Method and apparatus for controlling an electrically operated valve

Abstract

A control method and device for an electric valve, the control method comprising the steps of: setting a corresponding set torque according to the requirement of each stage of the opening and closing process of the valve; driving an AC asynchronous motor to execute corresponding valve opening or closing action with the set torque as the output torque or the output torque limit; measuring the real-time torque of the AC asynchronous motor or the valve; correcting the output torque by using a PID control algorithm with the set torque as the input and the real-time torque as the feedback, so as to adjust the response speed and control accuracy of the output torque according to the real-time torque; and repeating the steps of measuring and correcting until the valve opening or closing is completed, so as to realize torque closed-loop control of the valve opening or closing operation. The application also discloses a control device for an electric valve for realizing valve opening or closing by using the above control method.

Description

Technical Field

[0001] This invention relates to valve actuation technology, and in particular to a control method and apparatus for controlling an AC asynchronous motor to drive an electric valve using vector frequency conversion technology. Background Technology

[0002] Currently, many valve electric actuators use AC power to directly start AC asynchronous motors. These motors then drive a mechanical transmission mechanism to operate the valve, achieving opening and closing. AC asynchronous motors are widely used in electric actuators due to their simple structure, reliable operation, light weight, low cost, and high starting torque. However, problems such as "cannot open," "cannot close tightly," and "cannot stop accurately" exist during use.

[0003] 1) The torque control accuracy of AC asynchronous motors is low, and the dynamic range of torque and speed is small (peak torque and speed are limited). In addition, factors such as medium temperature, foreign objects, and corrosion can affect the driving torque of AC asynchronous motors, which cannot overcome the resistance torque, resulting in the valve not being able to open when opening. During valve operation, the speed of AC asynchronous motors is fixed, and the valve opening / closing speed is constant. When the valve reaches the stop point, it causes the dynamic load of the valve seat to be overloaded, resulting in the valve not being able to open after it is tightly closed.

[0004] 2) The valve opening / closing stopping method adopts point-to-point triggering, that is, a limit switch (or reed switch) is set at the valve body at the valve opening / closing stopping point, and the valve stops according to the limit switch (or reed switch) reaching the position signal; due to the inherent mechanical clearance of the limit switch (or reed switch) and the large error in repeatability control accuracy, the valve may not be closed tightly or may not be able to stop after being closed tightly, resulting in internal leakage of the valve or the AC asynchronous motor being unable to stop and burning out; in addition, the point-to-point triggering stopping method cannot achieve high-precision position control throughout the entire stroke, and the operator cannot obtain the real-time position information of the valve;

[0005] 3) The force on the valve seat when the valve is fully closed cannot be controlled, which can easily cause the valve to not close tightly and lead to internal leakage. The wear, aging, and electrical parameter drift of the valve during long-term use can cause changes in its characteristics, resulting in a large error between the theoretical output value and the actual output value, and the force on the valve seat when the valve is fully closed is unstable.

[0006] 4) Failure to consider the differences in physical characteristics of AC asynchronous motors resulted in poor control accuracy, small dynamic range of torque and speed, and inconsistent performance of batch products. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a control method and device for an electric valve, addressing the above-mentioned deficiencies of the prior art.

[0008] To achieve the above objectives, the present invention provides a control method for an electric valve, comprising the following steps:

[0009] S100, Set the corresponding torque according to the requirements of each stage of the valve opening and closing process;

[0010] S200: Drive the AC asynchronous motor to perform the corresponding valve opening or closing action with the set torque as the output torque or the output torque limit;

[0011] S300, Measure the real-time torque of the AC asynchronous motor or valve during operation;

[0012] S400. Based on the real-time torque and the set torque, using the set torque as input and the real-time torque as feedback, a PID control algorithm is used to correct the output torque, so as to adjust the response speed and control accuracy of the output torque according to the real-time torque; and

[0013] S500: Repeat steps S300-S400 during the valve opening and closing process until the valve opening or closing is completed, so as to realize the torque closed-loop control of the valve opening or closing operation.

[0014] In the above-mentioned control method for electric valves, in step S300, the real-time torque of the AC asynchronous motor or valve is obtained by current detection combined with vector transformation, or by using a torque sensor to obtain the torque directly from the output shaft of the AC asynchronous motor, the output shaft of the valve reduction gearbox, or the valve drive device.

[0015] The above-mentioned control method for electric valves, wherein the current detection combined with vector transformation method includes using the output current detection circuit in the valve driver to detect the physical parameters of the AC asynchronous motor and calculate the real-time torque, wherein the physical parameters include stator resistance, rotor resistance, stator-rotor mutual inductance, stator-rotor leakage inductance and no-load current.

[0016] In the aforementioned control method for electric valves, the three-phase AC signal of the AC asynchronous motor is converted into the torque component of the stator current through coordinate transformation. Excitation component of stator current The real-time torque is calculated and obtained by using rotor magnetic field orientation vector control, direct torque control, slip frequency vector control, stator magnetic field orientation vector control or air gap magnetic field orientation vector control, depending on the different magnetic field orientations.

[0017] The rotor field orientation vector control is wherein the field orientation is performed based on the rotor's total flux linkage vector direction, and the real-time torque is obtained using the following formula. :

[0018] ;

[0019] in, Let be the number of pole pairs of the AC asynchronous motor. The equivalent mutual inductance of one phase winding when the stator and rotor of the aforementioned AC asynchronous motor are coaxial. The equivalent self-inductance of one phase winding of the rotor of the AC asynchronous motor is given. This refers to the torque component of the stator current of the AC asynchronous motor. The rotor flux linkage of the aforementioned AC asynchronous motor;

[0020] The direct torque control obtains the real-time torque using the following formula. :

[0021] ;

[0022] in, Let be the number of pole pairs of the AC asynchronous motor. For mutual inductance between stator and rotor, For the self-inductance of one phase winding of the stator, The self-inductance of one phase winding of the rotor, For stator flux linkage, For rotor flux linkage, The torque angle is a vector. and The angle between them;

[0023] The slip frequency vector control orients the magnetic field based on the slip frequency vector and obtains the real-time torque using the following formula. :

[0024]

[0025] in, Let be the number of pole pairs of the AC asynchronous motor. The rotor electromagnetic time constant is The equivalent self-inductance of one phase winding of the rotor of the AC asynchronous motor is given. The rotor flux linkage of the aforementioned AC asynchronous motor. The slip angular frequency;

[0026] The stator magnetic field orientation vector control orients the magnetic field according to the stator flux linkage vector direction, and obtains the real-time torque using the following formula. :

[0027]

[0028] in, Let be the number of pole pairs of the AC asynchronous motor. The stator flux linkage of the aforementioned AC asynchronous motor. This refers to the torque component of the stator current;

[0029] The air gap magnetic field orientation vector control is performed based on the direction of the torque air gap flux linkage vector, and the real-time torque is obtained using the following formula. :

[0030]

[0031] in, Let be the number of pole pairs of the AC asynchronous motor. For air gap flux linkage, This represents the torque component of the stator current.

[0032] In the above-mentioned control method for electric valves, the stall torque error of the AC asynchronous motor is controlled within ±10% of the rated torque to stably and effectively control the sealing pressure when the valve is closed.

[0033] The above-mentioned control method for electric valves further includes:

[0034] The current speed of the valve is obtained by using current detection combined with vector transformation or feedback signal from a position sensor. Based on the deviation between the set speed and the current speed, the output speed of the AC asynchronous motor is corrected by a PID control algorithm, and the output torque is further superimposed to correct the speed, so as to meet the speed requirements of each stage of valve opening or closing.

[0035] The above-mentioned control method for electric valves further includes:

[0036] Based on the feedback signal from the position sensor, it is determined whether the position node of each stage of the valve opening or closing process has been reached, and the output torque is further adjusted according to the determination result to meet the control strategy and position accuracy requirements of each stage of the valve opening or closing process.

[0037] In the above-mentioned control method for electric valves, the position sensor is a full-stroke sensor and / or a point-position sensor to achieve high-precision position control throughout the stroke and / or accurate node position control.

[0038] The aforementioned control method for the electric valve further includes torque calibration of the AC asynchronous motor, and further includes:

[0039] The valve actuator changes the set torque of the AC asynchronous motor point by point and drives the AC asynchronous motor to load;

[0040] The output torque of the AC asynchronous motor at the corresponding detection point is detected using a torque calibration device, or the internal torque feedback value of the valve actuator at the corresponding detection point is collected; and

[0041] A graph showing the correspondence between the set torque at each detection point and the corresponding output torque or internal torque feedback value is generated to correct the output torque of the AC asynchronous motor.

[0042] To better achieve the above objectives, the present invention also provides a control device for an electric valve, wherein the above-described control method for the electric valve is used to adjust the output torque of the driving AC asynchronous motor in real time to meet the response speed and control accuracy requirements of each stage of the opening and closing process of the electric valve.

[0043] The technical advantages of this invention are as follows:

[0044] This invention uses a set torque as input and the real-time torque of the detected AC asynchronous motor or valve as feedback. It employs a PID control algorithm to correct the actual output torque during the drive process, adjusting the output torque in real-time based on the real-time torque. This achieves closed-loop torque control for the opening and closing of the electric valve, effectively improving response speed and control accuracy, ensuring the electric valve can "open smoothly," "close tightly," and "stop precisely." Furthermore, this invention can also use a multi-layered PID nesting method to establish torque loop (or current loop), speed loop, and position loop control from the inside out. The closed-loop level or nesting depth can be selected according to the needs of different stages of valve execution, thereby ensuring rapid, accurate, and effective valve execution.

[0045] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of a control method according to an embodiment of the present invention;

[0047] Figure 2 This is an equivalent circuit diagram for stator resistance identification according to an embodiment of the present invention;

[0048] Figure 3 This is an equivalent circuit of motor T according to an embodiment of the present invention;

[0049] Figure 4 Motor reversal according to an embodiment of the present invention Equivalent circuit;

[0050] Figure 5 This is a schematic diagram of the control device structure according to an embodiment of the present invention;

[0051] Figure 6This is a diagram showing the relationship between the set torque and the output torque in the torque calibration of an embodiment of the present invention. Detailed Implementation

[0052] The structural and working principles of the present invention will be described in detail below with reference to the accompanying drawings:

[0053] See Figure 1 Figure 1 is a schematic diagram of the control method according to an embodiment of the present invention. The control method for the electric valve of the present invention aims to ensure that the valve can be "opened," "closed tightly," and "stopped accurately" during its operation. Its core is a complete control method that uses vector frequency conversion technology to drive an AC asynchronous motor to move the valve. Based on the control strategy for the valve opening and closing process, the valve opening and closing process is divided into necessary stages. For example, the valve opening process can be divided into a starting stage, an acceleration stage, a constant speed stage, a deceleration stage, an approaching stage, and a stopping stage; the valve closing process can be divided into a starting stage, an acceleration stage, a constant speed stage, a deceleration stage, an approaching stage, a torque control stage, and a stopping stage; the valve intermediate position execution process can be divided into a starting stage, an acceleration stage, a constant speed stage, a deceleration stage, an approaching stage, and a stopping stage, etc. The control method includes the following steps:

[0054] Step S100: Select the corresponding control strategy according to the valve execution requirements; divide the valve opening or closing execution stage according to the control strategy; set the corresponding set torque according to the requirements of each stage;

[0055] Step S200: Drive the AC asynchronous motor to perform the corresponding valve opening or closing action with the set torque as the output torque or the output torque limit;

[0056] Step S300: Measure the real-time torque of the AC asynchronous motor or valve during operation;

[0057] Step S400: Based on the real-time torque and the set torque, using the set torque as input and the real-time torque as feedback, a PID control algorithm is used to correct the output torque, so as to adjust the response speed and control accuracy of the output torque according to the real-time torque; and

[0058] Step S500: Repeat steps S300-S400 during the valve opening or closing process until the valve is fully opened or closed, so as to realize the torque closed-loop control of the valve opening or closing operation process.

[0059] In step S300, the real-time torque of the AC asynchronous motor or valve can be obtained using a current detection combined with vector transformation, or directly from the output shaft of the AC asynchronous motor, the output shaft of the valve reduction gearbox, or the valve drive device using a torque sensor. When using a torque sensor to obtain the real-time torque, the torque sensor can be installed on the output shaft of the AC asynchronous motor, the output shaft of the valve reduction gearbox, or the input or output shaft of the valve drive device. The torque sensor is then connected to the valve driver or control module. After the measured real-time torque signal is transmitted to the valve driver or control module, a PID control algorithm is used to correct the output torque. In practice, the built-in calculation and control functions of the valve driver can be used directly, or the control module can be integrated into the valve driver, or the control module can be integrated into the control device or controller.

[0060] In this embodiment, when using a current detection combined with vector transformation method to obtain the real-time torque, it is preferable to use the output current detection circuit in the valve driver to detect the three-phase AC signal of the AC asynchronous motor. Combined with the physical parameters of the AC asynchronous motor (which may include stator resistance, rotor resistance, stator-rotor mutual inductance, stator-rotor leakage inductance, and no-load current, etc.), the three-phase AC signal is converted into the torque component of the stator current through coordinate transformation. Excitation component of stator current The real-time torque is obtained using various methods depending on the magnetic field orientation, such as rotor magnetic field orientation vector control, direct torque control, slip frequency vector control, stator magnetic field orientation vector control, or air gap magnetic field orientation vector control. In other words, vector torque control is used as the output method, with the detection result of a torque detection circuit (e.g., a current detection circuit) as the feedback signal. The output torque is adjusted through a PID closed-loop control to ensure that the actual output torque driving the valve operates within the set torque, i.e., the desired value.

[0061] To achieve more precise vector control, this invention may also include a physical parameter identification step for the AC asynchronous motor. This involves collecting parameters such as stator resistance, rotor resistance, stator-rotor mutual inductance, and stator-rotor leakage inductance of the AC asynchronous motor to ensure more accurate basic parameters in torque vector control. Specifically, this includes acquiring the physical parameters of the AC asynchronous motor for more accurate torque vector control. AC and DC excitation signals can be input to the AC asynchronous motor, and stator current feedback can be monitored in real time. The aforementioned parameters are calculated based on the voltage and current values ​​and phase relationships. The no-load current is used to estimate torque consumption during AC asynchronous motor operation (such as friction, ventilation, core loss, etc.) and to compensate for its output torque. This no-load current is preferably 20% to 50% of the motor's rated current.

[0062] This embodiment uses the output current detection circuit in the valve intelligent actuator for parameter detection, and collects the real-time torque (which can be calculated from the rotor equivalent self-inductance, rotor equivalent mutual inductance, rotor flux linkage, and stator current torque components) as feedback. Then, it uses PID control principles to perform closed-loop control and correction of the output torque, ultimately achieving torque vector control and ensuring torque response speed and control accuracy during valve operation. The stator resistance in this embodiment can be obtained in the following way:

[0063] When controlling the inverter to output a single-phase DC voltage, the motor circuit diagram in this case can be simplified as follows: Figure 2 As shown:

[0064]

[0065] in, =DC voltage, =Stator current, =Stator resistance.

[0066] Due to the voltage drop across the switching transistors, the actual voltage applied to the stator will have a certain error. To eliminate this error, multiple different voltage signals can be applied, and the slope between the stator voltage and stator current can be used as the stator resistance.

[0067]

[0068] The rotor resistance, stator-rotor mutual inductance, and stator-rotor leakage inductance in this embodiment can be obtained in the following way:

[0069] The electromagnetic phenomena of an AC asynchronous motor under single-phase sinusoidal signal excitation are basically the same as those under three-phase sinusoidal signal excitation. This method can be used for identification. At the same time, the motor torque is zero and the motor remains stationary. The equivalent circuit of the motor at this time can be replaced by a three-phase equivalent circuit.

[0070] The vector equations of the stator and rotor of an AC asynchronous motor are:

[0071]

[0072] in, , , , For differential operators, For stator resistance, For rotor resistance, For stator leakage, For rotor leakage inductance, For mutual inductance between stator and rotor, For rotor speed, squirrel-cage rotor .

[0073] The output W phase is disconnected, and the U and V phases are controlled by the H-bridge sinusoidal voltage modulation signal to switch the inverter on and off, thereby generating a sinusoidal voltage excitation signal. Let the sinusoidal voltages of the U and V phases be... The phase voltage and phase current in an AC asynchronous motor satisfy the following relationship:

[0074]

[0075]

[0076] in, These are the U-phase, V-phase, and W-phase relative midpoint voltages, respectively.

[0077] At this point, the motor torque is 0. The T-type equivalent circuit diagram of the motor at this time is shown in Figure 3. Generally, the stator leakage inductance is the same as the rotor leakage inductance, that is... . Figure 4 The equivalent circuit diagram of the motor inverse Γ according to an embodiment of the present invention is a circuit after equivalent transformation of T. The relationship between the circuit parameters and the equivalent circuit parameters of the T-type circuit after the transformation is as follows:

[0078]

[0079]

[0080]

[0081] From the diagram, we can see that:

[0082]

[0083]

[0084] In the above formula It is the initial phase of the voltage. It is the initial phase of the current.

[0085] From the formula ~style We can obtain:

[0086]

[0087] By counter The equivalent circuit yields the following expression for impedance:

[0088]

[0089] Apply a frequency of to the AC asynchronous motor respectively and A sinusoidal voltage signal is used to conduct a single-phase test on the motor, and the equivalent impedance of the stator current molecule is detected. (The last part, "and set...", appears to be a fragment and doesn't translate directly.) , by formula Can get the opposite Formulas for calculating motor parameters under equivalent circuit

[0090]

[0091]

[0092]

[0093] Based on the T-type equivalent circuit and inversion Equivalent circuit parameter conversion formula The formulas for calculating the motor rotor resistance, stator-rotor mutual inductance, and stator-rotor leakage inductance are as follows:

[0094]

[0095]

[0096]

[0097] In one embodiment of the present invention, rotor field orientation vector control is preferably used. The field orientation is performed according to the rotor's total flux linkage vector direction, and the real-time torque is obtained using the following formula. :

[0098]

[0099] in, Let be the number of pole pairs of the AC asynchronous motor. The equivalent mutual inductance of one phase winding when the stator and rotor of the aforementioned AC asynchronous motor are coaxial. The equivalent self-inductance of one phase winding of the rotor of the AC asynchronous motor is given. This refers to the torque component of the stator current of the AC asynchronous motor. The rotor flux linkage of the AC asynchronous motor is denoted as .

[0100] Its control principle is as follows:

[0101]

[0102]

[0103]

[0104] in, The M-axis component of the rotor's total flux linkage; The rotor's total flux linkage T-axis component; The rotor current is the M-axis component; This refers to the T-axis component of the rotor current. This represents the number of pole pairs of the motor. This is the equivalent self-inductance of one phase winding of the rotor; This refers to the equivalent mutual inductance of a single-phase winding when the stator and rotor are coaxial. This refers to the torque component of the stator current; For rotor flux linkage; The rotor electromagnetic time constant; It is a differential operator; This is the excitation component of the stator current.

[0105] In another embodiment of the present invention, direct torque control can also be used, and the real-time torque can be obtained using the following formula. :

[0106] ;

[0107] in, Let be the number of pole pairs of the AC asynchronous motor. For mutual inductance between stator and rotor, For the self-inductance of one phase winding of the stator, The self-inductance of one phase winding of the rotor, For stator flux linkage, For rotor flux linkage, The torque angle is a vector. and The angle between them.

[0108] This direct torque control is based on the mathematical model of the stator shaft system and uses the space vector analysis method to achieve motor control. Its control principle is as follows:

[0109] Stator flux linkage equation:

[0110]

[0111] in, This is the voltage vector of the stator shaft system.

[0112] Ignore stator resistance voltage drop ,have:

[0113]

[0114] The torque equation is:

[0115]

[0116] The torque angle is a vector. and The angle between them.

[0117] In the third embodiment of the present invention, slip frequency vector control can be used to orient the magnetic field according to the slip frequency vector, and the real-time torque can be obtained using the following formula. :

[0118]

[0119] in, Let be the number of pole pairs of the AC asynchronous motor. The rotor electromagnetic time constant is The equivalent self-inductance of one phase winding of the rotor of the AC asynchronous motor is given. For rotor flux linkage, This is the slip angular frequency.

[0120] Slip frequency vector control can be performed based on rotor magnetic field fixed vector control, and its control principle is as follows:

[0121]

[0122]

[0123] in, This is the slip angular frequency.

[0124] In the fourth embodiment of the present invention, stator magnetic field orientation vector control is employed. The magnetic field is oriented according to the direction of the stator flux linkage vector, and the real-time torque is obtained using the following formula. :

[0125]

[0126] in, Let be the number of pole pairs of the AC asynchronous motor. The stator flux linkage of the aforementioned AC asynchronous motor. This refers to the torque component of the stator current of the AC asynchronous motor.

[0127] In this embodiment, the magnetic field is oriented according to the direction of the stator flux linkage vector, and its control principle is as follows:

[0128]

[0129]

[0130]

[0131] in, For stator flux linkage; The M-axis component of the stator's total flux linkage; The T-axis component of the stator's total flux linkage; Let be the leakage flux coefficient; from the formula It can be seen that the stator flux linkage yes and The functions are coupled to each other, so a decoupling controller needs to be added. The control principle is as follows:

[0132]

[0133]

[0134] in, The stator current excitation component is given; Given the stator flux linkage; To decouple the control signal; the formula Substitute into formula From the first equation, we can obtain:

[0135]

[0136] To leverage accomplish Decoupling control enables:

[0137]

[0138] After transformation, we can obtain:

[0139]

[0140] Mode It is a decoupler module algorithm that can directly calculate the stator flux linkage vector from the voltage and current detected on the stator side. This achieves decoupling.

[0141] In the fifth embodiment of the present invention, air gap magnetic field orientation vector control is adopted. The magnetic field is oriented according to the direction of the torque air gap flux linkage vector, and the real-time torque is obtained using the following formula. :

[0142]

[0143] in, Let be the number of pole pairs of the AC asynchronous motor. For air gap flux linkage, This represents the torque component of the stator current.

[0144] In this embodiment, the magnetic field is oriented according to the direction of the air gap flux vector, and its control principle is as follows:

[0145]

[0146]

[0147]

[0148] In the aforementioned vector control method, the physical parameters determining the torque control accuracy can drift over long-term operation. Furthermore, the formula for the motor output torque in the aforementioned control method theoretically neglects factors such as system mechanical friction resistance. Therefore, in one embodiment of the present invention, torque calibration can be performed periodically to eliminate the adverse effects of the aforementioned factors and achieve long-term stability of the system's torque control accuracy. Specifically, the present invention may further include the following steps: calibrating the output torque of the AC asynchronous motor to correct the output torque of the AC asynchronous motor, effectively improving torque control accuracy and achieving precise control of the output torque. This step may further include:

[0149] Connect the AC asynchronous motor to the valve actuator or control module, correctly set the basic system parameters and perform parameter identification; select no less than 10 torque values ​​as detection points within the range of 10% to 200% of the rated torque of the AC asynchronous motor, and distribute the detection points evenly.

[0150] The torque calibration device is mounted and fixed on the output shaft of the AC asynchronous motor, and connected to the valve actuator or control module via a wired signal cable or wireless communication module. The valve actuator sequentially changes the set torque of the AC asynchronous motor according to the torque value at each detection point, drives the AC asynchronous motor to load, and detects the corresponding output torque. Each detection point is tested at least three times, and the arithmetic mean is taken as the output torque detection result for that detection point.

[0151] The valve actuator or control module collects and analyzes the above detection data, compares the deviation between the set torque and the corresponding output torque, and generates a set of statistical data. Based on the statistical data, it generates a graph or output showing the correspondence between the set torque and the corresponding output torque at each detection point (the display results can be graphs and curves, along with necessary prompts for confirmation), which is used to correct the output torque of the AC asynchronous motor. After the relevant corresponding graphs are confirmed, the valve actuator or control module can perform the correction.

[0152] This involves measuring the actual output torque of the AC asynchronous motor under a set torque and correcting the output torque based on the real-time torque to obtain a more accurate output torque for the torque control stage. This embodiment only uses the comparison between the set torque and the corresponding output torque as an example, as shown in the table below. The table uses an AC asynchronous motor with a rated power of 0.55kW, a rated speed of 1450rpm, and a rated torque of 3.6Nm as an example, showing the relationship between its output torque (i.e., the stall torque at the corresponding detection point) and the set torque. Controlling and correcting the low-speed and stall torque of the AC asynchronous motor allows for accurate sealing pressure during valve closure. The stall torque error of the AC asynchronous motor is preferably controlled within ±10% (preferably ±4%) of the rated torque to stably and effectively control the sealing pressure during valve closure. Simultaneously, the discrete detection point data in the statistical table can be integrated into a piecewise function describing the relationship between the set torque and the corresponding output torque (e.g., ...). Figure 6 As shown, the line segments are relatively continuous, with the first and last segments connected, and with different slopes, for querying and use in the torque control process.

[0153] Table 1 Comparison of Set Torque and Corresponding Output Torque

[0154] Serial Number Set torque / Nm Output torque / Nm error / % 1 0.50 0.47 0.83 2 1.00 0.88 3.31 3 1.50 1.40 2.76 4 2.00 2.10 2.76 5 2.50 2.58 2.21 6 3.00 3.05 1.38 7 3.50 3.38 3.31 8 3.70 3.60 2.76 9 4.00 3.90 2.76 10 4.50 4.18 8.84 11 5.00 4.56 12.15 12 5.50 5.11 10.77 13 6.00 5.47 14.64 14 6.50 5.81 19.06 15 7.00 6.14 23.76 16 7.50 6.49 27.90

[0155] The above data describes the relationship between the set torque and output torque of the AC asynchronous motor using a sufficiently dense, evenly distributed set of feature points. In this embodiment, when the set torque is within the rated torque range (which is also the torque range required for torque control), the error between the set torque and output torque is within ±10% (preferably ±4%) of the rated torque, showing a good linear relationship; when the set torque exceeds the rated torque, the error increases. The relationship between the set torque and output torque can be represented by a piecewise linear equation and used to correct the output torque. Because the test results in the corresponding table are discrete data, in actual use, the data between detection points are interpolated and supplemented using the line segment equation between adjacent points. For example, when the set torque is between 0.5 and 1.0 Nm, according to... Figure 6 The equation of the relationship curve can be obtained from the starting point (0.5, 0.47) and ending point (1.0, 0.88) of the leftmost line segment:

[0156] y = 0.82x + 0.06

[0157] Where x is the set torque, and 0.5≤x≤1.0, and y is the output torque.

[0158] Therefore, piecewise equations can be used to correlate the set torque with the output torque, thereby achieving the goal of accurately controlling the torque by correcting the output value.

[0159] To further improve control accuracy, in one embodiment of the present invention, the method may further include: calculating the current speed of the valve using a current detection combined with a vector transformation method or a feedback signal from a position sensor; correcting the output speed of the AC asynchronous motor using a PID control algorithm; and further superimposing and correcting the output torque to meet the speed requirements of each stage of valve opening or closing.

[0160] In another embodiment of the present invention, it may further include: determining whether the position nodes of each stage of the valve opening or closing process have been reached based on the feedback signal of the position sensor, and further adjusting the output torque based on the determination result to meet the control strategy and stop position accuracy requirements of each stage of the valve opening or closing process. In this embodiment, the position, speed, and torque of the valve can be monitored in real time. According to the nested relationship, a nested control mode of torque loop, speed loop, and position loop can be adopted from the inside out. Among them, the torque loop directly affects the torque, with fast response and high accuracy to meet the requirements of real-time control of motor output torque; the speed loop works on the basis of the torque loop, obtaining the current speed of the valve through the basic principle of current detection combined with vector transformation or feedback calculation from the valve position sensor, and applying influence through the torque loop to meet the speed requirements of different stages; the position loop, as an optional and supplementary item, works on the basis of the speed loop and torque loop, and is the outermost adjustment. It judges and adjusts the output based on the feedback of the position sensor to meet the control strategy and stop position accuracy requirements.

[0161] See Figure 5 Figure 5 is a schematic diagram of the control device structure according to an embodiment of the present invention. The control device for the electric valve of the present invention adopts the above-described control method, adjusting the output torque of the driving AC asynchronous motor in real time to meet the control strategy requirements of each stage of the electric valve's opening and closing process. The position sensor can be a full-stroke sensor and / or a point-position sensor to achieve high-precision position control throughout the entire stroke. That is, the present invention is compatible with both full-stroke and point-position sensors, and is applicable to combinations of full-stroke sensors, point-position sensors, full-stroke sensors, and point position sensors. In practice, the selection of the position sensor is related to the valve type, valve mechanical structure characteristics, valve operating environment, and valve manufacturing technology level, and generally does not change due to the requirements of the valve actuator. In a system pre-installed with a full-stroke sensor, different stages of valve execution are accurately divided based on continuous position signals (the present invention may include a start-up stage, acceleration stage, constant speed stage, deceleration stage, approach stage, torque control stage, and stop stage, etc.), and parameters such as the start position, end position, speed, torque, acceleration, and deceleration of each stage are reasonably controlled to achieve the expected execution effect. The present invention, in conjunction with different interface conversion hardware, can adapt to various types of full-stroke position sensors.

[0162] Node position sensors, due to their low cost, easy installation, and strong environmental adaptability, occupy a certain proportion in valve actuation systems and are of great significance for upgrading and retrofitting existing electric valves. In systems pre-installed with node position sensors, different stages of valve actuation are identified and divided based on discrete node position signals, ensuring the opening or closing execution result while ensuring safety. In systems pre-installed with full-stroke sensors or point position sensors, the control method is the same as in systems pre-installed with only full-stroke sensors; the point position sensors act as protective devices or safety redundancy devices for safety protection at extreme or special positions. This invention broadens its application scope and applicable environment through compatibility with various sensor types and forms, and also improves the safety of its application process.

[0163] This invention is applicable to the opening and closing control of various valves, meeting the control requirements of different working conditions such as sliding doors, swing doors, revolving doors, louvered doors, gate valves, globe valves, ball valves, butterfly valves, plug valves, and air valves. Among them, the regulating valve achieves control of different flow characteristics, such as percentage control, direct control, quick-opening control, and parabolic control, by precisely adjusting the valve opening degree or the speed of its phased movement. Each adjustment at any position within the regulating valve can be considered a complete working process. For example, in the process of adjusting the flow rate of a ball valve as the opening and closing angle changes from 45° to 60°, the working stages are the starting stage, acceleration stage, constant speed stage, deceleration stage, approach stage, and stopping stage. Since the switching valve needs to achieve opening and closing action at a certain speed and ensure sealing when closed, it can add a torque control stage compared to the regulating valve. For example, the closing stage of a gate valve can be divided into the starting stage, acceleration stage, constant speed stage, deceleration stage, approach stage, torque control stage, and stopping stage.

[0164] This invention is based on AC asynchronous motor torque vector control methods, torque calibration methods, and motor parameter identification methods, achieving dynamic control of output torque and static correction of set torque, respectively. It establishes torque loops, speed loops, and position loops from the inside out using a multi-layered PID nesting approach. The closed-loop level or nesting depth is selected according to the needs of different stages of valve execution, thereby ensuring rapid and precise valve execution, as well as accurate and effective execution results. Specifically, it employs an externally nested speed and position closed loop to nest and control the torque closed loop (such as a current closed loop). This method improves the response speed and control accuracy of output torque while also performing speed and position control during execution stages where ensuring operating speed and positioning accuracy is crucial, further enhancing the efficiency, stability, accuracy, and flexibility of the execution process.

[0165] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A control method for an electric valve, characterized in that, Includes the following steps: S100, Set the corresponding torque according to the requirements of each stage of the valve opening and closing process; S200: Drive the AC asynchronous motor to perform the corresponding valve opening or closing action with the set torque as the output torque or the output torque limit; S300, Measure the real-time torque of the AC asynchronous motor or valve during operation; S400. Based on the real-time torque and the set torque, with the set torque as input and the real-time torque as feedback, a PID control algorithm is used to correct the output torque, so as to adjust the response speed and control accuracy of the output torque according to the real-time torque. as well as S500: Repeat steps S300-S400 during the opening and closing process of the valve until the valve is opened or closed in place, so as to realize the torque closed-loop control of the valve opening or closing operation. In step S300, the real-time torque of the AC asynchronous motor or valve is obtained by current detection combined with vector transformation, or by a torque sensor directly from the output shaft of the AC asynchronous motor, the output shaft of the valve reduction gearbox, or the valve drive device. The current detection combined with vector transformation method includes using the output current detection circuit in the valve driver to detect the physical parameters of the AC asynchronous motor and calculate the real-time torque. The physical parameters include stator resistance, rotor resistance, stator-rotor mutual inductance, stator-rotor leakage inductance, and no-load current. The three-phase AC signal of the AC asynchronous motor is converted into the torque component of the stator current through coordinate transformation. Excitation component of stator current The real-time torque is calculated and obtained by using rotor magnetic field orientation vector control, direct torque control, slip frequency vector control, stator magnetic field orientation vector control or air gap magnetic field orientation vector control, depending on the different magnetic field orientations. The rotor field orientation vector control is wherein the field orientation is performed based on the rotor's total flux linkage vector direction, and the real-time torque is obtained using the following formula. : ； in, Let be the number of pole pairs of the AC asynchronous motor. The equivalent mutual inductance of one phase winding when the stator and rotor of the aforementioned AC asynchronous motor are coaxial. The equivalent self-inductance of one phase winding of the rotor of the AC asynchronous motor is given. Let be the torque component of the stator current of the AC asynchronous motor. The rotor flux linkage of the aforementioned AC asynchronous motor; The direct torque control obtains the real-time torque using the following formula. : ； in, Let be the number of pole pairs of the AC asynchronous motor. For mutual inductance between stator and rotor, For the self-inductance of one phase winding of the stator, The self-inductance of one phase winding of the rotor, For stator flux linkage, For rotor flux linkage, The torque angle is a vector. and The angle between them; The slip frequency vector control orients the magnetic field based on the slip frequency vector and obtains the real-time torque using the following formula: in, Let be the number of pole pairs of the AC asynchronous motor. The rotor electromagnetic time constant is The equivalent self-inductance of one phase winding of the rotor of the AC asynchronous motor is given. The rotor flux linkage of the aforementioned AC asynchronous motor. This is the slip angular frequency; The stator magnetic field orientation vector control orients the magnetic field according to the stator flux linkage vector direction, and obtains the real-time torque using the following formula. : in, Let be the number of pole pairs of the AC asynchronous motor. The stator flux linkage of the aforementioned AC asynchronous motor. This refers to the torque component of the stator current; The air gap magnetic field orientation vector control is performed based on the direction of the torque air gap flux linkage vector, and the real-time torque is obtained using the following formula. : in, Let be the number of pole pairs of the AC asynchronous motor. For air gap flux linkage, This represents the torque component of the stator current.

2. The control method for the electric valve as described in claim 1, characterized in that, The stall torque error of the AC asynchronous motor is controlled within ±10% of the rated torque to stably and effectively control the sealing pressure when the valve is closed.

3. The control method for the electric valve as described in claim 1 or 2, characterized in that, Also includes: The current speed of the valve is obtained by using current detection combined with vector transformation or feedback signal from a position sensor. Based on the deviation between the set speed and the current speed of the valve, the output speed of the AC asynchronous motor is corrected by a PID control algorithm, and the output torque is further superimposed to correct the speed, so as to meet the speed requirements of each stage of valve opening or closing.

4. The control method for the electric valve as described in claim 3, characterized in that, Also includes: Based on the feedback signal from the position sensor, it is determined whether the position node of each stage of the valve opening or closing process has been reached, and the output torque is further adjusted according to the determination result to meet the control strategy and position accuracy requirements of each stage of the valve opening or closing process.

5. The control method for the electric valve as described in claim 4, characterized in that, The position sensor is a full-stroke sensor and / or a point-to-point sensor to achieve high-precision position control throughout the stroke and / or accurate node position control.

6. The control method for the electric valve as described in claim 1, 2, 4 or 5, characterized in that, It also includes torque calibration of the AC asynchronous motor, further including: The valve actuator changes the set torque of the AC asynchronous motor point by point and drives the AC asynchronous motor to load; The output torque of the AC asynchronous motor at the corresponding detection point is detected using a torque calibration device, or the internal torque feedback value of the valve actuator at the corresponding detection point is collected; and A graph showing the correspondence between the set torque at each detection point and the corresponding output torque or internal torque feedback value is generated to correct the output torque of the AC asynchronous motor.

7. A control device for an electric valve, characterized in that, The control method for the electric valve according to any one of claims 1-6, by adjusting the output torque of the driving AC asynchronous motor in real time, satisfies the response speed and control accuracy requirements of each stage of the opening and closing process of the electric valve.

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