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....
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....
I had my first try at visualizing incoming data from the LIDAR last night. Good news is that it worked, and I got a successful SLAM map of the room. That’s pretty awesome. Bad news is I definitely have to redesign the pulley mechanism. Stepper motor is ridiculously loud, heavy and slow. I need to design a smaller pulley system that runs on an encoded DC motor. I used a Python library called BreezySLAM for the SLAM implementation....