Observability of a class of under-observation systems

Abstract

Exploring the deep space of the universe is crucial to promote research on basic scientific issues, such as the origin of the solar system, evolution of planets, and origin of life. Using probes to detect deep-space objects has become the focus of the development of various aerospace powers. As the deep-space exploration task is performed far away from the earth, it is difficult to guarantee the safe and reliable operation of deep-space probes by relying on ground control networks to guide their navigation; as such, deep-space probes should have autonomous navigation ability. An autonomous navigation system based on sequence images has the advantages of low cost, low power consumption, full application, and simple data structure, which can effectively reduce the space and energy burden of the autonomous navigation system of deep-space probes, and is an ideal means to realize autonomous navigation in deep-space probes. However, because of the lack of prior information about deep-space exploration targets and systematic error in a deep-space complex environment, the autonomous navigation system based on sequence images is a typical under-observable system. To improve the accuracy and engineering practicability of typical autonomous navigation systems, it is necessary to guide the design and engineering realization of autonomous navigation systems based on theoretical research on observability. In response to the actual needs of observability theory research, in this paper, we first systematically expound the current research status of existing theories and methods from three aspects: characterization, determination, and quantification of the observability of nonlinear systems. Then, the observability analysis method of a class of under-observation systems—autonomous navigation systems based on sequence images—is investigated. The research status of observability for such systems is given, and the advantages and disadvantages of each method are discussed. Finally, by summarizing existing results, limitations in the observability research of under-observation systems at present and future development trends are discussed.