Approximate output tracking for nonlinear non-minimum phase systems with an application to flight control

An unstable zero-dynamics is a known obstruction to inducing exact asymptotic tracking for an open set of output trajectories with internal stability. This paper proposes a procedure for achieving approximate tracking for a nonlinear system whose linearization possesses real right-half plane zeros. The method is guaranteed to remove the right-half plane zeros while the other zeros remain in their previous location; moreover, it provides information on the class of signals for which good approximate tracking can be obtained. With other methods, the right-half plane zeros are eliminated but the final location of the remaining zeros is not known a priori. The design procedure is illustrated on a trajectory control problem of an aircraft in rapid manoeuvres. Simulations illustrate the computations involved and show that precise lateral and longitudinal manoeuvres can be performed, even in the presence of uncertainties.     

Changing the role of the air traffic controller: how will free flight affect memory for spatial events?

At present, air traffic controllers (ATCOs) exercise strict control over routing authority for aircraft movement in airspace. The onset of a free flight environment, however, may well result in a dramatic change to airspace jurisdictions, with aircraft movements for the large part being governed by aircrew, not ATCOs. The present study examined the impact of such changes on spatial memory for recent and non-recent locations of aircraft represented on a visual display. The experiment contrasted present conditions, in which permission for manoeuvres is granted by ATCOs, with potential free flight conditions, in which aircrew undertake deviations without explicit approval from ATCOs. Results indicated that the ATCO role adopted by participants impacted differently on short-term and long-term spatial representations of aircraft manoeuvres. Although informing participants of impending deviations has beneficial effects on spatial representations in the short term, long-term representations of spatial events are affected deleteriously by the presentation of subsequent information pertaining to other aircraft. This study suggests strongly that recognition of the perceptual and cognitive consequences of changing to a free flight environment is crucial if air safety is not to be jeopardized.     

Issues of numerical accuracy and stability in inverse simulation

Inverse simulation algorithms based on integration have been widely applied to predict the control input time histories required for aircraft to follow ideally defined manoeuvres. Several different inverse simulation algorithms are available but these different methods are all subject to a number of numerical and stability problems, such as high frequency oscillation effects and also lower frequency oscillatory phenomena termed “constraint oscillations”. Difficulties can also arise in applications involving discontinuous manoeuvres, discontinuities within the model or input constraints involving actuator saturation. This paper has shown that the dynamic response properties of the internal system are the cause of the so-called “constraint oscillation” phenomenon. In addition, a new inverse simulation approach based on the constrained derivative-free Nelder–Mead search-based optimisation method has been developed to eliminate problems of discontinuities and saturation. Simulation studies involving nonlinear ship models suggest that this new approach leads to improved properties in terms of convergence and numerical stability.     

Control Algorithm for Taking off and Landing Manoeuvres of Quadrotors in Open Navigation Environments

International Journal of Control, Automation and Systems - This paper presents a control algorithm for the taking off and landing manoeuvres of a quadrotor aircraft in open navigation environments....     

Structural load alleviation using distributed delay shaper: Application to flexible aircraft

Lightweight flexible aircraft suffers from unwanted oscillatory vibrations during aircraft manoeuvres. A recently developed distributed-delay signal (DZV) shaper is therefore proposed to be applied as a feedforward controller to alleviate the manoeuvre loads, as an alternative to traditional structural filters used routinely in this context. Structural filters are essentially linear low-pass filters with bandwidth below the significant flexible modes, applied to control signals generated either by the pilot’s direct input or by the flight control system. It has been showed that if instead a properly tuned signal shaper is used, better performance can be achieved: first, the target modes are significantly attenuated while the responsiveness of the aircraft is less compromised and secondly, the oscillatory nature of the vibrations are reduced. The high fidelity simulation results on a full scaled dynamic model of a highly flexible blended wing–body (BWB) aircraft show that in comparison to traditional structural filters, signal shapers significantly reduce the wing root loading (forces and moments) which provides potential structural benefits.     

Non-linear anti-windup for manual flight control

In this paper we address the windup problem arising from actuator magnitude and rate saturation for the linearized longitudinal short-period dynamics of a tailless aircraft model around any trim flight condition. The proposed anti-windup scheme allows for more aggressive manoeuvres than the standard “command limiting” approach. Moreover, the compensation law guarantees stability of the controlled aircraft for any pilot command and enforces flight quality specifications whenever they are achievable within the given control constraints. “Pilot-in-the-loop” simulations confirm the effectiveness of the control strategy.     

飞机防滑刹车系统新型控制策略研究

飞机防滑刹车控制系统是重要的机载设备,对飞机的安全起飞和着陆有着重要作用.NASA研究数据表明,传统的PD+ PBM控制律在混合跑道刹车性能下降,且在低速段容易出现严重的打滑现象,导致系统刹车效率降低.对飞机防滑刹车系统的工作原理进行了分析,针对传统控制律的不足,提出了一种基于免疫PID的新型刹车控制策略.在计算机建立...     

基于WinCC组态的实验室气候试验综合监控系统设计

如何实现飞机实验室气候试验过程中各种环境试验工况的快速切换,保证试验的连续性,是飞机气候实验室综合监控系统必须解决的问题。针对飞机气候试验控制任务要求,提出一套基于WinCC组态的分布式综合试验监控系统,采用分布式网络对各个工艺设备进行协调控制,利用模块化的设计方法对各试验工况进行定义,实现不同气候环境的模拟;利用WinCC组态软件开发了友好、方便的人机界面接口,实现对试验过程和设备运行状态的实时监测,有效地满足了试验需求,为飞机气候试验安全可靠进行提供了有利保障。     

Optimal terrain-following for towed-aerial-cable sensors

Towed-aerial cable systems are often used for towing decoys from aircraft and for collecting electromagnetic data from low altitudes. Airborne cable systems are typically controlled by maneuvering the aircraft, which can limit the safe altitude of the towed-sensor package. In this paper, a real-time optimal control strategy for controlling a towed-cable system is proposed that uses cable winch control to control the altitude of the towed-body. The controller is based on a receding horizon control approach, where the aircraft senses the terrain profile ahead of the towed-body with a relatively short time horizon. This information is sent to the controller, which updates the cable winch reel acceleration to safely avoid colliding with the terrain, while keeping the towed-sensor close to the desired altitude for obtaining good measurements. The controller is developed for a simplified system model and implemented in a multibody cable system model that incorporates cable flexibility and elasticity.     

Eigenstructure versus optimal control for decoupling

A study about how to design a control law that not only keeps following a reference attitude but also maintains attitude decoupling due to the vehicle manoeuvres has been performed. A control law was designed for a satellite launcher vehicle using eigenstructure assignment and optimal control method in order that the vehicle tracks a reference attitude and also to decouple the yaw response from roll and pitch manoeuvres and to decouple the pitch response from roll and yaw manoeuvres. It has been noticed that in order to achieve this objective it is necessary to use a linear coupled model to design the control law instead of the usual linear uncoupled model used to design the tracking control law. The design was based on a complete linear coupled model obtained from the complete vehicle non-linear model by linearisation at each trajectory point. A comparison of the system stability working with both control laws has also been performed. After all, the design was assessed with the vehicle time varying non-linear model showing a good performance and robustness. The used design method is explained and a case study for the Brazilian satellite launcher VLS is reported. By the end of the work some suggestions about how to implement this control law have also been studied.     

基于闭合轮廓提取和部分特征匹配的飞机识别

飞机识别在军事遥感中具有重大意义。该文针对以往飞机识别方法的不足,为更准确地对高分辨率可见光机场区域图像进行飞机目标的定位和型号判别,提出了一种基于闭合轮廓提取,并通过部分特征匹配进行机型识别的疗法。首先对图像进行各向异性扩散处理,提取闭合轮廓并进行儿何特征分析,定位飞机目标,提取目标的关键特征参数,实现机型判别。实验证明,该方法具定位准确、识别率高,可准确识别飞机型号,能得到比较精确的飞机外形描述,可有效对抗阴影、遮挡等干扰,具有很好的稳健性。随着遥感成像技术不断发展,图像分辨率越来越高,能够获得更准确、更完整的飞机轮廓,因此,这种方法具有很好的发展趋势．     

无人机数字摄影测量系统的设计和应用

无人机数字摄影测量系统为适应城市规模化测绘生产需要而设计开发,项目从机体设计、航线设计、通讯设计、监控设计、数据处理等各个层面,对航空摄影的原理、方法及相关参数进行了深入探讨和简要总结;项目进行了自动驾驶实验、超视距飞行实验、控制飞行实验、发动机空中停车紧急处理实验、干扰实验等常规实验,完成了数百平方公里摄影任务,实现了无人机摄影测量一体化的整合集成;应用结果表明,该系统具有“三高一低”的重要特性（高机动性、高分辨率、高度集成、低成本）,而且更加适应城市规模化测绘生产需要.     

飞机拦阻网微机自动立网系统的设计

分析了所研制的飞机拦阻网微机自动立网系统的工作原理、组成和功能;该立网系统是飞机拦阻设备中自动立网的控制部分,能够计算飞机在跑道终端的滑跑速度,在飞机的滑跑速度不符合安全规定的情况下,可以快速、准确地做出判断,产生立网控制信号,立起拦阻网拦截色机,同时发出报警信号;在飞机拦阻网中应用泼自动立网系统能够提高飞机安全着陆的可靠性,有着重要的军事意义和经济效益。     

Sliding mode of control of flexible spacecraft under disturbance torque

A control system design is presented for large angle rotational manoeuvres of a spacecraft-beam-tip body (an antenna or a reflector) configuration. Although this approach is applicable to three-axis manoeuvres, for simplicity only single-axis control is treated here. It is assumed that an unknown but bounded disturbance torque acts on the spacecraft. A sliding mode attitude control law is derived for slewing of the space vehicle. This slewing control law requires only the attitude error and its derivative for feedback. It does not need any information on the elastic motion of the system. For the damping of the elastic motion, a stabilizer is seperately designed based on the asymptotically decoupled system describing the elastic deflections in two orthogonal planes. Simulation results are presented to show that precise large rotational manoeuvres can be performed using an attitude controller and elastic mode stabilizer in spite of the uncertainty in the system.     

Optimal horizontal guidance law for aircraft in the terminal area

The automation of many of the functions currently performed by the controllers and pilots is essential for a safe and efficient air traffic control (ATC) system. A major aspect of the overall ATC system is the guidance and flight control of aircraft. This paper deals with the horizontal guidance of aircraft in and near the terminal area. The problem of guiding an aircraft in minimum time from an arbitrary point to the outer marker is formulated as a nonlinear optimal control problem, and the control law solution is obtained by the application of the maximum principle. It is found that for some initial states the problem is singular. Furthermore, the extremal controls for this problem are not unique. Consequently, the optimal controls must be obtained on the basis of the value of the performance index. The control law is implemented in the form of a digital computer program which computes the optimal trajectory for arbitrary initial conditions.     

Maximizing the number of conflict-free aircraft using mixed-integer nonlinear programming

We address the conflict detection and resolution problem in air traffic control, where an aircraft conflict is a loss of separation between aircraft trajectories. Conflict avoidance is crucial to ensure flight safety and remains a challenging traffic control problem. We focus on speed control to separate aircraft and consider two approaches: (i) maximize the number of conflicts resolved and (ii) identify the largest set of conflict-free aircraft. Both problems are modeled using mixed-integer nonlinear programming and a tailored greedy algorithm is proposed for the latter. Computational efficiency is improved through a pre-processing algorithm which attempts to reduce the size of the conflict resolution models by detecting the existence of pairwise potential conflicts. Numerical results are provided after implementing the proposed models and algorithms on benchmark conflict resolution instances. The results highlight the benefits of using the proposed pre-processing step as well as the versatility and the efficiency of the proposed models.     

舵机速率饱和时的飞机尾旋改出控制

通过闭环控制进行飞机尾旋自动改出时, 由于控制能量不足舵机速率饱和有可能引起振荡问题. 本文基于反步法设计一种抗舵机速率饱和的尾旋自动改出控制方法. 将飞机模型看做角度、角速度和舵机三层级联结构, 首先利用反步法设计角度和角速度层控制律, 然后在舵机层控制律根据舵机速率饱和限制约束控制量, 同时通过Lyapunov函数保证闭环系统渐近稳定. 对所得控制方法抗舵机速率饱和的效果进行了分析. 以某现代歼击机模型为对象的仿真试验表明, 该方法在舵机存在速率饱和的情况下控制效果明显优于传统动态逆方法与传统反步法.     

Passification-based robust flight control design

A passification-based robust autopilot for attitude control of flexible aircraft under parametric uncertainty is designed. A high gain controller with forced sliding motions is used to secure good performance over a wide range of the aircraft model parameters. The shunting method is applied to ensure closed-loop system stability under lack of aircraft state information. The series reference model is used to assign the desired closed-loop system performance. An example illustrating a typical design procedure for aircraft attitude control in the horizontal plane for different flight conditions is given. The simulation results demonstrate the efficiency and high robustness of the suggested control system.     

一种简易的多回路控制系统优化设计方法研究

给出了一种简易的控制系统设计方法——标准特征多项式设计方法,多回路控制系统采用这种方法将使控制系统设计的工作量大为简化。在此基础上,采用NCD工具箱,用标准特征多项式方法得到的参数值作为NCD（nonlinear control design）模块的初始化值对控制系统的参数进一步进行优化,并与任意选择的6组参数值作为NCD模块初始化值而得到的优化效果进行了比较。还对飞行控制的多回路控制系统的鲁棒性进行了研究。结果证明,用标准特征多项式和NCD优化方法,设计方便,并且系统有很好的鲁棒性。     

基于自适应线性自抗扰控制的飞机防滑刹车系统重构控制

飞机防滑刹车系统是确保飞机安全起飞、着陆和滑跑的重要航空机电系统. 除了其动力学中的强非线 性、强耦合以及参数时变外, 潜在的执行器等组件故障也会严重降低防滑刹车系统的安全性与可靠性. 为满足故障 及扰动状态下系统的性能需求, 本文提出了一种基于自适应线性自抗扰控制的飞机防滑刹车系统重构控制方法. 根据飞机防滑刹车系统的组成结构及工作原理对其进行数学建模, 并对执行器注入故障因子. 设计了自适应线性 自抗扰重构控制器, 同时分析了整个闭环系统的稳定性. 该控制器将组件故障、外部干扰以及测量噪声等视为总扰 动, 根据状态误差反馈和系统输出信息, 利用BP神经网络在线优化更新扩张状态观测器和状态误差反馈律参数, 从 而更精确地观测与补偿总扰动带来的不利影响. 最后, 在不同跑道环境下的仿真结果验证了所提出重构控制器的适 应性和鲁棒性.