JP5850652B2 - Motor drive device and control method thereof - Google Patents

Description

  The present invention relates to a motor drive device having a motor provided with a position sensor for detecting the rotational position of a rotor magnet.

  The stepping motor (hereinafter abbreviated as “motor”) described in Patent Document 1 is provided with a position detection sensor (hereinafter abbreviated as “sensor”), and can detect the rotational position of the rotor magnet. . As a result, the feedback energization switching drive can be performed by switching the energization to the coil and switching the excitation of the yoke at an appropriate timing according to the desired speed and load, together with the normal step drive. As a result, the motor described in Patent Document 1 that performs feedback control using the output of the sensor has a wider speed range from a low speed range to a high speed range than a normal motor that does not perform feedback control using the output of the sensor. Can be used and at the same time high output torque can be achieved.

  FIG. 7 is a diagram showing a method for controlling the switching timing between the output of the sensor and the excitation of the yoke, and shows an example of controlling a motor having a two-phase yoke using the outputs of the two sensors. Hereinafter, two sensors will be described as an A sensor and a B sensor, respectively, and two phases will be described as an A phase yoke and a B phase yoke. When it is detected that the output of the A sensor has changed from a low level (hereinafter abbreviated as “L”) to a high level (hereinafter abbreviated as “H”) at the timing (1) in the figure, it is set in advance thereafter. The A-phase yoke is excited to + at the timing (2) in the figure after the time Ta1 has elapsed. After that, when it is detected that the output of the B sensor has changed from L to H at the timing (3) in the figure, the B phase is then outputted at the timing (4) in the figure after a preset time Tb1 has elapsed. Energize the yoke to +. Thereafter, the time Ta2 to Ta4 and Tb2 to Tb4 from the H / L switching of the sensor to the +/− switching of the excitation of the yoke are continuously increased or decreased or kept constant. By doing so, it is possible to rotate the motor even if it accelerates or decelerates, maintains a constant speed, or resists steep loads. In addition, the details of the configuration of the motor and the drive circuit, and the contents and effects of the drive control are as described in Patent Document 1.

Japanese Patent Laid-Open No. 09-331666

  First, correction necessary for equivalent control for all motors will be described even if the sensor mounting position is shifted for each motor due to mass production variations.

  FIG. 8 shows a plan view of the two motors. The motor shown in FIG. 8 (a) has a sensor mounted at a position corresponding to the nominal dimension. However, the motor shown in FIG. 8 (b) is shifted from the nominal dimension by θa and B sensor by θb due to mass production variations. A sensor is attached (in the figure, the displacement is exaggerated from the actual value). It is extremely difficult to produce a motor having no deviation as shown in FIG. Although it is theoretically possible to adjust and attach to a position where there is no misalignment using an optical sensor or the like, it is not practical for mass production.

  Here, in the motor shown in FIG. 8A, the time from the H / L switching of the sensor output to the +/− switching of the excitation of the yoke is expressed as Tmn (m = a or b, n = 1 to 4). Suppose that the control is set to. In the motor shown in FIG. 8B, in order to perform the equivalent control and output the same torque and the same speed, it is necessary to delay the switching time by the time corresponding to the deviation amounts θa and θb. When the deviation amount θm [°] (m = a or b) is known, the time ΔTmn (m = a or b, n = 1 to 4) passing through the deviation amount θm represents the angular velocity at that time as ωmn [° / sec. ] (M = a or b, n = 1 to 4), ΔTmn = θm / ωmn. Since ΔTmn changes according to ωmn, it is necessary to know ωmn for calculating ΔTmn from ωmn that changes every moment. As a method of knowing ωmn, for example, Pmn [sec] (m = a or b, n = 1 to 4) is actually measured, so that ωmn = 90 / Pmn can be calculated. As a result, the time ΔTmn corresponding to the shift amount θm and changing every moment can be calculated from the equation: ΔTmn = θm / ωmn. If switching is performed at time Tmn + ΔTmn obtained by adding ΔTmn to Tmn, the equivalent torque and the equivalent speed can be output in FIG. 8B by performing the equivalent control to (a). This is shown in FIG. 8 (b).

  As described above, by correcting by adding a time corresponding to the calculated ΔTmn, it is possible to absorb the deviation of the sensor mounting position caused by the mass production variation. Even with motors whose sensor mounting positions are deviated from each other, it is possible to perform equivalent control and output equivalent torque and equivalent speed.

  Here, the correction described above is based on the assumption that the shift amount θm is known. As a method for specifying the deviation amount θm for each motor, a method is known in which an actual measurement is performed after the motor is assembled and before it is incorporated into the apparatus. However, in this sensor deviation amount specifying method, a value measured for each motor needs to be stored in a device in which the motor is incorporated. Specifically, when a motor is shipped with a numerical value for each motor shipped and incorporated into the device, the numerical value is input to the device, but the production process becomes complicated and the production efficiency decreases. was there.

To achieve the above object, a motor driving apparatus according to one aspect of the present invention includes a motor including a coil, a rotor magnet, and a detector that detects a rotational position of the rotor magnet, and is fixed to an output shaft of the motor. The pinion gear, the transmission gear that meshes with the pinion gear, and the energization switching of the coil are performed to drive the motor, and the standard time from the energization switching of the coil to the change in the output of the detector is obtained. A control unit having a memory for storing the control unit, wherein the control unit has a first step number corresponding to a drive amount until the backlash between the pinion gear and the transmission gear is eliminated. After step driving in the first direction, the second step number equal to or less than the first step number is stepped in a second direction opposite to the first direction. Was driven, the motor while by driving the step in the second direction, the time from the energization switching of the coil to the output of the detector is changed are measured, and the standard time stored in said memory The detector mounting displacement amount is obtained from the difference from the measured time .

  In the motor drive device of the present invention, as described above, after the motor is assembled, it is not actually measured before being assembled into the device, but the sensor displacement amount can be specified after the device is assembled.

  As a result, it is possible to perform feedback control by applying the result of accurate sensor deviations without complicating the mass production process, improving the accuracy and reliability of speed control and position control in feedback control. Can be made.

It is a block diagram of the motor drive device of the present invention. It is a side view of the motor of the present invention. It is explanatory drawing of the sensor deviation | shift amount specific method of the motor of this invention. It is explanatory drawing of the angular velocity of the motor of this invention. It is a flowchart of an embodiment of the present invention. It is the schematic of the gear train of this invention. It is the figure which showed the switching timing of the excitation detection of the position detection sensor of the conventional motor, and a yoke. It is explanatory drawing of the sensor deviation | shift amount identification method of the conventional motor.

  Hereinafter, modes for carrying out the invention will be described.

  FIG. 1 is a block diagram of the motor drive device of the present invention. The motor driving apparatus according to the present embodiment includes a motor 101 and a motor control circuit 110 that controls the motor 101.

  The motor 101 of this embodiment is a stepping motor, and can be applied to, for example, a motor that drives a zoom lens of an imaging apparatus.

  The motor 101 includes a rotor 103, an A-phase coil 104a (first coil), a B-phase coil 104b (second coil), an A sensor 105a and a B sensor 105b that are detectors. The A sensor 105 a and the B sensor 105 b can detect the rotational position of the rotor 103. As a result, the feedback energization switching drive can be performed together with the normal step drive. In the feedback energization switching drive, energization to the A phase coil 104a is switched based on the output of the A sensor 105a, and energization to the B phase coil 104b is switched based on the output of the B sensor 105b. That is, in the feedback energization switching drive, the excitation of the yoke can be switched at an appropriate timing according to the speed and load.

  A cylindrical magnet 102 is fixed to the rotor 103. Different magnetic poles (N pole and S pole) in the circumferential direction are alternately magnetized on the outer peripheral surface of the magnet 102. The A sensor 105a and the B sensor 105b use Hall elements whose output voltage changes in an analog manner depending on the magnetic flux passing therethrough. The A sensor 105a and the B sensor 105b are arranged so as to face the N pole and the S pole magnetized on the outer peripheral surface of the magnet 102, and the output voltage changes in an analog manner as the rotor 103 rotates.

  That is, when the rotor 103 rotates, the A sensor 105a alternately detects the magnetic poles (N pole and S pole) of the rotor 103 and outputs a signal. When the rotor 103 rotates, the B sensor 105b alternately detects the magnetic poles (N pole and S pole) of the rotor 103 and outputs a signal having a phase different from that of the A sensor 105a.

  The motor control circuit 110 includes a detection unit 106, a timing unit 107, an energization control unit (control unit) 108, and a storage unit 109.

  The detection unit 106 binarizes the analog voltage signals output from the A sensor 105a and the B sensor 105b into H and L, respectively, and outputs a rectangular wave.

  The timer 107 counts and outputs the time from the H / L inversion of the rectangular wave output from the detection unit 106 to the H / L inversion. The timekeeping unit 107 includes an A counter and a B counter that can time and output independently of each other. The A counter measures and outputs the time A from when the rectangular wave based on the output of the A sensor 105a is H / L inverted to H / L inverted. The B counter measures and outputs the time B from when the rectangular wave based on the output of the B sensor 105b is H / L inverted until it is H / L inverted.

  That is, the timer 107 detects a second magnetic pole (eg, S pole) different from the first magnetic pole of the rotor 103 after the A sensor 105a detects the first magnetic pole (eg, N pole) of the rotor 103. It functions as a time measuring means for measuring the time until the first time. The time measuring unit 107 measures the time from when the B sensor 105b detects the first magnetic pole (for example, N pole) until it detects the second magnetic pole (for example, S pole) as the second time. Function as.

  The energization control unit 108 controls the energization switching timing of the A-phase coil 104a and the B-phase coil 104b based on the elapsed time from the H / L inversion of the A sensor 105a and the B sensor 105b measured by the timing unit 107. . The energization control unit 108 includes a calculation unit 108a that corrects the shift amount of the attachment position of the A sensor 105a and the B sensor 105b. A detailed method of correction will be described later.

  The storage unit 109 has a memory and stores the calculated deviation amount of the mounting position from the design value.

  FIG. 2 is a side view of the motor of the present invention. The case member, the coil, and the wiring member for energizing the coil are omitted. In FIG. 2, the A-phase yoke 201 is excited by energizing the A-phase coil 104a, and the B-phase yoke 202 is energized by energizing the B-phase coil 104b. N poles and S poles are alternately magnetized on the outer peripheral surface of the rotor magnet 204, and the rotor magnet 204 and the rotation center shaft 203 are integrated. The sensor 205 is disposed so as to face the outer peripheral surface of the rotor magnet 204 and detects the rotation of the rotor magnet 204. Since the position of the sensor 205 varies due to mass production, it is attached with a deviation amount with respect to the position of the design center.

  In the present embodiment, as a method of specifying the sensor displacement amount for each motor, a method of actually measuring the sensor in the apparatus after the motor is incorporated in the apparatus is adopted. That is, in this embodiment, after being incorporated into the apparatus, the time is not a feedback control using a sensor, but is step-driven at a constant speed, and the time from switching the excitation of the yoke to the H / L of the sensor is switched. And the amount of deviation is calculated from the difference from the previously stored design value.

  FIG. 3 is a diagram for specifically explaining this method. The motor shown in FIG. 3A has a sensor attached at a position corresponding to the nominal size, but the motor shown in FIG. 3B has a sensor attached with a deviation of θ from the nominal size due to variations due to mass production. Although it is not realistic to mass-produce motors with ideal dimensions as shown in FIG. 3A, it is possible to produce only a small amount in the design stage. The motor shown in FIG. 3 (a) is step-driven at a constant speed, and Trm (m = a or b) is the time from when the excitation of the yoke is switched to +/− to when the sensor is switched to H / L. Data is collected at the design stage as a standard value, and stored in advance as a standard value for all devices during mass production. In calculating Trm, it is desirable to calculate Trm1 to Trmn by averaging, and n is preferably set to an integer multiple of the number of poles of the rotor magnet, that is, a value corresponding to an integer multiple of one revolution of the motor. This is because periodic speed fluctuations corresponding to one revolution of the motor can be averaged.

  In the apparatus to which the motor of FIG. 3B is attached, first, step driving is performed at a constant speed, and time Tsm1 to Tsmn (m = a) from +/− switching of yoke excitation to H / L switching of the sensor. Alternatively, b) is actually measured and averaged to calculate Tsm. It is desirable to set n to a value corresponding to an integral multiple of the number of poles of the rotor magnet, that is, an integral multiple of one revolution of the motor, as in the case of calculating Trm. If Tsm can be calculated, assuming that the constant angular velocity (rotational angular velocity) driven stepwise is ω [° / sec], the sensor deviation amount is specified by calculating with the equation θm = (Trm−Tsm) × ω. Can do.

  As described above, in this embodiment, since the sensor deviation amount is specified after being incorporated in the apparatus and reflected in the apparatus, the problems of the conventional method are solved. However, as will be described later, since the deviation amount is calculated and specified from the average angular velocity at the time of step driving, if the partial angular velocity is not constant, the accuracy of specifying the deviation amount tends to be poor.

  First, in the sensor deviation amount specifying method of the present embodiment, the reason why the deviation amount identification accuracy is poor unless the partial angular velocity is constant will be described. When the average angular velocity is known from the drive pulse period, the partial angular velocity is not constant because the rotation is performed with some variation in angular velocity even in step driving. The graph of FIG. 4 shows an example thereof, and the alternate long and short dash line indicates the average angular velocity, and the solid line indicates the actual angular velocity, which is drawn corresponding to the operation of the motor of FIG. As shown in the graph, the actual angular velocity fluctuates periodically and randomly. However, in this graph, the variation of the angular velocity is exaggerated than the actual one. In this example, since the partial angular velocities when actually measuring Tsa1 to Tsan used for calculating θa are all larger than the average angular velocities, applying the average angular velocities to ω in the equation θa = (Tra−Tsa) × ω θa is calculated to be smaller than the actual value. Conversely, the partial angular velocity when actually measuring Tsb1 to Tsbn used for calculating θb may be smaller or larger than the average angular velocity, but the average of the partial angular velocities is smaller than the average angular velocity. Therefore, when the average angular velocity is applied to ω in the equation θb = (Trb−Tsb) × ω, θb is calculated to be larger than the actual value. As a result, if the difference between the partial angular velocity and the average angular velocity is large and the angular velocity is not constant, the accuracy of specifying the deviation amount tends to be poor.

  Next, an example in which the angular velocity is not constant will be given. The first example is a case where speed unevenness due to so-called cogging is large when step driving is performed in a low speed region. In order to avoid such a state and make the angular velocity as constant as possible, it is necessary to specify the sensor displacement amount in a region where the velocity is as fast as possible. The second example is a case where a load fluctuation of a control target such as a cam or a lever driven by a motor is large. In order to avoid such a state and make the angular velocity as constant as possible, it is necessary to specify the sensor displacement amount in a region where the load fluctuation is as small as possible.

  However, a device to which a motor is attached is not always driven at a speed or load suitable for specifying a sensor deviation amount that can keep the angular velocity constant. Therefore, when the sensor displacement amount is specified in a state where the angular velocity is not constant, the above-described method tends to have a poor accuracy in identifying the sensor displacement amount. Therefore, in the sensor deviation amount specifying method of the present embodiment, it is premised that the tendency of specifying accuracy of the sensor deviation amount is poor, and the elimination method will be described below.

  FIG. 5 is a flowchart illustrating an example of motor control according to the present embodiment, which is executed by the motor control circuit 110. FIG. 6 is a schematic diagram of a gear train driven by the motor 101 of the present embodiment. In FIG. 6, 1 is a pinion gear fixed to the output shaft of the motor 101, 2 is a transmission gear that meshes with the pinion gear 1 and transmits driving force, and 3 is a driven gear that meshes with the transmission gear 2 and transmits driving force. A cam groove 3a is formed in the driven gear 3, and a cam pin 4 connected to a driving object such as a lever is engaged. In FIG. 6, for the sake of simplification, one transmission gear 2 is configured. However, in an actual transmission gear train, a large number of transmission gears are used to reduce the driving force of the motor 101. In addition, the controlled objects such as the motor body and lever are shown in a conceptual diagram, and the gears are drawn with a solid circle of the tip circle, a dashed circle with a one-dot chain line, and a bottom circle with a thin line based on a general drawing method. The rotation center axis and the like are omitted.

  In Step 1, the A phase coil 104a and / or the B phase coil 104b are energized for a certain period of time. This energization is a general operation called so-called initial holding energization, and is an operation for positioning the rotor magnet stopped in an arbitrary direction in a stopped state in a predetermined direction.

  In Step 2, the motor 101 is step-driven in the CW direction (first direction) by a step number N1 at a constant speed. The step drive of the motor 101 in the CW direction at Step 2 is an example of the first drive step, and the step number N1 is an example of the first step number.

  Here, the transmission gear train is generally provided with a so-called backlash (δ1, δ2 in FIG. 6). This is because without such a clearance, the transmission efficiency is lowered when the rotational drive is actually transmitted. For example, in the case of a plastic gear with a module 1.5 or less, the backlash amount is about 6 to 10% of the module. The Therefore, even if the motor starts rotating, the rotation of the gear C does not start immediately. After the motor starts rotating, the gear 2 starts rotating after the backlash δ1 between the pinion gear 1 and the transmission gear 2 is clogged, and after the transmission gear 2 starts rotating, the transmission gear 2 and the driven gear 3 After the backlash δ2 is clogged, the driven gear 3 starts to rotate. In this way, a backlash is always provided between the gears, and the motor does not lose its own weight during the rotation angle until the backlash between the pinion gear 1 and the transmission gear is resolved and all gears transmit drive. It can rotate with a light load that resists only the load caused by Hereinafter, an area that can be rotated with a light load caused by the backlash is simply referred to as a “backlash light load area”. At Step 2, the motor 101 is step-driven in the CW direction by the number of steps N1, so in the state after the execution of Step 2, the backlash of at least the number of steps N1 in the CCW direction between the pinion gear 1 and the driven gear 3 is performed. There will be a light load area.

  In Step 3, the motor 101 is step-driven in the CCW direction (second direction) by N2 steps at a constant speed. The step drive of the motor 101 in the CCW direction at Step 3 is an example of the second drive step, and the N2 step number is an example of the second step number. The number of N2 steps is set to the number of N1 steps below, that is, the number of steps equal to or less than the first step number. As described above, since the backlash light load region is at least during the N1 step, the motor 101 can rotate with a light load that resists only the load caused by the weight of the gear. Therefore, the motor 101 can rotate at a very high speed without load fluctuation.

  In Step 4, during the operation of Step 3, time intervals Tsa and Tsb between the excitation switching timing of the yoke and the switching timing of the sensor are measured. That is, the time intervals Tsa and Tsb are measured while the motor 101 is step-driven in the CCW direction by N2 steps at a constant speed. At this time, it is desirable to take an average of several actual measurements, and it is desirable to set the number to a value corresponding to an integer multiple of the number of poles of the rotor magnet, that is, an integral multiple of one revolution of the motor. In this backlash light load region, the motor 101 can rotate at a very high speed and without load fluctuations, so there is almost no difference between the partial angular velocity and the average angular velocity, and the motor 101 rotates at a substantially constant angular velocity.

  In Step 5, the amount of displacement of the sensor mounting position is calculated from the time difference between the measured values Tsa and Tsb of the time interval actually measured in Step 5 and the standard values Tra and Trb of the time intervals stored in advance. The calculation method is a second conventional method, and is calculated from an equation of deviation amount: θm = (Trm−Tsm) × ω (m = a or b). Since Tsa and Tsb are actually measured in Step 4 in the backlash light load region, the shift amounts θa and θb specified in Step 5 are specified with very high accuracy.

  As described above, in the motor driving method of the present invention, after performing the rotation (Step 2) for generating the backlash light load region, actual measurement at predetermined time intervals in the backlash light load region while performing reverse rotation. (Steps 3 to 4) are performed. In this way, it is possible to perform an operation for specifying the sensor displacement amount in the backlash light load region that is always guaranteed to rotate at a high speed and at a constant load. As a result, it is possible to apply feedback control by applying a highly accurate sensor displacement amount determination result, and it is possible to improve the accuracy and reliability of speed control and position control in feedback control.

  In addition, as the number of steps N1 is larger, the backlash light load region is secured in the reverse direction. In order to maximize the backlash light load area to be secured, it is desirable that the number of steps is more than a considerable number in the backlash light load area of the entire transmission gear train. On the other hand, if the number of steps N2 is too large, the backlash light load region ends, and other regions are reached. In order to specify the amount of sensor deviation only in the region where the angular velocity is constant, the number of steps must be less than or equal to the backlash light load region of the entire transmission gear train.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment when the present invention is implemented.

  The present invention has a motor provided with a position sensor for detecting the rotational position of the rotor magnet, and can accurately identify the displacement amount of the sensor after the device is assembled.

1 Pinion Gear 2 Gear 105a A Sensor 105b B Sensor 108 Energization Control Unit

Claims (2)

A motor and a detector for detecting the coil and the rotor magnet rotation position of the rotor magnet,
A pinion gear fixed to the output shaft of the motor;
A transmission gear meshing with the pinion gear;
By performing the energization switching of the coil, the motor is driven, and a control unit having a memory for storing the standard time from the energization switching of the coil to the output of the detector is changed,
The control unit causes the motor to step-drive in the first direction by a first number of steps corresponding to a driving amount until the backlash between the pinion gear and the transmission gear is resolved . The second step number equal to or less than the first step number is step-driven in a second direction opposite to the first direction, and the motor is step-driven in the second direction . A motor that measures the time from when the power is switched to when the output of the detector changes, and obtains the amount of mounting deviation of the detector from the difference between the standard time stored in the memory and the measured time Drive device. A motor including a coil, a rotor magnet, and a detector that detects a rotational position of the rotor magnet, a pinion gear fixed to the output shaft of the motor, a transmission gear meshing with the pinion gear, and energization switching of the coil And a control unit having a memory for storing a standard time from when the coil is energized to when the output of the detector changes, by driving the motor. And
After the motor is step-driven in the first direction by the first step number corresponding to the drive amount until the backlash between the pinion gear and the transmission gear is resolved, the motor is less than the first step number. The step is driven in a second direction opposite to the first direction by the number of second steps, and the detection is performed from switching the energization of the coil while the motor is step-driven in the second direction. A method for controlling a motor drive device, comprising: measuring a time until the output of a detector changes, and obtaining an attachment displacement amount of the detector from a difference between the standard time stored in the memory and the measured time .