JP2002218787A - Controller of dc brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of sensorless position detection method of a DC brushless motor, wherein if the period of a spoke voltage is extended by a large motor current, a large motor reactance, etc., a period while a counter electromotive force of a rotor appears is reduced and the counter electromotive force will not cross the position-detection reference voltage, and hence the position of the rotor cannot be detected. SOLUTION: A current phase of a motor is controlled, so as to have the cross point of a counter electromotive force of a rotor appearing on a phase to which a current is not applied, hidden by a spike voltage. By controlling the phase of the rotor, which appears on the phase to which a current has not been applied, using this control method, reference voltage for the position detection and the counter electromotive force of the rotor can cross each other, so that stable position detection can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC brushless motor control device which detects a rotor position from a terminal voltage of a motor which appears in a non-energized phase of a DC brushless motor and performs speed control. It is.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional method for controlling a DC brushless motor to be energized at 120 degrees.

FIG. 8A is an explanatory diagram of a position detecting method.
1 is a motor U-phase terminal voltage, 2 is a U-phase current, 3 is a rotor back electromotive voltage, 4 is a position detection reference voltage, 5 is an intersection between the motor U-phase terminal voltage 1 and the position detection reference voltage 4, and 6 is a spike. Voltage. FIG. 8B is a drive circuit diagram, 7 is a DC brushless motor, 8 to 13 are switching elements, and 14 to
19 is a freewheeling diode, and 20 is a shunt resistor.

In FIG. 1A, considering only the U phase,
The periods I and II are the switching element 8 and the period I
V and V are periods when the switching element 11 is turned on,
Periods III and VI are periods in which both the switching elements 8 and 11 are off, and the U-phase motor terminal is open.
During this period, the back electromotive voltage 3 of the rotor appears at the terminal voltage 1 of the motor. Therefore, as shown in FIG. 2A, the rotor position is detected from the timing of the intersection 5 between the position detection reference voltage 4 and the motor terminal voltages 1 of periods III and VI, and the current phase with respect to the rotor position is determined. The speed of the motor is controlled by determining the applied voltage.

[0005]

However, in the above-mentioned conventional configuration, when the current phase is delayed, there is a problem that the rotor position cannot be detected depending on the magnitude of the motor current or the reactance of the motor.

First, in FIG. 8, periods III and VI
Will be described. FIG. 9 shows a change in the direction of the current in periods II to III. In the figure, the voltage on the collector side of the switching elements 8 to 10 is V _DC , and the voltage on the emitter side of the switching elements 11 to 13 is V _GND .

[0007] In period II, as shown in FIG.
During the period when the current flows from the phase to the W phase and the back electromotive voltage 3 of the period III rotor in which the phase of the upper arm is switched appears,
As shown in FIG. 9C, a current flows from the V phase to the W phase. The period in which the spike voltage 6 of the period III appears is a period in which the magnetic energy stored in the U-phase winding is released during the period II, and the energy is the free-wheeling diode 17, as shown in FIG. It is emitted by a circulating current flowing through the switching element 13. in this way,
Since the circulating current flows through the freewheel diode 17 during the period shown in FIG. 3B, the U-phase terminal voltage is substantially at V _GND , and the period of the spike voltage 6 is the period during which the circulating current flows.

If the period of the spike voltage 6 is prolonged due to factors such as a large motor current and a large reactance of the motor, the position detection by the method of FIG. 8A may not be possible. . FIG. 10 shows the relationship between the period of the spike voltage and the position detection in period III in FIG. 8A. As is clear from FIG. 10B, when the period of the spike voltage 6 is long, the period in which the back electromotive voltage 3 of the rotor appears becomes short, and the position detection reference voltage 4
The case where it does not cross occurs, leading to loss of synchronism.

In particular, the case as shown in FIG. 10B is likely to occur for the following reasons. Generally, the current phase of the motor is changed as shown in FIG. The reason for performing the control as shown in the figure is that the larger the load, the greater the effect of the armature reaction, and generally, the longer the current phase, the higher the motor efficiency. Therefore, when the load is high, the period during which the back electromotive voltage of the rotor can be detected is short because the circulating current is large, and if the control for delaying the current phase is further performed, the back electromotive voltage 3 and the position of the rotor as shown in FIG. A case occurs where the detection reference voltage 4 does not cross. In such a case, the position detection reference voltage 4 and the rotor back electromotive voltage 3
, It becomes impossible to detect the rotor position, and the step-out occurs.

As described above, conventionally, if the period during which the circulating current flows is long, it has been a problem that position detection cannot be performed by the 120-degree conduction method. During the period when the circulating current flows,
Since it is determined by the amount of magnetic energy stored in the motor winding, the longer the motor current and the larger the motor reactance, the longer.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide a DC brushless motor control device capable of performing stable position detection even when a circulating current flows for a long period of time.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, position detection is performed by hiding an intersection 5 between a back electromotive voltage 3 and a reference voltage 4 of a rotor appearing in a non-energized phase with a spike voltage 6. The current phase of the motor is controlled to prevent it from becoming impossible.

By controlling the phase of the back electromotive voltage of the rotor appearing in the non-energized phase by the current phase control of the motor, it becomes possible to cross the reference voltage for position detection with the back electromotive voltage of the rotor, thereby achieving stable operation. Position detection becomes possible.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 controls a current phase of a motor so that an intersection of a back electromotive voltage of a rotor used for position detection of a rotor and a reference voltage is not hidden by a circulating current. It is. By controlling in this manner, the phase of the back electromotive voltage of the rotor that appears in the non-energized phase is adjusted even when the period in which the circulating current of the motor flows is long due to a large motor current or a large motor reactance. It is possible to detect the intersection of the back electromotive voltage of the rotor and the reference voltage during the non-energization period, and to perform stable position detection.

According to a second aspect of the present invention, in the first aspect of the present invention, as a form of the current phase control, a delay limit is provided for the current phase of the motor. By controlling in this way, even when the period during which the circulating current flows becomes long, the current phase is optimized within a range where the intersection of the back electromotive voltage of the rotor and the reference voltage can be detected in the non-energized phase. Control and stable position detection.

According to a third aspect of the present invention, in the first aspect of the invention, the current phase is controlled according to a period during which the circulating current flows. By performing such control, it is possible to prevent the intersection of the back electromotive voltage of the rotor and the reference voltage from being hidden by directly detecting the period in which the circulating current flows.

According to a fourth aspect of the present invention, in the first aspect, the current phase is controlled in accordance with the load of the motor. In the case of the same motor (having the same motor reactance), the period during which the circulating current flows is determined by the magnitude of the load. Therefore, when the load is large, it is determined that the period in which the circulating current flows indirectly is long, and by controlling the current phase, the intersection point of the back electromotive voltage of the rotor and the reference voltage is always set during the non-energized period. The position can be detected, and stable position detection can be performed even when the period during which the circulating current flows is long.

According to a fifth aspect of the present invention, in the first aspect, the current phase is controlled according to the average motor current. In the case of the same motor, the period during which the circulating current flows is substantially determined by the magnitude of the average motor current.
Therefore, when the average current is large, it is determined that the period in which the circulating current flows indirectly is long, and by controlling the current phase, the intersection of the back electromotive voltage of the rotor and the reference voltage can be determined during the non-energized period. Detection can be always performed, and stable position detection can be performed.

According to a sixth aspect of the present invention, in the first aspect of the invention, the current phase is controlled according to the rotation speed of the motor. In the case of the same motor and the same load, the period during which the circulating current flows is substantially the same. When the circulating current flows in the same period, the period of each period is shorter as the rotation speed of the motor is higher.Therefore, the ratio of the period in which the circulating current flows in the non-energization period is larger, and the ratio between the back electromotive voltage of the rotor and the reference voltage is larger. Intersections are more likely to be hidden. Therefore, when the rotation speed of the motor is high, it is determined that the ratio of the period during which the circulating current flows during the non-energization period is large, and the current phase is controlled. The intersection of the reference voltage can always be detected,
Stable position detection can be performed.

According to a seventh aspect of the present invention, in the first aspect, the current phase is controlled according to the motor current and the rotation speed of the motor. In the case of the same motor, it can be determined that the larger the motor current, the longer the period during which the circulating current flows, and the higher the rotation speed of the motor, the higher the ratio of the period during which the circulating current flows during the non-energized period. Therefore, by performing such control, the intersection of the back electromotive voltage of the rotor and the reference voltage can be always detected during the non-energized period, and stable position detection can be performed.

According to an eighth aspect of the present invention, in the third aspect, a period during which the circulating current flows is detected from a terminal voltage of the motor. By using this method, the period in which the circulating current flows can be directly detected relatively easily, and the control according to claim 3 can be easily and accurately performed.

According to a ninth aspect of the present invention, in the third aspect of the present invention, a period during which a circulating current flows is detected from a voltage across the shunt resistor. Further, according to the present invention, an average motor current can be detected. By using this method, it is possible to directly detect the period during which the circulating current flows and the average value of the motor current, and it is possible to perform the control of claims 3 to 5 or both.

[0023]

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

(Embodiment 1) FIG. 1 shows a method of detecting the position of a rotor at 120-degree energization according to Embodiment 1 of the present invention. In FIG. 1, 1 is a motor U-phase terminal voltage, 2 is a U-phase current,
3 is a back electromotive voltage of the rotor, 4 is a position detection reference voltage, and 6 is a spike voltage.

FIG. 1 shows that the period in which the circulating current flows is longer due to factors such as a large motor current or a large motor reactance as compared with the conventional example of FIG. It is a figure in the case where becomes long. In such a case, especially when the load of the motor is large, the current phase is delayed in order to increase the efficiency as shown in FIG. With this control, there is a problem that the position detection reference voltage 4 does not intersect with the back electromotive voltage 3 of the rotor appearing in the terminal voltage 1 as shown in FIG. Was.

On the other hand, in the first embodiment, by advancing the current phase as shown in FIG. 1, the back electromotive voltage 3 of the rotor appearing at the terminal voltage 1 and the position detection reference voltage 4 can be crossed. When the current phase is advanced, the phase of the back electromotive voltage 3 of the rotor is delayed with respect to the terminal voltage 1 and an intersection with the reference voltage 4 appears, so that the rotor position can be detected.

Therefore, by limiting the current phase variable range as described above, it is possible to detect the intersection of the back electromotive voltage of the rotor and the reference voltage during the non-energized period even when the period during which the circulating current flows is long. Thus, stable position detection can be performed.

(Embodiment 2) FIG. 2 shows the relationship between the current circulation period and the current phase control in Embodiment 2. As shown in FIG. 2, in the second embodiment, a delay limit is provided for the current phase according to the period during which the circulating current flows, and control is performed so that the current phase does not delay beyond the limit.

As described above, when the load on the motor is large, the current phase is generally delayed in order to obtain the maximum efficiency. In the second embodiment, the range of the delay is controlled so that the position of the rotor can be detected. Things.

Therefore, by limiting the current phase variable range as described above, even when the period in which the circulating current flows is long, the current phase is controlled so that the intersection between the back electromotive voltage of the rotor and the reference voltage is not hidden. It is possible to do.

(Embodiment 3) FIG. 3 shows the relationship between the magnitude of the motor load and the current phase control in Embodiment 3. As shown in FIG. 3, in the third embodiment, a delay limit is provided for the current phase according to the magnitude of the motor load, and control is performed so that the current phase does not delay beyond the limit.

Same motor (same motor reactance)
In this case, the period and the absolute value of the circulating current flow are determined by the magnitude of the load. Therefore, when the load is large, it is possible to indirectly determine that the period during which the circulating current flows is long and control the current phase.

Therefore, by using this embodiment,
It is possible to indirectly detect the circulation period of the motor current,
The current phase can be controlled so that the intersection between the back electromotive voltage of the rotor and the reference voltage is not hidden.

(Embodiment 4) FIG. 4 shows the relationship between the average current of the motor and the current phase control in Embodiment 4. FIG. 4
As described above, in the fourth embodiment, a delay limit is set in the current phase according to the average current of the motor, and control is performed so that the current phase does not delay beyond the limit.

In the case of the same motor, the period during which the circulating current flows and the absolute value are determined by the magnitude of the average current of the motor.
When the average current of the motor is large, it is determined that the period in which the circulating current flows is long, and the current phase can be controlled.

Therefore, by using this embodiment,
The current circulation period can be detected indirectly, and the current phase can be controlled so that the intersection between the back electromotive voltage of the rotor and the reference voltage is not hidden.

(Embodiment 5) FIG. 5 shows the relationship between the rotation speed of the motor and the current phase control in Embodiment 5. As shown in FIG. 5, in the fifth embodiment, a delay limit is provided for the current phase according to the rotation speed of the motor, and control is performed so that the current phase does not delay beyond the limit.

When the load of the motor can be predicted for the same motor, the period during which the circulating current flows can also be predicted. When the period of the circulating current is the same, the period of each period is shorter as the rotation speed of the motor is higher.Therefore, the ratio of the period during which the circulating current flows during the non-energization period is larger, and the intersection between the back electromotive voltage of the rotor and the reference voltage is Easy to hide by spike voltage. Therefore, when the rotation speed of the motor is high, it is determined that the ratio of the period during which the circulating current flows during the non-energization period is large, and the current phase can be controlled.

Therefore, by using this embodiment,
By indirectly detecting the ratio of the current circulation period in the non-energization period, the current phase can be controlled so that the intersection between the back electromotive voltage of the rotor and the reference voltage is not hidden.

(Embodiment 6) FIG. 6 shows a means for detecting a period during which a circulating current flows in Embodiment 6. FIG.
In the case of AM (pulse amplitude modulation) control, (b) shows PWM.
This is the case of (pulse width modulation) control. In the figure, 2
Reference numeral 1 denotes a period during which a circulating current flows.

In the sixth embodiment, as shown in FIG. 6, the period in which the circulating current flows is detected by measuring the period of the spike voltage 6 that appears in the motor terminal voltage 1. In both cases (a) and (b), the measurement starts counting the timer immediately after the switching of the energized phase, and measures the time until the first falling or rising voltage is detected. As is clear from FIG. 3B, the period during which the circulating current flows can also be detected during the PWM control.

As described above, in the sixth embodiment, the period in which the circulating current flows is detected from the spike voltage period that appears in the motor terminal voltage 1 as shown in FIG. 6, and the current phase is controlled as shown in the second embodiment.

By using such a method, the period in which the circulating current flows can be detected directly and relatively easily, and the current phase is adjusted so that the intersection between the back electromotive voltage of the rotor and the reference voltage is not hidden. Can be controlled.

(Embodiment 7) FIG. 7 shows a means for detecting a period during which a circulating current flows in Embodiment 7. FIG. 7A shows P
In the case of the AM control, (b) shows the case of the PWM control.

In the seventh embodiment, as shown in FIG. 7, the period during which a circulating current appearing in the voltage across the shunt resistor flows is measured. In both cases (a) and (b) of FIG.
The time until the rising voltage detected first exceeds a certain determination value is measured. In this manner, the period during which the circulating current flows is detected from the voltage across the shunt resistor, and the current phase control as described in the second embodiment is performed.

Further, in the seventh embodiment, the average current of the motor is detected by measuring the voltage across the shunt resistor, and the current phase control based on the motor current shown in the fourth embodiment is simultaneously performed.

Therefore, in the seventh embodiment, by detecting the absolute value of the motor current and the period during which the circulating current flows, the current phase can be controlled so that the intersection between the back electromotive voltage of the rotor and the reference voltage is not hidden. it can.

The present invention is not limited to the above embodiment, and for example, the following modifications are possible.

That is, first, Embodiment 2 of the present invention
Alternatively, the circulating current detection method and the phase control method described in the seventh embodiment may be combined.

Further, the relationship between the current phase control element and the current phase described in any of the second to fifth embodiments of the present invention may be changed into a linear shape, a step shape, or a curved shape for control. .

[0051]

As is apparent from the above embodiment, the invention according to the first aspect of the present invention is designed to prevent the intersection of the back electromotive voltage of the rotor used for position detection and the reference voltage from being hidden by the circulating current. By controlling the current phase, it is possible to detect the intersection of the back electromotive voltage and the reference voltage of the rotor during the non-energized period even if the circulating current flows for a long period of time. Is achieved.

According to a second aspect of the present invention, in the first aspect of the present invention, the current phase is controlled by providing a delay limit to the current phase of the motor. The same effect as the invention described in Item 1 can be obtained.

According to a third aspect of the present invention, in the first aspect of the present invention, the current phase is controlled in accordance with the period during which the circulating current flows. Thus, the period during which the circulating current flows is directly detected. Accordingly, when the current phase is controlled, the intersection of the back electromotive voltage and the reference voltage of the rotor can be detected during the non-energized period even when the circulating current flows for a long period, and stable position detection can be performed. This has the effect.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the current phase is controlled according to the load of the motor. By judging that it is long and controlling the current phase, it is possible to detect the point of intersection of the back electromotive voltage of the rotor and the reference voltage during the non-energized period even if the period during which the circulating current flows is long. This has the effect that it can be performed.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the current phase is controlled in accordance with the average motor current. Is determined to be long and the current phase is controlled, so that even when the circulating current flows for a long time, the point of intersection between the back electromotive voltage of the rotor and the reference voltage can be detected during the non-energized period, and stable position detection Is achieved.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the current phase is controlled in accordance with the rotation speed of the motor.
When the rotation speed of the motor is high, it is determined that the ratio of the period in which the circulating current flows during the non-energization period is large, and the current phase is controlled. It is possible to detect the intersection of the back electromotive voltage of the rotor and the reference voltage, and it is possible to perform stable position detection.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the current phase is controlled according to the motor current and the rotation speed of the motor. The circulating current flows for a long period,
In addition, when the rotation speed of the motor is high, it is determined that the ratio of the period in which the circulating current flows is large, and the current phase is controlled. It is possible to detect the intersection of the electromotive voltage and the reference voltage, and it is possible to perform stable position detection.

According to an eighth aspect of the present invention, in the third aspect of the present invention, the period during which the circulating current flows is detected from the motor terminal voltage. There is an effect that a period during which a current flows can be detected.

According to a ninth aspect of the present invention, a period during which the circulating current flows according to the third aspect of the present invention and a motor average current according to the fifth aspect of the present invention are detected from the voltage across the shunt resistor. Yes, using this method,
It is possible to directly detect the period during which the circulating current flows and the average value of the motor current, so that there is an effect that the control of claim 3 or claim 5 or both can be performed.

[Brief description of the drawings]

FIG. 1 is a voltage-current waveform diagram according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a current phase control method according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a current phase control method according to a third embodiment of the present invention.

FIG. 4 is a diagram illustrating a current phase control method according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a current phase control method according to a fifth embodiment of the present invention.

FIG. 6A is a diagram showing a method of detecting a period during which a circulating current flows during PAM control according to the sixth embodiment of the present invention. (B) A method of detecting a period during which a circulating current flows during PWM control according to a sixth embodiment of the present invention. Illustration

FIG. 7A is a diagram illustrating a method of detecting a period during which a circulating current flows during PAM control according to a seventh embodiment of the present invention. (B) A method of detecting a period during which a circulating current flows during PWM control according to a seventh embodiment of the present invention. Illustration

8A is a diagram showing a rotor position detection method in a conventional 120-degree energization control, and FIG. 8B is a drive circuit diagram in a conventional 120-degree energization control.

9A is a diagram showing a current direction of a period II in a conventional 120-degree conduction control. FIG. 9B is a diagram showing a period II in a conventional 120-degree conduction control.
FIG. 11C shows the current direction during the spike voltage period of I. (c) Period II in the conventional 120-degree conduction control
The figure which shows the current direction of the back electromotive force period of the rotor of I

10A is a current-voltage characteristic diagram of the conventional example when the spike voltage is short; and FIG. 10B is a current-voltage characteristic diagram of the conventional example when the spike voltage is long.

FIG. 11 is a conceptual diagram showing a current phase control method for obtaining high efficiency in a conventional example.

[Explanation of symbols]

Reference Signs List 1 Motor U-phase terminal voltage 2 U-phase current 3 Rotor back electromotive voltage 4 Position detection reference voltage 5 Intersection between motor U-phase terminal voltage 1 and position detection reference voltage 4 6 Spike voltage 7 DC brushless motor 8, 9, 10, 10, 11, 12, 13 switching element 14, 15, 16, 17, 18, 19 free-wheeling diode 20 shunt resistor 21 period of circulating current 22 phase switching point

Claims (9)

[Claims] 1. A sensorless control device for a DC brushless motor, comprising: means for detecting a rotor position based on an intersection between a back electromotive voltage of a rotor and a reference voltage which appears during a non-energization period of a stator winding; Means for controlling the current phase of the motor (the phase of the motor current with respect to the back electromotive voltage of the rotor) so that the intersection with the reference voltage does not overlap with the circulation period of the current in which the motor current flows in the non-energized phase. A control device for a DC brushless motor. 2. A motor current phase control means for preventing an intersection between a back electromotive voltage of the rotor and a reference voltage from being hidden by overlapping with a circulation period of a motor current flowing in a non-energized phase. 2. A control device for a DC brushless motor according to claim 1, wherein means for providing a delay limit to the current phase of the motor is used. 3. The DC according to claim 1, wherein said motor current phase control means includes means for controlling a current phase in accordance with a circulation period of a current in which a motor current flows in a non-energized phase. Control device for brushless motor. 4. The DC brushless motor control device according to claim 1, wherein a means for controlling the current phase according to the load of the motor is used as the means for controlling the current phase of the motor. 5. The control device for a DC brushless motor according to claim 1, wherein a means for controlling a current phase according to an average current of the motor is used as the means for controlling the current phase of the motor. 6. The DC brushless motor control device according to claim 1, wherein a means for controlling the current phase according to the rotation speed of the motor is used as the means for controlling the current phase of the motor. 7. The DC brushless motor control according to claim 1, wherein a means for controlling a current phase according to an average current of the motor and a rotation speed of the motor is used as the means for controlling the current phase of the motor. apparatus. 8. The DC brushless motor control device according to claim 3, wherein the current circulation period is detected from a terminal voltage of the motor. 9. The DC brushless motor control device according to claim 3, wherein the current circulation period and the magnitude of the motor current are detected from the voltage across the shunt resistor.