Pixhawk - ardusub setup ( Roll hold)

In a technical forum post, engineer Ferbin_FJ has detailed the development of a custom Remotely Operated Vehicle (ROV) designed for a unique operational profile: attaching to and maneuvering along vertical surfaces. The system architecture centers on a Pixhawk autopilot running the specialized ArduSub firmware, which is commonly used for underwater drones. For higher-level computing and control interfacing, a Raspberry Pi companion computer runs the Robot Operating System 2 (ROS2) middleware alongside MAVROS, the ROS package that bridges ROS messages with the MAVLink protocol used by Pixhawk. The primary engineering goal is to achieve joystick-based control that provides the stability of a position-hold (POSHOLD) mode while deliberately allowing and maintaining controlled roll angles. This is critical for the vehicle to remain oriented and attached to a vertical plane during operations.

The technical challenge is heightened by the stated lack of external XY positioning systems, such as a Doppler Velocity Log (DVL) or other localization sensors, meaning the vehicle must rely on its internal attitude estimation and control loops. The request for a control scheme analogous to POSHOLD but with managed roll suggests the need for custom PID tuning or potentially modifications to the ArduSub control logic. This project sits at the intersection of several advanced open-source hardware and software platforms—Pixhawk, ArduPilot/ArduSub, ROS2, and Raspberry Pi—demonstrating their use in a demanding, non-standard robotics application beyond typical aerial or ground-based drones. Success would enable inspection, maintenance, or sampling tasks on underwater structures like ship hulls, dam walls, or offshore platform legs.