JP2006333599A - Controller for dc brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for a DC brushless motor capable of surely stopping a rotor at a determined position when the motor is rotated by an external force. <P>SOLUTION: This controller for the DC brushless motor includes a DC brushless motor 1, a magnet pole position sensor 2, an inverter circuit 3 which supplies an AC voltage to the DC brushless motor 1, a drive device 5 for driving a switching element, a calculating device 6 for calculating a motor speed and a deceleration speed from the signal of the magnet pole position sensor 2, and a duty controller 7 for controlling a duty of a PWM signal output by the drive device 5 on the basis of the result of the calculating device 6. When a fan is rotated by the external force before starting of the DC brushless motor 1, DC magnetization signals in two patterns are switched in synchronization with the output signal of the magnet pole position sensor, and the DC magnetization signals are duty-controlled in accordance with the deceleration speed, so that the motor can be surely braked and stopped even if an individual difference or characteristic of the motor is changed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for controlling a DC brushless motor.

  A DC brushless motor is often used to drive an outdoor fan of an air conditioner. The outdoor fan rotates when there is wind, and the rotation direction and speed are not uniform. If the motor is started in the rotation state, the motor may be heavily loaded depending on the rotation direction and rotation speed, and may be damaged in the worst case. There is.

  Therefore, if the outdoor fan is rotating at the start of operation of the air conditioner, the air conditioner is started after braking, stopping, and positioning.

  On the other hand, the DC brushless motor uses a magnetic pole position sensor to detect the magnetic pole position of the rotor. For braking, stopping, and positioning of the outdoor fan, the direction and the number of rotations are detected based on the output of the magnetic pole position sensor, and the current supplied to the stator winding is controlled accordingly. However, in the conventional driving device, since three magnetic pole position sensors are used, it has become a cause of increasing the cost.

Therefore, in Patent Document 1, for the purpose of reducing the cost, the motor is stopped after stopping the rotor at a predetermined position by performing direct current excitation or winding short-circuiting by the number of magnetic pole position sensors smaller than the number of winding phases. A technology to start is proposed.
Japanese Patent Application Laid-Open No. 10-290592

  However, when the external force acting on the motor is strong, the rotor cannot be stopped because the brake torque is weak when the winding is short-circuited. Moreover, since direct current excitation may or may not work depending on the position of the rotor, if the direct current excitation is weak, the rotor cannot be stopped and is shaken off.

  Although it is conceivable to increase the DC excitation in order to reliably stop the rotor, to increase the DC excitation, it is necessary to increase the amount of current flowing through the motor winding. If the amount of current flowing through the winding is increased, a strong magnetic field opposite to the direction of the magnetic field generated by the permanent magnet constituting the rotor may be generated in the winding, and the permanent magnet may be demagnetized. .

  An object of the present invention is to provide a control device for a DC brushless motor capable of reliably stopping a rotor at a predetermined position when the motor is rotated by an external force before starting.

In order to solve the above-described conventional problems, a control apparatus for a DC brushless motor according to the present invention includes a DC brushless motor, one magnetic pole position sensor for detecting the magnetic pole position of the rotor of the DC brushless motor, and a plurality of switching elements having a three-phase bridge. An inverter circuit that is connected and converts a DC voltage to an AC voltage by opening and closing the switching element and supplies the DC voltage to the DC brushless motor; a driving unit that drives the switching element; Computation means for computing the deceleration, and duty control means for controlling the duty of the PWM signal output from the drive means based on the result of the computation means, the drive means before starting the DC brushless motor When the fan is rotated by an external force, the magnetic pole position sensor In synchronization with a signal, it switches the DC excitation signals of the two patterns, but to control the duty cycle of the DC excitation signal in response to the deceleration.

  The control device for a DC brushless motor according to the present invention provides a drive circuit and a motor even when the rotation direction of the motor and the individual differences or characteristics of the motor change when the fan rotates due to external factors before starting. The DC brushless motor can be braked / stopped in a short time and reliably without imposing an excessive burden.

  In the first invention, a DC brushless motor, a magnetic pole position sensor for detecting a magnetic pole position of a rotor of the DC brushless motor, and a plurality of switching elements are connected in a three-phase bridge, and a DC voltage is changed to an AC voltage by opening and closing the switching elements. Inverter circuit for converting and supplying to the DC brushless motor, driving means for driving the switching element, computing means for calculating the motor rotation speed and deceleration from the signal of the magnetic pole position sensor, and driving means based on the result of the computing means Duty control means for controlling the duty of the PWM signal output from the motor, and the drive means is synchronized with the output signal of the magnetic pole position sensor when the fan is rotated by an external force before starting the DC brushless motor, Switch between the two patterns of DC excitation signal, and further select the DC excitation signal according to the deceleration. By controlling the parties are able to allow braking and stopping without overburdening the driver circuit and the motor.

According to a second aspect of the invention, the duty control means performs duty control so that the relationship between the rotational speed f obtained by the calculation means and the deceleration a satisfies a <f ² , so that individual differences and characteristics of the motor have changed. Even in this case, it is possible to prevent hunting in the rotation direction of the motor, so that braking and stopping can be performed more reliably.

  According to a third aspect of the present invention, by changing the initial duty of the duty control means according to the initial rotational speed by an external force, the hunting in the rotational direction is prevented and the motor is braked / stopped in a short time regardless of the load of the external force. Can be realized.

  According to the fourth aspect of the present invention, since the pulsation of the deceleration of the motor can be suppressed by averaging the calculation of the rotation speed and the deceleration in the calculating means, it is possible to realize more stable braking / stopping of the motor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
Hereinafter, a first embodiment in which the present invention is applied to a DC brushless motor that drives a fan provided in an outdoor unit of an air conditioner, for example, will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a control device for a DC brushless motor according to Embodiment 1 of the present invention. In FIG. 1, a DC brushless motor 1 is used as a motor for driving an outdoor fan provided in an outdoor unit of an air conditioner. The U-phase, V-phase, and W-phase stator windings of the DC brushless motor 1 are neutral. A star connection is made at point N, and a magnetic pole position sensor 2 is provided on the stator. Among these, the U, V, and W phase windings of the stator are connected to the inverter circuit 3, and the connection points are U, V, and W, respectively. In the inverter circuit 3, Qu, Qv, Qw, Qx, Qy, and Qz are three-phase bridge connected. That is, the series connection circuit of the switching elements Qu and Qx, the series connection circuit of the switching elements Qv and Qy, and the series connection circuit of the switching elements Qw and Qz are connected in parallel, and one end thereof is connected to the positive electrode of the DC power supply 4. The other end is connected to the negative electrode of the DC power source 4. These switching elements Qu, Qv, Qw, Qx, Qy, and Qz are connected to anti-parallel diodes Du, Dv, Dw, Dx, Dy, and Dz in antiparallel. In addition, in order to drive the switching elements Qu, Qv, Qw, Qx, Qy, Qz, the drive means 5 outputs a drive signal of Su, Sv, Sw, Sx, Sy, Sz. Further, the output signal line from the magnetic pole position sensor 2 is connected to the calculation means 6, and the duty control means 7 instructs the drive means 5 to command the duty of the drive signal based on the calculation result in the calculation means 6.

  The operation of the first embodiment configured as described above will be described below. Here, the switching elements Qu, Qv, and Qw are referred to as positive voltage side switching elements of the inverter circuit 3, and the switching elements Qx, Qy, and Qz are referred to as negative voltage side switching elements of the inverter circuit 3. The magnetic pole position sensor 2 outputs a high level signal when detecting the N magnetic pole of the rotor, and outputs a low level signal when detecting the S magnetic pole of the rotor. On the other hand, when the motor is rotated by an external force, the rotation direction of one magnetic pole position sensor is unknown, so it is necessary to reliably stop at a predetermined position and then start it. Here, the magnetic pole position which stops a rotor is demonstrated using FIGS. 2 to 4 show the internal structure of the DC brushless motor when the rotor has two poles and the stator has three slots. The magnetic pole position shown in FIG. 2 is the magnetic pole position where the magnetic pole position sensor 2 detects the S magnetic pole of the rotor and outputs a low level signal when the rotor rotates in the normal rotation direction (the direction of the arrow shown). If the rotation angle at this time is defined as 0 °, the magnetic pole positions in FIGS. 3 and 4 are 90 ° and 270 °, respectively. With these two magnetic pole positions, even with one magnetic pole position sensor, the magnetic pole position can be estimated regardless of the rotation direction.

  Next, a specific stopping method for stopping at the magnetic pole positions shown in FIGS. 3 and 4 will be described with reference to FIG. FIG. 5 shows the relationship between the signal level of the magnetic pole position sensor 2 and the DC excitation signal for braking the rotor. WY and VZ in the figure are DC excitation signal patterns. This DC excitation signal generates a magnetic field inside the motor to generate a braking torque. W-Y is a DC excitation signal for stopping at a 90 ° magnetic pole position shown in FIG. 3, and VZ is a DC excitation signal for stopping at a 270 ° magnetic pole position shown in FIG. These two DC excitation signal patterns are alternately output based on the change in the signal level of the magnetic pole position sensor 2 as shown in FIG. Note that Ving in FIG. 5 is the energization width of these two DC excitation patterns, and in this embodiment, Ving is 80 °.

  Next, FIG. 6 shows the change over time of the rotational speed of the fan and the signal of the magnetic pole position sensor 2 when braking is performed by the stopping method described above from the rotational speed f0 due to external force. The rotation speed of the fan can be obtained from the result of measuring the signal period of the magnetic pole position sensor 2 by a timer (not shown) in the calculation means 6. In principle, the signal of the magnetic pole position sensor 2 is a discrete value, and the calculation means 6 calculates and recognizes the rotational speed of the fan for each plot on the straight line in FIG. Further, when the calculation means 6 recognizes that the rotation speed is f1 or less, the switching of the two DC excitation signals is stopped, and one of the DC excitation signals is output, so that the positioning (stopped) state is entered and the activation becomes easy.

FIG. 7 shows the time variation of the rotational speed and the signal of the magnetic pole position sensor 2 when the motor characteristics (induced voltage, winding resistance, winding inductance, etc.) are different from those in FIG. Compared with the straight line shown in FIG. 6, the slope of the characteristic is different. This characteristic difference is due to temperature characteristics and manufacturing differences. In the case of FIG. 6, since the calculating means 6 can recognize a rotation speed within a predetermined rotation speed range (0 to f1), it can be stopped reliably. On the other hand, in FIG. 7, the calculating means 6 cannot recognize the rotational speed within a predetermined rotational speed range (0 to f1). In FIG. 7, it may be recognized after the number of rotations is 0 or less, that is, the rotation direction is different, or may not be recognized. As a result, since the rotation direction is unknown for one magnetic pole position sensor, a hunting phenomenon in the rotation direction occurs as shown in FIG. As described above, as the slope of the straight line in FIGS. 6 and 7 (hereinafter referred to as deceleration) becomes steeper, the hunting phenomenon occurs.

  Next, the theoretical value of deceleration at which the hunting phenomenon does not occur will be described with reference to FIG. FIG. 9 defines the time t corresponding to the change in the signal level of the magnetic pole position sensor 2, the number of revolutions f, and the deceleration a, and the deceleration a (n) (n is a natural number) is expressed as in Equation 1. be able to.

a (n) = (f (n−1) −f (n)) / (t (n) −t (n−1)) Equation 1
Further, the following relational expression is obtained from the relationship between the angular velocity ω and the rotation angle θ.

Δθ = ∫ωdt = π (f (n) + f (n−1)) · (t (n + 1) −t (n)) Equation 2
In Expression 2, since Δθ = π, (f (n) + f (n + 1)) · (t (n + 1) −t (n)) Expression 3
From Equation 1 and Equation 3,
f (n + 1) = √ (f (n) ** 2-a (n)) Equation 4
Equation 5 which is a condition for the solution of Equation 4 is a theoretical equation.

a (n) <f (n) ** 2 Formula 5
(Here, ** 2 represents the square)
Next, a control method for satisfying the relationship of Expression 5 will be described with reference to FIG. FIG. 10 shows the relationship between the signal of the magnetic pole position sensor 2 and the duty of the DC excitation signal. Every time the signal level of the magnetic pole position sensor 2 changes, the number of revolutions and deceleration are monitored by the computing means 6. Based on the current energization width D (n), the duty control means 7 controls D (n + 1) when the signal level of the magnetic pole position sensor 2 changes next as shown in the following equation (6). As a control method, the deceleration is proportionally controlled so as to become a preset target deceleration (as).

D (n + 1) = D (n) −kp (a (n) −as) (kp: proportional constant) Equation 6
It should be noted that the target deceleration can be arbitrarily changed within a range so as to satisfy Equation 5 according to the rotational speed. FIG. 11 shows the relationship between the rotational speed, duty, and time in the case of the above control, and FIG. 12 shows the relationship between the deceleration and the rotational speed. FIG. 11 shows the relationship between the rotational speed, duty, and time when the target deceleration is fixed. The duty becomes substantially constant after the time ts has elapsed from D0, which is the initial duty (ts: deceleration is the target deceleration as Time to reach). As for the rotational speed, the deceleration (inclination) becomes constant at as after the elapse of time ts. This control continues until the calculation means 6 recognizes the rotation speed f1 or less.

  FIG. 12 shows the experimental results when the target deceleration as (= 30 rpm) is controlled from the initial rotation speed near 100 rpm to the stop determination rotation speed fs (= 25 rpm). The relationship of Formula 5 can be satisfied in the entire region from the rotational speed f0 to f1.

  With the control described above, even when the fan is rotating due to natural wind, the deceleration can be controlled within the theoretical value, so that the fan can be reliably braked and stopped regardless of individual motor differences. Is possible.

In order to simplify the description in the first embodiment, the rotor has a structure of two poles and the stator has three slots as shown in FIGS. 2 to 4, but the number of poles of the rotor is 2 m and the number of slots of the stator is Even in the case of a motor having 3 m, the description so far is the same (m is a natural number).
.

(Embodiment 2)
1 to 12 are the same as those in the first embodiment, and thus description thereof is omitted. FIG. 13 shows the relationship between the initial duty D0 and the initial rotational speed f0 due to external force. When the external force is strong and the initial rotational speed is large, D0 is set large, and when the external force is relatively weak and the initial rotational speed is low, D0 is set small. Thus, by setting the initial duty D0 to be variable according to the magnitude of the external force, it is possible to prevent the deceleration from exceeding the theoretical value when the external force due to natural wind is relatively small, and when the external force is large. Can shorten the time required to stop.

(Embodiment 3)
1 to 13 are the same as those described in the first and second embodiments, and a description thereof will be omitted. The rotation speed and deceleration averaging process calculated by the calculation means 6 will be described with reference to FIG. FIG. 14 shows the calculated rotational speed fave and deceleration aave at time t (n) for each change in the signal level of the pole position sensor 2. Next, a calculation method in the case of averaging the rotation speed and deceleration calculation four times will be described. First, the rotational speeds fave (n) and fave (n + 1) at times t (n) and t (n + 1) are
fave (n-1) = 1 / (t (n-1) -t (n-5)) Equation 7
fave (n) = 1 / (t (n) -t (n-4)) Equation 8
Furthermore, the deceleration aave (n) after averaging four times at time t (n) is
ave (n) = (fave (n−1) −fave (n)) / (t (n) −t (n−1)) Equation 9
And calculate. Based on this result, the duty control means 7 controls the duty of the DC excitation signal as in the first embodiment. By averaging the calculations in this way, hunting occurs in the deceleration in the high rotation speed range in FIG. 12 (when the averaging process is not performed in the deceleration calculation), but as shown in FIG. When the average processing (4 times) is performed for the calculation of the number and the deceleration, the pulsation of the deceleration can be reduced over the entire rotational speed, and the condition shown in Expression 5 can be satisfied.

  As described above, the DC brushless motor control device according to the present invention suppresses the demagnetization of the permanent magnet without imposing an excessive burden on the drive circuit and the motor when the fan rotates due to an external factor. In addition, the fan can be braked and stopped even when individual motor differences or characteristics change, so it can be applied not only to the outdoor fan of an air conditioner, but also to a brushless motor that freely rotates during startup due to external factors. can do.

The block diagram which showed the structure of the DC brushless motor control means in Embodiment 1 of this invention The schematic diagram which defined the magnetic pole position of the rotation angle 0 degree in Embodiment 1 of this invention The schematic diagram which defined the magnetic pole position of the rotation angle 90 degrees in Embodiment 1 of this invention The schematic diagram which defined the magnetic pole position of the rotation angle 270 degrees in Embodiment 1 of this invention Explanatory drawing which showed the pattern of the direct current excitation signal in Embodiment 1 of this invention The characteristic figure which showed the time change of the number of rotations of the fan in Embodiment 1 of the present invention The characteristic view which showed the time change of the rotation speed of the fan on the conditions different from FIG. 6 in Embodiment 1 of this invention The characteristic view which showed the hunting phenomenon of the rotation direction in Embodiment 1 of this invention Explanatory drawing which defined time t, number of rotations f, and deceleration a with respect to the signal of magnetic pole position sensor 2 in Embodiment 1 of the present invention. Explanatory drawing which showed the relationship between the signal of the magnetic pole position sensor 2 in Embodiment 1 of this invention, and the duty of a DC excitation signal The characteristic figure which showed the rotation speed in Embodiment 1 of this invention, and the relationship between duty and time The characteristic view which showed the relationship between the deceleration and rotation speed in Embodiment 1 of this invention The characteristic view which showed the relationship between the initial duty and the initial rotation speed f0 in Embodiment 2 of this invention Explanatory drawing which showed the calculation method of the calculating means 6 in Embodiment 3 of this invention. The characteristic diagram which showed the relationship between the deceleration and rotation speed in Embodiment 3 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC brushless motor 2 Magnetic pole position sensor 3 Inverter circuit 4 DC power supply 5 Drive means 6 Calculation means 7 Duty control means

Claims (4)

A DC brushless motor, one magnetic pole position sensor for detecting the magnetic pole position of the rotor of the DC brushless motor, and a plurality of switching elements are connected in a three-phase bridge, and a DC voltage is converted into an AC voltage by opening and closing the switching elements, Inverter circuit supplied to the DC brushless motor, driving means for driving the switching element, arithmetic means for calculating the motor rotation speed and deceleration from the signal of the magnetic pole position sensor, and the driving based on the result of the arithmetic means Duty control means for controlling the duty of the PWM signal output from the means, and the drive means outputs an output signal of the magnetic pole position sensor when the fan is rotated by an external force before the DC brushless motor is started. Synchronously, the two patterns of DC excitation signals are switched and the DC excitation signals are switched. Controller of the DC brushless motor and controls in accordance with a duty signal to the deceleration. 2. The duty control unit according to claim 1, wherein the duty control unit performs duty control so that a relationship between a rotational speed f and a deceleration a obtained by the calculation unit satisfies a <f ** 2 (square of f). Control device for DC brushless motor. 2. The control apparatus for a DC brushless motor according to claim 1, wherein the initial duty of the duty control means is changed according to an initial rotational speed by an external force. 2. The DC brushless motor control apparatus according to claim 1, wherein the calculation of the rotation speed and the deceleration in the calculating means is averaged.

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