operating variable (u) of the driving assistance system generated for the steering intervention is multiplied by a weighting factor (f(a,b,c)), which is determined depending on a detected manual steering intervention of the driver and a predefined permissible steering intervention of the driver.

Description

[Technical field]

[0001] The present invention relates to a method for limiting steering interventions of a driving assistance system of a vehicle according to the preamble of claim 1. [Background technology]

[0002] Such a method is known from DE 10 2008 033 688 A1. This document discloses a method for operating a steering control device for controlling the lateral movement of a vehicle according to two setpoints (target parameters) generated externally to the steering control device. The first setpoint represents a steering angle setpoint or a yaw rate setpoint and is limited as a function of speed. The second setpoint represents a steering torque setpoint. The difference between the first setpoint limited as a function of speed and an actual variable assigned to the first setpoint is determined as a control deviation, which is converted into a manipulated variable (regulation parameter) according to a predefined control function. The manipulated variable is limited by weighting, gradient limiting and value limiting as a function of externally generated limiting parameters. The limited manipulated variable is added to the second setpoint to generate a control signal for controlling a steering actuator acting on the steering device of the vehicle.

[0003] Furthermore, from DE 10 2018200388 A1 a method is known for operating a vehicle with a driving assistance system which intervenes in the lateral dynamics of the vehicle, said method comprising the following steps: - detecting a driver intervention in the driving behavior of the vehicle resulting from an actuator intervention caused by a driving assistance system; - interpreting driver intervention as an override (deactivation, overcontrol) of actuator intervention; - reducing the actuator intervention in a defined manner in response to an interpretation of the driver intervention, so that the driving task is returned to the driver in a defined and controlled manner.

[0004] DE 10 2018200327 A1 describes a method for adjusting the support level of a driver assistance system in a vehicle, which can autonomously intervene in vehicle units that influence the driving dynamics. If the intensity of the driver's intervention exceeds an adjustable intervention limit value, the driver intervention leads to an override of the autonomous intervention carried out by the driver assistance system. The intervention limit value is adjusted as a function of the relationship between the driver state and the quality of the information on which the intervention by the driver assistance system is based.

[0005] From DE 10 2014 226 781 A1 a method for controlling the steering of a vehicle is known, in which setpoints for an automated steering mode and setpoints for a manual steering mode are determined, the setpoints are weighted and added together and the steering mode is transitioned between the automated and manual steering modes. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a novel method for limiting the steering intervention of a driver assistance system of a vehicle. [Means for solving the problem]

[0007] This object is achieved according to the invention by a method having the features of claim 1.

[0008] Advantageous embodiments of the invention are the subject of the dependent claims.

[0009] According to the present invention, in a method for limiting a steering intervention of a driving assistance system of a vehicle, in order to limit the steering intervention, an operating variable (operating amount, adjustment characteristic variable) of the driving assistance system generated for the steering intervention is multiplied by a weighting factor, and the weighting factor is determined depending on (in response to) the detected manual steering intervention of the driver and a predetermined permissible steering intervention (permitted steering intervention) of the driver.

[0010] The lateral control of the vehicle is achieved by superimposing the planning and control of the vehicle's movements, in particular with the steering angle control in the steering system. To guarantee the safety of the overall system, it is necessary to monitor the steering movements and limit them in case of errors. This means that especially semi-automated driver assistance functions that intervene in the vehicle's driving movements must be constantly monitored by the driver and the steering intervention must be limited so that it can be controlled by the driver. This limitation can be done in the steering actuator or in the commanding (master) control device.

[0011] The method allows steering interventions to be limited reliably (reliably) and safely, a particularly harmonious transition can be achieved during driver interventions, so that the steering feel during driver interventions is optimized, and a particularly acceptable high steering performance can be achieved while maintaining the driver's control of the vehicle.

[0012] According to a possible embodiment of the method, the permissible steering intervention is set as a function of the vehicle's driving speed, which makes it possible to further increase the reliability and safety of the limitation of the steering intervention.

[0013] According to a further possible embodiment of the method, the manual steering intervention comprises: -Steering angular velocity, and / or -Steering angle (steering angle), and / or - manual torque applied to the steering wheel of the vehicle; This allows, on the one hand, a very reliable and easy to implement detection of the manual steering intervention to be achieved, and, on the other hand, a very robust monitoring can be guaranteed by the time-dependent monitoring of at least one of these variables.

[0014] According to a further possible embodiment of the method, the predetermined permissible steering intervention is as the permissible steering angular velocity if a manual steering intervention is detected based on the steering angular velocity, and / or as the permissible steering angle if a manual steering intervention is detected based on the steering angle, and / or If a manual steering intervention is detected based on the manual torque, the permissible manual torque is: It is set in advance.

[0015] According to a further possible embodiment of the method, the weighting factor is formed (constructed, generated) from a plurality of individual weighting factors, one of which is a steering angular velocity weighting factor determined (calculated) depending on a predefined permissible steering angular velocity (set based on the detected steering angular velocity and the driving speed) based on the detected steering angular velocity and the driving speed, thereby making it possible to form the weighting factor easily and reliably (reliably).

[0016] According to a further possible embodiment of the method, for determining the steering angular velocity weighting factor, A deviation of the detected steering angular velocity from an allowable steering angular velocity is calculated (determined) and the deviation is normalized with respect to the allowable steering angular velocity to form a normalized deviation of the detected steering angular velocity; a robust steering angular velocity deviation is determined from a normalized deviation of the detected steering angular velocity such that the normalized deviation of the detected steering angular velocity results in a limitation of the steering intervention if a driver assistance system which performs a steering intervention is active and the determined (determined, calculated) driver intervention falls below a predefined limit value; the error integral is formed as the integral of the robust steering angular velocity deviation, The steering angle velocity weighting factor is determined from a characteristic map as a function of the value of the error integral.

[0017] This configuration allows the steering angular velocity weighting coefficient to be determined robustly in an easy and highly reliable manner.

[0018] According to a further possible embodiment of the method, the weighting factor is formed from a plurality of individual weighting factors, one of which is a steering angle weighting factor that is determined as a function of a predefined permissible steering angle based on the detected steering angle and the driving speed, so that the weighting factor can be formed easily and reliably.

[0019] According to a further possible embodiment of the method, for determining the steering angle weighting factor, a deviation of the detected steering angle from a permissible steering angle is calculated and the deviation is normalized with respect to the permissible steering angle to form a normalized deviation of the detected steering angle; - a robust steering angle deviation is determined from a normalized deviation of the detected steering angle such that the normalized deviation of the detected steering angle results in a limitation of the steering intervention if a driver assistance system which performs a steering intervention is active and the requested (determined, calculated) driver intervention is below a predefined limit value; the error integral is formed as the integral of the robust steering angle deviation, The steering angle weighting factor is determined from a characteristic map as a function of the value of the error integral.

[0020] This configuration allows the steering angle weighting coefficient to be determined robustly in an easy and highly reliable manner.

[0021] According to a further possible embodiment of the method, the weighting factor is formed from a number of individual weighting factors, one of which is a manual torque weighting factor that is determined depending on the detected manual torque and a predefined permissible manual torque based on the driving speed, so that the weighting factor can be formed easily and reliably.

[0022] According to a further possible embodiment of the method, to determine the manual torque weighting factor, a reduced manual torque is formed by subtracting a defined constant value from the permissible manual torque, The detected manual torque is compared with a reduced manual torque, If the detected manual torque value is less than or equal to the reduced manual torque, the manual torque weighting factor is assigned a value of 1; - if the value of the detected manual torque is greater than the reduced manual torque, the value of the manual torque weighting factor is assigned 0; If the detected manual torque value is between the permissible manual torque and the reduced manual torque, the manual torque weighting factor value is assigned a value between 0 and 1 determined by linear scaling.

[0023] This arrangement allows the manual torque weighting coefficient to be determined robustly in an easy and reliable manner.

[0024] In the following, an embodiment of the invention will be explained in detail with reference to the drawings. [Brief description of the drawings]

[0025] [Figure 1] 2 shows a schematic sequence of a method for limiting steering intervention of a driver assistance system; [Diagram 2] FIG. 2 is a block diagram illustrating a limiter for limiting steering intervention of a driving assistance system. [Diagram 3] 13 illustrates diagrammatically one possible process for generating individual weighting coefficients for weighting steering angular velocity. [Figure 4] 1 illustrates diagrammatically one possible process for generating individual weighting coefficients for weighting the steering angle. [Diagram 5] 13 illustrates diagrammatically one possible process for generating individual weighting coefficients for weighting manual torque. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] In all the figures, corresponding parts are provided with the same reference numerals.

[0027] FIG. 1 shows a sequence of one possible embodiment of a method for limiting steering intervention of a driver assistance system of a vehicle.

[0028] The lateral control of the vehicle is achieved by superimposing the planning and control of the vehicle motion, in particular with the steering angle control in the steering system. To guarantee the safety of the entire system, it is necessary to monitor the steering movement and to limit it in case of errors. This limitation is done either in the steering actuator or in the commanding (master) control device.

[0029] To achieve this limitation, in method step VS1, a detection of a manual steering intervention is performed on the basis of detection of the steering angular velocity v and / or the steering angle α and / or the manual torque M applied to the steering wheel of the vehicle.

[0030] In a second method step VS2, the robustness of the detection is increased by time-dependent monitoring.

[0031] In a third method step VS3, the steering intervention of the driver assistance system is limited, in particular by limiting the manipulated variable u, which is shown in more detail in FIG.

[0032] FIG. 2 shows a block diagram of one possible embodiment of a limiter 1 for limiting the steering intervention of a driver assistance system.

[0033] The limiter 1 includes four modules 1.1 to 1.4. The first module 1.1 is a steering angular velocity limiter, the second module 1.2 is a steering angle limiter, the third module 1.3 is a manual torque limiter, and the fourth module 1.4 is an overall (overall) limiter.

[0034] A first module 1.1 monitors the steering angular velocity v and generates a steering angular velocity weighting factor a as an individual weighting factor.

[0035] A second module 1.2 monitors the steering angle α and generates a steering angle weighting factor b as an individual weighting factor.

[0036] A third module 1.3 monitors the manual torque M and generates a manual torque weighting factor c as an individual weighting factor.

[0037] In a fourth module 1.4, all the individual weighting factors are weighted to generate a weighting factor f(a,b,c) as a function of the individual weighting factors.

[0038] The weighting coefficient f(a,b,c) is f(a,b,c) = min(a,b,c) As a minimum function according to f(a,b,c) = multiplication(a,b,c) as a multiplicative function according to f(a,b,c) = mean(a,b,c) It is determined (calculated) as an average value function according to

[0039] The steering intervention is then determined by the manipulated variable u, e.g. the required rack target force (required target rack force). u lim =f(a,b,c) u The limited operation variable (limited operation variable) u of the driver assistance system is limited by multiplying the weighting coefficient f(a,b,c) according to lim is obtained.

[0040] In other words, to limit the steering intervention, the operating variable u of the driving assistance system generated 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 above-mentioned individual weighting factors, the weighting factor f(a,b,c) is determined depending on the detected manual steering intervention of the driver of the vehicle and depending on the predetermined permissible steering intervention of the driver.

[0041] 3 shows one possible process for generating the individual weighting coefficients for weighting the steering angular velocity v, i.e. for generating the steering angular velocity weighting coefficients a, which is carried out, for example, in the first module 1.1 of FIG.

[0042] In block B1, the vehicle speed v Fzg and the steering angle velocity v from the characteristic map. Fzg The allowable steering angular velocity ev is calculated as a function of

[0043] Traveling speed v Fzg The calculation of the permissible steering angular velocity ev as a function of the vehicle speed v is based on a table having reference points, e.g. Fzg is plotted on the horizontal axis (x-axis) and the steering angular velocity v is plotted on the vertical axis (y-axis). Values ​​between the reference points are determined using any, for example linear, interpolation method. Fzg The reference point for the value of is predefined (pre-set) in km / h, e.g. v Fzg = [0, 10, 20, 30, 50, 80, 100, 130, 180, 250] is set. The reference points for the permissible steering angular velocity ev are determined, for example, using (with the help of) road tests and / or simulations. The aim here is to guarantee the controllability requirements of the steering angular velocity v with regard to the functional safety of the driver.

[0044] In a second block B2, a deviation (deviation amount) of the detected steering angular velocity v from an allowable steering angular velocity ev is determined (calculated) and normalized to the allowable steering angular velocity ev. The result of the normalization is a normalized deviation (normalized deviation) Δv of the detected steering angular velocity v, which will be hereinafter also referred to as a normalized steering angular velocity deviation Δv.

[0045] In the third block B3, the standardized steering angular velocity deviation Δv is filtered, and the robust steering angular velocity deviation Δv rThe filtered or robust steering angular velocity deviation Δv is formed so that the normalized steering angular velocity deviation Δv results in a limitation of the steering intervention only when a driving assistance system that performs a steering intervention is active and the driver's intervention is not excessively large, in particular when the driver does not perform excessively large counter-steering, for example, when the driver performs steering in the opposite direction to the steering intervention of the driving assistance system at most to a predefined extent (at most to a predefined extent (limit value)). r The formation of is carried out.

[0046] Robust steering angular velocity deviation Δv r For example, it can be calculated as follows: Δv r = Δv S c Here, Δv r is the robust steering angular velocity deviation Δv r where Δv represents the filtered normalized steering angular velocity deviation Δv. S represents a signal representing the activation state of the driving assistance system that executes the steering intervention, and has a value of 1 if the driving assistance system is active, and has a value of 0 if not. c is a driver intervention limiting coefficient that can take a value between 0 and 1, and takes a value of 0 if the driver's intervention is large, particularly if the counter-steering is excessively large, that is, if the steering in the opposite direction to the steering intervention of the driving assistance system is performed stronger than a predetermined range. The driver intervention limiting coefficient c is particularly the manual torque weighting coefficient c generated in the third module 1.3.

[0047] In the fourth block B4, the error integral ∫Δv r The robust steering angular velocity deviation Δv r The error integral ∫Δv r In particular, the lower limit (also called the lower bound) of is 0.

[0048] In the fifth block B5, the steering angular velocity weighting coefficient a is calculated by the error integral ∫Δv rThe steering angular velocity weighting coefficient a is calculated (determined) from a characteristic map depending on the value of . The calculation of the steering angular velocity weighting coefficient a is performed, for example, using a table having a number of reference points. For example, the error integral ∫ Δv r The values ​​of are plotted on the horizontal axis (x-axis) and the steering angular velocity weighting coefficient a is plotted on the vertical axis (y-axis). Values ​​between the reference points are determined using any, for example linear, interpolation method. The error integral ∫Δv r The reference point for the value of is, for example, predefined (pre-set), e.g., ∫Δv r = [0, 1, 2, 5, 10, 50] is set. The reference point of the steering angle velocity weighting coefficient a is determined using (with the aid of) road tests and / or simulations, and is, for example, a = [1, 1, 1, 1, 0, 0].

[0049] One possible process for generating the individual weighting factors for weighting the steering angle α, i.e. for generating the steering angle weighting factor b, is shown in Fig. 4. This process is carried out, for example, in the second module 1.2 of Fig. 2.

[0050] In block B6, the running speed v Fzg and the steering angle α from the characteristic map. Fzg The allowable steering angle eα is calculated as a function of

[0051] Traveling speed v Fzg The calculation of the permissible steering angle eα as a function of the vehicle speed v is based on a table with reference points, for example Fzg is plotted on the horizontal axis (x-axis) and the permissible steering angle eα is plotted on the vertical axis (y-axis). Values ​​between the reference points are determined using any, for example linear, interpolation method. Fzg The reference point for the value of is predefined (predetermined), for example in km / h, e.g. v Fzg= [0, 10, 20, 30, 50, 80, 100, 130, 180, 250] is set. The reference points for the permissible steering angle eα are determined, for example, using (with the aid of) road tests and / or simulations. The aim here is to guarantee the controllability requirements for the steering angle α with regard to functional safety for the driver.

[0052] In a second block B7, a deviation (deviation amount) of the detected steering angle α from the permissible steering angle eα is determined (calculated) and normalized to the permissible steering angle eα. The result of the normalization is a normalized deviation (normalized deviation) Δα of the detected steering angle α, which will be hereinafter also referred to as the normalized steering angle deviation Δα.

[0053] In the third block B8, the standardized steering angle deviation Δα is filtered, and the robust steering angle deviation Δα is obtained by the filtering. r The signal S is provided so that the normalized steering angle deviation Δα provides control of the steering intervention only when the driver assistance system that performs the steering intervention is active and the driver's intervention is not excessively large, in particular when the driver does not perform excessively large counter-steering, for example when the driver assistance system performs steering in the opposite direction at most to a predefined extent (counter-steering to a predefined extent at most) in response to the steering intervention of the driver assistance system. r The formation of is carried out.

[0054] Robust steering angle deviation Δα r For example, it can be calculated as follows: Δα r = Δα S c Here, Δα r is the robust steering angle deviation Δα r where Δα denotes the normalized steering angle deviation Δα, S denotes the signal representative of the activation state of the driver assistance system as described above, c denotes the driver intervention limiting factor as described above, in particular the manual torque weighting factor c generated by means of the third module 1.3.

[0055] In the fourth block B9, the error integral ∫Δα r is the robust steering angle deviation Δα r The error integral ∫Δα r In particular, the lower limit (also called the lower bound) of is 0.

[0056] In the fifth block B10, the steering angle weighting coefficient b is calculated by the error integral ∫Δα r The steering angle weighting coefficient b is calculated (determined) from a characteristic map depending on the value of . The calculation of the steering angle weighting coefficient b is performed, for example, using a table having a number of reference points. For example, the error integral ∫ Δα r The values ​​of are plotted on the horizontal axis (x-axis) and the steering angle weighting coefficient b is plotted on the vertical axis (y-axis). Values ​​between the reference points are determined using any, e.g. linear, interpolation method. The error integral ∫Δα r The reference point for the value of is, for example, predefined (preset), e.g., ∫Δα r = [0, 1, 2, 5, 10, 50] is set. The reference point of the steering angle weighting coefficient b is determined using (with the aid of) road tests and / or simulations, and is, for example, b = [1, 1, 1, 1, 0, 0].

[0057] One possible process for generating the individual weighting coefficients for weighting the manual torque M, i.e. generating the manual torque weighting coefficients c, is shown in Fig. 5. This process is carried out, for example, in the third module 1.3 of Fig. 2.

[0058] To determine the manual torque weighting coefficient c, first in a first block B11 it is determined whether the detected manual torque M results in a steering in the same direction + as the operating variable u of the driving assistance system or in the opposite direction -.

[0059] If the detected manual torque M is in the same direction +, then in a second block B12 the manual torque weighting factor c is set to a value of 1.

[0060] If the detected manual torque M is in the opposite direction, the input variable, the driving speed v Fzg Depending on the driving speed v Fzg The permissible manual torque eM is calculated as a function of

[0061] Traveling speed v Fzg The calculation of the permissible manual torque eM as a function of the driving speed v is carried out on the basis of a table with reference points, for example Fzg is plotted on the horizontal axis (x-axis) and the permissible manual torque eM is plotted on the vertical axis (y-axis). Values ​​between the reference points are determined using any, for example linear, interpolation method. Fzg The reference point for the value of is predefined (pre-set) in km / h, e.g. v Fzg = [0, 10, 20, 30, 50, 80, 100, 130, 180, 250] is set. The reference points for the permissible manual torque eM are determined, for example, using (with the help of) road tests and / or simulations. The aim here is to ensure the controllability requirements of the manual torque M with regard to the functional safety of the driver.

[0062] In a fourth block B14, a reduced manual torque rM is formed by subtracting a defined constant value, for example 0.5, from the permissible manual torque eM.

[0063] The detected manual torque M is then compared to the reduced manual torque rM. As shown in section A1, if the value of the detected manual torque M is less than or equal to the reduced manual torque rM, the manual torque weighting factor c is assigned a value of 1.

[0064] In contrast, as shown in section A2, if the value of the detected manual torque M is greater than or equal to the allowable manual torque eM, the manual torque weighting factor c is assigned a value of 0.

[0065] As shown in section A3, if the value of the detected manual torque M is between the allowable manual torque eM and the reduced manual torque rM, the manual torque weighting factor c is assigned a value between 0 and 1 determined by linear scaling. [Prior art documents] [Patent documents]

[0066] [Patent Document 1] DE 102008033688 A1 [Patent Document 2] DE 102018200388 A1 [Patent Document 3] DE 102018200327 [Patent Document 4] DE 102014226781 A1

Claims

1. 1. A method for limiting steering intervention in a driving assistance system for a vehicle, comprising: multiplying an operation variable (u) of the driving assistance system generated for the steering intervention by a weighting factor (f(a,b,c)) in order to limit the steering intervention; 4. The method of claim 3, wherein the weighting coefficients (f(a,b,c)) are determined depending on a detected manual steering intervention of the driver and a predetermined permissible steering intervention of the driver.

2. The permissible steering intervention depends on the vehicle's running speed (v Ｆｚｇ 2. The method according to claim 1, wherein the step of determining the number of times ...

3. The manual steering intervention includes: steering angular velocity (v), and / or - the steering angle (α), and / or - manual torque applied to the steering wheel of the vehicle (M), The method according to claim 1 or 2, characterized in that the detection is based on

4. The predetermined allowable steering intervention is as the permissible steering angular velocity (ev) if the manual steering intervention is detected based on the steering angular velocity (v), and / or as the permissible steering angle (eα) if the manual steering intervention is detected based on the steering angle (α), and / or as the permissible manual torque (eM) if the manual steering intervention is detected based on the manual torque (M), 4. The method of claim 3, characterized in that it is preset.

5. The weighting factor (f(a, b, c)) is formed from a plurality of individual weighting factors, and one individual weighting factor is determined based on the detected steering angular velocity (v) and the driving speed (v Ｆｚｇ 5. The method according to claim 4, wherein the steering angular velocity weighting factor (a) is determined in dependence on a predefined permissible steering angular velocity (ev) based on the steering angular velocity weighting factor (a).

6. To determine the steering angular velocity weighting coefficient (a), a deviation of the detected steering angular velocity (v) from the permissible steering angular velocity (ev) is calculated and this deviation is normalized with respect to the permissible steering angular velocity (ev) to form a normalized deviation (Δv) of the detected steering angular velocity (v); - determining a robust steering angular velocity deviation (Δv) from the normalized deviation (Δv) of the detected steering angular velocity (v) such that the normalized deviation (Δv) of the detected steering angular velocity (v) results in a limitation of the steering intervention if a driving assistance system which performs the steering intervention is active and the determined driver intervention is below a predefined limit value; ｒ ) is determined, -Error integral (∫Δv ｒ ) is the robust steering angular velocity error (Δv ｒ ), The steering angular velocity weighting coefficient (a) is the error integral (∫Δv ｒ 6. The method according to claim 5, wherein the value of the sigma-based coefficient is determined from a characteristic map as a function of the value of the sigma-based coefficient.

7. The weighting factor (f(a, b, c)) is formed from a plurality of individual weighting factors, and one individual weighting factor is determined based on the detected steering angle (α) and the driving speed (v Ｆｚｇ 7. The method according to claim 4, wherein the steering angle weighting factor (b) is determined in dependence on a predefined permissible steering angle (eα) based on the steering angle weighting factor (eα).

8. To determine the steering angle weighting coefficient (b), a deviation of the detected steering angle (α) from the permissible steering angle (eα) is calculated and this deviation is normalized with respect to the permissible steering angle (eα) to form a normalized deviation (Δα) of the detected steering angle (α); - determining a robust steering angle deviation (Δα) from the normalized deviation (Δα) of the detected steering angle (α) such that the normalized deviation (Δα) of the detected steering angle (α) results in a limitation of the steering intervention if a driving assistance system which performs the steering intervention is active and the requested driver intervention is below a predefined limit value; ｒ ) is determined, -Error integral (∫Δα ｒ ) is the robust steering angle deviation (Δα ｒ ), The steering angle weighting coefficient (b) is the error integral (∫Δα ｒ 8. The method according to claim 7, characterized in that the value of the sigma-based coefficient of the sigma-based coefficient is determined from a characteristic map as a function of the value of the sigma-based coefficient ....

9. The weighting factor is formed from a plurality of individual weighting factors, one individual weighting factor being a function of the detected manual torque (M) and the driving speed (v Ｆｚｇ 9. The method according to claim 4, wherein the manual torque weighting factor (c) is determined in dependence on a predetermined permissible manual torque (eM) based on the predetermined permissible manual torque (eM).

10. To determine the manual torque weighting factor (c): a reduced manual torque (rM) is formed by subtracting a defined constant value from the permissible manual torque (eM), - the detected manual torque (M) is compared with the reduced manual torque (rM), if the value of the detected manual torque (M) is less than or equal to the reduced manual torque (rM), the manual torque weighting factor (c) is assigned a value of 1; if the value of the detected manual torque (M) is greater than or equal to the permissible manual torque (eM), the value of the manual torque weighting factor (c) is assigned to 0; 10. The method according to claim 9, characterized in that if the value of the detected manual torque (M) is between the permissible manual torque (eM) and the reduced manual torque (rM), the value of the manual torque weighting coefficient (c) is assigned a value between 0 and 1 determined by linear scaling.

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