DE2633565A1 - METHOD AND DEVICE FOR CONTACTLESS SPEED MEASUREMENT - Google Patents

Description

R. 3 3 0Ü
Rs

Attachment to

Patent application I.

Robert Bosch GmbH June 22, 1976

7 Stuttgart

Method and device for non-contact speed measurement

The invention relates to a method for contactless measurement of the Relative speed of two bodies by means of two in the direction of relative movement on one of the bodies arranged one behind the other measuring sensors, which the physical structure; especially the surface structure of the other Body corresponding to a speed-dependent transit time to generate mutually offset signals that after delay of the signal in the direction the relative movement of the front measuring sensor with one another in an evaluation device be correlated, which is an indication of the relative speed and / or a quantity associated therewith, as well as a device for implementation this procedure.

One such method for non-contact speed measurement is known for example from DT-OS 2 133 942, according to which the comparative or signals to be correlated are quantized in limiters. According to In the known method, the signal coming from the front measuring sensor is automatically delayed by such a transit time that the mean square Deviation of the two signals is a minimum. The delay is controlled by an integral controller, which is relatively complex. Similar methods are known from DT-OSs 2 21.9 342, 2 331 145, 2 219 343 and 2 219 900. All known methods for non-contact speed measurement it is common that the correct delay of the output signal of the front measuring sensor is obtained in a control process that has a corresponding makes circuitry effort required, with the usual Criteria of the control technology must be strictly observed in order to avoid undesired oscillation processes and the like with a reasonable control duration, which is often only possible by additional devices, for example by a coarse control interacting with the fine control, which is a Setting the control loop to incorrect values prevented.

The invention is based on the object of a method and a device for non-contact speed measurement, in which or with which a fast and precise measurement of the relative speed is possible with little technical effort two bodies even with strong temporal changes in the

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Relative speed is made possible.

This task is thereby achieved in the method of the type described at the beginning solved that according to the invention, a plurality of signals with different degrees of delay are simultaneously generated from the signal from the front sensor, that each individual delayed signal is compared with the signal of the rear measuring sensor in the direction of the relative movement to determine that signal pair to determine in which the optimal match results, and that one of the delay of the delayed signal of this signal pair corresponding Speed display generated.

The method according to the invention therefore differs from the previously known Method at any moment a more or less large number of signals, depending on the accuracy requirements, are kept ready, which are different Times are delayed, and each of these signals is immediately compared with the signal from the rear probe to determine the pair of signals in which the optimal match results. That way it becomes tedious, technically complex approach to the correct delay time avoided, and it is achieved at the same time that speed changes can be recorded quickly and reliably without fear of incorrect measurements are, as they occur in the case of rapid speed changes in the known methods, where the control is due to too large control time constants can get out of step.

It is beneficial if the signals from the two sensors are used as is per se is known from DT-OS 2 219 900, converted into single-digit binary signals and by means of logic circuits with downstream analog integration elements compares. In this way, the circuit complexity for carrying out the method according to the invention can be kept particularly small.

It is advantageous if you assign the binary 0 and 1 to the Signal amplitudes as a function of the mean signal amplitude at the output regulates at least one of the sensors. Because in this way it is possible.

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Slow changes in the physical structure of the second body, for example slow changes in the surface structure of a road, in the sense of a to take into account the most accurate speed measurement possible.

A device has been used to carry out the method according to the invention particularly proven, which is characterized in that with the output of the front sensor a first threshold value circuit is connected, with the output of a clocked slide register arrangement is connected that the delayed Signals from different outputs of the shift register arrangement can be tapped, that each of these outputs of the shift register arrangement with one input of several logical gate circuits is connected to each input, at the second input of which the output signal is connected to the output of the the second threshold value circuit connected to the rear sensor is present, and that the output of each gate circuit is connected to a display device via an integration element.

The decisive advantage of the device according to the invention consists in this in that the signal processing behind the threshold circuits including The comparison of the two voltages is purely digital, so that here the low susceptibility of digital technology and the advantages of modern Being able to take full advantage of semiconductor technology. Another major advantage is also that the individual integration circuits, which are preferably are simply designed as RC elements, individually for the individual delay times can be tuned in such a way that with small delay times a shorter one and with large delay times a longer one Integration time is chosen. It is advantageous if it is used as a logical gate circuit Exclusive-OR gates are provided because of the use of these blocks the integration enables both the acquisition of those times in which both signals have the binary value 0 and the acquisition of the time intervals in which both signals have the binary value 1. This will allow the time to a decision on the similarity of the two to be compared Signals further shortened.

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It is also advantageous if the switching thresholds of the two threshold value circuits can be regulated, as this enables the Hess devices to be adapted slow mean structural changes of the body scanned by the sensors can be achieved. Such a possibility is particularly evident when measuring speeds from a moving motor vehicle as advantageous, since the mean structure of the surface of a road is in Depending on the weather conditions the building materials used etc. can change very much.

In this embodiment of the invention, it is advantageous if the control inputs the threshold value circuits with the output of one of the threshold value circuits via the series connection of an averaging unit and a Comparator are connected to the actuator. Another possibility is that with the output of one of the measuring sensors, a mean value converter is immediately generated is connected, of whose output the Schwelluertschaltungen one of their Voltage determining switching thresholds can be supplied.

In a further development of the invention, it is also advantageous if the shift clock is adjustable in steps for the shift register arrangement. Through this Measure a range switching is made possible, which is possible with a limited The number of delayed measurement signals allows a large speed range to be covered. Such a measuring range switchover preferably takes place according to the invention automatically. In a preferred embodiment the invention is to bring about an automatic measuring range switching a right-left shift register with two inputs is provided, which is connected to the outputs of the integration circuits for the largest or the smallest delay time are connected ^ and in which a single binary 1 can be shifted to the right or left when controlled by one of these two outputs, to a selected output of a divider chain connected downstream of a clock generator via an assigned output of the right-left shift register to be connected to the clock input of the slide register arrangement. A measuring range switchover takes place whenever the uppermost or lowest limit of a measuring range is reached. The measuring ranges are preferably like this

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chosen so that they partially overlap so that at one speed which falls at the end of a measuring range, not a permanent switch from one measuring range to the neighboring measuring range.

While the display device in devices according to the invention without measuring range switching can be formed simply by incandescent lamps or the like at the outputs of the individual integration elements, with between the incandescent lamp and the output of the respective integration element is preferably also inserted a logic circuit with a corresponding switching threshold, in particular an inverter, and wherein the incandescent lamps are arranged along a fixed scale on which the relevant speed values are plotted are, one must with a device according to the invention with measuring range switching provide several scales or the like, one of which is then activated depending on the position of the right-left slide register, for example is illuminated.

Finally, in a further development of the invention, it can be advantageous if a Converter arrangement is provided, with the help of which from the output signals of the integration circuits and optionally the right-left shift register a digital and / or analog speed signal can be derived.

Further details and advantages of the invention are provided below with reference to a drawing explained in more detail, the single figure of which is a schematic block diagram of a preferred embodiment of a device for implementation of the method according to the invention shows.

In the drawing, in the upper left part, a surface area B is one Body indicated, for example the surface of a street. All parts of the In contrast, the circuit shown in the drawing are located on a second body (not shown), for example on a road vehicle.

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The circuit under consideration has two sensors 1 and 2, the Surface area B are facing and, for example, as photocell arrangements which determine a changing reflectivity of the surface area B.

For the following consideration it is assumed that the measuring sensor 1 is located further forward in the direction of the relative movement, which is why this measuring sensor is referred to below as the front measuring sensor 1. Accordingly, the probe 2 is hereinafter referred to as the rear probe 2. The outputs of sensors 1 and 2 are connected to threshold value circuits 3 and 4, respectively. The output signal of the threshold value circuit 3, which is a sequence of binary 0 and 1 signals, is fed to a shift register arrangement which is made up of two individual shift registers 9 and 11. The shift register 9 delays the signal sequence from the output of the threshold circuit 3 by a time constant 'Cg, while each individual stage of the second shift register 11 delays d "> e delayed output signals from the first shift register 9 by a time constant ^ qVN. N means the number of stages of the second shift register 11, so that, provided that the entire delay caused by the shift register 11 is again equal to the time constant Tq, signal sequences result at the individual outputs 12 of this shift register which, compared to the signal sequence at the output of the threshold circuit 3, result in signal sequences which each UiDtT _n = T * g (1+ "£ -) are delayed, where η = 0.1 ... N.

The individual outputs 12 of the second shift register 11 of the shift register arrangement 9, 11 are each with one input of a series of exclusive-OR gates 13 connected, at the second input of which the output signal of the threshold value circuit 4 assigned to the rear measuring sensor 2 is applied = Der The output of each of the exclusive-or gates 13 is connected to an integration circuit connected, which, as indicated in the drawing, simply consist of an RC element can. With the outputs of the integration circuits f4 are inverters connected, the output of which in turn each with an incandescent lamp 16 or the like connected is. A scale 17 is assigned to the incandescent lamps, on which the speed values which are assigned to the individual incandescent lamps 16 are plotted.

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The circuit according to the invention works as follows: The two measuring sensors 1 and are arranged one behind the other at a distance L in the direction of the relative movement and each scan a point or a small area of the surface area B at the outputs of sensors 1 and 2, time-variable, statistical, electrical signals s ^ Ct) and S2 Ct) result. The signal S2 of the rear measuring sensor 2 now has essentially the same form as the signal sj of the front measuring sensor 1 and is only delayed relative to this by the transit time T which the measuring sensor 2 needs to cover the distance L. If the distance L is known and if the transit time T can be determined, then the relative speed ν results from the known equation v = L / T.

The transit time T is now determined in the method according to the invention in such a way that the _{output signals of the front measuring sensor 1 delayed by different time constants TT n} at the outputs 12 of the shift register are individually compared with the output signal of the rear measuring sensor 2 by the exclusive-OR gate 13 after digitization of this signal in the threshold value circuit 4. If this comparison shows that the two signals of a signal pair are the same or essentially the same, then it is known that the delay time TT _n by which the output signal of the front measuring sensor was delayed is equal to Running time T is. However, according to the equation given above, a fixed speed is assigned to this running time. In the circuit according to the invention, the exclusive-OR gates 13 only supply a 1-signal at their outputs if the signals at their inputs are different. These signals are integrated in the integration circuits 14, which control the downstream inverters 15 accordingly, in such a way that the associated incandescent lamps 16 do not light up. Only at the output of one of the exclusive-OR gates is there a constant binary 0 due to the equality of the signals at its inputs, so that the associated incandescent lamp is switched on via the relevant integration circuit 14 and the downstream inverter 15. At most, there is the possibility that a 1 appears at the outputs of two exclusive-or gates 13 only so briefly that two incandescent lamps respond at the same time, due to the extensive correspondence of the input signals. This is the case when the actual transit time T is exactly between

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two delay times T _n . In other old cases in which the transit time T does not exactly _{match one of the delay times Tj 1} , however, a defined speed display is ensured by optimally selecting the threshold voltages of the inverters 15 and the time constants of the integration elements.

With the circuit according to the invention, insofar as it has been described up to this point, only speeds within a certain range can be measured, which is determined by the time constant TH. In the exemplary embodiment under consideration, only transit times T between 1Tg and 2Xq can be recorded. The measuring accuracy within this range, if errors are excluded from the measuring sensors, depends on the number of outputs 12 and the triggering capacity of the downstream circuits. The absolute value of the delay time tg, on the other hand, is also _{dependent on the clock frequency f t} that is present at the input of the shift registers 9 and 11. In the circuit according to the invention, a measuring range control circuit can thus be carried out in a simple manner by changing the clock frequency fj- for the shift registers 9, 11.

In a further development of the invention, this measuring range switchover takes place in the circuit according to the invention automatically, as follows: The outputs of those Inverter 15, which at the largest possible delay time To + ^ n; i.e.

at the lowest speed and at the lowest possible delay time TTn, ⁺ T "-], ie respond at the highest speed, are connected to two inputs 19 and 20 of a right-left shift register 21, which in the exemplary embodiment is a four-digit shift register , in which there is a binary 1. This binary 1 is now pushed forward by one position when the upper or lower limit of a measuring range is reached, namely in the circuit shown with a 1 signal on the line downwards and upwards with a 1 signal on line 20. The right-left shift register 21 has four outputs, each of which is connected to an input of four AND shades 22. Each of the AND circuits 22 has a second input Output of a divider chain 26, the input of which is connected to a clock generator 25. The outputs of the four AND circuits

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are connected to the four inputs of an OR circuit 24, the output of which is connected to the clock inputs 10 of the shift registers 9 and 11. To the There are four clock frequencies fg, fn./2, frj / 4 and fg / 8 at the outputs of the ladder chain 26 available. Since via the outputs of the right-left shift register 21, respectively only one of the AND circuits 22 is controlled with a binary 1, only one of the frequencies mentioned is allowed to pass through to the clock inputs 10 of the shift registers 9 and 11. It is understood that on the described Way with the help of a right-left shift register of the corresponding number of digits Any number of measuring ranges can be created. The four outputs of the right-left shift register 21 are simultaneously via lines 28 with indicator lamps 29 connected, which are used to illuminate the scale 17 and three other scales 18. The fact that in the right-left shift register 21 only one binary 1 is contained, consequently only one of the scales 17, 18 is illuminated, so that a clear link between the burning bulb and a certain speed mark on one of the scales 17, 18 is guaranteed is. Since speeds outside the intended speed ranges cannot be displayed, it is useful to prevent the binary 1 in the right-left shift register 21 can be lost. For this reason a data buffer 27 is provided at the data input as well as at the data output of the right-left shift register 21, in which the binary 1 is provided when it is exceeded of the measuring range is saved until the speed is in one of the intended speed ranges. In particular, one of the data buffers 27 is used to generate a binary 1 at the beginning of a movement process Place of the shift register 21 to store the lowest speed assigned. Instead of the automatic devices for measuring range switching or in addition to these, manually operable devices for speed switching can also be provided, in particular in the case of a Failure to switch on the correct measuring range.

The circuit under consideration still has in a further embodiment of the invention a converter arrangement, which is used to convert the measured speed into electrical signals, which for further processing, for example are suitable for integration to determine the distance covered.

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In detail, the converter arrangement has two code converters 30 and 31, which are preferably designed as diode transmission matrices, as well as a digital dividing unit 32. Furthermore, a digital-to-analog converter 33 is provided, at its output a speed proportional to the measured speed analog signal can be tapped. The inputs of the code converters 30 and 31 are with the outputs of the right-left shift register 21 or with the outputs the inverter 15 is connected. As an example, the numbers for the two code converters 30 and 31 are entered when the relevant inputs are activated must be at the exit, so that the result under the condition that the Distance L and the clock frequency fg are correctly matched to each other at the output the dividing unit 32 appears in digital form in km / h.

So that with a changing surface area of the surface area B the binary values 0 and 1 of the quantized signals ~ Sj, "" I ^ on average over time are evenly distributed, is also in the circuit according to the invention a control loop is provided which is located between the output of the threshold value circuit and a control input of the same and which has an averaging unit 5 as well has an actuator 6. The averaging unit 5 has a very large one Time constant and then causes an adjustment of the actuator 6 when one of the binary values, for example 0, compared to the other binary value, for example the 1, occurs significantly more frequently over a longer period of time. the The actuator 6 is influenced in such a way that the threshold values of the Threshold circuit 3 are shifted so that there is again a balanced relationship between the occurrence of the binary 0 and the binary 1. That Actuator 6 is also connected to the threshold circuit 4 for the rear sensor 2, so that gradual changes in the surface properties are also taken into account on this channel.

As indicated by dashed lines in the drawing, there is also the possibility of to evaluate the output signal of the measuring sensor 1 directly in an integration element 5a with a large time constant and the time average of the voltage corresponding to analog signal s-j to threshold circuits 3 and 4 to be supplied via lines 7 and 8 as a threshold voltage.

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Claims (15)

-χ. Robert Bosch GmbH June 22, 1976 Stuttgart attorney's file 1945 Claims ι T.! Method for contactless measurement of the relative speed of two bodies by means of two measuring sensors arranged one behind the other in the direction of the relative movement on one of the bodies, which generate signals corresponding to the physical structure, in particular the surface structure, of the other body, offset from one another by a speed-dependent transit time Delay of the signal of the front sensor in the direction of the relative movement are correlated with each other in an evaluation device, which provides an indication of the relative speed and / or an associated variable, characterized in that from the signal Cs ^) of the front sensor CD, a plurality of differently delayed signals are obtained at the same time produces that each individual delayed signal is compared with the signal Cs-,) of the rear measuring sensor C2) in the direction of the relative movement, in order to determine that signal pair in which the optimum match is obtained, and d a speed display corresponding to the delay of the delayed signal of this signal pair was generated. 2. The method according to claim 1, characterized in that the signals Cs> |, S £) of the two sensors (1, 2) into single-digit binary signals Cs ^, "slp and compares them with each other through a logical link. 3. The method according to claim 1 or 2, characterized in that the Assignment of the binary 0 and 1 to the signal amplitudes depending on the mean signal amplitude at the output of at least one of the sensors ^ 1, 2) regulates. 4. Device for performing the method according to one of claims 1-3, characterized in that the front measuring sensor (1) has a delay circuit (9, ID is connected that the delay circuit (9, 11) several outputs ClZ), at which the differently delayed signals can be tapped that each of these outputs CI2) of the delay circuit C9, 11) 709885/0103 - 12 ORiGINAL INSPECTED each connected to one input of one of several logic gate circuits (13) whose second input is connected to the output of the second Sensor C2) is connected, and that the output of each of the gate circuits (13) Connected to a display device (15-18) via an integration member C14) is. 5. Device according to claim 4, characterized in that between the Output of the front sensor CD and the delay circuit (9, ID as well as between the output of the rear sensor (2) and the inputs of the Logical gate circuits (13) each with a threshold value circuit (3 or 4) is provided. 6. Device according to claim 5, characterized in that the switching thresholds of the two threshold value circuits (3, 4) can be regulated. 7. Device according to claim ό, characterized in that the control inputs the threshold value circuits (3, 4) with the output of one of the threshold value circuits (3) via the series connection of an averaging unit (5) and a comparator (6) are connected to the actuator. 8. Device according to claim 6, characterized in that with the output one of the measuring sensors CD is directly connected to an averaging unit (5) is, of the output of the threshold value circuits (3, 4) one of theirs. Voltage determining switching thresholds can be supplied. 9. Device according to one of claims 4-8, characterized in that a clocked shift register arrangement (9, 11) is provided as a delay circuit. 10. Device according to claim 9, characterized in that the clock frequency for the shift register arrangement (9, 11) for switching over the measuring range in stages is adjustable. - 13 - 709885/0103 11. Device according to claim 10, characterized in that the clock frequency automatically adjustable for the shift register arrangement (9, 11) is. 12. Device according to one of claims 4-11, characterized in that that exclusive-OR gates (13) are provided as logical gate circuits. 13. Device according to claim 11, characterized in that a right-left shift register (21) is provided with two inputs (19, 20) which are connected to the outputs of the integration circuits (14) for the largest or the smallest delay time are connected, and in which a single binary 1 when triggered by one of these two outputs (19, 20) to the right or can be shifted to the left via an associated output of the right-left shift register (21) a selected output (23) of a divider chain (26) connected downstream of a clock generator (25) with the clock input (10) to connect the shift register arrangement (9, 11). 14. Device according to claim 13, characterized in that a converter arrangement (30-33) is provided, with the aid of which from the output signals of the integration circuits (14) and possibly the right-left shift register (21) a digital and / or analog speed signal. can be derived. 15. Device according to one of claims 4-14, characterized in that that RC elements (14) are provided as integration circuits. 709885/0103