ArduPilot / ArduSub Engineer for Custom Control Layer – Pixhawk, Actuator Allocation, Altitude Hold

# ArduPilot / ArduSub Engineer Needed for Custom ROTV Control Layer – Pixhawk, Actuator Allocation, Altitude Hold I am developing a novel Remotely Operated Towed Vehicle (ROTV) for commercial subsea survey operations. I am looking for an experienced ArduPilot / ArduSub / Pixhawk engineer to build the low-level control layer for a non-standard towed subsea vehicle. This is not a general software, Python, UI, web app, ROS, or robotics hobby project. The topside interface is being handled separately. This role is specifically for the Pixhawk / ArduSub / ArduPilot control side. ## Project Objective The ROTV must maintain a stable operator-selected altitude above seabed while being towed and carrying survey payloads. The intended architecture is: * Pixhawk / ArduSub / ArduPilot / custom firmware: real-time vehicle control, actuator outputs, attitude control, actuator allocation, arming logic, safety and failsafes. * Companion computer: supervisory layer, telemetry, logging, command relay and sensor bridging where required. * Topside software: operator interface only, handled separately. The companion computer should not be treated as the primary high-rate flight controller. The Pixhawk / ArduSub / ArduPilot layer should own the real-time control and failsafe behaviour. ## Vehicle Control Concept The vehicle is expected to use: * 3 vertical thrusters; * 2 hydrodynamic control surfaces; * acoustic altimeter for altitude above seabed; * pressure/depth sensor for fallback or commissioning mode; * Pixhawk onboard IMU for initial attitude control unless a strong technical reason exists to use an external IMU. The core commercial function is acoustic-altimeter-based altitude hold above seabed. Depth hold alone is not the main requirement. Depth hold may be included as a commissioning or fallback mode, but the primary objective is altitude control above seabed. ## Required Work The work is expected to include: * custom ArduSub / ArduPilot frame, mixer or firmware development for a non-standard ROTV; * actuator allocation for 3 vertical thrusters and 2 hydrodynamic control surfaces; * roll, pitch and vertical/altitude control using the available actuators; * acoustic-altimeter-based altitude hold integration; * pressure/depth sensor fallback or commissioning mode; * MAVLink interface to companion computer for setpoints, telemetry and mode commands; * deterministic failsafe behaviour for command loss, sensor dropout, actuator saturation and emergency safe state; * bench-test procedures and actuator-output validation; * source-code handover, firmware files, configuration files and build instructions. ## Expected Development Stages The project will be delivered in stages. Expected stages may include: ### Stage 1 – Custom Control Skeleton and Actuator Mapping * ArduSub / ArduPilot firmware or configuration skeleton for the ROTV layout. * Defined output channels for 3 vertical thrusters and 2 control surfaces. * Documented actuator mapping. * Test method showing roll, pitch and vertical/heave demand producing expected actuator-output behaviour. * Build and flashing instructions. ### Stage 2 – Actuator Allocator Development * Custom actuator allocation for the non-standard ROTV layout. * Roll, pitch and vertical control contribution from thrusters and control surfaces. * Output limiting and actuator direction checks. * Bench-testable control response. ### Stage 3 – Sensor Integration and Altitude Hold * Acoustic altimeter integration for altitude above seabed. * Pressure/depth sensor integration for fallback or commissioning mode. * Altitude setpoint handling via MAVLink / companion computer interface. * Basic altitude-control behaviour suitable for bench/simulated validation. ### Stage 4 – Failsafes and Bench Validation * Companion-computer loss behaviour. * Topside command-loss behaviour. * Sensor dropout handling. * Safe-neutral output state. * Actuator saturation monitoring. * Bench-test procedure and validation notes. ### Stage 5 – Handover and Wet-Test Support * Source code handover. * Firmware/configuration files. * Build instructions. * Test notes. * Support for integration with the companion computer and topside interface. * Optional support during wet testing. ## Required Experience Please only respond if you have genuine experience with one or more of the following: * ArduPilot development; * ArduSub development; * Pixhawk custom vehicle control; * custom frame or mixer development; * actuator allocation; * MAVLink; * robotic vehicle control; * subsea, marine, UAV, AUV, ROV or similar control systems. The GUI/topside interface is not the focus of this role. This role is for the low-level control system and Pixhawk / ArduSub / ArduPilot implementation. ## Engagement Type I am open to either hourly or fixed-price milestone work. For hourly work, please indicate your hourly rate, availability and estimated hours for the first implementation stage. For fixed-price milestone work, please suggest a sensible milestone structure based on the stages above. I prefer staged delivery with usable technical outputs at each stage. ## Deliverables Expected deliverables may include: * ArduSub / ArduPilot source code or firmware modifications; * custom frame/mixer/actuator-allocation files; * Pixhawk parameter/configuration files; * MAVLink interface notes; * sensor integration notes; * bench-test procedures; * actuator mapping documentation; * build and flashing instructions; * handover documentation. ## IP and Confidentiality An NDA will be required before detailed vehicle drawings, geometry or confidential information are shared. Project-specific deliverables created specifically for this project must transfer to Cross Subsea Services Ltd upon full cleared payment for the relevant milestone or agreed deliverable. The contractor may retain pre-existing background IP, generic tools, general know-how and open-source components under their existing licences. The contractor must not use Cross Subsea’s confidential vehicle information, design arrangement or project-specific control architecture to develop, assist, sell or disclose a competing system without written permission. ## Important Note This is intended to become a commercial-grade subsea survey system. Development/debug tools such as QGroundControl, BlueOS or similar may be used where helpful, but the final commercial operator interface is being handled separately. The main requirement is not simply to hold depth. The key requirement is to support altitude hold above seabed using an acoustic altimeter.