A Novel Contactless Sensor for Helicopter Blade Motion In-Flight Measurements

This paper presents the comprehensive approach followed to design, implement and test an innovative sensor system aimed at the in-flight estimation of the helicopter main rotor state. This activity represents a fundamental step of MANOEUVRES, a project carried on in the framework of Clean Sky Green Rotorcraft 5 research programme, which is aimed at developing an integrated system capable of informing the pilot of the real-time noise generation and of suggesting possible corrective actions for low-noise maneuvering. The main rotor state is one of the most impacting factors on the helicopter noise generation, and cannot be measured with conventional rotorcraft instrumentation. The stereoscopic vision-based measurement system described in this paper overcomes this limitation, allowing the running estimation of the main rotor blade attitude in terms of lag, flap and pitch angles. Furthermore, such a sensor system could allow the implementation of enhanced attitude control laws based on rotor state feedback. The full development process of the sensor system, mounted on the main rotor head is presented, up to the flight trials on board an AgustaWestland AW139 prototype helicopter.