Daero Lee

Asymptotic Tracking Control for Spacecraft Formation Flying with Decentralized Collision Avoidance

This paper presents a tracking control scheme for spacecraft formation flying with a decentralized collision-avoidance scheme, using a virtual leader state trajectory. The configuration space for a spacecraft is the Lie group SE(3), which is the set of positions and orientations in three-dimensional Euclidean space. A virtual leader trajectory, in the form of attitude and orbital motion of a virtual satellite, is generated offline. Each spacecraft tracks a desired relative configuration with respect to the virtual leader in an autonomous manner, to achieve the desired formation. The relative configuration between a spacecraft and the virtual leader is described in terms of exponential coordinates on SE(3). A continuous-time feedback tracking control scheme is designed using these exponential coordinates and the relative velocities. A Lyapunov analysis guarantees that the spacecraft asymptotically converge to their desired state trajectories. This tracking control scheme is combined with a decentralized co...

Finite-time control for spacecraft body-fixed hovering over an asteroid

A finite-time control scheme for autonomous body-fixed hovering of a rigid spacecraft over a tumbling asteroid is presented. The relative configuration between the spacecraft and asteroid is described in terms of exponential coordinates on the Lie group SE(3), which is the configuration space for the spacecraft. With a Lyapunov stability analysis, the finite-time convergence of the proposed control scheme for the closed-loop system is proved. Numerical simulations validate the performance of the proposed control scheme.

Robust Position and Attitude Control for Spacecraft Formation Flying

AbstractAn integrated approach combining a state-dependent Ricatti equation (SDRE) and an extended Kalman filter (EKF) is applied to spacecraft formation flying for robust orbital and attitude maneuvers. The formation flying considered in this study is a two-spacecraft formation with a bounded out-of-orbit plane relative motion. The chaser is required to simultaneously perform large position and angle maneuvers with sufficient accuracy. The chaser is then required to maintain a relative orbit expressed in the local-vertical-local-horizontal frame with respect to the target and align its attitude with the target attitude for more than one orbital period. The controls of the chaser are formulated as a nonlinear optimal regulator problem using their highly nonlinear dynamics. To test the robustness of this integrated approach, highly nonlinear dynamics, including external disturbances, are employed as the truth plant that is then used to generate the measurements for an EKF. The tracking error is then comput...

Spacecraft Coupled Tracking Maneuver Using Sliding Mode Control with Input Saturation

AbstractThis paper presents a sliding mode control scheme on for autonomous spacecraft formation flying via a virtual leader state trajectory. The configuration space for a spacecraft is the Lie group SE(3), which is the set of positions and orientations of the rigid spacecraft in three-dimensional (3D) Euclidean space. A virtual leader trajectory, in the form of natural attitude and translational (orbital) motion of a satellite, is generated offline. Each spacecraft tracks a desired relative configuration with respect to the virtual leader in a decentralized and autonomous manner to achieve the desired formation. The relative configuration between each spacecraft and the virtual leader is described in terms of exponential coordinates on SE(3). A new feedback control scheme is proposed for coupled translational and rotational maneuver using a new sliding surface, which is defined as the exponential coordinates and velocity tracking errors such that the sliding surface converges to zero without explicit re...

A Nonlinear Observer Design for a Rigid Body in the Proximity of a Spherical Asteroid

We consider an observer design for a spacecraft modeled as a rigid body in the proximity of an asteroid. The nonlinear observer is constructed on the nonlinear state space of motion of a rigid body, which is the tangent bundle of the Lie group of rigid body motions in three-dimensional Euclidean space. The framework of geometric mechanics is used for the observer design. States of motion of the spacecraft are estimated based on state measurements. In addition, the observer designed can also estimate the gravity parameter of the asteroid, assuming the asteroid to have a spherically symmetric mass distribution. Almost global convergence of state estimates and gravity parameter estimate to their corresponding true values is demonstrated analytically, and verified numerically.Copyright

Kinematically Coupled Relative Spacecraft Motion Control Using the State-Dependent Riccati Equation Method

AbstractThis paper presents kinematically coupled relative spacecraft motion control in the close proximity of a tumbling target using the state-dependent Riccati equation method for proximity operation mission. In general, a rigid-body dynamics can be expressed as both translation and rotation about the center of mass. However, a kinematic coupling between the rotational and translational dynamics occurs when it is not expressed about the center of mass. Thus, kinematically coupled relative spacecraft motion model is derived to describe the relative motion about the selected arbitrary points on both the target and spacecraft. Then, spacecraft relative motion is represented by combining the relative translational and rotational dynamics of arbitrary points on the spacecraft. The spacecraft is required to achieve the desired position and attitude to track a tumbling spacecraft quickly in the effect of kinematic translation and rotation coupling. The state-dependent Riccati equation method is implemented to...

Decentralized guidance and control for spacecraft formation flying using virtual leader configuration

This paper proposes a novel guidance and control scheme for decentralized spacecraft formation flying on SE(3) via virtual leader configuration. The configuration space for a spacecraft modeled as a rigid body is the Lie group SE(3), which is the set of positions and orientations of the spacecraft moving in three-dimensional Euclidean space. A combined guidance and feedback control law in continuous time for the full (translational and rotational) motion of a rigid body under the influence of external disturbance is designed. The guidance scheme aims to reach a final relative configuration according to the desired formation where the relative configuration is described in terms of the exponential coordinates on SE(3). The control law then obtains the desired trajectory leading to the desired formation. The stability of the feedback control system is analyzed. Numerical simulation results demonstrates that the control law can effectively perform a decentralized formation flying for a selected rigid spacecraft formation between three spacecraft.

Robust Adaptive Unscented Kalman Filter for Spacecraft Attitude Estimation Using Quaternion Measurements

AbstractA robust unscented Kalman filter based on a multiplicative quaternion-error approach is proposed for high-precision spacecraft attitude estimation using quaternion measurements under measur...