In the conventional experiment to assess the towing operations, the towing stability of the towed vessel has been evaluated under the condition without lateral motion of the tug-boat. However, the tug-boats may have a lateral force to change the direction of the towed vessel. In this study, experiments have been conducted considering unsteady conditions in the towing system. First, a towing test system in a Circular Water Channel (CWC) using the conventional experimental method is built. Second, the towing characteristics of the towed vessel are investigated using the conventional method, and they are compared with other research results and stability discriminant criteria. Third, the lateral motion of the tug-boat was modeled as a sinusoidal motion using a forced oscillation device changing frequency and amplitude. Finally, the discussion is given in terms of both towing- and course-stability of the towed vessel according to the lateral motion of the tug-boat.

在评估拖曳操作的常规实验中，已在没有拖船横向运动的条件下评估了拖曳船的拖曳稳定性。但是，拖船可能会产生横向力来改变被拖船的方向。在这项研究中，已经进行了考虑牵引系统中不稳定条件的实验。首先，使用常规实验方法在圆形水道（CWC）中建立拖曳测试系统。其次，使用常规方法研究拖船的拖曳特性，并将其与其他研究结果和稳定性判别标准进行比较。第三，使用改变频率和幅度的强制振荡装置将拖船的横向运动建模为正弦运动。最后，