SU1376980A1 - Apparatus for stage control of air temperature in hothouse - Google Patents

Abstract

The invention relates to agriculture and can be used to control the temperature regime of multi-span greenhouses. The aim of the invention is to improve the quality control of the temperature regime of greenhouses during the transition from one level of stabilization of air temperature in the greenhouse to another. The device comprises a greenhouse 1 with a water heating system 2, supplying a direct water pipeline 3 with a direct water temperature sensor 9 and a direct water flow sensor. The return water pipe 4 comprises a return water temperature sensor 10. A connecting pump 6 is connected between the pipelines of the forward 3 and reverse 4 waters. The air temperature in the greenhouse is monitored by the temperature sensor 8. The constant temperature in the greenhouse is maintained by a three-way mixing valve 5 due to the influence of the temperature regulator 7 on it. The mode of operation of the regulator 7 sets the system for maintaining the optimum temperature in the greenhouse, consisting of filters 12 and 13, the computing unit 14 and the differentiator 15. 1 sludge. (L

Description

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Oi

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The invention relates to agriculture, namely to devices for regulating the air temperature in greenhouses, and can be used to control the temperature regime of multi-span thermal faces.

The aim of the invention is to improve the quality control of the temperature regime of greenhouses during the transition from one level of stabilization of air temperature in the greenhouse to another.

The drawing shows a functional diagram of a device for cascade control of air temperature in a greenhouse.

The device contains a heat table 1 with a water heating system 2, piping 3 direct and 4 reverse heating water, three-way mixing valve 5, mixing pump 6, controller 7, air temperature sensor 8, direct water temperature sensor 9, reverse temperature sensor 10 water, direct water flow sensor 11, tunable low-pass filters 12 and 13, computing unit 14, differentiator 15.

The device works as follows.

Computing unit 14 performs on the controlled values of the operation in accordance with the formula

(in-io) or in the simplest case

(in „-vo),

where Q is the capacity of the water heating system of the greenhouse;

G is the consumption of heating water; i / i, io-enthalpy of direct and reverse heating water; c is the heat capacity of the heating water;

®p, in-temperature direct and reverse heating water.

In the case of stationary operation of the water heating system of the greenhouse 1, the output signal of the computing unit 14 is proportional to its teddy power. When the temperature or flow rate of the coolant changes, the low-pass filters 12 and 13 damp the signals of the sensors 9 and 11, since otherwise, the output signal of block 4 varies in steps, although the heat input from the heating system due to its inertia cannot change in a jump-like manner.

They change exponentially at a rate inversely proportional to the length and mass of the water heating system. In the simplest case, when the filters 12 and 13 are a periodic link of the first order, the time constant of this link is equal to the time constant of the water heating system. And since and the time constant of the water heating system depends on the flow rate of the coolant, the constant 5 times of the filters 12 and 13 are corrected in accordance with the signal from the flow rate sensor 11. Thus, in all modes of operation of the water system, the output signal of the computing unit 14 is proportional to the current value of its power.

The use of differentiator 15 is due to the fact that, if it is present, the water temperature controller 7 can be proportional-integral, i.e. his law

5, functioning to the maximum extent corresponds to the dynamics of the control object. Since the temperature controller, built on the principle of control with a vanishing signal from an intermediate point of the object, indicates the information as

With the deviation of the regulated value and the rate of change of the intermediate parameter of the object, the temperature regime of the greenhouses is established with greater accuracy.

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Claims (1)

Invention Formula A cascade device for controlling the air temperature in the greenhouse, containing water nukes heating system connected to the heat network through a three-way mixing valve, mixing pump installed between the return water pipe and the vertical pipe of the three-way mixing valve connected to the last regulator with a temperature sensor installed in the greenhouse and A temperature sensor installed in a direct water pipeline, characterized in that, in order to improve the quality of temperature control in the greenhouse when switching from one level of stabilizing the air temperature in the greenhouse to another, The device is equipped with a differentiator, a computing unit, two tunable low-pass filters, a flow sensor installed in the direct water pipeline, and a return water temperature sensor, the return water temperature sensor connected to the computing unit, and the flow and temperature sensors are connected to the computing unit through tunable low-pass filters, parametric the inputs of which are connected to the flow sensor of the direct water, the output of the computing unit is connected to the input of the differentiator, the output of which is connected to the temperature controller.