Problem Overview
The Sea Perch is a "ROV" or "Remotely Operated Underwater Vehicle" is made of PVC pipes. The basic Sea Perch submersible does not allow for easy depth maneuverability. When used on its own, the standard cylindrical foam floats have buoyancy in shallow water but when submerged into deeper depths, it is harder for it to return to the surface just as easily. Therefore, when used in deep water, the buoyancy of the floats changes with depth. Additionally, the basic Sea Perch submersible can only be controlled by dropping it down in to the water and bringing it back to surface. The basic Sea Perch submersible cannot stay relatively stagnant at some water depth for this reason.
Design Constraints
This design must use the Sea Perch "ROV" submersible as its basic model and make modifications so that a human controller can easily maintain or change which water depth the robot is at. The basic unmodified Sea Perch "ROV" must be completed by Saturday, April 21st 2012 for an exhibition. The final deliverable must be completed within ten weeks. The size of the overall final submersible must be reasonable. Its weight must be small enough to withstand the propellers and motors. The overall cost of the Sea Perch "ROV" must be low. The submersible will be tested in the Schuylkill River in Philadelphia, Pennsylvania. The salt-water environment will be needed to take in to consideration as it will effect the productivity of the Sea Perch submersible differently than a fresh-water environment. The Sea Perch robot should be able to successfully maneuver at chosen depths.
Existing Solutions and Related Work
Existing Solutions
Currently, dynamic diving is the approach suggested by SeaPerch to better control the depths at which the submersible moves through. Dynamic diving involves the use of propellers to counteract the force created by the buoyancy of the submersible to push it underwater. Submersibles using this technique are often ballasted low in the water so that their speed downward is as slow as possible. This approach is relatively easy to accomplish with a SeaPerch submersible and will always return to the surface if the propellers are shut off because it is positively buoyant. However, it must be weighted low in to the water and the SeaPerch must be moving quickly for it to dive. Foam floats on the vehicle frame can also shortened or added in various places to adjust the buoyancy. Additionally, weights attached using clamps, fasteners, and tape have been used as ballast items.
Related Work
The Underwater Engineering Department from China Ship Scientific Department implemented a variable ballast system to control their submarine's buoyancy. A super high pressure hydraulic seawater system consisting of a super high pressure seawater piston pump and a deep-sea DC motor was used by the ballast system to pump water in and out of the ballast tank thereby increasing or decreasing the weight of the submarine. The seawater level in the ballast tank was detected by a magnetostrictive linear displacement transducer.
Design Goal
The goal of this project is to maneuver the Sea Perch submersible robot through various depths. To accomplish a suitable and more refined solution than those popularly used, a ballast tank system, comparable to the large-scale version used by the China Ship Scientific Department, will be added to the basic Sea Perch submersible model. To accommodate the ballast tank, the size of the PVC pipes in the standard vehicle frame of the Sea Perch "ROV" will be increased to widen the shape. The ballast tank will be made up of a large PVC pipe and secured with an endcap. The ballast tank will control the water flowing in and out and thus be able to either retain the submersible at a certain depth or move it more precisely to a higher or lower depth.To further modify the Sea Perch submersible for depth purposes, an Arduino microcontroller and depth sensor will be configured to quantitatively evaluate the submersible's water depth by using the PSI output. An Arduino microcontroller and depth sensor was chosen as the ideal depth reader because it is inexpensive and relatively easy to code.
Project Deliverables
The initial project deliverable will be a completed Sea Perch submersible that can be exhibited at International Science Festival at the Franklin Institute in Philadelphia, Pennsylvania. The final project deliverable will be a modified Sea Perch "ROV" that can easily maneuver through depths with the use of a ballast tank.
Project Schedule
A weekly outline of goals can be seen in Table 1 below.
Table 1: Project Schedule
Project Budget
A tabulated form of our basic project budget can be seen in Table 2 below.
Table 2: Project Budget
SeaPerch Kit:
The SeaPerch Kit contained all the materials required to build a basic Sea Perch model.Marine Glue:
This is needed because other glue does hold well because it reacts with salt water.An estimate of the "Marine Glue" can be found using the following link:
http://www.amazon.com/3M-5206-Marine-Adhesive-1oz/dp/B0000AY6DG/ref=sr_1_5?ie=UTF8&qid=1334898255&sr=8-5
Arduino Software:
This software is needed to program the depth sensor and can be found by downloading the compiler.Arduino Board:
This board is needed for the arduino system to function and control its necessary depth calculations.10 mm Tubing and various PVC Pipes:
These are both needed to modify the SeaPerch and construct the ballast system. Estimates of these materials were made based on prices found at a hardware store.12 DC 4mm 1/4" Normally Open Brass NBR 2-Way Solenoid Valve:
This valve is needed to control the water flow in and out of the ballast system. The online pricing for this part can be found using the following link:http://www.amazon.com/Normally-Brass-2-Way-Solenoid-Valve/dp/B005EP2KL8/ref=sr_1_6?s=industrial&ie=UTF8&qid=1334285590&sr=1-6
8.3 L/m (132GPH) Small DC12V Brushless Submersible Water/Oil Pump:
This pump is needed to propel water in and out of the ballast system using a force.The online pricing for this part can be found using the following link:
http://www.amazon.com/132GPH-Small-DC12V-Brushless-Submersible/dp/B0051HN0GS/ref=pd_sim_indust_8
Depth Sensor:
This sensor is needed to gauge the incoming data concerning its water depth from its location on the submersible. An estimate of its pricing can be found using the following link:http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MPX4250AP-ND
References
Link to Sea Perch Construction Manual:
http://www.seaperch.org/build
Link on Dynamic Diving and Static Diving:
www.rc-sub.com/resources/index.php5
Link to PDF Article on the Underwater Engineering Department from China Ship Scientific Department:
http://www.springerlink.com/content/x7674r3133lvqk83/?MUD=MP
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