JPH0486462A - Controller for absorption type freezer - Google Patents

Abstract

PURPOSE:To improve a stability of the controlling by a method wherein a difference between a cold or a hot water outlet port temperature and its set value is integrated for a specified period of time in a control device for use in controlling by using a fuzzy inference in response to external conditions so as to constitute fuzzy rules and membership functions. CONSTITUTION:A control device 26 of a fuel control valve 17 retains information of degree of opening of a valve 23 and varies a degree of opening of the fuel control valve 17 in response to an operating amount from a fuzzy inference processor 27. A memory device 28 for control rules stores fuzzy rules run at the fuzzy inference processor 27, membership functions at a condition part and a conclusion part. In addition, a calculator device 30 takes temperature data at each of the parts and calculates a temperature variation rate or the like. At this time, a difference between a cold water outlet temperature and a target value is a mean value of last 40 samples. This calculated value is sent to a micro-computer 25 to check its adaptability at the condition part of all control rules and then the membership functions at the conclusion part are corrected. Valve control device 26 calculates a new information of degree of opening in reference to these calculated outputs so as to adjust the fuel control valve 17.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a control device for an absorption refrigerating machine that controls the absorption refrigerating machine by fuzzy control.

(B) Conventional technology Conventionally, in absorption chiller/heaters and refrigerators, proportional control detects the chilled water outlet temperature and controls the heat input to the absorption chiller/heater and refrigerator based on the deviation from the set value. , or PID control based on the cold water outlet temperature was common.

These controls uniquely control the heat input to the absorption chiller based on a single physical quantity, the chilled water outlet temperature, and are therefore performed by skilled operators in response to all kinds of condition changes, such as start-up, stop, and slow and sudden load fluctuations. Compared to control, there was a problem in quick response. To improve this, we developed an absorption chiller/heater, a number of physical quantities representing the external conditions of the absorption chiller (deviation of the chilled water outlet temperature from a set value, its rate of change over time, etc.), and a water chiller/heater.

Fuzzy rules and members are created between multiple physical conditions representing the internal conditions of the refrigerator (high-temperature regenerator temperature, rate of change over time, etc.) and the amount of heat input to the absorption chiller/heater, the amount of heat input to the refrigerator, and the amount of circulation of the absorption liquid. A control method has been proposed in which a ship function is configured and an absorption chiller is controlled based on the ship function.

According to the control method, PID based only on the cold water outlet temperature
Compared to control methods, it is possible to detect the internal and external conditions of the absorption chiller/heater and absorption chiller, as well as changes in these conditions, and perform control based on integrated judgment, resulting in the same level of responsiveness as control performed by a skilled operator. Good control performance can be obtained.

However, the absorption chiller/heater and absorption chiller are operating stably! ! (In a state where the chilled water outlet temperature is controlled close to the set value), there is a problem in the set value follow-up performance, which is generally said to be the case with fuzzy control. In other words, ① An offset from the set value remains, ② It is susceptible to disturbances, etc.

(c) Problems to be Solved by the Invention The present invention improves the degree control performance near the set value, which was a problem in the conventional method described above.

(d) Means for Solving the Problems In the present invention, a refrigeration cycle is formed by connecting an evaporator, an absorber, a generator, a condenser, etc., and the heating amount of the generator is determined by external conditions including the chilled water outlet temperature. In a control device for an absorption chiller that uses fuzzy reasoning to control the cold and hot water outlet temperature, when the cold and hot water outlet temperature is close to the set value, the deviations from the cold and hot water outlet temperature from the set value are integrated over a finite period of time, and the average value is calculated. A fuzzy rule and a membership function are constructed between the heating amount and the heating amount based on the value.

(E) By adjusting the number of samples to be integrated, the followability of the cold water outlet temperature to the set value is improved, and it is less susceptible to the effects of evening disturbances.

(f) Example Figure 1 shows water as the refrigerant and lithium bromide as the absorbent (solution).
(LiBr) A double-effect absorption refrigerator using an aqueous solution, 1 is a high temperature generator equipped with burner IB, 2 is a low temperature generator, 3 is a condenser, 4 is an evaporator, 5 is an absorber, and 6 is a Absorption liquid pump, 7 and 8 are a low temperature heat exchanger and a high temperature heat exchanger, respectively, ] 0 is a box plate liquid collection pipe, 11 is an intermediate absorption liquid pipe, 12
is a concentrated liquid pipe, 13 is a refrigerant pipe, 14 is a refrigerant liquid down pipe,
15 is a refrigerant liquid circulation pipe, each of which is connected as shown in FIG. And refrigerant liquid circulation fiii'1
A refrigerant pump 15P is provided in the middle of 5. Also,
] 6 is a fuel supply pipe connected to burner IB, and a fuel control valve (heat amount control valve) 1 is installed in the middle of this fuel supply pipe 16.
7 is provided.

Further, 20 is a cold water pipe, and an evaporator heat exchanger 21 is provided in the middle of this cold water pipe 20.

Furthermore, 22 is a cooling water pipe.

Reference numeral 23 denotes a control unit, and 24 denotes a cold water outlet temperature detector provided in the cold water pipe 20. This cold water temperature detector 24 and the fuel control valve 17 are connected to the control panel 23. The control panel 23 is provided with a microprocessor 25 and a control device 26 for the fuel control valve 17. The microprocessor 25 is composed of a fuzzy inference processor 27 and a control rule storage device 28. The fuzzy inference processor 27 performs a logical operation on the manipulated variable KQ to the fuel control valve 17 and outputs the obtained manipulated variable KQ to the control device 26 . The control device 26 corrects the opening degree of the fuel control valve 17 based on the manipulated variable KQ. Specifically, this control section 726
holds the opening degree information Q of the valve 23, and this opening degree information Q
The opening degree of the fuel control valve 17 is adjusted accordingly. Then, each time the manipulated variable KQ is received, new opening information Q is created using the previously set opening information Q, -1 and the manipulated variable KQ.
, =Q, -1+KQ, are set. That is, in this embodiment, the opening degree of the fuel control valve 17 is changed by the manipulated variable KQ from the fuzzy inference processor 27. Further, the control rule storage device 28 stores control rules (fuzzy rules), conditional parts, and conclusion part membership functions necessary for fuzzy logic operations executed by the fuzzy inference processor 27.

Further, 30 is a calculation device, and 31 is a cold water inlet temperature detector provided in the cold water pipe 20 on the inlet side of the evaporator 4. 32
is a high temperature regenerator temperature detector that detects the high temperature regenerator temperature, 3
3 is a cooling water inlet temperature detector that detects the cooling water inlet temperature. The arithmetic unit 30 takes in the temperature data of the cold water outlet temperature detector 24, the cold water inlet temperature detector 31, the high temperature regenerator temperature detector 32, and the cooling water inlet temperature detector 33, and calculates the following data.

■ Deviation of chilled water outlet temperature (e t o) e t, o = current value - target value ■ Rate of change of deviation of chilled water outlet temperature (dto) dto - current value - previous value ■ Rate of change of cooling water inlet temperature ( dtci) dtci = Current value - Previous value ■ Rate of change in cold water inlet temperature (dti) dti = Current value - Previous value Average value of the past 40 samples of 0etO (e) e, = (Σ
e t o + ) / 40 ■ High temperature regenerator temperature change rate (d t g) c! tg = current value - previous value Next, the functional block diagram of the microprocessor 25 is shown in the second section.
As shown in the figure. In the figure, 34 is data eto, dto, dtci, dti, e, dt from the arithmetic unit 30.
This is a suitability calculation unit which calculates the suitability of each control rule from the condition part membership function and control rule stored in the control rule storage device 28 in response to g, and is defined by a plurality of condition part membership functions. is done, the minimum degree of conformity is taken as the degree of conformity. Here, as the conditional membership functions, eto, dto, dti, dt
NB, NS, ZR, for ci, dtg, and e, respectively.
It is defined as shown in FIGS. 3 to 8 using PS and PB. As you can see, clti, dtci, and e are each 0.4.0 to reduce the degree of influence.
．． A weighting of 5.0°5 is performed.

The control rules for eto, dto, and dtg are as shown in FIG. That is, here, rules are not defined for adjacent control rules, thereby reducing the time required to calculate the degree of suitability.

Furthermore, eto and dto are defined as shown in FIG. Here, NZ and PZ, which will be described later, are added to the conclusion section membership function to improve the degree of convergence of the control amount KQ when eto approaches the set value. dtci is defined in FIG. 11, dti in FIG. 12, and e in FIG. 13. Regarding e, control performance and convergence are improved by taking the average of the past 40 samples of eto only when eto is in the vicinity of ZH, as shown in (2) above.

Reference numeral 35 denotes a modification unit that modifies the conclusion part membership function in the control rule storage device 28 so as to cut the upper part of the conclusion part membership function in accordance with the degree of fitness obtained by the degree of fitness calculation unit 34. Note that the conclusion section membership function shown in FIG. 14 is defined. As can be seen from this figure, NZ and PZ are defined in the vicinity of ZR to improve control.

Reference numeral 36 denotes a disjunctive unit that superimposes the membership functions modified by the correcting unit 35 and calculates a logical sum; and 37 a centroid calculation unit that computes the centroid of the function generated by the disjunctive unit 36. , this calculated value is given to the control device 26 as the valve operation amount KQ.

In such a device, during operation of the absorption chiller, the arithmetic unit 30 detects the temperature from the chilled water outlet temperature detector 24, the chilled water inlet temperature detector 31, the high temperature regenerator temperature detector 32, and the chilled water inlet temperature detector 33. The signal is taken in, for example, every 5 seconds. From the temperature signal thus obtained, the deviation of the chilled water outlet temperature (eto), the rate of change of the deviation of the chilled water outlet temperature (dto), and the rate of change of the chilled water inlet temperature (dtci) are calculated.
, rate of change of chilled water inlet temperature (dti), past 40 of eto
Sample average value (e), high temperature regenerator temperature change rate (d
tg) and sends it to the microcomputer 25.

The suitability calculation section 34 in the microcomputer 25 examines the suitability of the condition parts of all control rules. Then, using this goodness of fit, the modification unit 35 modifies the member simp function of the corresponding conclusion section shown in FIG. 14. That is, the portion above the fitness level of each membership function is cut. The logical sum of the membership functions thus modified is taken by the logical sum section 36, and the center of gravity of the membership function is determined by the gravity/01 calculation section 37. The output of this center of gravity calculating section 37 is the manipulated variable KQ of the fuel control valve 17.

The output is closed.

The valve control device 26 generates new opening information Q,=Q based on the previous opening information Q,-,
−, +K Calculate Qyo. And during this time, the degree information Q
, adjust the fuel control valve]7 accordingly.

These operations are repeated at the above-mentioned 5 second period.

(G) Effects of the Invention As described above, the control device for the absorption refrigerator of the present invention connects the evaporator, absorber, generator, condenser, etc. to form a refrigeration cycle, and controls the heating amount of the generator. In an absorption chiller control device that uses fuzzy reasoning to control external conditions including the chilled water outlet temperature, when the chilled and hot water outlet temperature is close to the set value, the deviation from the set value of the chilled and hot water outlet temperature is kept constant at a finite value. Fuzzy rules and membership functions are created between the accumulated value over time and the amount of heating, which improves the followability of the cold water outlet temperature to the set value and makes it less susceptible to external disturbances. Control stability is improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an absorption chiller 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. Characteristic diagram of the conditional 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. DESCRIPTION OF SYMBOLS 1. High temperature generator, 2... Low temperature generator, 3... Condenser, 4... Evaporator, 5... Absorber, 17... Fuel control valve, 23... Control part, 24...・・Cold water outlet temperature detector,
25...Microprocessor, 26...Control device, 2
7... Fuzzy inference processor, 28... Control rule storage device, 30... Arithmetic device 31... Chilled water inlet temperature detector, 32... High temperature regenerator temperature detector, 33...
...Cold water inlet temperature detector 34...Compatibility calculating section, 35
...correction section, 36.. logical sum section, 37.. centroid calculation section.

Claims (1)

[Claims] (1) Absorption refrigeration, in which an evaporator, absorber, generator, condenser, etc. are connected to form a refrigeration cycle, and the amount of heat generated by the generator is controlled using fuzzy reasoning according to external conditions including the chilled water outlet temperature. In the control device of the machine, when the cold and hot water outlet temperature is close to the set value, the deviation from the cold and hot water outlet temperature from the set value is integrated over a finite fixed period of time, the average value is taken, and the difference between the heating amount and the heating amount is determined by that value. A control device for an absorption refrigerator, characterized in that a fuzzy rule and a membership function are configured.