METHOD FOR TERMINATING AN AUTOMATED DRIVING OPERATION OF A VEHICLE

Abstract

A method for terminating an automated driving function of a vehicle involves deactivating the driving function by a steering intervention of a driver of the vehicle in a steering system, which includes a steering column and a steering wheel. In order to determine the steering intervention, a steering column torque at the steering column is measured and a steering wheel angle is measured. A manual torque acting on the steering wheel is estimated based on the measured steering column torque and the measured steering wheel angle. The estimation is based on a model equation of the steering system, which takes into consideration a moment of inertia of the steering wheel and a frictional torque in the steering system.

Claims

1-10. (canceled)

11. A method for terminating an automated driving function of a vehicle, the method comprising: determining whether there is a steering intervention of a driver of the vehicle in a steering system, which comprises a steering column and a steering wheel, wherein, the determination of the steering intervention involves measuring a steering column torque at the steering column, measuring a steering wheel angle of the steering wheel, estimating a manual torque acting on the steering wheel based on the measured steering column torque and the measured steering wheel angle, wherein the estimation of the manual torque is based on a model equation of the steering system, wherein the model equation takes into consideration a moment of inertia of the steering wheel and a frictional torque in the steering system; and deactivating the automated driving function based on the determination of whether there is a steering intervention of the driver of the vehicle.

12. The method of claim 11, wherein the automated driving function is terminated if the determined steering intervention exceeds a predefined deactivation threshold.

13. The method of claim 12, wherein the predefined deactivation threshold is predefined depending on depending on whether the driver is holding the steering wheel with at least one hand, whether the driver is observing a traffic situation ahead of the vehicle, or whether there is a lateral collision risk in an effective direction of the estimated manual torque.

14. The method of claim 13, wherein the predefined deactivation threshold is predefined in such a way that the automated driving operation is deactivated if the driver is holding the steering wheel with the at least one hand and the estimated manual torque exceeds a first threshold; if the driver is not holding the steering wheel with any hands and the estimated manual torque exceeds a second threshold; if the driver is not observing the traffic situation ahead of the vehicle or if there is the lateral collision risk in the effective direction of the manual torque, and if the estimated manual torque exceeds a third threshold, wherein the second threshold is higher than the first threshold and the third threshold is higher than the second threshold.

15. The method of claim 14, wherein whether the driver is holding the steering wheel with the at least one hand is determined using a capacitive steering wheel, whether the driver is observing the traffic situation is determined based on a viewing direction recognition using a camera monitoring the driver, or whether there is the lateral collision risk is determined using radar, lidar, or a camera.

16. The method of claim 11, wherein the manual torque is estimated by subtracting, from the measured steering column torque, a product formed from the moment of inertia and a second time derivative of the steering wheel angle and also a product formed from the frictional torque and a first time derivative, which is dependent on a rotation direction, of the steering wheel angle.

17. The method of claim 16, wherein the first and second time derivatives are calculated via using a third-order Bessel filter.

18. The method of claim 17, further comprising: performing a parameterization modelling during which no manual torque is applied by the driver, wherein the parameterization comprises actuating, by a transverse controller, a steering actuator in such a way that the steering actuator applies predefined pulses of a simulated steering torque to the steering column; and comparing the simulated steering torque with the measured steering column torque, wherein the parameters constituted by moment of inertia, frictional torque and a dead time are modelled in such a way that the simulated steering torque matches the measured steering column torque.

19. The method of claim 16, wherein the model equation also accounts for an offset torque or a measurement filter.

20. A vehicle, comprising: an automated driving function; a steering system comprising a steering column and a steering wheel; a torque sensor arranged on the steering column and configured to measure a steering column torque; a steering wheel angle sensor configured to measure a steering wheel angle of the steering wheel; and a control unit configured to determine whether there is a steering intervention of a driver of the vehicle in a steering system, which comprises a steering column and a steering wheel, wherein, the determination of the steering intervention involves measuring a steering column torque at the steering column, measuring a steering wheel angle of the steering wheel, estimating a manual torque acting on the steering wheel based on the measured steering column torque and the measured steering wheel angle, wherein the estimation of the manual torque is based on a model equation of the steering system, wherein the model equation takes into consideration a moment of inertia of the steering wheel and a frictional torque in the steering system; and deactivate the automated driving function based on the determination of whether there is a steering intervention of the driver of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0025] In the drawings:

[0026] FIG. 1 shows a schematic view of a steering column with a steering wheel,

[0027] FIG. 2 shows a schematic graph with a time curve of a simulated steering torque and a measured steering column torque.

[0028] Parts corresponding to one another are provided in all figures with like reference signs.

DETAILED DESCRIPTION

[0029] FIG. 1 shows a schematic view of a steering column 1 with a steering wheel 2 for a vehicle 3, in particular a motor vehicle.

[0030] In a method according to the invention, a steering column torque M.sub.Mess_Lenkstange at the steering column 1 is measured, for example by means of a torque sensor 5. Furthermore, a steering wheel angle δ.sub.LR is measured, for example by means of a rotary angle sensor 6. A manual torque M.sub.Hand acting on the steering wheel 2 is not measured. The method is used to determine the manual torque M.sub.Hand from the steering column torque M.sub.Mess_Lenkstange.

[0031] It is known to determine the manual torque M.sub.Hand indirectly by measuring the steering column torque M.sub.Mess_Lenkstange in the vehicle 3. The steering column torque M.sub.Mess_Lenkstange is measured, for example, using a strain sensor, which is arranged in the vehicle 3 on the steering rod 1 directly above a steering system. The assumption that the manual torque M.sub.Hand at the steering wheel 2 is equal to the steering column torque M.sub.Mess_Lenkstange can be considered to be valid during automated driving for slow steering movements, but not for rapid, automated steering movements, since these likewise introduce a torque.

[0032] In accordance with the invention, a method is proposed that determines the steering column torque M.sub.Mess_Lenkstange, for example, by means of the strain sensor, and which also uses a rotary angle sensor 6 on the steering wheel 2. The method is modelled by means of parameters, for example a frictional torque M.sub.R of the steering rod 1 and a moment of inertia ⊖.sub.LR of the steering wheel 2, which can be obtained from measurement data of the vehicle 3. The method, using two information sources, for example sensors, together with the knowledge of identified system parameters, for example the frictional torque M.sub.R and the moment of inertia ⊖.sub.LR, allows an estimation of torque introduced by rapid automated steering movements, in order to filter this torque out, so that the remaining torque is at least approximately equal to the manual torque actually applied at the steering wheel.

[0033] The following model equation of the steering system forms the basis of the calculation of the manual steering torque M.sub.Hand (equation in the frequency range with the complex frequency s):

[00001]$\begin{array}{cc}{M}_{\mathrm{Mess}\_\mathrm{Lenkstange}}=e^{-s.Math.T_t}.Math.\frac{1}{T_{\mathrm{Mess}}.Math.s+1}.Math.\left(M_{\mathrm{Hand}}+{\Theta }_{\mathrm{LR}}.Math.{\stackrel{.Math.}{\delta }}_{\mathrm{LR}}+M_R.Math.\mathrm{sign}\left({\stackrel{.}{\delta }}_{\mathrm{LR}}\right)\right)& \left(\mathrm{equation}1\right)\end{array}$

[0034] The parameters have the following meaning here: [0035] T.sub.t dead time by CAN transfer of the measurement data

[00002]$\frac{1}{T_{\mathrm{Mess}}.Math.s+1}$

measurement filter, low-pass effect by measurement arrangement [0036] ⊖.sub.LR moment of inertia of the steering wheel [0037] {umlaut over (δ)}.sub.LR steering angle acceleration [0038] M.sub.R frictional torque [0039] {dot over (δ)}.sub.LR steering angle speed

[0040] The steering wheel angle δ.sub.LR is a discrete-time variable determined in a clocked manner. The determination of the time derivatives of such variables by subtraction can lead to high noise contributions on account of the discretization. Therefore, the time derivatives are preferably calculated via a low-pass filtering with a third-order Bessel filter. The following is then true:

[00003]$\begin{array}{cc}\stackrel{.Math.}{\delta }=\frac{s^2}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}{\delta }_{\mathrm{LR}}& \left(\mathrm{equation}2\right)\end{array}$$\begin{array}{cc}\stackrel{.}{\delta }=\frac{s}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}{\delta }_{\mathrm{LR}}& \left(\mathrm{equation}3\right)\end{array}$

[0041] The denominator N.sub.3ter_O_Bessel in this case represents the third-order Bessel polynomial (N.sub.3ter_O_Bessel=s.sup.3+6s.sup.2+15s+15). The advantage of the Bessel filtering lies in a linear phase delay, that is to say a constant group delay in the passband, the Bessel filtering leads to a phase delay. In order to avoid errors as a result of this phase delay, all elements of the equation must be subjected to the same phase delay. All elements of the equation are therefore extended by the denominator N.sub.3ter_O_Bessel. The following equation is obtained:

[00004]$\begin{array}{cc}\frac{M_{\mathrm{Mess}\_\mathrm{Lenkstange}}}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}=e^{-{\mathrm{sT}}_t}.Math.\frac{1}{T_{\mathrm{Mess}}.Math.s+1}.Math..Math.\left(\frac{M_{\mathrm{Hand}}}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}+{\Theta }_{\mathrm{LR}}.Math.\frac{s^2}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}.Math.{\delta }_{\mathrm{LR}}+M_R.Math.\mathrm{sign}\left(\frac{s}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}.Math.{\delta }_{\mathrm{LR}}\right)\right)& \left(\mathrm{equation}4\right)\end{array}$

[0042] For the measurement, it is advantageous to determine the parameters of this equation. This parameter determination (parameterization) is performed as follows:

A transverse controller, which in automated driving operation, that is to say in the normal operating mode, performs steering interventions at the steering system via a steering actuator, is switched to a parameterization mode. In the parameterization mode, the driver must keep his hands off the steering wheel (hands-off operation), so that M.sub.Hand=0. The driver is advantageously prompted to do this. In the parameterization mode, the steering column torque M.sub.Mess_Lenkstange and the steering wheel angle δ.sub.LR are also measured, and the steering actuator is actuated by the transverse controller in such a way that it applies predefined pulses of a simulated steering torque M.sub.Sim to the steering column. As a result of these steering torque pulses, a steering torque M.sub.Sim is simulated, which is created when the vehicle 3 travels over potholes. The simulated steering torque M.sub.Sim is compared with the measured steering column torque M.sub.Mess_Lenkstange The parameters constituted by moment of inertia ⊖.sub.LR, frictional torque M.sub.R, and dead time T.sub.t are modelled in such a way that the simulated torque M.sub.Sim matches the measured steering column torque M.sub.Mess_Lenkstange.

[0043] FIG. 2 shows a schematic graph with a time curve of the simulated steering torque M.sub.Sim and of the measured steering column torque M.sub.Mess_Lenkstange.

[0044] This parameterization is advantageously performed during the production of the vehicle 3, that is to say prior to delivery of the vehicle 3 to the customer, or alternatively during a visit to a garage.

[0045] To determine the manual torque M.sub.Hand, equation 4 is solved in terms of M.sub.Hand. The following is then obtained:

[00005]$\begin{array}{cc}\frac{M_{{\mathrm{Mess}}_{\mathrm{Lenkstange}}}}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}-e^{-{\mathrm{sT}}_t}.Math.\frac{1}{T_{\mathrm{Mess}}.Math.s+1}.Math..Math.\left({\Theta }_{\mathrm{LR}}.Math.\frac{s^2}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}.Math.{\delta }_{\mathrm{LR}}+M_R.Math.\mathrm{sign}\left(\frac{s}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}.Math.{\delta }_{\mathrm{LR}}\right)\right)==e^{-{\mathrm{sT}}_t}.Math.\frac{1}{T_{\mathrm{Mess}}.Math.s+1}.Math.\left(\frac{1}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}\right).Math.M_{\mathrm{Hand}}=M_{\mathrm{Hand}}^{*}& \left(\mathrm{equation}5\right)\end{array}$

[0046] The right side is equated to an estimated manual torque M.sub.Hand:

[00006]$\begin{array}{cc}{M}_{\mathrm{Hand}}^{*}=e^{-{\mathrm{sT}}_t}.Math.\frac{1}{T_{\mathrm{Mess}}.Math.s+1}.Math.\left(\frac{1}{N_{3\mathrm{ter}\_O\_\mathrm{Bessel}}}\right).Math.M_{\mathrm{Hand}}.& \left(\mathrm{equation}6\right)\end{array}$

[0047] The estimated manual torque M*.sub.Hand deviates from the sought manual torque M.sub.Hand, however, the deviation Δ=M*.sub.Hand−M.sub.Hand is so small that M*.sub.Hand is a good estimation for the sought manual torque M.sub.Hand, and therefore can be used for the decision to terminate the automated driving operation.

[0048] In an extension of the method, the parameters can be updated over the operating time of the vehicle 3. The update is based on equation 1. For an improved presentability of the method, the contributions of the dead time T.sub.t and of the measurement filter

[00007]$\frac{1}{T_{\mathrm{Mess}}.Math.s+1}$

can be ignored. A person skilled in the art, however, will readily be able to modify the following equations also to the extent that the contributions of the dead time T.sub.t and of the measurement filter

[00008]$\frac{1}{T_{\mathrm{Mess}}.Math.s+1}$

are also taken into consideration. Furthermore, in equation 1 an additional offset torque M.sub.off is also introduced. Proceeding from equation 1, this then results in:

M.sub.Mess_Lenkstange=M.sub.Hand+⊖.sub.LR.Math.{umlaut over (δ)}.sub.LR+M.sub.R{dot over (δ)}.sub.LR+M.sub.off  (equation 7)

[0049] Both sides of equation 7 are summed over a multiplicity n of measurement values (M.sub.Mess_Lenkstange, δ.sub.LR). The measurement values are temporarily stored for this purpose, for example in a ring buffer. The following is then obtained

[00009]$\begin{array}{cc}\stackrel{n}{.Math.}{M}_{\mathrm{Mess}\_\mathrm{Lenkstange}}=\stackrel{n}{.Math.}\left(M_{\mathrm{Hand}}+{\Theta }_{\mathrm{LR}}.Math.{\stackrel{.Math.}{\delta }}_{\mathrm{LR}}+M_R.Math.{\stackrel{.}{\delta }}_{\mathrm{LR}}+M_{\mathrm{off}}\right).& \left(\mathrm{equation}8\right)\end{array}$

[0050] If the sum on the right side is solved in terms of the constant factors, the following is obtained:

Σ.sup.nM.sub.Mess_Lenkstange=Σ.sup.nM.sub.Hand+⊖.sub.LR.Math.Σ.sup.n{umlaut over (δ)}.sub.LR+M.sub.R.Math.Σ.sup.n{dot over (δ)}.sub.LR+n.Math.M.sub.off  (equation 9)

[0051] The offset torque M.sub.off is determined for example as follows: From the multiple stored measurements, those measurements are identified for which the following is true:

Σ.sup.n{umlaut over (δ)}.sub.LR=0,Σ.sup.n{dot over (δ)}.sub.LR=0,Σ.sup.nM.sub.Hand=0

[0052] With longer-lasting measurements, this will only ever be the case. The following is then obtained from equation 9

Σ.sup.nM.sub.Mess_Lenkstange=n.Math.M.sub.off

and M.sub.off can be updated to

[00010]${\hat{M}}_{\mathrm{off}}=M_{\mathrm{off}}=\frac{{.Math.}^n{M}_{\mathrm{Mess}\_\mathrm{Lenkstange}}}{n}.$

[0053] The moment of inertia ⊖.sub.LR of the steering wheel can be determined as follows: From the multiplicity of stored measurements, those measurements are identified for which the following is true:

Σ.sup.n{umlaut over (δ)}.sub.LR≠0,Σ.sup.n{dot over (δ)}.sub.LR=0,Σ.sup.nM.sub.Hand=0

[0054] With longer-lasting measurements, this will only ever be the case. The following is then obtained from equation 9

Σ.sup.nM.sub.Mess_Lenkstange=⊖.sub.LR.Math.Σ.sup.n{umlaut over (δ)}.sub.LR+n.Math.{circumflex over (M)}.sub.off

and ⊖.sub.LR can be updated to

[00011]${\hat{\Theta }}_{\mathrm{LR}}={\Theta }_{\mathrm{LR}}=\frac{{.Math.}^n{M}_{{\mathrm{Mess}}_{\mathrm{Lenkstange}}}-n.Math.{\hat{M}}_{\mathrm{off}}}{{.Math.}^n{\stackrel{.Math.}{\delta }}_{\mathrm{LR}}}.$

[0055] The frictional torque M.sub.R can be determined as follows: From the multiplicity of stored measurements, those measurements are identified for which the following is true:

Σ.sup.n{umlaut over (δ)}.sub.LR=0,Σ.sup.n{dot over (δ)}.sub.LR≠0,Σ.sup.nM.sub.Hand=0

[0056] With longer-lasting measurements, this will only ever be the case. The following is then obtained from equation 9

Σ.sup.nM.sub.Mess_Lenkstange=M.sub.R.Math.Σ.sup.n{dot over (δ)}.sub.LR+n.Math.{circumflex over (M)}.sub.off.

and M.sub.R can be updated to

[00012]${\hat{M}}_R=M_R=\frac{{.Math.}^n{M}_{{\mathrm{Mess}}_{\mathrm{Lenkstange}}}-n.Math.{\hat{M}}_{\mathrm{off}}}{{.Math.}^n{\stackrel{.}{\delta }}_{\mathrm{LR}}}.$

[0057] In this way, parameter changes that occur on account of signs of wear or signs of aging during operation with the customer can also be corrected during operation.

[0058] The termination criterion is satisfied when the manual torque M.sub.Hand exceeds a predefinable deactivation threshold, wherein the deactivation threshold is predefined depending on the situation, in particular depending on whether the driver is holding the steering wheel by at least one hand or no hands (hands-on-/hands-off situation), whether or not the driver is monitoring the traffic situation ahead of the vehicle 3, and/or whether there is a lateral collision risk in the effective direction of the manual torque.

[0059] In particular, the deactivation threshold is predefined in such a way that, to terminate the automated driving operation, [0060] a small manual torque (for example 3 Nm) is sufficient if a hands-on situation is present, [0061] a medium manual torque for example 6 Nm) is necessary if a hands-off situation is present, [0062] a high manual torque (for example 8 Nm) is necessary if the driver is not observing the traffic situation ahead of the vehicle 3 or if there is a lateral collision risk in the effective direction of the manual torque.

[0063] The detection of whether a hands-on or hands-off situation is present can be implemented by sensor, for example by means of a capacitive steering wheel. The detection of whether the driver is observing the traffic situation can be implemented using a camera that monitors the driver, for example by means of viewing direction recognition. The detection of the lateral collision risk can be implemented using conventional ambient sensors, for example radar, lidar, or camera.

[0064] The method can be implemented in a control unit 4 arranged in the vehicle 3.

[0065] Although the invention has been illustrated and described in detail by way of preferred embodiments, the invention is not limited by the examples disclosed, and other variations can be derived from these by the person skilled in the art without leaving the scope of the invention. It is therefore clear that there is a plurality of possible variations. It is also clear that embodiments stated by way of example are only really examples that are not to be seen as limiting the scope, application possibilities or configuration of the invention in any way. In fact, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete manner, wherein, with the knowledge of the disclosed inventive concept, the person skilled in the art is able to undertake various changes, for example, with regard to the functioning or arrangement of individual elements stated in an exemplary embodiment without leaving the scope of the invention, which is defined by the claims and their legal equivalents, such as further explanations in the description.