Adaptive control applied to momentum unloading using the low earth orbital environment

An adaptive control technique for the unloading of spacecraft angular momentum is presented. The technique employs model reference adaptive control theory with Lyapunov stability analysis to synthesize a controller using multiple environmental sources in combination for unloading. Simulation studies are presented that employ magnetic, gravity gradient, and aerodynamic torques in a three-way controller. It is shown that momentum is contained within a dead zone introduced for disturbance compensation that is well below reasonable reaction wheel saturation limits for two model spacecraft of much different mass properties.