JPH10201289A - Method for controlling brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable rotation control by performing appropriate torque control to a load fluctuation during one rotation of a brushless motor. SOLUTION: A DC voltage obtained at an AC/DC conversion part 2 is switched with an inverter part 3, and applied to a brushless motor 4 rotate it. A control circuit 10, based on position detection of a rotator obtained at a position detecting circuit 5, controls an inverter part 3 for switching energization for the brushless motor 4, meanwhile one rotation of the brushless motor 4 is divided into a plurality of zones, so that a torque control is performed with a linear prediction control for correcting applied voltage for each zone. At that time, based on position detection, a time for each zone is measured, and an average zone time for one rotation of brushless motor is calculated, meanwhile, based on the average zone time and the time for each zone, speed fluctuation amount during one rotation is calculated, and based on the speed fluctuation amount, an applied voltage for each zone during current rotation is corrected for torque control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control technology of a sensorless DC brushless motor (hereinafter, referred to as a brushless motor) used for a motor such as an air conditioner (compressor), and more particularly, to a control technology suitable for load fluctuation. The present invention relates to a method of controlling a brushless motor that performs stable torque control and enables stable rotation control.

[0002]

2. Description of the Related Art In a method of controlling a brushless motor, a position of a rotor is detected by using an induced voltage generated in a non-conducting phase (a non-conducting armature winding) of the brushless motor, and based on the position detection. To switch the energization of the armature winding of the brushless motor.

For this reason, for example, a control device shown in FIG. 8 is required. This control device converts an AC power supply 1 into a predetermined DC power supply by an AC / DC conversion unit 2 and converts the DC power supply into switching elements Ua, Va, Wa, X,
Brushless motor (DCM) with Y and Z switching
4 is supplied to the armature winding. The position detection circuit 5 detects a half point of the induced voltage contained in the terminal voltages of the armature windings U, V, W of the brushless motor 4 and uses this 1/2 point as a position signal to the control circuit 6. Output.

The control circuit 6 detects a 1/2 point (rotor position detection point) of the induced voltage based on the input position signal, and based on the current position detection time t and the previous position detection time, performs the next energization. The switching time is estimated, and a predetermined drive signal is output to the inverter unit 3 via the drive circuit 7 to switch the energization at the estimated time. For example, when the brushless motor 4 is a three-phase four-pole motor, a time T of one rotation of the rotor is calculated from the position detection time, and the next energization switching time from the current position detection time t is calculated based on the calculated time T. (T +
T × 30/360) is calculated.

When the load fluctuates, the speed of the brushless motor 4 fluctuates. As a result, the brushless motor 4 generates mechanical vibration, which may cause not only noise but also step-out and the like. If the load variation is regular, for example, if the load is regular like a compressor load of an air conditioner, that is, if the pulsation is in units of one rotation, the speed variation can be canceled. in this case,
The load current value is detected, the torque fluctuation distribution, that is, the speed fluctuation distribution is obtained from the load current value, and the speed fluctuation may be smoothed by adjusting the voltage applied to the brushless motor 4.

[0006]

However, in the above-described method of controlling a brushless motor, at least a load current pickup or the like is required, so that the cost is inevitably increased. For example, the cost of an air conditioner is increased. become.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to perform appropriate torque control for a load change during one rotation, to perform stable rotation control, and to reduce cost. An object of the present invention is to provide a brushless motor control method capable of performing torque control without an increase.

[0008]

In order to achieve the above object, the present invention detects the position of a rotor of a brushless motor by using an induced voltage included in a terminal voltage of an armature winding of the brushless motor. In the brushless motor control method for switching the energization of the armature winding of the brushless motor based on the position detection, one rotation of the brushless motor is divided into a plurality of sections, and the brushless motor is provided for each section. The voltage applied to the motor is variable, and the rotation fluctuation during the previous one rotation is detected, and the torque control is performed by sequentially correcting the applied voltage in each section according to the rotation fluctuation. Features.

According to a brushless motor control method of the present invention, one rotation of the brushless motor is divided into a plurality of sections by the position detection, and the voltage applied to the brushless motor can be varied for each section. While measuring the time of each section based on the detection and calculating the average section time of one rotation of the brushless motor, 1 is calculated based on the average section time and the time of each section.
A brushless motor control method, wherein a speed change during rotation is calculated, and torque control is performed by correcting an applied voltage in each section of the current rotation based on the speed change. .

In this case, it is preferable to multiply the change in speed by a step gain when correcting the applied voltage in each section. Further, the average section time may be obtained by storing the time of each section of the one rotation in a memory and calculating based on the stored time. Furthermore, the average section time is calculated from the time of one rotation that is one rotation backward from the predetermined section of the previous rotation, and the speed change is calculated based on the calculated average section time and the time of the predetermined section of the previous rotation. You may make it calculate. Furthermore, the average section time is calculated based on the stored time after storing the time of each section of the one revolution in the memory, and calculating the average section time of each section based on the speed change. When correcting the applied voltage, the correction may be applied to the next rotation after at least one rotation.

According to the present invention, the position of a rotor of a brushless motor is detected by using an induced voltage included in a terminal voltage of an armature winding of the brushless motor, and the brushless motor is detected based on the detected position. In the brushless motor control method for switching the energization of the armature winding, one rotation of the brushless motor is divided into a plurality of sections of the position detection interval, and the applied voltage of the brushless motor can be varied for each section. Measuring the time of each section based on the position detection, and calculating the average section time of one rotation of the brushless motor, calculating the difference between the average section time and the time of each section, It is characterized in that each section voltage of one rotation is corrected according to the difference in each section, and torque control is automatically performed only when necessary.

In this case, during the acceleration and deceleration of the brushless motor, the torque control is not performed, and the applied voltage in each section of one rotation is determined using the average section time, so that the brushless motor enters a constant rotation state. It is sometimes preferable to perform the torque control again.

The rotation control of the brushless motor is performed by PWM.
When the torque control is performed by correcting the applied voltage in each section, the control method may be converted into the on-time of the PWM pulse.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. FIG.
In FIG. 8, the same parts as those in FIG.

The method of controlling a brushless motor according to the present invention is, for example, as shown in FIG.
11, the correction control in the time direction, so-called linear prediction control, is performed for each of the sections P0 to P11, and the torque control is performed during one rotation of the brushless motor.

A method of calculating a correction value for the correction control will be described. Assuming that the brushless motor is in a constant rotation state, one rotation time T is not equal to each section time Tpm (m; 0 corresponding to the number of divisions). New value of 11) can be obtained by the sum ΣTpm. Each section time Tpm is obtained by measuring the position detection interval time of the brushless motor. The average section time Thpn is T / 12 = ／ Tp (m, n) / 12
(Σ in m). n is a serial number of the rotation speed.

On the other hand, from the average section time Thp and the section time Tpm for one rotation, the speed difference (em is (Th
pn−Tp (m, n)) / Thpn · Tp (m, n), and the speed difference e (m, n) for each rotation is the speed difference (T
hpn−Tp (m, n) / Thpn · Tp (m, n) multiplied by a proportionality constant (speed coefficient) k1 k1 × e (m, n)
Can be represented by Further, the characteristic (torque τ) of the DC motor (brushless motor) is proportional to the difference (V−E (v)) between the induced voltage E (v) and the applied voltage V, and the induced voltage E (v) is k
2 · v (k2; proportional constant (voltage coefficient)), that is, it is proportional to the rotation speed. Therefore, when the applied voltage V is increased, the torque τ increases. Therefore, when the induced voltage E (v) is kept constant with respect to a load change, the applied voltage V may be adjusted to increase or decrease the torque τ. You can see that.

If the applied voltage in the section P (m, n + 1) is Vp (m, n + 1), the applied voltage V
p (m, n + 1) is converted to Vp (m, n) + α · e (m, n)
, The torque can be adjusted according to the load fluctuation. That is, the average section time T at the n-th rotation
The difference e (m, n) between hpn and the section time Tp (m, n)
Is multiplied by a proportional constant α, and this α · e (m, n) is converted into the current applied voltage Vp (m, n). The voltage can be predicted.

In this case, the proportionality constant α is k1 · k2 · s, where k1 is the above-mentioned velocity coefficient, 2π / 12 (rad).
Where k2 is a voltage coefficient and s is a step gain as shown below. When the induced voltage E (v) is transformed from the above-mentioned torque τ = k · (VE− (v)), V−τ / k =
k2 · v. Here, k is a proportional constant.

Here, assuming that the rotation speed v has changed by Δv, the induced voltage E (v + Δv) is k2 · (v + Δv)
v) = E (v) + E (Δv). That is, the load is reduced, and the rotation speed is increased by Δv. As a result, the torque τ decreases by Δτ, and the induced voltage E (v +
Δv) is V− (τ / k−Δτ / k) = E (v) + E (Δ
v), and E (Δv) is Δτ / k = k2 · Δv
Can be represented by

It is an object of the present invention to keep the rotation speed v constant, that is, to keep E (v) constant even when there is a load fluctuation. Therefore, if the applied voltage V is adjusted by the amount E (Δv) of the induced voltage, the change Δv in the rotation speed can be adjusted, and as a result, the rotation speed v can be kept constant. The addition and subtraction E (Δv) of the induced voltage is s · ΔV = s · k2
= S · k1 · k2 · Δt = α · e (m, n). Therefore, if α · e (m, n) is added to or subtracted from the applied voltage Vp (m, n) at the n-th rotation, the applied voltage at the (n + 1) -th rotation can be predicted adaptively to the rotation fluctuation.

The step gain s is a parameter related to a measure against noise generated in driving the motor and a prediction accuracy, and is set in a range of 0 ≦ s ≦ 1. When the value of s is large, the convergence of the rotation fluctuation can be accelerated, but errors due to prediction accuracy and noise also increase. A smaller value of s has the opposite effect.

For this reason, the control device to which the brushless motor control method of the present invention is applied has the configuration shown in FIG. In FIG. 1, this control device measures the time of the position detection interval based on the position signal from the position detection circuit 5 in addition to the function of the control circuit 6 shown in FIG. The correction value of the applied voltage in the section during the next rotation corresponding to ()) is calculated by the above-described processing, and the applied voltage in each section during the next rotation is predicted in consideration of the correction value. A control circuit 10 for controlling the rotation of the brushless motor 4 is provided.

Next, the operation of the control device having the above configuration will be described with reference to the flowchart of FIG. 3 and the schematic diagram of FIG. In the case of the three-phase four-pole brushless motor 4, the position detection interval during one rotation is 12, but for simplicity, one rotation is divided into four parts.

First, the control circuit 10 measures and stores the position detection interval Tpm (0 to 3) based on the position signal (step ST1), and average section time Thp (= T /
4) is calculated (step ST2).

Subsequently, as shown in FIG. 4, a difference em between the average section time Thp and each section time Tpm is calculated (step ST3), and the difference em is multiplied by a proportional constant α (step ST4). The applied voltage
m and the applied voltage V in each section during the next one rotation
Predict pm. Then, in each section during this one rotation, the applied voltage of the brushless motor 4 becomes the predicted applied voltage V
pm (step ST5).

As described above, the voltage applied to the brushless motor 4 in each section of the current rotation is corrected based on the difference em in each section of the previous rotation, so that rotation fluctuation during one rotation can be suppressed. Optimal torque control can be performed without increasing costs, and as a result, stable rotation control can be performed.

Further, the difference em is generated only when there is a load change, and the torque control is performed. That is, the torque control is automatically performed only when the load changes, and when there is no load change, unnecessary torque control is not applied. In addition, efficient rotation control can be performed. Furthermore, by introducing a step gain s to the proportional constant α for correcting each section voltage,
Appropriate torque control can be performed even when the measurement of each section time fluctuates, and strong torque control can be performed even with disturbance due to noise or the like.

Note that when the brushless motor 4 is accelerating or decelerating, that is, when it is not in a constant rotation state, the above-described calculation may not converge. Good to do.

FIG. 5 is a block diagram schematically illustrating the control method of the present invention. A case where the method shown in FIG. 4 is applied to this block diagram will be described. In this case, m = 4 because one rotation is divided into four in the method shown in FIG. If one rotation is divided into 12 parts, m =
Twelve.

First, an interval time counting unit 11 is operated by a position signal.
, While measuring the times Tp0 to Tp3 of the respective sections, and sequentially switching the switches SA0 to SAm to store the time intervals Tp0 to Tpm in the memory 12. At this time, the averaging unit 13 is reset and started at least during the counting of the first section P0.
3 stores the time Tpm of each section from the start of the section in the memory, adds the stored times, and divides the added value by the number of divisions m
To calculate the average section time Thp.

Subsequently, by the combination of the switches SB0 to SBm and the switches SC0 to SCm, for example, switching is sequentially performed from the combination of the switches SB0 and SC0 to the combination of the switches SBm and SCm. Then, a difference Δe0 to Δem between the average section time Thp and each section time Tp0 to Tpm is obtained by an adder 14, and the difference Δe0 to Δem is multiplied by a proportional constant α of a proportional constant unit 15 by a multiplier 16. The result of the multiplication is stored in the voltage output unit 17 as the correction value ΔV0 to ΔVm for each section.

The voltage output unit 15 adds the correction values .DELTA.V0 to .DELTA.Vm to each of the section voltages Vp0 to Vpm for one rotation which have already been determined and outputs them (Vp0 to Vpm). The switch SD is synchronized with the switching of the switch.
0 to SDm, and the voltage output unit 15
And outputs the respective section voltages as Vp0 to Vpm.

The torque control may be performed when the brushless motor 4 is in a constant rotation state, but may not be preferable when the motor is in an acceleration / deceleration state. Therefore, at the time of acceleration / deceleration, the switches SW1 and SW2 are switched so that the average section voltage section 18
Is output. The average section voltage section 18 constantly adds the output section voltages Vp0 to Vpm (for one rotation) from the voltage output section 15 and divides the addition result by the division number m. Therefore, the average value of each section voltage Vp0 to Vpm of the previous one rotation becomes each section voltage during the current one rotation, and the current one rotation is controlled based on the information of one rotation delay.

According to the above-described torque control, a microcomputer capable of high-speed operation is used to obtain each section voltage of one revolution this time based on the previous section voltage and the previous average section voltage. There is a need. But,
High-speed operation type microcomputers are expensive,
For example, when applied to a compressor of an air conditioner, the cost of the air conditioner increases, and the calculation speed is not so fast, that is, it is sufficient if a relatively inexpensive microcomputer can be used. It may be extremely difficult, especially in the first section P0.

Therefore, as shown in FIG. 6, the above-described problem can be easily solved by changing the method of calculating the average section time Thp for one rotation. In the case of the first modification, the average section time Thp is calculated from the time of one rotation that is one rotation backward from the predetermined section of the previous rotation.

The average section time Thp used for calculating the first section voltage Vp0 is calculated from the last section P1 to the previous section P0.
Using this time (one rotation time) T, the average section time Thp used in the calculation of the current section voltage V1 is the time (one rotation time) T from the previous section P2 to the previous section P1.
Is used.

In the same manner, by changing the calculation method of the average section time Thp for each section of each rotation, it is possible to apply a time corresponding to substantially one rotation to the calculation of the section voltages Vp0 to Vpm. It is not necessary to use a high-speed operation type microcomputer, and it is not necessary to increase the cost.

As shown in FIG. 7, the current section voltage may be calculated using the pre-rotation section times P0 to P3 and the average section time Thp. This second
According to the modified example, it is possible to apply the time of one rotation to the calculation of the section voltage at this time, and it is possible to use a microcomputer of a low-speed operation, thereby avoiding an increase in cost.

The first modification shown in FIG. 6 and FIG.
As for the voltage calculation in the second modification shown in FIG. 7, since the same processing as that described in the previous embodiment is executed, the description thereof will be omitted.

The above-described embodiment and the first and second modified examples can be applied to the case where the brushless motor 4 is controlled by PWM. In this case, when performing the above-described torque control, the voltage value may be converted into a PWM ON time (ON time of a PWM pulse). That is, PWM
This is because the ON time is directly related to the voltage applied to the brushless motor 4.

[0042]

As described above, according to the first aspect of the brushless motor control method, one revolution of the brushless motor is divided into a plurality of sections, and the voltage applied to the brushless motor is reduced for each section. It is variable and detects the rotation fluctuation during the previous one rotation, and performs the torque control by sequentially correcting the applied voltage in each section according to the rotation fluctuation. There is an effect that appropriate torque control can be performed with respect to the fluctuation, and stable rotation control can be performed.

According to the second aspect of the present invention, one rotation of the brushless motor is divided into a plurality of sections by detecting the position of the rotor, and the applied voltage of the brushless motor can be varied for each section. While measuring the time of each section, and calculating the average section time of one rotation of the brushless motor, the speed change during one rotation is calculated based on the average section time and the time of each section. The torque control is performed by correcting the applied voltage in each section of the current rotation based on the speed change, so that appropriate torque control can be performed with respect to load fluctuation, and stable. Rotation control can be performed, and software processing can be performed without adding hardware, which has the effect of not increasing the cost of the device.

According to the third aspect of the present invention, the step gain is multiplied by the speed change when correcting the applied voltage in each section in the second aspect.
In addition to the above effects, when the measurement of each section time fluctuates and the correction of the applied voltage in each section varies, the correction converges in a stable direction due to the averaging effect and suppresses the adverse effect on the torque control. In addition, there is an effect that strong torque control can be performed even with disturbance due to noise or the like.

According to the fourth aspect of the present invention, the time of each section of one rotation is stored in the memory and the average section time of the second or third aspect is calculated based on the stored time. Therefore, in addition to the effect of the second or third aspect, an accurate average section time can be calculated, and as a result, optimal torque control can be performed.

According to the fifth aspect of the present invention, the average section time according to the second or third aspect is calculated from at least one rotation time that is one rotation backward from a predetermined section of the previous rotation. The speed change is calculated based on the time and the time of the predetermined section of the previous rotation, so that in addition to the effect of claim 2 or 3, a microcomputer as a control means for performing the torque control has a high-speed operation type. Even without using the above, since the arithmetic processing can be performed in time, an inexpensive microcomputer can be used, and the cost is not increased.

According to the sixth aspect of the present invention, the time of each section of the one revolution is stored in the memory for the average section time of the second or third aspect, and the time is calculated based on the stored time. When the applied voltage in each section is corrected based on the speed change, the applied voltage is applied to the next rotation after at least one rotation, so that the torque control is performed in addition to the effect of claim 2 or 3. Even if a low-speed operation type microcomputer is used as the control means for performing the operation, the operation processing can be performed in a sufficient time, so that an inexpensive microcomputer can be used, and the cost can be increased. is there.

According to the present invention, one rotation of the brushless motor is divided into a plurality of sections by detecting the position of the rotor, and the voltage applied to the brushless motor can be varied for each section. Based on this, the time of each section is measured, and the average section time of one rotation of the brushless motor is calculated, and the difference between this average section time and the time of each section is calculated. In this way, each section voltage of one rotation is corrected and torque control is automatically performed only when necessary, so that appropriate and adaptive torque control can be performed with respect to load fluctuation, and stable rotation control can be performed. There is an effect that can be performed.

According to the present invention, the torque control is not performed when the brushless motor is accelerated or decelerated, and the applied voltage in each section of one rotation is determined using the average section time. Since the torque control is performed again when the brushless motor enters the constant rotation state, in addition to the effect of claim 7, it is possible to cope with a case where the acceleration / deceleration control is in an indefinite rotation state, and There is an effect that an erroneous calculation of the torque control is not performed and the rotation control is not adversely affected.

According to the invention of claim 9, according to claim 1,
In 2, 3, 4, 5, 6, 7 or 8, the rotation control of the brushless motor is a PWM control method, and when the torque control is performed by correcting the applied voltage in each section.
Since the conversion is performed in terms of the ON time of the pulse, in addition to the effects of claims 1, 2, 3, 4, 5, 6, 7 or 8,
There is an effect that the present invention can be applied to the case where the rotation of the brushless motor is controlled by the PWM control method.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a control device to which an embodiment of the present invention is applied, to which a control method of a brushless motor is applied.

FIG. 2 is a schematic diagram illustrating the operation of the control device shown in FIG. 1;

FIG. 3 is a schematic flowchart for explaining the operation of the control device shown in FIG. 1;

FIG. 4 is a schematic diagram illustrating the operation of the control device shown in FIG. 1;

FIG. 5 is a schematic diagram illustrating the operation of the control device shown in FIG. 1;

FIG. 6 is a schematic diagram illustrating a first modified example of the present invention.

FIG. 7 is a schematic diagram illustrating a second modified example of the present invention.

FIG. 8 is a schematic block diagram of a conventional control device for a brushless motor.

[Explanation of symbols]

3 Inverter section 4 Brushless motor (sensorless DC brushless motor) 5 Position detection circuit 6, 10 Control circuit (microcomputer) Pm, P (m, n) Section (one rotation) Thp, Thpn Average section time Tpm, Tp (m) , N) Section time Vhp Average section voltage Vpm Section voltage (section applied voltage of brushless motor 4) α proportional constant

Claims (9)

[Claims] 1. A brushless motor according to claim 1, wherein a position of a rotor of the brushless motor is detected using an induced voltage included in a terminal voltage of an armature winding of the brushless motor, and the motor of the brushless motor is detected based on the detected position. In the control method of the brushless motor for switching the energization of the slave winding, one rotation of the brushless motor is divided into a plurality of sections, and the applied voltage of the brushless motor is variable for each section, and during the previous one rotation And controlling the torque by performing a torque control by sequentially correcting the applied voltage in each section according to the rotation fluctuation. 2. The brushless motor according to claim 1, further comprising: detecting a position of a rotor of the brushless motor using an induced voltage included in a terminal voltage of an armature winding of the brushless motor; In the control method of the brushless motor for switching the energization of the slave winding, one rotation of the brushless motor is divided into a plurality of sections by the position detection, and the applied voltage of the brushless motor can be changed for each section. While measuring the time of each section based on the position detection and calculating the average section time of one rotation of the brushless motor, the time during one rotation is calculated based on the average section time and the time of each section. The speed change is calculated, and the torque control is performed by correcting the applied voltage in each section of one revolution this time based on the speed change. How to control a brushless motor. 3. The control method for a brushless motor according to claim 2, wherein a step gain is multiplied by the speed change when correcting the applied voltage in each section. 4. The brushless motor control according to claim 2, wherein the time of each section of the one revolution is stored in a memory and the average section time is calculated based on the stored time. Method. 5. The average section time is calculated from the time of one rotation, which is one rotation backward from a predetermined section of the previous rotation, and the speed is calculated based on the calculated average section time and the time of the predetermined section of the previous rotation. 4. The control method for a brushless motor according to claim 2, wherein the change is calculated. 6. The average section time is calculated based on the stored time after storing the time of each section of the one revolution in a memory, and based on the speed change, 4. The brushless motor control method according to claim 2, wherein the correction of the applied voltage in the section is applied to the next rotation after at least one rotation. 7. A brushless motor according to claim 1, wherein a position of a rotor of the brushless motor is detected using an induced voltage included in a terminal voltage of an armature winding of the brushless motor, and the brushless motor is driven based on the detected position. In the control method of the brushless motor for switching the energization of the child winding, one rotation of the brushless motor is divided into a plurality of sections of the position detection interval, and the applied voltage of the brushless motor can be varied for each section. The time of each section is measured based on the position detection, and one of the brushless motors is measured.
While calculating the average section time of rotation, the difference between the average section time and the time of each section is calculated, the voltage of each section of one rotation is corrected according to the difference in each section, and automatically only when necessary. A method for controlling a brushless motor, wherein torque control is performed. 8. When the brushless motor is in a constant rotation state, the torque control is not performed during acceleration / deceleration of the brushless motor, and the applied voltage for each section of one rotation is determined using the average section time. The control method for a brushless motor according to claim 7, wherein the torque control is performed again. 9. The rotation control of the brushless motor is performed by PW
8. An M control method, wherein the torque is controlled by correcting the applied voltage in each of the sections, and the torque control is performed by converting it into the ON time of the PWM pulse. Or the control method of the brushless motor according to 8.