Background technology
Ultrasound wave follows propagation law in elastic fluid for the common mechanical ripple, is characterized in along straightline propagation, has goodGood bunchy, good directionality, reflection and refraction effect can occur at the separating surface of medium, it vibrates width after entering mediumDegree can be decayed because of Absorption of Medium.The frequency of ultrasound wave can be very high, reaches a megahertz level.
Spread speed substantially constant in same medium for the ultrasound wave, passes through in the medium hence with measurement ultrasound waveTime used by one segment distance, it is possible to achieve contactless range finding.In order to improve the degree of accuracy of range finding it is necessary to accurate measurement is ultrasonicElapsed time (pacing the more time) when ripple is propagated in media as well.
In reflecting type ultrasonic ranging scheme, together with ultrasonic transmitter is located in ultrasonic receiver, whenDuring ultrasonic transmitter work, mechanical vibration can pass to receptor at first by circuit board, by airborne ultrasound waveReceptor can be reached, these ripples are referred to as crosstalk and lead directly to ripple (also referred to as leakage waves), when the signal of telecommunication of excitation ultrasonic transmitter stopsAfterwards, due to the factor of machinery inertial, ultrasonic transmitter oscillator still can vibrate several cycles.During this period, ultrasound wave receivesDevice is constantly subjected to crosstalk and leads directly to the impact of ripple it is impossible to correctly differentiate ultrasonic echo signal, and the impact of the only straight-through ripple of crosstalk disappearsAfter mistake, ultrasonic echo signal could correctly be differentiated by ultrasonic receiver；The time that wave action is led directly in crosstalk is exactly ultrasoundAway from blind area, generally to be represented with the distance that this period, ultrasound wave was propagated in media as well, existing transceiver ultrasonic wavesEnergy device there are about the range hole of 30cm.
Reduce range hole method mainly have two kinds.One is to start with from the structure of transducer, by suitable structureDesign, while considering to improve transducer sensitivity, takes appropriate measure suppression remained shock and attached frequency vibration, so that transducerThere is higher sensitivity and have less transmitted wave hangover, but this method is similarly faced with raising sensitivity and reduction is sent outThe contradiction of ejected wave hangover, limited use.Another kind of method is to start with from signal amplification circuit, using time-varying gain amplifier, that is,The feature that amplitude according to echo-signal exponentially decayed with the propagation time, reception amplifier is designed to gain in timeThe time-varying gain amplifier exponentially increasing, within the specific limits, makes far and near different echo-signal can balancedly putArrive greatly suitable amplitude, it is to avoid transmitted wave crossing of signal of trailing is amplified, and therefore, reduces measurement blind area to a certain extent.However, analysis understands, this method is by controlling gain to reach suppression measurement blind area.The transmitted wave of impact blind area size dragsTail signal can repressed precondition be the amplitude that echo signal amplitude have to be larger than relevant position hangover signal, can obtainBlind area least limit be echo-signal amplitude and relevant position launch hangover signal amplitude equal when corresponding measurement away fromFrom it is clear that actual blind area is also bigger than this.Want to reduce measurement blind area further, the method incapability of time-varying gain suppression isPower.
Content of the invention
The purpose of the present invention is for the deficiencies in the prior art, provides a kind of non-blind area based on the principle that inversely adds ultrasonicRipple distance-finding method.
The purpose of the present invention is achieved through the following technical solutions：A kind of non-blind area ultrasonic ranging probe, this spyHead includes ultrasonic transmitter T, the first ultrasonic receiver R in the same plane1With the second ultrasonic receiver R2, theOne ultrasonic receiver R1With the second ultrasonic receiver R2With ultrasonic transmitter T apart from identical and be in ultrasonic transmitter TThe same side；Second ultrasonic receiver R2Covered by the container of a groove at side surface, can be with separating echo, this container is slottedDirection faces ultrasonic transmitter T.
Further, described first ultrasonic receiver R1With the second ultrasonic receiver R2Can be subject to surpass in constant amplitude ground simultaneouslyThe impact of ripple is led directly in pinger T crosstalk.
Further, the impact that ripple is led directly in crosstalk is eliminated using the method that inversely adds.
Further, described first ultrasonic receiver R1With the second ultrasonic receiver R2Receive signal respectively throughAfter chopped-off head amplifier amplifies, common input secondary amplifier, the output signal of secondary amplifier is successively through final amplifier, rectificationAfter circuit, filter circuit, output carries the signal of telecommunication of echo-signal；Described chopped-off head amplifier adopts inverting amplifier, described timeLevel amplifier adopts the subtraction circuit of gain controllable, and described final amplifier adopts resonant selecting frequency amplifier.
A kind of non-blind area ultrasonic ranging method, the method using two with ultrasonic transmitter be in same plane and withUltrasonic transmitter is covered by the container of groove at side surface apart from identical ultrasonic receiver, one of ultrasonic receiver,The direction of this container fluting is just to ultrasonic transmitter；The signal inversion superposition of two ultrasonic receiver outputs, eliminates ultrasonicThe impact of ripple is led directly in wave launcher crosstalk, obtains echo-signal, completes to find range.
Further, after the signal of two ultrasonic receiver receptions is respectively through the amplification of chopped-off head amplifier, common inputSecondary amplifier, successively after final amplifier, rectification circuit, filter circuit, output carries the output signal of secondary amplifierThe signal of telecommunication of echo-signal, this signal of telecommunication input voltage comparator, when the amplitude of this echo-signal is more than the echo-signal settingAmplitude when, the output of voltage comparator is changed into high level from low level, controller measurement from output ultrasonic wave carrier signal toThe logic of voltage comparator output pin is changed into, from low level, the time Δ t that experienced between high level2, according to formulaObtain ultrasonic transmitter T and the distance between barrier l.
The invention has the beneficial effects as follows：A kind of non-blind area ultrasonic ranging method that the present invention provides, specific by havingThe mounting structure of feature and signal processing method, completely eliminate the impact that ripple is led directly in crosstalk, realize non-blind area ultrasonic ranging,Structure is simple, it is easy to accomplish, effect is good.
Specific embodiment
Describe the present invention below according to accompanying drawing in detail, the purpose of the present invention and effect will be apparent from.
A kind of non-blind area ultrasonic ranging probe based on the principle that inversely adds that the present invention provides, this probe includes oneUltrasonic transmitter T and two ultrasonic receiver R1、R2, two ultrasonic receiver R1、R2With ultrasonic transmitter T distanceThe same side that is identical and being in ultrasonic transmitter, ultrasonic transmitter T and ultrasonic receiver R1、R2It is in the same plane,As shown in Fig. 1 (a)；Second ultrasonic receiver R2With the first ultrasonic receiver R1Difference be, R2By a sideThe container of fluting covers, and the direction of this container fluting faces ultrasonic transmitter T, such as shown in Fig. 1 (b).
For the topology layout shown in Fig. 1 (b), ultrasonic receiver R1、R2, ultrasonic emitting can be subject in constant amplitude ground simultaneouslyThe impact of ripple is led directly in device T crosstalk, but for ultrasound echo signal, due to R2Covered by the container of a groove at side surface,Therefore do not receive echo-signal, and R1But echo-signal can unhinderedly be received.As long as therefore by R1、R2The telecommunications of outputNumber carrying out inversely adding just can be completely eliminated the impact that ripple is led directly in crosstalk, and for echo-signal, due to R2Receive notTo echo, the result inversely adding is exactly only to export R1The signal of telecommunication receiving, the impact that ripple is led directly in crosstalk is eliminated.
Fig. 2 describes to realize the system construction drawing of ultrasonic ranging based on above-mentioned probe, including ultrasonic transmitter T, theOne ultrasonic receiver R1, the second ultrasonic receiver R2, for driving the power driving circuit of ultrasonic transmitter T, it is used for puttingThe amplifier 1 of big ultrasonic receiver signal, amplifier 2, subtractor, amplifier 3, precise rectification circuit, filter circuit, voltageComparator, controller etc..
Controller output ultrasonic wave carrier signal, its frequency is corresponding with the operating frequency of ultrasonic transmitter T, usually40kHz, this signal is followed by ultrasonic transmitter T through power driving circuit amplification, because ultrasonic transmitter T is that machinery shakesSon, exponentially rule increases to fixed ampllitude from 0 to its Oscillation Amplitude, the acoustic pressure amplitude of the ultrasound wave of transmitting also exponentially rule increase,As shown in Fig. 3 (a).When controller stops output ultrasonic wave carrier signal, due to the reason of machinery inertial, the shaking of transmitting probeExponentially rule decays to 0 to dynamic amplitude, the acoustic pressure amplitude of ultrasound wave also exponentially rule decay to 0, as shown in Fig. 3 (a).When superWhen pinger T starts vibration, except to spatial emission ultrasound wave, its mechanical vibration can be in also fan along solid surface of shellShape is propagated, due to ultrasonic receiver R1、R2Equal with the distance of ultrasonic transmitter T and same propagation sector on, thereforeCan experience to constant amplitude this vibration, the speed due to propagating in solid housing is faster than the speed propagated in atmosphere simultaneously,Ultrasonic receiver R1、R2The vibration of solid housing propagation can first be received, then receive airborne vibration, final R1、R2DefeatedGo out is two kinds of overlaid waveforms with frequency ripple, such as shown in Fig. 3 (b), 3 (c).
Reflection can be produced when the ultrasound wave that in the air is propagated runs into barrier, due to R2Container by a groove at side surfaceCovered, therefore R2Do not receive echo, only R1Echo can be received, such as shown in Fig. 3 (b).
Ultrasonic receiver R1、R2The signal of telecommunication of output is extremely faint, just can must be used after amplifying, therefore Fig. 2In amplifier 1, amplifier 2 is first R1、R2After the signal of telecommunication of output amplifies certain multiple, just carry out subtracting computing by subtractor, putThe signal that subtractor exports is amplified by big device 3 further, and to improve the sensitivity receiving as far as possible, rectification and filter circuit will be handed overStream signal is transformed into DC pulse signal voltage supplied comparator and uses, when the amplitude of echo-signal is more than reference voltage VTWhen, electricityThe output of pressure comparator will be changed into high level from low level, such as shown in Fig. 3 (f).From controller output ultrasonic wave carrier signalStart, the logic to voltage comparator output pin is changed into high level from low level, between experienced time Δ t2, this period is justIt is that ultrasound wave travels to barrier from ultrasonic transmitter T and again returns to the time that ultrasonic transmitter T is experienced, therefore ultrasonicThe distance between wave launcher T and barrierWherein：C is the aerial spread speed of ultrasound wave,Unit is m/s, and T is ambient temperature.
Ultrasonic receiver R1、R2Identical to be kept to shake on straight propagation paths and ultrasonic transmitter T between as far as possibleDynamic condition and steric requirements, the explanation becoming apparent from is, mounting ultrasonic receptor R1、R2Circuit board with ultrasonic transmitter TTo avoid in R in design as far as possible1And T between, R2Mask placement device, fluting and T between, in order to avoid affect mechanical wave along circuit board by TTo R1、R2Vibration characteristics, affect R1、R2Receive the concordance being led directly to ripple by the crosstalk that circuit board is propagated；Spatially, R1With TBetween, R2Also try not to place obstacle and T between, in order to avoid impact R1、R2Receive and the consistent of ripple is led directly to by the crosstalk of spatial transmissionProperty, it is completely eliminated, after ensureing to inversely add, the impact that ripple is led directly in crosstalk as far as possible.
In circuit design, ultrasonic receiver R1、R2Signal processing adopt three-level amplify circuit structure, as Fig. 4 instituteShow.Select in the element of amplifier, low-noise amplifier LF356 becomes first-selected, in order to reduce resistance unit in chopped-off head amplifierThe influence of noise of part, chopped-off head amplifier adopts anti-phase amplification, and such resistance R1_2, R1_5 can select less resistance, thusAdvantageously reduce the noise of amplifier.In the selection of R1_2, R1_5 resistance, R1_2, R1_5 preferably try one's best and receive close to ultrasound waveDevice R1、R2Output resistance, accomplish power match as much as possible, improve sound-electric conversion efficiency.The resistance of balancing resistance R1_1, R1_4It is worth the parallel resistance value for R1_2, R1_3 and R1_5, R1_6, to reducing input offset current as much as possible to amplifier gainImpact；The voltage gain of chopped-off head amplifier byDetermine.
Secondary amplifier is realized by IC3, is the subtraction circuit of a gain controllable, and the signal of amplifier output is in-phase endThe signal of input is multiplied by resistance ratio after deducting the signal of end of oppisite phase againFinal amplifier is put for resonant selecting frequencyBig device, its objective is the bandwidth of operation of step-down amplifier, improves signal to noise ratio；Resistance R1_11 be used for adjusting resonant tank T1_1,The Q-value of C1_4, adjusts bandwidth of operation and the voltage gain of this grade of amplifier.C1_5, D1, D2 then constitute voltage doubling rectifing circuit, R1_13rd, C1_6, R1_14, C1_7 then constitute two-stage low-pass filter circuit, the amplitude for echo-signal of output, this signal after filteringIt is connected to the in-phase input end of voltage comparator ic 6, the inverting input of voltage comparator ic 6 connects to R1_15, C1_8, R1_16The voltage reference constituting, this reference voltage isWhen the amplitude of echo-signal exceedes this voltage referenceWhen, the output of voltage comparator ic 6 will become logic 1 from logical zero.
AVR single chip ATMEGA8-16AU selected by controller, and two pin PD6, PD7 outputs of its PD mouth are a string differentialSquare wave, under the 4 road parallel drives of logical drive chip 74HC573, promotes ultrasonic transmitter T to send ultrasound wave.Due to adoptingWith differential type of drive, the drive voltage amplitude being therefore added on ultrasonic transmitter T is the twice of supply voltage.
The invention provides a kind of non-blind area ultrasonic ranging probe and distance-finding method, by having the installation of special characteristicStructure and signal processing method, completely eliminate the impact that ripple is led directly in crosstalk, realize non-blind area ultrasonic ranging, and structure is simple,It is easily achieved, effect is good.
A kind of non-blind area ultrasonic ranging probe of present invention description and distance-finding method, described details is only preferablyEmbodiment, but be not intended to be limited to this, embodiments thereof is simultaneously not restricted to the described embodiments, other any based on thisThe change made under inventive principle, modification, combination, simplify, be accordingly to be regarded as equivalent substitute mode, be all contained in the protection of the present inventionWithin the scope of.