Underwater robot

Abstract

Provided is an underwater robot capable of executing proper attitude control.　An underwater robot 10 comprises: a machine body 15; a moving member 32 for changing the center of buoyancy or the center of gravity; and a drive device 50 for moving the moving member 32. The drive device 50 includes: a first slider 37 provided on the machine body 15 in a movable manner along the X-axis direction; a second slider 41 provided on the first slider 37 in a movable manner along the Y-axis direction and connected to the moving member 32; a first belt drive mechanism 54a including a first belt 53a; and a second belt drive mechanism 54b including a second belt 53b. The first belt drive mechanism 54a includes a first drive pulley 56a, a first bend pulley 58a, and a second bend pulley 58b. The second belt drive mechanism 54b includes a second drive pulley 56b, a third bend pulley 58c, and a fourth bend pulley 58d.

Description

Underwater Robot

[0001] The present invention relates to an underwater robot.

[0002] In recent years, efforts toward realizing a low-carbon society or a carbon-neutral society have become active, and even for vehicles, CO ２ research and development on electrification technology have been conducted to reduce emissions and improve energy efficiency.

[0003] Regarding electrification technology, a portable underwater robot provided with a movable float has been conventionally known (see, for example, Non-Patent Document 1). This underwater robot controls postures such as pitch angle and roll angle by including a float driven by a link mechanism or the like.

[0004] Norimitsu Sakagami, Mizuho Shibata, Tomohiro Ueda, Kensei Ishizu, Kenshiro Yokoi, and Sadao Kawamura, "Numerical and Experimental Analysis of Portable Underwater Robots with a Movable Float Device", Journal of Robotics and Mechatronics Vol.33 No.6, 2021

[0005] However, the conventional technology described in Non-Patent Document 1 requires many links and drive sources to move the float, which results in an increase in the size of the robot.

[0006] Here, a mechanism that moves a moving member for changing the center of buoyancy or the center of gravity, like a float, by two-dimensional translational movement is conceivable. As such a mechanism, a mechanism provided with two independent power sources called so-called H-Bot is known. In order to cause the moving member to perform two-dimensional translational movement, this mechanism includes a first slide member 137 (see FIG. 10) movable in the X-axis direction, and a second slide member 141 (see FIG. 10) movable on the first slide member 137 in the Y-axis direction intersecting the X-axis direction. The moving member moves together with the second slide member 141 by being attached to the second slide member 141.

[0007] Figure 10 is an explanatory diagram of a conventional drive mechanism 150. In this drive mechanism 150, a single drive belt 153 is stretched in an H shape to impart two-dimensional translational motion to the second slide member 141, and pulleys 156 are provided at each bending point and each turning point of the drive belt 153. In the illustrated example, the left and right pulleys 156 at the bottom of the drawing are drive pulleys 156a driven by a power source, and the left and right pulleys 156 at the top are driven pulleys 156b. Two bend pulleys 156c are provided on the left and right sides of the first slide member 137 to bend (change the direction of) the drive belt 153.

[0008] As shown in Figure 10(A), when both drive pulleys 156a rotate in opposite directions, the second slide member 141 moves in the X-axis direction together with the first slide member 137. As shown in Figure 10(B), when both drive pulleys 156a rotate in the same direction, the first slide member 137 does not move, and the second slide member 141 moves in the Y-axis direction.

[0009] However, in such a drive mechanism 150, a yaw moment may be generated in the first slide member 137. Figure 11 is an explanatory diagram of the mechanism of yaw moment generation in a conventional drive mechanism 150. As shown in Figure 11(A), when the second slide member 141 is moved in the X-axis direction together with the first slide member 137, tensile forces, indicated by white arrows, act equally on the left and right bend pulleys 156c of the first slide member 137. A resultant force, indicated by black arrows, acts on the bend pulleys 156c, but the lateral components of the resultant force of the left and right bend pulleys 156c cancel each other out. Therefore, no yaw moment is generated in the first slide member 137.

[0010] On the other hand, as shown in Figure 11(B), when the second slide member 141 is moved in the Y-axis direction without moving the first slide member 137, opposite tensile forces, indicated by the white arrows, act on the left and right bend pulleys 156c of the first slide member 137. As a result, a resultant force, indicated by the black arrows, that cannot cancel each other out acts on the left and right bend pulleys 156c. This generates a yaw moment in the first slide member 137. This problem also occurs when moving the second slide member 141 while moving the first slide member 137.

[0011] When a yaw moment is generated in the first slide member 137, if the first slide member 137 is guided by the guide portion 138, it twists relative to the guide portion 138, causing sliding resistance. On the other hand, if the first slide member 137 is not guided by the guide portion 138, the first slide member 137 rotates, causing the positions of the second slide member 141 and the moving member to shift. Therefore, in either case, proper attitude control of the robot is hindered.

[0012] In view of the above background, the present invention aims to provide an underwater robot that can suppress the yaw moment generated in the first slider when the second slider is moved, and that can perform proper attitude control.

[0013] To solve the above problems, one aspect of the present invention provides an underwater robot comprising: a body; a movable member provided on the body so as to be movable along a predetermined plane and for changing the center of buoyancy or center of gravity; and a drive device for moving the movable member relative to the body. The drive device comprises: a first slider provided on the body so as to be movable in the X-axis direction on the plane; a second slider provided on the first slider so as to be movable in the Y-axis direction intersecting the X-axis direction on the plane and connected to the movable member; a first belt drive mechanism including an annular first belt connected to the second slider from one side and the other side in the Y-axis direction; and a second belt drive mechanism including an annular second belt connected to the second slider from the other side and the one side in the Y-axis direction. The first belt drive mechanism includes a first drive pulley provided on one side of the machine body in the Y-axis direction for driving the first belt, a first bend pulley provided on one side of the first slider in the Y-axis direction for which the first belt is wound, and a second bend pulley provided on the other side of the first slider in the Y-axis direction for which the first belt is wound. The second belt drive mechanism includes a second drive pulley provided on the other side of the machine body in the Y-axis direction for driving the second belt, a third bend pulley provided on the other side of the first slider in the Y-axis direction for which the second belt is wound, and a fourth bend pulley provided on one side of the first slider in the Y-axis direction for which the second belt is wound.

[0014] According to the above embodiment, the yaw moment generated in the first slider when the second slider is moved is suppressed. Therefore, it is possible to provide an underwater robot that can perform proper attitude control.

[0015] Perspective view of the underwater robot according to an embodiment Perspective view of the buoyancy adjustment section of the underwater robot Plan view of the buoyancy adjustment section of the underwater robot Perspective view of the bracket Plan view of the drive unit in the buoyancy adjustment section Side view of the drive unit in the buoyancy adjustment section Operation diagram of the drive unit Operation diagram of the drive unit Plan view of the drive unit according to a modified example Explanation diagram of a conventional drive mechanism Explanation diagram of the yaw moment generation mechanism in a conventional drive mechanism

[0016] Hereinafter, embodiments of the underwater robot 10 according to the present invention will be described with reference to the drawings.

[0017] Figure 1 is a perspective view showing the configuration of an underwater robot 10 according to an embodiment. The underwater robot 10 of the embodiment may be an unmanned mobile vehicle on the surface and underwater, such as a UUV (Unmanned Undersea Vehicle) or a USV (Unmanned Surface Vehicle). The UUV, which is an unmanned submersible, may be a remotely operated ROV (Remotely Operated Vehicle) or an autonomous AUV (Autonomous Underwater Vehicle). The remotely operated ROV may be a so-called underwater drone.

[0018] As shown in Figure 1, the configuration of the underwater robot 10 will be described below based on three mutually orthogonal axes in three-dimensional space: the X-axis, Y-axis, and Z-axis. The X-axis direction is parallel to the front-to-back direction of the underwater robot 10, the Y-axis direction is parallel to the left-to-right direction of the underwater robot 10, and the Z-axis direction is parallel to the up-to-down direction of the underwater robot 10. The positive direction of the X-axis is the front direction of the underwater robot 10, the positive direction of the Y-axis is the left direction of the underwater robot 10, and the positive direction of the Z-axis is the up direction of the underwater robot 10.

[0019] The underwater robot 10 comprises a lower robot body 11 and an upper buoyancy adjustment unit 13 that are connected to each other. The robot body 11 comprises a lower body 21 that forms the skeletal structure and a plurality of connecting columns 22 that connect the lower body 21 and the buoyancy adjustment unit 13. The lower body 21 may be, for example, rectangular ladder-shaped. The lower body 21 supports various devices mounted on the robot body 11. Each of the plurality of connecting columns 22 is a column that extends in the vertical direction and may be rectangular prism-shaped, cylindrical, etc. The plurality of connecting columns 22 are fixed to corners of the lower body 21, etc., and are connected to the buoyancy adjustment unit 13 at the top.

[0020] The robot body 11 comprises two mechanical arms 23, six thrusters 25 (25a, 25b), a camera unit 27, a sensor 28, and three control units 29 (29a, 29b). The thrusters 25 have four first thrusters 25a and two second thrusters 25b. Hereinafter, when these are not distinguished or when they are referred to collectively, they will simply be referred to as thrusters 25. The control units 29 have one front control unit 29a and two rear control units 29b. Hereinafter, when these are not distinguished or when they are referred to collectively, they will simply be referred to as control units 29.

[0021] The base ends of the two mechanical arms 23 are fixed to the left and right corners of the front of the lower body 21. Each mechanical arm 23 is a manipulator and comprises a plurality of beams (links) and at least one hinge (joint) connecting the beams (links). The hinge (joint) is driven by an actuator. Each mechanical arm 23 is equipped with an end effector 23a (hand) at its tip for performing various tasks such as grasping and moving objects, and constitutes a work unit for performing predetermined tasks. Each mechanical arm 23 is equipped with a power unit 23b at its base end that outputs power for operation. When stopped, each mechanical arm 23 is positioned inside the left and right ends of the lower body 21, and when in operation, its tip protrudes outward (forward, etc.) from the underwater robot 10.

[0022] The four first thrusters 25a are arranged in a row of two on the left and right sides at the front and rear of the lower body 21. The two second thrusters 25b are arranged in a row of two on the left and right sides at the center of the lower body 21 in the longitudinal direction. Each first thruster 25a is a so-called azimuth thruster. Each first thruster 25a comprises a support that rotates around a first rotation axis along the vertical direction, and a propeller that is supported by the support and rotates around a second rotation axis perpendicular to the first rotation axis. Each first thruster 25a generates thrust in a direction perpendicular to the vertical direction. Each second thruster 25b comprises a propeller that rotates around a rotation axis that is inclined at an acute angle with respect to the vertical direction. Each second thruster 25b generates thrust in a direction that includes at least a vertical component.

[0023] The camera unit 27 is positioned in the center of the front of the lower body 21 in the left-right direction. The camera unit 27 includes a camera that images the area in front of the underwater robot 10 and a plurality of lights that illuminate the area in front of the underwater robot 10. The sensor 28 is positioned below the camera unit 27 in the front of the lower body 21. The sensor 28 may be, for example, a Doppler Velocity Log (DVL) that detects relative velocity based on the emission of sound waves and the detection of reflected and scattered waves. The camera unit 27 and the sensor 28 are external environment recognition sensors for recognizing the outside world of the underwater robot 10.

[0024] One front control unit 29a is positioned at the front of the lower body 21, behind the camera unit 27. Two rear control units 29b are positioned side by side at the rear of the lower body 21. Each control unit 29 comprises a box-shaped housing that seals the interior, and a power supply and electronic control unit etc. located inside the housing. These control units 29 control the operation of the mechanical arm 23, thruster 25, camera unit 27, sensor 28, and the drive device 50 of the buoyancy adjustment unit 13, which will be described later.

[0025] Figure 2 is a perspective view of the buoyancy adjustment unit 13 of the underwater robot 10. Figure 2 shows the buoyancy adjustment unit 13 with a portion of the cover member 31, which will be described later, removed. As shown in Figures 1 and 2, the buoyancy adjustment unit 13 comprises an upper body 30 that forms the frame and a cover member 31 that covers the upper body 30.

[0026] The lower body 21 and multiple connecting columns 22 of the robot body 11, as well as the upper body 30 and cover member 31 of the buoyancy adjustment unit 13, constitute the body 15 of the underwater robot 10.

[0027] Figure 3 is a plan view of the buoyancy adjustment unit 13 of the underwater robot 10. Figure 3 shows the buoyancy adjustment unit 13 with the cover member 31 removed. As shown in Figures 2 and 3, the buoyancy adjustment unit 13 includes a movable member 32, indicated by dashed lines, which is movably provided inside the cover member 31, and a drive device 50 for moving the movable member 32 inside the cover member 31. The cover member 31 is rectangular in shape and has a plurality of through holes that connect the inside and outside. The cover member 31 is detachably fixed to the upper body 30.

[0028] The upper body 30 is fixed to the upper ends of a plurality of connecting columns 22 (Figure 1) and supports the cover member 31 and the drive unit 50. The upper body 30 comprises a front member 33 extending in the left-right direction at the front, a left-side member 34 and a right-side member 35 extending rearward from both ends of the front member 33, and a rear member 36 extending in the left-right direction and connecting the left-side member 34 and the right-side member 35. The upper body 30 is generally rectangular in shape when viewed from above. The buoyancy adjustment unit 13 may include support members extending upward from the front, rear, or middle part of the upper body 30 in order to support and fix the cover member 31.

[0029] The movable member 32 is a buoyancy body that generates buoyancy and changes the position of the center of buoyancy of the underwater robot 10 by moving inside the cover member 31. The movable member 32 is preferably made of a known resin with a specific gravity lower than water, but is not limited to this. The movable member 32 is driven to maintain or change the posture of the underwater robot 10 when the underwater robot 10 is moving and when each mechanical arm 23 is operating. The movable member 32 only needs to be able to change at least one of the center of buoyancy and the center of gravity of the underwater robot 10, and is not limited to a buoyancy body, but may be a weight. In this case, the center of gravity of the underwater robot 10 moves as the movable member 32 moves.

[0030] The movable member 32 is movably supported on the body 15 of the underwater robot 10 by the following support structure. A first slider 37 is provided on the upper body 30 so as to be movable in the X-axis direction. Specifically, two first guide members 38 parallel to each other are provided on the left member 34 and the right member 35 of the upper body 30. Each first guide member 38 is made of a pipe member and extends in the X-axis direction. The first slider 37 comprises two brackets 39 (39a, 39b) that movably engage with the two first guide members 38 and a connecting member 40 that connects the two brackets 39. The connecting member 40 is made of a plate-shaped member that extends in the X-axis direction and the Y-axis direction and is fixed to the corresponding brackets 39 at its left and right ends. Hereinafter, the left bracket 39 will be referred to as the first bracket 39a, and the right bracket 39 as the second bracket 39b.

[0031] A second slider 41 is provided on the first slider 37 so as to be movable in the Y-axis direction. Specifically, two parallel second guide members 42 are provided below the front and rear edges of the connecting member 40 of the first slider 37. Each second guide member 42 is made of a pipe member and extends in the Y-axis direction. The second slider 41 has four engaging portions 41a that movably engage with the two second guide members 42. The engaging portions 41a are arranged in pairs on the front and rear sides, spaced apart in the Y-axis direction, and engage with the corresponding second guide members 42. Fixing members 43 for fixing the movable member 32 are provided at the four corners of the second slider 41. The fixing members 43 may be bolts, nuts, clips, etc.

[0032] As shown in Figure 2, the two second guide members 42 and the second slider 41 are positioned below the connecting member 40 of the first slider 37. On the other hand, the movable member 32 is positioned above the connecting member 40 of the first slider 37. In other words, the second guide members 42 and the second slider 41 and the movable member 32 are positioned on opposite sides of the connecting member 40. This configuration allows for effective use of the internal space of the cover member 31 and enables the movable member 32 to be made larger.

[0033] Figure 4 is a perspective view of the bracket 39. Although Figure 4 shows the second bracket 39b on the right, the first bracket 39a on the left has the same structure. As shown in Figures 3 and 4, each bracket 39 includes two engaging members 45 that engage with the first guide member 38, a base member 46 that connects the two engaging members 45, and an extension portion 47 that extends inward from the base member 46 into the upper body 30. Here, inward from the upper body 30 is one side (left) in the Y-axis direction in the case of the second bracket 39b on the right shown in the figure, and the other side (right) in the Y-axis direction in the case of the first bracket 39a on the left. Two bend pulleys 58 (58b, 58c) are pivotally supported at the extension end of the extension portion 47.

[0034] The two engaging members 45 are positioned at the outer end of the bracket 39, spaced apart in the X-axis direction. The two bend pulleys 58 are rotatable around the Z-axis and coaxially positioned at the inner end of the bracket 39. By positioning the two bend pulleys 58 on the same axis in this way, the number of axis members is reduced. Furthermore, the first slider 37 can be made smaller and lighter.

[0035] The extension portion 47 has a tapered shape that extends horizontally from the lower part of the base member 46 (along the XY plane formed by the X and Y axes). In other words, the extension portion 47 of the bracket 39 has a tapered shape that widens from the inner end to the outer end. Because the bracket 39 has a tapered shape that widens from the inner end to the outer end, when a yaw moment is generated in the first slider 37, twisting of the first slider 37 relative to the first guide member 38 is suppressed. Therefore, the first slider 37 becomes stronger against yaw moment.

[0036] As shown in Figure 3, the drive unit 50 comprises two power sources 51 (51a, 51b) and a transmission mechanism 52 (52a, 52b). Each power source 51 is an electric motor and is housed together with a driver 48 in a liquid-tight motor case 61 (61a, 61b). The two power sources 51 are fixed to the left and right corners at the rear of the upper body 30. Hereinafter, the left power source 51 will be referred to as the first power source 51a, and the right power source 51 will be referred to as the second power source 51b. The first power source 51a is housed in the first case 61a. The second power source 51b is housed in the second case 61b. The two power sources 51 supply power to the transmission mechanism 52 to move the movable member 32.

[0037] In a plan view, i.e., a orthogonal view of the XY plane, the first guide pulley 59a is positioned to overlap with the second case 61b, and the second guide pulley 59b is positioned to overlap with the first case 61a. Since the guide pulleys 59 are provided in a position that overlaps with the motor case 61 for the power source 51, the layout efficiency is improved, and the movable member 32 can be made larger or its range of motion can be widened. As a result, the posture of the underwater robot 10 becomes easier to control.

[0038] As described above, since the mechanical arm 23, which includes the camera unit 27 and the sensor 28, is provided on the front end of the body 15, the underwater robot 10 tends to have a forward center of gravity. In this embodiment, the first drive pulley 56a, the second drive pulley 56b, the first power source 51a, and the second power source 51b are arranged on the rear end of the body 15. By placing the heavy power source 51 at the rear of the body 15 in this way, it becomes easier to balance the underwater robot 10. In addition, since the guide pulley 59 is placed at the rear of the body 15, space is created at the front of the body 15, and this space can be used to move the moving member 32 forward a large distance.

[0039] The transmission mechanism 52 is a mechanism that moves the moving member 32 by two-dimensional translational motion in a two-dimensional Cartesian coordinate system using the X and Y axes. The transmission mechanism 52 may be a so-called H-BOT or H-type gantry robot, etc.

[0040] The transmission mechanism 52 includes a first transmission mechanism 52a that transmits power from the first power source 51a and a second transmission mechanism 52b that transmits power from the second power source 51b. Each transmission mechanism 52 is composed of a belt drive mechanism 54 (54a, 54b) that includes a power transmission belt 53 (53a, 53b). Hereinafter, the belt 53 that transmits power from the first power source 51a will be referred to as the first belt 53a, and the belt 53 that transmits power from the second power source 51b will be referred to as the second belt 53b. Also, the belt drive mechanism 54 that includes the first belt 53a will be referred to as the first belt drive mechanism 54a, and the belt drive mechanism 54 that includes the second belt 53b will be referred to as the second belt drive mechanism 54b.

[0041] Figure 5 is a plan view of the drive device 50 in the buoyancy adjustment unit 13. Figure 6 is a side view of the drive device 50 in the buoyancy adjustment unit 13. As shown in Figure 5, the first transmission mechanism 52a transmits power from the first power source 51a to the first slider 37 or the second slider 41 via the first belt 53a. The second transmission mechanism 52b transmits power from the second power source 51b to the first slider 37 or the second slider 41 via the second belt 53b. The first belt drive mechanism 54a drives the first belt 53a with power from the first power source 51a. The second belt drive mechanism 54b drives the second belt 53b with power from the second power source 51b.

[0042] The first belt 53a is annular in shape and is connected to the second slider 41 from the left and right sides in the Y-axis direction. The second belt 53b is annular in shape and is connected to the second slider 41 from the right and left sides in the Y-axis direction. The first belt 53a and the second belt 53b may be separated at the second slider 41 or they may be continuous. That is, the first belt 53a and the second belt 53b may be a single straight belt with both ends, or they may be an annular endless belt.

[0043] As shown in Figure 6, the second belt 53b is positioned below the first belt 53a. That is, the first belt 53a and the second belt 53b are positioned offset from each other in the Z-axis direction perpendicular to the XY plane.

[0044] As shown in FIG. 5, the first belt drive mechanism 54a includes a first drive pulley 56a driven by a first power source 51a, a first driven pulley 57a, a first bend pulley 58a, a second bend pulley 58b, and a first guide pulley 59a.

[0045] The first drive pulley 56a is arranged at the left rear portion of the upper body 30 (see FIG. 3). The first driven pulley 57a is arranged at the left front portion of the upper body 30. The first bend pulley 58a is arranged at the upper portion of the left first bracket 39a. The second bend pulley 58b is arranged at the upper portion of the right second bracket 39b. The first guide pulley 59a is arranged at the right rear portion of the upper body 30.

[0046] The first belt 53a is wound around the first bend pulley 58a, the first driven pulley 57a, the first drive pulley 56a, the first guide pulley 59a, and the second bend pulley 58b in order from the left portion of the second slider 41, and extends to the right portion of the second slider 41.

[0047] The second belt drive mechanism 54b includes a second drive pulley 56b driven by a second power source 51b, a second driven pulley 57b, a third bend pulley 58c, a fourth bend pulley 58d, and a second guide pulley 59b.

[0048] The second drive pulley 56b is arranged at the right rear portion of the upper body 30 (see FIG. 3). The second driven pulley 57b is arranged at the right front portion of the upper body 30. The third bend pulley 58c is arranged at the lower portion of the right second bracket 39b. The fourth bend pulley 58d is arranged at the lower portion of the left first bracket 39a. The first guide pulley 59a is arranged at the right rear portion of the upper body 30.

[0049] That is, the first driven pulley 57a and the second driven pulley 57b are arranged on the front end side of the upper body 30. The first drive pulley 56a, the second drive pulley 56b, the first guide pulley 59a, and the second guide pulley 59b are arranged on the rear end side of the upper body 30.

[0050] The second belt 53b is wrapped around the third bend pulley 58c, the second driven pulley 57b, the second drive pulley 56b, the second guide pulley 59b, and the fourth bend pulley 58d in order from the right side of the second slider 41, and reaches the left side of the second slider 41.

[0051] As explained with reference to Figure 4, in each bracket 39, the two bend pulleys 58 are arranged coaxially with each other. That is, in the left first bracket 39a, the upper first bend pulley 58a and the lower fourth bend pulley 58d are arranged coaxially with each other. In the right second bracket 39b, the upper second bend pulley 58b and the lower third bend pulley 58c are arranged coaxially with each other.

[0052] Here, as shown in Figure 3, the line segment connecting the first bend pulley 58a and the fourth bend pulley 58d with the second bend pulley 58b and the third bend pulley 58c is defined as the first line segment L1. The line segment connecting the first guide pulley 59a and the second guide pulley 59b is defined as the second line segment L2. The line segment connecting the first drive pulley 56a and the second drive pulley 56b is defined as the third line segment L3. The first line segment L1, the second line segment L2, and the third line segment L3 are parallel to each other.

[0053] Let the line segment connecting the first drive pulley 56a and the first driven pulley 57a be the fourth line segment L4. Let the line segment connecting the second drive pulley 56b and the second driven pulley 57b be the fifth line segment L5. The fourth line segment L4 and the fifth line segment L5 are parallel to each other. Therefore, even when the first belt 53a and the second belt 53b are driven by the first drive pulley 56a and the second drive pulley 56b and the moving member 32 moves, loosening of the first belt 53a and the second belt 53b is suppressed.

[0054] The portion of the first belt 53a between the first drive pulley 56a and the first guide pulley 59a, and the portion of the second belt 53b between the second drive pulley 56b and the second guide pulley 59b, are parallel to each other and coincide in a plan view. Alternatively, the two portions may intersect each other at a small angle. As a result, the first belt 53a and the second belt 53b do not loosen even when the drive device 50 drives the moving member 32.

[0055] Furthermore, the first belt 53a and the second belt 53b intersect at two points: the outer circumference of the first bend pulley 58a and the outer circumference of the third bend pulley 58c, and overlap (contend in a plan view) or intersect between the two guide pulleys 59 (the portion between the first drive pulley 56a and the first guide pulley 59a for the first belt 53a, and the portion between the second drive pulley 56b and the second guide pulley 59b for the second belt 53b). This is made possible by the fact that the first belt 53a and the second belt 53b are offset in the Z-axis direction, as described above. With the two belts 53 arranged in this way, it becomes possible to arrange the two belts 53 to pass through a desired path. Therefore, there is a high degree of freedom in the arrangement of the belts 53.

[0056] The paths of the first belt 53a and the second belt 53b are symmetrical with respect to the center line 15x of the machine body 15, that is, a line extending in the X-axis direction through the center in the Y-axis direction. This makes it easier to balance the underwater robot 10.

[0057] Next, the operation of the buoyancy adjustment unit 13 will be described with reference to Figures 7 and 8.

[0058] Figure 7 is an explanatory diagram of the operation of the drive device 50, showing the operation when the movable member 32 (see Figure 3) is moved in the X-axis direction. When the two first drive pulleys 56a and the second drive pulley 56b rotate in opposite directions, the second slider 41 and the movable member 32 move in the X-axis direction.

[0059] Specifically, as shown in Figure 7(A), when the first drive pulley 56a rotates clockwise and the second drive pulley 56b rotates counterclockwise, the second bend pulley 58b and the fourth bend pulley 58d, supported by the first slider 37, are both pulled towards the corresponding guide pulleys 59 (59a, 59b). As a result, the first slider 37 moves backward, and the second slider 41 and the moving member 32 also move backward.

[0060] As shown in Figure 7(B), when the first drive pulley 56a rotates counterclockwise and the second drive pulley 56b rotates clockwise, the second bend pulley 58b and the fourth bend pulley 58d, supported by the first slider 37, are both pulled towards the corresponding driven pulley 57. As a result, the first slider 37 moves forward, and the second slider 41 and the moving member 32 also move forward.

[0061] Whether the second slider 41 and the moving member 32 are driven backward or forward, a compressive force in the Y-axis direction acts on the first slider 37, but no yaw moment is generated.

[0062] Figure 8 is an explanatory diagram of the operation of the drive device 50, showing the operation when the movable member 32 is moved in the Y-axis direction. When the two first drive pulleys 56a and the second drive pulley 56b rotate in the same direction, the second slider 41 and the movable member 32 move in the Y-axis direction.

[0063] Specifically, as shown in Figure 8(A), when the first drive pulley 56a and the second drive pulley 56b both rotate counterclockwise, the second slider 41 is pulled towards the first bend pulley 58a and the fourth bend pulley 58d, which are supported by the first slider 37. As a result, the second slider 41 and the moving member 32 move to the left.

[0064] As shown in Figure 8(B), when the first drive pulley 56a and the second drive pulley 56b both rotate clockwise, the second slider 41 is pulled toward the second bend pulley 58b and the third bend pulley 58c, which are supported by the first slider 37. As a result, the second slider 41 and the moving member 32 move to the right.

[0065] When the second slider 41 and the moving member 32 are driven to the left, as shown in Figure 8(A), the first bend pulley 58a receives a force from the first belt 53a, which is subjected to tensile force, in a forward-diagonal-right direction as indicated by the black arrow. On the other hand, the fourth bend pulley 58d receives a force from the second belt 53b, which is subjected to tensile force, in a backward-diagonal-right direction as indicated by the black arrow. The forward component of the force received from the first belt 53a and the backward component of the force received from the second belt 53b cancel each other out. Therefore, no yaw moment is generated in the first slider 37.

[0066] Similarly, when the second slider 41 and the moving member 32 are driven to the right, as shown in Figure 8(B), the second bend pulley 58b receives a force from the first belt 53a, which is subjected to tensile force, in a diagonal left-rear direction as indicated by the black arrow. On the other hand, the third bend pulley 58c receives a force from the second belt 53b, which is subjected to tensile force, in a diagonal left-front direction as indicated by the black arrow. The forward component of the force received from the first belt 53a and the backward component of the force received from the second belt 53b cancel each other out. Therefore, no yaw moment is generated in the first slider 37.

[0067] Therefore, twisting of the first slider 37 relative to the first guide member 38, which causes sliding resistance, is suppressed. Furthermore, if the first slider 37 is not guided by the first guide member 38, displacement of the second slider 41 and the moving member 32 due to the rotation of the first slider 37 is suppressed. In either case, proper attitude control of the underwater robot 10 is possible. <Modification>

[0068] Figure 9 is a plan view of a modified drive device 50. As shown in Figure 9, this drive device 50 differs from the above embodiment in the arrangement of the four bend pulleys 58. Specifically, the first bend pulley 58a is positioned at the front of the left end of the first slider 37, and the second bend pulley 58b is positioned at the rear of the right end of the first slider 37. In addition, the third bend pulley 58c is positioned at the front of the right end of the first slider 37, and the fourth bend pulley 58d is positioned at the rear of the left end of the first slider 37.

[0069] Specifically, at the left end of the first slider 37, the first bend pulley 58a and the fourth bend pulley 58d are positioned offset front to back, and at the right end of the first slider 37, the third bend pulley 58c and the second bend pulley 58b are positioned offset front to back.

[0070] The portion of the first belt 53a from the first bend pulley 58a to the second slider 41 lies on the extension of the portion of the second belt 53b from the third bend pulley 58c to the second slider 41. Furthermore, this portion of the first belt 53a is parallel to the portion of the second belt 53b from the fourth bend pulley 58d to the second slider 41, and may overlap in a plan view.

[0071] The portion of the first belt 53a from the second bend pulley 58b to the second slider 41 lies on the extension of the portion of the second belt 53b from the fourth bend pulley 58d to the second slider 41. Furthermore, this portion of the first belt 53a is parallel to the portion of the second belt 53b from the third bend pulley 58c to the second slider 41, and may overlap in a plan view.

[0072] Thus, the two bend pulleys 58 provided at the left or right end of the first slider 37 may be offset in the front-rear direction rather than being coaxial with each other. By arranging them in this way, the points of application of the tensile forces acting on the second slider 41 from the first belt 53a and the second belt 53b become closer or coincide in a plan view, thereby suppressing the generation of a moment on the second slider 41 due to the difference in tensile forces between the two belts 53.

[0073] This concludes the description of the embodiments, but the present invention is not limited to the above configuration and can be broadly modified and implemented. For example, the underwater robot 10 in the above embodiment performs work while submerged in water, but it may also perform work while floating on the surface of the water. Also, in the above embodiment, the first slider 37 is guided by two first guide members 38, but the first slider 37 may be guided by one guide member, or may not be guided by any guide member at all. Similarly, the second slider 41 is guided by two second guide members 42, but the second slider 41 may be guided by one guide member, or may not be guided by any guide member at all. Furthermore, the specific configuration, arrangement, and quantity of each member and part can be changed as appropriate, as long as it does not depart from the spirit of the present invention. On the other hand, not all of the components shown in the above embodiment are necessarily essential, and can be selected as appropriate.

[0074] In conclusion, the above embodiments can be summarized as follows:

[0075] One embodiment is an underwater robot 10 comprising a body 15, a movable member 32 provided on the body 15 so as to be movable along a predetermined plane and for changing the center of buoyancy or center of gravity, and a drive device 50 for moving the movable member 32 relative to the body 15. The drive device 50 comprises a first slider 37 provided on the body 15 so as to be movable in the X-axis direction (front-back direction) on the plane, a second slider 41 provided on the first slider 37 so as to be movable in the Y-axis direction (left-right direction) intersecting the X-axis direction on the plane and connected to the movable member 32, a first belt drive mechanism 54a including an annular first belt 53a connected to the second slider 41 from one side (left) and the other side (right) in the Y-axis direction, and a second belt drive mechanism 54b including an annular second belt 53b connected to the second slider 41 from the other side (right) and the one side (left) in the Y-axis direction. The first belt drive mechanism 54a includes a first drive pulley 56a provided on one side (left side) of the machine body 15 in the Y-axis direction for driving the first belt 53a, a first bend pulley 58a provided on one side (left side) of the first slider 37 in the Y-axis direction for winding the first belt 53a, and a second bend pulley 58b provided on the other side (right side) of the first slider 37 in the Y-axis direction for winding the first belt 53a. The second belt drive mechanism 54b includes a second drive pulley 56b provided on the other side of the machine body 15 in the Y-axis direction for driving the second belt 53b, a third bend pulley 58c provided on the other side of the first slider 37 in the Y-axis direction for winding the second belt 53b, and a fourth bend pulley 58d provided on one side (left side) of the first slider 37 in the Y-axis direction for winding the second belt 53b.

[0076] According to this embodiment, when the movable member 32 is moved in the X-axis direction, the yaw moment acting on the first slider 37, which is provided with the first bend pulley 58a, the second bend pulley 58b, the third bend pulley 58c, and the fourth bend pulley 58d, is suppressed.

[0077] In the above embodiment, preferably, the first bend pulley 58a and the fourth bend pulley 58d are arranged on the same axis, and the second bend pulley 58b and the third bend pulley 58c are arranged on the same axis.

[0078] According to this embodiment, the number of shaft members can be reduced. In addition, the first slider 37 can be made smaller and lighter.

[0079] In the above embodiment, preferably, the first belt drive mechanism 54a further includes a first driven pulley 57a provided on the side (front side) opposite to the first drive pulley 56a of the machine body 15 in the X-axis direction, and a first guide pulley 59a provided on the other side (right side) of the machine body 15 in the Y-axis direction. The second belt drive mechanism 54b further includes a second driven pulley 57b provided on the side (front side) opposite to the second drive pulley 56b of the machine body 15 in the X-axis direction, and a second guide pulley 59b provided on the one side (left side) of the machine body 15 in the Y-axis direction.

[0080] According to this embodiment, the first slider 37 can be moved in the X-axis direction. Furthermore, it is not necessary to provide the first belt 53a and the second belt 53b so that the second slider 41 passes in the Y-axis direction. Therefore, the design freedom of the second slider 41 and the moving member 32 is improved.

[0081] In the above embodiment, preferably, the first belt drive mechanism 54a is housed in a first case 61a and further includes a first power source 51a for driving the first drive pulley 56a, and the second belt drive mechanism 54b is housed in a second case 61b and further includes a second power source 51b for driving the second drive pulley 56b, and in a plane orthogonal view, the first guide pulley 59a is positioned to overlap the second case 61b, and the second guide pulley 59b is positioned to overlap the first case 61a.

[0082] In this embodiment, the guide pulley 59 is positioned to overlap with the motor case 61 for the power source 51 in a planar orthogonal view, which improves layout efficiency and allows for a larger moving member 32 and a wider range of motion for the moving member 32. This makes it easier to control the posture of the underwater robot 10.

[0083] In the above embodiment, preferably, the first driven pulley 57a and the second driven pulley 57b are arranged on one end (front end) of the machine body 15 in the X-axis direction, the first drive pulley 56a, the second drive pulley 56b, the first power source 51a and the second power source 51b are arranged on the other end (rear end) of the machine body 15 in the X-axis direction, and a mechanical arm 23 as a work section including a camera unit 27 and a sensor 28 as external environment recognition sensors is provided on the one end (front end) of the machine body 15 in the X-axis direction.

[0084] In this configuration, the underwater robot 10 tends to have a forward center of gravity due to the external environment recognition sensors and working parts, but by placing the heavy power source 51 at the rear of the body 15, it becomes easier to balance the underwater robot 10. In addition, since the guide pulley 59 is placed at the rear of the body 15, space is created at the front of the body 15, and this space can be used to move the moving member 32 far forward.

[0085] In the above embodiment, preferably, the first line segment L1 connecting the first bend pulley 58a and the fourth bend pulley 58d with the second bend pulley 58b and the third bend pulley 58c, the second line segment L2 connecting the first guide pulley 59a and the second guide pulley 59b, and the third line segment L3 connecting the first drive pulley 56a and the second drive pulley 56b are parallel to each other. The fourth line segment L4 connecting the first drive pulley 56a and the first driven pulley 57a, and the fifth line segment L5 connecting the second drive pulley 56b and the second driven pulley 57b are parallel to each other. The first driven pulley 57a and the second driven pulley 57b are positioned on the one end (front end) side in the X-axis direction. The first drive pulley 56a, the second drive pulley 56b, the first guide pulley 59a, and the second guide pulley 59b are arranged on the other end (rear end) side in the X-axis direction.

[0086] According to this embodiment, it is possible to suppress the loosening of the belt 53 when the movable member 32 is moved out.

[0087] In the above embodiment, preferably, the paths of the first belt 53a and the second belt 53b are symmetrical with respect to a center line 15x that passes through the center of the machine body 15 in the Y-axis direction and extends in the X-axis direction.

[0088] According to this configuration, it is easier to balance the underwater robot 10.

[0089] In the above embodiment, preferably, the first belt 53a and the second belt 53b are arranged offset from each other in a direction perpendicular to the plane, and intersect at least one point in a perpendicular view of the plane.

[0090] According to this embodiment, the two belts 53 can be arranged to pass through a desired path. The arrangement of the belts 53 offers a high degree of freedom.

[0091] In the above embodiment, preferably, the machine body 15 includes a cover member 31 that covers the movable member 32 to allow the movement of the movable member 32, and a pair of first guide members 38 provided inside the cover member 31 and extending in the X-axis direction to support the first slider 37 so as to be movable in the X-axis direction. The first slider 37 includes a first bracket 39a having an outer end that slidably engages with one of the pair of first guide members 38 and an inner end that supports the first bend pulley 58a and the fourth bend pulley 58d, a second bracket 39b having an outer end that slidably engages with the other of the pair of first guide members 38 and an inner end that supports the second bend pulley 58b and the third bend pulley 58c, and a connecting member 40 that connects the first bracket 39a and the second bracket 39b and supports the second slider 41 so as to be movable in the Y-axis direction. The first bracket 39a and the second bracket 39b have a tapered shape that widens from the inner end to the outer end.

[0092] According to this embodiment, when a yaw moment is generated in the first slider 37, twisting of the first slider 37 relative to the first guide member 38 is suppressed. Therefore, the first slider 37 becomes stronger against yaw moment.

[0093] In the above embodiment, preferably, the first slider 37 further comprises at least one second guide member 42 provided on the connecting member 40 and extending in the Y-axis direction to support the second slider 41 so as to be movable in the Y-axis direction. The second guide member 42 and the second slider 41 and the movable member 32 are arranged on opposite sides of the connecting member 40.

[0094] According to this embodiment, the internal space of the cover member 31 can be effectively utilized, and the movable member 32 can be made larger.

[0095] 10: Underwater robot 11: Robot body 13: Buoyancy adjustment unit 15: Airframe 15x: Centerline 23: Mechanical arm (example of work unit) 27: Camera unit (example of external environment recognition sensor) 28: Sensor (example of external environment recognition sensor) 30: Upper body 31: Cover member 32: Moving member (buoyancy body) 37: First slider 38: First guide member 39: Bracket 39a: First bracket 39b: Second bracket 40: Connecting member 41: Second slider 42: Second guide member 50: Drive unit 51a: First power source 51b: Second power source 53a: First belt 53b: Second belt 54a: First belt drive mechanism 54b: Second belt drive mechanism 56a: First drive pulley 56b: Second drive pulley 57a: First driven pulley 57b: Second driven pulley 58: Bend pulley 58a: First bend pulley 58b: Second bend pulley 58c: Third bend pulley 58d: Fourth bend pulley 59a: First guide pulley 59b: Second guide pulley 61a: First case 61b: Second case L1: First line segment L2: Second line segment L3: Third line segment L4: Fourth line segment L5: Fifth line segment

Claims

1. An underwater robot comprising: a body; a movable member provided on the body so as to be movable along a predetermined plane and for changing the center of buoyancy or center of gravity; and a drive device for moving the movable member relative to the body, wherein the drive device comprises: a first slider provided on the body so as to be movable in the X-axis direction on the plane; a second slider provided on the first slider so as to be movable in the Y-axis direction intersecting the X-axis direction on the plane and connected to the movable member; a first belt drive mechanism including an annular first belt connected to the second slider from one side and the other side in the Y-axis direction; and a second belt drive mechanism including an annular second belt connected to the second slider from the other side and the one side in the Y-axis direction, wherein the first belt drive mechanism comprises: a first drive pulley provided on the one side of the body in the Y-axis direction and for driving the first belt; and a first bend pulley provided on the one side of the first slider in the Y-axis direction and around which the first belt is wound. An underwater robot comprising: a second bend pulley provided on the other side of the first slider in the Y-axis direction, around which the first belt is wound; a second belt drive mechanism provided on the other side of the body in the Y-axis direction, for driving the second belt; a third bend pulley provided on the other side of the first slider in the Y-axis direction, around which the second belt is wound; and a fourth bend pulley provided on one side of the first slider in the Y-axis direction, around which the second belt is wound.

2. The underwater robot according to claim 1, wherein the first bend pulley and the fourth bend pulley are arranged on the same axis, and the second bend pulley and the third bend pulley are arranged on the same axis.

3. The underwater robot according to claim 1 or 2, wherein the first belt drive mechanism further includes a first driven pulley provided on the side of the robot body opposite to the first drive pulley in the X-axis direction, and a first guide pulley provided on the other side of the robot body in the Y-axis direction, and the second belt drive mechanism further includes a second driven pulley provided on the side of the robot body opposite to the second drive pulley in the X-axis direction, and a second guide pulley provided on the one side of the robot body in the Y-axis direction.

4. The underwater robot according to claim 3, wherein the first belt drive mechanism is housed in a first case and further includes a first power source for driving the first drive pulley, and the second belt drive mechanism is housed in a second case and further includes a second power source for driving the second drive pulley, and in a plane orthogonal view, the first guide pulley is positioned to overlap the second case and the second guide pulley is positioned to overlap the first case.

5. The underwater robot according to claim 4, wherein the first driven pulley and the second driven pulley are arranged on one end of the machine in the X-axis direction, the first drive pulley, the second drive pulley, the first power source and the second power source are arranged on the other end of the machine in the X-axis direction, and a work section including an external environment recognition sensor is provided on the one end of the machine in the X-axis direction.

6. The underwater robot according to claim 5, wherein the line segments connecting the first bend pulley and the fourth bend pulley with the second bend pulley and the third bend pulley, the line segment connecting the first guide pulley with the second guide pulley, and the line segment connecting the first drive pulley with the second drive pulley are parallel to each other, the line segment connecting the first drive pulley with the first driven pulley, and the line segment connecting the second drive pulley with the second driven pulley are parallel to each other, the first driven pulley and the second driven pulley are arranged on one end side in the X-axis direction, and the first drive pulley, the second drive pulley, the first guide pulley and the second guide pulley are arranged on the other end side in the X-axis direction.

7. The underwater robot according to claim 6, wherein the paths of the first belt and the second belt are symmetrical with respect to a center line extending in the X-axis direction through the center of the machine body in the Y-axis direction.

8. The underwater robot according to claim 7, wherein the first belt and the second belt are arranged offset from each other in a direction perpendicular to the plane and intersect at least one point in a perpendicular view of the plane.

9. The underwater robot according to claim 1 or 2, wherein the machine body comprises a cover member that covers the moving member so as to allow the movement of the moving member, and a pair of first guide members provided inside the cover member and extending in the X-axis direction to support the first slider so as to be movable in the X-axis direction, the first slider comprises a first bracket having an outer end that slidably engages with one of the pair of first guide members and an inner end that supports the first bend pulley and the fourth bend pulley, a second bracket having an outer end that slidably engages with the other of the pair of first guide members and an inner end that supports the second bend pulley and the third bend pulley, and a connecting member that connects the first bracket and the second bracket and supports the second slider so as to be movable in the Y-axis direction, the first bracket and the second bracket have a tapered shape that widens from the inner end to the outer end.

10. The underwater robot according to claim 9, wherein the first slider further comprises at least one second guide member provided on the connecting member and extending in the Y-axis direction to support the second slider so as to be movable in the Y-axis direction, and the second guide member, the second slider, and the moving member are arranged on opposite sides of the connecting member.

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