JPH0213207A - Speed control method for linear induction motor - Google Patents

Abstract

PURPOSE:To enable highly accurate thrust control and positioning by controlling current flowing through a linear induction motor through two-phase current control method based on vector control method. CONSTITUTION:Currents iu-iv flowing through linear induction motors 21a-21c are converted through a converting section 31 into exciting components ides and thrust components iques. A thrust command operating section 32 operates a thrust command iqes* corresponding to the difference between a speed command and a speed feedback value. A q-axis voltage command operating section 36 operates a thrust component voltage corresponding to the difference between the thrust command iques* and the thrust component iques while a d-axis voltage command operating section 37 operates the exciting component voltage corresponding to the difference between the exciting command ides* and the exciting component ides. Then the phase theta is determined based on the sum of a position signal fed from a phase operating section 34 and a slip phase fed from a slip phase operating section 33. Thereafter, three-phase voltage command is produced based on the respective component voltages and the phase theta.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a conveyance system using a slider of a linear induction motor, and particularly to an improvement in a method for controlling the speed of the slider.

(Prior art) Fig. 3 shows a conventional speed control method for a linear induction motor, which is shown in, for example, the literature "Mechanical Design", Vol. 29, No. 12 (10th issue, 1985), pp. In the figure, (1a), (lb), and (1c) are sliders (2
) is a linear induction motor for accelerating and decelerating the motor, and is placed at stopping stations and at locations where acceleration and deceleration are required. (
2) is a slider as the secondary side of a linear induction motor,
It is accelerated and decelerated by linear induction motors (1a), (1b), and (lc) and moves arbitrarily on the orbit.

(3a), (3b), (3c), and (3d) are sensors for detecting the slider, and the speed control of the slider (2) is performed by these sensors (3a), (3b), (3C), and (3d). It is done.

A conventional speed control method for a linear induction motor is configured as described above. For example, when the slider (2) is traveling in the direction of the arrow shown in FIG. 3 and is stopped on the next coil, The slider (2) is detected by the sensor (3a), and the linear induction motor (1a) is excited in the reverse phase (excitation in the opposite direction to the arrow). This causes the slider (2) to decelerate. Next, when the senna (3c) detects the slider (2), the linear induction motor (1a) is excited in the direction of the arrow, and the linear induction motor (1b) is excited in the direction opposite to the arrow. . As a result, the slider (2) stops at the exactly balanced position, and positioning is completed. Note that in some cases, a mechanical auxiliary device may be used to position the slider (2).

[Problem to be solved by the invention]

In the conventional speed control method for linear induction motors as described above, when determining the stop position, both linear induction motors (1a),
Since it is necessary to excite (1b) in opposite directions, two inverters are required, which increases cost.
There were problems such as the impossibility of highly accurate speed control.

The present invention was made to solve these problems, and aims to provide a speed control method for a near induction motor that enables highly accurate thrust control, as well as highly accurate and inexpensive positioning control. ·do.

[Means to solve the problem]

A speed control method for a linear induction motor according to the present invention includes a conversion function that converts a current flowing through the linear induction motor into a two-phase DC amount of an excitation component of the linear induction motor and a thrust component for generating thrust; An excitation component control function that controls the voltage of the excitation component so that it becomes a constant value, and a voltage control function that controls the voltage of the thrust component according to the difference between the thrust command obtained according to the difference between the speed command and the speed feedback value and the above thrust component. and a phase control function that determines the phase based on the position and sliding phase of the slider.
A three-phase voltage command is obtained from the two-phase DC flow rate, and a voltage corresponding to this voltage command is generated by an inverter to perform speed control.

[Effect]

In this invention, the current flowing through the linear induction TA machine is converted into a two-phase DC flow rate of an excitation component and a thrust component, and speed control is performed by a two-phase current control method based on vector control theory. Therefore, highly accurate thrust control and positioning control are possible.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which (2
1a), (21b), and (21c) are linear induction motors, which can be placed in any number and at any position depending on constraints on stop position, acceleration/deceleration, etc. In the case of Fig. 1, three motors are placed in parallel. There is. A sensor (22) is installed at the stop position and is capable of detecting the slider (24) with a resolution of □. (23a), (23b), (
23c), (23d) are sensors for detecting whether or not the slider (24) has entered the linear induction motor (21a), (21b), (21c).
3a), (23b), (23c), and (23d) turn the switches (25a), (25b), and (25c) ON10FF. In other words, any linear induction motor (21a), (21b) can be used depending on the position of the slider (24).
, (21c) are supplied with power. (24) A slider as the secondary side of the beam near bending conductor wJm, its length is
Linear induction motors (21a), (21b), (21c
) is set to be an integral multiple (N times) of the pole pitch. (26) is a controller for controlling this slider (24).

FIG. 2 is a control processing block diagram showing the speed control method according to this embodiment, in which (31) is a current (1u) flowing through the linear induction motors (21a), (21b), and (21c); (iv) and converts it into a two-phase DC flow, the -phase near conduction motor (21a), (
21b) and (21c), the other phases are thrust components for generating thrust, and these two current values (ldss
), (1q a g) are used as feedback values.

(32) is a thrust command calculation unit that calculates a thrust command (Iq@l″) according to the difference between the speed command (vl) and the speed feedback value, (33) is a slip phase calculation unit that calculates the slip phase, and (34) ) is the phase calculation unit that calculates the position of the slider (24), (3S) is the speed detection calculation unit that calculates the speed feedback value, and (36) is the thrust command (lqes″) mentioned above.
The q-axis voltage command calculation unit (37) determines the voltage of the thrust component according to the difference between the current value (lqas) and the current value (lqas).
d@voltage command calculation unit that determines the voltage of the excitation component according to the difference between the current value (tdat) and the current value (tdat), (38)
is the voltage component and phase (θ
) to return the two-phase to three-phase voltage command (VU″
), (vv”), (vw”)
Three-phase voltage command (V u '), (Vv'')
, (Vw'') using an inverter to control the speed of the slider (24).

Next, the speed control method of this embodiment will be explained.

In order to perform speed control with high precision, it is necessary to control the thrust generated by the linear induction motors (21a), (21b), and (21c) with high precision, and in this embodiment, the control shown in FIG. This is done through software processing.

First, linear induction motors (21a), (21b), (2
The currents OU) and (iν) flowing in 1c) are the converter (31)
is detected and converted into a two-phase DC flow of an excitation component and a thrust component. These two current values (fdam), (t,.

, ) are used as feedback values.

Normally, the rEJ magnetic component is controlled to have a constant value (id-g"). In other words, the d-axis A voltage command calculation unit (37) determines the voltage of the excitation component.

In addition, the thrust component is composed of the speed command (V') and the speed detection calculation section (
A thrust command (IQ., ") corresponding to the difference from the speed feedback value from the
The voltage of the thrust component is determined in the q@voltage command calculation unit (38) according to the difference between the q@voltage command calculation unit (38) and the q@voltage command calculation unit (38).

Furthermore, the phase (θ) is the length of the slider (24) on the secondary side, the linear induction motor (21a), (21b),
By setting it to be an integral multiple (N times) of the ball pitch in (21c), it can be calculated using a function of N.

In other words, the length corresponding to the pole pitch is 2π in phase angle.
Then, the phase (θ) is determined by the sum of the position of the slider (24) from the phase calculation unit (34) and the slip phase from the slip phase calculation unit (33).

Next, depending on the voltage component and phase (θ) of each of the above components,
A conversion unit (38) converts the two-phase voltage back to three-phase voltage to create three-phase voltage commands (Vu'), (vv'), and (vw'). Then, these three-phase voltage commands (Vu"), (VV"), (V
The speed of the slider (24) is controlled by generating a voltage in accordance with w'') with an inverter.

Although not specifically explained in the above embodiment, the slider (24) may be supported by magnetic or air support, or may be supported by wheels.

Also, linear induction motors (21a), (21b), (21
The arrangement c) is not limited to the arrangement in the above embodiment, and can be freely changed as necessary.

〔Effect of the invention〕

As explained above, in this invention, the linear induction motor is controlled by two-phase DC current, so the thrust can be controlled with high accuracy, and if a high-resolution position detector is used, the This has the advantage of enabling precise positioning control.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram implementing a speed control method for a linear induction motor according to an embodiment of the present invention, FIG. 2 is a block diagram of its control processing, and FIG. 3 is a diagram showing a conventional speed control method for a linear induction motor. 1 is a system configuration diagram shown in FIG. (21a), (ob), (21C)...Linear induction wJ! l, (24)...Slider, (2B)-
... Controller, (31), (38) ... Conversion section,
(32)...Thrust command calculation unit, (33)...Slip phase calculation unit, (34)...Phase calculation unit, (35)...
・Speed detection calculation section, (36)...Q-axis voltage command calculation section, (37)...D-axis voltage command calculation section. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A conversion function that converts the current flowing through the linear induction motor into a two-phase DC amount of the excitation component of the linear induction motor and the thrust component for generating thrust, and controls the voltage so that the excitation component is a constant value. A thrust component control function that controls the voltage of the thrust component according to the difference between the thrust command and the thrust component determined according to the difference between the speed command and the speed feedback value, and a thrust component control function that controls the voltage of the thrust component according to the difference between the slider position and the It is equipped with a phase control function that determines the phase based on the slip phase, and calculates the three-phase voltage command from the two-phase DC amount based on the voltage components and phases of the excitation component and thrust component, and responds to this voltage command. A speed control method for a linear induction motor, characterized in that the speed is controlled by generating a voltage with an inverter.