METHOD AND CONTROL DEVICE FOR PREVENTING A STEER-BY-WIRE MOTOR VEHICLE TO TIPPING

Description

[0001] The present invention relates to a method and a control device for a motor vehicle to prevent the motor vehicle from tipping over. The invention further relates to a correspondingly equipped motor vehicle.

[0002] Especially when driving a motor vehicle manually, there is a risk of it tipping over. This can be caused, for example, by excessively sharp steering inputs at high speed, sudden and repeated changes in direction and lateral load (i.e., swaying), or similar maneuvers. To improve safety, there are already approaches to stabilizing motor vehicles to prevent such tipping through automatic control interventions. Similarly, it can be problematic if a motor vehicle's wheels enter the shoulder of a roadway, resulting in a shoulder crossing. EP 3 738 861 A1 describes a method for ending a shoulder crossing. In this method, the steering intensity of a manual steering maneuver is determined upon detection of a shoulder crossing. Depending on this, the steering maneuver is then assigned one of at least two predefined steering parameters.Depending on the situation, an automatic intervention in the vehicle's control system is then carried out via a control unit. This concept enables a quick, safe, and reliable end to the shoulder driving situation.

[0003] German patent application DE 10 2014 202 230 A1 describes a method for preventing a steerable vehicle, particularly a rear-wheel-steered vehicle, from tipping over. This method determines a tipping criterion using a steering angle and the vehicle's speed. A correction signal for the steering angle is then provided when the tipping criterion indicates a risk of the vehicle tipping over. This correction signal represents a smaller deflection of at least one steerable wheel of the vehicle than the steering angle, in order to prevent tipping.

[0004] Another approach described in DE 10 2005 046 776 A1 involves roll stabilization using a four-wheel drive system. Specifically, a method for controlling a vehicle with a 4x4 drive system is disclosed. This method aims to determine a potential rollover condition and transfer drive torque to the front wheels via an electronically controlled center differential or an electronically controlled transfer case to prevent overtaking.

[0005] German patent application DE 10 2018 101 182 A1 describes a method for preventing rollovers of a motor vehicle during lateral load changes using torque vectoring. The motor vehicle in this application has an individual wheel drive designed to drive a wheel subjected to the lateral load change independently of at least one other wheel of the motor vehicle. The method described therein is intended to detect a critical state of the motor vehicle during a lateral load change. Furthermore, a drive torque is to be applied by an individual wheel drive to the wheel subjected to the lateral load change in such a way that the wheel subjected to the lateral load change is made to slip. Finally, the method provides for steering the wheel subjected to the lateral load change in the direction of travel in such a way as to prevent the motor vehicle from rolling over.

[0006] The object of the present invention is to enable particularly safe driving behavior of a motor vehicle while simultaneously providing particularly high driving dynamics.

[0007] This problem is solved according to the invention by the subject matter of the independent claims. Possible embodiments and further developments of the present invention are disclosed in the dependent claims.

[0008] The method according to the invention serves to prevent a motor vehicle from tipping over if it has an electric steering system without a mechanical connection between the steering wheel or steering handle and the steered wheels of the vehicle. In other words, the method is applicable to motor vehicles that have a so-called steer-by-wire steering system. In one step of the method according to the invention, predefined parameters describing the current driving situation of the vehicle are automatically monitored. These parameters, or rather their parameter values, are then automatically analyzed for a risk of the vehicle tipping over based on predefined criteria.These parameters can include, for example, a steering angle, a rate or speed of change of the steering angle, a vehicle speed, a roll angle during a vehicle's longitudinal axis movement, the operating state of a braking system, wheel-specific slip, and / or similar parameters. The criteria defined for analysis can include, for example, reaching or exceeding a threshold value for one or more parameter values, or for a value calculated from one or more parameter values, and / or similar criteria. Monitoring and analysis can be performed continuously or at regular intervals during vehicle operation.

[0009] A risk of tipping over in the present sense may exist in particular if the operation of the motor vehicle, extrapolated according to the respective current parameter values ​​or continued without corrective control interventions, would foreseeably lead to tipping over or a probability of tipping over that lies above a predetermined intervention threshold.

[0010] In a further step of the inventive process, when a tipping hazard is detected, a predetermined, graduated cascade of several different automatic control interventions to influence the driving situation of the motor vehicle—that is, in particular one or more of the predetermined parameters—is executed sequentially, escalating from stage to stage of the cascade until there is no longer a tipping hazard or until the probability of tipping is less than a predetermined safety threshold. In other words, different or further control interventions can be automatically initiated or executed successively to counteract the potential tipping or the risk of tipping in an increasingly strong or aggressive manner.

[0011] The predefined cascade system, in its first stage, limits the steering speed of the electric power steering to a predetermined maximum value. During or when this first stage is activated, a limit can be imposed on the maximum rate of change of the steering angle, at least in the direction of a smaller turning radius. This prevents or dampens vehicle roll caused by steering interventions, lateral load changes, and / or decreasing turning radii. The steering speed limitation implemented in this first stage can represent a relatively weak or gentle control intervention, for example, compared to an automatic change in the steering angle or a relatively strong automatic braking intervention, as is the case with conventional ESC or purely brake-based rollover prevention systems.The first stage of the cascade can be initiated or executed earlier, before the vehicle is likely to tip over, or even when the probability of tipping is lower, than a conventionally implemented braking intervention. This is possible because influencing or controlling the electric steering system is an additional measure, meaning that braking intervention does not have to be the first and only action. Limiting the steering speed is particularly easy and transparent for the driver through appropriate electrical or electronic control of the electric steering system.

[0012] The predefined cascade includes a second stage that limits the steering angle of the electric power steering to a predetermined first maximum steering angle. In other words, a corresponding control intervention in the electric power steering prevents the driver from manually adjusting the steering angle, or turning the steering wheel, to a greater angle than the first maximum steering angle, which would result in a smaller turning radius. This effectively prevents or dampens the vehicle's tendency to roll due to repeated opposing steering movements. Furthermore, if the actual steering angle exceeds the first maximum steering angle when the second stage is activated, it can be automatically reduced or reset to the first maximum steering angle.

[0013] The predefined cascade includes a third stage that limits the steering angle to a predetermined, smaller second maximum steering angle. This second maximum steering angle is smaller than the first, meaning it corresponds to a larger turning radius. If the actual steering angle exceeds the second maximum, the third stage actively reduces it to at least the second maximum. This dampens or suppresses rollover, i.e., the vehicle's tendency to roll around its longitudinal axis. The third stage of the cascade can be applied or triggered, for example, when such rollover is detected, particularly if it exceeds a predefined threshold.The third stage also includes automatic active braking intervention to reduce the vehicle's speed. Because this system not only uses active braking to prevent rollovers, but also influences the electric steering through the described control interventions, the active braking intervention can occur later than a conventional rollover prevention system based solely on ESC or brakes.

[0014] The first and / or second maximum steering angle can be fixed or dynamically adjusted or predefined depending on the situation, for example, based on speed, road gradient, and / or other factors. For instance, the maximum steering angle can be smaller or reduced at higher vehicle speeds and / or reduced at greater road gradients in the lateral direction of the vehicle, particularly asymmetrically for both steering directions. For example, a reduction of the maximum steering angle can be implemented or activated only when steering uphill, or it can be greater for uphill than for downhill. This allows for effective rollover prevention with minimal impairment of manual control or the vehicle's range of motion.

[0015] Compared to conventional rollover prevention systems based solely on ESC or brake intervention, the present invention provides for earlier control intervention to prevent rollover, which, however, has a less pronounced impact on the vehicle's handling. Thus, the present invention enables particularly linear vehicle handling across a particularly wide limit range, within which a vehicle control device configured to implement the inventive method intervenes to prevent rollover. The present invention can therefore avoid or reduce abrupt changes in the vehicle's handling. This results in improved driving and user comfort, as well as better or easier control of the vehicle at the limit. Furthermore, the earlier intervention can enhance safety.

[0016] Improved safety is also achieved through the combination of several different types of control interventions, namely interventions in the electric power steering and the brake intervention provided for at least in the third stage. This intended combination of different types of control interventions allows for greater correction potential and thus permits higher driving dynamics—i.e., a larger steering angle, higher driving speed, and / or a larger rollover angle of the vehicle—at the vehicle's limits, without compromising safety. In particular, the third stage, or...The highest level of the cascade of control interventions is applied significantly later than with stabilization systems without steer-by-wire support, because with corresponding purely ESC- or brake-based control interventions in a corresponding critical situation, an outside front wheel of the vehicle may no longer be sufficiently braked, and therefore a conventional rollover prevention system based on this must initiate full braking of this wheel earlier in order to prevent the vehicle from rolling over.

[0017] The additional limitation and, if necessary, reduction of the steering angle provided for in the invention can, due to the electrical design or control of the steering system - for example, compared to purely mechanical steering systems - be carried out more quickly and thus activated later, while still preventing the vehicle from tipping over.

[0018] In one possible embodiment of the present invention, the predetermined cascade in the first and / or second stage also provides for an automatic active braking intervention that is weaker than the automatic active braking intervention provided in the third stage. Such a weakened braking intervention at a correspondingly earlier point in time allows the kinetic energy of the vehicle to be reduced particularly early, thereby preventing or dampening the vehicle's oscillation at a correspondingly early stage. Because this weakened braking intervention occurs so early, it can be weaker than the braking intervention provided in the third stage, thus preventing an abrupt or sudden, automatically triggered change in the vehicle's driving behavior or driving state.Thus, the proposed embodiment of the present invention can achieve not only improved safety, but also improved comfort and, where applicable, improved acceptance of the automatic vehicle control system for rollover prevention, i.e., a corresponding driver assistance system. If active braking intervention is provided in each stage of the cascade, this intervention can increase in intensity from stage to stage, thereby achieving or supporting a particularly smooth or linear change in the vehicle's handling characteristics despite the graduated cascade of control interventions.

[0019] In a further possible embodiment of the present invention, the specified cascade also provides, in at least one stage, for limiting the motor vehicle's response to an acceleration signal from the driver. In other words, the motor vehicle's throttle response or the power output from the vehicle's traction battery in response to a corresponding operating action, for example, the driver pressing the accelerator or gas pedal, can be limited or reduced compared to normal operation outside the limit range. In this way, the build-up of additional kinetic energy, which could lead to further, increased, or faster oscillation of the motor vehicle, can be avoided particularly easily and effectively.Such a limitation of the reaction can be a less severe or less abrupt intervention in the vehicle's handling or driving state than, for example, an active braking intervention. The limitation of the vehicle's reaction proposed here can therefore also achieve a smoothing or linearization of the vehicle's handling at the limit or across the multiple stages of the cascade, which can improve the vehicle's safety, controllability, and comfort. As described elsewhere in connection with braking interventions, corresponding limitations can be implemented in one or more stages of the cascade. These limitations can become more stringent from stage to stage.In a possible further development of the present invention, the predetermined cascade can thus provide for a weaker first limitation of the reaction in the first stage and / or in the second stage, and a stronger second limitation of the reaction in the third stage. For example, in the first stage, the reaction to the acceleration signal, or the effect of the acceleration signal, can be reduced or limited to approximately 50%, in the second stage to approximately 25%, and / or in the third stage to approximately 0% to 10%. Likewise, other values ​​or gradations are possible, for example, depending on the design or requirements profile for a specific application.By limiting the vehicle's response to the acceleration signal as proposed here, a further control or intervention option is available to prevent the vehicle from tipping over, thereby achieving an overall improvement in the vehicle's safety and comfort.

[0020] In a further possible embodiment of the present invention, the automatic escalation from stage to stage of the cascade occurs according to a predetermined schedule, depending on a predicted tipping point at which the vehicle would likely tip over without control intervention. In other words, an assignment can be predefined, specifying at what time interval from the tipping point which stage, or the measures or control interventions of which stage, are to be automatically applied or triggered. It can be provided, in particular, that at a given time interval from the tipping point, the highest stage to be executed or applied up to that point, according to the predefined assignment, is executed or applied. Lower stages can then be skipped if necessary, if the first predetermined time interval from the tipping point already provides for the application or execution of a higher stage.The proposed embodiment of the present invention allows for two things: firstly, at least in most cases, a particularly predictable behavior of the vehicle, meaning consistent behavior across multiple imminent rollover events, and secondly, improved safety. The latter is achieved because, in critical situations, it is not necessarily required to first execute or undergo control interventions at a lower level.

[0021] In a further possible embodiment of the present invention, sensors in the vehicle monitor whether one or more wheels lift off the ground, and the cascade of control interventions is applied accordingly. For example, the sensors of an adaptive chassis control system (Dynamic Chassis Control, DCC) and / or a headlight range control system can be used. The lifting of at least one wheel from the ground can be detected, for example, by observing or monitoring the suspension state of the vehicle, a corresponding part of the sensor system, or a damping device. The application of the cascade of control interventions can then occur, for example, depending on the result of the monitoring or on the detection of one or more wheels lifting off the ground.This can mean, for example, that if a lift-off is detected or depending on the extent or degree of such a lift-off, predefined threshold values, such as intervention thresholds, the aforementioned limits or maximum steering angles and / or the like, can be adjusted, in particular tightened, and / or if a lift-off is detected or if a detected lift-off reaches or exceeds a predefined threshold, the system automatically escalates to the next stage of the cascade.

[0022] Adjusting thresholds, limits, maximum steering angles, and / or similar parameters can be done either only for the current driving or rollover hazard situation or permanently. In the latter case, the procedure can be automatically adapted to the individual behavior or characteristics of the respective vehicle—that is, automatically learning this behavior or these characteristics. This allows, for example, user-initiated modifications to the vehicle that could influence its driving or rollover behavior to be automatically taken into account.

[0023] The proposed use of sensors to detect when one or more wheels of the vehicle lift off the ground enables a particularly accurate and reliable determination of the risk of rollover, since, for example, the risk of rollover does not have to be inferred solely from the vehicle speed and the current steering angle, while other influencing factors, such as the properties of the road surface, crosswinds, the vehicle's load, and / or the like, remain unconsidered. Instead, the sensors can detect and take into account the actual, current state of the vehicle that is relevant to the potential for rollover. The use of the adaptive chassis control and / or the headlight range control, or their respective sensors, enables a particularly efficient, and especially component- and cost-saving, implementation of the present invention through the corresponding dual use of the sensors.

[0024] In a further possible embodiment of the present invention, a tilting movement of the vehicle is detected or monitored by means of acceleration sensors and / or rotation sensors. The application of the cascade is then finely controlled depending on the detected tilting movement. This can mean, for example, that for the control interventions or corresponding intervention strengths, thresholds, limits, maximum steering angles, and / or the like, a respective control or regulation interval around the respective value is predefined for the individual stages, and the control interventions can be controlled, regulated, or shifted within these intervals. The control or regulation intervals of different stages can, in particular, be non-overlapping. Through the fine control of the cascade proposed here,By applying the cascade system, i.e., by executing the corresponding control interventions, it can be ensured that the control interventions are set or executed in such a way that the vehicle's rollover is limited or dampened only to the extent necessary to prevent rollover or to achieve or establish a specific, predetermined, or particularly smooth or consistent vehicle behavior. This allows for automatic adjustments to react to, in particular, unpredictable, situation-specific circumstances or conditions, such as road gradient, a (possibly uneven) vehicle load, tire pressure, user-initiated modifications to the vehicle that affect handling, crosswind conditions or influences, and / or the like.In this way, not only can the behavior of the vehicle remain as consistent as possible in correspondingly different situations, but improved safety can also be achieved through an adapted or adaptable control or regulation scope. To implement the proposed embodiment of the present invention particularly efficiently, the sensors of an adaptive chassis control system of the vehicle can, for example, be used in conjunction with it.

[0025] In a further possible embodiment of the present invention, the application or execution of the different control interventions provided according to the cascade is automatically coordinated by a vehicle dynamics controller. The vehicle dynamics controller is configured to simulate whether a given current trajectory of the vehicle, with the current operating parameters and / or with the application of specific control interventions, can be traversed without the vehicle tipping over. The vehicle dynamics controller can therefore, for example, be or comprise a control unit configured to coordinate different control interventions, for instance, with regard to their strength and / or timing and / or duration. The vehicle dynamics controller can thus simulate the influences or combined effects of different control interventions on the driving or tipping behavior.The vehicle's trajectory must be taken into account. This, or rather the respective simulation, can be performed, for example, considering the control interventions of a single or the current stage, or considering the control interventions of multiple stages or across multiple stages of the cascade. If the simulation shows that the vehicle's current trajectory, with the current operating parameters and / or control interventions, cannot be traversed without a likely rollover or with a rollover probability exceeding a predefined threshold, the vehicle dynamics controller can then execute or adjust the control interventions to prevent rollover or reduce the rollover probability below the threshold.This can be achieved, for example, through iterative simulation with modified parameters representing the control interventions, their strength, application timing, and / or duration. The proposed coordination of the various planned or possible control interventions allows for the identification and application of an optimal or particularly effective combination. This can lead not only to improved rollover stability but also, for example, to improved vehicle handling and controllability.For example, a combined application of several different control interventions in a central area of ​​their respective control or regulation intervals may allow more flexibility or room for reaction for further automatic or manual control interventions by the driver of the motor vehicle than an application of one or more control interventions at an edge area, i.e. an end or maximum value of its control or regulation interval.

[0026] Another aspect of the present invention is a control device for a motor vehicle. The control device according to the invention has an interface for acquiring parameter values ​​of parameters that describe the current driving situation or driving state of the motor vehicle, and for outputting control signals for controlling the motor vehicle. A single or shared interface, or an input interface and a separate output interface, can be provided for acquiring and outputting the parameters. Furthermore, the control device according to the invention has a data processing unit for automatically processing the acquired parameter values ​​to determine a risk of the motor vehicle tipping over and to generate the control signals according to a predetermined cascade of control interventions.The control device according to the invention is configured for the automatic execution of at least one embodiment or variant of the method according to the invention. For this purpose, the data processing device can comprise a processor, such as a microprocessor, microchip, or microcontroller, and an associated data storage device. An operating or computer program can be stored on this data storage device, which encodes or implements the processes, measures, or procedure steps described in connection with the method according to the invention and can be executed by the processor to effect or initiate the execution of the corresponding method.The recorded parameter values ​​can be, for example, the driving speed, the steering angle, measurement or sensor values ​​of an acceleration sensor, a rotation sensor and / or other sensors of the motor vehicle and / or the like, as described in connection with the method according to the invention.

[0027] Another aspect of the present invention is a motor vehicle that has an electric steering system without a mechanical connection between a steering wheel or steering handle and the steered wheels of the motor vehicle, i.e., a steer-by-wire steering system, a controllable braking system, and a control device according to the invention. The control device is configured here to control the electric steering system and the braking system according to the method of the invention, i.e., for example, it is connected or coupled to the braking system and the control device accordingly. The motor vehicle according to the invention can also have the sensors mentioned elsewhere and / or further sensors coupled to the control device, as well as some or all and / or further devices mentioned, such as adaptive chassis control, headlight range control, vehicle dynamics control, and / or the like.The motor vehicle according to the invention can, in particular, be the motor vehicle mentioned in connection with the method according to the invention and / or in connection with the control device according to the invention. Accordingly, the motor vehicle according to the invention can have some or all of the properties or features mentioned in these contexts.

[0028] Further features of the invention can be seen from the following description of the figures and from the drawing.

[0029] The drawing shows in the single figure a partial schematic representation of a motor vehicle with electric steering, which is equipped for automatic rollover prevention.

[0030] Fig. 1Figure 1 shows a partial schematic representation of a motor vehicle 1 equipped with electric power steering. A steering wheel 2 is coupled to a steering signal generator 3, which, upon operation or actuation of the steering wheel 2 by the driver of the motor vehicle 1, generates a corresponding steering signal and transmits it to an electromechanical actuator 4. The electromechanical actuator 4 converts the steering signal into a mechanical steering movement of the steered wheels 5 of the motor vehicle 1.

[0031] The motor vehicle 1 further comprises a braking device 6, by means of which wheels, for example the steered wheels 5, can be braked. The braking device 6 can also be controlled by the electromechanical actuator 4.

[0032] Furthermore, a driving condition sensor 7 is provided here, which can detect a driving condition of the vehicle 1, for example, its current speed and steering angle, as well as an operating or actuation state of the braking system 6. In addition, the vehicle 1 has a height sensor 8 and a rotation sensor 9. The height sensor 8 can, for example, monitor or detect when individual wheels of the vehicle 1 lift off the ground by observing a suspension compression state. Tilting or rolling movements of the vehicle 1, in particular about a longitudinal axis of the vehicle 1, can be detected by the rotation sensor 9. The rotation sensor 9 can, for example, include a dedicated rotation sensor and / or one or more acceleration sensors.

[0033] The motor vehicle 1 is also equipped with a rollover prevention device 10. This, like the other components mentioned, is schematically connected here to an on-board network 11, via which data, signals and control commands can be transmitted.

[0034] The rollover prevention device 10 has an interface 12 for acquiring data or signals from one or more of the other aforementioned devices, in particular the steering signal generator 3, the driving condition sensor 7, the height sensor 8, and the rotation sensor 9. Data or signals acquired in this way can be processed by the rollover prevention device 10 using a processor 13 and a data storage device 14 to generate signals or control commands for initiating control interventions, i.e., automatic control of the electric steering and / or the braking system 6. These control signals can, for example, be output via the interface 12 and transmitted via the vehicle electrical system 11, for instance, to the electromechanical actuator 4. The rollover prevention device 10 is configured here to automatically execute a predefined procedure during operation of the vehicle 1 in order to prevent the vehicle 1 from tipping over.

[0035] So-called roll-up interventions, i.e., control interventions to prevent the vehicle 1 from tipping over or to prevent or limit the lifting of one or more wheels of the vehicle 1, can be carried out or initiated automatically by the roll-up prevention device 10. The time window for recognizing whether such a roll-up intervention is necessary is typically relatively short. If the roll-up of the vehicle 1 is then to be prevented solely by using the braking device 6, this can lead to very sudden and strong interventions or changes in the behavior or driving state of the vehicle 1. To avoid this, the electric steering is also integrated into the roll-up prevention system.

[0036] Firstly, this allows the roller shutter interventions to be applied later than with conventional systems, at their full extent or intensity, which overall permits greater driving dynamics. Secondly, initial, relatively weak roller shutter interventions can be applied earlier than with conventional systems, thus preventing abrupt changes in the vehicle's handling characteristics and ensuring that the vehicle remains controllable at its limits.

[0037] The rollover prevention device 10 can control the electric steering system, in particular the electromechanical actuator 4, to limit the steering speed in rollover-critical situations where the vehicle 1 is likely to roll over without steering intervention. This prevents unnecessary oscillation of the vehicle 1. This can occur relatively early, i.e., in the first stage of a predefined cascade of steering or rollover interventions. Furthermore, the vehicle 1's throttle response can be reduced or limited, and / or an initial, relatively weak braking intervention can be applied to reduce the vehicle 1's kinetic energy.

[0038] At a later point, for example in a second stage of the cascade, a situation-dependent limitation of the steering angle can be initiated by the rollover prevention device 10 in order to prevent or reduce oversteering and lateral acceleration peaks. This can be supported by a reduction in throttle and / or brake intervention, i.e., automatic control of the braking device 6, to further reduce the energy of the vehicle 1.

[0039] If, however, a roll or tipping motion of the vehicle 1 occurs, particularly one that reaches or exceeds a predetermined threshold, the rollover prevention device 10 can, for example in a third stage of the cascade, initiate a further limitation and / or a reduction of the steering angle down to a predetermined maximum steering angle in order to suppress the tipping motion. This is combined here with a vehicle deceleration also initiated by the rollover prevention device 10, i.e., a second or third braking intervention, particularly a stronger one. This ensures that the driver of the vehicle 1 can continue to follow a desired trajectory. This third intervention stage of the cascade can be activated significantly later, i.e., much closer to the anticipated tipping point, than a final control measure of conventional rollover stabilization systems without support or integration of the steer-by-wire steering system.

[0040] The described roller shutter interventions can be coordinated here by a vehicle dynamics controller, which can, for example, be integrated or implemented in the rollover prevention device 10. This vehicle dynamics controller can continuously simulate whether the current trajectory of the vehicle 1 is still safe to travel with regard to rollover or whether a critical rollover situation already exists. Depending on the time interval to a corresponding critical rollover point, at which the vehicle 1 would likely roll over without control or roller shutter intervention, the described roller shutter interventions can be initiated – if necessary, adapted to each other, coordinated, or aligned with each other by the vehicle dynamics controller. The electrical or...Electronic control of the steering and, if applicable, the braking system 6 makes it possible to catch the motor vehicle 1 relatively late and to prevent it from tipping over or from lifting off one or more wheels of the motor vehicle 1.

[0041] In the manner described here, automatic rollover prevention interventions can be supported by appropriately controlling the steer-by-wire steering system. Particularly early prevention of the vehicle 1's tendency to roll can be achieved by limiting the steering speed, and potentially critical situations can be prevented particularly early by preventing oversteering. This allows for relatively late intervention when the vehicle 1 begins to roll, thus permitting particularly high driving dynamics even at the limits of performance without compromising the vehicle 1's stability. Furthermore, particularly linear vehicle behavior can be achieved across the entire limits of performance.

[0042] Overall, the examples described demonstrate how rollover avoidance or tilt stabilization maneuvers can be made more agile using a steer-by-wire steering system in a vehicle. Reference symbol list

[0043] 1. Motor vehicle 2. Steering wheel 3. Steering signal transmitter 4. Electromechanical actuator 5. Steered wheels 6. Braking system 7. Driving condition sensors 8. Height sensors 9. Rotation sensors 10. Rollover prevention system 11. On-board electrical system 12. Interface 13. Processor 14. Data storage

Claims

1. Method for preventing a motor vehicle (1) from tipping over, which motor vehicle has an electric steering system (3, 4) in which there is no mechanical connection between a steering wheel (2) and steered wheels (5) of the motor vehicle (1), in which method - predetermined parameters that each describe a current driving situation of the motor vehicle (1) are monitored and analyzed on the basis of predetermined criteria for a risk of tipping over, - if a risk of tipping over is recognized, a predetermined stepped cascade consisting of a plurality of different automatic control interventions for influencing the driving situation of the motor vehicle (1) is executed sequentially, escalating from step to step of the cascade until there is no longer a risk of tipping over, wherein the cascade provides for - in a first step, a limitation of a steering speed of the electric steering system (3, 4) to a predetermined maximum value, - in a second step, a limitation of a steering angle of the electric steering system (3, 4) to a predetermined first maximum steering angle, and - in a third step, a limitation of the steering angle to a predetermined smaller second maximum steering angle and, if the actual steering angle is greater than the second maximum steering angle, an active reduction of the actual steering angle at least to the second maximum steering angle and an active braking intervention for reducing a driving speed of the motor vehicle (1), all of which is performed automatically.

2. Method according to claim 1, characterized in that the cascade also provides for, in the first step and / or in the second step, an active braking intervention which is lighter than the active braking intervention provided for in the third step.

3. Method according to either of the preceding claims, characterized in that the cascade also provides for, in at least one step, a limitation of a response of the motor vehicle (1) to an acceleration signal from a driver.

4. Method according to claim 3, characterized in that the cascade provides for a lesser first limitation of the response in the first step and / or in the second step and for a greater second limitation of the response in the third step.

5. Method according to any of the preceding claims, characterized in that the escalation from step to step is carried out on the basis of an expected tipping instant at which the motor vehicle (1) would be expected to tip over without a steering intervention.

6. Method according to any of the preceding claims, characterized in that by means of a sensor system (8, 9) of the motor vehicle (1), in particular an adaptive chassis control and / or a headlight range control, the motor vehicle (1) is monitored for a wheel lifting off of a surface being driven on and the cascade is applied on the basis thereof.

7. Method according to any of the preceding claims, characterized in that by means of an acceleration sensor system (7, 8, 9), in particular an adaptive chassis control (8), and / or by means of a rotation sensor system (9) of the motor vehicle (1), a tilting movement of the motor vehicle (1) is detected and application of the cascade is finely controlled on the basis of the detected tilting movement.

8. Method according to any of the preceding claims, characterized in that application of the different control interventions provided for in accordance with the cascade is coordinated by a driving dynamics controller (10) of the motor vehicle (1), which driving dynamics controller is configured to simulate whether a current trajectory of the motor vehicle (1), with respective current operating parameters and / or with application of certain control interventions, can be traversed without the motor vehicle (1) tipping over.

9. Control device (10) for a motor vehicle (1), having an interface (12) for detecting parameter values of parameters that each describe a current driving situation of the motor vehicle (1) and for outputting control signals for controlling the motor vehicle (1), and a data processing apparatus (13, 14) for processing the detected parameter values to determine a risk of the motor vehicle (1) tipping over and to generate the control signals in accordance with a predetermined cascade of control interventions, wherein the control device (10) is configured to automatically carry out a method according to any of the preceding claims.

10. Motor vehicle (1), having an electric steering system (3, 4) in which there is no mechanical connection between a steering wheel (2) and steered wheels (5) of the motor vehicle (1), having a controllable braking apparatus (6) and having a control device (10) according to claim 9 configured to control the electric steering system (3, 4) and the braking apparatus (6).