AN APPARATUS FOR RECORDING THE SPEED OF A VEHICLE

Abstract: In a speed recording apparatus for vehicles, speed values are preliminarly stored in an apparatus installed in the vehicle comprising a pulse generator (2) coupled to a speed sensor (1), a microprocessor (4) and an electronic memory (14), and a visual speed reconstruction is provided by reading out data from the memory (14) to an external recording instrument (32). The pulses generated with separations corresponding to a given road length act as interrupt signals for a counting operation performed in the microprocessor (4) so that the count or a maximum value for it or, a speed value derived therefrom is transferred for each interrupt signal to the memory (14). The memory (14) comprises a number of series-arranged memory blocks (15-18) having cyclically addressed memory locations arranged as "circular lists" and divided into sections having an equal number of memory locations and with a marking of the first memory location in each section. At the addressing of a marked memory location, a single function value is generated on the basis of the data content of all the memory locations in the actual section, said function value being transferred to a memory location in the next memory block. The power supply to microprocessor (4) and the memory (14) may be switched over from the battery (29) of the vehicle to internal voltage sources (10, 28) at decline of battery (29) as well as at stops of the vehicle.

Description: An apparatus for recording the speed of a vehicle. The invention relates to an apparatus for continu¬ ously recording the speed of a vehicle over a predeter¬ mined, road travelling length, comprising a pulse genera- tor adapted for connection with a velocity sensor in the vehicle for generating control pulses with a pulse sepa¬ ration corresponding to a given road length, means for producing measuring values on the basis of said control pulses and internally generated clock indications and an electronic memory for storing said measuring values with a data depletion dependent on the travelled road length as well as read-out means associated with the memory for connection with a recording instrument for producing a visual speed reconstruction by reading-out the stored data. Hitherto, the application of such apparatuses as speed recorders for use in the reconstruction of the speed course of a vehicle over a given road length pre¬ ceding a certain reading time, for example in case of traffic accidents, has mainly been limited to greater vehicles like trucks and busses. In prior art devices having built-in, at least partly mechanically operating curve-drawing instruments, the apparatuses have been relatively complicated and, in addition, sensitive to mechanical influences during operation, so that they have often been rather inefficient with respect to the solution of the task of producing a speed reconstruction • in connection with an accident. In more recent devices of the kind mentioned, such as described, for instance, in DE-A-29 29 168 and 31 23 879, the problems caused by mechanically operating parts have been remedied through a fully electronic data stor¬ age in the apparatus installed in the vehicle itself in combination with a separate external recording instru- ment, by means of which a visual speed reconstruction ' may be produced through connection to the electronic apparatus in the vehicle and reading out the data re¬ corded therein. However, the devices known from the above mention¬ ed publications suffer from the disadvantages that they have either been made relatively complicated with con¬ siderable demands on storage capacity of the electronic memory due to a desire of recording other operational parame ' tres than the speed, for instance a clock indica¬ tion for each record, number of revolutions and consump- tion of fuel, or offer only the possibility of speed reconstruction for a very limited road length due to the memory design itself. In the apparatus described in DE-A-29 29 168, there is stored in an electronic memory having three series- connected FIFO-shift registers for each road length pulse from a road length sensor a clock indication in the first location in the first shift register. For each pulse, the clock indication is advanced in the first shift register, and at the transfer to the next and the following shift registers, a data depletion is accomp¬ lished in that said shift registers are clocked with lower frequences than the shift frequency for the first shift register, for instance the half or one fifth of this frequency, whereby only every second or every fifth record, respectively, will be transferred from one shift register to the next. In practice, with this memory de¬ sign the speed reconstruction will be limited to a road length of some hundred meters. In the apparatus according to DE-A-31 23 879, a buffer-controlled CMOS-memory is used as the electronic memory and in addition to speed, data is stored for se¬ veral operational parametres with a clock indication associated with each record. The data concentration in the memory is accomplished in this case by a discontinu- ous storage, whereby new data are only recorded if they -have either changed to a predetermined extent, since the OMPI preceding record, or a predetermined maximum road length between two records has been exceeded. The microproces¬ sor used as calculating unit must be programmed to per¬ form the comparison operations necessary therefore on several levels. It is the object of the invention to provide a simply designed and cheap apparatus of the kind mention¬ ed which with respect to costs as well as operation is suitable for installation even in private motor cars and may without diffuculty be installed also in existing vehicles. With this object in mind, the apparatus according to the invention is characterized in - that the pulse generator is connected to a first interrupt input of a microprocessor having a working memory space operating as a counter and incre¬ mented by internally generated clock pulses, said memory space being connected with said first interrupt input to transfer, at each pulse from the pulse generator func- tioning as an interrupt signal or by an internal inter¬ rupt signal generated by exceeding a stored predetermin¬ ed maximum value of said count, said count or said maxi¬ mum value, respectively, or a speed value derived there¬ from for recording in the electronic memory, - that the electronic memory comprises a number of memory blocks coupled in series and each having a number of memory locations in a circular arrangement, said lo¬ cations being individually addressable from a working memory space in the microprocessor functioning as an address register in a continuous cyclically repeated ' order of succession, said memory locations in each block except the last one being arranged in a number of memory sections with a marking associated with the first ad¬ dressed location in each section, whereby - a first memory block is addressed from the micro- ' .processor in response to each interrupt signal at said OMPI first interrupt input or said internal interrupt for continuous individual recordal of said counts or said maximum value, respectively, or the speed value derived therefrom in the memory locations of the first memory block, - all memory blocks except the last one have a data output connected on one hand to all memory locations of the memory section containing the last addressed memory location and, on the other hand, to a data input connect— - ed with the arithmetic-logic unit of the microprocessor for transferring the measuring values in said memory locations to said arithmetic-logic unit at each address¬ ing of a marked memory location in the actual memory block for producing a single function value on the basis of the measuring values in all said memory locations, and - each memory block af er the first one is addressed by the microprocessor in response to each addressing of a marked memory location in the preceding memory block for continuous individual recordal of function values originating from preliminary data in memory sections in the preceding memory block. With this design, only the counts directly obtain¬ ed by the road length pulses or possibly speed values derived therefrom by a simple calculation are stored in the electronic memory, i.e. without simultaneous clock indications,for each of the interrupt signals supplied from the pulse generator with a pulse separation corres¬ ponding to the constant road length, the speed value for • each record being produced as a constan -divided by the number corresponding to the count obtained since the preceding interrupt signal either in the microprocessor in the apparatus installed in the vehicle or in the ex¬ ternal recording instrument which may be designed as a portable terminal. The data depletion is performed continuously by 'BUREA OMPI means of a very fast storage algorithme requiring only a very simple calculating operation, such as a compari¬ son operation, at the transfer from one memory block to the next. Both of these factors imply that with a memory which is very limited in respect of capacity as well as current consumption, such as a 2 Ixbyte CMOS-RAM-memory, continuous recording may be made of speed values for reconstruction of the speed course over a considerable road length exceeding one hundred kilometers with a logarithmically increased data depletion backwards in time, so that the most recently travelled road length is reproduced with a relatively fine resolution corresponding, for instance, to a road length of only 2 meters between succeeding records.. In the following, the invention will be further explained with reference to the drawings, in which Fig. 1 is a block diagram of an embodiment of a speed recording apparatus according to the invention, and Fig. 2 is a flow card for explaining the operation of the apparatus. In the embodiment shown in Fig. 1, a pulse genera¬ tor 2 is coupled to a speed sensor 1 in a vehicle, for instance the speedometer cable of the vehicle, for gene¬ ration of pulses with a separation corresponding to a given constant road length. For example, the pulse gene¬ rator 2 may be an optical device with an apertured disc arranged between a light source and a photo detector and proportioned so as to supply a pulse, for example, for every 2 m travelled by the vehicle. The pulses from the pulse generator 2 are supplied as control signals to a first interrupt input 3 of a microprocessor 4, which may be of the CMOS-type and are used therein as interrupt signals for a counting opera- tion in a space 5a in the working memory 5 of the micro- processor 4 functioning as counter. Counter 5a counts the clock pulses supplied from the internal clock control 6 of the microprocessor 4 between every two succeeding interrupt signals at the input 3. At each interrupt sig- nal, the count is read, and the counter 5a reset to zero. Additionally, a maximum value for the count is stored in a separate memory location 5b in the working memory 5. If the count between an interrupt signal and the expected occurrence of the next interrupt signal exceeds this maximum value, for instance because the vehicle has stopped, which excession is tested continu¬ ously by a comparison operation in the microprocessor 4, a second internal interrupt signal is generated,by means of which the maximum value is read, and the counter re- set to zero. The count assumed at an interrupt signal or said maximum value, respectively, represents a time indica¬ tion which is inversely proportional to the speed, and the stored maximum value may per de inition be taken as an expression of the speed 0 km/h. In addition to the units already mentioned, the microprocessor 4 comprises in a manner known per se a program memory 7 containing the programs necessary for the performance of the control and calculating opera- tions as well as addressing and data input/output gates 8 and 9 , respectively, and an internal voltage source 10 and said units may communicate with each other through bus lines 11, 12 and 13. For the purpose of recording the count occurring at each interrupt signal or the- speed value derived therefrom which may be calculated by a simple division in the arithmetic-logic unit 6a, the microprocessor 4 is connected with an electronic memory 14. The memory 14 comprises a number of series-arranged memory blocks, of which the block diagram in Fig. 1 shows four such memory blocks 15, 16, 17 and 18, this OMPI number being, however, preferably greater, for instance eight, such as indicated by a dashed line. Each of the memory blocks 15 to 18 has a number of memory locations L, , I_2 •••» *■ -., L n arranged as a so-called "circular list" addressed from an independent register block func¬ tioning as a counter 19, 20, 21 and 22, respectively, in a space 5c of the working memory 5 of the micropro¬ cessor' 4 operating as an address counter. Each of the register blocks 19, 20, 21 and 22 may have the form of an m-bit counter, which is incremented by pulses from the clock control 6, m being determined in dependence of the number of memory locations in the blocks 15 to 18 by 2 ≥n. A suitable proportioning may be, for instance, Q 2 memory locations in each block and an 8-bit register block in the address counter space 5c. In this way, the memory locations of a block are addressed in a continu¬ ous cyclically repeated order of succession for indivi¬ dual writing of count or speed data^ supplied from the microprocessor 4 in individual memory locations. In addition, in each of the memory blocks 15 to 18 the memory locations L, to L are arranged in a number of memory sections preferably, but not necessarily, with an equal number of memory locations, for instance two, in each section, and in each of the memory blocks 15 to 18 with the exception of the last block 18, the first memory location, in each section is marked, which in the case of two memory locations in each section may be ac¬ complished by means of the least significant bit in the address indications for the memory locations, so that for instance the value 0 for the least significant bit is associated with a marked memory location. In the cyclic continuous addressing of the memory locations, these are individually connected successively to the microprocessor 4 for the reception of data there- from and transfer of data thereto, respectively, such as explained in the following and illustrated in the flow card in Fig. 2. The first memory block 15 is addressed fr microprocessor 4 in response to each interrupt signal at the input 3 or each of the above mentioned internal in¬ terrupt signals generated by the excession of the pre- determined maximum value by the count, and in this way the counts occurring at the interrupt signals or said maximum value, respectively, are individually written into the memory locations of the first memory block 15. Thus, at each time data expressing a speed value will normally be recorded in each of the memory locations in the first memory block 15, and in the continuous re¬ cording of new data, the above mentioned marking of the first memory location in each of the sections consisting, for instance, of two memory locations is now utilized in the first block 15 for transferring data to the next memory block 16 in connection with a data depletion, by which data are only transferred to a single memory loca¬ tion in the next block 16 for each memory section of the block 15. For this purpose, there is generated in the micro¬ processor at each addressing of a marked memory location in a memory block by means of the associated register block in the address counter 5c, i.e. for instance when the least significant bit in the memory location address changes from 1 to 0, an internal interrupt signal in re¬ sponse to which the microprocessor 4 reads out the data content in all memory locations in the relevant section, i.e. both in the marked and the following memory loca¬ tion, so as to empty these memory locations before writ- ing new data into the marked memory location, and their data content is transferred to the micro processor 4, the arithmetic-logic unit 6a of which on the basis of the data thus supplied, for instance two speed values, calculates a single function value which is transferred to and written into an addressed memory location in the next memory block 16. This function value may typically be the minimum or maximum value or the average of the data recorded in individual memory locations in the emptied memory section so that the calculation thereof may be performed as a simple calculating or comparing operation in the micro¬ processor 4. The continuous recording of data in the memory block 16 , the transfer of data from this block to the following block, the writing of data into the latter, and so on, is performed in an entirely analog manner, so that in each of the blocks with the exception of the last block 18, emptying of the memory locations of the relevant section is accomplished by the addressing of a marked memory location, and the data content thereof is transferred to the micro processor 4 for calculation of a single function value to be transferred to the follow¬ ing memory block. As mentioned, in the last memory block 18 no marking is"made of the memory locations, and in the writing of the function values calculated on the basis of data from the memory sections of the block 17 into the individual memory locations of the block 18, a simple overwriting is made by which the oldest speed value is continuously cancelled for each new record written into the block 18. Thus, the data recordal and transfer may be de¬ scribed as recording for each interrupt signal at the input 3 of a new count or said maximum value, respective¬ ly, or a speed value corresponding thereto from the microprocessor 4 into the first memory block 15 of the memory 14 and for each addressing of a marked memory location in either of the blocks 15, 16 and 17 transfer of a function value from this block to the following block 16, 17 and 18, respectively. It will, thus, appear that in case of m memory blocks, a value will be cancelled in the last memory block 18 for each number of 2 new values written into the first memory block 15. If a new value is introduced into the memory block 15 for each road length L, and each memory block has 2? memory locations, speed records will be stored in the electronic memory having a capaci- ty of m • 2 **5 memory locations covering a ' road length of . 2* - (2 m -l) with a fine resolution for the most recently travelled length, for which the records are stored in the block 15 and a gradually lower resolution for the road lengths which are further backwards in time and for which the records are stored in the succeeding memory blocks up to and including the block 18. Thus, with the above-exemplified proportions'. It = 2 meter, p — 8 and = 8, the -speed recordings for a road length of some 131 kms will be stored in an apparatus having an electronic memory 14 with a capacity of only 2 Kbyte. The data communication and transfer of address signals between the microprocessor 4 and the memory 14 take place by means of bus lines 26 and 27, . respectively. In the same way as the microprocessor 4, the me¬ mory 14 is provided with a built-in voltage source 28. Normally, during operation the power supply to the microprocessor 4 and the memory 14 takes place from the battery 29 of the vehicle. In connection with the in¬ ternal voltage sources 10 and 28, battery voltage detec¬ tors 30 and 31, respectively, are provided in the micro¬ processor 4 and the memory 14 by means of which switch¬ ing over to the internal voltage sources 10 and 28 is accomplished in case of decline of the battery 29. When stopping the vehicle, the voltage source 10 in the microprocessor 4 is actuated in response to re¬ cording the speed 0 km/h by means of the above mentioned internal interrupt signal generated in the microproces- sor when the predetermined maximum value of the counts is exceeded. URE QMPI In order to provide a visual speed reconstruction on the basis of the data recorded in the memory 14, the apparatus is adapted for connection of an external re¬ cording instrument 32, such as a curve drawing instrument which may possible, in addition, have a display screen, such as illustrated by dashed lines in Fig. 1. Read-out from the memory 14 is actuated by means of a contact 33, whereby all memory locations in the blocks 15 to 18 are addressed successively, for instance with a reverse order of succession relative to the one used in the recording whereby the record data are transferred to the recording instrument 32 starting with the most recently recorded data. The read-out and the speed reconstruction produced thereby may be interrupted at any point within the total road length covered by the records in the memory 14, if a need only exists for examination of a limited part of this length. For the purpose of indicating correct operation of the apparatus to the driver of the vehicle, an indi¬ cator 34, which may comprise a photo diode, may be pro¬ vided to indicate the function of the apparatus. As a special feature of the invention, such an indicator may serve as a connecting member for the re- cording instrument 32 which may for this purpose have a shielded photo sensitive detector which is brought into an optical transfer communication with said photo diode, whereby the stored data may be transferred as optical signals, and the apparatus installed in the vehicle may be designed as a closed box having small dimensions and no accessible electrical terminals. According to a further feature of the invention, the microprocessor 4 may be utilized in a simple manner for generating an alarm when a maximum speed selected by the driver and corresponding, for instance, to a local speed limit is exceeded by the vehicle. For this purpose, an alarm setting contact 35 operated by the driver when the vehicle has reached the desired maximum speed is connected to a second interrupt input 36. In operation of the contact 35, an interrupt signal is supplied to the microprocessor 4 which in response to the signal transfers the count assumed at the next pulse from the pulse generator 2 functioning as an interrupt signal at the input 3 as a minimum value to a memory location 5d in the working memory 5 adapted for this purpose. Subsequent to this alarm adjustment the counts actually assumed at each succeeding interrupt signal of the input 3 is compared with the minimum value in the arithmetic-logic unit 6a, and when the actual count is lower than the minimum value, an alarm signal is supplied to an acustic or optical alarm device 37. O-f-.PI

Claims: P A T E N T C L A I M S 1. An apparatus for continuously recording the speed of a vehicle over a predetermined road travelling length, comprising a pulse generator (2) adapted for connection with a velocity sensor (1) in the vehicle for generating control pulses with a pulse separation corresponding to a given road length, means for producing measuring values on the basis of said control pulses and internally gene¬ rated clock indications and an electronic memory (14) for storing said measuring values with a data depletion dependent on the travelled road length as well as read¬ out means associated with the memory (14) for connection with a recording instrument (32) for producing a visual speed reconstruction by reading-out the stored data, characterized in - that the pulse generator (2) is connected to a first interrupt input (3) of a microprocessor (4) having a working memory space (5a) operating as a counter and incremented by internally generated clock pulses, said memory space being connected with said first interrupt input (3) to transfer, at each pulse from the pulse generator (2) functioning as an interrupt signal or by an internal -.interrupt signal generated by exceeding a stored predetermined maximum value (5b) of said count, said count or said maximum value, respective- ly, or a speed value derived therefrom for recording in the electronic memory (14) , - that the electronic memory (14) comprises a number of memory blocks (15, 16, 17, 18) coupled in series and each having a number of memory locations (L, ... L ) in a circular arrangement, said locations being individual¬ ly addressable from a working memory space (5c) in the microprocessor functioning as an address register in a continuous cyclically repeated order of succession, said memory locations in each block except the last one (18) ' being arranged in a number of memory sections with a O PI marking associated with the first addressed location in each section, whereby - a first memory block (15) is addressed from the microprocessor (4) in response to each interrupt signal at said first interrupt input or said internal inter¬ rupt for continuous individual recordal of said counts or said maximum value, respectively, or the speed value derived therefrom in the memory locations of the first memory block (15) , - all memory blocks (15, 16, 17) except the last one (18) have a data * output connected on one hand to all memory locations of the memory section containing the last addressed memory location and, on the other hand, to a data input (9) connected with the arithmetic-logic unit (6) of the microprocessor (4) for transferring the measuring values in said memory locations to said arith¬ metic—logic unit (6) at each addressing of a marked memory location in the actual memory block (15, 16, 17) for producing a single function value ' on the basis of the measuring values in all said memory locations, and - each memory block (16, 17, 18) after the first one (15) is addressed by the microprocessor (4) in response to each addressing of a marked memory location in the preceding memory block for continuous individual recordal of function values originating from preliminary data in memory sections in the preceding memory block (15, 16, 17). 2. An apparatus as claimed in claim 1, characterized in that the electronic memory (14) has eight memory blocks (15 to 18) , each having 256 memory locations ar¬ ranged with two memory locations in each memory section and that the addressing means (19 to 22) associated with each memory block (15 to 18) is an 8-bit shift register. 3. An apparatus as claimed in any of the preceding claims, having power supply means for connection with the battery (29) of the vehicle, cha ac erized in that OMPI internal voltage sources (10, 28) are associated with the microprocessor (4) and the electronic memory (14), and that means are provided for switching over from the battery of the vehicle to said internal voltage sources (10, 28) at decline of the battery of the vehicle. 4. An apparatus as claimed in claim 3, characterized by separate visual indicator means (34) for the opera¬ tion of the apparatus with power supply from the battery (29) of the vehicle and from said internal voltage sources (10, 28), respectively. 5. An apparatus as claimed in claim 4, characterized in that the indicator means (34) may be coupled to said read-out means for the electronic memory (14) , and that said recording apparatus (33) has a shielded, photo- sentitive detector adapted for connection with the in¬ dicator means (34) for receiving optical read-out sig¬ nals therefrom. 6. An apparatus as claimed in any of the preceding claims, characterized in that a second input of the microprocessor (4) is connected to an alarm adjustment contact (36) and to the program memory (7) of the.micro¬ processor .(4) to transfer in response to actuation of said contact (36) the count assumed at the following interrupt signal at said first interrupt input (3) or the speed derived therefrom as a minimum or maximum value, respectively, to a separate memory location (5d) in the working memory (5) and to subsequently compare at each following interrupt signal at said first input (3) the actual count with said minimum or maximum value, respectively, and supply an alarm signal to an alarm device (37) connected with the microprocessor (4) , if the actual count is lower than the minimum value or higher than the maximum value, respectively. " B U E 0?ΛPI

Inventors: JOHANSEN KENT, SKOVGAARD HELGE, JOHANSEN, KENT, SKOVGAARD, HELGE
Applicants: KENT JOHANSEN, SKOVGAARD HELGE, JOHANSEN, KENT, SKOVGAARD, HELGE
Application year: 1983
Main classification: G07C5
IPC codes: G07C5