Review of Captive Trajectory Testing Techniques

In the past two decades captive trajectory testing has been performed using hardware dictated by the current state-of-the-art in computer technology and the type of wind tunnel in which testing was conducted. Some of the earlier systems were installed in blowdown tunnels, and it was imperative that these systems used for trajectory generation be relatively fast. These systems used an analog computer as the trajectory generation computer since it afforded an easy solution to the store model equations of motion and, with the proper time scaling, could easily generate store trajectories within the 30 to 45 sec during which the desired test conditions were prevalent.

捕获轨迹试验技术的回顾

前20年中，进行捕获轨迹试验所使用的硬件设备，受到当时的计算机技术水平和做试验的风洞类型的支配。一些早期的试验装置安装在下吹式风洞中，因此，这些用来生成外挂轨迹的装置的运动速度必须比较快才行。这些装置用模拟计算机作为轨迹生成计算机，因为这种计算机容易解出外挂模型的运动方程组，而且，如果规定适当的时标的话，还能很容易地在30～45秒内（这是一般下吹风洞理想的试验时间）生成外挂物的轨迹。

The outputs from the analog computer to the store model positioning rig were the store component velocities in some cases and store position in others. In the latter case, the positions were continually being updated and, to an outside observer, the model movement would appear as velocity-based control. 

The balance force and moment signals obtained during the trajectory were digitized and stored on magnetic tape for off-line analysis. From the digitized data a "digital trajectory" was computed to determine the trajectory that should have been generated by the store model in response to the recorded forces and moments. The "digital trajectory" was then compared to the "analog trajectory" for verification of the controlsystem operation during on-line trajectory generation. The basic disadvantages associated with the analog computer method were the long initial setup and checkout time, typically 20 to 40 hr, and electronic drifts.

从模拟计算机输出到外挂模型定位装置的量，有些情况下是外挂物的分速度；而在其他情况下是外挂的位置。在后一种情况下，位置量是不断更新的，因此，在洞外观察者看来，模型的运动表现为利用速度控制的形式。

轨迹生成期间从天平上测得的力与力矩信号，在进行数字化处理之后，储存到磁带上供脱机分析之用。利用这种数字化的数据，计算出“数字轨迹”，以决定外挂模型在所记录的力与力矩作用下本应生成的轨迹。然后，将“数字轨迹”同“模拟轨迹”进行比较，来验证联机轨迹生成期间控制系统的工作情况。这种模拟计算机方法的基本缺点是，开始工作之前的准备和检查时间长，一般要花20 ~40小时；再有就是会出现电子漂移现象。