Modeling, dynamics, and control of a battery-powered helicopter

Rotorcraft offer several operational advantages, including the ability to perform vertical take-off and landing (VTOL), hover, and maneuver in all directions. Despite these capabilities, rotary-wing aircraft exhibit highly coupled dynamics and inherent instability, making advanced flight control systems essential for safe and efficient operation. A widely adopted approach for developing such systems is Model-Based Design (MBD), in which a mathematical model represents the core of the entire development process, from requirements definition to design, implementation, verification, and validation. By placing the system model at the center of the workflow, MBD enables requirement traceability, collaborative development, simulation of multiple scenarios, system-level optimization, automatic code generation, and early error detection. The Flight Mechanics Laboratory of the University of Bologna operates an unmanned SAB Goblin Raw 700 helicopter for which new flight control systems are under development. To support this objective, the first stage of the present work focuses on the development of a high-fidelity simulator, designed to be extensible to other classes of small unmanned helicopters. The simulation model is then refined through the experimental identification of key physical parameters, including the helicopter moments of inertia, and subsequently validated. Once validated, the trim conditions and stability characteristics are determined, followed by an aeromechanical stability and control analysis over forward-flight speeds ranging from 0 to 35 m/s, considering both coupled and uncoupled dynamic models. Finally, two flight control systems are designed and evaluated: a PX4-based architecture employing PID and proportional controllers, and a modified version in which the angular-rate PID controller is replaced by a Linear Quadratic Regulator (LQR). Their performance is then assessed and compared.