JP7414417B2 - Motor control device, motor control method, and imaging device - Google Patents

Description

The present invention relates to a motor control device, a motor control method, and an imaging device.

2. Description of the Related Art Conventionally, there is a technique described in Patent Document 1 as a method for controlling a stepping motor that drives a mechanical component of a device. By switching the stepping motor drive method (1-2 phase excitation method/2 phase excitation method) according to the external temperature of the device, this technology eliminates mechanical operation problems due to insufficient torque at low temperatures and excess torque at high temperatures. This is a technology that solves the mechanical noise problem caused by

Japanese Patent Application Publication No. 2004-104904

In recent years, network cameras that are connected to a network and distribute captured images have become popular as surveillance cameras. Such a network camera has a pan mechanism and a tilt drive, and in order to maintain the instructed pan and tilt positions, the pan motor and the tilt motor continue to output a predetermined holding torque through excitation processing.
Therefore, simply changing the drive method during mechanical drive according to the temperature at the start of motor drive, as in the technology described in Patent Document 1, cannot reduce the power consumption of the motor in the phase holding state after stopping mechanical drive. I can't.
Therefore, an object of the present invention is to reduce power consumption in a phase holding state in which the rotational position of the motor is held.

In order to solve the above problems, one aspect of the motor control device according to the present invention includes a first excitation means for supplying a first excitation current to a motor to rotate the motor, and a second excitation means for supplying a first excitation current to the motor to rotate the motor. a second excitation unit that supplies current to maintain the rotational position of the motor; an acquisition unit that acquires the temperature of the motor; determining means for determining the second excitation current to be supplied to the motor by the excitation means , the determining means determining a reference excitation current based on the temperature of the motor acquired by the acquisition means. a first derivation means for deriving the value; a second derivation means for deriving the first adjustment value of the reference excitation current based on the rate of increase in the temperature of the motor acquired by the acquisition means; and a third derivation means for deriving a second adjustment value of the reference excitation current based on the operating time of the motor and the rate of increase in temperature of the motor, the second adjustment value being derived by the first derivation means. The reference excitation current is adjusted by the larger adjustment value of the first adjustment value and the second adjustment value, and is determined as the second excitation current .

According to the present invention, power consumption in a phase holding state in which the rotational position of the motor is held can be reduced.

1 is a schematic configuration diagram of a network camera system in this embodiment. FIG. 2 is a configuration diagram of a network camera main body. This is an example of the hardware configuration of a network camera. It is a flow chart which shows a motor control processing procedure of a first embodiment. FIG. 2 is an explanatory diagram of a stepping motor. FIG. 3 is a diagram showing the relationship between motor operating state and excitation current. FIG. 3 is a diagram showing the relationship between motor temperature and reference holding excitation current. FIG. 3 is a diagram showing an example of motor temperature characteristics. It is an explanatory view of the adjustment value of holding excitation current in a first embodiment. It is a flow chart which shows a motor control processing procedure of a second embodiment. It is an explanatory view of the adjustment value of holding excitation current in a second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
The embodiment described below is an example of means for realizing the present invention, and should be modified or changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions. The invention is not limited to this embodiment.

FIG. 1 is a network connection diagram showing the configuration of a network camera system 1000 in this embodiment.
The network camera system 1000 includes a network camera (hereinafter simply referred to as "camera") 100, a network device 200, and a client device 300.
Camera 100 and network device 200 are connected by a network cable. The network cable is, for example, a LAN cable. Further, the network device 200 and the client device 300 are connected by a network 400 and can communicate with each other using a predetermined communication protocol. Note that the communication standard, size, and configuration of the network 400 do not matter as long as the network device 200 and the client device 300 can communicate with each other. Further, the physical connection form to the network 400 may be wired or wireless.

The camera 100 is an imaging device that performs imaging processing to image a subject according to a camera control command transmitted from the client device 300, and obtains a captured image. Further, the camera 100 can perform a distribution process of distributing the acquired captured image to the client device 300 and the like via the network device 200 and the network 400. In the present embodiment, the camera 100 can perform continuous imaging processing and perform distribution processing of streaming-distributing continuously captured images (videos).
Further, the camera 100 is a PT camera (Pan Tilt camera) that can change the imaging direction. The camera 100 has a drive mechanism such as a pan mechanism and a tilt mechanism, and can change the imaging direction to the left and right or up and down. Note that the camera 100 may be a PTZ camera (Pan Tilt Zoom camera) that can change the imaging direction and the imaging angle of view.

The client device 300 can be a device such as a personal computer (PC) that can be operated by a user. The client device 300 can provide the user with a user interface (UI) for inputting camera control commands, displaying execution results of camera control commands, captured images captured by the camera 100, and the like.

The configuration of the camera 100 will be specifically described below.
As shown in FIG. 1, the camera 100 includes a lens 110, a system control unit 111, an image sensor 112, a signal processing circuit 113, an imaging control circuit 114, a memory transfer circuit 115, a memory 121, and a network I /F122. The camera 100 also includes a motor control section 130, a power supply control circuit 140, and a temperature sensor control section 150.

The camera function of the camera 100 is realized by a lens 110, a system control unit 111, an image sensor 112, a signal processing circuit 113, an imaging control circuit 114, and a memory transfer circuit 115.
The lens 110 is a lens device including a lens group including a zoom lens, a focus lens, an anti-vibration lens, and an aperture blade. The lens 110 is equipped with a CPU, and controls each block of the lens group according to instructions input from the main body of the camera 100. Specifically, it controls the zoom lens, the focus lens, the anti-shake lens, and the aperture blades. The lens 110 can be attached to and detached from the main body of the camera 100. Note that the lens 110 may be configured integrally with the main body of the camera 100.

The image sensor 112 converts the light imaged through the lens 110 into electric charge and generates an image signal.
The signal processing circuit 113 inputs and digitizes the image signal generated by the image sensor 112 to generate a captured image.
The imaging control circuit 114 controls the imaging device 112 in the same cycle as the output cycle of captured images. Further, if the accumulation time in the image sensor 112 is longer than the output cycle of the captured image, the signal processing circuit 113 causes the signal processing circuit 113 to hold the captured image in the frame memory of the signal processing circuit 113 during a period when the image sensor 112 cannot output the image signal. control.
The memory transfer circuit 115 transfers the captured image digitized by the signal processing circuit 113 to the memory 121.

The network communication function of camera 100 is realized by system control unit 111, memory 121, and network I/F 122.
The system control unit 111 transmits the captured image transferred to the memory 121 by the memory transfer circuit 115 to the network device 200 via the network I/F 122. As a result, the imaging device is distributed to the client device 300 via the network 400.
Further, the network I/F 122 receives a camera control command transmitted from the client device 300 via the network 400 and transmits it to the system control unit 111. In this case, the system control unit 111 transmits a response to the camera control command to the client device 300 via the network 400 by transmitting the response to the camera control command to the external network device 200 via the network I/F 122.

The system control unit 111 analyzes the camera control command transmitted via the network I/F 122, and performs processing according to the command. For example, it instructs the signal processing circuit 113 to set the image quality, and instructs the motor control unit 130 to perform panning and tilting operations. In this case, the signal processing circuit 113 performs image processing based on setting instructions from the system control unit 111. Further, the motor control unit 130 controls a pan drive unit 131 that implements a pan mechanism and a tilt drive unit 132 that implements a tilt mechanism based on operation instructions from the system control unit 111. Here, the pan driving section 131 and the tilt driving section 132 each include a motor, a gear, and a belt. The configurations of the pan drive section 131 and the tilt drive section 132 will be described later.

The power supply control unit 140 is, for example, a DC-DC converter, and includes a switch circuit for switching the control module to be energized. The power supply control unit 140 receives power from the network device 200 or the external power supply 500 via a network cable or a power cable, and controls the power supply of the camera 100.
In other words, the network device 200 can not only receive captured images from the camera 100 to the client device 300, but also can supply power to the camera 100 via the network cable. The network device 200 is, for example, a hub that can supply power using PoE (Power over Ethernet (registered trademark)) that complies with the IEEE802.3af standard. Note that the network device 200 may be capable of supplying power using PoE+ (PoE Plus) compliant with the IEEE802.3at standard. Further, the network device 200 may be equipped with a power supply function of the UPoE (Universal Power over Ethernet) standard, which can use even more power than PoE+. Furthermore, the network device 200 may be other than a hub device.

The external power supply 500 is a commercial power supply or a DC power supply, and can supply power to the camera 100 via a power cable.
The temperature sensor control unit 150 can perform data communication processing with the temperature sensor 151 and acquires temperature information measured by the temperature sensor 151. Temperature sensor 151 measures the temperature of the pan motor and tilt motor that pan drive section 131 and tilt drive section 132 have, respectively.

FIGS. 2(a) to 2(c) are diagrams illustrating the configurations of the pan driving section 131 and the tilt driving section 132. Here, FIG. 2(a) is a diagram of the camera 100 viewed from above, FIG. 2(b) is a diagram of the camera 100 viewed from the side, and FIG. 2(c) is a skeleton of the camera 100 viewed from the front. FIG. 2 is a simplified diagram for showing a motor and gears.
As shown in FIGS. 2(a) to 2(c), the camera 100 includes a bottom case 161, a turntable 162, a camera head support 163, and a camera head 164. Further, as shown in FIG. 2C, the camera 100 includes a pan motor 171, a tilt motor 172, motor gears 173 and 174, belts 175 and 176, and drive mechanical gears 177 and 178.

The pan drive section 131 includes a bottom case 161, a turntable 162, a pan motor 171, a motor gear 173, a belt 175, and a drive mechanical gear 177. The pan motor 171 rotates a motor gear 173, transmits power to a drive mechanical gear 177 through a belt 175, and can rotate the turntable 162 in the horizontal direction. By rotating the turntable 162 in the horizontal direction, the camera head 164 can rotate from -175 degrees to +175 degrees in the left-right direction.
The tilt drive section 132 includes a camera head support 163 provided on the turntable 162, a camera head 164, a tilt motor 172, a motor gear 174, a belt 176, and a drive mechanical gear 178. The tilt motor 172 can rotate a motor gear 174 and transmit power to a drive mechanical gear 178 via a belt 176 to rotate the camera head 164 in the vertical direction. The camera head 164 can rotate from -45 degrees diagonally downward to 90 degrees directly upward, with the horizontal direction being 0 degrees.
In this way, the camera 100 of the present embodiment can take images while changing the imaging direction to the left-right direction and the up-down direction by rotating the camera head 164 in the horizontal direction and the vertical direction.

FIG. 3 is an example of the hardware configuration of the camera 100.
The camera 100 includes a CPU 101, a ROM 102, a RAM 103, an imaging unit 104, a secondary storage device 105, and a communication I/F 106. The CPU 101, ROM 102, RAM 103, imaging unit 104, secondary storage device 105, and communication I/F 106 are connected to an internal bus 107.
CPU 101 centrally controls operations in camera 100 . The ROM 102 is a nonvolatile memory that stores programs and data necessary for the CPU 101 to execute processing. The RAM 103 functions as the main memory, work area, etc. of the CPU 101. When executing processing, the CPU 101 loads necessary programs and the like from the ROM 102 into the RAM 103 and implements various functional operations by executing the programs and the like.

The imaging unit 104 can include a lens 110, an imaging device 112, etc. shown in FIG. 1. The secondary storage device 105 is a nonvolatile storage device represented by an HDD (hard disk drive), flash memory, SD card, etc., and may have a removable configuration. The secondary storage device 105 can include the memory 121 shown in FIG. The communication I/F 106 can include the network I/F 122 shown in FIG.

The camera 100 of this embodiment rotates each motor by supplying an excitation current to the pan motor 171 of the pan drive section 131 or the tilt motor 172 of the tilt drive section 132 during the imaging operation, and the respective drive sections 131 and 132 are rotated. Performs PT operation to drive. The camera 100 also performs a phase holding operation in which the rotation of each motor is stopped to stop each drive unit 131, 132 at a target position, and then the rotational position of the motor is maintained by supplying a holding excitation current to each motor. I do. At this time, the camera 100 determines the holding excitation current based on the temperature of each motor.
As described above, in this embodiment, a case will be described in which the camera 100 operates as a motor control device that controls the drive of a motor.

Next, the operation of the camera 100 in this embodiment will be explained.
FIG. 4 is a flowchart showing the procedure of motor control processing executed by the camera 100. The process shown in FIG. 4 is started, for example, at the timing when the camera 100 starts an imaging operation. However, the start timing of the process in FIG. 4 is not limited to the above timing. The camera 100 can implement each process shown in FIG. 4 by having the CPU 101 read and execute necessary programs. Hereinafter, the alphabet S shall mean a step in the flowchart.

First, in S1, the camera 100 acquires the motor temperature at predetermined intervals while performing an imaging operation. Specifically, the temperature sensor control unit 150 performs data communication processing with the temperature sensor 151, and acquires temperature data of the pan motor 171 and the tilt motor 172 measured by the temperature sensor 151 at a predetermined cycle. The system control unit 111 performs data communication processing with the temperature sensor control unit 150 at a predetermined cycle, acquires temperature data, and temporarily stores it in a RAM or the like.
Next, in S2, the system control unit 111 calculates the temperature increase rate ΔT of the motor. The temperature increase rate can be calculated, for example, from the latest motor temperature and the motor temperature acquired one time previously among the periodically acquired motor temperatures.

In S3, the system control unit 111 determines whether there is a pan drive or tilt drive operation request (PT drive request). For example, the system control unit 111 determines whether a PT drive request is included in the camera control command transmitted from the client device 300 via the network 400. Then, when the system control unit 111 determines that there is no PT drive request, the process returns to S1, and when it determines that there is a PT drive request, the process proceeds to S4.
In S4, the motor control section 130 starts driving the pan drive section 131 or the tilt drive section 132. That is, the system control unit 111 transmits a drive request to the motor control unit 130, and the motor control unit 130 receives the drive request and drives the motor mounted on the pan drive unit 131 or the tilt drive unit 132. .

Here, a method for driving the motor will be explained.
The camera 100 includes a pan motor 171 and a tilt motor 172 for operating a pan mechanism and a tilt mechanism. Here, the pan motor 171 and the tilt motor 172 are stepping motors capable of microstep driving.
Here, the microstep drive is a function that allows the basic step angle of the stepping motor to be divided into small parts without mechanical elements such as a speed reduction mechanism. Since the step angle when one pulse is input becomes fine, the motor rotates smoothly and vibrations of the motor can be significantly reduced.

As shown in FIG. 5, the stepping motor has a microstep stop resolution of, for example, eight divisions, and is driven by a 1-2 phase excitation method. Furthermore, as shown in FIG. 6, after the power is turned on, the stepping motor starts to be driven by PWM control using the excitation current Im, and transitions from an acceleration state to a constant velocity state and then to a deceleration state. , stop at the target microstep position.
Furthermore, the stepping motor can maintain the motor phase at a designated microstep position by controlling the amount of current (excitation current) of the A phase and B phase using a current control method. During phase holding, by continuously supplying the holding excitation current Is, a predetermined holding torque can be generated in the motor and the rotational position of the motor can be held. In this embodiment, the holding excitation current Is is determined according to the motor temperature. Here, the holding excitation current Is is set to a smaller value than the excitation current Im.
The motor drive start process in S4 in FIG. 4 is a process for transitioning the motor from the acceleration state to the constant velocity state by PWM controlling the motor using the excitation current Im.

In S5, the system control unit 111 determines a reference holding excitation current (reference holding excitation current) Ia based on the latest motor temperature acquired in S1. As shown by the solid line in FIG. 7, the reference holding excitation current Ia has a value that decreases in proportion to the motor temperature until the motor temperature reaches the saturation temperature. Note that the reference holding excitation current Ia is designed to have a current value that is larger by a predetermined amount than the minimum excitation current Imin shown by the broken line in FIG. Here, the minimum excitation current Imin is an excitation current that provides the minimum torque for maintaining the motor phase.
In S6, the system control unit 111 determines whether the temperature increase rate of the motor is high or low based on the value of the temperature increase rate ΔT calculated in S2. Specifically, the system control unit 111 compares the temperature increase rate ΔT and a predetermined value TH1. If the system control unit 111 determines that the temperature increase rate ΔT is less than or equal to the predetermined value TH1, the system control unit 111 determines that the temperature increase rate of the motor is low and proceeds to S7. On the other hand, if the system control unit 111 determines that the temperature increase rate ΔT is larger than the predetermined value TH1, it determines that the temperature increase rate of the motor is high and proceeds to S8.

Here, the temperature characteristics of the motor will be described.
First, the temperature increase rate of the motor will be explained using FIG. 8. As the motor continues to be energized, the motor temperature continues to rise until it reaches the saturation temperature, as shown in FIG. At this time, the rate of increase in motor temperature varies depending on the environmental temperature in which the motor is installed and the shape of the motor (diameter Φ, etc.). For example, as shown in FIG. 8, the smaller the diameter Φ of the motor, the higher the rate of temperature rise of the motor.
In this embodiment, the pan motor 171 and the tilt motor 172 are mounted at different positions on the camera 100, and therefore have large differences in heat dissipation characteristics and different temperature rise rates. Specifically, it is thought that a difference of about 10 to 60 minutes occurs in the time it takes for the motor temperature to reach the saturation temperature between the pan motor 171 and the tilt motor 172.

Next, differences in excitation torque characteristics depending on motor temperature will be explained. As shown in FIG. 5, the stepping motor includes a stator 181, a rotor 182, and a coil 183. The holding excitation torque, which is the excitation torque for maintaining the phase when the motor is stopped, is determined by the magnetic force of the coil 183 and the magnetic force of the stator 181. Here, the coil 183 generates magnetic force by passing current, and the magnitude of the magnetic force can be controlled by the amount of current flowing. Further, the stator 181 has a permanent magnetic force, and the magnetic force increases as the temperature increases.
In other words, the stepping motor has a characteristic that the higher the motor temperature, the more the same holding excitation torque can be achieved even if the excitation current for phase holding is reduced.

In S7, the system control unit 111 determines whether the motor temperature has reached the saturation temperature or is just before the saturation temperature. Specifically, the system control unit 111 compares the temperature increase value ΔT and the predetermined value TH2. If the system control unit 111 determines that the temperature increase rate ΔT is larger than the predetermined value TH2, the system control unit 111 determines that the motor temperature is increasing and has not reached the saturation temperature or is not just before the saturation temperature, and proceeds to S9. Transition. On the other hand, if the system control unit 111 determines that the temperature increase rate ΔT is less than or equal to the predetermined value TH2, the system control unit 111 determines that the motor temperature has reached the saturation temperature or is just before the saturation temperature, and proceeds to S10.

In S8, the system control unit 111 determines the adjustment value ΔI of the holding excitation current, and proceeds to S11. The adjustment value ΔI is a value determined based on the temperature increase rate ΔT, and in this S8, the adjustment value ΔI=Ix when the temperature increase rate ΔT is high.
In S9, the system control unit 111 sets the adjustment value ΔI of the holding excitation current to the adjustment value ΔI=Iy when the temperature increase rate ΔT is low, and proceeds to S11.
In S10, the system control unit 111 sets the adjustment value ΔI of the holding excitation current to the adjustment value ΔI=0 when the motor temperature is the saturation temperature, and proceeds to S11.

In S11, the system control unit 111 adjusts the reference holding excitation current Ia derived based on the motor temperature using the adjustment value ΔI derived based on the temperature increase rate ΔT, and determines the holding excitation current Is. Specifically, the system control unit 111 calculates the holding excitation current Is by subtracting the adjustment value ΔI from the reference holding excitation current Ia.
Here, the adjustment value ΔI of the holding excitation current will be explained. The adjustment value Ix determined in S8 and the adjustment value Iy determined in S9 have a relationship of Ix>Iy as shown in FIG. That is, when the temperature increase rate ΔT of the motor temperature is larger than a predetermined value, the adjustment value ΔI for reducing the reference holding excitation current Ia is derived larger than when the temperature increase rate ΔT is less than the predetermined value. This reduces the holding excitation current Is to maintain the phase of the motor. Thereby, the power saving effect in a transient state of motor temperature can be further improved. Note that the adjustment value ΔI is set so that the holding excitation current Is has a larger value than the above-mentioned minimum holding excitation current Imin.

As shown by two-dot chain lines a and b in FIG. 9, when the motor temperature increases proportionally to the saturation temperature, the temperature increase rate ΔT of the motor temperature becomes as shown by dotted lines c and d. Here, when the diameter Φ of the motor is small and the motor temperature changes as shown by the two-dot chain line a, the temperature increase rate ΔT during temperature rise increases as shown by the dotted line c. If the temperature increase rate ΔT at this time is larger than the predetermined value, the adjustment value ΔI is set to Ix. On the other hand, when the diameter Φ of the motor is large and the motor temperature changes slowly as shown by the two-dot chain line b, the temperature increase rate ΔT during temperature rise becomes low as shown by the dotted line d. If the temperature increase rate ΔT at this time is less than or equal to the predetermined value, the adjustment value ΔI is set to Iy.

In S12, the motor control section 130 stops the pan drive section 131 or the tilt drive section 132. That is, the system control unit 111 transmits a stop request to the motor control unit 130, and the motor control unit 130 receives the stop request and stops the rotation of the motor mounted on the pan drive unit 131 or the tilt drive unit 132. . The motor drive stop process in S12 is a process for transitioning the motor from the constant velocity state in FIG. 6 to the deceleration state by subjecting the motor to PWM control using the excitation current Im.

Next, in S13, the motor control section 130 performs processing to maintain the mechanical phase of the pan drive section 131 or the tilt drive section 132. Specifically, the motor control unit 130 performs PWM control on the pan motor or tilt motor using the holding excitation current Is determined in S11 by the system control unit 111 so that the phase of the pan motor or tilt motor is maintained at the designated microstep position. do.
Here, the motor phase holding process will be explained. In the phase holding process, by continuing to output a holding excitation current Is to the motor, a predetermined holding torque is generated and the motor phase is maintained. In other words, the holding excitation current Is is not changed during the phase holding process.
If the holding excitation current Is is changed during the phase holding process, the phase of the stepping motor becomes unstable. Under this influence, the panning and tilting positions change and the imaging direction changes, which is undesirable because the quality of the captured image deteriorates in a network camera that constantly captures images. For the above reasons, in the camera 100 according to the present embodiment, after the motor stops operating, the holding excitation current during phase holding is not switched and is kept constant.

As described above, the camera 100 in this embodiment includes motors (pan motor 171, tilt motor 172) for changing the imaging direction. The camera 100 supplies an excitation current Im to the motor to rotate the motor, thereby realizing the PT operation. Further, after the PT operation is completed, the camera 100 performs a phase holding operation in which the holding excitation current Is is supplied to the motor to hold the rotational position of the motor. At this time, the camera 100 acquires the temperature of the motor, and determines the holding excitation current Is based on the acquired motor temperature.
Specifically, the camera 100 derives the reference holding excitation current Ia based on the motor temperature, and derives the adjustment value ΔI of the reference holding excitation current Ia based on the temperature increase rate ΔT of the motor. Then, the camera 100 adjusts the reference holding excitation current Ia by the adjustment value ΔI by subtracting the adjustment value ΔI from the reference holding excitation current Ia, and determines the result as the holding excitation current Is.

In this way, the camera 100 can determine an appropriate holding excitation current Is in consideration of the temperature characteristics of the motor. Thereby, it is possible to appropriately reduce the power consumption while the phases of the pan motor 171 and the tilt motor 172 are being maintained after the drive of the pan mechanism and the tilt mechanism included in the camera 100 is stopped. Further, since the holding excitation current Is can be adjusted according to the temperature increase rate ΔT of the motor, the phase of the motor can be maintained with appropriate power consumption even in a transient state of the motor temperature. Further, even if the temperature increase rate ΔT of the motor differs depending on the shape and mounting position of the motor and the installation environment of the camera 100, the phase of the motor can be maintained with appropriate power consumption. In addition, since the reference holding excitation current Ia derived based on the motor temperature can be adjusted by the adjustment value ΔI derived based on the temperature rise rate ΔT and the holding excitation current Is can be determined, the holding excitation current Is can be determined for each motor. There is no need to have a table for determining the excitation current Is.

Further, when determining the holding excitation current Is, the camera 100 can derive the reference holding excitation current Ia to be smaller as the motor temperature is higher. In this way, an appropriate reference holding excitation current Ia can be derived by taking into account the excitation torque characteristic that the same holding torque can be achieved even if the excitation current for phase holding is made smaller as the temperature increases.
Furthermore, when the temperature increase rate ΔT of the motor is larger than a predetermined value, the camera 100 derives a larger adjustment value ΔI for reducing the reference holding excitation current Ia than when the temperature increase rate ΔT is less than the predetermined value. can do. Therefore, it is possible to appropriately adjust the reference holding excitation current Ia in a transient state of the motor temperature and derive an appropriate holding excitation current Is.
Further, the camera 100 can determine the holding excitation current Is to be a value smaller than the excitation current Im. Therefore, it is possible to appropriately reduce power consumption in the phase holding state of the motor.

Furthermore, the camera 100 continuously images the subject, and does not switch the holding excitation current Is in the phase holding state. That is, in the phase holding state, the holding excitation current Is can be kept constant and supplied to the motor. This prevents the phase of the motor from becoming unstable in a state where the phase of the motor should be maintained, and prevents the pan and tilt positions from changing.
Therefore, the imaging direction can be appropriately fixed, and when consecutively captured images (videos) are streamed and distributed, the quality of the distributed video can be ensured.

Furthermore, the camera 100 can be a network camera that can receive power from the network device 200 via a network cable. In recent years, power consumption of network cameras used in surveillance cameras and the like has increased significantly as image sensors have become larger and image processing engines have become more sophisticated. Among them, the power consumed by the PT motor is particularly large. The camera 100 in this embodiment can be a network camera that can appropriately reduce power consumption when the PT motor is in a phase holding state.

Here, the network device 200 can be a power source compatible with PoE. In PoE, the maximum power that can be supplied by the network device 200 serving as a power supply device is 15.4W. In this way, even if there is an upper limit on the power that the camera 100 can receive from the network device 200 according to the PoE standard, the total power consumption of the main modules that make up the camera 100 can be kept within the PoE power supply capacity. Can be done. For example, PoE+ can supply more power than PoE, but requires a PoE+-compatible hub, which increases costs; however, in this embodiment, by using the network device 200 as a PoE-compatible power source, It is possible to reduce costs.

(Second embodiment)
Next, a second embodiment of the present invention will be described.
In the first embodiment described above, a case has been described in which the adjustment value ΔI of the holding excitation current is determined based on the temperature increase rate of the motor. In this second embodiment, a case will be described in which the adjustment value ΔI of the holding excitation current is determined in further consideration of the temperature rise rate of the motor per unit operation time.

The configuration of the network camera system in this embodiment is similar to the network system 1000 shown in FIG.
However, the camera 100 in this embodiment differs from the first embodiment in that it executes the motor control process shown in FIG. 10 instead of the motor control process shown in FIG. Note that in FIG. 10, steps that perform the same processing as in FIG. 4 are given the same step numbers as in FIG. 4, and hereinafter, different parts of the processing will be mainly described.

In S21, the system control unit 111 calculates an integral value ΔTi of the temperature increase rate ΔT of the pan motor 171 and the tilt motor 172. Specifically, the integral value ΔTi corresponding to the temperature increase rate per unit operation time is calculated using the temperature increase rate ΔT and the predetermined operating time t. Here, the operating time t is an arbitrary time, and in this embodiment, it is 60 seconds.
Next, in S22, the system control unit 111 calculates the adjustment value Ii of the holding excitation current based on the temperature increase rate ΔTi per unit operation time calculated in S21 and the predetermined reference adjustment value Ib. The adjustment value Ii becomes a larger value as the temperature increase rate ΔTi per unit operation time is higher.

Next, in S23, the system control unit 111 compares the adjustment value Ii calculated in S22 with the adjustment value Iy used in S9. If the system control unit 111 determines that Ii<Iy, the process proceeds to S11, and if it determines that Ii≧Iy, the process proceeds to S24.
In S24, the system control unit 111 determines the adjustment value Ii calculated in S22 as the adjustment value ΔI, and proceeds to S11. In this way, the temperature increase rate ΔTi per unit operation time is high, and the adjustment value Ii determined based on the temperature increase rate ΔTi per unit operation time is the adjustment value determined based on the temperature increase rate ΔT. If it is greater than or equal to Iy, the adjustment value Ii is determined as the adjustment value ΔI.

Here, the characteristics of the temperature rise of the motor will be described.
In the camera 100, immediately after startup, processing that is not performed during normal imaging operation is performed, such as initialization processing of the pan drive section 131 and tilt drive section 132, initialization processing of the lens, and initialization processing of the optical filter. Therefore, the power consumption immediately after startup is large, and the amount of heat generated is large. Due to this influence, the temperature rise rate of the motor immediately after startup tends to increase. After a while after starting up, the camera 100 enters a stable operating state such as image capturing processing and distribution processing to the network, and its temperature becomes almost stable. Therefore, the amount of heat conducted to the motor is stable, and the motor temperature continues to rise at a very low temperature rise rate just before reaching the saturation temperature.

That is, after starting the camera 100, the motor temperature rises to the saturation temperature according to a curve as shown by the two-dot chain line in FIG. Therefore, the temperature increase rate ΔTi of the motor temperature increase rate per unit operation time is relatively large immediately after startup, and gradually decreases as time passes, as shown by the dotted line. In this case, the adjustment value Ii determined based on the temperature increase rate ΔTi per unit operating time is relatively large immediately after startup, as shown by the solid line, and gradually becomes smaller as time passes.

In this way, the camera 100 in this embodiment derives the adjustment value Ii of the reference holding excitation current Ia based on the temperature increase rate ΔTi of the motor per unit operation time. Then, the camera 100 sets the larger of the adjustment value Iy derived based on the temperature increase rate ΔT of the motor and the adjustment value Ii derived based on the temperature increase rate ΔTi per unit operation time as the adjustment value ΔI. The holding excitation current Ia is adjusted and determined as the holding excitation current Is.
This makes it possible to determine the holding excitation current Is in consideration of the influence of heat generation factors immediately after the network camera is started. Therefore, power consumption in the phase holding state of the PT motor can be appropriately reduced.

At this time, the camera 100 can derive a larger adjustment value Ii for reducing the reference holding excitation current Ia as the temperature increase rate ΔTi of the motor per unit operation time is higher. Since the holding excitation current can be determined linearly according to the rate of temperature rise of the motor, it is possible to achieve more appropriate power savings.

As described above, according to each embodiment of the present invention, it is possible to set an appropriate holding excitation current according to the rate of increase in motor temperature. Further, it is possible to set an appropriate holding excitation current depending on the influence of temperature rise at the time of starting the network camera. Furthermore, it is possible to set an appropriate holding excitation current when the rate of temperature increase just before the motor's saturation temperature is small. This makes it possible to save power while the motor phase is maintained, regardless of whether the motor temperature is in a transient state or in a stable state.

(Modified example)
In each of the above embodiments, a case has been described in which the motors to be controlled by the motor control device are the pan motor 171 and the tilt motor 172 included in the network camera 100, but the invention is not limited to the above. The motor to be controlled may be a stepping motor that can maintain the phase, and may be, for example, a motor included in a lens drive mechanism that moves a lens such as a focus lens or a zoom lens in the optical axis direction.
Further, in each of the above embodiments, a case has been described in which the network camera 100 operates as a motor control device, but the present invention is not limited to the above. The motor to be controlled by the motor control device may be a motor mounted on a device other than the network camera, and the device other than the network camera can also operate as the motor control device.

(Other embodiments)
The present invention provides a system or device with a program that implements one or more of the functions of the embodiments described above via a network or a storage medium, and one or more processors in the computer of the system or device reads and executes the program. This can also be achieved by processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

DESCRIPTION OF SYMBOLS 100... Network camera, 110... Lens, 111... System control part, 130... Motor control part, 131... Pan drive part, 132... Tilt drive part, 150... Temperature sensor control part, 151... Temperature sensor, 171... Pan motor, 172 ...Tilt motor, 200...Network device, 300...Client device, 400...Network, 500...External power supply, 1000...Network camera system

Claims (15)

a first excitation means for supplying a first excitation current to a motor to rotate the motor;
second excitation means for supplying a second excitation current to the motor to maintain the rotational position of the motor;
acquisition means for acquiring the temperature of the motor;
determining means for determining the second excitation current to be supplied to the motor by the second excitation means, based on the temperature of the motor acquired by the acquisition means ;
The determining means is
first derivation means for deriving a reference excitation current based on the temperature of the motor acquired by the acquisition means;
a second derivation means for deriving a first adjustment value of the reference excitation current based on the rate of increase in temperature of the motor acquired by the acquisition means;
and third derivation means for deriving a second adjustment value of the reference excitation current based on a predetermined operating time and a rate of increase in temperature of the motor,
The reference excitation current derived by the first derivation means is adjusted by the larger adjustment value of the first adjustment value and the second adjustment value, and is set as the second excitation current. A motor control device characterized in that : The first derivation means is
The motor control device according to claim 1 , wherein the higher the temperature of the motor acquired by the acquisition means, the smaller the reference excitation current is derived. The second deriving means is
When the rate of increase in the temperature of the motor acquired by the acquisition means is greater than a predetermined value, the first The motor control device according to claim 1 or 2 , characterized in that a large adjustment value is derived. The third derivation means is
The motor according to claim 1, wherein the second adjustment value for reducing the reference excitation current is derived larger as the rate of increase in temperature of the motor per unit operating time is higher. Control device. The determining means is
According to any one of claims 1 to 4 , the second excitation current is determined to be a value smaller than the first excitation current supplied to the motor by the first excitation means. motor control device. The motor is a stepping motor,
6. The motor control device according to claim 1, wherein the first excitation means drives the stepping motor in microsteps . an imaging means for imaging a subject;
A motor control device according to any one of claims 1 to 6 ,
An imaging device comprising: the motor. 8. The imaging device according to claim 7 , wherein the motor is at least one of a pan motor and a tilt motor for changing the imaging direction of the imaging means. The imaging means continuously images the subject,
The imaging device according to claim 7 or 8 , wherein the second excitation means supplies the second excitation current to the motor at a constant value. 10. The imaging apparatus according to claim 9 , further comprising a distribution unit configured to stream-distribute the captured images continuously captured by the imaging unit. The imaging device according to any one of claims 7 to 10 , further comprising a power receiving unit that receives power from a network device via a network cable. The imaging device according to claim 11 , wherein the network device is compatible with PoE (Power over Ethernet (registered trademark)). supplying a first excitation current to the motor to rotate the motor;
supplying a second excitation current to the motor to maintain the rotational position of the motor;
obtaining the temperature of the motor;
determining the second excitation current to be supplied to the motor based on the obtained temperature of the motor ;
The step of determining includes:
a substep of deriving a reference excitation current based on the temperature of the motor;
a substep of deriving a first adjustment value of the reference excitation current based on the rate of increase in temperature of the motor;
a substep of deriving a second adjustment value of the reference excitation current based on a predetermined operating time and a rate of increase in temperature of the motor;
a substep of adjusting the derived reference excitation current by the larger adjustment value of the first adjustment value and the second adjustment value, and determining it as the second excitation current; A motor control method comprising : A program for causing a computer to function as each means of the motor control device according to claim 1 . A program for causing a computer to function as each means of the imaging device according to any one of claims 7 to 12 .

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