阅读说明：本技术 磁悬浮平面电机的电流控制方法和系统 (Current control method and system of magnetic suspension planar motor ) 是由 黄苏丹 胡智勇 曹广忠 杨晓生 符兴东 于 2020-04-02 设计创作，主要内容包括：本发明实施例公开了一种磁悬浮平面电机的电流控制方法和系统。该电流控制方法包括：建立磁悬浮平面电机的电流环模型,并采集电流环输入和电流环输出；根据所述电流环输入和所述电流环输出,辨识所述电流环模型的电感参数；根据所述电感参数,求解所述磁悬浮平面电机的控制器的最优参数。与现有技术相比,本发明实施例提升了电流环模型的精度,实现了磁悬浮平面电机的高精度运动。(The embodiment of the invention discloses a current control method and a current control system of a magnetic suspension planar motor. The current control method comprises the following steps: establishing a current loop model of the magnetic suspension planar motor, and collecting current loop input and current loop output; identifying inductance parameters of the current loop model according to the current loop input and the current loop output; and solving the optimal parameters of the controller of the magnetic suspension planar motor according to the inductance parameters. Compared with the prior art, the embodiment of the invention improves the precision of the current loop model and realizes the high-precision motion of the magnetic suspension planar motor.)

1. A current control method of a magnetic suspension planar motor is characterized by comprising the following steps:

establishing a current loop model of the magnetic suspension planar motor, and collecting current loop input and current loop output;

identifying inductance parameters of the current loop model according to the current loop input and the current loop output;

and solving the optimal parameters of the controller of the magnetic suspension planar motor according to the inductance parameters.

2. Method for current control of a magnetic levitation planar motor as claimed in claim 1, characterised in that the least squares method is used for identifying the inductance parameters of the current loop model.

3. Method for current control of a magnetic levitation planar motor as claimed in claim 2, wherein identifying the inductance parameters of the current loop model comprises:

obtaining an s-domain current loop transfer function according to the current loop input and the current loop output;

discretizing the s-domain current loop transfer function to obtain a z-domain current loop transfer function;

converting the z-domain current loop transfer function into a difference equation; the difference equation comprises a parameter to be identified;

identifying the parameters to be identified in the difference equation by adopting a least square method;

and obtaining the inductance parameter of the current loop model according to the parameter to be identified.

4. Method for current control of a magnetic levitation planar motor as claimed in claim 3, characterized in that the s-domain current loop transfer function is expressed as the following formula:

wherein i_inFor current loop input, i_outFor current loop output, a_c＝R/L，b_c(U/L), U is voltage, R is resistance, L is inductance;

the z-domain current loop transfer function is expressed as follows:

wherein, a_dAnd b_dAs the parameter to be identified, a_d＝-e^-(R/L)T，b_d(U/L), T is the sample time;

the difference equation is expressed as follows:

wherein y (k) ═ i_out(k)，k is the current sampling moment;

the least square method is adopted to represent the following formula:

wherein K is a gain matrix, P is a covariance matrix, and α is a forgetting factor;

the inductance parameter is expressed as the following equation:

5. method for current control of a magnetic levitation planar motor as claimed in claim 1, characterised in that the current loop model further comprises a filter;

the transfer function of the filter is expressed as follows:

wherein, T_fliterThe inverse of the filter cut-off frequency.

6. Method for current control of a magnetic levitation planar motor as claimed in claim 5, characterized in that the transfer function of the controller is expressed as the following formula:

wherein, T_ControlTo control the period, K_pAs a proportional control parameter, K_iIs an integral control parameter;

alternatively, the transfer function of the controller is expressed as the following equation:

wherein, K_pAs a proportional control parameter, K_iIs an integral control parameter.

7. Method for current control of a magnetic levitation planar motor as recited in claim 6, wherein the optimal parameters comprise proportional control parameters and integral control parameters.

8. Method for current control of a magnetic levitation planar motor as claimed in claim 6, characterized in that the transfer function of the current loop is expressed as the following formula:

where U is the voltage, R is the resistance, and L is the inductance.

9. Method for current control of a magnetic levitation planar motor as claimed in claim 8, characterised in that the current loop model further comprises a driver;

the transfer function of the driver is expressed as follows:

wherein D is_maxIs a control quantity corresponding to a duty ratio of 1, T_PWMIs a PWM period;

alternatively, the transfer function of the driver is expressed as the following equation:

G_PWM(s)＝D_max

wherein D is_maxThe duty ratio is 1.

10. The current control method of a magnetic levitation planar motor as recited in claim 9, wherein the system damping ratio of the current loop model is 0.707;

obtaining the proportional control parameter and the integral control parameter according to the transfer function of the current loop, the transfer function of the driver and the transfer function of the filter, wherein the proportional control parameter and the integral control parameter are respectively expressed as the following formulas:

11. a current control system for a magnetically levitated planar motor, comprising:

the acquisition module is used for acquiring current loop input and current loop output;

the inductance identification module is used for identifying inductance parameters of the current loop model according to the current loop input and the current loop output;

and the optimal parameter solving module is used for solving the optimal parameters of the controller of the magnetic suspension planar motor according to the inductance parameters.

Technical Field

The embodiment of the invention relates to the technical field of motor control, in particular to a current control method and system of a magnetic suspension planar motor.

Background

The magnetic suspension planar motor is a novel two-dimensional planar direct-drive device, has the advantages of simple structure, low cost, low heat consumption, high reliability and the like, and has a wide application prospect in the field of micro-nano ultra-precise manufacturing. The high-precision operation of the magnetic suspension planar motor is a key point concerned by various research institutions and the industry at present, and the precise current directly influences the high-precision operation of the magnetic suspension planar motor, so that how to realize the high-precision control of the current is a key technical problem which is urgently needed to be solved for the high-precision operation of the magnetic suspension planar motor.

In the prior art, a current control method of a magnetic suspension planar motor generally equates a current loop to a first-order model, and then a controller is designed to realize current control. However, due to the influence of noise, time delay, inductance change and the like, the method is difficult to realize high-precision control of the current. Specifically, the technical problems to be solved urgently by the high-precision control of the current of the existing magnetic suspension planar motor coil include:

(1) the method for equivalent of the current loop into the first-order model is simple and convenient to calculate and easy to implement, but negative effects caused by output noise and actual system delay are not considered, so that the difference between the simulation model and the actual model is large, and the optimal control parameters of the actual system are difficult to obtain;

(2) because inductance is influenced by factors such as current, a current loop model is a time-varying model in nature, and the existing controller with fixed parameters is difficult to realize high-precision control of current.

In summary, the current control method of the existing magnetic suspension planar motor has the problem of low accuracy of the current loop model, so that the motion control accuracy of the magnetic suspension planar motor is low.

Disclosure of Invention

The embodiment of the invention provides a current control method and a current control system of a magnetic suspension planar motor, which are used for improving the precision of a current loop model and realizing the high-precision motion of the magnetic suspension planar motor.

In a first aspect, an embodiment of the present invention provides a current control method for a magnetic levitation planar motor, where the current control method includes:

establishing a current loop model of the magnetic suspension planar motor, and collecting current loop input and current loop output;

identifying inductance parameters of the current loop model according to the current loop input and the current loop output;

and solving the optimal parameters of the controller of the magnetic suspension planar motor according to the inductance parameters.

Optionally, identifying the inductance parameter of the current loop model uses a least squares method.

Optionally, identifying an inductance parameter of the current loop model comprises:

obtaining an s-domain current loop transfer function according to the current loop input and the current loop output;

discretizing the s-domain current loop transfer function to obtain a z-domain current loop transfer function;

converting the z-domain current loop transfer function into a difference equation; the difference equation comprises a parameter to be identified;

identifying the parameters to be identified in the difference equation by adopting a least square method;

and obtaining the inductance parameter of the current loop model according to the parameter to be identified.

Optionally, the s-domain current loop transfer function is expressed as the following formula:

wherein i_inFor current loop input, i_outFor current loop output, a_c＝R/L，b_c(U/L), U is voltage, R is resistance, L is inductance;

the z-domain current loop transfer function is expressed as follows:

wherein, a_dAnd b_dAs the parameter to be identified, a_d＝-e^-(R/L)T，b_d(U/L), T is the sample time;

the difference equation is expressed as follows:

wherein y (k) ═ i_out(k)，k is the current sampling moment;

the least square method is adopted to represent the following formula:

wherein K is a gain matrix, P is a covariance matrix, and α is a forgetting factor;

the inductance parameter is expressed as the following equation:

optionally, the current loop model further comprises a filter;

the transfer function of the filter is expressed as follows:

wherein, T_fliterThe inverse of the filter cut-off frequency.

Optionally, the transfer function of the controller is expressed as the following formula:

wherein, T_ControlTo control the period, K_pAs a proportional control parameter, K_iIs an integral control parameter;

alternatively, the transfer function of the controller is expressed as the following equation:

wherein, K_pAs a proportional control parameter, K_iIs an integral control parameter.

Optionally, the optimal parameters include a proportional control parameter and an integral control parameter.

Optionally, the transfer function of the current loop is expressed by the following formula:

where U is the voltage, R is the resistance, and L is the inductance.

Optionally, the current loop model further comprises a driver;

the transfer function of the driver is expressed as follows:

wherein D is_maxIs a control quantity corresponding to a duty ratio of 1, T_PWMIs a PWM period;

alternatively, the transfer function of the driver is expressed as the following equation:

G_PWM(s)＝D_max

wherein D is_maxThe duty ratio is 1.

Optionally, the system damping ratio of the current loop model is 0.707;

obtaining the proportional control parameter and the integral control parameter according to the transfer function of the current loop, the transfer function of the driver and the transfer function of the filter, wherein the proportional control parameter and the integral control parameter are respectively expressed as the following formulas:

in a second aspect, an embodiment of the present invention further provides a current control system for a magnetic levitation planar motor, where the current control system includes:

the acquisition module is used for acquiring current loop input and current loop output;

the inductance identification module is used for identifying inductance parameters of the current loop model according to the current loop input and the current loop output;

and the optimal parameter solving module is used for solving the optimal parameters of the controller of the magnetic suspension planar motor according to the inductance parameters.

The embodiment of the invention provides a method for calculating optimal control parameters of current, which considers the inductance parameter change caused by the problems of noise, actual system time delay and the like, and calculates the optimal parameters of a controller at each sampling moment according to the inductance parameters obtained by identification and the expected performance indexes of a closed-loop system, namely, the online real-time adjustment of the optimal parameters of the controller is realized, so that the method is favorable for improving the current control performance, improving the robustness and the precision of current control and realizing the high-precision motion of a magnetic suspension planar motor. The embodiment of the invention is easy to realize and has wide application range. In addition, for a simulation system, the simulation model established by the embodiment of the invention is close to an actual model, and the optimal parameters obtained by simulation adjustment can be directly applied to the actual control system.

Drawings

Fig. 1 is a flowchart of a current control method of a magnetic levitation planar motor according to an embodiment of the present invention;

fig. 2 is a block diagram of a current loop model according to an embodiment of the present invention;

fig. 3 is a schematic flow chart of a current control method of a magnetic levitation planar motor according to a second embodiment of the present invention;

fig. 4 is a block diagram of a current loop model according to a third embodiment of the present invention;

fig. 5 is a block diagram of a current control system of a magnetic levitation planar motor according to a fourth embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.