JPH06197587A - Detecting method for rotation angle of motor - Google Patents

Abstract

PURPOSE:To decide the reference position of the rotor of a motor by fixing the conducting pattern given to the stator of the motor while only the conducting value of the pattern is left variable and driving a power converting section under two conducting conditions, and then, finding the angle difference between the rotor and an encoder from the detected position and conducting value when the motor reaches a stable position at each conducting value. CONSTITUTION:A PWM power converting section 3 is driven by only changing the conducting value of the conducting pattern given to the stator of a three- phase synchronous motor 1 against a current command given to a three-phase distributor 5. When the motor 1 reaches a stable position with the conducting value, the position detecting signal of an encoder 9 and the conducting value are stored. When the measurement is executed by a prescribed number of times, the reference position of the rotor of the motor 1 is found by calculation from the calculating formula of the method of least squares, etc., by using the stored values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a rotation angle of a synchronous motor, and more particularly to a method for accurately detecting an angular difference between a magnetic reference of a rotor of a synchronous motor and a reference value of a rotational position detection sensor. The present invention relates to a rotation angle detection method.

[0002]

2. Description of the Related Art A drive device for driving a synchronous motor of this type mainly includes a position detection sensor capable of detecting the position of the synchronous motor and a phase detection device such as a pole sensor for detecting a rotational position signal of each phase of the synchronous motor. A sensor, a position / speed control device that forms a current command from a position detection signal from the position detection sensor and a position command, and a power conversion command signal from the current command and the rotational position signal of each phase from the pole sensor. Is generally provided, and a PWM power conversion unit that performs power conversion based on the power command signal from the three-phase distribution device.

In such a driving device, the position of the rotor of the synchronous motor is detected by using a phase detection sensor such as a pole sensor, and the detected rotational position signal of each phase is taken into a three-phase distribution device to generate electric power. The conversion command signal is formed, and the PWM power conversion unit is driven by these power conversion command signals to energize each phase of the synchronous motor to control the rotation of the synchronous motor. Therefore, in the above drive device, a phase detection sensor such as a pole sensor is an essential requirement, and there is a disadvantage that the manufacturing cost increases due to the use of expensive parts.

In order to solve the above-mentioned inconvenience, it has been considered to use an encoder which is a position detecting sensor for positioning instead of the phase detecting sensor such as the pole sensor. When using an encoder instead of a phase detection sensor such as a pole sensor, the angle difference between the magnetic reference between the stator and rotor of the synchronous motor and the origin of the encoder must be adjusted to zero. There is an inconvenience that the efficiency of the rotation control of the synchronous motor is reduced and, in some cases, three-phase distribution cannot be performed.

On the contrary, if the magnetic reference of the rotor of the synchronous motor and the origin of the encoder are measured and the angle difference can be corrected by the measured values, the encoder is replaced with a phase detection sensor such as a pole sensor. It can be said that it can be used.

Therefore, as an example of a method of measuring the above-mentioned angle difference, for example, by controlling a PWM power converter, a predetermined stator winding of the synchronous motor is energized to rotate the rotor of the synchronous motor to a stable position. After that, a method of using the stable position as a reference of the rotor is provided (see, for example, JP-A-58-119794).

According to this measuring method, every time the synchronous motor drive device is operated, a predetermined stator winding of the synchronous motor is energized to rotate the rotor of the synchronous motor to a stable position. It means that the processing for obtaining the angle difference is performed by the fact that the position reaches the stable position.

[0008]

However, in the conventional method for detecting the rotation angle of the electric motor as described above, as in the robot, the gravity load and other disturbances are always applied to the rotor of the synchronous electric motor as described above. When the operation is performed, the measured value becomes a value with an error due to the disturbance, and there is a drawback that the efficiency of the rotation control of the synchronous motor is reduced.

An object of the present invention is to provide a method for detecting the rotation angle of a motor, which can improve the efficiency of rotation control of the synchronous motor.

[0010]

In order to achieve such an object, the present invention forms a current detection command from a position detection sensor capable of detecting the position of a synchronous motor, and a position detection signal from the position detection sensor and a position command. A position / speed control device, a distribution device that forms a power conversion command signal from a current command and a rotational position signal of each phase of the synchronous motor, and a power conversion unit that converts power based on the power command signal from the distribution device. In the method for measuring the rotation angle in the motor control device, the current command given to the distribution device, only the energization value can be changed in a state where the energization pattern given to the stator of the synchronous motor is fixed, and at least two energization conditions are applied. Therefore, by driving the power conversion unit, from the position detection signal from the position detection sensor when the synchronous motor reaches a stable position under each energization value and the energization value, It is thus determine the angular difference between the reference position of the magnetic reference and encoder rotor phases motor.

[0011]

Therefore, for example, in the case of a three-phase synchronous motor, the angular difference between the magnetic reference of the rotor of the synchronous motor and the reference position of the encoder can be obtained by the following principle. Hereinafter, description will be given with reference to FIG. 3 showing the relationship between the current value i _SJ and the rotor angle δ.

First, if it is possible to know the position of the U-phase, V-phase, and W-phase voltages applied to the three-phase synchronous motor with respect to the reference position (= 0) of the encoder. , The relationship is known to persist. Therefore, based on the output (angle) of the encoder, U
The phases of the V-phase, V-phase, and W-phase voltages are determined.

Therefore, a current is made to flow from the PWM power converter to each phase of the stator of the three-phase synchronous motor, and a command current vector i _s as shown in FIG. ^* (Current magnitude (= energization value i), angle from U phase is angle θ _S (= energization pattern)) is established.
As a result, the rotor of the three-phase synchronous motor 1 is attracted in the direction of i _s ^* and stopped.

If the load disturbance torque τ applied to the rotor of the three-phase synchronous motor is zero, the rotor is attracted to the command current vector i _s ^* and the rotor angle δ becomes zero. However, in the case of a three-phase synchronous motor applied to an industrial robot or the like, a force such as gravity is applied to the rotor of the three-phase synchronous motor, and as shown in FIG. Since the torque is applied to the rotor as a constant torque τ, the rotor angle has a deviation of δ.
That is, in order to balance with this torque τ, the rotor of the three-phase synchronous motor, as shown in FIG. 3 (A), comes to rest at an angle of δ with respect to the direction of the command current vector i _s ^*. . If you balance in such a state,

[Equation 1] Will be established.

The command current vector i _s ^* generated by the stator of the three-phase synchronous motor is known because it is a vector formed by the current supplied from the power converter. The actual value you want to obtain is the reference position of the encoder attached to the three-phase synchronous motor (the position where the position detection output becomes zero).
Is the detected value of each phase (U, V, W). That is, if the angle ψ _S from the command current vector i _s ^* to the origin of the reference position of the encoder is obtained, then U,
The angles ψ _U , ψ _V , and ψ _W from the reference positions of the V and W phases are obtained.

[0016]

[Equation 2]

On the other hand, in Expression 1, the angle δ cannot be directly detected. The angle Φ from the actual reference position can be detected by the encoder. This angle Φ is

[Equation 3] Is. Therefore, the following Expression 4 is obtained from Expression 1.

[Equation 4] Further transforming Equation 4,

[Equation 5] Becomes Here, Φ and i _s are known, and τ and ψ _S are unknown. Then, ψ _S is calculated from this equation 5.

In this ψ _S , the angle θ _S of the command current vector i _s ^* is fixed, the current value i _S is made variable, and each current value i _sJ
We obtain Φ _{J in} and obtain from these Φ _J.

Now, the angle θ _{S of} the command current vector i _s ^*
With the (energization pattern) fixed, the current value i _S (absolute value)
As shown in FIGS. 3B to _3E , i _S1 , i _S2 , i
_{If S3} and i _S4 are increased, the angle δ is
Naturally, it becomes smaller as δ ₁ , δ ₂ , δ ₃ , and δ ₄ . The above-mentioned formula 5 can be expressed as the following formula 6.

[Equation 6]

Equation 6 is a linear equation, and X _a = 1 / i
_S and (value of the current flowing to the stator of the synchronous motor (value based on the absolute value)), y = sin .PHI obtained by the detection value Φ obtained from the encoder definitive its current value, the value of X _b = cosΦ, α _a, That is, α _b is obtained, and ψ _S is obtained from α _b . That is, basically, two types of (y ₁ , X
_a1 , X _b1 ), (y ₂ , X _a2 , X _b2 ), α _a , α
_b and ψ _S can be obtained by the following Expression 7.

[0021]

[Equation 7]

When variations and noises are taken into consideration, more (y _J , X _aJ , X _bJ ) data is taken and these many data are averaged by the least square method or the like, A more accurate value can be obtained.

That is, according to the present invention, based on the above-described principle, the current command given to the three-phase distributor is given to the energization pattern (angle θ _{S of the} command current vector i _s ^* given to the stator of the synchronous motor). ) Is fixed, only the energization value (current value i _s ) can be varied, the power converter is driven with at least two energization values, and the position detection when the three-phase synchronous motor is stopped with each energization value Position detection signal (= Φ) from the sensor and the energization value (i _S to X _a = 1)
/ I _S )), the reference position of the rotor of the synchronous motor is obtained.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to the embodiments shown in the drawings. The present embodiment is applied to a three-phase synchronous motor.

FIG. 1 shows an apparatus for realizing the method of detecting the rotation angle of a motor according to the present invention. In FIG. 1, a motor drive device is a device that drives a three-phase synchronous motor 1, and mainly includes
A PWM power conversion unit 3, a three-phase distribution device 5, a position / speed control device 7, and an encoder 9 are provided. Then, by adding the measuring device 11 to the drive device of the electric motor, the method for detecting the rotation angle of the electric motor of the present invention is realized.
It should be noted that components such as a current feedback system and a DC power supply unit are omitted.

An encoder 9 as a position detecting sensor is fixed to the rotary shaft of the electric motor 1. The encoder 9 can detect the rotational position of the rotor of the electric motor 1. The output of the encoder 9 is connected to the three-phase distributor 5, the position / speed controller 7 and the measuring device 11. Also, the position
A position (speed) command is input to the speed control device 7. The position / speed control device 7 forms a torque command based on the above-mentioned position (speed) command and the detection signal from the encoder 9. The torque command from the position / speed control device 7 is
It is input to the three-phase distributor 5. The three-phase distributor 5
The power conversion command signals iu, iv, and iw are formed from the detection signal from the encoder 9 and the torque command. The power conversion command signals iu, iv, and iw from the three-phase distribution device 5 are PWM.
It is input to the power conversion unit 3.

The PWM power converter 3 forms a PWM signal based on the power conversion command signals u, v, w to obtain an alternating current. The alternating current from the PWM power converter 3 is supplied to the electric motor 1.

The measuring device 11 is composed of a measurement processing device 13 having an input / output unit for executing a measurement process and performing a calculation from a measurement result, and an input device 15 for inputting conditions necessary for the measurement. Has been done. Then, the measurement processing device 13 gives the control signal to the three-phase distributor 5 through an input / output unit (not shown), and takes in and processes the detection signal from the encoder 9 through the input / output unit (not shown). Is. The input device 15 is operated by the measurer to measure the number of measurements J, the initial current value i _S1 , the current addition width Δi, U.
It is a device that gives the angle θ _S from the phase to the measurement processing device 13.

<Operation of Embodiment> The operation of the above-described embodiment will be described with reference to FIGS. 1, 2 and 3.

FIG. 2 shows a flowchart processed by the measuring apparatus 11 of the present invention.

First, when the measuring device 11 starts to operate,
From the input device 15, the number of measurements J = 0, the initial current value i _S1 ,
Provide current added width .DELTA.i, the angle theta _S from U-phase, the maximum value J _{ma x} number of measurements to the measurement processor 13 (step S10
0). Here, the number of times of measurement J is used to recognize the number of times of measurement, and is set to zero at the time of setting. The initial current value i _S1 is
It is a current value given to the three-phase synchronous motor 1 at the beginning of measurement. The current addition width Δi is used by adding it to the initial current value i _S1 in order to change the current value after the second time. U
The angle θ _S from the phase is used as the current pattern.
The maximum value J _max of the number of times of measurement defines the number of times of measurement, and a minimum value of 2 is set.

Next, the measuring device 11 inputs a command of the angle θ _S from the U phase and the current value i _s1 to the three-phase distributor 5 (step S101). As a result, in the three-phase distributor 5, the command current vector i _s1 ^* has the three-phase synchronous motor 1
The PWM power converter 3 is driven so as to occur in the stator. A current based on the power conversion command flows from the PWM power conversion unit 3 to the stator of the three-phase synchronous motor 1. As a result, in the stator of the three-phase synchronous motor 1,
A command current vector i _s1 ^* is generated.

Then, as shown in FIG. 3B, the rotor of the three-phase synchronous motor 1 operates in accordance with the command current vector i _s1 ^* and stands still in balance with the external force τ. Here, the measuring device 11 monitors the detection signal from the encoder 9 and confirms that the rotor of the three-phase synchronous motor 1 has completely stopped (step S102).

At this time, the measuring device 11 uses the encoder 9
The detected value Φ ₁ is detected (step S103). Then, the measuring apparatus 11 stores the set of (i _S1 , Φ ₁ ) in the memory (not shown) (step S104).

Next, the measuring device 11 executes the variable process of the current value and the increment process of the number of times of measurement J. That is, from the preset current addition width Δi, i _S2
= I _S1 + Δi, and J = J + 1 = 0 + 1 = for the number of processing times J (because the initial value J = 0).
1 is calculated (step S105).

After that, the measuring device 11 determines the number of times of processing J based on the preset maximum value J _{max of the} number of times of processing (assuming that J _max = 4 is set) (step S4). S106). As described above, since J = 1 (step S106; N), the process is returned to step 101 again.

The processing from step 101 is executed again in the measuring device 11. That is, the command of the angle θ _S from the U phase and the current value i _s2 is input from the measuring device 11 to the three-phase distributor 5 (step S101). Accordingly, the three-phase distribution device 5 drives the PWM power conversion unit 3 so that the command current vector _is2 ^* is generated in the stator of the three-phase synchronous motor 1. A current based on the power conversion command flows from the PWM power conversion unit 3 to the stator of the three-phase synchronous motor 1. As a result, the command current vector i _s2 ^* is generated in the stator of the three-phase synchronous motor 1.

When it is confirmed that the rotor of the three-phase synchronous motor 1 is stationary (step S102), the state becomes as shown in FIG. 3 (C). Here, the measuring device 11 detects the angle Φ ₂ from the encoder 9 (step S103),
The measuring device 11 stores the set of (i _S2 , Φ ₂ ) in the memory (not shown) (step S104).

Next, the measuring device 11 executes the current value changing process and the process number incrementing process. That is, from the preset current addition width Δi, i _S3 = i
_S2 + Δi is calculated and the number of processing times J is
J = J + 1 = 1 + 1 = 2 is calculated (step S1)
05).

[0040] The measurement device 11 performs determination processing times J the maximum value J _max number of processing times that has been set in advance (J _{ma x} = 4) to the group (step S106). In this case, J = 2 (step S106; N), and the process returns to step 101 again.

The processing from step 101 is executed again. That is, from the measuring device 11 to the three-phase distributor 5,
The command of the angle θ _S from the U-phase and the current value i _s3 is input (step S101). As a result, the three-phase distributor 5
_Drives the PWM power conversion unit 3 so that the command current vector _is3 ^* is generated in the stator of the three-phase synchronous motor 1.
A current based on the power conversion command flows from the PWM power conversion unit 3 to the stator of the three-phase synchronous motor 1. As a result, the command current vector i _s3 ^* is generated in the stator of the three-phase synchronous motor 1.

When it is confirmed that the rotor of the three-phase synchronous motor 1 has stopped (step S102), the state becomes as shown in FIG. 3 (D). Here, the measuring device 11 detects the angle Φ ₃ from the encoder 9 (step S103),
The measuring device 11 stores the set (i _S3 , Φ ₃ ) in a memory (not shown) (step S104).

Then, the measuring device 11 executes the current value changing process and the process number incrementing process. That is, from the preset current addition width Δi, i _S3 =
i _S2 + Δi is calculated and J = J + 1 = 2 + 1 = 3 is calculated for the number of processing times J (step S105).

[0044] The measurement device 11 performs determination processing times J the maximum value J _max number of processing times that has been set in advance (J _{ma x} = 4) to the group (step S106). In this case, J = 3 (step S106; N), and the process returns to step 101 again.

The processing from step 101 is executed again. That is, the command of the angle θ _S from the U phase and the current value i _s4 is input from the measuring device 11 to the three-phase distributor 5 (step S101). As a result, the three-phase distribution device 5 drives the PWM power converter 3 so that the command current vector i _s4 ^* is generated in the stator of the three-phase synchronous motor 1. A current based on the power conversion command flows from the PWM power conversion unit 3 to the stator of the three-phase synchronous motor 1. As a result, the command current vector i _s4 ^* is generated in the stator of the three-phase synchronous motor 1.

When it is confirmed that the rotor of the three-phase synchronous motor 1 has stopped (step S102), the state becomes as shown in FIG. 3 (E). Here, the measuring device 11 detects the angle Φ ₄ which is the detection signal from the encoder 9 (step S103), and the measuring device 11 stores the set (i _S4 , Φ ₄ ) in the memory (not shown) (step S104). ).

Next, the measuring device 11 executes the current value changing process and the process number incrementing process. That is, from the preset current addition width Δi, i _S5
= I _S4 + Δi is calculated, and J = J + 1 = 3 + 1 = 4 is calculated for the number of processing times J (step S105).

[0048] The measurement device 11 performs determination processing times J the maximum value J _max number of processing times that has been set in advance (J _{ma x} = 4) to the group (step S106). In this case, since J = 4 (step S106; Y), the process proceeds to the mathematical expression process (step S107).

In this mathematical formula processing, ψ _S can be obtained by calculating α _a and α _b by the least square method shown in Formula 8 or Formula 9 below.

[0050]

[Equation 8]

Then, the measuring apparatus 11 can obtain ψ _U , ψ _V , ψ _W based on the mathematical expression 2 (step S107). Then, all the processes are finished.

In this embodiment, after operating as described above, (i _SJ , Φ _J ) is obtained, and then α _a , α _b , ψ _S are accurately calculated based on these, and ψ _U , Ψ _V , ψ _W can be obtained.

Therefore, according to the above embodiment, even when the three-phase synchronous motor 1 is assembled to a robot or the like and gravity or the like is applied to the rotor of the three-phase synchronous motor 1, the three-phase synchronous motor 1 can be used. The reference position of the rotor can be obtained.

Further, according to the above-mentioned embodiment, since the reference position of the rotor of the three-phase synchronous motor 1 is obtained, the pole sensor can be eliminated, the cost can be reduced, and the maintainability for the user can be improved. improves.

The above-described embodiment is an example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, in the present embodiment, the measuring device 11 is used to automatically perform the above processing, but of course, the measuring device 11 may be provided externally for the measurement, or the position / speed control device 7 may be provided. The measuring device 11 may be configured, and further, a human may perform the above processing to perform the measurement. Further, although the present embodiment has been mainly described in the case of being applied to a three-phase synchronous motor, the present invention is not particularly limited to this and can be applied to other synchronous motors of three phases or more or less.

[0056]

As is apparent from the above description, according to the present invention, even when the synchronous motor is mounted on the robot or the like, that is, even when gravity is applied to the rotor of the synchronous motor, The reference position of the rotor can be obtained. Therefore, when obtaining the angle difference between the magnetic reference of the rotor and the reference position of the encoder, the work can be performed without removing the synchronous motor from the robot or the like, and the teaching and origin search of the robot need not be redone again.

Further, according to the present invention, since the reference position of the rotor of the synchronous motor is obtained, the pole sensor can be eliminated, the cost can be reduced, and the maintainability for the user can be improved. In particular, when it is used in a device for positioning such as a robot or an NC device, a position detecting sensor originally required for positioning can be used and this can be used as a pole sensor of a detecting means for controlling an electric motor. The pole sensor in the motor is not needed, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a device including a drive device for an electric motor that realizes an embodiment of a method for detecting a rotation angle of an electric motor according to the present invention.

FIG. 2 is a flow chart for explaining an embodiment of the present invention.

FIG. 3 is a principle view of the present invention.

[Explanation of symbols]

 1 Three-Phase Synchronous Motor 3 PWM Power Converter 5 Three-Phase Distribution Device 7 Position / Speed Control Device 9 Encoder 11 Measuring Device 13 Measurement Processing Device 15 Input Device

[Procedure amendment]

[Submission date] March 5, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

On the contrary, if the magnetic reference of the rotor of the synchronous motor and the origin of the encoder are measured and the angle difference can be corrected by the measured value, the encoder is replaced with a phase detection sensor such as a pole sensor. Rutoieru can be used.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

Therefore, a current is caused to flow from the PWM power conversion unit to each phase of the stator of the three-phase synchronous motor, and a command current vector i _s as shown in FIG. ^* (Current magnitude (= energization value i), angle from U phase is angle θ _S (= energization pattern)) is established. As a result, the rotor of the three-phase synchronous motor 1 is controlled by the command current.
It is sucked in the direction of the vector i _s ^* and stops.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Here, if the load disturbance torque τ applied to the rotor of the three-phase synchronous motor is zero, the rotor is attracted to the command current vector i _s ^* and the rotor angle δ becomes zero. However, in the case of a three-phase synchronous motor applied to an industrial robot or the like, a force such as gravity is applied to the rotor of the three-phase synchronous motor, and as shown in FIG. Since the torque is applied to the rotor as a constant torque τ, the rotor angle has a deviation of δ. That is, in order to balance with this torque τ, the rotor of the three-phase synchronous motor, as shown in FIG. 3 (A), comes to rest at an angle of δ with respect to the direction of the command current vector i _s ^*. . If you balance in such a state,

[Equation 1] Will be established.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

On the other hand, in Expression 1, the angle δ cannot be directly detected. The angle Φ from the actual reference position can be detected by the encoder. This angle Φ is

[Equation 3] Is. Therefore, the following Expression 4 is obtained from Expression 1.

[Equation 4] If you change equation 4 further,

[Equation 5] Becomes Here, Φ and i _s are known, and τ and ψ _S are unknown. Then, ψ _S is calculated from this equation 5.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction content]

In this mathematical formula processing, ψ _S can be obtained by calculating α _a and α _b by the least square method shown in Formula 7 or Formula 8 below.

Claims (1)

[Claims] 1. A position detection sensor capable of detecting the position of a synchronous motor, a position / speed control device for forming a current command from a position detection signal from the position detection sensor and a position command, and a current command and a synchronous motor. A rotation angle measuring method in a control device for an electric motor, comprising: a distribution device that forms a power conversion command signal from rotational position signals of each phase; and a power conversion unit that converts power based on the power command signal from the distribution device. In regard to the current command given to the distributor,
Only the energization value can be changed in a state where the energization pattern applied to the stator of the synchronous motor is fixed, the power conversion unit is driven under at least two energization conditions, and the synchronous motor has a stable position under each energization value. From the position detection signal from the position detection sensor when reaching and the energization value, an angle difference between the magnetic reference of the rotor of the synchronous motor and the reference position of the encoder is obtained. Detection method.