Xiaowei Shao

Satellite rendezvous using differential aerodynamic forces under J2 perturbation

Purpose – The purpose of this paper is to present a method to conduct small satellite rendezvous mission by using the differential aerodynamic forces under J2 perturbation in low earth orbit (LEO). Design/methodology/approach – Each spacecraft is assumed to be equipped with two large flat plates, which can be controlled for generating differential accelerations in all three directions. Based on the kinetic theory, the aerodynamic lift and drag generated by a flat plate are calculated. To describe the relative dynamics under J2 perturbation, a modified model is derived from the high-fidelity linearized J2 equations proposed by Schweighart and Sedwick. Findings – Simulation results demonstrate that the proposed method is valid and efficient to solve satellite rendezvous problem, and the modified model considering J2 effect shows better accuracy than the Horsley’s Clohessy–Wiltshire-based model. Research limitations/implications – Because aerodynamic force will reduce drastically as orbital altitude rises, t...

Roto-Translational Spacecraft Formation Control Using Aerodynamic Forces

This paper investigates the problem of controlling both translational and rotational motions for small-satellite formation using only aerodynamic forces. A new arrangement for actuators with six plates mounted on each spacecraft is suggested, such that aerodynamic forces and torques are produced simultaneously. In this work, the coupling between the position and attitude dynamics is unique, which mainly comes from the features of the aerodynamic models and the configuration of atmospheric-based actuators. Thus, a novel coupled orbit-attitude model is established. Considering the uncertainties in the atmospheric-density model at low-Earth orbit, a sliding-mode controller is developed based on the coupled model. An optimal process is proposed to determine the particular command, such that it can accurately drive each individual aerodynamic plate, while minimizing the variations of the commands. A series of simulations are performed to validate the effectiveness of the method, demonstrating that both positio...

A novel relative navigation method based on thrust on-line identification for tight formation keeping

Purpose The purpose of this paper is to present a novel high-precision relative navigation method for tight formation-keeping based on thrust on-line identification. Design/methodology/approach Considering that thrust acceleration cannot be measured directly, an on-line identification method of thrust acceleration is explored via the estimated acceleration of major space perturbation and the inter-satellite relative states obtained from space-borne acceleration sensors; then, an effective identification model is designed to reconstruct thrust acceleration. Based on the identified thrust acceleration, relative orbit dynamics for tight formation-keeping is established. Further, using global positioning system (GPS) measurement information, a modified extended Kalman filter (EKF) is suggested to obtain the inter-satellite relative position and relative velocity. Findings Compared with the normal EKF and the adaptive robust EKF, the proposed modified EKF has better estimation accuracy in radial and along-track directions because of accurate compensation of thrust acceleration. Meanwhile, high-precision relative navigation results depend on high-precision acceleration sensors. Finally, simulation studies on a chief-deputy formation flying control system are performed to verify the effectiveness and superiority of the proposed relative navigation algorithm. Social implications This paper provides a reference in solving the problem of high-precision relative navigation in tight formation-keeping application. Originality/value This paper proposes a novel on-line identification method for thrust acceleration and shows that thrust identification-based modified EKF is more efficient in relative navigation for tight formation-keeping.

Satellite formation keeping using differential lift and drag under J2 perturbation

Purpose The purpose of this paper is to present a method to achieve small satellite formation keeping operations by using the differential lift and drag to control the drift caused by J2 perturbation in circular or near-circular low earth orbits (LEOs). Design/methodology/approach Each spacecraft is equipped with five large flat plates, which can be controlled to generate differential accelerations. The aerodynamic lift and drag acting on a flat plate is calculated by the kinetic theory. To maintain the formation within tracking error bounds in the presence of J2 perturbation, a nonlinear Lyapunov-based feedback control law is designed. Findings Simulation results demonstrate that the proposed method is efficient for the satellite formation keeping and better accuracy advantage in comparison with classical approaches via the fixed maximum differential aerodynamic acceleration. Research limitations/implications Because the aerodynamic force will reduce drastically as the orbital altitude increases, the formation keeping control strategy for small satellites presented in this paper should be limited to the scenarios when satellites are in LEO. Practical implications The formation keeping control method in this paper can be applied to solve satellite formation keeping problem for small satellites in LEO. Originality/value This paper proposes a Lyapunov control strategy for satellite formation keeping considering both lift and drag forces, and simulation results show better performance with high accuracy under J2 perturbation.

Kalman filtering through the feedback adaption of prior error covariance

Abstract For Kalman filtering problems with inaccurate or mismatched process noise statistics, through proposing the feedback excavation based covariance adaption scheme, this paper elaborates a new adaptive Kalman filter for linear time-invariant systems. To relief Kalman theorys requirement on the accurate and a priori knowledge about process noise statistics, the original covariance prediction step of Kalman filter is removed in the new approach; instead, with proposed covariance adaption scheme, the prior error covariance is directly reconstructed through online excavating posterior sequence, which is also the main innovation of this work. Since the process noise covariance is not used in the new adaption scheme, the negative influence of mismatched noise statistics can be significantly reduced in proposed adaptive Kalman filter. In addition, the positive semi-definiteness of the online adapted prior error covariance is mathematically guaranteed in the new adaption scheme without imposing extra computational cost. The new approachs advantages in filtering adaptability, accuracy and simplicity are demonstrated using numerical simulations of an object tracking scenario.

Modified fuel-balanced formation keeping strategy based on actively rotating satellites in formation

Purpose The purpose of this paper is to propose a modified fuel-balanced formation keeping strategy based on actively rotating satellites in the formation in the J2 perturbed environment. Design/methodology/approach Based on the relative orbital elements theory, the J2 perturbed relative motions between different satellites in the formation are analyzed, and then, the method to estimate fuel required to keep the in-plane and out-of-plane relative motions is presented, based on which a modified fuel-balanced formation keeping strategy is derived by considering both in-plane and out-of-plane J2 perturbations. Findings Numerical simulations demonstrate that the modified fuel-balanced formation keeping strategy is valid, and the modified fuel-balanced formation keeping strategy requires less total fuel consumption than original Vadali and Alfriend’s method. Research limitations/implications The modified fuel-balanced formation keeping strategy is valid for formation flying mission whose member satellite is in circular or near-circular orbit. Practical implications The modified fuel-balanced formation keeping strategy can be used to solve formation flying keeping problem, which involves multiple satellites in the formation. Originality/value The modified fuel-balanced formation keeping strategy is proposed by considering both in-plane and out-of-plane J2 perturbations, which further reduce the fuel consumption than the original Vadali and Alfriend’s method.