DESC:
FIELD OF INVENTION:

The present invention relates to the field of underwater vehicles. More specifically the present invention relates to a vehicle for underwater exploration which can be navigated in an unmanned manner.

BACKGROUND OF INVENTION:

Autonomous Underwater Vehicle, abbreviated to AUV and also known as Uncrewed Underwater Vehicle has many important applications such as conducting survey missions for the detection and mapping of submerged wrecks, landforms, rocks and other obstructions that can cause difficulty for the navigation of commercial and recreational vessels in rivers and seas. Traditionally, Remote Operated Vehicles (ROV) have been in used for exploring the depths of water bodies. As suggested by the name, these vehicles are required to be operated by humans and cannot accomplish any tasks without human intervention. The connection between an ROV and its operator is often established via the implementation of tether cables. The usage of tether with underwater vehicles creates a number of significant problems. The long and long and bulky and long tether cable disturbs the life present within the water body being explored. A more critical issue which arises with the usage of tether cables is that there exists a risk of the tether cable getting caught up with underwater objects or even getting damaged. Hence, researchers have been working on Autonomous Underwater Vehicles (AUVs), which are designed to overcome the disadvantages associated with ROVs so that these vehicles can autonomously go and explore the different underwater areas without the risk of losing connection with vehicle and losing it.

The development of AUV started in 1957 with the Special Purpose Underwater Research Vehicle (SPURV) at University of Washington, funded by the US Office of Naval Research. It was followed by SPURV II, which improved on the hydrodynamic design of its predecessor, and increased the number of sensors onboard. It had 50 kg weight and was used for mid-water research. Similarly, the AUV MAYA was designed and developed in India and had a weight of 55 kg. These AUVs cost more than 100,000 USD and it was not possible to make the vehicle take-on applications where there may be a chance for the AUV to get lost or drowned. It was imperative to have a low-cost AUV that could be put in different underwater scenarios. There have been some low-cost AUVs developed in the recent past. One of them is SEMBIO. It had a weight of 6.5 kg with 4 thrusters; and mainly built for energy management. However it can go up to the depth of 10m only. Similarly, the Bluefin Sandshark weighs 5.12kg and has 1 propeller and 2 fin actuators. It could go up to 200m depth but there is no communication module. Importantly, in order to cover a large area, one needs multiple such small or micro AUVs that can cover the whole area.

“Sparus ii auvaa Hovering Vehicle for Seabed Inspection” by M. Carreras, J. D. Hernandez, E. Vidal, N. Palomeras, D. Ribas, and P. Ridao as disclosed in IEEE Journal of Oceanic Engineering, Vol. 43, No. 2, pp. 344–355, 2018 is a conventional hovering type vehicle which has fins for rotational movement, has a weight of 50Kg and is mainly used for seabed inspection. However the proposed shallow water AUV uses thrusters only for rotational movement. Also, the weight of the AUV is huge, which makes it very expensive.

“Mechanical Design and Development Aspects of a Small AUV-MAYA” by R. Madhan, E. Desa, S. Prabhudesai, et al, in 7th IFAC Conference MCMC2006. Citeseer, 2006, is India’s first conventional AUV and is used for scientific applications. It has a weight of 55 Kg which is very huge; and makes the vehicle very expensive.

“Hippocampus: A Micro Underwater Vehicle for Swarm Applications,” by A. Hackbarth, E. Kreuzer, and E. Solowjow, in IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS). IEEE, pp. 2258–2263, 2015 is a micro AUV which has a weight of only 700g, mainly used for swarm networks. However the main disadvantage of this AUV is the power to weight ratio is far beyond the needs. Hence it was not successfully driven. On the other hand, the present invention has a battery capacity 18 Ah which is pretty much sufficient for naval applications.

“SEMBIO - A Small Energy-Efficient Swarm AUV,” by A. Amory and E. Maehle, published in IEEE OCEANS MTS, pp. 1-7, IEEE, 2016 weighs 6.5 kg and was mainly built for energy management. However it can go unto the depth of 10m only. On the other hand, the present invention can go unto 100m depth.

“Design and Experiments with Loco-AUV: A Low Cost Open-Source Autonomous Underwater Vehicle,” by C. Edge, S. S. Enan, et al., in 2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS). IEEE, 2020, pp. 1761–1768 weighs 18kg. Also, it does not have a communication module. On the other hand, the present invention has acoustic communication for underwater communication and wireless module (Xbee) for on surface communication.

U.S. Patent No. 5,995,882 published on 30 Nov. 1999 and titled "Modular autonomous underwater vehicle system" is the only modular AUV that comes closer to our proposed design. However, it is a heavyweight AUV and is of 6 feet length which is quite large. On the other hand, the present invention is light weight 2.24 feet long, portable thus making in capable of being deployed by a single person.

Further, in case of conventional AUV, there is a single heavy pressure case which is approximately 30 to 120 Kg weight, depending on the overall weight of the AUV. This is required to have a stable navigation system and it uses rudders and fins for propulsion which makes the propulsion system complicated. These types of AUV can go much deeper, to the tune of several hundreds of meters. However, the cost of these AUVs are very high (nearly in hundreds of lakhs, i.e., tens of million rupees). Notably, deploying these AUVs must require huge manpower and cranes which leads to more deployment cost. This makes the AUV non-affordable for most of the civilian applications and use cases such as surveillance, exploration, etc.

SUMMARY OF THE INVENTION:

The Underwater Vehicle of ‘H’-configuration, abbreviated as H-AUV, is designed and developed to be a modular system based compact autonomous underwater vehicle whose components can be easily replaced as and when required. The primary aspect of the present invention is to provide a first cylindrical shaped hollow structure and a second cylindrical shaped hollow structure which are both sealed at both their ends in a watertight manner.

Another object of the present invention is to provide at least one clamping system for fastening the first cylindrical pressure case to the second cylindrical pressure case parallel to each other, i.e., in an H shape. In the preferred embodiment of the present invention two clamping assemblies are provided. One of the said clamping assemblies is provided to clamp the said two pressure cases on one side of the centre of gravity of the underwater vehicle and another clamping assembly is provided to clamp the said two pressure cases together on the other side of the plane perpendicular to the axes of the pressure tubes passing through the centre of gravity of the vehicle.

The said underwater vehicle is provided with a first set of propellers, i.e., the vertical propellers for the movement of the underwater vehicle in the vertical direction. The said underwater vehicle is further provided with a second set of propellers, i.e., the linear propellers for the movement of the underwater vehicle in the linear direction. A combination of the propulsive forces imparted by the vertical and the linear propellers moves the said underwater vehicle in various directions under water.

BRIEF DESCRIPTION OF DRAWINGS:

The drawings constitute a part of this invention and include exemplary embodiments of the present invention illustrating various objects and features thereof.

Figure 1: Illustration of the underwater vehicle of an H configuration.
Figure 2: Illustration of the underwater vehicle of an H configuration having one vertical propeller.
Figure 3: Illustration of the underwater vehicle of an H configuration with SONAR,
Figure 4: Block Diagram of the Embedded Control System of the Underwater Vehicle of H Configuration.
Figure 5: Block Diagram of the detailed components of the Embedded Control System of the Underwater Vehicle of H Configuration.
Figure 6: Illustration of the computer generated 3-axis model of the underwater vehicle of H configuration.
Figure 7: Illustration of the pressure contour map of the simulated model of the underwater vehicle of H configuration.
Figure 8: Illustration of the velocity contour map of the simulated model of the underwater vehicle of H configuration.
Figure 9: Illustration of the centre of gravity of the underwater vehicle of H configuration.
Figure 10: Illustration of the types of front end caps.
Figure 11: Illustration of the types of rear end caps.

DETAILED DESCRIPTION OF THE INVENTION:

For the purpose of promoting, an understanding of the principles of the invention, references will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Reference herein to “one embodiment” or “another embodiment” means that a particular feature, structure, or characteristics described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in a specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Further, the diagrams representing one or more embodiments of the invention do not inherently indicate any particular order nor imply any limitations in the invention.

In an embodiment of the underwater vehicle of H configuration, shortened to H-AUV, the physical structure comprises two elongated enclosures which are sealed at both the ends by caps in a watertight manner. It is necessary to have the enclosures watertight so as to keep the components placed inside the said enclosures safe from water damage. The said two watertight enclosures are placed parallel to each other and are affixed with respect to each other in the said parallel position.

The rear end caps of the two pressure cases are provided with a plurality of hole for the passage of the connecting wires and cables between the said two pressure cases and to the plurality of propellers. In the preferred embodiment of the present invention, the lengths of the said two enclosures are equal. In the preferred embodiment of the present invention, the said two watertight enclosures also called pressure cases are cylindrical in shape, i.e. the pressure cases have a circular cross-section.

The said pressure cases are fastened with respect to each other by a clamping mechanism. In order to prevent the flexing of the clamp leading to the rotation of the enclosures with respect to each other, two clamps are implemented to fasten the enclosures at two points. The said clamping mechanism is composed of a rigid band going around the circumference of the enclosure wherein each of the two pressure cases is provided with a rigid band going around the said enclosure. A said rigid band’s going around the circumference of a cylindrical enclosure forms a ring like structure to hold on to the said enclosure. For the fastening at a particular point, the enclosure are fastened at two parallel points and a bridge is provided between the said circular clamps connecting the said two circular clamps in a rigid manner thus fixing the positions of the two pressure cases with respect to each other.

One clamping assembly is provided at the distal end of the pressure case and another clamping assembly is provided towards the front end of the pressure case. The two distal circular clamps provided in the distal regions of the two pressure cases are equidistant from the respective distal ends of the two pressure cases. Similarly, the two front circular clamps for the two pressure cases are provided in the region closer to the front end of the said two pressure cases at points equidistant from the respective front ends or rear ends of the respective pressure cases.

The autonomous underwater vehicle of H configuration is further provided with a plurality of sets of propellers for the propulsion of the said vehicle. The propeller is a propulsive device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. The said underwater vehicle is required to be moved against the force of gravity and also against the drag and buoyant forces of the water.

For the said movement, the underwater vehicle of the H configuration is provided with two set of propellers. One set of propellers is responsible for the movement of the underwater vehicle in the linear direction and the other set of propellers is provided for enabling motion of the said vehicle in the vertical direction. A combination of the forces generated by the said two sets of propellers is used to move the underwater vehicle in all the intermediate directions.

The first set of propellers is a set of linear propellers provided at the distal region i.e., the distal end of the underwater vehicle. In an embodiment of the present invention, two linear propellers are provided in the rear of the underwater vehicle. One linear propeller is attached to each of the two pressure cases. The said propeller is attached with the respective pressure case via an extender. The extender is an elongated structure with its one end attached to the circular clamp in the distal region of an enclosure. The said extender projects parallel to the length of the said pressure case in a direction away from the front end of the pressure case. The other end, i.e., the projecting end of the said extender is rigidly attached to a propeller. The said extender creates a distance between the rear end of the pressure case and the propeller which is necessary to allow the flow of the water across the said propeller during propulsion.

The set of propellers is provided for the propulsion of the underwater vehicle in the vertical direction. The preferred embodiment of the present invention is provided with two vertical propellers. The first of the said two vertical propellers is attached to the bridge connecting the front two circular clamps and the second vertical propeller is attached to the bridge connecting the rear two circular clamps. Thus, the two vertical propellers are provided between the two pressure cases. The said vertical propellers maybe attached to the bridge of the clamping assembly by propeller supports which are rigidly attach the propeller to the bridge of the clamping assembly while allowing for the detachment of the said propeller from the bridge.

In the preferred embodiment of the present invention, the two vertical propellers are positioned with respect to the centre of gravity of the said underwater vehicle with the said two vertical propellers being equidistant from the said centre of gravity. The said positioning of the vertical propellers increases the pitch degree of freedom of the present underwater vehicle with respect to the underwater vehicle of the prior art.

In one embodiment of the present invention, the pressure cases and its front end caps and rear end caps are made of an acrylic material which ensures the underwater vehicle remains light weight.

The figure 1 illustrates a preferred embodiment of the present invention. Two parallel watertight cylindrical enclosures, pressure cases 1a and 1b, having equal length are provided which are affixed with respect to each other by two clamping assemblies. The said two pressure cases 1a and 1b are hollow structures which are sealed at both the ends by end caps. The first pressure case 1a is sealed at the front end by a front end cap 2a and similarly the second pressure case 1b is sealed at its front end by the second front end cap 2b. Moreover, the two pressure cases 1a, 1b are placed side by side, which decreases the H-AUV’s forward profile allowing it to move through the water with less resistance. In a similar manner, the rear ends of the said pressure cases 1a and 1b are sealed as well. The rear end of the first pressure case 1a is sealed with a rear end cap 3a. The rear end of the second pressure case 1b is sealed with a second rear end cap 3b.

The said to pressure cases 1a and 1b are positioned parallel to each other and are fastened with respect to each other by clamping at two points. A first clamping assembly is provided to clamp the two pressure cases 1a and 1b together at points closer to their respective front ends, and another clamping assembly is provided in a region closer to the rear ends of the two pressure cases 1a and 1b.

The first clamping assembly 4, near the front of the autonomous underwater vehicle of H configuration, has two front ring members 4a and 4b going around the lateral circumferences of the two pressure cases 1a and 1b respectively to hold them in an immovable manner. A joining member is provided between the said two ring members 4a and 4b, i.e., the front bridge 4c which rigidly connects the two ring members 4a and 4b and thus the two pressure cases 1a and 1b.

A second clamping assembly 5 is provided near the rear end of the H-AUV wherein the two pressure cases 1a and 1b are held together by two rear ring members 5a and 5b. The said two rear ring members 5a and 5b are rigidly connected by a rear bridge 5c thus fastening the pressure cases 1a and 1b with respect to each other.

The autonomous underwater vehicle of H configuration is provided with two sets of propellers which are for the movement of the vehicle in the linear and vertical direction. In the preferred embodiment of the present invention, two vertical propellers are provided. The first vertical propeller 6a is provided closer to the front of the vehicle. The first vertical propeller 6a is attached to the front bridge 4c of the first clamping assembly 4. The said first vertical propeller 6a connects to the bridge 4c by a detachable connector propeller support 13a. The second vertical propeller 6b is provided closer to the rear end of the vehicle. The said second vertical propeller 6b is attached to the rear bridge 5c of the second clamping assembly 5. The second vertical propeller 6b connects to the bridge 5c by another detachable connector propeller support 13b. The rotational axes of the both the vertical propellers 6a and 6b are perpendicular to the plane formed by the two longitudinal axes of the cylindrical pressure cases 1a and 1b.

In the preferred embodiment of the present invention, two linear propellers 8a and 8b are provided for the movement of the H-AUV in the linear direction. The first linear propeller 8a is attached to the rear end of first pressure case 1a. For the attachment first linear propeller 8a to the first pressure case 1a, a first propeller extender 7a is provided. The first propeller extender 7a is a straight elongated structure is having one end rigidly attached to the first rear ring member 5a of the second clamping assembly 5 and projecting away from the said pressure case 1a in parallel manner with respect to the longitudinal axis of the said pressure case 1a. Similarly, the second linear propeller is attached to the second pressure case 1b by a second propeller extender 7b which has its one end attached rigidly to the second rear ring member 5b of the second clamping assembly 5 and projects away from the said pressure case 1b in parallel manner with respect to the longitudinal axis of the said pressure case 1b.

The figure 2 illustrates an embodiment of the present invention having only one vertical propeller 6. The said vertical propeller 6 is provided at the front of the vehicle wherein the said vertical propeller 6 is attached to the bridge 4c of the first clamping assembly 4 by a detachable propeller support 13. The said illustrated embodiment of the H-AUV is provided with two linear propellers. Another embodiment of the present invention may have only one vertical propeller to provide one degree of freedom of heave and two linear propellers which provide another two degrees of freedom of surge movement and yaw. The yaw movement of the said embodiment may be executed by configuring the said propellers to have their axes of rotation to be rotatable.

In the said illustrated embodiment of the present invention, two vertical propellers 3a and 3b. Due to the presence of two vertical propellers positioned in a parallel manner with respect to the pressure cases 1a and 1b, the said embodiment of the present invention has a higher pitch stability as compared to the AUVs of the prior art having single hull design.

The Figure 3 illustrates another embodiment of the present invention where components in addition to the embodiment illustrated in the figure 1 have been included. In the said embodiment of the present invention, as illustrated in the Figure 3, at the front end of the H-AUV, a ping SONAR 9 is provided at the front end cap 2a or 2b of one of the pressure cases 1a or 1b. SONAR stands for sound navigation and ranging. The said ping SONAR measures the distance of object or obstructions from the present underwater vehicle. The said ping SONAR 9 is attached to a pressure case by a SONAR support clamp 9a.

The said embodiment of the present invention is further provided with lights 10 located at the front end of the underwater vehicle. In the illustrated embodiment of the present invention, two lights 10a and 10b are provided, one above the front end of each of the two pressure cases 1a and 1b. A light 10a is attached to the pressure case 1a by a light extender 11a attached to the front circular clamp 4a, extending towards the front end cap 2a of the said pressure case 1a. Similarly, a light 10b is attached to the pressure case 1b by a light extender 11b attached to the front circular clamp 4b, extending towards the front end cap 2b of the said pressure case 1b.

Further, the said embodiment of the present invention is provided with an acoustic modem 12 which is used to communicate inside the water. The said acoustic modem allows the plurality of the H-AUVs to communicate with each other and form swarms. The acoustic modem is attached to the front circular clamp 4b of the pressure case 1b by an acoustic modem support 12a.

A central aspect of the underwater vehicle of the present invention is the modularity achieved due to the specific design of the said underwater vehicle. As the pressure cases 1a and 1b provided for two different compartmentalised spaces, with each of the said pressure cases being watertight, a basic level of modularity is achieved. Most of the control-related electronics are located in the left-hand pressure case 1b and the battery is placed in the right-hand pressure case 1a.

Any type of modifications to the underwater vehicle of the present invention, in a manner of inclusions and exclusions of hardware such as sensors, can be made with minimum effort due to the dual-compartment design of the present invention. The said manner of arrangement of the components also ensures the uniform distribution of the mass within the H-AUV. The said uniform distribution of weight across the structure of the underwater vehicle keeps the vehicle statically and dynamically balanced during movement and hovering action.

A tested embodiment of the present invention is composed of the pressure case 1a and 1b of 4inch 508mm long acrylic tube which can cable or withstand the 10 bar pressure upto 100 m. The linear propellers 8a and 8b are arranged at the back orthogonal to centre of gravity to balance the buoyancy force. These linear propellers 8a and 8b provide forward, backward propulsion, left rotation and right rotation to the H-AUV which gives two degrees of freedom of surge and yaw. The propeller extenders 7a and 7b provide sufficient space to linear propellers 8a and 8b and H-AUV to propel the water for backward motion. The rear end caps 3a and 3b having fourteen holes provide all the actuators and power connections to each other's pressure cases 1a and 1b while maintaining the watertight nature of the said two pressure cases 1a and 1b. The first clamping assembly 4 and the second clamping assembly 5 provide ruggedness to the H-AUV to form the H-configuration to the design. The vertical propellers 6a and 6b provide the vertically up and down propulsion, and pitch movement by rotation which provides another two degrees of freedom of heave and pitch. The said vertical propellers are placed equidistant from the centre of gravity of the H-AUV with the help of the clamping assemblies 4 and 5 to balance the buoyancy of the H-AUV when it travels in vertical direction. The front end plates 2a, 2b are transparent acrylic plates to provide the components physical status.

The Figure 9 illustrates the location of the centre of gravity of the underwater vehicle of the present invention. The two sets of propellers, i.e., the vertical propellers 6a and 6b and the linear propellers, 8a and 8b are located in a symmetrical manner with respect to the centre of gravity of the underwater vehicle. The vertical propellers 6a and 6b are provided to be collinear with the centre of gravity of the underwater vehicle and are equidistant on either side of the said centre of gravity. The linear propellers 8a and 8b are present in the plane defined by the axes yb-zb which is orthogonal to the plane xb-yb. The linear propellers 8a and 8b are equidistant from the xb-yb plane and are also equidistant from the plane xb-zb while being on either side of the said plane xb-zb.

The Figure 10 illustrates two types of front end caps which may be implemented to seal the front ends of the two pressure cases 1a and 1b. The first type denoted by 12-a is a hemispherical type having a spherical curvature. The said hemispherical end cap is transparent to allow for the transmission of visual information in and out of the pressure case. The other type of the front end cap 12-b is the flat type.

The Figure 11 illustrates the different types of rear end caps. The first type 13-a is a type of rear end cap is one without any openings. The other illustrated types including 13-b and 13-c are rear end caps having a plurality of openings for allowing the passage of electrical connections.

The embedded control system blocks shown in illustrate two major blocks on the surface embedded system and AUV embedded system which are communicated through wireless modules. The detailed components of each block are shown in Figure 5. As shown, in the block diagram of an embodiment of the present invention, the water level sensor 122 and the battery 121 are placed in the second pressure case 1b and the rest of the components like the GPS 105, Camera 106 etc. are places in the first pressure case 1a.

In Figure 4 the internal embedded components of two blocks 1 and 2 are shown. Block 1 represents internal components of AUV and block 2 represents the GUI on the surface.

Explanation of the various blocks of the Embedded Control System:

101: The block 101 is an 8 bit microcontroller used to control all the actuators, interface all serial communication/ UART interfaced and analog input sensors. In this system the microcontroller used is Arduino Mega 2560 which has ATmega 2560 processor, 15 PWM output pins used to control the actuators, 3 hardware serial ports used to interface UART based sensors and 16 analog input pins to interface analog sensors.

102: The block 102 is a 64-bit real time controller used to perform all the real time computational operations in AUV. The real time controller used in this system is Raspberry pi 3 model B. It has Quad Core 1.2GHz Broadcom BCM2837 64bit CPU for computations 1GB RAM and can able to integrate up to 128GB memory for storing the data logs, It has on board BCM43438 wireless LAN and Bluetooth Low Energy (BLE) for wireless deploying the operational algorithms. It also has 100 Base Ethernet cable for wired transmission, 40-pin extended GPIO pins for sensor interface and 4 USB 2 ports for serial communication. It takes all the sensor data inputs and processes it in real time, sending commands for actuations.

103: The block 103 is a battery distribution circuit which distributes the power to all the sensors, propellers and lights. In this system Matek PDB-XT60 with BEC 5V and 12V Power Distribution Board is used. It distributes power from 3~4S LiPo packs upto 6 ESCs, as well as provides synchronized and regulated DC 5V outputs for RC Receivers. It also provides linear regulated DC 12V for powering Cameras, Servos, RC receivers, Flight Controllers, Video Transmitters, LEDs, etc. It offers an XT60 socket to connect the LiPo pack conveniently.

104: The block 104 is an inertial measurement unit which gives angular orientation of the AUV with respect to magnetic north and known as Attitude Heading Reference System (AHRS). The sparkfun razor IMU with AHRS 9 degrees of freedom is used as IMU for this system. It incorporates three sensors - an ITG-3200 (MEMS triple-axis gyro), ADXL345 (triple-axis accelerometer), and HMC5883L (triple-axis magnetometer) - to give nine degrees of inertial measurement. The outputs of all sensors are processed by an on-board ATmega328 and output over a serial interface. This enables the 9DOF Razor to be used as a very powerful control mechanism for autonomous vehicles.

105: The block 105 is a Global Positioning System (GPS) which is used to provide the position coordinates of AUV when it is on the surface in Geo-coordinates. These coordinates are further used for localization and navigation algorithms. In this system SmartElex GSM/GPRS/GNSS Bluetooth HAT for Raspberry Pi is used as a GPS receiver unit.

106: The block 106 is a camera used to capture the underwater images. The camera module used in this system is raspberry Pi 8MP NoIR camera module V2 features an ultra-high quality 8 megapixel Sony IMX219 image sensor and a fixed focus camera lens which is capable of 3280 x 2464 pixel static images, and also supports 1080p30, 720p60 and 640x480p90 video.

107: The block 107 is an acoustic based altimeter sonar which measures the altitude of the AUV from sea bed. The Ping Sonar Altimeter and Echosounder is used in this system. The Ping sonar is a single-beam echosounder that measures distances up to 50 meters (164 feet) underwater. A 30 degree beam width, 300 meter (984 foot) depth rated.

108: The block 108 is an acoustic modem used to communicate inside the water which gives the facility to form swarms of AUVs. The M64 acoustic modem is used in this system. This transmit data wirelessly underwater with two-way-communication at 64 bps. It has a proprietary data transfer protocol that provides reliable omnidirectional communication coupled with auto-synchronization. The M64 modem is the chosen for wireless monitoring of underwater sensors, AUV telemetry and command and carry out synchronised warm operations.

109: The block 202 is a wireless module used to communicate with surface computers and when AUV is on the water surface. This module receives all the data logs from the H-AUV and provide to the surface computer for computations. It also takes the commands from the surface computer and sends them to AUV. The wireless module used in this system is digi mesh xbee-pro 900HP RF module which operate at long range 900 MHZ frequency with data rate 10kbps up to 610m or 200kbs upto 305m in indoor whereas in outdoor mode 10kbps up to 15.5km or 200kbps up to 4.5km.

110: The block 110 is LED light used to provide illumination to the H-AUV. The LED lights used in this system are Lumen Subsea Light which are pre connected. These lights output over 1500 lumens at 15 Watts with servo signal control, daisy-chain connection for multiple lights, and smart over-temp protection. It has a 135 degree beam angle for wide illumination in front of the H-AUV. The colour temperature is 5700K.

111: The block 111 is a water level sensor used to detect water entry. In this system a low cost water level depth detection module is used to detect the entry of water in pressure case1.

112, 113, 114, 115: The blocks 112, 113, 114 and 115 are electronic speed controls which are used to control the speed of the thrusters. The ESC used in this system are blue robotics basic ESC. These are 30A simple bidirectional electronic speed controllers based on the BLHeli ESC design with upgraded features and performance. The servo input for these ESC ranges from 1100 micro sec to 1900 micro sec. 1500 micro sec is for stop, 1500 micro sec to 1900 micro sec is for clockwise rotation and 1100 micro sec to 1500 micro sec is for anti-clockwise rotation.

116, 117, 118, 119: The blocks 116, 117, 118 and 119 are thrusters used for propulsion of the system. In this system three blue robotics powerful T200 thrusters are used. These T200 Thruster comes ready to use and includes both clockwise and counter-clockwise propellers. These operate 7 to 20V voltage. The maximum full throttle forward / reverse thrust is 5.25 / 4.1 kg f at 16v and 6.7 / 5.05 kg f at 20V. The minimum thrust required is 0.02 Kg f. The full throttle power is 390 watts at 16V and 645 watts at 20V.

120: The block 120 is an XT60 connector used to connect the battery with BEC.

121: The block 121 is a pressure sensor which gives the depth of the AUV when it travels depending on the pressure of the water as every 10m depth of water 1 bar pressure increases. The blue robotics bar30 sensor is used as a pressure sensor. This sensor has the Measurement Specialties MS5837-30BA, which can measure up to 30 bar (300m/1000ft depth) with 0.2 mbar resolution, it has an amazing depth measurement resolution of 2mm in the water column. This sensor includes a temperature sensor accurate to ±1°C.

122: The block 122 is an underwater switch used to power on or off the AUV when it is on the surface of water. The blue robotics switch is used in this system to turn on or off the AUV without opening the water tight enclosure. It handles up to 5A of current and 120V AC or 26V DC.

123: The block 123 is a battery which provides the power to the entire system. The battery used in this system is blue robotics four cell Lithium-ion Battery of 14.8V, 18Ah capacity.

124: The block 124 is a water level sensor used to detect water entry in the pressure cases. In this system a low cost water level depth detection module is used to detect the entry of water in the two pressure cases.

201: The block 201 is a surface computer used to perform on surface computations like retrieving the data logs from the AUV when it comes on the surface of the water and displays all the essential parameters on graphical user interface. It is also used as an interface to users to send commands to the AUV. The system which can have high processing power can be used as a surface computer. In this system Laptop with I6 processor is used as a surface computer.

202: The block 202 is a wireless module used to communicate with surface computers and on surface AUV. This module receives all the data logs from the AUV and provides them to the surface computer for computations. It also accepts the commands from the surface computer and sends them to AUV. The wireless module used in this system is digi mesh xbee-pro 900HP RF module which operate at long range 900 MHZ frequency with data rate 10kbps upto 610m or 200kbs upto 305m in indoor whereas in outdoor mode 10 kbps upto 15.5 km or 200 kbps upto 4.5km.

Figure 5 illustrates the internal connections of the components in the AUV embedded system. The Arduino mega 2580 is used as an 8 bit microcontroller 101 and the raspberry pi is used as a 64 bit quad core arm processor 102. These two are connected together with I2c communication along with bar30 pressure sensor 106. GPS 105 is connected to the pi using UART communication and Xbee 109 is connected to pi with USB serial. The battery is connected to BEC using an xt60 connector which is to provide power to all the components. The thruster controllers are connected to Ardiuno mega 2580 with pwm signals, Acoustic modem, altimeter and IMU is connected to Ardiuno with hardware serial ports and finally water entry sensor and voltage monitor connected to analog ports.

The H configuration or shape of the present invention, i.e., the double-hull design is advantageous over the single-hull design of the prior art by providing an improved positional stability and as well as a reduced generation of drag force while the said vehicle is in motion underwater. The Figure 6 illustrates a 3-axis 3D model of the autonomous underwater vehicle wherein, the roll, pitch and yaw axes have been indicated. Rotation around the front-to-back axis is called roll. Rotation around the side-to-side axis is called pitch. Rotation around the vertical axis is called yaw. The said embodiment of the underwater vehicle is more stable in roll and pitch degree of freedom due to two modular hulls or pressure cases i.e., the two pressure cases and placement of the two vertical propellers. The said Figure 6 illustrates the present invention in all the rotational and translational degrees of freedom.

Another advantage of the H-shaped design of the present underwater vehicle is the elimination of requirement of any control surface planes. Control surface planes are aerodynamic devices allowing a pilot to adjust and control the vehicles attitude and orientation. They create a difference in fluid pressure to produce a force on the vehicle in a desired direction. As the design and manufacturing of control surface planes is highly resource-intensive, the elimination of the control surface planes from the present invention makes the present underwater vehicle economical in comparison to underwater vehicles having control surface planes.

The Figure 7 illustrates the pressure contour around the preferred embodiment of the underwater vehicle under simulated conditions. Further, the Figure 8 illustrates the velocity contour around the present invention under simulated conditions.

From the pressure contour plot shown Figure 7, it is observed that pressure is not evenly distributed uniformly over the body of the AUV. The high-pressure zones were observed in the forward direction of the AUV as it does not have streamlined body i.e., flat end cap and other irregularities such as lights, clamps, etc. The pressure on most of the areas was in the range of 0.1 MPa. As the AUV will be used for low-speed, i.e., 0.25 m/s application the performance is not affected. The velocity contour plot shown in Figure 8 is for the flow velocity of 0.25m/s over the AUV.
Table 1: Velocity versus Drag Force
Velocity(m/s) Drag Force (N)
0.25 0.88
0.5 3.5
0.75 7.8
1 13.9
1.25 21.73
1.5 31.36
1.75 42.69
2 55.73
2.25 70.48
2.5 87.17
The Table 1 shows velocity versus drag force. As the velocity of the vehicle increase drag force also increases. The thruster maximum thrust force at 16V is 5.25 Kg f which is 51.4 N and we have two thrusters for forward and vertical. The thrust available for forward and vertical movement is nearly 100 N. Hence the proposed H-AUV can be used upto a speed of 2.5m/s. The Three axis model of AUV is shown in Figure 6. The restoring force for stability of the vehicle is given in equation (1).
Restoring force expressed as ( df_r^b ) : d f_r^b = R_b^n (T_nb )-1 df_r^n
=- ?g[¦(-sin?(?)@cos?(?)sin?(Ø)@cos?(?)cos?(Ø))] ?_0^z¦Awp (?)d? ------------(1)
Where,
Awp (?) is the water plane area of the vessel as a function of heave position
? is the density of water
g is an acceleration of gravity
f_(b )^n is force with line of action through the point Ob expressed in {n}
T_nb is Euler angles between {n} and {b}
R_b^n is the rotation matrix between {n} and {b} used for navigation and control. {b} and {n} are the expressed as perturbations which are related to the motions in the body frame and North-East-Down frame using kinematic Transformations.
? and ? are the generalized positions used to describe the degrees of freedom.
Another embodiment of the H-AUV maybe be provided with hemispherical front end caps for the reduction of the drag force. The said drag force depends on the drag coefficient.
F_d=1/2 ?v^2 AC_d --------------(2)
Here, C_d is drag coefficient, F_d is drag force, ? is density of water, v is velocity of the fluid flow of the object, A is frontal area.
C_d for flat surface caps is 1.28 and for Hemisphere caps is 0.295. Hence hemispherical front end caps may be used for the further reduction of drag force on the H-AUV. The different type of end plates are shown in Figure 3.
The preferred embodiment of An autonomous underwater vehicle having an H configuration characterized by a first cylindrical shaped hollow structure pressure case 1a sealed in a watertight manner in the front end by a front end cap 2a and sealed in a watertight manner in the rear end by a rear end cap 3a; a second cylindrical shaped hollow structure pressure case 1b sealed in a watertight manner in the front end by a front end cap 2b and sealed in a watertight manner in the rear end by a rear end cap 3b; the said first pressure case 1a and the second pressure 1b coupled with each other by a first clamping assembly 4 in a first region at a first distance from the centre of gravity of the said underwater vehicle; the said first pressure case 1a and the second pressure 1b coupled with each other by a second clamping assembly 5 at a second region at a second distance from the centre of gravity in an opposite direction of the first clamping assembly 4 with respect to the said centre of gravity of the said underwater vehicle; at least one propeller 6 attached to one of the clamping assemblies first clamping assembly 4 or the second clamping assembly 5 for the movement of the underwater vehicle in the vertical direction; at least one propeller 8 attached to the rear second clamping assembly 5 for the movement of the underwater vehicle in the linear direction.
A first compartment is formed by the hollow space of the first pressure case 1a and a second compartment is formed the hollow space of the second pressure case 1b with one of the said compartments houses the battery powering the underwater vehicle of the present invention and the other compartment houses the rest of the components.
The first clamping assembly 4 fastens the first pressure case 1a by an annular structure first front ring member 4a wrapping around the circumference of the said pressure case 1a, fastens the second pressure case 1b by another annular structure second front ring member 4b wrapping around the circumference of the said second pressure case 1b and fastens the first pressure case 1a to the second pressure case 1b by a rigid joining member front bridge 4c between the first front ring member 4a and the second front ring member 4b. The second clamping assembly 5 fastens the first pressure case 1a by an annular structure first rear ring member 5a wrapping around the circumference of the said pressure case 1a, fastens the second pressure case 1b by another annular structure second rear ring member 5b wrapping around the circumference of the said second pressure case 1b and fastens the first pressure case 1a to the second pressure case 1b by a rigid joining member front bridge 5c between the first rear ring member 5a and the second rear ring member 5b. The first pressure case 1a and the second pressure case 1b are clamped to each other by the first clamping assembly 4 and the second clamping assembly 5 with the said first pressure case 1a and the second pressure case 1b parallel to each other.
A first vertical propeller 6a is attached to the bridge 4c of the first clamping assembly 4 by a detachable propeller support 13a and a second vertical propeller 6b is attached to the bridge 5c of the second clamping assembly 5 by a detachable propeller support 13b.
A first linear propeller 8a is attached to the rear end of the first pressure case 1a by a rigid elongated structure propeller extender 7a attached to the first rear ring member 5a creating a distance between the rear end cap 3a of the first pressure case 1a and a second linear propeller 8b is attached to the rear end of the second pressure case 1b by a rigid elongated structure propeller extender 7b attached to the second rear ring member 5b creating a distance between the rear end cap 3b of the second pressure case 1b. The front end caps 2a and 2b are chosen from flat and hemispherical designs.
,CLAIMS:Claims:
I/We Claim,
1. An underwater vehicle having an H configuration characterized by:
a first cylindrical shaped hollow structure pressure case 1a sealed in a watertight manner in the front end by a front end cap 2a and sealed in a watertight manner in the rear end by a rear end cap 3a;
a second cylindrical shaped hollow structure pressure case 1b sealed in a watertight manner in the front end by a front end cap 2b and sealed in a watertight manner in the rear end by a rear end cap 3b;
the said first pressure case 1a and the second pressure 1b coupled with each other by a first clamping assembly 4 in a first region at a first distance from the centre of gravity of the said underwater vehicle;
the said first pressure case 1a and the second pressure 1b coupled with each other by a second clamping assembly 5 at a second region at a second distance from the centre of gravity in an opposite direction of the first clamping assembly 4 with respect to the said centre of gravity of the said underwater vehicle;
at least one propeller 6 attached to one of the clamping assemblies first clamping assembly 4 or the second clamping assembly 5 for the movement of the underwater vehicle in the vertical direction;
at least one propeller 8 attached to the rear second clamping assembly 5 for the movement of the underwater vehicle in the linear direction.

2. The underwater vehicle having an H configuration as claimed in claim 1, wherein a first compartment is formed by the hollow space of the first pressure case 1a and a second compartment is formed the hollow space of the second pressure case 1b with one of the said compartments houses the battery powering the underwater vehicle of the present invention and the other compartment houses the rest of the components.

3. The underwater vehicle having an H configuration as claimed in claim 1, wherein the first clamping assembly 4 fastens the first pressure case 1a by an annular structure first front ring member 4a wrapping around the circumference of the said pressure case 1a, fastens the second pressure case 1b by another annular structure second front ring member 4b wrapping around the circumference of the said second pressure case 1b and fastens the first pressure case 1a to the second pressure case 1b by a rigid joining member front bridge 4c between the first front ring member 4a and the second front ring member 4b.

4. The underwater vehicle having an H configuration as claimed in claim 1, wherein the second clamping assembly 5 fastens the first pressure case 1a by an annular structure first rear ring member 5a wrapping around the circumference of the said pressure case 1a, fastens the second pressure case 1b by another annular structure second rear ring member 5b wrapping around the circumference of the said second pressure case 1b and fastens the first pressure case 1a to the second pressure case 1b by a rigid joining member front bridge 5c between the first rear ring member 5a and the second rear ring member 5b.

5. The underwater vehicle having an H configuration as claimed in claim 1, wherein the first pressure case 1a and the second pressure case 1b are clamped to each other by the first clamping assembly 4 and the second clamping assembly 5 with the said first pressure case 1a and the second pressure case 1b parallel to each other.

6. The underwater vehicle having an H configuration as claimed in claim 1, wherein a first vertical propeller 6a is attached to the bridge 4c of the first clamping assembly 4 by a detachable propeller support 13a and a second vertical propeller 6b is attached to the bridge 5c of the second clamping assembly 5 by a detachable propeller support 13b.

7. The underwater vehicle having an H configuration as claimed in claim 1, wherein a first linear propeller 8a is attached to the rear end of the first pressure case 1a by a rigid elongated structure propeller extender 7a attached to the first rear ring member 5a creating a distance between the rear end cap 3a of the first pressure case 1a and a second linear propeller 8b is attached to the rear end of the second pressure case 1b by a rigid elongated structure propeller extender 7b attached to the second rear ring member 5b creating a distance between the rear end cap 3b of the second pressure case 1b.

8. The underwater vehicle having an H configuration as claimed in claim 1, wherein the front end caps 2a and 2b are chosen from flat and hemispherical designs.

9. The underwater vehicle having an H configuration as claimed in claim 1, wherein the linear propellers 8a and 8b provide forward, backward propulsion, left rotation and right rotation to the H-AUV which gives two degrees of freedom of surge and yaw.

10. The underwater vehicle having an H configuration as claimed in claim 1, wherein the vertical propellers 6a and 6b provide the vertically up and down movement, and pitch movement by rotation which provides two degrees of freedom of heave and pitch.

Dated this 10th Day of April 2023
Signature:
Name: Bhavik Patel
Applicant’s Agent: IN/PA-1379
INFINVENT IP