Energy-saving control method of online water quality automatic sampler

Abstract

According to the energy-saving control method of the on-line water quality automatic sampler, intelligent control over the refrigeration unit is achieved through the sampling state and weighing feedback, the energy-saving effect is achieved, and meanwhile the temperature control precision is improved. When the control unit of the water quality automatic sampler executes a standby state and completes sampling, the control unit outputs a digital quantity signal to the refrigeration unit through a port, so that the refrigeration unit is not electrified. When the control unit of the automatic water quality sampler is in an execution operation state and a sampling completion state, the control unit outputs a digital quantity signal to the refrigeration unit through a port, so that the refrigeration unit is electrified and started, and the refrigeration unit completes refrigeration of a water sample at a preset temperature. And the refrigeration unit in the running state runs according to an energy-saving control algorithm of the sampling weight.

Description

Technical Field

[0001] This application relates to the technical field of water quality sampling equipment, and particularly to an energy-saving control method for an online water quality automatic sampler. Background Art

[0002] A water quality automatic sampler is an intelligent water quality sampling device that can realize water sampling of water bodies, and is used for subsequent water quality detection and analysis to determine the concentration of water pollutants. It is an essential link in environmental monitoring.

[0003] The refrigeration unit of the water quality automatic sampler is one of its main power-consuming components. Long-term standby operation will increase power consumption. Currently, water quality automatic samplers on the market have the function of refrigerating water samples. The water sample refrigeration unit and the sampler are powered on and work simultaneously. When there is no water sample to be stored in the refrigeration unit, the opening of the refrigeration unit will generate ineffective power consumption. Traditional water quality automatic samplers usually adopt a continuous refrigeration operation mode. Even when no sampling is carried out, the refrigeration unit still remains in the working state, resulting in a large amount of electric energy waste. In the actual use process of water quality automatic samplers, most water quality automatic samplers are in the standby state for a long time. When there is no water sample stored in the refrigeration unit and it is in an empty bottle state, the refrigeration unit is still in the working state. On the one hand, this causes unnecessary electric energy consumption. On the other hand, in order to maintain the refrigeration temperature, the compressor of the refrigeration unit will continuously start and stop to maintain the set temperature in the refrigeration unit, which affects the service life of the compressor.

[0004] In the prior art, there is a lack of an effective energy-saving control scheme and it is impossible to dynamically adjust the working mode of the refrigeration unit according to the actual sampling state. In addition, the temperature control accuracy of the existing sampler is insufficient, and it is impossible to perform power control according to the sampling volume, so the best energy efficiency ratio cannot be achieved.

[0005] Chinese Patent CN202210609176.1 discloses an analysis and monitoring method and system for the water quality of stormwater runoff in a drainage pipe network. The method includes: S1, controlling multiple water quality analyzers to switch and operate to generate continuous water quality data of the water body in the forebay; S2, controlling the valves in the flow path adjustment components at the inflow port of the forebay according to the flow path adjustment equation set and the collected data; S3, calculating the water quality data of the three-path flow by combining the continuous water quality data and the control signals of each valve; S4, positioning the tributary path that causes the water quality data to exceed the standard based on the runoff with the water quality data exceeding the standard and the label of the water inflow path in the front section of the runoff; S5, performing corresponding processing based on the calculated water quality data of the three-path flow. However, it lacks real-time monitoring of the water quality changes of multi-source runoff, resulting in difficult positioning of pollution points when the water quality exceeds the standard. In addition, the existing technology has a high transformation cost, it is difficult to achieve accurate pollution source positioning and treatment, and energy-saving control cannot be realized.

[0006] Therefore, it is particularly important to design an on-line water quality automatic sampler that, when the automatic sampler is in the standby state without sampling or saving samples, the refrigeration unit does not operate, reducing power consumption; at the same time, when the refrigeration unit is working, the refrigeration power is controlled according to the sampling volume to achieve the best energy efficiency ratio. Summary of the Invention

[0007] The present invention provides an energy-saving control method for an on-line water quality automatic sampler, which realizes intelligent control of the refrigeration unit through sampling status and weighing feedback, achieves energy-saving effects, and improves temperature control accuracy at the same time.

[0008] To achieve the above object, the technical solution adopted by the present invention is divided into two layers of logic. The first layer of control logic: start-stop control of the refrigeration unit based on the sampling status. In the waiting sampling stage (standby state), the refrigeration unit is controlled by the control unit to be powered off and is in a power-off state; in the water sample sampling (running state) and the water sample sampling completion stage (completion state), the refrigeration unit is controlled by the control unit to be powered on and is in a powered-on state; when the sampling of the collected water sample is completed and the standby state control unit of the next cycle is carried out at the same time, the refrigeration unit is controlled to be powered off. The second layer of control logic: an energy-saving control algorithm based on the sampling weight.

[0009] In a first aspect, the present application provides an energy-saving control method for an on-line water quality automatic sampler, the sampler having a control unit and a refrigeration unit, including:

[0010] When it is determined according to the working state of the sampler that it is in the standby state or the sampling state, the control unit outputs a low-level signal to cut off the power supply of the refrigeration unit and stop its operation;

[0011] When the sampler is in the running state or the completion state, the control unit outputs a high-level signal to turn on the power supply of the refrigeration unit and start its operation;

[0012] The current mass of the water sample in the sampler is obtained in real time, and the ratio of the current mass to the maximum capacity of the sampler is calculated;

[0013] According to the ratio and a preset adjustment coefficient, the refrigeration power is dynamically adjusted through a non-linear function relationship, so that the refrigeration power increases according to the power function law as the current mass increases;

[0014] According to the ratio and the preset minimum temperature and maximum temperature range, the temperature set value of the refrigeration unit is dynamically adjusted, so that the temperature set value transitions from the minimum temperature to the maximum temperature according to the exponential function law as the current mass increases;

[0015] Based on the above ratio, the proportional coefficient, integral coefficient, and derivative coefficient are independently adjusted respectively, including that the proportional coefficient increases at the first exponential rate with the increase of the current mass; the integral coefficient increases at the second exponential rate with the increase of the current mass, and the growth rate is lower than that of the proportional coefficient; the derivative coefficient increases at the third exponential rate with the increase of the current mass, and the growth rate is higher than that of the proportional coefficient.

[0016] Execute closed-loop temperature control according to the adjusted PID parameters to stabilize the temperature of the refrigeration unit at the temperature set value.

[0017] Preferably, in the dynamic refrigeration power regulation, the calculation formula of the refrigeration power is:

[0018]

[0019] where P is the current refrigeration power, P max is the maximum refrigeration power, m is the current sampled mass, m max is the maximum capacity of the sampler, and α is the adjustment coefficient, and the value range is 0.5 to 1.5.

[0020] Preferably, the calculation formula of the temperature set value is:

[0021]

[0022] where T set is the current temperature set value (unit: °C), T min is the preset minimum temperature set value, and the value is 2 °C, T max is the preset maximum temperature set value, and the value is 6 °C, m is the current mass of the water sample in the sampler (unit: kg), m max is the maximum capacity of the sampler (unit: kg).

[0023] Preferably, in the improved dynamic PID parameter adjustment, the calculation formulas of the proportional coefficient, integral coefficient, and derivative coefficient are respectively:

[0024]

[0025] where K p0 、K i0 、K d0 are the initial PID parameters.

[0026] Preferably, the value of the adjustment coefficient α is 0.8 to 1.2, and preferably 1.0.

[0027] Preferably, the minimum temperature set value T min is 2 °C, the maximum temperature set value T max is 6 °C, and the exponent of the exponential function for temperature transition is 0.3.

[0028] Preferably, the first exponential rate is 0.8, the second exponential rate is 0.5, the third exponential rate is 1.2, and the initial PID parameters are determined by experimental calibration of the refrigeration unit model.

[0029] Preferably, the refrigeration unit is a semiconductor refrigeration module with a maximum refrigeration power of 200 - 500W, and the maximum capacity of the sampler is 1 - 5kg.

[0030] Preferably, the control unit integrates a weighing sensor with a range of 0 - 5kg and an accuracy of ±0.1%, and the temperature sensor is of the PT100 type with an accuracy of ±0.2°C.

[0031] In a second aspect, the present application provides an on - line water quality sampler for implementing the energy - saving control method of the on - line water quality automatic sampler as described in the first aspect, including a sampling mechanical unit, a refrigeration unit, a control unit, a weighing feedback unit, a power supply module, a communication module, a user interaction module, an alarm module, and an auxiliary function unit.

[0032] The technical solution has the following beneficial effects:

[0033] Remarkable energy - saving effect: Through the double - layer control logic of the sampling state and weighing feedback, the refrigeration unit works as needed with a high energy efficiency ratio. Precise temperature control: Adopting a dynamic PID control algorithm, the temperature control is precise. High degree of intelligence: Intelligent control throughout the standby state, running state, completion state, and sampling process. Description of the Drawings

[0034] Figure 1 is the start - stop logic of the control unit controlling the refrigeration unit in an embodiment of the present invention.

[0035] Figure 2 is a schematic structural diagram of an energy - saving on - line water quality automatic sampler in an embodiment of the present invention. Detailed Embodiments

[0036] The present invention will be further described below in conjunction with embodiments and the accompanying drawings.

[0037] As Figure 1 shown, after the installation of the energy - saving on - line water quality automatic sampler, when powered on and the sampling mode is set, during the waiting - for - sampling stage (standby state), the refrigeration unit is controlled by the control unit and is not powered on, being in a power - off state; during the water sample sampling (running state) and the water sample sampling completion stage (completion state), the refrigeration unit is controlled by the control unit to be powered on, being in a powered - on state, providing a refrigerated temperature for the collected water samples. When the sampling of the collected water samples is completed, the sampling is completed and the control unit controls the refrigeration unit to be not powered on for the next cycle of standby state simultaneously.

[0038] Energy-saving control algorithm based on sampling weight. Refrigeration power adjustment: Calculate the refrigeration power P according to the sampling mass m; Calculate the refrigeration power P according to the temperature deviation ΔT=T set -T actual Adjust PID parameters; Temperature control: Execute PID control algorithm, adjust cooling power, and maintain set temperature.

[0039] In another embodiment, this embodiment takes the outlet monitoring of a certain city sewage treatment plant as an example, and the discharged water body needs to be sampled and refrigerated for 24 hours for subsequent pollutant concentration analysis. The system is deployed next to an outdoor manhole and needs to adapt to high temperature and humid environment, and meet the requirements of unattended, remote monitoring and low power operation.

[0040] In the first step, the control unit (STM32F407 microcontroller) starts the sampling process according to a preset schedule (such as once an hour) or an external trigger signal (such as a sudden change in water flow detected by the flowmeter). The sampling mechanical unit starts working, and the sampling pump (diaphragm pump, flow rate 2L / min) extracts water samples from the water body through a corrosion-resistant silicone hose. The switching valve (electric three-way valve) directs the water sample to the designated sampling bottle (12-bottle rotating sub-packaging rack) to avoid cross-contamination of samples at different times. Then the auxiliary unit intervenes, and the pre-filter (50μm stainless steel filter) removes suspended particles and protects the pipeline and pump body. The flowmeter (accuracy ±1%) monitors the sampling volume in real time to ensure that each bottle of water sample is 500±10mL. Automated sampling reduces manual intervention; multi-bottle sub-packaging design supports long-term monitoring; the filtration system extends the life of the equipment.

[0041] The second step is the weighing feedback unit intervention: the weighing sensor (range 0-5kg, accuracy ±0.1%) measures the mass in the sampler in real time (m = 2.5kg, m max =5kg). The control unit is based on the formula P = 500 × (2.5 / 5) 1.0 =250W dynamically adjusts the cooling power. Then the refrigeration unit responds: the semiconductor refrigeration module (TEC1-12706) starts with 250W power, the box temperature starts to drop from the ambient temperature of 30℃, and the temperature sensor (PT100) continuously feeds back the actual temperature to the control unit. It can adjust the power on demand, the power consumption is 0W when no load, and the energy saving rate is 60%; avoid frequent start and stop of the compressor, and extend the life of the equipment.

[0042] The third step is dynamic PID temperature control and temperature setting. The control unit is based on the formula T set =2+(6-2)×(2.5 / 5) 0.3 ≈3.8℃ set the target temperature. Then the PID parameters are adjusted dynamically, the proportional coefficient K p =K p0 ×(2.5 / 5) 0.8 =0.6Kp0 , K i = K i0 ×(2.5 / 5) 0.5 = 0.7K i0 , K d = K d0 ×(2.5 / 5) 1.2 = 0.4K d0 . Then perform closed-loop control execution. If the actual temperature deviates from the set value (such as detecting T = 4.5 °C), the PID algorithm outputs an adjustment signal to increase the refrigeration power and gradually stabilize it to 3.8 ± 0.3 °C. It can achieve dynamic PID to improve the temperature control accuracy (fluctuation ≤ ±0.5 °C) and avoid sample deterioration caused by overcooling or heating up.

[0043] The above specific embodiments are only used to explain and illustrate the present invention, rather than limiting the present invention. Any changes and substitutions made to the present invention without creative efforts within the concept and scope of protection of the claims of the present invention shall fall within the protection scope of the present invention patent.

Claims

1. An energy-saving control method for an on-line water quality automatic sampler, the sampler having a control unit and a refrigeration unit, characterized in that, Including: When it is determined to be in the standby state or the sampling state according to the working state of the sampler, the control unit outputs a low-level signal to cut off the power supply of the refrigeration unit and stop it from running; When the sampler is in the running state or the completed state, the control unit outputs a high-level signal to turn on the power supply of the refrigeration unit and start it to run; Obtain the current quality of the water sample in the sampler in real time and calculate the ratio of the current quality to the maximum capacity of the sampler; According to the ratio and the preset adjustment coefficient, dynamically adjust the refrigeration power through a non-linear function relationship, so that the refrigeration power increases according to the power function law as the current quality increases; According to the ratio and the preset minimum temperature and maximum temperature range, dynamically adjust the temperature setting value of the refrigeration unit, so that the temperature setting value transitions from the minimum temperature to the maximum temperature according to the exponential function law as the current quality increases; Based on the ratio, independently adjust the proportional coefficient, integral coefficient and differential coefficient respectively, including that the proportional coefficient increases at the first exponential rate as the current quality increases; the integral coefficient increases at the second exponential rate as the current quality increases, and the growth rate is lower than that of the proportional coefficient; the differential coefficient increases at the third exponential rate as the current quality increases, and the growth rate is higher than that of the proportional coefficient; Execute closed-loop temperature control according to the adjusted PID parameters to keep the temperature of the refrigeration unit stable at the temperature setting value.

2. The energy-saving control method of the on-line water quality automatic sampler according to claim 1, characterized in that, In the dynamic refrigeration power adjustment, the calculation formula of the refrigeration power is: ， Among them, P is the current refrigeration power, and P max is the maximum refrigeration power, m is the current sampling mass, and m max is the maximum capacity of the sampler, and α is the adjustment coefficient, with a value range of 0.5 to 1.

5.

3. The energy-saving control method of the on-line water quality automatic sampler according to claim 1, characterized in that, The calculation formula of the temperature setting value is: ， Among them, T set is the current temperature set value (unit: °C), T min is the preset minimum temperature set value, with a value of 2 °C, T max is the preset maximum temperature set value, with a value of 6 °C, m is the current mass of the water sample in the sampler (unit: kg), m max is the maximum capacity of the sampler (unit: kg).

4. The energy-saving control method of the on-line water quality automatic sampler according to claim 3, characterized in that, In the dynamic adjustment of the improved PID parameters, the calculation formulas of the proportional coefficient, integral coefficient and differential coefficient are respectively: , , , where K p0 , K i0 , K d0 are the initial PID parameters.

5. The energy-saving control method of the on-line water quality automatic sampler according to claim 1, wherein the value of the adjustment coefficient α is 0.8 to 1.2, preferably 1.

0.

6. The energy-saving control method of the online water quality automatic sampler according to claim 1, characterized in that The minimum temperature setting value T min is 2 °C, and the maximum temperature setting value T max is 6 °C, and the exponent of the exponential function for temperature transition is 0.

3.

7. The energy-saving control method of the on-line water quality automatic sampler according to claim 1, characterized in that The first exponential rate is 0.8, the second exponential rate is 0.5, the third exponential rate is 1.2, and the initial PID parameters are determined by experimental calibration of the refrigeration unit model.

8. The energy-saving control method of the online water quality automatic sampler according to claim 1, characterized in that, The refrigeration unit is a semiconductor refrigeration module, the maximum refrigeration power is 200-500W, and the maximum capacity of the sampler is 1-5kg.

9. The energy-saving control method of the on-line water quality automatic sampler according to claim 1, characterized in that The control unit integrates a weighing sensor with a range of 0-5kg and an accuracy of ±0.1%, and the temperature sensor uses a PT100 type with an accuracy of ±0.2°C.

10. An on-line water quality sampler for implementing the energy-saving control method of the on-line water quality automatic sampler as described in claims 1-9, including a sampling mechanical unit, a refrigeration unit, a control unit, a weighing feedback unit, a power supply module, a communication module, a user interaction module, an alarm module, and an auxiliary function unit.

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