Scheduling of Multi-Rod Hydraulic Infinite Linear Actuators for Medium-Heavy UAVs

The Hydraulic Infinite Linear Actuator with Multiple Rods (HILA-MR) enables multiple outputs to share a common hydraulic piston through independently controlled clamping mechanisms. This architecture has the potential to reduce actuation-system mass, volume, sensor count, and complexity in medium-heavy unmanned aerial vehicles (UAVs). However, because multiple control surfaces compete for a shared actuation resource, actuator performance depends strongly on the scheduling strategy used to allocate piston motion. This work investigates the feasibility of using HILA-MR for primary flight-control applications and evaluates three scheduling algorithms: time-division multiplexing (TDM), round-robin (RR), and multi-grip (MG). Simulation results were validated experimentally using a three-rod HILA-MR test rig. The algorithms were assessed using representative flight control commands and subsequently evaluated in coupled flight dynamics simulations. Results show good agreement between simulation and experiments. Compared with TDM, the RR and MG algorithms significantly improve tracking performance through adaptive allocation of actuation effort. Flight-dynamics simulations further demonstrate that the HILA-MR actuator achieved acceptable tracking performance during representative climb and turning maneuvers. The results indicate that HILA-MR is a promising actuation concept for future UAV flight-control systems.