JPH06197415A - Magnetic levitation slider - Google Patents

Abstract

PURPOSE:To provide a magnetic levitation slider in which a slider can be levitated stably irrespective of the time of no-loading and loading. CONSTITUTION:A feedback voltages from levitation gap sensors 2a, 2b are compared with a reference voltage from a slider levitation position reference voltage generator 31 by a comparator 32, its differential voltage is amplified by a deviation amplifier 33, and a phase delay of a control system is compensated by a phase compensator 34. Gains are varied at the times of loading and no-loading, levitation electromagnets 1a, 1b power amplified by a power amplifier 35 are driven to reduce the gain at the time of no-loading to decrease dynamic stiffness and to enhance the gain at the time of loading to increase the stiffness, thereby improving stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic levitation slider, and more particularly to a magnetic levitation slider which is provided in a clean room such as a semiconductor manufacturing factory and runs on a rail while being magnetically levitated by a levitation electromagnet.

[0002]

2. Description of the Related Art FIG. 3 is a vertical sectional view of a conventional magnetic levitation slider. In FIG. 3, the magnetic levitation slider includes levitation electromagnets 1a and 1b, levitation gap sensors 2a and 2b, a control circuit 4, a power supply battery 5, and the like. This magnetic levitation slider includes a levitation gap sensor 2 provided on the magnetic levitation slider 10 with respect to magnetic rails 3a and 3b.
The displacement of the slider in the flying direction between the rails 3a and 3b is detected by a and 2b, and the detection output is given to the control circuit 4. The control circuit 4 controls the electromagnetic force of the levitation electromagnets 1a and 1b by amplifying the deviation between the displacement and the set value, performing phase compensation, and then amplifying the power.

[0003]

FIG. 4 is a characteristic diagram showing the relationship between dynamic rigidity and frequency in a conventional magnetic levitation slider, and FIG. 5 is a characteristic diagram showing relationship between frequency and gain and phase.

When it is desired to use the magnetic levitation slider shown in FIG. 3 with maximum rigidity, the gain of the control system is increased from the curve a shown in FIG. 5 to the curve b and the crossover frequency is increased. By raising the value, the dynamic rigidity shown by the solid line in FIG. 4 can be increased to the dynamic rigidity shown by the dotted line. With the gain shown by the curve b in FIG. 5, there is still a phase margin, and the control system can be operated stably.

Generally, when setting the gain of the slider control system, it is necessary to select a constant that allows stable flying in the range of no load to the mounted load. However, in order to stably levitate the range from no load to the mounted load state with one fixed gain constant, the wider the range, the more difficult it becomes to select the constant. That is, when the slider is in the no-load state while the slider is flying and the load is loaded, if the gain of the control system with respect to the load is unnecessarily high, some disturbance will occur on the rails 3a and 3b and the slider. When added, the levitation electromagnets 1a and 1b have too strong a levitation force, so that the slider does not stop at a predetermined flying fixed position and repeats overshooting in the flying direction and the landing direction, so that it does not settle at the floating fixed position, and oscillation occurs. The phenomenon of being done occurs.

Therefore, a main object of the present invention is to provide a magnetic levitation slider which can stably levitate irrespective of no load and load.

[0007]

The present invention receives a levitation electromagnet, a gap sensor for measuring a levitation gap between a rail and a levitation electromagnet, and an output of the gap sensor as a feedback input to control the levitation electromagnet. In the magnetic levitation slider including the control means, the control means includes a gain varying means for varying the gain between no load and load.

More preferably, the gain varying means varies the gain of either the phase compensation circuit, the comparison circuit or the deviation amplification circuit.

[0009]

The magnetic levitation slider according to the present invention makes it possible to stabilize the levitation fixed position of the slider under load and to obtain high rigidity when the load is loaded by varying the gain between no load and load.

[0010]

1 is a schematic block diagram of an embodiment of the present invention. In FIG. 1, the control circuit 30 includes a slider flying position reference voltage generation circuit 31, a comparison circuit 32, a deviation amplification circuit 33, a phase compensation circuit 34, and a power amplification circuit 35. The slider flying position reference voltage generating circuit 31 generates a constant reference voltage indicating a reference position in the flying direction of the slider. The comparison circuit 32 is a floating gap sensor 2a,
The feedback voltage from 2b and the reference voltage given from the slider flying position reference voltage generating circuit 31 are compared,
It outputs the voltage difference between the two. The deviation amplification circuit 33 amplifies the difference voltage as the deviation output from the comparison circuit 32 and supplies it to the phase compensation circuit 34. The phase compensation circuit 34 compensates the phase delay of the control system. The power amplification circuit 35 is the phase compensation circuit 3
The output of No. 4 is amplified to an appropriate level required for the operation of the levitation electromagnets 1a and 1b.

FIG. 2 is a specific electric circuit diagram of the variable gain circuit. The variable gain circuit shown in FIG. 2 is built in the phase compensation circuit 34 shown in FIG. That is, the phase compensation circuit 34 includes the operational amplifier 341. The output of the deviation amplification circuit 33 is given to one input terminal (-) of the operational amplifier 341 via the resistor R1. Operational amplifier 341
A feedback resistor R2 is connected between the one input terminal and the output terminal, and a series circuit of a resistor R3 and a normally closed relay contact 55 is connected in parallel to the feedback resistor R2. Operational amplifier 34
The other input terminal (+) of 1 is grounded via a resistor R4.
The output terminal of the operational amplifier 341 is connected to the power amplification circuit 35 shown in FIG.

By configuring the phase compensation circuit 34 as described above, the normally closed contact 55 of the phase compensation circuit 34 is closed when there is no load, and the resistors R2 and R3 are connected in parallel to the operational amplifier 341. It will be inserted in the feedback loop, and the gain will decrease. Further, when a load is mounted, switching is performed with the normally-closed contact 55 of the phase compensation circuit 34 opened, and only the resistor R2 is inserted into the feedback loop in the operational amplifier 341, and the gain becomes large.

Therefore, according to an embodiment of the present invention,
When there is no load, the gain shown in FIG. 5 is lowered as shown by the curve a to reduce the dynamic rigidity as shown by the solid line in FIG. 4, and the gain after mounting the load is as shown by the curve b in FIG. The dynamic rigidity can be increased as shown by the dotted line in FIG.

In the above embodiment, the gain switching circuit is incorporated in the phase compensation circuit 34, but the present invention is not limited to this, and the same effect can be obtained by incorporating it in the comparison circuit 32 or the deviation amplification circuit 33. it can.

Further, in the above-described embodiment, the gain is switched in two steps only when there is no load and when the load is mounted. However, the gain is switched in two or more steps depending on the mounted load amount. Good.

Further, the switching of the normally-closed contact 55 may be performed by a manual switch or by detecting a no-load state and a load state by a sensor.

[0017]

As described above, according to the present invention, the gain can be changed between no load and load, so that the phenomenon that the slider is not fixed at the flying fixed position can be prevented, and the stability is improved. Can be improved.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an embodiment of the present invention.

FIG. 2 is a specific electric circuit diagram of a gain variable circuit.

FIG. 3 is a vertical sectional view of a conventional magnetic levitation slider.

FIG. 4 is a characteristic diagram showing a relationship between dynamic rigidity and frequency in a conventional magnetic levitation slider.

FIG. 5 is a characteristic diagram showing the relationship between frequency and gain and phase.

[Explanation of symbols]

 1a, 1b Floating electromagnet 2a, 2b Floating gap sensor 3a, 3b Rail 4 Control circuit 5 Power supply battery 10 Magnetic levitation slider 30 Control circuit 31 Slider levitation position reference voltage generation circuit 32 Comparison circuit 33 Deviation amplification circuit 34 Phase compensation circuit 35 power amplification circuit 55 normally closed contact 341 operational amplifier R1 to R4 resistance

Claims (4)

[Claims] 1. A levitation electromagnet, a gap sensor for measuring a levitation gap between a rail and the levitation electromagnet, and control means for receiving the output of the gap sensor as a feedback input and controlling the levitation electromagnet. A magnetic levitation slider, comprising: a magnetic levitation slider, wherein the control means includes a gain varying means for varying a gain between no load and a load. 2. The control means includes a phase compensating circuit for compensating for a phase delay of a control system, and the gain varying means varies the gain of the phase compensating circuit. Magnetic levitation slider. 3. The control means includes a comparison circuit for comparing a reference voltage with the output of each of the gap sensors, and the gain changing means changes the gain of the comparison circuit. Item 1. A magnetically levitated slider. 4. The control means includes a deviation amplification circuit that amplifies a deviation between a reference voltage and an output of the gap sensor, and the gain changing means changes the gain of the deviation amplification circuit. Item 1. A magnetically levitated slider.