JIT's electrical infrastructure provides power distribution, safety control, onboard computing, vehicle control, and network communication for the vehicle's various systems. The current configuration combines a fail-safe emergency-stop circuit with regulated power conversion, a Blue Robotics Navigator flight controller, two Raspberry Pi computers, and an onboard Ethernet network to support both low-level vehicle control and higher-level autonomy.
JIT's E-stop circuit uses a fail-safe architecture to remove power from the motors in the event of a system failure or emergency. The circuit uses two relays: a physical safety relay controlled by the external E-stop switch and a software relay controlled through a Raspberry Pi GPIO line. The software relay controls power to the larger physical relay, allowing both hardware and software systems to independently remove power from the motors.
Both relays are nominally open, meaning that power must be actively supplied to close the circuit and enable the motors. If power is lost or an error occurs, the relays return to their nominally open state, removing power from the motors. The E-stop circuit also provides a feedback signal to the Raspberry Pi, allowing the software to detect whether the physical E-stop has been activated and update the indicator panel accordingly.
JIT uses a Tobsun 15A 5V step-down converter to provide regulated 5V power to both Raspberry Pi computers, three cooling fans, and the LED indicator panel. The converter is intentionally oversized relative to the expected current draw to provide additional electrical margin and accommodate potential changes in performance caused by temperature variations.
JIT uses the Blue Robotics Navigator flight controller as the primary low-level control computer for vehicle operation. The Navigator runs ArduPilot's ArduSub software and is responsible for processing and fusing localization information from sensors including the DVL, IMU, and GPS to support the vehicle's autonomy and locomotion objectives. The flight controller also generates commands for the vehicle's motors and executes the control loops required for locomotion.
JIT uses two Raspberry Pi 4B computers to divide configuration, sensor management, autonomy, and perception tasks across separate computing environments.
One Raspberry Pi runs BlueOS and serves as the primary configuration interface for the Navigator flight controller. It also provides a routing interface for sensors and systems such as the barometer, DVL, and GPS. The second Raspberry Pi runs Ubuntu 22.04 with ROS 2 Humble and is dedicated to higher-level autonomy and perception processing. This computer also interfaces with the vehicle's indicator panel and E-stop system through its GPIO pins, allowing software to monitor and control these systems.
IT uses a Blue Robotics unmanaged 5-port Ethernet switch to provide network communication between onboard computers, sensors, and other connected components. The switch provides the necessary network connections for the vehicle's current systems while leaving additional ports available for future components as JIT's electrical and sensing systems develop.
The EV200HAANA relay serves as the primary high-power safety relay within JIT's E-stop circuit. It controls the power path to the vehicle's motors and is designed to open the circuit when the E-stop system is activated or when the control power required to maintain the relay state is lost. This behavior supports the fail-safe operation of the vehicle's motor power system.
