JP6202996B2 - Stepping motor control device - Google Patents

Description

  The present invention relates to a control device for a stepping motor (pulse motor).

  Stepping motors are conventionally used as actuators such as a focus lens and a zoom lens of a photographing apparatus. In particular, in the case of an imaging apparatus that can be retracted or an imaging apparatus having a mechanism in which a group of focus lenses is extended and retracted during focusing, the user touches the movable part to cause disturbance of the motor drive. In order to detect an abnormality of the stepping motor due to the influence of this disturbance, particularly a step-out, an actuator provided with a rotation detecting means for detecting the rotation of the stepping motor is considered. For example, Patent Document 1 proposes a method of detecting a step-out using a stepping motor and a pulse detection element and using a difference between the number of drive pulses of the stepping motor and the number of detection pulses from the pulse detection element.

Japanese Patent Laid-Open No. 4-150796

  The presence or absence of step-out is determined by whether or not the difference exceeds a predetermined value. If the predetermined value is reduced, step-out can be detected more quickly and the process can be promptly shifted to the return process. However, step-out is erroneously detected due to disturbance in the number of detected pulses from the pulse detection element due to motor vibration or the like. There is a fear. In particular, in a driving method such as two-phase driving or 1-2 phase driving, the vibration of the stepping motor is increased, so that step-out is easily detected erroneously.

The present invention quickly performs out detection of the stepping motor, an exemplified object to provide a control equipment which can reduce the erroneous detection.

The control device of the present invention is a control device for controlling the driving of the stepping motor, wherein the first counting means for counting a change in the drive signal pattern for driving the stepping motor and the rotation of the stepping motor A second count unit that counts a change in the output signal; and a step-out determination unit that performs a step-out determination that is a determination as to whether or not the stepping motor has stepped out based on the output of the first count unit. And the step-out determination unit is driven by the second driving method in which the vibration of the stepping motor is larger than that of the first driving method compared to when the stepping motor is driven by the first driving method. The step-out determination is performed so that it is difficult to determine that step-out has occurred .

According to the present invention, it is possible to provide a control equipment that can quickly perform out detection of the stepping motor, reducing false positives.

It is a block diagram of the imaging device of this embodiment. It is a figure which shows the drive waveform and sensor pulse output of a stepping motor. It is a figure which shows the sensor pulse output for step-out detection. It is a figure which shows the drive waveform and sensor pulse output of a stepping motor at the time of step-out generation | occurrence | production. It is a figure which shows the sensor pulse output when the vibration of a stepping motor is large. It is a flowchart which shows operation | movement of the step-out detection sensor pulse count part of CPU shown in FIG. 3 is a flowchart showing operations of a drive speed setting unit, a drive amount count unit, and a drive waveform generation unit of the CPU shown in FIG. 1. It is a flowchart which shows operation | movement of the step-out determination part of CPU shown in FIG.

  FIG. 1 is a block diagram illustrating the photographing apparatus of the present embodiment. The imaging device includes a focus lens group 100, a lens holding unit 101, a gear unit 102, a stepping motor 103, a pulse plate 104, a photo interrupter 105, a signal processing circuit 106, a motor driver 107, and a CPU 108.

  The focus lens group 100 is composed of one or a plurality of lenses, constitutes a photographing optical system, and moves in the optical axis direction of the photographing optical system to perform focus adjustment. The photographing optical system forms an optical image of the subject. The focus lens group 100 is held by a movable lens holding unit 101 such as a cam ring mechanism.

  The CPU (control means) 108 may be configured as a microcomputer by performing various processes on motor drive control and signals from various sensors. The CPU 108 functions as a control device (control unit) by itself, but the control device (control unit) may be conceived including rotation detection means for detecting the rotation of the stepping motor.

  In response to a command from the CPU 108, the rotation shaft of the stepping motor 103 is rotated, the gear unit 102 connected thereto is rotated, and the lens holding unit 101 as the driven unit and the focus lens group 100 are integrally moved. The driven portion may be a holding member for the zoom lens group.

  A drive signal for driving the stepping motor 103 is generated by a drive waveform generation unit 112 in the CPU 108, converted into current / voltage necessary for the motor driver 107, and supplied to the stepping motor 103. The driving amount of the stepping motor 103 (the driving amount of the focus lens group 100) is detected by a driving amount counting unit 111 in the CPU. The drive amount counting unit 111 counts changes in the excitation pattern generated by the drive waveform generation unit 112.

  A pulse plate 104 in which light shielding portions and transmission portions are alternately arranged is attached to the tip end portion of the rotating shaft of the stepping motor 103. When the light shielding portion of the pulse plate 104 passes through the optical paths of the photo interrupters 105a and 105b, the output of the photo interrupter 105 changes, and the rotation amount of the stepping motor 103 can be detected. By using a plurality of photo interrupters, the detection accuracy of the rotation amount is improved, and the rotation direction can also be detected. Here, two photo interrupters are used, and the rotation direction can be determined by shifting the output phase by 90 °. In the present embodiment, a rotation amount detection sensor including the photo interrupter 105 and the pulse plate 104 is used as a step-out detection sensor. Outputs from the two photo interrupters are amplified and level-converted by the signal processing circuit 106 and input to the CPU 108.

  The rotation detecting means of the stepping motor 103 is not limited to the pulse plate 104 and the photo interrupter 105, and other sensors may be used as long as the rotation of the stepping motor can be detected.

  The CPU 108 includes a drive speed setting unit 110, a drive amount count unit 111, a drive waveform generation unit 112, a step out detection sensor pulse count unit 113, a step out determination unit 114, a pulse count value comparison unit 115, a ROM 116, a RAM 117, and a shooting mode setting. Part 118.

  A drive speed setting unit (drive speed setting means) 110 determines the drive speed of the stepping motor 103 in response to a speed command necessary for focus adjustment. The drive waveform generation unit 112 generates a drive signal pattern according to the set drive speed. Specifically, the drive waveform generation unit 112 generates an excitation pattern for each phase of the stepping motor 103 in accordance with a driving method such as two-phase driving, 1-2 phase driving, or microstep driving. The driving amount counting unit 111 is a first counting unit that counts the driving amount of the focus lens group 100 by incrementing or decrementing the counter every time the excitation pattern of the driving waveform generating unit 112 changes. The drive amount count unit 111 counts the drive amount of the focus lens group 100 as a first count step (procedure).

  The step-out detection sensor pulse count unit 113 is a second count unit that increments or decrements the counter in accordance with a pattern change of an output pulse of the step-out detection sensor (a signal output according to the rotation of the stepping motor). The increment or decrement of the counter by the step-out detection sensor pulse count unit 113 is defined as a second count step (procedure). The pulse count value comparison unit 115 compares the drive amount count value output from the drive amount count unit 111 with the step out detection sensor pulse count value output from the step out detection sensor pulse count unit 113.

  The step-out determination unit 114 determines whether or not the stepping motor has stepped out based on the output from the pulse count value comparison unit 115. More specifically, if the output result (difference) of the pulse count value comparison unit 115 is equal to or greater than a threshold value, it is determined that the stepping motor 103 is out of step, and if it is less than the threshold value, the stepping motor 103 is in a normal state. It is judged that.

  The ROM 116 stores the above-described operation program, other control programs, fixed data, and the like. The RAM 117 is used for temporarily storing calculation results used in the above-described operation program and other control programs and data to be held.

  In this embodiment, the shooting mode setting unit (shooting mode setting unit) 118 can set the type of moving image and still image according to an operation input from an operation unit (not shown). In order to record moving images, the stepping motor 103 is required to be quiet during operation. For still images, it is required to drive the stepping motor 103 quickly so as not to miss a photo opportunity.

  Therefore, in this embodiment, when the shooting mode setting unit 118 sets moving image shooting, the driving speed setting unit 110 sets a speed corresponding to microstep driving, and when still image shooting is set, the driving speed. The setting unit 110 sets 1-2 phase driving or two phase driving.

  FIG. 2 shows a driving voltage (current) waveform of the stepping motor 103 and an ideal output pulse of the step-out detection sensor composed of the pulse plate 104 and the photo interrupter 105. In the figure, assuming a two-phase stepping motor, a drive signal having a sinusoidal waveform is applied to the A phase and the B phase (microstep drive). Further, it is assumed that there are eight stop positions at which the stepping motor 103 can stop at an electrical angle of 360 degrees. Since the driving waveform of the microstep driving has a sine wave shape, the number of stop positions is not limited to 8 points such as 16 points.

  A pulse count of the driving amount of the stepping motor 103 by the driving amount counting unit 111 is performed at each illustrated stop position. In FIG. 2, the output of the photo interrupter 105a is the sensor A phase, and the output of the photo interrupter 105b is the sensor B phase. The output voltage of the step-out detection sensor when the stepping motor 103 is rotating at a constant speed is, as shown in the figure, the repetition of High (High) and Low (Low) with a duty of about 50% for both the sensor A phase and the sensor B phase. It becomes.

  The photo interrupter 105b is arranged with a phase shift of about 90 ° with respect to the photo interrupter 105a so that the rotation direction of the stepping motor 103 can be understood. Further, the relationship between one pulse in the driving amount of the stepping motor 103 and one pulse in the step-out detection sensor is determined by the width of the light shielding part and the transmission part of the pulse plate 104. In FIG. 2, the relationship between the driving amount of the stepping motor 103 and the step-out detection sensor pulse is 8: 4. That is, the resolution of the driving amount of the stepping motor is different from the resolution of the output of the step-out detection sensor.

  FIG. 3 is a diagram illustrating the output of the step-out detection sensor. The step-out detection sensor pulse count unit 113 performs the increment / decrement of the pulse count by using the high / low switching edge of the sensor A phase and the sensor B phase as a trigger. In FIG. 3, the count is incremented, but is decremented when the drive direction is reversed.

  FIG. 4 shows a difference between the drive waveform of the stepping motor 103, the output pulse of the step-out detection sensor, and the output result of the pulse count value comparison unit 115 when the step-out occurs. In the figure, it is assumed that driving is started at time ts and step-out occurs due to external force at time to. Also in FIG. 4, the driving waveform of the stepping motor 103 is a sine wave, so that it is driven by microstep driving.

  When the rotation of the stepping motor 103 stops due to step-out at time to, the output of the step-out detection sensor does not change even if a drive waveform is input to the stepping motor 103. In FIG. 2, the relationship between the drive amount pulse of the stepping motor 103 and the pulse of the step-out detection sensor is 8: 4. For this reason, the pulse count value comparison unit 115 compares a value obtained by dividing the output result of the drive amount counting unit 111 by 2 (a value multiplied by a constant) with the output value of the step-out detection sensor pulse count unit 113, and the difference therebetween. Is output. That is, the difference is a difference when the resolution of the output of the first count unit and the output of the second count unit are combined. The “constant” is a constant for equalizing the resolution of the driving amount of the stepping motor 103 and the resolution of the output of the step-out detection sensor. The step-out determination unit 114 determines that step-out has occurred when the output result of the pulse count value comparison unit 115 exceeds the threshold value. Here, the output result of the drive amount count unit 111 is divided by 2. However, the resolution may be adjusted by doubling the output result of the step-out detection sensor pulse count unit 113.

  In the case of the figure, if the threshold value is 2, the output of the pulse count value comparison unit 115 becomes 2 at time t1, so it is determined that the step-out has occurred at that time. On the other hand, if the threshold value is 6, the output of the pulse count value comparison unit 115 becomes 6 at t2, so it is determined that the step-out has occurred at that time. Thus, the step-out determination unit 114 can detect step-out more quickly as the threshold value is smaller.

  FIG. 5 shows a case where noise due to vibration of the stepping motor 103 is generated in the output pulse of the step-out detection sensor in FIG. Two-phase driving and 1-2-phase driving can be considered as a driving method in which the vibration of the stepping motor 103 is large. Here, a driving waveform when the 1-2-phase driving is performed will be described as an example.

  Here, the “drive system in which the vibration of the stepping motor 103 is large” will be described.

  Considering micro-step driving as the first driving method and two-phase driving or 1-2-phase driving as the second driving method, the former has a sinusoidal driving waveform as shown in FIG. As shown, it is a rectangular wave waveform. For this reason, a sine wave changes continuously, but a rectangular wave does not change continuously (it is discontinuous). In this case, since the driving method that does not change continuously has a heavy load on the mechanism that follows the driving method, the second driving method is the “driving method in which the vibration of the stepping motor 103 is large”.

  On the other hand, when both the first drive method and the second drive method are drive methods that do not change continuously, the drive method with a smaller number of stop positions is the “drive method with greater vibration of the stepping motor 103”. For example, consider a 1-2 phase drive as the first drive method and a two phase drive method as the second drive method. In this case, when it can be a stop position in 1-2 phase driving (A phase 100%, B phase 0%), (A phase 0%, B phase 100%), (A phase 100%, B phase 100%) The number of stop positions is eight. On the other hand, the case where the stop position can be reached in the two-phase drive is only the case of (A phase 100%, B phase 100%), and the number of stop positions is four. If the number of stop positions is small, the change becomes abrupt and the burden on the drive to follow it becomes large. Therefore, the second drive method with a small number of stop positions becomes the “drive method with large vibration of the stepping motor 103”. .

  When the vibration of the stepping motor 103 is large, the output pulse of the step-out detection sensor does not have an ideal waveform as shown in FIG. 4, and the difference output from the pulse count value comparison unit 115 is not stepped out. Regardless, it may be a non-zero value.

  For example, if the step-out determining unit 114 determines that the step-out is 1, the output of the pulse count value comparing unit 115 is 1 at time t11, so that the step-out is erroneously determined. If the threshold value is 2, the output of the pulse count value comparison unit 115 becomes 2 at time t12, so that it is erroneously determined to be out of step. On the other hand, if the threshold value is 3, the output of the pulse count value comparison unit 115 becomes 3 for the first time at the time t13 after the step-out, so that the step-out can be accurately detected without erroneous determination. Thus, when the vibration of the motor is large, the step-out is erroneously determined if the threshold value is small.

  Therefore, in the present embodiment, by changing the threshold according to the driving method of the stepping motor 103, the step-out is quickly detected while reducing the erroneous detection of the step-out. That is, the threshold value when the stepping motor 103 is driven by the first driving method is smaller than the threshold value when the stepping motor 103 is driven by the second driving method having a larger vibration than the first driving method.

  As an example, in this embodiment, the threshold is set to 1 when microstep driving with small vibration of the stepping motor 103 is set, and the threshold is set to 3 at 1-2 phase driving with high vibration of the stepping motor 103. Note that these threshold values may be larger values in consideration of, for example, the influence of the driving delay of the stepping motor 103 or the detection delay of the output pulse of the step-out detection sensor with respect to the input driving pulse.

  FIG. 6 is a flowchart showing the operation of the step-out detection sensor pulse count unit 113 of the CPU 108, where “S” represents a step. The flowchart shown in FIG. 6 can be embodied as a program for causing a computer to execute each procedure. This is also true for other flowcharts.

  First, in S201, it is determined whether or not the stepping motor 103 is in a stopped state. Here, the “stop state” is a state where the drive waveform is not generated and is held at the stop position. If it is stopped (YES in S201), the drive amount count value and the pulse count value of the step-out detection sensor are cleared to zero in S202, and the process returns to S201. S202 corresponds to an initialization process when the stepping motor 103 is normally stopped from the driving state.

  If the stepping motor 103 is not in a stopped state (NO in S201), in S203, the process waits until the rising or falling edge of the step-out output sensor output is detected. This processing can reduce the processing load by using the external input interrupt function of the CPU.

  When an edge is detected in S203, in S204, using the rising edge and falling edge of the two step-out detection sensors as triggers, the previous combination of High and Low of the two step-out detection sensors and the rotation direction from the current combination are detected. Determine. When the rotation direction is the plus direction, the process proceeds to S205, and the step-out detection sensor pulse count is incremented. On the other hand, when the rotation direction is the minus direction, the process proceeds to S206, and the step-out detection sensor pulse count is decremented. After counting, the process returns to step 201 again. If the stepping motor 103 is being driven, a series of operations are repeated. With the above operation, it is possible to detect the count value of the step-out detection sensor.

  Next, FIG. 7 is a flowchart showing operations of the drive speed setting unit 110, the drive amount count unit 111, and the drive waveform generation unit 112.

  In S301, the drive speed setting unit 110 determines whether or not there is a drive start instruction for performing focus adjustment. The user's focusing operation or the start of autofocusing is an instruction to start driving.

  If there is no drive start instruction, the drive amount counting unit 111 clears the value of the drive amount count to zero in S302. When there is an instruction to start driving, the driving speed setting unit 110 sets a required driving speed in S303. The driving speed of the stepping motor 103 is slow when the interval for switching the excitation pattern is lengthened, and fast when it is shortened. The unit is generally pps (pulses / second).

  In S304, the drive waveform generation unit 112 generates a substantially sinusoidal microstep drive waveform or a 1-2 phase drive waveform by repeatedly switching the A-phase and B-phase excitation patterns according to the speed set in S303. In addition, there is a method of switching which drive waveform is to be generated, for example, in a shooting mode of the camera. For example, in the still image shooting mode, a 1-2 phase drive waveform that can be driven at a high speed is generally generated. In the moving image shooting mode, a micro step drive waveform that is generally quiet in driving noise is generated. May be.

  In S305, the drive amount count unit 111 increments or decrements the drive amount counter for each excitation pattern at the stop position, and in S306, stores the counted drive amount count value in the RAM area. Finally, it is determined whether or not the drive amount specified in S307 is driven. If the drive is completed, the drive amount count value is cleared in S302 so that step-out detection can be performed at the next drive. If the driving is not completed, the process returns to S304 and continues to generate a driving waveform.

  FIG. 8 is a flowchart showing an operation until the step-out determination unit 114 determines that the stepping motor 103 is out of step. The process of FIG. 8 is performed by the step-out determination unit 114 and the pulse count value comparison unit 115.

  In step S401, the step-out determination unit 114 checks whether the drive waveform generated by the drive waveform generation unit 112 is a microstep waveform. In the case of microstep driving, the process proceeds to S402, and the step-out determination unit 114 sets the threshold value to 1. On the other hand, if it is not microstep driving, the process proceeds to S403, and the step-out determination unit 114 sets the threshold value to 3. Note that, as described above, the step-out determination unit 114 does not necessarily have to have the threshold values of 1 and 3.

  In S404, the drive amount count value output from the drive amount count unit 111 is compared with the pulse count value output from the step-out detection sensor pulse count unit 113. At this time, as described above, it is necessary to reconvert so that the ratio of the count values of the two becomes a relationship of 1: 1. In the case of FIG. 4 and FIG. 5, since both are in the relationship of 8: 4, the value obtained by dividing the output value of the drive amount count unit 111 by 2 is compared with the output value of the step-out detection sensor pulse count unit 113. Output the difference. In S405, it is determined whether or not the result of comparison in S404 (output from the pulse count value comparison unit 115) is equal to or greater than a threshold value.

  If it is determined in step S405 that step-out has occurred, a return operation is performed in step S406, and the process ends. S405 If it is determined that the step-out has not occurred, the process is terminated as it is because the drive is normally performed.

  As described above, according to the present embodiment, the threshold used for determining whether or not a step-out state is detected from the comparison result between the driving amount count of the stepping motor and the pulse count of the step-out detection sensor is the stepping motor driving method. Change accordingly. Thereby, step-out detection of the stepping motor can be quickly performed, and erroneous detection of the step-out state due to motor vibration or the like can be reduced.

  In addition, although the control apparatus of this embodiment is applied to the imaging device, it can be applied to an apparatus using a stepping motor such as an office machine, a game machine, a toy, and an industrial product. In this case, the change of the threshold value is not limited to the type of shooting mode. Further, even in the same moving image shooting, the step-out determination unit 114 may provide two types of thresholds using two types of driving methods of the stepping motor 103.

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

  The present invention can be applied to an application for controlling the driving of a stepping motor.

DESCRIPTION OF SYMBOLS 103 ... Stepping motor, 108 ... CPU (control apparatus, control unit), 111 ... Drive amount count part (1st count means), 113 ... Out-of-step detection sensor pulse count part (2nd count means)

Claims (9)

A control device for controlling the driving of a stepping motor,
First counting means for counting a change in a drive signal pattern for driving the stepping motor;
Second counting means for counting a change in a signal output according to the rotation of the stepping motor;
A step-out determination unit that performs a step-out determination that is a determination as to whether or not the stepping motor has stepped out based on the output of the first count unit and the output of the second count unit;
The step-out determination unit is driven by the second driving method in which the vibration of the stepping motor is larger than that of the first driving method compared to when the stepping motor is driven by the first driving method. In addition, the control device performs the step-out determination so that it is difficult to determine that the step-out has occurred . The step-out determination unit determines that the difference between the output of the first count unit and the output of the second count unit exceeds the threshold when the resolution of the output of the first count unit and the output of the second count unit is matched. 2. The control device according to claim 1, wherein, in the case of the failure, it is determined that the stepping motor is out of step. The control device according to claim 2, wherein a threshold value when the stepping motor is driven by the first driving method is smaller than a threshold value when the stepping motor is driven by the second driving method. 2. The driving waveform applied to the stepping motor in the first driving method continuously changes, and the driving waveform applied to the stepping motor in the second driving method is discontinuous. 4. The control device according to any one of items 1 to 3 . The drive waveform applied to the stepping motor in the first drive method is a sine wave waveform, and the drive waveform applied to the stepping motor in the second drive method is a rectangular waveform. Item 5. The control device according to Item 4 . Resolution of the output of said first counting means by said first drive system, in any one of claims 1 to 5, characterized in that higher than the resolution of the output of said first counting means by said second drive method The control device described. A stepping motor,
A control unit for controlling the driving of the stepping motor;
A device comprising:
The control unit is
First counting means for counting a change in a drive signal pattern for driving the stepping motor;
Second counting means for counting a change in a signal output according to the rotation of the stepping motor;
A step-out determination unit that performs a step-out determination that is a determination as to whether or not the stepping motor has stepped out based on the output of the first count unit and the output of the second count unit;
The step-out determination unit is configured to step out when the stepping motor is driven by a second drive method that is more vibrated than the first drive method as compared to when the stepping motor is driven by the first drive method. The step-out determination is performed so that it is difficult to determine that it is in progress. 8. The apparatus according to claim 7 , further comprising detection means for outputting a signal corresponding to the rotation of the stepping motor. It further has a shooting mode setting means capable of setting the shooting mode to a movie shooting mode and a still image shooting mode,
When the moving image shooting mode is set by the shooting mode setting means , the control unit drives the stepping motor by the first drive method, and is set to the still image shooting mode by the shooting mode setting means. If, according to claim 7 or 8, wherein the benzalkonium to drive the stepping motor in the second drive mode.