DE102022203076A1 - Method and device for controlling a steering device of a vehicle whose wheels at least one axle move on areas of a road with different coefficients of friction - Google Patents

Abstract

The approach presented here creates a method (700) for controlling a steering device (127) of a vehicle (100), the wheels (117) of which are located on at least one axle (129, 130) on areas (110, 115) of a roadway (105). each move with a different coefficient of friction. The method (700) includes a step of reading in (710) a vehicle yaw value (147), which represents yaw behavior of the vehicle (100) about a vertical axis. The method (700) further comprises a step of determining (720) a compensation steering angle (150) in order to minimize and/or reduce the yaw behavior of the vehicle (100). Finally, the method (700) comprises a step of controlling (730) a deflection of the wheels (117) of the at least one axle (129, 130) of the vehicle (100) by the steering device (137) by means of the compensation steering angle (150).

Description

The present invention relates to a method and a device for controlling a steering device of a vehicle, the wheels of which move at least one axle on areas of a road, each with a different coefficient of friction, according to the preamble of the independent claims.

In the event that a vehicle drives on areas of the road where the wheels on different sides of the vehicle move in areas with different coefficients of friction, precautions should be taken against critical driving conditions. These result from the fact that, for example when accelerating or braking, the wheels on the different sides of the vehicle have different traction on the road, which can lead to strong yaw and thus to safety-critical driving conditions when the vehicle is moving. When brake control systems are used, vehicle acceleration is significantly slowed down. Intervention on the front axle is generally not intended as this would result in the steering wheel being adjusted.

Against this background, the present invention creates an improved method and an improved device for controlling a steering device of a vehicle, the wheels of which move at least one axle on areas of a road, each with a different coefficient of friction, according to the main claims. Advantageous refinements result from the subclaims and the following description.

• - Einlesen eines Fahrzeuggierwertes, der eine Gierbewegung des Fahrzeugs um eine Hochachse repräsentiert;
• - Bestimmen eines Kompensationslenkwinkels, um eine Minimierung und/oder eine Verringerung der Gierbewegung des Fahrzeugs zu bewirken; und
• - Ansteuern einer Auslenkung der Räder der zumindest einen Achse des Fahrzeugs durch die Lenkvorrichtung mittels des Kompensationslenkwinkels.

The approach presented here creates a method for controlling a steering device of a vehicle whose wheels at least one axle move on areas of a road with different coefficients of friction, the method having the following steps:

• - Reading in a vehicle yaw value, which represents a yaw movement of the vehicle about a vertical axis;
• - determining a compensation steering angle to minimize and/or reduce the yaw motion of the vehicle; and
• - Controlling a deflection of the wheels of the at least one axle of the vehicle by the steering device using the compensation steering angle.

The steering device is preferably a steer-by-wire steering system, which is preferably used at least on the rear axle of the vehicle as additional rear axle steering that is independent of the front axle steering. Steer-by-wire steering is a mostly electromechanical unit that is decoupled from a mechanical steering handle, e.g. a steering wheel. Steering signals are generated in a control unit based on steering signals and one or more parameters such as vehicle speed, steering wheel angle, current steering angles on the front and/or rear axle, yaw acceleration and/or lateral acceleration of the vehicle, etc. The steering movement is carried out by means of at least one actuator of the steer-by-wire steering, which receives steering signals from the control unit. For example, a spindle or handlebar can be linearly displaced in the actuator by means of a spindle drive, which is directly or indirectly articulated to wheel carriers. By moving the spindle, the wheel carriers can be pivoted about their vertical axis, so that the wheels rotatably mounted on the wheel carriers can be subjected to a change in the wheel steering angle of the respective wheel carrier. The compensation steering angle can be sent as a signal from a control device to the steer-by-wire steering, which changes the wheel steering angle by deflecting the wheels of at least one axle of the vehicle.

According to a particularly favorable embodiment, in the step of reading in, a speed value representing a vehicle speed, a steering angle with which the steering device controls the vehicle with respect to straight-ahead travel and a coefficient of friction variable can be read in, which represent or map the different coefficients of friction in the areas of the road Vehicle yaw value is determined using the speed value, the steering angle and the coefficient of friction.

In the present case, a vehicle can be understood to mean, for example, a motor vehicle, such as a passenger car, a truck, an omnibus or the like. The vehicle should have at least two lanes, with the wheels on one axle being able to move on different areas of the road that have different coefficients of friction. A coefficient of friction variable can generally be understood as a parameter that represents different coefficients of friction in the areas of the road on which the wheels move on an axle. For example, the coefficient of friction can be a two-dimensional parameter that represents the individual coefficients of friction in the respective areas of the road. Alternatively or additionally, however, the coefficient of friction can also represent a difference between the two relevant coefficients of friction or as a parameter relating to a speed of the wheel(s) and/or as a parameter about a brake pressure of a brake - in combination, for example, with the speed or acceleration of the wheel in question - on the wheel or wheels gives an indirect indication of what coefficient of friction is currently present on the wheel in question with respect to the road. A vehicle yaw value can be understood as a parameter that represents information about yaw behavior and/or a current yaw movement of the vehicle.

The approach presented here is based on the knowledge that it is very efficient and simple by controlling the deflection of the wheels of at least one axle of the vehicle, for example taking into account the vehicle speed, the steering angle and the coefficients of friction of the road areas on which the wheels of the axle move possible to increase the driving safety of the vehicle. This takes advantage of the fact that active steering devices or driver assistance systems are usually already present in the vehicle, which, on the one hand, can already collect and/or process a large number of vehicle and/or driving parameters and, on the other hand, can also carry out physical interventions in vehicle components, for example a steering movement affect the movement of the vehicle. In this way, the sensors or actuators that are often already present can be used to achieve additional benefits for the vehicle components that are often present using the new linking of parameters proposed here, using technically simple means.

An embodiment of the method proposed here is particularly advantageous in which, in the control step, a deflection of the wheels of a rear axle of the vehicle is controlled by the steering device. Such an embodiment offers the advantage that the control of the deflection of the wheels of a rear axle of the vehicle in particular acts on the vehicle movement very quickly and efficiently, so that safety-critical driving states can be ended as quickly as possible. At the same time, a reaction of the steering to a manual steering input acting on the wheels of the front axle, which could, for example, lead to irritation for the driver, can be avoided.

An embodiment of the approach proposed here can be implemented very efficiently, in which, in the reading step, a coefficient of friction is read in as the coefficient of friction of those areas of the road on which the wheels of the vehicle move and/or where the coefficient of friction is a difference between two coefficients of friction Areas of the road on which the vehicle's wheels move are read. Alternatively or additionally, at least one speed information about a speed of at least one of the wheels of the vehicle and / or at least a brake pressure of a brake unit on one of the wheels can also be read in as a coefficient of friction in order to determine the coefficient of friction from the speed information and / or the brake pressure. Such an embodiment offers the advantage of being able to implement the approach proposed here with parameters that are usually already recorded in the vehicle. In addition, these parameters can also be recorded or processed very easily from a technical point of view.

The method proposed here can be used particularly efficiently and advantageously if, in the actuation step, the steering device of the vehicle is actuated when the vehicle is accelerating and/or driving up an incline, in particular where in the actuation step the steering device of the vehicle is then not actuated when the vehicle brakes and/or travels on a downhill road. Such an embodiment offers the advantage that these roadway inequalities can be efficiently compensated for, especially in vehicle actions in which driving on road areas with different coefficients of friction is particularly problematic for vehicle safety.

For example, in other areas in which no particular safety-critical relevance occurs given different road characteristics, a corresponding numerical and/or circuitry effort can be avoided.

According to a further embodiment of the approach presented here, in the control step, an output of a larger torque on the wheels can be controlled to that wheel of the wheels which is located on an area of the road that has a higher coefficient of friction. Alternatively or additionally, in the control step, the wheels can be deflected in the direction of that area of the road that has a lower coefficient of friction. Such an embodiment offers the advantage of being able to bring the vehicle into a very safe driving state particularly quickly.

In order to implement the most efficient algorithm possible and to avoid unnecessary effort, according to a further embodiment of the approach proposed here, the steering signal can not be output in the step of determining the vehicle yaw value and/or in the step of driving if it is recognized that the wheels of the Vehicles each move in an area of the road whose coefficients of friction are the same within a tolerance range.

An embodiment of the approach proposed here is also conceivable, in which the compensation steering angle is output in the actuation step if the vehicle yaw value is greater than a predetermined yaw threshold value and/or if the speed value represents a vehicle speed that is greater than a speed threshold value and/or if the compensation steering angle is greater than a compensation angle threshold value. In particular, for example, the steering signal cannot be output in the actuation step if the vehicle yaw value is not greater than a predetermined yaw threshold value and/or if the speed value represents a vehicle speed that is not greater than a speed threshold value and/or if the compensation steering angle is not greater than is a compensation angle threshold value. Such an embodiment offers the advantage of tolerating minor deviations in the vehicle yaw rate, the vehicle speed and/or a corresponding compensation steering angle, without, for example, requiring active intervention through an embodiment of the approach proposed here. In this way, the available numerical or circuit capacity can be used efficiently without possibly only achieving very minor advantages at great expense.

In order to cushion the strongest possible interventions of an assistance function in the driving behavior, which may trigger a frightening behavior of vehicle occupants or significantly reduce the comfort of the vehicle occupants, according to a further embodiment of the approach proposed here, in the reading step, a speed value representing vehicle speeds averaged over several time intervals, a via several time intervals averaged steering angle, with which the steering device controls the vehicle with respect to straight-ahead travel and / or a coefficient of friction averaged over several time intervals, which represent the different coefficients of friction in the areas of the road, are read. Alternatively or additionally, in the step of determining the compensation steering angle can be determined using a control unit, in particular using P, I and/or D control units.

The approach presented here also creates a device that is designed to carry out, control or implement the steps of a variant of a method presented here in corresponding devices. This embodiment variant of the invention in the form of a device can also solve the problem on which the invention is based quickly and efficiently.

Such a device can be an electrical device that processes electrical signals, for example sensor signals, and outputs control signals depending on them. Such a device can be designed as a control device. The device can have one or more suitable interfaces, which can be designed in hardware and/or software. In the case of a hardware design, the interfaces can, for example, be part of an integrated circuit in which functions of the device are implemented. The interfaces can also be their own integrated circuits or at least partially consist of discrete components. In the case of software training, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.

Also advantageous is a computer program product with program code, which can be stored on a machine-readable medium such as a semiconductor memory, a hard drive memory or an optical memory and is used to carry out the method according to one of the embodiments described above if the program is on a computer or a device is performed.

• 1 eine schematische Darstellung eines Fahrzeugs mit einer Vorrichtung gemäß einem Ausführungsbeispiel, wobei das Fahrzeug auf einer Fahrbahn fährt;
• 2 eine Blockdarstellung eines Ausführungsbeispiels einer Vorrichtung gemäß einem Ausführungsbeispiel;
• 3 eine Blockdarstellung zur Erläuterung eines Teils der hier vorgeschlagenen Vorgehensweise zur Ermittlung des Kompensationslenkwinkels unter Verwendung von Raddrehzahlen als Richtgrößen für die Reibwertgröße;
• 4 eine schematische Darstellung zur Erläuterung einer Vorgehensweise zur Ermittlung des Kompensationslenkwinkels;
• 5 ein Blockschaltbild zur Erläuterung einer Vorgehensweise zur Bestimmung der Aktivierung einer Überlagerung des Kompensationswinkelsignals über den Lenkwinkel;
• 6 eine Darstellung zur Erläuterung einer Vorgehensweise, wie ein Steuersignal zur Ansteuerung des Steuereingangs des Schalters bestimmt werden kann; und
• 7 ein Ablaufdiagramm eines Ausführungsbeispiels eines Verfahrens zum Ansteuern einer Lenkvorrichtung eines Fahrzeugs.

The invention is explained in more detail using the accompanying drawings. Show it:

• 1 a schematic representation of a vehicle with a device according to an exemplary embodiment, the vehicle traveling on a road;
• 2 a block diagram of an exemplary embodiment of a device according to an exemplary embodiment;
• 3 a block diagram to explain part of the procedure proposed here for determining the compensation steering angle using wheel speeds as guidelines for the coefficient of friction;
• 4 a schematic representation to explain a procedure for determining the compensation steering angle;
• 5 a block diagram to explain a procedure for determining the activation of a superposition of the compensation angle signal on the steering angle;
• 6 a representation to explain a procedure for determining how a control signal can be determined to control the control input of the switch; and
• 7 a flowchart of an exemplary embodiment of a method for controlling a steering device of a vehicle.

When a vehicle accelerates with a road friction coefficient that deviates from the left and right sides of the vehicle, called a µ-split situation, a vehicle yaw moment arises, which should be compensated for by the driver in order to avoid leaving the lane or a safety-critical driving condition. This compromises security. Likewise, the drive torque on a high-friction side is usually reduced via an active traction control system. This results in delayed or slowed acceleration. This also occurs more frequently when driving off on a slope. It may not be possible to drive off easily here.

In the following description of preferred exemplary embodiments of the present invention, the same or similar reference numbers are used for the elements shown in the various figures and having a similar effect, with a repeated description of these elements being omitted.

1 shows a schematic representation of a vehicle 100 which is traveling on a road 105. The roadway 105 has a first area 110 and a second area 115, which have different coefficients of friction. For example, in the second area 115 the road is icy, so that adhesion between the wheels 117 of the vehicle 100 is not as high as the wheels 117 in the first area 110. Furthermore, in the 1 shown that the vehicle 100 is traveling in the area of a curve 119 of the road 105 at the speed v. In order to be able to control the travel of the vehicle 100 in the curve 119, the wheels 117 of the front axle are, for example, turned to the left with a steering angle 120, so that the vehicle 100 remains on the road 100 when driving through the curve 119 and the direction of travel, Here you can follow curve 119. In the 1 The steering angles 120 are shown exaggerated for reasons of clarity.

If the vehicle 100 were to drive on the roadway 105 in the curve 119 and no compensation for the different coefficients of friction in the areas 110 or 115 of the roadway 105 were provided, this could lead to the different grip behavior of the wheels 117 in the areas 110 or 115 causes the vehicle 100 to go into an uncontrolled yaw motion and possibly skid. In order to avoid this, the following approach is now presented, which on the one hand uses already known vehicle parameters and at the same time also uses actuators that are usually already implemented in modern vehicles 100 and thus enables additional use of these components.

According to an exemplary embodiment of the approach presented here, a device 125 is proposed for controlling a steering device 127 of the vehicle 100, the wheels 117 of which are located on at least one axle, for example the front axle 129 and/or the rear axle 130, on areas 110 and 115 of the roadway 105 move with different coefficients of friction, e.g. roll. The device 125 comprises a reading interface 132, a determination unit 135 and a control unit 137. For reasons of clarity, the steering devices 126, 127 are shown here in simplified form as steering devices for deflecting the wheels 117 of the front axle 129 and the rear axle 130; However, without limiting the generality, this steering device 127 can also be understood as a unit which can alternatively or additionally steer the wheels 117 of the front axle 129 in the desired direction.

For example, a speed value 140 representing a vehicle speed v, the steering angle 120 detected, for example by means of a steering wheel sensor 142, and a coefficient of friction 145 are read into the read-in interface 132. The coefficient of friction can, for example, be divided into several partial variables such as the first partial variable of friction 145a and the second partial variable of friction 145b, for example the first partial variable of friction 145a a speed, a brake pressure on a brake, a current of a motor of the steering and / or another parameter of the wheels 117 represents which move in the area 110 of the road 105 with the higher coefficient of friction. Analogously to this, for example, the second coefficient of friction variable 145b can represent a speed, a brake pressure on a brake, a current of a motor of the steering and/or another parameter of the wheels 117, which move in the area 115 of the road 105 with the lower coefficient of friction. It is also conceivable that a difference is formed in the read-in interface 132 from the first coefficient of friction 145 a and the second coefficient of friction 145 b, from which the difference between the two coefficients of friction in the areas 110 and 115 can be seen, which is necessary for the following Determination of the compensation steering angle can also be used advantageously.

In the read-in interface 132, a vehicle yaw value 147 is now determined, for example using the speed value 140, the steering angle 120 and the coefficient of friction, which describes a yaw behavior or a yaw movement of the vehicle 100 about a vertical axis. However, it is also conceivable that the vehicle yaw value is 147 is determined or read directly by another vehicle unit not described in detail here.

Finally, in the determination unit 135, a compensation steering angle 150 is determined on the basis of the vehicle yaw value 147 in order to effect a reduction in the yaw movement of the vehicle 100. This means that the determination in the determination unit 135 is carried out in such a way that when a deflection of wheels 117 is controlled in accordance with a total steering angle, which is obtained from a superposition or addition of the compensation steering angle 150 with the steering angle 120, a reduction in the yaw of the vehicle 100 is effected. In the control unit 137, the deflection of the wheels 117 of the at least one axle 129, 130 of the vehicle 100 is then carried out or controlled by the steering device 127 using the compensation steering angle 150.

By engaging the steering of the wheels 117 of at least one axle 129, 130 by means of the steering device 127 (see Fig. 1 ), the yaw moment can be compensated for and the vehicle 100 remains in the lane on the road 105 without driver intervention. In addition, through the stabilizing intervention on the rear axle steering, the traction control system can enable more torque to be applied to the wheels on the high friction side and starting off is thereby accelerated, for example.

Below are exemplary embodiments of two alternative algorithms for recognizing a driving situation with acceleration on µ-split, i.e. H. on a road area with different coefficients of friction μ, e.g. per wheel 117 of an axle, as well as two algorithms for calculating an overlay steering angle as the compensation steering angle 150, which compensates for the introduced yaw moment. The solution presented here is designed in such a way that the angle calculated from the µ-split compensation only corresponds to the general rear axle steering angle, i.e. H. is superimposed on the angle that is specified for vehicle guidance, for example by an autonomous vehicle control unit, when the μ-split detection detects a corresponding driving situation that requires automatic intervention to ensure driving safety.

2 shows a block diagram of an exemplary embodiment of a device 125 for controlling a control unit 137 of a vehicle. First, for example, the steering angle 120, the vehicle speed 140 and the coefficient of friction 145 are read in via the read-in interface 132, the coefficient of friction being read in, for example, in several sub-sizes 145a and 145b or as wheel speed or brake pressure of one or more wheels 117. Optionally, the vehicle yaw value 147 or an optional surface friction value and/or a signal can also be read in directly as to whether traction control is active. These values are transmitted from the read-in interface 132 to a unit 200, which corresponds to the representation from the 1 takes over the function of the determination unit 135 and the control unit 137. In this unit 200, the algorithm described in more detail below for calculating the compensation steering angle 150 is then carried out, which can be referred to here above, for example, as the overlay rear axle angle and which can compensate for the movement of the vehicle 100, especially when accelerating on surfaces with different coefficients of friction μ. At the same time, it can also be recognized in the unit 200 or in the determination unit 135 or the control unit 137 that a situation exists in which the coefficients of friction of those areas 110, 115 of the road 105 on which the wheels 117 move are different and whether a decision to activate the control of the steering device 127 using the compensation steering angle 150 is required at all. If it is recognized that activation of the control of the steering device 127 using the compensation steering angle 150 is necessary, an activation or, if necessary, a deactivation of the superimposition of the compensation steering angle 150 on the steering angle 120 can be switched on or off using a switch 210. The switch 210 can be activated via a control input S1. The manner in which the control signal to be applied to the control input S1 can be determined will be explained in more detail below. Furthermore, in a limitation unit 220, a limitation of the size of the compensation steering angle 150 and/or the angular velocity, that is to say the speed of change of the compensation steering angle 150 or the overall angle, can be done, for example by superimposing an increasing proportion of the compensation steering angle 150 on the steering angle 120. This limitation can be carried out, for example, during activation but also during deactivation and during active operation in order to avoid large jumps in the overall steering angle occurring, which in turn could trigger critical driving situations. Finally, the total steering angle 230 determined from this can be obtained by linking or superimposing the compensation steering angle 150 with the steering angle 120, which is provided, for example, by a driver assistance system 232, in a summer 235.

3 shows a block diagram to explain part of an exemplary procedure for determining the compensation steering angle 150 using wheel speeds as reference variables for the coefficient of friction variable 145. Here, the wheel speeds are first read in as coefficients of friction 145a and 145b of the wheels on different vehicle sides of an axle. From this, a calculation of the wheel speed deviation is carried out in a difference speed determination unit 300, which is then output as a corresponding signal 310. At the same time, for example, the speed value 140 and a steering angle 120 are read in, the steering angle 120 now representing, for example, a deflection of the rear wheels of the vehicle. In a model unit 320, a calculation of the expected wheel speed difference in cornering situations is now carried out using a vehicle model with knowledge of the track width of the vehicle. The corresponding expected wheel speeds are then output in a signal 325, each linked to one another and a deviation between the measured and expected wheel speed difference is determined in a comparator unit 330, which is provided via a wheel speed difference signal 335. This wheel speed difference signal 335 is now smoothed using a moving average filter 340 in order to avoid larger jumps in this signal as far as possible, which could also lead to unsafe vehicle situations. This obtained smoothed wheel speed difference signal 335 'is now fed to a control unit 345, which now, for example, regulates a deflection of the wheels to a region with a lower coefficient of friction. This control unit 345 can, for example, have several sub-units that carry out, for example, P, I and/or D control. It is also conceivable that the results of the individual sub-units are finally summed up and thus combined to form the compensation steering angle 150. The control unit 345, which is designed, for example, as a PID control with the aim of regulating the deviation between the expected and measured wheel speed deviation to 0, enables, for example, rear wheel steering, which is intended to deflect the wheels in the direction of the low coefficient of friction side. This allows the vehicle's yaw impulse to be reduced or prevented.

A control function is also conceivable in which a scaling unit 350 is used for the control unit 345 in order to scale the gain of the control with the average coefficient of friction of the road surface. If the coefficient of friction is low, a higher gain is generally desirable.

The Indian 3 The process shown thus corresponds, for example, to an algorithm for calculating a compensation steering angle 150 as an overlay rear axle steering angle which can compensate for the yaw movement of the vehicle, for example when accelerating on surfaces with different coefficients of friction.

4 shows a schematic representation to explain an exemplary procedure for determining the compensation steering angle 150 from coefficients of friction 145a and 145b, which are derived from brake pressures from brakes on the individual wheels 117 as shown 1 be determined. Here, the calculation of the difference in the wheel brake pressures, for example on a driven axle, is first determined in a difference formation unit 400 and output as a corresponding signal 410. This signal 410 can, for example, also be in a moving average filter 340, as already mentioned with reference to 3 was shown, can be filtered in order to obtain a smoothing of the brake pressure deviations. From this, a corresponding smoothed signal 410' is obtained, which then represents the smoothed unexpected wheel speed difference. The smoothed signal 410 'can also be fed to a controller unit 345, which, for example, again corresponds to the explanation 3 is trained.

5 shows a block diagram to explain an exemplary procedure for determining the activation of a superposition of the compensation steering angle signal 150 over the steering angle 120. Essentially, the illustration shows 5 The exemplary procedure explains how the switch 210 is actuated via the control input S1 as shown 2 can be controlled. First, for example, the speed value 140 can be read in and converted into an expected yaw rate 505 of the vehicle in a speed model 500. Furthermore, a measured yaw rate 510 can be read in and linked to the expected yaw rate 505, with a threshold value unit 515 then checking whether the difference between the expected and calculated yaw rates is above a threshold or a further threshold value unit 520 checking whether the Vehicle yaw rate, ie the measured yaw rate 510 is above the threshold. The results of the threshold value units 515 and 520 are then ANDed and deliver a signal 525. Furthermore, a pedal signal 530 can be read in, which characterizes the degree of actuation of a vehicle pedal, whereby this pedal signal 530 can be checked in a further threshold value unit 535 to determine whether the accelerator pedal position is above a deflection threshold. Furthermore, the compensation steering angle 150 can be integrated in an integrator 540 on the one hand and the result in another Threshold value unit 545 can be checked to see whether the integral of the compensation steering angle 150 is above a threshold over a certain predetermined period of time. Finally, a further threshold value unit 550 can also be used to check whether the calculated compensation steering angle 150 itself lies above a threshold. The signal 525 and the results from the further threshold value unit 535, 545 and 550 are then ANDed again, for example, to check whether all conditions are met. However, not all of the signals mentioned above need to be ANDed; it is also conceivable to combine just some of these signals. Through this link, a signal 555 is finally obtained, which outputs an activation signal 565 to the control input S1 using an activation unit 560 in order to close the switch 210 and cause the compensation angle 150 to be superimposed on the steering angle 120.

6 shows an illustration to explain an exemplary further procedure of how the control input S1 of the switch 210 can be controlled. In a first step, a traction control flag signal 600 and the compensation steering angle 150 are read in. In a threshold value unit 610 it can be recognized whether a value of the traction control flag signal 600 is greater than a threshold value and, for example, optional recognition of the driving situation via the traction control system is also possible. The compensation steering angle 150 can be analogous to the illustration in the 5 an integrator 540 and a downstream threshold value unit 545 and in parallel to a further threshold value unit 550. The results from the threshold value units 610, 545 and 550 can then, for example, be ANDed again and fed as a signal 555 to the activation unit 560, which outputs the activation signal 565 to the control input S1.

7 shows a flowchart of an exemplary embodiment of a method 700 for controlling a steering device of a vehicle whose wheels at least one axle move on areas of a roadway, each with a different coefficient of friction. The method 700 includes a step 710 of reading in a vehicle yaw value, which represents a yaw movement of the vehicle about a vertical axis. Furthermore, the method 700 includes a step 720 of determining a compensation steering angle to minimize and/or reduce the yaw motion of the vehicle. Finally, the method 700 includes a step 730 of controlling a deflection of the wheels of the at least one axle of the vehicle by the steering device using the compensation steering angle.

The exemplary embodiments described and shown in the figures are only chosen as examples. Different exemplary embodiments can be combined with one another completely or with regard to individual features. An exemplary embodiment can also be supplemented by features of a further exemplary embodiment.

Furthermore, method steps according to the invention can be repeated and carried out in an order other than that described.

Reference symbols

100

vehicle

105

roadway

110

Area of the road with a high coefficient of friction

115

Area of the road with a low coefficient of friction

117

Wheels

119

Curve

120

Steering angle

125

contraption

126

Steering device

127

Steering device

129

Front axle

130

rear axle

132

Reading interface

135

Determination unit

137

Control unit

140

Speed value

142

Steering wheel sensor

145

Friction value

145a, 145b

Friction value part size

147

Vehicle greed value

150

Compensating steering angle

200

Unit

210

Switch

S1

Control input of switch 210

220

Limiting unit

230

Total steering angle

232

Driver assistance system

235

Summerizer

300

Differential speed determination unit

310

signal

320

Model unit

325

signal

330

Comparator unit

335

Wheel speed difference signal

335'

smoothed wheel speed difference signal

340

moving average filter

345

Regulator unit

350

Scaling unit

400

Difference formation unit

410

signal

410'

smoothed signal

500

Velocity model

505

expected yaw rate

510

measured yaw rate

515

Threshold unit

520

another threshold unit

525

signal

530

Pedal signal

535

another threshold unit

540

Integrator

545

another threshold unit

550

another threshold unit

555

signal

560

Activation unit

565

Activation signal

600

Traction control flag signal

610

Threshold unit

700

Method for controlling a steering device of a vehicle

710

Reading step

720

Step of determining

730

Control step

v

speed

µ

Friction coefficient

Claims (12)

Method (700) for controlling a steering device (127) of a vehicle (100) whose wheels (117) of at least one axle (129, 130) move on areas (110, 115) of a roadway (105) with different coefficients of friction (µ). , wherein the method (700) has the following steps: - reading in (710) a vehicle yaw value (147), which represents a yaw movement of the vehicle (100) about a vertical axis; - Determining (720) a compensation steering angle (150) to minimize and/or reduce the yaw movement of the vehicle (100); and - Controlling (730) a deflection of the wheels (117) of the at least one axle (129, 130) of the vehicle (100) by the steering device (127) using the compensation steering angle (150). Procedure (700) according to Claim 1 , characterized in that in step (710) of reading in, a speed value (140) representing a vehicle speed (v), a steering angle (120) with which the steering device (127) controls the vehicle (100) with respect to straight-ahead travel and a coefficient of friction ( 145, 145a, 145b) are read in, which represent or map the different coefficients of friction (µ) in the areas (110, 115) of the roadway (105), the vehicle yaw value (147) being determined at least using the speed value (140), the steering angle (120) and the coefficient of friction (145, 145a, 145b) is determined. Method (700) according to one of the preceding claims, characterized in that in the step (730) of controlling, a deflection of the wheels (117) of a front and/or rear axle (129, 130) of the vehicle (100) is carried out by the steering device (127 ) is controlled. Method (700) according to one of the preceding claims, characterized in that in the step (710) of reading in, a coefficient of friction (µ) is read in as the coefficient of friction (145, 145a, 145b) of those areas of the road (105) on which the wheels (117) of the vehicle (100) move and / or a difference between two coefficients of friction (µ) of those areas of the road (105) on which the wheels (117) of the vehicle are read in as the coefficient of friction (145, 145a, 145b). (100) move and/or wherein the coefficient of friction (145, 145a, 145b) is at least one speed information about a speed of at least one of the wheels (117) of the vehicle (100) and/or at least one brake pressure of a brake unit on one of the wheels (117 ) is read in to obtain the coefficient of friction (µ) of those areas of the road from the speed information and/or the brake pressure (105) to determine on which the wheels (117) of the vehicle (100) move. Method (700) according to one of the preceding claims, characterized in that in the step (730) of activation, the steering device (127) of the vehicle (100) is activated when the vehicle (100) accelerates and / or drives up an incline, in particular wherein in step (730) of control, the steering device (127) of the vehicle (100) is not controlled when the vehicle (100) brakes and / or drives on a slope. Method (700) according to one of the preceding claims, characterized in that in the step (730) of controlling, an output of a larger torque on the wheels (117) is controlled to that wheel of the wheels (117) which is in an area (110 ) of the roadway (105), which has a higher coefficient of friction and/or wherein in step (730) of the control, the wheels (117) are deflected in the direction of that area (115) of the roadway (105) which has a lower coefficient of friction which has coefficients of friction. Method (700) according to one of the preceding claims, characterized in that in the step (720) of determining the vehicle yaw value (147) and/or in the actuation step, the steering signal is not output if it is recognized that the wheels (117) of the vehicle (100) each move in an area of the road (105) whose coefficients of friction are the same within a tolerance range. Method (700) according to one of the preceding claims, characterized in that in the step (730) of controlling the compensation steering angle (150) is output if the vehicle yaw value (147) is greater than a predetermined yaw threshold value and/or if the speed value (140) represents a vehicle speed (v) that is greater than a speed threshold and / or if the compensation steering angle (150) is greater than a compensation steering angle threshold. Method (700) according to one of the preceding claims, characterized in that in the step (710) of reading in, a speed value (140) representing vehicle speeds averaged over several time intervals, a steering angle (120) averaged over several time intervals, with which the steering device (127) controls the vehicle (100) to drive straight ahead and/or a coefficient of friction (145, 145a, 145b) averaged over several time intervals, which represents the different coefficients of friction in the areas (110, 115) of the roadway (105), is read in and/or wherein in step (720) of determining the compensation steering angle (150) is determined using a controller unit (345), in particular using a P, I and/or D controller unit. Device (125) which is set up to carry out and/or control the steps (710, 720, 730) of the method (700) according to one of the preceding claims in corresponding units (132, 135, 137). Computer program that is set up to carry out the steps (710, 720, 730) of the method (700). Claim 10 to execute and/or control. Machine-readable storage medium on which the computer program can be written Claim 11 is stored.

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