JP5581174B2 - Obstacle detection device - Google Patents

Description

  The present invention relates to an obstacle detection device that detects an obstacle using a reflected wave.

  Conventionally, an obstacle is detected using a signal wave propagating in a space such as a microwave. For example, the high frequency signal from the transmission circuit is turned on / off to be pulsed and transmitted to the outside of the apparatus, the reflected wave from the obstacle of the transmission is received, and the high frequency signal and the reception wave from the transmission circuit are received. And AM detection. The obtained detection waveform is differentiated by a differentiation circuit, the rising edge of the reflected wave is detected from the positive differential output to obtain the reception start time, and the distance to the object is calculated based on the time difference from the transmission start time. An obstacle detection device that detects an obstacle is known (see, for example, Patent Document 1). In this apparatus, in order to acquire a time difference, a voltage-time conversion process of a sawtooth waveform is performed, or a process of counting the number of sampling pulses is performed.

  Here, with reference to FIG. 12 and FIG. 13, a general example of the related art for obtaining a time difference using a pulse counter and obtaining a distance to an obstacle will be described. As shown in FIG. 12, the circuit portion related to the time difference acquisition includes a transmission unit 91, a reception unit 92, a clock generation unit 93, and a counter 94. For example, it is assumed that the reception start time is detected by differential output as described above. Based on the information on the transmission start time from the transmission unit 91 and the information on the reception start time from the reception unit 92, the counter 94 counts the number of clock pulses (n Count). The obtained time difference δT is the time difference between the rising times of the transmission signal and the reception signal as shown in FIGS. 13A and 13B, and the clock pulse is larger than the time difference δT as shown in FIG. 13C. This is a pulse train of high frequency (frequency fc = 1 / Tc) with a sufficiently short period Tc. As shown in FIG. 13D, the counter 94 obtains the time t1 = n / fc = n × Tc as the measurement value of the time difference δT. The time t1 is a round trip time of the signal wave to the obstacle, and the distance L to the obstacle using the propagation velocity c of the signal wave (radio wave, light, ultrasonic wave, etc.) is L = c × t1 / 2 Desired.

JP 2002-365362 A

However, in order to obtain the distance L, in the obstacle detection apparatus using the time t1, which is a measured value of the time difference δT as shown in Patent Document 1 and FIGS. In addition, it is necessary to increase the frequency fc of the clock pulse. The propagation speed c of the signal wave at the distance L = c × t1 / 2 is c≈3 × 10 ⁸ m when the signal wave is a radio wave or light. The distance error ΔL is ΔL = c / fc / 2. Therefore, for example, when fc = 150 MHz, ΔL = 1 m. In order to improve the distance error ΔL to 5 cm, it is necessary to set the frequency of the clock pulse to fc = 3 GHz. In general, an electric circuit is more expensive as the frequency is higher. If the actual circuit configuration is increased in speed, it becomes an expensive circuit configuration, which is not economical.

  The present invention solves the above-described problem, and is a low-cost obstacle detection method that can accurately determine the distance to an obstacle using a signal wave such as light, radio wave, or ultrasonic wave and its reflected wave. An object is to provide an apparatus.

To achieve the above object, obstacle detecting apparatus of the present invention, in the obstacle detection device for determining the distance to the object by obtaining the phase difference between the reflected waves from the object of the signal wave and the signal wave A signal generation unit that generates a sine wave signal wave, a transmission unit that transmits the signal wave generated by the signal generation unit toward the object, and a reflected wave from the object of the signal wave transmitted from the transmission unit determined a receiving unit for receiving a sampling section that acquires sample row signal strength of the received reflected wave by sampling by the receiver, out of phase with each other in the specimen columns 90 ° two different average values of the sample column, respectively And an arithmetic unit that obtains a phase difference between the signal wave and the reflected wave based on an arctangent value of a ratio of two average values and a known parameter depending on a sampling start timing .

The obstacle detection device includes a phase shift unit that shifts the phase of the signal wave generated by the signal generation unit or the reflected wave received by the reception unit by 90 °, and the sampling unit includes the first and second sampling units. A first sampling unit that samples the signal intensity of the reflected wave for each period of the signal wave generated by the signal generation unit to obtain a first sample string, and the second sampling unit includes a phase shift The phase of either the signal wave or the reflected wave is shifted by 90 ° by the unit, the signal intensity of the reflected wave is sampled for each period of the signal wave, and a second sample sequence is obtained . It is preferable to acquire the second sample row as two sample rows whose phases are different from each other by 90 ° .

  These obstacle detection devices include a multiplication unit that generates a multiplied wave obtained by multiplying the frequency of the signal wave generated by the signal generation unit, and the sampling unit calculates the signal intensity of the reflected wave for each cycle of the multiplied wave. It is preferable to obtain a sample string by sampling.

  In these obstacle detection devices, the sampling unit preferably includes an AD converter used for sampling.

  In these obstacle detection devices, it is preferable that the signal generation unit can switch the frequency of the signal wave to be generated between two or more types of frequencies.

  According to the obstacle detection device of the present invention, since the phase difference between the signal wave and the received wave is obtained based on the average values of the two series of sample sequences having different phases, the phase difference can be obtained without using an expensive high-speed circuit. Accordingly, the distance to the obstacle can be obtained with high accuracy, and a low-cost obstacle detection device can be realized.

The block block diagram of the obstruction detection apparatus which concerns on the 1st Embodiment of this invention. (A) and (b) are timing charts for explaining the operation of the apparatus. The block block diagram of the obstruction detection apparatus which concerns on 2nd Embodiment. The block block diagram which shows the modification of the apparatus. The block block diagram of the obstruction detection apparatus which concerns on 3rd Embodiment. (A) (b) (c) is a timing chart for demonstrating operation | movement of the apparatus. The block block diagram which shows the modification of the apparatus. The block block diagram which shows the other modification of the apparatus. The block block diagram of the obstruction detection apparatus which concerns on 4th Embodiment. The block block diagram which shows the modification of the apparatus. The block block diagram of the obstruction detection apparatus which concerns on 5th Embodiment. The block block diagram of the general time difference detection part in the conventional obstacle detection apparatus. (A)-(d) is a timing chart for demonstrating operation | movement of the apparatus.

(First embodiment)
Hereinafter, an obstacle detection device according to an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show a first embodiment. As shown in FIG. 1, the obstacle detection device 1 of the present embodiment includes a signal generation unit 2 that generates a sinusoidal signal wave, a transmission unit 3 that transmits the signal wave toward an object, and a signal wave A receiving unit 4 that receives a reflected wave from an object, a sampling unit 5, and a calculation unit 6 are provided. The sampling unit 5 samples the signal intensity of the reflected wave received by the receiving unit 4 and acquires a sample string. The computing unit 6 obtains an average value of signal intensities for each sample point of the same phase in the sample sequence, and based on two average values of the average values that are 90 ° out of phase with each other, the phase difference (θ ). The obstacle detection device 1 measures a phase difference θ between two waves including a reflected wave, that is, a transmitted wave and a reflected wave (received wave), and uses a reflector from the phase difference θ and a known propagation velocity of the signal wave. The distance to an obstacle can be obtained, that is, the obstacle can be detected.

  As shown in FIGS. 2A and 2B, the transmission signal (transmission wave) is a continuous sine wave corresponding to the appropriate wave number, and the reception signal (reflection wave) is transmitted from the transmission unit 3 via the reflector to the reception unit 4. Is a signal delayed by a time difference δT corresponding to the path length leading to. When the period of the transmission wave is a period T, the phase difference θ = 2π × δT / T (radian) is obtained using the time difference δT, and conversely, the time difference δT = T × θ / (2π). The sampling unit 5 acquires two series of sample sequences whose phases are different from each other by 90 ° (π / 2 radians). The sample point in each sample row is a measurement value (received signal intensity value) in the same phase state in the reflected wave, and is a measurement value for each period T or a measurement value for every integer multiple of the period T. In FIG. 2B, among the measurement points indicated by white circles in the drawing, a series of upper measurement points and a series of lower measurement points are sample rows whose phases are 90 ° different from each other. The calculation unit 6 obtains average values (measured as V0 and V1 respectively) of the measurement values in each sample sequence.

Next, a method of obtaining the phase difference θ from the average values V0 and V1 and obtaining the distance L to the obstacle will be described. The angular frequency of the signal wave is ω, the initial phase is α, the time variable is t, and using the phase difference θ, the signal wave S = A × sin (ωt + α) and the reflected wave R = B × sin (ωt + α + θ). . The above-described V0 and V1 are represented by the following equations. Here, β is a parameter that depends on the sampling start timing, and is generally known or can be set to β = 0 by setting. The calculation unit 6 calculates the phase difference θ, and thus the time difference δT, as described below, and calculates the distance L using the propagation speed c of the signal wave.
V0 = B × sin (β + θ),
V1 = B × sin (β + θ−π / 2) = B × cos (β + θ).
V0 / V1 = tan (β + θ).
θ = arctan (V0 / V1) −β.
L = c × δT / 2 = c × T × θ / (4π).

  According to the present embodiment, the phase difference is obtained by using statistical processing for obtaining the average value of the sample sequence, so that it is possible to detect the phase difference with little influence on measurement such as noise. In addition, since the distance is obtained based on the phase difference between the signal wave and the received wave, the distance to the obstacle can be obtained accurately without using an expensive high-speed circuit, and a low-cost obstacle detection device can be realized. . Note that radio waves, light, ultrasonic waves, and the like can be used as the signal wave medium, and each unit of the obstacle detection apparatus 1 such as the transmission unit 3 and the reception unit 4 is configured according to each medium. For example, when light is used as a medium, the light intensity may be amplitude-modulated with a sine wave. The wave number of the transmission wave, that is, the length of the signal wave may be a length that can obtain the number of measurement points necessary for appropriate averaging of the sample points. If the signal wave is too long, the repetition time interval of the repeated distance measurement cannot be shortened, so the length of the signal wave is set according to the measurement conditions.

(Second Embodiment)
3 and 4 show the second embodiment and its modification. As shown in FIG. 3, the obstacle detection apparatus 1 of the present embodiment further includes a phase shift unit 7 that shifts the phase of the signal wave by 90 ° in the obstacle detection apparatus 1 of the first embodiment described above, and performs sampling. The unit 5 includes first and second sampling units 51 and 52. The first sampling unit 51 samples a reflected wave for each period of the signal wave to obtain a first sample row, and the second sampling unit 52 is a signal wave whose phase is shifted by 90 ° by the phase shift unit 7. The reflected wave is sampled for each period to obtain a second sample string. Moreover, the calculating part 6 calculates | requires each average value of a 1st and 2nd sample row | line, and calculates | requires the phase difference of a signal wave and a reflected wave based on the average value.

  Further, in the obstacle detection device 1 of the modification shown in FIG. 4, the phase shift unit 7 shifts the phase of the reflected wave by 90 °, and the second sampling unit 52 shifts the phase by 90 ° for each period of the signal wave. The reflected wave is sampled to obtain the second sample row, and the others are the same as those shown in FIG. According to this embodiment and its modification, it is possible to reliably acquire two series of sample sequences whose phases are different from each other by 90 °.

(Third embodiment)
5 to 8 show the third embodiment and its modification. As shown in FIG. 5, the obstacle detection device 1 of the present embodiment is a multiplication unit 8 that generates a multiplied wave obtained by multiplying the frequency of the signal wave in the obstacle detection device 1 of the first embodiment described above. The sampling unit 5 samples the reflected wave for each period of the multiplied wave and obtains a sample string. FIGS. 6A, 6B, and 6C show examples of sampling based on a quadruple wave. In the case of this example, four series of sample sequences with a phase interval of π / 2 are obtained every 1/4 period of the signal wave. Further, the sampling timing is the same as the phase of the signal wave or a phase timing shifted by a multiple of π / 2 (that is, the β value is known and β = 0, π / 2, π, or 3π / 2). Four average values are obtained from these four series of sample strings. Therefore, the phase difference θ can be obtained using an arbitrary average value whose phases are different from each other by 90 °. Therefore, the phase difference θ can be obtained with higher accuracy by selecting and using an average value that is considered to have a small measurement error, for example, by comparing the magnitudes of measurement value fluctuations in each sample row. Each modification shown in FIGS. 7 and 8 includes a multiplier 8 in the obstacle detection apparatus 1 in FIGS. 3 and 4 of the second embodiment described above.

(Fourth embodiment)
9 and 10 show the fourth embodiment and its modification. As shown in FIG. 9, the obstacle detection device 1 of the present embodiment is such that the sampling unit 5 includes an AD converter used for sampling in the obstacle detection device 1 of the first embodiment described above. Further, as shown in FIG. 10, in the obstacle detection device 1 in the above-described third embodiment, the sampling unit 5 includes an AD converter, and in other embodiments, the sampling unit 5 includes an AD converter. can do. By providing such an AD converter, the sample sequence can be acquired as a digital value, and digital processing can be performed in the subsequent calculation unit 6, so that an apparatus with a small processing load and simple processing is obtained. It is done.

(Fifth embodiment)
FIG. 11 shows the fifth embodiment. The obstacle detection device 1 according to the present embodiment further includes a frequency shift unit 2a that shifts the frequency of the signal wave generated by the signal generation unit 2 in the obstacle detection device 1 according to the first embodiment described above. . The signal generation unit 2 and the frequency shift unit 2a can be considered to constitute a new signal generation unit 20 as a whole. With such a configuration, it is possible to obtain the variable-frequency obstacle detection device 1 in which the frequency of the signal wave can be switched between two or more types of frequencies. In general, in a device that determines the distance to an obstacle based on the phase difference between a transmitted wave and a reflected wave, the farthest distance that can be uniquely determined is limited by the wavelength of the signal wave. That is, due to the fact that the phase is defined within one period, an uncertainty of an integral multiple of the wavelength is involved at a distance farther than the wavelength. In addition, when a signal wave having a long wavelength is used, it is necessary to obtain a sample row having a sufficient number of sample points over a plurality of cycles, and thus a problem such as taking a long time for measurement at a short distance occurs. In other words, the higher the frequency, the higher the distance resolution and the more accurate distance measurement becomes possible. In addition, the lower the frequency, the longer the period of one cycle and the longer distance objects can be detected. According to the present embodiment, the frequency shift unit 2a is provided to switch the frequency of the signal wave, thereby lowering the frequency when the object is far away or undetected, and the object is detected. When higher accuracy is required, a usage method of increasing the frequency is possible.

  The present invention is not limited to the above-described configuration, and various modifications are possible, and the configurations of the above-described embodiments can be combined with each other. For example, the configuration including the frequency shift unit 2a in the fifth embodiment can be applied to the second to fourth embodiments. In the above description, it has been described that the signal generation unit 2 generates a sinusoidal signal wave. However, the signal wave is not limited to a sinusoidal signal wave, and a signal wave that can define a phase difference θ with respect to a reflected wave, for example, , Triangular wave, sawtooth wave and other periodic waves.

DESCRIPTION OF SYMBOLS 1 Obstacle detection apparatus 2 Signal generation part 2a Frequency shift part 3 Transmission part 4 Reception part 5 Sampling part 51 1st sampling part 52 2nd sampling part 6 Calculation part 7 Phase shift part 8 Multiplication part T Period (theta) Phase difference

Claims (5)

The obstacle detection device for determining the distance to the object by obtaining the phase difference between the reflected waves from the object of the signal wave and the signal wave,
A signal generator for generating a sinusoidal signal wave;
A transmission unit that transmits the signal wave generated by the signal generation unit toward an object;
A receiving unit that receives a reflected wave from an object of the signal wave transmitted from the transmitting unit;
A sampling unit that samples the signal intensity of the reflected wave received by the receiving unit to obtain a sample string;
An average value of two samples columns phases are different from each other by 90 ° in the specimens columns acquired by the sampling unit, respectively, and the known parameters depending on the arctangent value and timing of start of sampling ratio of the two averages An obstacle detection device comprising: an arithmetic unit that obtains a phase difference between the signal wave and the reflected wave based on A phase shift unit that shifts the phase of the signal wave generated by the signal generation unit or the reflected wave received by the reception unit by 90 °;
The sampling unit includes first and second sampling units,
The first sampling unit samples the signal intensity of the reflected wave for each period of the signal wave generated by the signal generation unit to obtain a first sample sequence,
The second sampling unit samples the signal intensity of the reflected wave for each period of the signal wave after shifting the phase of either the signal wave or the reflected wave by 90 ° by the phase shift unit. Sample sequence of
The obstacle detection apparatus according to claim 1 , wherein the sampling unit acquires the first and second sample sequences as the two sample sequences whose phases are different from each other by 90 ° . A multiplier for generating a multiplied wave obtained by multiplying the frequency of the signal wave generated by the signal generator;
The obstacle detection device according to claim 1, wherein the sampling unit samples the signal intensity of the reflected wave for each period of the multiplied wave to acquire the sample string.   The obstacle detection device according to claim 1, wherein the sampling unit includes an AD converter used for the sampling.   The obstacle detection device according to any one of claims 1 to 4, wherein the signal generation unit is capable of switching a frequency of a signal wave to be generated between two or more types of frequencies.

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