Patent Application
20080061999
The invention will be described in further detail together with references to appended drawings where
The object determination system will initially be described with references to
The object awareness determination system 10 furthermore includes a controller 20 for determining awareness of the user to an object 22 that recently have entered the detecting range 16 of the external object sensor system. The controller 20 is arranged to determine awareness of the object 22 which have recently entered the detecting range 16 of the sensor system 12 based on an assessed observation of the recently entered object 18 by the user before the object has entered the detecting range 16 of said external object sensor system. With the expression “recently have entered the detecting range” is intended that the object has entered into the detecting range such that relevant input data concerning the object, including position and speed and optionally acceleration may be determined. In some know sensor systems these input data may be determined at entry into the detecting range, while other systems relies on a plurality of samples in order to determine speed and acceleration. Since accuracy of estimation of past trajectories decreases with increased distance from the time of observation it is preferred to base the past trajectory estimation on an observation made as early as possible. For this reason, the past trajectory should preferably be based on an observation of the external object made at its entry into the detecting range or at least based on an early set of observations made by the sensor systems. If the sensor system only may determine position, two consecutive observations will be needed in order to determine velocity and three will be needed in order to determine the acceleration of the external object. A suitable sampling interval for the sensor system is at least 10 Hz. The position, velocity and acceleration may the be determined within approximately 0.2 seconds from entry into the detecting range. If the sensor system may detect the velocity of an object The position, velocity and acceleration may the be determined within approximately 0.1 seconds from entry into the detecting range by using a sampling rate of 10 Hz
The object awareness determination system 10 further includes an eye gaze monitor 24 arranged for determining the direction of gaze φrel of a user relative to the host vehicle. Eye gaze monitors 24 are well known in the art. Eye gaze monitors are used to determine the direction of gaze of the user relative to the host vehicle. In order to determine the absolute direction of gaze φabs of the driver the host vehicle yaw angle Ψ relatively to the road must be determined. The host vehicle yaw angle Ψ and host vehicle position (x,y) is determined by a host vehicle movement tracker 26 arranged on the host vehicle 14. The absolute direction of gaze can be calculated as φabs=φrel+Ψ. Host vehicle movement trackers are well known in the art. The host vehicle movement tracker 26 is arranged to determine past host vehicle position and past host vehicle yaw angle, preferably by use of recorded past host vehicle yaw angle and the calculation based on the model below.
An eye gaze recorder 25 arranged for recording the direction of gaze of a user determined by the eye gaze monitor is included in the system.
A past trajectory estimator 28 is included in the object awareness determination system. The past trajectory estimator 28 is arranged to, after entry of an object into the detecting range 16 of the external object sensor system 12, estimate the past trajectory of the object which has recently entered into the detecting range 16 within a time span [t−n, t0] preceding a time of first entry (t0) of said object into said detecting range.
The past trajectory estimator 28 is arranged to, for each object that have recently entered the detecting range, retrieve object position (x, y), object velocity |({dot over (x)}, {dot over (y)}) and object direction of movement (({dot over (x)}, {dot over (y)})/|({dot over (x)}, {dot over (y)})|) at or after the time of first entry (t0), from said external object sensor system, and to determine the past trajectory based on the (x, y), object velocity |({dot over (x)}, {dot over (y)})| and object direction of movement (({dot over (x)}, {dot over (y)})/|({dot over (x)}, {dot over (y)})|) at or after the time of first entry (t0).
The past trajectory estimator 28 may estimate the object position (x, y)(t−x) at a point of time t−x within said time span [t−n, t0] preceding a time of first entry (t0) as:
(x, y)(t−i)=(x, y)(t0)−({dot over (x)}, {dot over (y)})(t0)Δt−({umlaut over (x)}, ÿ)(t0)Δt2/2, where the acceleration ({umlaut over (x)}, ÿ)(t0), may be detected by the external object sensor system, calculated from change detected external object velocities or neglected. Here t−i is a set of discrete point in time before an external object has entered the detecting range 16, which set of points in time forms a time span [t−n, t−1]. The time span is delimited by the end point t−n since the information available concerning the movement of the external object does not allow accurate estimation of the past position of the external object for very long time spans. Δt is t0−t−i.
The controller 20 is arranged to determine awareness of an object 22 that have recently entered into the detecting range based on an assessed observation, which observation is being assessed by use of a past host vehicle position (x,y)host,past, host vehicle yaw angle ψrec, recorded direction of gaze φrel,rec of the user, and estimated past trajectory of the object (x,y)obj,est which has entered the detecting range 16 of the external object sensor system. The past trajectory of the host vehicle may be a recorded position given by GPS sensor, a recorded position given by a vehicle tracking system or calculated from data representing the motion of the vehicle. A calculation may be based on a Newtonian model as for the external object, preferably, since recorded vehicle yaw angle may be available a calculation based on the following model should be used since very accurate past host vehicle positions may be obtained:
Here (x′,y′)−i;host,rec is the past position (x,y)host, past of the host vehicle at discrete pointis in time −i, Ts is the sample interval; {dot over (ψ)}abs,−k is the absolute host vehicle yaw angle rate at time t−k; φ−i,rec the yaw angle at time t−i;; (x′,y′)−i;host,rec is the position of the host vehicle at time t−i; φ−k is the yaw angle at time t−k.
In
In practice, the time span [t−n, t−1] includes a set of discrete points of time ti {i=−n:−1}, wherein the past trajectory estimator is arranged to determine the object position (x, y)(tl) at said discrete points of time ti {i=−n:−1}. The controller 20 is arranged to determine that the user is observing the object within the time span [t−n, t−1] preceding a time of first entry (t0) if the object position (x, y)(tl) is within a sector around the absolute direction of gaze at any of said discrete points of time ti {i=−n:−1}.
In one embodiment of the invention, the controller 20 is arranged to start with determining if the user is observing the object at a point of time (t−1) immediately preceding said time of first entry (t0), and to continue with points of time ti consecutively being more distant from time of first entry (t0). The controller may be arranged to stop the evaluation for points of times being more distant from the time of first entry (t0) than a point of time t−i as soon as the controller has determined that the user is observing the object at the point of time t−i due to that the object position is determined to be within a sector around said absolute direction of gaze at the point of time t−i
A suitable size of the time span [t−n, t0] preceding a time of first entry (t0) of an external object into a detecting range of the sensor system 12, during which the past trajectory of the external object is estimated is around 2-10 seconds, preferably around 5 seconds.
Instead of using a fixed time interval, the size of the interval may depend on the velocity of the host vehicle or of an aggregated average value of the velocities of the external objects observed by the sensor system.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06120345.1 | Sep 2006 | EP | regional |
