RU2405308C1 - Method of automatic control of temperature and light modes in greenhouse and system for its implementation - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: invention relates to agricultural machinery, namely to methods and systems for automatic control of temperature and light modes in greenhouses or other structures of a protected ground. Automatic control system for temperature and light regime in greenhouse, implementing the claimed method, contains the control loop of temperature in a greenhouse, including a temperature sensor which output is connected with the object of regulation through the comparing element with the adjuster, a signal multiplier of maladjustment the current and the calculated temperatures, as well as an actuator supporting at the facility the calculated temperature, as well as the computing unit, which calculates an optimum temperature. Also the system contains an additional control loop of lighting.

EFFECT: invention enables to improve accuracy of maintaining temperature and lighting in cultivating area and stability of the system operation, as well as increase efficiency of photosynthesis mechanism in plants due to adjustment of such environmental factors as temperature and irradiance.

4 cl

Description

The invention relates to agricultural machinery, and in particular to methods and systems for automatically controlling the temperature and light regime in greenhouses or other structures of protected soil.

A known method of automatically controlling the temperature in a greenhouse [a.s. USSR No. 1503711, IPC 4 A01G 9/26], in which the entire period of plant growth is divided into equal time intervals, the duration of which is 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 energy consumption per unit of production is equal to zero. In accordance with this temperature, the setpoint of the temperature setter changes, ensuring that it remains constant for a selected period of time.

However, the proposed method does not allow to solve the urgent problem of the production of vegetables in greenhouses, the solution of which is to increase the efficiency (COP) of the photosynthesis mechanism of plants. Under conditions of natural irradiation, average planting densities use only 1% of the incoming energy of solar radiation, which is much lower than theoretically possible.

It is believed that the energy efficiency of plant photosynthesis can be increased by coordinating the main environmental factors with irradiation. This is all the more important at the present time, with the modern intensification of greenhouse vegetable growing, which involves a thickened planting of plants on 1 m ^{2 of} usable area (multi-tier growing method), in which up to 10 plants are planted per square meter, while the traditional method planting only 3-4 plants. This allows you to increase productivity from 30 to 300 kg / m ² . Such a planting density requires mandatory clarification, and this should lead to very high energy costs. However, the profit from a large crop covers the cost of additional crops. Although sometimes in conditions of a total deficit of energy resources, it may be desirable to reduce the costs of both re-lighting and heating of protected ground.

A known method of optimizing environmental factors when growing plants [and.with. USSR No. 456595, IPC 4 A01G 9/26], in which optimization of plant photosynthesis is carried out by means of irradiation regulation. In this case, the method of automatic optimization of plants is reduced to finding the optimal point on the light curve of photosynthesis.

The system for the automatic optimization of plant photosynthesis, which ensures the implementation of this method, consists of an assimilation chamber where plants are placed that are irradiated with a controlled radiation source. An indicator of plant photosynthesis is the concentration of carbon dioxide (CO ₃ ), which is measured with an Infralit-1 device. Using information on plant photosynthesis, which can be judged by the rate of absorption of carbon dioxide from the volume of the assimilation chamber, and on the basis of which the target control function with an extremum is formed in accordance with the accepted criterion. Using the DKSTV-6000 xenon lamp ballast, they control the level of plant irradiation, which is measured by the Yanushevsky pyranometer. The search for the maximum of the objective function is carried out by the extreme regulator ERB-5, which subsequently maintains the obtained value of irradiation. The system contains a computer complex for processing incoming information about the photosynthesis rate and plant irradiation and, based on it, generates a control signal that enters the extreme regulator ERB-5. The regulator changes the direction of rotation of the electric motor if the system is not at the optimum point of the selected criterion, and the motor through the gearbox moves the RNO voltage regulator slider, which slowly changes the power of the DKSTV-6000 arc xenon lamp, thereby changing the irradiation of plants.

In this method of optimizing environmental factors during plant cultivation and the system ensuring its implementation, one can detect a number of disadvantages. Firstly, the interaction of two main factors of the microclimate - temperature and illumination - has not been taken into account. If, while changing the illumination, the air temperature in the greenhouse is not changed at the same time, making a series of consecutive steps, then the controller will not find the actual maximum photosynthesis intensity. Secondly, extreme regulation is not the fastest and most economical way to control microclimate modes, as the regulator has to take several steps to determine the maximum, and this reduces the reliability of the system that is constantly in self-oscillation mode. Thirdly, the system contains bulky devices for determining CO ₂ gas exchange in an assimilation chamber, such devices are suitable in scientific laboratories where they will be serviced by specialists, in greenhouses such systems are not very functional.

There is also known a method of controlling the temperature in the greenhouse [a.c. USSR No. 1438657, IPC 4 A01G 9/26. The method of automatic temperature control in a greenhouse / F.L.Izakov, S.A. Popova. E.V. Strelnikova and L.V. Grebenkina (USSR). - No. 3738938 / 30-15; claimed January 20, 1984; publ. 11/23/1988, Bull. No. 43], selected for the prototype, in which, to increase the efficiency, the entire period of growing plants is divided into equal time intervals and for each, 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 changes.

System [a.s. USSR No. 1438657, IPC 4 A01G 9/26], which provides the method selected for the prototype, consists of a computing unit where information from sensors for monitoring the state of the environment is supplied and where information is processed and the temperature necessary to control the air temperature in the greenhouse is calculated, in accordance with which the setpoint setting is changed; an internal temperature sensor that measures and transmits a signal from the object to the comparison element, where two temperatures are compared; an amplifier; clock generator, the signal of which resets the previous calculation and the beginning of a new one; a switch that transmits a control signal to an actuator that must maintain the calculated temperature for a discrete period of time.

The considered method and the system that implements it have several disadvantages. Firstly, there are still no mathematical models of the crop as the final product of the plant vegetation process, which means that this method is difficult to implement. Secondly, prices for greenhouse products and fuel during the growing season cannot be predicted, they are constantly changing and greatly affect the calculation of the optimum temperature according to the proposed criterion. Thirdly, the mathematical model of the crop does not contain important indicators of the phytomicroclimate: the duration of the light factor and air humidity. Fourth, there is no possibility of changing the natural light in favor of increasing it in case of cloudy days, especially since modern greenhouse plants are equipped with illuminating plants, the operation of which can be regulated by some criterion.

The aim of the invention is to increase the accuracy of maintaining temperature and illumination in the cultivation room and the stability of the system, as well as increasing the efficiency of the plant photosynthesis mechanism due to the coordination of environmental factors such as temperature and irradiation, which increase the productivity of greenhouse crops and shorten the growing season before fruiting .

The invention consists in the following. In the proposed method, the time of growing plants in a greenhouse 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. In contrast to the prototype, it is not the external microclimate parameters that are measured, but in each of these time periods, the illumination, the air humidity inside the greenhouse, the age of the plants are measured, the average temperature of the previous night and the duration of the light period are determined. According to the measurement results, a one-dimensional optimum daily temperature is determined by the productivity criterion, which is maintained constant over a selected period of time. The one-dimensional optimal temperature is determined from the condition that the derivative of the photosynthesis rate with respect to temperature is equal to zero. In addition to this function, a one-dimensional illumination optimum in productivity should be calculated from the condition that the derivative of the photosynthesis rate with respect to illumination is equal to zero. In the case when the actual illumination in the greenhouse is lower than the calculated one, the lighting equipment should be turned on for the period set by the agricultural technician.

The productivity criterion was obtained using the mathematical model of the growth of cucumber varieties "Moscow greenhouse" [Popova S.A. Energy-saving system of automatic temperature control in a greenhouse: Dis. Cand. tech. Sciences 05.13.06. Chelyabinsk, 1995]. In general terms, the mathematical model of CO ₃ gas exchange, obtained during the experiment in an artificial microclimate chamber, is written as follows:

where t ₁ - the current value of the daily temperature in the cultivation room, ° C;

E ₁ - the current value of illumination;

T ₂ is the arithmetic mean of the temperature of the previous night, ° C;

τ ₁ - the duration of the photoperiod, hours;

τ ₂ - plant age, day;

φ ₁ - the current value of the humidity in the greenhouse,%;

a ₀ , a ₁ , a ₂ , etc. - coefficients of a mathematical model of photosynthesis intensity.

For the proposed method and system for automatic control of the temperature and light regime in the greenhouse, the criterion of maximum productivity is used, that is, partial derivatives of the intensity of photosynthesis are equal to zero

and determine the one-dimensional values of temperature and illumination at which there is a maximum intensity of photosynthesis, an indirect indicator of productivity.

The one-dimensional optimal daily temperature t _{21 is} calculated by the formula:

where a ₂ , a ₁₂ , a ₂₂ , etc. - coefficients of a mathematical model of photosynthesis intensity;

a ₂ = 0.1881;

and ₁₂ = 0.0125;

a ₂₂ = -0.0215;

and ₂₃ = 0.0014;

a ₂₄ = -0.0087;

and ₂₅ = 0.0000;

a ₂₆ -0.0107;

E ₁ - established as a result of the functioning of the system and taking into account the effect of solar radiation, the current value of illumination, klk;

T ₂ - arithmetic mean temperature of the previous night, ° C;

τ ₁ - the duration of the photoperiod or after-exposure set by the technician, hour;

τ ₂ - plant age, day;

φ ₁ - the current value of the humidity in the greenhouse,%.

One-dimensional optimal illumination in the greenhouse E _{21 is} calculated by the formula:

where a ₁ , a ₁₁ , etc. - coefficients of a mathematical model of photosynthesis intensity;

a ₁ = 1.9788;

a ₁₁ = -0.0141;

and ₁₂ = 0.0125;

a ₁₃ = -0.0034;

a ₁₄ = -0.0046;

a ₁₅ = -0.0174;

a ₁₆ = -0.0147;

t ₁ - established as a result of the functioning of the system, the current temperature, ° C;

T ₂ is the arithmetic mean of the temperature of the previous night, ° C;

τ ₁ - the duration of the photoperiod (or exposure) specified by the operator-technician, hours;

τ ₂ - plant age, day;

φ ₁ - the current value of the humidity in the greenhouse,%.

In accordance with the values of temperature and illumination determined in this way, the settings of the adjusters are changed.

The automatic temperature-light control system in the greenhouse implementing this method comprises an internal temperature control loop in the greenhouse, including an internal temperature sensor, the output of which is connected to the control object through a comparison element with a setpoint, an amplifier of the signal of the temperature and current temperature mismatch, as well as an executive a mechanism that maintains the calculated temperature in the object, as well as a computing unit that calculates the optimal temperature. Unlike the prototype, the system contains an additional illumination control circuit, consisting of an ambient light sensor, a comparing element, an amplifier, and an actuator, which controls the lighting equipment according to the values of the illumination parameters by a specific computer setter, the lighting equipment is turned on and off by a magnetic starter by means of a signal from a time relay , setting the duration of the light period from which the computer also enters the input Terni setpoint and the system is provided with a sensor the air humidity, plant age counter and a computing unit and dial the dial are combined in the computer, which generates signals as the optimal temperature and the optimal illumination for the two control loops.

The set of features of the proposed method and system for its implementation are not known and do not follow explicitly from the prior art, which allows us to conclude that the technical solution meets the criteria of "novelty" and "inventive step".

The drawing shows a diagram of a system for automatically controlling the temperature and light regime in a greenhouse according to the productivity criterion. The system of the automatic optimization of air temperature, which implements this method, consisting of a sensor 5, a comparing element 1, an amplifier 2, an actuator 3, and a regulator 4, maintains the temperature calculated by the computer controller 12 until a new calculation occurs.

The automatic illumination optimization loop system, consisting of a sensor 9, a comparative element 6, an amplifier 7, an actuator 8, a relay mechanism 10, and a magnetic starter 11, controls the illumination equipment according to the values of the illumination parameters determined by a computer setter 12.

The method is as follows. The signals from temperature sensors 5, illumination 9, air humidity 13 and the plant age counter 14 are fed to a computer control unit 12, where, according to formulas (3) and (4), temperature and light conditions that are optimal for productivity are calculated. First, the optimal daily temperature t _{21 is} determined from the initial parameters of the operating mode of the irradiating equipment E ₁ and τ ₁ specified by the agricultural technicians. Inside the greenhouse, the temperature corresponding to the daily period rises. Then, the optimal illumination E _{21 is} calculated taking into account the daily air temperature established inside the greenhouse. Then the lighting equipment comes into operation. The order of inclusion of the program is embedded in the algorithm of the computer master. Subsequent computational operations occur upon the fact of a change in a parameter included in equation (3) or (4). For example, when changing age τ ₂ or humidity φ ₂ . The calculation of the optimal values is carried out for a period of time, the duration of which is an order of magnitude less than the time constant of the fastest perturbation (for example, 0.1 min).

The system responsible for the contour of automatic optimization of illumination according to the claimed method, works as follows. According to the sensors 5, 13, 14 and manually set the duration of the photoperiod, which corresponds to the duration of the irradiation equipment carried out using the relay mechanism 10, the computer controller 12 generates an output signal E ₂₁ according to equation (4), which is the task for the lighting optimization system. On the comparison element 6, the reference E ₂₁ is compared with the signal from the light sensor 9, which also takes into account natural illumination (coming from the sun), the value of the mismatch of the two signals is amplified by element 7, and then the actuator of the lighting equipment is switched on, which changes the height of the lamp suspension, which leads to a change in the current value of illumination. In turn, this change is monitored by the light sensor 9. After the expiration of the dwell time set by the technicians, the relay mechanism 10 is activated and the magnetic starters of the dyeing equipment 11 are turned off. Since thickened plantings requiring dyeing are planted in a multi-tier way, the dosing device is lowered between the plants. For this reason, the light sensor should also be located between the plants, since the lower tiers of the plantations suffer greatly from a lack of light.

The system responsible for the automatic temperature optimization channel is as follows. According to the sensors 13 and 14, the values of the preliminary light mode E ₁ and τ ₁ established by the technicians, and the average temperature of the previous night, the computer adjuster generates, according to equation (3), the driving signal t ₂₁ supplied to the comparison element 1. Another signal to the comparison device comes from the air temperature sensor 5 in the greenhouse, which takes into account the temperature change due to the inclusion of additional equipment or the influence of external environmental conditions. The mismatch signal received at the output of the device 1 is converted in accordance with the necessary control law and amplified by the device 2, after which it is supplied to the actuator 3, which drives the regulating body 4, which changes the coolant supply in the pipe heating system of the greenhouse.

The combined use of the method and system significantly increases the efficiency of the use of the light energy of the sun and the irradiation plant by cultivated plants, which means that it reduces the duration of the growing season before fruiting, increases the productivity of the plants themselves, and also improves the commercial quality of the fruits and the content of sugars and vitamins in them.

Claims (4)

1. A method for automatically controlling the temperature and light conditions in a greenhouse, including dividing the vegetation period of plants in the greenhouse into equal time intervals, the duration of which is an order of magnitude shorter than the time constant of the fastest disturbance, calculating an optimal temperature for each time interval and maintaining this optimum temperature constant for the entire period of time, characterized in that they measure air humidity, air temperature and illumination in the greenhouse to obtain of signals from air, temperature, and light sensors, respectively, measure the age of the plants to obtain a signal from the plant’s age counter, determine the duration of the light period, and the data are fed to a computer controller that calculates the average value of the night temperature, then determines the one-dimensional day temperature optimal by the productivity criterion air and further determines the one-dimensional optimum in terms of productivity illumination, after which, in accordance with certain values of the tempo Aturi and illumination change setpoint. 2. The method according to claim 1, characterized in that they establish a one-dimensional productivity-optimal air temperature in the greenhouse for daytime using the formula:

where a ₂ , a ₁₂ , a ₂₂ , etc. - coefficients of a mathematical model of photosynthesis intensity;
a ₂ = 0.1881;
₁₂ = 0.0125;
a ₂₂ = -0.0215;
₂₃ = 0.0014;
a ₂₄ = -0.0087;
and ₂₅ = 0.0000;
₂₆ = 0.0107;
E ₁ - established as a result of the functioning of the system and taking into account the effect of solar radiation, the current value of illumination, klk;
T ₂ - arithmetic mean temperature of the previous night, ° C;
τ ₁ - the duration of the photoperiod or after-exposure specified by the operator-technician, h;
τ ₂ - plant age, days;
φ ₁ - the current value of the humidity in the greenhouse,%. 3. The method according to claim 1, characterized in that they establish a one-dimensional optimal performance lighting according to the formula:

where a ₁ , a ₁₁ , etc. - coefficients of a mathematical model of photosynthesis intensity;
a ₁ = 1.9788;
a ₁₁ = -0.0141;
₁₂ = 0.0125;
a ₁₃ = -0.0034;
a ₁₄ = -0.0046;
a ₁₅ = -0.0174;
a ₁₆ = -0.0147;
t ₁ - established as a result of the functioning of the system, the current temperature, ° C;
T ₂ - arithmetic mean temperature of the previous night, ° C;
τ ₁ - the duration of the photoperiod or after-exposure specified by the operator-technician, h;
τ ₂ - plant age, days;
φ ₁ - the current value of the humidity in the greenhouse,%. 4. A system for automatically controlling the temperature and light regime in the greenhouse, comprising a temperature control loop in the greenhouse, including a temperature sensor, the output of which is connected to the control object through a comparing element with a setter, an amplifier for the signal of the temperature and current temperature mismatch, as well as an actuator supporting the object the calculated temperature, as well as a computing unit that calculates the optimal temperature, characterized in that the system contains an additional con ur lighting control, consisting of a light sensor, a comparing element, an amplifier and an actuator and controlling the lighting equipment according to the values of the lighting parameters by a specific computer setter, the lighting equipment is turned on and off by a magnetic starter by means of a signal from a relay time mechanism, setting the duration of the light period from which also enters the input of the computer master, and the system is equipped with a wet sensor air STI, plant age counter and a computing unit and dial the dial are combined in the computer, which generates signals as the optimal temperature and the optimal illumination for the two control loops.