A control method for heating and refrigeration target values

Abstract

The application discloses a control method of heating and refrigeration target value, which is suitable for constant temperature control under normal temperature. Two-way output of a temperature regulator is used to control heating and refrigeration respectively, and heating and refrigeration mode identification is set in the temperature regulator measurement and control program. Only heating adjustment can be output in the heating mode, and only refrigeration adjustment can be output in the refrigeration mode. Based on the temperature change caused by heating or refrigeration adjustment, compared with the temperature change caused by heat absorption or heat dissipation, the duration is shorter and the speed is faster. Three automatic conversion methods of heating and refrigeration mode are provided, which can avoid the interference between heating and refrigeration adjustment, and realize more accurate constant temperature control.

Description

Technical Field

[0001] This invention belongs to the field of temperature control technology, and mainly targets constant temperature control technology for specific target values ​​within the normal temperature range; specifically, it is a control method for heating and cooling target values ​​being the same. Background Technology

[0002] The domestic invention patent CN215282533U discloses a multi-layer water-air dual-circulation cement specimen curing chamber based on water spray drive. Its control method, where heating and cooling target values ​​are the same, uses a dual-output temperature controller to separately control heating and cooling, with a third output relay controlling the interlocking and switching between heating and cooling. By setting the setpoint and hysteresis of the third output, if the temperature is less than the setpoint minus the hysteresis, it enters heating mode; if the temperature is greater than the setpoint plus the hysteresis, it enters cooling mode. The problem is that if the hysteresis value is set too small, it will be affected by overshoot, leading to incorrect switching; if the hysteresis value is set too large, the switching will be untimely, causing the corresponding adjustment to fail to start in time, affecting the constant temperature control effect. Summary of the Invention

[0003] To address the shortcomings and defects of existing technologies, the inventors, through experimentation and research, discovered that current temperature controllers cannot distinguish whether temperature changes are caused by heating or cooling regulation, or by heat absorption or dissipation from the curing chamber or the heating of the cement test block. This leads to incorrect mode switching and affects the effectiveness of constant temperature control. Therefore, the inventors propose a precise and easy-to-implement constant temperature control method that achieves more accurate constant temperature control through the accurate and timely switching between heating and cooling regulation. Specifically, this invention is implemented as follows:

[0004] The main technical solution of this invention is a control method for achieving the same target values ​​for heating and cooling, which has the following functions:

[0005] 1. Add a function to interlock and switch between heating and cooling modes on the temperature controller;

[0006] Method 1,

[0007] The main control output relay of the temperature controller serves as a mode indicator, controlling the interlocking and switching between heating and cooling modes. The upper limit alarm output and the lower limit alarm output control cooling and heating respectively. In heating mode, the main control output relay connects the lower limit alarm output power and disconnects the upper limit alarm output power; in cooling mode, the main control output relay disconnects the lower limit alarm output power and connects the upper limit alarm output power.

[0008] Method 2,

[0009] The main control output and upper limit alarm output of the temperature controller are used to control heating and cooling respectively. A mode identifier is added to the temperature controller's measurement and control program. Before activating the main control output, the mode identifier is checked. If it is heating mode, an output is made; otherwise, no output is made. Similarly, before activating the upper limit alarm output, the mode identifier is checked. If it is cooling mode, an output is made; otherwise, no output is made.

[0010] Second, add a function to the temperature controller's measurement and control program to automatically determine the heating and cooling mode identifiers based on preset parameters and temperature change characteristics. Utilizing the fact that temperature changes caused by heating and cooling occur at a faster rate than those caused by heat dissipation and absorption, three mode identifier determination schemes are formed based on the duration of temperature change, the rate of temperature change, or a segmented preset conversion difference ΔT, from which any one of these schemes can be selected.

[0011] Option 1: Set the following in the temperature controller's measurement and control program: target value T; conversion difference ΔT; measurement counting threshold N.

[0012] When the temperature is ≤ T - ΔT, the measurement count n records the number of readings. If n ≥ the measurement count threshold N, the mode identifier is set to heating. During the counting process, if a reading with a temperature > T - ΔT occurs, the measurement count n is reset to zero and the counting starts again.

[0013] When the temperature is ≥ T + ΔT, record the measurement count n. If n ≥ the measurement count threshold N, the mode identifier is set to cooling. During the counting process, if a reading of temperature < T + ΔT occurs, the measurement count n is cleared to zero and the counting starts again.

[0014] Note: Temperature fluctuations exceeding "T±ΔT" caused by heating and cooling are unstable fluctuations with short durations; temperature changes caused by heat dissipation and absorption by a constant-temperature object are stable and have a long duration. The former mode does not switch to avoid overshoot interference.

[0015] Option 2: Add the following to the temperature controller's measurement and control program: measurement counting threshold N.

[0016] Take two adjacent measured values ​​T0 and T1, and count the measurement n+1. If |T1-T0| < amplitude set value temperature difference threshold A, then take the next reading T2, and count the measurement n+1. Continuously read the values ​​and record the measurement count n.

[0017] When |Tn-T0|≥ temperature difference threshold A, then compare the measurement count n with the measurement count threshold N.

[0018] If the interval n between Tn and T0 is less than the measurement count threshold N, the mode identifier remains unchanged, the heating judgment count j is reset to zero, and the cooling judgment count z is reset to zero.

[0019] If n≥N and Tn>T0, then the cooling judgment count z+1, the heating judgment count j is cleared to zero, and when z≥the judgment count threshold M, the mode identifier is set to cooling mode;

[0020] If n≥N and Tn<T0, then the heating judgment count j+1, the cooling judgment count z is cleared to zero, and when j≥ the judgment parameter threshold M, the mode identifier is set to heating mode.

[0021] The above process is repeated cyclically with the measurement and control program.

[0022] Note: When the temperature changes rapidly, it can be assumed that the change is caused by heating or cooling adjustments, and the mode will not switch. When the temperature rises slowly, it can be assumed that the change is caused by heat absorption and heating of the cement sample, and the mode will switch to cooling mode. When the temperature drops slowly, it can be assumed that the change is caused by heat dissipation, and the mode will switch to heating mode.

[0023] Option 3: Add the following to the temperature controller's measurement and control program: target value T; segmented conversion differences ΔT0, ΔT1, ΔT2; segmented time thresholds t1, t2 or measurement counting thresholds N1, N2;

[0024] The conversion differences ΔT0, ΔT1, and ΔT2, or ΔT0 and ΔT1 (the conversion differences can also be set to two different values), are set in segments. Timing t or recording the measurement count n begins after the heating or cooling adjustment is completed. In the first time segment, when the temperature ≤ T - ΔT0, the mode indicator is set to heating mode; when the temperature ≥ T + ΔT0, the mode indicator is set to cooling mode. In the second time segment, when the temperature ≤ T - ΔT1, the mode indicator is set to heating mode; when the temperature ≥ T + ΔT1, the mode indicator is set to cooling mode. In the third time segment, when the temperature ≤ T - ΔT2, the mode indicator is set to heating mode; when the temperature ≥ T + ΔT2, the mode indicator is set to cooling mode.

[0025] Note: The conversion difference ΔT is set in segments. After heating or cooling output stops, a larger ΔT0 value is used in the first time period to avoid overshoot and incorrect mode conversion; a moderate ΔT1 value is used in the second time period to ensure normal mode conversion; and a smaller ΔT2 value is used in the third time period when the temperature changes slowly to ensure timely mode conversion.

[0026] The working principle and beneficial effects of this invention: This invention employs three schemes to achieve its purpose in constant temperature control. First, temperature fluctuations exceeding the "target value T ± ΔT" caused by overshoot in heating and cooling are unstable and short-lived; temperature changes caused by heat dissipation and absorption in the curing chamber and heating of the test block are stable and long-lasting. The former does not switch modes to avoid overshoot interference. Second, when the temperature changes rapidly, it can be assumed to be caused by heating or cooling adjustments, and the mode does not switch. When the temperature rises slowly, it can be assumed to be caused by heat absorption and heating of the cement test block, and the cooling mode is activated. When the temperature drops slowly, it can be assumed to be caused by heat dissipation, and the heating mode is activated. Third, the switching difference ΔT is set in segments. After heating or cooling adjustments stop, a larger ΔT0 value is used in the first time period to avoid incorrect mode switching caused by overshoot; a moderate ΔT1 value is used in the second time period to ensure normal mode switching; and a smaller ΔT2 value is used in the third time period when the temperature changes slowly to ensure timely mode switching. Attached Figure Description

[0027] Figure 1 These are temperature control schematic diagrams for Embodiments 1 and 2 of the control method of the present invention, which uses the same target values ​​for heating and cooling.

[0028] Figure 2 This is a temperature control schematic diagram of Embodiment 5 of the control method of the present invention, which uses the same target values ​​for heating and cooling. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0030] Example 1:

[0031] The main control output relay of the temperature controller serves as a mode identifier, while the lower limit alarm output and upper limit alarm output control heating and cooling respectively. Setting parameters: target value T, conversion difference ΔT, and measurement count threshold N.

[0032] When the temperature is ≤ T - ΔT, the system starts counting n for consecutive temperature readings ≤ T - ΔT. If the count n ≥ the count threshold N, the main control output relay activates the lower limit alarm power supply and deactivates the upper limit alarm power supply, entering heating mode. During the counting process, if a temperature reading > T - ΔT occurs, the count n is reset to zero.

[0033] When the temperature is ≥ T + ΔT, record the measurement count n for consecutive temperature readings ≥ T + ΔT. If the measurement count n ≥ the measurement count threshold N, the main control output relay shuts off the lower limit alarm power and connects the upper limit alarm power, entering cooling mode. During the counting process, if a temperature reading < T + ΔT occurs, the measurement count n is reset to zero.

[0034] Example 2

[0035] The main control output and upper limit alarm output of the temperature controller control heating and cooling respectively. Add heating mode and cooling mode identifiers to the measurement and control program, and store the measurement count n. Add preset parameters: target value T; conversion difference ΔT; measurement count threshold N.

[0036] When the temperature is below the heating start point, before activating the main control output, it checks if the heating mode flag is equal to 1. If it is, it outputs; otherwise, it does not. When the temperature is above the cooling start point, before activating the upper limit alarm output, it checks if the cooling mode flag is equal to 1. If it is, it outputs; otherwise, it does not.

[0037] When the temperature is ≤ T - ΔT, the continuous measurement count n is saved. If n ≥ N, it is considered that the instability exceeds the limit due to heat dissipation, and the mode flag is set to heating mode, i.e., the heating mode flag is set to 1 and the cooling mode flag is set to 0. During the counting process, if the temperature is > T - ΔT, it is considered that the instability exceeds the limit due to cooling, and the measurement count n is reset to zero.

[0038] When the temperature is ≥ T + ΔT, the continuous measurement count n is saved. If n ≥ N, it is considered a stable over-limit caused by heat absorption, and the system is switched to cooling mode, i.e., the heating mode flag is set to 0 and the cooling mode flag is set to 1. During the counting process, if the temperature is < T + ΔT, it is considered an unstable over-limit caused by heating, and the measurement count n is reset to zero.

[0039] Example 3

[0040] The main control output and upper limit alarm output of the temperature controller control heating and cooling respectively. The mode identifier is set in the measurement and control program. The main control can output in heating mode and the upper limit alarm can output in cooling mode.

[0041] Preset parameters: temperature difference threshold A; measurement number threshold N; judgment number threshold M.

[0042] Storage counts: measurement count n; heating judgment count j; cooling judgment count z.

[0043] Take two adjacent measurements T0 and T1, and count the measurements n+1. If |T1-T0| < temperature difference threshold A, meaning the temperature change is not large enough, take the next reading T2, and count the measurements n+1. Continue judging subsequent readings until |Tn-T0| ≥ temperature difference threshold A, and save the measurement count n. At this point, we can determine the time taken for a certain temperature change. Similarly, we can determine the temperature change that occurs within a certain time period, that is, the rate of temperature change.

[0044] When |Tn-T0|≥ temperature difference threshold A, compare the measurement count n and the measurement number threshold N.

[0045] If the interval n between Tn and T0 is less than N, it means that the time taken for a certain temperature change is short, that is, the temperature change rate is fast. It is considered to be caused by heating or cooling. Keep the mode identifier unchanged, clear the heating judgment count j to zero, clear the cooling judgment count z to zero, and interrupt the heating and cooling judgment counts.

[0046] If n≥N and Tn>T0, it is considered that the temperature rise is caused by heat absorption, so the cooling judgment count z+1, the heating judgment count j is cleared to zero, the heating judgment count is interrupted, and when z≥judgment number threshold M, it is considered that the cooling judgment result is obtained continuously, and the mode identifier is set to cooling mode.

[0047] If n≥N and Tn<T0, it is considered that the temperature drop is caused by heat dissipation. Then, the heating judgment count j+1, the cooling judgment count z is cleared to zero, and the cooling judgment count is interrupted. When j≥ the judgment count threshold M, it is considered that the heating judgment result is obtained continuously, and the mode identifier is set to heating mode.

[0048] The above process is repeated cyclically with the measurement and control program.

[0049] Example 4

[0050] The main control output relay of the temperature controller serves as a mode identifier, while the upper limit alarm output and lower limit alarm output control cooling and heating, respectively.

[0051] Preset parameters: Set the main control hysteresis value Hy0 and Hy1 in two segments, and the timing threshold t or measurement counting threshold N.

[0052] After heating or cooling stops, start timing or record the measurement count n.

[0053] Within the time range of 0 to t or the count range of 0 to N, a larger hysteresis value Hy0 is selected. If the temperature is ≤ T - Hy0, the main control output relay connects the lower limit alarm power supply and disconnects the upper limit alarm power supply, entering the heating mode. If the temperature is ≥ T + Hy0, the main control output relay connects the upper limit alarm power supply and disconnects the lower limit alarm power supply, entering the cooling mode.

[0054] After time t or count N, the overshoot effect disappears, and a smaller hysteresis value Hy1 is selected. If the temperature ≤ T - Hy1, the main control output relay connects the lower limit alarm output power, entering heating mode. If the temperature ≥ T + Hy1, the main control output relay connects the upper limit alarm output power, entering cooling mode.

[0055] Example 5

[0056] The main control output and upper limit alarm output of the temperature controller control heating and cooling respectively. The measurement and control program sets the mode identifier and timer or stores the count. The conversion difference ΔT0, ΔT1, and ΔT2 are set in three segments, and the timing thresholds t1 and t2 or the measurement count thresholds N1 and N2 are set.

[0057] When the mode identifier is 1, it is heating mode, heating adjustment can be output, and cooling adjustment is prohibited from output; when the mode identifier is 0, it is cooling mode, cooling adjustment can be output, and heating adjustment is prohibited from output.

[0058] After heating or cooling is completed, the timer starts timing or the measurement counter (n) starts counting the number of measurements.

[0059] Within the time range of 0 to t1 or the count range of 0 to N1, a larger value ΔT0 is selected to avoid overshoot interference during mode transition. If the temperature is ≤ T - ΔT0, the mode indicator is set to 1, and the mode is entered into heating mode. If the temperature is ≥ T + ΔT0, the mode indicator is set to 0, and the mode is entered into cooling mode.

[0060] Within the time interval t1 to t2 or the count interval N1 to N2, the overshoot effect disappears. A suitable value for ΔT1 is selected, ensuring stable and reliable switching between heating and cooling. If the temperature is ≤ T - ΔT1, the mode indicator is set to 1, entering heating mode. If the temperature is ≥ T + ΔT1, the mode indicator is set to 0, entering cooling mode.

[0061] When the temperature changes slowly after time t2 or count N2, a smaller value ΔT2 is selected to ensure timely mode switching. If the temperature is ≤ T - ΔT2, the mode indicator is set to 1, entering heating mode. If the temperature is ≥ T + ΔT2, the mode indicator is set to 0, entering cooling mode. See the working process... Figure 2 .

Claims

1. A control method for achieving the same target values ​​for heating and cooling, characterized in that... Includes the following steps: Step S1: In the temperature controller's measurement and control program, set the heating and cooling mode indicators, or use one of the temperature controller's output relays as the mode indicator. Step S2: The temperature regulator control program includes: before the heating regulation output, first determine the mode identifier; heating is only started when the heating mode is active, otherwise no output is output; before the cooling regulation output, first determine the mode identifier; cooling is only started when the cooling mode is active, otherwise no output is output. Step S3: In the temperature controller's measurement and control program, add preset parameters and counting variables, or add a timer; the preset parameters and counting variables added will vary depending on the method used. The preset parameters include: target value T; conversion difference ΔT, or ΔT0, ΔT1 and ΔT2; measurement counting threshold N, or N1 and N2; timing threshold t, or t1 and t2; temperature difference threshold A; judgment counting threshold M; and the counting variables include: measurement count n; heating judgment count j; and cooling judgment count z. Step S4: In the temperature controller's measurement and control program, add a function to automatically determine the heating and cooling mode identifiers based on preset parameters and temperature change characteristics; taking advantage of the fact that temperature changes caused by heating and cooling are faster than those caused by heat dissipation and heat absorption, three mode identifier determination schemes are formed by the duration of temperature change, the rate of temperature change, or the segmented preset conversion difference ΔT. One approach: Determine the mode identifier based on the duration of the temperature change; When the temperature is ≤ T - ΔT, the measurement count n records the number of readings that meet the condition. If n ≥ the measurement count threshold N, the mode identifier is set to heating mode. During the counting process, if a reading that does not meet the condition of temperature ≤ T - ΔT occurs, the counting stops, the measurement count n is cleared to zero, and the mode identifier remains unchanged. When the temperature is ≥ T + ΔT, the measurement count n records the number of readings that meet the condition. If n ≥ the measurement count threshold N, the mode identifier is set to cooling mode. During the counting process, if a reading that does not meet the condition of temperature ≥ T + ΔT occurs, the counting stops, the measurement count n is cleared to zero, and the mode identifier remains unchanged. Option Two: Determine the mode identifier based on the rate of temperature change; Take a measurement value T0 as the initial value, then take the next reading T1, and the measurement count n+1. If |T1-T0|≥Temperature difference threshold A is not satisfied, take the next reading T2, and the measurement count n+1. Continue taking readings in this way until |Tn-T0|≥Temperature difference threshold A, and obtain the measurement count n. When |Tn-T0|≥T temperature difference threshold A, compare the measurement count n and the measurement number threshold N; If n < N, the mode identifier remains unchanged, the heating judgment count j is cleared to zero, and the cooling judgment count z is cleared to zero; If n≥N and Tn>T0, then the cooling judgment count z+1, the heating judgment count j is cleared to zero, and when z≥the judgment count threshold M, the mode identifier is set to cooling mode; If n≥N and Tn<T0, then the heating judgment count j+1, the cooling judgment count z is cleared to zero, and when j≥ the judgment count threshold M, the mode identifier is set to heating mode; Option 3: Determine the mode identifier based on the pre-set conversion difference for each segment; After heating or cooling adjustment is completed, timer t starts counting, or measurement count n starts counting; in the first time period or counting segment, when the temperature ≤ T - ΔT0, the mode indicator is set to heating mode; when the temperature ≥ T + ΔT0, the mode indicator is set to cooling mode; in the second time period or counting segment, when the temperature ≤ T - ΔT1, the mode indicator is set to heating mode; when the temperature ≥ T + ΔT1, the mode indicator is set to cooling mode; in the third time period or counting segment, when the temperature ≤ T - ΔT2, the mode indicator is set to heating mode; when the temperature ≥ T + ΔT2, the mode indicator is set to cooling mode.

2. The control method for achieving the same target values ​​for heating and cooling according to claim 1, characterized in that, Steps S1, S2, S3, and S4 include one of the following methods: The main control output relay of the temperature controller serves as a mode indicator, while the lower limit alarm output and the upper limit alarm output control heating and cooling respectively. When the temperature is ≤ T - ΔT, the measurement count n records the number of readings that meet the condition. If n ≥ the measurement count threshold N, the main control output relay connects the lower limit alarm power supply and disconnects the upper limit alarm power supply, entering the heating mode. During the counting process, if a reading that does not meet the condition of temperature ≤ T - ΔT occurs, the measurement count n is cleared to zero, and the mode identifier remains unchanged. When the temperature is ≥ T + ΔT, the measurement count n records the number of readings that meet the conditions. If n ≥ the measurement count threshold N, the main control output relay turns off the lower limit alarm power supply and turns on the upper limit alarm power supply, entering the cooling mode. During the counting process, if a reading that does not meet the condition of temperature ≥ T + ΔT occurs, the measurement count n is reset to zero, while the mode identifier remains unchanged.

3. The control method for achieving the same target values ​​for heating and cooling according to claim 1, characterized in that, Steps S1, S2, S3, and S4 include method two: The main control output and upper limit alarm output of the temperature controller control heating and cooling respectively. In the measurement and control program, heating mode identifier and cooling mode identifier are set. When the temperature is lower than the heating start point, before starting the main control output, check if the heating mode flag is =1. If it is, output; otherwise, do not output. When the temperature is higher than the cooling start point, before starting the upper limit alarm output, check if the cooling mode flag is =1. If it is, output; otherwise, do not output. When the temperature is ≤ T - ΔT, the measurement count n records the number of readings that meet the condition. If n ≥ the measurement count threshold N, the system switches to heating mode, i.e., the heating mode flag is set to 1 and the cooling mode flag is set to 0. During the counting process, if a reading that does not meet the condition of temperature ≤ T - ΔT occurs, the measurement count n is cleared to zero, and the mode flag remains unchanged. When the temperature is ≥ T + ΔT, the measurement count n records the number of readings that meet the conditions. If n ≥ the measurement count threshold N, the mode is switched to cooling mode, that is, the heating mode flag is set to 0 and the cooling mode flag is set to 1. During the counting process, if a reading that does not meet the condition of temperature ≥ T + ΔT occurs, the measurement count n is reset to zero, while the mode identifier remains unchanged.

4. The control method for achieving the same target values ​​for heating and cooling according to claim 1, characterized in that: The main control output and the upper limit alarm output of the temperature controller control heating and cooling respectively. A mode identifier is set in the measurement and control program. The main control output is only output after the heating mode is determined, and the upper limit alarm output is only output after the cooling mode is determined. Take a measurement number T0 as the initial value, and continuously judge the subsequent readings until Tn satisfies |Tn-T0|≥ temperature difference threshold A, and obtain the measurement count n; When |Tn-T0|≥T temperature difference threshold A, compare the measurement count n and the measurement number threshold N; If n < N, the mode identifier remains unchanged, the heating judgment count j is cleared to zero, and the cooling judgment count z is cleared to zero; If n≥N and Tn>T0, the cooling judgment count z+1, the heating judgment count j is cleared to zero, and when z≥the judgment count threshold M, the mode identifier is set to cooling mode; If n≥N and Tn<T0, then the heating judgment count j+1, the cooling judgment count z is cleared to zero, and when j≥ the judgment count threshold M, the mode identifier is set to heating mode.

5. The control method for achieving the same target values ​​for heating and cooling according to claim 1, characterized in that: The main control output relay of the temperature controller serves as a mode indicator, while the upper limit alarm output and lower limit alarm output control cooling and heating respectively. After the lower limit alarm output or the upper limit alarm output stops, the timer t starts counting or the measurement count n starts counting; Within the time interval 0 to t or the count interval 0 to N, if the temperature is ≤ T - ΔT0, the main control output relay connects the lower limit alarm power supply and disconnects the upper limit alarm power supply, entering the heating mode; if the temperature is ≥ T + ΔT0, the main control output relay connects the upper limit alarm power supply and disconnects the lower limit alarm power supply, entering the cooling mode. After time t or count N, if the temperature is ≤ T - ΔT1, the main control output relay connects the lower limit alarm output power and enters the heating mode; if the temperature is ≥ T + ΔT1, the main control output relay connects the upper limit alarm output power and enters the cooling mode.

6. The control method for achieving the same target values ​​for heating and cooling according to claim 1, characterized in that: The main control output and upper limit alarm output of the temperature controller control heating and cooling respectively; a mode identifier is set in the measurement and control program; when the mode identifier is 1, it is heating mode, heating regulation can be output, and cooling regulation is prohibited from output; when the mode identifier is 0, it is cooling mode, cooling regulation can be output, and heating regulation is prohibited from output. After the main control output or the upper limit alarm output stops, the timer t starts counting or the measurement counter n starts counting; Within the time interval 0 to t1 or the count interval 0 to N1, if the temperature is ≤ T - ΔT0, the mode indicator is set to 1, and the heating mode is entered; if the temperature is ≥ T + ΔT0, the mode indicator is set to 0, and the cooling mode is entered. During time intervals t1 to t2 or within the count range N1 to N2, if the temperature is ≤ T - ΔT1, the mode indicator is set to 1, and the system enters heating mode; if the temperature is ≥ T + ΔT1, the mode indicator is set to 0, and the system enters cooling mode. After time t2 or count N2, if the temperature is ≤ T-ΔT2, the mode identifier is set to 1, and the heating mode is entered; if the temperature is ≥ T+ΔT2, the mode identifier is set to 0, and the cooling mode is entered.

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