Spanwise Adaptive Wing: Shape Memory Alloy Actuation Systems For In-flight Wing Folding
The Boeing effort on the Spanwise Adaptive Wing (SAW) project included the development, integration, and test of a compact integrated SMA actuator system to fold the outboard wing sections of the Prototype-Technology Evaluation Research Aircraft (PTERA) UAV during flight. NiTiHf SMA torsional components were processed by Boeing to produce stable actuation at loads up to 400 in-lbs and 88° of angular range. The SMA components were incorporated into a hinge assembly that mechanically coupled the inboard wing and the outboard folding winglet. A compact on-board control system used angle, torque, and temperature readings to command and maintain a range of wingtip angles over a wide variety of flight and test conditions. An integrated simulation of the SMA actuators was developed to aid in the design of the actuator control system and for preflight performance predictions. The simulation was deployed using compact electronics and integrated into NASA’s PTERA flight simulator. This complete actuator system was tested using a combination of bench and wind tunnel testing prior to integration into the PTERA vehicle. The performance of the actuator control system, the SMA actuation, and the actuator simulation model were validated during three flight tests at Roger’s Dry Lake in December of 2017.