CN117657291A - Operating strategy for a steer-by-wire system and motor vehicle - Google Patents

Abstract

The invention relates to a method for operating a motor vehicle (1) having a steer-by-wire system (2) on a roadway (3). When a fault in the primary system (4) of the steer-by-wire system (2) is detected, the motor vehicle (1) is operated by the control device (5) in such a way that, in the event of an additional fault in the secondary system (6) of the steer-by-wire system (2), a safety control of the motor vehicle (1) by means of the brake system (8) of the motor vehicle (1) is ensured. The invention further relates to a motor vehicle (1), which motor vehicle (1) is designed to carry out the method according to the invention.

Description

Operating strategy for a steer-by-wire system and motor vehicle

Technical Field

The invention relates to a method for operating a motor vehicle with a steer-by-wire system on a roadway. The invention further relates to a motor vehicle having a steer-by-wire system.

Background

Motor vehicles are known in which there is no mechanical connection between a steering wheel and a steering shaft. In such steering systems, steering commands are transmitted electronically via cables to a steering actuator for generating a steering torque on a steering shaft. At the same time, the steering actuator is used to determine the forces and moments acting on the steering shaft from the roadway and to transmit signals relating to these electronically to the steering wheel actuator for generating feedback from the roadway to the steering wheel about reality.

Steer-by-wire systems may be particularly advantageous for use with automatic and autonomous driving motor vehicles. The steer-by-wire system may enable folding and folding of the steering wheel during full-automatic driving (class 4 according to SAE definition). Thereby creating more space for the driver who becomes a passenger during full-automatic driving for activities such as sleeping, looking at newspapers, surfing the internet, etc. Also, a new interior space concept can be achieved by folding and stowing the steering wheel, for example with a rotatable seat and a table that can be flipped open.

Furthermore, the mechanical decoupling between the steering wheel and the steering actuator avoids accidental incorrect operation during full-automatic driving. Accidental touching of the steering wheel does not result in an undesirable vehicle response even when the steering wheel is not folded and stowed. In autonomous motor vehicles (defined as class 5 according to SAE, such as robotic taxis), by definition no driver is present, so that a steer-by-wire system must be installed here in a mandatory manner.

In addition, steer-by-wire systems offer various advantages even in conventional vehicles without autopilot functionality. For example, the safety of a motor vehicle may be improved with a steer-by-wire system. The stabilizing function, for example crosswind stabilization, mount stabilization, etc., can now also be performed with the steering device, since the driver no longer feels steering interventions at the steering wheel. In the case of an avoidance maneuver, the avoidance maneuver can now be executed in an emergency independently of the steering wheel position and thus controlled beyond the driver if necessary.

Furthermore, the comfort of the motor vehicle can be improved by means of a steer-by-wire system. For example, the steering wheel may be folded up when getting on and off, which thus eases the process, as the driver gets more free space. At the time of parking, it is often necessary to set a relatively large steering angle for steering. For example, for a steer-by-wire system, only a small movement of the steering wheel is required for this purpose. This is ensured by an electronic adaptation of the transmission ratio between the steering angle and the steering wheel angle.

Finally, steer-by-wire systems have particularly advantageous personalizable properties. The steering behavior of the steer-by-wire system can be individually adapted to the driver and thus personalized. Haptic feedback from the roadway, i.e. steering wheel feedback to the driver, may be softer or stiffer, sports or comfort, directly or damped. Such a setting can be transferred from an old motor vehicle to a new motor vehicle, for example, when a new motor vehicle is purchased.

In a steer-by-wire system, the mechanical connection between the steering wheel and the steering gear is broken at the axle and replaced by a redundant data line. As a "mechanical backset", the possibility of transmitting steering torque from the driver to the steering gear is dispensed with. Therefore, the overall system affecting the lateral dynamics of the motor vehicle (which is usually only implemented in the steering device) must meet the safety and usability requirements ASIL D.

In order to meet this safety requirement, steering-by-wire systems according to the state of the art must be designed at least simply and redundantly. This is ensured, for example, by the double windings in the motor, the double reserved control device, the double electrical energy supply and the double design of the data communication line.

In the case of simple redundancy, after a fault in the steer-by-wire system, the motor vehicle must expediently be stopped after a short time, since further faults will lead to the motor vehicle not being steered. Purely statistically, the second failure is unlikely, but at least within the range possible. For this reason, in this case, an auxiliary braking action of the braking system of the motor vehicle is required in order to decelerate the motor vehicle to a stationary state. Thus, in the event of a fault, simple redundancy actually results in what is known as a "hard stop" directly after the fault. Continued travel using such a defective primary system of the steer-by-wire system is not possible for legal reasons.

Thus, dual redundancy or a second fallback level for a steer-by-wire system is in principle desirable, since the motor vehicle can continue to travel after a fault has occurred, wherein in the case of a fault of the first fallback level the requirements for the second fallback level can be significantly reduced compared to a single fault situation and a zero fault situation. For example, dual redundancy may be achieved by reserving additional techniques, such as by triple reserved control devices, motors with triple windings, triple redundant data lines, and the like. Such measures are known, for example, from aircraft technology.

The known steer-by-wire system has the disadvantage that in the event of a defect in the primary system, continued travel is not allowed for legal reasons and the motor vehicle must be brought to a standstill in a targeted manner using the secondary system. Due to the additional required technical components, the cost of the multiple redundant steer-by-wire system is very high, with additional installation space requirements, and also increases the overall weight of the motor vehicle.

Disclosure of Invention

The object of the present invention is therefore to eliminate or at least partially eliminate the aforementioned disadvantages in a method for operating a motor vehicle having a steer-by-wire system on a roadway. In particular, the object of the present invention is to provide a method for operating a motor vehicle having a steer-by-wire system and a motor vehicle having a steer-by-wire system, which method and motor vehicle can avoid the motor vehicle being forced to stop in a simple and cost-effective manner and/or do not require an increase in the installation space requirement or the overall weight of the motor vehicle.

The above-mentioned task is solved by the present invention. The object is therefore achieved by the method according to the invention for operating a motor vehicle having a steer-by-wire system on a roadway and by a motor vehicle having a drive system, a brake system and a steer-by-wire system according to the invention. Other features and details of the invention are set forth in the description and drawings. The features and details described in connection with the method according to the invention are of course also applicable in connection with the motor vehicle according to the invention and vice versa, so that reference is always made to each other in respect of the disclosure of the various aspects of the invention.

According to a first aspect of the invention, the object is achieved by a method for operating a motor vehicle having a steer-by-wire system on a roadway. The method comprises the following steps:

-identifying, by a control device of the motor vehicle, a failure of a primary system of the steer-by-wire system;

-operating a secondary system of the steer-by-wire system by the control device;

-detecting, by a detection device of the motor vehicle, a surrounding parameter of the surrounding of the motor vehicle; and is also provided with

The control device is designed to operate the motor vehicle in such a way as to ensure reliable control of the motor vehicle by the brake system of the motor vehicle in the event of an additional failure of the secondary system of the steer-by-wire system.

The method is preferably performed on a motor vehicle having a steer-by-wire system with a primary operating level and a redundant fallback level. Within the scope of the present invention, the primary operation level is also referred to as the "primary system" and the first fallback level is referred to as the "secondary system". In addition, the motor vehicle has a brake system which can be configured for individual braking of the individual wheels of the motor vehicle. Preferably, the motor vehicle has an Electronic Stability Program (ESP).

First, a failure of the primary system of the steer-by-wire system is detected by a control device of the motor vehicle. As possible reasons for the failure of the primary system, consider, for example, failures of controllers, actuator windings, electrical control lines, etc. of the primary system.

The secondary system of the steer-by-wire system can still be used to steer the motor vehicle as prescribed, i.e. without technical performance limitations, due to a primary system failure. In order to ensure safe further travel of the motor vehicle, the control device of the secondary system is operated for steering the motor vehicle.

Furthermore, a detection device of the motor vehicle detects a surrounding parameter of the motor vehicle. For this purpose, sensors of the motor vehicle, such as radar sensors, lidar sensors, ultrasonic sensors, camera sensors, etc., are preferably used. Alternatively or additionally, a receiving device, such as a GPS receiver, a radio data receiver, etc., may also be used to detect the ambient parameters. Ambient parameters are understood to be factors in the environment of the motor vehicle that can influence the continued driving of the motor vehicle (for example steering or braking). For example, this includes the lane width or the number of lanes of the lane. The detection of the ambient parameters of the motor vehicle is preferably oriented substantially forward in the direction of travel of the motor vehicle, since there is usually the most frequent occurrence of a probability for the reason of the required braking and steering actuation. However, it is also possible to provide for the parameters of the environment in the rear, for example other motor vehicles with higher speeds. For example, such a motor vehicle can exclude a cut on a multi-lane highway from the operating options for operating the motor vehicle, since thereby a danger of road traffic may occur. The control device preferably builds an operating strategy for the targeted operation of the motor vehicle within this range, which takes into account the faulty primary system and the surrounding parameters, and is preferably designed to operate the motor vehicle with as little limitation as possible.

Based on the detected ambient parameters, the control device operates the motor vehicle, preferably using an operating strategy. The control device operates the motor vehicle in such a way that, in the event of an additional failure of the secondary system of the steer-by-wire system, a safe control of the motor vehicle by the brake system of the motor vehicle is ensured. Within the scope of the invention, safety control is understood to be control in which collisions with obstacles, such as other traffic participants, pillars, etc., are prevented or reduced to a level tolerable for the occupants of the motor vehicle and other traffic participants. In this case, the motor vehicle should be brought safely to a standstill. For example, such a control should be possible by means of a correspondingly configured brake device of the motor vehicle.

For example, the motor vehicle is operated in a targeted manner in such a way that the steering angle for the steering of the motor vehicle is kept as small as possible without thereby creating additional risks for road traffic. In the same way, the targeted operation of the motor vehicle is carried out in such a way that the risk of abrupt steering at a relatively large steering angle is reduced with respect to the normal operation of the motor vehicle. For example, within this range, a preventive reduction in vehicle speed may be achieved to avoid collisions. For this reason, a targeted operation of the motor vehicle is achieved as a function of the detected ambient parameters, in order to thus keep the degree of intervention in the operation of the motor vehicle as small as possible, so that an almost normal continued travel of the motor vehicle is ensured despite a failure of the primary system. In other words, the motor vehicle is operated in defensive driving mode. By implementing this method, sporty or aggressive driving patterns are preferably prevented.

The method according to the invention for operating a motor vehicle with a steer-by-wire system on a traffic lane has the advantage over conventional methods that, by means of simple means and in a cost-effective manner, even in the event of a failure of the primary system of the steer-by-wire system, safe further travel with the motor vehicle is ensured and, as a result, forced parking of the motor vehicle can be avoided. In addition, a targeted operation of the motor vehicle ensures that the motor vehicle is used to continue traveling as normally as possible, for example in a defensive driving mode. In this way, the driving comfort for the driver of the motor vehicle is improved relative to conventional methods.

According to a preferred development of the invention, it can be provided in a method that a fault of the primary system is signaled by a signaling device of the motor vehicle. As a result of the targeted operation of the motor vehicle taking into account the surrounding parameters, it may sometimes happen that the driver does not feel the primary system failure or at least notices it only when a sporty driving maneuver is attempted. This is especially the case in the case of drivers with defensive or at least mainly defensive driving modes. For this reason, the signaling device signals to the driver and preferably also to the occupants of the motor vehicle that the primary system has failed. The signaling is preferably done visually, for example by means of an alarm light, inserting a display device (such as an instrument panel, head up display, etc.). Alternatively or additionally, the signaling is effected acoustically, for example as a beep, a voice prompt, etc., preferably simultaneously with an intervention in the entertainment system of the motor vehicle, for example by stopping or temporarily pausing the playback, changing, in particular reducing the playback volume, etc. Alternatively or additionally, the indication is signaled in a tactile manner, for example by increasing the steering resistance of the steering wheel, vibrating the steering wheel, etc. This has the advantage that the driver can prepare the motor vehicle in a simple manner and in a cost-effective manner for driving modes of the motor vehicle which may deviate from their preference, and can learn about the need to go to the maintenance station as soon as possible. In this way, the safety of the motor vehicle during operation is increased.

According to the invention, it is preferred that the lane direction of the traffic lane and/or the longitudinal inclination of the traffic lane and/or the transverse inclination of the traffic lane and/or the traffic lane topology and/or the traffic lane friction values and/or obstacles on or next to the traffic lane and/or other traffic participants and/or weather data are/is taken into account as ambient parameters by the detection device. For example, the lane direction trend may be determined by sensors of the motor vehicle, such as cameras, radar, lidar, etc. In addition or alternatively, the lane direction progression may also be determined from navigation data or map data of the motor vehicle. For example, the longitudinal inclination may represent a downward gradient or an upward gradient. The longitudinal inclination and the transverse inclination of the traffic lane can be acquired, for example, by means of sensors of the motor vehicle, such as inclination sensors or front sensors, or by means of map data. The topology of a roadway is understood to be, for example, irregularities in the roadway, such as ruts, potholes, etc. For example, the road topology can be acquired by sensors of the motor vehicle or by map data. The lane friction value represents the friction value between the tire and the lane and thus the smoothness of the lane can be identified, for example. For example, it can be determined from which forces a slip or float of the motor vehicle can occur. The obstacle may be, for example, a post or a guardrail arranged at the edge of the roadway and an object on the roadway. In detecting other traffic participants, it is preferable to determine the size, speed change, direction, and direction change of the traffic participant. Weather can have a significant impact on the driving characteristics of a motor vehicle. By determining the weather data, these effects can be taken into account in a targeted operation of the motor vehicle. This has the advantage that the safety of operation during operation of the motor vehicle is further increased by simple means and in a cost-effective manner.

It is further preferred that at least one ambient parameter is predictively detected when detecting the ambient parameter. Predictive detection is built up by changes in ambient parameters within the scope of prediction. Preferably, the actual state and/or the actual state change of the ambient parameter is also determined. In this context, it can be inferred, for example, from the driving direction of the motor vehicle in the surroundings, in which direction and at what speed the motor vehicle is moving forward. For example, it is envisioned that a cut-in maneuver will occur as it exits onto a cut-in lane. Also, a braking maneuver may be imminent due to a lack of a safe option for overtaking. In addition, other vehicles are conceivable here, which can exert an indirect or direct influence on the operation of the vehicle, for example. Weather data predictions may be made in addition to predicting movement of other traffic participants. This has the advantage that the operational safety during operation of the motor vehicle can be further increased by simple means and in a cost-effective manner.

In a particularly preferred embodiment of the invention, it can be provided in a method that a targeted operation of the motor vehicle has a determination of a trajectory in the curve, which has a trajectory radius that is greater than the curve radius of the curve. The motor vehicle thus has a smaller distance from the lane edge outside the curve than in the middle curve region, for example, when driving into the curve and when driving out of the curve. If traffic conditions allow, driving of multiple lanes can also be performed within this range, further increasing the track radius. Due to the increased radius, in the event of a complete failure of the steer-by-wire system, for example by means of an ESP, only a small steering angle has to be used instead, so that the risk of a runaway or loss of lateral guidance via the motor vehicle is reduced. In this case, it is preferable to ensure that a minimum distance from the lane edges is maintained in each case, in order to reduce the risk of slipping out of the lane in the event of an additional failure of the secondary system. This has the advantage that the safety of operation during operation of the motor vehicle is further increased by simple means and in a cost-effective manner.

The targeted operation of the motor vehicle preferably has an active correction of the desired trajectory to the safety trajectory preset by the driver of the motor vehicle and/or an assistance to the safety trajectory. The safety trajectory has a larger radius and a defined distance from the edges of the roadway relative to the desired trajectory, so that less intervention for controlling the motor vehicle is required in the event of an additional failure of the steer-by-wire system. Active correction is understood as an active intervention in the steering angle. For example, the driver steers one steering angle, while the steering system steers the other steering angle and thus overrides the driver's desire. For example, the steering resistance may be increased to assist the driver, and the driver sets a steering angle different from the desired steering angle for this movement. The driver is thus guided on a trajectory which is determined for safe operation of the motor vehicle, without this giving him a feeling of steering control of the motor vehicle. This has the advantage that the safety of operation during operation of the motor vehicle is further increased by simple means and in a cost-effective manner.

According to a preferred embodiment of the invention, the targeted operation of the motor vehicle has an active correction from a desired speed preset by the driver of the motor vehicle to a reduced safety speed and/or an assistance to the safety speed. In this case, active correction means, for example, that the control device reduces the speed of the motor vehicle during the driving into a curve in a targeted manner relative to the desired speed selected by the driver. In this way, the centrifugal force can be reduced in a targeted manner, so that in the event of an additional failure of the secondary system of the steer-by-wire system, less intervention for steering or lateral guidance of the motor vehicle is required. Furthermore, a shorter braking distance and thus a faster stopping is thereby ensured. The assistance to the safe speed is achieved, for example, by increasing the resistance of the accelerator pedal, so that the driver can independently reduce the speed and continue to maintain a feeling of control over the motor vehicle. This has the advantage that the safety of operation during operation of the motor vehicle is further increased by simple means and in a cost-effective manner.

In particular, the motor vehicle is preferably operated in a targeted manner in such a way that a safety path is determined by the control device, said safety path being as close as possible to the desired path, and/or a safety speed is determined, said safety speed being as close as possible to the desired speed. In the event of a failure of the primary system, the limitation in the driving operation should fail as little as possible, so that the driver can continue to operate the motor vehicle in what can be considered a legitimate driving style. Excessive intervention in the driving operation should therefore be avoided. In this way, the driver is provided with the possibility of temporarily continuing to maneuver the motor vehicle without having to accept unreasonable restrictions. The need for direct travel to the workshop is therefore also eliminated, since the motor vehicle can continue to run safely and with acceptable power. This has the advantage that particularly low power losses can be accepted by simple means and in a cost-effective manner, so that the acceptance of the motor vehicle by the driver can be improved.

According to the invention, the motor vehicle is preferably operated in a targeted manner in such a way that, in the event of an additional failure of the secondary system, the motor vehicle can be brought to a standstill by a braking actuation on the driving lane. Within the scope of the invention, this is to be understood as meaning that the motor vehicle remains on the driving lane during the entire braking operation and also comes to rest on the driving lane, for example at the driving lane edge. The control device thus coordinates the speed, the distance from the edges of the roadway and the steering angle in such a way that a specific braking of the individual wheels can bring about a yaw movement of the motor vehicle and a braking that prevents the motor vehicle from slipping out of the roadway, taking into account the ambient parameters. This has the advantage that the safety of operation during operation of the motor vehicle is further increased by simple means and in a cost-effective manner.

According to a second aspect of the invention, the object is achieved by a motor vehicle. The motor vehicle has a drive system, a brake system and a steer-by-wire system. According to the invention, the motor vehicle is configured to carry out the method according to the invention. The brake system is preferably designed in such a way that a coordinated braking of the individual wheels, in particular with a suitable power, is ensured. The motor vehicle has a control device and a detection device for carrying out the method according to the invention. The control device is configured to control the steering system, the braking system and the preferred drive system.

All the advantages already described for the method according to the first aspect of the invention for operating a motor vehicle with a steer-by-wire system on a roadway are achieved in a motor vehicle according to the invention. The motor vehicle according to the invention thus has the advantage over conventional motor vehicles that, by means of simple means and in a cost-effective manner, even in the event of a failure of the primary system of the steer-by-wire system, safe continued travel with the motor vehicle is ensured, and thus forced parking of the motor vehicle can be avoided. In addition, the targeted operability of the motor vehicle ensures that the motor vehicle is used to continue traveling as normally as possible, for example in a defensive driving mode. In this way, the driving comfort for the driver of the motor vehicle is improved with respect to conventional motor vehicles.

Drawings

The method according to the invention and the motor vehicle according to the invention are explained in more detail below with reference to the figures. Schematically, respectively:

fig. 1 shows a preferred embodiment of a motor vehicle according to the invention in a side view;

fig. 2 shows a typical trajectory according to the prior art in a top view;

fig. 3 shows a targeted trajectory in a top view according to a preferred embodiment of the invention;

FIG. 4 shows in a flow chart a drive control system for predictive deceleration for performing a preferred embodiment of the method according to the invention; and is also provided with

Fig. 5 shows a preferred embodiment of the method according to the invention in a flow chart.

Elements having the same function and mode of action are provided with the same reference numerals in fig. 1 to 5, respectively.

Detailed Description

Fig. 1 schematically shows a preferred embodiment of a motor vehicle 1 according to the invention in a side view. The motor vehicle 1 has a steer-by-wire system 2 for steering the motor vehicle 1, a brake system 8 for braking the motor vehicle 1 and a drive system, not shown, for driving the motor vehicle 1. The steer-by-wire system 2 has a primary system 4, a secondary system 6 and a steering wheel 10. The brake system 8 has wheel brakes 11 that can be actuated individually in a targeted manner. For operating the steer-by-wire system 2, the brake system 8 and the drive system, the motor vehicle 1 has a control device 5. For detecting the ambient parameters, the motor vehicle 1 has a plurality of detection devices 7, which are configured, for example, as sensors, navigation systems, on-board computers, etc.

Fig. 2 schematically shows a typical trajectory T according to the prior art in a top view. In this illustration, the motor vehicle 1 runs on a normal trajectory T over a curve of the traffic lane 3, approximately at the outer third of the traffic lane 3. In a steer-by-wire system 2 with a primary system 4 and a secondary system 6 that are operating properly, such a trajectory T can be driven through without problems. In the steering-by-wire system 2 with a defective primary system 4, such a trajectory T can be driven without problems by means of the secondary system 6. Nevertheless, an additional failure of the secondary system 6 will lead to the illustrated failure track a of the motor vehicle 1. The motor vehicle 1 will leave the traffic lane 3 and thus be very likely to cause an accident, for example due to a collision with a guardrail or other obstacle. Therefore, such a trajectory T is not preferable in case of failure of the primary system 4.

Fig. 3 schematically shows a specific path T according to a preferred embodiment of the invention in a top view. The trajectory T has a significantly larger radius than the curve of the traffic lane 3. The motor vehicle 1 therefore moves on the outer lane edge of the curve when driving into the curve, on the inner lane edge of the curve in the middle region of the curve, and on the outer lane edge of the curve again when driving out of the curve. If the secondary system 6 fails while driving over the trajectory T, the motor vehicle 1 runs on the failure trajectory a, which continues on the traffic lane 3, so that a collision with the guardrail is avoided.

Fig. 4 schematically shows in a flow chart a driving control system for predictive deceleration for performing a preferred embodiment of the method according to the invention. The track formation 13 of the track T is realized by the lane direction 12 of the lane 3. Here, two important sub-models are attracting attention. This is, on the one hand, a driving state calculation 14 for evaluating predictability of lateral guidance demands on the motor vehicle 1, and on the other hand, a vehicle model 15 of the motor vehicle 1 for calculating lateral guidance potentials. In the matching of the two sub-models by the control device 5, a predictive degradation 16 then occurs, so that the transverse guidance requirements can be safely met by the transverse guidance potential. Thus, it should be ensured that the motor vehicle 1 moves in a safe driving state.

A preferred embodiment of the method according to the invention is schematically shown in a flow chart in fig. 5. In a first method act 100, the control device 5 of the motor vehicle 1 recognizes a fault of the primary system 4 of the steer-by-wire system 2. In a second method act 200, the control device 5 operates the secondary system 6 of the steering system 2, so that continued travel of the motor vehicle 1 is continued.

In a third method act 300, the detection device 7 detects ambient parameters of the ambient environment of the motor vehicle 1, such as curves, uphill gradients, downhill gradients, other traffic participants, lane friction values, weather data, etc. In a fourth method act 400, the control device 5 specifically operates the motor vehicle 1. For this purpose, the control device 5 determines a safe speed and a safe trajectory for operating the motor vehicle 1, so that a safe control of the motor vehicle 1 by the brake system 8 of the motor vehicle 1 is ensured even in the event of a possible failure of the secondary system 6 of the steer-by-wire system 2.

List of reference numerals

1. Motor vehicle

2. Steer-by-wire system

3. Traffic lane

4. Primary system

5. Control device

6. Secondary system

7. Detection device

8. Braking system

9. Signal device

10. Steering wheel

11. Wheel brake

12. Direction of traffic lane

13. Track formation

14. Driving state calculation

15. Vehicle model

16. Predictive degradation

100. First method action

200. Second method action

300. Third method action

400. Fourth method action

A fault track

T track

Claims (10)

1. A method for operating a motor vehicle (1) having a steer-by-wire system (2) on a driving lane (3), the method having:

-identifying, by a control device (5) of the motor vehicle (1), a failure of a primary system (4) of the steer-by-wire system (2);

-operating a secondary system (6) of the steer-by-wire system (2) by means of the control device (5);

-detecting, by means of a detection device (7) of the motor vehicle (1), a surrounding parameter of the surrounding of the motor vehicle (1); and is also provided with

-operating the motor vehicle (1) by means of the control device (5) in a targeted manner as a function of the detected ambient parameters in such a way that in the event of an additional fault of the secondary system (6) of the steer-by-wire system (2), a safety control of the motor vehicle (1) by means of the brake system (8) of the motor vehicle (1) is ensured.

2. Method according to claim 1, characterized in that the failure of the primary system (4) is signaled by a signaling device (9) of the motor vehicle (1).

3. Method according to claim 1 or 2, characterized in that the lane direction trend (12) of the roadway (3) and/or the longitudinal inclination of the roadway (3) and/or the lateral inclination of the roadway (3) and/or the roadway topology and/or the roadway friction values and/or obstacles and/or other traffic participants and/or weather data on or beside the roadway (3) are taken into account as ambient parameters by the detection device (7).

4. The method according to any of the preceding claims, wherein at least one ambient parameter is predictively detected when detecting the ambient parameter.

5. Method according to any one of the preceding claims, characterized in that the targeted operation of the motor vehicle (1) has a determination of a trajectory (T) in a curve, which trajectory has a trajectory radius that is greater than the curve radius of the curve.

6. Method according to any of the preceding claims, characterized in that the targeted operation of the motor vehicle (1) has an active correction from a desired trajectory preset by the driver of the motor vehicle (1) to a safety trajectory and/or an assistance to the safety trajectory.

7. Method according to any of the preceding claims, characterized in that the targeted operation of the motor vehicle (1) has an active correction from a desired speed preset by the driver of the motor vehicle (1) to a reduced safety speed and/or an assistance to the safety speed.

8. Method according to claim 5 or 6, characterized in that the targeted operation of the motor vehicle (1) is performed in such a way that a safety trajectory is determined by the control device (5), said safety trajectory being as close as possible to the desired trajectory, and/or a safety speed is determined, said safety speed being as close as possible to the desired speed.

9. Method according to any of the preceding claims, characterized in that the targeted operation of the motor vehicle (1) is carried out in such a way that the motor vehicle (1) can be brought to a standstill by a braking maneuver on the traffic lane (3) in the event of an additional fault of the secondary system (6).

10. Motor vehicle (1) with a drive system, a brake system (8) and a steer-by-wire system (2), characterized in that the motor vehicle (1) is configured for carrying out the method according to any of the preceding claims.