Integrated aeroelastic control optimization of laminated composite lifting surfaces

Abstract

An integrated design approach for aeroelastic control of laminated composite lifting surfaces is formulated and demonstrated. The design is posed as an optimization problem to determine the optimum ply orientation angles and the control law which maximizes the aeroelastic instability speed of an actively controlled laminated composite lifting surface subject to limited control authority and structural frequency constraints. The lifting surface is simulated by a rectangular symmetric cantilevered composite plate. The formulation incorporates the Rayleigh-Ritz energy method, two-dimensional incompressible unsteady aerodynamic theory, optimum control design, and parameter optimization techniques. The particular control configuration consists of two point-force inputs applied at the leading and trailing edges of the lifting surface. In conjunction with the laminated compositeplate structural model, the control configuration effectively simulates an active flexible lifting surface. The effectiveness of the integrated approach is evaluated by comparing the optimum designs obtained by the method with designs obtained by a design procedure using aeroelastic tailoring and optimum control design as well but in a nonintegrated fashion. The illustrative studies resulted in a design that exhibited 102% higher aeroelastic instability speed with 294.4% lower control cost than designs obtained by a nonintegrated design procedure.