Active oxygen concentration control method and active oxygen concentration control system

Abstract

An active oxygen concentration control method and an active oxygen concentration control system using the control method are suitable for an electrochemical performance test using an electrode, and the control method comprises the following steps: collecting current electrochemical impedance spectroscopy data corresponding to a current test solution; determining a cut-off frequency according to the current electrochemical impedance spectroscopy data; dividing the current electrochemical impedance spectroscopy data into a concentration characteristic area with the frequency lower than the cut-off frequency and an electrode characteristic area with the frequency higher than the cut-off frequency; obtaining the current active oxygen concentration according to the current electrochemical impedance spectroscopy data in the concentration characteristic region; generating a control parameter at least according to a difference value between the current active oxygen concentration and a preset active oxygen concentration; and adding a concentration adjusting solution for adjusting the active oxygen concentration into the current test solution according to the control parameters, so that the active oxygen concentration in the current test solution reaches the preset active oxygen concentration.

Description

Technical Field

[0001] This application relates to the field of electrochemical performance testing technology, specifically to a method for controlling reactive oxygen species concentration and a control system for reactive oxygen species concentration. Background Technology

[0002] Medical implants such as pacemaker casings and biodegradable stents typically require electrochemical testing, including in vitro life testing, to assess their expected lifespan. Accelerated life testing is commonly used to shorten the testing cycle. In such accelerated life testing, simulating the oxidative stress environment in vivo is crucial for evaluating the material's corrosion resistance and degradation cycle. For accurate and reliable test results, the concentration of reactive oxygen species (ROS) in the test solution must be precisely and stably controlled within a set value. Furthermore, to test the implant's performance throughout its entire lifespan, accelerated life testing is usually lengthy; specifically, depending on the acceleration factor, the testing time can last for weeks or even months. Therefore, long-term stability of ROS concentration control is also required.

[0003] Currently, reactive oxygen species (ROS) concentration control methods mainly employ a combination of single-frequency electrochemical impedance signal monitoring and feedback control. This involves determining ROS concentration by collecting electrode impedance characteristics and then replenishing the electrolyte based on the difference between the obtained concentration and the set value. However, during long-term testing, the monitoring electrodes are prone to passivation or aging due to contamination. The increase in interfacial impedance caused by electrode aging and the increase in diffusion impedance caused by a decrease in ROS concentration exhibit highly similar impedance characteristics at a single frequency point. This makes it difficult for the system to distinguish the actual cause of the impedance increase, easily misinterpreting the impedance increase caused by electrode aging as insufficient ROS concentration. This leads to incorrect electrolyte replenishment, causing the ROS concentration to deviate significantly from the set value and damaging the testing environment. Summary of the Invention

[0004] The technical problem to be solved by this application is to provide a method and system for controlling reactive oxygen species concentration, which can prevent the reactive oxygen species concentration from being incorrectly adjusted due to impedance changes caused by electrodes.

[0005] To achieve the above objectives, this application provides a method for controlling reactive oxygen species (ROS) concentration, applicable to electrochemical performance testing using electrodes. The method includes: acquiring current electrochemical impedance spectroscopy (EIS) data corresponding to the current test solution; determining a cutoff frequency based on the current EIS data, wherein the cutoff frequency is the frequency at which the ROS mass transfer diffusion process and the interfacial charge transfer process of the electrode are distinguished within the current EIS data; dividing the current EIS data into concentration characteristic regions with frequencies lower than the cutoff frequency and electrode characteristic regions with frequencies higher than the cutoff frequency; obtaining the current ROS concentration based on the current EIS data within the concentration characteristic regions; generating control parameters based at least on the difference between the current ROS concentration and a preset ROS concentration; and adding a concentration adjustment solution to the current test solution according to the control parameters to adjust the ROS concentration, thereby achieving the preset ROS concentration in the current test solution.

[0006] According to the reactive oxygen species concentration control method of this application, the electrochemical impedance spectroscopy is divided into a concentration characteristic region and an electrode characteristic region by using the cutoff frequency. This physically separates the reactive oxygen species mass transfer and diffusion process from the electrode interface charge transfer process, avoiding the problem of overlapping impedance characteristics caused by electrode aging and concentration changes, which can easily trigger incorrect liquid replenishment.

[0007] Furthermore, in the reactive oxygen species concentration control method of this application, the cutoff frequency is preferably obtained as follows: a frequency range near the lowest frequency point is selected from the current electrochemical impedance spectroscopy data, and the average value of the phase angle corresponding to the frequency in the frequency range is calculated as the phase baseline; the baseline deviation point is searched point by point from low frequency to high frequency, and the first point that satisfies the absolute value of the difference between the corresponding phase angle and the phase baseline is greater than a preset tolerance is taken as the baseline deviation point, and the frequency of the baseline deviation point is taken as the cutoff frequency.

[0008] Therefore, the cutoff frequency can be adaptively adjusted according to the drift of factors such as test environment temperature and solution matrix, avoiding the problem of failure when the environment changes due to fixed frequency division. In long-term accelerated life test of implants, the accuracy and reliability of reactive oxygen concentration control can be guaranteed at all times.

[0009] Furthermore, in the reactive oxygen species concentration control method of this application, it is preferred to obtain the current reactive oxygen species concentration based on the current electrochemical impedance spectroscopy data within the concentration characteristic region in the following manner: selecting the lowest frequency point within the concentration characteristic region and calculating the current reactive oxygen species concentration based on the impedance modulus value corresponding to the lowest frequency point; or selecting a frequency range close to the lowest frequency point within the concentration characteristic region and calculating the current reactive oxygen species concentration based on the average impedance modulus value corresponding to each frequency point within the frequency range.

[0010] Therefore, the current reactive oxygen species concentration can be calculated using the impedance modulus value corresponding to the frequency as far away from the electrode characteristic region as possible, thereby better avoiding the influence of electrode interface charge transfer on reactive oxygen species concentration control.

[0011] Furthermore, in the reactive oxygen species concentration control method of this application, it is preferred to calculate the predicted reactive oxygen species concentration at a future moment based on the rate of change of the current reactive oxygen species concentration; and generate the control parameters based on the difference between the predicted reactive oxygen species concentration and the preset reactive oxygen species concentration.

[0012] This compensates for the inherent physical lag of several minutes in the diffusion and mixing of reactive oxygen species in the solution, solves the problems of large concentration fluctuations, slow response, and high overshoot in previous feedback control, and significantly improves the dynamic response speed of concentration control.

[0013] Furthermore, in the reactive oxygen species (ROS) concentration control method of this application, it is preferably applicable to an ROS concentration control system, which includes an ROS injection unit equipped with a pump and a solenoid valve. The pump and the solenoid valve are respectively connected to the test solution and the concentration adjustment solution. In the process of adding the concentration adjustment solution to the current test solution according to the control parameters, the method includes: instructing the pump to add the concentration adjustment solution to the current test solution according to the control parameters generated by the difference between the predicted ROS concentration and the preset ROS concentration; and instructing the solenoid valve to add the concentration adjustment solution to the current test solution according to the control parameters generated by the difference between the current ROS concentration and the preset ROS concentration.

[0014] Thus, the pump enables rapid concentration adjustment in large steps, while the solenoid valve enables precise concentration correction, balancing adjustment speed and control accuracy.

[0015] Furthermore, in the reactive oxygen species concentration control method of this application, the reactive oxygen species concentration control system includes a stirring device for stirring the test solution. During the process of adding the concentration adjustment solution to the current test solution according to the control parameters, the method further includes: while instructing the pump to add the concentration adjustment solution to the current test solution according to the control parameters generated by the difference between the predicted reactive oxygen species concentration and the preset reactive oxygen species concentration, the stirring device is instructed to increase the stirring speed.

[0016] Therefore, by increasing the speed of the stirring device in conjunction with the pump during the liquid replenishment process, the dead zone time of solution mixing is greatly shortened, ensuring that the concentration of active oxygen reaches the preset target value quickly and uniformly.

[0017] Furthermore, in the reactive oxygen species concentration control method of this application, the control method preferably includes: obtaining a confidence factor negatively correlated with the aging degree of the electrode based on the current electrochemical impedance spectroscopy data in the electrode characteristic region; and using the confidence factor to perform a multiplicative weighting on the control parameters generated based on the difference between the predicted reactive oxygen species concentration and the preset reactive oxygen species concentration, and the difference between the current reactive oxygen species concentration and the preset reactive oxygen species concentration.

[0018] Therefore, by weighting the control parameters with a confidence factor, the more severe the electrode aging, the more conservative the control gain becomes. This avoids problems such as adjustment oscillation and excessive addition of reactive oxygen caused by control parameter mismatch after electrode aging. Under extreme conditions, the response sensitivity can be automatically reduced, ensuring the safe operation of the test system throughout its entire life cycle.

[0019] Furthermore, in the reactive oxygen species concentration control method of this application, the control method preferably includes: determining whether the baseline deviation point has been successfully found; if the baseline deviation point has been successfully found, using the frequency corresponding to the baseline deviation point as the cutoff frequency; if the baseline deviation point has not been successfully found, using the frequency corresponding to the previously found baseline deviation point as the cutoff frequency, or using a preset default frequency as the cutoff frequency.

[0020] Therefore, when the baseline deviation point is not successfully locked, the historical valid value or the preset default value is automatically used to avoid unexpected interruption of the control process and adapt to the long-term continuous operation requirements of implant accelerated life test.

[0021] This application also provides a reactive oxygen species (ROS) concentration control system, which controls the ROS concentration in a test solution during electrochemical performance testing using an electrode, and includes: an impedance scanning unit for acquiring electrochemical impedance spectroscopy data of the test solution; an ROS injection unit for injecting a concentration adjustment solution into the test solution to adjust the ROS concentration; a stirring device for stirring the test solution; and a processing unit configured according to the above-described ROS concentration control method to adjust the ROS concentration in the test solution to a preset ROS concentration. Attached Figure Description

[0022] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of an implant testing module and a reactive oxygen species concentration control system according to an embodiment of this application; Figure 2 This is a flowchart of a reactive oxygen species concentration control method according to an embodiment of this application; Figure 3 The EIS data of the test solution before and after environmental drift are presented in the form of Bode plots. Figure 4 This is a flowchart illustrating an embodiment of a reactive oxygen species concentration control method according to this application.

[0023] Explanation of reference numerals in the accompanying drawings for specific embodiments: 100 Implant testing module; 110 Implant sample; 120 Three-electrode system; 130 Test solution; 140 Test container; 150 Waste tank; 200 Active oxygen concentration control system; 210 Wideband impedance scanning unit; 220 Processing unit; 230 Execution unit; 231 Pump set; 232 Solenoid valve array; 233 Stirring device; 240 Storage tank. Detailed Implementation

[0024] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein, and therefore this application is not limited to the specific embodiments disclosed below.

[0026] As illustrated in this application, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0027] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0028] The following is a brief description of the application of the reactive oxygen species concentration control method and the implant testing module 100 of the control system in this application.

[0029] Figure 1 This is a schematic diagram of an implant testing module 100 and a reactive oxygen species concentration control system 200 according to an embodiment of this application. Figure 1As shown, the implant testing module 100 of this embodiment includes an implant sample 110, a three-electrode system 120, a test solution 130, a test container 140, and a waste liquid tank 150. Furthermore, the implant testing module 100 also includes a heating device and a temperature sensor to maintain the test solution 130 at a constant temperature, and may also include other components for simulating the in vivo environment.

[0030] Implant sample 110 is an implant sample undergoing accelerated life testing, such as an implant made of medical titanium alloy.

[0031] The three-electrode system 120 is an electrochemical testing system consisting of a working electrode, a counter electrode, and a reference electrode. The three-electrode system 120 is connected to the broadband impedance scanning unit 210 in the reactive oxygen concentration control system 200 described later. The three electrodes are immersed in the test solution 130 and generate a current as a feedback current through the voltage provided by the broadband impedance scanning unit 210. The broadband impedance scanning unit 210 can collect the feedback current in real time and generate a broadband electrochemical impedance spectrum (hereinafter referred to as "EIS").

[0032] The test solution 130 is a solution used to simulate the in vivo environment in which the implant sample 110 is implanted. Its composition can be selected according to actual needs. The test container 140 contains the implant sample 110, the test solution 130, the three-electrode system 120 and other components.

[0033] Waste liquid tank 150 is connected to test container 140 via pipeline. Waste liquid generated during accelerated life test of implant sample 110 can be recycled to waste liquid tank 150 via pipeline to prevent waste liquid from adversely affecting test results.

[0034] Next, the reactive oxygen species concentration control system 200 of this embodiment will be described.

[0035] like Figure 1 As shown, the reactive oxygen species concentration control system 200 includes a wideband impedance scanning unit 210, a processing unit 220, and an execution unit 230.

[0036] The wideband impedance scanning unit 210 is a unit used for electrochemical testing. It includes, for example, an electrochemical workstation that provides voltage to the electrodes in the three-electrode system 120 and acquires feedback current. An EIS is generated based on the voltage and the acquired feedback current. Specifically, sinusoidal AC excitation signals of different frequencies are applied between the working electrode and the counter electrode, and the feedback signal of the generated AC current is acquired simultaneously. Data processing is performed on the excitation signal and the feedback signal to obtain the impedance magnitude, phase angle, real impedance, and imaginary impedance at different frequencies. An EIS is generated through a full-band frequency scan. In this embodiment, the scanned frequency range is a wideband range from 0.1 Hz to 100 kHz.

[0037] The processing unit 220 processes the EIS obtained in the wideband impedance scanning unit 210 and generates instructions for controlling the execution unit 230 based on the processing results. The specific working method of the processing unit 220 will be described later.

[0038] The execution unit 230 in this embodiment includes a pump group 231 consisting of multiple pumps and a solenoid valve array 232 consisting of multiple solenoid valves. Both the pump group 231 and the solenoid valve array 232 are connected to the test container 140 through pipelines, and are also connected to the storage tank 240 storing hydrogen peroxide solution through pipelines. The hydrogen peroxide solution in the storage tank 240 is added to the test solution 130 in the test container 140 by the operation of the pump group 231 or the solenoid valve array 232.

[0039] The pump constituting pump assembly 231 is a precision peristaltic pump used to accurately inject high-concentration hydrogen peroxide solution or purified water into the test solution 130. The pump has millisecond-level start-stop response capability to achieve rapid concentration adjustment in large steps. The solenoid valves constituting solenoid valve array 232 are high-speed opening and closing solenoid valves used to control the switching of the inlet and waste liquid pipelines. Solenoid valve array 232 employs pulse width modulation (PWM) or time proportional control strategies. When micro-adjustment is required, the opening duty cycle or pulse width duration of the solenoid valve can be adjusted to achieve precise fluid addition and liquid level balance at the μL level through high-frequency micro-injection.

[0040] In addition, the execution unit 230 also includes a stirring device 233, which is built into the implant testing module 100 and is used to generate eddies in the test solution 130 to uniformly stir the test solution 130, thereby accelerating the mixing of solutions when a solution of active oxygen source (hydrogen peroxide solution in this embodiment) is added to the test solution 130.

[0041] The reactive oxygen species concentration control method of this application will now be described. This reactive oxygen species concentration control method is used, for example, in the reactive oxygen species concentration control system 200 described above, to control the reactive oxygen species concentration in the test solution 130 in the implant test module 100 described above.

[0042] Figure 2 This is a flowchart of a reactive oxygen species concentration control method according to an embodiment of this application. Figure 2 As shown, the reactive oxygen species concentration control method of this embodiment includes the following steps: S1: Collect EIS data across the entire frequency band; S2: Determine the dynamic cutoff frequency based on full-band EIS data; S3: Determine the variables reflecting reactive oxygen concentration and electrode state from EIS data based on the dynamic cutoff frequency; S4: Generate control instructions to adjust the concentration of reactive oxygen species to a preset value based on the determined variables; S5: Drive the execution unit 230 according to the above control command to add hydrogen peroxide solution to the test solution 130 and adjust the concentration of active oxygen in the test solution 130 to a preset value.

[0043] The following is a detailed explanation of steps S1 to S5.

[0044] In step S1, as described above, the full-band EIS data of the current test solution 130 can be obtained through the wideband impedance scanning unit 210. Here, "full-band" refers to the entire range of scanning frequencies of the wideband impedance scanning unit 210, i.e., from 0.1 Hz to 100 kHz. Furthermore, in step S1, a smoothing filter or other filtering device is used to remove high-frequency electromagnetic noise while retaining electrochemical characteristic peaks.

[0045] In step S2, the dynamic cutoff frequency is determined based on the full-band EIS data obtained in S1, and in step S3, variables reflecting reactive oxygen species concentration and electrode state are determined based on the dynamic cutoff frequency determined in S2. The following, in conjunction with... Figure 2 The relevant calculation and determination methods in S2 and S3 are explained in detail.

[0046] Figure 3 The EIS data of test solution 130 before and after environmental drift are presented in the form of Bode plots. The horizontal axis is the logarithm of frequency f, and the vertical axis is the phase angle Φ. The EIS data before environmental drift is shown by solid lines, and the EIS data after environmental drift is shown by dashed lines.

[0047] like Figure 3As shown, when the environment of test solution 130 experiences environmental drift due to changes in factors such as temperature and solution matrix, the overall EIS of test solution 130 undergoes a frequency shift. Consequently, the cutoff frequency used to determine the variables reflecting reactive oxygen concentration and electrode state also changes. Specifically, in Figure 3 The cutoff frequency is from f before environmental drift. cut1 f after environmental drift cut2 Therefore, if the same cutoff frequency is always used to determine the variables, it will be impossible to cope with changes in the cutoff frequency caused by environmental drift, which will lead to errors in the determination of variables, and consequently, errors in the control of reactive oxygen species concentration, affecting the test results.

[0048] Therefore, in step S2, it is necessary to determine the cutoff frequency of the current test environment of the test solution 130, i.e., the dynamic cutoff frequency f. cut In step S2, the processing unit 220 determines the dynamic cutoff frequency f in the following manner. cut : Calculate the mean of the phase angle data within the lowest frequency band. Specifically, the lowest frequency band includes the lowest frequency f. min The sampling frequency range is 0.1Hz to 100kHz, and 5 to 10 sampling points are set for each tenth octave. The lowest frequency band can be set to 0.1Hz to 1Hz. The mean of the calculated phase angle data is used as the phase baseline Ф. base The Ф base It is a plateau with a relatively stable phase angle in the region dominated by reactive oxygen diffusion. In this embodiment, Ф base Theoretically, it is a value close to -45°. A permissible phase deviation tolerance δ is set, which is adaptively determined, for example, based on the phase angle fluctuation within the low-frequency baseline range according to δ=max(δ0,k·σ). Ф ) is set, where σ Ф The standard deviation of the phase angle within the low-frequency baseline range is represented by δ0, the minimum tolerance is represented by k, and the amplification factor is represented by k. δ0 can be 2° to 5°, and k can be 2 to 4. In this embodiment, δ is preferably about 5°. Scanning point by point along the frequency axis from low to high frequency, calculate the phase angles Ф(f) and Ф at each frequency f. base The absolute value of the difference, and satisfying that the absolute value of the difference is greater than the phase deviation tolerance (i.e., satisfying |Ф(f)-Ф). base The first point of |>δ) is determined as the baseline deviation point, and the frequency of this baseline deviation point is taken as the dynamic cutoff frequency f. cut .

[0049] The dynamic cutoff frequency f is determined in step S2 as described above. cut It can determine the dynamic cutoff frequency f in real time based on the current environment of the test solution 130. cut This ensures the accuracy and reliability of subsequent variable determination from EIS, effectively solving the problem that previous variable determination based on fixed frequencies would fail when the environment drifts.

[0050] In step S3, the processing unit 220 specifically determines the variables reflecting the active oxygen concentration and electrode state in the following manner: Based on the dynamic cutoff frequency f determined in step S2 cut The full-band EIS data is decoupled into two independent regions: a concentration characteristic region and an electrode characteristic region (e.g., referencing...). Figure 3 The frequency within the concentration characteristic region is lower than f. cut Furthermore, the impedance characteristics are mainly controlled by the diffusion rate of reactive oxygen molecules to the electrode surface, while the frequency within the electrode characteristic region is higher than f. cut Furthermore, the impedance characteristics are mainly controlled by the charge transfer resistance at the electrode-solution interface and the double-layer capacitance. Variables reflecting reactive oxygen species (ROS) concentration and electrode state are extracted from two defined regions. Specifically, in the concentration characteristic region, the impedance modulus of the characteristic points or the Warburg coefficient obtained by fitting the impedance modulus is used as the variable reflecting ROS concentration and defined as the concentration control variable S. conc Specifically, the aforementioned feature points are preferably selected from the lowest frequency f within the current scanning cycle. min The point (e.g., f in this embodiment) min Use 0.1Hz as the feature point, or select the low frequency range [f min ,β×f cut Multiple frequency points within the range of β (0.05 to 0.2, preferably 0.1 in this embodiment) are used as feature points, and the average impedance magnitude of these multiple frequency points is used as the impedance magnitude of the feature point. Since the frequency of the feature point selected in this way is far away from the mixing region near the dynamic cutoff frequency, the impedance response is mainly dominated by the diffusion process and is less affected by the charge transfer process at the electrode-solution interface. It has a high monotonicity to changes in active oxygen concentration. In addition, when the measurement repeatability of the lowest frequency point meets the preset threshold, the method of anchoring the lowest frequency point at a single point is beneficial to improving the control update speed. When the lowest frequency point is greatly affected by instantaneous noise, the average impedance magnitude in the low frequency range is beneficial to reduce random errors and improve the stability of concentration judgment. In the electrode characteristic region, the real part of the impedance at the characteristic point or the radius of the arc at the characteristic point fitted in the Nyquist plot is used as a variable reflecting the electrode state, and is defined as the electrode state variable S. ageIn order to accurately characterize the charge transfer resistance at the electrode-solution interface, a frequency higher than f is preferably selected. cut The point with the largest absolute value of the imaginary impedance in the frequency band is taken as the feature point, or the point with the largest absolute value of the phase angle is selected as the feature point. Since the feature point selected in this way corresponds to the Nyquist semicircle vertex or its nearest neighbor, it is more sensitive to the charge transfer resistance and the double layer interface state. It can more stably characterize the passivation, contamination or roughness changes of the electrode surface. Compared with the low-frequency diffusion-dominated feature, it is less directly affected by the fluctuation of active oxygen concentration.

[0051] The variables S for reactive oxygen species concentration and electrode state are determined in step S3 as described above. conc and S age Based on the dynamically determined cutoff frequency in real time, the impedance characteristics are divided into two independent regions, which are mainly affected by the reactive oxygen species concentration and the electrode state. Characteristic points suitable for reflecting the reactive oxygen species concentration and the electrode state are selected from each of the two regions, and the variables are calculated. The variable S is thus determined. conc and S age The physical meanings of these variables do not interfere with each other, and even in long-term testing, these variables can always be reliably determined through real-time dynamic cutoff frequencies.

[0052] In step S4, the processing unit 220 specifically generates an instruction for adjusting the reactive oxygen species concentration to a preset value using the following method: Calculate the concentration control variable S determined in step S3. conc The first derivative of the concentration change rate is used as the rate of change. Based on this rate of change, the reactive oxygen species (ROS) concentration at a future time point is predicted. The concentration difference between the predicted future ROS concentration and the preset ROS concentration is calculated, and the feedforward control variable U is dynamically calculated based on this concentration difference. ff ; Based on the concentration control variable S determined in step S3 conc Given the current reactive oxygen species (ROS) concentration, calculate the concentration difference between the current ROS concentration and the preset ROS concentration, and calculate the feedback control quantity U according to the proportional-integral-derivative (PID) algorithm. pid ; Based on the calculated feedforward control quantity U ff and feedback control quantity U pid According to U base =K ff ·U ff +K pid ·U pid Calculate the basic control quantity U base , where K ff K is the preset feedforward gain coefficient. pidThese are preset feedback gain coefficients, which are used to balance the weights of feedforward control and feedback control in the total control quantity. Based on the electrode state variable S determined in step S3 age The current electrode confidence factor α is calculated according to relevant formulas, for example, based on α=1 / [1+γ·(ΔR)]. 2 The current electrode reliability factor α is calculated using the following method: γ is a preset sensitivity coefficient, which is set according to the actual situation; for example, γ could be 5. ΔR is the impedance drift rate, which is calculated, for example, by ΔR = (S... age -R base ) / R base Calculate, where R is the baseline value. base It is the charge transfer resistance of the electrode in its initial state, which is equivalent to the S of the new electrode before the test begins. age value; Based on the calculated basic control quantity U base And electrode reliability factor α, according to U total =α·U base Calculate the final control quantity U total And based on this final control quantity U total A control command is generated to adjust the concentration of reactive oxygen species to a preset value. This control command, in addition to the final control quantity U, is used to generate the control command. total In addition, it is based on parameters such as the flow rate of the pump group 231 and the solenoid valve array 232 in the execution unit 230, and the concentration of the added hydrogen peroxide solution.

[0053] By generating a control command to adjust the concentration of reactive oxygen species to a preset value in step S4 as described above, and using the electrode confidence factor α, which represents the state of the electrode such as the degree of aging, to weight and correct the control quantity, α approaches zero under extreme conditions such as severe electrode aging or sensor failure, thereby reducing the response sensitivity and preventing safety accidents caused by excessive addition of hydrogen peroxide solution, thus playing a protective role.

[0054] Furthermore, in step S4, based on the concentration control variable S determined in step S3... conc An example of a specific method for calculating reactive oxygen species concentration is as follows: 1. Calibration Curve / Table Lookup / Model Fitting: Before the system is put into concentration control, multiple standard solutions with known reactive oxygen species concentrations are prepared under calibration conditions consistent with or equivalent to the actual test. Electrochemical impedance spectroscopy data are collected for each solution, and the concentration control variable S is obtained by following the same feature extraction method as the operation phase. conc Based on the known reactive oxygen species concentrations and corresponding S values ​​of each standard solution. conc Establish S concThe calibration relationship between reactive oxygen species (ROS) and reactive oxygen species (ROS) concentration can be a lookup table relationship, a linear fitting relationship, a piecewise linear fitting relationship, a polynomial fitting relationship, or a fitting relationship based on equivalent circuit parameters. During the operation phase, the processing unit extracts S based on the current cycle's reactive oxygen species (ROS) concentration. conc Based on the calibration relationship, the current reactive oxygen species concentration is calculated.

[0055] 2. Calibration Conditions: Calibrate all conditions, including at least temperature, solution matrix, ionic strength, pH, working electrode material, reference electrode type, working electrode geometry, stirring conditions, AC perturbation amplitude, scan frequency range, and sampling interval. The calibration conditions should preferably be consistent with the actual accelerated lifetime test conditions. If any of the temperature, solution matrix, ionic strength, or pH changes beyond a preset threshold, recalibrate, or call up a lookup table or model parameter that matches the current conditions.

[0056] 3. The reactive oxygen species concentration determined by the above method can be expressed as: C=F cal (S conc ;T, M, I, pH), where C represents the current reactive oxygen species concentration, S conc The following variables represent concentration control variables: T represents temperature, M represents solution matrix, I represents ionic strength, pH represents solution acidity / alkalinity, and F represents the solution pH. cal This refers to a mapping function or lookup table relationship obtained through pre-calibration.

[0057] In step S5, the execution unit 230 receives data from the processing unit 220 based on the final control quantity U. total The received control commands are translated into physical actions of the pump assembly 231 and solenoid valve array 232 included in the execution unit 230. Specifically, the pump assembly 231 responds to the control commands and the feedforward control quantity U. ff The relevant part involves adding hydrogen peroxide solution to the test solution 130 to achieve rapid concentration adjustment in large steps, while the solenoid valve array 232 responds to the control command and feedback control quantity U. pid In related aspects, hydrogen peroxide solution is added to the test solution 130 to achieve precise concentration adjustment through high-frequency micro-injection.

[0058] Therefore, the physical hysteresis of the fluid can be compensated by feedforward control, and steady-state concentration correction can be achieved by combining feedback control. This significantly improves the dynamic response speed of concentration control while ensuring that the concentration of reactive oxygen species in the test solution 130 is kept at the preset value.

[0059] Furthermore, steps S1 to S5 above constitute a control cycle. By repeatedly executing steps S1 to S5 within this control cycle during the accelerated life test of the implant, the concentration of reactive oxygen species in the test solution 130 is accurately and reliably maintained at a preset value throughout the accelerated life test.

[0060] The above describes a method for controlling reactive oxygen species (ROS) concentration according to an embodiment of this application. However, in some embodiments, the method further includes: controlling S... age A threshold is preset, which is the value of S obtained in step S3 due to excessive electrode aging. age When the value exceeds the threshold, the processing unit 220 generates a command to issue a maintenance alarm. This command is sent, for example, to a buzzer included in the reactive oxygen species concentration control system 200 or a smart terminal capable of communicating with the reactive oxygen species concentration control system 200, and an audible alarm is emitted to alert personnel. It should also be noted that the generation of the maintenance alarm command is parallel to the reactive oxygen species concentration control process described above and does not affect the operation of the concentration control.

[0061] In addition, in some embodiments, the active oxygen concentration control method further includes: when the pump group 231 injects hydrogen peroxide solution into the test solution 130, the stirring speed of the stirring device 233 is increased in conjunction with the operation of the pump group 231, so that the solution can be quickly mixed after a relatively large amount of hydrogen peroxide solution is injected, minimizing the physical dead time of solution mixing, thereby assisting the above-mentioned feedforward control to achieve maximum efficiency.

[0062] Furthermore, in some embodiments, the reactive oxygen species concentration control method further includes: between steps S2 and S3, determining whether a cutoff frequency was successfully determined in step S2; if the cutoff frequency was successfully determined in step S2, the determined cutoff frequency is taken as the current dynamic cutoff frequency, and the process proceeds to S3; however, if a baseline deviation point is not found in step S2 due to significant signal noise, it is determined that the cutoff frequency was not successfully determined in step S2, and the previously determined dynamic cutoff frequency is taken as the current dynamic cutoff frequency, or a preset default value is taken as the current dynamic cutoff frequency. The specific control flow in this case can be found in [reference needed]. Figure 4 The control flow is illustrated in the example. In this way, even if a sudden situation such as high signal noise prevents the cutoff frequency from being successfully determined in step S2, the control operation of the reactive oxygen species concentration control system 200 will not be interrupted, ensuring continuous system operation and continuous control of the reactive oxygen species concentration.

[0063] In addition, in some embodiments, solutions other than hydrogen peroxide solution can be used to adjust the concentration of reactive oxygen species in the test solution. For example, urea peroxide solution can be used to adjust the concentration of reactive oxygen species in the test solution.

[0064] This application can produce the following beneficial effects: (1) The EIS is divided into two independent frequency bands dominated by reactive oxygen concentration and electrode state such as electrode aging by the cutoff frequency. Variables reflecting reactive oxygen concentration and electrode state are extracted from the two frequency bands respectively. Signal decoupling is achieved from the physical level, fundamentally avoiding misjudging electrode aging as insufficient reactive oxygen concentration, preventing incorrect liquid replenishment from damaging the test environment, and ensuring the authenticity and reliability of test data. (2) The coordinated control of concentration trend prediction feedforward and PID steady-state feedback is adopted. The feedforward compensates for the time lag of solution diffusion and mixing in advance, and the feedback accurately eliminates the concentration deviation, significantly reducing concentration fluctuation and shortening the adjustment time, so as to achieve high-precision and fast-response reactive oxygen concentration control. (3) By determining the dynamic cutoff frequency in real time, the feature segmentation point can be adaptively adjusted according to environmental changes such as temperature and solution matrix, solving the problem of fixed frequency division failing under environmental drift, and meeting the continuous and stable control requirements of long-cycle accelerated life test for several weeks to several months. (4) Calculate the nonlinear electrode confidence factor based on the electrode state variables, dynamically correct the control gain. The more severe the electrode aging, the more conservative the system response. It can automatically reduce the sensitivity under extreme conditions, avoid excessive injection of hydrogen peroxide solution, ensure test safety, and the electrode state monitoring does not interfere with the concentration control work. (5) No additional concentration or electrode status sensors are required. Concentration control and electrode health assessment can be achieved simultaneously by simply reusing EIS data. The system hardware architecture is simple, reducing the cost of testing equipment and the complexity of operation and maintenance.

[0065] The basic concepts have been described above. Obviously, for those skilled in the art, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0066] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

Claims

1. A method for controlling reactive oxygen species concentration, applicable to electrochemical performance testing using electrodes, characterized in that, The control method includes: Collect the current electrochemical impedance spectroscopy data corresponding to the current test solution; The cutoff frequency is determined based on the current electrochemical impedance spectroscopy data. The cutoff frequency is the frequency at which the reactive oxygen mass transfer diffusion process and the interfacial charge transfer process of the electrode are distinguished in the current electrochemical impedance spectroscopy data. The current electrochemical impedance spectroscopy data is used to delineate concentration characteristic regions with frequencies below the cutoff frequency and electrode characteristic regions with frequencies above the cutoff frequency. The current reactive oxygen species concentration is obtained based on the current electrochemical impedance spectroscopy data within the concentration characteristic region. Control parameters are generated based at least on the difference between the current reactive oxygen species concentration and the preset reactive oxygen species concentration; According to the control parameters, a concentration adjustment solution for adjusting the concentration of reactive oxygen species is added to the current test solution to achieve the preset concentration of reactive oxygen species in the current test solution.

2. The method for controlling reactive oxygen species concentration as described in claim 1, characterized in that, The cutoff frequency is obtained in the following way: Select a frequency range near the lowest frequency point from the current electrochemical impedance spectroscopy data, and calculate the average value of the phase angles corresponding to the frequencies within that frequency range as the phase baseline; The baseline deviation point is found by scanning point by point from low frequency to high frequency. The first point where the absolute value of the difference between the corresponding phase angle and the phase baseline is greater than the preset tolerance is taken as the baseline deviation point, and the frequency of the baseline deviation point is taken as the cutoff frequency.

3. The method for controlling reactive oxygen species concentration as described in claim 2, characterized in that, The current reactive oxygen species concentration is obtained from the current electrochemical impedance spectroscopy data within the concentration characteristic region as follows: The lowest frequency point is selected from the concentration feature region, and the current reactive oxygen species concentration is calculated based on the impedance modulus value corresponding to the lowest frequency point. Alternatively, a frequency range close to the lowest frequency point is selected from the concentration feature region, and the current reactive oxygen species concentration is calculated based on the average impedance modulus value corresponding to each frequency point in the frequency range.

4. The method for controlling reactive oxygen species concentration as described in any one of claims 1 to 3, characterized in that, The control method further includes: Calculate the predicted reactive oxygen species concentration at a future moment based on the current rate of change of reactive oxygen species concentration; The control parameters are generated based on the difference between the predicted reactive oxygen species concentration and the preset reactive oxygen species concentration.

5. The method for controlling reactive oxygen species concentration as described in claim 4, characterized in that, An active oxygen concentration control system is applicable, comprising an active oxygen dispensing unit equipped with a pump and a solenoid valve, wherein the pump and the solenoid valve are respectively connected to the test solution and the concentration adjustment solution, and the process of adding the concentration adjustment solution to the current test solution according to the control parameters includes: The pump is instructed to add the concentration adjustment solution to the current test solution based on the control parameters generated by the difference between the predicted reactive oxygen species concentration and the preset reactive oxygen species concentration. The solenoid valve is instructed to add the concentration adjustment solution to the current test solution based on the control parameters generated by the difference between the current reactive oxygen species concentration and the preset reactive oxygen species concentration.

6. The reactive oxygen species concentration control method as described in claim 5, characterized in that, The reactive oxygen species concentration control system includes a stirring device for stirring the test solution, and further includes the following during the process of adding the concentration adjustment solution to the current test solution according to the control parameters: While instructing the pump to add the concentration adjustment solution to the current test solution based on the control parameters generated by the difference between the predicted reactive oxygen species concentration and the preset reactive oxygen species concentration, the stirring device is instructed to increase the stirring speed.

7. The method for controlling reactive oxygen species concentration as described in claim 4, characterized in that, The control method further includes: A confidence factor negatively correlated with the degree of aging of the electrode is obtained based on the current electrochemical impedance spectroscopy data within the electrode characteristic region. Using the reliability factor, the control parameters generated based on the difference between the predicted reactive oxygen species concentration and the preset reactive oxygen species concentration, and the difference between the current reactive oxygen species concentration and the preset reactive oxygen species concentration are multiplied and weighted.

8. The method for controlling reactive oxygen species concentration as described in claim 2, characterized in that, The control method further includes: A determination is made as to whether the baseline deviation point has been successfully found. If the baseline deviation point is successfully found, the frequency corresponding to the baseline deviation point is used as the cutoff frequency. If the baseline deviation point is not successfully found, the frequency corresponding to the previously found baseline deviation point is used as the cutoff frequency, or a preset default frequency is used as the cutoff frequency.

9. A reactive oxygen species concentration control system, wherein the reactive oxygen species concentration control system controls the reactive oxygen species concentration in the test solution during electrochemical performance testing using electrodes, characterized in that, include: Impedance scanning unit, which is used to acquire electrochemical impedance spectroscopy data of the test solution; An active oxygen dispensing unit is used to dispense a concentration adjustment solution for adjusting the concentration of active oxygen into the test solution; A stirring device for stirring the test solution; as well as A processing unit configured to adjust the reactive oxygen species concentration in the test solution to a preset reactive oxygen species concentration using the reactive oxygen species concentration control method according to any one of claims 1 to 8.

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