Robust Mission Design Through Evidence Theory and Multi-Agent Collaborative Search

In this paper, the preliminary design of a space mission is approached introducing uncertainties on the design parameters and formulating the resulting reliable design problem as a multiobjective optimization problem. Uncertainties are modelled through evidence theory and the belief, or credibility, in the successful achievement of mission goals is maximised along with the reliability of constraint satisfaction. The multiobjective optimisation problem is solved through a novel algorithm based on the collaboration of a population of agents in search for the set of highly reliable solutions. Two typical problems in mission analysis are used to illustrate the proposed methodology

Evaluation of the Metal Fatigue Solutions Electrochemical Fatigue Sensor System, March 2018

The electrochemical fatigue sensor was developed to detect very small fatigue cracks that are actively growing. To evaluate the fatigue crack capabilities and gain a better understanding of implementation needs, a laboratory test and a field monitoring program were developed to evaluate the EFS system using the CrackChek and FatigueWatch sensors, respectively. The laboratory test program consisted of evaluating the adequacy of Crackchek sensors for crack detection. The Crackchek sensors were installed on a standard steel plate specimen. An electrical discharge machining (EDM) notch was induced in the mid-length of the steel plate and a pair of sensors were installed adjacent to the notch tip. The field monitoring program consisted of evaluating the adequacy of the FatigueWatch sensors for crack detection and the general capabilities of the system for use in field applications. The sensors were installed on the Cherry Creek Bridge near Newton, Iowa, on a sacrificial specimen and on a bridge girder web in a known fatigue-sensitive location. The sacrificial specimen was a standard steel plate exactly the same as the one used for evaluating the CrackChek sensors. The EDM notch was also generated in the edge and mid-length of the specimen and a pair of sensors were installed near the notch tip. After a 13-month data collection and analysis period, no crack formed in either the sacrificial specimen or the bridge girder web where the sensors were installed. In summary, the CrackChek and FatigueWatch sensors perform well for crack detection