RU2049380C1 - Method for automated control of temperature in greenhouse - Google Patents

Abstract

FIELD: agriculture; agricultural equipment. SUBSTANCE: method involves determination of age of plants in the greenhouse, photoperiod duration, air humidity in the greenhouse, and relative day or night time. A value of temperature best for the production is specified depending on the aforesaid values, and the value of temperature for sparing use of energy is compared to the least permissible temperature. If the optimum temperature is higher than the permissible value, the system is set for optimum temperature. And the system is set for permissible temperature is the value of optimum temperature is lower than that of permissible temperature. EFFECT: higher temperature optimization accuracy. 1 dwg, 1 tbl

Description

 The invention relates to agricultural machinery, and in particular to methods of automatically controlling the temperature regime in a greenhouse, and more particularly to greenhouse industrial cultivation of crops by providing a microclimate in buildings of closed and protected soil. Mainly the invention can be used in film greenhouses, but it can find application in optimizing the temperature regime in hangar and block greenhouses.

 A known method for automatically controlling the temperature regime in a greenhouse, in which, to increase efficiency, the entire period of growing plants is divided into equal time intervals, the duration of which is at least an order of magnitude less than the time constant of the fastest disturbance. For this period of time, the optimum temperature is calculated from the condition that the derivative of the economic criterion is equal to zero. In accordance with this temperature, the setpoint of the temperature setter is changed, which ensures that the temperature remains constant over a selected period of time.

 However, the method has high energy consumption and is not very reliable.

 Also known is a method of automatically controlling the temperature in a greenhouse. In the proposed method, adopted as a prototype, instead of estimating the maximum profit, an estimate is made of the minimum specific energy consumption. Instead of the parameters of the productivity model, the parameters of the models of photosynthesis intensity and dark respiration are introduced into the computing device. Instead of calculating the specific energy intensity and searching for the extremum, the temperature at which this extremum is ensured is determined from the condition that the derivative of the specific energy intensity is equal to zero. The setpoint of the setter is changed in accordance with the temperature determined in this way. The transition from day to night temperature is carried out by changing the coefficients of the model.

 The calculation of the optimum temperature is preceded by an estimate of the discriminant. If it turns out to be negative, then the optimum temperature is determined from the conditions of maximum productivity. In addition, they check the conditions under which the temperature, naturally set in the greenhouse without heating, should be less than the optimum temperature. If this condition is not met, then the system is switched to summer mode, when ventilation works instead of heating.

However, the method has several disadvantages. Firstly, it does not take into account the age of plants, the duration of the photoperiod, and the humidity in the greenhouse. This reduces the accuracy of determining the optimum temperature. Secondly, in some cases, the temperature determined by the proposed method is lower than the permissible one (t _opt <t _extra ), as a result of which this leads either to the death of plants or to a deterioration in their consumer qualities. Moreover, even at an acceptable temperature, the plant may die if this temperature lasts long enough. In other words, restrictions should be not only on permissible temperature, but also on its duration of standing.

 Third, more accurate mathematical models of productivity have recently been obtained, on the basis of which refined expressions for determining optimal temperatures have been obtained.

For the intensity of photosynthesis, a model is obtained
lgF A ₀ + A ₁ + E + A ₂ t _in + A ₃ T ₂ + A ₄ τ _fp +
+ A ₅ τ _in + A ₆ φ + A ₇ τ _s + A ₁₁ E ² + A ₂₂ t ² _in +
+ A ₃₃ T ₂ ² + A ₄₄ τ _fp ² + A ₅₅ τ _in ² + A ₆₆ φ ² + A ₇₇ τ _s ² +
+ A ₁₂ Et _in + A ₁₃ ET ₂ + A ₁₄ Et _fp + A ₁₅ E τ _in +
+ A ₁₆ E φ + A ₁₇ E _c + A ₂₃ t _at T ₂ + A ₂₄ t _at τ _fp +
+ A ₂₅ t _in τ _in + A ₂₆ t _in φ + A ₂₇ t _in τ _s + A ₃₄ T ₂ τ _fp +
+ A ₃₅ T ₂ τ _in + A ₃₆ T ₂ φ + A ₃₇ T ₂ τ _s + A ₄₅ τ _fp τ _in +
+ A ₄₆ τ _fp φ + A ₄₇ τ _fp τ _c + A ₅₆ τ _in φ + A ₅₇ τ _in τ _s +
+ A ₆₇ φ τ _s , where E is the illumination, clk;
t _{in the} room temperature, ^о С;
T _{2 is the} average temperature of the previous night;
τ _fp photoperiod duration, h;
τ _{in the} age of the plant, days

φ indoor humidity
τ _s relative time of day.

 A similar model was obtained for the intensity of dark breathing D. Only in this model, instead of the current illumination, is the average illumination of the previous day, instead of the average temperature of the previous night, the average temperature of the day, and instead of the relative time of the day, the relative time of the night.

а относительное время ночи
τ_c=

где τ текущее время;
τ_восх время восхода солнца;
τ_зах время захода солнца;
n число переходов через 24.00 (0 или 1).Relative time of day
τ _c =

and the relative time of night
τ _c =

where τ is the current time;
τ _delight sunrise time;
τ _zh sunset time;
n the number of transitions after 24.00 (0 or 1).

 The numerical values of the coefficients of the model for cucumber varieties "Moscow" are given in the table.

 The objective of the invention is that it is necessary to increase the accuracy of optimization of the temperature regime and to exclude operation at temperatures lower than permissible.

 To do this, in a method for automatically controlling the temperature in a greenhouse, which includes dividing the period of plant growth into equal time intervals, measuring in each of these intervals the illumination, the flux density of solar radiation, the outside temperature, the wind speed and the humidity of the outside air, determining the optimal result from these measurements by productivity and natural temperature, a comparison of these temperatures and when the first is higher than the second, the heating system is turned on and its temperature is maintained, optimal in productivity, otherwise, the inclusion of a ventilation system, the adjustment of the mathematical model of productivity (the intensity of photosynthesis or dark breathing) and its coefficients in the day-night and night-day transitions, determination of the magnitude and sign of the discriminant characterizing the presence of a minimum of energy intensity and , in the case of its positivity, the determination of the optimum energy intensity temperature, as well as the change in accordance with this temperature the setpoint setter, additionally determine the age of the plant, The duration of the photoperiod, the humidity in the greenhouse, as well as the relative time of the day or night, specify in accordance with these measurements the optimum temperature both in terms of productivity and energy intensity, and the resulting optimal temperature is compared with the minimum acceptable, and if the optimum temperature is more than acceptable then the optimum temperature is set, and if the optimum temperature is less than the permissible, then the permissible temperature is set, upon reaching the maximum duration of which temperature set value, the optimum in terms of productivity.

 A device is known for automatic control of temperature-wet conditions in industrial houses, which takes into account the age of the bird. However, productivity is affected not only by the age in days, but also by the time of day, which is not taken into account in existing systems.

In the invention, these drawbacks are eliminated, firstly, by the fact that the above factors (plant age, photoperiod duration, air humidity in the greenhouse) are included in the mathematical model and taken into account when calculating the optimum temperature; secondly, in the case when the optimum temperature is less than the allowable one, the system maintains an allowable temperature, and thirdly, by the fact that the allowable temperature is maintained for a time τ _add , and then rises to the optimum in productivity.

В связи с уточнением математической модели оптимальная по энергоемкости температура
t_оптэ=

+

где
t_ест= t_н+

D

+ Δ
Δ

t_н наружная температура, ^оС;
Q поток солнечной радиации, Вт/м²;
К коэффициент теплоотдачи, Вт/м² х х ^оС.Thus, the claimed method is characterized in that more accurate mathematical models of photosynthesis Φ and dark respiration D are used, and, therefore, more accurate models of temperature, optimal in productivity
t _opt =

In connection with the refinement of the mathematical model, the temperature is optimal in terms of energy intensity
t _opte =

+

Where
t _eats = t _n +

D

+ Δ
Δ

t _n outdoor temperature, ^о С;
Q flux of solar radiation, W / m ² ;
K heat transfer coefficient, W / m ² x x ^o C.

 The drawing shows a functional diagram of a device that implements this method.

 The device contains a relay 1 and comparing 2 elements, an amplifier 3, an actuator 4, a regulating body 5 and an air temperature sensor 6 in the greenhouse, as well as a device 7 for calculating the optimum energy intensity temperature.

 A device for calculating a temperature optimum in energy intensity includes a unit 8 for calculating an optimum temperature in productivity, a unit 9 for calculating a natural temperature, a discriminant determination unit 10, comparators 11 and 12, an adder 13, a heat loss coefficient calculating unit 14, a mode switch 15, and light integrators 16 and day temperature 17, a clock generator 18, a pulse counter 19, averagers of illumination 20 and day temperature 21, a memory device 22 and a data input unit 23. The device is also equipped with humidity sensors for outdoor air 24, solar radiation 25, light 26, light relay 27, sensors 28 for wind speed and outdoor temperature 29. In addition, the system also includes age sensors (timer) 30 and indoor humidity 31. B the composition of the device for calculating the optimum temperature, additional blocks 32 for determining the duration of the photoperiod, a unit 33 for comparing the optimum temperature with the permissible temperature, and a unit 34 for comparing the duration of the standing of the permissible temperature are introduced ry with an acceptable duration, as well as block 35 calculating the relative time of day and night.

 The method is as follows.

 The growing season of plant growth is divided into equal, previously calculated by duration, time intervals. Moreover, they proceed from the condition that their duration should be an order of magnitude less than the time constant of the fastest perturbation itself. Then, for each period of time, the optimal temperature is determined, which should be kept constant during this period. After determining the duration of the time interval, the clock generator 18 (GTI) is tuned to this period.

 The generator gives out pulses at the indicated equal intervals of time during which the information received from the sensors 6, 24, 25, 26, 28, 29, 30 and 31 is processed. Signals from the light sensor 26, the age sensor (timer) 30, the humidity sensor air indoors 31 enter the block 8 calculation of the optimum temperature productivity. The signal from the block for determining the duration of the photoperiod 32 (which in turn is determined using the timer 30 by fixing the time of rising and setting of the light relay 27) and the unit for calculating the relative time 35 (receiving information from the timer 30 and the block for determining the duration of the photoperiod 32) also come here. The signals from the humidity sensor of the outdoor air 24 and the wind speed sensor 28 are sent to the heat loss coefficient determining unit 14, the results of which, together with the signals of the solar radiation sensors 25 and the outdoor temperature 29, are sent to the natural temperature measuring unit 9 in the greenhouse. The results of calculations and the output of blocks 8 and 9 are sent to comparator 11. If the natural temperature is more than optimal, the ventilation system is automatically turned on, and the heating control system and heating itself are turned off using relay element 1. If the natural temperature is less than optimal, then the result of determination natural temperature from block 9 and the signal from block 8 for calculating the optimum temperature productivity are sent to the discriminant determination block 10, where they are preliminarily inputted Strongly data input unit 23, the productivity model coefficients (from the same block in the block of calculation of heat loss 14). From the first output of block 10, the signal is supplied to the comparator 12, and from the second output of block 10 and the output of block 9 to the adder 13, which calculates the optimum energy consumption temperature. If the discriminant is positive, the signal to the comparing element 2 is supplied from the adder 13, otherwise from block 8. Switching is carried out by a switch 15 controlled by comparators 11 and 12. Thus, for each discrete period of time, the computing unit 7 determines the optimal temperature. In addition, with the help of block 37, the optimum temperature is compared with the permissible one, entered from block 23. If the optimum temperature turns out to be greater than the permissible one, then the optimum temperature is supplied to switch 15, if lower, then the permissible one. Block 23 fixes the duration of the permissible temperature and if it turns out to be greater than the set value (the set value is issued from block 23), then, instead of the permissible temperature, switch 15 is supplied with a temperature that is optimal in productivity.

 The automatic optimization system, consisting of an internal temperature sensor 6, a computing unit 7, a comparing element 2, an amplifier 3, an actuator 4, and a regulator 5, maintains this temperature for a selected period of time, after which the clock generator 18 resets the result of the previous calculation and starts a new one. The clock generator 18 simultaneously controls the operation of blocks 13, 8, 9 and 10. The timer 30 can also play the role of a clock generator, which significantly reduces the cost of the system.

 Switching from day to night mode is carried out by an illumination relay 27, which, instead of the coefficients of the day model, connects from the data input device 23 to the discriminant calculation unit 10 and the optimal temperature productivity calculator 8, the night model coefficients, the values of which are entered during commissioning. At the same time, a device 22 is connected to the computing device 8, receiving signals from the averager 20 of illumination and the averager 21 of the day temperature, which during the day period give the quotient of dividing the signals from integrators 16 and 17 to the readings of the pulse counter 19, operating from a clock generator 18 and relays 27 illumination.

 At the same time, a heat loss coefficient calculation unit 14 with sensors 24 and 28, as well as solar radiation sensors 25 and light 26 are disconnected from the computing device. The outdoor temperature sensor 29 is constantly connected to the computing device. Switching from night mode to day mode is similar.

 The proposed method implements, for example, a device for calculating the optimum temperature, consisting of the following elements: a central processor; two read-only memory ROM devices; random access memory RAM; memory address decoder; decoder addresses input and output; timer with crystal oscillator and control device; governing bodies; indicators; sensor control devices; interrupt devices.

 As a central processor, a processor of type K1801BM1 can be used; as permanent storage devices of the chip K573RF4 and K573RF5, random access memory on the chip K573RU10.

 The volume of the program recorded in the ROM will be 10 kilobytes, the memory capacity of RAM is 2 kbytes.

 As a timer and at the same time an age sensor, LSI type K512VI1 is used. The clock frequency that determines the time is set by a crystal oscillator.

 All sensors are made in the form of autonomous modules, which are located in the corresponding points of the greenhouse and perform the function of converting the controlled parameters of the medium into an electric DC signal with a voltage in the range of 0.10 V.

 Autonomous modules receive power from the control team and issue information signals to a single communication and power channel coaxial cable.

 To power the sensor circuits, a sensor power module is designed that generates a frequency of 20 kHz.

 To control the sensor modules, a controller module is proposed operating at a frequency of 250.375 kHz.

 As a temperature sensor, a resistance thermometer is used, as a sensor of humidity of internal air a hygrometer of design API; as a sensor of humidity of external air, a system consisting of a dielectric plate and two electrodes of metals with different work function.

 To measure wind speed, a combination of a tachometric device for autosw. N 1140047 and optoelectronic N 857882.

 Light sensor Arsenide-Galium photocell, solar radiation sensor battery of Peltier elements.

 All sensors are equipped with standardizing converters on operational amplifiers K551UD1 or K140UD6.

 However, instead of a hardware solution, it is possible purely software.

 An example of the implementation of the method (when optimizing the temperature regime of growing cucumber varieties "Moscow greenhouse").

a) Let the sensors show the following measured values
E = 21.1 klx; φ = 80% τ _at = 22 days. τ _fp 15 h; T _n 30.5 ^about C.

Then the optimum temperature for productivity
t _opt 31.1 ^about C.

If the environmental parameters
t _n -2.5 ^o C; V 15 m / s; At 80% Q 215 W / m ² , the natural temperature in the greenhouse is 22.5 ^o C.

+

-156,2 Поскольку D < 0, оптимума по энергоемкости не существует и система работает при 31,3^оС.Discriminant
D

+

-156.2 Since D <0, there is no optimum energy intensity and the system operates at 31.3 ^o C.

b) Assume a humidity of 60% then
t _opt 13.2 ^about With
Let further wind speed be 5 m / s.

In this case, the natural temperature rises to
t _eats 42.3 ^about C. Since t _eats > t _opt , then the ventilation is turned on.

Let the humidity in the greenhouse, 80% of the length of photoperiod τ _pn 9 hours. Then t _wholesale 30.6 ^° C

Let t _n -27.5 ^{° C;} V 15 m / s; At 80%, the natural temperature dropped to t _eats -2.5 ^o C.

D 99.2> 0. Therefore, t _opte 24.4 ^about C, which is installed.

As can be seen, the optimal temperature of the energy intensity at ^about 6 C lower than the optimum in terms of productivity, which gives a great saving of heat.

c) Let E = 10.5 klx; At 80% τ _at 14 days. τ _fp 15 h; T _n = 19.5 ^about With
Then t _{opt is} 18.9 ^about C.

At t _n -27.5 ^{° C;} V = 15 m / s; At 80% t _eats = -15.3 ^about C.

Since D 117.7> 0, then t _opte 12.6 ^about C.

Since the temperature t _opt <t _add 14 ^о С, then the temperature is set to 14 ^о С. If the temperature does not rise within three days, the system will switch to t _opt 18.9 ^о С.

Claims (1)

METHOD FOR AUTOMATIC TEMPERATURE CONTROL IN A GREENHOUSE, including dividing the growing period of plants into equal time intervals, measuring in each of these intervals the illumination, solar radiation flux density, outdoor temperature, wind speed and humidity of the outdoor air, determining the optimum productivity and natural temperature of the air in the greenhouse, a comparison of these temperatures and when the first increases above the second, the heating system is turned on and its temperature is maintained optimal productivity, otherwise the inclusion of the ventilation system, the adjustment of the mathematical model and its coefficients during day-night and night-day transitions, the determination by the algorithm of the model of processes in the greenhouse of the magnitude and sign of the discriminant characterizing the presence of a minimum of energy intensity, and in case of positivity determination of the optimum energy intensity temperature, as well as a change in accordance with this temperature setpoint setter, characterized in that it further determines the age of the plant, longitudinal the photoperiod duration, air humidity in the greenhouse, as well as the relative time of day and night, the mentioned discriminant values are determined from the expression

where t _{o p t} temperature, optimal in productivity;
t _{e c t} air temperature in the greenhouse, which is set in the absence of additional heating;
A _{2 2} the regression coefficient of the productivity model at the square of the temperature in the greenhouse;
and the optimal energy intensity temperature t _opt.e from the expression

and in accordance with this, the temperature is optimized for productivity, and the energy-optimal temperature is compared with the minimum allowable air temperature in the greenhouse, and if the optimum temperature is greater than the minimum allowable air temperature in the greenhouse, then the optimal temperature is set, and if the optimum temperature is less than the allowable, then set the permissible temperature, and when the last specified maximum period of its standing is reached, set the temperature optimal for the product activity.

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