In-flight Rotor Blade Tip Damage Detection of Small Multirotor using Ultrasonic Sensors

Abstract

The prevalence of serious incidents involving small, unmanned multirotors may escalate when such devices are operated within densely populated regions. The development of system fault detection techniques is required to prevent flight-related mishaps. A method utilizing an ultrasonic anemometer to detect damage to the rotor blade tip of a small multirotor has been introduced. This method can detect blade tip damage by analyzing the downwash speed, calculated by incorporating an extended Kalman filter. However, the efficiency of this approach in system fault detection remained ambiguous. To demonstrate the method's feasibility, a comprehensive investigation of rotor downwash was conducted. Employing smoke visualization, hot-wire velocimetry, and ultrasonic anemometry, the mechanics were thoroughly examined. Utilizing the experimental data derived from a quadrotor affixed to a test stand, a novel damage index value was postulated. This index value was then applied in a simulated scenario where one blade tip of a rotor was compromised during hovering flight. The simulation allowed for the detection of a 2-mm blade tip loss on a rotor with a 228.6 mm diameter. This study verified a technique for blade-tip damage detection predicated on sensing wake flow, thereby contributing to multirotor construction with robust failure tolerance mechanisms.