JP2988853B2 - DC linear motor - Google Patents

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 (electrical angle) of a field magnet on a moving body with respect to an armature coil on the ground side and controlling the speed of the moving body. About.

[0002]

FIG. 6 shows a basic configuration 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 supplied to a first phase coil by a flip-flop inverter (FF inverter) 3 corresponding to the position of a 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 armature coil 1 on the ground side as a rectangular wave-shaped current intermittent in one direction.

[0003] Since the current of the armature coil 1 on the ground side always flows in one direction, the field magnet 4 can obtain a thrust between the field magnet 4 and the vertical side of the armature coil 1. When 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 a floating force as well as a thrust.

The DC constant current converter 2 can control acceleration, coasting, and braking while maintaining a constant levitation force only by controlling the switching timing of the current of the armature coil 1 by making the output current constant. . In response to this, the load voltage of the DC constant current converter 2 changes within a positive / negative range, and power supply and regeneration are automatically performed.

[0005] The thrust of the DC linear motor is controlled by the commutation phase of the FF inverter 3 while the supply current is kept 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 cut by θ), the field magnet 4 receives a thrust between the electrical angles θ and π and a braking force between the electrical angles π and (π + θ).

Accordingly, the average thrust generated between θ and (π + θ) can be adjusted by the electrical angle θ. This electrical angle θ is calculated as FF
The relationship with the thrust when the commutation phase angle of the inverter is obtained is a characteristic shown in FIG. In the figure, F _m represents a maximum thrust determined by the vertical side length L or the like of the armature coil, when the commutation phase angle θ to zero (electrical angle 0~π up flowing) is thrust becomes F _m thrust becomes zero when the [pi / 2, when the [pi indicates that thrust is -F _m.

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

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

The commutation control of the FF inverter 14 is performed by determining the position of the field magnet 16 with respect to the armature coil 15 by the position detector 1.
7, a 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 _Vset and the detected speed.
9 to obtain a control signal for acceleration or deceleration by performing a proportional-integral operation on the deviation.
Calculates the required commutation phase angle θ from the position signal of the position detector 17.

When the armature coil is multi-phase,
The armature coils of each phase are arranged in series, and the FF inverter is
The current is sequentially switched to each phase 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, in place of the FF inverter 3 (14), as shown in FIG.
A, or a three-phase bridge type inverter.

[0012]

In the conventional control method,
In order to obtain the levitation force and the thrust at the same time, the levitation force is secured by keeping the current flowing through the converter 11 constant, and the thrust is adjusted by controlling the commutation angle of the inverter 14.

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

Further, even when thrust is not required, a constant current is applied to the armature coil to generate a levitation force, and power loss occurs.

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

The calculation result of the speed control system 19 is the current control system 1
In response to the current command of 3, the speed control is performed by the current control of the converter 11.

The commutation phase angle selector 21 is provided with a speed control system 19
Judgment of acceleration and deceleration according to increase / decrease of 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).

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

In this method, a DC linear motor is exclusively used for thrust. Thus, it is not necessary to make 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, the calculation and adjustment of the commutation phase angle of the inverter 14 become unnecessary, and the commutation phase angle selection unit 21 instead of the commutation phase angle calculation unit 20 performs acceleration. Alternatively, it is a simple calculation that only needs to switch 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 the deceleration.

Also, in order to adjust the thrust by 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. However, if the current value is reduced to near zero for coasting operation which does not require acceleration or deceleration, the current is interrupted due to ripple. And the DC reactor 12
When the current is interrupted, an overvoltage is generated, which may damage the switching elements of the converter and the inverter.

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.

It is an object of the present invention to provide a DC linear motor in which a thrust is controlled by controlling a current flowing through a converter and in which no overvoltage is generated when the current value of the converter is reduced to near zero. It is in.

It is another object of the present invention to provide a DC linear motor capable of reducing the size of a DC reactor while expanding the speed control range to zero.

[0026]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an armature coil disposed on the ground side and a field magnet provided on a moving body and generating a thrust by a current of the armature coil. A DC linear motor including a converter having a current control system capable of controlling a DC current, and an inverter that commutates the output current of the converter to each phase of an armature coil according to the position of the field magnet. A speed control system that obtains a speed control output corresponding to a deviation between a speed setting value and a speed detection value of the moving body; and a limiter that uses the speed control output as a current command and limits a lower limit value. A current control system for controlling the speed control output, and a commutation phase angle of the inverter according to acceleration and deceleration determined from the increase / decrease direction of the speed control output. 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]

According to the present invention, the DC linear motor is exclusively used for thrust.
By limiting the lower limit value of the current control system with a limiter in the speed control method that controls thrust by controlling the current flowing through the converter, when the output current of the converter is narrowed, current interruption due to ripple is eliminated and overvoltage generation is prevented. I do.

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

By limiting the current of the converter to the lower limit value, it is possible to make the DC reactor relatively small and small in inductance.

The mode switching between the acceleration and the deceleration is performed through the coasting mode, so that the torque shock due to the nonlinear change of the output current by the limiter is reduced.

[0031]

FIG. 1 is a block diagram showing one embodiment of the present invention, and the same parts as those in FIG. 11 are denoted by the same reference numerals.

The lower limit value of the calculation result of the speed control system 19 is limited by a limiter 22 serving as an input stage of the current control system 13, and the current command is given to the current control system 13. The lower limit value A ₀ of the limiter 22 is set by the setting device 23. Note that 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.
Current command acceleration or deceleration becomes the output from the speed control system 19 is below the lower limit value A ₀ is limited to the value A _0. Accordingly, the lower limit value of the current of the converter 11 is limited to the value A _0.

Next, the commutation phase angle selector 21A determines acceleration and deceleration according to the increase / decrease of the speed control output of the speed control system 19, and switches the operation mode. comparing the a ₀ and a speed control output switches to coasting mode when the speed control output falls below the lower limit value a _0.

FIG. 3 shows the mode selection characteristics of the commutation phase angle selecting section 21A, and the acceleration mode (commutation phase angle 0) and the deceleration mode (commutation phase angle π) according to the output from the speed control system 19. I switched and controls the FF inverter 14 went in, when less than or equal to the lower limit a ₀ is switched to coasting mode (commutation phase angle [pi / 2), to zero thrust.

Therefore, the control characteristics of this embodiment are as shown in FIG.
As shown in the figure, when the speed command output from the speed control system 19 is equal to or lower than the lower limit A ₀ , the operation is performed in the coasting mode, the output of the converter 11 maintains a low current output corresponding to the lower limit A ₀ , 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 converter 11 is limited to lower limit value A _{0, so} that it is possible to prevent the current of converter 11 from becoming too small to cause current interruption due to ripples, and to eliminate the occurrence of overvoltage by DC reactor 12. be able to.

Accordingly, a relatively large amount of ripple is allowed in the output current of converter 11, so that it is not necessary to increase the inductance of DC reactor 12, which is advantageous in terms of cost, size, and loss. Become.

Also, by providing the coasting mode for the operation of the inverter, it is possible to operate the converter with the speed control range expanded to zero even though the converter is limited to the lower limit.

FIG. 5 shows a mode selection flowchart of the commutation phase angle selector 21A. Commutation phase angle selector 21A
Determines whether acceleration is necessary (step S1) based on whether the output of the speed control system 19 is accelerating (the current value increases from the previous value) (step S1), and decelerates (the current value decreases from the previous value). The necessity of deceleration is determined based on whether or not there is (step S2).

When acceleration is required in the determination in step S1, a control mode in which 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 determined.
Then, acceleration is continued as it is, and at the commutation phase angle π / 2 where coasting occurs, the acceleration is changed to the acceleration side (commutation phase angle 0) and switched to acceleration (step S4).

At the commutation phase angle π on the deceleration side, the commutation phase angle is changed to π / 2, and the mode is temporarily switched to coasting (step S5). .

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 without change, and at the commutation phase angle π / 2 where coasting occurs, the commutation phase angle is changed to π to switch to deceleration (step S7).

At the commutation phase angle 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 the present embodiment is as follows.

(1) At the time of acceleration or running at a constant speed, the commutation phase angle is set to 0 rad so that the maximum thrust is generated, and the thrust is adjusted by current control.

(2) If the vehicle must be decelerated due to excessive acceleration, 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 and the vehicle is decelerated.

(3) Even if the deceleration in this 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. The adjustment of the braking force at this time is performed by current control.

(4) When the vehicle must be accelerated after deceleration 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, that is, the current speed. To maintain.

(5) Even when maintaining the current speed in the coasting mode, when acceleration is required, the commutation phase angle is set to 0 rad and the mode is switched to the acceleration mode in which the maximum thrust is achieved. The adjustment of the thrust at this time is performed by current control.

Therefore, switching from the acceleration mode to the deceleration mode or 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), the occurrence of torque shock in the linear motor can be reduced by passing through the coasting mode.

In the embodiment, the switching between the acceleration mode and the deceleration mode is performed by first performing deceleration or acceleration control for narrowing the current of the converter near the lower limit value, and this current control alone requires insufficient acceleration or deceleration. Sometimes, it is preferable that the commutation phase angle selection unit 21A switches 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,
Smooth speed control can be obtained by eliminating a sudden change in current in mode switching.

It is preferable to limit the switching between the acceleration mode and the deceleration mode depending on whether the actual speed is approaching or away from the set speed. In this case, the frequency of switching between acceleration and deceleration can be reduced, and the speed control can be further smoothed.

[0054]

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

Further, by limiting the current of the converter 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, thereby reducing the size. be able to.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing current limiting characteristics of a converter according to an embodiment.

FIG. 3 is a diagram showing a commutation phase angle characteristic of an inverter according to an 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 a relationship between a field position and a thrust.

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

FIG. 9 is a conventional block diagram.

FIG. 10 is a modified example of a 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 magnet 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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-351275 (JP, A) JP-A-56-125990 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02P 5/00 B60L 13/03

Claims (1)

(57) [Claims] 1. A converter having an armature coil disposed on the ground side, a field magnet provided on a moving body and generating a thrust by a current of the armature coil, and a current control system capable of controlling a DC current. A DC linear motor including an inverter that commutates the output current of the converter to each phase of the armature coil in accordance with the position of the field magnet. 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 sets the speed control output as a current command and limits a lower limit, from a direction in which the speed control output increases or decreases. 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 a coasting mode with an electrical angle of π / 2 according to the determined acceleration and deceleration. DC linear motor, characterized in that a commutation phase angle selection unit for switching the flow control system to the regenerative supply.