JP2011101478A - Motor drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive device capable of determining loss of synchronization with high accuracy. <P>SOLUTION: The motor drive performs pulse energization to a coil in accordance with a prescribed interval, and thereby makes a rotor rotate. The motor drive includes a position sensor for detecting a position of the rotor, and a loss of synchronization determination means of determining the presence or the absence of loss of synchronization, based on the output of the position sensor; the loss of synchronization determination means does not determine the presence or the absence of loss of synchronization, based on an output of the position sensor between a position preceding an aimed stop position of the rotor by a prescribed number of pulses and a position preceding the aimed stop position of the rotor by one pulse. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a motor drive device, and more particularly to a motor drive device having a position sensor for detecting the position of a rotor.

  In motor drive devices that perform motor drive control by switching between open-loop drive and feedback drive, switching from feedback drive to open-loop drive is usually performed when the rotational speed of the rotor detected based on the position sensor reaches a predetermined value. When done.

  Patent Document 1 discloses that switching between open-loop driving and feedback driving is performed at a timing according to the output of a motor position sensor. In the drive control disclosed in Patent Document 1, the rotor (driven body) is stopped at the target position by open loop drive. Usually, during such an open loop drive, the presence or absence of a motor step-out is determined using the output of the position sensor. For this reason, even when the motor has stepped out, it is possible to instantly cope with returning from the stepping out.

JP-A-10-150798

  However, when open-loop driving is performed at a relatively low driving frequency, the rotor may vibrate greatly. If the presence / absence of step-out is determined using the output of the position sensor in a state where such vibration occurs, step-out may be erroneously determined.

  Therefore, the present invention provides a motor drive device that can perform a step-out determination with high accuracy.

  A motor drive device according to one aspect of the present invention is a motor drive device that rotates a rotor by applying a pulse current to a coil according to a predetermined time interval, the position sensor detecting the position of the rotor, and the position Out-of-step determination means for determining the presence or absence of out-of-step based on the output of the sensor, and the out-of-step determination means from a position a predetermined number of pulses before the target stop position of the rotor, It is characterized in that determination of the presence or absence of step-out based on the output of the position sensor is not performed between the stop position and the position one pulse before.

  Other objects and features of the present invention are illustrated in the following examples.

  ADVANTAGE OF THE INVENTION According to this invention, a highly accurate motor drive device can be provided.

It is a disassembled perspective view of the motor in a present Example. It is a block block diagram of the motor drive device in a present Example. In the motor of a present Example, it is sectional drawing of the axial direction which shows the phase relationship of a yoke, a position sensor, and a rotor. In a present Example, it is a graph which shows the relationship between a rotor position and a motor torque, and the relationship between a rotor position and the output of a position sensor. It is a block diagram of the advance angle circuit in a present Example. In the motor of a present Example, it is sectional drawing of the axial direction which shows the operation | movement at the time of FB drive. In this embodiment, when the advance angle signal has a predetermined advance angle α, the relationship between the rotation angle of the rotor and the motor torque and the relationship between the rotation angle of the rotor and the output of each signal are shown. In a present Example, it is a graph which shows the relationship between a torque when changing an advance angle, and rotation speed. It is a figure which shows the mode (from a drive start to a drive end) of the drive of the motor drive apparatus in a present Example. In a present Example, it is a figure which shows the relationship between the rotational speed of a rotor immediately before a rotor stop, and a pulse (output of a position sensor). In this example, it is a figure which shows the electricity supply order to the coil at the time of OP drive. It is an output waveform figure (binary) of each position sensor in a present Example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and redundant description is omitted.

  First, the configuration of a motor driven by the motor drive device of this embodiment will be described. FIG. 1 is an exploded perspective view of a motor 101 of this embodiment. Reference numeral 202 denotes a rotor having a magnet 202a and a shaft portion 202b. The magnet 202a is a cylindrical permanent magnet whose outer periphery is multipolarly magnetized, and has a magnetization pattern in which the strength of the magnetic force in the radial direction changes in a sine wave shape with respect to the angular position. Reference numerals 403 and 404 respectively denote a first bearing and a second bearing that pivotally support the shaft portion 202b of the rotor 202. Reference numeral 203 denotes a first coil wound around a bobbin 401 formed of a first nonconductive member. Reference numeral 204 denotes a second coil wound around a bobbin 402 formed of a nonconductive member. Reference numerals 205 and 206 denote a first yoke and a second yoke formed of electromagnetic steel plates or the like, respectively.

  Reference numeral 405 denotes a ring member for positioning the bobbins 401 and 402, respectively. Reference numeral 406 denotes a flexible printed board for energizing the first coil 203 and the second coil 204. Reference numerals 207 and 208 respectively denote a first position sensor and a second position sensor (position detection element) which are mounted on the flexible printed circuit board 406 and arranged in the circumferential direction of the rotor 202.

  Next, the correlation between the components will be described. The rotor 202 is pivotally supported by a bearing 403 on the long axis side and a bearing 404 on the short axis side. The bearings 403 and 404 are inserted into holes 401 a and 402 a (inner diameter portions of the first coil 203 and the second coil 204) provided in the bobbins 401 and 402. The outer diameter portions of the bearings 403 and 404 are fixed to the respective hole portions 205a and 206a of the first yoke 205 and the second yoke 206 by press-fitting. At that time, the magnetic pole teeth 205b and 206b of the first yoke 205 and the second yoke 206 are inserted into holes 401b and 402b provided in the bobbins 401 and 402, respectively.

  As described above, the bobbin 401 (including the coil), the first yoke 205 and the bearing 403, and the bobbin 402 (including the coil), the second yoke 206, and the bearing 404 are integrated. Bobbin inner diameter portions 401 c and 402 c are fitted into outer diameter portions 405 a of ring member 405, respectively. At this time, the first yoke 205 and the second yoke 206 are disposed so that the tips of the magnetic pole teeth 205 b and 206 b are opposed to the magnet surface of the rotor 202.

  Coiled portions 401d and 402d of coil terminals applied to bobbins 401 and 402 are inserted into holes 406a and 406b provided on flexible printed circuit board 406, respectively. Further, the protrusions 205c and 206c provided on the first yoke 205 and the second yoke 206 are inserted into the holes 406c and 406d, respectively.

  The six places inserted are connected and fixed to the flexible printed circuit board 406 by soldering. The hole portion 406 a and the binding portion 401 d are connected for energization of the first coil 203, and the hole portion 406 b and the binding portion 402 d are connected for energization of the second coil 204. The hole 406c and the protrusion 205c, and the hole 406d and the protrusion 206c are connections for fixing the flexible printed circuit board 406 to the motor body. During the above-described soldering, the first position sensor 207 and the second position sensor 208 mounted on the flexible printed circuit board 406 are disposed in the storage portion 405b of the ring member 405 by the bent portion 406e.

  Next, the configuration of the motor driving device in the present embodiment will be described. FIG. 2 is a block configuration diagram of the motor drive device 1. The motor drive device 1 rotates the rotor by applying a pulse current to the coil according to a predetermined time interval.

  A position sensor signal processing circuit 301 processes the outputs of the first position sensor 207 and the second position sensor 208 included in the motor 101. Reference numeral 302 denotes a control unit that selects either a feedback drive circuit 303 or an open loop drive circuit 304, which will be described later, and performs drive control such as acceleration, constant speed, deceleration, and stop drive. Reference numeral 303 is a feedback drive circuit, and 304 is an open loop drive circuit. One of the feedback drive circuit 303 and the open loop drive circuit 304 selected by the control unit 302 generates a drive signal for the motor 101. A motor driver 305 drives the motor 101 based on a drive signal from the feedback drive circuit 303 or the open loop drive circuit 304. The motor drive device 1 includes the above components.

  The open loop drive circuit 304 and the motor driver 305 (first drive means) perform open loop drive (OP drive) on the motor 101. The OP driving is a driving method for switching energization to the motor coil in accordance with a predetermined time interval, similarly to the open loop control of a normal step motor. That is, the open loop drive circuit 304 and the motor driver 305 sequentially switch energization to the first coil 203 and the second coil 204 according to the drive pulse interval (drive frequency) and the rotation direction. By such control, the rotor 202 can be rotated at a desired speed (speed control). It is also possible to rotate the rotor 202 by a desired angle according to the number of drive pulses (position control).

  Thus, in OP driving, energization of the coil is switched according to a predetermined time interval (drive pulse interval). For this reason, it is possible to control the coil energization switching timing without being affected by the detection result of the position sensor. However, if the drive pulse interval is shortened, it becomes difficult for the rotor to respond to switching of the coil energization, which may cause a step-out. Therefore, the maximum speed of the rotor during OP driving is the maximum speed that the rotor can follow for switching the coil energization.

  The feedback drive circuit 303 and the motor driver 305 (second drive means) perform feedback drive (FB drive) with respect to the motor 101. The FB drive is a drive method that switches energization to the motor coil in accordance with the output of a position sensor (first position sensor 207, second position sensor 208) that detects the position of the rotor 202. In other words, the feedback drive circuit 303 and the motor driver 305 are configured so that the first coil 203 and the second coil are in accordance with the number of drive pulses, the rotation direction, and the advance signal generated based on the detection signal output from the position sensor. The energization with 204 is sequentially switched. By such control, it is possible to rotate the rotor 202 by a desired angle (position control). Further, by controlling the current or voltage flowing through the first coil 203 and the second coil 204, the rotor 202 can be rotated with a desired torque (current / voltage control). Furthermore, by controlling the phase difference (advance angle) between the detection signal and the advance angle signal, it is possible to change the torque-rotation speed characteristic (advance angle control). The advance angle control will be described later.

  In the FB drive, the energization switching of the coil is performed in accordance with the position of the rotor. For this reason, the occurrence of step-out due to the response delay of the rotor can be reduced, and high-speed driving is possible.

  Next, the phase relationship between the yoke and the position sensor in the motor 101 of this embodiment will be described. FIG. 3 is a cross-sectional view in the axial direction showing the phase relationship between the yoke, the position sensor, and the rotor in the motor 101. In FIG. 3, the clockwise direction is the positive direction. Reference numeral 205 b denotes magnetic pole teeth of the first yoke 205, and reference numeral 206 b denotes magnetic pole teeth of the second yoke 206. In this embodiment, the number of poles of the magnet is 8 and the magnetization angle P is 45 °. When the first yoke 205 is used as a reference, the phase P / 2 of the second yoke 206 is −22.5 °, the phase β1 of the first position sensor 207 is + 22.5 °, and the second position sensor 208 is used. The phase β2 is −45 °.

Hereinafter, the operation of the motor will be described using the electrical angle. The electrical angle is expressed by assuming that one period of the magnet magnetic force is 360 °. When the number of poles of the rotor is M and the actual angle is θ ₀ , the electrical angle θ is expressed by the following equation (1). The

θ = θ ₀ × M / 2 (1)
The phase difference between the first yoke 205 and the second yoke 206, the phase difference between the first position sensor 207 and the second position sensor 208, and the phase difference between the first yoke 205 and the first position sensor 207 are all The electrical angle is 90 °. In FIG. 3, the magnetic pole tooth center of the first yoke 205 and the north pole center of the magnet 201 are opposed to each other. This state is the initial state of the rotor, and the electrical angle is 0 °.

  Next, the relationship between the rotation angle of the rotor and the motor torque in the motor 101 and the relationship between the rotation angle of the rotor and each signal will be described. FIG. 4 is a graph showing the relationship between the rotation angle of the rotor, the motor torque, and the output of the position sensor.

  FIG. 4A is a graph showing the relationship between the rotation angle (rotor position) of the rotor and the motor torque, where the horizontal axis represents the electrical angle and the vertical axis represents the motor torque. In FIG. 4A, the motor torque that rotates the rotor clockwise is positive. When a positive current is passed through the first coil 203, the first yoke 205 is magnetized to the N pole, and an electromagnetic force is generated between the magnetic pole of the magnet 201. Further, when a positive current is passed through the second coil 204, the second yoke 206 is magnetized to the N pole, and an electromagnetic force is generated between the magnetic poles of the magnet. When the two electromagnetic forces are combined, a substantially sinusoidal torque is obtained as the rotor 202 rotates (torque curve A + B +). Similarly, a substantially sinusoidal torque can be obtained in other energized states (torque curves A + B−, AB−, and AB−). The first yoke 205 is disposed with a phase of 90 ° in electrical angle with respect to the second yoke 206. For this reason, the four torques have a phase difference of 90 ° in electrical angle.

  FIG. 4B is a graph showing the relationship between the rotation angle of the rotor (rotor position) and the output of each signal, where the horizontal axis indicates the electrical angle and the vertical axis indicates the output of each signal. The magnet 201 is magnetized so that the strength of the magnetic force in the radial direction is substantially sinusoidal with respect to the electrical angle. Therefore, a substantially sinusoidal signal is obtained from the first position sensor 207 (position sensor signal A). In the present embodiment, the first position sensor 207 outputs a positive value when facing the north pole of the magnet 201.

  The second position sensor 208 is arranged with a phase of 90 ° in electrical angle with respect to the first position sensor 207. Therefore, a substantially cosine wave-like signal is obtained from the second position sensor 208 (position sensor signal B). In the present embodiment, the second position sensor 208 has an inverted polarity with respect to the first position sensor 207. For this reason, the second position sensor 208 outputs a positive value when facing the south pole of the magnet 201.

  Outputs of the first position sensor 207 and the second position sensor 208 are subjected to a predetermined calculation by the position sensor signal processing circuit 301 and are input to an advance angle circuit constituting a part of the feedback drive circuit 303. The advance angle circuit outputs a first advance angle signal and a second advance angle signal having an arbitrary advance angle set by the control unit 302. Hereinafter, a method for calculating these advance signals will be described.

  Assuming that the electrical angle is θ, the output of the first position sensor 207 is HE1, and the output of the second position sensor 208 is HE2, each output is expressed by the following equations (2-1) and (2-2). expressed.

HE1 = sin θ (2-1)
HE2 = cos θ (2-2)
Here, if the first advance signal advanced by the advance angle α is PS1, and the second advance signal advanced by the advance angle α is PS2, the following equation (3- It can be calculated as 1) and (3-2).

PS1 = sin (θ + α) = HE1 × cos α + HE2 × sin α (3-1)
PS2 = cos (θ + α) = HE2 × cos α−HE1 × sin α (3-2)
In the present embodiment, the advance circuit is configured based on the arithmetic expressions (3-1) and (3-2). FIG. 5 is a diagram showing the configuration of the advance angle circuit 401 in the present embodiment. The advance angle circuit 401 is composed of an analog circuit as shown in FIG. 5, for example. Such an advance circuit makes it possible to realize the above calculation. First, a signal obtained by amplifying each position sensor output with a predetermined amplification factor A and a signal obtained by inverting those outputs are generated (Asin θ, Acos θ, −Asin θ, −A cos θ). These signals are multiplied by appropriate resistance values R1 and R2 and added to generate an advance angle signal. The first advance signal PS1 and the second advance signal PS2 are expressed by the following equations (4-1) and (4-2).

PS1 = A × (R / R1) × sin θ + A × (R / R2) cos θ (4-1)
PS2 = A × (R / R1) × cos θ−A × (R / R2) sin θ (4-2)
By selecting the resistor R and the variable resistors R1 and R2 in the advance angle circuit so as to satisfy the following expressions (5-1) and (5-2), an advance angle signal advanced by an arbitrary advance angle α is generated. be able to.

R / R1 = cos α (5-1)
R / R2 = sin α (5-2)
The first advance signal PS1 and the second advance signal PS2 are binarized by a comparator, and a binarized signal is output from the comparator.

  The method of generating the advance signal in the present embodiment is not limited to the method using the above-described analog circuit. An advance angle signal may be generated using a digital circuit, or an advance angle signal may be generated by adjusting a pulse interval for switching energization using a high-resolution encoder.

  Next, energization switching in the FB drive will be described. First, the operation of the FB drive when the advance angle of the advance signal output from the advance circuit is zero will be described. In FIG. 4B, the advance angle signal A and the advance angle signal B are signals obtained by performing the aforementioned advance angle calculation on the position sensor signal A and the position sensor signal B, and giving the advance angle. FIG. 4 (2) shows a case where the advance angle is zero. For this reason, the sensor signal A and the advance angle signal A, which are the outputs of the first position sensor 207, and the sensor signal B and the advance angle signal B, which are the outputs of the second position sensor 208, coincide with each other. The binarized signal A and the binarized signal B are signals obtained by binarizing the advance angle signal A and the advance angle signal B with a comparator.

  In the FB drive, the motor driver 305 switches the energization of the first coil 203 based on the binarized signal A and switches the energization of the second coil 204 based on the binarized signal B. That is, the motor driver 305 causes a current in the positive direction to flow through the first coil 203 when the binarized signal A has a positive value, and a current in the reverse direction through the first coil 203 when the binarized signal A has a negative value. Shed. The motor driver 305 causes a current in the positive direction to flow through the second coil 204 when the binarized signal B is a positive value, and causes a current in the reverse direction to flow through the second coil 204 when the signal is negative. Shed.

  FIG. 6 is a cross-sectional view in the axial direction showing the operation during the FB drive in the motor 101 of this embodiment. FIG. 6A shows a state in which the rotor is rotated 135 ° in electrical angle. At this time, as represented by (a) in FIG. 4B, the binarized signal A indicates a positive value, and the binarized signal B indicates a negative value. Therefore, a positive current flows through the first coil 203, and the first yoke 205 is magnetized to the N pole. On the other hand, a reverse current flows through the second coil 204, and the second yoke 206 is magnetized to the south pole. At this time, a clockwise torque corresponding to the torque curve A + B− in FIG. 4A is activated, and the rotor 202 receives the rotational force in the θ direction and rotates.

  FIG. 6B shows a state where the rotor 202 is rotated by 180 ° in electrical angle. At this time, the binarized signals A and B are represented by (b) in FIG. The first position sensor 207 is located at the boundary between the N pole and the S pole of the magnet 201. For this reason, the binarized signal A is switched from a positive value to a negative value at an electrical angle of 180 °, and the energization direction of the first coil 203 is switched from the positive direction to the reverse direction. This electrical angle coincides with the electrical angle at the intersection of the torque curve A + B− and the torque curve AB−.

  FIG. 6B ′ shows a state where the rotor has rotated 180 ° in electrical angle and the energization direction of the first coil 203 has been switched. A reverse current flows through the first coil 203 and the first yoke 205 is magnetized to the south pole, and a reverse current flows through the second coil 204 and the second yoke 206 is magnetized to the south pole. To do. At this time, the clockwise torque corresponding to the torque curve AB in FIG. 4A works, and the rotor 202 receives the rotational force in the θ direction and rotates.

  FIG. 6C shows a state in which the rotor 202 is rotated by 225 ° in electrical angle. At this time, as shown by (c) in FIG. 4B, the binarized signals A and B both show negative values. Accordingly, a current in the reverse direction (negative direction) flows through the first coil 203, the first yoke 205 is magnetized to the south pole, and a current in the reverse direction also flows through the second coil 204, causing the second yoke to flow. 206 is magnetized to the south pole. At this time, the clockwise torque corresponding to the torque curve AB in FIG. 4A works, and the rotor 202 receives the rotational force in the θ direction and rotates.

  FIG. 6D shows a state in which the rotor 202 is rotated by 270 ° in electrical angle. The binarized signals A and B are represented by (d) in FIG. At this time, the second position sensor 208 is located at the boundary between the N pole and the S pole of the magnet 201. For this reason, the binarized signal B is switched from a negative value to a positive value at an electrical angle of 270 °, and the energization direction of the second coil 204 is switched from the reverse direction to the positive direction. This electrical angle coincides with the electrical angle at the intersection of the torque curve AB- and the torque curve AB +.

FIG. 6 (d ′) shows a state where the rotor 202 has rotated 270 ° in electrical angle and the energization direction of the second coil 204 has been switched. A positive current flows through the second coil 204 and the second yoke 206 is magnetized in the N pole, and a reverse current flows through the first coil 203 and the first yoke 205 is magnetized in the S pole. To do. At this time, clockwise torque corresponding to the torque curve A−B + in FIG. 4A acts on the rotor 202, and the rotor 202 rotates by receiving rotational force in the θ direction.
By repeating the above operation, the rotor 202 can be continuously rotated. Further, by reversing the positive and negative values of the binarized signals A and B, it is possible to rotate them in reverse.

  Next, the operation of the FB drive when the advance signal output from the advance circuit has a predetermined advance α will be described. FIG. 7 is a graph showing the relationship between the rotation angle of the rotor, the motor torque, and the output of each signal when the advance angle signal has a predetermined advance angle α.

  FIG. 7 (1) shows the relationship between the rotation angle of the rotor (rotor position) and the motor torque, the horizontal axis shows the electrical angle, and the vertical axis shows the motor torque. FIG. 7B is a graph showing the relationship between the rotation angle of the rotor (rotor position) and the output of each signal, where the horizontal axis indicates the electrical angle and the vertical axis indicates the output of each signal. In FIG. 7 (2), the advance angle signal A is advanced with respect to the sensor signal A by a predetermined advance angle α. Similarly, the advance angle signal B is advanced by a predetermined advance angle α with respect to the sensor signal B. The binarized signals A and B generated based on the advance signals A and B are also advanced by the advance angle α with respect to the sensor signals A and B, respectively. In the FB drive, energization to the first coil 203 is switched based on the binarized signal A, and energization to the second coil 204 is switched based on the binarized signal B. For this reason, the energization switching timing of the coil is earlier by the advance angle α than when the advance angle is zero.

  FIG. 8 is a graph showing the relationship between the torque and the rotational speed when the advance angle is changed (when the advance angle value θp = 0, α). The horizontal axis represents the motor torque, and the vertical axis represents the motor speed. As shown in FIG. 8, the relationship between the torque and the rotational speed changes depending on the advance angle α. In the FB drive, the advance angle control for changing the advance angle α according to the drive condition is performed using this property. When FB driving is performed under a certain load condition, the driving speed can be controlled by controlling the advance angle α.

FIG. 9 is a diagram illustrating a driving state (from driving start to driving end) of the motor driving device in the present embodiment. The vertical axis represents the rotational speed (V) of the rotor 202, and the horizontal axis represents time (t). In FIG. 9, _{t 1} is the acceleration drive period, _{t 2} is the steady driving period, _{t 3} is the reduction drive period. Of the deceleration drive period t ₃ , t _3a is a deceleration drive period by FB drive, and t _3b is a deceleration drive period by OP drive. That is, the period from t _{1 to} t _3a is the FB driving period, and the period from t _3b is the OP driving period. P _s is a switching point from the FB drive to the OP drive. As described above, the motor driving apparatus according to the present embodiment performs FB driving from the start of driving to the switching point P _s and performs OP driving from the switching point P _s to the end of driving.

The motor drive device of this embodiment constantly monitors the rotational speed V of the rotor 202. The rotation speed V of the rotor 202 is calculated by the control unit 302 (calculation means) based on the outputs of the first position sensor 207 and the second position sensor. In OP driving, the rotation speed V of the rotor 202 is determined by the coil. If the speed is higher than the maximum speed that the rotor 202 can follow to switch the power to the motor, step-out or vibration may occur, and therefore OP driving is only performed at a speed that is less than or equal to the maximum speed V _s that the rotor 202 can follow. Therefore, the condition of the switching point P _s is that the rotational speed V is first lower than the maximum speed of the rotor during OP driving (OP driving maximum speed V _s or lower).

In acceleration drive period _{t 1,} the rising in FB driven from a stopped state, the rotor 202 reaches the maximum rotational speed _{V m} by the driving voltage _{V a} from the motor driver 305. After the rotor 202 has reached the maximum velocity V _m, the FB driving at a substantially constant speed is carried out at a steady driving period t _2. Thereafter, the deceleration is performed toward the target position at a reduced driving period t _3. In the deceleration driving period _{t 3a} by FB driving, for example, performs deceleration by reducing the drive voltage to _V b _{(<V a).} As a method for reducing the drive voltage, for example, when the drive signal is a PWM signal, a method for reducing the duty ratio is used. Such deceleration can also be achieved by controlling the amount of current to the exciting coil or by controlling the advance angle.

P _m in the deceleration drive period t _3a is the maximum point of deceleration acceleration due to the FB drive. In the deceleration driving period _{t 3a,} through the maximum point _{P m} of deceleration to decelerate the rotor 202 by FB drive until the following OP drive maximum speed _{V s.} After passing the maximum point P _m, after the rotational acceleration of the rotor 202 is controlled to be equal to or less than a predetermined value, a state in which the rotor 202 becomes substantially constant speed, switch to the OP drive from FB driven at the switching point P _s. Thereafter, in the deceleration driving period _t3b by OP driving, driving to the target position is performed by OP driving according to a predetermined driving frequency. In this embodiment, after the rotor 202 reaches the OP drive maximum speed V _s or less, the rotor 202 is driven at a substantially constant speed for a predetermined period (constant speed period t _c ). This constant speed drive is performed, for example, by calculating the input value to the motor from the deviation between the target position and speed and the actual position and speed, the integrated value of the deviation, etc., and adjusting the advance value and drive voltage. ing.
As described above, by shifting to the OP drive while the speed change of the rotor 202 is reduced, stable switching from the FB drive to the OP drive becomes possible. The control unit 302 switches between the first driving unit that performs OP driving and the second driving unit that performs FB driving. As described above, the control unit 302 performs the acceleration, constant speed, and deceleration driving of the rotor 202 by the feedback driving circuit 303, and switches the feedback driving circuit 303 to the open loop driving circuit 304 to stop the rotor 202. For this reason, according to the motor drive device of the present embodiment, the occurrence of step-out and vibration can be suppressed.

Next, a detailed description will be given of the control from the switching to the OP drive until the rotor is stopped at the target position. After switching from the FB drive to the OP drive, stop drive (deceleration drive) is performed while gradually decreasing the drive frequency. FIG. 10 is a diagram illustrating the relationship between the rotational speed of the rotor and the pulse (position sensor output) immediately before the rotor is stopped. FIG. 10 corresponds to an enlarged view of a portion (a second half portion of the deceleration driving period _t3b by OP driving) from immediately before the stop to the stop in FIG.

  FIG. 11 is a diagram showing the energization sequence to the coil during OP driving in this embodiment. In FIG. 11, two binding portions 401d to the first coil 203 are respectively represented as signals A + and A-, and two binding portions 402d to the second coil 204 are respectively represented as signals B + and B-. Further, assuming that “H (High)” is applied with a positive voltage and “L (Low)” is a voltage 0 (GND), the step pattern is four patterns of STEP1 to STEP4 (generally, two-phase driving). be called). By sequentially repeating these four patterns, the motor rotates.

  As shown in FIG. 10, when the target stop position of the rotor is STEP4, the energization pattern before 4STEP is STEP4. When STEP is sequentially sent from 4 STEP to the stop position, STEP 1 → STEP 2 → STEP 3 → STEP 4 (stop). FIG. 12 is an output waveform diagram (binary) of the first position sensor 207 (upper stage) and the second position sensor 208 (lower stage). As shown in FIG. 12, after the energization of STEP 4, the output of the first position sensor 207 becomes “L” and the output of the second position sensor 208 becomes “H”. These sensor outputs sequentially change to “L” and “L”, “H” and “L”, “H” and “H”, and “L” and “H”. Thus, there are four output patterns for the output patterns of the first position sensor 207 and the second position sensor 208, and the outputs of the two position sensors are uniquely determined corresponding to STEP1 to STEP4.

  The control unit 302 as step-out determination means detects the position of the rotor 202 even in the case of OP driving, and determines whether or not the motor drive device 1 is out of step. For this reason, the step-out state can be detected instantaneously. By monitoring whether or not the output of each position sensor is sequentially switched when it is driven step by step, it is possible to determine the presence or absence of step-out. That is, the number of steps in which “L” and “H” of the output signal of the position sensor signal processing circuit 301 are input to the control unit 302 shown in FIG. 2 is counted in the control unit 302.

  However, as described above, the intermittent rotation phenomenon of the motor appears in the output of the position sensor at a relatively low frequency in the deceleration region. For this reason, the position sensor cannot accurately detect “H” and “L”, and erroneous position detection may be performed. That is, since the rotor vibrates, “H” and “L” which are not based on the pulse are repeatedly output, and there is a possibility that the number of pulses is counted more than the original number.

  Accordingly, when normal driving (STEP 1: “L” and “L”) is confirmed by the position sensor when application is performed at the third STEP before the target stop position, the second STEP before the target stop position, The output of each position sensor in the first STEP is ignored. That is, in the two STEPs before the target stop position, the output of each position sensor is not used.

  Then, after the rotor 202 is applied at the target stop position, it is confirmed whether or not it is normally driven by the position sensor. At this time, when normal driving can be confirmed, step-out has not occurred in the two STEPs ignoring the output of the position sensor. This is because if the step-out occurs in the two ignored STEPs, the output of the position sensor at the target stop position is not a combination (“L” and “H”) that should originally be.

  For this reason, according to the present embodiment, erroneous detection of the rotor position can be avoided even when two ignored STEPs are driven at a frequency at which the above-described output disturbance of the position sensor occurs. Even if the output of the position sensor is ignored only by two STEPs, it is possible to confirm the presence or absence of step-out during the ignored period by checking the output of the position sensor at the target stop position. For this reason, the position of the rotor of the whole area is monitored substantially.

  As described above, the control unit 302 uses the output of each position sensor in the first period from the start of the stop control by the open loop drive circuit 304 to the predetermined number of pulses (STEP 1) immediately before the rotor 202 stops. The position of the rotor 202 is detected. On the other hand, the control unit 302 detects the position of the rotor using the number of drive pulses for the rotor 202 without using the output of each position sensor in the second period after the predetermined number of pulses until the rotor 202 stops. . In addition, the output of each position sensor after the rotor 202 is stopped is used to determine whether or not the motor has stepped out in the second period. That is, the controller 302 determines whether or not there is a step-out based on the output of the position sensor from a position a predetermined number of pulses before the target stop position of the rotor 202 to a position one pulse before the target stop position of the rotor 202. Do not make a decision.

  With such a configuration, the output of the position sensor can always be obtained stably and can be accurately stopped at the target position without erroneous count. For this reason, according to the present embodiment, it is possible to provide a motor drive device capable of performing a step-out determination with high accuracy.

  In this embodiment, the case of two-phase driving has been described as an example. However, the present invention is not limited to this, and can be applied to other driving as long as stepwise driving is performed. At this time, a predetermined number of pulses Pi that can be ignored can be calculated using the following equation (6).

Pi ≦ P / M (6)
Here, P is the number of pulses required to rotate the rotor once, and M is the number of magnetic poles of the rotor. Thus, in this embodiment, when the predetermined number of pulses Pi is P / M or less, the number of pulses Pi can be ignored. For example, when P = 20 and M = 10 (two-phase driving), the number of pulses Pi is 2 or less, and when P = 40 and M = 10 (1-2-phase driving), the number of pulses Pi is 4 or less. .

  The embodiment of the present invention has been specifically described above. However, the present invention is not limited to the matters described as the above-described embodiments, and can be appropriately changed without departing from the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Motor drive device 101 Motor 202 Rotor 203 1st coil 204 2nd coil 207 1st position sensor 208 2nd position sensor 302 Control part 303 Feedback drive circuit 304 Open loop drive circuit 305 Motor driver

Claims (2)

A motor driving device that rotates a rotor by energizing a coil according to a predetermined time interval,
A position sensor for detecting the position of the rotor;
Step out determination means for determining the presence or absence of step out based on the output of the position sensor,
The step-out determination means determines whether or not there is step-out based on the output of the position sensor from a position a predetermined number of pulses before the target stop position of the rotor to a position one pulse before the target stop position of the rotor. The motor drive device characterized by not performing determination of.   2. The predetermined number of pulses is set to P / M or less, where M is the number of magnetic poles formed on the rotor and P is the number of pulses required to rotate the rotor once. The motor drive device described in 1.