CN114337378B - Control method and control system of magnetic suspension pump - Google Patents

Abstract

The invention discloses a control method and a control system of a magnetic suspension pump, which are used for adjusting the radial offset of a rotor by implementing different control modes according to different rotation speeds of the rotor in the magnetic suspension pump system; when the rotating speed of the rotor is low, adopting a linear control method to adjust the radial offset of the rotor; when the rotating speed of the rotor is high, adjusting the radial offset of the rotor by adopting a humanoid intelligent integral control method; the unilateral magnetic pulling force of the rotor is calculated in the humanoid intelligent integral control method, and the radial levitation force required by the rotor is calculated according to the unilateral magnetic pulling force of the rotor, so that the control accuracy of controlling the radial offset of the rotor is improved; the humanoid intelligent integral control method improves the steady-state performance of the rotor in the magnetic suspension pump system at high rotating speed. The invention can avoid the problem that a single control method cannot give consideration to control precision and response.

Description

A control method and control system for a magnetic levitation pump

Technical field

The invention belongs to the technical field of magnetic levitation control, and specifically relates to a control method and control system for a magnetic levitation pump.

Background technique

The magnetic levitation pump is a pump that uses magnetic bearings as the rotor support. There is no mechanical contact between the rotor and the stator. The rotor relies on magnetic force to achieve levitation. It has the advantages of good sealing, no wear and long life. It can be used in vacuum, radiation and prohibited lubricant media. In pollution and other applications, it has superior performance that traditional mechanical pumps cannot match.

The torque control of magnetic levitation pumps and mechanical pumps both work by using the motor rotor to drive the pump wheel to rotate. The magnetic levitation pump realizes the rotation of the rotor through magnetic bearings, while the mechanical pump realizes the rotation of the rotor with the help of mechanical bearings. The torque of both is controlled. They are all realized by the rotating magnetic field generated by the changing current, and the levitation force control of the magnetic levitation pump is achieved by adjusting the amplitude and direction of the current in the levitation winding. The radial suspension of the rotor has always been a key research direction in magnetic levitation pump technology. The size of the radial suspension force determines the radial deflection of the rotor, and the strength of the radial stability determines the rotor's ability to resist external interference. Although the concept of magnetic levitation pump has been proposed in recent years, domestic research on magnetic levitation pump is mostly in the theoretical stage, and its control method also has many shortcomings. In the traditional control scheme, the transmission of flux linkage information between the torque winding and the suspension winding will cause the suspension performance and torque performance of the rotor to mutually restrict each other, which increases the complexity of the control algorithm. PID control is often used, and the control scheme is single. It cannot meet the actual operation needs of the magnetic levitation pump and reduces the flexibility of the control module group. In addition, traditional PID control is linear control and is difficult to adapt to the multi-variable, nonlinear control environment of the magnetic levitation system. The positive feedback caused by the unilateral magnetic pull further increases the instability of the displacement control module group. Therefore, there is an urgent need for a control method that can improve the dynamic characteristics of the rotor and has high precision and flexibility to improve the working performance of the magnetic levitation pump.

Contents of the invention

In view of the shortcomings of the existing technology, the present invention proposes a control method and control system for a magnetic levitation pump that uses two different control schemes to control the levitation force of the rotor according to the operating conditions of the rotor, so as to enhance the dynamic performance of the rotor and avoid a single The control scheme brings the disadvantages of complex control algorithm, slow response, and high power consumption.

A method for controlling a magnetic levitation pump of the present invention is as follows:

Before the maglev pump works, the control module group sets the rotor speed n _s in the maglev pump system; the control module group determines whether the set speed n _s is low speed or high speed; when the speed is judged to be low speed, the control module group uses linear The control method calculates the radial offset of the rotor; when the target speed is a high speed, the control module group uses the human-like intelligent integral control method to calculate the radial offset of the rotor; then, the control module group starts the magnetic levitation pump system The suspension device keeps the rotor in a suspended state; at this time, the detection system detects the radial offset of the rotor and transmits the radial offset of the rotor to the control module group through the data transmission system; the control module group determines the radial offset of the rotor. Whether the radial offset r _c meets the required value of the corresponding control method. If it does not meet the required value, the control module group calculates the control quantity u corresponding to the radial suspension force according to the speed n _s set to low speed or high speed, and The control quantity u is transmitted to the PLC, and the PLC controls the frequency converter to make the magnetic levitation pump system change the radial levitation force on the rotor; then, it starts the rotating device in the magnetic levitation pump to drive the rotor to rotate; it detects the radial offset of the rotor by the system. r _c is detected in real time and fed back to the control module group through the data transmission system; the control module group selects the corresponding control method according to the rotation speed n _s of the rotor in the magnetic levitation pump system to calculate the control quantity u corresponding to the radial levitation force, so that the magnetic levitation The pump system changes the radial suspension force on the rotor and controls and adjusts the radial offset r _c of the rotor in real time.

Preferably, the control processes of the linear control method and the human-like intelligent integral control method in the control module group are as follows:

The radial levitation force F of the rotor and the levitation system current I in the magnetic levitation pump system satisfy the following relationship:

F＝k·I

Among them, k is a linear constant;

When the rotor speed n _s is a low speed, the control module group uses a linear control method to adjust the radial offset r _c of the rotor; the control module group calculates the amount of time required to adjust the rotor based on the actual radial offset r _c of the rotor. The radial suspension force F is calculated according to the above formula, and the current I corresponding to the radial suspension force F is calculated. The control quantity u ₀ is calculated through the current I. The control module group transmits the control quantity u ₀ to the PLC as the total control quantity u _n . , PLC controls the magnetic levitation pump system through the frequency converter, so that the magnetic levitation pump system changes the radial levitation force F on the rotor, and adjusts the rotor until the radial offset r _c of the rotor meets the required value;

When the rotor's rotational speed n _s is high, the control module group uses a human-like intelligent integral control method to adjust the radial offset r _c of the rotor; the detection system detects the radial offset r _c of the rotor and calculates the radial offset The difference e between the displacement r _c and the radial offset limit requirement r _s and the difference change rate ec are then transmitted to the control module group; the control module group is based on the control rules of the human-like intelligent integral control method The control quantity - u ₁ is calculated and obtained; at the same time, the control module group calculates the unilateral magnetic pulling force acting on the rotor through the radial offset r _c of the rotor, and then calculates the radial adjustment required based on the unilateral magnetic pulling force. The size of the suspension force F is used to obtain the control quantity two u ₂ required to adjust the unilateral magnetic pulling force; the control module group takes the sum of the control quantity one u ₁ and the control quantity two u ₂ as the total control quantity u _n , and the total control quantity u _n Transmitted to the PLC, the PLC controls the magnetic levitation pump system through the frequency converter to adjust the radial offset r _c of the rotor until it meets the required value.

More preferably, the difference e between the radial offset r _c of the rotor and the radial offset limit requirement r _s in the magnetic levitation pump system ranges from 0 to 80um; the radial offset of the rotor The range of the difference change rate ec between r _c and the radial offset limit requirement value r _s is -5 ~ 5um/s.

Preferably, the detection system can detect the deviation value n _c of the rotor speed in the magnetic levitation pump system and feed it back to the control module group. The control module group calculates the control amount u' required to adjust the rotor speed according to the speed control method, Then u' is transmitted to the PLC, and the PLC controls the frequency converter to adjust the rotor speed until it meets the required value.

Preferably, the data transmission system is composed of an A/D converter and a D/A converter; the A/D converter converts the analog signals measured by the rotation speed sensor and the displacement sensor in the detection system into digital signal, and then transfer the digital signal to the control module group; the control module group transfers the calculated digital signal of the total control quantity u _n to the D/A converter, and the D/A converter converts the digital signal into an analog signal passed to PLC.

Preferably, when the rotation speed of the rotor in the magnetic levitation pump system is a low rotation speed, the required value range of the rotor radial offset is 0 ≤ r _c <50um; when the rotation speed of the rotor in the magnetic levitation pump system is a high rotation speed, the radial offset of the rotor The required value range of offset is 0≤r _c <20um.

Preferably, the process of stopping the magnetic levitation pump is controlled through a control module group, as follows:

When the control module group receives the stop command, the control module group automatically generates a linear objective function based on the current rotor speed; where the linear constant value in the linear objective function is less than 1; the current rotor speed is brought into the independent variable of the linear objective function , obtain the rotor speed at the next moment, and then repeatedly bring the rotor speed at the next moment into the independent variable of the linear objective function to obtain the rotor speed at the next moment; the control module group performs real-time calculation of the rotor speed based on the calculation results of the linear objective function Adjustment; repeat the calculation several times until the rotor speed is close to zero; at this time, the control module group outputs a control value of zero, causing the rotor to stop rotating.

A magnetic levitation pump control system of the present invention includes a PLC, a frequency converter, a magnetic levitation pump system, a detection system, a data transmission system and a control module group; the control module group is connected to the data transmission system for mutual transmission of data and signals; The data transmission system transmits the signal to the PLC; the PLC processes the signal and transmits it to the frequency converter; the frequency converter controls the magnetic levitation pump system according to the processed signal; the detection system controls the magnetic levitation pump system. Detect and transmit the signal to the control module group through the data transmission system; the detection system includes a displacement sensor and a rotational speed sensor; the control module group includes a displacement control module, a rotational speed control module, a signal processing module and a human-computer interaction module .

The beneficial effects of the present invention are:

According to the different rotational speeds of the rotor in the magnetic levitation pump system, the present invention implements different control methods to adjust the radial offset of the rotor; when the rotational speed of the rotor is low, a linear control method is used to adjust the radial offset of the rotor; when When the rotation speed of the rotor is high, the human-like intelligent integral control method is used to adjust the radial offset of the rotor; in the human-like intelligent integral control method, the unilateral magnetic pull force on the rotor is calculated, and the unilateral magnetic pull force on the rotor is calculated according to the unilateral magnetic pull force on the rotor. The radial levitation force required to adjust the rotor is calculated, which improves the control accuracy of controlling the radial offset of the rotor; the human-like intelligent integral control method improves the steady-state performance of the rotor at high speeds in the magnetic levitation pump system. The dual control method of the present invention effectively improves the dynamic performance of the rotor, avoids the defects of complex control algorithms, slow response, and high power consumption caused by using complex control methods at low rotational speeds, and avoids the problems of inaccurate simple control methods at high rotational speeds. , therefore, avoiding the problem that a single control method cannot take into account both control accuracy and response.

Description of drawings

Figure 1 is a block diagram of the control system of the present invention;

Figure 2 is a control principle diagram of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

A method for controlling a magnetic levitation pump of the present invention is as follows:

As shown in Figure 1, before the maglev pump works, the control module group sets the rotor speed n _s in the maglev pump system; the control module group determines whether the set speed n _s is low speed (0≤n _s <300rpm) or high speed (n _s ≥ 300rpm); when the speed is judged to be low speed, the control module group uses the linear control method to calculate the radial offset of the rotor; when the target speed is high speed, the control module group uses the human-like intelligent integral control method to calculate The radial offset of the rotor; then, the levitation device in the magnetic levitation pump system is started through the control module group to keep the rotor in a suspended state; at this time, the detection system detects the radial offset of the rotor and transmits it through the data transmission system The radial offset of the rotor is transmitted to the control module group; the control module group determines whether the radial offset r _c of the rotor meets the required value of the corresponding control method. If it does not meet the required value, the control module group determines whether the rotor's radial offset r _c meets the required value. Set to low speed or high speed, calculate the control quantity u corresponding to the radial levitation force (u is the three-phase current and voltage, unit: V), and transmit the control quantity u to the PLC. The PLC controls the frequency converter to change the magnetic levitation pump system. The radial suspension force experienced by the rotor; then, start the rotating device in the magnetic levitation pump to drive the rotor to rotate; the detection system detects the radial offset r _c of the rotor in real time, and feeds it back to the control module group through the data transmission system; control According to the rotation speed n _s of the rotor in the magnetic levitation pump system, the module group selects the corresponding control method to calculate the control quantity u corresponding to the radial levitation force, so that the maglev pump system changes the radial levitation force on the rotor and controls the radial direction of the rotor in real time. The offset r _c is controlled and adjusted; through real-time detection and control of the rotor radial offset r _c , the magnetic levitation pump system maintains stable operation.

As a preferred embodiment, the control process of the linear control method and the human-like intelligent integral control method in the control module group is as follows:

The radial levitation force F of the rotor and the levitation system current I in the magnetic levitation pump system satisfy the following relationship:

F＝k·I

Among them, k is a linear constant;

As shown in Figure 2, when the rotor speed _ns is a low speed, the control module group uses a linear control method to adjust the radial offset r _c of the rotor; the control module group calculates based on the actual radial offset r _c of the rotor Calculate the radial suspension force F required to adjust the rotor, and calculate the current I corresponding to the radial suspension force F according to the above formula. Calculate the control quantity u ₀ (-5≤u ₀ <5V) through the current I. The control module group The control quantity u ₀ is transmitted to the PLC as the total control quantity u _n . The PLC controls the magnetic levitation pump system through the frequency converter, so that the magnetic levitation pump system changes the radial levitation force F on the rotor and adjusts the rotor until the radial offset of the rotor. r _c meets the required value requirements;

When the rotor's rotational speed n _s is high, the control module group uses a human-like intelligent integral control method to adjust the radial offset r _c of the rotor; the detection system detects the radial offset r _c of the rotor and calculates the radial offset The difference e between the displacement r _c and the radial offset limit requirement r _s and the difference change rate ec are then transmitted to the control module group; the control module group is based on the control rules of the human-like intelligent integral control method The control quantity - u ₁ (-2V≤u ₁ <2V) is calculated and obtained; at the same time, the control module group calculates the size of the unilateral magnetic pull acting on the rotor (the direction of the unilateral magnetic pull) through the radial offset r _c of the rotor. is the deflection direction of the rotor), and then calculate the radial suspension force F required for adjustment based on the size of the unilateral magnetic pull (the direction of the radial suspension force is opposite to the unilateral magnetic pull), and obtain the control amount 2 required to adjust the unilateral magnetic pull. u ₂ (0V≤u ₂ <2V); the control module group takes the sum of control quantity one u ₁ and control quantity two u ₂ as the total control quantity u _n , and transmits the total control quantity u _n to the PLC, and the PLC passes the frequency converter The magnetic levitation pump system is controlled to adjust the radial offset r _c of the rotor until it meets the required value.

As a preferred embodiment, the difference e between the radial offset r _c of the rotor and the radial offset limit requirement r _s in the magnetic levitation pump system ranges from 0 to 80um; the radial offset r of the rotor The range of the difference change rate ec between _c and _the radial offset limit requirement value rs is -5~5um/s.

As a preferred embodiment, the detection system can detect the deviation value n _c of the rotor speed in the magnetic levitation pump system and feed it back to the control module group. The control module group calculates and adjusts the rotor according to the speed control method (conventional linear control method is sufficient). The control quantity u' required for the rotation speed is then transmitted to the PLC. The PLC adjusts the rotor speed by controlling the frequency converter until it meets the required value; the speed control method for adjusting the rotor speed in the control module group and the adjustment of the rotor radial offset The linear control method or the human-like intelligent integral control method are independent of each other and do not interfere with each other.

As a preferred embodiment, the data transmission system consists of an A/D converter and a D/A converter; the A/D converter will detect the rotational speed sensor (used to detect the rotational speed of the rotor) and the displacement sensor (used to detect the rotational speed of the rotor) in the system. The analog signal measured by detecting the radial offset of the rotor is converted into a digital signal, and then the digital signal is transmitted to the control module group; the control module group transmits the calculated digital signal of the total control amount u _n to the D/A Converter, D/A converter converts digital signals into analog signals and transmits them to PLC, which transmits signal instructions to the frequency converter to control the magnetic levitation pump system.

As a preferred embodiment, when the rotation speed of the rotor in the magnetic levitation pump system is low, the required value range of the rotor radial offset is 0≤r _c <50um; when the rotation speed of the rotor in the magnetic levitation pump system is high speed, The required value range of the rotor radial offset is 0≤r _c <20um.

As a preferred embodiment, the process of stopping the magnetic levitation pump is controlled through the control module group, as follows:

When the control module group receives the stop command, the control module group automatically generates a linear objective function based on the current rotor speed; where the linear constant value in the linear objective function is less than 1; the current rotor speed is brought into the independent variable of the linear objective function , obtain the rotor speed at the next moment, and then repeatedly bring the rotor speed at the next moment into the independent variable of the linear objective function to obtain the rotor speed at the next moment; the control module group performs real-time calculation of the rotor speed based on the calculation results of the linear objective function Adjust; repeat the calculation several times until the rotor's speed is close to zero; at this time, the control module outputs a control value of zero, causing the rotor to stop rotating; the linear attenuation method of the rotor speed can effectively avoid the rotor from being greatly impacted due to emergency stop. Maglev The pump system is damaged.

A magnetic levitation pump control system of the present invention includes a PLC, a frequency converter, a magnetic levitation pump system, a detection system, a data transmission system and a control module group; the control module group is connected to the data transmission system for mutual transmission of data and signals; The data transmission system transmits the signal to the PLC; the PLC processes the signal and transmits it to the frequency converter; the frequency converter controls the magnetic levitation pump system according to the processed signal; the detection system controls the magnetic levitation pump system. Detect and transmit the signal to the control module group through the data transmission system; the detection system includes a displacement sensor and a rotational speed sensor; the control module group includes a displacement control module, a rotational speed control module, a signal processing module and a human-computer interaction module ; The displacement control module, speed control module and human-computer interaction module are all connected to the signal processing module; the signal processing module is connected to the data transmission system; the displacement control module is used to control the radial offset of the rotor, and the speed control module is used to control the rotor The speed; the signal processing module is used to receive signals from the data transmission system and human-computer interaction module, and send signals to the data transmission system, human-computer interaction module, displacement control module and speed control module.

Claims (7)

1. A control method for a magnetic levitation pump, which is characterized by: specifically as follows: Before the maglev pump works, the control module group sets the rotor speed n _s in the maglev pump system; the control module group determines whether the set speed n _s is low speed or high speed; when the speed is judged to be low speed, the control module group uses linear The control method calculates the radial offset of the rotor; when the target speed is a high speed, the control module group uses the human-like intelligent integral control method to calculate the radial offset of the rotor; then, the control module group starts the magnetic levitation pump system The suspension device keeps the rotor in a suspended state; at this time, the detection system detects the radial offset of the rotor and transmits the radial offset of the rotor to the control module group through the data transmission system; the control module group determines the radial offset of the rotor. Whether the radial offset r _c meets the required value of the corresponding control method. If it does not meet the required value, the control module group calculates the control quantity u corresponding to the radial suspension force according to the speed n _s set to low speed or high speed, and The control quantity u is transmitted to the PLC, and the PLC controls the frequency converter to make the magnetic levitation pump system change the radial levitation force on the rotor; then, it starts the rotating device in the magnetic levitation pump to drive the rotor to rotate; it detects the radial offset of the rotor by the system. r _c is detected in real time and fed back to the control module group through the data transmission system; the control module group selects the corresponding control method according to the rotation speed n _s of the rotor in the magnetic levitation pump system to calculate the control quantity u corresponding to the radial levitation force, so that the magnetic levitation The pump system changes the radial suspension force on the rotor and controls and adjusts the radial offset r _c of the rotor in real time. 2. A control method for a magnetic levitation pump according to claim 1, characterized in that: the control processes of the two control methods corresponding to low rotational speed and high rotational speed in the control module group are as follows: The radial levitation force F of the rotor and the levitation system current I in the magnetic levitation pump system satisfy the following relationship: F＝k·I Among them, k is a linear constant; When the rotor speed n _s is a low speed, the control module group uses a linear control method to adjust the radial offset r _c of the rotor; the control module group calculates the amount of time required to adjust the rotor based on the actual radial offset r _c of the rotor. The radial suspension force F is calculated according to the above formula, and the current I corresponding to the radial suspension force F is calculated. The control quantity u ₀ is calculated through the current I. The control module group transmits the control quantity u ₀ to the PLC as the total control quantity u _n . , PLC controls the magnetic levitation pump system through the frequency converter, so that the magnetic levitation pump system changes the radial levitation force F on the rotor, and adjusts the rotor until the radial offset r _c of the rotor meets the required value; When the rotor's rotational speed n _s is high, the control module group uses a human-like intelligent integral control method to adjust the radial offset r _c of the rotor; the detection system detects the radial offset r _c of the rotor and calculates the radial offset The difference e between the displacement r _c and the radial offset limit requirement r _s and the difference change rate ec are then transmitted to the control module group; the control module group is based on the control rules of the human-like intelligent integral control method The control quantity - u ₁ is calculated and obtained; at the same time, the control module group calculates the unilateral magnetic pulling force acting on the rotor through the radial offset r _c of the rotor, and then calculates the radial adjustment required based on the unilateral magnetic pulling force. The size of the suspension force F is used to obtain the control quantity two u ₂ required to adjust the unilateral magnetic pulling force; the control module group takes the sum of the control quantity one u ₁ and the control quantity two u ₂ as the total control quantity u _n , and the total control quantity u _n Transmitted to the PLC, the PLC controls the magnetic levitation pump system through the frequency converter to adjust the radial offset r _c of the rotor until it meets the required value. 3. The control method of a magnetic levitation pump according to claim 2, characterized in that: the radial offset r _c of the rotor in the magnetic levitation pump system is between the radial offset limit requirement r _s The range of the difference e is 0 ~ 80um; the range of the difference change rate ec between the rotor's radial offset r _c and the radial offset limit requirement value r _s is -5 ~ 5um/s. 4. The control method of a magnetic levitation pump according to claim 1, characterized in that: the detection system detects the deviation value n _c of the rotor speed in the magnetic levitation pump system, and feeds it back to the control module group. The control module The group calculates the control quantity u' required to adjust the rotor speed according to the speed control method, and then transmits u' to the PLC. The PLC controls the frequency converter to adjust the rotor speed until it meets the required value. 5. The control method of a magnetic levitation pump according to any one of claims 1 to 4, characterized in that: the data transmission system consists of an A/D converter and a D/A converter; The above-mentioned A/D converter converts the analog signals measured by the rotation speed sensor and the displacement sensor in the detection system into digital signals, and then transmits the digital signals to the control module group; the control module group will calculate the total control amount u The digital signal of _n is passed to the D/A converter, and the D/A converter converts the digital signal into an analog signal and passes it to the PLC. 6. The control method of a magnetic levitation pump according to claim 2 or 3, characterized in that: when the rotation speed of the rotor in the magnetic levitation pump system is a low rotation speed, the required value range of the rotor radial offset is 0≤r _c <50um; when the rotation speed of the rotor in the magnetic levitation pump system is high, the required value range of the rotor radial offset is 0≤r _c <20um. 7. The control method of a magnetic levitation pump according to any one of claims 1 to 4, characterized in that the process of stopping the magnetic levitation pump is controlled through a control module group, specifically as follows: When the control module group receives the stop command, the control module group automatically generates a linear objective function based on the current rotor speed; where the linear constant value in the linear objective function is less than 1; the current rotor speed is brought into the independent variable of the linear objective function , obtain the rotor speed at the next moment, and then repeatedly bring the rotor speed at the next moment into the independent variable of the linear objective function to obtain the rotor speed at the next moment; the control module group performs real-time calculation of the rotor speed based on the calculation results of the linear objective function Adjustment; repeat the calculation several times until the rotor speed is close to zero; at this time, the control module group outputs a control value of zero, causing the rotor to stop rotating.