A Smart Position Sensor for Articulated Rotors

Modern articulated rotors utilize an elastomeric bearing on the root of each blade to allow multi-axis articulation through a single component. The bearing forms a spherical joint that makes measuring angular displacements in specific blade axes both coupled and difficult to measure. A smart sensing concept is developed to uncouple and separately measure the blade flapping, feathering, and lead-lag position. The sensor concept projects a magnetic field from the blade root to the rotor hub such that flap, lag and pitch displacements can be derived from a hub mounted pickup array. The device utilizes permanent magnets on the blade root and an array of Anisotropic Magnetoresitive (AMR) sensors on the hub. The sensor array is integrated with other electronic components, including a microprocessor in a printed circuit board, forming a self contained sensing system. The 'smart' sensor is software driven, self checking, and can be networked with other sensors for application flexibility. The sensor accuracy is ensured through a process that develops calibration coefficients that are loaded into system non-volatile memory. The sensor system is designed for initial application on an articulated tail rotor for flight test purposes. Risk reduction testing is conducted in simulated tail rotor environmental conditions including vibration and shock, elevated centrifugal force (CF), temperature extremes and electromagnetic emissions / susceptibility. All development and test results indicate the new sensor technology is valid and ready for use in its initial flight test application.