DETERMINATION OF AN OPTIMUM SPEED FOR A MOTOR VEHICLE APPROACHING A TRAFFIC LIGHT

Abstract

The invention relates to a method for determining an optimum speed (V.sub.OPT) to be adopted by a motor vehicle (1) when said motor vehicle (1) is approaching a traffic light (2). According to said method a first GLOSA-type on-board system (10) determines, upon receiving a message emitted by said traffic light (2), a total distance (D.sub.TL) of travel separating the motor vehicle (1) from the traffic light (2), then estimates the time necessary for the motor vehicle (1) to travel said total distance (D.sub.TL), and finally defines a recommended speed (V.sub.Q) based on the status of the traffic light (2) at the end of the estimated time. The method is characterised in that it also uses at least one speed limitation produced via a second system (12; 13) on board said motor vehicle such as to determine said recommended speed (V.sub.Q) and/or said optimum speed (V.sub.QPT).

Claims

1. A method for determining an optimum speed to be adopted by a motor vehicle when said motor vehicle approaches a traffic light, said optimum speed being a function of a recommended speed estimated by a first on-board system, the method comprising: receiving a message sent by said traffic light including location information: calculating a total distance of the route separating the motor vehicle and the traffic light, using the location information in the message; estimating a time required for the motor vehicle to cover said total distance; and determining the recommended speed as a function of a state held by the traffic light at the end of the estimated time, wherein said recommended speed and/or said optimum speed is also a function of at least one speed limit obtained via a second system on board said motor vehicle.

2. The method as claimed in claim 1, wherein said total distance of the route is broken down into a succession of road sections, and said recommended speed is a function of a plurality of speed limits obtained via the second on-board system, each of the plurality of speed limits corresponding to a regulatory maximum speed value allowed on each section of said succession of road sections.

3. The method as claimed in claim 2, wherein the time required for the motor vehicle to cover said total distance is estimated by the first on-board system according to the relation: $\underset{i}{.Math.}.Math..Math.\frac{L_i}{\mathrm{MIN}\left({\mathrm{SL}}_i;U_0\right)}$ wherein L.sub.i corresponds to a length of each section i associated with a regulatory maximum speed value SL.sub.i, and U.sub.0 is the usual speed of the motor vehicle.

4. The method as claimed in claim 3, wherein a length of each section and the regulatory maximum speed value associated with each section are delivered by a navigation system forming said second system and including a receiver on board the motor vehicle.

5. The method as claimed in claim 1, wherein the second on-board system is a speed control system suitable for detecting the presence and for estimating the speed of another vehicle in front of said motor vehicle, and wherein said at least one speed limit corresponds to the estimated speed of the another vehicle.

6. The method as claimed in claim 5, wherein said optimum speed is determined by taking the minimum value between said estimated speed of the another vehicle and the recommended speed.

7. A system for determining an optimum speed to be adopted by a motor vehicle when said motor vehicle approaches a traffic light, the system comprising: a first on-board system configured to: estimate said optimum speed as a function of a recommended speed, receive a message sent by said traffic light, determine a total distance of a route separating the motor vehicle and the traffic light, estimate a time required for the motor vehicle to cover said total distance, and determine a recommended speed as a function of a state held by the traffic light at an end of the estimated time; and a second on-board system configured to: provide at least one speed limit to the first on-board system so that the first on-board system determines said recommended speed and/or said optimum speed as a function of the at least one speed limit.

8. The system as claimed in claim 7, wherein the second on-board system is a navigation system configured to provide a length of each section of a succession of road sections breaking down said total distance of the route, and a regulatory maximum speed value associated with each section, and wherein the first on-board system is further configured to estimate the time required for the motor vehicle to cover said total distance as a function of the length and of the regulatory speed associated with each section.

9. The system as claimed in claim 7, wherein the second on-board system is a speed control system configured to: detect presence and estimate a speed of another vehicle in front of said motor vehicle, and determine said optimum speed as a function of said speed recommended by the first on-board system and of the estimated speed of the another vehicle.

Description

[0031] The invention will be better understood from the following description, with reference to the appended figures, in which:

[0032] FIG. 1 schematically illustrates a motor vehicle provided with a system according to the invention, approaching a traffic light;

[0033] FIG. 2 shows a simplified block diagram of a known GLOSA algorithm;

[0034] FIGS. 3a and 3b explain an example of implementing the method using the data provided by a navigation system;

[0035] FIGS. 4a and 4b explain an example of implementing the method using the data provided by a speed control system.

[0036] Hereafter, the elements common to the various figures have the same references.

[0037] The invention therefore starts from the acknowledgement that most vehicles are today provided with other driver assistance systems, such as a GPS navigation system, and/or a speed control system.

[0038] Thus, referring to FIG. 1, the motor vehicle 1 generally also has: [0039] for navigation assistance, a receiver 11, for example a GPS satellite signal receiver; and/or [0040] for speed control, a sensor 12 such as a camera or a radar, for monitoring the space located in front of the vehicle 1, and calculating the distance, the direction and the speed of other vehicles in front thereof.

[0041] The presence of one and/or of the two additional systems on board the motor vehicle will be able to be utilized to refine the recommended speed V.sub.G given by the GLOSA system 10, as will be described using the various following non-limiting situations:

[0042] FIG. 3a particularly illustrates the case where several speed limits, represented in this case by two traffic signs 3 (one at 70 km/hour, the other at 50 km/hour), are present on the route of distance D.sub.TL between the motor vehicle 1 and the traffic light 2.

[0043] In other words, the route of total distance D.sub.TL can be broken down into a succession of road sections, in the present example two sections of respective length L.sub.1 and L.sub.2, each section being associated with a regulatory maximum speed value allowed for the section, namely 70 km/hour for the section of length L.sub.1, and 50 km/hour for the section of length L.sub.2. Yet, this data can be extracted from the navigation system since the latter can anticipate the route that the motor vehicle will follow, and generally has, in the map database thereof, information on length of sections and associated regulatory speed limits.

[0044] Rather than only taking account of the usual speed U.sub.0 of the motor vehicle 1 for estimating the route time T.sub.TL (step 112 in FIG. 1), the present invention proposes, as illustrated in FIG. 3b, changing this step 112 such that it takes into account all of the section length/associated regulatory speed limit pairs provided by the navigation system 11.

[0045] The time T.sub.TL required for the motor vehicle 1 to cover the total distance D.sub.TL is estimated by the first on-board system 10 by applying preferably the according to the relation:

[00005]$T_{\mathrm{TL}}=\underset{i}{.Math.}.Math..Math.\frac{L_i}{\mathrm{MIN}\left({\mathrm{SL}}_i;U_0\right)}$

[0046] wherein L.sub.i corresponds to a length of each section i associated with a regulatory maximum speed value SL.sub.i and U.sub.0 is the usual speed of the motor vehicle.

[0047] In an alternative embodiment, the pairs (SL.sub.i, L.sub.i) can be provided by a system other than a navigation system, for example a system for imaging using images captured by an on-board camera, that can recognize the traffic signs 3 arranged on the road.

[0048] In all cases, a recommended speed V.sub.G is obtained at the end of the more reliable GLOSA processing algorithm.

[0049] FIG. 4a shows another situation in which another vehicle 4 is present on the route separating the motor vehicle 1 and the traffic light 2. In this case, this other vehicle 4 will be detected by the speed control system 12 which will be able to deliver the speed V.sub.F of this other vehicle 4.

[0050] A first possibility according to the invention, and illustrated schematically in FIG. 4b consists in determining, during a step 150, an optimum speed V.sub.OPT to be adopted by the vehicle by taking the minimum value between the estimated speed V.sub.F of the other vehicle 4 and the speed V.sub.G recommended by the GLOSA system.

[0051] Another possibility would consist in refining the estimation step 112 for the route time T.sub.TL by also taking into account the estimated speed V.sub.F of the other vehicle.

[0052] The various systems presented above can be combined without departing from the scope of the invention.