Lessons Learned and Future Steps
The biggest breakthrough occurred in getting the hub motors spinning with the custom controller. One of the most important lessons learned involved a fundamental electrical engineering tenant: power dissipation of a linear voltage regulator versus switching power supply. The initial design used a linear voltage regulator that was consistently being damaged. The power that needed to be dissipated was too large, and the high temperature would then damage the regulator. This caused additional problems because the higher battery voltage would be applied to the motor drivers and damage them as well. Once this setup was replaced with a switching power supply, the controller was significantly more reliable. There were a lot of unknowns that were exposed throughout the duration of this project: sensors needed for SLAM, the importance of suspensions, basic ROS node architectures, static stability, and practical construction techniques.
The final goal of this project was to use to a Wiimote to drive the Rover, thereby testing the movement model and suspension. This was unable to be accomplished because the motor controllers were not robust enough for extended use. Both controllers were damaged when attempting to test the change of direction command. The time and cost to repair the controllers would extend the project outside the allotted time. There are multiple improvements that can be implemented in order improve the construction and reliability of the motor controllers. Continuing to reverse engineer the low-cost Alilbaba controllers will hopefully result in more gained knowledge that can be applied to future versions. The quality of construction of the current Rover could be improved as well. The frame would need to be disassembled and welded with higher quality tooling.
Once the controllers are stable, the plan will be to implement a SLAM algorithm with one or two cameras. The laptop will be replaced with the Nvidia TX1. This will allow Open Rover to map an area that has been digitally fenced off. A simple smartphone app could be used to create the digital boundaries. Providing simple straightforward navigation APIs are a foundational feature of Open Rover. Additional hub motors will need to be acquired as well so that prototypes of the four wheel and six wheel Rovers can be constructed.