GPS Robot Navigation Bi-Weekly Report3/28/04 - 4/11/04Chis FoleyKris HornRichard Neil PittmanMichael WillisGPS Robot Navigation Bi-Weekly Report3/28/04 - 4/10/04Goals for Two Week PeriodThe team for this development period has sought to complete most of itsfabrication and prototyping. These include integration of all hardware in the system withsoftware and provide a demo of the system and its algorithms thus far.The team seeks to make up time lost attempting to use the throttle servo whichhas at this point been removed in favor of another solution; using an H-bridge. The teamdesired to have this hardware installed in the system early in the development period tofacilitate continued progress in other areas of the project. After the installation of thenew H-bridges the team will write software to control the output of the DC motor usingthe H-bridge including a proportional-integral-differential feedback controller algorithmto regulate the speed of the robot car to the desired speed of two feet per second.Additionally, the team works towards installation of the navigation hardwareincluding the compass and GPS modules. The team will install these components andbegin writing software to interface them and use them for navigation. The installation ofthe compass will be fairly simple as we have code and resources available to us. The firststep in the GPS integration process will be to establish how the GPS and OOPic willcommunicate and how to retrieve only the desired position information from what theGPS sends on it data lines. Then the team can finish writing the navigation software forthe robot car.Midway into the development period the professor requested a demo of the carsability to steer and ascertain its bearing. The demo that was decided upon was to havethe car begin from arbitrary orientation and it must drive itself and turn in such a way asto reorient itself to a north facing position. This demo is a test and of the integration ofthe steering control/navigation, compass, and speed control.AccomplishmentsIn the first half the development period the team finished modifying the robot carto use the H-bridge speed control interface instead of the steering servo. Due to thecurrent of the system it was necessary to use two H-bridges with heat sinks and two 7.2volt batteries to supply the necessary voltage for them. This has eliminated the pastproblem regarding the fast speed of the wheels at initial start up. Instead, the wheels canthen be set at a much slower speed more easily. After the H-bridges were installed theteam moved ahead with writing new speed control software for the H-bridge interface.The software incorporated a proportional-integral-differential feed back controller usingthe optical encoder for the feedback. The team experimented with the car using thisalgorithm and through trial and error arrived at PID constants that appear to smoothlyregulate the speed of the robot car to the desired two feet per second.The team has successfully interfaced the OOPic with the compass. They havealso determined how to ascertain the orientation of the compass relative to north and willsoon incorporate this into our navigation software. The team has also established aninterface between the OOPic and the GPS module. The team is not yet able to parse outthe desired information from the data provided by the GPS but a break through will comeshortly. Significant progress has been made in the steering/navigation algorithms. Thesimulation software for the navigation code in MATLAB has been completed and workhas begun to port these algorithms to the OOPic to control the car’s actions in order todirect it to its destination. These will also be used in the demo to control the steering toorientate the car north.During this two week period we obtained GPS coordinate data from the TexasA&M golf course. Using a golf cart we traveled around the same portion of the golfcourse six times. We taped the GPS receiver on the back of the golf cart as shown infigure 1. Figure 1 - Golf Cart with GPS unit attachedUsing Microsoft’s Hyperterminal we were able to capture the GPS output and save it to atext file. All that was required was to change a few of the default settings withinHyperterminal and were able to read the ASCII output of the GPS. Since we have a textfile with the GPS data, we were able to use Microsoft Excel to extract the necessary datafrom the text file and plot it onto a graph. Figure 3 is the graph obtained when we plottedGPS antennaLaptopall six of the “rounds” of the golf course data onto the same plot. We were pleased withthe accuracy of the data. From the graph you can see that there is not much variancebetween the different “rounds”. During the third “round” we had to go off course toavoid a parked golf cart. This is why on the lower left portion of the graph, there is avariance from the rest of the paths.3036.93036.9530373037.053037.13037.153037.23037.253037.39619.7 9619.75 9619.8 9619.85 9619.9 9619.95 9620 9620.05 9620.1123456Figure 3 GPS data from TAMU golf courseWe also obtained some GPS data near Kyle field to test how the GPS responded when itwas near a building. The results were not as good as we were hoping. Figure 4 shows thegraph of the GPS coordinates taken near buildings. As you can see from Figure 4 the datanear buildings is not as accurate.Kyle Field3036.593036.5953036.63036.6053036.613036.6153036.623036.6253036.633036.6353036.649620.3 9620.32 9620.34 9620.36 9620.38 9620.4 9620.42 9620.44WestNorthSeries1Series23Series4Figure 4 - GPS data near Kyle FieldProblems FacedThe fundamental problem faced throughout the development period was thefrequent tendency of the OOPic boards to stop programming after a fashion. This hasresulted in significant delays. The team originally thought the problem could have arisendue to the EEPROMs but after discussions with the TA, this has come into doubt. Theteam is able to get a limited ability to program the OOPics a majority of the time. This isenough to make some progress but progress is coming slow.Future GoalsThe team will continue to work towards completion of the requirements for therequested demo. Once the direction finding demo has been completed the team willthrow all it efforts into completing navigation system installation and software the finishthe entire project by the end of the