JP7724687B2 - Air conditioning device and method - Google Patents

Description

The present invention relates to an air conditioning system and method that performs PID control of a compressor.

In order to properly air-condition a space, air conditioners have been developed that use PID control of the compressor's rotational frequency.

For example, Japanese Patent Laid-Open Publication No. 9-119696 (Patent Document 1) discloses an air conditioning system that uses PID control with the temperature of the air-conditioned space and the indoor heat exchanger temperature as controlled variables, and the frequency of the power supplied to the compressor drive motor as a manipulated variable. According to Patent Document 1, it is possible to prevent temperature hunting.

However, PID control can be affected by various conditions, such as the structure of the space to be air-conditioned, heat sources present within the space, climate, and other environmental factors. Therefore, it is preferable to set the control constants of PID control appropriately according to the conditions, but setting the control constants requires specialized knowledge of control. Therefore, in conventional air conditioning systems, it was common to use control constants that were set during the manufacturing stage of the system, and there was no thought of changing the control constants afterwards.

As a result, conventional air conditioning systems were unable to properly PID control the compressor, which could result in issues such as indoor temperature hunting. Therefore, there was a need for further technology to properly PID control the compressor.

Japanese Patent Application Publication No. 9-119696

The present invention was made in consideration of the problems with the conventional technology described above, and aims to provide an air conditioning system and method that feedback controls a compressor using appropriate control constants.

That is, according to the present invention,
An air conditioning apparatus comprising: a compressor constituting a refrigeration cycle; a temperature sensor that measures the temperature of an environment constituting the refrigeration cycle; and control means that feedback-controls the operation of the compressor based on the temperature measured by the temperature sensor,
The control means
a manual setting means for setting a control constant of the feedback control based on an operation input by a user;
an automatic setting means for setting the control constant based on the temperature measured by the temperature sensor;
The manual setting means and the automatic setting means can be switched to each other.
An air conditioning system is provided.

The present invention provides an air conditioning system and method that feedback controls a compressor using appropriate control constants.

FIG. 1 is a diagram showing a schematic configuration of an air conditioning apparatus in each embodiment. FIG. 2 is a diagram showing a refrigeration cycle that constitutes the air conditioning apparatus of each embodiment. FIG. 3 is a software block diagram included in a control unit of the air conditioning apparatus of each embodiment. FIG. 2 is a control block diagram according to the first embodiment. 4 is a graph showing a response of PID control in the first embodiment. 4 is a flowchart showing feedback control in the first embodiment. 4 is a graph showing the progress of room temperature under the air conditioning apparatus of the first embodiment. FIG. 10 is a control block diagram according to a second embodiment. FIG. 10 is a control block diagram according to a third embodiment.

The present invention will be described below using several embodiments, but the present invention is not limited to the embodiments described below. In the figures referenced below, the same reference numerals will be used for common elements, and their description will be omitted where appropriate. In the following embodiments, the air conditioning device 10 is described as a room air conditioner (RAC), but the type of air conditioning device 10 is not particularly limited and may be a package air conditioner (PAC), a building multi-air conditioner (VRF), or the like. Figures 1 to 3 illustrate the configuration common to each embodiment.

Figure 1 is a diagram showing the general configuration of an air conditioning device 10 in each embodiment. As shown in Figure 1, the air conditioning device 10 includes an indoor unit 20, an outdoor unit 30, and a remote control 40.

The indoor unit 20 is placed in the target space to be air-conditioned, and provides the air conditioning desired by the user via a remote control terminal such as a remote controller 40 operated by the user. The outdoor unit 30 is installed outside the target space and includes an expansion valve 31, an outdoor heat exchanger 32, a compressor 35, etc.

The air conditioning system 10 has an indoor unit 20 and an outdoor unit 30 connected by piping to form a closed circuit. A refrigerant is sealed within this closed circuit, and the refrigerant circulates within the closed circuit, exchanging heat between the refrigerant and the air to achieve a refrigeration cycle. Details of the refrigeration cycle are explained below with reference to Figure 2.

Figure 2 is a diagram showing the refrigeration cycle that constitutes the air conditioning apparatus 10 of each embodiment. As shown in Figure 2, the refrigeration cycle in the air conditioning apparatus 10 is composed of an indoor unit 20 and an outdoor unit 30, which are connected via piping.

The indoor unit 20 includes an indoor fan 21, an indoor heat exchanger 22, a control unit 23, and a temperature sensor 24. The outdoor unit 30 includes an expansion valve 31, an outdoor heat exchanger 32, an outdoor fan 33, a four-way valve 34, and a compressor 35. The arrows in Figure 2 indicate the direction of refrigerant flow when the air conditioning unit 10 is in cooling operation. For convenience, the following explanation of the refrigeration cycle will focus on operation during cooling operation. During heating operation, the direction of refrigerant flow is reversed from the direction of the arrows in Figure 4.

The indoor unit 20 conditions the indoor space by using the indoor fan 21 to exchange heat between the air in the indoor space and the refrigerant flowing through the indoor heat exchanger 22 and then discharging the air back into the room. During cooling operation, the indoor heat exchanger 22 functions as an evaporator, exchanging heat between low-temperature, low-pressure liquid refrigerant and the air blown by the indoor fan 21. The indoor unit 20 can lower the temperature of the indoor space by discharging the air that has been subjected to heat exchange. The refrigerant that flows out of the indoor heat exchanger 22 is a low-temperature, low-pressure gas refrigerant and flows to the outdoor unit 30 via refrigerant piping.

The control unit 23 controls the operation of each piece of hardware that makes up the air conditioning unit 10 based on signals received from, for example, the remote control 40. This allows the air conditioning unit 10 to perform the specified operating operation desired by the user, such as cooling operation, dehumidification operation, or heating operation. As an example, the control unit 23 can be configured as an information processing device such as a CPU.

The temperature sensor 24 is a sensor that measures the temperature that is the target of PID control, and can measure, for example, the room temperature of the target space or the temperature of the refrigerant flowing through the indoor heat exchanger 22, or other environmental temperatures that make up the refrigeration cycle. The temperature sensor 24 outputs the measured temperature data to the control unit 23. This allows the control unit 23 to perform PID control based on the measured temperature. Note that the indoor unit 20 may be equipped with multiple temperature sensors 24.

Next, the outdoor unit 30 will be described. The compressor 35 compresses the low-temperature, low-pressure gas refrigerant that flows in from the outdoor unit side by driving the motor, and discharges it as high-temperature, high-pressure gas refrigerant. The operating frequency of the compressor 35 in the embodiment being described is controlled by a drive signal from the control unit 23. The gas refrigerant discharged from the compressor 35 passes through the four-way valve 34 and flows into the outdoor heat exchanger 32. The outdoor heat exchanger 32 exchanges heat between the refrigerant flowing through it and the outside air sent in by the outdoor fan 33. During cooling operation, the outdoor heat exchanger 32 functions as a condenser, and discharges the refrigerant as a high-temperature liquid through heat exchange. During heating operation, the outdoor heat exchanger 32 functions as an evaporator.

The refrigerant discharged from the outdoor heat exchanger 32 is expanded in volume by the expansion valve 31, and its temperature is lowered by reducing its pressure. The refrigerant then flows into the indoor unit 20, where it performs cooling operation to lower the temperature of the indoor space as described above.

The four-way valve 34 switches the refrigerant flow path depending on the operating mode of the air conditioning unit 10. That is, during cooling operation, the connection is as shown by the solid lines in Figure 2, and during heating operation, the connection is as shown by the dashed lines. This allows either the indoor heat exchanger 22 or the outdoor heat exchanger 32 to operate as a condenser, and the other as an evaporator, allowing for appropriate air conditioning operation.

Next, the control unit 23 that performs PID control in the embodiments will be described with reference to Figure 3. Figure 3 is a software block diagram included in the control unit 23 of the air conditioning device 10 in each embodiment. The control unit 23 includes the following functional means: a target temperature setting unit 231, a temperature acquisition unit 232, a control constant setting unit 233, and a compressor control unit 234. Each of these functional means may be realized by a program stored in a memory area, a circuit, or the like.

The target temperature setting unit 231 is a means for setting a target temperature, which serves as a parameter in feedback control using PID control. For example, in the case of PID control based on room temperature, the target temperature setting unit 231 sets the temperature set by the remote control 40 as the target temperature. Also, in the case of PID control based on the temperature of the refrigerant in the indoor heat exchanger 22, the target temperature setting unit 231 sets the evaporation temperature (in the case of cooling operation) or condensation temperature (in the case of heating operation) of the refrigerant as the target temperature.

The temperature acquisition unit 232 is a means for acquiring the measured value measured by the temperature sensor 24. The control constant setting unit 233 is a means for setting the control constant for PID control. The control constant may be set automatically based on the measured temperature value acquired by the temperature acquisition unit 232, or may be set manually. An example of manual setting is when an operator with specialized knowledge sets the control constant when inspecting the air conditioning unit 10, but this is not a limitation of the embodiment.

The compressor control unit 234 is a means for calculating the operating frequency of the compressor 35 and controlling the operation of the compressor 35 based on the control constants set by the control constant setting unit 233, the set temperature, and the measured temperature.

The software blocks described above correspond to functional means realized by causing each piece of hardware to function when a CPU or the like executes a program according to the embodiment being described. Furthermore, the functional means shown in each embodiment may be realized entirely in software, or some or all of them may be implemented as hardware that provides equivalent functionality. Therefore, the air conditioning apparatus 10 may be equipped with a CPU, circuits, memory area, etc. to realize these processes. Furthermore, the air conditioning apparatus 10 may be equipped with communication means to realize all or some of these functions on an external server, cloud, etc. via a communication network.

So far, we have explained the configuration common to each embodiment. Below, we will explain more specific embodiments.

First, we will explain the first embodiment. In the first embodiment, PID control is performed based on room temperature. Figure 4 is a control block diagram for the first embodiment.

As shown in FIG. 4, the remote control 40 outputs the desired room temperature set by the user in the target space as the set temperature. The temperature acquisition unit 232 also acquires the measurement value from the temperature sensor 24 and outputs it as the room temperature. The difference between the set temperature and the room temperature is output to the compressor control unit 234.

The control constant setting unit 233 outputs the set control constant to the compressor control unit 234. When the control constant setting unit 233 is in automatic setting mode, the control constant setting unit 233 calculates the control constant for PID control based on the indoor temperature output by the temperature acquisition unit 232. When the control constant setting unit 233 is in manual setting mode, the control constant setting unit 233 determines the control constant for PID control based on setting information received from the user. Note that selection between automatic setting mode and manual setting mode can be made, for example, from the remote control 40.

Furthermore, when the control constant setting unit 233 is in manual setting mode, the user can set the control constants for the proportional term, integral term, and derivative term through operation. In the manual setting mode, the user can set a combination of the control constants for the proportional term, integral term, and derivative term by, for example, arbitrarily setting the control constants using the remote control 40, selecting control constants set during device development, or selecting various operation modes and setting control constants corresponding to the operation mode. For example, the user can set the control constants by selecting a mode from a controller such as the remote control 40 from multiple operation modes in which sets of control constants _Kp , _Ki , _Kd, etc. are pre-adjusted and classified according to high load, low load, etc. In this case, for an operation mode corresponding to a high load and a need to quickly lower the indoor temperature, a combination with a large control constant _Ki may be selected to facilitate output relative to the controlled variable. Setting the control constants requires specialized knowledge about control, but by pre-setting combinations of operation modes and control constants and allowing the user to select from these combinations, even users without specialized knowledge can set the control constants. This allows the control constants to be easily changed by manual setting even in cases where temperature adjustment is unstable due to various conditions even in the automatic setting mode, or when the automatic setting environment is not suitable due to user preferences.

The compressor control unit 234 outputs the difference between the set temperature and the room temperature and the control constant set by the control constant setting unit 233 as a manipulated variable for PID control of the operating frequency of the compressor 35.

Next, a description will be given of the manipulated variable and the control constant in the PID control of the compressor 35. The manipulated variable u _n of the compressor 35 can be calculated by the following formula (1).

Here, u _n-1 is the manipulated variable in the previous PID control, and Δu is expressed by the following equation (2).

In equation (2), e _n , e _n-1 , and e _n-2 respectively indicate the control variables (for example, the room temperature in the first embodiment) during the current, previous, and previous-previous PID control, and K _p , K _i , and K _d respectively indicate the constant of the proportional term, the constant of the integral term, and the constant of the differential term.

In the first embodiment to be described, the control constant setting unit 233 sets _Kp , Ki, and _Kd based on the indoor temperature, which allows the compressor 35 to be operated appropriately in accordance with the environment of the target space and prevents indoor temperature hunting. The control constant setting unit 233 in the first embodiment can set the control constants _Kp , _Ki , and _Kd based on the time from the start of the _compressor 35 until the indoor temperature reaches a predetermined amount of change and the amount of change in the indoor temperature that is the control target.

That is, the control constants _Kp , _Ki , and _Kd can be set based on the graph shown in Fig. 5. Fig. 5 is a graph showing the response of PID control in the first embodiment. In the graph of Fig. 5, the vertical axis represents the controlled variable (room temperature in the first embodiment) and the horizontal axis represents time t, with the compressor 35 starting operation at t = 0.

5, when the compressor 35 starts, the indoor temperature generally does not change immediately, and it takes a certain amount of time for the operation of the compressor 35 to affect the indoor temperature. Here, assuming that the dead time L is the time from the start of control (t=0) until the line extending the slope in the case where the controlled variable changes linearly intersects with the line extending the controlled variable at the start of control (t=0), and the slope of the controlled variable in the linear change is the maximum slope R, the control constant setting unit 233 calculates the control constants _Kp , _Ki , and _Kd for the proportional, integral, and differential terms using the following equation (3). In equation (3), a, b, and c represent coefficients.

The control constant setting unit 233 outputs the control constant calculated using equation (3) to the compressor control unit 234. The compressor control unit 234 applies the output control constant to equations (1) and (2) to calculate the operating frequency of the compressor 35, i.e., the manipulated variable, and controls the operation of the compressor 35.

By performing PID control using control constants calculated based on the maximum slope R and dead time L in this way, the compressor control unit 234 in the first embodiment can control the compressor 35 while taking into account the variability of the indoor temperature. This allows the air conditioning unit 10 to prevent hunting of the indoor temperature, which is the object of control, and enables efficient air conditioning.

Next, feedback control in the first embodiment will be described. Figure 6 is a flowchart showing feedback control in the first embodiment. The processing shown in Figure 6 is mainly performed by the control unit 23.

The control unit 23 starts processing from step S1000. In step S1001, the control unit 23 starts the compressor 35. During start-up control, the compressor 35 is operated at a higher speed than during steady-state operation for a certain period of time, in order to ensure the reliability of the compressor 35.

Next, in step S1002, the temperature acquisition unit 232 acquires the indoor temperature measured by the temperature sensor 24. Then, in step S1003, the control constant setting unit 233 calculates the control constants for PID control. The control constant setting unit 233 outputs the calculated control constants to the compressor control unit 234. That is, in the embodiment being described, after transitioning to normal control, the operation of the compressor 35 is controlled using the control constants calculated based on the temperature change during startup control.

In step S1004, the compressor control unit 234 calculates the operating frequency of the compressor 35 as a manipulated variable based on the calculated control constant, and controls the operation of the compressor 35.

After step S1004, the process proceeds to step S1005, where it ends. By performing the above-described processing, the control unit 23 can perform PID control using the indoor temperature as the controlled variable. The processing shown in Figure 6 allows PID control to be performed with appropriately set control constants, and the air conditioning device 10 can perform air conditioning while preventing indoor temperature hunting.

Figure 7 shows an example of an air conditioning device 10 that performs PID control using the first embodiment. Figure 7 is a graph showing the progress of room temperature using the air conditioning device 10 of the first embodiment. The solid line in Figure 7 shows the room temperature when PID control is performed by adjusting the control constants using the method of the first embodiment, and the dashed line shows the room temperature when PID control is performed without adjusting the control constants.

As shown in Figure 7, by applying the method according to the first embodiment, hunting of the indoor temperature is suppressed, and the indoor temperature approaches the set temperature in a short time. Therefore, it has been demonstrated that efficient air conditioning can be achieved by applying the first embodiment.

So far, the first embodiment has been described. Next, the second embodiment will be described. In the second embodiment, the control variable in PID control is the refrigerant temperature of the indoor heat exchanger 22. Note that in the following description of the second embodiment, matters common to the first embodiment will be omitted as appropriate.

Figure 8 is a control block diagram for the second embodiment. In the second embodiment, the target temperature setting unit 231 calculates the target value of the refrigerant temperature, which is the controlled variable, and outputs it as the set temperature. The target refrigerant temperature may be calculated from the indoor temperature setting using the remote control 40, or may be entered as a numerical value directly.

In addition, the temperature acquisition unit 232 in the second embodiment acquires the refrigerant temperature from a temperature sensor 24 installed near the indoor heat exchanger 22. Here, the temperature acquisition unit 232 acquires the refrigerant evaporation temperature when the air conditioning unit 10 is in cooling operation, and acquires the refrigerant condensation temperature when the air conditioning unit 10 is in heating operation. The temperature acquisition unit 232 outputs the acquired temperature to the control constant setting unit 233.

The control constant setting unit 233 sets the control constant for PID control based on the acquired refrigerant temperature. The control constant in the second embodiment is calculated from equation (3) based on the dead time L and the maximum slope R of the refrigerant temperature, similar to the method described in the first embodiment. The control constant setting unit 233 outputs the calculated control constant to the compressor control unit 234.

The compressor control unit 234 outputs the difference between the set temperature and the refrigerant temperature and the control constant set by the control constant setting unit 233 as a manipulated variable for PID control of the operating frequency of the compressor 35.

In this way, in the second embodiment, the control constant is set using the refrigerant temperature as the controlled variable, and PID control is performed. This prevents refrigerant temperature hunting, and ultimately prevents indoor temperature hunting, allowing air conditioning to be performed.

Next, a third embodiment will be described with reference to Figure 9. Figure 9 is a control block diagram for the third embodiment. The third embodiment is PID control of the compressor 35 in an air conditioning apparatus 10 equipped with multiple indoor units 20 for one outdoor unit 30. For example, in the case of an air conditioning apparatus 10 equipped with multiple indoor units 20, such as VRF, the compressor 35 is controlled as in the third embodiment. When attempting to PID control the compressor 35 when multiple indoor units 20 are installed, the conditions of the spaces in which the indoor units 20 are installed differ, and in the past, this has prevented the compressor 35 from operating appropriately as required by each indoor unit, resulting in indoor temperature hunting. Therefore, in the third embodiment, the control constants for PID control are appropriately set to prevent hunting.

In the third embodiment described below, an example is shown in which PID control is performed based on the room temperature, as in the first embodiment, but this is not a limitation on the embodiment. Therefore, in the third embodiment, PID control may also be performed based on the refrigerant temperature, as in the second embodiment.

In the third embodiment, each of the multiple indoor units 20 includes a temperature acquisition unit 232 and a control constant setting unit 233. Here, as shown in Figure 9, it is assumed that there are two indoor units 20a and 20b. Note that the number of indoor units 20 shown in Figure 9 is an example, and there may be three or more indoor units 20 in the third embodiment.

In the third embodiment, each of the indoor units 20a and 20b calculates a control constant. That is, the indoor unit 20a sets a control constant based on the indoor temperature acquired by the temperature acquisition unit 232a and outputs it to the compressor control unit 234, and the indoor unit 20b sets a control constant based on the indoor temperature acquired by the temperature acquisition unit 232b and outputs it to the compressor control unit 234.

The compressor control unit 234 calculates the operation amount of the compressor 35 based on the control constants output by the control constant setting units 233a, 233b of each indoor unit 20a, 20b, and controls its operation. If the control constants differ for each indoor unit, an average value may be calculated, or one of the control constants may be selected depending on the conditions. Furthermore, if there are three or more indoor units 20, the operation amount may be calculated by weighting the values of each control constant.

In the third embodiment described above, even when there are multiple indoor units 20, the control constants can be set appropriately, thereby preventing hunting of indoor temperatures.

As explained above, according to the first to third embodiments, the control constants in PID control can be appropriately set. In particular, in the past, setting the control constants required specialized knowledge, and it was difficult to change the control constants after the air conditioning unit 10 was installed. However, according to the embodiments described above, the control constants can be calculated based on the maximum slope R and dead time L, making it possible to set the control constants according to the state of the air-conditioned space. This allows the indoor temperature to be quickly brought to the desired temperature, providing comfortable and efficient air conditioning.

Furthermore, while the embodiment described employs PID control of the compressor 35, this is not a limitation of the embodiment. Therefore, even when PID control is performed on a device related to the refrigeration cycle other than the compressor 35, the control constants may be set using the method described and PID control may be performed.

The embodiments of the present invention described above provide an air conditioning apparatus and method that feedback controls a compressor using appropriate control constants.

The functions of the above-described embodiments of the present invention can be realized by a device-executable program written in C, C++, C#, Java (registered trademark), etc. The program of this embodiment can be stored and distributed on a device-readable recording medium such as a hard disk drive, CD-ROM, MO, DVD, flexible disk, EEPROM (registered trademark), or EPROM, and can also be transmitted over a network in a format that can be used by other devices.

The present invention has been described above using embodiments, but the present invention is not limited to the above-described embodiments. Any embodiment that can be conceived by a person skilled in the art is within the scope of the present invention as long as it achieves the functions and effects of the present invention.

10...Air conditioning device,
20...indoor unit,
21...Indoor fan,
22...Indoor heat exchanger,
23...control unit,
24...Temperature sensor,
30...Outdoor unit,
31...expansion valve,
32...Outdoor heat exchanger,
33...Outdoor fan,
34...Four-way valve,
35...Compressor,
40...Remote control,
231...Target temperature setting section,
232...Temperature acquisition unit,
233...control constant setting unit,
234...Compressor control unit

Claims (6)

An air conditioning apparatus comprising: a compressor constituting a refrigeration cycle; a temperature sensor that measures the temperature of an environment constituting the refrigeration cycle; and control means that feedback-controls the operation of the compressor based on the temperature measured by the temperature sensor,
The control means
a manual setting means for setting a control constant of the feedback control based on an operation input by a user;
an automatic setting means for setting the control constant based on the temperature measured by the temperature sensor;
The manual setting means and the automatic setting means can be switched to each other.
Air conditioning equipment. The automatic setting means
setting the control constant based on the temperature measured by the temperature sensor during a certain period of time from the start of the compressor;
The air conditioning apparatus according to claim 1. The automatic setting means
The control constant is calculated based on the slope when the temperature change becomes linear and the dead time after the compressor is started.
The air conditioning apparatus according to claim 1 or 2. The temperature measured by the temperature sensor is the temperature of the space to be air-conditioned.
The air conditioning apparatus according to any one of claims 1 to 3. The temperature measured by the temperature sensor is the temperature of the refrigerant in the indoor heat exchanger.
The air conditioning apparatus according to any one of claims 1 to 3. The air conditioning apparatus includes a plurality of indoor units each equipped with the control means and the temperature sensor.
The air conditioning apparatus according to any one of claims 1 to 5.