JP2016129448A - Motor driving circuit, motor driving method, and program for motor driving - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor driving circuit capable of reducing the vibration generated at a prescribed speed in stepping motor driving.SOLUTION: A motor driving circuit 110 comprises a speed determination unit 122, an excitation system selection unit 124, a driving signal generation unit 126, and a driving unit 128. The speed determination unit 122 determines a speed related to the amount of driving per unit time of the stepping motor driven by any of a plurality of excitation systems. The excitation system selection unit 124 selects one excitation system from the plurality of excitation systems as a driving excitation system on the basis of the determined speed. The driving signal generation unit 126 generates a driving signal corresponding to the speed according to the driving excitation system. The driving unit 128 drives the stepping motor by a driving signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor drive circuit, a motor drive method, and a motor drive program.

  In general, a stepping motor that rotates by a predetermined step unit when a pulse signal is input is known. In the stepping motor, the rotation angle and the rotation speed are controlled by the number of input pulses and the frequency of the input pulses. For this reason, the control of the stepping motor is relatively easy. A stepping motor is a kind of brushless motor, and has a feature of high reliability and long life.

  Various techniques for reducing vibration in the operation of a stepping motor have been proposed. For example, in Patent Document 1, when a stepping motor is started, vibration caused by a gap generated between a drive gear fixed to the rotation shaft of the stepping motor and a transmission gear meshing with the drive gear is reduced. Techniques for disclosing are disclosed. That is, in the technique according to Patent Document 1, when starting with a gap between the drive gear and the transmission gear, an excitation method with a small output torque and a high resolution is used, and after the gap is eliminated, the resolution is low. The operation of the stepping motor is controlled using an excitation method with a large output torque.

  Further, for example, Patent Document 2 discloses a technique for reducing vibration caused by a torque difference between each winding of a stepping motor. That is, in the technique according to Patent Document 2, the vibration of the stepping motor is detected, and the excitation current supplied to each winding is controlled so as to reduce the vibration.

JP 2006-106209 A Japanese Patent Laid-Open No. 10-290598

  In general, vibration is likely to occur at a predetermined frequency according to the vibration characteristics of the structure, and vibration may not easily occur at other frequencies. That is, even in a stepping motor, vibration may increase at a predetermined speed.

  It is an object of the present invention to provide a motor driving circuit, a motor driving method, and a motor driving program that can reduce vibration generated at a predetermined speed in driving a stepping motor.

  According to an aspect of the present invention, the motor drive circuit includes a speed determination unit that determines a speed that is a value related to a drive amount per unit time of a stepping motor driven by any of a plurality of excitation methods, and the speed An excitation method selection unit that selects one excitation method from among the plurality of excitation methods as a drive excitation method, and a drive signal generation unit that generates a drive signal according to the speed according to the drive excitation method, And a drive unit for driving the stepping motor by the drive signal.

  According to one aspect of the present invention, a method for driving a motor includes determining a speed that is a value related to a driving amount per unit time of a stepping motor driven by any of a plurality of excitation methods, And selecting one excitation method from among the plurality of excitation methods as a drive excitation method, generating a drive signal according to the speed according to the drive excitation method, and using the drive signal to generate the stepping signal. Driving the motor.

  According to one aspect of the present invention, a program for driving a motor determines a speed that is a value related to a driving amount per unit time of a stepping motor driven by any of a plurality of excitation methods, Selecting one excitation method as a drive excitation method from among the plurality of excitation methods based on the speed, generating a drive signal according to the speed according to the drive excitation method, and depending on the drive signal Driving the stepping motor is executed by a computer.

  According to the present invention, it is possible to provide a motor driving circuit, a motor driving method, and a motor driving program capable of reducing vibrations generated at a predetermined speed in driving a stepping motor.

The block diagram which shows the outline of the structural example of the endoscope system which concerns on 1st Embodiment. The timing chart for demonstrating a full step and a half step about an excitation system. The schematic diagram for demonstrating operation | movement of the stepping motor in the case of a full step. The schematic diagram for demonstrating operation | movement of the stepping motor in the case of a half step. The figure for demonstrating the change of the rotational speed of a stepping motor. 5 is a flowchart illustrating an example of a motor drive process according to the first embodiment. The block diagram which shows the outline of the structural example of the endoscope system which concerns on 2nd Embodiment. The flowchart which shows an example of operation | movement of the endoscope system which concerns on 2nd Embodiment. The flowchart which shows an example of the switching speed determination process which concerns on 2nd Embodiment.

[First Embodiment]
An endoscope system according to a first embodiment will be described with reference to the drawings. FIG. 1 is a diagram illustrating an outline of a configuration example of an endoscope system 10 according to the present embodiment. The endoscope system 10 includes a rigid endoscope 210, a camera head 220, a camera control unit 100, a light source device 260, and a display device 270.

  The rigid endoscope 210 is a general rigid endoscope. The rigid endoscope 210 is a medical rigid endoscope used for, for example, laparoscopic surgery. The rigid mirror 210 may be an industrial rigid mirror. For example, the rigid mirror 210 has an elongated metal tube, an objective lens portion is provided at the distal end portion of the metal tube, an eyepiece lens portion is provided at the proximal end side, and the objective lens portion is disposed between the eyepiece lens portion and the eyepiece lens portion. Is provided with a relay lens portion. The rigid endoscope 210 forms an image of the observation object on the distal end side on the eyepiece lens unit side. Further, an illumination window is provided at the distal end portion of the rigid endoscope 210. A light guide for guiding illumination light emitted from the illumination window is provided along the longitudinal axis of the rigid mirror 210 inside the rigid mirror 210.

  The camera head 220 is attached to the eyepiece part of the rigid mirror 210. The camera head 220 captures an image that has passed through the eyepiece of the rigid endoscope and generates an image signal. The camera head 220 outputs the acquired image signal to the camera control unit 100.

  The camera head 220 includes an imaging unit 222, a lens unit 224, and a stepping motor 230. The imaging unit 222 includes an imaging element. The imaging unit 222 captures an image that has passed through the rigid endoscope 210 and generates an image signal. The lens unit 224 forms an optical image on the imaging element of the imaging unit 222 for the image that has passed through the rigid endoscope 210. The lens unit 224 may include a plurality of lenses. The lens unit 224 includes a focus lens that moves in the optical axis direction for focusing. The stepping motor 230 displaces the focus lens of the lens unit 224 in the optical axis direction.

  The light source device 260 is a light source for illumination light emitted from the distal end portion of the rigid mirror 210. The light emitted from the light source device 260 is guided to the distal end portion of the rigid mirror 210 via the light guide in the rigid mirror 210 and is emitted from the illumination window of the rigid mirror 210.

  The camera control unit 100 controls the operation of the camera head 220. The camera control unit 100 includes a motor drive circuit 110, an image processing unit 152, and an AF control unit 154.

  The image processing unit 152 performs general image processing on the image signal acquired by the imaging unit 222. The image processing unit 152 outputs the processed image signal to the display device 270 and causes the display device 270 to display an image. The AF control unit 154 acquires information related to the image signal acquired by the imaging unit 222 from the image processing unit 152 and performs a calculation related to autofocus (AF) of the camera head 220. That is, the AF control unit 154 calculates how much the focus lens included in the lens unit 224 should be moved in which direction. The AF control unit 154 may perform an AF calculation based on the contrast of the image, or may perform an AF calculation based on a method using a phase difference, for example.

  The motor drive circuit 110 is a circuit for driving the stepping motor 230. The motor drive circuit 110 includes a speed determination unit 122, an excitation method selection unit 124, a drive signal generation unit 126, a drive unit 128, and a switching speed storage unit 130.

  The speed determination unit 122 determines a rotation direction and a rotation speed for the stepping motor 230 to operate based on the calculation result of the AF control unit 154. Here, the rotational speed means a driving amount of the stepping motor per unit time. For example, when the speed determination unit 122 acquires information that the lens should be moved in the closest direction from the AF control unit 154, the speed determination unit 122 determines to move the currently stationary lens in the close direction. Further, at this time, the speed determination unit 122 performs a determination that, for example, the moving speed of the lens is gradually increased and is moved at a constant speed when a predetermined moving speed is reached.

  The excitation method selection unit 124 drives one of the excitation methods from among a plurality of excitation methods using the information stored in the switching speed storage unit 130 based on the rotational speed determined by the speed determination unit 122. Select as excitation method. Here, examples of the plurality of excitation methods include full-step driving and half-step driving. Full step driving and half step driving will be described with reference to the drawings.

  FIG. 2 shows on / off switching of the A phase, B phase, / A phase, and / B phase of the stepping motor 230. Here, / A indicates the inverted logic of A. The diagram shown in the upper part (A) of FIG. 2 shows a timing chart in the case of full-step driving. Two widths separated by a broken line are one step, and one step is four steps. The diagram shown in the lower part (B) of FIG. 2 shows a timing chart in the case of half-step driving. One width divided by a broken line is one step, and eight steps constitute one cycle.

  FIG. 3 is a schematic diagram for explaining the operation of the stepping motor in the case of full-step driving. FIG. 3 shows that one cycle consists of four steps. (1) to (4) in FIG. 3 correspond to (1) to (4) shown in the upper part (A) of FIG. FIG. 4 is a schematic diagram for explaining the operation of the stepping motor in the case of half-step driving. FIG. 4 shows that one cycle consists of 8 steps. (1) to (8) in FIG. 4 correspond to (1) to (8) shown in the lower part (B) of FIG. Thus, in the case of half step driving, the step angle is smaller than in the case of full step driving.

  As shown in the upper part (A) of FIG. 2, in the full step drive, each phase is excited continuously for two steps and excited while being shifted by one step from the next phase. Therefore, two phases are excited in any period. For this reason, full-step driving generates a larger torque than half-step driving.

  As shown in the lower part (B) of FIG. 2, in the half step drive, each phase is excited continuously for 3 steps, and is excited while being shifted by 2 steps from the next phase. Therefore, a period in which two phases are excited, a period in which one phase is excited, and a period in which two phases are excited are sequentially provided. According to half-step driving, the step angle is smaller than that of full-step driving, and resonance can be suppressed.

  In addition, the step angle of the stepping motor 230 can be designed to an arbitrary value as appropriate.

  Returning to FIG. 1, the description will be continued. The switching speed storage unit 130 stores information as to whether or not full-step driving should be performed or half-step driving for each rotation speed of the stepping motor as switching determination information. Switching between full-step driving and half-step driving will be described with reference to FIG. FIG. 5 shows an example of a change in rotational speed determined by the speed determination unit 122. For example, the rotation speed is controlled to gradually increase from r0, controlled to operate at a constant speed at r3, and then controlled to gradually decrease to r0. Here, if full step driving is always performed, vibration larger than the threshold value occurs when the rotational speed is between r1 and r2, and as a result, noise is generated. The vibration state of the device changes for each frequency (rotational speed) according to the frequency characteristics related to the vibration of the device. In the case shown in FIG. 5, the full-step drive with a large torque is operated from r0 to r1, the half-step drive with a small vibration from r1 to r2, and the full-step drive with a large torque from r2 to r3. By operating, both a large torque and low noise can be achieved. Therefore, the switching speed storage unit 130 should operate with full step drive from r0 to r1, for example, operate with half step drive from r1 to r2, and perform full step drive from r2 to r3. It is stored that it should operate.

  The drive signal generator 126 generates a drive signal according to the excitation method selected by the excitation method selector 124. For example, a signal as shown in the upper part (A) or lower part (B) of FIG. 2 is generated. The drive unit 128 is a drive circuit for the stepping motor 230 and drives the stepping motor 230 according to the drive signal.

  As described above, the motor drive circuit 110 includes a central processing unit (CPU), an application specific integrated circuit (ASIC), and the like, and performs various calculations. The operation of the motor drive circuit 110 can be performed according to a program recorded in a recording unit (not shown).

  The display device 270 is a general display device such as a liquid crystal display. The display device 270 displays an image captured by the camera head 220 and subjected to image processing by the camera control unit 100. Further, the display device 270 may display the state of the camera control unit 100, information related to the operation of the camera control unit 100, and the like.

  Next, an example of the motor driving process will be described with reference to the flowchart shown in FIG.

  In step S101, the speed determination unit 122 determines the rotation direction and rotation speed of the stepping motor.

  In step S102, the excitation method selection unit 124 determines whether or not full-step driving should be performed using the switching determination information. When full-step driving is to be performed, the process proceeds to step S103. In step S <b> 103, the drive signal generation unit 126 generates a full-step drive signal and outputs it to the drive unit 128. Thereafter, the process proceeds to step S105.

  When it is determined in step S102 that full-step driving should not be performed, that is, when it is determined that half-step driving should be performed, the process proceeds to step S104. In step S <b> 104, the drive signal generation unit 126 generates a half-step drive signal and outputs it to the drive unit 128. Thereafter, the process proceeds to step S105.

  In step S <b> 105, the drive unit 128 applies a voltage to the stepping motor 230 based on the drive signal generated by the drive signal generation unit 126. As a result, the stepping motor 230 operates.

  According to the present embodiment, since the half-step drive is selected in the rotational speed band where vibration and noise are large, noise during driving of the stepping motor 230 is reduced. Since full-step driving is selected in a rotational speed band where vibration and noise are not large, high torque can be obtained.

  Note that the stepping motor according to the present embodiment can also be applied to lens driving of a flexible electronic endoscope. Further, the stepping motor is not limited to lens driving, and can be used for driving various driving parts. The stepping motor is not limited to a rotary type, and the same applies to a linear stepping motor.

  Further, the present invention is not limited to switching between full-step drive and half-step drive, and other methods such as microstep may be used. However, the configuration in which full-step driving and half-step driving are selectively used as in the present embodiment is preferable because the circuit configuration of the driving unit 128 is easy.

[Second Embodiment]
A second embodiment will be described. Here, differences from the first embodiment will be described, and the same portions will be denoted by the same reference numerals and description thereof will be omitted. FIG. 7 shows an outline of a configuration example of the endoscope system 10 according to the present embodiment. In the endoscope system 10 of the present embodiment, in addition to the configuration of the endoscope system 10 according to the first embodiment, a state detection unit 242 is provided in the camera head 220, and a switching speed determination unit is provided in the motor drive circuit 110. 142 is provided.

  The state detection unit 242 detects the state of the stepping motor 230. In particular, the state detection unit 242 detects a vibration state of the stepping motor 230 and a state related to noise generated by the vibration. That is, the state detection unit 242 is a piezoelectric vibration sensor, for example, and detects the vibration of the stepping motor 230. Further, the state detection unit 242 may be a microphone, for example. According to the state detection unit 242 that is a microphone, the noise of the stepping motor 230 can be detected. In this case, the microphone as the state detection unit 242 may be disposed in the camera head 220 or may be disposed outside the camera head 220. Further, vibration of the stepping motor 230 may be detected based on an image acquired by the imaging unit 222. In this case, the part that detects image blur functions as the state detection unit 242. In this case, the state detection unit 242 can be arranged not in the camera head 220 but in the camera control unit 100.

  The switching speed determination unit 142 acquires information related to the rotation speed of the stepping motor 230 from the speed determination unit 122, and acquires information related to vibration of the stepping motor 230 at the rotation speed from the state detection unit 242. Based on these pieces of information, the switching speed determination unit 142 determines whether full step driving or half step driving should be selected for each rotation speed, and stores that information as switching determination information. Stored in the unit 130.

  An example of the operation of the motor drive circuit 110 according to the present embodiment will be described with reference to the flowchart shown in FIG. This operation is started when the motor drive circuit 110 is started, for example.

  In step S201, the motor drive circuit 110 performs a switching speed determination process. In other words, in the present embodiment, when the endoscope system 10 is activated, a switching speed determination process is first performed. The switching speed determination process is the following process. That is, the motor driving circuit 110 rotates the stepping motor 230 while changing the rotation speed by full-step driving, and acquires information related to the vibration of the stepping motor 230 at that time. The motor drive circuit 110 determines and stores whether to perform full step drive or half step drive for each rotation speed based on the rotation speed and vibration at that time.

  In step S202, the motor drive circuit 110 performs a motor drive process. The motor drive process is the same process as the motor drive process according to the first embodiment described with reference to FIG. In this motor driving process, information about whether to perform full step driving or half step driving determined in the switching speed determination process in step S201 is used.

  An example of the switching speed determination process will be described with reference to the flowchart shown in FIG.

  In step S301, the speed determination unit 122 sets the rotation speed of the stepping motor 230. In step S <b> 302, the switching speed determination unit 142 acquires the rotation speed of the stepping motor 230 from the speed determination unit 122. In step S <b> 303, the switching speed determination unit 142 acquires information related to the vibration state of the stepping motor 230 from the state detection unit 242.

  In step S304, the switching speed determination unit 142 determines whether the vibration of the stepping motor 230 is smaller than a predetermined threshold value. When the vibration is smaller than the threshold value, the process proceeds to step S305. In step S305, the switching speed determination unit 142 determines that full step driving should be performed at the current rotational speed. Thereafter, the process proceeds to step S307.

  In step S304, when the vibration is equal to or greater than the threshold value, the process proceeds to step S306. In step S306, the switching speed determination unit 142 determines that half step driving should be performed at the current rotational speed. Thereafter, the process proceeds to step S307.

  In step S307, the switching speed determination unit 142 causes the switching speed storage unit 130 to store the relationship between the excitation method selected from the full step driving and the half step driving and the rotation speed.

  In step S308, the switching speed determination unit 142 determines whether or not to end the process, that is, whether or not the relationship between the rotation speed and the excitation method has been obtained for all the rotation speeds that the stepping motor 230 can take. If not, the process returns to step S301, and the above-described process is performed by changing the rotation speed. On the other hand, when the process ends, the switching speed determination process ends, and the process returns to the process described with reference to FIG.

  According to the present embodiment, even if the vibration characteristics of the stepping motor 230 change due to aging or usage environment, the vibration characteristics are acquired every time the power is turned on. As a result, even if the vibration characteristic of the stepping motor 230 changes, an optimal excitation method that suppresses vibration can be selected.

  It should be noted that the switching speed determination process may not be performed every time of activation. It may be performed only once every several activations. Moreover, it may only be performed at the time of manufacture. Moreover, it may be performed many times during one activation.

[Modification]
In the second embodiment, the rotation speed and the excitation method to be used are stored in the switching speed storage unit 130. The excitation method selection unit 124 selects an excitation method based on this information. On the other hand, the excitation method may always be selected based on the output of the state detection unit 242. That is, in the motor driving process, the switching speed determination unit 142 continuously acquires information related to the vibration of the stepping motor 230 from the state detection unit 242. The switching speed determination unit 142 determines whether or not the current vibration exceeds a threshold value, and outputs the determination result to the excitation method selection unit 124. The excitation method selection unit 124 selects half-step driving when the current vibration exceeds the threshold value, and selects full-step driving when the current vibration does not exceed the threshold value.

  According to this modification, when the vibration state can change even at the same rotation speed, the excitation method can be appropriately selected according to the actual vibration state.

  DESCRIPTION OF SYMBOLS 10 ... Endoscope system, 100 ... Camera control unit, 110 ... Motor drive circuit, 122 ... Speed determination part, 124 ... Excitation system selection part, 126 ... Drive signal generation part, 128 ... Drive part, 130 ... Switching speed memory | storage part , 142 ... switching speed determination unit, 152 ... image processing unit, 154 ... AF control unit, 210 ... rigid endoscope, 220 ... camera head, 222 ... imaging unit, 224 ... lens, 230 ... stepping motor, 242 ... state detection unit, 260: Light source device, 270: Display device.

Claims (8)

A speed determining unit that determines a speed that is a value related to a driving amount per unit time of a stepping motor driven by any of a plurality of excitation methods;
An excitation method selection unit that selects one excitation method as a drive excitation method from the plurality of excitation methods based on the speed;
A drive signal generator for generating a drive signal according to the speed according to the drive excitation method;
A motor drive circuit comprising: a drive unit that drives the stepping motor by the drive signal. A storage unit that stores switching determination information that is a relationship between the speed and the drive excitation method to be selected for the speed;
The excitation method selection unit selects the drive excitation method based on the switching determination information.
The motor drive circuit according to claim 1. A switching determination unit that creates switching determination information that is a relationship between the speed and the drive excitation method to be selected for the speed based on the information related to vibration of the stepping motor and the speed,
The excitation method selection unit selects the drive excitation method based on the switching determination information.
The motor drive circuit according to claim 1.   The motor drive circuit according to claim 3, further comprising a storage unit that stores the switching determination information.   The excitation method selection unit selects a first excitation method with a large step angle at the speed at which the vibration of the stepping motor is small, and a second excitation with a small step angle at the speed at which the vibration of the stepping motor is large. The motor drive circuit according to claim 1, wherein a system is selected.   The motor drive circuit according to claim 5, wherein the first excitation method is a full-step drive excitation method, and the second excitation method is a half-step drive excitation method. Determining a speed that is a value related to a driving amount per unit time of a stepping motor driven by any of a plurality of excitation methods;
Selecting one excitation method as the drive excitation method from the plurality of excitation methods based on the speed;
Generating a drive signal according to the speed according to the drive excitation method;
Driving the stepping motor with the drive signal. Determining a speed that is a value related to a driving amount per unit time of a stepping motor driven by any of a plurality of excitation methods;
Selecting one excitation method as the drive excitation method from the plurality of excitation methods based on the speed;
Generating a drive signal according to the speed according to the drive excitation method;
A motor driving program for causing a computer to execute the stepping motor in response to the driving signal.

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