Description: Strain sensor information is used in nature to achieve robust flight, good rejection of wind disturbances, and stable head motion. Similar man-made sensing devices will be used to demonstrate flight control using Fly-by-Feel, with the overall objective of achieving similarly good performance with piloted and autonomous vehicles. The Phase I work demonstrated the feasibility of using strain sensor arrays for flight control applications. This was done using hardware testing on a wing in a laboratory setting. An important part of showing feasibility was the use of novel frequency domain identification techniques, which were used to identify both modal frequencies and strain mode shapes. The proposed work will develop the ACES system: Attitude Control Enhancement using Strain sensors using both wind tunnel and flight test demonstrations. Acceleration feedback is known to improve the gust disturbance rejection, and the same will be demonstrated in an active control experiment using strain sensors in a wind tunnel. A second experiment will be conducted using a different and more flexible wing to demonstrate active control of shape. Modeling and simulation will be used to begin the transition of this technology to larger commercial vehicles.

Benefits: This project supports the NASA FY14 Strategic Plan Objective 2.1, specifically: "assured autonomy for aviation transformation" and "safe, sustainable growth in the overall global aviation system." The ACES technology applies to both rigid body and dynamic servoelastic (DSE) flight control problems for small and large vehicles, including disturbance rejection, active shape control, load control, flutter suppression, precision flying task performance, and assessing and adapting to major damage. The proposed work will help to transition NASA's support for stain sensor technology to flight control applications of this technology. The benefits are improved performance and safer operation in the shared national airspace.

The commercial application of this technology is the development of advanced sensor and control suite for current and future aircraft configurations with distributed strain sensing. Strain sensing for load measurements is routine, but use of multiple strain measurements for other control applications is a new product idea. This type of sensing will increase both the safety and performance of aircraft with flexible and lightweight structures. Many new Unmanned Air Vehicles (UAV) fall into this category. Vehicles of many different sizes can benefit from this technology, from micro air vehicles (less than 6 inch wing span) to small (less than 4 foot wing span) to large. Markets will include commercial and military UAVs, where its role will be to improve performance and disturbance rejection via wing load sensing. With the growth of the UAV market and the continued trend of aircraft manufacturers employing lighter, more flexible materials, understanding and utilizing dynamic servoelastic control (DSE) phenomena is of utmost importance.