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The task of aircraft motion control has to be solved under conditions of numerous heterogeneous uncertainties both in the aircraft motion model and in the environment in which the aircraft is flying. These uncertainties, in particular, are caused by the fact that in the flight of the aircraft can occur various kinds of abnormal situations caused by failures of equipment and systems of the aircraft, damage to the airframe and propulsion system of the aircraft. Some of these failures and damages have a direct impact on the dynamic characteristics of the aircraft as a control object. In this regard, the problem arises of such an adjustment of aircraft control algorithms that would provide the ability to adapt to the changed dynamics of the aircraft. It is extremely difficult, and in some cases impossible, to foresee in advance all possible damages, failures and their combinations. Hence, it is necessary to implement adaptive flight control algorithms that are able to adjust to the changing situation. One of the effective tools for solving such problems is reinforcement learning in the Approximate Dynamic Programming (ADP) variant, in combination with artificial neural networks. In the last decade, a family of methods known as Adaptive Critic Design (ACD) has been actively developed within the ADP approach to control the behavior of complex dynamic systems. In our paper we consider the application of one of the variants of the ACD approach, namely SNAC (Single Network Adaptive Critic) and its development through its joint use with the method of dynamic inversion. The effectiveness of this approach is demonstrated on the example of longitudinal motion control of a supersonic transport airplane. [ABSTRACT FROM AUTHOR]

This paper presents the key components in the Universal(U)-control framework for designing dynamic control systems from model-based to model-free paradigms, in which the pillars include U-control system configuration, open-loop dynamic inversion, closed-loop dynamic inversion, general model-free cancellation of nonlinear-dynamic-coupling effect, model-free-sliding-mode control (MFSMC) and model-free composite nonlinear feedback (CNF) control. This paper is devoted to delivering intuitive and easy-to-understand explanations for the involved approaches with a series of schematic diagrams. Readers can refer to the corresponding publications for more details on the theoretical analyses. In addition, some showcase examples are provided in this paper to facilitate the understanding of certain important concepts. [ABSTRACT FROM AUTHOR]

This paper presents an active fault-tolerant flight control system (FCS) design for the dual-system/hybrid VTOL UAV configuration that maximally exploits its inherent over-actuation abilities to provide higher levels of fault-tolerance and reliability compared to that of the other VTOL UAVs configurations up to this point. The significance of this study is to convert the main drawback of having the vertical rotors as dead weights during the cruise to a key advantage where all the UAV's controls are kept active during all the flight phases raising the UAV's fault-tolerance and maneuverability abilities. The FCS proposed elaborates on a new architecture for the hierarchical automatic control loops using the dynamic inversion control to design the trajectory tracking virtual commands and employing optimal dynamic control allocation to optimally resolve the controls redundancy. Regarding fault-tolerance, the presented FCS handles simultaneous failures and jamming of all the control surfaces during flight where the control commands to the healthy controls (vertical rotors) were automatically adapted such that the trimming and trajectory tracking were successfully maintained till the mission end. Additionally, this paper addresses for the first time the employment of the controls redundancy to enhance the VTOL UAV's maneuverability in fault-free cases, where we present a study of reducing the minimum turn radius of the UAV when the vertical rotors are employed with the control surfaces during the maneuver. A reduction of 38% in the coordinated steady-level minimum turn radius turn at 35 m/sec flight speed was achieved. [ABSTRACT FROM AUTHOR]

A novel trajectory generation and control architecture for fully autonomous autorotative flare that combines rapid path generation with model-based control is proposed. The trajectory generation component uses optical Tau theory to compute flare trajectories for both longitudinal and vertical speed. These flare trajectories are tracked using a nonlinear dynamic inversion (NDI) control law. One convenient feature of NDI is that it inverts the plant model in its feedback linearization loop, which eliminates the need for gain scheduling. However, the plant model used for feedback linearization still needs to be scheduled with the flight condition. This key aspect is leveraged to derive a control law that is scheduled with linearized models of the rotorcraft flight dynamics obtained in steady-state autorotation, while relying on a single set of gains. Computer simulations are used to demonstrate that the NDI control law is able to successfully execute autorotative flare in the UH-60 aircraft. Autonomous flare trajectories are compared to piloted simulation data to assess similarities and discrepancies between piloted and automatic control approaches. Trade studies examine which combinations of downrange distances and altitudes at flare initiation result in successful autorotative landings. [ABSTRACT FROM AUTHOR]

This paper presents a new method to calculate the inversion of the controlled linear/nonlinear dynamic plants which are described by input–output differential equation models. This new U-model-based inverter (U-inverter), cancels both system dynamics and nonlinearities, can be used directly to facilitate the control system design, which the design of U-model-based control (U-control) systems is selected for demonstration in this study. The most important advantage of this U-inverter is that it does not require system state variables, only uses the input/output measurements from the controlled plants. A nonlinear disturbance observer is introduced into the U-control design framework to increase its robustness. The analysis explains the properties of this developed the disturbance observer-based U-control (DOBUC) method and its design procedures. Finally, a wind energy conversion system is simulated to illustrate the design of this DOBUC and the corresponding performance. [ABSTRACT FROM AUTHOR]

Morphing aircraft are able to keep optimal performance in diverse flight conditions. However, the change in geometry always leads to challenges in the design of flight controllers. In this paper, a new method for designing a flight controller for variable-sweep morphing aircraft is presented—dynamic inversion combined with L 1 adaptive control. Firstly, the dynamics of the vehicle is analyzed and a six degrees of freedom (6DOF) nonlinear dynamics model based on multibody dynamics theory is established. Secondly, nonlinear dynamic inversion (NDI) and incremental nonlinear dynamic inversion (INDI) are then employed to realize decoupling control. Thirdly, linear quadratic regulator (LQR) technique and L 1 adaptive control are adopted to design the adaptive controller in order to improve robustness to uncertainties and ensure the control accuracy. Finally, extensive simulation experiments are performed, wherein the demonstrated results indicate that the proposed method overcomes the drawbacks of conventional methods and realizes an improvement in control performance. [ABSTRACT FROM AUTHOR]

The possibility of simplifying the mathematical model of aircraft motion, used to design an adaptive controller based on the principle of dynamic inversion, is considered. The effectiveness of a controller synthesized using such a simplified model is tested in standard piloting conditions and in the case of a pilot–aircraft system failure. To assess the accuracy of a tracking task for different variants of controller synthesis, flight simulator-based experiments were carried out. [ABSTRACT FROM AUTHOR]

This paper presents a real-time trajectory planning method for highly dynamic tracking control of wheeled inverted pendulum (WIP) systems. A generic form of dynamic inversion problem for the class of WIPs is defined by combining a set of kinematic and dynamic differential constraints related to the system’s output expressed by the state variables, whose time evolution is to be sought as the solution of the trajectory planning. Instead of simply integrating forward the set of differential equations, which would lead only to an unbounded solution due to its non-minimum phase nature, an asymptotic expansion technique, transforming the original differential equations into a sequence of algebraic equations parameterized by the system’s characteristic constant, is used to allow for a stable and asymptotically exact solution of the dynamic inversion problem. To implement the proposed method for a real-time application where the reference command is not previously known, a command input filter is designed and applied to adjust the real-time input into a sufficiently differentiable reference command suitable for the inversion. Simulation and experimental studies are provided to validate the proposed method using our experimental WIP system.

In order to realize the fast response control for turboshaft engine with variable rotor speed, a dynamic inversion (DI) control method based on state variable model of turboshaft engine is proposed. Meanwhile, in order to expand the application of dynamic inversion controller, the linear parameter varying (LPV) model of turboshaft engine is applied, which constitutes the LPV/DI controller together. The simulation results shows that compared with the conventional PID controller, the LPV/DI controller can effectively reduce the overshoot/droop of the power turbine speed to less than 1% under different flight conditions. The control effect is remarkable and the robust performance is superior. [ABSTRACT FROM AUTHOR]

Current methods for the analysis of channeling-path phenomena in reservoirs cannot account for the influence of time and space on the actual seepage behavior. In the present study, this problem is addressed considering actual production data and dynamic characteristic parameters quantitatively determined in the near wellbore area by fitting the water-cut curve of the well. Starting from the dynamic relationship between injection and production data, the average permeability is determined and used to obtain a real-time quantitative characterization of the seepage behavior of the channeling-path in the far wellbore area. For the considered case study (Jidong oilfield), it is found that the seepage capacity of the channeling-path in the far wellbore area is far less (10 times smaller) than that of the channeling-path in the near wellbore area. The present study and the proposed model (combining near wellbore area and far wellbore area real-time data) have been implemented to support the definition of relevant adjustment measures to ultimately improve oil recovery. [ABSTRACT FROM AUTHOR]

A novel trajectory generation and control architecture for fully autonomous autorotative flare that combines rapid path generation with model-based control is proposed. The trajectory generation component uses optical Tau theory to compute flare trajectories for both longitudinal and vertical speed. These flare trajectories are tracked using a nonlinear dynamic inversion (NDI) control law. One convenient feature of NDI is that it inverts the plant model in its feedback linearization loop, which eliminates the need for gain scheduling. However, the plant model used for feedback linearization still needs to be scheduled with the flight condition. This key aspect is leveraged to derive a control law that is scheduled with linearized models of the rotorcraft flight dynamics obtained in steady-state autorotation, while relying on a single set of gains. Computer simulations are used to demonstrate that the NDI control law is able to successfully execute autorotative flare in the UH-60 aircraft. Autonomous flare trajectories are compared to piloted simulation data to assess similarities and discrepancies between piloted and automatic control approaches. Trade studies examine which combinations of downrange distances and altitudes at flare initiation result in successful autorotative landings.

Morphing aircraft are able to keep optimal performance in diverse flight conditions. However, the change in geometry always leads to challenges in the design of flight controllers. In this paper, a new method for designing a flight controller for variable-sweep morphing aircraft is presented—dynamic inversion combined with L1 adaptive control. Firstly, the dynamics of the vehicle is analyzed and a six degrees of freedom (6DOF) nonlinear dynamics model based on multibody dynamics theory is established. Secondly, nonlinear dynamic inversion (NDI) and incremental nonlinear dynamic inversion (INDI) are then employed to realize decoupling control. Thirdly, linear quadratic regulator (LQR) technique and L1 adaptive control are adopted to design the adaptive controller in order to improve robustness to uncertainties and ensure the control accuracy. Finally, extensive simulation experiments are performed, wherein the demonstrated results indicate that the proposed method overcomes the drawbacks of conventional methods and realizes an improvement in control performance.

The frequent and sudden increase of load in electric vehicles depletes oxygen from the fuel cell cathode, leading possibly to oxygen starvation. This paper presents the design of an air flow controller for fuel cell systems (FCS) that aims to replenish the depleted oxygen. A dynamic inversion is used as the feed-forward compensation for the disturbance effect coming from the load current change. However, the inverted dynamics have negative relative degree (improper) and not physically realizable. To make it proper, an augmentation by delay is done, with the same delay added into demand current. The current-dependent time delay introduced in the demand current gives the FCS the opportunity to prepare a sufficient air flow that can withstand the dip in oxygen excess ratio (OER). Besides, the FCS plant is linearized at various operating points, and the dynamic feedforward controller is designed at several operating points with interpolation applied for in-between values. The simulation results show a considerable improvement in the OER response where the constraint is met and the recovery time is reduced. • A combined delay-based governor and inversion-based feedforward. • Theoretically exact disturbance compensation. • The time delay can be made dependent on the demand current increment or decrement. • In autonomous vehicles, the load delay is replaced by advance in the command. • Linear controllers are scheduled at multiple operating points to tackle nonlinearity. [ABSTRACT FROM AUTHOR]

Ground resonance is an aero-mechanical instability in helicopters that use soft in-plane rotors. Traditionally, ground resonance is mitigated by using passive lead–lag dampers that provide sufficient in-plane damping. However, these dampers because of their passive nature cannot adapt to all operating conditions. In this work, a magnetorheological fluid–based semi-active lead–lag damper is proposed to offer controllable damping. Two nonlinear control strategies are reported to operate the voltage to be supplied to the magnetorheological damper. The first strategy is a model-based control using dynamic inversion. The second is a fuzzy logic control integrated with a particle swarm optimization algorithm to optimize the control parameters. Both control strategies are shown to be effective in eliminating ground resonance. Unlike bang–bang control, the prescribed control algorithms can make use of complete voltage level available in the magnetorheological damper with smooth voltage updates. A comparative study of the controller performances is made through appropriate performance indices and system responses. Finally, the most optimum control strategy to mitigate ground resonance is inferred. [ABSTRACT FROM AUTHOR]

This study proposes a double sliding mode control-augmented U-control ( U DSM -control) method for a class of single-input single-output nonlinear systems with internal uncertain parameters, model mismatching and external system noise/disturbance to improve robustness in nonlinear dynamic inversion in the U-control system design. For the configuration, the U DSM -control system takes up (1) a double sliding mode dynamic inverter to cancel nonlinearities and dynamics of the plant, (2) a linear invariant controller, the other dynamic inverter of the specified whole desired system performance, so that the whole system dynamic inversion is split into two designs in double feedback loops. For using the framework, this study analyses the associated properties on (1) global stability, (2) double sliding from a switching control driving the states to a sliding band and an equivalent control driving the states to a sliding line and (3) robustness against uncertainties/disturbances and a potential data-driven prototype. To validate the developed control system, it selects bench test examples for simulation studies using Matlab/Simulink, which demonstrates the U DSM -control in terms of accuracy, tracking, and robustness. The tests also present a step-by-step design procedure for potential applications. [ABSTRACT FROM AUTHOR]

Landslides present a significant hazard for humans, but continuous landslide monitoring is not yet possible due to their unpredictability. Post-event reconstruction based on field survey and remote sensing cannot provide full insight into the landslide movement process. Analysis and inversion of the seismic signals generated by landside movement has started to provide valuable data for understanding the entire process of landslide movement, from initiation to cessation, along with numerical simulation, but each method has shortcomings. Simple seismic signal analysis can detect landslide occurrence, but the propagation effect generates lags. Dynamic inversion based on long-period seismic signals gives the low-frequency curve of landslide dynamic parameters, but not the high-frequency characteristics. Numerical simulation can simulate the entire movement process, but results are strongly influenced by choice of model parameters. Developing a method for combining the three techniques has become a focus for research in recent years. Here, we develop such a protocol based on analysis of the 2018 Baige landslide (China). Seismic signal dynamic inversion results are used to verify the numerical simulation, and then the numerical simulation is dynamically constrained and optimized to obtain the best numerical value. We apply the procedure to the Baige event and, combined with field/geological survey, show it provides a comprehensive and accurate method for dynamic process reconstruction. We found that the Baige landslide was triggered by detachment of the weathered layer, with severe top fault segmentation. The landslide process comprised four stages: initiation, main slip, blocking, and deposition. Multi-method mutual verification effectively reduces the inherent ambiguity of each method, and multi-method joint analysis improves the rationality and reliability of the results. The approach outlined in this study could be used to support hazard prevention and control in sensitive areas. [ABSTRACT FROM AUTHOR]

A neural networks(NN) hysteresis compensator is proposed for dynamic systems. The NN compensator uses the back-stepping scheme for inverting the hysteresis nonlinearity in the feed-forward path. This scheme provides a general step for using NN to determine the dynamic pre-inversion of the reversible dynamic system. A tuning algorithm is proposed for the NN hysteresis compensator which yields a stable closed-loop system. Nonlinear stability proofs are provided to reveal that the tracking error is small. By increasing the gain we can reduce the stability radius to some extent. PI control without hysteresis compensation requires much higher gains to achieve similar performance. It is not easy to guarantee the stability of such highly nonlinear dynamical system if only a PI controller is used. Initializing the NN weights is simple. The initial weights of hidden layer are randomly selected and initial weights of output layer are set to zero. A PI loop with integerted an unity gain feedforward path keeps the system stable until the NN starts learning. Simulation results show its efficacy of the NN hysteresis compensator on a system. This work is applicable to xy table-like precision control system and also shows neural network stability proofs. Moreover, the NN hysteresis compensation can be further extended and applied to dead-zone, backlash, and other actuator nonlinear compensation. [ABSTRACT FROM AUTHOR]

The paper presents a nonlinear dynamic model for DGMSCMGs, sometimes used as actuators to control the attitude of large satellites. The developed models describe the translation dynamics, the rotation dynamics of the Active Magnetic Bearing Rotor, as well as the rotation dynamics of the two mobile gimbals. Two control architectures are initially designed by using the dynamic inversion concept, proportional-integrator-derivative/proportional-derivative dynamic compensators, linear observers, and a neural network to compensate the effect of the dynamic inversion error. One also develops a similar adaptive control architecture consisting of a proportional-integrator dynamic compensator, a feed-forward neural network, and a linear observer. The latter system models two interconnected nonlinear servo-systems and controls the angular rates of the two mobile gimbals actuated by the attitude controller of the satellite. The validation of the novel control architectures is achieved in Matlab/Simulink, the obtained results proving a very good angular rate precision and the robustness of the control systems in relation to the external disturbances. [ABSTRACT FROM AUTHOR]

In this work, a Model-Based Control method for a single horizontal degree of freedom shaking table is presented. The proposed approach relies on the real-time inversion of a previously identified linear state-space model of the hydraulic servoactuator which drives the table. The inputs to the model are the control command and the force exerted on servoactuator rod. The latter contains all the relevant information related to the external actions acting on the servoactuator, thus making control system performance independent from the specimen with which the table is loaded and enabling it to cope with specimen non-linear behavior and eventual external forces exerted on it. A parallel proportional integral derivative controller, which accounts for non-modeled dynamics and a feedback linearization scheme, aimed at minimizing servovalve flow non-linearity, complement the previous architecture. The effectiveness of the method has been assessed numerically. According to the simulation results, the performance of the proposed technique appears quite promising; however, several factors must be carefully considered to achieve successful actual implementation. [ABSTRACT FROM AUTHOR]

• Proposed a dynamic inversion and correction method of gas pressure without pressure sensing device. • Measure the real-time temperature to determine the spreading factor and combine it with the half-height full-width value to calculate the real-time pressure value before correction. • Discover system errors and correct pressures. • The maximum value of the calculated pressure uncertainty was 0.913 %. Laser absorption spectroscopy is widely applied in gas concentration detection while the measurement accuracy would be affected by fluctuations in the environmental pressure (pressure fluctuations inside the gas cell under vacuum conditions). In this paper, a dynamic inversion and correction method of gas pressure without pressure sensors was proposed. Ammonia within the range of 6611–6614 cm−1 was selected as the research object. In contrast to previous reports, this method does not investigate the effect of pressure on gas concentration detection from a single point of view, or obtain pressure values from pressure sensors. Instead, the real-time temperature was measured to determine the broadening coefficient, which was then utilized along with full width at half-maximum (FWHM) of the spectral lines to calculate the real-time pressure value before correction. The directly acquired pressure has an error, and based on the error analysis, the pressure is corrected to get the corrected real-time pressure value. Finally, the effect of systematic error was eliminated by correcting the concentration using the corrected real-time pressure value and the measured real-time temperature. Experimental results show that the average residual of the corrected real-time pressure compared to the measured true values was 0.1993 torr with a standard deviation of 0.7387 torr. The correlation coefficient R2 between the inverted pressure value and the measured true value was 0.999, with a maximum fitting error of 1.19 %, error fluctuations within 2 %, and pressure uncertainty ranging from 0.545 % to 0.913 %. Furthermore, the ammonia concentration was corrected, and the maximum error compared to the standard ammonia concentration injected in the experiment was 1.025 % (with an effective optical path length of the detection gas cell of 15 cm). This work demonstrated the effectiveness of the proposed method in accurately inverting dynamic real-time pressure values and improving the accuracy of gas concentration measurement. [ABSTRACT FROM AUTHOR]

For the existence of aerodynamic coupling and big turbulence of reentry vehicle in large aerodynamic flight status, Conventional method for RCS controller designing is difficult to track the bank angle command quickly and accurately. To solve the problem, according to the feature that the lateral/directional coupling is significant and the yaw channel is more effective and stronger to turbulence when tracking the bank angle, a strategy is proposed by using the roll and yaw channel simultaneously to control the bank angle dynamic. Double loop dynamic inversion controller is designed in which the bank angle loop conduct as outer loop and the roll and yaw angle rate loop as inner loop. The convergence of sideslip angle is guaranteed by improving the design of roll angle rate controller and the influence of the controller parameters to converge mode is analyzed. PWPF modulator is applied to convert command moment into pulse signals. Numerical simulation is carried out to verify the benefits of the proposed control method, the results shows that the present method solved the problem that RCS controller designed in conventional manner, and improve control ability of RCS in large aerodynamic condition.

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a linear active disturbance rejection controller (LADRC) for nonaffine nonlinear systems with strict-feedback form. The proposed LADRC results in a closed-loop system with a three-time-scale structure, in which a reduced-order linear extended state observer estimates unmeasured states and total disturbance in the fastest time scale and dynamic inversion based on sector conditions is used to deal with nonaffine inputs in the intermediate time scale while the system dynamics evolves in the slowest time scale. The singular perturbation method is used to analyze the stability and performance of the system. The effectiveness of the proposed LADRC is demonstrated through simulation studies and experimental validation on a linear motor servo system with nonaffine uncertainties.

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Future launch vehicle concepts and technologies for expendable and reusable launch vehicles are currently investigated by the DLR research projects Akira and X-tras. In particular, the winged Liquid Fly-back Booster concept Lfbb based on an LOX/LH2 propellant combination for vertical takeoff and vertical landing (VTVL), as well as the delta-winged horizontal takeoff and horizontal landing (HTHL) concept Aurora based on an LOX/Kerosene propellant combination are considered in these projects. Because of the complexity and risks involved in on-line trajectory optimization, off-line reference trajectories are still considered important for tracking purposes. In that sense, the goal of this paper is to investigate an off-line and general-purpose guidance and control (G&C) architecture for preliminary studies of reusable launch vehicles. This is done by using trajectory optimization combined with Modelica models for the generation of optimal guidance commands, and then trajectory tracking is performed by means of inner-loop feedback controls in terms of nonlinear dynamic inversion with prescribed desired dynamics. We showcase the advantages of this baseline G&C architecture in terms of early stability and controllability aspects during the preliminary design studies of an example configuration of a reusable launch vehicle investigated in the context of the research projects above mentioned. • Preliminary guidance and control architecture for launch vehicle design studies. • Optimal guidance commands obtained with off-line trajectory optimization. • Nonlinear dynamic inversion (NDI) provides early assessment about controllability. • NDI control provides a direct link to the required angular impulse along trajectory. • Nonlinear flight control simulations are performed for the RLV concept AURORA. [ABSTRACT FROM AUTHOR]

The work presented in this research focuses on the design of a robust nonlinear flight control system for a small fixed-wing UAV against uncertainties and external disturbances. Toward this objective, an integrated UAV waypoints guidance scheme based on Carrot Chasing guidance law (CC) is adopted. The designed attitude angles guidance law is applied to the flight control loop. Nonlinear Dynamic Inversion (NDI) awards the flight control system researchers a straight forward method of deriving control laws for nonlinear systems. The control inputs are used to eliminate unwanted terms in the equations of motion using negative feedback of these terms. However precise dynamic models may not be available and that leads to system instability in the presence of external disturbances or model uncertainties. Therefore a modified incremental dynamic inversion (MINDI) is presented to compensate the model uncertainties and increase robustness and system behavior when compared to incremental NDI. Simulation results showed that the MINDI flight control system is robust against wind disturbances and model mismatch which leads to superior path following performance. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Geology & Recovery Efficiency is the property of Petroleum Geology & Recovery Efficiency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The presence of pulse width modulation driven components, limiters, and electronic switches constrain the magnitude of control input in electrical and electro-mechanical systems. The presence of nonlinearities in these system models and unavailability of full state measurements, further complicate the controller design process. This brief introduces a novel saturated output feedback design to solve the tracking problem for a class of feedback linearizable circuits. The feedback scheme comprises of a modified approximate dynamic inversion controller in conjunction with a standard high gain observer. Unlike the Lyapunov-based approaches, the proposed contraction theory-based methodology details a quantitative framework for the convergence analysis of closed loop trajectories. This, in turn, serve the dual purpose of proving ultimate boundedness and quantifying the convergence bounds in terms of known parameters. [ABSTRACT FROM AUTHOR]

The control of the unmanned aerial vehicles is a difficult problem because of their light weight and the strong coupling between the longitudinal and lateral modes. Motivated by this, a backstepping and dynamic inversion-based automatic landing system is designed in this paper for the flight control of a fixed wing unmanned aerial vehicle subject to wind shears, atmospheric disturbances, and wind gusts. Two backstepping-based controllers are designed for the stabilization of the attitude angles, while the controller associated to the forward velocity uses the dynamic inversion technique to obtain a constant forward velocity during all the three stages of landing. To provide an estimation of the wind shears, atmospheric turbulences, and wind gusts, a nonlinear disturbance observer is introduced in the control architecture. The lateral deviation with respect to the runway is canceled while the unmanned aerial vehicle maintains its desired trajectory slope angle. The novel adaptive automatic landing system is software implemented and validated by complex numerical simulations; the results of the numerical simulations prove the stability and robustness of the new control architecture for different initial conditions and wind type disturbances. • A backstepping and dynamic inversion based automatic landing system is designed. • The control system is robust to wind shears, atmospheric disturbances, and wind gusts. • The unmanned aerial vehicle maintains its desired trajectory. • The lateral deviation with respect to the runway is canceled. [ABSTRACT FROM AUTHOR]

The fault-tolerant anti-disturbance control problem for air-breathing hypersonic vehicles with variable geometry inlet (AHV-VGI) is investigated. The VGI technique enlarges the AHV flight envelope at the expense of the system to inevitably possess unknown disturbances, model uncertainties and actuator faults. A novel fault-tolerant control strategy is proposed under the back-stepping control scheme based on extended state observer (ESO) and dynamic inversion. In each step, two ESOs are designed. The first one estimates the virtual control signals, and the second one approximates the total uncertainties. Dynamic inversion is introduced into the controller to deal with the non-affine actuator faults. In particular, the ESOs are activated successively in the designed controller. ESO estimation errors and output tracking errors of the AHV-VGI system are proved to be arbitrarily small in theory. Simulation results are provided to demonstrate the effectiveness and superiority of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid attitude control scheme of L1 adaptive and dynamic inversion for unmanned aerial vehicle with actuator faults, where both gain fault and bias fault are considered. Firstly, dynamic inversion is employed to track attitude angles in the outer loop and ensures the rapid response. Secondly, an L1 adaptive controller for the inner loop is established to compensate for system uncertainty and uncertainty caused by actuator failures. Thirdly, the analysis of steady-state and transient performance is given by Lyapunov theory. Finally, simulation results prove the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]