JP2001045783A - Motor control method - Google Patents

Abstract

(57) [Summary] In a motor control method, a negative torque due to a harmonic component included in an induced voltage is used as a positive torque to improve efficiency. A DC voltage is switched by a switching element of an inverter circuit and applied to a motor, and a position detection signal is obtained by a position detection circuit based on an induced voltage generated in a non-energized phase of the motor. The control circuit 11 detects the position of the rotor by a signal to switch the energization of the motor 4 and to drive the motor 4 by PWM-controlling the switching elements. The motor 4 is operated by previously superimposing a voltage component such that a harmonic component included in the induced voltage is a positive torque on the applied voltage of the motor 4, and a waveform pattern corresponding to the applied voltage when the operation is most efficient. (Voltage (PW
M) pattern) is obtained and stored in the ROM 10. The control circuit 11 performs PWM control of the switching element using the waveform pattern of the ROM 10 and drives the motor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control technique for detecting the position of a rotor using an induced voltage waveform generated in a non-energized phase of a motor (for example, a brushless DC motor) and switching energization. The present invention relates to a method of controlling a motor using a harmonic component included in an induced voltage due to a structural cause of the motor as a positive torque.

[0002]

2. Description of the Related Art Inverter control of a motor requires, for example, a control device shown in FIG. First, the commercial power supply 1
Is converted to DC by an AC / DC converter 2, and the converted DC power is switched by a transistor matrix unit 3 and applied as a three-phase rectangular wave voltage to a three-phase four-pole motor 4, and a drive current is supplied to the motor 4. Flow to obtain rotational torque. Then, the position of the rotor is detected by a position detection circuit 5, and a signal of the position detection is inputted to a control circuit (microcomputer) 6, and the control circuit 6 drives the transistors of the transistor / matrix section 3 to drive the stator. Switch the winding current.

As a method of detecting the position, for example, there is a method of detecting a zero cross point from a back electromotive force (induced voltage) waveform induced in a non-energized phase, and detecting the position of the rotor based on the zero cross point. In the case of this position detection method, the position detection circuit 5 synthesizes and divides the terminal voltages of the armature windings U, V, and W with the synthesizing circuit 5a, divides the voltage, and generates a voltage waveform corresponding to the neutral point voltage of the motor (virtual medium And the virtual neutral point voltage (ie, induced voltage) and the voltage generating circuit 5b.
The comparison circuit 5c compares the predetermined voltage (reference voltage) generated in the step (c) with the comparison result, and outputs the comparison result to the control circuit (microcomputer) 6 as a position detection signal.

When the PWM control method is adopted, the control circuit 6 switches the energization of the armature winding based on the position detection signal and generates a PWM signal.
A drive signal including the M waveform is output to the transistor matrix unit 3 via the drive circuit 7. Then, each of the transistors Ua, Va, W of the transistor matrix section 3
“a”, “X”, “Y”, and “Z” are turned on and off in a predetermined manner, and the energization of the armature winding of the motor 4 is switched. Thus, a rectangular wave voltage is applied to the motor 4, so that a current flows through the motor 4 and a rotating torque is obtained.

[0005] As the motor 4, a motor that uses not only magnet torque but also reluctance torque has been proposed from the viewpoint of increasing the efficiency of the motor 4. For example, a magnetic path from one q-axis to the other q-axis from the stator is secured in consideration of the shape and arrangement of the magnet embedded in the rotor, and a slit is formed along the magnetic path to form a d-axis. By increasing the inductance difference between the q axis and the q axis, reluctance torque can be generated.

[0006]

However, in the above-described motor control method, since the structural problem of the motor 4 is not taken into account, the induced voltage waveform contains harmonic components due to its structural cause. Become. Therefore, the organic voltage waveform including the harmonic component appears not only as a negative torque in the motor 4 but also as a vibration component (vibration torque) of the motor 4 and is not reflected in the effective torque of the motor.
For example, when the reluctance torque is used, ripples (higher harmonics) are superimposed on the induced voltage due to the interaction between the slots of the stator 1 and the reluctance torque. In particular, when 24 slots are used as the stator in the three-phase four-pole motor 4, as shown in FIGS. 5A and 5B, the ripple superimposed on the induced voltage is the eleventh harmonic (the eleventh harmonic). Wave).

The present invention has been made in view of the above problems, and has as its object to improve the efficiency of a motor by utilizing a harmonic component included in an induced voltage generated due to a structural cause of the motor for a positive torque. It is an object of the present invention to provide a motor control method capable of realizing the above.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for controlling a DC voltage by switching a switching element of an inverter and applying the DC voltage to the motor. Get the position detection signal,
The position of the rotor is detected based on the position detection signal, and the energization of the motor is switched.
In the motor control method for driving the motor by performing WM control, the motor is operated by superimposing a voltage component such that a harmonic component included in the induced voltage is a positive torque on the applied voltage of the motor in advance. A waveform pattern (voltage (PWM) pattern) corresponding to the applied voltage during the operation is obtained and stored in the ROM, and the switching element is PWM-controlled using the waveform pattern of the ROM to drive the motor. It is characterized by doing.

According to the present invention, a DC voltage is switched by a switching element of an inverter and applied to the motor, a position detection signal is obtained by an induced voltage generated in a non-energized phase of the motor, and the position of the rotor is determined by the position detection signal. In the control method of the motor that drives the motor by PWM-controlling the switching element while detecting the energization of the motor while detecting the vibration of the motor, the vibration torque of the motor due to a harmonic component included in the induced voltage in advance is positive. The motor is operated by superimposing a voltage component such as a torque on the applied voltage of the motor, and a waveform pattern (voltage (PWM) pattern) corresponding to the applied voltage when the operation is most efficient is obtained. The motor is stored in a ROM, and the switching element is PWM-controlled using a waveform pattern of the ROM to drive the motor. It is characterized in that there was Unishi.

[0010] The waveform pattern of the ROM is obtained by equally dividing the interval for detecting the position of the motor into a plurality of parts, and for each division, a PWM
Of the motor, and the motor
When controlling, the time of the position detection interval is measured by the position detection signal of the motor, and the output timing of the waveform pattern is generated by dividing the position detection interval by the number of equal divisions. Preferably, the waveform pattern of the ROM is output at the generated output timing on the basis of a signal. This makes it possible to output a waveform pattern at an appropriate timing for each division of the position detection interval, and to increase the number of divisions, it is possible to control the rotation of the motor more finely.

The position detection interval time may be obtained from the previous position detection and the current position detection, or may be obtained by averaging a plurality of past position detection intervals. Thereby, the waveform pattern is output stably, and in particular, the output timing error of the waveform pattern due to the rotation fluctuation is offset,
The output is further stabilized.

In controlling the speed of the motor, a PWM buffer serving as a reference is prepared in advance, and the value of the PWM buffer is increased or decreased according to the rotation speed of the motor, and the value of the PWM buffer is adjusted. May be added to the waveform pattern of the ROM. The PWM buffer stores a reference value in consideration of the speed control range in advance.
A method of adding the value of the buffer for ROM to the waveform pattern of the ROM is such that the value of the buffer for PWM is multiplied by the waveform pattern of the ROM, and the value is divided by the maximum value of the waveform pattern. The recalculation result may correspond to the speed control of the motor. Thereby, even during the rotation speed control of the motor, the negative torque due to the harmonic component can be used as the positive torque.

In the deceleration control of the motor speed control, a waveform pattern at each position detection interval is output, and then the last waveform pattern of the same waveform pattern is continuously output until the next position detection is performed. Good. In the acceleration control of the motor speed control, when the next position is detected before outputting the waveform pattern at each position detection interval, the waveform pattern at the next position detection interval may be forcibly output. As a result, even when the motor is decelerated or accelerated, the problem of the output of the waveform pattern is eliminated.

[0014]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to FIG. In FIG. 1,
The same parts as those in FIG.

In FIG. 1, a control apparatus to which the motor control method of the present invention is applied obtains a voltage component such that a harmonic component included in an induced voltage waveform becomes a positive torque in advance, and determines a voltage applied to the motor 4. And a control circuit (microcontroller) that continuously supplies the motor 4 with the voltage (PWM) pattern of the ROM 10 on the basis of an arbitrary position detection timing. Computer 11. The control circuit 11 has the function of the control circuit 6 shown in FIG.

The contents of the ROM 10 will be specifically described. First, the synchronous motor is represented by a block diagram shown in FIG. V is a DC voltage applied to the motor 4, 1 / (LS +
R) is a transfer function based on the inductance L and resistance R of the motor coil, kB is a transfer function for converting current and torque, and 1 / J.
S is a moment of a load or the like, Tl is a load torque, E is an induced voltage, and is generated in proportion to the rotational angular velocity ω. According to FIG. 2, the ideal feedback system of the DC motor is expressed as a speed feedback system regarding the induced voltage constant k and the magnetic flux density B. For details, refer to other books and the like.

However, due to the structural origin of the motor 4,
Since the feedback loop is distorted, if the motor 4 is driven without considering the distortion, the distortion becomes a harmonic component, and the torque includes an oscillating component, which has been described in the conventional example. Appears as negative torque. Therefore,
The motor 4 is operated by superimposing a voltage component such that a harmonic component included in the induced voltage, particularly a harmonic component that becomes an oscillation torque, into a positive torque is applied to the voltage applied to the motor 4. Empirically find a voltage pattern that provides high efficiency.

When the motor 4 is a three-phase four-pole motor, as shown in FIG. 3, the voltage pattern only needs to be a half turn (energization 1 to N), and the position detection interval is equally divided into n. According to this division number, n data are obtained. Also,
The voltage pattern is the duty of the PWM output timer, and the maximum value of the magnitude is set to, for example, 100%.

Next, the operation of the control device having the above configuration will be described. First, the control circuit 11 calculates the phase angle and switches the energization based on the position detection signal from the position detection circuit 5 in the same manner as in the related art, and controls the rotation of the motor 4 by the PWM control method. At this time, the control circuit 11 measures the position detection interval time based on the position detection signal, and calculates, for example, a division time of the position detection interval time Tm-1 at the timing A of the position detection. That is, the division time (Tm-1 / n) is obtained by dividing the position detection interval time Tm-1 already measured by the division number n. Note that the division time may be obtained by dividing the average value of the past plurality of position detection interval times by the division number n.

Subsequently, a voltage pattern (duty value of PWM) is read from the ROM 10 for each energization switching corresponding to the energization 1 to N, and the read duty value is set in the PWM timer, and the divided time (Tm) is set. Every time (−1 / n) elapses, the read duty value is sequentially set in the PWM timer. As a result, a voltage for operating the motor 4 most efficiently is applied,
That is, the negative torque is effectively used as the positive torque.

When the present invention is applied to variable speed control, unless the optimum duty value is set in the PWM timer according to the rotation speed, the negative torque cannot be used effectively as the positive torque, and the motor 4 Is not operated most efficiently. For this reason, a PWM buffer storing a reference value determined in advance in consideration of the rotation speed range in the internal RAM of the control circuit 11 is secured, and the reference value of the PWM buffer is increased or decreased according to the rotation speed. The increased or decreased value is set in the PWM timer in consideration of the duty value read from the ROM 10. The variable range for increasing or decreasing the reference value of the PWM buffer is 0 or the maximum duty of the voltage pattern, stopping at 0, full duty at the maximum value, and increasing or decreasing the value during speed acceleration.
At the time of speed deceleration, the value of the increase / decrease is set to minus.

As a method of increasing or decreasing the reference value of the PWM buffer to take into account the PWM duty value, for example, as shown in FIG.
The reference value of the M buffer (the duty increased or decreased according to the current rotational speed) is multiplied by the duty value of the ROM 10, and the result is divided by the maximum duty of the voltage pattern (for example, 100%). The duty value obtained by this calculation is set as an output duty in the PWM timer, and the duty value obtained by this calculation is sequentially set in the PWM timer for each division time (Tm-1 / n) of the position detection interval as described above. I do.

The calculation of the output duty is performed, for example, only for the position detection interval (for n units). Therefore, the output duty is counted, for example, the number of times the PWM timer is set is counted, and when this count value reaches a preset value (number of divisions n), the duty value is obtained again by the above-described calculation, and the PWM timer is calculated. set. When the above process is repeated and the voltage pattern for a half turn makes one round, the same process is repeated again from the first voltage pattern.
As a result, even when the speed variable control is performed, the voltage that drives the motor 4 most efficiently is applied, that is, the negative torque is effectively used as the positive torque.

At the time of deceleration, for example, the current position detection interval time Tm is longer than the previous position detection interval time Tm-1, that is, Tm> (Tm-1 / n) .n. The output duty at the end of is insufficient. Therefore, the calculated last output duty is continued to the end of the section of the current position detection interval time Tm to compensate for the shortage.
In this case, the n-th output duty in the current section is P
After the WM timer has been set, the counter for counting the number of times the PWM timer has been set is stopped so that the output duty calculation process is not performed.

During acceleration, for example, the current position detection interval time Tm is shorter than the previous position detection interval time Tm-1, that is, Tm <(Tm-1 / n) · n, and the calculated interval The next position detection timing comes before the last of the output duty is set in the PWM timer.
Therefore, when the position detection timing is obtained, the next energization is forcibly performed without setting the remaining output duty to the PWM timer, that is, the output which becomes the voltage pattern for the next energization as described above. The duty is calculated, and the duty is sequentially set in the PWM timer.

In the above-described embodiment, the case where the terminal voltages of the three-phase armature windings U, V, and W are filtered has been described. The present invention is also applicable to a case where a position detection (energization switching) timing is obtained using a voltage waveform (induced voltage waveform) obtained by combining three-phase terminal voltages.

[0027]

According to the present invention described above, the following effects can be obtained. According to the present invention, a motor is operated by superimposing a voltage component such that a harmonic component included in an induced voltage is set to a positive torque on an applied voltage of the motor in advance, and a waveform pattern (voltage (PWM) pattern is obtained and stored in the ROM, and the switching element is PWM-controlled using the waveform pattern of the ROM to apply a voltage to the motor to drive the motor. The torque contributes as a positive torque, so that the motor torque can be effectively generated and the motor can be driven with high efficiency.

As the waveform pattern stored in the ROM, a voltage component that makes the vibration torque of the motor a positive torque by a harmonic component included in the induced voltage is superimposed on the applied voltage of the motor, so that the motor is driven. During the operation, since the applied voltage is equivalent to the applied voltage in the case of the most efficient operation at the time of the operation, the vibration torque that is a negative torque contributes as a positive torque and only exerts the effects described above. In addition, there is an effect of suppressing vibration of the motor.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a control device according to a first embodiment of the present invention, to which a motor control method is applied;

FIG. 2 is a schematic block diagram of a motor for explaining the operation of the control device shown in FIG. 1;

FIG. 3 is a schematic time chart for explaining the operation of the control device shown in FIG. 1;

FIG. 4 is a schematic block diagram of a conventional motor control device.

FIG. 5 is a schematic diagram of an induced voltage waveform and a harmonic waveform for explaining the problem of the control device shown in FIG. 4;

[Explanation of symbols]

 4 Motor (sensorless DC motor) 5 Position detection circuit 6, 11 Control circuit (microcomputer) 10 ROM

Claims (8)

[Claims] 1. A DC voltage is switched by a switching element of an inverter and applied to the motor, and a position detection signal is obtained by an induced voltage generated in a non-energized phase of the motor.
The position of the rotor is detected based on the position detection signal, and the energization of the motor is switched.
In the motor control method for driving the motor by performing WM control, the motor is operated by superimposing a voltage component such that a harmonic component included in the induced voltage is a positive torque on the applied voltage of the motor in advance. A waveform pattern (voltage (PWM) pattern) corresponding to the applied voltage during the operation is obtained and stored in the ROM, and the switching element is PWM-controlled using the waveform pattern of the ROM to drive the motor. A method for controlling a brushless motor. 2. A DC voltage is switched by a switching element of an inverter and applied to the motor, and a position detection signal is obtained by an induced voltage generated in a non-energized phase of the motor.
The position of the rotor is detected based on the position detection signal, and the energization of the motor is switched.
In a motor control method for driving the motor by performing WM control, a voltage component such that a vibration torque of the motor due to a harmonic component included in the induced voltage is set to a positive torque is superimposed on a voltage applied to the motor in advance. Waveform pattern (voltage (PWM) pattern) corresponding to the applied voltage when the motor is operated in the most efficient manner.
And controlling the switching element by PWM using the waveform pattern of the ROM to drive the motor. 3. The waveform pattern of the ROM divides an interval for detecting the position of the motor into a plurality of equal parts, and a PW
M is obtained by calculating the duty of the motor.
When performing the M control, the position detection signal of the motor is used to measure the time of the position detection interval, and the position detection interval is divided by the number of equal divisions to generate the output timing of the waveform pattern. 3. The motor control method according to claim 1, wherein a waveform pattern of the ROM is output at the generated output timing based on a detection signal. 4. The motor according to claim 3, wherein the position detection interval time is obtained from a previous position detection and a current position detection, or obtained by averaging a plurality of previous position detection intervals. Control method. 5. In the speed control of the motor, a reference PWM buffer is prepared in advance.
Increase or decrease the value of the buffer for the motor according to the number of rotations of the motor,
5. The motor control method according to claim 1, wherein the value of the PWM buffer is added to the waveform pattern of the ROM. 6. The PWM buffer stores in advance a value that is a reference in consideration of the speed control range.
A method of adding the value of the buffer for ROM to the waveform pattern of the ROM is such that the value of the buffer for PWM is multiplied by the waveform pattern of the ROM, and the value is divided by the maximum value of the waveform pattern. 6. The motor control method according to claim 5, wherein the control is performed in accordance with the rotation speed control, and the recalculation result corresponds to the speed control of the motor. 7. In the deceleration control of the speed control of the motor, after outputting a waveform pattern at each position detection interval, the last waveform pattern of the same waveform pattern is continuously output until the next position detection is performed. The motor control method according to claim 5 or 6, wherein the output is performed. 8. In the acceleration control of the motor speed control, when the next position is detected before outputting the waveform pattern at each position detection interval, the waveform pattern at the next position detection interval is forcibly applied. The motor control method according to claim 5, wherein the control signal is output.