A Study of Digital Adaptive Command Augmentation System

Referring to the adaptive scheme proposed by U.Hartmann et al.,this paperpresents a simplified model for parameter-estimation and an extended Kalman filterparameter-estimation algorithm.As a result,computation work is decressed to50% of the original.During the determination of feedback gains,the concepts ofequivalent inherent frequency and equivalent damping ratio specified by MIL-F-8785C are utilized.Considering the influence of actuator dynamics and reasonablepole-assignment,we deduce approximate feedback gain formulas.A simplified andappropriate logic condition for the start of gain adaptation is recommended.Thusthe system stability and good flight handling quality are ensured.The estimation oftime varying parameters during the climbing maneuver with decreasing speed anddescending maneuver with increasing speed,the climbing or descending maneuverwith nearly invariant speed,is studeid in detail including the role of probe-signals.The divergence phenomenon encountered in the conditions mentioned above isanalyzed and means for overcoming it are investigated.