Projects
Seagull
The team’s 1st prototype, Seagull was designed and fabricated with the primary intent of testing all of the electronics, control and vision based navigation algorithms. It served as a proof of concept for the catamaran design which consists of two hulls joined at the helm with the help of a super structure. The material used for the fabrication of the hulls included a space frame structure using aluminium struts and high density polyurethane foam. The high density polyurethane foam provides positive buoyancy to the boat while the aluminium frame provides it structural stability. The Battery pack consisted of two high discharge lithium polymer batteries which provided ample power for long term operation.
The propulsion was provided by using two thrusters manufactured in house using off the shelf components like DC motors, PVC tubes, propellers, silicon sealant and quick drying adhesive. The coupler between the motor and propeller was custom made on a CNC machine using nylon material. The payload on the prototype comprised of a camera and digital compass to provide sensory data for the autonomous functioning of the boat. The video stream captured using the camera was used for blob detection and distance measurement between the buoys in order to localise itself to the aid the navigation process. The digital compass was used to provide a fixed heading to achieve a smoother and more reliable navigation algorithm.
The complete operation of Seagull enabled the team to understand the fundamentals required to effectively design control and vision based algorithms, while also giving insights on the optimisation of the hull structure.
Lakshya
Using data obtained from the testing of Lakshya, the team researched on different hull configurations and fabrication techniques and this resulted in the design of a trimaran hull. The design was made keeping in consideration manufacturing constraints and the level of craftsmanship available and thus made completely of planes yet optimized for low drag. Seagull SR was made with marine grade plywood of 6mm thickness, cut and bonded together with a special quick drying adhesive. The outer layer of the ASV was waterproofed with wood polish and the joints with Silicon Sealant.
The propulsion system comprised of two BlueRobotics T-200 thrusters attached to the hull directly on the planar surface. The payload on the prototype comprised of a camera and digital compass to provide sensory data and a GPS device on board was used for Waypoint Navigation. The video stream captured using a Microsoft LifeCam Studio camera was used to aid the process of fine navigation along with the digital compass to obtain a Vision based Fine Navigation algorithm to effectively manoeuvre between all the obstacles in its path. The ASV was also capable of being remotely switched from Autonomous Mode to Manual Mode using a FlySky FS-TH9X 2.4 GHz Radio Transmitter/Receiver enabling User Control over the ASV.
Lakshya served as a proof of concept for a trimaran hull design and brought to notice the need for better streamlining and precision manufacturing techniques. Further testing also brought to the forefront the benefits of a modular electronics design over the conventional electronics layout. It also laid down the path for a more robust vision system and highlighted the necessity of sufficient processing power.
Trishul
The third and the final iteration of the ASV was designed with an emphasis placed on drag reduction. The availability of better manufacturing techniques and a higher budget allocation to the mechanical domain enabled the hull to be designed with emphasis on streamlining. The hull was made with fiberglass by hand-laying over a mold crafted using foam board. The data gathered previously using the second prototype enabled efficient exploitation of the trimaran configuration. Thruster and cable penetrator mounts were included in the hull to ensure rigidity and ease of fixing. Other fixtures include handles for ease of transportation and harness points for deployment. The superstructure of Trishul includes three sensors – GPS, camera and Li-Dar. These three sensors are mounted on a single sensor pod to free up space for other payload on the deck.
Electronics in Trishul were fabricated keeping in mind a modular design. Each module is fixed on its mount with the ability to be quickly detached for troubleshooting or replacement. The purpose of every mount is to provide stability, a rigid support as well as power to the corresponding boards. All PCBs were fabricated and optimized for minimum size, heat dissipation and error-free functioning giving the power distribution system an output efficiency of 98.5%.
Trishul uses a sophisticated navigation algorithm involving localization through a Garmin 19x HVS GPS module along with the implementation of a Kalman Filter on the IMU data received using a Sparton AHRS-8 module to achieve Dead Reckoning and further increase localization accuracy. The Communication System allows access to critical system commands in a server over Wi-Fi accessing JSON messages using HTTP requests. The Software suite also comprises of a Mission Planner and Tracking system to allow Trishul to always be aware of what task is being executed and update its status. The Computer Vision system in the boat is designed to accomplish the preliminary and mission tasks and to assist in navigation of Trishul. The algorithms were developed and tested using the MATLAB and Simulink platform due to their rich library and availability of vision critical functions. After a number of testing in real time conditions the thresholds for buoys and shape detection have been optimized and the control signals were hence mapped. Efforts have been done to eliminate the errors due to factors such as ambient light, reflection, etc. and to optimize the execution speed of the System.