Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C23/00—Devices for measuring, signalling, controlling, or distributing tyre pressure or temperature, specially adapted for mounting on vehicles; Arrangement of tyre inflating devices on vehicles, e.g. of pumps or of tanks; Tyre cooling arrangements
  • B60C23/06—Signalling devices actuated by deformation of the tyre, e.g. tyre mounted deformation sensors or indirect determination of tyre deformation based on wheel speed, wheel-centre to ground distance or inclination of wheel axle

Definitions

• the present invention relates to a method for diagnosing the condition of tires of a front wheel and a rear wheel of a motor vehicle arranged on the same side of the vehicle and connected to the body thereof by means of suspensions. , the method comprising a step of acquiring vertical accelerations of said wheels in a reference system of the vehicle.
• the present invention also relates to a diagnostic system implementing such a method.
• the object of the present invention is to solve the aforementioned problem by proposing a method and a system capable of diagnosing tire anomalies, such as a treadwearing or treadwearing, and this even if it is inflated properly.
• the subject of the invention is a method for diagnosing the condition of tires of a front wheel and a rear wheel of a motor vehicle arranged on the same side of the vehicle and connected to the body of the vehicle. by means of suspensions, the method comprising a step of acquiring the vertical accelerations of said wheels in a reference system of the vehicle, characterized in that it comprises:
• the step of time registration comprises a step of calculating the intercorrelation of the accelerations acquired and a step of applying a delay corresponding to the maximum inter-correlation calculated at the acceleration gained from the front wheel;
• the step of estimating the coefficients of stiffness is capable of estimating them from single-wheel mechanical models of said wheels connected to the vehicle body by means of the suspensions;
• the step of estimating the stiffness coefficients is suitable for estimating them by relying on a discrete time modeling of the recalibrated accelerations of said wheels according to the relation:
• Avr (k) where k is the k th sampling instant, mrr and mra are the masses of the front and rear wheels respectively, Avr and Ava are the vertical accelerations of the rear and front wheels, respectively, and Zvr Zva are the altitudes of the rear wheel centers and before respectively in the reference system of the vehicle, Kpr and Kpa are the stiffness coefficients of the tires of the front and rear wheels respectively, and n is a time of registration corresponding to a time difference between the rear and front wheels undergoing the same portion of roadway ;
• the estimation step is capable of estimating said stiffness coefficients based on a discrete time modeling of the corrected accelerations of the front and rear wheels according to the relation:
• Ava (k) where k is the k th sampling instant, mrr and mra are the masses of the front and rear wheels respectively, Avr and Ava are the vertical accelerations of the rear and front wheels, respectively, and Zvr Zva are the altitudes of the rear wheel centers and before respectively in the reference system of the vehicle, Kpr and Kpa are the stiffness coefficients of the tires of the front and rear wheels respectively, and n is a time of registration corresponding to a time difference between the rear and front wheels undergoing the same portion of roadway ; the estimation step is capable of estimating said coefficients of stiffness from a mechanical bicycle model of the body assimilated to a mass connected to the front and rear wheels by means of the suspensions; the estimation step is capable of estimating said stiffness coefficients based on a discrete time modeling of the corrected accelerations of the front and rear wheels according to the relation:
• k is the k J'e e m e th sampling instant
• mrr and mra are the masses of the front and rear wheels respectively
• Avr and Ava are the vertical accelerations of the rear and front wheels, respectively
• Zvr Zva are height of the centers of the rear and front wheels respectively in a vehicle reference system
• Kpr and Kpa are the stiffness coefficients of the tires of the front and rear wheels respectively
• n is a time of registration corresponding to a time difference between the rear and front wheels undergoing the same portion of the roadway
• Kca and Kcr are the stiffness coefficients of the suspensions of the front and rear wheels respectively
• Zva and Zvr are the speeds of the centers of the front and rear wheels respectively
• the step of estimating stiffness coefficients of the tires is suitable for implementing a recursive algorithm of the least squares in real time
• the step of determining the state of the tires comprises, for each tire, a step of comparing its determined stiffness coefficient with a predetermined threshold value and a step of diagnosing the state of the tire, which determines that the it is defective if its determined stiffness coefficient is greater than the threshold value;
• the invention relates to a system for diagnosing the condition of tires of a front wheel and a rear wheel of a motor vehicle arranged on the same side of the vehicle and connected to the body thereof by means of suspensions. , the system comprising means for acquiring vertical accelerations of said wheels in a reference system of the vehicle, characterized in that it is suitable for implementing a method as defined above.
• the invention also relates to a system adapted to implement the aforementioned method.
• FIG. 1 is a diagram illustrating the calculation hypothesis used by the system according to the invention.
• FIG. 2 is a schematic view of a first embodiment of the system according to the invention
• - Figure 3 is a schematic view of a mechanical model of a motor vehicle wheel connected to the body thereof by means of a suspension;
• FIG. 4 is a schematic view of a second mechanical model of a front and rear wheel of a motor vehicle arranged on the same side of the vehicle and connected to the body thereof by means of suspension;
• FIG. 5 is a flowchart of the method according to the invention implemented by the system of FIG. 3.
• FIG. 1 illustrates the progress of a motor vehicle on a roadway between two instants t and t + ⁇ t.
• the front and rear wheels arranged on the same side of the vehicle undergo with a time shift ⁇ t depending on the speed V and the wheelbase d of the vehicle, the same road profile.
• This phenomenon can be modeled according to the relation:
• Zsa (t) Zsr (t + ⁇ t) (1)
• t is the time
• ⁇ t is the time between the passage of the rear wheel on a point of the road, the passage of the front wheel on the same point
• Zsa is the altitude of the ground at the level of the front wheel
• Zsr is the altitude of the ground at the level of the rear wheel.
• FIG. 2 schematically illustrates, under the general reference 10, a first embodiment of the system according to the invention for diagnosing the condition of tires of a front wheel and a rear wheel of a vehicle.
• This system 10 comprises an accelerometer 12, 14 fitted to each of these wheels to measure the acceleration Ava, Avr at its center along a vertical axis in a reference system of the vehicle.
• This accelerometer 12, 14 is for example a single-axis accelerometer or tri-axis mounted in the center of the wheel. It is adapted to provide, via a wired link 16, a signal representative of the vertical acceleration Avr, Ava in the center of the wheel.
• Means 20 are provided in the system 10 for receiving the signals emitted by the accelerometers 12, 14 and extracting from these signals the accelerations Avr, Ava measured by them.
• the means 20 are connected to a bandpass filter 22 adapted to process the accelerations Avr, Ava of the wheels delivered by the means 20 by applying a band-pass filtering.
• This filtering is implemented in a frequency range in which the power of the modes of the front and rear wheels is concentrated. This frequency range corresponds to the rolling resistance range and is for example substantially equal to the range [8; 20] Hz.
• the band-pass filter 22 is furthermore connected to an analog-to-digital converter 24, for example a 0-order sample-and-hold device, adapted to digitize according to a predetermined sampling period Te, for example between approximately 0.001 seconds and 0, 02 second, filtered accelerations and thus output numerical accelerations Avr (k), Ava (k) of the front and rear wheels, where k represents the k ' th sampling time.
• an analog-to-digital converter 24 for example a 0-order sample-and-hold device, adapted to digitize according to a predetermined sampling period Te, for example between approximately 0.001 seconds and 0, 02 second, filtered accelerations and thus output numerical accelerations Avr (k), Ava (k) of the front and rear wheels, where k represents the k ' th sampling time.
• sampling of the accelerations may be, for example, applied previously to a bandpass filtering performed in discrete time.
• the system 10 also comprises means 26 of time registration connected to the converter 24 and adapted to time shift the digital acceleration Ava (k) of the front wheel on the digital acceleration Avr (k) of the rear wheel for outputted accelerations Avr (k), Ava (kn) of the front and rear wheels, corresponding to the same altitude of the ground to apply the hypothesis according to the relationship (1) described above.
• These adjustment means 26 comprise, for this purpose, calculation means 28 adapted to estimate the digital intercorrelation IC (N) of the accelerations Avr (k), Ava (k) delivered by the converter 24 according to the relation:
• IC (N) ⁇ Avr (k) xAva (N -k) (2)
• the calculation means 28 are adapted to implement an estimator of this cross-correlation, as is known per se in the field of signal processing.
• the retiming means 26 also comprise, connected to the calculation means 28, means 30 for determining the maximum of the intercorrelation IC (N) and the sampling instant n corresponding to this maximum. This instant n corresponds to the time shift nxTe between the front and rear wheels undergoing the same portion of roadway.
• Time-shift means 32 are connected to the means 30 and to the converter 24, and are suitable for applying a delay of n samples to the acceleration Ava (k) of the front wheel and thus to deliver an acceleration Ava (kn) set back temporally on the acceleration Avr (k) of the rear wheel.
• the system 10 also comprises means 34 for estimating the coefficients of pneumatic stiffness Kpr, Kpa of the front and rear wheels. These means 34 are connected to the converter 24 to receive the accelerations Avr (k), Ava (k) of the rear and front wheels and the means 26 of registration to receive the acceleration Ava (k-n) recaled from the front wheel.
• the means 34 are based on the mechanical model of Figure 3 to model the dynamic behavior of each of the front and rear wheels.
• a single-wheel mechanical model of a wheel R of a four-wheeled motor vehicle connected to the body C of the latter by means of a suspension Su, the wheel R being in contact with soil So.
• the body C is modeled by a mass brought back to the wheel occupying me, on a vertical axis OZ of the vehicle of a reference system thereof, an altitude Z c with respect to a reference level NRef, for example the altitude So soil at the front wheel when starting the vehicle.
• the suspension Su is modeled by a stiffness coefficient spring Kc in parallel with a damper damping coefficient Rc.
• the wheel R is modeled by a mass Mr occupying on the axis OZ an altitude Zr with respect to the reference level Nref.
• the tire of the latter is modeled by a stiffness coefficient spring Kp in contact with the ground So which occupies on the axis OZ an altitude Zs relative to the reference level Nref.
• K (k + 1) gi '1 S (k) X ⁇ (k + l) ( ⁇ 2 (k) + GT 1 A (k + l) s (k) ⁇ (k + 1)) "1 (6)
• S (k + I) GJ "1 (S (k) -K (k + 1) A (k + 1) S (k)) (7)
• the means 34 are suitable for calculating the altitudes Zvr (k), Zva (kn) of the centers of the rear wheels and before each sampling instant as a function of the vertical accelerations Avr (k) and Ava (kn), by example by performing a double integration thereof after filtering between 8 Hz and 20 Hz.
• Another example of a calculation of the altitude of a wheel according to its vertical acceleration is described in the French patent application FR 2,858,267 in the name of the applicant.
• the estimation means 34 are adapted to implement a real-time least-squares recursive algorithm based on the relation (4) in a manner analogous to that previously described.
• the means 34 are suitable for implementing an inversion or deconvolution algorithm based on the relation (3) or (4) for estimating the stiffness coefficients.
• the estimation means 34 are thus adapted to deliver at each sampling instant estimated values Kpa (k) and Kpr (k) of the pneumatic stiffness coefficients of the front and rear wheels.
• the system 10 finally comprises means 36 for diagnosing the operating state of the accelerometers 12, 14 and the condition of the tires of the front and rear wheels, connected to the estimation means 34 and to the converter 24.
• the means 36 comprise means 38 for diagnosing the operating state of the accelerometers adapted to test the coherence of the accelerations Avr (k) and Ava (k) with each other over a predetermined period of time, for example between 5 minutes and 10 minutes. minutes. As it has been described previously, it is known that the vertical accelerations of the front and rear wheels are consistent because the wheels undergo with a time shift the same portion of roadway.
• the means 38 are adapted to calculate the frequency spectra of these accelerations by means of a fast Fourier transform accelerations included in the predetermined period of time and to compare the calculated spectra. If these differ by more than a predetermined value, for example in quadratic error, then the accelerometers are diagnosed as defective by the means 38.
• the means 38 are further adapted to predict the vertical acceleration of the rear wheel as a function of the vertical acceleration of the front wheel delivered by the converter 24 and the stiffness coefficients of the front and rear wheels calculated by the means 34, to from relation (3) by varying the sampling instant n.
• the means 38 are also adapted to test the coherence between this predicted acceleration of the rear wheel and the acceleration of the front wheel delivered by the converter 24, for example in the manner previously described for the accelerations delivered by the converter 24. If, in addition, the coherence between these accelerations is not proven, then the means 38 diagnose a malfunction of the accelerometers 12, 14.
• the means 36 also comprise means 40 for determining the state of the tires connected to the estimating means 34.
• the means 40 are able to compare each of the stiffness coefficients Kpr (k), Kpa (k) estimated at a predetermined threshold value K threshold and to determine that the corresponding tire is defective if the stiffness coefficient Kpr (k), Kpa ( k) estimated has at least N values greater than the threshold value Kthreshold, where N is a predetermined integer number for example equal to 100.
• the means 36 are connected to means 42 for delivering to the driver of the vehicle the results of the diagnosis. realized by the means 36, for example, indicator lights arranged on the dashboard of the vehicle and / or a buzzer of the defective state of the tires or the defective state of the accelerometers.
• Figure 4 is a schematic view of a mechanical model generally referred to as the "bicycle model". This type of model allows in particular to take into account the case of active suspensions equipping the vehicle and applies to front and rear wheels arranged on the same side of the vehicle.
• Zvr (k) mrr where Zva and Zvr are the first derivatives of the altitudes of the centers of the front and rear wheels respectively, that is to say the speeds of vertical displacement of these.
• the estimation means 34 are then adapted to implement a recursive algorithm of the least squares in real time based on the relation (11).
• a (k) f - Ava (k - n) - (Zva (k - n) - Zvr (k)) - Zva (k - n) - - Zvr (k) 1 (13) mrr mrr mnr mrr J
• the altitudes Zvr (k), Zva (k -n) of the centers of the wheels with respect to the reference level and their first derivatives Zvr (k), Zva (kn) are calculated at each sampling step in a manner similar to the first embodiment, for example by integrating the corresponding vertical accelerations or in a manner described in the French patent application FR 2 858 267.
• the application of the recursive least squares algorithm in real time based on the bicycle model makes it possible to simultaneously estimate the pneumatic stiffness coefficients Kpa, Kpr as well as the stiffness coefficients Ra and Rr of the suspensions. .
• FIG. 5 is a flowchart of the method according to the invention implemented by the system of FIG. 2.
• a first step 100 consists in initializing at zero a front wheel tire anomaly counter and an anomaly counter of FIG. pneumatic rear wheel.
• a next acquisition step 102 the vertical accelerations Ava, Avr of the front and rear wheels are measured, filtered and sampled.
• a step 104 of resetting the acceleration Ava of the front wheel on the acceleration Avr of the rear wheel is then triggered.
• This step 104 comprises a step 106 for calculating the inter-correlation of the numerical accelerations Ava (k), Avr (k) of the front and rear wheels followed by a step 108 for calculating the sampling instant n of the maximum of 1 calculated intercorrelation.
• the numerical acceleration Ava (k) of the front wheel is then reset to 110 of the instant n on the numerical acceleration Avr (k) of the rear wheel.
• Kpa (k), Kpr (k) are calculated at 112 according to the digital accelerations recaled by implementing a least-square recursive algorithm in real time based on the single-wheel model or the bicycle model, as previously described.
• a diagnostic step 114 of the state of the accelerometers 12, 14 is then triggered, as previously described.
• a test is then performed at 116 to see if at least one of them is defective. If the result of this test is negative, the step 116 loop on the step 102. Otherwise, an audible and / or visual alarm is triggered at 118 to warn the driver of the vehicle of a failure of the accelerometers.
• a step 120 for determining the condition of the tires is also triggered.
• This step 120 comprises a step 122 of comparing each coefficient of stiffness Kpa (k), Kpr (k) estimated at 112 to the threshold value K threshold.
• a test is performed at 124 to find out if the coefficient of stiffness has at least one value greater than the threshold value Kthreshold. If the result of this test is positive, the anomaly counter corresponding to the coefficient of stiffness is incremented in 126 by the number of values of it greater than the threshold value.
• a test is then implemented at 128 to know if the value of this counter is greater than N. If this is the case, the corresponding tire is diagnosed at 130 as defective and step 118 triggered to warn the driver.
• step 128 loops on step 102 of acquisition.
• step 124 loops on step 102 acquisition.
• the system and method according to the invention diagnose a defective state of a tire and this even if it is properly inflated.
• the system and the method according to the invention make it possible to detect the presence of under-inflation or wear of the tire band and of a break-off thereof.

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• Vehicle Body Suspensions (AREA)

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• 2005
  • 2005-09-16 FR FR0509504A patent/FR2890898B1/fr not_active Expired - Fee Related
• 2006
  • 2006-09-11 US US12/067,172 patent/US20090118894A1/en not_active Abandoned
  • 2006-09-11 EP EP06808306A patent/EP1924450A2/de not_active Withdrawn
  • 2006-09-11 WO PCT/FR2006/050868 patent/WO2007031678A2/fr not_active Ceased

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