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 195 09 492 A1 discloses a method and a device for limiting the speed of a motor vehicle to a set maximum speed. The method comprises an acceleration-controlling system intervention with a predetermined acceleration setpoint dependent on a difference between the maximum speed and the actual speed, if the difference between the set maximum speed and the actual speed is greater than a predetermined value and the actual acceleration reaches the acceleration setpoint.

[0005] The method further comprises a speed control system intervention if the difference between maximum speed and actual speed is less than the specified value and a driver-requested speed is above the maximum speed.

[0006] DE 10 2011 102 435 A1 describes a method for operating a longitudinal driver assistance system of a motor vehicle, wherein the speed of the motor vehicle is controlled depending on a control data item. Curve data relating to a curve the motor vehicle will next negotiate is taken into account as additional control data during the control process.

[0007] The invention is based on the object of providing a novel method and a novel device for longitudinal control of a vehicle.

[0008] 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.

[0009] Advantageous embodiments of the invention are the subject of the subclaims.

[0010] In the method according to the invention for longitudinal control of a vehicle depending on a target trajectory that specifies a series of target positions to be assumed by the vehicle over time, a set acceleration for trajectory control is determined based on the actual state of the vehicle, by means of which the vehicle is to be accelerated according to the specifications of the target trajectory. Based on an actual speed of the vehicle and a predetermined maximum speed that is not to be exceeded when departing from the target trajectory, a set acceleration for cruise control is determined by means of which the vehicle is to be accelerated in order to guide it at the maximum speed. Both set accelerations are fed to an arbiter, which determines a resulting set acceleration from them, wherein the vehicle is accelerated according to the resulting set acceleration.

[0011] 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.

[0012] A control loop intended for automated vehicle control, for example, is a complex system with various system limitations that must be taken into account. In such a system, a speed limit plays a particularly important role. For example, a defined maximum speed, e.g., less than 130 km / h, is specified for the vehicle as a system limitation, and at the same time, legal speed limits must be taken into account. Furthermore, a maximum permissible deviation from a trajectory speed stored in the specified target trajectory may be specified. These limitations must be observed and correctly classified, especially if there is a discrepancy between the actual position of the vehicle and a target position derived from the target trajectory.

[0013] Using this method, all of the aforementioned constraints can be taken into account, enabling reliable trajectory control with the goal of reaching a planned position at the corresponding time according to a target trajectory. The actuating acceleration specified as the target value for trajectory control and / or the actuating acceleration for speed control are limited by the resulting actuating acceleration if they do not match the specified actual position. This can be the case, for example, if a longitudinal position control error has developed.

[0014] In contrast to conventional approaches to automated vehicle operation, in which a speed limit generally runs parallel to trajectory control and thus always influences the control quality, the present method makes it possible to activate the limit only shortly before a speed limit is reached. Consequently, the control quality can be maintained until this point in time. Nevertheless, activation can occur sufficiently early to reliably prevent exceeding the speed limit.

[0015] This means that using this method, speed limits or speed restrictions in a complex automated vehicle can be reliably observed and correctly classified, even if there is a discrepancy between the actual position and the target position. The speed limit does not impair trajectory control all the time, but rather only when there is a risk of violating the speed limits or speed restrictions.

[0016] Furthermore, the specified maximum speed is determined from a minimum of a maximum trajectory speed, a legally permissible maximum speed, and an absolute system-defined maximum speed. This enables a particularly reliable determination of the specified maximum speed.

[0017] The maximum trajectory speed is determined from the sum of a local reference speed specified in the target trajectory at an actual position of the vehicle and a maximum permissible deviation from the local reference speed depending on the actual speed and a curvature of the target trajectory at the actual position of the vehicle. This enables reliable limitation of the actuating acceleration at the actual position, even in the event of a large discrepancy between the actual and target positions of the vehicle.

[0018] In one possible embodiment of the method, a curvature of the target trajectory is taken into account when determining the actuating acceleration. This allows for reliable trajectory control.

[0019] In another possible embodiment of the method, the actual state of the vehicle is determined from at least the actual speed, the actual acceleration, and / or the actual position of the vehicle. Using these variables, the actual state can be very accurately mapped, allowing a reliable determination of the actuating acceleration for trajectory control.

[0020] 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 resulting 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.

[0021] In another possible embodiment of the method, the vehicle is decelerated when the resulting actuating acceleration assumes a negative value. This enables deceleration of the vehicle and thus particularly safe operation.

[0022] 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 set acceleration for trajectory control, by means of which the vehicle is to be accelerated according to the specifications of the target trajectory. Furthermore, the device comprises a speed controller which, based on an actual speed of the vehicle and a predeterminable maximum speed that should not be exceeded when departing from the target trajectory, determines a set acceleration for speed control, by means of which the vehicle is to be accelerated in order to guide it at the maximum speed.Furthermore, the device comprises an arbiter which determines a resulting actuating acceleration based on the two determined actuating accelerations, and an acceleration control unit subordinate to the trajectory controller which accelerates the vehicle according to the resulting actuating acceleration.

[0023] The present device enables reliable trajectory control with the goal of reaching a planned position at the corresponding time according to a target trajectory. The actuating acceleration specified as the target value for trajectory control and / or the actuating acceleration for speed control can be limited by the resulting actuating acceleration if they do not match the specified actual position. This can be the case, for example, if a longitudinal position control error has developed.

[0024] In contrast to conventional approaches to automated vehicle operation, in which a speed limit generally runs parallel to trajectory control and thus always influences the control quality, the present device makes it possible to activate the limit only shortly before a speed limit is reached. Consequently, the control quality can be maintained until this point in time. Nevertheless, activation can occur sufficiently early to reliably prevent the speed limit from being exceeded. When the limit is activated shortly before the speed limit is reached, the trajectory controller is used to switch to a speed limit or to override an existing actuating acceleration. The trajectory controller thus enables a complete solution for trajectory control of an automated vehicle.

[0025] This means that the device can reliably observe and correctly classify speed limits or restrictions in a complex automated vehicle, even if there is a discrepancy between the actual position and the target position. The speed limit does not affect trajectory control all the time, but rather only when there is a risk of violating the speed limits or restrictions.

[0026] In one possible embodiment of the device, the acceleration control unit is a vehicle braking system. This allows the resulting actuating acceleration to be easily and reliably adjusted.

[0027] Embodiments of the invention are explained in more detail below with reference to drawings.

[0028] 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 speeds for a vehicle, Fig. 3 schematically shows a block diagram of a device for longitudinal control of a vehicle, Fig. 4 schematically shows a block diagram of a speed controller of a vehicle and Fig. 5 schematically shows a block diagram of an arbiter for arbitrating between trajectory control and speed control of a vehicle.

[0029] Corresponding parts are provided with the same reference numerals in all figures.

[0030] In Figure 1 is a plan view of a traffic situation with a vehicle 1 in an actual position P actual and a target position P k as well as a target trajectory T target with several trajectory sections T target1 to T target3.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] Figure 2 shows a course of speeds v for the vehicle 1 as a function of time t, where the speeds v include a maximum trajectory speed v max_orth , a legally permissible maximum speed v max_legal , an absolute system-defined maximum speed v max_sys and a target speed v soll derived from the target trajectory T soll .

[0035] According to the speed profile assigned to the target trajectory T soll with the target speed v soll, it is intended 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 speed profile provided for the trajectory section T soll3 is not suitable for use with a road geometry in the trajectory section T soll2.

[0036] However, as in Figure 1shown, 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 .

[0037] In Figure 3 a block diagram of a possible embodiment of a device 2 for longitudinal control of a vehicle 1 is shown.

[0038] 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.

[0039] To do this based on the Figures 1 and 2 In order to solve the problem presented that if the actual position P ist deviates from the target position P k the vehicle 1 is moved in automated driving mode with an inappropriate speed v, the target trajectory T soll is fed to a further computing unit 5 with a speed controller 5.1, a trajectory controller 5.2 and an arbiter 5.3.

[0040] A trajectory control performed by the trajectory controller 5.2 and a speed limitation performed by the speed controller 5.1 run in parallel and the outputs of the two controllers must be coordinated.

[0041] By means of the trajectory controller 5.2, a set acceleration a ctrl_trj for trajectory control is determined based on the target trajectory T soll supplied to it and 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.

[0042] Furthermore, a set acceleration a ctrl_v for a speed control is determined by means of the speed controller 5.1, by means of which the vehicle 1 is to be accelerated in order to drive it at a speed in Figure 4 to the maximum speed v max shown in more detail.

[0043] The two determined positioning accelerations a ctrl_trj , a ctrl_v are fed to the arbiter 5.3, which determines a resulting positioning acceleration a ctrl.

[0044] The resulting control acceleration a ctrl is fed to an acceleration control unit 6 subordinate to the trajectory controller 5.2, which accelerates the vehicle 1 according to the resulting control acceleration a ctrl. The acceleration control unit 6 is, for example, a vehicle braking system.

[0045] This means that by means of the trajectory control, the vehicle 1 is controlled in such a way that it follows the target trajectory T soll , and by means of the speed limitation together with the arbiter 5.3, the vehicle 1 is kept within defined speed limits.

[0046] In Figure 4 is a block diagram of a possible embodiment of the speed controller 5.1 according to Figure 3 shown.

[0047] The speed controller 5.1 comprises a characteristic curve 5.1.1, a multiplier 5.1.2, a limiting unit 5.1.3 and a control unit 5.1.4 and determines, based on the actual speed v actual of the vehicle 1, which is measured in particular, and a predefinable maximum speed v max which should not be exceeded when departing from the target trajectory T target, the actuating acceleration a ctrl_v for the speed control, by means of which the vehicle 1 is to be accelerated in order to guide it at the maximum speed v max.

[0048] The maximum speed v max is calculated using the limiting unit 5.1.3 from a minimum of a maximum trajectory speed v max_orth , the legally permissible maximum speed v max_legal and the absolute system-defined maximum speed v max_sys.

[0049] The maximum trajectory speed v max_orth is determined from a local reference speed v refPtOrth stored in the specified target trajectory T soll and specified for the actual position P ist of vehicle 1 as well as from a maximum permissible deviation Δv of the local reference speed v refPtOrth inDependence on the actual speed v ist and a curvature K of the target trajectory T soll at the actual position P ist is determined from the characteristic curve 5.1.1. In the characteristic curve 5.1.1, a percentage %v characterizing the deviation Δv is determined as a two-dimensional function, whereby this percentage %v is inversely proportional to the curvature K and the actual speed v ist. The percentage %v indicates a percentage of the local reference speed v refPtOrth, which forms the permitted deviation Δv. A sum of the deviation Δv and the local reference speed v refPtOrth results in the maximum trajectory speed v max_orth at the actual position P ist .

[0050] For example, for a local reference speed v refPtOrth from 130 km / h, a percentage %v of 5% is permitted, resulting in a permissible deviation Δv of 6.5 km / h. At a local reference speed v refPtOrth from For example, at 30 km / h, a %v percentage of 20% may be permitted, resulting in a permissible deviation Δv of 6 km / h. These %v percentages apply, for example, to straight stretches and decrease with increasing curvature K, for example, in tight curves.

[0051] Such a limitation based on the local reference speed v refPtOrth offers the advantage that even in the case of a larger discrepancy between the actual position P ist and the target position P k, the target speed v soll at the actual position P ist can be limited accordingly. This is described in the Figures 1 and 2illustrated using the example of vehicle 1 driving through the roundabout, where a target specification expects a higher speed v, while the maximum trajectory speed v max_orth derived from the local reference speed v refPtOrth does not allow vehicle 1 to drive any faster. The control unit 5.1.4 then calculates the actuating acceleration a ctrl_v , which is required to minimize a difference between the actual speed v ist and the maximum speed v max , i.e. to reach the maximum speed v max and maintain its value.

[0052] In Figure 5 is a block diagram of a possible embodiment of an arbiter 5.3 according to Figure 3 for arbitration between a trajectory and a speed control of the vehicle 1.

[0053] The arbiter 5.3 comprises a crossfading module 5.3.1, a characteristic curve 5.3.2, a comparator 5.3.3, a switch 5.3.4 and a limiting unit 5.3.5.

[0054] The outputs of the trajectory controller 5.2 and the speed controller 5.1 are blended in the blending module 5.3.1, for example, using a min function, a fuzzy function, or another suitable function, and a blended control acceleration a ctrl_v_trj is formed from the control accelerations a ctrl_v and a ctrl_trj. The blended control acceleration a ctrl_v_trj is only passed through the switch 5.3.4 to the limiting unit 5.3.5 if the speed limitation is activated. Otherwise, only the trajectory control is connected to the output of the arbiter 5.3.

[0055] To determine whether the speed limitation is activated, a speed offset v offset is determined based on the characteristic curve 5.3.2 as a function of the actual speed v ist, and this speed offset is subtracted from the actual speed v ist. The resulting value is subtracted from the maximum speed v max, and the resulting result is fed to comparator 5.3.3 together with the actual speed v ist. If the actual speed v ist is greater than or equal to the result of the subtraction, comparator 5.3.3 outputs a signal that is greater than zero, indicating that the speed limitation is activated. If the actual speed v ist is less than the result of the subtraction, comparator 5.3.3 outputs a signal that is zero, indicating that the speed limitation is inactive.

[0056] The speed offset v offset is a function of the actual speed v and is particularly dependent on the dynamic properties of vehicle 1. The speed offset v offset is determined experimentally, for example, and can be implemented in the form of a lookup table.

[0057] Such a function of arbiter 5.3 offers the advantage that speed control is not active all the time, as would be the case, for example, if only a minimum function of the set acceleration a ctrl_trj were used for arbitration. Rather, speed control is only active shortly before the maximum speed v max is reached, allowing trajectory control to remain active for most of the time. Because speed control is activated early, exceeding the maximum speed v max can be reliably avoided. List of reference symbols

[0058] 1Vehicle 2Device 3Computing unit 3.1Trajectory planning module 4Environment detection sensors 5Computing unit 5.1Speed ​​controller 5.1.1Characteristic curve 5.1.2Multiplier 5.1.3Limiting unit 5.1.4Control unit 5.2Trajectory controller 5.3Arbiter 5.3.1Crossfade module 5.3.2Characteristic curve 5.3.3Comparator 5.3.4Switch 5.3.5Limiting unit 6Acceleration control unit a ctrl resulting actuating acceleration a ctrl_trj actuating acceleration a ctrl_v actuating acceleration a ctrl_v_trj blended actuating acceleration a ist actual acceleration KKurve P is actual position P k target position tTime T soll target trajectory T soll1 to T soll3 trajectory section UDData vGeschwindigkeit v ist actual speed v max maximum speed v max_legal legally permissible maximum speed v max_orth maximum trajectory speed v max_sys absolute system-defined maximum speed v offset speed offset v refPtOrth local reference speed v soll target speed ZIst-Status %vPercentage ΔvDeviation

Claims

1. Method for closed loop longitudinal control of a vehicle (1) according to a target trajectory (Tsoll) which specifies a series of target positions (Pk) to be assumed by the vehicle (1) over time (t), wherein - an actual state (Z) of the vehicle (1) is taken as a basis for determining a control acceleration (actrl_trj) for closed loop trajectory control by means of which the vehicle (1) is supposed to be accelerated in accordance with specifications of the target trajectory (Tsoll), - an actual velocity (vist) of the vehicle (1) and a specified maximum velocity (vmax) which is not supposed to be exceeded when travelling along the target trajectory (Tsoll) are taken as a basis for determining a control acceleration (actrl_v) for closed loop velocity control by means of which the vehicle (1) is supposed to be accelerated in order to guide it at the maximum velocity (vmax), - the two control accelerations (actrl_trj, actrl_v) are supplied to an arbiter (5.3) which uses them to determine a resulting control acceleration (actrl), - the vehicle (1) is accelerated in accordance with the resulting control acceleration (actrl), - the specified maximum velocity (vmax) is determined from a minimum from a maximum trajectory velocity (vmax_orth), a legally permissible maximum velocity (vmax_legal) and an absolute system-defined maximum velocity (vmax_sys), - the maximum trajectory velocity (vmax_orth)is determined from a sum of a local reference velocity (vrefPtOrth), specified in the target trajectory (Tsoll), at an actual position (Pist) of the vehicle (1) and a maximum permitted deviation (Δv) of the local reference velocity (vrefPtOrth) according to the actual velocity (vist) and a curvature (K) of the target trajectory (Tsoll) at the actual position (Pist) of the vehicle (1) and - the absolute system-defined maximum velocity (vmax_sys) is specified as a system restriction in the form of a maximum velocity defined for the vehicle in a system intended for automated control of the vehicle.

2. Method according to Claim 1, wherein a curvature (K) of the target trajectory (Tsoll) is taken into account when determining the control acceleration (actrl_trj) .

3. Method according to either of the preceding claims, wherein the actual state (Z) of the vehicle (1) is formed from at least the actual velocity (vist), an actual acceleration (aist) and / or an actual position (Pist) 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 closed loop controller control acceleration (actrl) is supposed to be used to accelerate the vehicle (1) in accordance with the specifications of the target trajectory (Tsoll), and - the resulting control acceleration (actrl) is supplied to a closed loop acceleration control unit (6) which is subordinate to the closed loop trajectory controller (5.2) and which open loop controls and / or closed loop controls a real acceleration of the vehicle (1).

5. Method according to one of the preceding claims, wherein the vehicle (1) is decelerated when the resulting control acceleration (actrl) assumes a negative value.

6. Apparatus (2) for closed loop longitudinal control of a vehicle (1) according to a target trajectory (Tsoll) which specifies a series of target positions (Pk) to be assumed by the vehicle (1) over time (t), wherein - there is provision for a closed loop trajectory controller (5.2) which uses a target trajectory (Tsoll) supplied to it to take an actual state (Z) of the vehicle (1) as a basis for determining a control acceleration (actrl_trj) for closed loop trajectory control by means of which the vehicle (1) is supposed to be accelerated in accordance with specifications of the target trajectory (Tsoll), - there is provision for a closed loop velocity controller (5.1) which takes an actual velocity (vist) of the vehicle (1) and a specifiable maximum velocity (vmax) which is not supposed to be exceeded when travelling along the target trajectory (Tsoll) as a basis for determining a control acceleration (actrl_v) for closed loop velocity control by means of which the vehicle (1) is supposed to be accelerated in order to guide it at the maximum velocity (vmax), - there is provision for an arbiter (5.3) which uses the two determined control accelerations (actrl_trj, actrl_v) to determine a resulting control acceleration (actrl), - there is provision for a closed loop acceleration control unit (6) which is subordinate to the closed loop trajectory controller (5.2) and which accelerates the vehicle (1) in accordance with the resulting control acceleration (actrl), - the closed loop velocity controller (5.1) comprises a limiting unit (5.1.3) which forms the specified maximum velocity (vmax) from a minimum from a maximum trajectory velocity (vmax_orth), a legally permissible maximum velocity (vmax_legal) and an absolute system-defined maximum velocity (vmax_sys), - the maximum trajectory velocity (vmax_orth)is determined from a sum of a local reference velocity (vrefPtOrth), specified in the target trajectory (Tsoll), at an actual position (Pist) of the vehicle (1) and a maximum permitted deviation (Δv) of the local reference velocity (vrefPtOrth) according to the actual velocity (vist) and a curvature (K) of the target trajectory (Tsoll) at the actual position (Pist) of the vehicle (1) and - the absolute system-defined maximum velocity (vmax_sys) is specified as a system restriction in the form of a maximum velocity defined for the vehicle in a system intended for automated control of the vehicle.

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