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I made some solid progress on the v2 design of the rover during last week and finally assembled an initial test version last night. The difference is incredible. Even with no PID implementation, it drives in an almost perfect straight line. I believe the added weight of the motors and bearings help, but the real star are the new encoded motors. I found a couple of cheap 12V brushed motors with magnetic encoders on Amazon and designed a custom chassis around them in Fusion 360. Now that I understand the concepts behind Fusion better, I was able to make very quick progress on the design. I kept it as large as possible, within the limitations of the printer bed. ...

I spent the last few days experimenting with PID algorithms and tuning parameters for straight driving using only motor encoders. There were tons of learnings along the way, and I’ll try to summarize them in this post. First off: After a lot of frustration, I realized that there was something wrong with my motor setup. Whatever I did, there was a huge discrepancy between the two geared motors. They are identical models with the same 48:1 gear boxes. However some simple encoder analysis showed that left motor was going at around 60% the speed of the right one. ...

After implementing the simple straight driving sample for the rover, and integrating the XBee wireless protocol, it was time to test things out. I installed the new gearboxes (they came with motors installed and cables soldered, yay!) and did a test run. However, the first issue I ran into after switching to the battery setup was the OLED screen not starting up. I lost a bit of time on this, because the screen was actually working well when I connected the Arduino to the computer. ...

One of the goals of the self driving rover project has always been to have it controlled by a base “brain” unit that does the actual analysis and motion control. I have a few XBee S1 units I had purchased a long time ago and I wanted to put them to good use for this. XBees are quite versatile but notoriously hard to configure. There are tons of configuration options available and the XCTU software is not the most friendly. ...

I made some OK progress on the driving unit last night. I finally got the T connector for the LiPo battery, so I could hook everything up and power both the Arduino and the motors from a portable source. I was worried about powering them together but it turned out to be simple. I soldered a buck converter (voltage down) between the battery line and the motor shield. Set it up to give out a constant 4.5V, which should be more than enough for the 3V motors I have in there. ...