Inventing a Biologically Inspired, Energy Efficient Micro Aerial Vehicle

In recent years, research efforts have focused on the design, development and deployment of unmanned systems for a variety of applications ranging from intelligence and surveillance to border patrol, rescue operations, etc. Micro Aerial Vehicles are viewed as potential targets that can provide agility and accurate small area coverage while being cost-effective and can be easily launched by a single operator. The small size of MAVs allows such flight operations within confined space but the control effectors must provide sufficient maneuverability, while maintaining stability, with only limited sensing capability onboard the platform. To meet these challenges, researchers have long been attracted by the amazing attributes of biological systems, such as those exhibited by birds and insects. Birds can fly in dense flocks, executing rapid maneuvers with g-loads far in excess of modern fighter aircrafts, and yet never collide with each other, despite the absence of air traffic controllers. This paper introduces a novel framework for the design and control of a Micro Air Vehicle. The vehicle’s conceptual design is based on biologically-inspired principles and emulates a dragonfly (Odonata–Anisoptera). A sophisticated multi-layered Hybrid & Linear/Non-Linear controller to achieve extended flight times and improved agility compared to other Rotary and Flapping Wing MAV designs. The paper addresses the design and control features of the proposed QV design and gives an overview on the developmental efforts towards the prototyping of the flyer. The potential applications for such a high endurance vehicle are numerous, including air-deployable mass surveillance in cluster and swarm formations. The disposable nature of the vehicle would help in battle-field deployment as well, where such a MAV would be made available to soldiers for proximity sensing and threat level assessment. Other applications would include search and rescue operations and civilian law-enforcement.     

From the Test Benches to the First Prototype of the muFly Micro Helicopter

The goal of the European project muFly is to build a fully autonomous micro helicopter, which is comparable to a small bird in size and mass. The rigorous size and mass constraints infer various problems related to energy efficiency, flight stability and overall system design. In this research, aerodynamics and flight dynamics are investigated experimentally to gather information for the design of the helicopter’s propulsion group and steering system. Several test benches are designed and built for these investigations. A coaxial rotor test bench is used to measure the thrust and drag torque of different rotor blade designs. The effects of cyclic pitching of the swash plate and the passive stabilizer bar are studied on a test bench measuring rotor forces and moments with a 6–axis force sensor. The gathered knowledge is used to design a first prototype of the muFly helicopter. The prototype is described in terms of rotor configuration, structure, actuator and sensor selection according to the project demands, and a first version of the helicopter is shown. As a safety measure for the flight tests and to analyze the helicopter dynamics, a 6DoF vehicle test bench for tethered helicopter flight is used.     

An inversion-based Feedback/Feedforward control for robust and precise payload positioning in gantry crane systems

This paper deals with Feedback/Feedforward (FB/FF) control of a gantry crane system intended for the transport of payloads that take values over a known interval. It is also assumed that the crane is affected by unmeasurable disturbances. A new 2DoF control architecture is proposed whose purpose is to speed up the horizontal payload transition while minimizing its oscillations. The main features of the control design procedure are as follows: (1) The output FB controller is designed to ensure robust closed loop stability and steady-state exact payload positioning; (2) the disturbance is estimated by means of an observer, and its transient effect is compensated through the FF action; and (3) the robust FF control action is given by the optimally weighted sum of the two contributions due to FF Plant Inversion (FFPI) and FF Closed Loop Inversion (FFCLI) control schemes.     

Dynamic output feedback control of a flexible air-breathing hypersonic vehicle via T–S fuzzy approach

By utilising Takagi–Sugeno (T–S) fuzzy set approach, this paper addresses the robust H_∞ dynamic output feedback control for the non-linear longitudinal model of flexible air-breathing hypersonic vehicles (FAHVs). The flight control of FAHVs is highly challenging due to the unique dynamic characteristics, and the intricate couplings between the engine and fight dynamics and external disturbance. Because of the dynamics’ enormous complexity, currently, only the longitudinal dynamics models of FAHVs have been used for controller design. In this work, T–S fuzzy modelling technique is utilised to approach the non-linear dynamics of FAHVs, then a fuzzy model is developed for the output tracking problem of FAHVs. The fuzzy model contains parameter uncertainties and disturbance, which can approach the non-linear dynamics of FAHVs more exactly. The flexible models of FAHVs are difficult to measure because of the complex dynamics and the strong couplings, thus a full-order dynamic output feedback controller is designed for the fuzzy model. A robust H_∞ controller is designed for the obtained closed-loop system. By utilising the Lyapunov functional approach, sufficient solvability conditions for such controllers are established in terms of linear matrix inequalities. Finally, the effectiveness of the proposed T–S fuzzy dynamic output feedback control method is demonstrated by numerical simulations.     

Adaptive hierarchical tuning of fuzzy controllers

Fuzzy controller design includes both linear and non-linear dynamic analysis. The knowledge base parameters associated within the fuzzy rule base influence the non-linear control dynamics while the linear parameters associated within the fuzzy output signal influence the overall control dynamics. For distinct identification of tuning levels, an equivalent linear controller output and a normalized non-linear controller output are defined. A linear proportional-integral-derivative (PID) controller analogy is used for determining the linear tuning parameters. Non-linear tuning is derived from the locally defined control properties in the non-linear fuzzy output. The non-linearity in the fuzzy output is then represented in a graphical form for achieving the necessary non-linear tuning. Three different tuning strategies are evaluated. The first strategy uses a genetic algorithm to simultaneously tune both linear and non-linear parameters. In the second strategy the non-linear parameters are initially selected on the basis of some desired non-linear control characteristics and the linear tuning is then performed using a trial and error approach. In the third method the linear tuning is initially performed off-line using an existing linear PID law and an adaptive non-linear tuning is then performed online in a hierarchical fashion. The control performance of each design is compared against its corresponding linear PID system. The controllers based on the first two design methods show superior performance when they are implemented on the estimated process system. However, in the presence of process uncertainties and external disturbances these controllers fail to perform any better than linear controllers. In the hierarchical control architecture, the non-linear fuzzy control method adapts to process uncertainties and disturbances to produce superior performance.     

Development of a Rotorcraft Micro air Vehicle for Indoor Flight Research

Autonomous flight of micro air vehicles (MAVs) in hostile indoor environments poses significant challenges in terms of control and navigation. In order to support navigation and control research for indoor micro air vehicles, a four-wing tail-sitter type rotorcraft MAV weighing less than 350g has been designed in this paper. In an effort to achieve autonomous indoor flight, an embedded integrated avionic system has been developed. The modeling process has been conducted to obtain accurate six degrees of freedom dynamical model for the designed rotorcraft MAV. In addition, aerodynamic coefficients are evaluated from the results of Computational Fluid Dynamics A PI-ADRC double loop controller with inner-loop outer-loop control scheme has been proposed which takes into account the system’s nonlinearities and uncertainties. The proposed flight controller was implemented on the designed rotorcraft MAV that has undergone various simulation and indoor flight tests. Experimental results that demonstrate robustness of the proposed controller with respect to external disturbances and the capabilities of the designed rotorcraft MAV are presented.     

Contraction analysis of non-linear distributed systems

Contraction theory is a comparatively recent dynamic analysis and non-linear control system design tool based on an exact differential analysis of convergence. This paper extends contraction theory to local and global stability analysis of important classes of non-linear distributed dynamics, such as convection-diffusion-reaction processes, Lagrangian and Hamilton–Jacobi dynamics, and optimal controllers and observers. By contrast with stability proofs based on energy dissipation, stability and convergence can be determined for energy-based systems excited by time-varying inputs.

The Hamilton–Jacobi–Bellman controller and a similar optimal non-linear observer design are studied based on explicitly computable conditions on the convexity of the cost function. These stability conditions extend the well-known conditions on controllability and observability Grammians for linear time-varying systems, without requiring the unknown transition matrix of the underlying differential dynamics.     

A parallel fuzzy-controlled flexible manipulator using optical tip feedback

Investigation and development of a fuzzy-controlled highly non-linear two-axis manipulator with a single-flexible link using a novel patented optical tip displacement feedback is described. The controller comprises a parallel fuzzy supervisor that is used to alter the derivative term of a linear classical PD controller, which is updated in relation to the measured tip error and error rate.Implementation of the supervisory fuzzy controller is described using both serial and parallel operation on transputers.The design of the fuzzy rules was made with a modified closed-loop phase-plane method. The design approach results in a controller implementation that uses only 14 rules and is suitable for cheaper CPU-constrained and memory-challenged embedded processors.The benefits introduced by this procedure include a method to decide where and when the action takes effect in the controller and a greatly reduced rule base. The parallel operation achieved rise times of 0.033 s and settling times of 0.064 s for a payload of 0.7 kg considerably better than other workers did.An 128% increase in payload, 73.5% faster settling time and a reduction of steady-state error of over 50% were achieved using fuzzy control over its classical counterpart.     

PIXHAWK: A micro aerial vehicle design for autonomous flight using onboard computer vision

We describe a novel quadrotor Micro Air Vehicle (MAV) system that is designed to use computer vision algorithms within the flight control loop. The main contribution is a MAV system that is able to run both the vision-based flight control and stereo-vision-based obstacle detection parallelly on an embedded computer onboard the MAV. The system design features the integration of a powerful onboard computer and the synchronization of IMU-Vision measurements by hardware timestamping which allows tight integration of IMU measurements into the computer vision pipeline. We evaluate the accuracy of marker-based visual pose estimation for flight control and demonstrate marker-based autonomous flight including obstacle detection using stereo vision. We also show the benefits of our IMU-Vision synchronization for egomotion estimation in additional experiments where we use the synchronized measurements for pose estimation using the 2pt+gravity formulation of the PnP problem.     

Adaptive control with optimal robust tracking

The problem of optimal robust tracking in two-parameter adaptive control systems under non-linear time-varying unmodelled dynamics is examined. A new robust stability criterion is derived for analysing the robustness of adaptive control systems with non-linear time-varying model errors. Based on the concept of excess robustness and the theory of the minimum H^∞norm, a simple and feasible design algorithm is presented to synthesize a two-parameter adaptive controller which ensures that adaptive control systems can achieve the object of optimal robust tracking in the presence of non-linear time-varying unmodelled dynamics. Simulation results that demonstrate features of the two-parameter adaptive controller with optimal robust tracking in the light of the design algorithm are included.     

扑翼飞行的气动建模与仿真分析

用计算流体力学的数值仿真方法对微扑翼飞行的非定常空气动力学问题进行了建模与仿真研究。在对昆虫扑翼飞行运动的仿生模拟基础上，建立了简化的扑翼运动二维翼型的运动学与空气动力学模型。利用任意拉格朗日欧拉（ALE）有限元方法求解出N-S方程的数值解，将流场仿真结果与实验进行了对比，并分析了扑翼运动产生的前缘漩涡对升力的作用。文中的建模、分析方法和结论对微扑翼飞行器的分析设计和应用提供了一定的理论依据。     

基于领航-跟随的有人/无人机编队队形保持控制

针对有人/无人机编队飞行过程中的队形保持问题,采用领航-跟随策略设计一种有人/无人机编队队形保持控制器.首先从编队作战体系和控制原理角度设计有人/无人机编队控制系统结构;然后基于领航有人机与跟随无人机平面位姿的几何关系,建立编队内相对距离-角度运动学模型;最后在考虑僚机控制系统时变扰动的情况下,针对编队运动学模型特点设计动态反馈自适应编队队形保持控制器,并利用李雅普诺夫理论证明编队控制器的稳定性.仿真结果表明,所设计的控制器能够克服僚机控制模型不确定性带来的扰动影响,可以实现编队由初始误差到期望队形的快速调整以及稳定队形的保持.     

Design of a Commercial Hybrid VTOL UAV System

For the last four decades Unmanned Air Vehicles (UAVs) have been extensively used for military operations that include tracking, surveillance, active engagement with weapons and airborne data acquisition. UAVs are also in demand commercially due to their advantages in comparison to manned vehicles. These advantages include lower manufacturing and operating costs, flexibility in configuration depending on customer request and not risking the pilot on demanding missions. Even though civilian UAVs currently constitute 3 % of the UAV market, it is estimated that their numbers will reach up to 10 % of the UAV market within the next 5 years. Most of the civilian UAV applications require UAVs that are capable of doing a wide range of different and complementary operations within a composite mission. These operations include taking off and landing from limited runway space, while traversing the operation region in considerable cruise speed for mobile tracking applications. This is in addition to being able traverse in low cruise speeds or being able to hover for stationary measurement and tracking. All of these complementary and but different operational capabilities point to a hybrid unmanned vehicle concept, namely the Vertical Take-Off and Landing (VTOL) UAVs. In addition, the desired UAV system needs to be cost-efficient while providing easy payload conversion for different civilian applications. In this paper, we review the preliminary design process of such a capable civilian UAV system, namely the TURAC VTOL UAV. TURAC UAV is aimed to have both vertical take-off and landing and Conventional Take-off and Landing (CTOL) capability. TURAC interchangeable payload pod and detachable wing (with potential different size variants) provides capability to perform different mission types, including long endurance and high cruise speed operations. In addition, the TURAC concept is to have two different variants. The TURAC A variant is an eco-friendly and low-noise fully electrical platform which includes 2 tilt electric motors in the front, and a fixed electric motor and ducted fan in the rear, where as the TURAC B variant is envisioned to use high energy density fuel cells for extended hovering time. In this paper, we provide the TURAC UAV’s iterative design and trade-off studies which also include detailed aerodynamic and structural configuration analysis. For the aerodynamic analysis, an in-house software including graphical user interface has been developed to calculate the aerodynamic forces and moments by using the Vortex Lattice Method (VLM). Computational Fluid Dynamics (CFD) studies are performed to determine the aerodynamic effects for various configurations For structural analysis, a Finite Element Model (FEM) of the TURAC has been prepared and its modal analysis is carried out. Maximum displacements and maximal principal stresses are calculated and used for streamlining a weight efficient fuselage design. Prototypes have been built to show success of the design at both hover and forward flight regime. In this paper, we also provide the flight management and autopilot architecture of the TURAC. The testing of the controller performance has been initiated with the prototype of TURAC. Current work focuses on the building of the full fight test prototype of the TURAC UAV and aerodynamic modeling of the transition flight.     

考虑关节柔性的绳驱动空中机械臂关节空间鲁棒控制

空中机械臂在外部环境交互作业方面表现出很强的研究和应用价值,但当前系统位姿控制性能较弱、负载能力不足以及续航时间短的问题严重制约其作业能力的提升.鉴于此,设计一种带有绳驱动机械臂的新型空中机械臂系统,并将引入绳驱动机制带来的柔性效应等价到关节处,建立考虑关节柔性的刚柔耦合动力学模型.首先,针对系统在集总干扰下的关节空间轨迹跟踪控制,采用线性扩张状态观测器对集总干扰进行估计和补偿,并采用超螺旋算子和分数阶非奇异终端滑模以保证系统在到达阶段和滑模阶段均有较好的控制性能;然后,在Lyapunov稳定性框架下验证所设计控制器的稳定性;最后,通过可视化仿真和地面实验对所设计控制器的有效性进行验证.实验结果表明,所设计的鲁棒控制器比其他两种现有的控制器具有更快的响应速度、更强的抗干扰能力以及更高的跟踪精度,能够满足绳驱动空中机械臂的控制需求.     

Design, Modeling and Validation of a T-Tail Unmanned Aerial Vehicle

This paper addresses the design and modeling process of a T-tail unmanned aerial vehicle (UAV). A methodology is presented of how to make tradeoffs among the payload requirements, energy efficiency and aerodynamic stability. A linear decoupled model of longitudinal and lateral dynamics is abstracted from a physical airframe. Instead of subjectively estimating the order, error and time delay for system identification (system ID), equations of motion derived from aerodynamics are employed to provide more precise estimation of the model structure. System ID is carried out with regard to the flight data collected by the autopilot data logger. The resulted model is refined based on the simulation and comparison.     

Flight control of tethered kites in autonomous pumping cycles for airborne wind energy

Energy harvesting based on tethered kites benefits from exploiting higher wind speeds at higher altitudes. The setup considered in this paper is based on a pumping cycle. It generates energy by winching out at high tether forces, driving an electrical generator while flying crosswind. Then it winches in at a stationary neutral position, thus leaving a net amount of generated energy.The focus of this paper is put on the flight control design, which implements an accurate direction control towards target points and allows for a flight with an eight-down pattern. An extended overview on the control system approach, as well as details of each element of the flight controller, is presented. The control architecture is motivated by a simple, yet comprehensive model for the kite dynamics.In addition, winch strategies based on an optimization scheme are presented. In order to demonstrate the real world functionality of the presented algorithms, flight data from a fully automated pumping-cycle operation of a small-scale prototype are given. The setup is based on a 30 m² kite linked to a ground-based 50 kW electrical motor/generator by a single line.     

The automation design advisor tool (ADAT): Development and validation of a model‐based tool to support flight deck automation design for nextgen operations

NextGen aviation will require an even greater reliance on automation than current‐day operations. Therefore, systems with problems in human–automation interaction must be identified and resolved early, well before they are introduced into operation. This paper describes a research and software development effort to build a prototype automation design advisor tool (ADAT) for flight deck automation. This tool uses models of human performance to identify perceptual, cognitive, and action‐related inefficiencies in the design of flight management systems. Aviation designers can use the tool to evaluate and compare potential flight deck automation designs and to identify potential human–automation interaction concerns. Designers can compare different flight management systems in terms of specific features and their ability to support pilot performance. ADAT provides specific, research‐based guidance for resolving problematic design issues. It was specifically designed to be flexible enough for both current‐day technologies and revolutionary NextGen designs. © 2012 Wiley Periodicals, Inc.     

Design Considerations of a Prototype VTOL Robotic Vehicle through Market Survey Data Collection

A detailed technical design and performance comparison of current unmanned Vertical Take-Off and Landing (VTOL) vehicles is presented as a function of vehicle maximum speed, payload, range, endurance, and propulsion configurations. Mission applications and VTOL market characteristics are used to define design specifications for a new prototype unmanned VTOL vehicle suitable for a wide range of (mostly) civilian applications. The proposed VTOL vehicle's design phase is presented, including: performance capabilities calculation, fuselage strength evaluation and weight optimization via crash/drop tests. Drop tests performed have followed standard regulations used for airworthiness certification of such vehicles. The proposed VTOL vehicle is currently under prototype development.     

Small-signal modeling and controller design of energy sharing controlled distributed battery system

This paper presents small-signal modeling, analysis and closed-loop controller design guidelines for a distributed battery energy storage system with energy sharing controller which has recently been presented in the literature in order to achieve cell balancing with high cell balancing speed and energy efficiency. The derived small signal models provide deeper insight into the dynamics of the energy sharing controlled battery system under different operating modes, including discharge mode, constant current charging mode and constant voltage charging mode. Based on the derived small signal models, closed-loop controller design guidelines are provided based on rule-of-thumb frequency-domain design criteria. The small signal models and designed controllers are validated by MATLAB®/SIMULINK simulation and experimental prototype results.