The invention relates to a method and a device for determining the rotary, rotationally immobile or mobile, state of a vehicle wheel fitted with an active motion sensor suitable for delivering an oscillatory output signal during a rotation of said wheel. By way of examples of motion sensors to which the invention is specifically directed, mention may be made of impact sensors, magnetic sensors for detecting variations in the terrestrial magnetic field, termed “EMF” (Earth Magnetic Field) sensors, or tangential accelerometers.
More and more motor vehicles are possessing systems for monitoring and/or measuring parameters comprising sensors mounted on said vehicle.
By way of example relating to such systems, mention may be made of monitoring systems comprising sensors fitted to each of the wheels of vehicles, dedicated to measuring parameters, such as pressure and/or temperature of the tires mounted on these wheels, and intended to inform the driver of any abnormal variation in the measured parameter.
These monitoring systems conventionally comprise:
Moreover, usually, these monitoring systems comprise a displacement sensor suitable for being incorporated into each electronic housing and intended to provide information representative of the rotary, rotationally immobile or mobile, state of the wheel, and hence representative of the state of displacement of the vehicle (stationary or rolling).
Such information makes it possible, among other things, to institute two modes of operation of the monitoring systems determining an “awake” state and an “awoken” state of the electronic housings. These two modes of operation are differentiated in particular by the frequency of emission of the signals output by the electronic housings, and are adapted in such a way that this emission frequency is reduced when the electronic housings are in an “awake” state corresponding to the stationary state of the vehicle.
This management of the emission frequency of the signals emitted by the electronic housings leads, in fact, when the vehicle is stationary, to reducing, on the one hand, the consumption of the batteries energizing the onboard microprocessors, and on the other hand, the “pollution” of the environment surrounding the vehicle, and consequently, in particular, the risks of parasitic interference between close vehicles.
The first family of displacement sensors conventionally used for the aforesaid purposes consists of sensors of the accelerometer type whose output signal varies linearly as a function of the speed of rotation of the wheel.
An essential advantage of such sensors lies in the fact that they turn out to lead to low electrical energy consumption, a paramount quality in view of the necessary requirements, in particular regarding lifetime, which the batteries incorporated in the electronic housings must satisfy. Specifically, the response curve of these sensors as a function of the speed of rotation of the wheels being linear, the determination of the rotary state of a wheel entails simply fixing a rolling threshold, and activating the associated sensor instantly for a time of small duration, so as to achieve the comparison of the value of the signal delivered with the rolling threshold.
On the other hand, such sensors exhibit two major drawbacks residing, on the one hand, in their high retail cost, and on the other hand, in their relative fragility in view of the conditions of use.
The second family of displacement sensors conventionally used for the purpose of determining the rotary state of the wheels of vehicles consists of sensors whose output signal exhibits a waveform of variable amplitude, for example sinusoidal, and synchronous with the speed of rotation of the wheel. Such sensors, of the type of impact sensors, magnetic sensors for detecting variations in the terrestrial magnetic field, termed “EMF” sensors, tangential accelerometers, turn out to have a lower retail price and greater robustness relative to those of the sensors of the first family mentioned above.
On the other hand, the current solutions implemented to ensure the processing of the signal delivered by such sensors with a view to determining the rotary state of a wheel turn out to involve significant electrical energy consumption.
The first solution, of the analog type, which consists in using systems of amplifiers and of comparators, makes it necessary, in particular on account of problems of average value, hysteresis, etc., to energize these components for a duration corresponding to the time required for the wheel to perform a revolution at low speed (detection of the starting of the vehicle). Now, such a duration turns out to be very detrimental within the framework of the use of a button battery.
The second solution, of the digital type, which consists in using a conversion system comprising a filter and an analog/digital converter, demands a set-up time equivalent to that of the analog solution, hence likewise very detrimental within the framework of the application to which the invention is directed.
The present invention is directed at alleviating this electrical consumption drawback related to the use of sensors whose output signal exhibits a waveform of variable amplitude, and its main objective is to provide a solution leading to an appreciable reduction in the consumption generated by such sensors during a procedure for determining the rotary state of wheels of vehicles.
For this purpose, the invention is directed, firstly, at a method of determining the rotary, rotationally immobile or mobile, state of a vehicle wheel, according to which the wheel is fitted with an active motion sensor suitable for delivering an oscillatory output signal during a rotation of said wheel, and said output signal is analyzed instantly so as to deduce from its form the rotary state of the wheel.
According to the invention, each instant analysis of the output signal delivered by the motion sensor consists:
Firstly according to the invention, the expression “active sensor” is understood to define a sensor suitable for delivering a usable signal, that is to say, usually, a sensor comprising a measurement cell and means for amplifying the signal delivered by this measurement cell.
Moreover, usually, the equality “V1=V2” is understood to define, apart from perfect equality, an equality which builds in the conventional tolerances related to the various dispersions in the measurements.
The invention therefore lies in a solution of analog type consisting in storing reference values in a capacitor, then in comparing these reference values with values measured subsequently, so as to deduce directly from these comparisons the rotary state of the wheel, by applying the following principle related to the form of the signal delivered by the sensors:
Consequently, a procedure for determining the rotary state of a wheel entails simply:
Such a principle thus leads to an optimal decrease in the electrical energy consumption generated by sensors suitable for delivering an oscillatory output signal, during a procedure for determining the rotary state of vehicle wheels.
By way of comparative example, directed at two installations having equivalent objectives:
According to an advantageous embodiment of the invention, each instant analysis of the output signal delivered by the motion sensor consists in storing a reference value V1, and then in successively repeating step (B) n times, with n>1.
This arrangement makes it possible to reduce the energy consumption because it leads to a reduction in the number of measurements of the reference value. Moreover, it makes it possible to carry out different strategies based on different values of the variable “n”, with a view to guarding against parasitic measurements resulting for example from electromagnetic disturbances, etc.
The invention extends to a device for determining the rotary, rotationally immobile or mobile, state of a vehicle wheel fitted with an active motion sensor suitable for delivering an oscillatory output signal during a rotation of said wheel. According to the invention, this device comprises:
Moreover, advantageously, the electrical connection members comprise a first switch for controlling the electrical energizing of the motion sensor and of the breakers, and a second switch for controlling the electrical energizing of the comparison means.
This arrangement which provides for independent energizing of the comparison means makes it possible to optimize the overall electrical consumption.
Additionally, the comparison means comprise two comparators for detecting, respectively, variations (V1−V2)>0 and (V1−V2)<0.
Other characteristics, aims and advantages of the invention will emerge from the detailed description which follows with reference to the appended drawings which represent by way of nonlimiting example thereof a preferential embodiment. In these drawings:
a to 2d are graphs on which are represented the various control signals (
a to 3d are graphs representing a readout of measurements corresponding to a rotationally immobile state of a wheel,
and
The device according to the invention, represented by way of example in
This determining device comprises, furthermore, according to the invention:
Moreover, the comparison means are suitable for delivering, in a conventional manner, a signal Vdiag representative if either of an equality between the values of the voltages at the level of the first and second input (in the example Vdiag=0), or of a positive or negative difference between these two voltage values (in the example Vdiag=1). For this purpose, these comparison means 4 may consist of two comparators dedicated, respectively, one to the positive differences and the other to the negative differences.
Finally, the calculation unit 5 is linked to the breakers of the switch C1, and to the switches C2 and C3, in such a way as to control the changes of state of said breakers and switches.
According to the invention, this calculation unit is, additionally, programmed to institute a procedure for analyzing the signals delivered by the motion sensor Cp, consisting chronologically, with a predetermined polling period T, and such as represented in
It should be noted, moreover, as represented dashed in
These steps are also partially illustrated in
According to
According to
The device according to the invention therefore does not invoke the current source other than for brief periods (n times “ε”) during a polling period T, and therefore leads to optimized reduction of the consumption of current required for determining the rotary state of a vehicle wheel.
Number | Date | Country | Kind |
---|---|---|---|
06 10510 | Dec 2006 | FR | national |
Number | Name | Date | Kind |
---|---|---|---|
3503042 | Skinner | Mar 1970 | A |
6002249 | Futsuhara | Dec 1999 | A |
6549002 | Ito et al. | Apr 2003 | B2 |
6909278 | Hernitscheck et al. | Jun 2005 | B2 |
7382118 | Kosaka | Jun 2008 | B2 |
7432851 | Dulac | Oct 2008 | B2 |
20040095129 | Furlong | May 2004 | A1 |
20050068021 | Mager et al. | Mar 2005 | A1 |
20050206371 | Tsukamoto et al. | Sep 2005 | A1 |
20060043966 | Izawa et al. | Mar 2006 | A1 |
20060097717 | Tokuhara et al. | May 2006 | A1 |
20070247144 | Tokuhara et al. | Oct 2007 | A1 |
Number | Date | Country |
---|---|---|
2 186 979 | Aug 1987 | GB |
2 357 847 | Jul 2001 | GB |
Number | Date | Country | |
---|---|---|---|
20080133079 A1 | Jun 2008 | US |