Ran Sun, Aidang Shan, Chengxi Zhang and Qingxian Jia
This paper aims to investigate the feasibility of using the combination of Lorentz force and aerodynamic force as a propellantless control method for spacecraft formation.
Abstract
Purpose
This paper aims to investigate the feasibility of using the combination of Lorentz force and aerodynamic force as a propellantless control method for spacecraft formation.
Design/methodology/approach
It is assumed that each spacecraft is equipped with several large flat plates, which can rotate to produce aerodynamic force. Lorentz force can be achieved by modulating spacecraft’s electrostatic charge. An adaptive output feedback controller is designed based on a sliding mode observer to account for unknown uncertainties and the absence of relative velocity measurements. Aiming at distributing the control input, an optimal control allocation method is proposed to calculate the electrostatic charge of the Lorentz spacecraft and control commands for the atmospheric-based actuators.
Findings
Numerical examples are provided to demonstrate the effectiveness of the proposed control strategy in the presence of J2 perturbations. Simulation results show that relative motion in a formation can be precisely controlled by the proposed propellantless control method under uncertainties and unavailability of velocity measurements.
Research limitations/implications
The controllability of the system is not theoretically investigated in the current work.
Practical implications
The proposed control method introduced in this paper can be applied for small satellites formation in low Earth orbit.
Originality/value
The main contribution of the paper is the proposal of the propellantless control approach for satellite formation using the combination of Lorentz force and aerodynamic force, which can eliminate the requirement of the propulsion system.
Details
Keywords
Robert G. Tian and Yan Wu
The purpose of this paper is to examine the construction of virtual community identities among Chinese internet users and their motivation for lurking, posting or flaming.
Abstract
Purpose
The purpose of this paper is to examine the construction of virtual community identities among Chinese internet users and their motivation for lurking, posting or flaming.
Design/methodology/approach
Taking Qiangguo Luntan as an online study site the authors apply an ethnographic approach for the research, a method that is becoming more and more favourable by scholars in study virtual communities. The data gathered are mainly through participant observation and in‐depth interviews.
Findings
The findings suggest that internet bulletin boards enable ordinary Chinese to have their identities as politically activated citizens constructed in cyberspace. A consistent enthusiasm for political participation can be found in user's pennames, signature files, political clusters, and online behaviours.
Originality/value
This is an original case study.