A 4-DOF Virtual Flight Test in a Wind Tunnel

A conventional virtual flight test generally refers to a 3-DOF dynamic flight test in a wind tunnel. In the wind tunnel test, the model aircraft is connected to the strut through a 3-DOF rotation mechanism and installed in the wind tunnel test section so that the model displacement is constrained but has 3 degrees of angular motion freedom. Open-loop and closed-loop control of the aircraft model is achieved by directly driving the rudder surface or by using commands from the flight control system.4-DOF Virtual Flight Test not only has three axes of freedom of rotation around the center of mass but can also rise and sink in the vertical direction. The 4-DOF virtual flight test can simulate real flight in a wind tunnel more realistically than the 3-DOF virtual flight test [12]. It fills the gap between actual test flights and traditional wind tunnel tests, and can simulate flight conditions more realistically before actual test flights, which has outstanding advantages in shortening the development cycle of aircraft, reducing risks and costs.常规虚拟飞行试验通常指风洞中的三自由度（3-DOF）动态飞行试验。在风洞试验中，飞行器模型通过三自由度转动机构与支撑杆相连，并安装于风洞试验段内，使得模型的平动位移受到约束，但保留三个角运动自由度。通过直接驱动舵面或接入飞行控制系统的指令，即可实现飞行器模型的开环与闭环控制。四自由度（4-DOF）虚拟飞行试验不仅具备绕质心转动的三个轴系自由度，还可在垂直方向完成升降运动。相较于三自由度虚拟飞行试验，四自由度虚拟飞行试验能够在风洞中更真实地模拟实际飞行场景[12]。该试验填补了实际试飞与传统风洞试验之间的技术空白，可在实际试飞前更逼真地模拟飞行工况，在缩短飞行器研发周期、降低研发风险与成本方面具备显著优势。