International Journal of Control, Automation and Systems 18(X) (2020) 1-14 http://dx.doi.org/10.1007/s12555-019-0487-5 ISSN:1598-6446 eISSN:2005-4092 http://www.springer.com/12555 Adaptive Neural Network Model-based Event-triggered Attitude Track- ing Control for Spacecraft Hongyi Xie, Baolin Wu*, and Weixing Liu Abstract: This article investigates the problem of attitude tracking control for spacecraft with limited communica- tion, unknown system parameters, and external disturbances. An adaptive control scheme with an event-triggered mechanism (ETM) is proposed to alleviate the communication burden. Radial Basis Function Neural Network (RBFNN) estimation model is developed to provide the input signals for the control module in this control scheme. Estimated attitude information of the spacecraft generated from the estimation model will only be transmitted to the control module at the instants when the ETM is violated. The neural network (NN) and the estimation model will be updated complying with an adaptive algorithm at the discrete triggering instants. It’s substantiated that all the errors of attitude tracking converge towards corresponding residuals and there are no accumulated triggering instants. Numerical simulation also demonstrates the effectiveness of the proposed control method. Keywords: Attitude tracking, event-triggered control (ETC), impulsive dynamics system, limited communication, neural networks. 1. INTRODUCTION Recently, cellular satellites have received widespread attention. This conception was proposed by Tanaka in 2006 [1]. In place of a monolithic one, Tanaka divided a satellite into several standardized modules in harmony with the subsystems of the monolithic satellites, including sensor cubic-cell cellular satellites, reaction wheel cellular satellites, power cellular satellites, etc. Since all the cellu- lar satellites are hardware-specific with shapes and struc- tures appropriate for connecting with others, they own the priority of strong flexibility, thanks for the standardized design, even a micro spacecraft could be extended to an immense one, which is nearly impossible for a traditional monolithic spacecraft without special design. Motivated by the great potential value and the extensive prospect of application of the technology of cellular satellites, DARPA (Defense Advanced Research Projects Agency) proposed the Phoenix project [2] with a purpose to recycle the malfunctioned spacecraft. Then DLR (Deutsches Zen- trum fuer Luft-und Raumfahrt e.V) proposed iBOSS (in- telligent building blocks for on-orbit-satellite servicing) [3] to practice the idea of on-orbit service and extend the lifetime of their spacecraft by cellular satellites. Inspired by the Phoenix project and actuated by the strong need of removing the space rubbish, Chang pro- posed that cellular satellites can take over the control of malfunctioned spacecraft [4], which is called cellular satellites attitude takeover control [5, 6]. Supposing a typ- ical scene that an optical spacecraft with disabled attitude control system is rolling rapidly on its orbit around Earth, while with the aid of the orbit-serving robots (OSR) [7], it’s probable to attach attitude control cellular satellites to the surface of this uncontrolled spacecraft [4]. Then the attitude control cellular satellites can generate control torques by themselves to stabilize the satellite, and the re- stored spacecraft can track a desirable attitude according to specific requirements. Since none of the known disabled spacecraft owns the standardized interfaces as the cellular satellites do, the attitude control cellular satellites connect with the disabled spacecraft without any wire or interface. Hence, both the data transmission and the energy trans- mission between a cellular satellite and a served spacecraft are wireless. Since cellular satellites are small modules and wireless communication is employed, the communi- cation capability for cellular satellites is quite limited. So it’s necessary to take limited communication into consid- eration when designing the attitude control approaches for attitude takeover control by cellular satellites. Even if a variety of control schemes have been inves- tigated in the field of spacecraft attitude control, for in- stance, adaptive control [8, 9] is used to deal with the Manuscript received June 30, 2019; revised December 30, 2019 and March 5, 2020; accepted March 24, 2020. Recommended by Associate Editor Choon Ki Ahn under the direction of Editor Chan Gook Park. This work was supported by the National Natural Science Foundation of China under Grant 61873312 Hongyi Xie, Baolin Wu, and Weixing Liu are with the Research Center of Satellite Technology, Harbin Institute of Technology, Harbin 150001, China (e-mails: 18S118205@hit.edu.cn, wuba0001@e.ntu.edu.sg, liuweixing@hit.edu.cn). * Corresponding author. c ICROS, KIEE and Springer 2020