JP2020205716A - Motor control device and offset amount calculation method - Google Patents

Abstract

To calculate the offset amount of an angle sensor with a load connected to a motor.SOLUTION: A motor control device according to an embodiment includes a current instruction unit and an offset amount calculation unit. The current instruction unit controls a three-phase current such that the torque of a three-phase AC motor is reversed on the basis of the current phase of a dq current. The offset amount calculation unit calculates the offset amount included in a rotation angle of the three-phase AC motor detected by an angle sensor on the basis of the current phase of the dq current and the rotation angle. Further, the offset amount calculation unit calculates the offset amount by using the rotation angle that changes on the basis of the margin of a gear connected to the three-phase AC motor.SELECTED DRAWING: Figure 2

Description

The present invention relates to a motor control device and a method for calculating an offset amount.

Conventionally, there is a motor control device that calculates an offset amount of an angle sensor that detects a rotation angle of a motor. Such a motor control device calculates an offset amount based on an induced voltage generated when the motor is rotated from the outside (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 9-56199

However, in the prior art, it is not possible to calculate the offset amount of the angle sensor when the load is connected to the motor.

The present invention has been made in view of the above, and an object of the present invention is to provide a motor control device and an offset amount calculation method capable of calculating an offset amount of an angle sensor in a state where a load is connected to a motor. To do.

In order to solve the above-mentioned problems and achieve the object, the motor control device according to the embodiment includes a current indicator unit and an offset amount calculation unit. The current indicator controls the three-phase current so that the torque of the three-phase AC motor is reversed based on the current phase of the dq current. The offset amount calculation unit includes an offset included in the rotation angle based on the current phase of the dq current controlled by the current indicator unit and the rotation angle of the three-phase AC motor detected by the angle sensor. Calculate the amount. Further, the offset amount calculation unit calculates the offset amount by using the rotation angle that changes based on the play of the gear connected to the three-phase AC motor.

According to the present invention, the offset amount of the angle sensor can be calculated with the load connected to the motor.

FIG. 1A is a diagram showing an outline of a motor system. FIG. 1B is a schematic view showing the play of gears. FIG. 2 is a block diagram of the control device. FIG. 3 is a diagram (No. 1) showing the relationship between the current phase and the sensor value. FIG. 4 is a diagram (No. 2) showing the relationship between the current phase and the sensor value. FIG. 5 is a diagram showing the relationship between the offset amount and the dq current. FIG. 6 is a flowchart (No. 1) showing a processing procedure executed by the motor control device. FIG. 7 is a flowchart (No. 2) showing a processing procedure executed by the motor control device.

Hereinafter, the motor control device and the offset amount calculation method according to the embodiment will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

First, the outline of the motor control device and the offset amount calculation method according to the embodiment will be described with reference to FIG. 1A. FIG. 1A is a diagram showing an outline of a motor control system. The motor system 100 shown in FIG. 1A includes a motor control device 1, a motor 2, an angle sensor 3, and an inverter 4.

The motor 2 is, for example, a surface magnet type (SPM: Surface Permanent Magnet) synchronous motor in which a permanent magnet is attached to the rotor surface, and is connected to, for example, a load 5. The angle sensor 3 is provided on the motor 2 and detects an angle position indicating how much the motor 2 has rotated from the reference position.

The motor control device 1 controls the motor 2 by current vector control. The motor control device 1 controls the motor 2 by performing current control in the dq coordinate system and outputting the voltage converted into the three-phase coordinate system to the motor 2 via the inverter 4.

Further, the motor control device 1 controls the motor 2 based on the rotation angle of the motor 2 detected by the angle sensor 3. Here, for example, the installation position of the angle sensor 3 may deviate from the reference position due to an mounting error of the angle sensor 3. In this case, the amount of offset corresponding to the amount of deviation of the installation position of the angle sensor 3 may be included in the detection result of the angle sensor 3 (hereinafter, referred to as a sensor value).

Therefore, in general, the correction process for correcting the sensor value of the angle sensor is performed by calculating the offset amount included in the sensor value of the angle sensor in advance. As a method for calculating the offset amount, there is a technique for calculating the offset amount based on the induced voltage generated when the motor is rotated from the outside.

However, in such a technique, the offset amount cannot be calculated in the situation where the load is connected to the angle sensor. Therefore, when the motor is installed, the offset amount must be calculated when the load is not connected to the motor, which limits the manufacturing process.

Therefore, the motor control device 1 according to the embodiment makes it possible to calculate the offset amount even when the load 5 is connected to the motor 2. Specifically, in the motor control device 1 according to the embodiment, the offset amount is calculated by paying attention to the play of the gear connected to the motor, so-called backlash.

FIG. 1B is a schematic view showing the play of gears. In FIG. 1B, it is assumed that the motor 2 is connected to either the first gear G1 or the second gear G2, and the load 5 is connected to the other.

As shown in FIG. 1B, play A refers to a gap between the teeth of the first gear G1 and the teeth of the second gear G2. That is, in the motor control device 1 according to the embodiment, the offset amount is calculated by paying attention to the point that the motor 2 rotates in a no-load state by the amount of play A even when the load 5 is connected to the motor 2. It was decided to.

As a result, in the motor control device 1 according to the embodiment, even if the load 5 is connected to the motor 2, the offset amount can be calculated in the same situation as when the load 5 is not connected. It becomes. A specific example of the method for calculating the offset amount will be described with reference to the drawings in FIGS. 3A and after.

Next, a configuration example of the motor control device 1 according to the embodiment will be described with reference to FIG. FIG. 2 is a block diagram of the motor control device 1. In addition, in FIG. 2, the motor system 100 is also shown.

As shown in FIG. 2, the motor control device 1 is a microcomputer provided with a CPU (Central Processing Unit), a storage unit (not shown), and the like, and controls the entire motor system 100.

The motor control device 1 includes a current indicator unit 10, a current control unit 20, and an offset amount calculation unit 30.

The CPU of the motor control device 1 functions as a current indicator unit 10, a current control unit 20, and an offset amount calculation unit 30 by reading and executing a program stored in the ROM, for example.

Further, at least one or all of the current indicator unit 10, the current control unit 20, and the offset amount calculation unit 30 may be configured by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). it can.

The current indicator 10 determines the current value of each phase current to be energized to the motor 2 via the inverter 4, and notifies the current control unit 20 of the command information based on the current value. This command information includes information on the current phase, information on the magnitude of the current, and the like.

By the way, as described above, the motor control device 1 has a "calculation mode" for calculating the offset amount. This calculation mode is, for example, a mode performed before the product is shipped, such as in the manufacturing stage.

In the calculation mode, the current indicating unit 10 notifies the current control unit 20 of command information for calculating the offset amount included in the sensor value of the angle sensor 3. In the present embodiment, in the calculation mode, the current indicator 10 controls the three-phase current so that the torque of the motor 2 is reversed based on the current phase of the dq current.

Further, in the calculation mode, the current indicator 10 sets an initial value of each phase current based on the current sensor value of the angle sensor 3, and gradually causes a current in one direction (positive direction or negative direction) from the initial value. By changing the phase, the torque of the motor 2 is reversed.

At this time, the current indicator 10 can monitor the sensor value of the angle sensor 3 and determine whether or not the torque is reversed based on the sensor value. Then, the current indicator 10 updates the current phase when the sensor value does not change, that is, when the torque does not reverse, and offsets the information regarding the current phase when the sensor value changes. Notify the calculation unit 30.

The current control unit 20 generates a PWM signal based on the command information notified from the current instruction unit 10 and outputs the PWM signal to the inverter 4. As a result, the three-phase current corresponding to the command information is energized from the inverter 4 to the motor 2. Further, the current control unit 20 feeds back the value of the three-phase current flowing through the motor 2 to correct the deviation between the current phase based on the command information and the actual current phase of each phase current and the deviation of the magnitude of the current. Control.

The offset amount calculation unit 30 calculates the offset amount included in the rotation angle (sensor value) based on the current phase of the dq current and the rotation angle (sensor value) of the motor 2 detected by the angle sensor 3. To do. In the present embodiment, the offset amount calculation unit 30 calculates the offset amount based on the rotation angle that changes based on the play A of the gear connected to the motor 2 when the torque of the motor 2 is reversed.

3 and 4 are diagrams showing the relationship between the current phase and the sensor value. Note that A in FIG. 3 and A in FIG. 4 show the current phase of the dq current, and B in FIG. 3 and B in FIG. 4 show the sensor value of the angle sensor 3, respectively. Further, here, the case where the offset amount is small to some extent (the current phase is in the range of −30 ° to 30 °) will be described.

As shown in FIG. 3, when the current phase is gradually increased from −30 °, if the offset amount is “0”, that is, if the sensor value of the angle sensor 3 does not include the offset amount, the current phase At time t1 when becomes "0 °", the torque of the motor 2 reverses from the negative torque to the positive torque.

On the other hand, when the offset amount is other than "0", as shown in FIG. 3, the current phase is other than "0 °" and the sensor value changes in the positive direction.

The offset amount calculation unit 30 calculates the first offset amount θ1 on the positive torque side based on the current phase when the sensor value changes in the positive direction. In the example shown in FIG. 3, it is shown that the current phase when the sensor value changes in the positive direction deviates from 0 ° by θ1. Therefore, the deviation between the installation position of the angle sensor 3 and the reference position is “θ1-0 °”, which is the first offset amount θ1.

Further, as shown in FIG. 4, the current indicating unit 10 changes the current phase so that the torque of the motor 2 reverses from the positive torque to the negative torque, and the offset amount calculating unit 30 changes the sensor value to negative. It is also possible to calculate the second offset amount θ2 based on the value of the current phase at the time.

In this way, the motor control device 1 changes the current phase of the dq current until the torque is reversed, and calculates the offset amount based on the current phase when the sensor value changes. Further, in the motor control device 1, by paying attention to the play A shown in FIG. 1B, it is possible to calculate the offset amount in the state where the load 5 is connected to the motor 2.

In the above example, the case where the current phase is changed in the range of −30 ° to + 30 ° has been described, but the present invention is not limited to this. That is, the initial value of the current phase and the range in which the current phase is changed may be arbitrarily changed.

Further, since the offset amount can be calculated when the torque is reversed, the "calculation mode" may be terminated when the torque is reversed.

By the way, the motor control device 1 can also determine the final offset amount based on the first offset amount θ1 and the second offset amount θ2 shown in FIGS. 3 and 4, respectively. Specifically, for example, the offset amount calculation unit 30 calculates the average value of the first offset amount θ1 and the second offset amount θ2 as the final offset amount θ.

That is, in the motor control device 1 according to the embodiment, the final offset amount θ is calculated based on both offset amounts when the negative torque is reversed to the positive torque and the positive torque is reversed to the negative torque.

As a result, in the motor control device 1 according to the embodiment, it is possible to improve the calculation accuracy of the offset amount θ. FIG. 5 is a schematic diagram showing the relationship between the offset amount and the dq current. As shown in FIG. 5, the d-axis and the q-axis before correction are offset by an offset amount θ from the true d-axis and the true q-axis, which are the true d-axis and the true q-axis.

Therefore, the motor control device 1 can obtain the true d-axis and the true q-axis by rotating the d-axis and the q-axis by the offset amount θ.

Next, the processing procedure executed by the motor control device 1 according to the embodiment will be described with reference to FIGS. 6 and 7. 6 and 7 are flowcharts showing a processing procedure executed by the motor control device 1. FIG. 6 shows a procedure for calculating the first offset amount θ1 or the second offset amount θ2.

First, as shown in FIG. 6, when the motor control device 1 first acquires the sensor value of the angle sensor 3 (step S101), the motor control device 1 sets the initial value of the current phase based on the sensor value (step S102).

Subsequently, the motor control device 1 energizes the motor 2 at such an initial value (step S103), and then determines whether or not the sensor value of the angle sensor 3 has changed in a predetermined direction (step S104).

In the determination process of step S104, when the sensor value has not changed in a predetermined direction (step S104, No), the motor control device 1 updates the current phase (step S105) and shifts to the process of step S103. ..

On the other hand, in the determination process of step S104, when the sensor value changes in a predetermined direction (step S104, Yes), the motor control device 1 acquires the value of the current phase when the sensor value changes (step S106). The offset amount (first offset amount θ1 or second offset amount θ2) is calculated based on the value of the current phase (step S107), and the process ends.

Subsequently, with reference to FIG. 7, a processing procedure for determining the final offset amount θ based on the first offset amount θ1 and the second offset amount θ2 will be described. As shown in FIG. 7, the motor control device 1 calculates the first offset amount θ1 and the second offset amount θ2, respectively, by the processing procedure as shown in FIG. 6 (step S111).

Subsequently, the motor control device 1 determines the final offset amount θ based on the first offset amount θ1 and the second offset amount θ2 (step S112), and ends the process.

As described above, the motor control device 1 according to the embodiment includes a current indicating unit 10 and an offset amount calculating unit 30. The current indicator 10 controls the three-phase current so that the torque of the motor 2 (corresponding to the three-phase AC motor) is reversed based on the current phase of the dq current. The offset amount calculation unit 30 calculates the offset amount included in the rotation angle based on the current phase of the dq current and the rotation angle of the three-phase AC motor detected by the angle sensor 3.

Further, the offset amount calculation unit 30 calculates the offset amount by using the rotation angle that changes based on the play of the gear connected to the three-phase AC motor. Therefore, according to the motor control device 1 according to the embodiment, the offset amount of the angle sensor 3 can be calculated in a state where the load 5 is connected to the motor 2.

Further effects and variations can be easily derived by those skilled in the art. For this reason, the broader aspects of the invention are not limited to the particular details and representative embodiments expressed and described as described above. Further, the gear is not limited to the gear according to the present embodiment, and can be applied to, for example, slack of a belt. Therefore, various modifications can be made without departing from the spirit or scope of the general concept of the invention as defined by the appended claims and their equivalents.

1 Motor control device 2 Motor 3 Angle sensor 4 Inverter 5 Load 10 Current indicator 20 Current control 30 Offset amount calculation 100 Motor system A Play

Claims (4)

A current indicator that controls the three-phase current so that the torque of the three-phase AC motor is reversed based on the current phase of the dq current, and
An offset amount that calculates the offset amount included in the rotation angle based on the current phase of the dq current controlled by the current indicator and the rotation angle of the three-phase AC motor detected by the angle sensor. Equipped with a calculation unit
The offset amount calculation unit
A motor control device, characterized in that the offset amount is calculated by using the rotation angle that changes based on the play of a gear connected to the three-phase AC motor. The offset amount calculation unit
The motor control device according to claim 1, wherein the difference between the rotation angle that changes based on the play of the gear and the rotation angle indicated by the current phase is calculated as the offset amount. The current indicator
The three-phase current is controlled so that the torque is reversed in the forward direction and the reverse direction, respectively.
The offset amount calculation unit
The motor control device according to claim 1 or 2, wherein the final offset amount is determined based on the offset amount in each of the forward direction and the reverse direction. A current instruction process that controls the three-phase current so that the torque of the three-phase AC motor is reversed based on the current phase of the dq current, and
An offset amount that calculates the offset amount included in the rotation angle based on the current phase of the dq current controlled by the current instruction step and the rotation angle of the three-phase AC motor detected by the angle sensor. Including the calculation process
The offset amount calculation step is
A method for calculating an offset amount, which comprises calculating the offset amount by using the rotation angle that changes based on the play of a gear connected to the three-phase AC motor.

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