The purpose of this paper is to investigate the problem of the initial attitude detumbling and acquisition for micro‐satellite using geomagnetism with the aid of the pitch…
Abstract
Purpose
The purpose of this paper is to investigate the problem of the initial attitude detumbling and acquisition for micro‐satellite using geomagnetism with the aid of the pitch momentum bias, and the application of the feedback linearization method, H∞ and μ‐synthesize control theory in the robust attitude acquisition controller design.
Design/methodology/approach
The pitch flywheels establish the momentum bias state in the beginning of the detumbling stage and keep the momentum bias state thereafter. The geomagnetic change rate feedback detumbling controller is used to detumble the micro‐satellite and the gyroscope rigidity is utilized to capture orbital negative normal orientation in the detumbling and attitude acquisition phase. Feedback linearization method is adopted to obtain the linear attitude dynamics. Based on the feedback linearization model, a quasi proportion differential (PD) controller is designed, meanwhile H∞ and μ‐synthesis control theories are adopted to synthesis the robust attitude acquisition controllers.
Findings
The pitch momentum bias‐aided attitude detumbling and acquisition method make the capture of the orbital negative normal orientation faster and more accurate than the classical initial operation process. Quasi PD and H∞ have greater robustness than the classical PD attitude acquisition controller in normal geomagnetic case; quasi PD and μ‐synthesis have greater robustness than the classical PD attitude acquisition controller in magnetic storm case.
Originality/value
Provides pitch momentum bias‐aided attitude detumbling and acquisition method for the micro‐satellite and the robust attitude acquisition controller design technology.
Details
Keywords
Taking urban-rural disparity into account, this research examines the current service provision of preschool education at the local level in China.
Abstract
Purpose
Taking urban-rural disparity into account, this research examines the current service provision of preschool education at the local level in China.
Design/methodology/approach
Following a qualitative design, the research is based on a case study on the preschool service provision in Luochuan County in China, with data collected from semi-structured interviews with grassroots officials and residents from the county’s rural and urban regions.
Findings
This research finds that preschool services are inefficiently delivered between the county’s rural and urban areas. While services are oversupplied in rural regions, the popular demand for urban kindergartens is inadequately addressed. Moreover, the tuition subsidy offered by the local government has drastically decreased in recent years.
Research limitations/implications
This research is confined to a single-case study, so its findings are not necessarily applicable to all Chinese localities. Nevertheless, it proves that these problems in preschool service provision can be a result of the central authority’s tight control.
Social implications
Given China’s rapid urbanization and fertility decline, this research argues that overinvestment in rural kindergartens can be a widespread phenomenon throughout China. It also suggests a decreasing popular demand for other public services, such as childcare, in Chinese rural regions. This research calls for special attention to the persistent regional discrepancy in preschool service standards and the welfare cuts after the revenue centralization reform.
Originality/value
This research contributes to a clearer picture of the current preschool service delivery by Chinese local governments, which remains largely underexplored by far. It also provides updates on the country’s long-existing urban-rural discrepancy in preschool services.