JPH02218963A - Speed detector - Google Patents

Abstract

PURPOSE:To cope with a wide measuring range and to enhance measuring accuracy by obtaining the good S/N of two photodetectors by a differential output means to amplify the same and controlling the detection output from an amplifying means on the basis of the output of an addition output means. CONSTITUTION:The projected light from a light source is reflected from the unevenness of the object to be measured on a road surface during running and, on the basis of the outputs of photodetectors 50, 51 detecting the reflected light, the output corresponding to the difference between said outputs is calculated by a differential output means 53 and amplified by an amplifying means 54. The output of the sum of the outputs of the photodetectors 50, 51 calculated by an addition output means 52 is compared with reference voltage VREF becoming a predetermined amplyfying degree variable start level by a comparing means 55. The amplifying gain of the amplifying means 54 is controlled on the basis of the output of the means 55 by a variable gain control means 56 so as to become variable. By this method, the detection output corresponding to a change of a speed is calculated from the means 54.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a speed detection device used in a speed measurement device, and in particular, an object of the present invention is to obtain a speed measurement device that has a simple configuration, can support a wide measurement range, and can improve measurement accuracy. This relates to a speed detection device.

[Industrial application field]

The present invention relates to a speed detecting device used in a speed measuring device that measures the traveling speed of a train, automobile, motorcycle, or other vehicle during a running test, or when recording the speed of a running vehicle over time.

[Conventional technology]

A light source is installed on a running train, car, motorcycle, or other vehicle, and the light from the light source is irradiated onto the road surface on which the vehicle is running.The light reflected from the road surface is received, and the vehicle's running is determined based on the intensity of the reflected light. 2. Description of the Related Art Traveling speed measuring devices that can measure speed are known.

Such a traveling speed measuring device may include a light receiving element that receives the reflected light, and a change in the physical quantity detected by the light receiving element is converted into, for example, a voltage change, which is then amplified by a simple amplifier circuit. The amplifier circuit outputs an alternating current signal whose amplitude changes depending on the "unevenness" of the object to be measured such as the road surface as a signal corresponding to the change in speed (hereinafter simply referred to as speed signal). The small amplitude portion of the speed signal tends to have a low S/N due to noise from the background. However, outdoors, there is a large difference in object brightness between day and night, and a speed measuring device used in such an environment will be able to extract a high-quality speed signal. It is difficult to create an optimal state of the hysteresis width (2xVs) indicated by +Vs and Vs and indicated by a dotted line.As a result, the optimal signal strength of the speed signal is often not obtained.

Therefore, in order to improve this problem, for example, an automatic gain control amplifier (hereinafter referred to as AGC amplifier) as shown in FIG.
The signal is amplified by the AGC amplifier, and the output level is kept constant by the AGC amplifier. Based on the output, a control signal for a gate that controls the passage of count pulses from a counter (not shown) is generated. The AGC amplifier has a variable gain element 1 that utilizes the properties of, for example, an operational amplifier or a FET, and a voltage change el corresponding to a change in the physical quantity detected by the light receiving element is input to the variable gain element 1. . On the output side of the variable gain element 1, there is a DC converter 2 having a diode and a capacitor.
is input to one input terminal of the comparator 3. On the other hand, the other input terminal of the comparator 3 is supplied with a reference voltage VIIEF, which is the amplification variable start level of the variable gain element 1, and the comparator 3 outputs the rectified and smoothed output E0 and the reference voltage vlItF. Compare the size with. The relationship between the rectified and smoothed output Eo and the reference voltage VIIEF is Be>V■
When F, the output e2 of the comparator 3 is er=A (Eo
VIEF), an output e1 corresponding to the difference between Eo and VREF is obtained from the comparator 3 as a gain control signal as shown in FIG. 7(b). This output e7 is integrated over a certain period of time by an integrator 4 and provided with a time constant, thereby stabilizing the tracking operation of the variable gain element 1 to the gain control signal. Note that in the above equation, A is the amplification gain. Further, when Eo≦V ltF, AGC does not function and the voltage change e occurs.

is amplified with a constant amplification gain, and the corresponding output e
, is obtained from the variable gain element as shown in FIG. 7(a).

[Problem to be solved by the invention]

By the way, when the above-mentioned simple amplifier circuit is used as a means for amplifying the voltage change corresponding to the change in the physical quantity detected by the light-receiving element, it is difficult to obtain a good S/N ratio and the dynamic range is narrow. If a signal is input, the output signal will be distorted. Therefore, a speed detection device that can cover a wide measurement range cannot be obtained. Also,
When the conventional AGC amplifier as described above obtains a gain control signal that responds to an input signal in a low frequency range, the ripple of the gain control signal tends to become large due to the time constant for smoothing, and as a result, The AGC operation becomes unstable and the AG
The output signal of the C amplifier is distorted.

Therefore, the AGC amplifier has the disadvantage that a good AGC effect cannot be obtained unless it is operated in a rather high frequency range, avoiding operation in the low frequency range that causes such unstable operation. Therefore, there is a problem in that even if a conventional AGC amplifier is used in a speed detection device that needs to have a wide dynamic range over a wide speed measurement range from low speed to high speed, accurate measurement results cannot be obtained. Ta.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a speed detection device that can cope with a narrow measurement range with a simple configuration and improve measurement accuracy.

[Means to solve the problem]

FIG. 1(a) is a block diagram showing the principle as one means of the present invention. In the speed detection device of the present invention, the sensor that receives reflected light from the object to be measured has two sets of light receiving elements 50 and 51 arranged close to each other and on substantially the same plane. The addition output means 52 obtains an output corresponding to the sum of the respective outputs of the light receiving elements. Moreover, the differential output means 5
3 obtains an output corresponding to the difference between the respective outputs of the light receiving elements. The amplification means 54 amplifies the output of the differential output means 53.

On the other hand, the comparison means 55 compares the output of the addition output means 52 with a predetermined amplification degree variable start level VIIEF. The variable gain control means 56 receives a signal based on the output of the comparison means 55 and controls the amplification gain of the amplification means 54 to be variable.

FIG. 1(b) is a block diagram showing the principle of another means of the present invention. In the speed detection device of the present invention, the sensor that receives reflected light from the measurement target includes two sets of light receiving elements 50 and 51 arranged close to each other and on substantially the same plane.
has. The addition output means 52 obtains an output corresponding to the sum of the respective outputs of the light receiving elements. Further, the differential output means 53 obtains an output corresponding to the difference between the respective outputs of the light receiving elements. The amplification means 54 amplifies the output of the differential output means 53.

On the other hand, the light source projection amount control means 58 controls the addition output means 52.
The output of the amplifying means is inputted, and the amount of light emitted from the light source 57 that contributes to the reflected light received by the sensor is controlled to obtain a detection output corresponding to the change in speed from the amplifying means.

[For production]

A signal corresponding to a change in speed is generated by light emitted from a light source reflecting on "unevenness" such as unevenness of the measurement object such as the road surface under the vehicle, and the reflected light is captured by the light receiving element 50, 51 and sent to the light receiving element. Based on the output of 50.51, the addition output means 52 and the differential output means 53 provide an alternating current signal whose amplitude changes in accordance with the change in speed. Then, the addition output means 52 outputs a signal that faithfully follows the change in brightness of the object to be measured, such as the road surface on which the vehicle is traveling, and the signal is used to amplify the output of the differential output means 53 to obtain a detection signal. intensity is controlled. As a result, when the amplification gain of the amplification means 54 that amplifies the output of the differential output means 53 is controlled based on the output of the addition output means 52, the intensity of the light incident on the light receiving element 50.51 is high. When the amplification gain of the amplification means 54 is small, and the intensity of the light incident on the light receiving element 50.51 is weak, the amplification gain of the amplification means 54 is increased to increase the detection output level obtained from the amplification means 54. is controlled.

Further, based on the output of the addition output means 52, the light source 5
When controlling the amount of light projected from 7, the amplifying means 54
When the operation of the amplifying means 54 approaches a saturated state, the intensity of the light incident on the light receiving element 50.51 is reduced, and conversely, when the operation of the amplifying means 54 approaches an unattended state, the intensity of the light incident on the light receiving element 50.51 decreases. said amplifying means 5 in such a way as to increase the intensity;
The detection output level obtained from 4 is controlled.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a circuit diagram showing an example of a circuit configuration applied to the speed detection device of the present invention. In the figure, the light receiving element 5
．． 6, in order to obtain almost the same characteristics, a light receiving part is formed of a photodiode, CdS, amorphous solar cell, or other photoelectric conversion material on the substrate surface of steatite, for example, in close proximity to each other and on the same plane. Two pairs of leads are drawn out through electrodes formed by vacuum evaporation or the like, and the whole is housed in a container having a light-receiving window. Incidentally, this light receiving element 5.6 is mounted on a printed circuit board, for example, in a large number of
It is also possible to provide two sets of 0 phototransistors connected in parallel and to accommodate the whole in a container having a light-receiving window as described above.

Although not shown, one lead of the light receiving element 5.6 is connected to an earth potential and a common line of the power supply (hereinafter referred to as grounded), and the other lead of the light receiving element 5.6 is connected to the operational amplifier 7. It is input to each of the 8 inverting input terminals.

The non-inverting input terminals of these operational amplifiers 7 and 8 are grounded. The output terminal of the operational amplifier 7 is connected to a non-inverting input terminal of an operational amplifier 10 via a resistor 9 and to an inverting input terminal of an operational amplifier 12 via a resistor 11.

On the other hand, the output terminal of the operational amplifier 8 is connected to the inverting input terminal of the operational amplifier 10 via a resistor 13 and to the inverting input terminal of the operational amplifier 12 via a resistor 14. Note that resistors 15 and 16 connected to the output terminal of the operational amplifier 7 and the respective inverting input terminals are feedback resistors for negative feedback.

Further, the non-inverting input terminal of the operational amplifier 0 is grounded via a resistor 17, and the non-inverting input terminal of the operational amplifier 12 is directly grounded.

The output terminal of the operational amplifier 10 is connected to the inverting input terminal of the operational amplifier 20 via a DC blocking capacitor 18 and a resistor 19, and is also connected to the inverting input terminal of the operational amplifier 10 via a resistor 21. There is. The output terminal of the operational amplifier 12 is connected to the non-inverting input terminal of the operational amplifier 23 via a resistor 22 and to the inverting input terminal of the operational amplifier 12 via a parallel circuit of a resistor 24 and a capacitor 25.

Further, the non-inverting input terminal of the operational amplifier 23 is grounded via a resistor 26. The inverting input terminal of the operational amplifier 23 is connected via a resistor 27 to the output terminal of an operational amplifier 28 operating as a voltage follower.
It is connected to the output terminal of the operational amplifier 23 via. The non-inverting input terminal of the operational amplifier 28 is connected to a stabilized reference voltage V REF that is a level at which the amplification degree of the operational amplifier 20 starts to be varied.
is applied. The inverting input terminal of the operational amplifier 28 is connected to the output terminal of the direct liquid operational amplifier 28.

On the other hand, the output terminal of the operational amplifier 23 is connected to the base of a transistor 30 and grounded through a diode 31 in the reverse direction to prevent reverse voltage from being applied to the transistor 30. Further, the collector of the transistor 30 is connected to a positive terminal of a power supply (not shown), and a power supply voltage VDD is applied thereto. The emitter of the transistor 30 is grounded via a light emitting diode 33 of a CdS photocoupler 32 and a resistor 34.

A Cd535 functioning as a variable resistance element of the CdS photocoupler 32 is connected between the inverting input terminal and the output terminal of the operational amplifier 20. Also, the C
A resistor 36 is connected in parallel to d535.

The operational amplifier 7 and the resistor 15 and the operational amplifier 8 and the resistor 16 constitute a current/voltage conversion amplifier that converts a change in the current flowing through the light receiving element 5.6 into a voltage change. This may be omitted if the light receiving element 5.6 is a photodiode or an amorphous solar cell that generates a voltage by itself when it receives light.

Furthermore, when CdS is used, a bias voltage is applied to each of the light receiving elements 5.6, although not shown.

the operational amplifier 10, the resistor 9, the resistor 13,
The configuration of the resistor 17 and the resistor 21 is a differential operational amplifier circuit,
It functions as a differential output means.

Further, the configuration of the operational amplifier 12, resistor 11, resistor 14, and resistor 24 is an addition operational amplifier circuit, and functions as addition output means. Furthermore, the configuration of the operational amplifier 20, resistor 19, Cd535, and resistor 36 is an amplification circuit, and functions as an amplification means. The comparator circuit is composed of the operational amplifier 23, the resistor 22, the resistor 26, the resistor 29, and the resistor 27, and to which the operational amplifier 28 applies a reference voltage V REF that becomes the amplification degree variable start level of the amplifier circuit. It functions as a means of comparison.

Further, the structure of the transistor 30, the resistor 34, the CdS photocoupler 32, and the diode 31 is an emitter follower, and functions as a variable gain control means in cooperation with the Cd535.

When light is projected from a light source such as a halogen lamp onto the road surface on which the vehicle is traveling, the reflected light reflected from the road surface enters the light receiving element 5.6. Changes in the current flowing through the light receiving element 5.6 corresponding to the strength of the reflected light are converted into voltage changes by the operational amplifier 7.8, and voltages el and ez are obtained from their output terminals. Both voltages else2 are input to the operational amplifier 10, and a voltage e3 is obtained at its output terminal, the magnitude of which is eff=1 (e+ez). However, 1 is the amplification gain. This voltage e3 is suppressed to such an extent that the common mode component of the voltages el and ez is hardly included, so that the S/N ratio is increased (improved). , the AC component is further amplified by the operational amplifier 20. The amplification gain of the operational amplifier 20 is determined by the resistance value of the resistor 19.36 and the Cd535, and as the resistance value of the Cd535 increases, the amplification gain increases. , if the resistance value decreases, the amplification gain decreases.

On the other hand, the voltage e4 obtained at the output terminal of the operational amplifier 12 is e4 "" Kz (e+ + 1 e2)
It is. However, Kz is the amplification gain. In the present invention, the sensor has two sets of light receiving elements disposed close to each other and on substantially the same plane, so that the sensor functions not only as a speed signal detection but also as a light intensity sensor,
The magnitude of the voltage e4 corresponding to the sum of the detection signals of the two sets of light receiving elements faithfully reflects the brightness of the measurement target, and is averaged by the action of the capacitor 25 as shown in FIG. The value is used as a light intensity signal.

The voltage e4 is compared with the reference voltage V REF applied via the operational amplifier 28 in the operational amplifier 23, and a voltage e5 is obtained at the output of the operational amplifier 23, the magnitude of which is e5.
=3Ce4VREF). However, K
3 is the amplification gain. When the voltage e4 and the reference voltage V REF are equal, the voltage e5 becomes zero (e
s=o), the voltage e4 is the reference voltage VIIEF
When Cea>VIIEF), the voltage e5 becomes a positive voltage (es>O). Further, when the voltage e4 is smaller than the reference voltage V REF (e 4 <
VREF ), since the diode 31 is conductive,
The voltage e5 is kept almost zero (ei ′io)
.

The voltage e is applied to the base of the transistor 30, and the voltage e5 is at a positive voltage level (2). N or more, that is, as shown in FIG. 3(a), the voltage e4 is equal to or higher than the reference voltage V.
In a range exceeding a certain value above REF, the transistor 30 operates as an emitter follower, and its emitter current increases or decreases in accordance with the increase or decrease in the voltage e4. As a result, the current flowing through the light emitting diode 33 changes as the voltage e4 increases or decreases as shown in FIG.
The amount of light emitted changes. Therefore, the resistance value of the Cd535 that receives this light emission increases or decreases depending on the increase or decrease of the voltage e4.
It changes as shown in Figure (C). That is, the Cd535
If the current flowing through 1lds35 increases, the resistance value of the Cd535 decreases, and conversely, if the current flowing through the 1lds35 decreases, the resistance value of the Cd535 increases. Therefore, as the resistance value of the Cd535 changes, the operational amplifier 20 increases the amplification gain when the resistance value is large.
When the resistance value is small, the amplification gain decreases. In this way, the amplification gain of the operational amplifier 20 can be automatically varied in accordance with the increase or decrease in the voltage ee2. In this embodiment, CdS is used as the variable resistance element, but the variable resistance element can also be formed by an FET.

Output ■ of the speed detection device configured as above. LIT
is used as a gate control signal etc. to control the passage of count pulses from a counter, and is applied to speed measuring devices.

FIGS. 4(a) and 4(b) are schematic configuration diagrams showing other embodiments. In the figure, the operational amplifier 1
The output e3 of 0 is applied to the inverting input terminal of the operational amplifier 39 via the capacitor 37 and the resistor 3. The output terminal of the operational amplifier 39 is connected to a resistor 40.
is connected to the inverting input terminal via the inverting input terminal. Further, the non-inverting input terminal of the operational amplifier 39 is grounded.

On the other hand, the output e5 of the operational amplifier 12 is applied to a transistor 41, and the emitter of the transistor 41 is grounded via a resistor 42, and is connected via a diode 43 to a lamp 4 that emits light onto a road surface, etc. to be measured.
It is connected to one electrode of 4. Further, one electrode of the lamp 44 is grounded via a resistor 45. and,
The other electrode of the lamp 44 and the collector of the transistor 41 are connected to the positive terminal of the power supply, and the power supply voltage v
DD is applied. Note that a diode 46 provided between the base of the transistor 41 and the ground is for preventing a reverse voltage from being applied to the transistor 41. Further, the transistor 41. The configuration of the diode 46 and the resistor 42 functions as a current amplification circuit using an emitter follower, and the diode 4
3 and the resistor 45, the light source 44 as a whole
This is a light source light emission amount control means for controlling the light emission amount of the light source.

Even if the light intensity received by the light receiving element 5.6 changes significantly, the amplification gain of the amplifier circuit may be controlled by the variable gain means as described above to obtain the optimum signal from the amplification means. As shown in this embodiment, it is also possible to change the amount of reflected light reflected from the object to be measured. By controlling the amount of light emitted from the light source, the light receiving element 5.
The amount of light received by 6 is adjusted.

That is, in this embodiment, the operational amplifier 10
The output e3 is amplified by the operational amplifier 39 with a constant amplification gain, but in order to adjust the amount of light received by the light receiving element 5.6, the amount of light emitted from the lamp 44 is adjusted according to the increase or decrease in the voltages el and e2. By making it variable, it is possible to obtain an output with a good S/N ratio proportional to the speed signal.

That is, in response to an increase or decrease in the output e5 of the operational amplifier 23, the current flowing through the resistor 42 connected to the emitter of the transistor 41 increases or decreases. As a result, when the potential at point A shown in FIG. 4 et al. becomes higher than the potential at point B, a current starts to flow from point A to point B, and the current flowing through the resistor 45 increases accordingly.

Therefore, the potential at point B increases, the voltage applied to the lamp 44 decreases, and the illuminance of the lamp 44 decreases. Conversely, when the potential at point A becomes lower than the potential at point B, the current flowing from point A to point B decreases, and as a result, the voltage applied to the lamp 44 increases, and the illuminance of the lamp 44 decreases. increase. In this way, as the input signal based on the light receiving element 5.6 increases, the amount of light emitted from the lamp 44 is reduced, and as the input signal becomes weaker, the amount of light emitted is controlled to increase, thereby achieving a wide measurement range. It is possible to obtain a speed detecting device for obtaining a speed measuring device that is compatible with the present invention and can improve measurement accuracy.

〔Effect of the invention〕

As explained in detail above, according to the present invention, a good S/N is obtained by the differential output means that obtains an output corresponding to the difference between the two sets of light receiving elements, and the amplification means amplifies the output corresponding to the difference between the two sets of light receiving elements. Since the detection output obtained from the amplifying means is controlled based on the output of the adding output means that obtains an output corresponding to the sum of the outputs of the respective light receiving elements, distortion is less likely to occur even in the low frequency region. It is possible to obtain a speed detection device that can handle a wide measurement range and improve measurement accuracy.

[Brief explanation of the drawing]

1(a) and (b) are block diagrams showing the principle of the present invention, FIG. 2 is a circuit diagram showing an example of a circuit configuration applied to the speed detection device of the present invention, and FIG. 3(a) represents the relationship between the voltage e4 obtained at the output terminal of the operational amplifier 12 and the voltage e5 obtained at the output of the operational amplifier, and
Figure 3 (°C) is an explanatory diagram showing the base voltage VON at which 0 is in the active state. , FIG. 3(C) shows the voltage e4 obtained at the output terminal of the operational amplifier 12.
FIG. 4(a) is a circuit diagram showing an amplifier circuit in another embodiment, and FIG. 4(b) is another embodiment. 5 is an explanatory diagram showing the voltage e4 obtained at the output terminal of the operational amplifier 12, and FIG. 6 is a block diagram showing the configuration of a conventional AGC amplifier. , FIG. 7(a) is an explanatory diagram showing the input/output characteristics of a conventional AGC amplifier in a range where the rectified and smoothed output Eo is equal to or smaller than the reference voltage VREF (Eo≦VREF). °C), in a conventional AGC amplifier, the rectified and smoothed output Eo is larger than the reference voltage VREF (Ea >
FIG. 8 is an explanatory diagram showing the relationship between the speed signal obtained by a conventional Schmitt circuit and the hysteresis width of the Schmitt circuit. 50.51... Light receiving element, 52... Addition output means, 53... Differential output means, 54... Amplification means, 55... Comparison means, 56... Variable gain control means, 57...Light source, 58...Light source emission amount control means. Patent applicant Toyota Industries Corporation (b) Figure 1 Figure 3vA 4υ Figure 0O Vo. Figure Figure Figure

Claims (2)

[Claims] (1) A sensor having two sets of light receiving elements disposed close to each other and on substantially the same plane, an addition output means for obtaining an output corresponding to the sum of the respective outputs of the light receiving elements, and each of the light receiving elements. differential output means for obtaining an output corresponding to the difference in the outputs, the output of the differential output means is input to the amplification means, and the output of the addition output means and a predetermined amplification variable start level are provided. Comparing means for comparison is provided, variable gain control means is provided for controlling the amplification gain of the amplification means to be variable based on the output of the comparison means, and a detection output corresponding to a change in speed is obtained from the amplification means. A speed detection device featuring: (2) A sensor having two sets of light-receiving elements arranged close to each other and on substantially the same plane, a light source that contributes to the reflected light received by the sensor, and an output corresponding to the sum of the outputs of each of the light-receiving elements. and differential output means for obtaining an output corresponding to the difference between the respective outputs of the light receiving elements, the output of the differential output means is input to the amplification means, and the output of the addition output means is increased or decreased. A speed detection device comprising a light source light emission amount control means for controlling the light emission amount of the light source in response to a change in speed, and obtaining a detection output corresponding to a change in speed from the amplification means.