METHOD AND DEVICE FOR AUTOMATED LONGITUDINAL GUIDANCE OF A MOTOR VEHICLE

Description

[0001] The present invention relates to a method for the automated longitudinal guidance of a motor vehicle, particularly during cornering. Furthermore, the present invention relates to a control device configured to at least partially execute the method, as well as to a computer program and a computer-readable storage medium, each comprising instructions that, when the program or instructions are executed by a computer, cause the computer to at least partially execute the method.

[0002] Devices and methods are generally known from the prior art which can automatically influence the lateral and / or longitudinal guidance of a motor vehicle and can automatically control or steer the motor vehicle through a curve by influencing the lateral and / or longitudinal guidance.

[0003] For example, a driver assistance system for a vehicle is known from DE 10 2019 128 910 A1. The driver assistance system comprises a detection unit configured to detect an impending exit maneuver from a roadway involving cornering; and a control unit configured to determine, based on at least one route parameter and at least one vehicle parameter, a time and / or a position for the start of a coasting of the vehicle, such that a speed of the vehicle at the start of cornering is equal to a first threshold value and at the end of cornering is equal to a second threshold value, wherein the first threshold value is greater than the second threshold value.

[0004] However, such conventional predictive control for turns or curves typically has a basic dynamic according to which the vehicle accelerates after passing an event, i.e., after passing the curve. This means that the vehicle initially accelerates (positively) after passing the curve, regardless of the further course of the road, and then decelerates again, if necessary, at a subsequent curve in the road.

[0005] This acceleration behavior may be perceived as too dynamic and unreliable on a route or route with several turns in close succession, such as a U-turn. This suggests to the driver or user of the vehicle that the driver assistance system cannot handle this situation.

[0006] Furthermore, accelerating between several closely spaced turns leads to increased energy consumption, which, depending on the type of drive of the vehicle, results in increased fuel consumption and a decreasing range.

[0007] Document FR 3 096 328 A1 discloses a method for controlling a speed of a vehicle in order to achieve a next recommendation, comprising a step of determining a speed setpoint of said vehicle, during which, in a step, a plateau speed is calculated from a distance travelled at a stabilized speed by considering the acceleration profile and the deceleration profile of the vehicle.

[0008] Document US 2013 / 013164 A1 discloses a vehicle control device that generates a speed pattern that alternately repeats an acceleration travel pattern including a portion that accelerates a host vehicle and an inertial travel pattern including a portion with zero acceleration driving force and zero deceleration braking force with respect to the wheels of the host vehicle. The speed pattern is generated by reducing the speed of the host vehicle before any position of an intersection of the road on which the host vehicle is traveling and an exit leading to the road. The intersection and the exit may encounter another vehicle and include a traffic flow of other vehicles on a road with a host vehicle.By adapting a checked speed by reducing the vehicle speed of a speed pattern to the position of an intersection or exit, the host vehicle can cooperate with the traffic flow to improve fuel efficiency.

[0009] Document DE 10 2007 036794 A1 discloses a method and a device for determining the driving strategy of a motor vehicle, wherein for a given driving route a corridor for a possible target driving speed with an upper and a lower speed limit is defined over the driving distance.

[0010] Against the background of this prior art, the object of the present invention is to provide a device and a method which are each suitable for overcoming at least the above-mentioned disadvantages of the prior art.

[0011] The problem is solved by the features of the independent claim. The subclaims contain preferred developments of the invention.

[0012] The problem is then solved by a method for the automated longitudinal guidance of a motor vehicle.

[0013] The method is characterized by the fact that it includes detecting whether there are or exist two turns in a section of road ahead.

[0014] The method is further characterized in that it comprises maintaining a speed of the motor vehicle at a constant target speed value after passing through a first of the two turns until reaching a second of the two turns, if it is recognized that there are two turns in the section of road ahead.

[0015] In other words, a method is provided for controlling and / or regulating the speed of an automated motor vehicle. For this purpose, it is first checked whether the motor vehicle has to negotiate two consecutive curves or turns within a forthcoming section of road. The section of road can have a static or always constant length or a length that changes, e.g., depending on the speed of the motor vehicle. If two turns are detected, the speed of the motor vehicle is adjusted in such a way that an increase in the speed of the motor vehicle between the two curves, as is the case with conventional methods, is avoided. This means that, ideally, no intervention in the longitudinal dynamics of the motor vehicle is necessary when negotiating the two turns. This makes it possible to avoid the acceleration and subsequent braking between the two turns described above.This is primarily beneficial for the vehicle's energy consumption, meaning that the predictive driving style avoids unnecessary energy consumption due to acceleration and braking. However, it is also beneficial for the user's or driver's confidence in the vehicle's automated driving, as the acceleration and braking described above are avoided. Therefore, the method can overcome the disadvantages of the prior art described above.

[0016] Preferred further developments of the method described above are discussed in detail below.

[0017] Detecting whether there are two turns in the upcoming section of road may involve summing an angle of the first turn and an angle of the second turn to obtain a total angle. The total angle may be compared to a threshold value. If the total angle exceeds the threshold value, it may be detected that there are two turns in the upcoming section of road.

[0018] In other words, so that the method can detect whether two turns are present at all and then set the constant target speed value described above, the angles of the upcoming turns are first determined and then summed. The respective turn can essentially be recorded as a circular arc. The angle of the turn can then correspond to the central angle of the circular arc. It is also conceivable, additionally or alternatively, that the (at least) two turns are part of a roundabout. However, a turn is not limited to a circular arc or a circular road layout.It is also conceivable, additionally or alternatively, that at least one of the two turns occurs as part of an intersection, i.e., for example, as part of a turn to the right or left at an intersection where the road layout has a bend that, for example, essentially encloses an interior angle of 90°. The turns detected in this way, and in particular their central angles and interior angles, are then summed, i.e. added together. The sum of the two angles is then compared with a limit value or threshold. The limit value can be a fixed or static limit value. However, it is also conceivable that the limit value changes dynamically, for example, depending on the current speed of the motor vehicle.

[0019] It is conceivable that the constant target speed value is selected depending on the total angle.

[0020] In particular, the constant target speed value may decrease with increasing value of the total angle, i.e. when two sharp curves follow each other, the constant target speed value may be lower than when two less sharp curves follow each other.

[0021] The method may include setting the speed of the motor vehicle to the constant target speed value before the motor vehicle reaches the first turn if it is detected that there are two turns in the upcoming section of road.

[0022] In other words, the method can adjust the speed of the motor vehicle at an early stage by intervening in the longitudinal guidance of the vehicle or regulate and / or control it to the constant target speed value, so that the vehicle is already traveling at the constant target speed before reaching the first of the two turns. This can prevent braking in the curve. This is advantageous because with every steering maneuver, the frictional force of the tires on the ground must provide the necessary centripetal force. This lateral guidance force, transverse to the rolling direction, prevents the vehicle from leaving the roadway in a curve. When braking in the longitudinal direction, the tire must also transmit the longitudinal force in the longitudinal direction. These two forces add up vectorially to a resulting total force, which can be greater the better the grip of the road surface and tires. However, in wet and slippery conditions, only relatively low forces can be transmitted.This means that by adjusting the speed of the motor vehicle to the constant target speed value before reaching the first curve, not only can the user of the motor vehicle's confidence in automated driving be increased, but a relatively safe cornering can also be enabled.

[0023] The method may comprise setting the speed of the motor vehicle to a target speed value exceeding the constant target speed value during or after passing the second turn if it is detected that there are two turns in the upcoming section of the road.

[0024] This means that the method can provide for (positive) acceleration of the vehicle after reaching the second curve. It is particularly conceivable that acceleration occurs from the apex of the second turn.

[0025] Detecting whether there are two turns in a section of road ahead can be done based on map data and a planned trajectory of the vehicle.

[0026] It is conceivable, for example, that map data from a navigation device installed in the motor vehicle is used, which contains information about the road layout of the upcoming section of the route. The trajectory can include information about which part of the upcoming section of the route the motor vehicle will pass through, i.e. which route the motor vehicle will choose. The trajectory can also be referred to as a trajectory. The trajectory can, as described above, have bends and / or arcs, which are necessary in order to be able to drive through turns. These bends and arcs can be determined, and their interior angle or central angle can be used to determine whether a turn is present. This can be the case if the respective angle of the arc or bend exceeds a further predetermined limit or threshold. This limit can also be a fixed or static limit.However, it is also conceivable that this limit value changes dynamically, for example depending on the current speed of the vehicle.

[0027] The above description can be summarized in other words and in relation to a specific design as follows.

[0028] The method described above allows for improved interpretation of the road geometry of closely spaced turns ahead, as at least two turns can be combined into a single event, e.g., a U-turn. Such an event, such as a U-turn, can be detected if two turns are located within a specific, configurable road section whose combined turning angles exceed a configurable total angle.

[0029] The target speed, which can be parameterized if necessary, can then be determined from the summation of the turning angles of both intersections or turns. A new event can thus be generated from two turns, each of which represents an event in conventional methods, for which the longitudinal guidance or driving dynamics of the vehicle are independently intervened.

[0030] The new event generated in this way can have two target points to be traveled to one after the other. Starting at the first of the two target points, which can be located at a parameterizable distance before the first turn, the vehicle speed can be reduced, allowing both turns to be completed without (driver) intervention in the longitudinal dynamics. The target speed can then be maintained until the second of the two target points, which should also enable the driver to yield right of way to crossing traffic in a timely manner. The second of the two target points can be located at the location of the second intersection.

[0031] Furthermore, a control device is provided. The control device is characterized in that it is designed to at least partially execute the method described above.

[0032] The control device can be part of a driver assistance system or represent it. The control device can be, for example, an electronic control unit (ECU). The electronic control unit can be an intelligent processor-controlled unit that can communicate with other modules via a central gateway (CGW) and can form the vehicle's on-board network via fieldbuses such as the CAN bus, LIN bus, MOST bus, and FlexRay, or via automotive Ethernet together with telematics control units. The electronic control unit can control functions relevant to the vehicle's driving behavior, such as engine management, power transmission, braking system, or tire pressure monitoring system.In addition, all driver assistance systems such as the parking assistant, adaptive cruise control, lane keeping assistant, lane change assistant, traffic sign recognition, traffic light recognition, start-off assistant, night vision assistant, intersection assistant, and many more can be controlled by the electronic control unit.

[0033] It is conceivable that the control device is connected to a longitudinal guidance control unit which, based on a control signal received from the control device, enables automated intervention in the speed of the motor vehicle. This longitudinal guidance control unit can also be referred to as cruise control. The longitudinal guidance control unit can have a position control, i.e. this can be designed to set the speed and, if applicable, an acceleration of the motor vehicle at a possibly parameterizable location to a target speed value based on the control signal received from the control device. The control device and / or the longitudinal guidance control unit can further be connected to a navigation system which can transmit map attributes of the road ahead, in particular in the form of segments and their properties, to the longitudinal guidance control unit or the control device.The control device can be designed to be able to react automatically based on events (e.g. curves, roundabouts, turns, and / or traffic lights, etc.) from the digital map, ie to be able to intervene in the longitudinal and / or lateral guidance of the motor vehicle.

[0034] What has been described above with reference to the method also applies analogously to the control device and vice versa.

[0035] Furthermore, an automated motor vehicle is provided. The automated motor vehicle is characterized in that it has the control device described above.

[0036] The motor vehicle may be an automobile. The automated motor vehicle is designed to at least partially and / or temporarily assume longitudinal and, if applicable, lateral guidance during automated driving of the motor vehicle. Automated driving may be implemented in such a way that the motor vehicle's movement is (largely) autonomous.

[0037] The motor vehicle may be a Level 1 autonomy motor vehicle, i.e. it may have certain driver assistance systems that support the driver in operating the vehicle, such as adaptive cruise control (ACC).

[0038] The motor vehicle may be a motor vehicle of autonomy level 2, i.e. be so partially automated that functions such as automatic parking, lane keeping or lateral guidance, general longitudinal guidance, acceleration and / or braking are taken over by driver assistance systems.

[0039] The motor vehicle can be a Level 3 autonomy vehicle, meaning it is so conditionally automated that the driver does not need to continuously monitor the vehicle system. The vehicle performs functions such as activating the turn signal, changing lanes, and / or keeping in lane independently. The driver can attend to other matters but will be prompted by the system to take over control within a pre-warning period if necessary.

[0040] The motor vehicle can be a Level 4 autonomy vehicle, meaning it is so highly automated that the vehicle system permanently assumes control of the vehicle. If the system can no longer handle the driving tasks, the driver can be requested to take over.

[0041] The motor vehicle can be a Level 5 autonomy vehicle, meaning it is so fully automated that the driver is not required to perform the driving task. Other than setting the destination and starting the system, no human intervention is required. The motor vehicle can operate without a steering wheel or pedals.

[0042] What has been described above with reference to the method and the control device also applies analogously to the motor vehicle and vice versa.

[0043] Furthermore, a computer program is provided. The computer program is characterized in that it includes instructions which, when executed by a computer, cause the computer to at least partially execute the method described above.

[0044] A program code of the computer program may be in any code, in particular in a code suitable for motor vehicle controls.

[0045] Furthermore, a computer-readable storage medium is provided. The computer-readable storage medium is characterized in that it comprises instructions that, when the program is executed by a computer, cause the computer to at least partially execute the method described above.

[0046] This means that a computer-readable medium containing a computer program as defined above can also be provided. The computer-readable medium can be any digital data storage device, such as a USB stick, a hard drive, a CD-ROM, an SD card, or an SSD card. The computer program does not necessarily have to be stored on such a computer-readable medium to be made available to a driver; it can also be obtained externally via the Internet or otherwise.

[0047] What has been described above with reference to the method, the control device and the automated motor vehicle also applies analogously to the computer program and the computer-readable storage medium and vice versa.

[0048] Below is an embodiment with reference to Figures 1 to 4 described. Fig. 1 shows schematically a motor vehicle with a control device which is designed to carry out a method for the automated longitudinal guidance of the motor vehicle, Fig. 2 shows a schematic flow diagram of the method for automated longitudinal guidance of the motor vehicle, Fig. 3 shows schematically and exemplarily a section of road ahead with two turns, and Fig. 4 shows schematically and by way of example a speed curve of the method according to Figure 2 controlled motor vehicle when driving through the two turns Figure 3 .

[0049] In Figure 1an automated motor vehicle 1 is shown in a schematic side view, wherein the motor vehicle 1 has a control unit 2 which is connected to a navigation system 3 and a cruise control system 4 of the motor vehicle.

[0050] Together, the control unit 2, the navigation system 3 and the cruise control system 4 form a driver assistance system which is designed to carry out the method for the automated longitudinal guidance of the motor vehicle 1.

[0051] As from Figure 2 As can be seen, the method for automated longitudinal guidance of the motor vehicle 1 essentially comprises three steps S1, S2, S3.

[0052] In a first step S1 of the method, the control unit 2 receives map data 6 from the navigation system 3 regarding a route section ahead, wherein the map data 6 contains a trajectory or planned route 5 of the motor vehicle 1. This trajectory 5 is indicated by arrows in the map data 6 in Figure 3 shown.

[0053] In the second step S2 of the method, it is detected whether there are two turns 7, 8 in the upcoming section of the road. As in Figure 3 As can be seen, there are two consecutive turns 7, 8 along the trajectory 5 of the motor vehicle 1, each having a central angle of 90°.

[0054] The detection of the two turns 7, 8, which is performed by the control unit 2 based on the map data 6 and the trajectory 5, comprises summing the angle of the first turn 7 and the angle of the second turn 8 to obtain a total angle. In this case, the total angle is therefore 180°. This total angle is compared with at least one limit value, in this case with several predetermined limit values stored in a database (not shown). Each of the limit values is assigned a specific event, such as, for example and appropriately in this case, the U-turn event. The limit value for a U-turn can be 170°, for example. Since the total angle exceeds the limit value, the control unit 3 detects that there are two turns 7, 8 in the upcoming section of the road that can be assigned to the U-turn event.

[0055] In a third step S3 of the method, since it was recognized in the second step S2 of the method that the two turns 7, 8 are located in the upcoming section of the road, the control unit 2 outputs a control signal to the cruise control system 4.

[0056] This control signal causes the cruise control system 4 to intervene in the longitudinal dynamics of the motor vehicle 1, more precisely to adapt its speed depending on a position of the motor vehicle 1, as described in detail in Figure 4 is shown.

[0057] In Figure 4 The target speed value 9, which can also be referred to as the desired speed value, is shown as a function of a position P of the motor vehicle 2 relative to the two turns 7, 8. Therefore, on the vertical axis of the diagram, Figure 4 the speed V and the position P on the horizontal axis.

[0058] As can be seen from a summary of Figures 3 and 4As can be seen, the control signal causes the cruise control system 4 to reduce the target speed value 9 until a constant target speed value is reached. In doing so, the cruise control system 4 reduces the target speed value 9 such that the constant target speed value is reached at a first target point 10, which lies before the first turn 7. This means that the cruise control system 4 sets the speed of the motor vehicle 1 to the constant target speed value before the motor vehicle 1 reaches the first turn 7. The cruise control system 4 then keeps the target speed value 9 constant until a second target point 11, which lies in the second turn 8, is reached, so that the speed of the motor vehicle 1 remains constant even after passing through a first turn 7 until the second turn 8 is reached.This is a key difference from known methods in which the target speed value 12 increases between the two turns 7, 8, since the control unit conventionally considers each of the two turns 7, 8 as an independent event. This intermediate acceleration and deceleration is consequently prevented according to the present method. The constant target speed value is selected by the control device 2 as a function of the total angle of the two turns 7, 8 described above. Upon reaching the second target point 11, the target speed value 9 is increased by the cruise control system 4, so that the motor vehicle 1 accelerates. Accordingly, the speed of the motor vehicle 1 is set to a target speed value that exceeds the constant target speed value when passing through the second turn 11 (or possibly also after, but not shown here). List of reference symbols

[0059] 1Motor vehicle 2Control device 3Navigation system 4Cruise control system 5Trajectory 6Map data 7First turn 8Second turn 9Target speed value 10First target point 11Second target point 12Conventional target speed value PPosition S1-S3Steps of the procedure VSpeed

Claims

1. A method for the automated longitudinal guidance of a motor vehicle (1), comprising: detecting (S2) whether two turns (7, 8) are present in an upcoming road section, and if it is detected that two turns (7, 8) are present in the upcoming road section, maintaining (S3) a speed of the motor vehicle (1) after passing through a first of the two turns (7, 8) until reaching a second of the two turns (7, 8) at a constant target speed value (9), wherein the method is characterized in that the detection (S2) as to whether two turns (7, 8) are present in the upcoming road section comprises: summing up an angle of the first turn (7) and an angle of the second turn (8) in order to obtain a total angle, comparing the total angle with a threshold value, and detecting that two turns (7, 8) are present in the upcoming road section if the total angle exceeds the threshold value.

2. The method according to claim 1, wherein the constant target speed value (9) is selected depending on the total angle.

3. The method according to any one of claims 1 to 2, wherein the method comprises: if it is detected that two turns (7, 8) are present in the upcoming road section, adjusting the speed of the motor vehicle (1) to the constant target speed value (9) before the motor vehicle (1) reaches the first turn (7).

4. Method according to any one of claims 1 to 3, wherein the method comprises: if it is detected that two turns (7, 8) are present in the upcoming road section, adjusting the speed of the motor vehicle (1) to a target speed value (9) which exceeds the constant target speed value (9) at or after passing through the second turn (8).

5. The method according to any one of claims 1 to 4, wherein the detection as to whether two turns (7, 8) are present in an upcoming road section is further based on map data (6) and a planned trajectory (5) of the motor vehicle (1).

6. A control device (2) adapted to perform the steps of the method according to claims 1 to 5.

7. An automated motor vehicle (1), wherein the motor vehicle (1) comprises the control device (2) according to claim 6.

8. A computer program, wherein the computer program comprises commands that cause the control device of claim 6 to perform the method steps according to claims 1 to 5.

9. A computer-readable storage medium is stored on the computer program according to claim 8.