An extended Kalman filter is derived for estimating the relative position and attitude of a pair of uninhabited air vehicles, designated leader and follower. All leader states are assumed known, while the relative states are estimated using line-of-sight measurements between the vehicles along with angular rate and acceleration measurements of the follower. Noise is present on all measurements,...

The paper addresses quaternion-based energy and time optimal spacecraft reorientation in the presence of complex attitude constrained zones. Designing an optimal reorientation trajectory for a rigid body spacecraft is posed as a nonlinear optimal control problem. In this direction, attitude constrained zones are defined with respect to the onboard instrument under two categories, forbidden and ...

This paper presents an algorithm to average a set of quaternion observations. The average quaternion is determined by minimizing the weighted sum of the squared Frobenius norms of the corresponding attitude matrix differences, subject to the unit-norm constraint in the determined solution. Two cases are presented: one that incorporates scalar weights and one that incorporates general weights on...

The robust optimal attitude control problem for a flexible spacecraft is considered. Two optimal sliding mode control laws that ensure the exponential convergence of the attitude control system are developed. Integral sliding mode control ISMC is applied to combine the first-order sliding modewith optimal control and is used to control quaternion-based spacecraft attitudemanoeuvres with externa...

A new approach for spacecraft absolute attitude estimation based on the unscented Kalman filter (UKF) is extended to relative attitude estimation and navigation. This approach for nonlinear systems has faster convergence than the approach based on the standard extended Kalman filter (EKF) even with inaccurate initial conditions in attitude estimation and navigation problems. The filter formulat...

In this paper, a quaternion-based finite-time sliding mode attitude controller is designed for a spacecraft performing high-thrust orbital maneuvers, with cold gas thrusters as its actuators. The proposed controller results are compared with those of a quaternion feedback controller developed for the linearized spacecraft dynamics, in terms of settling time, steady-state error, number of thrust...

Position and attitude set-point regulation of autonomous underwater vehicles (AUVs) in 6 degrees of freedom (DOF) is presented. Euler parameters are used in the representation of global attitude. Three quaternion feedback controllers are derived based on vector quaternion, Euler rotation and Rodrigues parameter feedback, respectively. Global asymp-totic stability is proven in the rst and second...

Predictive control technique is applied to the three-axis attitude control of spacecraft. The principal idea of predictive control is to construct a priori reference trajectory and build control command so that the actual system follows the reference trajectory. In the case of this study, the controlled variables are the quaternion attitude parameters and angular rates of spacecraft body axes. ...

A position and attitude tracking control law for autonomous underwater vehicles (AUVs) in 6 degrees of freedom (DOF) is derived. The 4-parameter unit quaternion (Euler parameters) is used in a singularity-free representation of attitude. Global convergence of the closed-loop system is proven. In addition several 3-parameter representations in terms of the Euler parameters are discussed with app...

Loss-of-Control (LOC) is a major factor in fatal aircraft accidents. LOC is generally associated with flight outside of the normal flight envelope almost always involving nonlinear behaviors and often including extreme attitude conditions. Recent and ongoing work at the NASA Langley Research Center has focused on building aerodynamic models adequate for simulation and analysis in these regimes....