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.

捕獲軌跡試驗(yàn)技術(shù)的回顧

前20年中，進(jìn)行捕獲軌跡試驗(yàn)所使用的硬件設(shè)備，受到當(dāng)時(shí)的計(jì)算機(jī)技術(shù)水平和做試驗(yàn)的風(fēng)洞類型的支配。一些早期的試驗(yàn)裝置安裝在下吹式風(fēng)洞中，因此，這些用來(lái)生成外掛軌跡的裝置的運(yùn)動(dòng)速度必須比較快才行。這些裝置用模擬計(jì)算機(jī)作為軌跡生成計(jì)算機(jī)，因?yàn)檫@種計(jì)算機(jī)容易解出外掛模型的運(yùn)動(dòng)方程組，而且，如果規(guī)定適當(dāng)?shù)臅r(shí)標(biāo)的話，還能很容易地在30～45秒內(nèi)（這是一般下吹風(fēng)洞理想的試驗(yàn)時(shí)間）生成外掛物的軌跡。

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.

從模擬計(jì)算機(jī)輸出到外掛模型定位裝置的量，有些情況下是外掛物的分速度；而在其他情況下是外掛的位置。在后一種情況下，位置量是不斷更新的，因此，在洞外觀察者看來(lái)，模型的運(yùn)動(dòng)表現(xiàn)為利用速度控制的形式。

軌跡生成期間從天平上測(cè)得的力與力矩信號(hào)，在進(jìn)行數(shù)字化處理之后，儲(chǔ)存到磁帶上供脫機(jī)分析之用。利用這種數(shù)字化的數(shù)據(jù)，計(jì)算出“數(shù)字軌跡”，以決定外掛模型在所記錄的力與力矩作用下本應(yīng)生成的軌跡。然后，將“數(shù)字軌跡”同“模擬軌跡”進(jìn)行比較，來(lái)驗(yàn)證聯(lián)機(jī)軌跡生成期間控制系統(tǒng)的工作情況。這種模擬計(jì)算機(jī)方法的基本缺點(diǎn)是，開(kāi)始工作之前的準(zhǔn)備和檢查時(shí)間長(zhǎng)，一般要花20 ~40小時(shí)；再有就是會(huì)出現(xiàn)電子漂移現(xiàn)象。