JP6004830B2 - Control device and stepping motor control method - Google Patents

Description

  The present invention relates to a control device and a stepping motor control method.

  The stepping motor is mounted on, for example, an optical apparatus such as an imaging device, and various driving methods have been proposed. The stepping motor can easily obtain high resolution by open-loop control by microstep drive using a sine wave as a control waveform. Therefore, generally, a stepping motor driving method based on open loop control has been proposed.

  On the other hand, the stepping motor has a problem of stepping out during high-speed rotation. Therefore, there has been proposed an advance angle control technique in which a rotational position detection mechanism is provided to the stepping motor and the phase of the control waveform is advanced by a predetermined angle to rotate at a high speed without stepping out.

  For example, Patent Document 1 discloses a control technique that can be used by a control unit by switching a control mode of a stepping motor to two types of operation modes, a stepping mode that uses a two-phase stepping motor and a closed loop mode that uses a DC motor. . Patent Document 2 discloses a technique for controlling a motor at an arbitrary speed by previously measuring a maximum speed corresponding to an advance angle used in closed-loop control and performing advance angle control using the actually measured data. ing.

US Pat. No. 4,963,808 US Pat. No. 6,879,346

  However, in the technique of controlling the stepping motor at an arbitrary speed by the advance angle control, there is a problem that the response and linearity when the advance angle is changed are actually not good. Therefore, conventionally, in order to perform closed loop control using an advance angle, the effect of variations such as motor characteristics and mechanical loads connected to the motor is taken into account, and the advance angle according to the speed is individually measured to the device. It is necessary to store in advance and calculate an advance angle corresponding to the target speed based on the measurement result.

  Here, in the imaging apparatus that automatically focuses using the imaging sensor, the rotation speed of the stepping motor that controls the focus adjustment lens is determined according to the focal depth of the lens and the frame rate of the imaging sensor. Since the speed of the stepping motor required for the control differs depending on the focal length of the lens, the condition of the subject, etc., it is necessary to accurately control the stepping motor at an arbitrary speed. When conventional advance angle control is applied to a device that needs to be controlled at a constant speed at an arbitrary speed, such as the above-described imaging device, all the advance measurement data corresponding to the drive speed of the device is stored in the device. Must be memorized in advance. Therefore, in a device that needs to be controlled at a constant speed at an arbitrary speed, the advance angle control is rarely used.

  An object of the present invention is to provide a control device that controls the advance angle of a stepping motor accurately at an arbitrary speed without storing all the measurement data of the speed and the advance angle.

A control device according to an embodiment of the present invention includes a generation unit that generates a detection signal of a rotation position of a rotation unit of a stepping motor, and a motor that controls the rotation speed of the stepping motor at a timing according to the detection signal of the rotation position. Control means, and the motor control means is designated based on correspondence information between the advance angle and the rotation speed in a predetermined range of the rotation speed of the rotation unit, which is stored in advance in the storage means. Further, an advance angle calculating means for calculating an advance value of the control waveform according to the rotation speed of the rotating portion as a target advance angle, and an advance angle of the control waveform at the timing according to the detection signal of the rotation position is the target advance angle. Based on the correspondence information in the storage means, the advance angle control means for controlling the rotation position, the rotation speed detection means for detecting the rotation speed of the rotation portion in the generation period of the detection signal of the rotation position, Comprising a voltage control means for controlling the driving voltage of the stepping motor so that the speed deviation between the detected rotational speed rotational speed and by the rotational speed detecting means is in the range of a predetermined threshold value of the rotation portion which is The storage means uses the correspondence information as a linear approximation formula calculated based on a locus indicating a correspondence relationship between the advance angle and the rotation speed on a graph indicating a relationship between the advance angle and the rotation speed. The correspondence information stored and stored as the linear approximation formula is shifted according to the voltage value within a limited speed range .

  The control device of the present invention performs advance angle control of the stepping motor based on correspondence information between the advance angle and the drive speed within a predetermined drive speed range. Therefore, according to the present invention, it is possible to designate an arbitrary speed and perform the advanced speed control with high accuracy without storing all the measured values of the advance angle and the drive speed in the apparatus.

It is a figure which shows the structural example of this embodiment. It is a block diagram of a stepping motor unit. It is a flowchart explaining the example of an advance angle control process. It is a figure explaining the calculation process of target advance angle. It is a figure explaining the relationship between the advance angle and speed for every drive voltage. It is a figure explaining the example of an advance angle control process. It is a figure explaining the example of the speed control by voltage feedback. It is a flowchart explaining the detailed example of a drive voltage control process.

  FIG. 1 is a diagram illustrating a configuration example of the present embodiment. The control device 100 is a device that controls the stepping motor unit 200. The control device 100 controls the rotation of the stepping motor 101 while detecting the rotational position of the stepping motor 101. The control device 100 has a function of performing advance angle control using advance angle data corresponding to the rotation speed, and a function of performing speed control with a drive voltage. Specifically, the stepping motor unit 200 includes a stepping motor 101, a rotor 102, a pulse plate 105, and photo interrupters (hereinafter referred to as “PI”) 103 and 104.

  FIG. 2 is a configuration diagram of the stepping motor unit. The stepping motor unit 200 has a position detection function. An encoder having a pulse plate 105 on the rotor 102 of the stepping motor 101 provided in the stepping motor unit 200 will be described as an example. The pulse plate 105 is designed with a ratio of light area to dark area of 50:50. Two PIs 103 and 104 are attached at mechanically designed positions, and the pulse plate 105 changes the output signal of the PI as the rotor rotates. Here, the PI 103, 104 and the pulse plate 106 are combined to form a two-phase encoder.

  Returning to FIG. 1, the control device includes a comparator 106, an encoder circuit 107, a CPU 108, a sine wave generator 109, a PWM generator 111, and a motor driver 112. The comparator 106 receives the analog signal output from the PIs 103 and 104 and outputs a signal binarized by the set threshold voltage to the subsequent stage. That is, the comparator functions as a generating unit that generates a detection signal of the rotational position of the rotor that is the rotating part of the stepping motor. The signals obtained by binarizing the photo interrupter signal are respectively input to the encoder circuit 107 to acquire the rise and fall timings of the signal. In accordance with this timing, the encoder circuit 107 counts the motor position and the signal period.

  The encoder circuit 107 can interrupt the CPU 108 at the signal input timing. The CPU 108 has a function of executing a program stored in advance, and the program is sequentially executed according to interrupt processing. The CPU 108 also controls the encoder circuit 107, the sine wave signal generator 109, and the PWM generator 111 via the bus 110. The sine wave generator 109 sends a PWM value to the PWM generator 111 with a resolution corresponding to one cycle of the sine wave in accordance with an instruction from the CPU 108 and amplifies the PWM signal output from the PWM generator 111 by the motor driver 112. This is transmitted to the stepping motor 101.

  The motor driver 112 controls the output voltage according to the DUTY ratio (%) of PWM, and effectively applies a sinusoidal voltage signal to the motor coil. In the following, for simplicity of explanation, the voltage applied to the coil is treated as a sine wave. The rotation speed of the stepping motor 101 is controlled by applying the sinusoidal voltage signal. That is, the CPU 108, the sine wave generator 109, the PMW generator 111, and the motor driver 112 function as motor control means for controlling the rotation speed of the stepping motor at a timing according to the detection signal of the rotor.

  The A-phase coil 113 and the B-phase coil 114 included in the stepping motor 101 receive a sine wave signal emitted from the motor driver 112. The A-phase coil 113 and the B-phase coil 114 generate four types of sine wave voltages having different phases with respect to the subsequent stator A + 115, stator A-116, stator B + 117, and stator B-118. When the Sin wave and the Cos wave are output to the B-phase coil 114 to the A-phase coil 113, the B-phase has a waveform that is 90 degrees ahead of the A-phase, and the motor rotates forward. Conversely, if a waveform delayed 90 degrees from the A phase is output to the B phase, the motor reverses.

  Hereinafter, a case where the light-dark phase of the pulse plate 105 of the encoder is attached to the magnetization phase of the rotor magnet 119 will be described. If the amount of phase shift between the magnetizing phase of the rotor magnet 119 and the light / dark phase of the pulse plate 105 of the encoder is known in advance, the same control can be performed in consideration of the amount of phase shift.

  FIG. 3 is a flowchart for explaining the advance angle control processing of the stepping motor by the control device in the present embodiment. Assume that the stepping motor 101 is rotated at a specified speed S. The CPU 108 calculates a target advance angle θ corresponding to the designated speed S (step S100).

  FIG. 4 is a diagram illustrating the target advance angle calculation process in step S100 of FIG. FIG. 4A is a graph showing the relationship between the motor advance angle and speed at a predetermined drive voltage. Hereinafter, a locus indicating the relationship between the advance angle and the speed on the graph is described as an advance angle-speed characteristic curve. As the horizontal axis of the graph is advanced to the left and the advance angle is decreased, the driving speed is also reduced. The driving speed increases as the horizontal axis of the graph advances to the right and the advance angle increases. However, there is a feature that the driving speed is reduced when the predetermined advance angle is exceeded.

  Corresponding information (advance angle-velocity data) indicating the correspondence relationship between the advance angle and the speed is actually measured and tabulated, and stored in the control device, it is possible to drive by designating an arbitrary speed. However, the target advance value can be calculated. However, when the advance angle / velocity data is stored in the form of a table, the amount of data increases.

  Therefore, the control device according to the present embodiment stores advance angle-speed data within a limited speed range in advance in storage means (not shown), and calculates the target advance angle using the advance angle-speed data. . Thereby, the data amount used for target advance angle calculation is reduced.

  In the present embodiment, a region having a relatively high linearity in the advance angle / velocity data of FIG. 4A is linearly approximated to obtain a mathematical expression, and the obtained mathematical formula data (linear approximate expression) is stored in the storage unit. This is used to calculate the target advance angle θ in step S100 in FIG. Specifically, the advance angle-velocity data in a region where the linearity in the advance angle-speed characteristic curve is high within the controllable driving speed range is calculated by linear approximation and stored. That is, the CPU 108 calculates the advance value of the control waveform corresponding to the designated speed S based on the correspondence information between the advance angle and the rotation speed in a predetermined range of the rotation speed of the rotor, which is stored in advance in the storage unit. It functions as an advance angle calculation means for calculating as a target advance angle.

  FIG. 5 is a diagram illustrating the relationship between the advance angle and speed for each drive voltage. FIG. 5A shows the advance angle / velocity data measured for each drive voltage. When the drive voltage is changed within a predetermined range, the advance-velocity characteristic curve when the voltage is V0 is shifted according to the voltage value when the voltage is increased from the voltage V0 to the voltage V1 and the voltage V2. If the advance angle-speed data for each drive voltage is tabulated and stored in the apparatus, the target advance angle value can be obtained even when driving is performed by designating an arbitrary speed or drive voltage. Can be calculated. However, if the advance angle / velocity data for each drive voltage is tabulated, the amount of data increases.

  Therefore, the control device of the present embodiment stores advance angle-speed data corresponding to each of a plurality of predetermined drive voltages within a limited speed range in the storage means in advance. The drive voltage is controlled using the angle-speed data to control the rotation speed of the motor. Thereby, the data amount used for control of the rotational speed of the motor is reduced. The control of the rotation speed is executed in steps S105 and S106 in FIG. 3, and details thereof will be described later with reference to FIG.

  FIG. 5B is a diagram illustrating an example in which a region where the linearity of the advance angle-velocity data at each drive voltage in FIG. As shown in FIG. 4B, the controllable drive speed and the advance angle that can be set are limited, but the controllable range of the speed and advance angle can be controlled by combining approximate expressions of advance angle-speed data with different drive voltages. It is possible to spread. That is, according to the control device of the present embodiment, it is possible to control the driving speed even if the voltage is changed with a predetermined advance angle or the advance angle is changed with a predetermined voltage. Further, since the relationship between the advance angle and the speed data according to the drive voltage is a relationship shifted up and down, the characteristic according to the voltage can be expressed by an intercept of an approximate expression. As a result, the amount of advance-speed data corresponding to the voltage can be reduced.

  Returning to FIG. 3, the CPU 108 calculates the phase delay angle ω by detecting the rotational position of the motor in synchronization with the interrupt signal of the encoder obtained from the encoder circuit 107 (step S <b> 101). The calculated phase delay angle ω is caused by the counter electromotive force of the rotating motor.

  Next, the CPU 108 sets the phase deviation ω−θ between the phase delay angle ω and the target advance angle θ calculated in step S100 as a control advance angle (step S102). Then, the CPU 108 controls the drive waveform so as to compensate for the phase deviation ω−θ, and performs advance angle control so as to maintain the advance angle θ state (step S103). Specifically, the CPU 108 sets the waveform phase of the sine wave generator 109 so that the phase deviation ω−θ is advanced by the phase deviation ω−θ by the timing at which the interrupt signal of the next encoder is generated. Control. That is, the CPU 108 functions as an advance angle control unit that controls the advance angle of the control waveform to be the target advance angle at a timing according to the detection signal of the rotational position of the rotor.

  FIG. 6 is a diagram illustrating an example of the advance angle control process in step S103 of FIG. FIG. 6A shows an output waveform of an encoder signal attached to the rotor shaft 102 of the stepping motor 101. The CPU 108 performs phase detection and phase control of the drive waveform at the timing when the encoder switches between light and dark.

  FIG. 6B is a diagram illustrating an example of a drive waveform when the advance angle is 0 degree. FIG. 6C shows an example of a driving waveform at the time of driving by open loop control, and shows that the phase is delayed as compared with the waveform of FIG. 6B. FIG. 6D shows a drive waveform when the control is switched from the open loop control of FIG. 6C to the advance angle control.

  The waveform shown in FIG. 6B shows an ideal drive waveform (lead angle 0 degree) with no current delay. The waveform shown in FIG. 6C shows a drive waveform at the time of open loop control. Referring to the waveform shown in FIG. 6C, the phase delay is Cn at the timing In switching from light to dark in FIG. 6A, and the phase delay of Cn + 1 is generated at the timing In + 1 after ¼ period. I understand.

  As shown in FIG. 6D, when switching from open loop control to advance angle control at timing In, the CPU 108 cycles the control waveform so that the control waveform becomes the target phase after ¼ cycle (In + 1). To control. For example, if the target phase is an advance angle of 0 degrees, the CPU 108 performs control so that the period of the control waveform is changed in a quarter period so that the phase delay Dn + 1 becomes 0 degrees. If the phase of the control waveform is advanced immediately after the timing In, the waveform becomes discontinuous, which causes problems such as motor vibration, abnormal noise, and step-out. Therefore, in this example, the CPU 108 controls the period of the control waveform so that the phases are matched in a predetermined period (for example, a quarter period) in which no problem occurs. The advance angle control has been described with reference to FIG. 6 in which the advance angle control is performed so that the advance angle is 0 degrees. However, when the advance angle control is performed so that the phase delay remains by δ, The advance angle control may be performed with the advance angle δ.

  Returning to FIG. 3, simultaneously with the execution of the above-described advance angle control, the CPU 108 executes speed control by voltage feedback and controls the rotation speed of the stepping motor 101 so as to be the designated speed S. Specifically, the CPU 108 measures the detection interval of the interrupt signal of the encoder and calculates the rotation speed of the stepping motor 101 (step S105). That is, the CPU 108 functions as a rotation speed detection unit that detects the rotation speed of the rotor in the generation cycle of the detection signal of the rotation position of the rotor. Then, the CPU 108 reflects the deviation amount between the rotation speed calculated in step S105 and the target speed S in the drive voltage, and controls the rotation speed of the motor (step S106). The feedback control of the advance angle and drive speed described above is performed in synchronization with the interrupt signal of the encoder.

  FIG. 7 is a diagram for explaining an example of speed control by voltage feedback. A steady driving voltage when driving the stepping motor at a predetermined target speed is set to V0. V0 is a drive voltage that is the median value of the control range of the drive voltage set by the CPU. In this example, it is assumed that mathematical formula data corresponding to the advance / velocity data at the time of V0 is stored in the storage means. The CPU 108 extracts mathematical formula data corresponding to the advance angle / velocity data at the drive voltage V0 from the storage means.

  The CPU 108 calculates an advance value corresponding to the target speed based on the extracted mathematical formula data. When the CPU 108 performs advance angle control so as to achieve the calculated advance angle, the motor rotates at a speed near the target speed with the steady drive voltage V0. At this time, the actual motor drive speed is calculated in step S105 of FIG. 3, and if there is a deviation from the target speed, the drive speed is controlled by changing the drive voltage (step S106). That is, the CPU 108 makes a speed deviation between the designated speed S and the rotational speed calculated in step S105 based on mathematical formula data corresponding to the advance angle-speed data in the storage means within a predetermined threshold range. It functions as voltage control means for controlling the drive voltage.

  Here, when the speed control of the motor by the drive voltage is performed, a limit range is set for the drive voltage for reasons such as system power design. In the example shown in FIG. 7, the upper limit voltage is α and the lower limit voltage is β. The CPU 108 controls the motor so as to achieve the target speed while changing the drive voltage between α and β. As described above, the control device of the present embodiment can perform speed control at an arbitrary speed while using high-speed driving that cannot be performed by open-loop control by using both advance angle control and speed control by voltage. . Furthermore, since variations such as environmental temperature and individual differences can be absorbed within the voltage control range, high-accuracy speed control that is difficult to achieve with only measured advance-speed data is possible.

  Returning to FIG. 3, the CPU 108 determines whether there is a stop instruction (step S104). If there is no stop instruction, the process returns to step S101 to repeat a series of processes. When there is a stop instruction, the CPU 108 stops the stepping motor 101.

  FIG. 8 is a flowchart for explaining a detailed example of the drive voltage control process in the present embodiment. Steps S104 and S105 in FIG. 8 are the same as steps S104 and S105 in FIG.

  First, the CPU 108 starts driving the motor drive voltage at the steady drive voltage V0 (step S300). Subsequently, the CPU 108 calculates the driving speed of the rotor 119 from the detection interval of the detection signal of the encoder attached to the motor (step S105).

  Next, the CPU 108 determines whether or not the detected rotational speed of the rotor is within the target speed range, that is, whether or not the speed deviation between the detected rotational speed of the rotor and the target speed is within the threshold range ( Step S301). When the CPU 108 determines that the detected rotation speed of the rotor is within the target speed range, the CPU 108 continues to monitor the rotor drive speed from the detection period until the detection signal of the next encoder. When the CPU 108 determines that the detected rotational speed of the rotor is not within the target speed range, the CPU 108 converts the speed deviation from the target speed into the voltage Vd and reflects it in the immediately preceding drive voltage Vn (step). S302). Specifically, the drive voltage V = Vn + Vd. That is, when the speed deviation is not within a predetermined threshold range, the CPU 108 refers to the advance angle-speed data stored in the storage means and sets the drive voltage to a voltage value within which the speed deviation is within the threshold range. Change to

  Next, the CPU 108 determines whether or not the calculated drive voltage V is within the limit range of the drive voltage. When the drive voltage V is higher than the upper limit voltage α, the drive voltage is set to α, and when the drive voltage V is lower than the lower limit voltage β. The drive voltage is β (step S303).

  Next, the CPU 108 changes the calculated drive voltage V at the timing when the detection signal of the next encoder is detected (step S304). The CPU 108 further performs speed control using the drive voltage by repeating a series of operations for obtaining a speed deviation from the target speed from the drive speed during the period until the detection signal of the encoder detected next. If there is a stop instruction, the motor is de-energized from the motor driver and the motor is stopped (Yes in S104). According to the control device of the present embodiment described above, it is possible to perform advance speed control with high accuracy by designating an arbitrary speed without storing all measured values of advance angle and drive speed in the apparatus. .

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed. In this case, the program and the storage medium storing the program constitute the present invention.

DESCRIPTION OF SYMBOLS 100 Control apparatus 101 Stepping motor 102 Rotor shaft 103,104 Photo interrupter 105 Pulse plate 106 Comparator 107 Encoder circuit 108 CPU
109 Sine Wave Generator 110 Bus 111 PWM Generator 112 Motor Driver

Claims (4)

Generating means for generating a detection signal of the rotational position of the rotating part of the stepping motor;
Motor control means for controlling the rotational speed of the stepping motor at a timing according to the detection signal of the rotational position;
The motor control means includes
A control waveform corresponding to the specified rotation speed of the rotation unit based on correspondence information between the advance angle and the rotation speed in a predetermined range of the rotation speed of the rotation unit, which is stored in advance in a storage unit An advance angle calculating means for calculating the advance value of the target advance angle;
Advance angle control means for controlling the advance angle of the control waveform at the timing according to the detection signal of the rotational position to be the target advance angle;
Rotational speed detection means for detecting the rotational speed of the rotating part at a generation cycle of the detection signal of the rotational position;
Based on the correspondence information in the storage means, the speed deviation between the designated rotational speed of the rotating part and the rotational speed detected by the rotational speed detecting means is within a predetermined threshold range. Voltage control means for controlling the driving voltage of the stepping motor ,
The storage means stores the correspondence information as a linear approximation formula calculated based on a locus indicating a correspondence relationship between the advance angle and the rotation speed on a graph indicating a relationship between the advance angle and the rotation speed. And
The correspondence information stored as the linear approximation equation is shifted according to a voltage value within a limited speed range . Before KiSusumu angle calculation unit, when the speed deviation is not within range of a predetermined threshold value, by referring to the correspondence information stored in the storage means, the speed deviation the driving voltage of the stepping motor The control device according to claim 1, wherein the control device changes the voltage value to fall within the threshold range. Wherein the correspondence information in the predetermined range of rotational speed of the rotating part, the control device according to claim 1 or 2, characterized in that a mathematical expression data indicating a correspondence relationship between the advance angle and the rotational speed. A stepping motor control method comprising:
A generation step of generating a detection signal of the rotational position of the rotating part of the stepping motor;
A motor control step of controlling the rotational speed of the stepping motor at a timing according to the detection signal of the rotational position,
The motor control process includes
A control waveform corresponding to the specified rotation speed of the rotation unit based on correspondence information between the advance angle and the rotation speed in a predetermined range of the rotation speed of the rotation unit, which is stored in advance in a storage unit An advance angle calculation step of calculating the advance value of the target advance angle;
An advance angle control step of controlling the advance angle of the control waveform to be the target advance angle at a timing according to the detection signal of the rotational position;
A rotational speed detecting step of detecting a rotational speed of the rotating portion at a generation cycle of the detection signal of the rotational position;
Based on the correspondence information in the storage means, the speed deviation between the rotation speed of the designated rotating unit and the rotation speed detected by the rotation speed detection step is within a predetermined threshold range. It has a voltage control step of controlling the driving voltage of the stepping motor,
The storage means stores the correspondence information as a linear approximation formula calculated based on a locus indicating a correspondence relationship between the advance angle and the rotation speed on a graph indicating a relationship between the advance angle and the rotation speed. And
The correspondence information stored as the linear approximation formula is shifted according to a voltage value within a limited speed range .

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