WO2020027350A1 - Commutation method and calibration method for absolute encoder-based bldc motor, and controlling system of bldc motor - Google Patents

Abstract

Provided is a method for commutating, on the basis of an absolute encoder, a BLDC (Brushless DC) motor having a stator and a rotor. Here, the absolute encoder is constructed to rotate dependently on rotation of the rotor, and the method comprises the steps of: obtaining the output value of the absolute encoder; determining the location of the rotor of the BLDC motor on the basis of the output value of the absolute encoder; and applying a control signal to the BLDC motor on the basis of the determined location of the rotor. Thus, since a Hall sensor is not included, minimization and weight reduction is possible and a thorough control of the rotation in a stationary state and a control in a low speed and low torque is also possible.

Description

Rectification method, calibration method and BLDC motor control system of BLDC motor based on absolute encoder

The present invention relates to a brushless DC (BLDC) motor, and more particularly to a method and system for controlling a BLDC motor based on an absolute encoder.

In the conventional DC motor, a rotor including a coil rotates in a relationship with a stator including a magnet, but commutates the motor using a plurality of brushes contacting the rotor. That is, the current supplied to each of the plurality of terminals of the rotor was controlled based on the contact between the brush and the commutator. Therefore, the operation of the DC motor is accompanied by repeated contact between the brush and the commutator generates heat and wear problems due to friction, and has the disadvantage of noise generation and durability degradation.

In order to solve this drawback, the BLDC motor eliminates mechanical friction loss by eliminating the brush and the commutator. The BLDC motor converts the mechanical switching of the brush and commutator included in the conventional DC motor into electronic switching using a semiconductor device. it means. BLDC motors are used for speed control and torque control, are easy to miniaturize, and have strong durability.

In general, a BLDC motor is composed of a plurality of phases such as, for example, three phases of U, V, and W, and may be driven by sequentially applying different voltages to terminals corresponding to each phase. However, since the BLDC motor does not have a brush and a commutator, another means for sensing the relative rotational position of the rotor with respect to the stator is required to determine the current that can be supplied to each terminal of each phase.

Traditional BLDC motors have detected the position of the rotor by having a plurality of Hall sensors that detect a magnetic field between the terminals of each phase. Since then, there has been a discussion of a method of determining the position of the rotor by detecting a back electromotive force (BEMF) according to the rotation of the rotor without the hall sensor in terms of miniaturization and circuit simplification.

In certain industries, such as robots, there is a demand for miniaturization and lightening of BLDC motors, and considering the problem of deteriorating the accuracy of the hall sensor in a high temperature or high pressure working environment, it is not necessary to apply the hall sensor to the stator. It is advantageous to determine the relative position of the former. On the other hand, the mechanism for the control of the sensorless BLDC motor based on the counter electromotive force according to the rotation of the conventional rotor, the position of the rotor can not be determined while the motor is stopped, the rotor is a certain speed depending on the driving of the motor The position of the rotor could be determined only after the measurement of counter electromotive force was made by rotating with.

However, in the robot field, for example, it is necessary to control the joint to rotate at a predetermined angle according to the user's request in the stationary state, and further, the required driving speed is low or the required torque is low, so Since the detection may not be easy, there is a problem that the conventional sensorless BLDC motor control mechanism cannot be applied.

One object of the present invention for solving the above problems is a relative position to the stator of the rotor based on the output value of the absolute encoder, which rotates depending on the rotor of the BLDC motor and is widely used for detecting the rotation angle of the motor shaft. Rectification and calibration of BLDC motors based on absolute value encoders, without the Hall sensor, which makes it possible to miniaturize and reduce the weight, while allowing precise rotation control at standstill and control at low speed or low torque. To provide a way.

Another object of the present invention for solving the above problems is a relative position of the rotor relative to the stator based on the output value of the absolute encoder which rotates depending on the rotor of the BLDC motor and is widely used for detecting the rotation angle of the motor shaft. It is possible to provide a BLDC motor control system based on an absolute encoder that can be miniaturized and lightened by not having a Hall sensor, but also capable of precise rotation control at standstill and control at low speed or low torque. It is.

However, the problem to be solved of the present invention is not limited thereto, and may be variously extended within a range without departing from the spirit and scope of the present invention.

In order to achieve the above object, a rectification method of a BLDC motor includes an absolute encoder (BDC) that includes a brushless DC (BLDC) motor including a stator and a rotor. A method of commutation based on said absolute value encoder, said absolute value encoder is configured to rotate in dependence of said rotation of said rotor, said method comprising the steps of: (a) obtaining an output value of an absolute value encoder; (B) determining a position of the rotor of the BLDC motor based on the output value of the absolute encoder; And (c) applying a control signal to the BLDC motor based on the determined position of the rotor.

According to one aspect, the step (b) of determining the position of the rotor, based on the pre-stored calibration data to determine the position of the rotor according to the output value of the absolute encoder, the calibration data, the absolute value The encoder may include information about a plurality of output values of the encoder and rotor positions corresponding to the plurality of output values, respectively.

According to one aspect, the calibration data, (d) setting the BLDC motor to the calibration mode; (E) determining a position of the rotor based on a back electromotive force (BEMF) generated by the rotation of the rotor; (F) obtaining an output value of an absolute value encoder at the time of determining the position of the rotor based on the counter electromotive force; And (g) storing information on the position of the rotor determined based on the counter electromotive force and the obtained absolute value encoder output value as at least part of the calibration data, before setting the driving mode of the BLDC motor. It may have been.

According to an aspect, the step (e) of determining the position of the rotor based on the counter electromotive force may determine the position of the rotor based on a zero crossing point (ZCP) of the counter electromotive force.

According to an aspect, the zero crossing point of the counter electromotive force is obtained for each of a plurality of phases constituting the stator of the BLDC motor, and the step (e) of determining the position of the rotor based on the counter electromotive force is The reference positions of the rotor may be determined based on a combination of zero crossing points of the respective phases.

According to an aspect, the storing step (g) further determines n detailed positions having a uniform spacing between the reference positions, and determines an absolute value encoder corresponding to the reference positions and the reference positions, respectively. Output values and output values of the absolute value encoder corresponding to the detailed positions and the detailed positions may be stored as at least a part of the calibration data.

According to an aspect, the control signal may control the BLDC motor to compensate for torque ripple according to the operation of the BLDC motor based on the reference position and the detailed position information.

According to an aspect, steps (a) to (c) may be performed in a driving mode of the BLDC motor, and the BLDC motor may be controlled to rotate the rotor at a lower speed in the driving mode than in the calibration mode. have.

According to an aspect, the steps (a) to (c) may be performed in the driving mode of the BLDC motor, and the BLDC motor may be controlled to rotate in the driving mode by the required angle from the stopped state without idling. have.

According to one aspect, the control signal is a commutation signal, and may be configured to transmit different electrical signals to each of the plurality of phases constituting the stator of the BLDC motor.

According to an aspect, the electrical signal may include at least one of a current signal and a voltage signal.

According to an aspect, the absolute encoder may be an absolute encoder provided for at least one of rotational position control and speed control of a device driven by the BLDC motor.

According to one aspect, the rotation of the rotor of the BLDC motor in the calibration mode may be performed based on the power transmitted from the outside of the BLDC motor.

The BLDC motor control system according to another embodiment of the present invention is a BLDC motor control system for commutating a BLDC (Brushless DC) motor based on an absolute encoder, including a stator and a rotor. BLDC motor including (Rotor); An absolute encoder configured to rotate in dependence of the rotation of the rotor; A positioning unit determining a position of the rotor of the BLDC motor based on an output value of the absolute encoder received from the absolute encoder; And a controller configured to apply a control signal to the BLDC motor based on the determined position of the rotor.

According to an aspect of the present disclosure, the apparatus may further include a storage unit configured to store calibration data including a plurality of output values of the absolute encoder and information about rotor positions corresponding to the plurality of output values, respectively, wherein the position determiner includes: The position of the rotor according to the output value of the absolute value encoder may be determined based on the calibration data previously stored in the storage unit.

According to an aspect, the calibration data may include: setting the BLDC motor to a calibration mode; Determine a position of the rotor based on a Back Electromotive Force (BEMF) generated as the rotor rotates; Acquiring an output value of an absolute value encoder at the time of determining the position of the rotor based on the counter electromotive force; And storing the information on the position of the rotor determined based on the counter electromotive force and the output value of the obtained absolute value encoder as at least a part of the calibration data to be previously generated before setting the driving mode of the BLDC motor. It may be stored in.

In example embodiments, the storage unit may be a nonvolatile memory.

According to another embodiment of the present invention, a method for calibrating a BLDC motor based on an absolute encoder may include a brushless DC (BLDC) motor including a stator and a rotor. The absolute value encoder is configured to rotate in dependence of the rotation of the rotor, the method comprising: setting the BLDC motor to a calibration mode; Determining a position of the rotor based on a back electromotive force (BEMF) generated by the rotation of the rotor; Acquiring an output value of an absolute value encoder at the time of determining the position of the rotor based on the counter electromotive force; And storing the information on the position of the rotor determined based on the counter electromotive force and the output value of the obtained absolute value encoder as at least part of the calibration data.

A computer readable storage medium according to another embodiment of the present invention is a computer readable storage medium including processor executable instructions, wherein the instructions include a brushless DC (BLDC) including a stator and a rotor. Instructions for commutating the motor based on an absolute encoder, wherein the absolute encoder is configured to rotate in dependence of the rotation of the rotor, and when the instructions are executed by the processor, Obtain an output value of the absolute encoder; Determine a position of the rotor of the BLDC motor based on the output value of the absolute encoder; And it may be configured to apply a control signal to the BLDC motor based on the determined position of the rotor.

A computer readable storage medium according to another embodiment of the present invention is a computer readable storage medium including processor executable instructions, wherein the instructions include a brushless DC (BLDC) including a stator and a rotor. Instructions for calibrating a motor based on an absolute encoder, wherein the absolute encoder is configured to rotate in dependence of the rotation of the rotor, and when the instructions are executed by the processor, the BLDC motor Set to calibration mode; Determine a position of the rotor based on a Back Electromotive Force (BEMF) generated as the rotor rotates; Acquiring an output value of an absolute value encoder at the time of determining the position of the rotor based on the counter electromotive force; And store the information about the position of the rotor determined based on the counter electromotive force and the output value of the obtained absolute value encoder as at least part of the calibration data.

The published technology may have the following effects. However, since a specific embodiment does not mean to include all of the following effects or only the following effects, it should not be understood that the scope of the disclosed technology is limited by this.

According to the method and control system for rectifying and calibrating a BLDC motor based on the absolute encoder according to the embodiment of the present invention described above, the rotor is based on the output value of the absolute encoder rotating in dependence on the rotor of the BLDC motor. By determining the relative position with respect to the stator of the, it is possible to rectify the BLDC motor without a Hall sensor, and to control the position or speed of the device driven by the BLDC motor without a separate encoder for rectification The absolute encoder provided can be used for rectifying the BLDC motor as it is. Therefore, there is an advantage that the size and weight of the BLDC motor can be reduced.

In addition, in the driving mode of the BLDC motor, the position of the rotor can be determined based on the output value of the absolute encoder without detecting the counter electromotive force, so that precise rotation control is possible according to the user's request even when the BLDC motor is stopped. It is possible to control the drive of a BLDC motor at low speed or low torque, which is not easy to measure counter electromotive force.

Furthermore, by using a high resolution absolute encoder, the position of the rotor can be determined in more detail than conventional Hall sensor based control or counter electromotive force based control, and the BLDC motor can be more precisely based on the detailed position of the rotor. It is advantageous to control.

1 shows a configuration of a Hall sensor based BLDC motor.

FIG. 2 illustrates state and applied voltage control according to Hall sensor values of the Hall sensor-based BLDC motor of FIG. 1.

3 shows a configuration of a sensorless BLDC motor.

4 illustrates a zero crossing point of counter electromotive force of the sensorless BLDC motor of FIG.

5A illustrates a configuration of a BLDC motor according to an embodiment of the present invention.

5B illustrates an absolute value encoder of a BLDC motor according to an embodiment of the present invention.

FIG. 6 illustrates a configuration of a BLDC motor control system based on an absolute encoder according to an embodiment of the present invention.

7 illustrates a comparison of an encoder value and a hall sensor value respectively corresponding to a plurality of states of a BLDC motor.

8 is a flowchart illustrating a procedure of absolute encoder based BLDC motor control according to an embodiment of the present invention.

9 is a flowchart of a method of rectifying a BLDC motor based on an absolute encoder according to an embodiment of the present invention.

10 is a flowchart illustrating a calibration method of a BLDC motor based on an absolute encoder according to an embodiment of the present invention.

11 is a conceptual diagram of zero crossing point detection of counter electromotive force.

12 is a conceptual diagram of a BLDC motor calibration according to an embodiment of the present invention.

FIG. 13 illustrates an example of executing an application for calibration of FIG. 12.

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description.

However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is said to be "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that another component may be present in the middle. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present disclosure does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. In the following description of the present invention, the same reference numerals are used for the same elements in the drawings and redundant descriptions of the same elements will be omitted.

Hall sensor based BLDC motor control

FIG. 1 illustrates a configuration of a Hall sensor-based BLDC motor, and FIG. 2 illustrates control of states and applied voltages according to Hall sensor values of the Hall sensor-based BLDC motor of FIG. 1. As shown in Figs. 1 and 2, the Hall sensor based BLDC motor detected the position of the rotor by having a plurality of Hall sensors detecting a magnetic field between the terminals of each phase. More specifically, referring to FIG. 1, a Hall sensor-based BLDC motor includes, for example, a stator having three phases of U, V, and W, and a magnetic field disposed at a predetermined distance from the stator and generated in the stator. It includes a rotor that rotates based on. The rotor may consist of a permanent magnet, the U phase of the stator comprising a U ₁ coil and a U ₂ coil connected to each other, the V phase comprising a V ₁ coil and a V ₂ coil connected to each other, and the W phase connected to each other _{It includes 1} coil and W ₂ coils. Thus, the BLDC motor can be divided into six zones separated by terminals of each coil, and can be classified into six states according to the relative position of the rotor to the stator. To allow the rotor to rotate by being pushed or pulled by a particular coil of the stator in response to the application of positive and negative voltages to specific ones of the terminals respectively corresponding to the coils of each phase of the stator. It is composed.

Here, three Hall sensors H _U , H _V , H _W are arranged to detect different magnetic fields depending on the position of the rotor. Hall sensors may output a value of 1 or 0, respectively, upon detection or no detection of a magnetic field, and by combination of the output values of each of the three Hall sensors, the relative position of the current rotor relative to the stator may be detected. . As shown on the right side of FIG. 1, the three Hall sensors H _U , H _V , H _W are repeated with different values of O or 1 as the rotor rotates. As shown in FIG. 2, while the state according to the position of the rotor relative to the stator changes while repeating the first to sixth states according to the rotation of the rotor, the H _U Hall sensor (Hall) U), H _V Hall sensor (Hall V), H _W Hall sensor (Hall W) value is changed, the combination of the values of the three Hall sensors (H _U , H _V , H _W ) match each state (Eg, 001 in a first state, 011 in a second state, 010 in a third state, 110 in a fourth state, 100 in a fifth state, 101 in a sixth state). In other words, while the rotor rotates once, the combination of Hall sensor values may be configured to have six different values corresponding to six regions.

The three phases included in the motor are not active at the same time, and depending on the position of the rotor, the controller can only activate two phases at a time. Therefore, the position of the rotor is required for the proper activation sequence of the motor, and the process of switching the voltage applied to each phase can be referred to as commutation. That is, the position of the rotor is used for commutation. Therefore, in the Hall sensor-based BLDC motor, the position of the rotor can be determined according to the acquisition of the Hall sensor value, and respective phases of U, V, and W as shown in the lower portion of FIG. 2 according to the position of the rotor. The rotation of the rotor can be controlled by controlling the voltage applied to the.

However, as BLDC motors are being applied to various industrial fields, there is a need for miniaturization and light weight of BLDC motors. Furthermore, adding Hall sensors not only increases the cost for the fabrication of BLDC motors, but it is also not easy to correctly position the Hall sensors, which can result in errors for positions typically up to about 10%. In addition, when the BLDC motor is used in a harsh environment such as high temperature or high pressure, or when the BLDC motor is driven for a long time, the hall sensor may be easily damaged, which may result in an increase in the error rate. In addition, since the combination of output values by the Hall sensor has a low resolution (only six steps for each cycle), it is difficult to perform sinusoidal commutation or torque ripple compensation.

Sensorless BLDC Motor Control

3 shows the configuration of the sensorless BLDC motor, and FIG. 4 shows the zero crossing point of the counter electromotive force of the sensorless BLDC motor of FIG. In order to solve the above-mentioned problems of Hall sensor-based control, a sensorless BLDC motor control which does not include a hall sensor and determines the position of the rotor by detecting back electromotive force (BEMF) according to the rotation of the rotor is provided. It is possible.

When the rotor rotates while changing its relative position with the stator, a specific voltage called back electromotive force is generated in the stator. By monitoring this counter electromotive force and detecting the zero crossing point (ZCP) of the counter electromotive force generated for each of the plurality of phases constituting the stator, the controller can determine the relative position of the rotor with respect to the stator. Can be determined. As shown in FIG. 3, the detection and control circuit 310 can be connected to the corresponding terminals of each phase A, B, C of the BLDC motor 330 and the neutral point N of each phase. . Therefore, as shown in FIG. 4, the counter electromotive force generated in each phase of the stator according to the rotation of the rotor can be monitored, and a point at which the counter electromotive force for each phase becomes zero can be detected as a zero crossing point. . Using the combination of the plurality of zero crossing points, the detection and control circuit 310 may determine a state according to the relative position of the rotor, and the BLDC motor 330 based on the determined state according to the position of the stator. The inverter unit 320 may be controlled so that an appropriate voltage may be applied to terminals of the respective phases.

The main advantage of this counter electromotive force based sensorless BLDC motor control method is the simplicity of hardware configuration. In addition, in certain industrial fields such as robots, there is a demand for miniaturization and lightening of the BLDC motor, and considering the problem of deteriorating the accuracy of the hall sensor in a high temperature or high pressure working environment, the hall sensor is not applied to the stator. It is advantageous to determine the relative position of the rotor relative to.

However, since the counter electromotive force is generated only while the rotor is rotating along the stator, it is difficult to start driving in the stationary state. That is, the sensorless BLDC motor control method based on counter electromotive force cannot determine the position of the rotor when the motor is stopped, and only after the rotor is rotated at a certain speed according to the driving of the motor to measure the counter electromotive force. The position of the former can be determined. Therefore, smooth and accurate drive initiation is impossible. In addition, the counter electromotive force can be monitored only when the rotational speed of the motor reaches a certain value.

However, in the field of robots, for example, it is necessary to control the joint to rotate at an angle according to the user's request in the stationary state, and slow motion tends to be required more frequently than high speed motion. Therefore, since the required driving speed is low or the required torque is low, it may not be easy to detect the counter electromotive force due to the rotation of the rotor. Therefore, the counter electromotive force-based sensorless BLDC motor control mechanism is difficult to be applied in the robot field.

BLDC motor control system based on absolute encoder

The absolute value encoder based BLDC motor control according to an embodiment of the present invention is to solve the above-described problems of the conventional BLDC motor control, and is based on the output value of the absolute value encoder that rotates depending on the rotor of the BLDC motor. It is possible to determine the relative position of the rotor with respect to the stator. Therefore, it is possible to miniaturize and reduce the weight by not providing a hall sensor, but at the same time, it is possible to control precise rotation in a stationary state and control at low speed or low torque.

5A illustrates a configuration of a BLDC motor according to an embodiment of the present invention, and FIG. 5B illustrates an absolute value encoder of a BLDC motor according to an embodiment of the present invention. As shown in FIG. 5A, a BLDC motor according to an embodiment of the present invention may include a stator 10 and a rotor 20 that rotates while changing a relative position in relation to the stator 10. The rotor 20 may be connected to an absolute encoder 30 which rotates in dependence on the rotation of the rotor 20. Here, according to one aspect, the BLDC motor may be a three-phase motor and does not have a hall sensor. The absolute value encoder 30 may be used, for example, a high resolution absolute value encoder having a resolution of 16 bits, so that when the rotor 20 rotates one turn, the absolute value encoder 30 subordinate to the absolute value encoder is 0 to 65535. You can print the value. In place of the hall sensor, the output of the absolute encoder 30 can be used to determine the position of the rotor 20.

The absolute encoder may be, for example, one of an optical encoder and a magnetic encoder, but is not limited thereto. Any one of an absolute encoder capable of outputting a rotation position may be used. For example, when an optical encoder is used, as shown in FIG. 5B, the absolute encoder 30a forms different slits for each rotation angle of the disc so that the position according to the rotation of the absolute encoder can be accurately determined. Can be. For example, by checking the pattern of the slit through a detector such as a laser provided at a fixed position, the absolute value encoder can output a value that accurately indicates the rotational position. BLDC motor control based on an absolute encoder according to an embodiment of the present invention, the output value of the absolute encoder configured to rotate in accordance with the rotation of the rotor (for example, share the same axis of rotation with the rotor) It is possible to detect the relative position of the rotor with respect to the stator on the basis, it is possible to control the commutation (through this).

According to one aspect, it is possible to add an absolute encoder to the BLDC motor to control the precise rotational position of the device driven by the BLDC motor. In this case, the BLDC motor control based on the absolute encoder according to the embodiment of the present invention does not use a Hall sensor without adding an additional hardware configuration, and does not require back electromotive force detection in a driving mode. Motor commutation is possible.

To determine the relative position of the rotor with respect to the stator based on the output of the absolute encoder, the position of the rotor and its corresponding absolute in advance, through at least one calibration mode operation before the BLDC motor operates in drive mode. It is required to obtain calibration information that corresponds to the output value of the value encoder. According to an embodiment, obtaining the motor calibration information may be a procedure of recording the output values of the absolute encoder corresponding to the measured values of the hall sensors. 7 illustrates a comparison of an encoder value and a hall sensor value respectively corresponding to a plurality of states of a BLDC motor. As shown in FIG. 7, a BLDC motor having three phases of U, V, and W can be divided into six regions according to the position of the stator of the rotor. Each area has a hall sensor output value (710-1, 710-2, 710-3, 710-4, 710-5, 710-6). In the case of a BLDC motor without a Hall sensor according to an exemplary embodiment of the present invention, when the rotor is positioned at a position having respective Hall sensor output values, the output values 720-1 and 720- of corresponding absolute value encoders are used. 2, 720-3, 720-4, 720-5, and 720-6 may be matched and stored as calibration data, which may be obtained by measuring a zero crossing point of counter electromotive force in the calibration mode.

Therefore, when performing the absolute encoder-based BLDC motor control according to an embodiment of the present invention, there is no Hall sensor, it is possible to simplify the system and to reduce the error rate and reduce the cost. As noted above, the absolute encoder has the advantage that it can be used in parallel for the purpose of commutation as well as the position control (main purpose) of the device using the BLDC motor. In addition, absolute encoders can provide positional information with much higher resolution than Hall sensors, such as, for example, 16 bits, allowing sinusoidal commutation and torque ripple compensation. It is possible to control the BLDC motor while applying.

FIG. 6 illustrates a configuration of a BLDC motor control system based on an absolute encoder according to an embodiment of the present invention. As shown in FIG. 6, a BLDC motor control system based on an absolute encoder according to an embodiment of the present invention includes a power supply unit 610, an inverter unit 620, a BLDC motor 630, and an absolute encoder ( 640, a location determiner 650, a storage 660, and a controller 670.

The power supply unit 610 is a configuration for supplying power to the BLDC motor 630 and may supply operating power of the BLDC motor 630 as a voltage and a current. The inverter unit 620 receives the DC power from the power supply unit 610 and, according to the control of the control unit 670, a positive voltage or a negative voltage to a specific terminal among the three phase terminals included in the BLDC motor 630. Can be configured to be applied. As described above, the BLDC motor 630 may include three phases of U, V, and W, and each phase is configured to apply a voltage from the inverter unit 620. The absolute value encoder 640 may be configured to output a value indicating an accurate rotation position by using a disk configured to rotate in dependence on the rotation of the rotor included in the BLDC motor 630 and a sensor detecting the rotation position of the disk. Can be. The storage unit 660 may store information on the output value of the absolute encoder corresponding to the position of the rotor of the BLDC motor as calibration data, and the positioning unit 650 may determine the BLDC motor based on the output value of the absolute encoder. The relative position of the rotor of the rotor with respect to the stator can be determined. Based on the determined position of the rotor, the controller 670 determines the terminal of each phase of the BLDC motor 630 to which the inverter unit 620 will apply a positive voltage and a negative voltage, respectively, to apply an appropriate voltage. A control signal for enabling the signal may be applied to the inverter unit 620.

More specifically, a BLDC motor control system for commutating a brushless DC (BLDC) motor based on an absolute encoder according to an embodiment of the present invention includes a stator and a rotor ( A BLDC motor 630 including a rotor, and an absolute encoder 640 configured to rotate depending on the rotation of the rotor, and then received by the positioning unit 650 from the absolute encoder 640. The relative position of the rotor of the BLDC motor 630 with respect to the stator may be determined based on the output value of the absolute encoder. The controller 670 may apply a control signal to the BLDC motor 630 based on the determined position of the rotor. According to one aspect, the control signal may be transmitted to the BLDC motor 630 via the inverter unit 620.

According to an aspect, the storage unit 660 stores calibration data including information on the plurality of output values of the absolute encoder and the rotor positions corresponding to the plurality of output values, respectively, and the positioning unit 650. May be configured to determine the position of the rotor according to the output value of the absolute value encoder based on the calibration data previously stored in the storage unit 660.

According to an aspect, the calibration data may be previously acquired in the calibration mode before the BLDC motor operates in the driving mode. The storage unit 660 in which the calibration data is stored may be, for example, a nonvolatile memory such as an EEPROM. Therefore, after the at least one calibration procedure is performed, when the BLDC motor is powered off, the operation mode is again driven. Even without calibrating, it is possible to rectify and control the BLDC motor based on the absolute encoder.

Here, the position determiner 650 and the controller 670 may be implemented as a processor including a computing device, and the position determiner 650 and the controller 670 may be implemented by a single processor or each as a separate processor. May be In addition, the location determiner 650 and the controller 670 may be implemented as a software module implemented on a processor.

The calibration data sets the BLDC motor to calibration mode, determines the position of the rotor based on the Back Electromotive Force (BEMF) generated by the rotation of the rotor, and determines the position of the rotor based on the back EMF. After obtaining the output value of the absolute value encoder at the time point, the information about the position of the rotor determined based on the counter electromotive force and may be generated by storing the output value of the obtained absolute value encoder as at least part of the calibration data. The generation procedure of the calibration data is described below in detail with respect to a method of calibrating a BLDC motor based on an absolute encoder according to an embodiment of the present invention.

How to control BLDC motor based on absolute encoder

8 is a flowchart illustrating a procedure of absolute encoder based BLDC motor control according to an embodiment of the present invention. According to an embodiment of the present invention, the driver module for controlling the BLDC motor may be driven by firmware, and the firmware may include two modes, a driving mode and a calibration mode. According to one aspect, the conversion of the mode may be performed via the EtherCAT SDO interface, and the information about the mode setting may be stored, for example, in the mode flag in the EEPROM.

Therefore, as shown in FIG. 8, when the operation of the BLDC motor is started, the mode flag in the EEPROM may be first checked (step 810). By checking whether the BLDC motor is in the calibration mode (step 820), in the calibration mode, the measurement of the back electromotive force (BEMF) is activated (step 830), and the front / rear calibration is performed (step 840). Calibration data (eg, a look up table that includes the position of the rotor and corresponding absolute value encoder outputs) that are the result of the calibration may be stored in the EEPROM (step 850).

On the other hand, if it is determined whether the BLDC motor is in the calibration mode (step 820), and in the driving mode other than the calibration mode, the calibration data is loaded from the EEPROM (step 860) to perform the driving mode based on the loaded calibration data. May be step 870.

Hereinafter, a calibration method of a BLDC motor based on an absolute value encoder associated with an operation in a calibration mode of a BLDC motor according to an embodiment of the present invention, and based on an absolute value encoder related to an operation in a drive mode of a BLDC motor, according to an embodiment of the present invention. Each rectifying method of the BLDC motor will be described in detail.

Calibration method of BLDC motor based on absolute encoder

10 is a flowchart illustrating a calibration method of a BLDC motor based on an absolute encoder according to an embodiment of the present invention. As shown in FIG. 10, a method of calibrating a BLDC motor based on an absolute encoder according to an embodiment of the present invention is started by setting the BLDC motor to a calibration mode (step 1010). In the calibration mode, the output value of the absolute encoder according to the position of the rotor included in the BLDC motor can be correlated and stored as calibration data. To this end, according to an embodiment, the position of the rotor may be determined based on a back electromotive force (BEMF) generated by the rotation of the rotor (step 1020).

As previously described, when the rotor rotates and moves in relation to the stator, a voltage different from the voltage applied for driving the BLDC motor may be formed in the stator, which may be referred to as counter electromotive force, and zero crossing of counter electromotive force. It is possible to determine the position of the rotor based on the point (Zero Crossing Point, ZCP). 11 is a conceptual diagram of zero crossing point detection of counter electromotive force. As illustrated in FIG. 11, a back-electromotive force (BEMF) 1130 may be monitored, and a signal may be detected by detecting a zero crossing point (1110). It can be seen that the position of the rotor can be detected when compared with the corresponding Hall sensor signal 1120.

More specifically, the zero crossing points of the counter electromotive force may be obtained for each of the plurality of phases constituting the stator of the BLDC motor, and the reference positions of the rotor may be determined based on the combination of the zero crossing points of the counter electromotive force. Can be. For example, through the sensorless BLDC motor control mechanism described above, positioning of the rotor using the counter electromotive force while the rotor is rotating can be performed.

According to one aspect, the rotation of the rotor of the BLDC motor to generate the counter electromotive force in the calibration mode may be performed based on the power transmitted outside the BLDC motor. That is, a separate calibration tool may be used instead of the BLDC motor.

On the other hand, according to an aspect of the present invention, the reference position of the above-described rotor, a plurality of areas divided by the position of the rotor of the BLDC motor (for example, in the case of a three-phase BLDC motor each represents six states Representative regions). That is, in the conventional Hall sensor-based BLDC motor control or sensorless BLDC motor control method, it is possible to determine the position to which degree the rotor is located in six areas, but the absolute value encoder according to an embodiment of the present invention. For example, since the position may be determined by any one of 16 bits (65536 positions), reference positions of the rotor determined according to the combination of the zero crossing points may be positions representing each region. According to one aspect, the detected zero crossing point may indicate the turning point of each phase, the reference position may indicate the boundary point of each region, and detailed positions that may indicate the position of the rotor more precisely between the reference positions Can be set.

At the time of determining the position of the rotor based on counter electromotive force, an output value of an absolute encoder corresponding to the position of the rotor may be obtained (step 1030), and information about the position of the rotor determined based on the counter electromotive force And store the obtained output value of the absolute value encoder as at least part of the calibration data (step 1040). As described above, the calibration data may be stored in a nonvolatile memory such as an EEPROM.

On the other hand, the reference positions determined by the combination of zero crossing points of the counter electromotive force of the respective phases may represent, for example, positions representing six regions (for example, boundary points of each region), and the absolute encoder indicates the boundary point of such region. More detailed locations may be indicated. Therefore, in storing the calibration data, it is further determined that n detailed positions (n is a natural number of 1 or more) having a uniform interval between the reference positions, and the absolute value encoder corresponding to the reference positions and the reference positions, respectively. The output values as well as the output values of the absolute value encoder corresponding to the detail positions and detail positions may also be stored as at least part of the calibration data. Therefore, it is possible to detect the position of the rotor more precisely, and in the future, it is possible to apply torque ripple attenuation or sinusoidal commutation in the drive mode of the BLDC motor.

12 is a conceptual diagram of a BLDC motor calibration according to an embodiment of the present invention. As shown in FIG. 12, an external drive motor 1220 may provide power for rotating the rotor of the BLDC motor 1210 for calibration of the BLDC motor 1210. Back EMF monitoring is performed for each of the three phases (eg, U, V, and W phases) constituting the BLDC motor 1210 to perform detection of zero crossing points and absolute encoder readings for each of the plurality of phases ( 1230, the position of the rotor based on the zero crossing point and the output value of the absolute encoder may be correlated and stored as calibration data. The calibration data may have the form of a look up table 1240, as shown in FIG. 12. FIG. 13 illustrates an example of executing an application for calibration of FIG. 12. The firmware for driving the BLDC motor includes a calibration mode, and may perform the calibration mode as an interface as shown in FIG. 13.

Rectification Method of BLDC Motor Based on Absolute Encoder

9 is a flowchart of a method of rectifying a BLDC motor based on an absolute encoder according to an embodiment of the present invention. In the rectification method of a BLDC motor based on an absolute encoder according to an embodiment of the present invention, a brushless DC (BLDC) motor including a stator and a rotor may be used as an absolute encoder. Commutation is possible based on this. Here, the absolute encoder is configured to rotate in dependence of the rotation of the rotor. As shown in FIG. 9, in the rectifying method of a BLDC motor based on an absolute encoder according to an embodiment of the present disclosure, first, an output value of an absolute encoder may be obtained (step 910). As mentioned above, the absolute value encoder can have a resolution of 16 bits, for example, so that the rotational position can be measured more precisely.

Thereafter, the position of the rotor of the BLDC motor may be determined based on the obtained output value of the absolute encoder (step 920). In determining the position of the rotor, the position of the rotor according to the output value of the absolute encoder can be determined based on the pre-stored calibration data. The calibration data includes a plurality of output values of the absolute encoder and information about the rotor positions corresponding to the plurality of output values, respectively. The calibration data may be obtained by a calibration method of a BLDC motor based on an absolute encoder according to an embodiment of the present invention. The obtained calibration data is stored in a non-volatile memory such as, for example, EEPROM, so for BLDC motors that have performed at least one calibration procedure, the absolute value is not provided without a Hall sensor and without monitoring back EMF in the drive mode. By simply obtaining the output of the encoder, the relative position of the rotor of the BLDC motor with respect to the stator can be determined. As such, the relative position of the rotor with respect to the stator is determined based on the output value of the absolute encoder that rotates depending on the rotor of the BLDC motor, so that the BLDC motor can be rectified without a hall sensor, thereby miniaturizing the BLDC motor. And it is possible to reduce the weight.

Once the position of the rotor is determined, a control signal may be applied to the BLDC motor based on the determined position of the rotor (step 930). The control signal is a commutation signal, and the commutation signal may be configured to transmit different electrical signals to each of the plurality of phases constituting the stator of the BLDC motor, wherein the electrical signal is one of a current signal and a voltage signal. It may include at least one. More specifically, for commutation of the BLDC motor, the control signal applies a positive voltage to one of the terminals corresponding to the plurality of phases constituting the stator according to the position of the rotor, and to the other ( -) Can be configured to apply a voltage.

Meanwhile, the method of rectifying the absolute encoder-based BLDC motor according to an embodiment of the present invention may be performed in a driving mode of the BLDC motor, and the BLDC motor may be controlled to rotate the rotor at a lower speed than in the calibration mode in the driving mode. have. Also in accordance with one aspect, the BLDC motor can be controlled to rotate in the drive mode by the required angle from the stationary state without idling. More specifically, in the driving mode of the BLDC motor according to an embodiment of the present invention, since the position of the rotor can be determined based on the output value of the absolute encoder without a separate counter electromotive force, the conventional sensorless BLDC motor control In the case of the control, the position of the rotor can be detected even when the BLDC motor is stopped. It is possible to control the precise rotation to rotate the BLDC motor by the precise angle according to the user's request. In addition, since the position of the rotor is detected based on the absolute encoder, it is possible to control the operation of the BLDC motor at low speed or low torque, which is difficult to measure the counter electromotive force. Accordingly, in the case of the conventional sensorless BLDC motor control, the counter electromotive force cannot be sufficiently sensed at a low speed or a low torque, thereby preventing the problem of detecting the position of the rotor.

Furthermore, according to one aspect, by using a high-resolution absolute encoder, it is possible to determine the position of the rotor in much more detail than conventional Hall sensor-based control or back electromotive force-based control, BLDC based on the detailed position of the rotor It is possible to control the motor more precisely. That is, as described in the calibration method of the BLDC motor based on the absolute encoder, in addition to the combination of zero crossing points, the calibration data includes n detailed positions between the reference positions and output values of the corresponding absolute encoder. The position of the rotor can be detected more accurately. Thus, the control signal for the BLDC motor is controlled based on information about the reference position and the detailed position included in the calibration data, for example, to control the BLDC motor to compensate for torque ripple due to the operation of the BLDC motor, Like performing rectification, it may be configured to perform precise control on the BLDC motor.

On the other hand, a device in which a BLDC motor is used may include a mechanical element such as a joint, for example, and an absolute encoder may be added for precise position control of such a mechanical component. In the case of a robot, an encoder is essential for controlling the position or speed of the robot joint, and without using a separate encoder for rectifying the BLDC motor, the encoder for controlling the position or speed of the joint may be used for rectifying the BLDC motor as it is. Can be. In this case, the absolute encoder is used not only for the control of the position or speed of the component that is its original purpose, but also for commutation control by detecting the position of the rotor of the BLDC motor itself, thereby achieving the effect of simplifying the hardware configuration. can do.

The method according to the present invention described above can be embodied as computer readable code on a computer readable recording medium. Computer-readable recording media include all kinds of recording media having data stored thereon that can be decrypted by a computer system. For example, there may be a read only memory (ROM), a random access memory (RAM), a magnetic tape, a magnetic disk, a flash memory, an optical data storage device, and the like. The computer readable recording medium can also be distributed over computer systems connected over a computer network, stored and executed as code readable in a distributed fashion.

As described above with reference to the drawings and examples, the protection scope of the present invention is not meant to be limited by the above drawings or embodiments, and those skilled in the art will be aware of the present invention described in the following claims. It will be understood that various modifications and changes can be made in the present invention without departing from the spirit and scope.

Specifically, the described features may be implemented within digital electronic circuitry, or computer hardware, firmware, or combinations thereof. The features may be executed in a computer program product implemented in storage in a machine readable storage device, for example, for execution by a programmable processor. And features may be performed by a programmable processor executing a program of instructions to perform functions of the described embodiments by operating on input data and generating output. The described features include at least one programmable processor, at least one input device, and at least one output device coupled to receive data and directives from a data storage system, and to transmit data and directives to a data storage system. It can be executed within one or more computer programs that can be executed on a programmable system comprising a. A computer program includes a set of directives that can be used directly or indirectly within a computer to perform a particular action on a given result. A computer program is written in any form of programming language, including compiled or interpreted languages, and included as a module, element, subroutine, or other unit suitable for use in another computer environment, or as a standalone program. Can be used in any form.

Suitable processors for the execution of a program of instructions include, for example, both general purpose and special purpose microprocessors, and one of a single processor or multiple processors of another kind of computer. Computer program instructions and data storage devices suitable for implementing the described features are, for example, magnetic memory such as semiconductor memory devices, internal hard disks and removable disks such as EPROM, EEPROM, and flash memory devices. Devices, magneto-optical disks and all forms of non-volatile memory including CD-ROM and DVD-ROM disks. The processor and memory may be integrated in application-specific integrated circuits (ASICs) or added by ASICs.

Although the present invention described above has been described based on a series of functional blocks, the present invention is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes without departing from the technical spirit of the present invention. It will be apparent to one of ordinary skill in the art that this is possible.

Combinations of the above-described embodiments are not limited to the above-described embodiments, and various types of combinations as well as the above-described embodiments may be provided according to implementation and / or need.

In the above-described embodiments, the methods are described based on a flowchart as a series of steps or blocks, but the present invention is not limited to the order of steps, and any steps may occur in a different order or at the same time than the other steps described above. Can be. Also, one of ordinary skill in the art would appreciate that the steps shown in the flowcharts are not exclusive, that other steps may be included, or that one or more steps in the flowcharts may be deleted without affecting the scope of the present invention. I can understand.

The foregoing embodiments include examples of various aspects. Although not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the present invention cover all other replacements, modifications and variations that fall within the scope of the following claims.

Claims (20)

1. A method of commutating a brushless DC (BLDC) motor including a stator and a rotor based on an absolute encoder, wherein the absolute encoder is dependent on the rotation of the rotor. Configured to rotate, the method comprising:

   (A) obtaining an output value of the absolute encoder;

   (B) determining a position of the rotor of the BLDC motor based on the output value of the absolute encoder; And

   (C) applying a control signal to the BLDC motor based on the determined position of the rotor, the absolute value encoder based commutation method of the BLDC motor.
2. The method of claim 1,

   Determining the position of the rotor, the position of the rotor according to the output value of the absolute encoder based on the pre-stored calibration data,

   And the calibration data comprises a plurality of output values of the absolute encoder and information on rotor positions corresponding to the plurality of output values, respectively.
3. The method of claim 2,

   The calibration data,

   (D) setting the BLDC motor to a calibration mode;

   (E) determining a position of the rotor based on a back electromotive force (BEMF) generated by the rotation of the rotor;

   (F) obtaining an output value of an absolute value encoder at the time of determining the position of the rotor based on the counter electromotive force; And

   (G) previously storing the information on the position of the rotor determined based on the counter electromotive force and the obtained absolute value encoder output value as at least a part of the calibration data, prior to setting the driving mode of the BLDC motor. The rectification method of the BLDC motor based on the absolute encoder.
4.  The method of claim 3, wherein

   (E) determining the position of the rotor based on the counter electromotive force is based on an absolute value encoder which determines the position of the rotor based on a zero crossing point (ZCP) of the counter electromotive force. Rectification method of BLDC motor.
5. The method of claim 4, wherein

   The zero crossing point of the counter electromotive force is obtained for each of the plurality of phases constituting the stator of the BLDC motor,

   (E) determining the position of the rotor based on the counter electromotive force is a BLDC motor based on an absolute encoder, which determines reference positions of the rotor based on a combination of zero crossing points of the respective phases. Rectification method.
6. The method of claim 5, wherein

   The storing step (g) further determines n detailed positions having a uniform interval between the reference positions, and outputs and outputs the absolute values of the absolute value encoder corresponding to the reference positions and the reference positions, respectively. A method of rectifying a BLDC motor based on an absolute encoder, storing output values of absolute encoders corresponding to positions and the detailed positions, respectively, as at least a part of the calibration data.
7. The method of claim 6,

   The control signal, based on the information on the reference position and the detailed position, the rectifying method of the BLDC motor based on the absolute encoder, controlling the BLDC motor to compensate for the torque ripple according to the operation of the BLDC motor.
8. The method of claim 3, wherein

   Step (a) to (c) is performed in the drive mode of the BLDC motor,

   And the BLDC motor can be controlled to rotate the rotor at a lower speed than in the calibration mode in the drive mode, based on an absolute encoder.
9. The method of claim 3, wherein

   Step (a) to (c) is performed in the drive mode of the BLDC motor,

   And the BLDC motor is controlled to rotate in the drive mode to the required angle from the stop state without idling, based on an absolute encoder.
10. The method of claim 1,

    The control signal is a commutation signal, and is configured to transmit different electrical signals to a plurality of phases constituting a stator of the BLDC motor, respectively.
11. The method of claim 10,

    And wherein the electrical signal comprises at least one of a current signal and a voltage signal.
12. The method of claim 1,

    And the absolute value encoder is an absolute value encoder provided for at least one of rotational position control and speed control of a device driven by the BLDC motor.
13. The method of claim 3, wherein

    Rotation of the rotor of the BLDC motor in the calibration mode is performed based on the power transmitted from the outside of the BLDC motor, rectification method of a BLDC motor based on an absolute encoder.
14. BLDC motor control system for commutating BLDC (Brushless DC) motors based on Absolute Encoder,

    A BLDC motor including a stator and a rotor;

    An absolute encoder configured to rotate in dependence of the rotation of the rotor;

    A positioning unit determining a position of the rotor of the BLDC motor based on an output value of the absolute encoder received from the absolute encoder; And

    And a control unit for applying a control signal to the BLDC motor based on the determined position of the rotor.
15. The method of claim 14,

    The apparatus may further include a storage unit configured to store calibration data including information about a plurality of output values of the absolute encoder and rotor positions corresponding to the plurality of output values, respectively.

    The positioning unit, BLDC motor control system for determining the position of the rotor according to the output value of the absolute encoder based on the calibration data stored in advance in the storage.
16. The method of claim 15,

    The calibration data,

    Set the BLDC motor to a calibration mode;

    Determine a position of the rotor based on a Back Electromotive Force (BEMF) generated as the rotor rotates;

    Acquiring an output value of an absolute value encoder at the time of determining the position of the rotor based on the counter electromotive force; And

    By storing the information on the position of the rotor determined based on the counter electromotive force and the output value of the obtained absolute value encoder as at least a portion of the calibration data is generated in advance before setting the drive mode of the BLDC motor to the storage unit The stored, BLDC motor control system.
17. The method of claim 15,

    The storage unit is a non-volatile memory, BLDC motor control system.
18. A method of calibrating a brushless DC (BLDC) motor including a stator and a rotor based on an absolute encoder, wherein the absolute encoder rotates in dependence of the rotation of the rotor. And the method is

    Setting the BLDC motor to a calibration mode;

    Determining a position of the rotor based on a back electromotive force (BEMF) generated by the rotation of the rotor;

    Acquiring an output value of an absolute value encoder at the time of determining the position of the rotor based on the counter electromotive force; And

    And storing information on the position of the rotor determined based on the counter electromotive force and the obtained output value of the absolute encoder as at least part of the calibration data.
19. A computer-readable storage medium containing processor executable instructions, the instructions commutating a brushless DC (BLDC) motor including a stator and a rotor based on an absolute encoder. And the absolute encoder is configured to rotate in dependence of the rotation of the rotor, when the instructions are executed by the processor.

    Obtain an output value of the absolute encoder;

    Determine a position of the rotor of the BLDC motor based on the output value of the absolute encoder; And

    And apply a control signal to the BLDC motor based on the determined position of the rotor.
20. A computer readable storage medium containing processor executable instructions, the instructions for calibrating a brushless DC (BLDC) motor including a stator and a rotor based on an absolute encoder. Instructions, wherein the absolute encoder is configured to rotate in dependence of the rotation of the rotor, the instructions being executed by the processor,

    Set the BLDC motor to a calibration mode;

    Determine a position of the rotor based on a Back Electromotive Force (BEMF) generated as the rotor rotates;

    Acquiring an output value of an absolute value encoder at the time of determining the position of the rotor based on the counter electromotive force; And

    And store information about the position of the rotor determined based on the back electromotive force and the output value of the obtained absolute value encoder as at least part of the calibration data.

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