JP2815992B2 - Absorption chiller control device - Google Patents

Description

The present invention relates to a control device for an absorption refrigerator that controls an absorption refrigerator by fuzzy control.

(B) Conventional technology Various devices for performing fuzzy control using physical quantities representing various external conditions and internal conditions have been conventionally considered. For example, in the case of an absorption type chiller / heater or absorption chiller, in addition to a plurality of external conditions such as a deviation from a set value of a chilled water outlet temperature, a deviation of a change rate and a deviation of a chilled water inlet temperature, and a change rate, a high temperature generator A plurality of internal conditions, such as a temperature change rate and a circulating pump drive frequency change rate, are simultaneously input as input variables to perform fuzzy control.

In such a device, when fuzzy rules (hereinafter, rules) are created, so-called production rules (IF to THEN rules) are used. However, in many cases, the logical AND of other input variables is taken and fuzzy inference is performed. For example, if the input variables are A,
If B and C and D are output variables, Rule 1: IF A is PB AND B is ZR AND C is NB THEN D is ZR (However, PB is positively large, ZR is zero, and NB is negative. Large, fuzzy label is shown). In the case of an absorption refrigerator, in many cases, the fuel supply to the evaporator is controlled using a deviation from a set value of the actual chilled water outlet temperature as an input variable.

(C) Problems to be Solved by the Invention In such a device, when the chilled water outlet temperature approaches a set value, there is a problem that control accuracy is deteriorated.

(D) Means for Solving the Problems In the present invention, a refrigerating cycle is formed by connecting an evaporator, an absorber, a generator, a condenser, and the like, and the amount of heating of the generator is controlled by external conditions including a chilled water outlet temperature. In the control device of an absorption refrigerator controlled by using fuzzy inference, at least one of the fuzzy control rules out of the fuzzy control rules forming the basis of fuzzy inference has two inputs based on the external conditions. A variable and two conditional part membership functions for each input variable, wherein the conclusion part membership function of the fuzzy control rule is arranged in a matrix corresponding to the two conditional part membership functions. A control unit, wherein one of the two input variables is a deviation between the chilled water outlet temperature and its set value,
In the matrix of the control unit, in a portion where the chilled water outlet temperature is near a set value, a conclusion membership function corresponding to the other input variable is defined without an interval in a row direction or a column direction of the matrix. In addition, the operation amount for adjusting the heating amount of the generator is characterized in that the conclusion membership function near the zero is finely defined by narrowing the mutual interval.

(E) Operation The device of the present invention performs fine control when the chilled water outlet temperature is close to the set value.

(F) Example FIG. 1 shows a double-effect absorption refrigerator using water as a refrigerant and an aqueous solution of lithium bromide (LiBr) as an absorbent (solution), wherein 1 is a high-temperature generator equipped with a burner 1B, 2 is a low-temperature generator, 3 is a condenser, 4 is an evaporator, 5 is an absorber, 6 is an absorbent pump, 7, 8 are a low-temperature heat exchanger and a high-temperature heat exchanger, respectively, 10 is a diluted absorbent pipe, 11 Is an intermediate absorption liquid pipe, 12 is a concentrated liquid pipe, 13 is a refrigerant pipe, 14 is a refrigerant liquid flow down pipe, and 15 is a refrigerant liquid circulation pipe, each of which is connected as shown in FIG. A refrigerant pump is provided in the middle of the refrigerant liquid circulation pipe 15.
15P is provided. Reference numeral 16 denotes a fuel supply pipe connected to the burner 1B. A fuel control valve (heating amount control valve) 17 is provided in the fuel supply pipe 16. Reference numeral 20 denotes a cold water pipe, and an evaporator heat exchanger 21 is provided in the middle of the cold water pipe 20. Further, 22 is a cooling water pipe.

Reference numeral 23 denotes a control unit, and reference numeral 24 denotes a chilled water outlet temperature detector provided in the chilled water pipe 20. The chilled water temperature detector 24 and the fuel control valve 17 are connected to a control panel 23. And control panel 23
The control device of the microprocessor 25 and the fuel control valve 17
26 are provided. The microprocessor 25 includes a fuzzy inference processor 27 and a control rule storage device. The fuzzy inference processor 27 performs a logical operation on the operation amount KQ for the fuel control valve 17 and outputs the obtained operation amount KQ to the control device 26. The control device 26 corrects the opening of the fuel control valve 17 based on the operation amount KQ. Specifically, the control device 26 holds the opening information Q of the valve 23, and adjusts the opening of the fuel control valve 17 according to the opening information Q. Then, the operation amount each time receiving a KQ _n, opening information has been set up to now Q _n-1 and the operating amount of the new opening information by the KQ _n Q _n = Q
Set _n-1 + KQ _n . That is, in this embodiment, the opening of the fuel control valve 17 is changed by the operation amount KQ from the fuzzy inference processor 27. The control rule storage device 28 stores a control rule (fuzzy rule) necessary for the fuzzy logic operation executed by the fuzzy inference processor 27, a condition part, and a conclusion part membership function. 30 is an arithmetic unit,
Reference numeral 31 denotes a chilled water inlet temperature detector provided in the chilled water pipe 20 on the inlet side of the evaporator 4. 32 is a high-temperature generator temperature detector for detecting the high-temperature generator temperature, and 33 is a cooling water inlet temperature detector for detecting the cooling water inlet temperature. The arithmetic unit 30 takes in the temperature data of the chilled water outlet temperature detector 24, the chilled water inlet temperature detector 31, the high temperature generator temperature detector 32, and the cooling water inlet temperature detector 33, and calculates the next data.

Coil water outlet temperature deviation (eto) eto = current value-target value Chilled water outlet temperature deviation rate of change (dto) dto = current value-previous value Chilled water inlet temperature change rate (dtci) dtci = current value-previous Value Change rate of chilled water inlet temperature (dti) dti = current value-previous value Average value of the past 40 samples of eto (e) High-temperature generator temperature change rate (dtg) dtg = current value-previous value Next, the functional block diagram of the microprocessor 25 is shown in FIG.
Shown in the figure. In the figure, reference numeral 34 denotes data eto, dto, dtci, dti, e, and dtg from the arithmetic unit 30 and receives data eto, dto, dtci, dti, e, and dtg from the condition part member shop function and control rules stored in the control rule storage device 28, and A fitness calculation unit for determining the fitness of the control rule. When a plurality of conditional part membership functions are defined, the minimum fitness is defined as the fitness. Here, eto, dto, dti, dtci, dtg, and e are N
3 to 8 using B, NS, ZR, PS, and PB. As can be seen, dti, dtci, and e are 0.4 and 0.
Weighting of 5, 0.5 is performed.

The control rules for eto, dto, and dtg are as shown in FIG. That is, here, the rule is not defined for the adjacent control rules, and the calculation time of the degree of conformity is shortened. Also, eto and dto are defined as shown in FIG. Here, NZ and PZ, which will be described later, are added to the conclusion part membership function, and the degree of convergence of the manipulated variable KQ when eto approaches the set value is improved. Fig. 11 for dtci, Fig. 12 for dti, 1 for e
The ones in Figure 3 are defined. In addition, about this e, e
Only when to is near ZR, as shown above,
Control performance and convergence are improved by taking the average of 0 samples.

35 is a member of the conclusion part in the control rule storage device 28
This is a correction unit that corrects the ship function so as to cut off the upper part in accordance with the fitness obtained by the fitness calculating unit. The conclusion part membership function is defined in FIG. As you can see from this figure, ZR
In the vicinity, NZ and PZ are defined to improve control.

Reference numeral 36 denotes a logical sum unit that superimposes the respective membership functions corrected by the correction unit 35 to obtain a logical sum, and reference numeral 37 denotes a gravity center calculation unit that calculates the center of gravity of the function generated by the logical sum unit 36. The calculated value is provided to the control device 26 as the valve operation amount KQ.

In such a device, during the operation of the absorption refrigerator, the arithmetic unit 30 includes the cooling outlet temperature detector 24 and the chilled water inlet temperature detector.
31, temperature signals are taken in from the high-temperature generator temperature detector 32 and the cooling water inlet temperature detector 33, for example, every five seconds. Then, from the temperature signal thus obtained, the deviation of the chilled water outlet temperature (eto) and the rate of change of the deviation of the chilled water outlet temperature (dt)
o), the rate of change of cooling water inlet temperature (dtci), the rate of change of cooling water inlet temperature (dti), the average value of the past 40 samples of eto (e), and the rate of change of high temperature generator temperature (dtg) Send to computer 25.

The fitness calculation unit 34 in the microcomputer 25 checks the fitness of the condition parts of all the control rules. And
Using the degree of matching, the correction unit 35 corrects the membership function of the corresponding conclusion part shown in FIG. That is, the portion above the fitness of each membership function is cut. The logical sum of the membership functions corrected in this way is obtained by the logical sum unit 36, and the center of gravity of the membership function is obtained by the center of gravity calculating unit 37. The output of the center-of-gravity calculation section 37 is output as the operation amount KQ _n of fuel control valve 17.

The valve control device 26 calculates the operation amount KQ _n and the opening degree information Q
calculates a new opening information _{Q n = Q n-1 +} KQ n based on the _n-1. Then, to adjust the fuel control valve 17 in response to the opening information Q _n.

 Such an operation is repeated in the above-described 5-second cycle.

(G) Effects of the Invention As described above, according to the control device for an absorption refrigerator of the present invention, when the chilled water outlet temperature approaches the set value, the conclusion membership function is defined in the matrix. There is no state, and furthermore, the conclusion part membership function when the manipulated variable is near zero is finely set, so even if the chilled water outlet temperature is near the set value, it does not vibrate and is kept stable .

Therefore, the chilled water outlet temperature is finally set to the set value with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram of an absorption refrigerator to which the control device of the present invention is applied, FIG. 2 is a functional block diagram of a microcomputer used in the device of the present invention, and FIGS. 3 to 8 are used in the present invention. Characteristic diagram of conditional part membership function,
9 to 13 are explanatory diagrams of the control rules, and FIG. 14 is a characteristic diagram of the membership function of the conclusion part. 1 high temperature generator, 2 low temperature generator, 3 condenser
4 ... Evaporator, 5 ... Absorber, 17 ... Fuel control valve, 23 ...
... Control unit, 24 ... Cold water outlet temperature detector, 25 ... Microprocessor, 26 ... Control device, 27 ... Fuzzy inference processor, 28 ... Control rule storage device, 30 ... Computing device, 31 ... ... Cooled water inlet temperature detector, 32 ... High temperature generator temperature detector, 33 ... Cooled water inlet temperature detector, 34 ... Compatibility calculation unit, 35 ... Correction unit, 36 ... OR unit, 37 ... ... Center of gravity calculation unit.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hidetoshi Arima 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-4-32668 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F25B 15/00 306

Claims (1)

(57) [Claims] 1. An absorption system in which an evaporator, an absorber, a generator, a condenser, etc. are connected to form a refrigeration cycle, and a heating amount of the generator is controlled by fuzzy inference based on external conditions including a chilled water outlet temperature. In the control device of the type refrigerator, at least one of the fuzzy control rules out of the fuzzy control rules on which the fuzzy inference is based has two input variables based on the external conditions and two for each input variable. A control unit comprising a condition part membership function, and a conclusion part membership function of the fuzzy control rule arranged and arranged in a matrix corresponding to the two condition part membership functions; One of the two input variables is a difference between the chilled water outlet temperature and its set value, and the matrix of the control unit includes a portion where the chilled water outlet temperature is near the set value. Therefore, the conclusion membership function corresponding to the other input variable is defined without any interval in the row or column direction of the matrix, and the conclusion that the manipulated variable for adjusting the heating amount of the generator is near zero is obtained. A control device for an absorption refrigerator, characterized in that the member membership functions are finely defined by narrowing the mutual intervals.