JP2006340422A - Controller of dc brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control means of a DC brushless motor in which the rotor can be stopped surely at a predetermined position when the motor is rotating with an external force. <P>SOLUTION: The controller of a DC brushless motor comprises a DC brushless motor 1 and a magnetic pole position sensor 2, an inverter circuit 3 supplying the DC brushless motor 1, a means 5 for driving a switching element, a means 6 for operating the r. p. m. and deceleration of the motor based on a signal from the magnetic pole position sensor 2, and a means 7 for controlling the conduction width of a DC excitation signal outputted from the drive means 5 based on the results from the operating means 6. When a fan is rotating with an external force before the DC brushless motor 1 is started, the DC excitation signal is switched between two patterns in synchronism with the output signal from the magnetic pole position sensor and conduction width of the DC excitation signal is controlled depending on the deceleration thus braking and stopping the motor even when the individual difference or the characteristics are varied. <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 energization width control means for controlling the energization width of the DC excitation signal output from the drive means based on the result of the computation means, the drive means comprising the DC brushless motor When the fan is rotating by external force before starting,
Two patterns of DC excitation signals are switched in synchronization with the output signal of the magnetic pole position sensor, and the energization width of the DC excitation signal is controlled in accordance with 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 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 two patterns of DC excitation signals and control the energization width of the DC excitation signals according to the deceleration. It is thus possible to allow the braking and stopping without overburdening the driver circuit and the motor.

According to the second aspect of the invention, the individual difference and characteristics of the motor can be obtained by controlling the energization width of the DC excitation signal so that the relationship between the rotational speed f obtained by the calculation means and the deceleration a satisfies a <f ^2. Even if it changes, the motor rotation direction can be prevented from hunting, so that braking and stopping can be performed more reliably.

  According to a third aspect of the present invention, by changing the initial energization width of the energization width control means in accordance with the initial rotational speed due to external force, the hunting in the rotational direction can be prevented and the motor braking / A stop 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 based on the calculation result in the calculation means 6, the energization width control means 7 instructs the drive means 5 to specify the energization width of the drive signal. Yes.

  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 is unknown for one magnetic pole position sensor, 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 patterns of DC excitation signals, respectively. 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. Ving in FIG. 5 represents the energization width of these two DC excitation patterns.

  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 energization width of the DC excitation signal. The calculation means 6 monitors the rotational speed and deceleration every time the signal level of the magnetic pole position sensor 2 changes. Based on the above, the energization width control means 7 controls Ving (n + 1) when the signal level of the magnetic pole position sensor 2 is changed next from the current energization width Ving (n) 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).

Ving (n + 1) = Ving (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, the energization width, and the 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, the energization width, and the time when the target deceleration is fixed. The energization width becomes substantially constant after the time ts has elapsed from the initial energization width Ving0 (ts: the deceleration is the target). Time to reach deceleration as)). 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.

  By adopting the control described above, the deceleration can be controlled within the theoretical value even when the fan is rotating due to natural wind, so it is reliable regardless of individual differences in motors or changes in characteristics. The fan can be braked and stopped.

  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 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 energization width Ving0 and the initial rotational speed f0 due to external force. When the external force is strong and the initial rotational speed is large, Ving0 is set large. When the external force is relatively weak and the initial rotational speed is low, Ving0 is set small. By making the initial energization width Ving0 variable according to the magnitude of the external force in this way, 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. It is possible to reduce the time required for stopping.

(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 energization width of the DC excitation signal is controlled by the energization width control means 7 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 conduction width of a DC excitation signal. The characteristic view which showed the relationship between the rotation speed and energization width and time in Embodiment 1 of this invention The characteristic view which showed the relationship between the deceleration and rotation speed in Embodiment 1 of this invention The characteristic figure which showed the relationship between the initial stage energization width and the initial 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 Current supply width 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 The drive means for controlling the conduction width of the DC excitation signal output by the means, and the drive means is configured to detect the magnetic pole position sensor when the fan is rotated by an external force before the DC brushless motor is started. Switching between two patterns of DC excitation signals in synchronization with the output signal, the DC excitation signal Controller of the DC brushless motor and controls in accordance with conducting width to the deceleration. The energization width control means controls the energization width of the DC excitation signal so that the relationship between the rotational speed f obtained by the arithmetic means and the deceleration a satisfies a <f ** 2 (square of f). The control device for a DC brushless motor according to claim 1. 2. The control device for a DC brushless motor according to claim 1, wherein an initial energization width of the energization width control means is changed according to an initial rotational speed by an external force. 2. The control device for a DC brushless motor according to claim 1, wherein the calculation means averages the calculation of the rotational speed and the deceleration.

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