CN104678398B - A kind of ultrasonic ranging method - Google Patents
A kind of ultrasonic ranging method Download PDFInfo
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- CN104678398B CN104678398B CN201510036902.5A CN201510036902A CN104678398B CN 104678398 B CN104678398 B CN 104678398B CN 201510036902 A CN201510036902 A CN 201510036902A CN 104678398 B CN104678398 B CN 104678398B
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- 238000005259 measurement Methods 0.000 description 13
- 238000002604 ultrasonography Methods 0.000 description 7
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
- G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
- G01S15/06—Systems determining the position data of a target
- G01S15/08—Systems for measuring distance only
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
- G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
- G01S15/06—Systems determining the position data of a target
- G01S15/08—Systems for measuring distance only
- G01S15/10—Systems for measuring distance only using transmission of interrupted, pulse-modulated waves
- G01S15/12—Systems for measuring distance only using transmission of interrupted, pulse-modulated waves wherein the pulse-recurrence frequency is varied to provide a desired time relationship between the transmission of a pulse and the receipt of the echo of a preceding pulse
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- Acoustics & Sound (AREA)
- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
Abstract
The present invention relates to a kind of ultrasonic ranging method, it includes：T1 earthward launches n ultrasonic pulse to ultrasonic wave emitting head successively at predetermined intervals, and the frequency of n ultrasonic pulse is incremented by successively or successively decrease according to default frequency step；Ultrasonic wave reception head receives the n ultrasonic pulse by ground return successively, and when receiving ultrasonic pulse every time, corresponding ranging time △ T are calculated according to formula onen, formula one is △ Tn=Trn‑Ttn, wherein, TtnAt the time of during for ultrasonic wave emitting head n-th of ultrasonic pulse of transmitting, TrnAt the time of n-th of ultrasonic pulse being received for ultrasonic wave reception head；When obtaining corresponding ranging time △ T every timenWhen, calculate the current distance d between unmanned vehicle and groundn.The present invention can improve the speed and precision of ultrasonic ranging, meet ranging requirement of the unmanned vehicle in flight course.
Description
Technical Field
The invention relates to a distance measurement technology of an unmanned aerial vehicle.
Background
With the development of scientific technology, agricultural technology gradually tends to develop automatically. Currently, unmanned aerial vehicles are available for seeding large fields within a predetermined height. The unmanned aerial vehicle generally adopts an ultrasonic ranging technology to judge the flight height between the unmanned aerial vehicle and the ground. The ultrasonic distance sensor has great advantages in the aspects of cost, precision, reliability and directivity. The principle of ultrasonic ranging is that the propagation speed of ultrasonic waves in the air is known, the time of the sound waves reflected back when encountering an obstacle after being transmitted is measured, and the actual distance from a transmitting point to the obstacle is calculated according to the time difference between transmitting and receiving. It follows that the principles of ultrasonic ranging are the same as those of radar.
As shown in fig. 1, the ranging formula is expressed as: d is (Δ t C cos α)/2, d is the length of the measurement distance, Δ t is the time from the beginning of the sound of the ultrasonic transmitter 1 to the time when the ultrasonic receiver 2 receives the reflected sound from the ground 3, C is the propagation speed of the sound in the air (344m/s (20 ℃)), and α is the angle between the ultrasonic transmitter 1 or the ultrasonic receiver 2 and the normal 4. Thus, the distance d can be obtained by accurately measuring Δ t.
In the conventional method for measuring distance by ultrasonic waves, assuming that the frequency of the used ultrasonic waves is fixed at 40kHz, the working beat of an ultrasonic wave transmitting head in a measuring process can be divided into: 1. the transmitting head transmits 10 ultrasonic wave pulses and times t 1; 2. the transmitting head is silent; 3. opening the receiving head; 4. waiting for echo reflection 5, confirming echo reflection and timing t 2; 6. calculating the distance; 7. and returning to 1 and repeating the steps.
The transmitting head starts to work at the time t1, 10 waveforms are transmitted in a pulse mode and then stop working, the time when the receiving head receives the reflected echo is recorded as t2, △ t is t2-t1, namely △ t is the minimum time required by the traditional measuring method for completing one-time distance measurementThe consumption also takes into account the time taken by the microprocessor to perform the calculation according to the equation d (△ t C cos α)/2, denoted tc. Total measurement time ta＝△t+tc△ t increases with increasing measured distance, total measurement time taAnd moreover, when the measuring distance reaches 5 meters, △ t reaches 29ms, the response frequency of the measuring system is lower than 20 Hz. plus a software filtering algorithm matched with the ultrasonic ranging, the accurately measured frequency is lower than 2Hz, and the response frequency obviously does not meet the practical requirement for the unmanned aerial vehicle with the flying speed of more than 15 m/s.
Disclosure of Invention
The invention aims to provide an ultrasonic ranging method which can solve the problem of low ranging frequency of an unmanned aerial vehicle.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the ultrasonic ranging method is applied to a signal control processing module of an unmanned aerial vehicle, the unmanned aerial vehicle is provided with an ultrasonic transmitting head and an ultrasonic receiving head, the ultrasonic transmitting head and the ultrasonic receiving head are both connected with the signal control processing module, and the method comprises the following steps:
step 1, closing an ultrasonic receiving head, wherein the ultrasonic transmitting head sequentially transmits n ultrasonic pulses to the ground at a preset time interval T1, the frequencies of the n ultrasonic pulses are sequentially increased or decreased according to a preset frequency step length, wherein n is a natural number greater than 1;
step 2, when the nth ultrasonic pulse is emitted by the ultrasonic wave emitting head, the ultrasonic wave receiving head is opened, the ultrasonic wave receiving head sequentially receives the n ultrasonic pulses reflected by the ground, and when the ultrasonic wave pulses are received each time, corresponding ranging time △ T is calculated according to a formula InThe formula one is △ Tn＝Trn-TtnWherein, TtnFor the time at which the ultrasonic wave emitting head emits the nth ultrasonic pulse, TrnThe moment when the ultrasonic receiving head receives the nth ultrasonic pulse;
step 3, obtaining corresponding distance measuring time △ T each timenThen, the current distance d between the unmanned aerial vehicle and the ground is calculated according to a formula IIn；
The second formula is dn(△ Tn C cos α)/2, where C is the speed of sound and α is the angle between the ultrasound transmitting or receiving head and the normal, which is perpendicular to the ground.
Preferably, step 1 is preceded by the following steps: and opening the ultrasonic receiving head, transmitting an ultrasonic pulse to the ground by the ultrasonic transmitting head, calculating the test time delta T of the ultrasonic pulse from the transmission of the ultrasonic pulse to the arrival of the ultrasonic pulse after the ultrasonic receiving head receives the ultrasonic pulse, and obtaining the number n of the transmitted ultrasonic pulses allowed in one period by using a formula n as delta T/T1.
Preferably, in step 1, the time when the ultrasound transmitting head transmits one ultrasound pulse is denoted as T2, and the time between two adjacent ultrasound pulses is denoted as T3, so that T1 is T2+ T3.
Preferably, T1 is 1 ms.
Preferably, in step 1, each ultrasonic pulse has 10 waveforms.
Preferably, in step 1, if the frequency of the 1 st ultrasonic pulse emitted from the ultrasonic emission head is 36kHz, the frequency of the nth ultrasonic pulse is 44 kHz.
Preferably, in step 1, if the frequency of the 1 st ultrasonic pulse emitted from the ultrasonic emission head is 44kHz, the frequency of the nth ultrasonic pulse is 36 kHz.
Preferably, in step 2, when a super is received each timeDuring the sound wave pulse, the frequency of the received ultrasonic pulse is also calculated to judge Tr corresponding to the currently received ultrasonic pulsen。
The invention has the following beneficial effects:
the beat of 1 sending and 1 receiving of the traditional ultrasonic ranging method is expanded into n sending and n receiving. The number of measurements per unit time is increased by a factor of n. In the receiving process, the emission must be stopped, so that the measurement efficiency in actual continuous measurement is improved by n/2 times compared with the traditional ultrasonic ranging method, and the frequency of ultrasonic ranging is effectively improved, namely, the invention can improve the speed and the precision of ultrasonic ranging and meet the ranging requirement of the unmanned aerial vehicle in the flying process.
Drawings
Fig. 1 is a schematic diagram of the principle of ultrasonic ranging.
FIG. 2 is a flowchart illustrating an ultrasonic ranging method according to a preferred embodiment of the present invention.
Detailed Description
The invention is further described with reference to the drawings and the detailed description.
As shown in fig. 2, an ultrasonic ranging method is applied to a signal control processing module of an unmanned aerial vehicle, where the unmanned aerial vehicle is provided with an ultrasonic transmitting head and an ultrasonic receiving head, and both the ultrasonic transmitting head and the ultrasonic receiving head are connected with the signal control processing module. The signal control processing module is provided with electronic devices such as a timer, an MCU, an ADC and the like.
The ultrasonic ranging method of the embodiment specifically includes the following steps:
and step S1, after the unmanned aerial vehicle takes off, primarily judging the flight altitude by using a traditional ultrasonic ranging method. And opening the ultrasonic receiving head, transmitting an ultrasonic pulse to the ground by the ultrasonic transmitting head, calculating the test time delta T of the ultrasonic pulse from the transmission of the ultrasonic pulse to the arrival of the ultrasonic pulse after the ultrasonic receiving head receives the ultrasonic pulse, and obtaining the number n of the transmitted ultrasonic pulses allowed in one period by using a formula n as delta T/T1. T1 is the preset time interval for the ultrasonic wave transmitting head to transmit the ultrasonic wave pulse. T1 of the present embodiment is 1 ms.
This is because the ultrasonic transmitter emits ultrasonic waves directly below the ultrasonic receiver due to the multi-directional sound transmission, and the ultrasonic receiver can receive the same frequency sound waves while the ultrasonic transmitter emits sound. Because the ultrasonic wave transmitting head and the ultrasonic wave receiving head rest are very close, the interference of the sound wave transversely conducted by the transmitting head on the receiving head is very serious, so that the ultrasonic wave receiving head can not distinguish whether the currently received sound wave signal is the transversely conducted sound wave or the sound wave reflected by the ground. Therefore, at the beginning of the measurement, the approximate distance from the ground must be determined initially.
And S2, closing the ultrasonic receiving head, and sequentially transmitting n ultrasonic pulses to the ground by the ultrasonic transmitting head at a preset time interval T1, wherein the frequencies of the n ultrasonic pulses are sequentially increased (or decreased) according to a preset frequency step (such as 1kHz), and n is a natural number greater than 1. For example, when the time when the ultrasound transmitting head transmits one ultrasound pulse is denoted as T2 and the time between two adjacent ultrasound pulses is denoted as T3, T1 is T2+ T3. In this embodiment, T2 is 500 μ s, and T3 is 500 μ s. That is, T2 is the time when the ultrasonic wave transmitting head transmits one ultrasonic wave pulse, and T3 is the silent time after the ultrasonic wave transmitting head has transmitted the current ultrasonic wave pulse.
Specifically, the ultrasonic transmitting heads have certain frequency response bandwidth, the resonance center frequency of one ultrasonic transmitting head is 40kHz, and the frequency response bandwidth reaches 8kHz, namely, good frequency response can be obtained within the frequency range of 40kHz +/-4 kHz. This feature exists so that the ultrasonic wave emitting head can emit ultrasonic waves at frequencies off the center resonance frequency. The ultrasonic transmitting head takes 36kHz as the starting point of the sound frequency and 44kHz as the end point of the sound frequency, 10 waveform sound waves are transmitted each time, after the transmitting head stops oscillating, 1KHz is taken as a stepping interval, and the steps are gradually increased, namely 36.0kHz, 37.0kHz,38.0kHz … … to 44.0kHz, and the process is repeated.
That is, the frequency of the 1 st ultrasonic pulse emitted from the ultrasonic wave emitting head of the present embodiment is 36kHz, and the frequency of the nth ultrasonic pulse is 44 kHz. And each ultrasonic pulse has a number of waveforms of 10.
Step S3, when the ultrasonic wave transmitting head finishes emitting the nth ultrasonic wave pulse, the ultrasonic wave receiving head is opened, the ultrasonic wave receiving head receives the n ultrasonic wave pulses reflected by the ground in sequence, and when the ultrasonic wave pulses are received each time, the corresponding distance measuring time △ T is calculated according to a formula InThe formula one is △ Tn＝Trn-TtnWherein, TtnFor the time at which the ultrasonic wave emitting head emits the nth ultrasonic pulse, TrnThe time when the ultrasonic receiving head receives the nth ultrasonic pulse is calculated, and the frequency of the received ultrasonic pulse is calculated to judge the Tr corresponding to the currently received ultrasonic pulsenIn the process, ADC (analog to digital converter) with the sampling rate exceeding 2M/s can be used for sampling the received waveform at a high speed and carrying out FFT (fast Fourier transform) conversion to calculate the frequency of the received ultrasonic pulse, so that the aim of better distinguishing the reflected echo from other interference waves is fulfilled, interference is eliminated, and Tr (Tr) is realizednAnd TtnAnd (6) accurately corresponding.
Step S4, when obtaining the corresponding ranging time △ T each timenThen, the current distance d between the unmanned aerial vehicle and the ground is calculated according to a formula IIn；
The second formula is dn＝(△TnC cos α)/2, wherein C is the sound velocity, and α is the included angle between the ultrasonic transmitting head or the ultrasonic receiving head and the normal, and the normal is perpendicular to the ground.
Put simplyFor example, the ultrasonic transmitting head sequentially transmits ultrasonic pulses with frequencies of 36.0kHz, 37.0kHz,38.0kHz, … …, and 44.0kHz, and transmits 9 ultrasonic pulses in total, and the ultrasonic receiving head sequentially receives the 9 ultrasonic pulses, for example, if the ultrasonic receiving head receives the ultrasonic pulse with the frequency of 36.0kHz (the 1 st ultrasonic pulse), then △ T is used for obtaining the flight height1＝Tr1-Tt1According to △ T1The current distance d between the unmanned aerial vehicle and the ground can be calculated1And so on for other current distances.
Therefore, the embodiment expands the beat of 1 transmitting and 1 receiving into n transmitting and n receiving according to the traditional ultrasonic ranging method. The number of measurements per unit time is increased by a factor of n. Since the transmission must be stopped during reception, the efficiency of the measurement in the actual continuous measurement is increased by a factor of n/2 compared to the conventional ultrasonic ranging method. The efficiency improvement is very obvious in the range of 1 to 5 meters. Because the measurement speed is increased, the signal control processing module has enough samples during the filtering in the later period, and the measurement precision is also improved after the filtering is carried out by the signal control processing module. The frequency conversion sequence is added in the transmitting process, the frequency change sequence of the received sequence is the same as the frequency change sequence of the transmitting sequence, the ADC high-speed sampling receiving waveform with the sampling rate exceeding 2M/s is utilized to carry out FFT conversion, the receiving frequency is calculated, and the aim is to better distinguish the reflected echo and other interference waves, thereby eliminating the interference and leading Tr to be more effectivenAnd TtnCan correspond precisely.
In step 1 of the above embodiment, if the frequency of the 1 st ultrasonic pulse emitted from the ultrasonic emitting head is 44kHz, the frequency of the nth ultrasonic pulse is 36 kHz. That is, the frequency of the ultrasonic pulses may also be transmitted in a decreasing manner.
Various other changes and modifications to the above-described embodiments and concepts will become apparent to those skilled in the art from the above description, and all such changes and modifications are intended to be included within the scope of the present invention as defined in the appended claims.
Claims (7)
1. The ultrasonic ranging method is applied to a signal control processing module of an unmanned aerial vehicle, the unmanned aerial vehicle is provided with an ultrasonic transmitting head and an ultrasonic receiving head, and the ultrasonic transmitting head and the ultrasonic receiving head are both connected with the signal control processing module, and the ultrasonic ranging method is characterized by comprising the following steps of:
step 1, closing an ultrasonic receiving head, wherein the ultrasonic transmitting head sequentially transmits n ultrasonic pulses to the ground at a preset time interval T1, the frequencies of the n ultrasonic pulses are sequentially increased or decreased according to a preset frequency step length, wherein n is a natural number greater than 1; step 1 is preceded by the following steps: after the unmanned aerial vehicle takes off, primarily judging the flight altitude by using a traditional ultrasonic ranging method, wherein an ultrasonic receiving head is opened, an ultrasonic wave pulse is emitted to the ground by the ultrasonic emitting head, after the ultrasonic receiving head receives the ultrasonic wave pulse, the testing time delta T of the ultrasonic wave pulse from the emitting of the ultrasonic emitting head to the arrival of the ultrasonic receiving head is calculated, and the number n of the emitted ultrasonic wave pulses allowed in one period is obtained by using a formula n delta T/T1;
step 2, when the nth ultrasonic pulse is emitted by the ultrasonic wave emitting head, the ultrasonic wave receiving head is opened, the ultrasonic wave receiving head sequentially receives the n ultrasonic pulses reflected by the ground, and when the ultrasonic wave pulses are received each time, corresponding distance measuring time delta T is calculated according to a formula InThe formula I isWherein,the time when the ultrasonic wave transmitting head transmits the nth ultrasonic wave pulse,the moment when the ultrasonic receiving head receives the nth ultrasonic pulse;
step 3, obtaining corresponding distance measuring time delta T each timenThen, the current distance d between the unmanned aerial vehicle and the ground is calculated according to a formula IIn；
The second formula is dn＝(ΔTnC cos α)/2, wherein C is the sound velocity, and α is the included angle between the ultrasonic transmitting head or the ultrasonic receiving head and the normal, and the normal is perpendicular to the ground.
2. The ultrasonic ranging method according to claim 1, wherein in step 1, the time when the ultrasonic transmitting head transmits one ultrasonic pulse is denoted as T2, and the time between two adjacent ultrasonic pulses is denoted as T3, so that T1 is T2+ T3.
3. The ultrasonic ranging method of claim 1, wherein T1 is 1 ms.
4. The ultrasonic ranging method of claim 1, wherein in step 1, each ultrasonic pulse has a number of waveforms of 10.
5. The ultrasonic ranging method as claimed in claim 1, wherein in the step 1, if the frequency of the 1 st ultrasonic pulse transmitted from the ultrasonic transmitting head is 36kHz, the frequency of the nth ultrasonic pulse is 44 kHz.
6. The ultrasonic ranging method as claimed in claim 1, wherein in the step 1, if the frequency of the 1 st ultrasonic pulse transmitted from the ultrasonic transmitting head is 44kHz, the frequency of the nth ultrasonic pulse is 36 kHz.
7. The ultrasonic ranging method of claim 1, wherein in step 2, the frequency of the received ultrasonic pulse is further calculated every time the ultrasonic pulse is received to determine the currently received ultrasonic pulse corresponding to the received ultrasonic pulse
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| TWI596367B (en) * | 2016-02-26 | 2017-08-21 | 凌通科技股份有限公司 | Distance detection method and distance detection device using the same |
| CN105549022B (en) * | 2016-03-04 | 2019-01-29 | 陈武强 | A kind of automobile ultrasonic method for detecting and sensor |
| CN105911537B (en) * | 2016-04-13 | 2019-04-26 | 中国科学院声学研究所 | A method of reducing active sonar detection blind area |
| CN107121675B (en) * | 2017-05-04 | 2020-12-29 | 成都零点科技有限公司 | Remote displacement measuring device, system and method with clutter suppression function |
| CN107749925B (en) * | 2017-10-31 | 2020-12-04 | 北京小米移动软件有限公司 | Audio playing method and device |
| CN109407099A (en) * | 2018-09-04 | 2019-03-01 | 佛山科学技术学院 | A kind of ultrasonic ranging method and its system |
| CN109901172A (en) * | 2019-03-28 | 2019-06-18 | 如皋忠广电子技术有限公司 | Ultrasonic ranging method, device and the electronic equipment adjusted based on frequency |
| CN109901173A (en) * | 2019-03-28 | 2019-06-18 | 如皋忠广电子技术有限公司 | Ultrasonic ranging method, device and electronic equipment based on duty cycle adjustment |
| CN113567991B (en) * | 2020-04-28 | 2023-11-10 | 深圳市万普拉斯科技有限公司 | Ultrasonic ranging method and device, readable storage medium and electronic equipment |
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| DE3800800A1 (en) * | 1988-01-14 | 1989-08-03 | Honeywell Regelsysteme Gmbh | Method and device for distance measurement (separation measurement) |
| CN100455999C (en) * | 2006-06-30 | 2009-01-28 | 北京奥麦特科技有限公司 | Device for ultrasonic measuring liquid level and method thereof |
| CN102109600B (en) * | 2009-12-24 | 2013-02-20 | 占志彪 | Method for detecting moving object based on ultrasonic waves |
| CN102841352A (en) * | 2012-09-18 | 2012-12-26 | 江南大学 | Ultrasonic wave range finder |
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