Patent Description:
Elongated facilities, such as pipelines laid on a water bottom, can be efficiently inspected by using a submersible vessel. The submersible vessel that performs the inspection includes an inspection tool and a movable arm that positions the inspection tool at an arbitrary position (see PTL <NUM>). To move the inspection tool along the inspection target, while making the submersible vessel sail, a positional relation between the inspection tool and the inspection target may be detected, and the movable arm may be controlled such that the positional relation becomes constant. Document <CIT> discloses a similar submersible vessel. Nevertheless it does not comprise a position detector and it does not take into consideration the parameter of time.

However, according to the above control method, correction is not performed before a positioning error between the inspection tool and the inspection target is generated, but the correction is performed after the positioning error is generated. Therefore, the followability of the inspection tool with respect to the inspection target is not necessarily satisfactory.

The present invention was made under these circumstances, and an object of the present invention is to provide a submersible vessel that is configured to inspect an elongated inspection target disposed on a water bottom and has satisfactory followability of an inspection tool with respect to an inspection target.

A submersible vessel according to one aspect of the present invention is a submersible vessel that is configured to inspect an elongated inspection target disposed on a water bottom. The submersible vessel includes: a hull; a propulsor that is configured to propel the hull; a front sensor that is configured to sequentially detect locations of the inspection target in front of the hull; a controller that is configured to control the propulsor such that the hull passes through above the detected locations; a movable arm attached to an arm reference point of the hull; an inspection tool that is disposed at the movable arm and is configured to inspect the inspection target; and a position detector that is configured to acquire positional information including at least one of a position, an attitude, or a speed of the hull. Based on the positional information acquired by the position detector, the controller is configured to estimate a pass-through position of the arm reference point after a predetermined time. The controller is configured to control the movable arm such that before the predetermined time elapses, a positional relation between the arm reference point and the inspection tool becomes a positional relation between the estimated pass-through position and a target point on or above each location.

According to this configuration, since the position of the inspection tool can be appropriately adjusted before the inspection tool passes through above the location of the inspection target, the followability of the inspection tool with respect to the inspection target improves.

According to the above configuration, the submersible vessel having satisfactory followability of the inspection tool with respect to the inspection target can be provided.

Hereinafter, a submersible vessel <NUM> according to an embodiment will be described. First, an entire configuration of the submersible vessel <NUM> will be described. <FIG> is a side view of the submersible vessel <NUM>. The submersible vessel <NUM> according to the present embodiment inspects an elongated inspection target <NUM> disposed on a water bottom. One example of the inspection target <NUM> is a pipeline.

As shown in <FIG>, the submersible vessel <NUM> includes a hull <NUM>, a propulsor <NUM>, a front sensor <NUM>, a movable arm <NUM>, an inspection tool <NUM>, and a position detector <NUM>. The hull <NUM> is a base portion of the submersible vessel <NUM>, and various devices are attached to the hull <NUM>.

The propulsor <NUM> is a device that propels the hull <NUM>. The propulsor <NUM> includes propulsion structures and a rudder that changes the route of the hull <NUM>. Examples of the propulsion structures include: a main propulsion thruster that moves the hull <NUM> forward; a vertical thruster that moves the hull <NUM> in an upper-lower direction; and a horizontal thruster that moves the hull <NUM> in a left-right direction. The propulsor <NUM> is not limited to the above configuration and may include, for example, a swing thruster that can change a direction in which thrust is generated.

The front sensor <NUM> is a device that sequentially detects locations of the inspection target <NUM> (a position of the inspection target <NUM>) in front of the hull <NUM>. The detection of the front sensor <NUM> is performed at a predetermined sampling interval (for example, <NUM> milliseconds). The front sensor <NUM> is disposed at the hull <NUM> and performs the detection during the propulsion of the hull <NUM>. The front sensor <NUM> of the present embodiment is a so-called multibeam sonar. However, the front sensor <NUM> may be a shape recognition laser or may be a combination of the multibeam sonar and the shape recognition laser.

The movable arm <NUM> is a device that positions the inspection tool <NUM> at an arbitrary position. A base end portion of the movable arm <NUM> is attached to the hull <NUM>, and the inspection tool <NUM> is disposed at a tip portion of the movable arm <NUM>. A portion of the hull <NUM> to which the movable arm <NUM> is attached is referred to as an "arm reference point. " The position of an arm reference point <NUM> is not especially limited. The arm reference point <NUM> of the present embodiment is located at a rear portion of the hull <NUM> and behind the front sensor <NUM>. A positional relation between the arm reference point <NUM> and the inspection tool <NUM> can be adjusted by controlling the movable arm <NUM>.

The movable arm <NUM> includes: a parallel link <NUM>; a first joint <NUM> located between the parallel link <NUM> and the hull <NUM>; and a second joint <NUM> located between the parallel link <NUM> and the inspection tool <NUM>. However, the movable arm <NUM> is not limited to the above configuration and may include, for example, parallel links. Moreover, instead of the parallel link <NUM>, the movable arm <NUM> may include a coupler whose positional relation with the hull <NUM> or the inspection tool <NUM> is not limited.

The inspection tool <NUM> is a device that inspects the inspection target <NUM>. The inspection tool <NUM> of the present embodiment is an imaging camera (for example, a TV camera) that takes an image of the inspection target <NUM>. Instead of or in addition to the imaging camera, the inspection tool <NUM> may include, for example, one or both of: an anticorrosion inspector that inspects the degree of deterioration of an anticorrosion treatment (for example, anticorrosion painting) over the entire length of the pipeline; and a thickness inspector that inspects the thickness of the pipeline to inspect the degree of corrosion and the presence or absence of damage.

The position detector <NUM> is a device that acquires positional information including the position (an X-axis direction position, a Y-axis direction position, and a Z-axis direction position) of the hull <NUM>, the attitude (angles around an X-axis. and a Z-axis) of the hull <NUM>, and the speed (an X-axis direction speed, a Y-axis direction speed, and a Z-axis direction speed, and angular speeds around the X-axis, the Y-axis, and the Z-axis) of the hull <NUM>. The position detector <NUM> of the present embodiment is an inertial navigation system (INS) and acquires the positional information by using an acceleration sensor and a gyro sensor. However, the position detector <NUM> may be a device other than the inertial navigation system. Moreover, the positional information may include at least one of the position, attitude, or speed of the hull <NUM>.

Next, the configuration of a control system of the submersible vessel <NUM> will be described. <FIG> is a block diagram of the control system of the submersible vessel <NUM>. As shown in <FIG>, the submersible vessel <NUM> according to the present embodiment includes a controller <NUM>. The controller <NUM> includes a processor, a volatile memory, a non-volatile memory, an I/O interface, etc. The non-volatile memory of the controller <NUM> stores a below-described sail program, a below-described follow program, and various data, and the processor of the controller <NUM> performs calculation processing based on the programs by using the volatile memory.

The controller <NUM> is electrically connected to the front sensor <NUM> and the position detector <NUM>. The controller <NUM> can acquire the location of the inspection target <NUM> from the front sensor <NUM> and can acquire the positional information from the position detector <NUM>. Moreover, the controller <NUM> is electrically connected to the propulsor <NUM> and the movable arm <NUM> and can transmit a control signal to the propulsor <NUM> and the movable arm <NUM> to control the propulsor <NUM> and the movable arm <NUM>. In the present embodiment, a time interval (hereinafter referred to as an "update interval) at which the controller <NUM> acquires the location of the inspection target <NUM> and the positional information is <NUM> milliseconds, and a time interval (hereinafter referred to as a "command interval") at which the controller <NUM> outputs the control signal to the movable arm <NUM> is <NUM> milliseconds.

Next, the sail program executed by the controller <NUM> will be described. The sail program is a program by which the hull <NUM> sails along the inspection target <NUM>. <FIG> is a flow chart of the sail program. As shown in <FIG>, when the sail program starts, the controller <NUM> first acquires the location of the inspection target <NUM> (Step S1). The location can be acquired from the front sensor <NUM>. <FIG> is a diagram for explaining the movements of the submersible vessel <NUM> when the sail program is executed. In Step S1, the controller <NUM> acquires, for example, a position shown by a sign A in <FIG> as the location (herein, the controller <NUM> acquires only one location).

Next, the controller <NUM> controls the propulsor <NUM> such that the hull <NUM> passes through above the locations (Step S2). In the present embodiment, the hull <NUM> is propelled toward above the location acquired by the controller <NUM>. In Step S2, for example, the controller <NUM> propels the hull <NUM> toward above the position shown by the sign A which is the location in <FIG> (see a white arrow in <FIG>). After Step S2, the controller <NUM> returns to Step S1 and repeats the respective steps. With this, the hull <NUM> can move along the inspection target <NUM>.

Next, the follow program executed by the controller <NUM> will be described. The follow program is a program that makes the inspection tool <NUM> follow the inspection target <NUM>. <FIG> is a flow chart of the follow program. The follow program is executed in parallel with the above-described sail program. As shown in <FIG>, when the follow program starts, the controller <NUM> first acquires the positional information (the position, attitude, and speed of the hull <NUM>) (Step S11). The positional information can be acquired from the position detector <NUM>.

Next, based on the positional information, the controller <NUM> estimates a pass-through position of the arm reference point <NUM> after a predetermined time (herein, the predetermined time is <NUM> milliseconds but is not limited to this) (Step S12). <FIG> is a diagram for explaining the movements of the submersible vessel <NUM> when the follow program is executed. In Step S12, as the pass-through position of the arm reference point <NUM> after the predetermined time, the controller <NUM> estimates, for example, a position shown by a sign B in <FIG>. The position of the submersible vessel <NUM> shown by broken lines in <FIG> is an estimated position of the submersible vessel <NUM> after the predetermined time.

In Step S12, the pass-through position of the arm reference point <NUM> after the predetermined time is estimated on the assumption that the hull <NUM> is maintained in a latest state. To be specific, when the latest ones among the positions, attitudes, and speeds of the hull <NUM> acquired by the position detector <NUM> are respectively referred to as a "latest position," a "latest attitude," and a "latest speed," the pass-through position of the arm reference point <NUM> after the predetermined time is estimated on the assumption that the hull <NUM> moves for the predetermined time from the latest position at the same speed as the latest speed while maintaining the latest attitude. However, the pass-through position of the arm reference point <NUM> after the predetermined time may be estimated by a different method. For example, the pass-through position of the arm reference point <NUM> after the predetermined time may be estimated without considering the angular speed of the hull <NUM>.

Next, the controller <NUM> acquires the location of the inspection target <NUM> (Step S13). As described above, the location of the inspection target <NUM> can be acquired from the front sensor <NUM>. In Step S13, as the location, the controller <NUM> acquires, for example, the position shown by the sign A in <FIG>.

Next, the controller <NUM> controls the movable arm <NUM> such that before the above-described predetermined time (<NUM> milliseconds) elapses, the positional relation between the arm reference point <NUM> and the inspection tool <NUM> becomes a positional relation between the estimated pass-through position (B) and a target point on or above the location (A) (Step S14). With this, at a time point after the above-described predetermined time has elapsed, the inspection tool <NUM> can be located at the target point on or above the location.

The target point may be set on an upper surface of the inspection target <NUM> or may be set at a position upwardly away from the upper surface of the inspection target <NUM> by a predetermined distance. Moreover, the location in Step S14 may be a latest location acquired by the controller <NUM> or may be a location other than the latest location. The selection of the location depends on the update interval of the location, the dimension of the hull <NUM>, the speed of the hull <NUM>, and the like.

After Step S14, the controller <NUM> returns to Step S11 and repeats the respective steps. With this, the inspection tool <NUM> can move above the inspection target <NUM>. In addition, according to the present embodiment, since the inspection tool <NUM> can be positioned at an appropriate position in advance, the followability of the inspection tool <NUM> with respect to the inspection target <NUM> improves.

The foregoing has described the follow program when the update interval of the location of the inspection target <NUM>, the update interval of the positional information, and the command interval of the movable arm <NUM> are equal to each other (<NUM> milliseconds). However, when each of the update interval of the positional information and the command interval of the movable arm <NUM> is shorter than the update interval of the location of the inspection target <NUM>, a below-described "virtual" location is set, and with this, the followability of the inspection tool <NUM> with respect to the inspection target <NUM> can be improved. Details are as below.

Herein, it is assumed that the update interval of the location of the inspection target <NUM> is <NUM> milliseconds, and each of the update interval of the positional information and the command interval of the movable arm <NUM> is <NUM> milliseconds. In this case, the controller <NUM> sets three virtual locations between the adjacent locations. The virtual locations can be set on a straight line connecting the adjacent two locations. However, the virtual locations may be set by a different method.

Next, the controller <NUM> acquires the positional information and estimates, based on the acquired positional information, the pass-through position of the arm reference point <NUM> after the predetermined time (herein, the predetermined time is <NUM> milliseconds but is not limited to this). Moreover, the controller <NUM> controls the movable arm <NUM> such that before the above predetermined time elapses, the positional relation between the arm reference point <NUM> and the inspection tool <NUM> becomes the positional relation between the estimated pass-through position and the target point on or above the virtual location (or the target point on or above the location). By repeating the above steps, the inspection tool <NUM> can move above the inspection target <NUM>. According to this control method, the position of the inspection tool <NUM> can be further finely adjusted. As a result, the followability of the inspection tool <NUM> with respect to the inspection target <NUM> improves.

The submersible vessel according to the present embodiment is a submersible vessel that inspects an elongated inspection target disposed on a water bottom. The submersible vessel includes: a hull; a propulsor that propels the hull; a front sensor that sequentially detects locations of the inspection target in front of the hull; a controller that controls the propulsor such that the hull passes through above the detected locations; a movable arm attached to an arm reference point of the hull; an inspection tool that is disposed at the movable arm and inspects the inspection target; and a position detector that acquires positional information including at least one of a position, an attitude, or a speed of the hull. Based on the positional information acquired by the position detector, the controller estimates a pass-through position of the arm reference point after a predetermined time. The controller controls the movable arm such that before the predetermined time elapses, a positional relation between the arm reference point and the inspection tool becomes a positional relation between the estimated pass-through position and a target point on or above each location.

According to this configuration, since the position of the inspection tool can be appropriately adjusted before the inspection tool passes through above the location, the followability of the inspection tool with respect to the inspection target improves.

Moreover, in the submersible vessel according to the present embodiment, the controller acquires a latest position, a latest attitude, and a latest speed of the hull from the position detector, and the controller estimates the pass-through position of the arm reference point after the predetermined time on an assumption that the hull moves for the predetermined time from the latest position at a same speed as the latest speed while maintaining the latest attitude.

According to this configuration, the pass-through position of the arm reference point after the predetermined time can be easily estimated.

Moreover, in the submersible vessel according to the modified example of the present embodiment, the controller sets a virtual location between two adjacent locations among the locations. Based on the positional information acquired by the position detector, the controller estimates the pass-through position of the arm reference point after the predetermined time. The controller controls the movable arm such that before the predetermined time elapses, the positional relation between the arm reference point and the inspection tool becomes the positional relation between the estimated pass-through position and the target point on or above the virtual location.

According to this configuration, when each of the update interval of the positional information and the command interval of the movable arm is shorter than the update interval of the location of the inspection target, the followability of the inspection tool with respect to the inspection target can be improved.

Moreover, in the submersible vessel according to the modified example of the present embodiment, the controller sets the virtual location on a straight line connecting the two adjacent locations.

Claim 1:
A submersible vessel configured to inspect an elongated inspection target disposed on a water bottom,
the submersible vessel comprising:
a hull;
a propulsor configured to propel the hull;
a front sensor configured to sequentially detect locations of the inspection target in front of the hull;
a controller configured to control the propulsor such that the hull passes through above the detected locations;
a movable arm attached to an arm reference point of the hull;
an inspection tool that is disposed at the movable arm and configured to inspect the inspection target; and
a position detector configured to acquire positional information including at least one of a position, an attitude, or a speed of the hull, wherein:
based on the positional information acquired by the position detector, the controller is configured to estimate a pass-through position of the arm reference point after a predetermined time; and
the controller is configured to control the movable arm such that before the predetermined time elapses, a positional relation between the arm reference point and the inspection tool becomes a positional relation between the estimated pass-through position and a target point on or above each location.