AUTHOR=Yang Rui , Du Changping , Yu Jiahao , Fang Tianrui , Du Zean 
  
TITLE=Corridor-constrained incremental TD3 for nacelle tilt scheduling in quad-tiltrotor UAV level transition
  
JOURNAL=Aerospace Research Communications
  
VOLUME=Volume 4 - 2026
  
YEAR=2026
  
URL=https://www.frontierspartnerships.org/journals/aerospace-research-communications/articles/10.3389/arc.2026.17000
  
DOI=10.3389/arc.2026.17000
  
ISSN=2813-6209
  
ABSTRACT=Level-flight transition of quad-tiltrotor unmanned aerial vehicles requires a nacelle tilt scheduler that adapts to closed-loop transition states while satisfying actuator-rate limits and a speed-dependent admissible transition corridor. Offline tilt schedules provide useful nominal references, but their feedback adaptability is limited under disturbances, measurement noise, and variations in low-level closed-loop response. In contrast, absolute-action reinforcement learning (RL) policies treat consecutive nacelle commands as independent setpoints, which may induce abrupt inter-sample variations and excessive nacelle-rate demand. This paper proposes an energy-aware mooth incremental tilt strategy based on a corridor-constrained incremental Twin Delayed Deep Deterministic Policy Gradient (TD3) framework. Instead of learning the absolute nacelle angle, the actor outputs a bounded nacelle-angle increment. The command is then generated through bounded integration, rate saturation, and projection onto a tightened transition corridor. This action generation mechanism converts the policy from an independent setpoint generator into a constrained nacelle-evolution generator, embedding command continuity and actuator-rate compatibility while enforcing corridor feasibility. The scheduling objective combines altitude regulation, forward-speed buildup, longitudinal smoothness, and a rotor-speed-based effort proxy under a gain-scheduled low-level control architecture. The feasibility layer provides corridor admissibility of the sampled command, and a post-training analysis characterizes the conditional closed-loop boundedness. The simulations show that the proposed scheduler generates smoother nacelle trajectories than absolute-action TD3 and act-penalty-based TD3, reducing nacelle-rate demand and longitudinal jerk, while maintaining corridor feasibility, bounded altitude response, terminal-speed buildup, and comparable rotor-speed-based effort.