JPH1198884A - Method for controlling brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the erroneous detection of the position of the rotor of a brushless motor by removing noise, etc., and, in addition, to accurately detect the position in detecting the position with software by using the terminal voltages of the armature windings of the motor. SOLUTION: In a method for controlling brushless motor, a brushless motor 4 is PWM-controlled by impressing DC power upon the motor 4 by switching the power by means of the transistors in an inverter section 3. A/D-converting sections 10, 11, and 12 sample the waveforms of the terminal voltages of the armature windings of the motor 4 and convert the sampled waveforms into digital data (numerical data). A microcomputer 13 fetches the digital data and, on the other hand, low-pass filters the digital data through numerical and arithmetic processing. At the same time, the microcomputer 13 detects the position of the rotor of the motor 4 by comparing the low-pass filtered values with a prescribed value and calculates the conduction switching timing of the motor 4 by driving the transistors of the inverter section 3 based on the detected position of the rotor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control technique for a sensorless DC brushless motor (hereinafter referred to as "brushless motor"), and more particularly, to numerically operating numerical data obtained by sampling armature winding voltage of a brushless motor. The present invention relates to a method for controlling a brushless motor that processes and detects the position of a rotor by software and obtains a timing for switching power supply based on the detected position.

[0002]

2. Description of the Related Art The rotation control of a brushless motor detects the position of a rotor and switches the energization of the armature winding current of the brushless motor based on the detected position. For example,
As shown in FIG. 10, a commercial power supply 1 is connected to an AC / DC converter 2
, And the converted DC power is switched by the inverter unit 3 and supplied to the brushless motor 4 as three-phase AC.

At this time, in order to detect the position of the rotor of the brushless motor 4, the position detection circuit 5 compares the terminal voltages of the armature windings U, V, W with a predetermined voltage (reference voltage) (see FIG. 1). 11 (a)), and outputs to the control circuit (microcomputer) 6 as a position detection signal including the intersection information (the intersection of the induced voltage and the predetermined voltage). The control circuit 6 detects the position of the rotor based on the position detection signal.
As shown in (b), when the induced voltage is rising, the first rising edge after the energization switching is set as the position detection point, and when the induced voltage is falling, the first falling edge after the energization switching is set as the position detection point. And

When the position detection point is obtained in this way, a time after a predetermined phase from this position detection point, that is, the energization switching timing time is calculated, and the PWM waveform is superimposed on a signal using this time as the energization switching timing. A drive signal is generated, and the drive signal is output to the inverter unit 3 via the drive circuit 7. As a result, each of the transistors Ua, Va, Wa, X, Y, and Z of the inverter section 3 is turned on in a predetermined manner,
It can be turned off to switch the energization of the armature winding of the brushless motor 4. Further, in the above-described digital system, the terminal voltage is compared with a predetermined voltage, and the time until the energization switching is obtained from the result of the comparison (the intersection of the induced voltage and the predetermined voltage; the position detection point). Optimal energization switching is possible.

[0005]

However, the control method of the brushless motor has a disadvantage that it is easily affected by noise. That is, since the position detection point is obtained by the edge of the position detection signal, the noise is not detected. If it is included in the signal, erroneous position detection is likely to occur, and as a result, not only rotation control will not be stable, but also worst step-out and stop will occur.

Further, in the PWM control method, when an intersection between an induced voltage and a reference voltage is used as a position detection point, the position detection point may be delayed or advanced from normal depending on the state of generation of the induced voltage. As a result, the energization switching timing is delayed or advanced. For example, in FIG. 11A, when the intersection of the induced voltage and the reference voltage corresponds to the off section of the PWM control, the position detection point becomes the rising edge of the pulse after the crossing, that is, the position detection point is later than normal. . Conversely, if the induced voltage waveform is falling, the falling edge of the pulse before the intersection becomes the position detection point, that is, the position detection point is earlier than normal.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to remove noise contained in the terminal voltage of an armature winding by low-pass filtering of software and to perform erroneous position detection (erroneous power switching). It is another object of the present invention to provide a brushless motor control method capable of preventing the occurrence of an error, performing accurate position detection in consideration of the state of an induced voltage, and reducing the cost.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention detects a position of a rotor by an induced voltage included in a terminal voltage of an armature winding of a brushless motor. A brushless motor control method for switching the energization of the armature windings of the brushless motor and performing PWM control on the brushless motor, wherein digital data obtained by sampling the waveform of the terminal voltage is taken in, The digital data is filtered by numerical operation processing, the filtered value (the value of the induced voltage waveform) is compared with a predetermined value to detect the position of the rotor of the brushless motor, and based on the position detection, The present invention is characterized in that a current supply switching timing of the armature winding is calculated.

According to the brushless motor control method of the present invention, the waveform of the neutral point voltage obtained by synthesizing the terminal voltages is sampled, and the digital data obtained by the sampling is fetched. The position of the rotor of the brushless motor is detected by comparing the filtered value (the value of the induced voltage waveform) with a predetermined value, and the armature winding is determined based on the position detection. The present invention is characterized in that a line energization switching timing is calculated.

In this case, the predetermined value is a half value (a value of a reference voltage) of digital data obtained by sampling the voltage applied to the brushless motor (terminal voltage) in the ON period of the PWM control. A point at which the magnitude relationship of the filtered value is inverted with respect to a reference voltage value may be set as the rotor position detection point.

The digital data in the off period of the PWM control is calculated on the basis of the digital data in the on period of the PWM control, and the digital data obtained by the calculation is regarded as the value of the induced voltage waveform. It is preferable to be able to compare with a predetermined value. One of the plurality of digital data in the ON section is a representative value, one of the plurality of digital data in the ON section adjacent to the ON section is a representative value, and the OFF section is represented by the two representative values. It is preferable to create a linear equation corresponding to the value of the induced voltage waveform, and compare the linear equation with the predetermined value to obtain a position detection point of the rotor.

A linear equation corresponding to the value of the induced voltage waveform in the off section is created from the plurality of digital data in the on section and the plurality of digital data in the on section adjacent to the on section. It is preferable to obtain a position detection point of the rotor by comparing with a predetermined value. An average value of at least two or more digital data of the plurality of digital data of the ON section and at least two of a plurality of digital data of an ON section adjacent to the ON section.
A linear equation corresponding to the value of the induced voltage waveform in the off section is created based on the average value of one or more digital data, and the linear equation is compared with the predetermined value to obtain a position detection point of the rotor. Good.

A regression line is calculated using the plurality of digital data in the ON period, and the regression line is regarded as the value of the induced voltage waveform, and is compared with the predetermined value to obtain a position detection point of the rotor. Good. An interpolation straight line corresponding to the induced voltage waveform is calculated from the digital data of the ON interval before the position detection in the ON interval of the PWM control, and the interpolation straight line is compared with the predetermined value to determine the position of the rotor. A detection point may be obtained.

When a position detection point of the rotor is obtained when a value obtained by performing low-pass filtering in the ON section of the PWM control is compared with a predetermined value, the numerical operation processing and position detection are performed at least until the next energization switching. Should not be performed. The numerical processing may be an FIR or IIR low-pass digital filter. Preferably, a plurality of coefficients of the low-pass digital filter are stored in a table format so that a coefficient pattern of the low-pass digital filter can be changed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. 1 and 9, the same parts as those in FIG. 10 are denoted by the same reference numerals, and redundant description will be omitted. According to the brushless motor control method of the present invention, if the terminal voltage of the armature winding is sampled and filtered by software operation processing, not only can noise be removed, but also the A / D converted value obtained by the sampling. Paying attention to the fact that the state of the induced voltage (the crossing state of the chopping waveform and the reference voltage) can be grasped by (numerical data), the position detection processing is performed in consideration of the state of the induced voltage, and an accurate position detection point is obtained. Get.

For this purpose, as shown in FIG. 1, a control device to which the brushless motor control method of the present invention is applied, samples terminal voltages of armature windings U, V, and W and performs digital control of a predetermined number of bits. A / D converters 10, 11, and 12 for converting data (numerical data), filtering the numerical data by taking in the numerical data, and obtaining a value (numerical data) obtained by the filtering and a predetermined voltage (reference voltage). ) Is obtained by comparing with the value of (1), and when the crossing of the induced voltage and the reference voltage is in the off section of the chopping waveform (PWM waveform), the induced voltage waveform (straight line) in the off section is represented by numerical data. Position detection calculation units 13a, 13b,
13c, an energization switching timing calculation unit 13d that calculates energization switching timings based on the position detection signals of these intersections, and the transistors Ua, Va, Wa of the inverter unit 3 by superimposing a PWM carrier signal on the calculated energization switching timing signals. , X, Y, and Z, and a microcomputer 13 having a signal generation unit 13e for generating drive signals. The microcomputer 1
3 has an A / D conversion function, the A / D conversion unit 1
0, 11, and 12 may be included. The microcomputer 13 corresponds to the control circuit 6 shown in FIG.

Each of the position detection calculation units 13a, 13b, 13c
Is realized by software operation processing. One of the position detection operation sections 13a will be specifically described with reference to the schematic diagram of FIG. 2. First, numerical data is taken in and filtered. This filtering is performed by the FI shown in FIG.
In the R-type digital filter 13aa, the coefficients a0 to an to be low-pass filters are selected and realized by software. Therefore, a difference equation based on the coefficients a0 to an is created in advance, the difference equation is solved by the fetched numerical data, and the calculation result is output to the zero-cross comparison calculation unit 13ab. Note that the digital filter 13aa shown in FIG. 2 includes a delay register, a filter coefficient multiplier, and an adder.

The zero-cross comparison operation unit 13ab compares the numerical data subjected to low-pass filtering with the reference voltage, and outputs a signal of the comparison result to the energization switching timing calculation unit 13d. As shown in FIG. 3, the reference voltage is a positive voltage applied to the one-phase armature winding among the sampled numerical data, and is used to turn on PWM control (active LO).
W) is obtained by halving the sampling value of the section. Further, the A / D converter may be increased by one, that is, the output of the externally provided reference voltage generating circuit may be converted into numerical data by the A / D converter.

Therefore, as shown in FIG. 3, the induced voltage waveform (low-pass filtered numerical data) is compared with the reference voltage, and a point (intersection) at which the numerical data matches the reference voltage is obtained. Let the intersection be a position detection point. However, since the numerical data is a sampled value, the numerical data may not match the reference voltage in the ON period of the PWM control. In this case, the point where the magnitude relationship of the numerical data is inverted with respect to the reference voltage (intersection point)
And this point is set as a position detection point.

Further, the zero-cross comparison operation section 13ab
No comparison is made for the off section of the PWM control. Then, as shown in FIG. 4, since the induced voltage waveform is an intermittent waveform due to chopping, the coincident point may fall in the off section of PWM control (the missing section of the induced voltage waveform), and an accurate position detection point is obtained. As a result, the detected position detection point is delayed or advanced as in the related art.

Therefore, as shown in FIG. 4, a predetermined number of low-pass filtered numerical data are sequentially stored in the memory. However, the numerical data corresponding to the OFF section of the PWM control is ignored, and the numerical data of the ON section is ignored. (For example, D0, D1,
D2, D5, D6, D7) are stored in the memory. Then, numerical data D0, D1, D of adjacent ON sections
It is determined whether or not there is an intersection between the reference voltage and the linear equation calculated by 2, D5, D6, and D7. In this case, since there is no intersection, the values D5, D6, D7, D10, D11, and D1 of the adjacent ON sections are provided as described above.
2 is stored, and it is determined again whether or not there is an intersection between the linear equation calculated based on these values and the reference voltage. As is clear from FIG. 4, since the linear equation intersects with the reference voltage, the intersection Dp is set as a position detection point.

By the way, as a method of calculating the above-mentioned linear equation, one of the values in the ON section is set as a representative value, and
Is a representative value, and furthermore, an average value of all values or a plurality of values in the ON section is a representative value, and a linear equation (that is, an equation which is regarded as an induced voltage waveform in the OFF section) is represented by those representative values.
Get. For example, as shown in FIG. 5, the linear equation (see the broken line in the figure) y is α · t + Da, and α is ΔD / Δt = /
((T2−Tb) − (t1−Ta)) = ΔD / ((t2
−t1) − (Ta−Tb)). Here, α is the slope, and ΔD is the representative value Da,
The difference value of Db, t1 is the start time of the first ON section, t2
Is the end time of the next ON section, and Ta is the representative value Da from t1.
Tb is the time from the time of the representative Db to t2. Therefore, in order to obtain an intersection between the linear equation and the reference voltage, the reference voltage is set as y = Dp, and Dp = α · ΔT +
Obtain Da. By transforming this, (Dp−Da) / α =
ΔT. This ΔT is calculated from the time of the representative point Da to the intersection Dp.
The time t of the intersection Dp is t1 +
It can be expressed as Ta + ΔT. Therefore, after time t2, t1, t2, Ta, Tb, Da, Db, ΔD, and Dp (reference voltage value) are obtained, so that time t at intersection Dp can be calculated from them. .

According to the above calculation method, each position detection calculation unit 13
a, 13b, and 13c output the time of the position detection point of the calculation result to the energization switching timing unit 13d, and the energization switching timing unit 13d calculates a time after a lapse of a predetermined time (a predetermined phase) from the time, and calculates this time. It is assumed that the energization switching timing of the armature windings U, V, W is set. The signal generating unit 13e generates a driving signal in which a PWM signal is superimposed on the energization switching timing, and drives the transistors Ua, Va, Wa, X, Y, and Z of the inverter unit 3 via the driving circuit 7.

In the above-described method using the representative values of the two ON sections, the calculation for obtaining the position detection points cannot be started until the values of each section are stored, and the position detection points are slightly delayed. Therefore, the slope of the induced voltage waveform may be obtained using the value of one ON section, the straight line of this slope may be used as the interpolation straight line in the OFF section, and the intersection of the interpolation straight line and the reference voltage may be calculated. . For example, assuming the first time t1 of the ON section and the last time t2 of the ON section, an interpolation linear equation for interpolating the induced voltage waveform of the next OFF section is calculated by the above-described calculation method. Calculate the intersection with. Thereby, the delay of the position detection point becomes substantially zero, which is extremely useful, for example, when the position detection point and the energization switching timing are close (in the case of lead angle control).

Further, as shown in FIG. 6, the envelope of the induced voltage may pulsate or may contain noise. Therefore, a regression line may be calculated using all or part of the values in the ON section, and an intersection between the regression line and the reference voltage may be calculated. As a result, for example, variations (pulsations) in sampling values (numerical data)
And noise.

As described above, since the terminal voltages of the armature windings U, V, W are subjected to low-pass filtering, noise and the like can be removed, and thus, erroneous position detection can be prevented. In addition, when the position detection point corresponds to the off section of the PWM control, in order to obtain the position detection point by calculation,
Accurate position detection points can be obtained, and appropriate rotation control can be achieved. After the position detection point of the rotor is calculated by the above-described method, the position detection processing (including the calculation processing of a linear equation, an interpolation straight line, and a regression straight line) is not performed at least until the next energization switching. It is preferable not to perform the filtering process. As a result, no extra load is imposed on the microcomputer 13 and other processes can be executed.

In the case of the position detection method using external hardware (conventional example), since the position detection point is obtained by detecting the edge of the position detection signal, the position detection point cannot be obtained unless the edge appears. . That is, the state of the induced voltage waveform is not known. For example, when the position detection is significantly delayed due to a load change or the like, it is impossible to determine whether the position detection is caused by a rotation change or a missing edge of the position detection signal. As a result, position detection cannot be corrected, and rotation control cannot be performed.

However, according to the present invention, since the terminal voltage is sampled and the numerical data of the waveform is obtained, the state of the terminal voltage waveform can be constantly monitored, and spikes generated by switching the energization can be reduced. The state can be identified. Therefore, for example, when a rotational pulsation occurs and the position detection point fluctuates, by monitoring the coefficient (slope) of the above-described linear equation, it is possible to know the state of the induced voltage (envelope) by the slope, The power supply switching timing can be adjusted according to the state of the inclination, that is, adaptive control can be performed on the pulsating load.

FIG. 7 is a schematic block diagram for explaining another embodiment of the present invention. In the figure, the same parts as those in FIG. 7, a control device to which the brushless motor control method of the present invention is applied includes a resistor circuit 14 for synthesizing a terminal voltage of the brushless motor 4 and a neutral point voltage waveform synthesized by the resistor circuit 14 sampled. A / D converter 1 for converting digital data (numerical data) having a predetermined number of bits
An A / D converter 16 for sampling the terminal voltage waveforms of the 5-phase and one-phase armature windings and converting them into numerical data; taking in the numerical data and performing low-pass filtering by numerical calculation; In the numerical data obtained in step 16, the numerical data in the ON section of the PWM control is used as a reference voltage, and the numerical data obtained by the low-pass filtering is compared with the reference voltage to obtain a position detection point. Microcomputer 1 having arithmetic unit 17a
7 is provided. Note that the position detection calculation unit 17 a
1 has the same functions as the position detection calculation units 13a, 13b and 13c.

Therefore, the other embodiment has exactly the same operation and effect as the previous embodiment. The description is omitted because it is redundant. Further, in order to perform low-pass filtering on the neutral point voltage waveform obtained by synthesizing the terminal voltages and then obtain the position detection points of each phase, the number of A / D converters is smaller than in the previous embodiment.
The number of input ports can be reduced, and when the A / D converter is included in the microcomputer, the number of channels can be smaller than in the previous embodiment. That is, it is possible to suppress an increase in cost as compared with the previous embodiment, and there is also a possibility of reducing the capacity of the software program.

FIGS. 8 and 9 are schematic diagrams for explaining a modification of the position detection calculation units 13a, 13b, 13c and 17a shown in the above embodiment. The position detection calculation unit 18 shown in FIG.
8a to perform low-pass filtering. Note that the zero-cross comparison operation unit 18b has the same function as the zero-cross comparison operation unit 13ab shown in FIG.

In the above-described embodiment, an FIR type digital filter is used. This FIR type can obtain a non-cyclic type and stable characteristics (filter characteristics). Has a lot of computation,
Result calculation takes time. On the other hand, since the IIR type requires a small amount of calculation, the calculation time is short and the low-pass filtering process is fast. Therefore, it is extremely effective when low-pass filtering processing needs to be performed at high speed, for example, when the brushless motor 4 is controlled to rotate at high speed.

The position detection calculation unit 19 shown in FIG.
The coefficient of the digital filter 19a is stored in the ROM 20, and the filter characteristic of the digital filter is programmably changed using the coefficient, that is, the low-pass filtering is adaptively changed. The zero-cross comparison operation unit 19b has the same function as the zero-cross comparison operation unit 13ab shown in FIG.

In this case, a plurality of coefficients are stored in the ROM 20 in the form of a table. For example, a coefficient corresponding to a change in load or other circuit configuration, etc., and a coefficient in consideration of a noise situation or a driving state is empirically determined in advance. Then, this is stored in the ROM 20. Thereby, if the microcomputers 13 and 17 read the optimum filter coefficients from the ROM 20 according to the situation and set them in the digital filter 19a, that is, create a new difference equation, adaptive filtering can be performed.

[0035]

As described above, according to the first aspect of the brushless motor control method, when PWM control of the brushless motor is performed, digital data obtained by sampling the waveform of the terminal voltage of the brushless motor is obtained. While filtering the captured digital data by numerical calculation processing, and comparing the filtered value (the value of the induced voltage waveform) with a predetermined value to detect the position of the rotor of the brushless motor. Therefore, noise and the like included in the terminal voltage can be removed, so that erroneous position detection (erroneous energization switching) can be prevented. Further, since software processing can be performed, reliable position detection can be performed. There is an effect that the cost can be reduced by the reduction of the wear circuit and the like.

According to the second aspect of the present invention, when the brushless motor is subjected to PWM control, the waveform of the neutral point voltage obtained by synthesizing the terminal voltages of the brushless motor is sampled, and the digital data obtained by the sampling is sampled. While filtering the captured digital data by numerical calculation processing, and comparing the filtered value (the value of the induced voltage waveform) with a predetermined value to detect the position of the rotor of the brushless motor. Therefore, noise and the like included in the terminal voltage can be removed, so that erroneous position detection (switching of erroneous energization) can be prevented. Further, since software processing can be performed, reliable position detection is possible. It suffices to sample the neutral point voltage waveform and minimize the number of A / D conversion circuits. With fewer number of channels of the microcomputer to execute the software processing, there is an effect that it is possible to dispense more expensive including the reduction of such a hardware circuit.

According to a third aspect of the present invention, the predetermined value in the first or second aspect is a half of digital data obtained by sampling in the ON section of the PWM control with the applied voltage (terminal voltage) of the brushless motor. 3. A value (reference voltage value), and a point at which the magnitude relationship of the filtered value is inverted with respect to the reference voltage value is set as the rotor position detection point. Since no new reference voltage generating circuit is required, the cost can be reduced. Further, since the reference voltage is obtained from the currently applied voltage, for example, fluctuations in the applied voltage (induced voltage) waveform can be prevented. Also, there is an effect that an appropriate reference voltage can always be obtained, and thus accurate position detection can be performed.

According to the fourth aspect of the present invention, the digital data in the off-period of the PWM control according to the first or second aspect is calculated based on the digital data in the on-period of the PWM control, and this operation is performed. The digital data obtained is regarded as the value of the induced voltage waveform and can be compared with the predetermined value. Therefore, in addition to the effect of the first or second aspect, the position detection point of the rotor is set to the off period of PWM control (that is, the induced voltage waveform). (Missing section), the position can be detected, so that an accurate position detection point can always be obtained, and accordingly, there is an effect that appropriate rotation control can be performed.

According to a fifth aspect of the present invention, in claim 4, one of the plurality of digital data in the ON section is set as a representative value, and one of the plurality of digital data in the ON section adjacent to the ON section is set as a representative value. One of the representative values is used as a representative value, and a linear expression corresponding to the value of the induced voltage waveform in the off section is created based on the two representative values, and this linear expression is compared with the predetermined value to detect the position detection point of the rotor. In addition to the effect of claim 4, in addition to the effect of claim 4, since the calculation processing of the linear equation representing the missing section of the induced voltage waveform is simple, the processing time may be short, and the surplus capacity of the microcomputer for the control is obtained. Can be used for other processing.

According to a sixth aspect of the present invention, the value of the induced voltage waveform in the off-period is determined by the plurality of digital data in the on-period and the plurality of digital data in the on-period adjacent to the same on-period. A corresponding linear equation is created, and the linear equation is compared with the predetermined value to obtain the position detection point of the rotor. Since the linear expression is closer to the current induced voltage waveform, there is an effect that more accurate position detection is possible.

According to a seventh aspect of the present invention, in the fourth aspect, out of the plurality of digital data in the ON period,
The value of the induced voltage waveform in the off section is determined by the average value of at least two or more digital data and the average value of at least two or more digital data of the plurality of digital data in the on section adjacent to the on section. Since a corresponding linear equation is created and the linear equation is compared with the predetermined value to obtain the position detection point of the rotor, in addition to the effect of claim 4, for example, ripples appear on the induced voltage waveform. Even when the ripple is not removed by filtering, the linear equation is calculated using the average value of the digital data in the ON section, so that the influence of the ripple can be reduced, and the position detection can be accurately performed. This has the effect.

According to the invention of claim 8, according to claim 1,
A regression line is calculated using a plurality of digital data in the 2 or 4 ON section, and the regression line is regarded as the value of the induced voltage waveform and compared with the predetermined value to determine the position detection point of the rotor. As a result, in addition to the effects of Claims 1, 2 and 4, the regression line is close to the current induced voltage waveform even when ripples and noise are present in the induced voltage waveform and are not removed by filtering. Therefore, the effect of ripple and noise can be reduced, and the position detection can be accurately performed.

According to the invention of claim 9, according to claim 1,
In the on section of the PWM control in 2 or 4,
Since an interpolation straight line corresponding to the induced voltage waveform is calculated based on the digital data of the ON section before the position detection, and the interpolation straight line is compared with the predetermined value to obtain a position detection point of the rotor. In addition to the effects of the first, second, and fourth aspects, there is an effect that an accurate position detection point can be estimated, that is, there is no slight delay in position detection, and appropriate rotation control can be performed.

According to the tenth aspect, the first aspect is provided.
9. The method according to claim 4, wherein when a value detected by low-pass filtering is compared with a predetermined value in an ON section of the PWM control and a position detection point of the rotor is obtained. Is not performed. In addition to the effects of claim 1 or 2, there is an effect that not only the detection of an erroneous position is prevented but also the surplus capacity of the microcomputer for the control can be used for other processing. .

According to the eleventh aspect of the present invention, the first aspect
In (2) or (3), since the numerical operation processing is an FIR type or IIR type low-pass digital filter, it is possible to remove noise and the like in the same manner as in the conventional hardware circuit in addition to the effects of claim 1 or 2. In addition, erroneous position detection due to noise or the like can be prevented, and the cost can be reduced because of the hardware circuit.
Advanced processing is possible while realizing cost reduction if conversion is included in the control microcomputer.
Further, in the case of the FIR type, a stable filter characteristic is obtained,
In other words, noise that always occurs can be accurately removed, and in the case of the IIR type, the numerical calculation capacity is small,
That is, there is an effect that an extra burden is not imposed on the microcomputer for the control.

According to the twelfth aspect of the present invention, a first aspect is provided.
In FIG. 1, a plurality of coefficients of the low-pass digital filter are stored in the form of a table, and the coefficient pattern of the low-pass digital filter can be changed. Can be accurately removed, and an erroneous position can be prevented from being detected.

[Brief description of the 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 for explaining a position detection calculation unit of the control device shown in FIG. 1;

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

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

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

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

FIG. 7 is a schematic block diagram of a control device for a brushless motor according to another embodiment of the present invention.

FIG. 8 is a schematic diagram for explaining a modification of the position detection calculation unit of the control device shown in FIG. 1;

FIG. 9 is a schematic diagram for explaining a modification of the position detection calculation unit of the control device shown in FIG. 1;

FIG. 10 is a schematic block diagram of a conventional brushless motor control device.

FIG. 11 is a schematic time chart for explaining the operation of the control device shown in FIG. 10;

[Explanation of symbols]

2 AC / DC converter 3 Inverter 4 Brushless motor (sensorless DC brushless motor) 6 Control circuit (microcomputer) 10, 11, 12 A / D converter 13, 17 Microcomputer 13a, 13b, 13c, 18, 19 Position Detection calculation section 13d, 17b Energization switching timing calculation section 13e, 17c Signal generation section 13aa, 19a Digital filter (FIR type) 13ab, 18b, 19b Zero-cross comparison calculation section 18a Digital filter (IIR type) 20 ROM

Claims (12)

[Claims] 1. A brushless motor, comprising detecting a position of a rotor by an induced voltage included in a terminal voltage of an armature winding of the brushless motor, and switching energization of the armature winding of the brushless motor based on the detected position. A method of controlling a brushless motor that PWM-controls the brushless motor, wherein digital data obtained by sampling a waveform of the terminal voltage is taken in, while the taken-in digital data is filtered by a numerical operation process, and the filtered value is obtained. (The value of the induced voltage waveform) is compared with a predetermined value to detect the position of the rotor of the brushless motor, and the energization switching timing of the armature winding is calculated based on the position detection. A method for controlling a brushless motor. 2. A brushless motor, comprising: detecting a position of a rotor by an induced voltage included in a terminal voltage of an armature winding of the brushless motor; and switching energization of the armature winding of the brushless motor based on the detected position. A method of controlling a brushless motor that PWM-controls the brushless motor, wherein a waveform of a neutral point voltage obtained by synthesizing the terminal voltages is sampled, and digital data obtained by the sampling is taken in. The digital data is filtered by a numerical calculation process, and the filtered value (the value of the induced voltage waveform) is compared with a predetermined value to detect the position of the rotor of the brushless motor. A method for controlling a brushless motor, wherein a timing for switching energization of an armature winding is calculated. 3. The predetermined value is a half value (a value of a reference voltage) of digital data obtained by sampling the voltage (terminal voltage) of the brushless motor during an on-period of the PWM control. 3. The brushless motor control method according to claim 1, wherein a point at which the magnitude relationship of the filtered value is inverted with respect to a voltage value is set as a position detection point of the rotor. 4. The digital data in the off period of the PWM control is calculated based on the digital data in the on period of the PWM control, and the digital data obtained by the calculation is regarded as the value of the induced voltage waveform. 3. The control method for a brushless motor according to claim 1, wherein the predetermined value can be compared with the predetermined value. 5. A method according to claim 1, wherein one of the plurality of digital data in the ON section is a representative value, and one of the plurality of digital data in an ON section adjacent to the ON section is a representative value. 5. The brushless device according to claim 4, wherein a linear expression corresponding to the value of the induced voltage waveform in the off section is created based on the value, and the linear expression is compared with the predetermined value to obtain a position detection point of the rotor. Motor control method. 6. A linear equation corresponding to the value of the induced voltage waveform in the off section is created from the plurality of digital data in the on section and the plurality of digital data in the on section adjacent to the on section. 5. The control method for a brushless motor according to claim 4, wherein a position detection point of the rotor is obtained by comparing the position of the rotor with the predetermined value. 7. An average value of at least two or more digital data of the plurality of digital data in the ON section, and at least two or more digital data of a plurality of digital data in an ON section adjacent to the ON section. 5. A linear equation corresponding to the value of the induced voltage waveform in the off section is created by using the average value of the rotor section, and the linear equation is compared with the predetermined value to obtain a position detection point of the rotor. The control method of the brushless motor according to the above. 8. A method for calculating a regression line using a plurality of digital data in the ON period, comparing the regression line with a value of the induced voltage waveform, and comparing the regression line with a predetermined value, the position detection point of the rotor. The brushless motor control method according to claim 1, 2 or 4, wherein 9. An interpolating straight line corresponding to the induced voltage waveform is calculated from digital data of an on-period before the position detection in the on-period of the PWM control, and the interpolating straight line is compared with the predetermined value. 5. A control method for a brushless motor according to claim 1, wherein the position detection point of the rotor is obtained. 10. A comparison between a low-pass filtered value and a predetermined value in an on-period of the PWM control, and when a position detection point of the rotor is obtained, the numerical operation processing is performed at least until the next energization switching. 3. The control method for a brushless motor according to claim 1, wherein position detection is not performed. 11. The brushless motor control method according to claim 1, wherein said numerical processing is a FIR type or IIR type low-pass digital filter. 12. The control method for a brushless motor according to claim 11, wherein a plurality of coefficients of said low-pass digital filter are stored in a table format, and a coefficient pattern of said low-pass digital filter can be changed.