URSA Underwater Remotely Operated Vehicle Nikko Miniello, Jashua Gonzalez, Carlos Sosa, Sabri Tosunoglu Florida International University Department of Mechanical and Materials Engineering Miami, Florida 33174 (305) 348-1091

[email protected], [email protected], [email protected], [email protected] ABSTRACT

2. Proposed Design

Navigating in deep, icy waters more often than not is quite treacherous. Having a ROV that can easily maneuver and display conditions readily on screen would cut down on both costs and human casualties greatly. Our motivation for this MATE ROV project design is to attempt to make difficult operations, that would normally take multiple people and machines to accomplish, simple. This specific paper is on the Robotic Claw development aspect of the design.

This design allows for a solid approach to construction, maintenance, and troubleshooting. The design is centered on a flow-through frame that encapsulates a waterproof dive box for the control components and telemetry unit. At the top sits an aluminum bar with brushless motors affixed, used to control the elevation of the ROV. Mounted on the back in a similar fashion are the two other brushless motors used for forward and reverse propulsion along with yaw capabilities. Additionally, located on the front plane is the main navigational camera. This camera is a full color wide angle camera that helps for macro scale navigation. The camera is centered in a way to assist the claw in the finer details of arm manipulation. There will be weights located on the bottom plane to provide for increased stability, in addition to the floats used along the top plane to ensure that the ROV stays properly oriented through all maneuvers.

Keywords Robot, Claw, Manipulator, Underwater, ROV, Xbox

1. INTRODUCTION With the ever increasing demand for petroleum-based products, reaching further and digging deeper have never been more in need. From maintaining undersea pipelines to conducting experimental science underneath ice and around hot gas vents, there is a specific place for the remote operated vehicle. A major challenge today is keeping people and equipment safe while still being able to conduct required inspections and experimentation. Our aim is to construct a prototype, remotely operated vehicle for use in maintenance and inspection of underwater pipelines; one which has the dual functionality to conduct biological research in icy water conditions. This vehicle will be equiped with a MK-II Robotic Claw. The claw will have four main functions: right, left, open, and close. These movements will be controled by two HS-5086WP Metal Gear Micro Digital Waterproof Servos, one servo will control the right and left movement while the other will control the claws ability to open and close as well as provide the necessary power to for the claw to maintain a strong grip. There is no need for the claw to move up and down since the ROV will have the capability to move in both the up and down direction and the forward and back direction.

Figure 1 - URSA UW ROV

3. SIMULATION STUDIES

The tips of the claw will be coated with a plastic membrane to fasiltate the claw ability to grasp objects of different shapes and textures.

Design and analysis of a system are important tasks to accomplish well during any experimental process. In this section a complete analysis will be done of our entire system. The topics of analysis are as follows: Flow, Stress, Strain, Vibrational, and Displacement, but further analytical iterations may be added when necessary. These following sections will cover our design choices as well as a brief explanation on why our choice was made.

The team plan for future versions of this project to incorporate a claw that uses more then just two prongs in order to perform more dynamic forms of movements and to maintain a better grasp on an object without nessesarliy adding more force to it. Sensors would be another advancement the team would like to incorporate into this design. The ability to have the claw sense what it is grabbing and be able to adjust its grip accordinly would open new oppertunites to implement this claw into more delicate tasks. With these sensors the operator will not only be able to use the claw to perform a specific task but also record data from the sensors.

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3.1 Flow Analysis The Kinematic Analysis is performed by setting up our frame in a simulated space with an approximate velocity of 20 MPH in the direction of motion. By setting up in this manner we are able to

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accurately mimic the underwater motion that our system would undergo. The pressure is set to 29 kPa (4.2 psi) which is the pressure of water at 3 meters (9.8 feet). The water is also set to be at ambient temperature.

3.2 Force Analysis The structure has been modeled as a solid body as to avoid contact errors within our simulation program. By fixing the opposite end as to where the force is applied to, we were able to properly indicate the reflected force upon the structure. First by simulating the mounting bar that the motors will be mounted on and then applying a point load upon the point of contact of 5 lb.-f (Which is beyond the indicated force of the motors, 1200g), we are able to properly see if the beam itself would be able to withstand the motors driving force under maximum conditions. After ensuring that the beam could withstand these conditions we subject the frame that the beam would be mounted to, to the same conditions. This ensures that our frame can even withstand the potential, maximum force that the beam could exert from the motors. With this data we also calculate the factor of safety to make sure our system is well beyond the safety margin, before we actually would physically test this.

Figure 2 - 3D Isosurface Flow In order to properly obtain the drag coefficient of our simulated model, we first had to remove the back section of the assembly, effectively disjointing the front portion of the assembly in order to get the frontal surface area. By doing this and then using the build in mass evaluation feature of SolidWorks2013, we were able to properly find the surface area of 259.75 square Inches.

Figure 4 - Force Load By using the built in stress/ strain analysis of SolidWorks which using the Von Mises Stress theory as well as the Equivalent Strain to calculate the minimum and maximum stress/ strain values throughout the system. Figure 3 - Front Section of ROV Equation 1: C

∗

∗

GG Force X 1 ∗

∗

∗

2 1000 ∗ 9 ∗ . 17

.

Figure 5 - Stress Diagram

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4. CONSTRUCTION The overall design of the MATE ROV will be centered on the idea of a central, water-tight, enclosed main body that houses the electrical components that govern the control and data gathering of the system. A sealed camera will be used to gather optical and sensory data which will be then be analyzed onshore via a laptop display. A robotic claw will be used to physically move or adjust specific objects in question. The whole body will be constructed out of water resistant materials such as PVC and Nylon. Any moveable components will rely on water-safe bearings. Initially we went with a more rectangular design because we thought the bull bar (angled frontal bars) in the front would make mounting things easier; however, it proved to not be that beneficial so we switched back to a more square design. The bars at the front of the design will serve for mounting our lights. We are planning on housing the electronics in a dive box that we will have to mount towards the center of the ROV. In addition we are leaving some space towards the back just in case we want to put our horizontal thrusters mounted internally too.

Figure 6 - Strain Diagram The factor of safety was also calculated when running the analysis of the system. This is the overall best approach for approximating whether or not our design is able to withstand the maximum allotted force that it can be subjected to.

Figure 7 - Factor of Safety Diagram Just as the load and stress analysis that were done, the deflection analysis was also generated using the same simulation parameters. With this test we will be able to note if the apparatus will deflect beyond safe operating conditions. Figure 9 - URSA Construction

Figure 8 - Displacement Diagram

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4.1.1

4.1 Components Table 1 - Part List Part

Count

Computer Power Supply 12V

1

HobbyKing Donkey ST3508 730KV Brushless DC Motor

4

HobbyKing® ™ Brushless Car ESC 100A w/ Reverse (Upgrade version)

3

HS-5086WP Metal Gear, Micro Digital Waterproof Servo

1

HS-5646WP High Voltage, High Torque, Programmable Digital Waterproof Servo

1

Microsoft Xbox 360 Wireless Controller

1

Arduino UNO Kit

1

Octura X470 1.4 Dia Beryllium Copper Propeller

4

PVC Piping

MK-II Robotic Claw

Simplicity, lightness, and structural rigidity were the key points in which we looked at when purchasing a manipulator. At a relatively affordable price the MK-II robotic claw was the appropriate choice for what we intended to accomplish. Being fabricated from cut aluminum and brass sleeves the system is more rigid and less likely to come loose. This will be the ideal design for grabbing and maneuvering small objects that need to be transported or hinder the movement of the underwater ROV.

20’

GoPro Hero 3 /W Underwater Enclosure

1

Robotic Manipulator Assembly (No Servo)

2

Propeller Adapter to suit 5.0 mm motor Suit (Collet)

4

Microsoft Xbox 360 Wireless Receiver for Windows

1

Pelican Micro 1060 Underwater Diving Box

1

Astra Depot Aluminum High Powered 6W 6000k Xenon White LED

3

Everbilt Flat Bar Aluminum (2 in x 1/8 in x 36 in)

1

Everbilt Zinc Machine Screws Round Head Combo #8-32x1-1/2 inch (6pk)

5

Everbilt Zinc Machine Screws Round Head Combo #8-32x1-3/4 inch (8pk)

1

Hex Bolt (1/4 in x 1-1/2 in)

8

Hex Nut Zinc (1/4 in)

8

Southwire Low Voltage Landscape Wire Black Stranded RoHS Compliant 14/2 50 ft)

1

Cerrowire Appliance Wiring Rated T90 Nylon (50 ft)

1

3M Marine Adhesive Sealant 5200 (3fl oz)

1

Scotch Outdoor Mounting Tape (1.66 YD)

1

Heat Shrink Tubing Assorted Pack (150 pcs)

1

BernzOmatic Electric Solder Lead-Free Rosin Core (3 oz)

1

Figure 10 - MK-II Claw [5]

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4.1.2

MK-II Robotic Pan/Tilt Bracket

As well as being able to grasp small objects in front of it, the system needed to be able to change directions when necessary in order to simplify the whole process and prevent excess expenditure of energy. The MK-II has a compatible pan/tilt bracket in which we feel would also be adequate for the desired purpose we have. This will enable our claw to move more effectively and grab objects on the left or right of the front of the ROV without having to turn the entire system.

Figure 11 - MK-II Pan/Tilt [5]

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4.1.3

Wiring

4.2 Waterproofing

One important aspect to test of the apparatus is to make sure that the voltage supplied remains as constant as possible through the extended distances of the cabling. Since all wires have an internal resistance and a slight drop of voltage through them, it is important to test these parameters, both under and not under load. We accomplished testing these specific parameters first theoretically and then compared them to the observed values. The values were read off of a Square D Power Logic Energy Meter which allows for very accurate measurements of amperage under high loads.

The most complex and important design consideration when constructing any underwater apparatus is the water proofing. Since we have multiple electronic devices that need to be housed internally we had to look into specific enclosures that were capable of withstanding water at a specified depth. Ideally we wanted to find something that was rated to IP68, but the cost goes upward from $200 for any sort of prefabricated device of that grade. The first thing we did was take a trip to Divers Direct to see what kind of a possible product we could purchase or reproduce. Upon detailed research we were able to determine that the Pelican Micro 1060 Diving Box rated to IP67 would be sufficient for the prototyping purposes that we required it for. The only issue with this enclosure was that it did not have an entry port for cabling.

The parameters for these values are set to 50 feet cabling and 12 gage AWG wire. The resistivity of copper at 20 C is approximately ρ=1.724*〖10〗^(-8) ohm m the diameter is approximately 0.0808 inches for 12 gage wiring and the resistance per 1000 feet comes out to be around 1.588 ohms. And the maximum allowable current is 41 amperes

Since a water tight entry tube was required for our design, we immediately discussed using a threaded tube with a hex nut on each end. After ample design discussion this was clearly the most simplistic and effective method possible. We tapped a ¾ inch hole into the top of the pelican box, which we determined to be an adequate size which would not damage the integrity of the box itself. The threaded tube was put into place with a layer of PTFE tape wrapped tightly around the diameter of the tube. The tube was put into place with a marine grade sealant and tightly secured at both ends of the lid so that the sealant could properly permeate both surfaces providing optimal coating and preventing any air bubbles that may have persisted. As you can see from figures 19-23 the design is quite simplistic and allows for a cluster of cables to be tightly packed within its inner diameter.

Equation 2: 1.724 ∗ 10

50

0.00673333 2 0.024 Equation 3: 12 .024 ∗ 25

∗

11.4 From the values indicated above we were able to see that there is a minimal voltage loss through the 50 ft cabling. This is the ideal scenario because it will ensure that our device gets an ample supply of voltage to the components that are housed within the dive box. The wire that was used is Southwire landscape Wire that runs for low voltage and has 14 gauge 2 copper stranded wires. The voltage loss is very low as assumed; if you take into an account much higher amperage such as 100 amps a larger loss would be expected.

Figure 12 - Wire Entry Rendering

Figure 13 - Wire Entry

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5. DATA

5.1 Buoyancy

Table 2 - Stress Name Stress

Type VON: von Mises Stress

Stress Min 0.00083[psi]

Max 619.654 [psi]

5.71 [N/m^2]

4.27e+006 [N/m^2]

It is important to calculate the buoyancy of our system. Our apparatus must have a slightly positive buoyancy so that it can resurface slowly over time if need be. In order to calculate the buoyancy a volumetric analysis of the system to determine the displacement of water compared to the actual weight of the apparatus must be performed. The major addition to the volumetric differences is the fact that the cavity that houses the electronic components is hollow and thus full of air. Results below indicate that our apparatus has very small, but positive buoyancy, which will be further increased when we add the floatation foam to the top portion of the ROV. This is good because if the ROV fails it will naturally resurface over time. Table 8 - Buoyancy

Table 3 - Strain Name Strain

Strain Type ESTRN: Equivalent Strain

Min 4.16807e-009

Max 0.00125933

Density of Water 1000 [kg/m^3]

Table 4 - Factor of Safety FOS Name Factor of Safety

Type Automatic

Min 12.9104

1.940 [slugs/ft^3]

Max 9.66213e+006

Buoyancy Volume Weight of Displaced URSA 0.00095 [m^3] 0.94 [kg] 0.03355 [ft^3]

2.08 [lb]

Buoyancy . .

. .

. .

6. CONCLUSIONS AND FUTURE WORK Our specific goals that we set out to accomplish were mostly met; we were able to progress to the level we intended for the prototype. A successful model was built on the concepts we previously laid out before starting the actual build. Our device preformed successfully under the heat and force load that was generated from the motors and electronic speed controls having a theoretical minimum safety value of 12 which is well beyond the required amount. We credit the exploratory heat dissipation to the fact that our apparatus uses forced convection from cold water conditions naturally. We were able to get the claw to operate as desired and it was capable of panning as well as clamping down upon an object without destroying it. URSA theoretically was able to travel through the water at speeds up to 20 MPH with an average drag coefficient of around 0.11 which is the expected ideal of our flowthrough system that we carefully designed.

Table 5 - Displacement Name Strain

Type URES: Resultant Displacement

Displacement Min 0 [in]

Max 0.0128933 [in] 0.0327489 [cm]

0 [cm]

Table 6 - Volumetric Properties Volumetric Properties Mass Volume Density Weight

English 0.823555 [lb] 22.3489 [in^3] 0.0368498 [lb/in^3] 0.822997 [lbf]

SI 0.373558 [kg] 0.000366234 [m^3] 1020 [kg/m^3] 3.66087 [N]

Table 7 - Material Properties Material Properties

English

The future goal of this project would be to market to companies that require delicate underwater procedures to be done, such as underwater scavenging, harvesting, or maintenance. Various companies such as NAVSEA, Odyssey Marine Exploration, and Global Marine Exploration would be companies that could benefit from our product development and design. Making the product run as efficiently as possible at a minimal costs is our most prominent consideration. Lowering the overall cost of the product while at the same time simplifying the total process of assembly and maintenance are the key goals to making our product marketable to the public. The lower cost will allow us to sell the product at a healthy profit margin, while at the same time making replacement of faulty components a hassle-free process. The simplistic design and hope for an even further simplistic approach will allow anyone to be able to assembly and use the product regardless of technical knowhow or experience with engineering. We also aim to make the device modular so that different components that are approved could be easily swapped on and off for the specific purposes the user desires, thus also effectively reducing the overall cost to the consumer based on their specific need.

SI PVC

Name Model type

Linear Elastic Isotropic

Default failure criterion

Max von Mises Stress

Yield strength

8000 [psi]

5.51581e+007 [N/m^2]

Tensile strength

4351.13 [psi]

3e+007 [N/m^2]

Elastic modulus

290075 [psi]

2e+009 [N/m^2] 0.394

Poisson's ratio Mass density

0.0368498 [lb/in^3]

1020 [kg/m^3]

Shear modulus

46252.5 [psi]

3.189e+008 [N/m^2]

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We would love to continue working on this design; the time and effort we put in to produce a working prototype was significant so we wish to finalize our design and produce a complete working apparatus in the future. Having a lighter frame with the same or similar structural stability would be ideal, to accomplish this we would need to construct the chassis out of titanium or aluminum which would provide ample strength to weight ratio compared to PVC. Flattening the front of the frame would allow for better mounting of the claw and lights, as well as simplify the design overall. Adding on bumpers for the safety of the claw is also a thought about improvement. Ideally if we were able to get our system to be rated an IP68 we would be able to go much deeper in the water for longer periods of time without the worry of minor leaks getting into the circuitry. More efficient and powerful motors that are constructed specifically for underwater use would be the ideal scenario. At the moment we are using brushless motors, which are fine for prototyping or small scale designs underwater, but we would want a motor with an IP68 rating, graded for deep underwater usage. Higher quality wires that are able to maintain a perfect 12 Volt supply without dropping over the extended distance would also be a noted improvement.

Our special thanks are also expressed to our major professor, Dr. Tosunoglu for allowing us to work on and complete this project.

8. REFERENCES [1] Bowman, B., Debray, S. K., and Peterson, L. L. Reasoning about naming systems. ACM Trans. Program. Lang. Syst., 15, 5, 795-825, Nov. 1993. [2] Angela Dawson, Martin Rides and Crispin Allen. "Measurement of heat transfer coefficients." Polymeric Materials IAG (Wednesday 12 March 2008): 36. PDF. [3] C Harrold, K Light and S Lisin. "Distribution, Abundance, and Utilization of Drift Macrophytes in a Nearshore Submarine Canyon System." 1993. [4] Christ, Robert D and Sr. Robert L. Wernli. The ROV Manual a User Guide for Remotely Operated Vehicles. Burlington: Elsevier Science, 2013. Print. [5] Electronics, Spark Fun. https://www.sparkfun.com/. n.d. Electronic. 17 Februrary 2015. [6] Engineering Toolbox. http://www.engineeringtoolbox.com/hydrostatic-pressurewater-d_1632.html. 8 April 2015. Document.

Besides all of the potential design improvements we would like to look into developing a micro model of the underwater ROV. We are looking to be able to design a complete simple micro-scale UWROV capable of operating under limited conditions for a short period of time for the purpose of teaching our juniors the joy of mechanics as well as underwater exploration at a low cost and space capacity.

[7] Jutras, Ian. http://blogs.solidworks.com/teacher/2013/01/external-flowsimulation-on-a-sae-car-body.html. 7 January 2013. Article. 8 April 2015

7. ACKNOWLEDGMENTS Our thanks are extended to ACM SIGCHI for allowing us to modify templates they had developed previously.

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