AA STEMM Report

SeaPerch Remotely Operated Vehicle STEMM Assessment

Introduction

Figure 1 Cutlet ROV

Scenario/problem

            The remotely operated vehicle, or ROV, has been around for the use of scientists and engineers for decades. The first true modern ROV arrived during the 1950’s with the Royal Navy ROV Cutlet, which was used to retrieve unexploded naval ordinance such as torpedoes and mines. The Cutlet can is seen in figure 1 (Hughes and Waldo Howard 2010), the Cutlet has a very primitive mechanical arm and propulsion system.  ROV’s also conduct research and tasks where humans cannot go; water depth, pressure, darkness and water temperature stop humans from going deeper into the ocean depths. ROV’s are able to function in these inhospitable conditions while also performing various tasks. Only recently have ROV’s become more widely known to the scientific and world community. The British Petroleum Oil Spill, which occurred on 20 April 2010, required the use of ROV’s to cap the actual oil pipe, which was leaking crude oil into the open ocean and the Gulf of Mexico. Due to the fact that oil was continuously pouring out of the damaged oil well, humans were unable to reach the well due to the harmful effects of oil. The oil also clouded much of the water, which caused visibility to drop below safe levels. This meant that British Petroleum and other investors needed to create a ROV capable of withstanding the depth, darkness, cloudy visibility and harmful effects of the crude oil while also being able to perform tasks to cap the leaking oil well. In figure 2 (BP/Reuters – Macondo Well Spillcam, 12 April 2013) a ROV can be seen attempting to perform a task on the damaged wellhead.

Figure 2 Macondo Well Spillcam

Figure 3 WHOI Returns to the TItanic

Aside from performing engineering and mechanical related tasks , ROV’s also perform research related tasks where humans are unable to travel and explore. Research includes documenting marine species and/or collecting marine species, observing shipwrecks, rummaging through debris and various other tasks. In figure 3 (WHOI.edu – WHOI Returns to the Titanic, 17 January 2014), a ROV is seen observing an empty porthole into the wreckage of the titanic to conduct historical research and/or possibly analyze engineering faults of the titanic.
 

To replicate the challenges most ROV’s face in the natural world and to simulate the types of missions ROV’s carry out, the SeaPerch ROV challenge was conceived. The MAST Systems Engineering SeaPerch team needs to design and construct a fully submersible ROV with a fully functional arm to perform various tasks in a pool of depths of twelve feet while the team is remotely operating the ROV from dry land. Andrew Ahn’s specific role in the project is to design and construct a ROV frame and propulsion system.

Design Solution

Figure 4 Final Design Solution

Figure 5 Full Assembly

Of the four previous design solutions, design solution three was chosen as the best design for the SeaPerch ROV challenge. Below, figure 4 (Ahn – Final Design Solution) depicts design solution three as a three dimensional AutoCAD rendering. Excluding the propulsion systems and the mounting pieces, the entirety of the ROV frame is constructed of one inch PVC piping due to the fact that PVC piping is relatively cheap and easy to manipulate. The ballast tanks above the ROV frame consists of two inch PVC piping with end caps glued onto the pipes to create a sealed closed system; which provides positive buoyancy to the entire ROV frame. The ROV frame possesses a peculiar shape; the bottom flat segment of the frame is a standard rectangle but the side mounts of the ROV are splayed out at a forty-five degree angle. The reason for the angle is to provide the ROV with a wide stable frame when maneuvering and operating the mechanical arm. The full assembly of the actual frame without the ballast tanks is seen below in figure 5 (Ahn – Full Assembly)

The propulsion systems consist of a five-volt motor sealed inside of a thirty-five millimeter film canister using wax. The film canister have a two millimeter hole drilled into the bottom and cap which allows the wiring and the drive shaft to protrude from the film canister once it is sealed. After the cap is placed onto the film canister, the propeller can then be glued onto the drive shaft. The propeller direction reverses once the polarity of the electrical current is reversed, which is controlled by the arduino. A break down of the propulsion systems assembly is seen in figure 6 (Ahn – Propulsion System Exploded View)

Figure 6 Propulsion System Exploded View

Systems Engineering

Innovation

            In today’s technological and science focused society, many inventions and creations have already been patented and thought of. The concept of a ROV is a very old idea and has been established well over sixty years. The SeaPerch ROV is no exception and is an innovation rather than an invention. All ideas and concepts are just improvements or differentiated from other ROV designs. The SeaPerch also utilizes existing components and materials such as PVC piping and motors. The SeaPerch ROV is essentially a blending of these various ideas and materials into a single product.

System Component

            The specific MAST Systems Engineering II SeaPerch ROV focuses upon three main areas of engineering. These three areas consist of electrical engineering, naval architecture and mechanical engineering. Andrew specializes as the naval architect of the group; Andrew designs and builds the ROV frame and propulsion systems which provide a frame to mount the mechanical arm and electrical systems. The propulsion system is responsible for properly providing thrust to power and maneuver the entire ROV through the water. The frame and propulsion systems, however, are only a segment of the entire project.

Specific Engineering

            Naval architecture on its own is not a specific field of science or engineering, rather it covers a wide range of engineering specifics and physics. A naval architect uses several different types of engineering and physics to accomplish a product. These fields include hydrostatics, hydrodynamics, arrangement aesthetics and construction.

    Hydrostatics

figure 7 Buoyancy

            Hydrostatics is a specific field of physics and more specifically fluid mechanics. Hydrostatics focuses upon the principles of volume, displacement and buoyancy. These principles primarily concern the stability of an object when at rest in a stable still fluid. Essentially, hydrostatics when concerning the ROV helps to calculate the stability and buoyancy of the ROV frame at rest. This includes the general buoyancy of the frame, displacement of the frame and balance of the ROV both on top of a fluid and in the fluid. Figure 7 (Yupi666 – Buoyancy, 5 November 2011) depicts a general concept of hydrostatics with a simple image of the concept of an object’s buoyancy resting on top of a still fluid.

Figure 8 CFD Module

            Hydrodynamics

            The science of hydrodynamics focuses primarily upon the flow and resistance of fluids against a vehicle’s hull and protruding features such as propellers and rudders or any other object that may create drag. Propulsion also plays a large part in hydrodynamics. The ROV frame was designed and constructed with the aspects of drag, resistance and hydrodynamics in mind. Because the entire ROV is submerged, every aspect of the ROV accounts to the overall surface area which later equates to resistance and drag when maneuvering through the water. Vessel motion with propellers also greatly involves hydrodynamics since the flow of water across the propeller planes effects the motion of the entire craft. Figure 8 (Comsol – CFD Module) depicts the nature of water flowing across propellers blades and the vortex of motion created behind the propeller props.

            Arrangement Aesthetics

            The ROV frame is heavily involved in arrangement aesthetics since the entire is essentially a mounting platform for additional electronics, wiring and equipment. Thus the ROV frame must be able to accommodate all the extra equipment comfortably and also retain its aesthetic appeal to give a sense of adventure and science to its overall mood. In terms of ergonomics, the ROV frame needs to be able to function with all the equipment and wiring mounted. So the frame must have enough space.

           

            Construction

            Construction is extremely important to the entire ROV project, especially the frame. All angles, measurements, cutting and assembling needs to be exact and precise. Otherwise, errors throw off the balance and performance of the entire ROV. Measuring, cutting and gluing PVC piping occupies majority of the final construction process and is critical to the performance of the ROV. Cutting the PVC is essential; any errors throw off the overall dimensions of the frame and cause the frame to not properly fit.

Manufacturing Types

            Construction and assembly of the ROV was relatively simple and did not require too much struggle. The ROV frame required two primary types of production; the two types include the American system of manufacturing and just in time manufacturing.

            American System

            The ROV frame production and assembly in a way resembled some characteristics of the American system of manufacturing. Numerous different identical parts and pieces were either machined or acquired. Once these numerous different pieces were acquired or made, they were then assembled into a final product.

            Just in Time Manufacturing

            The procurement of pieces also resembled just in time manufacturing. Pieces of PVC piping, joints and elbows were only purchased when needed to reduce the cost of purchasing parts. Once one segment of the frame was finished, more parts or pieces were purchased to know exactly what exactly was needed and no excess materials were procured. This system worked so well only twenty-four dollars have been spent so far on the ROV frame.

Manufacturing Categories

            When considering how the ROV frame was manufactured, a few different categories of manufacturing come to mine. Construction is immediately one category of manufacturing the ROV frame fits into. After PVC parts were cut and gathered, the frame needed to be pieced together and essentially “constructed”. Furthermore, the pieces for the frame needed to be machined and created from PVC piping which also fits into the category of construction. Also, the use of PVC piping and various other plastics means that the ROV frame fits somewhat into the category of plastics manufacturing since plastic PVC was cut and assembled together.

Science

Scientific Laws/Principles

            Throughout the design process and testing process, numerous different scientific principles and laws need to be taken into account. The world operates on the laws of physics and when dealing with machinery, specific laws need to be accounted for in order for a specific task to be accomplished.

            Archimedes Principle

Figure 9 Archimedes Principle

            When dealing with ships, submarines or any other aquatic/marine based vehicle, Archimedes principle is the primary rule of physics one must take into account. Simply put, the Archimedes principle states that the buoyant force of an object is equal to the amount of water displaced by the object. In other words, the less dense an object, the greater buoyant force it will have in the water. Figure 9 (Bradley W. Carroll – Archimedes Principle) displays Archimedes principle at work in simple terms. The ROV frame is reliant upon Archimedes Principle in order to stay as close to neutrally buoyant as possible. The ROV frame with all equipment on it must cancel out the positive buoyancy of the ballast to stay neutrally buoyant. So the buoyant force of the ROV frame with equipment is clearly negative; however, the buoyant force of the ballast tanks are clearly positive since air is much dense than water.

            Newton’s Third Law

Figure 10 Newton's Third Law

            Newton’s third law specifically states that every action has an equal and opposite reactionary force. All vehicles upon this principal, especially marine vessels. In the water, whatever force a vessel applies to the water, the water pushes back to propel a ship or vessel. The same applies for a ROV; what force the propellers and motor provides, the water pushes back to propel the ROV forward, backward, up or down. Figure 10 (Tutorvista.com – Newton’s third law) provides an example of how a swimmer in the water applies Newton’s third law. As the swimmer pushes against the water, the water pushes back to push the swimmer forward. ROV’s and ships do the same thing except with propellers or water pumps.

Technology

            Within the ROV frame and propulsion systems, the technology utilized is somewhat narrow. Majority of the ROV frame focused upon materials technology such as plastics and metals. The ROV frame is entirely constructed of PVC piping, seen in figure 11 (Ahn – all parts) and is held together using a material solvent, or PVC glue, seen in figure 12 (Home Depot - Oatey X-15 16 Oz. PVC Bonding Adhesive). The ballast tanks are also held onto the frame using aluminum hose clamps, seen in figure 13 (Ahn – hose clamps).

           

           

Figure 12 PVC glue

Figure 11 all parts

Figure 13 hose clamps

In addition to material technologies used in the construction of the ROV frame, some electrical technology is incorporated with propulsion systems. Within the thirty-five millimeter film canisters is the five-volt motor. The five-volt motor, seen in figure 14 (eBay - Details about DC 5V 4350RPM 2mmx12mm Shaft 2P 2 Pin Mini Motor Replacement Parts), incorporates some aspects of electrical components since these motors must be able to accommodate the arduino of the electrical engineer. Additionally, to reverse the motor the polarity, or flow of current, must be also reversed.

Figure 14 Details about DC 5V 4350RPM 2mmx12mm Shaft 2P 2 Pin Mini Motor Replacement Parts

Mathematics

Conceptual

Until recently, not many mathematical computations were made. However, buoyancy needs to be calculated. Using Archimedes Principle, buoyancy can be calculated by comparing the weight of the object in air and the displacement of the object in the water. To determine the buoyant force of the entire ROV, the entire ROV and its equipment must be weighed in dry land on a scale. After this, the volume of the ROV is calculated and then multiplied by the weight of the water. This then gives the displacement of the object in the water. The difference between displacement and weight determines how buoyant the ROV is. Figure 15 (Hyper Physics – Density and Buoyancy, August 2000) displays the formula for Archimedes Principle. Buoyancy force (Fb) is equal to the weight (on dry land) minus the weight in the water (displacement).

Figure 15 Density and Buoyancy

Actual Calculations

Figure 16 Parts one and two assembled

            Thus far, the only calculations computed have been the combined conceptual displacement of the PVC ballast tanks, seen in figure 16 (Ahn – parts one and two assembled). To calculate the displacement of the two ballast tanks, the volume needs to be calculated first. To find the volume of a cylinder, the area of the top circle is calculated and then multiplied by the height. Area = π × r², in this case r = 1 inch so pi is the area of the circle. Since there are two cylinders, the total height is now 29 inches rather than 14.5 inches.

Now, 29 x pi =  91.1061869541 inches cubed. Now, inches cubed needs to be converted into feet cubed in order to attain a standard unit.

91.1061869541in³ = 0.052723ft³

After converting the units, the volume of the cylinders needs to be multiplied by the weight of freshwater which 62.4 lbs. per cubic foot.

0.052723ft³ x 62.4 lbs/ ft³ = 3.2899152 lbs.

After all the calculations, the buoyant force of the two ballast tanks is about 3.29 pounds of positive buoyancy.

Conclusion

            All in all, the SeaPerch ROV frame and propulsion systems is a naval architecture project that heavily focuses on principles such as the Archimedes Principal and Newton’s Third Law. Although naval architect is a separate branch of engineering, other fields and specialties blend into naval architecture, these include hydrostatics, hydrodynamics, arrangement aesthetics and construction. Through the manufacturing process, elements of both Just in Time and American manufacturing can be identified. The most important aspect of science and mathematics involved in the ROV frame is the concept of buoyancy. So far, only the displacement of the two ballast tanks have been accurately calculated. All in all, the final design solution is entirely constructed of PVC piping. The side support structures of the ROV frame are splayed out at a 45-degree angle in order to provide the ROV with a wider base. The frame is assembled using PVC glue while the ballast tanks are secured using aluminum hose clamps. The propulsion systems are then constructed using 35-millimeter film canisters and five-volt motors. To conclude, the naval architecture aspect of the MAST SeaPerch ROV is heavily laden with aspects of STEMM throughout its design, manufacturing, mathematic calculations and overall concept.

Works Cited

22newcentury. "Details about  DC 5V 4350RPM 2mmx12mm Shaft 2P 2 Pin Mini Motor             Replacement Parts." EBay. EBay, n.d. Web. 29 Jan. 2014.

BP/Reuters. Macondo Well Spillcam. Digital image. Jsg.utexas.edu. Jackson School of             Geosciences, 12 Apr. 2013. Web. 28 Jan. 2014.

"Buoyancy." Hyper Physics. N.p., Aug. 2000. Web. 29 Jan. 2014.

Calvert, J. B. "Hydrostatics." Du.edu. N.p., 11 May 2000. Web. 28 Jan. 2014.

Carroll, Bradley W. Archimedes Principle. Digital image. Physics.Weber.edu. Bradley W.             Carroll, n.d. Web. 29 Jan. 2014.

CFD Module. Digital image. Comsol. Comsol Inc., n.d. Web. 28 Jan. 2014.

"Density and Buoyancy." Hyper Physics. Hyper Physics, Aug. 2000. Web. 29 Jan. 2014.

Hughes, Waldo, and Howard Hughes. "Remotely Operated Vehicles: History, Waldos &             Howard Hughes." Innovational Musings. N.p., 8 July 2010. Web. 28 Jan. 2014.

Mack, Pamela E. "The American System of Manufacture." Clemson.edu. Clemson University,             10 Mar. 2005. Web. 29 Jan. 2014.

Newton's Third Law. Digital image. Tutorvista.com. Tutorvista.com, n.d. Web. 30 Jan. 2014.           

"Oatey X-15 16 Oz. PVC Bonding Adhesive." Www.homedepot.com. Home Depot, n.d. Web. 29 Jan. 2014.

Seaperch. Digital image. SeaPerch.org. AUVSI Foundation, n.d. Web. 28 Jan. 2014.

STEM. Digital image. Scollege.edu. Santiago Canyon College, n.d. Web. 28 Jan. 2014.

WHOI Returns to the Titanic. Digital image. Whoi.edu. Woods Hole Oceanographic Institution, 17 Jan. 2014. Web. 28 Jan. 2014.

Yupi666. Buoyancy. Digital image. Pressure. Wikimedia Foundation, 5 Nov. 2011. Web. 28 Jan. 2014.