The ORCA XI Vehicle

Overview

This year's sub follows a design philosophy of simplicity, modularity, and reliability. Most of the parts in the ORCA XI have been rebuilt while most of the sensors are the same. We used a depth sensor and a magnetic compass for navigation and a forward-facing Prosilica EC750C camera for imaging processes. ORCA XI also includes a passive sonar system to determine a bearing to the acoustic pinger.

Hull Design

The ORCA XI hull is an acrylic glass tube with two end caps made of high density polyurethane which is both durable and lightweight. Two more tubes are fitted to the bottom of the vehicle as battery housing. In addition a compartment for the camera will be fitted to the forward end of the sub.

The vehicle has been very carefully designed to have great upright stability. The batteries, since they are extremely heavy, are placed as low as possible under the hull, giving the sub very good static stability.The main hull slides out allowing for easy access to the electronics assemblage.

Software

The computer will run predominantly Python programming. ORCA XI will have two levels of control: the Low Level Controller (LLC) and High Level Controller (HLC). The LLC manages all of the real time tasks, namely: depth control, altitude control, heading control, velocity control, and pitch control. Upon interacting with new sensor input, it will use a PID (proportional-integral-derivative) algorithm to minimize error from desired set points, using one or more of a library of low-level commands. Similarly, the HLC translates sensor data into a command. Unlike the LLC, however, the HLC implements mission-level control. For each state (different for each of the tasks the vehicle is performing), the HLC uses pre-programmed algorithms to establish new set points. In other words, the HLC determines the path, whereas the LLC ensures that the robot remains on that path.

Additional Information

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