Design and development of non- rotary propulsion for autonomous underwater vehicles

Autonomous underwater vehicles that are propelled by altering buoyancy have been in demand in recent years as they have the ability to operate at sea for long periods. The buoyancy of an object in a fluid can be varied by two methods. One method changes the buoyancy of the vehicle by changing the mass without changing the volume and the other varies the buoyancy of the vehicle by changing its volume without altering the mass. The non-rotary propulsion system (Variable Buoyancy Engine) is the key component in the efficient design of autonomous underwater vehicles which enables it to ascend and descend through the water column by varying the buoyancy of the vehicle by changing its volume. The variable buoyancy system is capable of operating at a maximum depth of 500 m. The system consists of micro hydraulic pump, DC electric motor, internal reservoir, external rubber bladder, oil level sensor and valves. The design uses a micro hydraulic pump to increase buoyancy by transferring fluid from oil reservoir to an external bladder. Subsequently, a proportional control valve and the internal vacuum of the housing used for achieving negative buoyancy by decreasing the volume of the external bladder.