JPH0382391A - Position detecting system for brushless motor - Google Patents

Abstract

PURPOSE:To accurately detect the rotating position of a rotor by A/D-converting an induced voltage generated in a stator winding into digital data, and calculating the magnitude of a variation by a microprocessor. CONSTITUTION:A stator has 6-pole teeth and stator windings wound thereon and connected in three phases. A microcomputer 28, comparators 21-23, A/D- converters 24-27 are connected to the stator windings. Terminal voltages are converted to digital data by the converters 24-27. The states of induced voltages in the windings are compared in amplitudes by the comparators 21-23. The microcomputer 28 calculates the detected values of the comparators 21-23 and terminal voltage waveforms by a straight approximation, subtracts to correct them to detect the accurate position of a rotor. Thus, even if conduction to the windings is intermittent, the rotating position of the rotor can be accurately detected.

Description

[Detailed Description of the Invention] Kui〉Industrial Application Field The present invention energizes a stator winding that is not energized based on a change in induced voltage that occurs in a stator winding that is not energized due to the rotation of a rotor that has a plurality of permanent magnets. This invention relates to a brushless motor in which the combination of stator windings can be changed.

<Explanation> Conventional technology In general, there is a conventional technology as described in Japanese Patent Publication No. 36519/1983. What is described in this publication is that the induced voltage waveform generated in the stator winding is
After converting to a triangular wave signal through a second-order lag filter,
The rotational position of the rotor was detected by comparing the size with the virtual neutral point.

However, in this case, it has been difficult to operate the motor at high speed because the response is reduced due to the influence of the first-order lag filter and the triangular wave signal has an advanced phase due to the influence of the spike-like voltage that occurs when switching the energization of the winding.

Furthermore, a device such as that described in U.S. Patent No. 4,495,450 changes the combination of energized stator windings based on the change in the induced voltage generated in the stator windings that are not energized. there were. In this case, when the voltage and current supplied to the motor are increased, the voltage applied to the stator windings is applied intermittently (chopping at a predetermined period, PWM
waveform, etc.). When the stator winding is energized in this way, the stator winding is turned off.
When this happens, the accuracy of position detection using induced voltage deteriorates.

<C> Problems to be Solved by the Invention In the conventional technology configured as described above, since the stator windings are energized intermittently, there are periods when the induced voltage cannot be detected, and the rotation of the rotor is interrupted. The accuracy of position detection deteriorated.

In order to solve these problems, the present invention provides a position detection method in which changes in the induced voltage during a period in which the induced voltage cannot be detected are determined by calculation.

<2> Means for solving the problem The present invention has a rotor having a plurality of permanent magnets, and a plurality of stator windings arranged so as to apply a rotating magnetic field to the rotor when energized. The stator windings are energized to obtain a rotating magnetic field by energizing some of the plurality of stator windings, and the stator windings are energized based on the change in the induced voltage that occurs in the stator windings that are not energized. In a brushless motor configured to change the combination of the stator windings, the stator windings are energized intermittently, and the induced voltage is A/D converted in accordance with the intermittent energization. The rotational position of the rotor is detected from the magnitude of a predetermined direct current voltage and a continuous change in induced voltage calculated based on digital data.

(Refer to) Operation In the brushless motor position detection method configured as described above, the change in the induced voltage during the period in which the induced voltage cannot be detected can be calculated by calculation.

(f) Examples Examples of the present invention will now be described based on the drawings. FIG. 1 is a top view of the motor with the bracket and bearing removed. In this figure, the first stator core is
It has six poles of teeth 2 to 7. Stator windings 8 to 13 are wound around the teeth 2 to 7, respectively, so that the opposing teeth 2 and 5, teeth 3 and 6, and teeth 4 and 7 are excited to the same polarity. Stator windings 8 to 13 are connected to each other. Incidentally, these stator windings are connected in three phases as shown in FIG.

A rotor 14 is housed in a housing hole formed by teeth 2 to 8, and is rotated by a rotating magnetic field obtained by changing the energization combination of stator windings 8 to 13. The rotor 14 includes four permanent magnets 15 to 18, a rotor core 19, and a rotating shaft 20. Permanent magnets 15.17 are N poles, permanent magnets 16.18 are S poles, and rotor core 1
It is attached so that it is located on the outer periphery of 9.

FIG. 3 is a block diagram showing the configuration of a control circuit that switches energization to stator windings 8 to 13. Comparators 21 to 23 compare the voltages of the U-phase, ■-phase, and W-phase terminals of the motor with the DC voltage, and output an output when the voltage of each terminal exceeds the DC voltage. 24-27 are A/D
It is a converter (analog/digital converter) that converts the voltage at each terminal into digital data in response to an A/D conversion timing signal.

28 is a microprocessor, and comparators 21 to 28
23, the outputs of the A/D converters 24 to 27 are input, and after arithmetic processing is performed internally, the energization of the fixed 1,000-winding wires 8 to 13 is switched. 29 is the stator winding 8 to 1 of the motor 30
This is a group of switching elements that control energization to 3. This switching element group mainly consists of six transistors (or F
Semiconductor devices such as ETs) are connected in a three-phase bridge configuration, and the outputs of this bridge circuit are given to the U-phase terminal, V-phase terminal, and W-phase terminal, respectively.

Figure 4 shows the U-phase terminal (V-phase terminal, W-phase terminal has a phase of 120
The same voltage waveform can be obtained by simply moving back and forth. ) is a voltage waveform diagram showing changes in voltage. In this figure, each position detection point by the hum comparator indicates a point in time when the comparator 21 outputs an output. The corrected position detection point is a position detection time point obtained by the position detection method according to the present invention. The U-phase switching element drive signal is 0 of the upper and lower switching elements of the U-phase arm of the switching element group 29.
This shows the N10FF state.

FIG. 5 is an explanatory diagram showing the position detection method, and shows the state of induced voltage generated in the stator winding which is not energized. In this figure, motor terminal voltages 32-a and 3L-b are compared in magnitude with DC voltage 31-11.31-b by a comparator. 33-a and 33-b are waveform charts showing changes in the output of the comparator. This waveform 33-a, 33
In -b, time points A and B are the position detection points by the humpator, but as in A, while the drive signal 34 of the switching element is ON (current is being energized to the stator winding in intermittent control). If there is an output from the humparator, this time point A can be processed as a position detection point without any correction. However, when the position is detected by the comparator at the rising edge of the drive signal 35 as at time B, that is, at the same time as the start of energization to the winding, the normal position detection point T is TD from time B.
Since the timing is earlier by the amount of time, it is necessary to correct this point B.

Therefore, the motor terminal voltages (U-phase terminal voltage, V-phase terminal voltage, W-phase terminal voltage) are sequentially A/D converted and taken into the microprocessor 28 at timings 36 and 37 that are synchronized with the rising and falling edges of the drive signal 35. It will be done. In this microprocessor 28, 38-
Normal detection point T using ~38-n sampling points.

The time delay TD from to point B detected by the comparator is calculated by linear approximation of the terminal voltage waveform, and
By subtracting and correcting the position detection timing delay TD from the point in time, a normal position detection point T can be obtained.

In FIG. 5(b), sampling point 38-1.3
8-m sampling results as (vz, tt)t(vm,
tm), the DC voltage is vda, and the timing of detection point B by the comparator is T, then the correction numerator is Tb-((vm-vdc)/(vm-vt))
The normal detection point T, which is calculated as X (t m -tt), can be obtained as T, -T, -Tfl.

In this way, it is determined whether the position detection point by the comparator is at the normal timing, and if it is normal, the detection point by the comparator is processed as the position detection point, and the timing is as shown at points C and D in Figure 4. If the detection by the comparator is not normal, these points are corrected to make them normal position detection points E and F, and the switching elements are turned ON and OFF at timings G and H delayed by 30 degrees in electrical angle from this point. .

In this example, the A/D converter and microcomputer are configured separately, but by using a microcontroller with a built-in A/D conversion function, the system configuration can be simplified, and the microcomputer processing can also be simplified. It is. In addition, it is naturally possible to adopt a detection method in which each terminal voltage is set as a star-shaped wire using a resistor and the virtual neutral point voltage is used as a DC voltage. can also be simplified.

(G) Effects of the Invention The present invention energizes some of the stator windings among a plurality of stator windings, and adjusts the stator windings based on the change in induced voltage that occurs in the stator windings that are not energized. In a brushless morph that obtains a rotating magnetic field by sequentially switching the energization of the
The stator windings are energized intermittently, and the induced voltage is A/D converted (analog/digital conversion) in accordance with this intermittent operation, and based on the digital data obtained by this A/D conversion, Since the rotational position of the rotor is detected from the magnitude of the continuous change in the calculated induced voltage and the predetermined DC voltage, the rotational position of the rotor can be detected even when the stator windings are energized intermittently. By correcting the detection, it is possible to always accurately detect the rotational position.

[Brief explanation of drawings]

Fig. 1 is a front view of the rotor and stator of a brushless motor showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing the connection state of the stator windings shown in Fig. 1, and Fig. Figures 1 and 2
FIG. 4 is a block diagram of a circuit for controlling energization to the stator winding shown in the figure, FIG. 4 is a voltage waveform diagram of a U-phase terminal, and FIG. 5 is an explanatory diagram showing a method of correcting a position detection point. 8-13... Stator winding, 21-23... Comparator, 24-27... A/D converter, 2
8... Microprocessor, 29... Switching element group.

Claims (1)

[Claims] (1) It has a rotor having a plurality of permanent magnets, and a plurality of stator windings arranged so as to apply a rotating magnetic field to the rotor when energized, and among the plurality of stator windings, A brushless motor that energizes some of the stator windings to obtain a rotating magnetic field, and also changes the combination of stator windings that are energized based on changes in the induced voltage that occurs in the stator windings that are not energized. In a motor, the stator winding is energized intermittently, and the induced voltage A increases in accordance with this intermittent operation.
/D conversion (analog/digital conversion) and
A brushless motor position detection method that detects the rotational position of the rotor based on the magnitude of a predetermined DC voltage and continuous changes in induced voltage calculated based on digital data obtained by this A/D conversion. .