JP2001275384A - Method and apparatus for controlling motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the problems due to displacement of a position detection sensor from its installation position or variation in its accuracy and compensate fluctuations in commutation phase angle for enhanced quality and reliability, with respect to the controlling method for a motor with the sensor. SOLUTION: The phase current of the motor is detected (step ST1). The phase difference between the voltage across armature windings (drive voltage) of the motor and its phase current is detected, and the phase difference is compared with a preset constant value (t) to determine which is larger (Step ST2). If the phase difference is smaller than the constant value (t), the time period from motor position detection to excitation switching is shortened (step ST3), but if the phase difference is larger than the constant value (t), the time period from motor position detection to excitation switching is lengthened (step ST4). Thus, the phase difference is kept equal to the constant value (t).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of detecting the position of a rotor of a motor (eg, a brushless DC motor with a sensor) by a position detecting sensor such as a Hall element, and changing the polarity of a driving current of a winding by detecting the position. More particularly, the present invention relates to a motor control method and a motor control method for compensating for a change in a current phase angle due to a position shift or an error of the current detection sensor.

[0002]

2. Description of the Related Art In a motor control method, for example, a control device shown in FIG. 4 is required. 4, a DC power supply DC is switched by switching elements Ua, Va, Wa, X, Y, and Z of upper and lower arms of an inverter circuit 1 and applied to a motor (for example, a three-phase four-pole motor) 2 as a three-phase sine wave voltage. Then, a drive current is supplied to the motor 2 to obtain a rotational torque.

[0003] Three position detecting sensors 3 (for example, Hall elements) are disposed at predetermined positions of the motor 2 at 120-degree intervals, and output signals of these position detecting sensors 3 are input to a position detecting circuit 4. 5 (a), and inputs the position detection signal to the control circuit (microcomputer) 5.

The control circuit 5 measures the time from the position detection to the energization switching (preset time), and after this time has elapsed, the switching elements Ua, Va, Wa, X, Y, and Y of the inverter circuit 1 according to the commutation pattern. The switching of Z is switched, and the control of switching the energization of the armature windings U, V, W of the stator is performed.

The control circuit 5 switches the energization of the armature windings U, V, W based on the above-mentioned position detection signal, while the line voltage (drive voltage) of the armature windings of the motor 2 is switched.
Is a sine wave (see FIG. 5B). In addition, a drive signal including a PWM waveform for turning on and off the switching elements Ua, Va, Wa, X, Y, and Z at predetermined times in order to set the rotation speed to the target rotation speed is output to the inverter circuit 1 via the base amplifier circuit 6. Output to

Then, the respective transistors Ua, Va, Wa, X, Y, Z of the inverter circuit 1 are turned on and off in a predetermined manner, and the energization of the armature windings U, V, W of the motor 2 is switched. As a result, a sine wave voltage is applied to the motor 2, so that a drive current flows through the motor 2 to generate a rotational torque. Although FIG. 5 shows the position detection signal and the drive voltage for only one phase, the description is omitted for the other two phases because the same is true.

[0007]

However, in the above-described motor control method, the position detecting sensor 3 is mounted so as to be displaced from the proper position, or the rotor is not fixed due to a variation in detection accuracy of the position detecting sensor 3 or the like. An error occurs in the detection of the position, and the commutation phase angle fluctuates. This means not only that the rotation of the motor 2 is not performed properly, but also that the quality and reliability are reduced.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to solve the problems caused by misalignment of a position detection sensor and variations in the accuracy of the position detection sensor, thereby suppressing fluctuations in the commutation phase angle, and It is an object of the present invention to provide a motor control method and a motor control device capable of appropriately rotating and improving the quality of a motor and further improving reliability.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method in which a DC voltage is switched by a switching element of an inverter and applied to a motor, and the position of a rotor of the motor is detected by a position detecting sensor. Then, in the motor control method for switching the energization of the motor based on the position detection signal and controlling the rotation of the motor, the phase current of the motor is detected while the voltage between the armature windings of the motor is detected. (Drive voltage) and the phase difference between the phase current,
It is characterized in that the time from the position detection to the energization switching is corrected so that the phase difference becomes a predetermined constant value t.

In this case, the phase current is detected by a shunt resistor connected to a phase line between the inverter and the motor or by a CT arranged on a common-mode line. If the phase difference is smaller than a predetermined value t, the position detection is performed. From the current to the energization switching is shortened by a predetermined value, and the phase difference becomes a constant value t.
If it is larger, the time from the position detection to the energization switching may be lengthened by a predetermined value. This can be realized only by adding a shunt resistor or CT. In particular, if a shunt resistor is used, it can be realized at low cost. Further, if the predetermined value is set to a value corresponding to the phase difference, the phase difference can be quickly brought close to the constant value t.

According to the present invention, a DC voltage is switched by a switching element of an inverter and applied to a motor, a position of a rotor of the motor is detected by a position detection sensor, and the motor is detected based on the position detection signal. A motor control device for switching the energization of the motor and controlling the rotation of the motor, comprising a current detection means for detecting a phase current of the motor, wherein the control means for controlling the motor is controlled by a current detection signal from the current detection means. While obtaining a phase current and calculating a zero crossing point of the phase current, an armature winding voltage (drive voltage) is obtained based on the motor control information,
Further, a zero-cross point of the drive voltage is calculated, a phase difference between the drive voltage and the phase current is detected based on the zero-cross point, and power is supplied from the position detection so that the phase difference becomes a predetermined constant value t. It is characterized in that the time until switching is corrected.

In this case, the phase current is detected by a shunt resistor connected to a phase line between the inverter and the motor or by a CT disposed on a common line. If the phase difference is smaller than a predetermined value t, the position detection is performed. From the current to the energization switching is shortened by a predetermined value, and the phase difference becomes a constant value t.
If it is larger, the time from the position detection to the energization switching may be lengthened by a predetermined value. This can be realized only by adding a shunt resistor or CT. In particular, if a shunt resistor is used, it can be realized at low cost. Further, if the predetermined value is set to a value corresponding to the phase difference, the phase difference can be quickly brought close to the constant value t.

[0013]

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. 2,
The same parts as those in FIG.

In FIG. 2, a control device to which the motor control method of the present invention is applied includes a shunt resistor 10 of a current detecting means for detecting at least one phase current (armature winding current) of the motor 2 and a current. A detection circuit 11 for detecting a phase difference between the phase current and the drive voltage of the motor 2 (voltage between armature windings) and correcting the time from position detection to energization switching according to the phase difference ( Microcomputer 12). Note that the control circuit 12 also has the function of the control circuit 4 shown in FIG.

The shunt resistor 10 is connected to a one-phase line, and a voltage applied to both ends of the shunt resistor 10 is detected by a position detecting circuit 11. The control circuit 12 calculates a phase current based on the voltage detected by the position detection circuit 11 and obtains its zero cross point. Also, the PW currently output
The drive voltage is calculated based on the M waveform to obtain the zero cross point, and the phase difference between the zero cross points is calculated.

Here, when the energization switching of the motor 2 is appropriately performed, the drive voltage and the phase current (drive current)
Is in a relationship of a certain fixed value t (for example, a time corresponding to 5 degrees in electrical angle) t.

However, if the position of the position detecting sensor 3 is shifted or an error occurs in the detection of the position detecting sensor 3, the commutation phase angle varies, and the phase difference becomes larger than the constant value t. Shift. Therefore, if the phase difference is obtained, it is possible to estimate a displacement of the installation position of the position detection sensor 3 and a detection error of the position detection sensor 3.

Further, if the time from the position detection to the energization switching is corrected so that the phase difference becomes a constant value t, the displacement due to the displacement of the installation position of the position detection sensor 3 or the detection error of the position detection sensor 3 is caused. Problems caused by variations in the flow phase angle can be eliminated.

Based on the above, the operation of the control device having the above configuration will be described in detail with reference to the flowchart of FIG. 1 and the time chart of FIG.

First, the control circuit 12 controls the rotation of the motor 2 by switching the energization of the motor 2 based on the position detection signal, and controls the rotation speed of the motor 2 to the target rotation speed. I do. At this time, the control circuit 12 measures the phase current based on the detection signal from the current detection circuit 11 (step ST1), and obtains a zero cross point of the phase current (FIG. 3).
(See the wavy arrow in (b)).

Subsequently, as described above, the zero cross point of the drive voltage of the motor 2 (see the point b in FIG. 3A) is obtained, and the difference between this zero cross point and the zero cross point of the phase current (FIG. 3). (Time from point b to point c), that is, the phase difference is calculated, and it is determined whether the phase difference is larger or smaller than the fixed value t (step ST2).

If the phase difference is smaller than the fixed value t, the time from the position detection to the energization switching is shortened by a predetermined value (step ST3), and a correction is made to advance the current energization switching timing, and the phase of the driving voltage and the phase current is corrected. The phase difference is made closer to the constant value t. If the phase difference is larger than the fixed value t, the time from the detection of the rotation position to the energization switching is lengthened by a predetermined value (step ST4), and the correction for delaying the current energization switching timing is performed so that the positions of the drive voltage and the phase current are corrected. The phase difference is made closer to the constant value t.

If the phase difference is a constant value t and an optimum value, there is no displacement of the installation position of the position detection sensor 3 or a detection error of the position detection sensor 3, and the energization switching timing is appropriate. The above-mentioned correction is not performed.

Incidentally, step ST3 or ST4
As the predetermined value in, which is previously obtained empirically,
Depending on the magnitude of the phase difference, one of the routines shown in FIG.
In some cases, the phase difference may not be close to the constant value t due to the number of times of execution. Therefore, instead of the predetermined value, an average value is empirically obtained and determined as a reference value, and the reference value is changed to a predetermined value according to the magnitude of the phase difference. That is, as the phase difference is smaller than the fixed value t, the time from position detection to energization switching is shorter, and as the phase difference is larger than the fixed value t, the time from position detection to energization switching is shorter. To be longer. Thereby, the phase difference can be quickly brought close to the vicinity of the constant value t.

The routine shown in FIG. 1 may be repeatedly executed at predetermined time intervals so that the phase difference converges to a constant value t. In this case, if the predetermined value is determined to be too large, the control may hunt, so the predetermined value may be set relatively small.
Further, as described above, if the predetermined value is changed according to the magnitude of the phase difference, the phase difference can be surely converged to a constant value t.

In the above-described embodiment, the shunt resistor 10 is used as the current detecting means.
(Current transformer) or the like, and the shunt resistor 10 is connected to all the phase lines,
The control may be performed for all three phases.
Further, in the present embodiment, a case where the present invention is applied to a three-phase four-pole motor has been described, but it is apparent that the present invention can be applied to other motors.

[0027]

According to the present invention described above, the following effects can be obtained. The present invention relates to a method for controlling a motor including a position detection sensor for detecting a position of a rotor, wherein a phase current of the motor is detected and a voltage between an armature winding of the motor (drive voltage) and the phase current is detected. Since the phase difference is detected and the time from position detection to energization switching is corrected so that the phase difference becomes a predetermined constant value t,
Problems caused by the position detection sensor being displaced from the proper position or by variations in the detection accuracy of the position detection sensor are eliminated by setting the phase difference to a constant value t, and the fluctuation of the commutation phase angle is eliminated. Is compensated to improve quality and reliability.

Further, the motor control device of the present invention includes current detection means for detecting a phase current of the motor, and the control means for controlling the motor obtains a phase current based on a current detection signal from the current detection means. And the phase difference between the driving voltage and the phase current is detected based on the control information of the armature winding, and the phase difference is set to a predetermined constant value t. Since the time from the position detection to the energization switching is corrected, in addition to the above-described effects, it is sufficient to use only the microcomputer of the control means of the motor and add only the current detection means in terms of hardware. This has the effect of reducing costs.

[Brief description of the drawings]

FIG. 1 is a schematic flowchart for explaining a motor control method of the present invention.

FIG. 2 is a schematic block diagram of a control device to which the motor control method of the present invention is applied.

FIG. 3 is a schematic time chart for explaining the operation of the control device shown in FIG. 2;

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

FIG. 5 is a schematic time chart for explaining the operation of the control device shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter circuit 2 Motor 3 Hall element (position detection means) 4,11 Position detection circuit 5,12 Control circuit (microcomputer) 10 Shunt resistance (current detection means) t Constant value (appropriate position of drive voltage and phase current) Difference)

Claims (4)

[Claims] A DC voltage is switched by a switching element of an inverter and applied to a motor, a position of a rotor of the motor is detected by a position detection sensor, and the motor is energized based on a signal of the position detection. In the motor control method for controlling the rotation of the motor, a phase current of the motor is detected, and a phase difference between an armature winding voltage (drive voltage) of the motor and the phase current is detected. A method for controlling a motor, wherein the time from the position detection to the energization switching is corrected so that the phase difference becomes a predetermined constant value t. 2. The phase current is detected by a shunt resistor connected to a phase line between the inverter and the motor or by a CT arranged on a common-mode line. If the phase difference is smaller than a predetermined value t, the phase current is detected. 2. The motor control according to claim 1, wherein the time until the energization switching is shortened by a predetermined value, and when the phase difference is larger than a predetermined value t, the time from the position detection to the energization switching is lengthened by a predetermined value. apparatus. 3. A DC voltage is switched by a switching element of an inverter and applied to a motor, a position of a rotor of the motor is detected by a position detection sensor, and the motor is energized based on the position detection signal. And a motor control device for controlling the rotation of the motor, comprising a current detection means for detecting a phase current of the motor, wherein the control means for controlling the motor includes a phase current based on a current detection signal from the current detection means. And calculating the zero-cross point of the phase current, while obtaining the armature winding voltage (drive voltage) based on the control information of the motor, and calculating the zero-cross point of the drive voltage. The phase difference between the drive voltage and the phase current is detected based on the zero cross points, and the time from the position detection to the energization switching is set so that the phase difference becomes a predetermined constant value t. A motor control device, wherein the motor is corrected. 4. The phase current is detected by a shunt resistor connected to a phase line between the inverter and the motor or by a CT disposed on a common-mode line. If the phase difference is smaller than a predetermined value t, the phase current is detected. 4. The motor according to claim 3, wherein a time until the energization switching is shortened by a predetermined value, and when the phase difference is larger than a predetermined value t, a time from the position detection to the energization switching is lengthened by a predetermined value. 5. Control device.