ACTIVE SAFETY SYSTEM FOR A VEHICLE AND A METHOD FOR OPERATION IN AN ACTIVE SAFETY SYSTEM

Abstract

An active safety system for a vehicle includes an external object sensor system arranged on a host vehicle. The sensor system designed to sense objects external to the host vehicle and generate input data relating to the objects, wherein the input data includes an object position ((R, ψrel)(t)). Additionally, a threat indicator is included to assign a threat level (Tk(t)) to each external object (k) detected by the sensor system.

Description

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described in further detail together with references to appended drawings where

FIG. 1 is a block scheme of an object active safety system according to the invention,

FIG. 2 shows a traffic situation including a host vehicle and a set of external objects,

FIG. 3 illustrates the geometry of a situation including an host vehicle and an external object.

FIG. 4 show a matrix storing awareness of external objects, and

FIG. 5 shows a matrix in which the threat levels for each external object are stored.

SPECIFICATION

An embodiment of the invention will be described in further detail with references to FIGS. 1 and 2, where FIG. 1 shows an embodiment of an active safety system 10 according to the invention and FIG. 2 shows a traffic situation including a host vehicle 12 and a set of external objects 14-20 being inside a detecting range 22 of a sensor system 24 arranged on the host vehicle 12.

The sensor system 24, included in the active safety system 10, is arranged to, within the detecting range 22, sense objects and generate input data relating to objects external to said host vehicle, wherein said input data at least include an object position (R, ψ_rel). Here R indicates the distance to the object and ψ_rel indicates the angle relative to the vehicle. Suitable sensor systems are well known in the art. An example of a suitable system is sold under the trade name Mobile Eye.

The active safety system 10 furthermore includes a threat indicator 26 which is arranged to assign a threat level to each external object detected by the sensor system 24. Threat indicators are well known in the art. An example of a threat indicator is described in U.S. Pat. No. 7,034,668. A thorough description of how to enable a threat level indicator is described in “Collision avoidance theory”, Jansson J., Linköping Studies in Science and technology, Dissertation no 950, Linköping 2005. In particular chapters 5.3.6-5.3.8 relates to equations describing required longitudinal acceleration and required lateral acceleration for collision avoidance, which entities suitably may be used as threat level, particularly if these entities have been normalized by dividing with maximum available longitudinal acceleration and lateral acceleration respectively.

An eye gaze recorder 28, included in the active safety system 10, is arranged for recording the direction of gaze of a user φ determined by an eye gaze monitor 30. Eye gaze monitors are well known in the art. A camera registers characteristic features of the users head, suitably the eyes. The eye gaze monitor determines, via image recognition the direction of the gaze φ relative to the vehicle. In the eye gaze recorder 28 the direction of gaze determined by the eye gaze monitor 30 are stored in a memory.

An awareness detector 32 is arranged to determine awareness of an object based on an assessed observation. An observation is being assessed by use of a recorded direction of gaze φ of the user and the position of the detected objects (R, ψ_rel)_object-k. An observation of an object k is assessed when the direction of the gaze φ corresponds to the direction to an object k ψ_relobject-k at a given time t_k0 With corresponds is here intended that the difference between the direction of gaze φ and the direction to an object k ψ_relobject-k is smaller than a predetermined angle, suitably 2°.

A controller 34 is arranged to, for objects detected by said sensor system 24 and objects which the awareness detector 32 has determined that the user is aware of, collect threat level data T_k(t) from the threat indicator 26, to store threat level data T_k(t) collected at different points in time, to assign a threat level awareness (T_k(t_k0)) by selecting the threat level (T_k(t)) at which the object (k) was observed, and to compare the current threat level (T_k(t)) of the object with the threat level awareness (T_k(t_k0)).

In a method according to the invention, the following process steps may be performed:

In a set of process steps S10, within a detecting range 22 of a sensor system 24 arranged on a host vehicle 12, sensing objects 14-20 external to the host vehicle. Input data relating to objects external to said host vehicle is generated. The input data include an object position (R, ψ_rel). The input data may be processed in a state observer based on a Kalman filter process as is conventional in the art. A conventional observer X_k suitably includes the states x_n; y_n; β_n; a_n; and v_n, where x_n is a coordinate along the length of the road for object number k; y_n is a coordinate in the width direction of the road for object number k; β_n is an angle between the travelling direction and the coordinate length extension of the road for object number k; a_n is the acceleration for object number k; and v_n is the velocity of object k, such that the observer X_k may be expressed as X_k=[x_n y_n β_n a_n v_n]. for an external object k. The input data may also include host vehicle measurement data such as host vehicle velocity V_H, acceleration a_H, host vehicle yaw angle θ_H. A suitable observer for the host vehicle may be Y_H=[x_H y_H β_H], where x_H is a coordinate along the length of the road for the host vehicle; y_H is a coordinate in the width direction of the road for the host vehicle; β_H is an angle between the travelling direction and the coordinate length extension of the road for the host vehicle.

In a set of process steps S20, recording the direction of gaze φ of a user, determined by an eye gaze monitor 30.

In a set of process steps S30, determining awareness of an object based on an assessed observation, which observation is being assessed by use of a recorded direction of gaze φ(t) of the user and the position of the objects (R, ψ_rel). In FIG. 3 the relation between the coordinates of the host vehicle (x_H, y_H), the coordinates of an object (x_k, y_k), the distance to the object R and the angle ψ_rel between a heading direction of the vehicle and the object k is shown. The awareness detector determines that the driver is aware of an object k if the direction of gaze φ(t) at a time t and the angle ψ_rel(t) between a heading direction of the vehicle and the object k is within a predetermined narrow sector, preferably abs(φ(t)−ψ_rel(t))<2°. The awareness detector may determine that the driver is no longer aware of an object if to long time of to long travelling distance has lapsed since the last observation of the object.

The observations of external object may suitably be stored in a matrix B_k(t) as exemplified in FIG. 4. In the matrix 1 denotes that the driver is aware of the object and 0 that the driver is not aware of the object. When a certain time or travelling distance has passed since the observation, an assumption of that the driver is no longer aware of the object is made. The awareness detector may thus be arranged to determine that a user is no longer aware of an object if the time span Δ since the user observed the object exceeds an awareness time threshold value. The awareness time threshold value S_time may depend on the velocity of the host vehicle.

In a set of process steps S40 a threat level T_k is assigned to each external object detected by the sensor system. The threat levels T_k(t) for each external object k is suitably stored in a matrix T as exemplified in FIG. 5. Preferably a relative threat number between 0 and 1 is used, where 1 means that a collision between the external object and the host vehicle can not be avoided.

At least for objects detected by said sensor system and objects which the user is aware of, the following set of process steps S60 are performed: collecting threat level data from said threat indicator, storing threat level data collected at different points in time, assigning a threat level awareness by selecting the threat level at which the object was observed, and comparing the current threat level T_k(t) of the object k with the threat level awareness T_k(t_k0), which corresponds to the threat level at the time t_k0 when the object k was observed.

The controller preferably generates a control signal 36 in the event, for any of the objects detected by the sensor system, the current threat level T_k(t) exceeds the threat level awareness T_k(t_k0) by more than a threshold value S.

The threshold value may depend on the derivative of the threat level or on the time interval between the time of observation and the current time.

The control signal 36 is preferably constituted by a warning transmitted visually to the driver.

Claims

1. An active safety system for a vehicle comprising: an external object sensor system arranged on a host vehicle, said sensor system being arranged to, within a detecting range of said sensor system, sense objects (k) external to said host vehicle and generate input data relating to said objects (k), wherein said input data includes an object position ((R, ψrel)(t)),a threat indicator which is arranged to assign a threat level (Tk(t)) to each external object (k) detected by the sensor system; characterised in that said active safety system further includes:an eye gaze recorder arranged for, recording the direction of gaze (φ(t)) of a user, determined by an eye gaze monitor;an awareness detector which is arranged to determine awareness (Ak(t)) of an object (k) based on an assessed observation, which observation is being assessed by use of a recorded direction of gaze (φ(t)) of the user and said object position ((R, ψrel)(t)); anda controller which is arranged to, for objects (k) detected by said sensor system and objects which the user is aware of ((Ak(t))=1), collect threat level data (Tk(t)) from said threat indicator, to store threat level data (Tk(t)) collected at different points in time, to assign a threat level awareness (Tk(tk0)) by selecting the threat level (Tk(t)) at which the object (k) was observed (tk0), and to compare the current threat level (Tk(t)) of the object (k) with the threat level awareness (Tk(tk0)).

2. An active safety system according to claim 1, characterised in that said controller is arranged to generate a control signal in the event, for any of the objects (k) detected by the sensor system, the current threat level (Tk(t)) exceeds the threat level awareness (Tk(tk0)) by more than a threshold value (S).

3. An active safety system according to claim 2, characterised in that said threshold value (S) depends on the time interval between the time of observation (tk0) and the current time (t).

4. An active safety system according to claim 2, characterised in that said threshold value (S) depends on the derivative of the threat level (Tk(t)).

5. An active safety system according to claim 1, characterised in that said awareness time threshold value (Stime) depends on the velocity of the host vehicle.

7. An active safety system according to any of claim 1, characterised in that said control signal (36) generates a warning to the user.

8. A method operated in an active safety system for a vehicle comprising the following process steps: within a detecting range of a sensor system arranged on a host vehicle, sensing objects (k) and generating input data relating to objects external to said host vehicle, wherein said input data include an object position ((R, ψrel)(t)),recording the direction of gaze (φ(t)) of a user, determined by an eye gaze monitor,determining awareness (Ak(t)) of an object (k) based on an assessed observation, which observation is being assessed by use of a recorded direction of gaze (φ(t)) of the user and said object position;assigning a threat level (Tk(t)) to each external object (k) detected by the sensor system; characterised in that the following further process steps are performed:for objects detected by said sensor system and objects which the user is aware of, collecting threat level data (Tk(t)) from said threat indicator, storing threat level data (Tk(t)) collected at different points in time, assigning a threat level awareness (Tk(tk0)) by selecting the threat level (Tk(t)) at which the object was observed (tk0), and comparing the current threat level (Tk(t)) of the object (k) with the threat level awareness (Tk(tk0)).

9. A method according to claim 8, characterised in that said controller generates a control signal in the event, for any of the objects detected by the sensor system, the current threat level (Tk(t)) exceeds the threat level awareness (Tk(tk0)) by more than a threshold value (S).

10. A method according to claim 9, characterised in that said threshold value (S) depends on the time interval (Δ) between the time of observation (tk0) and the current time (t).

11. A method according to claim 9, characterised in that said threshold value (S) depends on derivative of the threat level.

12. A method according to any of claim 8, characterised in that said awareness detector determines that a user is no longer aware of an object if the time span (Δ) since the user observed the object exceeds an awareness time threshold value (stime).

13. A method according to claim 12, characterised in that said awareness time threshold value (stime). depends on the velocity of the host vehicle.

14. A method according to any of claims 9, characterised in that said control signal (36) generates a warning to the user.