Oxygen generator system and control method

Abstract

The invention discloses an oxygen generator system and a control method, and the system comprises a compressor which is used for generating high-pressure hot air; the adsorption tower module comprises a heat exchange unit and a molecular sieve unit, the molecular sieve unit comprises a first molecular sieve tower and a second molecular sieve tower, the compressor is communicated with the heat exchange unit, and at least part of the heat exchange unit is located between the first molecular sieve tower and the second molecular sieve tower; the valve group comprises a main valve located at the air inlet end of the molecular sieve unit and a pressure equalizing valve located at the oxygen outlet end of the molecular sieve unit, and high-pressure hot air enters the main valve after being subjected to heat exchange through the heat exchange unit and enters the first molecular sieve tower or the second molecular sieve tower through the main valve; the heat dissipation module comprises a heat dissipation fan, and an air outlet of the heat dissipation fan corresponds to an air outlet of the compressor; and the control module is used for controlling the duty ratio of the cooling fan. The waste heat of the compressor is recycled and directly used for molecular sieve desorption, the low-temperature desorption efficiency is remarkably improved, and the service life of the molecular sieve is prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oxygen generator, and particularly relates to an oxygen generator system and a control method. BACKGROUND

[0002] An oxygen generator, particularly a medical and household oxygen generator based on pressure swing adsorption (PSA) technology, is mainly used to separate oxygen and nitrogen in air by utilizing the characteristics of molecular sieve (such as lithium type 13X molecular sieve) in adsorbing nitrogen under pressure and desorbing nitrogen under decompression, so as to continuously produce medical oxygen. The efficiency of PSA cycle, especially whether the adsorbed nitrogen can be fully desorbed in the desorption stage, directly determines the oxygen yield, purity and service life of the molecular sieve of the oxygen generator.

[0003] In practical application, especially in low-temperature environments (≤5℃) such as winter in northern China and highland border defense, the existing PSA oxygen generation technology faces severe challenges. From the perspective of adsorption thermodynamics, the adsorption capacity of molecular sieve for nitrogen increases significantly with the decrease of temperature. This means that in a low-temperature environment, more energy is needed to break the van der Waals force between nitrogen molecules and molecular sieve pores in order to achieve effective desorption. However, the temperature of the adsorption tower and the molecular sieve body of the existing oxygen generation system is usually similar to the ambient temperature in a low-temperature environment, which cannot provide the necessary heat energy for deep desorption. This contradiction leads to a sharp drop in oxygen yield, such as a rated 5L / min machine that may actually produce 4-4.5L / min at-5℃; system startup delay, which poses a risk in emergency oxygen therapy scenarios; and a significant reduction in the service life of the molecular sieve due to incomplete desorption, resulting in a sharp increase in user maintenance costs.

[0004] To address the above challenges, various attempts have been made in the industry. One type of solution focuses on optimizing the structure or control process, such as Chinese patent CN202322243527.4, which balances the gas pressure between the towers by improving the flow assembly, or Chinese patent CN202223529243.3, which adjusts the compressor operating frequency to improve oxygen concentration. However, none of these solutions addresses the core contradiction of insufficient desorption heat in low-temperature environments.

[0005] Therefore, there is an urgent need in the art for a systematic solution that accurately maintains or improves the temperature of the molecular sieve during the desorption stage, thereby fundamentally solving the technical difficulties of low desorption efficiency, high energy consumption, and short service life of core components of PSA oxygen generators in low-temperature environments. SUMMARY

[0006] The present application provides an oxygen generator system and control method, which effectively recovers the waste heat generated during the operation of the compressor to maintain or improve the temperature of the molecular sieve during the desorption stage, thereby fundamentally solving the technical difficulties of low desorption efficiency, high energy consumption, and short service life of core components of PSA oxygen generators in low-temperature environments.

[0007] The technical scheme adopted by the present application is: An oxygen generator system comprises: A compressor for generating high-pressure hot air; An adsorption tower module comprising a heat exchange unit and a molecular sieve unit, the molecular sieve unit comprising a first molecular sieve tower and a second molecular sieve tower, the compressor being in communication with the heat exchange unit to deliver the high-pressure hot air to the heat exchange unit, at least part of the heat exchange unit being located between the first molecular sieve tower and the second molecular sieve tower to allow heat of the high-pressure hot air to be transferred to the molecular sieve unit through a side wall of the heat exchange unit; A valve group comprising a total valve at an air inlet end of the molecular sieve unit and an equalizing valve at an oxygen outlet end of the molecular sieve unit, the high-pressure hot air entering the total valve after heat exchange by the heat exchange unit and entering the first molecular sieve tower or the second molecular sieve tower through the total valve; A heat dissipation module comprising a heat dissipation fan, an air outlet of the heat dissipation fan corresponding to an air outlet of the compressor for adjusting the air outlet temperature of the compressor; A control module for controlling a duty cycle of the heat dissipation fan.

[0008] The oxygen generator system disclosed in the present application also has the following additional technical features: The control module further comprises a temperature sensor group comprising a first temperature sensor and a second temperature sensor, the first temperature sensor being used to measure a temperature at a piston cylinder of the compressor, and the second temperature sensor being used to measure an ambient temperature.

[0009] The present application also provides an oxygen control method for the system, characterized in that, A plurality of sampling time points are set, the heat exchange unit temperature and the molecular sieve unit target temperature at each sampling time point are obtained, and the temperature deviation of the heat exchange unit temperature and the molecular sieve unit target temperature at each sampling time point is obtained; According to the temperature deviation, the duty cycle of the heat dissipation fan is controlled.

[0010] The heat exchange unit temperature and the molecular sieve unit target temperature at at least four sampling time points are obtained, including the kth sampling time point, the k-1th sampling time point, the k-2th sampling time point, and the k-3th sampling time point, According to the heat exchange unit temperature and the molecular sieve unit target temperature, the temperature deviation at each sampling time point is obtained, and is denoted as e(k), e(k-1), e(k-2), and e(k-3), respectively; The temperature deviation change amounts of adjacent sampling instants are respectively denoted as Δe(k), Δe(k-1), and Δe(k-2), wherein Δe(k) = e(k) - e(k-1), Δe(k-1) = e(k-1) - e(k-2), and Δe(k-2) = e(k-2) - e(k-3); According to the temperature deviation change rate, the duty cycle of the heat dissipation fan is controlled.

[0011] The duty cycle increment of the heat dissipation fan is specifically: Δu(k) = Kp × [Δe(k) - Δe(k-1)] + Ki × e(k) + Kd × [Δe(k) - 2 × Δe(k-1) + Δe(k-2)], wherein Δu(k) is the duty cycle increment of the heat dissipation fan, which is used to control the duty cycle of the heat dissipation fan, Kp, Ki, and Kd are respectively a proportional coefficient, an integral coefficient, and a differential coefficient.

[0012] The proportional coefficient, the integral coefficient, and the differential coefficient are specifically: A critical proportional coefficient Kp0 is set to be 1-100, and a critical oscillation period Tp0 is greater than or equal to 10 seconds; According to the critical proportional coefficient Kp0, a proportional coefficient Kp is obtained, wherein Kp = 0.5 × Kp0; According to the proportional coefficient Kp, a current heat exchange unit temperature T, and the critical oscillation period Tp0, an integral coefficient Ki is obtained, wherein Ki = Kp × T / (0.5 × Tp0); According to the proportional coefficient Kp, the current heat exchange unit temperature T, and the critical oscillation period Tp0, a differential coefficient Kd is obtained, wherein Kd = Kp × (0.125 × Tp0) / T.

[0013] The target temperature of the molecular sieve unit is obtained, and the target temperature of the molecular sieve unit is specifically: The outlet gas pressure and the ambient temperature of the heat exchange unit are obtained, and the target temperature of the molecular sieve unit is determined according to the ambient temperature.

[0014] The target temperature of the molecular sieve unit is determined, and the method further includes: When the target temperature is greater than 40℃, the target temperature is taken as 40℃, When the target temperature is less than 5℃, the target temperature is taken as 5℃.

[0015] The heat exchange unit temperature at each sampling instant is obtained, and the heat exchange unit temperature at each sampling instant is specifically: The temperature at the compressor at each sampling instant is obtained, and the temperature of the heat exchange unit is obtained according to the temperature at the compressor.

[0016] The control method further includes: when the rate of change of the ambient temperature is greater than 5℃ / min, increasing the target temperature of the molecular sieve unit and decreasing the duty cycle of the heat dissipation fan; and / or, when the absolute value of the temperature deviation at the current time is less than or equal to 0.5℃, not adjusting the duty cycle of the heat dissipation fan; and / or, when the compressor pressure is greater than 220kPa, decreasing the duty cycle of the compressor and increasing the duty cycle of the heat dissipation fan.

[0017] As a result of adopting the above technical solutions, the present application has the following beneficial effects: 1. In the present application, at least part of the heat exchange units are located between the first molecular sieve tower and the second molecular sieve tower, so that the heat of the high-pressure hot air is transmitted to the molecular sieve unit through the side wall of the heat exchange unit. This forms an efficient waste heat directional transmission channel. This structure directly targets the core defect of low desorption efficiency at low temperature. Instead of discharging waste heat, it ensures that the excess heat generated during the operation of the compressor can be directly and efficiently transmitted to the molecular sieve body through structural integration, providing the necessary heat energy supplement for the desorption stage.

[0018] The system uses the inherent, originally wasted compressor waste heat in the PSA oxygen production process as a heat source, without introducing additional electric heating elements or heat pump systems as in the alternative scheme of electric heating assisted desorption. The system improves the desorption efficiency while not increasing the additional power consumption of the entire machine, realizing the internal circulation and efficient use of energy.

[0019] In addition, the high-pressure hot air enters the total valve after heat exchange through the heat exchange unit, and enters the first molecular sieve tower or the second molecular sieve tower through the total valve. This gas path connection relationship ensures that the high-temperature compressed gas can still be used as raw material gas directly after completing heat exchange. This design avoids the structural complexity, large size, cost increase and potential reliability problems caused by adding a complex, independent circulation system for waste heat utilization. It seamlessly embeds the heat recovery function into the existing PSA gas path, realizing the unity of function integration and structure simplification.

[0020] This integrated structure is a passive, motionless physical heat exchange system, which has much higher reliability than the scheme of adding active heating elements such as electric heating wires inside or outside the adsorption tower. By providing continuous and gentle heat supplement for the molecular sieve at low temperature, it fundamentally avoids the permanent degradation of the performance of the molecular sieve due to incomplete desorption. It effectively improves the problem of life degradation of the molecular sieve due to incomplete desorption, prolongs the service life of the core consumables by improving the working environment of the molecular sieve, and reduces the maintenance cost of the user. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings: Figure 1 A schematic diagram of the principle of the oxygen generator system according to an embodiment of the application; Figure 2 A schematic diagram of the explosion structure of the adsorption tower module according to an embodiment of the application; Figure 3 A sectional view of the adsorption tower module according to an embodiment of the application, wherein the arrows represent the flow direction of the gas in the heat exchange unit; Figure 4 A partial sectional view of the adsorption tower module according to an embodiment of the application; Figure 5 A partial bottom view of the adsorption tower module according to an embodiment of the application, wherein the arrows represent the flow direction of the gas in the heat exchange unit; Figure 6 A schematic diagram of the structure of the oxygen generator system according to an embodiment of the application.

[0022] wherein, 1, compressor; 11, heat dissipation fan; 2, adsorption tower module; 21, heat exchange unit; 211, total valve; 22, molecular sieve unit; 221, first molecular sieve adsorption tower; 222, second molecular sieve adsorption tower; 223, pressure equalizing valve; 3, control module; 31, temperature sensor group. DETAILED DESCRIPTION

[0023] In order to more clearly illustrate the overall concept of the present application, the following will be described in detail with reference to the accompanying drawings.

[0024] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can be practiced in other ways different from those described herein, therefore, the scope of protection of the present application is not limited by the specific embodiments disclosed below.

[0025] As Figures 1 to 6 shown, an oxygen generator system comprises: a compressor 1, the compressor 1 is used to generate high-pressure hot air; An adsorption tower module 2, which comprises a heat exchange unit 21 and a molecular sieve unit 22, the molecular sieve unit 22 comprising a first molecular sieve tower and a second molecular sieve tower, the compressor 1 being in communication with the heat exchange unit 21 to deliver the high-pressure hot air to the heat exchange unit 21, at least part of the heat exchange unit 21 being located between the first molecular sieve tower and the second molecular sieve tower to transfer the heat of the high-pressure hot air to the molecular sieve unit 22 through the side wall of the heat exchange unit 21; A valve group, which comprises a total valve 211 located at the air inlet end of the molecular sieve unit 22 and an equalizing valve 223 located at the oxygen outlet end of the molecular sieve unit 22, the high-pressure hot air entering the total valve 211 after heat exchange by the heat exchange unit 21 and entering the first molecular sieve tower or the second molecular sieve tower through the total valve 211; A heat dissipation module, which comprises a heat dissipation fan 11, the air outlet of the heat dissipation fan 11 corresponding to the air outlet of the compressor 1 to adjust the air outlet temperature of the compressor 1; A control module 3, which is used to control the duty cycle of the heat dissipation fan 11.

[0026] The present application aims to provide an oxygen generator system. The main purpose is to directly and efficiently transfer the waste heat generated by the compressor 1 during operation to the molecular sieve unit 22 through integrated structural design, thereby providing the necessary heat energy for the desorption process of the molecular sieve, solving the problems of low desorption efficiency and short molecular sieve life caused by low temperature in the prior art.

[0027] The core of the present system is the adsorption tower module 2. This module realizes the structural integration of heat exchange function and adsorption separation function.

[0028] The adsorption and desorption processes of the first molecular sieve tower and the second molecular sieve tower in the present embodiment are prior art and will not be described in detail here.

[0029] The heat exchange unit 21, as shown in Figure 2 and Figure 3 , preferably comprises a cylindrical or tunnel-shaped heat exchange cavity, the outer wall of the heat exchange cavity being made of high thermal conductivity material (such as aluminum alloy AL6061 or ADC12). Its core function is to act as a carrier and transfer medium for the waste heat of the compressor 1.

[0030] At least part of the heat exchange unit 21 is located between the first molecular sieve tower and the second molecular sieve tower. Preferably, as shown in Figure 1 and Figure 2As shown, two molecular sieve adsorption towers (first molecular sieve adsorption tower 221 and second molecular sieve adsorption tower 222) can be symmetrically arranged on both sides of the heat exchange unit 21 and achieve large-area structural adhesion with the outer wall of the heat exchange unit 21. This surrounding or adhesion layout ensures that an efficient and low-thermal-resistance heat transfer path can be formed between the side wall of the heat exchange unit 21 and the molecular sieve adsorption tower.

[0031] Specifically, as shown in Figure 2 , Figure 4 and Figure 5 , the heat exchange unit 21 further includes an end cover located at one end of the first molecular sieve tower, the second molecular sieve tower and the heat exchange cavity, and an air inlet is provided on the end cover, which is directly communicated with the exhaust port of the compressor 1 through a pipeline. In this way, the high-temperature and high-pressure gas of 80-100°C discharged by the compressor 1 can first enter the inside of the heat exchange unit 21.

[0032] When the high-temperature compressed gas flows through the inside of the heat exchange unit 21, the heat energy carried thereby is directly transferred to the wall of the molecular sieve adsorption tower in close contact with the side wall of the heat exchange unit 21 by means of heat conduction, thereby increasing the overall temperature of the molecular sieve in the tower. This process is passive and continuous, and as long as the compressor 1 is running, heat will be continuously supplied to the molecular sieve.

[0033] The gas outlet end of the heat exchange unit 21 is communicated with the molecular sieve unit 22 through a total valve 211. As shown in Figure 2 , Figure 4 and Figure 5 , the high-pressure hot air after heat exchange by the heat exchange unit 21 enters the total valve 211 and then enters the first molecular sieve tower or the second molecular sieve tower through the total valve 211.

[0034] Therefore, after completing the heat exchange, the temperature of the gas is reduced to 40-50°C, and the pressure is still maintained at the working pressure (such as 0.08-0.2 MPa) required by the PSA cycle. This air is then distributed to the adsorption tower which is in the adsorption stage through the total valve 211 according to the PSA cycle timing. For the adsorption tower which is in the desorption stage, since the body thereof has been preheated by the above structure, the nitrogen molecules adsorbed in the molecular sieve pores obtain higher kinetic energy and are more easily detached from the van der Waals force, thereby realizing heat-assisted desorption.

[0035] To realize the pressure swing adsorption (PSA) cycle of the two towers alternately, as shown in Figure 1 , the system further provides an equalizing valve 223. The equalizing valve 223 is provided at the oxygen outlet end of the molecular sieve unit 22 and connected between the two adsorption towers, for balancing the pressure between the towers when the cycle is switched.

[0036] In addition, the control module 3 in the system accurately controls the time sequence of the adsorption, desorption, and pressure equalization steps of the double towers by sending on-off instructions to the valve group, and more importantly, ensures the coordination and continuity of the entire PSA oxygen production and waste heat recovery process by controlling the duty cycle of the cooling fan 11.

[0037] It should be noted that the system provides desorption heat energy for the molecular sieve through structural design, especially for low temperature environment, effectively overcomes the desorption problem caused by the increase of molecular sieve adsorption capacity with the decrease of temperature, thereby stabilizing the oxygen production, improving the desorption efficiency, and shortening the system startup time.

[0038] Moreover, the system utilizes the waste heat of the compressor 1 generated during the oxygen production process, without consuming additional electrical energy for heat production as in the electric heating scheme, achieving zero additional energy consumption.

[0039] The integrated module design reduces external connecting pipelines and interfaces, not only making the system structure more compact, but also reducing the risk of failure caused by joint leakage and the like. In addition, the heat transfer process has no moving parts, long service life, and high reliability, which is much higher than the active heating scheme of external electric heating wires, and has compact structure and high reliability.

[0040] As shown in Figure 6 The cooling fan 11 is located above the compressor 1, and the air outlet of the cooling fan 11 is arranged corresponding to the gas outlet of the compressor 1, for adjusting the outlet gas temperature of the compressor 1.

[0041] As a preferred embodiment of the present application, as shown in Figure 1 The control module 3 further comprises a temperature sensor group 31, the temperature sensor group 31 comprising a first temperature sensor and a second temperature sensor, the first temperature sensor being used for measuring the temperature at the piston cylinder of the compressor 1, and the second temperature sensor being used for measuring the ambient temperature.

[0042] The core of the present application is to realize waste heat recovery through structural integration, however, the stable and efficient operation of the system depends on the perception of key states. The main purpose of the present embodiment is to equip the system with a perception component to monitor the temperature parameters closely related to heat transfer and PSA cycle in real time.

[0043] Firstly, it solves the problem that the running state of the system cannot be quantitatively monitored, so that the control module 3 can make decisions based on objective data rather than preset models. Secondly, the temperature at the piston cylinder of the compressor 1 and the ambient temperature are measured for adjusting the outlet gas temperature of the compressor 1, realizing intelligent thermal management of the system.

[0044] Specifically, the first temperature sensor is arranged at an air outlet of the compressor 1 to measure the temperature at a piston cylinder of the compressor 1 and perceive the temperature change of high-temperature gas discharged from the compressor 1; and the second temperature sensor is arranged outside a shell of the system to directly measure the ambient temperature.

[0045] It should be noted that the core function of the control module 3 is to maintain the stability of the temperature in the heat exchange unit 21. Since the high pressure (0.2 MPa) and alternating pressure (0.08-0.2 MPa cycle) environment in the molecular sieve unit 22 can shorten the service life of the directly-installed sensor and cause safety hazards, the first temperature sensor is used to indirectly obtain the temperature of the heat exchange unit 21.

[0046] The second temperature sensor is arranged outside the shell of the system to accurately collect the temperature of the environment in which the device is located. The ambient temperature is a key variable for determining how much heat needs to be supplied to the molecular sieve, especially in wide-temperature-range (-15℃ to 40℃) applications.

[0047] The temperature sensor group 31 is added to the embodiment to achieve accurate temperature measurement, thereby controlling the heat dissipation fan 11 and adjusting the temperature of the heat exchange unit 21, so as to achieve fine control of the oxygen generator system oxygen generation cycle.

[0048] The application further discloses an oxygen generator control method for the system, and the method comprises the following steps. A plurality of sampling time points are set, the temperature of the heat exchange unit at each sampling time point and the target temperature of the molecular sieve unit are obtained, and the temperature deviation between the temperature of the heat exchange unit and the target temperature of the molecular sieve unit at each sampling time point is obtained. The duty cycle of the heat dissipation fan is controlled according to the temperature deviation.

[0049] The main purpose of the control method is to control the duty cycle of the heat dissipation fan by constructing an intelligent temperature control strategy, so as to achieve fine management of desorption heat energy and ensure that the system can maintain desorption efficiency and long-term operation reliability in a wide-temperature-range environment. The system controls the temperature of the heat exchange unit by controlling the duty cycle of the heat dissipation fan, thereby avoiding the adverse effects of high temperature of the heat exchange unit on the adsorption of the molecular sieve and preventing the desorption of the molecular sieve due to low temperature of the heat exchange unit; and the oxygen generator system can have the best adsorption efficiency and desorption efficiency.

[0050] It should be noted that the temperature of the heat exchange unit at each sampling time point is obtained as follows. The temperature of the compressor at each sampling time point is obtained, and the temperature of the heat exchange unit is obtained according to the temperature of the compressor.

[0051] The micro control unit (MCU) of the control module continuously reads the temperature sensor value installed on the compressor box or exhaust passage, i.e. the compressor temperature (T_box), at a fixed sampling period (e.g. once per second). The system maintains a data queue in the memory to record the T_box history data at the current time (k).

[0052] After obtaining the temperature data, the system does not directly use T_box, but converts each T_box value at each time into the temperature of the heat exchange unit (T_exch) through a pre-established temperature correlation model verified by a large number of experiments.

[0053] The model can be a high-precision linear equation, for example, T_exch=a×T_box+b (where a and b are constants determined by experimental data fitting). Specifically, the model is T_exch=T_box+36.15℃, and the fitting goodness R² is as high as 0.94, and the actual measurement error is within ±1℃, fully meeting the control accuracy requirement.

[0054] This step ingeniously uses the stable and quantifiable physical correlation between the compressor temperature and the heat exchange unit temperature, and converts the controlled variable (T_exch) which is difficult to directly and safely measure into an intermediate variable (T_box) which is easy to accurately and reliably measure, thereby bypassing the technical difficulty of installing a sensor in the high-pressure adsorption tower.

[0055] Dynamic target tracking and deviation calculation: the control module compares the calculated T_exch values with a dynamically set target temperature (T_set) one by one, and calculates the temperature deviation e(k)=T_set-T_exch(k) at each sampling time.

[0056] This step introduces target tracking, and through the calculation of the real-time deviation e(k), the system can quantify the gap between the current state and the ideal state, which is used for the control of the heat dissipation fan duty cycle.

[0057] As a preferred embodiment of the present application, at least four sampling times of heat exchange unit temperature and molecular sieve unit target temperature are obtained, including the kth sampling time, the (k-1)th sampling time, the (k-2)th sampling time and the (k-3)th sampling time, According to the heat exchange unit temperature and the molecular sieve unit target temperature, the temperature deviation at each sampling time is obtained, which is denoted as e(k), e(k-1), e(k-2) and e(k-3), respectively; The temperature deviation changes at adjacent sampling instants are obtained and denoted as Δe(k), Δe(k-1), and Δe(k-2), wherein Δe(k)=e(k)-e(k-1), Δe(k-1)=e(k-1)-e(k-2), and Δe(k-2)=e(k-2)-e(k-3). According to the temperature deviation change rate, the duty cycle of the heat dissipation fan is controlled.

[0058] In the embodiment, the control module calculates the control amount of the duty cycle of the heat dissipation fan according to the obtained multiple temperature deviation changes (for example, Δe(k), Δe(k-1), and Δe(k-2)).

[0059] The core control idea of the method is to adjust based on the change trend of the deviation. It not only looks at how large the current deviation e(k) is, but also pays attention to how the deviation changes. The change amount (i.e., the first-order difference of the deviation Δe(k)=e(k)-e(k-1)) of the deviation in consecutive periods is calculated to perceive the trend and acceleration of the temperature change.

[0060] When the system detects that T_exch is rapidly moving away from T_set (i.e., Δe(k) is a large positive value), even if the current absolute deviation e(k) is not large, the system will apply a stronger control action (such as significantly increasing the duty cycle of the fan) in advance to suppress the rising trend, thereby effectively predicting and preventing overshoot. Conversely, when the temperature tends to be stable, the control action will also become gentle. This control based on the change history of the deviation responds more quickly and controls more smoothly.

[0061] It should be noted that directly controlling according to the deviation at a single moment can easily lead to slow response or excessive regulation of the system, causing temperature oscillation. By introducing the deviation data at multiple historical moments to analyze the change trend (i.e., the temperature deviation change rate), the predictability and damping characteristics of the control are improved, so that the regulation of the fan speed is smooth and gradual, avoiding sudden changes, and improving the stability of the system and the service life of the heat dissipation fan.

[0062] As a preferred embodiment under the present embodiment, the duty cycle increment of the heat dissipation fan is specifically: Δu(k)=Kp×[Δe(k)-Δe(k-1)]+Ki×e(k)+Kd×[Δe(k)-2×Δe(k-1)+Δe(k-2)], wherein Δu(k) is the duty cycle increment of the heat dissipation fan, which is used to control the duty cycle of the heat dissipation fan, Kp, Ki, and Kd are respectively a proportional coefficient, an integral coefficient, and a differential coefficient.

[0063] The core purpose of the embodiment is to output a smooth and undamped control quantity by precisely analyzing the temperature deviation and its change trend in multiple dimensions and weighted synthesis, so as to realize fine adjustment of the duty ratio of the heat dissipation fan and ensure the stability of the system temperature.

[0064] Kp x [Δe(k) - Δe(k-1)], which focuses on the speed of deviation change (i.e., acceleration). [Δe(k) - Δe(k-1)] quantifies the change trend of the deviation change rate itself. When the deviation is accelerating to expand or shrink, this term will immediately produce a suppression or promotion effect. It can sense the trend of the temperature about to lose control (such as rapid heating), and regulate in advance before the deviation becomes too large, thereby effectively suppressing the oscillation and overshoot of the system, and making the temperature curve smoothly approach the target value.

[0065] Ki x e(k) is directed to the current static deviation e(k) itself. As long as there is a steady-state error (i.e., there is a fixed difference between the system temperature and the target temperature), this term will continue to accumulate the error value over time and gradually increase the control effect until the static error is completely eliminated. In this way, the system can be long-term stable at the set target temperature and not affected by small disturbances.

[0066] Kd x [Δe(k) - 2 x Δe(k-1) + Δe(k-2)] is the reinforcement and supplement of the proportional term, which can be understood as reacting to the trend of the change trend by introducing earlier historical data (Δe(k-2)) to evaluate the trend of the deviation change to a higher order. When the temperature of the system changes too fast, this term can control the change, making the entire control process more stable, further reducing the adjustment time and improving the dynamic stability of the system.

[0067] Specifically, the proportional coefficient, the integral coefficient, and the differential coefficient are as follows: The critical proportional coefficient Kp0 is set to 1-100, and the critical oscillation period Tp0 is greater than or equal to 10 seconds; According to the critical proportional coefficient Kp0, the proportional coefficient Kp is obtained, wherein Kp = 0.5 x Kp0; According to the proportional coefficient Kp, the current heat exchange unit temperature T, and the critical oscillation period Tp0, the integral coefficient Ki is obtained, wherein Ki = Kp x T / (0.5 x Tp0); According to the proportional coefficient Kp, the current heat exchange unit temperature T, and the critical oscillation period Tp0, the differential coefficient Kd is obtained, wherein Kd = Kp x (0.125 x Tp0) / T.

[0068] The critical proportional coefficient and the critical oscillation period in the embodiment are related parameters of the PID control in the prior art.

[0069] The main purpose of this embodiment is to ensure that the control system is more rapid and accurate.

[0070] First, set the integral coefficient Ki and the differential coefficient Kd to zero, so that the controller is temporarily degraded to a pure proportional (P) controller. Start with a small value of the proportional coefficient Kp (for example, 0) and gradually increase it in small steps (for example, by 0.1 each time).

[0071] After each increase in Kp, observe the response curve of the controlled temperature (T_exch) of the system. When Kp is increased to a certain value Kp0 = 2.0, the system output exhibits a constant-amplitude oscillation, i.e., the temperature fluctuates around the target value with a fixed amplitude (for example, ±2°C) and a fixed period (Tp0 = 10 seconds), neither decaying nor diverging.

[0072] The essence of this step is to excite and measure the inherent oscillation characteristics of the system through experiments. The critical proportional coefficient Kp0 and the critical oscillation period Tp0 are two key inherent parameters that describe the dynamic characteristics of the controlled object. They quantify the maximum gain and natural oscillation frequency of the system before it loses stability.

[0073] With these two parameters obtained, the dynamic characteristics of the system are identified, providing a basis for accurately calculating the complete PID parameters in the next step, completely avoiding the drawbacks of relying on personal experience.

[0074] After obtaining Kp0 and Tp0, calculate the basic PID parameters: the proportional coefficient Kp = 0.5 × Kp0, in this example, Kp = 0.5 × 2.0 = 1.0.

[0075] This is a treatment at the critical stability point. While ensuring that the system has sufficient response speed, it provides sufficient stability margin to prevent oscillation of the system in actual operation.

[0076] The integral coefficient Ki = Kp × T / (0.5 × Tp0). Where T is the sampling period (such as 1 second). In this example, Ki = 1.0 × 1 / (0.5 × 10) = 0.2. The integral action is associated with the oscillation period of the system. It ensures that the integral action is fast enough to effectively eliminate the static error, but not so fast as to introduce additional phase lag and cause oscillation, achieving a balance between response speed and stability.

[0077] The differential coefficient Kd = Kp × (0.125 × Tp0) / T. In this example, Kd = 1.0 × (0.125 × 10) / 1 = 1.25. The strength of the differential action is set, and its value is proportional to the oscillation period of the system. This means that for a slower reacting system (Tp0 is larger), stronger differential action is needed to predict and suppress overshoot. The introduction of the differential term significantly increases the damping of the system, effectively suppressing the overshoot in the control process and speeding up the transition process.

[0078] Specifically, obtaining the proportional coefficient, the integral coefficient, and the differential coefficient further includes: According to the ambient temperature, determining a low-temperature environment or a high-temperature environment; According to the determination result, adjusting the integral coefficient and the differential coefficient, wherein Based on the low-temperature environment, positively adjusting the integral coefficient and the differential coefficient, Based on the high-temperature environment, negatively adjusting the integral coefficient and the differential coefficient.

[0079] The embodiment further proposes a parameter self-adaptive adjustment strategy. The main purpose is to solve the technical problem that the fixed parameter PID controller is difficult to maintain optimal control performance under all working conditions (wide ambient temperature range). By dynamically fine-tuning the control parameters according to the key disturbance factor of ambient temperature, it is ensured that the system can exhibit fast, stable and accurate temperature control characteristics in the entire design temperature range from low temperature to high temperature (-15℃ to 40℃).

[0080] The identification and determination of the environmental conditions, the control module reads the environmental temperature sensor data (T_env) located outside the device shell in real time. The system presets at least two temperature criteria: Low-temperature environment: triggered when T_env≤0℃.

[0081] High-temperature environment: triggered when T_env≥30℃.

[0082] When it is between 0℃ and 30℃, it is a normal temperature environment, and the basic PID parameters are used.

[0083] Parameter dynamic fine-tuning based on working conditions, according to the above determination result, the integral coefficient Ki and the differential coefficient Kd are adjusted in opposite directions and with fine amplitude: Positive adjustment based on low-temperature environment, integral coefficient Ki adjustment, increase by 10% based on the basic value. For example, Ki is adjusted from 0.2 to 0.22.

[0084] In a low-temperature environment, the system has relatively large thermal inertia, it is difficult to warm up, and it is more likely to have static error. Enhancing the integral action can more actively accumulate the deviation, so as to more quickly eliminate the slow warming problem caused by low temperature, and ensure that the system can reach and maintain the set temperature.

[0085] Differential coefficient Kd adjustment, increase by 5% based on the basic value. For example, Kd is adjusted from 1.25 to 1.31.

[0086] When starting at low temperature, the system has a strong demand for temperature rise. Enhancing the differential action can improve the sensitivity and predictability of the control system to the trend of temperature rise, thus providing stronger initial control force, accelerating the response speed during the system startup phase, and shortening the time to reach the target temperature.

[0087] Based on the negative adjustment of high-temperature environment, the integral coefficient Ki is adjusted by 10% less than the base value. For example, Ki is adjusted from 0.2 to 0.18.

[0088] In a high-temperature environment, the system itself has a high ambient temperature, and the compressor waste heat is more likely to cause the temperature to exceed the target value. At this time, weakening the integral action can effectively avoid integral saturation and prevent the control system from producing severe overshoot during cooling due to excessive integration, and even causing oscillation, ensuring the stability of the cooling process.

[0089] The differential coefficient Kd is adjusted by 5% less than the base value. For example, Kd is adjusted from 1.25 to 1.19.

[0090] In high temperature, the heat dissipation demand of the system dominates, and excessive differential action may overreact to small temperature fluctuations, leading to frequent start-stop or dramatic changes in fan speed. Properly weakening the differential action can reduce the sensitivity of the system to high-frequency noise, making the control action smoother and helping to reduce temperature fluctuations in high temperature and improve steady-state accuracy.

[0091] The controlled system is a nonlinear thermodynamic system, and its dynamic characteristics (such as heat capacity, thermal resistance, and heat dissipation efficiency) will change significantly with the ambient temperature. Therefore, the controller parameters are adapted to the changes in the ambient temperature and adjusted adaptively to achieve accurate control of the fan duty cycle.

[0092] As a preferred embodiment of the present control method, the target temperature of the molecular sieve unit is obtained, specifically: The outlet gas pressure and ambient temperature of the heat exchange unit are obtained, and the target temperature of the molecular sieve unit is determined according to the ambient temperature.

[0093] The purpose of setting the target temperature (T_set) in this embodiment is to break the limitation of fixed target temperature in traditional temperature control systems, and to dynamically and finely set the target temperature according to the actual heat demand of the molecular sieve under different outlet gas pressures of the heat exchange unit, thereby maximizing the desorption efficiency and overall energy efficiency of the system while ensuring the safety of the molecular sieve.

[0094] The control module reads the outlet gas pressure (P2) of the heat exchange unit in real time. The system has a built-in judgment logic: If P2≥0.5MPa (this threshold is close to the adsorption pressure 0.8MPa), according to the collected ambient temperature (T_env), the reference target temperature is determined, that is, T_set1=T_env+15℃; If P2≤0.2MPa (this threshold is close to the desorption pressure 0.1MPa), according to the collected ambient temperature (T_env), the reference target temperature is determined, that is, T_set1=T_env+20℃.

[0095] The core of this step is to take advantage of the strong correlation between the adsorption tower pressure and the PSA cycle stage. By judging by pressure, the strategy is accurate and responsive, and a differentiated temperature control strategy is realized.

[0096] A higher temperature (+20℃) is needed at the desorption pressure. Because the essence of desorption is to provide the energy required for the desorption of nitrogen molecules (break Van der Waals force). Higher temperature can significantly increase the kinetic energy of nitrogen molecules, greatly accelerate the desorption rate, ensure complete desorption, and thus directly improve oxygen production and protect the molecular sieve life.

[0097] Only a moderate temperature (+15℃) is needed at the adsorption pressure. In the adsorption stage, the molecular sieve needs to adsorb nitrogen, and too high a temperature will reduce the adsorption capacity of the molecular sieve for nitrogen (according to the adsorption isotherm). Therefore, providing a heat slightly higher than the ambient temperature is mainly to prevent the molecular sieve temperature from being too low, while avoiding unnecessary energy waste.

[0098] Determining the target temperature of the molecular sieve unit also includes: When the target temperature is greater than 40℃, the target temperature is taken as 40℃, When the target temperature is less than 5℃, the target temperature is taken as 5℃.

[0099] The upper limit protection (40℃) is based on the inherent characteristics of the molecular sieve material. Lithium-type molecular sieve will accelerate aging when the temperature exceeds 40℃, resulting in irreversible decrease in its adsorption capacity. This upper limit protection ensures the long-term life of the molecular sieve and the equipment.

[0100] The lower limit protection (5℃) is based on the efficiency critical point of the desorption process. When the temperature is lower than 5℃, the desorption rate will decrease sharply, and even if more heat is provided, the energy efficiency ratio will be too low. Setting this lower limit ensures that the system maintains a feasible and effective working point in any extremely low temperature environment, avoiding inefficient energy input.

[0101] As a preferred embodiment of the control method, the control method further includes: When the change rate of the ambient temperature is greater than 5℃ / min, the target temperature of the molecular sieve unit is adjusted larger, and the duty cycle of the heat dissipation fan is adjusted smaller; and / or, When the absolute value of the temperature deviation at the current time is less than or equal to 0.5°C, the duty cycle of the heat dissipation fan is not adjusted; and / or, When the compressor pressure is greater than 220 kPa, the duty cycle of the compressor is reduced, and the duty cycle of the heat dissipation fan is increased.

[0102] The present embodiment introduces a set of targeted anti-interference optimization measures. The main purpose is to improve the stability, response speed and reliability of the control system when facing external environmental mutations, internal steady-state fluctuations and abnormal working conditions of equipment and other real interferences, and to ensure that the system can perform robustly in various complex application scenarios.

[0103] The present embodiment includes three optimization strategies that can be used independently or in combination.

[0104] Measure 1: Feed-forward compensation control for sudden changes in environmental temperature.

[0105] The control module calculates the rate of change of the environmental temperature (T_env) in real time. When the system detects that |ΔT_env / Δt|>5℃ / min (for example, from 10℃ to 0℃), this measure is triggered.

[0106] Increase the target temperature, immediately increase the dynamically set target temperature (T_set) by 2-3℃. Reduce the duty cycle of the heat dissipation fan, reduce the PWM duty cycle of the heat dissipation fan by 10%-15% (for example, from 50% to 35%).

[0107] This measure belongs to feed-forward control. It does not react after the environmental temperature has affected the controlled temperature (T_exch), but predicts its impact and applies compensation as soon as the disturbance (environmental sudden change) occurs.

[0108] Increasing T_set is to set a buffer target to cope with the upcoming cooling trend; reducing the fan duty cycle is to immediately reduce the heat dissipation intensity and save the internal heat of the system. In this way, the system can effectively resist the rapid drop of T_exch caused by the sudden drop of T_env, shorten the temperature recovery time of the system, and greatly improve the response speed and stability of the system in extreme weather.

[0109] Measure 2: Dead zone control for steady-state fluctuations.

[0110] The control module calculates the absolute value of the current temperature deviation |e(k)| in real time. When |e(k)|≤0.5℃ (for example, T_set=10℃, T_exch=9.8℃), this measure is triggered.

[0111] Under this condition, the control module maintains the current duty cycle of the compressor module (heat dissipation fan) unchanged and does not perform any incremental adjustment Δu(k) output by the PID algorithm.

[0112] This strategy aims to eliminate the frequent micro-movement of the actuator near the balance point. When the system has entered the steady-state error range, small deviations and measurement noise can cause the controller output to have high-frequency, small-amplitude positive and negative adjustment instructions.

[0113] Setting a reasonable insensitive zone (±0.5℃) can effectively filter out these harmless small fluctuations. This measure can reduce the number of times the fan starts and stops or adjusts the speed, greatly reducing mechanical wear and tear, prolonging the life of the fan, and avoiding additional temperature fluctuations caused by frequent actuator movements.

[0114] Measure three: joint protection control for compressor overload.

[0115] The control module monitors the compressor discharge pressure (P1) in real time. When P1>220kPa (indicating that the compressor may be overloaded due to excessive air intake resistance, etc.), this measure is triggered.

[0116] Increase the duty cycle of the cooling fan, immediately increase the PWM duty cycle of the cooling fan to 90%-100% (maximum cooling power). In addition, reduce the duty cycle of the compressor, reduce the compressor speed by 10%-20% (for example, from 1000rpm to 800rpm) through the PWM signal.

[0117] This measure is a multi-variable collaborative overload protection mechanism. When the compressor is overloaded, its heat production will increase sharply, causing T_box and T_exch to rise rapidly, with a risk of exceeding the 40℃ safety limit and damaging the molecular sieve. Increasing the fan duty cycle is to maximize the cooling capacity and quickly remove excess heat. Reducing the compressor speed is to reduce the heat generation from the source and alleviate the overload state. This quickly suppresses the temperature surge under the overload condition, effectively prevents T_exch from exceeding 40℃, and protects the molecular sieve and compressor, the two major components.

[0118] The places not mentioned in the present application can be realized by using or referring to existing technology.

[0119] Each embodiment in the specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0120] The above only describes the embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various changes and modifications to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of the claims of the present application.

Claims

1. An oxygen generator system, characterized in that, include: The compressor is used to generate high-pressure hot air; An adsorption tower module, comprising a heat exchange unit and a molecular sieve unit, wherein the molecular sieve unit comprises a first molecular sieve tower and a second molecular sieve tower, the compressor being connected to the heat exchange unit to deliver the high-pressure hot air to the heat exchange unit, and at least a portion of the heat exchange unit being located between the first molecular sieve tower and the second molecular sieve tower, so that the heat of the high-pressure hot air is transferred to the molecular sieve unit through the sidewall of the heat exchange unit. The valve group includes a main valve located at the inlet end of the molecular sieve unit and a pressure equalization valve located at the outlet end of the molecular sieve unit. High-pressure hot air enters the main valve after heat exchange through the heat exchange unit, and then enters the first molecular sieve tower or the second molecular sieve tower through the main valve. A heat dissipation module, including a cooling fan, wherein the air outlet of the cooling fan is configured to correspond to the air outlet of the compressor, and is used to regulate the air outlet temperature of the compressor; A control module is provided for controlling the duty cycle of the cooling fan.

2. The system according to claim 1, characterized in that, The control module also includes a temperature sensor group, which includes a first temperature sensor and a second temperature sensor. The first temperature sensor is used to measure the temperature at the piston cylinder of the compressor, and the second temperature sensor is used to measure the ambient temperature.

3. An oxygen generator control method, used in the system described in claim 1 or 2, characterized in that, Multiple sampling times are set up to obtain the temperature of the heat exchange unit and the target temperature of the molecular sieve unit at each sampling time, and the temperature deviation between the temperature of the heat exchange unit and the target temperature of the molecular sieve unit at each sampling time is obtained. The duty cycle of the cooling fan is controlled based on the temperature deviation.

4. The control method according to claim 3, characterized in that, The temperatures of the heat exchange unit and the target temperature of the molecular sieve unit are obtained at least four sampling times, including the k-th sampling time, the (k-1)-th sampling time, the (k-2)-th sampling time, and the (k-3)-th sampling time. Based on the temperature of the heat exchange unit and the target temperature of the molecular sieve unit, the temperature deviation at each sampling time is obtained and denoted as e(k), e(k-1), e(k-2) and e(k-3), respectively. The temperature deviation changes between adjacent sampling times are obtained and denoted as Δe(k), Δe(k-1), and Δe(k-2), respectively, where Δe(k) = e(k) - e(k-1), Δe(k-1) = e(k-1) - e(k-2), and Δe(k-2) = e(k-2) - e(k-3). The duty cycle of the cooling fan is controlled based on the temperature deviation change rate.

5. The control method according to claim 4, characterized in that, The duty cycle increment of the cooling fan is specifically as follows: Δu(k)=Kp×[Δe(k)-Δe(k-1)]+Ki×e(k)+Kd×[Δe(k)-2×Δe(k-1)+Δe(k-2)], Where Δu(k) is the duty cycle increment of the cooling fan, used to control the duty cycle of the cooling fan, and Kp, Ki, and Kd are the proportional coefficient, integral coefficient, and derivative coefficient, respectively.

6. The control method according to claim 5, characterized in that, The proportional coefficient, integral coefficient, and differential coefficient are as follows: Set the critical proportional coefficient Kp0 = 1~100, and the critical oscillation period Tp0 ≥ 10 seconds; Based on the critical proportionality coefficient Kp0, the proportionality coefficient Kp is obtained, where Kp = 0.5 × Kp0; Based on the proportional coefficient Kp, the current heat exchange unit temperature T, and the critical oscillation period Tp0, the integral coefficient Ki is obtained, where Ki = Kp × T / (0.5 × Tp0); Based on the proportional coefficient Kp, the current heat exchange unit temperature T, and the critical oscillation period Tp0, the differential coefficient Kd is obtained, where Kd = Kp × (0.125 × Tp0) / T.

7. The control method according to claim 3, characterized in that, The target temperature of the molecular sieve unit is obtained as follows: The outlet pressure and ambient temperature of the heat exchange unit are obtained, and the target temperature of the molecular sieve unit is determined based on the ambient temperature.

8. The control method according to claim 7, characterized in that, Determining the target temperature of the molecular sieve unit further includes: When the target temperature is greater than 40°C, the target temperature is taken as 40°C. When the target temperature is less than 5°C, the target temperature is taken as 5°C.

9. The control method according to claim 3, characterized in that, The temperature of the heat exchange unit at each sampling time is obtained as follows: The temperature at the piston cylinder of the compressor at each sampling time is obtained, and the temperature of the heat exchange unit is obtained based on the temperature at the piston cylinder of the compressor.

10. The control method according to claim 3, characterized in that, Also includes: When the rate of change of ambient temperature is greater than 5°C / minute, increase the target temperature of the molecular sieve unit and decrease the duty cycle of the cooling fan; And / or, When the absolute value of the temperature deviation at the current moment is less than or equal to 0.5℃, the duty cycle of the cooling fan is not adjusted; and / or, When the compressor pressure is greater than 220 kPa, reduce the duty cycle of the compressor and increase the duty cycle of the cooling fan.

Images