Xia Guoqing

A GA path planner based on domain knowledge for AUV

Autonomous underwater vehicle (AUV) is extensively used for marine engineering, oceanography research and some other civil area. Path planning is a necessary and fundamental technology for AUV autonomy, its goal is to search an optimized path according to some optimization criteria in a certain environment and makes AUV fulfill its mission objectives along the collision-free path. Based on the theory and the application of GA, This work presents a global path planning method for AUV based on GA and domain knowledge in a large-scale chart. The grid method is adopted to set up a discrete space model for path planning based on known chart data, and each data structure of a grid stores some property such as digital elevation, permit and so on. A kind of decimal grid-coordinate coding scheme which adopting a variable length chromosome encoding is presented. The generating method of initial population, the fitness evaluation function, the evolve strategy and some superiority genetic operators are all designed and introduced in detail. And some measures are also adopted to improve the searching capability and to speed up convergence of the algorithm. The planning results show that the GA path planner has some advantages such as more stronger ability for searching a global optimized and viable path, efficiency superiority, convergence rapidly, path described more simply and perspicuous. The GA path planner based on domain knowledge becomes an important element of AUV autonomy ability and can be potentially applied as an on-line path planner for AUV.

Simulation analysis of static and dynamic characteristics of once-through steam generator in concentric annuli tube

The once-through steam generator (OTSG) in concentric annuli tube is a new type of steam generator which applies double side to transfer heat. The heat flux between the water of centric tube, outside annuli tube and that of annulus channel is assumed to be equal, and then the steam generator’s model is built by lumped parameters with moving boundary. In the basis of the built model, static and dynamic characteristics are analyzed. The static characteristics are proved by experiment results in a 19-tube once-through steam generator of Babcock & Wilcox. The characteristics that the lengths of three regions (subcooled region, nucleate boiling region, superheat region) change with power can be explained by theory analysis. The dynamic characteristics accord with the heat and hydraulics and the results of analysis according to the mechanism.

Analysis of Aircraft Sortie Generation Process Using a Closed Queuing Network Model

Sortie generation rate (SGR) is a key factor of military aircraft’s combat effectiveness. An approximate analytical method is presented to analyzing aircraft sortie generation process by modeling the process as a closed queuing network (CQN). Each station in the CQN provides a kind of service to aircraft. The service time of servers in a same station can be unequal. A modified mean value analysis (MVA) algorithm is used to capture the aircraft’s sortie generation rate and the other performance measures such as queue length and resource utilization. The bottle-neck of the sortie generation rate can be ascertained. The quality of the analytical approximation is demonstrated through comparison with simulation result.

Approximate mean value analysis of airport sortie generation process on condition aircrafts launch in batches

Sortie generation rate (SGR) which means sustainable number of airport launches per period is a key factor of military aircrafts combat effectiveness. An approximate mean value analysis (MVA) method is presented to evaluate airport sortie generation process which is modeled as a closed queuing network (CQN). N aircrafts circle in the process and each batch which is to launch contains Nb readied aircrafts. The approximate MVA algorithm is used to capture the aircrafts sortie generation rate and the other performance measures such as queue length in each station and resource utilization of servers. The bottle-neck of the airport sortie generation process can be found out through the utilization. The quality of the analytical approximation is demonstrated through comparison with simulation results.