JP2013031294A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device which can determine the operating condition of a stepping motor more accurately than in the past.SOLUTION: A motor control device 10 is a motor control device to control an N-phase stepping motor 2 (N is equal to or greater than 2), which comprises a drive circuit 11 and a determination circuit 12. The drive circuit 11 drives the rotation of the stepping motor 2 by a method in which drive coils CLA, CLB in plural phases among N phases have electricity thereto turned on at the same time. Further, the drive circuit 11 temporarily turns electricity to all drive coils CLA, CLB off. During an electricity turned off period, or a period in which electricity to all drive coils CLA, CLB is temporarily turned off, the determination circuit 12 detects counter electromotive force occurring in a drive coil in at least one phase, and, on the basis of the magnitude of the detected counter electromotive force, determines the operating condition of the stepping motor 2.

Description

  The present invention relates to a motor control device having a function of detecting an operation state such as rotation, stop, and step-out of a stepping motor.

  There is known a method for detecting an operation state such as rotation, stop, and step-out of a stepping motor based on a back electromotive force (BEMF) induced in a drive coil of a rotor. For example, Japanese Patent Laid-Open No. 2009-261045 (Patent Document 1) provides a period in which a signal is stopped for a short period of time that does not affect the rotation of a motor within a period of each step unit in a control signal, Disclosed is a technique in which a step-out state can be detected with high accuracy by measuring an induced back electromotive voltage. More specifically, this stop period is provided before and after the time point when the sign of the current value is inverted, and the counter electromotive voltage is measured during this stop period.

  On the other hand, in a position sensorless permanent magnet three-phase synchronous motor, the rotor position is often estimated based on the counter electromotive force. For example, in the case of the 120-degree energization method, any one phase of the three-phase inverter is in a non-energized state where both the upper and lower switch elements are turned off. An induced voltage (counterelectromotive force) corresponding to the rotational speed of the motor appears in the terminal voltage of the non-energized phase, so the rotor position is estimated based on the terminal voltage of the non-energized phase. Is done.

  In the case of the 180 ° energization method, the switch element of each phase of the three-phase inverter is always turned on either on the upper side or the lower side, so that the back electromotive force can be easily detected as in the 120 ° energization method. I can't do it. Therefore, in the technique described in Japanese Patent Laid-Open No. 2009-106141 (Patent Document 2), all switch elements of the three-phase inverter are turned off at an arbitrary timing, and the terminal voltage of the motor is measured in a state where all the phases are not energized. By doing so, the rotor position is estimated.

  Japanese Patent Application Laid-Open No. 2009-11088 (Patent Document 3) detects whether or not a three-phase motor has stopped by detecting a back electromotive force when the main switch of the three-phase synchronous motor is turned off. Safety equipment is described.

JP 2009-261045 A JP 2009-106141 A JP 2009-11088 A

  The technique described in the above Japanese Patent Application Laid-Open No. 2009-106141 (Patent Document 2) is intended to estimate the rotor position of the three-phase synchronous motor, and therefore all the phases of the three-phase inverter are not energized. It is necessary to measure the terminal voltages of all three phases during this non-energization period. Japanese Patent Laid-Open No. 2009-11088 (Patent Document 3) is intended to detect the stop state of the three-phase synchronous motor when the power is shut off, and is premised on the non-energization of all phases.

  On the other hand, in the case of the stepping motor targeted by the present invention, the purpose is to determine whether or not the motor is stopped or stepped out according to the magnitude of the counter electromotive force. It is not necessary to de-energize all phases during the measurement. For example, in the case of a one-phase excitation type two-phase stepping motor, the magnitude of the back electromotive force can be detected from the terminal voltage of the drive coil that is not excited.

  In the case of a two-phase excitation type two-phase stepping motor, energization is stopped for only one phase for detecting the counter electromotive force for a short time that does not affect the rotation of the motor. For example, in the example shown in FIG. 2 of the above Japanese Unexamined Patent Publication No. 2009-261045 (Patent Document 1), the B phase is energized at times T2 to T3 and T8 to T9 when the energization of the A phase is stopped. The A phase is energized from time T5 to T6 and from T11 to T12 when the energization of the B phase stops.

  By the way, when determining the stepping motor operation state, various causes for erroneous determination are conceivable. For example, if there is variation in the characteristics of the comparator used for determining the level of the back electromotive force, an erroneous determination is likely to occur. Even if there is a manufacturing variation in a mechanism such as a pickup device in which the stepping motor is incorporated, the operation of the stepping motor is affected, which may cause an erroneous determination. Furthermore, the environment in which the stepping motor is used, the operating frequency of the motor, and the like also affect the determination of the operating state. In order to accurately detect the operating state of the motor while minimizing these influences, it is necessary to detect the counter electromotive force under conditions such that the counter electromotive force detected when the motor rotates is as large as possible.

  The inventor of the present application studied the detection conditions of the counter electromotive force from the above viewpoint, and completed the present invention. An object of the present invention is to provide a motor control device capable of more accurately determining the operation state of a stepping motor than in the prior art.

  A motor control device according to an embodiment of the present invention is a motor control device that controls an N-phase (N ≧ 2) stepping motor, and includes a drive circuit and a determination circuit. The drive circuit rotationally drives the stepping motor by simultaneously energizing a plurality of drive coils of N phases. The drive circuit further temporarily stops energization of all the drive coils. The determination circuit detects a counter electromotive force generated in at least one phase of the drive coil during the energization stop period in which energization of all the drive coils is temporarily stopped, and based on the detected back electromotive force The operation state of the stepping motor is determined.

  According to the above embodiment, since the back electromotive force is detected in a state where the energization to all the drive coils is stopped, the rotation speed of the motor when the energization is stopped is smaller than when the energization is stopped only for the one-phase drive coil. Can be suppressed. For this reason, the operation state of the stepping motor can be determined more accurately than in the past.

It is a block diagram which shows an example of a structure of the motor control apparatus 10 by one Embodiment of this invention. It is a figure which shows the input voltage waveform and output current waveform of the driver 11 of FIG. It is a figure which shows typically the position of the rotor 2A with respect to the drive coil in each of the sections I-IV of FIG. It is a figure for demonstrating the problem in the case of stopping energization only for 1 phase. It is a top view which shows typically the transfer mechanism 1 of an optical BIC up.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Configuration of motor controller]
FIG. 1 is a block diagram showing an example of the configuration of a motor control device 10 according to an embodiment of the present invention.

  Referring to FIG. 1, a motor control device 10 drives and controls a PM (Permanent Magnet) type two-phase stepping motor 2. The motor control device 10 is configured as a semiconductor device in which semiconductor elements are integrated on a semiconductor substrate. The motor control device 10 includes an externally applied A-phase input voltage VinA and B-phase input voltage VinB (sometimes collectively referred to as a control signal) and a reference voltage that serves as a reference for determining the logic levels of these input voltages VinA and VinB. REF is input. When the A-phase input voltage VinA is higher than the reference voltage REF, the A-phase input voltage VinA is high level (H level). When the A-phase input voltage VinA is lower than the reference voltage REF, the A-phase input voltage VinA is low level. (L level). The same applies to the B-phase input voltage VinB.

  As shown in FIG. 1, the motor control device 10 includes a drive circuit (driver) 11 and a determination circuit 12 that determines rotation / stop of the rotor 2A. The determination circuit 12 includes a timing calculation circuit (also referred to as a timing control unit) 13, a selection circuit (selector) 14, and a comparison circuit 15.

  The driver 11 supplies current to the A-phase drive coil CLA and the B-phase drive coil CLB based on the change in the logic level of the A-phase input voltage VinA and the B-phase input voltage VinB. FIG. 2 shows a two-phase excitation method. The driver 11 is provided with output terminals A + and A− for supplying an excitation current to the A-phase drive coil CLA and output terminals B + and B− for supplying an excitation current to the B-phase drive coil CLB. Yes.

  The timing calculation circuit 13 receives the A-phase input voltage VinA and the reference voltage REF. The timing calculation circuit 13 energizes both the A-phase drive coil CLA and the B-phase drive coil CLB (that is, all the energized drive coils) with reference to the timing at which the logic level of the A-phase input voltage VinA is switched. Decide when to temporarily stop. Then, the timing calculation circuit 13 generates a current interruption signal 16 for instructing to stop energization at the determined timing, and outputs it to the driver 11. In response to the current cutoff signal 16, the driver 11 temporarily stops energization of all the drive coils. Hereinafter, a period in which energization to the drive coil is stopped is referred to as an energization stop period.

  The timing calculation circuit 13 further outputs a select signal 17 for instructing the selector 14 to switch the connection in order to detect a counter electromotive force generated in the drive coil during the energization stop period.

  The selector 14 selects one of the A phase and the B phase according to the select signal 17 and outputs a voltage applied to both ends of the drive coil of the selected phase. More specifically, the selector 14 has terminals CMP + and CMP− connected to the non-inverting input terminal and the inverting input terminal of the comparison circuit 15, respectively. The selector 14 switches the connection between these terminals CMP +, CMP− and the output terminals A +, A−, B +, B− of the driver 11 according to the select signal 17.

  Specifically, as shown in FIG. 1, there are four states for the connection of the terminals of the selector 14. In the 0th state, the terminal CMP + is connected to the output terminal A−, and the terminal CMP− is connected to the output terminal A +. In the first state, the terminal CMP + is connected to the output terminal B +, and the terminal CMP− is connected to the output terminal B−. In the second state, the terminal CMP + is connected to the output terminal A +, and the terminal CMP− is connected to the output terminal A−. In the third state, the terminal CMP + is connected to the output terminal B−, and the terminal CMP− is connected to the output terminal B +.

  The comparison circuit 15 sets the output signal Dout to the H level when the output voltage of the selector 14 (that is, the difference voltage between the terminals CMP + and CMP−) exceeds a predetermined threshold voltage. Therefore, when the output signal Dout of the determination circuit 12 is at the H level, it is determined that the stepping motor 2 is rotating. When the output signal Dout of the determination circuit 12 is at the low level (L level), the stepping motor 2 is stopped. Or it determines with it being in a step-out state.

[Operation of motor controller]
FIG. 2 is a diagram showing an input voltage waveform and an output current waveform of the driver 11 of FIG. Hereinafter, the operation of the motor control device 10 according to the A-phase input voltage VinA and the B-phase input voltage VinB will be described with reference mainly to FIGS.

(About input voltage waveform)
FIG. 2A shows the input voltage waveforms of the A phase and the B phase and the waveform of the counter electromotive force generated in the drive coil. The A-phase input voltage VinA is at the H level in the section I (from time t1 to time t4) and in the section II (from time t4 to time t7), and in the section III (from time t7 to time t10) and section IV (time t10). To time t13). The B-phase input voltage VinB is at the L level in the sections I and IV, and is at the H level in the sections II and III.

(When there is no energization stop period)
FIG. 2B shows A-phase and B-phase current waveforms output from the driver 11. In the case of FIG. 2B, unlike the case of the present invention, the energization stop period is not provided.

  Hereinafter, the signs of the A-phase current and the B-phase current in this specification will be defined. Regarding the A-phase current, the case where it flows from the output terminal A + to the output terminal A− through the drive coil CLA is positive, and the case where it flows in the opposite direction is negative. When the A-phase input voltage is at the H level, a positive A-phase current flows. When the A-phase input voltage is at the L level, a negative A-phase current flows. Similarly, regarding the B-phase current, the case where it flows from the output terminal B + through the drive coil CLB to the output terminal B− is positive, and the case where it flows in the reverse direction is negative. When the B-phase input voltage is at the H level, a positive B-phase current flows. When the B-phase input voltage is at the L level, a negative B-phase current flows.

  Regarding the electrical angle of the A phase current, the electrical angle of the A phase current when the A phase current switches from the negative direction to the positive direction (time t1, t13) is 0 ° (or 360 °), and the A phase current is in the positive direction. The electrical angle of the A-phase current when switching from negative to negative (time t7) is 180 °. A period during which a positive A-phase current flows (that is, an electrical angle from 0 ° to 180 °) is referred to as a first energization period, and a period during which a negative A-phase current flows (that is, from an electrical angle of 180 ° to 360 °) Two energization periods are called.

  Similarly, when the B-phase current is switched from the negative direction to the positive direction (time t4), the electrical angle of the B-phase current is 90 °, and when the B-phase current is switched from the positive direction to the negative direction (time t10). The electrical angle of the B phase current is 270 °. A period during which a positive B-phase current flows (that is, an electrical angle of 90 ° to 270 °) is referred to as a third energization period, and a period during which a negative B-phase current flows (that is, from an electrical angle of 270 ° to 90 °) This is referred to as a 4 energization period.

  FIG. 3 is a diagram schematically showing the position of the rotor 2A relative to the drive coil in each of the sections I to IV in FIG. 2 correspond to FIGS. 3A to 3D, respectively. In FIG. 3, when a positive current flows through the drive coil, the coil becomes the N pole, and the S pole of the rotor 2A is pulled. Conversely, when a negative current flows through the drive coil, the coil becomes the S pole and the N pole of the rotor 2A is pulled.

  Referring to FIG. 3A, when a positive current flows through the A-phase drive coil and a negative current flows through the B-phase drive coil (corresponding to section I in FIG. 2), the S pole of the rotor 2A is The position is close to the A-phase drive coil, and the N pole of the rotor 2A is close to the B-phase drive coil.

  Referring to FIG. 3B, when a positive current flows in both the A-phase drive coil and the B-phase drive coil (corresponding to section II in FIG. 2), the S pole of rotor 2A is the A-phase drive coil and B-phase. The position is close to both of the drive coils.

  Referring to FIG. 3C, when a negative current flows through the A-phase driving coil and a positive current flows through the B-phase driving coil (corresponding to section III in FIG. 2), the N pole of the rotor 2A is The position is close to the A-phase drive coil, and the south pole of the rotor 2A is close to the B-layer drive coil.

  Referring to FIG. 3D, when negative current flows in both the A-phase drive coil and the B-phase drive coil (corresponding to section IV in FIG. 2), the N pole of rotor 2A is the A-phase drive coil and B-phase. The position is close to both of the drive coils. Thereafter, the state shown in FIGS. 3A to 3D is repeated, whereby the rotor 2A continuously rotates clockwise.

(When energization stop period is provided)
With reference to FIGS. 1 and 2 again, the operation of the motor control device 10 in the case of providing an energization stop period in which energization to the A-phase and B-phase drive coils is temporarily stopped will be described.

  FIG. 2C shows the A-phase and B-phase current waveforms output from the driver 11. However, unlike the case of the present invention, in the case of FIG. 2C, power supply is stopped only for one of the A-phase and B-phase drive coils during the energization stop period. The back electromotive force detects the voltage applied to both ends of the drive coil that has stopped feeding.

  More specifically, power supply to the A-phase drive coil is stopped between time t2 and time t3 in section I. During this energization stop period, the back electromotive force generated in the A-phase drive coil is detected by setting the connection state of the selector 14 to the second state. Power supply to the B-phase drive coil is stopped between time t5 and time t6 in section II. During the energization stop period, the back electromotive force generated in the B-phase drive coil is detected by setting the connection state of the selector 14 to the first state. Power supply to the A-phase drive coil is stopped between time t8 and time t9 in section III. During this energization stop period, the back electromotive force generated in the A-phase drive coil is detected by setting the connection state of the selector 14 to the 0th state. Power supply to the B-phase drive coil is stopped between time t11 and time t12 in section IV. During this energization stop period, the back electromotive force generated in the B-phase drive coil is detected by setting the connection state of the selector 14 to the third state.

  In summary, in the section I (the first half of the first energization period, ie, electrical angle 0 ° to 90 °) and the section III (the first half of the second energization period, ie, the electrical angle 180 ° to 270 °), the A-phase drive coil The counter electromotive force generated in the Back electromotive force generated in the B-phase drive coil in section II (first half of the third energization period, ie, electrical angle 90 ° to 180 °) and section IV (first half of the fourth energization period, ie, electrical angle 270 ° to 360 °) Is detected. The reason for setting the back electromotive force detection period in this way is to detect the back electromotive force in a state where the largest possible back electromotive force is generated. As shown in FIG. 2A, the magnitude (absolute value) of the A-phase back electromotive force is larger in the sections I and III than in the sections II and IV, and the magnitude of the B back electromotive force is This is because the sections II and IV are larger than the sections I and III.

  Further, the detection timing of the back electromotive force may be shifted back and forth without matching with the energization stop period in which the power supply to the drive coil is stopped. This is because the back electromotive force may be larger than the point where the power supply to the drive coil is stopped and the drive current crosses 0 A (0 cross point).

  However, when energization is stopped only for one phase as described above, another problem occurs as follows.

  FIG. 4 is a diagram for explaining a problem that occurs when energization of only one phase is stopped. FIG. 4 shows the position of the rotor 2A with respect to the drive coil when the energization to the A-phase drive coil is stopped in the state of FIG. In this case, since the south pole of the rotor 2A is attracted to the current magnetic field generated from the B-phase drive coil, torque in the reverse rotation direction (counterclockwise) is generated in the rotor 2A. For this reason, since the rotational speed of the motor decreases, the magnitude of the counter electromotive force decreases, and the probability of erroneously determining that the rotational state is stopped or step out increases.

  In order to solve this problem, in the motor control device 10 according to the first embodiment, the power supply to all the drive coils is temporarily stopped when the back electromotive force is detected. That is, as shown in FIG. 2D, during the energization stop period, the phase in which the counter electromotive force is not detected, that is, the B phase in the section I and the section III, and the A phase in the section II and the section IV (FIG. 2 ( The energization of the drive coil (shown in a circle in D) is also stopped simultaneously. As a result, the counter electromotive force detected at the time of motor rotation can be increased as compared with the case of FIG. 2C, so that the operation state of the stepping motor can be determined more accurately.

[Application example of motor control device]
Hereinafter, an optical pickup transport mechanism will be described as an example of a device incorporating a stepping motor driven and controlled by the motor control device.

  FIG. 5 is a plan view schematically showing the optical Bickup transfer mechanism 1. Referring to FIG. 5, the transfer mechanism 1 includes a stepping motor 2, a screw shaft 3, a guide shaft 4, a mounting base 5, an optical pickup 6 mounted on the mounting base 5, a stopper 7, and a stepping motor. 2 includes a motor control device 10 that rotationally drives 2 and a control device 8.

  The stepping motor 2 drives the screw shaft 3 to rotate. The screw shaft 3 has a spiral groove formed on the surface. The mounting base 5 is provided with a through hole 5 </ b> A through which the guide shaft 4 passes, and a protrusion 5 </ b> B that matches the spiral groove of the screw shaft 3. The mounting base 5 moves along with the optical pickup 6 along the guide shaft 4 according to the rotation of the stepping motor 2. The stopper 7 is disposed so as to come into contact with the mount 5 when the optical pickup 6 moves in the left direction of the drawing. The control device 8 controls the entire device (for example, an optical disk drive device) including the optical pickup transfer mechanism 1. Specifically, the control device 8 outputs the A-phase input voltage VinA, the B-phase input voltage VinB, and the reference voltage REF described with reference to FIG. 1 to the motor control device 10 and the determination result Dout of the operation state of the stepping motor 2. Is received from the motor control device 10.

  In order to control the position of the optical pickup 6, it is first necessary to move the optical pickup 8 to the origin OP and cause the control device 8 to detect that the origin OP has been reached. For this reason, the optical pickup 6 is moved in the left direction in the drawing together with the mounting base 5 so that the mounting base 5 collides with the stopper 7. At this time, it is detected by the motor control device 10 that the stepping motor 2 has stopped, and when the control device 8 receives this detection result, it is possible to detect that the optical pickup 6 is located at the origin OP.

  When the origin OP is detected by the above method, it is desirable to reduce the impact when the mount 5 collides with the stopper 7. For this reason, it is necessary to move the mounting base 5 as slowly as possible (that is, to lower the operating frequency of the stepping motor 2). However, if the operating frequency of the stepping motor 2 is lowered, the counter electromotive force is reduced, so that it is difficult to determine the rotation / stop of the stepping motor 2.

  According to the motor control apparatus 10 according to this embodiment, the counter electromotive force generated when the motor rotates can be increased as compared with the prior art, so that the range of the detectable operating frequency can be expanded. As a result, it is possible to reduce the impact when the mount 5 collides with the stopper 7 in order to detect the origin. Further, it is possible to suppress erroneous determination due to the influence of play, friction, ambient temperature, and the like of the transfer mechanism 1, and to reduce manufacturing variations (offsets and characteristic variations) of the comparator (comparison circuit 15) used for threshold determination. be able to. The smaller the motor, the smaller the back electromotive force, but even in such a case, it is possible to reduce the probability of erroneously determining whether the motor is rotating or stopping.

[Modification]
In the above embodiment, a two-phase excitation type two-phase stepping motor has been described as an example. However, a stepping motor to which the present invention can be applied is not limited to the above example. The present invention can be widely applied to N-phase (N ≧ 2) stepping motors such as a three-phase excitation type three-phase stepping motor and a four-phase excitation type four-phase stepping motor.

  The embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  2 stepping motor, 2A rotor, 10 motor control device (semiconductor device), 11 driver (drive circuit), 12 determination circuit, 13 timing calculation circuit (timing control unit), 14 selector (selection circuit), 15 comparison circuit, CLA, CLB drive coil, VinA, VinB Input voltage (control signal).

Claims (5)

A motor control device for controlling an N-phase (N ≧ 2) stepping motor,
A drive circuit that rotationally drives the stepping motor by simultaneously energizing drive coils of a plurality of phases of N phases;
The drive circuit temporarily stops energization of all drive coils,
The stepping motor detects the counter electromotive force generated in at least one phase of the drive coil during the energization stop period in which energization to all the drive coils is temporarily stopped, and based on the magnitude of the detected counter electromotive force The motor control apparatus further provided with the determination circuit which determines the operation state of. The stepping motor is a two-phase stepping motor,
The drive circuit is provided with a first energization stop period in which energization of all the drive coils is temporarily stopped in the first half of the first energization period in which a current in the first direction flows through the first phase drive coil.
2. The motor control device according to claim 1, wherein the determination circuit detects a back electromotive force generated in the first phase drive coil during the first energization stop period. The drive circuit further temporarily energizes all the drive coils in the first half of the second energization period in which a current in the second direction opposite to that during the first energization period is passed through the first phase drive coil. The second energization stop period to stop is provided,
3. The motor control device according to claim 2, wherein the determination circuit detects a back electromotive force generated in the first-phase drive coil during the second energization stop period. The determination circuit further includes a first half of a third energization period in which a current in the first direction flows through the second-phase drive coil, and a second opposite to the second energization period in the second-phase drive coil. In the first half of the fourth energization period for flowing the current in the direction, the third and fourth energization stop periods for temporarily stopping energization of all the drive coils are provided,
4. The motor control device according to claim 3, wherein the determination circuit detects a back electromotive force generated in the second-phase drive coil during the third and fourth energization stop periods. In response to a control signal received from the outside of the motor control device, the drive circuit energizes the drive coil of each phase,
The determination circuit includes:
A timing control unit that determines a timing for temporarily stopping energization of all the drive coils based on the control signal, and commands the drive circuit to stop energization at the determined timing;
A selection circuit that selects one of the N phases based on the timing determined by the timing control unit and outputs a voltage applied to both ends of a drive coil of the selected phase;
The motor control device according to claim 1, further comprising a comparison circuit that compares an output voltage of the selection circuit with a predetermined threshold value.

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