WO2022199991A1

WO2022199991A1 - Method for controlling a vehicle, control device, and vehicle

Info

Publication number: WO2022199991A1
Application number: PCT/EP2022/055117
Authority: WO
Inventors: Benjamin Bieber; Thomas Dieckmann; Klaus PLÄHN; Janik RICKE
Original assignee: Zf Cv Systems Global Gmbh
Priority date: 2021-03-22
Filing date: 2022-03-01
Publication date: 2022-09-29
Also published as: DE102021106978A1

Abstract

The invention relates to a method for controlling a vehicle (2) having one steered and one unsteered vehicle axle (6, 7) and a steering device (4) for steering the vehicle (2) at a predetermined target steering angle, wherein upon establishing that the steering forces (Fl) which are and/or can be applied by the steering device (4) are not sufficient to steer the vehicle (2) at the target steering angle via the steered vehicle axle (6), at least the following steps are carried out: - executing an emergency steering function by setting a brake torque difference at the steered vehicle axle (6), wherein setting the brake torque difference causes the steered wheels to turn in such a way that the vehicle (2) is steered, resulting in a steering brake deceleration; - executing a compensation function by setting compensation torques at least at the unsteered wheels (7l, 7r), wherein the compensation torques result in a compensation acceleration. According to the invention, the steering brake torques and the compensation torques are set in such a way that the resulting compensation acceleration compensates for the steering brake deceleration, so that the vehicle (2) is steered at the target steering angle and a current acceleration simultaneously approaches a predetermined target acceleration and/or the predetermined target acceleration is maintained.

Description

Method for controlling a vehicle, control device and vehicle

The present invention relates to a method for controlling a driving tool, in particular a road vehicle, when steering forces are not or are insufficiently applied or can be applied to a steering device. Furthermore, the present invention relates to a control device designed to carry out the method and a vehicle with such a control device.

In the following, the control of a vehicle is understood to mean, on the one hand, the steering of a vehicle, through which the direction of movement of the vehicle can be influenced. The direction of movement of the vehicle is usually influenced by changing a PRE-defined target steering angle by means of a steering device of the vehicle, for example by actively turning one or more wheels of the vehicle.

On the other hand, controlling a vehicle also means influencing the speed of the vehicle. This is usually done by braking or accelerating the vehicle, i.e. changing a specified target acceleration, for example by braking or driving individual wheels of the vehicle or by applying positive torques via a drive or negative torques (braking torques) to the respective wheels wheels over brakes.

Safe and reliable control is an essential safety component for the safety of road users and the vehicle itself. It is true that modern steering devices allow vehicles to be steered easily and conveniently, or even automatically or automatically, for example with the aid of power assistance using electrical, Hydraulic or pneumatic servo actuators or purely electrically controlled steering actuators, so-called steer-by-wire systems, but these modern steering devices are complex and therefore associated with a risk of failure. For example, the failure of the on-board electronics, the hydraulic pumps or the compressor can lead to severe or complete impairment of the steering and thus the control of the vehicle. On the other hand, even the simplest, directly mechanical steering devices with steering rods or cable pulls can have defects.

Such defects or impairments of the steering device can overwhelm the driver while driving. It is particularly problematic if the driver applies the brakes of the vehicle strongly as a reflex when recognizing the defect or the impairment. This knee-jerk braking can possibly result in an unintended reaction from the vehicle, such as skidding.

In addition, it can happen that a vehicle cannot be steered manually or automatically using the steering device due to poor road surface properties, or can only be steered with difficulty, for example because it has sunk in or is moving on such a surface that the steering forces that can be applied by the steering device are not sufficient for steering is sufficient, in particular a predetermined target steering angle cannot be reached.

In order to react to an impairment or a defect in the steering device, a vehicle with an emergency steering function is known from the prior art, in particular DE 102016223 766 A1 Steering of the vehicle with the target steering angle is still possible. To do this, the vehicle is steered by applying a braking torque difference to the steered wheels of a steered vehicle axle. directs. In DE 102016223766 A1, the vehicle is simultaneously braked to a standstill by applying the braking torque difference. The disadvantage, therefore, is that with such an emergency steering function, the vehicle may come to a standstill in a position that is not safe, for example on a freeway.

Against this background, the invention is based on the object of further improving the safety and reliability of methods for controlling a vehicle when steering forces on a steering device are not applied or can be applied insufficiently or not at all.

According to the invention, a method for controlling a vehicle is therefore provided, the vehicle having at least:

- a steered vehicle axle with at least one left steered wheel and one right steered wheel,

- an unsteered vehicle axle with unsteered wheels, and

- A steering device, wherein the steering device is designed to act with a steering force on the steered wheels of the steered vehicle axle in such a way that the steered wheels of the steered vehicle axle turn in order to steer the vehicle with a predetermined target steering angle, wherein when it is detected that the steering forces applied and/or which can be applied by the steering device are not sufficient to steer the vehicle via the steered vehicle axle with the target steering angle, at least the following steps are carried out:

- Carrying out an emergency steering function by setting a braking torque difference between a first steering braking torque on the left steered wheel and a second steering braking torque on the right steered wheel, with the setting of the braking torque difference causing the steered wheels of the steered vehicle axle to turn in such a way, that this vehicle is steered and steering brake deceleration of the vehicle is effected;

- Carrying out a compensating function by setting compensating torques on at least the unsteered wheels of the unsteered vehicle axle, with the compensating torques causing a compensating acceleration of the vehicle, with the steering braking torques and the compensating torques being set or superimposed in this way that the compensating acceleration caused by the compensating function compensates for the steering brake deceleration caused by the emergency steering function, so that the vehicle is steered with the target steering angle and at the same time an actual acceleration of the vehicle is approximated to a predetermined target acceleration and/ or the specified target acceleration is maintained.

According to the invention, a control device is also provided, designed to carry out the method according to the invention, and a corresponding vehicle with such a control device.

Advantageously, the method also allows the vehicle to continue driving in a controlled manner with a specified target acceleration and a specified target steering angle while the emergency steering function is being carried out. The changes in the longitudinal dynamics of the vehicle, which result from the setting of the braking torque difference, are advantageously compensated for by the superimposed or parallel compensation function, so that the vehicle ideally continues to be controlled without a noticeable change in driving dynamics, ie both steered and (positively or negatively) accelerated or can continue driving without acceleration. The steering braking torques and balancing torques (positive or negative or zero) can be coordinated with one another and superimposed accordingly in order to achieve this. The vehicle is usually a road vehicle, in particular a commercial vehicle. The steered vehicle axle corresponds, for example, to the front axle of the vehicle, but another axle of the vehicle can also be steered (actively or passively) and a braking torque difference can also be built up on this vehicle axle in order to carry out the emergency steering function. The steered wheels of the steered vehicle axle can be arranged on a steerable rigid axle or an independent wheel suspension can be provided, via which a side-specific braking of the steered wheels with a corre sponding steering braking torque is made possible. This can be achieved, for example, by activating brake components, disc brakes or drum brakes on the respective steered wheels individually for each side.

The vehicle can normally also be driven via the non-steered wheels of the non-steered vehicle axle or at least one of the non-steered vehicle axles, preferably one of the flinter axles of the vehicle. Usually, the unsteered wheels are connected to each other via an axle and to a drive unit by means of a differential in order to enable positive balancing torques to be built up at these wheels.

In the simplest form, a steering device is understood to mean, for example, a steering wheel with a steering column and a mechanical steering system in the form of steering rods or cables directly coupled to it. However, the steering device can also include electrical, hydraulic or pneumatic tables servo actuators, steer-by-wire components and additional control electronics. In general, the steering device includes components which, in regular operation, allow the steering angle of the vehicle to be influenced and controlled as desired. This influencing and control of the vehicle takes place by specifying a desired steering angle by the steered wheels being turned accordingly by the steering device, for which purpose steering forces have to be applied by the steering device. These steering forces are applied, for example, by a human driver by turning the steering wheel and, after possible reinforcement, are transmitted to the steered wheels by electrically, hydraulically or pneumatically controllable servo actuators or a mechanical transmission, which are then turned accordingly. In the case of an autonomous vehicle, for example, a control computer specifies a target steering angle and, in order to achieve the target steering angle, issues a steering command to the servo actuators in order to turn the steered wheels with the appropriate steering forces.

If the steering forces applied and/or which can be applied by the steering device are not sufficient to set the autonomously or manually specified setpoint steering angle on the steered wheels of the steered vehicle axle, the emergency steering and compensation functions according to the invention are carried out. For example, the steering forces may not be sufficient if individual components of the steering device are defective or impaired, so that sufficient steering forces cannot be transmitted to the steered wheels. These defects can be caused, for example, by leaking hydraulic or pneumatic components, defective electrical components or mechanical breaks. Even if the steering device is fully functional, a poor road surface can, for example, require very high steering forces to swivel or turn the steered wheels, so that the maximum steering forces that can be applied by the steering device may not be sufficient to steer the vehicle with a specified target steering angle . The vehicle remains controlled by the method according to the invention in all of these cases controllable, in particular steerable according to a predetermined target steering angle, since this can be achieved by adjusting the braking torque difference. This increases the general traffic safety and the safety of the vehicle itself, since the vehicle can continue to be controlled, in particular remains steerable.

In order to determine whether or not the steering forces applied and/or which can be applied by the steering device are sufficient to achieve a target steering angle, torque monitoring on the steering column of the steering device, for example on a torsion bar, or performance parameter monitoring of electrical, hydraulically or pneumatically controllable servo actuators of the steering device possible.

If, for example, a maximum torsion bar torque is exceeded on the torsion bar for transferring the steering force from the steering wheel to the steered wheels, or if a maximum performance parameter such as a control current or a control pressure on the electrically, hydraulically or pneumatically controllable servo actuators of the steering device is exceeded, then in it can be concluded in a simple manner that the predetermined target steering angle cannot be reached by means of the steering device and that an emergency steering function must therefore be carried out in order to steer the vehicle accordingly. Alternatively or in addition, it can also be checked whether or not the actual steering angle has reached the target steering angle during operation of the steering device and/or whether the steering device is outputting a status signal from which the functionality of the steering device can be inferred. Therefore, with simple means that are already present in the vehicle, such a monitoring of the functionality of the steering device can be achieved.

The steering braking torques on the steered wheels are preferably achieved by means of brakes on the individual steered wheels that can be controlled individually for each side. A steered wheel, for example As the left steered wheel unbraked, while the other, in the example the right steered wheel, is braked. The first steering braking torque or the second steering braking torque is zero and the respective other steering braking torque is negative while the braking torque difference is being adjusted. As a result, the braking torque difference between the right-hand steered wheel and the left-hand steered wheel required for the emergency steering function is generated, with the steering brake deceleration resulting from the emergency steering function being minimized at the same time. Due to the difference in braking torque, the steered wheels pivot or turn or turn, on the one hand, to the extent that a predetermined target steering angle is ideally achieved. On the other hand, the braking of an individual steered wheels also results in the steering brake deceleration, which causes negative acceleration, i.e. braking of the vehicle. In particular, when a nominal vehicle acceleration of zero or greater than zero is specified, the lowest possible steering brake deceleration is desirable, since compensation for the steering brake deceleration through the compensating acceleration requires only low compensating torques on the unsteered vehicle axle. A unilateral setting of a steering braking torque of zero to achieve the braking torque difference is therefore particularly advantageous for this reason.

Since the braking of the vehicle due to the steering brake deceleration is not wanted under certain circumstances, since the vehicle is to be transported to the next parking space, for example, in a minimal-risk maneuver, a compensation function is carried out. For this purpose, compensatory torques are generated on at least the non-steered wheels of the non-steered vehicle axle, so that a predetermined target acceleration of the vehicle is achieved as far as possible. The vehicle can be influenced longitudinally dynamically in a variety of ways, with the compensating torques on at least the non-steered wheels of the non-steered vehicle axle being able to be positive in order to set a positive compensating Acceleration (driving) and can be negative to set negative compensation acceleration (braking).

The target acceleration is specified, for example, by the human driver, a cruise control or a control computer of an autonomous vehicle. If the target acceleration is zero, i.e. the vehicle should continue to drive at the same speed, a compensating torque is generated at least on the unsteered wheels of the unsteered vehicle axle by driving the unsteered wheels, so that the compensatory acceleration resulting from the compensating torques of the magnitude and direction of the steering brake deceleration from the emergency steering function is in the opposite direction, i.e. it is compensated. In this way, an actual acceleration of zero acts, which results from the sum or superimposition of all accelerations, ie the steering brake deceleration (negative acceleration) and the positive compensatory acceleration in this case. For the example, the actual acceleration therefore also corresponds to the target acceleration.

If, for example, the target acceleration is positive, i.e. the vehicle should accelerate, the compensating torques are chosen to be positive (drive) in such a way that the magnitude and direction of the compensating acceleration are greater and act in the opposite direction to the steering brake deceleration due to the emergency steering function carried out .

For example, if the target acceleration is negative, i.e. the vehicle is to brake, the compensating torques are selected in such a way that the amount and direction of the compensating acceleration is smaller and opposite to the steering brake deceleration (slightly driving) or in the direction of the Steering brake delay (braking) act. The compensating acceleration can therefore be positive or negative, depending on the extent of the steering brake deceleration, in order to enable a negative setpoint acceleration. If the actual acceleration and the target acceleration deviate from one another, the compensation acceleration is adjusted accordingly in order to bring them closer together again. If the actual acceleration and the target acceleration cannot be brought into agreement, for example because a specified target acceleration cannot be achieved with the drive power available, the deviation between the actual acceleration and the target acceleration is at least mi nimated. In addition, a decision can be made as to whether the emergency steering function is to be suppressed or canceled entirely, for example in the event of emergency braking.

In a further embodiment of the method, the at least one non-steered vehicle axle is arranged on a towing vehicle of the vehicle, for example as a flinter axle, and/or as a trailer axle on a trailer of the vehicle.

This makes it possible to carry out the compensating function carried out on the at least one non-steered vehicle axle on several axles of the vehicle. The wheels of the trailer axle can also be used for braking, particularly in the case of a negative compensating acceleration, so that higher negative compensating accelerations or actual accelerations can be achieved, which in turn leads to shorter braking distances and a resulting increase in road safety and controllability of the vehicle.

In a further embodiment of the method, the emergency steering function is carried out exclusively by adjusting the braking torque difference on the articulated vehicle axle. This means that the same amount and direction of balancing torques are set on the left and right wheels of the non-steered vehicle axles, so that there is no difference in braking torque on the non-steered vehicle axles. stands. This makes it easier to carry out the emergency steering function, since only two steering braking torques have to be set and contribute to steering the vehicle at the setpoint steering angle. In addition, the driving dynamics and driving stability of the vehicle are easier to control.

In a further embodiment of the method, the compensation function is carried out exclusively by setting compensation torques on the non-steered vehicle axle. This also makes a significant contribution to simplifying the implementation of the compensation function, since only the compensation torques of the non-steered wheels have to be set in such a way that a corresponding compensation acceleration results.

In an alternative embodiment, the compensating function can be performed by additionally setting compensating torques, in particular negative compensating torques, on the steered wheels of the steered vehicle axle by superimposing the compensating torques on the steering-braking torques on the steered wheels while maintaining the braking torque difference will.

This enables a particularly high negative actual acceleration, as is required, for example, in the case of emergency braking, that is to say a high negative setpoint acceleration. In addition, a more uniform exploitation of the adhesion can be achieved due to the use of a large number of wheels of the vehicle to generate the compensating torques, which are negative in this case. The resulting negative actual acceleration shortens the braking distance and thus increases traffic safety, especially in the event of emergency braking.

In a further embodiment of the method, a temperature of the brake components is monitored and the vehicle is brought to a standstill. brought if the monitored temperature exceeds a limit temperature.

While the emergency steering function is being carried out, the brake components of the steered vehicle axle in particular are heavily loaded, since these brake components are actuated and used accordingly to generate a steering braking torque or to adjust the braking torque difference. In the event that the vehicle is not brought to a standstill directly after determining that the steering forces applied and/or which can be applied by the steering device are not sufficient to set a target steering angle by the steering device, but continues to drive to generate different steering braking torques, the brake components are heavily and continuously stressed.

Due to this heavy and constant stress, in the worst case, these brake components can fail due to overheating, which means that parts of the safety-relevant brake system of the vehicle are defective on the one hand, and on the other hand the vehicle can no longer be steered because the target steering angle is exceeded the actual steering device can no longer be adjusted.

Temperature monitoring prevents the brake components from overheating by stopping the vehicle before the brake components overheat. The limit temperature is selected such that after the limit temperature has been exceeded by the temperatures present at the brake components, the brake components can still be used to brake the vehicle until it comes to a standstill without overheating and causing consequential damage. Preferably, the human driver or a control computer of an autonomous vehicle cannot influence this braking if the limit temperature is exceeded by the temperatures present at the brake components, so that emergency braking is carried out.

The invention is explained in more detail below with reference to the accompanying drawings of some embodiments. Show it:

Fig. 1 is a schematic plan view of a vehicle in regular ferry operation,

FIG. 2 shows the vehicle according to FIG. 1 during the implementation of an embodiment of the method according to the invention,

3 shows the vehicle according to FIG. 1 while a further embodiment of the method according to the invention is being carried out,

4 shows the vehicle according to FIG. 1 while a further embodiment of the method according to the invention is being carried out,

5a, 5b, 5c an overview of the accelerations acting in FIGS. 2, 3, 4,

6, 7 flow charts of an embodiment of the method according to the invention.

FIG. 1 shows a schematic plan view of a vehicle 2, which consists of a towing vehicle 3 and a trailer 8, with the trailer 8 being designed as a semi-trailer. The towing vehicle 3 has a steered or steerable vehicle axle 6 with a left steered wheel 6I and a right steered wheel 6r, which are actively steered in the present case or steerable front axle VA is formed. Brake components 12a, 12b are attached to the steered wheels 6I, 6r of the steered front axle VA, which are designed, for example, in the form of disc brakes or drum brakes.

The steering takes place in regular ferry operation via a steering device 4, which is shown schematically as a steering wheel and steering linkage in FIG. These are representative of a large number of possible steering devices 4, for example cables, mechanical coupling elements, electrical and/or hydraulic and/or pneumatic actuators and control means. In regular ferry operation, the steering forces Fl applied and/or which can be applied by the steering device 4 are sufficient to turn the steered wheels 6I, 6r of the steered front axle VA in such a way that the vehicle 2 is at a predetermined target steering angle Ls relative to a longitudinal axis 5 of the Vehicle 2 is steered. The steering device 4 is operated manually by a human driver or autonomously, for example controlled by a control computer.

Furthermore, the towing vehicle 3 has an unsteered or unsteerable vehicle axle 7 with a left unsteered wheel 7I and a right unsteered wheel 7r, which in the present case is the unsteered rear axle HA.

The non-steered vehicle axle 7 or rear axle HA is usually the drive axle of the vehicle 2, although in principle the articulated vehicle axle 6 can also have a drive. In addition to the non-steered rear axle HA shown, the towing vehicle 3 can also have at least one further non-steered vehicle axle 7 or rear axle HA.

The trailer 8 designed as a semi-trailer has a trailer axle 9 with a left wheel 9I and a right wheel 9r, which in the present case is basically non-steered but can also be (passively) steered. There are multi-axle trailers 8 are also conceivable, with the multiple trailer axles 9 (passively) being steered and/or unsteered.

FIG. 2 shows the vehicle 2 according to FIG. 1 in a driving situation in which the method according to the invention is carried out, which is shown as an example in FIG.

In a first step ST1, after the initialization of the system, it is first determined whether the steering forces Fl applied and/or which can be applied by the steering device 4 are sufficient to set a manually or autonomously specified target steering angle Ls by the steering device 4 or to turn the vehicle 2 to steer with the target steering angle Ls. In the case shown in FIG. 2, it is assumed that the steering forces F1 applied and/or capable of being applied by the steering device 4 are not sufficient to set a predetermined setpoint steering angle Ls. This can be due, for example, to the fact that the steering device 4 has a defect, the ground on which the vehicle 2 is moving does not permit or makes steering difficult, or a combination of these is present.

The determination in the first step ST1 can be done, for example, by evaluating feedback from mechanical, electrical, pneumatic, and/or hydraulic components of the steering device 4, which can be done, for example, using mechanical, electrical, pneumatic, and/or hydraulic parameters that are monitored . For example, torque monitoring can be provided on the steering column of the steering device 4, for example on a torsion bar 4a, or performance parameter monitoring of electrical, hydraulic or pneumatic servo actuators 4b of the steering device 4. If, for example, a maximum torsion bar torque DTMax is measured on the torsion bar 4a for transferring the steering force Fl from the steering wheel to the steered wheels 6I, 6r is exceeded or is a maximum performance parameter ter LMax such as a maximum control current or a maximum control pressure for electric, hydraulic or pneumatic servo actuators 4b of the steering device 4 is exceeded, it can be concluded that the specified target steering angle Ls cannot be reached by means of the steering device 4 and therefore an emergency steering function 23 is to be carried out in order to steer the vehicle 2 accordingly.

However, status signals S normally output by the steering device 4 can also be monitored. An alternative or additional type of determination can be monitoring of the target steering angle Ls, for example a comparison between a currently existing actual steering angle Li and the specified target steering angle Ls. In the event that the comparison shows a clear discrepancy between the actual steering angle Li and the target steering angle Ls, it can be concluded that the steering forces Fl applied and/or which can be applied by the steering device 4 are not sufficient to achieve the specified target -Adjust steering angle Ls. The comparison can be done, for example, using sensors that measure the actual steering angle Li and which are part of electronic driver assistance systems in the vehicle 2, for example.

In the event that the steering forces Fl applied and/or which can be applied are sufficient to steer the vehicle 2 accordingly with the target steering angle Ls (y, see FIG. 6), regular ferry operation takes place with steering only via the steering device 4. In the event that the steering forces Fl applied and/or which can be applied are not sufficient to steer the vehicle 2 as specified with the target steering angle Ls (n, see FIG. 6), more follow according to FIG Steps:

Due to the determination that the raised by the steering device 4 th and / or steering forces Fl not sufficient (n), an emergency steering function 23 is performed in a second step ST2, which by a Control device 10 is monitored and executed in order to be able to continue to control the vehicle 2 at least in a minimal risk maneuver as manually or autonomously requested.

For this purpose, in the second step ST2, by wheel-specific braking, at least one of the steered wheels 6I, 6r of the steered vehicle axle 6 or front axle VA generates different steering braking torques MI1, MI2 for each side. At the steered front axle VA there is thus a braking torque difference dM from a first steering braking torque MI1 at the left steered wheel 6I and a second steering braking torque MI2 at the right steered wheel 6r of the steered front axle VA. This braking torque difference dM leads to turning of the steered wheels 6I, 6r of the steered front axle VA due to a normally present negative scrub radius (steering roll radius) and thus to steering of the vehicle 2 depending on the set braking torque dM.

In the context of the method according to the invention, this is used and the braking torque difference dM is specifically adjusted in such a way that the vehicle 2 is steered with the specified setpoint steering angle Ls even despite the defective or impaired steering device 4 . A missing differential steering angle Ld due to the defect or the impairment of the steering device 4 is thus compensated for by applying the braking torque difference dM, i.e. the braking torque difference dM is selected as a function of the missing differential steering angle Ld, e.g. from Ld=Ls-Li.

The steering braking torques MI1, MI2 for setting the braking torque difference dM on the steered front axle VA are set in the embodiment shown in Figure 2 in such a way that only the left-hand steered wheel 6I of the steered front axle VA is braked according to a first steering braking torque MI1 becomes and the right steered wheel 6r of the steered front axle VA remains unbraked, corresponding to a second steering braking torque MI2 of "zero". In principle, however, both steered wheels 6r, 6l of the steered front axle VA can also be braked in order to set the braking torque difference dM, since only the difference in braking torques MI1, MI2 is decisive for the emergency steering function 23. With the same effect, the braking torque difference dM could also be set with a corresponding design of the vehicle 2 by driving a steered wheel 6I, 6r of the steered front axle VA and decelerating a steered wheel 6r, 6I of the steered front axle VA.

The forces on the respective steered wheels 6r, 6l of the steered front axle VA resulting from the laterally different steering braking torques MI1, MI2 are shown in FIG. Since the force on the right-hand steered wheel 6r of the steered front axle VA that follows from the second steering-braking torque MI2 is “zero”, it is only shown as a point. The forces acting on the respective steered wheels 6r, 6I of the steered front axle VA due to the steering braking torques MI1, MI2 are directly proportional to the applied steering braking torques MI1, MI2, so that the force difference is also proportional to the braking torque difference dM.

Since the left-hand steered wheel 6I of the steered front axle VA due to the heavier braking exerts a greater backward-directed force (braking force) than the right-hand steered wheel 6r of the steered front axle VA, on which no force acts, the vehicle 2 in the exemplary embodiment shown makes a left turn , since the steered wheels 6I, 6r of the steered front axle VA are turned in accordingly by the present braking torque difference dM. In the driving situation in FIG. 3, the respective other steered wheel 6r, 6l of the steered front axle VA is braked or unbraked, which corresponds to a reversed steering angle or a right turn. Depending on the existing impairment of the steering device 4, steering with the target steering angle Ls in the respective direction can be achieved with the braking torque difference dM set in each case.

In addition, the braking force resulting from the respective steering braking torque MI1, MI2 on the respective steered wheel 6I, 6r of the steered front axle VA also has a braking effect on the vehicle 2, which is caused by an emergency steering deceleration ZL (corresponding to a negative acceleration ) can be characterized. If the emergency steering function 23 were to be carried out alone, an actual acceleration AI of the vehicle 2 would no longer always correspond to a predetermined target acceleration AS.

In order to avoid an unwanted impairment of the longitudinal dynamics of the vehicle 2 (deceleration or acceleration) by the emergency steering function 23 during a minimum-risk maneuver with an impaired steering device 4, a compensation function 24 is carried out in addition to the emergency steering function 23 in a third step ST3. through which this emergency steering delay ZL is balanced or compensated. A steering implemented by the emergency steering function 23 thus ideally remains unnoticed by the driver, since the braking effected at the same time is compensated for by the compensation. The actual acceleration AI thus approaches the target acceleration AS again through the compensation function 24 or the target acceleration AS is maintained depending on the response behavior.

For this purpose, the emergency steering deceleration ZL (emergency steering function 23) is superimposed in the third step ST3 on the vehicle 2 by a specific compensating acceleration AA without changing the braking torque difference dM that is present in each case. The compensating acceleration AA is chosen such that the sum of the emergency steering deceleration ZL (corresponds to a negative acceleration) and the compensating acceleration AA for the current one Driving situation specified target acceleration AS corresponds or is approximated. The compensation acceleration AA can be positive (drive), negative (decelerate) or zero. The vehicle 2 can thus continue to drive, be braked (AS=AI<0) or even accelerate (AS=AI>0) while an emergency steering function 23 is being carried out at a constant speed (AS=AI=0).

In the exemplary embodiment in Figure 2, the setpoint acceleration AS is negative, for example, i.e. the vehicle 2 is to be decelerated in the current driving situation in which the emergency steering function 23 is also being carried out. A negative compensating torque Ma3, Ma4 (braking torque) is applied to the unsteered wheels 71, 7r of the unsteered flinter axle FIA, these being identical for each wheel in the present case, which is indicated qualitatively by the force arrows in FIG. In addition, a negative compensating torque Ma5, Ma6 (braking torque) can also be set on the wheels 91, 9r of the trailer axle 9.

The deceleration (and the steering) of the vehicle 2 is achieved in the driving situation shown by laterally different braking forces on the steered wheels 61, 6r of the steered front axle VA, which are ten-wise identical braking forces on the non-steered wheels 7r, 71 of the non-steered rear axle HA and possibly superimposed on the wheels 9r, 91 of the trailer axle 9. The balancing torques Ma3, Ma4 (wheels 71, 7r of the rear axle HA), Ma5, Ma6 (wheels 91, 9r of the trailer axle 9) are accordingly set in such a way that the actual acceleration AI due to the negative compensation acceleration AA caused when the emergency steering deceleration ZL is superimposed, it approaches the specified target acceleration AS or the specified target acceleration AS is maintained. If the negative compensation acceleration AA caused by the compensation torques Ma3, Ma4 (wheels 7I, 7r of the rear axle HA), Ma5, Ma6 (wheels 9I, 9r of the trailer axle 9) on the available unsteered vehicle axles 7, 9 is not sufficient To decelerate the vehicle 2 according to the target acceleration AS together with the emergency steering delay ZL, for example in the event of emergency braking, the steering braking torques MI1, MI2 on the steered wheels 6I, 6r of the steered front axle VA can be reduced Maintaining the braking torque difference dM, additional compensating torques Mal, Ma2 on the steered wheels 61, 6r are superimposed symmetrically (causing no steering) (see FIG. 4, trailer 8 not shown). As a result, the actual acceleration AI is again approximated to the specified setpoint acceleration AS, for example in the event of an emergency braking.

Depending on the specified target acceleration AS, the emergency steering deceleration ZL can also have a positive compensating acceleration AA superimposed, as shown in FIG. 3 (tag 8 not shown), or a compensating acceleration AA of zero. This is the case in particular when the emergency steering deceleration ZL decelerates the vehicle 2 more or just as much as specified by the setpoint acceleration AS. Under these circumstances, the unsteered wheels 7r, 71 of the unsteered rear axle HA, which can be driven via a drive 11, are to be driven with a corresponding positive compensation torque Ma3, Ma4 or operated in a freely rolling manner in order to bring the actual acceleration AI to the target - Approach or maintain acceleration AS. In addition, other driven wheels, e.g. on other vehicle axles or on the trailer axle or axles 9, can also be included with the same effect.

Thus, by appropriately superimposing emergency steering function 23 and compensating function 24 in a fourth step ST4, the target steering angle Ls and also the setpoint acceleration AS, which can be positive, zero or negative, can be maintained or set in the corresponding driving situation (minimal risk maneuver) without the driver noticing a restriction.

5a, 5b, 5c shows an overview of the accelerations AS, AA, ZL acting in FIGS. Ma2, Ma3, Ma4, Ma5, Ma6 result. The arrows qualitatively represent the directions and magnitudes of the respective accelerations AS, AA, ZL, with the steering brake deceleration ZL corresponding to a corresponding negative acceleration.

In the exemplary embodiment from FIG. 2, the specified negative desired acceleration AS is shown in FIG. The steering brake deceleration ZL, which is caused by the steering braking torques MI1 and MI2 on the steered front axle VA, is added or superimposed on the compensation acceleration AA, which is caused by the negative compensation torques Ma3, Ma4 on the unsteered flinter axle FIA of the towing vehicle 3 are caused, and the compensating acceleration AA, which are caused by the negative compensating torques Ma5, Ma6 on the trailer axle 9 of the trailer 8, so that the actual acceleration AI ideally corresponds to the target acceleration AS .

In the exemplary embodiment from FIG. 3, the specified target acceleration AS is shown as a point in FIG. 5b, ie it is “zero”. This means that the vehicle 2 should continue to drive at an unchanged speed while the emergency steering function 23 is being carried out. In order to achieve this, the steering braking torque MI1 on the steered front axle VA, Compensate MI2 generated steering brake deceleration ZL by on the rear axle HA of the towing vehicle 3 by positive compensation torques Ma3, Ma4 a correspondingly oppositely aligned positive compensation acceleration AA is effected. The compensating acceleration AA generated at the rear axle HA is selected in such a way that the setpoint acceleration AS=0(=AI) is achieved.

In the exemplary embodiment from FIG. 4, the specified setpoint acceleration AS in FIG. 5c is shown in the opposite direction to the direction of travel, similar to that in FIG. In the present case, however, the target acceleration AS is so negative (heavy braking, e.g. emergency braking) that a compensating acceleration AA must be generated both by the rear axle HA and by the front axle VA in order to be able to achieve the target acceleration AS at all. On the steered wheels 61, 6r of the front axle VA, a compensating torque Mal, Ma2, which contributes to the compensating acceleration AA, is superimposed in addition to the steering braking torques MI1, MI2 that cause the steering brake deceleration ZL. The superimposition takes place in such a way that the braking torque difference dM on the steered front axle VA is maintained. The steering brake deceleration ZL generated on the front axle VA and the compensation acceleration AA (Mal, Ma2, Ma3, Ma4) generated on the front axle VA and on the rear axle HA add up or are superimposed in such a way that the heavy braking with the high negative target acceleration AS is reached, i.e. AI ~ AS. In addition, equalizing torques Ma5, Ma6 can also act on a trailer axle 9 in this exemplary embodiment if a trailer 8 is present.

In the illustrated embodiments, it is always possible to reach setpoint acceleration AS or to approach actual acceleration AI thereto. However, it is also conceivable that the target acceleration AS des Vehicle 2 is specified so that it is not possible to achieve a compensation acceleration AA by a corresponding setting of the compensation torques Mal, Ma2, Ma3, Ma4, Ma5, Ma6, which when superimposed with the steering brake deceleration ZL or the steering braking torques MI1, MI2 leads to the specified setpoint acceleration AS, ie AI=/=AS. In this case, a situational decision can be made as to whether emergency steering or braking is given higher priority and emergency steering function 23 is reduced or suspended, if necessary, in order to achieve target acceleration AS in any case, for example in the event of emergency braking.

FIG. 7 shows an extension of the method according to the invention shown in FIG. 6 with additional temperature monitoring:

The continuous implementation of the emergency steering function 23 puts a particularly heavy load on the brake components 12a, 12b (e.g. brake disks) on the steered front axle VA of the vehicle 2, since the vehicle 2 is not necessarily brought to a standstill immediately if the steering device 4 fails at least partially continues driving in a minimal-risk maneuver, for example to reach a parking space or the next exit. In the case of continuous braking due to the emergency steering function 23 being carried out continuously, the brake components 12a, 12b can heat up or overheat considerably, so that safe and reliable ferry operation can no longer be guaranteed. Therefore, in a supplementary monitoring step STÜ, temperature monitoring of the brake components 12a, 12b is provided.

Temperatures Ta, Tb of brake components 12a, 12b of front axle VA are compared with a predefined limit temperature Tg, for example in control device 10. Temperatures Ta, Tb of brake components 12a, 12b can be measured, for example, using temperature sensors, with the values of the temperature measurement to the Control device 10 are transmitted. There, a comparison with the limit temperature Tg takes place. If the limit temperature Tg is exceeded, the vehicle 2 is immediately brought to a standstill, in particular without the driver or the control device 10 being able to prevent this. Emergency braking is therefore carried out, since in particular controlled steering via the brake components 12a, 12b on the front axle VA can no longer be ensured.

The monitoring step STÜ can, for example, precede the third step ST3, the implementation of the equalization function 24, or run parallel thereto. The monitoring step STÜ restricts the choice of setpoint acceleration AS, which is otherwise free for the human driver or the autonomous control computer, as follows:

Thus, the left-hand branch shown in the monitoring step STÜ in Fig. 7 can still be freely selected, i.e. positive (+) if the temperatures Ta and Tb of the brake components 12a, 12b do not yet exceed the limit temperature Tg. , negative (-), or zero (0). Here, the vehicle 2 can continue driving as required in a minimal-risk maneuver.

In the event that the temperatures Ta, Tb of the brake components 12a, 12b exceed the limit temperature Tg, ie one or both of the brake components 12a, 12b are overheated, according to the right-hand branch of the monitoring step STÜ in FIG. Acceleration AS fixed negative. Flierby the vehicle 2 is inevitably brought to a standstill.

It is also possible for the braking components on the non-steered vehicle axles 7 (HA), 9 of the vehicle 2 to be subjected to temperature monitoring in the monitoring step STÜ. List of reference symbols (part of the description)

2 vehicle

3 towing vehicle

4 steering device

4a Torsion bar of the steering device 4

4b servo actuator

5 longitudinal axis

6 steered vehicle axle 61 left steered wheel of steered vehicle axle 6 6r right steered wheel of steered vehicle axle 6

7 unsteered vehicle axle 71 left unsteered wheel of unsteered vehicle axle 7 7r right unsteered wheel of unsteered vehicle axle 7

8 followers

9 trailer axle 91 left wheel of trailer axle 9 9r right wheel of trailer axle 9

10 control device 11 drive

12a, 12b brake components

23 Emergency steering function

24 Compensation function AA Compensation acceleration AI Actual acceleration AS Target acceleration dM Braking torque difference

DTMax maximum torsion bar torque

Fl steering force

HA rear axle

LMax maximum power parameter MI1, MI2 steering braking torque times, Ma2 compensating torque on the front axle VA Ma3, Ma4 compensating torque on the rear axle HA Ma5, Ma6 compensating torque on the trailer axle 9 S status signal

Ta, Tb temperature of the brake components 12a, 12b Tg limit temperature VA front axle ZL steering brake deceleration

Ls target steering angle

Li Actual steering angle

Ld differential steering angle

ST1, ST2, ST3, ST4, STU steps of the method according to the invention

Claims

patent claims

1. A method for controlling a vehicle (2), the vehicle (2) having at least:

- a steered vehicle axle (6; VA) with at least one left steered wheel (6I) and one right steered wheel (6r),

- An unsteered vehicle axle (7;FIA) with unsteered wheels (7I, 7r), and

- a steering device (4), wherein the steering device (4) is designed to act with a steering force (Fl) on the steered wheels (6I, 6r) of the steered vehicle axle (6; VA) in such a way that the steered wheels (6I, 6r ) of the steered vehicle axle (6) in order to steer the vehicle (2) with a predetermined setpoint steering angle (Ls), wherein when it is determined (20) that the steering forces ( Fl) are not sufficient to steer the vehicle (2) via the steered vehicle axle (6; VA) with the target steering angle (Ls) (ST1), at least the following steps are carried out:

- Carrying out an emergency steering function (23) by setting a braking torque difference (dM) between a first steering braking torque (MI1) on the left steered wheel (6I) and a second steering braking torque (MI2) on the right steered wheel (6r) (ST2), with the setting of the braking torque difference (dM), the steered wheels (6I, 6r) of the steered vehicle axle (6; VA) turn in such a way that the vehicle (2) is steered and a steering brake deceleration (ZL) of the vehicle (2) is effected;

- Carrying out a compensation function (24) by setting compensation torques (Ma3, Ma4) on at least the non-steered wheels (7I, 7r) of the non-steered vehicle axle (7;FIA) (ST3), with the compensation torques (Ma3 , Ma4) a compensation Acceleration (AA) of the vehicle (2) is effected, characterized in that the steering-braking torques (MI1, MI2) and the balancing torques (Ma3, Ma4) are adjusted in such a way that the balancing function (24) caused by the balancing - Acceleration (AA) compensates for the steering brake deceleration (ZL) caused by the emergency steering function (23), so that the vehicle (2) is steered with the target steering angle (Ls) and at the same time an actual acceleration (AI) of the vehicle ( 2) a predefined target acceleration (AS) is approached and/or the predefined target acceleration (AS) is maintained (ST4).

2. The method according to claim 1, characterized in that

- the steering brake deceleration (ZL) caused by the emergency steering function (23) is superimposed by the compensation function (24) with a negative compensation acceleration (AA) in such a way that a negative actual acceleration (AI) of the vehicle (2) follows, or

- The steering brake deceleration (ZL) caused by the emergency steering function (23) is superimposed by the compensation function (24) with a positive compensation acceleration (AA) in such a way that a negative or a positive actual acceleration (AI) of the vehicle (2) or an actual acceleration (AI) of the vehicle (2) follows from zero, the compensation acceleration (AA) being set in such a way that the actual acceleration (AI) approaches the target acceleration (AS) or that this to match.

3. The method according to any one of the preceding claims, characterized in that the compensating torques (Ma3, Ma4) on at least the unsteered wheels (7I, 7r) of the unsteered vehicle axle (7;HA) are positive for setting a positive compensating Acceleration (AA), or negative are used to set a negative Balance Acceleration (AA) or zero are for setting a Balance Acceleration (AA) of zero.

4. The method according to any one of the preceding claims, characterized in that the steered vehicle axle (6; VA) for implementing the emergency steering function (23) is a front axle (VA) of the vehicle (2) and the at least one non-steered vehicle axle (7; FIA ) to implement the compensation function (24) a flinter axle (HA) of the vehicle (2).

5. The method according to any one of the preceding claims, characterized in that the at least one non-steered vehicle axle (7; HA) on a towing vehicle (3) of the vehicle (2) and/or as a trailer axle (9) on a trailer ( 8) of the vehicle (2) is arranged.

6. The method according to any one of the preceding claims, characterized in that the first steering braking torque (MI1) or the second steering braking torque (MI2) is zero and the other steering braking torque (MI2, MI1) is negative during the adjustment the braking torque difference (dM) (ST2).

7. The method according to any one of the preceding claims, characterized in that the emergency steering function (23) is carried out exclusively by adjusting the braking torque difference (dM) on the steered vehicle axle (6; VA).

8. The method according to any one of the preceding claims, characterized in that the compensation function (24) exclusively by setting compensation torques (Ma3, Ma4) on the unarticulated th vehicle axle (7; HA) is carried out.

9. The method according to any one of claims 1 to 7, characterized in that the compensating function (24) by setting compensating torques (Mal, Ma2) on the steered wheels (61, 6r) of the steered vehicle axle (6; VA ) is carried out by the equalizing torques (Mal, Ma2) on the steered wheels (61, 6r) superimposed on the steering braking torques (MI1, MI2) on the steered wheels (61, 6r) while maintaining the braking torque difference (dM). will.

10. The method according to any one of the preceding claims, characterized in that the steering-braking torques (MI1, MI2) on the articulated vehicle axle (6; VA) by a side-specific activation of brake components (12a, 12b) on the respective steered wheels ( 6I, 6r) takes place.

11. The method according to claim 10, characterized in that a temperature (Ta, Tb) of the brake components (12a, 12b) on the steered wheels (6I, 6r) of the steered vehicle axle (6; VA) is monitored (ST5) and that Vehicle (2) is brought to a standstill when the monitored temperature (Ta, Tb) exceeds a limit temperature (Tg).

12. The method according to any one of the preceding claims, characterized in that in order to determine whether the steering forces (Fl) applied and/or which can be applied by the steering device (4) are sufficient to move the vehicle (2) via the steered vehicle axle (6; VA ) to steer with the target steering angle (Ls) (ST1) is monitored to determine whether

- a torsion bar (4a) of the steering device (4) is subjected to a maximum torsion bar torque (DTMax), and/or

- a servo actuator (4b) with a maximum performance parameter (LMax) is controlled, and/or

- A status signal (S) is issued by the steering device (4), and/or

- An actual steering angle (Li) corresponds to the specified target steering angle (Ls).

13. Control device (10), designed to carry out the method according to any one of the preceding claims.

14. Vehicle (2), having at least:

- An unsteered vehicle axle (7;HA) with unsteered wheels (7I, 7r), and

- a steering device (4), wherein the steering device (4) is designed to act with a steering force (Fl) on the steered wheels (6I, 6r) of the steered vehicle axle (6; VA) in such a way that the steered wheels (6I, 6r ) of the steered vehicle axle (6) in order to steer the vehicle (2) with a predetermined target steering angle (Ls), and

- a control device (10) according to claim 13 for carrying out a method according to one of claims 1 to 12.