The Minion Research Platform

Vehicle Architecture

The Minion ASV platform was conceived as more than a one-off competition entry. From the earliest design reviews, the team prioritized modularity and upgradeability, understanding that each competition cycle would bring new challenges and new hardware requirements. The result is a catamaran-style hull with a central payload bay that can be reconfigured between missions without structural modification.

At roughly 16 feet in length, the Minion platform provides ample deck space for sensor arrays, computing enclosures, and mission-specific payloads. The twin-hull design delivers inherent stability in the rough open-water conditions typical of competition venues, from the harbors of Singapore to the Pacific swells off Hawaii. Each hull is fabricated from marine-grade fiberglass, with internal bulkheads providing both structural rigidity and watertight compartmentalization.

The platform integrates mechanical, electrical, and software subsystems through a central bus architecture. Power distribution, communication links, and sensor data all route through standardized connectors on the MAST (Minion Autonomous Systems Tray), which sits between the hulls. This centralized architecture means that swapping a sensor or upgrading a motor controller does not require rewiring the entire vessel, a practical advantage when competition prep involves weeks of late-night debugging in the lab.

The team draws on expertise from aerospace engineering, mechanical engineering, and software engineering disciplines. This interdisciplinary approach is central to the vehicle's design philosophy: no single subsystem is developed in isolation, and every major design decision is reviewed across disciplines before fabrication begins. Learn more about the team behind these systems on our About Team Minion page.

Hydrophone Array

Acoustic detection is central to several RobotX challenge tasks. Minion carries a diamond-shaped planar array of four Teledyne Reson hydrophones capable of detecting underwater acoustic pingers. Signals from the hydrophones are amplified, digitized, and processed through custom digital signal processing algorithms that determine the bearing and range to each pinger.

A linear actuator rotates the hydrophone mounting pole 90 degrees downward into the water during operation, positioning the sensors deep enough to minimize surface reflection interference. When not in use, the array stows flat against the hull, reducing drag and protecting the sensitive transducers during transit. This deploy-and-stow mechanism was designed after the team observed that fixed-mount arrays on other competition vessels suffered from wave-induced noise at the surface.

Signal processing for the hydrophone array runs on a dedicated single-board computer with custom firmware written by the team's electrical engineering members. The software implements time-difference-of-arrival (TDOA) algorithms that cross-correlate signals across the four hydrophone channels to triangulate the position of an acoustic pinger to within a few meters at ranges up to 50 meters. Noise immunity improvements introduced in the 2016 cycle significantly reduced false-positive detections caused by propeller-induced cavitation during high-speed transit.

Autonomous Navigation and Control

Minion's navigation stack is built on the Robot Operating System (ROS), adapted for the latency and reliability requirements of open-water autonomous operation. A Vectornav VN-200 inertial navigation system provides high-rate attitude and position data, fused with GPS via an extended Kalman filter running at 100 Hz. This fusion approach delivers position estimates that remain stable even when GPS signals are temporarily obscured by competition venue structures or when the vessel is maneuvering aggressively.

Waypoint navigation uses a pure pursuit controller tuned specifically for Minion's hydrodynamic response characteristics. The team characterizes the vessel's turning radius, thrust response, and drag at various speeds during pre-competition sea trials, updating the controller parameters to match the current payload configuration and water conditions. This tuning process has been systematized into a calibration protocol that can be completed in under 90 minutes at the competition venue.

Mission planning runs as a separate node that interprets task parameters communicated from the shore station over a dedicated 900 MHz RF link. The mission planner generates waypoint sequences, assigns subtasks to the appropriate subsystems (perception, acoustics, launch mechanisms), and monitors task completion before transitioning to the next objective. Fallback modes allow the vessel to complete partial task sequences even when a subsystem reports a fault, maximizing the competition points earned per run.

The Lackey Subvehicle

Lackey is Minion's deployable subvehicle, based on the SWASH (Small Waterplane Area Single Hull) concept. At 29 inches long and 4.8 inches in diameter, its hydrodynamically tailored hull minimizes drag while maximizing internal volume for electronics and sensors. The 3D-printed hull features a mast for GPS and RF communications, a downward-facing color camera with high-intensity illuminator, an IMU/magnetometer combination, and Wi-Fi-based data links back to the mothership.

The SWASH design allows Lackey to operate with minimal interaction with the water surface, delivering a more stable sensing platform than conventional surface craft of similar size. This stability is critical for the close-range inspection tasks that Lackey performs, where wave-induced motion would blur camera imagery and corrupt IMU readings.

Lackey is launched from a custom cradle mounted on Minion's port side. When the mission planner determines that an inspection task requires close-range visual confirmation, it commands Lackey to deploy autonomously, navigate to the target under its own power, complete the inspection, and return to a recovery waypoint where Minion retrieves it. This fully autonomous deployment-and-recovery sequence was one of the most complex integration challenges the team undertook during the 2016 development cycle.

Power and Energy Management

Minion's power system is built around a bank of lithium-iron phosphate (LiFePO4) cells housed in the MAST systems tray. LiFePO4 chemistry was selected for its superior cycle life, thermal stability, and tolerance to partial-state-of-charge operation, all critical considerations when the vessel may sit on standby for hours between competition runs. The battery bank provides enough energy for a full 30-minute autonomous mission with a 20% reserve, sufficient to complete recovery maneuvers if the primary mission run encounters unexpected delays.

A custom battery management system (BMS) designed by the team monitors cell voltages, temperatures, and state of charge in real time. The BMS communicates with the mission computer over a CAN bus, allowing the navigation software to make energy-aware planning decisions. If battery state of charge drops below a configurable threshold during a run, the mission planner automatically prioritizes higher-scoring tasks and skips those with lower expected point yields.

Shore power is provided through a filtered, regulated DC-DC converter that brings the competition venue's 120V AC supply down to the voltages required by the vessel's subsystems. A kill switch circuit on the power distribution board allows the vessel to be immediately de-energized from the shore station in the event of an anomaly, satisfying the safety requirements mandated by the Maritime RobotX Challenge safety committee.

Bodyguard Racquetball Turret

The detect-and-deliver task in the Maritime RobotX Challenge requires teams to launch racquetballs at designated targets from a moving platform. Bodyguard is Minion's pneumatic delivery system, featuring an actively stabilized two-axis gimbal that keeps the launcher pointed at its target regardless of wave-induced platform motion. A pneumatic reloading mechanism enables rapid successive launches, giving the team more attempts per run and more time for subsequent tasks.

The gimbal controller uses real-time attitude data from the vessel's IMU to compute the correction angles needed to keep the launcher on target. A servo loop operating at 200 Hz compensates for roll and pitch induced by wave action, maintaining aim accuracy to within 2 degrees under sea states typical of competition venues. The pneumatic supply for the launcher is stored in a regulated pressure vessel rated to 120 psi, with a solenoid valve actuated by the mission computer to trigger each shot.

For more about how these systems have performed under competition conditions, see our Competitions page, or explore how our industry partners have supported the development of these technologies.