CUT-IN-SAFE ADAPTIVE CRUISE CONTROL SYSTEM FOR VEHICLES

Abstract

The invention relates to an adaptive cruise control system for a vehicle configured for determining, for each preceding vehicle driving ahead of the vehicle, a candidate target acceleration for modifying the acceleration of the vehicle depending on whether the vehicle is in an inevitable collision state and on how comfortably a respective safety distance can be established. Thereby, the acceleration of the vehicle is always adapted with an optimal balance between safety and comfort. The invention further relates to a vehicle incorporating such an adaptive cruise control system and to a corresponding method of determining a target acceleration of a vehicle.

Claims

1-29. (canceled)

30. An adaptive cruise control (ACC) system for a vehicle comprising: a detection module configured for detecting one or more preceding vehicles driving ahead of the vehicle and for determining a respective velocity and a respective distance of each of the detected preceding vehicles with respect to the vehicle wherein the detection module is further configured for determining whether each of the determined distances is smaller than a respective safety distance; and a safety module connected to the detection module wherein the safety module is configured for determining, for each preceding vehicle of at least a part of the one or more detected preceding vehicles for which the determined distance is smaller than the respective safety distance, a respective candidate target acceleration of the vehicle wherein the safety module comprises: an inevitable collision state (ICS) control unit configured for determining whether the vehicle is or will be in an inevitable collision state with respect to the corresponding preceding vehicle wherein the inevitable collision state corresponds to a state of the vehicle in which a collision with the corresponding preceding vehicle is inevitable regardless of a modification of an acceleration of the vehicle wherein the ICS control unit is further configured for determining the respective candidate target acceleration corresponding to a minimal possible acceleration of the vehicle when the ICS control unit determines that the vehicle is in an inevitable collision state; and an emergency control unit configured for determining the candidate target acceleration when the ICS control unit determines that the vehicle is not in an inevitable collision state with respect to the corresponding preceding vehicle according to an emergency acceleration modification scheme, wherein the emergency acceleration modification scheme is defined for achieving the respective safety distance within a predefined time and/or without the acceleration of the vehicle falling below a first predefined acceleration lower limit.

31. The ACC system of claim 30, wherein the safety module further comprises: a nominal control unit configured for determining, when the ICS control unit determines that the vehicle is not in an inevitable collision state with respect to the corresponding preceding vehicle whether the respective safety distance can be achieved by modifying the acceleration of the vehicle according to a comfort acceleration modification scheme, wherein the comfort acceleration modification scheme is defined for achieving the respective safety distance within the predefined time and without a time derivative of the acceleration of the vehicle falling below a predefined acceleration derivative lower limit and/or without an acceleration of the vehicle falling below a second predefined acceleration lower limit, wherein the comfort acceleration modification scheme is different from the emergency acceleration modification scheme, wherein the nominal control unit is further configured for determining the respective candidate target acceleration according to the comfort acceleration modification scheme when the nominal control unit determines that the respective safety distance can be achieved by modifying the acceleration of the vehicle according to the comfort acceleration modification scheme; and wherein the emergency control unit is further configured for determining the candidate target acceleration according to the emergency acceleration modification scheme when the nominal control unit determines that the respective safety distance cannot be achieved by modifying the acceleration of the vehicle according to the comfort acceleration modification scheme and the ICS control unit determines that the vehicle is not in an inevitable collision state with respect to the corresponding preceding vehicle.

32. The ACC system of claim 31, wherein the nominal control unit is configured for determining whether the respective safety distance can be achieved according to the comfort acceleration modification scheme assuming that the corresponding preceding vehicle moves at a constant velocity corresponding to the determined respective velocity.

33. The ACC system of claim 31, wherein the emergency control unit is further configured for determining, based on the respective distance and the respective velocity: an emergency jerk profile defining a time evolution of the time derivative of the acceleration of the vehicle allowing to achieve the respective safety distance within the predefined time and/or without the acceleration of the vehicle falling below the first predefined acceleration lower limit; and/or an emergency acceleration profile defining a time evolution of the acceleration of the vehicle allowing to achieve the respective safety distance within the predefined time and/or without the acceleration of the vehicle falling below the first predefined acceleration lower limit; and wherein the emergency control unit is configured for determining the respective candidate target acceleration according to the emergency jerk profile and/or to the emergency acceleration profile.

34. The ACC system of claim 33, wherein the nominal control unit is further configured for, when the nominal control unit determines that the respective safety distance can be achieved by modifying the acceleration of the vehicle according to the comfort acceleration modification scheme, determining, based on the respective distance and the respective velocity determined for the corresponding preceding vehicle: a comfort jerk profile defining a time evolution of the time derivative of the acceleration of the vehicle allowing to achieve the respective safety distance within the predefined time without a time derivative of the acceleration of the vehicle falling below the predefined acceleration derivative lower limit and/or without the acceleration of the vehicle falling below the second predefined acceleration lower limit; and/or a comfort acceleration profile defining a time evolution of the acceleration of the vehicle allowing to achieve the respective safety distance within the predefined time without a time derivative of the acceleration of the vehicle falling below the predefined acceleration derivative lower limit and/or without the acceleration of the vehicle falling below the second predefined acceleration lower limit; and wherein the nominal control unit is configured for determining the respective candidate target acceleration according to the comfort jerk profile and/or the comfort acceleration profile.

35. The ACC system of claim 34, wherein the emergency control unit is configured for determining said emergency jerk profile and/or said emergency acceleration profile when the nominal control unit determines that the respective safety distance cannot be achieved by modifying the acceleration of the vehicle according to the comfort acceleration modification scheme and/or when the ICS control unit determines that the vehicle is not in an inevitable collision state with respect to the corresponding preceding vehicle.

36. The ACC system of claim 30, wherein the ICS control unit is configured for determining whether the vehicle is in an inevitable collision state with respect to the corresponding preceding vehicle assuming a predetermined safety acceleration for the corresponding preceding vehicle.

37. The ACC system of claim 31, wherein determining the respective candidate target acceleration according to the comfort acceleration modification scheme by the nominal control unit comprises determining the respective candidate acceleration as a first acceleration value; and wherein determining the respective candidate target acceleration according to the emergency acceleration modification scheme by the emergency control unit comprises determining the respective candidate acceleration as a second acceleration value; wherein the first acceleration value is greater than the second acceleration value.

38. The ACC system of claim 31, wherein a minimal value of the acceleration of the vehicle or the time derivative thereof according to the comfort acceleration modification scheme is greater than a minimal value of the acceleration of the vehicle or the time derivative thereof according to the emergency acceleration modification scheme.

39. The ACC system of claim 30, further comprising a distance control module connected with the detection module and configured for, for each of at least a part of the one or more preceding vehicles for which the determined respective distance equals or exceeds the respective safety distance, determining whether the vehicle is in a potential collision state with respect to the corresponding preceding vehicle wherein the potential collision state corresponds to a state of the vehicle in which when the corresponding preceding vehicle initiates a full braking manoeuvre, a distance between the vehicle and the corresponding preceding vehicle will become smaller than the respective safety distance within a predefined time interval unless the acceleration of the vehicle is modified; wherein, when the distance control module determines that the vehicle is in a potential collision state with respect to the corresponding preceding vehicle the distance control module is further configured for: determining the corresponding candidate target acceleration according to a predetermined distance control acceleration modification scheme.

40. The ACC system of claim 30, wherein said at least a part of the one or more detected preceding vehicles for which the determined distance is smaller than the respective safety distance and/or said at least a part of the one or more preceding vehicles for which the determined distance equals or exceeds the respective safety distance comprises preceding vehicles for which an exclusion condition is not fulfilled, wherein the exclusion condition is fulfilled for a given preceding vehicle when another preceding vehicle exists for which the determined distance and the determined velocity are respectively smaller than the distance and velocity determined for said given preceding vehicle; and/or a difference between the distance determined for said given preceding vehicle and a stopping distance of the vehicle is equal to or greater than zero or a security margin, wherein the stopping distance of the vehicle corresponds to a minimal distance covered by the vehicle until the vehicle comes to a zero-velocity state, in particular according to a predefined braking acceleration modification scheme.

41. The ACC system of claim 39, further comprising a selection module configured for selecting, among all candidate target accelerations determined by the safety module or the distance control module a minimal candidate target acceleration, wherein the minimal candidate target acceleration is smaller than all other candidate target accelerations.

42. The ACC system of claim 30, wherein the respective safety distance corresponds to a distance between the vehicle and the corresponding preceding vehicle over which the vehicle can stop without a collision with the corresponding preceding vehicle in case of a full braking of the corresponding preceding vehicle.

43. The ACC system of claim 30, further comprising a velocity control module connected with the detection module and configured for determining a target velocity of the vehicle configured for not exceeding a detection range velocity, wherein the detection range velocity is a maximal velocity from which the vehicle can transition to a zero-velocity state over a detection range distance, wherein the detection range distance is the maximum distance from the vehicle at which a preceding vehicle can be detected by the detection module in particular from a state of maximal acceleration of the vehicle and/or according to a predefined braking acceleration modification scheme.

44. A vehicle comprising: a vehicle trajectory control system configured for controlling an acceleration and/or a velocity of the vehicle; and an adaptive cruise control (ACC) system comprising: a detection module configured for detecting one or more preceding vehicles driving ahead of the vehicle and for determining a respective velocity and a respective distance of each of the detected preceding vehicles with respect to the vehicle wherein the detection module is further configured for determining whether each of the determined distances is smaller than a respective safety distance; and a safety module connected to the detection module wherein the safety module is configured for determining, for each preceding vehicle of at least a part of the one or more detected preceding vehicles for which the determined distance is smaller than the respective safety distance, a respective candidate target acceleration of the vehicle wherein the safety module comprises: an inevitable collision state (ICS) control unit configured for determining whether the vehicle is or will be in an inevitable collision state with respect to the corresponding preceding vehicle wherein the inevitable collision state corresponds to a state of the vehicle in which a collision with the corresponding preceding vehicle is inevitable regardless of a modification of an acceleration of the vehicle wherein the ICS control unit is further configured for determining the respective candidate target acceleration corresponding to a minimal possible acceleration of the vehicle when the ICS control unit determines that the vehicle is in an inevitable collision state; and an emergency control unit configured for determining the candidate target acceleration when the ICS control unit determines that the vehicle is not in an inevitable collision state with respect to the corresponding preceding vehicle according to an emergency acceleration modification scheme, wherein the emergency acceleration modification scheme is defined for achieving the respective safety distance within a predefined time and/or without the acceleration of the vehicle falling below a first predefined acceleration lower limit, wherein the vehicle trajectory control system is configured for controlling the acceleration and/or the velocity of the vehicle according to a target velocity and/or to a candidate target acceleration determined by the ACC system.

45. A method of determining a target acceleration of a vehicle, the method comprising: detecting one or more preceding vehicles driving ahead of the vehicle; determining a velocity and a distance of each of the one or more detected preceding vehicles with respect to the vehicle; and determining the target acceleration by determining for each preceding vehicle of at least a part of the one or more detected preceding vehicles, a respective candidate target acceleration of the vehicle and by selecting as the target acceleration the minimal candidate target acceleration, wherein determining the corresponding candidate target acceleration for a corresponding preceding vehicle comprises in each case: determining whether the corresponding determined distance is smaller than a respective safety distance, and, when the corresponding determined distance is smaller than the respective safety distance: determining whether the vehicle is or will be in an inevitable collision state with respect to the corresponding preceding vehicle wherein the inevitable collision state corresponds to a state of the vehicle in which a collision with the corresponding preceding vehicle is inevitable regardless of a modification of an acceleration of the vehicle and when the vehicle is in an inevitable collision state with respect to the corresponding preceding vehicle determining the corresponding candidate target acceleration as a minimal possible acceleration of the vehicle; and if the vehicle is not in an inevitable collision state with respect to the corresponding preceding vehicle determining the corresponding candidate target acceleration according to an emergency acceleration modification scheme, wherein the emergency acceleration modification scheme is defined for achieving the respective safety distance within a predefined time and/or without the acceleration of the vehicle falling below a first predefined acceleration lower limit.

46. The method of claim 45, wherein when the corresponding determined distance is smaller than the respective safety distance and the vehicle is not in an inevitable collision state with respect to the corresponding preceding vehicle determining the corresponding candidate target acceleration for a corresponding preceding vehicle further comprises: determining whether it is feasible to achieve the respective safety distance by modifying the acceleration of the vehicle according to a comfort acceleration modification scheme, wherein the comfort acceleration modification scheme is defined for achieving the respective safety distance within a predefined time and/or without a time derivative of the acceleration of the vehicle falling below a predefined acceleration derivative lower limit and/or without an acceleration of the vehicle falling below a second predefined acceleration lower limit, and if it is feasible to achieve the respective safety distance according to the comfort acceleration modification scheme, determining the corresponding candidate target acceleration according to the comfort acceleration modification scheme; and wherein the corresponding candidate target acceleration is determined according to the emergency acceleration modification scheme when the vehicle is not in an inevitable collision state with respect to the corresponding preceding vehicle and it is not feasible to achieve the respective safety distance according to the comfort acceleration modification scheme.

47. The method of claim 46, wherein determining whether it is feasible to achieve the respective safety distance by modifying the acceleration of the vehicle according to the comfort acceleration modification scheme comprises assuming that the corresponding preceding vehicle moves at a constant velocity, corresponding to the determined respective velocity.

48. The method of claim 45, wherein determining the corresponding candidate target acceleration (cta.sub.i) according to the emergency acceleration modification scheme comprises determining (130.sub.i), based on the respective distance (d.sub.i) and the respective velocity (v.sub.i) determined for the corresponding preceding vehicle (V.sub.i): an emergency jerk profile (j.sub.emergency(t)) defining a time evolution of the time derivative of the acceleration of the vehicle allowing to achieve the respective safety distance (sd.sub.i) within the predefined time (t.sub.c) and/or without the acceleration of the vehicle falling below the first predefined acceleration lower limit; and/or an emergency acceleration profile (a.sub.emergency(t)) defining a time evolution of the acceleration of the vehicle allowing to achieve the respective safety distance (sd.sub.i) within the predefined time (t.sub.c) and/or without the acceleration of the vehicle falling below the first predefined acceleration lower limit; and wherein the respective candidate target acceleration (cta.sub.i) for the corresponding preceding vehicle (V.sub.i) is determined according to the emergency jerk profile (j.sub.emergency(t)) and/or to the emergency acceleration profile (a.sub.emergency(t)).

49. The method of claim 46, wherein determining the corresponding candidate target acceleration according to the comfort acceleration modification scheme comprises determining based on the respective distance and the respective velocity determined for the corresponding preceding vehicle: a comfort jerk profile defining a time evolution of the time derivative of the acceleration of the vehicle allowing to achieve the respective safety distance within the predefined time without a time derivative of the acceleration of the vehicle falling below the predefined acceleration derivative lower limit and/or without the acceleration of the vehicle falling below the second predefined acceleration lower limit; and/or a comfort acceleration profile defining a time evolution of the acceleration of the vehicle allowing to achieve the respective safety distance within the predefined time without a time derivative of the acceleration of the vehicle falling below the predefined acceleration derivative lower limit and/or without the acceleration of the vehicle falling below the second predefined acceleration lower limit; and wherein the respective candidate target acceleration for the corresponding preceding vehicle is determined according to the comfort jerk profile and/or the comfort acceleration profile.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0103] FIG. 1 shows a schematic representation of a vehicle according to embodiments of the invention.

[0104] FIG. 2 schematically illustrates an adaptive cruise control system according to embodiments of the invention connected to a vehicle trajectory control system.

[0105] FIG. 3 schematically illustrates a first traffic situation of a vehicle with no preceding vehicles driving ahead of the vehicle.

[0106] FIG. 4 schematically illustrates an exemplary predefined braking jerk profile.

[0107] FIG. 5 schematically illustrates a second traffic situation of a vehicle with preceding vehicles driving ahead of the vehicle.

[0108] FIG. 6 schematically illustrates a third traffic situation of a vehicle with preceding vehicles driving ahead of the vehicle.

[0109] FIG. 7 shows a flow diagram schematically illustrating a method of determining a candidate target acceleration of a vehicle according to embodiments of the invention.

[0110] FIG. 8 schematically illustrates an exemplary comfort jerk profile (FIG. 8a) and an exemplary emergency jerk profile (FIG. 8b).

[0111] FIG. 9 shows a flow diagram schematically illustrating a method of determining a target acceleration of a vehicle according to embodiments of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0112] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to a preferred embodiment illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated apparatus and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur now or in the future to one skilled in the art to which the invention relates.

[0113] FIG. 1 schematically illustrates a situation in which a vehicle V.sub.o comprising a vehicle trajectory control system 40 and an adaptive cruise control (ACC) system 10 is driving on a road. The vehicle trajectory control system 40 is configured for controlling an acceleration a.sub.o and a velocity v.sub.o of the vehicle V.sub.o and can comprise, for example, the motor, the transmission system and the braking system of the vehicle V.sub.o. The vehicle trajectory control system 40 is operatively connected with the ACC system 10 and can adjust the acceleration and the velocity of the vehicle V.sub.o based on a control instruction received from the ACC system 10.

[0114] Ahead of the vehicle V.sub.o, at a distance d.sub.1 from the vehicle V.sub.o, a preceding vehicle V.sub.1 is driving in the same direction as the vehicle V.sub.o with a velocity v.sub.1. As seen in FIG. 1, the distance d.sub.1 is measured between the front bumper of the vehicle V.sub.o and the rear bumper of the preceding vehicle V.sub.1.

[0115] FIG. 2 shows a schematic view of the components of the ACC system 10 of the vehicle V.sub.o. The ACC system 10 comprises a detection module 12, a safety module 14, a distance control module 20, a selection module 22 and a velocity control module 24. Each of the safety module 14, the distance control module 20 and the velocity control module 24 are connected with the detection module 12. The safety module 14 and the distance control module 20 are connected with the selection module 22. The safety module 14 comprises a nominal control unit 16, an emergency control unit 18 and an ICS control unit 17. Although not shown in FIG. 2, the ACC system 10 comprises a connection port, by which the ACC system 10, in particular the selection module 22 and the velocity control module 24, are connected with the vehicle trajectory control system 40 in order to provide control instructions to the vehicle trajectory control system 40. Each of the modules 12, 14, 20, 22, 24 and 40 and each of the control units 16, 17 and 18 can be corresponding modules of a software product that are executed by one or more processors, but they can also correspond to one or more independent processors. For example, each of the modules 12, 14, 20, 22, 24 and 40 and each of the control units 16, 17 and 18 can be an independent processor. In other examples, the modules 12, 14, 20, 22, 24 and the control units 16, 17 and 18 can correspond to one processor while the system 40 corresponds to another processor.

[0116] The detection module 12 comprises a system of radar sensor devices mounted at the front of the vehicle V.sub.o that are configured for detecting the preceding vehicle V.sub.1 (and any other preceding vehicle driving ahead of the vehicle V.sub.o) and for measuring, for each preceding vehicle, a corresponding distance with respect to the vehicle V.sub.o, such as the distance d.sub.1 in FIG. 1, and a corresponding velocity with respect to the vehicle, such as velocity v.sub.1 in FIG. 1. The detection module 12 can detect and measure the distance and velocity of any preceding vehicle driving ahead of the vehicle V.sub.o within a detection range distance d.sub.dr, which is the maximum distance from the vehicle V.sub.o, at which a preceding vehicle can be detected by the detection module 12.

[0117] In the situation schematically shown in FIG. 3, the vehicle V.sub.o is driving on the middle lane L.sub.2 of a three-lane road having three lanes L.sub.1, L.sub.2, and L.sub.3, with no preceding vehicle driving ahead of the vehicle V.sub.o within the detection range distance d.sub.dr. In this situation, no preceding vehicle is detected by the detection module 12 and the velocity control module 24 is activated by the detection module 12. The velocity control module 24 then determines a target velocity v.sub.target of the vehicle V.sub.o, which is transmitted to the vehicle trajectory control system 40 being implemented as the velocity of the vehicle V.sub.o.

[0118] The target velocity v.sub.target is configured for not exceeding a detection range velocity v.sub.dr, which is the maximum velocity from which the vehicle V.sub.o can transition to a zero-velocity or rest state over the detection range distance d.sub.dr when driving with the maximal possible acceleration of the vehicle and according to a customisable predefined braking jerk profile j.sub.brake(t), i.e. according to:

a.sub.o(t+Δt)=a.sub.o(t)+∫.sub.t.sup.t+Δtj.sub.brake(τ)dτ.

[0119] wherein Δt is the iteration interval, which in the example under consideration is Δt=0.02 s.

[0120] FIG. 4 shows an exemplary braking jerk profile j.sub.brake(t). The braking jerk profile j.sub.brake(t) is a predefined function that is stored in a storage device (not shown) comprised in the ACC system to which the velocity control module 24 is connected. The predefined braking jerk profile j.sub.brake(t) is designed for providing a comfortable deceleration of the vehicle V.sub.o.

[0121] The velocity control module 24 hence limits the velocity of the vehicle V.sub.o such that, if a standing preceding vehicle having a zero velocity were to appear suddenly within the detection range distance d.sub.dr, the vehicle V.sub.o, even if currently accelerating at the maximal possible acceleration, could brake according to the corresponding predefined braking jerk profile and come to a zero velocity state over the detection range distance d.sub.dr without colliding with such standing preceding vehicle. In the situation illustrated in FIG. 3, the safety module 14, the distance control module 20 and the selection module 22 can remain deactivated.

[0122] FIG. 5 schematically illustrates a further exemplary situation on the same three lane road shown in FIG. 3, but in which three preceding vehicles V.sub.1, V.sub.2, and V.sub.3 are driving ahead of the vehicle V.sub.o. The preceding vehicle V.sub.3 is driving entirely within the same lane L.sub.2 as the vehicle V.sub.o. The preceding vehicle V.sub.1 is moving laterally and changing lane from lane L.sub.2 to lane L.sub.1, i.e. exiting the lane L2, but still being partly within it. The preceding vehicle V.sub.2 is moving laterally and changing lane from lane L.sub.3 to lane L.sub.2, i.e. entering the lane L2, but still being partly within lane L.sub.3. The detection module 12 is however configured for detecting not only the preceding vehicle V.sub.3, but also each of the preceding vehicles V.sub.1 and V.sub.2 as preceding vehicles.

[0123] FIG. 6 schematically illustrates a further exemplary situation in which a preceding vehicle V.sub.4 is driving ahead of the vehicle V.sub.o, changing from the lane L.sub.1 into the lane L.sub.2, on which the vehicle V.sub.o is driving.

[0124] FIGS. 5 and 6 illustrate different possible situations, which may coexist. In the following, it will be assumed for explanatory purposes that the situations illustrated in FIGS. 5 and 6 coexist and all four preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4 are driving in front of the vehicle V.sub.o and are detected by the detection module 12.

[0125] The ACC system 10 determines a target acceleration a.sub.target of the vehicle V.sub.o by determining, for each of the preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4 a candidate target acceleration according to a method 200 that is schematically illustrated in FIGS. 7 and 9.

[0126] For each of the preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4, the ACC system executes, at 202.sub.i, the method 100.sub.i illustrated in FIG. 7, which starts by detecting, at 102.sub.i, each of the preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4 by the detection module 12, any by determining, at 104.sub.i, the corresponding distance and velocity d.sub.i, v.sub.i, namely (d.sub.1, v.sub.1), (d.sub.2, v.sub.2), (d.sub.3, v.sub.3) and (d.sub.4, v.sub.4), respectively, for example by direct measurement using the radar sensor devices of the detection module 12. Based on the corresponding distance and velocity d.sub.i, v.sub.i determined for each preceding vehicle, the detection module 12 determines in each case the corresponding safety distance sd.sub.i as the distance from the vehicle V.sub.o over which the vehicle V.sub.o can stop according to the predefined braking jerk profile j.sub.brake(t) without a collision with the corresponding preceding vehicle V.sub.i in case of a full braking of the corresponding preceding vehicle V from a state of maximal acceleration of the vehicle V.sub.o.

[0127] In the situation shown in FIGS. 5 and 6, the preceding vehicles V.sub.1 and V.sub.2 are at a distance d.sub.1, d.sub.2 from the vehicle V.sub.o smaller than a respective safety distance sd.sub.1 and sd.sub.2, respectively, while the preceding vehicles V.sub.3 and V.sub.4 are at a respective distance d.sub.3, d.sub.4 from the vehicle V.sub.o greater than the corresponding safety distance sd.sub.3 and sd.sub.4.

[0128] At 106.sub.i, the detection module 12 compares, for each preceding vehicle V.sub.i, the computed safety distance sd.sub.i to the respective determined distance d.sub.i and, based thereon, activates the safety module 14 or the distance control module 20 for determining a corresponding candidate target acceleration cta.sub.i.

[0129] If the outcome of 106.sub.i reveals that the determined distance d.sub.i is greater than or equal to the corresponding safety distance sd.sub.i, as is the case for the preceding vehicles V.sub.3 and V.sub.4, the method 100.sub.i proceeds to 108.sub.i, where it is checked whether any of the preceding vehicles V.sub.3 and V.sub.4 fulfils an exclusion condition.

[0130] The exclusion condition is fulfilled for a preceding vehicle V if [0131] there exists another preceding vehicle V.sub.j for which the determined distance d.sub.j and the determined velocity v; are respectively smaller than the distance and velocity determined for said given preceding vehicle (d.sub.j<d.sub.i, v.sub.j<v.sub.i); and/or [0132] a difference between the distance determined for said given preceding vehicle d.sub.j and a stopping distance d.sub.stop of the vehicle V.sub.o is equal to or greater than zero or a security margin, wherein the stopping distance d.sub.stop of the vehicle corresponds to a distance covered by the vehicle V.sub.o until the vehicle comes to a zero-velocity state when decelerating according to the predefined braking jerk profile.

[0133] In the situation shown in FIGS. 5 and 6, if for example the preceding vehicle V.sub.3 is further away from the vehicle V.sub.o and moving faster than the preceding vehicles V.sub.4, the preceding vehicle V.sub.3 fulfils the first condition and hence the exclusion condition too. Therefore, the method 100.sub.3 (i.e. the method 100.sub.i when carried out for determining the candidate target acceleration for the preceding vehicle V.sub.3) ends after 108.sub.3 and returns no candidate target acceleration (cf. “END” in FIG. 7).

[0134] For a preceding vehicle not fulfilling the exclusion condition, for example for the preceding vehicle V.sub.4, the method continues to 110.sub.i with the activation of the distance control module 20 for determining the candidate target acceleration cta.sub.i.

[0135] At 110.sub.i, the distance control module 20 solves the equation of motion of the vehicle V.sub.o and the preceding vehicle V.sub.4 taking into account the velocity and acceleration of the vehicle V.sub.o, the determined velocity v.sub.4 of the preceding vehicle V.sub.4 and the determined distance d.sub.4 between the vehicle V.sub.o and the preceding vehicle V.sub.4 and determines whether the respective safety distance sd.sub.4 will be violated during the next iteration, i.e. during the coming predefined time interval Δt from a current time t.sub.now assuming that the velocities of the vehicle V.sub.o and the preceding vehicle V.sub.4 remain unchanged. If this is the case, the candidate target acceleration cta.sub.4 is determined, at 114.sub.i, according to the predefined braking jerk profile j.sub.brake(t) shown in FIG. 4. Otherwise, cta.sub.4 is determined, at 112.sub.i, to correspond to the current acceleration a.sub.o of the vehicle, such that the trajectory of the vehicle V.sub.o is left unaffected.

[0136] If the outcome of 106.sub.i reveals that the determined distance d.sub.i is smaller than the corresponding safety distance sd.sub.i, as is the case for the preceding vehicles V.sub.1 and V.sub.2, the safety module 14 is activated for determining the corresponding candidate target accelerations. The method 100.sub.i proceeds to 120.sub.i, wherein the ICS control unit 17 determines whether the vehicle V.sub.o is in an ICS with respect to the corresponding preceding vehicle V.sub.i, assuming that the corresponding preceding vehicle V.sub.i is decelerating with a predetermined safety acceleration a.sub.safe, for example a predetermined safety acceleration a.sub.safe=−3 ms.sup.−2. If the result of this test is positive, the corresponding candidate target acceleration cta.sub.i is determined to correspond to the minimal possible acceleration a.sub.o.sup.min of the vehicle V.sub.o, i.e. the candidate target acceleration is chosen to correspond to the vehicle V.sub.o initiating a full braking manoeuvre.

[0137] If the result of the test at 120.sub.i is negative, meaning that the corresponding preceding vehicle V.sub.i is not in an ICS situation, the nominal control unit 16 determines, at 124.sub.i, by solving the equations of motion of the vehicle V.sub.o and the corresponding preceding vehicle V.sub.i (e.g. V.sub.1 or V.sub.2 in this case), whether it is feasible to establish the corresponding safety distance sd.sub.i by modifying the acceleration a.sub.o of the vehicle V.sub.o according to a comfort acceleration modification scheme, e.g. within a predefined time limit t.sub.c and without the jerk j.sub.o=da.sub.o/dt of the vehicle V.sub.o falling below a predefined jerk lower limit j.sub.lim, and assuming that the corresponding preceding vehicle V.sub.i moves at a constant velocity corresponding to the determined respective velocity v.sub.i. In other configurations, the acceleration modification scheme may additionally or alternatively impose the condition that the acceleration a.sub.o of the vehicle V.sub.o should not fall below a predefined acceleration lower limit, for example a.sub.min=−5 ms.sup.−2. In the example under consideration, the predefined time is t.sub.c=2 s and the predefined jerk lower limit is j.sub.lim=−10 ms.sup.−3.

[0138] If the nominal control unit 16 determines at 124.sub.1 that it is feasible to establish the corresponding safety distance sd.sub.i by modifying the acceleration a.sub.o of the vehicle V.sub.o according to a comfort acceleration modification scheme, i.e. if the result of the test at 124.sub.i is positive, the nominal control unit 16 determines, at 126.sub.i, a comfort jerk profile j.sub.comfort(t) configured for modifying the acceleration a.sub.o of the vehicle V.sub.o according to the comfort acceleration modification scheme with the minimal possible jerk and taking into account the corresponding distance d.sub.i and velocity v.sub.i determined for the corresponding preceding vehicle V.sub.i.

[0139] The comfort jerk profile j.sub.comfort(t) is determined by determining solutions to the equations of motion of the vehicle V.sub.o and the corresponding preceding vehicle V.sub.i imposing the aforesaid boundary conditions defined by the comfort acceleration modification scheme and choosing, among all possible solutions, the solution j(t) for which the minimal value of the jerk of the vehicle j.sub.comfortm in is maximal, i.e. for which j.sub.comfortm in closest to zero, in order to maximise comfort.

[0140] An exemplary comfort jerk profile j.sub.comfort(t) is schematically illustrated in FIG. 8a. As seen in FIG. 8a, the jerk according to the comfort jerk profile j.sub.comfort(t) does not fall below the predefined jerk lower limit j.sub.lim.

[0141] After determining the comfort jerk profile j.sub.comfort(t) for the preceding vehicle V.sub.i, the nominal control unit 16 then sets, at 128.sub.i, the corresponding candidate target acceleration cta.sub.i to a first acceleration value a.sub.1 determined according to the comfort jerk profile j.sub.comfort(t), i.e. according to:

cta.sub.i=a.sub.1=a.sub.0(τ=0)+∫.sub.τ.sup.τ+Δtj.sub.comfort(τ)dτ.

[0142] Otherwise, if the result of the test at 124.sub.i is negative, the emergency control unit 18 is activated to determine, at 130.sub.i, an emergency jerk profile j.sub.emergency(t) configured for modifying the acceleration a.sub.o of the vehicle V.sub.o according to an emergency modification scheme, i.e. within the predefined time t.sub.c and such that the acceleration of the vehicle a.sub.o does not fall below a predefined acceleration lower limit a.sub.min=−10 ms.sup.−2, but without the jerk of the vehicle being bound by j.sub.lim.

[0143] The emergency jerk profile j.sub.emergency(t) is determined by determining solutions to the equations of motion of the vehicle V.sub.o and the corresponding preceding vehicle V.sub.i imposing the aforesaid boundary conditions defined by the emergency acceleration modification scheme and choosing, among all possible solutions, the solution j(t) for which the minimal value of the jerk of the vehicle j.sub.emergency.sup.min is maximal, i.e. for which j.sub.emergency.sup.min is closest to zero, in order to maximise comfort.

[0144] An exemplary emergency jerk profile j.sub.emergency(t) is schematically illustrated in FIG. 8b. As seen in FIG. 8b, the jerk according to the emergency jerk profile j.sub.emergency(t) does fall below the predefined jerk lower limit j.sub.lim, unlike the comfort jerk profile j.sub.comfort(t). The minimal jerk value of the comfort jerk profile j.sub.comfort.sup.min is greater than a minimal jerk value of the emergency jerk profile j.sub.emergency.sup.min (cf. FIG. 8a). Thus, the acceleration of the vehicle V.sub.o can be more rapidly reduced according to the emergency jerk profile j.sub.emergency(t) than according to the comfort jerk profile j.sub.comfort(t) but causing to the occupants a lower degree of comfort.

[0145] After determining the emergency jerk profile j.sub.emergency(t) for the preceding vehicle V.sub.i at 130.sub.i, the emergency control unit 18 sets, at 132.sub.i, the corresponding candidate target acceleration cta.sub.1 or cta.sub.2 to a second acceleration value a.sub.2 determined according to the emergency jerk profile j.sub.emergency(t), i.e. according to:

cta.sub.i=a.sub.2=a.sub.0(τ=0)+∫.sub.τ.sup.τ+Δtj.sub.emergency(τ)dτ.

[0146] FIG. 9 schematically illustrates how the target acceleration a.sub.target is determined by the ACC system 10 by determining for each of the preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4 corresponding candidate target acceleration is. The method 100.sub.i is carried out, sequentially or in parallel, for each of the preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4 at 202.sub.1 to 202.sub.4, respectively.

[0147] For each of the preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4, the corresponding method 100.sub.i produces, as an output, a corresponding candidate target acceleration cta.sub.i, depending on the relative situation of that particular preceding vehicle V.sub.i with respect to the vehicle V.sub.o.

[0148] In the exemplary situation illustrated in FIG. 5, no ICS is determined for either of the preceding vehicles V.sub.1 or V.sub.2. For the preceding vehicle V.sub.1, the nominal control unit 16 determines at 124.sub.1, according to the equations of motion of the vehicle V.sub.o and the preceding vehicle V.sub.1, that it is not feasible to establish the safety distance sd.sub.1 within the predetermined time t.sub.c by modifying the acceleration a.sub.o of the vehicle V.sub.o without the jerk of the vehicle falling below the predefined jerk lower limit is j.sub.lim. Therefore, the candidate target acceleration cta.sub.i is determined by the emergency control unit 18 at 132.sub.1 as the outcome of the method 100.sub.1 to correspond to

cta.sub.1=a.sub.2=a.sub.0(τ=0)+∫.sub.τ.sup.τ+Δtj.sub.emergency(τ)dτ.

[0149] This corresponds to the value a.sub.2, which is smaller than the value a.sub.1 that would have been determined for the preceding vehicle V.sub.1 if the result of the test at 124.sub.1 had been positive.

[0150] For the preceding vehicle V.sub.2, the nominal control unit 16 determines at 124.sub.2, according to the equations of motion of the vehicle V.sub.o and the preceding vehicle V.sub.2, that it is feasible to establish the safety distance sd.sub.2 within the predetermined time t.sub.c without the jerk of the vehicle falling below the predefined jerk lower limit is j.sub.lim by modifying the acceleration a.sub.o of the vehicle V.sub.o according to the comfort jerk profile j.sub.comfort(t) determined at 126.sub.2 for the preceding vehicle V.sub.2. Therefore, the candidate target acceleration cta.sub.2 is determined by the nominal control unit 16 at 128.sub.2 as the outcome of the method 100.sub.2 to correspond to

cta.sub.2=a.sub.0(τ=0)+∫.sub.τ.sup.τ+Δtj.sub.comfort(τ)dτ.

[0151] For the preceding vehicle V.sub.3, the exclusion condition check at 108.sub.3 is positive, for which no candidate target acceleration is determined (cf. 204.sub.3 in FIG. 9).

[0152] For the preceding vehicle V.sub.4, the distance control module 20 determines at 110.sub.4 that the corresponding safety distance sd.sub.4 would be violated in the course of the current predefined time interval Δt, for which, in order to avoid that, the candidate target acceleration cta.sub.4 is determined by the distance control module 20 at 114.sub.4 as the outcome of the method 100.sub.4 to correspond to

cta.sub.4=a.sub.0(τ=0)+∫.sub.τ.sup.τ+Δtj.sub.brake(τ)dτ.

[0153] The outcomes of the methods 100.sub.i carried out for each of the preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4 are determined (cf. 204.sub.1, 204.sub.2, 204.sub.3, 204.sub.4 in FIG. 9) and transmitted to the selection module 22 at 206, which selects as the target acceleration a.sub.target the minimal candidate target acceleration, i.e. the smallest of values of cta.sub.1, cta.sub.2 and cta.sub.4 min(cta.sub.1, cta.sub.2, cta.sub.4).

[0154] In the example under consideration, assuming for example cta.sub.1<cta.sub.2<cta.sub.4, the selection module 22 selects, at 206, cta.sub.1 as the target acceleration a.sub.target.

[0155] The ACC system 10 then transmits, at 208, the value a.sub.target=cta.sub.1 to the vehicle trajectory control system 40 for being implemented as the new acceleration of the vehicle V.sub.o before returning to steps 202.sub.i to restart the iteration loop. As a consequence, the vehicle reacts to the current traffic situation with respect to the preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4 with the best possible balance between safety and comfort.

[0156] Notably, if an ICS had been determined by the ICS control unit 17 for any of the preceding vehicles V.sub.1, V.sub.2, V.sub.3 and V.sub.4 at the corresponding 120.sub.i, the respective cta.sub.i would have corresponded to the minimal possible acceleration of the vehicle a.sub.o.sup.min, for which the outcome of the selection at 206 would have delivered a.sub.o.sup.min as an output and the vehicle trajectory control system 40 would have initiated at 208 a full braking manoeuvre of the vehicle V.sub.o.

[0157] Although preferred exemplary embodiments are shown and specified in detail in the drawings and the preceding specification, these should be viewed as purely exemplary and not as limiting the invention. It is noted in this regard that only the preferred exemplary embodiments are shown and specified, and all variations and modifications should be protected that presently or in the future lie within the scope of protection of the invention as defined in the claims.