GB2401956A

GB2401956A - Vehicle Control System

Info

Publication number: GB2401956A
Application number: GB0410232A
Authority: GB
Inventors: A Alexander Maass
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-05-13
Filing date: 2004-05-07
Publication date: 2004-11-24
Anticipated expiration: 2024-05-07
Also published as: FR2854963B1; GB0410232D0; FR2854963A1; DE10321412B4; GB2401956B; DE10321412A1

Abstract

The system for longitudinal guidance of a motor vehicle comprises a sensor 12 for the position fixing of preceding vehicles on the lane 32 occupied by the vehicle equipped with the system and on at least one adjoining lane 30. A regulator 14 for use in regulating of the speed of the equipped vehicle based on a desired speed Vs (cruise control setting) or to a target spacing from one of the preceding vehicles. An evaluating device 26 for evaluating the traffic on the adjoining lane and for temporary replacement of the desired speed Vs by a target speed Vs', which is dependent on the evaluation result, for further travel on the lane occupied by the equipped vehicle. Preferably the system is capable of calculating the probability of a proceeding vehicle moving from an adjoining lane to the lane occupied by the equipped vehicle. The speed regulator modifies the vehicles speed based on the calculated probability, thus avoiding a collision.

Description

VEHICLE CONTROL SYSTEM

The present invention relates to a vehicle control system and has particular reference to a system for position-fixing of preceding vehicles and regulating the vehicle equipped with the system to a desired speed or to a target spacing from one of the preceding vehicles.

Devices of this kind are known as and frequently also termed adaptive speed regulator or ACC (Adaptive Cruise Control) systems. The system typically includes an angle-resolving radar sensor capable of measuring the spacings from and relative speeds of preceding vehicles and deciding on the basis of the angle data whether a positionally fixed object is disposed on the travel lane of the equipped vehicle, i.e. own lane, or on an adjoining lane.

If there is no preceding vehicle on the own lane (free travel), regulation is to the desired speed selected by the driver. If, thereagainst, preceding vehicles are disposed on the own lane, then the speed of the equipped vehicle is adapted so that the immediately preceding vehicle, i.e. the target object, is tracked at a suitable, speed-dependent safety distance (following travel).

A device of this kind is known from DE 101 14 187 A1 in which under certain conditions, namely when a wish of the driver of the equipped vehicle to overtake is recognizable or foreseeable, the speeds of the vehicles on an adjoining lane, thus the overtaking lane, are taken into consideration in order to facilitate threading into traffic on the overtaking lane.

According to the present invention there is provided a system for longitudinal guidance of a motor vehicle, with a sensor device for position fixing of preceding vehicles on the own travel lane and at least one adjoining lane, and with a regulator for regulating the speed of the own vehicle to a desired speed or to a target spacing from one of the preceding vehicles, characterized by an evaluating device for evaluating the traffic on the adjoining lane and for temporary replacement of the desired speed by a target speed, which is dependent on the evaluation result, for further travel on the own travel lane.

Preferably, the evaluating device is constructed for the purpose of gradually reducing the target speed when at least one vehicle, the relative speed of which is negative and in terms of amount lies above a defined threshold value, is located on the adjoining lane.

Alternatively or additionally the evaluating device is constructed for the purpose of gradually reducing the target speed when at least two vehicles are located on the adjoining lane and at least the relative speed of the forward one of these vehicles is negative and in terms of amount lies above a defined threshold value. Moreover, the evaluating device can be constructed for the purpose of calculating on the basis of spacings and relative speeds, which are measured by the sensor device, of two vehicles on the adjoining lane the probability that the rearward one of these vehicles will pull out onto the own lane for overtaking and of determining the target speed as a descending function of this probability.

In that case the evaluating device can be constructed for the purpose of calculating the probability in dependence on the spacing between the two vehicles and in dependence on the speed difference of these two vehicles as well as optionally in dependence on the acceleration or deceleration of the rearward vehicle, wherein the probability increases with decreasing spacing, with increasing speed difference between the vehicles and in a given case with increasing positive acceleration of the rearward vehicle. Additionally or alternatively, the probability can be dependent on the lateral offset of the paths of the two I vehicles and/or on the change in this offset.

Such a system may offer the advantage that a better adaptation of the speed to the respective traffic situation is achieved and thus traffic safety is increased and/or traffic flow improved. In effect, the speed of vehicles on at least one adjoining lane, particularly an inside adjoining lane, is taken into consideration when there are no indications that the driver of the equipped vehicle intends a change to this adjoining lane.

According to experience, accidents frequently occur on motorways, particularly in holiday periods when a large proportion of road users is made up of drivers who are relatively inexperienced and unpractised in driving on the motorway, because car drivers do not correctly estimate distances and speeds and pull out unexpectedly from an inner lane onto an overtaking lane and thus oblige sudden braking manoeuvres by the following traffic on; the overtaking lane. It is frequently the case that on the inside travel lane a large number of vehicles collect behind a particularly slow-moving vehicle so that a longer column forms on that lane. The probability that a car driver may unexpectedly pull out of this column is then particularly high and it is advisable for drivers on the overtaking lane to adapt their speed so that reaction in good time to vehicles which pull out is still possible. If, however, I such a column is overtaken there are frequently longer free stretches of road in which travel can be at a higher speed without risk. A system embodying the invention makes it possible to also take such situations into account within the scope of adaptive speed regulation.

In the simplest case, in the event of presence of at least one significantly slower vehicle on an adjoining lane the own travel speed is gradually reduced, but in a way hardly perceptibly by the driver, by the system. Alternatively, the speed of the own vehicle is reduced only when several vehicles are located on the inside adjoining lane, so that the relative speed between the overtaking vehicle and the vehicles on the adjoining lane I remains within manageable limits and the own deceleration is hardly detectable. After a column of slower vehicles has been overtaken the speed is then automatically increased back to the original desired speed. In this manner a significantly higher level of traffic safety can be achieved, the risk of necessary strong braking is reduced and, in the case of a necessary braking, the jolt is smaller because the vehicle is already decelerating.

In case of overtaking one or more slower vehicles it is, on the other hand, desirable in the I interests of an interrupted flow of traffic to shorten the overtaking process as much as possible so that the overtaking lane is freed again as quickly as possible for faster vehicles. If the absolute speed of the overtaken vehicle is only slightly smaller than the desired speed selected by the driver of the own vehicle, it is also possible to temporarily increase the own speed within certain limits so that the overtaking process is more quickly concluded.

A typical problem arises on motorways when two vehicles are located on the inside adjoining lane, of which the front one, for example a truck, is slower than the following vehicle, for example a car. In this case it is foreseeable that the driver of the car will prepare to overtake as soon as possible and pull out onto the overtaking lane. An anticipating driver will neutralise this situation in that depending on the respective situation he or she either slows down the own vehicle in order to make overtaking possible for the; car or temporarily increases the own speed in order to conclude the overtaking process more quickly so that the car behind the own vehicle can pull out before he or she has driven too closely up to the truck and has to brake. In a particularly advantageous embodiment of the device this behaviour of a driver is simulated by the system. In principle, it is sufficient for that purpose for the two immediately preceding vehicles on the I inside adjoining lane to be taken into consideration. According to a refinement, however, comparable situations can be evaluated and taken into consideration for vehicles travailing; even further in front.

In the case of roads with three or more lanes it is also possible in analogous manner to take into consideration the situation on the two inside adjoining lanes in order to predict whether a vehicle on the outermost one of those lanes is preparing to overtake and thereby a vehicle travailing on the middle lane is in turn obliged to change to the overtaking lane, as is frequently the case particularly on inclines. The same also applies to two-lane roads in the vicinity of acceleration lanes at motorway access slip roads.

In the case of three-lane roads the driver of the equipped vehicle, when it is located on the middle lane, frequently has the possibility of deviating to the overtaking adjoining lane. It is accordingly advantageous in situations in which account is to be taken of pulling out of a vehicle from the inside lane to the middle lane to provide the driver of the equipped vehicle with a warning, by an optical or an unobtrusive acoustic signal, before the speed of that vehicle is regulated in downward direction. If the driver then changes to the overtaking I lane or allows recognition, by actuating the overtaking indicator, that he or she intends this, the original speed can be maintained or automatically restored.

In many cases it is also recognizable by the system that the equipped vehicle is located on the centre lane of a three-lane road, for example because vehicles, which were overtaken at an earlier point in time not too far in the past, were located on the overtaking lane. In this case the behaviour of the device can be dependent on whether the travel lane moved along at that time is the overtaking lane of a two-lane road or the middle lane of a three- lane road.

All described functions can be taken up as standard in the ACC function or also only in stages selectable by the driver, for example in a stage "comfort", but not in a stage "sport".

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of a system embodying the invention; Figs. 2 and 3 are diagrams showing examples of traffic situations, for illustration of the mode of operation of the system of Fig. 1; and Fig. 4 is a flow chart illustrating operation of the system. s

Referring now to the drawings, there is shown in Fig. 1 an adaptive cruise control unit 10, which forms the core of a system for distance and speed regulation in a motor vehicle and the functions of which can be executed by, for example, one or more suitably programmed microprocessors. The driver can input different commands by way of an input device 12, which is arranged at the dashboard or at the steering wheel of the vehicle, in order to activate or deactivate different functions of the unit 10 and, in particular, in order to input a desired speed Vs for speed regulation in free travel operation. A regulator 14 compares the desired speed with the actual speed V of the vehicle, which is measured by a speed sensor (not shown), and intervenes in the drive system 18 by way of an output unit 16 and, if required, also in the braking system 20 of the vehicle in order to regulate the vehicle speed to the desired speed.

A position-fixing device 22, for example in the form of an angleresolving radar sensor, locates stationary and mobile objects in the foreground of the vehicle and reports the measured distances, relative speeds and azimuth angle of the located objects to a selector device 24. On the basis of the speed and angle data the selector device 24 checks whether each object is disposed inside or outside a defined travel loop which approximately represents the course and the width of the travel lane along which the own vehicle, i.e. the vehicle equipped with the system, moves. If at least one movable object is located within the travel loop, then this object - or in the case of several objects that with the smallest distance - is selected as target object for the difference regulation. The distance and relative speed data of this target object are communicated to the regulator 14 which so modifies the speed of the vehicle on the basis of these data that the target object is tracked at a defined target spacing. In that case there is calculated in the regulator 14 a target speed Vacc which is required for maintenance of the desired target spacing.

The position data of objects which are disposed on adjoining lanes and accordingly are not relevant for the distance regulation per se are reported by the selector device 24 to an evaluating device 26. The evaluating device 26 decides on the basis of these data whether account is to be taken of slower vehicles pulling out from one of the adjoining lanes onto the own travel lane and, if this condition is fulfilled, temporarily replaces the desired speed Vs selected by the driver by a target speed Vs' which better takes account of this situation.

In the simplest case, the evaluation undertaken by the evaluating device 26 can consist in Checking whether a specific number (greater than or equal to two) of slower vehicles is located on the inside adjoining line. In this case it is not improbable that one of these vehicles any pull out onto the own lane. The target speed Vs' is then so selected in departure from the original desired speed Vs that the column on the adjoining lane is overtaken at a limited relative speed, for example at most 40 km/in. This relative speed can in a given case be selectable by the driver or be dependent in accordance with a suitable regularity on the selected desired speed Vs.

At least the inside adjoining lane or lanes is or are evaluated by the evaluating device 26.

However, in addition, possible outside adjoining lanes can selectably also be included in the evaluation so that the system can also react to sudden jams on the outside adjoining or overtaking lane. This obviously applies particularly to countries in which it is allowed to overtake on an inside lane. Depending on the respectively applicable traffic regulations the traffic on the overtaking or outside adjoining lane can also be taken into consideration so that overtaking on an inside lane is prevented in every case, or- in a given case below a specific maximum speed - only overtaking at a limited relative speed of, for example, up to 20 km/in is made possible.

Another situation which can be evaluated by the evaluating device 26 is that at least one vehicle is located on the inside adjoining lane and the desired speed Vs selected by the driver varies only slightly, for example only 1 to 3 km/in, above the speed of the vehicle on the adjoining lane. In this case the evaluating device 26 can be programmed so that it replaces the desired speed Vs by a speed up to, for example, 10 km/in higher so that the overtaking process is concluded more rapidly.

Since the distance regulation to vehicles on the own lane has priority in every case, the target speed Vs' determined by the evaluating device 26 is linked in the regulator 14, according to the principle of minimum selection, with the target speed Vacc for the distance regulation.

In the described example the evaluating device 26 is programmed so that in the case of least two vehicles on the inside adjoining lane it checks whether a conflict situation is to be expected, because not only the own vehicle, but also the rearward one of the two vehicles on the adjoining lane would reach the longitudinal position of the foremost vehicle on the adjoining lane approximately simultaneously if they maintained their current speed. In such a situation account has thus to be taken that the rearward vehicle may either pull out onto the overtaking lane and oblige the own vehicle to carry out a braking manoeuvre, which in some circumstances is abrupt, or, however, the rearward vehicle may remain on the righthand lane and in turn have to brake because it travels up to the front vehicle. The decisive criteria for the evaluation of such situations are the distances and relative speeds of the participating vehicles. Since these magnitudes can be directly measured with the help of the radar sensor, such situations can be evaluated substantially more accurately and reliably by the system than possible by the driver.

The evaluation criteria applicable to that extent are explained on the basis of Figs. 2 and 3.

Fig. 2 shows a two-lane carriageway 28 with an inside lane 30 (a righthand lane, for a country with driving on the left) and an overtaking lane 32. The own vehicle 34 travels at a speed V = 130 km/in on the overtaking lane. Disposed in front of this vehicle on the inside lane are a rearward vehicle 36 and a front vehicle 38 which both travel at a speed of 100 km/in. The spacing D between the vehicles 36 and 38 is 100 m. Since the vehicles 36 and 38 are travailing at the same speed and have a sufficient safety distance from one another there is no risk that the vehicle 36 will pull out onto the overtaking lane. The evaluating device 26 accordingly so evaluates the situation that no conflict situation arises and the own vehicle 34 can therefore continue travel at its previous speed of 130 km/in. This speed in the illustrated example is the desired speed Vs. since no further vehicle is disposed on the overtaking lane in front of the vehicle 34. In the case of following travel, when the vehicle 34 follows another vehicle on the overtaking lane, the actual speed of the vehicle 34 will be the target speed Vacc for the distance regulation.

Figure 3 shows a situation which is slightly modified by comparison with Fig. 2, in which the front vehicle travels only at a lower speed Vv of 80 km/in, whilst the rearward vehicle 36 has a higher speed Vh of 100 km/in, which, however, is still lower than the speed V of the own vehicle 34. The distance D between the vehicles 36 and 38 is still only 70 m and thus lies in the proximity of the safety distance appropriate to this speed. In future, this distance will further decrease due to the speed difference. It is accordingly to be expected that the vehicle 36 will pull out onto the overtaking lane, as is indicated in Fig. 3 by a dotted line. In this situation the evaluating device 26 accordingly reduces the target speed Vs' to the speed of the vehicle 36, thus to 100 km/in or to a value between the actual speed V of the own vehicle (130 km/in) and 100 km/in so that if the vehicle 36 does, in fact, pull out it is only necessary to brake at a comfortable low deceleration in order to avoid a collision.

If in the further course it results from the measured relative speed of the vehicle 36 that the driver of this vehicle reduces his speed, then it can be concluded therefrom that he or she will not overtake. In this case the target speed can be Increased back to the original speed of 130 km/in or even to a somewhat higher value so that the overtaking process is concluded as quickly as possible. If the distance between the vehicle 36 and the own vehicle 34 has diminished to such an extent that pulling-out of the vehicle 36 is no longer to be taken into account, the target speed is similarly raised back to the original value or to a somewhat higher value in order to rapidly bring the overtaking process to a conclusion.

Fig. 4 is a flow chart which illustrates the above-described mode of operation of the system in more detail. In step S1 the evaluating device 26 checks whether at least two vehicles are disposed on the adjoining inside lane. If more than two vehicles are located on that adjoining lane, initially account is taken of only the two vehicles with the smallest distance.

If only one vehicle or even no vehicle is disposed on the adjoining lane, there takes place in step S2 a freeing of the speed, i.e. the speed regulation in the regulator 14 is carried out solely in accordance with the desired speed Vs selected by the driver or in accordance with the spacing from a vehicle travailing in front on the own travel lane. Consecutively to the step S2 there is carried out a return to step S1 for a new evaluation cycle.

If in step S1 at least two vehicles are established on the righthand lane 30, as in Fig. 3, then the evaluating device 26 calculates in step S3, on the basis of the distance and speed data of the vehicles 36, 38, two speeds V+ and V-. For that purpose it is initially calculated at which instant in time the vehicle 36 will overtake the vehicle 38 if both vehicles keep their speed unchanged. This instant in time is obtained in that the spacing D (70m) between the vehicles 36 and 38 plus a safety spacing is divided by the relative speed of 20 km/in. At that monent the vehicles 36 and 38 are thus probably disposed at approximately the same level, with the vehicle 38 on the inside lane and the vehicle 36 on the overtaking lane. The own vehicle 34 must at this instant in time accordingly have either already overtaken both vehicles 36 and 38 or, however, be disposed at a sufficient safety distance behind the vehicle 36. V+ is defined as the speed which the own vehicle 34 must at least have so that the overtaking process for the two vehicles 36 and 38 is already concluded at the calculated point in time. V- is defined as the speed which the own vehicle 34 must have at most so that it is disposed at the calculated point in time at a sufficient safety spacing behind the vehicle 36.

In step S4 the actual speed V of the own vehicle 34 is compared with the calculated speeds V- and V+ in order to establish whether a conflict situation will occur, i.e. whether V lies in the interval between V- and V+. If this is not the case, then no conflict situation is to be expected and a return to step S1 takes place by way of the freeing step S2. In the converse case, it is checked in step S5 whether a free travel situation is present, i.e. whether the overtaking lane 32 is free in front of the own vehicle 34 so that the own vehicle in case of need could also accelerate. If this is the case, it is checked in step S6 whether the speed V of the own vehicle is greater than the mean value of V+ and V-. Otherwise, it is checked whether V+ exceeds the desired speed Vs selected by the driver by not more than 10 km/in. If these two conditions are fulfilled, this means that the own vehicle 34 can overtake both vehicles 36 and 38 at a slightly increased speed, which lies at most 10 km/in above the desired speed selected by the driver, in order to neutralise the situation. In this case, in step S7 the target speed Vs' is set to V+ and the own vehicle is correspondingly accelerated. If, thereagainst, it is established in S5 that no free travel situation is present or if the conditions interrogated in the step S6 are not fulfilled the target speed Vs' is set to V- in step S7 and the own vehicle is correspondingly decelerated. The driver of the vehicle 36 thus obtains the possibility of overtaking the vehicle 38 before the own vehicle 34 has to change to the overtaking lane.

Alternatively, a strategy is also conceivable in which the target speed Vs' is reduced in every instance to V-. This strategy has the advantage that excessive deceleration of the own vehicle is avoided and the decision between overtaking and allowing threading-in is undertaken in such a manner that the speed of the own vehicle 34 departs as little as possible from the actual speed or the desired speed.

Consecutively to step S6 or S7 there takes place a return to step S1 and a new evaluation cycle begins.

The criterion interrogated in step S1 is designed so that vehicles on the adjoining lane are ignored if they are disposed at such a small spacing in front of the own vehicle 34 that a change to the overtaking lane is no longer to be expected in normal circumstances. Thus, if the own vehicle 34 has already come up very close to the vehicle 36 the interrogation in S1 has a negative result and a freeing of the speed takes place in step S2. Moreover, the criterion in step S1 can also be designed so that a freeing takes place in step S2 if the relative speed of the vehicle 36 has reduced and it can thus be recognised that the driver of this vehicle will not overtake.

In a modified embodiment the target speed Vs' in step S7 Is not set to V-, but calculated according to the equation: Vs' = (1 - P) * V + P * V-.

In that equation, V is the actual speed of the own vehicle 34 and P is a parameter between O and 1 which indicates the probability that the vehicle 36 will pull out. This parameter is calculated, according to an appropriate algorithm, from the distance D and the speed difference of the vehicles 36 and 38 and is greater the greater the speed difference and the smaller the spacing D. Vs' is then smaller the closer the parameter P is to 1.

Moreover, P can be set to 1 if the vehicle 36 accelerates and to O or almost O if the vehicle 36 is slower. The determination of P can also include reference to the paths of the vehicles 36 and 38. If the path of the vehicle 36 increasingly departs from the path of the vehicle 38 (because the vehicle 36 prepares to overtake), a higher parameter P can be inferred.

Claims

1. A vehicle control system comprising determining means for determining positions of preceding vehicles in front of the vehicle equipped with the system and on the lane occupied by that vehicle and an adjoining lane, regulating means for regulating the speed of the equipped vehicle to a desired speed or to a target spacing from a preceding vehicle and evaluating means for evaluating the traffic state on the adjoining lane and causing, for continued travel of the equipped vehicle on the lane it occupies, temporary replacement of the desired speed by a target speed dependent on the evaluation result.

2. A system as claimed in claim 1, the evaluating means being arranged to cause the target speed to be gradually reduced when the result of the evaluation is that the adjoining lane contains a vehicle having a speed relative to the equipped vehicle which is negative and lies above a predetermined threshold value.

3. A system as claimed in claim 1, the evaluating means being arranged to cause the target speed to be gradually reduced when the result of the evaluation is that the adjoining lane contains two vehicles of which the forward one has a speed relative to the equipped vehicle which is negative and lies above a predetermined threshold value.

4. A system as claimed in claim 1, the evaluating means being arranged to calculate on the basis of vehicle spacings and vehicle relative speeds measured by the determining means a probability of movement of a rearward one of two preceding vehicles on the adjoining lane to the lane occupied by the equipped vehicle and to set the target speed as a descending function of the calculated probability.

5. A system as claimed in claim 5, the determining means being arranged to so calculate the probability in dependence on the spacing and speed difference of the two preceding vehicles that the probability is Increased with decreasing spacing and increasing speed difference.

6. A system as claimed in claim 5, the determining means being arranged to so calculate the probability in dependence on the acceleration or deceleration of the rearward one of the two preceding vehicles that the probability is increased with increasing positive acceleration of that rearward vehicle.

7. A system as claimed in any one of claims 4 to 6, the determining means being arranged to calculate the probability in dependence on at least one of lateral offset of the paths of the two preceding vehicles and change in that offset.