CN104251824A - Method for building temperature compensation model of multispectral crop growth sensor - Google Patents

Abstract

The invention discloses a method for building a temperature compensation model of a multispectral crop growth sensor. The method can realize temperature compensation of reflectivity by carrying out temperature compensation on output voltage of the sensor. The method is based on temperature and at the same time is suitable for building prediction models of output voltages of a 720 nm uplink optical sensor and a 810 nm downlink optical sensor, and obtains the temperature compensation models of the uplink optical sensor and the downlink optical sensor through the prediction models; the reflectivity is calculated according to the output voltage after temperature compensation to realize temperature compensation for the reflectivity of the multispectral crop growth sensor. The method builds the low-calculation-amount and high-precision temperature compensation model of the multispectral crop growth sensor, and improves the temperature stability of the sensor during field application, the temperature characteristic of the multispectral crop growth sensor can be understood, the temperature prediction models of the output voltage of the sensors are built, and the temperature compensation of the reflectivity of the sensor is realized.

Description

A kind of construction method of multispectral plant growth Sensor Temperature Compensation model

Technical field

The invention belongs to crop growthing development control technique field, particularly relate to a kind of construction method of multispectral plant growth Sensor Temperature Compensation model.

Background technology

Obtain plant growth information quickly and accurately, to crop growth regulation and control, there is important directive significance.Traditional Field sampling, in office analysis test obtain the method for plant growth information, although reliable results, poor in timeliness, is difficult to the needs of satisfied modern precision agriculture development.Make the difference of biochemical component and institutional framework in object, some specific reflection spectrum marked change can be caused, high spectrum resolution remote sensing technique is utilized to monitor these special spectrums, and then can the accurately multiple growth information of perception crop, as leaf area index, chlorophyll content, biomass, nitrogen content, sugared nitrogen than etc.In order to promote crop growing state spectrum monitoring technology in production line.Sensor is in photoelectric conversion process, and photoelectric device is comparatively large by the impact of environment temperature, thus makes the output signal of sensor vary with temperature generation drift.In Field information, irradiate with seasonal temperature change and sunlight, the internal temperature of sensor can reach 10-60 DEG C, and temperature is obvious on the impact of sensor output signal, therefore need do temperature compensation.Realize temperature compensation by designing corresponding hardware circuit cocoa, but the method hardware circuit is complicated, compensation precision is low.Compared with hardware compensating, software compensation cost is low, and precision is high, as the intelligent algorithm such as artificial neural network, least square method supporting vector machine is used widely; The model of temperature compensation that each temperature is special and total temperature scope is general is constructed when research and utilization near infrared reflectivity detects apple soluble solid content.Although model of temperature compensation precision is high constructed by such algorithm, model is too complicated, is difficult to be integrated in the limited single-chip microcomputer of arithmetic capability, and then limits the application in intelligent sensor and intelligent instrument.

Summary of the invention

The object of the embodiment of the present invention is the construction method providing a kind of multispectral plant growth Sensor Temperature Compensation model, is intended to solve traditional multispectral plant growth Sensor Temperature Compensation circuit complexity, cost is high, precision is low, the problem of poor stability.

The embodiment of the present invention is achieved in that a kind of construction method of multispectral plant growth Sensor Temperature Compensation model, and the construction method of this multispectral plant growth Sensor Temperature Compensation model comprises:

Step one, builds the sensor output voltage forecast model based on temperature with the output voltage of the up optical sensor of 720nm and descending optical sensor, the up light of 810nm and descending optical sensor output voltage is done verification msg;

Step 2, with the output voltage V of up light during room temperature 25 DEG C and descending optical sensor different-waveband _{25 λ}represent the λ wave band incident light energy received; The main effect of temperature and temperature and V should be had in the model built _{25 λ}interaction item; Temperature is obvious to the affecting laws of sensor output voltage, and the main effect polynomial expression of temperature is simulated, and polynomial expression will consider once item, quadratic term, cubic term and four items; Then the prototype of sensor output voltage temperature prediction model is as shown in formula (4):

V _Tλ＝a+bV _25λ+cT+dT ²+eT ³+fT ⁴+gT·V _25λ 4()

T is Celsius temperature, V _{t λ}for the output voltage of λ band upstream light or descending optical sensor under temperature T; Utilize the non-linear regression function of modeling data and SPSS16.0 to obtain the coefficient of formula (4), wherein e=0, f=0, therefore model rejects the cubic term of temperature and four items obtain formula (5);

V _Tλ＝0.041+0.909V _25λ-0.002T+10 ^-5T ²+0.004T·V _25λ 5()

Step 3, by the V of 720nm and 810nm _{25 λ}substitute into the predicted value that formula (5) obtains different temperatures lower sensor, and computational reflect rate, model also presents very high degree of fitting to the verification msg of 810nm; The R of model ²=0.9998, RRMSE=2.31%;

Step 4, does pro forma conversion to formula (5), obtains formula (6); Formula (6) is by the output voltage V of up, the descending optical sensor under condition of different temperatures _{t λ}compensate to 25 DEG C of corresponding voltage V _{25 λ};

$V_{25\mathrm{\λ}}=\frac{V_{\mathrm{T\λ}}-0.041+0.002T-{10}^{-5}{T}^2}{0.909+0.004T}---6\left(\right)$

Utilize V _{25 λ}computational reflect rate can realize the temperature compensation of multispectral plant growth sensor reflectivity.

Further, after the construction method of this multispectral plant growth Sensor Temperature Compensation model is temperature compensated, within the scope of 5 DEG C ~ 60 DEG C, the fluctuation range of 720nm reflectivity drops to 0.1% by 3%, 820nm drops to 0.4% by 7.7%, and the reflectivity after these two wave band temperature compensations is all close to reflectivity during measured data 25 DEG C, show that the model of temperature compensation precision of reflectivity is high, applicability is good.

Further, in the construction method of this multispectral plant growth Sensor Temperature Compensation model, multispectral plant growth sensor gathers crop canopies 720nm and 810nm spectral reflectivity, coupling plant growth Monitoring Indexes model, inverting crop growing state information; Sensor take sunshine as light source, adopts optical filter light splitting; Reflectivity is defined as the reflected energy of object and the ratio of projectile energy, and spectral reflectivity is then the object reflectance under specific wavelength; Crop canopies is the solar spectrum reflectivity ρ of λ to wavelength _λfor:

${\mathrm{\ρ}}_{\mathrm{\λ}}=\frac{\mathrm{\π}{L}_{\mathrm{\λ}}}{E_{\mathrm{\λ}}}---1\left(\right)$

In formula, L _λfor the spectral reflectance radiance of crop canopies λ wavelength, Wsr ^-1m ^-2, E _λthe parallel irradiance incided on crop canopies of solar spectrum for λ wavelength, Wm ^-2, π is solid angle, solid angle unit sphere degree sr; From formula (1), utilize L _λand E _λcalculate the spectral reflectivity of crop canopies.

Further, in order to obtain L _λand E _λ, multispectral plant growth sensor is structurally divided into up optical sensor and descending optical sensor, has 4 passages; Up optical sensor receives the incident light of 720nm and 810nm, and carries out cosine correction; Descending optical sensor is for receiving corresponding wave band crop canopies reflected radiation brightness; The aperture of the diaphragm of sensor is 12.8mm, hole depth 26mm, field angle 27 °, spectral filter bandwidth 10nm, and transmitance is 65%-70%; Sensor photodetector sensitivity used is 0.55AW ^-1, spectral responsivity is 0.011AW ^-1cm ^-2.

Further, sensor adopts the encapsulation of aluminum casing, aperture 38mm, high 50mm.

The construction method of multispectral plant growth Sensor Temperature Compensation model provided by the invention, constructs that operand is low, precision much higher spectrum plant growth Sensor Temperature Compensation model, improves the temperature stability of sensor Field information; The reflectivity of sensor is divided by by the descending optical sensor of wave band identical in sensor and the output voltage of up optical sensor to obtain; The affecting laws of temperature to reflectivity is more complicated, and essence is that temperature affects caused by the output voltage of sensor.Therefore the present invention have studied the temperature characterisitic of multispectral plant growth sensor, constructs the temperature prediction model of sensor output voltage on this basis, and then achieves the temperature compensation of sensor reflectivity.

The present invention constructs the temperature prediction model of sensor output voltage, and model can obtain the sensor output voltage under different temperatures according to the output voltage prediction of sensor when 25 DEG C; On this basis, model is done pro forma conversion, and then constructing the model of temperature compensation of reflectivity, the fluctuation range that reflectivity Yin Wendu impact produces by model is reduced to by 1.0%-7.0% and is no more than 0.45%, significantly reduces the impact of temperature on sensor reflectivity; Improve the temperature stability in sensor use.

The cost of temperature compensation of the present invention is low, and precision is high, overcomes routine hardware implementing temperature-compensation circuit complicated, and interference is large, and compensation precision is low, and the drawback of bad adaptability; The model of temperature compensation operand that the present invention builds is low, precision is high, stability is strong, is suitable for being integrated in intelligent instrument and intelligent sensor applying.

Accompanying drawing explanation

Fig. 1 is the construction method process flow diagram of the multispectral plant growth Sensor Temperature Compensation model that the embodiment of the present invention provides;

Fig. 2 is that the temperature that provides of the embodiment of the present invention affects schematic diagram to sensor output voltage;

Fig. 3 is that the temperature that provides of the embodiment of the present invention affects schematic diagram to sensor reflectivity;

Fig. 4 be the model predication value that provides of the embodiment of the present invention with measured value compare schematic diagram;

In figure: the predicted value of A. sensor output voltage and measured value; B. the predicted value of reflectivity and measured value;

Fig. 5 is comparison diagram schematic diagram before and after the reflectivity temperature compensation that provides of the embodiment of the present invention;

In figure: A.720nm comparison diagram before and after reflectivity temperature compensation; B.810nm comparison diagram before and after reflectivity temperature compensation;

Fig. 6 is the reflectivity change schematic diagram before and after the check data that provides of the embodiment of the present invention and temperature compensation;

In figure: the output voltage that A. is sensor during monitoring target with 40% reflectivity standards gray scale plate; B. with 40% reflectivity standards gray scale plate for comparison diagram before and after sensor 720nm reflectivity temperature compensation during monitoring target; C. with 40% reflectivity standards gray scale plate for comparison diagram before and after sensor 810nm reflectivity temperature compensation during monitoring target; D. with the output voltage that 60% reflectivity standards gray scale plate is sensor during monitoring target; E. with 60% reflectivity standards gray scale plate for comparison diagram before and after sensor 720nm reflectivity temperature compensation during monitoring target; F. with 60% reflectivity standards gray scale plate for comparison diagram before and after sensor 810nm reflectivity temperature compensation during monitoring target.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with embodiment, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

Below in conjunction with drawings and the specific embodiments, application principle of the present invention is further described.

As shown in Figure 1, the construction method of the multispectral plant growth Sensor Temperature Compensation model of the embodiment of the present invention comprises the following steps:

S101: build the sensor output voltage forecast model based on temperature with the output voltage of the up optical sensor of 720nm and descending optical sensor, the up light of 810nm and descending optical sensor output voltage are done verification msg;

S102: with the output voltage V of up light during room temperature 25 DEG C and descending optical sensor different-waveband _{25 λ}represent the λ wave band incident light energy received; The main effect of temperature and temperature and V should be had in the model built _{25 λ}interaction item; Temperature is obvious to the affecting laws of sensor output voltage, and the main effect of temperature can be simulated with polynomial expression, and simultaneously for avoiding imperial lattice phenomenon, polynomial expression only will consider once item, quadratic term, cubic term and four items;

S103: by the V of 720nm and 810nm _{25 λ}substitute into the predicted value that formula obtains different temperatures lower sensor, and computational reflect rate, model also presents very high degree of fitting to the verification msg of 810nm;

S104: do pro forma conversion to formula, to obtain the output voltage compensation of up, the descending optical sensor under condition of different temperatures to 25 DEG C of corresponding voltages, can realize the temperature compensation of multispectral plant growth sensor reflectivity.

Concrete steps of the present invention are:

Step one, builds the sensor output voltage forecast model based on temperature with the output voltage of the up optical sensor of 720nm and descending optical sensor, the up light of 810nm and descending optical sensor output voltage is done verification msg;

Step 2, with the output voltage V of up light during room temperature 25 DEG C and descending optical sensor different-waveband _{25 λ}represent the λ wave band incident light energy received; The main effect of temperature and temperature and V should be had in the model built _{25 λ}interaction item; Temperature is obvious to the affecting laws of sensor output voltage, and the main effect of temperature can be simulated with polynomial expression, and simultaneously for avoiding imperial lattice phenomenon, polynomial expression only will consider once item, quadratic term, cubic term and four items; Then the prototype of sensor output voltage temperature prediction model is as shown in formula (4):

V _Tλ＝a+bV _25λ+cT+dT ²+eT ³+fT ⁴+gT·V _25λ 4()

T is Celsius temperature, V _{t λ}for the output voltage of λ band upstream light or descending optical sensor under temperature T; Utilize the non-linear regression function of modeling data and SPSS16.0 can obtain the coefficient of formula (4), wherein e=0, f=0, therefore model rejects the cubic term of temperature and four items obtain formula (5);

V _Tλ＝0.041+0.909V _25λ-0.002T+10 ^-5T ²+0.004T·V _25λ 5()

Step 3, by the V of 720nm and 810nm _{25 λ}substitute into the predicted value that formula (5) obtains different temperatures lower sensor, and computational reflect rate, model also presents very high degree of fitting to the verification msg of 810nm; The R of model ²=0.9998, RRMSE=2.31%;

Step 4, does pro forma conversion to formula (5), obtains formula (6); Formula (6) can by the output voltage V of up, the descending optical sensor under condition of different temperatures _{t λ}compensate to 25 DEG C of corresponding voltage V _{25 λ};

$V_{25\mathrm{\λ}}=\frac{V_{\mathrm{T\λ}}-0.041+0.002T-{10}^{-5}{T}^2}{0.909+0.004T}---6\left(\right)$

Utilize V _{25 λ}computational reflect rate can realize the temperature compensation of multispectral plant growth sensor reflectivity; Before and after the temperature compensation of this test reflectivity, Fig. 5 is shown in contrast, visible temperature compensated after, within the scope of 5 DEG C ~ 60 DEG C, the fluctuation range of 720nm reflectivity drops to 0.1% by 3%, 820nm drops to 0.4% by 7.7%, and the reflectivity after these two wave band temperature compensations is all close to reflectivity during measured data 25 DEG C, show that the model of temperature compensation precision of reflectivity is high, applicability is good.

Principle of work of the present invention: the temperature variant basic reason of sensor reflectivity is temperature on the impact of up optical sensor and descending optical sensor output voltage, therefore by doing temperature compensation to sensor output voltage, the temperature compensation of reflectivity can be realized; The present invention builds based on the forecast model being applicable to the up optical sensor of 720nm and 810nm and descending optical sensor output voltage while temperature, is obtained the model of temperature compensation of up optical sensor and descending optical sensor by forecast model; The temperature compensation to multispectral plant growth sensor reflectivity is realized according to the output voltage computational reflect rate after temperature compensation.

Specific embodiments of the invention:

1 multispectral plant growth sensor:

Multispectral plant growth sensor gathers crop canopies 720nm and 810nm spectral reflectivity, coupling plant growth Monitoring Indexes model, inverting crop growing state information; Sensor take sunshine as light source, adopts optical filter light splitting; Reflectivity is defined as the reflected energy of object and the ratio of projectile energy, and spectral reflectivity is then the object reflectance under specific wavelength; Crop canopies is the solar spectrum reflectivity ρ of λ to wavelength _λfor:

${\mathrm{\ρ}}_{\mathrm{\λ}}=\frac{\mathrm{\π}{L}_{\mathrm{\λ}}}{E_{\mathrm{\λ}}}---1\left(\right)$

In formula, L _λfor the spectral reflectance radiance of crop canopies λ wavelength, Wsr ^-1m ^-2, E _λthe parallel irradiance incided on crop canopies of solar spectrum for λ wavelength, Wm ^-2, π is solid angle, solid angle unit sphere degree sr; From formula (1), utilize L _λand E _λthe spectral reflectivity of crop canopies can be calculated; In order to obtain L _λand E _λ, multispectral plant growth sensor is structurally divided into up optical sensor and descending optical sensor, has 4 passages; Up optical sensor receives the incident light of 720nm and 810nm, and carries out cosine correction; Descending optical sensor is for receiving corresponding wave band crop canopies reflected radiation brightness; The aperture of the diaphragm of sensor is 12.8mm, hole depth 26mm, field angle 27 °, spectral filter bandwidth 10nm, and transmitance is 65%-70%; Sensor photodetector sensitivity used is 0.55AW ^-1, spectral responsivity is 0.011AW ^-1cm ^-2; Sensor adopts the encapsulation of aluminum casing, aperture 38mm, high 50mm, and volume is little, lightweight, easy to carry, is extremely applicable to Field information;

2 test design:

Test of the present invention has two parts, and test 1 is for building model, and test 2 builds the applicability of model for inspection institute;

Test 1: utilize program-controlled formula climatic chamber RP-80 to control probe temperature, RP-80 temperature regulating range is-20 DEG C-150 DEG C, and control accuracy is ± 0.5 DEG C, and regulation of relative humidity scope is 20%-98%RH, and control accuracy is ± 2.5%RH; With the monitoring target that gray scale plate (reflectivity is for 40%) is multispectral plant growth sensor; By the light of outer for RP-80 case halogen tungsten lamp by integrating sphere in optical fiber leading-in box, as test light source; The supply voltage stablizing halogen tungsten lamp is 10V, can ensure that the light intensity of light source is constant; Different supply voltages is provided, then can changes light source intensity; Test Plays gray scale plate is placed in climatic chamber, and up optical sensor and descending optical sensor are fixed on vertical direction 10cm place, standard grayscale plate center; Light source is placed in 45 °, multispectral sensor upper right side, with multispectral plant growth sensor at a distance of 15cm place; Up optical sensor receives radiation of light source information, and descending optical sensor receives standard grayscale plate reflected light radiation information; Constant temperature and humidity the temperature inside the box is set to 6 DEG C, 11 DEG C, 15 DEG C, 20 DEG C, 25 DEG C, 30 DEG C, 35 DEG C, 40 DEG C, 44 DEG C, 49 DEG C, 54 DEG C, 62 DEG C respectively, and it is constant that relative humidity remains 40%RH; Gather the output voltage of the up optical sensor of 720nm and 810nm and descending optical sensor at every temperature, collection period is set to 3s, and continuous acquisition 200 secondary data is averaged;

Test 2: temperature arrange with test 1, the supply voltage of light source is set to 11V to obtain different light intensity, respectively with the standard grayscale plate of 40% and 60% reflectivity for monitoring target;

3 results and analysis:

3.1 temperature are on the impact of Sensor Output Characteristic:

Light intensity remains unchanged, and the output voltage of different temperatures lower sensor is shown in Fig. 2; As shown in Figure 2, raise with temperature, the output voltage of sensor is increase trend, shows that sensor has positive temperature characterisitic; When 6 DEG C, the output voltage of the arbitrary passage of sensor is higher, then the output voltage amplification raising this passage with temperature will be larger, i.e. the comparatively large (Δ k=(V of average rate of change Δ k ₆₂-V ₆)/(62-6), V ₆₂and V ₆the output voltage of sensor each passage when being respectively 62 DEG C and 6 DEG C); At identical temperature, the incident light ENERGY E of the photoelectric detector of this passage of the higher explanation of output voltage of sensor the same band passage is larger, and therefore the difference of Δ k should be temperature and the coefficient result of E, and namely temperature and E also exist reciprocation;

Fig. 2 data are utilized to calculate 720nm and 810nm reflectivity (Fig. 3); As seen from Figure 3, raising reflectivity with temperature is non-linear downtrending, very fast in the decline of 5 DEG C ~ 40 DEG C scope internal reflection rates, eases up subsequently; In test, the output voltage of descending optical sensor is less than the output of identical band upstream optical sensor, and the output voltage amplification raising up optical sensor with temperature will be greater than the amplification of descending optical sensor, so reflectivity performance is downtrending;

In Fig. 2, the output voltage of sensor raises with temperature increases in approximately linear, and can simply represent with y=a+bx, y is sensor output voltage, and x is temperature; Then reflectivity R can be expressed as:

$R=\frac{a_1+b_{1}x}{a_2+b_{2}x}---2\left(\right)$

$R^{\′}=\frac{a_2{b}_1-a_1{b}_2}{{(a_2+b_{2}x)}^2}---3\left(\right)$

A in the known formula of composition graphs 2 (3) ₂and b ₂all be greater than 0, so raise with temperature, the derivative R' of reflectivity trends towards 0, and the change of reflectivity will ease up;

3.2 Sensor Temperature Compensation model constructions:

The temperature variant basic reason of sensor reflectivity is temperature on the impact of up optical sensor and descending optical sensor output voltage, therefore by doing temperature compensation to sensor output voltage, can realize the temperature compensation of reflectivity; The present invention builds based on the forecast model being applicable to the up optical sensor of 720nm and 810nm and descending optical sensor output voltage while temperature, is obtained the model of temperature compensation of up optical sensor and descending optical sensor by forecast model; The temperature compensation to multispectral plant growth sensor reflectivity is realized according to the output voltage computational reflect rate after temperature compensation;

3.2.1 sensor output voltage temperature prediction model construction:

Sensor 720nm is identical with 810nm channel monitoring principle, and structurally only optical filter is variant, and the affecting laws of temperature to the different passage output voltage of sensor is inevitable consistent; Therefore, the present invention builds the sensor output voltage forecast model based on temperature with the output voltage of the up optical sensor of 720nm in Fig. 2 and descending optical sensor, and the up light of 810nm and descending optical sensor output voltage are done verification msg; The output voltage of multispectral plant growth sensor is by incident light energy affect, and when environmental baseline is constant, the output voltage of the higher then sensor of incident light energy is larger; Therefore at identical temperature, the output voltage of sensor represents the incident light energy of the corresponding wave band that it receives, and the present invention is with the output voltage V of up light during room temperature 25 DEG C and descending optical sensor different-waveband _{25 λ}represent the λ wave band incident light energy received; According to conclusion above, the main effect of temperature and temperature and V in the model of structure, should be had _{25 λ}interaction item; As seen from Figure 2, temperature is obvious to the affecting laws of sensor output voltage, and the main effect of temperature can be simulated with polynomial expression, and simultaneously for avoiding imperial lattice phenomenon, polynomial expression only will consider once item, quadratic term, cubic term and four items; Then the prototype of sensor output voltage temperature prediction model is as shown in formula (4):

V _Tλ＝a+bV _25λ+cT+dT ²+eT ³+fT ⁴+gT·V _25λ 4()

T is Celsius temperature, V _{t λ}for the output voltage of λ band upstream light or descending optical sensor under temperature T; Utilize the non-linear regression function of modeling data and SPSS16.0 can obtain the coefficient of formula (4), wherein e=0, f=0, therefore model rejects the cubic term of temperature and four items obtain formula (5);

V _Tλ＝0.041+0.909V _25λ-0.002T+10 ^-5T ²+0.004T·V _25λ 5()

By the V of 720nm and 810nm _{25 λ}substitute into the predicted value that formula (5) obtains different temperatures lower sensor, and computational reflect rate, the identical situation of predicted value and measured value is shown in Fig. 4; As seen from Figure 4, model also presents very high degree of fitting to the verification msg of 810nm; The R of model ²=0.9998, RRMSE=2.31%;

3.2.2 sensor reflectivity model of temperature compensation builds:

Pro forma conversion is done to formula (5), obtains formula (6); Formula (6) can by the output voltage V of up, the descending optical sensor under condition of different temperatures _{t λ}compensate to 25 DEG C of corresponding voltage V _{25 λ};

$V_{25\mathrm{\λ}}=\frac{V_{\mathrm{T\λ}}-0.041+0.002T-{10}^{-5}{T}^2}{0.909+0.004T}---6\left(\right)$

Utilize V _{25 λ}computational reflect rate can realize the temperature compensation of multispectral plant growth sensor reflectivity; Before and after the temperature compensation of this test reflectivity, Fig. 5 is shown in contrast, visible temperature compensated after, within the scope of 5 DEG C ~ 60 DEG C, the fluctuation range of 720nm reflectivity drops to 0.1% by 3%, 820nm drops to 0.4% by 7.7%, and the reflectivity after these two wave band temperature compensations is all close to reflectivity during measured data 25 DEG C, show that the model of temperature compensation precision of reflectivity is high, applicability is good;

3.3 modelling verifications:

The model testing data of test 2 are shown in Fig. 6; As seen from Figure 6, with 40% and 60% reflectivity standards gray scale plate for monitoring target, the amplitude of variation varying with temperature sensor 720nm and 810nm reflectivity is 1.0-2.6%, and the fluctuation range of temperature compensation back reflection rate diminishes, and maximum fluctuation scope is no more than 0.45%; Checking being paired t with the fluctuation range compensating back reflection rate before temperature compensation, obtaining P=0.015 < 0.05, showing that the model of temperature compensation of reflectivity can reduce the impact of temperature on reflectivity significantly.

The present invention is when light intensity keeps invariable, the multispectral plant growth sensor of national information agricultural engineering technology center development is within the scope of 5 DEG C-60 DEG C, the output voltage performance raising sensor with temperature is ascendant trend, reflectivity is then in non-linear decline, decline within the scope of 5 DEG C-40 DEG C very fast, ease up subsequently;

The present invention constructs the temperature prediction model of sensor output voltage, and model can obtain the sensor output voltage under different temperatures according to the output voltage prediction of sensor when 25 DEG C, the R of model ²=0.9998, RRMSE=2.31%; On this basis, model is done pro forma conversion, and then construct the model of temperature compensation of reflectivity, the fluctuation range that reflectivity Yin Wendu impact produces by model is reduced to by 1.0%-7.0% and is no more than 0.45%, and paired t assay shows that constructed model can reduce the impact of temperature on sensor reflectivity significantly; Considerably improve the temperature stability in sensor use.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.

Claims (5)

1. a construction method for multispectral plant growth Sensor Temperature Compensation model, is characterized in that, the construction method of this multispectral plant growth Sensor Temperature Compensation model comprises:

Step one, builds the sensor output voltage forecast model based on temperature with the output voltage of the up optical sensor of 720nm and descending optical sensor, the up light of 810nm and descending optical sensor output voltage is done verification msg;

Step 2, with the output voltage V of up light during room temperature 25 DEG C and descending optical sensor different-waveband _{25 λ}represent the λ wave band incident light energy received; The main effect of temperature and temperature and V should be had in the model built _{25 λ}interaction item; Temperature is obvious to the affecting laws of sensor output voltage, and the main effect polynomial expression of temperature is simulated, and polynomial expression will consider once item, quadratic term, cubic term and four items; Then the prototype of sensor output voltage temperature prediction model is as shown in formula (4):

V _Tλ＝a+bV _25λ+cT+dT ²+eT ³+fT ⁴+gT·V _25λ 4()

T is Celsius temperature, V _{t λ}for the output voltage of λ band upstream light or descending optical sensor under temperature T; Utilize the non-linear regression function of modeling data and SPSS16.0 to obtain the coefficient of formula (4), wherein e=0, f=0, therefore model rejects the cubic term of temperature and four items obtain formula (5);

V _Tλ＝0.041+0.909V _25λ-0.002T+10 ^-5T ²+0.004T·V _25λ 5()

Step 3, by the V of 720nm and 810nm _{25 λ}substitute into the predicted value that formula (5) obtains different temperatures lower sensor, and computational reflect rate, model also presents very high degree of fitting to the verification msg of 810nm; The R of model ²=0.9998, RRMSE=2.31%;

Step 4, does pro forma conversion to formula (5), obtains formula (6); Formula (6) is by the output voltage V of up, the descending optical sensor under condition of different temperatures _{t λ}compensate to 25 DEG C of corresponding voltage V _{25 λ};

$V_{25\mathrm{\&lambda;}}=\frac{V_{\mathrm{T\&lambda;}}-0.041+0.002T-{10}^{-5}{T}^2}{0.909+0.004T}---6\left(\right)$

Utilize V _{25 λ}computational reflect rate can realize the temperature compensation of multispectral plant growth sensor reflectivity.

2. the construction method of multispectral plant growth Sensor Temperature Compensation model as claimed in claim 1, it is characterized in that, after the construction method of this multispectral plant growth Sensor Temperature Compensation model is temperature compensated, within the scope of 5 DEG C ~ 60 DEG C, the fluctuation range of 720nm reflectivity drops to 0.1% by 3%, 820nm drops to 0.4% by 7.7%, and the reflectivity after these two wave band temperature compensations is all close to reflectivity during measured data 25 DEG C, show that the model of temperature compensation precision of reflectivity is high, applicability is good.

3. the construction method of multispectral plant growth Sensor Temperature Compensation model as claimed in claim 1, it is characterized in that, in the construction method of this multispectral plant growth Sensor Temperature Compensation model, multispectral plant growth sensor gathers crop canopies 720nm and 810nm spectral reflectivity, coupling plant growth Monitoring Indexes model, inverting crop growing state information; Sensor take sunshine as light source, adopts optical filter light splitting; Reflectivity is defined as the reflected energy of object and the ratio of projectile energy, and spectral reflectivity is then the object reflectance under specific wavelength; Crop canopies is the solar spectrum reflectivity ρ of λ to wavelength _λfor:

${\mathrm{\&rho;}}_{\mathrm{\&lambda;}}=\frac{\mathrm{\&pi;}{L}_{\mathrm{\&lambda;}}}{E_{\mathrm{\&lambda;}}}---1\left(\right)$

In formula, L _λfor the spectral reflectance radiance of crop canopies λ wavelength, Wsr ^-1m ^-2, E _λthe parallel irradiance incided on crop canopies of solar spectrum for λ wavelength, Wm ^-2, π is solid angle, solid angle unit sphere degree sr; From formula (1), utilize L _λand E _λcalculate the spectral reflectivity of crop canopies.

4. the construction method of multispectral plant growth Sensor Temperature Compensation model as claimed in claim 3, is characterized in that, in order to obtain L _λand E _λ, multispectral plant growth sensor is structurally divided into up optical sensor and descending optical sensor, has 4 passages; Up optical sensor receives the incident light of 720nm and 810nm, and carries out cosine correction; Descending optical sensor is for receiving corresponding wave band crop canopies reflected radiation brightness; The aperture of the diaphragm of sensor is 12.8mm, hole depth 26mm, field angle 27 °, spectral filter bandwidth 10nm, and transmitance is 65%-70%; Sensor photodetector sensitivity used is 0.55AW ^-1, spectral responsivity is 0.011AW ^-1cm ^-2.

5. the construction method of multispectral plant growth Sensor Temperature Compensation model as claimed in claim 3, is characterized in that, sensor adopts the encapsulation of aluminum casing, aperture 38mm, high 50mm.