Electromagnetic forces generated by the inter-action of component satellites can be used to release companion satellites. Optimal release trajectories for companion satellite system using inter-electromagnetic forces ...Electromagnetic forces generated by the inter-action of component satellites can be used to release companion satellites. Optimal release trajectories for companion satellite system using inter-electromagnetic forces were investigated. Firstly,nonlinear relative motion dynamic equations of a two-craft electromagnetic companion satellite system were derived in spatial polar coordinates. Then principles of electromagnetic satellite formation flying were introduced. Secondly,the characteristics of the electromagnetic companion satellites release were analyzed and optimal release trajectories of companion satellites using electromagnetic forces were obtained using Gauss pseudospectral method. Three performance criteria were chosen as minimum time,minimum acceleration of the separation distance and minimum control acceleration. Finally,three release examples including expansion along separation distance, rotation in orbital plane and stable formation reconfiguration were given to demonstrate the feasibility of this method. Results indicated that the release trajectories can converge to optimal solutions effectively and the concept of release companion satellites using electromagnetic forces is practicable.展开更多
According to the consequences of software failures, software faults remaining in safety-critical systems can be classified into two sets： common faults and fatal faults. Common faults cause slight loss when they are ...According to the consequences of software failures, software faults remaining in safety-critical systems can be classified into two sets： common faults and fatal faults. Common faults cause slight loss when they are activated. A fatal fault can lead to significant loss, and even damage the safety-crltical system entirely when it is activated. A software reliability growth model for safety-critical systems is developed based on G - 0 model. And a software cost model is proposed too. The cost model considers maintenance and risk costs due to software failures. The optimal release policies are discussed to minimize the total software cost. A numerical exampie is provided to illustrate how to use the results we obtained.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.11102007)
文摘Electromagnetic forces generated by the inter-action of component satellites can be used to release companion satellites. Optimal release trajectories for companion satellite system using inter-electromagnetic forces were investigated. Firstly,nonlinear relative motion dynamic equations of a two-craft electromagnetic companion satellite system were derived in spatial polar coordinates. Then principles of electromagnetic satellite formation flying were introduced. Secondly,the characteristics of the electromagnetic companion satellites release were analyzed and optimal release trajectories of companion satellites using electromagnetic forces were obtained using Gauss pseudospectral method. Three performance criteria were chosen as minimum time,minimum acceleration of the separation distance and minimum control acceleration. Finally,three release examples including expansion along separation distance, rotation in orbital plane and stable formation reconfiguration were given to demonstrate the feasibility of this method. Results indicated that the release trajectories can converge to optimal solutions effectively and the concept of release companion satellites using electromagnetic forces is practicable.
基金Sponsored by the Ph.D. Programs Foundation of Ministry of Education of China (Grant No. 20020213017).
文摘According to the consequences of software failures, software faults remaining in safety-critical systems can be classified into two sets： common faults and fatal faults. Common faults cause slight loss when they are activated. A fatal fault can lead to significant loss, and even damage the safety-crltical system entirely when it is activated. A software reliability growth model for safety-critical systems is developed based on G - 0 model. And a software cost model is proposed too. The cost model considers maintenance and risk costs due to software failures. The optimal release policies are discussed to minimize the total software cost. A numerical exampie is provided to illustrate how to use the results we obtained.
