Maiden Voyage = Epic Fail 04/02/2009Posted by aliasmrjones in The Build.
In the last post, we finished all the initial programming and It’s time for the maiden voyage of Deathpod3000! The first test drive of the car was less than perfect…Ok, it sucked big time. There are two videos showing all the fun.
Here is a little video of me showing the parts:
And here’s a vid of the first drive, which mostly features driving around in circles:
The main problem seems to be that the cpu only gets updates from the gps about once every 2 seconds and it is getting current heading data from the gps.
As the car turns, the gps computes heading based on where it was at the last fix and where it is at the current fix. Unfortunately, while it’s turning, it is pointing way past this direction so it constantly overshoots where it is trying to turn. This coupled with the fact that it only gets updates to its heading (as bad as that heading data may be) every 2 seconds means it can’t figure out where it is heading and spins around in a circle until it decides to spin around in a circle the other directions.
If the car is pointing where it should be going, it does drive straight. So, it is computing where it wants to go correctly. The problem is with the current sensor array, it can’t accurately point the car in the desired direction.
The good news is it looks like the basic programming and navigation software work. So, it looks like we need to upgrade our sensor array. I ordered a new gps that updates 5(!) times per second and a digital compass. Hopefully more frequent updates from the gps will help. More importantly, though, the digital compass should allow the cpu to get heading readings in real time so it can track to the desired heading accuratly.
The compass uses i2c, a synchronous serial interface and the gps is 3.3v, which will require a level converter. In the next post, we’ll hook up the new hardware.