JP5343259B2 - Brushless motor control device and brushless motor step control method - Google Patents

Description

  The present invention relates to a brushless motor control device and a stepless control method for a brushless motor, which are used in medical equipment and the like and control the rotation of a brushless motor over a wide range from an ultra-low speed to a high-speed rotation.

  Conventionally, for example, the following methods are known as methods for controlling the rotation of a motor. In a brushless motor, in order to replace the brush function of a motor with a brush with a semiconductor circuit, a magnetic sensor is built in and the rotation angle of the rotor (permanent magnet) is detected in a non-contact manner or occurs when the rotor rotates. There is a method of detecting the position of the rotor using a back electromotive force. Furthermore, a method of performing rotation speed control according to binary code information from an encoder is also known.

  A DC motor is basically a motor with excellent controllability, but is not suitable for a low rotation speed (about several rpm) or an inching operation such as a stepping motor. This is because the DC motor is based on a control method that determines the control by detecting the movement of the rotor immediately before the control.

Problems to be solved by the invention

  The brushless motor is basically used for continuous rotation, and has a motor structure that is not suitable for controlling the rotational speed at an ultra-low speed with stability. In addition, stepping motors are basically configured to perform intermittent rotation (step control) in response to pulse energization. If continuous rotation is performed, problems such as noise and vibration due to cogging occur. To do.

  In order for a stepping motor to move one step reliably regardless of external factors (torque fluctuation), a margin is required for the motor torque. On the other hand, since the brushless motor detects the immediately preceding angular velocity and determines and controls the next energization condition, it cannot perform stable low-speed rotation. For this reason, in the case of a motor incorporated in a device with a very wide range of rotation speeds to be used, that is, to control in the range from ultra low speed to high speed rotation, a stepping motor or a brushless motor is used. However, no matter which motor is used, if a wide range of rotation speed is required with one motor, the requirement for high accuracy and low power consumption cannot be satisfied. There was a problem.

  The present invention has been made in view of the above, and by combining the advantages of the brushless motor and the stepping motor, it is possible to realize rotation control in a wide rotation speed range with high accuracy and low power consumption. With the goal.

Means for solving the problem

In order to achieve the above object, the brushless motor control apparatus according to claim 1 is a brushless motor control for controlling the rotation of an inner rotor, slotless type two-phase brushless motor. In the apparatus, the two Hall elements are arranged to face each other at an angle of 90 degrees, the magnetic poles of the rotor magnet are formed in the radial direction N / S2 poles, the rotor position detecting means for detecting the position of the rotor, and the Hall elements arranged between a coil energizing means for coil energization in accordance with the rotor position pattern which is detected for each quarter rotation time determined by the magnetic pole of the rotor magnet, the position of the rotor obtained by the rotor position detection means immediately after energization The current rotor position pattern is recognized by the CPU from the signal, and the next robot determined by the rotation direction. Energization is continued until the motor position pattern is reached, and the energization is stopped when the next rotor position pattern is recognized by the CPU, and the energization direction is switched in accordance with the next rotor position pattern after ¼ rotation time, and the coil The coil energizing means is controlled so as to start energization, and when the rotor position pattern is deviated by 1/4 rotation time for the next energization, the coil energizing is performed via the coil energizing means. Motor control means for controlling the energization means .

  According to this invention, in the brushless motor control device, the rotor position immediately after energization is detected by the rotor position detection means, and the current rotor position pattern (for example, NS pattern) is detected from the rotor position detected by the rotor position detection means. Recognize and set the next rotor position pattern (N-N pattern) determined by the rotation direction, continue energization, and stop energization at the timing when the current rotor position pattern matches the next rotor position pattern. Time can be set, and low-power-consumption rotation that is not affected by load and disturbance factors is realized.

Further , according to the present invention, when the rotor position pattern is deviated by a predetermined time for performing the next energization, the coil is further subjected to the correction energization to realize the positioning of the rotor when the misalignment occurs.

In the brushless motor control apparatus according to claim 2 , the coil energization means performs energization by pulse width modulation or intermittent energization by chopper control.

  According to the present invention, in the first aspect, the energization control to the coil is a control in which the average voltage is intermittently applied by pulse width modulation (PWM) or the like. It becomes possible to respond finely according to the rotation state of the rotor.

Further, in the step control method of the brushless motor according to claim 3 , the N / S2 poles in the radial direction formed on the rotor magnet by the magnetic pole detection means in which the two Hall elements face each other and are arranged at an angle of 90 degrees . In the step control method of the inner rotor and slotless type two-phase brushless motor for detecting the magnetic pole position , the first rotor position pattern is recognized by the CPU from the magnetic pole position signal of the rotor obtained by the magnetic pole detection means immediately after energization. And the current rotor position pattern recognized in the first step, the next rotor position pattern determined in the rotation direction is set, and the arrangement of the hall elements and the rotor are determined in a predetermined coil energization pattern. A second step of energizing every ¼ rotation time determined by the magnetic pole of the magnet, and the current state Energization is continued until the rotor position pattern coincides with the next rotor position pattern, and the rotor position pattern is shifted by the third rotation time when the energization is stopped and the 1/4 rotation time when the next energization is performed. And a fourth step of performing correction energization at the time.

  According to the present invention, when the magnetic pole detection means is arranged to face each other by 90 degrees with a two-pole rotor magnet, the magnetic pole position signal of the rotor magnet is acquired by the magnetic pole detection means after an instruction to energize the motor is given. Then, the current rotor position pattern is recognized from the signal, energization is continued, energization is stopped when the next pattern determined in the rotation direction is reached, and energization is performed for a short time at least every ¼ rotation. As a result, low power consumption is realized.

Further, in the step control method for a brushless motor according to claim 4, wherein the energization of the second to fourth step is to perform the intermittent energization by energization or chopper control by pulse width modulation.

According to the present invention, in the third aspect , the energization control to the coil is a control in which the average voltage is intermittently applied by pulse width modulation (PWM), etc. It becomes possible to respond finely according to.

In the brushless motor step control method according to the fifth aspect , the correction energization is not performed even when the rotor position is set too much.

  According to the present invention, the coil is energized when it is determined that the position is the previous rotor position (not the target rotor position pattern), and further power saving is possible by not energizing when the rotor is excessive. Since the return control is not performed, vibration and noise are further reduced.

  Embodiments of a brushless motor control device and a brushless motor step control method according to the present invention will be described below in detail with reference to the accompanying drawings. The present invention is not limited to this embodiment.

  The present invention combines the advantages of a brushless motor (such as continuous operation) with the good step control of a stepping motor (such as low speed / intermittent operation), and this can be varied within a specified range by a microcomputer system. It is something to control. Hereinafter, in this embodiment, a small brushless motor having a configuration in which two two-phase full waves and two Hall effect devices (Hall effect devices) are arranged to face each other by 90 degrees will be described as an example.

  FIG. 1 is an explanatory view showing a configuration of a brushless motor 10 according to an embodiment of the present invention, and shows a schematic cross section viewed from the axial direction of the motor. In the figure, reference numeral 11 denotes a housing that serves as a motor outer case, reference numerals 12a and 12b are provided by being shifted by 90 degrees, and a Hall element (magnetic pole sensor) for detecting the position of the rotor magnet, and reference numeral 13 is a cup shape. Winding coil for driving, symbol 14 is a rotor magnet formed of a rare earth magnet suitable for a small motor, for example, in a cylindrical shape with N / S 2 poles in the radial direction, and symbol 15 is a rotating shaft of the rotor magnet 14. It is a shaft which becomes a rotation output shaft.

  That is, the brushless motor 10 is a two-phase full-wave motor with two magnets and a coil surface facing a cylindrical surface. The brushless motor 10 is arranged in a coil arrangement that rotates by a step angle of 90 degrees and has four coils (or two coils). ) Is rotated by 90 degrees by energizing, and when energization is continued with a predetermined coil energization pattern, it is configured to be one of the four rotor position patterns shown in the drawings to be described later.

  FIG. 2 is a block diagram showing the configuration of the control system of the brushless motor 10 shown in FIG. In the figure, reference numeral 20a is an amplifier that amplifies the magnetic pole detection signal output from the hall element 12a to a constant level, reference numeral 20b is an amplifier that amplifies the magnetic pole detection signal output from the hall element 12b to a constant level, and reference numeral 21a is an amplifier 20a. An A / D converter that converts the magnetic pole detection signal (analog signal) amplified in step 1 to a digital signal. Reference numeral 21b denotes an A / D that converts the magnetic pole detection signal (analog signal) amplified by the amplifier 20b into a digital signal. It is a converter.

  The A / D converters 21a and 21b perform pattern detection with an A / D conversion value of 8 bits and 0 to 255 values. In this example, the rotor position pattern has 128 or more as N poles and less than 128 as S poles. Set. Further, this numerical value may be appropriately changed depending on the detection accuracy.

  Reference numeral 22 is a CPU that sets the rotor position pattern from the detected magnetic pole detection signal via the A / D converters 21a and 21b, and controls the motor. Reference numeral 23 is a control program that the CPU 22 executes. The ROM 24 is a RAM used during control such as a working memory.

  Reference numeral 25 denotes a motor control unit including the A / D converters 21a and 21b, the CPU 22, the ROM 23, and the RAM 24 described above. Reference numeral 26 denotes a driver that drives the brushless motor 10 in accordance with an output signal from the motor control unit 25, and is configured by an FET (Field Effect Transistor). In FIG. 2, the power supply circuit portion supplies normal power and is omitted here.

  Next, operations that are characteristic of the brushless motor control system configured as described above will be described. FIGS. 3A to 3D are explanatory views showing rotor position patterns according to the embodiment of the present invention. Four patterns are obtained by rotating the N pole 14a and the S pole 14b of the rotor magnet 14 (CW direction). Are detected by the A / D converters 21a and 21b using the magnetic pole detection signals from the Hall elements 12a and 12b, and the rotor position pattern is recognized by the CPU 22.

That is, by rotating by 90 degrees, among the four patterns (a) NS pattern, (b) NN pattern, (c) SN pattern, and (d) SS pattern in FIG. By detecting this pattern, the energization control is performed until the next pattern is detected. Further, the patterns of FIGS. 3A to 3D are transitioned at predetermined energization timings in the order indicated by the arrows.
Hereinafter, an example of the operation will be described with reference to the flowcharts of FIGS.

  As a method of energizing the coil, a method of applying a voltage intermittently by pulse width modulation (PWM) or a chopper control method is used. This makes it possible to finely respond to the applied voltage in accordance with the rotation state of the rotor with the pulse width, substantially changing the average voltage and changing the starting torque.

  FIG. 4 is a flowchart showing a motor control procedure according to the embodiment of the present invention. First, it is determined whether or not a rotation instruction has been issued by the motor control unit 25 (step S11). If it is determined that there is an instruction for rotation, a predetermined coil energization process (see FIGS. 5 and 6) is executed (step S12). On the other hand, if it is determined that no rotation instruction has been given, a coil energization stop process (step S13) is performed.

  FIG. 5 is a flowchart showing energization timing in the motor control according to the embodiment of the present invention. First, it is determined whether or not it is ¼ rotation time (step S21). Here, when it is determined that the time is 1/4 rotation time, the energization is forcibly stopped (step S22), the target pattern Pb is advanced to the next and the coil energization is started (step S23), and the process returns to the previous step S21. The subsequent processing is repeatedly executed.

  FIG. 6 is a flowchart showing a coil energization process in the motor control according to the embodiment of the present invention. First, the current pattern Pa is recognized, the next target pattern Pb corresponding to the current pattern Pa is set, and coil energization is performed (step S31). That is, if the current pattern Pa is a cycle of Pa1 → Pa2 → Pa3 → Pa4, the target pattern Pb is changed in the order of Pb2 → Pb3 → Pb4 → Pb1.

  Subsequently, it is determined whether or not the current pattern Pa has become the target pattern Pb (step S32). Here, when it is determined that the current pattern Pa matches the target pattern Pb, the coil energization is stopped (step S33). In order to detect whether or not the rotor position has shifted after the coil energization is stopped, it is further determined whether or not Pa = Pb (step S34). If it is determined that Pa = Pb, energization is stopped (step S35), and the process returns to the previous step S34. If it is determined in step S34 that Pa = Pb, it is assumed that the rotor position is shifted, correction energization is executed (step S36), the rotor is returned to the previous position, the process returns to step S34, and the same operation is performed. Is repeatedly executed up to 1/4 rotation time.

  That is, the magnetic pole detection signals by the Hall elements 12a and 12b are amplified by the amplifiers 20a and 20b, and the amplified signals are digitally converted by the A / D converters 21a and 21b, respectively, and supplied to the CPU 22. The CPU 22 executes control according to the procedure shown in FIGS. 4 to 6 in accordance with the control program stored in the ROM 23. In other words, from the rotor position pattern (see FIGS. 3A to 3D) obtained by A / D conversion, the next rotor target pattern determined by the rotation direction (if NS pattern, the next pattern is N- N pattern) is set. The energization is continued until the current rotor position pattern obtained by A / D conversion matches the target pattern. At the point in time coincident with the target pattern, the motor is rotated by 1/4 (90 degrees).

  During the time until the next ¼ rotation, if the current position pattern matches the target pattern, the current is applied as it is. If not, the current is supplied in the energizing direction that matches the target pattern. For example, in FIG. 3, when the (a) N-S pattern is recognized as the current pattern, energization is performed until the next (b) N-N pattern is obtained. Alternatively, if the current pattern is recognized to be (c) the SN pattern, the current pattern has been overrun, so that the current pattern is energized until the pattern returns to the (b) NN pattern. Therefore, during the energization time, the process is performed until the target pattern matches the current pattern regardless of the load and disturbance factors, so that the rotation accuracy is maintained.

  In the above-described control, correction energization is performed when the rotor goes too far. However, if the current pattern matches the target pattern, the energization is turned off and the correction energization need not be performed. As a result, low noise, low vibration, and low power consumption are realized.

  By the way, since a general stepping motor has a tooth of an iron core, there is detent torque (detent torque: zero current cogging), and therefore it takes time to start rotation of the rotor. On the other hand, the motor according to the present invention is advantageous in terms of low power consumption because the zero current cogging is extremely small (close to 0) at the start of rotation in an inner rotor, slotless type brushless motor.

  For example, when the gear ratio is 200: 1, the rotational accuracy of the brushless motor in this embodiment is 90/200 degrees because the gear ratio is 1/200 even if the rotor position is shifted by 90 degrees. become. Therefore, the speed accuracy is determined by the time accuracy of 1/4 rotation. The resolution is controlled by a microcomputer and can be realized by increasing the number of digits. However, the present inventor has decided by the interrupt time. For example, calculation was performed with a resolution of 0.2 msec, and it was verified that the accuracy of 1% or less was ensured in the time of 1/4 rotation at the shortest high-speed rotation. Since the rotational speed setting has a width of 1200 times, the accuracy of 1/1200% or less is realized in the longest time.

  Therefore, motor control is performed with a resolution of 0.2 msec, and the current is cut off at the rotor position (at least 1/4 rotation in this embodiment) that matches the target pattern as described above. The brushless motor can be controlled with high accuracy and low power consumption without the need for a motor. Further, unlike the conventional brushless motor, since the previous rotation state is fed back and the next rotation speed is determined and not controlled, high-precision control can be ensured as calculated within the resolution range. In this case, the accuracy of the magnetic pole sensor such as a Hall element is not necessarily required to be high, and can be realized.

Effect of the invention

  As described above, according to the brushless motor control device (claim 1) of the present invention, the rotor position immediately after energization is detected, and the current rotor position pattern (for example, NS pattern) is detected from the detected rotor position. To set the next rotor position target pattern (N-N pattern) determined by the rotation direction and continue energization, and stop energization at the timing when the current rotor position pattern matches the next rotor position target pattern. Rotational control in a wide rotational speed range can be realized with high accuracy and low power consumption.

  According to the brushless motor control device (claim 2) of the present invention, in claim 1, since the coil is further subjected to correction energization when the rotor position pattern is deviated by a predetermined time for performing the next energization, When the rotor is displaced, it can be returned to the normal rotor position.

  According to the brushless motor control device (claim 3) of the present invention, in claim 1, the energization control to the coil is a control for intermittently applying a voltage by pulse width modulation (PWM) or the like. The applied voltage can be finely adapted to the rotation state of the rotor by the pulse width, and the actual average voltage can be changed.

  According to the brushless motor step control method of the present invention (Claim 4), when the magnetic pole detection means is arranged to face, for example, 90 degrees, the magnetic pole detection means is instructed after energization of the motor is instructed. Until the magnetic pole position signal of the rotor magnet is obtained, the current rotor position pattern is recognized from the signal, and energization is continued until the next target pattern determined in the rotation direction is reached. Since energization is required to move the rotor position until rotation, unnecessary current supply considering disturbance factors and load fluctuations is eliminated, and high accuracy and low power consumption are realized.

  Further, according to the step control method for a brushless motor according to the present invention (Claim 5), the energization control to the coil according to Claim 4 is a control in which a voltage is intermittently applied by pulse width modulation (PWM) or the like. Therefore, it is possible to finely cope with the applied voltage in accordance with the rotation state of the rotor with the pulse width, and the actual average voltage can be changed.

  According to the brushless motor step control method according to the present invention (Claim 6), when it is determined that the rotor position is the previous rotor position (not the target rotor position pattern), the coil is energized and the rotor goes too far. Since no energization is performed, further power reduction is realized, and quietness and vibration are realized.

  It is explanatory drawing which shows the internal structure of the brushless motor concerning embodiment of this invention.   It is a block diagram which shows the structure of the control system of the brushless motor shown in FIG.   It is explanatory drawing which shows the rotor position pattern concerning embodiment of this invention.   It is a flowchart which shows the motor control procedure concerning embodiment of this invention.   It is a flowchart which shows the electricity supply timing in the motor control concerning embodiment of this invention.   It is a flowchart which shows the coil energization process in the motor control concerning embodiment of this invention.

10 Brushless motor
12a, 12b Hall element
13 coils
14 Rotor magnet
14a N pole
14b S pole
21a, 21b A / D converter
22 CPU
25 Motor controller
26 Drivers

Claims (5)

In a brushless motor control device that controls the rotation of an inner rotor and slotless type two-phase brushless motor, two Hall elements face each other at an angle of 90 degrees, and the magnetic poles of the rotor magnet are N / S2 poles in the radial direction. is formed, performs a rotor position detecting means for detecting the position of the rotor, the coil current in accordance with the rotor position pattern which is detected for each placement and the quarter-rotation time determined by the magnetic pole of the rotor magnet of the Hall element coil The current rotor position pattern is recognized by the CPU from the energization means and the rotor position signal obtained by the rotor position detection means immediately after energization, and energization is continued until the next rotor position pattern determined in the rotation direction is reached. When the rotor position pattern is recognized by the CPU , the energization is stopped, The energization direction is switched in accordance with the next rotor position pattern after 1/4 rotation time, the coil energization means is controlled to start coil energization, and the rotor position pattern is shifted by 1/4 rotation time for the next energization. A brushless motor control device comprising: motor control means for controlling the coil energization means so as to execute correction energization via the coil energization means . 2. The brushless motor control apparatus according to claim 1, wherein the coil energization means performs energization by pulse width modulation or intermittent energization by chopper control. Step of an inner rotor, slotless type two-phase brushless motor that detects the magnetic pole position of the radial N / S2 pole formed on the rotor magnet by the magnetic pole detection means arranged with the two hall elements facing each other at an angle of 90 degrees In the control method, a first step of recognizing a current rotor position pattern by a CPU from a magnetic pole position signal of the rotor obtained by the magnetic pole detection means immediately after energization, and a current rotor position pattern recognized in the first step Then, a second rotor position pattern determined in the rotation direction is set, and a second coil is energized every 1/4 rotation time determined by the arrangement of the Hall element and the magnetic pole of the rotor magnet with a predetermined coil energization pattern. And energizing until the current rotor position pattern matches the next rotor position pattern. And a third step of stopping the energization to a consistent point in time, a fourth step of performing correction energized when the rotor position pattern is shifted by a quarter rotation time for performing next energization, to include A stepless control method for a brushless motor. 4. The brushless motor step control method according to claim 3 , wherein the energization in the second to fourth steps is performed by pulse width modulation or intermittent energization by chopper control. The brushless motor step control method according to claim 3 , wherein correction energization is not performed even when the rotor position is set too much.

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