System for Determining Inflating Pressures of Tyres Mounted on a Motor Vehicle Front and Rear Wheels

• US 20080208515A1
• Filed: 07/04/2006
• Published: 08/28/2008
• Est. Priority Date: 07/26/2005
• Status: Active Grant

• Current Assignee: Peugeot Citroen Automobile SA (Stellantis NV)
• Original Assignee: Peugeot Citroen Automobile SA (Stellantis NV)
• Inventors: Djama, Zahir
• Granted Patent: US 7,823,443 B2
• Time in Patent Office: Days
• US Class Current: 702/138
• CPC Class Codes: B60C 23/04 mounted on the wheel or tyre
• CPC Class Codes: B60C 23/0481 System diagnostic, e.g. monitoring battery voltage, detecting hardware detachments or identifying wireless transmission failures

Abstract

The invention concerns a system for determining inflating pressure of tires mounted on a motor vehicle front and rear wheels. Said system comprises means (12, 14) for acquiring inflating pressures of the front and rear wheels, means (16, 18) for acquiring vertical accelerations of the front and rear wheels, and means (32) for emerging the acquired pressures and the acquired accelerations to estimate the inflating pressures of the front and rear tires.

Claims

1. System for determining the inflating pressures of tires mounted on front and rear wheels of a motor vehicle, comprising:

means for acquiring inflating pressures of the tires of the front and rear wheels;

means for acquiring vertical accelerations of the front and rear wheels; and

means for merging the acquired pressures and the acquired accelerations to estimate the inflating pressures of the tires of the front and rear wheels.

2. System according to claim 1, wherein the merging means comprise:

means for estimating the coefficients of stiffness of the tires of the front and rear wheels as a function of the acquired vertical accelerations of these wheels; and

means for estimating the inflating pressures of the tires of the front and rear wheels as a function of the acquired inflating pressures and of the acquired coefficients of stiffness of the tires of the front and rear wheels.

3. System according to claim 2, wherein the means for estimating the coefficients of stiffness comprise means for temporally resetting one of the acquired accelerations on the other of the acquired accelerations and means for calculating the coefficients of stiffness as a function of the thus temporally reset accelerations.

4. System according to claim 2, wherein the means for estimating the coefficients of stiffness comprise means for bandpass filtering the acquired accelerations arranged between means for acquiring the accelerations and the temporally resetting means.

5. System according to claim 4, wherein the passband filtering means are adapted to perform filtering in a range of frequencies substantially equal to [8, 20] Hz.

6. System according to claim 3, wherein the temporally resetting means comprise means for calculating the inter-correlation of the acquired accelerations and means for applying a delay corresponding to the maximum of the calculated inter-correlation to the acquired acceleration of the front wheel.

7. System according to claim 3, wherein the means for calculating the coefficients of stiffness are adapted to implement a recursive least square algorithm in real time based on a predetermined mechanical model of the wheel.

8. System according to claim 2, wherein the estimation means are adapted to estimate said coefficients of stiffness from a mono-wheel mechanical model of the front and rear wheels.

9. System according to claim 8, wherein the estimation means are adapted to estimate said coefficients of stiffness based on a model in discrete time of the temporally reset accelerations of the front and rear wheels according to the equation:

$\mathrm{Avr}<br><br>\left(k\right)=\frac{1}{\mathrm{mrr}}<br><br>\left(\mathrm{mra}\times <br><br>\mathrm{Ava}<br><br>\left(k-n\right)<br><br><br><br>\mathrm{Zva}<br><br>\left(k-n\right)-\mathrm{Zvr}<br><br>\left(k\right)\right)<br><br>\left(\begin{array}{c}\mathrm{Kpr}<br><br>\left(k\right)/\mathrm{Kpa}<br><br>\left(k\right)\\ \mathrm{Kpr}<br><br>\left(k\right)\end{array}\right)$

where k is the k^th sampling instant, Avr and Ava are the vertical accelerations of the rear and front wheels, respectively, Zvr and Zva are the altitudes of the centers of the rear and front wheels, respectively, Kpr and Kpa are the coefficients of stiffness of the tires of the rear and front wheels, respectively, and n is a sampling instant corresponding to a time shift between the rear and front wheels subjected to a same portion of the roadway.

10. System according to claim 8, wherein the estimation means are adapted to estimate said coefficients of stiffness based on a model in discrete time of the temporally reset accelerations of the front and rear wheels according to the equation:

$\mathrm{Ava}<br><br>\left(k\right)=\frac{1}{\mathrm{mra}}<br><br>\left(\mathrm{mrr}\times <br><br>\mathrm{Avr}<br><br>\left(k+n\right)<br><br><br><br>\mathrm{Zvr}<br><br>\left(k+n\right)-\mathrm{Zva}<br><br>\left(k\right)\right)<br><br>\left(\begin{array}{c}\mathrm{Kpa}<br><br>\left(k\right)/\mathrm{Kpr}<br><br>\left(k\right)\\ \mathrm{Kpa}<br><br>\left(k\right)\end{array}\right)$

where k is the k^th sampling instant, Avr and Ava are the vertical accelerations of the rear and front wheels, respectively, Zvr and Zva are the altitudes of the centers of the rear and front wheels, respectively, Kpr and Kpa are coefficients of stiffness of the tires of the rear and front wheels, respectively, and n is a sampling instant corresponding to a time shift between the rear and front wheels subjected to a same portion of the roadway.

11. System according to claim 2, wherein the estimation means are adapted to estimate said coefficients of stiffness from a bicycle mechanical model thereof.

12. System according to claim 11, wherein the estimation means are adapted to estimate said coefficients of stiffness based on a model in discrete time of the temporally reset accelerations of the front and rear wheels according to the equation:

$\mathrm{Avr}<br><br>\left(k\right)={\left(\begin{array}{c}\frac{\mathrm{mra}}{\mathrm{mrr}}<br><br>\mathrm{Ava}<br><br>\left(k-n\right)\\ \frac{1}{\mathrm{mrr}}<br><br>\left(\mathrm{Zva}<br><br>\left(k-n\right)-\mathrm{Zvr}<br><br>\left(k\right)\right)\\ \frac{1}{\mathrm{mnr}}<br><br>\stackrel{.}{Z}<br><br>\mathrm{va}<br><br>\left(k-n\right)\\ -\frac{1}{\mathrm{mrr}}<br><br>\stackrel{.}{Z}<br><br>\mathrm{vr}<br><br>\left(k\right)\end{array}\right)}^T<br><br>\left(\begin{array}{c}\mathrm{Kpr}<br><br>\left(k\right)/\mathrm{Kpa}<br><br>\left(k\right)\\ \mathrm{Kpr}<br><br>\left(k\right)\\ \left(\mathrm{Kpr}<br><br>\left(k\right)/\mathrm{Kpa}<br><br>\left(k\right)\right)\times <br><br>\mathrm{Ra}<br><br>\left(k\right)\\ \mathrm{Rr}<br><br>\left(k\right)\end{array}\right)$

where k is the k^th sampling instant, Avr and Ava are the vertical accelerations of the rear and front wheels, respectively, Zvr and Zva are the altitudes of the centers of the rear and front wheels, respectively, Kpr and Kpa are coefficients of stiffness of the tires of the rear and front wheels, respectively, n is a sampling instant corresponding to a time shift between the rear and front wheels subjected to a same portion of the roadway, Ra and Rr are coefficients of stiffness of the suspensions of the front and rear wheels, respectively, and Ż

va and Ż

vr are first derivatives of the altitudes of the centers of the front and rear wheels, respectively.

13. System according to claim 2, wherein the means for estimating the inflating pressures are adapted to implement, for each of the front and rear wheels, a Kalman estimator based on a model linking the inflating pressure and the coefficient of stiffness of the wheel tire.

14. System according to claim 1, wherein the merging means are adapted to implement a Kalman estimator based on a model linking the inflating pressures of the tires and the vertical accelerations of the front and rear wheels.

15. System according to claim 1, wherein the system further comprises means for diagnosing the operating state of the means for acquiring the inflating pressures and the mounting states of the tires as a function of the estimated and acquired inflating pressures and of the acquired vertical accelerations of the front and rear wheels.

16. System according to claim 15, wherein, if an acquired inflating pressure and its associated estimated pressure differ by more than X %, where X is a predetermined number, the diagnostic means are adapted to calculate the inflating pressures of the tires of the front and rear wheels as a function of the acquired vertical accelerations of these wheels, so as to compare the acquired pressure to the calculated pressures and to determine that, if the acquired pressure corresponds to one of the calculated pressures, the tire associated to the calculated pressure corresponding to the acquired pressure has been mounted in reverse.

17. System according to claim 16, wherein, if none of the tires is mounted in reverse, then the diagnostic means are adapted to diagnose that the acquisition means associated to the acquired pressure are defective.