Keywords: UAV dynamics, control, guidance and navigation, Guidance, control and estimation theory, Control algorithms implementation
Abstract: We describe an experimental platform for testing the DarkO tail-sitter drone in an open wind tunnel experiment. The DarkO convertible UAV is developed and 3D printed at the Ecole Nationale de l'Aviation Civile (ENAC), in Toulouse (France). The objective of the experimental platform is to allow testing control laws in a realistic and secure context. We propose a test bench with a single degree of freedom corresponding to the drone pitch axis. We design a linear proportional/integral feedback hovering stabilizer in the presence of constant wind, and we illustrate its effectiveness in stabilizing a hovering position through experimental results.

Keywords: UAV dynamics, control, guidance and navigation, Control algorithms implementation
Abstract: This paper presents the design and the stability analysis of an adaptive position controller for Unmanned Aerial Vehicles (UAVs). Considering a hierarchical control scheme, the novelty of this work is the definition of a systematic approach to design a position controller based on Model Reference Adaptive Control (MRAC) theory taking into account not-fast closed-loop attitude dynamics. After having reformulated the problem considering the attitude dynamics as pseudo-actuator, the authors exploit an existing Linear Matrix Inequality (LMI) based hedging framework designed such that the adaptation performance is not affected by the presence of actuator dynamics. Results from simulations and from experiments on a platform designed to replicate the longitudinal motion of quadrotors are provided to illustrate the performance of the proposed control scheme.

Keywords: UAV dynamics, control, guidance and navigation, Guidance, control and estimation theory, Flight dynamics identification
Abstract: In this paper, a neural controller with disturbance observer is presented, in order to control a quadrotor Unmanned Aerial Vehicle (UAV) subject to aerodynamic disturbances. As a novel feature, the controller is formulated in a way to be implemented directly to a second-order system, such as the one of the quadrotor. Feedforward neural networks are employed in the control system design to compensate for internal disturbances, while the external disturbances and approximation error of the neural network are estimated by a disturbance observer. Moreover, composite learning is used to improve the overall performance, by estimating the state variables in real-time and using the estimation error in the updating rules of both the controller and the disturbance observer. An accurate disturbance modeling for the quadrotor is given, which considers wind and attitude changes, in order to evaluate the effectiveness of the controller. The controller successfully fulfills the task of trajectory tracking in the presence of wind and measurement noises, proving itself to be robust.

Keywords: UAV dynamics, control, guidance and navigation, Control algorithms implementation
Abstract: In this article, a finite-time sliding mode controller (FTSMC) is designed with the aim of attitude tracking of the coaxial tilt-rotor UAV (CTRUAV) under external disturbance. The CTRUAV is a multi-input multi-output (MIMO) and highly coupled system, which leads to the complexity of the controller design. Based on the dynamic model of the CTRUAV, an FTSMC is designed to improve the tracking performance of attitude control and robustness under uncertain disturbance, the stability of FTSMC is proved based on Lyapunov theory, and the power distribution is adjusted to solve the control-allocation problem of the CTRUAV. At last, simulation results are provided to show the effectiveness of FTSMC.

Keywords: UAV dynamics, control, guidance and navigation, Control algorithms implementation, Air traffic management/communication, navigation and surveillance
Abstract: The paper proposes a method for generating and automatically executing smooth evasive maneuvers which allow to enforce a geofence for an optionally piloted fixed-wing aircraft. Feasible trajectories are planned online based on the current aircraft state and performance limitations, including finite roll rates. Collision checks are continuously carried out in the background to take over control from the pilot before violating the geofence becomes inevitable. The system automatically executes an evasive maneuver before giving back control to the pilot. The approach can readily be applied to the general collision avoidance problem for convex obstacles. We validate the feasibility and geofencing accuracy of the proposed framework by showcasing results of flight tests of an unmanned, fixed-wing aircraft.

Keywords: UAV dynamics, control, guidance and navigation
Abstract: In this paper, a Synergetic Control (SC) is proposed for a transformable quadrotor exposed to external disturbances. This control strategy has a simple structure, smooth dynamics and good tracking performance. The SC is applied to our system, which has the particularity of changing its morphology during the flight. Numerical simulations are performed to demonstrate the efficiency of the suggested control approach, of which a qualitative and quantitative comparison with respect to Sliding Mode Controller (SMC) is made. Overall, the investigations show that this control technique outperforms in terms of accuracy and robustness.

Keywords: Launcher, RLV and ARV guidance and control, Space exploration and transportation
Abstract: Optimization of terminal phase descent trajectory of winged reusable launch vehicle is studied in this paper. This trajectory consists of 'Terminal Area Energy Management (TAEM)' phase and 'Approach and Landing (AL)' phase. Three dimensional dynamics of an unpowered winged launch vehicle over a rotating Earth and an oblate gravitational field, is considered. The objective of the trajectory optimization is to land the vehicle horizontally on a predefined runway, using angle of attack and bank angle command, satisfying the path constraints of dynamic pressure, load factor and control limits, and terminal constraints of position, horizontal velocity, sink rate and heading. Trajectory is optimized using Chebyshev pseudospectral knotting method, wherein the state and control variables are discretized at Chebyshev-Gauss-Lobatto (CGL) points and the problem is converted to a nonlinear programming problem. The versatility of the formulation is demonstrated by obtaining optimum trajectories for a variety of initial conditions and cost functions and the analysis of the optimum trajectories are presented.

Keywords: Launcher, RLV and ARV guidance and control, Control algorithms implementation
Abstract: During its course from a launch site to an intended orbit, a launch vehicle faces an adverse environment and withstand a plethora of disturbances. The set of disturbance forces acting on each stage of the vehicle depends on the configuration of that stage. Different methodologies are used to predict the magnitude of static disturbances before the flight. To ensure the launch success, performance of a flight control system is validated using a high fidelity six degrees of freedom simulation testbed, in the presence of predicted magnitude of these disturbances. Magnitude experienced by the launch vehicle during its maiden flight, might vary from the predicted set. Actual magnitude of these disturbances is known only after the flight in post-flight exercise of matching launch vehicle dynamics using ground simulations. Correct information of the magnitude of these disturbances is of significant importance for subsequent developmental flights. Control power plant sizing, preflight actuator biasing to nullify lift-off disturbance and autopilot integrator limit setting are all dependent on the exact knowledge of these sources of disturbances. Flight data measurements of a launch vehicle offer a rich galore of information in this regard. This paper presents an analytical technique which uses flight measurements to compute static disturbances experienced during the flight by a launch vehicle. The main sources of steady disturbances considered in this paper are center of gravity, thrust-line offset and thrust misalignment.

Keywords: Launcher, RLV and ARV guidance and control
Abstract: Stability and dynamic behaviour of a linear multivariable system mainly depend on the pole locations of the plant in the complex s plane. For general linear time-invariant multi-input multi-output (MIMO) systems, static (constant gain) output feedback pole-placement is an open nondeterministic polynomial time (NP) hard problem. This problem has attracted much attention from the control community for the last four decades. Even today, the general problem has not been solved analytically because of its highly nonlinear nature. In this paper, we have addressed the issue of finding gains without using the procedure of sequential loop closure. We have proposed an iterative numerical algorithm to solve the pole placement problem with a minimum number of feedback gains. The proposed method is used to compute the state feedback gain matrix for coupled yaw-roll dynamics of a typical reusable launch vehicle (RLV) during the reentry phase.

Keywords: Mico- and Nano aerospace vehicles/satellites, UAV dynamics, control, guidance and navigation, Guidance, control and estimation theory
Abstract: The plants of nano aerial vehicles (NAVs) are inherently unstable. Hence, a NAV needs a flight controller to accomplish a mission. Furthermore, the sensing and computational capabilities of NAV's autopilot hardware are limited. Therefore, the implementation of the full state feedback controllers with gain scheduling is difficult. This paper proposes a flight controller scheme that consists of two parts: a Simultaneously Stabilizing Output Feedback Linear (SSOFL) controller and a Proximal Policy Optimization (PPO) deep reinforcement learning agent, which is connected in parallel to the SSOFL controller. In this scheme, the single SSOFL controller provides stabilization and nominal tracking performance to the NAV throughout its flight envelope by accomplishing simultaneous stabilization (SS). Additionally, the PPO agent is trained using the closed-loop (CL) nonlinear plant with this SSOFL controller to enhance the tracking performance. The effectiveness of the proposed flight controller scheme is verified using the six-degree-of-freedom nonlinear simulations of the fixed-wing nano aerial vehicle.

Keywords: Space robotics, including rovers, Spacecraft dynamics, control, guidance and navigation
Abstract: The paper deals with the problems on further development of a rational strategy for the space robot’s approaching a geostationary satellite and visual checking its state. Original methods are proposed for predicting the influence of gravitational disturbances, as well as solar pressure forces in the synthesis of the robot guidance laws for its interorbital flights. The developed methods and algorithms for a space robot control are based on the local optimizing the fuel consumption of the plasma electric propulsion unit. Simulation results on developed guidance and control algorithms are presented that demonstrate their effectiveness.

Keywords: Space robotics, including rovers, Guidance, control and estimation theory, Space exploration and transportation
Abstract: A spherical robot has many practical advantages as the entire electronics are protected within a hull and can be carried easily by any Unmanned Aerial Vehicle (UAV). However, its use is limited due to finding mounts for sensors. Pendulum actuated spherical robot provides space for mounting sensors at the yoke. We study the non-linear dynamics of a pendulum-actuated spherical robot to analyze the dynamics of internal assembly (yoke) for mounting sensors. For such robots, we provide a coupled dynamic model that takes care of the relationship between forward and sideways motion. We further demonstrate the effects of wobbling and precession captured by our model when the bot is controlled to execute a turning maneuver while moving with a moderate forward velocity – a practical situation encountered by spherical robots moving in an indoor setting. A simulation setup based on the developed model provides visualization of the spherical robot motion.

Keywords: Spacecraft dynamics, control, guidance and navigation, Control algorithms implementation
Abstract: This paper addresses the attitude stabilization problem for fractionated space systems where the onboard computers cannot run continuously. An auxiliary filter is constructed to imitate the intermittent computer or state acquisition of a small size, power, and weight constrained spacecraft such a CubeSat. The proposed controller does not require angular rate or inertia knowledge and guarantees attitude stabilization and boundedness for all closed loop signals for persistently excited gains driving the auxiliary filter. A novel Lyapunov function is constructed to guarantee stability including auxiliary functions for strictification of the controller. Simulation of a 3U form factor CubeSat example is carried out to demonstrate the feasibility of the controller.

Keywords: Spacecraft dynamics, control, guidance and navigation, Mico- and Nano aerospace vehicles/satellites
Abstract: Magnetic attitude control is an essential topic in attitude determination and control (ADC) studies as it can be used as the main or backup attitude control method in different scenarios. The magnetic actuation system is advantageous for its low cost, reliability, and ease of implementation when the pointing accuracy requirement is not high. The major issue in using magnetorques for attitude control is that it provides controllability over a period. In this study, a magnetic attitude control algorithm is designed for a low Earth orbit sun-synchronous small satellite by using a model predictive control approach which is an advanced control technique that generates control input using the system model to predict the future behavior of the system. The control algorithm is integrated into the overall ADC algorithm and the complete algorithm is tested via simulations. The simulation results show that the three-axis attitude control can be achieved with an accuracy of below 10 deg in around 10 orbits from the tumbling status of the satellite.

Keywords: Spacecraft dynamics, control, guidance and navigation, Space exploration and transportation, Guidance, control and estimation theory
Abstract: Due to lack of spacecraft’s global position and attitude information on small solar system bodies (SSSBs) like asteroids, only relative state measurements are available for navigation. Therefore, relative navigation with respect to a local reference frame is the basis for in-situ autonomous exploration on the asteroids. The relative navigation changes a local reference frame during the flight, which guarantees local accuracy of state estimation and mapping. In this paper, we present the relative navigation framework using surfel grid map-based scan-to-map matching for localization and mapping on asteroid surface. We also propose a terrain-based path planning that makes use of inherent terrain surface properties of surfel grid maps. A thorough validation of our navigation approach and comparison to a global flash LiDAR-based navigation in different flight scenarios and in both MIL (model-in-the-loop) and real-time PIL (processor-in-the-loop) tests show the viability of this novel navigation framework.

Keywords: Spacecraft dynamics, control, guidance and navigation
Abstract: An optimal Mars entry guidance scheme is presented in this paper using the Model Predictive Static Programming (MPSP) technique accounting for the applicable state and control constraints. The guidance scheme is designed to maximize the terminal parachute deployment altitude while applying minimum control effort and satisfying hard constraints on desired terminal conditions such as final velocity and downrange. The proposed guidance computes the optimal bank angle profile to shape the trajectory of the spacecraft. Path constraints on heat rate, dynamic pressure, aerodynamic load, and bounds on bank angle are considered to guide the vehicle safely through the martian atmosphere. Moreover, in order to generate practically realizable bank angle profiles, an additional constraint on the bank angle rate is also applied. Next, using the MPSP technique, the nonlinear constrained optimal control problem is converted into a static quadratic optimization problem with linear equality and inequality constraints to solve it in a computationally efficient manner. The concept of flexible final time MPSP is incorporated to update the final time in an optimal fashion. Numerical simulations illustrate the ability of the proposed method to solve the guidance problem efficiently while satisfying the path and terminal constraints within the desired accuracy.

Keywords: Spacecraft dynamics, control, guidance and navigation
Abstract: In this paper, a novel, attitude-constrained, structured adaptive control strategy is proposed for a spacecraft in the presence of parametric uncertainties. A set of cone angles are defined as a way to quantify the relative orientation error between two reference frames. While tracking the desired attitude, the corresponding cone angles are driven to zero while being constrained to lie within a maximum value. Using an error transformation, the restriction on the cone angles is converted into quaternion constraints that are subsequently used in barrier Lyapunov function (BLF) based controller synthesis. Attitude error constraints are satisfied by ensuring the boundedness of BLFs in the closed-loop Lyapunov stability analysis. Eventually, an adaptive control law is synthesized that drives the spacecraft to the desired attitude with the help of approximate and nominal spacecraft dynamics. While doing so, a function approximation strategy is used to obtain a stable weight update rule to estimate the disturbance term. Finally, the effectiveness of the proposed adaptive control law is demonstrated via numerical simulations.

Keywords: Spacecraft dynamics, control, guidance and navigation, Space exploration and transportation
Abstract: Safe spacecraft navigation on small solar system bodies requires an accurate and high-resolution representation of the surface. This work develops a super-resolution mapping algorithm based on flash LiDAR measurements for unstructured terrain. It integrates a novel approach of processing multiple range values per pixel per measurement to increase the measurement redundancy and thus the map accuracy. The proposed algorithm is thus able to overcome the limitations of the low flash LiDAR resolution. Micro- and macro-motion strategies are recommended to guarantee subpixel displacements crucial for the super-resolution algorithm, and measurement constraints are introduced to ensure high measurement quality. Computational experiments based on an advanced Flash LiDAR model in a realistic simulation environment of comet 67P/Churyumov-Gerasimenko compare the resulting digital elevation model (DEM) with a baseline DEM and demonstrate the advantages of our algorithm.

Keywords: Guidance, control and estimation theory, Missile dynamics, control, guidance and navigation, Control algorithms implementation
Abstract: In this paper, a different approach guidance technique is evolved by generating an angle, to guide an anti-ship cruise missile in terminal phase. The present work focuses to model and simulate a guidance scheme for terminal phase of an anti-ship Bank to Turn (BTT) cruise missile. The targeted ships are relatively slow compared to missile speeds.

The modified guidance law of Pure Pursuit and Proportional Navigation (PN) in terms of course angle is implemented for stationary as well as moving targets in the lateral plane.

The longitudinal guidance is achieved by computing the commanded altitude as a function of range to go.

Keywords: Control algorithms implementation, Aircraft/Helicopter dynamics, control, guidance and navigation, Guidance, control and estimation theory
Abstract: Gyroscopes are autonomous devices important in aerospace vehicle guidance, navigation, and control systems. They are one of the primary units used in aerospace vehicles for attitude control, steering mechanisms, and inertial guidance systems. While nonlinear sliding mode control (SMC) is one of the leading variable structure control and has greatly emphasized solving nonlinear problems, extended Kalman filter (EKF) has proven to be an effective real-time estimator and handles mismatched uncertainties well. This paper extends previous research on nonlinear control formulation based on SMC with EKF to design a fault-tolerant control system to handle actuator faults and bounded uncertainties that may occur during the real-time operation of the system. This control formulation is implemented on a gyroscope test bed. The result shows the efficacy of this approach by its robust tracking performance after the fault occurs in the system, obtaining a bounded and smooth control profile, and keeping states and controls within the bounds of the system.

Keywords: Spacecraft dynamics, control, guidance and navigation, Space robotics, including rovers, Space exploration and transportation
Abstract: This paper proposes an idea for configuration of actuators for a small space robot for asteroid exploration using coupled dynamics of attitude and position. Space-robot configuration includes variable-speed control moment gyroscope (VSCMG), reaction wheel (RW) and a body fixed thruster. Since a single body fixed thruster cannot have the full position control, so the problem is under actuated, and this makes it a coupled problem of attitude and position control. A stable PID control law is developed for position control and sliding mode using Modified Rodrigues Parameter (MRP) is used for developing the control law for attitude control. The closed loop stability of the system is proven using Lyapunov stability criteria for attitude control. The asteroid gravity is modelled by taking an arbitrary shaped asteroid. In this paper maneuvering and hovering is performed using the proposed design. Finally the simulations and results are demonstrated for showing the effectiveness of the proposed actuator configuration for maneuvering and hovering a space-robot.

Keywords: Missile dynamics, control, guidance and navigation, Decision making and autonomy, Cooperative/distributed guidance and control
Abstract: The paper presents the conduction of the experiments and motion camouflaged approach to determine how a bee is chasing and intercepting the moving target. The experimental setup is made ready, and the bee-target motion episodes are recorded for various target movements. The bee-target position tuples are generated at all-time instances, followed by the simulation of trajectories. The verification of motion camouflage strategies by the bee is carried out. Then a kinematic model with three phases is hypothesized and compared with motion camouflaged data and found that both are interrelated. Then, switching between camouflage strategies is concluded. Concluding remarks on the future scope were discussed at the end. This research work is first of its kind in observing the aggressive behaviour in the bees and looking into their motion strategies.

Keywords: UAV dynamics, control, guidance and navigation, Spacecraft dynamics, control, guidance and navigation, Mission control and operations
Abstract: Uncrewed Flight Vehicle (UFV) for a particular mission should move from an initial point to a target point along a precogitated nominal trajectory following some waypoints. Sometimes, it may face some obstructions during the journey. There is a probability of collision between obstacles and vehicles along their trajectory. It should have some mechanism to avert this kind of unintentional collision. All the sensing and avoidance methodologies on board should be autonomous as the information of the intruder is not available a priori to the vehicle. From the practical point of view, obstacles are available in different geometrical shapes (square, triangular, circular, and polygonal), kinematics (static and dynamic), and numbers (single and multiple). The proposed geometric collision avoidance approach described in this paper encompasses the avoidance of all types of obstacles mentioned above.

Keywords: UAV dynamics, control, guidance and navigation, Control algorithms implementation, Guidance, control and estimation theory
Abstract: We present the experimental validation of a recently developed anti-windup design to guarantee stability and a desired level of performance in the presence of propellers saturation in quadrotor UAVs. The considered solution exploits a decentralized LMI-based compensator to mitigate directionality issues affecting saturated multi-variable plants and to achieve satisfactory time-domain performance for reference signals of interest. After discussing saturation effects in quadrotors, we first show how the compensator can be implemented on top of a popular cascade control architecture for underactuated multi-rotors and then how it can be tuned to prioritize position/heading direction control objectives. The design is finally validated through experiments in representative flight conditions.

Keywords: UAV dynamics, control, guidance and navigation, Control algorithms implementation, Guidance, control and estimation theory
Abstract: This research paper proposes a super twisting-based sliding mode controller for quadcopter’s attitude and position tracking in the presence of uncertainties. In the design of a super twisting-based sliding mode controller, the PID sliding surface is taken into account, which can improve the tracking performance. The Lyapunov-based stability analysis has been shown to ensure finite time stability of the sliding variables, and then the convergence of error trajectories has been discussed. The designed controller has been validated by simulations in MATLAB and Software-In-The-Loop (SITL) simulations in a ROS-Gazebo based environment simulator for the Iris model. The simulations demonstrate the robustness of the proposed controller to different wind disturbances.

Keywords: UAV dynamics, control, guidance and navigation, Decision making and autonomy, Mico- and Nano aerospace vehicles/satellites
Abstract: This paper deals with the aerial survey of a closed region using the Space-Filling curve, particularly Sierpinski curve. The specified region is triangulated, and the Sierpinski curve is used to explore each triangular region. The entire region may have one or more obstacles. An algorithm is presented which suggests evasive maneuver if an obstacle is detected. The algorithm is online; that is, it does not require prior knowledge of the location of obstacles and can be used while the robotic system traverses the designated path. The fractal nature of the Sierpinski curve and simple geometric observations were used to formulate and validate the algorithm. The non-uniform coverage and multiple obstacle problems are also dealt with towards the end.

Keywords: UAV dynamics, control, guidance and navigation, Guidance, control and estimation theory
Abstract: In order to allow the quadrotor to perform the hover maneuver at the desired altitude, a unique controller design based on modified super-twisting sliding mode control is proposed in this research. The proposed controller can operate even for significant state deviations from their nominal values because it is constructed inside a nonlinear framework without performing linearization of quadrotor dynamics. The control designer can assign values to the gains without knowing the precise values of the disturbance or their upper bounds due to the proposed dynamic adaptation law. This makes it easier to implement the suggested controller in real-world circumstances. Numerical simulations validate the robust hovering control of the quadrotor performance in the presence of disturbance. To evaluate the controller effectiveness, the performance of the modified super twisting control is compared with that of the super twisting control, and the proposed controller outperforms the existing one.

Keywords: Avionics and on-board equipment, Air traffic management/communication, navigation and surveillance
Abstract: Designing a robust carrier tracking loop for GNSS receivers is a challenging task under strong scintillation, multipath, clock uncertainty, interference, and vehicle high dynamics. The conventional tracking methods such as proportional integral filter (PIF), Wiener filter (WF), and Kalman filter (KF) are known to perform well under given GNSS signal model parameters and noise characteristics. If it is not the case, then performance deteriorates and may result in loss of the carrier lock. To circumvent this problem, we propose a robust control and filtering method based on the well-known sliding mode approach. In this paper, a sliding mode control and state estimation framework is developed for GNSS carrier tracking. The efficacy of the proposed method is proved by simulation studies for GPS(L1) signal. From static to high dynamics operating cases are simulated for proving its usage on the high dynamics vehicles such as high speed trains, fighter jets, and missile systems. The achieved results are promising for use of the proposed method on these vehicles and the receiver operating in the adverse (weak GNSS signal) conditions.

Keywords: Space debris mitigation, Space robotics, including rovers, Spacecraft dynamics, control, guidance and navigation
Abstract: Active Debris removal using robotic manipulators onboard satellites is a promising way of cleaning up the space junk. However, complexities and non-linearities associated with the control of such coupled space-based systems present difficulties in their feasible implementation. Lack of a fixed base arises serious problems in controlling the space manipulators for precision tasks like capture of an orbiting space debris. This paper presents systematic modelling and control approaches for Rotation floating space robots in order to draw a comparison between them while tracking a moving target representing autonomous debris capture. We propose a Nonlinear Model Predictive Controller (NMPC) for the space robot in order to design an optimal path that the end-effector can follow while being controlled to capture the target. To the best of the knowledge of the authors, such a controller has not been tested for a Rotation floating space robot before. Further, the current work implements and reviews one of the most commonly used Transpose Jacobian Cartesian (TJC) controller for Rotation floating space robots through the use of Generalized Jacobian Matrix (GJM). The results provide sufficient evidence of the superior performance of the nonlinear model predictive controller over the TJC controller. Finally, the current work also implements the same nonlinear model predictive controller on a more popular state of the art Free floating space robot and compares it with the Rotation floating space robot.

Keywords: Health monitoring, diagnosis and reconfiguration
Abstract: Inspired by recent progress in machine learning, a data-driven fault diagnosis and isolation (FDI) scheme is explicitly developed for failure in the fuel supply system and sensor measurements of the laboratory gas turbine system. A passive approach to fault diagnosis is implemented where a model is trained using machine learning classifiers to detect a given set of fault scenarios in real-time on which it is trained. Toward the end, a comparative study is presented for well-known classification techniques, namely Support vector classifier, Linear discriminant analysis, K-neighbor, and Decision trees. Several simulation studies were carried out to demonstrate and illustrate the proposed fault diagnosis scheme's advantages, capabilities, and performance.

Keywords: Flexible structure control, Guidance, control and estimation theory, Control algorithms implementation
Abstract: In this paper, Robust Integral of Sign of Error (RISE) based partial feedback linearized controller for active flutter suppression (AFS) of a two dimensional aerofoil is proposed. The aeroelastic system has two degrees of freedom i.e. pitch and plunge. To design the controller, linearized pitch dynamics of the aerofoil is considered. A significant feature of the proposed controller is that it does not need an accurate model of the plant as well as any knowledge of external disturbance or parametric uncertainty. Zero dynamics stability and closed loop stability of the overall system have been established. Simulations prove the robustness and efficacy of the designed controller against variation in free stream velocity, parametric uncertainty and external disturbances as compared to existing designs. Results prove that the designed controller has increased the flutter boundary by 48% more than critical flutter speed.

Keywords: Guidance, control and estimation theory, Decision making and autonomy, Avionics and on-board equipment
Abstract: In this paper, an adaptive nonlinear droop-based control approach is proposed for converter-based self-contained electrical power systems (EPS) designed for electric aircraft applications to ensure tight voltage regulation and accurate load power distribution among parallel sources. By taking into account the accurate nonlinear dynamic models of the power converters, we mathematically prove an upper bound for the input current of each converter separately by means of Lyapunov methods and ultimate boundedness theory. In particular, the adopted nonlinear droop-based controller introduces a virtual voltage and a virtual resistance in series with the inductance and parasitic resistance of each DC/DC boost converter. To verify the proposed controller performance and its underlying developed theory, simulation results of the low-voltage bus dynamics have been presented for an onboard aicraft DC microgrid (MG).