Three-Gridfin Architecture
Our vehicle employs a three-gridfin control architecture, selected to exploit the compact form with strong aerodynamic control authority. During descent from balloon release they maintain stability and moderate speed in the transconic regime. In aerodynamic flight they provide robust control authority for precision landing.
This unconventional configuration required the development of a custom control mixing algorithm typical of missile systems. Standard flight control frameworks assume conventional control surface layouts and do not natively support tri-gridfin geometries.
Gridfin wind tunnel testing for aerodynamic characterization
Flight Software
To accelerate development, we built on the open-source ArduPilot ecosystem. While robust and widely validated, it does not natively support multi-fin mixing for this configuration out of the box.
We modified the firmware to implement custom actuator mixing logic, enabling stable control across all flight phases.
Extended ArduPilot Fork
Custom multi-fin mixing implementation for tri-gridfin control architectures.
Simulation & Validation
To evaluate performance and tune the control system, we developed PLAV (Python Laptop Air Vehicles), a 6 Degree-of-Freedom flight simulator designed for rapid iteration of custom airframes.
PLAV allows users to quickly define their own aerodynamic models and simulate flight in a realistic Earth environment. Our implementation incorporates aerodynamic coefficients derived from both CFD analysis and wind tunnel testing.
This enabled high-fidelity software-in-the-loop validation prior to real-world flight testing.
PLAV Flight Simulator
6-DoF simulation environment with integrated BRGR flight model for software-in-the-loop testing.