Applications of self-tuning control for spacecraft tracking: theory and experiment

A three-axis self-tuning feedforward/feedback controller has been developed to improve spacecraft tracking performance using standard rate sensors for measurements and reaction wheels for actuation. The self-tuning control gains consist of the fully populated inertia matrix and the constant angular momentum vector, each of which are identified in real time using a minimum variance technique operating on rate gyro measurements, tachometer measurements, and known control inputs. These parameters are used to approximately cancel nonlinear gyroscopic coupling as well as to provide open-loop torque commands to follow an accelerating tracking profile. Both computer-simulated and experimental results demonstrate the potential of the nonlinear self-tuning controller in conjunction with a standard quaternion based linear feedback control law.