JP2006211879A - Information processing apparatus and motor controlling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information processing apparatus and a motor controlling method, which prevent noise, vibration, step-out produced when an stepping motor is driven by switching between drive processes of the stepping motor in the optimal switching timing specific to the motor. <P>SOLUTION: Noise conditions, vibration conditions and the like of a stepping motor having a plurality of phases (for example, three-phase) that drives drive system equipment are measured, and a drive process of the stepping motor is switched, for example, to 1- and 2-phase excitation processes in a low speed rotation range, or 2-phase excitation process in a high speed rotation range, with a switching timing detected according to the measured values. Thereby, a drive process can be switched to the optimal timing specific to the motor according to the conditions of a motor used for an information processing apparatus. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a stepping motor control technique for driving a drive system device provided in a copying machine, a printer, a personal computer, etc. Specifically, the stepping motor driving method is switched between a low-speed rotation region and a high-speed rotation region. Thus, the present invention relates to a control technique for controlling the stepping motor.

In recent years, in an information processing apparatus such as a copying machine, a printer, or a personal computer, a rotation angle is displaced according to the number of pulses of an input pulse signal as a driving source for driving a driving system device such as a photosensitive drum, a conveyance roller, or an HDD. However, stepping motors whose rotational speed changes according to the frequency of the input pulse signal have come to be used frequently.
In general, when the stepping motor is used, so-called conventionally known slow-up / down control is performed in order to prevent the motor from stepping out and reduce noise. This slow-up / down control is performed by changing the frequency of an input pulse signal for driving the stepping motor in a stepwise manner based on a speed control pattern stored in a predetermined storage unit in advance. This is a control method for accelerating / decelerating the rotational speed stepwise.
On the other hand, in Patent Document 1, the driving method of the above stepping motor is switched to a one-two-phase excitation method or a double one-two-phase excitation method with a small torque in the low-speed rotation range but smooth rotation and low noise and vibration. Reduces noise generated during slow-up / down control of stepping motors by switching to the two-phase excitation method, which has higher torque in the high-speed rotation range than the 1- and 2-phase excitation methods, but generates more noise and vibration during low-speed rotation. Techniques to do this are disclosed.
JP 2000-25978 A

However, even in the same type of stepping motor, there is a difference in characteristics between the motors. Therefore, strictly speaking, the optimum switching timing in the driving method described in Patent Document 1 is different for each motor. Therefore, it is not preferable to uniformly determine the switching timing even for the same type of stepping motor. Of course, if a motor with a margin sufficient to absorb the above characteristic difference with respect to the required torque is selected, the switching timing can be set uniformly, but a motor with performance (torque etc.) that is more than necessary can be determined. This is a problem especially in terms of cost. On the other hand, if a stepping motor having the minimum necessary torque is selected with priority given to cost, if the drive system is switched at a uniform switching timing, a deviation from the optimal switching timing occurs, and the motor and the motor It may appear as noise or vibration of a device having a motor, or the motor may step out. The driving method disclosed in Patent Document 1 is to rotate the stepping motor with low noise. However, the known technique does not consider the above-mentioned problems, and the above-mentioned problems cannot be solved by such a technique. .
Accordingly, the present invention has been made in view of the above circumstances, and its object is to switch the stepping motor drive system at an optimum switching timing specific to the motor, thereby generating noise generated when the stepping motor is driven, An object of the present invention is to provide an information processing apparatus and a motor control method capable of preventing vibration and step-out.

In order to achieve the above object, the present invention measures a predetermined amount of state of a stepping motor composed of a plurality of phases for driving a drive system device, and determines the driving method of the stepping motor based on the measured value. Then, the information to control the stepping motor by switching to the n-1 / n-phase excitation method that repeats n-1 phase excitation and n-phase excitation alternately, and to the simultaneous excitation method that always excites two or more phases in the high-speed rotation range. It is configured as a processing device.
As a result, the drive method can be switched at an optimum timing specific to the motor in accordance with the state of the motor used in the information processing apparatus.
Here, specific examples of the n-1 / n-phase excitation method include a 1-2 phase excitation method, a double 1-2 phase excitation method, and a 2-3 phase excitation method. A specific example of the simultaneous excitation method is a two-phase excitation method.
The predetermined state quantity of the stepping motor to be measured may represent one or more of a noise state in the information processing apparatus, a vibration state of the stepping motor, or a step-out state thereof.

  The predetermined state quantity is preferably measured based on an analog signal output from a sensor used for image forming processing in the information processing apparatus when the stepping motor is driven on a trial basis. Of course, a device such as a sensor for measuring a predetermined state quantity of the stepping motor may be newly provided, but it is more preferable to eliminate the addition of the device such as the sensor by using the existing sensor. Specific examples of the sensor include a jam sensor or a transport sensor that includes an optical sensor such as a photo interrupter provided in a paper transport path.

Further, the switching timing of the driving method of the stepping motor is detected based on the measured value of the predetermined state quantity, and the detected switching timing is stored in a storage medium (switching timing storage means) such as a nonvolatile semiconductor memory. It is also conceivable that the driving method of the stepping motor is switched to either the n−1 / n-phase excitation method or the simultaneous excitation method at the stored switching timing. Since it becomes possible to switch at the switching timing stored in this way, the optimal switching timing can be obtained if the complicated process of measuring the predetermined state quantity is performed at least once.
It is also conceivable that the switching timing stored in the storage medium is updated. Specifically, an example is conceivable in which the predetermined state is measured again and the switching timing detected based on this is updated by overwriting the storage medium. As a result, for example, even when the predetermined state of the stepping motor changes with time, it is possible to switch the driving method at the optimal switching timing.
It is also conceivable that the switching timing stored in the storage medium is changed to an arbitrary value of the user in accordance with information input by information input means such as a numeric keypad provided in the information processing apparatus. Thus, for example, even when the optimum switching timing is not detected because the predetermined state of the stepping motor cannot be measured accurately, it is possible to cope with the problem by changing the switching timing of the storage medium. Become.

  Further, the stepping motor driving system composed of a plurality of phases for driving the drive system device is changed to the n−1 · n phase driving method at the switching timing detected based on the predetermined state quantity of the stepping motor. It can also be understood as a motor control method characterized by switching to either the excitation method or the simultaneous excitation method.

  According to the present invention, the driving method is changed to the one- and two-phase excitation method in the low-speed rotation region at the optimum switching timing specific to the stepping motor detected based on the measured value of the predetermined state quantity of the stepping motor. In the high-speed rotation range, it is possible to switch to the two-phase excitation method.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a schematic configuration diagram for explaining the overall configuration of a copying machine X as an example of an information processing apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing the schematic configuration of a control unit of the copying machine X. 3 is a block diagram showing a schematic configuration of a motor driver, FIG. 4 is a flowchart for explaining an example of a procedure of switching timing detection processing executed by the CPU, and FIG. 5 is a driving method executed by the CPU and sequence control unit. FIG. 6 is a flow chart for explaining an example of the procedure of the switching process, and FIG.

First, an outline of the overall configuration of the copying machine X according to the embodiment of the present invention will be described with reference to FIG. In this embodiment, the copying machine X is described as an example of the information processing apparatus. However, the present invention is not particularly limited to this, and is not limited to this, and may be any kind of scanner apparatus or personal computer using a stepping motor. The present invention can be applied to an information processing apparatus. Here, FIG. 1A is a front sectional view of the copying machine X, and FIG. 1B is a plan view seen from the arrow AA of FIG.
As shown in FIG. 1, the copying machine X is roughly divided into an image reading unit 20 for reading a document image, and an automatic document feeder 10 (hereinafter referred to as “ADF 10”) disposed above the image reading unit 20. ), An operation display unit 30 (see FIG. 1B) disposed on the front side surface, an image forming unit 16 disposed below the image reading unit 20, a fixing device 17, an internal The sheet feeding device 18 that transports the recording paper stored in the image forming unit 16 and the control unit 15 that comprehensively controls the main components of the copying machine X including the above-described units.

In the copying machine X configured as described above, when a start button (not shown) of the operation display unit 30 is pressed, a motor (not shown) is driven in the ADF 10, and the document S set in the document setting unit 11 is moved to the motor. Are picked up one by one by a plurality of transport rollers R1 rotated by the ink and sequentially transported in a sub-scanning direction through a predetermined reading position on the contact glass 26. Since the ADF 10 is not housed in the casing of the copying machine X as shown in the figure, the vibration sound of the motor that drives the transport roller R1 and the like easily leaks to the outside and causes noise. Generally, the ADF 10 Uses stepping motors with low vibration and noise.
When the document S is transported to a predetermined reading position on the contact glass 26, the image reading unit 20 irradiates light onto the document S moving in the sub-scanning direction by the exposure device 21, and the reflected light is reflected. , The light is condensed by the optical lens 24 guided through the light guide mirrors 22, 23 a, and 23 b, and then the CCD 25 converts the image information contained in the collected reflected light into an electrical signal, A signal is input to the control unit 15.
When the original S is placed on the contact glass 26 and the original image is read without using the ADF 10, the exposure device 21 and the light guide mirror 22 are moved in the sub-scanning direction by a motor (not shown). Since the movement of the exposure device 21 and the light guide mirror 22 needs to minimize blurring at the time of reading the reflected light and increase the accuracy of the movement distance and position, it usually has less vibration than other motors. A stepping motor is used as the driving means.

  The image forming unit 16 includes known image forming components such as a photosensitive drum 161, a charging device 162, a developing device 163, a transfer device 164, and a cleaning device 165. In the image forming unit 16, an electrostatic latent image is formed by irradiating a uniformly charged photosensitive member 161 with laser light, and toner is attached to the electrostatic latent image by the developing device 163. Thus, a toner image is formed on the photosensitive member 161, and then the toner image is transferred to a predetermined recording sheet by the transfer device 164.

  On the other hand, in the paper feeding device 18 provided at the lower part of the copying machine X, when the start button of the copying machine X is pressed, the recording paper to be accommodated is taken out by rotating the pickup roller 18a. Thereafter, the recording paper is sent out to the transport path by a pair of paper feed rollers 18b arranged opposite to each other and transported to the registration roller 19 by a plurality of transport rollers R2 provided in the transport path. Since the registration roller 19 needs to be driven so that the leading edge of the conveyed recording paper and the leading edge of the toner image appearing on the photosensitive member 161 are aligned, in general, positioning control is easily performed without food back control. Stepping motors that can be used are used.

  The recording paper on which the toner image is transferred by the transfer device 164 is conveyed to a fixing device 17 provided on the downstream side in the conveyance direction, and faces the fixing roller 171 (with a built-in fixing heater) of the fixing device 17. The toner on the recording paper is melted and fixed by the heat of the fixing roller 171 through the pressure roller 172. The pressure roller 172 is for pressing the recording paper against the fixing roller 171 to ensure toner fixing.

  On the front side surface of the copying machine X, an operation which is an example of means for performing setting input of various functions in the copying machine X, input or display of predetermined information, switching of the operation mode or setting mode of the copying machine X, etc. A display unit 30 (an example of information input means) is provided. The operation display unit 30 includes an operation input unit such as a push button switch or a numeric keypad, and a display unit such as a liquid crystal display. There are various operation modes of the copying machine X. In this embodiment, the copying machine X has a switching timing for detecting a switching timing for switching the driving method of the stepping motor, as will be described later. A detection mode is provided.

  In addition, there is paper in the transport path for transporting the document in the ADF 10, the transport path for transporting the recording paper from the paper feeding device 18, or the transport path until the paper is discharged from the image forming unit 16. A plurality of optical sensors such as photo interrupters for detecting whether the paper has passed or whether the paper is not jammed are arranged. This optical sensor is generally composed of a light projector such as an LED and a light receiver such as a phototransistor. The optical sensor detects that the light emitted from the light projector is blocked by the paper and detects whether the paper has passed or is jammed. However, by monitoring (detecting) ripples (fluctuations) in analog signals (current signals, voltage signals, etc.) output from photoreceivers such as phototransistors, nearby vibration and noise (predetermined) It can also be used as a sensor for detecting a state quantity). In this case, the optical sensor corresponds to the state quantity measuring means. In this embodiment, the optical sensor is used to detect a stepping motor and vibration and noise caused by the stepping motor.

Next, the schematic configuration of the control unit 15 of the copying machine X will be described with reference to the block diagrams of FIGS.
As shown in FIG. 2, the control unit 15 reads the network communication unit 155 that controls communication with an external host device 31 such as a PC, print job data received from the external host device 31, and the image reading unit 20. An image processing control unit 156 that performs image processing on the image data of the original document, an engine control unit 157 that controls each component of the image forming unit 16, and a stepping motor used in the ADF 10 and the paper feeding device 18. Motor drivers 158 and 159 for controlling the driving, a ROM 153 for storing control programs, a RAM 152 used as a development area for image processing or arithmetic processing, and a nonvolatile semiconductor memory for storing switching timing and various data described later. An EEPROM 154 (an example of switching timing storage means) and these Is constructed and a CPU151 for centrally controlling the parts. With this configuration, the CPU 151 reads the control program stored in the ROM 153, and executes a calculation process according to the read control program, thereby executing a switching timing detection process described later. .
Next, the motor driver 159 will be described with reference to the block diagram of FIG. Here, the motor driver 159 that controls the three-phase stepping motor 181 in the paper feeder 18 will be described. However, the configuration of the other motor drivers is substantially the same, and thus the description thereof is omitted.
The motor driver 159 includes a sequence control unit 1591 that shapes an input pulse signal input from a pulse oscillator (not shown) and distributes it to each phase, and amplifies the pulse signal output from the sequence control unit 1591 to a stepping motor 181. And an amplifier 1592 that supplies the pulse signal to each phase (each winding) of the stepping motor 181 in a predetermined order. Specifically, like the driving method described in Patent Document 1 described above, the driving method of the stepping motor 181 is changed to a one- or two-phase excitation method in which one-phase excitation and two-phase excitation are alternately repeated in a low-speed rotation range. It is configured to control the stepping motor by switching to the two-phase excitation method (corresponding to the simultaneous excitation method) that always excites two phases in the high-speed rotation range (equivalent to the n−1 / n-phase excitation method). . The motor driver having such a configuration is not particularly different from the conventional one, but the sequence controller 1591 switches the driving method of the stepping motor 181 at the switching timing specific to the copying machine X detected by the CPU 151. The point that the method switching process is executed is different from the conventional one. Hereinafter, a switching timing detection process executed by the CPU 151 and a drive system switching process executed by the CPU 151 and the sequence control unit 1591 will be described.
As shown in FIG. 3, the stepping motor 181 of the paper feeding device 18 is provided with a speed sensor 182 for detecting the rotational speed, and the detection signal is fed back to the CPU 151.

First, an example of the procedure of the switching timing detection process executed by the CPU 151 when performing slow-up control of the stepping motor will be described with reference to the flowchart of FIG. In the figure, S10, S20,... Indicate processing procedure (step) numbers. The process starts from step S10. This switching timing detection process is a process performed for each copying machine. For this reason, the detected switching timing differs for each copying machine.
First, when the operation mode of the copying machine X is set to the switching timing detection mode by operating the operation display unit 30 (FIG. 1) of the copying machine X by the operator (Yes side of step S10), the CPU 151 will be described. Gives a command to the sequence control unit 1591 to drive the stepping motor 181 on a trial basis by a two-phase excitation method in which two phases are always excited (step S20). Here, the setting of the switching timing detection mode (that is, the start of switching timing detection) can be performed at any time of the operator, but is generally performed when the copier X is delivered to the user. It is preferable to perform the initial setting or every predetermined maintenance period.
When the switching timing detection mode is set, in step S30, the CPU 151 starts monitoring the analog output of the optical sensor for detecting the presence or absence of paper passing, jamming, and the like. Detect noise. In this case, it is preferable to detect an analog signal of an optical sensor arranged in the vicinity of a stepping motor that is a source of noise and vibration.
As described above, the stepping motor 181 is driven by the two-phase excitation method as described above. As shown in FIG. 6, the two-phase excitation method is a high-torque drive method, but noise (vibration) in a low-speed rotation region is generated. This is because the rotation speed V ₁ (that is, the switching timing) that is less than the predetermined noise P needs to be obtained because it is larger than the low torque type 1- and 2-phase excitation methods. The predetermined noise P serving as a threshold is determined to be an arbitrary value by comparing the output torque and the noise.

Subsequently, in step S40, the CPU 151 determines whether or not the detected noise has decreased below the predetermined noise P (FIG. 6). Such determination processing is executed until the detected value falls below the noise P. Here, if it is determined that the detected value is equal to or lower than the noise P, the rotational speed V ₁ of the stepping motor at that time is stored in the EEPROM 154 (FIG. 2) in the control unit 15 (step S50). The rotation speed V ₁ stored at this time is the switching timing for switching the driving method in the driving method switching process described later. Thus CPU151 for executing a process for detecting the rotational speed V ₁ is equivalent to the switching timing detection means. If it is determined in step S40 that the detected value is greater than or equal to the noise P, it is determined in step S41 whether or not a predetermined time has elapsed since the start of the switching timing detection process. , The switching timing detection process ends without detecting the switching timing. If the predetermined time has not elapsed, the processes of steps S40 and S41 are repeatedly executed.
The switching timing thus obtained can be said to be the optimum timing specific to the motor according to the noise state and vibration state of the motor used in the copying machine.
As described above, in this embodiment, the example of processing for detecting the switching timing when the switching timing detection mode is set has been described. However, for example, at every predetermined time or in the copying machine X An example of processing in which the switching timing is automatically detected and stored (overwritten) in the EEPROM 154 when the main power is turned on, and the switching timing is updated may be used.
Although the switching timing detection process when the stepping motor is slow-up controlled has been described here, the switching timing detection process during the slow-down control is also performed in the same procedure.

Next, an example of the procedure of the drive system switching process executed by the CPU 151 and the sequence control unit 1591 will be described using the flowchart of FIG. In the figure, S110, S120,... Indicate processing procedure (step) numbers. The process starts from step S110.
First, when the user presses a start button (not shown) of the operation display unit 30 (FIG. 1) of the copying machine X (Yes side in step S110), the sequence control unit 1591 causes the stepping motor 181 to move from the two-phase exemplary method. Are driven by the 1- and 2-phase excitation method with low noise (vibration) in the low-speed rotation region (step S120).
In step S130, the CPU 151 measures the rotational speed V of the stepping motor 181. This measurement process is performed based on the output value of the speed sensor 182 (FIG. 3). Thereafter, the measured rotational speed is detected by the switching timing detection process described above, and it is compared whether or not it is smaller than the rotational speed V ₁ stored in the EEPROM 154. This comparison process is a process performed to determine whether the stepping motor 181 or the noise (vibration) resulting therefrom is lower than the predetermined noise P (FIG. 6). This comparison process is repeated until the measured rotation speed V becomes equal to or less than the rotation speed V ₁ .
If the CPU 151 determines that the rotation speed V is equal to or less than the rotation speed V ₁ in the step S140, the CPU 151 subsequently sets the drive method of the stepping motor 181 to the sequence control unit 1591. A command signal for switching from the two-phase excitation method to the two-phase excitation method is output, and the sequence control unit 1591 receives this command signal and executes a process for switching the driving method of the stepping motor 181 to the two-phase excitation method (step S150). ). Further, when the rotational speed V at step S140 is determined to be the rotation speed V ₁ or more, followed by the step S141, the driving mode if a predetermined time from the switching process is started has elapsed is determined, If it has elapsed, the drive system switching process ends after an error process (not shown) that displays a warning such as “abnormal drive system switching” without switching the drive system. If the predetermined time has not elapsed, the processes of steps S140 and S141 are repeatedly executed.
In this way, since the driving method of the stepping motor is switched, it is possible to switch the driving method of the stepping motor from the 1-2 phase excitation method to the 2-phase excitation method at an optimal switching timing that differs for each copying machine. Become.

In the above-described embodiment, the example of switching the stepping motor drive system to the 1- or 2-phase excitation system or the 2-phase excitation system has been described. It does not matter if the area is switched to the double 1 or 2 phase excitation system or the 2 or 3 phase excitation system.
In addition, as the state quantity measuring means, the existing optical sensor for detecting the presence or absence of paper passing or jamming in the copying machine X is exemplified, but in order to measure the noise and vibration of the stepping motor with higher accuracy, the existing sensor In this embodiment, a vibration sensor and a noise sensor for newly detecting and measuring the noise and vibration of the stepping motor may be provided. In addition to the above-described sensor for detecting noise and vibration, an embodiment may be provided in which a sensor or device for detecting the step-out state of the stepping motor, which is one of the causes of noise and vibration, is provided.

  In the above-described embodiment, the switching timing stored in the EEPROM 154 (FIG. 2) is stored in the EEPROM 154 according to information input from the operation display unit 30 (FIG. 2) of the copying machine X or the external host device 31. It is also conceivable that the switching timing is changed to an arbitrary value of the user. When circumstances such as inability to accurately measure the noise and vibration of the stepping motor occur, the user convenience can be improved by adopting a configuration in which the switching timing can be changed to any value of the user.

1 is a schematic configuration diagram illustrating an overall configuration of a copying machine X according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a schematic configuration of a control unit of the copier X according to the embodiment of the present invention. The block diagram showing the schematic structure of a motor driver. The flowchart explaining an example of the procedure of the switching timing detection process performed by CPU. The flowchart explaining an example of the procedure of the drive system switching process performed by CPU and a sequence control part. The figure explaining the switching timing of a 1 * 2 phase excitation system and a 2 phase excitation system.

Explanation of symbols

X ... copier 10 ... automatic document feeder (ADF)
DESCRIPTION OF SYMBOLS 15 ... Control part 16 ... Image formation part 17 ... Fixing apparatus 18 ... Paper feeder 20 ... Image reading part 30 ... Operation display part 151 ... CPU
152 ... RAM
153 ... ROM
154… EEPROM
155 ... Network communication unit 156 ... Image processing control unit 157 ... Engine control unit 158 ... Motor driver 159 ... Motor driver 181 ... Stepping motor 182 ... Speed sensor 1591 ... Sequence control unit 1592 ... Amplifier

Claims (8)

A stepping motor consisting of multiple phases to drive the drive system equipment;
The stepping motor drive system is the n-1 / n-phase excitation system that repeats n-1 phase excitation and n-phase excitation alternately in the low-speed rotation area, and the simultaneous excitation system that always excites two or more phases in the high-speed rotation area. An information processing apparatus comprising motor control means for controlling the stepping motor by switching to
Comprising a state quantity measuring means for measuring a predetermined state quantity of the stepping motor;
The information processing system characterized in that the motor control means switches the driving system of the stepping motor to either the n-1 / n-phase excitation system or the simultaneous excitation system based on the measured value by the state quantity measuring means. apparatus.   The n-1 / n-phase excitation method is a 1,2-phase excitation method, a double 1,2-phase excitation method, or a 2,3-phase excitation method, and the simultaneous excitation method is a two-phase excitation method. The information processing apparatus described.   The information processing apparatus according to claim 1, wherein the predetermined state quantity represents one or more of a noise state in the information processing apparatus, a vibration state of the stepping motor, or a step-out state thereof.   The state quantity measuring means measures the predetermined state quantity based on an analog signal output from a sensor used for image forming processing in the information processing apparatus when the stepping motor is driven on a trial basis. The information processing apparatus according to claim 1. A switching timing detecting means for detecting a switching timing of the driving method of the stepping motor by the motor control means based on a measurement value by the state quantity measuring means;
Switching timing storage means for storing the switching timing detected by the switching timing detection means,
2. The motor control means switches the driving system of the stepping motor to either the n−1 / n-phase excitation system or the simultaneous excitation system at the switching timing stored in the switching timing storage means. Information processing apparatus in any one of -4.   6. The information processing apparatus according to claim 5, further comprising switching timing update means for updating the switching timing stored in the switching timing storage means.   6. The information processing according to claim 5, further comprising switching timing changing means for changing the switching timing stored in the switching timing storage means in accordance with information input by the information input means provided in the information processing apparatus. apparatus. The drive system of the multi-step stepping motor that drives the drive system equipment is changed to the n-1 / n-phase excitation system in which the n-1 phase excitation and the n phase excitation are alternately repeated in the low speed rotation range, and always 2 in the high speed rotation range. A motor control method for controlling the stepping motor by switching to the simultaneous excitation method for exciting the above phases,
Motor control characterized in that the stepping motor drive system is switched to the n-1 / n-phase excitation system or the simultaneous excitation system at a switching timing detected based on a predetermined state quantity of the stepping motor. Method.

Images