Control procedures for the safe operation of a vehicle with automated steering, as well as a control system

Abstract

Control method for the safe operation of a vehicle with automated steering that uses a steering angle control variable (δ) lim ) provides for deflecting at least one wheel, wherein the automated steering system comprises a steering angle control unit (2), in particular a trajectory tracking controller, and a lateral acceleration limiter (3), wherein the lateral acceleration limiter (3) comprises a controller (31) and a switching logic (32), wherein the method comprises at least the following steps: a. Determining a first target steering angle (δ traj ) by the steering angle control unit (2); b. Comparing an actual value of the lateral acceleration (a y ) with a lower and an upper limit (a y,safety,min , a y,safety,max ) for the permissible lateral acceleration of the vehicle, where the lower and upper limits (a y,safety,min , a y,safety,max) define a permissible lateral acceleration range and provide the first target steering angle (δ) traj ) as steering angle control variable (δ lim ), if the actual value of the lateral acceleration (a y ) less than the upper limit (a y,safety,max ) and greater than the lower limit (a y,safety,min ) is; c. Activation of the lateral acceleration limiter (3) using the switching logic (32) when the actual value (a y ) greater than or equal to the upper limit (a y,safety,max ) or less than or equal to the lower limit (a y,safety,min ) is; d. Determining a second target steering angle (δ limiter ) by means of the controller (31) of the switched-on lateral acceleration limiter (3) and provision of the second target steering angle (δ limiter ) as steering angle control variable (δ lim ); e. Repeating procedural steps a. to d. until one of the following termination criteria is met: - if in step c. the actual value of the lateral acceleration (a y ) greater than or equal to the upper limit (a y,safety,max ) was - the second target steering angle (δ limiter ) is greater than the first target steering angle (δ traj ); or - if in step c. the actual value of the lateral acceleration (a y ) less than or equal to the lower limit (a y,safety,min ) was - the second target steering angle (δ limiter ) is smaller than the first target steering angle (δ traj ); f. Deactivating the lateral acceleration limiter (3) and providing the first target steering angle (δ) traj ) as steering angle control variable (δ lim ), if one of the termination criteria mentioned in step e. is met.

Description

[0001] The invention relates to a control method for the safe operation of a vehicle with automated steering. Furthermore, the invention relates to a control system for the safe operation of a vehicle with automated steering.

[0002] The further development of highly and fully automated vehicles means that the vehicle and its control systems are continually being assigned more tasks. Such systems also include, in particular, steering systems, which primarily support the driver in lateral control of the vehicle. The form of support provided by the system can vary from simple driver assistance systems to fully automated steering. In fully automated steering systems, the vehicle's steering angle and other parameters are managed, for example, by artificial intelligence systems or highly complex systems. As development progresses, these systems assume more tasks in vehicle control and must therefore meet higher requirements, particularly safety aspects.These systems perform necessary perception and planning tasks, allowing the driver to follow the desired path, for example, without the driver actively intervening in the vehicle's steering. Automated steering systems face particularly challenging tasks in highly dynamic environments, such as those frequently found in urban areas. In these situations, an automated steering system may exhibit unpredictable and incomprehensible behavior. Such behavior, similar to that of a black box, makes it difficult to understand the steering system's behavior.

[0003] Therefore, such systems require safety mechanisms to increase driving safety. Such safety mechanisms can, for example, influence the strength of the steering system's intervention through a control variable, keeping the vehicle safely on the road. However, such safety mechanisms primarily serve to avoid collisions, with collision avoidance also encompassing the evasive aspect. This allows a system to react comprehensibly to the current traffic situation.

[0004] Such systems are already known from DE 11 2019 000 860 T5 and DE 10 2012 215 228 A1. Using vehicle data, a highly or fully automated steering system can regulate the lateral guidance of the vehicle. However, intervention in the lateral guidance of a vehicle by the steering system cannot be carried out at any price. For example, it is conceivable that if the vehicle's guidance is severely intervened, the lateral acceleration of the vehicle becomes unreasonable for the vehicle occupants or the vehicle's stability is affected, so that the safety of the vehicle occupants can no longer be guaranteed. Furthermore, the steering system must also be able to react to the current traffic situation. Using limit values, the vehicle's lateral guidance can be regulated within a framework that prevents collisions or dangerous situations in traffic.

[0005] Automated steering functions for lateral guidance of a vehicle up to a predefined lateral acceleration limit are known in the prior art, such as from EP 3 875 350 A1. For example, in automated steering, a limit value for lateral acceleration is typically specified. This value limits the intervention of the automated steering in the lateral guidance of the vehicle and thus increases vehicle safety. According to the prior art, the manipulated variable to be controlled by the automated steering is either the steering torque or the steering angle. Electric power steering systems that generate a steering torque are already known from EP 3 611 078 A1, wherein an overlay torque can be selectively provided by an automated steering function. This overlay torque is limited based on a lateral acceleration limit value, thus enabling the vehicle to follow a lane up to the lateral acceleration limit value.

[0006] State-of-the-art systems assume a stationary relationship between the manipulated variable of the automated steering and the variable to be limited. In reality, the relationships are not stationary, but rather dynamic. In particular, the control of the torque or, for example, the steering angle of an axle adjacent to the steering requires dynamic control, as otherwise the vehicle's behavior cannot be optimally controlled. Fixed relationships are assumed, even though numerous parameters can influence the control of the torque or the steering angle. This means that, on the one hand, the full potential of automated steering cannot be utilized, and, on the other hand, model inaccuracies or external disturbances can lead to errors in limiting lateral acceleration.

[0007] Against this background, the task arises to provide an optimized and more efficient control method for trajectory following control using a steering angle.

[0008] The problem is solved by a control method according to the features of claim 1.

[0009] According to the invention, the automated steering system controls a steering angle control variable, whereby the lateral guidance of the vehicle is supported or taken over by means of the steering angle. The automated steering system is preferably a fully automated steering system, which can take over steering in highly dynamic environments by means of complex control systems or AI applications. For this purpose, the automated steering system according to the invention comprises a steering angle specification unit and a lateral acceleration limiter. The steering angle specification unit can comprise a planner or, preferably, a trajectory follower controller. Furthermore, the steering angle specification unit can also have only one controller, which can convert an input signal, for example from a driver or a steering person, into a steering angle. The trajectory follower controller preferably enables predictive vehicle lateral guidance control based on a target route and available vehicle measurement data.The steering angle specification unit can fully or partially control the vehicle's lateral guidance. In a fully automated steering system, the primary control of lateral guidance can preferably be taken over by the trajectory following controller, whereby the steering angle of a steered wheel or at least one steered axle of a vehicle can be determined by the trajectory following controller. The lateral acceleration limiter can serve as a safeguard for the steering angle specification unit; this can intervene in the steering angle control to regulate the vehicle's lateral acceleration within a permissible range. This permissible lateral acceleration range can be defined by what is reasonable for the vehicle occupants and / or by vehicle safety. Vehicle safety here includes collision avoidance and, for example, any associated evasive maneuvers, as well as safe lateral guidance of the vehicle.This advantageously prevents collisions with objects located in the vehicle's trajectory. For this purpose, the lateral acceleration limiter according to the invention has a controller and switching logic. The switching logic can have a plurality of switches, wherein the switches interconnect the steering angle specification unit with the controller in such a way that the function of the lateral acceleration limiter can be selectively enabled. According to the invention, in a first step of the control method, a first target steering angle is determined by the steering angle specification unit, preferably by the trajectory follower controller. During normal operation, this predetermined manipulated variable, e.g. a first target steering angle, can be forwarded to a controlled system, at least one wheel to be steered, wherein the controlled system implements the manipulated variable.The trajectory sequence controller preferably serves to control the vehicle's lateral guidance, whereby steering intervention by the trajectory sequence controller can sometimes, for example, negatively influence lateral acceleration and impact vehicle safety. Furthermore, the vehicle may be on a collision course with an object on a target trajectory of the steering angle specification unit. To avoid such a situation, according to the invention, in a second method step, an actual value of the lateral acceleration currently present on the vehicle is compared with a lower and an upper limit value for the permissible lateral acceleration on the vehicle. The lower and upper limit values ​​define a permissible lateral acceleration range. This step is preferably carried out by the lateral acceleration limiter.Particularly preferably, the lower and upper limits of the permissible lateral acceleration are dependent on the current traffic situation, so that objects on a collision course are taken into account. If the actual value of the lateral acceleration is greater than or equal to the upper limit or less than or equal to the lower limit, the lateral acceleration limiter is activated using the switchover logic. Subsequently, a second target steering angle is determined using the controller of the activated lateral acceleration limiter, which is then provided as the steering angle control variable instead of the established target steering angle. The controller can determine the second target steering angle from available data and / or measured data and / or determined data.The available data preferably comprise a target lateral acceleration, the value of the respective limit value exceeded or undershot being assigned to the target lateral acceleration. The measured data or determined data, such as the actual value of the lateral acceleration or the vehicle speed, are preferably measured and fed to the steering angle specification unit and the controller, or the steering angle specification unit determines relevant variables from the measured data, which are then fed to the controller. Preferably, the second target steering angle is then transmitted to the controlled system instead of the first target steering angle. The switching logic can have a switch which is connected in such a way that the paths of the first target steering angle and the second target steering angle are arranged parallel to one another, with only the switch being switched in order to define the respective desired target steering angle as the steering angle manipulated variable. Steps a. to d.are repeated according to the invention until one of the following termination criteria is met: 1. if in step c. the actual value was greater than or equal to the upper limit value - the second target steering angle is greater than the first target steering angle; or 2. if in step c. the actual value was less than or equal to the lower limit value - the second target steering angle is less than the first target steering angle. This step thus compares the current second target steering angle with the current first target steering angle, whereby the condition of the comparison is dependent on the limit value previously exceeded or undershot. The set conditions preferably relate to the current or last determined or measured value of the respective variable. Method step e. also preferably relates only to the last limit value exceeded or undershot. According to the invention, method steps a. to e. are carried out until one of the termination criteria is met.If one of the termination criteria is met, the lateral acceleration limiter is deactivated, and the first target steering angle is again provided as the steering angle control variable. This advantageously provides an efficient control method, as the lateral acceleration limiter is only used situationally. Furthermore, it is a dynamic control system, which enables optimized control. The lack of stationary relationships in the lateral acceleration limiter controller enables an optimized design of the second target steering angle, which not only optimizes the design but also increases vehicle stability and safety. Negative effects due to model inaccuracies or external disturbances, which could lead to a permanent error, are minimized by the dynamic control.Advantageously, the lateral acceleration limiter intervenes in the control of the steering angle setting unit when the steering angle setting unit is on a collision course with an object. The lateral acceleration limiter can define the permissible lateral acceleration range in such a way that, for example, the collision course is avoided.

[0010] Furthermore, the problem is solved by a control system having the features of claim 10. The control system can achieve the same technical effects and advantages as were described in connection with the control method according to the invention for the safe operation of a vehicle.

[0011] According to an advantageous embodiment of the invention, the actual value of the lateral acceleration is measured directly by means of a lateral acceleration sensor or is calculated or determined from vehicle data. The lateral acceleration is preferably measured directly by the lateral acceleration sensor, thereby advantageously eliminating a calculation step. Alternatively, the lateral acceleration can also be calculated or determined from vehicle data by the steering angle specification unit. The vehicle data preferably include at least the yaw rate and the vehicle speed. This yaw rate can be determined by means of a yaw rate sensor. The vehicle speed can either be measured by means of a suitable sensor or determined from other measured variables, in particular the engine speed.Based on the yaw rate and the vehicle speed, the steering angle setting unit can determine the actual value of the lateral acceleration using simple mathematical relationships.

[0012] According to an advantageous embodiment of the invention, the automated steering system comprises an observer; preferably, the steering angle specification unit comprises the observer, and particularly preferably, the trajectory follower controller comprises the observer. An observer can determine a non-measurable variable using an observed reference system and known input and output variables. The observer's primary task can be predictive lateral vehicle guidance. The observer is preferably part of the trajectory follower controller and can determine variables relevant to the control. Thus, difficult-to-measure variables can be determined using the observer. For example, the observer can determine the actual value of the lateral acceleration from the vehicle data presented above. Furthermore, the vehicle's yaw rate can also be transmitted to the observer.

[0013] According to an advantageous embodiment of the invention, it is provided that the controller of the lateral acceleration limiter is a PI controller, PID controller, state controller or sliding mode controller.

[0014] According to an advantageous embodiment of the invention, the controller of the lateral acceleration limiter has a feedforward control and / or an anti-windup measure. The feedforward control can represent disturbance compensation. The anti-windup measure is particularly applicable if the controller has an integrating component. The anti-windup measure prevents the integral component of the controller from accumulating a significant error if a manipulated variable enters saturation. For example, the steering angle of a wheel is physically limited, so that the steering angle manipulated variable on the part of the controller cannot become greater than the wheel can steer. If the steering angle specification unit or the controller of the lateral acceleration limiter outputs a first or second target steering angle that is greater than the available steering angle at the wheel, a windup effect can occur in combination with an integrating component.This must be avoided with an anti-windup measure in order to reduce the risk of overshoot and potential instability of the controller.

[0015] According to an advantageous embodiment of the invention, the controller has at least one control parameter, wherein the control parameter is dependent on the current vehicle state, wherein the current vehicle state comprises measured data or determined data of the vehicle. The vehicle state can, on the one hand, comprise measured data of the vehicle, wherein in particular the vehicle speed, the yaw rate, the longitudinal acceleration, the current steering angle, and the lateral acceleration are measured or determined. Preferably, the steering angle specification unit, in particular the observer, can determine vehicle states, which are fed to the controller of the lateral acceleration limiter. This allows the system complexity of the controller to be reduced.

[0016] In an alternative, advantageous embodiment of the invention, the first target steering angle is transmitted to the controller, with the controller also determining a second target steering angle as a function of the first target steering angle. This advantageously facilitates steering transitions if, for example, the steering angle control variable is no longer provided by the first target steering angle, but by the second target steering angle. Significant differences between the first target steering angle and the second target steering angle can thus be reduced or prevented. In particular, only the first target steering angle, which is present when the lateral acceleration limiter is first activated, is fed to the controller.

[0017] According to an advantageous embodiment of the invention, the value of the first target steering angle is assigned to the second target steering angle directly after the lateral acceleration limiter is activated. Preferably, the first target steering angle, which was determined by the steering angle specification unit when the lateral acceleration limiter was first activated, is fed to the controller of the lateral acceleration limiter. The controller can determine a first, second target steering angle as a function of the first target steering angle or adopt the first target steering angle as the first, second target steering angle. This advantageously prevents a significant steering angle jump at the wheel to be steered. For example, it is conceivable that after the lateral acceleration limiter is activated, the controller's second target steering angle differs significantly from the previously available steering angle manipulated variable, thus generating a jerky steering movement.This jerky steering movement should be advantageously reduced or avoided. When the lateral acceleration limiter is activated for the first time, the control process runs through process steps a. to e. for the first time. This is preferably understood as the first cycle, with each subsequent cycle generating cycles (n+1). Thus, it is conceivable that several cycles may occur until one of the termination criteria is met. After the lateral acceleration limiter is deactivated, the lateral acceleration limiter can be activated again, provided condition c. is met, in which case the number of cycles restarts at one.

[0018] According to an advantageous embodiment of the invention, the upper and lower limit values ​​can be variably adjusted by the lateral acceleration limiter, with the upper and lower limit values ​​being set in an intermediate step between a. and b. The limit values ​​are preferably dynamically adjustable so that the lateral acceleration limiter can adapt the limit values ​​to the current traffic situation. This restricts the permissible lateral acceleration range to be controlled by the steering angle specification unit in such a way that, for example, collisions with objects on the trajectory are avoided. Furthermore, the lateral acceleration limit values ​​are preferably determined as a function of the vehicle speed. In addition, the driver can influence the respective limit values ​​depending on different driving modes; for example, a sport mode would permit higher lateral acceleration values ​​than an eco mode.Advantageously, the limit values ​​are adapted to the requirements of the respective driving situation and to the respective driver.

[0019] According to an advantageous embodiment of the invention, the automated steering system has at least two modes, wherein a free-drive mode comprises the provision of the first target steering angle as a steering angle control variable and a limited-drive mode comprises the provision of the second target steering angle as a steering angle control variable. It is also conceivable for the limited-drive mode to be subdivided into a negatively limited-drive mode and a positively limited-drive mode. The negatively limited-drive mode can be present when the actual value of the lateral acceleration is less than or equal to the lower limit value. The positively limited-drive mode can be present when the actual value of the lateral acceleration is greater than or equal to the upper limit value.

[0020] The advantageous embodiments and features explained in connection with the control method for the safe operation of a vehicle can also be used in the control system, alone or in combination.

[0021] Further details and advantages of the invention will be explained below with reference to the exemplary embodiment shown in the drawing. Herein: Fig. 1 a simplified schematic representation of an embodiment of a control system; Fig. 2 a schematic embodiment of a control method according to the invention; Fig. 3 an embodiment of a circuit of a lateral acceleration limiter with a controller, a switching logic and several switches; and Fig. 4 an exemplary application of the method according to the invention.

[0022] In Fig. 1 schematically shows an embodiment of a control system 1. The control system 1 preferably has a processor unit that can execute the control method according to the invention.

[0023] For this purpose, the control system 1 in Fig. 1, a steering angle specification unit 2 and a lateral acceleration limiter 3. Preferably, the steering angle specification unit 2 comprises a trajectory follower controller. According to the invention, the steering angle specification unit 2 and the lateral acceleration limiter 3 are part of an automated steering system, wherein the automated steering system serves to deflect at least one wheel by means of a steering angle manipulated variable. The steering angle specification unit 2 can primarily assume the task of vehicle lateral guidance, wherein the intervention strength by the steering angle specification unit 2 is to be limited to a manipulated variable based on critical parameters by the lateral acceleration limiter 3. The steering angle specification unit 2 can have a desired trajectory traj, wherein the steering angle specification unit 2 determines a first desired steering angle δ based on input data of the vehicle and the desired trajectory traj. trajThe automated steering system, preferably the steering angle setting unit 2 and particularly preferably the trajectory follower controller, preferably has an observer for this purpose. By means of the first target steering angle δ traj The steering angle of a wheel can usually be controlled and thus also the lateral guidance of the vehicle. In normal operation, the steering angle setting unit 2 determines the first target steering angle δ traj, wherein a vehicle, in particular a passenger car, is operated safely. However, the behavior of the steering angle specification unit 2 and a planner, which may be included in the steering angle specification unit 2, may be partially unpredictable and incomprehensible, particularly in a highly dynamic environment. Highly dynamic environments also include, in particular, critical or dangerous traffic situations in which objects are located on the trajectory of the vehicle. In such situations, the steering angle specification unit 2 can, for example, determine a first target steering angle δ trajThis value would generate a lateral acceleration on the vehicle that would be unreasonable for the occupants or would no longer allow safe vehicle control, thus making a collision unavoidable. The lateral acceleration limiter 3 can advantageously intervene in the control of the steering angle setting unit 2, whereby the lateral acceleration limiter 3 is provided with both lateral acceleration limit values ​​a y,safety,min , a y,safety,max in the form of a vector limit values ​​of the lateral acceleration a y,safety be transmitted, whereby on the basis of one or both values ​​the lateral acceleration limiter 3 determines a second target steering angle, which instead of the first target steering angle δ traj the steering angle setting unit 2 can be transmitted to the control system. This can advantageously prevent a collision, for example, or ensure safe lateral vehicle control. The steering angle control variable δ limIn other words, in a free-drive mode, a normal steering intervention by the steering angle setting unit 2 and in a limited-drive mode, a steering intervention limited by a limit value, which keeps the lateral acceleration of the vehicle within a reasonable or safe range and can either be the value of the first target steering angle δ traj or the second target steering angle. This primarily enables safe lateral guidance of the vehicle, particularly addressing the collision avoidance aspect.

[0024] Fig. Figure 2 shows an embodiment of the control method according to the invention. In particular, Fig. 2 shows the conditions of the control method according to the invention in which the control system slips into a negative limitation 11 of the lateral acceleration or into a positive limitation 12 of the lateral acceleration. Fig. 2 also the condition that must be met so that the control can transition from the respective negative limitation 11 or the positive limitation 12 back to a free run procedure 10. In the free run procedure 10, the lateral acceleration currently present on the vehicle, the so-called actual value of the lateral acceleration a y , in a permissible lateral acceleration range. This permissible lateral acceleration range can be limited by a lower limit of the lateral acceleration a y,safety,min and an upper limit of the lateral acceleration a y,safety,max As long as the actual value of the lateral acceleration a y is within the permissible lateral acceleration range, i.e. greater than the lower limit a y,safety,min and less than the upper limit of the lateral acceleration a y,safety,max is, according to the invention a first target steering angle δ determined by the steering angle setting unit 2 traj as steering angle control variable δ limprovided and the control is continued in the free travel procedure 10. For this purpose, the actual value of the lateral acceleration a y be measured directly by means of a lateral acceleration sensor or calculated or determined from vehicle data. In particular, the calculation can be carried out by the steering angle setting unit 2, preferably by the trajectory follower controller, and an observer can measure the lateral acceleration a y from existing data. The vehicle data preferably includes the vehicle speed v and the vehicle's yaw rate.

[0025] In order to guarantee the safe operation of the vehicle with the automated steering or to make it as optimal as possible, the actual value of the lateral acceleration a y , preferably always, with the lower and upper limit a y,safety,min , a y,safety,maxThis comparison makes it possible to determine whether a permissible lateral acceleration is present. This condition is defined in Fig. 2 shown: ay≤ay,safety,min and ay≤ay,safety,max. If one of these conditions occurs, the lateral acceleration limiter 3 is switched on by means of a switching logic 32, so that the control of the steering angle control variable δ lim by a corresponding negative limitation 11 or positive limitation 12. For the negative limitation 11, the actual value of the lateral acceleration a y less than or equal to the lower limit of the lateral acceleration a y,safety,min For the positive limitation 12, the actual value of the lateral acceleration a y greater than or equal to the upper limit of the lateral acceleration a y,safety,max It is conceivable that the upper and lower limit a y,safety,max , a y,safety,minare variably adjustable by the lateral acceleration limiter 3, with the upper and lower limit values ​​being set in an intermediate step between a. and b. The limit values ​​are preferably determined depending on the vehicle speed and the current traffic situation.

[0026] The lateral acceleration limiter 3 comprises a controller 31, which sets a second desired steering angle δ limiter determined and this second target steering angle δ limiter according to the invention as steering angle control variable δ lim provided that the control is within the negative or positive limits 11, 12. The lateral acceleration limiter 3 is Fig. 3 in more detail. The limitation of lateral acceleration a ycan limit the scope of the control of the steering angle setting unit 2 and thus avoid a trajectory which could have a collision course with another object.

[0027] The control remains in the respective negative or positive limit 11, 12 until a termination criterion corresponding to the respective negative or positive limit 11, 12 is met. This means that the second target steering angle δ limiter preferably as long as the respective limitation 11, 12 is determined and as steering angle control variable δ lim is provided until the corresponding termination criterion is met. This creates a cycle that is repeated repeatedly, whereby the second target steering angle δ limiterpreferably based on current vehicle data in each cycle. A cycle preferably comprises one run of the process steps a. to e. The comparisons of the respective variables (first target steering angle δ traj , second target steering angle δ limiter , Actual value of lateral acceleration a y , lower limit a y,safety,min , upper limit a y,safety,max preferably take place in a cycle-related manner.

[0028] The termination criteria according to the invention are Fig. 2 is defined as follows: δtraj>δlimiter and δtraj<δlimiter. If the control is carried out by the negative limitation 11, the first target steering angle δ traj the steering angle setting unit 2 must be greater than the second target steering angle δ limiter If the control is carried out by the positive limitation 12, the first target steering angle δ trajthe steering angle setting unit 2 must be smaller than the second target steering angle δ limiter . Only when one of the two termination criteria is reached, the control can return to the free travel procedure 10. According to the invention, the lateral acceleration limiter 3 is then switched off and the first target steering angle δ traj is again used as steering angle control variable δ lim provided.

[0029] Fig. 3 shows an embodiment of a circuit of a lateral acceleration limiter 3 with a controller 31, a switching logic 32 and several switches 33. The function of the lateral acceleration limiter was described in the context of Fig. 1 and Fig. 2 clearly explained. Fig. 3 rather serves to disclose the structure of the lateral acceleration limiter 3 and to go into more detail about the switching logic 32.

[0030] The switching logic 32 can Fig. 2, whereby on the basis of these conditions the present switches 33 are preferably switched in such a way that the corresponding first or second target steering angle δ traj , δ limiter as steering angle control variable δ lim In the present embodiment, the switches 33 are connected to the switching logic 32 by means of signal paths, wherein the switching function of the switches 33 is clearly and unambiguously Fig. 3. The switches 33 can switch between two states, with one switch 33 setting the respective lower or upper limit a y,safety,min , a y,safety,max This is selected depending on the respective exceeded limit (lower or upper limit). The respective exceeded limit is then sent to controller 31 as a soll with the actual value a y (in the Fig. 2 a ist) and the vehicle speed v, whereby the controller uses these variables to calculate the second target steering angle δ limiter Another switch 33 is used to switch between the first or the second target steering angle δ traj , δ limiter , where the respective relevant variable is then called the steering angle control variable δ lim is provided.

[0031] The switching logic 32 can also reset the controller 31, provided that the second target steering angle δ limiter was determined and as steering angle control variable δ lim was provided, and the respective termination criterion was not met, the controller 31 sets a new second target steering angle δ limiter must be determined. For this purpose, the current data is transmitted again to controller 31, whereby a reset is advantageous.

[0032] Furthermore, when the lateral acceleration limiter 3 is switched on for the first time in combination with determining the second target steering angle δ limiter to avoid a direct steering angle jump caused by the newly provided steering angle. A steering angle jump could pose a greater threat to vehicle stability than a possibly too high or too low actual value of the lateral acceleration a y . Therefore, the second target steering angle δ limiter Immediately after the lateral acceleration limiter 3 is activated, the value of the first target steering angle δ traj This is assigned in Fig. 3 is also indicated by δ0 in the controller 31, which is directly connected to the first target steering angle δ traj It is also conceivable that during control by the controller 31 of the lateral acceleration limiter 3, the first target steering angle δ trajis taken into account. Thus, significant differences between the first and the second target steering angle δ traj , δ limiter be avoided.

[0033] Controller 31 can be implemented as a PI controller, PID controller, state controller, or sliding-mode controller. Furthermore, controller 31 can have a feedforward control and / or, depending on the selected controller type, an anti-windup measure. This is particularly relevant for controller types with an integrating component.

[0034] In addition, the controller 31 can have at least one control parameter, which can depend on the current vehicle state. The vehicle state can be the yaw rate, the vehicle speed, the actual value of the lateral acceleration a y and / or the longitudinal acceleration. Examples of the variables that preferably influence the control parameters of the controller 31 are shown in Fig. 3 inside the controller 31.

[0035] Fig. Figure 4 shows an exemplary application of the method according to the invention. Here, an intervention in the steering by the method according to the invention occurs, and the associated advantage becomes apparent. The vehicle 100 has an actual value of the lateral acceleration a ist which is heading directly towards a potential collision object 101. The permissible lateral acceleration range a y,safety,min , a y,safety,max is set in such a way that the steering angle setting unit 2 would not avoid the collision object 101 at a first point in time. The limit values ​​of the lateral acceleration are preferably dynamically adjustable, so that a new lower limit a y,safety,min,neu can be determined in order to guide the vehicle 100 past the collision object 101. The lateral acceleration limiter 3 can then, provided the actual value of the lateral acceleration a istless than or equal to the new lower limit a y,safety,min,neu is switched on and the vehicle 100 by means of the second target steering angle δ limiter influence so that a collision is avoided and a new actual value of the lateral acceleration a ist,neu is within the new permissible lateral acceleration range. List of reference symbols 1 control system 2 Steering angle setting unit 3 lateral acceleration limiters 10 Free travel 11 negative limitation 12 positive limitation 31 controllers 32 switching logic 33 switches 100 vehicles 101 Collision object a y Actual value of lateral acceleration a y,safety Limit values ​​of lateral acceleration a y,safety,min lower limit a y,safety,min,neu new lower limit a y,safety,max upper limit a istActual value of the lateral acceleration in the controller a ist,neu new actual value of the lateral acceleration in the controller a soll Limit value of lateral acceleration in the controller δ lim Steering angle control variable δ limiter second target steering angle δ traj first target steering angle traj target trajectory

Claims

[1] Control method for the safe operation of a vehicle with an automated steering system that uses a steering angle control variable (δ lim ) for deflecting at least one wheel, wherein the automated steering comprises a steering angle setting unit (2), in particular a trajectory follower controller, and a lateral acceleration limiter (3), wherein the lateral acceleration limiter (3) comprises a controller (31) and a switching logic (32), wherein the method comprises at least the following steps: a. Determine a first target steering angle (δ traj ) by the steering angle setting unit (2); b. Comparing an actual value of the lateral acceleration (a y ) with a lower and an upper limit (a y,safety,min , a y,safety,max ) for the permissible lateral acceleration of the vehicle, where the lower and upper limit values (a y,safety,min , a y,safety,max) define a permissible lateral acceleration range and provide the first target steering angle (δ traj ) as steering angle control variable (δ lim ) if the actual value of the lateral acceleration (a y ) less than the upper limit (a y,safety,max ) and greater than the lower limit (a y,safety,min ) is; c. Activation of the lateral acceleration limiter (3) by means of the switching logic (32) when the actual value (a y ) greater than or equal to the upper limit (a y,safety,max ) or less than or equal to the lower limit (a y,safety,min ) is; d. Determining a second target steering angle (δ limiter ) by means of the controller (31) of the switched-on lateral acceleration limiter (3) and providing the second target steering angle (δ limiter ) as steering angle control variable (δ lim ); e. Repeat steps a to d until one of the following termination criteria is met: - if in step c. the actual value of the lateral acceleration (a y ) greater than or equal to the upper limit (a y,safety,max ) was - the second target steering angle (δ limiter ) is greater than the first target steering angle (δ traj ); or - if in step c. the actual value of the lateral acceleration (a y ) less than or equal to the lower limit (a y,safety,min ) was - the second target steering angle (δ limiter ) is smaller than the first target steering angle (δ traj ); f. Switching off the lateral acceleration limiter (3) and providing the first target steering angle (δ traj ) as steering angle control variable (δ lim ) if one of the termination criteria mentioned in step e. is met. [2] Method according to claim 1, characterized by that the actual value of the lateral acceleration (a y ) is measured directly using a lateral acceleration sensor or is calculated or determined from vehicle data. [3] Method according to one of the preceding claims, characterized by that the automated steering has an observer, preferably the steering angle setting unit (2) has the observer. [4] Method according to one of the preceding claims, characterized by that the controller (31) of the lateral acceleration limiter (3) is a PI controller, PID controller, state controller or sliding mode controller. [5] Method according to one of the preceding claims, characterized by that the controller (31) of the lateral acceleration limiter (3) has a pre-control and / or an anti-windup measure. [6] Method according to one of the preceding claims, characterized by that the controller (31) has at least one control parameter, wherein the control parameter is dependent on the current vehicle state, wherein the current vehicle state comprises measured data or determined data of the vehicle. [7] Method according to one of the preceding claims, characterized by that the second target steering angle (δ limiter ) immediately after the lateral acceleration limiter (3) is switched on, the value of the first target steering angle (δ traj ) is assigned. [8] Method according to one of the preceding claims, characterized by that the upper and lower limit (a y,safety,min , a y,safety,max ) are variably adjustable by the lateral acceleration limiter (3), whereby in an intermediate step between a. and b. the upper and lower limit values (a y,safety,min , a y,safety,max ) can be set. [9] Method according to one of the preceding claims, characterized by that the automated steering has at least two modes, wherein a free-drive mode provides the first target steering angle (δ traj ) as steering angle control variable (δ lim ) and a limited-drive mode includes providing the second target steering angle (δ limiter ) as steering angle control variable (δ lim ) includes. [10] Control system (1) for the safe operation of a vehicle with an automated steering system which provides a steering angle control variable (δ lim ) for deflecting at least one wheel, wherein the automated steering comprises a steering angle setting unit (2), in particular a trajectory following controller, and a lateral acceleration limiter (3), wherein the lateral acceleration limiter (3) comprises a controller (31) and a switching logic (32), wherein the control system comprises a processor unit configured to carry out the following steps: a. Determine a first target steering angle (δ traj ) by the steering angle setting unit (2); b. Comparing an actual value of the lateral acceleration (a y ) with a lower and an upper limit (a y,safety,min , a y,safety,max ) for the permissible lateral acceleration on the vehicle by means of the lateral acceleration limiter (3), whereby the lower and upper limit values (ay,safety,min , a y,safety,max ) define a permissible lateral acceleration range and provide the first target steering angle (δ traj ) as steering angle control variable (δ lim ) if the actual value of the lateral acceleration (a y ) less than the upper limit (a y,safety,max ) and greater than the lower limit (a y,safety,min ) is; c. Activation of the lateral acceleration limiter (3) by means of the switching logic (32) when the actual value (a y ) greater than or equal to the upper limit (a y,safety,max ) or less than or equal to the lower limit (a y,safety,min ) is; d. Determining a second target steering angle (δ limiter ) by means of the controller (31) of the switched-on lateral acceleration limiter (3) and providing the second target steering angle (δ limiter ) as steering angle control variable (δ lim ); e. Repeat steps a to d until one of the following termination criteria is met: - if in step c. the actual value of the lateral acceleration (a y ) greater than or equal to the upper limit (a y,safety,max ) was - the second target steering angle (δ limiter ) is greater than the first target steering angle (δ traj ); or - if in step c. the actual value of the lateral acceleration (a y ) less than or equal to the lower limit (a y,safety,min ) was - the second target steering angle (δ limiter ) is smaller than the first target steering angle (δ traj ); f. Switching off the lateral acceleration limiter (3) and providing the first target steering angle (δ traj ) as steering angle control variable (δ lim ) if one of the termination criteria mentioned in step e. is met.

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