KR19990050901A - Magnetic Bearing Controller for Linear Motion Tables - Google Patents

Abstract

The disclosed high precision equipment relates to a magnetic bearing controller for a linear motion table. The present invention is a linear motion table supported by a magnetic bearing, the input signal correction unit for removing the noise of the displacement signal introduced from the sensor of the magnetic bearing, and the signal output from the input signal correction unit through the respective calculator A PID operation unit which executes feedback control to the system by summing, a summation and phase compensation unit which amplifies / adds the signal output from the PID operation unit to secure the support stability of the table, and reduces the phase delay; The low-pass filter and offset adjuster and the low-pass filter and offset adjuster, which prevents the vibration of noise and current generated during the operation of the controller through the signal output from the phase compensator, converts the voltage signal of the low-pass filter and the offset adjuster into a current signal. It is composed of a current amplifier for outputting the control current of the magnetic bearing. Therefore, the computer is prevented from being overloaded by the controller dedicated to the magnetic bearing, and the table is actively acted on external load or disturbance by measuring the exact displacement of the table.

Description

Magnetic Bearing Controller for Linear Motion Tables

The present invention relates to ultra-precision equipment, and more particularly to a magnetic bearing controller for a linear motion table.

Recently, the demand for various ultra-precision machines is increasing due to the rapid development of the semiconductor industry and the optical industry. In particular, the development of linear motion units, which determine the precision of semiconductor equipment, ultra-precision processing equipment, and measuring equipment, is urgently needed, leading to an important time for research and development and securing of basic technology.

In the case of the sensor device inspection equipment currently in use, the transfer table and the microscope must be manually adjusted to inspect the device by the manual method. This results in a decrease in the work efficiency as well as in the accuracy of the inspection.

In addition, the high precision equipment such as semiconductor equipment and optical measuring equipment has a linear motion table as a key element, which determines the accuracy of the entire system. Recently, due to the remarkable development of ultra-precision technology, many researches on linear motion devices with high precision have been conducted, and the demand is also increasing.

Ball bearings and roller bearings are commonly used as support bearings of conventional linear motion systems. However, there are limitations in making the position accuracy extremely accurate due to the up and down swing and frictional forces caused by the elastic deformation and non-uniformity of the ball and roller. have. Therefore, in order to exhibit a high precision of 1 m or less, the fluid bearing that supports the table using lubricating fluid such as oil or air is applied so that the table and the guide surface are in contact with each other. In particular, in the case of tables supported by air bearings, the rigidity is somewhat small, but due to the low viscosity of the air itself, it shows very small frictional loss characteristics and is widely used to obtain higher precision than other methods.

However, in order to use air or oil as a lubricating fluid of a bearing as in the related art, a compressor for raising the fluid to a constant pressure and a filter for removing impurities from the fluid are essential, which is expensive and the configuration of the conveying system is large. It is difficult to maintain and manage, and the noise caused by the rotation of the compressor affects the system, which requires special efforts to improve the feeding accuracy. Once determined, it is a so-called manual system that is difficult to change its characteristics during operation.

In addition, some semiconductor manufacturing equipment or special processing equipment such as ion beam processing requires a vacuum environment, and when a fluid is used as the guide surface lubricant of the linear motion system, there are problems in that the application of the system is difficult in such a special environment.

Therefore, in recent years, in order to solve the above-mentioned shortcomings, a linear motion table equipped with a magnetic bearing incorporating an electromagnet and a sensor is widely used. The table equipped with the magnetic bearing is moved along the guide surface in the state of being injured by the magnetic force, so that it is possible to obtain a precise linear motion with little driving force due to the complete frictionlessness, while such a magnetic bearing has a displacement between the table and the guide. It is very important to accurately measure and precisely control the spacing.

Therefore, the magnetic force of the conventional magnetic bearing is controlled by the computer, the magnitude of the magnetic force of the electromagnet, that is, in the case of the traction-type magnetic bearing is applied a certain amount of traction force when the table is located in the center of the bearing, any of the plurality of electromagnet When the magnetic pole is close to one electromagnet, the magnetic pole reduces the traction and the opposite electromagnet increases the traction to control the displacement of the table, thereby overloading the computer and failing to accurately measure the displacement of the table. .

Accordingly, an object of the present invention devised to solve the conventional problems as described above is to prevent the computer from being overloaded through a controller dedicated to magnetic bearings, and to measure the displacement of the correct table to determine the table against external load or disturbance. It is to provide a magnetic bearing controller for a linear motion table to make this active.

1 is a control block diagram showing a preferred embodiment of a magnetic bearing controller for a linear motion table according to the present invention;

2 is a detailed circuit diagram of a magnetic bearing controller for a linear motion table according to the present invention;

3 is an overall perspective view showing a state of use of the linear motion table according to the present invention,

4 is a perspective view of main parts of the linear motion table according to the present invention.

Explanation of symbols on the main parts of the drawings

40: magnetic bearing 42: sensor

100: input signal correction unit 110: PID operation unit

111: proportional calculator 112: derivative operator

113: integral calculator 120: sum and phase compensation unit

121: summation circuit 122: phase compensation circuit

130: low pass filter and offset control unit 140: current amplifier

150: sensor amplifier Q1 to Q11: operational amplifier

R1 to R32: resistors C1 to C5: capacitors

A magnetic bearing controller for a linear motion table according to the present invention for achieving the above object is, in the linear motion table supported by the magnetic bearing, the input signal for removing the noise of the displacement signal introduced from the sensor of the magnetic bearing Compensation unit, PID operation unit for performing feedback control to the system by summing the signals output from the input signal correction unit, and the output signal from the PID operation unit amplification / summation to improve the stability of the table Low pass filter and offset control to prevent noise and current oscillation occurring in the operation of the controller through the summation and phase compensation unit to secure and reduce the phase delay, and the signal output from the summation and phase compensation unit. Current and voltage signals of the low pass filter and the offset control unit. Converted into is composed of a current amplifier for outputting a control current of the magnetic bearing.

In addition, the sensor amplification unit for adjusting the sensitivity and the offset of the displacement signal introduced from the sensor of the magnetic bearing to output to the input signal correction unit is further provided.

The summation and phase compensator comprises a summation circuit for amplifying / summing the signal output from the PID calculator and a phase compensator for reducing the phase delay thereof.

Therefore, the computer is prevented from being overloaded by the controller dedicated to the magnetic bearing, and the table is actively acted on external load or disturbance by measuring the exact displacement of the table.

Hereinafter, a preferred embodiment of a linear motion table supported by a magnetic bearing according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a control block diagram showing a preferred embodiment of a magnetic bearing controller for a linear motion table according to the present invention, Figure 2 is a detailed circuit diagram of a magnetic bearing controller for a linear motion table according to the present invention.

1 and 2, the magnetic bearing controller for the linear motion table includes an input signal corrector 100 and a PID operator 110 using a plurality of operational amplifiers (OP-Amps), condensers (C), resistors (R), and the like. ), A summation and phase compensator 120, a low pass filter and an offset adjuster 130, a current amplifier 140, and a sensor amplifier 150. The sensor amplification unit 150 adjusts the sensor signals detected from the sensors 42 embedded in the table 30 to have a desired sensitivity and offset, where the displacement signals of the sensors 42 are applied to all the sensors 42. It is adjusted to have the same sensitivity with respect to.

The input signal corrector 100 attenuates the noise component of the displacement signal input from the sensor amplifier 150, and the PID operator 110 controls the proportional, derivative, and integral operators 111, 112, and 113. Each operation is performed on the same pressure signal, and then the sum is performed according to the gain level of each given operator to perform the feedback control of the system by mixing the unique feedback control characteristics of each operator.

The summation and phase compensator 120 inputs a signal passed through the PID operation unit 110 and sums it using the summation circuit 121 to secure the stability of the table at low frequency. The signal passing through the summation circuit 121 has a phase delay, and thus, the phase delayed signal is compensated for using the compensation circuit 122.

The low pass filter and the offset adjusting unit 130 remove high frequency noise, and in this process, the signal voltage is offset to fit the operating region of the actuator and the currents of the coils facing each other for one control axis. It is sent to the amplifier 140. The current amplifier 140 is used as a control current to control the magnetic bearing 40 by converting a voltage signal into a current signal through each of the first current amplifier 141 and the second current amplifier 142. .

3 is an overall perspective view showing a state of use of the linear motion table according to the present invention, Figure 4 is a perspective view of the main portion of the linear motion table according to the present invention.

According to FIG. 3, the linear guide 11 is formed at both sides of the upper end of the bed 10. The Y-axis table 20 is mounted on the bed 10 and supported by the linear guide 11 and driven by the linear motor 12 and the linear scale 13 provided under the bed 10 to be transferred in the Y-axis direction. The X-axis table 30 uses the Y-axis table 20 as a bed, is supported by a plurality of magnetic bearings 40, and driven by the linear motor 21 and the linear scale 22 to be transferred in the X-axis direction. Preferably, the linear motors 12 and 21 apply a brushless DC (BLDC) motor.

In addition, the linear motor drive servo amplifier 51 for controlling the drive of the linear motor 12, 21 and the magnetic bearing controller 50 and the system according to the present invention for controlling the drive of the magnetic bearing 40 A computer (not shown) for performing overall control is provided. The servo amplifier 51 for driving the linear motors 12 and 21 is composed of a BLDC servo amplifier and a power supply device for the servo amplifier. The servo amplifier 51 receives signals from the Hall sensors of the linear motors 12 and 21 to locate the permanent magnets and serves to flow three-phase currents through the heads of the linear motors 12 and 21. .

According to FIG. 4, the Y-axis table 20 fixes the guide plate 23 to the upper and side surfaces of both sides thereof with bolts 24. Laminated guides 25 are provided on the top and bottom and sidewalls of the guide plate 23, respectively. In addition, a linear scale head and a linear motor head (not shown) are provided below the rectangular X-axis table 30. The magnetic bearings 40 are fixed to the four corners of the X-axis table 30. The plurality of magnetic bearings 40 are composed of an electromagnet 41 for generating a magnetic force against the laminated guide 25 of the Y-axis table 20 and a displacement sensor 42 for measuring the displacement thereof. Therefore, the X-axis table 30 is conveyed with the laminated guide 25 inside the vertical and horizontal guide plates 23 on the Y-axis table 20 as the guide surface, and the driving thereof is located at the center. Is made by a linear motor 21 and the conveying position is measured by a linear scale 22.

Referring to the operation of the present invention configured in this way in more detail as follows.

The linear motion table according to the present invention is composed of a Y axis supported by the linear guide 11 and an X axis supported by the magnetic bearing 40, both of which are driven by the linear motors 12 and 21. The linear motors 12 and 21 receive the position signals by the linear scales 13 and 22 and control them using a DSP board of a computer (not shown). According to FIG. 3, the Y-axis table 20 is driven by the linear motor 12 and the linear scale 13 provided below the Y-axis direction while being supported by the linear guides 11 on both sides of the bed 10. Is transferred to. Here, the BLDC servo amplifier 51 controls the linear motor 12 under the control of a computer (not shown) in order to drive the linear motor 12, but the signal from the Hall sensor of the linear motor 12 It receives the position of the permanent magnet and transfers the three-phase current to the linear motor head (not shown) to transfer the Y-axis table 20.

4, the X-axis table 30 is inside the guide plate 23 in the vertical and horizontal directions on the Y-axis table 20 by respective magnetic bearings 40 fixed to the four corners thereof. In the state of magnetic levitation at a constant distance between the laminated guide 25 of the conveyed as a guide surface, the drive is made by a linear motor 21 located in the center and the conveying position is on the linear scale 22 Is measured.

The magnetic bearing 40 is controlled by the magnetic bearing controller 50, by using the magnetic force generated by the current flowing through the coil of the electromagnet 41 built therein, without the physical contact X-axis table ( 30), and by measuring the displacement through the output signal of the displacement sensor 42 embedded with the electromagnet 41 to control the amount of current flowing through the coil of the electromagnet 41 to maintain a constant distance at all times It is.

In the linear motion table driven as described above, the magnetic bearing controller 50 of the present invention for controlling the magnetic bearing 40 will be described with reference to FIG. 2. First, the magnetic bearing 40 of the table 30 will be described. Sensor signals sensed from the built-in sensors 42 are adjusted to have the desired sensitivity and offset via the sensor amplifier 150. The displacement signal is adjusted to have the same sensitivity for all the sensors 42 and then passes through the PID operation unit 110 via the input signal correction unit 100.

In the input signal corrector 100, the displacement signal of the displacement sensor 42 for detecting the displacement of the table 30 is a voltage divider having a plurality of resistors R1 and R2 so as to have a ratio of 1/11. Pass through the inverting amplifier (Q1). The displacement signal introduced from the displacement sensor 42 includes noise that is not related to the displacement of the table 30, such as power supply noise and ground noise. This noise is often at the same level as the displacement signal. Therefore, in order to minimize these effects, the displacement signals are reduced to a ratio of 1/11 using the resistors R1 and R2 as control criteria.

The displacement sensor 42 has a reference gap between the tables 30, and thus the output voltage of the sensor 42 at the reference position is present, so that the input offset correction unit (0) is used to adjust the initial offset voltage to 0 V. 100) an offset adjustment device shall be attached. As shown in FIG. 2, first, the voltage V1, which is an input signal, passes through a voltage divider consisting of resistors R1 and R2. Here, the input voltage is defined by the following equation.

In addition, by using the variable resistor R3 for offset adjustment, V1 is adjusted to be 0V when the table 30 is at the reference position. The sensitivity of the displacement sensor 42 is different for each sensor, and in order to make the same, the correction of the signal is designed so that the amplification ratio can be adjusted in the sensor amplifier 150.

The PID operation unit 110 uses a three-mode parallel analog PID operator in which proportional, derivative, and integration operators 111, 112, and 113 are connected in parallel to sum their gains. Each operator performs each operation on the same pressure signal and sums them according to the gain level of each given operator to perform feedback control for the system by mixing the unique feedback control characteristics of each operator. In the dynamic control system, the response characteristics of the gain change in either proportional or derivative operation change, and there is an optimum value of each gain that can keep the system most stable from the change in the system response characteristics. Done. Therefore, the PID operator 110 must be designed to change the respective gains. The gain is adjusted using a 10turn potentiometer.

The proportional calculator 111 is an inverting amplifier having a gain of 10 times and a proportional gain is determined by the variable resistor of R9 as shown in FIG. 2.

The operating region of the integral amplifier Q3 of the integration operator 112 is a gain limit frequency. f _a And gain frequency f _b Determined by The output gain of this integrator 112 is adjusted by R9. The gain limit frequency f _a And gain frequency f _b Is defined by each equation below.

In this case, the output gain of the integration operator 112 is set to 0 to improve the stability of the table 30.

In addition, the operating region of the differential amplifier Q4 of the differential calculator 113 has a gain frequency of 0 dB. f _a And gain limit frequency f _b Is determined by Equations 4 and 5 below, and the output gain of the derivative operator 113 is adjusted by R9.

here, f _b Of f _a = 10, f _b = 100 ms.

The signal passing through the PID operation unit 110 is input to the summation and phase compensation unit 120, and the summation and phase compensation unit 120 has a phase delay through the summation circuit 121. 122) to compensate.

That is, the derivative gain 112 of the PID operator 110 changes the output gain according to the frequency characteristic of the input signal. The derivative operation has the characteristic that the output gain increases with increasing frequency of the input signal. The differential calculator 112 has a characteristic that its role gradually increases as it becomes a high frequency, while at the low frequency, the differential gain is too small, so that the table is difficult to stably support. Therefore, the summation and phase compensator 120 performs the summation operation in a state in which the result of the derivative operator 112 is amplified 10 times than the result of the proportional amplification operation to secure the support stability of the table 30 at low frequency. . 2 shows a summing circuit 121 for summing the PID operation results at different ratios.

Each output value from the PID operation unit 110 V _p , V _I , V _D Is summed as in Equation 6 through the summation circuit 121.

The output summed up through the summing circuit 121 is input to the phase compensation circuit 122 shown in FIG. 2 to reduce the phase delay of the system. In this case, the phase compensation angle should be selected in consideration of the phase delay angle in the summing circuit 121 and increases the stability of the system.

The signal passing through the summation and phase compensator 120 is then sent to the low pass filter and the offset adjuster 130 to remove high frequency noise. In this process, the signal voltage is offset to match the actuator's operating area.

The low pass filter prevents undesirable noise and current generated during the operation of the sensor and the controller and vibration of the current between the electromagnet coil. Each impedance by 2 Z ₁ = R ₂₅ , Equation 7 below holds.

Therefore, the equation (7) V _E In summary, the following Equation 8 can be obtained.

Here, the offset voltage is set so that the output current when the table 30 touches the magnetic pole through the variable resistor (R27) to be zero, so that the table 30 is guided by a sudden vibration or the like during the operation of the linear motion table. ) To prevent it from sticking.

The signal voltage whose offset is adjusted by the low pass filter and the offset adjuster 130 is sent to the current amplifier 140 of the coil facing each other with respect to one control shaft.

The current amplifier 140 is composed of a first amplifier 141 constituting the inverting unit, a second amplifier 142 constituting the follower as shown, the current amplification ratio of the voltage is designed to 1 A / V It was. Accordingly, the voltage signal is converted into a current signal by the current amplifier 140 to be used as a control current of the magnetic bearing 40.

As described above, according to the magnetic bearing controller for the linear motion table according to the present invention, the table is active against external loads or disturbances by preventing the computer from being overloaded and measuring the exact displacement of the table through the controller dedicated to the magnetic bearing. It is effective to act as.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

Claims (3)

A linear motion table supported by a magnetic bearing, comprising: an input signal correction unit for removing noise of a displacement signal introduced from a sensor of the magnetic bearing; A PID calculator configured to perform feedback control to the system by summing signals output from the input signal corrector through respective calculators; An adder and a phase compensator for amplifying / summing the signals outputted from the PID operator to ensure the stability of the table and reducing the phase delay thereof; A low pass filter and an offset adjuster which prevents vibration of noise and current generated during a calculation process of a controller through a signal output from the sum and phase compensator; And And a current amplifier converting the voltage signal of the low pass filter and the offset adjusting unit into a current signal to output a control current of the magnetic bearing. The magnetic bearing controller of claim 1, further comprising a sensor amplifier configured to adjust the sensitivity and the offset of the displacement signal introduced from the sensor of the magnetic bearing to output the input signal corrector. The magnetic bearing controller of claim 1, wherein the summing and phase compensating unit comprises a summing circuit for amplifying / summing the signal output from the PID calculating unit and a phase compensating circuit for reducing the phase delay thereof. .