METHOD AND DEVICE FOR LONGITUDINAL CONTROL OF A VEHICLE

Description

[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.

[0003] DE 10 2017 010 180 B3 discloses a device and a method for controlling a longitudinal position of a vehicle by means of a longitudinal position controller that generates a longitudinal acceleration control signal for a subordinate acceleration control unit from a longitudinally dynamic pilot control setpoint variable and from longitudinally dynamic control error variables. A current control reference point corresponding to a current point in time and a preceding control reference point corresponding to a predeterminable look-ahead point in time are determined as control-relevant points in time. For each of the control reference points, current or predicted actual-target deviations of a longitudinal position, a driving speed, and an acceleration are determined and used to generate the longitudinally dynamic control error variables. Furthermore, acceleration setpoint values ​​are determined for each of the control reference points and used to generate the longitudinally dynamic pilot control setpoint variable.The longitudinal dynamic pilot control setpoint is formed by summing the acceleration setpoints determined for the control reference points in a weighted manner.

[0004] Furthermore, DE 10 2018 125 250 A1 discloses a method for automated longitudinal and lateral guidance of a vehicle based on a system model of the vehicle. The method comprises: Determining a value of a first state component as a deviation of an actual value of a state variable of the vehicle from a planned value of the state variable dependent on a target trajectory; wherein the state variable of the vehicle is dependent on a manipulated variable via the system model; Determining time-varying constraints of the first state component and the manipulated variable for N points in time from time k, with N > 1; Determining values ​​of one or more second state components of a constraint model at time k such that the determined, time-varying constraints of the first state component and the manipulated variable are approximated by values ​​of a second state component at the N points in time from time k;Determining a value of the manipulated variable at time k, based on the value of the first state component and on the values ​​of the one or more second state components at time k and on the basis of a predefined function configured to assign a value of the manipulated variable to different value combinations of the first state component and the one or more second state components; and operating a vehicle guidance system for automated longitudinal and lateral guidance of the vehicle depending on the determined value of the manipulated variable.

[0005] US 2021 / 078573 A1 describes a driver assistance device, a driver assistance method, and a driver assistance system. The risk of a vehicle deviating from a drivable width of a road on which the vehicle is traveling is determined based on a driving environment in front of the vehicle. Furthermore, based on the risk of deviation from an actuator operation, variable information relating to an actuator operation is determined. This variable information is related to a steering operation, braking operation, or driving operation that causes the vehicle to travel along the target trajectory. Furthermore, the variable information relating to the actuator operation is output to the actuator.

[0006] EP 1 008 482 A2 describes a motor vehicle comprising: a drivetrain comprising an engine having a throttle valve that is selectively operated to apply an acceleration force to the vehicle through wheels that support and propel the vehicle on a surface below it; a vehicle speed controller for selectively throttling the engine through the throttle valve to zero the difference between the actual vehicle speed and the preset vehicle speed; a distance and distance change measurement device for providing distance and distance change measurement signals corresponding to the distance and distance change measurement of the immediately preceding lead vehicle;and a vehicle following distance controller acting through the vehicle speed controller to zero the difference between the distance to the leading vehicle obtained by the distance change measuring device and a reference distance that changes with the timed following distance; ;

[0007] The distance and distance change measuring device and a vehicle speed sensor form feedback loops to the vehicle following distance control. The vehicle following distance control calculates a speed reference signal, which provides a command input to the vehicle speed control. The speed reference signal comprises an algebraic summation of a term proportional to the vehicle's own speed as measured by the vehicle speed sensor, a term proportional to the lead vehicle's distance as measured by the distance signal, and a term proportional to the lead vehicle's distance change measurement as measured by the distance change measurement signal.

[0008] The invention is based on the object of providing a novel method and a novel device for longitudinal control of a vehicle.

[0009] The object is achieved according to the invention by a method which has the features specified in claim 1 and by a device which has the features specified in claim 6.

[0010] Advantageous embodiments of the invention are the subject of the subclaims.

[0011] In the method according to the invention for longitudinal control of a vehicle as a function of a target trajectory which specifies a series of target positions to be assumed by the vehicle over time, a controller actuating acceleration for trajectory control, by means of which the vehicle is to be accelerated according to the specifications of the target trajectory, is determined based on an actual state of the vehicle. While the vehicle is traversing the target trajectory, a curvature of the target trajectory at a current position of the vehicle is determined from a local course of the target trajectory, wherein an acceleration offset which decreases with increasing curvature is determined based on the curvature. Furthermore, while the vehicle is traversing the target trajectory, a longitudinal acceleration resulting from the target trajectory at the current position of the vehicle is determined as the current trajectory acceleration.The controller actuating acceleration is limited to a value which corresponds at most to a sum of the current trajectory acceleration and the acceleration offset, and the vehicle is accelerated according to the limited controller actuating acceleration.

[0012] Trajectory control of an automated vehicle, especially a highly automated or autonomous vehicle, is a fundamental prerequisite for implementing automated driving. Based on data from environmental detection, decisions are made about which actions the vehicle should perform in the future. The result of this decision is a trajectory that, for example, maps the vehicle's position on a roadway over time and serves as a movement reference in a known vehicle environment. Trajectory control is designed to follow the trajectory as accurately as possible. If, for any reason, a significant longitudinal position control error has developed, a trajectory specification at the target position will not correspond to a trajectory specification at the actual position on the roadway where the vehicle is currently located. This means that a "target time" continues to run.There is a risk that the vehicle is, for example, in a tight curve and accelerates automatically because a temporal reference point, i.e. the target position, is already further ahead in the trajectory, for example on a straight line following the curve.

[0013] In this method, a discrepancy between the local reference point, i.e., the actual position of the vehicle, and the temporal reference point, i.e., the target position of the vehicle in the trajectory, is taken into account during longitudinal vehicle control. The method limits a target acceleration if it is too high at the actual position. Such curvature-dependent acceleration limitation at the actual position can prevent dangerous situations resulting from excessive acceleration, such as excessive acceleration in a tight curve.

[0014] In other words, the method enables safe trajectory control with the aim of reaching a planned position at a corresponding time, whereby, if necessary, the acceleration at the actual position is limited by a curvature-dependent acceleration limit below the value of the acceleration specification at the target position.

[0015] In one possible embodiment of the method, the actual state of the vehicle is determined from at least the actual vehicle speed, the actual vehicle acceleration, and / or the actual vehicle position. These variables provide a good representation of the actual state, allowing a reliable determination of the controller's actuating acceleration.

[0016] In another possible embodiment of the method, an actual position or the next target position from 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 for determining the curvature.

[0017] In another possible embodiment of the method, the longitudinal acceleration resulting from the target trajectory is determined from a temporal change in the distances between successive target positions of the target trajectory. This makes it easy to determine the current trajectory acceleration.

[0018] In another possible embodiment of the method, the target trajectory is fed to a trajectory controller, which, based on the controller's set acceleration, is to accelerate the vehicle according to the specifications of the target trajectory. The limited controller set acceleration is fed to an acceleration control unit subordinate to the trajectory controller, which controls and / or regulates the actual acceleration of the vehicle.

[0019] In another possible embodiment of the method, if a specified difference between the specified controller actuating acceleration and the limited controller actuating acceleration is exceeded, the target trajectory is recalculated. This minimizes any deviation of the target trajectory from the actual trajectory and, consequently, any deviation of the controller actuating acceleration from the corrected controller actuating acceleration.

[0020] The device according to the invention for longitudinal control of a vehicle depending on a target trajectory, which specifies a series of target positions to be assumed by the vehicle over time, comprises a trajectory controller which, based on a target trajectory supplied to it and based on an actual state of the vehicle, determines a controller actuating acceleration for trajectory control, by means of which the vehicle is to be accelerated according to the specifications of the target trajectory. The device further comprises a preprocessing unit which, while the vehicle is traversing the target trajectory, determines a curvature of the target trajectory at a current position of the vehicle from a local course of the target trajectory.Furthermore, the preprocessing unit uses the curvature to determine an acceleration offset that decreases with increasing curvature, and during the descent of the target trajectory at the current position of the vehicle, it determines a longitudinal acceleration resulting from the target trajectory as the current trajectory acceleration. Additionally, the device comprises a limiting unit that limits the controller set acceleration to a value that corresponds at most to the sum of the current trajectory acceleration and the acceleration offset, as well as an acceleration control unit subordinate to the trajectory controller that accelerates the vehicle according to the limited controller set acceleration.

[0021] Using this device, a discrepancy between the local reference point, i.e., the actual position of the vehicle, and the temporal reference point, i.e., the target position of the vehicle in the trajectory, can be taken into account during longitudinal vehicle control. The device limits a target acceleration if it is too high at the actual position. Such curvature-dependent acceleration limitation at the actual position can prevent dangerous situations resulting from excessive acceleration, such as excessive acceleration in a tight curve.

[0022] In other words, the device enables safe trajectory control with the aim of reaching a planned position at a corresponding time, whereby, if necessary, the acceleration at the actual position is limited by a curvature-dependent acceleration limit below the value of the acceleration specification at the target position.

[0023] In one possible embodiment of the device, the acceleration control unit is a vehicle braking system. This allows the limited controller acceleration to be easily and reliably adjusted.

[0024] In a further possible embodiment of the device, this comprises a control error monitoring unit which, if a predetermined

[0025] The difference between the specified controller actuating acceleration and the limited controller actuating acceleration is used to recalculate the target trajectory. This minimizes any deviation of the target trajectory from the actual trajectory and, consequently, any deviation of the controller actuating acceleration from the corrected controller actuating acceleration.

[0026] Embodiments of the invention are explained in more detail below with reference to drawings.

[0027] Showing: Fig. 1 schematically shows a plan view of a traffic situation with a vehicle in an actual position and a desired position, Fig. 2 schematically shows temporal courses of an acceleration and a speed of a vehicle, Fig. 3 schematically shows a block diagram of a device for longitudinal control of a vehicle and Fig. 4 schematically shows a course of a desired trajectory of a vehicle.

[0028] Corresponding parts are provided with the same reference numerals in all figures.

[0029] In Figure 1 is a plan view of a traffic situation with a vehicle 1 in an actual position P ist and a target position P k as well as a target trajectory T soll with several trajectory sections T soll1 to T soll3. In Figure 2 are curves of an acceleration a and a speed v of the vehicle 1 according to Figure 1 as a function of time t.

[0030] Vehicle 1 is designed for automated, particularly highly automated or autonomous, driving operation. Trajectory control is a fundamental prerequisite for implementing such an automated driving function.

[0031] This trajectory control is based on Figure 3Based on the data UD shown in more detail from an environment detection, a decision is made as to which actions vehicle 1 should perform in the future. The result of this decision is the target trajectory T target , which, for example, maps a position of vehicle 1 on a road over time t and serves as a movement reference in a known vehicle environment. The trajectory control is designed to follow the trajectory as accurately as possible. If, for any reason, a larger longitudinal position control error has built up, a trajectory specification at the target position P k does not correspond to a trajectory specification at the actual position P actual on the road at which vehicle 1 is currently located. This means that a "target time" continues to run.

[0032] The illustration uses a roundabout as an example to show that the actual position P ist of the automated vehicle 1 is located behind the target position P k . The actual position P ist is located inside the roundabout, while the target position P k is already outside the roundabout after leaving it.

[0033] How Figure 2 As shown, according to the speed profile and the acceleration profile assigned to the target trajectory T soll, it is provided that vehicle 1 should travel within the roundabout on the trajectory section T soll2 at a low, constant speed v and should accelerate more strongly on the trajectory section T soll3 after the roundabout until a higher speed v is reached. The acceleration profile provided for the trajectory section T soll3 is not suitable for use with a road geometry in the trajectory section T soll2.

[0034] However, as in Figure 1 shown, the temporal reference point, i.e. the target position P k in the trajectory section T soll3 , and the local reference point, i.e. the actual position P ist in the trajectory section T soll2 , are far apart, there is a risk that the vehicle 1 is located within the roundabout on the trajectory section T soll2 and accelerates automatically because the temporal reference point is already further ahead in terms of location, in this case on a straight line following the roundabout in the trajectory section T soll3 .

[0035] In this situation, a typical trajectory controller would attempt to compensate for an existing longitudinal position error, and vehicle 1 would accelerate more strongly in the roundabout. Depending on the magnitude of the curvature K in the route, such a situation is generally undesirable and potentially dangerous.

[0036] Such errors can also occur if a so-called control error monitoring module is present in the system for the automated operation of vehicle 1, which replans the target trajectory T target when a control error becomes larger. This is the case, for example, if the control error is relatively large but lies below a specified threshold for re-determining the target trajectory T target.

[0037] However, if the actual position P ist is still in the trajectory section T soll1 instead of the trajectory section T soll2 , contrary to the representation, and vehicle 1 is still decelerating, this does not result in a safety-relevant problem. In this case, the control error would increase even further, but without undesirable acceleration a.

[0038] In Figure 3 a block diagram of a device 2 for longitudinal control of a vehicle 1 is shown.

[0039] The device 2 comprises a first computing unit 3 with a trajectory planning module 3.1, which plans the target trajectory T target based on data UD acquired by means of an environmental detection sensor 4.

[0040] To do this based on the Figure 1 and 2 In order to solve the problem presented that, when the actual position P ist deviates from the target position P k, inappropriate accelerations a of the vehicle 1 occur in automated driving mode, the target trajectory T soll is fed to a further computing unit 5 with 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.

[0041] During a departure of the target trajectory T soll by the vehicle 1, the preprocessing module 5.1 derives a curvature K of the target trajectory T soll at a current position of the vehicle 1 from a local course of the target trajectory T soll.

[0042] Based on the characteristic curve 5.3, which represents the acceleration a of the vehicle 1 as a function of the curvature K, the preprocessing module 5.1 determines, as a function of the curvature K and, in particular, using predicted future information, an acceleration offset a offset that decreases with increasing curvature K. This acceleration offset a offset can also be calculated as a function of a coefficient of friction of a road surface and constitutes a permissible acceleration deviation.

[0043] Furthermore, during the departure of the target trajectory T soll at a current position of vehicle 1, for example, the actual position P ist , the preprocessing module 5.1 determines a longitudinal acceleration resulting from the target trajectory T soll as the current trajectory acceleration a refPtOrth and feeds it to the limiting unit 5.5. This trajectory acceleration a refPtOrth forms a reference acceleration at a trajectory point closest to the current position of vehicle 1.

[0044] In contrast to the actual position P ist of vehicle 1, the current position of vehicle 1 can also be a next target position P k from a Figure 4 The series of target positions P kn to P k+m of the target trajectory T shown in more detail should be used.

[0045] The longitudinal acceleration resulting from the target trajectory T soll can be calculated from a temporal change of distances between Figure 4The successive target positions P kn to P k+m of the target trajectory T shown in more detail are to be determined.

[0046] The acceleration offset a offset and the trajectory acceleration a refPtOrth are added, whereby a resulting sum is also fed to the limiting unit 5.5.

[0047] Furthermore, by means of the trajectory controller 5.2, a controller actuating acceleration a ctrl for trajectory control is determined on the basis of the target trajectory T soll supplied to it and based on an actual state Z of the vehicle 1, by means of which the vehicle 1 is to be accelerated according to the specifications of the target trajectory T soll. The actual state Z of the vehicle 1 is characterized, for example, by an actual speed v ist , an actual acceleration a ist and the actual position P ist of the vehicle 1.

[0048] By means of the limiting unit 5.5, a limited controller actuating acceleration a ctrl_lim is calculated from the minimum of the sum of the acceleration offset a offset as well as the trajectory acceleration a refPtOrth and the actuating acceleration a ctrl according to a ctrl _ lim = min a ctrl , max Par a refPtOrth + a offset certainly.

[0049] Only trajectory accelerations a refPtOrlh that are greater than a positive parameter Par are considered, since otherwise vehicle 1 would remain stationary during a deceleration phase. A negative trajectory acceleration a refPtOrth is always smaller than a positive controller control acceleration a ctrl in a subsequent acceleration phase.

[0050] The limited controller actuating acceleration a ctrl_lim is fed to an acceleration control unit 6, which is subordinate to the trajectory controller 5.2 and accelerates the vehicle 1 according to the limited controller actuating acceleration a ctrl_lim. The acceleration control unit 6 is, for example, a vehicle braking system. Thus, the control system output is never greater than the local trajectory acceleration a refPtOrth , offset upwards by a permissible curvature-dependent deviation.

[0051] It is therefore possible that vehicle 1 in the Figure 1 In the situation shown, at the actual position P, there would be no undesirable acceleration. On a straight stretch of road, however, vehicle 1 can accelerate sufficiently and compensate for a control error.

[0052] Figure 4shows a course of a possible target trajectory T soll of a vehicle 1. The target trajectory T soll specifies a series of target positions P kn to P k+m to be assumed by the vehicle 1 over the time t at respective times t kn to t k+m. List of reference symbols

[0053] 1Vehicle 2Device 3Computing unit 3.1Trajectory planning module 4Environment detection sensors 5Computing unit 5.1Processing module 5.2Trajectory controller 5.3Characteristic curve 5.4Maximum value detector 5.5Limiting unit 6Acceleration control unit aAcceleration a ctrl Controller actuating acceleration a ctrl_lim Limited controller actuating acceleration a ist Actual acceleration a offset Acceleration offset a refPtOrth Trajectory acceleration KKurvature ParParameter P ist Actual position P kn to P k+m Target position tTime t kn to t k+m Time T soll Target trajectory T soll1 to T soll3 Trajectory section UDData vSpeed ​​v is Actual speed ZIst-Status

Claims

1. Method for the closed loop longitudinal control of a vehicle (1) as a function of a target trajectory (Tsoll) which specifies a series of target positions (Pk-n to Pk+m) to be assumed by the vehicle (1) over the time (t), wherein - based on an actual state (Z) of the vehicle (1), a closed loop controller actuating acceleration (actrl) for closed loop trajectory control is determined, by means of which the vehicle (1) is to be accelerated in accordance with specifications of the target trajectory (Tsoll), - during following of the target trajectory (Tsoll) by the vehicle (1), a curvature (K) of the target trajectory (Tsoll) is determined from a local course of the target trajectory (Tsoll) at a current position of the vehicle (1), - an acceleration offset (aoffset) which decreases with increasing curvature (K) is determined based on the curvature (K), - during the following of the target trajectory (Tsoll), a longitudinal acceleration resulting from the target trajectory (Tsoll) is determined at the current position of the vehicle (1) as the current trajectory acceleration (arefPtOrth), - the closed loop controller actuating acceleration (actrl) is limited to a value which corresponds at most to a sum of the current trajectory acceleration (arefPtOrth) and the acceleration offset (aoffset), and - the vehicle (1) is accelerated in accordance with the limited closed loop controller actuating acceleration (actrl_lim).

2. Method according to Claim 1, wherein the actual state (Z) of the vehicle (1) is formed at least from an actual speed (vist), an actual acceleration (aist) and / or an actual position (Pist) of the vehicle (1).

3. Method according to Claim 1 or 2, wherein an actual position (Pist) or a next target position (Pk) from the series of target positions (Pk-n to Pk+m) is used as the current position of the vehicle (1).

4. Method according to one of the preceding claims, wherein - the target trajectory (Tsoll) is supplied to a closed loop trajectory controller (5.2), by means of which the vehicle (1) is to be accelerated according to the specifications of the target trajectory (Tsoll) on the basis of the closed loop controller actuating acceleration (actrl), and - the limited closed loop controller actuating acceleration (actrl_lim) is supplied to a closed loop acceleration control unit (6) which is subordinate to the closed loop trajectory controller (5.2), which open loop controls and / or closed loop controls a real acceleration (a) of the vehicle (1).

5. Method according to one of the preceding claims, wherein a recalculation of the target trajectory (Tsoll) is carried out when a predetermined difference between the predetermined closed loop controller actuating acceleration (actrl) and the limited closed loop controller actuating acceleration (actrl_lim) is exceeded.

6. Apparatus (2) for the closed loop longitudinal control of a vehicle (1) as a function of a target trajectory (Tsoll) which specifies a series of target positions (Pk-n to Pk+m) to be assumed by the vehicle (1) over the time (t), wherein - a closed loop trajectory controller (5.2) is provided which, on the basis of a target trajectory (Tsoll) supplied to it, based on an actual state (Z) of the vehicle (1), determines a closed loop controller actuating acceleration (actrl) for trajectory control, by means of which the vehicle (1) is to be accelerated in accordance with specifications of the target trajectory (Tsoll), - a pre-processing unit (5.1) is provided which - during following of the target trajectory (Tsoll) by the vehicle (1), determines a curvature (K) of the target trajectory (Tsoll) from a local course of the target trajectory (Tsoll) at a current position of the vehicle (1), - uses the curvature (K) to determine an acceleration offset (aoffset) which decreases with increasing curvature (K), and - during the following of the target trajectory (Tsoll), determines a longitudinal acceleration resulting from the target trajectory (Tsoll) at the current position of the vehicle (1) as the current trajectory acceleration (arefPtOrth), - a limiting unit (5.5) is provided which limits the closed loop controller actuating acceleration (actrl) to a value which corresponds to at most a sum of the current trajectory acceleration (arefPtOrth) and the acceleration offset (aoffset), - a closed loop acceleration control unit (6), which is subordinate to the closed loop trajectory controller (5.2), is provided, which accelerates the vehicle (1) in accordance with the limited closed loop controller actuating acceleration (actrl_lim).

7. Apparatus (2) according to Claim 6, wherein the closed loop acceleration control unit (6) is a vehicle braking system.

8. Apparatus (2) according to Claim 6 or 7, comprising a closed loop control fault monitoring unit which, when a predetermined difference between the predetermined closed loop controller actuating acceleration (actrl) and the limited closed loop controller actuating acceleration (actrl_lim) is exceeded, carries out a recalculation of the target trajectory (Tsoll).