The ORCA II Vehicle

Overview

The underlying goal of our design is a robust, flexible, modular vehicle that can be easily modified. The physical infrastructure is designed to provide our programmers a large solution space and a great deal of strategic freedom.  The vehicle uses a magnetic compass, a sonar altimeter, and a pressure sensor to follow a depth contour through the six gates. Improvements over last year include an inertial measurement unit with three axes of rate gyros and a Kalman filter to combine all sensor data and make the vehicle less susceptible to periodic measurement error.

Hull Design

The ORCA II hull is designed to be a stable, flexible platform. Like its predecessor, ORCA-2 is divided fore-and-aft into three separate modules. The central section of the vehicle consists of two sealed electronics tubes stacked vertically with powerful thrusters mounted on either side. The bow and stern sections are faired, flooded modules containing vertical thrusters, environmental sensors, and mission-specific payloads.

We took great pains to make the vehicle stable and easy to use. Like last year, the batteries are placed low in the center of the hull to maximize static stability. The bow and stern sections swing away from the central hull module, allowing easy access to the vehicle electronics. The pressure hulls could be opened in under thirty seconds, and backplane connectors on the mounting cards eliminated the wiring harnesses and plugs in the ORCA-1 design.

Sensors and Electronics

ORCA-2 contains a refined suite of sensors tailored to the AUVSI mission. The vehicle contains an internal compass/inclinometer unit by Precision Navigation Inc., and a homemade inertial measurement unit with three axes of rate gyros. The vehicle senses its immediate environment through the use of a precision pressure sensor and a Tritech sonar range finder.

The vehicle control system runs on a fully-featured pentium-class single-board computer running the Linux operating system. The control program can be accessed and modified remotely via a 900 MHz radio modem when the vehicle is near the surface, or via an ethernet cable tether for deeper operation at close range.

Additional Information

Additional information about ORCA II can be found in the Articles and Press section of this site.