EP0854443A1 - Method and device for avoiding fraud on a taximeter or a tachograph - Google Patents

Abstract

The fraud avoidance system addresses fraud perpetrated by connecting an electronic pulse generator at the input of the taximeter or tachygraph. The speed of the vehicle is estimated from its engine note, and this measure is compared with the speed input to the taximeter or tachygraph. A microphone (26) detects the sound of the engine, and this is selectively filtered (33) to determine whether it contains the range of frequencies that correspond to the speed measure applied to the input of the taximeter. If the two measures differ beyond a set tolerance over a set period, the microprocessor (11) blocks continued operation of the taximeter or tachygraph, and/or activates an alert signal.

Description

The present invention relates to a method, and to a device, for avoid fraud on a taximeter or on a tachograph.

A taximeter is, very generally, a device which has for its object indicate the price to be paid for a taxi trip, this price depending several parameters, including the distance traveled by the taxi, i.e. finally the number of wheel turns performed by this vehicle during the race.

The sensor used to measure this number of wheel turns is then the sensor normally associated with the vehicle dashboard and therefore connected the speedometer which indicates both the instantaneous speed of this vehicle and the mileage covered by it.

Modern vehicles are almost all equipped with a sensor electromagnetic or electronic of the number of wheel revolutions, called "sensor electronic ", which is provided at the gearbox, and which is equipped an output connector to which a cable is connected which collects and conveys the electrical impulses representative of the number of wheel turns to the speedometer fitted to the dashboard. The dashboard is then conventionally equipped with an auxiliary output, which is electrically connected in parallel on this cable, and to which we just plug the input corresponding of the taximeter: the pulses which are conveyed on this cable They therefore simultaneously supply the vehicle speedometer and the taximeter.

The situation is quite similar with regard to tachographs with which trucks must be equipped, and which, as we know, serve at least to record on a disc the speed of truck, kilometers traveled, and driver's working time. So he is generally planned to interpose, on the cable which connects the sensor to the counter of speed, an electronic adapter that is powered by the battery through a fuse and which delivers pulses, deducted from those delivered by the sensor, in direction of the tachograph to which this adapter is connected by a cable electric provided for this purpose.

These two types of measuring devices, taximeters or tachographs, are sealed by the Weights and Measures Services, but unfortunately this is not enough to avoid more and more fraud frequent.

One form of fraud seen frequently to date is connect, between the sensor and the taximeter or the tachograph, a small auxiliary pulse generator whose frequency is controlled by that of pulses from the sensor and which consequently delivers pulses whose frequency differs, in a defined ratio which is for example of the order of 1.2, from that of the pulses delivered by this sensor.

In the case of a taximeter for example, the frequency of the pulses applied to it is then chosen 1.2 times greater than that pulses delivered by the sensor, so that everything happens as if the taxi was traveling at a speed 1.2 times faster than its real speed, which affects the displayed price which is then 1.2 times higher than the price that the customer should actually pay.

In the case of a counter chronotachograph, the device of the fraudster is then set to deliver frequency pulses 1.2 times lower than that of the sensor pulses and, for the tachograph, everything is goes as if the truck was traveling at a speed 1.2 times slower than its speed real.

Of course, this ratio is mostly adjustable manually.

The invention therefore aims to prohibit any fraud based on a falsification of the speed information which is delivered to the taximeter or to the tachograph.

• on capte par un moyen autre que ce capteur tachymétrique une information variant avec la vitesse de rotation du moteur,
• on filtre selon un filtrage sélectif passe-bande ladite information variant avec la vitesse de rotation du moteur,
• on vérifie au moins par moments qu'il existe une relation entre ladite vitesse du véhicule et cette dernière information,
• et on déclenche une action anti-fraude si cette relation disparaít au moins pendant un temps prédéfini.

To this end, it relates to a method for avoiding fraud on a taximeter or on a tachograph, one associated with a taxi and the other with a truck both equipped with a tachymeter sensor which provides , to this taximeter or to this tachograph, electrical information, such as a pulse train, which is representative of the speed of the vehicle. According to the invention:

• information varying with the engine speed is captured by means other than this tachometer sensor,
• this information varying with the speed of rotation of the motor is filtered according to a selective bandpass filtering,
• at least at times it is checked that there is a relationship between said vehicle speed and this latter information,
• and an anti-fraud action is triggered if this relationship disappears at least for a predefined time.

Advantageously, this anti-fraud action consists in displaying a particular information and / or to prohibit the operation of the taximeter or tachograph.

Typically, it is considered that said relation, therefore between the speed of the vehicle and the engine speed, disappears if the signal level of output of said filtering is less than a minimum value.

Preferably, this process is characterized in that the anti-fraud test during which we verify at least at times that there is a relation between said vehicle speed and this information, is carried out several times at over a relatively long period of time compared to that of a single test, and in what we finally trigger this anti-fraud action if this relationship disappears at least for a predefined time over this period of time.

Typically, this anti-fraud test is carried out several times during a predefined and relatively long period of time compared to that of a single test, and in that we finally trigger this anti-fraud action only if, after this relatively long period of time, the number of tests that find fraud is greater than a predefined percentage of the total number of tests performed during this amount of time.

According to an embodiment, the information captured varying with the motor speed is the noise of the motor and the sensor of this last information is a microphonic element.

According to another embodiment, the information collected associated with the motor speed is an electrical signal whose frequency is proportional to the motor rotation speed. Advantageously, one can use as signal a signal existing on the vehicle and whose frequency is proportional to the speed engine rotation such as an ignition signal or a speed signal used by vehicle electronics.

• à partir de ladite information variant avec la vitesse de rotation du moteur, on détermine une première grandeur représentative de la vitesse de rotation du moteur,
• à partir de l'information électrique du capteur tachymétrique représentative de la vitesse du véhicule, on détermine une deuxième grandeur représentative de la vitesse du véhicule,
• on détermine et on enregistre la relation « de référence » existant entre ces première et deuxième grandeurs,

et en ce que l'on considère que ladite relation précitée, entre donc la vitesse du véhicule et la vitesse de rotation du moteur, disparaít si, pour ce rapport de boite donné et pour cette vitesse donnée, la relation qui est alors déterminée, pendant ledit temps prédéfini, entre lesdites première et deuxième grandeurs diffère au moins d'une valeur minimale de cette relation « de référence ».Advantageously, this method is characterized in that, in addition, for at least one of the gearbox ratios of the vehicle and for at least one given speed :

• on the basis of said information varying with the speed of rotation of the motor, a first quantity representative of the speed of rotation of the motor is determined,
• from the electrical information of the tachometer sensor representative of the vehicle speed, a second quantity representative of the vehicle speed is determined,
• the “reference” relation existing between these first and second quantities is determined and recorded,

and in that it is considered that said aforementioned relationship, between the vehicle speed and the engine rotation speed, disappears if, for this given gear ratio and for this given speed, the relationship which is then determined, during said predefined time, between said first and second quantities differs at least by a minimum value from this "reference" relation.

If the information collected associated with the engine speed is proportional to its speed of rotation, the two quantities are then proportional to the vehicle speed and the engine rotation speed and, for the same gear ratio, their ratio is constant.

The invention also relates to a device for implementing this process, the taximeter or tachograph being equipped with at least one unit calculation and command logic that receives and processes information from speed from the tachometer sensor, characterized in that it comprises additionally a microphonic engine noise sensor, this microphonic sensor being connected to a selective bandpass filter.

• comporte un filtre sélectif commandé dont l'entrée de commande de sa fréquence de calage est reliée à ladite unité logique,
• ladite unité logique est programmée pour calculer la fréquence des impulsions fournies par le capteur tachymétrique, et pour en déduire, par application d'un facteur représentatif des différents rapports de la boite de vitesses, la fréquence de calage qu'elle communique audit filtre sélectif,
• et ce filtre sélectif est associé à des moyens de discrimination de son signal de sortie, ces moyens fournissant à l'unité logique une information de concordance entre la fréquence de calage du filtre et ladite raie de fréquence moteur qui est mesurée par le capteur microphonique, cette information de concordance étant appliquée à ladite unité logique qui la considère alors comme une indication de l'état non fraudé du taximètre ou chronotachygraphe.

According to one embodiment, this device:

• includes a controlled selective filter whose control input for its setting frequency is connected to said logic unit,
• said logic unit is programmed to calculate the frequency of the pulses supplied by the tachometer sensor, and to deduce therefrom, by applying a factor representative of the different ratios of the gearbox, the stall frequency that it communicates to said selective filter,
• and this selective filter is associated with means for discriminating its output signal, these means supplying the logic unit with information of agreement between the setting frequency of the filter and said motor frequency line which is measured by the microphone sensor, this concordance information being applied to said logical unit which then considers it as an indication of the non-defrauded state of the taximeter or tachograph.

According to another embodiment, this filter is calibrated once for all on a frequency which corresponds to a motor rhythm, for example 3500 RPM approximately, which is found for all gearbox reports successive, and it is only when the rhythm of the motor passes by this frequency there that the microprocessor of the taximeter or tachograph performs a comparison between the speed of the vehicle which it then calculates according to the ratio of the gearbox currently engaged and the speed it deduces from the tachometer sensor information.

Preferably, said logical unit has memory factors multiplication which are each characteristic of a determined ratio of the box of speeds, so that it calculates said real speed given by the sensor microphone according to each gear ratio, and does not then considers the test thus carried out as being a test which does not detect any fraud only if one of these real speeds, corresponding to the various reports of box, results in said concordance information.

Advantageously, the said unit is determined and stored logic, several factors each related to a specific ratio of the box speeds, for the calculation by the logical unit of said real speed, by making drive the vehicle successively with the different ratios of the gearbox speeds and by determining each time the multiplication factor which allows to obtain said agreement of the two vehicle speed measurements.

In any case, the invention will be well understood, and all its advantages and different characteristics will emerge more clearly from the following description of two nonlimiting exemplary embodiments, with reference to the single figure attached which is a block diagram.

Referring to the single figure, the reference 1 designates the sensor tachometer which is mounted on the vehicle to operate the taximeter 2.

A so-called "electronic" tachometer sensor of a motor vehicle is a transducer that tests a rotating mechanical part of the vehicle, the speed of rotation of this mechanical member being representative of the number of wheel turns carried out by the vehicle, and the generally alternating electrical signal supplied by this transducer corresponding to electrical pulses representative of this number of wheel turns. Traditionally, this rotary mechanical organ is the more often one of the gears of the gearbox. However, vehicles nowadays are more and more often provided with a system of braking says "A.B.S. Which uses an electronic sensor for each wheel of the vehicle, and we then use one of these sensors to also operate the taximeter. Generally, these vehicles are equipped with disc brakes on the four wheels, and therefore each electronic sensor is a proximity which comes to test the presence of notches which are practiced for this purpose on the outer edge of the brake disc.

The sensor 1, which is therefore in practice placed either at the level of the box either at one of the vehicle's wheels, therefore delivers on its terminals output 3, 4 of the pulses representative of the number of wheel turns performed by the vehicle.

These pulses are applied on the one hand, by connections 5, 6 to taximeter 2, and on the other hand, by connections 7, 8 to the counting circuits of speed and total mileage which are part of the dashboard of the vehicle, as well as possibly to the “A.B.S.” braking circuits of this vehicle.

In taximeter 2, the pulses from sensor 1 are first of all applied to a separation and adaptation amplifier 9, the output signals are applied to one of the inputs 10 of a microprocessor 11 which constitutes the central logical unit, or "C.P.U. ", From this taximeter.

In particular, the microprocessor 11 receives, by pressures exerted on 12-15 pushbuttons placed on the front side of the taximeter, signals which are for example either price or operation of the taximeter, either setting signals from the taximeter, or code signals.

Anyway, when the microprocessor 11 receives pulses coming from sensor 1 on its input 10, it emits in response, on an output 16, pulses whose frequency is representative, taking into account the parameters previously introduced into the microprocessor 11 by the keyboard 12-15, the number of wheel revolutions performed, since the last start-up of the taximeter by means of the keyboard 12-15, by the vehicle.

These pulses are applied, as they should, to circuit 18 of counting and display of the price to pay.

A possible fraud consists in connecting in series on the line output speed sensor 1, for example between terminals 3, 4 and terminals 19, 20 bypassing connections 5 and 6, a pulse generator controlled which multiplies the rhythm of incoming pulses by a factor determined (manually adjustable if necessary), for example a factor 1, 2.

• on détecte, par capteur microphonique, le bruit du moteur du véhicule,
• on filtre ce bruit pour déterminer s'il comporte une raie de fréquence qui correspond à la fréquence moteur que l'on calcule en fonction, en particulier, de ladite information du capteur tachymétrique,
• et on déclenche une action anti-fraude si, pendant au moins un ou des temps prédéfinis, on ne constate pas l'existence d'une telle raie de fréquence.

According to the invention, and therefore to avoid this type of fraud based on falsification of the train of pulses emitted by the sensor 1:

• we detect, by microphonic sensor, the noise of the vehicle engine,
• this noise is filtered to determine whether it has a frequency line which corresponds to the motor frequency which is calculated as a function, in particular, of said information from the tachometer sensor,
• and an anti-fraud action is triggered if, for at least one or more predefined times, there is no existence of such a frequency line.

Typically, this anti-fraud action consists of displaying, for example on the front of the taximeter or tachograph, specific information, for example "Err", and / or to prohibit the operation of the taximeter or the tachograph.

According to the embodiment shown in the drawing, a pellet microphone 26 is stuck on the engine 27 of the vehicle or on one of the elements of its exhaust system. This tablet 26 is for example a tablet piezoelectric, ceramic, or electrostatic microphone. Preferably, this pad is a shock sensor, for example of the piezo-ceramic type.

If the vehicle engine is an internal combustion engine, or essence, and to a lesser extent but in a detectable way, if this engine is a combustion engine, or diesel engine, a noise peak will be emitted by this motor at each impulse communicated to a cylinder by an explosion or combustion of the mixture. Depending on the speed of the motor itself, the pad 26 will therefore generate a series of electrical pulses.

In reality, the microphone or shock detector 26 will detect, in addition repetitive shocks due to explosions of the mixture, a host of other noises repetitive occurring at other repetition frequencies.

The output signal 28, which therefore includes a whole spectrum of frequencies, from the microphone or shock detector 26, is applied to a filter digital 33, which is a bandpass filter, with steep sides, for example of order 4 at 7, whose bandwidth at 3 dB is for example of the order of 20% compared to its central setting frequency, that is to say corresponds substantially, in percentage with respect to this center frequency, to a percentage of tolerance ± 10%.

The microprocessor 11 receives, on its input 10, the pulses in from the tachometer sensor. It measures their period, deduces their frequency, and applies that frequency, after multiplying it by a factor of correction which is characteristic of one of the gearbox reports, on the control input 34 of the bandpass filter 33, thereby imposing this frequency corrected as central setting frequency.

Among the frequency spectrum it receives on its input 28, the filter bandpass 33 will only select, to the percentage due to its bandwidth, that, if it exists, the frequency line which corresponds to this central frequency of wedging.

Of course, you should only select this frequency if it actually corresponds to that of the motor, and therefore if consequently the signal in output 35 of filter 33 is of amplitude greater than a determined threshold.

For this reason, the output 35 of the filter 33 is applied to a Analog to Digital Converter 36, whose digital output 37 is applied to microprocessor 11. The latter deduces the amplitude of the signal in output of filter 35, and, if this amplitude is greater than a determined threshold, it validates the information. Otherwise, the microprocessor multiplies the pulse frequency of the tachometer sensor by a representative factor from another gearbox report, and reapply the result on connection 34, as a new setting frequency, and so on until you have tried all the factors respectively representative of each of the reports of this gearbox. If then no signal at output 35 of filter 33 has been validated is that there is a presumption of fraud, and the microprocessor consequently records this test as negative and therefore possibly characteristic of fraud, and therefore as falsification information.

The above factors are stored, upon installation and route of the taximeter or tachograph by an approved installer, in the microprocessor 11 to which it is connected by the bidirectional link 32, making drive the vehicle successively with the different ratios of the gearbox speeds and by determining each time the multiplication factor which corresponds to the concordant detection of a frequency line.

If falsification information is recorded by the microprocessor 11 continuously for a predefined minimum time, for example of a few minutes is that there is fraud and the microprocessor 11 then blocks the taximeter.

The latter then displays an error signal, and it cannot be reset. wheel by typing, on the keyboard 12-15, a secret code which is only known to accredited technicians.

Note that when we return to neutral at each change speed, a falsification signal is necessarily recorded, none of the said factors then does not correspond to the movement of the vehicle in neutral. The weather aforementioned minimum of for example a few minutes then makes it possible to get rid of this situation because it takes much less than several minutes to change gears.

However, it should be noted that the driver may in certain case decide to drive in freewheeling, therefore in neutral, for a good time more than a few minutes, which would lead to an unfortunate blocking command.

To remedy this, the invention provides, generally and whatever the implementation device used, to carry out a test anti-fraud - performed as described above - a large number of times during a predefined and relatively long period of time compared to that of a single test. For example, if each test lasts five minutes, this test is performed every five minutes and for a period of time that can range from several hours to example a day. We can also typically perform these successive tests on a time of one day and half a day, all this being done under microprocessor control 11.

At the end of this time, the microprocessor checks if the number of tests concluding that a fraud is greater than a determined percentage, by example of the order of 5%, of the total number of tests carried out during this period of time. If so, it issues a tampering signal that blocks the taximeter or tachograph. If not, no falsification signal is issued.

Using one of the previous examples, the time span is one day, and the driver is therefore allowed to coast for approximately one hour without blocking his taximeter or tachograph.

Similarly, when the vehicle is stationary and as a result no pulse is applied to the microprocessor 11 on its input 10, the microprocessor 11 does not take into account the falsification pulses which it then receives on its input 32.

According to another exemplary embodiment, we always refer to the figure single, but link 34 does not exist (or is not activated if it exists), and the filter 33 is not a controlled filter, or at least at its fixed setting frequency once for all.

According to this other embodiment, the bandpass filter 33 is calibrated on a central frequency which corresponds to a usual engine speed, typically around 3,500 rpm for example, which is found when the vehicle drives normally, in each of the different reports in its gearbox speeds. We then compare the speed of the vehicle, at this time where the speed motor goes to this stall frequency, that the microprocessor 11 of the taximeter or tachograph calculates according to the gearbox ratio then engaged, at that provided by the tachometer sensor, and the anti-fraud action is triggered above if these two speed measurements do not match, under the conditions of sufficient tolerance and repetition of the test that have been defined above.

In other words, the filter 33 is set once and for all on a frequency which corresponds to a usual motor rhythm, for example of 3,500 RPM approximately, which is found for all gearbox reports successive, and it is only when the rhythm of the motor passes by this frequency there that the microprocessor 11 of the taximeter or tachograph performs a comparison between the speed of the vehicle which it then calculates according to the ratio of the gearbox currently engaged and the speed it deduces from the tachometer sensor information 1.

It goes without saying that the invention is not limited to the two examples. which have just been described. This is how, alternatively, the information sensed associated with the engine speed is an electrical signal whose frequency is proportional to the engine speed. Advantageously, one can use as signal a signal existing on the vehicle and whose frequency is proportional to the engine speed such as an ignition signal or a speed signal used by the vehicle electronics.

Claims (13)

Method for avoiding fraud on a taximeter or on a tachograph, associated with a taxi or a truck, each equipped with a tachymeter sensor (1) which provides electrical information representative of the speed of the vehicle,
characterized in that: by means (26) other than this tachometer sensor (1), information is received varying with the speed of rotation of the engine, the information varying with the speed of rotation of the motor is filtered according to a selective bandpass filtering, it is checked at least at times that there is a relationship between said vehicle speed and this latter information, and an anti-fraud action is triggered if this relationship disappears at least for a predefined time. Method according to claim 1, characterized in that one considers that said relationship, therefore between the speed of the vehicle and the speed of motor rotation, disappears if the level of the output signal of said filtering is less than a minimum value. Method according to one of claims 1 or 2, characterized in that that the information captured varying with the engine speed is the engine noise and in that the sensor for this latter information is a microphonic element (26). Method according to one of claims 1 or 2, characterized in that that the information collected associated with the engine speed is an electrical signal the frequency of which is proportional to the speed of rotation of the motor. Method according to one of claims 1 to 4, characterized in that this anti-fraud action consists of displaying specific information and / or prohibit the operation of the taximeter or the tachograph. Method according to claim 1, characterized in that, in addition, for at least one of the gearbox ratios of the vehicle and for at least one given speed : from said information (26) varying with the speed of rotation of the motor, a first quantity representative of the speed of rotation of the motor is determined, from the electrical information of the tachometer sensor (1) representative of the vehicle speed, a second quantity representative of the vehicle speed is determined, the “reference” relation existing between these first and second quantities is determined and recorded, and in that it is considered that said aforementioned relationship, between the vehicle speed and the engine rotation speed, disappears if, for this given gear ratio and for this given speed, the relationship which is then determined, during said predefined time, between said first and second quantities differs at least by a minimum value from this "reference" relation. Method according to claim 1, characterized in that the anti-fraud test during which we verify at least at times that there is a relation between said vehicle speed and this information, is carried out several times at over a relatively long period of time compared to that of a single test, and in what we finally trigger this anti-fraud action if this relationship disappears at least for a predefined time over this period of time. Device for implementing the method according to one of claims 1 to 7, the taximeter or tachograph being equipped with minus a logic unit for calculation and control (11) which receives and processes the speed information from the tachometer sensor (1), characterized by which it further comprises a microphonic sensor (26) of the engine noise, this microphone sensor being connected to a selective bandpass filter (33). Device according to claim 8, characterized in that this filter is calibrated on usual engine speed. Device according to claim 8, characterized in that the setting frequency of this filter is controlled by said logic unit Device according to one of Claims 8 to 10, characterized in that that said microphone sensor (26) is fixed to the engine of the vehicle. Device according to one of Claims 8 to 10, characterized in that that said microphone sensor (26) is fixed to an element of the circuit exhaust. Device according to one of Claims 8 to 12, characterized in that that said microphone sensor (26) is a shock sensor, for example of the type piezo-ceramic.

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