JP3298267B2 - Control device for DC brushless motor without position sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control of a position sensorless DC brushless motor for obtaining a commutation signal to a stator winding by utilizing a back electromotive force generated in the stator winding as the rotor rotates. Regarding the device, in particular, when the startup is performed in a synchronous operation, and even when there is a change in load and a change in the power supply voltage at the time of the startup, a start-up of a position sensorless DC brushless motor that realizes a start with extremely few failures and shifts to the position sensorless operation promptly is realized. It relates to a control device.

[0002]

2. Description of the Related Art In recent years, a commutation signal to a stator winding is obtained by utilizing a back electromotive force generated in a stator winding due to rotation of a rotor, and a position where a rotor position detector is not required is provided. Sensorless D
A drive system for a C brushless motor has been proposed. (Suzuki, Ogasawara, and Akagi, "A Method for Constructing a Brushless DC Motor Using Position Sensors," No. 34, 1988, The Institute of Electrical Engineers of Japan.

In order to start the motor in such a drive system, the motor is first excited by a drive signal of an arbitrary excitation pattern for a predetermined period based on a start sequence.
The position is determined by moving the rotor to a position corresponding to the excitation pattern, and then the motor is rotated by applying an arbitrary commutation signal and switching the excitation pattern. As a result, the rotor position is detected based on the back electromotive force generated in the stator winding due to the rotation of the motor, and appropriate commutation is performed.

However, the back electromotive force is proportional to the number of revolutions of the rotor, and when the rotation of the rotor is low, the back electromotive force is small and difficult to detect. Unless the rotation speed of the motor is increased, the operation without position sensor cannot be performed. Therefore, as a start sequence, the excitation pattern is switched one after another in an open loop by a synchronous operation, and a control is shifted to a position sensorless operation by obtaining a rotational speed at which a back electromotive force can be detected.

[0005] Then, it is determined whether the motor operation is normally performed after the start of the position sensorless operation, and
If it is determined that the operation is normal, the position sensorless operation is continued. If it is determined that the operation is not normal, the start operation by the synchronous operation is repeated again. However, in the restarting operation, a device has been devised such as changing the switching timing of the excitation voltage and the excitation pattern from the time of the first startup.

[0006]

However, in the above-described conventional control device for a position sensorless brushless DC motor, a certain number of rotations is required to obtain a stable commutation signal by detecting a back electromotive force. However, in order to obtain the rotation speed, the excitation voltage must be increased, and since the start-up determination is performed after the start-up operation is performed by the synchronous operation, it is not possible to shift to the position sensorless operation in one trial of the start-up operation. If the restart is to be performed, the start operation has to be performed many times until the excitation voltage that allows the start is selected.

Therefore, when the operation is switched from the synchronous operation to the position sensorless operation, the excitation voltage in this excitation interval is changed based on the detection timing of the rotor position detection signal based on the back electromotive force in the excitation interval at the time of the switch. By adding or subtracting 0, the start operation is not repeated many times, realizing start-up without failure that can cope with any situation from high load to low load, high power supply voltage to low voltage, and achieve position sensorless operation The purpose is to shift in a short time.

[0008]

A control device for a brushless DC motor without a position sensor according to the present invention is started in a synchronous operation, and after the start, is switched to a position sensorless operation using a back electromotive force. A motor, a drive circuit for generating an excitation voltage and driving the motor, and utilizing a back electromotive force of the motor.
A rotor position detection signal for outputting a rotor position detection signal of an excitation phase to be excited next, and an output from the rotor position detection circuit.
A control means for switching the drive circuit from the synchronous operation to the position sensorless operation based on the rotor position signal to be performed.
The control means measures the elapsed time from the last excitation of the synchronous operation with a timer, and
The control mode is changed according to the overtime, and the rotor
The elapsed time when the position signal is input is within the specified time
Wherein the position is <br/> configured to switch to sensorless operation, characterized in Tei Rukoto when there. Further, the control means
Is the number of counts the timer T. C. When represented by A <T. C. In the case of ≦ B, increasing the excitation voltage, the rotor position detection signal from the rotor position detection circuit
The operation is switched to the position sensorless operation when an input is made . Further, the control means sets the count number of the timer to T.V. C. When represented by T. C. ≤A
The rotor position detection signal from the rotor position detection circuit.
No. characterized in that the Ru switched before <br/> Symbol position sensorless operation after reducing the excitation voltage as they are entered.
Further, the control means sets the count number of the timer to T.V. C. When represented by B <T. C. In this case, the excitation voltage is set to zero and the rotation of the motor is stopped. Further, the control means sets the count number of the timer to T.V. C. When represented by A <T. C. Place of ≦ B
In case, to increase the excitation voltage, from the rotor position detection circuit
When the rotor position detection signal is input, the operation is switched to the position sensorless operation. C. In the case of ≦ A, a rotor position detection signal from the rotor position detecting circuit is input
In this case, the operation is switched to the position sensorless operation to reduce the excitation voltage. Further, the control means sets the count number of the timer to T.V. C. When represented by A <
T. C. In the case of ≦ B, increasing the pre-Symbol excitation voltage, the rotor position detection signal from the rotor position detecting circuit is input
At this time, the operation is switched to the position sensorless operation. C. ≤
In the case of A, the rotor position detection from the rotor position detection circuit
When an output signal is input, the excitation voltage is reduced
From the position sensorless operation, and B <T. C.
In this case, the rotation of the motor is stopped by setting the excitation voltage to zero. Here, A and B are predetermined count numbers, respectively, in a relation of A <B.

In the start-up by the synchronous operation, the detection timing of the back-emergence detection mode of the last excitation phase by the synchronous operation is monitored, and the excitation voltage is changed within the excitation interval based on the detected timing. It is configured to start with the current and torque of

[0010]

In the present invention, the position sensorless brushless DC motor is started by the control means in a synchronous operation. This synchronous operation is realized by gradually switching the excitation phase in an open loop. When the synchronous rotation speed increases, a rotor position detection signal based on the back electromotive force is detected by the rotor position detection means.

Therefore, in the last excitation phase of the synchronous operation, the excitation voltage of this excitation phase is adjusted or set to 0 depending on the time when this signal is detected from the time when this last excitation was started. That is, when the position detection signal is detected earlier in time than the detection timing during the normal position sensorless operation, it is considered that a sufficient rotation speed is obtained, and the excitation voltage is reduced. On the other hand, when the detection signal is not obtained, it is considered that a sufficient rotation speed is not obtained, and the exciting voltage is slightly increased. This control is repeated several times in the same excitation phase. However, if the position detection signal is not detected even after the excitation time of the last synchronous rotation speed is exceeded, the excitation voltage is set to 0 and the excitation to the motor is stopped.

When a position detection signal is obtained, the operation shifts to a position sensorless operation by the control device. By such a control means, the motor is started at a necessary and sufficient excitation voltage, and the operation immediately shifts to the position sensorless operation.

[0013]

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

FIG. 2 shows a drive circuit (120-degree conducting voltage type inverter circuit) for driving a brushless DC motor. As shown in FIG. 2, the brushless DC motor 1
Consists of a rotor 2 and a stator 3, and the stator 3 has U,
Three-phase windings of V and W are mounted, and four magnetic poles are formed on the rotor 2 by permanent magnets.

The drive circuit 4 includes a freewheel diode D
a-side transistor to which a ⁺ , Db ⁺ , and Dc ⁺ are connected;
Ta ⁺ , Tb ⁺ , Tc ⁺ and freewheeling diodes Da ⁻ , D
b ⁻ , Dc ⁻ connected N-side transistor, Ta ⁻ ,
Tb ^-, Tc ^- is composed of a.

Further, by performing a chopper control by combining a P-side transistor and an N-side transistor of the drive circuit 4 and changing the duty of the chopper,
A three-phase DC current is sequentially and selectively excited in two of the windings of each phase to form a magnetic field and rotate the rotor at a variable speed.

In this type of drive system, the speed is controlled by PWM control using a 120-degree conduction type voltage source inverter circuit (motor drive circuit) as a main circuit, that is, U, V, W Back electromotive force e _a , e _b , e _c , which is generated by the rotation of the rotor in the stator winding of each phase
And a drive signal applied to a pair of transistor circuits of the inverter circuit, each phase has an open angle of 60 ° × 2 times within a 360 ° electrical angle period (a period during which no drive signal is applied to the transistor is an open phase). ).

The control device of the present invention includes rotor position detecting means 5 for detecting a rotor position by detecting a back electromotive force generated in each winding of the motor 1 in the open section.

The control means 6 controls the drive circuit 4 based on the rotor position detection signal from the rotor position detection means 5 to switch the excitation phase.

As shown in FIG. 3, the excitation phases for continuing the normal rotation of the motor 1 are preset at 5 to 0, and the correlation between each excitation phase, the rotor position detection phase and the conduction diode is shown in FIG. The motor is driven to rotate by the commutation in this order. In synchronous operation, commutation occurs in an open loop such as excitation phase 5-4--3-2-1-0-5. In sensorless mode, conduction of the rotor position detection phase corresponding to the excitation phase occurs. Based on the conduction state of the diode, the control means 6 switches a transistor switch and commutates. For example, when the excitation of the excitation phase 5 has been made, the control means 6 the rotor position detects phase W ^-, conducting diode Dc ^- monitors the conductive state of the commutation command of the excitation phase 4 on the basis of the conductive state It is sent to the inverter circuit 4.

A control means 6 for switching each transistor of the inverter circuit 4 based on the rotor position detection signal from the rotor position detection circuit 5 is connected to the inverter circuit 4.

In response to a command from the control means 6, the transistors Ta ⁺ , Tb ⁺ ,
Tc ⁺ and Ta ⁻ , Tb ⁻ , Tc ⁻ perform a switching operation.

Next, means for switching from the start control of the motor to the operation without the position sensor by the control means having the above configuration will be described with reference to the flowchart of FIG.

In response to a start command, synchronous operation is started in step S1, and when the last excitation by synchronous operation is started in step S2, a timer is started in step S3. In step S4, the count number of the timer is evaluated.
C. If (the count number of the timer) is smaller than A (predetermined count number), it is determined in step S5 whether a rotor position detection signal is detected. If it is detected, it is determined that a sufficient number of revolutions is obtained, and the excitation voltage is reduced in step S6, and the process proceeds to sensorless operation in step S7. If the signal has not been detected, step S8 follows and the process returns to step S4.

T. C. If A is between A (the predetermined count number) and B (A <B with the predetermined count number), the excitation voltage is increased in step S9, and it is determined in step S10 whether the rotor position detection signal is detected. I do. If detected, the process shifts to sensorless operation in step S7. If not, the process returns to step S4 through step S11.

T. C. Is larger than B, step S1
In step 2, the excitation voltage is set to 0, and the motor is stopped in step S13.

With these controls, the final excitation by the synchronous operation starts, and when the rotor position detection signal is obtained, the control is immediately shifted to the position sensorless operation. When the rotor position detection signal is not obtained, the excitation voltage is increased to increase the torque. To obtain the signal. However, if the same excitation phase is excited for a long time, problems such as an increase in motor current and demagnetization of the permanent magnet of the rotor will occur. Stop the driving operation.

[0028]

As described above, according to the present invention,
In controlling a position sensorless brushless DC motor,
Switching from start-up control to position sensorless operation with optimal excitation voltage and commutation timing based on rotor position detection by back electromotive force, under various load and power supply voltage conditions,
There is no failure in starting, and it can be started without repeating the starting operation.

[Brief description of the drawings]

FIG. 1 is a flowchart showing control at the time of switching from startup to operation without a position sensor according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a position sensorless brushless DC motor according to an embodiment of the present invention.

FIG. 3 is a diagram showing an excitation pattern according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Brushless DC motor 2 Rotor 4 Drive circuit (inverter circuit) 5 Rotor position detecting means 6 Control means

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 5-227787 (JP, A) JP 5-219785 (JP, A) JP 5-219784 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H02P 6/18

Claims (6)

(57) [Claims] 1. A control device for a position sensorless DC brushless motor which starts in a synchronous operation and switches to a position sensorless operation using a back electromotive force after the start, and generates a motor and an excitation voltage to drive the motor. And the next excitation using the back electromotive force of the motor
A rotor position detecting circuit for outputting a rotor position detection signal of the phase, the rotor position signal output from the rotor position detection circuit
Said drive circuit and control means for switching the position sensorless operation from the synchronous operation based on the item, the system
Control means measures the time elapsed since the last excitation of the synchronous operation.
Measure with a timer and control according to the elapsed time of the timer
When the mode is changed, the rotor position signal is input.
Position when the elapsed time when the
Controller position sensorless DC brushless motor, characterized in Tei Rukoto configured to switch to sensorless operation. 2. The method according to claim 1, wherein the control means sets the count number of the timer to T. C. When represented by A <T. C. For ≦ B to <br/>, increasing the excitation voltage or the rotor position detection circuit
2. The control device according to claim 1 , wherein the operation is switched to the position sensorless operation when a rotor position detection signal is input from the controller. Here, A and B are predetermined count numbers, respectively, in a relation of A <B. 3. The control means according to claim 1 , wherein said count value of said timer is set to T. C. When represented by T. C. In the case of a ≦ A,
A rotor position detection signal is input from the rotor position detection circuit.
Is the excitation voltage sensorless DC brushless motor control apparatus according to claim 1, wherein the Ru switched to the position sensorless operation after reducing the when the.
Here, A is a predetermined count number. 4. The control means according to claim 1 , wherein the timer counts the count value of the timer. C. When represented by B <T. C. In the case of
2. The control device for a position sensorless DC brushless motor according to claim 1, wherein the excitation voltage is set to zero to stop the rotation of the motor. Here, B is a predetermined count number. 5. The control device according to claim 1, wherein the control means counts the count of the timer to T. C. When represented by A <T. C. In the case of ≦ B
To increased the excitation voltage, times from the rotor position detection circuit
When the trochanter position detection signal is input, the operation is switched to the position sensorless operation. C. ≦ A, when a rotor position detection signal is input from the rotor position detection circuit
2. The control device for a position sensorless DC brushless motor according to claim 1 , wherein the operation is switched to the position sensorless operation to reduce the excitation voltage. Here, A and B are predetermined count numbers, respectively, in a relation of A <B. 6. The control device according to claim 1, wherein the control means sets the count number of the timer to T. C. When represented by A <T. C. In the case of ≦ B
The increased pre Symbol excitation voltage, whether the rotor position detection circuit
When the rotor position detection signal is input from the controller, the operation is switched to the position sensorless operation. C. In the case of ≦ A, the rotor position detection signal from the rotor position detecting circuit is input
At this time, the operation is switched to the position sensorless operation after the excitation voltage is reduced , and B <T. C. 2. The control device for a position sensorless DC brushless motor according to claim 1, wherein in the case of (1) , the excitation voltage is set to zero and the rotation of the motor is stopped. Here, A and B are predetermined count numbers, respectively, in a relation of A <B.