Method for operating a motor vehicle, control device, motor vehicle

Abstract

The invention relates to a method for operating a motor vehicle (1), wherein the motor vehicle (1) has a steering system (5) with a steering handle (6) operable by a driver, in particular a steering wheel rotatable by a driver, for indicating a steering input, and wherein the motor vehicle (1) has at least one wheel (2) whose steering angle is adjustable by the steering system (5). It is provided that, when an actual and / or expected deviation of the actual trajectory of the motor vehicle from a target trajectory of the motor vehicle (1) is detected, a steering profile for the steering handle (6) for controlling an actuator associated with the steering system (5) is modified asymmetrically such that a change in the steering angle of the wheel (2) in the direction of the target trajectory is more strongly supported when the steering handle (6) is operated by the driver than a change opposite to the direction of the target trajectory.

Description

[0001] The invention relates to a method for operating a motor vehicle, wherein the motor vehicle has a steering system with a steering handle operable by a driver, in particular a steering wheel rotatable by a driver, for specifying a steering request, and wherein the motor vehicle has at least one wheel whose steering angle is adjustable by the steering system.

[0002] Furthermore, the invention relates to a control device specially designed for carrying out such a method, as well as a motor vehicle with such a control device. State of the art

[0003] It is known to use a steering profile for the steering handle to control an actuator associated with the steering system. Such steering profiles are usually designed symmetrically, for example, in a rack and pinion steering system with respect to the center of the gear teeth. This means that regardless of the actuating device, especially the direction of rotation in the case of a steering wheel, a steering command is implemented consistently.

[0004] From the applicant's patent specification EP 1 888 394 B1, a lane keeping assistant for motor vehicles is known, comprising a sensor device for detecting the lanes on the road, a control device which exerts a force on the steering of the vehicle via an actuator in order to keep the vehicle in the lane, and a device for detecting an intention of the driver to change lanes, wherein the control device is configured to modify the force exerted on the steering asymmetrically in the sense of making the lane change easier when an intention to change lanes is detected. Disclosure of the invention

[0005] The method according to the invention, with the features of claim 1, is characterized in that, when an actual and / or expected deviation of the actual trajectory of the motor vehicle from a target trajectory of the motor vehicle is detected, a steering profile for the steering handle is modified asymmetrically for controlling an actuator associated with the steering system such that a change in the steering angle of the wheel in the direction of the target trajectory is supported more strongly when the steering handle is actuated by the driver than a change opposite the direction of the target trajectory. Thus, if the driver attempts to counter-steer in order to regain the set target trajectory, he is advantageously supported by the modification of the steering profile according to the invention, which is asymmetrical in that it is more pronounced in the direction of the set trajectory, and in particular, only acts in the direction of the set trajectory.In the event of such a deviation of the actual trajectory from the intended trajectory, caused, for example, by certain external conditions that are only present on one side of the vehicle's direction of travel, it is advantageous to deviate from the aforementioned symmetry of the steering profile and to favor a specific steering direction, namely the one that leads back to the original intended trajectory. In the corresponding driving situations, an asymmetrical steering profile is provided, for example, in the presence of micro-split conditions, when crossing lane markings, and / or when leaving the roadway. The driver is then specifically assisted by the method according to the invention in steering in a desired direction, for example, if wheels have already left the roadway.Preferably, the system provides support only for a change in the steering angle of the wheel in the direction of the desired trajectory when the driver operates the steering handle. The modification is active at least temporarily, i.e., at least as long as the actual trajectory deviates from the desired trajectory. In particular, it is a steering system based on the steer-by-wire principle, so that, for example, not only the steering assistance but also the steering ratio can be adjusted accordingly. Further deviation from the trajectory is advantageously made more difficult because, for example, the steering assistance is comparatively lower and / or the steering ratio is more indirect. Thus, in the aforementioned lane keeping assist system, an actuator is designed to asymmetrically modify the force exerted on the steering in the context of an intended lane change.The actuator is designed to directly influence the trajectory of the motor vehicle by performing a direct automatic steering intervention. The asymmetry of the actuator ensures that the driver does not have to overcome any counterforce from the actuator when steering in the "correct" direction. In this respect, the method according to the invention achieves a result similar to the aforementioned lane keeping assist system, with the difference that there is no active / direct automatic steering intervention for lane keeping; instead, corrective steering inputs by the driver are more strongly supported, and in particular, translated more directly. Conversely, the method according to the invention is fundamentally suitable for functionally supporting or even replacing such a lane keeping assist system. It should be noted, purely as a precaution, that the invention is not limited to a specific type of steering mechanism; however, a steering wheel or a joystick are particularly conceivable.

[0006] According to a preferred embodiment of the invention, the steering profile assigns at least one input variable characterizing the actuation of the steering handle to at least one output variable used to actuate the actuator. This assignment advantageously ensures that the behavior resulting from the steering profile is repeatably consistent. For example, an actuation path, in particular the rotation angle of a steering wheel or the displacement path of a joystick, is taken into account and assigned to an output variable that, in particular, characterizes a steering effect. Preferably, a plurality of input variables are taken into account and assigned to corresponding output variables. For example, at least one control variable for the actuator, in particular an electrical control current, and / or a steering angle to be achieved is defined as the output variable.Preferably, the steering profile is provided as a characteristic curve or map in order to assign the corresponding quantities to each other in a consistent manner.

[0007] It is particularly preferred that the steering assist and / or steering ratio of the steering profile be modified. The steering assist and / or steering ratio each ensure a particularly advantageously simple modification of the steering profile. For example, a corresponding steering maneuver in the direction of the desired trajectory is supported by stronger steering assist and / or a more direct steering ratio. The steering assist can, in particular, be applied directly to the steering handle, thus facilitating its operation by controlling the actuator, and / or include enhanced control of the actuator associated with the steering system in the sense of power steering, whereby the actuator then directly changes the steering angle of the wheel depending on the operation of the steering handle. The actuator is, in particular, designed as a rack actuator of a rack steering system or as an individual wheel actuator.Preferably, several controllable actuators are provided.

[0008] According to a preferred embodiment of the invention, the steering assistance is increased in the direction of the desired trajectory and / or the steering ratio becomes more direct. By appropriately adjusting the steering assistance and / or steering ratio, it is advantageously ensured that the actuation of the steering handle in the direction of the desired trajectory is directly promoted by supporting, for example, the active steering back onto the road. A more direct steering ratio, in this context, means that a gear ratio is reduced, for example, with a constant rotation angle of the steering handle (designed as a steering wheel), a larger steering angle is set at the wheel than before the modification. This allows the desired trajectory to be reached more quickly when the steering handle is actuated in its direction.

[0009] It is particularly preferred that the steering assistance is reduced in the opposite direction to the intended trajectory and / or that the steering ratio of the steering profile becomes more indirect. By appropriately adjusting the steering assistance and / or steering ratio, it is advantageously ensured that the steering hand's operation in the opposite direction to the intended trajectory is indirectly encouraged by counteracting further deviation, for example, from the road. A more indirect steering ratio, in this context, means that a ratio is increased, for example, with a constant rotation angle of the steering hand designed as a steering wheel, a smaller steering angle is set at the wheel than before the modification. This makes it more difficult to deviate further from the intended trajectory when the steering hand is operated in the opposite direction.

[0010] According to a preferred embodiment of the invention, the steering profile, in particular the steering assistance and / or steering ratio of the steering profile, is modified depending on the steering handle's travel, especially the steering wheel's rotational position, the steering direction, the current steering angle, the magnitude of the deviation, and / or the driving situation. Such dependent modification advantageously ensures that the steering profile is precisely adapted to the situation. The asymmetry can, for example, begin halfway in the steering handle's travel or off-center. A division into more than two areas is also conceivable. It is also conceivable to make the modification dependent solely on the steering direction, especially the direction of the steering movement, so that steering in a specific direction is more strongly assisted regardless of the current steering angle.The strength of the modification, in particular a changed steering assist and / or steering ratio, therefore depends, for example, on actuation distance, steering direction, steering angle, deviation and / or driving situation.

[0011] It is particularly preferred that the steering profile, especially steering assistance and / or steering ratio, is / are modified by a predetermined constant or characteristic curve. This offers the advantage that the steering profile can be modified particularly easily and consistently.

[0012] According to a preferred embodiment of the invention, the center return of the steering handle to a position associated with straight-ahead driving of the motor vehicle, in particular a rotational position, is modified by shifting a center point used as a reference in the steering profile. This provides a particularly robust means of modifying the steering profile.

[0013] It is particularly preferred that a drive system and / or brake system, which is / are assigned to the same wheel of the vehicle as the steering system, is / are additionally controlled within the steering profile. Such additional control of the brake system and / or drive system offers the advantage of further increased support during steering correction. The drive system and / or brake system can also be assigned to a different wheel than the steering system, particularly within the context of torque vectoring.In particular, a corresponding actuator of the braking system and / or drive system is controlled, resulting in an advantageous multi-actuator control system. This means that not only is an actuator assigned to the steering system controlled, but additional acceleration and / or braking interventions are also carried out to stabilize the vehicle or return it to the intended trajectory as the originally specified course. For example, a corresponding electric drive motor and / or a wheel brake device at the respective wheel is / are controlled.

[0014] According to a preferred embodiment of the invention, the motor vehicle and / or its surroundings are monitored to detect deviations of the actual trajectory from the intended trajectory, the presence of micro-split conditions, and / or the vehicle leaving a lane, roadway, and / or a route specified by a navigation system. Such monitoring advantageously ensures that any such deviation is always detected reliably and promptly. In particular, the asymmetry is used to support certain driving directions or directional decisions, for example, in combination with the aforementioned navigation system. Preferably, the steering profile is then modified asymmetrically such that a direction corresponding to the route specified by the navigation system is easier to steer than a "wrong" turn.In particular, the modification only occurs when a deviation in the trajectories actually exists, or alternatively, when a deviation is expected with at least a certain probability, for example, depending on an environmental and / or surrounding condition, especially road surface, road friction coefficient, and / or weather. Preferably, monitoring is carried out by means of a suitable sensor arrangement comprising, for example, an optical sensor, in particular a camera sensor, and / or an inertial sensor / accelerometer.

[0015] It is particularly preferred that the modification of the steering profile is terminated when the actual trajectory again corresponds to the target trajectory. This offers the advantage that the method is only applied as needed, with the modified steering profile being maintained only as long as the deviation is detected, after which the system reverts to an initial, and in particular symmetrical, steering profile. To detect whether the trajectories again correspond to each other, the vehicle is monitored, in particular as described in the previous paragraph.

[0016] The control device with the features of claim 12 is characterized in that it is specifically designed to carry out the method according to the invention. This results in the advantages already mentioned. In particular, the control device is designed as a computer device assigned to a motor vehicle, preferably arranged in a motor vehicle. For example, the control device is assigned to the steering system.

[0017] The motor vehicle with the features of claim 13 comprises a steering system with at least one steering handle operable by a driver, in particular a steering wheel rotatable by a driver, for indicating a steering input, and at least one wheel whose steering angle is adjustable by the steering system, and is characterized by the control device according to the invention. The advantages already mentioned also result from this.

[0018] Further preferred features and combinations of features will become apparent from the foregoing and from the claims. The invention will now be explained in more detail with reference to the drawings. These drawings show... Fig. 1 a motor vehicle, and Fig. 2 a method for operating the motor vehicle.

[0019] Fig. Figure 1 shows a motor vehicle 1. The motor vehicle 1 has four wheels 2, wherein at least one of the wheels 2, in particular at least two wheels 2 of the same axle, is each assigned a drive system 3, a braking system 4 and a steering system 5 of the motor vehicle 1 in order to accelerate, brake and / or steer the motor vehicle 1. For this purpose, each of the systems 3, 4, 5 has at least one controllable actuator.

[0020] Furthermore, the motor vehicle 1 has a steering handle 6, which is specifically designed as a steering wheel. The steering handle 6 is designed to be operated by a driver to indicate a steering request.

[0021] The steering request is then implemented by the steering system 5 depending on a predefined steering profile, in particular by controlling the corresponding actuator, which is not shown here, so that the steering angle of at least one of the wheels 2 is set by the steering system 5.

[0022] Finally, the motor vehicle also has a control device 7 which is designed to convert an actuation of the steering handle 6, detected in this case by a corresponding sensor arrangement 8 assigned to the steering handle 6, comprising in particular a displacement sensor and / or rotation angle sensor, into a corresponding control signal for the steering system 5.

[0023] The following refers to Fig. 2. An advantageous method for operating the motor vehicle 1 is described. For this purpose, the Fig. 2. The procedure is described using a flowchart. In particular, the procedure ensures that a change in the steering angle of at least one of the wheels in the direction of a desired trajectory is supported when the steering handle 6 is actuated by the driver. The procedure is carried out in particular by means of the control unit 7.

[0024] In step S1, the procedure begins by comparing an actual trajectory of the motor vehicle with a target trajectory of motor vehicle 1.

[0025] If an actual and / or expected deviation is detected, the procedure continues with step S2.

[0026] In order to detect the corresponding deviation of the actual trajectory from the target trajectory, the motor vehicle 1 and / or the environment of the motor vehicle 1 are monitored, in particular for the presence of µ-split conditions and / or for leaving a lane, roadway and / or a route specified by a navigation system.

[0027] In step S2, the steering profile for the steering handle 6 for controlling the actuator assigned to the steering system 5 is modified asymmetrically in such a way that a change in the steering angle of at least one wheel 2 assigned to the steering system, in particular the two corresponding wheels 2 of the front axle of the motor vehicle 1, in the direction of the desired trajectory is supported more strongly when the steering handle 6 is actuated by the driver than a change in the opposite direction to the desired trajectory.

[0028] The steering profile assigns at least one input variable characterizing the actuation of the steering handle 6, for example a rotation angle of the steering wheel, to at least one output variable used to actuate the actuator.

[0029] Preferably, the steering assistance and / or the steering ratio of the steering profile is / are modified, wherein, for example, the steering assistance in the direction of the desired trajectory is increased, the steering assistance opposite the direction of the desired trajectory is decreased, the steering ratio in the direction of the desired trajectory is made more direct, and / or the steering ratio opposite the direction of the desired trajectory is made / be made more indirect.

[0030] The steering profile, in particular the steering assistance and / or steering ratio, is / are preferably modified depending on an actuation path of the steering handle 6, in particular a rotational position of the steering wheel, a steering direction, a current steering angle, an amount of deviation and / or a driving situation, for example by a predetermined constant or characteristic curve.

[0031] Alternatively or additionally, the center return of the steering handle 6 to a position associated with a straight-ahead driving of the motor vehicle 1, in particular a rotational position, is modified by moving a center used as a reference in the steering profile.

[0032] Particularly preferably, the drive system 3 and / or the brake system 4, which is / are assigned to the same wheel 2 of the motor vehicle 1 as the steering system 5, are additionally controlled in the steering profile.

[0033] If, for example through continued monitoring as described above, it is detected that the actual trajectory again corresponds to the target trajectory, the modification of the steering profile is terminated. The procedure then ends with step S3. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 1 888 394 B1

[0004]

Claims

[1] Method for operating a motor vehicle (1), wherein the motor vehicle (1) has a steering system (5) with a steering handle (6) operable by a driver, in particular a steering wheel rotatable by a driver, for indicating a steering request, and wherein the motor vehicle (1) has at least one wheel (2) whose steering angle is adjustable by the steering system (5), characterized by , that if an actual and / or expected deviation of an actual trajectory of the motor vehicle from a target trajectory of the motor vehicle (1) is detected, a steering profile for the steering handle (6) for controlling an actuator assigned to the steering system (5) is modified asymmetrically in such a way that a change in the steering angle of the wheel (2) in the direction of the target trajectory when the steering handle (6) is actuated by the driver is supported more strongly than a change in the opposite direction to the target trajectory. [2] Method according to claim 1, characterized by, that the steering profile assigns at least one input variable characterizing an actuation of the steering handle (6) to at least one output variable used for actuation of the actuator. [3] Method according to any one of the preceding claims, characterized by , that the steering assistance and / or the steering ratio of the steering profile is / are modified. [4] Method according to claim 3, characterized by , that the steering assistance in the direction of the desired trajectory is increased and / or the steering ratio becomes more direct. [5] Method according to one of claims 3 and 4, characterized by , that the steering assistance is reduced in the opposite direction to the intended trajectory and / or the steering ratio becomes more indirect. [6] Method according to any one of the preceding claims, characterized by, that the steering profile, in particular a steering assistance and / or steering ratio of the steering profile, is / are modified depending on an actuation path of the steering hand (6), in particular a rotational position of the steering wheel, a steering direction, a current steering angle, an amount of deviation and / or a driving situation. [7] Method according to any one of the preceding claims, characterized by , that the steering profile, in particular steering assistance and / or steering ratio of the steering profile, is / are modified by a predetermined constant or characteristic curve. [8] Method according to any one of the preceding claims, characterized by , that a center return of the steering handle (6) is modified into a position associated with a straight-ahead driving of the motor vehicle (1), in particular a rotational position, by moving a center used as a reference in the steering profile. [9] Method according to any one of the preceding claims, characterized by, that a drive system (3) and / or brake system (4), which is / are assigned in particular to the same wheel of the motor vehicle as the steering system, is / are additionally controlled in the steering profile. [10] Method according to any one of the preceding claims, characterized by , that the motor vehicle (1) and / or the environment of the motor vehicle (1) is / are monitored to detect deviations of the actual trajectory from the intended trajectory, the presence of µ-split conditions and / or the departure from a lane, roadway and / or a route specified by a navigation system. [11] Method according to any one of the preceding claims, characterized by , that the modification of the steering profile is terminated when the actual trajectory again corresponds to the target trajectory. [12] Control device (7), characterized bythat the control device (7) is specifically designed to carry out the procedure according to one of the preceding claims. [13] Motor vehicle (1) with a steering system (5) having at least one steering handle (6) operable by a driver, in particular a steering wheel rotatable by a driver for indicating a steering request, and with at least one wheel (2) whose steering angle is adjustable by the steering system (5), characterized by a control device (7) according to claim 12.

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