GPS Robot Navigation Bi-Weekly Report2/07/04 - 2/21/04Chris FoleyKris HornRichard Neil PittmanMichael WillisGPS Robot Navigation Bi-Weekly Report2/07/04 - 2/21/04Goals for Two Week PeriodFor the first week, the team set out to complete their research and make thenecessary purchase orders. The two major purchases to be made for this work period arethe Garmin 15L GPS receiver, and the Traxxas Stampede RC electric truck. The teamdesired to have these components available as soon as possible to allow for greaterprogress in the overall project.The second week, in the case that the ordered GPS and RC truck arrive by thistime, were to have the RC truck moving at a controlled two feet per second and to surveypossible navigation test sights for noise using the GPS receiver. In order to makecollision avoidance and navigation simpler, the team has decided on a speed ofapproximately 2 feet per second. This is to allow the robot to detect obstacles in time toavoid them rather moving to fast to register the obstacle before colliding. One of themajor obstacles in creating a functioning navigation system is finding a way to getreliable readings about the robot’s current position. Interference from buildings andvegetation can create noise that will reduce the reliability of the GPS readings. At thispoint in the project the team seeks a test location that has a minimal amount ofinterference in order to prove the team’s concept for the robot before attempting tocorrect for the noise in other environments.AccomplishmentsOver the course of this work period the team has been able to accomplish most ofits goals in addition to some additional progress. The team double checked its research ofpotential components to reassure themselves that the settled upon components wereappropriate for the project. The team then completed the purchase orders for thesecomponents and turned them in by the end of the week.The RC truck arrived the following Tuesday, February 17, 2004, and the team setout the day after to assess its capabilities and to plan how to go about reverse engineeringthe controls of the servos to control throttle and steering. After some experimentationwith controlling servos via the OOPic, the team managed to determine what positions onthe servo correspond to the lowest speed available on the truck, stop and neutral. Usingthis knowledge the team was able to write programs commanding the truck to go, coast,and stop.During this period, the team also learned how to interface sonar devices with theOOPic in order to determine the distance to an obstacle. This is an important part of ourcollision avoidance capability. Since the throttle control and sonar were working, theteam desired to take the next logical step and put them together. The OOPic, RC truck,and sonar were wired together and a new program was written. The program told thetruck to move forward unless it detected an obstacle. If an obstacle was detected, thetruck would stop and wait and then check again. If the obstacle is no longer there it willattempt to move forward again otherwise it will sit idle waiting for the obstacle to move.Problems FacedAt the time of this report, the team had received notification that the GPS hadarrived but not in time for the team to pick it up and begin testing locations on campus fornoise to decide on a future test site. The team plans to acquire the GPS as soon aspossible the following week and begin these surveys of possible test sites.A problem that has arisen is that lowest speed supported by the truck is very fastwhen running on the tile floors of the H.R. Bright building, but is quite slow whenrunning on the grass outdoors. Since the final test of the robot truck will be outdoors on agrass surface the team feels this not something to be concerned with yet. Possiblesolutions to this problem may be to reduce the voltage given to the motor by the servotransmission system with additional resistance. However this might remove powernecessary to move on grassy surfaces where friction is greater. The idea of an acceleratorto help in speed regulation has been discussed.Future GoalsSince the GPS has arrived, the surveying of possible test sites for noiseinterference becomes a priority for the team. The team has already pre-selected severalsites as potentially suitable for team’s proof of concept. These possible sites include thepolo fields, the golf course, and Research Park. These sites will be tested by the teamusing the GPS received that will later become part of the robot truck.Now that the team has control of the RC truck’s throttle and has some collisionavoidance built in, the team desires to reverse engineer the cars steering, making itpossible to then control the truck completely from the board. This milestone will markthe end of the reverse engineering aspect of this project.Once complete control of the has been established, the team can devote time toadding sensors such as additional sonar and the compass and writing software to controlthe car. More attention can also be given to interfacing the GPS module that has arrivedwith the OOPic and writing the navigation
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