Trajectory tuning for the tracking problem of the underactuated mechanical systems: application to the PVTOL aircraft

The Planer vertical take-off and landing (PVTOL) aircraft is a typical example of an underactuated mechanical system and has a nonminimum-phase nature. When considering output tracking control, the Input/Output (I/O) linearization method is not appropriate since the stability of the internal dynamics is not guaranteed. Hauser et al. regarded this system as a slightly nonminimum-phase system which approximates to a minimum-phase one. Their control scheme yielded good results when the coupling factor was small, but the results were not acceptable when the coupling factor increased. In this article, we propose two approaches to improve the control performance. First, we consider the approximation error of Hauser's scheme as uncertainty, and apply the Linear Quadratic Regulator (LQR) method, which possesses robustness against uncertainty, to determine the stabilizing feedback coefficients. Second, from the fact that the tracking error is unavoidable, we use the “virtual reference trajectory” to design the tracking control law, and optimize this trajectory to reduce the tracking error between the “actual reference trajectory” and the “resulting trajectory”. This optimization also improves the control performance by choosing a suitable performance index. By using our approach, we achieve better performance even if the coupling factor is increased. We show these results by numerical simulation. This work was presented, in part, at the Seventh International Symposium on Artificial Life and Robotics, Oita, Japan, January 16–18, 2002     

Modelling of Bird Strike on an Aircraft Wing Leading Edge Made from Fibre Metal Laminates – Part 2: Modelling of Impact with SPH Bird Model

Fibre Metal Laminates with layers of aluminium alloy and high strength glass fibre composite have been reported to possess excellent impact properties and be suitable for aircraft parts likely to be subjected to impacts such as runway debris or bird strikes. In a collaborative research project, aircraft wing leading edge structures with a glass-based FML skin have been designed, built, and subjected to bird strike tests that have been modelled with finite element analysis. In this second part of a two-part paper, a finite element model is developed for simulating the bird strike tests, using Smooth Particle Hydrodynamics (SPH) for modelling the bird and the material model developed in Part 1 of the paper for modelling the leading edge skin. The bird parameters are obtained from a system identification analysis of strikes on flat plates. Pre-test simulations correctly predicted that the bird did not penetrate the leading edge skin, and correctly forecast that one FML lay-up would deform more than the other. Post test simulations included a model of the structure supporting the test article, and the predicted loads transferred to the supporting structure were in good agreement with the experimental values. The SPH bird model showed no signs of instability and correctly modelled the break-up of the bird into particles. The rivets connecting the skin to the ribs were found to have a profound effect on the performance of the structure.     

多电飞机混合作动系统工作模式优化研究

采用液压作动器/电静液作动器(HA/EHA)非相似余度配置的混合作动系统是未来多全电飞机作动系统的发展趋势,为解决混合作动系统能耗大、发热严重的问题,首先对构成混合作动系统的EHA进行效率分析,通过对比效率特性,提出根据不同工况自动切换至高效率通道进行工作的优化方法;分析飞机飞行空气负载四象限工况特点,以负载力F和作动筒运动速度v构成的工况网络作为切入点,提出了自适应工况与能量回收的混合作动系统工作模式,相较于传统工作模式能耗降低50%以上,并通过仿真验证该方法的有效性。     

Mathematical model and algorithm of toolpath optimisation on aircraft structural parts

An intelligent toolpath (processing sequence) planning for fabricating aircraft structural parts is developed to obtain a minimum-length toolpath while maintaining the required machining time. The problem is first solved in the following ways. Firstly, an abstraction of the machining process is proposed to pick up the feed/retract points of each feature to be machined as the toolpath calculation basis. Secondly, the chaotic simulated annealing method is improved through storing the optimal solution, adding the control condition and selecting each parameter reasonably during the iteration of the algorithm so as to enhance its performance. What’s more, three solution-generating methods are used chaotically to obtain a better result. Lastly, the verification is conducted on four different aircraft structural parts, and the results prove that the proposed algorithm performs very well in terms of toolpath quality and computation time.     

某型发动机燃油流量调节规律研究

发动机良好的燃油流量调节规律是发动机稳定工作的保证,为了更好的改善某型发动机燃油调节规律,本研究通过对燃油流量通道的建立,并对燃油通道执行机构电磁活门和回油活门占空比的分析,来研究燃油流量的调节规律。通过研究得出,燃油系统回油活门输出的位移信号与回油活门占空比成线性的关系,此结论可作为进一步改善此型发动机燃油流量调节规律的研究基础。     

飞机机翼微小创伤修复模具的设计

针对飞机机翼被鸟击后的快速修复提出了简便、经济、精确的精模衬垫微敲修复法,该方法的关键是衬模设计,为此分析了机翼微小创伤的修复原理,提出了三种修复方案,并对比其优缺点,最终以木质叠板为衬模材料,三坐标测量仪为数据获取工具,数控铣床及磨床为加工设备的理念完成机翼衬模的设计,并得到实际应用验证,其结果良好能够满足修复要求。     

Fatigue crack growth and damage tolerance

The problems arising as a result of aging aircraft, rail and civil infrastructure have focused attention on tools for predicting the growth of cracks from small naturally occurring material discontinuities. To this end, the present paper discusses on the difference between the analysis tools needed for ab initio design and sustainment, modelling of cracks that grow from small naturally occurring material discontinuities and ways to determine the short crack da/dN versus ΔK data from long crack American Society for Testing and Materials (ASTM) tests. It also discusses how existing equations can be used to predict short crack growth and how to account for the variations seen in crack growth histories. Attention is also focused on the recent Federal Aviation Administration limit of validity ruling and the effect of the environment on widespread fatigue damage in civil transport aircraft.     

Reconditioning rotor components of gas turbine engines produced from titanium alloys by welding using modified submicrocrystalline filler materials

Experimental results show that the application of standard methods of reconditioning components of titanium alloys reduces the mechanical properties of welded joints by up to 30%. The main reasons for this are structural changes and weld defects. The modified (La, Y and B) filler materials were developed from titanium alloys with a submicrocrystalline structure. These materials produce the equiaxed and ductile structures in welded joints in titanium alloys so that the mechanical properties of the welded joints equal 0.9 of the properties of the parent metal. Consequently, the range of repairs of rotors of gas turbine engines can be greatly widened.     

Manpower supply planning for aircraft line maintenance under stochastic incidents

We plan the manpower supply for aircraft line maintenance, taking into account two types of stochastic incidents: manpower demands for a flight and the number of aircraft needing to be serviced at one time. The problem is solved to find the shift and maintenance group combinations best suited for the given airline. The optimal aircraft maintenance certification for a crew is also analyzed to improve the entire manpower structure. In addition, the addition of temporary manpower required for actual daily operations is also considered as a part of understanding the total manpower utilized in actual operations. An integrated method including scenario generation and a stochastic model is developed to deal with the problem. Finally, we perform a case study based on operating data obtained from a major airline in Taiwan. The results and findings are compared with the airline’s current manpower plan in the discussion, and suggestions for improvement are made.     

Fault‐tolerant control using command‐filtered adaptive back‐stepping technique: Application to hypersonic longitudinal flight dynamics

In this paper, the adaptive back‐stepping controller is investigated for a class of strict‐feedback systems using the command filter technique. Adaptive laws are designed for updating the controller parameters when both the plant parameters and actuator‐failure parameters are unknown. Furthermore, the auxiliary dynamics is developed to deal with the input constraints. Closed‐loop stability and asymptotic‐state tracking are ensured. The method is applied to the longitudinal dynamics of a generic hypersonic aircraft in the presence of actuator faults and input constraints. Based on the parameter estimation, the command‐filtered adaptive back‐stepping control is presented. Simulation results on the control‐oriented model show that the proposed approach achieves good tracking performance. Copyright © 2015 John Wiley & Sons, Ltd.