CN103941259B - A kind of ultrasonic ranging method possessing high noise immunity and range unit - Google Patents
A kind of ultrasonic ranging method possessing high noise immunity and range unit Download PDFInfo
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- CN103941259B CN103941259B CN201410150609.7A CN201410150609A CN103941259B CN 103941259 B CN103941259 B CN 103941259B CN 201410150609 A CN201410150609 A CN 201410150609A CN 103941259 B CN103941259 B CN 103941259B
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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
- G01S15/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
- G01S15/325—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of coded signals, e.g. of phase-shift keyed [PSK] signals
Abstract
The present invention provides a kind of ultrasonic ranging method possessing high noise immunity and range unit, sine wave signal sine-wave generator produced by pseudo-code carries out frequency modulation(PFM), produce launch ultrasound wave and launch, ultrasonic echo is carried out echo demodulation of frequency discriminator, achieve the identification of echo, make detection more accurate, additionally, owing to pseudo-code has good oneself, cross correlation, it is typically employed in spread spectrum communication, show good anti-noise jamming, the performances such as anti-mutual crosstalk, therefore, the mutual cross-interference issue of ultrasound wave can be overcome, make result accurate, further, owing to adopting FFT technique, use a small amount of sampled data just can demodulate reception ripple exactly, while ensureing frequency resolution, shorten the data acquisition time receiving ripple, substantially improve the real-time of range unit work, realize accurate quick distance measurement location for autonomous mobile robot and provide a kind of efficient solution。
Description
Technical field
The invention belongs to ultrasonic sensing technical field, particularly to a kind of ultrasonic sensor distance measurement method possessing high anti-interference energy and related device。
Background technology
Ultrasonic sensor range finding operation principle is simple, not by ambient light interference, is usually selected as mobile apparatus people's distance measuring sensor。But conventional ultrasound range-measurement system is subject to the interference of outside noise sound wave, particularly it is susceptible between group when many group ultrasonic transducer concurrent workings crosstalk, causes that range finding was lost efficacy。Hence for crosstalk between noise jamming and group, exploitation has the ultrasonic ranging method of high anti-interfering performance and has actual application value with device。The present invention provides a kind of ultrasonic ranging method possessing high noise immunity and range unit with regard to this, adopt a kind of special fast Fourier transform techniques with packet zero padding pretreatment, can effectively overcome the impact of crosstalk between noise jamming and group, it is achieved range measurement accurately in real time。
Summary of the invention
For drawbacks described above or deficiency, it is an object of the invention to provide a kind of ultrasonic ranging method possessing high noise immunity and range unit。
For reaching object above, the technical scheme is that
A kind of ultrasonic ranging method possessing high noise immunity, comprises the following steps:
1), first, adopt the sine wave signal that sine-wave generator is produced by the first pseudo-code from DSP module to carry out frequency modulation(PFM), produce the sine wave after pseudo-code frequency modulation(PFM)；Then, the sine wave after pseudo-code frequency modulation(PFM) is carried out voltage amplification；Finally, through transmitting terminal ultrasonic transducer, the sine wave after voltage amplification is sent, produce to launch ultrasound wave, and start timing；
2), receive the ultrasonic echo after reflection, and described ultrasonic echo is divided into two road ultrasonic echos after straight amplification: a road ultrasonic echo is filtered, and another road ultrasonic echo carries out commutating ratio relatively；Filtered ultrasonic echo is sent into DSP and is carried out A/D sampling, commutating ratio relatively after binary signal send into DSP module as interrupt signal so that timing module in DSP module stops timing；
3), filtered ultrasonic echo is sent into DSP module and carry out A/D sampling, ultrasonic echo after A/D sampling carries out FFT, obtain the frequency spectrum profile of echo-signal, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, obtain the second pseudo-code that echo frequency is corresponding, and the second pseudo-code and the first pseudo-code are carried out correlation computations, it is judged that ultrasonic echo and the hyperacoustic corresponding relation of transmitting, it is achieved ultrasonic echo demodulation of frequency discriminator；
4), when echo-signal is corresponding former transmitting signal, then ultrasonic propagation time is obtained according to timing, it is thus achieved that measure distance。
Described employing carries out frequency modulation(PFM) from the sine wave signal that sine-wave generator is produced by the first pseudo-code of DSP module, produces pseudo-code frequency modulation(PFM) sinusoidal wave, specifically includes:
2.1, produce, by the pseudo-code generation module in DSP module, the first pseudo-code m that length is l1, and in the first pseudo-code, the minimum hold time of each bit position is T1, T1Meet range unit real-time and the requirement of demodulation of frequency discriminator submodule medium frequency resolution；
2.2, by the first pseudo-code m1In each bit position deliver to ultrasonic emitting module by turn, every send keep minimum time T1；
2.3, when the first pseudo-code bit was ' 0 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f1Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f1Ultrasound wave；When the first pseudo-code bit was ' 1 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f2Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f2Ultrasound wave；When driving ultrasonic transducer first time to send ultrasound wave, start timing。
Demodulation of frequency discriminator submodule is based on this frequency spectrum profile, obtain the second pseudo-code that echo frequency is corresponding, and the second pseudo-code and the first pseudo-code are carried out correlation computations, it is judged that ultrasonic echo and the hyperacoustic corresponding relation of transmitting, realize ultrasonic echo demodulation of frequency discriminator, specifically include:
3.1, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, and identifying frequency is f1Ultrasound wave and frequency be f2Ultrasound wave；
3.2, obtain, according to the ultrasonic frequency identified, the second pseudo-code m2 that ultrasonic echo frequency is corresponding；
3.3, the second pseudo-code m2 and the first pseudo-code m1 being carried out correlation computations, when being equal to 1 according to the correlation after correlation computations, then ultrasonic echo is for launching ultrasound wave, is not otherwise launch ultrasound wave。
Ultrasonic echo after described A/D sampling carries out FFT, obtains the frequency spectrum profile of echo-signal, specifically includes:
4.1, the ultrasonic echo after A/D is sampled sends hold period according to the pseudo-code bit set and carries out packet zero padding pretreatment, to improve the apparent resolution of spectrogram；
4.2, to the packet pretreated ultrasonic echo FFT of zero padding, obtain the frequency spectrum profile of echo-signal。
The described measurement distance that obtains specifically includes:
Timing computing module in DSP module obtains hyperacoustic propagation time T0, and computation and measurement distance d:
D=C*T0/2
Wherein, C is the aerial spread speed of ultrasound wave。
A kind of supersonic range finder possessing high noise immunity, including DSP module, ultrasonic emitting module, ultrasound wave receiver module, display module and power module；
Wherein, ultrasonic emitting module, for the sine wave signal that sine-wave generator is produced by the first pseudo-code from DSP module being carried out frequency modulation(PFM), produce the sine wave after pseudo-code frequency modulation(PFM)；Then, the sine wave after pseudo-code frequency modulation(PFM) is carried out voltage amplification；Finally, through transmitting terminal ultrasonic transducer, the sine wave after voltage amplification is sent, produce to launch ultrasound wave；
Ultrasound wave transmitting/receiving module, for receiving the ultrasonic echo after reflection, and is divided into two road ultrasonic echos by described ultrasonic echo after straight amplification, and a road ultrasonic echo is filtered, and another road ultrasonic echo carries out commutating ratio relatively；
DSP module includes pseudo-code generation module, A/D sampling module, FFT module, demodulation of frequency discriminator module and timing computing module, and wherein, pseudo-code generation module is used for producing pseudo-code；A/D sampling module is for changing filtered ultrasonic echo simulation/digital quantity；FFT module carries out FFT for the ultrasonic echo after being sampled by A/D, obtains the frequency spectrum profile of echo-signal；Demodulation of frequency discriminator submodule is based on this frequency spectrum profile, it is thus achieved that the second pseudo-code that echo frequency is corresponding, and the second pseudo-code and the first pseudo-code are carried out correlation computations, it is judged that ultrasonic echo and the hyperacoustic corresponding relation of transmitting, it is achieved ultrasonic echo demodulation of frequency discriminator；Timing computing module is used for regularly obtaining ultrasonic propagation time, and according to ultrasonic propagation time computation and measurement distance；
Display module is for showing computed measurement distance；
Power module, for providing reference power supply for modules。
Described ultrasonic emitting module specifically for, producing length by the pseudo-code generation module in DSP module is the pseudo-code m1 of l, and the minimum hold time of each bit position is that T1, T1 meet range unit real-time and the requirement of demodulation of frequency discriminator submodule medium frequency resolution in pseudo-code；Then, each the bit position in pseudo-code m1 being delivered to ultrasonic emitting module by turn, every sends maintenance minimum time T1；When pseudo-code bit was ' 0 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f1Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f1Ultrasound wave；When pseudo-code bit was ' 1 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f2Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f2Ultrasound wave。
Described demodulation of frequency discriminator submodule specifically for, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, and identifying frequency is f1Ultrasound wave and frequency be f2Ultrasound wave；Then obtain, according to the ultrasonic frequency identified, the pseudo-code m2 that ultrasonic echo frequency is corresponding；Finally, m2 and m1 being carried out correlation computations, when being equal to 1 according to the correlation after correlation computations, then ultrasonic echo is for launching ultrasound wave, is not otherwise launch ultrasound wave。
Described FFT module specifically for, first, to A/D sample after ultrasonic echo according to set pseudo-code bit send hold period carries out packet zero padding pretreatment, to improve the apparent resolution of spectrogram；Then, the packet pretreated ultrasonic echo of zero padding is carried out FFT, obtains the frequency spectrum profile of echo-signal。
Timing computing module in described DSP module is used for obtaining hyperacoustic propagation time T0 computation and measurement distance d:
D=C*T0/2
Wherein, C is the aerial spread speed of ultrasound wave。
Compared with the prior art, the invention have the benefit that
The present invention provides a kind of ultrasonic ranging method possessing high noise immunity and range unit, sine wave signal sine-wave generator produced by pseudo-code carries out frequency modulation(PFM), produce to launch ultrasonic emitting, and ultrasonic echo is carried out echo demodulation of frequency discriminator, achieve the identification of echo, make detection more accurate, additionally, owing to pseudo-code has good oneself, cross correlation, it is typically employed in spread spectrum communication, show good anti-noise jamming, the performances such as anti-mutual crosstalk, therefore, the mutual cross-interference issue of ultrasound wave can be overcome, make result accurate, further, owing to adopting a kind of packet zero padding FFT technique, use a small amount of sampled data just can demodulate reception ripple exactly, while ensureing frequency resolution, shorten the data acquisition time receiving ripple, substantially improve the real-time of range unit work, realize accurate quick distance measurement location for autonomous mobile robot and provide a kind of efficient solution。
Further, owing to adopting the FFT technique with packet zero padding pretreatment, a small amount of sampled data is used just can to demodulate reception ripple exactly, to improve the apparent resolution of spectrogram。
Accompanying drawing explanation
Fig. 1 is supersonic range finder DSP workflow diagram of the present invention；
Fig. 2 is sampled data of the present invention packet zero padding pretreatment figure；
Fig. 3 is supersonic range finder functional module structure schematic diagram of the present invention；
Fig. 4 is supersonic range finder ultrasonic emitting end illustrative view of functional configuration of the present invention；
Fig. 5 is supersonic range finder ultrasound wave receiving terminal illustrative view of functional configuration of the present invention。
Detailed description of the invention:
Below in conjunction with accompanying drawing, the present invention is described in detail。
Embodiment 1:
The invention discloses a kind of ultrasonic ranging method possessing high noise immunity, as it is shown in figure 1, comprise the following steps:
1), first, adopt the sine wave signal that sine-wave generator is produced by the first pseudo-code from DSP module to carry out frequency modulation(PFM), produce code frequency modulated sinusoid；Then, frequency modulation(PFM) sine wave is carried out voltage amplification；Finally, through transmitting terminal ultrasonic transducer, the sine wave after voltage amplification is sent, produce to launch ultrasound wave, and start timing；
Described employing carries out frequency modulation(PFM) from the sine wave signal that sine-wave generator is produced by the first pseudo-code of DSP module, produces the sine wave after pseudo-code frequency modulation(PFM), specifically includes:
1.1, produce, by the pseudo-code generation module in DSP module, the first pseudo-code m that length is l1, and in the first pseudo-code, the minimum hold time of each bit position is T1, T1The pseudo-code bit being setting sends hold period, meets range unit real-time and the requirement of demodulation of frequency discriminator submodule medium frequency resolution；
1.2, by the first pseudo-code m1In each bit position delivered to ultrasonic emitting module by turn, every send keep minimum time T1；
1.3, when the first pseudo-code bit was ' 0 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f1Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f1Ultrasound wave；When the first pseudo-code bit was ' 1 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f2Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f2Ultrasound wave；；When driving ultrasonic transducer first time to send ultrasound wave, start timing。
2), receive the ultrasonic echo after reflection, and described ultrasonic echo is divided into two road ultrasonic echos after straight amplification: a road ultrasonic echo is filtered, and another road ultrasonic echo carries out commutating ratio relatively；Filtered ultrasonic echo is sent into DSP and is carried out A/D sampling, commutating ratio relatively after binary signal send into DSP module as interrupt signal so that timing module in DSP module stops timing；
3), filtered ultrasonic echo is sent into DSP module and carry out A/D sampling, A/D sampling after ultrasonic echo carry out packet zero padding after FFT, obtain the frequency spectrum profile of echo-signal, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, obtain the second pseudo-code that echo frequency is corresponding, and the second pseudo-code and the first pseudo-code are carried out correlation computations, it is judged that ultrasonic echo and the hyperacoustic corresponding relation of transmitting, it is achieved ultrasonic echo demodulation of frequency discriminator；
As in figure 2 it is shown, the ultrasonic echo after described A/D sampling carries out packet zero padding FFT, obtain the frequency spectrum profile of echo-signal, specifically include:
First, the ultrasonic echo after A/D is sampled sends hold period T1 according to the pseudo-code bit set and carries out packet zero padding pretreatment, to improve the apparent resolution of spectrogram；
Then, to the packet pretreated ultrasonic echo FFT of zero padding, the frequency spectrum profile of echo-signal is obtained。
Demodulation of frequency discriminator submodule is based on this frequency spectrum profile, it is thus achieved that the second pseudo-code that echo frequency is corresponding, and the second pseudo-code and the first pseudo-code is calculated, it is judged that ultrasonic echo and the hyperacoustic corresponding relation of transmitting, it is achieved ultrasonic echo demodulation of frequency discriminator, specifically includes:
2.1, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, and identifying frequency is f1Ultrasound wave and frequency be f2Ultrasound wave；
2.2, obtain, according to the ultrasonic frequency identified, the second pseudo-code m2 that ultrasonic echo frequency is corresponding；
2.3, the second pseudo-code m2 and the first pseudo-code m1 being carried out correlation computations, when being equal to 1 according to the correlation after correlation computations, then ultrasonic echo is for launching ultrasound wave, is not otherwise launch ultrasound wave。
4), when echo-signal is corresponding former transmitting signal, then ultrasonic propagation time is obtained according to timing, it is thus achieved that measure distance。The described measurement distance that obtains specifically includes:
Timing computing module in DSP module obtains hyperacoustic propagation time T0, and computation and measurement distance d:
D=C*T0/2
Wherein, C is the aerial spread speed of ultrasound wave。
Embodiment 2:
As shown in Fig. 3,4,5, the invention also discloses a kind of supersonic range finder possessing high noise immunity, including DSP module, ultrasonic emitting module, ultrasound wave receiver module, display module and power module；
Wherein, ultrasonic emitting module, for the sine wave signal that sine-wave generator is produced by the first pseudo-code from DSP module being carried out frequency modulation(PFM), produce frequency modulation(PFM) sinusoidal wave；Then, the sine wave after pseudo-code frequency modulation(PFM) is carried out voltage amplification；Finally, through transmitting terminal ultrasonic transducer, the sine wave after voltage amplification is sent, produce to launch ultrasound wave；
Ultrasound wave transmitting/receiving module, for receiving the ultrasonic echo after reflection, and is divided into two road ultrasonic echos by described ultrasonic echo after straight amplification, and a road ultrasonic echo is filtered, and another road ultrasonic echo carries out commutating ratio relatively；
DSP module includes pseudo-code generation module, A/D sampling module, FFT module, demodulation of frequency discriminator module and timing computing module, and wherein, pseudo-code generation module is used for producing pseudo-code；A/D sampling module is for changing filtered ultrasonic echo simulation/digital quantity；FFT module carries out packet zero padding FFT for the ultrasonic echo after being sampled by A/D, obtains the frequency spectrum profile of echo-signal；Demodulation of frequency discriminator submodule is based on this frequency spectrum profile, it is thus achieved that the second pseudo-code that echo frequency is corresponding, and the second pseudo-code and the first pseudo-code are carried out correlation computations, it is judged that ultrasonic echo and the hyperacoustic corresponding relation of transmitting, it is achieved ultrasonic echo demodulation of frequency discriminator；Timing computing module is used for regularly obtaining ultrasonic propagation time, and according to ultrasonic propagation time computation and measurement distance；
Display module is for showing computed measurement distance；
Power module, for providing reference power supply for modules。
Described ultrasonic emitting module specifically for, producing length by pseudo-code generation module in DSP module is the pseudo-code m of l1, and in pseudo-code, the minimum hold time of each bit position is T1, T1Meet range unit real-time and the requirement of demodulation of frequency discriminator submodule medium frequency resolution；Then, by pseudo-code m1In each bit position delivered to ultrasonic emitting module by turn, every send keep minimum time T1；When pseudo-code bit was ' 0 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f1Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f1Ultrasound wave；When pseudo-code bit was ' 1 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f2Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f2Ultrasound wave。
Described demodulation of frequency discriminator submodule specifically for, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, and identifying frequency is f1Ultrasound wave and frequency be f2Ultrasound wave；Then obtain, according to the ultrasonic frequency identified, the pseudo-code m2 that ultrasonic echo frequency is corresponding；Finally, m2 and m1 being carried out correlation computations, when being equal to 1 according to the correlation after correlation computations, then ultrasonic echo is for launching ultrasound wave, is not otherwise launch ultrasound wave。
Described FFT module specifically for, first, to A/D sample after ultrasonic echo according to set pseudo-code bit send hold period T1Carry out packet zero padding pretreatment, to improve the apparent resolution of spectrogram, as shown in Figure 2；Then, to the packet pretreated ultrasonic echo FFT of zero padding, the frequency spectrum profile of echo-signal is obtained。
Timing computing module in described DSP module is used for obtaining hyperacoustic propagation time T0, and computation and measurement distance d:
D=C*T0/2
Wherein, C is the aerial spread speed of ultrasound wave。
Embodiment 3:
Ultrasonic piezoelectric transducer TCT40-16T and TCT40-16R selected respectively by ultrasonic emitting, the ultrasonic transducer received in two modules, both mid frequency 40.0 ± 1.0kHz, acoustic pressure >=114db, sensitivity≤-68db, field angle 60 °, capacitance 2500pF, operating temperature-20～70 DEG C。Two modules are arranged side by side in same one end of range unit。
Ultrasonic emitting module realizes the pseudo-code frequency modulation(PFM) sine wave ultrasound wave output of 15Vp-p。In view of transducer mid frequency is about 40kHz, select f1=42kHz and f2=38kHz is for launching sound wave modulating frequency。Single-chip integration functional generator XR2206 selected by sine-wave generator, can produce the high-precision frequency modulation(PFM) sine wave signal of high stability under the pseudo-code code bit of DSP output controls。Voltage amplification adopts high-accuracy low noise fast amplifier OP-27, its ± 15V output stage has good load driving force。
Ultrasound wave receiver module adopts the electric capacity of a 0.1uf every directly, adopting two grades of OP-27 of cascade, it is achieved amplification 1～200 times is adjustable。After two grades are amplified, the ultrasonic echo signal of about 3Vp-p can be obtained。Bandwidth-limited circuit is built by resistance capacitance (RC) discrete device。Commutating ratio relatively adopts diode 1N4007 and NOT gate chip 7404 to build, it is achieved 0～3.3V square-wave signal exports。
DSP module adopts the dsp chip TMS320F28335 of TI company, is 32 high performance float-point DSP, and aboundresources in sheet, including ADC, intervalometer, peripheral interrupt, GPIO etc., it may be achieved multiple spot FFT。
Numeral method module receives the distance of timing ga(u)ge operator module output in DSP, and shows output。
Battery functi on module adopts standard lithium battery。
The main working process of described device as shown in Figure 4, comprises the steps:
(1) power-up initializing。Complete the setting of DSP interrupt priority, ADC depositor, intervalometer。
(2) programming of tabling look-up generates m1And preserve。First, selected pseudo-code length l, selects short, to improve the real-time of range unit as far as possible。Then, conventional primitive polynomial table is searched, it is determined that primitive polynomial coefficient。And then, building linear feedback shift register structure, given non-zero initial values, computing obtains desired m1And preserve。
(3) judge whether external interrupt 1 occurs。External interrupt 1 is used for realizing the enable triggering that whole range unit is started working。When external interrupt 1 occurs timer to start working。On the one hand, pseudo-code generation submodule starts to send by turn m to ultrasonic emitting module1, every keeps minimum time T1, to ensure that receiving terminal can collect enough points, it is achieved accurately demodulation of frequency discriminator。T1Completed by timer internal 1。Pseudo-code often starts to send one, and intervalometer 1 starts timing, T1Being timed to, pseudo-code sends next bit, and then intervalometer 1 restarts timing, so repeatedly, until having sent m1All l positions。On the other hand, start to send pseudo-code m1While, timing ga(u)ge operator module starts intervalometer 0, and intervalometer 0 completes ultrasonic propagation time T0Measurement。
(4) judge whether external interrupt 2 occurs。External interrupt 2 judges whether receiving terminal transducer receives ultrasonic echo。
A) when receiving terminal transducer receives echo-signal, trigger external interrupts 2。External interrupt 2 stops the timing of intervalometer 0, and triggering A/D sampling submodule starts echo signal sample simultaneously。And then pass sequentially through FFT submodule, demodulation of frequency discriminator submodule realizes demodulation of frequency discriminator。
Hybrid ranging device real-time and demodulation of frequency discriminator submodule frequency resolution two aspect demand, and the internal ADC Performance Constraints of TMS320F28335, the present invention selects DSP sampling rate to be 100kHz, pseudo-code length l is 7, every minimum hold time T1 is 100us, thus 4 same frequency sine waves, collected sample point 7 to 9 can be sent during every maintenance of pseudo-code。Gather 56 sample points altogether in the whole pseudo-code transmission cycle, be divided into 7 groups, often group 8。For improving the frequency apparent resolution of spectrogram, as in figure 2 it is shown, in FFT submodule, mend 8 zero to after often group, so often organize and be just extended for 16 points。Each group is the FFT of 16, makes 7 16 FFT altogether。
7 spectrograms are found the frequency that spectral line peak point is corresponding by demodulation of frequency discriminator submodule one by one, thus the modulating frequency f of this group sample point that reflects outi', i=1,2。This results in pseudo-code m2。Seek pseudo-code m2With pseudo-code m1Correlation function value, if result is 1, then pseudo-code demodulation result is true, the ultrasonic echo namely received be exactly transmitting terminal launch ultrasound wave, proceed to timing ga(u)ge operator module, otherwise proceed to next time measure circulation。
Timing ga(u)ge operator module calculates ultrasonic propagation distance, is finally sent to numeral method module, completes distance display。
If b) intervalometer 0 reaches maximum timing, interrupt 2 and do not occur, then numeral method maximal detectable range。
(5) judge whether shutdown, be, then shutdown terminates；No, then proceed to and measure circulation next time。
2) implementation result
In supersonic range finder 10 meters, error precision is less than 0.03%, the mutual cross-interference issue of ultrasound wave can be overcome, and owing to adopting a kind of special FFT technique with packet zero padding pretreatment, use a small amount of sampled data just can demodulate reception ripple exactly, while ensureing frequency resolution, shorten the data acquisition time receiving ripple, substantially improve the real-time of range unit work, realize accurate quick distance measurement location for autonomous mobile robot and provide a kind of efficient solution。
Claims (10)
1. the ultrasonic ranging method possessing high noise immunity, it is characterised in that comprise the following steps:
1), first, adopt the sine wave signal that sine-wave generator is produced by the first pseudo-code from DSP module to carry out frequency modulation(PFM), produce the sine wave after pseudo-code frequency modulation(PFM)；Then, the sine wave after pseudo-code frequency modulation(PFM) is carried out voltage amplification；Finally, through transmitting terminal ultrasonic transducer, the sine wave after voltage amplification is sent, produce to launch ultrasound wave, and start timing；
2), receive the ultrasonic echo after reflection, and described ultrasonic echo is divided into two road ultrasonic echos after straight amplification: a road ultrasonic echo is filtered, and another road ultrasonic echo carries out commutating ratio relatively；Filtered ultrasonic echo is sent into DSP and is carried out A/D sampling, commutating ratio relatively after binary signal send into DSP module as interrupt signal so that timing module in DSP module stops timing；
3), filtered ultrasonic echo is sent into DSP module and carry out A/D sampling, ultrasonic echo after A/D sampling carries out FFT, obtain the frequency spectrum profile of echo-signal, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, obtain the second pseudo-code that echo frequency is corresponding, and the second pseudo-code and the first pseudo-code are carried out correlation computations, it is judged that ultrasonic echo and the hyperacoustic corresponding relation of transmitting, it is achieved ultrasonic echo demodulation of frequency discriminator；
4), when echo-signal is corresponding former transmitting signal, then ultrasonic propagation time is obtained according to timing, it is thus achieved that measure distance。
2. the ultrasonic ranging method possessing high noise immunity according to claim 1, it is characterized in that, described employing carries out frequency modulation(PFM) from the sine wave signal that sine-wave generator is produced by the first pseudo-code of DSP module, produces the sine wave after pseudo-code frequency modulation(PFM), specifically includes:
2.1, produce, by the pseudo-code generation module in DSP module, the first pseudo-code m that length is l1, and in the first pseudo-code, the minimum hold time of each bit position is T1, T1Meet range unit real-time and the requirement of demodulation of frequency discriminator submodule medium frequency resolution；
2.2, by the first pseudo-code m1In each bit position deliver to ultrasonic emitting module by turn, every send keep minimum time T1；
2.3, when the first pseudo-code bit was ' 0 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f1Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f1Ultrasound wave；When the first pseudo-code bit was ' 1 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f2Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f2Ultrasound wave；When driving ultrasonic transducer first time to send ultrasound wave, start timing。
3. the ultrasonic ranging method possessing high noise immunity according to claim 2, it is characterized in that, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, obtain the second pseudo-code that echo frequency is corresponding, and the second pseudo-code and the first pseudo-code are carried out correlation computations, judge ultrasonic echo and launch hyperacoustic corresponding relation, it is achieved ultrasonic echo demodulation of frequency discriminator, specifically including:
3.1, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, and identifying frequency is f1Ultrasound wave and frequency be f2Ultrasound wave；
3.2, obtain, according to the ultrasonic frequency identified, the second pseudo-code m2 that ultrasonic echo frequency is corresponding；
3.3, the second pseudo-code m2 and the first pseudo-code m1 being carried out correlation computations, correlation is equal to 1, then ultrasonic echo is for launching ultrasound wave, is not otherwise launch ultrasound wave。
4. the ultrasonic ranging method possessing high noise immunity according to claim 1, it is characterised in that the ultrasonic echo after described A/D sampling carries out FFT, obtains the frequency spectrum profile of echo-signal, specifically includes:
4.1, the ultrasonic echo after A/D being sampled sends hold period according to the pseudo-code bit set and carries out packet zero padding pretreatment, to improve the apparent resolution of spectrogram；
4.2, the packet pretreated ultrasonic echo of zero padding is carried out FFT, obtain the frequency spectrum profile of echo-signal。
5. the ultrasonic ranging method possessing high noise immunity according to claim 1, it is characterised in that described acquisition is measured distance and specifically included:
Timing computing module in DSP module obtains hyperacoustic propagation time T0, and computation and measurement distance d:
D=C*T0/2
Wherein, C is the aerial spread speed of ultrasound wave。
6. the supersonic range finder possessing high noise immunity, it is characterised in that include DSP module, ultrasonic emitting module, ultrasound wave receiver module, display module and power module；
Wherein, ultrasonic emitting module, for the sine wave signal that sine-wave generator is produced by the first pseudo-code from DSP module being carried out frequency modulation(PFM), produce the sine wave after pseudo-code frequency modulation(PFM)；Then, the sine wave after pseudo-code frequency modulation(PFM) is carried out voltage amplification；Finally, through transmitting terminal ultrasonic transducer, the sine wave after voltage amplification is sent, produce to launch ultrasound wave；
Ultrasound wave receiver module, for receiving the ultrasonic echo after reflection, and is divided into two road ultrasonic echos by described ultrasonic echo after straight amplification, and a road ultrasonic echo is filtered, and another road ultrasonic echo carries out commutating ratio relatively；
DSP module includes pseudo-code generation module, A/D sampling module, FFT module, demodulation of frequency discriminator module and timing computing module, and wherein, pseudo-code generation module is used for producing pseudo-code；A/D sampling module is for changing filtered ultrasonic echo simulation/digital quantity；FFT module carries out FFT for the ultrasonic echo after being sampled by A/D, obtains the frequency spectrum profile of echo-signal；Demodulation of frequency discriminator submodule is based on this frequency spectrum profile, it is thus achieved that the second pseudo-code that echo frequency is corresponding, and the second pseudo-code and the first pseudo-code are carried out correlation computations, it is judged that ultrasonic echo and the hyperacoustic corresponding relation of transmitting, it is achieved ultrasonic echo demodulation of frequency discriminator；Timing computing module is used for regularly obtaining ultrasonic propagation time, and according to ultrasonic propagation time computation and measurement distance；
Display module is for showing computed measurement distance；
Power module, for providing reference power supply for modules。
7. the supersonic range finder possessing high noise immunity according to claim 6, it is characterized in that, described ultrasonic emitting module specifically for, producing length by the pseudo-code generation module in DSP module is the pseudo-code m1 of l, and the minimum hold time of each bit position is that T1, T1 meet range unit real-time and the requirement of demodulation of frequency discriminator submodule medium frequency resolution in pseudo-code；Then, each the bit position in pseudo-code m1 being delivered to ultrasonic emitting module by turn, every sends maintenance minimum time T1；When pseudo-code bit was ' 0 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f1Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f1Ultrasound wave；When pseudo-code bit was ' 1 ' period, the sine-wave generator tranmitting frequency in ultrasonic emitting module is f2Sine wave, after amplifying, driving ultrasonic transducer, to send frequency be f2Ultrasound wave。
8. the supersonic range finder possessing high noise immunity according to claim 7, it is characterised in that described demodulation of frequency discriminator submodule specifically for, demodulation of frequency discriminator submodule is based on this frequency spectrum profile, and identifying frequency is f1Ultrasound wave and frequency be f2Ultrasound wave；Then obtain, according to the ultrasonic frequency identified, the pseudo-code m2 that ultrasonic echo frequency is corresponding；Finally, m2 and m1 being carried out correlation computations, when being equal to 1 according to the correlation after correlation computations, then ultrasonic echo is for launching ultrasound wave, is not otherwise launch ultrasound wave。
9. the supersonic range finder possessing high noise immunity according to claim 6, it is characterized in that, described FFT module specifically for, first, ultrasonic echo after A/D is sampled sends hold period according to the pseudo-code bit set and carries out packet zero padding pretreatment, to improve the apparent resolution of spectrogram；Then, the packet pretreated ultrasonic echo of zero padding is carried out FFT, obtains the frequency spectrum profile of echo-signal。
10. the supersonic range finder possessing high noise immunity according to claim 6, it is characterised in that the timing computing module in described DSP module is used for obtaining hyperacoustic propagation time T0 computation and measurement distance d:
D=C*T0/2
Wherein, C is the aerial spread speed of ultrasound wave。
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