JP2007107603A - Device for robust control of magnetic bearing by loop shaping method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic bearing control device which simplifies arithmetic processing and realizes multiple input and multiple output robust control suitable for central control of a plurality of magnetic bearings. <P>SOLUTION: A first mathematical model of a detailed control target 20 comprising an actuator 21, a rotary body 1, an amplifier 22 and a position sensor 23 is derived. An order reduction of the first mathematical model is performed, and a second mathematical model of an enlarged control target Ga(s) comprising a PI control section 13, a subtracter 14, a PD control section 15 and the detailed control target 20 is derived by using the order-reduced first mathematical model. The order of the second mathematical model is set to be low, and an expression is derived by employing a loop shaping method for the second mathematical model. The robust control is performed according to the expression. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control apparatus for a magnetic bearing having a multi-input multi-output robust control unit, and specifically designed using an H∞ loop shaping technique or a linear matrix inequality (LMI: Linear Matrix Inequality) loop shaping technique. The present invention relates to a magnetic bearing control device including a multi-input multi-output robust control unit.

In HTGR gas turbine power generation systems, oil and water lubricants from existing fluid bearings are mixed into the gas coolant and corrode equipment and facilities in the system, so magnetic bearings are required.
The gas turbine rotor and the generator rotor are two-span rotors in which two ends (a total of four points) are supported by magnetic bearings and both rotors are connected by joints. For a long rotor, the rigidity of the magnetic bearing is low, and the natural frequency of the bending mode of the rotor is relatively low. For this reason, the rated rotational speed needs to be in a high speed rotational speed region exceeding the bending mode natural frequency of the rotor. (See Non-Patent Document 1)
When such a magnetic bearing supporting the rotor is distributedly controlled by a 1-input 1-output control device for each magnetic bearing, it is caused by high-order bending mode vibration of the rotor or mutual interference vibration between the two rotors. The problem is that stable control is not possible.

  In such a case, the control device of the magnetic bearing is multi-input multi-output control, and a plurality of magnetic bearings are coupled to control the vibration of the rotor, thereby enabling stable and highly accurate control. A robust control system is suitable for multi-input multi-output control.

  Conventionally, as a control device for a robust magnetic bearing, an error between a radial position of a rotating body and a target position is calculated, and based on this error, a controller performs an LMI gain schedule H∞ calculation. Some control the current in the electromagnet coil forming the magnetic bearing to control the radial position of the rotating body to the target position.

For example, Japanese Patent Laid-Open No. 10-220475 (Patent Document 1) discloses a control device for a magnetic bearing that employs LMI gain schedule H∞ control.
In the control device disclosed in Patent Document 1, a plurality of H∞ compensators are designed on an LMI basis for different rotational speeds. In order to perform gain scheduling, coefficients are added to the H∞ compensator by interpolation. The coefficients can be changed continuously so that the sum is 1 and depending on the number of rotations measured by the rotating body (Patent Document 1, pages 4-8 and 5). (See figure).
Japanese Patent Laid-Open No. 10-220475 Takada et al., Power Generation System Design of HTGR Gas Turbine Power Generation System (GTHTR300), Japanese Atomic Energy Society, Vol. 1, No. 4, pp. 341-351 (2002) K. Zhou, JC Doyle and K. Glover: Robust and Optional Control, Prentice-Hall (1995) G. Vinnicombe: The robustness of feedback systems with bounded complexity controllers; IEEE Transaction on Automatic Control, AC-41, No. 6, pp. 795-803 (1996) Miyamoto: Design of fixed-structure H∞ controller based on rule-resolved expression and LMI optimization; System / Control / Information, VOL.43, NO.2, PP.80-86 (1999)) System Control Information Society, Nobuhide Suda, Author Representative, PID Control, Asakura Shoten, p75, 2001

  However, when supporting a single elastic rotor or when a multi-span rotor in which a plurality of elastic rotors are connected by joints is to be controlled, the above-mentioned problems can be solved by using multi-input multi-output control. On the other hand, there is a problem that the order of the arithmetic expression of the controller becomes high and the processing becomes complicated.

  In general, it is known that the solution to the H∞ standard problem is such that the order of the arithmetic expression of the controller is greater than or equal to the order of the transfer matrix of the generalized plant. It is known that a high-order controller is not desirable because it not only causes a problem in mounting, but also increases the computation time and deteriorates robustness. (See Non-Patent Documents 2 and 3.)

  The processing speed can be increased by simply lowering the order of higher-order controllers, but the control performance such as controller stability and responsiveness is reduced as the accuracy of the reduced-order arithmetic expressions decreases. Will deteriorate.

If the robust controller can reduce the order of the arithmetic expression while satisfying the robust stability condition, coupled control of a plurality of magnetic bearings by multi-input multi-output control becomes possible.
The present invention has been made in order to solve the above-mentioned problem. By satisfying the robust stability condition and reducing the order of the arithmetic expression of the robust controller, the control device in the operation of the rotating body is reduced. It is an object of the present invention to provide a magnetic bearing control device capable of speeding up the processing and enabling coupled control of a plurality of magnetic bearings by multi-input multi-output control.

  In order to achieve the above object, a magnetic bearing control device for performing radial position control of a rotating body according to the present invention includes a target position in the radial direction of the rotating body and the rotating body measured by a position measuring unit. Subtracting means for receiving a measurement position in the radial direction of the sensor and outputting a difference between the target position and the measurement position, and a robust control for receiving the difference between the target position and the measurement position and outputting robust control information based on the difference And PID control means for performing PID control, the PID control means for receiving the robust control information and outputting the PID control information to the drive means for driving the rotating body based on the robust control information. And the robust control means derives a first mathematical model to be controlled in detail comprising the driving means, the rotating body, and the position measuring means, and the derived first mathematical model The equation model is reduced in dimension, and the second equation model to be enlarged controlled by the PID control unit, the driving unit, the rotating body, and the position measuring unit is converted into the first equation model reduced in dimension. And the degree of the derived second mathematical model is set to a low dimension, and the second mathematical model set to the low dimension is robust by an arithmetic expression derived using a loop shaping method. Control is performed.

  According to one aspect of the present invention, the PID control means includes a PI control means for performing PI control and a PD control means for performing PD control, the PI control means receives the robust control information, and the robust control information PI control information is output on the basis of the second control unit, and another subtracting unit is provided between the PI control unit and the PD control unit, and the other subtracting unit outputs the PI control information from the PI control unit. The difference from the measurement position from the position measurement means is output, the PD control means receives the difference, outputs the PID control information including PD control information based on the difference, and the calculation formula is It is preferably derived based on the enlargement control target further including another subtraction means.

  According to another aspect of the present invention, a plurality of the robust control means are provided, each of the plurality of robust control means has a different arithmetic expression adapted to each of the different rotational states of the rotating body, It is preferable to further include gain scheduling means for selecting one robust control means from the plurality of robust control means based on the number of rotations.

  According to still another aspect of the present invention, it is preferable that the loop shaping method is an H∞ loop shaping method or a loop shaping method based on a linear matrix inequality.

According to the magnetic bearing control device of the present invention, the robust control means performs the robust control by the arithmetic expression designed using the loop shaping method, and thus has the low-order arithmetic expression while satisfying the robust stability condition. It becomes possible to design a controller. Accordingly, it is possible to speed up processing that is indispensable for a multi-input multi-output control device for controlling a plurality of magnetic bearings in combination. According to the present invention, the robust control means includes a plurality of magnetic bearings. It is possible to obtain the difference between the target position and the measurement position in the radial direction of the rotating body as input information and perform robust control.

  Since the robust control means is a multi-input multi-output system, including the object to be controlled (elastic rotor or multi-span rotor) and multiple magnetic bearings that support them, the arithmetic expression such as the transfer matrix becomes a high order, and the conventional design In the method, the controller also has a high order comparable to that of the controlled object.

  However, the robust control means is designed using a loop shaping method (H∞ loop shaping, LMI loop shaping method, etc.), so that the robust stability condition is satisfied even under such design conditions in a multi-input multi-output system. A robust controller having a low-order arithmetic expression can be obtained (see Non-Patent Document 4).

The present invention can be applied not only to an elastic body but also to a rigid body that is easier to control, and can also be applied to a state in which a plurality of rotating bodies are connected. It is.
In one aspect of the present invention, not only the robust control unit but also another subtraction unit is provided between the PI control unit and the PD control unit as the feedback unit, and the feedback unit is included in the other subtraction unit. Since the measurement position is fed back, the control is two-degree-of-freedom control, and has a structure equivalent to so-called target value filter type two-degree-of-freedom control (see Non-Patent Document 5). In a one-degree-of-freedom control system that does not feed back to another subtracting means, the target value followability and the disturbance control characteristic cannot be optimized at the same time, but in two-degree-of-freedom control, the target value is appropriately calculated and then fed back. Take control. For this reason, the target value followability and the disturbance control characteristics can be individually adjusted to optimum values, so that the control performance can be improved. Further, since the two-degree-of-freedom control is one method of PID control methods that have been used conventionally, it is possible to easily estimate the calculation result and the like at the design stage. As a result, the design time can be shortened and a control system with excellent control performance can be designed.

  In another aspect of the present invention, a plurality of the robust control means are provided, each of the plurality of robust control means has a different arithmetic expression adapted to each of the different rotational states of the rotating body, Since it further comprises a gain scheduling means for selecting one robust control means from the plurality of robust control means based on the number of revolutions, the robust control means employed for the control is changed according to the number of revolutions of the rotating body. It becomes possible. Thereby, optimal control according to the characteristics of the rotating body can be realized.

  In yet another aspect of the present invention, control is performed while satisfying a robust stability condition in the design stage by using H∞ loop shaping or loop shaping based on a linear matrix inequality for designing an arithmetic expression used by the robust control means. It is possible to efficiently lower the order of the vessel.

An embodiment of a magnetic bearing control device according to the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a control model of a magnetic bearing according to an embodiment of the present embodiment. Here, the magnetic bearing supports the rotating body 1 in a non-contact manner and controls the position of the rotating body 1.

  As shown in FIG. 1, the rotating body 1 includes a pair of magnetic bearings 2 and 3 for controlling the position of the rotating body 1 in the X-axis direction and a pair for controlling the position of the rotating body 1 in the Y-axis direction. Magnetic bearings 4 and 5 are provided. As shown in this figure, the magnetic bearings 2 to 5 are modeled by a damper C and a spring K.

The magnetic bearings 2 to 5 are controlled by a control device having a configuration as shown in FIG. 2 in order to maintain the radial position of the rotating body 1 at a desired position.
FIG. 2 is a block diagram showing a schematic configuration of the magnetic bearing control device according to the present embodiment.

  As shown in FIG. 2, the magnetic bearing control device 10 includes a subtractor (subtraction means) 11, a robust control section (robust control means) 12, a PI control section (PI control means) 13, a subtractor (another subtractor). Subtraction means) 14 and a PD control unit (PD control means) 15 are provided.

  In the magnetic bearing control device 10, each element other than the robust control unit 12, that is, the subtractor 11, the PI control unit 13, the subtractor 14, and the PD control unit 15 are arranged in the radial direction of the rotating body controlled by the magnetic bearing. One is provided corresponding to each position. In the present embodiment, as shown in FIG. 1, since four magnetic bearings 2 to 5 are provided, the subtractor 11, the PI control unit 13, the subtractor 14, and the PD control unit 15 are also included in each magnetic bearing 2. Four each is provided so as to correspond to .about.5.

  The subtractor 11 is a target position r1, r2, r3, r4 of the rotating body 1 calculated by another control device, and a radial measurement position of the rotating body 1 (x, The displacement in the y-axis direction (see FIG. 1)) y1, y2, y3, and y4 are received, and the difference between the target position and the measurement position is generated and output to the robust control unit 12 connected to the subtractor 11.

  The robust control unit 12 is connected to each PI control unit 13. Each PI control unit 13 is connected to a corresponding subtracter 14. Each subtractor 14 is connected to a corresponding PD control unit 15. The PD control unit 15 is connected to a corresponding driving device (driving means), for example, an actuator 21. The actuator 21 drives each of the magnetic bearings 2 to 5 based on the command value supplied from the corresponding PD control unit 15. Although not shown in FIG. 2, each of the magnetic bearings 2 to 5 is located between each of the actuators 21 and the rotating body 1. Thereby, it becomes possible to hold the rotating body 1 at the target position r.

Next, the operation of the magnetic bearing control device 10 having the above configuration will be described.
First, as described above, the target positions r1, r2, r3, r4 of the rotator 1 calculated by another control device are input to the subtractor 11, and the rotator 1 of the rotator 1 is input from the feedback unit 16 described later. The measurement position in the radial direction (the displacement of the rotating body 1 in the x and y axis directions, see FIG. 1) y1, y2, y3, and y4 are input, and the difference between the target position and the measurement position is output to the robust control unit 12. The

  The robust control unit 12 is a multi-input multi-output robust controller that centrally controls a plurality of magnetic bearings based on a plurality of inputs of the difference between the target position and the measurement position. Specifically, the robust control unit 12 performs robust control by adopting the input information in an arithmetic expression designed using a loop shaping method. Details of the design method of the robust control unit 12, that is, the calculation method of the arithmetic expression will be described later.

  The outputs of the robust control unit 12 are respectively input to four PI control units 13 provided individually corresponding to the magnetic bearings 2 to 5 shown in FIG. Each PI control unit 13 acquires the output of the robust control unit 12 as input information and performs PI control. Here, the PI control unit 13 also has a filter function for removing noise in a predetermined frequency band.

  The output of the PI control unit 13 is input to the subtracter 14. The subtractor 14 acquires, as input information, the output of the PI control unit 13 and each measurement position in the radial direction of the rotating body 1 fed back by a feedback unit 16 described later, and outputs this difference.

  The output of the subtracter 14 is input to the PD control unit 15. The PD control unit 15 acquires the output of the subtracter 14 as input information and performs PD control. As a result, the information output from the PD control is a current command value for the actuator 21 provided corresponding to each of the magnetic bearings 2 to 5. Each actuator 21 supplies a current based on the current command value input from the PD control unit 15 to each of the magnetic bearings 2 to 5. Thereby, the magnetic bearings 2 to 5 shown in FIG. 1 are controlled, and as a result, the rotating body 1 is held at a desired position.

  The position of the rotating body 1 in the radial direction is detected by a position sensor (not shown), and detected values y1 to y4 by the position sensor are fed by the feedback unit 16 to the robust control unit 12 and each subtractor 14 of the magnetic bearing control device 10. Feedback.

By repeatedly performing the above-described control, the rotating body 1 can always be held at a desired position.
As described above, according to the magnetic bearing control device according to the present embodiment, the robust control unit 12 performs the robust control by the low-order arithmetic expression designed by using the loop shaping method, so that rapid processing is performed. Is possible.

  Here, the feedback unit 16 is a two-degree-of-freedom control that feeds back the measurement position to the subtractor 14 as well as the robust control unit 12 that has passed through the subtractor 11, and is equivalent to a so-called target value filter type two-degree-of-freedom control. It has a structure. In the two-degree-of-freedom control, the target value followability and the disturbance control characteristic can be individually adjusted to optimum values, so that the control performance of the basic loop can be improved. Before deriving an arithmetic expression of the robust controller by the loop shaping method, it is necessary to form a compensator to make it easy to control the frequency characteristics and response characteristics of the expansion control system. Since the basic loop is a main component of the enlargement control target to be described later, the frequency characteristics and response characteristics of the control target can be formed by making the basic loop a two-degree-of-freedom control system.

In the above-described embodiment, the case where four magnetic bearings are controlled has been described, but the present invention is not particularly limited in the number of magnetic bearings.
For example, in a high temperature gas furnace or the like, as shown in FIG. 3, a coupling of two rotating bodies 1 is used. Even in such a case, the magnetic bearing control device 10 according to the present embodiment can be applied. In this case, since the position in the radial direction of each rotating body 1 is controlled by four magnetic bearings, a total of eight magnetic bearings are controlled by the magnetic bearing control device 10.

  The above-described magnetic bearing control device 10 may be realized by hardware such as an analog circuit, or may be realized by software such as processing by a microcomputer. When realized by a microcomputer, the functions realized by the constituent elements of the magnetic bearing control device 10 are stored in a memory in the form of a program, and the CPU reads the program from the memory and executes it, thereby executing the above-described operation. Realize operation.

Next, a control device for a magnetic bearing according to a second embodiment of the present invention will be described.
FIG. 4 is a block diagram showing a schematic configuration of the magnetic bearing control device according to the present embodiment. As shown in FIG. 4, the magnetic bearing control device according to the present embodiment has substantially the same configuration as the magnetic bearing control device 10 according to the first embodiment described above, but each corresponds to a different rotational speed. And a plurality of robust control units 12a, 12b, and 12c, and a gain scheduling unit that selects one robust control unit from among the plurality of robust control units 12a, 12b, and 12c based on the number of rotations of the rotating body 1 17.

  As described above, in the magnetic bearing control device 10 according to the present embodiment, the rotational speed of the rotating body 1 detected by a rotational speed detection sensor (not shown) provided in the rotating body 1 is input to the gain scheduling unit 17. The For example, the gain scheduling unit 17 selects an optimal one of the three robust control units 12a, 12b, and 12c based on the number of rotations. Thereby, the robust control is performed by the selected one robust control unit, and this output is input to the PI control unit 13 of each basic loop. Thereafter, the same processing as in the first embodiment described above is realized.

  As described above, according to the magnetic bearing control device according to the present embodiment, the plurality of robust control units 12 a, 12 b, 12 c provided according to the number of rotations of the rotating body 1, and the rotation of the rotating body 1, respectively. And a gain scheduling unit 17 that selects one robust control unit from among the plurality of robust control units 12a, 12b, and 12c based on the number, and thus the robustness employed in the control according to the rotational speed of the rotating body 1 It is possible to change the control unit. Thereby, the optimal control according to the characteristic of the rotary body 1 is realizable.

In the present invention, the number of installed robust control units is not particularly limited.
Moreover, also in the control apparatus of the magnetic bearing which concerns on this embodiment, the number of the magnetic bearing used as a control object is not limited. For example, the present invention can be applied to a control target as shown in FIG.

Next, a method for designing the above-described magnetic bearing control device will be described with reference to FIG.
FIG. 5 is a flowchart showing a procedure of a method for designing a magnetic bearing control device according to an embodiment of the present invention.

In the design stage, first, as shown in FIG. 5, a detailed control target model is derived (step SA1).
For example, as illustrated in FIG. 6, the detailed control target of the control device according to the present embodiment includes elements such as the rotating body 1, the actuator 21, the amplifier 22, and the position sensor 23.

  Here, FIG. 6 is a diagram showing a model of the control device and the control target of the magnetic bearing according to the first embodiment of the present invention shown in FIG. The detailed control target 20 is a target composed of constituent elements in a range from the actuator 21 to the position sensor 23 including the rotating body 1.

In the present invention, the rotating body 1 may be either a rigid rotor or an elastic rotor.
In the derivation process of the detailed controlled object model (step SA1 in FIG. 5), the mathematical model of each element constituting the detailed controlled object 20 shown in FIG. 6 is derived, and then the mathematical model of each element is combined. Then, a mathematical model of the detailed control object 20 is derived.

  Here, the variables used for modeling are as shown in Table 1 below.

  For example, in the case of the mathematical model of the rotating body 1 shown in FIG. 6, the mass matrix M, the attenuation matrix C, the gyro matrix G, the stiffness matrix K, and the matrix F determined by the position of the electromagnet shown in Table 1 are used. It can be expressed as (1).

  However, q and f are the following vectors.

Here, x _i and y _i are displacements of the i-th element, and θ _xi and θ _yi are angles of the i-th element. f _mi is a force (attraction force) generated by the i-th actuator. Further, the vector f _d in the equation (1) is a disturbance.

  Similarly, mathematical formula models are obtained for the other components such as the actuator 21, the amplifier 22, and the position sensor 23. For example, in the case of the actuator 21, a mathematical model is derived based on the attractive force characteristics.

When the mathematical model of each component is derived in this way, the mathematical model of the detailed control target 20 is derived by combining these mathematical models.
First, a vector q _mj (j = 1 to N) consisting of displacement at the position of the actuator 21 is expressed by the following equation (2) from the generalized vector q.

However, the matrix E _a is a matrix for selecting only the q _m from the vector q, the matrix E _a is the transposed matrix of F. Similarly, q _sj (j = 1 to N) is a vector composed of displacement at the position of the position sensor 23 and is expressed as the following equation (3).

However, the matrix E _S is a matrix for selecting only the q _S from the vector q.
Then, by replacing f and q, the mathematical model of the detailed control object 20 is expressed as the following equation (4).

  However, the suction force f of the actuator 21 is expressed as shown in Equation (5).

Here, K _i , K _m , and i are each expressed by Equation (6).

On the other hand, the state variable x _p of the detailed control object 20 is expressed as the following equation.

Here, x _S and x _a are system state variables of the position sensor 23 and the actuator 21.
Further, the output of the PD control unit 15, that is, the input _{ic of the} actuator 21 is set as the following equation.

u = i _c (8)

Then, K _i , K _m , i in the above equation (4) are replaced as in equation (6), and from the above equations (7) and (8), One is derived.

  Moreover, the state space expression of the position sensor 23 can be expressed as follows.

Here, y represents the output of the position sensor 23.
Another one of the state equations of the detailed control object 20 is derived using the above equations (7), (10), and (11).

Thereby, the state equation of the mathematical model of the detailed control object 20 can be finally obtained as the above formulas (9) and (12).
When the mathematical model of the detailed control object 20 is derived in this way, the dimension of the derived mathematical model of the detailed control object 20 is subsequently reduced (step SA2 in FIG. 5).

  Specifically, the order is reduced by a method based on the rule decomposition expression or a method based on the mode decomposition. When the rotating body 1 is an elastic rotor, the reduction in dimension is performed such that the control object reduced in dimension includes an eigenvalue corresponding to the bending mode vibration of the elastic rotor to be considered in the design. Since this technique is a well-known technique, the details are omitted.

  The reduction formulas of the equations (9) and (12) are respectively expressed as follows.

Here, the subscript r indicates a matrix or vector that has been reduced in dimension.
When the reduction of the detailed control target 20 is completed in this way, the basic loop (see FIG. 7) configured by the PD control unit 15 and the PI control unit 13 shown in FIG. 6 is subsequently designed (see FIG. 7). Step SA3 of 5).

The PD control unit 15 is an element having a transfer function K _1i shown in the following formula (13), and the PI control unit 13 is an element having a transfer function K _2i shown in the following formula (14). Here, the PI control unit 13 has a filter function.

  In the design process of the basic loop, each parameter of the PD control unit 15 and the PI control unit 13, that is, all control parameters in the equations (13) and (14) are determined. Specifically, these control parameters a10i, a20i, b10i, b11i, b20i, b21i, ζa1i, ωai, ζbi, and ωbi are determined in consideration of frequency characteristics such as a band.

  Here, the detailed control object 20 and the basic loop are regarded as the expansion control object Ga (s), and the state equation of the expansion control object Ga (s) is obtained. In FIG. 6, the enlargement control target Ga (s) is a component included in a portion surrounded by a dotted line, that is, the PI control unit 13 excluding the subtractor 11 and the robust control unit 12 in the magnetic bearing control device 10, The subtractor 14 and the PD control unit 15, the detailed control object 20 (that is, the actuator 21, the amplifier 22, the rotating body 1, and the position sensor 23) and the feedback unit 16 are included.

  The state equation of the PI control unit 13 can be expressed as follows.

Here, v ₁ is an input to the PI control unit 13.
The state equation of the PD control unit 15 can be expressed as follows.

Here, y represents the output of the position sensor 23.
Next, the PI control unit 13 and the PD control unit 15 are combined.
Specifically, when y _PI is deleted from the equation (17), the following equation is obtained.

On the other hand, when y _PI is eliminated from the equation (18), the following equation is obtained.

  Equation (19) is replaced as follows:

Here, x _cp and v are respectively represented by the following equations.

  Equation (20) is replaced as follows:

  The following equation of state of the expansion control object Ga (s) is obtained by eliminating y and u from the equations (9a) and (12a) and the equations (21) and (22).

  After that, the basic loop is reduced in dimension together with the previously reduced control object (that is, the expansion control object Ga (s) is reduced in dimension). The reduction method may be the above-described known method similar to the reduction of the mathematical model of the detailed control object 20.

In this way, when the basic loop design process is completed, the robust control unit 12 is designed (step SA4 in FIG. 5).
The design of the robust control unit 12 is performed using loop shaping, and is preferably performed using, for example, H∞ loop shaping. Here, loop shaping refers to a control system design method for obtaining a controller Ka that maximizes the robust stability margin shown in the following equation (25) for the enlargement control target Ga (s). At this time, since the order of the controller can be designated, a low-order controller can be designed while satisfying the robust stability condition.

The above solution is shown in Non-Patent Document 4, for example.
In summary, the order of the state equation (formula model) of the expansion control object Ga (s) is set to a low dimension, the expansion control object Ga (s) is reduced in dimension, and the reduced-dimensional expansion control object Ga is reduced. For (s), the controller Ka that maximizes the robust stability margin shown in equation (25) is obtained. This problem is equivalent to the H∞ 4-BLOCK problem and can be analyzed by existing methods.

  The state equation of the robust control unit 12 can be obtained by combining with the subtractor 11 as the following equation (26).

  When designing the magnetic bearing control device according to the second embodiment described above, several operating points (number of rotations) are selected, and the robust control unit at each operating point is selected by the same method as described above. design.

In this way, when the design process of the robust control unit 12 is completed, the performance is confirmed by a simple model (step SA5 in FIG. 5).
In the performance confirmation using this simple model, the state equation (26) of the robust control unit 12 designed in step SA4, the reduced detailed control object 20 and the expanded control object Ga (s) (PI control is performed on the detailed control object 20). State equation (that is, including the unit 13 and the PD control unit 15) (that is, the state equations reduced in the order of the equations (9a), (12a), (13), (14), (23), and (24)) A simple model is created by combining. When the rotating body 1 is an elastic rotor, the order of the bending mode vibration of the elastic rotor is limited in the reduced-scale expansion control object Ga (s), but the order of the bending mode vibration sufficient for the design of the control system is limited. Lower the dimensions to enter. The simple model has a shorter calculation time than the detailed model described later, and can be evaluated quickly.

  And the system stability (frequency characteristics, sensitivity characteristics, complementary sensitivity characteristics, disturbance sensitivity characteristics, open loop characteristics, etc.), response characteristics (target value step response, disturbance step response, disturbance impulse response, etc.), imbalance by simple model Confirm performance such as position deviation by response.

  When stable operation can be confirmed by performance confirmation using the simple model, subsequently, performance confirmation (stability, response characteristics, position deviation) similar to that of the above-described simple model is performed using the detailed model (step SA6 in FIG. 5). ).

  The detailed model includes the state equation (26) of the robust control unit designed in step SA4 and the state equations (9), (12), (13), (14) of the detailed control object 20 and the expansion control object Ga (s). ), (23) and (24) are combined. Since the controlled object is not reduced in dimension, when the rotating body 1 is an elastic rotor, the order of bending mode vibration of the elastic rotor is not limited, and a highly accurate analysis is possible. However, the detailed model takes longer calculation time than the simple model. Therefore, after confirming the performance with the simple model, the final performance is confirmed with the detailed model.

  If stable performance is not obtained in the performance check using the detailed model (“NO” in step SA7 in FIG. 5), the process from step SA3 to step SA6 in FIG. 5 is repeated until stable operation is obtained. Make design changes. If stable performance is obtained in the performance confirmation (stability, response characteristics, position deviation) using the detailed model described above (“YES” in step SA7 in FIG. 5), the design of the magnetic bearing control device is completed. .

  As described above, according to the design method according to the present embodiment, the controller Ka of the robust control unit 12 is determined using the H∞ loop shaping method, so that the robust control unit 12 can be efficiently designed. And an arithmetic expression with a reduced dimension can be obtained. By adopting the robust control unit 12 in the control device for the magnetic bearing, the arithmetic processing in the control device during the operation of the rotating body 1 is simplified, and the processing time can be shortened.

  In the above design method, the robust control unit 12 is designed using the H∞ loop shaping method. Instead, the robust control unit 12 is designed using the loop shaping method based on linear matrix inequalities. Also good. By any of the methods, it is possible to design an optimal robust control unit 12 that is reduced in dimension, and it is possible to efficiently perform arithmetic processing.

  In the embodiment shown in FIG. 2, a double feedback system that is a two-free control system using the subtractor 14 is used. However, depending on the application, a single-free control system may be used. A single feedback system in which 14 is omitted can also be adopted. Without the subtractor 14, the feedback system is simpler than in the embodiment shown in FIG. 2, so it is clear that each of the above state equations can be obtained by a process similar to the above derivation process. The robust control unit can be designed with a flow similar to the flow described with reference to FIG.

When there is no subtracter 14, the PI control unit 13 and the PD control unit 15 can be integrated to form a PID control unit.
For example, when the present invention is applied to a magnetic bearing device in a HTGR gas turbine power generation system, the order of the arithmetic expression of the robust controller is reduced from several hundred orders to several tens orders when the order is not applied. Is possible.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.

FIG. 1 is a diagram illustrating a control model of a magnetic bearing that supports a rotating body according to an embodiment of the present invention. FIG. 2 is a block diagram showing a schematic configuration of the magnetic bearing control device according to the first embodiment of the present invention. FIG. 3 is a view showing a modified example of the magnetic bearing control device according to the first embodiment of the present invention. FIG. 4 is a block diagram showing a schematic configuration of a magnetic bearing control device according to the second embodiment of the present invention. FIG. 5 is a flowchart showing a procedure of a method for designing a magnetic bearing control device according to an embodiment of the present invention. FIG. 6 is a diagram showing a model of the control device for the magnetic bearing shown in FIG. 1 and its control target. FIG. 7 is a diagram showing a basic loop to be considered when designing a magnetic bearing control device excluding the robust control shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating body 2, 3, 4, 5 Magnetic bearing 10 Magnetic bearing control apparatus 11 Subtractor 12 Robust control part 13 PI control part 14 Subtractor 15 PD control part 16 Feedback part 17 Gain scheduling part 21 Actuator

Claims (4)

A control device for a magnetic bearing for performing radial position control of a rotating body,
Subtracting means for receiving a target position in the radial direction of the rotating body and a measurement position in the radial direction of the rotating body measured by a position measuring means, and outputting a difference between the target position and the measured position;
Robust control means for receiving a difference between the target position and the measurement position and outputting robust control information based on the difference;
PID control means for performing PID control, comprising: PID control means for receiving the robust control information and outputting PID control information to a drive means for driving the rotating body based on the robust control information,
The robust control means derives a first mathematical model to be controlled in detail consisting of the driving means, the rotating body, and the position measuring means, performs a reduction in the order of the derived first mathematical model, A second mathematical model of an enlargement control target composed of the PID control unit, the driving unit, the rotating body, and the position measurement unit is derived using the first mathematical model reduced in dimension, and the derived A control device that sets the order of the second mathematical model to a low dimension and performs robust control using an arithmetic expression derived by using a loop shaping method for the second mathematical model set to the low dimension. The PID control means comprises a PI control means for performing PI control and a PD control means for performing PD control,
The PI control means receives the robust control information, outputs PI control information based on the robust control information,
Another subtracting means is provided between the PI control means and the PD control means,
The other subtraction means outputs a difference between the PI control information output from the PI control means and the measurement position from the position measurement means,
The PD control means receives the difference, and outputs the PID control information including PD control information based on the difference,
The control device according to claim 1, wherein the arithmetic expression is derived based on the enlargement control target further including the other subtracting unit. A plurality of the robust control means are provided,
Each of the plurality of robust control means has a different arithmetic expression adapted to each of the different rotational states of the rotating body,
3. The control device according to claim 1, further comprising gain scheduling means for selecting one robust control means from among the plurality of robust control means based on the number of rotations of the rotating body.   The control device according to any one of claims 1 to 3, wherein the loop shaping method is an H∞ loop shaping method or a loop shaping method based on a linear matrix inequality.

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