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MECHANICAL DOMAIN

The mechanical design for Alphues was planned with the goal of making the AUV modular, compact and lightweight. The hull contains a sliding deck with a rack system, facilitating removal and centralized access to the electronic components. The external frame is designed to foster future modification of the AUV with minimal effort. The software tools used in modeling and analysis are SolidWorks, Catia and ANSYS.



VEHICLE SPECIFICATIONS


Depth rating :

50ft (Acrylic Hull)

Max speed: 0.6 m/s

Overall Dimensions: 48″ L x 24″ W x 21″ H,

Weight:45kg

Run time: 1 hours 30 minutes

8 x Thrusters for active Yaw, Pitch, Heave, Surge and Roll Control

 


HULL


Acrylic is the material chosen for construction of the hull. Acrylic refers to a family of synthetic or man-made plastic materials, containing one or more derivatives of acrylic acid. The hull has an inner diameter of 290 mm and an outer diameter of 300 mm. It is designed to be watertight in order to insulate the internal electrical systems from water damage. The hull end-cap features waterproof connectors, allowing external components to access the electrical systems inside the hull. The front and back end-caps are machined from Aluminum blocks to facilitate passive heat conduction. The cylinder is made from acrylic to provide a clear view of the hull components for inspection.



EXTERNAL FRAME


For the frame to be modular, a drill pattern is applied over its surface. The frame is made of aluminum and hard-anodized for structural stability. It was designed in such a way that the total deformation, von mission stress and strains are always minimum. All the components are directly secured to the frame. The frame design provides an unobstructed flow for the thrusters. Structural analysis using ANSYS is done to ensure structural rigidity. The frame consists of 2 side plates made up of Al-6061-T6 having a thickness of 6mm.The dimension of each plate is 1100mm x 500mm the width of the frame is 500mm. The frame accommodates 8 thrusters for Surge, Heave, Yaw and Pitch Control. Handles attached to the frame are provided for easy transportation of the AUV.


 

PNEUMATIC SYSTEMS


The pneumatics systems are used to drive the following manipulators attached to the frame :


Grabber Mechanism

Dropper Mechanism

Torpedo Mechanism


(i)Active grabber mechanism:


The grabbing mechanism is powered by a pneumatic piston which allows controlled grabbing and release using compressed air. The pneumatic grabber is utilized to grab underwater mission objects.To grab, the piston extends and the grabber arms close around the PVC object, securing it for transport to the second recovery area.


To release, a second set of valves is opened to force air into the other half of the piston, opening the grabber.


A CO2 cartridge is provided to contain compressed air .Here we use a Rexroth PRA-D32 pneumatic cylinder which can effectively functional even at higher pressures.


(ii)Dropper mechanism:


Two droppers are mounted below the hull. A magnetic coil is used to actuate the dropper using an electric pulse. This provides for dropping markers in competition bins. The dropper is made heavy so it can fall directly in line with the marker bins. Custom electromagnet actuation is used for this purpose.


The dropper actuation mechanism weighs at 0.5 kg.


(iii) Torpedo


Two independent pneumatic torpedo-shooting mechanisms are provided which have been 3D printed with a drag-optimized profile. The torpedo is activated using a pressure release valve that is solenoid controlled. Neutrally buoyant torpedoes provides stable water dynamics and easy recoverability.


 

Custom Enclosures


Custom sensor/electronics/battery enclosures are designed using CAD software and optimal precision CNC fabrication techniques are chosen for fabrication using aluminium.


 

Battery Pod


A battery pod houses the Li-Po batteries onboard Alphues. Pressure release valves and connector slots are provided on the periphery. The pod is water tightened using an axial sealing mechanism and can easily be swapped to provide continuous vehicle operation.


 

Camera Enclosure


Two custom camera enclosures have been fabricated for the front and bottom vision cameras. Clear acrylic front panels provide an unrestricted field of view.