JPS62217804A - Control unit for ac motor - Google Patents

Abstract

PURPOSE:To smooth out the starting operation of a motor, by outputting the same rotating direction signal to a rotating direction detecting means as in the rotating direction of a rotating direction command signal when the motor rotating speed is zero. CONSTITUTION:A motor rotating direction discriminator 37 outputs a rotating direction signal Q of a motor 21 based on pulses P1 and P2 of different phases outputted from pulse generators 33 and 35. A CPU 27 inputs a step-in amount of an accelerator A, a rotating direction command signal FR, a rotating direction signal Q and a motor rotating speed N and gives a control signal to a PWM oscillator 39, which gives a PWM signal to an inverter in accordance with a control signal. In case a motor rotating speed N is zero, a change-over switch 38 is changed over and the rotating direction command signal FR is inputted to the CPU 27 as a rotating direction signal Q. Thus the powering operation in starting the motor can be smoothly performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control device for an AC motor, and more particularly, to a control device for an AC motor that improves the starting operation of the motor.

[Technical background of the invention and its problems] Conventionally, DC motors, which are easy to control, have been used as vehicle drive motors, that is, motors used in electric vehicles, etc.
Compared to DC motors, it has simple structure and handling, and has less wear and tear, so it is maintenance-free, compact, lightweight, can be mass-produced, and has high efficiency, which means it can travel a long distance per charge. The use of AC induction motors has come to be considered due to the fact that, by controlling the command value, they can now generate torque similar to that of a vehicle like a DC motor. ing.

By the way, in such a vehicle motor, it is necessary to determine its rotation direction, and there is a conventional motor rotation direction determination device that uses a flip-flop (Japanese Patent Laid-Open No. 120956/1989). ).

FIG. 3 is an example of a conventional motor rotation direction determination device using flip-flops, in which two pulses Pi, P with different phases are output from the motor according to the rotation.
2 to the clock input CL and data input of the D-type flip-flop 3, and the D-type flip-flop 3 is set or reset by the difference in phase between the two pulses due to the change in the rotational direction of the motor, and its output level, that is, "1"
Alternatively, the rotation direction of the motor was determined by rOJ.

However, in such a rotational direction determination device, the flip-flop always reads "Even when the motor is stopped rotating.
It is in the state of "0" or "1", indicating either the forward direction or the reverse direction of rotation.

Such a situation does not pose a particular problem when the motor is not operating, but becomes a problem when the motor starts.

In other words, in AC motors used for heavy duty,
In order to smoothly control forward and reverse rotation to perform power operation and regenerative operation such as engine braking, if a rotation command signal is output in the same direction as the motor rotation direction, the motor will perform power operation. When a rotation command signal in a direction opposite to the rotation direction of the motor is output, the motor is caused to perform a regenerative operation.

By the way, when the motor is started in the J direction from a stopped state, if the rotation direction of the rotation command signal to the motor is the same as the rotation direction output from the rotation direction discriminating device, there is no problem because the motor operates by force. As mentioned above, when the motor is stopped, it is unclear whether the rotation direction determining device is indicating the forward or reverse rotation direction, so the rotation direction output from the rotation direction determining device is the rotation command. Since the motor enters a regenerative operation mode when the rotation direction is different from the signal, the starting operation of the motor takes a long time until the rotational direction determining device returns to a normal state, resulting in a delay in the starting operation, and as a result, a good starting operation cannot be performed. There's a problem.

[Object of the Invention] The present invention has been made in view of the above, and an object thereof is to provide a control device for an AC motor that facilitates the starting operation of the motor.

[Summary of the Invention] To achieve the above object, when the rotational direction of the AC motor detected by the rotational direction detection means and the rotational direction of the motor rotational direction command signal output from the rotational direction switching commanding means match, the AC motor is activated. The present invention provides a control device for an AC motor that causes a motor to perform a power operation and performs a regenerative operation when they do not match. When the rotational speed is zero and a rotational direction command signal is output from the rotational direction switching commanding means, the rotational direction detection means detects the same rotation as the rotational direction of the rotational direction command signal output from the rotational direction switching commanding means. The gist is that the device is configured to output a direction signal.

[Embodiments of the invention] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram of an AC motor control device according to an embodiment of the present invention. The AC motor control device shown in the figure uses a motor 21 made of an induction motor as the AC motor, and this motor 21 drives a vehicle, for example, an electric vehicle such as a forklift. Therefore, this device uses an accelerator depression amount detector 23 that detects the amount of accelerator depression for controlling acceleration/deceleration of the running speed of the vehicle.
The acceleration/deceleration signal AG detected by the accelerator depression detector 23 is supplied to the CP (J27) via the 1tI10 interface 25. Forward/forward switching command signal generator 31 that outputs a forward command signal FR
is connected to the CPtJ 27 via the I10 interface 25.

The motor 21 has first and second pulses that generate two pulses Pi and P2 with different phases depending on the rotational direction of the motor.
pulse generators 33.35 are connected, and pulses Pi, P2 with different phases from these pulse generators 33.35 are connected.
is supplied to the motor rotation direction discriminator 37. The motor rotation direction discriminator 37 has, for example, a D-type flip-flop or the like, and discriminates the rotation direction of the motor 21 based on two pulses Pi and P2 having different phases supplied from the pulse generators 33 and 35. , the motor rotation direction signal Q from the motor rotation direction discriminator 37 is sent to the selector switch 3.
■10 interface 25 through 8 break contacts
from the I10 interface 25 to the CPtJ
It is supplied to 27. Since the pulse P1 outputted from the first pulse generator 33 is synchronized with the rotation of the motor 21, this pulse P1 is supplied to the CPU 27 via the I10 interface 25.
detects or reads the rotational speed N of the motor 21 from this pulse P1.

The pulse P1 from the first pulse generator 33 is also supplied to the changeover switch 38;
8 monitors this pulse P1, and when the pulse P1 is generated, that is, when the motor 21 is rotating,
The switching contact is connected to the break contact side as shown, and the motor rotation direction signal Q from the motor rotation direction discriminator 37 is supplied to the CPU 27. However, the motor 21 stops, that is, the motor rotation speed N becomes zero,
When the pulse P1 from the first pulse generator 33 is not generated, the changeover switch 38 connects its changeover contact to the meter contact side, thereby causing the forward/reverse switching command signal generator 3
A rotation direction signal based on a forward/reverse command signal FR outputted from 1 is supplied to the CPU 27. As a result,
When the motor 21 is started from a stopped state, the motor rotation direction signal Q is controlled to be the same as the motor rotation direction by the forward/reverse command signal FR from the forward/backward switching command signal generator 31, and the motor rotation direction signal Q is controlled to be the same as the motor rotation direction. A forward or reverse start is provided.

A memory 29 consisting of a ROM, RAM, etc. is connected to the CPU 27 for storing various temporary data, programs, and the like. In addition, a pulse width modulation oscillator, that is, a PWM oscillator 39 is connected to the I10 interface 25, and this PWM oscillator 39 is supplied with a motor control command signal from the CPLI 27 via the I10 interface 25, and the output of the PWM oscillator 39 is sent to an inverter 41. The motor 21 is driven and controlled by the output of the inverter 41. An in-vehicle battery 43 is connected to the inverter 41, and the inverter 41 converts the DC voltage from the battery 43 into an AC signal, and the AC signal drives the motor 21 to operate the vehicle. It is something.

Next, the operation of the AC motor control device shown in FIG. 1 will be explained with reference to the flowchart shown in FIG. 2.

First, when the motor 21 is rotating normally, the pulse generators 33 and 35 generated as the motor 21 rotates.
The motor rotation direction discriminator 37 detects the rotation direction of the motor 21 based on the output pulses Pi and P2. Also,
The output pulse P1 from the first pulse generator 33 is supplied to the changeover switch 38, which determines that the motor 21 is rotating and changes the changeover contact to the break contact side as shown. It's switching.

Therefore, the rotational direction signal @Q of the motor 21 detected by the motor rotational direction discriminator 37 is outputted via the changeover switch 38.

In such a state, the CPU 27 first detects the output pulse P1 from the first pulse generator 33, reads the motor rotation speed N from this pulse P1, reads the accelerator depression ff1A from the accelerator depression amount detector 23, and performs switching. Changeover switch 3 whose contact is connected to the break contact side
The motor rotation direction signal Q is read from the motor rotation direction discriminator 37 via the motor rotation direction discriminator 37 via the motor rotation direction discriminator 37, and the forward/reverse command signal FR, ! t', that is, read the rotation direction command signal FR (
Sudepp 110-140). The motor rotation direction signal Q is +1 when the rotation direction is forward rotation, and -1 when the rotation direction is reverse rotation, and the rotation direction command signal FR is also +1 when the rotation direction is forward rotation. , and -1 in the case of reverse rotation, and by these polarizations, the operation of the motor 21 shown below is set to the power running mode when the two rotation directions are the same, and is set to the regeneration mode when they are different.

Based on the motor rotation direction signal Q and motor rotation speed N read as described above, the CPU 27 first determines the rotation angle θ0.
is calculated by the formula shown in step 150, furthermore, the angular velocity ωS@ of the slip frequency is calculated by the formula shown in step 160 based on the forward/reverse command signal FR and the accelerator depression faA, and the motor applied voltage command signal v0 is calculated by the formula shown in step 170.
Calculate using the formula shown in and from the six values calculated above, motor 2
The three-phase sinusoidal signals iu, iv, and iw supplied to the terminals 1 and 1 are calculated from the equation shown in step 180. Note that in the equations shown in steps 160 and 170, + and 2 are constants that provide parameters for the optimum slip and optimum voltage during power running or regeneration, and are determined in advance for the power running or regeneration mode, respectively.

The values calculated as above are from CPU 27 to I1.
The signal is supplied to the PWM oscillator 39 via the 0 interface 25 and pulse width modulated, and further via the inverter 41 to drive the motor 21 as a three-phase sine wave signal.

Furthermore, when the motor 21 is stopped, the pulse P1 is not output from the first pulse generator 33, so the changeover switch 38 senses this and connects the changeover contact to the make contact side, causing forward and backward movement. The forward/reverse command signal FR1 from the switching command signal generator 31, that is, the rotational direction signal I10 of the rotational direction command signal FR is supplied to the interface 25.

Therefore, the motor rotation direction signal Q read by the CPU 27 via the I10 interface 25 is forward/backward V'J.
This is the rotation direction command signal FR from the M command signal generator 31.

In this state, if the forward/reverse switching command signal generator 31 is activated to start the motor 21, then the forward/reverse command signal F read from the forward/reverse switching command signal generator 31
R, t, that is, the rotation direction command signal FR and the changeover switch 38
Since the motor rotation direction signal Q1 read through the motor rotation direction signal Q1, which is the rotation direction command signal FR from the forward/reverse switching command signal generator 31 at this time, matches the motor rotation direction signal Q, the motor starting operation is forward or reverse. As a result, it becomes a brute force operation and is carried out smoothly without any delay. Note that the other operations are the same as those described above.

In the above embodiment, the changeover switch 38 senses the rotational speed of the motor 21, and when the motor 21 is stopped, switches its changeover contact to change the direction of rotation from the forward/reverse switching command signal generator 31. Although the case where the command signal FR is supplied to the CPIJ 27 as the motor rotation direction signal Q has been described, the present invention is not limited to this, and there are various other methods, such as a method using software within the CPtJ 27, or a separate independent method. This may be carried out by a method using hardware or the like.

[Effects of the Invention] As explained above, according to the present invention, when the rotational direction switching commanding means outputs a rotational direction command signal to start the motor when the rotational speed of the motor is zero, the rotational direction detection means detects the rotational speed. Since the rotation direction signal is designed to be the same as the rotation direction output from the direction switching command means,
Since the power operation at the time of starting the motor is performed smoothly, the motor starts smoothly, there is no delay in the starting operation, and a good starting operation is possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an AC motor control device showing an embodiment of the present invention, Fig. 2 is a flowchart showing the operation of the device shown in Fig. 1, and Fig. 3 shows the main parts of a conventional rotation direction determining device. FIG. 21... Motor 27... CPU 31... Forward/forward switching command signal generator 37... Motor rotation direction discriminator 38... Changeover switch patent applicant Nissan Motor Co., Ltd. Figure 1 Figure 3

Claims (1)

[Claims] When the rotational direction of the AC motor detected by the rotational direction detection means matches the rotational direction of the motor rotational direction command signal output from the rotational direction switching commanding means, the AC motor is caused to perform a power operation, and when they do not match, a regenerative operation is performed. The control device for an AC motor has a rotation speed detection means for detecting the rotation speed of the motor, and when the motor rotation speed detected by the rotation speed detection means is zero, the rotation direction is changed from the rotation direction switching command means. When the command signal is output,
A control device for an AC motor, wherein the rotational direction detection means is configured to output a rotational direction signal that is the same as the rotational direction of the rotational direction command signal output from the rotational direction switching commanding means.