FR2757663A1 - METHOD AND DEVICE FOR PREVENTING FRAUD ON A TAXIMETER OR CHRONOTACHYGRAPHE - Google Patents

Abstract

Method and device for preventing fraud, on a taximeter or on a tachograph, by connecting an auxiliary generator between the tachometer sensor (1) and the taximeter (2) or tachograph. According to the invention, the noise of the engine (27) of the vehicle is detected by a microphone sensor (26), this noise is filtered by a selective filter (33) to determine whether it comprises a frequency line which corresponds to the motor frequency that is calculated (11) as a function of the information from the tachometer sensor (1), and an anti-fraud action is triggered if, for at least one or more predefined times, the existence of such a frequency line.

Description

METHOD AND DEVICE FOR PREVENTING FRAUD ON A

TAXIMETER OR CHRONOTACHYGRAPHE

  The present invention relates to a method and a device for preventing tampering with a taximeter or a tachograph. A taximeter is, in a very general way, an apparatus which is intended to indicate the price to be paid for a race carried out by the taxi, this price depending

  several parameters, including the distance traveled by the taxi, ie

  finally say the number of wheel turns made by this vehicle during the

race.

  The sensor used to measure this number of wheel revolutions is then the sensor normally associated with the vehicle dashboard and therefore connected to the meter which indicates both the instantaneous speed of this vehicle and the

mileage traveled by it.

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

  simultaneously the vehicle speedometer and the taximeter.

  The situation is quite similar with respect to the tachographs which trucks must be equipped with, and which, as we know, are used to at least record on a disc the speed of the truck, the kilometers traveled, and the working time of the truck. driver. It is then generally planned to insert, on the cable connecting the sensor to the speedometer, an electronic adapter which is fed by the battery through a fuse and which delivers pulses, deduced from those delivered by the sensor, in the direction of the tachograph to which this adapter is connected by a cable

provided for this purpose.

  These two types of measuring devices, taximeters or tachographs, are sealed by the Weights and Measures Services, but this

  Unfortunately, this is not enough to avoid more and more frequent frauds.

  A form of fraud frequently observed to date consists in connecting, between the sensor and the taximeter or the tachograph, a small auxiliary pulse generator whose frequency is controlled by that of the pulses of the sensor and which consequently delivers pulses whose frequency differs, in a defined ratio which is for example of the order of 1.2, of

  that of the pulses delivered by this sensor.

  As for a taximeter for example, the frequency of the pulses that are actually applied to it is then chosen to be 1.2 times greater than that of the pulses delivered by the sensor, so that everything happens as if the taxi were driving at a speed of 1.2 times faster than its actual speed, which has an impact on the posted price which is then 1.2 times higher than the price the customer should

actually pay.

  In the case of a tachograph, on the other hand, the fraudster's apparatus is then set to deliver pulses with a frequency 1.2 times lower than that of the sensor pulses and, for the tachograph, everything happens.

  passes as if the truck was traveling at a speed 1.2 times lower than its actual speed.

  Of course, this report is mostly manually adjustable. The invention therefore aims to prohibit any fraud based on a falsification of the speed information that is issued to the taximeter or tachograph. It relates for this purpose to a method to avoid fraud on a taximeter or on a tachograph, associated with one to a taxi and the other to a 3 <0 truck equipped with both a sensor tachometer which provides, at this taximeter or tachograph, electrical information, such as a pulse train, which is representative of the speed of the vehicle. According to the invention: it is sensed by means other than this tachometric sensor information varying with the speed of rotation of the engine, s a. it is verified at least at times that there is a relationship between said vehicle speed and this last information, λ, and an anti-fraud action is triggered if this relation disappears at least

for a predefined time.

  Advantageously, this anti-fraud action consists in displaying a 1) particular information and / or prohibiting the operation of the taximeter or tachograph.

  Preferably, this method is characterized in that the anti-

  Fraud during which it is verified at least at times that there is a relationship between said vehicle speed and this information, is performed several times over a relatively long period of time compared to that of a single test, and in that this anti-fraud action is finally triggered if this relationship disappears

  at least for a predefined time on this lapse of time.

  Typically, this anti-fraud test is performed several times over a predefined period of time and relatively long compared to that of a single test, and in that this anti-fraud action is finally triggered only if, at the end of this relatively long period of time, the number of tests that conclude to a fraud is greater than a predefined percentage of the total number of tests performed during that time.

time lapse.

  According to one embodiment, the sensed information varying with the engine speed is the noise of the engine and the sensor of the latter information

is a microphone element.

  According to another embodiment, the sensed information associated with the engine speed is an electrical signal whose frequency is proportional to the rotational speed of the engine. Advantageously, it is possible to use as a signal an existing signal on the vehicle whose frequency is proportional to the speed of rotation of the motor such as an ignition signal or a speed signal used by

vehicle electronics.

  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: from said information varying with the speed of rotation of the engine, determining a first magnitude representative of the speed of rotation of the engine, A from the electrical information of the tachometric sensor representative of the speed of the vehicle, determining a second magnitude representative of the speed of the vehicle, * determining and recording the "reference" relation existing between these first and second quantities, and in that it is considered that said relation, between the speed of the vehicle and the speed of rotation of the engine, disappears if, for this given gear ratio and for this given speed, the relation which is then determined, during said predefined time, between said first and second quantities differs in

  less than a minimum value of this "reference" relationship.

  If the sensed information associated with the speed of the motor is proportional to its speed of rotation, the two quantities are then proportional to the speed of the vehicle and the speed of rotation of the engine and,

  for a gearbox ratio, their ratio is constant.

  Preferably, the filter is filtered according to band pass selective filtering.

  information varying with the speed of rotation of the engine.

  Typically then, it is considered that said relationship, between the vehicle speed and the engine rotation speed, disappears if the level of the

  output signal of said filtering is less than a minimum value.

  The invention also relates to a device for implementing this method, the taximeter or tachograph being equipped with at least one logic unit for calculation and control that receives and processes the speed information from the tachometer sensor. , characterized in that it further comprises a microphonic sensor of the engine noise, this microphonic sensor being

  connected to a selective bandpass filter.

  According to one embodiment, this device: 5. comprises a controlled selective filter whose control input of its calibration frequency is connected to said logic unit, said logic unit is programmed to calculate the frequency of the pulses provided by the sensor tachometer, and to deduce from it, by applying a factor representative of the different ratios of the gearbox, the calibration frequency that it communicates to said selective filter, * and this selective filter is associated with discrimination means of its output signal, these means providing the logic unit with information of concordance between the filter stall frequency and said motor frequency line which is measured by the microphonic sensor, this concordance information being applied to said logical unit which considers it then as an indication of the non-defrauded status of the taximeter or tachograph. According to another embodiment, this filter is set once and for all on a frequency which corresponds to a motor speed, for example of approximately 3500 revolutions / minute, which is found for all the successive gear ratios, and it is only when the rate of the motor passes through this frequency that the microprocessor of the taximeter or tachograph makes a comparison between the speed of the vehicle which it then calculates according to the ratio of gearbox presently engaged and the speed that he deduces from

  tachometer sensor information.

  Preferably, said logic unit has in memory multiplying factors which are each characteristic of a given gearbox ratio, so that it calculates said actual speed given by the microphone sensor according to each of the ratios of the gearbox. of speeds, and then considers the test thus realized as being a test which does not detect fraud if one of these real speeds, corresponding to the various reports of box,

  causes a said concordance information.

  Advantageously, several factors each relating to a given ratio of the gearbox, for calculation by the logical unit of said actual speed, are determined and memorized in said logical unit, by rolling the vehicle successively with the various ratios of the gearbox and determining each time the multiplication factor which makes it possible to obtain said agreement

  two vehicle speed measurements.

  In any case, the invention will be well understood, and all its advantages and

  different characteristics will stand out better in the following description of

  two nonlimiting embodiments, with reference to the single appended figure

which is a synoptic diagram.

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

taximeter 2.

  A so-called "electronic" tachometer sensor for a motor vehicle is a transducer that tests a rotary mechanical member of the vehicle, the rotational speed of this mechanical member being representative of the number of wheel revolutions made by the vehicle, and the generally alternative electrical signal provided. by this transducer corresponding to electrical pulses representative of this number of wheel revolutions. Traditionally, this rotary mechanical member is most often one of the gears of the gearbox. However, modern vehicles are now more and more often equipped with an "ABS" braking system that uses an electronic sensor for each wheel of the vehicle, and one of these sensors is then used to operate the taximeter. . Generally, these vehicles are equipped with disc brakes on all four wheels, and consequently each electronic sensor is a proximity sensor that tests the presence of notches that are made 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 gearbox or at one of the wheels of the vehicle, thus delivers on its output terminals 3, 4 pulses representative of the number of wheel revolutions effected.

by the vehicle.

  These pulses are applied on the one hand, by the connections 5, 6 to the taximeter 2, and on the other hand, by the connections 7, 8 to the counting circuits of speed and totaling kilometer which are part of the vehicle dashboard. as well as possibly to the "ABS" braking systems of this vehicle. In the taximeter 2, the pulses coming from the sensor I are first applied to a separation and matching amplifier 9, whose output signals are applied to one of the inputs 10 of a microprocessor 11.

  which constitutes the central logical unit, or "C.P.U.", of this taximeter.

  In particular, the microprocessor 11 receives, by pressure exerted on pushbuttons 12-15 placed on the front face of the taximeter, control signals which are, for example, tariff or operating signals of the taximeter, or signals of parameterization of the taximeter, ie

code.

  Nevertheless, when the microprocessor 11 receives pulses from the sensor I on its input 10, it transmits in response, on an output 16, pulses whose frequency is representative, given the

  parameters previously introduced into the microprocessor 1 1 by the keyboard 12-

  15, of the number of wheel turns effected since the last start of the

  taximeter by means of the keyboard 12-15, by the vehicle.

  These pulses are applied, as appropriate, to circuit 18 of

  counting and posting the price to pay.

  A possible fraud consists in connecting in series on the tachometric output line of the sensor 1, for example between the terminals 3, 4 and the terminals 19, 20 of the branching connections 5 and 6, a controlled pulse generator which multiplies the rate incoming pulses by a factor

  determined (manually adjustable if necessary), for example a factor 1, 2.

  According to the invention, and therefore to avoid this type of fraud based on falsification of the pulse train emitted by the sensor 1: A detects, by microphonic sensor, the noise of the vehicle engine, this noise is filtered to determine if it comprises a frequency line which corresponds to the motor frequency which is calculated in function, in particular, of said tachometer sensor information, on and an anti-fraud action is triggered if, during at least one or more times predefined, we do not see the existence of such a line

frequency.

  Typically, this anti-fraud action consists of displaying, for example on the front face of the taximeter or tachograph, a particular piece of information, for example "Err", and / or to prohibit the operation of the taximeter or tachograph. According to the embodiment shown in the drawing, a microphonic patch 26 is bonded to the motor 27 of the vehicle or to one of the elements of its exhaust circuit. This pellet 26 is for example a piezoelectric, ceramic or electrostatic microphonic pellet. Preferably,

  this pellet is a shock sensor, for example of the piezoceramic type.

  If the engine of the vehicle is an internal combustion engine, or gasoline engine, and, to a lesser extent but in a manner still detectable, if this engine is a combustion engine, or diesel engine, a sound peak will be emitted by this motor at each pulse imparted to a cylinder by an explosion or combustion of the mixture. Depending on the speed of the motor itself, the tablet

  26 will therefore generate a series of electrical pulses.

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

  repetitive occurring at other repetition frequencies.

  The output signal 28, which thus comprises a whole spectrum of frequencies, of the microphone or shock detector 26, is applied to a digital filter 33, which is a bandpass filter, with steep sides, for example of order 4 to 7, whose 3 dB bandwidth is for example of the order of 20% with respect to its central calibration frequency, that is to say substantially corresponds, in percentage with respect to this central frequency, to a percentage of tolerance

I0 of + 10%.

  The microprocessor 11 receives, on its input 10, the pulses coming from the tachometer sensor. It measures their period, deduces their frequency, and applies this frequency, after having multiplied by a correction factor which is characteristic of one of the reports of the gearbox, on the control input 34 of the pass filter. band 33, thus imposing on him this

  frequency corrected as centering frequency.

  Of the spectrum of frequencies that it receives on its input 28, the band-pass filter 33 will only select, at the percentage due to its bandwidth, that, if it exists, the frequency line which corresponds to this central frequency of

rigging.

  Of course, it is necessary to select this frequency only if it corresponds effectively to that of the motor, and therefore if consequently the signal in

  output 35 of the filter 33 is of amplitude greater than a determined threshold.

  For this reason, the output 35 of the filter 33 is applied to an Analog / Digital Converter 36, whose digitized output 37 is applied to the microprocessor 11. The latter deduces the amplitude of the signal at the output of the filter 35, and if this amplitude is greater than a determined threshold, it validates the information. In the opposite case, the microprocessor multiplies the frequency of the pulses of the tachometric sensor by a factor representative of another gear ratio, and again applies the result obtained on the connection 34, as a new frequency. calibration, and so on until all the factors respectively representative of each report of this gearbox have been tried. If then no signal at the output of the filter 33 has been validated, it is presumed fraud, and the microprocessor accordingly records this test as negative and therefore possibly characteristic of a

  fraud, and therefore as falsification information.

  The aforementioned factors are stored in the memory, at the installation and start-up of the taximeter or tachograph by an authorized installer, in the microprocessor 11 to which it is connected by the bidirectional link 32, by rolling the vehicle successively with the different gear ratios. the gearbox and 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 a few minutes, it is that there is fraud and the microprocessor 11 then blocks the taximeter. The latter then displays an error signal, and it can not be re-wheeled by typing, on the keyboard 12-15, a secret code which is only known to

accredited technicians.

  Note that when returning to neutral at each change of speed, a falsification signal is necessarily recorded, none of said factors then corresponds to the movement of the vehicle in neutral. The aforementioned minimum time of for example a few minutes then makes it possible to overcome

  this situation, because it takes much less than several minutes to change gears.

  It should be noted, however, that the driver may in some cases decide to coast without stopping for a period well over a few minutes, which would then lead to an unfortunate

blocking control.

  To remedy this, the invention provides, in a general manner and 3o regardless of the implementation device used, to perform an Il-fraud test - performed as described above - a large number of times during

  predefined and relatively long time compared to that of a single test.

  For example, if each test lasts five minutes, this test is carried out every five minutes and for a period of time ranging from several hours to for example a day. These successive tests can also typically be carried out over a period of one day and a half day, all of which is done under

microprocessor control 11.

  At the end of this period of time, the microprocessor checks whether the number of tests concluding to a fraud is greater than a certain percentage, for example of the order of 5%, of the total number of tests carried out during this lapse of time. If this is the case, it emits a forgery signal which blocks the taximeter or

  tachograph. If this is not the case, no falsification signal is issued.

  By taking one of the previous examples, the lapse of time is one day, and therefore the driver is allowed to coast for about

  one hour without blocking his taximeter or tachograph.

  Similarly, when the vehicle is stationary and therefore no pulse is applied to the microprocessor 11 on its input 10, the microprocessor 11 does not take into account the falsification pulses that it

then receives on his entry 32.

  According to another embodiment, reference is still made to the single figure, but the link 34 does not exist (or is not activated if it exists), and the filter 33 is not a controlled filter, or the less than its calibration frequency set a

once and for all.

  According to this other embodiment, the bandpass filter 33 is set to a central frequency which corresponds to a standard engine speed, typically of the order of 3500 revolutions per minute, for example, which is found when the vehicle rolls normally, in each of the different gearbox ratios. The speed of the vehicle is then compared, at this moment when the engine speed passes at this calibration frequency, that the microprocessor 11 of the taximeter or tachograph calculates according to the box ratio then engaged, to that provided by the tachometer sensor, and the aforementioned anti-fraud action is triggered if these two speed measurements do not match, under the conditions of

  tolerance and sufficient repetition of the test as defined above.

  In other words, the filter 33 is wedged once and for all on a frequency which corresponds to a usual motor speed, for example of approximately 3500 revolutions / minute, which is found for all the successive gear ratios. , and it is only when the rate of the motor passes through this frequency that the microprocessor 11 of the taximeter or tachograph makes a comparison between the speed of the vehicle which it then calculates according to the gear ratio o presently engaged and the speed that he deduces from

  tachometer sensor information 1.

  It goes without saying that the invention is not limited to the two embodiments which have just been described. Thus, in a variant, the sensed information associated with the speed of the motor is an electrical signal whose frequency is proportional to the speed of rotation of the motor. Advantageously, it is possible to use as a signal an existing signal on the vehicle whose frequency is proportional to the speed of rotation of the motor such as an ignition signal or

  a speed signal used by the vehicle electronics.

Claims (12)

  1. A method for preventing fraud on a taximeter or a tachograph, associated with a taxi or a truck, both equipped with a tachometer sensor (1) which provides electrical information representative of the speed of the vehicle, characterized in that by means (26) other than this tachometric sensor (1), information varying with the rotational speed of the engine is detected, 10. it is verified at least occasionally that there is a relationship between said vehicle speed and this last information, * and an anti-fraud action is triggered if this relationship disappears at less for a predefined time.   2. Method according to claim 1, characterized in that the sensed information varying with the speed of the engine is the noise of the engine and in   what the sensor of this last piece of information is a microphonic element (26).   3. Method according to claim 1, characterized in that the sensed information associated with the engine speed is an electrical signal whose   frequency is proportional to the rotational speed of the motor.   4. Method according to one of claims I to 3, characterized in that   this anti-fraud action consists of displaying particular information and / or   prohibit the operation of the taximeter or tachograph.   5. Method according to claim 1, characterized in that in addition, for at least one of the gear ratios of the vehicle and for at least a given speed: * from said information (26) varying with the the rotational speed of the motor, a first quantity representative of the rotational speed of the motor is determined, ò from the electrical information of the tachometric sensor (1) representative of the speed of the vehicle, a second quantity representative of the speed is determined; of the vehicle, ò is determined and records the "reference" relationship existing between these first and second quantities, and in that it is considered that said relationship, between the speed of the vehicle and the speed of rotation of the motor, disappears if, for this given box ratio and for this given speed, the relation which is then determined, during said predefined time, between said first and second quantities of iffer   10 less than a minimum value of this "reference" relationship.   6. Method according to claim 1, characterized in that the anti-test   Fraud during which it is verified at least at times that there is a relationship between said vehicle speed and this information, is performed several times over a relatively long period of time compared to that of a single test, and in that this anti-fraud action is finally triggered if this relationship disappears   at least for a predefined time on this lapse of time.   7. Method according to one of claims I to 6, characterized in that   the band-pass selective filtering is filtered, said information varying with the motor rotation speed.   8. Method according to claim 7, characterized in that it is considered that said relationship, between the vehicle speed and the engine rotation speed, disappears if the level of the output signal of said filtering is less than a minimum value.   9. Device for implementing the method according to one of the   1 to 8, the taximeter or the tachograph being equipped with at least   a calculation and control logic unit (11) which receives and processes the speed information from the tachometer sensor (1), characterized in that it further comprises a microphone sensor (26) of the engine noise,   microphonic sensor being connected to a selective bandpass filter (33).   10. Device according to claim 9, characterized in that this filter   is stalled on a standard engine speed.   He. Device according to claim 9, characterized in that the clamping frequency of this filter is controlled by said logic unit   ; 12. Device according to one of claims 9 to 11, characterized in that   said microphone sensor (26) is attached to the vehicle engine.   13. Device according to one of claims 9 to 11, characterized in that   said microphone sensor (26) is attached to an element of the exhaust circuit.   14. Device according to one of claims 9 to 13, characterized in that   that said microphonic sensor (26) is a shock sensor, for example of the piezo-ceramic type.