EP4313729A1

EP4313729A1 - System and method for actuating an electromechanical steering system of a vehicle

Info

Publication number: EP4313729A1
Application number: EP22716328.4A
Authority: EP
Inventors: Stefan Feick; Philipp Kessler
Original assignee: Continental Autonomous Mobility Germany GmbH
Current assignee: Continental Autonomous Mobility Germany GmbH
Priority date: 2021-03-22
Filing date: 2022-03-09
Publication date: 2024-02-07
Also published as: WO2022199761A1; CN117083217A; JP2024508501A; US20240174292A1; DE102021202740A1

Abstract

The invention relates to a system for actuating an electromechanical steering system (2) of a vehicle, comprising a driver assistance system (3), which is designed to generate a first item of steering control information (L1), and a control unit (4) with at least one first controller unit (5), wherein the control unit (4) has a first interface (S1), which is designed to receive driver torque information (M), and at least one second interface (S2), which is designed to receive at least one item of adjustment information (A1, A2) which is dependent on the driving state and/or the driving situation, wherein the control unit (4) is designed to provide a second item of steering control information (L2) which is dependent on the driver torque information (M) and the at least one item of adjustment information (A1, A2), and wherein the system (1) is designed to provide a modified item of steering control information (L3) to the steering system (2) of the vehicle based on the first and the second item of steering control information (L1, L2), a steering movement being executed on the electromechanical steering system (2) based on said modified item of steering control information.

Description

description

System and method for controlling an electromechanical steering system of a vehicle

The invention relates to a system and a method for controlling an electromechanical steering system of a vehicle.

Electromechanical steering systems for vehicles (also EPS: Electric Power Steering) are known in principle. A program-controlled electric servomotor supports and superimposes the driver's steering movements by transferring forces to the steering mechanism.

Lane-guided driver assistance systems use captured environmental information to control the vehicle laterally and longitudinally along a planned trajectory. In most cases, the electromechanical steering is used as an actuator for lateral vehicle guidance, which receives suitable control information from a trajectory follower controller.

On the one hand, systems with a first interface variant are known in which the vehicle's lateral dynamics are influenced by an additive superimposition of torque values with the motor torque of the control motor of the electromechanical steering. On the other hand, systems with a second interface variant are known in which the vehicle's lateral dynamics are controlled by specifying a target steering angle. In this case, a steering angle controller is implemented on the electromechanical steering control unit.

The main design goal for driver assistance systems is to achieve high control quality in lane guidance. Simultaneously striving for a high degree of steering comfort when oversteering by the driver often leads to a conflict of objectives. Under "oversteering" is understood here that the driver at the Steering device performs a steering movement that deviates from the steering movement specified by the driver assistance system.

Regardless of the interface variant, known implementations have the disadvantage that the level, course and direction of the steering torque when the driver oversteers are only partially understandable or perceived as unnatural, since their effect is undifferentiated because they are not adapted to the respective driving situation and the steering wheel movement of the driver are always in the opposite direction.

In known implementations, for example, in the event of oversteering, even with small steering wheel deflections, the torque that the driver must apply to the steering device, hereinafter also referred to as driver torque, can increase continuously up to a value that corresponds to the level of the safety barrier that is due to the limitation of the engine torque of the servomotor of the electromechanical steering to ensure oversteerability by the driver. This increase in the driver's torque is due to the fact that the driver's actions are interpreted as a disturbance torque directly acting on the angle control loop and also as a disturbance variable for the trajectory following control loop due to the resulting change in vehicle alignment. This disturbance by the driver is then corrected using the dynamics of the overall disturbance transfer function of the lateral control. The higher the dynamics of the overall disturbance transfer function, the faster the counter-torque for the driver increases. In addition, the counter-torque for the driver rises all the higher in absolute terms, the higher the direct component amplification of the overall disturbance transfer function.

The effects described above have the disadvantage that in extreme cases, for example during emergency steering manoeuvres, the driver assistance system works against the driver without taking into account the driving situation and impedes him by the driver having to apply an additional steering torque in order to meet the specification of the driver assistance system, which is currently pursuing a different management goal , to overrule. In general, the above-described effects in cooperative driving, ie when the driver interacts with the driver assistance system, lead to reduced driving comfort and thus to less acceptance of the driver assistance function.

Proceeding from this, it is the object of the invention to specify a system for controlling an electromechanical steering system of a vehicle, which enables a cooperative driving behavior that is understandable and more natural for the driver, without significantly impairing the performance of the driving function.

The object is solved by a system having the features of independent patent claim 1 . Preferred embodiments are the subject matter of the dependent claims. A method for controlling an electromechanical steering system of a vehicle is the subject matter of independent claim 15.

According to a first aspect, the invention relates to a system for controlling an electromechanical steering system of a vehicle. The vehicle includes a driver assistance system that is designed to generate a first piece of steering control information. In addition, the system has a control unit with at least one first regulator unit. The control unit includes a first interface that is designed to receive driver moment information. In addition, the control unit includes at least one second interface, which is designed to receive at least one piece of adjustment information that is dependent on the driving condition and/or the driving situation. First and second adjustment information is preferably provided via the second interface. At least one of the items of adjustment information is dependent on the driving status or driving situation. The control unit is configured to provide second steering control information that is obtained from the

Driver moment information and the at least one adjustment information is dependent. Furthermore, the system is designed to provide the steering system of the vehicle with modified steering control information based on the first and second steering control information, based on the one steering movement is carried out on the electromechanical steering system. "Perform a steering movement based on the modified steering control information" means that either the modified steering control information itself or a variable derived from it, which is formed, for example, by the transfer function of a safety barrier, is used to initiate steering movements on the electromechanical steering system.

The technical advantage of the system according to the invention is that the driver torque that the driver feels on the steering device during cooperative driving can be adjusted as a function of the driving condition or driving situation, resulting in a driving behavior that feels natural to the driver. Preferably, only in extreme cases, for example during emergency steering maneuvers, is it made more difficult to override the specification of the driver assistance system in such a way that the driver is signaled that it is better, depending on the driving situation, to comply with the specification of the driver assistance system.

According to one exemplary embodiment, the first steering control information item is angle information, torque information for the servomotor of the electromechanical steering system, or information that is proportional to the torque of the servomotor of the electromechanical steering system. The driver assistance system thus controls the electromechanical steering either based on setpoint steering angle information or a setpoint torque specification, and this setpoint steering angle information or setpoint torque specification is converted into the modified steering control information depending on the driver's influence through the second steering control information. As a result, the system can be used both in an interface variant with an angle interface and in an interface variant with a torque interface.

According to one exemplary embodiment, first adjustment information is a driver torque threshold value. The control unit is designed to generate second steering control information, which is a modification of the first steering control information provided by the driver assistance system, when the amount of driver moment information is above the driver moment threshold value causes. In this way, the specification of the driver assistance system is only modified by the oversteering driver when the driver torque threshold value has been exceeded. As a result, unintentional, weak steering movements by the driver, for example, do not affect the specification of the driver assistance system.

According to one exemplary embodiment, second adjustment information is oversteering stiffness information, which is a measure of the steering resistance that the driver has to overcome at the steering device in order to oversteer the steering behavior specified by the driver assistance system. the

Oversteering stiffness information, for example, forms information similar to a variable spring constant of a spring, via which a force that has to be overcome in order to compress the spring can be adjusted. The oversteering stiffness information indicates how sluggish the steering behavior that is specified by the driver assistance system can be influenced by the driver. By changing the oversteering stiffness information, it is thus possible to set, depending on the situation, how the driver's torque on the steering device must be in order to bring about a predetermined steering movement of the electromechanical steering system.

According to one exemplary embodiment, the control unit is designed to adapt the control behavior of the first control unit of the control unit based on the oversteering stiffness information. At least one amplification factor of the first controller unit is preferably adjusted as a function of the oversteering stiffness information. A function can be provided that maps the required degree of oversteering stiffness to the at least one amplification factor. There is preferably a reciprocal dependency such that a higher oversteering stiffness is converted to a lower control loop gain and vice versa. In addition, it can be advantageous for at least one limit frequency of the first controller unit to be adapted in order to meet stability criteria. The adjustment of the cut-off frequency can, for example, depend on the

Oversteering stiffness information done. A function can also be provided here be that maps the required level of oversteering stiffness to the at least one cut-off frequency.

According to one exemplary embodiment, the control unit is designed to receive first and second adjustment information, with either one of the two adjustment information having a fixed value and the other adjustment information having a value dependent on the driving status or driving situation, or the first and second adjustment information being both dependent on the driving status or driving situation. As a result, the steering behavior of the driver assistance function can be designed as a function of the driving status and driving situation in such a way that the most natural possible cooperative driving behavior is achieved.

According to one exemplary embodiment, the control unit is designed such that the first controller unit receives a torque difference that is zero when the amount of driver torque information is less than or equal to the driver torque threshold value and has an amount of driver torque information reduced by the driver torque threshold value as soon as the amount of driver torque information reaches the driver torque threshold value exceeds. In this way it can be achieved that the specification of the steering assistance system is only influenced by the driver when he applies a significant torque to the steering device.

According to one exemplary embodiment, the first controller unit has an absolute value characteristic that falls monotonically above a limit frequency. Such a control behavior is advantageous for a cooperative driving behavior, since vibrations in the steering wheel, for example, as a result of the control circuit created by the negative feedback of the driver's moment, can thereby be effectively avoided.

According to one exemplary embodiment, the first controller unit has a control behavior in accordance with a PT1 controller. This type of controller is advantageously suitable for the interactive control of the vehicle through influences by the driver and the driver assistance system. According to one exemplary embodiment, the first controller unit has a control behavior such that the modification of the first steering control information item by the second steering control information item reduces the torque difference supplied to the first controller unit as an input variable. This achieves a control behavior of the system such that the driver assistance function is increasingly adjusted to the driver's steering specifications and the driver assistance system therefore directs less counter-torque to the driver.

According to one exemplary embodiment, if the first item of steering control information is angle information, yaw rate information or curvature information, a second controller unit is provided which is designed to convert setpoint torque information from the steering angle controller for the servomotor of the electromechanical steering system or information proportional to this setpoint torque information implement steering angle information, yaw rate information or curvature information as second steering control information. This makes it possible to convert the output information influenced by the driver moment information by means of the second controller unit in such a way that the second steering control information provided by the system can be used to directly modify the first steering control information, for example by an arithmetic operation of a sum or difference formation.

According to one exemplary embodiment, the second controller unit is designed to receive setpoint torque information from the steering angle controller for the servomotor of the electromechanical steering system that is weighted with an activation factor, with the activation factor being provided by the first controller unit. Torque information is preferably received from the control circuit of the second control unit and an arithmetic operation is carried out with a setpoint value. The moment information is provided, for example, by the steering angle controller of the electromechanical steering system. For example, the torque information is subtracted from the setpoint and the the resulting control difference is multiplied by the activation factor. The result of this multiplication is then fed to the second controller unit as input information. In the case of oversteering by the driver, the magnitude of the torque of the servomotor is mainly a measure of the torque applied to the driver. The fact that the second controller unit now tries to reduce the control difference multiplied by the activation factor effectively reduces the working of the driver assistance function against the driver. The extent of this reduction is determined by the level of the activation factor.

According to one exemplary embodiment, the second controller unit is designed to receive the oversteering stiffness information and to adapt the control behavior of the second controller unit based on the oversteering stiffness information. At least one amplification factor of the second controller unit is preferably adjusted as a function of the oversteering stiffness information. A function can be provided that maps the required degree of oversteering stiffness to the at least one amplification factor. There is preferably a reciprocal dependency such that a higher oversteering stiffness is converted to a lower control loop gain and vice versa. In addition, it can be advantageous for at least one limit frequency of the second controller unit to be adapted in order to meet stability criteria. The cut-off frequency can be adapted, for example, as a function of the oversteering stiffness information. A function can also be provided here that maps the required degree of oversteering stiffness to the at least one limit frequency.

According to one exemplary embodiment, the second controller unit has an absolute value characteristic that falls monotonously above a limit frequency and/or a control behavior in accordance with a PT1 controller. Such a controller behavior or this type of controller is advantageously suitable for the interactive control of the vehicle through influences of the driver and the driver assistance system.

According to a further aspect, the invention relates to a method for controlling an electromechanical steering system of a vehicle Driving assistance system that provides first steering control information and a control unit with at least one first controller unit, wherein the control unit receives driver moment information that the human driver applies to the steering device, and receives at least one piece of adjustment information dependent on the driving state and/or the driving situation, wherein the control unit receives a second providing steering control information dependent on the driver moment information and the at least one adjustment information and the system modifying the steering system of the vehicle based on the first and second steering control information

Provides steering control information based on which a steering movement is performed on the electromechanical steering system.

The terms “approximately”, “substantially” or “roughly” mean deviations from the exact value by +/-10%, preferably by +/-5% and/or deviations in the form of changes that are insignificant for the function .

Further developments, advantages and possible applications of the invention also result from the following description of exemplary embodiments and from the figures. All of the features described and/or illustrated are fundamentally the subject matter of the invention, either alone or in any combination, regardless of how they are summarized in the claims or how they relate back to them. The content of the claims is also made part of the description.

The invention is explained in more detail below with reference to the figures of exemplary embodiments. Show it:

1 shows an example of a schematic representation of a first embodiment of a system for controlling an electromechanical steering system of a vehicle, the electromechanical steering system being controlled by the driver assistance system by means of moment information; and 2 shows an example of a schematic representation of a second embodiment of a system for controlling an electromechanical steering system of a vehicle, wherein the electromechanical steering system is controlled by the driver assistance system by means of desired steering angle information.

FIG. 1 shows, by way of example and schematically, a block diagram of a first exemplary embodiment of a system 1 which is used to control a steering system 2 with an electromechanical drive (EPS: electric power steering). In a steering system 2 of this type, a program-controlled electric servomotor supports the steering movements of the driver or, in the case of autonomous or semi-autonomous driving, carries out at least some of its own steering movements.

The steering system 2 according to the first exemplary embodiment has a torque interface, i.e. the steering system 2 is designed to receive, as input information, torque information for the servomotor of the steering system 2 or information proportional to the torque, for example information regarding the current through the servomotor of the steering system 2 to obtain.

The system 1 has a driver assistance system 3 that provides a first item of steering control information L1 at an output interface. The driver assistance system can, for example, have an environment recognition unit 3.1, which creates an environment model in the vehicle area by means of a sensor system. Furthermore, the driver assistance system 3 can have a trajectory planner unit 3.2. The trajectory planner unit 3.2 is coupled at least indirectly to the environment recognition unit 3.1 and is designed to receive information from the environment recognition unit 3.1 and to plan travel trajectories based thereon. In addition, the driver assistance system 3 preferably has a trajectory following control 3.3. This is coupled at least indirectly to the trajectory planner unit 3.2 and is designed to calculate control information for the vehicle in order to move the vehicle on a calculated and selected travel trajectory. The output information of the trajectory following control 3.3 is preferably a target steering angle cpsoii, which is used to drive along a selected travel trajectory.

The driver assistance system 3 preferably also has a steering angle controller 3.4. This steering angle controller 3.4 is coupled at least indirectly to the trajectory following control 3.3 and receives control information from this trajectory following control 3.3, in particular the setpoint steering angle. The steering angle controller 3.4 is preferably designed to provide torque information for the servomotor of the steering system 2 or information proportional to the torque, for example information regarding the current through the servomotor of the steering system 2, as a setpoint specification. In addition, the steering angle controller 3.4 can be designed to suppress disruptive effects such as an oscillating steering behavior. The steering angle controller 3.4 preferably provides the first item of steering control information L1.

At least some of the aforementioned units 3.1 to 3.4 of the driver assistance system 3 can be connected to a unit 7, as indicated by the vertical arrows in FIG. The unit 7 can, for example, be a functional component of the driver assistance system 3 , ie it can be provided in a control unit of the driver assistance system 3 or else in a control unit which is separate from the driver assistance system 3 . The unit 7 can also have means for observing the driver in order to record and process the behavior of the driver, the direction in which he is looking and/or his actions in order to be able to draw conclusions about future driving commands from the driver. The system 1 also has a control unit 4 which is designed to provide a second piece of steering control information L2. The system 1 uses the second item of steering control information L2 to modify the first item of steering control information L1 in such a way that the third, modified item of steering control information L3 created by the modification enables improved cooperative driving, in which the human driver, depending on the driving state and/or the driving situation, even when the driving assistance function is activated, one Lateral control of the vehicle causes greater freedom to participate in the control of the vehicle, so that the impression of externally determined driving behavior is reduced depending on the driving state and/or the driving situation.

The control unit 4 has a first interface S1, which is designed to receive driver moment information M. The driver torque information M is torque information or a variable that is proportional to this torque information and indicates what torque the driver applies to the steering device of the vehicle.

The driver moment information M is preferably first subjected to an absolute value formation using an absolute value unit 4.1. A sign-independent driver moment information |M| provided.

It should be noted that in the exemplary embodiment shown, a counting arrow system was selected in which a positive driver torque is defined in such a way that it has the same effect as a positive motor torque of the electromechanical steering system 2 or as a positive steering angle, which usually indicates cornering to the left.

The control unit 4 also has a second interface S2, at which first and second adjustment information A1, A2 are provided. The first and a second piece of adjustment information A1 , A2 are preferably provided by the unit 7 . At least one of the pieces of adjustment information A1, A2 is a variable dependent on the driving state and/or driving situation, ie dependent The first and/or second adjustment information A1, A2 is changed based on the driving condition or the driving situation that the unit 7 recognizes. The first and second pieces of adjustment information A1, A2 are preferably adjusted as a function of the driving state and/or the driving situation.

The first adjustment information A1 is preferably a driver torque threshold value, i.e. a threshold value for torque information or a variable proportional to this torque information. The first adjustment information A1 is used in the control unit 4 to define a threshold which, when exceeded, is intended to enable the driver to influence the steering behavior specified by the driver assistance system 3 . For this purpose, the sign-independent driver moment information |M| and the first adjustment information A1 fed to a subtraction point 4.2, which provides moment difference information DM on the output side.

The torque difference information DM is supplied to a first controller unit 5 as input information. This receives the second adjustment information A2 as further input information. The controller unit 5 has the effect of a limiting controller, in such a way that by adapting the control behavior of the first controller unit 5 using the second adaptation information A2, the hardness can be adjusted by means of which the steering behavior specified by the driver assistance system can be overridden by the driver. In other words, the first controller unit 5 specifies the torque that the driver has to apply to the steering wheel, above which the driver assistance system becomes increasingly flexible with regard to a different direction desired by the driver. The degree of this compliance is defined by the adjustment information. In other words, the severity of the steering resistance that the driver feels when oversteering the steering input from the driver assistance system is variably adjusted. The second piece of adjustment information A2 is therefore also referred to below as “oversteering stiffness”. The control behavior of the first control unit 5 is changed based on the second adjustment information A2. In particular, the controller gain within the first controller unit 5 is influenced by the second adjustment information A2. One or more amplification factors of the first controller unit 5 are influenced in such a way that the desired oversteering stiffness is achieved.

For example, there is a reciprocal dependency between the second adjustment information A2 and the control loop gain in the first controller unit 5, i.e. a higher second adjustment information A2 or oversteering stiffness results in lower controller gains and vice versa. In other words, a required lower oversteering stiffness is mapped to a higher controller gain of the first controller unit 5 and vice versa. In the first extreme case, with maximum second adjustment information A2 or maximum oversteering stiffness, the control loop gain becomes zero, i.e. the control unit 4 is virtually inactive as a result and the oversteering stiffness is determined exclusively or almost exclusively by the interference suppression property of the steering angle controller 3.4.

In the second extreme case of minimal second adjustment information A2 or minimal oversteering stiffness, the controller gains assume high values. In terms of their amount, these are only limited, for example, by the effort invested in the design and implementation of stabilization measures.

If the oversteering stiffness is low, the driver perceives the assistance system to be more flexible and less commanding when driving cooperatively. Especially with a predetermined low oversteering stiffness, an adjustment of the cut-off frequencies of the first controller unit 5 may be necessary due to the higher loop gain in order to comply with stability criteria. The adjustment of the filter limit frequency(s) of the first controller unit 5 is preferably also based on the second adjustment information A2.

The control unit 4, in particular the first regulator unit 5, preferably has a saturation function. For example, the saturation function is like this selected that the maximum value of the output information of the first controller unit 5 or the maximum value of the second steering control information L2 is limited.

The amount of the output information of the first controller unit 5 is thus limited by the saturation function in definable thresholds. The definition of these thresholds represents a further degree of freedom for the design of the oversteering behavior. The thresholds can have a defined fixed value or can also be designed depending on the driving situation. Low thresholds allow the counter-torque for the driver to increase again from a certain degree of oversteering. The reason is that with a comparatively low threshold, the amount of first steering control information L1 exceeds the second steering control information L2 from a certain degree of oversteering and the modified steering control information L3 formed by summation point 8 thus increasingly represents the desire of the driver assistance system, which the driver sees as Disturbance of the control circuit corrected. As a result, the counter-torque for the driver increases again. One application is that the driver torque is initially relatively low when the desired deviation from the specification of the driver assistance system is small and only increases when the desired deviation is larger, whereby a tolerance zone for the oversteering is haptically transmitted to the driver.

High limiting thresholds for the second item of steering control information L2 mean that the first item of steering control information L1 can be overruled. The modified steering control information L3 thus increasingly represents the driver's intention to oversteer, and the control objective of the driver assistance system is pushed further and further back. As a result, the required steering torque for a steering maneuver can be smaller than is necessary without a driver assistance function. An application for this is e.g.

The output information provided by the first controller unit 5 is then multiplied by the sign of the driver's moment, as is shown in Fig. 1 is represented by the "sign" block. The “sign” function determines the sign of the driver moment information M, and the second steering control information item L2 is formed by multiplying the output information of the first controller unit 5 by the sign of the driver moment information M. The result of this is that the control unit 4 provides steering control information L2, independently of the steering direction, which is directed in such a way that the driver's torque is reduced.

The second steering control information L2 is transmitted to an addition point 8. FIG. There, the second steering control information L2 and the first steering control information L1 are added and the third steering control information L3 is provided. It goes without saying that in the case of an inverted counting arrow system, the addition point 8 can be replaced by a subtraction point, which results in a functionally identical system.

The third item of steering control information L3 is fed to a safety barrier SB, which provides fourth item of steering control information L4 on the output side. The safety barrier SB is a unit that monitors and actively limits the manipulated variable before it is physically taken into account in terms of absolute height and gradient.

The safety barrier SB is configured, for example, to monitor the modified steering control information L3 with regard to compliance with safety goals and, if necessary, to modify it if the safety goals are not being met. For example, the absolute level of the modified steering control information L3 and its gradient can be monitored and, if necessary, also actively limited.

The fourth steering control information L4 forms the input variable of the electromechanical steering system 2. Depending on the driver moment information M, and the first and second adjustment information A1, A2, the first controller unit 5 generates a second steering control information L2, which changes the first steering control information L1 generated by the driver assistance system 3, so that the driver influences steering system 2 of the vehicle, which is dependent on first and second adjustment information A1, A2.

As indicated by the arrows running from the driver assistance system 3 and from the steering system 2 upwards to the unit 7, information from the functional units 3.1 to 3.4 of the driver assistance system 3 and the electromechanical steering system 2 can be used to record the driving condition or the driving situation.

FIG. 2 shows, by way of example and schematically, a block diagram of a second exemplary embodiment of a system 1 that is used to control a steering system 2 with an electromechanical drive.

The steering system 2 according to the second exemplary embodiment has an angle interface, i.e. the steering system 2 is designed to receive angle information, in particular setpoint steering angle information cpsoii, as input information. In this case, the steering angle controller is preferably integrated into the steering system 2 . The driver assistance system 3 provides the setpoint steering angle information cpsoii as first steering control information L1 at an output interface.

The driver assistance system in turn has, for example, an environment detection unit 3.1, which creates an environment model in the vehicle area by means of a sensor system. Furthermore, the driver assistance system 3 can have a trajectory planner unit 3.2. The trajectory planner unit 3.2 is coupled at least indirectly to the environment recognition unit 3.1 and is designed to receive information from the environment recognition unit 3.1 and to plan travel trajectories based thereon.

In addition, the driver assistance system 3 preferably has a trajectory following control 3.3. This is coupled at least indirectly to the trajectory planner unit 3.2 and is designed to calculate control information for the vehicle in order to move the vehicle on a calculated and selected travel trajectory. the In the exemplary embodiment shown, output information of trajectory following control 3.3 is first steering control information L1 in the form of setpoint steering angle information cpsoii, according to which a selected travel trajectory is traveled.

At least some of the aforementioned units 3.1 to 3.3 of the driver assistance system 3 can, as indicated by the vertical arrows in FIG. 2, be connected to a unit 7, by means of which a driving state detection or driving situation detection is provided. The unit 7 can, for example, be a functional component of the driver assistance system 3, i.e. it can be provided in a control unit of the driver assistance system 3 or else in a control unit that is separate from the driver assistance system 3. The unit 7 can also have means for observing the driver in order to record and process the behavior of the driver, the direction in which he is looking and/or his actions in order to be able to draw conclusions about future driving commands from the driver.

The system 1 in turn has a control unit 4 which is designed to provide a second piece of steering control information L2. The system 1 modifies the first steering control information L1 by means of the second steering control information L2 in such a way that by means of the modified steering control information L3 resulting from the modification, improved cooperative driving, in which the human driver, depending on the driving state and/or driving situation, is provided with an activated driving assistance function, which provides lateral control of the Vehicle causes greater freedom in the participation of the control of the vehicle is granted, so that the impression of externally determined driving behavior depending on the driving status and / or driving situation is reduced.

The interfaces S1 and S2 of the control unit 4 and the processing of the information received at the interfaces S1 and S2 by the amount unit 4.1 and the first controller unit 5 is identical to the first exemplary embodiment according to FIG 1, so that reference is made to the previous statements. These also apply in the same way to the exemplary embodiment in FIG.

A significant difference from the exemplary embodiment according to FIG. 1 is that in the exemplary embodiment according to FIG. 2 the second steering control information L2 is not provided directly by the first controller unit 5, but the first controller unit 5 provides an activation factor AF.

The control unit 4 also has a subtraction point 4.2. On the one hand, this subtraction point 4.2 is supplied with a target value, in the exemplary embodiment shown the target value “0” and torque information D1 of the electromechanical steering system 2. The torque information D1 corresponds, for example, to the requested actuating torque of the steering angle controller of the electromechanical steering system 2 or also to a current that is directly proportional to the requested current through the servomotor. The total torque derived from the resulting actual motor current can also be used for this purpose after deduction of the torque or current requirements by the other functions on the control unit of the electromechanical steering system 2 .

At the subtraction point 4.2, the torque information D1 is subtracted from the setpoint. The result of this difference is modified based on the activation factor AF. In particular, the output information of the subtraction point 4.2 is multiplied by the activation factor AF and the result of the multiplication is supplied to the second controller unit 6 as input information. The activation factor is preferably a rational number in the range between 0 and 1 (AF e [0,1]). The activation factor is influenced by driver moment information M and first and second adjustment information A1, A2. A value of "0" means that the driver perceives hard steering, ie cooperative driving is strongly suppressed. A value of “1”, on the other hand, means that the steering system 2 allows the driver to participate to a large extent and the steering requirements of the driver assistance system 3 are weighted less in comparison. The second controller unit 6 receives the difference weighted with the activation factor AF. The second controller unit 6 is designed, for example, as a torque control loop. The second controller unit 6 is preferably designed as a PT1 controller.

In a preferred embodiment, the second controller unit 6 is linked to the first controller unit 5 in that the first controller unit 5 generates an activation factor AF with a value between 0 and 1 at its output interface, with which the control difference of the second controller unit 6 is scaled. Without driver interaction, the first controller unit generates an activation factor of 0, as a result of which the torque information of the steering system 2, in particular of the steering angle controller of the steering system 2, is not fed back. When the driver interaction is present, the first controller unit 5 generates an activation factor AF greater than 0 depending on the first and second adjustment information A1, A2. The contribution of the second adjustment information A2 (i.e. the oversteering stiffness) to the activation factor AF is preferably such that a higher second adjustment information A2 , i.e. a higher oversteering stiffness causes a smaller activation factor AF at the output interface of the first controller unit 5.

The contribution of the deviation of the driver moment information M from the first adjustment information A1 (i.e. the driver moment threshold) to the activation factor AF is designed in such a way that the activation factor AF becomes greater the further the driver moment information M exceeds the first adjustment information A1, i.e. the activation factor AF becomes all the greater, the greater the driver torque residue.

Preferably, the contributions made by the adjustment information to achieve a desired result can be weighted and, in particular, subjected to a minimum operation. In this case, weighting factors k1, k2 are used, which offer degrees of freedom in the design of the first controller unit. The second piece of adjustment information A2 preferably assumes values in the range between 0 and 1.

With the assignment

DM=min(1,max(0,(|M|−A1))) where DM is the torque difference (as input information of the first controller unit 5), |M| is the amount of the driver torque information and A1 is the first adjustment information (driver torque threshold value), and the impulse response g(t) of the first controller unit 5, with which the torque difference DM is convoluted (convolution operator ^* ) is obtained for the adaptation factor AF:

AF(t) = min (1 , max (0, (min(k1 (AM(t) ^* g(t)), k2 (1 - A2(t))))))

As shown in FIG. 2, the second adjustment information A2 can also be used to influence the control behavior of the second control unit 6. For example, the second adjustment information A2 can be used to increase the controller gain of the second controller unit 6 when the second adjustment information A2 decreases. Depending on the stability reserve, it can be advantageous to also adjust the parameters of the second controller unit 6 that determine the frequency response at the same time, for example in the form of a shift in pole and/or zero points.

In the exemplary embodiment according to FIG. 2 , the driver interaction can also be adjusted as a function of the current driving situation using only the first adjustment information A1 , only the second adjustment information A2 or a combination of both adjustment information A1 , A2 . If only one of the two items of adjustment information A1, A2 is changed dynamically as a function of the driving condition or the driving situation, the respective other item of adjustment information is opened set a fixed value. This value is preferably selected in such a way that, viewed on its own, it leads to an activation factor AF of 1, ie allows maximum dynamic driver intervention.

The second provided by the second controller unit 6

Steering control information L2 is transferred to an addition point 9. There, the second item of steering control information L2 and the first item of steering control information L1 are added, thereby providing modified item of steering control information L3.

The third item of steering control information L3 is preferably in turn fed to a safety barrier SB, which provides fourth item of steering control information L4 on the output side. The safety barrier SB is a unit that monitors and actively limits the manipulated variable before it is physically taken into account in terms of absolute height and gradient.

The fourth steering control information L4 forms the input variable of the electromechanical steering system 2. Depending on the driver moment information M and the first and second adjustment information A1, A2, the second controller unit 6 generates a second steering control information L2, which changes the first steering control information L1 generated by the driver assistance system 3, so that a dynamic influence of the driver on the steering system 2 of the vehicle that is dependent on the first and second adjustment information A1, A2 is possible.

The operation of the control unit 4 is such that the control unit 4, for example, a target value of torque information Dl an angle controller of the electromechanical steering system 2 and depending on the magnitude of the torque difference DM and the second adjustment information A2, this torque difference DM is reduced with the aid of the second controller unit 6. For this purpose, the second controller unit 6 generates a second item of steering control information L2 (steering angle bias signal), which is added to the first item of steering control information L1 provided by the trajectory following control 3.3. As a result, a control loop is formed which increasingly reduces the torque difference DM.

As indicated by the arrow running upwards from the steering system 2 to the unit 7, information from the electromechanical steering system 2 can also be used to record the driving condition or the driving situation.

As described above, the unit 7 is designed to recognize and evaluate the driving situation or the driving state. The unit 7 can also observe the driver, for example using a camera, and derive the driver's behavior from this. In particular, the unit can provide information as to whether the driver is being steered in the same direction as the specification of the driver assistance system or whether the driver is steering against the specification of the driver assistance system.

The unit 7 can, for example, react to driving situations or driving states or to the driver's behavior as follows:

- If the driver steers into a danger area, the counter-torque of the driver assistance system 3 should be clearly noticeable and act in the direction of the safe lane area. The amount of the first adjustment information A1 (driver torque threshold value) and the second adjustment information A2 (oversteering stiffness) assume high values;

- If the driver steers in the direction of the safe lane area, the driver should not be inhibited in this maneuver. The first adjustment information A1 (driver moment threshold) and the second Adaptation information A2 (oversteering stiffness) assumes low values in terms of absolute value.

- If the driver signals to the driver assistance system 3, for example via the Flandmoment, that there is a desire for cooperation, this should be possible with little steering torque effort, i.e. with low intensity. Examples of this would be the selection of an alternative driving route past an obstacle on the right instead of on the left, or the driver's desire for a constant lateral offset instead of an exact lane center guidance, which he communicates to the driver assistance system 3 via appropriate steering. In these cases, the first adjustment information A1 (driver torque threshold value) and the second adjustment information A2 (oversteering stiffness) assume low values in terms of absolute value.

- If the driver assistance system 3 reaches the limits of the electromechanical steering system when cornering and the driver would like to support the lateral lateral guidance in order to prevent the vehicle from leaving the curve, this should not appear to the driver as countersteering with the result of a high counter-torque expressed on the steering wheel, but as a support steering. With this type of assisted steering, the driver only has to apply a portion of the steering force that remains after deducting the maximum steering force of the electromechanical steering system that is due to the limitation. The first adjustment information A1 (driver torque threshold value) and the second adjustment information A2 (oversteering stiffness) assume high values in terms of amount, so that the control unit 4 leaves the first steering control information L1 unchanged and this remains unchanged or almost unchanged (i.e. the second steering control information is zero or very small) via the safety barrier SB to the electromechanical steering system 2.”

If the driver performs an evasive emergency steering maneuver (e.g. characterized by a high steering angle speed), which the If the emergency steering assistance function has not yet triggered (or because this is not part of the assistance functionality), the steering torque directed towards the driver by the steering angle controller of the electromechanical steering should be very small so as not to impede the driver in his evasive manoeuvre. In this case, first adjustment information A1 (driver torque threshold value) and second adjustment information A2 (oversteering stiffness) assume low values in terms of absolute value.

- If the driver carries out an evasive emergency steering maneuver (e.g. characterized by a high steering angle speed) which does not yet trigger the emergency steering assistance function (or because this is not part of the assistance functionality), the driver can also receive active steering assistance by using the controller unit 5 does not limit or only limits at high values of the output signal.

- When the emergency steering assistance function is activated (i.e. when the driver assistance system performs an evasive emergency steering maneuver), first adjustment information A1 (driver torque threshold value) and second adjustment information A2 (oversteering stiffness) are set to high values as long as the driver steers less than it corresponds to the specification of the optimal avoidance trajectory. This optimal evasion trajectory is characterized by the fact that the vehicle can drive past the obstacle with a safe distance, without putting too much strain on the adhesion potentials on the wheels and causing vehicle instability.

- When the emergency steering assistance function is activated, the amount of first adjustment information A1 (driver torque threshold) and second adjustment information A2 (oversteering stiffness) is set to high values if the driver steers more dynamically than the specification of a determined limit evasion trajectory. This limit avoidance trajectory is defined by the fact that the vehicle This trajectory will be far away from the obstacle, but at the same time there is a high probability that it will lose traction and become unstable.

- When the emergency steering assistance function is activated, the amount of first adjustment information A1 (driver torque threshold) and second adjustment information A2 (oversteering stiffness) is set to low values if the driver selects a trajectory through his steering maneuver that is between the optimum and the limit -Avoidance trajectory lies. The optimal avoidance trajectory and the limit avoidance trajectory are continuously re-determined and the driver's action is re-evaluated in each case.

- In the case of roadway narrowings, particularly at construction sites, the probability of a necessary correction of the driven trajectory through intervention by the driver tends to be greater due to the sometimes poorer quality of the roadway markings located there. In order to ensure the correction by the driver with little steering effort, the amount of first adjustment information A1 (driver torque threshold value) and second adjustment information A2 (oversteering stiffness) is set to low values when the lane width is narrow or roadworks are detected.

- In general, if the quality of the road markings is lower, the probability of a necessary correction of the lane driven by the driver's intervention increases. In order to ensure correction by the driver with as little steering effort as possible, first adjustment information A1 (driver torque threshold value) and second adjustment information A2 (oversteering stiffness) are again set to low values

If the vehicle threatens to leave the lane due to inattention on the part of the driver, the assistance system first intervenes and begins to bring the vehicle into the safe lane area, but the driver then takes over full control, the steering torque felt should at no time oppose the driver's steering intention, provided that the trajectory selected by the driver will not lead to a predicted instability of the vehicle . Under this condition, the amount of first adjustment information A1 (driver torque threshold value) and second adjustment information A2 (oversteering stiffness) is set to low values.

- If the driver has selected a sporty driving mode (if this option is provided in the vehicle equipment), the steering should provide more feedback. In line with this, the commanding torque should also be higher when the driver countersteers. The amount of first adjustment information A1 (driver torque threshold value) and second adjustment information A2 (oversteering stiffness) is set to high values.

The first adjustment information A1 (driver torque threshold value) is preferably designed as a function of internal control error variables of the lateral control, for example as follows:

- The greater the lateral distance of the vehicle from the target trajectory, the higher the first adjustment information A1;

- The first adjustment information A1 is higher, the greater the difference between the actual steering wheel angle and the target steering wheel angle;

- The first adjustment information A1 is higher, the greater the difference between the actual yaw rate and the target yaw rate.

The second adjustment information A2 (oversteering stiffness) is preferably also designed as a function of internal control error variables of the lateral control, specifically as follows, for example:

- The second adjustment information A2 is higher, the greater the lateral distance of the vehicle from the target trajectory; - The second adjustment information A2 is higher, the greater the difference between the actual steering wheel angle and the target steering wheel angle;

- The second adjustment information A2 is higher, the greater the difference between the actual yaw rate and the target yaw rate.

Furthermore, the first and second adjustment information A1, A2 is preferably selected to be smaller if the driver steers against the specification of the driver assistance system and selects an alternative route that does not result in less driving safety.

Conversely, the first and second adjustment information A1, A2 are preferably selected to be larger if the driver has the same vehicle guidance goal as the driver assistance system or if the driver's alternative route leads or will lead to less driving safety. The driving safety can be evaluated by an expert system on the basis of the predicted collision probability and the predicted loss of adhesion potential at the wheels.

Like the unit 7 , the control unit 4 can be present, for example, on a control unit of the driver assistance system 3 . As an alternative to this, the control unit 4 can also be implemented on the control device of the electromechanical steering system 2 . For this purpose, for example, the interface between the control unit of the driver assistance system 3 and the control unit of the electromechanical steering system 2 is expanded for the transmission of the first and second adjustment information A1, A2.

The system 1 can advantageously also have one or more of the following functionalities:

If switching between discrete values for the first and second adjustment information A1, A2 should be provided, the values may need to be smoothed/interpolated before the conversion by the control unit 4 in order to avoid an unwanted jerk in the steering wheel. Preferably they have first and second adjustment information A1, A2 have a continuous character and are determined, for example, by fuzzy logic operations.

If there are conflicting requirements of the rules of influence on the fleas of the driver moment, e.g. an activation of the emergency avoidance assistant with a high value for the first adjustment information A1 within a construction site area, in which in principle a low first adjustment information A1 should be selected, this can be done, for example, by an arbitrator unit in of the driving status detection.

The driver moment can also be influenced, for example, by the control unit 4 replanning the target trajectory as a function of the steering activity of the driver, instead of the limitation regulation described above. The planning of a trajectory, which leads e.g. exactly along the lane chosen by the driver, results in a counter-torque of 0 Nm for the driver, neglecting the initial states of the controller. Planning a trajectory to the right or left of the trajectory currently being driven leads to a steering recommendation to the right or left.

The disadvantage of this approach is that in the course of replanning, the initial states of the controller (e.g. the I component in the steering angle controller) have to be reduced in a targeted manner, meaning that measures are not just left at the planning level. Furthermore, the effort to achieve seamless transitions and thus a constant steering torque curve is higher with this approach.

A new trajectory due to driver steering, which leads to less driver steering torque, also implicitly becomes part of a control loop, so that additional precautions on the part of trajectory planning are necessary to ensure stability, especially with regard to the generally larger latency between a triggered one rescheduling and the impact on driver momentum. In the case of emergency steering maneuvers in which the driver must not be impeded, the trajectory would have to be replanned in each scanning step (e.g. every 10 ms). of the currently impressed vehicle movement by the driver. This is associated with a high computational effort and yet cannot eliminate angle controller components with a damping character. If, instead, the first or second adjustment information A1, A2 with the value “0” is selected, an inhibiting contribution of zero can be achieved at the torque interface to the electromechanical steering system 2 by the angle control. In the case of a steering angle interface to the electromechanical steering system 2, the inhibition by the angle controller can be greatly reduced in practice with adaptation factors A1, A2 from zero down to low residual torques. A coordinated overall behavior can only be achieved from the interaction of driver torque limitation and a new trajectory planning.

The second adjustment information A2 (oversteering stiffness) can also be implicitly influenced in that the first adjustment information A1 (driver torque threshold value) is controlled as a function of the steering wheel deflection. However, the effort to ensure stability is also higher here.

The method described can also be used if, instead of a steering angle specification for the steering system 2, a yaw rate or curvature specification takes place. Instead of a steering angle bias, the control unit 4 then generates correction variables for the target yaw rate or target curvature.

In a driver assistance system 2 based on an angle interface to the electromechanical steering system 2, the actual steering wheel angle can also be used within the first control unit 4 in order to limit the driver torque more dynamically when oversteering. For this purpose, in an intermediate step, the target steering angle is mixed proportionally with the actual steering angle at a driver torque above the first adjustment information A1, until the target steering angle ultimately corresponds to the actual steering angle as the driver torque information M continues to rise. As a result, the control difference of the steering angle controller of the electromechanical steering system 2 becomes zero and the torque requirement for the servomotor of the steering system 2 cannot initially continue to rise. In order to discharge the controller integral components in the steering angle controller of the electromechanical steering system 2, however, a negative feedback of the torque request using the second controller unit is still required.

In a driver assistance system 2 based on an angle interface to the electromechanical steering system 2, the setpoint torque information of the steering angle controller minus a defined proportion can be taken into account within the control unit 4 instead of feeding back the entire setpoint torque information of the steering angle controller in the fixed value control. This proportion is then to be defined on the basis of the first and second adjustment information A1, A2. If the second adjustment information (oversteering stiffness) is high or if the driver torque information M is still low, this proportion is selected to be high. If the driver moment information M increases or if less second adjustment information A2 (oversteering stiffness) is required, this proportion is selected to be small with the end value of 0. This procedure can be

Steering angle controller implementations on the steering system 2 with high dynamics may be required, since otherwise the steering angle setpoint torque working against the driver is completely reduced too early and the second adjustment information A2 (oversteering stiffness) is perceived as too low. Alternatively, the subtraction of a portion of the steering angle setpoint torque can also be converted into a corresponding setpoint value of the second controller unit.

The invention has been described above using exemplary embodiments. It goes without saying that numerous changes and modifications are possible without leaving the scope of protection defined by the patent claims. reference list

1 system

2 steering system

3 driver assistance system

3.1 environment recognition unit

3.2 trajectory planner unit

3.3 Trajectory tracking control

3.4 Steering angle controller

4 control unit

4.1 Amount Unit

4.2 Subtraction point

5 first controller unit

6 second controller unit

7 unit

8 addition point 9 addition point

A1 first fitting information

A2 second fitting information

AF activation factor

Dl torque information

L1 first steering control information

L2 second steering control information

L3 third/modified steering control information

L4 fourth steering control information

M driver moment information

DM torque difference

51 first interface

52 second interface

SB safety barrier cpsoii target steering angle information

Claims

patent claims

1) System for controlling an electromechanical steering system (2) of a vehicle, comprising a driver assistance system (3) which is designed to generate a first piece of steering control information (L1) and a control unit (4) with at least one first control unit (5), the control unit ( 4) a first interface (S1) for receiving

driver moment information (M), and at least one second interface (S2), which is designed to receive at least one piece of adjustment information (A1, A2) dependent on the driving condition and/or the driving situation, the control unit (4) being designed to provide second steering control information (L2) which is dependent on the driver moment information (M) and the at least one piece of adjustment information (A1, A2) and that the system (1) is designed to provide the steering system (2) of the vehicle based on the first and second steering control information (L1, L2) to provide modified steering control information (L3), based on which a steering movement on the electromechanical steering system (2) is carried out.

2) System according to claim 1, characterized in that the first steering control information (L1) is an angle information, torque information for the servomotor of the electromechanical steering system (2) or the torque of the servomotor of the electromechanical steering system (2) is proportional information.

3) System according to claim 1 or 2, characterized in that a first piece of adjustment information (A1) is a driver torque threshold value and wherein the control unit (4) is designed to, if the amount of driver torque information (M) is above the driver torque threshold value, second steering control information (L2) to generate, which causes a modification of the first steering control information (L1) provided by the driver assistance system. 4) System according to any one of the preceding claims, characterized in that second adjustment information (A2) is oversteering stiffness information, which is a measure of the steering resistance that the driver applies to the steering device for oversteering the steering behavior specified by the driver assistance system (3). has overcome.

5) System according to claim 4, characterized in that the control unit (4) is designed to adapt the control behavior of the first control unit (5) of the control unit (4) based on the second adjustment information (A2).

6) System according to any one of the preceding claims, characterized in that the control unit (4) is designed to receive a first and a second piece of adjustment information (A1, A2), wherein either one of the two pieces of adjustment information (A1, A2) has a fixed value and the other adjustment information has a value that is dependent on the driving state or driving situation, or the first and second adjustment information items (A1, A2) are both dependent on the driving state or driving situation.

7) System according to any one of claims 3 to 6, characterized in that the control unit (4) is designed such that the first controller unit (5) receives a torque difference (DM) which is zero when the amount of driver torque information (M) is less than or equal to the driver torque threshold and has an amount of driver torque information reduced by the driver torque threshold as soon as the amount of driver torque information exceeds the driver torque threshold.

8) System according to any one of the preceding claims, characterized in that the first controller unit (5) has a magnitude characteristic that falls monotonously above a limit frequency.

9) System according to claim 8, characterized in that the first controller unit (5) has a control behavior according to a PT1 controller. 10) System according to any one of the preceding claims, characterized in that the first controller unit (5) has a control behavior such that by modifying the first steering control information (L1) by the second steering control information (L2) that of the first controller unit (5) as an input variable supplied torque difference (DM) is reduced.

11) System according to any one of the preceding claims, characterized in that in the event that the first steering control information (L1) is angle information, yaw rate information or curvature information, a second controller unit (6) is provided, which is designed to provide setpoint torque information of the steering angle controller for the servomotor of the electromechanical steering system (2) or information proportional to this setpoint torque information into steering angle information, yaw rate information or curvature information as second steering control information (L2).

12) System according to claim 11, characterized in that the second controller unit (6) is designed to receive weighted setpoint torque information from the steering angle controller for the servomotor of the electromechanical steering system (2) with an activation factor (AF), the activation factor (AF) is provided by the first controller unit (5).

13) System according to any one of claims 11 or 12, characterized in that the second controller unit (6) is designed to receive the second adjustment information (A2) and the control behavior of the second controller unit (6) based on the second adjustment information (A2) is adjusted.

14) System according to any one of claims 11 to 13, characterized in that the second controller unit (6) has a magnitude characteristic that falls monotonically above a limit frequency and/or has a control behavior in accordance with a PT1 controller. 15) A method for controlling an electromechanical steering system (2) of a vehicle comprising a driver assistance system (3) that provides first steering control information (L1) and a control unit (4) with at least one first controller unit (5), the control unit (4) driver moment information (M) receives the human driver at the

Steering device applied and receives at least one item of adjustment information (A1, A2) dependent on the driving condition and/or the driving situation, with the control unit (4) providing second steering control information (L2) which is derived from the driver moment information (M) and the at least one item of adjustment information (A1 , A2) is dependent and that the system (1) dem

Steering system (2) of the vehicle based on the first and second steering control information (L1, L2) provides a modified steering control information (L3), based on which a steering movement on the electromechanical steering system (2) is completed.