METHOD FOR DETERMINING A MAXIMUM TOP SPEED

Description

[0001] The present invention relates to a method for determining a maximum final speed of a motor vehicle before entering a speed limit zone. Furthermore, the invention relates to a control unit for implementing the method. State of the art

[0002] Modern vehicles increasingly offer automated driving functions to reduce driver workload, such as highway or parking assistants, or in the future, piloted functions. Such functions can also control longitudinal control, i.e., the acceleration or deceleration of the vehicle.

[0003] Document FR 3 096 328 A1 discloses a method for determining a maximum final speed of a motor vehicle before entering a speed limit zone using acceleration and deceleration profiles.

[0004] The document US 2013 / 013164 A1 presents a method for controlling a maximum final speed before the start of a speed limit zone depending on traffic light cycles.

[0005] The document DE 10 2007 036794 A1 shows a procedure for the basic definition of driving strategies.

[0006] DE 10 2009 058 393 A1 discloses a method for automatically changing a cruise control speed from a current speed zone to the next speed zone. A location in front of a moving vehicle at which the maximum permitted speed of the zone changes from the current maximum permitted speed to the next maximum permitted speed is determined. A speed profile is determined to change the vehicle speed from the current maximum permitted speed to the next maximum permitted speed. The speed profile includes nonlinear changes in the vehicle speed between the current speed zone and the next speed zone to eliminate abrupt changes in the vehicle speed.

[0007] The problem now is when a traffic sign appears a little further away and the ego vehicle isn't at the maximum speed limit. How much and for how long does the ego vehicle need to accelerate in order to avoid unnecessarily braking at the traffic sign, for example, but also not drive too slowly for too long?

[0008] The object underlying the invention is therefore to provide a method which calculates an ideal target speed in order not to accelerate unnecessarily or to drive unnecessarily slowly before an area with a speed limit.

[0009] To achieve this objective, a method for determining a maximum final speed of a motor vehicle before entering a speed limit zone is proposed, having the features of claim 1. Furthermore, a control unit for a driver assistance system with a computing unit for implementing the method is provided, having the features of claim 11. Preferred embodiments are set forth in the dependent claims. Disclosure of the invention

[0010] The invention provides a method for determining a maximum final speed of a motor vehicle before the beginning of a speed limit zone. The speed limit zone is a zone in which a lower speed than the maximum final speed should be driven. This lower speed, referred to below as the speed limit, can result from safety considerations or legal regulations. The maximum final speed is the maximum speed to which the motor vehicle can accelerate before entering the speed limit zone.

[0011] To determine this maximum speed, the current vehicle speed, the speed limit of an upcoming speed limit zone, and the distance to the start of the speed limit zone are first determined. Based on these values, a time to the speed limit zone is estimated. This provides an estimate of approximately how long the vehicle will need to reach the start of the speed limit zone. A speed increase relative to the current vehicle speed is then determined, dependent on the time to the speed limit zone. This speed increase is preferably calculated using a vehicle-specific algorithm. The speed increase corresponds to a difference between the current vehicle speed and the maximum final speed.Adding the current speed and the speed increase results in the maximum final speed.

[0012] In the next step, a deceleration is estimated so that, based on the current vehicle speed, the speed increase, and the distance to the start of the speed limit zone, the speed limit is determined at the start of the speed limit zone. The determined speed increase is reduced if the estimated deceleration exceeds a deceleration limit. The deceleration limit can be predefined or varied within certain limits by the driver. It is also possible to reduce the deceleration limit depending on road conditions, such as snow or rain.

[0013] This method has the advantage of being implemented using simple calculations, thus reducing the computing power required to perform the process. Furthermore, unnecessary braking and acceleration are avoided, thus saving fuel. Furthermore, safety is increased because deceleration is kept within a specified range. Using this method in a driver assistance system also increases driving comfort for the driver.

[0014] In a preferred embodiment of the invention, the speed increase is read from a characteristic map. This characteristic map can, for example, contain a value for a speed increase at the time of the speed limit range. Such a characteristic map can, for example, be stored at the factory. Using such a characteristic map significantly simplifies the determination of the speed increase. The method can thus be carried out faster and more easily. Furthermore, the computing capacity can be significantly reduced.

[0015] In a further preferred embodiment of the invention, the reduction in the determined speed increase is calculated using a characteristic map for the estimated deceleration. A speed reduction value can be stored in such a characteristic map for the determined deceleration. A factor between zero and one can also be stored in the characteristic map. The speed increase is multiplied by this factor to determine a resulting speed increase. This allows a resulting speed increase to be determined quickly and easily. Using a characteristic map also significantly simplifies the calculations for this purpose.

[0016] Preferably, the characteristic maps are selected according to a selected driving mode of the motor vehicle. The driver can choose between different driving modes, such as a sport mode or a fuel-saving mode. Accordingly, a corresponding characteristic map is used to implement the method. In contrast to a sport mode, the speed increase and, accordingly, the deceleration are lower in a fuel-saving mode. The method can thus be adapted to the driver's preferences, significantly improving driving comfort.

[0017] In an advantageous refinement, a constant deceleration is assumed for estimating the deceleration. It is thus assumed that the vehicle, starting from its maximum final speed, decelerates at a constant deceleration value. Using a constant deceleration simplifies the estimation of the deceleration, even though constant deceleration is not normally used. This further significantly reduces the computational effort.

[0018] Alternatively, a predefined delay function is used for the delay. These delay functions are based on real-world delays. Using such delay functions allows the delay to be determined much more accurately. Furthermore, the maximum delay value can be more accurately predicted.

[0019] In a further advantageous embodiment, the distance to the start of the speed limit zone is determined using map data and / or sensor data and / or cloud data. Based on the current position, which is determined via GPS, for example, the distance to the start of the speed limit zone can be determined within the map. The distance to the speed limit zone can also be determined using a radar sensor, for example. Such a sensor is already installed in many cars for other assistance systems, so no additional sensor is necessary. In addition to this or alternatively, the distance can also be determined based on GPS data from a cloud. Thanks to these options, the distance to a speed limit zone can be determined simply and economically.

[0020] According to a practical implementation, the speed limit is determined based on legally prescribed limits and / or route-specific limits. A legally prescribed limit could be, for example, a speed restriction or another speed specified for a specific area. This speed restriction can be indicated, for example, by signs. The limit can also be determined, for example, by a curve, an on-ramp, or the road condition.

[0021] According to another practical embodiment, the speed limit is determined based on map data and / or camera data and / or cloud data. The speed limit can be determined based on values stored in the map. A speed limit can also be determined based on a route detected on the map, such as a curve. The curve radius or a maximum curve radius of a curve can be determined in the map. The speed limit is then determined based on this curve radius. This ensures that unnecessary braking is not required in the curve, thus increasing safety. The speed limits of the legal and route-specific limits can also be retrieved from a cloud. This can reduce the computing power of such a system.

[0022] Advantageously, after determining the maximum final speed, the vehicle is accelerated from its current speed to this speed and then decelerated to the speed limit until the beginning of the speed limit zone. These steps, provided as part of a driver assistance system, reduce the driver's workload, thus increasing driving comfort.

[0023] The object of the present invention is additionally achieved by a control unit for a driver assistance system for controlling longitudinal control of a motor vehicle, comprising a computing unit for implementing the method according to the invention. Such a control unit can thus be integrated into a motor vehicle, thus achieving the advantages described for the method.

[0024] The method described above can, in particular, be computer-implemented, for example, and thus embodied in software. The invention therefore also relates to a computer program with machine-readable instructions that, when executed on one or more computers, cause the computer(s) to execute the described method. In this sense, control units for vehicles and embedded systems for technical devices that are also capable of executing machine-readable instructions are also to be considered computers.

[0025] The invention also relates to a machine-readable data carrier and / or a downloadable product containing the computer program. A downloadable product is a digital product that can be transmitted over a data network, i.e., downloaded by a user of the data network, and which can be offered for immediate download, for example, in an online shop.

[0026] Embodiments of the invention are illustrated in the drawing and explained in more detail in the following description. It shows: FigureEmbodiment of a method according to the invention.

[0027] The figure shows an embodiment of a method according to the invention. This method is used to determine a maximum final speed v max of a motor vehicle before entering a speed limit zone. In a first step A1, the current vehicle speed v is determined. This speed v is determined, for example, directly from the current vehicle speeds. The speed v can also be determined using the values of the GPS system.

[0028] In the first step A2, a speed limit v G of an upcoming speed limit zone is also determined. The speed limit v G can be determined based on legal values. The speed limit v G can also be determined using a speed limit sign detected by a vehicle camera. The speed limit v G can also be determined using speed limits v G entered on a map. In addition, a speed limit v G can be determined from the map based on, for example, the curve radius.

[0029] In the first step A3, a distance dZ to the beginning of the speed limit zone is also determined. The distance dZ, like the speed limit vG, can be determined from map data. Alternatively or additionally, this distance dZ can be determined using sensors on the vehicle, such as a radar sensor.

[0030] Based on the current vehicle speed v, the speed limit v G , and the distance d Z to the beginning of the speed limit zone, a time t until the beginning of the speed limit zone is estimated in a next step B. The time t can be calculated, for example, using the formula t = d Z / ((v G +v) / 2). Since the time t is calculated based on the current speed v, this is only an estimate.

[0031] In a next step C, a speed increase Δv is determined based on time t. To do this, a speed increase Δv is determined at time t using, for example, a characteristic map. Then, in step D, based on this speed increase Δv, a necessary deceleration a V is estimated so that the speed limit value v G is present at the start of the speed limit range. To estimate the deceleration a V, a constant deceleration can be assumed, so that the deceleration a V is calculated using the following formula: a V =(v G 2< -v 2< ) / (2*d Z ). Alternatively, the deceleration a V can also be determined using a characteristic map.

[0032] Based on the deceleration a V thus determined, it is compared with a deceleration limit a G. This deceleration limit a G represents a maximum deceleration, which has been determined, for example, based on driving comfort, the technical specifications of the vehicle, or the road conditions. If the determined deceleration a V is greater than the deceleration limit a G, the determined speed increase Δv is reduced in a next step E. The amount of the reduction can be determined, for example, from a characteristic map.

[0033] After the speed increase Δv has been reduced, or if the deceleration a V does not exceed the deceleration limit a G, the motor vehicle is accelerated in a next step F to the final speed v max resulting from the vehicle speed v and the speed increase Δv. In a subsequent step G, the motor vehicle is then decelerated to the speed limit v G until the beginning of the speed limit range.

Claims

1. Method for determining a maximum final speed (vmax) of a motor vehicle before the start of a speed limit area, comprising the steps of: - determining (A1, A2, A3) a current motor vehicle speed (v), a speed limit value (vG) of an imminent speed limit area and a distance (dz) from the start of the speed limit area, - estimating (B) a time (t) to the speed limit area on the basis of the previously determined values (v, vG,dz), - determining (C) a speed increase (Δv) with respect to the current motor vehicle speed (v), - estimating (D) a deceleration (aV) such that, on the basis of the current motor vehicle speed (v), the speed increase (Δv) and the distance (dz) from the start of the speed limit area, the speed limit value (vG) is present at the start of the speed limit area, and - reducing (E) the determined speed increase (ΔV), characterized in that - the speed increase (Δv) with respect to the current motor vehicle speed (v) depends on the time (t) to the speed limit area, - the determined speed increase (Δv) is reduced if the estimated deceleration (aV) is above a deceleration limit value (aG).

2. Method according to Claim 1, characterized in that the speed increase (Δv) is read out from a characteristic map.

3. Method according to Claim 1 or 2, characterized in that the reduction in the determined speed increase (Δv) is calculated on the basis of a characteristic map for the estimated deceleration (aV).

4. Method according to Claim 2 or 3, characterized in that the characteristic maps are selected in accordance with a selected driving mode of the motor vehicle.

5. Method according to one of the preceding claims, characterized in that a constant deceleration is assumed for estimating the deceleration (aV).

6. Method according to one of Claims 1 to 4, characterized in that a predefined deceleration function is used for the deceleration (aV).

7. Method according to one of the preceding claims, characterized in that the distance (dz) from the start of the speed limit area is determined on the basis of map data and / or sensor data and / or cloud data.

8. Method according to one of the preceding claims, characterized in that the speed limit value (vG) is determined on the basis of legally predefined limit values and / or route-related limit values.

9. Method according to Claim 8, characterized in that the speed limit value (vG) is determined on the basis of map data and / or camera data and / or cloud data.

10. Method according to one of the preceding claims, characterized in that, after the maximum final speed (vmax) has been determined, the motor vehicle is accelerated (F) from the current speed (v) to this speed and is then decelerated (G) to the speed limit value (vG) until the start of the speed limit area.

11. Control unit for a driver assistance system for controlling longitudinal control of a motor vehicle, having a computing unit for carrying out the method according to one of the preceding claims.

12. Computer program product comprising program code means for carrying out the method according to one of Claims 1 to 10 when the computer program product is executed on a control unit according to Claim 11.

13. Machine-readable data carrier and / or download product, on which the computer program product according to Claim 12 is stored.