JPH0446079B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for an induction motor used for changing the gear ratio of a mechanical continuously variable transmission.

It is known that an induction motor is used as a servo motor in an automatic control system, and is driven by a two-phase converter, so that the speed is variable depending on the magnitude of the deviation input, and the motor can be rotated forward or reverse depending on the polarity of the deviation input. 1st
The figure shows a conventional control device, where 1 is an input terminal to which the difference between the detected output value of the mechanical continuously variable transmission and its target set value is given as a deviation input, 2 and 3 are input terminals for forward rotation and reverse rotation. Error amplifier circuit, 4 and 5 are frequency/voltage generation circuits for forward and reverse rotation, 6 and 7 are drive circuits for forward and reverse rotation, 8 is a servo motor (induction motor), and 9 is a power supply (commercial power supply) terminal. It is.

A voltage according to the difference between a target set value of a controlled object, for example, a mechanical continuously variable transmission (not shown) and a detected output value from the controlled object, is applied to input terminal 1 as a deviation input, and the voltage is applied depending on the polarity. For example, a positive polarity deviation input is given to the forward rotation error amplification circuit 2, and a negative polarity deviation input is given to the reverse rotation error amplification circuit 3, where it is amplified and sent to the forward rotation frequency/voltage generation circuit 4 or It is given to the frequency/voltage generation circuit 5 for reverse rotation.

Then, in accordance with the deviation input, the driving frequency and input voltage required to drive the servo motor 8 are determined so as to reduce the deviation input. This is applied to the forward rotation drive circuit 6 or the reverse rotation drive circuit 7. As a result, the speed of the servo motor 8 is changed, and at the same time, the input voltage applied from the power supply terminal 9 is controlled.

According to such a configuration, the servo motor 8 can be controlled in either the forward or reverse drive direction according to the polarity of the deviation input, and the drive frequency and input voltage can also be controlled, which is convenient. and negative, it is necessary to prepare an error amplification circuit, a frequency/voltage generation circuit, etc., respectively, which has the disadvantage that the configuration is complicated.

The present invention varies the speed of the induction motor and controls the input voltage in response to a deviation input corresponding to a deviation between a detected output value of a controlled object controlled by the induction motor and its target set value. Hits the,
It is an object of the present invention to simplify the configuration and also to realize forward/reverse control of the induction motor with a simple circuit configuration.

FIG. 2 shows the basic configuration of the present invention, and 11 indicates the reference voltage corresponding to the target setting value of a controlled object, for example, a mechanical continuously variable transmission, and output detection from the controlled object, as described above. 12 is an absolute value circuit that outputs the absolute value b of the deviation input a, and 13 is a frequency/voltage generation circuit that outputs the absolute value of the deviation input a. It has a pulse width of 50% duty which is inversely proportional to b, and the power supply (commercial power supply) terminal 14
A two-phase pulse c with a phase difference of 90 degrees and asynchronous with the power supply voltage given by , and a pulse θ having a pulse width proportional to the absolute value b and synchronized with the power supply voltage e of the induction motor (servo motor). Outputs ((absolute value pulse).

The pulse width of the pulse c determines the driving frequency of the servo motor, and as the deviation input a becomes smaller, the pulse width becomes longer and the driving frequency, that is, the converter frequency becomes lower. The pulse width of the pulse θ determines the repeated energization time of the power supply voltage e applied from the power supply terminal 14, and specifically, the pulse width of the thyristor (this is the configuration of the drive circuit 15) that is turned on every half wave of the power supply voltage. Determine the conduction angle of

The drive circuit 15 received the pulses c and θ as input, and controlled the voltage e according to the drive frequency determined by the frequency of the pulse c and the conduction angle determined by the pulse θ as described above. Outputs converter voltage f, thereby causing servo motor 1
6 is driven.

17 is a forward/reverse discrimination circuit which discriminates the polarity of the deviation input a, and is effective when the deviation input a is positive polarity;
When the polarity is negative, an invalid output d is output. The output d is input to the drive circuit 15. When the output d is valid, the drive circuit 15 selects to drive the servo motor 16 in the forward rotation direction, and when the output d is invalid, the drive circuit 15 selects to drive the servo motor 16 in the reverse rotation direction. be done.

Specifically, when the servo motor 16 is a two-phase induction motor, the pulse c is a two-phase pulse with a phase difference of 90 degrees, but when the output d is valid, one of the two-phase pulses One of the pulses may be inverted. In this way, the advance/delay relationship between both pulses is reversed, so that the servo motor is reversed.

In the above configuration, when the pulse c is valid, the drive circuit 15 outputs a positive half-wave voltage of the power supply voltage e only during the valid period of the pulse θ. When pulse c is invalid, a negative half-wave voltage of power supply voltage e is output from drive circuit 15 only during the valid period of pulse θ. These outputs from the drive circuit 15 are the output f.

FIG. 3 is a time chart for explaining the operation showing the waveforms of input and output signals in each component shown in FIG. As the deviation input a becomes smaller, the output b of the absolute value circuit 12 also becomes smaller,
Therefore, the frequency of pulse c decreases, and the pulse width of pulse θ also decreases.

If the frequency of the pulse c decreases, the frequency of the output f also decreases, and therefore the converter frequency also decreases, and the servo motor 16 decelerates. Furthermore, as the pulse width of the pulse θ becomes narrower, the input voltage of the servo motor 16, that is, the output f also decreases.

Note that when changing the frequency to make the servo motor variable speed, it is necessary to change the input voltage to prevent excessive input so that the frequency and input voltage always have a nearly constant ratio. pulse θ to
The width of the input voltage is changed to increase or decrease the input voltage.

As mentioned above, the rotation direction of the servo motor 16 is determined according to the polarity of the deviation input a, and this polarity is determined by the forward/reverse discrimination circuit 17, and the output d at this time determines the pulse c. The phase of
It advances or lags by 90 degrees (for two-phase induction motors), which determines the direction of rotation.

Regarding the offset of the absolute value circuit 12, if the gain of the absolute value circuit 12 is increased to improve control accuracy, the offset becomes minute when converted into the deviation input a.

On the other hand, regarding the slight hysteresis that the forward/reverse discrimination circuit 17 has, the deviation input a includes ripples,
Particularly in the settled state, the output d of the forward/reverse discrimination circuit 17 is reversed due to the ripple, so the servo motor 16 is dynamically stopped. Therefore, the influence of slight hysteresis in the settling state on the output d is minimal, and the servo motor 1
6's torque depends on ripple.

In the settled state, the ripple-based forward/reverse discrimination circuit 17
The output d of is for forward rotation and reverse rotation, respectively.
50% at a time, and the servo motor 16 is alternately excited at a converter frequency of several Hz and is in a stopped state.

Figure 4 is a block diagram when this invention is applied to control a variable speed pilot motor (two-phase induction motor) of a mechanical continuously variable transmission, and Figure 6 shows the waveforms of the input and output signals. This is a time chart.

The rotational speed of the output shaft of the continuously variable transmission 21 is detected by the AC rotary generator 22, and the output h thereof is converted into a rectified voltage i by the rectifier circuit 23.
This rectified voltage i is smoothed by a smoothing circuit 24,
The DC voltage becomes j. This DC voltage j is determined by the comparator 25
This is one input.

As another input of the comparator 25, the speed setter 26
A voltage g is given according to the rotation speed set by , and the voltage difference between the two voltages j and g is the deviation input a
becomes. Further, this polarity is determined by a forward/reverse discrimination circuit 17. The subsequent operations are the same as in the case of FIG.

In the example shown in FIG. 4, the rotational direction and rotational speed of the pilot motor 27 are controlled, and the rotation of the pilot motor 27 is controlled until the deviation input a becomes zero.

The pilot motor 27 used here uses a two-phase induction motor as described above, so the frequency/voltage generation circuit 13 generates two-phase pulses c ₁ and c ₂ with a phase difference of 90 degrees. do.

When one of the two-phase pulses c ₁ and c ₂ is valid, _the pulse θ is applied during the positive polarity period of the power supply voltage e, and when the pulse c ₁ is invalid, During the negative polarity period of the power supply voltage e, the pulse θ is
Each output is switched by a switching means.
The output is given as a conduction pulse to one thyristor connected to one stator winding of the induction motor.

When the other pulse c ₂ and the output d of the forward/reverse discrimination circuit 17 have the same logic, the pulse θ is applied during the negative half-wave period of the power supply voltage e, and when they have different logic, the pulse θ is The pulses θ are switched and outputted by the respective switching means during the positive half-wave period. Its output is given as a conduction pulse to the other thyristor connected to the other stator winding of the induction motor.

By applying a conduction pulse to each thyristor as described above, the output f ₁ ,
f ₂ is output, and this is applied to each stator winding of the induction motor, causing the induction motor to rotate.

Therefore, when the rotational speed of the output shaft of the continuously variable transmission 21 is lower than the speed set by the speed setting device 26, the rotational speed of the continuously variable transmission 21 increases, and conversely, when it is higher than the set speed, Continuously variable transmission 2
The pilot motor 27 rotates in a direction in which the rotational speed of the pilot motor 27 decreases.

Then, due to the converter frequency generated according to the deviation input a, as the deviation input a becomes smaller, the rotation speed becomes lower.

When the settling state is reached, as shown in Fig. 5, the deviation input a is zero on average, but it repeats positive and negative changes due to ripples included in the DC voltage j, so the output d has a duty of 50%. The pilot motor 27 repeats forward and reverse rotation, and is dynamically stopped.

FIG. 7 is a circuit diagram showing a detailed example of the drive circuit 15 and pilot motor 27 shown in FIG. 4, and FIG. 8 is a time chart thereof.

In FIG. 7, 31 to 33 are exclusive OR circuits, 34 and 35 are AND circuits, and 36 is a power supply voltage e.
37 and 38 are thyristors, and 39 and 40 are stators of the pilot motor 27. It is a winding.

The output e' from the comparison circuit 36 is input to exclusive OR circuits 32 and 33. Also, exclusive OR circuit 3
2 receives one of the two-phase pulses c ₁ from the frequency/voltage generating circuit 13, and outputs an output q that becomes valid when the output e' and the two-phase pulse c ₁ have different logics.

The AND circuit 34 inputs the pulse q and the pulse θ, and its output s is given to the thyristor 37 as its conduction pulse, and the one stator winding 39 of the pilot motor 27 is excited by these outputs f ₁ .

On the other hand, the exclusive OR circuit 31 inputs the other two-phase pulse c ₂ of the frequency/voltage generation circuit 13 and the output d of the forward/reverse discrimination circuit 17, and outputs an output p. The output p is the other input of the exclusive OR circuit 33,
Gives output r.

The output is input to the AND circuit 35 together with the pulse θ. And the output t from now on is thyristor 3
8 as its conduction pulse, and the output f ₂ from this excites the other stator winding 40 of the pilot motor 27.

Then, based on the logic of the output d of the forward/reverse discrimination circuit 17, the output f ₂ is either advanced or delayed relative to the output f ₁ .

When the deviation input a becomes smaller, the pulse width of the pulse θ becomes narrower, and when the deviation input a becomes zero, the pulse width of the pulse θ also becomes zero, and the thyristors 37 and 38
becomes non-conducting. As a result, the excitation of the pilot motor 27 is cut off.

As described in detail above, according to the present invention, the induction motor can be controlled in forward/reverse direction as well as in the deviation direction without using separate error amplification circuits, frequency/voltage generation circuits, drive circuits, etc. according to the polarity of the deviation input. It is possible to control the rotation in a direction in which the input is zero, and therefore the circuit configuration can be simplified.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional example, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is a block diagram showing a conventional example.
4 is a block diagram when used to control the variable speed pilot motor of the mechanical continuously variable transmission of this invention, and FIGS. 5 and 6 are time charts for explaining the operation of the invention. FIG. 4 is a time chart for explaining the operation, FIG. 7 is a circuit diagram showing an example of a drive circuit and an induction motor, and FIG. 8 is a time chart for explaining the operation of FIG. 11... Input terminal, 12... Absolute value circuit, 13... Frequency/voltage generation circuit, 15... Drive circuit, 16, 2
7... Servo motor (induction motor), 17... Forward/reverse discrimination circuit, 37, 38... Thyristor, 39, 40...
Stator winding, e...power supply voltage, _c1 , _c2 ...two-phase pulse, θ...absolute value pulse.

Claims (1)

[Claims] 1. Absolute deviation input between a reference voltage corresponding to a target setting value of a controlled object controlled by a two-phase induction motor and a detected voltage corresponding to an output detection value of the controlled object. an absolute value circuit that outputs a value; the output of the absolute value circuit is input, and the pulse width has a duty of 50% that is inversely proportional to the absolute value;
and a frequency/voltage generation circuit that outputs a two-phase pulse having a phase difference of 90 degrees and an absolute value pulse having a pulse width proportional to the absolute value and synchronized with the power supply voltage of the induction motor; and the deviation input. a forward/reverse discrimination circuit that discriminates the polarity of the signal and outputs an output, and receives the two-phase pulse from the frequency/voltage generation circuit, the absolute value pulse, and the output from the forward/reverse discrimination circuit as input, and drives the induction motor. a drive circuit configured to generate the absolute value pulse at the positive polarity of the power supply voltage of the induction motor when one of the two-phase pulses is effective; a first switching means that respectively switches and outputs the absolute value pulse in the negative polarity of the power supply voltage when the voltage is invalid; and the other pulse of the two-phase pulse and the output of the forward/reverse discrimination circuit. a second circuit which switches and outputs the absolute value pulse at the negative polarity of the power supply voltage when the logics are the same, and outputs the absolute value pulse at the positive polarity of the power supply voltage when the logics are different; switching means; and first and second thyristors connected in series to each stator winding of the induction motor, wherein one of the first and second thyristors is connected to the first switching means. A control device for an induction motor, wherein the output from the second switching means is supplied as a conduction pulse to the second switching means.