Systems and methods for driver intervention in an automatic steering system
A vehicle steering system includes an automatic steering control unit configured to control the vehicle steering system when in an automatic operational state and a driver intervention unit is configured to determine driver intervention during the automatic operational state. The driver intervention unit comprising a decision software module configured to determine driver intervention.
1. A method, for performance by a tangible device at a vehicle comprising a steering angle sensor, for controlling a vehicle steering system of the vehicle, the method comprising:
receiving, by the tangible device comprising a processor executing instructions stored on a non-transitory computer-readable medium of the tangible device, a measured steering angle obtained by the steering angle sensor of the vehicle;
calculating, by the tangible device executing the instructions stored on a non-transitory computer-readable medium of the tangible device, a moment of inertia, yielding a calculated moment of inertia, according to a relationship amongst factors comprising:
the measured steering angle;
an equivalent damping of the vehicle steering system;
an equivalent stiffness of the vehicle steering system; and
a torque sum, comprising:
a driver-applied steering torque;
an equivalent motor-assist torque; and
an equivalent tire-alignment torque; and
determining, by the tangible device executing the instructions stored on a non-transitory computer-readable medium of the tangible device, during an automatic operational state of the vehicle, as a function of a hands-off moment of inertia and the calculated moment of inertia, whether a driver-intervention condition exists;
wherein:
the relationship is represented by an equation as follows:
J
e
′
=
(
∑
T
)
-
B
e
θ
.
s
+
K
e
θ
s
θ
¨
s
J e ′ is the calculated moment of inertia;
θ s is the measured steering angle;
B e is the equivalent damping of the vehicle steering system;
K e is the equivalent stiffness of the vehicle steering system; and
ΣT is the torque sum, comprising:
a driver-applied steering torque;
an equivalent motor-assist torque; and
an equivalent tire-alignment torque.
2. The method of claim 1 , wherein the tangible device comprises the steering angle sensor configured to measure a steering angle, yielding the measured steering angle.
3. The method of claim 2 , wherein the tangible device comprises an automatic steering control unit configured to control an electric-power component of the vehicle steering system.
4. The method of claim 2 , wherein the tangible device is a part of a driver-intervention unit for use in the vehicle.
5. The method of claim 2 , wherein:
J e is the equivalent moment of inertia of the vehicle steering system;
θ s is the measured steering angle;
B e is the equivalent damping of the vehicle steering system;
K e is the equivalent stiffness of the vehicle steering system;
ΣT is the torque summary;
T d is the driver-applied steering torque;
T m is the equivalent motor-assist torque;
T a is the equivalent tire-alignment torque;
an equivalent transfer function, providing a relationship between the measured steering angle (θ s ) and the equivalent stiffness of the vehicle steering system (K e ), is as follows:
Θ
s
(
s
)
T
(
s
)
=
K
e
ω
n
2
s
2
+
2
ζω
n
s
+
ω
n
2
;
ζ is an equivalent damping ratio of the vehicle steering system; and
ω n is an equivalent natural frequency of the vehicle steering system.
6. A vehicle steering system, for use in a vehicle, comprising:
a processor; and
a computer-readable storage device comprising:
data indicating a hands-off moment of inertia of the vehicle steering system; and
computer-executable instructions that, when executed by the processor, cause the processor to perform operations comprising:
calculating a moment of inertia, yielding a calculated moment of inertia, according to a relationship amongst factors comprising:
a measured steering angle;
an equivalent damping of the vehicle steering system;
an equivalent stiffness of the vehicle steering system; and
a torque sum, comprising:
a driver-applied steering torque;
an equivalent motor-assist torque; and
an equivalent tire-alignment torque; and
determining, during an automatic operational state of the vehicle, as a function of the hands-off moment of inertia and the calculated moment of inertia,
whether a driver-intervention condition exists;
wherein:
the relationship is represented by an equation as follows:
J
e
′
=
(
∑
T
)
-
B
e
θ
.
s
+
K
e
θ
s
θ
¨
s
J e ′ is the calculated moment of inertia;
θ s is the measured steering angle;
B e is the equivalent damping of the vehicle steering system;
K e is the equivalent stiffness of the vehicle steering system; and
ΣT is the torque sum, comprising:
a driver-applied steering torque;
an equivalent motor-assist torque; and
an equivalent tire-alignment torque.
7. The vehicle steering system of claim 6 , further comprising an automatic steering control unit configured to control an electric-power component of the vehicle steering system.
8. The vehicle steering system of claim 6 , further comprising a steering angle sensor configured to measure a steering angle, yielding the measured steering angle.
9. The vehicle steering system of claim 6 , wherein the computer-readable storage device is a part of a driver-intervention unit for use in the vehicle.
10. The vehicle steering system of claim 6 , wherein:
J e is the equivalent moment of inertia of the vehicle steering system;
θ s is the measured steering angle;
B e is the equivalent damping of the vehicle steering system;
K e is the equivalent stiffness of the vehicle steering system;
ΣT is the torque summary;
T d is the driver-applied steering torque;
T m is the equivalent motor-assist torque;
T a is the equivalent tire-alignment torque;
an equivalent transfer function, providing a relationship between the measured steering angle (θ s ) and the equivalent stiffness of the vehicle steering system (K e ), is as follows:
Θ
s
(
s
)
T
(
s
)
=
K
e
ω
n
2
s
2
+
2
ζω
n
s
+
ω
n
2
;
ζ is an equivalent damping ratio of the vehicle steering system; and
ω n is an equivalent natural frequency of the vehicle steering system.
11. A computer-readable storage device comprising computer-executable instructions that, when executed by a processor, cause the processor to perform, in a vehicle steering system, operations comprising:
calculating a moment of inertia, yielding a calculated moment of inertia, according to a relationship amongst factors comprising:
a measured steering angle;
an equivalent damping of the vehicle steering system;
an equivalent stiffness of the vehicle steering system; and
a torque sum, comprising:
a driver-applied steering torque;
an equivalent motor-assist torque; and
an equivalent tire-alignment torque; and
determining, during an automatic operational state of the vehicle, as a function of a hands-off moment of inertia of the vehicle steering system and the calculated moment of inertia, whether a driver-intervention condition exists;
wherein:
the relationship is represented by an equation as follows:
J
e
′
=
(
∑
T
)
-
B
e
θ
.
s
+
K
e
θ
s
θ
¨
s
J e ′ is the calculated moment of inertia;
θ s is the measured steering angle;
B e is the equivalent damping of the vehicle steering system;
K e is the equivalent stiffness of the vehicle steering system; and
ΣT is the torque sum, comprising:
a driver-applied steering torque;
an equivalent motor-assist torque; and
an equivalent tire-alignment torque.
12. The computer-readable storage device of claim 11 , wherein the computer-readable storage device is a part of a driver-intervention unit for use in the vehicle.
13. The vehicle steering system of claim 11 , wherein:
J e is the equivalent moment of inertia of the vehicle steering system;
θ s is the measured steering angle;
B e is the equivalent damping of the vehicle steering system;
K e is the equivalent stiffness of the vehicle steering system;
ΣT is the torque summary;
T d is the driver-applied steering torque;
T m is the equivalent motor-assist torque;
T a is the equivalent tire-alignment torque;
an equivalent transfer function, providing a relationship between the measured steering angle (θ s ) and the equivalent stiffness of the vehicle steering system (K e ), is as follows:
Θ
s
(
s
)
T
(
s
)
=
K
e
ω
n
2
s
2
+
2
ζω
n
s
+
ω
n
2
;
ζ is an equivalent damping ratio of the vehicle steering system; and
ω n is an equivalent natural frequency of the vehicle steering system.