JPH0923677A - Dc linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the generation of an overvoltage when narrowing the current value of a converter down to about zero, and to reduce the size of a DC reactor, in a speed control method of a DC linear motor whose thrust is controlled by the control of the energization current of the converter. SOLUTION: An FF inverter 14 for commutating the output current of a converter 11 to the respective phases of an armature coil 15 provided on the ground side responding to the relative position of a mobile body to the armature coil 15 is provided. A speed control system 19 outputs the speed control output responding to the preset speed value of the mobile body and its sensed speed value, and the lower limit of this output is restricted by a limiter 22 to give a current command to a current control system 13 and then to restrict the lower limit of the current of the converter 11. A commutation-phase-angle selecting portion 21A switches, responding to the acceleration and deceleration of the mobile body which are decided from the variational direction of its speed control output, the commutation-phase-angle of the FF converter 14 from the acceleration mode of zero in electrical angle to the deceleration mode of πin electrical angle via the coasting mode of π/2 in electrical angle, and vice versa.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC linear motor, and more particularly to a speed control system for detecting the position of a field magnet (electrical angle) on the moving body side with respect to an armature coil on the ground side to control the speed of the moving body. Regarding

[0002]

2. Description of the Related Art FIG. 6 shows a basic structure of a DC linear motor. The armature coils 1 on the ground side are connected in series one by one to form a first phase coil and a second phase coil. The DC current from the DC constant current converter (converter) 2 is fed to the first phase coil by the flip-flop inverter (FF inverter) 3 in correspondence with the position of the field magnet (electromagnet or permanent magnet) 4 on the moving body side. The current is alternately distributed to the second phase coil and supplied to the ground side armature coil 1 as a rectangular wave-shaped current which is intermittent in one direction.

Since the current of the armature coil 1 on the ground side always flows in one direction, the field magnet 4 can obtain thrust between it and the vertical side of the armature coil 1. Further, if the magnetic field of the field magnet 4 is set such that the magnetic flux of the field magnet 4 is linked to the horizontal side of the armature coil 1 at the same time, the field magnet 4 can obtain the levitation force at the same time as the thrust force.

The DC constant current converter 2 can perform acceleration, coasting, and braking control with the levitation force kept constant by only controlling the switching timing of the current of the armature coil 1 by keeping the output current constant. . Corresponding to this, the load voltage of the DC constant current converter 2 changes within the range of positive and negative, and power supply and regeneration are automatically performed.

The thrust of the DC linear motor is controlled by the commutation phase of the FF inverter 3 while keeping the supply current constant.
In the positional relationship between the armature coil 1 and the field magnet 4 shown in FIG. 7, the current flows through the armature coil at an electrical angle θ, and the electrical angle (π +
When it is cut at θ), the field magnet 4 receives a thrust force in the electrical angle θ to π and a braking force in the electrical angle π to (π + θ).

Therefore, the average thrust generated between θ and (π + θ) can be adjusted by the electrical angle θ. This electrical angle θ is FF
The relationship with the thrust when the commutation phase angle of the inverter has the characteristics shown in FIG. In the figure, F _m represents the maximum thrust determined by the longitudinal side length L of the armature coil, etc. When the commutation phase angle θ is set to zero (electric current flows from 0 to π), the thrust becomes F _m . , Π / 2, the thrust becomes zero, and when π, the thrust becomes −F _m .

From the above, in order to continuously change the thrust, it is necessary to calculate the commutating phase angle from the position detection signal and continuously change it.

FIG. 9 is a block diagram showing a conventional control method. A constant DC current is obtained by the converter 11 and the DC reactor 12. This constant current control is automatically controlled by the current control system 13 which performs proportional integral calculation of the deviation between the set current I _set according to the required levitation force and the detected current.

In the commutation control of the FF inverter 14, the position of the field magnet 16 relative to the armature coil 15 is detected by the position detector 1.
7, the speed detection is obtained by the speed detector 18 from the position change rate, and the speed control system 1 is obtained from the set speed V _set and the detected speed.
9, the deviation is proportionally integrated to obtain a control signal for acceleration or deceleration, and the commutation phase angle calculation unit 20 is used as a thrust command.
Calculates the required commutation phase angle θ from the position signal of the position detector 17.

When the armature coil has multiple phases,
Armature coils of each phase are arranged in series, and the FF inverter is
The current is switched to each phase sequentially according to the position of the field magnet,
Further, the commutation phase angle is calculated and adjusted according to the thrust command of the speed control system.

Further, instead of the FF inverter 3 (14), as shown in FIG.
In some cases, A, or a three-phase bridge type inverter may be used.

[0012]

In the conventional control method,
In order to obtain the levitation force and the thrust force at the same time, the current supplied to the converter 11 is kept constant to secure the levitation force, and the commutation angle of the inverter 14 is controlled to adjust the thrust force.

However, the commutation phase angle θ changes from the end (0 rad) of the armature coil depending on the speed of the moving body, and it is necessary to perform interpolation by acceleration. Further, since θ itself also changes depending on the acceleration / deceleration status of the moving body, there is a problem that the commutation phase angle calculation unit 20 requires considerably complicated calculation processing.

Further, even when the thrust is unnecessary, a constant current is applied to the armature coil to generate the levitation force, resulting in power loss.

As a method for solving these problems, FIG.
The applicant of the present application has already proposed the control method shown in FIG.

The calculation result of the speed control system 19 is the current control system 1.
3 is used as the current command, and the speed is controlled by the current control of the converter 11.

The commutation phase angle selector 21 includes a speed control system 19
Acceleration and deceleration are judged according to the increase or decrease of the speed deviation output of
Based on this determination and the current commutation phase angle, the commutation phase angle of the FF inverter 14 is switched to zero (maximum thrust) or π (maximum deceleration force).

In addition, the current control system 1 is determined from the acceleration and deceleration judgments.
The control phase of 3 is switched (polarity switching), current is supplied from the converter 11 to the armature coil 15 during acceleration, and regeneration is switched from the armature coil 15 to the converter 11 during deceleration.

In this system, the DC linear motor is dedicated to thrust. Accordingly, it is not necessary to keep the current of the converter 11 constant, and the thrust or the braking force is adjusted by controlling the current supplied from the converter 11 with the output of the speed control system 19.

Further, since the thrust can be adjusted by the current of the converter 11, it is not necessary to calculate and adjust the commutation phase angle of the inverter 14, and the commutation phase angle selector 21 instead of the commutation phase angle calculator 20 accelerates. Alternatively, it is a simple calculation that can be performed by selectively switching the mode of the electrical angle 0 at which the maximum thrust is obtained or the electrical angle π at which the maximum braking force is obtained according to deceleration.

Since the thrust is adjusted by the current control,
The loss due to the armature coil resistance can be reduced as compared with the conventional constant current drive system, and the temperature rise of the coil is also reduced.

In the above method, the current of the converter 11 is controlled for speed control, but if the current value is narrowed to near zero for coasting operation that does not require acceleration or deceleration, the current is intermittent due to ripple. DC Reactor 12
If the current is cut off, an overvoltage may occur, which may damage the switching elements of the converter or inverter.

Further, in order to reduce the ripple component and expand the current control range (speed control range) of the converter to near zero, it is necessary to increase the inductance of the DC reactor 12 to suppress the ripple component. This is problematic in terms of cost, size, and loss due to the large size of the DC reactor.

An object of the present invention is to provide a DC linear motor which eliminates the occurrence of overvoltage when the current value of the converter is reduced to near zero in a speed control system in which the thrust is controlled by controlling the current flowing through the converter. It is in.

Another object of the present invention is to provide a DC linear motor which enables downsizing of the DC reactor while expanding the speed control range to zero.

[0026]

In order to solve the above-mentioned problems, the present invention provides a field magnet which is arranged on the ground side and a field magnet which is provided in a moving body and generates thrust by the current of the armature coil. In a DC linear motor including a converter having a current control system capable of controlling a DC current, and an inverter that commutates an output current of the converter to each phase of an armature coil according to the position of the field magnet, An output current of the converter having a speed control system for obtaining a speed control output according to a deviation between the speed setting value of the moving body and a speed detection value, and a limiter for setting the speed control output as a current command and limiting a lower limit value. And a current control system for controlling the commutation phase angle of the inverter in accordance with the acceleration and deceleration determined from the increase / decrease direction of the speed control output in an acceleration mode of electrical angle zero and a deceleration mode of electrical angle π. DC linear motor, characterized in that a commutation phase angle selection unit for switching the switching and the current control system via the coasting mode of the air angle [pi / 2 to regeneration and the supply.

[0027]

In the present invention, the DC linear motor is dedicated to thrust,
In the speed control method that controls the thrust by controlling the energizing current of the converter, by limiting the lower limit value of the current control system with a limiter, the current interruption due to ripple is eliminated when the output current of the converter is narrowed down, and the overvoltage is prevented. To do.

By providing the coasting mode for the operation of the inverter, the speed control range is expanded to zero even for the lower limit value of the output current of the converter.

By limiting the converter current to the lower limit, it is possible to reduce the size of the DC reactor by making it relatively small in inductance.

By switching the mode between acceleration and deceleration through the coasting mode, the torque shock due to the non-linear change of the output current by the limiter is alleviated.

[0031]

1 is a block diagram showing an embodiment of the present invention, in which the same parts as in FIG. 11 are designated by the same reference numerals.

The lower limit value of the calculation result of the speed control system 19 is limited by the limiter 22 which is the input stage of the current control system 13, and is used as the current command of the current control system 13. The lower limit value A ₀ of the limiter 22 is set by the setter 23. The limiter 22 may be configured to limit the output of the current control system 13.

FIG. 2 shows the control characteristics of the limiter 22,
When the current command for acceleration or deceleration output from the speed control system 19 is equal to or lower than the lower limit value A ₀ , the value is limited to the value A ₀ . As a result, the lower limit value of the current of converter 11 is limited to value A ₀ .

Next, the commutation phase angle selection unit 21A determines acceleration and deceleration according to the increase or decrease of the speed control output of the speed control system 19 and switches the operation mode, and the lower limit value from the setter 23. A ₀ is compared with the speed control output, and when the speed control output becomes the lower limit value A ₀ or less, the coasting mode is switched to.

FIG. 3 shows the mode selection characteristics of the commutation phase angle selection section 21A, and shows the acceleration mode (commutation phase angle 0) and deceleration mode (commutation phase angle π) according to the output from the speed control system 19. The FF inverter 14 that has been switched over is controlled, and when the lower limit value A ₀ or less is reached, the coasting mode (commutation phase angle π / 2) is switched over and the thrust is made zero.

Therefore, the control characteristic of this embodiment is shown in FIG.
As shown in, when the speed command output from the speed control system 19 is equal to or lower than the lower limit value A ₀ , the operation is performed in the coasting mode, and the output of the converter 11 maintains a low current output according to the lower limit value A ₀ , and FF The inverter 14 is operated at a commutation phase angle of π / 2 and the thrust becomes zero.

As a result, the minimum current of the converter 11 is limited to the lower limit value A ₀ , the current of the converter 11 is prevented from becoming too small, and the current interruption due to the ripple can be prevented, and the generation of the overvoltage by the DC reactor 12 is eliminated. be able to.

As a result, a relatively large ripple is allowed in the output current of the converter 11, so that it is unnecessary to increase the inductance of the DC reactor 12, which is advantageous in terms of cost, size, and loss. Become.

Further, by providing the coasting mode for the operation of the inverter, the speed control range can be expanded to zero even though the converter is limited to the lower limit value.

FIG. 5 shows a mode selection flowchart of the commutation phase angle selection unit 21A. Commutation phase angle selector 21A
Determines whether or not acceleration is necessary depending on whether the output of the speed control system 19 is acceleration (the current value is higher than the previous value) (step S1), and the speed is decelerated (the current value is lower than the previous value). Whether or not deceleration is necessary is determined based on whether or not there is any (step S2).

When acceleration is required in the determination in step S1, the control mode of whether the current commutation phase angle is 0, π / 2 or π is determined (step S3), and the commutation phase angle 0 on the acceleration side is 0.
Then, the acceleration is continued as it is, and when the commutation phase angle π / 2 becomes coasting, it is changed to the acceleration side (commutation phase angle 0) and switched to acceleration (step S4).

Further, when the commutation phase angle π on the deceleration side is changed to the commutation phase angle π / 2, the coasting mode is once switched (step S5), and the coasting mode is switched from the coasting mode to the acceleration mode when acceleration is required for the next judgment. .

Similarly, when deceleration is required in the determination in step S2, the control mode in which the current commutation phase angle is 0, π / 2, or π is determined (step S6), and the commutation on the deceleration side is performed. At the phase angle π, deceleration is continued as it is, and at the commutation phase angle π / 2 where coasting occurs, the deceleration is switched to the commutation phase angle π (step S7).

When the commutation phase angle is 0 on the acceleration side, the commutation phase angle is changed to π / 2 to switch to deceleration (step S
5).

Therefore, the speed control according to this embodiment is as follows.

(1) When accelerating or traveling at a constant speed, the commutation phase angle is set to 0 rad to obtain the maximum thrust, and the thrust is adjusted by current control.

(2) When it is necessary to decelerate by accelerating too much, the commutation phase angle is set to π / 2 rad, and the operation is temporarily performed in the coasting mode. In this coasting mode, the thrust is reduced to zero to decelerate.

(3) When the deceleration in the coasting mode requires further deceleration, the commutation phase angle is set to πrad and the mode is switched to the deceleration mode in which the maximum braking force is obtained. Adjustment of the braking force at this time is performed by current control.

(4) When it is necessary to accelerate the vehicle by decelerating too much, the commutation phase angle is set to π / 2 rad, and the vehicle is temporarily operated in the coasting mode. In this coasting mode, the thrust is reduced to zero to reduce the braking force. To maintain.

(5) When acceleration is required even when maintaining the current speed in the coasting mode, the commutation phase angle is set to 0 rad and the acceleration mode is switched to the maximum thrust. The thrust is adjusted at this time by current control.

Therefore, the switching from the acceleration mode to the deceleration mode or the switching from the deceleration mode to the acceleration mode is performed via the coasting mode.
Although a non-linear portion occurs in the output current output (motor output) of, the torque shock in the linear motor can be alleviated by passing through the coasting mode.

In the embodiment, the switching between the acceleration mode and the deceleration mode requires deceleration or acceleration control by first narrowing down the converter current to near the lower limit value, and this current control alone requires insufficient acceleration or deceleration. At this time, it is preferable that the commutation phase angle selection unit 21A switch the mode via the coasting mode. As a result, acceleration or deceleration due to mode switching is a change that increases the current from the lower limit value,
It is possible to obtain smooth speed control by eliminating a sudden change in current when switching modes.

Further, it is preferable to limit the switching between the acceleration mode and the deceleration mode depending on whether the actual speed is close to or far from the set speed. In this case, the frequency of switching between acceleration and deceleration can be reduced and the speed control can be made smoother.

[0054]

As described above, according to the present invention, in the speed control system in which the direct current linear motor is dedicated to the thrust and the thrust is controlled by controlling the energizing current of the converter, the lower limit value of the current control system is limited by the limiter. Therefore, when the output current of the converter is reduced, current interruption due to ripple can be eliminated, and overvoltage can be prevented.

Further, by limiting the converter current to the lower limit value and providing the coasting mode for the operation of the inverter, the inductance of the DC reactor is made relatively small while the speed control range is expanded to zero, and its size is reduced. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a current limit characteristic diagram of the converter in the embodiment.

FIG. 3 is a commutation phase angle characteristic diagram of the inverter in the embodiment.

FIG. 4 is an output characteristic diagram of the linear motor in the embodiment.

FIG. 5 is a flowchart of a commutation phase angle selection unit in the embodiment.

FIG. 6 is a basic configuration diagram of a DC linear motor.

FIG. 7 is a diagram showing the relationship between field position and thrust.

FIG. 8 is a diagram showing the relationship between commutation phase angle and thrust.

FIG. 9 is a conventional block diagram.

FIG. 10 shows a modification of the DC linear motor.

FIG. 11 is a block diagram of another conventional example.

[Explanation of symbols]

 1, 15 ... Armature coil 2, 11 ... Converter 3 ... FF inverter 4, 16 ... Field electromagnet 13 ... Current control system 14 ... Inverter 17 ... Position detector 18 ... Speed detector 19 ... Speed control system 21, 21A ... Commutation phase angle selection unit 22 ... Limiter 23 ... Setting device

Claims (1)

[Claims] 1. An armature coil arranged on the ground side, a field magnet provided on a moving body for generating thrust by a current of the armature coil, and a converter having a current control system capable of controlling a direct current, In a DC linear motor equipped with an inverter that commutates the output current of the converter to each phase of the armature coil according to the position of the field magnet, according to the deviation between the speed setting value and the speed detection value of the moving body. A speed control system that obtains a speed control output, a current control system that controls the output current of the converter by using a limiter that limits the lower limit value by using the speed control output as a current command, and from the increasing / decreasing direction of the speed control output. The commutation phase angle of the inverter is switched between an acceleration mode with an electrical angle of zero and a deceleration mode with an electrical angle of π via an coasting mode of an electrical angle of π / 2 according to the acceleration and deceleration to be determined, and DC linear motor, characterized in that a commutation phase angle selection unit for switching the flow control system to the regenerative supply.