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首頁> 外文學(xué)位 >Semi-active control of helicopter vibration using controllable stiffness and damping devices.
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Semi-active control of helicopter vibration using controllable stiffness and damping devices.

機譯：使用可控制的剛度和阻尼裝置半主動控制直升機的振動。

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Semi-active concepts for helicopter vibration reduction are developed and evaluated in this dissertation. Semi-active devices, controllable stiffness devices or controllable orifice dampers, are introduced; (i) in the blade root region (rotor-based concept) and (ii) between the rotor and the fuselage as semi-active isolators (in the non-rotating frame). Corresponding semi-active controllers for helicopter vibration reduction are also developed. The effectiveness of the rotor-based semi-active vibration reduction concept (using stiffness and damping variation) is demonstrated for a 4-bladed hingeless rotor helicopter in moderate- to high-speed forward flight. A sensitivity study shows that the stiffness variation of root element can reduce hub vibrations when proper amplitude and phase are used. Furthermore, the optimal semi-active control scheme can determine the combination of stiffness variations that produce significant vibration reduction in all components of vibratory hub loads simultaneously. It is demonstrated that desired cyclic variations in properties of the blade root region can be practically achieved using discrete controllable stiffness devices and controllable dampers, especially in the flap and lag directions. These discrete controllable devices can produce 35–50% reduction in a composite vibration index representing all components of vibratory hub loads. No detrimental increases are observed in the lower harmonics of blade loads and blade response (which contribute to the dynamic stresses) and controllable device internal loads, when the optimal stiffness and damping variations are introduced. The effectiveness of optimal stiffness and damping variations in reducing hub vibration is retained over a range of cruise speeds and for variations in fundamental rotor properties. The effectiveness of the semi-active isolator is demonstrated for a simplified single degree of freedom system representing the semi-active isolation system. The rotor, represented by a lumped mass under harmonic force excitation, is supported by a spring and a parallel damper on the fuselage (assumed to have infinite mass). Properties of the spring or damper can then be controlled to reduce transmission of the force into the fuselage or the support structure. This semi-active isolation concept can produce additional 30% vibration reduction beyond the level achieved by a passive isolator. Different control schemes (i.e. open-loop, closed-loop, and closed-loop adaptive schemes) are developed and evaluated to control transmission of vibratory loads to the support structure (fuselage), and it is seen that a closed-loop adaptive controller is required to retain vibration reduction effectiveness when there is a change in operating condition. (Abstract shortened by UMI.)
機譯：本文開發(fā)并評估了直升機減振的半主動概念。引入了半主動裝置，可控剛度裝置或可控孔阻尼器。 （i）在葉片根部區(qū)域（基于轉(zhuǎn)子的概念），以及（ii）在轉(zhuǎn)子和機身之間作為半主動隔離器（在非旋轉(zhuǎn)框架中）。還開發(fā)了用于減少直升機振動的相應(yīng)半主動控制器。基于旋翼的半主動減振概念（使用剛度和阻尼變化）的有效性已在中速至高速向前飛行的4葉片無鉸鏈旋翼直升機上得到證明。敏感性研究表明，當使用適當?shù)姆群拖辔粫r，根??部元素的剛度變化可以減少輪轂振動。此外，最佳的半主動控制方案可以確定剛度變化的組合，這些變化會同時降低振動式輪轂負載的所有分量中的振動。已經(jīng)證明，使用離散的可控制的剛度裝置和可控制的阻尼器，尤其是在襟翼和滯后方向上，實際上可以實現(xiàn)葉片根部區(qū)域的特性的期望的周期性變化。這些離散的可控設(shè)備可以使代表振動輪轂載荷的所有分量的復(fù)合振動指數(shù)降低35-50％。當引入最佳剛度和阻尼變化時，在葉片負載和葉片響應(yīng)（有助于動態(tài)應(yīng)力）和可控制的設(shè)備內(nèi)部負載的低次諧波中，沒有觀察到有害的增加。最佳剛度和阻尼變化在降低輪轂振動方面的有效性在一定的巡航速度范圍內(nèi)以及基本轉(zhuǎn)子特性的變化中得以保持。通過簡化的表示半主動隔離系統(tǒng)的單自由度系統(tǒng)，證明了半主動隔離器的有效性。轉(zhuǎn)子由諧波力激勵下的集總質(zhì)量表示，由彈簧和平行減震器支撐在機身上（假定具有無限質(zhì)量）。然后可以控制彈簧或減震器的特性，以減少將力傳遞到機身或支撐結(jié)構(gòu)中。這種半主動隔離的概念可以使振動降低30％以上，這比被動隔離器要達到的水平要低。開發(fā)和評估了不同的控制方案（即開環(huán)，閉環(huán)和閉環(huán)自適應(yīng)方案），以控制振動載荷向支撐結(jié)構(gòu)（機身）的傳遞，并且可以看出，閉環(huán)自適應(yīng)控制器是需要在工作條件發(fā)生變化時保持減振效果。 （摘要由UMI縮短。）

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