Detection and reconstruction of roll rate sensor fault
A method of reconstructing a detected faulty signal. A roll sensor fault is detected by a processor. A signal of the detected faulty roll sensor is reconstructed using indirect sensor data. The reconstructed signal is output to a controller to maintain stability.
1. A method of reconstructing a detected faulty signal comprising the steps of:
detecting a roll sensor fault by a processor;
reconstructing, by the processor, a signal of the detected faulty roll sensor using indirect sensor data; and
outputting the reconstructed signal to a controller to execute a control action on a vehicle system to maintain stability;
wherein detecting the roll sensor fault by the processor comprises the steps of:
obtaining sensory data from a faulted roll sensor, the faulted roll sensor dedicated to monitor a roll instability condition,
obtaining sensory data from at least one non-faulted sensor other than the roll sensor,
determining a virtual sensor value as a function of the sensory data from the at least one non-faulted sensor,
generating a residual as a function of the sensory data from the faulted roll sensor and virtual sensor value from the at least one non-faulted sensor,
comparing the residual to a threshold, and
detecting the sensor roll fault in response to the residual exceeding the threshold.
2. The method of claim 1 wherein determining a virtual sensor value as a function of the sensory data from the at least one non-faulted sensor is determined utilizing a roll dynamics of a vehicle model and is represented by the following formula:
[
ϕ
.
v
ϕ
¨
v
]
=
[
0
1
-
K
ϕ
(
I
x
+
m
s
H
RC
2
)
-
C
ϕ
(
I
x
+
m
s
H
RC
2
)
]
[
ϕ
v
ϕ
.
v
]
+
[
0
m
s
H
RC
(
I
x
+
m
s
H
RC
2
)
]
[
v
.
y
+
v
x
ψ
.
+
g
sin
(
ϕ
v
+
Φ
r
)
]
,
where φ v is the roll angle of the sprung mass, {dot over (φ)} v is the vehicle roll rate, H RC represents a distance between a center of gravity and the roll center, {dot over (v)} y is the rate of change of lateral velocity; v x represents longitudinal velocity; I x represents a moment of inertia about the x axes of a body coordinate system; {dot over (ψ)} is the yaw rate; Φ r is the road bank angle; m S is the sprung mass; g is the gravitational acceleration; C φ is the roll damping; K φ is the stiffness coefficients for roll.
3. The method of claim 2 wherein an observer used to estimate a roll state with an unknown input is represented by the following equation:
x
^
ϕ
[
k
+
1
]
=
E
ϕ
x
^
ϕ
[
k
]
+
F
ϕ
y
ϕ
[
k
:
k
+
L
]
u
^
ϕ
[
k
]
=
[
B
ϕ
D
ϕ
]
-
1
[
x
^
ϕ
[
k
+
1
]
-
A
ϕ
x
^
ϕ
[
k
]
y
ϕ
[
k
]
-
C
ϕ
x
ϕ
k
]
where E φ and F φ are the observer gain matrices for the roll observer, where B φ and D φ are bound gain parameters, where x φ [k] is an estimate roll state, and where û φ [k] is an estimate of an unknown input.
4. The method of claim 1 wherein the threshold includes an adaptive threshold.
5. The method of claim 4 wherein the adaptive threshold is estimated based on a current driving condition and dynamic region.
6. The method of claim 5 wherein the current driving conditions and dynamic region are determined using the vehicle model and sensory data.
7. The method of claim 4 wherein the adaptive threshold for the roll rate is determined utilizing the following equation:
T d φ =max( T φ ( k ), T φ ( k− 1) . . . , T φ ( k−W φ )):
where T φ is a respective instantaneous threshold, and where W φ is a length of time of the time window during the roll sensing operation to calculate the threshold.
8. The method of claim 7 wherein the instantaneous adaptive threshold is determined utilizing the following equation:
T {dot over (φ)} =B s φ +B d φ (| a y |)
where B s φ is a static bound that determines a fixed minimum value for the threshold, and B d φ is a constant gain that adds effects of lateral excitation to the threshold.
9. The method of claim 1 wherein determining a virtual sensor value of the roll rate as a function of the sensory data from the at least one non-faulted sensor is determined utilizing the following equation:
{circumflex over ({dot over (φ)})} −ij ={circumflex over ({dot over (φ)})} v−ij +R ({circumflex over (θ)} v−ij ,{circumflex over (φ)} v−ij ){circumflex over ({dot over (φ)})} r−ij
where {circumflex over ({dot over (φ)})} −ij is the estimated vehicle roll rate in the form of a virtual sensor, {circumflex over ({dot over (φ)})} v−ij is the estimated body roll rate calculated using respective vehicle sensors not indexed by ij subscript, R is the rotation matrix describing orientation of vehicle sprung mass with respect to frame reference coordinate system; {circumflex over (θ)} v−ij is the estimated vehicle pitch angle, {circumflex over (φ)} v−ij is the estimated vehicle roll angle, and {circumflex over ({dot over (Φ)})} r−ij is the estimated rate of change of the road bank angle, all calculated using vehicle sensors not indexed by ij subscript.
10. The method of claim 9 wherein generating the residual as a function of the sensory data from the faulted roll sensor and the virtual sensor value from the at least one non-faulted sensor is determined by the following equation:
R {dot over (φ)}−ij =|{dot over (φ)} s −{circumflex over ({dot over (φ)})} −ij |
wherein {circumflex over ({dot over (φ)})} −ij is the virtual sensor value and {dot over (φ)} s measured value from the roll rate sensor.
11. The method of claim 1 wherein detecting the sensor fault in response to the residual exceeding the threshold further comprises the step of determining whether the fault persists for a period of time.
12. The method of claim 11 wherein determining whether the fault persists for the period of time further comprises the steps of:
incrementing a fault count each time the residual exceeds the adaptive threshold;
detecting the fault when the fault count exceeds a predetermined count threshold.
13. The method of claim 12 wherein the fault count is reset to zero in response to a residual not exceeding the adaptive threshold.
14. The method of claim 1 wherein reconstructing the signal of the detected faulty sensor using indirect sensor data is determined using the following equation:
{circumflex over ({dot over (φ)})}= w −ij {circumflex over ({dot over (φ)})} −ij
where {circumflex over ({dot over (φ)})} is the reconstructed roll rate signal; w −ij represent weight factors.
15. The method of claim 1 wherein the outputting the reconstructed signal to a controller includes outputting the signal to a vehicle braking system for mitigating a vehicle instability condition.
16. The method of claim 1 wherein the outputting the reconstructed signal to a controller includes outputting the signal to a powertrain control system for mitigating a vehicle instability condition.
17. The method of claim 1 wherein the outputting the reconstructed signal to a controller includes outputting the signal to a vehicle traction control system for mitigating a vehicle instability condition.
18. The method of claim 1 wherein the outputting the reconstructed signal to a controller includes outputting the signal to a steering system for mitigating a vehicle instability condition.