Kinematic estimator for vehicle lateral velocity using force tables
A system and method for estimating vehicle lateral velocity. The method uses a kinematic estimator constructed as a closed-loop Leunberger observer. The kinematic estimator is based on a kinematic relationship between lateral acceleration measurement and rate of change of lateral velocity. The method provides measurement updates based on virtual lateral velocity measurements from front and rear axle lateral force versus axle side-slip angle tables using the lateral acceleration, yaw-rate, longitudinal speed, and steering angle measurements. The method calculates front and rear axle lateral forces from the lateral acceleration and yaw-rate measurements. The method estimates front and rear axle side-slip angles from the calculated front and rear axle lateral forces using the tables. The method calculates multiple virtual lateral velocities from the front and rear side-slip angles and selects one of the virtual lateral velocities that minimizes an error between a measured force and an estimated force as the lateral velocity.
1. A method for estimating vehicle lateral velocity, said method comprising:
providing vehicle measurements including vehicle lateral acceleration, vehicle yaw-rate, longitudinal speed, and steering angle;
defining a kinematic relationship between vehicle lateral acceleration measurements and a rate of change of lateral velocity;
providing measurement updates based on virtual lateral velocity measurements from front and rear axle lateral force versus axle side-slip angle tables using the lateral acceleration, yaw-rate, longitudinal speed, and steering angle measurements;
calculating front and rear axle lateral forces from the lateral acceleration and yaw-rate measurements;
estimating front and rear axle side-slip angles from the calculated front and rear axle lateral forces using the tables;
calculating multiple virtual lateral velocities from the front and rear axle side-slip angles; and
selecting one of the virtual lateral velocities that minimizes an error between a measured force and an estimated force as the lateral velocity.
2. The method according to claim 1 wherein the kinematic relationship between the lateral acceleration measurements and the rate of change of the lateral velocity is defined by the equations:
{dot over (v)} y =a y −rv x
a y,m =a y −b ay
where b y is the lateral velocity, a y is the lateral acceleration, r is the yaw-rate, v x is the vehicle forward velocity and b ay is a bias of a lateral accelerometer.
3. The method according to claim 1 wherein calculating the front and rear axle lateral forces includes using the equation:
[
F
yF
,
m
F
yR
,
m
]
=
[
1
m
cos
δ
1
m
a
I
z
cos
δ
-
b
I
z
]
-
1
[
a
y
,
compensated
r
.
]
where F yF,m is the front axle force, F yR,m is the rear axle force, m is the vehicle mass, I is the vehicle moment of inertia, a y,compensated is the vehicle lateral acceleration compensated for gravity due to vehicle roll, r is the vehicle yaw-rate, δ is the steering angle and a and b are the longitudinal distances of the front and rear axles.
4. The method according to claim 1 wherein selecting the virtual lateral velocity that minimizes the error includes using the equation:
F y,err =|F yF,m −F yF,estimated |+|F yR,m −F yR,estimated |
where F y,err is the error, F yF is the force at the front axle and F yR is the force at the rear axle.
5. The method according to claim 1 wherein the method is performed in a kinematic estimator.
6. The method according to claim 5 wherein the kinematic estimator is part of a closed-loop Leunberger observer.
7. The method according to claim 1 further comprising adaptively changing observer gains based on the lateral forces and a difference between measured front and rear axle lateral velocities.
8. The method according to claim 1 further comprising compensating the lateral acceleration measurements for vehicle roll.
9. A method for estimating vehicle lateral velocity, said method comprising:
constructing a kinematic estimator as a closed-loop Leunberger observer;
providing vehicle measurements including vehicle lateral acceleration, vehicle yaw-rate, longitudinal speed, and steering angle;
basing the kinematic estimator on a kinematic relationship between lateral acceleration measurements and a rate of change of lateral velocity;
calculating virtual lateral velocities using front and rear axle lateral forces versus side-slip angle tables using the measured lateral acceleration, yaw-rate, longitudinal speed, and steering angle;
calculating front and rear axle lateral forces from the lateral acceleration and yaw-rate measurements;
estimating front and rear axle side-slip angles from the calculated front and rear axle lateral forces using the tables;
calculating multiple virtual lateral velocities from the front and rear side-slip angles;
selecting one of the virtual lateral velocities that minimizes an error between a measured force and an estimated force as the lateral velocity; and
adaptively changing observer gains based on the lateral forces and a difference between the measured front and rear axle lateral velocities.
10. The method according to claim 9 wherein the kinematic relationship between the lateral acceleration measurements and the rate of change of the lateral velocity is defined by the equations:
{dot over (v)} y =a y −rv x
a y,m =a y −b ay
where b y is the lateral velocity, a y is the lateral acceleration, r is the yaw-rate, v x is the vehicle forward velocity and b ay is a bias of a lateral accelerometer.
11. The method according to claim 9 wherein calculating the front and rear axle lateral forces includes using the equation:
[
F
yF
,
m
F
yR
,
m
]
=
[
1
m
cos
δ
1
m
a
I
z
cos
δ
-
b
I
z
]
-
1
[
a
y
,
compensated
r
.
]
where F yF,m is the front axle force, F yR,m is the rear axle force, m is the vehicle mass, I is the vehicle moment of inertia, a y is the vehicle lateral acceleration compensated for gravity due to vehicle roll, r is the vehicle yaw-rate, δ is the steering angle and a and b are the longitudinal distances of the front and rear axles.
12. The method according to claim 9 wherein selecting the virtual lateral velocity that minimizes the error includes using the equation:
F y,err =|F yF,m −F yF,estimated |+|F yR,m −F yR,estimated |
where F y,err is the error, F yF is the force at the front axle and F yR is the force at the rear axle.
13. The method according to claim 9 further comprising compensating the lateral acceleration measurements for vehicle roll.
14. A system for estimating vehicle lateral velocity, said system comprising:
means for providing vehicle measurements including vehicle lateral acceleration, vehicle yaw-rate, longitudinal speed, and steering angle;
means for defining a kinematic relationship between vehicle lateral acceleration measurements and a rate of change of lateral velocity;
means for providing measurement updates based on virtual lateral velocity measurements from front and rear axle lateral force versus axle side-slip angle tables using the lateral acceleration, yaw-rate, longitudinal speed, and steering angle measurements;
means for calculating front and rear axle lateral forces from the lateral acceleration and yaw-rate measurements;
means for estimating front and rear axle side-slip angles from the calculated front and rear axle lateral forces using the tables;
means for calculating multiple virtual lateral velocities from the front and rear side-slip angles; and
means for selecting one of the virtual lateral velocities that minimizes an error between a measured force and an estimated force as the lateral velocity.
15. The system according to claim 14 wherein the means for defining a kinematic relationship between the lateral acceleration measurements and the rate of change of the lateral velocity uses the equations:
{dot over (v)} y =a y −rv x
a y,m =a y −b ay
where b y is the lateral velocity, a y is the lateral acceleration, r is the yaw-rate, v x is the vehicle forward velocity and b ay is a bias of a lateral accelerometer.
16. The system according to claim 14 wherein the means for calculating the front and rear axle lateral forces uses the equation:
[
F
yF
,
m
F
yR
,
m
]
=
[
1
m
cos
δ
1
m
a
I
z
cos
δ
-
b
I
z
]
-
1
[
a
y
,
compensated
r
.
]
where F yF,m is the front axle force, F yR,m is the rear axle force, m is the vehicle mass, I is the vehicle moment of inertia, a y is the vehicle lateral acceleration, compensated for gravity due to vehicle roll, r is the vehicle yaw-rate, δ is the steering angle and a and b are the longitudinal distances of the front and rear axles.
17. The system according to claim 14 wherein the means for selecting the virtual lateral velocity that minimizes the error uses the equation:
F y,err =|F yF,m −F yF,estimated |+|F yR,m −F yR,estimated |
where F y,err is the error, F yF is the force at the front axle and F yR is the force at the rear axle.
18. The system according to claim 14 wherein the system includes a kinematic estimator.
19. The system according to claim 18 wherein the kinematic estimator is part of a closed-loop Leunberger observer.
20. The system according to claim 14 further comprising means for adaptively changing observer gains based on the lateral forces and a difference between measured front and rear axle lateral velocities.