SIPI Turtle is Born!
A 3D printable autonomous vehicle designed and built by SIPI
The new and improved Swarmie is a culmination of three years of robotic projects the SIPI research and development team have been involved with. The Swarmathon Swarmies first introduced the team to a small robot with a handful of equipment to make the rover work. The Swarmies were taken apart to see what is needed to build a rover. During the Swarmathon competition, there were problems the team noticed with the Swarmies. Some problems were programming constraints, weight, safety, and construction issues.
While programming the Swarmie, some problems arose with the motor controller (power controller). There was a limited amount of memory in the controller and the power amplifier the controller plugged into was a custom board. The number of connections the board had available was limited and new parts would need to be created to expand the capabilities of the power controller.
The Intel NUC used in the Swarmathon Swarmie was a nice computer, but it uses up to 18 watts of power with a 19.6-volt connection. The NUC can operate from a 12 to 21-volt range, but it requires a large battery to power it. The NUC at the time was expensive because it was a bare bones device meaning memory (RAM), a hard drive, and a wireless adapter needed to be purchased in addition to the computer to make it work. At SIPI, the team began using an updated Intel NUC, but power was an issue. Later, an intern came across the Zotac PI225 micro computer that uses up to 4 watts of power. Also, the computer requires a 5-volt connection and can be powered through a USB port. The processing power is better than the original Intel NUC used in the Swarmathon Swarmies and the smaller part reduced the weight of the rover.
The battery was another challenge because the Swarmathon Swarmies used a heavy custom lithium ion battery. In the SIPI ROV-S project, an external backup laptop battery was used to power an Intel NUC and 12 motors. The battery used in the ROV-S project was lighter, cheaper, and was an off the shelf part that could easily be ordered. But that battery is no longer available causing the SIPI team to rethink what battery requirements are needed for the new SIPI Swarmie. To power the SIPI Swarmie, two 5-volts connections are needed for the Zotac computer and gripper with one 12-volt connection needed to power the Arduino Mega 2560 power controller. So, a much smaller, lighter USB power bank battery was selected and has been tested in the new SIPI Swarmie.
For the new Swarmie, the team wanted the robot to have a unique look and a turtle was decided on. The overall look of the SIPI Swarmie will be a turtle like appearance that will be called the SIPI Turtle. To create the SIPI Turtle appearance, 3D printing will be used to create a unique appearance. With 3D printing, the SIPI Turtle is not restricted to a particular chassis dimension. Due to the smaller parts used to make the SIPI Turtle, 3D printing is needed to build small unique rover.
Finally, the sensors and motors used in the SIPI Turtle are updated parts of what was used in the Swarmathon Swarmies. The end product of the new SIPI Turtle is a smaller, lighter, energy efficient, more versatile, with a unique appearance.
Connecting the gripper, gripper wrist, IMU (Inertial Measurement Unit), 3 sonar sensors, and 4 motors with wheel encoders already used all available expansion slots of the power controller. Since the board is custom, to expand the board would need either a new custom board or to send more data through the limited pins. But, with the memory already reaching full capacity, it would be better to use something off the shelf, rather than custom. The SIPI R&D team began with experimenting with the Arduino Uno and later upgraded to the Arduino Mega 2560 because it provided more memory than the original power controller and has more available connections for sensors and parts expansion.