CN111530722A - Ultrasonic transducer, directional sound wave bird repelling system and method - Google Patents
Ultrasonic transducer, directional sound wave bird repelling system and method Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
- B06B1/0603—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a piezoelectric bender, e.g. bimorph
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01M—CATCHING, TRAPPING OR SCARING OF ANIMALS; APPARATUS FOR THE DESTRUCTION OF NOXIOUS ANIMALS OR NOXIOUS PLANTS
- A01M29/00—Scaring or repelling devices, e.g. bird-scaring apparatus
- A01M29/16—Scaring or repelling devices, e.g. bird-scaring apparatus using sound waves
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01M—CATCHING, TRAPPING OR SCARING OF ANIMALS; APPARATUS FOR THE DESTRUCTION OF NOXIOUS ANIMALS OR NOXIOUS PLANTS
- A01M29/00—Scaring or repelling devices, e.g. bird-scaring apparatus
- A01M29/16—Scaring or repelling devices, e.g. bird-scaring apparatus using sound waves
- A01M29/18—Scaring or repelling devices, e.g. bird-scaring apparatus using sound waves using ultrasonic signals
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
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- B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
- B06B2201/50—Application to a particular transducer type
- B06B2201/55—Piezoelectric transducer
- B06B2201/56—Foil type, e.g. PVDF
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
- B06B2201/70—Specific application
- B06B2201/75—Repelling animals, insects, humans
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Abstract
The invention relates to the field of sound wave control, and discloses an ultrasonic transducer, a directional sound wave bird repelling system and a directional sound wave bird repelling method. The invention can realize the aim of directionally repelling birds, and the superposition of the waveform in the transmission process is enhanced through the wavy PVDF film, so that the difficulty in enhancing the sound wave in the transmission process is avoided, and the invention is more favorable for directionally repelling birds.
Description
Technical Field
The invention relates to the field of sound wave control, in particular to an ultrasonic transducer, a directional sound wave bird repelling system and a directional sound wave bird repelling method.
Background
Bird strike events frequently happen in civil aviation airports, and the proportion of accident signs is increased, so that the safety of civil aviation transportation is influenced. The number of accident signs in china due to bird strikes accounts for 1/3, and the economic loss due to bird strikes in the united states is as high as $ 6 billion per year. Since 1988, crash accidents caused by bird strikes have resulted in over 190 deaths. Therefore, a set of scientific and efficient bird repelling system is built, and has great significance for dispelling bird groups and bird situations and preventing bird strikes in airports. The bird repelling system integrates directional sound wave bird repelling equipment and an equipment management system, and realizes the functions of effectively repelling birds in airports, centralized prevention and control and the like.
However, in the existing directional acoustic wave bird repelling device, an audio amplifying circuit is often adopted to amplify the power of an audio signal to effectively eliminate sound distortion or make the ratio of the amplitudes of a low-frequency signal and a carrier signal (i.e., the modulation ratio m) small enough to ensure a small distortion rate.
The former audio amplifier circuit has frequency response problems of the amplifier circuit and the speaker in practical use, that is, it is necessary to ensure that the amplifier circuit has the same amplification performance (amplification factor) for signals of all frequencies, and it is also necessary to ensure that the speaker has the same response performance for signals of all frequencies, which is difficult to realize in practical design. It is not difficult to ensure that the amplification circuit has substantially the same amplification performance for all frequencies of signals in the audio frequency range, but it is almost impossible to ensure that the speaker has the same response performance for all frequencies of signals because the speaker is not a simple purely resistive load, but is composed of a combination of a coil and a permanent magnet, has a resistive property, an inductive property (the coil cuts magnetic lines of force), and a property capable of inducing an electromotive force, and thus has a very complicated frequency response characteristic. Meanwhile, the frequency response characteristics of speakers of different structures and different sizes are also different. Therefore, it is inconvenient to perform power amplification on an audio signal using an audio amplification circuit to remove distortion or ensure small distortion.
The latter method is to make the ratio of the amplitudes of the low-frequency signal and the carrier signal (i.e. the modulation ratio m) small enough to ensure that the small distortion rate also needs to consider the size of the signal frequency band range in practical application, but the existing directional acoustic wave transmitter does not give the influence of the signal frequency band range on the distortion, thereby being unfavorable to avoiding the distortion of sound.
And the class-D digital high-power multi-channel audio amplifier in the existing directional acoustic wave bird repelling device can be completely started (saturated) or completely closed (cut off) at an output MOSFET, and the effects of the class-D digital high-power multi-channel audio amplifier are that the power consumption of a transistor is reduced, and the efficiency of the amplifier is increased. Unfortunately, there is always a loss in switching time and non-switching time (switching losses and conduction losses) which is detrimental to a more efficient increase in amplifier efficiency.
Moreover, the ultrasonic transducer in the existing directional acoustic wave bird repelling device adopts piezoelectric crystals or piezoelectric ceramics as a mechanical vibration medium, the ultrasonic transducer using the piezoelectric crystals or the piezoelectric ceramics as the mechanical vibration medium has a complex structure and low stability, and meanwhile, an acoustic reactance group of the ultrasonic transducer is not close to air, cannot be well matched with the air medium, and is not beneficial to radiating ultrasonic waves into the air by using the ultrasonic transducer.
Meanwhile, the sound beam released by the existing directional sound wave bird repelling device is difficult to be strengthened in the specified direction, so that the bird group in the specific direction cannot be effectively dispelled by the weighted ultrasonic wave.
Therefore, an ultrasonic transducer, a directional sound wave bird repelling system and a directional sound wave bird repelling method which are beneficial to directional bird repelling are urgently needed.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides the ultrasonic transducer, the directional sound wave bird repelling system and the directional sound wave bird repelling method, which can realize the purpose of directionally repelling birds, and can avoid the difficulty in strengthening the sound waves in the transmission process and the difficulty in strengthening the sound waves in the transmission process by strengthening the superposition of waveforms in the transmission process through the wavy PVDF membrane, thereby being more beneficial to directionally repelling birds.
In order to achieve the purpose, the invention adopts the following technical scheme:
an ultrasonic transducer includes a piezoelectric wafer made of a PVDF film having a wave-shaped cross section.
In the invention, the piezoelectric wafer is used for transmitting and receiving ultrasonic waves, the piezoelectric wafer is made of a PVDF film, the cross section of the PVDF film is wavy, the waveforms at the peak and valley positions of the PVDF film are favorably overlapped in transmission, and because the force and the displacement caused by excitation are equal and opposite in direction on the intersecting line of the adjacent peak and valley positions of the PVDF film, the position is not moved but only allowed to rotate, the intersecting line becomes a virtual axis to form a virtual boundary, namely, the PVDF film can be fixed without using a clamping piece, thereby realizing the aim of directionally driving birds. The invention can realize the aim of directionally repelling birds, and the superposition of the waveform in the transmission process is enhanced through the wavy PVDF film, so that the difficulty in enhancing the sound wave in the transmission process is avoided, and the invention is more favorable for directionally repelling birds.
As a preferred mode, still include casing, two electrode wires and earth connection, casing one end is equipped with the protection film, and piezoelectric wafer hugs closely with the protection film in the casing, is equipped with the absorption piece in the casing, and two electrode wires connect respectively at the up end of piezoelectric wafer and terminal surface down and pass the absorption piece and stretch out outside the casing, and coupling is connected with matching inductance on the electrode wire of being connected with piezoelectric wafer up end in the casing, and casing and earth connection are connected.
In a preferred mode, the difference h between the heights of the adjacent peaks and troughs of the PVDF film of the piezoelectric wafer is approximately equal to lambda/2, wherein lambda is the wavelength of the ultrasonic wave in the sound-transmitting medium.
A directional acoustic bird repelling system, the ultrasonic transducer of any one of claims 1 to 3, comprising:
the low-pass filter receives the audio signal output from the sound source, filters high-frequency noise and then generates an analog signal;
the A/D converter is used for receiving the analog signal output by the low-pass filter and outputting a digital audio limited signal with limited frequency spectrum after the analog signal is sampled by the A/D signal;
the signal processor receives the digital audio limited signal output by the A/D converter and outputs a time-delayed and signal-weighted PCM audio data stream after signal processing;
the D-type power amplifier receives the PCM audio data stream output by the signal processor and outputs an amplified audio signal after signal processing;
the directional sound wave bird repeller is characterized in that a sounding unit in the directional sound wave bird repeller is an ultrasonic transducer, the ultrasonic transducer is the ultrasonic transducer according to any one of claims 1 to 3, and a plurality of directional sound wave bird repellers are arranged around an airstrip in a rectangular array mode, receive amplified audio signals output by a D-type power amplifier and release sound wave beams with directivity towards a bird group.
In the invention, a sound source outputs an audio signal, a low pass filter receives the audio signal and outputs an analog signal after filtering high-frequency noise of the audio signal, an A/D converter receives the analog signal from the low pass filter and outputs a digital audio limited signal with limited frequency spectrum after sampling the analog signal by the A/D converter, a signal processor receives the digital audio limited signal with limited frequency spectrum output from the A/D converter and outputs a PCM audio data stream with time delay and signal weighting after processing the signal, a D-type power amplifier receives the PCM audio data stream with time delay and signal weighting output from the signal processor and outputs an amplified audio signal after processing the signal, a directional sound wave bird repeller receives the amplified audio signal and radiates directional ultrasonic waves to a scattering area, and a plurality of directional sound wave repellers are arranged in a rectangular array around an airplane runway, according to the bird group direction, finally, a sound wave beam with directivity is obtained by summing the sound wave beams output by the directional sound wave bird repeller, and the purpose of outputting the sound wave beam with directivity in a specific direction is achieved. The directional sound wave beam driver can realize the purpose of outputting the directional sound wave beam in a specific direction, time delay and weighting are carried out on the audio signal amplified by the directional sound wave bird driver, and then the directional sound wave beam is obtained by summing the sound wave beams output by the directional sound wave bird driver, so that bird groups are favorably driven.
As a preferable mode, the system further comprises a system core server for controlling the operation among the low-pass filter, the a/D converter, the signal processor and the class-D power amplifier, and the system core server is provided with a system management base platform electrically connected with the system core server.
The system comprises a system core server, a mobile terminal, an airport network and a firewall, wherein the system core server is provided with a switch electrically connected with the system core server, a system management basic platform is electrically connected with the switch, the airport network is connected with the system core server through the switch after accessing the firewall, and the mobile terminal is wirelessly connected with the airport network.
In a preferred mode, the signal processor comprises an ideal algorithm module requiring an infinite bandwidth, a physically realizable approximation algorithm module, a relation analysis module for carrying out error analysis on a waveform amplitude time function obtained by the approximation algorithm module relative to a waveform amplitude time function obtained by the ideal algorithm module under a modulation coefficient, and a control module for enabling time delay and signal weighting of the PCM audio data stream,
the ideal algorithmic module of infiniband is a spectrally limited digital audio limited signal as a function of waveform amplitude time according to the following equation:
y (t) is a waveform amplitude time function, f (t) is a spectrally limited digital audio limited signal, ωcIs an angular frequency (omega)c2 pi x f), t is time, f is frequency, m is modulation factor;
the approximation algorithm module (232) is configured to apply a spectral limited digital audio limited signal to a waveform amplitude time function according to the following equation:
P1(t) is a waveform amplitude time function, f (t) is a spectrally limited digital audio limited signal, ωcIs an angular frequency (omega)c2 pi x f), t is time, f is frequency, and m is a modulation coefficient;
the relation analysis module is used for obtaining the relative error analysis of the n-order waveform amplitude time function under the modulation coefficient m variable by the approximate algorithm module, and the relative error analysis accords with the following formula:
wherein: μ (m) is the error function of the waveform amplitude time function of the approximation algorithm module relative to the waveform amplitude time function of the ideal algorithm module under the variation of the modulation factor m, P1(t) is the waveform amplitude function obtained by the approximation algorithm module, and y (t) is the waveform amplitude function obtained by the ideal algorithm module;
the control module is used for enabling the functional relation between the PCM audio data stream and three variables of the signal weight of the ith ultrasonic transducer, the time delay of the ith ultrasonic transducer and the audio signal before the PCM audio data stream enters the class-D power amplifier to accord with the following formula:
wherein: wiIs the signal weight of the ith ultrasonic transducer; tau isiIs the time delay of the ith ultrasonic transducer; χ (t) is the audio signal output by the audio source, and b (t) is the output sound beam.
Preferably, the class D power amplifier comprises an equal-bit digital processor for converting the PCM audio data stream into a PWM data stream, a conventional crystal output tube, and an LC low-pass filter, wherein a pulse train with variable width generated by the PWM data stream of the equal-bit digital processor controls the conduction and non-conduction of the conventional crystal output tube, and the LC low-pass filter receives the pulse train and performs smoothing to restore the sound waveform, and then outputs the amplified audio signal.
Preferably, the emission angle of the ultrasonic transducer relative to the ground is ± 15 °.
A directional sound wave bird repelling method, the directional sound wave bird repelling system according to any one of claims 4 to 9, comprising the following steps:
step 1: the low-pass filter filters high-frequency noise of the audio signal output by the sound source to obtain an analog signal;
step 2: the A/D converter receives the analog signal transmitted by the low-frequency filter, samples and holds the analog signal, enters the holding time after the sampling is finished, and converts and codes the sampled analog signal into a digital audio limited signal with limited frequency spectrum in the holding time;
and step 3: the signal processor receives the digital audio signal with limited frequency spectrum transmitted by A/D converter, calculates the waveform amplitude function of the digital audio signal with limited frequency spectrum by using an ideal algorithm module which needs an infinite bandwidth, calculates the n-order waveform amplitude function of the digital audio signal with limited frequency spectrum by using an approximate algorithm module, analyzes the approximate algorithm module by using a relation analysis module to obtain the relation between the n-order waveform amplitude time function of the digital audio signal with limited frequency spectrum and the modulation coefficient m and relative error, selects the order and the modulation coefficient m for the n-order waveform amplitude time function to output PCM audio data stream, and then uses the PCM audio data stream on the signal processor
The formula carries out time delay and signal weighting processing on the PCM audio data stream and outputs the PCM audio data stream after the time delay and weighting processing.
And 4, step 4: the class-D power amplifier receives the PCM audio data stream output by the signal processor after time delay and weighting processing, the equal-bit digital processor on the class-D power amplifier converts the PCM audio data stream into a PWM data stream to form pulse-width-variable penetration, the PWM data stream controls the conduction and the non-conduction of a conventional crystal output tube on the class-D power amplifier, and an LC low-pass filter on the class-D power amplifier receives the pulse string and carries out smoothing processing on the pulse string to recover sound waveforms and then outputs amplified audio signals;
and 5: according to the bird group direction, after the directional sound wave bird repeller in the rectangular array receives the audio signals output and amplified by the D-type power amplifier, the sound beams output by the directional sound wave bird repeller are summed to obtain a sound beam with output directivity in the bird group direction.
In the invention, when the existence of a bird group is detected, an audio signal is output from an audio source, a low-pass filter receives the audio signal and outputs an analog signal after high-frequency noise is filtered, an A/D converter receives the analog signal and samples and holds the analog signal, converts and codes the analog signal into a frequency spectrum limited signalThe signal processor receives the digital audio signal transmitted by the a/D converter, because the infinite bandwidth does not exist in real life, that is, the waveform amplitude function calculated by the ideal algorithm module is an ideal curve, n approximate curves obtained by calculating the waveform amplitude functions of 1 st order, 2 nd order, 3 rd order. The output PCM audio data stream obtains weak sound distortion due to small error value, keeps signal balance and then is reused
The PCM audio data stream is subjected to time delay and signal weighting processing by a formula, a class D power amplifier receives the PCM audio data stream subjected to time delay and weighting processing and output by a signal processor, an equal-bit digital processor on the class D power amplifier converts the PCM audio data stream into a PWM data stream, after PWM is adopted, the PCM audio data stream becomes a series of pulse trains with variable widths and represented by '0' and '1', and the wider the pulse width is, the larger the amplitude of the signal is. The PWM data streams are pushed to a conventional crystal output tube of the power amplifier, and the conventional crystal output tube is subjected to the action of the PWM data streams, so that the conventional crystal output tube can be rapidly switched on in a saturation mode and switched off and does not work. The longer the on-state time of the conventional transistor is, the larger the signal amplitude is, so that the current provided by the output tube of the conventional transistor for the loudspeaker is sometimes conducted by the tube and has current flowing, sometimes the tube is cut off and has no current flowing, the audio information is contained in the on-off periods, the pulse train is amplified by the conventional transistor and then smoothed by the LC low-pass filter, and the audio information is recoveredThe amplified audio signal is output for the original sound waveform. The two paths of output voltages driven by the switch are almost in phase when no signal is input, the voltage applied to the LC low-pass filter is almost 0 at this time, and the voltage applied to the LC low-pass filter is almost 0 due to the two paths of in-phase output, and the load current is extremely small at this time, so that the static power consumption is very small. That is, at zero signal input, the two PWM channels are in phase and have 50% duty cycle. However, when a signal is input, the duty ratios of the two paths of PWM will change along with the input signal, if the duty ratio of one path of output pulse becomes larger, the duty ratio of the other path of output pulse becomes smaller, that is, the two paths of PWM are "reverse width", and the two paths of signals are called as two-path reverse width signals. The maximum benefit of adopting PWM with 'inverse width' as the BTL circuit driving signal of the D class amplifier is that the static loss at the input of a zero signal is restrained, and the efficiency of the amplifier is further improved. According to the bird group direction, the sound beams are output through the directional sound wave bird repellers on the periphery of the runway, the sound beams are subjected to time delay and weighting processing at the signal processor, and the nonlinear interaction of the sound beams in the air enables the multiple directional sound wave bird repellers to output the sound beams which are superposed in the bird group direction to form a high-directivity sound beam, so that the directional sound wave repelling of the bird group is realized, and the aim of efficiently repelling the bird group by the directional sound waves with weak sound distortion, stable signals and high audio signal amplification efficiency is fulfilled. The invention can realize the purpose of efficiently driving the bird group by using the directional sound wave with weak sound distortion, stable signal and high audio signal amplification efficiency, the waveform amplitude time function order with small error value and the modulation coefficient m which are calculated by the signal processor are used for determining the PCM audio data stream which is subjected to time delay and weighting, and the PWM with reversed width is used as the BTL circuit driving signal of the D-type power amplifier and transmitting the amplified audio signal to the directional sound wave bird driving device of the rectangular array, thereby avoiding the problem that the bird driving effect is not good due to sound distortion, unstable signal, small sound and low directivity of the directional sound wave bird driving system, and efficiently driving the bird group.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention can realize the aim of directionally repelling birds, and the superposition of the waveform in the transmission process is enhanced by the wavy PVDF film, so that the difficulty in enhancing the sound wave in the transmission process and the transmission process is avoided, and the invention is more favorable for directionally repelling birds
(2) The invention can realize the purpose of outputting the directional sound wave beams in a specific direction, time delay and signal weighting are carried out on the PCM audio data stream input into the D-type power amplifier, so that the time and the intensity of the sound wave beams output by the directional sound wave bird repeller around the runway are different, and the sound wave beams output by a plurality of directional sound wave bird repellers are summed to obtain one directional sound wave beam, thereby being beneficial to repelling a bird group.
(3) The invention can realize the purpose of efficiently driving bird groups by directional sound waves with weak sound distortion, stable signals and high audio signal amplification efficiency, a signal processor calculates a waveform amplitude time function with small error value to determine a PCM audio data stream of a signal frequency band and a modulation coefficient m, PWM of 'inverse width' is used as a BTL circuit driving signal of a D-type power amplifier, and an ultrasonic transducer which transmits time delay and weighted amplified audio signals to a rectangular array is matched with each other, so that the problem that the bird driving effect is poor due to sound distortion, unstable signals, small sound and low directivity of the directional sound waves is avoided, and the bird groups can be efficiently driven;
drawings
FIG. 1 is a schematic diagram of the system of the apparatus of the present invention.
Fig. 2 is an overall architecture diagram of the bird repelling system of the invention.
FIG. 3 is a graph comparing the waveform amplitude versus time for curves of an approximation algorithm and an ideal algorithm.
Fig. 4 is a graph of the amplitude time function of the waveform of order n with the modulation factor m and the relative error.
Fig. 5 is a schematic diagram of algorithm-related modules of the signal processor.
Fig. 6 is a schematic diagram of an audio signal entering a directional acoustic bird repeller array.
Fig. 7 is a signal propagation flow diagram of a class D power amplifier.
Fig. 8 is a schematic structural diagram of the directional sound wave bird repeller at the runway.
Fig. 9 is a schematic structural diagram of an ultrasonic transducer.
Fig. 10 is a schematic view of the concavo-convex structure of the PVDF film.
The system comprises an ultrasonic transducer 1, a shell 110, an electrode wire 120, a grounding wire 130, a protective film 140, a piezoelectric wafer 150, an absorption block 160, a matching inductor 170, a system core server 2, a low-pass filter 210, a 220A/D converter 230, a signal processor 231, an ideal algorithm module 231, an approximate algorithm module 232, a relationship analysis module 233, a control module 234, a class-D power amplifier 240, a bit digital processor such as 241 and the like, a conventional crystal output tube 242, a 243LC low-pass filter, a directional sound wave bird repeller 3, a system management basic platform 4, a mobile terminal 5, an airport network 6, a firewall 7 and an exchanger 8.
Detailed Description
The invention will be further described with reference to the accompanying drawings. Embodiments of the present invention include, but are not limited to, the following examples.
Example 1:
referring to fig. 9 and 10, an ultrasonic transducer includes a piezoelectric wafer 150 made of a PVDF film having a wave-shaped cross section. .
In this example, the piezoelectric wafer 150 is used for transmitting and receiving ultrasonic waves, the piezoelectric wafer 150 is made of a PVDF film, and the cross section of the PVDF film is wavy, so that the waveforms at the peak and valley of the PVDF film are favorably overlapped with each other in propagation, and on the intersecting line of adjacent peaks and valleys of the PVDF film, because the forces and displacements caused by excitation are equal and opposite in direction, the position is not moved but only allowed to rotate, the intersecting line becomes a virtual axis, a virtual boundary is formed, that is, the PVDF film is not fixed by using a clamping piece, and the purpose of directionally driving birds is achieved. The invention can realize the aim of directionally repelling birds, and the superposition of the waveform in the transmission process is enhanced through the wavy PVDF film, so that the difficulty in enhancing the sound wave in the transmission process is avoided, and the invention is more favorable for directionally repelling birds.
Referring to fig. 9 and 10, as a preferred mode, the piezoelectric element package further includes a housing 110, two electrode wires 120 and a ground wire 130, wherein a protective film 140 is disposed at one end of the housing 110, a piezoelectric wafer 150 is closely attached to the protective film 140 in the housing 110, an absorption block 160 is disposed in the housing 110, the two electrode wires 130 are respectively connected to an upper end surface and a lower end surface of the piezoelectric wafer 150 and penetrate through the absorption block 160 to extend out of the housing 110, the electrode wires 120 connected to the upper end surface of the piezoelectric wafer 150 in the housing 110 are coupled and connected to a matching inductor 170, and the housing 110 is connected to the ground wire 130.
Make electrode line 120 and the electric wire electricity that is used for inputing the ultrasonic wave connect, make the earth connection 130 ground connection on the casing 110, can effectively filter the higher harmonic composition that switch mode power output square wave exists with electrode line 120 coupling connection's matching inductance 170, audio signal transmits piezoelectric wafer 150 through matching inductance 170, piezoelectric wafer 150 is used for transmitting and receiving the ultrasonic wave, protection film 140 is used for protecting piezoelectric wafer 150, absorption piece 160 is used for suppressing unnecessary vibrations and absorbs stray callback, can realize ultrasonic transducer sound production.
Referring to fig. 9, as a preferred mode, the PVDF film of the piezoelectric wafer 150 has a peak-valley height difference h ≈ λ/2 between adjacent peaks and valleys, where λ is the wavelength of the ultrasonic wave in the sound-transmitting medium, and by h ≈ λ/2, it is realized that the waveforms generated at the peaks and valleys of the PVDF film are mutually superimposed and reinforced in the propagation.
The formula for calculating the resonant frequency of the piezoelectric wafer 150 is:
wherein f is0For harmonic frequencies, Y is the average young's modulus of the PVDF film (containing the silver coating), ρ is the average density, and R is the radius of curvature.
The relationship between the curvature radius of the PVDF film with the wavy cross section and the harmonic frequency can be obtained through the calculation formula of the resonance frequency of the piezoelectric wafer 150, so that the optimal curvature radius is obtained.
Example 2:
referring to fig. 1, 6 and 8, a directional sound wave bird repelling system, the ultrasonic transducer 1 according to any one of claims 1 to 3, comprising:
a low pass filter 210 for receiving the audio signal outputted from the sound source and filtering high frequency noise to generate an analog signal;
an a/D converter 220 for receiving the analog signal output by the low pass filter 210 and outputting a digital audio limited signal with limited frequency spectrum after a/D signal sampling;
a signal processor 230 receiving the spectrally limited digital audio limited signal output by the A/D converter 220 and performing signal processing thereon to output a time delayed and signal weighted PCM audio data stream;
a class-D power amplifier 240 for receiving the PCM audio data stream output by the signal processor 230 and outputting an amplified audio signal after signal processing;
the directional sound wave bird repeller 3 is characterized in that a sounding unit in the directional sound wave bird repeller 3 is an ultrasonic transducer 1, the ultrasonic transducer 1 is the ultrasonic transducer described in any one of claims 1 to 3, and the directional sound wave bird repellers 3 are arranged around an airstrip in a rectangular array mode, receive amplified audio signals output by a D-type power amplifier 240 and release sound wave beams with directivity towards a bird group.
In this example, the sound source outputs audio signals, the low pass filter 210 receives the audio signals and outputs analog signals after filtering high frequency noise from the audio signals, the a/D converter 220 receives the analog signals from the low pass filter 210 and outputs digital audio limited signals with limited frequency spectrum after a/D signal sampling, the signal processor 230 receives the digital audio limited signals with limited frequency spectrum output from the a/D converter 220 and outputs PCM audio data streams with time delay and signal weighting after signal processing, the class D power amplifier 240 receives the PCM audio data streams with time delay and signal weighting output from the signal processor 230 and outputs amplified audio signals after signal processing, the directional acoustic bird repeller 3 receives the amplified audio signals and radiates directional ultrasonic waves to a dispelling area, and the directional acoustic bird repellers 3 are arranged in a rectangular array around the runway, according to the bird group direction, finally, a sound wave beam with directivity is obtained by summing the sound wave beams output by the directional sound wave bird repeller 3, and the purpose of outputting the sound wave beam with directivity in a specific direction is achieved. The invention can realize the purpose of outputting sound wave beams with directivity in a specific direction, time delay and weighting are carried out on the audio signals amplified by the directional sound wave bird repeller 3, and then a sound wave beam with directivity is obtained by summing the sound wave beams output by the directional sound wave bird repeller 3, thereby being beneficial to repelling the bird groups.
The low-pass filter 210 adopts a third-order RC active low-pass filter in the embodiment, the a/D converter 220 adopts an ADS7809 chip in the embodiment, the signal processor 230 adopts a DSP signal processor TMS320VC5409 in the embodiment, and the directional acoustic wave bird repeller 3 can adopt MHDW-1000 in the invention.
Referring to fig. 2, as a preferred mode, the system further includes a system core server 2 for controlling operations among the low pass filter 210, the a/D converter 220, the signal processor 230, and the class D power amplifier 240, and the system core server 2 is provided with a system management base platform 4 electrically connected thereto. The system management basic platform 4 is used for controlling the system core server 2 which operates among the low-pass filter 210, the A/D converter 220, the signal processor 230 and the D-type power amplifier 240, and the system management basic platform 4 can adopt a computer on which an integrated management software platform is installed, so that the directional sound wave bird repelling system can be controlled.
Referring to fig. 2, as a preferred mode, the system further includes a mobile terminal 5, an airport network 6 and a firewall 7, the system core server 2 is provided with an exchange 8 electrically connected with the system core server, the system management base platform 4 is electrically connected with the exchange 8, the airport network 6 is connected with the system core server 2 through the exchange 8 after accessing the firewall 7, and the mobile terminal 5 is wirelessly connected with the airport network 6. The mobile terminal 5 is connected to the airport network 6 via a wireless connection access firewall 7 and then connected to the system core server 2 via the switch 8, thereby realizing control of the system core server 2 by the mobile terminal 5.
Referring to fig. 4, 5 and 6, the signal processor 230 includes an ideal algorithm module 231 requiring an infinite bandwidth, a physically realizable approximation algorithm module 232, a relationship analysis module 233 for performing an error analysis on the waveform amplitude time function derived from the approximation algorithm module with respect to the waveform amplitude time function derived from the ideal algorithm module under the modulation factor, and a relationship analysis module 234 for enabling the time delay of the PCM audio data stream to be weighted with the signal,
the ideal algorithm module 231 for infiniband is a spectrally limited digital audio limited signal with a waveform amplitude time function that conforms to the following equation:
y (t) is a waveform amplitude time function, f (t) is a spectrally limited digital audio limited signal, ωcIs an angular frequency (omega)c2 pi x f), t is time, f is frequency, and m is a modulation coefficient;
the approximation algorithm module 232 is a spectrally limited digital audio limited signal that is related to the waveform amplitude time function according to the following equation:
P1(t) is a waveform amplitude time function, f (t) is a spectrally limited digital audio limited signal, ωcIs an angular frequency (omega)c2 pi x f), t is time, f is frequency, and m is a modulation coefficient;
the relation analysis module 233 is configured to analyze an error of the n-th order waveform amplitude time function obtained by the approximation algorithm module 232 with respect to the waveform amplitude time function obtained by the ideal algorithm module under the modulation coefficient variable according to the following formula:
wherein: μ (m) is the relative error function of the waveform amplitude time function of the approximation algorithm module with respect to the waveform amplitude time function of the ideal algorithm module under the variation of the modulation factor m, P1(t) is the waveform amplitude function obtained by the approximation algorithm module, and y (t) is the waveform amplitude function obtained by the ideal algorithm module;
the functional relationship between the PCM audio data stream and the signal weight of the ith ultrasonic transducer, the time delay of the ith ultrasonic transducer, and the audio signal before entering the class-D power amplifier 240 by the relationship analysis module 234 conforms to the following formula:
wherein: wiIs the signal weight of the ith ultrasonic transducer; tau isiIs the time delay of the ith ultrasonic transducer; χ (t) is the audio signal output by the audio source, and b (t) is the output sound beam.
The infiniband ideal algorithm module 231 employs a square root signal processing algorithm that requires an infiniband physical system that is not present in real life. The square root double integration method is a signal processing algorithm adopted by a remote sound dispersion device, double integration is to compensate 12 dB/octave of a signal from a time domain, but the compensation can also be carried out through a frequency domain, because the double integration of the time domain is realized by a digital signal processing device, the estimation of the range of the numerical value after the integration is a difficult problem and is difficult to realize through a program. However, in the frequency domain implementation, the frequency tilt response compensation of 12 dB/octave can be implemented only by one filter, which is easy to implement, and therefore, the frequency domain compensation mode is generally adopted. This 12 dB/octave frequency response tilt can be performed separately from the time domain signal processing method.
Square root signal processing algorithm of ideal algorithm module for infinite bandwidth
And (4) expressing the formula.
The approximate algorithm module 232 adopts an approximate square root algorithm, which is improved on the basis of a square root signal processing algorithm, and overcomes the defect that the square root algorithm requires infinite bandwidth, namely, the approximate algorithm modules can be physically realized.
Approximate square root algorithm of physically implementable approximate algorithm module 232
The waveform amplitude function calculated by the ideal algorithm module 231 is an ideal curve, n approximate curves obtained by calculating 1 st, 2 nd and 3 rd order as well as n th order waveform amplitude functions of the digital audio signal with limited frequency spectrum by the approximate algorithm module 232 are calculated, the error of the n order waveform amplitude time function of the digital audio signal with limited frequency spectrum relative to the ideal algorithm module 231 under the variable of the modulation coefficient m is obtained by analyzing the approximate algorithm module 232 by the relation analysis module 233, so that the higher the order of the waveform amplitude time function is, the smaller the modulation coefficient is and the smaller the relative error value is, the PCM audio data stream determined by the waveform amplitude time function order with small error value and the modulation coefficient m can be selected from the calculation, comparison and analysis, thereby being beneficial to ensuring that the output PCM audio data stream avoids sound distortion because the error value is small and keeping signal balance, and then time delay and signal weighting are carried out on the PCM audio data stream, so that the direction and the angle of sound beams output by the directional sound wave bird repeller 3 around the runway can be changed after superposition.
When the waveform amplitude function of the approximation algorithm module 232 selects 1 st order, 2 nd order and 3 rd order respectively,
according to the above three equations, compared with the infinite bandwidth requirement of the waveform amplitude function of the ideal algorithm module 231, when ω is 2 pi × 40000 (i.e. the carrier frequency is 40KHz), the first order approximation only requires the signal frequency band range to be 20-60KHz, the second order requirement bandwidth is 0-80 KHz, and the third order requirement bandwidth is 0-100 KHz. I.e. these approximation algorithms can be physically implemented.
Compared with the waveform amplitude time function obtained by the ideal algorithm module 231, when the order of the approximation is larger, the waveform amplitude time function obtained by the approximation algorithm module 232 is closer to the waveform amplitude time function (original curve) obtained by the ideal algorithm module 231, that is, the error is smaller, but the required bandwidth is correspondingly wider, the algorithm is more complex, and the calculation time is longer. When the order number exceeds a certain limit, the defect that the real-time performance cannot meet the requirement is brought. When the modulation coefficient is 0.5, the relative error between the first order, second order and third order approximation curves and the ideal curve can be obtained.
It can be found from the relational analysis module 233 that the maximum relative error of the first order approximation is 6.1%, the relative error of the second order approximation is 1.65%, and the relative error of the third order error is only 0.55%.
In summary, the approximation algorithm module 232 may be implemented by a physical system. By carefully selecting the approximate order and the modulation coefficient, the precision of the system can meet the requirement, the sound distortion is avoided, and the signal balance is ensured.
Referring to fig. 3, comparing the graphs of the waveform amplitude time functions obtained by the approximation algorithm module 232 and the ideal algorithm module 231, it is found that the higher the order is, the closer the waveform amplitude time function obtained by the approximation algorithm module 232 is to the waveform amplitude time function of the ideal algorithm module 231 when the same m is, so that the larger the order approximated by the verification relationship analysis module 233 is, the closer the waveform amplitude time function obtained by the approximation algorithm module 232 is to the waveform amplitude time function (original current) obtained by the ideal algorithm module 231 is, that is, the smaller the error is.
Referring to fig. 7, as a preferred mode, the class D power amplifier 240 includes an equal-bit digital processor 241 for converting the PCM audio data stream into a PWM data stream, a conventional crystal output tube 242, and an LC low-pass filter 243, wherein a pulse train with variable width generated by the PWM data stream of the equal-bit digital processor 241 controls the conduction and non-conduction of the conventional crystal output tube 242, and the LC low-pass filter 243 receives the pulse train and performs a smoothing process to restore the sound waveform and output the amplified audio signal.
The class D power amplifier 240 receives the PCM audio data stream from the signal processor 230, and the equal bit digital processor 241 of the class D power amplifier 240 converts the PCM audio data stream into a PWM data stream, and after PWM, the PCM audio data stream becomes a series of pulse trains with variable widths, which are denoted by "0" and "1", and the wider the pulse width is, the larger the amplitude of the signal is. These PWM data streams are pushed to the conventional crystal output transistor 242 of the power amplifier, and the conventional crystal output transistor 242 will be rapidly turned on in time saturation and turned off in time due to the PWM data streams. The longer the on-state time of the conventional transistor is, the larger the signal amplitude is, so that the current provided by the output tube 242 of the conventional transistor for the ultrasonic transducer sometimes flows due to the conduction of the tube, and sometimes no current flows due to the cut-off of the tube, and the audio information is contained in the on-state and off-state periods, and after the pulse train is amplified by the conventional transistor, the smoothing process is performed by the LC low-pass filter 243, so that the original sound waveform is restored, and the amplified audio signal is output. The two output voltages of the switch drive are almost in phase when no signal is input, the voltage applied to the LC low-pass filter 243 is almost 0 at this time, and the voltage applied to the LC low-pass filter 243 is almost 0 due to the two in-phase outputs, and the load current is extremely small at this time, so that the static power consumption is very small. That is, at zero signal input, the two PWM channels are in phase and have 50% duty cycle. However, when a signal is input, the duty ratios of the two paths of PWM will change along with the input signal, if the duty ratio of one path of output pulse becomes larger, the duty ratio of the other path of output pulse becomes smaller, that is, the two paths of PWM are "reverse width", and the two paths of signals are called as two-path reverse width signals. The maximum benefit of adopting PWM with 'inverse width' as the BTL circuit driving signal of the D class amplifier is that the static loss at the input of a zero signal is restrained, and the efficiency of the amplifier is further improved.
The constant bit digital processor 241 may employ TMS320VC5409 in the present embodiment, the conventional crystal output tube 242 may employ 2SC1623 in the present embodiment, and the LC low pass filter 243 may employ LBP30/S12-D18 in the present embodiment.
Preferably, the emission angle of the ultrasonic transducer 1 is ± 15 ° with respect to the ground. The sound pressure level of the ultrasonic transducer 1 is obviously reduced beyond the emission angle of +/-15 degrees relative to the ground.
The other parts of this embodiment are the same as embodiment 1, and are not described herein again. The above is an embodiment of the present invention.
Example 3:
referring to fig. 1, 3, 4, 5, 6, 7 and 8, a directional sound wave bird repelling method according to any one of claims 4 to 9 comprises the following steps:
step 1: the low-pass filter 210 filters high-frequency noise from the audio signal output by the sound source to obtain an analog signal;
step 2: the A/D converter 220 receives the analog signal transmitted by the low-frequency filter, samples and holds the analog signal, enters the holding time after the sampling is finished, and converts and codes the sampled analog signal into a digital audio limited signal with limited frequency spectrum in the holding time;
and step 3: the signal processor 230 receives the spectrum limited digital audio signal transmitted from the A/D converter 220, calculates a waveform amplitude function of the spectrum limited digital audio signal using an ideal algorithm module 231 requiring an infinite bandwidth, calculates an n-th order waveform amplitude function of the spectrum limited digital audio signal using an approximation algorithm module 232, analyzes the approximation algorithm module 232 using a relation analysis module 233 to find a relation between the n-th order waveform amplitude time function of the spectrum limited digital audio signal and a modulation coefficient m and a relative error, selects an order and a modulation coefficient m for the n-th order waveform amplitude time function, outputs a PCM audio data stream, and then uses the PCM audio data stream output by the signal processor 230
The formula carries out time delay and signal weighting processing on the PCM audio data stream and outputs the PCM audio data stream after the time delay and weighting processing.
And 4, step 4: the class-D power amplifier 240 receives the PCM audio data stream output by the signal processor 230 after time delay and weighting processing, the PCM audio data stream is converted into a PWM data stream by using an equal-bit digital processor 241 on the class-D power amplifier 240 to form pulse-width-variable transmission, the PWM data stream controls the conduction and the non-conduction of a conventional crystal output tube 242 on the class-D power amplifier 240, and an LC low-pass filter 243 on the class-D power amplifier 240 receives the pulse train and carries out smoothing processing on the pulse train to recover sound waveforms and then outputs amplified audio signals;
and 5: according to the bird group direction, after the directional sound wave bird repeller 3 in the rectangular array receives the audio signal output and amplified by the D-type power amplifier 240, the sound beams output by the directional sound wave bird repeller 3 are summed to obtain a sound beam with high directivity output in the bird group direction.
In this example, when detecting the presence of a bird group, the sound source outputs an audio signal, the low pass filter 210 receives the audio signal and outputs an analog signal after filtering high frequency noise, the a/D converter 220 receives the analog signal and samples and holds the analog signal to convert and encode the analog signal into a digital audio signal with limited frequency spectrum, the signal processor 230 receives the digital audio signal with limited frequency spectrum transmitted by the a/D converter 220, because infinite bandwidth does not exist in real life, i.e. the waveform amplitude function calculated by the ideal algorithm module 231 is an ideal curve, the approximation algorithm module 232 calculates n approximation curves obtained by the waveform amplitude functions of 1 st, 2 nd, and 3 rd orders of the digital audio signal with limited frequency spectrum, the relationship analysis module 233 analyzes the approximation algorithm module 232 to obtain an n-order waveform amplitude time function of the digital audio signal with limited frequency spectrum relative to the ideal algorithm module 231, the n-order waveform amplitude time function of the digital audio signal with limited frequency spectrum is obtained by the relationship analysis module 233 analyzing the approximation m variable error, so as to obtain the PCM audio data stream with higher order of waveform amplitude time function, smaller modulation coefficient and smaller relative error value, and the waveform amplitude time function order with small error value and modulation coefficient m can be selected from the above-mentioned calculation, comparison and analysis, so that the output PCM audio data stream can obtain weak sound distortion and keep signal balance due to small error value, and then the signal balance is retained, and the error value is reduced
Formulation of PCM audio data streamTime delay and signal weighting processing, the class-D power amplifier 240 receives the time-delayed and weighted PCM audio data stream output by the signal processor 230, the equal-bit digital processor 241 on the class-D power amplifier 240 converts the PCM audio data stream into a PWM data stream, and after PWM, the PCM audio data stream becomes a series of pulse trains with variable widths, which are represented by "0" and "1", and the wider the pulse width, the larger the amplitude of the signal. These PWM data streams are pushed to the conventional crystal output transistor 242 of the power amplifier, and the conventional crystal output transistor 242 will be rapidly turned on in time saturation and turned off in time due to the PWM data streams. The longer the on-state time of the conventional transistor is, the larger the signal amplitude is, so that the current provided by the output tube 242 of the conventional transistor for the speaker sometimes flows because the tube is on, and sometimes no current flows because the tube is off, and the audio information is contained in the on-state and off-state periods, and after the pulse train is amplified by the conventional transistor, the smoothing process is performed by the LC low-pass filter 243, so that the original sound waveform is restored, and the amplified audio signal is output. The two output voltages of the switch drive are almost in phase when no signal is input, the voltage applied to the LC low-pass filter 243 is almost 0 at this time, and the voltage applied to the LC low-pass filter 243 is almost 0 due to the two in-phase outputs, and the load current is extremely small at this time, so that the static power consumption is very small. That is, at zero signal input, the two PWM channels are in phase and have 50% duty cycle. However, when a signal is input, the duty ratios of the two paths of PWM will change along with the input signal, if the duty ratio of one path of output pulse becomes larger, the duty ratio of the other path of output pulse becomes smaller, that is, the two paths of PWM are "reverse width", and the two paths of signals are called as two-path reverse width signals. The maximum benefit of adopting PWM with 'inverse width' as the BTL circuit driving signal of the D class amplifier is that the static loss at the input of a zero signal is restrained, and the efficiency of the amplifier is further improved. The sound beams are output by the directional sound wave bird repeller 3 around the runway according to the bird group direction, and the non-linear interaction of the sound beams in the air causes a plurality of directions due to the time delay and weighting processing at the signal processor 230The sound wave bird repeller 3 outputs sound wave beams which are superposed in the direction of the bird group to form a sound wave beam with high directivity, so that directional sound wave driving of the bird group is realized, and the aims of efficiently driving the bird group by directional sound waves with weak sound distortion, stable signals and high audio signal amplification efficiency are fulfilled. The invention can realize the purpose of efficiently driving the bird group by using the directional sound wave with weak sound distortion, stable signal and high audio signal amplification efficiency, the signal processor 230 calculates the waveform amplitude time function order with small error value and the modulation coefficient m to determine the PCM audio data stream which is subjected to time delay and weighting, and the PWM with reversed width is used as the BTL circuit driving signal of the D-type power amplifier 240 and transmits the amplified audio signal to the directional sound wave bird driving device 3 of the rectangular array, thereby avoiding the problem that the bird driving effect of the directional sound wave bird driving system is not good due to sound distortion, unstable signal, small sound and low directivity, and efficiently driving the bird group.
The other parts of this embodiment are the same as embodiment 1, and are not described herein again. The above is an embodiment of the present invention.
The embodiments and specific parameters in the embodiments are only used for clearly illustrating the verification process of the invention and are not used for limiting the patent protection scope of the invention, which is defined by the claims, and all the equivalent structural changes made by using the contents of the description and the drawings of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. An ultrasonic transducer comprising a piezoelectric wafer (150) made of a PVDF film having a waved cross-section.
2. The ultrasonic transducer of claim 1, wherein: still include casing (110), two electrode wires (120) and earth connection (130), casing (110) one end is equipped with protection film (140), pressure piezocrystal piece (150) hug closely with protection film (140) in casing (110), be equipped with in casing (110) and absorb piece (160), two electrode wires (130) connect respectively in the up end of piezocrystal piece (150) and terminal surface down and pass and absorb piece (160) and stretch out outside casing (110), coupling connection has matching inductance (170) on electrode wire (120) of being connected with piezocrystal piece (150) up end in casing (110), casing (110) and earth connection (130).
3. The ultrasonic transducer of claim 1, wherein: the peak-valley height difference h of adjacent peak troughs of the PVDF film of the piezoelectric wafer (150) is approximately equal to lambda/2, wherein lambda is the wavelength of ultrasonic waves in the sound transmission medium.
4. A directional sound wave bird repelling system is characterized by comprising:
a low pass filter (210) for receiving the audio signal outputted from the sound source and filtering the high frequency noise to generate an analog signal;
an A/D converter (220) for receiving the analog signal output by the low-pass filter (210) and outputting a spectrum-limited digital audio-limited signal after A/D signal sampling;
a signal processor (230) receiving the spectrally limited digital audio limited signal output by said A/D converter (220) and performing signal processing to output a time delayed and signal weighted PCM audio data stream;
the D-type power amplifier (240) receives the PCM audio data stream output by the signal processor (230) and outputs an amplified audio signal after signal processing;
a directional sound wave bird repeller (3), wherein a sound production unit in the directional sound wave bird repeller (3) is an ultrasonic transducer (1), and the ultrasonic transducer (1) is the ultrasonic transducer as claimed in any one of claims 1-3; the directional sound wave bird repellers (3) are arranged around the runway in a rectangular array mode, receive the amplified audio signals output by the D-type power amplifier (240) and release sound wave beams with directivity towards the direction of a bird group.
5. The directional acoustic bird repelling system of claim 4, wherein: the system is characterized by further comprising a system core server (2) used for controlling operation among the low-pass filter (210), the A/D converter (220), the signal processor (230) and the D-type power amplifier (240), wherein a system management basic platform (4) electrically connected with the system core server (2) is arranged on the system core server.
6. The directional acoustic bird repelling system of claim 5, wherein: still include mobile terminal (5), airport network (6) and prevent hot wall (7), be equipped with switch (8) rather than the electricity connection on system core server (2), system management basic platform (4) are connected with switch (8) electricity, airport network (6) visit and are connected with system core server (2) through switch (8) behind preventing hot wall (7), mobile terminal (5) and airport network (6) wireless connection.
7. The directional acoustic bird repelling system of claim 4, wherein: the signal processor (230) comprises an ideal algorithm module (231) requiring an infinite bandwidth, a physically realizable approximation algorithm module (232), a relation analysis module (233) for performing error analysis on the waveform amplitude time function obtained by the approximation algorithm module (232) relative to the waveform amplitude time function obtained by the ideal algorithm module (231) under the modulation coefficient, and a control module (234) for enabling the time delay and signal weighting of the PCM audio data stream,
the spectrum limited digital audio limited signal of the infinite bandwidth ideal algorithm module (231) is related to the waveform amplitude time function according to the following equation:
y (t) is a waveform amplitude time function, f (t) is a spectrally limited digital audio limited signal, ωcIs an angular frequency (omega)c2 pi x f), t is time, f is frequency, and m is a modulation coefficient;
the approximation algorithm module (232) is configured to apply a spectral limited digital audio limited signal to a waveform amplitude time function according to the following equation:
P1(t) is a waveform amplitude time function, f (t) is a spectrally limited digital audio limited signal, ωcIs an angular frequency (omega)c2 pi x f), t is time, f is frequency, and m is a modulation coefficient;
the relation analysis module is used for analyzing the error of the waveform amplitude time function of the n-th order obtained by the approximation algorithm module relative to the waveform amplitude time function obtained by the ideal algorithm module under the modulation coefficient variable according to the following formula:
wherein: μ (m) is the relative error function of the waveform amplitude time function of the approximation algorithm module with respect to the waveform amplitude time function of the ideal algorithm module under the variation of the modulation factor m, P1(t) is the waveform amplitude function obtained by the approximation algorithm module, and y (t) is the waveform amplitude function obtained by the ideal algorithm module;
the functional relation between the control module (234) and three variables of the signal weight value of the ith ultrasonic transducer, the time delay of the ith ultrasonic transducer and the audio signal before the PCM audio data stream enters the D-type power amplifier (240) conforms to the following formula:
wherein: wiIs the signal weight of the ith ultrasonic transducer; tau isiIs the time delay of the ith ultrasonic transducer; χ (t) is the audio signal output by the audio source, and b (t) is the output sound beam.
8. The directional acoustic bird repelling system of claim 4, wherein: the class-D power amplifier (240) comprises an equal-bit digital processor (241) for converting PCM audio data flow into PWM data flow, a conventional crystal output tube (242) and an LC low-pass filter (243), wherein pulse trains with variable widths generated by the PWM data flow of the equal-bit digital processor (241) control the conduction and the non-conduction of the conventional crystal output tube (242), and the LC low-pass filter (243) receives the pulse trains, performs smoothing processing on the pulse trains, recovers sound waveforms and outputs amplified audio signals.
9. The directional acoustic bird repelling system of claim 4, wherein: the emission included angle of the ultrasonic transducer (1) relative to the horizontal direction is +/-15 degrees.
10. A directional sound wave bird repelling method is characterized by comprising the following steps: the directional sound wave bird repelling system according to any one of claims 4 to 9, comprising the steps of:
step 1: the low-pass filter (210) filters high-frequency noise of the audio signal output by the sound source to obtain an analog signal;
step 2: the A/D converter (220) receives the analog signal transmitted by the low-frequency filter, samples and holds the analog signal, enters the holding time after the sampling is finished, and converts and codes the sampled analog signal into a digital audio limited signal with limited frequency spectrum in the holding time;
and step 3: a signal processor (230) receives the spectrally limited digital audio signal transmitted by the A/D converter (220), calculates a waveform amplitude function of the spectrally limited digital audio signal using an ideal algorithm module (231) requiring an infinite bandwidth, calculates an n-th order waveform amplitude function of the spectrally limited digital audio signal using an approximation algorithm module (232), analyzes the approximation algorithm module (232) using a relationship analysis module (233) to obtain a relative error of the n-th order waveform amplitude time function of the spectrally limited digital audio signal with respect to the ideal algorithm module waveform amplitude time function at a modulation coefficient m, selects an order and a modulation coefficient m for the n-th order waveform amplitude time function to output a PCM audio data stream, and then outputs the PCM audio data stream on the signal processor (230)
The time delay and signal weighting process is carried out to PCM audio data stream by formula, and the PCM audio after time delay and weighting process is outputA data stream;
and 4, step 4: the class D power amplifier (240) receives the PCM audio data stream after time delay and weighting processing output by the signal processor (230), the PCM audio data stream is converted into a PWM data stream by an equal-bit digital processor (241) on the class D power amplifier (240) to form pulse-width-variable transmission, the PWM data stream controls the conduction and the non-conduction of a conventional crystal output tube (242) on the class D power amplifier (240), and an LC low-pass filter (243) on the class D power amplifier (240) receives the pulse train and carries out smoothing processing on the pulse train to restore the sound waveform and then outputs an amplified audio signal;
and 5: according to the bird group direction, after the directional sound wave bird repeller (3) in a rectangular array receives the audio signals output and amplified by the D-type power amplifier (240), the sound beams output by the directional sound wave bird repeller (3) are summed to obtain a sound beam with output directivity in the bird group direction.
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| CN112735366A (en) * | 2020-12-24 | 2021-04-30 | 青岛鼎信通讯消防安全有限公司 | PWM (pulse-width modulation) variable-frequency sound driving device for automatic fire alarm system and design method |
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