Haizhou Pan

Adaptive nonlinear control for spacecraft formation flying with coupled translational and attitude dynamics

We address a tracking control problem for the coupled translational and attitude motion of a follower spacecraft relative to a leader spacecraft. Using the vectrix formalism the translational and attitude dynamics of the leader and follower spacecraft are modeled, where the mutual coupling in each spacecrafts translational and attitude motion induced by their gravitational interaction is duly accounted. Using a Lyapunov framework, nonlinear control and adaptation laws are designed that ensure the global asymptotic convergence of the relative translational and attitude position tracking errors, despite the presence of unknown mass and inertia parameters of the leader and follower spacecraft.

Output feedback control for spacecraft formation flying with coupled translation and attitude dynamics

In this paper, we address an output feedback tracking control problem for the coupled translation and attitude motion of a follower spacecraft relative to a loader spacecraft. It is assumed that the leader spacecraft is tracking a given desired translation and attitude motion trajectory and the translation and angular velocity measurements of the two spacecraft are not available for feedback. First, the mutually coupled translation and attitude motion dynamics of the follower spacecraft relative to a leader spacecraft are described. Next, a suitable high-pass filter is employed to estimate the follower spacecraft relative translation and angular velocities using measurements of its relative translational position and attitude orientation. Using a Lyapunov framework, a nonlinear output feedback control law is designed that ensures the semi-global asymptotic convergence of the follower spacecraft relative translation and attitude position tracking errors, despite the lack of translation and angular velocity measurements of the two spacecraft. Finally, an illustrative numerical simulation is presented to demonstrate the effectiveness of the proposed control design methodology.

Control of systems with actuator saturation non-linearities: An LMI approach

In this paper, we develop a static, full-state feedback and a dynamic, output feedback control design framework for continuous-time, multivariable, linear, time-invariant systems subject to time-invariant, sector-bounded, input non-linearities. The proposed framework directly accounts for robust stability and robust performance over the class of input non-linearities. Specifically, the problem of feedback control design in the presence of time-invariant, sector-bounded, input non-linearities is embedded within a Lure-Postnikov Lyapunov function framework by constructing a set of linear-matrix-inequality conditions whose solution guarantees closed-loop asymptotic stability with guaranteed domains of attraction in the face of time-invariant, sector-bounded, actuator non-linearities. A detailed numerical algorithm is provided for solving the linear-matrix-inequality conditions arising in actuator saturation control. Three illustrative numerical examples are presented to demonstrate the effectiveness of the proposed approach.

Adaptive learning control for spacecraft formation flying

Considers the problem of spacecraft formation flying in the presence of periodic disturbances. In particular, the nonlinear position dynamics of a follower spacecraft relative to a leader spacecraft are utilized to develop a learning controller which accounts for the periodic disturbances entering the system model. Using a Lyapunov-based approach, a full state feedback control law, a parameter update algorithm, and a disturbance estimate rule are designed which facilitate the tracking of given reference trajectories in the presence of unknown spacecraft masses. Illustrative simulations are included to demonstrate the efficacy of the proposed controller.

LMI-based control of linear systems with actuator amplitude and rate nonlinearities

This paper addresses the control design problem for linear systems subject to actuator amplitude and rate saturation. Motivated by the desire to provide efficient computational algorithms for the actuator amplitude and rate saturation control design, we develop linear matrix inequality (LMI) formulations for the full-state feedback and dynamic, output feedback actuator saturation control. We also provide a direct methodology to determine the stability multipliers that are essential reducing the conservatism of the weighted circle criterion-based saturation control design. A detailed numerical algorithm for computing the LMI-based actuator amplitude and rate saturation controllers is also included. Finally, a numerical example is given to illustrate the proposed control design framework.

Output feedback control for spacecraft with coupled translation and attitude dynamics

In this paper, we address a tracking control problem for a spacecraft with coupled translation and attitude motion, in, the absence of translation and angular velocity measurements. We begin by describing the mutually coupled translation and attitude dynamics of the spacecraft. Next, a suitable high-pass filter is employed to estimate the spacecraft translation and angular velocities using measurements of its translational position and attitude orientation. Using a Lyapunov framework, a nonlinear output feedback control law is designed that ensures the semi-global asymptotic convergence of the spacecraft translation and attitude position tracking errors, despite the lack of translation and angular velocity feedback.

LMI-based control of discrete-time systems with actuator amplitude and rate nonlinearities

In this paper, we address the control design problem for discrete-time systems subject to actuator amplitude and rate saturation. In particular, we develop linear matrix inequality formulations for the full-state feedback and dynamic, output feedback control designs for discrete-time systems with simultaneous actuator amplitude and rate saturation. Furthermore, we provide a direct methodology to determine the stability multipliers that are essential for reducing the conservatism of the weighted circle criterion-based saturation control design. Finally, we give an illustrative numerical example to demonstrate the efficacy of the proposed control design framework.

Control of systems with actuator nonlinearities: an LMI approach

We develop a static, full-state feedback and a dynamic, output feedback control design framework for continuous-time, multivariable, linear, time-invariant systems subject to time-invariant, sector-bounded, input nonlinearities. The proposed framework directly accounts for robust stability and robust performance over the class of input nonlinearities. Specifically, the problem of feedback control design in the presence of time-invariant, sector-bounded, input nonlinearities is embedded within a Lure-Postnikov Lyapunov function framework. Next, a set of linear matrix inequalities are constructed whose solution guarantees closed-loop asymptotic stability, with guaranteed domains of attraction, in the face of time-invariant, sector-bounded, actuator nonlinearities. An illustrative numerical example is presented to demonstrate the effectiveness of the proposed approach.

Control of discrete-time systems with actuator nonlinearities: an LMI approach

This paper considers the problem of stabilization of discrete-time systems with actuator nonlinearities. The proposed framework is based on a linear matrix inequality (LMI) approach and directly accounts for robust stability and robust performance over the class of actuator nonlinearities. Furthermore, it is directly applicable to actuator saturation control and provides state feedback controllers with guaranteed domains of attraction.

Control of discrete-time systems with actuator non-linearities: An LMI approach

This paper considers the problem of stabilization of discrete-time systems with actuator non-linearities. Specifically, full-state feedback and dynamic, output feedback control designs for discrete-time systems with time-varying, sector-bounded, input non-linearities are addressed. The proposed framework is based on a linear matrix inequality approach and directly accounts for robust stability and robust performance over the class of actuator non-linearities. Furthermore, it is directly applicable to actuator saturation control and provides state feedback and dynamic, output feedback controllers with guaranteed domains of attraction. The effectiveness of the approach is illustrated by two numerical examples.