OUTPUT-FEEDBACK VARIABLE-STRUCTURE ADAPTIVE-CONTROL OF AN AEROELASTICSYSTEM

The question of control of a class of aeroelastic systems with structu ral nonlinearities based on the variable structure model reference ada ptive control theory is treated. It is assumed that the system paramet ers are unknown and unmodeled nonlinear functions are present in the m odel. Control lans for the trajectory control of pitch angle and plung e displacement are derived. For the synthesis of controllers, only mea sured output variable (pitch angle or plunge displacement) is used for feedback. The feedback loop includes two relays, whose outputs are fu nctions of certain auxiliary error signals. Modulation functions of th e the relays are generated on line using bounds on uncertain functions and signals derived from the input and output of the system. Digital simulation results are presented that show that in the closed-loop sys tem with only output feedback, pitch angle, and plunge displacement ar e smoothly regulated to zero in spite of the uncertainty and unmodeled functions in the system.