JP2007017293A - Stationary wave range finder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stationary wave range finder which is compatible with higher precision in measuring distance and improvement in measuring speed. <P>SOLUTION: The transmission signal with frequency changed in a step is transmitted from the signal transmission/reception part 2, and the sampling part 3 samples the stationary wave in the receiving signal with a timing synchronized with the frequency of transmission signal. The 1st distance measuring part 22 calculates the 1st distance value R1 from the time width of the amplitude fluctuation interval of the sampling wave form corresponding to the spatial propagation delay time for every frequency, and the 2nd distance measuring part 23 the 2nd distance value R2 from the vibration period of the vibration waveform generated by laying out the oscillation information in the region except the interval where the amplitude is fluctuating for every frequency of the transmission signal. The distance R1 can be obtained for every step, therefore the distance R2 of higher precision and also higher speeding can be attained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a standing wave distance measuring device that measures a distance to an object based on observation of a standing wave.

As a radar that measures the distance to an object based on a transmission signal and a reflected signal from the object, a distance measuring device that measures the distance to the object using a standing wave is disclosed in Japanese Patent Laid-Open No. 2002-357656. It is disclosed. This is because the frequency of the transmission signal is modulated stepwise, the standing wave generated by the reflected signal from the object is observed for each transmission frequency, and the phase change between the standing waves is detected. Is calculated. This method can obtain higher accuracy in short-distance measurement than a method of calculating a distance based on a delay time from transmission signal transmission to reflection signal reception.
Here, in the distance measurement by the standing wave shown in the above publication, in order to achieve both distance resolution and maximum detection distance, the frequency of the standing wave is modulated by performing frequency modulation in a wide frequency range with fine frequency steps. It is necessary to increase the number of observations.
JP 2002-357656 A

Incidentally, propagation media used for radar include electromagnetic waves, light, and ultrasonic waves. For example, simple ultrasonic waves are often used for detecting the vicinity of a vehicle.
However, when ultrasonic waves are used as the propagation medium, the propagation speed is about six orders of magnitude lower than that of electromagnetic waves, so that there is a problem that the observation time becomes longer when the number of standing wave phase observations is increased. .

In addition, when a relative speed is generated between the object and the object, an error is included in the distance measurement value. For example, Japanese Patent Application Laid-Open No. 2004-325085 discloses a technique for further improving accuracy. There has also been proposed a method of correcting the above error by performing measurement using two standing waves having different frequency steps. However, this method requires twice as much observation time.
As described above, the distance measurement using the conventional standing wave has a problem that high accuracy is obtained but it takes time.

  Therefore, in view of the above problems, an object of the present invention is to provide a standing wave distance measuring device capable of measuring a distance to an object with high accuracy and high speed regardless of a propagation medium.

  For this reason, the present invention sends a transmission signal whose frequency is changed in steps, and samples the standing wave of the reception signal due to reflection of the object at a timing synchronized with the frequency of the transmission signal. The first distance value is calculated based on the time width of the section in which the amplitude of the sampled signal varies for each frequency by the distance measuring unit, and the amplitude of the sampled signal varies by the second distance measuring unit. The second distance value is calculated based on the vibration period of the vibration waveform generated by arranging the amplitude information of the region excluding the section to be arranged for each frequency of the transmission signal, and the first distance value and the second distance value are calculated from the output control unit. The distance signal to the object is output based on the distance value.

Since the time width of the section in which the amplitude fluctuation occurs in the sampling waveform for each frequency corresponds to the spatial propagation delay time, the first distance measurement unit uses the first distance value based on the delay time and the propagation speed of the medium. Can be calculated at high speed.
In addition, since the second distance measurement unit 23 calculates the second distance value from the vibration period of the vibration waveform in which the amplitude information in the portion where the amplitude does not vary is arranged in the order of frequency, the second distance value is determined by the conventional constant. It is as accurate as the distance measurement using standing waves.
Therefore, even when a medium having a low propagation speed is used, the first distance value obtained at high speed and the second distance value with high accuracy are complemented each other, thereby increasing the accuracy and speeding up the distance measurement to the object. And can be compatible.

Next, embodiments of the present invention will be described by way of examples.
FIG. 1 is a diagram showing the configuration of the first embodiment.
The distance measuring device 1 includes a signal transmission / reception unit 2, a sampling unit 3, and a signal processing unit 4.
The signal transmission / reception unit 2 includes a frequency variable oscillator 11, an ultrasonic oscillation element 12 that outputs an ultrasonic transmission signal based on an oscillation signal from the frequency variable oscillator 11, and an ultrasonic wave that receives the ultrasonic wave and converts it into a reception signal. The receiving element 13 and the signal amplifier 14 that amplifies the reception signal of the ultrasonic receiving element 13 are provided.
The ultrasonic oscillating element 12 and the ultrasonic receiving element 13 are installed parallel to each other in the same direction, and the reflected signal from the object of the transmission signal irradiated from the ultrasonic oscillating element 12 is received by the ultrasonic receiving element 13. It is like that.

  The sampling unit 3 receives the oscillation signal from the frequency variable oscillator 11 and generates a sampling timing signal (for example, a rectangular wave having the same frequency as the transmission signal) synchronized with the transmission signal, and the sampling timing signal A reception signal sampling circuit 16 is provided for sampling and detecting the output of the signal amplifier 14 (ie, the amplified reception signal) at the timing of and storing the sampling data for each frequency step to be described later.

  Next, the signal processing unit includes a transmission frequency control unit 21 connected to the frequency variable oscillator 11, a first distance measurement unit 22 connected to the reception signal sampling circuit 16, a transmission frequency control unit 21, and a first distance measurement unit 22. And a second distance measuring unit 23 connected to the first distance measuring unit 22 and an output control unit 25 connected to the second distance measuring unit 23.

The transmission frequency control unit 21 controls the frequency of the transmission signal transmitted from the ultrasonic oscillation element 12 by controlling the oscillation signal of the frequency variable oscillator 11.
The first distance measurement unit 22 calculates the distance to the target object from the delay time between the transmission signal and the reception signal based on the amplitude fluctuation information of the sampling data output from the reception signal sampling circuit 16.

The second distance measurement unit 23 determines the amplitude information of the fixed amplitude portion of the sampling data used in the first distance measurement unit 22 based on the vibration frequency (or vibration cycle) of the vibration waveform arranged for each frequency step. Calculate the distance.
The distances to the object calculated by the first distance measuring unit 22 and the second distance measuring unit 23 are input to the output control unit 25, respectively. The output control unit 25 performs a predetermined complement processing based on the two distances input from the first distance measurement unit 22 and the second distance measurement unit 23, and outputs a final distance signal as a distance measuring device.

Hereinafter, the distance measuring operation in this embodiment will be described.
As described above, the transmission frequency control unit 21 controls the frequency variable oscillator 11 to change the frequency of the transmission signal transmitted from the ultrasonic oscillation element 12 from the minimum frequency f0 to the frequency Δf as shown in FIG. The difference is sequentially changed in steps.
In FIG. 2, a step-like transmission signal and a reception signal based on the reflection signal are shown superimposed in time series. The reception signal appears in steps like the transmission signal with a spatial propagation delay time with respect to the transmission signal.

The reception signal sampling circuit 16 samples the amplitude of the standing wave of the reception signal at a predetermined time difference Δt from the frequency change point (t0, t1, t2,...) Of the transmission signal. Thereby, a phase change appears in the amplitude of the standing wave according to the frequency change.
That is, FIG. 3 shows an example of amplitude variation of the standing wave when the frequency of the transmission signal (transmission frequency) is changed from 40.04 kHz to 0.06 kHz when the object is at a distance of 1 m. In FIG. 3, the frequency is increased downward.
When the amplitude at the time tm after the above-described time difference from the time tm of the frequency change point, that is, the amplitude at the time tm + Δt is seen, it can be seen that the phase change is caused by changing the frequency.

Furthermore, FIG. 4 shows a waveform when the frequency of the transmission signal is changed from 40 kHz to 50 kHz with respect to different distances to the object, and the amplitude at the time difference Δt from the frequency change point is sampled. From this, it can be seen that the vibration frequency of the sampling waveform increases (the period decreases) as the distance to the reflecting object increases.
Therefore, the distance can be obtained from the state of amplitude fluctuation at each frequency step of the standing wave of the reception signal sampled by the reception signal sampling circuit 16.

More specifically, when the frequency of the transmission signal is f, the observation position of the standing wave of the reception signal is x, and the amplitude is 1, the transmission signal St is generally expressed by Expression (1).
St (f, x) = exp (j · 2πf · x / V) (1)
Here, V is the speed of propagation through the propagation medium, and is about 340 m / sec for ultrasonic waves.
When an object exists at a position of distance d (m), its reflection efficiency is γ, and the phase change amount is φ (radian), the reflection signal Sr is expressed by equation (2).
Sr (f, x) = γ · exp (jφ) · exp (j · 2πf · (2d−x) / V)
... (2)

From Expressions (1) and (2), the combined signal A of the transmission signal and the reception signal is expressed by Expression (3).
A (f, x) = | St (f, x) + Sr (f, x) |
= | Exp (j · 2πf · x / V) {1 + γ · exp (j · 2πf · (2d−x) / V + φ)} | (3)
The power P of the combined signal is expressed as shown in Equation (4).
P (f, x) = {A (f, x)} ²
= 1 + γ ² + 2γ · cos {2πf · 2 (d−x) / V + φ}
... (4)

From equation (4), the power P (f, 0) of the combined signal when observed at the observation position x = 0 (m) is
P (f, 0) = 1 + γ ² + 2γ · cos {2πf · 2d / V + φ} (5)
Thus, it can be seen that P (f, 0) in the equation (5) is periodic with respect to the frequency f, and the period is V / 2d.
Therefore, the distance d to the object can be calculated by observing the phase variation period (or frequency) of the power P (f, 0) of the combined signal for each frequency of the transmission signal.

In the reception signal sampling circuit 16 of the present embodiment, sampling is performed at a frequency 2 × (f0 + Δf) of the frequency f0 + Δf at one frequency step of the transmission signal in FIG. 2, for example, the frequency step from time t1 to t2.
Here, the received signal is observed at the frequency f0 for the delay time portion of the spatial propagation, and is observed at the frequency f0 + Δf thereafter. Therefore, the sampling waveform is shown by a solid line in FIG. 5, and the phase change occurs due to the difference in frequency in the delay time portion, and the amplitude fluctuation occurs. In addition, the broken line in FIG. 5 shows the case where it samples with the frequency of a transmission signal.

The first distance measuring unit 22 measures the time width in which the amplitude fluctuation due to the phase change occurs to obtain the spatial propagation delay time Δt, and calculates the distance R1 to the object by the following equation.
R1 = V · Δt / 2 (6)
The first distance measurement unit 22 outputs the calculated distance R1 to the output control unit 25, and outputs amplitude information after the spatial propagation delay time Δt to the second distance measurement unit 23.

The second distance measuring unit 23 obtains the distance to the object based on the phase fluctuation period detailed with the respective equations.
The amplitude information acquired by the second distance measurement unit 23 from the first distance measurement unit 22 changes according to the frequency of the transmission signal, and the signal intensity of the sampling waveform shown in FIG.
In the second distance measuring unit 23, the amplitude information is rearranged in order of frequency, and a vibration waveform for each frequency step similar to that shown in FIG. 4 is obtained, and from the phase variation period of the power P in Expression (5) to the object. The distance R2 is calculated.

In the present embodiment, the transmission frequency control unit 21, the variable frequency oscillator 11 and the ultrasonic oscillation element 12 constitute a transmission means in the invention, and the ultrasonic reception element 13 and the signal amplifier 14 constitute a reception means.
The sampling unit 3 including the sampling timing generation circuit 15 and the reception signal sampling circuit 16 constitutes sampling means.

The present embodiment is configured as described above, and the received signal is sampled at the sample timing synchronized with the transmission signal within the time width of one frequency step, and the first distance measuring unit 22 samples the sampling waveform for each frequency step. Since the distance R1 is calculated on the basis of the delay time and the propagation speed of the medium, the time width in which the amplitude fluctuations occur in the space propagation delay time, the so-called data update cycle is short and the distance to the object at high speed Is required.
On the other hand, the second distance measuring unit 23 calculates the distance R2 from the vibration period (or frequency) of the vibration waveform in which the amplitude information in the portion where the amplitude does not vary in the same sampling waveform is arranged in the frequency order. The distance to the object is calculated with high accuracy as in the distance measurement using waves.

Therefore, the output control unit 25 acquires the distance R1 which is high speed but slightly low in accuracy from the first and second distance measurement units 22 and 23 and the distance R2 which is high in accuracy but takes time to update data. Depending on the setting, the distance R1 can be output quickly, and then the distance R2 can be output, or a distance signal that complements the distances R1 and R2 can be output.
In particular, with respect to complementation, when the distance R2 is used as a base, the distance R1 is used to compensate for the change in distance until the next distance output from the second distance measurement unit, thereby substantially increasing the data update cycle. Can be
For this reason, both high accuracy of measurement by standing wave ranging and high speed sufficient for in-vehicle use are achieved even though ultrasonic waves having a low propagation speed are used as the propagation medium.

In the above embodiment, the frequency of the transmission signal is changed so as to increase sequentially with the frequency difference from the minimum frequency f0 to Δf as shown in FIG. 2, but as a modification, with a relatively large frequency difference. It can also be raised while repeating high and low.
FIG. 6 shows an example of this, which corresponds to an alternate arrangement of the first half and the second half of the time axis in FIG. That is, when the total number of frequencies is n, the transmission frequency control unit 21 controls the frequency variable oscillator 11 to perform frequency steps from the first half minimum frequency f0 to the intermediate frequency f0 + ((n / 2) −1) · Δf. And frequency steps from the intermediate frequency f0 + (n / 2) · Δf to the maximum frequency f0 + (n−1) · Δf are alternately set, and the minimum frequency f0 and the times t1 to t2 are set between the times t0 and t1. F0 + (n / 2) · Δf during the period, f0 + Δf between the times t2 and t3, f0 + ((n / 2) +1) · Δf between the times t3 and t4, and f0 + 2Δf between the times t4 and t5. Next, the transmission frequency is changed.

  According to this, for example, the received signal in the frequency step from the time t1 to the time t2 is observed at the frequency f0 in the delay time part, and thereafter observed at f0 + (n / 2) · Δf. Increases as (n / 2) · Δf, and as shown in FIG. 7, the amplitude fluctuation in the delay time portion in the sampling waveform is particularly noticeable. In the figure, the solid line indicates sampling at a frequency twice the frequency of the transmission signal, and the broken line indicates sampling at the frequency of the transmission signal.

As the frequency of the transmission signal changes, as shown in FIG. 8, the signal intensity of each sampling waveform varies greatly depending on the frequency in accordance with the change.
The second distance measurement unit 23 sorts the amplitude information in order of frequency and observes the vibration waveform for each frequency step.
In this modified example, since the amplitude fluctuation of the delay time portion in the sampling waveform appears significantly as described above, the spatial propagation delay time Δt can be observed with higher accuracy, and the accuracy of the distance R1 calculated by the first distance measuring unit 22 can be observed. The advantage that is improved.

Next, a second embodiment will be described.
FIG. 9 shows the configuration of the second embodiment.
The distance measuring device 1A includes a signal transmission / reception unit 2, a sampling unit 3, and a signal processing unit 4A.
The signal processing unit 4A includes a relative speed calculation unit 24, and the relative speed calculation unit 24 is connected to the first distance measurement unit 22, the second distance measurement unit 23A, and the output control unit 25A, respectively.
The relative speed calculation unit 24 calculates the relative speed with the object based on the output of the first distance measurement unit 22, and outputs the result to the second distance measurement unit 23A and the output control unit 25A. Processing in the second distance measurement unit 23A and the output control unit 25A will be described later.
Other configurations are the same as those of the first embodiment.

The relative speed calculation unit 24 observes the change of the distance R1 calculated by the first distance measurement unit 22 for each frequency step, and calculates the relative speed with the object.
The change of the distance R1 for each frequency step is a change of the distance R1 over time because the frequency step changes every predetermined time, and becomes a relative speed.

In the first embodiment, the power of the combined signal of the transmission signal and the received signal is expressed by Equation (5) on the assumption that there is no relative speed, but when there is a relative speed between the object and the object, The power P is expressed by the following equation including a time parameter, where s is the relative speed and dk is the distance to the object at time tk.
P (f, 0, t) = {A (f, 0, t)} ²
= 1 + γ ² + 2γ · cos {4πf · {dk
+ S · (t−tk)} / V + φ} (7)
That is, if the time required for observation is T, the phase variation period of the power of the combined signal is generalized to V / {2 (d + s · T)}, and therefore information on the relative speed s is used to obtain the distance d. Need.

Therefore, in the second distance measurement unit 23A of the present embodiment, the relative speed s calculated by the relative speed calculation unit 24 is substituted into Expression (7), and the amplitude varies in the sampling waveform from the first distance measurement unit 22. The distance R <b> 2 is calculated by observing the vibration period (or frequency) of the vibration waveform in which the amplitude information in the part that has not been arranged in order of frequency.
The output control unit 25A outputs a distance signal obtained by mutually complementing the distances R1 and R2 in the same manner as the output control unit 25 in the first embodiment, and the relative speed input from the relative speed calculation unit 24 upon request. Output.

The present embodiment is configured as described above, and the relative speed s is obtained from the change for each frequency step of the distance R1 obtained by the first distance measurement unit 22 by the relative speed calculation unit 24, that is, the change with respect to time. The speed is used for vibration waveform observation in the second distance measuring unit 23A. For this reason, it is possible to suppress “error due to relative speed” that occurs when information on the relative speed s is lacking even though there is actually a relative speed.
Therefore, this is particularly effective for a vehicle in which the relative speed with respect to an object such as a preceding vehicle on the traveling path fluctuates from start to finish.

Note that the modification of the first embodiment can be applied to the second embodiment as it is.
In each embodiment, an ultrasonic wave is used as a signal medium. However, the present invention is not limited to this, and light including electromagnetic waves, infrared rays, and the like can be arbitrarily selected.

It is a figure which shows the structure of a 1st Example. It is a figure which shows a transmission signal and a received signal. It is a figure which shows the amplitude fluctuation | variation of a standing wave when changing a transmission frequency. It is a figure which shows the change of the frequency of the amplitude fluctuation | variation by the distance change with a target object when changing a transmission frequency. It is a figure which shows the sampling result in one frequency step. It is a figure which shows the transmission signal and reception signal in a modification. It is a figure which shows the sampling result in one frequency step in a modification. It is a figure which shows the change for every frequency of a sampling waveform. It is a figure which shows the structure of a 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A ranging apparatus 2 Signal transmission / reception part 3 Sampling part 4, 4A Signal processing part 11 Frequency variable oscillator 12 Ultrasonic oscillation element 13 Ultrasonic reception element 14 Signal amplifier 15 Sampling timing generation circuit 16 Reception signal sampling circuit 21 Transmission frequency control Unit 22 First distance measurement unit 23, 23A Second distance measurement unit 24 Relative speed calculation unit 25, 25A Output control unit

Claims (6)

Transmitting means for transmitting a transmission signal whose frequency is changed stepwise;
A receiving means for detecting a reflected signal reflected from the object by the transmission signal and outputting it as a received signal;
Sampling means for sampling the standing wave of the received signal at a timing synchronized with the frequency of the transmitted signal;
A first distance measuring unit that calculates a first distance value based on a time width of a section in which the amplitude varies for each frequency in the signal sampled by the sampling unit;
Second distance for calculating the second distance value based on the vibration period of the vibration waveform generated by arranging the amplitude information of the region excluding the section where the amplitude fluctuates in the sampled signal for each frequency of the transmission signal. A measurement unit;
An output control unit that outputs a distance signal to an object based on the first distance value calculated by the first distance measurement unit and the second distance value calculated by the second distance measurement unit; A standing wave distance measuring device comprising: A relative speed calculation unit that calculates a relative speed of the object based on a change in the frequency step of the distance calculated by the first distance measurement unit;
The second distance measuring unit corrects an error due to the relative speed of the second distance value calculated by the second distance measuring unit, using the relative speed calculated by the relative speed calculating unit. The standing wave ranging device according to claim 1. Transmitting means for transmitting a transmission signal whose frequency is changed stepwise;
A receiving means for detecting a reflected signal reflected from the object by the transmission signal and outputting it as a received signal;
Sampling means for sampling the standing wave of the received signal at a timing synchronized with the frequency of the transmitted signal;
A standing wave ranging apparatus comprising: a distance measuring unit that calculates a distance to an object based on a time width of a section in which an amplitude varies for each frequency in a signal sampled by the sampling unit. 4. The transmission device according to claim 1, wherein the transmission unit alternately transmits a frequency step from a minimum frequency to an intermediate frequency and a frequency step from the intermediate frequency to the maximum frequency as a transmission signal. 5. The standing wave ranging device described. 5. The constant according to claim 1, wherein the transmission unit includes an ultrasonic oscillation element, the reception unit includes an ultrasonic reception element, and the medium of the transmission signal is an ultrasonic wave. Standing wave ranging device. A distance measuring method in a standing wave ranging device,
Send a transmission signal with the frequency changed in steps,
Sample the standing wave of the received signal at a timing synchronized with the frequency of the transmitted signal,
In the sampled signal, the first distance value is calculated based on the time width of the section where the amplitude varies for each frequency,
Arranging the amplitude information of the region excluding the section where the amplitude varies in the sampled signal for each frequency of the transmission signal, and calculating the second distance value based on the vibration period of the vibration waveform,
A distance measuring method in a standing wave ranging apparatus, wherein a distance signal to an object is output based on the first distance value and the second distance value.

Images