GB2452835A

GB2452835A - Method and vehicle system for adjusting the speed of a vehicle before traffic signals

Info

Publication number: GB2452835A
Application number: GB0816597A
Authority: GB
Inventors: Peter Kreft
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2007-09-13
Filing date: 2008-09-10
Publication date: 2009-03-18
Anticipated expiration: 2028-09-10
Also published as: DE102007043602A1; GB2452835B; GB0816597D0; FR2921183A1; SE0801934L

Abstract

A method and vehicle system for adjusting the speed of a vehicle 1 leading up to traffic signals 2 comprising transmission by the signal 2 of signal-installation-specific information allowing determination of its position plus information of its switching state and time until a change thereof; receipt of this information by the vehicle 1 and determination of the distance to the signal 2 taking account of its own position; and on the basis of the determined distance, switching state, and time until a change thereof, a recommendation of a speed or speed range. Vehicle position may be determined by GPS via a vehicle navigation or information system. Signal position may be transmitted and/or signal identity may be transmitted to be combined with navigation data. A warning may be given if a stop is unavoidable of if a collision may be imminent and automatic braking action taken. The speed recommendation may link to a cruise control system. The system may consider actual or expected traffic queues.

Description

Description Title

Method of adjusting the speed of a vehicle before a signal installation, and vehicle system

Prior art

The invention is based on a method of adjusting the speed of a vehicle before a signal installation.

In the case of signal installations in the form of traffic lights, outputting the remaining time to switching from "red to green" or "green to red", or also speed recommendations, via supplementary equipment, so that the driver of a motor vehicle reaches the next traffic light at "green" and can pass it ("green wave"), is known.

From US-20040225434 Al, a vehicle navigation system which transmits the time to the phase change of a traffic light system to the vehicle is known. The navigation system warns the driver so that the driver can adjust his or her speed accordingly.

Disclosure of the invention

Advantages of the invention In the method of adjusting the speed of a vehicle before a signal installation according to the invention, a signal installation sends a signal-installation-specific signal, by means of which its position can be determined, plus information about the instantaneous switching state and at least the time until the change to a different switching state. The vehicle receives the signal-installation--specific signal and the information, and determines, taking account of its own position, the distance to be driven to the signal installation. On the basis of the determined distance, the instantaneous switching state and the time until the change to a different switching state, a speed or at least a speed range is determined and output as a speed recommendation.

In contrast, tJS-20040225434 Al, if the time for the phase change at a traffic light system is below a limit, outputs a warning signal to the vehicle. In this case the navigation system is used only to test whether the vehicle is near the traffic light or traffic sign, to generate a warning if required.

The present invention is not primarily about warning the driver about a phase change shortly before the traffic light, but about early adjustment of the vehicle's speed, to reach the traffic light at green whenever possible.

Since adjusting the speed a few metres before the traffic light has little effect on when the traffic light is reached, in the case of the invention communication with the traffic light / infrastructure takes place much earlier. To make this possible, the methods of selecting the relevant signal installations are quite different: the vehicles position is no longer enough, the calculated route of the navigation system is also used to detect the correct signal installations, particularly in ambiguous situations. To detect the correct signal installations where there are multiple signal installations, a signal-installation-specific signal of the signal installation, e.g. its ID (identification), is analysed, and the distance to be driven to this signal installation is then determined. On the basis of this distance, the instantaneous switching state and the time until the change to a different switching state, the speed is then determined, and output as a recommendation, preferably by display and/or acoustically.

Thus a speed recommendation for the driver is given virtually predictively, so that the driver can pass the signal installation / traffic light at green. The result is a saving of fuel, because of even driving and avoidance of stops at the red traffic light. Because of a harmonious traffic flow, accidents are avoided. In cases where the recommended speed is above the current vehicle speed and the driver would no longer pass the traffic light at green without the recommendation, the result is a time saving.

An advantage compared with speed recommendation systems installed on the roadside is the lower investment costs for transmission systems which transmit the required information into the vehicles. A further advantage is that navigation systems can continually adjust a recommended speed. The speed recommendation does not only apply at one point, but can be adjusted continuously on the route to the traffic light if the speed recommendation is temporarily overshot or undershot.

This can be achieved by the methods of Claim 2.

In the case of a too high or too low determined speed, i.e. the green phase cannot be reached, instead of a speed recommendation information that a stop at the signal installation is unavoidable is output. This too saves fuel and can prevent risky driving manoeuvres.

To determine the speed, information from a digital map, e.g. the co-ordinates of the traffic light or crossing, can be used. This saves, for instance, transmitting the co-ordinates or position of the signal installation, since this can be uniquely determined on the basis of its ID.

The determined speed recommendation can be transmitted by the driver, or automatically, to the driver's cruise control system. The driver is thus less stressed, and does not have to make active driving manoeuvres.

Modifying the distance to be driven on the basis of a forecast, taking account of probable queues before the signal installation or depending on the traffic density to be expected, also makes a contribution to fuel saving.

Additionally, without great additional cost, data which usually exists in any case, from traffic messages, car-to-car communication, car-to-infrastructure communication and updating data for the on-board navigation system, can be used.

In a further characteristic, the method according to the invention increases the traffic safety by a warning function -if the driver could possibly cross the traffic lights at red because of the existing data (traffic light phase, vehicle dynamics) -and by activating a connected accident avoidance system, e.g. for emergency braking.

To determine the vehicles own position, it is also possible to access data which usually exists in any case, e.g. via a GPS receiver. In the case of a vehicle system according to Claim 8, it is possible to access mostly existing hardware and software of the navigation system.

Only an interface for receiving the information which the signal installation transmits is necessary. For this purpose, a car-to-car communication system which may be provided can also be networked with the navigation system, so that no additional hardware cost in the vehicle is necessary. Even a vehicle without an on-board navigation system can use the method according to the invention, if the driver information system is equipped with a receiver for signal installation information and for receiving GPS signals.

Drawings Embodiments of the invention are shown in the drawings and explained in more detail in the following description.

Fig. 1 shows a vehicle in front of a signal installation, with a communication connection to the signal installation, and Fig. 2 shows a block diagram of an arrangement for adjusting the speed of a vehicle.

R. 32059 Embodiments of the invention The invention is based on an infrastructure (signal installation 2, particularly traffic light system and transmitter), which makes it possible to transmit information about the switching state of a signal installation, e.g. a traffic light, into the vehicles 1 (Fig. 1). This includes: -the current phase or switching state of the traffic light (red/green), -the residual duration of the red/green phase, i.e. the time until the change of switching state, -optionally additionally, the duration of the subsequent red/green phase.

Additionally, a signal-installation-specific signal of the signal installation is sent, to identify the signal installation / traffic light by an ID and/or co-ordinates of the traffic light or crossing.

Furthermore, in the vehicle 1 a navigation system, a driver information system FIS or another system (called FIS below) is installed, and is capable of receiving and decoding this information of the signal installation 2.

The FIS now determines the current distance s to be driven to the traffic light, on the basis of the ordered vehicle position and a digital map. The digital map is available in the vehicle 1, or is transmitted into the vehicle via a provider or the signal installation itself. If the traffic light is at red, on the basis of the residual duration tred of the red phase, the maximum recommended speed of the vehicle is determined from distance arid time (vmax = S/tred) so that the vehicle does not reach the traffic light system until it is at green. If this calculated recommended speed is very high, it is possible to calculate, from the duration of the subsequent green phase, how high the vehicle's speed must be at minimum if it is to cross the crossing at green: Vmjn 5/(tred+tgreen) . In this case, Vmin is less than Vmax. The vehicle speed should move between vmin and VmaX to pass the traffic light at green.

If the traffic light is at green, the calculation is analogous: Vmin s/tgreen and Vmax = 5/(tgreen+tred) . In this case, vmin is greater than Vifiax. The vehicle should either move faster than vmin or slower than Vmax.

In the examples given above, for simplification the amber phases are included in either the red or the green phase.

The invention now assumes that a recommended speed is displayed to the driver in the cockpit, e.g. via a display of the FIS. Alternatively, acoustic output of the speed recommendation is possible. For one thing, it is possible that either a speed value is recommended on the basis of the speeds Vmfl and vmax, or a speed range is recommended (traffic light is now red), or a minimum/maximum speed is recommended (traffic light is now green) Fig. 2 shows, in a block diagram, an arrangement for determining and adjusting the speed of a vehicle. The driver information system (FIS) 4 is equipped with a receiver 3 for the signal-installation_specific signal, by means of which the position of the signal installation can be determined. Either the geographical position is encoded directly, or it can be determined on the basis of the transmitted ID, with the aid of digital map information.

The vehicle's own position can be determined via its navigation system 5, in association with a GPS receiver.

The driver information 4 and navigation system 5 can also form one unit. The driver information system 4 has one interface to each of the braking system 6, the safety system 7 and the comfort electronics 8. Additionally, at least one interface is provided for output of the determined speed recommendation. In the shown embodiment, an interface 9 is provided to the vehicle's speed control system, an interface 10 to the speedometer or instrument cluster, an interface 11 to the display for visual information, and an interface 12 to the loudspeaker for acoustic information.

In a version of the invention, it is provided that the process of recommended speed calculation is repeated cyclically. Either new time information from the traffic light system (infrastructure) is used, or old time information from the traffic light system is kept up to date by means of an internal clock of the driver information system 4 or other available equipment. The distance s to be driven is redeterinined each time on the basis of an up to date location position. By this method, up to date recommendations can be displayed to the driver each time.

Additionally, the following further forms are possible: -If Vmin and/or Vmax are too high, either no speed recommendation referring to them or a restriction of the recommended speed range occurs; -If the whole recommended speed range is useless (speed too high or too low), an indication is given to the driver that stopping at the red traffic light is unavoidable; -Particularly in the higher range, the recommended speeds are reconciled with information from the digital map (within town / outside town, road classes such as main road, residential road, etc., speed limits, etc.), or transmitted information of the infrastructure; if appropriate, on the basis of the above-mentioned calculations, an unavoidable stop at the red traffic light is determined, or the recommended speed range is adjusted; -Recommended speeds and/or speed ranges are identified directly in the speedometer, e.g. on an LCD speedometer; -The recommended speed can be transmitted, if the driver wishes or automatically, directly to a speed control display (cruise control); -For further calculation, the distance s to be driven is modified according to a forecast to a distance s to be driven. The distance s' is shorter than the distance s, and in particular, in the case of a red traffic light (Vmax calculation), takes account of possible queues before the traffic light; -The distance s' is derived from the distance s depending on the day of the week, the time of day and/or the road class (traffic density to be assumed) ; -In complicated traffic situations (possibilities for turning off before the traffic light), the relevance of a traffic light or also the distance s/s' to be driven is determined using the route which is calculated in the driver assistance system; -During a green phase, additionally the remaining time to the green/red phase is displayed; -During a red phase, the remaining time to the green phase is displayed; -If the current speed is too high in relation to the distance s/s' to be driven and the braking distance to be assumed during or preceding a red phase, a warning signal occurs; -If the current speed is too high in relation to the distance s/s' to be driven and the braking distance to be assumed during or preceding a red phase, the braking system 6 is informed via the interface that potentially emergency braking by the driver is about to occur. On the basis of this information, the braking system 6 can optimise the braking power, e.g. by moving the brake pads near the brake discs or, for instance, increasing the brake pressure; -If the current speed is too high in relation to the distance s/s' to be driven and the braking distance to be assumed during or preceding a red phase, the braking system 6 is informed of this via the interface. The braking system then automatically carries out an emergency braking; -If the current speed is too high in relation to the distance s/s' and the braking distance to be assumed during or preceding a red phase, so that an accident could occur, the vehicle 1 is prepared for the accident on the basis of this information. For this purpose, the interface to the safety system 7 and the comfort electronics 8 is provided, e.g. to close the sun roof and windows and tighten the belts; -In this invention, speed recommendations, time data, warnings and indications are given optically and/or acoustically; -For calculation purposes, amber phases are included in the red and/or green phases; -Instead of a traffic light, the signal installation can be the signal installation at a railway level crossing or another installation which determines traffic, e.g. a display device over several lanes of a motorway. Here the invention can even, via the driver information system 4, take account of different prescribed speeds together for the speed recommendation in the case of a lane change.

Claims

Claims 1. Method of adjusting the speed of a vehicle (1) before a signal installation (2), with the following steps: -a signal installation (2) sends a signal-installation_specific signal, by means of which its position can be determined, plus information about the instantaneous switching state and at least the time until the change to a different switching state, -the vehicle (1) receives the signal-insta11aion_ specific signal and the information, and determines, taking account of its own position, the distance to be driven to the signal installation (2), on the basis of the determined distance, the instantaneous switching state and the time until the change to a different switching state, a speed or at least a speed range is determined and output as a speed recommendation.
2. Method according to Claim 1, characterized in that the determination of the speed recommendation is repeated cyclically, the distance to be driven being redetermjned each time on the basis of a current position.
3. Method according to Claim 1 or 2, characterized in that in the case of a too high or too low determined speed, instead of a speed recommendation information that a stop at the signal installation (2) is unavoidable is output.
4. Method according to one of Claims 1 to 3, characterized in that to determine the speed, information from a digital map or transmitted navigation data is taken into account.
5. Method according to one of Claims 1 to 4, characterized in that the determined speed recommendation is transmitted by the driver, or automatically, to the cruise control system of the vehicle (1).
6. Method according to one of Claims I to 5, characterized in that the distance to be driven is modified on the basis of a forecast, taking account of probable queues before the signal installation (2) or depending on the traffic density to be expected.
7. Method according to one of Claims 1 to 6, characterized in that if the speed is determined to be too high in relation to the distance to be driven and the braking distance, a warning signal is output, emergency braking is prepared, and/or a safety system is activated, to prepare for an imminent accident.
8. Vehicle system for adjusting the speed of a vehicle (1) before a signal installation (2), with the following features: -a device to receive signal_instal1ation_SpeCifj signals from signal installations (2), to determine their positions, plus information about their instantaneous Switching state and at least the time until the change to a different Switching state, -means of determining the vehicle's (1) own position, -means of determining the distance to be driven to a signal installation (2), -means of determining a speed or at least a speed range on the basis of the distance to be driven, the instantaneous switching state and the time until the change to a different switching state, - means of outputting a speed recommendation on the basis of the determined speed.
9. Vehicle system according to Claim 8, characterized in that to determine the vehicle's (1) own position, a navigation system (5) is provided, and/or a driver information system (4), which is equipped to receive position data, e.g. via a GPS receiver, and analyse it.
10. Vehicle system according to Claim 8 or 9, characterized in that to determine the position of the signal installation (2), an appropriately encoded identification signal, which in association with navigation data makes it possible to determine the position of the signal installation, can be transmitted, or that in the signal-instailajo_ specific signal which the signal installation (2) transmits, the geographical position of the signal installation (2) itself is encoded.
11. A method of adjusting a speed of a vehicle substantially as herein described.
12. A vehicle system for adjusting the speed of a vehicle, substantially as herein described with reference to the accompanying drawing.