JPH0691682B2 - Magnetic levitation control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control method for keeping a gap between a linear motor and a scale constant in a levitating body using a linear motor or the like.

(Prior Art) Conventionally, in order to keep the above-mentioned gap constant, the output of the gap sensor is fed back to change the attraction force between the coils. In addition to the magnet, a separate power supply for the moving secondary-side electromagnetic coil (hereinafter abbreviated as coil) is required.

(Problems to be solved by the invention) When the floating body on which the moving secondary coil is installed is completely levitated and travels without contact with a guide rail or the like, quantification is not possible. It is important and laying cables for power supply is inconvenient for complete contactless travel.

Furthermore, since a cable is not required, problems such as battery maintenance and replacement occur even when the battery is placed on the levitation body.

(Means for Solving Problems) In order to solve the above problems, in the present invention, a large number of primary side electromagnetic coils that are repeatedly installed continuously on the ground or on the floor and movable with a constant gap maintained therebetween are provided. The secondary electromagnetic coil provided, and a variable resistor or a transistor chopper connected as a load to the secondary electromagnetic coil in order to change the attractive force between the primary and secondary electromagnetic coils, the primary electromagnetic coil AC current is applied to the secondary side electromagnetic coil to generate a current by mutual induction,
The output of the gap sensor is fed back to the variable resistor or the transistor chopper to control the current of the secondary side electromagnetic coil to maintain a constant gap between the primary and secondary coils.

The transistor chopper circuit controls the induced current generated in the coil flowing through the resistor by the output of the gap sensor. Accelerometers are sometimes used for finer control.

(Operation) The basic principle and operation of the present invention are as follows.

In FIG. 1, if the resistance (R) connected to the secondary coil (B) is infinite, that is, if it is not connected, the flowing current is zero, and both the primary and secondary coils (A).
The attraction force between (B) becomes maximum.

If R = O, that is, if the secondary coil (B) is short-circuited,
The suction power is minimized.

If the resistance value is changed, the current changes and the attractive force also changes.

Instead of physically changing the resistance value, the resistance value is set to the minimum (current maximum) and the secondary coil (B) is set as shown in FIG.
A transistor chopper circuit (C) may be inserted between the resistor and the resistor (R).

If the gap between the coils (A) and (B) becomes narrower and the output of the gap sensor (D) connected to the chopper circuit (C) increases, the duty ratio of the chopper circuit (C) changes and the resistance increases. The current flowing through (R) decreases. As a result, the suction force is reduced and the gap widens.

If the gap becomes too wide, the output of the gap sensor (D) will decrease and the duty ratio of (C) of the chopper circuit will be reversed, increasing the current.

In order to set the gap to a certain value, the duty ratio may be set appropriately in advance. Chopper circuit (C)
It is necessary to appropriately determine how much the chopping frequency is set in consideration of the power supply frequency flowing in the primary coil (A), the vibration and noise during suction, and the like.

(Example) Hereinafter, the example shown in FIG. 3 will be described.

Four secondary coils (1), (2), (3) and (4) are attached to the front, rear, left and right of the upper surface of the carriage (13), and the front ends of the front coils (1) and (3) and the rear coil (2) are attached. ) (4) at the rear end, the gap sensor (5) (7) (6) respectively
(8) is attached.

The secondary coil (1) on the lower surface of the horizontal arm (18) protruding from the upper end of the pillar (17) installed on the floor (16)
The primary side coils (9), (10), (11) and (12) are attached to the locations corresponding to (2), (3) and (4) repeatedly and continuously in the traveling direction.

Thus, when an alternating current is passed through the primary coils (9) to (12), the primary coils (9) to (12) move to the secondary coils (1) to (12).
The iron core (4) to (1a) (2a) (3a) (4a) are sucked.

In the secondary side coils (1) to (4), the chopper circuit (c) in which the resistance (R) can be changed as shown in FIGS. 1 and 2 and described in the explanation of the above operation.
A current control circuit (not shown) for controlling the current of the secondary coil of is connected.

In this current control circuit, the primary coils (9) to (12) are iron cores (1a) (2a) (3a) of the secondary coils (1) to (4).
The suction force for sucking (4a) can be changed, and the lower surfaces of the primary side coils (9) to (12) and the secondary side coil (1) to be detected by the gap sensors (5) to (8).
The gap between the upper ends of the iron cores (1a) to (4a) of (4) is detected, and the amount of the gap is negatively feedback controlled so as to correspond to the control current, so that the gap is always kept constant.

As a result, the primary side coils (9) to (12) located above are
The secondary coils (1) to (4) located below are attracted while maintaining a constant gap, and the carriage (13) floats in a suspended state.

To drive the carriage (13) horizontally, the carriage (13)
A linear motor scale (14) facing the front-rear direction is attached to the center of the upper surface of the, and a linear motor (15) is attached to the lower surface of the horizontal arm (18) so as to face the linear motor scale.

As the carriage (13) travels, the relative positions of the coils on the primary side and the secondary side deviate. Therefore, as described above, the coils (9) to (12) on the primary side cover the entire traveling range. Installed repeatedly, and always the secondary coil (1) to (4)
The iron cores (1a) to (4a) of the secondary side coils (1) to (4) constantly exert an attractive force so that an electric current can be generated.

Since the power for the gap sensor is small enough, it can be obtained from the power generated in the secondary coil through a constant voltage power supply.

(Effects of the Invention) Since a fixed position can be maintained in a state of being completely floating in the air without using a cable or a battery for supplying power to a moving carriage, for example, a transfer system in a clean room When used for, there are no elements that generate dust and maintenance is easy.

[Brief description of drawings]

FIG. 1 and FIG. 2 are circuit diagrams for explaining the principle of the present invention, FIG. 3 is a plan view schematically showing an embodiment of the present invention, and FIG. FIG. 5 is a right side view of the same. (1) (2) (3) (4) Secondary coil (5) (6) (7) (8) Gap sensor (9) (10) (11) (12) Primary coil (13) Truck ( 14) Linear motor scale (15) Linear motor (16) Floor (17) Pillar (18) Horizontal arm

Claims (1)

[Claims] 1. A primary-side electromagnetic coil, which is repeatedly installed on the ground or floor in a continuous manner, a secondary-side electromagnetic coil movably provided with a constant gap therebetween, and suction between the primary and secondary electromagnetic coils. In order to change the force, a variable resistor or a transistor chopper connected as a load to the secondary side electromagnetic coil is provided, and an alternating current is passed through the primary side electromagnetic coil, and a current due to mutual induction is applied to the secondary side electromagnetic coil. Along with
The output of the gap sensor is fed back to the variable resistor or the transistor chopper to control the current of the secondary side electromagnetic coil, thereby maintaining a constant gap between the primary and secondary coils. Characteristic magnetic levitation control method.