Method for quantitatively analyzing steer characteristics to acquire steering stability of vehicles/tires

• US 20060074535A1
• Filed: 12/17/2004
• Published: 04/06/2006
• Est. Priority Date: 10/05/2004
• Status: Active Grant

• Current Assignee: Hankook Tire Company Limited
• Original Assignee: Hankook Tire Company Limited
• Inventors: Kim, Jung Sik, Gim, Gwang Hun
• Granted Patent: US 7,142,961 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B60T 2270/86 Optimizing braking by using ESP vehicle or tire model
• CPC Class Codes: B60T 8/172 Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• CPC Class Codes: G01M 17/06 Steering behaviour; Rolling behaviour

Abstract

A method for quantitatively analyzing steer characteristics to acquire steering stability of vehicles/tires. The method divides the steer characteristics into understeer, oversteer, and power-off reaction characteristics, separately analyzes the understeer, oversteer, and power-off reaction characteristics, analyzes the understeer characteristic using a tuning curvature and a turning velocity characteristic in association with a vehicle turning path, analyzes the oversteer characteristic using a slope of a nose angle and a nose-angle time rate in association with a vehicle attitude, analyzes the power-off reaction characteristic using a nose-angle slope, a nose-angle change rate, and a nose-angle change amount, and compares the above-mentioned characteristics with reference data obtained from a Quasi steady-state condition test during which a vehicle driving state is stable, such that it can quantitatively determine the steer characteristics upon receipt of the result of the comparison.

Claims

1. A method for quantitatively analyzing steer characteristics to acquire steering stability of a vehicle and a tire, comprising the steps of:

mounting a real-vehicle measurement device to a vehicle;

performing a variety of real-vehicle tests, i.e., a lane-changing test, a severe lane-changing test, a circuit cornering test, and a power on/off test in a vehicle turning operation, and acquiring measurement data;

calculating a turning curvature, a turning velocity, a nose angle, and a nose-angle time rate on the basis of the acquired measurement data;

comparing the turning curvature, the turning velocity, the nose angle, and the nose-angle time rate with reference data, i.e., a reference turning curvature, a reference turning velocity, and reference nose-angle data, respectively;

calculating a slope of the nose angle, a change rate, and a change amount during the power on/off test; and

determining a steer characteristic degree on the basis of the result of the comparison.

2. The method according to claim 1, wherein the lane-changing test is indicative of a first lane changing test, determines a lane-changing width to be 2.5˜

4.5 m, has a handle entry signal in the form of a sinusoidal signal, determines a handle entry angle to be −

180°

˜

+180°

, and determines vehicle speed to be a constant speed in the range of 40˜

350 kph.

3. The method according to claim 1, wherein the severe lane-changing test is used to return to an original lane after changing a first lane of the vehicle to another lane, turns off an acceleration paddle simultaneously with performing a handle entry operation while the vehicle travels straight on the assumption that a lane-changing width is 2.5˜

4.5 m and vehicle speed is in the range of 60˜

200 kph.

4. The method according to claim 1, wherein the power on/off test in the vehicle turning operation is performed by suddenly pressing an acceleration paddle during a normal turning operation of the vehicle, maintaining the pressed acceleration paddle, and suddenly releasing the pressed acceleration paddle, wherein

if an initial normal turning velocity is determined to be equal to or higher than lateral acceleration of 0.5 g, the pressed time (i.e., entry time) of the acceleration paddle is determined to be 1.0˜

5.0 seconds, and a maximum entry magnitude of the acceleration paddle is determined to be A₀ (mm) during the 1.0˜

5.0 seconds, an acceleration paddle entry magnitude is determined in the range of ½

˜

1.0 ratio associated with a value of A₀.

5. The method according to claim 1, wherein the reference data is acquired by a normal circle-turning test indicative of a Quasi steady-state condition test during which a vehicle driving state is stable, a weave steering test, or a progressive steering test after a real-vehicle measurement device has been mounted to the vehicle, and allows a tuning curvature, a turning velocity, and a nose angle associated with understeer and oversteer of the vehicle to be fit to a curve using a steering function, such that it is denoted by a function.

6. The method according to claim 5, wherein the normal circle-turning test uses a test method for changing a turning radius at a predetermined vehicle speed, determines vehicle speed to be 40˜

350 kph for use in a real-vehicle estimation test, and determines a tuning radius to be 10˜

200 m so that a handle entry range is determined to be −

360°

˜

360°

.

7. The method according to claim 5, wherein the weave steering test slowly sweeps a steering angle using a triangular or sinusoidal wave at a predetermined vehicle speed, determines a handle entry angle to be −

360°

˜

+360°

, includes reference data associated with an area having a large steering angle, determines a handle entry speed to be a low value of 1˜

50 degrees/s or less, determines vehicle speed to be 40˜

350 kph for use in a real vehicle estimation test, is capable of performing a variety of tests associated with one or more periods in the case of a handle entry operation, averages data associated with handle entry operations of several periods, uses the averaged result as reference data.

8. The method according to claim 5, wherein the progressive steering test separately performs a left-side turning test and a right-side turning test at a predetermined vehicle speed, adds left data and right data, uses the added result as reference data, determines a handle entry range to be −

360°

˜

+360°

, includes reference data associated with an area having a large steering angle, determines a handle entry speed to be a low value of 1˜

50 degrees/s, and determines vehicle speed to be 40˜

350 kph for use in a real vehicle estimation test.

9. The method according to claim 1, wherein the measurement data, i.e., the turning curvature, the tuning velocity, the nose angle, and the nose-angle time rate, and the reference data, i.e., the reference turning curvature, the reference turning velocity, and the reference nose angle, are measured in a driver'"'"'s seat or a vehicle'"'"'s center of gravity (i.e., a vehicle barycenter).

10. The method according to claim 1, wherein the method for analyzing the understeer includes the steps of:

mounting the real-vehicle measurement device to the vehicle;

performing a real-vehicle test associated with understeer estimation to acquire measurement data;

calculating a turning curvature and a turning velocity on the basis of the acquired measurement data;

comparing the turning curvature and the turning velocity with a reference turning curvature and a reference turning velocity, respectively; and

determining the degree of understeer on the basis of the result of the comparison.

11. The method according to claim 10, wherein the understeer analysis method includes the steps of:

indicating the reference turning curvature κ

_d(N) and the turing curvature κ

_d measured during the real-vehicle test on a Y-axis, and using a predetermined turning curvature graph in which a time or steering angle is determined to be an X-axis;

calculating a difference in turning curvature using the tuning curvature graph and the following equation Δ

κ

_d=|κ

_d(N)−

κ

_d|;

indicating the reference turning velocity ω

_d(N) and the turning velocity measured during the real-vehicle test on a Y-axis, and using a predetermined turning velocity graph in which a time or steering angle is determined to be an X-axis; and

calculating a difference in turning velocity using the turning velocity graph and the following equation Δ

ω

_d=|ω

_d(N)−

ω

_d|, wherein

according to the understeer analysis method, an understeer coefficient (US) is determined by the following equation US≡

w_us1Δ

κ

_d+w_us2Δ

w_d>

0 using the turning curvature difference Δ

ω

_d and the turning velocity difference Δ

ω

_d, wherein

the turning curvature difference Δ

κ

_d and the turning velocity difference Δ

ω

_d are quantitatively analyzed by selecting a maximum value or a mean value from the turning curvature graph and the turning velocity graph obtained by the real-vehicle test, and

the values of w_us1≧

0 and w_us2≧

0 are indicative of understeer weighting factors, and are determined by an estimator'"'"'s desire.

12. The method according to claim 1, wherein the method for analyzing the oversteer includes the steps of:

mounting the real-vehicle measurement device to the vehicle;

performing a real-vehicle test associated with oversteer estimation to acquire measurement data;

calculating a nose angle and a nose-angle time rate on the basis of the acquired measurement data;

comparing the nose angle and the nose-angle time rate with a reference nose angle and a reference nose-angle time rate, respectively; and

determining the degree of oversteer on the basis of the result of the comparison.

13. The method according to claim 12, wherein the oversteer analysis method includes the steps of:

indicating the reference nose angle φ

_d(N) and the nose angle φ

_d measured during the real-vehicle test on a Y-axis, and using a predetermined nose angle graph in which a time or steering angle is determined to be an X-axis;

calculating a difference in nose angle using the nose angle graph and the following equation Δ

φ

_d=|φ

_d−

φ

_d(N)|;

indicating the nose-angle time rate {dot over (φ

)}_d measured during the real-vehicle test on a Y-axis, and using a predetermined nose-angle time rate graph in which a time or steering angle is determined to be an X-axis; and

calculating a nose-angle time rate using the nose-angle time rate graph and the following equation Δ

{dot over (φ

)}_d=|{dot over (φ

)}_d|, wherein

according to the oversteer analysis method, an oversteer coefficient (OS) is determined by the following equation OS≡

w_os1Δ

φ

_d+w_os2Δ

{dot over (φ

)}_d>

0 using the nose-angle difference Δ

φ

_d and the nose-angle time rate Δ

{dot over (φ

)}_d, wherein

the nose-angle difference Δ

φ

_d and the nose-angle time rate Δ

{dot over (φ

)}_d are quantitatively analyzed by selecting a maximum value or a mean value from the nose angle graph and the nose-angle time rate graph obtained by the real-vehicle test, and

the values of w_os2≧

0 and w_os2≧

0 are indicative of oversteer weighting factors, and are determined by an estimator'"'"'s desire.

14. The method according to claim 1, wherein the method for analyzing the power-off reaction includes the steps of:

mounting the real-vehicle measurement device to the vehicle;

performing a real-vehicle test associated with power-off reaction estimation to acquire measurement data;

calculating a nose angle on the basis of the acquired measurement data; and

indicating the calculated nose angle on a Y-axis, and using a predetermined graph in which time is determined to be an X-axis, wherein

the power-off reaction is quantitatively analyzed by a nose-angle slope |φ

<sub>d—

slope</sub>|, a nose-angle change rate |φ

<sub>d—

pp</sub>|/Δ

t, and a nose-angle change amount |φ

<sub>d—

pp</sub>| contained in the following equation

$\mathrm{PR}\equiv <br><br>w_{\mathrm{pr1}}<br><br><br><br>{\mathrm{\phi <br><br>}}_{\mathrm{d\_slope}}<br><br>+w_{\mathrm{pr2}}<br><br>\frac{<br><br>{\mathrm{\phi <br><br>}}_{\mathrm{d\_pp}}<br><br>}{\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>t}+w_{\mathrm{pr3}}<br><br><br><br>{\mathrm{\phi <br><br>}}_{\mathrm{d\_pp}}<br><br>><br><br>0,$

where w_pr1≧

0, w_pr2≧

0 and w_pr3≧

0 are indicative of power-off reaction weighting factors and are determined by an estimator'"'"'s desire.