Topology Optimization in Aircraft and Aerospace Structures Design

Topology optimization has become an effective tool for least-weight and performance design, especially in aeronautics and aerospace engineering. The purpose of this paper is to survey recent advances of topology optimization techniques applied in aircraft and aerospace structures design. This paper firstly reviews several existing applications: (1) standard material layout design for airframe structures, (2) layout design of stiffener ribs for aircraft panels, (3) multi-component layout design for aerospace structural systems, (4) multi-fasteners design for assembled aircraft structures. Secondly, potential applications of topology optimization in dynamic responses design, shape preserving design, smart structures design, structural features design and additive manufacturing are introduced to provide a forward-looking perspective.     

Multidisciplinary aircraft design and evaluation software integrating CAD,analysis, database,and optimization

The development of an overall strategy to design the aircraft using analysis codes is presented. The procedure is automated through the integrated software MADE (multidisciplinary aircraft design and evaluation) developed in this research that enables the determination of an optimum set of aircraft configurations. The core ingredients of MADE are (i) analysis codes, which utilizes initial sizing, aerodynamics, mass, stability and control, propulsion, performance, and RCS (radar cross section) analyses, (ii) optimization utilizing gradient-based optimization technique, response surface modeling, and Carpet plot, (iii) database utilizing commercial Oracle 8i database management system (DBMS) and OCI (Oracle call interface) to save design parameters and aircraft configurations. The complexity of input and output containing massive amounts of data has previously placed severe limitations on the use of aircraft analysis codes by the general aerospace engineering community. By using C++ and the Microsoft Foundation Classes to develop a graphical user interface (GUI) and using DBMS, it is believed that use of MADE can avoid the additional cumbersome, and sometimes tedious, task of preparing the required input files manually and can make the transition to general usability in an aerospace engineering environment. For detail explanation, examples of E–R diagram, class diagram, and data flows between codes for the MADE are also presented.     

Two approaches for truss topology optimization: a comparison for practical use

This paper discusses ground structure approaches for topology optimization of trusses. These topology optimization methods select an optimal subset of bars from the set of all possible bars defined on a discrete grid. The objectives used are based either on minimum compliance or on minimum volume. Advantages and disadvantages are discussed and it is shown that constraints exist where the formulations become equivalent. The incorporation of stability constraints (buckling) into topology design is important. The influence of buckling on the optimal layout is demonstrated by a bridge design example. A second example shows the applicability of truss topology optimization to a real engineering stiffened membrane problem.     

Robust multidisciplinary UAS design optimisation

There are many applications in aeronautical/aerospace engineering where some values of the design parameters/states cannot be provided or determined accurately. These values can be related to the geometry (wingspan, length, angles) and or to operational flight conditions that vary due to the presence of uncertainty parameters (Mach, angle of attack, air density and temperature, etc.). These uncertainty design parameters cannot be ignored in engineering design and must be taken into the optimisation task to produce more realistic and reliable solutions. In this paper, a robust/uncertainty design method with statistical constraints is introduced to produce a set of reliable solutions which have high performance and low sensitivity. Robust design concept coupled with Multi-Objective Evolutionary Algorithms (MOEAs) is defined by applying two statistical sampling formulas; mean and variance/standard deviation associated with the optimisation fitness/objective functions. The methodology is based on a canonical evolution strategy and incorporates the concepts of hierarchical topology, parallel computing and asynchronous evaluation. It is implemented for two practical Unmanned Aerial System (UAS) design problems; the first case considers robust multi-objective (single-disciplinary: aerodynamics) design optimisation and the second considers a robust multidisciplinary (aero-structures) design optimisation. Numerical results show that the solutions obtained by the robust design method with statistical constraints have a more reliable performance and sensitivity in both aerodynamics and structures when compared to the baseline design.     

基于LPV的航空发动机鲁棒变增益控制

随着我国现代化进程的不断加快,航天航空技术标准越来越高,对于航空发动机运转工况的鲁棒性和适应性提出了更高的要求。传统的航空发动机变增益设计步骤繁琐,不能将发动机置于整个航空器的运转去考虑设计,使发动机变增益缺乏相应的稳定性和适应性,易出现系统问题。为此,提出一般基于LPV的航空发动机鲁棒变增益控制系统,依据航空发动机结构参数,考虑到航空器在空中负载特性,计算出新的约束极点 模糊变增益,在航空器发动机工作范围连续增益,避免了传统增益切换情况,在转速控制上确定误差等因素,将非线性控制设计分解为多个线性子问题,使航空器控制系统能够沿着LPV参数轨迹保持良好的运转,保持稳定性能。仿真实验证明,提出的基于LPV的航空发动机鲁棒变增益控制系统控制效果优于传统方法,在航空器发动机转速改变时,控制精度能够满足要求 ,改变航空器负载时,有效对目标进行变增益控制。提出的控制方法对航空发动机鲁棒变增益控制问题提供了新的解决办法,具有较大应用价值。     

基于工作流驱动的航天产品分布式协同设计环境

在分析目前航天产品研制面临形势和存在问题的基础上,引入了构建分布式协同设计环境的解决途径,同时针对产品协同设计过程中知识、任务、对象、人员和流程的统一描述问题,提出了协同设计环境中定义和运行的唯一数据源——任务统一模型(Task Unified Model,简称为TUM)的概念,并对TUM定义、组织、视图转换及运行机制进行了详细论述。然后基于Eclipse RCP和Web Portal技术构建了分布式协同设计环境APEngine,实现了面向产品设计全过程的 TUM 建模、实例化和运行过程。最后通过某航天历史型号设计的工程实际应用,证明了本文研究成果具有较强的工程应用价值。     

A multi-regulator sliding mode control strategy for output-constrained systems

This paper proposes a multi-regulator control scheme for single-input systems, where the setpoint of a regulated output must be changed under the constraint that a set of minimum-phase outputs remain within prescribed bounds. The strategy is based on a max–min selector system frequently used in the aerospace field. The regulators used for the regulated and limited outputs are of the sliding mode type, where the sliding variable is defined as the difference between an output and its allowable limit. The paper establishes overall asymptotic stability, as well as invariance properties leading to limit protection. The design methodology is illustrated with a detailed simulation example on thrust control of a turbofan engine.     

基于矢量控制的电动伺服控制系统设计

目前在航空航天等领域,电动伺服系统被越来越多地应用于火箭和导弹的矢量推进控制、飞机和导弹的舵面控制、飞机的转弯和刹车控制等;电动伺服系统作为飞行器控制系统的关键子系统,其性能直接影响着飞行器的机动性能乃至飞行安全,因而对其技术指标和可靠性都有着很高的要求;文章所介绍的电动伺服控制系统采用基于矢量控制的软件策略和基于DSP的电力电子电路设计技术,具有超调小、响应快、抗负载干扰能力强及实时性好等优点,目前已经过工程的应用验证。     

Controller certification

A modern problem from aerospace control involves the certification of a large set of potential controllers with either a single plant or a fleet of potential plant systems, with both plants and controllers being MIMO and, for the moment, linear. Experiments on a limited number of controller/plant pairs should establish the stability and a certain level of margin of the complete set. We consider this certification problem for a set of controllers and provide algorithms for selecting an efficient subset for testing. This is done for a finite set of candidate controllers and, at least for SISO plants, for compact infinite set. In doing this, the ν-gap metric will be the main tool. Computational examples are given, including one of certification of an aircraft engine controller. The overarching aim is to introduce truly MIMO margin calculations and to understand their efficacy in certifying stability over a set of controllers and in replacing legacy single-loop gain and phase margin calculations.     

Optimal design of controlled multibody dynamic systems for performance,robustness and tolerancing

The multidisciplinary design approach has gained increasing popularity in recent years due to its ability to deal with conflicting design requirements imposed by discipline-specific objectives. The traditional design process involving multiple disciplines is typically a sequential process where the design objectives are met one at a time in a sequence of designs. However, in doing so, unnecessary limitations are imposed on the design parameters and the final design is far from being optimal. The effectiveness of integrated design methodology has been proven and such designs are being obtained in many applications. However, most of the work in this area has been problem and/or system specific and does not address important manufacturing considerations, such as tolerance allocation, robustness with respect to machining tolerances, etc. The results presented in this paper are intended to contribution towards filling these gaps. In particular, the new approach will help designers avoid a common known pitfall of performance optimization, i.e. the fact that designs that are optimized for performance alone are notoriously sensitive to deviations from the nominal design. Thus, optimizing for performance alone leads to designs that fall below acceptable standards of robustness; they are also expensive to manufacture because the tolerances must be kept very tight to ensure acceptable performance. The approach presented here will allow the user to systematically tradeoff performance versus robustness and tolerancing concerns. A proof-of-concept example that was solved to evaluate this methodology is also presented in this paper. This example provides a convincing demonstration of the fact that small sacrifices in performance can yield huge benefits in the other areas, provided a methodology is available for making these tradeoffs in a systematic way. This especially can be used by designers in various fields such as automotive, aerospace, deployable structures, machine tools (including hexapods), robotic systems, precision machinery, etc.     

Short-time parameter optimization with flight control application

A design approach is presented for systems operating over a relatively short period of time about various operating points with state variable constraints. This class of problems is especially relevant to certain flight control problems. The design approach is applied to a simplified model of longitudinal dynamics of the F-4 aircraft operating in three widely separated flight conditions. A linear model is assumed about each operating point. Control is achieved via constrained state feedback. The basic problem is then to minimize a suitable integral quadratic performance measure subject to state variable constraints. The main theoretical result is theorem 1 which supplies the inequality constraints required to guarantee short-time stability. The short-time optimization problem is ultimately reduced to a nonlinear programming problem with inequality constraints.     

网格技术在航空制造业的应用研究

基于中国航空工业第二集团公司对网格的技术需求分析,探讨航空企业施行网格技术的必要性,提出实施网格技术的具体技术方案,以飞机结构大规模优化计算为实例验证网格计算的应用,证明了网格技术在航空制造业应用中的有效性．     

A Novel Intelligent Multiobjective Simulated Annealing Algorithm for Designing Robust PID Controllers

This paper proposes an intelligent multiobjective simulated annealing algorithm (IMOSA) and its application to an optimal proportional integral derivative (PID) controller design problem. A well-designed PID-type controller should satisfy the following objectives: 1) disturbance attenuation; 2) robust stability; and 3) accurate setpoint tracking. The optimal PID controller design problem is a large-scale multiobjective optimization problem characterized by the following: 1) nonlinear multimodal search space; 2) large-scale search space; 3) three tight constraints; 4) multiple objectives; and 5) expensive objective function evaluations. In contrast to existing multiobjective algorithms of simulated annealing, the high performance in IMOSA arises mainly from a novel multiobjective generation mechanism using a Pareto-based scoring function without using heuristics. The multiobjective generation mechanism operates on a high-score nondominated solution using a systematic reasoning method based on an orthogonal experimental design, which exploits its neighborhood to economically generate a set of well-distributed nondominated solutions by considering individual and overall objectives. IMOSA is evaluated by using a practical design example of a super-maneuverable fighter aircraft system. An efficient existing multiobjective algorithm, the improved strength Pareto evolutionary algorithm, is also applied to the same example for comparison. Simulation results demonstrate high performance of the IMOSA-based method in designing robust PID controllers.     

The implementation of a knowledge-based framework for the aerodynamic optimization of a morphing wing device

In the field of aerospace engineering currently a lot of research effort is directed towards the reduction of cruise drag of civil transport aircraft in order to reduce fuel burn, and hence environmental impact and costs. In order to reduce cruise drag, a promising method is under consideration by adjusting, or rather morphing the rear part of the aircraft’s wing during cruise flight. Given the premature state of knowledge of such a design implementation, a knowledge-based computational framework is developed. The purpose of this framework is to allow for an aerodynamic optimization of a section of the wing. The framework is set up in such a way that all relevant design knowledge generated in the process can be captured and used in a subsequent mechanical design process. In this fashion, the complex design process of a novel morphing wing device can be automated to a certain degree. This automation can be used to construct a large number of different feasible and optimized designs with varying boundary conditions of a complex experimental device.This article describes the initial 2-dimensional aerodynamic design step of the morphing device under consideration and how it is implemented in a knowledge-based optimization framework. It describes the initial stage of the development of this tool, as it will be expanded by a number of design steps that each adds more detail to the design in all relevant aspect fields (aerodynamic, structural, actuation, etc.). Ultimately, this tool will be used to obtain a thorough evaluation of a number of different proposed structural solutions and allow for a comparison between them.     

基于LMI的综合飞行/推进控制系统设计

飞机在飞行时,外界气流总存在不确定的扰动,对飞机的性能甚至稳定性会产生消极的影响。以某型飞机作为研究对象,在建立了综合飞行/推进系统（纵向）小偏离线性化数学模型后,根据H∞鲁棒控制理论所推导出的线性矩阵不等式,设计出干扰情况下的状态反馈控制器。仿真结果表明,所设计出的鲁棒控制器能够到达控制要求,在存在较大干扰时有一定的抑制作用。对于（LMI）线性矩阵不等式的H∞鲁棒控制方法在设计综合飞行/推进鲁棒控制系统时,是可行的,且能较好的解决飞行时存在的扰动问题。     

Direct computation of solution spaces

In engineering, it is often desirable to find a subset of the set of feasible designs, a solution space, rather than a single solution. A feasible design is defined as a design which does not violate any constraints and has a performance value below a desired threshold. Performance measure, threshold value and constraints depend on the specific problem. For evaluation of a design with respect to feasibility, a model is required which maps the design parameters from the input space onto the performance measures in the output space. In state-of-the-art methodology, iterative sampling is used to generate an estimate of the frontier between feasible and infeasible regions in the input space. By evaluating each sample point with respect to feasibility, areas which contain a large fraction of feasible designs are identified and subsequently resampled. The largest hypercube containing only feasible designs is sought, because this results in independent intervals for each design parameter. Estimating this hypercube with sufficient precision may require a large number of model evaluations, depending on the dimensionality of the input space. In this paper, a novel approach is proposed for modeling the inequality constraints and an objective function in a way for which a linear formulation can be used, independently of the dimensionality of the problem. Thereby the exact solution for the largest feasible hypercube can be calculated at much lower cost than with stochastic sampling as described above, as the problem is reduced to solving a linear system of equations. The method is applied to structural design with respect to the US-NCAP frontal impact. The obtained solution is compared to numerical solutions of an identical system, which are computed using reduced order models and stochastic methods. By this example, the high potential of the new direct method for solution space computation is shown.     

Self-organizing approximation-based control for higher order systems.

Adaptive approximation-based control typically uses approximators with a predefined set of basis functions. Recently, spatially dependent methods have defined self-organizing approximators where new locally supported basis elements were incorporated when existing basis elements were insufficiently excited. In this paper, performance-dependent self-organizing approximators will be defined. The designer specifies a positive tracking error criteria. The self-organizing approximation-based controller then monitors the tracking performance and adds basis elements only as needed to achieve the tracking specification. The method of this paper is applicable to general nth-order input-state feedback linearizable systems. This paper includes a complete stability analysis and a detailed simulation example.     

作战飞机方案设计评估指标体系研究

作战飞机方案设计评估是飞机研制过程的关键环节,而方案设计评估指标体系的建立是保证方案设计科学合理的重要基础.针对现代作战飞机发展的新技术、新思想以及作战飞机方案设计的特点,提出以系统效能、寿命周期费用和研制周期作为上层评估指标,并对以上指标进行了分解,给出构造的作战飞机方案设计的评估指标体系,同时对该评估指标体系作了简要介绍与可用性分析,最后给出了具体的设计方案验证的方法并运用实例对该评估指标体系进行了验证,结果表明该指标体系在对作战飞机设计方案评估时具有一定的实用性.     

基于能量管理的飞翼飞行器迫降轨迹设计

针对飞翼类飞行器迫降轨迹设计问题,建立力学运动模型对无动力滑翔过程进行分析,采用满足始末端约束和飞行器性能约束的Dubins轨迹进行轨迹搜索,并提出根据迫降初始能量状态采用广义Dubins类型航线规划低能迫降轨迹和高能迫降轨迹。通过批量仿真验证了迫降飞行阶段分段管理和能量实时评估实现迫降轨迹设计的方法使飞行器精确回收到迫降点的同时兼具适应环境干扰的鲁棒性,对实际工程应用具有重要意义。