Error estimation for a vehicle environment detection system
A vehicle environment detection system ( 2 ) including a control unit ( 4 ) and a sensor arrangement ( 3 ) that in turn includes at least two sensor arrangement parts ( 3 a, 3 b ). The control unit ( 4 ) is arranged to determine one or more systematic errors in a certain direction ( 9, 10 ) for one sensor arrangement part ( 3 a, 3 b ) by combining acquired sensor data for the sensor arrangement part ( 3 a, 3 b ) with acquired sensor data from another sensor arrangement part ( 3 b, 3 a ). The another sensor arrangement part ( 3 b, 3 a ) has a lower degree of systematic error in the certain direction ( 9, 10 ) than the sensor arrangement part ( 3 a, 3 b ).
1. A vehicle environment detection system comprising, a control unit and a sensor arrangement that in turn includes at least first and second sensor arrangement parts, the control unit determines one or more systematic detection errors in a measurement in a certain direction for the first sensor arrangement part by combining acquired sensor data for the first sensor arrangement part with acquired sensor data from the second sensor arrangement part, which one of the first and second sensor arrangement parts has a lower degree of the systematic detection error in the measurement in a certain direction than another of the first and second sensor arrangement parts.
2. The vehicle environment detection system according to claim 1 further comprising, the vehicle environment detection system is arranged to be mounted to an ego vehicle adapted to be running forward in an x-direction, where the first sensor arrangement part is in the form of a camera sensor device and the second sensor arrangement part is in the form of a radar sensor device, where the camera sensor device has a detection error in the x-direction, and where the radar sensor device has a detection error in a y-direction, perpendicular to the x-direction.
3. The vehicle environment detection system according to claim 2 further comprising, the camera sensor device is arranged to assume a fixed width (w f ) of all targets while a target vehicle has a real target vehicle width (w r ), where a camera measured detection is detected at a camera measured distance (d c ) that differs from a radar measured distance (d ra ) of a detected radar measured detection, where the radar measured distance (d ra ) is closer to a real distance (d r ) than the camera measured distance (d c ), where the control unit is arranged to calculate an estimate of the real target vehicle width (w r ) by multiplying the fixed width (w f ) with a relation between the radar measured distance (d ra ) and the camera measured distance (d c ).
4. The vehicle environment detection system according to claim 2 further comprising, the radar sensor device is adapted to provide a radar measured distance (d ra ) to a certain detection on a target vehicle, while the camera sensor device is adapted to provide a detected pixel width (w p ) of the target vehicle in camera pixels, where the control unit is arranged to calculate an estimated real width (w r ) of the target vehicle according to:
w
r
=
d
r
a
f
·
w
p
.
wherein f is a focal length of the camera sensor device.
5. The vehicle environment detection system according to claim 4 further comprising, the camera sensor device is adapted to provide a pixel displacement (d dp ) in camera pixels corresponding to a lateral displacement in the y-direction of the target vehicle relative to the ego vehicle, where the control unit is arranged to calculate a displacement angle (φ d ) as:
arcsin
(
φ
d
)
=
d
d
p
f
.
6. The vehicle environment detection system according to claim 5 further comprising, the control unit is arranged to calculate a real displacement (d dr ) as:
d
dr
=
d
r
f
·
d
d
p
.
7. A method for determining one or more systematic detection errors in a measurement in a certain direction for at least one sensor arrangement part used in a vehicle environment detection system having at least first and second sensor arrangement parts comprising the steps of:
acquiring sensor data from one of the first and second sensor arrangement parts;
acquiring sensor data from another of the first and second sensor arrangement parts, which another sensor arrangement part has a lower degree of the systematic detection error in a measurement in the certain direction than the one sensor arrangement part; and
determining one or more systematic detection errors in the measurement in certain direction for the one sensor arrangement part by combining the acquired sensor data from the first and second sensor arrangement parts.
8. The method according to claim 7 further comprising the steps of, the vehicle environment detection system is used in an ego vehicle adapted to be running forward in an x-direction, where the first sensor arrangement part is in the form of a camera sensor device and the second sensor arrangement part is in the form of a radar sensor device, where the camera sensor device has a detection error in a measurement in the x-direction, and where the radar sensor device has a detection error in a measurement in the y-direction, perpendicular to the x-direction.
9. The method according to claim 8 further comprising the steps of, assuming a fixed width (w f ) of all targets for the camera sensor device, while a target vehicle has a real target vehicle width (w r ), where a camera measured detection is detected at a camera measured distance (d c ) that differs from a radar measured distance (d ra ) of a detected radar measured detection, where the radar measured distance (d ra ) is closer to a real distance (d r ) than the camera measured distance (d c ), where the method further includes calculating an estimate of the real target vehicle width (w r ) by multiplying the fixed width (w f ) with a relation between the radar measured distance (d ra ) and the camera measured distance (d c ).
10. The method according to claim 8 further comprising the steps of, providing a radar measured distance (d ra ) to a certain detection on a target vehicle, while the camera sensor device is used for providing detected a pixel width (w p ) of the target vehicle in camera pixels, and calculating an estimation of a real width (w r ) of the target vehicle according to:
w
r
=
d
r
a
f
·
w
p
,
where f is a focal length of the camera sensor device.
11. The method according to claim 10 further comprising, the camera sensor device is used for providing a pixel displacement (d dp ) in camera pixels corresponding to a lateral displacement in the y-direction of the target vehicle relative to the ego vehicle, where the method further includes calculating a displacement angle (φ d ) as:
arcsin
(
φ
d
)
=
d
d
p
f
.
12. The method according to claim 11 further comprising the step of, calculating a real displacement (d dr ) as:
d
dr
=
d
r
f
·
d
d
p
.