JPH1141989A - Drive gear for stepping motor and monitor camera system using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive gear of a stepping motor whose circuit structure is simple and which prevents the increase in vibration at a low-speed range by enabling the stepping motor to be driven by a microstepped drive method from low speed to high speed. SOLUTION: A control circuit 8, constituted of CPUs, outputs a clock pulse when driven at low speed, two clock pulses at a medium speed and four clock pulses at a high speed for each interrupt handling. An excited wave-form generating circuit 9 and a drive circuit 4 drive a stepping motor 6 by a microstepped driving method, based on the clock pulses. Because the motor 6 is driven by the microstepped drive method from a low speed to high speed, a complex structure is not required for changing the drive method depending on speed. The system of generating a plurality of the clock pulses in one interrupt handling of the CPUs enables the stepping motor to be driven at a speed much higher than before.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a stepping motor and a surveillance camera device using the same, and more particularly, to a television camera rotated in a pan direction and a tilt direction.
The present invention relates to a driving device for a stepping motor used in a rotating mechanism for displacing a photographing direction up, down, left, and right, and a monitoring camera device using the same.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an example of a conventional driving device for a stepping motor. In the figure, a clock pulse generated by a control circuit 1 constituted by a central processing unit (CPU) is supplied to an excitation waveform generation circuit 3. The excitation waveform generation circuit 3 is composed of, for example, an address counter, a read only memory (ROM), a D / A converter, etc., counts the above clock pulses by an address counter, and supplies the clock pulses to an address terminal of the ROM. By generating pattern data stored in the ROM in advance and passing it through a D / A converter,
An excitation waveform which is an analog signal is generated in synchronization with the clock pulse.

The excitation waveform output from the excitation waveform generation circuit 3 is switched by the output of the excitation switching circuit 2 according to the driving method. Here, a full step drive system is used. The output excitation waveform of the excitation waveform generation circuit 3 is converted into a drive current by the drive circuit 4 and the coils 5a and 5b
Are supplied in a predetermined sequence to rotate the rotor of the two-phase stepping motor 6.

This conventional stepping motor driving device employs a full-step driving system. As shown in FIG. 5C, an exciting current generated by a first clock is supplied to a coil 5a in a predetermined direction (this direction is referred to as a positive direction). ), The phase A of the two-phase stepping motor 6 is excited, and the exciting current by the second clock is supplied to the coil 5b.
Is supplied in the forward direction to excite the B phase, and the excitation current by the third clock is supplied to the coil 5a in the reverse direction.

[0005]

[Outside 1] Is excited, and the exciting current by the fourth clock is supplied to the coil 5b in the opposite direction.

[0006]

[Outside 2] Is excited, and the same operation is repeated thereafter.

Therefore, according to this full-step driving method, the clock rotates at a low speed when the clock frequency is low as shown in FIG. 5A, and at a high speed when the clock frequency is high as shown in FIG. 5B. Can rotate. However, this full-step drive method has a disadvantage that the rotor vibrates at low speed. Therefore, conventionally, the excitation switching circuit 2 generally uses a different driving method depending on the rotation speed.

That is, at the time of high speed, the above-described full-step driving method is used, but at the time of low speed, a known micro-step driving method is used. In this micro-step driving method, a clock shown in FIG. 6A is generated from the control circuit 1 in FIG. 4 and a stepped excitation waveform is generated from the excitation waveform generation circuit 3, which is passed through the drive circuit 4 to the coils 5 a, 5b is shifted by 1/4 cycle.

Thus, for example, when an eight-step staircase waveform is supplied to the coils 5a and 5b as an exciting current shifted by a quarter period, as shown in FIG.
As the ratio of the exciting currents supplied simultaneously to 5b gradually changes, it takes 8 pulses from when only the A phase is excited to when only the B phase is excited, and the step angle per one clock pulse is reduced to the full step drive. Compared with this, resolutions of 1/8 and 8 times can be obtained.

[0010] The driving device for such a stepping motor includes:
For example, it is used as a rotating mechanism for moving the shooting direction of a monitoring camera. For example, a surveillance camera device having a configuration as shown in FIG.
No.). In FIG. 1, a panning stepping motor and a tilting stepping motor are provided in a turntable 11 together with a speed reduction mechanism, and a shaft of the pan direction stepping motor is connected to a first speed reduction mechanism (in each case). And a shaft of a stepping motor for tilt direction is monitored via a second speed reduction mechanism (neither shown) and a shaft 14. Is rotatably connected to a television camera (surveillance camera) 15 for use.

When the stepping motor for the pan direction rotates, the turntable 11 rotates in the pan direction.
When the stepping motor in the tilt direction rotates, the monitoring camera 15 rotates. In this way, by using the stepping motor having the feature that the positioning accuracy is excellent, the monitoring camera 15 can be positioned and monitored with high accuracy in the monitoring target direction.

[0012]

However, in the above-described conventional stepping motor driving apparatus, in order to drive from a low speed to a high speed, it is necessary to use a different driving method according to the speed. The part 2 becomes complicated.

On the other hand, since it is ideal to use the micro-step driving system even in a region other than the low-speed region, it is conceivable to use the micro-step driving system from low speed to high speed. Therefore, there is a problem that the frequency of the clock output cannot be increased so much because of the performance of the control circuit 1. That is, the control circuit 1 that generates the clock pulse is
Since one clock pulse is generated each time the interrupt processing of U is performed, the interrupt cycle needs to be shortened as the clock pulse frequency increases.
This is because there is a certain limitation in shortening the interrupt cycle due to the processing capability of U.

Further, in the conventional surveillance camera device, due to the above-mentioned problem of the stepping motor driving device, in order to capture the object to be monitored at high speed, an expensive CPU having a large processing capability is used as the CPU. There is a problem that must be.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a driving device for a stepping motor which has a simple circuit configuration and does not increase vibration at low speed.

Another object of the present invention is to provide a surveillance camera device capable of positioning at high speed with high accuracy and monitoring at low speed with low noise.

[0017]

In order to achieve the above object, a stepping motor driving apparatus according to the present invention comprises: a stepping motor for rotating a driven body; Clock pulse generating means for generating and outputting the number of clock pulses corresponding to the above, and driving means for driving the stepping motor in a micro-step drive system based on the clock pulses from the clock pulse generating means.

In the present invention, since a plurality of clock pulses are generated by one interrupt processing of the arithmetic unit, the stepping motor can be driven by the micro step drive system from low speed to high speed, and accordingly, according to the drive speed. Means for switching the driving method can be eliminated.

In order to achieve the above object, a surveillance camera device according to the present invention is configured such that a stepping motor for rotating and positioning a surveillance camera is driven by the above-described stepping motor driving device.

According to the present invention, the monitoring camera can be rotated by the stepping motor driven by the micro-step driving method during both the high-speed rotation and the low-speed rotation.

[0021]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a driving device for a stepping motor according to the present invention. In the figure, the same components as those of FIG.
The description is omitted. The embodiment shown in FIG. 1 is characterized by the configuration of the control circuit 8, and drives the stepping motor 6 that rotationally drives the driven body from a low speed to a high speed by a micro-step driving method.

The control circuit 8 is constituted by a CPU, generates a clock pulse according to the flowchart shown in FIG. The excitation waveform generation circuit 9 and the drive circuit 4 are set to have a circuit configuration that drives the stepping motor 6 by a micro-step driving method.

Next, the operation of the embodiment shown in FIG.
This will be described with reference to FIGS. The control circuit 8
In the interrupt processing of the CPU, first, the step motor 6
Is determined based on an external input signal (step 101). If it is determined that the drive is to be driven at a low speed, a clock is output once (step 102). Thereafter, after waiting for a certain period of time (step 108), the process returns to the first step 101 again to determine whether or not low-speed driving is performed.

Therefore, at the time of low-speed driving, step 10
By repeating the processing of 1, 102 and 108,
As shown in FIG. 3A, one clock pulse is output for each interruption process. As a result, as described with reference to FIG. 6, at the time of low-speed driving, the stepping motor 6 is driven by the micro-step driving method in the same manner as at the time of conventional low-speed driving.

When the control circuit 8 determines in step 101 that the drive is not the low-speed drive, the control circuit 8 determines whether the drive is the medium-speed drive (step 103). The distinction between the low speed, the medium speed and the high speed varies depending on the device in which the stepping motor 6 is used, and thus cannot be unconditionally determined. For example, when applied to a surveillance camera device, “low speed” is, for example, one second. About 2 °, “medium speed” is 10
About 0 [deg.] And "high speed" are about 240 [deg.] Per second for rotating the monitoring camera.

The control circuit 8 outputs a clock twice when it is determined in step 103 that the drive is at the medium speed (step 1).
04). Then, after waiting for a certain period (step 10)
8) Returning to the first step 101 again, it is determined whether or not the drive is at a low speed. Therefore, at the time of medium speed drive, step 10
By repeating the processing of steps 1, 103, 104, and 108, two clock pulses are output for each interrupt processing as shown in FIG. 3B.

On the other hand, when the control circuit 8 determines at step 103 that the driving speed is not the medium speed, it determines whether the driving is at a high speed (step 105). If it is determined that the driving is the high-speed driving, the control circuit 8 outputs the clock four times in one interrupt process (step 104). Thereafter, after waiting for a certain period of time (step 108), the process returns to the first step 101 again to determine whether or not low-speed driving is performed.

Therefore, at the time of high-speed driving, step 10
By repeating the processing of 1, 103, 105, 106, and 108, four clock pulses are output for each interrupt processing as shown in FIG. 3C.
During the high-speed driving and the medium-speed driving, similarly to the low-speed driving, the excitation waveform generating circuit 9 generates the excitation phase of the stepping motor 6 as shown in FIG. Is generated. As a result, the stepping motor 6 is driven by the micro step driving method at both the middle speed driving and the high speed driving. In FIG. 3D, numbers indicate the order of generation of clock pulses.

When the control circuit 8 determines in step 105 that the driving is not high-speed, the control circuit 8 determines that the driving instruction is not issued and stops the generation of the clock (step 1).
07), after waiting for a certain period of time (step 108), return to step 101 and wait for a drive instruction input. The wait process for a certain period of time in step 108 is a process of waiting for a period from the output of the first clock to the output of the first clock by the next interrupt process. The wait process shown in FIG. The cycle such as between the first clock and the third clock in FIG. 3B is the same as the cycle between the first clock and the fifth clock in FIG. 3C, for example.

According to this embodiment, during middle-speed driving and high-speed driving, two or four clocks are continuously output by one interrupt processing of the CPU constituting the control circuit 8. Therefore, compared with the conventional device that generates one clock in one interrupt process, there is a margin in the processing period other than the interrupt process, and even when a CPU having the same processing capacity as the conventional device is used. A clock having a higher average frequency can be generated as compared with the conventional case, and therefore, the stepping motor 6 can be driven by the micro-step driving method which is much faster than the conventional case.

When the driving device for a stepping motor according to this embodiment is applied to the driving device for a stepping motor in a monitoring camera device shown in FIG. 7, low-speed driving is performed by a microstep driving method at low speed. Because the surveillance camera can be rotated, it can be monitored in environments where low noise is required, such as at night, and in environments where it is necessary to capture and monitor the monitoring target at high speed, the stepping motor can be driven at high speed. It is possible, and since it is a microstep drive system from low speed to high speed, there is no need for a complicated configuration that changes the drive system according to the speed. can do.

The present invention is not limited to the above-described embodiment. For example, the stepping motor 6 has been described as a two-phase motor, but the same can be applied to a four-phase motor or a five-phase motor. Further, the rotation speed of the stepping motor is not limited to three types of low speed, medium speed and high speed,
It goes without saying that two or four or more types may be used.

[0033]

As described above, according to the driving apparatus for a stepping motor of the present invention, the stepping motor can be driven from a low speed to a high speed by a micro step driving method. Since the means for switching between them can be eliminated, the configuration can be simplified as compared with the related art. According to the present invention,
At the time of high-speed driving or medium-speed driving of the stepping motor by the micro-step driving method, a plurality of clock pulses are generated by one interrupt processing of the CPU, so that a CPU having the same processing capacity as the conventional one is used. In this case, the stepping motor can be driven at a higher speed than before.

According to the surveillance camera device of the present invention,
The monitoring camera can be rotated by the stepping motor driven by the micro-step drive system during both high-speed rotation and low-speed rotation, enabling high-speed, high-precision positioning, and low-speed rotation of the monitoring camera from low-speed rotation. Monitoring can be performed with low noise, and a complicated configuration such as changing the drive method according to the speed is not required as compared with the conventional one, and therefore, the entire monitoring camera device can be configured at a lower cost than the conventional one. .

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a driving device for a stepping motor according to the present invention.

FIG. 2 is a flowchart for explaining an operation of a main part of FIG. 1;

FIG. 3 is a diagram for explaining clock pulses and phase excitation of main parts in FIG. 1;

FIG. 4 is a block diagram of an example of a conventional driving device for a stepping motor.

FIG. 5 is a diagram illustrating clock pulses and phase excitation by a full-step driving method.

FIG. 6 is a diagram illustrating clock pulses and phase excitation by a micro-step driving method.

FIG. 7 is a configuration diagram of an example of a conventional monitoring camera device.

[Explanation of symbols]

 Reference Signs List 4 drive circuit (drive means) 5a, 5b coil 6 stepper motor 8 control circuit (clock pulse generation means) 9 excitation waveform generation circuit (drive means)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshito Kurihara 3-12-12 Moriyacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside of JVC, Ltd. (72) Hideaki Goda 3-chome Moriyacho, Kanagawa-ku, Yokohama-shi, Kanagawa No. 12 Inside Victor Company of Japan

Claims (3)

[Claims] 1. A stepping motor for rotating and driving a driven body, clock pulse generating means for generating and outputting a number of clock pulses corresponding to a desired rotation speed for each interruption process by an arithmetic unit, and said clock pulse generating means And a driving means for driving the stepping motor in a micro-step driving method based on a clock pulse from the stepping motor. 2. A clock pulse generating means for performing a first process for determining a rotation speed input from the outside, and generating a greater number of clock pulses as the rotation speed obtained by the first process is higher. 2. The stepping device according to claim 1, further comprising an arithmetic unit that performs a second process of performing a second process and a third process of waiting for a certain period after the second process during one interrupt period. Motor drive. 3. A surveillance camera device in which a surveillance camera is rotationally positioned by rotation of a stepping motor, wherein a clock pulse generation means for generating and outputting a number of clock pulses corresponding to a desired rotation speed every time an interruption process is performed by an arithmetic unit. And a driving means for driving the stepping motor in a micro-step driving method based on a clock pulse from the clock pulse generating means.