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CA4,- Z37 CONCEPTUAL DESIGN OF A REMOTELY OPERATED VEHICLE r FOR BEACH SURVEYING William R. Dally Florida Institute of Technology Oceanography and Ocean Engineering 150 West University Boulevard Melbourne, Florida 32901 and Robert G. Dean University of Florida Coastal and Oceanographic Engineering Department 336 Well Hall Gainesville, Florida 32611 Flnal-Rgport Submitted to: Florida Department of Natural Resources Division of Beaches and Shores 3900 Commonwealth Boulevard Tallahassee, Florida 32399 In Fulfillment of Contract No. C-5758 "Funds for this project were provided by the Department of Environmental Regulation, Office of Coastal Management using funds made available through the National Oceanic and Atmospheric Administration under the Coastal Zone Management Act of 1972, as amended." D EXECUTIVE SUMMARY This project addresses the conceptual design of new technology for conducting topographic surveys in the coastal zone. The central component of the system is a remotely operated, semi -autonomous, amphibious vehicle that is specifically designed for use in the surf zone, Work included 1) a literature search for existing technology, 2) conducting a workshop attended by experts in surf zone surveying and potential users of the system, 3) extensive telephone and written contact with experts in the fields of coastal engineering, surveying, all-terrain vehicles, power systems, ocean systems design, guidance of marine vehicles, and robotics, 4) development of a set of design and operation requirements the new surveying technology, 5) development of the conceptual design for the ROV system, 6) a literature search of model studies and methods for predicting loads induced by breaking waves, 7) preliminary design calculations for power requirements and vehicle stability, and 8) a preliminary cost estimate. 1Z 2 BACKGROUND The Need for Date The ability to effectively manage the coastal zone is for the most part determined by the quality of the tools available to aid in the decision making process. Efforts to improve our basic knowledge of the land-sea Interface and to develop better tools with which to apply this knowledge, are continually hampered by a lack of viable and cost-effective means of conducting routine operations in the high wave energy environment of the surf zone. These operations include 1) site investigation for recreational, biological, and sometimes even historic resources, 2) bottom topographic surveying, 3) dredging and other methods of earthmoving, 4) rubble mound, concrete and pile construction, and 5) structure inspection. Of these, topographic surveying is the most fundamentally important, as survey data of high accuracy and resolution is essential to many other activities. A fundamental component of coastal zone management is the ability to model and predict the effects of hurricanes and other high energy events on the beach. Development, calibration, and verification of these models requires accurate, high resolution surveys conducted repeatedly before, during, and after major storms. However, due to limitations imposed by operating conditions, mobilization time, and the costs of present beach surveying technology, efforts to collect these short-term data sets have been frustrated. Many important coastal management programs and engineering projects also require the support of high quality data collected over large areas for extended periods of time. In the State of Florida, such programs include 1) the Coastal Construction Control Line Program, 2) an ambitious beach restoration and renourishment program, and 3) the processing of permit applications for coastal construction and dredging. This data is needed to document cumulative effects of storms, beach recovery, and cyclical and long-term trends (especially those associated with sea level rise), To address these needs, the Florida Department of Natural Resources, Division of Beaches and Shores operates the most comprehensive large-scale beach monitoring effort in the nation. The need for more survey data is ever-expanding however, and so there is a continuing effort to seek technology that Improves cost efficiency and accuracy. Eresent Technology Common practice in beach surveying utilizes standard land survey techniques landward of wading depth. Seaward of this point, three methods have typically been used: 11 a boat equipped with a recording fathometer and mini-ranging system Is brought in as close to the beach as safely possible, 2) the prism cluster for an electronic "total station" surveying device is attached to the mast of a sea sled, which is then towed along the bottom in the surf zone using a boat or amphibious landing craft (LARC), and 3) a shuttle that vertically tracks the beam of a shore-mounted laser level is carried by a LARC, measurements from which are added to those from a fathometer. Because they employ boats or other floating plat-forms to traverse the surf zone, all of these methods are restricted in use to times when the wave climate 3 is relatively benign, generally the breaker height must be less than I m. This survey window is quite restrictive for many coastlines. They also require a large support crew, and incur substantial mobil ization/demobil izatlon costs. In addition the first method, which is the most common of the three, often results in a gap in the transect over the most active region of the beach profile. This method is subject to fathometer errors induced by the boat's movement in the waves and changes in water temperature, and also requires estimates of the tide stage (Clausner, Birkemeier, and Clark, 1986). Survey closure is also a problem if the onshore and offshore portions of the survey often are not conducted concurrently. A limited number of specialized vehicles have been developed for operation in the surf zone under more energetic conditions, and Include one built by the Great Lakes Dredge and Dock Company and another by the U.S. Army Coastal Engineering Research Center (CERC). These vehicles are large tetrahedrons, nominally 10 m high, which ride on three hydraulically driven' wheels. An engine, hydraulic pump, reservoir, controls, and instrument prisms are carried on top of the vehicle and remain above the sea surface. An onboard operator is required however, and because of the limits imposed by vehicle stability they are confined to operations in breaker heights less than 2 m. Even so, unexpected encounters with soft mud and holes have caused them to tip over during routine operations. These vehicles do provide the means to collect survey data that is at the state- of-the-art in resolution and accuracy, and have proven themselves to be extremely cost-effective when compared to the standard methods described above. Birkemeier and Mason (1984) report that CERC's Coastal Research Amphibious Buggy (CRAB) cut the cost of a single bathymetric survey of 26 profile lines from $35,000 down to $2,000, mostly due to personnel and time reductions. Clausner, et al. (1986) intercompared the performance of the CRAB, sled, and boat/fathometer systems, along with an experimental "hydrostatic profiler" described in Seymore, Higgins, and Bothman (1978). Figure I shows the results of repeated surveys of the same profile with the CRAB and with a digital fathometer system. Note the large variability in the fathometer data. As indicated by their findings, although vehicles like 'he CRAB are a major step beyond the other systems in terms of the wave climate in which they can operate, these large self-propelled vehicles are not widely used due to 1) large initial expense, 2) large mobilization costs, 3) the still somewhat restrictive survey window imposed by operator safety in large waves, and 4) their inability to recognize and negotiate soft mud, steep slopes, and obstructions. The CRAB would cost an estimated $150,000 to build at present day, and because it weighs 18,000 lbs. and cannot be dismantled, It cannot be moved from the Field Research Facility (FRF) in Duck, North Carolina in a cost-effective manner. Storm conditions are often beyond the safe operating window, and some nearshore regions contain natural or man-made obstructions, or soils too soft to operate effectively with these vehicles. 4 @.7 30 "XI" YOTICAL DlrrVWMM U 6. Z' 1.0 10. V, Lai 0.5 > M 0- 0 LLJ CRAO VAYCY -30 0 5;0 1060 1300 2000 2.500 3000 DISTANCE, FT a) Envelope of six digital fathometer surveys. 30 2.2 mAxiwuw YERTim Dimon= 7 2.0 2t - 1.8 LO M --77- 0.0 0 LJ -j LLJ -20- -30 T 5;0 1000 1500 2.@00 2500 3000 DISTANCE, FT b) Envelope of five CRAB surveys. MAO FIGURE I Comparison of repeated survey results using a) boat/fathometer and b) CRAB systems. (Figures from Clausner, et. al, 1986) 7 7 OBJECTIVES AND METHODS The overall goal of any surf zone surveying system is to perform fast, accurate, high resolution surveys cheaply and efficiently. The system must also be easily transported, and must operate In a wide variety of wave, weather, and bottom conditions. Given the inability of boats and other surface craft to effectively conduct routine operations in breaking waves, and the cost, mobilization, safety, and mobility problems of the large CRAB type vehicles, it appears that a more viable and cost effective methodology is required in order to fulfill data requirements. The objectives of this research effort were therefore to: A) Identify a basic approach/system that would significantly Improve beach surveying technology. B) Establish a specific set of design requirements for the system, C) Develop a conceptual design that satisfies these requirements. D) Devise a research and development plan that will validate the design. To gather the background information needed to achieve the above objectives, a literature search was first conducted to identify existing beach surveying capabilities; plus, a workshop was held at the Field Research Facility to tap the vast experience of FRF and Corps district personnel and to seek their opinions and recommendations. During the course of this project, input was sought from approximately 30 manufacturers, private consultants, and state and federal agencies that have expertise in surveying technology, coastal engineering, and ocean engineering systems, A list of those contacted Is provided in Appendix A. These experts provided 'Insight on data needs, available technology, costs of system, components, and cost restrictions and feasibility of the proposed system. APPROACH In the original proposal it was envisioned that the beach survey vehicle would be similar to the CRAB in concept, but with the added capability to dismantle it for transport to any site. However, one of the conclusions of the workshop and personnel at FDNR was that such a system still could not overcome problems with beach access, submerged obstructions and soft bottom, and the inherent danger of operating a manned vehicle in the surf zone. It was therfore necessary to identify a more viable approach. In the past few decades, the development of remotely operated vehicles (ROVs) has greatly expanded man's abilities to explore and function in a broad variety of harsh environments. Of particular note Is the extensive use of ROVs in the offshore oil and sea-floor nineral industries, where they have played a major role in increased productivity. ROVs and mobile robots have been developed to operate In the vacuum of outer space, under lethal, levels of heat and radiation, and in environments contaminated by toxic chemicals and hazardous micro-organisms. In short, the whole purpose of an ROV is to remove the human operator from a dangerous environment. Because the surf zone is arguably the 6 most difficult and dangerous marine environment in which to operate with conventional equipment, the consensus of expert opinion is that the concept of a ROV is particularly appropriate to this problem. Also, because the need for an onboard operator is removed, the ROV can be much smaller than a CRAB type vehicle, thereby avoiding problems with beach access and mobility. The approach using a ROV is adopted accordingly, and so design requirements can now be established. SYSTEM REQUIREMENTS A review of the literature on existing beach surveying technology, the input from those on the contact list, and the past beach surveying experience of the PIs and the attendees of the workshop, was used -to determine the characteristics and requirements of the proposed ROV system. This experience encompasses all existing nearshore surveying hardware and techniques, both conventional and unconventional. Eleven primary requirements were established: 1) AccunAcy and high rRsol-iLtIQn are needed to maintain the value and reliability of the survey data. The positioning hardware/methodology should be accurate, both vertically and horizontally, over long distances. Consequently the frequency at which the gear must be set up and taken down is reduced, thereby reducing costs. The ability to perform data analysis and plotting on site is also desired, which will enable important topographic features to be identified immediately and complete coverage of the study area ensured. 2) Increand sucygy sr)egg is required to reduce manpower costs@ thereby allowing more detail in surveys and expansion of monitoring programs. The vehicle should have a maximum speed of approximately 2.2 mls (5 mph), and the surveying hardware/methodology employed must minimize the time required to take an individual measurement. 3) The ROV must be able to operate in 2 m brgaking wayes and out to water denthA of-10 These conditions match those of the CRAB and are necessary for expanding the survey window, and to reach depth of closure for sand transport. 4) A system for hazar@ reugnition 4nd_a_yoidUre is required to protect the survey operation from costly down-time due to entanglements and damage to the vehicle. The ROV operator should be assisted by systems that enable him to recognize holes, reefs, debris, etc., and maneuver over or around them. 5) In the event the vehicle breaks down or does become entangled, a system for jelf rescue is needed. Without outside assistance, the operators should be able to first activate a rescue system that lifts the vehicle from the bottom, and then retrieve it to the beach to make repairs. 6) Continuous -operati.0 for at least four hours Is needed to conduct uninterrupted surveys and maintain efficiency. 7) Mobi]izajionZdempbjljzatign must be a top priority during design if the technology is to be am improvement over the CRAB or sled systems, and for it to receive widespread use. The vehicle must be easily transported between Job sites using conventional means, and quickly set up for operation. 7 IF Bgach _Ac"ss Is a major factor in vehicle design because most beaches are b ocked by buildings, dunes, or vegetation. The ROV system must be able to utilize narrow walkways and dune crossovers, which are the only common and reliable means of access. 9) In order to minimize costs, no more than thteg gersgnnel are required to transport, operate and support the system. 10) -LQw fAbn1catiort colt is of course desired; in general less than $50,000 for the vehicle alone. This guideline was established by potential users in private industry and district personnel of the Corps of Engineers. 11) The detign- Mst_ be_simplc, and the vehicle fabricate-d frgm _commercially available coMponentk. This will facilitate repairs, and allow the ROV to adapt to different surveying and research needs. CONCEPTUAL DESIGN To address the major system requirements listed above, the following conceptual design is proposed. Figure 2 is a CAD drawing of the remotely operated vehicle in its basic form. Its major features consist of 1) an aluminum frame which rides on two tracks and a caster type wheel, 2) a watertight housing, and 3) a snorkel, The rationale used in reaching this basic design, and the iterative procedure used to determine design loads and vehicle size is presented in Appendix 8. Supporting calculations for motion-induced drag forces and breaking wave induced forces are provided in Appendix C and Appendix D, respectively. These calculations indicate that for the immersed weight of the vehicle (approx. 1500 lbs), the frame should be approximately 5 m wide. The two front arms have pin joints at each end so that they can be drawn together to reduce the width of the vehicle to only 1.2 m. This feature will allow the ROV to climb a straight stairwell or travel a footpath. Tracks were chosen to provide propulsion because of their low contact pressure and proven mobility over a wide '@'arlety of terrains (Karafiath and Nowatzki, 1978). Unlike water-filled tires, tracks do not add unwanted buoyancy when the vehicle is submerged, nor do they add weight when on land, Each track is driven by a hydraulic motor, with steerage provided by a difference In their relative speeds. The free-spinning caster allows the vehicle to turn almost within its own length. Although a third track would aid in propulsion, this option was discarded because a complicated actuator and control system would be required to synchronize it with the other tracks. The aluminum housing contains a diesel engine, hydraulic pump, fuel and hydraulic fluid tanks, computer controlled valves, and UHF transmitter/receiver. The housing is 0-ring sealed, and designed so that its cover can be quickly removed for repairs and maintenance. A larger diameter section is necessary for the engine (0.75 m diam.) while to minimize buoyancy, a narrow section (0.25 m diam) will contain the remainder of the equipment. The structural members of the frame are to be aluminum I-beam, with 4 in. web and 4 in. flange to support the dry weight of the vehicle. Tubular sections were not. chosen because corrosion and cracks on inside surfaces are hidden from visual inspection. If necessary, cylindrical cowlings can be retrofitted to the 8 UIF ANTEMA EXHAUST INTAKE NOMINAL DIMENSIONS MAST HO-GH7i 12 PRISM ARRAY OVERALL LENGTtt 6 m VLDT" 1.2 m Legs Votded 1iUY WIRES 5.0 m Operattorml CLEARANCE* 0.7 n C-RING JUIPIT MAST/SN13RKEL ENGME RMSING ELECTRONICS PIN JUINT CASTER WHUL CiD w CAMERA/SlINAR SURF ZONE RON, TRACKS----- Flgurr 2o CONCEPTUAL DRAWING 12/8/99 _J]Dr-own Ryo Mi I-beams to reduce drag. Aluminum is chosen to reduce corrosion in salt water, and to allow simple welding fabrication. The use of structural composites was considered, but rejected due to the likelihood of galvanic coupling, and high costs. Initial power calculations based on drag on the vehicle at the design speed in deep water, presented in Appendix C, indicate a 20 to 30 hp. engine is required. The engine is to be water-cooled using an external heat exchanger. When extended operations in the dry are required, the engine is air-cooled by removing the housing cover. Concentric snorkels provide separate intake and exhaust, and serve as a positioning rod for a prism cluster and mast for the radio antenna. The intake also vents the housing, while the exhaust snorkel Is connected directly to the exhaust manifold. When being transported to a site or maneuvered across a dune, the mast is disconnected at'an O-ring joint. The hydraulic system consists of pump, reservoir, manifold, valves, motors, and high pressure hydraulic line. The engine is attached to a variable displacement pump capable of 30 gal/min. A REXROTH axial piston swashplate pump Is the preferred model. Two disc valve hydraulic motors (CHARLIN 6000 series) are used to drive the tracks. Due to their high torque, a gear box will not be required. The motors are controlled by a manifold port box (DAMAN) and two independent solenoid valves that vary both flow rate and direction (REXROTH "Hydronorma" model). This design for the hydraulic system will provide smooth turning and speed control, as well as allowin the vehicle to back up. The system requires 2000 psi hydraulic hose, and wI?l have fluid filtration systems at both the intake to the manifold and the intake to the reservoir. Guidance for the vehicle is provided by directional sonar and a low light level video camera. Signals are transmitted back to shore by the same onboard UHF system used to control the hydraulic valves. Both video and acoustic signals are displayed on a CRT so the operator has a real time video and acoustic image ahead of the vehicle. Experts indicate that there has been little experience with this type of equipment in the surf zone, and due to air bubbles and turbidity it is unclear how well these guidance systems will perform. It is expected that significant testing and development will be required for this component of the ROV system. To conduct topographic surveys and aid in guidance, a self-tracking total station laser device is used to follow the prism array from shore and report its coordinates to a computer. This device is the key to increased survey speed and resolution. During the workshop at the FRF one such device was demonstrated in use with the CRAB. Previously it was necessary to stop for a minimum of fifteen seconds for the instrument to take each shot; but, with the self-tracking feature position was monitored continuously, and recorded once per second. The time required to cover one survey line was reduced by 40%, and was limited only by the maximum speed of the CRAB (2.5 mph). The number of data points recorded was increased from approximately 60 to over 250. With a self-tracking system, vehicle position can also be continually updated and plotted in a window on the operator's screen. A tilt cube and electronic compass are also mounted on the vehicle, output from which are telemetered to correct the survey data in real time. This information will also provide the operator with the attitude and orientation of the vehicle, and help identify potentially hazardous situations. 10 P. In the case of vehicle breakdown or entanglement, a system of inflatable salvage bags is carried by the ROV. An actuator mounted on the mast allows a swimmer or rescue boat to start the inflation sequence. After raising the vehicle off the bottom, the ROV Is towed back to shore by an inflatable boat. It is then pulled from the water by a truck or winch, and repairs made. The ROV will most likely be transported to the job site on a small flatbed trailer (2 m x 6 m). The trailer is drawn by a four wheel drive truck or carryall, which also houses the data acquisition and communications equipment, and the operator. To set up the system, the ROV is driven right off the trailer and maneuvered over a stairway or other suitable beach access. The legs are then spread to their operational configuration, and the snorkel raised and guyed, The surveying device Is set up on the dune and attended by a second crew member if necessary. The trailer also carries the inflatable rescue boat, while the truck is available to tow the ROV ashore if a breakdown occurs. A summary of the conceptual design is provided In Table 1. TABLE I - DESIGN FEATURES OF REMOTELY OPERATED VEHICLE -- _ FOR BEACH SURYEYING-- CONFIGURATION - Bottom crawling tripod (5 m x 6 m) WEIGHT Dry: 2,150 K9 (2,500 lbs) Immersed: 680 Kg (1@500 lbs) POWER Diesel engine (20-30 hp), snorkel intake and exhaust, water cooled DRIVE TRAIN Hydraulic PROPULSION Tracks (2) CONTROL - Computer-controlled solenoid valves COMMUNICATION/TELEMETRY - UHF GUIDANCE - Video, forward looking sonar NAVIGATION/POSITION - Land based total station equipped with self-tracking laser ORIENTATION - Electronic compass, tilt cube RESCUE - Self-contained lift bag system TRANSPORT - Pickup truck and trailer COST ESTIMATE The conceptual design of the ROV has been conducted in detail sufficient to make the cost estimate for equipment listed in Table 2. All components are commercially aval I able except the caster whee I, housing, mast/snorkel , and frame. Fabrication requires welding and some machining, and should require roughly 120 man-hours. TAQLF 2 - COST ESTIMA7F FOR EQUIPMENT Engine 3,000 Pump 1,000 Reservoir 300 Hydraulic Hose 400 Fittin S $00 Contro? Valves 2,500 Hydraulic motors (2) 2,000 Tracks (2) 4,000 Caster Wheel 500 Housing 2,500 Mast/snorkel 11000 Frame 3,000 Control Computer 4;000 UHF Communications 2,000 Tilt cube 2,500 Digital compass 1,000 Trailer 2,000 Recovery system Boo Miscellaneous LILO Total for vehicle equipment alone S 34,000 Data aquisition and plotting hardware 6,000 Sonar 20,000 Video camera 5,000 Generator 400 FWD truck 28,000 Geodimeter surveying system with tracking laser 8Q'OO0 Total for peripheral equipment 139,400 12 7 :77 FURTHER DEVELOPMENT AND VALIDATION OF THE DESIGN Initial feedback from several users of conventional surveying systems, and experts in all-terrain vehicles and marine ROVs, Indicates that the basic design of the ROV is a sound one. Tracked vehicle technology is well established, and diesel engines have been successfully operated underwater with snorkels since the turn of the century. UHF communication and control is also commonplace. Although drag on the ROV due to Its own motion can be reliably calculated, the major question that remains open is vehicle stability in the surf zone in big waves. The results of a literature review made it clear that due to Its complex shape, forces and moments Induced on the vehicle due to breaking waves cannot be predicted reliably with the present state-of-the-art. As discussed in Appendix B, even model studies of simple small-scale vertical cylinders cannot provide valid estimates of breaking wave forces at full scale. It is therefore recommended that a full-sized mock-up of the vehicle be fabricated, in which the hydraulic system Is run by an electric motor that is powered by an umbilical from the beach. Thus the diesel engine, control, orientation, and communications systems can be left out, The mock-up can then be deployed during as many storm events as. possible, without risk to most of the expensive equipment. Such a testing program would firmly establish the allowable operating conditions of the vehicle. The mock-up can also be used to conduct mobility and beach access tests. As mentioned previously, off-the-shelf sonar and video guidance systems may not function satisfactorily in the surf zone, and will require development and testing. Fortunately in conducting these experiments, the mock-up would serve as a unique mobile test bed with which to gain access to the surf zone. SUMMARY AND CONCLUSIONS Based on requirements for high quality nearshore survey data, and the recommendations of experts in the fields of coastal engineering, surveying, all- terrain vehicles, ocean systems design, guidance of marine vehicles, and robotics, the conceptual design of a system for nearshore topographic surveying has been presented, The central component of the system is a remotely operated, semi -autonomous, amphibious vehicle that is specifically designed for use in the surf zone. The system is easily transported, requires minimal support personnel, and has relatively low fabrication and maintenance costs. It is also readily adapted for use with a variety of existing land surveying hardware. If this technology were developed, beach surveys could be conducted faster, during higher wave conditions, at greater accuracy, and with higher resolution than with conventional technology. Cost savings of at least 75v/0 are expected. Aside from surveying, the ROV has great potential for use in conducting a number of other routine operations. These uses include deployment of various instruments, inspection tasks, and even robotic construction. It is possible that the proposed ROV system will eventually serve as a "workhorse" for the nearshore zone. 13 REFERENCES/81BLIOGRAPHY Alpelt, C.J. and Piorewicz, J. , 1987, "Laboratory Studies of Breaking Wave Forces Acting on Vertical Cylinders in Shallow Water," Coast-EngiL., Vol.11, pp-263- 282, Birkemeier, W.A. and Mason, C., 1984, "The CRAB: a UniQue Nearshore Surveying Vehicle," ASCE Journ. Sury. Eng., Vol.110, No.1, pp.1-7. Clausner, J.E,j Birkemeier, W.A., and Clark, G.R., 1986, "Field Comparison of Four Nearshore Survey Systems," USACE CERC Misc. Pap. CERC-86-6. Goda, Y., Harnaka, S. and Kitahata, M., 1966, "Study of Impulsive Breaking Wave Forces on Piles, Port Harb. Res. Inst., Minist, Trans., Yokosuka, Japan, Vol.5, Rep.6. Hallj M.A.@ 1958, "Laboratory Study of Breaking Wave Forces on Piles," Beach Erosion Board Tech. Memo., No.106. Hawkes, G. and Earle, S., 1987, "Deep Flight: A New Approach to Autonomous Underwater Search and Survey Vehicles," Unmaored Syltems, Spring 1987, pp.33- 36. Herr, W.J., 2968, "AUV Technology Development and Demonstration Program," Prkr, Qceang_'_8a Conf., pp.1290-1299. Honda, T. and Mitsuyasu, H., 1974, "Experimental Study of Breaking Wave Force on a Vertical Circular Cylinder," Coa:t. Enq.-Jnan, Vol.17, pp.59-70. Karafiath, L.C. and NowatzkI, E., 1978, @oil -Mechanics of Off Road Vehicle Enineering, 7rans Tech Publications, Ist ed. KJeldsen, S.P. and Akre, A.B., 1985, "Summary of Experiments Performed with Wave Forces on a Vertical Pile Near the Free Surface," MARINTEK, Rept. No. 1.16, Trondheim, Norway. Kolessar, M.A. and Reynolds, J.L., 1966, "The Sears Sea Sled for Surveying in the Surf Zone," U.S. Army f.orps Engin., CERC Bull. 2, pp.47-53. McFarlane, J.R., Jackson, E., Hartley, P.. 1987, "Robotic Marine Vehicles for Surveying," UnmAnned__Syqems, Spring, 1987', pp.17-23, Michel, D., 1987, "An Introduction to Selected Commercial Underwater ROV's," Unmanned Jystems, Spring 1987, pp.13-16. Reddish, H.O. and Basco, D.R., 1987, "Breaking Wave Force Distribution on a Slender Pile," pZoc, Conf. CoAst, Hydrodynam., ASCE, pp.184-195. Ross, C.W.@ 1955, "Laboratory Study of Shock Pressure of Breaking Waves," Beach Erosion Board Tech. Memo., No.59. Sallenger, A.H., Howard, P.C., Fletcher, C.H., and Howd, P.A., 1983, "A System for Measuring Bottom Profile, Waves and Currents In the High-Energy Nearshore Environment," Marine Vol.51, pp.63-76. 14 Dec 19 '89 10:54 FLA. Sawaragi, T. and Nochino, M., 1984, "Impact Forces of Nearly Beaking Waves on a Vertical Cylinder, Coast. Eng. Japan, Vol. 27, pp. 249-263. Seymore, R. J., Higgins, A.L., and Bothman, D.P., 1978, "Tracked Vehicle for Continuous Nearshore Profiles," Proc. 16th Conf. Coast. Eng., Vol. 2, pp. 1542- 1554. Shore Protection manual, 1984, U.S. Army Coastal Engineering Research Center, Vicksburg, Miss., 39180. Swift, R.H., 1989, "Prediction of Breaking Wave Forces on Vertical Cylingers," Coast, Eng., Vol. 13, pp. 97-116. 15 APPENDIX A CONTACT LIST @ompanyagency Exj)ertia Adcour Battery Technology 18 Billings St. Sharon, MA 02067 (sales engineer) (203) 777-8673 Alupower, Inc. Battery Technology 6 Claremont Rd. Barnardsville, NJ 07924 J.F. Davis (201) 766-7750 C.A. Richards and Associates Sonar and Video Equipment One Elridge Pl. Houston, TX 77079 Charles Richards (713) 531-74117 Center for Intelligent Machines Control Systems, Robotics, and Robotics and Artificial Intelligence Mechanical Engineering University of Florida Gainesville, FL 32611 Joseph Duffy (904) 392-0814 Circuit Engineering Hydraulic Power and Motion $421 Atlantic Blvd. Control Jacksonville, FL 32211 Chris Stankiewicz (904) 721-1414 Coast Machinery All-Terrain, Tracked Vehicles 10012 Umbehagen Lane Baton Rouge, LA 70817 John Coast (504) 293-1323 Coastal Planning and Engineering Nearshore Surveying (Boat and 3200 North Federal Highway, #123 Fathometer Systems), Coastal Boca Raton, FL 33431 Engineering Consulting Thomas Campbell (407) 391-8102 Coastal Technology Corporation Coastal Engineering Consulting $00 20th Place, Suite 6 Vero Beach, FL 32960 Michael Walther (407) 562-8580 16 0 : T Field Research Facility, U.S. Arny Nearshore Surveying (CRAB, Coastal Engineering Research Center LARC, Sled, Boat/Fathometer SR Box 271 Systems), Surf Zone Operations Kitty Hawk, NC 27949 William A. Birkemeler (919) 261-3511 Florida Department of Natural Resources Nearshore Surveying (Boat and Division of Beaches and Shores Fathometer System) 3900 Commonwealth Blvd. Tallahassee, FL 32399 Kirby Green, Hal Bean (904) 487-4471 Franklin Electric Submersible Electric Motors 402 East Spring St. Bluffton, IN 46714 Vaghn Hoffactor (219) 824-2900 Gahagan and Bryant, Inc. Nearshore Surveying (LARC and Grady Bryant (813) 831-4408 Laser Level System) Geodetic Enterprises, Inc, Land Surveying Hardware, Self 1401 North Mound Rd. Tracking Laser Systems Nacogdoches, TX 75961 Fred Tucker (409) 564-4035 Great Lakes Dredge and Dock Company Nearshore Surveying (CRAB type 9432 Baymeadows Road, #150 Amphibious Vehicles) Jacksonville, FL 32256 Richard Myers (904) 737-2739 Hughes Aircraft Company Robotics and Artificial Loc. CL, Bld. 150@ MS A600 Intelligence 23901 Calabasas Rd. Calabasas, CA 91302 John Harris (818) 702-5279 Intelligent inspection Systems Underwater Video, Sonar and P.O. Box 32128 Guidance Systems Palm Beach Gardens, FL 33420 Donald Darling (407) 863-1030 MDL, Inc. Trim Cube, Digital Compass, 21211 Richmond Ave. Laser Tracking Systems Suite 106 Houston, TX 77082 Ian Padgham (713) 556-7745 17 Mesotech Systems Sonar Systems 2830 Hunigton Pl. Port Coquitlam B.C. Canada V3C 4T3 Marshall Ancoin (604) 464-8144 Mobility Research Command, U.S. Army Mobility of All-Terrain Waterways Experiment Station Vehicles P.O. Box 631 Vicksburg, MS 39180-0631 New York District, U.S. Army Corps Nearshore Survey Data Needs of Engineers 26 Federal Plaza New York, NY 10278 Raymond V. Elmore Richard Kiss (212) 264-0180 North American Hydraulic's Hydraulic Motors 9951 Mammoth Ave. Baton Rouge, LA 70814 John Neswadi (504) 927-8094 Offshore and Coastal Technologies, Inc. Nearshore Surveying (Sled 510 Spencer Rd System) Avondale, PA i9311 William Grosskopf (215) 268-0410 Olsen Associates, Inc. Survey Data Needs, Coastal 4438 Herschel St. Engineering Consulting Jacksonville, FL 32210 Erik Olsen (904) 387-6114 Perry Oceanographic Underwater Vehicles 275 West 10th St. Riviera Beach, FL 33040 Steve Mesuzik (407) 842-5261 Seacon / Brantner and Assoc., Inc. Underwater Cable and 1240 Vernon Way Connectors El Cajon, CA 92020 Chuck Richards (619) 562-7070 Sea Engineering Survey Data Needs, Ocean Robert Rocheleau (802) 259-7966 Engineering Consulting Star Power Services Diesel Engines S217 River Rd. Harahan, LA 70123 Dan Richards (504) 733-6897 Structural Composites Laboratory Marine Applications of Florida Institute of Technology Structural Composite Materials 250 W. University Blvd. Melbourne, FL 32901 Scott Lewitt (407) 768-8000 ex.6842 Suma Corporation Diesel Engines 2085 Castle Rd. Woodstock, IL 60098 Ted Jerominsky (815) 338-6705 19 -77 APPENDIX 8 - DESIGN PROCEDURE In order to provide a stable platform for accurate measurements, and to assure continuity across the land-sea boundary, it was decided that the ROV would be a bottom-crawling device. Next, options for power for the vehicle were Identified and explored. Supplying power via an umbilical was not viable because of the desire to facilitate large operating distances, and the likelihood of entanglements; see Seymore, et al.(1978) and Clausner, et al.(1986). With It established that the vehicle must carry its own power plant, options for batteries, gasoline engines, diesel engines, and even the more esoteric Sterling engine and aluminum fuel cells were identified and investigated. From discussion with battery manufacturers and designers of propeller-driven ROVs (which require low torque and high rpm), it was determined that because propulsion for all-terrain vehicles requires high torque and low rpm (Karafiath and Nowatzki, 1978), batteries could not meet power requirements. A gasoline engine has an associated risk of fire or explosion, while Sterling engine and fuel cell technology are not yet established as reliable, cheap, and "off-the-shelf", Because power must therefore be supplied by a diesel engine, the need for a snorkel was established. Unfortunately, this exposes the vehicle to increased drag force and overturning moment, especially under conditions at the maximum design speed and depth. Such a surface-piercing staff Is unavoidable in the design anyway, due to telemetry and positioning requirements. At this point in the design process, It was necessary to estimate the loads the vehicle would experience during operation, Two types of loads are important: 1) the drag on the vehicle induced by its own motion through the water, and 2) the overturning force induced by the impact of breaking waves. Analytical methods for calculating drag forces due to unidirectional flow around idealized shapes are well established, and were followed during design (see Appendix Q. To estimate forces on the vehicle induced by breaking waves, it was originally thought that small-scale model tests conducted in a wave flume would provide some insight. However, a literature review of experimental studies of forces induced by breaking waves on vertical cylinders (see References/BiDliography) Indicated that due to scale effects, the results of testing with a small scale model of the ROV would have little meaning in regards to the stability of the prototype at full scale. As described by Apelt and Piorewicz (1987), this is because at small scale the requirement for Reynolds Numbers in the supercritical range cannot be met. In fact they recommend in their conclusions, "It is very desirable that experimental studies be carried out on breaking wave forces on full-size cylinders in real seas.'I This is the reason it is recommended that stability tests be conducted in the surf zone with a full scale mock-up of the ROV. With the idea of inferring breaking wave impact forces from a model test eliminated, a literature review was performed to learn from available studies conducted at full scale, and to determine the state-of-the-art in methods for predicting these forces. Ross (1955), Hall (1958), and Kjeldsen and Akre (1985) presents results from tests of forces on vertical cylinders performed at full scale in large wave tanks, while the Shore Protection Manual (1984) and Swift (2989) present methods for calculating them. Although certainly the state-of-the-art in detail and sophistication, the method of Swift (1989) was found to be too computationally intensive for use in this conceptual study. However, the method recommended in the Shore Protection Manual (1984) was 20 DD: found to be more suitable to the needs of this project, and is calibrated to the large scale results of Ross (1955) and Hall (1958). This method is followed in Appendix D to calculate breakIng wave loads on the vehicle, and these results In turn used to determine Ne required lengths for the legs. The iterative procedure followed to estimate the required size and weight of the vehicle is as follows; 1) Assume a diameter for the snorkel, diameter for the engine housing, and frontal area for the frame and tracks. 2) Calculate the drag force on the snorkel, housing, frame and tracks at a speed of 2.2 m/s in a water depth of 10 m (Appendix C). 3) Calculate required horsepower (Appendix C). 4) Choose an appropriate diesel engine, check Its dimensions to make sure it will fit within the assumed housing size, and that the assumed snorkel diameter will provide sufficient intake and exhaust. 5) Iterate steps 1-4. 6) Calculate the overturning moment due to impact of a 2 m breaking wave (Appendix D). 7) Estimate the approximate immersed weight of vehicle (Appendix 0). 8) Determine splay required for immersed weight to resist overturning. Add ballast if necessary to reduce splay to manageable size (Appendix D). 9) Iterate steps 6-8. 10) Determine track length from dry weight and desired soil contact pressure. 11) Size structural members to carry dry weight of vehicle. 12) Check weight of structural members. The design proceeded from the assumption of a snorkel diameter of 6 in. This was found to provide plenty of intake and exhaust, and did not have to be altered during subsequent Iterations. The final iteration of the design loads are provided In Appendices C and D. 21 Dec 18 '89 10:58 FLA. APPENDIX C- DRAG AND POWER CALCULATIONS Drag Calculations The drag force on an object moving at a constant velocity through a still fluid (or conversely unidirectional flow aroung a stationary object) is given by the expression: F- 1/2 p c a u(2) where F- drag force (Newtons) e- mass density of seawater (1030 kilograms/cubic meter) c(d)- drag coefficient (dimensionless) A- projected area of object (square meters) U- velocity of object (meters/second) Drag on Mast Mast area is 0.15 m (6 in.) x 9.1 m (30 ft.) = 1.37 m(2) Reynolds number for flow field= (2.2)x(0.15)/(9.3x10(-7)) therefore C(d)-1 (cylinder) F(m)- 1/2 (1030)(1)(1.37)(2.2)2 Drag on Engine Housing Housing diameter Is 0.762 m (30 in.) Housing area is ir (0.762)'/4 - 0.456 m' Reynolds number for flow field - (2.2)x(O.762)/(9.3x1O'7) - 1.8xio, therefore CD m 0.5 (sphere) FN W 1/2 (1030)(0.5)(0.456)(2'.2)' FN 0 558 N Drag on Tracks Track area Is 0.356 m (14 in.) high x 0.61 m (2 ft.) wide 0.22 m2 Reynolds number for flow field - (2,2)x(O.61)/(9.3x1 0,7) = 1.2410' therefore C. 1.2 (rectangular flat plate; h/w-0-57) FT 1/2 (1030)(0.22)(1.2)(2.2 )2 FT 658 N x 2 tracks - 1316 N Total Drag Force FDtot FM + Ff + FH + FT FDtot 6818 N Powgr Reouiremcnts Power - Force x Velocity 6818 x 2.2 - 15,000 Nm/s 1 horsepower 745 N4qm/s Required power - 20.1 hp Mechanical and hydraulic losses are in the range of 45 to 46044, therefore approximate total power required to run the vehicle is 820.01 X 41.45 - 4340 8hp 23 APPENDIX D - CALCULATION OF FORCES AND OVERTURNING MOMENT DUE TO BREAKING WAVE IMPACT These calculations on based on the "worst case" scenario of a 2 m breaking wave striking the vehicle broadside. A reasonable estimate of the depth at which breaking takes place is the wave height, i.e. h - 2 m. Following the Shore Protection Manual, the force per unit length on a vertical cylinder due to the impact of a wave at incipient breaking is given by the expression: f im - 0.88 g D Hb where f is the impact force per unit length, D is the cylinder diameter, g is gravitational acceleration, and Hb is the breaking wave height. For the design conditions we find: fim = 0.88 (1030)(9.8)(0.15)(2.0) fim = 2665 N/m Fim = f x 2.0 m - 5330 N Because the engine and electronics housings are below the mean water level during this scenario, they are only subjected to the drag force induced by the water particle motion associated with the wave. From shallow water linear wave theory (see S.P.M.) this velocity is given by U =(H/2)x(g/hb)1/2 U = 2.2 m/s (coincidentally equal to the design speed) Engine Housing The length of the engine housing is required to be approximately 0.89 m (35 in.) to fit a 30 hp engine. Projected area of housing is therefore 0.76 x 0.89 - 0.677 m2. Fih = 1/2 (1030)(1)(0.677)(4.9) Fih = 1708 N Electronics Housing The diameter and length of the electronics housing are required to be approximately 0.2 m (8 in.) and 1.0 m (40 in.) respectively. Projected area is therefore 0.2 x 1.0 - 0.21 m2. F eh = 1/2 (1030)(1)(0.21)(4.9) F eh = 530 N 24 Overturning Moment The base of the vehicle housings is to be 1.0 m above the bottom, which dictates that the appropriate moment arms for this calculation are: LM = 3.0 m Llh =1.0 + 0.38 =1.38 m Lah = 1.0 + 0.1 1.1 m The sum of the moments is M = (5330)(3.0) + (1708)(1.38) + (530)(1.1) M = 18,930 Nm Vehicle Splay Estimating the immersed vehicle weight, including ballast, as approximately 6,672 N (1,500 lbs), the required splay for one leg of the vehicle is (overturning moment / immersed weight) - (1/2 track width) (18930 /6672) - 0.305 - 2.5 m Therefore the total vehicle splay is 5 m. Calculations of the buoyancy of the vehicle housings indicates a buoyant force of 4,400 (1000 lbs). Therefore the dry weight of the vehicle and ballast is approximately 11,100 N (2,500 lbs). 4 1 ' - NOAA COASTAL SERVICES CTR LIBRARY 1111, lll@l 3 6668 14111404 3