JPH0345106A - Magnetic levitation carrier - Google Patents

Abstract

PURPOSE:To perform highly accurate zero power feedback control by arranging first and second gap sensors then calibrating the output from the first gap sensor with reference to the output from the second gap sensor and carrying out feedback control. CONSTITUTION:A complex electromagnet comprises yoke 9 arranged through a predetermined gap on a guide rail 2, electromagnets 11 for electromagnet coils 10, and permanent magnets 12. First gap sensor, i.e. an optical gap sensor 13, for detecting the gap length between the complex electromagnet and the under face of the guide rail 2 and a second gap sensor, i.e. an eddy current gap sensor 14, are provided. Output B from the eddy current gap sensor 14 is divided by the output A from the optical gap sensor 13 then multiplied by the output A from the optical gap sensor 13 for the purpose of calibration, then the calibrated value is inputted to a feedback control system in order to control the gap length. By such arrangement, calibration can be carried out correctly regardless of aging.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a magnetic levitation type conveyance device for conveying small items such as documents and cash, and particularly relates to a gap sensor used when performing levitation control. This invention relates to a magnetic levitation transfer device with improved reliability.

(Prior art) Recently, as part of office automation, slips and documents are transferred between multiple points within a building.

BACKGROUND OF THE INVENTION The use of transport devices to move cash, samples, etc. is widely practiced.

Conveyance devices used for such applications are required to be able to move the conveyed object quickly and quietly. For this reason, in this type of transport device, the transport vehicle is supported on a guide rail in a non-contact manner. Among them, the method of magnetically supporting the transport vehicle without contact is
Excellent in following the guide rail and preventing noise and dust generation.

However, when the transport vehicle is supported by magnetic force.

If all of this magnetic force were to be provided by electromagnets, the electromagnets would have to be energized all the time, resulting in large power consumption.
I have no choice but to do so.

Therefore, we first attempted to reduce power consumption by providing most of the magnetomotive force required by electromagnetic force using permanent magnets. A so-called zero power feedback control method was proposed. (
(Refer to Japanese Unexamined Patent Publication No. 102105/1982) This control method attempts to control the gap between the two so that even if the weight of the transport vehicle changes, the magnetic force of the permanent magnet and the weight of the transport vehicle are always averaged. That is. As a result, magnetic levitation can be achieved with almost no current flowing through the electromagnet, and the capacity of the battery mounted on the transport vehicle can be reduced.

FIG. 3 shows the specific calibration. In the figure, the conveyance path consists of a track frame 1 having an inverted U-shaped cross section, two guide rails 2 made of ferromagnetic material buried at separate positions on the lower surface of the upper wall of the track frame 1, and the track frame 1. The emergency guide rail 3 is installed on the inner surface of the side wall of the track frame 1, and the emergency guide rail 3 has a shape of a square cross section and is attached with the open sides facing each other, and the guide rail 2 is disposed between the two guide rails 2 of the track frame 1, and extends in the longitudinal direction. It is calibrated from the stator 4 of the linear induction motor, which is attached at a predetermined distance. In addition, the conveyance vehicle 5, which is freely movable along the conveyance path, has composite electromagnets 7 arranged on the upper part of the conveyance vehicle frame 6 with a predetermined gap between each of the guide rails 2 described above, and these composite electromagnets 7. A flat base 8 is attached to the guide rail 2, which is fixed thereto and is arranged so as to face the lower surface of the guide rail 2. As shown in FIG. 4, the composite electromagnet 7 consists of two sets of yokes 9 arranged on both sides of the guide rail 2 with a predetermined gap, and electromagnetic coils 10 respectively wound around the yokes 9. It is calibrated from an electromagnet 11 and a permanent magnet 12 placed between two yokes 9, and has a U-shape as a whole, and the two electromagnetic coils 10 are connected so that the magnetic flux φ they form is added to each other. be done.

Note that an optical gap sensor 13 is attached to the composite electromagnet 7 to detect the gap length between the composite electromagnet 7 and the lower surface of the guide rail 2.

In addition, when driving the transport vehicle 5, the stator 4 on the negative side is placed at an appropriate distance on the transport path side.

On the other hand, it is driven by a linear induction motor that serves as the secondary conductor.

(Problems to be Solved by the Invention) When performing zero power feedback control on the transport vehicle 5, the gap between both the guide rail 2 and the transport vehicle 5 must always be detected correctly.

However, the conventional optical gap sensor 13
In this case, a change over time occurs as shown in an example in Fig. 5.As time passes, the light intensity of the light emitting diode decreases, and the output of the optical gap sensor 13 increases even though the gap remains the same, making it appear as if the gap has increased. It becomes a characteristic.

As a result, the levitation control of the transport vehicle is affected, the zero power feedback control is disrupted, battery consumption increases, control becomes impossible, and accidents such as the transport vehicle falling may occur.

For example, an eddy current type sensor is known as a gap sensor that does not change over time. Since this type of sensor measures the gap using electromagnetic phenomena, accurate measurement values cannot be obtained in the vicinity of something that generates a strong and inconsistent magnetic field, such as the composite electromagnet 7. Therefore, when using an eddy current gap sensor, the sensor must be placed as far away from the composite electromagnet as possible on the carrier 5 so as not to be affected by the magnetic field of the composite electromagnet 7.

By the way, what is intended to be strictly controlled by the zero power feedback control is the gap between the composite electromagnet 7 and the guide rail 2, and the eddy current type gap sensor is installed on the relatively large carrier 5 to control the gap between the composite electromagnet 7 and the guide rail 2.
If it is installed at a considerable distance from the control target area (
Since the gap at the position of the composite electromagnet 7 is significantly different from the gap measurement site, the difference between the sensor measurement value and the actual gap at the target site may be affected by the slight tilt or vibration of the transport vehicle 5 that occurs while traveling. It causes irregular deviations. Therefore, it was not possible to employ the eddy current type gap sensor as the zero power feedback @ service.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a magnetic levitation type transfer device that can perform the zero power feedback control with high precision and stability over a long period of time.

[Structure of the Invention] (Means for Solving the Problems) Therefore, the present invention provides a first gap sensor (the influence of the magnetic field is A second gap sensor that measures the gap length between the transport vehicle and the transport path at a position away from the composite electromagnet (such as an optical gap sensor that does not change over time but changes over time); The output of the first gap sensor is calibrated based on the output of the second gap sensor while the transport vehicle is stationary, and the output of the first gap sensor is calibrated based on the output of the second gap sensor. The calibration was performed by performing feedback control of the air gap based on the output of the gap sensor No. 1.

(Function) When the conveyance vehicle is stopped, the output value of the second gap sensor is the control target part (position of the composite electromagnet).
almost equal to the void length at .

By appropriately calibrating the output of the first gap sensor based on the output of the second gap sensor in this state, changes over time in the first gap sensor can be compensated for at any time, and the The zero feedback control is performed while the vehicle is running based on the output of the gap sensor.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram of a control circuit showing an embodiment of the present invention. The difference from the conventional calibration example shown in FIG. 3 is that an eddy current type gap sensor 14 is added at a distance LM away from the influence of the composite electromagnet 7.

Next, the control circuit configuration diagram shown in FIG. 2 will be explained.

The divider 20 outputs the output B of the eddy current gap sensor 14.
is divided by the output A of the optical gap sensor 13, and the division result B/A is input to the AD converter 21. When the control signal S is on, this AD converter 21 sequentially converts the input B/A into digital and outputs the control signal S.
When turned off, the output value at that time is memorized and retained.

The digital output B/A of the AD converter 21 is sent to the multiplier 2
2 and is multiplied by the output A of the optical gap sensor 13, and the multiplication result is input to a feedback control system (not shown) as a calibrated gap measurement value.

The optical gap sensor 13 is calibrated using the AD converter 21.
This is done by updating the data. For example, transport vehicle 5
almost regularly stops at a charging station to charge the battery, but during that stop, the AD converter 2
The control signal S of the optical gap sensor 1 is temporarily turned on, and the output of the stopped eddy current gap sensor 14 is used to control the optical gap sensor 1.
3 and latches the latest correction coefficient B/A in the AD converter 21. Until the next calibration, the correction coefficient B/A is used by the multiplier 22, and zero power feedback control while the vehicle is running is performed according to the output of the calibrated optical gap sensor 13.

[Effects of the Invention] As explained above, according to the present invention, eddy current type gap sensors, etc., which do not change over time but are affected by the composite electromagnet, and optical type sensors, which are not affected by the composite electromagnet but have a large change over time. By combining the features of both systems, such as a gap sensor, it is possible to correct correctly even if there is a change over time, and it is possible to control the magnetically levitated conveyance device stably over a long period of time.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a circuit block diagram showing an embodiment of the present invention, Fig. 3 is a block diagram of a conventional magnetic levitation transfer device, and Fig. 4 is a block diagram showing an embodiment of the present invention. FIG. 5, which is a block diagram showing a composite electromagnet of a conventional magnetically levitated carrier, is an example showing changes over time in an optical gap sensor. 1... Track frame 2... Guide rail 3... Emergency guide rail 4... Linear induction motor stator 5...
Conveyance vehicle 6... Conveyance vehicle frame 7... Composite electromagnet 11... Electromagnet 12... Permanent magnet 13... Optical gap sensor (first gap sensor) 14... Eddy current gap sensor ( 2nd gap sensor) 20...Divider 1...Analog. Digital converter 22...multiplier

Claims (1)

[Claims] A linear induction motor is formed by combining a conveyance path with ferromagnetic guide rails, a primary stator placed at a predetermined interval along the length of this conveyance path, and this stator. A composite electromagnet that generates a magnetic force between the secondary conductor and the guide rail, a control device that adjusts the current flowing through the composite magnet, and the secondary conductor, the composite electromagnet, and the control device. In a magnetically levitated conveyance device comprising a conveyance vehicle that levitates due to the magnetic force and travels along the conveyance path due to the formation of the linear induction motor, a connection between the conveyance vehicle and the conveyance path is provided. a first gap sensor that measures the gap length between the conveyor vehicle and the conveyance path at a position of the composite electromagnet; and a second gap sensor that measures the gap length between the conveyance vehicle and the conveyance path at a position away from the composite electromagnet. a sensor; a means for calibrating the output of the first gap sensor based on the output of the second gap sensor while the conveyance vehicle is stopped; and a means for calibrating the output of the first gap sensor based on the output of the first gap sensor. 1. A magnetic levitation type conveyance device, comprising: means for feedback controlling the air gap by adjusting a current flowing through the composite electromagnet.