Friday, May 4, 2012

AVC: Ready for Saturday Demo? Uhh...

I attended my first Robot Party tonight! I probably should have been coding but I needed a little break. It was really fun and I highly recommend it.

Team Daisy Rover, another 2011 AVC veteran, will be joining us on Saturday with a robot! That's a 100% increase in robot fun, folks!

Even better, after sitting on the waiting list for months, Sparkfun just told Ted and Daisy Rover that they are now officially entered into the 2012 AVC! Congratulations!

As for Data Bus, the good news is that the robot sort of works outside my house, albeit slowly and with lagging steering correction. My single test at the demo site went poorly so I'm not too confident about Saturday.

Using the Venus high dynamic range firmware reduced smoothing a bit, but not gps lag. I was able to prototype a basic, time-shifted feedback in Octave. The algorithm compares gps heading to integrated gyro heading from one second prior and then adjusts the current heading and gyro bias by a fraction of that error.

Here's a plot of the result for one of the autonomous runs. The shifted/corrected gyro heading is in red, the smoother GPS heading in green. Blue is the current gyro heading.

I ran the algorithm using data collected from a couple of autonomous runs, generated position estimates by combining heading and distance traveled, then displayed in Google Earth. The light red and light blue paths are based on raw gps heading. The dark red and blue paths are based on corrected gyro heading.


Truth be told, these plots don't look too bad. I implemented the algorithm as carefully as I could on the robot, but the real world tests were a miserable failure. Data Bus even crashed and rolled on the second run, plotted below. Yay.

The GPS path is in light blue and is fairly close to the real path taken (can you see where the robot went up on the curb and crashed?) The dark blue line is the path based on corrected gyro heading. This is the path Data Bus thought it was following. Data Bus was off by quite a distance! Stupid robot.

I  have some ideas as to what happened, but I don't think I can get this working reliably before Saturday. I'll most likely revert the code changes and run the Bus slowly with waypoints carefully selected to accommodate the lag.

Wish me luck. I need a lot more than I've been having lately.

But, enough doom and gloom. Tomorrow is going to be a Cinco-de-Mayo Robot blast of a good time and I'll post the video to prove it! Stay tuned...

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