CN-116794985-B - High-precision current control method for program-controlled degaussing current source

CN116794985BCN 116794985 BCN116794985 BCN 116794985BCN-116794985-B

Abstract

The invention provides a high-precision current control method of a program-controlled demagnetizing current source. Firstly, a mathematical model under the nonlinear load of a program-controlled demagnetizing current source is established according to kirchhoff's law, and a state space expression of the program-controlled demagnetizing current source is established based on the mathematical model. Then, aiming at various disturbances such as current fluctuation, electronic element parameter perturbation and the like caused by nonlinear load parameter time variation in the program-controlled degaussing current source system, a cascading expansion state observer is designed to observe the lumped disturbance, and the observed lumped disturbance is compensated through a feedforward channel. Finally, a composite controller based on the combination of a cascading expansion state observer and sliding mode control is designed, the influence of lumped disturbance on the output current of the program-controlled degaussing current source is restrained, and high-precision degaussing current output is achieved. The invention realizes the high-precision demagnetizing current output under the existence of various disturbances such as nonlinear load parameter time variation, and the like, thereby improving the demagnetizing performance of the magnetic shielding device.

Inventors

LI HAITAO
YANG SIYI
WEN TONG
ZHENG SHIQIANG
ZHANG DI
YU SHICHENG

Assignees

北京航空航天大学

Dates

Publication Date: 20260508
Application Date: 20230626

Claims (4)

1. A program-controlled demagnetizing current source high-precision current control method is characterized by comprising the following steps: Step1, establishing a mathematical model under a nonlinear load of a program-controlled demagnetizing current source according to kirchhoff's law, and establishing a state space expression of the program-controlled demagnetizing current source based on the mathematical model; Step 2, designing a cascade expansion state observer to observe lumped disturbance in the program-controlled degaussing current source system and compensating the observed disturbance in the controller through a feedforward channel, wherein the lumped disturbance comprises various disturbances, and the various disturbances comprise current fluctuation caused by nonlinear load parameter time variation and electronic element parameter perturbation; And step 3, designing a composite controller based on the combination of the cascade expansion state observer and the sliding mode control, inhibiting the influence of lumped disturbance on the output current of the program-controlled degaussing current source, and realizing high-precision degaussing current output.
2. The method for controlling a high-precision current of a programmable degaussing current source according to claim 1, wherein the step 1 comprises: According to kirchhoff's law, the mathematical model of a single-phase full-bridge inverter under nonlinear load is: ; Wherein, the 、、 The voltage of the direct current bus, the output voltage of the inverter and the load voltage are respectively, u is the control input, 、、 Respectively inductance current, capacitance current and load current, For the equivalent resistance of the inverter, 、 The inductance and capacitance of the LC filter respectively, 、 The inductor and the resistor are respectively nonlinear loads; Selecting a system state variable as , Representing load current , Representing the first derivative of the load current , Representing the second derivative of the load current The system state equation is written as: 。
3. the method for controlling the high-precision current of the program-controlled demagnetizing current source according to claim 2, wherein in the step 2, designing the cascade extended state observer comprises: Considering disturbances, the system state equation is further written as: ; Wherein, the , , , , 、、 In order to account for the uncertainty in the system parameters, Is an external disturbance; the system state space expression is further expressed as: ; Let lumped disturbance Including parameter uncertainty, internal unknown perturbations, and external unknown perturbations, expressed as: ; Will lumped disturbance As an expansion state variable of the system, i.e. , , Representing lumped perturbations Assuming that the perturbations and the derivatives of the perturbations are bounded and continuous, the expansion state equation of the programmed degaussing current source system is written as: ; Wherein, the Based on the expansion state equation, three cascaded second-order expansion state observers with the same parameters are designed for reducing parameters of the observer to be set and simplifying parameter configuration of the observer; Defining state variables as , wherein, Estimation , Estimation , Estimation , Estimating lumped perturbations , And Is an intermediate variable of the cascade of extended observers, and the estimation error is defined as , , , , , The state equation of the cascade extended state observer is as follows: ; Wherein, the 、 Is a parameter of a linear cascade extended state observer, For loading current Is used for the observation of errors in the (c), For the first derivative of load current Is used for the observation of errors in the (c), For the second derivative of the load current Is used for the observation of errors in the (c), For lumped disturbance Is used for the observation of errors in the (c), 、 Is the difference between the intermediate variable and the output of the previous stage extended state observer.
4. A method for controlling a high precision current of a programmable degaussing current source according to claim 3, wherein said step 3 comprises: and (3) taking the difference between the state equation and the expansion state equation of the cascade expansion state observer to further obtain an error equation of the cascade expansion state observer, wherein the error equation is as follows: Let the load current reference command be Define the tracking error vector as Selecting a sliding die surface The method comprises the following steps: Wherein, the 、 Is positive real number, pair The derivation is as follows: Wherein, the And combining the system state space expression to further obtain a sliding mode control law as follows: the exponential approach law is selected as follows: Wherein, the For the switching gain to be achieved, In order to approach the speed parameter of the vehicle, Is a sign function; The exponential approach law is brought into the sliding mode control law, and the lumped disturbance observed by the cascade extended state observer is used for compensating the disturbance in the sliding mode control law, then the composite control law based on the cascade extended state observer and the sliding mode control is designed as follows: 。

Description

High-precision current control method for program-controlled degaussing current source Technical Field The invention belongs to the technical field of demagnetizing power supply control, and particularly relates to a program-controlled demagnetizing current source high-precision current control method. Background At present, the near-zero magnetic field environment has wide and unique application in various fields such as quantum information technology, bioelectromagnetism, aerospace, national defense engineering and the like. The magnetic shielding device is an effective method for shielding an external environment magnetic field and realizing a near-zero magnetic field environment, and is often combined by a passive shielding system and an active magnetic compensation system to meet the requirement of the near-zero magnetic field. The shielding layer of the magnetic shielding device is generally composed of a high magnetic conductive material (such as permalloy) for shielding a low frequency magnetic field based on a magnetic flux shunt effect, and a high conductive material for shielding a high frequency magnetic field based on an eddy current effect. In general, a passive shielding system of a magnetic shielding device adopts a plurality of layers of soft magnetic materials such as permalloy to form a plurality of layers of shielding layers, so that the shielding layers can be incompletely and reversibly magnetized while shielding an external environment magnetic field, and the shielding materials generate remanence. In addition, during installation and transportation, residual magnetism is generated in the shielding material due to the stress. The residual magnetic field of the magnetic shielding device depends on the sum of an external static magnetic field and the magnetic field of the shielding material, and the excessive residual magnetism of the shielding material can influence the shielding performance of the magnetic shielding device. Therefore, demagnetizing the shielding material is one of key technologies for reducing the residual magnetic field of the magnetic shielding device and improving the shielding performance. The common demagnetizing methods include static demagnetizing, thermally induced demagnetizing and dynamic demagnetizing. Static demagnetization requires the provision of a strong opposing magnetic field, and the strength of the applied strong magnetic field varies with the change in operating temperature. The thermally induced demagnetizing is to heat the material to be demagnetized to a temperature above the curie temperature, and this method, although effective in eliminating the residual magnetization of the material, at the same time, also destroys other physical properties of the material, and is not suitable for the large and medium-sized magnetic shield apparatus that has been assembled. The dynamic demagnetization can be classified into direct current demagnetization and alternating current demagnetization, and the working principle is that a workpiece to be demagnetized is placed in an alternating attenuation magnetic field, and demagnetization is performed along a decreasing hysteresis loop. Dc demagnetization requires frequent changes in dc direction and the magnitude of the decay of the current should be as small as possible. The alternating current demagnetizing method can be divided into a passing method and an attenuation method, and the passing method is suitable for batch demagnetizing of medium and small workpieces and is not suitable for large and medium-sized multilayer complex-structure magnetic shielding devices. At present, most of the whole demagnetizing of the magnetic shielding device is an easy-to-realize attenuation method, a demagnetizing coil is reasonably wound on the magnetic shielding device, and a sine demagnetizing current with alternating attenuation is introduced into the demagnetizing coil, so that the whole magnetic shielding device is demagnetized. In order to achieve effective demagnetizing of the magnetic shielding material, the demagnetizing current needs to meet the following requirements that (1) the initial value of the demagnetizing current should be large enough to saturate the magnetic shielding material, (2) the attenuation step length of the demagnetizing current should be as small as possible, and (3) the parameters of the demagnetizing current are adjustable. The special requirements of the demagnetizing current correspondingly put higher requirements on the design of the demagnetizing power supply, and the demagnetizing power supply has the advantages that the current dynamic range output by the demagnetizing power supply is large in requirements, various controllable decaying sinusoidal currents are required to be generated, and the control precision of the small-amplitude current is high. In addition, as the load of the demagnetizing power supply, the electrical parameters of the demagnetizing coil of the magnetic shieldin