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Passive and active compensation of uncertainty in trussed architectures.

机译：被动和主动补偿桁架结构中的不确定性。

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This thesis numerically investigates dynamic stiffness versus strength trades of imperfect passive and active trusses that fail in local elastic-stability modes and are relevant to space vehicle programs. First, nominal deterministic design scaling laws of trussed architectures are derived as functions of a primary design variable set. The laws describe the dynamic stiffness versus strength trades found as simultaneously optimized structural-controller Pareto fronts. The laws are functions of the primary design variables which are non-dimensional terms forming a design framework. These terms include descriptions of structural systems' slenderness, strength, tensioning, and active control mass fraction properties as well as a key active control power term. The laws are derived again in the presence of member straightness or eccentricity imperfections as well as sensor and actuator noise. These two imperfections are each characterized as a statistical uncertainty. Reliability-based design optimization techniques are employed to propagate the uncertainty distributions. The resulting nondeterministic scaling laws can be compared to the deterministic laws to study the pathology of the architectures. The pathology is how the architectures' non-deterministic performance departs from deterministic performance as a consequence of statistical imperfections.;Unlike previous studies, this design framework finds sensitivities to statistical imperfections in terms of non-dimensional design variables. Also, design decision points are probabilistically understood, e.g., when it is favorable to integrate active control. Member eccentricity statistical characterizations either position the active control favorability decision point at approximately 10% compensator mass fraction or shift the point to many multiples of this fraction. The former decision point occurs if eccentricity scales with truss member length and the latter decision points occur if eccentricity scales with truss member radius. In either case, a roughly 30% probabilistic performance penalty across the design space studied is paid for the statistical uncertainties considered.;The principal contributions of this investigation concern control design for active structures. Dynamically distinct high-authority control designs were discovered to coexist with low-authority control designs at traditionally low-authority compensator power rates. In the high-authority regime power is expended to dampen and, unlike in the low-authority regime, also stiffen the closed-loop structural systems. High-authority designs are feasible irrespective of truss topology and connectivity. The active control power term accurately predicts the pivotal compensator power rates delineating the two control authority regimes within the non-dimensional design framework. These predictions are statistically insensitive to active control mass fraction and imperfection uncertainty.
机译：本文数值研究了不完善的被动和主动桁架的动态刚度与强度的关系，这些桁架在局部弹性稳定模式下失效，并且与航天器程序有关。首先，将桁架结构的名义确定性设计缩放定律推导为主要设计变量集的函数。这些定律描述了动态刚度与强度的关系，同时发现了同时优化的结构控制器Pareto前沿。这些定律是主要设计变量的功能，这些主要设计变量是构成设计框架的无量纲术语。这些术语包括对结构系统的细长，强度，张紧和主动控制质量分数特性的描述，以及关键的主动控制功率项。在存在零件平直度或偏心度缺陷以及传感器和执行器噪声的情况下，再次得出定律。这两个缺陷分别被表征为统计不确定性。采用基于可靠性的设计优化技术来传播不确定性分布。可以将由此产生的不确定性缩放定律与确定性定律进行比较，以研究架构的病理学。病理学是由于统计缺陷导致体系结构的非确定性性能偏离确定性性能的原因；与以往的研究不同，此设计框架从无量纲设计变量中发现了对统计缺陷的敏感性。而且，例如当有利于集成主动控制时，概率地理解设计决策点。成员偏心率统计特征要么将主动控制偏好决策点定位在补偿器质量分数的10％左右，要么将该点偏移到该分数的许多倍。如果偏心率随桁架构件的长度成比例，则发生前一个决策点；如果偏心率随桁架构件的半径成比例，则出现后一个决策点。在这两种情况下，由于所考虑的统计不确定性，在研究的整个设计空间中大约要支付30％的概率性能损失。此项研究的主要贡献涉及活动结构的控制设计。发现动态不同的高权限控制设计可以与低权限控制设计在传统的低权限补偿器功率率下共存。在高权限状态下，功率被消耗，与低权限状态下不同，它也使闭环结构系统变硬。无论桁架的拓扑结构和连接性如何，高权限设计都是可行的。主动控制功率项可以准确地预测在无量纲设计框架内描述两个控制权制度的枢轴补偿器功率率。这些预测在统计上对主动控制质量分数和缺陷不确定性不敏感。

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