The Concept Of A Hybrid Auv Rov Engineering Essay
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. In the electrical engineering field they also deal with power, electronics, control system, signal processing and also telecommunications. Mechanical engineering is a discipline of engineering that applies the principles and materials science for analysis, design, manufacturing and maintenance of mechanical system. It is the branch of engineering that involves the production and usage of heat and mechanical power for the design, production and operation of machines and tools. Mechanical engineers use tools like computer-aided engineering and product life cycle management to design and analyze manufacturing plants, industrial equipments and machinery, heating and cooling system motor vehicles, aircraft, robotics and underwater vehicles.
Electrical engineers always work with mechanical engineers as a team in solving many types of problem and issues that happen around human kind. Olden day, many type of mechanical system need man power to make it work and make it operate. After many years of revolution and the development of the technology, man power operate machinery has been evolved and change to more advance which it can operate without man power. By introducing the electrical and electronic, man power mechanical system has been replaced.
Recently, environment problems, including global warming, have become important issues. Oceanographic observations are an important means of investigating the trends of environmental change because about 70% of the Earth’s surface is under the sea. The conditions of the sea, including ocean currents, the temperature of the water can generally be observed by human. However, since the deep sea and the seabed are extreme environments, the use of underwater robots or vehicles instead of human is expected in the future. Underwater robots and vehicles all run the mechanical system and the mechanical system all are run by the electrical and electronic circuit inside the system.
Unmanned underwater vehicles are generally classified into two types, one is remotely operated vehicles (ROV) and other one is autonomous underwater vehicles (AUV). A remotely operated vehicle (ROV) is tethered underwater robot. They are common in deepwater industries such as offshore hydrocarbon extraction. An ROV may sometimes be called a remotely operated underwater vehicle to distinguish it from remote control vehicles operating on land or in the air. ROVs are unoccupied, highly maneuverable and operated by a person aboard a vessel. They are linked to the ship by a tether, a group of cables that carry electrical power, video and data signals back and forth between the operator and the vehicle. High power applications will often use hydraulics in addition to electrical cabling.
Most ROVs are equipped with at least a video camera and lights. Additional equipment is commonly added to expand the vehicle’s capabilities. There may include sonars, magnetometers, a still camera, a manipulator or cutting arm, water samplers, and instruments that measure water clarity, light penetration and temperature. Most ROVs are equipped with manipulators, which are operated remotely by human operator who are on the ground and in a support vessel. Since the operational commands and the power are supplied though a power cable, the operational area of a ROV is limited. In order to avoid these limitations and be able to investigate wider area, AUV which has no cables have been developed.
Many researches had been to develop the new remotely operated underwater vehicle. One of the most difficult part in design and develop the ROV is the dynamics movement and the control of the underwater vehicle. The controlling of the movement of the ROV required the mechanical engineering knowledge to create a flexible movement of ROV when it is under the deep water. Then, with the help of electrical and electronic parts the mechanical system able to operate under the deep water.
There will be on-board vehicle system come with the ROV. The on-board vehicle control system controls and monitors all vehicle sensors and actuators in response to real-time commands from a surface control system. The on-board control system will use a data concentrator (DCON).
The data concentrator module will independently control the power and data telemetry for an entire vehicle subsystem or scientific payload. The data concentrator will receive commands from the surface control computer, monitor the status and report the data from on-board vehicle subsystems and instruments. Each data concentrator operates asynchronously and will communicate to the surface control computer via a high bandwidth fiber-optic telemetry-link.
The remotely operated underwater vehicle (ROV) has a surface control system that located on the ground or onshore. The surface control system is the central brain of the ROV control system. It is comprised of a core system of safety critical system that are essential for safety and control of the ROV and an extended system providing non safety critical systems such as data logging and video recording. The safety critical core system is comprised of the vehicle computer and user interfaces for the vehicle pilot and engineer. The pilot station provides real-time video, navigation instruments, has joystick controls for closed loop control of the vehicles reference trajectories and navigation way-point and has controls for the vehicle’s manipulator arms. The engineer station has a more comprehensive set of real time vehicle status indicators and enables the engineer to control all the vehicles subsystems.
Another type of underwater vehicle is autonomous underwater vehicle (AUV). An autonomous underwater vehicle (AUV) is a robot which travels underwater. In military application, AUVs are also known as unmanned undersea vehicles (UUVs). AUVs constitute part of larger group of undersea system known as unmanned underwater vehicles, a classification that includes non-autonomous remotely operated underwater vehicles (ROVs). Unlike many other areas of mobile robots, AUVs have an immediate application area conducting various sub-sea surveillance and manipulation tasks for the resource industry. Most autonomous mobile robot applications can also use wireless communication to a host stations, this is a lot harder for an AUV. Once submerged, none of the standard communication methods work; Bluetooth or WLAN only operates up to a water depth of about 50cm. The only wireless communication method available is sonar with a very low data rate, but unfortunately these systems have been designed for the open ocean and can usually not cope with signal reflections as they occur when using them in a pool. So unless some wire-bound communication method is used, AUV applications have to be truly autonomous.
Autonomous underwater vehicle (AUV) are programmed to swim at a constant pressure or altitude or to vary their dept or heading as they move through the water, so that undulating sea saw survey patterns covering both vertical and horizontal swaths may be formed. AUVs are also well suited to perform long linear transects, sea sawing through the water as they go or traveling at a constant pressure. They also provide a highly productive means of performing seafloor survey using acoustic or optical imaging systems. An AUV is typically on the operation for 8 to 50 hours. Most vehicles can vary their velocity between 0.5 and 2.5 m/s. The optimum speed and the corresponding greatest range of the vehicle occur when its hotel load is twice the propulsive load. For most AUV, this occurs at a velocity near 1.5m/s. Bidirectional acoustic, radio frequency, and satellite based communications systems offer the capability to monitor and redirect AUV missions worldwide from a ship or from land. For this reason, semi-autonomous operations offer distinct advantages over fully autonomous operations.
For the motion and movement of the ROV, most of them are using the motor and connected to the controller to control the movement of the ROV during the operation. Most of the motor to that produce the mechanical movement are powered and controlled by the electronic devices inside the motor. The electronics part that used is an Eyebot controller. The hull was split and extended by a trolling motor for active diving which allows the AUV to hover. Besides that, it also uses active rubber control during a forward motion for diving. There will be a infrared sensors placed on the hull. Since the front part of the hull was made out of clear Perspex, the infrared sensor able to place inside the AUV hull without worry about the waterproofing sensors and cabling. Numerous sensors are connected to the EyeBot on board controller. These include a digital camera, analog infrared distance sensors, a digital compass, three-axes solid state accelerometer and a dept pressure sensor. There will have a Bluetooth wireless communication system that only can be use when AUV has surfaced or is diving close to the surface of water. Then for the AUV energy control subsystem, it contains of voltage regulators and level converters, additional voltage and leakage sensors. There will also a motor drivers for the sterm main diving motor, the rudder servo, the diving trolling motor and the bow thruster pump.
The search for offshore hydrocarbons has taken the oil industry into increasingly deep water. Over the past decade activities have gone beyond the continental shelf in the West Africa, North West Europe and the Mediterranean Sea. Oil is now being produced from fields in 1000m water depth, with field developments in progress in double there depths. Traditional hydrographic survey technology has struggled to keep space with these trends. The water column between surface and seabed significantly degrades the resolution of data. Deployment of sensors closer to the seabed requires an increasingly long tether. There long umbilical have made deep-water surveys less productive with cost almost exponentially proportional to the water depth. It became increasingly obvious to us that applying the traditional vessel mounted and tower sensor techniques of the late 20th century required a radical change in deeper water.
The maintenance engineering potential of AUV technology is beyond the scope of detailed analysis in this paper, but worthy of a brief mention, if only because the potential savings to one operator alone have been calculated at $50 million per year. ROV have the same disadvantages as deep-tow survey systems. It is limited in excursion, prone to entanglement except in open locations and a physical drag in the water column limiting productivity. However in the engineering applications they bring important advantages. Power of the vehicles can be supplied from the surface and is not a limiting factor. So, with appropriate manipulators on the vehicle, intervention with subsea hardware is possible.
With the development of the technology, mechanical engineers and electrical engineers have come out a concept to combine the autonomous underwater vehicle and the remotely operated underwater vehicle. They called it as hybrid AUV-ROV. The concept of a hybrid AUV-ROV would be an ideal for the application in many industries. A free- swimming AUV could be housed at the central production facility and dispatched to any of the distant seabed production facilities when required. There it would latch with a docking station containing a reeled control umbilical which would have connections back to the control centre built into the seabed facilities. Thus, it can then operate as an ROV with all of the advantages that entails.
From the word by Paul Valery- the trouble with our times is that the future is not what it used to be. Finding better ways of observing and reporting on the interior of the ocean, its seafloors and coastal boundaries remain principal objectives of the oceanographic community. Utilizing productive and affordable technologies that offer a new perspective of the ocean by providing sampling methodologies that merge the high spatial resolution of ship-based surveys with the endurance and temporal resolution of moorings may be one “better way”.
Survey class AUVs are still an emerging technology. They are delivering a limited but important suite of data of tremendous quality. We expect to see their capabilities increased in the very near future through the real-time integration of sensor interpretation with the vehicle control system, bringing a pipe and cable inspection capability. Hybrid AUVROVs are coming. An autonomous intervention is a possibility. Thus, the mechanical engineers and the electrical engineer still need to work as a team to improve autonomous underwater vehicle (AUV).
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