JP7836364B2 - Tripod head device, control method and program for the tripod head device - Google Patents

Description

This invention relates to a tripod head device, a control method for the tripod head device, and a program.

A pan-tilt head device is known that houses an imaging device used for surveillance or video distribution, and includes a pan drive unit for horizontal rotation and a tilt drive unit for vertical rotation, allowing control of the imaging range. The positions of these pan and tilt drive units are controlled by a control unit or similar mechanism.

The pan and tilt drive units of such tripod head devices sometimes have a configuration that rotates the output shaft via a reduction mechanism with multiple gears from the motor shaft of the motor in order to obtain the required torque output. This reduction mechanism has a gap, or backlash, between the multiple gears. This backlash becomes the amount of deviation in position control (also called the backlash amount). Therefore, a technique for determining this backlash amount has been disclosed.

For example, Patent Document 1 discloses a technique in which a position detector is provided for each drive unit of a television camera, and the drive of each drive unit is controlled based on the output of this position detector. In the technique of Patent Document 1, the operator uses a joystick to drive the drive unit to a preset position, detects the position by operating control buttons, and calculates the aforementioned amount of deviation.

Japanese Patent Application Publication No. 9-247504

However, in the prior art disclosed in Patent Document 1 mentioned above, the operator needs to operate a joystick or the like, which places a significant burden on the operator in calculating the amount of backlash.

Therefore, the present invention provides a technology that can reduce the burden on the operator when calculating the amount of backlash.

To solve this problem, for example, the tripod head device of the present invention has the following configuration. That is,
A pan-tilt head device for changing the shooting direction of an imaging means used to photograph a subject,
A drive source that outputs driving force,
A reduction mechanism for reducing the driving force of the aforementioned drive source,
An output shaft connected to the reduction mechanism to which the reduced driving force is transmitted and which changes the shooting direction of the imaging means,
An output shaft position detection means for detecting the output shaft position, which is the position of the output shaft,
Control means for controlling the drive source,
Equipped with,
The control means acquires at least one of the control position, which is the position of the drive source, and the output shaft position based on predetermined conditions, and determines the amount of backlash based on the acquired control position and output shaft position.

According to this invention, the burden on the operator can be reduced when calculating the amount of backlash.

A diagram illustrating the overall configuration of the control system of the pan/tilt head device according to this embodiment. Plan view and side view of a tripod head device according to an embodiment. A diagram illustrating the drive transmission system of the drive unit according to an embodiment. This diagram illustrates the relationship between the motor control position and the output shaft position of the drive unit in the first embodiment. A flowchart illustrating the backlash calculation process for the tripod head device of the first embodiment. This diagram illustrates the relationship between the motor control position and the output shaft position of the drive unit in the second embodiment. A flowchart illustrating the backlash calculation process for the tripod head device of the second embodiment. A diagram illustrating another relationship between the motor control position and the output shaft position of the drive unit in the second embodiment. A flowchart illustrating another backlash calculation process for the tripod head device of the second embodiment. A block diagram showing the hardware configuration of the system control unit.

The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While multiple features are described in the embodiments, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

(First embodiment)
Figure 1 is a diagram illustrating the overall configuration of the control system of the pan/tilt head device 1000 according to this embodiment. The overall configuration of the pan/tilt head device 1000 will be described with reference to Figure 1.

The pan/tilt head unit 1000 holds the imaging device 2000, which photographs the subject, and changes the shooting direction, including the pan and tilt directions of the imaging device 2000. The pan/tilt head unit 1000 is connected to the imaging device 2000 and the client device 3000. The pan/tilt head unit 1000 comprises a pan drive unit 1004, a tilt drive unit 1005, a system control unit 1006, and a communication unit 1007.

The pan drive unit 1004 performs the panning motion of the pan/tilt head device 1000. Panning is the motion of rotating the imaging device 2000 in the left-right direction (i.e., horizontal direction), which is a rotational motion around the vertical axis. The pan drive unit 1004 is connected to the system control unit 1006 for communication, enabling it to send and receive signals such as rotation instructions. The pan drive unit 1004 achieves panning through a mechanism, such as an actuator like a brushless DC motor, and an encoder for detecting the pan position. In this embodiment, the pan drive unit 1004 is built into either the bottom case 1101 or the turntable 1102, which will be described later.

The tilt drive unit 1005 performs the tilt operation of the pan/tilt head device 1000. The tilt operation is the movement of rotating the imaging device 2000 in the vertical direction (i.e., vertical direction), which is a rotational movement around a horizontal axis extending left and right. The tilt drive unit 1005 is connected to the system control unit 1006 for communication, enabling it to send and receive signals such as rotation instructions. The tilt drive unit 1005 achieves tilt operation through a mechanism, such as an actuator like a brushless DC motor, and an encoder for detecting the tilt position. In this embodiment, the tilt drive unit 1005 is built into either the camera head support column 1103 or the camera head 1104, which will be described later.

The system control unit 1006 is responsible for the overall control of the pan/tilt head device 1000. The system control unit 1006 is equipped with a processor such as a CPU (Central Processing Unit). The system control unit 1006 is connected to the client device 3000, which is an information processing device (also called a computer), via the communication unit 1007, enabling it to send and receive signals. The system control unit 1006 communicates signals, including commands and responses, with the client device 3000 to control the pan/tilt head device 1000. In other words, the system control unit 1006 receives commands transmitted from the client device 3000, analyzes the acquired commands, and executes processing according to the commands. Then, the system control unit 1006 sends a response to the command to the client device 3000. For example, the system control unit 1006 controls the imaging device 2000 based on instructions for camera control commands. The system control unit 1006 controls the pan drive unit 1004 and the tilt drive unit 1005 based on commands related to pan-tilt control, rotating the imaging direction of the imaging device 2000 in the pan and tilt directions. The system control unit 1006 receives image data, which is the data of the image generated by the imaging device 2000 capturing the subject. The system control unit 1006 transmits the received image data to the client device 3000 via the communication unit 1007. The term "image" may include still images, moving images, video footage, and their data. The system control unit 1006 is equipped with non-volatile memory and stores and registers various data, such as preset positions, which will be described later.

The communication unit 1007 is connected to the client device 3000 via network and serial communication, and transmits and receives signals to and from each other. The communication unit 1007 receives commands related to pan-tilt control and camera control from the client device 3000. The communication unit 1007 transmits the response from the system control unit 1006 to the client device 3000. The communication unit 1007 also transmits image data received from the imaging device 2000 to the client device 3000.

The imaging device 2000 comprises a lens, an image sensor, and a control circuit. The imaging device 2000 receives light from a subject that is imaged by an imaging optical system including the lens, and converts the light image of the subject into an electrical signal by photoelectric conversion. The imaging device 2000 generates image data by performing image processing such as development, compression, and encoding on the photoelectrically converted electrical signal. The imaging device 2000 is equipped with an optical zoom control mechanism that can change the imaging angle of view. The imaging device 2000 is equipped with a focus control mechanism that can adjust the focus of the captured image. The imaging device 2000 is connected to the pan/tilt head device 1000. Based on instructions from the client device 3000 obtained from the pan/tilt head device 1000, the imaging device 2000 adjusts the shooting angle of view by zoom control and adjusts the focus of the captured image by focusing. The imaging device 2000 transmits the generated image data to the pan/tilt head device 1000. As a result, the image data is transmitted to the client device 3000 via the pan/tilt head device 1000.

Figure 10 is a block diagram showing the hardware configuration of the system control unit 1006. The system control unit 1006 is, for example, a computer. The system control unit 1006 includes a processor 1191, memory 1192, storage 1193, input IF 1195, output IF 1196, and bus 1197. The processor 1191, memory 1192, storage 1193, input IF 1195, and output IF 1196 are connected to each other via bus 1197, enabling them to send and receive information.

The processor 1191 is an arithmetic processing unit, such as a CPU (Central Processing Unit). The system control unit 1006 may have other processors, such as an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), and a QPU (Quantum Processing Unit), in place of or in addition to the CPU. The processor 1191 performs various functions and processes by reading programs stored in the storage 1193 and loading them into the memory 1192. For example, the processor 1191 executes each step of the backlash calculation process described later by reading a computer program. Furthermore, some or all of the backlash calculation steps may be performed by one or more circuits, such as an ASIC (Application Specific Integrated Circuit) and an FPGA (Field Programmable Gate Array).

Memory 1192 is a high-speed read/write storage device, such as RAM (Random Access Memory). Memory 1192 functions as a work area when the processor 1191 executes a program. Memory 1192 temporarily stores the program and parameters necessary for program execution. For example, in the backlash calculation process, Memory 1192 stores the detected motor control position, output shaft position, and the backlash amount resulting from the processing.

The storage device 1193 is a non-volatile storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). The storage device 1193 retains programs, parameters necessary for program execution, and program execution results even when power is not supplied.

Input IF 1195 is an interface for receiving information from an input device. Examples of input devices include a mouse, keyboard, and touch panel.

Output IF1196 is an interface for outputting information such as processing results to a display device such as a display.

Next, with reference to Figure 2, the details of the mechanical configuration of the pan/tilt head device 1000 will be described. Figure 2 is a plan view and a side view of the pan/tilt head device 1000 according to this embodiment. Figure 2(a) is a plan view of the mechanical mechanism of the pan/tilt head device 1000 from above along the vertical axis. Figure 2(b) is a side view of the pan/tilt head device 1000. As shown in Figure 2, the pan/tilt head device 1000 includes a bottom case 1101, a turntable 1102, a support column for the camera head 1103, and a camera head 1104. In this embodiment, the imaging device 2000 is built into the camera head 1104. In this embodiment, the pan drive unit 1004 is built into either the bottom case 1101 or the turntable 1102, which will be described later.

The bottom case 1101 functions as the base for the entire pan-drive unit 1000, including the pan drive unit 1004 and the tilt drive unit 1005. The bottom case 1101 is positioned beneath the turntable 1102.

The turntable 1102, which supports the camera head support column 1103 (described later), rotates around its vertical axis to drive the panning motion, that is, to perform the panning operation of the pan/tilt head device 1000. The turntable 1102 can rotate from -175 degrees to +175 degrees in the panning direction.

In other words, the mechanism, actuator, and encoder for the pan drive unit 1004 are housed in either the bottom case 1101 or the turntable 1102. This allows the pan drive unit 1004 to rotate the imaging device 2000 in the pan direction from -175 degrees to +175 degrees. In this embodiment, the pan drive unit 1004 is housed in either the bottom case 1101 or the turntable 1102, but other configurations are also possible. For example, the pan drive unit 1004 may not be housed in either the bottom case 1101 or the turntable 1102, but may be located in another component.

The camera head support column 1103 extends vertically and supports the camera head 1104, which will be described later. The camera head support column 1103 is positioned on the central axis of the turntable 1102. The camera head support column 1103 holds the camera head 1104 on the side opposite the turntable 1102 (in this case, the upper end).

The camera head 1104 is hollow. The camera head 1104 houses the imaging device 2000. The camera head 1104 is positioned at the upper end of the camera head support column 1103. The camera head 1104 performs tilt movement, i.e., the tilt operation of the pan/tilt head device 1000, with an axis perpendicular to the vertical axis as its central axis. The camera head 1104 can rotate from -45 degrees diagonally downwards forward to +90 degrees upwards, with the horizontal direction being 0 degrees.

In other words, the mechanism, actuator, and encoder for the tilt operation of the tilt drive unit 1005 are built into either the camera head support column 1103 or the camera head 1104. This allows the tilt drive unit 1005 to rotate the imaging device 2000 from -45 degrees diagonally downwards forward to +90 degrees upwards.

Furthermore, in this embodiment, the tilt drive unit 1005 is built into either the camera head support column 1103 or the camera head 1104, but other configurations are also possible. For example, the tilt drive unit 1005 may not be built into either the camera head support column 1103 or the camera head 1104, but may be located in another component.

Thus, the pan/tilt mount device 1000 of this embodiment allows the camera head 1104 to rotate in the pan and tilt directions, thereby changing the imaging direction and enabling the imaging device 2000 to capture images. Note that the pan and tilt drive ranges in this embodiment are merely examples and are not limited to them. For example, the pan and tilt drives may be configured to rotate endlessly.

Figure 3 illustrates the drive transmission system of the pan drive unit 1004 and the tilt drive unit 1005. Referring to Figure 3, the configuration of the internal drive transmission system of the pan drive unit 1004 and the tilt drive unit 1005 will be described. The pan drive unit 1004 and the tilt drive unit 1005 have generally the same configuration. The pan drive unit 1004 and the tilt drive unit 1005 each include a motor 1201, a motor shaft encoder 1202, a reduction mechanism 1203, an output shaft 1204, and an output shaft encoder 1205.

Motor 1201 outputs driving force as rotational driving force and functions as a drive source for the pan drive unit 1004 and the tilt drive unit 1005. The rotation of motor 1201 rotates the output shaft 1204, which is the rotation axis for either pan or tilt, via the reduction mechanism 1203. This causes motor 1201 to rotate the imaging device 2000 in either the pan or tilt direction. Motor 1201 may be, for example, a brushless DC motor.

The motor shaft encoder 1202 is mounted on the motor shaft. The motor shaft encoder 1202 may be an incremental encoder or the like. The motor shaft encoder 1202 functions as a position detector that detects the position of the motor shaft (also called the motor control position). The motor shaft encoder 1202 outputs the detected motor shaft position information to the processor 1191 of the system control unit 1006. The motor shaft encoder 1202 is an example of a drive control position detection means.

The reduction mechanism 1203 consists of multiple gears and belts. The reduction mechanism 1203 reduces the rotational speed of the motor 1201, i.e., reduces the driving force, and outputs the necessary torque to the output shaft 1204.

The output shaft 1204 is connected to the reduction mechanism 1203. Therefore, the output shaft 1204 receives the driving force from the reduced-speed motor 1201 via the reduction mechanism 1203 and outputs the transmitted rotational drive. This causes the output shaft 1204 to rotate the camera head 1104 in the pan or tilt direction, thereby changing the imaging direction of the imaging device 2000.

The output shaft encoder 1205 is mounted on the output shaft 1204. The output shaft encoder 1205 may be an absolute value encoder or the like. The output shaft encoder 1205 functions as a position detector that detects the position (also called the output shaft position) of the output shafts of the pan drive unit 1004 and the tilt drive unit 1005. The output shaft encoder 1205 outputs the detected output shaft position information to the processor 1191 of the system control unit 1006. The output shaft encoder 1205 is an example of an output shaft position detection means.

Here, a brushless DC motor is used as an example for the drive source motor 1201, but the motor 1201 is not limited to this; other types of actuators may be used. Furthermore, while a configuration with an incremental encoder as the motor shaft position detector and an absolute encoder as the output shaft position detector is shown, other types of position detectors may be used. Also, a configuration in which the position of the output shaft 1204 is directly detected using the output shaft encoder 1205 provided on the output shaft 1204 is shown, but this is not the only configuration. Alternatively, an encoder may be provided on a rotating shaft that rotates via a reduction mechanism (not shown) from the output shaft 1204, and the position on the output shaft 1204 may be indirectly detected using that encoder.

In this embodiment, the processor 1191 of the system control unit 1006 of the pan-tilt head device 1000 registers preset information in the storage 1193 that associates the position of the pan drive unit 1004, the position of the tilt drive unit 1005, the zoom control position of the imaging device 2000, and a preset number. Alternatively, the processor 1191 may register preset information that associates at least one of the pan drive unit 1004 position, the tilt drive unit 1005 position, and the zoom control position with a preset number. Furthermore, the processor 1191 may register preset information including image quality settings and other information in addition to the pan drive unit 1004 position, the tilt drive unit 1005 position, and the zoom control position.

Here, the pan-tilt head unit 1000 is configured to allow remote control of the pan drive unit 1004 and the tilt drive unit 1005 via a network and dedicated line. Therefore, when the processor 1191 receives a predetermined command and a registered preset number from, for example, a remote operator, it retrieves the preset information associated with the preset number. Based on this preset information, the processor 1191 controls the pan drive unit 1004 and the tilt drive unit 1005, etc., to execute a preset function that moves them to the preset position. Furthermore, the system control unit 1006 instructs the pan drive unit 1004 and the tilt drive unit 1005 to move to the preset position in a predetermined time, realizing a function called a shot, which synchronizes and controls the pan and tilt movement times.

Figure 4 illustrates the relationship between the motor control position and the output shaft position of the drive unit in the first embodiment. In Figure 4, the horizontal axis represents time, and the vertical axes represent the motor control position and output shaft position. The motor control position is the position detected by the motor shaft encoder 1202. The output shaft position is the position detected by the output shaft encoder 1205. The solid line shows the movement trajectory LA of the motor control position detected by the motor shaft encoder 1202. The dotted line shows the movement trajectory LB of the output shaft position detected by the output shaft encoder 1205.

Assume that at time t0, motor 1201 is at position me1 in the positive direction. The system control unit 1006 drives motor 1201 from position me1 in the negative direction to position me0 at 0 degrees. At this time, the system control unit 1006 controls motor 1201 based on the motor control position detected by the motor shaft encoder 1202. In this case, the motor control position changes linearly, as shown by the movement trajectory LA. On the other hand, even when motor 1201 rotates, due to the backlash of the reduction mechanism 1203, there is a period from the start of driving during which the output shaft 1204 does not rotate. Therefore, the output shaft position, which is the value of the output shaft encoder 1205, does not change from time t0 to time t1.

Subsequently, the output shaft position detected by the output shaft encoder 1205 begins to change after time t1, as shown in the movement trajectory LB, and changes linearly thereafter. Then, at time t2, when the motor control position detected by the motor shaft encoder 1202 reaches 0 degrees, the output shaft position detected by the output shaft encoder 1205 does not reach 0 degrees, but takes the value of position oe1.

Next, the system control unit 1006 drives the motor 1201 from position me0 to position me2 in the negative direction. Assume that at time t3, the motor 1201 is at position me2 in the negative direction. The system control unit 1006 drives the motor 1201 in the positive direction from position me2 to position me0 at 0 degrees. At this time, the system control unit 1006 controls the motor 1201 based on the motor control position detected by the motor shaft encoder 1202. In this control, the motor control position changes linearly as shown in the movement trajectory LA. Here, for a certain period from the start of driving, due to the backlash of the reduction mechanism 1203, there is a section where the output shaft 1204 does not rotate even though the motor rotates. Therefore, the output shaft position detected by the output shaft encoder 1205 does not change from time t3 to time t4, as shown in the movement trajectory LB.

After this, the movement trajectory LB of the output shaft encoder 1205 begins to change after time t4 and changes linearly thereafter. Here, the time between time t3 and time t4 is approximately the same as the time between time t0 and time t1. Due to the change in the motor control position between time t3 and time t4, the output shaft position approaches the motor control position, and at time t4, the output shaft position and the motor control position are at the same position. Then, at time t5, when the motor 1201 reaches the 0-degree position, the output shaft position detected by the output shaft encoder 1205 becomes approximately the 0-degree position oe2, as shown in the movement trajectory LB. Here, the difference between the values of position oe1 and position oe2 is the amount of backlash. Therefore, the system control unit 1006 can calculate the amount of backlash by calculating the difference in output shaft position when controlled to the same position (in this case, the 0-degree position) from both the positive and negative directions, without requiring any operation from the operator. The system control unit 1006 may also calculate the backlash amount by calculating the difference between the motor control position and the output shaft position at time t2. In other words, the system control unit 1006 may calculate the backlash amount by calculating the difference between the motor control position and the output shaft position at the time when the motor control position becomes 0 degrees. Furthermore, the system control unit 1006 may calculate the backlash amount by calculating the difference between the amount of movement of the motor control position and the amount of movement of the output shaft position from time t1 onwards, when the output shaft position begins to change.

Here, the system control unit 1006 calculates the backlash amount as the difference in detected positions by the motor shaft encoder 1202 and the output shaft encoder 1205 when controlled from the positive and negative directions, respectively, at the 0-degree position. However, it is not limited to this. The system control unit 1006 may also calculate the backlash amount as the difference in positions of the motor shaft and the output shaft when similarly controlled to the same position from the positive and negative directions, respectively, at a different location.

Figure 5 is a flowchart illustrating the backlash calculation process of the pan/tilt head device 1000 in the first embodiment. This flowchart shows the process executed by the processor 1191 of the system control unit 1006, which reads a computer program from the storage 1193 and loads the program and various data into the memory 1192. The system control unit 1006 executes the flowchart in Figure 5 when it receives a command to calculate backlash. In this flowchart, the system control unit 1006 acquires the output axis position based on predetermined conditions and calculates the backlash amount based on that output axis position. For simplicity, this embodiment describes the control process in the pan direction, but the control process in the tilt direction follows a similar flowchart.

In step S1001, the system control unit 1006 controls the motor 1201 to drive the pan drive unit 1004 to a predetermined position in the positive direction. The amount of movement here is a predetermined amount that eliminates backlash and is sufficient, for example, 10 degrees. In this flowchart, the amount of movement of the pan drive unit 1004 is, for example, the motor control position detected by the motor shaft encoder 1202 of the motor 1201, and is the movement trajectory LA.

In step S1002, the system control unit 1006 controls the motor 1201 to drive the pan drive unit 1004 to the 0-degree position. Since the pan drive unit 1004 was driven from the +10-degree position to 0 degrees in step S1001, the system control unit 1006 will drive the pan drive unit 1004 10 degrees in the negative direction. Driving to the 0-degree position in step S1002 is an example of a predetermined condition.

In step S1003, the system control unit 1006 obtains the output shaft position from the output shaft encoder 1205 as the position of the output shaft of the pan drive unit 1004. For example, the system control unit 1006 obtains +0.01 degrees as the output shaft position.

In step S1004, the system control unit 1006 controls the motor 1201 to drive the pan drive unit 1004 to a predetermined position in the negative direction. The amount of movement here is similarly sufficient to eliminate backlash, for example, 10 degrees.

In step S1005, the system control unit 1006 controls the motor 1201 to drive the pan drive unit 1004 to the 0-degree position. Since the pan drive unit 1004 was driven from the -10-degree position to 0 degrees in step S1004, it will be driven 10 degrees in the positive direction. Driving to the 0-degree position in step S1005 is just one example of a predetermined condition.

In step S1006, the system control unit 1006 obtains the output shaft position of the pan drive unit 1004 from the output shaft encoder 1205. For example, the system control unit 1006 obtains -0.02 degrees as the output shaft position.

In step S1007, the system control unit 1006 calculates the backlash amount from the acquired output shaft position. Specifically, the system control unit 1006 calculates the backlash amount based on the difference between the output shaft position when driven from a 10-degree position in the positive direction to a 0-degree position, and the output shaft position when driven from a 10-degree position in the negative direction to a 0-degree position. For example, in the above case, the system control unit 1006 calculates the backlash amount as 0.03 degrees using the following formula.

0.01 - (-0.02) = 0.03 degrees. As a result, the system control unit 1006 terminates this process.

The system control unit 1006 processes the tilt control of the pan/tilt head device 1000 in the same manner as the pan control described above.

Thus, the pan-head unit 1000 can determine the amount of backlash included in the pan-drive unit 1004 and the tilt-drive unit 1005 based on the motor control position and output shaft position when the pan-drive unit 1004 and the tilt-drive unit 1005 are controlled to the same position from different directions. This allows the pan-head unit 1000 to easily calculate the amount of backlash without requiring any operation from the operator. Furthermore, by using the determined amount of backlash in the control of the pan-drive and tilt-drive, the pan-head unit 1000 can reduce stopping position errors caused by backlash.

Here, we have shown an example of a configuration in which a brushless DC motor is used as the drive source motor 1201 for the pan drive unit 1004 and the tilt drive unit 1005, and a motor shaft encoder 1202 is provided on the motor shaft to detect the motor's position, and the motor 1201 is controlled using the motor control position detected by the motor shaft encoder 1202 as the control variable for the motor 1201. However, the system is not limited to this configuration. For example, a similar method may be used in a configuration where a stepping motor is used as the drive source motor 1201, and the position is controlled using the number of pulses or steps of the stepping motor as the control variable.

In the first embodiment described above, the backlash amount was calculated by driving in both the positive and negative directions, but the calculation method is not limited to this. For example, the system control unit 1006 may drive the motor 1201 in either direction and calculate the backlash amount based on the motor control position and output shaft position when the motor control position is driven to a predetermined position (e.g., the 0-degree position). Specifically, the system control unit 1006 may drive the motor 1201 in either direction and calculate the backlash amount based on the difference between the amount of movement of the output shaft position and the amount of movement of the motor control position (in this case, the 0-degree position) when the motor control position is driven to a predetermined position (e.g., the 0-degree position).

(Second embodiment)
Next, referring to Figures 6 to 9, the method for calculating backlash at the start of drive during reversal operation will be mainly described for the second embodiment. For components similar to those in the first embodiment, the same reference numerals used previously will be used, and their detailed explanations will be omitted. The explanation will focus on the differences from the first embodiment. This method of omitting explanations will be the same for other embodiments described later.

Figure 6 illustrates the relationship between the motor control position and the output shaft position of the drive unit in the second embodiment. In Figure 6, the horizontal axis represents time, and the vertical axis represents the motor control position (i.e., the value of the motor shaft encoder 1202) and the output shaft position (i.e., the value of the output shaft encoder 1205). The solid line represents the movement trajectory LA of the motor shaft encoder 1202. The dotted line represents the movement trajectory LB of the output shaft encoder 1205.

Figure 6 shows the behavior during reversal, that is, when the motor is driven in the negative direction and then starts moving in the positive direction. Assume that at time t0, the motor 1201 is at position me0 at 0 degrees. The system control unit 1006 drives the motor 1201 from position me0 in the positive direction to position me2. At this time, the system control unit 1006 controls the motor 1201 based on the motor control position, which is the value of the motor shaft encoder 1202. In this case, the motor shaft encoder 1202 changes linearly, as shown in the movement trajectory LA. On the other hand, for a certain period from the start of driving, there is a section in which the output shaft 1204 does not rotate even though the motor 1201 rotates due to the backlash of the reduction mechanism 1203. Therefore, the output shaft position, which is the value of the output shaft encoder 1205, does not change from time t0 to time t1. Then, the output shaft position detected by the output shaft encoder 1205 begins to change after time t1, that is, after the motor shaft encoder 1202 has driven to position me1, as shown in the movement trajectory LB, and thereafter changes linearly. At time t2, when the motor control position detected by the motor shaft encoder 1202 reaches position me2, the output shaft position detected by the output shaft encoder 1205 becomes a slightly less advanced position oe2.

Here, the difference between the position me0 value and the position me1 value detected by the motor shaft encoder 1202 is the amount of backlash. In this way, the amount of backlash can be calculated from the motor shaft encoder value by observing the change in the output shaft encoder 1205 at the start of the drive during the reversal operation.

Figure 7 is a flowchart illustrating the backlash calculation process of the pan/tilt head device 1000 in the second embodiment. This flowchart is executed by the processor 1191 of the system control unit 1006, which reads a computer program from the storage 1193 and loads various programs and data into the memory 1192. The system control unit 1006 executes the flowchart in Figure 7 when it receives a pan drive command. In this flowchart, the system control unit 1006 acquires the motor control position based on predetermined conditions and calculates the backlash amount based on that motor control position. For simplicity, this embodiment describes the control process in the pan direction, but the control process in the tilt direction follows a similar flowchart.

In step S2001, the system control unit 1006 determines whether the new driving direction is different from the previous driving direction. If the system control unit 1006 determines that the driving direction is different, i.e., that the driving direction has reversed, it proceeds to step S2002. On the other hand, if the system control unit 1006 determines that the driving direction is the same, it terminates this process.

In step S2002, the system control unit 1006 obtains the motor control position and output shaft position of the pan drive at the start of driving after reversal from the motor shaft encoder 1202 and the output shaft encoder 1205. Here, the system control unit 1006 obtains, for example, 0.01 degrees for both the motor control position and the output shaft position. The start of driving after reversal is an example of a predetermined condition.

In step S2003, the system control unit 1006 controls the motor 1201 to start driving the pan drive unit 1004.

In step S2004, the system control unit 1006 determines whether or not there has been a change in the output shaft position. Specifically, the system control unit 1006 obtains the output shaft position of the pan drive unit 1004 from the output shaft encoder 1205. The system control unit 1006 compares the newly obtained output shaft position with the output shaft position at the start of the drive to determine whether or not there has been a change. If the system control unit 1006 determines that the output shaft position has changed, it proceeds to S2005. On the other hand, if the system control unit 1006 determines that there has been no change in the output shaft position, it returns to the process in S2004 and continues processing until it determines that there has been a change. "There has been a change in the output shaft position" is an example of a predetermined condition.

In step S2005, the system control unit 1006 obtains the motor control position from the motor shaft encoder 1202. For example, 0.03 degrees is obtained as the motor control position.

In step S2006, the system control unit 1006 calculates the backlash amount from the difference between the motor control position at the start of driving and the motor control position at the start of the change in the output shaft position detected by the output shaft encoder 1205. For example, in the case of the above values, the system control unit 1006 calculates the backlash amount as 0.02 degrees using the following formula.

0.03 - 0.01 = 0.02 degrees. As a result, the system control unit 1006 terminates this process.

The system control unit 1006 processes the tilt control of the pan/tilt head device 1000 in the same manner as the pan control described above.

Thus, the pan/tilt head unit 1000 determines the amount of backlash in the drive unit using the motor control position during the reversal operation of the pan drive unit 1004 and the tilt drive unit 1005, and the motor control position at the start of the change in the output shaft position. This allows the pan/tilt head unit 1000 to calculate the amount of backlash without requiring any operator intervention. Furthermore, by using the determined amount of backlash in its control, the pan/tilt head unit 1000 can reduce stopping position errors caused by backlash.

Figure 8 illustrates another relationship between the motor control position and the output shaft position of the drive unit in the second embodiment. In Figure 8, the horizontal axis represents the time axis, and the vertical axis represents the motor control position (i.e., the value of the motor shaft encoder 1202) and the output shaft position (i.e., the value of the output shaft encoder 1205). The solid line represents the movement trajectory LA of the motor shaft encoder 1202. The dotted line represents the movement trajectory LB of the output shaft encoder 1205.

Figure 8 shows the behavior during reversal, that is, when the motor is driven in the negative direction and then starts moving in the positive direction. Assume that at time t0, the motor 1201 is at position me0 at 0 degrees. The system control unit 1006 drives the motor 1201 from position me0 in the positive direction to position me2. At this time, the system control unit 1006 controls the motor 1201 based on the motor control position, which is the value of the motor shaft encoder 1202. During this time, the movement trajectory LA of the motor shaft encoder 1202 changes linearly. On the other hand, there is a period when the output shaft position, which is the value of the output shaft encoder 1205, is driven by a small amount from the start of driving. Specifically, from time t0 to time t1, that is, until the motor control position detected by the motor shaft encoder 1202 reaches position me1, the output shaft position detected by the output shaft encoder 1205 changes to position me1. This change shows a phenomenon that can be seen due to the characteristics of the drive transmission system, in particular the spring component of the drive transmission system. This occurs because, during the drive phase before the motor 1201 reverses direction, the backlash becomes compressed at the point when the negative direction drive is completed, and the spring force of the drive transmission system is charged into the drive transmission system.

Subsequently, when the reverse operation occurs, the charged force is released, causing the output shaft 1204 to move by a small amount, as shown from time t0 to time t1. After the small amount of movement, as described above, there is a period of time during which the output shaft 1204 does not rotate even though the motor 1201 rotates due to the backlash of the reduction mechanism 1203. Specifically, the output shaft position detected by the output shaft encoder 1205 does not change from time t1 to time t2. After time t2, that is, after the motor control position detected by the motor shaft encoder 1202 exceeds position me2, the output shaft position detected by the output shaft encoder 1205 begins to change. From then on, the output shaft position detected by the output shaft encoder 1205 follows a linearly changing movement trajectory LB. Then, at time t3, when the motor control position detected by the motor shaft encoder 1202 reaches position me3, the output shaft position detected by the output shaft encoder 1205 takes the value of position oe3, which is slightly below the target position.

In the case of a drive mechanism with such characteristics, the amount of backlash can be measured not at the start of driving, but by the difference between the value of position me1 and the value of position me2 detected by the motor shaft encoder 1202 from the point when the change after a small change following the start of driving ceases until the next change occurs.

Figure 9 is a flowchart illustrating another backlash calculation process for the pan/tilt head device 1000 of the second embodiment. This flowchart shows that the processor 1191 of the system control unit 1006 executes this process by reading a computer program from the storage 1193 and loading the program and various data into the memory 1192. The system control unit 1006 executes the flowchart in Figure 9 when it receives a pan drive command. For simplicity, this embodiment describes the control process in the pan direction, but the control process in the tilt direction follows a similar flowchart.

In step S3001, the system control unit 1006 determines whether the new driving direction is different from the previous driving direction. If the system control unit 1006 determines that the driving direction is different, i.e., that the driving direction has reversed, it proceeds to step S3002. On the other hand, if the system control unit 1006 determines that the driving direction is the same, it terminates this process.

In step S3002, the system control unit 1006 obtains the motor control position and output shaft position of the pan drive unit 1004 at the start of driving after reversal, from the motor shaft encoder 1202 and the output shaft encoder 1205.

In step S3003, the system control unit 1006 controls the motor 1201 to start driving the pan drive unit 1004.

In step S3004, the system control unit 1006 determines whether or not there has been a change in the output shaft position. Specifically, the system control unit 1006 obtains the output shaft position of the pan drive unit 1004 from the output shaft encoder 1205. The system control unit 1006 compares the newly obtained output shaft position with the previously obtained output shaft position and determines whether or not there has been a change, i.e., whether the change has stopped. If the system control unit 1006 determines that the change has stopped and there is no change, it proceeds to S3005. On the other hand, if the system control unit 1006 determines that there is a change, it repeats step S3004 until it determines that the change has stopped and there is no change. The fact that there has been no change in the output shaft position after reversal is one example of a predetermined condition.

In step S3005, the system control unit 1006 obtains the motor control position and output shaft position of the pan drive unit 1004 from the motor shaft encoder 1202 and the output shaft encoder 1205. Here, the system control unit 1006 obtains, for example, 0.02 degrees as the motor control position.

In step S3006, the system control unit 1006 determines whether there has been a change in the stopped output shaft position. Specifically, the system control unit 1006 obtains the output shaft position of the pan drive unit 1004 from the output shaft encoder 1205. The system control unit 1006 compares the newly obtained output shaft position with the output shaft position obtained in step S3005 at the point when the change in the output shaft position ceased, and determines whether the output shaft position has changed. If the system control unit 1006 determines that the output shaft position has changed, that is, that the change in the output shaft position that had stopped has resumed, it proceeds to S3007. On the other hand, if the system control unit 1006 determines that the output shaft has not changed, it returns to the process in S3006 and continues processing until it determines that there has been a change. The resumption of the change in the output shaft position that had stopped is one example of a predetermined condition.

In step S3007, the system control unit 1006 obtains the motor control position from the motor shaft encoder 1202. Here, the system control unit 1006 obtains, for example, 0.03 degrees as the motor control position.

In step S3008, the system control unit 1006 calculates the backlash amount based on the difference between the motor control position at the point when the output shaft position change stops and the motor control position at the point when the output shaft position change resumes. The point when the output shaft position change stops is time t1 in Figure 8. The point when the output shaft position change resumes is time t2 in Figure 8. For example, in the above case, the system control unit 1006 calculates the backlash amount as 0.01 degrees using the following formula.

0.03 - 0.02 = 0.01 degrees. As a result, the system control unit 1006 terminates this process.

The system control unit 1006 processes the tilt control of the pan/tilt head device 1000 in the same manner as the pan control described above.

Thus, the pan/tilt head unit 1000 determines the amount of backlash in the drive unit using the motor control position at the time the change in the output shaft position stops and resumes after the start of the reversal operation of the pan drive unit 1004 and the tilt drive unit 1005. This allows the pan/tilt head unit 1000 to calculate the amount of backlash without requiring any operation from the operator. Furthermore, by using the determined amount of backlash in its control, the pan/tilt head unit 1000 can reduce the stopping position error caused by backlash.

This example demonstrates the reversal operation at 0 degrees, but it is not limited to this; measurements can also be taken at any predetermined position other than 0 degrees. Similarly, this example demonstrates the reversal operation from the negative direction to the positive direction, but it is not limited to this; measurements can also be taken when the reversal operation is performed from the positive direction to the negative direction.

The embodiments described above may be combined. For example, the backlash calculation process of each embodiment may be configured to be executable on a single pan/tilt head device, allowing the operator to select which one to use.

In the above-described embodiment, an example was given in which the imaging device 2000 and the pan/tilt head device 1000 are separate components. However, the configuration of the pan/tilt head device 100 is not limited to this. For example, the pan/tilt head device may be integrated with the imaging device.

(Other examples)
The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. Furthermore, the present invention can also be realized by a circuit (for example, an ASIC) that implements one or more functions.

This disclosure includes the following pan/tilt head devices, control methods for pan/tilt head devices, and programs.
(Item 1)
A pan-tilt head device for changing the shooting direction of an imaging means used to photograph a subject,
A drive source that outputs driving force,
A reduction mechanism for reducing the driving force of the aforementioned drive source,
An output shaft connected to the reduction mechanism to which the reduced driving force is transmitted and which changes the shooting direction of the imaging means,
An output shaft position detection means for detecting the output shaft position, which is the position of the output shaft,
Control means for controlling the drive source,
Equipped with,
The control means is characterized by acquiring at least one of the control position, which is the position of the drive source, and the output shaft position, based on predetermined conditions, and determining the amount of backlash based on the acquired control position and output shaft position.
(Item 2)
The pan/tilt head device according to item 1, characterized by comprising drive control position detection means for detecting the control position of the drive source.
(Item 3)
The aforementioned drive source is a stepper motor,
The pan/tilt head device according to item 1, characterized in that the control means uses the number of pulses of the stepping motor as the control position of the drive source.
(Item 4)
The control means is
The tripod head device according to any one of items 1 to 3, characterized in that the amount of backlash is calculated based on the position of the first output shaft at the time the drive source is driven to a predetermined position in a first direction.
(Item 5)
The control means is
The tripod head device according to item 4, characterized in that the amount of backlash is calculated based on the difference between the second output shaft position and the first output shaft position at the time the drive source is driven to the predetermined position in a second direction opposite to the first direction.
(Item 6)
The control means is
The tripod head device according to item 4, wherein the drive source is driven in a second direction opposite to the first direction by an amount of movement that eliminates the amount of backlash, before being driven in the first direction.
(Item 7)
The control means is
The first control position of the drive source at the start of driving when the drive source, which is being driven in a first direction, starts driving in a second direction opposite to the first direction, is obtained.
The second control position of the drive source is obtained after the start of the drive and at the point when the output shaft position changes.
The tripod head device according to any one of items 1 to 6, characterized in that the difference between the first control position and the second control position is calculated as the amount of backlash.
(Item 8)
The control means is
The first control position of the drive source is obtained when the drive source, which is being driven in a first direction, starts to be driven in a second direction opposite to the first direction, and there is no longer any change in the output shaft position.
The second control position of the drive source is obtained at the point when the change in the output shaft position resumes.
The tripod head device according to any one of items 1 to 7, characterized in that the difference between the first control position and the second control position is calculated as the amount of backlash.
(Item 9)
A drive source that outputs driving force,
A reduction mechanism for reducing the driving force of the aforementioned drive source,
An output shaft connected to the reduction mechanism to which the reduced driving force is transmitted and which changes the shooting direction of the imaging means,
An output shaft position detection means for detecting the output shaft position, which is the position of the output shaft,
Control means for controlling the drive source,
A control method for a pan/tilt head device that changes the shooting direction of an imaging means for photographing a subject, comprising:
A method for controlling a tripod head device, characterized by acquiring at least one of the control position, which is the position of the drive source, and the output shaft position, based on predetermined conditions, and determining the amount of backlash based on the acquired control position and output shaft position.
(Item 10)
A program to cause a computer to function as a control means for the pan/tilt head device described in any one of items 1 through 8.

The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the claims are attached to disclose the scope of the invention.

1000...Trolling head unit, 2000...Imaging unit, 3000...Client unit, 1004...Pan drive unit, 1005...Tilt drive unit, 1006...System control unit, 1201...Motor, 1202...Motor shaft encoder, 1203...Reduction mechanism, 1204...Output shaft, 1205...Output shaft encoder.

Claims (11)

A pan-tilt head device for changing the shooting direction of an imaging means used to photograph a subject,
A drive source that outputs driving force,
A reduction mechanism for reducing the driving force of the aforementioned drive source,
An output shaft connected to the reduction mechanism to which the reduced driving force is transmitted and which changes the shooting direction of the imaging means,
An output shaft position detection means for detecting the output shaft position, which is the position of the output shaft,
Control means for controlling the drive source,
Equipped with,
The tripod head device is characterized in that the control means acquires at least one of the control position, which is the position of the drive source, and the output shaft position, based on predetermined conditions, and determines the amount of backlash based on the acquired control position and output shaft position. The tripod head device according to claim 1, further comprising drive control position detection means for detecting the control position of the drive source. The aforementioned drive source is a stepper motor,
The pan/tilt head device according to claim 1, characterized in that the control means uses the number of pulses of the stepping motor as the control position of the drive source. The control means is
The tripod head device according to claim 1, characterized in that the amount of backlash is calculated based on the first output shaft position at the time the drive source is driven to a predetermined position in a first direction. The control means is
The tripod head device according to claim 4, characterized in that the amount of backlash is calculated based on the difference between the second output shaft position and the first output shaft position at the time the drive source is driven to the predetermined position in a second direction opposite to the first direction. The control means is
The tripod head device according to claim 4, wherein the drive source is driven in a second direction opposite to the first direction by an amount of movement that eliminates the amount of backlash, before being driven in the first direction. The control means is
The first control position of the drive source at the start of driving when the drive source, which is being driven in a first direction, starts driving in a second direction opposite to the first direction, is obtained.
The second control position of the drive source is obtained after the start of the drive and at the point when the output shaft position changes.
The tripod head device according to claim 1, characterized in that the difference between the first control position and the second control position is calculated as the amount of backlash. The control means is
The first control position of the drive source is obtained when the drive source, which is being driven in a first direction, starts to be driven in a second direction opposite to the first direction, and there is no longer any change in the output shaft position.
The second control position of the drive source is obtained at the point when the change in the output shaft position resumes.
The tripod head device according to claim 1, characterized in that the difference between the first control position and the second control position is calculated as the amount of backlash. The pan/tilt head device according to claim 1, wherein the output axis position detection means is an absolute value encoder. A drive source that outputs driving force,
A reduction mechanism for reducing the driving force of the aforementioned drive source,
An output shaft connected to the reduction mechanism to which the reduced driving force is transmitted and which changes the shooting direction of the imaging means,
An output shaft position detection means for detecting the output shaft position, which is the position of the output shaft,
Control means for controlling the drive source,
A control method for a pan/tilt head device that changes the shooting direction of an imaging means for photographing a subject, comprising:
A method for controlling a tripod head device, characterized by acquiring at least one of the control position, which is the position of the drive source, and the output shaft position, based on predetermined conditions, and determining the amount of backlash based on the acquired control position and output shaft position. A program for causing a computer to function as a control means for the pan/tilt head device described in any one of claims 1 to 9 .