UNMANNED UNDERWATER SURVEILLANCE ROBOT
UNMANNED UNDERWATER SURVEILLANCE.pdf (Size: 1.73 MB / Downloads: 74)
Unmanned underwater surveillance robot is designed to fulfill the need for autonomous solution of underwater control. This study is performed as a bachelor graduation thesis project of IZTECH and can be counted as developed prototype of industrial surveillance robots. Aim of the project is to increase knowledge of students on remotely operated vehicles (ROV) and teach them how teamwork is accomplished. Therefore, each subtask that has done in this project is 100% work-based and financially supported by students.
Surveillance is key element of control and risk management. Especially in areas where conditions are not suitable for human or there are risks aganist human health, need of surveillance and control is even more significant than it is already. As engineers and designers are volunteers and responsible persons for serving humans and providing solutions to problems, there has to be solution that has been created and provided by them.
Surveillance underwater has increased it’s importance since number of fish farms started to increase as well. Back then, control of these farms was done by divers but apart from divers, nobody was able to see what is going on underwater. So the need has come up and engineers developed the solutions. ROV’s or unmanned surveillance robots are high-tech solutions to this problem and provide reliable and accurate data to fish farms.
Figure 1. Remotely Operated Vehicle (ROV)
In this project, we have provide solution for underwater surveillance. Our robot is able to dive underwater (15m), move and record data at desired depths.
Following parts of this thesis will briefly summary the work done from the beginning of project. In addition, design criteia and constraints, work breakdown structure, linear responsibility chart, comments and budget information will be provided.
Design Criteria & Constraints
Design criteria and constraints are set early, when this project was given to us. The reason for that was, these criteria and constraints lead our pathway and develop our design specifications. That is why this step of the project has crutial significance in success of the project.
Design criteria and constraints are;
Meet with the budget estimations
Meet time schedule
Care for animals
Care for human health
Comply with the laws
Use 4 bilge pumps
Use aluminium body
Visable drive box
Withstand heavy whether conditions
Use waterproof materials
Use waterproof glues
Use screw joints
User friendly system
Easy to build system
High battery life
Use lipo battery
Use ESC to control motors
Long production life
Positive buoyant system
Center of Gravity & Centre of Buoyacy distance
Avoid sharp corners Easy to carry
Work Breakdown Structure (WBS)
Work breakdown structure divides project into small subgroups and steps, so each work can be done at the same time. This WBS can be changed as the project proceeds. Changes in WBS also provides tidiness and orderliness along the project and team members. WBS for this project can be seen below.
Figure 2. Work Breakdown Structure (WBS)
Linear Responsibility Chart (LRC)
Linear responsibility chart (LRC) is used to assign subtasks to team members. Generally each team member has one prior responsibility in each subtask. When the number of subtasks are high and team has a few members, everbody has one prior responbility, one asistance and one consultation duty among the subtasks. This LRC can also be changed during the ongoing project. Linear responsibility chart (LRC) for this project can be seen below.
Table 1. Linear Responsibility Chart of the project
Gantt charts illustrate the start and finish dates of the terminal elements and summary elements of a project. Terminal elements and summary elements comprise the work breakdown structure of the project. Gannt chart helps groups to see whether they are behind the schedule or not, so that they can hurry up or slow down during th project proceeds. Gannt chart of this project can be seen below.
Table 2. Gannt Chart of the project
Motors & Propellers
Motors and propellers have important effect on ROV design. This importance had two main categories. First is that, thrust that is supplied by motors provide movement underwater. Second, because ROV is operating underwater, thrusters are expected and needed to be water isolated. Otherwise reliability of system will not be satisfied.
Before deciding what kind of motor should be used, we have searched for thrusters that can be work underwater, in other terms thruster which is waterproof under 15 m. Couple of motors was found which are perfectly isolated and no water leakage is present. However due to high prices, we can not efford to by them. Then we found that, home made ROV’s are designed with bilge pumps. Bilge pumps is a water pump used to remove bilge water. Since fuel can be present in the bilge, electric bilge pumps are designed to not cause sparks .
As seen from the above figure, bilge pump has one hole to move the water out. However we can use it as a thruster by moving its head off and placing shaft and propeller on it.
Figure 4. Bilge Pump (Head cut off) .
Bilge pump has shaft but is not long enough for us to provide torque which is necessary for robot to move underwater. So additional shaft and propeller is prepared.
Figure 5. Thruster with 60 mm diameter Figure 6. Thruster with 90 mm diameter
For 2 thrusters which are designed to supply horizontal movement of robot has propeller with diameter of 60 mm. Other thrusters that provides vertical movement to robot has propeller with diameter of 90 mm. These difference in diameters is a must because force that is necessary for robot to go down or deep under the water is 1.5 time greater than force needed to move in horizontal axis. This 1.5 times greater force necessity is calculation based and will be explained in calculations part briefly.
Each of these thrusters were designed in same steps. Propellers were made of brass with molding and welding operations. Shaft height also differs for different diameters. 60 mm diameter thruster has 60 mm shaft lenght, on the other hand, 90 mm diameter thruster has 80 mm shaft lenght. Shaft lenght can be longer however, longer the shaft is, higher vibrations will be present.
In order to reduce turbulances and minimize harm to sea animals and plants, each thruster has duct on them. These ducts are not only for natural life but also for protection from any harm aganist propellers. Ducks are connected to bilge pumps and does not have any effect on their efficiency or energy consumption rates.
It can easily be said and noted that, in this study, the most important and most difficult task was water isolation or in other words drive box impermeability. The importance of drive box isolation has the highest priority since it contains electronic devices and cables which can not be in contact with even a drop of seawater.
Due to these big concerns, we have made alot of test on drive box impermeability and think about worst case scenerios. As a additional safety precaution, we have use water proof esc (motor drivers) and cover cables with electric tapes.