JPH0697868B2 - Electric motor speed control device and electric motor speed control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for an electric motor, and in particular, for driving a pulsating load having a periodicity, the period is divided into n periods, and each period is divided. Perform speed detection for each area
The present invention relates to an electric motor speed control apparatus and method for reducing rotational pulsation based on the detected value.

[Conventional technology]

As a speed control device for an electric motor that drives a pulsating load having periodicity, the inventors of the present invention have proposed a speed control device disclosed in Japanese Patent Laid-Open No. 61-173690. This is done by dividing the above cycle into n, detecting the speed for each divided region, and using this detected speed value, at least one of the n data of voltage or current applied to the motor so as to reduce the rotational pulsation.
One data is corrected, and the voltage or current applied to the electric motor is controlled according to at least one of the above n data.

[Problems to be Solved by the Invention]

The above control device can be rephrased as follows.
That is, the speed [N ₀ , N ₁ , ... N _n ] and n voltage or current data [I ₀ , I ₁ , ... I _n ] for each region divided into n with respect to the cycle of the pulsating load. There is a control method for creating the i-th cycle data group based on the difference between the (i-1) -th cycle data group and the command speed and the (i-1) th divided speed group. Focusing on one divided area,
One data item of voltage or current, eg 1 for I _K
This is a control method in which the speed in one region, for example N _K, is repeatedly corrected so as to match the commanded speed.

Therefore, if there is an error in the speed for each divided area, the error is superimposed on the voltage or current data that is corrected based on the speed for each divided area that includes the error, and the command speed and the actual speed are The phenomenon that does not match occurs.

That is, the above-mentioned conventional technique does not consider the detection speed error, and when driving a pulsating load, it is created based on the divided region speed including an error, and the voltage applied to the motor or the current flowing in the electric motor is It may be too large or too small for the correct voltage or current, and the operation may be continued as the load output torque does not match the motor output torque, for example, and the rotation or speed pulsation may not decrease rapidly and sufficiently. is there.

The object of the present invention is to control the motor by dividing the cycle into n to drive a pulsating load having a periodicity even when the speed of each of the divided areas includes an error. It is an object of the present invention to provide a speed control device or method for an electric motor, which is capable of reducing the speed (rotation) pulsation over the entire period by applying the control method described in 1 above.

[Means for Solving the Problems]

The above-mentioned purpose is to detect the average speed of the load pulsating cycle or the load of a longer cycle, create a correction speed by the difference between the speed and the average speed, and use this correction speed,
It is achieved by selecting at least one data of voltage or current data to be applied to n motors, and creating the above data with two combinations of the speed of the divided area from which this data is created and the above correction speed. It

Specifically, the average speed detecting means for detecting the average speed of the load torque fluctuation cycle or a cycle longer than the cycle, and the division according to the difference between the average speed and the speed obtained from the average speed detecting means. Correction speed calculating means for generating a correction speed for the speed of the divided area, and correcting the current command or the voltage command for each of the divided areas by the correction data obtained by the correction speed calculating means. It is achieved by applying to an electric motor.

[Action]

Considering the case where the surroundings of the pulsating load are divided into n and at least one of the n speeds in each divided area includes a detection error, the speed of the divided area is as shown above. The voltage generated based on the above and printed on the motor or the current flowing through the motor has an error with respect to the correct value. Therefore, for example, the electric motor output torque increases or decreases below the load torque, and the deviation torque affects at least the average speed for the pulsating load cycle.

Therefore, while correcting the voltage or current data to be applied to the n motors so that the speeds of the regions divided into n match, the average deviation speed is corrected by using the correction data created from the above-mentioned average deviation speed. So that n becomes 0
In order to correct at least one of the individual pieces of data, the speed is corrected for each divided area which is the basis of the data creation.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. The embodiment is an example of a brushless DC motor using a compressor as a load. The compressor is a load that has a periodicity and pulsates, and varies greatly with one rotation as a cycle.
In this embodiment, one rotation is required for this fluctuating load torque.
The motor output torque is determined in order to reduce the speed pulsation so that the speed of each divided area is made to match the command speed.

FIG. 4 shows the overall structure of a speed control device for a brushless DC motor, which is described in, for example, Japanese Patent Application Laid-Open No. 61-173690, to which the present invention is applied.

Reference numeral 1 denotes an AC power supply, which drives the inverter 4 by obtaining the illustrated DC voltage E _d from the rectifier circuit 2 and the smoothing capacitor 3 from the AC power supply 1.

The inverter 4 is a 120 ° conduction inverter comprising the transistors TR ₁ to Tr ₆ and the reflux diode D ₁ to D ₆ Tokyo, the AC output voltage, the positive potential side transistors TR ₁ ~ DC voltage E _d The current flow period of TR ₆ (electrical angle 120 °) is controlled by performing chopper operation by pulse width modulation.

Also, low resistance R ₁ is connected between the common anode terminal of the common emitter terminal of the transistor TR ₁ to Tr ₆ and the reflux diode D ₄ to D _6.

Reference numeral 5 denotes a compressor section, which is composed of a synchronous motor 5-1 having a permanent magnet of four poles of a brushless DC motor as a field, and a compressor 5-2 as its load.

The winding current flowing through the armature winding of the synchronous motor 5-1 also flows through the low resistance R ₁ described above, and the winding current I _L can be detected as the voltage drop of the low resistance R ₁ .

The speed control circuit consists of a microcomputer 7 and a synchronous motor 5.
-1, a magnetic pole position detection circuit 6 for detecting the magnetic pole of the rotor, a current controller 8 for controlling the armature winding current of the synchronous motor 5-1,
The base driver 9 for the transistors TR _{1 to} TR ₆ and a speed command circuit 12 for transmitting the speed of the synchronous motor 5-1 to the microcomputer 7 as a speed command NCMD shown in the figure.

The magnetic pole position detection circuit 6 is a circuit that forms a position detection signal 6S corresponding to the rotor position by using a filter circuit from the armature winding terminal voltages V _{A to} V _C of the synchronous motor 5-1. Then, using the position detection signal 6S, the microcomputer 7 obtains the rotational speed of the synchronous motor 5-1 by measuring and calculating the time interval.

The microcomputer 7 is composed of a CPU 7-1, a ROM 7-2, a RAM 7-3, a timer (not shown) for measuring time, etc., and an address bus, a data bus and a control bus (not shown), respectively. ) Are connected by.

The ROM 7-2 stores various programs necessary for driving the synchronous motor 5-1 related to the brushless DC motor, such as those related to speed calculation processing, command fetch processing and speed control device. .

On the other hand, the RAM 7-3 is related to the main memory 7-3a for reading and writing various data necessary for executing the various processing programs, and the winding current value to be passed for each rotor position. The commutation pattern storage unit 7-3b stores the 12 current data.

The current control unit 8 controls the winding current I _L according to the current output data 11 output for each rotational position based on the current data in the current pattern storage unit 7-3b of the microcomputer 7. Incidentally, 10 is a chopper signal described later.

That is, in the brushless DC motor, the winding current flowing through the armature winding corresponds to the output torque of the motor, and by controlling the winding current for each rotational position, the output torque can be controlled for each rotational position. It will be.

FIG. 5 shows the details of the current control unit 8 described above.

That is, the D / A converter 17 as the current command circuit, the amplifier 13 as the current detection circuit, the current command value 11a and the current detection value V _IL.
It is composed of a current comparator 14 for comparing the above, a triangular wave oscillator 15, and a comparator 16 for producing a chopper signal 10 for chopper-operating the transistors TR _{1 to} TR ₆ described above.

From the 12 current data stored in the current pattern storage unit 7-3b of the microcomputer 7, output to the outside of the microcomputer 7 based on the current data read out one by one according to the rotational position. The 8-bit current output data 11 thus converted is converted into an analog amount by the D / A converter 17, and becomes the illustrated current command value 11a.

Then, the winding current I _L obtained as the voltage drop of the low resistance R ₁ is amplified by the amplifier 13 and becomes the illustrated current detection value V _IL , and the current command value 1
The output 14S is compared with 1a, the triangular wave signal 15S which is the output of the triangular wave oscillator 15 is compared with the comparator 16, and the chopper signal 10 is formed as the output.

FIG. 2 is an operation explanatory diagram showing the time relationship between the position detection signal 6S and the speed N _i and twelve current data I _i for each divided area at each position.

Since the synchronous motor 5-1 is a 4-pole machine, (1) in the figure.
One cycle of the position detection signal 6S representing the magnetic pole position of the rotor of corresponds to a mechanical angle of 180 °, and for one rotation of the rotor 360 °, from the illustrated position “0” to the position “11”, 1 every 30 °
It is divided into two areas.

Then, for each of the divided areas, the 12 pieces of 8-bit current data I _i (i = 0) stored in the current pattern storage unit 7-3b are stored.
~ 11) is read according to each position.

Here, as shown in FIG. 2C, the current data I _i is read out in each area, and the current data I _i is read out.
The current output data 11 is output from the microcomputer 7 based on I _i .

Then, the divided region position i and position (i + 1) 60 °
The pulse interval time of the position detection signal during the period is measured by the microcomputer 7, and the speed N _i (i = 0 to 11) for each divided area (position) is obtained by calculation. FIG. 2 (2) closes the relationship between the speed N _i and the position i for each of the divided areas.

Further, one current command I _i is calculated according to the following equation by an internal speed command INCMD described later and a speed N _i detected for each divided area.
It is corrected every rotation.

Where K _I is the modified gain. For example, as shown in FIG. 2, the speed N ₁ in the area “1” can be detected.
I ₁ is corrected from N ₁ according to the equation (1), and the current data I ₁ is output as the current output data 11 at the position “1” in the next rotation cycle.

Here, it is assumed that the phase of the position detection signal 6S at the time of t = 0 shown in FIG. 2 has an error of Δt for each rotation. At this time, the velocities N ₄ and N ₆ of the divided regions are corrected and have an error with respect to the velocity. For example, the speed N ₄ of the divided area is detected as a speed lower than the correct speed. Therefore, the current data I ₄ created by the equation (1) based on the speed N ₄ of the divided area is added with the error included in the speed N ₄ of the divided area for each rotation to obtain a correct value. It will increase more. As a result, the current output data created on the basis of the current data I ₄ has an unnecessarily large value, and the output torque of the electric motor increases.

In order to solve the above problems, in the present embodiment, the microcomputer 7 executes the speed correction processing 20 in the divided areas, which will be described later.

That is, to explain according to the above example, as a result of the processing torque being increased in the region (position) “4”, based on the current data I ₄ increased more than necessary due to the error Δt included in the position detection signal 6S, The average speed based on one rotation also increases. By utilizing this phenomenon, the speed of the divided area
The method of this embodiment is to add a correction to N ₄ .

Specifically, the internal speed command INCMD and the average speed AVRN of one rotation
The corrected speed HOSEN is created for each rotation according to the following formula.

Where K _H is the correction gain.

On the other hand, in order to find out in which divided area the speed includes an error, the following method is performed in this embodiment.

That is, two pieces of adjacent data I _i and I _{i + 1} are compared with each other, and the position where the difference (I _i −I _{i + 1} ) becomes maximum is the correction target region position, and the position number i is i = Expressed as HNO, the detected speed CU after correction is applied to the speed N _{HNO of} each divided area.
RN _HNO is calculated from the following formula.

CURN _HNO = N _HNO- HOSEN (3) Here, HOSEN is the correction speed obtained by the equation (2).

In the example shown in FIG. 2, (I ₄ −I ₅ ) is maximum and the correction target position number HNO is HNO = 4, and correction is added to the detected speed N ₄ of the divided areas.

FIG. 1 is a block diagram showing the processing contents of the microcomputer 7 in the present embodiment in a block form.

The inputs are the position detection signal 6S from the magnetic pole position detection circuit 6 and the speed command NCMD from the speed command circuit 12.

In the division speed calculation process 18, the position detection signal 6S of 30 °
The detection speed N _i is calculated for each area divided from the rotation time of the rotor for each 60 ° period.

Further, in the command fetch processing 19, the speed command, NCMD is read and the internal speed command INCMD described above is created.

The current pattern storage section 7-3b is composed of 12 pieces of current data I _i (i = 0 to 11) shown in the figure, and is formed by two software-based changeover switches SW1 and SW2 provided on the input side and the processing side. It is selected every 30 °, corrected according to the equation (1), subtracted by the proportional term P, and output as current output data 11 to the D / A converter 17.

On the other hand, the speed correction processing unit 20 for each divided area selects the speed N _HNO for each divided area having an error from the speed N _{i for} each of the 12 divided areas as described above, and (2 ) The correction speed NOSEN is calculated according to the equation), and the detection speed N _{HNO of} each area of the correction target position is corrected according to the equation (3).

FIG. 3 is a detailed block diagram showing in block form the processing contents of the above-described division speed correction processing unit 20.

As input, the internal speed command INCMD, the position detection signal 6S, the speed N _{i for} each divided area, and the two current data I _i and I _{i + 1} selected every 30 ° from the current pattern storage unit 7-3b. Yes, the corrected detection speed CURN _i is output.

The speed correction processing unit 20 for each divided area is divided into four processing blocks, that is, processing I to processing IV as shown in FIG.

The process II is executed for each rotation, and the time for one rotation is calculated from the sum of 12 consecutive 30 ° pulse interval times t ₁ (i = 0 to 11) of the position detection signal 6S, and one rotation is performed according to the following formula. Is a process of obtaining the average speed AVRN of the above by calculation and transmitting it to the correction speed calculating unit of the process I.

The above process I is executed for each rotation and the internal speed command INCM
This is a process of calculating a correction speed from D and the above-described average speed AVRN according to the equation (2) shown above, and transmitting it to the corrected detection speed calculation processing 18 of the processing III.

This process III is a process executed every 30 °, and based on the correction speed HOSEN described above and the correction target position number HNO transmitted from the process IV described later, only the speed for each divided area to be corrected (3) The corrected detection speed CURN _HNO is created according to the formula. That is, it is executed only when HOSEN <0, and for the speed N _i for each divided region detected at every 30 °, if i = HNO, the correction of equation (3) is performed, and i ≠ HNO If curN _i = is not corrected as N _i, a speed N _i directly divided per area, the detected speed curN _i
Output as.

Next, the process IV is executed every 30 ° and is a process of finding out which position is the correction target position, that is, the correction target position number HNO. For this reason, the maximum value MAXHL of the difference between the two current data adjacent to each other is created every 30 °, and which position is the maximum is checked as the correction target position HNO every 30 °.

Specifically, the following processing is performed. The difference I _i −I _{i + 1} between the two current data at a certain time point is compared with the maximum value MAXHL of the difference so far. In the case of MAXHLI _i −I _{i + 1} , the position number i at that time point is If i = HNO, the maximum value of the difference as MAXHL = I _i −I _i-1 is corrected. Conversely, if MAXHL ≤ I _i −I _i-1, then MAXHL
= I _i −I _i−1 , the maximum value of the difference is corrected, and the position number i at that time is corrected as the target position number HNO.

In the embodiment described above, the position detection signal generated by using the filter circuit from the armature winding terminal voltages V _{A to} V _C is used to detect the rotation speed. The pulse interval of this position detection signal has a large error due to the above-mentioned disturbance of the waveform of the armature winding terminal voltage, and the speed correction method for each divided area as in the present invention is particularly effective.
As a result, the influence of the error contained in the speed of the divided areas is removed, so that the winding current at the predetermined position does not increase and the speed pulsation does not occur. Further, it becomes easy to match the output torque of the electric motor with the pulsating load torque of the compressor, and it is possible to effectively suppress the mechanical vibration of the compressor portion caused by the difference between the two torques.

In the previous example, one revolution was chosen as the average speed,
For the correction in the case where this average speed is higher than the command speed, the maximum value (> 0) of the difference (I _i −I _{i + 1} ) between two current data adjacent to the correction target position, that is, I _i > I
_Although the correction in which i _i is subtracted and corrected as the position to be _{i + 1} has been shown, the present invention is not limited to this and can be applied to the following example.

(1) A method of selecting I _i −I _i-1 (> 0) as a difference between data of two currents adjacent to each other when searching for a correction target position.

(2) As the correction target position, (I _i −I) in the previous embodiment
_{i + 1)} is the maximum value, and the above _{(1) (I i -I i} -1) is a method of performing correction on the speed of the maximum value and different two divided regions.

(3) As a correction when the average speed becomes lower than the command speed, when HOSEN> 0, for example, a correction is made to the divided area speed N _{i + 1} as the position where (I _i −I _{i + 1} ) becomes maximum. A method for increasing and correcting the current data I _{i + 1} .

(4) Further, although the case where the speed of the divided area is corrected is shown, a method of continuously correcting the speed deviation of the divided area represented by (INCMD-N _i ).

Further, in the above-described embodiment, the case where the present invention is applied to the brushless DC motor for driving the compressor has been shown, but the present invention is not limited to this, and for example, it has a pulsating load with periodicity. An electric motor for driving a load, the electric motor having a device for controlling the speed by detecting the speed of each division by dividing the cycle into n and controlling the current or voltage applied to the electric motor for each division. It is a general-purpose type that can be applied to the speed control device of.

〔The invention's effect〕

As described above, according to the present invention, the average speed detecting means for detecting the average speed of the fluctuation cycle of the load torque or the cycle longer than this, the average speed data obtained from the average speed detecting means, and the command speed are used for each of the regions. Average deviation speed data creating means for creating average deviation speed data for each, and to reduce the average deviation speed of at least one area divided by the above based on the average deviation speed data created by the average deviation speed data creating means Since the current command data or the voltage command data is corrected, there is no speed pulsation even when driving a load in which the load torque fluctuates significantly, and smooth operation is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a speed control device showing an embodiment of the present invention, FIG. 2 is a time chart showing a current control technique of the present invention, and FIG. 3 is a processing technique of the present invention. FIG. 4 is a flow chart showing the steps, FIG. 4 is a diagram showing a conventional development example to which the present invention is applied, and FIG. 5 is a detailed configuration diagram of a current control portion in FIG. 1 ... AC power supply, 4 ... Inverter, 5-1 ... Synchronous motor, 5-2 ... Compressor, 6 ... Magnetic pole position detection circuit, 7
...... Microcomputer, 7-3b ...... Current pattern storage unit, 8 ...... Current control unit, 12 ...... Speed command circuit, 17 ......
D / A converter, 18 ... division speed calculation processing, 20 ... division speed correction processing, I _{0 to} I ₁₁ ... current data, N _i ... division speed, H
OSEN …… correction speed, AVRN …… average speed, HNO …… correction target position number.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Kishi 800 Tomita, Ohira-cho, Shimotsuga-gun, Tochigi Inside the Tochigi factory, Hitachi, Ltd. (56) References JP-A-61-173690 (JP, A)

Claims (3)

[Claims] 1. An electric motor for driving a load in which load torque changes cyclically, n regions obtained by dividing one cycle of variation of the load torque into n regions, and regions divided respectively. The speed of the electric motor comprising means for detecting the speed of each electric motor, and a controller for adjusting and controlling the current or voltage applied to the electric motor so as to match the speed of the electric motor with the command speed by using the speed data detected by this means. In the control device, the average speed detection means for detecting the average speed of the load torque fluctuation cycle or a cycle longer than this, and the average speed data obtained from the average speed detection means and the command speed are averaged for each of the regions. Average deviation speed data creating means for creating deviation speed data, and the above-mentioned division based on the average deviation speed data created by the average deviation speed data creating means A speed control device for an electric motor, comprising: a correction unit that corrects the current command data or the voltage command data so as to reduce the average deviation speed of at least one region. 2. A speed control method for an electric motor for driving a load in which load torque changes cyclically, wherein one cycle of fluctuation of the load torque is divided into n, and the speed is divided into respective divided areas. In the speed control method of the motor to match the speed of the motor to the command speed using the speed data detected for each region, the cycle of the fluctuation of the load torque or the average speed of the cycle longer than this The average deviation speed is calculated for each of the regions from the average speed and the command speed, and the current command data or the voltage command data is reduced to the next cycle so as to reduce the average deviation speed of at least one region showing the largest average deviation speed. In order to reduce the average deviation speed of the region with the largest average deviation speed in this cycle, and to correct it in the next cycle, repeat the correction in sequence. Speed control method for electric motors. 3. The method according to claim 2, wherein current data or voltage data corresponding to the speed of each divided area is created, and the difference between the current data or voltage data of adjacent areas is created. And the current command data or voltage command data of at least one of the two regions having the largest difference are corrected in the next cycle.