WO2021072801A1 - 活立木木材密度测量方法及装置 - Google Patents

活立木木材密度测量方法及装置 Download PDF

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WO2021072801A1
WO2021072801A1 PCT/CN2019/113686 CN2019113686W WO2021072801A1 WO 2021072801 A1 WO2021072801 A1 WO 2021072801A1 CN 2019113686 W CN2019113686 W CN 2019113686W WO 2021072801 A1 WO2021072801 A1 WO 2021072801A1
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wood
signal
standing
density
microwave signal
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PCT/CN2019/113686
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English (en)
French (fr)
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吴炳方
吴方明
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中国科学院遥感与数字地球研究所
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Priority to US17/621,844 priority Critical patent/US20220326207A1/en
Priority to EP19949004.6A priority patent/EP3982107A4/en
Publication of WO2021072801A1 publication Critical patent/WO2021072801A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N22/00—Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0098—Plants or trees
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/46—Wood
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
    • G01N9/24—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by observing the transmission of wave or particle radiation through the material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
    • G01N9/36—Analysing materials by measuring the density or specific gravity, e.g. determining quantity of moisture
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2617—Measuring dielectric properties, e.g. constants
    • G01R27/2623—Measuring-systems or electronic circuits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
    • G01R29/08—Measuring electromagnetic field characteristics
    • G01R29/0864—Measuring electromagnetic field characteristics characterised by constructional or functional features
    • G01R29/0892—Details related to signal analysis or treatment; presenting results, e.g. displays; measuring specific signal features other than field strength, e.g. polarisation, field modes, phase, envelope, maximum value
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H04B1/0475—Circuits with means for limiting noise, interference or distortion
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/023—Solids
    • G01N2291/0238—Wood

Definitions

  • the invention relates to the technical field of measurement, in particular to a method and device for measuring the density of standing timber timber.
  • Wood density is an important physical property of standing timber, which is closely related to the mechanical properties of standing timber, such as elastic modulus, bending resistance and compression resistance, and wood utilization. It is an important indicator to evaluate the characteristics of wood quality, grade, strength, etc. It is a common indicator to study the correlation between the symbolic utilization of living standing trees and the cultivation of living standing trees, and it is also the basic quantity of biomass measurement in ecosystem research.
  • the near-infrared spectroscopy method As for the near-infrared spectroscopy method, the near-infrared spectra of samples from different sections of trees have a large difference, which has a greater impact on the prediction accuracy. In addition, the thickness of the sample also has an impact on the prediction accuracy, resulting in a relatively large error in wood density measurement. Big.
  • Some researchers have used the Pilodyn method to detect and study the wood density of living standing wood.
  • the working principle of this method is: with a preset energy, a probe with a certain diameter is injected into the living standing wood, according to the steel needle.
  • the correlation between depth and wood properties is used to predict the wood density of standing timber.
  • This method has the advantages of rapid determination and less damage to the living standing wood, but the disadvantage is that the penetration depth of the probe is limited.
  • the probe only stays at the sapwood of the living standing wood.
  • the outside density of live standing timber has a good predictive effect, but the whole radial density prediction of live standing timber is not ideal.
  • the bark has a greater impact on the test, and sometimes it is necessary to peel off the bark for the test to get a better result, which will bring new wounds to the standing timber.
  • the embodiments of the present invention provide a method and device for measuring the density of standing timbers, which reduces the measurement.
  • the time-consuming and damage to the wood density of the living standing wood increases the density measurement range of the whole radial direction of the living standing wood and thus improves the accuracy of the measured wood density.
  • a method for measuring the density of standing timber wood including:
  • the microwave is emitted at the first height in the air so that the microwave penetrates the part to be measured of the standing timber, and the microwave is received at the first distance from the emitting position of the microwave.
  • Microwave measuring the second ratio of the transmitted microwave signal to the second received microwave signal at different frequencies;
  • the relationship between the wood density of the living standing wood and the dielectric constant and the attenuation constant is determined, and the wood density of the living standing wood is calculated according to the relationship.
  • the measurement method further includes:
  • the calculating the dielectric constant and the attenuation constant of the standing wood according to the first ratio, the second ratio, and the diameter includes:
  • the calculating the transmission time and amplitude attenuation of the microwave at the part to be measured of the living standing tree according to the first time domain data and the second time domain data includes:
  • the amplitude attenuation is calculated.
  • the relationship between the wood density of the living standing timber and the dielectric constant and attenuation constant is:
  • ⁇ is the wood density of the live standing wood
  • ⁇ is the dielectric constant of the live standing wood
  • ⁇ is the attenuation constant of the live standing wood
  • a, b, p, and q are pre-calibrated relative to the live standing wood. Parameters related to tree species.
  • a device for measuring the density of standing timber wood which includes:
  • Transmitter used to generate and transmit microwave signals in the preset frequency range according to the control signal
  • the receiver is used to receive the first received microwave signal after the first distance propagated in the air at a first distance greater than the diameter of the part to be measured of the living standing wood, and to transfer the first Quadrature demodulation of the received microwave signal and the transmitted microwave signal to convert the first received microwave signal into a first baseband signal and a second baseband signal,
  • the controller is connected to the transmitter and the receiver, and is used to provide the control signal to the transmitter, collect and store the first and second baseband signals, and the third The baseband signal and the fourth baseband signal, and the timber of the standing timber is calculated according to the transmitted microwave signal, the first baseband signal and the second baseband signal, the third baseband signal and the fourth baseband signal density;
  • the touch screen is used to set parameters, send user instructions to the controller and display the calculation results of the controller;
  • the communication interface module is used to obtain the relevant parameters in the relationship between the wood density of the standing timber and the dielectric constant and the attenuation constant from the server, and send the calculation result of the controller to the touch screen;
  • a reference clock module for generating a clock reference required by the controller and the transmitter
  • Voltage converter used to process the input power to provide various types of secondary power required.
  • the receiver includes: a pre-selection filter, a pre-amplifier, a PI-type attenuator, a post-amplifier, a quadrature demodulator, a low-pass filter, and an analog-to-digital converter,
  • the preselection filter is used to filter out interference signals in the first received microwave signal and the second received microwave signal;
  • the pre-amplifier and the post-amplifier are used to amplify the first received microwave signal and the second received microwave signal after preselection and filtering;
  • the PI-type attenuator is used to adjust the amplification gain of the entire receiving link
  • the quadrature demodulator is configured to orthogonally demodulate the first received microwave signal output by the post amplifier and the transmitted microwave signal to obtain the first baseband of the first received microwave signal Signal and the second baseband signal,
  • Quadrature demodulation of the second received microwave signal output by the post amplifier and the transmitted microwave signal to obtain the third baseband signal and the fourth baseband signal of the second received microwave signal
  • the low-pass filter is configured to filter out interference high-frequency signals of the first baseband signal, the second baseband signal, the third baseband signal, and the fourth baseband signal;
  • the analog-to-digital converter is used to convert the first baseband signal and the second baseband signal, the third baseband signal and the fourth baseband signal into a first digital signal and a second digital signal, respectively Signal, the third digital signal and the fourth digital signal.
  • the controller includes: a data acquisition module, a data storage module, a data processing module, a system control module, and a data transmission module,
  • the data storage module is used to store the first digital signal and the second digital signal, the third digital signal and the fourth digital signal, the wood density and the dielectric constant and the attenuation of the standing wood The relevant parameter and the diameter in the relational expression of the constant;
  • the data processing module is configured to calculate a first ratio of the transmitted microwave signal to the first received microwave signal at different frequencies based on the first digital signal and the second digital signal,
  • the calculation formula of the dielectric constant and the attenuation constant is used, and the wood density of the living standing wood is compared with the dielectric constant and the attenuation constant.
  • the relational expression is used to calculate the wood density of the standing timber;
  • the data transmission module is used to provide a data path between the various modules of the controller.
  • a computer-readable storage medium characterized in that the computer-readable storage medium stores computer instructions, and when the computer instructions are executed, the density measurement of standing timber as described above is realized. method.
  • the wood density measurement process of the embodiment of the present invention is simple, and there is no need to sample and make standard-volume test pieces according to the standard, thus saving manpower, material resources and time-consuming, and there is no need to take samples from the living standing wood, which realizes Non-destructive measurement of standing timber, convenient for on-site measurement.
  • the relevant parameters in the relational formula for calculating the wood density are obtained through pre-tests, and they have passed the detection and meet the measurement accuracy. Therefore, the obtained wood density also meets the measurement accuracy, which ensures the measurement accuracy of the embodiment of the present invention.
  • the microwave can penetrate the test part of the living standing wood to measure the wood density in the whole radial direction, which increases the measuring range of the whole radial wood density of the living standing wood and improves the accuracy of the measured wood density.
  • Fig. 2 shows an application scene diagram of the method for measuring the density of standing timber according to an embodiment of the present invention.
  • Fig. 3 shows a waveform diagram of time-domain data transmitted by microwaves in the air according to an embodiment of the present invention.
  • Fig. 5 shows a schematic flow chart of a method for measuring the transmission time and amplitude attenuation of microwaves at the test site of a living standing tree according to an embodiment of the present invention.
  • Fig. 7 shows a comparison diagram of the measured density and the actual density of the living standing timber wood density according to an embodiment of the present invention.
  • Fig. 9 shows a block diagram of a receiver of an embodiment of the present invention.
  • Fig. 10 shows a block diagram of a controller of an embodiment of the present invention.
  • the invention uses a microwave method to measure the wood density of living standing wood, and its measurement mechanism is: the dielectric constant of the wood is a physical parameter that characterizes the polarization of the wood under the action of an alternating electric field and the capacity of the dielectric to store charges.
  • the dielectric constant of wood is not constant.
  • the factors that affect the dielectric constant of wood are usually wood moisture content, wood density, microwave frequency, tree species and other factors.
  • wood density increases, it is actually the increase in the volume percentage of the cell wall substance. Because the volume percentage of the substance increases, the number of dipoles per unit volume of wood increases, which enhances the polarization reaction of the wood, so the wood’s
  • the dielectric constant also increases accordingly.
  • the attenuation constant is one of the transmission constants, which indicates the attenuation of the amplitude or power of electromagnetic waves or electrical signals during transmission.
  • the microwave penetrates the living standing wood, its amplitude will be attenuated due to the reflection, absorption and scattering of the living standing wood, and its propagation speed will be reduced due to the dispersion of the living standing wood, which is characterized as an attenuation constant. Therefore, when the dielectric constant and the attenuation constant are related to the density of the wood, the wood density can be obtained through the dielectric constant and the attenuation constant.
  • Fig. 1 is a schematic flow chart of a method for measuring the density of standing timber wood according to an embodiment of the present invention. It includes the following steps:
  • step S110 the diameter of the part to be measured at the first height of the standing timber from the ground is measured.
  • the diameter d of the part to be measured at the first height H of the standing timber from the ground is measured.
  • the first height H is, for example, the breast height position of the standing timber, and the corresponding diameter is the diameter d at breast height of the standing timber.
  • microwaves of a preset frequency range are emitted in the air, where the microwaves of the preset frequency range are microwave bands that are compatible with the density of the live wood to be tested, that is, the microwave that is most sensitive to the density of the live wood to be tested Band, such as 2GHz to 8GHz.
  • the first distance D is greater than the diameter d.
  • the height of the transmitting position and the receiving position of the microwave from the ground is the first height H.
  • step S130 the microwave is emitted in the air at the first height so that the microwave penetrates the part to be tested of the standing timber, and is separated from the emitting position of the microwave by the first The microwave is received at a distance, and the second ratio of the transmitted microwave signal to the second received microwave signal at different frequencies is measured.
  • Fig. 2 is an application scene diagram of the method for measuring the density of standing timber according to an embodiment of the present invention.
  • the live standing wood 210 to be tested is located between the transmitting end 220 and the receiving end 230 of the microwave in the preset frequency range.
  • the microwave is transmitted through the transmitting end 220 and then penetrates the tested part of the live standing wood 210 to the receiving end 230.
  • the transmitting end 220 and the receiving end 230 are separated by a first distance D.
  • the distance from the ground of the standing timber 210 to the ground is a first height H, and the corresponding diameter of the standing timber 210 at the first height H is d.
  • microwaves with a preset frequency range are emitted at the first height H in the air so that the microwaves penetrate the part to be tested of the living standing wood 210, and are in contact with the emission of microwaves.
  • the position (transmitting terminal 220) is separated by a first distance D (receiving terminal 230) to receive microwaves, and the second ratio H w (of the transmitted microwave signal X ( ⁇ ) to the second received microwave signal Y w ( ⁇ ) at different frequencies ⁇ is measured ⁇ ).
  • step S140 the dielectric constant and the attenuation constant of the standing wood are calculated according to the first ratio, the second ratio and the diameter.
  • the dielectric constant ⁇ and the attenuation constant ⁇ of the standing wood are calculated.
  • Fig. 3 is a waveform diagram of time-domain data transmitted by microwaves in the air according to an embodiment of the present invention, and specifically shows a waveform diagram of the first time-domain data h 0 (t).
  • the ordinate of the first time domain data h 0 (t) is the amplitude value
  • the abscissa is time
  • the maximum value of the amplitude of the waveform of the first time domain data h 0 (t) is the point M 0 (t 0 ,A 0 ).
  • the ordinate of the second time domain data h w (t) is the amplitude value
  • the abscissa is time
  • the maximum value of the waveform of the second time domain data h w (t) is the point M 1 (t 1 ,A 1 ).
  • Fig. 5 is a schematic flow chart of a method for measuring the transmission time and amplitude attenuation of microwaves at the test site of a living standing tree according to an embodiment of the present invention. It includes the following steps:
  • step S510 select the maximum amplitude value M 0 (t 0 , A 0 ) of the waveform of the first time domain data h 0 (t) shown in FIG. 3, and determine the maximum amplitude value M 0 (t 0 , A 0 ) corresponding to the first time t 0 and the first amplitude A 0 .
  • step S520 select the maximum amplitude M 1 (t 1 , A 1 ) of the waveform of the second time domain data h w (t) shown in FIG. 4, and determine the maximum amplitude M 1 (t 1 , A 1 ) corresponding to the second time t 1 and the second amplitude A 1 .
  • step S530 the transmission time ⁇ t is calculated according to the first time t 0 , the second time t 1 and the diameter d.
  • the formula for calculating the transmission time ⁇ t of the microwave at the test part of the living standing wood is:
  • ⁇ t is the transmission time of the microwave at the part to be measured on the standing wood
  • t 1 is the maximum amplitude of the second time domain data h w (t) waveform transmitted by the microwave in the standing wood and the air at M 1 (t 1 ,A 1 ) corresponding to the second time
  • t 0 is the first time domain data h 0 (t) transmitted by microwaves in the air at the maximum amplitude of the waveform of the first time domain data h 0 (t) corresponding to the first time M 0 (t 0 ,A 0 )
  • d is the diameter of the part to be measured at the first height H of the standing timber from the ground
  • c is the propagation speed of the microwave in the air.
  • step S540 the amplitude attenuation ⁇ A is calculated according to the first amplitude A 0 and the second amplitude A 1.
  • the formula for calculating the amplitude attenuation ⁇ A of the microwave transmission at the test part of the living standing wood is:
  • ⁇ A is the amplitude attenuation during the transmission of the microwave on the standing wood to be measured
  • a 1 is the maximum amplitude of the second time domain data h w (t) of the microwave transmitted in the standing wood and the air.
  • M 1 (t 1 ,A 1 ) corresponds to the second amplitude
  • t 0 is the maximum amplitude of the waveform of the first time domain data h 0 (t) transmitted by microwaves in the air
  • M 0 (t 0 ,A 0 ) Corresponds to the first amplitude.
  • ⁇ is the dielectric constant of the standing wood
  • ⁇ t is the transmission time of the microwave in the part to be tested
  • d is the diameter of the part to be tested at the first height H of the standing wood from the ground
  • c is the microwave in the air. transmission speed.
  • the amplitude attenuation ⁇ A and the diameter d calculate the attenuation constant ⁇ of the standing wood.
  • the calculation formula of the attenuation constant ⁇ of the standing wood corresponding to the microwave in the preset frequency range is:
  • ⁇ is the attenuation constant of the standing wood
  • ⁇ A is the amplitude attenuation of the microwave transmission at the part to be measured of the standing wood
  • d is the diameter of the part to be measured at the first height H of the standing wood from the ground.
  • step S150 the relationship between the wood density of the standing timber and the dielectric constant and attenuation constant is determined, and the wood density of the standing timber is calculated according to the relationship.
  • the dielectric constant of wood is not constant.
  • the factors that affect the dielectric constant of wood are usually wood moisture content, wood density, microwave frequency, tree species and other factors.
  • Fig. 6 is a diagram showing the relationship between wood density, moisture and dielectric constant of living standing trees according to an embodiment of the present invention, specifically showing that the living standing trees to be tested are cedar.
  • the abscissa is the dielectric constant ⁇ of the standing wood corresponding to the microwave in the preset frequency range
  • the ordinate is the wood density of the standing wood.
  • the moisture corresponding to multiple test points in the figure is different.
  • the relationship between density, moisture and dielectric constant of fir is linear.
  • ⁇ is the wood density of the standing wood
  • ⁇ is the dielectric constant of the standing wood corresponding to the microwave in the preset frequency range
  • ⁇ is the attenuation constant of the standing wood corresponding to the microwave in the preset frequency range
  • a, b, p, q It is a pre-calibrated parameter related to the tree species of the standing tree and other attributes.
  • Tree species and other attributes refer to standing tree species, tree parts, tree age, and growing area.
  • Fig. 7 is a comparison diagram of the measured density and the actual density of the living standing timber wood density according to an embodiment of the present invention.
  • the wood density is measured multiple times.
  • the average error of the measured living standing wood density and the actual density of the living standing wood is 0.03 g/m 3 .
  • the diameter of the position to be measured at the first height of the standing timber from the ground is measured. Transmit and receive microwaves in a preset frequency range at a first distance in the air, and measure the first ratio of the transmitted microwave signal to the first received microwave signal at different frequencies.
  • the microwave is emitted at the first height in the air to make the microwave penetrate the part to be tested of the living standing wood, and the microwave is received at a first distance from the microwave emitting position.
  • the emitted microwave signal is the same as the second received microwave signal.
  • the second ratio According to the first ratio, the second ratio and the diameter, the dielectric constant and attenuation constant of the standing wood are calculated.
  • the wood density measurement process of the embodiment of the present invention is simple, and there is no need to sample and make standard-volume test pieces according to the standard, thus saving manpower, material resources and time-consuming, and does not need to take samples from the living standing wood, and realizing the comparison of the living standing wood
  • the non-destructive measurement is convenient for on-site measurement.
  • the relevant parameters in the relational formula for calculating the wood density are obtained through pre-tests, and they have passed the detection and meet the measurement accuracy. Therefore, the obtained wood density also meets the measurement accuracy, which ensures the measurement accuracy of the embodiment of the present invention.
  • the microwave can penetrate the test part of the living standing wood to measure the wood density in the whole radial direction, which increases the measuring range of the whole radial wood density of the living standing wood and improves the accuracy of the measured wood density.
  • step S120 to step S150 are repeated to measure the wood density of the test part of the living standing wood from different directions, that is, the microwave signal is emitted when multiple measurements of different frequencies are performed in different directions of the test part of the living standing wood.
  • the second ratio with the second received microwave signal; according to the first ratio, the second ratio and the diameter of multiple measurements, the dielectric constant and the attenuation constant of the tested parts of the standing wood in different directions are calculated respectively; according to the relationship, respectively Calculate the wood density of the parts to be tested of the standing timbers in different directions; calculate the average wood density of the parts to be tested of the standing timbers in different directions to obtain the average wood density of the parts to be tested.
  • the wood density of the test parts of the living standing wood in the whole radial direction can be measured from different directions, and the average wood density of the test parts of the living standing wood in different directions can be calculated. Value, which further improves the accuracy of the measured wood density.
  • Fig. 8 is a block diagram of an apparatus for measuring the density of standing timber according to an embodiment of the present invention.
  • the device for measuring the density of standing timber includes: a transmitter 810, a receiver 820, a controller 830, a touch screen 840, a communication interface module 850, a reference clock module 860, and a voltage converter 870.
  • the transmitter 810 includes a transmitting antenna 811
  • the receiver 820 includes a receiving antenna 821.
  • the transmitter 810 mainly includes a phase-locked loop frequency synthesizer, a power divider, and a power amplifier, and is used to generate frequency stepping microwaves with a certain power according to the control signal and transmit microwave signals in a preset frequency range.
  • the receiver 820 is used to receive the first received microwave signal propagated in the air for the first distance at a first distance greater than the diameter of the part to be measured of the living standing wood, and connect the first received microwave signal to Transmit the microwave signal quadrature demodulation to convert the first received microwave signal into the first baseband signal and the second baseband signal, and then extract the amplitude and phase information, and receive the second received microwave that penetrates the part to be measured of the living tree Signal, quadrature demodulate the second received microwave signal and the transmitted microwave signal to convert the second received microwave signal into a third baseband signal and a fourth baseband signal, and then extract amplitude and phase information.
  • the transmitting antenna 811 of the transmitter 810 and the receiving antenna 821 of the receiver 820 both use broadband directional antennas.
  • the transmitting antenna 811 and the receiving antenna 821 are respectively connected to the transmitter 810 and the receiver 820 through a cable assembly.
  • the transmitting antenna 811 transmits microwave signals to the object to be measured, and the receiving antenna 821 receives the first received microwave signal and the second received microwave signal.
  • the controller 830 is connected to the transmitter 810 and the receiver 820, and is used to provide control signals to the transmitter 810, including trigger signals and timing control signals, and collect and store the first baseband signal and the second baseband signal from the receiver 820 , The third baseband signal and the fourth baseband signal, and calculate the wood density of the standing timber based on the transmitted microwave signal, the first baseband signal, the second baseband signal, the third baseband signal, and the fourth baseband signal.
  • the controller 830 is also used to provide a trigger signal and a timing control signal to the receiver 820.
  • the controller 830 is also used to transmit data to the server.
  • the touch screen 840 is used to set parameters, send user instructions to the controller 830 and display the calculation results of the controller 830.
  • the communication interface module 850 is used to realize the data interaction between the controller 830 and the server, obtain from the server the relevant parameters in the relationship between the wood density and the dielectric constant and the attenuation constant of the standing wood (formula (5)), and change The calculation result of the controller 830 is sent to the touch screen 840.
  • the reference clock module 860 is used to generate a clock reference required by the controller 830 and the transmitter 810.
  • the voltage converter 870 is used to process the input power to provide various types of secondary power required by each functional module and device in the living standing timber wood density measurement device.
  • the wood density measurement of standing wood is carried out in the field.
  • the wood density measurement device of standing wood is powered by a lithium battery.
  • the voltage converter 870 also has a power management function and can switch between lithium battery power supply and input power supply.
  • Fig. 9 is a block diagram of a receiver according to an embodiment of the present invention.
  • the receiver 820 includes: a preselection filter 910, a preamplifier 920, a PI attenuator 930, a post amplifier 940, and a quadrature solution.
  • Tuner 950 low-pass filter 960, and analog-to-digital converter 970.
  • the pre-amplifier 920, the PI-type attenuator 930, and the post-amplifier 940 in the receiver 820 adopt two-stage amplification and one-stage PI-type attenuator to complete the front-end amplification of the radio frequency signal.
  • the preselection filter 910 is used to filter out interference signals in the first received microwave signal and the second received microwave signal.
  • the pre-amplifier 920 and the post-amplifier 940 are used to amplify the first received microwave signal and the second received microwave signal after preselection and filtering.
  • the PI-type attenuator 930 is used to adjust the amplification gain of the entire receiving link to ensure that all devices in the receiver 820 work in the linear region.
  • the quadrature demodulator 950 is used to demodulate the first received microwave signal and the transmitted microwave signal output by the post amplifier 940 to obtain the first baseband signal and the second baseband signal of the first received microwave signal, and the post amplifier
  • the second received microwave signal output by the 940 and the transmitted microwave signal are quadrature demodulated to obtain the third baseband signal and the fourth baseband signal of the second received microwave signal, and then extract the first received microwave signal and the second received microwave signal. Amplitude and phase information.
  • the first baseband signal and the second baseband signal are a set of orthogonal signals, and the phase difference between the first baseband signal and the second baseband signal is 90 degrees.
  • the first baseband signal is an I baseband signal
  • the second baseband signal is a Q baseband signal.
  • the third baseband signal and the fourth baseband signal are a set of orthogonal signals, and the phase difference between the third baseband signal and the fourth baseband signal is 90 degrees.
  • the third baseband signal is an I baseband signal
  • the fourth baseband signal is a Q baseband signal.
  • the low-pass filter 960 is used to filter out interference high-frequency signals of the first baseband signal, the second baseband signal, the third baseband signal, and the fourth baseband signal.
  • the I baseband signal and the Q baseband signal are vectors. Therefore, the amplitude attenuation and phase shift of the first received microwave signal and the amplitude attenuation and phase shift of the second received microwave signal can be calculated using the triangle identity equation as follows:
  • ⁇ is the amplitude of the first microwave receiving signal or the second received microwave signal attenuation
  • V Q is the first or second microwave signals Q digital signals for receiving microwave signals.
  • I the phase shift of the first received microwave signal or the second received microwave signal
  • V I is the I digital signal of the first received microwave signal or the second received microwave signal
  • V Q is the first received microwave signal or the second received microwave signal The Q-channel digital signal.
  • Fig. 10 is a block diagram of a controller according to an embodiment of the present invention.
  • FPGA is used to realize the logic control of the controller 830 in the measurement device, and give full play to the FPGA's
  • the advantages of high integration, low power consumption, etc., and the programmable feature of FPGA facilitates future upgrades of the controller 830.
  • the controller 830 includes: a data acquisition module 1010, a data storage module 1020, a data processing module 1030, a system control module 1040, and a data transmission module 1050.
  • the data acquisition module 1010 is used to control the analog-to-digital converter 970 to collect the first digital signal and the second digital signal of the first received microwave signal, and the third digital signal and the fourth digital signal of the second received microwave signal .
  • the data storage module 1020 is used to store the first digital signal and the second digital signal of the first received microwave signal, the third digital signal and the fourth digital signal of the second received microwave signal, the wood density and the density of the standing wood.
  • the data processing module 1030 is used to analyze the received digital signal, and use formulas (6) and (7) to calculate the first received microwave signal based on the first digital signal and the second digital signal stored in the data storage module 1020. Amplitude attenuation and phase shift. The first ratio of the frequency domain signal of the transmitted microwave to the frequency domain signal of the first received microwave is calculated according to the amplitude attenuation and phase shift of the first received microwave signal. According to the third digital signal and the fourth digital signal stored in the data storage module 1020, formulas (6) and (7) are used to calculate the amplitude attenuation and phase shift of the second received microwave. A second ratio of the frequency domain signal of the transmitted microwave to the frequency domain signal of the second received microwave is calculated according to the amplitude attenuation and phase shift of the second received microwave.
  • the calculation formulas for the first ratio of the transmitted microwave signal of different frequencies to the first received microwave signal and the second ratio of the transmitted microwave signal of different frequencies to the second received microwave signal are:
  • H( ⁇ ) is the first ratio of the transmitted microwave signal of different frequency ⁇ to the first received microwave signal or the second ratio of the transmitted microwave signal of different frequency ⁇ to the second received microwave signal
  • ⁇ is the amplitude attenuation of the first received microwave signal or the second received microwave signal.
  • the first ratio, the second ratio, the diameter and related parameters (the related parameters in formula (5)), the calculation formulas of dielectric constant and attenuation constant (formula (1) to formula (4)) are used to calculate the wood of living standing wood.
  • the relationship between density, dielectric constant and attenuation constant (formula (5)) is used to calculate the wood density of standing timber.
  • the system control module 1040 is configured to receive parameters set by the touch screen 840, user instructions, and/or calculation results of the data processing module 1030, and transmit control signals to the transmitter 810, or send the calculation results to the communication interface module 850;
  • the data transmission module 1050 is used to provide a data path between the various modules of the controller 830.
  • an embodiment of the present invention provides a computer-readable storage medium that stores computer instructions that, when executed, implement the operations specified in the above-mentioned method for measuring the density of standing timber.
  • an embodiment of the present invention also provides a computer program product, including a computer program, the computer program including program instructions, when the program instructions are executed by a mobile terminal, the mobile terminal is caused to execute the above-mentioned living standing timber density. Steps of the measurement method.
  • the flowcharts and block diagrams in the drawings illustrate the possible system framework, functions, and operations of the systems, methods, and devices of the embodiments of the present invention.
  • the blocks on the flowcharts and block diagrams can represent a module, a program segment, or just a segment.
  • Code, the modules, program segments, and codes are all executable instructions used to implement prescribed logic functions. It should also be noted that the executable instructions that implement the prescribed logic functions can be recombined to generate new modules and program segments. Therefore, the blocks in the drawings and the sequence of the blocks are only used to better illustrate the process and steps of the embodiment, and should not be used as a limitation to the invention itself.

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Abstract

一种活立木木材密度测量方法及装置，方法包括：测量活立木的距离地面第一高度处的待测部位的直径（S110）；在空气中相隔第一距离发射与接收预设频率范围的微波，测量不同频率时发射微波信号与第一接收微波信号的第一比值（S120）；在空气中于第一高度处发射微波使得微波穿透活立木的待测部位，并且在与微波的发射位置相隔第一距离处接收微波，测量不同频率时发射微波信号与第二接收微波信号的第二比值（S130）；根据第一比值、第二比值和直径，计算活立木的介电常数和衰减常数（S140）；确定活立木的木材密度与介电常数和衰减常数的关系式，并根据关系式计算活立木的木材密度（S150）。

Description

活立木木材密度测量方法及装置
本申请要求了2019年10月16日提交的、申请号为201910982349.2、发明名称为“活立木木材密度测量方法及装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及测量技术领域，具体涉及一种活立木木材密度测量方法及装置。
背景技术
木材密度是活立木重要的物理性质，与活立木力学性质如弹性模量、抗弯曲性和抗压性以及木材利用有着密切的关系。它是评价木材质量、等级、强度等特性的一个重要指标，是研究活立木标志性利用与活立木培育相关性的常用指标，还是生态系统研究中生物量测定的基础量。
相关技术中，部分研究者采样活立木后，分别测定样品的体积和质量，利用质量和体积之比求得活立木的木材密度。部分研究者采样活立木后，将测定样品粉碎成木粉后利用傅立叶变换光谱仪扫描和采集近红外光谱，利用已获得的快速测定模型可测出样木相应的木材基本密度或生材密度。传统的称重法虽然原理简单、易于实践、估测结果精度高，但是需要按照标准采样，制作标准体积的试件，劳动强度大、花费时间长，而且需要直接在原材料上取试样，测量时间长，不利于现场检测。而对于近红外光谱测量法，树木不同切面试样的近红外光谱有较大的差异，对预测精度有较大影响，另外，试样厚度也对预测精度有影响，造成了木材密度测量误差较大。
部分研究者采用Pilodyn方法对活立木的木材密度进行了检测研究，该方法工作原理是：以预先设定好的能量，将具有一定直径的探针射入到活立木内部，根据钢针射入深度与木材性质之间的相关性，来预测活立木的木材密度。该方法具有快速测定和对活立木损伤较小等优点，但存在的不足是，探针的射入深度有限，对于直径较大的活立木，探针仅停留在活立木边材部位，因而对于活立木的外侧密度具有较好预测效果，而对活立木整个径向的密度预测并不理想。另外，树皮对测试具有较大的影响，有时需要剥去树皮进行测试才能得到比较理想的结果，这样则会对活立木带来新的创伤。
发明内容
为了克服相关技术中存在的活立木木材密度测量方法耗时、对活立木有损伤和木材密度测量误差大的问题，本发明实施例提供了一种活立木木材密度测量方法和装置，降低了测量活立木 的木材密度的耗时和对活立木的损伤，提高了对活立木整个径向的密度测量范围进而提高了测得的木材密度的准确性。
根据本发明的一方面，提供一种活立木木材密度测量方法，包括：
测量活立木的距离地面第一高度处的待测部位的直径；
在空气中相隔大于所述直径的第一距离发射与接收预设频率范围的微波，测量不同频率时发射微波信号与第一接收微波信号的第一比值；
在空气中于所述第一高度处发射所述微波使得所述微波穿透所述活立木的所述待测部位，并且在与所述微波的发射位置相隔所述第一距离处接收所述微波，测量不同频率时所述发射微波信号与第二接收微波信号的第二比值；
根据所述第一比值、所述第二比值和所述直径，计算所述活立木的介电常数和衰减常数；
确定所述活立木的木材密度与所述介电常数和衰减常数的关系式，并根据所述关系式计算所述活立木的所述木材密度。
可选地，所述测量方法还包括：
在所述活立木的所述待测部位的不同方向多次测量所述第二比值；
根据所述第一比值、多次测量的所述第二比值和所述直径，分别计算不同方向的所述活立木的所述待测部位的介电常数和衰减常数；
根据所述关系式，分别计算不同方向的所述活立木的所述待测部位的木材密度；
计算所述不同方向的所述活立木的所述待测部位的木材密度的平均值，得到所述活立木的所述待测部位的平均木材密度。
可选地，所述根据所述第一比值、所述第二比值和所述直径，计算所述活立木的介电常数和衰减常数包括：
利用傅里叶逆变换计算所述第一比值和所述第二比值对应的第一时域数据和第二时域数据；
根据所述第一时域数据和所述第二时域数据，计算所述微波在所述活立木的所述待测部位的传输时间和幅度衰减；
根据所述传输时间和所述直径计算所述活立木的介电常数；以及
根据所述幅度衰减和所述直径计算所述活立木的衰减常数。
可选地，所述根据所述第一时域数据和所述第二时域数据，计算所述微波在所述活立木的所述待测部位的传输时间和幅度衰减包括：
选取所述第一时域数据的波形的幅值最大值处，确定所述幅值最大值处对应的第一时间和第一幅值；
选取所述第二时域数据的波形的幅值最大值处，确定所述幅值最大值处对应的第二时间和第二幅值；
根据所述第一时间、所述第二时间和所述直径，计算所述传输时间；
根据所述第一幅值和所述第二幅值，计算所述幅度衰减。
可选地，所述活立木的木材密度与所述介电常数和衰减常数的关系式为：
Figure PCTCN2019113686-appb-000001
其中，ρ为所述活立木的木材密度，ε为所述活立木的介电常数，α为所述活立木的衰减常数，a、b、p、q是预先标定的与所述活立木的树种相关的参数。
根据本发明的另一方面，提供一种活立木木材密度测量装置，包括：
发射机，用于根据控制信号产生并发射预设频率范围的微波信号；
接收机，用于在与所述发射机相隔大于活立木的待测部位的直径的第一距离处，接收在空气中传播所述第一距离后的第一接收微波信号，将所述第一接收微波信号与发射微波信号正交解调以将所述第一接收微波信号转换为第一路基带信号和第二路基带信号，
接收穿透所述活立木的待测部位的第二接收微波信号，将所述第二接收微波信号与所述发射微波信号正交解调以将所述第二接收微波信号转换为第三路基带信号和第四路基带信号；
控制器，与所述发射机和所述接收机连接，用于向所述发射机提供所述控制信号、采集和存储所述第一路基带信号和第二路基带信号、所述第三路基带信号和第四路基带信号并且根据所述发射微波信号和所述第一路基带信号和第二路基带信号、所述第三路基带信号和第四路基带信号计算所述活立木的木材密度；
触摸屏，用于设置参数、发送用户指令给所述控制器和显示所述控制器的计算结果；
通信接口模块，用于从服务器获取所述活立木的木材密度与介电常数和衰减常数的关系式中的相关参数，并且将所述控制器的计算结果发送给所述触摸屏；
基准时钟模块，用于产生所述控制器和所述发射机所需的时钟基准；以及
电压转换器，用于对输入电源进行处理以提供所需的各类二次电源。
可选地，所述接收机包括：预选滤波器、前置放大器、PI型衰减器、后置放大器、正交解调器、低通滤波器和模数转换器，
所述预选滤波器，用于滤除所述第一接收微波信号和所述第二接收微波信号中的干扰信号；
所述前置放大器和所述后置放大器，用于放大预选滤波后的所述第一接收微波信号和所述第二接收微波信号；
所述PI型衰减器，用于调节整个接收链路的放大增益；
所述正交解调器，用于将所述后置放大器输出的所述第一接收微波信号与所述发射微波信号正交解调得到所述第一接收微波信号的所述第一路基带信号和第二路基带信号，
将所述后置放大器输出的所述第二接收微波信号与所述发射微波信号正交解调得到所述第二接收微波信号的所述第三路基带信号和第四路基带信号；
所述低通滤波器，用于滤除所述第一路基带信号和第二路基带信号、所述第三路基带信号和第四路基带信号的干扰高频信号；
所述模数转换器，用于将所述第一路基带信号和第二路基带信号、所述第三路基带信号和第四路基带信号分别转换为第一路数字信号和第二路数字信号、第三路数字信号和第四路数字信号。
可选地，所述控制器包括：数据采集模块、数据存储模块、数据处理模块、系统控制模块和数据传输模块，
所述数据采集模块，用于控制所述模数转换器以采集所述第一接收微波信号的所述第一路数字信号和第二路数字信号、所述第二接收微波信号的所述第三路数字信号和第四路数字信号；
所述数据存储模块，用于存储所述第一路数字信号和第二路数字信号、所述第三路数字信号和第四路数字信号、所述活立木的木材密度与介电常数和衰减常数的关系式中的所述相关参数、所述直径；
所述数据处理模块，用于根据所述第一路数字信号和第二路数字信号来计算不同频率时所述发射微波信号与所述第一接收微波信号的第一比值，
根据所述第三路数字信号和第四路数字信号来计算不同频率时所述发射微波信号与所述第二接收微波信号的第二比值，
根据所述第一比值、所述第二比值、所述直径和所述相关参数，利用所述介电常数和衰减常数的计算公式、所述活立木的木材密度与介电常数和衰减常数的所述关系式来计算所述活立木的木材密度；
所述系统控制模块，用于接收所述触摸屏设置的参数、用户指令和/或所述数据处理模块的计算结果，向所述发射机发射所述控制信号，或将所述计算结果发送给所述通信接口模块；
所述数据传输模块，用于为所述控制器的各个模块之间提供数据通路。
根据本发明的又一方面，提供一种计算机可读存储介质，其特征在于，所述计算机可读存储介质存储有计算机指令，所述计算机指令被执行时实现如上所述的活立木木材密度测量方法。
根据本发明的再一方面，提供一种计算机程序产品，包括计算机程序产品，所述计算机程序包括程序指令，当所述程序指令被移动终端执行时，使所述移动终端执行上述活立木木材密度测 量方法的步骤。
本发明的实施例具有以下优点或有益效果：
(1)本发明实施例的木材密度测量过程简单，无需按照标准来采样、制作标准体积的试件，因而节省了人力、物力和耗时，并且不需要从活立木上取试样，实现了对活立木的无损测量，方便现场测量。计算木材密度的关系式中的相关参数是通过预先试验得到的，并且其通过了检测，符合测量精度，因而得到的木材密度也符合测量精度，保证了本发明实施例的测量精度。微波可以穿透活立木的待测部位，测量整个径向方向的木材密度，提高了对活立木整个径向的木材密度测量范围进而提高了测得的木材密度的准确性。
(2)从不同方向测量活立木的待测部位的木材密度，计算不同方向的活立木的待测部位的木材密度的平均值，得到活立木的待测部位的平均木材密度。由于微波可以从不同方向穿透活立木的待测部位，可以从不同方向测量待测部位的整个径向方向的木材密度，计算不同方向的活立木的待测部位的木材密度的平均值，进而进一步提高了测得的木材密度的准确性。
附图说明
通过以下参照附图对本发明实施例的描述，本发明的上述以及其他目的、特征和优点将更为清楚，在附图中：
图1示出本发明的一个实施例的活立木木材密度测量方法的流程示意图。
图2示出本发明的一个实施例的活立木木材密度测量方法的应用场景图。
图3示出本发明的一个实施例的微波在空气中传输的时域数据的波形图。
图4示出本发明的一个实施例的微波在活立木和空气中传输的时域数据的波形图。
图5示出本发明的一个实施例的微波在活立木的待测部位的传输时间和幅度衰减的测量方法的流程示意图。
图6示出本发明的一个实施例的活立木的木材密度、水分和介电常数的关系图。
图7示出本发明的一个实施例的活立木木材密度的测量密度和实际密度的对比图。
图8示出本发明的一个实施例的活立木木材密度测量装置的框图。
图9示出本发明的一个实施例的接收机的框图。
图10示出本发明的一个实施例的控制器的框图。
具体实施方式
以下基于实施例对本发明进行描述，但是本发明并不仅仅限于这些实施例。在下文对本发明 的细节描述中，详尽描述了一些特定的细节部分。对本领域技术人员来说没有这些细节部分的描述也可以完全理解本发明。为了避免混淆本发明的实质，公知的方法、过程、流程没有详细叙述。另外附图不一定是按比例绘制的。
本发明采用微波方法来测量活立木的木材密度，其测量机理为：木材的介电常数是表征木材在交流电场作用下介质的极化强度和介电体存储电荷能力的物理参数。木材的介电常数不是常量，影响木材介电常数的通常有木材含水率、木材密度、微波频率、树种等因素。当木材密度增大时，实际上就是细胞壁实质物质的体积百分率增大，由于实质物质的体积百分率增大，导致单位木材体积内偶极子数目增加，增强了木材的极化反应，所以木材的介电常数也随之增大。
衰减常数是传输常数之一，表示电磁波或电信号在传输过程中振幅或功率衰减的参数。微波穿透活立木时，其幅度会因为活立木的反射、吸收和散射而衰减，其传播速度会因为活立木的色散而变小，表征为衰减常数。因此，当将介电常数、衰减常数与木材的密度相关联时，可以通过介电常数和衰减常数获得木材密度。
图1是本发明的一个实施例的活立木木材密度测量方法的流程示意图。具体包括以下步骤：
在步骤S110中，测量活立木的距离地面第一高度处的待测部位的直径。
在本步骤中，针对待测量的活立木，测量活立木的距离地面第一高度H处的待测部位的直径d。第一高度H例如是活立木的胸高位置处，对应的直径是活立木的胸径d。
在步骤S120中，在空气中相隔第一距离发射与接收预设频率范围的微波，测量不同频率时发射微波信号与第一接收微波信号的第一比值。
在该步骤中，在空气中发射预设频率范围的微波，这里的预设频率范围的微波是与待测活立木的密度相适应的微波波段，即与待测活立木的密度最为敏感的微波波段，例如2GHz至8GHz。在与微波发射位置相隔第一距离D的位置接收预设频率范围的微波，测量不同频率ω时发射微波信号X(ω)与第一接收微波信号Y 0(ω)的第一比值H 0(ω)。第一距离D大于直径d。可选地，微波的发射位置和接收位置距离地面的高度为第一高度H。
在步骤S130中，在空气中于所述第一高度处发射所述微波使得所述微波穿透所述活立木的所述待测部位，并且在与所述微波的发射位置相隔所述第一距离处接收所述微波，测量不同频率时所述发射微波信号与第二接收微波信号的第二比值。
图2是本发明的一个实施例的活立木木材密度测量方法的应用场景图。如图2所示，待测活立木210位于预设频率范围的微波的发射端220和接收端230之间，微波经发射端220发射后穿 透活立木210的待测部位到达接收端230。发射端220和接收端230相隔第一距离D，活立木210的待测部位距离地面为第一高度H，相应的第一高度H处的活立木210的待测部位的直径为d。
在该步骤中，在如图2所示的应用场景中，在空气中于第一高度H处发射预设频率范围的微波使得微波穿透活立木210的待测部位，并且在与微波的发射位置(发射端220)相隔第一距离D处(接收端230)接收微波，测量不同频率ω时发射微波信号X(ω)与第二接收微波信号Y w(ω)的第二比值H w(ω)。
在步骤S140中，根据所述第一比值、所述第二比值和所述直径，计算所述活立木的介电常数和衰减常数。
在该步骤中，根据第一比值H 0(ω)、第二比值H w(ω)和直径d，计算活立木的介电常数ε和衰减常数α。
具体包括：利用傅里叶逆变换计算第一比值H 0(ω)和第二比值第二比值H w(ω)对应的第一时域数据h 0(t)和第二时域数据h w(t)。
根据第一时域数据h 0(t)和第二时域数据h w(t)，计算微波在活立木的待测部位的传输时间Δt和幅度衰减ΔA。图3是本发明的一个实施例的微波在空气中传输的时域数据的波形图，具体示出了第一时域数据h 0(t)的波形图。如图3所示，第一时域数据h 0(t)的纵坐标为幅度值，横坐标为时间，第一时域数据h 0(t)的波形的幅值最大值处为点M 0(t 0,A 0)。图4是本发明的一个实施例的微波在活立木和空气中传输的时域数据的波形图，具体示出待测活立木为香杉，距离地面高度为130cm的待测部位直径d＝13.3cm，微波的发射端220和接收端230相隔第一距离D＝30cm，测量得到的发射微波信号X(ω)与第二接收微波信号Y w(ω)的第二比值H w(ω)对应的第二时域数据h w(t)波形图。如图4所示，第二时域数据h w(t)的纵坐标为幅度值，横坐标为时间，第二时域数据h w(t)的波形的幅值最大值处为点M 1(t 1,A 1)。
图5是本发明的一个实施例的微波在活立木的待测部位的传输时间和幅度衰减的测量方法的流程示意图。具体包括以下步骤：
在步骤S510中，选取如图3所示的第一时域数据h 0(t)的波形的幅值最大值处M 0(t 0,A 0)，确定幅值最大值处M 0(t 0,A 0)对应的第一时间t 0和第一幅值A 0。
在步骤S520中，选取如图4所示的第二时域数据h w(t)的波形的幅值最大值处M 1(t 1,A 1)，确定幅值最大值处M 1(t 1,A 1)对应的第二时间t 1和第二幅值A 1。
在步骤S530中，根据第一时间t 0、第二时间t 1和直径d，计算传输时间Δt。微波在活立木的待测部位的传输时间Δt的计算公式为：
Δt＝t 1-t 0+d/c   (1)
其中，Δt为微波在活立木的待测部位的传输时间，t 1为微波在活立木和空气中传输的第二时域数据h w(t)的波形的幅值最大值处M 1(t 1,A 1)对应的第二时间，t 0为微波在空气中传输的第一时域数据h 0(t)的波形的幅值最大值处M 0(t 0,A 0)对应的第一时间，d为活立木的距离地面第一高度H处的待测部位的直径，c为微波在空气中的传播速度。
在步骤S540中，根据第一幅值A 0和第二幅值A 1，计算幅度衰减ΔA。微波在活立木的待测部位的传输时的幅度衰减ΔA的计算公式为：
ΔA＝-20lg(A 1/A 0)    (2)
其中，ΔA为微波在活立木的待测部位的传输时的幅度衰减，A 1为微波在活立木和空气中传输的第二时域数据h w(t)的波形的幅值最大值处M 1(t 1,A 1)对应的第二幅值，t 0为微波在空气中传输的第一时域数据h 0(t)的波形的幅值最大值处M 0(t 0,A 0)对应的第一幅值。
根据传输时间Δt和直径d计算活立木的介电常数ε。对应预设频率范围的微波的活立木的介电常数ε的计算公式为：
ε＝(Δtc/d) 2    (3)
其中，ε活立木的介电常数，Δt为微波在活立木的待测部位的传输时间，d为活立木的距离地面第一高度H处的待测部位的直径，c为微波在空气中的传播速度。
根据幅度衰减ΔA和直径d计算活立木的衰减常数α。对应预设频率范围的微波的活立木的衰减常数α的计算公式为：
α＝ΔA/(8.686d)    (4)
其中，α活立木的衰减常数，ΔA为微波在活立木的待测部位的传输时的幅度衰减，d为活立木的距离地面第一高度H处的待测部位的直径。
在步骤S150中，确定所述活立木的木材密度与所述介电常数和衰减常数的关系式，并根据所述关系式计算所述活立木的所述木材密度。
木材的介电常数不是常量，影响木材介电常数的通常有木材含水率、木材密度、微波频率、树种等因素。图6是本发明的一个实施例的活立木的木材密度、水分和介电常数的关系图，具体示出待测活立木为香杉。如图6所示，横坐标为对应预设频率范围的微波的活立木的介电常数ε，纵坐标为活立木的木材密度，图中的多个测试点对应的水分不同，从图中可以得到杉木密度、水分与介电常数的关系为线性关系。
在该步骤中，根据图6所示的活立木的木材密度、水分和介电常数的关系图以及水分和衰减常数的关系，可以推导出活立木的木材密度ρ与介电常数ε、衰减常数α的关系式为：
Figure PCTCN2019113686-appb-000002
其中，ρ为活立木的木材密度，ε为对应预设频率范围的微波的活立木的介电常数，α为对应预设频率范围的微波的活立木的衰减常数，a、b、p、q是预先标定的与活立木的树种等属性相关的参数。树种等属性是指活立木树种、树木部位、树龄和生长地区等。
图7是本发明的一个实施例的活立木木材密度的测量密度和实际密度的对比图。按照本发明实施例中的活立木木材密度测量方法多次测量木材密度，如图7所示，多次测量的活立木木材密度与活立木实际密度相比，平均误差为0.03g/m 3。
根据本发明实施例，针对待测量的活立木，测量活立木的距离地面第一高度处的待测部位的直径。在空气中相隔第一距离发射与接收预设频率范围的微波，测量不同频率时发射微波信号与第一接收微波信号的第一比值。在空气中于第一高度处发射微波使得微波穿透活立木的待测部位，并且在与微波的发射位置相隔第一距离处接收微波，测量不同频率时发射微波信号与第二接收微波信号的第二比值。根据第一比值、第二比值和直径，计算活立木的介电常数和衰减常数。确定活立木的木材密度与介电常数和衰减常数的关系式，并根据关系式计算活立木的木材密度。本发明实施例的木材密度测量过程简单，无需按照标准来采样、制作标准体积的试件，因而节省了人力、物力和耗时，并且不需要从活立木上取试样，实现了对活立木的无损测量，方便现场测量。计算木材密度的关系式中的相关参数是通过预先试验得到的，并且其通过了检测，符合测量精度，因而得到的木材密度也符合测量精度，保证了本发明实施例的测量精度。微波可以穿透活立木的待测部位，测量整个径向方向的木材密度，提高了对活立木整个径向的木材密度测量范围进而提高了测得的木材密度的准确性。
在本发明的一些实施例中，重复步骤S120至步骤S150，从不同方向测量活立木的待测部位的木材密度，即在活立木的待测部位的不同方向多次测量不同频率时发射微波信号与第二接收微波信号的第二比值；根据第一比值、多次测量的第二比值和直径，分别计算不同方向的活立木的待测部位的介电常数和衰减常数；根据关系式，分别计算不同方向的活立木的待测部位的木材密度；计算不同方向的活立木的待测部位的木材密度的平均值，得到活立木的待测部位的平均木材密度。由于微波可以从不同方向穿透活立木的待测部位，可以从不同方向测量整个径向方向的活立木的待测部位的木材密度，计算不同方向的活立木的待测部位的木材密度的平均值，进而进一步提高了测得的木材密度的准确性。
图8是本发明的一个实施例的活立木木材密度测量装置的框图。如图8所示，该活立木木材 密度测量装置包括：发射机810、接收机820、控制器830、触摸屏840、通信接口模块850、基准时钟模块860和电压转换器870。发射机810包括发射天线811、接收机820包括接收天线821。
发射机810，主要包括锁相环频率合成器、功分器和功率放大器，用于根据控制信号产生一定功率的频率步进微波并发射预设频率范围的微波信号。
接收机820，用于在与发射机810相隔大于活立木的待测部位的直径的第一距离处，接收在空气中传播第一距离后的第一接收微波信号，将第一接收微波信号与发射微波信号正交解调以将第一接收微波信号转换为第一路基带信号和第二路基带信号，进而提取出幅度和相位信息，接收穿透活立木的待测部位的第二接收微波信号，将第二接收微波信号与发射微波信号正交解调以将第二接收微波信号转换为第三路基带信号和第四路基带信号，进而提取出幅度和相位信息。
发射机810的发射天线811和接收机820的接收天线821均采用宽带定向天线。发射天线811和接收天线821分别通过电缆组件与发射机810和接收机820相连接，发射天线811向待测对象发送微波信号，接收天线821接收第一接收微波信号和第二接收微波信号。
控制器830，与发射机810和接收机820连接，用于向发射机810提供控制信号，包括触发信号和时序控制信号、从接收机820采集和存储第一路基带信号和第二路基带信号、第三路基带信号和第四路基带信号并且根据发射微波信号和第一路基带信号和第二路基带信号、第三路基带信号和第四路基带信号计算活立木的木材密度。在一些实施例中，控制器830还用于向接收机820提供触发信号和时序控制信号。在一些实施例中，控制器830还用于向服务器传送数据。
触摸屏840，用于设置参数、发送用户指令给控制器830和显示控制器830的计算结果。
通信接口模块850，用于实现控制器830与服务器之间的数据交互，从服务器获取活立木的木材密度与介电常数和衰减常数的关系式(公式(5))中的相关参数，并且将控制器830的计算结果发送给触摸屏840。
基准时钟模块860，用于产生控制器830和发射机810所需的时钟基准。
电压转换器870，用于对输入电源进行处理以提供活立木木材密度测量装置中各个功能模块、器件的所需的各类二次电源。活立木木材密度测量在野外进行，活立木木材密度测量装置采用锂电池供电，电压转换器870还具有电源管理功能，可以在锂电池供电和输入电源供电之间切换。
图9是本发明的一个实施例的接收机的框图。如图9所示，考虑到不同活立木的密度和含水量变化范围较大，接收机820包括：预选滤波器910、前置放大器920、PI型衰减器930、后置放大器940、正交解调器950、低通滤波器960和模数转换器970。接收机820中的前置放大器920、PI型衰减器930和后置放大器940采用两级放大和一级PI型衰减器来完成射频信号前端放大。
预选滤波器910，用于滤除第一接收微波信号和第二接收微波信号中的干扰信号。
前置放大器920和后置放大器940，用于放大预选滤波后的第一接收微波信号和第二接收微波信号。
PI型衰减器930，用于调节整个接收链路的放大增益，保证接收机820中所有器件都工作在线性区。
正交解调器950，用于将后置放大器940输出的第一接收微波信号与发射微波信号解调得到第一接收微波信号的第一路基带信号和第二路基带信号，将后置放大器940输出的第二接收微波信号与发射微波信号正交解调得到第二接收微波信号的第三路基带信号和第四路基带信号，进而提取出第一接收微波信号和第二接收微波信号的幅度和相位信息。
第一路基带信号和第二路基带信号是一组正交信号，第一路基带信号和第二路基带信号的相位相差90度。例如，第一路基带信号是I路基带信号，第二路基带信号是Q路基带信号。第三路基带信号和第四路基带信号是一组正交信号，第三路基带信号和第四路基带信号的相位相差90度。例如，第三路基带信号是I路基带信号，第四路基带信号是Q路基带信号。
低通滤波器960，用于滤除第一路基带信号和第二路基带信号、第三路基带信号和第四路基带信号的干扰高频信号。
模数转换器970，用于将第一路基带信号和第二路基带信号、第三路基带信号和第四路基带信号分别采样量化为第一路数字信号和第二路数字信号、第三路数字信号和第四路数字信号。例如，第一路数字信号是I路数字信号，第二路数字信号是Q路数字信号，第三路数字信号是I路数字信号，第四路数字信号是Q路数字信号。
I路基带信号和Q路基带信号为矢量，因此，可以用三角恒等式计算第一接收微波信号的幅度衰减和相移，以及第二接收微波信号的幅度衰减和相移，如下式：
Figure PCTCN2019113686-appb-000003
其中，τ为第一接收微波信号或第二接收微波信号的幅度衰减，V I为第一接收微波信号或第二接收微波信号的I路数字信号，V Q为第一接收微波信号或第二接收微波信号的Q路数字信号。
Figure PCTCN2019113686-appb-000004
其中，
Figure PCTCN2019113686-appb-000005
为第一接收微波信号或第二接收微波信号的相移，V I为第一接收微波信号或第二接收微波信号的I路数字信号，V Q为第一接收微波信号或第二接收微波信号的Q路数字信号。
图10是本发明的一个实施例的控制器的框图。考虑到活立木木材密度测量装置的控制功能具有周期性重复的特点及对控制信号的并行输出要求，如图10所示，采用FPGA来实现测量装置中控制器830的逻辑控制，充分发挥FPGA的高集成度、低功耗等优势，另外FPGA的可编程特性便于以后控制器830的升级换代。如图10所示，控制器830包括：数据采集模块1010、数据存储模块1020、数据处理模块1030、系统控制模块1040和数据传输模块1050。
数据采集模块1010，用于控制模数转换器970以采集第一接收微波信号的第一路数字信号和第二路数字信号、第二接收微波信号的第三路数字信号和第四路数字信号。
数据存储模块1020，用于存储第一接收微波信号的第一路数字信号和第二路数字信号、第二接收微波信号的第三路数字信号和第四路数字信号、活立木的木材密度与介电常数和衰减常数的关系式(公式(5))中的相关参数、活立木的待测部位的直径。
数据处理模块1030，用于分析接收到的数字信号，根据数据存储模块1020中存储的第一路数字信号和第二路数字信号，利用公式(6)和(7)计算第一接收微波信号的幅度衰减和相移。根据第一接收微波信号的幅度衰减和相移计算发射微波的频域信号与第一接收微波的频域信号的第一比值。根据数据存储模块1020中存储的第三路数字信号和第四路数字信号，利用公式(6)和(7)计算第二接收微波的幅度衰减和相移。根据第二接收微波的幅度衰减和相移计算发射微波的频域信号与第二接收微波的频域信号的第二比值。
不同频率的发射微波信号与第一接收微波信号的第一比值和不同频率的发射微波信号与第二接收微波信号的第二比值的计算公式为：
Figure PCTCN2019113686-appb-000006
其中，H(ω)为不同频率ω的发射微波信号与第一接收微波信号的第一比值或者不同频率ω的发射微波信号与第二接收微波信号的第二比值，
Figure PCTCN2019113686-appb-000007
为第一接收微波信号或第二接收微波信号的相移，τ为第一接收微波信号或第二接收微波信号的幅度衰减。
根据第一比值、第二比值、直径和相关参数(公式(5)中的相关参数)，利用介电常数和衰减常数的计算公式(公式(1)至公式(4))、活立木的木材密度与介电常数和衰减常数的关系式(公式(5))来计算活立木的木材密度。
系统控制模块1040，用于接收触摸屏840设置的参数、用户指令和/或数据处理模块1030的计算结果，向发射机810发射控制信号，或将计算结果发送给通信接口模块850；
数据传输模块1050，用于为控制器830的各个模块之间提供数据通路。
相应地，本发明实施例提供一种计算机可读存储介质，该计算机可读存储介质存储有计算机指令，所述计算机指令被执行时实现上述活立木木材密度测量方法所规定的操作。
相应地，本发明实施例还提供了一种计算机程序产品，包括计算机程序，所述计算机程序包括程序指令，当所述程序指令被移动终端执行时，使所述移动终端执行上述活立木木材密度测量方法的步骤。
附图中的流程图、框图图示了本发明实施例的系统、方法、装置的可能的体系框架、功能和操作，流程图和框图上的方框可以代表一个模块、程序段或仅仅是一段代码，所述模块、程序段和代码都是用来实现规定逻辑功能的可执行指令。也应当注意，所述实现规定逻辑功能的可执行指令可以重新组合，从而生成新的模块和程序段。因此附图的方框以及方框顺序只是用来更好的图示实施例的过程和步骤，而不应以此作为对发明本身的限制。
以上所述仅为本发明的一些实施例，并不用于限制本发明，对于本领域技术人员而言，本发明可以有各种改动和变化。凡在本发明的精神和原理之内所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种活立木木材密度测量方法，其特征在于，包括：
    测量活立木的距离地面第一高度处的待测部位的直径；
    在空气中相隔大于所述直径的第一距离发射与接收预设频率范围的微波，测量不同频率时发射微波信号与第一接收微波信号的第一比值；
    在空气中于所述第一高度处发射所述微波使得所述微波穿透所述活立木的所述待测部位，并且在与所述微波的发射位置相隔所述第一距离处接收所述微波，测量不同频率时所述发射微波信号与第二接收微波信号的第二比值；
    根据所述第一比值、所述第二比值和所述直径，计算所述活立木的介电常数和衰减常数；
    确定所述活立木的木材密度与所述介电常数和衰减常数的关系式，并根据所述关系式计算所述活立木的所述木材密度。
  2. 根据权利要求1所述的活立木木材密度测量方法，其特征在于，所述测量方法还包括：
    在所述活立木的所述待测部位的不同方向多次测量所述第二比值；
    根据所述第一比值、多次测量的所述第二比值和所述直径，分别计算不同方向的所述活立木的所述待测部位的介电常数和衰减常数；
    根据所述关系式，分别计算不同方向的所述活立木的所述待测部位的木材密度；
    计算所述不同方向的所述活立木的所述待测部位的木材密度的平均值，得到所述活立木的所述待测部位的平均木材密度。
  3. 根据权利要求2所述的活立木木材密度测量方法，其特征在于，所述根据所述第一比值、所述第二比值和所述直径，计算所述活立木的介电常数和衰减常数包括：
    利用傅里叶逆变换计算所述第一比值和所述第二比值对应的第一时域数据和第二时域数据；
    根据所述第一时域数据和所述第二时域数据，计算所述微波在所述活立木的所述待测部位的传输时间和幅度衰减；
    根据所述传输时间和所述直径计算所述活立木的介电常数；以及
    根据所述幅度衰减和所述直径计算所述活立木的衰减常数。
  4. 根据权利要求3所述的活立木木材密度测量方法，其特征在于，所述根据所述第一时域数据和所述第二时域数据，计算所述微波在所述活立木的所述待测部位的传输时间和幅度衰减包括：
    选取所述第一时域数据的波形的幅值最大值处，确定所述幅值最大值处对应的第一时间和第一幅值；
    选取所述第二时域数据的波形的幅值最大值处，确定所述幅值最大值处对应的第二时间和第 二幅值；
    根据所述第一时间、所述第二时间和所述直径，计算所述传输时间；
    根据所述第一幅值和所述第二幅值，计算所述幅度衰减。
  5. 根据权利要求1所述的活立木木材密度测量方法，其特征在于，所述活立木的木材密度与所述介电常数和衰减常数的关系式为：
    Figure PCTCN2019113686-appb-100001
    其中，ρ为所述活立木的木材密度，ε为所述活立木的介电常数，α为所述活立木的衰减常数，a、b、p、q是预先标定的与所述活立木的树种相关的参数。
  6. 一种活立木木材密度测量装置，其特征在于，包括：
    发射机，用于根据控制信号产生并发射预设频率范围的微波信号；
    接收机，用于在与所述发射机相隔大于活立木的待测部位的直径的第一距离处，接收在空气中传播所述第一距离后的第一接收微波信号，将所述第一接收微波信号与发射微波信号正交解调以将所述第一接收微波信号转换为第一路基带信号和第二路基带信号，
    接收穿透所述活立木的待测部位的第二接收微波信号，将所述第二接收微波信号与所述发射微波信号正交解调以将所述第二接收微波信号转换为第三路基带信号和第四路基带信号；
    控制器，与所述发射机和所述接收机连接，用于向所述发射机提供所述控制信号、采集和存储所述第一路基带信号和第二路基带信号、所述第三路基带信号和第四路基带信号并且根据所述发射微波信号和所述第一路基带信号和第二路基带信号、所述第三路基带信号和第四路基带信号计算所述活立木的木材密度；
    触摸屏，用于设置参数、发送用户指令给所述控制器和显示所述控制器的计算结果；
    通信接口模块，用于从服务器获取所述活立木的木材密度与介电常数和衰减常数的关系式中的相关参数，并且将所述设置参数及所述控制器的计算结果发送给所述服务器；
    基准时钟模块，用于产生所述控制器和所述发射机所需的时钟基准；以及
    电压转换器，用于对输入电源进行处理以提供所需的各类二次电源。
  7. 根据权利要求6所述的活立木木材密度测量装置，其特征在于，所述接收机包括：预选滤波器、前置放大器、PI型衰减器、后置放大器、正交解调器、低通滤波器和模数转换器，
    所述预选滤波器，用于滤除所述第一接收微波信号和所述第二接收微波信号中的干扰信号；
    所述前置放大器和所述后置放大器，用于放大预选滤波后的所述第一接收微波信号和所述第二接收微波信号；
    所述PI型衰减器，用于调节整个接收链路的放大增益；
    所述正交解调器，用于将所述后置放大器输出的所述第一接收微波信号与所述发射微波信号正交解调得到所述第一接收微波信号的所述第一路基带信号和第二路基带信号，
    将所述后置放大器输出的所述第二接收微波信号与所述发射微波信号正交解调得到所述第二接收微波信号的所述第三路基带信号和第四路基带信号；
    所述低通滤波器，用于滤除所述第一路基带信号和第二路基带信号、所述第三路基带信号和第四路基带信号的干扰高频信号；
    所述模数转换器，用于将所述第一路基带信号和第二路基带信号、所述第三路基带信号和第四路基带信号分别转换为第一路数字信号和第二路数字信号、第三路数字信号和第四路数字信号。
  8. 根据权利要求7所述的活立木木材密度测量装置，其特征在于，所述控制器包括：数据采集模块、数据存储模块、数据处理模块、系统控制模块和数据传输模块，
    所述数据采集模块，用于控制所述模数转换器以采集所述第一接收微波信号的所述第一路数字信号和第二路数字信号、所述第二接收微波信号的所述第三路数字信号和第四路数字信号；
    所述数据存储模块，用于存储所述第一路数字信号和第二路数字信号、所述第三路数字信号和第四路数字信号、所述活立木的木材密度与介电常数和衰减常数的关系式中的所述相关参数、所述直径；
    所述数据处理模块，用于根据所述第一路数字信号和第二路数字信号来计算不同频率时所述发射微波信号与所述第一接收微波信号的第一比值，
    根据所述第三路数字信号和第四路数字信号来计算不同频率时所述发射微波信号与所述第二接收微波信号的第二比值，
    根据所述第一比值、所述第二比值、所述直径和所述相关参数，利用所述介电常数和衰减常数的计算公式、所述活立木的木材密度与介电常数和衰减常数的所述关系式来计算所述活立木的木材密度；
    所述系统控制模块，用于接收所述触摸屏设置的参数、用户指令和/或所述数据处理模块的计算结果，向所述发射机发射所述控制信号，或将所述计算结果发送给所述通信接口模块；
    所述数据传输模块，用于为所述控制器的各个模块之间提供数据通路。
  9. 一种计算机可读存储介质，其特征在于，所述计算机可读存储介质存储有计算机指令，所述计算机指令被执行时实现如权利要求1至5中任一项所述的活立木木材密度测量方法。
  10. 一种计算机程序产品，包括计算机程序，所述计算机程序包括程序指令，当所述程序指令被移动终端执行时，使所述移动终端执行如权利要求1至5中任一项所述活立木木材密度测量 方法的步骤。
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