JP2001086800A - Field pole detection method of synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a field pole detection method, which can suppress the speed of a motor during the field pole detection, reduce rotation value (movement distance) and shorten the field pole detection time as possible. SOLUTION: This field pole detection method of a synchronous motor includes a process, in which a correction value γ of a phase ρ of an applied current is varied, and a current phase correction value δ0 with which a generated electromagnetic force is zero is obtained, regardless of the value of the applied current by the deciding the polarity of the generated electromagnetic force according to the polarity of an acceleration (processing 29), a process, in which a current phase correction value δ1 with which the generated electromagnetic power is maximum, is introduced by using the current phase correction value δ0 (processing 36) and a process in which the phase ρ of the applied current is determined in accordance with the current phase correction value δ1 and a temporary field pole position θ, detected by a position detector. After an electromagnetic force command output with a correction value in one estimation period is finished and when an electromagnetic command output with a correction in the next period, if the speed is not zero, it is waited until the speed becomes zero (processing 32), and if the motor is in operation, the next estimation torque command is not applied (processing 33).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a vector of a synchronous motor, and more particularly to a method for detecting a field pole position.

[0002]

2. Description of the Related Art Conventionally, in vector control of a synchronous motor, a position detector (a resolver or a pulse detector) detects a field pole position and controls the amplitude and phase of a sine wave current having a phase synchronized with the field pole position. And performs electromagnetic force control. Generally, the field pole position of the synchronous motor is φ, the detected field pole position is θ, the difference between φ and θ is δ1, the phase of the applied current is ρ, the correction amount of the current phase is γ, and the actual field pole position φ is Assuming that the phase difference of the applied current is δ, the following equation (1) is satisfied from the following equation (1). φ = θ + δ 1 (1) ρ = θ + γ (2) δ = φ−ρ = δ ₁ −γ (3) Further, the size of the field pole is Φ, and the size of the applied current is Φ. To I
Then, the generated electromagnetic force T is expressed by equation (4). T = K × Φ × I × cos (δ) (4) where K is a positive constant. The generated electromagnetic force T is a generated torque in the case of a rotary synchronous motor, and a generated thrust in the case of a direct-acting synchronous motor (linear motor).

[0003] Hereinafter, a description will be given of a rotary synchronous motor as an example. Basically, the correction amount γ (= δ ₁ ) of the current phase at which the generated torque is maximized depends on the generated electromagnetic force T regardless of the applied current.
Is shifted by 90 ° from the correction amount δ0 of the current phase at which is zero. As a method of obtaining the correction amount of the current phase, there is a method of updating the correction amount γ of the current phase according to the polarity of the generated torque (Japanese Patent Laid-Open No. 8-182399). This method uses the correction amounts γ ₁ , γ ₂ , (where γ ₁ <δ
_By giving a correction amount γ ₃ (eg, γ ₃ = (γ ₁ + γ ₂ ) / 2) within a range where ₀ <γ ₂ ) is a lower limit value and an upper limit value, respectively, the polarity of the generated torque is checked. when the polarity of the generated torque is different from the polarity of the torque generated when the correction amount gamma ₁ of the lower limit of the time to update the correction amount gamma ₂ upper limit correction amount gamma _3, generation of the time of the correction amount gamma ₂ upper updating the correction amount gamma ₁ lower limit correction amount gamma ₃ if different from the polarity of the torque. One time of the above processing is regarded as one estimation, and the final value of the correction amount γ obtained by repeating this estimation a predetermined number of times is δ ₀ . The polarity of the generated torque is determined as positive when the sign of the torque command and the sign of the speed change (acceleration) match, and negative when the sign does not match. The torque command is monotonically increased to a temporary target value, and the acceleration is obtained as needed. When the acceleration is large, the target value is decreased, and when the acceleration is small, the target value is increased.

[0004]

However, in the above-mentioned conventional method, since the time between estimations is constant, a long time leads to an increase in the field pole detection time. If the time is short, the motor may be running at the start of the next estimation, and if a torque command is given, the motor may accelerate from that speed, so that the speed increases and the moving distance increases. Furthermore, if the motor is coasting and decelerating due to friction at the start of the next estimation, the absolute value of the deceleration becomes the reference acceleration, and the torque command is increased until an acceleration exceeding that is detected. However, there has been a problem that the speed of the electric motor increases and the rotation amount (movement amount) also increases. Therefore, the present invention provides a field pole detection method for a synchronous motor that can suppress the speed of the motor during field pole detection, reduce the amount of rotation (movement), and shorten the field pole detection time. It is an object.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention changes the amount of correction (.gamma.) Of the phase (.rho.) Of an applied current so as to generate electromagnetic waves regardless of the magnitude of the applied current. A current phase correction amount (δ ₀ ) at which the force becomes zero is determined by determining the polarity of the generated electromagnetic force from the polarity of the acceleration,
The current phase correction amount ([delta] ₀₎ the generation electromagnetic force derives the current phase correction amount becomes maximum ([delta] ₁₎ using the current phase correction amount ([delta] ₁₎ and the detected provisionally in position detector In the synchronous motor field pole detection method for determining the phase (ρ) of the current to be applied from the field pole position (θ), the electromagnetic force command output in the correction amount in one estimation period ends and the correction amount in the next period When the electromagnetic force command is output, it is checked whether the speed is zero. If the speed is zero, the electromagnetic force command is output. If the speed is not zero, the process waits until the speed becomes zero. Further, the synchronous motor is a rotary synchronous motor or a linear synchronous motor (linear motor), and the speed is an average speed of an encoder. According to the method for detecting a field pole of a synchronous motor, in a rotary or direct-acting synchronous motor,
Between the estimation and the estimation, the motor was always stopped and the detected speed was confirmed to be zero. When the speed was confirmed to be zero, the next estimation process was started immediately. When the time is set, if the time is long, the time can be shortened, so that the increase in the field pole detection time can be suppressed. Alternatively, if the certain time between estimations is short, the next torque command is given while the motor is still running at the start of the next estimation, so that the speed is increased to accelerate from that speed. Inconvenient phenomena such as an increase in the amount of rotation and movement can be suppressed.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart of a detection process by a field pole detection method for a synchronous motor according to an embodiment of the present invention. FIG. 2 is a flowchart of the phase correction amount update processing shown in FIG. FIG. 3 is a block diagram of a vector control circuit of the synchronous motor to which the field pole detection method shown in FIG. 1 is applied. FIG. 4 is a block diagram of the microprocessor shown in FIG. FIG. 5 is a diagram showing a method of generating the torque command shown in FIG. FIG. 6 is a diagram in which the torque command shown in FIG. 5 is generated by a linear function. FIG. 7 is a diagram showing a case where the target value of the torque command shown in FIG. 6 is lowered. Figure 8 is an explanatory view for obtaining the phase correction amount [delta] ₁ shown in FIG. FIG.
FIG. 2 is a block diagram illustrating a circuit configuration of a drive device by vector control of a synchronous motor (three-phase) to which a field pole detection method of the synchronous motor is applied. The encoder 7 in the figure detects the rotational position of the synchronous motor 6. Microprocessor 1
Performs a calculation using the torque command i and the position x of the synchronous motor 6 detected by the counter 8, and performs a two-phase current command Iu,
The Iv is digitally / analog-converted by the D / A converters 2 and 3 and output to the two-phase / three-phase conversion circuit 4.
The two-phase / three-phase conversion circuit 4 converts the input two-phase current
The power amplifier 5 is converted into the phase current commands iu, iv, iw to control the power amplifier 5. The power amplifier 5 drives the synchronous motor 6 by supplying a current corresponding to these three-phase current commands iu, iv, iw to the synchronous motor 6. The synchronous motor 6
Is the same as in the case of a direct-acting synchronous motor (linear motor). In the case of a linear motor, the encoder 7 serves as a linear scale, and a pole sensor or the like is omitted as a sensorless device. The magnetic pole position is estimated by the magnetic pole estimation method, and the microprocessor 1 outputs a current command based on the position detection signal x from the linear scale, and controls the power amplifier 5 via the gate pulse generation circuit from the coordinate conversion circuit to control the power amplifier 3. The linear motor 6 is operated and driven by the phase current.

FIG. 4 is a block diagram of the microprocessor 1. The field pole position calculator 101 calculates a temporary field pole position θ from the position information x. The speed calculator 102 calculates the speed based on the time difference (differential) of the position information x. The acceleration calculator 103 calculates the acceleration based on the time difference (differential) of the speed information of the speed calculator 102. Torque command generator 10
Numeral 4 generates a torque command i according to a pattern described later during field pole detection, and generates a torque command i according to control after detection. The torque polarity determiner 105 determines the sign of cos (δ) relating to the phase difference δ between the actual field pole position φ and the phase ρ of the applied current command based on the acceleration information. That is, while the current phase correction amount δ1 is being estimated, the torque polarity determiner 105 first stores the speed change (acceleration) Acc1 when the torque command is 0 for an arbitrary current phase correction amount γ. Acc1 is acceleration due to disturbance. Here, the acceleration Acc1 is a predetermined acceleration Acc2.
The larger one is set as the reference acceleration Acc0 for determining the magnitude of the acceleration. If possible, Acc0 is set to a value larger than Acc1 by 5% or more. Acceleration A at regular intervals
cc3 is calculated, and the polarity of the generated torque is determined based on the sign of the acceleration when the acceleration becomes larger than the reference acceleration Acc0. If the acceleration Acc3 is smaller than the reference acceleration Acc0 even if the command becomes the maximum torque command, the acceleration A at that time is used.
The sign of cci is used to determine the polarity of the generated torque. The accelerations Acc1 and Acc3 are measured by the acceleration calculator 103. The current phase corrector 106 estimates the current phase correction amount δ ₀ by a method described later, and sets the current phase correction amount γ = δ ₁ (= δ ₀ + 90 °) or γ = δ such that the polarity of the generated torque becomes positive. ₁ (= δ ₀ -90 °) is output. Adder 10
7 adds the temporary field pole position θ output from the field pole position calculator 101 and the current phase correction amount γ output from the current phase corrector 106, and outputs a phase ρ of the applied current. The phase ρ of this current is sin by the sine function generator 110.
(Ρ). Also, the current phase ρ and -120 °
The output of the generator 108 is added by the adder 109 to become ρ−120 °, which is converted by the sine function generator 111 into sin (ρ−120 °). The sine function generators 110 and 111 respectively apply current phases ρ and ρ
By giving −120 ° as an address, the sine function stored in the program memory can be extracted. The multipliers 112 and 113 correspond to the torque command generator 10
4 respectively with the torque command i output from sin.
(Ρ) multiplied by sin (ρ−120 °) to output two-phase current commands Iu and Iv.

Next, a method for estimating the current phase correction amount δ1 in the present embodiment will be described with reference to the flowchart of FIG. (Process 21) Initial values are set. That is, the current phase correction amount γ = 0 °, the estimated number of times j = 1, and the time t = 0. Time t is a reference time for processing such as calculation of torque command i and measurement of acceleration. Proceed to process 22. (Process 22) The torque command i is calculated by a method described later. Proceed to process 23. (Process 23) The time t is determined. If t = 0, the process proceeds to step 24. When t = k · Δt, the process proceeds to processing 26. If t = t _IMAX , the process proceeds to processing 28. If t = t ₀ (t ₀ = 8 · t _IMAX ), process 3
Proceed to 2. Otherwise, the process proceeds to processing 31. Here, k is a positive integer, and k · Δt <t _IMAX . t _IMAX is the time when the torque command i becomes i _MAX . (Process 24) The acceleration Acc1 is measured. Proceed to process 25. (Process 25) The absolute value of the acceleration Acc1 is compared with a preset acceleration Acc2 (> 0), and the larger one is set as the reference acceleration Acc0 (> 0). Proceed to process 31. (Process 26) The acceleration Acc3 is measured. Proceed to process 27. (Process 27) Absolute value of acceleration Acc3 and reference acceleration Ac
Compare c0. If | Acc3 | is greater than Acc0, the process proceeds to step 29; otherwise, the process proceeds to step 31. (Process 28) The acceleration Acc3 is measured. Proceed to process 29. (Process 29) The current phase correction amount γ is updated by a method described later. Proceed to process 30. (Process 30) obtaining a reference time t ₁ to create a torque command i. Let t ₁ = t. Here, t is the time when the absolute value of the acceleration Acc3 becomes larger than the reference acceleration Acc0,
t _IMAX . Proceed to process 31. (Process 31) The time is updated. Let t = t + Δt. Proceed to process 22. In process 23, t = t ₀ = 8 · t
_{At 1 MAX} , (Process 32) The average speed during Δt is detected. If it is zero, the process proceeds to Process 33; (Process 33) The time is returned to the initial value. It is assumed that t = 0. Proceed to process 34. (Process 34) The estimated number of times j is compared with the maximum estimated number of times j _MAX . If j is smaller than j _{MAX, the} process proceeds to a process 35; otherwise, the process proceeds to a process 36. (Process 35) The estimated number j is updated. Let j = j + 1. Proceed to process 22. (Process 36) for determining the current phase correction amount [delta] ₁ by the method described below. The process ends.

Next, a method of updating the current phase correction amount γ will be described with reference to FIG. (Process 41) The estimated number j is determined. When j = 1, the process proceeds to a process 42, and when j = 2 to j _MAX , the process proceeds to a process 45. Note that j> j _MAX does not occur from the description of FIG. (Process 42) The sign of the acceleration Acc3 is checked. Acc3
If ≧ 0, the process proceeds to processing 43. If Acc3 <0, the process proceeds to step S44. (Process 43) A limit value (hereinafter abbreviated as a positive limit value) γ _p for obtaining a positive acceleration and a limit value (hereinafter abbreviated as a negative limit value) γ _m for obtaining a negative acceleration are initialized. γ _p = 0
° and γ _m = 180 °. Proceed to process 48. Note that γ
_{As p, the} current phase correction amount γ closest to δ ₀ when the acceleration Acc3 ≧ 0 is entered. γ _m is acceleration Acc3
A current phase correction amount γ closest to δ ₀ when it is determined to be <0 is inserted. (Process 44) The positive limit value γ _p and the negative limit value γ _m are initialized. It is assumed that γ _p = 180 ° and γ _m = 0 °. Proceed to process 48. (Process 45) The sign of the acceleration Acc3 is checked. Acc3
If ≧ 0, the process proceeds to processing 46. If Acc3 <0, the process proceeds to processing 47. (Process 46) The positive limit value γ _p is updated. _Let γ _p = γ. Proceed to process 48. (Process 47) to update the negative limit value gamma _m. Let γ _m = γ. Proceed to process 48. (Process 48) The current phase correction amount γ to be used next is calculated. γ = (γ _p + γ _m ) / 2. The process ends.

Next, a method of generating the torque command i will be described with reference to FIG. The time interval t ₂ -t ₀ is the processing 3
It is determined as follows based on t ₁ = t determined by 0. _{t 2 = 2 · t t 3} = 3 · t t 4 = 4 · t t 5 = 5 · t t 6 = 6 · t t 7 = 7 · t t 0 = 8 · t torque instruction i is as follows decide. When 0 ≦ t <t ₁ , i = f (t). The function f (t) is f
(0) = 0 and f (t ₁ ) = i _MAX , interval 0 ≦ t
It is assumed that the increase monotonically with ≦ t _1. Incidentally, i _MAX is the maximum torque command is desired, it may be smaller than the maximum torque. For example, 90% or 50% of the maximum torque command
% May be used. When t ₁ ≦ t <t ₂ , i = f (t ₂
−t). When t ₂ ≦ t <t ₃ , i = −f (t
−t ₂ ). When t ₃ ≦ t <t ₄ , i = −f
(T ₄ −t). When t ₄ ≦ t <t ₅ , i = −
and f (t-t _4). When t ₅ ≦ t <t ₆ , i =
−f (t ₆ −t). When t ₆ ≦ t <t ₇ , i
= F (tt- ₆ ). When t ₇ ≦ t <t ₈ ,
Let i = f (t ₆ -t). FIG. 6 shows that f (t) is 1
In the example using the following function, t ₁ = t _IMAX . f (t) = i _MAX / t _{IMAX ×} t FIG. 7 uses the same f (t) as FIG. 6, but before t becomes t _IMAX | Acc3 |> Acc0
_Is an example when t ₁ = t _IMID (<t _IMAX ). The absolute value of the target value of the torque command i is the torque command i _MID (<i _MAX ) at time t ₁ .

[0011] Figure 8 is a diagram for explaining a method of obtaining the current phase correction amount [delta] ₁ of the maximum torque is obtained from the current phase correction amount [delta] ₀ of the generated torque becomes 0 regardless of the magnitude of the current applied. In FIG. 8, the shaded area indicates the range of the current phase correction amount γ where Acc3 ≧ 0. Current phase correction amount γ =
The following combinations can be considered according to the sign of the acceleration Acc3 at 0 °. (1) When Acc3 ≧ 0 (corresponding to FIGS. 8 (1) and (4)) δ ₁ = δ ₀ −90 ° (2) When Acc3 <0 (corresponding to FIGS. 8 (2) and (3)) δ ₁ = δ ₀ + 90 ° Note that δ ₀ is always found between 0 ° and 180 °. that's all,
Although the rotary synchronous motor has been described, even in the case of a direct-acting synchronous motor (linear motor), the torque can be replaced with thrust, and the process of estimating and correcting the field pole position is similarly possible. As a result, highly accurate field pole estimation processing is possible for both synchronous and rotary motors.

[0012]

As described above, according to the present invention,
Since the next electromagnetic force command is not output until the motor stops,
Suppress the speed of the motor during the detection of the field pole, and the amount of rotation (the amount of movement)
And the field pole detection time can be shortened.

[Brief description of the drawings]

FIG. 1 is a flowchart of a detection process by a field pole detection method for a synchronous motor according to an embodiment of the present invention.

FIG. 2 is a flowchart of a phase correction amount update process shown in FIG. 1;

FIG. 3 is a block diagram of a vector control circuit of the synchronous motor to which the field pole detection method shown in FIG. 1 is applied;

FIG. 4 is a block diagram of the microprocessor shown in FIG. 3;

FIG. 5 is a diagram showing a method of generating the torque command shown in FIG.

6 is a diagram in which the torque command shown in FIG. 5 is generated by a linear function.

7 is a diagram showing a case where the target value of the torque command shown in FIG. 6 is lowered.

8 is an explanatory view for obtaining the phase correction amount [delta] ₁ shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microprocessor 2, 3 D / A converter 4 2/3 phase conversion circuit 5 Power amplifier 6 Synchronous motor 7 Encoder 8 Counter 101 Field pole position calculator 102 Speed calculator 103 Acceleration calculator 104 Torque command generator 105 Torque polarity Judge 106 Current phase corrector 107, 109 Adder 108 -120 ° generator 110, 111 Sine function generator 112, 113 Multiplier

Claims (3)

[Claims] 1. A method for changing a correction amount (γ) of a phase (ρ) of an applied current to obtain a current phase correction amount (δ ₀ ) at which generated electromagnetic force becomes zero regardless of the magnitude of the applied current, Determine the polarity of the generated electromagnetic force from the polarity of the acceleration,
The current phase correction amount ([delta] ₀₎ the generation electromagnetic force derives the current phase correction amount becomes maximum ([delta] ₁₎ using the current phase correction amount ([delta] ₁₎ and the detected provisionally in position detector In the synchronous motor field pole detection method for determining the phase (ρ) of the current to be applied from the field pole position (θ), the electromagnetic force command output in the correction amount in one estimation period ends and the correction amount in the next period When outputting the electromagnetic force command, the synchronization is characterized by checking whether the speed is zero, outputting the electromagnetic force command if the speed is zero, and waiting until the speed becomes zero if the speed is not zero. How to detect the field pole of the motor. 2. The method according to claim 1, wherein the synchronous motor is a rotary synchronous motor or a linear synchronous motor. 3. The method according to claim 1, wherein the speed is an average speed of an encoder.