JPH0947061A - Controller and control method for linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a thrust proportional to a thrust command by superposing a signal for compensating the variation in the thrust of a linear motor on the thrust command signal of linear motor and controlling the thrust of linear motor using the superposed signal thereby compensating for the effect of lowered thrust or reverse thrust. SOLUTION: The difference between a speed command signal 12 and the signal from a speed detector 11 is inputted to a speed controller 13. In response to the differential signal, the speed controller 13 produces an output signal for commanding the thrust of a linear motor. On the other hand, a signal corresponding to thrust reduction/reverse thrust of motor is operated by a compensator 14 which delivers an output signal to an adder 15. The adder 15 adds the outputs from speed controller 13 and compensator 14 and delivers an output signal to a current controller 16. An inverter 2 executes PWM control for controlling the output voltage and frequency thus controlling the current flowing through the linear motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in a linear motor control method and apparatus.

[0002]

2. Description of the Related Art Since a linear motor can directly control a driving unit, it has a feature that the entire system can be downsized.
For example, it is applied to a rope type linear motor elevator as disclosed in Japanese Patent Laid-Open No. 1-271381.
An induction machine type linear motor is applied to this, and the equivalent circuit is the same as that of the rotary type. Therefore, vector control can be applied and thrust can be controlled.

[0003]

However, unlike a normal rotary motor, a linear motor has an end portion of a motor, so that an end effect is produced. The thrust is reduced by the end effect, and there is a problem that the same thrust as the rotary type cannot be produced. In particular, when the slip is zero, there is a problem that the reverse thrust (in the case of a rotary motor, the thrust is zero when the slip is zero) occurs. Conventionally, there is a problem that thrust proportional to the thrust command is not output because control is performed without consideration of thrust reduction and reverse thrust. Therefore, there is a possibility that the accuracy of the thrust control may decrease, the speed control response may deteriorate, and pulsation of the speed and the thrust may occur. Further, when this is applied to a linear motor elevator, there is a risk that vibration of a car may occur or a landing error may occur.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a control method capable of compensating for the influence of thrust reduction and reverse thrust and producing thrust proportional to the thrust command. is there.

[0005]

Since the output of the speed control device is a signal proportional to thrust, a signal for compensating thrust change or reverse thrust is superimposed on the signal. The thrust of the motor is controlled by the signal after superposition.

[0006]

By doing so, the thrust of the linear motor is controlled so as to be proportional to the thrust command, and the thrust change and the reverse thrust originally generated from the linear motor are compensated. As a result, the thrust is generated in proportion to the thrust command, so that the thrust control accuracy does not deteriorate and the speed control response does not deteriorate under any operating condition. Therefore, the pulsation of speed and thrust can be eliminated.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.

In FIG. 1, the linear motor is an induction type,
There is a primary side 1 and a secondary side (not shown) around which the armature winding is wound. Electric power is supplied to the primary side 1 by an inverter 2. The primary side 1 of the linear motor is mounted on a driver (not shown), and its speed is detected by a speed detector 11 attached to the driver or the primary side 1 of the linear motor. For example, when applied to a rope type linear motor / elevator, the primary side is attached to a counterweight,
The secondary side is installed in the hoistway. The traveling speed of the linear motor is determined by the speed detector 11 attached to the counterweight.
Is detected by measuring the relative motion with the guide rail.

The deviation between the signal of the speed command 12 and the signal of the speed detector 11 is input to the speed control device 13. The speed control device 13 works according to this deviation, and its output signal becomes a signal instructing the thrust of the linear motor. On the other hand, a signal corresponding to the thrust reduction / reverse thrust of the motor is calculated by the compensator 14. The output signal of the compensator 14 is input to the adder 15. The adder 15 adds the outputs of the speed controller 13 and the compensator 14, and the output signal is the current controller 1
6 is input. The output of the current control device 16 is input to the inverter 2. In the inverter 2, PWM control is executed and the output voltage and output frequency of the inverter 2 are controlled. In this way, the current flowing through the linear motor is controlled. The compensating signal from the compensating device 14 may be given in advance as a pattern of the motor operating speed or the primary frequency, thrust command, etc. by analyzing the motor.

With the above arrangement, the compensator 14 compensates for the thrust reduction and the reverse thrust, so that the motor thrust proportional to the thrust command can be obtained. As a result, the thrust is generated in proportion to the thrust command, so that the thrust control accuracy does not deteriorate and the speed control response does not deteriorate under any operating condition. Therefore, the pulsation of speed and thrust can be eliminated.

FIG. 2 shows another embodiment in which the embodiment of FIG. 1 is simplified. Since it is an induction type linear motor, vector control can be applied. The compensator 141 is the compensator 1 of FIG.
4, adder 151 functions as adder 15 of FIG. The output of the speed control device 13 is a signal that commands thrust. A signal from the compensator 141 is added to this signal by an adder 15
Add 1 The output signal of the adder 151 is the thrust current component command signal I _{q *} of the primary current of the linear motor. The thrust current component command signal I _{q *} of the output signal of the adder 151 is input to the slip frequency setting device 161. The slip frequency setting device 161 performs the calculation of equation (1) and outputs a signal instructing the slip frequency f _s .

Slip frequency f _s = k · I _{q *} (1) The slip frequency f _s signal from the slip frequency setting device 161 and the output signal from the speed detector 11 are input to the adder 162. In the adder 162, the slip frequency f _s
The signal and the rotation frequency signal are added, and the output of the adding device 162 becomes a signal that commands the primary frequency f ₁ . Thus
A vector current control device that performs vector operation on the thrust current component command signal I _{q *} of the output signal of the adder 151, the exciting current component command signal I _{d *} (setter 163), and the primary frequency f ₁ of the output of the adder 162. 164 is input. The vector current control device 164 performs the same vector operation as that of a normal rotating machine to perform current control according to I _{d *} , I _{q *} , and f ₁ . Since this configuration and calculation are well known, description thereof will be omitted.

The input of the compensator 141 is a signal for instructing the primary frequency f ₁ and the thrust compensation signal T _c is the primary frequency f ₁
Give in proportion to. FIG. 3 is a diagram showing this principle, showing the thrust characteristics of the motor. This figure shows the characteristics when the slip s = 0, and it can be seen from the figure that thrust is generated even when s = 0 except f ₁ = 0. For example, at a certain f ₁ , a negative thrust is generated. This is called reverse thrust here. In the case of a rotary motor, the thrust (torque) is essentially zero when s = 0, but in the case of a linear motor, the thrust does not become zero due to the end effect. As a result of analysis, it was found that the reverse thrust characteristic is proportional to the primary frequency as shown in FIG. Further, due to the reverse thrust, the thrust except when s = 0 also decreases as a whole. According to this principle, the compensator 141 of FIG.
A signal T _c for compensating the reverse thrust is output in proportion to the next frequency f ₁ . Although the input of the compensating device 141 is the primary frequency here, it goes without saying that any other signal can be used as a substitute for the signal corresponding to the primary frequency. For example, a speed command signal or a speed detection signal can be used. With the simple structure as described above, when the reverse thrust is compensated, the motor thrust seen from the speed control device 13 becomes proportional to the output of the speed control device 13, that is, the thrust command signal, as in the case of the rotating machine. As a result, the thrust control accuracy does not deteriorate and the speed control response does not deteriorate under any operating condition. Therefore, the pulsation of speed and thrust can be eliminated.

FIG. 4 shows still another embodiment.

FIG. 5 is a diagram for explaining this control principle.
As a result of analyzing the characteristics of the linear motor, it was found that the equivalent circuit of the linear motor is simply represented as shown in FIG. 7B and the thrust characteristic is simply represented as shown in FIG. The equivalent circuit is almost the same as an ordinary rotating machine, except that the secondary circuit includes not only the slip s but also a slip constant s ₀ . Here, s ₀ is a substantially constant value that is not significantly affected by the primary frequency. From the characteristics shown in the figure, it can be seen that the decrease in thrust and the reverse thrust occur because the frequency shifts by s ₀ due to the end effect. That is, if the slip reduction s ₀ is compensated, it can be handled like an ordinary rotating machine.

FIG. 4 is a specific example of a control block diagram for compensating for the end effect based on this principle. Since it is an induction type linear motor, it is controlled by applying vector control. 4, the slip compensator 142 functions as the compensator 14 of FIG. 1, and the adder 152 functions as the adder 15 of FIG. The output of the speed control device 13 is a signal instructing thrust, and is a thrust current component command signal I _{q *} of the primary current. The slip frequency setting device 161 sets the slip frequency f _s0 by the calculation of the equation (1) based on the thrust current component command signal I _{q *} . On the other hand, the slip compensation device 142 calculates a signal f _sc (referred to as a compensation slip frequency) for correcting the above-mentioned slip frequency. The outputs of the slip frequency setting device 161 and the slip compensation device 142 are input to the adding device 152,
The sum of both signals is taken. The output of the adder 152 is the slip frequency f _s actually given to the motor. Further, the slip frequency f _s of the output of the adder 152 is added to the adder 162.
And the output signal from the speed detector 11 is input. As a result, as in the previous example, the output of the adder 162 becomes a signal instructing the primary frequency f ₁ .

In this way, the vector current control in which the thrust current component command signal I _{q *} , the exciting current component command signal I _{d *} of the output signal of the speed control device 13 and the primary frequency f ₁ of the output of the adder 162 perform vector calculation Input to the device 164. Vector current controller 164 is the same as the previous example.

Here, the slip constant s ₀ and the compensation slip frequency f _sc are determined by the following equation (2), and the slip compensation device 142
Performs this calculation.

Compensation slip frequency f _sc = s ₀ · f ₁ (2) As described above, when current is supplied to the primary side 1 of the linear motor by controlling so as to compensate the slip constant s ₀ , The motor thrust seen from the control device 13 becomes proportional to the output of the speed control device 13 as in the case of the rotating machine.

In the above description, the case where the exciting current is substantially constant is shown, but the exciting current may be variable. At this time, the compensation value is a value that also takes the exciting current into consideration. For example, since the thrust is proportional to the exciting current, the compensator 1 is used in the embodiment of FIG.
The input to 41 can be a signal proportional to the product of the primary frequency signal and the exciting current signal. Further, in the embodiment of FIG. 4, the input to the slip compensation device 142 can be a signal proportional to the product of the reciprocal of the primary frequency signal and the exciting current signal. Further, in order to accurately perform thrust compensation, the compensation signal may be given to the thrust current component command signal and the slip frequency signal independently, by performing a characteristic analysis of the motor with high precision.

When this embodiment is applied to a linear motor / elevator, a thrust proportional to the thrust command can be generated, so that the control performance is improved, and vibration and landing error are reduced. Further, there is an effect that starting compensation is facilitated and can be performed with high accuracy, and riding comfort is improved.

[0023]

As described above, according to the present invention, the thrust control accuracy does not deteriorate and the speed control response does not deteriorate regardless of the operating condition. Therefore, the pulsation of speed and thrust can be eliminated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the present invention.

FIG. 3 is an explanatory view of the principle of FIG.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

5 is an explanatory view of the principle of FIG.

[Explanation of symbols]

1 ... Linear motor primary side, 2 ... Inverter, 13 ... Speed control device, 14 ... Compensation device, 15 ... Addition device, 16 ... Current control device.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noboru Arahori 1070 Ma, Hitachinaka City, Ibaraki Prefecture Inside the Mito Plant of Hitachi, Ltd.

Claims (12)

[Claims] 1. In a linear motor driven by a variable voltage and variable frequency power converter, a signal for compensating a change in thrust of the linear motor is superimposed on a thrust command signal of the linear motor, and the superimposed signal is used. A method of controlling a linear motor, characterized in that the thrust of the linear motor is controlled. 2. The method of controlling a linear motor according to claim 1, wherein the change in thrust is due to the end effect of the motor. 3. A linear motor control method according to claim 1 or 2, wherein a signal for compensating for a change in thrust is given from a motor speed signal, a primary frequency signal and a thrust command signal. 4. The linear motor according to claim 1 or 2, wherein the linear motor is an induction type, vector control is applied to the linear motor, and a signal for compensating a thrust change is superimposed on the thrust command signal. Motor control method. 5. The compensation signal to be superposed according to claim 4,
A method of controlling a linear motor, which is proportional to a primary frequency or a signal corresponding thereto. 6. The compensation signal to be superposed according to claim 4,
A method of controlling a linear motor, wherein the linear frequency is made substantially proportional to the product of a signal corresponding to the exciting current and a signal corresponding to the primary frequency. 7. The method of controlling a linear motor according to claim 1 or 2, wherein the linear motor is an induction type, and a signal for compensating a thrust variation is superposed on a slip frequency thereof. 8. The compensation signal to be superimposed according to claim 7,
A method of controlling a linear motor, which is proportional to a primary frequency or a signal corresponding thereto. 9. The compensation signal to be superimposed according to claim 7,
A method for controlling a linear motor, wherein the linear frequency is controlled to be substantially proportional to a product of a primary frequency or a signal corresponding thereto and an inverse of a signal proportional to an exciting current. 10. The linear motor according to claim 1 or 2, wherein the linear motor is an induction type motor, and a thrust current command signal and a signal for compensating a thrust change amount are superimposed on each of the slip frequencies. Motor control method. 11. A linear motor control method, wherein the linear motor control method according to any one of claims 1 to 10 is used for an elevator. 12. A linear motor driven by a power converter of a variable voltage and a variable frequency, and a means for generating a signal for compensating for a change in thrust of the linear motor and a thrust command for the linear motor. A linear motor control device comprising means for controlling the thrust of the linear motor by a signal superimposed on the signal.