Gyro-Free Rigid-Body Attitude Stabilization Using only Vector Measurements

摘要

A novel attitude-stabilization controller is proposed that uses vector measurements obtained from inertial sensors directly for feed- back, without relying on the estimated attitude vector or angular velocity feedback. The control law is formulated in the classical passive systems framework and does not rely on observers of any kind. Although many classical results for angular velocity-free control laws are available in existing literature, they are typically formulated using some kind of attitude parameterization. As such, these control laws must be integrated with an attitude estimation scheme that can provide the attitude of the vehicle using a combination of gyro-rate and vector measurements. Thus, regardless of the approach, most existing control laws have either an explicit or implicit requirement for angular velocity measurements. The attitude control law proposed in this Note truly eliminates the need for either direct or indirect angular velocity information because it solely and directly employs vector measurements for control feedback. The proposed controller requires a minimum of two noncollinear vector measurements to satisfy the attitude-stabilization objective. Under this setting, rigorous analysis proves that the spacecraft converges to the desired attitude and zero angular velocity as long as some mild constraints on the initial conditions are satisfied. A simulation study conducted in the presence of measurement error shows that this control law drives the states to a bounded residual set in this case. Some technical limitations that prevent the extension of this control law to the full tracking case have been discussed in the Note. This work presents an important step toward dealing with a very realistic scenario for spacecraft missions in which failed or unreliable gyro-rate sensors prevent traditional control methods from being implemented for onboard attitude stabilization.