インターネットを利用した操船シミュレータの開発-II : ピア・ツー・ピア型レーダARPAシミュレータの改良

Abstract

There are some cases in which marine traffic lanes are modified with the construction of bridges or other marine structures. And, as the need arises, assessments of marine traffic environment are carried out using ship handling simulator. In these cases, it is important to investigate the difficulty of operations of a ship along the modified passage and ship operator's stresses and strains. Moreover, it is also significant to collect data as much as possible to make a fair judgment. However, the trial, which is carried out in cooperation with a selected mariner, usually takes much time and sufficient data is not always collected. Therefore, it is needed to develop cost-effective tools for maritime assessment. The author proposed a Radar/ARPA simulator based on the internet in the previous report. The simulator is a PC-based application program and the code is written in Microsoft Visual C++ and DirectPlay. DirectPlay is a low-level application programming interface (API) for creating multiplayer games and other network applications. The details of the proposed Radar/ARPA simulator were shown and problems encountered on developing were also reported. In this paper, improved parts of the simulation algorithm are described. Special attention was paid to synchronized time steps of computers. To validate the improvements, feasibility tests are carried out based on a wireless LAN. The discrepancies of trajectories between computers are investigated with/without installation of the network time protocol (NTP) and large time lag of system clocks. It was shown that trajectories of the improved algorithm satisfy the suitably provided permissible level.