Method for operating a steering unit during an assisted driving process, computer program product and vehicle

Abstract

Method (100) for operating a steering unit (10) of a vehicle (1) during a driving process assisted by a driver assistance module (21), wherein the steering unit (10) comprises a steering actuator (11) for setting a steering angle (200) of the vehicle (1) and a steering means (12) for influencing the steering angle (200) by manual steering, comprising: - Define (101) a target trajectory (201) of the driver assistance module (21) for the vehicle (1), - Determining (102) a target position (202) of the steering angle (200) depending on the target trajectory (201), - Determining (103) an amplification parameter (203) for the steering actuator (11) as a function of the target position (202), - Determining (104) a target state parameter (211) for a driving state of the vehicle (1) as a function of the target trajectory (201), - Determining (105) an actual state parameter (212), - Determining (106) a steering parameter (205) to achieve the target position (202) based on the amplification parameter (203) depending on the target state parameter (211) and the actual state parameter (212), - Output (107) of the steering parameter (205) to control the steering unit (10), wherein the determination (104) of the target state parameter (211) depending on a vehicle model (210) is performed to simulate the target state parameter (211) for the vehicle state depending on the target trajectory (201), wherein the steering actuator (11) is a reset actuator for resetting the steering means (12) and / or the steering actuator (11) to a target center position (202.1), wherein the target center position (202.1) is defined depending on the target position (202).

Description

[0001] The invention relates to a method for operating a steering unit of a vehicle during an assisted driving process, a computer program product and a vehicle.

[0002] Driver assistance systems in which an electronic controller intervenes in a vehicle's steering system are known from the prior art. For example, lane keeping assist systems are known, which constitute a safety and assistance system in vehicles to help the driver prevent unintentional lane departures. If a lane keeping assist system detects that the vehicle is tending to unintentionally leave its lane, the system intervenes in the steering. This can be done by making slight steering corrections to gently guide the vehicle back to the center of the lane.

[0003] With such driver assistance systems, manual intervention by the driver is usually possible or explicitly provided for. This allows adjustments to the steering system to influence both the driver assistance system and the driver's steering feel. Documents WO 2020 / 050759 A1 and DE 10 2019 119 572 A1 disclose systems for providing feedback to the driver, intended to improve the driving feel. However, this primarily concerns the haptics of the steering wheel based on feedback.

[0004] Another factor influencing steering feel is the steering assist, which defines the relationship between the steering wheel and the rack position of the respective steering actuator. However, tailoring this assist to the driver's steering feel can lead to reduced performance of the driver assistance system in certain operating ranges, resulting in less accurate execution of the intended trajectory. This can occur, for example, when only a low steering assist is selected. Conversely, if the steering assist is set too high, it can negatively impact the steering feel in other operating ranges, such as when oversteering beyond the intervention of the driver assistance system.

[0005] Steering systems are also known from documents DE 10 2014 200 994 A1 and DE 10 2016 215 724 A1.

[0006] It is an object of the present invention to at least partially overcome the aforementioned disadvantages known from the prior art. In particular, it is an object of the present invention to improve the coordination between the steering feel when manually steering the vehicle and the accuracy when following a desired trajectory.

[0007] The foregoing problem is solved by a method with the features of claim 1, a computer program product with the features of claim 7, and a vehicle with the features of claim 8. Further features and details of the invention will become apparent from the respective dependent claims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the computer program product and / or the vehicle according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always includes, or allows for, reciprocal reference.

[0008] According to a first aspect of the invention, a method for operating a vehicle's steering unit during a driving process assisted by a driver assistance module is provided. The steering unit comprises a steering actuator for setting the vehicle's steering angle and a steering device for influencing the steering angle by manual steering. The method comprises, in particular in the form of process steps: - Defining a target trajectory of the driver assistance module for the vehicle, in particular by the driver assistance module, - Determining a target steering angle position depending on the target trajectory, in particular by a vehicle control unit, - Determining a gain parameter for the steering actuator as a function of the target trajectory, preferably the target position, in particular by the control unit, - Determining a target state parameter for a driving state of the vehicle, in particular a current and / or regulated one, depending on the target position, especially by the control unit, - Determining an actual state parameter, preferably for the driving state, in particular by the control unit, - Determining a steering parameter to achieve the target position based on the amplification parameter as a function of the target state parameter and the actual state parameter, in particular by the control unit, - Output of the steering parameter to control the steering unit, especially by the control unit.

[0009] The vehicle can preferably be a motor vehicle, e.g., an electric vehicle. The control unit can comprise a processor and / or a microprocessor. Furthermore, the control unit can be at least partially or completely integrated into a central control unit of the steering system and / or the vehicle. However, it is also conceivable that the control unit is at least partially or completely integrated into one or more decentralized control units.

[0010] Assisted driving can be understood as a driving process of the vehicle that is at least partially or fully automated. This driving process can include, for example, driving along a section of road and / or changing lanes. The driver assistance module can be configured for assisted driving, in particular to perform adaptive lane guidance, curve assist, parking assist, and / or automated lane changes. Advantageously, the driver assistance module can be integrated into the control unit.

[0011] The steering angle preferably defines the vehicle's direction of travel. For example, the steering angle can be adjusted by a rack position on the steering unit. The steering actuator and the steering mechanism can be mechanically coupled or, for example, mechanically decoupled from each other in the form of a steer-by-wire system. The steering actuator can include a drive mechanism for changing the rack position to adjust the steering angle. For example, the steering actuator can include an electric motor and / or a steering gear for adjusting the steering angle. The steering mechanism preferably includes a steering wheel. Preferably, the steering unit has a calibration for generating a predefined steering response.

[0012] The target trajectory can preferably include a specification for a driving and / or steering trajectory of the vehicle. For example, the target trajectory can define a movement path for the vehicle as determined by the driver assistance system. To define the target trajectory, it can be calculated by the driver assistance module. However, it is also conceivable that the target trajectory, e.g., during straight-ahead driving, is at least partially specified by the driver assistance module. When determining the target position of the steering angle, an adjustment path of the steering actuator and / or the rack position to achieve the target trajectory can be calculated.

[0013] The amplification parameter can be understood as a control parameter for increasing the steering force when setting the target position. In particular, the amplification parameter can be used to define and / or influence the steering force of the steering actuator. The amplification factor can be determined directly as a function of the target trajectory or indirectly, for example, by taking the target position, which is based on the target trajectory, into account when determining the amplification factor.

[0014] To determine the target state parameter, it can be calculated, for example, as a function of the target rack position. The target state parameter can, in particular, be an expected value of a state parameter of the vehicle's driving state. For example, the vehicle's state parameter can include forces acting on the vehicle and / or acceleration, especially lateral acceleration. The target state parameter can preferably include a physical parameter of the vehicle's state when the target steering angle is reached and / or at an intermediate steering angle position during the adjustment to the target position. To determine the actual state parameter, it can be measured. Preferably, the determination of the actual state parameter and the determination of the target state parameter are performed continuously to capture dynamic changes in the driving state.

[0015] When controlling the steering unit, the steering actuator and / or the steering device can be controlled directly or indirectly. The steering parameter can, for example, include a target torque, in particular a target hand torque, when controlling the steering unit, i.e., in particular the steering actuator and / or the steering device. To achieve the target position, the target position, in particular, forms an input value for determining the steering parameter. The gain parameter can serve as the basis for determining the steering parameter. Furthermore, it can be provided that a comparison of the target state parameter and the actual state parameter is performed to determine the steering parameter. For example, the difference and / or a ratio between the target state parameter and the actual state parameter can be calculated to determine the steering parameter based on the gain parameter.When the steering parameter is output, the steering actuator can be controlled directly or indirectly based on the steering parameter. Controlling the steering unit can include direct control and / or regulation.

[0016] Thus, the method provides a steering parameter which, based on the target state parameter and the actual state parameter, is adjusted to the requirements of the current driving condition using the same steering actuator. Because the method is performed during the assisted driving process, manual steering can be carried out based on a predefined setting, for example, when the driver assistance module does not specify a target trajectory. It has therefore been recognized, in particular, within the scope of the present invention, that the target trajectory only requires a specific modification of the gain parameter under certain driving conditions, such as a slight curvature of the road, in order to increase the accuracy of following the target trajectory by controlling the steering unit.Driving conditions requiring a modification of the gain parameter can be identified based on the driving state and reflected in the steering actuator's control signal when determining the steering parameter, taking into account the target and actual state parameters. This can consequently improve the performance of the driver assistance system under these driving conditions. Simultaneously, it has been observed that the modification may be less significant or even reduced to zero under other driving conditions. This allows the steering feel, for which the steering unit can be calibrated to generate the predefined steering behavior, to be maintained under these driving conditions as well as during manual steering.

[0017] In a method according to the invention, the determination of the target state parameter is carried out using a vehicle model to simulate the target state parameter for the vehicle state as a function of the target trajectory. The vehicle model preferably comprises a single-track model of the vehicle, particularly a linear one. However, it is also conceivable that the vehicle model comprises a two-track model or another model for simulating the vehicle's driving behavior. Simulating the target state parameter for the vehicle state can, in particular, include calculating the target state parameter for a specified target trajectory. It can be provided that the vehicle's speed is taken into account when determining the target state parameter based on the vehicle model. The vehicle model can predict the expected behavior of the vehicle, taking the target state into account.The deviation from the expected behavior can be detected using the current state parameter, in order to determine the steering parameter based on the deviation and, for example, to provide a higher gain.

[0018] Furthermore, in a method according to the invention, it can advantageously be provided that a correction factor for correcting the gain parameter is calculated depending on the target state parameter and the actual state parameter, in particular wherein the gain parameter is factored in with the correction factor when determining the steering parameter. The correction factor can, in particular, form an offset for the gain parameter. It can also be provided that the gain parameter is factored in with the correction factor when determining the steering parameter by calculating the steering parameter as the product of the correction factor and the gain parameter. The correction factor thus allows the gain parameter to be modified depending on a deviation of the actual state parameter from the target state parameter. In particular, this allows the gain parameter to be adjusted depending on the driving conditions.This allows the steering parameter to be determined in a simple manner, thus minimizing the required computing power. For example, the process can be carried out entirely by the vehicle.

[0019] Furthermore, in a method according to the invention, it can advantageously be provided that the target state parameter is a target lateral acceleration of the vehicle and the actual state parameter is an actual lateral acceleration of the vehicle. The vehicle state can thus be an acceleration state, in particular a lateral acceleration state of the vehicle. Lateral acceleration can be understood as an acceleration of the vehicle acting along a transverse axis of the vehicle, i.e., in particular perpendicular to a vertical axis and a longitudinal axis of the vehicle. The lateral acceleration of the vehicle can be used to check whether the prevailing driving conditions deviate from the target trajectory. The lateral acceleration thus represents an advantageous state parameter.The correction factor for adjusting the gain parameter can be directly derived from the difference between the target and actual lateral acceleration. The actual lateral acceleration can preferably be measured by the vehicle's acceleration sensors to determine the current state parameter.

[0020] Furthermore, in a method according to the invention, it can advantageously be provided that an operating action performed on the steering device, in particular for influencing the steering angle by operating the steering device, is taken into account when determining the target position and / or when determining the amplification parameter. The operating action can include a hand torque applied to the steering device and / or a steering angle set on the steering device. Thus, the operating action can also be taken into account when determining the steering parameter via the amplification parameter. This allows the driver's input to be incorporated into the determination of the amplification parameter. By taking both the target position of the driver assistance module and the operating action into account when determining the amplification parameter, both automated and semi-automated driving maneuvers, as well as manual driving maneuvers, can be executed by the steering actuator.For example, the steering torque and the desired trajectory can be superimposed to detect and / or correct driver oversteer. This allows the steering unit to have a simple, cost-effective design without compromising performance or steering feel.

[0021] Furthermore, in a method according to the invention, the steering actuator is a reset actuator for returning the steering element and / or the steering actuator to a target center position, wherein the target center position is defined as a function of the target trajectory and / or the target position. The reset actuator enables the steering unit to have an active reset function. This allows the steering element to be automatically moved back to a center position after it has been deflected by an operating action in the form of steering movements by the driver. This already contributes fundamentally to the stability and safety of the vehicle. In this method, the reset function, as well as the automated specification of the target trajectory by the steering actuator, can be implemented in the form of the reset actuator.In particular, it has been recognized within the scope of the present invention that the reset actuator can be used for the assisted driving process by changing the target center position. By determining the steering parameter as a function of the target state parameter and the actual state parameter, the driver's steering feel can be maintained, especially independently of the target trajectory and / or the driving condition.

[0022] Preferably, a method according to the invention may include a predefined characteristic function for determining the gain parameter as a function of the target position and / or the operating action. The characteristic function may comprise a characteristic for steering behavior that describes the steering unit's reaction to driving conditions in order to actively steer the vehicle based on the target center position. By specifying the gain parameter, the characteristic function can define how the steering system reacts to deviations from the desired steering angle. For example, if the vehicle deviates from the desired lane, the characteristic function can define how strongly and how quickly the steering unit counter-steers to bring the vehicle back onto the correct course.The characteristic function can be speed-dependent to ensure that the feedback function reacts appropriately at different driving speeds. Thus, the characteristic function allows for tuning of the steering unit to produce reproducible steering behavior of the vehicle and / or improve steering feel. By considering the target state parameter and the actual state parameter, particularly through the correction factor, the gain parameter defined by the characteristic function can be adjusted for the target trajectory.

[0023] Furthermore, in a method according to the invention, it is conceivable that the characteristic function comprises an increasing profile of the gain parameter as a function of the target position. The increasing profile can be linear and / or exponentially increasing.

[0024] For example, at low speeds, the characteristic function can provide smoother steering correction, while at higher speeds, it can provide faster and / or more precise steering. This can improve driving comfort. Subsequent adjustment of the gain parameter based on the target and actual state parameters can further improve the accuracy of following the target trajectory. For instance, the correction factor can be higher at low speeds than at high speeds.

[0025] According to a further aspect of the invention, a computer program product is provided. The computer program product comprises instructions which, when executed by a control unit, cause the control unit to execute a method according to the invention.

[0026] Thus, a computer program product according to the invention offers the same advantages as those already described in detail with reference to a method according to the invention. The method can, in particular, be a computer-implemented method. The computer program product can be implemented as computer-readable instruction code. Furthermore, the computer program product can be stored on a computer-readable storage medium such as a data disk, a removable drive, volatile or non-volatile memory, or an embedded memory / processor. Furthermore, the computer program product can be made available or provided in a network such as the Internet, from which it can be downloaded or executed online by a user as needed. The computer program product can be implemented using software as well as one or more special electronic circuits, i.e.,It can be implemented in hardware or in any hybrid form, i.e., using software components and hardware components.

[0027] According to a further aspect of the invention, a vehicle is provided. The vehicle has a steering unit with a steering actuator for setting the steering angle of the vehicle and a steering means for influencing the steering angle by manual steering. Furthermore, the vehicle includes a control unit for carrying out a method according to the invention.

[0028] Thus, a vehicle according to the invention offers the same advantages as those already described in detail with reference to a method and / or a computer program product according to the invention. A driver assistance module for assisted driving of the vehicle can be integrated into the control unit.

[0029] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can be essential to the invention individually or in any combination. The drawings schematically show: Fig. 1 a sequence of a method according to the invention, and Fig. 2 a vehicle with a steering unit while performing the procedure.

[0030] In the following description of some embodiments of the invention, the same reference numerals are used for the same technical features even in different embodiments.

[0031] Fig. Figure 1 shows a sequence of a method 100 according to the invention for operating a steering unit 10 of a vehicle 1 during a driving process of the vehicle 1 assisted by a driver assistance module 21 in a first embodiment. The vehicle 1 is in Fig. Figure 2 shows that the vehicle 1 comprises a steering unit 10 with a steering actuator 11 for setting a steering angle 200 of the vehicle 1. The steering unit 10 also includes a steering device 12 for influencing the steering angle 200 by manual steering by the driver. Furthermore, the vehicle 1 has a control unit 20 for executing the procedure 100. For this purpose, a computer program is provided which includes commands that, when executed by the control unit 20, cause the control unit 20 to execute the procedure 100. In the present embodiment, a driver assistance module 21 for assisted driving is also integrated into the control unit 20. However, it is equally conceivable that the driver assistance module 21 is integrated into a separate control unit.

[0032] The procedure 100 comprises defining 101 a target trajectory 201 of the driver assistance module 21 for the vehicle 1. For this purpose, the driver assistance module 21 can calculate the target trajectory 201, for example, using sensor data. Based on the target trajectory 201, a target position 202 of the steering angle 200 is determined 102. The target position 202 includes, in particular, a rack position, which, as in Fig. Figure 2 shows how the steering actuator 11 can be adjusted. Specifically, the steering actuator 11 is a reset actuator for returning the steering device 12 and / or the steering actuator 11 to a target center position 202.1. To adjust the target trajectory 201, the target center position 202.1 can be defined by the control unit 20 depending on the target trajectory 201 and / or the target position 202, so that the reset function of the steering actuator 11 is activated to achieve the target position 202.

[0033] Subsequently, a determination 103 of an amplification parameter 203 for the steering actuator 11 is performed as a function of the target position 202 in order to specify the steering force amplification of the return function. An operating action 206 performed on the steering device 12 is also taken into account during the determination 102 of the target position 202 and / or during the determination 103 of the amplification parameter 203, so that the driver can override the steering unit 10. As in Fig.As shown in Figure 1, a predefined characteristic function 213 is specified to determine the gain parameter 203 as a function of the target position 202 and / or the operating action 206. The characteristic function 213 defines an increasing curve for the gain parameter 203 as a function of the target position 202. This allows for improved steering comfort during manual steering, especially with minor changes in the steering angle 200, e.g., due to slight curvature of the target trajectory 201 and a road surface, by using a low gain factor.

[0034] Therefore, in method 100, an additional step is to determine 104 a target state parameter 211 for a driving state of vehicle 1 as a function of the target position 202. For this purpose, the target state parameter 211 is calculated as a function of a vehicle model 210 to simulate the target state parameter 211 for the vehicle state and the target trajectory 201. In addition, method 100 performs a determination 105 of an actual state parameter 212 of the driving state. The target state parameter 211 is preferably a target lateral acceleration of vehicle 1, and the actual state parameter 212 is an actual lateral acceleration of vehicle 1.

[0035] Depending on the target state parameter 211 and the actual state parameter 212, a steering parameter 205 is then determined 106 to achieve the target position 202 based on the gain parameter 203. For this purpose, a correction factor 204 is calculated to correct the gain parameter 203, depending on the target state parameter 211 and the actual state parameter 212. To determine 106 the steering parameter 205, the gain parameter 203 is multiplied by the correction factor 204. The steering parameter 205 is therefore in particular a steering torque at the steering device 12 and / or at the steering actuator 11. To control the steering unit 10, in particular the steering device 12 and / or the steering actuator 11, the steering parameter 205 is output 107.

[0036] The preceding explanation of the embodiments describes the present invention solely by way of examples. Naturally, individual features of the embodiments can be freely combined with one another, provided this is technically feasible, without departing from the scope of the present invention. Reference symbol list 1 vehicle 10 Steering unit 11 Steering actuator 12 Steering devices 20 Control unit 100 procedures 101 Defining 201 102 Determining 202 103 Determining 203 104 Determining 211 105 Determining 212 106 Determining 205 107 Spending out of 205 200 steering angle 201 Target trajectory 202 Target position 202.1 Target center position 203 Gain parameters 204 Correction factor 205 Steering parameters 206 Operating procedure 210 vehicle model 211 Target state parameters 212 Current State Parameters 213 Characteristic function

Claims

[1] Method (100) for operating a steering unit (10) of a vehicle (1) during a driving process assisted by a driver assistance module (21), wherein the steering unit (10) comprises a steering actuator (11) for setting a steering angle (200) of the vehicle (1) and a steering means (12) for influencing the steering angle (200) by manual steering, comprising: - Define (101) a target trajectory (201) of the driver assistance module (21) for the vehicle (1), - Determining (102) a target position (202) of the steering angle (200) depending on the target trajectory (201), - Determining (103) an amplification parameter (203) for the steering actuator (11) as a function of the target position (202), - Determining (104) a target state parameter (211) for a driving state of the vehicle (1) as a function of the target trajectory (201), - Determining (105) an actual state parameter (212), - Determining (106) a steering parameter (205) to achieve the target position (202) based on the amplification parameter (203) depending on the target state parameter (211) and the actual state parameter (212), - Output (107) of the steering parameter (205) for controlling the steering unit (10), wherein the determination (104) of the target state parameter (211) is performed as a function of a vehicle model (210) to simulate the target state parameter (211) for the vehicle state as a function of the target trajectory (201), wherein the steering actuator (11) is a reset actuator for resetting the steering means (12) and / or the steering actuator (11) to a target center position (202.1), wherein the target center position (202.1) is defined as a function of the target position (202). [2] Method (100) according to claim 1, characterized by, that depending on the target state parameter (211) and the actual state parameter (212) a correction factor (204) is calculated to correct the gain parameter (203), wherein the gain parameter (203) is taken into account when determining (106) the steering parameter (205) with the correction factor (204). [3] Method (100) according to any one of the preceding claims, characterized by , that the target state parameter (211) is a target lateral acceleration of the vehicle (1) and the actual state parameter (212) is an actual lateral acceleration of the vehicle (1). [4] Method (100) according to any one of the preceding claims, characterized by , that an operating action (206) performed on the steering device (12) is taken into account when determining (102) the target position (202) and / or when determining (103) the gain parameter (203). [5] Method (100) according to any one of the preceding claims, characterized by, that a predefined characteristic function (213) is specified for determining (103) the gain parameter (203) depending on the target position (202) and / or the operating action (206). [6] Method (100) according to claim 5, characterized by , that the characteristic function (213) includes an increasing curve of the gain parameter (203) depending on the target position (202). [7] Computer program product comprising instructions which, when executed by a control unit (20), cause the control unit (20) to execute a method (100) according to any of the preceding claims. [8] Vehicle (1) exhibiting a steering unit (10) with a steering actuator (11) for setting a steering angle (200) of the vehicle (1) and a steering means (12) for influencing the steering angle (200) by manual steering, and a control unit (20) for carrying out a method (100) according to any one of claims 1 to 6.

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