Forward Flight System Identification for an Electric Medium-Sized Variable-Rotational Speed Rotor

The Joint Tactical Aerial Resupply Vehicle (JTARV) project is supporting the expansion of the Army's unmanned aerial reconnaissance capability by working to obtain high-quality test data that is scarce for group 2 and group 3 UAVs to validate physics-based models. This paper will evaluate the system identification results from transient testing at a wind tunnel speed of 29.2 kts (15 m/s) of the commercial off the shelf T-motor '28x9.2' rotor which is used on the TRV-80 platform, a group 3 UAV. Rotor angles of attack of -90° to 0°, which represent climb to edgewise flight respectively, were tested in the wind tunnel. Chirp Pulse-Width Modulation (PWM) sweep inputs that varied the ΔPWM amplitude by 50, 100, and 150 (approximately 3%, 6%, and 10% of the steady state PWM) were analyzed to derive an electric motor model that can be used in a physics-based simulation. Additionally, it was found that the identified coefficients of thrust and torque were higher in transient conditions versus steady for most angle of attack test conditions. Lastly, the closed loop wind tunnel system, thrust due to ΔPWM amplitude sweep, was compared to the closed loop system of the TRV-80. A similar motor lag frequency was identified in both systems which shows the relevance of the electric motor model and rotor performance data derived from wind tunnel data presented herein.