JPH07177787A - Method for detecting rotor of dc brushless motor - Google Patents

Abstract

PURPOSE:To accurately detect the position of a rotor by eliminating the PWM signal components of a voltage induced in an armature coil winding, inputting a detection signal obtained by discriminating processing to a frequency trigger counter, and then measuring the chattering continuation period of an edge part for determining a rising or a falling timing. CONSTITUTION:In a first position detection circuit 8, a PWM signal component is eliminated from an output voltage Eu by a filter circuit 9u and is compared with a reference voltage Vr by a comparison circuit 10u to obtain a detection signal Ku whose level changes according to the relative position between a rotor and a U-phase coil winding. Then, a count output signal Cu with a pulse having the same time width as the chattering continuation period of the edge part is obtained by a frequency trigger counter 11u. Then, the intermediate position is determined as the rising timing of the detection signal Ku to determine a position detection information Pu from the rising and falling timings of the count output signal Cu by an edge timing operation part 12u. Similar processing is performed also for V and W phases by the second and two-position detection circuits 8u and 8w.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor brush position detecting method for a DC brushless motor.

[0002]

2. Description of the Related Art In a DC brushless motor, the position of the rotor is detected from the induced voltage generated in the armature winding while the motor is rotating, and the current switching to each phase winding of the motor is controlled. A drive control method for a motor is known (for example, Japanese Patent Laid-Open No. 3-164089).
According to this conventional method, a pulse width modulation (PWM) signal component for switching excitation included in an induced voltage generated in an armature winding is removed by a filter and level discrimination is performed to obtain a rising edge of a rectangular wave signal. This is a configuration for detecting the position of the rotor from the timing.

[0003]

By the way, as described above, when the PWM signal component is to be removed from the induced voltage by using the filter, the cutoff frequency fc of the filter is lowered to sufficiently remove the PWM signal component. There is a need to. However, for example, in the case of the first-order filter, 1 of fc
Since the phase begins to lag at a frequency of about / 10,
In this type of control in which the delay of the phase is not allowed in the used frequency range of the fundamental wave, the value of fc must be set to about 10 times the upper limit value of the used frequency. Therefore, if the frequency band of the fundamental wave is close to the frequency of the PWM signal, it may be difficult to attenuate the PWM signal waveform to a level that does not affect the PWM signal waveform. If the frequency band of the fundamental wave is close to the frequency of the PWM signal, the PWM Chattering occurs at the rising edge of the output signal of the filter due to the influence of the signal waveform.

This chattering can be removed to some extent by adding a hysteresis to the output stage, but in this case, another problem that a phase is delayed occurs. There is also a means to remove this kind of chattering by software, but the frequency of interrupts is high, a microcomputer with a high processing speed is required, the cost is high, and depending on the software processing, the original rise of the fundamental wave, There is a problem that the falling point cannot be obtained accurately.

An object of the present invention is to provide a method for detecting the position of a rotor in a DC brushless motor, which can solve the above-mentioned problems in the prior art.

[0006]

A feature of the method of the present invention for solving the above-mentioned problems is that a pulse width modulation signal component included in an induced voltage induced in each phase of an armature winding of a DC busless motor is filtered. In the method for detecting the rotor position of a DC brushless motor, the position information of the rotor is obtained from the rising or falling timing of the output signal obtained by performing the level discrimination processing on the signal obtained by removing the The output signal is input to a frequency trigger counter that operates in synchronization with the carrier signal of the pulse width modulated signal being supplied, the length T of the chattering duration of the edge portion of the output signal is measured, and the measured chattering is performed. To determine the rising or falling timing of the output signal from the start or end timing of the duration and the length T thereof. Lies in the fact was.

[0007]

The frequency trigger counter, which operates in synchronization with the carrier signal of the PWM signal, operates in synchronization with the period of the chattering signal which can be regarded as substantially equal to the period of the PWM carrier signal. The length T of the chattering duration of the edge portion is measured. The true rise or fall timing of the output signal is T / 2 from the start or end timing of this chattering continuation period.
It is set at a point apart only.

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 shows a block diagram of an embodiment of a brushless DC motor for detecting the position of a rotor by the method of the present invention. FIG. 1 shows an embodiment in the case of a three-phase brushless DC motor 1, in which 2 denotes windings 2u, 2v, 2 of U-phase, V-phase and W-phase.
An armature winding in which w is star-connected and its neutral point is grounded, 3 is a rotor that is combined with the armature winding 2, 4 is a DC power supply, and 5 is DC power supply from the DC power supply 4. In order to supply the exciting current to the windings 2u, 2v, 2w of the respective phases of the receiving armature winding 2 at a required timing, the semiconductor commutator device is a known semiconductor commutator device including, for example, a semiconductor switching element with a control electrode.

Reference numeral 6 indicates three windings 2u,
Terminal output voltages Eu, Ev, Ew induced in 2v, 2w
In response to the above, the first to third controls for processing the output voltages of these terminals as described later to obtain the position information of the rotor 3 and controlling the ON / OFF of the switching element (not shown) of the semiconductor commutator device 5. Signals Su, Sv, Sw
Is a drive control circuit for outputting

Next, the drive control circuit 6 will be described in detail with reference to FIG.

The drive control circuit 6 has terminal output voltages Eu, E
Input terminals 7u, 7v, 7 to which v and Ew are applied respectively
First to third position detection circuits 8u and 8 corresponding to w, respectively.
v, 8w are provided. The first position detection circuit 8u
It has a filter circuit 9u for removing the PWM signal component contained in the terminal output voltage Eu, and the output from the filter circuit 9u is compared with the reference voltage Vr in the comparison circuit 10u, and the rotor 3 and the winding 2u are relatively opposed to each other. A detection signal Ku whose level changes depending on the position is obtained.

As shown in FIG. 3 (a), this detection signal Ku rises, falls, that is, due to the influence of the PWM signal for switching excitation of each phase winding 2u, 2v, 2w. Chattering occurs at the edge. In order to determine the timing of the true rise and fall of the detection signal Ku, the detection signal Ku is operated by the frequency trigger counter 1 that operates in synchronization with the carrier signal of the PWM signal.
1u, and a pulse having a time width equal to the chattering duration T of the edge portion is output as the count output signal Cu (see (b) of FIG. 3).

As can be seen by comparing the waveforms of FIGS. 3A and 3B, the count output signal Cu rises when the second chattering pulse is output at the rising portion of the detection signal Ku. On the other hand, the count output signal Cu falls at the timing t1 at the timing t2 when one chattering pulse has elapsed since the last chattering pulse in the rising portion of the detection signal Ku was output. However, since the period of the chattering portion is substantially equal to the frequency of the carrier signal described above, the shift described above is extremely small. Therefore, the rising timing t1 of the count output signal Cu is substantially equal to the start timing of the chattering duration of the detection signal Ku, while its falling timing t2 is substantially equal to the end timing of the chattering duration of the detection signal Ku. . The length T of the high level period of the count output signal Cu is equal to the chattering continuation period.

As described above, the count output signal Cu having information on the start and end timings of chattering of the edge portion of the detection signal Ku and its duration is
It is input to the edge timing calculation unit 12u, where the count output signal Cu rises to T
The timing t0 separated by / 2 is determined as the rising timing of the detection signal Ku. The position detection information Pu indicating the timing t0 thus determined is the control circuit 1
Input to 3.

Although the first detection circuit 8u has been described above, the remaining second and third detection circuits 8v and 8w are also configured in the same manner, and the position indicating the relative position of the rotor 3 with respect to the windings 2v and 2w. The detection information Pv and Pw are similarly provided to the control circuit 13.

In the control circuit 13, as shown in (c) of FIG. 3, for example, the rotor 3 rises at the falling timing t2 of the count output signal Cu and the rotor 3 starts from the timing t0 determined as the rising timing of the detection signal Ku. 9
The first control signal Su for controlling the excitation of the U-phase armature winding 2u, which falls at the timing ta when rotated by 0 °, is output. Second and third for controlling the excitation of the other windings 2v and 2w
The same applies to the control signals Sv and Sw.

In the control circuit 13, a PWM signal to be given for exciting each phase of the armature winding is created based on the position detection information Pu, Pv, Pw, and the first to third values are generated in accordance with these. Although the control signals Su, Sv, and Sw are output, detailed description thereof is omitted here.

According to the above structure, the position of the rotor can be accurately detected even if the chattering component is included in the signal for detecting the 12 rotor position as described above, so that the PWM signal component is removed. The degree of freedom in designing the filter for this purpose can be significantly increased, and since a frequency trigger counter is used, data processing for removing chattering components can be simplified, and an expensive micro-processor capable of high arithmetic processing speed can be used. Since it is not necessary to use a computer, the cost is reduced and the load on the microcomputer is reduced.

[0019]

As described above, according to the method of the present invention, the position of the rotor can be accurately detected even if the chattering component is included in the signal for detecting the rotor position. The degree of freedom in designing the filter for removing the PWM signal component can be markedly increased, and since the frequency trigger counter is used, data processing for removing the chattering component can be simplified and an expensive element is required. The position of the rotor can be accurately detected without any need.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a brushless DC motor configured to detect the position of a rotor by the method of the present invention.

FIG. 2 is a detailed block diagram of the drive control circuit shown in FIG.

FIG. 3 is a waveform diagram of signals at various parts for explaining the operation of the drive control circuit shown in FIG.

[Explanation of symbols]

 1 Brushless Motor 2 Armature Winding 2u Winding 2v Winding 2w Winding 3 Rotor 8u First Position Detection Circuit 8v Second Position Detection Circuit 8w Third Position Detection Circuit 9u Filter Circuit 10u Comparison Circuit 11 Frequency Trigger Counter 12u Edge Timing calculation unit Cu count output signal Eu terminal output voltage Ev terminal output voltage Ew terminal output voltage Ku detection signal Su first control signal Sv second control signal Sw third control signal T continuous period Vr reference voltage

Claims (1)

[Claims] 1. A rising edge of an output signal obtained by level-discriminating a signal obtained by removing a pulse width modulation signal component contained in an induced voltage induced in each phase of an armature winding of a DC bushless motor by a filter. A method for detecting a rotor position of a DC brushless motor, wherein rotor position information is obtained from a fall timing, a frequency trigger operating in synchronization with a carrier signal of a pulse width modulation signal supplied to the armature winding. The output signal is input to a counter, the length T of the chattering continuation period of the edge portion in the output signal is measured, and the output signal rises from the measured start or end timing of the chattering continuation period and the length T thereof. Alternatively, a rotor position detection method for a DC brushless motor is characterized in that the fall timing is determined.