JPH06313769A - Space filter type speed measuring apparatus, speed control system having the same and automobile - Google Patents

Abstract

PURPOSE:To provide a space filter type speed measuring apparatus, a speed control system having the same and an automobile in which an error in the case of averaging is reduced by sensing a period in which an amplitude of an output signal is smaller than a predetermined value and complementing an output in this period. CONSTITUTION:An amplitude discriminator 5 decides whether an output amplitude from a tracking filter 3 is larger than a predetermined value or not. A discriminator 7 selects an output of a waveform shaper 4 in response to a decision result if the amplitude is decided to be larger than the predetermined value, or the discriminator selects an output of a PLL circuit 6 if the amplitude is smaller to output it. The number of output pulses is measured to detect a speed. Thus, even if the amplitude is extremely small, the output is complemented by the circuit 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial filter type speed measuring device which has been subjected to processing for reducing measurement errors, a speed control system having the same, and an automobile.

[0002]

2. Description of the Related Art Conventionally, in a spatial filter type velocity measuring device of this type, a frequency signal proportional to the velocity of a relatively moving measuring object is converted into a voltage, a current, a digital code or the like and output. There is. This frequency signal is not a single frequency signal because the number of pitches of the spatial filter is generally finite and the measurement object has a random pattern, so it is not a narrow-band signal with a center frequency proportional to the speed of the measurement object. It is a regular signal. Therefore, in order to measure the speed with high accuracy, it is essential to perform averaging when converting the frequency signal into another physical quantity.

[0003]

However, in such an averaging process, the signal amplitude may be extremely small and binarization may not be possible due to the irregularity of the spatial filter output signal. In that case. Since it is not possible to measure the frequency, it becomes an error factor in averaging, and the speed measurement accuracy deteriorates.

The present invention solves the above-described problems, and detects a period in which the amplitude of the output signal is smaller than a predetermined value, and during this period, the output is complemented by a signal before that, so that averaging is performed. It is an object of the present invention to provide a spatial filter type speed measuring device with high measurement accuracy, a speed control system including the same, and an automobile, in which the error in the case of reducing the error is reduced.

[0005]

In order to achieve the above object, the invention of claim 1 is a spatial filter system for measuring a velocity by measuring a center frequency proportional to the velocity of a relative moving object. In the velocity measuring device, a waveform shaping circuit that converts a sinusoidal signal output from an analog processing system that processes reflected light from the measurement target into a pulse, and whether the amplitude of the sinusoidal signal is larger than a predetermined value. If the amplitude discriminating circuit discriminates that the amplitude is larger than a predetermined value, the amplitude discriminating circuit discriminating whether the amplitude is larger than a predetermined value is outputted from the waveform discriminating circuit. When the amplitude is determined to be smaller than a predetermined value, the PLL circuit outputs are respectively selected, and a discrimination circuit for outputting to the PLL circuit input is provided. . According to a second aspect of the present invention, in the spatial filter type velocity measuring device that measures the velocity by measuring the center frequency proportional to the velocity of the relatively moving measuring object, the reflected light from the measuring object is processed. A waveform shaping circuit that converts the sinusoidal signal output from the analog processing system into a pulse, an amplitude determination circuit that determines whether the amplitude of the sinusoidal signal is greater than a predetermined value, and a phase at the waveform shaping circuit output. A PLL circuit that outputs a locked pulse is provided, and the PLL circuit, when the amplitude determination circuit determines that the amplitude has become smaller than a predetermined value, controls the control voltage of a voltage controlled oscillation circuit incorporated in the PLL circuit. It has a sample hold circuit for holding the value before that.

According to a third aspect of the present invention, there is provided a spatial filter type velocity measuring device for measuring a velocity by measuring a center frequency proportional to a velocity of a measuring subject which moves relatively, and a reflected light from the measuring subject. A waveform shaping circuit for converting a sinusoidal signal output from an analog processing system for processing into a pulse, an amplitude discriminating circuit for discriminating whether or not the amplitude of the sinusoidal signal is larger than a predetermined value, and the waveform shaping circuit. The F / V conversion circuit for converting the frequency of the pulse output from the circuit into a voltage, and the output of the F / V conversion circuit when the amplitude is determined to be smaller than a predetermined value by the amplitude determination circuit, And a sample and hold circuit that holds the value of. According to a fourth aspect of the present invention, in the spatial filter type velocity measuring apparatus according to the first to third aspects, the amplitude discriminating circuit includes a low-pass filter for envelope detection, and the low-pass filter for envelope detection is proportional to the detection speed. It is a tracking low-pass filter whose pass band changes.

According to a fifth aspect of the present invention, in the spatial filter type velocity measuring apparatus according to the first to fourth aspects, it is detected that the output of the waveform shaping circuit does not exist for a predetermined time or longer, and the output is forcibly set to a stop level. It is provided with a running stop switching circuit for setting. The invention according to claim 6 is a speed control system comprising the spatial filter type speed measuring device according to claims 1 to 5, wherein the speed is controlled by controlling the brake or the accelerator by the output of this device. The invention according to claim 7 is an automobile equipped with the speed control system according to claim 6.

[0008]

According to the structure of the first aspect, the sine wave signal is output from the analog processing system that processes the reflected light from the measurement object, and the sine wave signal is pulsed by the waveform shaping circuit and output to the discrimination circuit. . Further, the amplitude discriminating circuit discriminates whether or not the amplitude of the sinusoidal signal is larger than a predetermined value, and according to the discrimination result, the discriminating circuit discriminates the waveform if the amplitude is larger than the predetermined value. The shaping circuit output is selected, and if it is determined to be small, the PLL circuit output is selected and output to the PLL circuit. The PLL circuit outputs a phase-locked pulse to the output of the waveform shaping circuit. The number of pulses output by the discrimination circuit is measured, and the speed is calculated from this measured number. As described above, when the amplitude is smaller than the predetermined value, the output of the PLL circuit is measured, so that even if the amplitude is extremely small, the output is complemented by the signal immediately before that.

According to the second aspect of the invention, the sine wave signal is output from the analog processing system that processes the reflected light from the object to be measured, and the sine wave signal is pulsed by the waveform shaping circuit and output to the PLL circuit. . When the amplitude determination circuit determines that the amplitude of the sinusoidal signal has become smaller than the predetermined value, the sample hold circuit with the built-in PLL circuit holds the control voltage of the voltage controlled oscillator circuit with the built-in PLL circuit at the immediately preceding value. . The PLL circuit outputs a phase-locked pulse to the output of the waveform shaping circuit. The number of pulses output by the PLL circuit is measured, and the speed is calculated from this measured number. As described above, when the amplitude is smaller than the predetermined value, the control voltage is held at the immediately preceding value, so that the output is complemented by the immediately preceding signal even when the amplitude is extremely small.

According to the third aspect of the present invention, the sine wave signal is output from the analog processing system that processes the reflected light from the object to be measured, and the sine wave signal is pulsed by the waveform shaping circuit to generate the F / V conversion circuit. To the sample hold circuit. Further, when the amplitude determination circuit determines that the amplitude of the sinusoidal signal has become smaller than the predetermined value, the sample hold circuit holds the output of the F / V conversion circuit at the previous value. The speed is calculated from the output of the sample hold circuit. By doing so, even when the amplitude is extremely small, the output is complemented by the signal immediately before that.

According to the fourth aspect of the invention, the envelope detection low-pass filter in the amplitude discriminating circuit is a tracking low-pass filter, whereby the pass band can be changed according to the detection speed, and a wide speed range can be detected. Can handle. According to the configuration of claim 5, by the running stop switching circuit,
When it is detected that the waveform shaping circuit output does not exist for a certain time or more, it is determined that the measurement object is in a stopped state, and the output is forcibly set to the stop level. As a result, the speed measuring device does not continue to output the speed signal corresponding to some speed even when the object to be measured is stopped. According to the configuration of claim 6, by controlling the brake or the accelerator by the output of this device, efficient braking or acceleration becomes possible. According to the configuration of claim 7, efficient braking / accelerating ability can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment embodying the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram of a processing circuit of a spatial filter type velocity measuring device. This processing circuit includes two sets of comb-tooth type photodiodes (hereinafter referred to as PD) 1 that form a spatial filter, and a differential amplifier circuit 2 that removes an in-phase component from the outputs of the two sets of comb-tooth type PD 1.
A tracking filter 3 for removing a noise frequency component by changing a pass band in proportion to a detection speed; a waveform shaping circuit 4 for converting a sinusoidal signal output from the tracking filter 3 into a pulse; and a tracking filter 3 The amplitude discriminating circuit 5 for discriminating whether or not the amplitude of the sinusoidal signal outputted from the circuit is larger than a predetermined value set in advance, and the PLL for outputting a phase locked pulse to the output of the waveform shaping circuit 4. Locked loop) circuit 6
And the waveform shaping circuit 4 based on the discrimination result of the amplitude discrimination circuit 5.
Discriminating circuit 7 for selecting and outputting either the output of the above or the output of the PLL circuit 6, a counter 8 for measuring the number of output pulses of the discriminating circuit 7, a latch circuit 9 for latching the output of the counter 8, and a latch The D / A converter 10 converts the output of the circuit 9 into an analog value.

FIG. 2 shows a specific configuration of the amplitude discriminating circuit 5 of this embodiment. The amplitude discrimination circuit 5 includes a tracking filter 3
An amplifier circuit 11 for amplifying the output from the amplifier, an absolute value circuit 12 for full-wave rectifying the amplified signal, an LPF (low-pass filter) 13 for detecting the envelope, and an amplitude of the signal passed through the LPF 13 and It is composed of a comparator 14 that compares a predetermined value that has been set. FIG. 3 shows waveforms at respective portions (a) to (f) in FIG. As shown in FIG. 3A, the output from the tracking filter 3 shows a sinusoidal waveform in which the period is substantially constant and the amplitude largely changes with time, and a portion A where the amplitude is extremely small and frequency measurement is difficult is performed. Contains.

The output from the tracking filter 3 is input to the amplitude discriminating circuit 5, amplified in the amplifying circuit 11, and full-wave rectified in the absolute value circuit 12 as shown in FIG. Then, as shown in FIG. 3C, the envelope is detected by the LPF 13, and the amplitude is measured. Then, in the comparator 14,
The measured amplitude is compared with a predetermined threshold value B set in advance, and as shown in FIG. 3D, when the amplitude is larger than the threshold value B, it is low (denoted as L) and small. At this time, it is outputted to the discrimination circuit 7 as a high (H) binary output.

On the other hand, from the waveform shaping circuit 4, FIG.
As shown in, the sinusoidal signal output from the tracking filter 3 is converted into a pulse and output. In the discrimination circuit 7, as shown in FIG.
When the output of L is L, the output of the waveform shaping circuit 4 is selected, and when the output of the amplitude discriminating circuit 5 is H, the output of the PLL circuit 6 is selected and output to the counter 8 and the input unit of the PLL circuit 6. To be done. Since the PLL circuit 6 continues to output the pulse locked to the output of the waveform shaping circuit 4 in the stable state, when the output amplitude of the tracking filter 3 becomes smaller than the threshold value B (the output of the amplitude determination circuit 5 is H In the case of), a pulse having the same frequency as the output of the waveform shaping circuit 4 immediately before becoming small is output to the counter 8 and the input part of the PLL circuit 6. Therefore, the leakage of the pulse to be input to the counter 8 is eliminated, stable frequency measurement becomes possible, and the error in averaging can be suppressed. Although the output of the discrimination circuit 7 is input to the counter 8 in this embodiment, the output of the PLL circuit 6 is input to the counter 8.
May be input to.

Next, a second embodiment will be described with reference to FIG. The PLL circuit 26 of this embodiment includes a phase comparator 21 for comparing the phases of the output of the waveform shaping circuit 4 and the output of the VCO (voltage controlled oscillator circuit) 24, an LPF 22, and
It is composed of an S / H (sample and hold) circuit 23 that holds a signal that has passed through the LPF 22, and a VCO 24 that changes the output oscillation frequency according to an input control voltage. When the amplitude discriminating circuit 5 discriminates that the output amplitude of the tracking filter 3 has become smaller than a predetermined value, the amplitude discriminating circuit 5 outputs a sample pulse to the S / H circuit 23, and the S / H circuit 23 outputs VCO2.
By holding the control voltage of No. 4 at the immediately preceding value, the same effect as that of the first embodiment can be obtained.

Next, a third embodiment will be described with reference to FIG. In this embodiment, the F / V conversion circuit 31 and the S / H circuit 3 are used instead of the PLL circuit 26 of the second embodiment.
3 is used. When the amplitude discriminating circuit 5 discriminates that the output amplitude of the tracking filter 3 has become smaller than a predetermined value, the S / H circuit 33 holds the output voltage of the F / V converting circuit 31 at the immediately preceding value.
It is possible to prevent sudden output changes such as waveform breakage, and stable voltage output is possible.

In the first to third embodiments described above, measures for improving the accuracy of amplitude discrimination will be described. Change cycle of output amplitude of tracking filter 3 (envelope cycle)
Is obviously an amount larger than the signal period and proportional to the signal period, that is, proportional to the velocity of the measuring object. Therefore, by using the envelope detection LPF 13 built in the amplitude determination circuit 5 as a tracking LPF whose pass band changes in proportion to the detection speed, reliable envelope detection can be performed even in a wide speed range. This enables the accuracy of amplitude discrimination.

Next, a fourth embodiment will be described with reference to FIGS. 6 and 7. The present embodiment is a measure for processing in a special case during the complementary processing. Consider a special case in which the target object stops while the output amplitude of the tracking filter 3 remains smaller than a predetermined value. At this time, since the circuit is in the process of complementing, there is an inconvenience of continuously outputting a value corresponding to some speed from the speed measuring device, which causes a measurement error. Therefore, by using the running stop switching circuit 32, this inconvenient state is avoided. This running stop switching circuit 3
2 detects that the output of the waveform shaping circuit 4 does not exist for a certain time or longer, and forcibly sets the output to the stop level.

This will be described in detail with reference to FIG. 7. The run stop switching circuit 32 detects the output state of the waveform shaping circuit 4, and the retriggerable one-shot multivibrator 41.
A stop voltage output circuit 42 that outputs a stop voltage (for example, 1 V), an output of the S / H circuit 33, and a stop voltage output circuit 4
It is composed of switching elements 43 and 44 for switching between the two outputs. The retriggerable one-shot multivibrator 41 has two output terminals Q and Q bar, and signals from each other are output from the output terminals Q, so that one of the switching elements 43 and 44 is turned on accordingly. The other one is made non-conductive. Under normal conditions,
The switching element 43 is turned on, and the output of the S / H circuit 33 becomes the output of the running stop switching circuit 32. When the output of the waveform shaping circuit 4 does not exist for a certain period of time or more, the switching element 44 is turned on, and the output of the stop voltage output circuit 42 becomes the output of the running / stop switching circuit 32, whereby the target object may be stopped. To be detected.

An antilock brake system (ABS) or a traction control system (TCL) is constructed by using the above spatial filter type speed measuring device and controlling the brake or accelerator by the output of this device. it can. And for cars such as passenger cars, buses, trucks, trailers,
By installing ABS or TCL, efficient braking / accelerating ability can be obtained.

[0022]

As described above, according to the invention of claim 1,
Since the spatial filter output signal is an irregular signal, the signal amplitude may be extremely small and binarization may not be possible.
Even at that time, the frequency can be measured by complementing with the PLL circuit. As a result, the error can be suppressed during averaging, and the speed measurement value becomes highly reliable. According to the second aspect of the present invention, when the signal amplitude is extremely small and binarization cannot be performed, the control voltage of the voltage controlled oscillation circuit with the built-in PLL circuit is held at the immediately preceding value and complemented. The same effect as in the case of can be obtained. According to the third aspect of the invention, when the signal amplitude is extremely small and binarization cannot be performed, the output of the F / V conversion circuit is held at the immediately preceding value, so that abrupt output changes such as waveform cracking can be prevented. , Stable voltage output is possible, and speed measurement accuracy is improved.

According to the invention of claim 4, since the low-pass filter for envelope detection in the amplitude discriminating circuit is a tracking low-pass filter, the pass band can be changed corresponding to the detection speed, and a wide speed range can be obtained. Even with this, reliable envelope detection is possible. Therefore, the accuracy of the amplitude determination in the amplitude determination circuit is improved, and the speed measurement accuracy is improved. According to the invention of claim 5, when the target object suddenly stops during the complementary measurement, the stop level is forcibly output after a certain period of time, so that the running level does not continue to be output when the target object stops. Therefore, it is possible to avoid malfunction caused by performing the complementary processing. According to the invention of claim 6, the speed measurement value becomes more accurate than the conventional one, so that it becomes possible to perform efficient braking or accelerator control by this output, thereby shortening the braking distance or achieving good acceleration. Can be expected. According to the invention of claim 7, since the braking distance is shortened and the acceleration performance is improved, the safety of the automobile is enhanced.

[Brief description of drawings]

FIG. 1 is a block diagram of a processing circuit of a spatial filter type velocity measuring device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an amplitude discriminating circuit in the speed measuring device.

FIG. 3 is a time chart showing waveforms in each part of FIG.

FIG. 4 is a block diagram of a processing circuit of a spatial filter type velocity measuring device according to a second embodiment.

FIG. 5 is a block diagram of a processing circuit of a spatial filter type velocity measuring device according to a third embodiment.

FIG. 6 is a block diagram of a processing circuit of a spatial filter type velocity measuring device according to a fourth embodiment.

FIG. 7 is a block diagram of a run / stop switching circuit in the speed measuring device.

[Explanation of symbols]

 3 tracking filter 4 waveform shaping circuit 5 amplitude discrimination circuit 6,26 PLL (phase locked loop) circuit 7 discrimination circuit 8 counter 23,33 S / H (sample hold) circuit 24 VCO (voltage controlled oscillation circuit) 31 F / V conversion Circuit 32 Run stop switching circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Takagi 10 Ouron Co., Ltd., Hanazono Dodocho, Ukyo-ku, Kyoto City, Kyoto Prefecture

Claims (7)

[Claims] 1. A spatial filter type velocity measuring device for measuring velocity by measuring a center frequency proportional to the velocity of a relatively moving measuring object, wherein an analog process for processing reflected light from the measuring object. A waveform shaping circuit that converts the sinusoidal signal output from the system into a pulse, an amplitude determination circuit that determines whether the amplitude of the sinusoidal signal is greater than a predetermined value, and a phase lock to the waveform shaping circuit output. A PLL circuit that outputs a pulse, and the waveform shaping circuit output when the amplitude is determined to be larger than a predetermined value by the amplitude determination circuit, and the PLL circuit is output when the amplitude is determined to be smaller than a predetermined value. A spatial filter type velocity measuring device, comprising: a discrimination circuit for selecting a circuit output and outputting the selected circuit output to the PLL circuit input. 2. A spatial filter type velocity measuring device for measuring a velocity by measuring a center frequency proportional to a velocity of a relative moving measuring object, wherein an analog process for processing reflected light from the measuring object. A waveform shaping circuit that converts the sinusoidal signal output from the system into a pulse, an amplitude determination circuit that determines whether the amplitude of the sinusoidal signal is greater than a predetermined value, and a phase lock to the waveform shaping circuit output. And a PLL circuit that outputs a pulse, wherein the PLL circuit sets the control voltage of the voltage controlled oscillation circuit built in the PLL circuit to the previous value when the amplitude is determined to be smaller than a predetermined value by the amplitude determination circuit. A spatial filter type velocity measuring device having a sample and hold circuit for holding at a value of. 3. A spatial filter type velocity measuring device for measuring a velocity by measuring a center frequency proportional to the velocity of a relative moving measuring target, wherein an analog process for processing reflected light from the measuring target. A waveform shaping circuit that converts the sinusoidal signal output from the system into a pulse, an amplitude determination circuit that determines whether the amplitude of the sinusoidal signal is greater than a predetermined value, and a pulse output from the waveform shaping circuit The F / V conversion circuit for converting the frequency of the above into a voltage and the output of the F / V conversion circuit is held at the previous value when the amplitude determination circuit determines that the amplitude has become smaller than a predetermined value. A spatial filter type velocity measuring device comprising a sample and hold circuit. 4. The spatial filter type velocity measuring device according to claim 1, wherein the amplitude discriminating circuit includes an envelope detection low-pass filter, and the envelope detection low-pass filter is proportional to the detection velocity. A spatial filter type velocity measuring device, which is a tracking low-pass filter having a variable pass band. 5. The spatial filter type speed measuring device according to claim 1, wherein the output of the waveform shaping circuit is detected for a predetermined time or more and the output is forcibly set to a stop level. A spatial filter type velocity measuring device comprising a circuit. 6. A speed control system comprising the spatial filter type speed measuring device according to any one of claims 1 to 5, wherein the speed is controlled by controlling a brake or an accelerator by an output of the device. 7. An automobile equipped with the speed control system according to claim 6.