Shadow Incorporated. Design Review #1 February 1, Mark Backman Ben Collins Jesus Gonzalez Suma Tumuluri Vinita Venkatesh

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1 February 1, 2005 Mark Backman Ben Collins Jesus Gonzalez Suma Tumuluri Vinita Venkatesh

2 Introduction: Shadow Incorporated Shadow Incorporated has created a product concept to help open water swimmers around the world. Within the span of one semester, this team hopes to create a working prototype model that can be accurately tested and used as a foundation for further design. The creation, an autonomous boat that follows a swimmer in open water, can later be modified and enhanced in several ways. In terms of marketability, this product seems to be quite useful and highly desirable. Currently, open water swimmers must either tie a buoy to their bodies while swimming under water, or hire a boatman to stay within a certain specified range of the swimmer to notify boats of his or her presence under water. The main criterion of Shadow Inc. s product is to be able to follow a swimmer wearing a tracking device, while maintaining stability and holding up a regulation sized flag. Additions that can later be added once this model is working include a GPS system to mark the exact location of the swimmer, and a radio system to notify nearby boats via special signal. These ideas can be worked onto the system following preliminary testing and operation. Following rigorous patent searches, Shadow Inc. has not found any products that mimic the design of this product, or any existing products for autonomously following a swimmer. Based on this search, Shadow Inc. is highly confident that this product is marketable and desirable. Product Conception: Boat & Hull Design: The boat will be prototyped before any final design is settled on. The boat s size and shape are constrained primarily by the size and weight of the electrical components that it must carry, in essence, the battery, microcomputer, dc motors, resistors, and op-amps. The boat must also be capable of withstanding the weight and drag forces placed on it by the regulation flag that it will bear. Thus, stability and maneuverability are the two main focuses when considering the hull design. Stability is the more vital of the two. A catamaran offers optimum stability. The boat will be equipped with two propellers attached to two separate dc motors. Having the two propellers, as opposed to just one with a rudder, eliminates the need for a stepper motor, and simplifies the controls quite significantly. With two motors, both motors can simply be turned on when the target is directly in front of the boat, and then the speeds of each motor can be varied when the boat needs to be turned in any particular direction. Signal Processing: The swimmer, or target, will carry a transmitter that will send out an ultrasonic pulse every x number of seconds. Those signals will, in turn be received by two sensors on opposite sides of the boat. The difference in time of flight, or the difference in the time it took the pulse to get to each signal, will dictate where and how the boat should turn, or which motor to turn on or off.

3 The pulse will be generated with a chip that will produce two signals. One signal will be just a pulse, and the other will be a square wave with a 40 khz frequency. When put through an AND gate, the result with be a 40 khz pulse. When that pulse gets to the boat, the microcomputer will process the difference in time of the signals and steer the boat accordingly. A third sensor will manage orientation and distance from the swimmer. Specifications: The specifications for the current design idea give a clearer image of the details involved in the designs of both the boat hull and the electronics. Currently, our prototype appears to take the shape of a catamaran with a crossbar where each hull is 29 inches long and 18 inches wide as its maximum. This appears to be a typical size for model boats and a sufficient size for the electronics that must sit atop it. One hull will house the electronics will the other will house the battery. Most likely, all contents of the hulls will be coated in a waterproof material as a precaution for splashing. Each hull will have a oneinch propeller at the back which will be controlled to increase or decrease in speed by the electronics as described above. The propellers will sit at ninety degrees from one another with the fan facing more towards the midline of the boat. Three sensors will be located on the boat body, two attached to rods perpendicular to the front of the hulls so they are completely submerged in water, ready to receive ping signals for the sensor on the human being and one closer to the back to control the distance between the boat and the human. The sensor on the human hip will be a piezoelectric transmitter, most likely the National Semiconductor LM555 Timer Semiconducter. A motor with a range from 1.5V to 3V ( will be the source of power for this water vehicle. Balsawood will be used for the body of the prototype while Styrofoam will be used for the ribbing. Ideally, the final version will be made of fiberglass. Risk Analysis: In designing an autonomous boat there are several risks and problems that are foreseen in the design. All of these problems must be dealt with, though some will be less important than others in the development of a prototype. Safety risks are crucial to marketability of the product, so they will be kept in mind, but will not be the focus in this phase of design. Other foreseeable problems are more urgent with our prototype and relate directly to functionality.

4 Safety Risks: 1. What if the boat runs over the swimmer? Shadow Incorporated a. If there is a collision between the boat and the swimmer, and the propeller hits the swimmer it could result in a cut to the skin. b. The prototype will have an overriding remote control unit, so that a person on land will have the ability to override the autonomous control, and steer the boat away from the swimmer. c. In a marketable design it may be important to include a safety feature which turns off the boat automatically when an object is within a certain range. 2. What if a swimmer is in distress, and wishes to use the boat for floatation? a. The prototype will most likely not be able to support a swimmer in distress, but a final product may have space for an inflatable tube, or other form of life saving device. b. For the prototype a label that reads Is not a lifesaving device. will be included in order to cover liability. Functionality Problems: 1. Will the boat be able to turn quickly enough to demonstrate in a pool? a. The longer the boat, the harder it will be to turn. b. Since two propellers which will aim away from each other at 90 will be used together the boat will go straight, but by varying the speed of one from another the boat will be able to turn. c. For demonstration purposes, pools other than the Columbia University pool, which will restrict the distance the boat will be able to follow the swimmer, will be considered. Leiman College has a pool which is over 2 meters deep and 25 meters by 50 meters. This facility will make the final demonstration& test more accurate. 2. How can disturbance be reduced for the sensors? a. Surface disturbance, as well as the pool walls and bottom will create noise that will make it hard to follow the signal on the swimmer. b. The prototype model will have a ping from the swimmer using a chip from National Semiconductor that is designed to create a pulse at an accurate time delay. Pinging from the swimmer will take out the need for reading reflections, and increase the chance of the boat hearing the correct signal.

5 3. How will the distance to the swimmer be controlled? Shadow Incorporated a. If the boat is turning with one motor on and the other off, it may slow down too much to keep up with the swimmer. b. There will be three sensors on the boat. Two will be attached to a processor which will increase or decrease voltage to just one motor depending on the direction of the boat (steering). The third sensor will be attached to a second circuit which will judge only the distance to the swimmer and add a voltage to both engines equally in order to increase or decrease the overall speed of the boat. 4. What if there are multiple swimmers using a Shadow Boat? a. The expected range of the sensors is 10 meters or less. Swimmers will have to be aware of others using the same system. Patent & Literature Searches: While searching the US Patent and Trademark Office s website, there were similar patents to Shadow Inc. s autonomous boat concept, but none that ran completely independent of a preplanned route or unmanned control system. Patents were found for Autonomous swimming cargo containers, a System and method for automatically controlling a path of a travel of a vehicle, and a Method and system for guiding vehicles. These were the most relevant finds that relate to Shadow Inc. s autonomous boat project. The Autonomous swimming cargo container allowed containers to approach a dock or shore by means of a preplanned or remote controlled path. This benefits the industry because it allows for a tighter schedule of delivery with a more specific order or arrival. It functions through a detachable propeller system, steering controller, engine controller, and processor and program for positioning. More specifically, the containers make use of at least one of the group of a satellite navigation unit, an inertial navigation unit, a directional beacon receiver, a radar, a sonar, and a processor and instructions operably responsive to at least one of position information and propulsion commands (Clarke and Teppig). All of these possibilities cut down on the risk of an accident, and help to allow for the best means of controlling the cargo container. This amount of backup controlling will not be possible on our smaller sized boat. In the patent for the System and method for automatically controlling a path of travel of a vehicle project, the system allows for planes, trains, buses, or boats to be controlled automatically via a preplanned path. It is necessary for the vehicle to be manned during technical navigation, such as take-

6 off and landing for an airplane. This system functions entirely on a preplanned route programmed into a processor. Including a remote control safety feature to make sure the boat does not run into the swimmer or leave the swimmer will help with this. A similar system was the Method and system for guiding a vehicle project. In this project, a guidance system is installed on a boat, which gives the vehicle a means to detect its surrounding environment, then realize where its obstacles are, and output a set of instructions for an instructor to operate. This project uses a sonar device in detecting surrounding objects along with a laser range finder, vision system, radar system, and a GPS circuit (Lacey and MacNamara). The overall goal is to navigate objects in a smaller, confined area by means of outputting a specified listing of the obstacles in the environment and instructions to be performed by a person. This idea uses a similar concept to the autonomous boat, but neglects sending the instructions to a processor to interpret and navigate the vehicle. Upon completing this patent search, it is encouraging to know that sensor systems exist to transmit and receive signals at or near the surface of the water, but also leaves Shadow Inc. with a question of how to control the boat at a completely autonomous level since none of the searched patents have employed this method. Information Sources: Girard, Anouck. Personal Interview. Spring Hull Design 101. Heritage Canoes. 31 January < RC Boat Modeling Hobby-Lobby International, Inc. 31 January 2005 < Stolfi, Fred R. Personal Interview. Spring Taylor, Captain L.G. The Principles of Ship Stability. 52 Darnley Street : Brown, Son & Ferguson, Ltd., Nautical Publishers, U. S. Patent and Trademark Office Home Page. 28 January US Patent and Trademark Office. 31 January 2005 < What makes the tunnel hull work? BoatDesign.Net. 31 January < Aeromarine Research Home Page. 28 January May Aeromarine Research. 31 January 2005 <

7 Brown, Eric D., Cameron, Douglas C., Krothapalli, Krish R., Klein, Walter von JR, and Williams, Todd M. System and method for automatically controlling a path of travel of a vehicle. US Patent and Trademark Office. Filed: Feb. 19, Serial Number: Serial Code: 10. Clarke, Robert A., and Teppig, William M. JR. Autonomous swimming cargo containers. US Patent and Trademark Office. Filed: May 18, Serial Number: Serial Code: 10. Lacey, Gerard, and MacNamara, Shane. Method and system for guiding a vehicle. US Patent and Trademark Office. Filed: September 15, Serial Number: Serial Code: 10. Future Sources include: Hans Henrik, Boat Builder in Miami, Florida Dive Shops in Florida Additional Hobby Shops

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