Embedded System

Real time processing on Bumblebee was achieved with the use of the Arduino Mega development board based on the ATMega 2560 microcontroller from AVR. The Embedded System was primarily used for sensing and actuation. A timer interrupt driven kernel was designed to handle the many sensitive timing requirements of the various sensors and actuators on board the AUV.

embedded

Internal Sensors

To monitor the internal status of the hull, the system was outfitted with an array of temperature sensors to detect overheating conditions of the electronics rack and also an array of water leak sensors lined at the bottom of the hull to detect for water leaks.

Pressure Sensor

The US300 Gauge Pressure Sensor from Measurement Specialities was used for depth measurement of the vehicle. Current loop sensing was used for signal acquisition and was coupled with a discrete low pass filter to clean up noise in the signal for stable readings from the sensor.

Actuators

The  six thrusters on the system are controlled by Polulu Motor Controllers which generate the PWM signal required for brushed DC motor control. These motor controllers were daisy chained together on a single serial bus to accept speed commands from the Arduino. This reduced the number of I/O required and simplified the wiring implementation. To reduce the amount of time taken for a single update of the motor speeds over all six motor controller, increased due to serialisation, the serial baud transfer rates were set to the maximum setting of 115200 bps.

The pneumatic manipulators are actuated from a total of seven Single Pole Single Throw(SPST) relays. Each individual relay controls one of the seven pneumatic actuators responsible for the actuation.

LCD Display

The vehicle has a 16 x 2 OLED LCD Display to provide feedback of the vehicle status for the diver or on the fly monitoring of the system. The LCD screen displays the current power levels of the four batteries, the temperature of the internal hull and also the presence of any water leaks.

schematic