WO1988005196A1

WO1988005196A1 - Method for storing run data of a vehicule in the memory of an electronic tachograph and apparatus for carrying out the method

Info

Publication number: WO1988005196A1
Application number: PCT/HU1987/000061
Authority: WO
Inventors: Levente SZÉKELY; Gábor RÁCZ; Károlyné OTTA
Original assignee: Szekely Levente; Racz Gabor; Otta Karolyne
Priority date: 1986-12-29
Filing date: 1987-12-29
Publication date: 1988-07-14
Also published as: EP0352260A1; AU1084588A; AU613891B2; CA1301292C; HUT49226A; US4987541A; HU206415B; EP0352260B1; DE3787975D1

Abstract

A method for storing run data of a vehicule in the memory of an electronic tachograph, in which data representing the velocity and distance taken by the vehicle are read in subsequent cells of an accident memory (31) which has a substantially smaller storage capacity than a data memory (32) storing the run data in a first rate substantially higher than a sampling rate associated with a prescribed accuracy, and the maximum and minimum values of the velocity and the value of said distance are determined during periods following each other with the sampling rate, and at least said minimum and maximum values of the velocity data and the distance value are entered in the data memory (32) in each sampling period, and the content of the accident memory (31) is shifted forward with said first rate and the content of the data memory (32) is shifted forward with said sampling rate, thus the accident memory (31) stores detailed data of the always last road section which can assist both in investigating the detailed run data of an accident and in generating the extreme values ot the velocity for efficient long-term storage in the data memory (32).

Description

METHOD FOR STORING RUN DATA OF A VEHICLE IN THE MEMORY OF AN ELECTRONIC TACHOGRAPH AND APPARATUS FOR CARRYING OUT THE METHOD

The invention relates to a method for storing run data of a vehicle in the memory of an electronic tachograph and displaying these data with a predetermined resolution, in which the movement of the vehicle is sensed by means of a road sensor, digital distance and velocity data are provided from the sensed signals proportional to the advance of the vehicle and the momentary velocity, respectively and these digital data are read in subsequent cells of a data memory of the tachograph in predetermined regular periods. The invention relates also to an apparatus for carrying out the method which comprises an input block with inputs coupled to pulse lines of a road sensor and to static signal line, the input block comprises signal forming circuits, a pulse generator and a frequency meter with first input connected to the pulse generator and second input connected to the signal forming circuits associated with the pulse lines, a microcomputer connected to the output of the input block and a memory unit coupled to the microcomputer.

In our Hungarian patent published on Augus,t 28, 1986 and having the application number 4841/84 entitled "electronic tachograph" the conditions for the reliable implementation of an electronic tachograph were discussed including the protection of the memory against disturbances in the power supply and against any possible erroneous processor operation. The patent dealt also with the reading of the stored data by means of light emitting diodes and with the questions of identification. These aspects are important for the implementation of the tachograph function, but it has also a similarly high significance how the large amount of information should be stored to provide an optimum utilization of the memory. The sparing with the available memo ry ca p a c i ty f orms no t only a n econom i c qu es t i on , b u t th e amount of information that can be stored defines the length of operation of the tachograph without the risk of data losses and without the need for reading out the stored data. Nowadays the storage of data from 1 or two weeks of running time forms a general requirement.

Although a number of sampling and data compression methods are known, the analysis thereof has shown that most of them are connected with problems when applied for the realization of a tachograph function.

In a known way of compressed data storage only changes in the sensed variable are recorded together with the associated time data. This method enables a compressed data recording if the sensed process is sufficiently slow. In vehicles, however, this condition cannot be met, the speed of the vehicle can vary within wide limits therefore such a method cannot be used.

The generally accepted sampling technique should take into account the frequent changes in the velocity, therefore the true reproduction of the velocity-time curve would require a very frequent sampling and the storage of the sampled data. The storage of such an amount of information would be rather redundant. In case of using a delta code modulation each sampling would be associated with 1 bit of information only, which means a decreased amount of information to be stored. From these information the changes in the vehicle speed can be reconstructed. The problem lies here also in the required high number of sampling points, since the speed of the vehicle can be changed in 10 to 20 seconds even up to 60 km/hours, therefore the signal reproduction would require a sampling in every 1 or 2 seconds. In view of the full operational period of about two weeks such a sampling would still require a considerably high storage capacity.

In addition to the appropriate data storage a further problem is connected with the reading out of this information. In a number of conventional data recording equipment the data carrier which stores the information (casette or memory) is removed and transported to a central location for reading out the stored information. If the data carrier is injured during the transport, the important information can get lost. A further problem arises form the possibility that the single data carrier can be manipulated if they can be accessed by unauthorized persons.

A further requirement can be imposed on an apparatus which aims at implementing the tachograph function electronically, and this lies in the exact reconstruction of the run data just preceding an accident. The term 'exact' intends to cover the reconstruction of the velocity-time curve with an accuracy being one or two orders of magnitude higher than the accuracy of of data readable from the tachograph chart. The object of the invention is to provide a method and an apparatus for carrying out the same, which can record information which is at least equivalent with the one stored in conventional tachographs using paper disc but which has an economic utilization of the available memory and which is capable of implementing at least certain ones of the aforementioned additional requirements.

The invention is based on the recogition that the thickness of the lines in the charts of tachographs using paper discs limit the resolution in time to about half minute, therefore it is sufficient to store data in such a rate, but in each half minute period it is important to know the extreme values of the velocity.

According to the invention data representing the velocity and distance taken by the vehicle are read in subsequent cells of an accident memory which has a substantially smaller storage capacity than a data memory storing the run data in a first rate substantially higher than a sampling rate associated with the prescribed accuracy, and the maximum and minimum values of the velocity and the value of said distance are determined during periods following each other with the sampling rate, and at least said minimum and maximum values of the velocity data and the distance value are entered in the data memory in each sampling period, and the content of the accident memory is shifted forward with said first rate and the content of the data memory is shifted forward with said sampling rate.

In a preferable embodiment the reading in the accident memory occurs when a predetermined distance e.g. 2 meters has been taken by the vehicle, and as many data are stored in the accident memory as required for the reconstruction of an accident e.g. which correspond to a distance of about 500 meters.

A substantial increase can be reached in the resolution if the extreme values of the velocity are stored in the data memory in the order as they actually follow each other in the associated period.

The resolution can further be increased by using an additional delta code modulation. In a further preferable embodiment for the retrieval of the stored data at a central location the content of the memories but at least that of the data memory is copied in a data storage means in such a way that the content of the memories remains unchanged during the copying operation. The apparatus for carrying out the method can be characterized in that the memory unit thereof comprises an accident memory with address lines and data bus coupled to a memory address controller associated with a microcomputer, a data memory with data bus and address bus coupled to a data compressor and memory controller belonging to the microcomputer and the microcomputer comprises a clock generator and an input data register.

In a preferable embodiment the memory unit comprises an assistant memory with data bus and address bus coupled to a delta code modulator which is implemented In the microcomputer. The high sampling rate in the accident memory enables the determination of the extreme values of the velocity in the correct order during the half minute intervals, which facilitates the effective and dense data storage and the reconstruction of any accident. The invention will now be described in connection with preferable embodiments thereof, In which reference will be made to the accompanying drawings. In the drawing:

Fig. 1 shows the functional block diagram of the apparatus according to the invention, Fig. 2 is a velocity-time curve with enlarged time scale, Fig. 3 is a diagram corresponding to Fig. 2 with a compressed time scale, Fig. 4 is a diagram illustrating the generation of a higher resolution, and Fig. 5 is a diagram illustrating the delta code modulation.

Figure 1. shows the functional block diagram of the apparatus according to the invention which comprises three main parts such as input block 12, microcomputer 20 and memory unit 30. Input block 12 receives through pulse line 10 pulses generated by a road sensor in response to actual movement of the vehicle in which the apparatus is arranged and further pulses generated by a fuel consumption sensor. In addition to these pulse signals certain status data are also required for the correct run recording (such data are e.g. the position of the ignition key, the on- or off-state of the brake lamps and in certain cases identification data of the driver). The input block 12 receives these status data through static signal lines 11. Pulse lines 10 are coupled through signal forming circuits 13 to gate inputs of frequency meters 15. Frequency meters 15 have pulse inputs receiving constant frequency output pulses from pulse generator 14. The frequency meters 15 pass the clock pulses of the pulse generator 14 to their outputs during the time periods defined between consecutive pulses appearing at their respective gating inputs, therefore the number of the pulses at the output of the frequency meters corresponds to the time elapsed between respective gating pulses. The number of the pulse-sensing channels is equal to the number of the quantities which should be measured, e.g. in the exemplary embodiment one channel is associated with the measurement of the distance covered by the vehicle (and with the velocity determined from the distance), while another channel is used for measuring the fuel consumption. The static signal lines 11 are coupled to inputs of further signal forming circuits 16.

The microcomputer 20 can be implemented by a general purpose microprocessor and Fig. 1 shows only those of its functional blocks which are required for understanding the operation. Data register 21 is used to receive output signals of the input block 21. The microcomputer 20 comprises a clock generator 24 which delivers output pulses e.g. in 30 second intervals, an accident memory address controller 22, a data compressor and memory controller 23 and a delta code modulator 25.

The memory unit 30 consists of three parts i.e. accident memory 31, data memory 32 and assistant memory 33. This latter memory is required only if higher accuracy requirements are imposed on the data storage.

Address lines 34 of the accident memory 31 are connected to the output of the accident memory address controller 22 and data lines of the accident memory 31 are coupled to data bus of the microcomputer 20. Predetermined outputs of the data register 21 are connected through line 29 to data lines of the accident memory 31 and a further output 28 thereof is connected to the input of the delta code modulator 25. The output of the clock generator 24 is coupled through line 26 to the delta code modulator 25 and through line 27 to the data compressor and memory controller 23.

Data lines of the accident memory 31 are coupled through bus 35 to the input of the data compressor and memory controller 23 and the output of this latter is coupled to data bus 36 and address bus 37 of the data memory 32. Data bus 38 and address bus 39 of the assistant memory 33 are coupled to the delta code modulator 25.

The operation of the apparatus according to the invention will be explained in connection with the time diagrams of Figs. 2 to 5.

The most general task lies in the implementation of the function of a tachograph. This requires a data storage which comprises sufficient amount of information on the basis of which a tachograph chart can be plotted. The line thickness of recorders used generally in tachographs renders the distinction of events longer than 30 seconds possible, i.e. the resolution in time is not better than 30 seconds. In accordance therewith the clock generator 24 delivers clock pulses in 30 second intervals.

When the vehicle moves, the road sensor generates respective gating pulses after every 2 meters of movement. The data regis ter 21 will store the number of pulses of the pulse generator 14 occurring in the time required for the completion of the distance of 2 meters. The microcomputer 20 calculates the velocity of the vehicle for each path sections of 2 meters and wr i te s th e se ve l o c i t y da t a i n succe s s i ve c e l l s o f the a cc i den t memory 31 having consecutive addresses. Seven bits are generally sufficient for the storage of the velocity data, whereby the velocity range of 0 to 128 km/hour can be recorded with an accuracy of 1 km/h. The accident memory 31 comprises 256 cells and it stores the data associated with the last 512 meters of the route with a high accuracy. When all cells of the accident memory 31 have been filled, the accident memory address controller 22 directs the next new data to be written in the first cell and it shifts the content of the memory 31 forward by one cell. The oldest data comprised in the last cell of the memory will then be lost.

A data storage with such a high resolution is not necessary for the long term run recording, and for the reconstruction of an accident the retrieval of the data associated with the last few hundred meters is sufficient and the capacity of the accident memory 31 has been chosen accordingly.

For the long term storage of the run data the efficient utilization of the available capacity of the data memory 32 and the necessary run reconstruction require and optimum amount of data compression. In each 30 second period the microcomputer 20 knows the velocity data determined in 2 meter road sections. From this information the data compressor and memory controller 23 determines for each period the maximum and minimum speed and the distance made by the vehicle and it writes these data to the cell at the always actual first available address of the data memory 32, then shifts further the whole content of the memory by one step. It can be appreciated that based on the data stored in the accident memory 31, the microcomputer 20 knows the order of the maximum and minimum speed in every 30 second period. In Fig. 2 the actual values of the velocity has been plotted for the periods i-1, i, i+1 and i+2, as well as the minimum and maximum and average values of the velocity which can be calcu Lated from the distance data. In the period i+2 the hatched area below the curve corresponds to the distance taken in that period, and this distance is known. If in the respective periods only the two extreme velocity values are stored, then the velocity run chart will have a linear form as shown in Fig. 3 which can be plotted as a round chart by means of an appropriate chart plotter. The line thickness corresponds to half minutes, thus the resolution corresponds to those of conventional tachographs. It is preferable if in each half minute period 4 bytes of information is stored. In a preferable embodiment a four bytes Lang cell of the data memory 32 looks like as follows:

F M M M M M M M

F m m m m m m m

K G₁ G₂ G₃ s s s s s s s s s s s s

in the table F designates the number of pulses of the fuel consumption meter in deciliter units, i.e. the maximum measurable fuel consumption is 8 dl/min, M designates the maximum velocity in km/hour units, in which the available 7 bits allow the recording of at most 128 km/h , m designates the minimum velocity values, also in 7 bits, K designates the state of the ignition key and bits G₁ to G₃ are freely definable constants, s designates the distance in meters.

If the maximum value of 128 km/h is not sufficient, then the data can be recorded in 2 km/h units instead of 1 km/h units, whereby a velocity range of 0 to 256 km/h will be storable, however, the resolution will be half as high. The widening of the range at the expense of the resolution (accuracy) can be increased by similar methods also in case of known paper disc tachograph systems.

The correct time data can be recorded in a separate memory cell, e.g. once in a week, whereafter the number of each cell will be equal to the number of the half-minute steps.

In a preferable embodiment of the invention three times higher resolution can be obtained without increasing the number of data to be stored. This can be accomplished if the extreme velocity values stored in the first two bytes be not written in a predetermined order any more (i.e. that the first byte comprise the maximum, while the second one the minimum values), but the order thereof should correspond to their actual order in the associated period. If in a particular period the minimum occurred first, then this should be stored in the first byte and thereafter the maximum and vica versa. In the possession of the detailed data in each period such a storage can be carried out without any difficulties.

If the extreme speed values are stored in a correct order, then more accurate run information can be obtained from these data if further information characteristic to certain properties of the vehicle (such as maximum acceleration and deceleration) are also taken into account (of course, by means of the microcomputer). This method will be illustrated in Fig. 4.

The beginning of an interval in the x-th period that corresponds to the maximum or minimum speed overlaps with the end of the previous (x-1)-th period in a predetermined range. As a first step of iteration it will be supposed that the curve that defines the actual variation of the speed falls in the middle of this overlapping range, then the x-th period will be divided in three equal parts which are all 10 seconds long. The first part will be associated with the first extreme value (which is the minimum in the exemplary case) and the second part will be associated with the other extremity (being the maximum in the example of Fig. 4) and the curve will be terminated at the middle of the overlap section between the x-th and (x+1)-th period.

This kind of approximation might have two limitations. The first one lies in that the area defined below the so-obtained curve is not equal to the actual distance taken during this period, while the other one lies in that the changes in speed are higher than allowed by the maximum acceleration or deceleration. In the latter case the location of the points 1 and 2 will be changed along the time axis until the limitations concerning the ma x imum ac c e l e r a t i o n and dece l er a t i on v a l u e s ar e f u l f i l l ed . T he area below the curve can be changed by shifting the point 3 along the vertical (speed) axis. If such changes still prove to be insufficient, then horizontal sections will be inserted at the minimum or maximum values depending on the fact whether the calculated distance is smaller or higher than the actually measured distance value. Practical experiences have shown, that already after 3 or 4 steps of iteration a curve was obtained which was very close to the actual one. The time scale of the chart should be changed according to the three-times higher accuracy, because if a full circle chart corresponds to e.g. one day, then the mechanical thickness of the lines of the recorder does not allow such a high resolution. The correct time scale in that case is 8 hours/full circle.

If still higher resolution is required, then the resolution in time can be increased to 4 seconds by means of delta code modulation in the expense of storing one more byte In every half minutes, which results in an increase of 25% in memory storage capacity. This embodiment requires the use of the optional units shown in Fig. 1, i.e. the delta code modulator 25 and the assistant memory 33. The essence of this method lies in that the analogue velocity-time curve will be approximated by linear sections characterized by a predetermined acceleration or deceleration. If at the end moment of such a section the actual speed is higher than the approximated speed, then a bit with value 1 is stored, while if it is lower, then a bit 0 is stored. Fig. 5 shows an example for a predictive delta code modulation, in which the above principle is modified by the fact that If in several consecutive sections identical bit values are found, then the steepness of the approximating linear curve is increased (doubled) or decreased (halved).

In Fig. 5 the linear approximating function of eight intervals of a 30 second long period was plotted by full line and the actual curve was shown with dashed line. The content of the memory cell corresponding to the Intervals a, b ,c ,d ,e , f ,g and h can be seen below the associated intervals. Following the interval a the actual curve is still above the approximating function, therefore the approximation continues with a double steepness. At the end of the interval c the condition changes which persists until the end of the interval f, therefore the approximation is gradually decreased whereafter it is increased and decreased. In spite of the fact that the delta code modulation can express the changes only within a predetermined error range, the approximation will be very accurate, since the data memory 32 will continue comprising the extreme speed values and the distance value, thus these values can also be taken into account at the iteration. On the basis of Fig. 5, however, the operation of the delta code modulator has become clear. The evaluation of the stored data takes place in central data processing locations by means of appropriate data processing equipment. The present invention is directed therefore primarily to the delivery and storage of data which can be reconstructed with sufficient accuracy.

A further characteristic feature of the apparatus according to the invention lies in the way how the stored data can be transferred to data processing centres. The fact that the whole content of the memory unit 30 will be shifted forward by one step in each sampling cycle results in the continuous refreshment of the stored information which can correspond e.g. to the data collected in the last two weeks. When the memory is read out its content need not and should not be cleared, and this readout step is carried out by copying the content of the memory unit 30 in an appropriate outer memory coupled to the apparatus. This copy operation can be performed by connecting the data and address lines of the outer memory to corresponding data and address buses of the microcomputer 20, and reading the data in the outer memory.

This way of information collection enables the safe sto r a ge of run data in the original memory unit which will not be lost by the reading out of the information. The data can be checked even after their readout and the information retrieval does not interfere with the internal operation of the apparatus which makes any manipulation with the data impossible.

Claims

1. Method for storing run data of a vehicle in the memory of an electronic tachograph and displaying these data with a predetermined resolution, comprising the steps of sensing the movement of the vehicle by means of a road sensor, providing digital distance and velocity data from signals of the sensing step proportional tα the advance of the vehicle and the momentary velocity, respectively, reading said digital data in subsequent cells of data memory (32) of the tachograph in predetermined regular periods corresponding to said resolution, characterized in that said data are read in subsequent cells of an accident memory (31) which has a substantially smaller storage capacity than said data memory (32) in a first rate substantially higher than a sampling rate associated with said predetermined regular periods , determining the maximum and minimum values o f the veloc itv and the value of said distance during each of said periods, and In said step of reading in the data memory (32) at least said minimum and maximum values of the velocity data and the distance value are entered, shifting forward the content of the accident memory (31) with said first rate and shifting forward the con- tent of the data memory (32) with said sampling rate.

2. The method as claimed in claim 1, characterized in that the reading in said accident memory (31) occurs when a predetermined distance e.g. 2 meters has been taken by the vehicle, and storing as many data in the accident memory (31) as required for the reconstruction of an accident e.g. which are associated with a distance of about 500 meters.

3. The method as claimed in claim 1, characterized in that said extreme values of the velocity are stored in the data memory (32) in the order as they actually followed each other in the associated period.

4. The method as claimed In claim 1, characterized in that each of said periods is divided in a predetermined number e.g. eight intervals and further comprises the step of approximating the velocity in that period by linear functions according to a delta modulation or to a predictive delta modulation and storing a bit value in each interval which depends on whether the approximated function is higher or lower than the velocity, and reading these bit values in each of said periods in a cell of an assistant memory (33) associated with the cell of the data memory (32) storing the data of this period.

5. The method as claimed in claim 1, characterized in that storing in each of said periods an information of four bytes with eight bits in each byte in the data memory (32), a few number of these bits are associated with sampled digital value of the fuel consumption of the vehicle during the associated period and with predetermined other condition data of the vehicle.

6. The method as claimed in claim 1, characterized in that said stored data are retrieved by copying the content of said memories in a data storage means in such a way that the content of said memories remains unchanged during the copying operation.

7. Apparatus for carrying out the method as claimed in any of claims. 1 to 6, comprising an input block (12) having inputs coupled to pulse lines (10) of a road sensor and to static sign a l l i ne ( 11 ) , the inp u t bl ock ( 12 ) compr i s es s i gn a l f ormi ng circuits (13, 16), a pulse generator (14) and a frequency meter (15) with first input connected to the pulse generator (14) and second input connected to the signal forming circuits (13) associated with the pulse lines (10), a microcomputer (20) connected to the output of the input block (12) and a memory unit (30) coupled to the microcomputer (20), characterized in that the memory unit (30) comprises an accident memory (31) with address lines (34) and data bus (35) coupled to memory address controller (22) associated with the microcomputer (20), data memory (32) with data bus (36) and address bus (37) coupled to a data compressor and memory controller (23) belonging to the microcomputer (20) and the microcomputer (20) comprises a clock generator (24) and an input data register (21).

8. The apparatus as claimed in claim 7, characterized in that the memory unit (30) comprises an assistant memory (33) with data bus (38) and address bus (39) coupled to a delta code modulator (25) realized in the microcomputer (20).