Method and device for determining the rotary state of a vehicle wheel fitted with an active motion sensor suitable for delivering an oscillatory output signal during a rotation of said wheel
A method of determining the rotary, rotationally immobile or mobile, state of a vehicle wheel, according to which the signal delivered by an active motion sensor fitted to the wheel is analyzed instantly according to a procedure consists, firstly, at time t 1 , in connecting the motion sensor to an analog circuit including at least one capacitor and interposed between the motion sensor and a first input of an electronic comparison element, so as to store in the capacitor reference value V 1 representing the value of the signal at t 1 . Thereafter, the motion sensor is connected to a second input of the comparison element, to compare V 1 with a value V 2 representing the value of the signal at time t 2 , and to deliver a diagnostic signal representing either a rotationally immobile state of the wheel when V 1 =V 2 , or a rotationally mobile state of the wheel when V 1 ≠V 2.
1. 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 (Cp) 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, said determining method being characterized in that each instant analysis of the output signal delivered by the motion sensor (Cp) consists:
A) firstly, at an instant t 1 , in connecting the motion sensor (Cp) to an analog circuit (I 1 , 3 ), termed the storage circuit, comprising at least one capacitor ( 3 ), and interposed between said motion sensor and a first input of electronic comparison means ( 4 ), and in electrically energizing the motion sensor (Cp) in such a way as to store in the capacitor ( 3 ) a value V 1 , termed the reference value, representative of the value of the output signal delivered by the motion sensor (Cp) at the instant t 1 ,
then B), at at least one instant t 2 =t 1 +Δt, with Δt predetermined time span, in connecting the motion sensor (Cp) to a second input of the comparison means ( 4 ), and in electrically energizing said motion sensor and said comparison means, in such a way as to compare the reference value V 1 with a value V 2 representative of the value of the output signal delivered by the motion sensor (Cp) at the instant t 2 , and to deliver a diagnostic signal representative:
of a rotationally immobile state of the wheel when V 1 =V 2 ,
of a rotationally mobile state of the wheel when V 1 ≠V 2 .
2. The determining method as claimed in claim 1 , characterized in that each instant analysis of the output signal delivered by the motion sensor (Cp) consists in storing a reference value V 1 , and then in successively repeating step (B) n times, with n>1.
3. A device for determining the rotary, rotationally immobile or mobile, state of a vehicle wheel fitted with an active motion sensor (Cp) suitable for delivering an oscillatory output signal during a rotation of said wheel, characterized in that it comprises:
an analog circuit (I 1 , 3 ), termed the storage circuit, linked to the motion sensor (Cp), and comprising a breaker (I 1 ) and at least one capacitor ( 3 ),
electronic comparison means ( 4 ) comprising a first input linked to the storage circuit (I 1 , 3 ), and a second input linked to the motion sensor (Cp) with interposition, between the latter and said second input, of a breaker (I 2 ),
members (C 2 , C 3 ) for electrically connecting the motion sensor (Cp), the breakers (I 1 , I 2 ) and the comparison means ( 4 ) to a current source,
and a management unit ( 5 ) programmed to control instant analyses of the output signal delivered by the motion sensor (Cp), in the course of each of which:
firstly, at an instant t 1 , it instructs the closure of the breaker (I 1 ) of the storage circuit (I 1 , 3 ) and the electrical energizing of the motion sensor (Cp), in such a way as to store in the capacitor ( 3 ) a value V 1 , termed the reference value, representative of the value of the output signal delivered by the motion sensor (Cp) at the instant t 1 ,
then, at at least one instant t 2 =t 1 +Δt, with Δt predetermined time span, it instructs the closure of the breaker (I 2 ) interposed between the motion sensor (Cp) and the second input of the comparison means ( 4 ), and the electrical energizing of said motion sensor and of said comparison means, in such a way as to compare the reference value V 1 with a value V 2 representative of the value of the output signal delivered by the motion sensor (Cp) at the instant t 2 , and to obtain at the output of the comparison means ( 4 ) a diagnostic signal representative:
of a rotationally immobile state of the wheel when V 1 =V 2 ,
of a rotationally mobile state of the wheel when V 1 ≠V 2 .
4. The determining device as claimed in claim 3 , characterized in that the electrical connection members comprise a first switch (C 2 ) for controlling the electrical energizing of the motion sensor (Cp) and of the breakers (I 1 , I 2 ), and a second switch (C 3 ) for controlling the electrical energizing of the comparison means ( 4 ).
5. The determining device as claimed in claim 3 , characterized in that the comparison means ( 4 ) comprise two comparators for detecting, respectively, variations (V 1 −V 2 )>0 and (V 1 −V 2 )<0.
6. The determining device as claimed in claim 4 , characterized in that the comparison means ( 4 ) comprise two comparators for detecting, respectively, variations (V 1 −V 2 )>0 and (V 1 −V 2 )<0.