Design of ESR Slag for Remelting 9CrMoCoB Steel under Simple Protective Ar Gas

Thermodynamic calculations by using Factsage 7.3 and simple protective gas electroslag remelting (ESR) experiments were conducted to design the appropriate ESR slag for remelting the qualified 9CrMoCoB ingot. First, the proper basic slag was determined based on the phase diagram of CaF2–CaO–Al2O3–x%MgO calculated using Factsage 7.3. Second, equilibrium reactions between 9CrMoCoB and the basic slag containing varied SiO2, and B2O3 contents were calculated to study the effects of B2O3 and SiO2 on B, Si, and Al contents in steel. Then, equilibrium reaction experiments were conducted to validate the calculated results. Finally, the appropriate slags were attained and the simple protective Ar gas ESR experiments were conducted to make a verification. Results showed that the liquid phase region of the slag of CaF2–CaO–Al2O3–x%MgO at 1300–1400 °C increased first, then decreased with the MgO addition. With the B2O3 content increasing, the boron content increased, while the Si, Al contents decreased, and at a given B2O3 addition, the B and Al contents decreased with the SiO2 content increasing, whereas the Si content increased. The appropriate slags for simple protective gas ESR remelting 9CrMoCoB were 55%CaF2–20%CaO–3%MgO–22%Al2O3–2%SiO2–1.3%B2O3 and 55%CaF2–20%CaO–3%MgO–22%Al2O3–3%SiO2–1.7%B2O3

Target assignment in formation reconfiguration for swarms of unmanned ships

[Objectives] To study the target assignment in the formation reconfiguration of unmanned ships,a target assignment method is proposed.[Methods] Firstly,a distance-based cost function is generated by the current positions of the unmanned ships and the fixed target points. Secondly,based on the auction theory and according to the rapidity requirement of the target assignment in the formation reconfiguration of the unmanned ship,an auction termination mechanism is proposed based on the maximum number of iterations for possible non-feasible solution in the assignment of the traditional auction algorithm, which disperses part of the simulations, thus shortening the assignment time.[Results] Finally,the simulation results show that this proposed method can quickly give an optimized target assignment scheme for the formation reconfiguration of swarms of the unmanned ships when compared with the classical Hungarian method.[Conclusions] The proposed method herein can provide an effective reference for the target assignment in the formation reconfiguration of swarms of the unmanned ships and for the study on the autonomous decision-making of the unmanned ships

Distributed neural control for cooperative tracking of uncertain nonlinear multi-agent systems under a directed network

Conference Name:2013 2nd International Symposium on Instrumentation and Measurement, Sensor Network and Automation, IMSNA 2013. Conference Address: Toronto, ON, Canada. Time:December 23, 2013 - December 24, 2013.This paper considers the cooperative tracking problem of uncertain nonlinear multi-agent systems over a directed network where only a fraction of followers have access to the state of the leader. Distributed neural cooperative controller based on the relative state information of neighboring agents is developed. An algebraic Riccati equation is employed to show the stability of overall multi-agent systems. Based on Lyapunov stability analysis, the developed controller guarantees that the state of each agent synchronizes to that of the leader if the leader has directed paths to all followers, and the synchronization errors are uniformly ultimately bounded. The main advantage of the developed controller is that it can be implemented in a distributed manner without requiring the accurate model of each agent. Future works include an extension to the output feedback case. ? 2013 IEEE

Extended-State-Observer-Based Collision-Free Guidance Law for Target Tracking of Autonomous Surface Vehicles with Unknown Target Dynamics

This paper is concerned with the target tracking problem of an autonomous surface vehicle in the presence of a maneuvering target. The velocity information of target is totally unknown to the follower vehicle, and only the relative distance and angle between the target and follower are obtained. First, a reduced-order extended state observer is used to estimate the unknown relative dynamics due to the unavailable velocity of the target. Based on the reduced-order extended state observer, an antidisturbance guidance law for target tracking is designed. The input-to-state stability of the closed-loop target tracking guidance system is analyzed via cascade theory. Furthermore, the above result is extended to the case that collisions between the target and leader are avoided during tracking, and a collision-free target tracking guidance law is developed. The main feature of the proposed guidance law is twofold. First, the target tracking can be achieved without using the velocity information of the target. Second, collision avoidance can be achieved during target tracking. Simulation results show the effectiveness of the proposed antidisturbance guidance law for tracking a maneuvering target with the arbitrary bounded velocity