JP2008040530A - Control device and temperature controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to linearize nonlinear characteristics of a control object. <P>SOLUTION: A linearizer 4 which compensates the influence of heat transfer between the control object 2 and an external world is set up. Temperature difference between sensed temperatures y<SB>1</SB>and y<SB>2</SB>of the control object 2 and temperature θ<SB>∞</SB>of the external world is fed back to an operation quantity side which is an input side of the control object 2 through the heat transfer items 10-1' and 10-2' and the influence of nonlinear heat transfer between the control object 2 and the external world is tried to be compensated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device and a temperature regulator for controlling a controlled object.

In general, a control target has nonlinear characteristics, and in order to cope with such nonlinear characteristics, a conventional PID control apparatus obtains a PID control parameter for each of a plurality of temperature regions in advance, Accordingly, there is a configuration in which the PID control parameters are switched (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 62-070904

  However, in the conventional example in which the PID control parameter is switched for each temperature region as described above, it is necessary to adjust the PID control parameter in advance for each temperature region. Not easy.

  The present invention has been made in view of the above points, and an object thereof is to easily cope with a non-linear control target.

  (1) The control device of the present invention includes linearization means for linearizing a nonlinear characteristic of a controlled object, and the linearizing means linearizes the influence of heat transfer between the controlled object and the outside world. is there.

  Heat transfer includes heat transfer and heat radiation.

  The outside world refers to the periphery of the controlled object.

  In the linearization means, it is preferable to completely cancel the influence of heat transfer, but it is sufficient that at least the influence of heat transfer can be reduced.

  According to the present invention, linearization is performed by canceling the influence of nonlinear phenomena such as heat transfer between the controlled object and the outside world, so that the control performance is improved.

  (2) The temperature controller of the present invention includes a temperature control unit that outputs an operation amount for the control target based on a detected temperature and a target temperature from a temperature detection unit that detects the temperature of the control target, and the control target Linearizing means for linearizing the non-linear characteristic, and the linearizing means cancels heat transfer between the controlled object and the outside world to linearize.

  According to the present invention, linearization is performed by canceling the influence of nonlinear phenomena such as heat transfer between the controlled object and the outside world, so that the control performance is improved.

  (3) In a preferred embodiment, the linearization means feeds back a temperature difference between the detected temperature and the outside temperature to the manipulated variable side through a heat transfer term.

  The heat transfer term preferably corresponds to the product of the surface area to be controlled and the heat transfer coefficient.

  According to this embodiment, the temperature difference between the detected temperature of the controlled object and the temperature of the external environment is controlled via the heat transfer term. Is fed back to the manipulated variable side, which is the input side, so that the effect of nonlinear heat transfer can be canceled and linearized.

  (4) In the embodiment of the above (3), the heat transfer term is based on the model structure of the controlled object, and the model structure virtually divides the controlled object into a plurality of parts. A heat capacity term corresponding to the heat capacity of each part, a heat conduction term corresponding to the heat conduction between the parts, and the heat transfer term corresponding to the heat transfer between each part and the outside. .

  Here, the term means a unit constituting the model and corresponds to a mathematical expression (not including a relational symbol such as equal sign or inequality sign).

  The model structure preferably comprises a plurality of inputs and a plurality of outputs individually corresponding to the parts. The input refers to an input to the model, and refers to an input given to the control target, for example, an operation amount. The output refers to the output of the model, and refers to the output of the control target, for example, the detected temperature.

  A plurality of heat capacity terms may be provided, and each input and each output of the plurality of inputs and the plurality of outputs may individually correspond to each heat capacity term.

  The difference on the output side of the heat capacity term may be fed back to the input side of the heat capacity term via the heat conduction term.

  The difference on the output side of the heat capacity term means a difference on the output side of the model, for example, a temperature difference.

  According to this embodiment, linearization can be performed using the heat transfer term included in the structure of the model to be controlled.

  (5) In the embodiment of the above (3), when the parameter of the heat transfer term is set by controlling the controlled object to the first and second target temperatures, respectively, the target temperature or the operation You may make it determine based on the change of the said detected temperature when changing quantity.

  The first and second target temperatures are preferably the target temperatures on the high temperature side and the low temperature side of the temperature range to be used.

  According to this embodiment, based on the change in the detected temperature when the target temperature or the manipulated variable is changed in a state where the first target temperature is set, for example, the parameter of the heat transfer term on the high temperature side And determining the parameter of the heat transfer term on the low temperature side based on the change in the detected temperature when the target temperature or the manipulated variable is changed in the state of being set to the second target temperature, Finally, the parameter of the heat transfer term, which is a function of temperature, can be determined.

  (6) In the embodiment of the above (4), a plurality of the temperature control means are provided, and each temperature control means operates on the control object based on each detected temperature and target temperature from the plurality of temperature detection means. Are provided with non-interference means for eliminating or reducing the influence of the control by each temperature control means on the control by other temperature control means, and the non-interference means has a difference between the detected temperatures. May be fed back to the manipulated variable side via the heat conduction term.

  The temperature change of the controlled object based on the movement of the amount of heat due to interference is caused by the temperature difference of the controlled object. According to this embodiment, the difference (temperature seat) of each detected temperature of the controlled object is expressed as the heat conduction term. Therefore, it is possible to feed back to the operation amount side so as to cancel the interference, and it is possible to achieve non-interference with high accuracy.

  ADVANTAGE OF THE INVENTION According to this invention, the influence of nonlinear phenomena, such as heat transfer with a control object and the external field, can be negated, and it can linearize, and control performance improves.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram of a temperature control system using a temperature controller according to an embodiment of the present invention.

The temperature controller 1 of this embodiment performs linearization using the structure of the model to be described later of the controlled object 2, and includes two detected temperatures y ₁ and y ₂ from the controlled object ₂ and each target temperature SP. ₁ , two PID control means 3 ₁ , 3 ₂ as temperature control means for calculating and outputting the manipulated variables u ₁ ′, u ₂ ′ based on the deviation from SP _2, and both PID control means 3 ₁ , And a linearizer 4 that processes the manipulated variables u ₁ ′ and u ₂ ′ from 3 ₂ so as to linearize them and outputs them to the controlled object 2.

Both the PID control means 3 ₁ , 3 ₂ and the linearizer 4 are constituted by a microcomputer.

  FIG. 2 is a block diagram of the structure of the linearizer 4 and the model of the controlled object 2.

  Here, prior to the description of the linearizer 4, a theoretical description will be given of the structure of the model of the controlled object 2 used for this linearization.

  The control target handled here is a concentrated heat capacity model that ignores the temperature distribution of the object and handles only the heat capacity as a concentrated system. In order to simplify the discussion, as shown in FIG. 3, it is assumed that the controlled object is divided into two cells 7-1 and 7-2 and can be expressed by a concentrated heat capacity model.

  First, consider the physical laws governing one cell.

  The cell die mix is determined by changes in internal energy, heat conduction between cells, and heat transfer between the cell and the outside world. First, the change of the internal energy of the cell is derived from the following formula from the law of conservation of energy of the first law of thermodynamics when the cell is composed of a homogeneous material having a volume V.

cρV (dθ / dt) = Q _in −Q _out + Vq _v (1)
Here, c and ρ are the specific heat [J / (kg · K)] and density [kg / m ³ ] of the cell, respectively, and q _v [W / m ³ ] is the calorific value per unit volume. The constant pressure specific heat and the constant volume specific heat are equally represented by c in consideration of the case where the volumes of the two cells are the same.

Next, the relationship between the cell surface and the air around the object is heat transfer because air is a fluid. Considering the direction of flow into the cell as positive, and θ _∞ as the ambient temperature at a location sufficiently away from the cell, from Newton's cooling law,
_{Q = -A s h (θ 1} -θ ∞) ... (2)
It becomes. Here, h [W / (m ² · K)] is a heat transfer coefficient. It should be noted that the heat transfer coefficient is not a substance-specific value such as heat conductivity, but changes depending on the state of fluid flow. Strictly speaking, since the flow state is different on each surface of the object, the heat transfer coefficient is locally different.

Finally, consider the heat conduction (interference) between two cells. In a flat plate having a cross-sectional area A [m ² ] and an inter-cell distance d [m], assuming that the temperatures of the two cells are θ ₁ and θ ₂ [K], respectively, the amount of heat transferred from the left side to the right side by heat conduction is From Fourier's law, it is expressed by the following equation.

Q = −Aλ {(θ ₂ −θ ₁ ) / d} (3)
Here, λ [W / (m · K)] is the thermal conductivity.

  Next, consider a physical model by combining two cells.

  A physical model in the case of a two-divided cell is derived by combining the above three physical laws. For convenience, the left cell 7-1 is referred to as cell 1, and the right cell 7-2 is referred to as cell 2. The formula of the thermal energy conservation law (the first law of thermodynamics) for each cell is as follows.

Cell 1: cρV ₁ (dθ ₁ / dt) = − Q ₁ −Q ₁₂ + H ₁ u ₁ (4)
Cell 2: cρV ₂ (dθ ₂ / dt) = − Q ₂ −Q ₁₂ + H ₂ u ₂ (5)
It becomes. However, Q ₁₂ has a heat flow from the cell 1 to cell 2 and positive. However, Q ₁₂ has a heat flow from the cell 1 to cell 2 and positive. H ₁ and H ₂ represent the transfer characteristics of the heater.

The heat conduction between the cell 1 and cell 2, the cross-sectional area between the cells 1 and 2 as A _12,
Q ₁₂ = −A ₁₂ λ {(θ ₂ −θ ₁ ) / d} (6)
The heat transfer, which is heat dissipation from the surface of each cell to the surroundings, is defined as θ _∞ as the ambient temperature at a location sufficiently away from the cell.
Cell 1: Q ₁ = −A ₁ h ₁ (θ ₁ −θ _∞ ) (7)
Cell 2: Q ₂ = −A ₂ h ₂ (θ ₂ −θ _∞ ) (8)
It becomes. When a block diagram to be controlled is constructed from these equations, FIG. 4 is obtained. However, A ₁ and A ₂ are the surface areas of the cells 1 and 2.

However, E ₁ = cρV ₁ , E ₂ = cρV ₂ , β = A ₁₂ λ / d, and β means the reciprocal of the thermal resistance due to the interference between the cells 1 and 2. Also, α ₁ = A ₁ h ₁ and α ₂ = A ₂ h ₂ , respectively, representing the reciprocal of the thermal resistance from the cell to the ambient temperature.

The model structure of FIG. 4 includes heat capacity terms 8-1 and 8-2 including 1 / E ₁ or 1 / E ₂ , a heat conduction term 9 composed of β, and a heat transfer term composed of α ₁ or α _2. 10-1 and 10-2. Reference numeral 20 denotes a heater block.

E ₁ or E ₂ of the heat capacity term 8-1 is E ₁ = cρV ₁ , E ₂ = cρV ₂ , respectively, corresponding to the heat capacity of each of the cells 7-1 and 7-2, and β of the heat conduction term 9 is , Β = A ₁₂ λ / d, which corresponds to the heat conduction according to the Fourier law described above, and α ₁ or α ₂ of the heat transfer terms 10-1 and 10-2 is α ₁ = A ₁ h ₁ , respectively. α ₂ = A ₂ h ₂ , which corresponds to the heat transfer by Newton's law of cooling described above.

  Referring again to FIG. 2, in this embodiment, the physical model of FIG. 4 derived as described above is used as the structure of the model of the controlled object 2, and the part corresponding to FIG. The same reference numerals are attached.

   In general, the non-linear characteristic of the controlled object is largely due to a non-linear phenomenon called heat transfer, and therefore can be linearized by canceling out the effect of this non-linear heat transfer phenomenon.

Therefore, in this embodiment, the linearizer 4 performs linearization by canceling the influence of heat transfer, and the temperature difference between the outputs y ₁ and y _{2 of the} controlled object ₂ and the temperature θ _{∞ of the} outside world is respectively obtained. The subtracters 5 and 6 to be calculated and the outputs from the subtracters 5 and 6 are used as heat transfer terms 10-1 for compensation corresponding to the heat transfer terms 10-1 and 10-2 of the model structure of the control target 2, respectively. ', 10-2', the compensation terms 11 and 12 for compensating the transfer characteristics H ₁ and H ₂ of the heater, respectively, and the outputs of the compensation terms 11 and 12 are inputted as manipulated variables u ₁ 'and u ₂ '. Are provided with subtractors 13 and 14 for subtracting from the subtracters 13 and 14, respectively.

In each of the subtractors 5 and 6 for calculating the temperature difference between the outputs y ₁ and y _{2 of the} controlled object 2 and the temperature θ _{∞ of the} external environment, in the opposite direction to the model structure of the controlled object 2, that is, the external temperature. The outputs y ₁ and y ₂ of the controlled object 2 are subtracted from θ _∞ .

  Next, a method for identifying the parameters of the heat transfer terms 10-1 ′ and 10-2 ′ for compensation of the linearizer 4 and, therefore, the heat transfer terms 10-1 and 10-2 of the model structure of the controlled object 2 Will be described.

Here, two equivalent control target circuits can be expressed as shown in FIG.
However, C ₁ : 1ch capacitive component, C ₂ : 2ch capacitive component, Z ₁ : 1ch thermal resistance [° C / W], Z ₂ : 2ch thermal resistance [° C / W] Z ₁₂ : between 1ch and 2ch Thermal resistance [° C./W], θ ₁ : temperature of ₁ ch [° C.], θ ₂ : temperature of ₂ ch [° C.], Q ₁ : amount of heat input to ₁ ch [W], Q ₂ : amount of heat input to ₂ ch [ W].

In the state where the capacitance components C ₁ and C ₂ are included, the identification of the parameters becomes complicated, so that the capacitance components C ₁ and C ₂ are saturated, that is, the input to the control target is given and the steady state is obtained. Consider the identification of thermal resistance in the case. Considering the steady state, it can be replaced with the equivalent circuit of FIG. 6 from which the capacitive components C ₁ and C ₂ are removed.

  From this FIG. 6, when Kirchhoff's current law is used, the following equation is obtained.

Q ₁ = (θ ₁ / Z ₁ ) + (θ ₁ −θ ₂ ) / Z ₁₂
Q ₂ = (θ ₂ / Z ₂ ) + (θ ₂ −θ ₁ ) / Z ₁₂
When rewritten into a determinant, the following equation is obtained.

Q = θ · Z
Therefore, the thermal resistance Z is
Z = θ ⁻¹ · Q
It becomes.

  Therefore, when the input Q of each channel is changed stepwise, for example, the thermal resistance Z can be obtained by measuring the change in the output θ, and the reciprocal number of the thermal resistance Z is α can be calculated.

  If the square matrix cannot be obtained, the thermal resistance Z may be calculated using a pseudo inverse matrix.

  In addition, in the three-point controlled object, as in the case of two points, in the equivalent circuit at the three-point, using Kirchhoff's current law, an equation relating to heat flow is obtained, rewritten into a determinant, and the temperature matrix The thermal resistance can be obtained by using the pseudo inverse matrix.

  FIG. 7 is a flowchart for explaining the procedure for determining the parameter of the heat transfer term.

  Α of the heat transfer term is a function α (θ) of the temperature θ. Therefore, in this embodiment, α of the heat transfer term is set between the high temperature side and the low temperature side of the temperature range in which the temperature controller 1 is used. Each is identified and linearly approximated to determine α (θ) of the heat transfer term with respect to temperature.

First, for example, the control target 2 is controlled by setting the set temperature (target temperature) θ _L on the low temperature side (step n1), and the low temperature side parameters are identified (step n2).

FIG. 8 is a diagram illustrating changes in the set temperature SP, the manipulated variable MV, and the detected temperature PV for explaining the identification of the parameters, where the solid line indicates 1ch and the broken line indicates 2ch.
The identification of this parameter is in a steady state was stabilized at the set temperature theta _L, firstly, the set temperature of the 1ch indicated by the solid line, as shown in FIG. 8 (a), for example, lowered 1 ° C., Figure in a stable state Changes in the manipulated variables Q1 and Q2 of each channel shown in FIG. 8B are measured, and changes θ1 and θ2 in the detected temperature PV of the control target 2 shown in FIG. 8C are measured. FIG. 8C shows an example in which the detected temperature PV of 2ch indicated by a broken line is not changed.

  Next, as shown by the broken line in FIG. 8A, similarly, the set temperature of 2ch is lowered by 1 ° C., and the change Q3 and Q4 of the operation amount of each ch shown in FIG. At the same time, changes θ3 and θ4 of the detected temperature PV of the controlled object 2 shown in FIG. FIG. 8C shows an example in which the detection temperature PV of 1ch indicated by a solid line is not changed.

  The thermal resistance Z is calculated from the measurement results of Q and θ and the above determinant, and the parameter of the heat transfer term on the low temperature side is calculated as the reciprocal thereof.

Next, as shown in FIG. 7, the control object 2 is controlled by setting the set temperature θ _H on the high temperature side (step n3), and the parameters of the heat transfer term on the high temperature side are identified in the same manner as the low temperature side (step n). n4).

Next, as shown in FIG. 9, it is what determines the parameter alpha (theta) of the heat transfer section with respect to the temperature from the parameters of the parameter and the high temperature side theta _H of the low-temperature side theta _L (step n5).

  The determination of the parameter of the heat transfer term as described above may be performed in advance using a host device such as a personal computer and a data logger, and the determined parameter of the heat transfer term may be set in the linearizer 4 of the temperature controller 1. Alternatively, as shown in FIG. 10, a parameter determiner 31 is built in the temperature controller 1, the target temperature is changed as described above, the change in the detected temperature at that time is measured, and the parameter of the heat transfer term is measured. May be determined and set in the linearizer 4.

(Embodiment 2)
In the above-described embodiment, linearization is performed using the heat transfer term of the model structure. However, the present invention may be made non-interfering using the heat conduction term of the model structure.

  FIG. 11 is a diagram corresponding to FIG. 2 of a temperature controller in which a decoupling device 25 is added in addition to the linearizer 4 described above, and corresponding portions are denoted by the same reference numerals.

The non-interference unit 25 calculates a difference between the two outputs y ₁ and y ₂ of the model structure of the controlled object 2, and outputs the output from the subtractor 26 to the heat conduction term 9 of the controlled object 2. Corresponding heat conduction term 9 'for compensation and the output of this heat conduction term 9' are manipulated variable u ₁ inputted via compensation terms 27 and 28 for compensating the transfer characteristics H ₁ and H ₂ of the heater, respectively. An adder 29 and a subtractor 30 for adding or subtracting to “, u ₂ ” are provided, and the output of the heat conduction term 9 ′ is positive or negative with respect to the output of the heat conduction term 9 of the structure of the controlled object 2 model. The feedback is reversed.

  According to this embodiment, linearization can be achieved by the linearizer 4 and non-interference can be achieved by the non-interference unit 25.

  The present invention is useful for a control device such as a temperature controller.

It is a block diagram of the temperature control system using the temperature regulator which concerns on one embodiment of this invention. FIG. 2 is a block diagram of a model structure to be controlled and a linearizer in FIG. 1. It is a figure where it uses for the theoretical description about the structure of a model. It is a figure which shows the structure of a model. It is an equivalent circuit diagram of two points of control object. It is an equivalent circuit diagram excluding the capacitive component. It is a flowchart which shows the identification procedure of the parameter of a heat transfer term. It is a wave form diagram with which it uses for description of the identification procedure of the parameter of a heat transfer term. It is a figure for demonstrating determination of the parameter of a heat transfer term. It is a block diagram corresponding to FIG. 1 of other embodiment of this invention. It is a block diagram corresponding to FIG. 2 of other embodiment of this invention.

Explanation of symbols

1 Temperature controller 2 Control target
4 Linearizer 25 Decoupler

Claims (6)

A linearization means for linearizing the nonlinear characteristic of the controlled object is provided,
The linearization means performs linearization by canceling the influence of heat transfer between the controlled object and the outside world. Temperature control means for outputting an operation amount for the control object based on a detected temperature and a target temperature from a temperature detection means for detecting the temperature of the control object;
Linearizing means for linearizing the nonlinear characteristic of the controlled object,
The temperature regulator is characterized in that the linearization means linearizes the heat transfer between the controlled object and the outside world.   The temperature regulator according to claim 2, wherein the linearization unit feeds back a temperature difference between the detected temperature and the temperature of the outside world to an operation amount side through a heat transfer term.   The heat transfer term is based on the structure of the model of the controlled object, and the structure of the model corresponds to the heat capacity of each part when the controlled object is virtually divided into a plurality of parts. The temperature regulator according to claim 3, further comprising: a heat conduction term corresponding to heat conduction between the parts, and the heat transfer term corresponding to heat transfer between the parts and the outside. Changes in the detected temperature when the target temperature or the manipulated variable is changed in a state where the parameter of the heat transfer term is set by controlling the control target to the first and second target temperatures, respectively. The temperature regulator according to claim 3 or 4, which is determined on the basis of. A plurality of the temperature control means are provided, each temperature control means outputs an operation amount for the control object based on each detected temperature and target temperature from the plurality of temperature detection means,
A non-interference means for eliminating or reducing the influence of the control by each temperature control means on the control by the other temperature control means,
The temperature regulator according to claim 4, wherein the non-interacting unit feeds back a difference between the detected temperatures to the manipulated variable side through the heat conduction term.

Images