Abstract: YIDOYU is a multi-constraint optimization system for aircraft structures. It utilizes the mathematical programming techniques to optimize the structural design under a variety of constraints-stress, displacement, natural frequency, flutter speed, static aeroela-sticity (control efficiencies, divergence speed) and minimum size constrain. It also has the following functions, displacement and stress analysis, natural vibration analysis, flutter analysis, static aeroelastic analysis and fully stressed design. It has been successfully used for several wing-type structures and its ability and efficientcy to solve different structural optimization problems are already shown. It has now been integrated into a CAD/CAM software-the Computer Integrated Kngineering and Manufacturing(CIEM)developed by CAE.

Key words: structural analysis, optimal design, approximation technique, constraint derivative