Precise temperature controller and dynamic control method thereof

Abstract

The invention discloses a precise temperature controller and a dynamic control method thereof.The precise temperature controller comprises a refrigerating unit, a precise temperature control unit and a multi-parameter decoupling controller, and a cooling water outlet of an evaporator in the refrigerating unit, the precise temperature control unit and a cooling water inlet of the evaporator are connected in a circulating mode; the precise temperature control unit comprises an auxiliary water tank, a main water tank, a constant-temperature water tank, an electromagnetic valve, an electric heater, a first temperature sensor, a second temperature sensor, a third temperature sensor, a fourth temperature sensor and a refrigerating unit. The electric heater of the precise temperature control unit, the control end of the electromagnetic valve, the first temperature sensor, the second temperature sensor, the third temperature sensor and the fourth temperature sensor are all connected with the parameter decoupling controller. The Smith predictor and the fuzzy PID are coupled for control, the rotating speed of the compressor and the opening degree of the electronic expansion valve are adjusted and corrected, condensation temperature dynamic optimization and water temperature fine adjustment control are combined, and the method has the advantages of being high in precision, quick in response and high in robustness.

Description

Technical Field

[0001] This invention relates to the field of temperature controller technology, specifically a precision temperature controller and its dynamic control method. Background Technology

[0002] Existing precision temperature control technologies suffer from numerous technical shortcomings, making it difficult to meet the demands of high-precision temperature control. Traditional PID control, limited by thermal inertia hysteresis, generally exhibits problems such as large overshoot and long settling times when controlling precision below high levels. Experimental data shows that when the temperature setpoint changes, conventional PID control exhibits high overshoot and long settling times. Furthermore, the refrigeration system suffers from severe multi-parameter coupling issues, with strong coupling relationships between parameters such as compressor speed, expansion valve opening, and condenser fan speed. Tests indicate that changes in compressor speed lead to fluctuations in evaporator temperature, thus affecting the overall system temperature stability. Existing systems have slow dynamic responses, with thermal response time constants within a certain range. Under sudden changes in heat load, the system's recovery time to steady state is long, failing to meet the requirements of rapid temperature changes. Moreover, due to factors such as sensor drift and actuator aging, the temperature control accuracy typically decreases significantly after prolonged continuous operation. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a precision temperature controller and its dynamic control method, which has the advantages of high precision, fast response and strong robustness.

[0004] The technical solution of this invention is as follows:

[0005] A precision temperature controller includes a refrigeration unit, a precision temperature control unit, and a multi-parameter decoupling controller;

[0006] The refrigeration unit includes an evaporator, a gas-liquid separator, a compressor, a condenser, and an electronic expansion valve, all connected in a loop, as well as a fan. The cooling unit's circulating pipe contains refrigerant, and the condenser releases heat through the fan to regulate the condensation efficiency. The cooling water outlet of the evaporator, the precision temperature control unit, and the cooling water inlet of the evaporator are connected in a loop.

[0007] The precision temperature control unit includes an auxiliary water tank, a main water tank, a constant temperature water tank, a solenoid valve, an electric heater, a first temperature sensor, a second temperature sensor, a third temperature sensor, and a fourth temperature sensor. The inlet of the auxiliary water tank is connected to the cooling water outlet of the evaporator, the outlet of the auxiliary water tank is connected to the inlet of the main water tank, the outlet of the main water tank is connected to the inlet of the electric heater, the outlet of the constant temperature water tank is connected to the inlet of the electric heater through the solenoid valve, and the outlet of the electric heater is connected to the cooling water inlet of the evaporator through a circulating return water pipe. The first temperature sensor is located at the cooling water inlet of the evaporator, the second temperature sensor is located at the cooling water outlet of the evaporator, the third temperature sensor is located inside the main water tank, and the fourth temperature sensor is located at the outlet of the electric heater.

[0008] The aforementioned refrigeration unit, the control terminals of the electric heater and solenoid valve of the precision temperature control unit, the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor are all connected to the parameter decoupling controller.

[0009] A float valve is installed inside the main water tank and at the inlet of the main water tank.

[0010] A dynamic control method for a precision temperature controller includes the following steps:

[0011] S1. Feedforward control: The first temperature sensor is used to collect the return water temperature of the evaporator cooling water, predict the heat load change, and pre-adjust the compressor speed.

[0012] S2, Smith predictor initialization: Apply an equal cooling capacity step input to the refrigeration unit and record the evaporator outlet temperature response curve;

[0013] S3, Coupling Compensation: Construct a mapping table between compressor speed and electronic expansion valve opening, and correct it in real time through subsequent PID feedback control;

[0014] S4, PID feedback control: The deviation of the evaporator cooling water outlet temperature is used as the PID input to correct the compressor speed and the opening of the electronic expansion valve;

[0015] S5. Dynamic optimization of condensing temperature: Real-time calculation of the difference and rate of change between condensing temperature and ambient temperature to dynamically optimize the condenser condensing temperature.

[0016] S6. Water temperature fine adjustment: After the cooling water is cooled by the evaporator, the electric heater and the constant temperature water tank compensate for the temperature difference, and then the cooling water flows back to the evaporator through the circulating return water pipeline.

[0017] The Smith predictor described above is based on the evaporator energy balance equation, which constructs a transfer function G(s) with a delay, as shown in equation (1) below:

[0018]

[0019] In equation (1), Q e This represents the heat exchange capacity of the evaporator, measured in W / m³. w This represents the mass flow rate of cooling water, expressed in kg / s; c w The specific heat capacity at constant pressure of cooling water, expressed in J / (kg*K); T out This represents the temperature of the refrigerant at the evaporator outlet, measured in Kelvin (K); Tel. in This represents the temperature of the refrigerant at the evaporator inlet, expressed in Kelvin (T). out -T in This reflects the degree of heat absorption by the refrigerant within the evaporator; m e This represents the mass of the refrigerant inside the evaporator, expressed in kg; c p τ represents the specific heat capacity at constant pressure of the refrigerant, in J / (kg*K); s represents the Laplace transform operator; τ represents the thermal inertia delay time.

[0020] Smith predictor model G e (s) is shown in equation (2) below:

[0021]

[0022] The thermal inertia delay time τ is determined based on the evaporator pressure balance equation, as shown in equation (3) below:

[0023]

[0024] In equation (3), V e This represents the evaporator volume, in cubic meters (m³). 3 m r The mass of refrigerant flowing through the evaporator per unit time, expressed in kg / s; v r The specific volume of the refrigerant, measured in cubic meters (m³). 3 / kg; P represents the supply pressure of the refrigerant in the evaporator, in Pa; P e R represents the pressure inside the evaporator, in Pa. e Represents the evaporator resistance coefficient; This represents the rate of change of pressure inside the evaporator over time, expressed in Pa / s.

[0025] The compensation Δu of the Smith predictor at time k smith (k) Predicted deviation ΔT from evaporator outlet temperature e The calculation is shown in the following formula (4):

[0026] Δu smith (k)=ΔT e (k-τ)=K1*Δn(k-τ)+K2*Δα(k-τ)+K3*

[0027] ΔV a (k-τ)+K4*Δm w (k-τ)+K5*ΔP s (k-τ)(4);

[0028] In equation (4), K1, K2, K3, K4, and K5 are all influence coefficients, with units of ℃ / Hz, ℃ / % opening degree, and ℃ / (10% V), respectively. a ), ℃ / (10% m w ), ℃ / Pa, respectively reflect the degree of influence of changes in compressor speed, electronic expansion valve opening, condensing air volume, cooling water flow rate, and refrigerant supply pressure on evaporator outlet temperature; Δn represents the change in compressor speed, in Hz; Δα represents the change in electronic expansion valve opening, expressed as a percentage (%); ΔV a This represents the change in condensate air volume, in meters (m). 3 / s;Δm w ΔP represents the change in cooling water flow rate, in kg / s. s This represents the change in refrigerant supply pressure, expressed in Pa.

[0029] The discretized expression of the PID feedback control is shown in equation (5):

[0030]

[0031] In equation (5), u(k) represents the output of the PID feedback control at time k; K p (k), K i (k) and K d (k) represent the coefficients of the proportional, integral, and derivative terms, respectively; e(i) represents the temperature deviation at time i, e(k) represents the temperature deviation at time k, and e(k-1) represents the temperature deviation at time k-1. The temperature deviation is the difference between the cooling water temperature at the evaporator cooling water outlet collected by the second temperature sensor and the target cooling water temperature at the cooling water inlet to be returned to the evaporator collected by the first temperature sensor; T represents the sampling period; proportional control adjusts the output proportionally according to the temperature deviation e(k) at time k; integral control accumulates historical temperature deviations to eliminate static errors; derivative control predicts the trend of temperature deviation changes, suppresses overshoot, and improves dynamic response.

[0032] The correction formula for PID feedback control is shown in equation (6) below:

[0033] u ′ (k)=u(k)+Δu smi (k) (6);

[0034] In equation (6), u ′(k) represents the output of the modified PID feedback control;

[0035] The control signal is generated based on the output of the modified PID feedback control, thereby correcting the compressor speed and the opening of the electronic expansion valve.

[0036] The real-time calculation of the difference and rate of change between the condensing temperature and the ambient temperature is used to dynamically optimize the condenser condensing temperature, as shown in the following formula (7):

[0037]

[0038] In equation (7), N f Represents the fan speed, in rpm; K6 and K7 are influence coefficients; T c Represents condensation temperature, in °C; T a Represents ambient temperature, in °C; Represents the rate of change of condensation temperature over time, in °C / s;

[0039] When T c Higher than T a When the difference between the two is greater, K6*(T) c -T a The larger the calculated value, the higher the fan speed should be to enhance the condenser's heat dissipation capacity and reduce the condensing temperature; conversely, when the difference is small, the fan speed should be reduced to avoid unnecessary energy consumption. It achieves dynamic adjustment based on the rate of change of condensation temperature, when When the value is positive and large, it indicates that the condensation temperature is rising rapidly. The larger the calculated value, the more related it is to K6*(T) c -T a The addition of these components causes the fan to rapidly increase its speed, proactively addressing potential high temperatures. When the value is negative, it indicates that the condensing temperature is decreasing, so the fan speed is reduced to prevent the condensing temperature from dropping excessively.

[0040] The specific steps for compensating for temperature difference using the electric heater and constant temperature water tank are as follows: After the cooling water is cooled by the evaporator, it enters the auxiliary water tank for primary temperature control, so that the temperature difference between the auxiliary water tank water temperature and the target water temperature is ≤ ±0.1℃. The target water temperature is the water temperature returning to the cooling water inlet of the evaporator. The water from the auxiliary water tank then enters the main water tank, where it undergoes secondary temperature control, so that the temperature difference between the cooling water outlet temperature of the main water tank and the target water temperature is ≤ 0.05℃. Then, the solenoid valve is opened, and the constant temperature water output from the constant temperature water tank mixes with the cooling water output from the main water tank to achieve temperature harmonization. The electric heater is then used for temperature regulation.

[0041] The control of the solenoid valve opening is shown in the following formula (8):

[0042] D = min(100%), max(0%), K s ×ΔT out +D0)) (8);

[0043] In equation (8), D represents the solenoid valve opening degree, in %; ΔT out =T set -T out , representing the target water temperature T set and the main water tank cooling water outlet temperature T out Temperature difference; K s The value represents the temperature difference coefficient, in % / ℃; D0 represents the minimum opening degree of the solenoid valve, in %; the min() and max() functions are used to limit the opening degree of the solenoid valve within the range of 0 to 100% to avoid overshoot;

[0044] The power control of the electric heater is specifically shown in the following formula (9):

[0045] P h =K8*ΔT m +K9*Q e +K 10 *m s (9);

[0046] In equation (9), P h Represents the power of the electric heater, in watts (W); ΔT m Q represents the temperature deviation between the mixed cooling water temperature from the main water tank outlet and the constant temperature water tank outlet, and the target cooling water temperature, expressed in °C. e This represents the heat exchange capacity of the evaporator, measured in W / m³. s The output flow rate of the constant-temperature water controlled by the solenoid valve is expressed in kg / s and is linearly related to the solenoid valve opening degree; K8, K9, and K 10 All are weighting coefficients, which quantify the impact of cooling water temperature deviation, evaporator heat exchange, and solenoid valve opening on electric heater power.

[0047] When the temperature of the mixed cooling water is not lower than the target cooling water temperature, then ΔT m If ΔT is positive, the electric heater power will decrease or stop working. m When the load is negative, the power of the electric heater is increased; when the heat exchange capacity Q of the evaporator... e If the output temperature of the cooling water from the evaporator increases, the temperature of the cooling water will decrease, causing the electric heater power to increase to compensate for the cooling water temperature. When the output of the constant-temperature water controlled by the solenoid valve increases, the temperature difference ΔT between the mixed cooling water and the target cooling water temperature increases. m If the power is reduced, the power of the electric heater will be reduced.

[0048] The float valve automatically opens according to the liquid level in the main water tank, and replenishes the main water tank with water through the auxiliary water tank. The replenishment flow rate matches the evaporation rate of the main water tank.

[0049] Advantages of this invention:

[0050] (1) This invention addresses the problems of overshoot, slow response time, and low accuracy in traditional temperature control systems using PID algorithms. It employs an algorithm combining fuzzy PID and a Smith predictor to achieve a more stable and highly adaptable intelligent control effect. The thermal inertia delay time is determined based on the evaporator pressure balance equation. Based on the current control quantity, the temperature change after the delay is calculated using the Smith predictor. This is compared with the actual measured value to generate a compensation signal to adjust and correct the compressor speed or electronic expansion valve opening. By coupling the Smith predictor with the fuzzy PID, and using the compensation quantity of the Smith predictor as the output correction term of the fuzzy PID, the control output of the PID algorithm is realized. This overcomes the parameter coupling problem in traditional refrigeration systems, improves adaptability to complex operating conditions, and ensures the stability of the precision temperature controller during long-term operation through the identification and precise compensation of the delay characteristics of key thermal parameters and comprehensive parameter analysis. The accuracy decay after long-term operation is minimal.

[0051] (2) The present invention regulates the condenser by means of a fan, including static regulation based on the difference between the condensing temperature and the ambient temperature and dynamic regulation based on the rate of change of the condensing temperature, so as to realize dynamic optimization and rapid response of the condensing temperature.

[0052] (3) The present invention uses an electric heater and a constant temperature water tank to compensate for the temperature difference, so that the temperature control accuracy reaches an extremely high level and the temperature fluctuation is controlled at an extremely low level. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the principle of the precision temperature controller of the present invention.

[0054] Figure 2 This is a flowchart of the dynamic control method of the present invention.

[0055] Figure 3 This is a graph showing the predicted deviation of the evaporator outlet temperature after iterative optimization of the influence coefficients K1, K2, K3, K4, and K5 of this invention. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] See Figure 1 A precision temperature controller includes a refrigeration unit, a precision temperature control unit, and a multi-parameter decoupling controller;

[0058] The refrigeration unit includes an evaporator 1, a gas-liquid separator 2, a compressor 3, a condenser 4, and an electronic expansion valve 5, which are connected in a circulation loop, as well as a fan 6. The circulating pipe of the refrigeration unit is filled with refrigerant. The condenser 4 releases heat through the fan 6, thereby adjusting the condensing efficiency. The cooling water outlet of the evaporator 1, the precision temperature control unit, and the cooling water inlet of the evaporator 1 are connected in a circulation loop.

[0059] The precision temperature control unit includes an auxiliary water tank 7, a main water tank 8, a constant temperature water tank 9, a solenoid valve 10, an electric heater 11, a first temperature sensor 12, a second temperature sensor 13, a third temperature sensor 14, a fourth temperature sensor 15, and a float valve 16. The float valve 16 is located inside the main water tank 8 and at its inlet. The inlet of the auxiliary water tank 7 is connected to the cooling water outlet of the evaporator 1, and the outlet of the auxiliary water tank 7 is connected to the inlet of the main water tank 8. The outlet of the main water tank 8 is connected to the inlet of the electric heater 11. The outlet of the constant temperature water tank 9 is connected to the inlet of the electric heater 11 via the solenoid valve 10. The outlet of the electric heater 11 is connected to the cooling water inlet of the evaporator 1 via a circulating return water pipe 17. The first temperature sensor 12 is located at the cooling water inlet of the evaporator 1, the second temperature sensor 13 is located at the cooling water outlet of the evaporator 1, the third temperature sensor 14 is located inside the main water tank 8, and the fourth temperature sensor 15 is located at the outlet of the electric heater 11.

[0060] The refrigeration unit (evaporator 1, gas-liquid separator 2, compressor 3, condenser 4, electronic expansion valve 5 and fan 6), the electric heater 11 of the precision temperature control unit, the control terminal of the solenoid valve 10, the first temperature sensor 12, the second temperature sensor 13, the third temperature sensor 14, and the fourth temperature sensor 15 are all connected to the parameter decoupling controller 16.

[0061] See Figure 2 A dynamic control method for a precision temperature controller includes the following steps:

[0062] S1. Feedforward control: The first temperature sensor is used to collect the return water temperature of the evaporator cooling water, predict the heat load change, and pre-adjust the compressor speed.

[0063] S2, Smith predictor initialization: Apply an equal cooling capacity step input to the refrigeration unit and record the evaporator outlet temperature response curve;

[0064] The Smith predictor is based on the evaporator energy balance equation: Construct the transfer function G(s) with delay, as shown in equation (1) below:

[0065]

[0066] In equation (1), Q e The heat exchange capacity of the evaporator, measured in W, is a measure of the heat exchange between the evaporator and the external environment; m w This represents the mass flow rate of cooling water, expressed in kg / s; c w The specific heat capacity at constant pressure of cooling water, expressed in J / (kg*K); T out This represents the temperature of the refrigerant at the evaporator outlet, measured in Kelvin (K); Tel. in This represents the temperature of the refrigerant at the evaporator inlet, expressed in Kelvin (T). out -T in This reflects the degree of heat absorption by the refrigerant within the evaporator; m e This represents the mass of the refrigerant inside the evaporator, expressed in kg; c p represents the isobaric specific heat capacity of the refrigerant, measured in J / (kg*K), which measures the ease with which the refrigerant absorbs or releases heat and its temperature changes; s represents the Laplace transform operator; τ represents the thermal inertia delay time.

[0067] Smith predictor model G e (s) is shown in equation (2) below:

[0068]

[0069] The thermal inertia delay time τ is based on the evaporator pressure balance equation: Confirmed, see formula (3) below:

[0070]

[0071] In equation (3), V e This represents the evaporator volume, in cubic meters (m³). 3 m r The mass of refrigerant flowing through the evaporator per unit time, expressed in kg / s; v r The specific volume of the refrigerant, measured in cubic meters (m³). 3 / kg; P represents the refrigerant supply pressure inside the evaporator, in Pa; p e R represents the pressure inside the evaporator, in Pa. e Represents the evaporator resistance coefficient; This represents the rate of change of pressure inside the evaporator over time, expressed in Pa / s.

[0072] The compensation Δu of the Smith predictor at time k smith (k) Predicted deviation ΔT from evaporator outlet temperature eThe difference between the target temperature and the measured temperature at the evaporator refrigerant outlet is calculated, as shown in formula (4) below:

[0073] Δu smith (k)=ΔT e (k-τ)=K1*Δn(k-τ)+K2*Δα(k-τ)+K3*

[0074] ΔV a (k-τ)+K4*Δm w (k-τ)+K5*ΔP s (k-τ)(4);

[0075] In equation (4), K1, K2, K3, K4, and K5 are all influence coefficients, with units of ℃ / Hz, ℃ / % opening degree, and ℃ / (10% V), respectively. a ), ℃ / (10% m w The parameters K1, K2, K3, K4, and K5, denoted by ℃ / Pa, respectively reflect the influence of compressor speed, electronic expansion valve opening, condensing air volume, cooling water flow rate, and refrigerant supply pressure changes on the evaporator outlet temperature. By comparing historical data with simulation results, the values ​​of K1, K2, K3, K4, and K5 were adjusted. After multiple iterative optimizations, the influence of each parameter on temperature was accurately quantified, ensuring an error ≤0.05℃ (see [link to evaporator outlet temperature prediction deviation after iterative optimization]). Figure 3 ); Δn represents the change in compressor speed, in Hz; Δα represents the change in electronic expansion valve opening, expressed as a percentage (%); ΔV a This represents the change in condensate air volume, in meters (m). 3 / s;Δm w ΔP represents the change in cooling water flow rate, in kg / s. s This represents the change in refrigerant supply pressure, expressed in Pa.

[0076] S3, Coupling Compensation: Construct a mapping table between compressor speed and electronic expansion valve opening (based on historical data), and correct it in real time through subsequent PID feedback control;

[0077] S4, PID feedback control: The deviation of the evaporator cooling water outlet temperature is used as the PID input to correct the compressor speed and the opening of the electronic expansion valve;

[0078] The discretized expression of PID feedback control is shown in equation (5):

[0079]

[0080] In equation (5), u(k) represents the output of the PID feedback control at time k; K p (k), K i (k) and K d(k) represent the coefficients of the proportional, integral, and derivative terms, respectively; e(i) represents the temperature deviation at time i, e(k) represents the temperature deviation at time k, and e(k-1) represents the temperature deviation at time k-1. The temperature deviation is the difference between the cooling water temperature at the evaporator cooling water outlet collected by the second temperature sensor and the target cooling water temperature at the cooling water inlet to be returned to the evaporator collected by the first temperature sensor; T represents the sampling period; proportional control adjusts the output proportionally according to the temperature deviation e(k) at time k; integral control accumulates historical temperature deviations to eliminate static errors; derivative control predicts the trend of temperature deviation changes, suppresses overshoot, and improves dynamic response.

[0081] The correction formula for PID feedback control is shown in equation (6) below:

[0082] u ′ (k)=u(k)+Δu sm (k) (6);

[0083] In equation (6), u ′ (k) represents the output of the modified PID feedback control;

[0084] The control signal is generated based on the output of the modified PID feedback control, thereby correcting the compressor speed and the opening of the electronic expansion valve;

[0085] S5. Dynamic optimization of condensing temperature: The difference and rate of change between the condensing temperature and the ambient temperature are calculated in real time to dynamically optimize the condenser condensing temperature, as shown in the following formula (7):

[0086]

[0087] In equation (7), N f Represents the fan speed, in rpm; K6 and K7 are influence coefficients; T c Represents condensation temperature, in °C; T a Represents ambient temperature, in °C; Represents the rate of change of condensation temperature over time, in °C / s;

[0088] When T c Higher than T a When the difference between the two is greater, K6*(T) c -T a The larger the calculated value, the higher the fan speed should be to enhance the condenser's heat dissipation capacity and reduce the condensing temperature; conversely, when the difference is small, the fan speed should be reduced to avoid unnecessary energy consumption. It achieves dynamic adjustment based on the rate of change of condensation temperature, when When the value is positive and large, it indicates that the condensation temperature is rising rapidly. The larger the calculated value, the more related it is to K6*(T) c -T a The addition of these components causes the fan to rapidly increase its speed, proactively addressing potential high temperatures. When the value is negative, it indicates that the condensing temperature is decreasing, so the fan speed is reduced to prevent the condensing temperature from dropping excessively.

[0089] S6. Water temperature fine adjustment: After the cooling water is cooled by the evaporator, the electric heater and the constant temperature water tank compensate for the temperature difference, and then the cooling water flows back to the evaporator through the circulating return water pipe.

[0090] The specific steps for compensating for temperature difference using an electric heater and a constant temperature water tank are as follows: After cooling water is cooled by the evaporator, it enters the auxiliary water tank for primary temperature control, ensuring that the temperature difference between the auxiliary water tank and the target water temperature is ≤ ±0.1℃. The target water temperature is the water temperature returning to the evaporator cooling water inlet. Water from the auxiliary water tank then enters the main water tank for secondary temperature control, ensuring that the temperature difference between the main water tank cooling water outlet temperature and the target water temperature is ≤ 0.05℃. Then, the solenoid valve is opened, and the constant temperature water output from the constant temperature water tank mixes with the cooling water output from the main water tank for temperature adjustment. The electric heater is then used for temperature regulation.

[0091] The control of the solenoid valve opening is shown in the following formula (8):

[0092] D = min(100%), max(0%), K s ×ΔT out +D0)) (8);

[0093] In equation (8), D represents the solenoid valve opening degree, in %; ΔT out =T set -T out , representing the target water temperature T set and the main water tank cooling water outlet temperature T out Temperature difference; K s The value represents the temperature difference coefficient, in % / ℃; D0 represents the minimum opening degree of the solenoid valve, in %; the min() and max() functions are used to limit the opening degree of the solenoid valve within the range of 0 to 100% to avoid overshoot;

[0094] The power control of the electric heater is specifically shown in the following formula (9):

[0095] P h =K8*ΔT m +K9*Q e +K 10 *m s (9);

[0096] In equation (9), P h Represents the power of the electric heater, in watts (W); ΔT mQ represents the temperature deviation between the mixed cooling water temperature from the main water tank outlet and the constant temperature water tank outlet, and the target cooling water temperature, expressed in °C. e This represents the heat exchange capacity of the evaporator, measured in W / m³. s The output flow rate of the constant-temperature water controlled by the solenoid valve is expressed in kg / s and is linearly related to the solenoid valve opening degree; K8, K9, and K 10 All are weighting coefficients, which quantify the impact of cooling water temperature deviation, evaporator heat exchange, and solenoid valve opening on electric heater power.

[0097] When the temperature of the mixed cooling water is not lower than the target cooling water temperature, then ΔT m If ΔT is positive, the electric heater power will decrease or stop working. m When the load is negative, the power of the electric heater is increased; when the heat exchange capacity Q of the evaporator... e If the output temperature of the cooling water from the evaporator increases, the temperature of the cooling water will decrease, causing the electric heater power to increase to compensate for the cooling water temperature. When the output of the constant-temperature water controlled by the solenoid valve increases, the temperature difference ΔT between the mixed cooling water and the target cooling water temperature increases. m If the power is reduced, then the power of the electric heater will be reduced;

[0098] S7. The float valve automatically opens according to the liquid level in the main water tank, and replenishes the main water tank with water through the auxiliary water tank. The replenishment water temperature in the auxiliary water tank is within ±0.1℃ of the main water tank temperature, and the replenishment water flow rate is matched with the evaporation rate of the main water tank (error ≤3%).

[0099] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A precision temperature controller, characterized in that: It includes refrigeration units, precision temperature control units, and multi-parameter decoupling controllers; The refrigeration unit includes an evaporator, a gas-liquid separator, a compressor, a condenser, and an electronic expansion valve, all connected in a circulating manner, as well as a fan; the circulating pipe of the cooling unit is filled with refrigerant, the condenser releases heat through the fan, and the cooling water outlet of the evaporator, the precision temperature control unit, and the cooling water inlet of the evaporator are connected in a circulating manner. The precision temperature control unit includes an auxiliary water tank, a main water tank, a constant temperature water tank, a solenoid valve, an electric heater, a first temperature sensor, a second temperature sensor, a third temperature sensor, and a fourth temperature sensor. The inlet of the auxiliary water tank is connected to the cooling water outlet of the evaporator, the outlet of the auxiliary water tank is connected to the inlet of the main water tank, the outlet of the main water tank is connected to the inlet of the electric heater, the outlet of the constant temperature water tank is connected to the inlet of the electric heater through the solenoid valve, and the outlet of the electric heater is connected to the cooling water inlet of the evaporator through a circulating return water pipe. The first temperature sensor is located at the cooling water inlet of the evaporator, the second temperature sensor is located at the cooling water outlet of the evaporator, the third temperature sensor is located inside the main water tank, and the fourth temperature sensor is located at the outlet of the electric heater. The aforementioned refrigeration unit, the control terminals of the electric heater and solenoid valve of the precision temperature control unit, the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor are all connected to the parameter decoupling controller.

2. The precision temperature controller according to claim 1, characterized in that: A float valve is installed inside the main water tank and at the inlet of the main water tank.

3. The dynamic control method for a precision temperature controller according to claim 2, characterized in that: It includes the following steps: S1. Feedforward control: The first temperature sensor is used to collect the return water temperature of the evaporator cooling water, predict the heat load change, and pre-adjust the compressor speed. S2, Smith predictor initialization: Apply an equal cooling capacity step input to the refrigeration unit and record the evaporator outlet temperature response curve; S3, Coupling Compensation: Construct a mapping table between compressor speed and electronic expansion valve opening, and correct it in real time through subsequent PID feedback control; S4, PID feedback control: The deviation of the evaporator cooling water outlet temperature is used as the PID input to correct the compressor speed and the opening of the electronic expansion valve; S5. Dynamic optimization of condensing temperature: Real-time calculation of the difference and rate of change between condensing temperature and ambient temperature to dynamically optimize the condenser condensing temperature. S6. Water temperature fine adjustment: After the cooling water is cooled by the evaporator, the electric heater and the constant temperature water tank compensate for the temperature difference, and then the cooling water flows back to the evaporator through the circulating return water pipeline.

4. The dynamic control method for a precision temperature controller according to claim 3, characterized in that: The Smith predictor described above is based on the evaporator energy balance equation, which constructs a transfer function G(s) with a delay, as shown in equation (1) below: In equation (1), Q e This represents the heat exchange capacity of the evaporator, measured in W / m³. w This represents the mass flow rate of cooling water, expressed in kg / s; c w The specific heat capacity at constant pressure of cooling water, expressed in J / (kg*K); T out This represents the temperature of the refrigerant at the evaporator outlet, measured in Kelvin (K); Tel. in This represents the temperature of the refrigerant at the evaporator inlet, expressed in Kelvin (T). out -T in This reflects the degree of heat absorption by the refrigerant within the evaporator; m e This represents the mass of the refrigerant inside the evaporator, expressed in kg; c p The specific heat capacity at constant pressure of the refrigerant, expressed in J / (kg*K); s represents the Laplace transform operator; τ represents the thermal inertia delay time; Smith predictor model G e (s) is shown in equation (2) below: The thermal inertia delay time τ is determined based on the evaporator pressure balance equation, as shown in equation (3) below: In equation (3), V e This represents the evaporator volume, in cubic meters (m³). 3 ; m r The mass of refrigerant flowing through the evaporator per unit time, expressed in kg / s; v r The specific volume of the refrigerant, measured in cubic meters (m³). 3 / kg; P represents the supply pressure of the refrigerant in the evaporator, in Pa; P e R represents the pressure inside the evaporator, in Pa. e Represents the evaporator resistance coefficient; This represents the rate of change of pressure inside the evaporator over time, expressed in Pa / s. The compensation Δu of the Smith predictor at time k smith (k) Predicted deviation ΔT from evaporator outlet temperature e The calculation is shown in the following formula (4): Thu smith (k)=ΔT e (k-τ)=K1*Δn(k-τ)+K2*Δα(k-τ)+K3* ΔV a (k-τ)+K4*Δm w (k-τ)+K5*ΔP s (k-t)(4); In equation (4), K1, K2, K3, K4, and K5 are all influence coefficients, with units of ℃ / Hz, ℃ / % opening degree, and ℃ / (10% V), respectively. a ), ℃ / (10% m w ), ℃ / Pa, respectively reflect the degree of influence of changes in compressor speed, electronic expansion valve opening, condensing air volume, cooling water flow rate, and refrigerant supply pressure on evaporator outlet temperature; Δn represents the change in compressor speed, in Hz; Δα represents the change in electronic expansion valve opening, expressed as a percentage (%); ΔV a This represents the change in condensate air volume, in meters (m). 3 / s;Δm w ΔP represents the change in cooling water flow rate, in kg / s. s This represents the change in refrigerant supply pressure, expressed in Pa.

5. The dynamic control method for a precision temperature controller according to claim 3, characterized in that: The discretized expression of the PID feedback control is shown in equation (5): In equation (5), u(k) represents the output of the PID feedback control at time k; K p (k), K i (k) and K d (k) represent the coefficients of the proportional term, integral term, and differential term, respectively; e(i) represents the temperature deviation at time i, e(k) represents the temperature deviation at time k, e(k-1) represents the temperature deviation at time k-1, and the temperature deviation is the difference between the cooling water temperature at the evaporator cooling water outlet collected by the second temperature sensor and the target cooling water temperature at the cooling water inlet to be returned to the evaporator collected by the first temperature sensor. T represents the sampling period; Proportional control adjusts the output proportionally based on the temperature deviation e(k) at the current time k. Integral control accumulates historical temperature deviations to eliminate static errors; derivative control predicts the changing trend of temperature deviations, suppresses overshoot, and improves dynamic response. The correction formula for PID feedback control is shown in equation (6) below: u′(k)=u(k)+Δu smith (k) (6); In equation (6), u′(k) represents the output of the modified PID feedback control; The control signal is generated based on the output of the modified PID feedback control, thereby correcting the compressor speed and the opening of the electronic expansion valve.

6. The dynamic control method for a precision temperature controller according to claim 3, characterized in that: The real-time calculation of the difference and rate of change between the condensing temperature and the ambient temperature is used to dynamically optimize the condenser condensing temperature, as shown in the following formula (7): In equation (7), N f Represents the fan speed, in rpm; K6 and K7 are influence coefficients; T c Represents condensation temperature, in °C; T a Represents ambient temperature, in °C; Represents the rate of change of condensation temperature over time, in °C / s; When T c Higher than T a When the difference between the two is greater, K6*(T) c -T a The larger the calculated value, the higher the fan speed should be to enhance the condenser's heat dissipation capacity and reduce the condensing temperature. Conversely, when the difference is small, the fan speed should be reduced to avoid unnecessary energy consumption; It achieves dynamic adjustment based on the rate of change of condensation temperature, when When the value is positive and large, it indicates that the condensation temperature is rising rapidly. The larger the calculated value, the more related it is to K6*(T) c -T a The addition of these components causes the fan to rapidly increase its speed, proactively addressing potential high temperatures. When the value is negative, it indicates that the condensing temperature is decreasing, so the fan speed is reduced to prevent the condensing temperature from dropping excessively.

7. The dynamic control method for a precision temperature controller according to claim 3, characterized in that: The specific steps for compensating for temperature difference using the electric heater and constant temperature water tank are as follows: After the cooling water is cooled by the evaporator, it enters the auxiliary water tank for primary temperature control, so that the temperature difference between the auxiliary water tank water temperature and the target water temperature is ≤ ±0.1℃. The target water temperature is the water temperature returning to the cooling water inlet of the evaporator. The water from the auxiliary water tank then enters the main water tank, where it undergoes secondary temperature control, so that the temperature difference between the cooling water outlet temperature of the main water tank and the target water temperature is ≤ 0.05℃. Then, the solenoid valve is opened, and the constant temperature water output from the constant temperature water tank mixes with the cooling water output from the main water tank to achieve temperature harmonization. The electric heater is then used for temperature regulation. The control of the solenoid valve opening is shown in the following formula (8): D=min(100%,max(0%,K s ×ΔT out +D0)) (8); In equation (8), D represents the solenoid valve opening degree, in %; ΔT out =T set -T out , representing the target water temperature T set and the main water tank cooling water outlet temperature T out Temperature difference; K s The value represents the temperature difference coefficient, in % / ℃; D0 represents the minimum opening degree of the solenoid valve, in %; the min() and max() functions are used to limit the opening degree of the solenoid valve within the range of 0 to 100% to avoid overshoot; The power control of the electric heater is specifically shown in the following formula (9): P h =K8*ΔT m +K9*Q e +K 10 *m s (9); In equation (9), P h Represents the power of the electric heater, in watts (W); ΔT m Q represents the temperature deviation between the mixed cooling water temperature from the main water tank outlet and the constant temperature water tank outlet, and the target cooling water temperature, expressed in °C. e This represents the heat exchange capacity of the evaporator, measured in W / m³. s The output flow rate of the constant-temperature water controlled by the solenoid valve is expressed in kg / s and is linearly related to the solenoid valve opening degree; K8, K9, and K 10 All are weighting coefficients, which quantify the impact of cooling water temperature deviation, evaporator heat exchange, and solenoid valve opening on electric heater power. When the temperature of the mixed cooling water is not lower than the target cooling water temperature, then ΔT m If ΔT is positive, the electric heater power will decrease or stop working. m When the load is negative, the power of the electric heater is increased; when the heat exchange capacity Q of the evaporator... e If the output temperature of the cooling water from the evaporator increases, the temperature of the cooling water will decrease, causing the electric heater power to increase to compensate for the cooling water temperature. When the output of the constant-temperature water controlled by the solenoid valve increases, the temperature difference ΔT between the mixed cooling water and the target cooling water temperature increases. m If the power is reduced, the power of the electric heater will be reduced.

8. The dynamic control method for a precision temperature controller according to claim 3, characterized in that: The float valve automatically opens according to the liquid level in the main water tank, and replenishes the main water tank with water through the auxiliary water tank. The replenishment flow rate matches the evaporation rate of the main water tank.

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