Flow valve linearization method and system based on automatic matching of fluid property parameters

Abstract

The application discloses a kind of flow valve linearization method and system based on fluid physical property parameter automatic matching, method includes: S1, preset fluid parameter table;Preset valve and actuator parameter, reynolds number and flow coefficient relationship model structure parameter;S2, obtain control parameter and carry out validity check;S3, call fluid physical property and calculate current working condition full-scale flow;S4, calculate target flow and judge whether normalization flow instruction is zero;S5, calculate target reynolds number;According to reynolds number, calculate flow coefficient;Calculate target effective flow area;S6, calculate valve core target lift and convert stepper motor target position;S7, according to the deviation between the pulse of stepper motor target position pulse and the actual position pulse of encoder, control stepper motor operation, make valve core move to the position corresponding to target lift.The application improves the linear relationship between normalization flow instruction and valve output flow, improves the applicability of fixed structure valve core to multiple fluids.

Description

Technical Field

[0001] This invention belongs to the field of fluid flow control technology, specifically relating to a flow valve linearization method and system based on automatic matching of fluid property parameters. Background Technology

[0002] In industrial temperature control, heat exchange and cooling, and fluid transport systems, it is often necessary to control heat exchange capacity or material transport volume by adjusting fluid flow rate. For applications requiring small flow rates, continuous regulation, and high adjustment resolution, needle valves are commonly used as flow regulation elements. With the development of electric actuators and digital control technologies, stepper motors and lead screw transmission mechanisms can be used to drive the movement of the needle valve spool. By controlling the spool lift, the effective flow area between the spool and the valve seat can be changed, thereby achieving continuous flow regulation.

[0003] The output flow rate of a needle valve is related to factors such as valve core lift, effective flow area, valve outlet coefficient, and fluid density and viscosity. Specifically, the effective flow area formed between the conical valve core and the valve seat changes non-linearly with the valve core lift; different fluids have different densities and viscosities, and fluid viscosity also affects the valve outlet coefficient through flow conditions. Therefore, even if the valve core lift can be accurately controlled, a linear correspondence between the valve core lift and the actual output flow rate is not necessarily established. Thus, linearizing the needle valve flow rate requires simultaneously addressing the geometric non-linearity between the valve core lift and the effective flow area, as well as the fluid characteristic non-linearity between the fluid Reynolds number and the valve outlet coefficient.

[0004] To address the aforementioned issues, existing technologies primarily employ three approaches: linearizing flow characteristics through valve core or flow channel structure; determining valve opening through measured calibration data, table lookup interpolation, or data correction; and integrating flow calculation and opening correction functions at the valve end.

[0005] For the first type of method, by designing a specific valve core profile or flow channel cross-section, the effective flow area changes according to a predetermined law with the valve core displacement or rotation angle. However, when different media all need to obtain similar flow linearity characteristics, different valve core profiles usually need to be designed or configured separately, which increases the work of valve core design, processing, assembly and material management. For the second type of method, when the medium or operating conditions change, it is usually necessary to supplement calibration data, adjust conversion parameters or re-establish the relationship between flow and opening, which is labor-intensive and tedious. For the third type of method, its control process also requires the configuration of temperature and pressure detection elements, and the results of flow estimation and opening adjustment will be affected by detection errors, the applicability of historical data and the iteration process. Summary of the Invention

[0006] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and to propose a flow valve linearization method and system based on automatic matching of fluid property parameters.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The flow valve linearization method based on automatic matching of fluid property parameters is executed by a stepper motor driver installed at the flow valve end. The stepper motor driver is connected to an external control device via a communication bus and controls the stepper motor to drive the valve core to generate axial lift based on encoder feedback.

[0009] The method includes the following steps:

[0010] S1, Preset fluid parameter table; Preset valve and actuator parameters, Reynolds number and discharge coefficient relationship model structural parameters;

[0011] S2. Obtain control parameters and perform validity checks;

[0012] S3. Call the fluid properties and calculate the full-scale flow rate under the current operating conditions;

[0013] S4. Calculate the target flow rate according to the normalized flow rate instruction; when the normalized flow rate instruction is 0, determine the mechanical shut-off position as the target position and proceed to step S7; when the normalized flow rate instruction is greater than 0, proceed to step S5.

[0014] S5. Calculate the target Reynolds number; calculate the outflow coefficient based on the Reynolds number; calculate the target effective circulation area;

[0015] S6. Calculate the target lift of the valve core and convert it to the target position of the stepper motor;

[0016] S7. Execute encoder closed-loop control. Control the stepper motor to run based on the deviation between the target position pulse of the stepper motor and the actual position pulse of the encoder, so that the valve core moves to the position corresponding to the target lift. After the valve core reaches the target position, the stepper motor driver applies a holding current to the stepper motor winding and returns to the stepper motor running state.

[0017] The present invention also includes a flow valve linearization system based on automatic matching of fluid property parameters, including a stepper motor driver, a stepper motor with an encoder, a lead screw and nut transmission mechanism, a needle valve assembly, and an external control device;

[0018] A stepper motor driver includes a communication interface, a processor, non-volatile memory, and a power drive circuit.

[0019] The communication interface is used to receive normalized flow commands, fluid numbers, pressure differences across valves, operation control commands, and commands to add or modify fluid parameters.

[0020] The non-volatile memory is used to store fluid parameter tables, valve and actuator parameters, structural parameters of the Reynolds number and discharge coefficient relationship model, and structural boundary results calculated from the relevant parameters in the valve and actuator parameters;

[0021] The processor is used to execute the flow valve linearization method based on automatic matching of fluid property parameters provided in this invention;

[0022] The power drive circuit is used to control the stepper motor to run according to the target position generated by the processor, and to apply a holding current to the stepper motor winding after the valve core is in place;

[0023] The needle valve assembly includes a valve body, a valve seat, and a conical valve core; the valve seat has a valve seat hole, and the valve core is coaxially fitted with the valve seat hole;

[0024] The stepper motor driver is connected to external control equipment via a communication bus;

[0025] The output shaft of the stepper motor is connected to the lead screw, and the lead screw and nut transmission mechanism converts the rotational motion of the stepper motor into the axial lifting motion of the valve core;

[0026] When the system is working, it adopts the flow valve linearization method based on automatic matching of fluid property parameters provided by this invention.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] 1. This invention establishes a geometric relationship between valve core lift and effective flow area, as well as a model of the relationship between Reynolds number and discharge coefficient for a fixed needle valve structure. The two are combined to inversely calculate the valve core lift corresponding to the target flow rate. Existing mechanical linearization schemes mainly form a predetermined area change law by changing the valve core profile or flow channel cross-section. However, this invention uses a conical valve core with the same fixed structure, determines the change of effective flow area with valve core lift by the valve port geometry, and calculates the discharge coefficient under different Reynolds numbers by using the Reynolds number and discharge coefficient relationship model corresponding to the valve model. This simultaneously handles two types of nonlinearity caused by valve port geometry and fluid characteristics.

[0029] 2. This invention establishes a correspondence between fluid number and fluid density and dynamic viscosity in the stepper motor driver, and calculates the target lift by combining the online input pressure difference across the valve. The driver calls the corresponding density and dynamic viscosity according to the fluid number, calculates the full-scale flow rate under the current operating condition at the maximum effective flow area, and then calculates the target flow rate and target Reynolds number according to the normalized flow command. The discharge coefficient is determined using the Reynolds number and discharge coefficient relationship model, and then the target effective flow area is calculated and the target lift of the valve core is calculated in reverse. Existing discrete data schemes mainly rely on pre-obtained flow rate and opening data for table lookup or interpolation. However, this invention completes continuous calculation through fluid property parameters, the Reynolds number and discharge coefficient relationship model, and the valve port geometry. When the medium is switched, the corresponding fluid parameters are recorded and entered into the same calculation process. This makes the valve body and valve core highly versatile and reduces the design, processing, and material management work of the valve core.

[0030] 3. This invention pre-sets fluid property parameter matching, full-scale flow calculation under current operating conditions, valve core target lift calculation, and encoder position closed-loop control within the digital needle valve actuator. An external control device sends a normalized flow command, fluid number, and pressure difference across the valve. The actuator performs the corresponding calculations at the valve end, generates the motor target position, and controls the valve core to reach the target lift based on the encoder feedback position. Compared to schemes where the upper control system stores multiple flow conversion programs or repeatedly adjusts the valve opening, this invention centralizes media-related model calculations and valve core position execution at the valve end, enabling different media to use a unified external control interface. This reduces parameter configuration and program adaptation work when connecting different valves to the control system and minimizes real-time control interaction between the upper control system and the actuator. Attached Figure Description

[0031] Figure 1 This is a flowchart of the method of the present invention.

[0032] Figure 2 This is a schematic diagram of the system of the present invention.

[0033] Figure 3 This is a schematic diagram of the needle valve assembly in the embodiment.

[0034] Figure 4 This is a graph showing the relationship between the normalized flow command and the actual flow in water medium in the embodiment.

[0035] Figure 5 This is a graph showing the relationship between the normalized flow rate command and the actual flow rate under glycerol medium in the embodiment.

[0036] Figure 6 This is a comparison chart of the relationship between normalized flow commands and actual flow under different media in the embodiments.

[0037] Figure 7This is a comparison chart of the maximum linearity error before and after compensation under different media in the embodiments.

[0038] Figure 8 This is a comparison chart of correct compensation and mismatch compensation under different media in the embodiments.

[0039] Figure 9 This is a comparison chart of the maximum linearity error between correct compensation and mismatch compensation under different media in the embodiments. Detailed Implementation

[0040] This invention provides a flow valve linearization method based on automatic matching of fluid property parameters. The implementation of this method is based on a flow valve linearization system based on automatic matching of fluid property parameters, such as... Figure 2 As shown, the system includes a stepper motor driver, a stepper motor with an encoder, a lead screw and nut transmission mechanism, a needle valve assembly, and external control equipment.

[0041] A stepper motor driver includes a communication interface, a processor, non-volatile memory, and a power drive circuit.

[0042] The communication interface is used to receive normalized flow commands, fluid numbers, pressure differences across valves, operation control commands, and commands to add or modify fluid parameters.

[0043] The non-volatile memory is used to store fluid parameter tables, valve and actuator parameters, structural parameters of the Reynolds number and discharge coefficient relationship model, and structural boundary results calculated from the relevant parameters in the valve and actuator parameters;

[0044] The processor is used to execute the flow valve linearization method based on automatic matching of fluid property parameters of the present invention;

[0045] The power drive circuit is used to control the stepper motor to run according to the target position generated by the processor, and to apply a holding current to the stepper motor windings after the valve core is in position.

[0046] like Figure 3 As shown, the needle valve assembly includes a valve body, a valve seat, and a conical valve core; the valve seat has a valve seat hole, and the valve core is coaxially fitted with the valve seat hole; the same valve core structure can be used for multiple fluids, and the stepper motor driver calculates the corresponding target lift based on the physical properties of the selected fluid. In actual implementation, the valve core and valve seat can adopt conical, spherical, parabolic, stepped, slotted, or composite shapes.

[0047] The stepper motor driver is connected to the external control device via a communication bus. The external control device sends normalized flow commands, fluid numbers, pressure differences across the valve, and operation control commands to the stepper motor driver. The stepper motor driver locally completes the following tasks: calling fluid property parameters, calculating target flow rate, Reynolds number, discharge coefficient, target effective flow area, calculating valve core target lift, and generating motor target position. It also completes closed-loop control of the stepper motor position based on encoder feedback.

[0048] The stepper motor output shaft is connected to the lead screw, and the lead screw and nut transmission mechanism converts the rotational motion of the stepper motor into the axial lifting motion of the valve core. After the valve core reaches the target position, the stepper motor driver applies a holding current to the motor winding to keep the valve core position stable.

[0049] This invention provides a flow valve linearization method based on automatic matching of fluid property parameters, such as... Figure 1 As shown, it includes the following steps:

[0050] S1, Preset fluid parameter table; Preset valve and actuator parameters, Reynolds number and discharge coefficient relationship model structural parameters; Specifically:

[0051] A fluid parameter table is preset in the non-volatile memory of the stepper motor driver. Each fluid parameter record includes:

[0052] ;

[0053] in, Number the fluids. For fluid density, Dynamic viscosity;

[0054] The stepper motor driver supports external control devices to add or modify fluid parameter records via the communication bus, and saves fluid parameter records that have passed validity checks to non-volatile memory;

[0055] The valve and actuator parameters are preset in the stepper motor driver. The parameters include:

[0056] ;

[0057] in, For valve seat bore diameter, The valve core half-cone angle, The maximum permissible lift of the machine, determined by the mechanical limit. For the lead screw, This refers to the number of pulses required per revolution of the motor. This represents the number of pulses corresponding to the mechanical closing position.

[0058] Based on the valve body, valve seat, conical valve core, and specified flow direction, a model relating Reynolds number and discharge coefficient is established, and the structural parameters a, b, and c of the model are preset in the actuator. The established model relating Reynolds number and discharge coefficient is as follows:

[0059] ;

[0060] in, Represents the Reynolds number. Represents the outflow coefficient, when hour ; This represents the limiting parameter of the outflow coefficient at the high Reynolds number end. Location parameters that represent the range of variation of the outflow coefficient. These three parameters represent the curve shape parameters. They are determined by the valve body structure and are associated with and stored in relation to the corresponding valve model.

[0061] Stepper motor driver based on valve seat bore diameter Valve core half-cone angle And the relationship between the effective flow area of ​​the valve port and the critical lift for calculation ,Pick As the maximum lift used for flow control, among which... This represents the absolute mechanical upper limit of the valve core's movement.

[0062] Finally, calculate the maximum effective circulation area:

[0063] .

[0064] S2. Obtain control parameters and perform validity checks; specifically:

[0065] External control devices send the following operating parameters to the stepper motor driver via a communication bus:

[0066] ;

[0067] in, For normalized flow instructions, When the flow control command is represented in integer form, the data is converted into a normalized value within the range of 0 to 1 according to the predefined range. ; Number the fluids. The differential pressure across the valve can be sent by an external control device, calculated from the upstream and downstream pressure signals of the valve, or obtained directly from the differential pressure signal.

[0068] Driver numbering of fluid Pressure difference across the valve When a fluid number changes, the actuator retrieves the fluid parameter record corresponding to the new number and updates subsequent calculations.

[0069] S3, invoke fluid properties and calculate the full-scale flow rate under the current operating conditions; specifically:

[0070] Stepper motor driver based on fluid number Read the corresponding fluid density from the fluid parameter table. and dynamic viscosity And the fluid parameters and pressure difference across the valve. Perform a rationality check; if the above parameters are missing or invalid, stop the target lift calculation and return the corresponding parameter abnormality status;

[0071] The stepper motor driver is determined in step S1. To maximize the effective flow area, the full-scale flow rate under current operating conditions is calculated based on the throttling flow rate relationship for single-phase, Newtonian, and approximately incompressible liquids:

[0072] ;

[0073] in, The outflow coefficient corresponding to the full-scale Reynolds number under the current operating conditions is calculated based on the Reynolds number and outflow coefficient relationship model.

[0074] Based on the average flow velocity at the valve seat orifice and the valve seat orifice diameter, the full-scale Reynolds number for the current operating condition is calculated as follows:

[0075] ;

[0076] The actuator obtains the positive flow solution through iterative solving and uses it as the current fluid, current pressure difference, and maximum effective lift. The corresponding full-scale flow rate; when the fluid number or differential pressure changes, the stepper motor driver updates. The remaining control cycles will use the current calculation results.

[0077] S4. Calculate the target flow rate and determine if the normalized flow rate command is zero; if the normalized flow rate command is greater than zero, proceed to step S5; otherwise, proceed to step S7; specifically:

[0078] The driver converts the normalized flow command into the target flow:

[0079] ;

[0080] when At that time, the actuator generates a mechanical shut-off position pulse. And proceed directly to step S7; when Then proceed to step S5.

[0081] S5. Calculate the target Reynolds number; calculate the outflow coefficient based on the Reynolds number; calculate the target effective flow area; specifically:

[0082] The actuator calculates the target Reynolds number based on the target flow rate, fluid density, dynamic viscosity, and valve seat orifice diameter:

[0083] ;

[0084] The outflow coefficient is calculated based on the Reynolds number and outflow coefficient relationship model.

[0085] The target effective circulation area is calculated as follows:

[0086] For a single-phase, Newtonian, nearly incompressible liquid, the volumetric flow rate of the fluid passing through the needle valve orifice is expressed as:

[0087] ;

[0088] in, Volumetric flow rate; Where A is the outflow coefficient; A is the effective flow area of ​​the valve; The pressure difference across the valve; For fluid density;

[0089] The actuator calculates the target effective flow area based on the target flow rate, discharge coefficient, pressure differential, and fluid density:

[0090] ;

[0091] in, .

[0092] S6. Calculate the target lift of the valve core and convert it to the target position of the stepper motor;

[0093] Specifically, the target lift of the valve core is calculated as follows:

[0094] like Figure 3 As shown, for a needle valve, let the valve seat orifice diameter be... The valve core semi-cone angle is The axial lift of the valve core is ;

[0095] After the valve core opens, an annular flow channel is formed between the conical surface of the valve core and the sharp edge of the valve seat. Considering the limitations of the annular flow area and the valve seat orifice area, the relationship between its geometrically effective flow area and the axial lift of the valve core is expressed as follows:

[0096] ;

[0097] in, The critical lift is the one where the annular flow area equals the valve seat orifice area, and it satisfies:

[0098] ;

[0099] Substituting the area of ​​the valve seat hole into the area of ​​the first segment to find the inverse relationship, we get:

[0100] ;

[0101] when At that time, the valve core has reached the upper limit of mechanical stroke before the annular flow area reaches the valve seat hole area, so the constant area segment does not enter the actual mechanical stroke range;

[0102] Online target ascent reverse only in Within this range; within this range, the target effective flow area and the target valve core lift satisfy the following:

[0103] ;

[0104] Right now:

[0105] ;

[0106] Based on the above regarding the target elevation Taking the quadratic equation and finding its smaller non-negative root that is continuous with the mechanical closing position, we get:

[0107] ;

[0108] The stepper motor driver uses the above formula to calculate the target lift and checks whether the expression within the square root is non-negative and whether the target lift is satisfied:

[0109] .

[0110] Specifically, the conversion of the stepper motor target position is as follows:

[0111] The actuator is based on the target lift of the valve core. Lead of the lead screw Number of pulses required per motor revolution Number of pulses corresponding to the mechanical closing position Calculate the target position pulse of the stepper motor ;

[0112] The pulse increment corresponding to the target lift is:

[0113] ;

[0114] Then the stepper motor target position pulse for:

[0115] ;

[0116] drive pair Perform rounding and positional limiting to ensure it does not exceed [the specified value]. The corresponding maximum flow control position, while not exceeding the mechanically permissible position range.

[0117] S7. Execute encoder closed-loop control; the stepper motor driver responds to the target position pulses of the stepper motor. and encoder actual position pulse The deviation between the valve core and the target position controls the operation of the stepper motor, causing the valve core to move to the position corresponding to the target lift. After the valve core reaches the target position, the stepper motor driver applies a holding current to the stepper motor winding and returns to the stepper motor running state.

[0118] Additionally, it should be noted that in actual implementation, the flow command can use a normalized value (0 to 1), a percentage, an integer scale, analog voltage, analog current, or a target value with flow unit. When using a direct target flow, the driver calculates the effective flow area and target lift from the target value; when using a normalized value, it is calculated according to... To generate the target flow.

[0119] Fluid density and dynamic viscosity can be retrieved via fluid ID, sent directly from external control equipment, or obtained based on medium name, formulation number, concentration, temperature, or batch number. For fluids whose properties change significantly with temperature or concentration, density and dynamic viscosity can be expressed as functions of temperature or concentration and updated by the actuator according to the current state; dynamic viscosity can also be calculated from kinematic viscosity and density.

[0120] In step S3, the full-scale flow rate under the current operating condition can also be obtained using fixed-point iteration, bisection root finding, Newton iteration, or other univariate equation solving methods. For products with a small pressure differential variation range, an analytical approximate relationship between pressure differential and full-scale flow rate can also be established based on the aforementioned continuous calculation relationship. All solution methods use the same maximum effective flow area. The boundary is defined as the maximum effective lift when the normalized flow command is 1. .

[0121] In step S5, the Reynolds number-discharge coefficient relationship of the valve port structure can be a rational power function, or an exponential function, power function, rational function, polynomial function, or a piecewise continuous relationship composed of multiple continuous functions. The function coefficients can be determined based on valve port geometry calculations, flow field simulations, or structural analysis during the product design phase, and stored in association with the corresponding valve model. The function relationship can also use valve core lift, valve port opening ratio, pressure difference, or temperature as additional independent variables to form a multi-parameter continuous function corresponding to the specific valve body structure.

[0122] In step S6, the target effective flow area and valve core lift can be determined using analytical geometric relationships or structural continuity functions of the corresponding surface. The maximum effective lift can be determined by the annular flow area reaching the valve seat orifice area, the flow rate stabilizing with increasing lift, mechanical stroke, or software limit. For valves with measurable leakage or closing gaps, leakage area or zero-position offset area can be added to the area model.

[0123] In step S6, the target lift of the valve core can be obtained analytically, or by using the bisection method, Newton's method, or other numerical root-finding methods. The target position of the stepper motor can be expressed as the number of motor pulses, encoder count value, motor rotation angle, linear displacement of the actuator, or internal position unit of the driver.

[0124] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0125] Example: This example illustrates the method of the present invention using water and glycerin as control media. In this example, both water and glycerin are within a specified pressure difference across the valve. The model calculations and control are performed separately. This embodiment includes the following steps:

[0126] Step 1: Calculate the full-scale flow rate under preset parameters and current operating conditions;

[0127] Pre-set a fluid parameter table in the driver; each fluid parameter record should include at least the fluid number. Medium name, fluid density and dynamic viscosity The fluid parameters used in this embodiment are shown in Table 1 below. The fluid density and dynamic viscosity in this embodiment are physical property parameters under specified temperature conditions (20°C). The glycerol parameters also correspond to specified concentration conditions. Each fluid number corresponds to a determined medium composition and physical property parameter record.

[0128] Table 1 Fluid Parameters

[0129]

[0130] Secondly, the valve and actuator parameters, as well as the structural parameters of the Reynolds number and outflow coefficient relationship model, are preset in the stepper motor driver, as shown in Table 2 below.

[0131] Table 2 Valve and Actuator Parameters and Model Structural Parameters for Relationship between Reynolds Number and Discharge Coefficient

[0132]

[0133] The stepper motor driver, based on the effective flow area relationship of the valve port described in step S6, determines the valve seat orifice diameter. and valve core half cone angle The critical lift was calculated. .because This embodiment uses The maximum lift used for flow control. This serves as the absolute mechanical upper limit of the valve core's movement.

[0134] Maximum effective circulation area Take the area of ​​the valve seat orifice. Calculate the area using the simultaneous equations and numerical solution method described in step S3:

[0135] ;

[0136] ;

[0137] The above values ​​are the model calculation results under the current fluid and current pressure difference.

[0138] Step 2: Flow linearization and control;

[0139] To evaluate the effectiveness of flow linearization control, under the same valve and actuator parameters, fluid properties, and pressure difference across the valve, the normalized flow command was adjusted. The flow rate gradually changes within the effective control range, and the steady-state flow rate corresponding to each instruction is recorded. .

[0140] In uncompensated operating conditions, the valve core lift is directly given according to the normalized flow command. .

[0141] In the compensated operating condition, the target valve lift is calculated based on the current fluid density, dynamic viscosity, Reynolds number, and discharge coefficient, following the methods described in steps S2 to S7. The uncompensated and compensated operating conditions use the same valve body, fluid, pressure differential, and maximum effective lift.

[0142] The ideal curve is taken from the closed endpoint. With full open endpoint The straight line formed by connecting these lines. The flow rate corresponding to any normalized flow command on this straight line is: The uncompensated working condition, the compensated working condition, and the ideal curve are compared.

[0143] The maximum linearity error for each operating condition is calculated using the following formula:

[0144] .

[0145] Normalized flow command For example, the online control process for water medium is as follows:

[0146] External control devices send normalized flow commands to the stepper motor driver Fluid number corresponding to water and the pressure difference across the valve .

[0147] Stepper motor driver according to Calling the fluid density of water Dynamic viscosity ;

[0148] according to Calculate the target flow and obtain ;

[0149] Following the method described in step S5, the Reynolds number is calculated based on the target flow rate, water density, water dynamic viscosity, and valve seat orifice diameter to obtain... ;

[0150] Based on the model relating Reynolds number and outflow coefficient, we obtain... ;

[0151] The target effective circulation area is calculated according to the target effective circulation area calculation method described in step S5. ;

[0152] According to the relationship between effective flow area and valve core lift described in step S6, Substituting into the inverse lift formula, we obtain the target lift. The target lift is less than It is within the effective flow control range.

[0153] according to , pulse / rev, The target lift is converted into the target position, and then rounded according to a preset rounding rule. pulse.

[0154] The stepper motor driver controls the stepper motor's operation and performs closed-loop control of the stepper motor's position based on encoder feedback. When the encoder feedback position reaches 1304 pulses and meets the preset positioning conditions, the valve core is determined to have reached the target position. After the valve core reaches the target position, the stepper motor driver applies a holding current to maintain the valve core position and returns the stepper motor status to the external control device.

[0155] The uncompensated, compensated, and ideal flow rates defined in the linearity evaluation method are compared respectively. The relationship between the normalized flow command and the actual flow rate under water medium is obtained as follows: Figure 4 As shown; Figure 4As shown, the uncompensated flow rate curve of the water medium deviates from the ideal flow rate curve in the middle command range, indicating that the geometric nonlinearity between the effective flow area of ​​the valve orifice and the valve core lift will cause a deviation between the normalized flow rate command and the output flow rate. After adopting the linearization control method, the compensated flow rate curve basically coincides with the ideal flow rate curve, and the relationship between the flow rate and the normalized flow rate command is closer to linear.

[0156] Normalized flow command For example, the online control process for glycerol medium is as follows:

[0157] External control devices send normalized flow commands to the stepper motor driver Fluid number corresponding to glycerol and the pressure difference across the valve .

[0158] Stepper motor driver according to Calling the fluid density of glycerol Dynamic viscosity ;

[0159] according to Calculate the target flow and obtain ;

[0160] Following the method described in step S5, the Reynolds number is calculated based on the target flow rate, the density of glycerol, the dynamic viscosity of glycerol, and the valve seat orifice diameter, to obtain... ;

[0161] According to the model relating Reynolds number and outflow coefficient, ;

[0162] The target effective circulation area is calculated according to the target effective circulation area calculation method described in step S5. ;

[0163] According to the relationship between effective flow area and valve core lift described in step S6, Substituting into the inverse lift formula, we obtain the target lift. The target lift is less than It is within the effective flow control range.

[0164] according to , Pulse / Revolution The target lift is converted into the target position, and then rounded according to a preset rounding rule. pulse.

[0165] The stepper motor driver controls the stepper motor's operation and performs closed-loop control of the stepper motor's position based on encoder feedback. When the encoder feedback position reaches 1578 pulses and meets the preset positioning conditions, the valve core is determined to have reached the target position. After the valve core reaches the target position, the stepper motor driver applies a holding current to maintain the valve core position and returns the stepper motor status to the external control device.

[0166] The relationship between the normalized flow command and the actual flow rate in glycerol medium is as follows: Figure 5 As shown; Figure 5 As shown, glycerol has a significantly higher dynamic viscosity than water. Under the same valve structure and pressure difference conditions, the Reynolds number corresponding to the glycerol condition is lower, and the influence of the discharge coefficient on the flow characteristics is more pronounced. In the uncompensated condition, the valve lift is directly given according to the normalized flow command, and the actual flow curve is affected by both the valve orifice geometry and the change in the discharge coefficient, thus exhibiting nonlinearity. In the compensated condition, software compensation is used to make the actual flow curve approach the ideal straight line determined by the closed and fully open endpoints, and to reduce the maximum linearity error.

[0167] Step S3: Comparison of control results under different media;

[0168] The test results of water and glycerol under various normalized flow commands were plotted on the same coordinate system to compare the uncompensated and compensated flow responses under different fluid property conditions. Figure 6 The figure shown is a comparison of the relationship between normalized flow commands and actual flow under different media.

[0169] like Figure 7 The figure shown is a comparison of the maximum linearity error before and after compensation under different media. Figure 7 The maximum linearity error for each operating condition is given, with the error decreasing from 11.30% before compensation to 0.76% after compensation for water medium, and from 6.03% to 0.91% for glycerol medium. The results show that calculating the Reynolds number and discharge coefficient based on fluid properties, and then using this to inversely calculate the target valve lift, can improve the linear relationship between the normalized flow command and the output flow rate under different media.

[0170] Furthermore, to verify the impact of fluid property parameter matching on the flow linearization effect, a property parameter mismatch condition was set up. Under this condition, for water medium, the actuator used the density and dynamic viscosity of glycerol; for glycerol medium, the actuator used the density and dynamic viscosity of water. The results are as follows: Figure 8 and Figure 9 As shown.

[0171] Depend on Figure 8It is evident that when the driver uses the density and dynamic viscosity corresponding to the actual medium, the output flow curves of water and glycerol are close to their respective ideal straight lines; when the physical properties of another medium are used, the curve deviation in the intermediate flow range increases significantly.

[0172] Figure 9 Quantitative results show that the maximum linearity errors for water media with correct matching and those with property mismatch are 0.7605% and 7.6485%, respectively, while for glycerol media they are 0.9082% and 12.1322%, respectively. This is because density and dynamic viscosity are involved in the calculation of Reynolds number and discharge coefficient, and property mismatch will cause deviations in the calculated results of the target effective flow area and the target valve core lift. The above results indicate that correctly selecting the fluid number and matching the corresponding property parameters according to the actual medium is an important condition for ensuring the linearization effect of flow rates for different media.

[0173] It should be noted that, in this specification, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0174] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A flow valve linearization method based on automatic matching of fluid property parameters, characterized in that, The method is executed by a stepper motor driver located at the flow valve end; the stepper motor driver is connected to an external control device via a communication bus, and controls the stepper motor to drive the valve core through a transmission mechanism to generate axial lift based on encoder feedback; The method includes the following steps: S1, Preset fluid parameter table; Preset valve and actuator parameters, Reynolds number and discharge coefficient relationship model structural parameters; S2. Obtain control parameters and perform validity checks; S3. Call the fluid properties and calculate the full-scale flow rate under the current operating conditions; S4. Calculate the target flow rate according to the normalized flow rate instruction; when the normalized flow rate instruction is 0, determine the mechanical shut-off position as the target position and proceed to step S7; when the normalized flow rate instruction is greater than 0, proceed to step S5. S5. Calculate the target Reynolds number; calculate the outflow coefficient based on the Reynolds number; calculate the target effective circulation area; S6. Calculate the target lift of the valve core and convert it to the target position of the stepper motor; S7. Execute encoder closed-loop control. Control the stepper motor to run based on the deviation between the target position pulse of the stepper motor and the actual position pulse of the encoder, so that the valve core moves to the position corresponding to the target lift. After the valve core reaches the target position, the stepper motor driver applies a holding current to the stepper motor winding and returns to the stepper motor running state.

2. The flow valve linearization method based on automatic matching of fluid property parameters according to claim 1, characterized in that, Step S1 is as follows: A fluid parameter table is preset in the non-volatile memory of the stepper motor driver. Each fluid parameter record includes: ； in, Number the fluids. For fluid density, Dynamic viscosity; The stepper motor driver supports external control devices to add or modify fluid parameter records via the communication bus, and saves fluid parameter records that have passed validity checks to non-volatile memory; The valve and actuator parameters are preset in the stepper motor driver. The parameters include: ； in, For valve seat bore diameter, The valve core half-cone angle, The maximum permissible lift of the machine, determined by the mechanical limit. For the lead screw, This refers to the number of pulses required per revolution of the motor. This represents the number of pulses corresponding to the mechanical closing position. Based on the valve body, valve seat, conical valve core and specified flow direction, establish a model relating Reynolds number and discharge coefficient, and preset the structural parameters a, b, and c of the relational model in the actuator; According to the valve seat bore diameter Valve core half-cone angle And the relationship between the effective flow area of ​​the valve port and the critical lift for calculation ,Pick As the maximum lift used for flow control, among which... As the absolute mechanical upper limit of the valve core movement; Finally, calculate the maximum effective circulation area: 。 3. The flow valve linearization method based on automatic matching of fluid property parameters according to claim 2, characterized in that, Based on the valve body, valve seat, conical valve core, and specified flow direction, the following model establishes the relationship between Reynolds number and discharge coefficient: ； in, Represents the Reynolds number. Represents the outflow coefficient, when hour ; This represents the limiting parameter of the outflow coefficient at the high Reynolds number end. Location parameters that represent the range of variation of the outflow coefficient. These three parameters represent the curve shape parameters. They are determined by the valve body structure and are associated with and stored in relation to the corresponding valve model.

4. The flow valve linearization method based on automatic matching of fluid property parameters according to claim 3, characterized in that, Step S2 is as follows: External control devices send the following operating parameters to the stepper motor driver via a communication bus: ； in, For normalized flow instructions, When the flow control command is represented in integer form, the data is converted into a normalized value within the range of 0 to 1 according to the predefined range. ; Number the fluids. The pressure difference across the valve; Numbering of fluids Pressure difference across the valve When a fluid number changes, the actuator retrieves the fluid parameter record corresponding to the new number and updates subsequent calculations.

5. The flow valve linearization method based on automatic matching of fluid property parameters according to claim 4, characterized in that, Step S3 is as follows: Stepper motor driver based on fluid number Read the corresponding fluid density from the fluid parameter table. and dynamic viscosity And the fluid parameters and pressure difference across the valve. Perform a rationality check; if the above parameters are missing or invalid, stop the target lift calculation and return the corresponding parameter abnormality status; The stepper motor driver is determined in step S1. To maximize the effective flow area, the full-scale flow rate under current operating conditions is calculated based on the throttling flow rate relationship for single-phase, Newtonian, and approximately incompressible liquids: ； in, The outflow coefficient corresponding to the full-scale Reynolds number under the current operating conditions; Based on the average flow velocity at the valve seat orifice and the valve seat orifice diameter, the full-scale Reynolds number for the current operating condition is calculated as follows: ； The positive flow solution is obtained through iterative solution and used as the current fluid, current pressure difference, and maximum effective lift. The corresponding full-scale flow rate; when the fluid number or differential pressure changes, the stepper motor driver updates. The remaining control cycles will use the current calculation results.

6. The flow valve linearization method based on automatic matching of fluid property parameters according to claim 5, characterized in that, Step S4 is as follows: Convert the normalized flow command into the target flow: ； when At that time, the actuator generates a mechanical shut-off position pulse. And proceed directly to step S7; when Then proceed to step S5.

7. The flow valve linearization method based on automatic matching of fluid property parameters according to claim 6, characterized in that, Step S5 is as follows: Calculate the target Reynolds number based on the target flow rate, fluid density, dynamic viscosity, and valve seat orifice diameter: ； The outflow coefficient is calculated based on the Reynolds number and outflow coefficient relationship model. The target effective circulation area is calculated as follows: For a single-phase, Newtonian, nearly incompressible liquid, the volumetric flow rate of the fluid passing through the needle valve orifice is expressed as: ； in, Volumetric flow rate; Where A is the outflow coefficient; A is the effective flow area of ​​the valve; The pressure difference across the valve; For fluid density; Calculate the target effective flow area based on the target flow rate, outflow coefficient, pressure difference, and fluid density: ； in, .

8. The flow valve linearization method based on automatic matching of fluid property parameters according to claim 1, characterized in that, In step S6, the calculation of the target lift of the valve core is specifically as follows: For needle valves, let the valve seat orifice diameter be... The valve core semi-cone angle is The axial lift of the valve core is ; After the valve core opens, an annular flow channel is formed between the conical surface of the valve core and the sharp edge of the valve seat. Considering the limitations of the annular flow area and the valve seat orifice area, the relationship between its geometrically effective flow area and the axial lift of the valve core is expressed as follows: ； in, The critical lift is the one where the annular flow area equals the valve seat orifice area, and it satisfies: ； Substituting the area of ​​the valve seat hole into the area of ​​the first segment to find the inverse relationship, we get: ； when At that time, the valve core has reached the upper limit of mechanical stroke before the annular flow area reaches the valve seat hole area, so the constant area segment does not enter the actual mechanical stroke range; Online target ascent reverse only in Within this range; within this range, the target effective flow area and the target valve core lift satisfy the following: ； Right now: ； Based on the above regarding the target elevation Taking the quadratic equation and finding its smaller non-negative root that is continuous with the mechanical closing position, we get: ； The stepper motor driver uses the above formula to calculate the target lift and checks whether the expression within the square root is non-negative and whether the target lift is satisfied: 。 9. The flow valve linearization method based on automatic matching of fluid property parameters according to claim 1, characterized in that, In step S6, the specific steps for calculating the target position of the stepper motor are as follows: Based on the target lift of the valve core Lead of the lead screw Number of pulses required per motor revolution Number of pulses corresponding to the mechanical closing position Calculate the target position pulse of the stepper motor ; The pulse increment corresponding to the target lift is: ； Then the stepper motor target position pulse for: ； right Perform rounding and positional limiting to ensure it does not exceed [the specified value]. The corresponding maximum flow control position, while not exceeding the mechanically permissible position range.

10. A flow valve linearization system based on automatic matching of fluid property parameters, characterized in that, Includes stepper motor driver, stepper motor with encoder, lead screw and nut transmission mechanism, needle valve assembly and external control equipment; A stepper motor driver includes a communication interface, a processor, non-volatile memory, and a power drive circuit. The communication interface is used to receive normalized flow commands, fluid numbers, pressure differences across valves, operation control commands, and commands to add or modify fluid parameters. The non-volatile memory is used to store fluid parameter tables, valve and actuator parameters, structural parameters of the Reynolds number and discharge coefficient relationship model, and structural boundary results calculated from the relevant parameters in the valve and actuator parameters; The processor is used to execute the flow valve linearization method based on automatic matching of fluid property parameters as described in any one of claims 1-9; The power drive circuit is used to control the stepper motor to run according to the target position generated by the processor, and to apply a holding current to the stepper motor winding after the valve core is in place; The needle valve assembly includes a valve body, a valve seat, and a conical valve core; the valve seat has a valve seat hole, and the valve core is coaxially fitted with the valve seat hole; The stepper motor driver is connected to external control equipment via a communication bus; The output shaft of the stepper motor is connected to the lead screw, and the lead screw and nut transmission mechanism converts the rotational motion of the stepper motor into the axial lifting motion of the valve core; The system employs the flow valve linearization method based on automatic matching of fluid property parameters as described in any one of claims 1-9 during operation.

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