Flight Control Applications Research Articles

Direct Multi‐Thread Adaptive Control With Attracting Manifold Design

ABSTRACTThis article presents a novel multi‐thread attracting manifold (MTAM) adaptive control scheme. The novel contribution of this new controller lies in how the attracting manifold design method is spread across multiple estimates of the truth while simultaneously weighting between said individual estimates to arrive at an adaptive composite estimate which outperforms single thread adaptive controllers. A notable benefit of this new formulation is that it allows for both the weighting of multiple threads and monotonic decrease of parameter error to aid the performance of transient error dynamics, without arbitrarily increasing adaptation gains. The benefits of the proposed controller over existing adaptive control schemes are analyzed through two aerospace flight control applications from the literature.

Anti‐windup compensation for model reference adaptive control schemes

AbstractActuator constraints, particularly saturation limits, are an intrinsic and long‐standing problem in the implementation of most control systems. Model reference adaptive control (MRAC) is no exception and it may suffer considerably when actuator saturation is encountered. With this in mind, this paper proposes an anti‐windup strategy for model reference adaptive control schemes subject to actuator saturation. A prominent feature of the proposed compensator is that it has the same architecture as well‐known nonadaptive schemes, namely model recovery anti‐windup, which rely on the assumption that the system model is known accurately. Since, in the adaptive case, the model is largely unknown, the proposed approach uses an “estimate” of the system matrices for the anti‐windup formulation and modifies the adaptation laws that update the controller gains; if the (unknown) ideal control gains are reached, the model recovery anti‐windup formulation is recovered. The main results provide conditions under which, if the ideal control signal eventually lies within the control constraints, then the system states will converge to those of the reference model, that is, the tracking error will converge to zero asymptotically. The article deals with open‐loop stable linear systems and highlights the main challenges involved in the design of anti‐windup compensators for model‐reference adaptive control systems, demonstrating its success via a flight control application.

A robust and efficient citrus counting approach for large-scale unstructured orchards

CONTEXTAccurately detecting and counting fruits is essential for orchard yield estimation and smart management. However, two drawbacks are inherent in the current citrus counting algorithms: First, the robustness needs to be improved, particularly illumination changes and dense occlusion. Secondly, the actual operating efficiency of the system is low. OBJECTIVETo tackle the above issues, this paper proposed a robust and efficient fruit-counting pipeline based on Unmanned Aerial Vehicle (UAV). METHODSFirst, to obtain UAV video streaming data online, a live broadcast platform and a flight control Application called FlyCounter were developed. Secondly, the Illumination-Adaptive-Transformer network is used to enhance the low-illumination citrus image in real-time. Then, for the specific challenging scenario, a novel model named Fruit-YOLO is designed to accurately detect citrus in data streams. Finally, the DeepSORT is adopted to track and count fruits in video sequences. RESULTS AND CONCLUSIONSThe results indicate that for detection performance, the P, R and mAP of the Fruit-YOLO of input enhanced image are 0.898, 0.854 and 0.929 respectively, which are 1.7%, 4.6% and 3.5% higher than the original image respectively. Regarding counting performance, for the daytime and evening scenes, the ID switch, MOTA and Error Mean of the pipeline are 63.7, 0.86 and 9.81% respectively. The MAPE of the offline and online operations of the pipeline are 4.36% and 12.66% respectively. The time and resources consumed by the system under parallel operations with different numbers of UAVs were analyzed. SIGNIFICANCEIn this study, an online counting pipeline based on UAVs that can work in low-light scenarios is implemented for the first time. The system has good performance in both daytime and nighttime scenarios, enabling efficient counting in orchards and extending operating time.

Stalls and Splines: Current Trends in Flight Testing and Aerodynamic Model Identification

Aerodynamic model identification remains essential for simulator operations and control system design and operations. In this paper, state-of-the-art methodologies for aerodynamic model identification and validation are presented, together with a number of novel applications of the identified models that were recently investigated and developed at the Faculty of Aerospace Engineering of Delft University of Technology. In particular, this paper focuses on methodologies for identifying models of aerodynamic stall from flight data, as well as multivariate spline-based aerodynamic model identification methods, together with their applications in flight simulation and advanced flight control.

Flow Field Simulation Tool of Solid Propulsion Control Systems for Missile Applications

In order to achieve hit-to-kill miss distances against manoeuvrable ballistic missile targets, future generation missiles calls for fast response non-conventional propulsion control systems during terminal homing period in high-endo to exo-atmosphere regions augmenting aero control. Based on advances in thrust modulation controlling throat area in solid propulsion pintle motor, control systems are developed for missile Divert and Attitude Control Systems (DACS) applications using multiple nozzles in pitch/yaw directions connected to common gas generator. Control thrust vector for lateral and attitude corrections is generated with proportional distribution of total thrust in pitch/yaw directions through real time thrust modulation of pintle nozzles
 Towards development of propulsion control systems based on solid propulsion, prototype systems: Thrust Controlled Motor (TCM) and Divert Thruster Flight Propulsion Control System (DTFPCS) are developed to demonstrate thrust modulation/ control thrust vector generation in solid propulsion and finalize unified controller for various missile control applications. Design & development process of prototype systems calls for flow field simulation tool for parametric design analysis/optimization and generate performance maps/control parameters based on detailed flow distributions. Present paper presents flow field simulation tools with Steady Flow Field (SFF) model and Dynamic Flow Field (DFF) model integrating dynamics of pintle movement with steady flow solver. Parametric analysis of geometrical profiles of pintle/throat regions and effect of pintle speed on system response are presented for system design optimization. Performance maps and controller maps of prototype systems are generated based on flow field distributions for nozzle thrust modulation. Simulated results are compared with open loop hot tests and unified controller parameters are updated for control thrust vector generation. Finally flow field distributions of DTFPCS operating modes: neutral-thrust and lateral-thrust are presented demonstrating the utility of simulation tool in design analysis and system development. Present simulation tool is critical in system design optimization and unified controller development for various flight control applications with minimum number of developmental tests. Further work of integrating propellant grain geometry variation during motor hot tests, with flow field model is in progress to predict control system performance for various missile control applications.

Robust performance comparison of PMSM for flight control applications in more electric aircraft.

This paper describes a robust performance comparison of flight control actuation controllers based on a permanent magnet synchronous motor (PMSM) in more electric aircraft (MEA). Recently, the PMSM has become a favorite for the flight control applications of more electric aircraft (MEA) due to their improved efficiency, higher torque, less noise, and higher reliability as compared to their counterparts. Thus, advanced nonlinear control techniques offer even better performance for the control of PMSM as noticed in this research. In this paper, three nonlinear approaches i.e. Feedback Linearization Control (FBL) through the cancellation of the non-linearity of the system, the stabilization of the system via Backstepping Control (BSC) using the Lyapunov candidate function as well as the robust performance with chattering minimization by applying the continuous approximation based Sliding Mode Control (SMC) are compared with generalized Field-Oriented Controller (FOC). The comparison of FOC, FBL, BSC and SMC shows that the nonlinear controllers perform well under varying aerodynamic loads during flight. However, the performance of the sliding mode control is found superior as compared to the other three controllers in terms of better performance characteristics e.g. response time, steady-state error etc. as well as the control robustness in the presence of the uncertain parameters of the PMSM model and variable load torque acting as a disturbance. In essence, the peak of the tolerance band is less than 20% for all nonlinear and FOC controller, while it is less than 5% for SMC. Steady state error for the SMC is least (0.01%) as compared to other three controllers. Moreover, the SMC controller is able to withstand 50% parameter variation and loading torque of 10 N.m without significant changes in performance. Six simulation scenarios are used to analyze the performance and robustness which depict that the sliding mode controller performs well in terms of the desired performance for MEA application.

Time‐varying sliding mode controller for over‐actuated systems with constrained and uncertain actuators in flight control applications

AbstractOne solution to the problem of distributing the control action among redundant actuators with uncertain dynamics is employing an adaptive control allocator. This paper proposes a sliding mode controller which exploits a time‐varying sliding surface to complement adaptive control allocation in the presence of actuator saturation. The proposed approach does not require error augmentation for tracking desired references, which diminishes the computational burden. Aerodata Model in Research Environment, which is an over‐actuated aircraft model, is adopted to demonstrate the efficacy of the proposed controller in simulation studies.

Robust Aircraft Performance using Hypersurface Gain Scheduling LQI Controller for Supermaneuverable Aircraft

A new approach to cater abrupt gain switching at boundaries of steady-state trim points in Conventional Gain Scheduling (CGS) applied to aircraft flight control applications. The primary purpose of this research is to improve the stability properties of a supermaneuverable aircraft during different mission task of flight envelope, controlled using a gain scheduled approach. An output feedback based on Linear Quadratic Integral (LQI) controller is proposed which is able to guarantee stability and performance of the required task of the entire flight envelope. The results are demonstrated using comparison of pilot control maneuvers using CGS with proposed scheduling scheme for angular rates control by keeping states and control input contraints under consideration.

Modeling and Extended State Observer-Based Backstepping Control of Underwater Electro Hydrostatic Actuator with Pressure Compensator and External Load

Electro hydrostatic actuator (EHA) has been successfully developed for flight control applications to replace the cumbersome centralized hydraulic system. It also has excellent potential for ocean applications due to its advantages on miniaturization and energy-savings. One of the special technologies for EHA’s underwater application is pressure compensation, which is used to equalize the return pressure of the hydraulic system and the seawater pressure. This paper investigates the modeling and control design of underwater EHA to improve performance, especially considering the effect of additional pressure compensator and uncertain external load. The nonlinear hydraulic model is extended by the dynamic characteristics of the pressure compensator. Two low-order extended state observers were constructed to cope with the external load fore and the effect of the pressure compensator, respectively. The backstepping methods were designed to guarantee the robust stability of the entire high-order nonlinear hydraulic system. Finally, the theoretical proving and simulation on Matlab/Simulink are conducted to demonstrate the high tracking performance of the proposed control strategy.

Design of a Nonlinear Roll Mechanism for Airplanes Using Lie Brackets for High Alpha Operation

A nonlinear controllability analysis for fixed-wing aircraft has been performed in an earlier effort by the authors, which revealed a novel roll mechanism due to a nonlinear interaction between elevator and aileron control inputs. In this effort, we perform a detailed investigation of this novel roll mechanism, called Lie Bracket Roll Augmentation (LIBRA). First, we show the nonlinear flight physics associated with the LIBRA mechanism. Second, using the Fliess functional expansion, we perform a theoretical study of the effectiveness (degree of controllability) of the LIBRA mechanism in comparison to the conventional mechanism (using ailerons only). Third, to simulate the airplane response to a LIBRA input, we cast the problem of executing the LIBRA mechanism as a nonholonomic motion planning problem. In such a problem, a Lie bracket input is applied to generate motion along an unactuated direction. A Lie bracket input represents a nonlinear interaction between two (or more) control inputs to steer the system along a direction that is not directly actuated by any of these inputs (or their linear combinations). In this language, the LIBRA mechanism is simply a Lie bracket interaction between the elevator and aileron control inputs. We modify existing nonholonomic motion planning algorithms for systems with drift to be more feasible for flight control applications with bounded controls. We show that the LIBRA novel roll mechanism is superior compared to the conventional one during stall, where the aileron sensitivity degrades. In particular, the novel roll mechanism can provide an order of magnitude enhancement in the rolling capability over the conventional roll mechanism near stall.

A survey on electro hydrostatic actuator: Architecture and way ahead

The nascent development in the field of the hydraulic actuator is the integration of various cutting edge technology like mechanical, hydraulic, control and electrical the result is the multidisciplinary final product which is high-performance Electro Hydrostatic Actuator (EHA). This is an independent direct actuation method which is also known as “power-by-wire” (PBW) technology. This technology is design to replace the cumbersome leak-prone centralized hydraulic system with a compact and reliable actuation system. This technology originally developed for flight control application but due to enhance reliability and increasing popularity currently, it is being used in many industrial applications for different purposes. This paper attempt to bring out the component level comprehensive insight of EHA and consolidate all available literature of this field in the form of literature survey. These papers also talk about the pros and cons of the system and various control methods to curb noted disadvantages. Most of the existing research literature considers the EHA with an asymmetrical cylinder which is widely used in aircraft. However, in industrial application, the asymmetrical cylinder is most suited and predominately used. The control of asymmetrical cylinder poses a greater challenge vis-a-vis symmetrical cylinder due to differences in the area of two-chamber. This paper also tries to throw some light on the methods of controlling the cylinders. Finally, this paper concludes by finding research gaps and further scope of improvements and application of EHA in armoured recovery vehicles.

Guardian maps based robust stability analysis with applications in flight control of hypersonic vehicles

Guardian maps provide a concise and practical approach to parametric robustness analysis. However, non-convexity and nonlinearity of high dimensional guardian maps restrict the application. In this paper, a closed-loop performance-oriented approach to parametric robustness analysis is proposed. First, a sufficient condition for the existence of parametric stable region satisfying the closed-loop performance is presented. To further identify the maximum stable region, a robustness criterion is provided, leading to a numerical approach for parametric stability margin. The superiority of the proposed method lies in the applicability to robust performance analysis with nonlinear high-dimensional parameters. Applications are discussed with emphasis on the flight control of hypersonic vehicles, including robust control design and robust stability analysis. Results are of significant that no prior knowledge on controller tuning is required, and parametric stability margin can be obtained automatically regardless of the dimension of parameter space.

Fault diagnosis and accommodation with flight control applications

ABSTRACTThis paper reviews some main results and process concerning with fault diagnosis and accommodation with flight control applications. The fault detection and diagnosis including the quantitative and qualitative methods and the fault-tolerant control including passive and active schemes are introduced, respectively. The control designs and developments of the fault diagnosis and accommodation for continuous-time systems and discrete-time systems, the fault diagnosis and fault-tolerant control for switched systems and interconnected systems as well as the applied flight control research including hypersonic vehicle, spacecraft and helicopter systems are summarised.

Optimization Techniques for Prognostics of On-Board Electromechanical Servomechanisms Affected by Progressive Faults

In relatively recent years, electromechanical actuators have gradually replaced systems based on hydraulic power for flight control applications. Electromechanical servosystems are typically operated by electrical machines that transfer rotational power to the controlled elements (e.g. the aerodynamic control surfaces) by means of gearings and mechanical transmission. Compared to electrohydraulic systems, electromechanical actuators offer several advantages, such as reduced weight, simplified maintenance and complete elimination of contaminant, flammable or polluting hydraulic fluids. On-board actuators are often safety critical; then, the practice of monitoring and analyzing the system response through electrical acquisitions, with the aim of estimating fault evolution, has gradually become an essential task of the system engineering. For this purpose, a new discipline, called Prognostics, has been developed in recent years. Its aim is to study methodologies and algorithms capable of identifying such failures and foresee the moment when a particular component loses functionality and is no longer able to meet the desired performance. In this paper, authors have introduced the use of optimization techniques in prognostic methods (e.g. model-based parametric estimation algorithms) and have proposed a new model-based fault detection and identification method, based on Genetic Algorithms optimization approach, able to perform an early identification of the aforesaid progressive failures, investigating its ability to identify timely symptoms alerting that a component is degrading.

Positional Precision Analysis of Orthomosaics Derived from Drone Captured Aerial Imagery

The advancement of drones has revolutionized the production of aerial imagery. Using a drone with its associated flight control and image processing applications, a high resolution orthorectified mosaic from multiple individual aerial images can be produced within just a few hours. However, the positional precision and accuracy of any orthomosaic produced should not be overlooked. In this project, we flew a DJI Phantom drone once a month over a seven-month period over Oak Grove Cemetery in Nacogdoches, Texas, USA resulting in seven orthomosaics of the same location. We identified 30 ground control points (GCPs) based on permanent features in the cemetery and recorded the geographic coordinates of each GCP on each of the seven orthomosaics. Analyzing the cluster of each GCP containing seven coincident positions depicts the positional precision of the orthomosaics. Our analysis is an attempt to answer the fundamental question, “Are we obtaining the same geographic coordinates for the same feature found on every aerial image mosaic captured by a drone over time?” The results showed that the positional precision was higher at the center of the orthomosaic compared to the edge areas. In addition, the positional precision was lower parallel to the direction of the drone flight.

Color identification for quadcopter flight control and object inspection

This study focuses on quadcopter flight control and image application. The proposed quadcopter can be applied to inspect rust or damage areas of ship hull. Real-time image identification with proper devices is also proposed. Proportional–integral–derivative control and fuzzy control are used in flight control design. Due to hardware limitation of the quadcopter, complicate control theory is avoid in controller design. A simple fuzzy control is used in this study. In sensor fusion, air pressure altimeter, Global Positioning System (GPS), ultrasonic sensor, and optical flow sensor are utilized to maintain altitude holding in outdoor and indoor environments. In color identification, Pixy (CMUcam5) camera is used to perform image processing and image tracking. Signals from different sensors are processed in the Arduino board. In flight simulation, pitch and roll angle commands are constructed in a rule table. Flight control can be performed by feedback tracking error, and software simulations for proportional–integral–derivative and fuzzy control are given.

Composite non-linear feedback control using Mittag-Leffler function

Transient performance of any physical system is very important concern for the controller design of that system. Composite non-linear feedback control (CNF) is one of such controls with which optimum transient performance can be achieved. It has a combination of linear feedback law and non-linear feedback law. In the conventional CNF control, non-linear feedback law uses a decaying exponential function as a non-linear function. In the proposed modified CNF, this exponential function is replaced with Mittag-Leffler function (MLF) for the non-linear control law. Mittag-Leffler function which is one of the special functions from fractional calculus and it is the generalization of exponential function. By fine tuning the parameters in MLF, better control over damping ratio can be achieved. This improves the performance of the system further, giving lesser rise time, settling time and the percentage overshoot. The modern flight control application is used to demonstrate the effectiveness of CNF controller using MLF.

Application of Bio-inspired Formation Flight Control to Two Fixed Wing Airplanes

Application of Bio-inspired Formation Flight Control to Two Fixed Wing Airplanes

Stability limit of human-in-the-loop model reference adaptive control architectures

ABSTRACTModel reference adaptive control (MRAC) offers mathematical and design tools to effectively cope with many challenges of real-world control problems such as exogenous disturbances, system uncertainties and degraded modes of operations. On the other hand, when faced with human-in-the-loop settings, these controllers can lead to unstable system trajectories in certain applications. To establish an understanding of stability limitations of MRAC architectures in the presence of humans, here a mathematical framework is developed whereby an MRAC is designed in conjunction with a class of linear human models including human reaction delays. This framework is then used to reveal, through stability analysis tools, the stability limit of the MRAC–human closed-loop system and the range of model parameters respecting this limit. An illustrative numerical example of an adaptive flight control application with a Neal–Smith pilot model is presented to demonstrate the effectiveness of developed approaches.

Robust MRAC augmented baseline LQR for tracking control of 2 DoF helicopter

This paper proposes a novel in-line direct adaptive Linear Quadratic Regulator (LQR) using Model Reference Adaptive Control (MRAC) scheme for tracking control of a 2 DoF helicopter. LQR is one of the most preferred controllers for flight control applications due to its inherent robustness and stability characteristics. However, the tracking performance of LQR gets degraded when the system is perturbed or subjected to model uncertainty. To address this issue, by cascading the adaptive control law with the baseline LQR, an adaptive controller framework is synthesized using an inverse Lyapunov function. The key advantage of the proposed framework is that it widens the operating horizon which significantly increases the stability and robustness of the system to accommodate both uncertainty and disturbance. The efficacy of the controller framework is tested on the benchmark 2 DoF helicopter testbed. The command tracking and maneuvering responses of the 2 DoF helicopter under nominal and perturbed operating conditions are assessed. The tracking responses accentuate that MRAC augmented LQR can result in quicker convergence with improved stability.