NameDescriptionWhile Loading/UnloadingTotalTotal2. Design ConstraintsThe goal of this project is to design and implement an autonomous robot to compete in the 2006SECon hardware competition. The rules provided by the competition dictate a variety ofrestrictions and necessary capabilities of the robot. Complying with these constraints will give therobot an optimal chance of completing the task successfully each round.2.1 Technical Design ConstraintsThere are several constraints for the robot design that were developed from the SEConcompetition rules and other technical requirements of the robot. These technical designconstraints are listed below in Table 2.1.Table 2.1 – Technical Design ConstraintsName DescriptionDimensions The robot must be able to store all twelve packages along with its internal mechanisms within a starting size of 7.75” x 7.75” x 11.875.”Navigation The robot must efficiently navigate the board.Speed The robot must travel at a minimum speed of 1.1 inches per second.Package Identification and ManipulationThe robot must be able to correctly identify and transport each of the 12 packages to their corresponding destination. Weight The robot must weigh less than 20 lbs with all packages on board.Power The robot needs a power system capable of supplying 30W of power during a 5-minute time interval.2.1.1 DimensionsCompliance with mandated size requirements will be verified at the competition by placing ahollow box over the robot. Because the box may be slightly warped and the robot may bedamaged if the box scrapes against its side, a buffer zone of 1/8” will be left around all outersurfaces. This reduces the starting size requirements to 7.75” wide by 7.75” long by 11.875”high.While SECon rules allow the robot to expand to 14” wide by 14” long by 20” high, the designwill not employ any expansion past the starting size requirements except that required by themechanism to retrieve packages from the vertical chute [1]. Eliminating extra expansion reducesoverall complexity and saves time that would be needed for initial unfolding and retraction at theend of the round when the robot must return to its starting size. 2.1.2 NavigationDetermining an efficient and effective route to traverse the playing field is a vital design issue.During the competition, the robot will be required to leave the starting square and travel to fourpreset destinations to accomplish the given task. To be competitive, the robot will need to travelthe shortest and quickest routes possible. To accomplish this, the robot must have an accuratenavigation system which places the robot within a quarter inch of its desired position. The robotwill also use sensors to verify its position throughout the competition and detect obstacles as nearas half an inch away and as far as two feet away. These measures ensure that the robot avoidscollisions with objects on the playing field and positions itself effectively for the loading andunloading of packages.2.1.3 SpeedThe speed the robot can travel at is as important, if not more so, than the route the robot takes.The robot must travel a total distance of 5.5 feet as it drives from the starting square to thepackage chute and then from the package chute to the first plane. Designating a maximum of twominutes (10 seconds per package) for loading and sorting leaves only 60 seconds for the robot totravel this distance if it is to stay within the 3-minute time restriction for the first delivery. Inorder to go 5.5 feet in 60 seconds, the robot must travel at an average speed of 1.1 inches persecond.2.1.4 Package Identification and ManipulationThe robot must be able to correctly identify each package by scanning a Codabar-formattedbarcode. After scanning, each package will be stored in one of three partitions on the robot.Storing all packages on the robot before delivery will decrease the time required to complete thetask since only one trip will be made to deliver all packages to each plane.After loading all 12 packages, the robot must travel to each of the three planes and deposit thecorresponding packages before the plane leaves. The average speed of 1.1 inches per secondderived in Section 2.1.3 is sufficient to carry out this task as long as the loading process lasts amaximum of 10 seconds per package.2.1.5 WeightThere is no weight requirement stipulated by the SECon competition rules; however, the weightof the robot has important repercussions for other design elements. A heavier robot will requirelarger stepper motors with higher torque ratings for locomotion. More powerful motors will alsodraw more current and require more batteries, which take up more space on the robot and addadditional weight themselves. To avoid adding large, heavy components to compensate forweight, the robot is designed to weigh no more than 20 lbs when fully loaded. This weight limitallows moderately sized (2” x 2” x 2”) stepper motors to propel the robot at the speeds discussedin Section 2.1.3.2.1.6 PowerThe robot will operate many stepper motors and servos to achieve the motions needed to loadpackages, maneuver around the playing field, and unload packages. The robot power source mustbe able to supply all these motors in addition to the onboard barcode scanner, sensors,microcontroller, and other control circuitry that will be required to carry out the task. All ofthese devices can be run with a 5V supply, but a supply voltage of 6V will produce betterperformance for some stepper motors and servos. Because of this, the robot power supply will berequired to provide both 5V and 6V.The power consumption of the robot will be set at a maximum of 30W. This allows sensors,locomotion stepper motors, and microcontroller circuitry to run continuously at the same timewhile the robot is driving around the playing field. The 30W allowance can also be distributed torun a barcode scanner, a microcontroller, and several servos or linear motion stepper motors,which would all be needed while loading and unloading packages. The maximum power allottedto each type of device during both phases of operation is broken down in Table 2.2.Table 2.2 – Maximum Power AllotmentsDevice Voltage While Driving While Loading/UnloadingCurrent Draw Power Current Draw PowerStepper Motors (Wheels)6V 3.5A 21W - -Barcode Scanner
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