Development, control, and test results of high-rate, hingeless trailing edge control surface for the Smart Wing Phase 2 wind tunnel model

The main goal of the Smart Wing Phase 2 Test 2 was to demonstrate high-rate actuation of hingeless, spanwise deflection variable control surfaces using smart materia based actuators. Requirement goals of 25 -degree flap deflection in 0.33 sec, producing a sweep rate of 75 deg/sec, were desired. This sweep rate is similar to those specified for many of the existing military platforms with hinged control surfaces. Numerous studies were performed on many different smart material and flexible structure configurations before arriving at the final design which used an a flexcore-elastomeric skin trailing edge structure with eccentuation using high power ultrasonic motors. The final trailing edge control surface was made up of 10 eccentuator-driven segments connected together by a continuous outer skin and a flexible hinge pin at the trailing edge tip. This pin allowed the segments partial freedom to rotate about each other, but constrained any lateral motion thus giving a smooth trailing edge shape for non-uniform spanwise deflections. To control the ten segments of trailing edge, a VME-based control system with high speed, simultaneously sampled A/D and D/A boards and a dedicated DSP board was developed. This paper describes the analysis and design of the flex structure, ultrasonic motor selection and performance, element and coupon tests to verify analysis, instrumentation to measure deflection, and control system development and integration that led to a highly successful test.