Method and device for longitudinal control of a vehicle

Abstract

The present invention relates to a method for detecting a target trajectory (T soll ) is a method for longitudinal control of a vehicle (1), wherein the target trajectory predetermines a series of target positions (P ) to be occupied by the vehicle (1) over time (t) k‑n To P k+m ), wherein the controller adjustment acceleration (a) for trajectory control is obtained based on the actual state (Z) of the vehicle (1) ctrl ), the controller is used to adjust the acceleration according to the target trajectory (T soll ) of the predetermined acceleration vehicle (1). When the vehicle (1) passes the target trajectory (T soll ) from the target trajectory (T soll ) to obtain the target trajectory (T soll ), wherein the acceleration offset (a) that decreases with increasing curvature (K) is determined from the curvature (K) offset In addition, when passing the target trajectory (T soll ) is calculated at the current position of the vehicle (1) by the target trajectory (T soll ) is used as the current trajectory acceleration (a refPtOrth ) and the controller adjusts the acceleration (a ctrl ) is limited to the following values, which is equal to the current trajectory acceleration (a refPtOrth ) and acceleration offset (a offset ). The acceleration (a ctrl_lim ) accelerates the vehicle (1). The invention further relates to a device (2) for longitudinal control of the vehicle (1).

Description

Technical Field

[0001] The invention relates to a method for longitudinal control of a vehicle.

[0002] The invention further relates to a device for longitudinal control of a vehicle. Background Art

[0003] Document DE 10 2017 010 180 B3 discloses a device and a method for controlling the longitudinal position of a vehicle by means of a longitudinal position controller, which generates a longitudinal acceleration adjustment signal for a downstream acceleration control unit from a pre-adjusted target variable of the longitudinal dynamics and a control error variable of the longitudinal dynamics. Here, a current control reference point corresponding to the current moment and an advanced control reference point corresponding to a predeterminable predicted moment are determined as control-related moments. For each of the control reference points, the current or predicted actual target deviation of the longitudinal position, the driving speed and the acceleration is determined and used as the basis for forming the control error variable of the longitudinal dynamics. In addition, a target value of the acceleration is determined for each of the control reference points and used as the basis for forming the pre-adjusted target variable of the longitudinal dynamics. Here, the pre-adjusted target variable of the longitudinal dynamics is formed by adding the acceleration target values ​​determined for the control reference points in a weighted manner.

[0004] In addition, DE 10 2017 114 471 A1 discloses a vehicle control device configured to enable the vehicle to drive autonomously. The vehicle control device includes:

[0005] - a longitudinal position checking unit configured to identify a longitudinal position corresponding to the position of the vehicle in an extending direction of a path along which the vehicle is traveling, based on image information from the camera and position information of a compass point on a map;

[0006] - a longitudinal position estimation unit configured to estimate the longitudinal position based on a detection result of an internal sensor detecting a vehicle state and a recognition result of the longitudinal position checking unit;

[0007] - an error estimation unit configured to estimate an error of the longitudinal position estimated by the longitudinal position estimation unit based on the detection accuracy of the internal sensor;

[0008] - a radius acquisition unit configured to acquire a curve radius of a curve ahead of the vehicle using the estimated longitudinal position and map information;

[0009] - a turning speed calculation unit configured to calculate a turning speed for autonomously driving the vehicle on a curved lane with the acquired turning radius based on the acquired turning radius and the estimated longitudinal position error;

[0010] - a speed control unit configured to decelerate the vehicle so that the vehicle speed becomes the turning speed when the front of the vehicle enters a curve if the vehicle speed is greater than or equal to the turning speed and the turning speed is greater than or equal to a preset reference speed, and configured to decelerate the vehicle so that the vehicle maintains the current speed or the vehicle speed becomes the reference speed when the front of the vehicle enters a curve if the vehicle speed is greater than or equal to the turning speed and the turning speed is lower than the reference speed; and

[0011] - a request unit configured to perform a manual operation request to change the control of the vehicle to a manual operation of the driver if the vehicle speed is higher than or equal to the turning speed and the turning speed is lower than a reference speed, wherein the turning speed calculation unit is configured to reduce the turning speed if the turning radius is small compared to if the turning radius is large, and is configured to reduce the turning speed if the longitudinal position error is large compared to if the longitudinal position error is small.

[0012] DE 10 2018 210 648 A1 describes a longitudinal driver assistance system in a motor vehicle, which has a detection system for predictive detection of a plurality of events, each of which leads to a change in a target speed based on a currently achieved target speed. In addition, the driver assistance system comprises a functional unit, in which a function for event selection can be activated when a plurality of events occur relatively close together within a predefined observation period. The event selection function can be used to determine a modified target speed for longitudinal guidance control in the following way: In a first step, only those events are selected which lead to a reduction in the target speed based on the actual speed. Summary of the invention

[0013] The invention is based on the object of specifying a novel method and a novel device for longitudinal control of a vehicle.

[0014] This object is achieved according to the invention by a method having the features of the invention and by a device having the features of the invention.

[0015] In the method for longitudinal control of a vehicle according to a target trajectory according to the present invention, the target trajectory predetermines a series of target positions to be occupied by the vehicle over time, and a controller adjustment acceleration (Regler-Stellbeschleunigung) for trajectory control is determined based on the actual state of the vehicle, with the aid of which the vehicle is to be accelerated according to the target trajectory. The curvature of the target trajectory at the current position of the vehicle is determined from a curve at the location of the target trajectory while the vehicle passes through the target trajectory, wherein an acceleration offset that decreases with increasing curvature is determined based on the curvature. In addition, the longitudinal acceleration resulting from the target trajectory is determined at the current position of the vehicle during the passage of the target trajectory as the current trajectory acceleration. The controller adjustment acceleration is limited to a value that is at most equal to the sum of the current trajectory acceleration and the acceleration offset; and the vehicle is accelerated according to the limited controller adjustment acceleration.

[0016] The trajectory control of an automated, especially highly automated or autonomous vehicle is a basic prerequisite for realizing automated driving functions. Here, it is determined based on the data of the environmental detection: which actions the vehicle should perform in the future. The result of this decision is a trajectory, which, for example, depicts the position of the vehicle on the lane over time and serves as a motion reference in a known vehicle environment. The trajectory control is provided here to drive through the trajectory as accurately as possible. If a larger longitudinal position control error has been formed for any reason, the trajectory predetermined at the target position does not correspond to the trajectory predetermined at the actual position on the lane where the vehicle is currently located. That is, the "target time" continues to run. The danger here is that the vehicle is, for example, located at a narrow bend and the automation accelerates, because the reference point in time, that is, the target position, is already located further ahead in the trajectory in terms of location, for example, on a straight line immediately following the bend.

[0017] In the method, the inconsistency between a reference point in location, i.e. the actual position of the vehicle, and a reference point in time, i.e. the target position of the vehicle in the trajectory, is taken into account in the longitudinal control of the vehicle. If the target acceleration specification is too high at the actual position, it is limited by means of the method. With this curvature-dependent acceleration limitation at the actual position, dangerous situations caused by too high acceleration, for example too high acceleration in a narrow bend, can be prevented.

[0018] In other words: the method enables safe trajectory control, which has the goal of achieving the planned position at the associated time, wherein the acceleration at the actual position is limited to below a predetermined value for the acceleration at the target position by a curvature-dependent acceleration limitation, if necessary.

[0019] In one possible embodiment of the method, the actual state of the vehicle is formed at least by the actual speed of the vehicle, the actual acceleration of the vehicle and / or the actual position of the vehicle. With the aid of these variables, the actual state can be well described, so that a reliable determination of the acceleration set by the controller can be achieved.

[0020] In another possible embodiment of the method, the actual position or the most recent target position of the series of target positions is used as the current position of the vehicle. This enables a simple and sufficiently accurate determination of the current position of the vehicle in order to determine the curvature.

[0021] In another possible embodiment of the method, the longitudinal acceleration resulting from the target trajectory is ascertained from the time profile of the distance between successive target positions of the target trajectory. This makes it possible to easily ascertain the current trajectory acceleration.

[0022] In another possible embodiment of the method, the target trajectory is fed to a trajectory controller, by means of which the vehicle is accelerated according to the controller-adjusted acceleration in accordance with the specification of the target trajectory. The limited controller-adjusted acceleration is fed to an acceleration control unit downstream of the trajectory controller, which regulates and / or controls the actual acceleration of the vehicle.

[0023] In another possible embodiment of the method, a recalculation of the target trajectory is carried out when a predetermined difference between a predetermined controller adjustment acceleration and a limited controller adjustment acceleration is exceeded. Thus, the deviation of the target trajectory from the actual trajectory and thus also the deviation of the controller adjustment acceleration from the corrected controller adjustment acceleration can be minimized.

[0024] According to the present invention, a device for longitudinal control of a vehicle according to a target trajectory includes a trajectory controller, which predetermines a series of target positions to be occupied by the vehicle over time, and the trajectory controller obtains a controller adjustment acceleration for trajectory control based on the actual state of the vehicle according to the target trajectory fed to the trajectory controller, and the vehicle should be accelerated according to the target trajectory by means of the controller adjustment acceleration. The device also includes a preprocessing unit, which obtains the curvature of the target trajectory at the current position of the vehicle from the curve at the location of the target trajectory during the vehicle passing through the target trajectory. In addition, the preprocessing unit obtains an acceleration offset that decreases with increasing curvature according to the curvature; and obtains the longitudinal acceleration obtained from the target trajectory at the current position of the vehicle during the passing of the target trajectory as the current trajectory acceleration. In addition, the device includes: a limiting unit, which limits the controller adjustment acceleration to a value that is at most equal to the sum of the current trajectory acceleration and the acceleration offset; an acceleration control unit placed after the trajectory controller, which accelerates the vehicle according to the limited controller adjustment acceleration.

[0025] The device can be used to take into account the inconsistency between a reference point in location, i.e. the actual position of the vehicle, and a reference point in time, i.e. the target position of the vehicle in the trajectory, in the longitudinal control of the vehicle. In this case, the device limits the target acceleration setting if it is too high at the actual position. With this curvature-dependent acceleration limitation at the actual position, dangerous situations caused by too high acceleration, for example too high acceleration in a narrow bend, can be prevented.

[0026] In other words: the device enables safe trajectory control, which has the goal of achieving a planned position at the associated time, wherein the acceleration at the actual position is limited to below a predetermined value for the acceleration at the target position by curvature-dependent acceleration limitation, if necessary.

[0027] In one possible embodiment of the device, the acceleration control unit is a vehicle brake system. By means of the limited control unit of the vehicle brake system, the acceleration can be set easily and reliably.

[0028] In another possible embodiment of the device, the device comprises a control error monitoring unit which, if a predetermined difference between a predetermined controller adjustment acceleration and a limited controller adjustment acceleration is exceeded, recalculates the target trajectory. Thus, the deviation of the target trajectory from the actual trajectory and thus also the deviation of the controller adjustment acceleration from the corrected controller adjustment acceleration can be minimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Embodiments of the present invention are explained in detail below with reference to the accompanying drawings. The accompanying drawings show:

[0030] Figure 1 A top view schematically showing a traffic situation with the vehicle at an actual position and a target position;

[0031] Figure 2 schematically showing the time curves of the acceleration and speed of the vehicle;

[0032] Figure 3 A block diagram schematically showing an apparatus for performing longitudinal control of a vehicle; and

[0033] Figure 4 A curve schematically illustrates a target trajectory for a vehicle.

[0034] Parts that correspond to one another are provided with the same reference symbols in all the figures. DETAILED DESCRIPTION

[0035] exist Figure 1 The vehicle 1 is shown in the actual position P ist and the target position P kand comprising a plurality of trajectory segments T soll1 to Tsoll3 The target trajectory T soll A bird's-eye view of the traffic situation. Figure 2 In accordance with Figure 1 Graphs of acceleration a and velocity v of vehicle 1 as functions of time t.

[0036] The vehicle 1 is configured for automated, in particular highly automated or autonomous driving operation. In order to realize such automated driving functions, trajectory control is a basic prerequisite.

[0037] In this trajectory control, based on environmental detection Figure 3 The data UD further shown in FIG. 1 determines which actions the vehicle 1 should perform in the future. The result of this decision is the target trajectory T soll , which describes, for example, the position of the vehicle 1 on the lane over time t and serves as a reference for the movement in a known vehicle environment. The trajectory control is provided in this case to follow the trajectory as accurately as possible. If a greater longitudinal position control error has occurred for any reason, then at the target position P k The trajectory predetermination at does not correspond to the vehicle 1 being in the lane in which it is currently located at the actual position P ist That is, the "target time" continues to run.

[0038] The figure shows the actual position P of an automatically driven vehicle 1 on the example of a traffic circle. ist At target position P k After that, the actual position P ist Here, the vehicle is located in a roundabout and the target position P k Already outside the roundabout after leaving it.

[0039] like Figure 2 As shown, according to the configuration, the target trajectory T soll The speed characteristics and acceleration characteristics of vehicle 1 stipulate that the trajectory section T of vehicle 1 in the roundabout soll2 The vehicle should be driven at a low constant speed v and in the trajectory section T soll3 After the roundabout, the vehicle should be accelerated even more until a higher speed v is reached. soll3 The specified acceleration characteristic is not suitable for the trajectory section T soll2 The road geometry in .

[0040] However, because Figure 1 It is shown that the reference point in time, that is, in the trajectory segment T soll3 The target position P in k With the reference point at the location, that is, in the trajectory section Tsoll2 The actual position P in ist are far from each other, so there is a risk that the vehicle 1 is located in the roundabout on the trajectory section T soll2 and automatically accelerates, since the temporal reference point is already located further ahead in terms of location, in this case in the trajectory section T immediately following the roundabout. soll3 On the straight line in .

[0041] In this case, during operation of a typical trajectory controller, an attempt would be made to compensate for the existing longitudinal position error and the vehicle 1 would accelerate to a greater extent in the roundabout. Depending on how great the curvature K is in the path, such a situation is generally undesirable and can be dangerous.

[0042] Such errors may also occur if there is a so-called control error monitoring module in the system for the automated operation of the vehicle 1, which replans the target trajectory T if the control error becomes large. soll This is the case, for example, when the control error is relatively large but is sufficient for redefining the target trajectory T soll below the determined threshold.

[0043] On the contrary, if the actual position P ist Unlike the illustration, it is still located in the trajectory section T soll1 In the track section T soll2 In which the vehicle 1 is still decelerating, so that no safety-related problems arise. In this case the control error will still increase further, but without the undesired acceleration a.

[0044] exist Figure 3 2 shows a block diagram of a device 2 for longitudinal control of a vehicle 1 .

[0045] The device 2 comprises a first computing unit 3, which comprises a trajectory planning module 3.1, which plans a target trajectory T according to the data UD detected by means of the environment detection sensor device 4. soll .

[0046] In order to solve the Figure 1 and 2 The problem shown is that at the actual position P ist and the target position P k In the case of deviations, an unadapted acceleration a of the vehicle 1 occurs during automated driving operation, the target trajectory T soll It is fed to a further computing unit 5 which comprises a preprocessing module 5.1, a trajectory controller 5.2, a characteristic curve 5.3, a maximum value detector 5.4 and a limiting unit 5.5.

[0047] Here, the preprocessing module 5.1 is used when the vehicle 1 passes the target trajectory Tsoll During the period from the target trajectory T soll The target trajectory T at the current position of the vehicle 1 is derived from the curve at the location soll The curvature K.

[0048] Based on characteristic curve 5.3, which shows the acceleration a of vehicle 1 as a function of curvature K, preprocessing module 5.1 ascertains the acceleration offset a which decreases with increasing curvature K as a function of curvature K and in particular using predicted future information. offset The acceleration offset a offset A permissible acceleration offset can also be formed and established as a function of the coefficient of friction of the road surface.

[0049] In addition, the preprocessing module 5.1 is used to drive over the target trajectory T soll During this period, the target trajectory T is obtained at the current position of the vehicle 1. soll The longitudinal acceleration obtained is taken as the current trajectory acceleration a refPtOrth And feed it to the limiting unit 5.5. The trajectory acceleration a refPtOrth The reference acceleration is formed at the trajectory point closest to the current position of the vehicle 1 .

[0050] Different from the actual position P of the vehicle 1 ist , the current position of the vehicle 1 can also be obtained from the target trajectory T soll in Figure 4 A series of target positions P are further shown in k-n To P k+m The nearest target position P k .

[0051] By the target trajectory T soll The resulting longitudinal acceleration can be obtained from the target trajectory T soll in Figure 4 The successive target positions P are further shown in k-n To P k+m The time variation of the distance between them is obtained.

[0052] Acceleration offset a offset With trajectory acceleration a refPtOrth The sum is added, wherein the sum formed is likewise fed to the limiting unit 5 . 5 .

[0053] Furthermore, the trajectory controller 5.2 is used to control the target trajectory T soll Based on the actual state Z of the vehicle 1, the controller adjustment acceleration a for trajectory control is obtained ctrl , with the help of this controller, the acceleration should be adjusted according to the target trajectory T sollThe actual state Z of the vehicle 1 is hereby determined, for example, by the actual speed v of the vehicle 1. ist , actual acceleration a ist and the actual position P ist express.

[0054] By means of limiting unit 5.5, the acceleration is offset from a offset and trajectory acceleration a refPtOrth and control acceleration a ctrl The minimum value of the sum is determined as follows: The limited controller adjusts the acceleration a ctrl_lim .

[0055] (1)

[0056] Here we only consider the trajectory acceleration a refPtOrth , which is greater than the positive parameter Par, since otherwise the vehicle 1 would remain in the deceleration phase. In this case, the negative trajectory acceleration a in the subsequent acceleration phase refPtOrth The controller adjusts the acceleration a which is always less than the positive ctrl .

[0057] The limited controller adjusts the acceleration a ctrl_lim The acceleration control unit 6 connected downstream of the trajectory controller 5.2 adjusts the acceleration a according to the limited controller ctrl_lim Accelerate the vehicle 1. The acceleration control unit 6 is, for example, a vehicle braking system. In this way, the control system outputs a trajectory acceleration a not greater than the location. refPtOrth , the allowed curvature-dependent deviation upward.

[0058] It is therefore possible that the vehicle 1 Figure 1 The case shown in the actual position P ist On straight sections, by contrast, the vehicle 1 can accelerate sufficiently and compensate for the control error.

[0059] Figure 4 The possible target trajectory T of vehicle 1 is shown soll The target trajectory T soll Here, a series of actions by vehicle 1 at corresponding times t is predetermined over time. k-n to k+m The target position P to be occupied k-n To P k+m .

[0060] Reference numerals list

[0061] 1 Vehicle

[0062] 2 Devices

[0063] 3 Arithmetic Unit

[0064] 3.1 Trajectory Planning Module

[0065] 4Environmental detection sensor device

[0066] 5 Arithmetic Unit

[0067] 5.1 Processing Module

[0068] 5.2 Trajectory Controller

[0069] 5.3 Characteristic curve

[0070] 5.4 Maximum Detector

[0071] 5.5 Restriction Unit

[0072] 6 Acceleration control unit

[0073] aAcceleration

[0074] a ctrl The controller adjusts the acceleration

[0075] a ctrl_lim Limited controller adjusts acceleration

[0076] a ist Actual acceleration

[0077] a offset Acceleration offset

[0078] a refPtOrth Trajectory acceleration

[0079] K curvature

[0080] Par Parameters

[0081] P ist Physical location

[0082] P k-n To P k+m Target location

[0083] t time

[0084] t k-n to k+m time

[0085] T soll Target trajectory

[0086] T soll1 To T soll3 Track segment

[0087] UD Data

[0088] Speed

[0089] v ist Actual speed

[0090] Z Actual status

Claims

1. According to the target trajectory (T soll ) is a method for longitudinal control of a vehicle (1), wherein the target trajectory predetermines a series of target positions (P) to be occupied by the vehicle (1) over time (t) k-n To P k+m ),in - Based on the actual state (Z) of the vehicle (1), the controller for trajectory control is determined to adjust the acceleration (a ctrl ), with the help of this controller, the acceleration should be adjusted according to the target trajectory (T soll ) is scheduled to accelerate the vehicle (1); - When the vehicle (1) passes the target trajectory (T soll ) from the target trajectory (T soll ) to obtain the target trajectory (T) at the current position of the vehicle (1). soll )’s curvature (K); - Ascertaining, from the curvature (K), the acceleration offset (a) which decreases with increasing curvature (K) offset ); - After passing the target trajectory (T soll ) is calculated at the current position of the vehicle (1) by the target trajectory (T soll ) is used as the current trajectory acceleration (a refPtOrth ); - The controller adjusts the acceleration (a ctrl ) is limited to the following value, which is equal to the current trajectory acceleration (a refPtOrth ) and acceleration offset (a offset ) and, thus the actual position (P ist The acceleration (a) at the target position (P) is limited by the curvature-dependent acceleration limit. k-n To P k+m ) is below a predetermined value of acceleration; and -According to the limited controller, adjust the acceleration (a ctrl_lim ) accelerate the vehicle (1).

2. The method according to claim 1, wherein: The actual state (Z) of the vehicle (1) is determined at least by the actual speed (v ist ), actual acceleration (a ist ) and / or actual position (P ist )form.

3. The method according to claim 1, wherein: The actual position (P) is used as the current position of the vehicle (1) ist ) or the series of target positions (P k-n To P k+m ) in the nearest target position (P k ).

4. The method according to any one of claims 1 to 3, wherein: By the target trajectory (T soll ) is obtained from the longitudinal acceleration at the target trajectory (T soll ) of the successive target positions (P k-n To P k+m ) is calculated by looking at the time variation of the distance between them.

5. The method according to any one of claims 1 to 3, wherein: - The target trajectory (T soll ) is fed to the trajectory controller (5.2), with the help of which the acceleration (a ctrl ) should follow the target trajectory (T soll ) to accelerate the vehicle (1); and -Limited controller adjusts acceleration (a ctrl_lim ) is fed to an acceleration control unit (6) which is connected downstream of a trajectory controller (5.2) and which regulates and / or controls the actual acceleration (a) of the vehicle (1).

6. The method according to any one of claims 1 to 3, wherein: When the controller adjusts the acceleration (a ctrl ) and the limited controller adjusts the acceleration (a ctrl_lim ) and execute the target trajectory (T soll ) is recalculated.

7. According to the target trajectory (T soll ) means (2) for longitudinal control of a vehicle (1), the target trajectory prescribing a series of target positions (P) to be occupied by the vehicle (1) over time (t) k-n To P k+m ),in - A trajectory controller (5.2) is provided, wherein the trajectory controller is configured to generate a target trajectory (T soll ), based on the actual state (Z) of the vehicle (1), the controller for trajectory control is used to adjust the acceleration (a ctrl ), with the help of this controller, the acceleration should be adjusted according to the target trajectory (T soll ) is scheduled to accelerate the vehicle (1); - A pre-processing unit (5.1) is provided, which: - When the vehicle (1) passes the target trajectory (T soll ) from the target trajectory (T soll ) to obtain the target trajectory (T) at the current position of the vehicle (1). soll )’s curvature (K); - Ascertaining, from the curvature (K), the acceleration offset (a) which decreases with increasing curvature (K) offset );as well as - After passing the target trajectory (T soll ) is calculated at the current position of the vehicle (1) by the target trajectory (T soll ) is used as the current trajectory acceleration (a refPtOrth ); - A limiting unit (5.5) is provided, which adjusts the controller to adjust the acceleration (a ctrl ) is limited to the following value, which is equal to the current trajectory acceleration (a refPtOrth ) and acceleration offset (a offset ) and, thus the actual position (P ist The acceleration (a) at the target position (P) is limited by the curvature-dependent acceleration limit. k-n To P k+m ) is below a predetermined value of acceleration; - an acceleration control unit (6) is provided downstream of the trajectory controller (5.2) and adjusts the acceleration (a) according to the limited controller ctrl_lim ) to accelerate the vehicle (1).

8. The device (2) according to claim 7, wherein: The acceleration control unit (6) is a vehicle braking system.

9. The device (2) according to claim 7 or 8, comprising a control error monitoring unit, which adjusts the acceleration (a ctrl ) and the limited controller adjusts the acceleration (a ctrl_lim ) and execute the target trajectory (T soll ) is recalculated.

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