Measuring and testing – Vibration – Resonance – frequency – or amplitude study
Reexamination Certificate
1999-09-29
2001-07-03
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
Resonance, frequency, or amplitude study
C073S146000, C073S146200, C152S158000, C152S520000
Reexamination Certificate
active
06253616
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the detection of the vibration signature of a safety insert fitted in a tire.
BACKGROUND OF THE INVENTION
Tires have been fitted with safety inserts which support the tires when there is a puncture or a serious loss of pressure.
However, the life of such a safety insert is limited, and it is therefore generally necessary to provide means for warning the driver of the occurrence of an incident in one of the tires of his vehicle.
A first solution, known in particular from patent application WO94/03338, consists in using systems for detecting one or more modes of resonance characteristic of running of a tire supported by its insert.
A system of this type includes one or more accelerometers, means for filtering the acceleration measurement signals in one or more frequency bands, and processing means which determine from these acceleration measurements characteristic values which are subsequently compared with warning detection thresholds.
Another solution uses safety inserts which include means of voluntarily degrading the vibration behavior of the vehicle during running supported by these inserts. The characteristic vibrations thus generated warn the driver of an abnormal pressure condition in one of his tires, by means of a suitable detection system for example.
In this respect, see U.S. Pat. No. 4,262,724 or U.S. Pat. No. 4,157,726, for example.
Regardless of whether the safety insert does or does not include means for generating a degraded vibration mode, it is desirable that the method used to detect the characteristic signature of running on the safety insert should be capable of allowing for the vibration level of the ground, in order to avoid the triggering of false alarms, particularly when the vehicle is running on rougher roads or tracks.
A first solution for this purpose could consist of determining a characteristic parameter of the vibration level of the ground, for example from acceleration measurements in certain frequency bands, and making the warning detection threshold or thresholds depend on this parameter.
However, a method of this kind would clearly require considerable computing power.
SUMMARY OF THE INVENTION
One object of the invention is to provide a simple detection method which allows for the vibration level of the ground but does not require a large amount of computing power.
According to one aspect of the invention there is provided a method for detecting vibrations generated by the running of a tire on a safety insert, wherein a vibration signal is measured within a given frequency band and the measurement thus made is processed to detect a mode of resonance generated by this running, the energy of the signal measured by a sensor in two frequency bands, one being narrow and the other being wide, which are centered on the same line of the mode of resonance, is determined, and the ratio of these two energies is compared with a given warning threshold.
The ratio between the two energies, one corresponding to a narrow band and the other to a wide band centered on the same frequency, is in fact independent of the ambient noise (in this case, the vibration level of the road).
The proposed method therefore makes it possible to operate independently of the ambient noise, in a particularly simple way.
This method is advantageously complemented by the following features, taken singly or in all their possible combinations:
to determine the energy of the signal in the two frequency bands, the detected signal is mixed with two periodic signals which are in phase quadrature and whose frequency corresponds to the frequency of the mode of resonance;
to determine the energy of the signal in the two frequency bands, the method determines the norm of a vector whose two coordinates correspond to the measured signal mixed with two periodic signals which are in phase quadrature and are integrated during a period equal to twice the reciprocal of the width of this frequency band;
the periodic signals are square-wave signals which are at a first level during one half-period and an opposite level during the following half-period;
the measured vibration signal is sampled and digitized, and is then multiplied with the square-wave signals in phase quadrature, whose frequency corresponds to the frequency of the mode of resonance, which have the value 1 during one half-period and −1 during the following half-period;
the norm determined is the sum of the absolute values of the coordinates.
According to a second aspect of the invention there is provided a system for detecting vibrations generated by the running of a tire on a safety insert, including a sensor for measuring a vibration signal in a given frequency band and means for processing the measurement from this sensor and detecting a mode of resonance generated by this running, wherein the processing means include means for implementing the processing of the previously cited method.
The processing means advantageously include an 8-bit microcontroller.
They may also include processing means including analog means.
They preferably include an application-specific integrated circuit.
REFERENCES:
patent: 4153095 (1979-05-01), Sarkissian
patent: 4157726 (1979-06-01), Brewer
patent: 4262724 (1981-04-01), Sarkissian
patent: 5186771 (1993-02-01), Carpentier et al.
patent: 5435636 (1995-07-01), Pender
patent: 5596141 (1997-01-01), Nishikawa et al.
patent: 6039099 (2000-03-01), Muhlhoff
patent: 0 421 065 (1991-04-01), None
patent: 0 695 653 (1996-07-01), None
patent: 0 844 111 A1 (1998-05-01), None
patent: 2762260 A1 (1998-10-01), None
patent: 5-65004 (1993-03-01), None
patent: 94 03338 (1994-02-01), None
French Search Report dated Jun. 23, 1999.
Breneol Laurent
Permuy Alfred
Miller Rose M.
Morgan & Finnegan , LLP
Valeo Electronique
Williams Hezron
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