JP5797478B2 - Brushless motor control device and control method - Google Patents

Description

  The present invention relates to a control device and a control method for a brushless motor.

  A brushless motor of a type in which the rotor has a permanent magnet may perform drive control without a position sensor without providing a position sensor for detecting the rotational position of the rotor. In this case, the rotational position of the rotor is detected from the edge interval of the pulse signal obtained by inputting the induced voltage and the equivalent neutral point potential appearing at the motor terminal in the open section (non-energized phase) to the comparator.

  This brushless motor, as a method for determining the rotor stop position during sensorless drive, generates a position detection signal based on the result of comparing the induced voltage of one phase when the rotor is free-runned and the average of the remaining two phases with a comparator. Thus, the rotor position is determined (see Patent Document 1). According to this brushless motor, by generating a free-run state at the time of start-up, the induced voltage generated at the motor terminal is detected without being affected by the pulse width modulation signal or the like, so that the rotor is not affected by disturbance. It is possible to detect the position correctly and detect the rotor position while free running, so that it is possible to detect the rotor position in a short time and shift to normal operation. ing.

JP 2008-092784 A

  However, the brushless motor described in Patent Document 1 is configured to detect the induced voltage when the rotor is free-runned, but the induced voltage when the rotor is free-runned is small, and is in the vicinity of the common-mode input voltage range of the comparator. Then, there is a problem that chattering occurs in the output signal of the comparator and the rotor position is erroneously detected.

  The present invention has been made in view of such circumstances, and can prevent chattering from occurring in the output signal of the comparator and erroneously detecting the rotor position, thereby improving the position detection accuracy of the rotor. It is an object of the present invention to provide a control device and a control method for a brushless motor.

  The present invention is a control device that controls the rotational drive of a brushless motor including a rotor and a stator, and energizes the brushless motor for an initial energization time with an excitation pattern that matches the rotor stop position when the brushless motor is started. After that, when detecting the position of the rotor by detecting the edge detection of the induced voltage generated during the free run by interrupting the rotation control means for stopping energization and free running the rotor of the brushless motor. Rotation direction determination means for determining the rotor position based on the detected phase and direction of the edge in a state where only interruption of edge detection to be detected next is permitted for each rotation direction of the rotor. It is characterized by.

  The present invention is a control method for controlling the rotational drive of a brushless motor including a rotor and a stator, wherein the brushless motor is energized for an initial energization time with an excitation pattern that matches the rotor stop position when the brushless motor is started. Thereafter, when detecting the position of the rotor by detecting by interruption the rotation control step of stopping energization and free-running the rotor of the brushless motor, and detecting the edge of the induced voltage generated during the free-run A rotation direction determination step for determining the rotor position based on the phase and direction of the detected edge in a state where only interruption of edge detection to be detected next is permitted for each rotation direction of the rotor. It is characterized by.

  According to the present invention, when edge detection is performed, an interrupt indicating that another edge other than the edge to be detected next is detected is masked, and the interrupt of the edge to be detected next is masked. Therefore, even if chattering occurs in the output signal of the comparator (position detection signals for the U phase, V phase, and W phase), it is possible to prevent erroneous detection of the position. . As a result, it is possible to improve the rotor position detection accuracy when the input voltage (induced voltage) of the comparator is in the vicinity of the common-mode input voltage range.

It is a block diagram which shows the structure of the control apparatus of the brushless motor by one Embodiment of this invention. It is a flowchart which shows the processing operation of the interruption process part 21 shown in FIG. It is a flowchart which shows the processing operation of the interruption process part 21 shown in FIG. It is explanatory drawing which shows an example of the pattern of the position detection signal for determining the rotation direction of a rotor. It is explanatory drawing which shows an example of the erroneous detection in a position detection. It is explanatory drawing which shows operation | movement of the control part 11 shown in FIG. It is explanatory drawing which shows the pattern of the edge which should be detected next. It is explanatory drawing which shows the pattern of the edge which should be detected next. It is explanatory drawing which shows edge detection operation | movement.

  A brushless motor control apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. In this figure, reference numeral 1 denotes a brushless motor having a rotor having a permanent magnet and a stator, and three-phase (U, V, W) coils wound around the stator in order in the circumferential direction. The brushless motor 1 is a sensorless type brushless motor that does not have a sensor for detecting the rotor position. Reference numeral 11 is a control unit configured by a microcomputer or the like, and controls the rotational drive of the brushless motor 1. Reference numeral 12 denotes an induced voltage I / F (interface) circuit that detects a voltage applied to a current-carrying wire that forms a three-phase coil of the brushless motor 1.

  Reference numeral 13 denotes a circuit formed by connecting two switching elements between the positive and negative terminals of the power supply 15 each, and a DC voltage supplied from the power supply 15 is input from the control device 11 to a pulse width modulation signal. It is an inverter that converts an alternating voltage based on (driving signal) and applies it to each phase of the brushless motor 1. Reference numeral 14 denotes a driver that inputs a drive signal for applying an excitation current to the coil of the brushless motor 1 output from the control unit 11 and switches the switching element in the inverter 13 on and off.

  The control unit 11 includes an interrupt processing unit 21, a rotation direction determination unit 22, and a rotation control unit 23. The interrupt processing unit 21 receives U-phase, V-phase, and W-phase position detection signals output from the induced voltage I / F circuit 12, and generates an interrupt that detects a rising edge or a falling edge of each position detection signal. When it occurs, an edge detection signal is output. The edge detection signal includes information for identifying one of the three phases and information for identifying whether the edge is a rising edge or a falling edge. The rotation direction determination unit 23 specifies excitation switching timing based on the edge detection signal output from the interrupt processing unit 21, and determines the position and rotation direction of the rotor from the specified excitation switching timing.

  The rotation control unit 23 determines an excitation pattern according to the rotor position based on the start command input from the outside and the excitation switching timing obtained in the rotation direction determination unit 22, and the brushless motor 1 of the brushless motor 1 is determined according to the determined excitation pattern. A signal for applying an exciting current to the coil is output to the driver 14. Further, the rotation control unit 23 energizes the start excitation pattern for a predetermined initial energization time, and then performs a process for detecting the rotor position by causing the brushless motor 1 to free run.

  The induced voltage I / F circuit 12 receives a voltage (analog signal) of each of the three-phase motor terminals and divides the voltage into a voltage that can be input to the comparators 17A to 17C (resistor R1 and resistor R2) and a pulse. Low pass filter circuits 15A, 15B and 15C composed of a primary CR filter (resistor R2 and capacitor C1) for removing noise of the width modulation signal, a circuit 16 for detecting an equivalent neutral point potential, and an equivalent neutral point potential Comparators 17A, 17B, and 17C that generate pulse signals from analog signals of induced voltages that appear in the non-conducting phase (open period), and a low-pass filter (primary CR filter) 18A that cuts high-frequency components from the outputs of the comparators 17A to 17C , 18B, 18C.

  Here, the circuit 16 that detects the equivalent neutral point potential employs a two-phase comparison method that detects the equivalent neutral point potential from the motor terminal voltages of the V phase and the W phase for the U phase, for example. ing. In this way, a substantially flat voltage is obtained as the equivalent neutral point potential. It should be noted that a three-phase comparison method for obtaining an equivalent neutral point potential using all three-phase signals of U, V, and W may be employed. In this case, the potential at the equivalent neutral point is a substantially triangular wave centered at 1/2 of the power supply voltage.

  The comparators 17A to 17C output a low level signal when the induced voltage analog signal is higher than the equivalent neutral point potential, and output a high level signal when the induced voltage analog signal is lower than the equivalent neutral point potential. A pulse signal is generated. In each of the comparators 17A to 17C, a pulse signal having a resolution of 120 electrical degrees is created. These signals are input to the interrupt input terminal of the interrupt processing unit 21 through the low-pass filter circuits 18A to 18C, respectively.

  Next, the principle of detecting the rotational direction of the rotor will be described with reference to FIGS. First, the principle of the rotational direction determination based on the excitation pattern will be described with reference to FIG. FIG. 4 shows the timings of the three position detection signals (the U-phase, V-phase, and W-phase position detection signals) output from the induced voltage I / F circuit 12 and the edge detection signal output from the interrupt processing unit 21. It is a timing chart. The output timing of the edge detection signal is such that Hi and Low are switched when a rising edge or a falling edge of any of the three position detections is detected. Further, the rotation direction can be specified by the pattern of each position detection signal.

  For example, in the example shown in FIG. 4, the U-phase position detection signal is “Hi”, the V-phase position detection signal is “Low”, and the W-phase position detection signal is “Hi” ((1) shown in FIG. 4). The U-phase position detection signal is “Hi”, the V-phase position detection signal is “Low”, and the W-phase position detection signal is “Low” ((2) shown in FIG. 4). When detected in the order of (1) to (9), it can be determined that the brushless motor 1 is rotating forward. Similarly, in the case of reverse rotation, when a predetermined output pattern is detected in a predetermined order, it can be determined that the brushless motor 1 is rotating in reverse.

  However, since the three position detection signals are the outputs of the comparators 17A, 17B, and 17C, and the induced voltage when the rotor is free-running is small, the comparator becomes close to the common-mode input voltage range of the comparators 17A, 17B, and 17C. Chattering may occur in the output signal, and the rotor position may be erroneously detected as shown in FIG. The period of each of the three position detection signals changes according to the rotation speed of the brushless motor 1, and when the rotation speed becomes high, the period becomes shorter. Therefore, setting the cutoff frequencies of the low-pass filters 18A, 18B, and 18C to be high Can not.

  Therefore, as shown in FIG. 6, in order to read the level of the position detection signal after the chattering convergence, the position detection signal level after a predetermined time (t) has been read from the interrupt detection ((1) in FIG. 6). The time t is set to be equal to or shorter than the time until the next edge is detected, and is calculated and determined from the initial energization time and inertia when the rotor is free-runned. The position detection signal level is detected only for the first time in order to determine the rotor position, and thereafter, the position detection signal level is determined based on the edge direction of the position detection signal. In the case of (1) shown in FIG. 6, the next edge to be detected can be predicted to be a V-phase rising edge during forward rotation, a W-phase rising edge during reverse rotation, and other edges can be predicted as noise. By interrupting only the rising edge and the rising edge of the W phase and masking other interrupts, erroneous detection of the position can be prevented even if chattering occurs in the output signal of the comparator.

  As shown in FIG. 7, there are six combinations of position detection signal levels. For each combination, the edge to be detected next time is known in advance for each of forward rotation and reverse rotation. For example, when the U phase is Hi, the V phase is Low, and the W phase is Hi (indicated as UH / VL / WH in FIG. 7), the edge to be detected next is W If the phase is falling (indicated as W ↓ in FIG. 7) and reverse rotation, the edge to be detected next is the falling edge of U phase (indicated as U ↓ in FIG. 7). is there. In FIG. 7, the rising edge is represented by an upward arrow (↑), and the falling edge is represented by a downward arrow (↓). Therefore, it is possible to accurately detect an edge by masking an interrupt indicating that another edge other than the edge to be detected next is detected.

  Next, in the case of (2) shown in FIG. 6, the next edge to be detected is the falling edge of the U phase, but when it is rotating in the reverse direction, it can be assumed that it is (2) ′. Since the edge to be detected at this time is the falling edge of the W phase, only the falling edge of the U phase and the falling edge of the W phase are allowed to interrupt, and the other interrupts are masked, so that the position can be reliably detected. . As shown in FIG. 8, there are six detection edges of the three position detection signals. After detecting the six edges, the edge to be detected is known in advance for each of forward rotation and reverse rotation. Yes.

  For example, when the rising edge of the U phase is detected (indicated as U ↑ in FIG. 8), if it is forward rotation, the edge to be detected next is the falling edge of the W phase (in FIG. 8, W ↓ In the case of reverse rotation, the next edge to be detected is the fall of the V phase (indicated as V ↓ in FIG. 8). In FIG. 8, as in FIG. 7, the rising edge is represented by an upward arrow (↑) and the falling edge is represented by a downward arrow (↓). Therefore, it is possible to accurately detect an edge by masking an interrupt indicating that another edge other than the edge to be detected next is detected.

  Thus, by masking interrupts, after detecting the rising edge of the V phase in (a), except the rising edge of the V phase and the falling edge of the W phase are masked as shown in FIG. Therefore, erroneous detection of the falling edge of the V phase in (b) can be prevented.

  Next, the processing operation of the control unit 11 shown in FIG. 1 will be described with reference to FIGS. 2 and 3 are flowcharts showing the processing operation of the control unit 11 shown in FIG. First, the rotation control unit 23 energizes the starting excitation pattern for a predetermined initial energization time, thereby free-running the brushless motor 1 and instructs the rotation direction determination unit 22 to perform the rotation direction determination. In response to this, the rotation direction determination unit 22 causes the interrupt processing unit 21 to execute interrupt processing based on edge detection. Thus, the interrupt processing unit 21 outputs an edge detection signal when an interrupt is generated by detecting the switching of the position detection signal.

  The rotation direction determination unit 22 waits until a predetermined time (time t shown in FIG. 6) has elapsed after the first edge detection signal is output (step S1), and specifies the levels of the three position detection signals. Then, the rotation direction determination unit 22 determines whether or not the position detection signal level is “UH / VL / WH” (step S2). As a result of this determination, if the position detection signal level is “UH / VL / WH”, the rotation direction determination unit 22 notifies the interrupt processing unit 21 of the falling edge of the W phase and the falling edge of the U phase. An instruction is given to permit only interrupts and prohibit interrupts at other edges (step S3).

  Next, when the position detection signal level is not “UH / VL / WH”, the rotation direction determination unit 22 determines whether the position detection signal level is “UH / VL / WL” (step S4). If the position detection signal level is “UH / VL / WL” as a result of this determination, the rotation direction determination unit 22 only interrupts the rising edge of the V phase and the rising edge of the W phase to the interrupt processing unit 21. An instruction is given to permit, and interrupts at other edges are prohibited (step S5).

  Next, when the position detection signal level is not “UH / VL / WL”, the rotation direction determination unit 22 determines whether the position detection signal level is “UH / VH / WL” (step S6). As a result of this determination, if the position detection signal level is “UH / VH / WL”, the rotation direction determination unit 22 notifies the interrupt processing unit 21 of the falling edge of the U phase and the falling edge of the V phase. An instruction is given to permit only interrupts and prohibit interrupts at other edges (step S7).

  Next, when the position detection signal level is not “UH / VH / WL”, the rotation direction determination unit 22 determines whether the position detection signal level is “UL / VH / WL” (step S8). If the position detection signal level is “UL / VH / WL” as a result of this determination, the rotation direction determination unit 22 only interrupts the rising edge of the W phase and the rising edge of the U phase to the interrupt processing unit 21. An instruction is given to permit, and interrupts at other edges are prohibited (step S9).

  Next, when the position detection signal level is not “UL / VH / WL”, the rotation direction determination unit 22 determines whether the position detection signal level is “UL / VH / WH” (step S10). As a result of this determination, if the position detection signal level is “UL / VH / WH”, the rotation direction determination unit 22 notifies the interrupt processing unit 21 of the falling edge of the V phase and the falling edge of the W phase. An instruction is given to permit only interrupts and prohibit interrupts at other edges (step S11).

  Next, if the position detection signal level is not “UL / VH / WH”, the rotation direction determination unit 22 allows the interrupt processing unit 21 to interrupt only the rising edge of the U phase and the rising edge of the V phase. The other edge interrupt is instructed to be prohibited (step S12).

  Next, with the interrupt mask (permitted / prohibited) set by the above-described processing operation, the interrupt processing unit 21 outputs an edge detection signal when an interrupt is generated by detecting the switching of the position detection signal. (Step S13). Receiving this, the rotation direction determination unit 22 determines whether or not the detected edge is a rising edge of the U phase (step S14). If the result of this determination is that the rising edge of the U phase, the rotational direction determination unit 22 permits the interrupt processing unit 21 to interrupt only the falling edge of the W phase and the falling edge of the V phase. Is instructed to be prohibited (step S15). Then, the process returns to step S13.

  Next, when it is not the rising edge of the U phase, the rotation direction determination unit 22 determines whether the detected edge is the falling edge of the W phase (step S16). As a result of the determination, if the rising edge is the W phase, the rotation direction determination unit 22 allows the interrupt processing unit 21 to interrupt only the rising edge of the V phase and the rising edge of the U phase, and other edges. Is instructed to be prohibited (step S17). Then, the process returns to step S13.

  Next, when it is not the rising edge of the W phase, the rotation direction determination unit 22 determines whether or not the detected edge is the rising edge of the V phase (step S18). As a result of this determination, if the rising edge is the V phase, the rotation direction determining unit 22 permits the interrupt processing unit 21 to interrupt only the falling edge of the U phase and the falling edge of the W phase. Is instructed to be prohibited (step S19). Then, the process returns to step S13.

  Next, when it is not the V-phase rising edge, the rotation direction determination unit 22 determines whether or not the detected edge is the U-phase falling edge (step S20). If the result of this determination is that the falling edge is the U phase, the rotational direction determining unit 22 permits the interrupt processing unit 21 to interrupt only the rising edge of the W phase and the rising edge of the V phase. An instruction is given to prohibit edge interruption (step S21). Then, the process returns to step S13.

  Next, when it is not the falling edge of the U phase, the rotation direction determination unit 22 determines whether or not the detected edge is the rising edge of the W phase (step S22). If the result of this determination is that the rising edge of the W phase, the rotational direction determining unit 22 permits the interrupt processing unit 21 to interrupt only the falling edge of the V phase and the falling edge of the U phase. Is instructed to be prohibited from interrupting the edge (step S23). Then, the process returns to step S13.

  Next, if the detected edge is not the rising edge of the W phase, the rotation direction determination unit 22 allows the interrupt processing unit 21 to interrupt only the rising edge of the U phase and the rising edge of the W phase. An instruction is given to prohibit interrupts other than (step S24). Then, the process returns to step S13.

  The rotation direction determination unit 22 repeatedly performs the processing operations of steps S13 to S24 shown in FIG. 3, and based on the edge detection signal obtained in step S13, the rotation direction is determined according to the pattern of each position detection signal as shown in FIG. When the process can be identified, the process is terminated.

  As described above, when edge detection is performed, an interrupt indicating that another edge other than the edge to be detected next is detected is masked, and an interrupt of the edge to be detected next is masked. Therefore, even if chattering occurs in the output signal of the comparator (position detection signals for the U phase, V phase, and W phase), erroneous detection of the position can be prevented. As a result, it is possible to improve the rotor position detection accuracy when the input voltage (induced voltage) of the comparator is in the vicinity of the common-mode input voltage range.

  The program for realizing the function of the control unit 11 in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read by the computer system and executed, thereby executing the position of the rotor. Detection processing may be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

  When a brushless motor is driven without a position detection sensor, it can be applied to an application in which it is essential to accurately determine the position of the rotor.

  DESCRIPTION OF SYMBOLS 11 ... Control part, 12 ... Induced voltage I / F circuit, 13 ... Inverter, 14 ... Driver, 21 ... Signal input part, 22 ... Rotation direction determination part, 23 ...・ Rotation control unit

Claims (6)

A control device for controlling the rotational drive of a brushless motor comprising a rotor and a stator,
Rotation control means for energizing the brushless motor for an initial energization time for an excitation pattern that matches the rotor stop position when starting the brushless motor, and then stopping energization to free run the rotor of the brushless motor;
When detecting the position of the rotor by detecting the edge detection of the induced voltage generated during the free run by interruption, only the edge detection interruption to be detected next is permitted for each rotation direction of the rotor. In this state, in response to an instruction from the rotation control means, an edge detection interrupt process is executed. When an interrupt is generated by detecting a switching of the position detection signal, an edge detection is output, and the first edge detection signal is output. A rotation direction determination means for reading a position detection signal level after a predetermined time has elapsed from the output of the signal and determining the rotor position based on the detected phase and direction of the edge. apparatus. 2. The brushless motor control device according to claim 1, wherein the predetermined time is equal to or shorter than a time until the next edge to be detected is detected. The brushless motor control device according to claim 1, wherein the rotation direction determination unit specifies a rotation direction of the rotor by a pattern of the position detection signal based on the detected edge. A control method for controlling the rotational drive of a brushless motor comprising a rotor and a stator,
A rotation control step of energizing the brushless motor for an initial energization time for an excitation pattern that matches the rotor stop position when the brushless motor is started, and then stopping energization and free-running the rotor of the brushless motor;
When detecting the position of the rotor by detecting the edge detection of the induced voltage generated during the free run by interruption, only the edge detection interruption to be detected next is permitted for each rotation direction of the rotor. In this state, in response to an instruction from the rotation control means, an edge detection interrupt process is executed. When an interrupt is generated by detecting a switching of the position detection signal, an edge detection is output, and the first edge detection signal is output. And a rotational direction determination step for determining a position of the rotor based on a detected edge phase and direction after reading a position detection signal level after elapse of a predetermined time. . 5. The brushless motor control method according to claim 4, wherein the predetermined time is equal to or shorter than a time until the next edge to be detected is detected. 5. The method of controlling a brushless motor according to claim 4, wherein in the rotation direction determination step, the rotation direction of the rotor is specified by a pattern of the position detection signal based on the detected edge.

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