A Unified MPC Strategy for a Tilt-rotor VTOL UAV Towards Seamless Mode Transitioning

TL;DR

The paper addresses seamless mode transitioning for tiltrotor VTOL UAVs in Urban Air Mobility by proposing a unified Model Predictive Control (MPC) framework that operates across all flight phases without explicit mode switching. The controller optimizes a single actuator set via a horizon-$N$ problem that minimizes $J(x_k,u_k)$ under nonlinear dynamics and constraints, while a least-norm control allocation distributes the wrench to all rotors and control surfaces. Key contributions include a velocity-loop MPC that covers both multirotor and fixed-wing configurations, a cohesive control allocation that accounts for actuator faults, and validation in a custom simulator showing smoother accelerations/decelerations, precise coordinated turns, and resilience to servo or motor failures. The approach advances practical VTOL-UAM systems by enabling continuous, robust performance with four independently controllable rotors and explicit handling of faults, with open-source code to support rapid prototyping and replication.

Abstract

Capabilities of long-range flight and vertical take-off and landing (VTOL) are essential for Urban Air Mobility (UAM). Tiltrotor VTOLs have the advantage of balancing control simplicity and system complexity due to their redundant control authority. Prior work on controlling these aircraft either requires separate controllers and switching modes for different vehicle configurations or performs the control allocation on separate actuator sets, which cannot fully use the potential of the redundancy of tiltrotor. This paper introduces a unified MPC-based control strategy for a customized tiltrotor VTOL Unmanned Aerial Vehicle (UAV), which does not require mode-switching and can perform the control allocation in a consistent way. The incorporation of four independently controllable rotors in VTOL design offers an extra level of redundancy, allowing the VTOL to accommodate actuator failures. The result shows that our approach outperforms PID controllers while maintaining unified control. It allows the VTOL to perform smooth acceleration/deceleration, and precise coordinated turns. In addition, the independently controlled tilts enable the vehicle to handle actuator failures, ensuring that the aircraft remains operational even in the event of a servo or motor malfunction.

Figures (16)

• Figure 1: The design of our VTOL tiltrotor aircraft includes four individual rotors, a tilting mechanism for the rotors, two ailerons, an elevator, and a rudder mousaei2022design. Notably, the quadrotor arms employ airfoil cross-sections.
• Figure 2: Rotor tilt in three different positions mousaei2022design
• Figure 3: Geometry setup in different views
• Figure 4: Effectiveness of aerodynamic with respect to Airspeed
• Figure 5: Overview of the proposed control architecture for the tiltrotor VTOL