Identification of vehicle CG height and mass for roll control
View Patent ↗A system and method for determining vehicle CG height and mass in real-time. The method includes selecting a set of vehicle parameters to be considered that includes the vehicle mass and the center of gravity height of the vehicle. Frequency responses are generated using the dynamic model and a plurality of different values for the selected vehicle parameters. During vehicle operation, frequency responses are calculated from a measured vehicle lateral acceleration to a roll angle and/or a roll rate of the vehicle. The generated frequency responses and the calculated frequency responses are compared to determine which of the generated frequency responses more closely matches the calculated frequency responses. The generated frequency responses that most closely match the calculated frequency responses are used to determine the center of gravity height and the vehicle mass from the values for the vehicle parameters.
1. A method for determining vehicle center of gravity height and vehicle mass, said method comprising:
selecting a set of vehicle parameters to be considered that includes the vehicle mass and the center of gravity height;
generating frequency responses using a predetermined model for a plurality of different values for the selected vehicle parameters, and storing the generated frequency responses for the selected parameters;
calculating frequency responses for a measured vehicle lateral acceleration to a roll angle and/or a roll rate of the vehicle;
comparing the generated frequency responses and the calculated frequency responses to determine which of the generated frequency responses more closely matches the calculated frequency responses; and
selecting the generated frequency responses that most closely match the calculated frequency responses to determine the center of gravity height and the vehicle mass.
2. The method according to claim 1 wherein generating frequency responses includes using a one degree-of-freedom model.
3. The method according to claim 2 wherein the one degree-of-freedom model is provided by the equation:
( I xx +M s h 2 ){umlaut over (φ)}+ b r {dot over (φ)}+k r φ=M s ha y
where I xx is the roll moment of inertia of a vehicle body, M s is the vehicle mass, h is the vehicle center of gravity height, φ is the roll angle, {dot over (φ)} is the roll rate, {umlaut over (φ)} is the roll acceleration, a y is the measured lateral acceleration, b r is roll damping coefficient and k r is roll stiffness.
4. The method according to claim 1 wherein calculating frequency responses includes using an estimated or measured roll angle and/or roll rate.
5. The method according to claim 1 where generating frequency responses for a roll angle includes using the equation:
F
Ay
,
Ra
(
s
)
=
M
s
h
(
I
xx
+
M
s
h
2
+
b
r
s
)
+
k
r
where F is the frequency response, I xx is the roll moment of inertia of a vehicle body, M s is the vehicle mass, h is the vehicle center of gravity height, b r is roll damping coefficient and k r is roll stiffness.
6. The method according to claim 1 wherein generating the frequency responses for a roll rate includes using the equation:
F
Ay
,
RR
(
s
)
=
M
s
hs
(
I
xx
+
M
s
h
2
)
s
2
+
b
r
s
+
k
r
where F is the frequency response, I xx is the roll moment of inertia of a vehicle body, M s is the vehicle mass, h is the vehicle center of gravity height, b r is roll damping coefficient and k r is roll stiffness.
7. The method according to claim 1 wherein the selected vehicle parameters includes the vehicle mass, the vehicle CG height and the vehicle roll moment of inertia.
8. The method according to claim 1 wherein the plurality of different values for the set of selected vehicle parameters includes values for low loads, values for nominal loads and values for high loads.
9. The method according to claim 1 wherein generating and calculating frequency responses includes generating and calculating frequency responses in a frequency range of interest between 0.1 Hz and 2 Hz.
10. The method according to claim 1 wherein comparing the generated frequency responses and the calculated frequency responses includes using a root mean square process.
11. A method for determining vehicle center of gravity height and vehicle mass, said method comprising:
selecting the vehicle center of gravity height, the vehicle mass and a moment of inertia as vehicle parameters to be considered;
generating frequency responses using a one degree-of-freedom vehicle model for a plurality of different values for the selected vehicle parameters for both vehicle roll angle and roll rate, and storing the generated frequency responses for the selected parameters;
calculating frequency responses from a measured vehicle lateral acceleration to a measured or estimate roll angle and/or roll rate of the vehicle during vehicle operation;
comparing the generated frequency responses and the calculated frequency responses to determine which of the generated frequency responses more closely matches the calculated frequency responses; and
selecting the generated frequency responses that most closely match the calculated frequency responses and using the values of the selected vehicle parameters to determine the center of gravity height and the vehicle mass.
12. The method according to claim 11 wherein the one degree-of-freedom model is provided by the equation:
( I xx +M s h 2 ){umlaut over (φ)}+ b r {dot over (φ)}+k r φ=M s ha y
where I xx is the roll moment of inertia of a vehicle body, M s is the vehicle mass, h is the vehicle center of gravity height, φ is the roll angle, {dot over (φ)} is the roll rate, {umlaut over (φ)} is the roll acceleration, a y is the measured lateral acceleration, b r is roll damping coefficient and k r is roll stiffness.
13. The method according to claim 11 where generating frequency responses for a roll angle includes using the equation:
F
Ay
,
Ra
(
s
)
=
M
s
h
(
I
xx
+
M
s
h
2
+
b
r
s
)
+
k
r
where F is the frequency response, I xx is the roll moment of inertia of a vehicle body, M s is the vehicle mass, h is the vehicle center of gravity height, b r is roll damping coefficient and k r is roll stiffness.
14. The method according to claim 11 wherein generating the frequency responses for a roll rate includes using the equation:
F
Ay
,
RR
(
s
)
=
M
s
hs
(
I
xx
+
M
s
h
2
)
s
2
+
b
r
s
+
k
r
where F is the frequency response, I xx , is the roll moment of inertia of a vehicle body, M s is the vehicle mass, h is the vehicle center of gravity height, b r is roll damping coefficient and k r is roll stiffness.
15. The method according to claim 11 wherein the plurality of different values for the set of selected vehicle parameters includes values for low loads, values for nominal loads and values for high loads.
16. The method according to claim 11 wherein generating and calculating frequency responses includes generating and calculating frequency responses in a frequency range of interest between 0.1 Hz and 2 Hz.
17. The method according to claim 11 wherein comparing the generated frequency responses and the calculated frequency responses includes using a root mean square process.
18. A method for determining vehicle center of gravity height and vehicle mass, said method comprising:
generating frequency responses using a predetermined model for a plurality of different values for the vehicle center of gravity height and the vehicle mass;
calculating frequency responses for a measured vehicle lateral acceleration to a roll angle and/or a roll rate of the vehicle; and
comparing the generated frequency responses and the calculated frequency responses to determine which of the generated frequency responses more closely matches the calculated frequency responses to determine the center of gravity height and the vehicle mass.
19. The method according to claim 18 wherein generating frequency responses includes using a one degree-of-freedom model.
20. The method according to claim 18 wherein the plurality of different values for the set of selected vehicle parameters includes values for low loads, values for nominal loads and values for high loads.