Air conditioner heating comfort evaluation method

Abstract

The invention relates to an air conditioner thermal performance evaluation technology, and discloses an air conditioner heating comfort evaluation method, which quickly evaluates the air supply characteristic of an air duct through an air speed field so as to indirectly evaluate the heating temperature field characteristic of a room, so that the qualification rate of temperature field comfort evaluation and the user experience of a product are improved. The method comprises the following steps: S1, carrying out a wind speed field test on an air conditioner hanging unit air duct in a heating state to obtain wind speed field distribution data; s2, evaluating the wind speed field distribution data based on a preset wind speed field standard, and if the wind speed field distribution data meets the preset wind speed field standard, executing a step S3; if not, the step S1 is executed after the air conditioner air channel is optimized; s3, a temperature field test is conducted on the room where the air conditioner is located, and temperature field distribution data are obtained; and S4, based on a preset temperature field standard, performing scoring evaluation on the temperature field distribution data to obtain a temperature field comfort evaluation result. The method is suitable for evaluating the heating comfort of the air conditioner.

Description

Technical Field

[0001] This invention relates to air conditioning thermal performance evaluation technology, specifically to an air conditioning heating comfort evaluation method. Background Technology

[0002] As a core device for regulating the indoor environment, air conditioning plays a crucial role in winter heating, especially in cold regions, directly impacting user comfort and energy efficiency. However, traditional air conditioning heating evaluations often focus on hard indicators such as energy efficiency ratings and temperature control accuracy, neglecting comfort during the heating process. This leads to frequent user experience issues in actual use. For example, some air conditioners exhibit excessive vertical temperature differences (significant temperature difference between head and feet), uneven room temperature distribution, and direct warm air blowing onto the body, causing dryness or stuffiness. These problems have become major causes of user complaints.

[0003] The scientific evaluation and optimization of air conditioning heating comfort is a core requirement for enhancing product competitiveness. A systematic evaluation method can not only provide clear guidance for companies to improve heating technology (such as optimizing airflow direction adjustment logic and fan speed parameter settings), but also ensure that users receive a natural and even warmth during winter heating, reducing discomfort caused by temperature fluctuations. However, existing technologies for evaluating heating comfort have significant shortcomings: On the one hand, although traditional temperature field tests can directly reflect the room heating effect, the test cycle is as long as 2 days and requires a special test environment, resulting in low evaluation efficiency and difficulty in meeting the needs of large-scale product iteration. On the other hand, wind speed field and temperature field are directly related, but their application in comfort evaluation has not yet formed a standardized method. It is impossible to quickly evaluate the air supply characteristics of the duct through the wind speed field, and thus indirectly predict the performance of the temperature field. This results in insufficient guidance for duct optimization in product development and affects the pass rate of temperature field comfort evaluation.

[0004] Therefore, there is an urgent need for an air conditioning heating comfort evaluation method that balances efficiency and accuracy. By establishing the correlation between wind speed field and temperature field, and taking advantage of the high efficiency of wind speed field testing (which can be completed in 1 hour) and the fact that it does not require a special working environment, a rapid screening and optimization of heating performance can be achieved. Then, combined with temperature field testing, a final evaluation can be conducted, thereby improving the heating comfort of the product and promoting the development of air conditioning heating technology towards a more intelligent and humanized direction. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for evaluating the comfort of air conditioning heating, which can quickly assess the air duct air supply characteristics through wind speed field to indirectly assess the room heating temperature field characteristics, thereby improving the pass rate of temperature field comfort evaluation and the user experience of the product.

[0006] The present application solves the above technical problems by adopting the technical scheme of: A method for evaluating the heating comfort of an air conditioner, comprising the following steps: S1. performing a wind speed field test on the air conditioner to be tested in a test room in a heating state to obtain wind speed field distribution data; S2. evaluating the wind speed field distribution data based on a preset wind speed field standard, and if the preset wind speed field standard is met, performing step S3; if not, optimizing the air conditioner air duct and returning to step S1; S3. performing a temperature field test on the air conditioner to be tested in a test room in a heating state to obtain temperature field distribution data; S4. evaluating the temperature field distribution data based on a preset temperature field standard to obtain a temperature field comfort evaluation Results.

[0007] Further, in step S2, the preset wind speed field standard includes standards in four dimensions of air supply distance, air supply angle, air flow thickness and floor surface distance.

[0008] Further, the preset wind speed field standard includes a wind speed field standard in a heating initial stage and a wind speed field standard in a heating stable stage; the heating initial stage is a time period in a heating mode after the air conditioner is turned on, during which the temperature has not reached a set target temperature; the heating stable stage is a time period in the heating mode, during which the temperature has reached the set target temperature.

[0009] Further, the wind speed field standard in the heating initial stage includes: Air supply distance: horizontal air blowing distance > 4.5 m, and maximum wind speed at the place > 0.5 m / s; Air supply angle: the included angle between the main air flow and the vertical direction is in the range of 25°-40°; Air flow thickness: air flow thickness at the 4.5 m position ≥ 20 mm, and air flow thickness at the 2 m position ≥ 60 mm; Floor surface distance: air flow falls at the 1.5 m-2 m position.

[0010] Further, the wind speed field standard in the heating stable stage includes: Air supply distance: horizontal air blowing distance > 4.5 m, and maximum wind speed at the place > 0.5 m / s; Air supply angle: the included angle between the main air flow and the vertical direction is in the range of 12°-30°; Air flow thickness: air flow thickness at the 4.5 m position ≥ 20 mm, and air flow thickness at the 1 m position ≥ 20 mm; Floor surface distance: air flow falls at the 1 m-1.5 m position.

[0011] Further, in step S2, the wind speed field distribution data is evaluated based on a wind speed field evaluation model, the wind speed field evaluation model includes four dimension indexes of air supply distance, air supply angle, air flow thickness and floor surface distance, each dimension index is assigned with a corresponding score according to a preset interval, and a total score of the wind speed field evaluation is calculated according to the wind speed field distribution data and the wind speed field evaluation model; if the total score of the wind speed field evaluation is greater than or equal to a threshold score, it is determined that the preset wind speed field standard is met.

[0012] Further, in the wind speed field evaluation model, each evaluation dimension is divided into intervals, and each interval is assigned with a corresponding score. The air supply distance is divided into six intervals from far to near according to the horizontal air supply distance, and the corresponding scores decrease from high to low in turn. The air supply angle is divided into six intervals according to the reasonable range of the included angle between the main air flow and the vertical direction, wherein the preset optimal angle interval is assigned with the highest score, and the corresponding scores decrease in turn for the angle ranges deviating from the interval. The air flow thickness is divided into six intervals from large to small according to the air flow thickness value, and the corresponding scores decrease from high to low in turn. The floor surface distance is divided into six intervals from near to far according to the air flow landing position, and the corresponding scores decrease from high to low in turn.

[0013] Further, the optimized air conditioner air duct includes at least one of the following modes: adjusting the air duct profile, adjusting the swing leaf shape, adjusting the swing leaf angle, adjusting the volute profile, optimizing the swing leaf curvature, optimizing the swing leaf width, and optimizing the swing leaf rotation center position.

[0014] Further, a plurality of test rods are arranged in the test room of the temperature field test, and a thermocouple and a wind speed test sensor are arranged at different heights on each test rod.

[0015] Further, in step S4, the preset temperature field standard adopts a preset temperature field evaluation model, which includes the following dimension indexes. Temperature difference: a plurality of intervals are divided according to the difference between the room average temperature and the air conditioner set temperature, the smaller the difference, the higher the corresponding score, and the larger the difference, the lower the corresponding score; the room average temperature is calculated based on the temperature of the preset measuring point in the room; Wind speed: a plurality of intervals are divided according to the average value of the wind speed in the test area, the smaller the wind speed, the higher the corresponding score, and the larger the wind speed, the lower the corresponding score; wherein the wind speed is calculated based on the average value of the wind speed test values of different preset measuring points at the height of the human sitting posture; Temperature rising speed: a plurality of intervals are divided according to the time for the room temperature to reach the preset target temperature, the shorter the time, the higher the corresponding score, and the longer the time, the lower the corresponding score. The temperature field comfort evaluation result is obtained by scoring and evaluating the temperature field distribution data based on the preset temperature field standard, including: scoring each dimension index according to the temperature field distribution data and the temperature field standard, summing the scores of each dimension index to obtain a total score of the temperature field evaluation, and determining that the temperature field is qualified when the total score of the temperature field evaluation reaches a preset qualified score, otherwise, determining that the temperature field is unqualified, and returning to step S1 after continuing to optimize the air conditioner air duct.

[0016] The beneficial effects of the present application are: (1) Improve evaluation efficiency and reduce test cost: The air conditioner air duct air supply characteristics are quickly evaluated by using the wind speed field test to replace the traditional evaluation mode relying only on the temperature field test. Through the pre-screening of the wind speed field, the air duct design can be quickly optimized before the temperature field test, the number of invalid temperature field tests is reduced, the overall evaluation period is shortened, the dependence on the special test environment is reduced, and the large-scale product iteration demand is adapted.

[0017] (2) Improve the temperature field comfort evaluation pass rate: Based on the direct correlation between the wind speed field and the temperature field, the air duct is optimized (such as adjusting the air duct profile, the swing leaf shape and angle, etc.) through the wind speed field test result, which can avoid the temperature field problems (such as large vertical temperature difference, uneven temperature distribution, etc.) caused by the air supply characteristics defects in advance, and improve the pass rate of the final temperature field comfort evaluation from the source.

[0018] (3) Scientific and comprehensive evaluation system: From the four dimensions of the wind speed field air supply distance, angle, air flow thickness and landing distance, and the three dimensions of the temperature field temperature difference, wind speed and temperature rise speed, the evaluation model is constructed in multiple dimensions to ensure that the evaluation of the air conditioner heating comfort is more systematic and accurate, and the limitations of single index evaluation are avoided. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The air conditioner heating comfort evaluation method flowchart in the embodiment of the present application. DETAILED DESCRIPTION

[0020] The application aims to provide an air conditioner heating comfort evaluation method, which indirectly evaluates room heating temperature field characteristics by quickly evaluating air duct air supply characteristics through air velocity field, so as to improve the qualified rate of temperature field comfort evaluation and product user experience. The core idea is to establish the correlation between the air velocity field and the temperature field, to use the air velocity field test as a pre-posed rapid screening method, to combine the temperature field test for final evaluation, and to form an efficient and accurate air conditioner heating comfort evaluation system. Specifically, first, the air duct of the air conditioner hanging machine is tested for the air velocity field under the heating state, the air supply characteristics (such as air supply distance, angle, air flow thickness, floor distance, etc.) are evaluated according to the preset standard, and the non-compliant ones are repeatedly tested by optimizing the air duct (such as adjusting the air duct profile, swing leaf parameters, etc.) until they meet the standard; then, the temperature field test is performed on the compliant models, and the comfort evaluation result is finally obtained based on the indexes such as temperature difference, air velocity, and temperature rise speed.

[0021] The scheme of the application will be further described below in combination with the drawings and examples.

[0022] The present embodiment provides an air conditioner heating comfort evaluation method. Before the scheme is implemented, first, the test preparation and environment construction are performed: A closed room with a length of 5 meters, a width of 3.8 meters, and a height of 2.8 meters is selected as the test room. The room size is close to the typical living room / bedroom space, and has universality. The room walls are made of heat insulation materials to avoid external environmental interference on the temperature field stability. Nine test rods are uniformly arranged in the room, distributed in a 3x3 matrix, with a spacing of 1.5-2.0 meters, to ensure that each area of the room is covered. A thermocouple and an air velocity sensor are fixed on each rod at a height of 0.1 meters, 0.7 meters, and 1.3 meters from the ground, respectively. The temperature at different heights is detected to comprehensively evaluate the vertical temperature difference. The air conditioner hanging machine is installed on the wall of one side of the room, and the air outlet is directed towards the center of the room to ensure that the air supply path is not blocked.

[0023] On the basis of the above test preparation and environment construction, the process of the air conditioner heating comfort evaluation method provided by the present embodiment is as shown in Figure 1 , which includes the following implementation process: S1. Air velocity field test: In this step, the air velocity field test of the air conditioner hanging machine to be tested is performed in the constructed test room under the heating state, and the air velocity field distribution data is obtained. Since the air velocity field directly determines the diffusion path and coverage range of the warm air, and the warm air diffusion characteristics are the premise of the uniformity of the temperature field, the air velocity field test can find the design defects of the air duct in advance, and the process of the air velocity field test is relatively fast, which can avoid the devices with design defects in the air duct from entering the invalid temperature field test.

[0024] In an exemplary embodiment, the process of the air velocity field test includes: Turn on the air conditioning heating mode and run for a period of time, such as 30 minutes, and record the wind speed data of each test point after the wind speed field is stable, and focus on analyzing the following core parameters: Air supply distance: along the horizontal air supply direction of the air conditioner, measure the farthest distance where the wind speed is >0.5m / s (0.5m / s is the critical wind speed for effective diffusion of warm air, and below this value, the warm air is easily diluted by the ambient airflow, and cannot effectively warm up).

[0025] Air supply angle: the maximum wind speed point recorded by the wind speed sensor is connected to fit the main airflow direction, and the angle with the vertical direction is calculated (the angle is too small, the air supply is too steep, and it is easy to concentrate under the air conditioner; the angle is too large, the air supply is too flat, and it is easy to blow directly to the human body, which affects comfort).

[0026] Airflow thickness: at horizontal distances of 4.5m, 2m, and 1m, the vertical range thickness of the airflow (the greater the thickness, the more evenly the warm air diffuses at that location, avoiding local overcooling or overheating).

[0027] Floor distance: record the horizontal distance at which the warm air first contacts the ground (too close and the ground is not covered enough, too far and the warm air is wasted too much on the way, affecting the warming efficiency).

[0028] S2. Based on the wind speed field test results, evaluate the air supply: In this step, based on the preset wind speed field standard, the wind speed field distribution data is evaluated, if it meets the preset wind speed field standard, step S3 is executed; if not, the air conditioner air duct is optimized and returned to step S1.

[0029] In an exemplary embodiment, first, according to user comfort demand analysis combined with a large amount of test data verification, two kinds of air conditioning heating mode wind speed field standards in different stages are set to adapt to different comfort needs, one is the wind speed field standard in the initial heating stage (the room temperature has not reached the set target value), and the other is the wind speed field standard in the stable heating stage (the room temperature has reached the set target value), as shown in Tables 1 and 2.

[0030] Table 1 Wind speed field standard in initial heating stage In the initial heating stage, the user's demand is to quickly warm up, and it is necessary to prioritize the warm air coverage range (long-distance air supply) and diffusion efficiency (thick airflow). The above standard makes the warm air quickly reach the far end of the room through a large angle and a long drop point, uses the heat rising characteristics to drive the overall temperature rise, avoids local low temperature area, and adapts to the demand of rapid temperature rise.

[0031] Table 2 Wind speed field standard in stable heating stage In the heating stable period, the user demand turns to uniform and windless, and it is required to avoid warm air blowing directly to the human body while ensuring the uniform ground temperature. The above standards make the warm air diffuse close to the ground by a smaller angle and a closer landing site, reduce the wind speed at the height of the human body, and ensure the uniform ground temperature, which adapts to the stable and comfortable demand.

[0032] The wind speed field standards in the above two different stages are the judgment standards for whether the wind speed field in the corresponding stage is qualified. In order to facilitate the comparison and judgment of the wind speed field test results and the standards, the wind speed field evaluation model is established in this embodiment. The specific index requirements of the above two wind speed field standards are embodied in the wind speed field evaluation model. The wind speed field test results are evaluated whether they are qualified by comparing the scores of different index levels with the set score threshold.

[0033] Specifically, the evaluation total score of the wind speed field evaluation model is 100 points, including four dimension indexes of air supply distance, angle, air flow thickness and landing surface distance. Each dimension index is given an evaluation total score, for example: air supply distance total score 30 points, angle total score 15 points, air flow thickness total score 30 points, and landing surface distance total score 25 points. And each dimension index is further divided into 6 evaluation levels, which are respectively given different scores, see Table 3.

[0034] Table 3 Wind speed field evaluation model The wind speed field test results are compared with the above wind speed field evaluation model, so as to obtain the respective scores of the four dimension indexes. The total score can be obtained by summation. The total score is compared with the set threshold score (such as 65 points). When the total score is greater than or equal to the threshold score, it is determined to be qualified, and the temperature field test in step S3 can be entered. Otherwise, it is determined to be unqualified, and the air duct needs to be optimized.

[0035] Among them, the optimization measures of the air duct include: adjusting the air duct profile, adjusting the swing leaf shape, adjusting the swing leaf angle, adjusting the volute profile, optimizing the swing leaf curvature, optimizing the swing leaf width, and optimizing the swing leaf rotation center position.

[0036] After optimization, the wind speed field test is performed again in step 1, and the wind speed field evaluation is performed again until the temperature field test in step S3 is entered after reaching the standard.

[0037] S3. Temperature field test: In this step, the temperature field test of the air conditioner hanging machine in the heating state is performed in the test room built, and the temperature field distribution data is obtained. Since the temperature field is a direct embodiment of the user's comfortable feeling, and the wind speed field optimization has laid a foundation for the uniformity of the temperature field, the test can accurately reflect the heating comfort at this time.

[0038] In an exemplary embodiment, the process of the temperature field test is as follows: Keep the air conditioning heating mode, continue to run until the room temperature is stable, record the temperature and wind speed data of each test point, and focus on the following indicators: Temperature difference △T: Calculate the difference between the average temperature of the 9 test points in the room (reflecting the overall temperature level) and the set temperature (the smaller the △T, the more accurate the temperature control, avoiding "overshoot" or "underheating").

[0039] Wind speed V: Take the average wind speed of the 9 test points at a height of 0.7 meters (breathing area for people in sitting position) (excessive wind speed can easily lead to skin moisture loss and dryness; too low wind speed will slow down the spread of warm air and temperature will not be uniform).

[0040] Temperature rise speed: Record the time it takes for the average temperature in the room to rise from the initial temperature (e.g. 15°C) to 25°C (the faster the speed, the weaker the user's discomfort, and the more efficient the use of energy).

[0041] S4. Comfort evaluation based on temperature field test results: In this step, based on the preset temperature field standard, the temperature field distribution data is scored and evaluated to obtain the temperature field comfort evaluation results.

[0042] In an exemplary embodiment, the temperature field standard adopts a preset temperature field evaluation model, also a 100-point system, and the evaluation factors include temperature difference, wind speed, and temperature rise speed, each of which is assigned a total score, such as: temperature difference total score 40 points, wind speed total score 20 points, temperature rise speed total score 40 points. And under each dimension index, it is divided into 6 evaluation grades, respectively assigned different scores, see Table 4.

[0043] Table 4 Temperature field evaluation model Compare the temperature field test results with the above temperature field evaluation model to obtain the respective scores of the three dimension indicators, and the total score can be obtained by summation. Compare the total score with the set threshold score (e.g. 65 points), if the total score is greater than or equal to the threshold score, it is determined to be qualified. Otherwise, it is determined to be unqualified, and the air duct needs to be optimized, returning to step S1 to continue testing and judging.

[0044] Although embodiments of the present application have been described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the present application, and all of them are within the protection scope of the present application.

Claims

1. A method for evaluating heating comfort of an air conditioner, characterized by, The method comprises the following steps: S1. Perform a wind speed field test on the air conditioner under test in a test room in a heating state to obtain wind speed field distribution data; S2. Evaluate the wind speed field distribution data based on a preset wind speed field standard. If the preset wind speed field standard is met, perform step S3. If the preset wind speed field standard is not met, optimize the air conditioner air duct and return to step S1; S3. Perform a temperature field test on the air conditioner under test in a test room in a heating state to obtain temperature field distribution data; S4. Score and evaluate the temperature field distribution data based on a preset temperature field standard to obtain a temperature field comfort evaluation result.

2. The air conditioner heating comfort evaluation method according to claim 1, wherein In step S2, the preset wind speed field standard comprises standards for four dimensions of air supply distance, air supply angle, air flow thickness, and floor surface distance.

3. The air conditioner heating comfort evaluation method according to claim 2, wherein The preset wind speed field standard comprises a wind speed field standard for a heating initial stage and a wind speed field standard for a heating stable stage. The heating initial stage is a time period during which the temperature has not reached a set target temperature after the air conditioner is turned on in a heating mode. The heating stable stage is a time period during which the temperature has reached the set target temperature in the heating mode.

4. The air conditioner heating comfort evaluation method according to claim 3, wherein The wind speed field standard for the heating initial stage comprises: Air supply distance: horizontal air supply distance > 4.5 m, and maximum wind speed at the position > 0.5 m / s; Air supply angle: the included angle between the main air flow and the vertical direction is in the range of 25°-40°; Air flow thickness: air flow thickness at the position of 4.5 m > 20 mm, and air flow thickness at the position of 2 m > 60 mm; Floor surface distance: air flow falls on the floor surface at the position of 1.5 m-2 m.

5. The air conditioner heating comfort evaluation method according to claim 3, wherein The wind speed field standard for the heating stable stage comprises: Air supply distance: horizontal air supply distance > 4.5 m, and maximum wind speed at the position > 0.5 m / s; Air supply angle: the included angle between the main air flow and the vertical direction is in the range of 12°-30°; Air flow thickness: air flow thickness at the position of 4.5 m > 20 mm, and air flow thickness at the position of 1 m > 20 mm; Floor surface distance: air flow falls on the floor surface at the position of 1 m-1.5 m.

6. The air conditioner heating comfort evaluation method according to claim 4 or 5, wherein In step S2, the wind speed field distribution data is evaluated based on a wind speed field evaluation model. The wind speed field evaluation model comprises four dimension indicators of air supply distance, air supply angle, air flow thickness, and floor surface distance. Each dimension indicator is assigned a corresponding score according to a preset interval. The wind speed field evaluation total score is calculated by comparing the wind speed field distribution data with the wind speed field evaluation model. If the wind speed field evaluation total score is greater than or equal to a threshold score, it is determined that the preset wind speed field standard is met.

7. The air conditioner heating comfort evaluation method according to claim 6, wherein In the wind speed field evaluation model, each evaluation dimension is divided into intervals, and each interval is assigned a corresponding score. ​ The air supply distance is divided into six intervals from far to near according to the horizontal blowing distance, and the corresponding scores decrease from high to low in turn; The air supply angle is divided into six intervals according to the reasonable range of the angle between the main airflow and the vertical direction, wherein the preset optimal angle interval corresponds to the highest score, and the angle range deviating from the interval corresponds to the scores decreasing in turn; The airflow thickness is divided into six intervals from large to small according to the airflow thickness value, and the corresponding scores decrease from high to low in turn; The floor surface distance is divided into six intervals from near to far according to the airflow landing position, and the corresponding scores decrease from high to low in turn.

8. The air conditioning heating comfort evaluation method of claim 1, wherein the optimized air conditioning air duct comprises at least one of the following modes: adjusting the air duct profile, adjusting the swing leaf shape, adjusting the swing leaf angle, adjusting the volute profile, optimizing the swing leaf curvature, optimizing the swing leaf width, and optimizing the swing leaf rotation center position.

9. The air conditioning heating comfort evaluation method of claim 1, wherein a plurality of test rods are arranged in the test room, and a thermocouple and a wind speed test sensor are arranged at different heights on each test rod.

10. The air conditioning heating comfort evaluation method of claim 1, wherein in step S4, the preset temperature field standard adopts a preset temperature field evaluation model, which includes the following dimensional indicators: Temperature difference: a plurality of intervals are divided according to the difference between the room average temperature and the air conditioning set temperature, the smaller the difference, the higher the corresponding score, and the larger the difference, the lower the corresponding score; the room average temperature is calculated based on the temperature of the preset test points in the room; Wind speed: a plurality of intervals are divided according to the average wind speed in the test area, the smaller the wind speed, the higher the corresponding score, and the larger the wind speed, the lower the corresponding score; wherein the wind speed is calculated based on the average value of the wind speed test values of different preset test points at the height of the human sitting posture; Temperature rising speed: a plurality of intervals are divided according to the time for the room temperature to reach the preset target temperature, the shorter the time, the higher the corresponding score, and the longer the time, the lower the corresponding score; based on the preset temperature field standard, the temperature field distribution data is scored and evaluated to obtain the temperature field comfort evaluation result, including: according to the temperature field distribution data, the scores of each dimension indicator are obtained by comparing the temperature field standard, the scores of each dimension indicator are summed up, the temperature field evaluation total score is obtained, when the temperature field evaluation total score reaches the preset qualified score, it is determined to be qualified, otherwise it is determined to be unqualified, and after the air conditioning air duct is continuously optimized, step S1 is returned. ​ ​ ​

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