Autonomous unmanned underwater vehicle and intermediate segment thereof

Abstract

Autonomous unmanned underwater vehicle (1) with a hull section (2) and a head section (3), wherein a sensor (4) is arranged on the head section (3), characterized by an intermediate segment (5) comprising a first connecting piece (6) designed for attachment to the hull section (2) and a second connecting piece (7) designed for attachment to the head section (3) and a stepper motor (10), wherein the first and second connecting pieces (6, 7) are mounted to rotate relative to each other about the longitudinal axis (L) of the underwater vehicle (1) and the stepper motor (10) is mounted with the first and second connecting pieces (6, 7) for controlled rotation of the head section (3) with its sensor (4) by rotation angle increments specified by the stepper motor (10),wherein the stepper motor (10) is enclosed in a pressure-waterproof housing and the interior of the intermediate segment (5) surrounding the stepper motor (10) is open to the outside and is flooded when the underwater vehicle (1) is submerged, and the intermediate segment (5) has buoyancy bodies (17).

Description

[0001] The invention relates to an autonomous unmanned underwater vehicle comprising a hull part and a head part, wherein a sensor is arranged on the head part.

[0002] The invention further relates to an intermediate segment for an autonomous unmanned underwater vehicle.

[0003] EP 2 830 934 B1 discloses an autonomous underwater vehicle with a hull section and a head section, as well as sensors permanently installed in the head section.

[0004] DE 10 2012 107 727 B4 discloses a distance determination method that can be used as part of a distance control method for a procedure for investigating a flooded tunnel, in particular a pipeline or a drinking water tunnel, using an autonomous underwater vehicle. Distances between the underwater vehicle and a tunnel body surrounding the underwater vehicle around its longitudinal axis are determined optically in different directions using a laser and a camera by means of laser triangulation.

[0005] Jan Albiez, Alexander Duda, Martin Fritsche, Felix Rehrmann, Frank Kirchner: “CSurvey – An autonomous optical inspection head for AUVs”, in: Robotics and Autonomous Systems, Vol. 67, May 2015, pages 72 to 79, discloses an autonomous underwater vehicle with a hull section and a head section rigidly attached to it. The head section has a manipulator with a sensor, e.g., a camera, mounted on the manipulator. The sensor's position is movable via the manipulator.

[0006] DE 10 2010 035 898 B3 discloses an unmanned underwater vehicle in which a sensor carrier is designed as a rotatable sensor head, which is rotatably arranged on a bow of the underwater vehicle or in the form of a sensor ring on the circumference of the boat hull.

[0007] The object of the present invention is to create an improved autonomous underwater vehicle in which the sensor in the head section can be rotated with high accuracy by defined angular increments relative to the hull section, even under environmental influences, using control signals and is stably mounted.

[0008] The problem is solved by the autonomous underwater vehicle with the features of claim 1 and by the intermediate segment with the features of claim 7. Advantageous embodiments are described in the dependent claims.

[0009] It is proposed that the autonomous underwater vehicle has an intermediate segment comprising a first connector designed for attachment to the hull section and a second connector designed for attachment to the head section, as well as a stepper motor. The first and second connectors are mounted to rotate relative to each other around the longitudinal axis of the underwater vehicle. The stepper motor is coupled to the first and second connectors for controlled rotation of the head section, including its sensor, by rotation angle increments specified by the stepper motor.

[0010] This ensures that the sensor head is mounted in a positionally stable manner yet rotatable around its axis of rotation. The rotatable attachment of the sensor head to the body section, with the intermediate segment that can be mounted between them, results in low-vibration and highly stable mounting. The intermediate segment, which incorporates a stepper motor as its drive element, can be used as needed when a change in the position of the sensor, which is fixed to the head, is required. Otherwise, the underwater vehicle can also be used without the intermediate segment according to the invention.

[0011] The stepper motor is housed in a pressure-waterproof enclosure, and the interior of the intermediate segment surrounding the stepper motor is open to the outside and flooded when the underwater vehicle is submerged. The intermediate segment incorporates buoyancy aids.

[0012] This has the advantage of counteracting changes in the weight proportions and buoyancy behavior of the underwater vehicle compared to a direct connection of the head section to the hull section without an intermediate segment, when the optional intermediate segment, which can be retrofitted for controlled orientation of the sensor, is mounted between the head section and the hull section.

[0013] The intermediate segment, which can be optionally installed as an additional component between the hull and head sections of an autonomous unmanned underwater vehicle, features a first connector with a flange designed for attachment to the hull and a second connector with a flange designed for attachment to the head section, as well as a stepper motor. The first and second connectors are mounted to rotate relative to each other around the longitudinal axis of the underwater vehicle. The stepper motor is coupled to the first and second connectors to control the rotation of the head section, including its sensor, by increments of rotation specified by the stepper motor.

[0014] With sensors pointing towards the bottom, structures alongside the underwater vehicle cannot be fully examined. To investigate laterally located structures with downward-facing sensors, the underwater vehicle would have to operate directly at the surface, making the measurements extremely susceptible to wave disturbances. Furthermore, the sensor beam angle would have to be significantly widened, reducing the resolution of the data. The upper portion of the structure under investigation cannot be captured in this way. Additional investigation of structures above the underwater vehicle is only possible with sensors fixed to the hull if an additional sensor, specifically aimed at this upper area, is mounted.

[0015] With the aid of the intermediate segment, complete and high-resolution datasets of structures alongside and above the underwater vehicle can now be acquired using sensors that can be rotated around the axis of rotation. This enables safety-oriented observation of maritime infrastructure, which is of great importance. This allows for the investigation of long structures such as sheet pile walls or ship hulls.

[0016] The rotating mounting of the sensor head on the hull section, facilitated by the intermediate segment, allows for the integration of even relatively large and heavy sensors, such as multibeam echo sounders suitable for inspection. The intermediate segment, with its stepper motor, prevents uncontrollable drift between the sensor's actual orientation and the software control. Furthermore, the use of an intermediate segment enables a high degree of modularity. Different sensor heads, each available as a set for selection and mounting on a hull section, can now be reconfigured by rotating them using the standardized intermediate segment. This eliminates the need for separate, individual actuators in the sensor heads to adjust their position.

[0017] Due to its modularity, the intermediate segment can expand the application possibilities of both existing and new sensor heads, but can also be quickly dismantled if there is no longer a need for it.

[0018] The use of a stepper motor with additional detection and feedback of the actual position improves the evaluation of the data captured by the sensors in the sensor head, taking into account their actual orientation, as well as the usability of the rotatable intermediate segment even over long autonomous missions without drift.

[0019] For the rotational movement, commercially available stepper motors with integrated control unit can be used, which preferably form a closed, waterproof and pressure-resistant unit and can be designed for different depths depending on the area of ​​application.

[0020] The stepper motor can be controlled, for example, directly from a computing unit of the autonomous underwater vehicle via a serial interface, or by a freely programmable microcontroller board housed in a waterproof pressure hull. The latter allows the use of existing, proprietary hardware and software to control the autonomous underwater vehicle without the need for a freely programmable serial interface. This enables the viewing angle to be changed as often as desired during an autonomous mission. The programming can include rotations at specific times after the mission begins or upon reaching a particular position in the global coordinate system, although this requires the availability of position data.

[0021] The intermediate segment can have a water-resistant ball bearing for rotatable mounting, which is surrounded by water when the underwater vehicle is submerged.

[0022] Except for the stepper motor and an optional pressure vessel for the control unit, the intermediate segment is open to the outside and flooded when submerged. The moving and stationary parts can be guided towards each other via seawater-resistant ball bearings, for example, made of plastic and glass. The ball bearings are also surrounded by the water. This eliminates the need for large sealing surfaces and a pressure test of the entire intermediate segment, thus simplifying modular use and assembly / disassembly in the field.

[0023] The stepper motor is housed in a pressure-resistant enclosure. The interior of the intermediate segment surrounding the stepper motor is open to the outside and is flooded when the underwater vehicle is submerged.

[0024] The intermediate segment incorporates buoyancy aids, such as buoyancy foam. These buoyancy aids may include cable entry points.

[0025] The intermediate segment is kept weight-neutral in the water by the use of buoyancy foam. This foam can be designed to simultaneously serve as a guide for the cables connecting the sensors to the main pressure hull of the autonomous underwater vehicle, preventing entanglement when the head rotates. Sufficient space is provided inside the intermediate segment for the cables in both radial and axial directions to allow for the intended rotation angles.

[0026] The first connecting piece of the intermediate segment can have a connecting flange with fastening elements which correspond to a connecting flange of the fuselage part for attaching the head section to the fuselage part.

[0027] The first connector can be arranged rotatably around the second connector of the intermediate segment, which is fixed to the body part, wherein the stepper motor has a stator and a rotor, and the stator of the stepper motor is coupled to the second connector and the rotor to the first connector.

[0028] The rotatable connection flange of the intermediate segment on the sensor head side is designed so that the sensor head can be mechanically attached to it in the same way as it would be attached to the main pressure hull of the autonomous underwater vehicle (i.e., the hull section) without the intermediate segment. The connection flange can be provided with feedthroughs and mounting points for adapter sockets, allowing the intermediate segment to be equipped with extension cables so that the sensor head's wiring can be carried out regardless of whether an intermediate segment is used or not.

[0029] In general, in the context of this application, the words "ein / eine" (a / an) are not to be understood as numerals, unless explicitly defined otherwise, but as indefinite articles meaning "at least one / an". Angles are given in degrees, with a full angle of 360°, where 1° (degree) corresponds to 180° / π radians.

[0030] The invention is described in more detail below using an exemplary embodiment.

[0031] They show: Fig. 1 - Side section view of an autonomous underwater vehicle with intermediate segment between the head section and the hull section; Fig. 2 - Side section view of the intermediate segment.

[0032] Fig. Figure 1 shows a side section view of an autonomous underwater vehicle 1 with a hull section 2 and a head section 3.

[0033] The head section has at least one sensor 4. The sensor 4 can be, for example, an optical camera, a laser rangefinder such as a LiDAR sensor, an ultrasonic sensor (echo sounder), or the like, mounted on or integrated into the head section 3. The head section 3 thus provides a sensor head.

[0034] An optionally retrofittable intermediate segment 5 is arranged between the fuselage section 2 and the head section 3. The intermediate segment 5 has a first connecting piece 6 for attachment to the front face of the fuselage section 2 and a second connecting piece 7 for attachment to the opposite front face of the head section 3.

[0035] The hull part 2 and the head part 3 have complementary connecting flanges designed for the detachable attachment of the head part 3 to the front, i.e. bow-side, end face of the hull part 2.

[0036] The intermediate segment 5 can have a first and second connection flange at each of the first and second connection pieces 6, 7. The first connection piece 6 is designed to complement a hull connection flange 8 of the hull section 2, in order to detachably fasten the bow-facing, bow-side end face of the hull arrow 3 to the hull connection flange 8, for example with fastening bolts or screws. The second connection piece 7 is designed to complement a sensor head connection flange 9 of the head section 3, in order to detachably fasten the stern-facing end face of the head section 3 to the sensor head connection flange 9, for example with fastening bolts or screws.

[0037] The intermediate segment 5 has a stepper motor 10, which has a stationary stator 11 and a rotor 12 rotatable about a rotational axis R. The stator 11 is non-rotatably connected to the second connector 7. Thus, when the intermediate segment 5 is installed, the stepper motor 10 is non-rotatably connected to the body section 2. The stator 11 is non-rotatably connected to the first connector 6 and, when installed, is non-rotatably coupled to the head section 3.

[0038] With the aid of the stepper motor 10, a rotation by precisely the specified number of rotation angles can be achieved by controlling the stepper motor 10 according to its predefined rotation angle increments. The rotational position of the head section 3 about the rotation axis R is therefore always precisely defined, largely unaffected by external disturbances, and known.

[0039] The rotation axis R of the stepper motor 10 is preferably located in the longitudinal axis L of the underwater vehicle 1.

[0040] A ball bearing 13 is provided for the stable mounting of the rotor 12, which rotates about the axis of rotation R and has an attached head section 3. The ball bearing 13 circumferentially surrounds the axis of rotation R. It can be arranged between the second connecting piece 7 and an intermediate segment housing 14 or the stator 11. The ball bearing 13 is preferably made of a seawater-resistant material, such as ceramic, glass, or stainless steel. It can be designed to be exposed to the water flow without a seal when the underwater vehicle 1 is submerged.

[0041] The stepper motor 10, on the other hand, is housed in a pressure-resistant enclosure. A control unit 15 for the stepper motor 10 can be arranged together with the stepper motor 10 adjacent to the mechanical parts of the stepper motor 10 and can also be housed in a pressure-resistant enclosure.

[0042] A space 16 surrounding the stepper motor 10 is open to the outside, allowing water to flow into and flood the space 16 when submerged. This has the advantage of counteracting changes in the weight proportions and buoyancy of the underwater vehicle 1 compared to a direct connection of the head section 3 to the hull section 2 without an intermediate segment 5, when the optional intermediate segment 5, which can be retrofitted for controlled orientation of the sensor 4, is mounted between the head section 3 and the hull section 2.

[0043] Furthermore, at least one buoyancy element 17 is arranged in the space 16 of the intermediate segment 5. This provides additional weight compensation, which approximates the weight proportions in the submerged state to those of the underwater vehicle 1 without the intermediate segment 5. The buoyancy element 17 can, for example, be made of buoyancy foam.

[0044] The buoyancy bodies 17 can have at least one cable gland 18 through which electrical cables are routed, leading from the rotatable head section 3 to the fuselage section 2. This allows the electrical cables to twist along with the rotation of the head section 3 while remaining securely mounted. Excessive twisting of the electrical cables can be prevented by limiting the rotation angle of the head section 3. For example, it can be limited to a total rotation angle of 360° or 180° in both directions from a neutral position. However, a further limitation is also conceivable, e.g., to 270° ±30° or 135° ±15° per direction of rotation. The maximum rotation angles achievable from the neutral position in both directions are the same in this symmetrical design.

[0045] Another conceivable design involves a rotation initiated by the stepper motor 10, covering a range from -90° to approximately +230°, with the rotation angle of 0° being the home position with sensors 4 facing downwards. The maximum rotation angles achievable from the home position in both directions of rotation are different in this asymmetrical design.

[0046] The hull section 2 has a propulsion unit 19, for example with a propeller drive, and a steering and stabilization unit 20 with fins and movable guide surfaces for the controlled movement of the underwater vehicle 1. It can also include a communication unit 21, which is functionally connected to the control unit 15, the propulsion unit 19, and the steering and stabilization unit 20 in order to receive control signals from a control center 22 for controlling the position and orientation of the underwater vehicle 1 and the rotational angle of the head section 3 with its at least one sensor 4. The sensor data acquired by the at least one sensor 4 can be transmitted to the control center 22, if necessary, even during the dive. This provides feedback from the environment of the underwater vehicle 1, enabling interactive control of the underwater vehicle 1 into the desired position and control of the sensor 4 into the desired orientation.

[0047] Fig. Figure 2 shows a side section view of the intermediate segment 5. It is evident that the intermediate segment 5 is designed as an element that can be mounted between the head section 3 and the body section 2 as needed. The first connecting piece 6 is arranged to rotate relative to the second connecting piece 7 about the axis of rotation R. For this purpose, the stepper motor 10 is coupled between the first and second connecting pieces 6, 7. The stepper motor 10 is controlled either by a pressure-resistant control unit 15 integrated into the stepper motor 10 or by an external control unit 15 via a cable connection. A control signal specifies the direction of rotation and the number of rotation angle increments, so that the rotational position of the stator 11 and rotor 12 of the stepper motor 10 is always precisely predefined and known.

[0048] A stable rotary bearing, which can withstand mechanical environmental influences such as wave action and impacts from objects and fish, is achieved by a ball bearing 13 in the rotary connection between the first and second connecting pieces 6, 7. This ensures that the at least one sensor 4 in the head section 3, which is rotatable relative to the body section 2 by means of the intermediate segment 5, is mounted on the body section 2 with low vibration and stability, yet still allows for position changes.

[0049] It can be seen that the intermediate segment 5 has buoyancy bodies 17, which surround the stepper motor 10. To guide the electrical cables running from the at least one sensor 4 in the head section 3 to the body section 2, at least one cable gland 18 is provided in the buoyancy body 17. This determines the position of the cables, even if they twist relative to the stationary body section 2 when the head section 3 rotates about the axis of rotation R. This prevents the cables from becoming jammed or from shifting uncontrollably. Reference symbol list 1 Autonomous underwater vehicle 2 hull section 3 Headboard 4 Sensor 5 Intermediate segment 6. First connecting piece for fuselage section 7 second connector for headboard 8 Hull connection flange 9 Sensor head connection flange 10 stepper motor 11 Stator 12 Rotor 13 ball bearings 14 Intermediate segment housings 15 Control unit 16 spaces 17 Buoyancy aids 18 cable glands 19 Drive unit 20 Steering and stabilization unit 21 Communication unit 22 Control Center L Longitudinal axis R axis of rotation

Claims

[1] Autonomous unmanned underwater vehicle (1) comprising a hull part (2) and a head part (3), wherein a sensor (4) is arranged on the head part (3), characterized byan intermediate segment (5) comprising a first connecting piece (6) designed for attachment to the hull part (2) and a second connecting piece (7) designed for attachment to the head part (3) and a stepper motor (10), wherein the first and second connecting pieces (6, 7) are rotatably mounted relative to each other about the longitudinal axis (L) of the underwater vehicle (1) and the stepper motor (10) is mounted with the first and second connecting pieces (6, 7) for controlled rotation of the head part (3) with its sensor (4) by rotation angle increments specified by the stepper motor (10), wherein the stepper motor (10) is enclosed in a pressure-waterproof housing and the interior of the intermediate segment (5) surrounding the stepper motor (10) is open to the outside and is flooded when the underwater vehicle (1) is submerged and the intermediate segment (5) has buoyancy bodies (17). [2] Autonomous unmanned underwater vehicle (1) according to claim 1, characterized by, that the intermediate segment (5) has water-resistant ball bearings (13) for rotatable support, which are surrounded by water when the underwater vehicle (1) is submerged. [3] Autonomous unmanned underwater vehicle (1) according to claim 1 or 2, characterized by , that the buoyancy bodies (17) of the intermediate segment (5) have a buoyancy foam. [4] Autonomous unmanned underwater vehicle (1) according to any one of claims 1 to 3, characterized by , that the buoyancy body (17) has cable passages (18). [5] Autonomous unmanned underwater vehicle (1) according to claim 1, characterized by , that the first connecting piece (6) of the intermediate segment is a connecting flange with fastening elements which correspond to a fuselage connecting flange (8) of the fuselage part (2) for attaching the head part (3) to the fuselage part (2). [6] Autonomous unmanned underwater vehicle (1) according to any one of the preceding claims, characterized by, that the first connector (6) is rotatable about the second connector (7) of the intermediate segment (5) which is fixedly attached to the body part (2), wherein the stepper motor (10) has a stator (11) and a rotor (12) and the stator (11) of the stepper motor (10) is coupled to the second connector (7) and the rotor (12) to the first connector (6). [7] Intermediate segment (5) for an autonomous unmanned underwater vehicle according to one of the preceding claims, characterized by, that the intermediate segment (5) has a first connecting piece (6) with a connecting flange designed for attachment to the body part (2) and a second connecting piece (7) with a connecting flange designed for attachment to the head part (3) and a stepper motor (10), wherein the first and second connecting pieces (6, 7) are mounted to rotate relative to each other about the axis of rotation (R) of the intermediate segment (5) and the stepper motor (10) is mounted with the first and second connecting pieces (6, 7) for controlled rotation of the head part (3) with its sensor (4) by rotation angle increments specified by the stepper motor (10), wherein the stepper motor (10) is enclosed in a pressure-waterproof housing and the interior of the intermediate segment (5) surrounding the stepper motor (10) is open to the outside for water flow and the intermediate segment (5) has a buoyancy body (17). [8] Intermediate segment (5) according to claim 7, characterized by, that the intermediate segment (5) has water-resistant ball bearings (13) for the rotatable mounting of the first and second connecting piece (6, 7) relative to each other around the axis of rotation (R) of the stepper motor (10). [9] Intermediate segment (5) according to one of claims 7 or 8, characterized by , that the buoyancy body (17) of the intermediate segment (5) has a buoyancy foam. [10] Intermediate segment (5) according to any one of claims 7 to 9, characterized by , that the buoyancy body (17) has cable feedthrough openings (18). [11] Intermediate segment (5) according to any one of claims 7 to 10, characterized by , that the first connecting piece (6) of the intermediate segment (5) is a connecting flange with fastening elements which correspond to a fuselage connecting flange (8) of the fuselage part (2) for attaching the head part (3) to the fuselage part (2). [12] Intermediate segment (5) according to any one of claims 7 to 11, characterized by, that the second connector (7) is rotatable about the second connector (6) of the intermediate segment (5) which can be fixedly attached to the body part (5), wherein the stepper motor (10) has a stator (11) and a rotor (12) and the stator (11) of the stepper motor (10) is coupled to the first connector (6) and the rotor (12) to the second connector (7).

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