讨论：如仅靠数字式电传飞控，能多大程度上克服su27系的 ...

拜读渣浪上@双垂尾Luna的围脖了解到EF2000在研制时也遇到了跨音速抬头问题，其根源是跨音速机动减速导致的压力中心前移以及激波/附面层变化导致的重心后升力损失造成飞机俯仰载荷突变，最初采用限制攻角的方式解决，后来发现对飞机性能影响较大，类似于苏27的“跨音速陷阱”，解决方式也是调整飞控采用非对称刚度反馈，而不是加强结构，下图可以看到，这个俯仰载荷突变很容易超过飞机的Nz max。使得飞机的跨音速过载包线仅降低1.5G。

现在基本已知筷子弟出于种种原因在气动上基本没有太考虑克服“跨音速陷阱”的问题，那么飞控就成了改善“跨音速陷阱”的唯一可能，如果参照台风机的经验（非对称刚度反馈）考虑仅靠数字式电传飞控的调整，能多大程度上克服su27系的跨音速过载陷阱？

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以下是原文献的abstract：This paper presents the control law functionality for mitigating the transonic pitch-up of the Eurofighter EF2000 aircraft. First, the aerodynamic problem of the transonic pitch-up on Eurofighter is outlined and solution strategies based on feedback control are discussed.Predicting the pitch-up from model information and measurements in theory allows a more
complete pitch-up reduction but is very sensitive to model and measurement errors.Detecting the pitch-up when it affects the aircraft leads to a late control surface response but is robust with respect to model and measurement errors. Then, the design of the Asymmetric Pitch Stiffness Feedback (a detection based control law measure), which is the core of Eurofighter's transonic pitch-up mitigation functionality is presented in detail. The linear and non-linear stability assessment approach for this function is reviewed. Additional features of the transonic pitch-up mitigation functionality for Eurofighter are discussed.
Finally, flight test results are presented. The solution implemented reduces the pitch-up transient to 1.5 g and constrains the maximum vertical load factor to respect the structural load limits.

以下是原文滴Conclusion
A transonic pitch up mitigation system for the Eurofighter EF2000 aircraft has been presented. The asymmetric stiffness feedback detects uncommanded pitch-up motion in the transonic flight regime. The feature reduces the transonic pitch up transient to max. 1.5g. Together with a transonic pitching down moment function and a vertical load factor authority rate limit, the asymmetric stiffness functionality allows keeping the load factor nz within the structural load limits of the aircraft. In addition, the handling characteristics in the transonic flight envelope are considerably improved.拜读渣浪上@双垂尾Luna的围脖了解到EF2000在研制时也遇到了跨音速抬头问题，其根源是跨音速机动减速导致的压力中心前移以及激波/附面层变化导致的重心后升力损失造成飞机俯仰载荷突变，最初采用限制攻角的方式解决，后来发现对飞机性能影响较大，类似于苏27的“跨音速陷阱”，解决方式也是调整飞控采用非对称刚度反馈，而不是加强结构，下图可以看到，这个俯仰载荷突变很容易超过飞机的Nz max。使得飞机的跨音速过载包线仅降低1.5G。

现在基本已知筷子弟出于种种原因在气动上基本没有太考虑克服“跨音速陷阱”的问题，那么飞控就成了改善“跨音速陷阱”的唯一可能，如果参照台风机的经验（非对称刚度反馈）考虑仅靠数字式电传飞控的调整，能多大程度上克服su27系的跨音速过载陷阱？

ef2k.png (50.84 KB, 下载次数: 8)

下载附件 保存到相册

2015-12-10 09:31 上传

以下是原文献的abstract：This paper presents the control law functionality for mitigating the transonic pitch-up of the Eurofighter EF2000 aircraft. First, the aerodynamic problem of the transonic pitch-up on Eurofighter is outlined and solution strategies based on feedback control are discussed.Predicting the pitch-up from model information and measurements in theory allows a more
complete pitch-up reduction but is very sensitive to model and measurement errors.Detecting the pitch-up when it affects the aircraft leads to a late control surface response but is robust with respect to model and measurement errors. Then, the design of the Asymmetric Pitch Stiffness Feedback (a detection based control law measure), which is the core of Eurofighter's transonic pitch-up mitigation functionality is presented in detail. The linear and non-linear stability assessment approach for this function is reviewed. Additional features of the transonic pitch-up mitigation functionality for Eurofighter are discussed.
Finally, flight test results are presented. The solution implemented reduces the pitch-up transient to 1.5 g and constrains the maximum vertical load factor to respect the structural load limits.

以下是原文滴Conclusion
A transonic pitch up mitigation system for the Eurofighter EF2000 aircraft has been presented. The asymmetric stiffness feedback detects uncommanded pitch-up motion in the transonic flight regime. The feature reduces the transonic pitch up transient to max. 1.5g. Together with a transonic pitching down moment function and a vertical load factor authority rate limit, the asymmetric stiffness functionality allows keeping the load factor nz within the structural load limits of the aircraft. In addition, the handling characteristics in the transonic flight envelope are considerably improved.