Autonomous underwater robotic systens, designated AUVs, developed by the Central Mechanical Engineering Institute (CMERI), Durgapur are gaining importance owing to their embedded advantages for applications like seabed mapping, costal surveillance, mine countermeasure and ocenographic measurements during adverse wether conditions. With no physical cable connection to the surface control station and possessing onboard intelligence and energy supply, an AUV carries payload for carrying out a specific task. The configuration and payload of an AUV depends on mission requirement. The communication is hybrid in nature - RF while on surface and acoustic while underwater. The objective of the present project is to develop an operational AUV capable of operating up to a depth of 150m in the sea as per specification. The developed system is capable of mapping sea floor and sensor based data collection. AUV can perform various jobs related to underwater inspection with camera, surveying etc. The project is sponsored by Ministry of Earth Sciences, Govt. of India.
The Vechile is programmed with a set of instructions that enable it to carry out an underwater mission without assistance from an operator on the surface. For autonomous free movement under water, the AUV determines its own geographical position with the help of navigational sensors and with navigational algorithms avoid collision with obstacles after their detection through forward looking sonar. The onboard software (preprogrammed) makes the vechile smart. The onboard intelligence helps it to take its own decisions and re-plans the mission accordingly.
The various issues considered during design are as follows.
a) Configuration, b) Modularity, c) Degrees of freedom, d) Stability, e) Near neutral buoyancy, f) Hydrodynamic modelling, g) Pressure Hull design, h) Energy system, i)Navigational Sensors, j) Communications, k) Payload sensors Thrusters are used to propel and maneuver the AUV. 5 thruststers are mounted on the AUV for generating motion in different directions to control surge, sway, heave, pitch and yaw. Lithium polymer batteries are used as power source considering its higher energy density, light weight, higher life and safety. For autonomous operation AUV is interfaced with obstacle avoidance sonar. The AUV is equipped with a number of navigational (Inertial Navigational System, Depth Sensor, Altimeter, Doopler Velocity Log, Forward Looking sonar, Global positioning system, APOS and payload sensors( side scan sonar, camera CTD) for execution of its peration successfully.
Three successfull testing were carried out near the chennai seacoast, in the Ldukki lake of cochin, and at the CMERI waterbody since past one year.
