KR101385977B1 - Driving system for controlling electromagnetic actuator in magnetic levitations and magnetic bearings - Google Patents

Abstract

The present invention relates to a PWM driving system of an electromagnetic actuator for magnetic levitation and magnetic bearing systems capable of effectively providing a high control voltage so that the electromagnetic actuator of magnetic bearing and magnetic levitation systems can be applied to a light load. The present invention provides the PWM driving system of the electromagnetic actuator for the magnetic levitation and magnetic bearing systems comprising; an electromagnetic driving control circuit connected to both ends of a coil which is wound around an electromagnetic; and a control unit including a direction determination unit and a duty controller for controlling the opening and closing of a switching element regarding the electromagnetic driving control circuit. The electromagnetic driving control circuit comprises; a power unit; and an H-bridge switching circuit including a first switching element connected to an anode of the power and one end of the coil, and a second switching element connected to a cathode of the power unit and the other end of the coil. The second switching element is operation-controlled according to a code of a coil control voltage by the direction determination unit. The first switching element is duty-controlled according to a ratio of the coil control voltage to an input voltage from the power unit by the duty controller. The PWM driving system performs a driving control of the electromagnetic with three output voltage states (Vdc, 0, -Vdc). [Reference numerals] (10) Control unit; (11) Duty controller; (13) PI controller; (17) Magnetic rise / magnetic bearing (location) controller; (AA) Gap measuring sensor; (BB) Gap

Description

PWM driving system for electromagnetic actuators for magnetic levitation and magnetic bearing systems {Driving system for controlling electromagnetic actuator in magnetic levitations and magnetic bearings}

The present invention relates to a PWM drive system of an electromagnet actuator for a magnetic levitation and magnetic bearing system, and more particularly, to provide a large control voltage effectively to be applicable to a large load in an electromagnet actuator of a magnetic bearing and a magnetic levitation system. The present invention relates to a PWM drive system of an electromagnet actuator.

Recently, magnetic levitation and magnetic bearing systems using magnetic force to realize high clean and high efficiency driving systems have been attracting attention.

For example, as a facility for preventing damage caused by fine dust particles due to friction in mechanical contact or lubrication in a semiconductor manufacturing process or the like, a facility to which a non-contact magnetic levitation system is applied has been studied in various ways.

Since the conveying system using the magnetic levitation floats the conveying body with magnetic force, it can minimize energy loss due to friction, and can realize a noiseless, low vibration, ultra-clean conveying system without mechanical contact or friction. In addition, in the magnetic levitation system, there is no friction, so that the precision can be increased, and since the lubricant is not used to reduce the friction, it has environmentally friendly characteristics.

In addition, as in the magnetic levitation system, magnetic bearings that support a rotating member or function as a guide, and magnetic guides share these characteristics, and as described above, have high efficiency, high precision, and environmentally friendly characteristics.

In such a magnetic levitation system or a magnetic bearing system, a high magnetic force is required depending on the situation, and an electromagnetic actuator is used to form such a high magnetic force.

The electromagnet actuator is made of a coil wound around an electromagnet core, and a control circuit for controlling current for the coil is connected.

Conventionally, as such a control circuit, a linear power amplifier capable of performing flexible control by giving analog dynamic characteristics may be applied.

However, while such linear power amplifiers are suitable for light load driving, it is difficult to increase the voltage and current, and there is a disadvantage in that they are difficult to apply in the case of heavy loads requiring high voltage, which makes them difficult to apply in a typical system requiring large force. There was a problem.

On the other hand, as a control circuit for such an electromagnet actuator, an H-bridge switching circuit can be used.

FIG. 1 shows a conventional H-bridge switching circuit, and FIG. 2 shows a control pattern for each switching element in the circuit of FIG.

The control of the coil current of the conventional electromagnet actuator is performed by on / off control of the switching element for a predetermined duty, and as such control is performed, the voltage applied to the load corresponds to Vdc and -Vdc during one period of the control signal. Is controlled by varying the dipole voltage for two states.

The voltage across the load in this control circuit is shown in FIG. 3.

As shown in FIG. 3, the average voltage Vavg during one period during which the control is performed corresponds to the difference between the area of the X region and the Y region on the voltage graph, and thus, the average voltage during the period can be expressed as follows.

Vavg = (2D-1) Vdc, 0 <D <1 (1)

That is, the above equation has a relationship of Vavg = 0 when D = 0.5, Vavg = Vdc when D = 1, and Vavg = -Vdc when D = 0.

However, in the case of such an H-bridge switching circuit, it is difficult to increase the voltage largely due to the EMI noise caused by the switching surge, and a large control voltage is required because of the high inductance. The problem is that the control accuracy in the magnetic levitation system or the magnetic bearing system is lowered and vibration occurs.

Accordingly, the present invention has been devised to improve the above-mentioned point, and improves the control accuracy of the output voltage in the driving system of an electromagnet actuator capable of driving high power even in an operating environment requiring high speed driving against a large load. It is an object of the present invention to provide a PWM drive system of an electromagnet actuator for magnetic levitation and magnetic bearing systems, which can stably and precisely drive a drive by reducing switching loss and reducing vibration in a magnetic levitation or magnetic bearing system.

The present invention to achieve the above object, the electromagnet drive control circuit connected to both ends of the coil wound on the electromagnet; And a controller including a duty controller and a direction determiner for controlling opening and closing of the switching element with respect to the electromagnet driving control circuit, wherein the electromagnet driving control circuit includes a power supply unit, a first terminal connected to an anode of the power supply unit and one end of the coil; And an H-bridge switching circuit including a switching element, a negative electrode of the power supply unit, and a second switching element connected to the other end of the coil, wherein the second switching element controls the operation according to a sign of a coil control voltage by the direction determiner. The first switching element is duty-controlled by the duty controller according to a ratio of a coil control voltage and an input voltage from the power supply to control driving of the electromagnet in three output voltage states Vdc, 0, -Vdc. Provided is a PWM drive system of an electromagnetic actuator for magnetic levitation and magnetic bearing system, characterized in that performing All.

In one embodiment of the present invention, a proportional integral controller for calculating a coil control voltage input to the duty controller and the direction determiner is connected to an input side of the duty controller and the direction determiner, wherein the proportional integral controller is configured of the command current and the feedback current. And proportional integral control on the difference to calculate the coil control voltage.

In another embodiment of the present invention, a proportional controller for calculating a coil control voltage input to the duty controller and the direction determiner is connected to an input side of the duty controller and the direction determiner, and the proportional controller is connected to the current value output from the error compensator. Configured to calculate the coil control voltage by proportionally controlling the difference of the feedback current, and the error compensator outputs the current value calculated by multiplying the input command current by (R + kp) / kp to the proportional controller side. It is composed. Where R is the resistance of the coil and kp is the proportional control gain.

In an embodiment of the invention, the control unit is configured to perform duty control according to the following i), ii) and i) from the coil control voltage Vc through the duty controller for each control period Ts.

Iii) Da = Vc / Vdc, Db = 1 when Vc> 0

Ii) when Vc = 0, Da = 0, Db = 1 or Da = 1, Db = 0

I) When Vc <0, Da = 1-(-Vc / Vdc), Db = 0

In the above, Vc is the coil control voltage, Da is the output control signal of the duty controller, Db is the output control signal of the direction determiner.

As described above, the PWM drive system of the electromagnet actuator according to the present invention has the effect of realizing a magnetic levitation and magnetic bearing system that provides an improved accuracy while providing sufficient output for driving a large load.

In addition, in the PWM drive system of the electromagnet actuator according to the present invention, compared to the conventional control method having two output voltage states (Vdc, -Vdc), by controlling to have three output voltage states (Vdc, 0, -Vdc) Therefore, the size of the controlled ripple current can be reduced, and switching losses can be reduced.

1 shows a typical H-bridge switching circuit,
2 shows a control pattern for each switching element in the circuit of FIG. 1,
3 shows the voltage applied to the load in the H-bridge switching circuit controlled according to the prior art,
Figures 4a to 4c schematically show the configuration of the PWM drive system of the electromagnet actuator according to the present invention, respectively
FIG. 5 schematically illustrates an electromagnet driving control circuit and a controller thereof according to an embodiment of the present invention;
Figure 6 shows the switching signal and the asymmetrical output voltage of each switching element in the PWM drive system of the electromagnet actuator according to the present invention, respectively
FIG. 7 illustrates an electromagnet driving control circuit according to a state change of each switching device in FIG. 6.
FIG. 8 schematically illustrates an electromagnet drive control circuit and a control unit according to another embodiment of the present invention,
9 shows the voltage applied to both ends of the coil of the electromagnet actuator for one period (Ts) in the PWM drive system of the electromagnet actuator of the present invention, compared with the conventional
Figure 10 shows the ripple current reduction ratio in the PWM drive system of the electromagnet actuator according to the present invention.

The present invention relates to a PWM drive system of an electromagnet actuator for a magnetic levitation and magnetic bearing system, and provides a magnetic levitation system by effectively implementing a voltage applied to a coil of an electromagnet actuator in three output voltage states (Vdc, 0, -Vdc). Provided is a drive system of an electromagnet actuator suitable for driving a magnetic bearing system.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the drive system of the electromagnet actuator according to the present invention.

When the actuator including the electromagnet is driven, EMI is generated due to noise caused by the PWM applied voltage, and serious distortion is caused to the measured values of the sensor and the like. Therefore, it is necessary to reduce the applied voltage of the system.

Control systems, including magnetic levitation and magnetic bearings, include electromagnet actuators and precision position sensors. At this time, the force generated by the electromagnetic actuator is proportional to the square of the current or the square of the number of coil turns wound.

High inductance actuators that require large forces, such as high load magnetic levitation systems or magnetic bearing systems for high speed rotation, have relatively low force slew rates.

Therefore, in order to compensate for the slew rate of the small force, it is necessary to increase the voltage applied to the electromagnet coil. In this case, EMI and sensor noise are increased.

In order to solve this problem, in the present invention, a coil drive system of an electromagnet actuator having a structure having an existing two voltage state, having a small input voltage and a large slew rate, has an electromagnet having three voltage states. It is configured by changing to the drive system of the actuator.

Therefore, in the present invention, having the hardware of a full bridge PWM converter and a half bridge PWM converter, the output voltage of each of the control period (Ts) Vdc and 0 or -Vdc and 0 or 0 (if Vc = 0) Controlled to have a shape, and through this, three output voltage states (Vdc, 0, -Vdc) are implemented to control the ripple current compared to the method of controlling to have two output voltage states (+ Vdc, -Vdc). We propose a driving system of an electromagnet actuator which can reduce the size of the circuit and reduce the switching loss by reducing the number of switching.

Electromagnets used in magnetic bearings and magnetically levitated systems are always positive, and the voltage has both positive (+) and negative (-) polarities.

In the present invention, a conventional full-bridge PWM converter or a half-bridge PWM converter is used. Also, in the present invention, the output voltage Vo is adjusted to three voltage states Vdc, 0, and -Vdc with respect to the H-bridge PWM converter, and is output according to the duty ratio set according to the coil control voltage during one control period. Through a control scheme for controlling the on duty, a driving system of an electromagnet actuator capable of greatly reducing ripple current is provided.

The configuration of the PWM drive system of the electromagnet actuator according to the present invention used in a position control system using an electromagnetic force such as a magnetic bearing and a magnetic levitation system is shown in FIGS. 4A to 4C, in particular, in the magnetic levitation system in FIG. 4A. A part of the diagram is schematically shown.

As shown in FIG. 4A, in the driving system of the electromagnet actuator according to the present invention, both ends of the coil 2 wound on the electromagnet core 1 installed to maintain a constant distance from the target rail are connected to the electromagnet drive control circuit 3. It is configured to be connected.

In the drive system of the electromagnet actuator according to the preferred embodiment of the present invention, a power supply unit 4 for generating a constant voltage and supplying it to the coil 2 side, and a plurality of switching to control the connection between the power supply unit 4 and the coil 2. An electromagnet drive control circuit 3 comprising an H-bridge switching circuit including elements T1 and T2, wherein the electromagnet drive control circuit 3 controls the coil drive in accordance with the opening and closing control of the switching element. .

The power supply unit 4 and the electromagnet drive control circuit, that is, the single-phase inverter connected between the power supply unit 4 and the electromagnet coil 2 may be illustrated as shown in FIG. 4B.

As shown in FIG. 4B, the power supply unit 4 includes an input power supply 5 for supplying an actually applied voltage and a DC / DC converter (or DC link) for generating a DC voltage Vdc from the power supply 5 ( 6) is configured to include.

The DC / DC converter 6 serves to generate a variable DC voltage (Vdc) from an AC or DC input power source, and may be configured as a buck converter, boost converter, or buck-boost converter structure, and input voltage It receives (Vin) and outputs DC voltage (Vdc).

The single-phase inverter serves to generate a variable coil control current (i _o ) from the generated DC voltage (Vdc), the coil control current (i _o ) flowing to the electromagnet coil 2 receives the DC voltage (Vdc) ), And can be configured as a linear inverter or a PWM inverter using a power amplifier (power amplifier), the PWM inverter has a structure of a full-bridge (Half-Bridge) inverter or a half-bridge (Half-Bridge) inverter May be used.

When a single phase PWM inverter is used, as shown in FIG. 4C, the control voltage Vc applied to the electromagnet actuator coil is continuous by using an L-C filter, an R-C filter, or an L-C-R filter. This reduces the EMI noise generated by the electromagnet actuators so that no noise is generated in the gap measurement sensor placed near the electromagnet actuators.

In this embodiment, a single-phase PWM inverter having a general structure as shown in FIG. 1 may be used as the electromagnet driving control circuit. Referring to FIG. 1, the electromagnet driving control circuit may include a first switching element T1 connected to an anode of a power supply unit and one end of a coil. ) And a second switching device T2 connected to the cathode of the power supply unit and the other end of the coil (or load), and a third switching device T3 connected to one end of the anode and the second switching device T2 of the power supply unit; It may be configured as a full bridge switching circuit including a fourth switching device (T4) connected to the cathode of the power supply unit and one end of the first switching device (T1).

In this case, when the switching elements T3 and T4 are turned off and operated as the diodes D3 and D4 in FIG. 1, the single-phase half-bridge inverter becomes.

Considering that the coil drive current io is a positive value, PWM control of the single-phase half-bridge circuit turns ON the switching element T2 according to the sign of the coil control voltage Vc necessary for driving the coil within the PWM control period Ts, and then-if The switching element T1 is turned off in proportion to the magnitude of the coil control voltage Vc (when Vc ≥ 0) or off in proportion to the magnitude of the coil control voltage Vc (when Vc ≤ 0).

5 schematically illustrates an electromagnet driving control circuit and a controller thereof according to an embodiment of the present invention.

In FIG. 5, a half bridge type switching circuit including two switching elements and two diodes is shown as a preferred example of an electromagnet driving control circuit according to the present invention.

As shown in FIG. 5, the two switching elements include a first switching element T1 connected to an anode of the power supply unit 4 and one end of an electromagnet coil 2, a cathode of the power supply unit 4, and the coil ( And a second switching element T2 connected to the other end of 2).

On the other hand, the control unit 10 for controlling the first and second switching elements (T1, T2) of the electromagnet drive control circuit 3 controls the opening and closing control of the first switching element (T1) and the second switching element (T2). Sends a signal for

The controller 10 is configured to include a duty controller 11 for determining the on duty period at the output and a direction determiner 12 for determining the sign of the output voltage.

Referring to FIG. 5, the configuration of the control unit 10 will be described in detail. According to a preferred embodiment of the present invention, the duty controller 11 and the direction determiner 12 are used to control the coil control voltage Vc from the coil control voltage Vc. The switching element T1 and the second switching element T2 are controlled.

The coil control voltage Vc is a target voltage value input for driving the coil. In the present embodiment, the current value of the load (coil) currently detected by the command current i _ref input into the system, that is, the feedback current ( i _fb ) is fed back to calculate the coil control voltage value Vc through the proportional integration (PI) controller 13.

As shown in Fig. 5, the coil control voltage value Vc can be obtained by performing proportional integral control on the difference (error) between the command current irf and the feedback current ifb, and the command current irf is obtained. ) Uses the output value calculated from the magnetic levitation and position controller 17 of the magnetic bearing system.

The coil control voltage value Vc calculated through the proportional integral controller 13 is input to the direction determiner 12, and the direction switch 12 receives the second switching element T2 according to the sign of the coil control voltage Vc. Control on / off.

In addition, in this embodiment, the coil control voltage value Vc calculated from the proportional integral controller 13 is input to the duty controller 11, and the duty controller 11 according to the magnitude and sign of the coil control voltage Vc. Duty control is performed on the first switching device T1.

The duty controller 11 performs duty control to determine an on duty region according to the magnitude ratio of the coil control voltage Vc and the input voltage Vdc from the power supply unit 4 and the sign of the input voltage Vdc.

In the drive system of the electromagnet actuator according to the present embodiment, the control unit 10 having the above-described configuration controls the opening and closing of the first and second switching elements T1 and T2 within one control period Ts (or each control). Each period Ts) Vdc and 0 or -Vdc and 0 or 0 (if Vc = 0) to form the output voltage to drive control of the electromagnet in three output voltage states (Vdc, 0, -Vdc) Be sure to

The specific structure of the duty controller in this embodiment is as shown in iv) to iv) below.

Iii) Da = Vc / Vdc, Db = 1 when Vc> 0

Ii) when Vc = 0, Da = 0, Db = 1 or Da = 1, Db = 0 (hysteresis region according to previous state)

I) When Vc <0, Da = 1-(-Vc / Vdc), Db = 0

Da is the duty ratio of the first switching element as the output control signal of the duty controller, Db is the duty ratio of the second switching element as the output control signal of the rudder, and as described above, the second switching element is 1 or 0. It is configured to have a duty value, so that it is simply controlled on / off during the control period Ts.

Meanwhile, in FIG. 6, the current control (or driving of the electromagnet) of the coil 2 is performed by the controller 10 including the duty controller 11 and the direction determiner 12 performing the duty control according to the above (i) to (i). Control signal and output voltages of the switching elements T1 and T2 are respectively shown in FIG. 7, and FIG. 7 shows an electromagnet driving control circuit according to the state of each switching element in FIG. have.

As can be seen from the graph shown in FIG. 6, in the electromagnet drive control circuit 3 according to the present embodiment, the magnitude of the output voltage is determined according to the on duty region of the first switching element T1. The sign of the output voltage is determined by opening and closing of the two switching elements T2.

Looking at the specific operation of the electromagnet drive control circuit, in the first cycle and the second cycle of Figure 6 the coil output voltage Vo is controlled in the form of Vdc and 0, and -Vdc and 0, respectively, three states (Vdc, 0, -Vdc) An example controlled by) is shown.

In the first period, the coil control voltage Vc is a positive state, and the on duty period is set according to the duty ratio Da of the first switching element T1 set by i) according to the coil control voltage value Vc. 2 The switching element T2 remains on (Db = 1).

In the first period, the electromagnet driving control circuit in the on duty section of the first switching element T1 may be configured as shown in FIG. 7A according to i), and the load (that is, the coil ), The output voltage (Vo) is applied to Vdc.

In addition, the electromagnet drive control circuit in the off duty section of the first switching element T1 in the first period may be configured as shown in FIG. The output voltage Vo is 0-.

Meanwhile, in the second period, the coil control voltage Vc is in a negative state, and the on duty period is set according to the duty ratio Da of the first switching element T1 set by i) according to the coil control voltage value, and the second switching is performed. The element T2 remains off (Db = 0).

Therefore, the electromagnet driving control circuit in the on-duty section of the first switching element T1 in the second period may be configured as shown in FIG. The output voltage Vo becomes 0+.

In addition, the electromagnet drive control circuit in the off duty section of the first switching element T1 in the second period may be configured as shown in FIG. The output voltage Vo is -Vdc.

Therefore, in the drive system of the electromagnet actuator according to the present invention, the electromagnet drive control circuit as in the present embodiment can be controlled to generate a monopolar output voltage having a constant magnitude and direction in accordance with the coil control voltage value Vc.

On the other hand, the average voltage by the control method of the electromagnet drive control circuit according to the present embodiment is as follows.

Vavg = DVdc, 0 <D <1 (2-a)

Vavg = (D-1) (-Vdc), 0 <D <1 (2-b)

Here, Dn = 1-D can be summarized as follows.

Vavg = -DnVdc, 0 <Dn <1 (2-c)

Therefore, according to the control method of the PWM drive system of the electromagnet actuator proposed from the preferred embodiment of the present invention, the duty ratio D = T _on / set to reduce the ripple current by the PWM control and the disturbance by the ripple current compared to the conventional The control accuracy is improved by the relationship between T _s (T _s is the control period and T _on is the on-duty state) and the output voltage V _o . A detailed description thereof will be described later with reference to FIGS. 9 and 10.

In addition, in the case of the half-bridge type electromagnet drive control circuit configured to include two switching elements, as in the present embodiment, one switching element performs switching to perform a function of direction control with respect to voltage according to on / off control. Since it corresponds to an element, the switching loss of the coil drive system of an electromagnet actuator can be reduced.

In the coil drive system of an electromagnet actuator according to an embodiment of the present invention, a simulation experiment for the case of the control method to have two existing output voltage states and the case of the control method to have three output voltage states according to the present invention As a result, when it is controlled to have three output voltage states according to the present invention, it can be seen that the generated ripple current is significantly reduced compared with the conventional.

Meanwhile, according to another exemplary embodiment of the present invention, the controller 10 may include the proportional controller 14 and the error compensator 15 connected to the input side of the duty controller 11 and the direction determiner 12 as shown in FIG. 8. It can be configured to include.

The proportional controller 14 generates a coil control voltage Vc by proportionally controlling the difference (error) between the command current irf and the feedback current ifb, and the error compensator 15 is generated by proportional control. To compensate for the error (error) to make '0', the input current (iref) is multiplied (multiplied) by the gain of (R + kp) / kp.

That is, in this embodiment, the error compensator 15 multiplies the gain of (R + kp) / kp by the command current (iref) to compensate for the error caused by the proportional control by using the command current (iref) as an input. When the current value is calculated and output, the output current (output of the error compensator) is used as a command current or a control command for proportional control (proportional control of the difference between the output current of the error compensator 15 and the feedback current ifb). Perform Where R is the resistance of the coil and kp is the proportional control gain.

In other words, the proportional controller 14 generates a coil control voltage Vc by proportionally controlling the difference between the current value output from the error compensator 15 and the feedback current ifb fed back from the electromagnetic coil 2. Accordingly, the feedback current ifb follows the command current irf without error.

In the drive system of the electromagnet actuator according to the present invention, since the transfer function of the proportional controller 14 is C (s) = kp and the transfer function of the plant is G (s) = 1 / (Ls + R), closed-loop control The transfer function is T (s) = kp / (Ls + R + kp).

As a result, a steady state error always occurs by kp / (R + kp) times for the step control input. Therefore, the difference (error) between the command current iref and the feedback current ifb may be compensated for through the error compensator 15 as described above.

The system becomes unstable due to the disturbance generated by using the feedback current ifb in proportional control. The error compensator can stabilize the system by compensating for an error with the feedback current ifb.

FIG. 8 shows a proportional integral derivative (PID) controller 16 connected to the input side of such error compensator 15. In an embodiment of the present invention, a precise position controller for making a steady state position error '0' An example of proportional integral derivative (PID) controller 16 may be used.

The proportional integral derivative controller 16 performs proportional integral control on the difference (position error) between the command pore Xref and the pore X to calculate an output value. It is input to the error compensator. Here, the command gap Xref is a control signal input to the magnetic levitation and magnetic bearing system as a command gap between the electromagnet core and the target rail, and X is a gap between the electromagnet and the target rail of the electromagnet actuator.

In the present invention, the proportional integral derivative (PID) controller 16 of the magnetic levitation and magnetic bearing system may constitute an outer control loop, and the error compensator may constitute an inner control loop.

In general, the inner control loop, that is, the error compensator 15 has to respond at least 10 times faster than the proportional integral derivative (PID) controller 16, and this requires a high control voltage, which is required by the power supply unit 4 DC voltage (Vdc). ) Means a voltage rise is required.

Therefore, even if the error compensator 15 does not completely compensate the error between the command current irf and the feedback current ifb with '0' and a part of the steady state error occurs, the proportional integral derivative controller 16 may cause a position error (command). Since the output value (calculated through proportional derivative control) calculated by inputting the value of the gap Xref and the gap X between the electromagnet and the target lane as an input, is input to the error compensator 15 as the command current (iref), As a result, precise position control of the magnetic levitation and magnetic bearing system is possible.

That is, as described above, the position error generated by the difference between the command gap Xref and the air gap X is calculated by calculating the command current inputted to the error compensator by performing proportional derivative control on the difference between the command gap Xref and the air gap X. Accordingly, the position control of the magnetic levitation and magnetic bearing system can be made precisely and without error.

In the embodiment of the present invention as shown in FIG. 8, the process of opening and closing the first and second switching elements T1 and T2 through the direction determiner 12 and the duty controller 11 by receiving the coil control voltage Vc is described above. The same is done as

Through the PWM drive system of the electromagnet actuator of the present invention, it is possible to reduce the ripple current (or peak current) during PWM control, thereby reducing the disturbance force caused by the ripple current, and reducing the instantaneous ripple current so that the required current capacity is reduced. This can be reduced so that the capacity of the power supply can be reduced.

In addition, as shown in Figure 9, the voltage applied to both ends of the coil of the electromagnet actuator for one period (Ts) is conventionally 2Vdc, but in the present invention is Vdc, so that the effect of reducing noise due to voltage can be obtained. The effect on the gap measuring sensor, which is located near the electromagnet actuator, can be reduced, and the effect of reducing the breakdown voltage required for coil insulation can be obtained.

)가 저항에 의한 전압강하(Ri₀)에 비해 훨씬 크므로, PWM 제어시의 짧은 순간 동안 저항은 무시될 수 있다.Typically, electromagnet actuators have a voltage drop due to inductance (

) Is much larger than the voltage drop Ri ₀ by the resistor, so the resistance can be neglected for a short time during PWM control.

Therefore, the voltage drop V ₀ of the electromagnet drive control circuit

가

로 근사화되며,

로 나타낼 수 있다. 이에 k번째 제어 주기에서의 제어 전류 i₀(k)에 대한 수식을 보면, 기존 PWM 방식은

end

Is approximated by

. Therefore, the formula for the control current i ₀ (k) in the k-th control period shows that the conventional PWM method

(3)

(3)

PWM control scheme in this embodiment

(4)

(4)

.

The magnitude of the peak current ripple by PWM control, that is, the magnitude of ripple current Δi ₀ (k),

(5)

(5)

PWM control scheme in this embodiment

(6)

(6)

.

In addition, as shown in FIG. 9, using the fact that the area difference between the X area and the Y area in the conventional method is equal to the area of the Z area in the present method, the duty becomes as shown in Equation (7) below.

(7)

(7)

Substituting this in the above formula (5),

(8)

(8)

.

Comparing the above formulas (8) and (6), it can be seen that the maximum value of the ripple current by the conventional method increases by 10 times or more when the duty is small. In practice, magnetic levitation and magnetic bearing systems have a duty near zero because the rate of change of current is not high due to the high inductance at stable steady state.

The force generated in the electromagnet is proportional to the square of the current flowing in the coil and inversely proportional to the square of the void.

If the current ripple due to PWM switching is Δip and the average current flowing through the electromagnet coil is I ₀ , the output current i ₀ = I ₀ + Δ i _p of the electromagnet coil, and the force f generated by the electromagnet is The following formula holds.

During the PWM switching, the disturbance force generated in the electromagnetic actuator as the PWM frequency can be thought of as a term which is proportional to the term (term) and △ _p ² i which is proportional to △ ip. At this time, as shown in FIG. 10, when the switching ripple current is reduced by 10 times, it can be seen that the disturbance generated in the electromagnet is reduced by 100 times or more, and when the Dopt value is smaller than 0.1, the influence of the PWM disturbance can be considerably reduced. It can be seen that.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. Modified forms are also included within the scope of the present invention.

1: electromagnet core
2: electromagnet coil
3: electromagnet drive control circuit
4: power supply
10:
11: duty controller
12: direction determiner
13: proportional integral controller
14: proportional controller
15: Error compensator
16: proportional integral derivative controller

Claims (5)

An electromagnet drive control circuit connected to both ends of the coil wound on the electromagnet;
And a controller including a duty controller and a direction determiner for controlling opening and closing of the switching element with respect to the electromagnet driving control circuit.
The electromagnet driving control circuit includes an H-bridge switching circuit including a power supply unit, a first switching element connected to an anode of the power supply unit and one end of the coil, and a second switching element connected to a cathode of the power supply unit and the other end of the coil. ,
The second switching element is operation controlled by the direction determiner according to the sign of the coil control voltage, and by the duty controller the first switching element is duty controlled according to the ratio of the coil control voltage and the input voltage from the power supply. , PWM drive system of the electromagnet actuator for the magnetic levitation and magnetic bearing system, characterized in that for performing the drive control of the electromagnet in three output voltage states (Vdc, 0, -Vdc).
The method according to claim 1,
A proportional integral controller for calculating a coil control voltage input to the duty controller and the direction determiner is connected to an input side of the duty controller and the direction determiner, and the proportional integral controller controls the proportional integral with respect to the difference between the command current and the feedback current. A PWM drive system for an electromagnet actuator for magnetic levitation and magnetic bearing systems, the coil control voltage being calculated.
The method according to claim 1,
A proportional controller for calculating a coil control voltage input to the duty controller and the direction determiner is connected to an input side of the duty controller and the direction determiner, and the proportional controller controls the proportion of the difference between the current value output from the error compensator and the feedback current. The PWM drive system of the electromagnet actuator for magnetic levitation and magnetic bearing system, characterized in that for calculating a coil control voltage.
The method of claim 3,
The error compensator is a PWM drive system of an electromagnet actuator for magnetic levitation and magnetic bearing system, characterized in that for outputting the current value calculated by multiplying the received command current (R + kp) / kp gain to the proportional controller side.
The method according to claim 1,
The control unit performs duty control according to the following i), ii) and i) from the coil control voltage Vc through the duty controller for each control period Ts. The electromagnetic actuator for the magnetic levitation and magnetic bearing system. PWM drive system.
Iii) Da = Vc / Vdc, Db = 1 when Vc> 0
Ii) when Vc = 0, Da = 0, Db = 1 or Da = 1, Db = 0
I) When Vc <0, Da = 1-(-Vc / Vdc), Db = 0

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