JPH07298676A - Drive controller of motor - Google Patents

Abstract

PURPOSE:To generate a trapezoidal wave with no stoppage of the driving current by a method wherein the voltage drop due to the driving current is subtracted from the sum of the counter electromotive force generated in driving coils and the voltage drop due to the driving current and a waveform of the driving current is calculated based on the subtraction result and then a phase is switched. CONSTITUTION:An MPU1 makes a control of a trapezoidal wave by means of driving currents i1-i3. When a motor rotates, the counter electromotive force is generated in three driving coils 2a-2c and the voltage drop is also generated due to coil resistances of the driving currents i1-i3. With the counter electromotive force and the voltage drop input into a group of buffer circuits 5, the outputs of the group of buffer circuits 5 are voltage signals Vm1-Vm3. The detected voltages Vm1-Vm3 are input into a group of A/D's 6 and then the value data DV1-DV3 are obtained. In a group of subtraction circuits 7, driving value data DD1-DD3 are subtracted from the detected value data DV1-DV3. Then, signals e1-e3 which are proportional only to the counter electromotive force are obtained. By this method, the optimum slope of trapezoidal waves of the driving signals can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive control device for rotating a sensorless brushless motor.

[0002]

2. Description of the Related Art In recent years, a motor as a driving device has been remarkably sensorless, and has become common knowledge in video and movies. This is because the Hall element, which is usually used as a sensor, is removed to reduce the cost, and in the surface-opposed motor, the thickness of the motor itself can be suppressed by the thickness of the Hall element.

In such a sensorless brushless motor, it is common to detect the voltage of the back electromotive force generated in the drive coil of the motor and execute the phase switching (for example, Japanese Patent Laid-Open No. 4-359693). Issue bulletin).

[0004]

However, in the above-mentioned sensorless brushless motor drive control device, in the case of a three-phase motor, since a square wave having a phase shift of 120 degrees is used as a drive signal, There is a problem that it causes unnecessary radiation and motor noise due to switching noise.

The present invention solves the above-mentioned problems of the prior art, and an object of the present invention is to provide a drive control device for a motor which can reduce unnecessary radiation and motor noise.

[0006]

To achieve this object, a drive control device for a motor according to the present invention comprises a drive means for supplying a drive signal to each phase coil of a motor having a plurality of phases, and the communication means. Voltage detection means for detecting a voltage signal generated in the phase coil, subtraction means for subtracting the voltage signal and the drive signal at a predetermined ratio, and phase switching of the drive means according to the output of the subtraction means. The configuration includes a phase passing means for determining the timing.

[0007]

According to the above structure, the motor drive control device of the present invention subtracts the contribution of the voltage drop due to the drive current from the total value of the voltage drop due to the back electromotive force and the drive current generated in the phase-pass coil, It is possible to calculate the waveform of the drive current from the result of the subtraction and switch the phases to generate a trapezoidal wave having no drive current pause period.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic block diagram of a drive control device for a motor according to this embodiment. In FIG. 1, reference numeral 1 is a microprocessor for controlling the phase-communication timing of the motor.
A unit (hereinafter referred to as MPU) 2, a motor having drive coils (stators) 2a to 2c and a rotor (rotor) 2d, 3 is a digital-analog conversion circuit (hereinafter referred to as D / A) 3a
3a to 3c D / A group, 4 a power amplifier circuit group consisting of power amplifier circuits 4a to 4c, 5 a buffer circuit group consisting of buffer circuits 5a to 5c, 6 an analog-digital conversion circuit
An A / D group consisting of 6a to 6c (hereinafter referred to as A / D) and a subtraction circuit group consisting of subtraction circuits 7a to 7c.

FIG. 2 shows (a) drive current signal waveform, (b) detection voltage signal waveform of the motor drive control device of this embodiment,
(c) Shows the calculation result of the subtraction circuit, where Mc is the phase-communication mode of 1 to 6, Ta is the phase-communication time, and Md is the detection of counter-electromotive force as the interrupt signal when the interrupt is enabled. It's a window. Here, the phase passing mode Mc and the detection window Md are switched every 60 degrees with respect to the rotation angle of the motor 2 as shown in FIGS. 2 (a) and 2 (c), and their phases are shifted by 30 degrees. . Although the calculation result of FIG. 2C is originally numerical data, it is displayed in analog as a signal proportional to only the back electromotive force for the sake of explanation in comparison with the drive current signal and the detection voltage signal. .

Next, the operation of the above embodiment will be described. First, the three output ports OP1 to O of the MPU1
The driving numerical data DD1 to DD3 from P3 are sent to the D / A group 3 to be converted into driving voltage signals VD1 to VD3, and sent to the power amplification circuit group 4. The power amplifier circuit group 4 has a drive current signal (hereinafter, referred to as a drive current signal proportional to the drive voltage signals VD1 to VD3).
I1 to i3 are referred to as drive currents and drive coils 2a of the motor 2 are
Pour into 2c.

As shown in FIG. 2 (a), the driving currents i1 to i3 at this time are trapezoidal waveforms, and the waveforms carry 180 degrees with respect to the rotation angle (electrical angle) of the motor 2. With the change of the drive currents i1 to i3, the magnetic fields generated in the drive coils 2a to 2c exhibit the same change, and a rotational force is generated by the pattern (8-pole magnetization) magnetized in the rotor 2d. However, at this initial stage, since the change in the electromagnetic field is not in a positional relationship that produces an optimum and maximum force with respect to the magnetic field of the rotor 2d, accelerating and decelerating such as hunting is repeated to make it gentle. It turns.

Now, the torque Tm generated by the motor 2 at the rotation angle θ [rad] of the motor 2 is given by (Equation 1).

[0014]

[Equation 1]

Here, Tmax is the peak value of the generated torque,

[0016]

[Equation 2]

It is K _T is the torque constant, Iamax is the maximum current flowing in one phase, Mc is the phase-conduction mode (1-6),
The change shown in FIG. 2 (a) is set. Also, the slope function S is

[0018]

[Equation 3]

Is given by Here, Ta is the phase passing time.

As described above, the generated torque is given by a non-linear function, and depending on the rotation angle θ, the torque in the desired rotation direction may not be obtained. In order to normally start such a sensorless brushless motor, the counter electromotive force that changes according to the rotation speed and the rotation phase of the motor generated in the drive coils 2a to 2c of the motor is detected and synchronized. Need to accelerate.

In order to accelerate the motor 2 as described above, the following procedure is required. In the flow chart showing the operation at the time of startup of this embodiment shown in FIG. 3 (a), T'is 1 to 6 of the phase passing mode Mc shown in FIG. 2 (a).
Td, the internal value of the counter that measures the cycle period
Is an internal value of a counter for generating an interrupt permission.

Here, as initialization, the counter value T'for reading the numerical data of the phase passing time Ta and measuring the phase passing period.
To the counter value Td for generating an interrupt permission, and the numerical data half of which is obtained by shifting the numerical value data of the phase-communication time Ta by 1 bit are set to 1 in the phase-communication mode Mc and the detection window Md ( Step 1).

Next, the slope S of the trapezoidal wave of each phase is calculated from the numerical data of the selected phase-communication mode Mc and the phase-communication time Ta within one phase-cycle and three-phase drive currents i1 to i3 are generated. (Step 2).

When the counter value Td for generating the interrupt permission is equal to the numerical data of the phase passing time Ta, the next detection window Md is selected to enable the interrupt, and the counter value T'of the passing phase is set. The occurrence of an interrupt is awaited until is the same as the numerical data of the communication time Ta (step 3).

When no interrupt is generated, the interruption is prohibited, the passing time Ta is moved to the next passing mode Mc, the counter value T'of the passing phase is set to 0, and the interruption permission is generated. The value of the counter value Td is shifted by 1 bit from the numerical value data of the phase transition time Ta to set the numerical value data to half (step 4).

The above steps 2 to 4 are repeated until an interrupt occurs. The process of the flowchart of the interrupt process shown in FIG. 3B will be described.

When an interrupt occurs in the detection window Md, the next phase-communication time Ta '(a value smaller than the previous phase-communication time Ta) is set to RO.
Read from the M table (step 5).

Select the next phase passing mode Mc and detection window Md,
The counter value T'of the phase-communication cycle is set to 0, and the numerical value of the phase-communication time Ta 'is shifted by 1 bit to the counter value Td for generating the interrupt permission, so that half the numerical value data is set and the interrupt processing is performed. Are restored (step 6).

Here, again, the operations of steps 2 to 4 are repeated until an interrupt occurs.

As shown in FIG. 2 (a), the MPU 1 has a drive current i
1 to i3 perform trapezoidal wave drive, and by performing such trapezoidal wave drive, changes in the drive currents i1 to i3 near the zero cross become gradual, and unnecessary electric radiation and abrupt electromagnetic field changes occur. It is possible to prevent mechanical vibration of the stator (coil) due to.

By carrying out such a drive, a back electromotive force is generated in the three drive coils 2a to 2c with the rotation of the motor 2, and a voltage drop due to the coil resistance of the drive currents i1 to i3 is also generated. To do. When these two are combined, the output of the buffer circuit group 5 becomes a waveform of the detection voltage signal (hereinafter referred to as the detection voltage) Vm1 to Vm3 as shown in FIG. 2B. The shaded area in FIG. 2B represents the voltage drop due to the coil resistance.

At this time, the detection voltage Vm generated in the detection windows Md = 1 to 6 is given by (Equation 4).

[0033]

[Equation 4]

Where ka is the power generation constant per phase, N
Is the rotation speed [rpm], ra is the winding resistance per phase [Ω],
Ia is the current [A] flowing in one phase, and Md is the number of the detection windows (1-6) shown in FIG. 2 (c).

As is clear from (Equation 4), the motor 2
In order to detect the term according to the rotation angle θ of
It is understood that the term (ra × Ia × S) proportional to i1 to i3 should be deleted.

As this processing, the detected voltages Vm1 to Vm3 are obtained as detected numerical data DV1 to DV3 by the A / D group 6. The detected numerical value data DV1 to DV3 are respectively subtracted from the driving numerical value data DD1 to DD3 in the subtraction circuit group 7 to obtain a signal proportional to only the back electromotive force as shown in FIG. E1 to e3 can be obtained.

In the acceleration process, it is detected that the zero-crosses of the power generation waveforms e1 to e3 shown in FIG. 2 (c) have entered the detection window Md selected during the interruption permission, and it is passed. This can be achieved by reducing the phase time Ta to a predetermined value. For example, when Md = 6 in FIG. 2 (a), if the power generation waveform e2 rises in the detection window, as shown in the flowchart in FIG. Read from the table and execute the shortening process. Detection of an interrupt occurrence by such a detection window Md is shown in FIG.
In the flow chart shown in FIG. 3, it is easy to set the phase-intermitting cycle that repeats the numerical data of the phase-communication time Ta of a certain phase-communication mode Mc to an interrupt permission after half the repetition, and to prohibit an interrupt in the next phase-communication mode Mc. Can be realized. During this interrupt permission, the selected detection window Md
3 (b) when the desired back electromotive force edge is input to
It suffices to perform the processing shown in.

The phase passing time Ta is given by (Equation 5).

[0039]

[Equation 5]

Here, n is a natural number, and

[0041]

[Equation 6]

Where N ₀ is the initial set rotational speed,
P is the number of rotor poles, A is the number of coils, T ₀ is the initial phase passing time, T is the motor drive torque [gf-cm], and Kj is a constant.

Although the operation at the time of start-up has been described in the present embodiment, the present embodiment is effective even during steady rotation. For example, constant speed rotation can be obtained unless the phase passing time Ta is shortened in the interrupt process. Further, in the deceleration processing, the ROM table may be reversely drawn from the current rotational speed up to the desired rotational speed.

As described above, according to this embodiment, since the desired starting rotational speed is calculated in advance from the ROM table of the target address, the slopes of the trapezoidal waves of the driving currents i1 to i3 are calculated and made as gentle as possible. be able to. Therefore, it is possible to prevent unnecessary radiation associated with electrical switching and mechanical vibration of the stator (coil) associated with a sudden change in electromagnetic field.

[0045]

As described above, according to the motor drive control apparatus of the present invention, the optimum inclination of the trapezoidal wave of the drive signal is realized in accordance with the target start speed or the steady drive speed, and the electrical Radiation and noise can be achieved by preventing unnecessary radiation associated with switching and mechanical vibration of the stator (coil) associated with a sudden change in electromagnetic field.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a drive control device for a motor according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing (a) drive current signal, (b) detection voltage signal, and (c) calculation result of the motor drive control device according to the embodiment of the present invention.

FIG. 3 is a flowchart showing an operation of the motor drive control device in the embodiment of the present invention.

[Explanation of symbols]

1 ... Microprocessor unit (MPU), 2 ...
Motor, 3 ... Digital / analog converter group (D / A
Group), 4 ... power amplification circuit group, 5 ... buffer circuit group,
6 ... Analog / digital converter group (A / D group), 7 ...
Subtraction circuit group.

Claims (1)

[Claims] 1. A drive unit for supplying a drive signal to each phase coil of a motor having a plurality of phases, a voltage detection unit for detecting a voltage signal generated in the phase coil, the voltage signal and the drive signal. A drive control device for a motor, comprising: a subtracting means for subtracting a predetermined ratio and a phase passing means for determining a timing of phase switching of the driving means according to an output of the subtracting means.