Abstract
According to the characteristics of space missions and space environment, to slow performance deterioration and possible reliability attenuation for aerospace mechanisms, an operational reliability system control methodology is proposed in this article. A space manipulator – a kind of typical complicated aerospace mechanism – is chosen as the research object. First, considering relevant materials and structure mechanism of joint and link parts, the influence factors of operational reliability for space manipulator are divided. Then, by introducing the responding layer factors, a mapping relationship between the influence factors of operational reliability and control variables is analysed. On this basis, a new method to build a hierarchical control system of operational reliability for the aerospace mechanisms is proposed. In this method, the mechanism how the influence factors of operational reliability are introduced into the control system is defined, and an operational reliability system control model is built, which is made up of task planning, path planning, and motion control. Finally, the proposed methodology is further explained with the operational stability of a space manipulator as an example. After analysing the mapping relationship among the influence factors of operational reliability, the factors of responding layer and control variables, a multi-objective optimization method based on Nondominated Sorting Genetic Algorithm II (NSGA-II) is proposed to ensure the operation stability for a space manipulator. These optimization objectives are introduced into the optimized control model at path planning level as constraints. According to these constraints, the optimized control system can be adjusted to improve the operation stability of the manipulator, and the operational reliability is also improved during this process correspondingly. Simulation results prove the effectiveness of the proposed method.
Highlights
It is necessary to achieve the high reliability and the long service life for space mechanisms to complete the Chinese manned space program, deep space exploration and many other national major projects
The mechanism how the influence factors of operational reliability are introduced into the control system is defined, and the operational reliability system control model that is made up of task planning, path planning and motion control is built
A hierarchical control system model based on the operational reliability is proposed in this article
Summary
It is necessary to achieve the high reliability and the long service life for space mechanisms to complete the Chinese manned space program, deep space exploration and many other national major projects. A prediction system that based on the onorbit fault tree of space manipulator is built by the analysis of operational reliability factors This system uses three control variables – joint angles, joint angular velocity and joint torque – as fault predictors to do research on prediction of joint fault and to obtain accurate judgment of on-orbit faults. The optimization to the stability of manipulator can improve its quality of the task implementation and reduce operation cost, so that the operational reliability is maintained effectively These controllable variables that include joint angular velocity, angular acceleration and joint torque are the concrete representation of stability on the control variable layer.
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