Older blog entries for Nic (starting at number 145)

April 30th, 2005

Today is Saturday. Our site visit is on Tuesday. I've been working non-stop on getting basic waypoint-following down, but it just won't work. I can't get rid of the weaving. The problem is that it doesn't ever know exactly which direction it's pointing. It's all a matter of heading. An artical from Circuit Cellar at http://www.circuitcellar.com/library/print/0404/Miller165/3. htm describes the problem:

"A single-antenna GPS can provide heading information, but it is not instantaneous. It inherently lags the movement of the robot or vehicle because the derived heading requires previous position data. A GPS could not tell you where you are heading if you were to stop and change directions. Like compasses, GPS receivers do not require external reference heading calibration. Once moving, the GPS heading update rate is a maximum of approximately 1 Hz, although some receivers add damping, which increases this time constant even more. A dual-antenna GPS receiver can provide instantaneous heading‧'or yaw‧'information, although the recommended distance between the two antennas is 1 m. This fact, along with its large price tag, can be a limiting factor for many mobile robot applications."

Because of this I have been using dead reckoning unless the Expeditor has been going straight for a few seconds, but it's still not that good. Today I bought a $400 GPS with a built in compass and switched it out, but the compass always thought the computer's harddrives were north. I raised it up on a PVC pipe a few feet, and it gave a good heading, but IT STILL LAGGED. It was better though. A little. It still works at speeds about 2 MPH but not higher. I did a lot of other work today also. I have a lot more work to do in the next two days.

April 27th, 2005

I took the robot out to the site visit field before school, and then remembered that the pull start was broken so I couldn't start the engine. I pushed it down the first waypoint-segment. It had the same weaving behavior as ever. This is extremely frustrating.

UPDATE: I went to Home Depot and got a ratchet socket to open the pull start cover, opened it, took it apart, fixed the spring, and put a new rope on it. Now it works.

April 26th, 2005

This week (except Friday) I start school two hours late, so I've been working in the morning on the robot. Today the pull start rope on the engine ripped and went into the engine. One more thing to do before the site visit... There's one week left.

At about 9 PM I went out to test the robot on the street, but the steering by remote control wouldn't work. After an hour I had fixed the problem. A wire had randomly broken in a connector. This is getting very frustrating.

25 Apr 2005 (updated 13 Aug 2009 at 18:48 UTC) »

April 24th, 2005

This morning I fixed the battery wiring, but accidentally melted a 5V regulator. Afterwards I got some orange buckets at Home Depot to use to mark the waypoints on the site visit route as well as two 32 gallon garbage cans and some free wood for lateral boundary markers. The garbage cans being green, I also bought some white spray paint in case the neural networks can't detect the green garbage cans in the green field.

At the field I marked the lateral boundaries of almost the whole course, and tested the waypoint following some more to observe the robot's behavior. I also recorded data while driving the course, avoiding the waypoint markers and garbage cans on the route.

Once home I modified the software in yet another attempt to perfect the waypoint following.

There are pictures at http://www.craterfish.org/teamprodigies

April 23rd, 2005

The waypoint following only works while driving at speeds under 3 MPH. The GPS position seems to lag behind a certain number of seconds, which makes sense assuming it's averaging many GPS positions every second - if it's moving forwards, of course the average of the locations will be somewhere behind it. The higher the speed goes the crazier it's driving gets, until at speeds above about 6 MPH it just seems random.

I obtained permission to use a new field and sent an email to DARPA about the site visit location change. At the field I used the GPS to mark a route, and then had the Expeditor drive it. I encountered the problem above, until the battery fell off the robot and ripped some wires. Heh.

April 22nd, 2005

I tested it and it finally works. Now I have to perfect the garbage can avoidance.

April 21st, 2005

Tested several new things and discovered and fixed several bugs. Still some problems.

April 20th, 2005

I didn't go to baseball practice after school because I wasn't feeling very good, so I had some daylight left when I got home to test the robot. Using a neural network trained on a couple minutes of data recorded from the robot it was able to successfully turn and avoid a garbage can in the street.

There were still some problems with position finding, however. I made some changes to the code and found a few bugs. I'll test next time I get the chance.

April 18th, 2005

I got the new OOPic chip in the mail and it works. That's a bit odd that the other one unexplainably stopped working. It isn't a good thing when parts of your autonomous ground vehicle stop working for no apparent reason.

April 16th, 2005

I took the Expeditor out to the site visit location again to try to test it. It started out sunny, but the field was almost completely under water. It doesn't seem very likely it will be dry by the site visit. After that our minivan got stuck in the mud until a helpful guy in a pick-up truck came and pulled it out. It started raining very hard soon afterwards. I still haven't waterproofed X. I need Chris to help with that but he's sick with Mono.

Before the site visit (within the next two weeks) I need to

-Waterproof the Expeditor -Find a new site visit location -Make a new route and mark it -Teach obstacle avoidance

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