JPH09285177A - Control of brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen possibilities of abnormal stoppage of a brushless motor due to a bad start-up and make it possible to surely shift to a position detecting operation mode by confirming that the motor has started up stably when starting up the motor using a position detecting operation and a synchronous operation. SOLUTION: A controlling circuit 11 supplies a predetermined voltage to a brushless motor 4 and starts it up, After it starts up the motor, it detects the position of a rotor based on output position detection signals of a position detecting circuit 10. Each time the position of the rotor is detected, the current conduction of armature windings U, V, W of the brushless motor 4 is switched. If the position cannot be detected within predetermined period of time, the current conduction of the armature windings is forcibly switched. When the conduction is switched at a given number of times and then an operation mode is shifted to a position detecting operation mode, the stability of rotation checked, based on the information (whether the position detection has been conducted, intervals of position detections, etc.) so far. When the rotation is judged unstable, the motor is restarted. When the rotation is judged stable, the operation mode is shifted to the position detecting operation mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a start-up control technology for a sensorless DC brushless motor (hereinafter referred to as a brushless motor) used for a motor such as a compressor, and more particularly, it enables a stable start and a reliable position detection operation mode. The present invention relates to a control method of a brushless motor that enables the transition to the.

[0002]

2. Description of the Related Art In this brushless motor control method, the position of a rotor is detected by using an induced voltage generated in a non-energized phase (non-energized armature winding) of the brushless motor. Then, the energization of the armature winding current of the brushless motor is switched.

At the start of the brushless motor start-up, since the rotor is stopped and no induced voltage is generated, synchronous operation or the like is performed. Thereafter, the brush is accelerated to an appropriate speed, and when the induced voltage is sufficiently generated, The mode is changed from synchronous operation to position detection operation.

Therefore, for example, the control device shown in FIG. 8 is required. In this control device, an AC / DC converter 2 converts an AC power supply 1 into a predetermined DC power supply, and this DC power supply is converted into switching elements Ua, Va, Wa, X,
Brushless motor (DCM) switching by Y, Z
4 armature windings.

The position detection circuit 5 outputs a position detection signal (solid line and alternate long and two short dashes line in FIG. 8) obtained by passing the terminal voltage of the brushless motor 4 to an analog integration circuit or the like to a control circuit (microcomputer) 6 for control. The circuit 6 uses the position detection signal to switch the switching elements Ua, V of the inverter unit 3.
A, Wa, X, Y, and Z are driven in a predetermined manner to switch the energization of the armature winding current of the brushless motor 4.

Recently, a digital system is expected to be improved in accuracy and efficiency. In this digital system, the position detection circuit 5 shown in FIG. 8 uses a terminal voltage (induced voltage) of the armature winding and a reference voltage. The voltage is compared and the comparison result (position detection signal) is output to the control circuit 6.

The control circuit 6 executes the rotor position detection processing based on the position detection signal, calculates the energization switching timing (mechanical angle 30 degrees or 90 degrees) of the brushless motor 4 based on this position detection, Energization is switched at this timing.

According to this digital system, since the position detection circuit 5 does not use an analog integration circuit or the like, energization switching during the position detection operation can be controlled with high accuracy, and from the synchronous operation of start to the position detection operation. The mode transition can be performed in a short time.

It is preferable to perform the start-up in accordance with such a digital control method, and it is conceivable that the optimum position-detecting operation for digital position detection and the synchronous operation are used together.

In this case, the fact that an induced voltage is generated in the non-energized armature winding from the start of energization of the armature winding current of the brushless motor 4 is used to detect the rotor position by this induced voltage. When the position is detected, the position detection operation for switching the energization at the same position detection point is executed, and when the position is not detected, the synchronous operation for switching the energization is executed at a predetermined time.

[0011]

However, at the time of starting the brushless motor 4, it is necessary to carry out synchronous operation at the start of the brushless motor 4. At this time, the starting characteristics fluctuate due to heavy load and the like, and the rotating magnetic field is changed. The rotor and the rotor are out of phase, which means that the startup may not be stable, resulting in step-out.

If the mode shifts to the position detection operation with such a step-out condition, that is, the so-called start failure, the brushless motor 4 vibrates and an overcurrent flows due to the lock current, resulting in an abnormal stop. Start again,
It is necessary to perform the transition process to the position detection operation mode.

The present invention has been made in view of the above problems, and an object thereof is to make it possible to confirm the stabilization of the start-up when the start-up is performed by using both the position detection operation and the synchronous operation, and it is possible to confirm the abnormality due to the start-up failure. It is an object of the present invention to provide a control method of a brushless motor that can significantly reduce the probability of stoppage and can surely shift to the position detection operation mode.

[0014]

In order to achieve the above object, the present invention is a method for controlling a brushless motor, which starts a brushless motor and shifts to a subsequent position detection operation. The position of the rotor of the brushless motor is detected, and when the position of the rotor is detected, the energization of the armature winding current of the brushless motor is switched based on the same position detection. While forcibly switching the energization of the armature winding current, at least the position detection can be performed a predetermined number of times continuously as the stable condition at the time of startup, and when the stable condition is not satisfied, the brushless motor is restarted. It is characterized by doing so.

In the brushless motor control method of the present invention, the position of the rotor of the brushless motor is detected from the start of starting the brushless motor, and when the position of the rotor is detected, the position of the rotor is detected. The energization of the armature winding current of the brushless motor is switched, and the energization of the armature winding current is forcibly switched within a predetermined time when there is no position detection, while at least the maximum and minimum of the position detection intervals It is characterized in that the ratio with the value is within a predetermined value as the starting stable condition, and when the stable condition is not satisfied, the brushless motor is restarted.

In the brushless motor control method of the present invention, the position of the rotor of the brushless motor is detected from the start of activation of the brushless motor, and when the position of the rotor is detected, the position is detected based on the same position detection. Switching the energization of the armature winding current of the brushless motor, forcibly switching the energization of the armature winding current in a predetermined time when there is no position detection, while at least the brushless motor of the brushless motor when performing the mode transition. It is characterized in that the rotation speed is within a predetermined margin as the starting stable condition, and when the stable condition is not satisfied, the brushless motor is restarted.

In the brushless motor control method of the present invention, the position of the rotor of the brushless motor is detected from the start of activation of the brushless motor, and when the position of the rotor is detected, the position is detected based on the same position detection. Switching the energization of the armature winding current of the brushless motor, forcibly switching the energization of the armature winding current in a predetermined time when there is no position detection, while the position detection can be performed a predetermined number of times continuously, The ratio of the maximum value and the minimum value among the position detection intervals is within a predetermined value or the same interval is constant, and the number of rotations of the brushless motor is within a predetermined margin when performing the mode transition. If there is at least two stable conditions among the three stable conditions, the brushless motor is It is characterized in that so as to restart.

In this case, when the number of energization switching of the armature winding current of the brushless motor reaches a predetermined value,
It may be determined whether or not the stability condition is satisfied.

Further, when the stable condition is not satisfied even after a lapse of a predetermined time from the start of the brushless motor, the brushless motor may be restarted. Further, it is preferable that the restart is performed a predetermined number of times. Furthermore, when the stability condition is satisfied, the brushless motor may be switched to the position detection operation mode.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. FIG.
In FIG. 8, the same parts as those in FIG.

Referring to FIG. 1, the control device to which the brushless motor control method of the present invention is applied inputs the terminal voltage (including the induced voltage) of the brushless motor 4 to the position detection circuit 10, and the terminal voltage (induced voltage). Is obtained, and the neutral point voltage is compared with a reference voltage (for example, ½ of the terminal voltage) to obtain a position detection signal, which is supplied to the control circuit 11 (microcomputer).

In addition to the function of the control circuit 6 shown in FIG. 6, the control circuit 11 has the same function when the rotor position can be detected by the position detection signal from the position detection circuit 10 when the brushless motor 4 is started. By detecting the position, the switching elements Ua, Va, Wa, X, Y, Z of the inverter unit 3 are driven in a predetermined manner to switch the energization of the armature windings U, V, W, and the position of the rotor is detected within a predetermined time. When it is not possible to do so, energization is forcibly switched.

Further, when the mode is shifted from the start (hybrid start) using both the position detecting operation and the synchronous operation described above to the position detecting operation, the control circuit 11 confirms a stable state at the time of starting (while starting). If it is unstable, it restarts, and if it is stable, it shifts to the position detection operation mode.

A continuous position detection signal (position detection) is used as a stability index (stable condition) of the start, and the energization switching interval and the position detection interval are substantially constant (the maximum value and the minimum value of the interval are The ratio is within a predetermined range), the period time (or rotation speed) is within a preset margin, etc.

In the position detection operation after the mode transition, the position of the rotor is detected by the position detection signal, the energization switching timing is calculated with reference to this position detection, and the energization of the brushless motor 4 is switched.

Next, the operation of the control device adopting the digital system will be described with reference to the schematic diagrams of FIGS. 2 and 4, the flowchart of FIG. 3, and the time charts of FIGS. 5 and 6. . In addition, in this embodiment, the case of the PWM control of the voltage variable system which is generally adopted will be described as an example.

First, in order to start the brushless motor 4, the control circuit 11 generates a driving signal for synchronous operation based on the starting parameter to drive a plurality of transistors of the inverter unit 3, and the armature winding of the brushless motor 4. Switch the power on. A rotating magnetic field is generated in the stator due to this switching of energization, and the rotor rotates so as to follow the rotating magnetic field.

Then, since an induced voltage is generated in the non-conducting armature winding of the brushless motor 4, the position detection circuit 1
0 outputs the position detection signal at the intersection (position detection) of the neutral point voltage including the induced voltage and the reference voltage to the control circuit 11.

The control circuit 11 switches the energization of the armature winding current by the position detection when the position detection is obtained by the position detection signal, and switches the energization at a predetermined time when the position detection is not obtained. Drive.

In the start-up (hybrid start-up) in which the position detection operation and the synchronous operation are used in combination, the locked state or the reverse rotation may occur immediately after the start depending on the position of the rotor.
Although it is unstable, if the rotating magnetic field of the stator and the rotor are in phase, stable position detection becomes possible.

Therefore, in the present invention, as shown in FIG. 2, the stable state is determined based on information such as position detection from a mode transition point (at a time point when energization switching is performed a predetermined number of times) to a predetermined time.

First, the control circuit 11 determines whether or not the rotor position is detected by the input position detection signal (step ST1). As shown in FIG. 4, when the synchronous operation is performed without position detection, that is, when there is no position detection and the energization is forcibly switched at a predetermined time, the internal n-bit buffer is used as the data without position detection this time. 1 is set to 0 (step ST2), and when position detection is performed and position detection operation is performed, 1 is set to 1 bit of the n-bit buffer as the data with the current position detection (step ST3).

In this case, when the n-bit buffer is already full, the lowest bit (LSB) of the n-bit buffer is returned to rewrite. That is, n pieces of position detection information are always stored.

Subsequently, the time of the position detection interval (or the energization switching interval) is measured using the internal counter and stored in the internal memory (step ST4), and it is determined whether or not the energization switching has been performed a predetermined number of times (step). ST5). As shown in FIG. 4, the internal memory stores the measurement time corresponding to each phase.

When the energization has not been performed for the predetermined number of times, the energization is switched (step ST6), the process returns to step ST1 and the above-mentioned processing is repeated. The energization switching at this time is performed by either the position detection operation or the synchronous operation. When the power has been supplied a predetermined number of times, the process proceeds from step ST5 to ST7, and it is determined whether or not the above-described stability condition is satisfied.

The data of all bits of the n-bit buffer is 1
If so, it is determined that there is a continuous position detection signal (position detection), but if there is even 1 bit of 0 data, it is determined that the activation has failed and the process proceeds from step ST7 to ST8 to determine whether the activation has failed a predetermined number of times. to decide. When the number of failure to start has not reached the predetermined number, the start parameters are initialized (restarted) (step ST9), and the process returns to step ST1. That is, if there is a missing position in the rotor position detection, the rotor is in an unstable rotation state, and the mode cannot be shifted to position detection operation.

Further, as shown in FIG. 5, the maximum value Tmax and the minimum value Tmi of the position detection interval time of the internal memory.
If n is selected and the ratio Tmax / Tmin is equal to or less than a predetermined allowable value, it is determined that the position detection interval is almost constant and the rotation is stable, but if it exceeds the allowable value, the start fails. Then, the process proceeds from step ST7 to ST8 to execute the above-mentioned processing. In other words, even if the position can be detected, the position detection intervals are different, the rotational state is unstable, and there is a possibility of step out.

Further, as shown in FIG. 6, the position detection interval times of the internal memory are summed to obtain the time of the cycle T. For example, in the case of a three-phase, four-pole motor, the rotor mechanically makes half rotation when switching the one-cycle (six-phase) energization. Therefore,
As shown in FIG. 6, the total value of the total time T1 to T6 of 6 phases) is set as the cycle T, or the total time of 12 phases is set as the rotation cycle.

If the time of the cycle T is within a predetermined range (in other words, if the rotation speed is within a preset margin), it is determined that the start is stable, but within the predetermined range. If not entered, the process proceeds from step ST7 to ST8 to execute the above-described processing.

When all of the above-mentioned three conditions are satisfied, the process (routine) for shifting to the mode of the position detection operation is proceeded from step ST7, and when any one of the conditions is not satisfied, the system is restarted. It should be noted that when the restart is performed a predetermined number of times, it is determined to be abnormal and the restart process is not performed.

As described above, when the mode is changed from the startup to the position detection operation, the rotation state is confirmed by the information including the information traced back up to the number of times of the predetermined energization switching. If so, the mode shifts to position detection operation.

Therefore, restarting can be performed several times, the probability of abnormal stop due to startup failure after the mode shifts to position detection operation can be significantly reduced, and position detection can be performed reliably. It is possible to shift to the operation mode.

FIG. 7 is a flow chart for explaining another embodiment of the present invention. Detailed description of the same processes in FIG. 7 as those in FIG. 3 will be omitted. Step ST1
From 0 to ST13, go to ST1 to ST4, step S
T14 to ST7, steps ST15 and ST16 to ST5 and ST6, steps ST17 and ST1
8 corresponds to ST8 and ST9.

First, the control circuit 11 judges from the input position detection signal whether or not the rotor position is detected (step ST10). When the position detection cannot be performed and the synchronous operation is performed, that is, there is no position detection. When the energization is forcibly switched at a predetermined time, 0 is set in 1 bit of the internal n-bit buffer (step ST11). When the position can be detected and the position detecting operation is performed, 1 is set to 1 bit of the n-bit buffer (step ST1).
2).

Subsequently, the time of the position detection interval (or the energization switching interval) is measured using the internal counter and stored in the internal memory (step ST13). The internal memory stores the measurement time corresponding to each phase.

Then, it is judged whether or not the three stability conditions described in the previous embodiment are satisfied (step ST1).
4) If the three stable conditions are satisfied, the mode shifts to the position detection operation.

When the above three stability conditions are not satisfied, the process proceeds to step ST15, and it is determined whether or not the number of times of energization switching so far has reached a predetermined value (maximum value). It should be noted that instead of the number of times of energization switching, the time during which activation is performed (limit value) may be used. Further, the maximum value and the limit value are empirically obtained and set in advance.

When the number of times of energization switching has not reached the maximum value (or when the activation time has not reached the limit value), the process proceeds from step ST15 to ST16, the energization is switched and the process returns to step ST10. Repeat the process.

Even if the number of times of energization switching reaches the maximum value, if the above three stability conditions are not satisfied, step ST
The process proceeds from ST15 to ST17, and it is determined whether or not the start-up fails a predetermined number of times. When the predetermined number of times has not been reached, the start-up parameters are initialized (restarted) (step ST1).
8) Return to step ST10 and repeat the above-mentioned processing.

As described above, even if the number of times of energization switching does not reach the predetermined value (maximum value) at the time of start-up, the mode can be shifted to the position detection operation when the above three stable conditions are satisfied. Moreover, the mode can be surely shifted to the position detection operation.

Of the three stable conditions, only one stable condition may be adopted, or two of the three stable conditions may be combined and adopted. In this case, the less stable conditions are, the easier the control is, the control program can be simplified, and there is an advantage in cost.

[0052]

As described above, according to the first aspect of the invention of the brushless motor control method of the present invention,
It becomes possible to switch to the position detection operation mode after confirming the stable state of startup, without changing to the position detection operation mode while the startup failed, that is, to reduce the probability of abnormal stop due to startup failure. Therefore, there is a useful effect that the mode can be surely shifted to the position detection operation.

According to the second aspect of the present invention, it depends on whether the ratio between the maximum value and the minimum value of the rotor position detection interval is within a predetermined range at the time of start-up, or whether the position detection interval is constant. Since the stable state of startup is determined and the system is restarted when it is determined to be unstable, the same effect as that of claim 1 is achieved.

According to the third aspect of the present invention, a stable start-up state is obtained depending on whether or not the time of the cycle obtained by summing the rotor position detection intervals during start-up is within a predetermined margin (rotation speed is within a predetermined margin). When it is determined to be unstable, the system is restarted, so that the same effect as that of claim 1 can be obtained.

According to the fourth aspect of the present invention, at the time of start-up, the position detection can be continuously performed a predetermined number of times, and the ratio of the maximum value and the minimum value of the position detection intervals is within a predetermined value or the same interval can be set. It is assumed that the stability is constant and the rotation speed is within a predetermined margin, and the stability of the startup is judged by whether or not at least two of the three stable conditions are satisfied, and When it is judged to be stable, the system is restarted.
The stable state can be confirmed more severely than in the case of 2 or 3, and is more useful than the effect of claim 1, 2 or 3.

According to the invention of claim 5, claims 1, 2,
The stability determination of the start in 3 or 4 is made when the number of times of switching the energization of the armature winding current of the brushless motor reaches a predetermined value.
In addition to the above effect, it is possible to determine the stability of the startup after the startup for a predetermined time, the probability that a stable startup state is obtained becomes high, and the probability that the startup fails can be reduced.

According to the invention of claim 6, claims 1, 2,
In 3 or 4, the stable state of the start is determined within a predetermined time from the start.
In addition to the effect of 3 or 4, since the number of times of confirmation of stability increases, it is possible to more accurately determine the stability of startup, the probability of obtaining a stable startup state increases, and the probability of startup failure decreases. it can.

According to the invention of claim 7, claims 1, 2,
Since the restart is performed a predetermined number of times in 3, 4, 5 or 6, in addition to the effect of claim 1, 2, 3, 4, 5 or 6, the probability of abnormal stop due to startup failure can be made extremely small. it can.

According to the invention of claim 8, claims 1, 2,
In 3, 4, 5, 6 or 7, when the stable condition is satisfied, the mode is shifted to the position detection operation. Therefore, in addition to the effect of claim 1, 2, 3, 4, 5, 6 or 7, When applied to claim 6, the time at startup can be minimized, that is, the mode transition from startup to position detection operation can be performed in a short time.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram illustrating the operation of the control device shown in FIG. 1;

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

FIG. 4 is a schematic diagram illustrating the operation of the control device shown in FIG. 1;

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

FIG. 6 is a schematic time chart diagram for explaining the operation of the control device shown in FIG. 1.

FIG. 7 is a schematic flow chart for explaining a brushless motor control method according to another embodiment of the present invention.

FIG. 8 is a schematic block diagram of a conventional control device for a brushless motor.

[Explanation of symbols]

3 Inverter part 4 Brushless motor (sensorless DC brushless motor) 6,11 Control circuit (microcomputer) 10 Position detection circuit k Reference voltage U, V, W Armature winding (of brushless motor 4)

Claims (8)

[Claims] 1. A brushless motor control method for starting a brushless motor and then switching to a position detection operation mode, wherein the position of the rotor of the brushless motor is detected from the start of starting the brushless motor, When the position is detected, the energization of the armature winding current of the brushless motor is switched based on the same position detection, and when the position is not detected, the energization of the armature winding current is forcibly switched over in a predetermined time. On the other hand, the brushless motor control method is characterized in that at least the position detection can be continuously performed a predetermined number of times as a stable condition at the time of starting, and when the stable condition is not satisfied, the brushless motor is restarted. 2. A brushless motor control method for starting a brushless motor and then switching to a position detection operation mode, wherein the position of the rotor of the brushless motor is detected from the start of starting the brushless motor, When the position is detected, the energization of the armature winding current of the brushless motor is switched based on the same position detection, and when the position is not detected, the energization of the armature winding current is forcibly switched over in a predetermined time. On the other hand, at least the ratio between the maximum value and the minimum value of the position detection intervals is within a predetermined value as the starting stable condition, and when the stable condition is not satisfied, the brushless motor is restarted. A method for controlling a brushless motor, which is characterized in that: 3. A method of controlling a brushless motor, which starts a brushless motor and then shifts to a position detection operation, detects the position of the rotor of the brushless motor from the start of starting the brushless motor, and detects the position of the rotor. When the position is detected, the energization of the armature winding current of the brushless motor is switched based on the same position detection, and when the position is not detected, the energization of the armature winding current is forcibly switched over in a predetermined time. On the other hand, at the time of performing the mode transition, at least the rotation speed of the brushless motor is within a predetermined margin as the stable condition of the start,
A method of controlling a brushless motor, wherein the brushless motor is restarted when the stability condition is not satisfied. 4. A brushless motor control method for starting a brushless motor and then switching to a position detection operation mode, wherein the position of the rotor of the brushless motor is detected from the start of starting the brushless motor, When the position is detected, the energization of the armature winding current of the brushless motor is switched based on the same position detection, and when the position is not detected, the energization of the armature winding current is forcibly switched over in a predetermined time. On the other hand, the position detection can be performed a predetermined number of times continuously, the ratio of the maximum value and the minimum value of the position detection intervals is within a predetermined value, or the same interval is constant, and the mode transition When performing, the rotation speed of the brushless motor is within a predetermined margin as the starting stable condition, and at least one of the three stable conditions is set. A brushless motor control method characterized in that the brushless motor is restarted when neither of the two stability conditions is satisfied. 5. The method for determining whether or not the stability condition is satisfied when the number of times of switching the energization of the armature winding current of the brushless motor reaches a predetermined value. Alternatively, the control method of the brushless motor according to the fourth aspect. 6. The brushless motor is restarted when the stable condition is not satisfied even after a lapse of a predetermined time from the start of the brushless motor.
The method for controlling the brushless motor according to 2, 3, or 4. 7. The control method for a brushless motor according to claim 1, 2, 3, 4, 5 or 6, wherein the restart is performed a predetermined number of times. 8. The method of controlling a brushless motor according to claim 1, wherein the brushless motor is mode-shifted to a position detection operation when the stability condition is satisfied.