Determining object motion and acceleration vector in a vehicle radar system
A vehicle radar system ( 3 ) which, for each one of a plurality of radar cycles, is arranged to, provide a measured azimuth angle (θ m ) and radial velocity (v dm ) for a first plurality of detections ( 9, 20 ). For each one of the plurality of radar cycles, the radar system ( 3 ) is arranged to select one of these detections for each one of two velocity components (v x , v y ) in a set of components (v x , v y , a x , a y ; a) to be determined; select one detection from a second plurality of detections ( 9, 20 ) for each one of at least one corresponding acceleration component (a x , a y ; a); calculate the components (v x , v y , a x , a y ; a) for the selected detections; determine a calculated radial velocity (v dc ) for each one of at least a part of the other detections in the first plurality of detections ( 9, 20 ) using the calculated components (v x , v y , a x , a y ; a); determine an error between each calculated and measured radial velocity (v dc , v dm ); and determine the number of inliers. The set of components (v x , v y , a x , a y ; a) that results in the largest number of inliers is then chosen.
1. A vehicle radar system, comprising:
processing circuitry configured to:
acquire, for each one of a plurality of radar cycles, a plurality of detections including a corresponding measured azimuth angle and a corresponding measured radial velocity for each detection thereof;
for each cycle of the plurality of radar cycles:
select one detection from a first plurality of detections of the corresponding cycle for each one of two velocity components comprised in a set of components to be determined for a target, where the two velocity components define a full velocity vector for a relative velocity of the target;
select one detection from a second plurality of detections for each one of at least one corresponding acceleration component comprised in the set of components;
calculate the set of components based on the selected detections;
determine a calculated radial velocity for each one of at least a part of non-selected detections in the first plurality of detections based on the calculated set of components;
determine an error between each calculated radial velocity and the measured radial velocity for each one of at least the part of non-selected detections; and
determine a number of inliers for the corresponding cycle, where an inlier corresponds to a detection with the corresponding error that falls below an inlier threshold; and
choose, as a determined set of components for the target, the set of components from the calculated sets of components of the plurality of radar cycles that corresponds to a largest number of inliers among the determined numbers of inliers of the plurality of radar cycles.
2. The vehicle radar system according to claim 1 , wherein the processing circuitry is further configured to group detections that correspond to inliers resulting from the chosen set of components, the grouped detections being identified as belonging to the target that is an extended object.
3. The vehicle radar system according to claim 1 , wherein the second plurality of detections is the same as the first plurality of detections.
4. The vehicle radar system according to claim 1 , wherein
the first plurality of detections and the second plurality of detections belong to different radar cycles, and
the processing circuitry is configured to, for each cycle of the plurality of radar cycles:
first calculate velocity components for the selected detections; and
then calculate the at least one acceleration component based on the calculated velocity components for the selected detections.
5. The vehicle radar system according to claim 4 , wherein the second plurality of detections belongs to a previous radar cycle prior to the corresponding radar cycle which the first plurality of detections belongs.
6. The vehicle radar system according to claim 1 , wherein the processing circuitry is configured to calculate the set of components by solving an expression of
V dm =( V x +a x Δt )cos(θ m )+( V y +a y Δt )sin(θ m )
for each selected detection, where θ m constitutes the measured azimuth angle between a radar system reference line and a direction towards the corresponding detection in question, V dm represents the measured radial velocity of the corresponding detection, V x represents an x-component of velocity of the set of components, V y represents a y-component of velocity of the set of components, a x represents an x-component of acceleration of the set of components, a y represents a y-component of acceleration of the set of components, and Δt represents a time difference of the selected detections.
7. The vehicle radar system according to claim 1 , wherein the processing circuitry is configured to calculate the set of components by solving an expression of
V
d
m
=
(
V
x
+
a
V
x
V
r
Δ
t
)
cos
(
θ
m
)
+
(
V
y
+
a
V
y
V
r
Δ
t
)
sin
(
θ
m
)
.
for each selected detection, where θ m constitutes the measured azimuth angle between a radar system reference line and a direction towards the corresponding detection in question, V dm represents the measured radial velocity of the corresponding detection, V x represents an x-component of velocity of the set of components, V y represents a y-component of velocity of the set of components, a represents an acceleration of the set of components, |V r | represents a magnitude of the relative velocity V r , and Δt represents a time difference of the selected detections.
8. The method according to claim 1 , wherein the set of components is calculated by solving an expression of
V
d
m
=
(
V
x
+
a
V
x
V
r
Δ
t
)
cos
(
θ
m
)
+
(
V
y
+
a
V
y
V
r
Δ
t
)
sin
(
θ
m
)
.
for each selected detection, where θ m constitutes the measured azimuth angle between a radar system reference line and a direction towards the corresponding detection in question, V dm represents the measured radial velocity of the corresponding detection, V x represents an x-component of velocity of the set of components, V y represents a y-component of velocity of the set of components, a represents an acceleration of the set of components, |V r | represents a magnitude of the relative velocity V r , and Δt represents a time difference of the selected detections.
9. A method for a vehicle radar system, comprising:
acquiring, for each one of a plurality of radar cycles, a plurality of detections including a corresponding measured azimuth angle and a corresponding measured radial velocity for each detection thereof;
for each cycle of the plurality of radar cycles:
selecting one detection from a first plurality of detections of the corresponding cycle for each one of two velocity components comprised in a set of components to be determined for a target, where the two velocity components define a full velocity vector for a relative velocity of the target;
selecting one detection from a second plurality of detections for each one of at least one corresponding acceleration component comprised in the set of components;
calculating the set of components based on the selected detections;
determining a calculated radial velocity for each one of at least a part of non-selected detections in the first plurality of detections based on the calculated set of components;
determining an error between each calculated radial velocity (v dc ) and the measured radial velocity for each one of at least the part of non-selected detections; and
determining a number of inliers for the corresponding cycle, where an inlier corresponds to a detection with the corresponding error that falls below an inlier threshold; and
choosing, as a determined set of components for the target, the set of components from the calculated sets of components of the plurality of radar cycles that corresponds to a largest number of inliers among the determined numbers of inliers of the plurality of radar cycles.
10. The method according to claim 9 , wherein the method further comprises:
grouping detections that correspond to inliers resulting from the chosen set of components, the grouped detections being identified as belonging to the target that is an extended object.
11. The method according to claim 9 , wherein the second plurality of detections is the same as the first plurality of detections.
12. The method according to claim 9 , wherein
the first plurality of detections and the second plurality of belong to different radar cycles, and
the method comprises, for each cycle of the plurality of radar cycles:
first calculating velocity components for the selected detections; and
then calculate the at least one acceleration component based on the calculated velocity components for the selected detections.
13. The method according to claim 12 , wherein the second plurality of detections belongs to a previous radar cycle prior to the corresponding radar cycle which the first plurality of detections belongs.
14. The method according to claim 9 , wherein the set of components is calculated by solving an expression of
V dm =( V x +a x Δt )cos(θ m )+( V y +a y Δt )sin(θ m )
for each selected detection, where θ m constitutes the measured azimuth angle between a radar system reference line and a direction towards the corresponding detection in question, V dm represents the measured radial velocity of the corresponding detection, V x represents an x-component of velocity of the set of components, V y represents a y-component of velocity of the set of components, a x represents an x-component of acceleration of the set of components, a y represents a y-component of acceleration of the set of components, and Δt represents a time difference of the selected detections.